Journal Articles
2024
14. Nweke, Chukwuebuka C; Shams, Rashid: Southern California basin and non-basin classification algorithm for ground-motion site amplification model applications. In: Earthquake Spectra, 2024. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1177/87552930241293568,
title = {Southern California basin and non-basin classification algorithm for ground-motion site amplification model applications},
author = {Chukwuebuka C Nweke and Rashid Shams},
url = {https://doi.org/10.1177/87552930241293568},
doi = {10.1177/87552930241293568},
year = {2024},
date = {2024-12-11},
journal = {Earthquake Spectra},
abstract = {In ground-motion modeling, the estimated level of ground shaking at any given location for an expected earthquake scenario depends on the contributions from the source component (type of fault mechanism and size of the fault slip), the path component (distance between the source and site of interest, and the geologic characteristics of that region), and the site component (the local geology at the site of interest). Each component captures some level of variability and uncertainty in the overall ground-motion estimate. In particular, the site component represents the potential amplification (or de-amplification) of the seismic waves that may lead to magnified and prolonged ground shaking at any given location. This feature is referred to as site effects and in current ground-motion models (GMMs) is dependent on the time-averaged shear wave velocity in the upper 30 m of the earth’s crust (Vs30) and the depth to a particular shear wave velocity iso-surface (“basin depth,”zx). The latter is responsible for determining the contributions of basin effects, which is additional ground-motion amplification due to three-dimensional effects such as trapped seismic waves that lead to surface wave generation. However, an evaluation of the relationship between zx and basin locations reveals cases of misclassification that is a result of geologic variability (i.e. zx is not sufficient in differentiating basins from non-basins). The study performed in this article proposes a resolution in the form of a statistical classification model that determines the probability of a location residing within or outside a basin based on simple geologic features such as ground surface texture.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
13. Ko, Kil-Wan; Kayen, Robert E; Kokusho, Takaji; Ilgac, Makbule; Nozu, Atsushi; Nweke, Chukwuebuka C: Energy-Based Liquefaction Evaluation: The Port of Kushiro in Hokkaido, Japan, 2003 Tokachi-Oki Earthquake. In: Journal of Geotechnical and Geoenvironmental Engineering, vol. 150, no. 10, 2024. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1061/JGGEFK.GTENG-11989,
title = {Energy-Based Liquefaction Evaluation: The Port of Kushiro in Hokkaido, Japan, 2003 Tokachi-Oki Earthquake},
author = {Kil-Wan Ko and Robert E Kayen and Takaji Kokusho and Makbule Ilgac and Atsushi Nozu and Chukwuebuka C Nweke},
url = {https://doi.org/10.1061/JGGEFK.GTENG-11989},
doi = {10.1061/JGGEFK.GTENG-11989},
year = {2024},
date = {2024-10-01},
journal = {Journal of Geotechnical and Geoenvironmental Engineering},
volume = {150},
number = {10},
abstract = {The magnitude (𝑀𝑤) 8.3 Tokachi-oki earthquake occurred in September 2003, causing extensive damage in Hokkaido, Japan, and triggering extensive soil liquefaction in the region. The Port of Kushiro was one of the locations where surficial evidence of liquefaction was observed but was also a well-instrumented location with four pore-water pressure transducers installed in the backfill of the quay wall. However, all of the sensors malfunctioned during the earthquake. As a result, the pore-water pressure response recorded by those sensors were inaccurate and unusable with regard to evaluating liquefaction triggering and extent. This study introduced the energy-based soil liquefaction evaluation to estimate the excess pore water pressure responses at the Port of Kushiro based on the cumulative strain energy of the soil during the 2003 Tokachi-oki earthquake. In order to apply the energy-based method to this case history, this study explored the empirical equation describing a relationship between normalized cumulative energy and excess pore water pressure ratio while incorporating the bidirectional shaking effect on strain energy development. Although the energy-based method allowed for the estimation of the time needed to trigger liquefaction at a target site, it was derived using the empirical coefficients that were developed for a different soil from those at the site of interest. This indicated that an adjustment to the estimated timing of liquefaction was needed, which was accomplished by additional evaluation through a Stockwell transform and Arias intensity-based liquefaction assessment. Both procedures indicated a similar timing of liquefaction at the site. Based on the updated time of liquefaction triggering, the empirical coefficient was recalibrated to estimate the excess pore water pressure ratio, and the result provided reasonable excess pore water pressure responses at the backfill of the Port of Kushiro during the 2003 Tokachi-oki earthquake.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
12. Mohammed, Shako; Shams, Rashid; Nweke, Chukwuebuka C; Buckreis, Tristan E; Kohler, Monica D; Bozorgnia, Yousef; Stewart, Jonathan P: Usability of Community Seismic Network Recordings for Ground Motion Modeling. In: Earthquake Spectra, 2024. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1177/87552930241267749,
title = {Usability of Community Seismic Network Recordings for Ground Motion Modeling},
author = {Shako Mohammed and Rashid Shams and Chukwuebuka C Nweke and Tristan E Buckreis and Monica D Kohler and Yousef Bozorgnia and Jonathan P Stewart},
url = {https://doi.org/10.1177/87552930241267749},
doi = {10.1177/87552930241267749},
year = {2024},
date = {2024-08-09},
journal = {Earthquake Spectra},
abstract = {A source of ground-motion recordings in urban Los Angeles that has seen limited prior application is the Community Seismic Network (CSN), which uses low-cost, micro\textendashelectro\textendashmechanical system (MEMS) sensors that are deployed at much higher densities than stations for other networks. We processed CSN data for the 29 earthquakes with M \> 4 between July 2012 and January 2023 that produced CSN recordings, including selection of high- and low-pass corner frequencies (fcHP and fcLP, respectively). Each record was classified as follows: (1) Broadband Record (BBR)\textemdashrelatively broad usable frequency range from fcHP \< 0.5 to fcLP \> 10 Hz; (2) Narrowband Record (NBR)\textemdashlimited usable frequency range relative to those for BBR; and (3) Rejected Record (REJ)\textemdashnoise-dominated. We compare recordings from proximate (within 3 km) CSN and non-CSN stations (screened to only include cases of similar surface geology and favorable CSN instrument housing). We find similar high- to medium-frequency ground motions (i.e. peak ground acceleration (PGA) and Sa for T \< 5 s) from CSN BBR and non-CSN stations, whereas NBRs have lower amplitudes. We examine PGA distributions for BBR and REJ records and find them to be distinguished, on average across the network, at 0.005 g, whereas 0.0015 g was found to be the threshold between usable records (BBR and NBR) and pre-event noise. Recordings with amplitudes near or below these thresholds are generally noise-dominated, reflecting environmental and anthropogenic ground vibrations and instrument noise. We find nominally higher noise levels in areas of high-population density and lower noise levels by a factor of about 1.5 in low-population density areas. By applying the 0.0015 g threshold, limiting distances for the network-average site condition, based on the expected fifth-percentile ground-motion levels, are 89, 210, 280, and 370 km for M 5, 6, 7, and 8 events, respectively.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2023
11. Ikeagwuani, Christopher C; Nweke, Chukwuebuka C; Onah, Hyginus N: Prediction of resilient modulus of fine-grained soil for pavement design using KNN, MARS, and random forest techniques. In: Arabian Journal of Geosciences, vol. 16, no. 388, 2023. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1007/s12517-023-11469-z,
title = {Prediction of resilient modulus of fine-grained soil for pavement design using KNN, MARS, and random forest techniques},
author = {Christopher C Ikeagwuani and Chukwuebuka C Nweke and Hyginus N Onah},
url = {https://doi.org/10.1007/s12517-023-11469-z},
doi = {10.1007/s12517-023-11469-z},
year = {2023},
date = {2023-05-27},
journal = {Arabian Journal of Geosciences},
volume = {16},
number = {388},
abstract = {This study was motivated by the difficulty in determining the resilient modulus of soils using the repeated load triaxial test (RLTT) recommended by the mechanistic-empirical pavement design guide (MEPDG). An alternative means to estimate the resilient modulus of fine-grained soils has been established in the form of three models that were developed using three supervised machine-learning techniques. This includes k-nearest neighbor (KNN), multivariate adaptive regression splines (MARS), and random forest. The data utilized for the development of the models were sourced from the long-term pavement performance (LTPP) database domiciled in the Infopave database in the USA. A total of twelve routine soil properties that have significant influence on the resilient modulus of fine-grained soils were considered in this study. Results obtained from this study revealed that the three developed models (KNN, MARS, and random forest) had high prediction accuracy and high generalization ability. However, the random forest model, based on the statistical indices used to evaluate the models, gave the best prediction accuracy (R2 = 0.9312 for the testing dataset) of the three developed model. It was followed closely by the MARS model with an R2 value of 0.9057. The last model in terms of prediction accuracy was the KNN model with an R2 value of 0.8748. Furthermore, based on parameter significance assessment using the random forest model, it was revealed that the nominal maximum axial stress and confining pressure are the best predictor variables for the estimation of the resilient modulus of fine-grained soils.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
10. Carey, Trevor J; Mason, Henry B; Asikmaki, Dominiki; Athanasopoulos-Zekkos, Adda; Garcia, Fernando E; Gray, Brian; Lavrentiadis, Grigorios; Nweke, Chukwuebuka C: The 2022 Chihshang, Taiwan, Earthquake: Initial GEER Team Observations. In: Journal of Geotechnical and Geoenvironmental Engineering, vol. 149, no. 5, 2023. (Type: Journal Article | Links | BibTeX) @article{doi:10.1061/JGGEFK.GTENG-11522,
title = {The 2022 Chihshang, Taiwan, Earthquake: Initial GEER Team Observations},
author = {Trevor J Carey and Henry B Mason and Dominiki Asikmaki and Adda Athanasopoulos-Zekkos and Fernando E Garcia and Brian Gray and Grigorios Lavrentiadis and Chukwuebuka C Nweke},
url = {https://doi.org/10.1061/JGGEFK.GTENG-11522},
doi = {10.1061/JGGEFK.GTENG-11522},
year = {2023},
date = {2023-03-07},
journal = {Journal of Geotechnical and Geoenvironmental Engineering},
volume = {149},
number = {5},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2022
