Moment budget and seismic potential of the Xianshuihe-Xiaojiang fault system, southeastern Tibetan Plateau

Abstract

The Xianshuihe-Xiaojiang fault system (XXFS) is an important boundary fault in the model of tectonic extrusion in the southeastern Tibetan Plateau. It is also seismically active, having produced seven M ≥ 7.5 earthquakes since 1480 CE. We compiled an integrated earthquake catalog to estimate seismic moment release rates along the XXFS since 1480 CE, and compared them with moment accumulation estimated from the updated GPS data. Our results show moment deficits of ∼2.49 × 1020 Nm for the northern (the Xianshuihe fault) and ∼ 1.28 × 1020 Nm for the central (the Aninghe-Zemuhe-Daliangshan fault) parts of the XXFS, equivalent to the moment release of MW 7.5 and Mw 7.4 events, respectively. The southern part (the Xiaojiang fault), on the other hand, has a moment surplus, suggesting a relatively low seismic potential. Analysis of moment budget on segments of the fault system indicates six sections of moment deficits along the XXFS, including the Luhuo segment, the Qanning-Kangding segment, the Moxi-Anninghe segment, the section connecting the Anninghe and Zemuhe faults, the northern Zemuhe segment and the connecting section between the Zemuhe and Xiaojiang faults. Each section of moment deficits could allow an MW ∼ 6.5 event, whereas the Qianning-Kangding segment has the potential for an MW ∼ 7.4 event. The Anninghe segment, where no M ≥ 6.5 event has occurred since 1536 CE, also deserves attention.