Search for: All records

Abstract: The datasets provided here are from the paper “Lee, J., Tsai, V. C., Trugman, D. T., Hirth, G., & Chatterjee, A. (2025). Fault network geometry modulates earthquake source spectra across scales. Geophysical Research Letters, 52, e2025GL115592. https://doi.org/10.1029/2025GL115592".   They include earthquake stress-drop and fault misalignment (Rm) measurements from Southern California (Shearer et al., 2022), Japan (Oth, 2013) and Italy (Kemna et al., 2021). The SCARDEC datasets provide estimated corner frequencies, moment-rate roughness (Radiated Energy Enhancement Factor; REEF) and mean Kagan angles computed within proximity of each event (count#). For more details, please refer to the paper.   Kemna, K. B., Verdecchia, A., & Harrington, R. M. (2021). Spatio-temporal evolution of earthquake static stress drop values in the 2016–2017 central Italy seismic sequence. Journal of Geophysical Research: Solid Earth, 126, e2021JB022566. https://doi.org/10.1029/2021JB0225 Oth, A. (2013). On the characteristics of earthquake stress release variations in Japan. Earth and Planetary Science Letters, 377–378, 132–141. https://doi.org/10.1016/j.epsl.2013.06.037 Shearer, P. M., Abercrombie, R. E., & Trugman, D. T. (2022). Improved stress drop estimates for M 1.5 to 4 earthquakes in southern California from 1996 to 2019. Journal of Geophysical Research: Solid Earth, 127, e2022JB024243. https://doi.org/10.1029/2022JB024243 Vallée, M., Charléty, J., Ferreira, A. M. G., Delouis, B., & Vergoz, J. (2011). SCARDEC: A new technique for the rapid determination of seismic moment magnitude, focal mechanism and source time functions for large earthquakes using body-wave deconvolution. Geophysical Journal International, 184(1), 338–358. https://doi.org/10.1111/j.1365-246X.2010.04836.x 

Abstract Understanding the generation of damaging, high‐frequency ground motions during earthquakes is essential both for fundamental science and for effective hazard preparation. Various theories exist regarding the origin of high‐frequency ground motions, including the standard paradigm linked to slip heterogeneity on the rupture plane, and alternative perspectives associated with fault complexity. To assess these competing hypotheses, we measure ground motion amplitudes in different frequency bands for 3 ≤ M ≤ 5.8 earthquakes in Southern California and compare them to empirical ground motion models. We utilize a Bayesian inference technique called the Integrated Nested Laplace Approximation (INLA) to identify earthquake source regions that produce higher or lower ground motions than expected. Our analysis reveals a strong correlation between fault complexity measurements and the high‐frequency ground motion event terms identified by INLA. These findings suggest that earthquakes on complex faults (or fault networks) lead to stronger‐than‐expected ground motions at high frequencies. 

Abstract Earthquake source spectra provide unique insights into the earthquake rupture process. Motivated by previous research suggesting that complex fault geometries enhance high‐frequency seismic radiation, we study the influence of fault network geometry on earthquake source spectra using multiple independent observations. At regional scales, we examine correlations of stress drop measurements with surface fault trace misalignment in Southern California, Japan, and Central Italy. At a global scale, we examine correlations of moment‐rate function complexity of large earthquakes with focal mechanism variability, a proxy for local fault complexity. Despite significant scatter in the observations, we find overall consistent positive correlations. The concept that elastic interactions of discrete fault structures during the earthquake rupture process generates high‐frequency ground motions offers a coherent framework for interpreting our observations. These findings suggest that variations in fault complexity explain why some earthquakes produce stronger high‐frequency ground motions than others.