关键词: 长白山, 火山, 速度结构, 接收函数

Abstract: The crustal and upper mantle S-wave velocity structures in Changbaishan volcanic region were obtained from surface wave tomography and teleseismic receiver function modeling.In Changbaishan region,the S-wave velocity shows a thin lithosphere,thick asthenosphere with relatively low S-wave velocity in upper mantle,which indicates the high temperature volcano system at least extends to asthenosphere. There exist distinct low velocity layers in the crust of the volcano area.Beneath WQD station near to the caldera,the low velocity layer at 8km depth is 20km thick with the lowest S-wave velocity about 2.2km/s.Beneath the EDO station located 50km north of Tianchi caldera,no obvious low velocity layer was detected in the crust.The average crustal V_P/V_S near the caldera is higher than those obtained in surrounding area.In the volcanic region,the thickness of crustal low velocity layer is greater and the lowest velocity is more obvious with the distance shorter to the caldera.It indicates the existence of the high temperature material or magma reservoir in the crust near the Tianchi caldera. The receiver functions and inversion result from different back azimuths at CBS permanent seismic station shows that the thickness of near surface low velocity layer and Moho depth change with directions. The near surface low velocity layer is obviously thicker in south direction.The Moho depth shows slightly rising in the direction of the caldera located.We consider that the special near surface velocity structure is the main cause of relatively lower prominent frequency of volcanic earthquake waveform recorded by CBS station.The slightly rising of Moho depth beneath Tianchi caldera indicates there is a material exchanging channel between magma reservoir and upper mantle.

Key words: Changbaishan, volcano, seismic velocity structure, receiver function