Nankai Forearc Structural and Seismogenic Segmentation Caused by a Magmatic Intrusion off the Kii Peninsula
Nankai Forearc Structural and Seismogenic Segmentation Caused by a Magmatic Intrusion off the Kii Peninsula
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DOI：
10.1029/2022gc010331
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发表时间：
2022-07
期刊：
影响因子：
3.7
通讯作者：
G. Kimura;Y. Nakamura;K. Shiraishi;G. Fujie;S. Kodaira;T. Tsuji;R. Fukuchi;A. Yamaguchi
中科院分区：
文献类型：
--
作者：
G. Kimura;Y. Nakamura;K. Shiraishi;G. Fujie;S. Kodaira;T. Tsuji;R. Fukuchi;A. Yamaguchi
弧前盆地和巨型逆冲断裂带分割的原因存在争议。日本南海弧前根据地形分为五个域：远州、熊野、室户、土佐和日向。这些区域的边界对应于大地震的破裂极限。我们利用多道地震反射数据检查了纪伊半岛附近熊野域和室户域之间边界区域的地质结构，以评估上部板块成分在控制分割中的作用。结果表明，在盐岬近海地区，厚覆盖层沉积物和下伏的增生棱柱在火成基底杂岩上向陆地倾斜，并分隔了弧前盆地。 1944年东南海地震和1946年南海地震震源区直接覆盖板块界面的火成岩基底杂岩。 1944年的地震起源于杂岩体的底部，破裂范围滑过其基底边界，而1946年的地震则在基底杂岩体的上倾边界处成核。致密的火成岩可能作为发震巨型逆冲断层的重载屏障，分隔了两次地震的破裂区域。上板块地质可能是控制南海海槽地震发生的重要因素，并可为了解其他俯冲带巨型逆冲滑动的控制提供范例。
The causes for forearc basin and megathrust rupture zone segmentation are controversial. The Nankai forearc, Japan, is separated into five domains based on topography: Enshu, Kumano, Muroto, Tosa, and Hyuga. The boundaries of these domains correspond to the rupture limits of large earthquakes. We examined the geologic structure of the boundary region between the Kumano and Muroto domains off the Kii Peninsula using multichannel seismic reflection data to evaluate the role of upper plate composition in controlling segmentation. The results suggest that thick cover sediments and underlying accretionary prism are obliquely thrust landward over the igneous basement complex rock in the region of offshore of Cape Shionomisaki and separate the forearc basin. The igneous basement complex rocks directly overlying the plate interface in the hypocentral regions of 1944 Tonankai and 1946 Nankai earthquakes. The 1944 earthquake originated at the base of the complex, and the rupture extent slipped past its basement boundary, whereas the 1946 event nucleated at the updip boundary of the basement complex. The dense igneous rocks might have worked as a heavily loaded barrier on the seismogenic megathrust and separated the rupture area of both the earthquakes. Upper plate geology may be an important factor in controlling seismogenesis in the Nankai Trough and may serve as an example for understanding the controls on megathrust slip in other subduction zones.