Rupture Behavior of the Litang Fault within the Sichuan-Yunnan Active Block, Southeastern Tibetan Plateau

Abstract

AbstractIn mainland China, approximately 86% of M≥7 earthquakes have occurred in the block boundary zone, which has been well explained by active block theory. However, a few large earthquakes have occurred within the active block, which provides us with an opportunity to better study the deformation of the Tibetan Plateau. The Litang Fault (LTF) is a strike-slip fault within the Sichuan-Yunnan Active Block and produced the 1948 Litang M7.3 earthquake. We presented the Holocene rupture behavior of the LTF based on detailed field investigations, paleoearthquake trenching, and radiocarbon dating. Specifically, we revealed 13 Holocene paleoearthquake events at four trenching sites and divided these events into 3 rupture cycles at the whole-fault scale. The seismic rupture behavior of the LTF is characterized by recurrent southeastward migration, and since the Holocene, the period of each rupture cycle has decreased rapidly from 8000 years to 500 years. Our results may provide geologic evidence for understanding the intrablock stress patterns and material transfer of the southeastern region of the Tibetan Plateau. The rapidly enhanced fault activity of the LTF since the late Holocene indicates that the LTF may have played an important role in accommodating the deformation of the southeastern region of the Tibetan Plateau.