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地震危险性概率分析(PSHA)自30年前被应用以来,基本没有受到任何异议和挑战。但越来越多的资料令人信服地表明,PSHA并不是一个完美无缺的方法。它的最大弱点是,概率理论取决于一个不再视为满足幂律的Gutenberg—Richter震级和重现关系。为了弥补这种不足,需要在概率计算中考虑古地震资料和特征地震,但这又会因资料不完整以及地震发生的时空不均匀性而导入其它误差。对概率所做的最不合适的纠正是电力研究院和Lawrence Livermore国家实验室提出的对多名专家意见进行平均的做法。由于不同模型的标准各导,专家意见是无法进行有意义的平均的。另一方面,地震危险性评价的确定性方法因排除了概率估计中使用的假精确的时间因素,而避免了上述缺点。地震重现率使用是大家认可的地质时间标准,如过去12 000年有过一次活动或过去500 000年有过多次活动。对于关键工程,其破坏后果是无法容忍的,要防止经合理预估可能发生的最坏情况(最大可信地震),因此作者极力推荐使用确定性方法。
The Seismic Hazard Probability Analysis (PSHA) has received almost no objections and challenges since its application 30 years ago. However, more and more data convincingly show that PSHA is not a perfect method. Its biggest weakness is that the theory of probability depends on a Gutenberg-Richter magnitude and recurrence relation that is no longer considered as a power law. In order to remedy this problem, we need to consider the paleo-seismic data and the characteristic data in the probability calculation, but this will lead to other errors due to incomplete data and temporal-spatial heterogeneity of earthquakes. The most improper correction of probability is the approach taken by the Electric Power Research Institute and Lawrence Livermore National Laboratory to average multiple expert opinions. Due to the different standards of different models, expert advice is not meaningful average. On the other hand, the deterministic method of seismic hazard assessment avoids the above drawbacks by excluding the false exact time factor used in the probability estimation. The use of seismic recurrence rates is an accepted geologic time standard. For example, there was one activity in the past 12,000 years or many activities in the past 500,000 years. It is intolerable for the destructive consequences of critical projects, preventing the worst-case scenario (the largest credible earthquake) that can reasonably be predicted, so the author strongly recommends a deterministic approach.