山东地区近期中小地震活动特征及其预报意义

CHARACTERISTICS OF RECENT MODERATE-SMALL EARTHQUAKES IN SHANDONG PROVINCE AND THIER PREDICTING SIGNIFICANCE

本文分析了山东及邻区近二十年来M_L≥3.0中小地震活动特征。结果表明,该区5、6级地震发生前,常以3、4级地震活动增强为先导,主要表现为:1.区内中小地震往往集中成带并随时间迁移,5级以上地震发生于地震条带内。这显示了局部地区构造活动和应力增强的变化;2.3级以上地震事件有序分节可数,5级以上地震位于节点附近;3.在统计单元内的4级以上地震累计频度,随时间分别呈线性均匀增长和指教加速增长及幂函数衰减三种类型。线性分布一般无较大地震发生,而指数型分布后期则大都发生较大地震。

This paper analyzed the characteristics of ML ≥ 3.0 moderate-small earthquakes in and around Shandong Province in the last 20 years. Results show that the increase of the activities of M3 and M4 earthquakes is often followed by the occurrence of M5 and M6 quakes in this, region; the main expressions are; 1. Moderate-small earthquakes in the region are usually concentrated into bands and migrate with time. Earthquakes with M≥5.0 occurred in the seismic bands. It shows variation of tectonic activitv and stress increase in the local region; 2. The ordered nodes of earthquakes with M≥3.0 can be counted, earthquakes with M≥5.0 often occurred near nodes; 3. The cumulative frequency of earthquakes with M≥4.0 in the statistic unit increases smoothly in linearity, exponent acceleration and attenuates in power function with time, respectively. Generally no greate earthquakes occurred for the situation of linear distribution, and greater earthquakes often occurred in later period of the exponent distribution. All these are probably the reflection of various physical-mechanical stages in the process of earthquake preparednees; Such a seismic phenomenon provides a new study factor for selecting the future risk regions.