@article{gann-phillips_cabas_ji_cramer_kaklamanos_boyd_2024, title={Regional seismic velocity model for the US Atlantic and Gulf Coastal Plains based on measured shear wave velocity, sediment thickness, and surface geology}, volume={40}, ISSN={["1944-8201"]}, DOI={10.1177/87552930231222960}, abstractNote={The Atlantic and Gulf Coastal Plains (CPs) are characterized by widespread accumulations of low-velocity sediments and sedimentary rock that overlay high-velocity bedrock. Geology and sediment thickness greatly influence seismic wave propagation, but current regional ground motion amplification and seismic hazard models include limited characterization of these site conditions. In this study, a new regional seismic velocity model for the CPs is created by integrating shear wave velocity (V S ) measurements, surface geology, and a sediment thickness model recently developed for the CPs. A reference rock V S of 3000 m/s has been assumed at the bottom of the sedimentary columns, which corresponds to the base of Cretaceous and Mesozoic sediments underlying the Atlantic CP and the Gulf CP, respectively. Measured V S profiles located throughout the CPs are sorted into five geologic groups of varying age, and median V S profiles are developed for each group by combining measured V S values within layer thicknesses defined by an assumed layering ratio. Statistical analyses are also conducted to test the appropriateness of the selected groups. A power law model with geology-informed coefficients is used to extend the median velocity models beyond the depths where measured data were available. The median V S profiles provide reasonable agreement with other generic models applicable for the region, but they also incorporate new information that enables more advanced characterizations of site response at regional scales and their effective incorporation into seismic hazard models and building codes. The proposed median velocity profiles can be assigned within a grid-based model of the CPs according to the spatial distribution of geologic units at the surface.}, number={2}, journal={EARTHQUAKE SPECTRA}, author={Gann-Phillips, Cassie and Cabas, Ashly and Ji, Chunyang and Cramer, Chris and Kaklamanos, James and Boyd, Oliver}, year={2024}, month={May}, pages={1269–1300} }
 @article{ji_cabas_kottke_pilz_macedo_liu_2023, title={A DesignSafe earthquake ground motion database for California and surrounding regions}, volume={39}, ISSN={["1944-8201"]}, DOI={10.1177/87552930221141108}, abstractNote={This article presents a ground motion database for California and its close surroundings (i.e. areas near the border in Nevada, Oregon, and Arizona) from earthquakes between 1999 and 2021. This data set includes events with magnitudes larger than 3.2 and focal depths less than 40 km, and it is available on DesignSafe. Ground motion records and events included in this data set are collected from 65 different seismic networks and processed with an automated software tool called gmprocess, which was developed by the United States Geological Survey (USGS). Path measures such as rupture distance and epicentral distance are computed, 5%-damped spectral accelerations, duration metrics, and other ground motion intensity measures (IMs) are provided for records that pass the quality assurance check performed by the gmprocess toolkit. The quality of processed ground motions is also screened by using outlier detection algorithms and a multiple wave-train arrivals identification algorithm. In addition, site metadata are provided, including wave velocity information (from proxy-based time-averaged shear-wave velocity for the top 30 m, Vs30, and from P- and S-wave measured velocity profiles when available), predominant frequency measured from microtremor-based horizontal-to-vertical ratios (mHVSR), and site-specific (high-frequency spectral decay) [Formula: see text] values computed from multiple ground motions recorded at sites when available. The final database contains 287,804 three-component ground motions recorded at 3709 stations from 2641 earthquakes with magnitudes and distances ranging from 3.2 to 7.2 and 0.15 to 335 km, respectively. This ground motion database contributes to advancing both engineering seismology studies and earthquake engineering applications in shallow crustal tectonic settings.}, number={1}, journal={EARTHQUAKE SPECTRA}, author={Ji, Chunyang and Cabas, Ashly and Kottke, Albert and Pilz, Marco and Macedo, Jorge and Liu, Chenying}, year={2023}, month={Feb}, pages={702–721} }
 @article{cabas_rodriguez-marek_green_ji_2022, title={Quantifying the Error Associated with the Elastic Halfspace Assumption in Site Response Analysis}, volume={148}, ISSN={["1943-5606"]}, DOI={10.1061/(ASCE)GT.1943-5606.0002893}, abstractNote={One of the fundamental decisions when performing one-dimensional (1D) site response analyses (SRA) involves the selection of the depth and dynamic properties of the elastic halfspace (EHS). This boundary condition assumes linear and homogenous material underlying the soil column for an infinite depth. This assumption implies that waves refracted into the EHS are fully absorbed, and as a result, energy from waves that are potentially reflected back toward the surface from deeper impedance contrasts in the actual geologic profile are not accounted for in the SRA. If a strong soil-rock seismic impedance contrast is present at the site of interest, the EHS boundary is typically set at that depth. However, the actual geologic profile below this impedance contrast may not be in accord with the assumed properties of the EHS, which can lead to systematic errors in the SRA. An analytical expression to quantify these errors is derived in this study, verified using an idealized three-layer profile, and compared to case studies of nine real sites in Charleston, South Carolina. Our results show that the presence of a single strong impedance contrast does not suffice as the sole condition to define the EHS boundary. Frequency-dependent errors in site amplification associated with the assumptions inherent to the EHS used in the SRA can be evaluated as a function of multiple impedance contrasts present in the profile. Smaller errors are associated with strong impedance contrasts at shallower layers and/or minimal impedance contrast among layer interfaces at depth. We also find that strong impedance contrasts located at great depths within deep soil deposits introduce nonnegligible errors to site response results.}, number={10}, journal={JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING}, author={Cabas, Ashly and Rodriguez-Marek, Adrian and Green, Russell A. and Ji, Chunyang}, year={2022}, month={Oct} }
 @article{ji_cabas_bonilla_gelis_2021, title={Effects of Nonlinear Soil Behavior on Kappa (kappa): Observations from the KiK-Net Database}, volume={111}, ISSN={["1943-3573"]}, DOI={10.1785/0120200286}, abstractNote={ABSTRACT}, number={4}, journal={BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA}, author={Ji, Chunyang and Cabas, Ashly and Bonilla, Luis Fabian and Gelis, Celine}, year={2021}, month={Aug}, pages={2138–2157} }
 @article{ji_cabas mijares_cotton_pilz_bindi_2020, title={Within station variability in kappa: evidence of directionality effects}, volume={110}, ISSN={["1943-3573"]}, DOI={10.1785/0120190253}, abstractNote={ABSTRACT}, number={3}, journal={Bulletin of the Seismological Society of America}, author={Ji, C. and Cabas Mijares, A. and Cotton, F. and Pilz, M. and Bindi, D.}, year={2020}, month={Apr}, pages={1247–1259} }