9. Nweke, Chukwuebuka C; Stewart, Jonathan P; Wang, Pengfei; Brandenberg, Scott J: Site response of sedimentary basins and other geomorphic provinces in southern California. In: Earthquake Spectra, 2022. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1177/87552930221088609,
title = {Site response of sedimentary basins and other geomorphic provinces in southern California},
author = {Chukwuebuka C Nweke and Jonathan P Stewart and Pengfei Wang and Scott J Brandenberg},
url = {https://doi.org/10.1177/87552930221088609},
doi = {10.1177/87552930221088609},
year = {2022},
date = {2022-05-31},
journal = {Earthquake Spectra},
abstract = {Ergodic site amplification models for active tectonic regions are conditioned on the time-averaged shear wave velocity in the upper 30 m (VS30) and the depth to a shear wave velocity isosurface (zx). The depth components of such models are derived using data from sites within many geomorphic domains. We provide a site amplification model utilizing VS30 and depth, with the depth component conditioned on type of geomorphic province: basins, valleys, and mountain/hills. As with current models, the depth component of our model is centered with respect to the VS30-scaling model using differential depth δzx, taken as the difference between a site-specific depth and a VS30-conditioned average depth. Using data from southern California, we find that long-period site response for all sites combined exhibits relative de-amplification and amplification for negative and positive differential depths, respectively. Individual provinces exhibit broadly similar trends with depth, but amplification levels are on average stronger in basins such that little relative de-amplification occurs at negative differential depths. Valley and mountain/hill sites have, on average, weaker amplification levels but stronger scaling with δzx. Site-to-site standard deviations vary appreciably across geomorphic provinces, with basins having lower dispersions than mountain/hill sites and the reference ergodic model.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
8. Nweke, Chukwuebuka C; Stewart, Jonathan P; Graves, Robert W; Goulet, Christine A; Brandenberg, Scott J: Validating Predicted Site Response in Sedimentary Basins from 3D Ground Motion Simulations. In: Earthquake Spectra, 2022. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1177/87552930211073159,
title = {Validating Predicted Site Response in Sedimentary Basins from 3D Ground Motion Simulations},
author = {Chukwuebuka C Nweke and Jonathan P Stewart and Robert W Graves and Christine A Goulet and Scott J Brandenberg},
url = {https://doi.org/10.1177/87552930211073159},
doi = {10.1177/87552930211073159},
year = {2022},
date = {2022-02-16},
journal = {Earthquake Spectra},
abstract = {We introduce procedures to validate site response in sedimentary basins as predicted using ground motion simulations. These procedures aim to isolate contributions of site response to computed intensity measures relative to those from seismic source and path effects. In one of the validation procedures, simulated motions are analyzed in the same manner as earthquake recordings to derive non-ergodic site terms. This procedure compares the scaling with sediment isosurface depth of simulated versus empirical site terms (the latter having been derived in a separate study). A second validation procedure utilizes two sets of simulations, one that considers three-dimensional (3D) basin structure and a second that utilizes a one-dimensional (1D) representation of the crustal structure. Identical sources are used in both procedures, and after correcting for variable path effects, differences in ground motions are used to estimate site amplification in 3D basins. Such site responses are compared to those derived empirically to validate both the absolute levels and the depth scaling of site response from 3D simulations. We apply both procedures to southern California in a manner that is consistent between the simulated and empirical data (i.e. by using similar event locations and magnitudes). The results show that the 3D simulations overpredict the depth-scaling and absolute levels of site amplification in basins. However, overall patterns of site amplification with depth are similar, suggesting that future calibration may be able to remove observed biases.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
7. Omoya, Morolake; Ero, Itohan; Esteghamati, Mohsen Zaker; Burton, Henry V; Brandenberg, Scott; Sun, Han; Yi, Zhengxiang; Kang, Hua; Nweke, Chukuebuka C: A relational database to support post-earthquake building damage and recovery assessment. In: Earthquake Spectra, 2022. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1177/87552930211061167,
title = {A relational database to support post-earthquake building damage and recovery assessment},
author = {Morolake Omoya and Itohan Ero and Mohsen Zaker Esteghamati and Henry V Burton and Scott Brandenberg and Han Sun and Zhengxiang Yi and Hua Kang and Chukuebuka C Nweke},
url = {https://doi.org/10.1177/87552930211061167},
doi = {10.1177/87552930211061167},
year = {2022},
date = {2022-01-27},
journal = {Earthquake Spectra},
abstract = {Systematically collected and curated data sets from historical events provide a strong basis for simulating the physical and functional effects of natural hazards on the built environment. This article develops a relational database to support post-earthquake damage and recovery modeling of building portfolios. The current version of the database has been populated with information on the 3695 buildings affected by the 2014 South Napa, California, earthquake. The associated data categories include general building characteristics, site properties and shaking intensities, building damage and repair permitting (timing and type) information, and census-block-level sociodemographics. The Napa data set can be used to validate post-earthquake recovery simulation methodologies and explore the effectiveness of different modeling techniques in predicting damage. The database can be expanded to include other earthquakes and the overall framework can be adapted to other types of natural hazards (e.g. hurricanes, flooding).},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2021
6. Goulet, Christine A.; Wang, Yongfei; Nweke, Chukwuebuka C.; Tang, Bo‐xiang; Wang, Pengfei; Hudson, Kenneth S.; Ahdi, Sean K.; Meng, Xiaofeng; Hudson, Martin B.; Donnellan, Andrea; Lyzenga, Gregory A.; Brandenberg, Scott J.; Stewart, Jonathan P.; Gallien, Timu; Winters, Maria A.: Comparison of Near‐Fault Displacement Interpretations from Field and Aerial Data for the M 6.5 and 7.1 Ridgecrest Earthquake Sequence Ruptures. In: Bulletin of the Seismological Society of America, 2021, ISSN: 0037-1106. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1785/0120200222,
title = {Comparison of Near‐Fault Displacement Interpretations from Field and Aerial Data for the M 6.5 and 7.1 Ridgecrest Earthquake Sequence Ruptures},
author = {Christine A. Goulet and Yongfei Wang and Chukwuebuka C. Nweke and Bo‐xiang Tang and Pengfei Wang and Kenneth S. Hudson and Sean K. Ahdi and Xiaofeng Meng and Martin B. Hudson and Andrea Donnellan and Gregory A. Lyzenga and Scott J. Brandenberg and Jonathan P. Stewart and Timu Gallien and Maria A. Winters},
url = {https://doi.org/10.1785/0120200222},
doi = {10.1785/0120200222},
issn = {0037-1106},
year = {2021},
date = {2021-08-24},
urldate = {2020-08-24},
journal = {Bulletin of the Seismological Society of America},
abstract = {Coseismic surface fault displacement presents a serious potential hazard for structures and for lifeline infrastructure. Distributed lifeline infrastructure tends to cover large distances and may cross faults in multiple locations, especially in active tectonic regions like California. However, fault displacement measurements for engineering applications are quite sparse, rendering the development of predictive models extremely difficult and fraught with large uncertainties. Detailed fault surface rupture mapping products exist for a few documented cases, but they may not capture the full width of ground deformations that are likely to impact distributed infrastructure. The 2019 Ridgecrest earthquake sequence presented an ideal opportunity to collect data and evaluate the ability of different techniques to capture coseismic deformations on and near the fault ruptures. Both the M 6.5 and 7.1 events ruptured the surface in sparsely populated desert areas where little vegetation is present to obscure surficial features. Two study areas (~400 m × 500 m each) around the surface ruptures from the two events were selected. Teams of researchers were deployed and coordinated to gather data in three ways: field measurements and photographs, imagery from small uninhabited aerial systems, and imagery from airborne light detection and ranging. Each of these techniques requires different amounts of resources in terms of cost, labor, and time associated with the data collection, processing, and interpretation efforts. This article presents the data collection methods used for the two study areas, and qualitative and quantitative comparisons of the results interpretations. While all three techniques capture the key features that are important for displacement design of distributed infrastructure, the use of remote sensing methods in combination with field measurements presents an advantage over the use of any single technique.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
5. Ikeagwuani, Chijioke Christopher; Nwonu, Donald Chimobi; Nweke, Chukwuebuka C: Resilient modulus descriptive analysis and estimation for fine-grained soils using multivariate and machine learning methods. In: International Journal of Pavement Engineering, vol. 0, no. 0, pp. 1-16, 2021. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1080/10298436.2021.1895993,
title = {Resilient modulus descriptive analysis and estimation for fine-grained soils using multivariate and machine learning methods},
author = {Chijioke Christopher Ikeagwuani and Donald Chimobi Nwonu and Chukwuebuka C Nweke},
url = {https://doi.org/10.1080/10298436.2021.1895993},
doi = {10.1080/10298436.2021.1895993},
year = {2021},
date = {2021-01-01},
journal = {International Journal of Pavement Engineering},
volume = {0},
number = {0},
pages = {1-16},
publisher = {Taylor \& Francis},
abstract = {ABSTRACTThe adoption of mechanistic-empirical approach to pavement design requires the use of resilient modulus of subgrade soils as a crucial input. The determination of in the laboratory is inexpedient due to the nature of the existing test protocols. This prompted the use of estimated values, which inadvertently has gained popularity lately. However, the accuracy of estimated values is questionable due to spatial variability of soil properties. This necessitated the aggressive search for robust and thorough approaches for predictive modelling of the . In the present study, a systematic approach was adopted for the descriptive analysis and estimation of . from routine soil properties using data from Long-Term Pavement Performance (LTPP) and considering the spatial variability of the soil properties. Descriptive analysis was executed using non-parametric correlation and principal component analysis (PCA), while the estimation was done using three machine learning methods which include gradient boosting regression (GBR), adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN). Based on the PCA, four factors which explained a total of 77.5% variance in the data had significant influence on the . These include the effect of moisture-induced changes on the soil consistency limits and physical condition, effect of the soil clay content, effect of the soil gradation and effect of the soil stress state. Various factors of the machine learning methods such as the learning rate, number of clusters and number of hidden layers had a significant effect on the prediction accuracy. The three machine learning methods were satisfactory for the prediction based on R2 values which were generally above 0.9. Also, when considering spatial variability of routine soil properties, the GBR and ANFIS have a comparative advantage over the ANN, since they exhibited a high stability in the prediction for both the training and testing dataset.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2020
