摘要
通过对甘肃、宁夏和青海三省（区）２０次地震的前兆异常进行统计分析，发现该地区地震前兆存在“地震异常范围小、异常幅度小、异常时间短和地震活动周期短”的区域特征．同时还发现甘、宁、青地区的地震前兆有以下５个方面的共性特征：（１）６级以上地震前都有空区出现，且不同震级的空区随逼近发震时间先后嵌套出现，呈现了介质逐渐硬化的过程；（２）多种前兆的趋势异常各具某种优势形态；（３）形变资料在大震前的反向（或加速）变化是本地区出现频率较高的一种前兆；（４）同一区域的多种前兆在时间进程上存在内在的协调一致性；（５）强震发震日期及其短临前兆与磁暴、朔望及大气压力变化等外部因素有关．
Through statistic analysis of the precursors of 20 earthquakes in the Gansu Ningxia Qinghai region,it is found that earthquake precursors in this region have regional characteristics,i.e.anomalous area is small, anomaly amplitude is small, anomaly lasting time is short and seismicity period is short. Furthermore, it is found that the earthquake precursors in this region have following five common characteristics: (1)Seismicity gaps always appear before M≥6 earthquakes and with approaching to earthquake occurrence time, seismicity gaps of different magnitude earthquakes appear subsequently and nestedly from strong events to small ones.The sclerous process of medium of seismogenic zone gradually is emerged.(2) The tendency anomalies of various kinds of precursors have their own dominant patterns.(3) Before an impending strong earthquake the inverse(or accelerating) variation of ground deformation is often appearing precursor in the region.(4) Various precursors in an area have inherent harmonic identity in earthquake developing period.(5) Occurrence time and short term precursor of a strong earthquake is relevant to some outtide factors such as magnetic storm, moon gravity and atmosphere pressure.
出处
《西北地震学报》
CSCD
1997年第3期1-10,共10页
Northwestern Seismological Journal
关键词
地震前兆
统计分析
共性
西北地区
中国
Northwest China, Earthquake precursor, Statistical analysis, Common characteristics
