地震前昌黎台地电阻率变化特征分析

Analysis of Variation Characteristics of Geoelectrical Resistivity at Changli Station before Earthquakes

应用曲线跟踪分析方法和NVRM方法处理,分析了昌黎台1999年1月-2013年5月的地电阻率观测资料,研究了2000年以来中国大陆及周边的4个远大地震和昌黎台周围约400km范围内中等地震前的地电阻率变化,认为昌黎台记录的2次趋势转折异常和3次破年变异常与远距离大震的发生有关联性,并与华北大范围背景的地壳介质力学状态的变化有一定联系。本文认为应该把破年变异常、趋势转折变化与NVRM方法结合处理分析地电阻率观测数据比较合理,如出现畸变、趋势转折异常,很可能与强地震有关,且变化速率异常持续时间在6-24个月左右,而4、5级地震一般不会引起年变畸变或趋势转折变化。

This study surveyed and analyzed the significant mutations of the original observations including observing systems of movement,the natural environment,and buildings affected facilities by examining resistivity observations at Changli station from January 1999 to May 2013.On the basis of this analysis,Changli station has used the curve tracking application and normalized variation rate method （NVRM）approach to analyze earthquakes occurring in the Chinese mainland and the surrounding region since 2000,which include the November 14,2001,West Kunlun Mountain Pass Ms8.1 earthquake; the December 26,2004,Sumatra Ms8.9 earthquake; the May 12,2008,Wenchuan Ms8.0 earthquake; the March 11,2011,level 4 far Ms9.0 earthquake in Japan;and the resistivity change of 400 km near Changli station before the earthquakes occurred.The results show a relationship among two trends and three record-breaking abnormalities and far earthquakes in addition to a relationship between these earthquakes and changes in the mechanical state of North crust in a wide range of backgrounds.According to the analysis of nine moderate earthquakes in Bohai area,five occurred within six months of abnormalities,including the abnormal frequency of EW Road between 2008 and 2009 and between 2012 and 2013 and that of NS Road in 2009.Based on the differences in intensity,seismic studies at various distances consider that the analysis of abnormal signals should be combined with the record-breaking abnormal changes,trend changes and transitions,and NVRM processing and analysis methods to analyze observations of Earth resistivity.These differences may be related to the strong earthquakes if there is a distortion or trend in abnormalities lasting 6 to 24 months.However,the level 4 and 5 earthquakes do not generally cause distortions or trend changes.