阿拉斯加西南近海内白令大陆架上地壳结构的地震和潜在实地制约因素

IF 2.7 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Rajesh Vayavur , Andrew J. Calvert
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引用次数: 0

摘要

阿拉斯加西南部包括一组以断层为界的构造地层,这些地层在中生代和古近纪期间增生到北美。为了描述这些地层的近海延伸以及在陆地上发现的几个重要断层,我们重新处理了三条相交的多道深层地震反射剖面,总长度达 750 线公里,这些剖面是 1994 年由 "尤因 "号考察船在白令大陆架内部拍摄的。由于最上层的地震剖面经常受到来自坚硬浅海底的高振幅水层多普勒的污染,因此我们在迁移反射图像的基础上,通过对记录到的最深达 2000 米的初至波进行行进时间层析成像,得出了高分辨率的 P 波速度模型。此外,我们还将其他地球物理数据集,如地震、测井记录、高分辨率卫星-测高重力、气载磁力、船载重力和磁力,纳入了综合区域解释。我们划定了主要测绘地质要素的近海延伸,包括托吉亚克断层(TGF)、东库卢卡克断层(EKF)、奇尔奇特纳断层(CF)、克拉克湖断层(LCF)、托吉亚克陆相(TT)、古德纽斯陆相(GT)、半岛陆相(PT)、北卡希尔特纳飞地(NKF)和南卡希尔特纳飞地(SKF)矿床以及区域缝合带。这项研究的地球物理证据表明,除 LCF 外,阿拉斯加西南部的主要断层和陆相边界不仅延伸至白令陆架近海下方,而且似乎还在旋转,形成了与不活跃的白令陆边缘平行的趋势。LCF 延伸至近海,但很可能终止于布里斯托尔湾盆地的东北部。此外,地震数据的制约表明,虽然阿拉斯加西南部的主要断层在陆上有一些活动,但在近海区域仍处于休眠状态。这些新发现将有助于更好地了解阿拉斯加西南部的地层增生过程和现有的断层模型。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Seismic and Potential Field Constraints on Upper Crustal Architecture of Inner Bering Shelf, Offshore Southwestern Alaska

Southwestern Alaska encompasses a group of fault-bounded tectonostratigraphic terranes that were accreted to North America during the Mesozoic and Paleogene. To characterize the offshore extension of these terranes and several significant faults identified onshore, we reprocessed three intersecting multichannel deep seismic reflection profiles totaling ∼750 line-km that were shot by the R/V Ewing across part of the inner Bering continental shelf in 1994. Since the uppermost seismic section is often contaminated by high amplitude water layer multiples from the hard and shallow seafloor, the migrated reflection images are supplemented with high-resolution P wave velocity models derived by traveltime tomography of the recorded first-arrivals to depths of up to 2000 m. Additionally, other geophysical datasets such as seismicity, well logs, high resolution satellite-altimetry gravity, air-borne magnetics, ship-board gravity and magnetics, are also incorporated into an integrated regional interpretation. We delineate the offshore extension of the major mapped geological elements, including the Togiak fault (TGF), East Kulukak fault (EKF), Chilchitna fault (CF), Lake Clark fault (LCF), Togiak terrane (TT), Goodnews terrane (GT), Peninsular terrane (PT), Northern Kahiltna flysch (NKF) and Southern Kahiltna flysch (SKF) deposits, and the regional suture zone. The geophysical evidence from this study suggest that the major faults and terrane boundaries of southwestern Alaska, excluding the LCF, not only extend beneath the Bering shelf offshore but also appear to rotate, forming a trend parallel to the inactive Beringian margin. The LCF extends offshore but likely terminates in the northeastern part of the Bristol Bay basin. Additionally, the constraints from seismicity data indicates that while the major faults in southwestern Alaska exihibit some activity onshore, they remain dormant in the offshore region. These new findings will contribute to a better understanding of terrane accretion processes and existing fault models of southwestern Alaska.

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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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