New hypothesis to explain Quaternary forearc deformation and the variety of plate boundary earthquakes along the Suruga–Nankai Trough by oblique subduction of undulations on the Philippine Sea Plate
New hypothesis to explain Quaternary forearc deformation and the variety of plate boundary earthquakes along the Suruga–Nankai Trough by oblique subduction of undulations on the Philippine Sea Plate
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通过菲律宾海板块起伏的倾斜俯冲来解释第四纪弧前变形和沿骏河-南海海槽的板块边界地震的变化的新假说
DOI：
10.1186/s40623-020-01183-5
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发表时间：
2020
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通讯作者：
M. Shishikura
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作者：
Y. Okamura;M. Shishikura
沿骏河-南海海槽俯冲带沿着的8级或更大的板块边界地震每隔90-150年重复一次，但震级和破裂区域变化很大。我们建议，根据地质资料的地壳运动的弧前楔，这些地震的变化是由两个独立的锁定区在较深的部分板块边界。长波地形起伏，由交替带的隆起和沉降沿着弧前楔，与2000至3000米的垂直浮雕，在第四纪积累。我们认为，这在弧前楔的地壳变形是由地震周期中的应力加载和释放，而是由垂直位移的板块边界所造成的波动在菲律宾海板块的斜向俯冲板块向西运动，因为它俯冲到日本西南部。对海贝壳化石的年代测定表明，位于海槽中部的隆起带纪伊山脉每隔400-600年发生一次隆升事件，最近一次隆升事件发生在1707年会荣大地震使整个板块边界沿海槽沿着断裂之时。我们推断，纪伊山脉下的板块边界是一个锁定带，该带的滑动，伴随着整个板块边界的断裂，通过减少板块边界深度引起山脉的隆起。在海槽东缘沿着的赤石山脉隆起带下推断出一个类似的锁定带，1854年的安西地震对可能是由该带的滑动引起的。在1854年的两次事件中，纪伊山脉下的锁定区可能限制了海槽东半部的破裂传播，然后在32小时内海槽西半部破裂。这些闭锁带被推断为每几百年独立滑动一次，并决定了骏河-南海海槽沿着特征断裂的主要模式。
Plate-boundary earthquakes of magnitude 8 or greater along the Suruga–Nankai Trough subduction zone have repeated at intervals of 90–150 years, but with widely varying magnitudes and rupture areas. We propose, based on geologic data on crustal movements of the forearc wedge, that these earthquake variations are controlled by two separate locked zones in the deeper part of the plate boundary. Long-wavelength topographic undulations, composed of alternating zones of uplift and subsidence along the forearc wedge, are associated with 2000 to 3000 m of vertical relief that has accumulated during Quaternary time. We suggest that this crustal deformation in the forearc wedge is caused not by stress loading and release during earthquake cycles, but rather by vertical displacements of the plate boundary caused by the westward movement of undulations in the obliquely subducting slab of the Philippine Sea Plate as it subducts beneath Southwest Japan. Dating of emergent marine shell fossil assemblages shows that the Kii Mountains, an uplift zone at the midpoint of the trough, has undergone uplift events at intervals of 400–600 year, and the latest event of those occurred when the 1707 Hoei earthquake ruptured the entire plate boundary along the trough. We infer that the plate boundary under the Kii Mountains is a locked zone and that slips of this zone, which accompanied ruptures of the entire plate boundary, caused uplift of the mountains by decreasing the plate boundary depth. A similar locked zone is inferred under the uplift zone of the Akaishi Mountains, along the eastern margin of the trough, and the 1854 Ansei earthquake pair was presumably caused by the slip of this zone. During the two 1854 events, the locked zone under the Kii Mountains presumably restricted the rupture propagation to the eastern half of the trough, then a rupture of the western half of the trough followed within 32 h. These locked zones are inferred to slip independently every few hundred years and determine the major patterns of characteristic ruptures along the Suruga–Nankai Trough.
(1)《化工日报》，2011 年 1 月 12 日
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