Hypocenter depths of large interplate earthquakes and their relation to seismic coupling
Hypocenter depths of large interplate earthquakes and their relation to seismic coupling
复制标题
板间大地震震源深度及其与地震耦合的关系
DOI：
10.1016/s0012-821x(03)00141-9
复制
发表时间：
2003
影响因子：
5.3
通讯作者：
T. Seno
中科院分区：
文献类型：
--
作者：
N. Kato;T. Seno
我们研究了板间大地震（M≥7.5）的震源相对于其破裂区在俯冲带的位置，以获得震源深度与地震耦合系数之间的关系，地震耦合系数是根据大地震的累积地震矩估计的长期滑移率与相对板块运动的比率。我们发现：（1）当地震耦合系数接近1.0时，震源深度接近破裂区深度范围的底部； (2)当地震耦合系数小于0.5左右时，震源深度相对于破裂区深度范围表现出由浅至深的较大分散性。为了解释这些观察结果，我们对板间地震的地震周期进行了数值模拟，其中假设板块边界上的摩擦应力遵循实验室推导的与速率和状态相关的摩擦定律。当临界断层长度（发生滑移成核过程的断层尺寸）远短于板块边界的发震带时，模拟中再现了观察到的结果（1）。在这种情况下，板块边界在震间期被强烈锁定，因此计算的地震耦合系数接近1.0。地震滑动开始于孕震带底部附近，因为由于更深的稳定板块运动，在孕震带底部附近产生了最大剪应力集中。另一方面，当临界断层长度较大时，在震源区发生明显的地震滑动，因此计算的地震耦合系数显着小于1.0。对于较大的临界断层长度，模拟大地震的震源深度往往较浅。板块边界上的非均匀摩擦特性可能会在震间期产生不均匀的抗震滑动。在这种情况下，地震耦合很小，并且地震滑移在地震发生带的各个部分开始。这可以解释观察到的结果（2）。
We examine locations of hypocenters of large interplate earthquakes (M≥7.5) at subduction zones relative to their rupture areas to obtain a relation between the hypocentral depth and the seismic coupling coefficient, which is the ratio of the long-term slip rate estimated from cumulative seismic moment of large earthquakes to the relative plate motion. We find: (1) that the hypocentral depth is close to the bottom of the depth extent of the rupture area when the seismic coupling coefficient is nearly equal to 1.0; and (2) that the hypocentral depth relative to the depth extent of the rupture area shows a large scatter from shallow to deep when the seismic coupling coefficient is smaller than about 0.5. To interpret these observations, we conduct a numerical simulation of seismic cycles of interplate earthquakes where the frictional stress on the plate boundary is assumed to obey a laboratory-derived rate- and state-dependent friction law. The observed result (1) is reproduced in the simulation when the critical fault length, which is the size of the fault where the slip nucleation process takes place, is much shorter than the seismogenic zone of the plate boundary. In this case, the plate boundary is strongly locked during an interseismic period, and accordingly the calculated seismic coupling coefficient is close to 1.0. Seismic slip starts near the bottom of the seismogenic zone, because the maximum shear-stress concentration is generated near the bottom of the seismogenic zone due to deeper steady plate motion. On the other hand, when the critical fault length is large, appreciable aseismic sliding occurs in the seismogenic zone and, therefore, the calculated seismic coupling coefficient becomes significantly smaller than 1.0. The hypocentral depths of simulated large earthquakes tend to be shallow for large critical fault lengths. Heterogeneous frictional properties on the plate boundary may produce non-uniform aseismic sliding during an interseismic period. In this case, the seismic coupling is small and seismic slip starts in various portions of the seismogenic zone. This can explain the observed result (2).
影响因子：
3
作者：
Kikuchi, M;Nakamura, M;Yoshikawa, K
通讯作者：
Yoshikawa, K
影响因子：
--
作者：
KELLEHER, J;SYKES, L;OLIVER, J
通讯作者：
OLIVER, J