Tomography of the 2016 Kumamoto earthquake area and the Beppu-Shimabara graben.
Tomography of the 2016 Kumamoto earthquake area and the Beppu-Shimabara graben.
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DOI：
10.1038/s41598-018-33805-0
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发表时间：
2018-10-19
影响因子：
4.6
通讯作者：
Toyokuni G
中科院分区：
文献类型：
--
作者：
Zhao D;Yamashita K;Toyokuni G
以2016年熊本地震（M7.3）的震源区为研究对象，测定了日本西南部九州地区地壳和上地幔的P波、S波速度和泊松比（σ）的详细三维图像，震源区位于存在4座活火山和许多活断层的别府岛原地堑（BSG）。2016年熊本地震发生在上地壳的高速低σ带，该带被上地幔的低速高σ异常所包围和覆盖。这一结果表明，在2016年熊本地震的震源区及其周围，存在与活火山和岩浆流体有关的强烈结构不均匀性，这可能会影响地震成因。沿着BSG，低速高σ异常并不是在上地幔各处都存在，而是主要存在于活火山下方，表明热地幔上涌不是地堑形成的唯一原因。冲绳海槽向北延伸、中央构造线向西延伸以及活火山下地幔楔热涌流共同作用形成了冲绳海槽。
Detailed three-dimensional images of P and S wave velocity and Poisson’s ratio (σ) of the crust and upper mantle beneath Kyushu in SW Japan are determined, with a focus on the source area of the 2016 Kumamoto earthquake (M 7.3) that occurred in the Beppu-Shimabara graben (BSG) where four active volcanoes and many active faults exist. The 2016 Kumamoto earthquake took place in a high-velocity and low-σ zone in the upper crust, which is surrounded and underlain by low-velocity and high-σ anomalies in the upper mantle. This result suggests that, in and around the source zone of the 2016 Kumamoto earthquake, strong structural heterogeneities relating to active volcanoes and magmatic fluids exist, which may affect the seismogenesis. Along the BSG, low-velocity and high-σ anomalies do not exist everywhere in the upper mantle but mainly beneath the active volcanoes, suggesting that hot mantle upwelling is not the only cause of the graben. The BSG was most likely formed by joint effects of northward extension of the Okinawa Trough, westward extension of the Median Tectonic Line, and hot upwelling flow in the mantle wedge beneath the active volcanoes.
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影响因子：
5.3
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