Long‐ and short‐term postseismic gravity changes of megathrust earthquakes from satellite gravimetry
Long‐ and short‐term postseismic gravity changes of megathrust earthquakes from satellite gravimetry
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DOI：
10.1002/2014gl060559
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发表时间：
2014-08
影响因子：
5.2
通讯作者：
Yusaku Tanaka;K. Heki
中科院分区：
文献类型：
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作者：
Yusaku Tanaka;K. Heki
利用卫星重力月报资料，研究了2004年苏门答腊-安达曼、2010年智利(茂勒)和2011年东北地区三次9级地震后的时变重力场。观测表明，重力通常(1)同震性下降，(2)持续下降几个月，(3)在较长时间内增加。因此，震后重力变化有两个不同时间常数和不同极性的分量。震后重力短期和长期变化的机制目前还不像同震变化那样清楚，但可以分别用余滑和Maxwell粘弹性在一定程度上解释。这两个分量很难与表面速度测量区分开来，因为弧前区域在两个阶段都向沟槽方向移动。它们在重力中表现为不同的极性，使卫星重力测量成为区分它们的独特工具。
Using monthly satellite gravimetry data, we studied time‐variable gravity field after three M9 class earthquakes, the 2004 Sumatra‐Andaman, 2010 Chile (Maule), and 2011 Tohoku‐oki earthquakes. The observations showed that the gravity typically (1) decreases coseismically, (2) continues to decrease for a few months, and (3) increases over a longer period. Therefore, postseismic gravity changes have two components with different time constants and polarities. The mechanisms of short‐ and long‐term postseismic gravity changes are not as clear as coseismic changes at the moment, but might be explained to some extent with afterslip and the Maxwell viscoelasticity, respectively. These two components are difficult to discriminate with surface velocity measurements because the forearc area moves trenchward at both stages. They appear in different polarities in gravity, making satellite gravimetry a unique tool to separate them.