4. Zimmaro, Paolo; Nweke, Chukwuebuka C.; Hernandez, Janis L.; Hudson, Kenneth S.; Hudson, Martin B.; Ahdi, Sean K.; Boggs, Matthew L.; Davis, Craig A.; Goulet, Christine A.; Brandenberg, Scott J.; Hudnut, Kenneth W.; Stewart, Jonathan P.: Liquefaction and Related Ground Failure from July 2019 Ridgecrest Earthquake Sequence. In: Bulletin of the Seismological Society of America, vol. 110, no. 4, pp. 1549-1566, 2020, ISSN: 0037-1106. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1785/0120200025,
title = {Liquefaction and Related Ground Failure from July 2019 Ridgecrest Earthquake Sequence},
author = {Paolo Zimmaro and Chukwuebuka C. Nweke and Janis L. Hernandez and Kenneth S. Hudson and Martin B. Hudson and Sean K. Ahdi and Matthew L. Boggs and Craig A. Davis and Christine A. Goulet and Scott J. Brandenberg and Kenneth W. Hudnut and Jonathan P. Stewart},
url = {https://doi.org/10.1785/0120200025},
doi = {10.1785/0120200025},
issn = {0037-1106},
year = {2020},
date = {2020-07-21},
journal = {Bulletin of the Seismological Society of America},
volume = {110},
number = {4},
pages = {1549-1566},
abstract = {The 2019 Ridgecrest earthquake sequence produced a 4 July M 6.5 foreshock and a 5 July M 7.1 mainshock, along with 23 events with magnitudes greater than 4.5 in the 24 hr period following the mainshock. The epicenters of the two principal events were located in the Indian Wells Valley, northwest of Searles Valley near the towns of Ridgecrest, Trona, and Argus. We describe observed liquefaction manifestations including sand boils, fissures, and lateral spreading features, as well as proximate non‐ground failure zones that resulted from the sequence. Expanding upon results initially presented in a report of the Geotechnical Extreme Events Reconnaissance Association, we synthesize results of field mapping, aerial imagery, and inferences of ground deformations from Synthetic Aperture Radar‐based damage proxy maps (DPMs). We document incidents of liquefaction, settlement, and lateral spreading in the Naval Air Weapons Station China Lake US military base and compare locations of these observations to pre‐ and postevent mapping of liquefaction hazards. We describe liquefaction and ground‐failure features in Trona and Argus, which produced lateral deformations and impacts on several single‐story masonry and wood frame buildings. Detailed maps showing zones with and without ground failure are provided for these towns, along with mapped ground deformations along transects. Finally, we describe incidents of massive liquefaction with related ground failures and proximate areas of similar geologic origin without ground failure in the Searles Lakebed. Observations in this region are consistent with surface change predicted by the DPM. In the same region, geospatial liquefaction hazard maps are effective at identifying broad percentages of land with liquefaction‐related damage. We anticipate that data presented in this article will be useful for future liquefaction susceptibility, triggering, and consequence studies being undertaken as part of the Next Generation Liquefaction project.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
3. Ahdi, Sean Kamran; Mazzoni, Silvia; Kishida, Tadahiro; Wang, Pengfei; Nweke, Chukwuebuka C.; Kuehn, Nicolas M.; Contreras, Victor; Rowshandel, Badie; Stewart, Jonathan P.; Bozorgnia, Yousef: Engineering Characteristics of Ground Motions Recorded in the 2019 Ridgecrest Earthquake Sequence. In: Bulletin of the Seismological Society of America, vol. 110, no. 4, pp. 1474-1494, 2020, ISSN: 0037-1106. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1785/0120200036,
title = {Engineering Characteristics of Ground Motions Recorded in the 2019 Ridgecrest Earthquake Sequence},
author = {Sean Kamran Ahdi and Silvia Mazzoni and Tadahiro Kishida and Pengfei Wang and Chukwuebuka C. Nweke and Nicolas M. Kuehn and Victor Contreras and Badie Rowshandel and Jonathan P. Stewart and Yousef Bozorgnia},
url = {https://doi.org/10.1785/0120200036},
doi = {10.1785/0120200036},
issn = {0037-1106},
year = {2020},
date = {2020-07-21},
journal = {Bulletin of the Seismological Society of America},
volume = {110},
number = {4},
pages = {1474-1494},
abstract = {We present a database and analyze ground motions recorded during three events that occurred as part of the July 2019 Ridgecrest earthquake sequence: a moment magnitude (M) 6.5 foreshock on a left‐lateral cross fault in the Salt Wells Valley fault zone, an M 5.5 foreshock in the Paxton Ranch fault zone, and the M 7.1 mainshock, also occurring in the Paxton Ranch fault zone. We collected and uniformly processed 1483 three‐component recordings from an array of 824 sensors spanning 10 seismographic networks. We developed site metadata using available data and multiple models for the time‐averaged shear‐wave velocity in the upper 30 m (VS30) and for basin depth terms. We processed ground motions using Next Generation Attenuation (NGA) procedures and computed intensity measures including spectral acceleration at a number of oscillator periods and inelastic response spectra. We compared elastic and inelastic response spectra to seismic design spectra in building codes to evaluate the damage potential of the ground motions at spatially distributed sites. Residuals of the observed spectral accelerations relative to the NGA‐West2 ground‐motion models (GMMs) show good average agreement between observations and model predictions (event terms between about −0.3 and 0.5 for peak ground acceleration to 5 s). The average attenuation with distance is also well captured by the empirical NGA‐West2 GMMs, although azimuthal variations in attenuation were observed that are not captured by the GMMs. An analysis considering directivity and fault‐slip heterogeneity for the M 7.1 event demonstrates that the dispersion in the near‐source ground‐motion residuals can be reduced.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2. Brandenberg, Scott J.; Stewart, Jonathan P.; Wang, Pengfei; Nweke, Chukwuebuka C.; Hudson, Kenneth; Goulet, Christine A.; Meng, Xiaofeng; Davis, Craig A.; Ahdi, Sean K.; Hudson, Martin B.; Donnellan, Andrea; Lyzenga, Gregory; Pierce, Marlon; Wang, Jun; Winters, Maria A.; Delisle, Marie‐Pierre; Lucey, Joseph; Kim, Yeulwoo; and Timu W. Gallien,; Lyda, Andrew; Yeung, Sean J.; Issa, Omar; Buckreis, Tristan; Yi, Zhengxiang: Ground Deformation Data from GEER Investigations of Ridgecrest Earthquake Sequence. In: Seismological Research Letters, vol. 91, no. 4, pp. 2024-2034, 2020, ISSN: 0895-0695. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1785/0220190291,
title = {Ground Deformation Data from GEER Investigations of Ridgecrest Earthquake Sequence},
author = {Scott J. Brandenberg and Jonathan P. Stewart and Pengfei Wang and Chukwuebuka C. Nweke and Kenneth Hudson and Christine A. Goulet and Xiaofeng Meng and Craig A. Davis and Sean K. Ahdi and Martin B. Hudson and Andrea Donnellan and Gregory Lyzenga and Marlon Pierce and Jun Wang and Maria A. Winters and Marie‐Pierre Delisle and Joseph Lucey and Yeulwoo Kim and and Timu W. Gallien and Andrew Lyda and Sean J. Yeung and Omar Issa and Tristan Buckreis and Zhengxiang Yi},
url = {https://doi.org/10.1785/0220190291},
doi = {10.1785/0220190291},
issn = {0895-0695},
year = {2020},
date = {2020-02-19},
journal = {Seismological Research Letters},
volume = {91},
number = {4},
pages = {2024-2034},
abstract = {Following the Ridgecrest earthquake sequence, consisting of an M 6.4 foreshock and M 7.1 mainshock along with many other events, the Geotechnical Extreme Events Reconnaissance association deployed a team to gather perishable data. The team focused their efforts on documenting ground deformations including surface fault rupture south of the Naval Air Weapons Station China Lake, and liquefaction features in Trona and Argus. The team published a report within two weeks of the M 7.1 mainshock. This article presents data products gathered by the team, which are now published and publicly accessible. The data products presented herein include ground‐based observations using Global Positioning System trackers, digital cameras, and hand‐measuring devices, as well as unmanned aerial vehicle‐based imaging products using Structure from Motion to create point clouds and digital surface models. The article describes the data products, as well as tools available for interacting with the products.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
1. Mangalathu, Sujith; Sun, Han; Nweke, Chukwuebuka C.; Yi, Zhengxiang; Burton, Henry V.: Classifying earthquake damage to buildings using machine learning. In: Earthquake Spectra, vol. 36, no. 1, pp. 183-208, 2020. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1177/8755293019878137,
title = {Classifying earthquake damage to buildings using machine learning},
author = {Sujith Mangalathu and Han Sun and Chukwuebuka C. Nweke and Zhengxiang Yi and Henry V. Burton},
url = {https://doi.org/10.1177/8755293019878137},
doi = {10.1177/8755293019878137},
year = {2020},
date = {2020-01-29},
journal = {Earthquake Spectra},
volume = {36},
number = {1},
pages = {183-208},
abstract = {The ability to rapidly assess the spatial distribution and severity of building damage is essential to post-event emergency response and recovery. Visually identifying and classifying individual building damage requires significant time and personnel resources and can last for months after the event. This article evaluates the feasibility of using machine learning techniques such as discriminant analysis, k-nearest neighbors, decision trees, and random forests, to rapidly predict earthquake-induced building damage. Data from the 2014 South Napa earthquake are used for the study where building damage is classified based on the assigned Applied Technology Council (ATC)-20 tag (red, yellow, and green). Spectral acceleration at a period of 0.3 s, fault distance, and several building specific characteristics (e.g. age, floor area, presence of plan irregularity) are used as features or predictor variables for the machine learning models. A portion of the damage data from the Napa earthquake is used to obtain the forecast model, and the performance of each machine learning technique is evaluated using the remaining (test) data. It is noted that the random forest algorithm can accurately predict the assigned tags for 66% of the buildings in the test dataset.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Conferences
2024
