Geomagnetic diurnal-variation anomalies and their relation to strong earthquakes  

作　　者：DING Jian-hai(丁鉴海) LIU Jie(刘杰) YU Su-rong(余素荣) XIAO Wu-jun(肖武军) 

机构地区：[1]Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China

出　　处：《Acta Seismologica Sinica(English Edition)》2004年第z1期85-93,共9页

基　　金：National Science Technology Tackle Key Project during the Tenth Five-year Plan (2001BA601B01-05-04)

摘　　要：The diurnal-variation anomalies of the vertical-component in geomagnetic field are mainly the changes of phase and amplitude before strong earthquakes. On the basis of data recorded by the network of geomagnetic observato- ries in China for many years, the anomalous features of appearance time of the minima of diurnal variations (i.e, low-point time) of the geomagnetic vertical components and the variation of their spatial distribution (i.e, phe- nomena of low-point displacement) have been studied before over 30 strong earthquakes with MS≥6.6 such as Kunlunshan MS=8.1 earthquake on November 14, 2001; Bachu-Jashi MS=6.8 earthquake on February 24, 2003; Xiaojin MS=6.6 earthquake on September 22, 1989, etc. There are good relations between such rare phenomena of geomagnetic anomalies and the occurrence of earthquakes. It has been found that most earthquakes occur in the vicinity of the boundary line of sudden change of the low-point displacement and generally within four days before and after the 27th or 41st day counting from the day of appearance of the anomaly. In addition, the anomalies of diurnal-variation amplitude near the epicentral area have been also studied before Kunlunshan MS=8.1 earthquake and Bachu-Jiashi MS=6.8 earthquake.The diurnal-variation anomalies of the vertical-component in geomagnetic field are mainly the changes of phase and amplitude before strong earthquakes. On the basis of data recorded by the network of geomagnetic observato- ries in China for many years, the anomalous features of appearance time of the minima of diurnal variations (i.e, low-point time) of the geomagnetic vertical components and the variation of their spatial distribution (i.e, phe- nomena of low-point displacement) have been studied before over 30 strong earthquakes with MS≥6.6 such as Kunlunshan MS=8.1 earthquake on November 14, 2001; Bachu-Jashi MS=6.8 earthquake on February 24, 2003; Xiaojin MS=6.6 earthquake on September 22, 1989, etc. There are good relations between such rare phenomena of geomagnetic anomalies and the occurrence of earthquakes. It has been found that most earthquakes occur in the vicinity of the boundary line of sudden change of the low-point displacement and generally within four days before and after the 27th or 41st day counting from the day of appearance of the anomaly. In addition, the anomalies of diurnal-variation amplitude near the epicentral area have been also studied before Kunlunshan MS=8.1 earthquake and Bachu-Jiashi MS=6.8 earthquake.

关 键 词：geomagnetic diurnal-variation anomalies geomagnetic low-point displacement diurnal-variation  amplitude strong earthquake 

分 类 号：P315.72+1[天文地球—地震学]