Geodetic evidence of viscoelastic relaxation after the 2008 Iwate-Miyagi Nairiku earthquake
Geodetic evidence of viscoelastic relaxation after the 2008 Iwate-Miyagi Nairiku earthquake
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DOI：
10.5047/eps.2012.04.001
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发表时间：
2012-09
期刊：
影响因子：
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通讯作者：
M. Ohzono;Y. Ohta;T. Iinuma;S. Miura;J. Muto
中科院分区：
文献类型：
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作者：
M. Ohzono;Y. Ohta;T. Iinuma;S. Miura;J. Muto
在2008年岩手-宫城内陆地震（Mj7.2）后，连续两年的GPS观测发现了长期的震后变形。震源区附近的位移场表现为东西向的缩短和沉降。这些特征归因于主震引起的粘弹性松弛。一个简单的两层结构模型，它包括一个弹性层的厚度为19.0-23.5公里和下面的麦克斯韦粘弹性层的粘度为2.4-4.8 × 1018 Pa·s，解释了远场变形图案，这可能反映了粘弹性响应。这些估计的参数与日本东北部上地壳孕震层的深度界限和以前的流变学模型是一致的。然而，近场变形需要额外的来源，以再现所观察到的震后变形，如长期的后滑和/或复杂的响应，由于高度不均匀的结构，建议由地震层析成像研究。
Continuous GPS observations, for over two years, detected long-term postseismic deformation after the 2008 Iwate-Miyagi Nairiku earthquake (Mj 7.2). The displacement field exhibits ESE-WNW shortening and subsidence near the focal area. These features are attributed to a viscoelastic relaxation caused by the mainshock. A simple two-layered structural model, which consists of an elastic layer having a thickness of 19.0–23.5 km and an underlying Maxwell viscoelastic layer having a viscosity of 2.4–4.8 × 1018 Pa s, explains the far-field deformation pattern, which probably reflects the viscoelastic response exclusively. These estimated parameters are consistent with the deeper limit of the seismogenic layer in the upper crust and the previous rheological model in northeastern Japan. However, near-field deformation requires additional sources in order to reproduce the observed postseismic deformation, such as long-term afterslip and/or a complicated response due to the highly heterogeneous structure suggested by seismic tomography studies.