Investigation of Seismic Hazard in Nile Delta Area

为了对钉三角洲地区进行地震危险性分析，需要掌握该地区的地面结构信息和地震运动的放大效应。然而，奈尔三角洲的地震观测和详细的地面勘探尚未开展。尽管从1950年初开始对开罗周边地区的地震活动和地壳结构及其运动以及重力异常进行了调查，但用于确定未来地震断层破裂参数的信息也没有得到纠正。本研究的目的是收集开罗周边历史和最近地震活动的数据，以估计地震的断层机制，这些地震对开罗的基础设施造成了严重破坏开罗的城市。根据这些数据，我们提出了未来的地震情景，以模拟适当的地震设计地震运动。并收集了土壤勘探资料。利用收集到的资料，通过叠加随机小地震运动来合成未来事件的地震运动。为了建立一种利用AR-MA过程合成随机小地震运动的方法，我们收集了开罗市几个地方观测到的小地震运动。研究了断层走向、断层倾角和破裂起点对峰值加速度衰减的影响。研究了模拟地震运动得到的峰值加速度衰减特性，探讨了峰值加速度与断层与观测点位置的关系。断裂起始点的不同、震级和震中距离的不同对断层附近的加速度峰值有较大的影响。

To conduct seismic hazard analyses in Nail delta area we need the information of ground structure and amplification effect of seismic motion in the area. However earthquake observations and detail ground explorations have not been conducted in Nail delta. The information to be used for determining fault rupture parameters of a future earthquake has not also been corrected although the seismic activities and crust structure and its movement as well as gravity anomaly in the area surrounding Cairo city has surveyed form the beginning of 1950The purpose of this study is to collect data of historical and recent seismic activities surrounding Cairo city for estimating fault mechanisms of earthquakes which caused sever damage to infrastructures in Cairo city. Based on these data we proposed future earthquake scenarios for simulating proper seismic design earthquake motions. The soil exploration data were also collected.Using collected data earthquake motions of a future event are synthesized by superposing stochastic small earthquake motion. To developed a method for synthesize stochastic small earthquake motions using the AR-MA process we collected observed small earthquake motions at several places in Cairo city. The effect of strike, dip angle of the fault and a starting point of rupture on an attenuation of peak acceleration was investigated. The attenuation characteristic of peak accelerations obtained from simulated earthquake motions were studied in order to investigate the relation between peak accelerations and positions of the fault to the observation points. The peak acceleration at the region near the fault was much influenced by the difference of the starting point of rupture as well as the magnitude and the epicenter distance.