Key PointsĪ heated debate about the tectonics of the Longmenshan (LMS) and the eastern margin of the Tibetan Plateau has been renewed in recent years due to its seismogenic role in the devastating 2008 Wenchuan ( M w 7.9) and 2013 Lushan ( M w 6.6) earthquakes (Figure 1 Bai et al., 2010 Clark & Royden, 2000 Hubbard & Shaw, 2009 Lei & Zhao, 2009 Li et al., 2009, 2010 Liu, Hilst, et al., 2014 Molnar & Tapponnier, 1975 Roger et al., 2010 Royden, 1996 Royden et al., 1997 Wang et al., 2011, Wang, Huang, et al., 2014, 2015 Zhang et al., 2009 Zhang, 2013 Zhao et al., 2012). Therefore, we deduce that a major earthquake on these faults is possible and that the magnitude could be larger than that of the Dayi earthquake ( M 6.2). Higher seismic activity was also observed along these faults than that above the low-velocity zone. The seismogenic environment of these faults is similar to the segments ruptured during the Wenchuan and Lushan earthquakes, both of which occurred above the westward extension of the strong Sichuan Basin. The heat transferred from the partial melting at the base of the seismic gap may increase the temperature of the faults to as high as 300–400 ☌ and cause the segment of the Longmenshan Fault in the seismic gap to become “aseismic.” In contrast, the Shuangshi-Dachuan Fault, Dayi Fault, and other blind faults to the east-southeast of the seismic gap are located above a high-velocity body. The results also show a low-velocity zone ( V s 67 km) beneath the seismic gap, which could be associated with partial melting. The results show that the upper crust of the Songpan-Ganzi terrane overthrusted onto the basement of the Sichuan Basin, indicating that the crustal shortening model may be the major mechanism that accounts for the growth of the Longmenshan. Based on a dense seismic array deployed to monitor the seismic gap between the Wenchuan and Lushan earthquakes, a joint inversion of dispersion curves and receiver functions yielded a fine velocity structure in this region with the highest resolution of approximately 20 km.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |