腾冲全新世火山区P波和S波速度及其比值

VELOCITIES OF P AND S WAVES AND THEIR RATIO IN TENGCHONG VOLCANO AREAS IN HOLOCENE EPOCH

9个发生于观测台网区域上地壳内的地震 ,用P波到时定位 ,从Tp～Ts -p图得出高Vp Vs值 ,显示了低速S波存在的信息。在资料有限情况下 ,假设震中距不变 ,反演震源深度 ,发震时 ,Vp和Vs ,得出Vp =5 90km s ,Vs =3 0 4km s ,Vp Vs =2 94。Vp比区域的同深度平均P波速度 6 0km s低 1 7% ,Vs比按弹性介质的S波速度 =Vp 1 732低 12 4%。这种低速结果符合富含液性物质介质的性质 ,在探测火山区内存在部分熔融岩石或岩浆囊有重要参考价值。

Location is made by arrival time of P wave of 9 shocks, which happened in the crust within the observational networks. High Vp/Vs obtained by plot of Tp-Ts-p shows information of low velocity of S wave. With the limited data, suppose the distance of epicenter keeps unchanged, inverse focal depth, origin time, Vp and Vs. Vp=5 90km/s, Vs=3 04km/s and Vp/Vs=2 94 are abtained. Vp is 1 7% lower than that of regional averaging velocity of 6 00km/s measured at same depth. Vs is 12 4% lower than regional velocity of S wave via Vp/1 732 for elastic medium. This phenomenon is consonant with property containing rich liquid substances. Partial melting rocks and magma pocket exist in the area has a significant value.