浙江珊溪水库地震：震源参数测定及断层结构和应力状态描述

利用遗传算法，搜索符合Brune ω^2模型的拐角频率（fc）及零频幅值（Ωc）的最佳值，测定浙江珊溪水库震区88条小震（1．5≤ML≤4．6）的地震矩（M0）、震源尺度（r）及静态应力降（△σ）。地震矩M0在10^10～10^14N·m范围内，与拐角频率fc遵循Mo∝fc^-3的规律；震源尺度和地震矩、应力降之间呈现多重标度特征，地震矩大于临界值2．3×10^12N·m（相应的震源尺度特征值约160m）时，震源尺度与地震矩的关系较强；而应力降（△σ）在震源尺度大于160m后基本趋向恒定，不随震源尺度的增大而增大。浙江珊溪水库震区自2002年7月以来，经历2次大规模的震群活动。震群释放的应力降大小与该震群的规模成正比关系，大的应力降集中在发震断层中段5～6km深度的区域，其发生时间既可以在主震之前，也可以在主震之后。

Earthquakes in the Shanxi-Reservoir,Zhejiang Province: source parameters determining and description of the tectonic fault and static stress status

The seismic moment（M0）, source dimension（r）, and static stress drop （△σ） of 88 small earthquake occurred in the Shanxi-Reservoir, Zhejiang Province, were determined using genetic algorithms to searching the low-frequency flat levels（Ωc） and corner frequencies（fc） with the best-fitting Brune ω^2 model. The seismic moment varied between 10^10-10^14 N·m, versus the corner frequency followed the scaling law M0 ∝ fc^-3; Source dimension, versus the seismic moment and static stress drop, were multi-scaling characteristic, dependency of the source dimension on the seismic moment were stronger while seismic moment greater than 2.3×10^12 N·m with the source dimension（r） equals 160 m; Stress drop tend to be invariant while source dimension greater than 160 m.Since July 2002, two greater earthquake swarms occurred in the Shanxi-Reservoir. The stress drop level depends on the magnitude of earthquake swarm. The greater stress drop concentrated in 5-6 km depth on the fault plane, after or before the main-shock.