Seismic Hazard Assessment with Microtremor Array Observation and Computational Simulation in the Metropolitan Beijing Area

Abstract eng:
Historic earthquake record indicates that mediate to strong earthquakes have been frequently striking the greater Beijing metropolitan area where is going to host the 2008 summer Olympic Games. During the last 500 years (the Ming and Qing Dynasties) there are at least 11 earthquakes with the maximum intensity of VI or greater occurred within a 100-km radius centered at the Tiananmen Square, the center of Beijing City. To quantitatively assess the seismic risk of Beijing at a few critical sites of the 2008 Olympic Games, we used the numerical simulation to study the strong ground motion scenarios based on historic earthquake records. To improve the modeling efficiency and accuracy, the high-resolution near-surface geologic information was studied with a microtremor array measurement campaign conducted in summer 2007. We have collected microtremor arrays data at more than 1,000 sites in the metropolitan Beijing area with 30 three-component short-period seismometers. The collected data are processed with both the horizontal to vertical spectral ratio method (H/V) to extract the resonant frequency, thickness of the sediments, and the ground motion amplification factor; and the space correlation method to extract near-surface shear wave velocity structure. As an example, the newly acquired engineering geological and seismological data were used to estimate the near-surface site effects caused by the strong ground motion in the Beijing area generated by an scenario event similar to one historic earthquake occurred in the city center. Local site effects expressed as the ground motion amplification were found in the northwest corner of Beijing area, similar to what has been observed for the 1976 Tangshan earthquake. This project is supported by the Ministry of Science and Technology of China with Project No. 2006DFA21650 and the Institute of Earthquake Science (Project No.0207690229).

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