14. Vyas, Piyush; Nweke, Chukwuebuka C: Characterizing the Degradation Threshold of Biocemented Sands for Transportation Infrastructure: Insights from Resonant Column Test.. Proceedings of the 5th International Conference on Transportation Geotechnics (ICTG) 2024, vol. 4, 2024. (Type: Conference | Abstract | Links | BibTeX) @conference{doi:10.1007/978-981-97-8225-3_23,
title = {Characterizing the Degradation Threshold of Biocemented Sands for Transportation Infrastructure: Insights from Resonant Column Test.},
author = {Piyush Vyas and Chukwuebuka C Nweke},
url = {https://doi.org/10.1007/978-981-97-8225-3_23},
doi = {10.1007/978-981-97-8225-3_23},
year = {2024},
date = {2024-10-25},
booktitle = {Proceedings of the 5th International Conference on Transportation Geotechnics (ICTG) 2024},
volume = {4},
pages = {215-224},
abstract = {Biocemented soils present a promising sustainable alternative to traditional Portland cement and asphalt in road embankment construction and remediation. However, the cyclic loading experienced by transportation infrastructures like roads over extended periods explicitly leads to performance degradation. Biocementation, achieved through Microbially Induced Calcite Precipitation (MICP) using ureolytic bacteria or Enzyme-Induced Calcite Precipitation (EICP) with urease enzymes, precipitates calcium carbonate (calcite) as a bonding agent within the soil matrix. Despite the environmental appeal of biocemented soils, their durability under cyclic and repeatable loads remains relatively unexplored. This paper investigates the modulus degradation of biocemented sand subjected to cyclic loading, considering various strain amplitudes and confinement levels. The experimental program involves subjecting two distinct specimens\textemdashone uncemented and the other cemented\textemdashto three confinement levels (50, 100, and 200 kPa). Each specimen undergoes incremental torque amplitudes to elucidate stiffness behavior across a spectrum of strain levels. Additionally, resilient modulus estimates are obtained for different strain levels, and a critical strain threshold is identified. The primary objective of this research is to unveil fatigue susceptibility criteria, offering crucial insights into the performance of biocemented soils. By doing so, this study contributes to the advancement of sustainable and durable infrastructural solutions, particularly in the context of road construction and maintenance.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
13. Ornelas, Francisco-Javier; Nweke, Chukwuebuka C; Torre, Christopher; Wang, Pengfei; Mai, Thanh Dat; Cox, Brady R; Brandenberg, Scott J; Stewart, Jonathan P: Reliability of low frequency mHVSR ordinates. 18WCEE, 2024. (Type: Conference | Abstract | Links | BibTeX) @conference{doi:z,
title = {Reliability of low frequency mHVSR ordinates},
author = {Francisco-Javier Ornelas and Chukwuebuka C Nweke and Christopher Torre and Pengfei Wang and Thanh Dat Mai and Brady R Cox and Scott J Brandenberg and Jonathan P Stewart},
url = {https://escholarship.org/uc/item/9731j6bz},
year = {2024},
date = {2024-07-01},
booktitle = {18WCEE},
abstract = {Microtremor horizontal-to-vertical spectral ratios (mHVSR) are frequency-dependent ratios of Fourier amplitude spectra of the horizontal to vertical components of a 3-component recording of ambient ground motions from microtremors. Results from mHVSR tests can identify the frequencies associated with site resonances at sites with large impedance contrasts, and hence have potential to provide useful parameters for predicting seismic site response. Site measurements are made by recording ground vibrations either from a temporarily deployed seismometer, typically recording for a relatively short period of time (~1-2 hrs.), or from a permanently-installed broadband seismometer. In this paper, we discuss ongoing work investigating the reliability of low frequency (\< ∼0.1 Hz) mHVSR ordinates. Such low frequency ordinates are potentially useful for sites that are known to have deep basins (e.g., LA Basin, Imperial Valley, Great Salt Lake basin), where fundamental frequencies may fall in this range and direct measurements of depth to bedrock are difficult to make. We have found that low-frequency mHVSR ordinates (\< ∼0.1-0.2 Hz) are for practical purposes not reliable in most cases, even when measured by high-quality temporary or permanent broadband sensors. In this paper, we discuss sensor drift and its limited impact on the reliability of mHVSR ordinates. We document the low frequency problem for multiple sites, although we do not have a solution as of this writing for how to improve the reliability of low-frequency results.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
12. Buckreis, Tristan E; Nweke, Chukwuebuka C; Wang, Pengfei; Brandenberg, Scott J; Shams, Rashid; Ramos-Sepulveda, Maria; Pretell, Renmin; Mazzoni, Silvia; Stewart, Jonathan P: User-interaction with a web-served global ground motion relational database. 18WCEE, 2024. (Type: Conference | Abstract | Links | BibTeX) @conference{doi:_27,
title = {User-interaction with a web-served global ground motion relational database},
author = {Tristan E Buckreis and Chukwuebuka C Nweke and Pengfei Wang and Scott J Brandenberg and Rashid Shams and Maria Ramos-Sepulveda and Renmin Pretell and Silvia Mazzoni and Jonathan P Stewart},
url = {https://escholarship.org/uc/item/9tw6k14c},
year = {2024},
date = {2024-07-01},
booktitle = {18WCEE},
abstract = {We present an application programming interface (API) which facilitates public access to a global relational database of earthquake ground motion intensity measures, associated metadata, and time-series data. Next Generation Attenuation (NGA)-East and NGA-West2 project spreadsheets have been adapted into a relational database format composed of multiple tables through a series of primary and foreign keys. The combined dataset has been expanded to include contributions from earthquakes, generally with magnitudes greater than M3.9, that have occurred since the conclusion of the data synthesis component of both projects in 2011. Currently the database includes 62,449 ground motions recorded at 9,092 stations for 899 events. The database is accessible through an API, which allows users to interact with and query the database directly without detailed knowledge of structure query language (SQL). Simple queries are constructed by appending relatively straightforward query string parameters to the end of a uniform resource location (URL) that serves as an endpoint, which returns only data that satisfy the query constraints. The web-served nature of the database means that users have immediate access to ground motion data as soon as it is collected, reviewed, and uploaded. Furthermore, integrated end-to-end workflows \textendash which do not require files to be downloaded and saved in local memory \textendash are possible through the API. The structure of the database has been designed to accommodate growth, with ongoing efforts to integrate global ground motion data in anticipation of the NGA-West3 project, and improve ease-of access through the API.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
11. Ornelas, Francisco-Javier; Buckreis, Tristan E; Nweke, Chukwuebuka C; Wang, Pengfei; Torre, Christopher; Brandenberg, Scott J; Stewart, Jonathan P: Preliminary observations of an ergodic site response model in California conditioned on Vs30 and HVSR Parameters. Japanese Geotechnical Society Special Publication, vol. 10, no. 47, 2024. (Type: Conference | Abstract | Links | BibTeX) @conference{doi:10.3208/jgssp.v10.OS-36-06,
title = {Preliminary observations of an ergodic site response model in California conditioned on Vs30 and HVSR Parameters},
author = {Francisco-Javier Ornelas and Tristan E Buckreis and Chukwuebuka C Nweke and Pengfei Wang and Christopher Torre and Scott J Brandenberg and Jonathan P Stewart},
url = {https://doi.org/10.3208/jgssp.v10.OS-36-06},
doi = {10.3208/jgssp.v10.OS-36-06},
year = {2024},
date = {2024-05-10},
booktitle = {Japanese Geotechnical Society Special Publication},
volume = {10},
number = {47},
pages = {1769-1774},
abstract = {Traditional ergodic models are derived based on time-averaged shear-wave velocity in the upper 30 m of the site. These models are not able to account for site resonances, the presence and frequency of which can be established from microtremor HVSR surveys. Not all California sites exhibit such resonances, but knowledge that peaks are or are not present affects site response over a wide range of frequencies, with the former producing a response spectral peak near the HVSR peak. Research is underway to develop a model using microtremor HVSR data, which will be novel relative to previous models that are based on earthquake HVSR data. Our model is being formulated as modification to a global VS30 and z1.0 relationship. This paper explains the model development approach and findings of a systematic assessment of how HVSR curves relate to features of site-specific (or non-ergodic) response, which is informing model development.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
10. Shams, Rashid; Nweke, Chukwuebuka C: Capturing the Path Dependency of Site Response in Basin and Non-Basin Southern California Locations. Geo-Congress 2024, 2024. (Type: Conference | Abstract | Links | BibTeX) @conference{doi:10.1061/9780784485316.043,
title = {Capturing the Path Dependency of Site Response in Basin and Non-Basin Southern California Locations},
author = {Rashid Shams and Chukwuebuka C Nweke},
url = {https://doi.org/10.1061/9780784485316.043},
doi = {10.1061/9780784485316.043},
year = {2024},
date = {2024-02-22},
booktitle = {Geo-Congress 2024},
pages = {411-419},
abstract = {The manifestation of ground shaking in sedimentary basins during an earthquake event depends on the energy released by the seismic source, the distance between the source and the basin in question, and the geologic characteristics of the basin. The combination of these components leads to amplification of ground shaking in basins relative to non-basin regions. Within sedimentary basins, spatial variability of ground shaking from location to location occurs due to the complexities associated with the interactions of seismic waves with the 3-dimensional characteristics of the subsurface and the variation of geologic material. This includes refraction which alters the propagation direction of seismic waves, diffraction which spreads and scatters the waves, reflection which can concentrate seismic energy, and their combinations which can generate propagating surface waves. The intensity of these basin-related site effects is drastically impacted by the path between the source and the site within basin (attenuation and basin boundary interactions). Both site effects and path effects are intertwined, and as such, the determination of site response in these geomorphic provinces requires proper understanding of their interactions in order to separate both effects. Using an expanded southern California ground motion dataset that comprises a subset of NGA-West2 plus recent event recordings, this study uses iterative mixed effects modelling scheme to propose a site-dependent path model for southern California. The site-dependent model attempts to partition path-site effects, and the regional model aims to release the ergodic assumption. It is expected that incorporating site dependence based on basin and non-basin features will show reduction in uncertainty in comparison to current in practice ergodic GMMs.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
