The tectonic structure,Quaternary activity,deep structure,stress and strain fields and seismicity on the faults in Tianjin offshore areas are studied through field surveying in order to determine the activity and tectonic features synthetically.Using seismo-geological data,as well as the historical and modem seismicity data,the frequency-magnitude relationship model reckoning by 500 years is established.Based on the relationship between the upper limit of maximum magnitude Mu and a/b,we calculate the maximum magnitude of the Haihe river fracture sea section and Haiyi fault.Then Poisson probability model is adopted and quantitative parameters such as the maximum magnitude,occurrence probability,recurrence period of the faults in south Tianjin offshore areas in coming 50-200 years are calculated.%以天津市近海海域断裂探测资料为基础,通过对海河断裂海域段和海一断裂的地质构造、第四纪活动性、深部构造、构造应力场与形变场以及地震活动性等的研究,综合判定了海河断裂海域段和海一断裂的活动性与构造特征.利用地震地质、历史与现今地震活动性资料,建立了按500a归算的震级-频度关系模型,根据天津地区的最大震级上限Mu与a/b的关系,计算出了海河断裂海域段和海一断裂的最大震级.采用泊松概率模型,估算出了海河断裂海域段和海一断裂未来50-200a发生地震的最大震级、发生概率以及复发周期等定量参数.
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