New insight into the velocity and anisotropy structures of the subduction zone in northern Sumatra

IF 2.7 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
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Abstract

In this study, we conducted seismic tomographic inversions to investigate the velocity and anisotropy structures of northern Sumatra, using 9774 P-wave and 8405 S-wave arrivals from regional earthquakes. Isotropic P-wave velocity, isotropic S-wave velocity, P-wave azimuthal anisotropy, and P-wave radial anisotropy models were generated using eikonal equation-based traveltime tomography methods. The study identified low-velocity zones beneath the Toba and Sinabung volcanoes, potentially indicating the presence of magma reservoirs. Furthermore, low-velocity anomalies above the subduction slab were detected, which were likely caused by the dehydration of the slab and interpreted as channels of upwelling flow. The tomographic results revealed a trench-parallel high-velocity belt in the uppermost mantle, representing the subducting slab of the India-Australian plate. The trench-parallel fast velocity directions in the slab suggested that the subducted oceanic slab retains its frozen-in anisotropy formed at the mid-ocean ridge, or that the anisotropy is induced by the lattice-preferred orientation of the B-type olivine. Negative radial anisotropy in the mantle wedge was observed, reflecting hot upwelling flows and transitions of olivine fabrics in the presence of water due to slab dehydration. The results also indicated a multilevel magma plumbing system beneath the Toba Caldera. In summary, the results of this study provided new insights into the structure and dynamic processes of the northern Sumatra subduction zone.
对苏门答腊岛北部俯冲带速度和各向异性结构的新认识
在这项研究中,我们利用来自区域地震的 9774 个 P 波和 8405 个 S 波到达数据进行了地震层析反演,以研究苏门答腊岛北部的速度和各向异性结构。利用基于 eikonal 方程的行进时间层析成像方法生成了各向同性 P 波速度、各向同性 S 波速度、P 波方位各向异性和 P 波径向各向异性模型。研究确定了多巴火山和西那榜火山下方的低速区,这可能表明存在岩浆储层。此外,还探测到俯冲板块上方的低速异常,这可能是板块脱水造成的,被解释为上升流通道。层析成像结果表明,在最上层地幔中有一条沟槽平行高速带,代表印度-澳大利亚板块的俯冲板块。板块中与海沟平行的快速速度方向表明,俯冲的大洋板块保留了在大洋中脊形成的冻结各向异性,或者说该各向异性是由 B 型橄榄石的晶格偏好取向引起的。在地幔楔中观察到了负径向各向异性,反映了板块脱水导致的热上升流和橄榄石结构在有水的情况下的转变。研究结果还表明,鸟羽破火山口下方存在多级岩浆管道系统。总之,这项研究的结果为了解苏门答腊岛北部俯冲带的结构和动态过程提供了新的视角。
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来源期刊
Tectonophysics
Tectonophysics 地学-地球化学与地球物理
CiteScore
4.90
自引率
6.90%
发文量
300
审稿时长
6 months
期刊介绍: The prime focus of Tectonophysics will be high-impact original research and reviews in the fields of kinematics, structure, composition, and dynamics of the solid arth at all scales. Tectonophysics particularly encourages submission of papers based on the integration of a multitude of geophysical, geological, geochemical, geodynamic, and geotectonic methods
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