关键词: 速度结构, 双差定位法, 体波走时, 层析成像, 低速区

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