Rupture kinematics of the 2005 Mw 8.6 Nias-Simeulue earthquake from the joint inversion of seismic and geodetic data
Rupture kinematics of the 2005 Mw 8.6 Nias-Simeulue earthquake from the joint inversion of seismic and geodetic data
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DOI：
10.1785/0120050632
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发表时间：
2007-01-01
影响因子：
3
通讯作者：
Meltzner, Aron
中科院分区：
文献类型：
--
作者：
Konca, A. Ozgun;Hjorleifsdottir, Vala;Meltzner, Aron
2005年的里氏8.6级Nias-Simeulue地震是由苏门答腊岛北部近海的巽他逆冲断层的一部分破裂引起的。这一事件发生在一系列连续的全球定位系统（GPS）站内，并在断层破裂上方的边缘珊瑚礁产生了可测量的垂直位移。因此，这次地震提供了一个独特的机会，通过地震数据和近场静态同震位移的联合分析来评估大逆冲事件的震源特征。基于正态数据和大地测量数据的激励，我们对地震矩和断层倾角进行了较为严格的约束，其中倾角确定为8°~ 10°，对应的矩分别为1.24 × 10(22) ~ 1.00 × 10(22) N in。对滑移分布的大地测量约束有助于消除破裂速度和滑移运动学之间的权衡。通过比较预测和观测的长周期地震波（100-500秒），对远震体波和大地测量资料的各种组合反演得到的震源模型进行了评价。我们的结果表明，地震的平均破裂速度相对较慢，为1.5至2.5 km/s，平均上升时间长达20秒。地震在两个独立的滑块之间形成核，一个在Nias下方，另一个在SimeLdue岛下方。两个斑块之间的间隙和震源位置似乎与弧前的局部地质破坏一致。在到达海沟之前，地壳滑动明显地逐渐减小到零，这可能是因为当它到达吸积棱镜时，断裂传播受到抑制。利用联合反演模型，我们估计尼亚斯岛的峰值地面速度约为30厘米/秒，比大陆地区的冲断事件慢一个数量级。本研究强调了在地震破裂成像中利用多个数据集的重要性。
The 2005 M-w 8.6 Nias-Simeulue earthquake was caused by rupture of a portion of the Sunda inegathrust offshore northern Sumatra. This event occurred within an array of continuous Global Positioning System (GPS) stations and produced measurable vertical displacement of the fringing coral reefs above the fault rupture. Thus, this earthquake provides a unique opportunity to assess the Source characteristics of a megathrust event from the joint analysis of seismic data and near-field static co-seismic displacements. Based on the excitation of the normal mode data and geodetic data we put relatively tight constraints on the seismic moment and the fault dip, where the dip is determined to be 8 degrees to 10 degrees with corresponding moments of 1.24 X 10(22) to 1.00 X 10(22) N in, respectively. The geodetic constraints on slip distribution help to eliminate the trade-off between rupture velocity and slip kinematics. Source models obtained from the inversion of various combinations of the teleseismic body waves and geodetic data are evaluated by comparing predicted and observed long-pcriod seismic waveforms (100-500 sec). Our results indicate a relatively slow average rupture velocity of 1.5 to 2.5 km/sec and long average rise time of up to 20 sec. The earthquake nucleated between two separate slip patches, one beneath Nias and the other beneath SimeLdue Island. The gap between the two patches and the hypocentral location appears to be coincident with a local geological disruption of the forearc. Coselsinic slip clearly tapers to zero before it reaches the trench probably because the rupture propagation was inhibited when it reached the accretionary prism. Using the models from Joint inversions, we estimate the peak ground velocity on Nias Island to be about 30 cm/sec, an order of magnitude slower than for thrust events in continental areas. This study emphasizes the importance of utilizing Multiple datasets in imaging seismic ruptures.