Basin-to-slab Seismic Imaging of the Alaska Subduction Zone

阿拉斯加俯冲带的盆地到板片地震成像

基本信息

批准号：
1251971
负责人：
Carl Tape
金额：
$ 59.79万
依托单位：
University of Alaska Fairbanks Campus
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2013
资助国家：
美国
起止时间：
2013-10-01 至 2020-09-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1251971&HistoricalAwards=false
关键词：
Basin slab Seismic Imaging Alaska

项目摘要

Forearc basins are fundamental components of a subduction system. The Cook Inlet forearc basin is the largest active forearc basin in North America, with dimensions 200 km by 100 km and a depth of 7.6 km. The basin has remained a site of sedimentation and subsidence over the past 160 Ma of convergence and accretion along the southern Alaska margin. The basin is part of a 50-km thick crust overlying a freely slipping plate interface, just downdip from the rupture extent of the Mw 1964 9.2 earthquake. A high-magnetic, low-gravity, continental-scale signal known as the Southern Alaska Magnetic High (SAMH) coincides with Cook Inlet basin. The origin of this signal has been proposed to result from either an ancient accreted magmatic arc within the crust, or a serpentinized zone within the mantle wedge. We assume that the structural body associated with the SAMH has driven forearc basin formation over geological time scales. By characterizing the three-dimensional seismic structure of the basin-crust-slab-mantle system, it should be possible to isolate the origin of the SAMH and, in turn, the origin of a globally significant forearc basin.Sedimentary basins pose major challenges for seismic imaging. Basin reverberations of seismic waves complicate efforts to image underlying and adjacent portions of the subduction system, including the lower crust, uppermost mantle, and subducting slab. Three components are needed to derive a high-quality seismic structural model of the Cook Inlet region: (1) seismic imaging capabilities to handle both the structural complexities of the three-dimensional model and details within full seismic waveforms; (2) maximal distribution local earthquakes to enhance resolution; and (3) an array of strategically placed broadband seismometers.We plan a two-year EarthScope FlexArray deployment of 30 seismic stations to target (1) the 50-km thick continental crust containing Cook Inlet basin, and (2) a 400-km long arc-normal transect of the subduction zone across the basin, through Redoubt volcano, and into the backarc region. With a phenomenal rate of seismicity within the crust and subducting slab, the region of Cook Inlet offers a world-class opportunity for seismic imaging of subduction tectonics. By isolating the seismic signals due to the basin, it will be possible to image deeper structure and processes within the lower crust, upper mantle, and subducting Pacific slab. We plan to harness the accuracy of full wavefield simulations within an adjoint-based imaging technique that has proven successful in southern California. A complete characterization of the structural setting will result from detailed investigations of local and teleseismic shear-wave splitting measurements to infer mantle flow patterns, in addition to a synthesis of tectonic stresses inferred from hundreds of M 3 moment tensors from earthquakes within the crust and slab.

弧前盆地是俯冲系统的基本组成部分。库克湾弧前盆地是北美最大的活动弧前盆地，面积为 200 公里 x 100 公里，深度为 7.6 公里。在过去 160 Ma 中，该盆地一直是沿阿拉斯加南部边缘汇聚和增生的沉积和沉降场所。该盆地是 50 公里厚的地壳的一部分，覆盖在自由滑动的板块界面上，正好从 1964 年 Mw 9.2 地震的破裂程度开始下倾。被称为南阿拉斯加磁高压 (SAMH) 的高磁、低重力大陆尺度信号与库克湾盆地重合。该信号的起源被认为是由地壳内古老的增生岩浆弧或地幔楔内的蛇纹石化区域引起的。我们假设与 SAMH 相关的结构体在地质时间尺度上驱动了弧前盆地的形成。通过表征盆地-壳-板-幔系统的三维地震结构，应该可以分离出SAMH的起源，进而分离出全球重要的弧前盆地的起源。沉积盆地对地震勘探提出了重大挑战。地震成像。地震波的盆地回响使得对俯冲系统的底层和邻近部分（包括下地壳、最上地幔和俯冲板片）进行成像的工作变得更加复杂。导出库克湾地区的高质量地震结构模型需要三个组成部分：（1）地震成像能力，可处理三维模型的结构复杂性和完整地震波形中的细节； (2)最大分布局部地震以提高分辨率；我们计划在两年内部署 30 个地震台站的 EarthScope FlexArray，以瞄准 (1) 包含库克湾盆地的 50 公里厚大陆地壳，以及 (2) 400 公里长的大陆地壳。俯冲带的长弧法线横断面，穿过盆地，穿过堡垒火山，进入弧后区域。库克湾地区地壳和俯冲板片内的地震活动率惊人，为俯冲构造地震成像提供了世界级的机会。通过隔离盆地产生的地震信号，将有可能对下地壳、上地幔和俯冲太平洋板片内更深层的结构和过程进行成像。我们计划在基于伴随的成像技术中利用全波场模拟的准确性，该技术在南加州已被证明是成功的。对当地和远震剪切波分裂测量的详细研究将产生结构背景的完整表征，以推断地幔流动模式，此外还通过地壳和板块内地震的数百个 M 3 力矩张量推断出构造应力的综合。

项目成果

期刊论文数量（9）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Crustal earthquakes in the Cook Inlet and Susitna region of southern Alaska

阿拉斯加南部库克湾和苏西特纳地区的地壳地震

DOI：
10.1016/j.tecto.2018.08.013
发表时间：
2018-10-01
期刊：
Tectonophysics
影响因子：
2.9
作者：
V. Silwal;C. Tape;A. Lomax
通讯作者：
A. Lomax

Seismic Response of Cook Inlet Sedimentary Basin, Southern Alaska

阿拉斯加南部库克湾沉积盆地的地震响应

DOI：
10.1785/0220190205
发表时间：
2019-10
期刊：
Seismological Research Letters
影响因子：
3.3
作者：
Smith, Kyle;Tape, Carl
通讯作者：
Tape, Carl

Bear Encounters with Seismic Stations in Alaska and Northwestern Canada

阿拉斯加和加拿大西北部的熊遭遇地震台

DOI：
10.1785/0220190081
发表时间：
2019-08
期刊：
Seismological Research Letters
影响因子：
3.3
作者：
Tape, Carl;Heath, David C.;Baker, Michael G.;Dalton, Scott;Aderhold, Kasey;West, Michael E.
通讯作者：
West, Michael E.

Seismic moment tensors and estimated uncertainties in southern Alaska: ALASKA MOMENT TENSORS AND UNCERTAINTIES

阿拉斯加南部的地震矩张量和估计的不确定性：阿拉斯加矩张量和不确定性