Constraining the Effect of Bathymetric High Subduction in an Accretionary Wedge: Evidence From the Tokai Area of the Nankai Trough, Japan

IF 3 2区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Andrzej Górszczyk, Rafael Almeida, Romain Brossier, Ludovic Métivier, Stéphane Operto
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Abstract

The Tokai area in the eastern Nankai Trough is characterized by the subduction of a rough plate interface caused by bathymetric highs related to the adjacent Izu-Bonin arc and fault fabrics in the oceanic crust. However, the effect of this process on the structural development of its accretionary wedge and megathrust seismicity is still poorly understood. To get better insight into Tokai area we apply full-waveform inversion to legacy wide-angle seismic data exploiting available signal frequency up to 15 Hz. From this model we extract pseudo-reflectivity attributes, which are complementary to the section obtained with Kirchoff pre-stack depth migration of streamer data. The high-resolution images reveal detailed geological characterization of the subducting oceanic crust, the geometry of the megathrust and splay faults, and the structure of the wedge. The latter is characterized by imbricate fans, out-of-sequence thrusts, and duplexes that significantly contribute to its thickening. We compare these features to published structural models and propose that the increased structural complexity in the Tokai segment is due to fault reactivation triggered by the subduction of the bathymetric highs. We suggest that this fault reactivation also controls the shallow seismogenic behavior of this region. We show that the evolution of the forearc basin is related to the ongoing underplating process and out-of-sequence thrusting within the wedge. We compare our seismic imaging results with bathymetric, magnetic, and gravity data, revealing no evidence of large ridges beneath our profile, which previous studies have proposed as a cause of the persistent Tokai seismic gap.

Abstract Image

增生楔体深水高俯冲的抑制作用:来自日本南开海槽东海地区的证据
南开海槽东部东海地区的特征是与邻近的伊豆-波宁弧和洋壳断裂构造相关的等深高引起的粗糙板块界面俯冲。然而,这一过程对其吸积楔构造发育和大逆冲地震活动的影响尚不清楚。为了更好地了解Tokai地区,我们对现有的广角地震数据进行了全波形反演,利用了高达15 Hz的可用信号频率。在此模型中,我们提取了伪反射率属性,这些属性与用Kirchoff叠前深度偏移得到的剖面相补充。高分辨率图像揭示了俯冲洋壳的详细地质特征,巨型逆冲断层和展断层的几何形状,以及楔的结构。后者的特征是叠瓦状扇、无序逆冲和双相构造,它们显著地促进了其增厚。我们将这些特征与已发表的构造模型进行了比较,并提出东海段构造复杂性的增加是由于深海高点的俯冲引发的断层再激活。我们认为这种断层的再活化也控制了该地区的浅层发震行为。研究表明,弧前盆地的演化与持续的底板作用和楔体内部的逆冲作用有关。我们将地震成像结果与测深、磁场和重力数据进行了比较,没有发现剖面下存在大型脊的证据,而之前的研究已经提出这是东海地震间隙持续存在的原因。
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来源期刊
Geochemistry Geophysics Geosystems
Geochemistry Geophysics Geosystems 地学-地球化学与地球物理
CiteScore
5.90
自引率
11.40%
发文量
252
审稿时长
1 months
期刊介绍: Geochemistry, Geophysics, Geosystems (G3) publishes research papers on Earth and planetary processes with a focus on understanding the Earth as a system. Observational, experimental, and theoretical investigations of the solid Earth, hydrosphere, atmosphere, biosphere, and solar system at all spatial and temporal scales are welcome. Articles should be of broad interest, and interdisciplinary approaches are encouraged. Areas of interest for this peer-reviewed journal include, but are not limited to: The physics and chemistry of the Earth, including its structure, composition, physical properties, dynamics, and evolution Principles and applications of geochemical proxies to studies of Earth history The physical properties, composition, and temporal evolution of the Earth''s major reservoirs and the coupling between them The dynamics of geochemical and biogeochemical cycles at all spatial and temporal scales Physical and cosmochemical constraints on the composition, origin, and evolution of the Earth and other terrestrial planets The chemistry and physics of solar system materials that are relevant to the formation, evolution, and current state of the Earth and the planets Advances in modeling, observation, and experimentation that are of widespread interest in the geosciences.
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