Seismic imaging of the deep structure under the Chinese volcanoes: An overview

Abstract

The rapid development of provincial seismic networks and portable seismic arrays has provided a good opportunity to image the detailed 3-D seismic structure of the upper mantle under the active volcanoes in the Chinese continent. Under the Changbaishan (Tianchi) volcano prominent low-velocity (low-V) anomalies are imaged above 400km depth, and high-velocity (high-V) anomalies are detected within the mantle transition zone, suggesting that the Changbaishan volcano is a back-arc volcano related to the dehydration of the subducted Pacific slab that is stagnant in the mantle transition zone. Seismic structures under the Tengchong volcano are similar to those under the Changbaishan volcano, whereas the subducted slab under the Tengchong volcano is the continental Indian slab. Regional and global tomographic models illustrate that obvious low-V anomalies are visible under the Hainan volcano from the crust down to the lower mantle, suggesting that the Hainan volcano is a hotspot. A recent local tomographic model shows that the Hainan plume is imaged as a southeast tilted low-V anomaly with depth in the upper mantle. A high-resolution upper-mantle tomographic model under the North China Craton shows a significantly Y-shaped low-V anomaly under the Datong volcano and Bohai Sea extending down to the lower mantle, which, for the first time, is inferred using precise teleseismic arrival times hand-picked from high-quality seismograms recorded at densely spaced stations from the Chinese provincial networks. The results indicate the possibility of a mantle plume beneath the region. These models suggest that the Changbaishan and Tengchong volcanoes share the history of deep mantle origin, whereas the Datong and Hainan volcanoes are comparable. All these results provide a better understanding of the dynamics of East Asia, and also call for future volcanic hazard mitigation.