9. KC, Sajan; Nweke, Chukwuebuka C; Stewart, Jonathan P; Graves, Robert W: Reconciling Bias in Moderate Magnitude Earthquake Ground Motions Predicted by Numerical Simulations. Geo-Congress 2024, 2024. (Type: Conference | Abstract | Links | BibTeX) @conference{doi:10.1061/9780784485316.044,
title = {Reconciling Bias in Moderate Magnitude Earthquake Ground Motions Predicted by Numerical Simulations},
author = {Sajan KC and Chukwuebuka C Nweke and Jonathan P Stewart and Robert W Graves},
url = {https://doi.org/10.1061/9780784485316.044},
doi = {10.1061/9780784485316.044},
year = {2024},
date = {2024-02-22},
booktitle = {Geo-Congress 2024},
pages = {420-429},
abstract = {Recent studies found a significant underprediction in ground motion intensity measures for finite-fault simulations of moderate magnitude events in southern California relative to established ground motion models. This study aims to understand the source(s) of this bias by evaluating ground motion residuals. For this, simulations have been performed for a total of 27 well-recorded earthquakes in southern California. Systematic efforts have been employed to identify the source(s) of bias by ruling out factors that are insignificant. Preliminary findings indicate that the magnitude-area scaling used in the simulations is the likely major cause of the observed bias. Adjustment in the source attributes on event-by-event basis is underway to study if the observed bias can be reconciled.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
2023
8. Buckreis, Tristan E; Nweke, Chukwuebuka C; Wang, Pengfei; Brandenberg, Scott J; Mazzoni, Silvia; Stewart, Jonathan P: Relational Database for California Strong Ground Motions. Geo-Congress 2023, 2023. (Type: Conference | Abstract | Links | BibTeX) @conference{doi:10.1061/9780784484692.047,
title = {Relational Database for California Strong Ground Motions},
author = {Tristan E Buckreis and Chukwuebuka C Nweke and Pengfei Wang and Scott J Brandenberg and Silvia Mazzoni and Jonathan P Stewart},
url = {https://doi.org/10.1061/9780784484692.047},
doi = {10.1061/9780784484692.047},
year = {2023},
date = {2023-03-26},
booktitle = {Geo-Congress 2023},
pages = {461-470},
abstract = {We present a relational database of earthquake ground motion intensity measures and associated metadata for the state of California. NGA-West2 project spreadsheets have been adapted into a relational database format, and the data set has been expanded to include contributions from earthquakes, generally with magnitudes greater than M3.9, that have occurred since the conclusion of the data synthesis component of the NGA-West2 project in 2011. Aside from the newly added information, some site metadata fields have been updated for some ground motion stations. The relational-database is composed of multiple tables connected through a series of primary and foreign keys. We use various data types (beyond integers and floats) to increase the storage efficiency for several types of data. Currently the database includes 33,422 ground motions recorded at 2,739 stations for 478 events within or close to California. The database was designed to also accommodate the various fields included in other NGA databases, including NGA-East and NGA-Sub. This will eventually allow for certain database tables to be merged for all event types (e.g., a single site table could be created) in one central location.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
2022
7. Birkel, Brianna C; Vidale, John E; Nweke, Chukwuebuka C: Comparison of Observed and Simulated Ground Motions in the Los Angeles Basin. AGU Fall Meeting 2022, 2022. (Type: Conference | Abstract | Links | BibTeX) @conference{doi:,
title = {Comparison of Observed and Simulated Ground Motions in the Los Angeles Basin},
author = {Brianna C Birkel and John E Vidale and Chukwuebuka C Nweke},
url = {https://ui.adsabs.harvard.edu/abs/2022AGUFM.S45B..04B/abstract},
year = {2022},
date = {2022-12-12},
booktitle = {AGU Fall Meeting 2022},
abstract = {The deep, soft sedimentary basin surrounding Los Angeles is a region of ongoing scientific interest and study, due to its overlying dense infrastructure and tendency to amplify 3-10s period seismic waves. In this study, we evaluate the accuracy of the latest seismic velocity models \textendash CVM-S4.26.M01 and CVM-H 15.1.0 \textendash by comparing observed seismograms from several recent moderate magnitude earthquakes to their synthetic counterparts. These synthetic seismograms are computed via forward modeling simulation software using both the octree-based full-3D tomography Hercules toolchain (Taborda et al. 2016) and the finite-difference code developed by Rob Graves. In the Los Angeles basin, we see significant differences between observations and predictions, even at periods longer than 5 seconds and particularly within the 3-5 second period range. These differences are quantified using the Anderson 2004 goodness-of-fit metrics, as well as via direct waveform comparison. We additionally identify smaller, more specific regions within the Los Angeles Basin that demonstrate the largest misfit and require more detailed study. These results suggest that earthquake hazard estimation in the Los Angeles basin will benefit from specific, focused improvements of the velocity models in this region.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
6. Nweke, Chukwuebuka C; Davis, Craig A; Hudson, Kenneth S; Hudnut, Kenneth W; Brandenberg, Scott J; Stewart, Jonathan P: Performance of Water Pipelines at Fault Crossings from the 2019 Ridgecrest Earthquakes. Lifelines 2022, 2022. (Type: Conference | Abstract | Links | BibTeX) @conference{doi:10.1061/9780784484449.031,
title = {Performance of Water Pipelines at Fault Crossings from the 2019 Ridgecrest Earthquakes},
author = {Chukwuebuka C Nweke and Craig A Davis and Kenneth S Hudson and Kenneth W Hudnut and Scott J Brandenberg and Jonathan P Stewart},
url = {http://dx.doi.org/10.1061/9780784484449.031},
doi = {10.1061/9780784484449.031},
year = {2022},
date = {2022-11-16},
booktitle = {Lifelines 2022},
pages = {343-355},
abstract = {The 2019 Ridgecrest earthquake sequence produced extensive surface rupture affecting the Naval Air Weapons Station, China Lake, and multiple water pipelines that service the towns of Trona and Argus. This paper documents observations of surface rupture and their effects on buried water pipelines at four pipeline-fault crossings. At these crossing locations surface ruptures ranged from about 0\textendash60 cm (V) and 2.1\textendash330 cm (H). Some surface ruptures displayed complicated patterns. The water pipes are made of multiple materials and they are approximately 30.5 to 40.5 cm in diameter. For each crossing, the surface rupture characteristics and the observed pipe damages are described. It is anticipated that the field data presented herein will serve as a resource for subsequent research to validate and enhance existing knowledge on the behavior of faulting surface rupture and impacts on buried water pipelines.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
5. Brandenberg, Scott J; Goulet, Christine A; Zimmaro, Paolo; Wang, Yongfei; Nweke, Chukwuebuka C; Tang, Bo‐xiang; Wang, Pengfei; Hudson, Kenneth S.; Ahdi, Sean K.; Meng, Xiaofeng; Hudson, Martin B.; Donnellan, Andrea; Lyzenga, Gregory A.; Stewart, Jonathan P.; Gallien, Timu; Winters, Maria A.: Fault Rupture and Liquefaction Feature Mapping with Unmanned Aerial Systems after the Ridgecrest Earthquake Sequence. 12NCEE 2022, 2022. (Type: Conference | Abstract | BibTeX) @conference{nweke2022faultrupture,
title = {Fault Rupture and Liquefaction Feature Mapping with Unmanned Aerial Systems after the Ridgecrest Earthquake Sequence},
author = {Scott J Brandenberg and Christine A Goulet and Paolo Zimmaro and Yongfei Wang and Chukwuebuka C Nweke and Bo‐xiang Tang and Pengfei Wang and Kenneth S. Hudson and Sean K. Ahdi and Xiaofeng Meng and Martin B. Hudson and Andrea Donnellan and Gregory A. Lyzenga and Jonathan P. Stewart and Timu Gallien and Maria A. Winters},
year = {2022},
date = {2022-08-01},
booktitle = {12NCEE 2022},
abstract = {TheM6. 5 and M7. 1 earthquakes that occurred as part of the 2019 Ridgecrest sequence produced surface fault rupture and liquefaction features that were mapped using unmanned aerial vehicles (UAV’s) operated by different research teams [1, 2, 3]. These included engineers, scientists, and remote sensing experts organized as a GEER (Geotechnical Extreme Events Reconnaissance) team and staff of the University of Washington RAPID facility. We also made ground measurements using traditional survey techniques and digital photography and coordinated with others on aerial Light Detection and Ranging (LiDAR) surveys. The combination of these measurements provided an opportunity to assess the ability of different UAV techniques to capture coseismic deformations on and near fault ruptures, as well as permanent deformations due to liquefaction-induced ground failure. Ground failure spatial distribution maps were also used leveraging synthetic aperture radar data. The events occurred in a desert environment where little vegetation is present to obscure surficial features. This presentation will discuss the field reconnaissance efforts performed after the earthquake sequence, and provide comparisons among the different methods.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
4. Nweke, Chukwuebuka C; Stewart, Jonathan P; Wang, Pengfei; Brandenberg, Scott J: Sedimentary Basin Site Response for Different Basin Types in Southern California. 12NCEE 2022, 2022. (Type: Conference | Abstract | Links | BibTeX) @conference{nweke2022sedimentarybasins,
title = {Sedimentary Basin Site Response for Different Basin Types in Southern California},
author = {Chukwuebuka C Nweke and Jonathan P Stewart and Pengfei Wang and Scott J Brandenberg},
url = {https://escholarship.org/uc/item/6vh7q486#author},
year = {2022},
date = {2022-07-01},
booktitle = {12NCEE 2022},
abstract = {Site response effects are described by ergodic ground motion models, which are developed using global data from sites with diverse site conditions, using the time-averaged shear-wave velocity in the upper 30 m (VS30) and isosurface depths (z1.0 or z2.5). Site responses in sedimentary basins may have specific dependencies on the geometry and extent of the sedimentary structure in addition to VS30 and isosurface depths. We investigate here the effects of basin-to-basin categorization on site response. Using southern California data, we highlight differences in mean site amplification for eight large sedimentary basins with different geologic origins. The mean response in all basins shows significant relative amplification at long periods (T \> 0.5 sec) and none at shorter periods (T \< 0.3 sec). Comparisons of basin-specific responses reveal that coastal basins exhibit greater levels of relative long-period amplification than inland, fault-bounded sedimentary basins.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
2018
3. Nweke, Chukwuebuka C.; Wang, Pengfei; Brandenberg, Scott J.; Stewart, Jonathan P.: Reconsidering basin effects in ergodic site response models. Proc. SMIP 2018 Seminar on Utilization of Strong Motion Data California Geological Survey: Strong Motion Implementation Program 2018. (Type: Conference | Links | BibTeX) @conference{nweke2018reconsidering,
