【摘要】 利用四川渡口及会东的两次矿山爆破的地震波走时进行反演,求得川西地区地壳及上地幔的P波速度结构模型。上地壳厚度约21公里,由中新生界沉积岩、古生界及前寒武系复理石建造和变质褶皱群组成。中地壳厚约14公里为低速层,推测为花岗岩层。下地壳厚约17公里,推测为玄武岩层。上地幔顶部P波速度仅7.8公里/秒。地壳平均厚度在龙门山及金河-箐河以东为52公里,一过断层急剧加深到60公里。证据在明地震活动性与甘孜-楚雄菱形块体上地壳向南南东方向运动有密切关系。更多还原

【Abstract】 A program of explosion seismic investigation was carried out by using twomine blasts in Dukou and Huidong, Sichuan province. By processing the dataof seismic wave arrival times the model of P-wave velocity structure of crustand mantle is obtained. The thickness of upper crust is about 21 km and itconsists of Mesozoic-Cenozoic sedimentary rocks, Palaeozoic and Precambrian flysch suite and metamorphic folded groups. The middle crust of 14 km thickis a low velocity zone suggesting granitic or equivalent composition. The lowercrust of about 17 km thick is indicated by a layer of basalt. The P-wavevelocity at the top of upper mantle is only 7.8 km/sec in this area. whichis lower than other areas of China. The average crustal thickness is changed rapidly from 52 km at the eastof the Longmenshan and Jinhe-Qinghe great fracture zones to 60 km at thewest of it. We conclude that the great fracture is through the Mohorovicicdiscontinuity. It is evident that there are strong relations between the seis-micity and the Ganzi-Chuxiong rhombic block moving south southeastward.According to the crustal model we conclude that the brittle blocks are cutby great fracture zones, which seem floating on the low velocity zone of themiddle crust. It can be driven by regional stresses and causes frequent earth-quake activities.更多还原