Inherited State of Stress as a Key Factor Controlling Slip and Slip Mode: Inference From the Study of a Slow Slip Event in the Longitudinal Valley, Taiwan. Issue 3 (29th January 2021)

• Record Type: Journal Article
• Authors: Canitano, Alexandre; Godano, Maxime; Thomas, Marion Y.
• Is Part Of: Geophysical research letters. Volume 48:Issue 3(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-01-29
• Subjects: borehole strainmeters -- earthquake repeaters -- Longitudinal Valley Fault -- slow slip event -- static triggering -- stress barrier; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL090278
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Using borehole strainmeters, we detected a 13‐day long slow slip event in 2011 with M w = 5.45 on the Longitudinal Valley Fault, Taiwan. It has been likely promoted by the significant Coulomb stress changes (∼0.5–1 MPa) imparted by a combination of coseismic and postseismic slip of the 2003 Chengkung earthquake. Using kinematic slip models, we infer that the slow event has accommodated about 15%–35% of the slip deficit accumulated from 1997 to 2011 in its source region. Further, we find that inherited state of stress may have controlled the slow event southward propagation. We also highlight a spatiotemporal correlation between the slow event and a cluster of repeating microearthquakes, suggesting a complex interplay between seismic and aseismic processes on the fault, where transient aseismic regions are adjacent to highly coupled zones. Plain Language Summary: Tectonic faults display a large range of slip behaviors, ranging from fast slip (earthquakes) to episodic or continuous aseismic slow slip. Episodic aseismic slip events (typically called 'slow slip events') are now widely observed in active regions and play an important role in stress redistribution in the Earth's crust. The Longitudinal Valley Fault is the most active fault in Taiwan, hosting large to destructive earthquakes. However, very little is known about the presence and the role of slow slip events on the fault deformation. We document a 13‐day long slow slip event with a magnitude of 5.45, which represe'nts the largest event detected on the fault to date. We demonstrate that the slow event was likely encouraged by stress accumulation due to the 2003 Chengkung earthquake. Monitoring and characterizing the sources of aseismic slip is fundamental to identify areas with high seismic hazard on the fault and to shed some light on the interactions between seismic and aseismic processes. Key Points: We document a slow slip event on the Longitudinal Valley Fault (Taiwan) with magnitude of 5.45, which represents the largest detection to date Slow slip has likely been induced by a combination of coseismic and postseismic stress changes (>0.5 MPa) from the 2003 Chengkung mainshock Inherited state of stress on the fault has likely controlled the slip distribution and slip mode