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2010年4月14日玉树MS7.1大地震发生后,周边固定观测台网和流动台站记录到大量余震事件,由于受台站分布、速度结构研究不足以及震相拾取可靠性等因素的影响,台网常规定位结果精度较低,很难从中获得有关余震活动时空分布特征和余震活动趋势的正确认识.本文利用固定台站远震波形数据,采用接收函数H-K扫描和反演对震区附近地下速度结构进行研究,获得了震区附近下方的结构特征.同时利用玉树地震序列的震相数据,采用双差法对地震序列进行重新定位.定位结果显示,玉树地震的主震深度为13km,余震序列主要沿甘孜-玉树断裂北西西向分布,长度约100km,多数余震集中分布在5～20km的范围内.结合地下速度结构,可推断此次地震主要错断了上地壳的高速地层.在断层西段(33.3°N,96.2°E)附近,余震几乎呈现垂直向下的柱状分布,推断此处出现粉碎性破裂且破裂从地下25km处贯穿到地表.
A large number of aftershocks were recorded on the fixed observational networks and mobile stations around the Yushu MS7.1 earthquake on April 14, 2010. Due to the station distribution, insufficient research on the velocity structure and the reliability of the phase picking up, , It is difficult to get the correct understanding about the spatiotemporal distribution characteristics of aftershock activity and the trend of aftershock activity.Using the teleseismic waveform data of fixed stations and the receiver function HK scanning and inversion, The structure of underground velocity structure is obtained and the structural characteristics of the area below the earthquake area are obtained.At the same time, the seismic sequences are repositioned by the double difference method based on the seismic facies data of Yushu earthquake sequence.The positioning results show that the main shock depth of Yushu earthquake is 13 km, The aftershock sequence mainly distributes northwest and west along the Ganzi-Yushu fault, with a length of about 100km and most of the aftershocks concentrated in the range of 5 ~ 20km. Combined with the subsurface velocity structure, it can be inferred that the epicenter of the earthquake mainly breaks down the high-velocity strata in the upper crust. Near the western segment (33.3 ° N, 96.2 ° E), the aftershocks show almost vertical downward columnar distribution, suggesting a comminuted rupture here and rupture from below 25km Department runs through to the surface.