title = {Reconsidering basin effects in ergodic site response models},
author = {Chukwuebuka C. Nweke and Pengfei Wang and Scott J. Brandenberg and Jonathan P. Stewart},
url = {https://escholarship.org/content/qt6048v74k/qt6048v74k.pdf},
year = {2018},
date = {2018-10-01},
organization = {California Geological Survey: Strong Motion Implementation Program},
series = {Proc. SMIP 2018 Seminar on Utilization of Strong Motion Data},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
2. Nweke, Chukwuebuka C.; Pestana, Juan M.: Modeling Bio-Cemented Sands: A Strength Index for Cemented Sands. IFCEE 2018, 2018. (Type: Conference | Abstract | Links | BibTeX) @conference{doi:10.1061/9780784481592.006,
title = {Modeling Bio-Cemented Sands: A Strength Index for Cemented Sands},
author = {Chukwuebuka C. Nweke and Juan M. Pestana},
url = {https://ascelibrary.org/doi/abs/10.1061/9780784481592.006},
doi = {10.1061/9780784481592.006},
year = {2018},
date = {2018-06-06},
booktitle = {IFCEE 2018},
pages = {48-58},
abstract = {The establishment of the bio-inspired and bio-mediated sub-disciplines in the emerging field of biogeotechnology has led to the developments of many innovative methods and techniques. These methods and techniques potentially provide sustainable alternatives to conventional approaches that may be less desirable due to their use of high-embodied energy materials and processes. In particular, research within the bio-mediated sub-discipline over the past decade has fostered advancements in biocementation ground improvement methods that currently allow for possible field scale implementation. As a result, the ability to incorporate and sufficiently factor the associated mechanical enhancements during design is needed. The development of a constitutive model that properly assesses the level of improvement and adequately predicts the expected performance for a given level of cementation is underway. However, in order to accomplish the aforementioned goal, there is a need to develop components that are capable of capturing the behavior and transition from the cemented to uncemented state, while maintaining adherence to influential factors in the volumetric and stress states. This paper focuses on the development of strength in biocemented soils (via microbial induced calcite precipitation, MICP) and its evolution with cementation level under loading. The proposed strength correlation accounts for the observed nonlinearity of failure envelopes in sands and describes the strength of cemented sands as a function of density, confinement, mineralogy, and cementation.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
2017
1. Nweke, Chukwuebuka C.; Pestana, Juan M.: Modeling Bio-Cemented Sands: Shear Strength and Stiffness with Degradation. Grouting 2017, 2017. (Type: Conference | Abstract | Links | BibTeX) @conference{doi:10.1061/9780784480793.004,
title = {Modeling Bio-Cemented Sands: Shear Strength and Stiffness with Degradation},
author = {Chukwuebuka C. Nweke and Juan M. Pestana},
url = {https://ascelibrary.org/doi/abs/10.1061/9780784480793.004},
doi = {10.1061/9780784480793.004},
year = {2017},
date = {2017-06-17},
booktitle = {Grouting 2017},
pages = {34-45},
abstract = {Over the past decade, recent developments between the geotechnical and life science disciplines have establish microbial induced calcite precipitation (MICP) as a novel ground improvement method. This method improves the static and dynamic mechanical properties of the soil while maintaining its environmentally friendly characteristics. Its application process lends itself to increased compatibility with varying infrastructure where other methods pose issues due to constraints. Currently, there are no established methods to properly assess the level of improvement, or adequately predict the expected performance for a given level of cementation. It is envisioned that numerical simulations will hold the key. With this in mind, a model was developed that incorporates the key aspects of the improved biomaterial for the purpose of comparing the lightly cemented and the original uncemented soils to illustrate the potential of the MICP method. Specifically, the model incorporates the ability to capture the behavior and transition from the cemented state to the uncemented state while maintaining adherence to the controlling factors of void ratio and confining stress. This paper focuses on the changes of shear stiffness and shear strength as a result of the degradation of the calcite (CaCO3) cementation in the MICP soils.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
Technical Reports
2024
6. O'Donnell, Timothy M; Hudson, Kenneth S; Stewart, Francisco-Javier G Ornelas Jonathan P; Brandenberg, Scott J; Nweke, Chukwuebuka C; Zimmaro, Paolo: Site Characterization and Liquefaction Analysis at Searles Lake, Ca following 2019 Ridgecrest Earthquake Sequence. The B. John Garrick Institute for the Risk Sciences no. GIRS-2024-03, 2024. (Type: Technical Report | Abstract | Links | BibTeX) @techreport{doi:10.34948/N3F302,
title = {Site Characterization and Liquefaction Analysis at Searles Lake, Ca following 2019 Ridgecrest Earthquake Sequence},
author = {Timothy M O'Donnell and Kenneth S Hudson and Francisco-Javier G Ornelas Jonathan P Stewart and Scott J Brandenberg and Chukwuebuka C Nweke and Paolo Zimmaro},
url = {https://doi.org/10.34948/N3F302},
doi = {10.34948/N3F302},
year = {2024},
date = {2024-04-01},
number = {GIRS-2024-03},
institution = {The B. John Garrick Institute for the Risk Sciences},
abstract = {Following and during the 2019 Ridgecrest Earthquake Sequence (July 4 M6.5 event and July 5 M7.1 event), the Geotechnical Extreme Events Reconnaissance (GEER) Association conducted reconnaissance in areas with extensive surface manifestation of liquefaction at Searles Lake, near Trona and Argus, CA (GEER 2019, Zimmaro et al. 2020). Searles Lake is an ancient endorheic lakebed currently used as a mineral mine by Searles Valley Minerals (SVM). The reconnaissance documented broad regions that had experienced surface manifestation of liquefaction and other regions with no ground failure. As such, this site was considered an ideal case history for investigations of the factors leading to surface manifestation of liquefaction or the lack thereof.},
keywords = {},
pubstate = {published},
tppubtype = {techreport}
}
5. Asimaki, Domniki; Mason, Henry B; Athanasopoulos-Zekkos, Adda; Carey, Trevor J; Garcia, Fernando E; Gray, Brian; Lavrentiadis, Grigorios; (USC), Chukwuebuka C Nweke; Chou, Chung-Che; Wu, Chiun-Lin; Lee, Zheng-Kuan; Chang, Wei-Kuang; Chen, Kuan-Yu; Lin, Shih-Jung; Lin, Chi-Hao; Lin, Che-Min; Wang, Kuo-lung; Lin, Jun-tin; Lee, Yi-hsuan: Geotechnical Engineering Reconnaissance Of The 2022 Chihshang Earthquake Sequence. Geotechnical Extreme Event Reconnaissance Association no. GEER-083, 2024. (Type: Technical Report | Abstract | Links | BibTeX) @techreport{doi:10.18118/G65M23,
title = {Geotechnical Engineering Reconnaissance Of The 2022 Chihshang Earthquake Sequence},
author = {Domniki Asimaki and Henry B Mason and Adda Athanasopoulos-Zekkos and Trevor J Carey and Fernando E Garcia and Brian Gray and Grigorios Lavrentiadis and Chukwuebuka C Nweke (USC) and Chung-Che Chou and Chiun-Lin Wu and Zheng-Kuan Lee and Wei-Kuang Chang and Kuan-Yu Chen and Shih-Jung Lin and Chi-Hao Lin and Che-Min Lin and Kuo-lung Wang and Jun-tin Lin and Yi-hsuan Lee},
url = {https://doi.org/10.18118/G65M23},
doi = {10.18118/G65M23},
year = {2024},
date = {2024-03-25},
number = {GEER-083},
institution = {Geotechnical Extreme Event Reconnaissance Association},
abstract = {The Chishang events nucleated on the high-angle, west-dipping Central Range Fault (CRF), which is blind in the south, and was not in the official active faults map issued by the Taiwan Geological Survey. The Mw6.9 Chihshang mainshock occurred on 9/18/2022 at 14:44:15.2 (Taiwan Standard Time: GMT+08:00). The event was preceded by a foreshock of Mw6.5 on 9/17/2022 at 21:41:19.1. The U.S. GEER team, arrived in Taipei on 15 and 16 October 2022 and traveled to the affected region on 17 October; it included eight U.S.-based members, and was hosted and accompanied by a team of geologists, geotechnical engineers, and researchers from Taiwan’s National Center for Research on Earthquake Engineering (NRCEE).},
keywords = {},
pubstate = {published},
tppubtype = {techreport}
}
2023
4. Stewart, Jonathan P.; Mohammed, Shako; Nweke, Chukwuebuka C.; Shams, Rashid; Buckreis, Tristan E; Kohler, Monica D.; Bozorgnia, Yousef: Usability of Ground Motions Recorded by Community Seismic Network. The B. John Garrick Institute for the Risk Sciences no. GIRS-2023-08, 2023. (Type: Technical Report | Links | BibTeX) @techreport{doi:10.34948/N36K5M,
title = {Usability of Ground Motions Recorded by Community Seismic Network},
author = {Jonathan P. Stewart and Shako Mohammed and Chukwuebuka C. Nweke and Rashid Shams and Tristan E Buckreis and Monica D. Kohler and Yousef Bozorgnia},
url = {https://doi.org/10.34948/N36K5M},
doi = {10.34948/N36K5M},
year = {2023},
date = {2023-10-13},
number = {GIRS-2023-08},
institution = {The B. John Garrick Institute for the Risk Sciences},
keywords = {},
pubstate = {published},
tppubtype = {techreport}
}
2022
3. Burton, Henry V; Dwima, Samuel; Gho, Danny; Guan, Xingquan; Gunay, Selim; Gupta, Abhineet; Zeyad, Khalil; Kusumayani, Novia; Marinkovic, Marko; Merino, Yvonne; Nweke, Chukwuebuka C.; Safiey, Amir; Mosalam, Khalid: StEER 2022 Mw 5.6 Indonesia Earthquake Preliminary Virtual Reconnaissance Report (PVRR). StEER DesignSafe-CI no. StEER 2022-12, 2022. (Type: Technical Report | Links | BibTeX) @techreport{doi:10.17603/ds2-e2vq-nq61,
title = {StEER 2022 Mw 5.6 Indonesia Earthquake Preliminary Virtual Reconnaissance Report (PVRR)},
author = {Henry V Burton and Samuel Dwima and Danny Gho and Xingquan Guan and Selim Gunay and Abhineet Gupta and Khalil Zeyad and Novia Kusumayani and Marko Marinkovic and Yvonne Merino and Chukwuebuka C. Nweke and Amir Safiey and Khalid Mosalam},
url = {https://www.designsafe-ci.org/data/browser/public/designsafe.storage.published/PRJ-3781/#details-3617915731608670701-242ac118-0001-012},
doi = {10.17603/ds2-e2vq-nq61},
year = {2022},
date = {2022-12-14},
number = {StEER 2022-12},
institution = {StEER DesignSafe-CI},
keywords = {},
pubstate = {published},
tppubtype = {techreport}
}
2020
2. Nweke, Chukwuebuka C.; Stewart, Jonathan P.; Brandenberg, Scott J: Site Response of Southern California Sedimentary Basins and Other Geomorphic Provinces. The B. John Garrick Institute for the Risk Sciences, Natural Hazards Risk and Resiliency Research Center, UCLA no. GIRS 2020-12, 2020. (Type: Technical Report | Links | BibTeX) @techreport{doi:10.34948/N3159F,
title = {Site Response of Southern California Sedimentary Basins and Other Geomorphic Provinces},
author = {Chukwuebuka C. Nweke and Jonathan P. Stewart and Scott J Brandenberg},
url = {https://static1.squarespace.com/static/54628adae4b0f587f5d3e03f/t/5f96d94e4185c82c6f754f65/1603721600075/Basin+Amplification+Report+-+USGS+ver03.pdf},
doi = {10.34948/N3159F},
year = {2020},
date = {2020-10-24},
urldate = {2020-10-24},
number = {GIRS 2020-12},
institution = {The B. John Garrick Institute for the Risk Sciences, Natural Hazards Risk and Resiliency Research Center, UCLA},
keywords = {},
pubstate = {published},
tppubtype = {techreport}
}
2019
