基于最邻近事件距离算法的华北地区地震丛集特征研究

摘要

Using the seismic data from north China since 2007,we calculate the earthquake clustering rate based on the nearest-neighbor distance algorithm.We study the characteristics of earthquake clustering of the seven seismic belts in north China,including Tanlu,Yanshan-Bohai,Hebei plain,Yinchuan-Hetao,Fenwei,Huai river,the lower reaches of the Yangtze river-Yellow sea,analyzing the characteristics of seismic activity in recent years.By analyzing the characteristics of earthquake clustering of Haicheng earthquake area,we consider that the earthquake sequence is weakening,and the occurrence of small earthquakes can be regarded as the background earthquake reflecting the regional stress state.Taking the Alxa M5.8 earthquake that happened on April 15,2015 as an example,we study the characteristics of earthquake clustering before significant moderate-strong earthquakes in north China,and find that earthquake clustering rate will appear high value firstly,followed by a low value in the main earthquake zone,then the earthquake will erupt.This corresponds to the phenomenon of seismic activity intensity-quietude course before moderate-strong earthquakes,and this phenomenon has certain significance to determine the potential seismic hazard areas in the future.%利用华北地区2007年以来的地震资料,基于最邻近事件距离算法计算地震丛集率,对郯庐、燕山-渤海、河北平原、银川-河套、汾渭、淮河、长江下游-黄海等7个地震带进行地震丛集特征研究.对海城老震区的地震丛集特征分析认为,地震序列的丛集性明显减弱,目前发生的小震可视为反映区域应力状态的背景地震.以2015-04-15内蒙古阿拉善左旗5.8级地震为例,对华北地区显著中强地震前的地震丛集特征进行研究,发现中强地震前,地震丛集率在空间区域上先出现高值,随后出现低值,继而发震,对应地震活动中强震前增强-平静的现象,这一特征对判定未来潜在地震危险区有一定的指示意义.