Rupture processes and Coulomb stress changes of the 2017 Mw 6.5 Jiuzhaigou and 2013 Mw 6.6 Lushan earthquakes

Abstract

Since the 2008 great M w 7.9 Wenchuan earthquake, two destructive earthquakes, the 2013 M w 6.6 Lushan earthquake and the 2017 M w 6.5 Jiuzhaigou earthquake, struck the eastern margin of the Tibetan Plateau, causing many casualties and significant property damage. The rupture processes and Coulomb stress change of the Lushan and Jiuzhaigou earthquakes are investigated in this study. The general patterns of the slip models of the two events are similar, where the slip is concentrated around the hypocenter and the primary ruptured zone extends about 20 km along strike. The rupture zone of the 2017 Jiuzhaigou earthquake spans a depth range of 4-16 km with a peak slip of ~ 115 cm, whereas the rupture zone of the 2013 Lushan earthquake is concentrated at 8 to 20 km depth with a peak slip of 125 cm. The coseismic static Coulomb stress changes induced by the two events are computed with the obtained slip models. The Tazang fault and the northern extremities of the Minjiang and Huya faults were strongly loaded by the Jiuzhaigou earthquake, whereas the Lushan earthquake mainly affected its surrounding faults. Therefore, we infer that the seismic hazard potential in these regions has probably been increased further, and the Lushan earthquake did not contribute significantly the occurrence of the Jiuzhaigou earthquake. Additionally, we also compute the stress changes imparted by the 2008 Wenchuan earthquake. The computed stress changes in both events' hypocenters exceed the trigger threshold (0.1 bar), which suggests that the Wenchuan earthquake played a pivotal role in the occurrence of these two earthquakes.

Joint Inversion of GPS, Leveling, and InSAR Data for The 2013 Lushan (China) Earthquake and Its Seismic Hazard Implications

“…We depict the stress changes on nearby active faults caused by the Wenchuan and Lushan earthquakes in Figure 10. Following the Lushan earthquake, the CFS increased on the PGF and BYF by nearly 0.1 bar and 0.2 bar, respectively, which agree well with the results of Lin et al [24]; it is possible that this stress change will result in future earthquakes. Following the Wenchuan earthquake, the CFS increased on the following faults (as shown in Figure 10a): the middle part of the XSHF, the WQF, the LRBF, the BYF and the southern segment of the PGF.…”

“…Our results demonstrate that the Wenchuan earthquake increased the CFS by up to 0.2 bar at the hypocenter of the Lushan earthquake, which exceeded the threshold value (0.1 bar) of earthquake triggering [58]. Lin et al [24] found that the Wenchuan earthquake had a significant impact on the surrounding area and verified that the Lushan earthquake was probably promoted (possibly triggered) by the 2008 Wenchuan earthquake. There were few aftershocks or smaller events about Mw 6 that occurred in this area between the 2008 Wenchuan and 2013 Lushan events.…”

“…The changes in the ∆CFS calculated from the uniform slip model and the slip distribution model show that the Coulomb stress increased in the epicentral area by more than 0.45 bar (shown in Figure 9), which is larger (by more than 0.3 bar) than the increase in the epicentral area reported by Lin et al [24] using teleseismic broadband waveforms. We depict the stress changes on nearby active faults caused by the Wenchuan and Lushan earthquakes in Figure 10.…”

“…Strain accumulation and stress change due to the mainshock have also been rigorously discussed in previous researches [21][22][23][24]. For instance, Shan et al [21] calculated the co-and post-seismic stress changes caused by the 2008 Mw 7.9 Wenchuan and 2013 Ms 7.0 Lushan earthquakes to investigate their relationship and the stress changes on the major faults in this region.…”

“…Zhang et al [18] found a Coulomb stress change of approximately 0.5 MPa that occurred on the secondary fault segments simultaneously with the initiation of coseismic slip on the main fault of the 2013 event, indicating that the slip was likely triggered by coseismic slip on the main blind thrust fault. In addition, Lin et al [24] investigated the Coulomb stress changes during the 2017 Mw 6.5 Jiuzhaigou and 2013 Mw 6.6 Lushan earthquakes and discussed their relationships to the 2008 Wenchuan earthquake.…”