Research And Development Of Seismic Hazard Analysis System For Xi’an Region Based On ArcGIS

As an earthquake-prone region, several major earthquakes have happened in China recently. Therefore it is necessary to exactly quantify and assess the seismic hazard of the main seismic zones of our country. Xi’an region has the considerable earthquake risk since it is located in the main seismic zone of Northwest. This study is from the project entitled as “Prediction and Application of Near-Fault Ground Motions” that is the subprogram of the National Science and Technology Support Program as “Study and Illustration of The Key Techniques of Simulation and Assessment for The Aged Buildings in The City”. The main focus of this study is to evaluate the seismic hazard of Xi’an region. To fulfil this demand, the software of Arc GIS Engine is adopted as the platform to form the seismic information database of Xi’an region. Moreover, seismic hazard analysis is performed for Xi’an region from both probabilistic and deterministic viewpoints. The main content are followings:1) Development of database. The seismic data base of Xi’an region was developed by cooperation with Seismological Bureau of Xi’an. Such a database offered the necessary information required by the following probabilistic and deterministic seismic hazard analysis.2) Probabilistic seismic hazard analysis(PSHA) of Xi’an region. Two methods currently used for PSHA, i.e., discretization algorithm and CPSHA algorithms, were compared with each other at first. The results confirm the accuracy of the discretization algorithm without consideration of uncertainty. Then the discretization algorithm was applied to Xi’an region to perform PSHA with inputting the region activity data and geometric information that were provided by Seismological Bureau of Xi’an. The calculated PSHA result was proved identical to the real seismic conditions of Xi’an in comparison with the National Seismic Map and the related studies by the others.3) Deterministic seismic hazard analysis(DSHA) of Xi’an region. The stochastic finite fault method was adopted to perform DSHA with the help of EXSIM. Such a consideration is based on the recognition of the fact that the point source model and the PSHA tool cannot match the demand of studies on near-fault earthquakes. The accuracy of EXSIM and its application were examined by simulating the Northridge earthquakes. Then the validated methodology of DSHA was used in the studies about the near-fault region of Xi’an with the impressive live fault. The maximum considered earthquake was simulated with the outputs of the peuso-acceleration spectra and the acceleration time history of the controlling points. As a further step, the obtained results were compared to the attenuation relationship of point source model and the difference of seismic hazard evaluation was evaluated.4) Development of the Arc Gis-based platform of seismic hazard analysis. The platform special for performing seismic hazard analysis of Xi’an region was developed based on the seismic database of Xi’an region. This platform was based on Arc Gis software involving the specific properties of Xi’an near fault, which can not only perform PSHA but also DSHA.