At 08:02 (local and Beijing time) on 20 April 2013, an earthquake of Ms 7.0 (Mw 6.6) struck Lushan County in Sichuan Province, southwestern China (hereafter referred to as the Lushan earthquake). The Lushan earthquake resulted in casualties and severe damage to the buildings and to the economic activities of the region. The earthquake left 193 dead, up to 10,000 injured, and 25 missing. The direct economic loss hit over $1.6 billion U.S.

The Lushan earthquake is the second destructive earthquake to have occurred in the southern segment of the Longmenshan fault zone since the 12 May 2008 Ms 8.0 Wenchuan earthquake (Fig. 1). The distance between the epicenters of the Lushan earthquake and the Wenchuan earthquake is about 87 km (Fang, Wu, Wang, Lü, et al., 2013). As happened following the Wenchuan earthquake, the occurrence of the Lushan earthquake also stimulated lots of discussions on the seismic risk potential and prediction in southwest China. In particular, whether it was a large aftershock of the Wenchuan earthquake has been heatedly debated (Chen et al., 2013; Du et al., 2013; J. Liu et al., 2013; Wang et al., 2013; Jia et al., 2014).