Crustal structure across the Jiangnan orogen from teleseismic virtual-source reflection method

The Jiangnan orogen belt （JOB） was formed by the collision between the Yangtze block （YB） and the Cathaysia block （CB）. The crustal structure of the JOB recorded the collisional process between the two blocks. Hence, studying crust of the JOB can illuminate the process between the YB and the CB, and thus better understand the tectonic evolution of the South China Plate （SCP）. In this study, we applied the teleseismic virtual reflection method to derive the phase of the reflection waves （PPdp） of large teleseismic earthquakes recorded by two temporary seismic arrays that were deployed around the JOB and obtained the upper crust structures. The results suggest that the thickness of the upper crust sediments on two sides of the Jiangshao fault changes obviously. It is also inferred that the Jiangshao fault is the eastern boundary between the Yangtze block and the Cathaysia block. The JOB and the YB have more apparent stratigraphic continuity than that of the CB. This result agrees with a multi-stage tectonic model which suggests that the JOB first bounded the YB and then collided with the CB. Hence the characteristics of the JOB are closer to that of the YB. The stratigraphic unconformities in the northwest of the Jiangshao fault and the fault structure in the northeast Jiangxi region provides a basic profile for understanding the subducting and colliding processes between the ancient Cathaysian ocean and the YB as well.