A kinematic model for evolution of island arc-trench systems
A kinematic model for evolution of island arc-trench systems
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岛弧-海沟系统演化的运动学模型
DOI：
10.1111/j.1365-246x.1993.tb06984.x
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发表时间：
1993
影响因子：
2.8
通讯作者：
M. Matsu'ura
中科院分区：
文献类型：
--
作者：
Toshinori Sato;M. Matsu'ura
板块俯冲带的典型特征是由岛弧高、海沟低和外隆平缓高组成的地表地形和重力异常模式。在106-107年的时间尺度上，这些图象是稳定的。在一些俯冲带，无论其年龄，也可以观察到稳定的上升的海平面变化形成的海阶在过去10 - 5年。地形和重力异常的稳定模式与海洋阶地的稳定抬升似乎相互矛盾。我们建立了一个可以解释岛弧-海沟系统演化过程的运动学模型，并证明了这个难题可以通过考虑板块边界的吸积效应来解决。在我们的模型中，岩石圈-软流圈系统是由一个分层的粘弹性重力半空间，它包括一个高粘度的表层和一个低粘度的底层。两层的流变特性被假定为剪切的麦克斯韦流体和散装的弹性固体。大洋板块和大陆板块之间的相互作用表现为板块边界切向位移不连续性的稳定增加。在我们的模型中考虑的其他基本因素是海洋沉积物在板块边界的加积，对土地的侵蚀，并在沟槽内壁的沉积。利用运动学模型计算了岛弧-海沟系统的演化过程，得到了以下结果：在板块俯冲的早期，岛弧-海沟系统几乎以恒定的速率生长。因此，在年轻的俯冲带，我们通常可以预期海洋阶地的稳定抬升。稳定的地形和重力异常格局是在板块俯冲开始后的几百万年内形成的。当增生过程在板块边界不断进行时，这些稳定的模式作为一个整体逐渐向海洋迁移。在这种情况下，我们可以预期，即使在古老的俯冲带，海洋阶地也会稳步上升。我们证明，我们的模型可以一致地解释所观察到的表面地形，重力异常，和隆起率的海洋阶地在俯冲带。
SUMMARY Plate subduction zones are typically characterized by the patterns of surface topography and gravity anomalies consisting of island-arc high, trench low, and outer-rise gentle high. These patterns are stable on the time scale of 106-107 yr. At some subduction zones, regardless of its age, steady uplift of marine terraces formed by eustatic sea-level changes during the last lo5 yr can be also observed. The stable patterns of topography and gravity anomalies and the steady uplift of marine terraces seem to contradict each other. We constructed a kinematic model which could explain the evolution process of island arc-trench systems and demonstrated that this puzzle could be solved by considering the effect of accretion at plate boundaries. In our model the lithosphere-asthenosphere system is represented by a stratified visco-elastic half-space under gravity, which consists of a high-viscosity surface layer and a low-viscosity substratum. The rheological properties of both layers are assumed to be a Maxwell fluid in shear and an elastic solid in bulk. Interaction between oceanic and continental plates is represented by the steady increase of discontinuity in tangential displacement across the plate boundary. The other essential factors considered in our model are accretion of oceanic sediments at plate boundaries, erosion on land, and sedimentation on inner trench wall. We computed the evolution process of island arc-trench systems by using the kinematic model and obtained the following results: the island arc-trench systems grow at nearly constant rates in the early stage of plate subduction. Therefore, at young subduction zones, we can generally expect the steady uplift of marine terraces. The stable patterns of topography and gravity anomalies are formed within several million years after the initiation of plate subduction. When the accretion process continuously proceeds at plate boundaries, these stable patterns gradually migrate seaward as a whole. In such a case, we can expect the steady uplift of marine terraces even at old subduction zones. We demonstrate that our model can consistently explain the observed surface topography, gravity anomalies, and uplift rates of marine terraces at subduction zones.