俯冲带地震动特征及其衰减规律探讨

随着我国南海不断开发建设，海洋工程的抗震问题日益受到重视.我国南海东部区域位于大陆板块与海洋板块共同作用的俯冲带地区，地震活动频繁，震级较大，潜在地震对南海开发建设有重要影响.为了研究俯冲带地震的地震动特征及其衰减规律，本文基于实际俯冲带地震数据，并结合数值模拟方法，分析和探讨了俯冲带板内、板缘地震与浅地壳地震的地震动特征和衰减规律的差异.研究结果表明：俯冲带地震动存在区域性差异，在地震动衰减特征方面，同一区域的俯冲带板缘地震要比浅地壳地震衰减慢，俯冲带板内地震要比浅地壳地震衰减得快；数值模拟分析不同深度海水对海底地震动的影响表明，海底地震动水平分量几乎不受海水介质的影响，但是竖向分量随海水深度的增加有减小的趋势.最终，基于数值模拟和经验关系的混合方法建立了南海俯冲带地震动衰减关系模型，其结果可为海域区划等相关研究和海域工程建设提供参考.

Characterization of strong motion of subduction earthquakes and its attenuation relationship

With the increasing exploitation and engineering construction in the South China Sea, the seismic design problems of marine engineering are becoming more and more important. The east part of the South China Sea is located in the joint section of the continental plate and the oceanic plate, which belongs to the subduction zone with high seismicity and relatively large earthquake magnitude. Thus potential earthquakes may have significant effects on the engineering construction and development of the South China Sea. In order to investigate the characteristics of subduction earthquake ground motion and its attenuation rules, based on the real data of ground motion and numerical modeling results, the ground motions of interface and intraslab earthquakes are investigated. Results indicate that there exists regional differences of subduction earthquake ground motions. The ground motion of interface earthquakes attenuates slower than shallow crustal earthquakes. While the ground motion of intraslab earthquakes attenuates faster than that of the shallow crustal earthquakes. The modeling results of horizontal seafloor ground motion shows almost no impact by the sea water, but the amplitude of vertical component decreases with increasing sea water depth. Then an attenuation relationship derived from a hybrid method based on ground motion modeling and empirical relationship is developed. This may provide a reference for the seismic zonation and engineering construction in the South China Sea.