Late Pleistocene crustal uplift and gravity anomaly in the eastern part of Kyushu, Japan, and its geophysical implications
Late Pleistocene crustal uplift and gravity anomaly in the eastern part of Kyushu, Japan, and its geophysical implications
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DOI：
10.1016/s0040-1951(02)00161-0
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发表时间：
2002-07
期刊：
影响因子：
2.9
通讯作者：
M. Nakada;M. Tahara;H. Shimizu;S. Nagaoka;K. Uehira;Sadaomi Suzuki
中科院分区：
文献类型：
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作者：
M. Nakada;M. Tahara;H. Shimizu;S. Nagaoka;K. Uehira;Sadaomi Suzuki
日本九州东部的宫崎平原在晚更新世和全新世具有显著的重力负异常和地震地壳隆升（~ 1 mm/年）的特征。我们研究了这两种现象之间的关系，这可能为九州-帕劳脊与前弧的碰撞和/或俯冲之间的相互作用提供重要的约束。利用上地壳重力异常和纵波速度结构估计了11km深度以下的质量缺失。荷载积累的起始时间为0.5 ~ 0.4 Ma，是根据河流阶地的运动来推断的。假定荷载历史是时间的线性函数。我们通过假设在20或30公里深度存在底板载荷的粘弹性板块变形来评估地壳反弹。岩石圈（地壳）黏度为1023 ~ 1024pa s的模型预测的地壳运动可以解释末次间冰期约125 kyr BP和全新世中期5 ~ 6 kyr BP形成的海相阶地岸线的观测高度。虽然我们不能限制浮力体的起源，九州-帕劳脊的俯冲，与四国盆地弧后开口有关的残弧，可能与这里所研究的隆升区域的浮力有关。另一方面，宫崎平原附近的浮力体可能在俯冲洋板与上覆弧前地壳的相互作用中起着重要作用。因此，在南开槽辐合边界上观测到的板块间耦合的横向变化可能归因于浮力体的存在。
The Miyazaki Plain, eastern part of Kyushu, Japan, is characterized by both significant negative gravity anomalies and aseismic crustal uplifting (∼1 mm/year) in the Late Pleistocene and Holocene. We examine the relationship between these two phenomena, which may provide important constraints on the interaction between the collision and/or subduction of the Kyushu-Palau Ridge and the forearc. We estimate the mass deficiency below 11-km depth by using the gravity anomalies and P-wave velocity structure of the upper crust. The onset of the load accumulation, 0.5–0.4 Ma, is inferred from the movement of the fluvial terraces considering the tephrochronology. The loading history is assumed to be a linear function of time. We evaluate the crustal rebound by assuming a viscoelastic plate deformation with an underplating load existing at 20- or 30-km depth. The predicted crustal movement for models with a lithospheric (crustal) viscosity of 1023–1024Pa s can explain the observed altitudes of the shoreline of the marine terraces formed at the Last Interglacial of about 125 kyr BP and the middle Holocene of 5–6 kyr BP. Although we cannot restrict the origin of the buoyant body, the subduction of the Kyushu-Palau Ridge, remnant arc associated with back-arc opening of the Shikoku Basin, may be related to the buoyancy for the uplifting region examined here. On the other hand, the buoyant body off the Miyazaki Plain probably plays an important role in the interaction between the subducting oceanic slab and the overriding forearc crust. Thus, the observed lateral variation of the interplate coupling on the convergent boundary along the Nankai Trough may be attributed to the existence of the buoyant body.