郯庐断裂带南段及邻区地震b值的空间分布特征

Spatial distribution characteristic of b-value in Dabie-Sulu and its adjacent areas

摘要:

郯庐断裂带是位于中国东部地区的一条主干断裂带，切穿了中国东部不同大地构造单元，控制着东部地区的构造活动。本文收集中国地震台网中心1970～2010年的地震目录，将研究区划分成1°×1°的网格，分别求出每个网格的b值，最后得出研究区b值的空间分布特征。研究结果发现:郯庐断裂带及周边地区为低b 值区，由于郯庐断裂附近的小震活动性比较弱，因此低b值可能反映了研究区内大震周期长的特征;断裂带两侧的苏鲁和大别造山带的b值分布特征与高压超高压变质带相似;华北中央造山带地区为高b值区，地震大多沿断裂带分布，地震频度高。通过结合已有地质和地球物理研究，发现b值的分布与岩性或介质物性参数的分布有一定的对应关系，说明研究区内的b 值分布(即地震活动特征)与该地区地壳介质不均匀性密切相关。

Abstract:

The Tanlu ( Tangcheng-Lujiang) fault is one of the major faults in eastern China， which cuts across different blocks and controls the tectonic activity． Using the seismic data from China Earthquake Networks Center，we investigated the spatial variations of b-value in the Dabie- Sulu organic belt by calculating b-value of each grid ( 1° × 1°) from 1970 to 2010． The study shows that: the b-value is smaller in the Tanlu fault and its adjacent area，which might suggest that the major earthquake recurrence period is relatively long due to the less frequency small earthquake activity; in the both sides of Tanlu fault，b-value is higher at the edge of Sulu block and eastern part of Dabie orogenic belt; the b-value is higher in North China Central orogenic belt，and small earthquake activity which occurred along Central Orogenic Belt is frequent． Additionally，combined with geological and geophysical study，we find out that the b-value shows directly the relationship with the lithologic distribution，which informs us that seismic activity features closely linked the inhomogeneous media in the crust．