Focal zone of a future Tokai earthquake inferred from the seismicity pattern around the plate interface
Focal zone of a future Tokai earthquake inferred from the seismicity pattern around the plate interface
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DOI：
10.1016/s0040-1951(96)00277-6
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发表时间：
1997-05-30
期刊：
影响因子：
2.9
通讯作者：
Matsumura, S
中科院分区：
文献类型：
--
作者：
Matsumura, S
自1976年发布首次警报以来，未来东海大地震一直被认为是日本列岛中部即将发生的灾难中最紧迫的问题。最近的观测进展提供了大量数据，从而使详细调查成为可能。本研究基于微地震数据的地震活动性和震源机制模式，对控制东海地区周围板块相互作用的力学状况进行了调查。研究发现，俯冲菲律宾海板块的地震活动由三个特征活动组组成：滨名湖下方有强烈的活动，从滨名湖向西北延伸的线性星团，以及在骏河湾西部内陆地区扩展的广阔星团。我们认为这些活动发生在俯冲洋壳内部，反映了当前作用在那里的应力状态。假设引发这些活动的机制来自两个应力源：板的横向拉伸以及两块板之间的部分锁定。这种解释导致了这样的假设：骏河湾西部的大群代表了由于锁定而产生的应力集中。滨名湖下方的活动被认为代表了那里引起的剪切运动，并被解释为形成了 1944 年东南海地震和未来东海大地震的破裂带之间的边界。这些分析结果确定，从骏河湾西海岸延伸到滨名湖的广阔内陆地区是未来东海地震的震源区。本研究提出的区域表明其走向与石桥提出的原始模型存在显着偏差，前者与南海海槽平行，而后者与骏河海槽平行。
A future large Tokai earthquake has been considered to be the most urgent problem of impending disasters in the central part of the Japanese islands since the first warning was announced in 1976. Recent progress in observations has provided a great amount of data, thus making a detailed investigation possible. In this study, based on the seismicity and the focal mechanism patterns of microearthquake data, the mechanical situation that governs plate interactions around the Tokai district was investigated. It was found that the seismicity in the subducting Philippine Sea slab is composed of three characteristic groups of activities; intense activity beneath Lake Hamana, a linear cluster extending from Lake Hamana toward the northwest, and a broad cluster expanding over the inland area in the west of Suruga Bay. We propose that these activities occur inside the subducting oceanic crust and reflect the present stress state acting there. The mechanism inducing these activities is assumed to come from two stress sources: the lateral stretching of the slab, and the partial locking between both plates. This interpretation leads to the hypothesis that the broad cluster in the west of Suruga Bay represents a stress concentration due to locking. The activity beneath Lake Hamana is proposed to represent shearing motion induced there, and is interpreted to form the boundary between the rupture zones of the 1944 Tonankai earthquake and a future large Tokai earthquake. These analyses resulted in identifying the wide inland area extending from the west coast of Suruga Bay to Lake Hamana to be a focal zone of a future Tokai earthquake. The zone proposed in this study indicates a significant deviation in its strike from the original model proposed by Ishibashi, in that the former parallels the Nankai trough, while the latter parallels the Suruga trough.