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.

中文翻译：

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通过菲律宾海板块起伏倾斜俯冲解释第四纪弧前变形和骏河-南海海槽板块边界地震变化的新假说

沿着骏河-南海海槽俯冲带发生的 8 级或更大的板块边界地震每隔 90-150 年重复发生一次，但震级和破裂区域差异很大。我们根据弧前楔地壳运动的地质数据提出，这些地震变化是由板块边界较深部分的两个独立锁定带控制的。长波长地形起伏由沿前弧楔的隆起和下沉交替带组成，与第四纪期间积累的 2000 至 3000 米的垂直起伏有关。我们认为弧前楔中的这种地壳变形不是由地震循环期间的应力加载和释放引起的，而是由于菲律宾海板块俯冲在日本西南部下方时，其倾斜俯冲板片中的起伏向西运动引起的板块边界的垂直位移。海相贝类化石组合的年代测定表明，位于海槽中点的隆起带纪伊山脉每隔 400 ～ 600 年就发生过一次隆起事件，其中最近一次发生在 1707 年的会荣地震使整个海槽破裂时。沿槽的板块边界。我们推断纪伊山脉下方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破裂，通过降低板块边界深度导致山脉隆升。在赤石山脉的隆起带下推断出类似的锁定带，沿着海槽的东缘，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，纪伊山脉下的锁定带可能限制了向槽东半部的破裂扩展，然后在 32 小时内发生了槽西半部的破裂。据推测，这些锁定带每隔几百年独立滑动一次，并决定了沿骏河-南海海槽的特征破裂的主要模式。