A Source Physics Interpretation of Nonself-Similar Double-Corner-Frequency Source Spectral Model JA19_2S

Chen Ji, & Ralph J. Archuleta

Published January 12, 2022, SCEC Contribution #11008

We investigate the relation between the kinematic double-corner-frequency (DCF) source spectral model JA19_2S (Ji and Archuleta, 2020) and static fault geometry scaling relations proposed by Leonard (2010). We find that the non-self-similar low-corner-frequency scaling relation of JA19_2S model can be explained using the fault length scaling relation of Leonard’s model combined with an average rupture velocity ~70% of shear wave speed for earthquakes 5.3<M<6.9. Earthquakes consistent with both models have constant average static stress drop and constant average dynamic stress drop around 3 MPa, though both source parameters are model dependent. Their scaled energy e ̃ (or apparent stress) is not a constant; the decrease of e ̃ with magnitude can be fully explained by the magnitude dependence of the fault aspect ratio. The high-frequency source radiation is generally controlled by seismic moment, static stress drop and dynamic stress drop but is further modulated by the fault aspect ratio and the relative location of the hypocenter. Based on these two models, the commonly quoted average rupture velocity of 70-80% of shear wave speed implies predominantly unilateral rupture.

Citation
Ji, C., & Archuleta, R. J. (2022). A Source Physics Interpretation of Nonself-Similar Double-Corner-Frequency Source Spectral Model JA19_2S. Seismological Research Letters, 93(2A), 777-786. doi: 10.1785/0220210098.

Related Projects & Working Groups
UCSB Broadband Kinematic Rupture Simulation With A Double Corner Source Spectrum, Seismology, Ground Motion Simulation Validation