Study of China lithosphere by receiver function and surface wave tomography

岩石圈的高分辨率地震观测受到许多因素的阻碍。(1)岩石圈-软流圈边界（LAB）作为一个梯度过渡带和低速带（软流圈）的上边界，体波和广角地震反射很难探测到；(2)由于台站分布稀疏，面波研究有时分辨率较低。然而，研究表明，通过加入更高模态的面波，可以大大提高面波层析成像的分辨率（Priestley et al., 2005）。最近发展的S接收函数法似乎提供了另一种观测LAB的方法（Li et al., 2004; Kumar et al., 2005 5a,b,c）。在过去几年中，中国将永久地震台网大幅扩展到80多个宽频站。本文提出将P、S接收函数方法与多模面波层析成像相结合，研究中国岩石圈结构。面波模型可以通过两种方式改善接收函数估计：首先，它们可以直接用于联合反演，在联合反演中，它们消除了与单独的接收函数反演相关的一些模糊性；其次，它们可以为接收函数的时深转换提供合适的模型。了解整个岩石圈，而不仅仅是地壳，将大大提高我们对中国板块构造、印亚碰撞和大型板内地震的理解。

High-resolution seismic observation of the lithosphere is hampered due to a number of factors. (1) As a gradient transition zone and as an upper boundary of a low-velocity zone (asthenosphere), the lithosphere-asthenosphere boundary (LAB) is hard to be detected by body waves or wide-angle seismic reflections; (2) Surface wave studies sometimes suffer from low resolution due to sparse station distribution. It is, however, shown that the resolution of surface wave tomography can be greatly improved by including higher mode surface waves (Priestley et al., 2005). The recently developed S receiver function method appears to provide another means to observe the LAB (Li et al., 2004; Kumar et al., 2005a,b,c). In the last several years China significantly expanded the permanent seismic network to more than 80 broadband stations. We propose here to combine applications of P and S receiver function methods with multi-mode surface wave tomography to study the lithospheric structure of China. Surface wave models might be used to improve the receiver function estimates in two ways: firstly they can straightforwardly be used in a joint inversion, where they remove some of the ambiguities associated with inversions of receiver functions alone; secondly they can provide appopriate models for time-depth conversion of the receiver functions. Knowledge about the the entire lithosphere, not only the crust, will significantly improve our understanding of plate tectonics of China and the Indo-Asian collision and of large intraplate earthquakes.