李玲利^1,3,,
黄显良^1,3,,,
姚华建^2,3,
缪鹏^1,3,
汪小厉^1,3,
鲍子文^1,3,
倪红玉^1,3,
李成^2,3,
杨元^2,3,
罗松^2,3,
胡少乾^2,3,
杨源源^1,3
1. 安徽省地震局, 合肥 230031
2. 中国科学技术大学地球和空间科学学院地震与地球内部物理实验室, 合肥 230026
3. 安徽蒙城地球物理国家野外科学观测研究站, 安徽省地震局, 安徽蒙城 233500

基金项目: 安徽省中央引导地方科技发展专项资金（YDZX20183400004456），中国地震局地震科技星火计划（XH19020和XH20026）共同资助


详细信息

作者简介: 李玲利, 女, 1981年生, 2012年获得中国科学技术大学固体地球物理专业博士学位, 主要从事地震背景噪声成像、结构反演等研究.E-mail:heartkey@mail.ustc.edu.cn

通讯作者: 黄显良, 男, 1972年生, 高级工程师, 主要从事地震活动性、地震监测预测等研究.E-mail:hxl818@sina.com

中图分类号: P315

收稿日期:2020-03-10
修回日期:2020-06-26
上线日期:2020-09-05

Shallow shear wave velocity structure from ambient noise tomography in Hefei city and its implication for urban sedimentary environment

LI LingLi^1,3,,
HUANG XianLiang^1,3,,,
YAO HuaJian^2,3,
MIAO Peng^1,3,
WANG XiaoLi^1,3,
BAO ZiWen^1,3,
NI HongYu^1,3,
LI Cheng^2,3,
YANG Yuan^2,3,
LUO Song^2,3,
HU ShaoQian^2,3,
YANG YuanYuan^1,3
1. Anhui Earthquake Agency, Hefei 230031, China
2. Laboratory of Seismology and Physics of Earth's Interior, School of Earth and Space Science, University of Science and Technology of China, Hefei 230026, China
3. Mengcheng National Geophysical Observation, Anhui Earthquake Agency, Mengcheng Anhui 233500, China


More Information

Corresponding author: HUANG XianLiang,E-mail:hxl818@sina.com

MSC: P315

--> Received Date: 10 March 2020
Revised Date: 26 June 2020
Available Online: 05 September 2020


摘要
摘要:合肥市位于合肥盆地东南缘，东侧紧邻郯庐断裂带，多条大型隐伏断裂穿过市区.为进一步认识合肥城市下方隐伏断裂的空间展布、性质，以及城市复杂的沉积环境，本文利用布设在合肥市区的58套三分量短周期地震仪组成的台阵，获得了37天的三分量连续波形数据，通过基于射线追踪的面波走时直接成像方法反演得到了合肥市地壳浅部0.6~3.6 km的三维剪切波速度结构，速度结构图像展现了地壳浅部的横向不均匀性和纵向成层性，揭示出NNE、NWW和近EW三组不同走向的隐伏断裂在城市地下浅部的构造特征.取得以下认识：（1）合肥市南、北方向在浅地表（2 km以内）存在显著速度差异，速度分界线位置与已知的近EW向的蜀山断裂一致，断裂南侧呈现低速凹陷，北侧则为高速隆起.低速中心深度达2~3 km，速度异常与该断裂在合肥盆地东部演化过程中的构造反转沉积了不同地层有关；（2）合肥市区存在明显的高速异常带，其走向、位置与穿过该区域的郯庐断裂带西支主干断裂相符，其中五河—合肥断裂在市区北部以东呈现低速凹陷特征，低速区范围与肥东凹陷晚白垩纪以来的沉积构造边界一致，认为肥东凹陷的最大沉积厚度可达2 km以上；（3）合肥市中心跨郯庐断裂带西支主干断裂之间呈现明显的凹、隆相间的复杂构造，推测其是在多组断裂的共同拉伸作用下形成的小型沉积盆地，沉积中心位于郯庐断裂带内部，最大厚度可达3~4 km.由于其展布方向在不同深度与该区域断裂的走向具有明显的相关性，推测不同深度的沉积形态与郯庐断裂带在不同时期的构造演化过程有关.
关键词: 背景噪声成像/
地壳浅部结构/
面波走时直接反演/
城市地质/
沉积环境

Abstract:Hefei is located in the south-east part of Hefei basin and west side of Tanlu fault zone in eastern China, with several large buried faults crossing the urban areas. To understand better of the distribution of Tanlu faults and complex sedimentary enviement in urben areas, we deplpyed an seismic array consisted of 58 stations with average spacing about 4 km. Cross-correlations of vertical component ambient noise data of different station pairs are computed in 1-day segments and stacked over 1 month from 30 September to 5 November 2018. Clear fundamental-mode Rayleigh waves are observed from 0.9 s to 4.5 s period. We then use the direct surface-wave tomographic method with period-dependent ray tracing and a wavelet-based sparsity-constrained to invert phase dispersion travel-time data simultaneously for 3-D shear-wave velocity structure. The shear-wave velocity model results from 0.6 km to 3.6 km depths are consistent with the known geologic features and reveal strong shallow crustal heterogeneity. The results are as follows: (1) It shows sharp velocity variation from north to south at the depths above 2 km which matches Shushan fault, also associated with gravity variations. As the boundary of different sedimentary strata in Hefei basin, it presents higher velocity to the north side of Shushan fault than the south, which related to the tectonic evolution of the eastern part of Hefei Basin; (2) Significant hight velocity is observed near the two west splay fractures of TanLu faults(Wuhe-Hefei fault and Zhuding-Shimenshan fault). The lower velocity area distributed in the east of Wuhe-Hefei fault is also consistent with the known shape of Feidong depression, infering that the depth of the central depression is more than 2 km at least; (3) A significant low velocity zone is found in the central of Hefei urban area, with the depths of 3~4 km, which is in the intersection of TanLu fault zone and the other two NWW-strike faults. The boundary of this velocity zone variouse from shellow to deep related to the strike directions of Tanlu faults zone and other faults in this area. We speculate it may be a strike slip pull apart basin controlled by Tanlu fault zone during different geologic times, which provides a seismic evidence in shallow depth that TanLu fault zone plays an important role in the sedimentary evolution of the eastern Hefei basin.
Key words:Ambient noise tomography/
Shallow crustal structure/
Direct inversion of surface wave dispersion/
Urban geology/
Sedimentary environment



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