Abstract: Large amounts of seismic records from Zhejiang digital seismic network are collected,and by double difference seismic tomography,fine velocity structure and local heterogeneity of upper crust in Zhejiang Province and its surrounding areas are studied,and the relationship of the crustal velocity structure to the local active faults,geological and geographical structure is discussed. Research shows that there is a large-area low velocity zone developed in northern Zhejiang at depths between 3.5km and 6.5km,and also some low velocity zones distributed sporadically in southern Zhejiang,mostly around Shanxi Reservoir in Wenzhou. The research indicates that most earthquakes happened along active faults or active fault segments,and are concentrated in zones. These zones are almost all in the transitions between low to high velocity zones,and are significantly related to the regional topographic features. The correlation relation derived by this paper between earthquake,active fault,and geological and geographical structure will be of theoretical value and practical significance to the study of seismogenesis and the prediction of future strong earthquakes.

Key words: Zhejiang digital seismic network, velocity structure, double difference earthquake location, body wave travel-time tomography, low velocity zone

摘要： 收集了浙江数字地震台网大量地震记录，通过地震波双差走时层析成像，研究浙江省及周边地区上地壳精细速度结构和局部各向异性，并探讨地壳速度结构与活动断裂及地质构造的关系。结果表明，浙江北部在深度3.5～6.5km分布了较大面积的低速异常区，浙江南部珊溪水库地区零星分布低速异常区，研究区域内的地震沿着活动断层和断层活动段分布或密集成带，基本都发生在低速区内或高、低速过渡带，且与区域内的地形特征有明显的相关性。

关键词: 速度结构, 双差定位法, 体波走时, 层析成像, 低速区