瑞利波相速度和椭圆率与远震P波联合反演蒙古中南部地壳高分辨率S波速度结构

利用蒙古中南部台阵记录的连续背景噪声数据、天然地震面波数据和远震P波波形数据, 开展瑞利波相速度、椭圆率和远震P波叠加波形的联合反演, 建立了蒙古中南部地壳三维S波速度模型.结果显示, 蒙古中南部的瑞利波相速度及椭圆率、沉积基底深度、莫霍面深度、地壳S波速度在蒙古—鄂霍茨克缝合线和蒙古主构造线南北两侧分布均有明显差异, 暗示了这两条缝合线至少为地壳级别的分界.中戈壁火山和Bus-Obo火山在地壳内相互连通, 在下地壳存在大面积低速层.我们推测杭盖穹隆上地幔热物质上涌在中戈壁带地壳底部形成岩浆囊, 为这两座板内火山活动提供了岩浆来源.

Sedimentary and crustal velocity structure of central and southern Mongolia from joint inversion of Rayleigh wave phase velocity,ellipticity and teleseismic P waveform

A high-resolution 3-D shear wave velocity model of the crust beneath central and southern Mongolia was established to understand suture zone and regional tectonics. The model was derived by a joint inversion of Rayleigh wave phase velocities and ellipticities and stacked teleseismic P waveforms. The surface and body wave measurements were made, respectively, from ambient noise and teleseismic data recorded by Central and Southern Mongolia Array. There are significant differences in Rayleigh wave phase velocities, Rayleigh wave ellipticities, sediment basement depths, Moho depths, average crustal shear wave velocity between two sides of the Mongolia-Okhotsk Suture and the Main Mongolian Lineament, suggesting that these two sutures are crustal faults at least. In the Middle Gobi Belt, Middle Gobi volcano and Bus-Obo volcano are interconnected in the crust, and there is a large low-velocity layer in the lower crust, which implies the magma chamber of the two intraplate volcanoes exists there. Furtherly it is speculated that the magma chamber is related with underplating by mantle convection beneath Hangay Dome.