概率方法应用于地震短期预测的探索

AN APPLICATION OF PROBABILITY METHOD TO THE SHORT TERM EARTHQUAKE PREDICTION

根据爆发地震和地震平静两项活动性前兆的统计结果，对地震发生的背景概率、条件概率和概率增益进行了估计，给出了张北地震发生前发震概率逐步增加的时间过程，由背景概率Ｐ（Ｅ）增至中期前兆Ａ（爆发地震）出现后的条件概率Ｐ（Ｅ｜Ａ），再增至短期前兆Ｂ（平静）出现后的联合条件概率Ｐ（Ｅ｜Ａ，Ｂ）。结果表明，在１９９７年１２月１７日后的一个月内，华北地区发生６级以上的条件概率达３８％，概率增益超过２０。对概率预测结果的使用进行了探讨，提出应充分注意发震概率的大小与地震发生的时空强范围之间的关系。对于短期预测，要求估算出很高的发震概率目前是很困难的，重要的是要有足够的概率增益。对于各种前兆和预测方法进行较为严格的统计检验是概率预测的基础，也是使地震预测健康发展的基础。对于各种实用的地震预测方法宜采取跟踪检验的方法，在提供预测意见同时。

Based on the statistical result of two seismicity precursors of blast earthquake and seismic quiescence, the background probability, conditional probability and probability gain of earthquake occurrence are estimated. The time history of probability of earthquake occurrence before Zhangbei earthquake is introduced. The background probability P(E) increased at first to the conditional probability P(E|A) after appearance of intermediate term precursor A (blast earthquake), then to the combined conditional probability P(E|A, B) after appearance of the short term precursor B (Seismic quiescence). Within a month after December 17, 1997, the combined conditional probability of earthquake occurrence with magnitude greater than 6 in North china was 38% with probability gain over 20. How to use the result of probability prediction is discussed in this paper. It is noticed that the probability of earthquake occurrence strongly depends on the time, space and magnitude span to be predicted. A high probability for a short term prediction is hard to be obtained at present, and a high probability gain is important. The hypotheses test for various precursors and prediction methods is essential for a sound development of earthquake prediction research. For the practical prediction methods the trace test is suggested. While a prediction is made by a certain method, the latest result of hypotheses test for the method is suggested to be provided if possible.