基于震例的前兆统计特征分析  

Analysis on statistical features of precursor based on earthquake cases in China mainland

作　　者：蒋海昆[1] 苗青壮[2] 吴琼[1] 宋金[1] 

机构地区：[1]中国地震台网中心,中国北京100045 [2]山东省地震局,中国济南250014

出　　处：《地震学报》2009年第3期245-259,共15页Acta Seismologica Sinica

基　　金：国家“十一五”科技支撑计划项目子专题(2006BAC01B03-02-02);地震行业科研专项经费项目(200708020)资助

摘　　要：依据《中国震例》(1966—1999年)收录的185次震例的2500多条地震活动及前兆异常资料,研究了各学科平均异常数量、空间分布范围、异常时间等统计特征及其与主震震级的关系.结果显示,地震学、形变、流体异常数量相对较多,且平均异常数量随震级增大有加速增长的趋势,前兆平均异常数量随震级的增加尤其明显.从地震学各方法来看,频次、空区、b值、条带等方法提供的异常数占总异常数量的1/2.前兆异常分布范围数倍于地震破裂尺度,形变、流体异常平均震中距随主震震级大体上呈线性增加.各类异常出现时间与未来主震震级定性正相关,即地震越大,出现的时间越早.研究结果还显示,当目标震级不高时(例如5—6级地震),现有预测方法及手段可能不足以提供年时间尺度的地震预测依据.同时,流体和电磁等前兆学科在3年地震大形势预测研究,甚至是在年度预测研究中所能够发挥的作用,可能也不如人们所期望的那么大.本文较多震例的平均统计结果显示,随主震的临近,前兆异常空间分布向震中附近集中、收缩,同时异常数量明显增加.这一现象始于年尺度的中短期阶段而非更短时间的临震,同时本文亦未能够检测到前兆异常空间分布向外围明显的扩散过程.最后对《中国震例》前兆异常选取范围的合理性及对本文统计结果的可能影响进行了初步讨论.Abstract： Based on 185 earthquake cases with about 2500 anomalies collected in 《Earthquake Cases in China》 from 1966 to 1999, the average numbers, spatial distribution ranges, average periods of the precursors, as well as the relationship between these quantities and the mainshock magnitudes, have been exam- ined. The result shows that the seismicity, deformation and underground fluid can offer more evidences for earthquake prediction, and their average numbers of precursors increase exponentially with the mainshock magnitude, especially for deformation and fluid precursors. For seismicity, the precursor numbers of earthquake frequency, seismic gap, b value and seismic belt are about 50~ of total precursor numbers. The spatial distribution range of precursors is several times of fracture size of the mainshock. Average epicentral distances of deformation and fluid precursors increase linearly with the mainshock magnitude. The anomaly periods are proportional to the magnitude of the mainshock, the larger the mainshock, the longer the anomaly period. The result also indicates that the current existing methods or observation items could not offer enough scientific evidences for yearly earthquake prediction, if the expecting mainshock is not large enough （for example, for MsS--6 earthquakes）. At the same time, the effects of fluid and electromagnetic precursors on long-or middle-term （several years） earthquake prediction, even on yearly earthquake prediction, may not be so powerful as we expected. With the approach of the mainshock, the precursor distribution concentrated to the epicenter region gradually and the number of precursors increases quickly. This tendency began from middle-or short-term phase within about one year or more before the mainshock, but not in the imme- diate-term in a very short time period. Further more, the obvious diffusing process of the precursor distribution proposed by other authors could not be identified in this paper. Finally, the selected spatial range for precursors in

关 键 词：中国震例 平均异常数量 平均异常震中距 平均异常时间 

分 类 号：P315.72[天文地球—地震学]