Distribution of Strike-Slip Displacement in the Middle and Southern Segments of the Daliangshan Fault Zone and Its Implication for Fault Rupturing Behavior

The Daliangshan Fault Zone is an important branch fault of the Xianshuihe-Xiaojiang Fault System, which is the eastern boundary of the Sichuan-Yunnan Rhombic Block. It plays a great role in understanding the tectonic activity in the southeast margin of the Qinghai-Tibet Plateau. In this paper, three left-lateral strike-slip faults in the middle and southern segments of the Daliangshan Fault Zone, including Puxiong Fault, Butuo Fault, and Jiaojihe Fault, are taken as the research objects. And high-precision topographic data with a resolution of 0.5 m is obtained by using UAV photography combined with SfM technology. Based on these data, the fault geomorphologic markers are interpreted and 517 left-lateral displacement values are measured along the 160-km-long middle and southern segments of the Daliangshan Fault Zone. By analyzing the displacement distribution, it is concluded that the three faults in the middle and southern segments of the Daliangshan Fault Zone share a relatively similar rupturing behavior. There have been at least three surface-rupturing earthquake events in the middle and southern segments of the Daliangshan Fault Zone, which is in good agreement with the results of previous paleo-seismic trenching researches. According to the paleo-seismic trenching researches, the latest surface-rupturing earthquake event is a cascading rupture, with an average co-seismic displacement of about 3.7 m; Combined with the empirical formulas, the estimated magnitude for a complete rupture of the middle and southern segments of the Daliangshan Fault Zone ranges from Mw 7.4 to Mw 7.7.