Seismic structure of the Longmenshan area in SW China inferred from receiver function analysis: Implications for future large earthquakes

摘要

Following the 2008 Mw 7.9 Wenchuan and 2013 Ms 7.0 Lushan earthquakes, the Longmenshan thrust-fault belt and the Songpan-Ganzi terrane have been the focus of several investigations. Here we use the H-k stacking technique and neighborhood algorithm to investigate the seismic structure of this area. Based on the presence of felsic lower crust and the Mesozoic crustal architecture of the Songpan-Ganzi and Longmenshan area, we exclude the model on the eastward flow of the middle and lower crust assigned as the cause for the crustal thickening in previous studies. In contrast, the E-W trending cumulative compression induced by the continued northward motion of the Indian plate and India-Asian collision are identified as the dominant factors leading to the crustal thickening in the Longmenshan thrust-fault region as well as the Songpan-Ganzi terrane. Particularly, the 2008 Mw 7.9 Wenchuan and 2013 Ms 7.0 Lushan earthquakes likely indicate the cumulative offsets and the E-W continuing compression.