Deep Postseismic Creep Following Large Earthquakes Revealed by Repeating Aftershocks in the Southeastern Tibetan Plateau

Abstract

Large earthquake occurrence and the subsequent postseismic period are the most dramatic part of a seismic cycle that usually lasts months to years. However, the fault dynamics that account for the postseismic events are yet to be fully understood. Here, we use the repeating aftershock sequences (RASs) to investigate postseismic slips following the Mw 6.6 Lushan, Mw 6.5 Jiuzhaigou, Mw 6.1 Jinggu, and Mw 6.2 Ludian earthquakes in the southeastern Tibetan Plateau and find 135 RASs following the mainshocks. The RAS seismicity suggests that seismogenic faults began to creep in depth within a few hours after the Lushan, Jiuzhaigou, and Jinggu mainshocks. The deep creeps mainly follow a velocity-strengthening friction mode and decay with an Omori law p-value of ∼1. The results suggest that the combination of fault healing and geometry together controls deep fault behaviors. We develop two conceptual models to explain our observations. Our results provide new insights into spatiotemporal fault evolution after large earthquakes.