利用面波频散与接收函数联合反演青藏高原东南缘地壳上地幔速度结构

Joint inversion of surface wave dispersion and receiver functions for crustal and uppermost mantle structure in Southeast Tibetan Plateau

青藏高原东南缘对于青藏高原的隆升、增厚和物质逃逸等问题有着重要的研究价值.本文对研究区内布设的大型流动地震台阵的观测记录进行处理,联合反演面波频散与接收函数数据,获得了地壳厚度、沉积层厚度分布情况以及地壳上地幔高精度S波速度结构.联合反演的结果表明:(1)研究区域内地壳厚度变化很大,从西北往东南方向地壳厚度逐渐变薄;(2)沉积层厚度与研究区内沉积盆地的分布情况较为一致;(3)在研究区中下地壳内由北向南呈条带状分布有两条主要的壳内低速体,其中一条从川西北次级块体向南延伸,穿过丽江断裂到达滇中次级块体下方,另一条低速体沿小江断裂分布,向南延伸到24°N左右,两条低速体在中地壳范围被四川盆地及峨眉山大火成岩省内带下方的高速异常所隔开.

The Southeast Tibetan is of great scientific value to the problems about the uplift,crustal thickening and escape of the Tibetan Plateau.Through the analysis of observational data recorded by the temporary seismic stations deployed in the study area,crustal thickness,sediment thickness and a high-resolution S wave velocity model of the crustal and upper mantle have been derived.The results demonstrate：（1）Regional crustal thickness varies strongly,the crustal thickness becomes thinner gradually from northwest to southeast.（2）The sediment thickness is consistent with the distribution of sedimentary basins in the research area.（3）Thereare two main NS-trending low-velocity zones（LVZs）observed in the mid-lower crust.One of the LVZs starts from Chuanxibei sub-block and goes across the Lijiang fault into Dianzhong subblock.The other one follows the trace of the Xiaojiang fault until about 24°N.These two LVZs are separated by the high velocity anomaly under Sichuan Basin and the inner zone of Emeishan Large Igneous Province in the middle crust.