1. Stewart, Jonathan P.; Brandenberg, Scott J.; Wang, Pengfei; Nweke, Chukwuebuka C.; Hudson, Kenneth; Mazzoni, Silvia; Bozorgnia, Yousef; Goulet, Christine A.; Hudnut, Kenneth W.; Davis, Craig A.; Ahdi, Sean K.; Zareian, Farzin; Fayaz, Jawad; Koehler, Richard D.; Chupik, Colin; Pierce, Ian; Williams, Alana; Akciz, Sinan; Hudson, Martin B.; Kishida, Tadahiro; Brooks, Ben; Gold, Ryan; Ponti, Dan; Scharer, Katherine; McPhillips, Devin; DuRoss, Chris; Ericksen, Todd; Hernandez, Janis; Patton, Jay; Olson, Brian; Dawson, Tim; Treiman, Jerome; Blake, Kelly; Buchhuber, Jeffrey; Madugo, Chris; Sun, Joseph; Donnellan, Andrea; Lyzenga, Greg; Conway, Erik: Preliminary report on engineering and geological effects of the July 2019 Ridgecrest earthquake sequence. Geotechnical Extreme Event Reconnaissance Association no. GEER-064, 2019. (Type: Technical Report | Links | BibTeX) @techreport{doi:10.18118/G6H66K,
title = {Preliminary report on engineering and geological effects of the July 2019 Ridgecrest earthquake sequence},
author = {Jonathan P. Stewart and Scott J. Brandenberg and Pengfei Wang and Chukwuebuka C. Nweke and Kenneth Hudson and Silvia Mazzoni and Yousef Bozorgnia and Christine A. Goulet and Kenneth W. Hudnut and Craig A. Davis and Sean K. Ahdi and Farzin Zareian and Jawad Fayaz and Richard D. Koehler and Colin Chupik and Ian Pierce and Alana Williams and Sinan Akciz and Martin B. Hudson and Tadahiro Kishida and Ben Brooks and Ryan Gold and Dan Ponti and Katherine Scharer and Devin McPhillips and Chris DuRoss and Todd Ericksen and Janis Hernandez and Jay Patton and Brian Olson and Tim Dawson and Jerome Treiman and Kelly Blake and Jeffrey Buchhuber and Chris Madugo and Joseph Sun and Andrea Donnellan and Greg Lyzenga and Erik Conway},
url = {https://doi.org/10.18118/G6H66K},
doi = {10.18118/G6H66K},
year = {2019},
date = {2019-07-19},
urldate = {2019-07-19},
number = {GEER-064},
institution = {Geotechnical Extreme Event Reconnaissance Association},
keywords = {},
pubstate = {published},
tppubtype = {techreport}
}
Data Collection
2024
11. Shams, Shako Mohammed Rashid; Buckreis, Tristan E; Nweke, Chukwuebuka C; Kohler, Monica D; Bozorgnia, Yousef; Stewart, Jonathan P: Data Files for Community Seismic Network (CSN) Ground Motion Study. In: Designsafe-CI, vol. PRJ-4701, 2024. (Type: Book Section | Abstract | Links | BibTeX) @incollection{DesignsafeDataCSN,
title = {Data Files for Community Seismic Network (CSN) Ground Motion Study},
author = {Shako Mohammed Rashid Shams and Tristan E Buckreis and Chukwuebuka C Nweke and Monica D Kohler and Yousef Bozorgnia and Jonathan P Stewart},
url = {https://doi.org/10.17603/ds2-3e79-4e07},
doi = {10.17603/ds2-3e79-4e07},
year = {2024},
date = {2024-06-18},
booktitle = {Designsafe-CI},
volume = {PRJ-4701},
abstract = {The Community Seismic Network (CSN) is a low-cost strong-motion network deployed at much higher density than traditional seismic networks. We performed semi-automated, component-specific data processing with the aim of optimizing usable bandwidth following procedures consistent with Next Generation Attenuation (NGA) project protocols for 29 earthquakes in Southern California for all CSN and non-CSN stations that recorded each event. The present dataset includes computed intensity metrics including peak velocity (PGV) and acceleration (PGA), 5% damped spectral accelerations (PSA), effective amplitude spectra (EAS) (Kottke et al. 2021), cumulative absolute velocity (CAV), thresholded cumulative absolute velocity (CAV5), Arias intensity (IA), and times to achieve every 5th percentile of the maximum Arias intensity (used to compute significant durations); metadata related to source, path, and site conditions; intensity metrics are computed for the as-recorded components (H1, H2, and V) and for the minimum, median, and maximum combined horizontal components as defined by Boore (2010) (RotD0, RotD50, and RotD100, respectively). Note that the unprocessed time-series in their original raw format can be obtained from the CSN webpage (http://csn.caltech.edu/data) for the CSN data and the Incorporated Research Institutions for Seismology (IRIS; Trabant et al. 2012) for the non-CSN data. The processed time-series data can be obtained at https://gmdatabase.org. These data were utilized by Stewart et al. (2023) to examine the usability of ground motions recorded by the CSN.},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
10. Nweke, Chukwuebuka C; Shams, Rashid; Vyas, Piyush; KC, Sajan; Ornelas, Francisco-Javier G: Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at Baldwin Hills, 2023. In: Designsafe-CI, vol. PRJ-4615, 2024. (Type: Book Section | Abstract | Links | BibTeX) @incollection{DesignsafeDatamHVSRBaldwinHills,
title = {Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at Baldwin Hills, 2023},
author = {Chukwuebuka C Nweke and Rashid Shams and Piyush Vyas and Sajan KC and Francisco-Javier G Ornelas},
url = {https://doi.org/10.17603/ds2-sekd-j098},
doi = {10.17603/ds2-sekd-j098},
year = {2024},
date = {2024-05-14},
booktitle = {Designsafe-CI},
volume = {PRJ-4615},
abstract = {The Baldwin Hills are a large mountainous region of the Los Angeles Basin (LAB). This area experiences seismic activity due to its proximity to the Newport-Inglewood fault and other faults within the LAB. In an effort to better understand the geology and also aid in future site response model development, microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) surveys were performed specifically near vertical arrays. Collaborative research between the University of Southern California (USC) and the University of California, Los Angeles (UCLA) have performed mHVSR surveys at 4 areas within Kenneth Hahn State Park in the Baldwin Hills area. The HVSR spectra developed using this dataset may be accessed in the United States Community Shear-Wave Velocity (VS) Profile Database (PDB) (https://vspdb.org). This work was supported by the Sonny Astani Department of Civil and Environmental Engineering at the Viterbi School of Engineering, University of Southern California(USC).},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
9. Nweke, Chukwuebuka C; Shams, Rashid; Vyas, Piyush; KC, Sajan; Ornelas, Francisco-Javier G: Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at Griffith Park, 2023. In: Designsafe-CI, vol. PRJ-4615, 2024. (Type: Book Section | Abstract | Links | BibTeX) @incollection{DesignsafeDatamHVSRGriffithPark,
title = {Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at Griffith Park, 2023},
author = {Chukwuebuka C Nweke and Rashid Shams and Piyush Vyas and Sajan KC and Francisco-Javier G Ornelas},
url = {https://doi.org/10.17603/ds2-bjq5-xv26},
doi = {10.17603/ds2-bjq5-xv26},
year = {2024},
date = {2024-05-14},
booktitle = {Designsafe-CI},
volume = {PRJ-4615},
abstract = {Griffith Observatory is situated on the Santa Monica mountains within the Los Angeles area. This area experiences seismic activity due to its proximity to the Hollywood fault and Santa Monica faults within the LAB. In an effort to better understand the geology and also aid in future site response model development, microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) surveys were performed specifically near vertical arrays. Collaborative research between the University of Southern California (USC) and the University of California, Los Angeles (UCLA) have performed mHVSR surveys at 6 areas within the observatory park area. The HVSR spectra developed using this dataset may be accessed in the United States Community Shear-Wave Velocity (VS) Profile Database (PDB) (https://vspdb.org). This work was supported by the Sonny Astani Department of Civil and Environmental Engineering at the Viterbi School of Engineering, University of Southern California(USC).},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
8. Nweke, Chukwuebuka C; buckers, Tristan E; Ornelas, Francisco-Javier G: Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at Brentwood, 2022. In: Designsafe-CI, vol. PRJ-4615, 2024. (Type: Book Section | Abstract | Links | BibTeX) @incollection{DesignsafeDatamHVSRBrentwood,
title = {Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at Brentwood, 2022},
author = {Chukwuebuka C Nweke and Tristan E buckers and Francisco-Javier G Ornelas},
url = {https://doi.org/10.17603/ds2-d56j-h615},
doi = {10.17603/ds2-d56j-h615},
year = {2024},
date = {2024-05-14},
booktitle = {Designsafe-CI},
volume = {PRJ-4615},
abstract = {The Brentwood Veteran Affairs (VA) Complex is situated near the Santa Monica mountains within the West Los Angeles area. This area experiences seismic activity due to its proximity to the Santa Monica fault and other faults within the LAB. In an effort to better understand the geology and also aid in future site response model development, microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) surveys were performed specifically near vertical arrays. Collaborative research between the University of Southern California (USC) and the University of California, Los Angeles (UCLA) have performed mHVSR surveys at 10 areas within the Heroes golf course area of the VA complex. The HVSR spectra developed using this dataset may be accessed in the United States Community Shear-Wave Velocity (VS) Profile Database (PDB) (https://vspdb.org). This work was supported by the Sonny Astani Department of Civil and Environmental Engineering at the Viterbi School of Engineering, University of Southern California(USC).},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
7. Nweke, Chukwuebuka C; buckers, Tristan E; Ornelas, Francisco-Javier G: Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at Tarzana, 2022. In: Designsafe-CI, vol. PRJ-4615, 2024. (Type: Book Section | Abstract | Links | BibTeX) @incollection{DesignsafeDatamHVSRTarzana,
title = {Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at Tarzana, 2022},
author = {Chukwuebuka C Nweke and Tristan E buckers and Francisco-Javier G Ornelas},
url = {https://doi.org/10.17603/ds2-ser9-8521},
doi = {10.17603/ds2-ser9-8521},
year = {2024},
date = {2024-05-14},
booktitle = {Designsafe-CI},
volume = {PRJ-4615},
abstract = {El Caballero country club is situated in Tarzana, which is a neighborhood in the San Fernando Valley (SFV) region of Los Angeles, CA. This area experiences seismic activity due to its proximity to the many faults within the SFV. In an effort to better understand the geology and also aid in future site response model development, microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) surveys were performed specifically near vertical arrays. Collaborative research between the University of Southern California (USC) and the University of California, Los Angeles (UCLA) have performed mHVSR surveys at 15 areas near the golf course area. The HVSR spectra developed using this dataset may be accessed in the United States Community Shear-Wave Velocity (VS) Profile Database (PDB) (https://vspdb.org). This work was supported by the Sonny Astani Department of Civil and Environmental Engineering at the Viterbi School of Engineering, University of Southern California(USC).},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
2023
6. Ornelas, Francisco-Javier G; Nweke, Chukwuebuka C; O'Donnell, Timothy M; Hudson, Kenneth S; Brandenberg, Scott J; Stewart, Jonathan P: Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at Searles Lake, 2023. In: Designsafe-CI, vol. PRJ-4064, 2023. (Type: Book Section | Abstract | Links | BibTeX) @incollection{DesignsafeDatamHVSRSearlesLake,
