Laboratory earthquakes along faults with a low velocity zone: Directionality and pulse-like ruptures
Low velocity zone (LVZ) is a common structural feature in geological faults. To examine the effect of LVZ on faulting, a laboratory fault model considering the LVZ is constructed and loaded to different levels. Subsequently ruptures are triggered on one of its contact boundaries with the host rock. The bilateral rupture propagation along this laboratory fault that separates different materials shows distinct directionality in both rupture speeds and rupture modes. The rupture in the positive direction with respect to the fault is always crack-like growing at the Generalized Rayleigh (GR) wave speed. However, in the negative direction both stable and unstable slip pulses are observed. Higher load and thinner LVZ facilitate the unstable slip pulses. The trailing tip for both types of pulses propagates at the GR wave speed, the leading tip of the stable pulse propagates with the GR wave speed while that of the unstable pulse features a supershear speed.
© 2021 Elsevier Ltd. Received 7 February 2021, Revised 3 April 2021, Accepted 6 April 2021, Available online 19 April 2021. This study was supported by the National Key R&D Program of China [#2018YFC1503302], and the Natural Science Foundation of Tianjin [#19JCZDJC40400]. K.X. was partially supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) through the Discovery Grant [#72031326]. Data availability: All data is available in the main text. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.