Temporal variation of frictional strength in an earthquake swarm in NE Japan caused by fluid migration
Temporal variation of frictional strength in an earthquake swarm in NE Japan caused by fluid migration
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日本东北部地震群中流体迁移引起的摩擦强度随时间变化
DOI：
10.1002/2016jb013022
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Takeyoshi Yoshida
中科院分区：
文献类型：
--
作者：
Keisuke Yoshida;A. Hasegawa;Takeyoshi Yoshida
根据山形-福岛边界震群震源区震源机制的多样性，研究了断层摩擦强度的时间变化，山形-福岛边界震群是日本东北部中部发生的一个重要震群，发生在2011年M9.0 Tohoku-Oki地震之后。使用P波极性数据以及直接P波的短周期（1.5-2.5 Hz）波形数据确定了该震群活动中事件的震源机制。通过对震源机制解资料进行应力张量反演，得到了震源区的应力场。基于估计的应力场，在均匀应力的假设下，我们计算了各个震源机制的相对摩擦强度。计算出的相对摩擦强度在一个很宽的范围内变化，但它们的平均值表现出一种特征性的时间变化，这种变化起初很小，但随着时间的推移在100至150天内稳步增加，然后变得近似恒定。通过假定应力是不均匀的，我们证实了平均相对摩擦强度随时间的变化。即使在这些情况下，也获得了平均相对摩擦强度的类似时间变化，证实了这种变化。观测到的平均相对摩擦强度随时间变化的最可能原因是震群源区孔隙流体压力随时间变化，这是由东北冲地震和随后的流体扩散促成的。
Temporal variations of the fault frictional strength was investigated based on the diversity of focal mechanisms in the source area of the Yamagata‐Fukushima border earthquake swarm, a significant earthquake swarm that occurred in central Tohoku, NE Japan, which started just after the 2011 M9.0 Tohoku‐Oki earthquake. The focal mechanisms of events in this swarm activity were determined using P wave polarity data as well as short‐period (1.5–2.5 Hz) waveform data from the direct P wave. The stress field in the source area of this swarm was estimated by applying stress tensor inversions to these focal mechanism data. Based on the estimated stress field, and under the assumption of uniform stress, we calculated relative frictional strengths for individual focal mechanisms. The calculated relative frictional strengths vary over a wide range, but their average value exhibits a characteristic temporal variation, which is at first small, but steadily increases with time for 100 to 150 days, and then becomes approximately constant. We confirmed this characteristic temporal variation of the average relative frictional strength by assuming the stress to be nonuniform. Similar temporal variations of the average relative frictional strength are obtained for even these cases, confirming the variation. The most likely cause for the observed temporal variation of the average relative frictional strength is the temporal variation of the pore fluid pressure in the source area of the swarm, facilitated by the Tohoku‐Oki earthquake and the subsequent fluid diffusion.
DOI：
10.5047/eps.2011.06.014
发表时间：
2011-09
期刊：
Earth, Planets and Space
影响因子：
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作者：
A. Kato;S. Sakai;K. Obara
通讯作者：
A. Kato;S. Sakai;K. Obara
影响因子：
3
作者：
Y. Okada
通讯作者：
Y. Okada
H.264编码器DCT的硬件实现及其评估
DOI：
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发表时间：
2009
期刊：
影响因子：
--
作者：
Choong Geun Lee;V. G. Moshnyaga and K. Hashimoto;宮田康治
通讯作者：
宮田康治