Exploring the effect of timing on the source properties of intershocks produced at asperities in a rate-and-state fault model

Junheng Li, Natalie Schaal, & Semechah K.Y. Lui

Submitted August 14, 2019, SCEC Contribution #9578, 2019 SCEC Annual Meeting Poster #173

Despite the countless observations of foreshocks before many large earthquakes, the mechanism responsible for their occurrence remains under debate. Moreover, the physical relationship between foreshocks and mainshocks remains uncertain. In this study, we explore the possible time-dependence of source properties from foreshock-like events, which occur as a result of the interaction between the protracted nucleation process of the mainshock and asperities in a rate-and-state fault model. These fault asperities (bumps) are modeled as circular patches of elevated compression, and produce smaller-scale seismic events, which we call “intershocks,” within the larger-scale seismogenic region over multiple mainshock cycles. Our goal is to explore whether the timing of these smaller-scale events within the mainshock recurrence interval, which physically relates to the status of the fault’s preparation for the upcoming mainshock, affects the source properties of these precursory events. So far, our focus has been on investigating rupture dimension. Our approach is to group intershocks into timing bins, and to compare representative source property values from late-stage bins to those from earlier bins, as the latest intershocks are the most foreshock-like. In addition to utilizing the data from long-term numerical simulations of laboratory-scale fault models with five patches from previous work [Schaal and Lapusta, JGR 2019], we are now constructing new field-scale simulations with 25 patches, in an effort to generate many more intershocks per cycle to be studied. If the advancement of the upcoming mainshock is noticeably manifested in the source properties of foreshocks, then this understanding could be a key ingredient in the potential development of a mechanics-based earthquake forecasting method.

Key Words
Microseismicity, earthquake nucleation, foreshocks, source properties, rate-and-state friction, numerical simulations, recurrence interval

Li, J., Schaal, N., & Lui, S. (2019, 08). Exploring the effect of timing on the source properties of intershocks produced at asperities in a rate-and-state fault model. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)