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.
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.
作者
薛霆虓
何诚
王敏玲
王亮
XUE Ting-xiao;HE Cheng;WANG Min-ling;WANG Liang(School of Civil Engineering,Anhui Jianzhu University,Hefei 230022,China;College of Earth Sciences,Guilin University of Technology,Guangxi Guilin 541004,China;Geophysics college,Chengdu University of Technology,Chengdu 610059,China)
出处
《地球物理学进展》
CSCD
北大核心
2019年第1期27-34,共8页
Progress in Geophysics
基金
国家自然科学基金(41364003)
广西自然科学基金(2018GXNSFAA138143)共同资助
作者简介
第一作者: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,(Email:xuetx@mail.ustc.edu.cn);通讯作者::何诚,男,1992年生,硕士研究生,从事地震勘探研究.(Email:326489950@qq.com)
