Seismic Image of the Central to Southern Andean Subduction Zone Through Finite-Frequency Tomography

IF 3.9 2区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS
Y. Kondo, M. Obayashi, H. Sugioka, H. Shiobara, A. Ito, M. Shinohara, H. Iwamori, M. Kinoshita, M. Miller, C. Tassara, J. Ojeda
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Abstract

This study presents new seismic imaging of the Andean subduction zone through P-wave hybrid finite-frequency and ray-theoretical tomography. We measured both differential and absolute traveltimes using broadband seismic waveforms from stations in an array of ocean-bottom seismographs near the Chile Triple Junction (CTJ) and stations within 30° of the array. These data were combined with the global traveltime data set to obtain a global P-wave velocity structure with a focus on central to southern South America. The new tomographic image showed the Nazca slab geometry as a continuous fast anomaly, which is consistent with seismic activity and prior slab models. Furthermore, two notable structures were observed: a broad extension of the fast anomaly beneath the Nazca slab at 26–35°S and a slow anomaly east of the CTJ. The checkerboard resolution and recovery tests confirmed the reliability of these large-scale features. The fast anomaly, isolated from the Nazca slab, was interpreted as a relic Nazca slab segment based on its strong amplitude and spatial coincidence with the current Pampean and past Payenia flat slab segments. The slow anomaly near the CTJ was consistent with the previously inferred extent of the Patagonian slab window. Moreover, the active adakitic volcanoes are aligned with the southern edge of the anomaly, and the plateau basalts are located within the anomaly. Our model showed that the slow anomaly extended to a depth of up to 250 km, suggesting a depth limit that the asthenospheric window can influence.

通过有限频率断层扫描观察安第斯俯冲带中部至南部的地震图像
本研究通过 P 波混合有限频率和射线理论层析成像技术,对安第斯俯冲带进行了新的地震成像。我们利用智利三交界处(CTJ)附近海底地震仪阵列中的台站以及该阵列 30° 范围内的台站的宽带地震波形,测量了差分和绝对的行进时间。这些数据与全球行进时间数据集相结合,获得了以南美洲中部至南部为重点的全球 P 波速度结构。新的层析成像显示,纳斯卡板块的几何形状是一个连续的快速异常,这与地震活动和先前的板块模型相一致。此外,还观测到两个值得注意的结构:南纬 26-35 度纳斯卡板块下快速异常的广泛延伸和 CTJ 以东的慢速异常。棋盘格分辨率和恢复测试证实了这些大尺度特征的可靠性。从纳斯卡板块中分离出来的快速异常被解释为纳斯卡板块的遗迹,依据是其强烈的振幅以及与目前的帕姆潘板块和过去的帕耶尼亚平板块在空间上的重合。CTJ 附近的缓慢异常与之前推断的巴塔哥尼亚板块窗口范围一致。此外,阿达基特活火山与异常的南侧边缘对齐,高原玄武岩位于异常范围内。我们的模型显示,慢异常延伸至 250 千米的深度,这表明了星体层窗口能够影响的深度极限。
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来源期刊
Journal of Geophysical Research: Solid Earth
Journal of Geophysical Research: Solid Earth Earth and Planetary Sciences-Geophysics
CiteScore
7.50
自引率
15.40%
发文量
559
期刊介绍: The Journal of Geophysical Research: Solid Earth serves as the premier publication for the breadth of solid Earth geophysics including (in alphabetical order): electromagnetic methods; exploration geophysics; geodesy and gravity; geodynamics, rheology, and plate kinematics; geomagnetism and paleomagnetism; hydrogeophysics; Instruments, techniques, and models; solid Earth interactions with the cryosphere, atmosphere, oceans, and climate; marine geology and geophysics; natural and anthropogenic hazards; near surface geophysics; petrology, geochemistry, and mineralogy; planet Earth physics and chemistry; rock mechanics and deformation; seismology; tectonophysics; and volcanology. JGR: Solid Earth has long distinguished itself as the venue for publication of Research Articles backed solidly by data and as well as presenting theoretical and numerical developments with broad applications. Research Articles published in JGR: Solid Earth have had long-term impacts in their fields. JGR: Solid Earth provides a venue for special issues and special themes based on conferences, workshops, and community initiatives. JGR: Solid Earth also publishes Commentaries on research and emerging trends in the field; these are commissioned by the editors, and suggestion are welcome.
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