【作者】 潘博；

【导师】 张长厚； 邓志辉；

【作者基本信息】 中国地质大学(北京) ， 构造地质学， 2012， 硕士

【摘要】 活动断裂的地震危险性研究已经由传统的定性分析发展到以概率性分析为主要手段的定量化研究。其中，实时概率模型方法是一种建立在地震原地复发理论和概率论基础之上，以地质学研究成果和大地形变测量资料为参数依据的中长期地震危险性定量分析方法。活动断裂概率性地震危险性研究主要包括三方面内容：地震复发模式、地震复发间隔和概率模型。河套断陷带位于鄂尔多斯块体北缘，断陷带北部边界均为晚更新世以来强烈活动的活断层，包括狼山山前断裂、色尔腾山山前断裂、乌拉山山前断裂和大青山山前断裂。近十年来以GPS为代表的大地形变监测新技术发展迅速，目前已经积累了关于中国大陆的相对完善的GPS观测数据。本文以“中国地壳运动观测网络”观测的运动速率场为基础，通过插值计算获得河套断陷带均匀网格化的GPS运动速率场。随后将GPS速率转化为应变率场，引入Savage利用Kostrov地震矩率累积释放公式所推导的最优地震矩率转换公式，将应变率转化为地震矩率，最后利用地震矩率法求得各断裂带的平均地震复发间隔。本文以河套及邻区83个古地震及历史地震样本，借鉴NB建模思想对复发间隔进行均一化，并利用最大似然法求得均一化的样本所服从的对数正态分布模型的参数，其中均值μ=-0.02254，标准差σ=0.2216。在概率模型的选取上，除对数正态模型外，本文还考虑了泊松模型和布朗时间过程模型，其中布朗时间过程模型的变异系数α取0.5。特征地震描述了地震原地复发行为，而其震级、即特征震级则决定地震的复发间隔。由于研究区没有发生7级以上震级的明确纪录以及破裂长度-震级经验关系具有不确定性，在特征震级的选取上本文综合考虑7级、7.5级和8级的震级并分别计算地震危险性。将求得不同震级地震的复发间隔和离逝时间参数代入预设的三个概率模型之中，利用计算机软件分别计算未来30年、50年、100年的地震复发条件概率值，并以此为依据对各断裂带的地震危险性做出评价：①狼山山前断裂地震危险性比较高，百年内发生7级地震的可能性较大，发生7.5级及以上大震的可能性则相对较低。②色尔腾山山前断裂百年内发生7级地震的可能性不能判断；发生7.5级地震的可能性则较大，并且不能排除发生8级地震的可能性。③乌拉山山前断裂未来百年发生7级及以上地震的可能性较大，而发生8级及以上地震的可能性很小。④大青山山前断裂百年内发生7.级地震的可能性相比其它断裂要高很多，同时也具备发生7.5级地震的可能性，而该断裂发生8级地震的可能性则较很小。更多还原

【Abstract】 Research on seismic hazard evaluation of active faults has evolved fromtraditional qualitative analysis to quantitative evaluation on the basis of probability.Real-time model method is a mid-long term seismic hazard evaluation which isderived from theory of characteristic earthquake and probability, and built ongeological research findings and observations of crustal deformation. The research onseismic hazard evaluation of active faults is consisted by three parts: earthquakerecurrence model, earthquake interval, and density distribution of earthquake events.The Hetao fault-depression zone is on the north boundary of Ordos block, ofwhich the north margin is consisted of four strong active faults since Late Pleistocene:Langshan piedmont fault, Se’ertengshan piedmont fault, Wulashan piedmont fault andDaqingshan piedmont fault.In the past decade, a new technology of crustal deformation observation calledGPS, short for Global Positioning System, has been rapidly developed, and adequateGPS data have been accumulated. On the basis of horizontal velocity data fromproject Crustal Movement Observation Network of China, a well-distributed grid ofGPS velocity on the Hetao fault-depression zone has been constructed by Kriginginterpolation. Then the GPS velocity rate is changed into strain rate, which is finallytransformed into seismic moment rate by the best formula proposed by Savageconverted form Kostrov’s moment rate calculation formula. The average earthquakerecurrence intervals of active faults are calculated with the moment rate.83samples of paleoearthquakes and historical earthquakes are collected in theHetao fault-depression zone and its neighboring area, and then constructed intoearthquake recurrence distribution. By the method of maximum likelihood estimation,the parameters of the lognormal distribution are determined, which are: μ=-0.02254,σ=0.2216. Besides the lognormal distribution, Poisson distribution model and BPTmodel, short for Brownian Passage Time model, are also considered in the paper. Thecoefficient of variation of BPT model is set as0.5. The event recurrence interval of each fault is determined by the characteristicmagnitude of that fault. Due to its lacking of historical record about earthquakes overmagnitude7and the uncertainty of empirical rupture-magnitude relationship,magnitude7,7.5, and8are all considered as characteristic magnitudes of each fault,and seismic hazard of each fault is evaluated separately according to the threemagnitudes and the recurrence intervals determined by them. In the end, recurrenceinterval and elapse time related to each characteristic magnitude are substituted intothe three selected probability-distribution models. The probabilities of occurrence ofstrong earthquake in the future30,50and100years are calculated, based on whichthe seismic hazard evaluation are made:①The seismic hazard of Langshan piedmont fault is relatively high. Within thenext100years, earthquakes of magnitude7are likely to strike, while the occurrenceof strong earthquakes of magnitude7.5and above is with relatively low possibility.②The possibility of an earthquake occurring in the next century of Se’ertengshanpiedmont fault cannot be judged; the possibility of a Ms7.5earthquake is relativelyhigh, and the likelihood of a Ms8earthquake cannot be completely excluded.③Thelikelihood of a earthquake of magnitude7and above occurring in Wulashan piedmontfault in the next100years is relatively high, while a earthquake of magnitude8isunlikely to happen.④Daqingshan piedmont fault is with high probability of strikingof a Ms7earthquake in the next century. An earthquake of magnitude7.5is likely tooccur, while an earthquake of magnitude8is also unlikely to happen.更多还原