The postseismic response to the 2002 M 7.9 Denali Fault earthquake: constraints from InSAR 2003-2005
The postseismic response to the 2002 M 7.9 Denali Fault earthquake: constraints from InSAR 2003-2005
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DOI：
10.1111/j.1365-246x.2008.03932.x
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发表时间：
2009-02-01
影响因子：
2.8
通讯作者：
Wright, Tim
中科院分区：
文献类型：
--
作者：
Biggs, Juliet;Burgmann, Roland;Wright, Tim
InSAR对垂直位移特别敏感，这在区分对大地震(余滑、粘弹性松弛)的震后反应的机制方面可能很重要。我们使用加拿大Radarsat-1卫星2003年夏季、2004年夏季和2005年夏季的数据，制作了2002年德纳利断层地震震后反应产生的地表位移地图。在2003年夏季至2004年夏季期间，在卫星视线上观测到了幅度为4厘米的峰谷信号。到2004年夏季至2005年夏季期间，移位率已降至InSAR在一年内进行观测所需的门槛以下。InSAR观测结果表明，震后主要弛豫过程的深度约为50公里，相当于地幔的顶部。然而，观测仍然不能区分分布变形(粘弹性松弛)和局部变形(后滑移)。施加的同震应力在下地壳最高，假设麦克斯韦流变学，要求下地壳和上地幔之间的粘度比至少为5才能解释这种行为差异。最低的失配是由地幔的粘弹性松弛和上地壳的浅层后滑的混合模型产生的。垂直于断层的剖面显示出明显的不对称性，这与断层上流变结构的差异是一致的。
InSAR is particularly sensitive to vertical displacements, which can be important in distinguishing between mechanisms responsible for the postseismic response to large earthquakes (afterslip, viscoelastic relaxation). We produce maps of the surface displacements resulting from the postseismic response to the 2002 Denali Fault earthquake, using data from the Canadian Radarsat-1 satellite from the periods summer 2003, summer 2004 and summer 2005. A peak-to-trough signal of amplitude 4 cm in the satellite line of sight was observed between summer 2003 and summer 2004. By the period between summer 2004 and summer 2005, the displacement rate had dropped below the threshold required for observation with InSAR over a single year. The InSAR observations show that the principal postseismic relaxation process acted at a depth of similar to 50 km, equivalent to the top of the mantle. However, the observations are still incapable of distinguishing between distributed (viscoelastic relaxation) and localized (afterslip) deformation. The imposed coseismic stresses are highest in the lower crust and, assuming a Maxwell rheology, a viscosity ratio of at least 5 between lower crust and upper mantle is required to explain the contrast in behaviour. The lowest misfits are produced by mixed models of viscoelastic relaxation in the mantle and shallow afterslip in the upper crust. Profiles perpendicular to the fault show significant asymmetry, which is consistent with differences in rheological structure across the fault.