陆缘伸展区的地震激发机制

江苏所处的中国东部被当代横贯欧亚的北西西向环球螺旋形扭转断裂带（其东段即大别—舟山断裂）分割为南部的褶皱山带隆升区和北部的沉降区。软流圈从太平洋方向面楔入北部区，使该区岩石圈减薄，陆壳向海洋伸展、离裂，产生郯庐断裂等具有直扭性质的近南北向软流（及地幔）底辟，并伴随有多层水平拆离面，所见为高导低速的水平破裂带。绝大多数地震沿着其中埋深１５ｋｍ（±５ｋｍ）的第一水平破裂带发生，使北部区成面积性地震区。结合高压物性实验所得的岩石微破裂规律（…分割—错位—嵌合—再分割…）判断得知，水平破裂带中的膨胀增厚部分的流体处在超压状态而成为储能体，在陆壳伸展运动中会突然释放能量而诱发地震。因此，根据已有实际分析认为：强震和频震区的发展的必要条件是软流楔入和陆壳伸展，而其充分条件是储能体在软流冲击和增温效应下的爆裂或突然塌缩事件。据此可根据软流运动和岩石圈结构预测未来震中，建立中、长期预报甚至短临预报的监控系统

MECHANISM OF EARTHQUAKE OCCURRED IN SPREAD AREA OF CONTINENT MARGIN

The lift region of south part and depressed one of north part in Jiangsu are divided by the NWW circumglobal spiry torisonal fracture zone of cross Eurasia, east segment of which is the Dabie Zhoushan fracture. Because of asthenosphere wedging into north region from the Pacific, the thinning of lithosphere of north region, and the spreading of continent crust toward ocean and rupture are made, producing the submeridional orientation asthenosphere diapire of the Tanlu fault zone, and accompaining the horizontal separative surface of multiple layers. Most earthquake have occurred in 15 km (±5 km) depth which is first horizontal ruptural zone, so north region becomes seismic area. Combing with the rock microrupture experiment under high pressure, it is inferred that the fluid is in dilate thichening part under ultra high pressure, hence becomes the energy storage body of inducing earthquake. It is concluded that necessary condition of strong earthquake occurrence is wedging of asthenosphere and spreading of continent crust, and full condition is energy storage body burst under asthenosphere push and increase temperature effect, or abruptly collapse event.