The Mw 6.6 Lushan earthquake (hereafter referred to as the Lushan earthquake) occurred in the early morning on 20 April 2013 (Fig. 1). The earthquake caused more than 200 casualties, injured more than ten thousand people, and caused huge economic loss. This event was the most damaging earthquake in China since the 2008 M 8.0 Wenchuan earthquake and the 2010 M 7.1 Yushu earthquake.

Figure 1.

Tectonic settings of Longmenshan fault system (after Zhang and Li, 2010; Liu et al., 2013). Red star, Lushan earthquake epicenter; black star, Wenchuan earthquake epicenter. Lower hemisphere focal mechanisms of the mainshock and two M5+ aftershocks are also shown. The box on the inset marks the study region in mainland China. F1, Wenchuan–Maowen fault; F2, Beichuan fault; F3, Pengguan fault; F4, Dayi fault.

The Lushan earthquake was widely felt as far as 500 km away, in an area of almost 1 million square kilometers. The area that suffered damage is also substantial (∼20,000 square kilometers). After five days of intensive field investigation, the intensity map was officially released based on the observed damage (http://www.cea.gov.cn/publish/dizhenj/464/478/20130425153642550719811/index.html, last accessed November 2013). The intensity map showed a northeast–southwest strike, and the maximum intensity was IX. The lengths of the long axis and short axis for the meizoseismal area are nearly 23 and 11 km, respectively, which agree well with rupture‐process inversion results (Wang et al., 2013).

The mainshock was well recorded by both local and global seismic networks, and the epicenter is located at latitude 30.3° N and longitude 103.0° E, which is about 80 km to the southwest of the epicenter of the 2008 Wenchuan earthquake. The shock occurred between the Pengguan fault (F3) and Dayi fault (F4) in the northeast‐trending Longmenshan fault system (Fig. 1). The Longmenshan fault …