Investigation of Seismic Hazard in Nile Delta Area

在纳尔三角洲地区进行地震危险性分析，需要了解该地区的地面结构和地震动放大效应。然而，地震观测和详细的地面勘探还没有在指甲三角洲进行。虽然从1950年初开始对开罗市周围地区的地震活动、地壳结构及其运动和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。本文的目的是收集开罗市周围地区历史和近期地震活动的资料，以估计未来地震的断层机制，对开罗市的基础设施造成严重破坏。根据这些数据，我们提出了未来的地震情景模拟适当的抗震设计地震运动。同时收集了土壤勘探数据，利用所收集的数据通过叠加随机小震运动来合成未来事件的地震运动。为了发展一种用AR-MA过程合成随机小震运动的方法，我们收集了开罗市几个地点的观测小震运动。研究了断层走向、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中峰值加速度的衰减特性，探讨了峰值加速度与断层相对于观测点位置的关系。在断层附近区域的峰值加速度受破裂起点的差异、震级和震中距的影响较大。

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.