publications
2026
- BSSAUsing a High- to Low-Frequency Spectral Ratio to Distinguish Variations in Earthquake Source PropertiesIan Vandevert, Peter M. Shearer, and Wenyuan FanBulletin of the Seismological Society of America, 2026In press
@article{vandevert2026nfi, journal = {Bulletin of the Seismological Society of America}, title = {Using a High- to Low-Frequency Spectral Ratio to Distinguish Variations in Earthquake Source Properties}, author = {Vandevert, Ian and Shearer, Peter M. and Fan, Wenyuan}, year = {2026}, note = {In press}, }
2025
- BSSAOverview of the SCEC/USGS Community Stress Drop Validation Study using the 2019 Ridgecrest earthquake sequenceRachel E. Abercrombie, Annemarie Baltay, Shanna Chu, and 41 more authorsBulletin of the Seismological Society of America, May 2025
We present initial findings from the ongoing Community Stress Drop Validation Study to compare spectral stress-drop estimates for earthquakes in the 2019 Ridgecrest, California, sequence. This study uses a unified dataset to independently estimate earthquake source parameters through various methods. Stress drop, which denotes the change in average shear stress along a fault during earthquake rupture, is a critical parameter in earthquake science, impacting ground motion, rupture simulation, and source physics. Spectral stress drop is commonly derived by fitting the amplitude-spectrum shape, but estimates can vary substantially across studies for individual earthquakes. Sponsored jointly by the U.S. Geological Survey and the Statewide (previously, Southern) California Earthquake Center our community study aims to elucidate sources of variability and uncertainty in earthquake spectral stress-drop estimates through quantitative comparison of submitted results from independent analyses. The dataset includes nearly 13,000 earthquakes ranging from M 1 to 7 during a two-week period of the 2019 Ridgecrest sequence, recorded within a 1^∘ radius. In this article, we report on 56 unique submissions received from 20 different groups, detailing spectral corner frequencies (or source durations), moment magnitudes, and estimated spectral stress drops. Methods employed encompass spectral ratio analysis, spectral decomposition and inversion, finite-fault modeling, ground-motion-based approaches, and combined methods. Initial analysis reveals significant scatter across submitted spectral stress drops spanning over six orders of magnitude. However, we can identify between-method trends and offsets within the data to mitigate this variability. Averaging submissions for a prioritized subset of 56 events shows reduced variability of spectral stress drop, indicating overall consistency in recovered spectral stress-drop values.
@article{abercrombie2025community, title = {Overview of the {{SCEC}}/{{USGS Community Stress Drop Validation Study}} using the 2019 {{Ridgecrest}} earthquake sequence}, author = {Abercrombie, Rachel E. and Baltay, Annemarie and Chu, Shanna and Taira, Taka'aki and Bindi, Dino and Boyd, Oliver S. and Chen, Xiaowei and Cochran, Elizabeth S. and Devin, Emma and Dreger, Douglas and Ellsworth, William and Fan, Wenyuan and Harrington, Rebecca M. and Huang, Yihe and Kemna, Kilian B. and Liu, Meichen and Oth, Adrien and Parker, Grace A. and Pennington, Colin and Picozzi, Matteo and Ruhl, Christine J. and Shearer, Peter and Spallarossa, Daniele and Trugman, Daniel and Vandevert, Ian and Wu, Qimin and Yoon, Clara and Yu, Ellen and Beroza, Gregory C. and Eulenfeld, Tom and Knudson, Trey and Mayeda, Kevin and Morasca, Paola and Neely, James S. and Roman-Nieves, Jorge and Satriano, Claudio and Supino, Mariano and Walter, William R. and Archuleta, Ralph and Atkinson, Gail Marie and Calderoni, Giovanna and Ji, Chen and Yang, Hongfeng and Zhang, Jiewen}, year = {2025}, month = may, journal = {Bulletin of the Seismological Society of America}, volume = {115}, number = {3}, pages = {734--759}, issn = {0037-1106}, doi = {10.1785/0120240158}, urldate = {2025-07-02}, }
2024
- BSSAEarthquake Source Spectra Estimates Vary Widely for Two Ridgecrest Aftershocks Because of Differences in Attenuation CorrectionsPeter M. Shearer, Ian Vandevert, Wenyuan Fan, and 7 more authorsBulletin of the Seismological Society of America, 2024
@article{shearer2024attenuation, title = {Earthquake {{Source Spectra Estimates Vary Widely}} for {{Two Ridgecrest Aftershocks Because}} of {{Differences}} in {{Attenuation Corrections}}}, author = {Shearer, Peter M. and Vandevert, Ian and Fan, Wenyuan and Abercrombie, R. and Bindi, Dino and Calderoni, Giovanna and Chen, Xiaowei and Ellsworth, William and Harrington, Rebecca and Huang, Yihe}, year = {2024}, urldate = {2024-12-18}, journal = {Bulletin of the Seismological Society of America}, doi = {10.1785/0120240134}, } - BSSARidgecrest Aftershock Stress Drops from P- and S-Wave Spectral DecompositionIan C. Vandevert, Peter M. Shearer, and Wenyuan FanBulletin of the Seismological Society of America, Nov 2024
Seismic moment and stress drop are crucial for understanding earthquake rupture processes, but their estimates often have large uncertainties for small earthquakes. Stress drop is typically inferred from an earthquake’s source spectrum based on theoretical models, but poorly constrained path corrections and other modeling assumptions limit the accuracy of stress-drop estimates. Here, we compute stress drops using both P and S waves for the 2019 Ridgecrest earthquake sequence, compare their estimates, and evaluate the associated uncertainties. We use spectral decomposition and apply the analysis to both types of waves for the same set of earthquakes, adjusting some S-wave parameter choices to obtain overall consistency with our P-wave results. Our approach fixes the corner frequency of small calibration earthquakes to reduce scatter in the estimated source parameters of the larger earthquakes. We find that assuming a lower high-frequency fall-off rate for S waves yields more consistent absolute stress-drop estimates between P and S waves. Our stress-drop estimates appear to increase slightly with magnitude for earthquakes with magnitudes >∼3.4. Furthermore, we find that the stress-drop estimates using both types of data exhibit coherent spatial variations. Earthquakes near the Coso geothermal field tend to have lower stress drops, and earthquakes near the M 7.1 hypocenter have higher stress-drop estimates. This spatial pattern is consistently observed in both the P- and S-wave results. We find no strong correlation between our stress-drop estimates and the M 7.1 Ridgecrest earthquake slip distribution, suggesting a heterogeneous stress environment for the Ridgecrest fault system.
@article{vandevert2024ridgecrest, title = {Ridgecrest {{Aftershock Stress Drops}} from {{P}}- and {{S}}-{{Wave Spectral Decomposition}}}, author = {Vandevert, Ian C. and Shearer, Peter M. and Fan, Wenyuan}, year = {2024}, month = nov, journal = {Bulletin of the Seismological Society of America}, issn = {0037-1106}, doi = {10.1785/0120240133}, urldate = {2024-11-27}, copyright = {All rights reserved}, file = {/Users/ivandevert/Zotero/storage/VRQG4LJE/Vandevert et al. - 2024 - Ridgecrest Aftershock Stress Drops from P‐ and S‐W.pdf;/Users/ivandevert/Zotero/storage/C7KAABIE/Ridgecrest-Aftershock-Stress-Drops-from-P-and-S.html} }