地球物理学进展 ›› 2019, Vol. 34 ›› Issue (1): 27-34.doi: 10.6038/pg2019CC0392

• 固体地球物理及空间物理学(大气、行星、地球动力学、重磁电及地震学、地热学) • 上一篇    下一篇

尼泊尔—喜马拉雅地区中上地壳噪声成像

薛霆虓1,2,何诚2,*(),王敏玲2,王亮2,3   

  1. 1. 安徽建筑大学土木工程学院,合肥 230022
    2. 桂林理工大学地球科学学院,广西桂林 541004
    3. 成都理工大学地球物理学院,成都 610059
  • 收稿日期:2018-09-03 修回日期:2018-11-27 出版日期:2019-02-20 发布日期:2019-04-15
  • 通讯作者: 何诚 E-mail:326489950@qq.com
  • 作者简介:薛霆虓,男,1974年生,固体地球物理学博士,副教授,主要从事地震学与地球动力学研究.(E-mail: xuetx@mail.ustc.edu.cn)
  • 基金资助:
    国家自然科学基金(41364003);广西自然科学基金共同资助.(2018GXNSFAA138143)

Tomography of middle-upper crust in Nepal-Himalaya from ambient seismic noise

XUE Ting-xiao1,2,HE Cheng2,*(),WANG Min-ling2,WANG Liang2,3   

  1. 1. School of Civil Engineering, Anhui Jianzhu University, Hefei 230022, China
    2. College of Earth Sciences, Guilin University of Technology, Guangxi Guilin 541004, China
    3. Geophysics college, Chengdu University of Technology, Chengdu 610059, China
  • Received:2018-09-03 Revised:2018-11-27 Online:2019-02-20 Published:2019-04-15
  • Contact: Cheng HE E-mail:326489950@qq.com

摘要:

本文利用HIMNT台网1年左右的宽频带连续波形记录,利用背景噪声信息的互相关函数提取了6~26 s的瑞利波相速度频散曲线,并反演得到了尼泊尔—喜马拉雅地区中上地壳横波速度结构.成像结果显示尼泊尔—喜马拉雅下方存在10 km左右厚的横波低速层(也是相对的低密度层).根据分析,我们认为这一相对低速度层对应了下插的印度地壳和上伏的喜马拉雅构造楔之间的滑脱面——MHT(Main Himalayan Thrust)附近的高温层.两大板块间沿着滑脱面MHT处摩擦产热,由于较低的热传导,热量积累导致了10 km厚的高温层,初步估算高喜马拉雅和特提斯喜马拉雅交界处下方MHT处温度高达,因此我们认为在高喜马拉雅下方MHT界面可能已经处于蠕滑状态,或者处于蠕滑-黏滑的过渡状态.这也解释了喜马拉雅地区的历史大地震为什么多发生在高喜马拉雅以南一侧.

关键词: 台阵层析成像, 背景噪声, 尼泊尔—喜马拉雅, 地壳温度结构

Abstract:

Using the wide-band continuous wave record of HIMNT network for about 1 year, the cross correlation functions of the background noise information are calculated. Then we extract velocity dispersion curves of the Rayleigh wave phase of 6~26 s, and invert transverse wave velocity structure of the Nepal-Himalayas. The imaging results shows that there is a low velocity layer of about 10 km thick beneath the Nepal-Himalaya. According to the analysis, we think that this relatively low velocity layer corresponds to the high temperature zone near the detachment—MHT (Main Himalayan Thrust) between the lower part of the India crust and the upper Himalaya orogenic belt. A large amount of heat generated by the friction between the plates along MHT was produced. The heat accumulation resulted in a 10 km thick layer of high temperature because of the lower heat conduction. It is preliminarily estimated that the temperature of MHT under the junction of the High-Himalaya and the Tethyan-Himalaya is up to,we infer that MHT below the High Himalaya is in brittle-ductile transition state or ducile state. This also explains why great earthquakes in Himalaya occurred to the south of the high Himalaya.

Key words: Array tomography, Ambient seismic noise, Nepal-Himalaya, Crustal temperature structure

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