BUOYANT ZONES, GREAT EARTHQUAKES, AND UNSTABLE BOUNDARIES OF SUBDUCTION
BUOYANT ZONES, GREAT EARTHQUAKES, AND UNSTABLE BOUNDARIES OF SUBDUCTION
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DOI：
10.1029/jb081i026p04885
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发表时间：
1976-01-01
影响因子：
--
通讯作者：
MCCANN, W
中科院分区：
文献类型：
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作者：
KELLEHER, J;MCCANN, W
沿俯冲边界的浅层大地震的分布与从简单的板块构造模型中可以预测的分布模式不一致。也就是说，在有记录的历史中，沿着一些岛弧的大片区域，大地震很少发生或根本没有发生过。这些长期静止区中的大多数几乎与边缘的部分相连，在那里，海山、无地震海脊或俯冲板块的其他水深高点似乎正在与俯冲过程相互作用。这种空间相关性表明，至少部分长期的大地震缺失可能是构造成因造成的，而不是应变积累的暂时间隔造成的。在许多情况下，隆起与活动海沟相互作用的地带的特点还包括几乎没有低角度推进型机制，中等深度震中存在缺口，活火山线存在缺口和偏移量。因此，在重要的水深特征与会聚边缘相互作用的地方，可能会发生与经典俯冲活动的重大背离。为了解释这些观测，我们倾向于这样的假设，即无震脊或其他隆起区可能划定了大洋岩石圈的区域，这些区域相对浮力较大，在与活动海沟碰撞时抵抗俯冲。因此，代替“典型的”大洋岩石圈，大洋岩石圈可能存在广泛的平均密度谱，俯冲边缘附近的俯冲和逆冲板块的相对浮力可能对俯冲构造的发展和大地震的位置和频率起主导作用。
The distribution of large shallow earthquakes along subduction boundaries does not agree with the distribution pattern that might be predicted from a simple model of plate tectonics. That is, along extensive sections of some island arcs, large shocks occurred infrequently or not at all during recorded history. Most of these zones of long‐term quiescence are nearly coterminous with segments of the margin where zones of seamounts, aseismic ridges, or other bathymetric highs of the underthrust slab appear to be interacting with the subduction process. This spatial correlation suggests that at least some of the long‐term absences of great shocks may result from a tectonic origin and not from temporary intervals of strain accumulation. The zones where rises interact with active trenches are also characterized in many instances by a near absence of low‐angle thrust type mechanisms, by gaps in intermediate depth hypocenters, and by gaps and offsets in the line of active volcanoes. Thus major departures from classic subduction activity may develop where significant bathymetric features interact with a convergent margin. To explain these observations, we favor the hypothesis that aseismic ridges or other uplifted regions may delineate zones of oceanic lithosphere which are relatively buoyant and resist subduction upon collision with an active trench. In place of ‘typical’ oceanic lithosphere therefore there may exist a broad spectrum of average densities for oceanic lithosphere, and the relative buoyancy of both the underthrusting and the overthrusting slabs near the subducting margin may be a dominant influence in the development of subduction tectonics and in the locations and frequency of great earthquakes.