Seismic velocity structure in the source region of the 2016 Kumamoto earthquake sequence, Japan
Seismic velocity structure in the source region of the 2016 Kumamoto earthquake sequence, Japan
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DOI：
10.1002/2017gl074593
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发表时间：
2017-08-16
影响因子：
5.2
通讯作者：
Okubo, Makoto
中科院分区：
文献类型：
--
作者：
Shito, Azusa;Matsumoto, Satoshi;Okubo, Makoto
研究了2016年熊本地震序列震源区的地震波速结构和地震活动性的空间分布。一维平均速度表明，相对于九州岛的平均速度结构，孕震带具有高速度和低Vp/VS比值。这表明地壳相对较强，能够维持足够高的应变能，以促进两次快速相继发生的大地震(M-j>；6.5)。对2016年熊本地震序列震源周围孕震带进行三维层析成像，得到Vp=6公里/S，Vs=3.5公里/S。7.3级地震的大部分大位移区(凹凸体)与孕震带和上覆表层重叠。余震活动分布在比常规孕震带更深的地方，这表明由于流体或应力增加而导致的强度降低，两者都是由同震滑动引起的。
We investigate seismic wave velocity structure and spatial distribution of the seismicity in the source region of the 2016 Kumamoto earthquake sequence. A one-dimensional mean velocity shows that the seismogenic zone has a high-velocity and low-Vp/Vs ratio relative to the average velocity structure of Kyushu Island. This indicates that the crust is relatively strong, capable of sustaining sufficiently high strain energy to facilitate two large (M-j > 6.5) earthquakes in close proximity to one another in rapid succession. Three-dimensional tomography of the seismogenic zone around the source of the 2016 Kumamoto earthquake sequence yields Vp = 6 km/s and Vs = 3.5 km/s. Most large-displacement areas (asperities) of the M-j 7.3 event overlap with the seismogenic zone and the overlying surface layer. Aftershock seismicity is distributed deeper than the conventional seismogenic zone, which suggests decreased strength due to fluids or increased stress, both caused by coseismic slip.