Segmentation in continental forearcs: Links between large-scale overriding plate structure and seismogenic behavior associated with the 2010 M 8.8 Maule, Chile earthquake
Segmentation in continental forearcs: Links between large-scale overriding plate structure and seismogenic behavior associated with the 2010 M 8.8 Maule, Chile earthquake
复制标题
DOI：
10.1016/j.tecto.2019.228164
复制
发表时间：
2019-09
期刊：
影响因子：
2.9
通讯作者：
Brandon T. Bishop;S. Beck;G. Zandt
中科院分区：
文献类型：
--
作者：
Brandon T. Bishop;S. Beck;G. Zandt
沿着大陆板块活动边缘的俯冲作用发生在这样的背景下，即覆盖板块的地壳和岩石圈地幔可能包含明显早于边缘现今构造条件的继承性结构。这些结构在很长的时间尺度上（> 105年至> 106年）是持续存在的，被认为在巨型逆冲断层的孕震过程和沿着海岸线的地形发展中起着重要作用。我们使用接收器功能计算的宽带地震数据收集沿着智利前弧之间的~33°S和38.5°S附近的2010年Mw8.8马乌莱地震，以确定结构的覆盖南美大陆板块和俯冲纳斯卡大洋板块沿着和内侧的地震部分的巨型逆冲断层。我们表明，智利的前弧分为三个结构不同的区域：一个北方区，在这里大陆地壳与俯冲板块在海岸内侧约35-40公里深处相交;一个中央区，在这里大陆地壳在海岸处逐渐变薄，厚度小于20公里，然后在15-20公里深处与俯冲板块相交，南部区域大致对应于快速隆起的阿劳科半岛，在那里我们发现大陆地壳形成了一个厚度约35-40 km的楔形特征，与俯冲板块在海岸内侧相交。薄地壳的中心地带与致密，高速地幔体（Cobquecura异常），可能发挥了重要作用，稳定这一段智利前弧晚古生代以来。
Subduction along the active margin of a continental plate occurs in a context where the overriding plate's crust and lithospheric mantle may contain inherited structures significantly predating the present tectonic conditions of the margin. These structures are persistent over very long-term time scales (>105to >106years) and are thought to play an important role in both seismogenic processes on the megathrust and development of topography along coastlines. We use receiver functions calculated from broadband seismic data collected along the Chilean forearc between ~33°S and 38.5°S in the vicinity of the 2010 Mw8.8 Maule earthquake to determine the structure of the overriding South American continental plate and subducting Nazca oceanic plate along and inboard of the seismogenic portion of the megathrust. We show that the Chilean forearc is divided into three structurally distinct zones: a northern zone where the continental crust intersects the subducting plate well inboard of the coast at ~35–40 km depth, a central zone where the continental crust tapers to <20 km thickness at the coast before intersecting the subducting plate at 15–20 km depth, and a southern zone corresponding approximately to the rapidly uplifting Arauco Peninsula where we find that the continental crust forms a wedge-shaped feature ~35–40 km in thickness which intersects the subducting plate well inboard of the coast. The thin crust of the central zone is associated with a dense, high velocity mantle body (the Cobquecura anomaly) that may have played an important role in stabilizing this segment of the Chilean forearc since the late Paleozoic.