摘要
深入研究了全国地电台网内M_s≥5.0的45次地电前兆震例,用统计方法按大震、强震、中强地震分别研究其地电前兆特征。 通过研究得到:大震地电阻率异常范围,其半径超过200km,在700km以内,异常时间在12—20个月内发震的概率最高,为97.8％;强震地电阻率异常范围大多在300km以内,趋势异常的时间在12个月以内发震的概率最高,为86.5％;中强地震地电阻率异常范围,半径一般在200km以内,趋势异常时间在180天之内发震的概率最高,为95.0％。大震、强震、中强地震地电趋势异常时间似乎存在着20个月、12个月、6个月三个不同的异常时间段。 临震异常类型一般可分为加速型、转向型和波动型三类。对7级和7级以上大震能观测到临震异常前兆的震例只有33.3％、强震和中强地震能观测到临震异常前兆的震例均为50.0％。出现临震异常后1—20天发震的概率最高,达94.4％。 1988年11月以来,西部地区先后发生澜沧-耿马7.6、巴塘6.7、天祝6.2级地震。震前都曾依据地电前兆短临异常特征,作过某种程度的监测预报工作,取得了较好的短临预报效果。
45 cases of earthquakes with M≥5.0 recorded by Chinese geoelectric array have been deeply discussed , and the precurory features of those earthquakes have been studied through classifying them into large, strong and moderate events.The results show that the anomaly range of earth resistivity before a large event is more than 200 km and less than 700 km, and the highest possibility of earthquake occurrence within 12-20 months is 97.8%; that range of a strong event is mostly within 300 km, and that possibility within 12 months is 86.5%; the range of a moderate shock is within 200 km, the possibility within 180 days is 95.0%. There seems to be 3 different time periods of 20 months, 12 months and 6 months for the geoelectrictrend anomalies of large, strong and moderate shocks, respectively.The types of impending earthquake anomalies can be devided into the accelerating type, converting type and wavine type. Large earthquakes with M≥7 withch have impending precursory anomalies account for 33.3% of all the cases, and 50% for the strong and moderate events. The possibility of earthquake occurrence within 1-20 days after the beginning of impending anomalies is 94.4%.There have been events of Lancang-Gengma ( M = 7.6), Batang ( M = 6.7) and Tianzhu ( M = 6.2), since November of 1988. Some prediction has been made before these earthquakes.
出处
《地震》
CSCD
北大核心
1995年第3期240-245,共6页
Earthquake
基金
地震科学联合基金资助课题(900303)
关键词
地电阻率
地震前兆
短临异常
异常形态
地震预报
Ground resistivity, Earthquake precursor, Short-term and impending anomalies, Type of anomalies
