Fine crustal and uppermost mantle S-wave velocity structure beneath the Tengchong volcanic area inferred from receiver function and surface-wave dispersion: constraints on magma chamber distribution

Abstract

The Tengchong volcanic area is located in the southeastern margin of the collision zone between the Indian and Eurasian Plates. It is one of the youngest intraplate volcano groups in mainland China. Imaging the S-wave velocity structure of the crustal and uppermost mantle beneath the Tengchong volcanic area is an important means of improving our understanding of its volcanic activity and seismicity. In this study, we analyze teleseismic data from nine broadband seismic stations in the Tengchong Earthquake Monitoring Network. We then image the crustal and uppermost mantle S-wave velocity structure by joint analysis of receiver functions and surface-wave dispersion. The results reveal widely distributed low-velocity zones. We find four possible magma chambers in the upper-to-middle crust and one in the uppermost mantle. The chamber in the uppermost mantle locates in the depth range from ~ 55 to ~ 70 km. The four magma chambers in the crust occur at different depths, ranging from the depth of ~ 7 to ~ 25 km in general. They may be the heat sources for the high geothermal activity at the surface. Based on the fine crustal and uppermost mantle S-wave velocity structure, we propose a model for the distribution of the magma chambers.