江苏—南黄海地区地震活动时空分布特征及其孕震构造分析

江苏—南黄海地区城市密集,人口众多,是中国东部经济最发达的地带之一。同时,该地区历史上曾频发中—强以上级别的地震,地震及次生地质灾害是威胁该区经济社会发展的自然灾害之一。该区的地震活动时空特征和发震机制还不清楚。本文通过整理江苏—南黄海地区的历史和仪器记录地震数据,分析了该区地震活动时空分布格局,发现地震活动主要集中于若干条区域活动断裂带,在时间上具有约60年的平静期,目前仍处于地震活跃期。深部构造研究还表明该区域内地震活跃的南部坳陷和勿南沙隆起区均存在显著的地球物理异常,表明地震活动与区域深部构造有关。东部菲律宾海板块的俯冲作用和印度—欧亚大陆碰撞引起的板块边界挤压力和大陆边缘因地形高程差异伴随的重力势能是中国海洋地震的主要驱动力。上述认识不仅加深了对江苏—南黄海地区地震构造环境的理解,同时也能对该区防震减灾公益事业提供科学参考。

Spatiotemporal Pattern of Earthquake Activities and Seismotectonics in Jiangsu and Adjacent Southern Yellow Sea Area

Jiangsu Province and the adjacent Southern Yellow Sea area is one of the most economically developed regions in eastChina, along with dense cities, large population and integrative infrastructures. This area is, unfortunately, vulnerable to earthquakehazard threatening its socio-economic development. Historically a number of medium and strong magnitude earthquakes frequentlyoccur this area. The seismogenic mechanism for this area is not well understood. Here we collect all the historical and instrumentalearthquake data available in this area, to investigate the spatiotemporal pattern of the seismicity and its seismotectonics. We found thatthe earthquakes are clustered and generally associated with several main active fault zones; the seismically quiescent period for thisarea approximates to 60 years, and it is now still at the active phase. In addition, integrative geophysical analysis demonstrates that theWunansha Uplift and Southern Depression of the Jiangsu and Southern Yellow Sea areas, where the seismicity is comparativelyintensive, show prominent deep structure anomalies, suggesting a genetic link between the seismicity and deep structure. The westwardsubduction of the Philippian Sea Plate and the far field effect of the Indo-Asia continental collision, along with the gravity potentialdifference derived from the elevation contrast between the craton and shelf area, account for the driving force trigging the earthquake.The results presented here not only promote our understanding of seismotectonics in this region but also have important significance forearthquake hazard mitigation in the Jiangsu and Southern Yellow Sea area.