Geometry and spatial variations of seismic reflection intensity of the upper surface of the Philippine Sea plate off the Boso Peninsula, Japan
Geometry and spatial variations of seismic reflection intensity of the upper surface of the Philippine Sea plate off the Boso Peninsula, Japan
复制标题
日本房总半岛菲律宾海板块上表面地震反射强度的几何形状和空间变化
DOI：
10.1016/j.tecto.2017.05.001
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发表时间：
2017
期刊：
影响因子：
2.9
通讯作者：
Azuma Ryousuke
中科院分区：
文献类型：
--
作者：
Kono Akihiro;Sato Toshinori;Shinohara Masanao;Mochizuki Kimihiro;Yamada Tomoaki;Uehira Kenji;Shinbo Takashi;Machida Yuya;Hino Ryota;Azuma Ryousuke
在日本博索半岛附近，太平洋板块在本州岛弧和菲律宾海板块下向西俯冲，而菲律宾海板块在本州岛弧下向西北俯冲。这些复杂的构造相互作用导致了过去发生的许多地震事件。为了更好地理解这些地震事件，确定板块边界的几何形状，特别是菲律宾海板块的上表面，是很重要的。我们在2009年7月和8月进行了一次有源地震折射调查，从中获得了沿216公里剖面的二维纵波速度结构模型。我们使用速度模型和先前发表的数据表明，俯冲的菲律宾海板块上表面的纵波速度为5.0 km/s，以划定其与上覆的本州岛弧的边界。我们对菲律宾海板块上表面的等深等高线显示，它的倾角很浅，深度为10至15公里，远离博索半岛。这种浅倾斜可能是由于太平洋板块板块的干扰，太平洋板块板块在菲律宾海板块下向西俯冲。在我们的调查数据中，我们识别出许多不同强度的地震反射，其中一些来自菲律宾海板块的上表面。地震反射强度高的区域与博索慢滑事件的主滑区相对应。我们的模拟表明，这些反射可以用靠近菲律宾海板块上表面的非均匀层来解释。
In the region off the Boso Peninsula, Japan, the Pacific plate is subducting westward beneath both the Honshu island arc and Philippine Sea plate, while the Philippine Sea plate is subducting northwestward beneath the Honshu island arc. These complex tectonic interactions have caused numerous seismic events occurred in the past. To better understand these seismic events, it is important to determine the geometry of the plate boundary, in particular the upper surface of the Philippine Sea plate. We conducted an active-source seismic refraction survey in July and August 2009 from which we obtained a 2-D P-wave velocity structure model along a 216-km profile. We used the velocity model and previously published data that indicate a P-wave velocity of 5.0 km/s for the upper surface of the subducting Philippine Sea plate to delineate its boundary with the overriding Honshu island arc. Our isodepth contours of the upper surface of the Philippine Sea plate show that its dip is shallow at depths of 10 to 15 km, far off the Boso Peninsula. This shallow dip may be a result of interference from the Pacific plate slab, which is subducting westward under the Philippine Sea plate. Within our survey data, we recognized numerous seismic reflections of variable intensity, some of which came from the upper surface of the Philippine Sea plate. An area of high seismic reflection intensity corresponds with the main slip area of the Boso slow slip events. Our modeling indicates that those reflections can be explained by an inhomogeneous layer close to the upper surface of the Philippine Sea plate.