The 2013 Lushan Ms 7.0 Earthquake: Varied Seismogenic Structure from the 2008 Wenchuan Earthquake

Abstract

On 20 April 2013, nearly 5 years after the Wenchuan M s 8.0 event of 12 May 2008, an earthquake of M s 7.0 struck the Longmenshan fault zone in Lushan county of Sichuan province, China. Because the epicenters of the two events were only 90 km apart, and the aftershock areas were separated (Fig. 1), there has been great interest in both how the seismogenic structures of the two events interrelate, and whether events of M s 7.0 or greater could recur in the southern segment of the Longmenshan fault zone. However, there are few data available on the late Quaternary activity of this section, and the degree of activity is disputed (Zhao et al. , 1990; Yang et al. , 1999; Densmore et al. , 2007; Institute of Geology, China Earthquake Administration, 2009; Zhang and Li, 2010; Chen et al. , 2013a). Since the 2008 Wenchuan earthquake, we have investigated the area repeatedly, acquiring evidence of fault activity. In particular, in the disaster area of the Lushan earthquake, we have undertaken 1:50,000 mapping, trenching, and shallow‐seismic exploration. Based on our observations, this paper discusses the seismogenic structure of the Lushan event and its relation to the 2008 Wenchuan earthquake. Figure 1. Map showing (a) the Longmenshan thrust system and (b) major faults in the disaster area of the Lushan event. (1) Yutian, Xinjiang M s 7.3 of 20 March 2008; (2) Wenchuan, Sichuan M s 8.0 of 12 May 2008; (3) Yushu, Qinghai M s 7.1 of 14 April 2010; (4) Lushan, Sihchuan M s 7.0 of 20 April 2013. Red lines indicate the surface rupture of the 2008 Wenchuan earthquake. Yellow circles show relocated aftershocks of the Lushan event, provided by L. H. Fang. WMF, Wenchuan–Maoxian fault; BYF, Beichuan–Yingxiu fault; PGF, Pengxian–Guanxian fault; RFF, Range‐Front buried fault; YWF, Yanjin–Wulong fault (southern segment of the BYF); …