利用双差层析成像方法反演阿拉斯加地区岩石圈速度结构

周少贤 薛梅

周少贤,薛梅. 2022. 利用双差层析成像方法反演阿拉斯加地区岩石圈速度结构. 地震学报,44(3):374−387 doi: 10.11939/jass.20210122
引用本文: 周少贤,薛梅. 2022. 利用双差层析成像方法反演阿拉斯加地区岩石圈速度结构. 地震学报,44(3):374−387 doi: 10.11939/jass.20210122
Zhou S X,Xue M. 2022. Lithospheric velocity structure of Alaska revealed by double difference tomography. Acta Seismologica Sinica,44(3):374−387 doi: 10.11939/jass.20210122
Citation: Zhou S X,Xue M. 2022. Lithospheric velocity structure of Alaska revealed by double difference tomography. Acta Seismologica Sinica44(3):374−387 doi: 10.11939/jass.20210122

利用双差层析成像方法反演阿拉斯加地区岩石圈速度结构

doi: 10.11939/jass.20210122
基金项目: 国家自然科学基金面上项目(42076064)和上海佘山地球物理国家野外科学观测研究站开放基金(2020K03)共同资助
详细信息
    作者简介:

    周少贤,在读硕士研究生,主要从事双差层析成像和横波分裂方面的研究,e-mail:zhoushaoxian@tongji.edu.cn

    通讯作者:

    薛梅,博士,副教授,主要从事西太平洋边缘海内部构造和地震背景噪声机制研究,e-mail:meixue@tongji.edu.cn

  • 中图分类号: P315.2

Lithospheric velocity structure of Alaska revealed by double difference tomography

  • 摘要: 阿拉斯加地区由不同地质时期的地体向北增生而成,经历了漫长的构造演化,地质构造复杂。ANF (Array Network Facility)网站新近提供的来自USArray地震台网记录的地震台站观测数据填补了阿拉斯加地区西部和北部的观测空白,本文选取该区域中345个台站记录的5 638个地震事件的P波、S波到时数据,采用区域双差地震层析成像方法反演得到了该地区的岩石圈三维P波速度模型和地震重定位结果。研究结果显示:阿拉斯加西部太平洋板块的俯冲倾角较大,深部地幔楔表现为P波低速异常,推测由俯冲板块顶部脱水产生的流体释放到地幔楔并触发部分熔融所致,这些熔融物质上升到达地表形成阿留申火山岛链;中部亚库塔特(Yakutat)地体与太平洋板块发生耦合,俯冲倾角减小,一方面使地壳压应力增加,引起地壳增厚和楚加奇(Chugach)山脉隆升,另一方面导致该处地幔楔降温从而使产生的熔体减少,并随着地壳压应力的增加部分地壳裂隙闭合,阻断了熔体上升至地表,从而形成迪那利(Denali)火山空区;亚库塔特地体与东部兰格尔(Wrangell)火山区之间存在较明显的分界,兰格尔火山区下方的低速区(与岩浆活动对应)集中于西北侧,火山区的岩浆来源可能与环形地幔流沿太平洋—亚库塔特板块边缘的上升流相关。这些结果表明,阿拉斯加地区深部复杂的地球动力学过程导致了其地表复杂的地质构造。

     

  • 图  1  阿拉斯加构造背景图

    两个箭头分别给出了太平洋板块向北美板块俯冲的速度(DeMets,Dixon,1999)和亚库塔特地体向北美板块俯冲的速度(Sauber et al,1997)。F1:廷蒂纳断层;F2:迪那利断层;F3:塔基特纳断层;F4:接触断层;F5:边界山脉断层,下同

    Figure  1.  Tectonic settings of Alaska

    The two arrows represent subduction velocity of Pacific Plate to North America Plate (DeMets,Dixon,1999) and Yakutat Plate to North America Plate (Sauber et al,1997). F1: Tintina fault;F2:Denali fault;F3:Talkeentna fault;F4:Contact fault;F5:Border Range fault,the same below

    图  2  本文所用的地震和台站分布图

    Figure  2.  Distribution of events and stations used in this study

    图  3  筛选前(a)、后(b)的P波和S波时距曲线

    黑线代表拟合的时距曲线,绿线代表观测与拟合的到时差为±10 s,反演中仅保留绿线以内的震相数据

    Figure  3.  Time-distance curves of P and S waves before (a) and after (b) selection

    The black line represents the fitting time-distance curve,and the green line represents the difference of arrival time between observation and fitting is ±10 s,only the seismic phase data within the green lines are retained to ensure the data quality

    图  4  阻尼参数及平滑因子权重均衡曲线

    Figure  4.  Trade-off curves of damping and smoothing weight parameters

    图  5  研究区不同深度水平剖面的vP棋盘测试结果(白色实线内部为DWS>1 000的区域)

    Figure  5.  Checkerboard test results of vP at different depths in the studied area where the white solid line delineates the area with DWS>1000

    图  6  阿拉斯加地区不同深度处P波速度结构

    Ⅰ . 育空盆地;Ⅱ . 塔纳纳盆地;Ⅲ . 铜河盆地;Ⅳ . 库克湾盆地

    Figure  6.  P-wave velocity structure in Alaska at different depths

    Ⅰ . Yukon Flat basin;Ⅱ . Middle-Tanana basin;Ⅲ . Copper River basin;Ⅳ . Cook Inlet basin(a) 10 km;(b) 25 km;(c) 45 km;(d) 60 km;(e) 80 km;(f) 100 km;(g) 120 km;(h) 140 km;(i) 180 km

    图  7  不同位置的P波速度垂直剖面图(剖面位置见图6i,白色实线以上代表DWS>1 000的区域)

    Figure  7.  vP models along ten cross sections at different positions (The profile location is shown in Fig. 6i,and the region above the white solid line is the region with DWS>1 000)

    (a) AA′; (b) BB′; (c) CC′; (d) DD′; (e) EE′; (f) FF′; (g) GGG′′; (h) HHH′′; (i) II′; (j) JJ

    表  1  本文所采用的初始一维速度模型(Eberhart-Phillips et al,2006

    Table  1.   Initial ID velocity model used in this study (Eberhart-Phillips et al,2006

    深度/kmvP/(km·s−1深度/kmvP/(km·s−1
    0 2.90 48.0 7.87
    2.0 5.10 65.0 8.12
    6.0 6.05 85.0 8.20
    15.0 6.35 110.0 8.24
    24.0 6.60 140.0 8.30
    33.0 7.15 190.0 8.44
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出版历程
  • 收稿日期:  2021-07-05
  • 修回日期:  2021-09-29
  • 网络出版日期:  2022-04-29
  • 刊出日期:  2022-06-27

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