The 2013 Lushan Earthquake in China Tests

Following the devastating 2008 Wenchuan earthquake that ruptured the central–northern segments of the Longmenshan fault in Sichuan, China, many studies assessed its impact on other major faults in this region (e.g., Parsons et al., 2008; Toda et al., 2008). On 20 April 2013, theMw 6.6 Lushan earthquake ruptured the southern segment of the Longmenshan fault, allowing these assessments to be tested. The 2008 Wenchuan earthquake (Mw 7.9) came as a surprise, because the Longmenshan fault zone, which separates the growing Tibetan Plateau from the rigid Sichuan basin (Fig. 1), slips slowly (less than 3 mm=yr; Shen et al., 2009); with only moderate seismicity (Burchfiel et al., 2008; Wang et al., 2010). The earthquake-hazard map by the Global Seismic Hazard Assessment Program shows the entire Longmenshan fault zone as being relatively safe, as shown in E Figure S1 (available in the electronic supplement to this paper). The same cannot be said for the Mw 6.6 Lushan earthquake, which occurred in the morning of 20 April 2013, killing ∼200 people and injuring ∼12; 000. After the Wenchuan earthquake, the Longmenshan fault zone and the neighboring faults have been intensively studied in an attempt to assess earthquake hazard in this region. Are these assessments useful in forecasting the Lushan earthquake?