全球大地震破裂空间复杂度特征研究

基于有限断层反演得到的滑移数据, 用独立滑移单元的数量表征地震破裂复杂度, 据此对大地震破裂进行分组, 并研究破裂复杂度与主要震源参数之间的关系, 探讨破裂复杂度的全球及区域空间分布特征。结果表明, 矩震级很大(Mw ≥ 8.5)的事件, 地震破裂复杂度更大; 破裂复杂度较高的地震分布在浅层地壳(≤ 30 km)内的概率最大, 随着震源深度增加, 破裂复杂度对震源深度的敏感性逐渐消失; 走滑断层机制占比较大的事件, 破裂复杂度较高; 破裂复杂度与地震能矩比没有明确的关系; 破裂复杂度的空间分布特征与区域地质构造环境相关。破裂复杂度的空间分布特征可以分为3类, 第一类是板块之间简单碰撞产生的俯冲带, 板块交界处的滑动速率和方向较为一致, 这种情形下以比较简单的事件类型为主; 第二类是多板块交界处, 或者板块交界处的滑动速率和方向在整个区域内存在差异; 第三类是大陆内部的强烈挤压地带。与第一类空间分布特征相比, 第二类和第三类情形下破裂复杂度相对更高。地震破裂复杂度可以在一定程度上反映区域应力场的复杂性。

Study on Rupture Spatial Complexity of Global Large Earthquakes

Based on the displacement data obtained from finite fault inversion, the number of independent slip units is used to characterize the magnitude of the seismic rupture complexity and group the events statistically, to study the relationship between rupture complexity and source parameters, to explore the global spatial distribution and regional characteristics of fracture complexity. The results show that for events with a large moment magnitude (Mw ≥ 8.5), the rupture complexity tends to be greater; the earthquake with higher rupture complexity is more likely to be distributed in the shallow crust (≤ 30 km), and the sensitivity of the rupture complexity to the focal depth gradually disappears as the focal depth increases; the events with higher strike-slip fault mechanism components tend to have higher fracture complexity; there is no clear relationship between rupture spatial complexity and seismic energy-moment ratio; the spatial distribution characteristics of rupture complexity is associated with regional geological tectonic environment. The spatial distribution characteristics of fracture complexity can be divided into three categories. The first category is the subduction zone caused by simple collisions between plates and the slip rate and direction at the boundary of the plates are relatively high, and relatively simple event types are main in this case. The second type is the junction of multiple plates, or the sliding rate and direction at the junction of the plates are different in the whole area. The third type is the strong compression inside the continent. The rupture complexity of the second and third types of cases tends to be higher than that of the first type. The rupture complexity can reflect the complexity of the regional stress field to a certain extent.