南海海槽巨型冲断带板间耦合的海底大地测量约束
Seafloor geodetic constraints on interplate coupling of the Nankai Trough megathrust zone
摘要：
板间逆冲断层地震给人类社会带来了灾难性的破坏。一个极其危险的大推力地震预计将发生在日本西南部的南海海槽，这是一个经济活跃和人口稠密的地区，有大推力地震的历史记录。大型逆冲断层地震是板块俯冲机制的结果，发生在板间滑动亏损（或耦合）区域。过去的许多研究都试图捕捉滑失亏损率（SDR）的分布，以评估未来的地震灾害。然而，由于没有海底大地测量数据，他们无法捕捉到巨型逆冲断层震源区的全貌。日本海岸警卫队水文和海洋部一直在开发一个部署在这一俯冲带的高精度和可持续的海底大地测量观测网络，以广泛获取与近海SDR有关的直接信息。在这里，我们提出了海底大地测量观测数据和离岸板间SDR分布模型。我们的数据表明，在这个俯冲带的大多数近海地区有积极的SDR。具体而言，我们的观察表明，以前未知的高SDR地区是重要的海啸灾害缓解和低SDR地区是一致的分布浅慢地震和俯冲海山。这是第一个直接的证据表明，耦合条件与这些地震地质现象。这些观测结果为推断南海海槽俯冲带的大规模逆冲断层地震情景和解释研究提供了新的基础信息。
英文摘要：
Interplate megathrust earthquakes have inflicted catastrophic damage on human society. An extremely hazardous megathrust earthquake is predicted to occur along the Nankai Trough off southwestern Japan, an economically active and densely populated area with historical records of megathrust earthquakes. Megathrust earthquakes are the result of a plate subduction mechanism and occur at interplate slip-deficit (or coupling) regions. Many past studies have attempted to capture slip-deficit rate (SDR) distributions for assessing future earthquake disasters. However, they could not capture a total view of the megathrust earthquake source region because they had no seafloor geodetic data. The Hydrographic and Oceanographic Department of the Japan Coast Guard (JHOD) has been developing a highly precise and sustainable seafloor geodetic observation network deployed in this subduction zone to broadly obtain direct information related to offshore SDR. Here, we present seafloor geodetic observation data and an offshore interplate SDR distribution model. Our data suggests that most offshore regions in this subduction zone have positive SDRs. Specifically, our observations indicate previously unknown high-SDR regions that are important for tsunami disaster mitigation and low-SDR regions that are consistent with distributions of shallow slow earthquakes and subducting seamounts. This is the first direct evidence suggesting that coupling conditions are related to these seismological and geological phenomena. These observations provide new fundamental information for inferring megathrust earthquake scenarios and interpreting research on the Nankai Trough subduction zone.
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