A transient subduction zone slip episode in southwest Japan observed by the nationwide GPS array
A transient subduction zone slip episode in southwest Japan observed by the nationwide GPS array
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DOI：
10.1029/2001jb000456
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发表时间：
2003-02-11
影响因子：
3.9
通讯作者：
Segall, P
中科院分区：
文献类型：
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作者：
Miyazaki, S;McGuire, JJ;Segall, P
[1]我们调查的时空变化的断层滑动俯冲界面在日本西南部的两个1996年日向田地震（6.7级）使用连续GPS观测。Hirose等人[1999年]报告了一个无声的逆冲滑动事件，这些地震发生在丰后海峡以北约100公里处。采用网络反演滤波器对断层滑动量的时空分布进行严格反演。GPS时间序列被建模为以下各项的总和：（1）长期变形;（2）同震台站位移;（3）瞬时断层滑动;（4）随机基准运动;（5）参考框架移位;以及（6）观测误差。非负性约束有效地阻止了俯冲界面上的正断层。空间和时间平滑参数估计的扩展卡尔曼滤波器。估计的断层滑动率图像震后滑动后的两个日向地震。与无声逆冲事件相关的滑动在第二次地震后大约1个月开始，但类似于日向田地震东北100公里处开始。缓慢的事件向西南方向传播，并在丰后海峡下方下倾，持续约1年，最大滑动速率为0.6米/年。等效地震力矩为M-W，类似于7.2。我们可以排除滑动从日向地震的震源区传播到无声地震位置的可能性。然而，事件发生的时间表明了一种因果关系，可能是由于静态应力转移。这种瞬变事件，或称无声地震，可能反映了不同的断层带特征，并可能负责容纳在大地震中释放的应变。
[1] We investigate the spatiotemporal variation of fault slip on the subduction interface in southwest Japan following the two 1996 Hyuganada earthquakes (M 6.7) using continuous GPS observations. A silent thrust slip event has been reported by Hirose et al. [1999], following these earthquakes approximately 100 km to the north beneath the Bungo channel. We employ the Network Inversion Filter to rigorously invert for the fault slip distribution in space and time. The GPS time series is modeled as a sum of: (1) secular deformation; (2) coseismic station displacements; (3) transient fault slip; (4) random benchmark motion; (5) reference frame shifts; and (6) observational errors. Nonnegativity constraints effectively prohibit normal faulting on the subduction interface. Spatial and temporal smoothing parameters are estimated by the extended Kalman filter. The estimated fault slip-rate images postseismic slip following the two Hyuganada earthquakes. Slip associated with the silent thrust event began roughly 1 month after the second earthquake but initiated similar to100 km to the northeast of the Hyuganada earthquakes. The slow event propagated southwest and downdip beneath the Bungo channel, lasting approximately 1 year with maximum slip-rates of 0.6 m/yr. The equivalent seismic moment was M-W similar to 7.2. We can rule out the possibility that slip propagated from the source region of the Hyuganada earthquakes to the location of the silent earthquake. However, the timing of the events suggests a causal connection, perhaps due to static stress transfer. This kind of transient event, or silent earthquake, may reflect different fault zone characteristics and may be responsible for accommodating strain that would otherwise be released in large earthquakes.