中文摘要：

使用2003年7月21日和10月20日云南省大姚县M6．2、M6．1地震震后流动数字化地震监测台网所记录的地震走时和波形资料，反演了震中区的Vp、Vs和Qp的三维结构．前人根据余震分布推测该震区存在一条北西西走向右旋走滑断裂带．三维结果表明，Vp和Qp的低值异常可以佐证该断裂带的存在；但除此断裂带，可能还存在一条北北东向断裂带，倾向西，表现为低Vp、Vs以及低Qp异常，并且异常深度达到8—10km．因此，大姚震中区可能存在两条相互交错的断层，这与整个南北带断层的交错特征非常相似．另外我们推断该北北东向断裂带在南北方向可能有较长的延伸。

英文摘要：

By inversion of travel time and waveform data recorded by a temporary seismic network installed after the 21 July 2003 M6.2 and the 20 October 2003 M6.1 Dayao earthquakes in Yunnan province, threedimensional （3-D） Vp, Vs and Qp structures of the focal area were obtained. The 3-D imaging results show obvious low-Vp and low-Qp anomalies, which corroborates the previous speculation from aftershoek distribution that a NWW right lateral fault exists in the focal area. Besides that fault, there probably also exists a NNE fault which dips westward and exhibits low-Vp, low-Vs and low-Qp features down to the depth of 8 - 10 km. According to these observations, we infer that in the Dayao focal area there are likely two faults intersecting with each other, similar to the intersecting faults ubiquitously observed in the whole North-South zone. We also suggest that the NNE fault may extend further to both north and south.