Rupture passing probabilities at fault bends and steps, with application to rupture length probabilities for earthquake early warning

Glenn P. Biasi, & Steven G. Wesnousky

Under Review March 9, 2021, SCEC Contribution #10941

Earthquake early warning (EEW) systems can quickly identify the beginning of a significant earthquake rupture, but the first seconds of seismic data have not been found to predict the final rupture length. We present two approaches for estimating probabilities of rupture length given the rupture initiation from an EEW system. In the first approach bends and steps on the fault are interpreted as physical mechanisms for rupture arrest. Arrest probability relations are developed from empirical observations and depend on bend angle and step size. Probability of arrest compounds serially with increasing rupture length as bends or steps are encountered. In the second approach, time-independent rates among ruptures from the Uniform California Earthquake Rupture Forecast v3 (UCERF3) are interpreted to apply to the time-dependent condition where rupture grows from a known starting point. Length probabilities from a Gutenberg-Richter (GR) magnitude-frequency relation provide a reference of comparison. We illustrate the new approach using the discretized fault model for California developed for UCERF3. We put forth as example a case of rupture initiating on the southeast end of the San Andreas fault to find the geometric complexity of the Mill Creek section impedes most ruptures, and only ~5% are predicted to reach to San Bernardino on the eastern edge of the greater Los Angeles region. Conditional probabilities of length can be precompiled in this manner for any initiation point on the fault system and thus are of potential value in seismic hazard and EEW applications.

Citation
Biasi, G. P., & Wesnousky, S. G. (2021). Rupture passing probabilities at fault bends and steps, with application to rupture length probabilities for earthquake early warning. Bulletin of the Seismological Society of America, (under review).