title = {Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at Searles Lake, 2023},
author = {Francisco-Javier G Ornelas and Chukwuebuka C Nweke and Timothy M O'Donnell and Kenneth S Hudson and Scott J Brandenberg and Jonathan P Stewart},
url = {https://doi.org/10.17603/ds2-1fcj-p013},
doi = {10.17603/ds2-1fcj-p013},
year = {2023},
date = {2023-09-18},
booktitle = {Designsafe-CI},
volume = {PRJ-4064},
abstract = {The Searles Valley Basin consists of a large endorheic dry lake which contains sediments such as Borax and rock salt, which formed around the late quaternary period. This lakebed exhibited surface manifestation of liquefaction in the form of sand boils in different areas around the lake, following the Ridgecrest Earthquake sequence (RES) on July 4-5, 2019. In an effort to better understand amplification of earthquake ground motions at the site, microtremor Horizontal-to-Vertical-Spectral-Ratios(mHVSR) surveys were performed. The information that these surveys provide can give us insight on site resonances which are anticipated to be significant due to large impedance contrasts. Moreover, we can better understand the geology when multiple surveys are evaluated at different areas around the site. Collaborative research between the University of California, Los Angeles (UCLA) and University of Southern California (USC) has performed mHVSR surveys at 5 sites in the lakebed, close to the sand boils which occurred after the RES. The HVSR curves developed using this dataset may be accessed in the United States Community Shear-Wave Velocity (VS) Profile Database (PDB) (https://uclageo.com/VPDB/). This work was supported by the United States Geological Survey under contract G22AP00320.},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
5. Ornelas, Francisco-Javier G; Torre, Christopher; Nweke, Chukwuebuka C; buckers, Tristan E; Wang, Pengfei; Bradley, Branden; Brandenberg, Scott J; Stewart, Jonathan P: Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at California Downhole Vertical Array Sites, 2022. In: Designsafe-CI, vol. PRJ-4064, 2023. (Type: Book Section | Abstract | Links | BibTeX) @incollection{DesignsafeDatamHVSRCAVerticalArraysites,
title = {Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at California Downhole Vertical Array Sites, 2022},
author = {Francisco-Javier G Ornelas and Christopher Torre and Chukwuebuka C Nweke and Tristan E buckers and Pengfei Wang and Branden Bradley and Scott J Brandenberg and Jonathan P Stewart},
url = {https://doi.org/10.17603/ds2-by4m-ed67},
doi = {10.17603/ds2-by4m-ed67},
year = {2023},
date = {2023-08-20},
booktitle = {Designsafe-CI},
volume = {PRJ-4064},
abstract = {The State of California has multiple sites with vertical arrays consisting of surface and downhole sensors, which are used to investigate shallow site response under earthquake excitations. Characterization of these sites typically includes a boring log and seismic velocity profiles (Vs and Vp). We augment the site characterization using microtremor Horizontal-to-Vertical-Spectral-Ratios (mHVSR), where the ground vibrations are caused for example by wind, ocean waves, and anthropogenic sources. This information is useful to identify potential site resonances, which in some cases may be associated with impedance contrasts at depths beyond the limits of the array, and the consistency of the geology when multiple mHVSR are evaluated at different locations relative to the vertical array. Collaborative research between the University of California, Los Angeles (UCLA), University of Southern California (USC), and the University of Canterbury in New Zealand has performed mHVSR at 16 vertical array sites in California. At each site, 4 tests were performed in 4 concentric circles of increasing diameter to better understand the spatial and azimuthal variation of mHVSR for each of the 16 sites. The HVSR curves developed using this dataset may be accessed in the United States Community Shear-Wave Velocity (VS) Profile Database (PDB) (https://uclageo.com/VPDB/). This work was supported by Pacific Gas and Electric Company, Viterbi School of Engineering, University of Southern California Faculty Award, United States Geological Survey (USGS) EHP G23AP00066-00 Award 2023-0106, New Zealand Earthquake Commission(EQC) and QuakeCoRE.},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
2022
4. Nweke, Chukwuebuka C.; Stewart, Jonathan P.; Wang, Pengfei; Brandenberg, Scott; Buckreis, Tristan: Data Files for Ground Motion Studies Pertaining to Southern California Basins and Other Geomorphic Provinces. In: Designsafe-CI, vol. PRJ-3373, 2022. (Type: Book Section | Abstract | Links | BibTeX) @incollection{DesignsafeDataSoCal,
title = {Data Files for Ground Motion Studies Pertaining to Southern California Basins and Other Geomorphic Provinces},
author = {Chukwuebuka C. Nweke and Jonathan P. Stewart and Pengfei Wang and Scott Brandenberg and Tristan Buckreis},
url = {https://doi.org/10.17603/ds2-93rk-hz83},
doi = {10.17603/ds2-93rk-hz83},
year = {2022},
date = {2022-01-13},
booktitle = {Designsafe-CI},
volume = {PRJ-3373},
abstract = {This database is part of an on-going effort to compile and process recent earthquake ground motion data for seismic hazard assessment/analysis and model development. The provided database contains computed ground motion intensity measures (pseudo spectral accelerations, peak ground velocities) for processed earthquake time histories from events in Southern California. This includes records from the Next Generation Attenuation West-2 (NGA-West2) Project and data from earthquakes that have occurred since the completion of the NGA-West2 compilation (post-2010) such as, the 2019 Ridgecrest Earthquake Sequence and others. The data provide here was used to assess the site response of basins and other geomorphic provinces in southern California.},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
3. Burton, Henry V; Dwima, Samuel; Gho, Danny; Guan, Xingquan; Gunay, Selim; Gupta, Abhineet; Zeyad, Khalil; Kusumayani, Novia; Marinkovic, Marko; Merino, Yvonne; Nweke, Chukwuebuka C.; Safiey, Amir; Mosalam, Khalid: 2022 Mw 5.6 Indonesia Earthquake Media Repository. In: Designsafe-CI, vol. PRJ-3781, 2022. (Type: Book Section | Abstract | Links | BibTeX) @incollection{DesignsafeDataM5_6Indonesia,
title = {2022 Mw 5.6 Indonesia Earthquake Media Repository},
author = {Henry V Burton and Samuel Dwima and Danny Gho and Xingquan Guan and Selim Gunay and Abhineet Gupta and Khalil Zeyad and Novia Kusumayani and Marko Marinkovic and Yvonne Merino and Chukwuebuka C. Nweke and Amir Safiey and Khalid Mosalam},
url = {https://www.designsafe-ci.org/data/browser/public/designsafe.storage.published/PRJ-3781/#details-3617915731608670701-242ac118-0001-012},
doi = {10.17603/ds2-e2vq-nq61},
year = {2022},
date = {2022-12-14},
booktitle = {Designsafe-CI},
volume = {PRJ-3781},
abstract = {The first product of StEER’s Level 1 response to the M5.6 Indonesia Earthquake is this Preliminary Virtual Reconnaissance Report (PVRR), which is intended to: (1) provide details of the November 22 M 5.6 earthquake, (2) summarize the tectonic features of the event, (3) synthesize the recording ground motions and provide comparisons with design-level shaking, (4) briefly encapsulate the local building codes and construction practices and (5) provide a preliminary assessment of the damage to buildings and other infrastructure as well as the broader societal impacts. The PVRR includes both the official report as well as a supplementary media repository containing additional imagery gathered by the VAST. As the product of entirely virtual reconnaissance, the PVRR is not based upon detailed field investigations by StEER.},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
2021
2. Omoya, Morolake; Ero, Itohan; Esteghamati, Mohsen Zaker; Burton, Henry V.; Brandenberg, Scott J.; Nweke, Chukwuebuka C.: Relational Database for Post-Earthquake Damage and Recovery Assessment: 2014 South Napa Earthquake. In: Designsafe-CI, vol. PRJ-3025, 2021. (Type: Book Section | Abstract | Links | BibTeX) @incollection{DesignsafeDataNapa,
title = {Relational Database for Post-Earthquake Damage and Recovery Assessment: 2014 South Napa Earthquake},
author = {Morolake Omoya and Itohan Ero and Mohsen Zaker Esteghamati and Henry V. Burton and Scott J. Brandenberg and Chukwuebuka C. Nweke},
url = {https://doi.org/10.17603/ds2-3nvj-4127},
doi = {10.17603/ds2-3nvj-4127},
year = {2021},
date = {2021-02-01},
booktitle = {Designsafe-CI},
volume = {PRJ-3025},
abstract = {The Earthquake Recovery relational database uploaded to DesignSafe contains damage and recovery information for buildings affected by the 2014 South Napa earthquake. This project contains a Jupyter notebook (RecoveryDatabaseExampleQueries.ipynb) that runs several basic queries on the Earthquake Recovery relational database. The Jupyter notebook establishes a connection to the database and illustrates how to query information about the buildings affected by the 2014 South Napa earthquake including various properties (e.g. geometry, structural and occupancy), the type and level of damage, the recovery and census-level sociodemographics. The MySQL file (EarthquakeRecovery.sql) containing the database is attached to this project. The relational database schema (Earthquakerecoveryschema.png) and a spreadsheet showing the number of entries for each attribute (EarthquakeRecoveryAttributeEntries.xslx) are also included.},
type = {Database},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
2019
1. Nweke, Chukwuebuka; Graves, Robert; Goulet, Christine; Brandenberg, Scott; Stewart, Jonathan: Southern California Earthquake Center (SCEC) Simulation Validation for Southern California Basins using Ground Motion Recordings. In: Designsafe-CI, vol. PRJ-2620, 2019. (Type: Book Section | Abstract | Links | BibTeX) @incollection{DesignsafeDataSCECBasinSim,
title = {Southern California Earthquake Center (SCEC) Simulation Validation for Southern California Basins using Ground Motion Recordings},
author = {Chukwuebuka Nweke and Robert Graves and Christine Goulet and Scott Brandenberg and Jonathan Stewart},
url = {https://www.designsafe-ci.org/data/browser/public/designsafe.storage.published/PRJ-2620#anchor-3723106075728613866-242ac11a-0001-012},
doi = {10.17603/ds2-762f-sg15},
year = {2019},
date = {2019-06-01},
booktitle = {Designsafe-CI},
volume = {PRJ-2620},
abstract = {This objective of this project is to validate long-period ground motion site amplification associated with basin effects as provided by three-dimensional numerical simulations. Site effects are evaluated from mixed effects residuals analyses, as described for example in Stewart et al. (2017). The simulations are performed for source conditions (location and earthquake size) for which ample recordings are available. This allows site effects in basins to be evaluated in a consistent manner from recorded data and from simulations. The project team was coordinated under the Ground Motion Simulation Validation (GMSV) group within SCEC and include: Chukwuebuka Nweke (UCLA), Jonathan Stewart (UCLA), Scott Brandenberg (UCLA), Robert Graves (USGS), Christine Goulet (USC). References: Stewart, J.P., Afshari, K., Goulet, C.A., 2017. Non-ergodic site response in seismic hazard analysis, Earthquake Spectra, 33, 1385-1414.},
type = {Dataset},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}