刘巧霞^1,,
邱勇¹,
曾祥方²,
王夫运¹,
段永红¹,
贾宇鹏¹,
周铭¹
1. 中国地震局地球物理勘探中心, 郑州 450002
2. 中科院测量与地球物理研究所大地测量与动力学国家重点实验室, 武汉 430077

基金项目: 国家重点研发计划（2017YFC1500202），国家自然科学基金（41604049），国家自然科学基金（41774066）和中国地震局星火计划项目（XH18065Y）共同资助


详细信息

作者简介: 刘巧霞, 女, 1983年生, 博士, 主要从事地震学研究.E-mail:llqqxx@126.com

中图分类号: P315

收稿日期:2018-11-02
修回日期:2019-11-16
上线日期:2020-07-05

Distribution characteristics of Rayleigh wave noise sources derived from records of a large-aperture seismic array in Northwest China

LIU QiaoXia^1,,
QIU Yong¹,
ZENG XiangFang²,
WANG FuYun¹,
DUAN YongHong¹,
JIA YuPeng¹,
ZHOU Ming¹
1. Department of Integrated Geophysics, Geophysical Exploration Center of China Earthquake Administration, Zhengzhou 450002, China
2. State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China


MSC: P315

--> Received Date: 02 November 2018
Revised Date: 16 November 2019
Available Online: 05 July 2020


摘要
摘要:Rayleigh面波地震背景噪声成像技术已被成功运用到全球范围不同尺度的地球内部结构的研究中，并以背景噪声场是时空均匀分布为前提假设.然而真实的噪声源分布的时空非均匀性将导致经验格林函数提取存在偏差，最终影响噪声成像结果的精准性.近年来，噪声源分布特征研究逐步成为提高噪声成像精准度、深化地震背景噪声成像的关键问题.本文利用频率-波束域分析法对中国西北地区的一个大孔径台阵（WuTan Array，简称WTA）在2014全年的垂直分量连续记录做了聚束分析，研究了Rayleigh波噪声源分布特征.结果显示：WTA台阵成功探测到了10~20 s周期范围的来自于全球不同方位的Rayleigh波噪声信号，其源区分布具有明显的季节变化特征：冬季集中分布在北大西洋方位，而夏季则转为印度洋方位噪声信号最强.此外，Rayleigh波噪声源区空间分布还表现出一定的频率依赖性，即在较低频段（0.0488~0.0635 Hz）在北大西洋、北太平洋、印度洋及西太平洋四个方位均有分布；而在频率较高频段（0.0928~0.1025 Hz）则集中分布于西太平洋方位.Rayleigh波噪声源时空分布特征和频率依赖性与海洋活动本身的季节性变化和频谱特征有关.并初步推测本文所观测到的Rayleigh波是由加剧的海浪运动直接作用于海岸、大陆架或海底而激发产生的第一类地脉动噪声信号.
关键词: Rayleigh面波/
噪声源分布/
地脉动/
地震台阵

Abstract:Ambient Noise Tomography (ANT) has been successfully applied in studying the structure of the earth interior. The theory behind this technique presupposes a diffuse symmetric noise field. However, the actual anisotropy usually exists in the noise which causes the bias of Green's functions and accordingly leads to errors of corresponding ANT results. Recently, the characteristic of microseisms sources distribution has become a critical issue to improve accuracy of the ANT. This paper presents a study on Rayleigh wave microseisms distribution characteristic based on the vertical component continuous seismogram recorded by a large-aperture array (WuTan Array, WTA) deployed in northwest China during 2014 using the conventional frequency-wavenumber (f-k) method. It is noted that Rayleigh wave microseisms at periods of 10~20 s are globally observed in various directions and have distinct seasonal variations. In winter, the North Atlantic is the strongest microseism source while in summer, the intense wave activity across the Indian Ocean dominates the Rayleigh microseism generation. Additionally, the azimuth distribution of the Rayleigh microseisms displays obvious frequency dependence. That is, Rayleigh microseisms are scattered in the orientations of the North Atlantic, the North Pacific, the West Pacific and the Indian Ocean at the lower frequency band while concentrating only in the direction of the West Pacific region at the relatively higher frequency band. The seasonality and frequency dependence of Rayleigh microseisms sources distribution is due to seasonal variation and the spectrum characteristic of the ocean activity itself. It is inferred that Rayleigh waves are the primary microseisms which are created by the direct action of ocean waves on the coast, continental shelf or sloping seafloor.
Key words:Rayleigh wave/
Seismic noise sources distribution/
Seismic array/
Microseisms



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