云南壳幔S波速度结构与强震的构造背景  

The S-wave velocity structure in the crust and upper mantle as well as the tectonic setting of strong earthquake beneath Yunnan region

作　　者：张晓曼[1] 胡家富[1] 胡毅力[1] 杨海燕[1] 陈佳[1] 彭恒初[1] 文丽敏[1] 

机构地区：[1]云南大学地球物理系,昆明650091

出　　处：《地球物理学报》2011年第5期1222-1232,共11页Chinese Journal of Geophysics

基　　金：国家自然科学基金(U0933602;40964001);云南省基金项目(2007D013M)资助

摘　　要：本文选取云南及周边65个台站记录到的47个地震事件,利用相匹配滤波技术分离出了基阶Rayleigh面波信号.选取与震中处于同一大圆弧上的两个台站,利用双台格林函数法获取了台间相速度频散,频散的周期范围在10～80 s之间.从2000个波形记录中提取了152个台站对之间的相速度频散,最后,利用台间的相速度频散反演得到云南地区0～200km深度范围内的S波速度结构.结果表明:云南地区地壳厚度整体上呈南北向变化趋势,从南部的30 km变化到北部的60 km.在局部地区Moho面呈现出隆起和凹陷,基本上呈"一隆两凹"的特征.另外,滇西地区大致以红河断裂为界,其两侧的岩石圈结构存在明显的差异.西侧从70 km深处开始,滇缅泰块体上的保山、畹町、沧源、思茅一带大范围内均为低速区,并且一直延伸到120 km深处.而红河断裂东侧的滇中块体,只有在康滇古隆起区存在上地幔低速区,其余大部分地区上地幔S波速度在4.4～4.6 km/s之间.The technique of phase matched filter is applied to extract the fundamental Rayleigh surface waves from 47 seismic events recorded by 65 digital seismic stations, which are deployed in Yunnan and its adjacent region. The phase velocity dispersion between two stations that are located on the same great circle with the epicenter, in the period range of 10-80 s, is computed by the inter-station Green＇s function. We extract the phase velocity dispersion within 152 pairs of stations from 2000 waveforms, and then invert it for the S-wave velocity structure in a depth of 04200 km. The result shows that the overall variation of the crust thickness beneath Yunnan has a south north trend, increasing gradually from 30 km in the south to 60 km in the north. The Moho shows uplift and depression locally, and is basically featured with one uplift and two depressions. Additionally, the lithosphere structures are significantly different across the Redriver fault in western Yunnan. Beneath the Baoshan, Wanding, Cangyuan, and Simao areas that are geologically located in the Yunnan-Myanmar-Thailand block, there are low-velocity areas from depth 70 km to 120 km on the west side of Red-river fault. In contrast, in the Central- Yunnan block that is located on the east side of the fault, the low-velocity zone in upper mantle only exists beneath the Kangdian palaeo-uplift, and the S-wave velocity in upper mantle varies between 4.4 to 4.6 km/s beneath most areas.

关 键 词：基阶Rayleigh波 相速度频散 S波速度结构 强震 孕震背景 

分 类 号：P315[天文地球—地震学]