大别—苏鲁造山带及其邻区岩石圈速度结构特征  

Lithospheric velocity structure of Dabie-Sulu orogenic belt and its adjacent areas

作　　者：于悦颖 顾勤平[1] 张海江[2,3] 李正楷 周昱辰 高磊 韩守诚 YU YueYing;GU QinPing;ZHANG HaiJiang;LI ZhengKai;ZHOU YuChen;GAO Lei;HAN ShouCheng(Jiangsu Earthquake Agency,Nanjing 210014,China;School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China;Mengcheng National Geophysical Observatory,Mengcheng Anhui 233527,China)

机构地区：[1]江苏省地震局,南京210014 [2]中国科学技术大学地球和空间科学学院,合肥230026 [3]安徽蒙城地球物理国家野外科学观测研究站,安徽蒙城233527

出　　处：《地球物理学报》2024年第12期4681-4697,共17页Chinese Journal of Geophysics

基　　金：国家重点研发计划项目(2022YFF0800701);江苏省地震局青年科学基金项目(202207,202308,202303);江苏省地震局局长基金项目(202301);中国地震局地震星火科技计划项目(XH23018C)共同资助.

摘　　要：大别—苏鲁造山带是我国东部重要的碰撞造山带,精细的岩石圈三维速度结构有助于更好地认识这里的构造演化和地球动力学过程.本文收集了大别—苏鲁造山带及其周缘各区域地震台网2008—2021年间记录的天然地震走时资料,其中添加了江苏、安徽、河南三省103个自建台站的观测资料.结合区域内8~70 s瑞雷面波频散数据,采用体波面波联合反演方法获得了水平方向上0.5°×0.5°网格的Vp、Vs模型,并进行了地震重新定位.研究表明:(1)大别和苏鲁造山带的壳内速度分布具有上凸下凹的相似结构,中地壳同时存在高、低速异常,但苏鲁造山带的岩石圈厚度相对更薄.(2)襄樊—广济断裂南侧、晓天—磨子潭断裂以及嘉山—响水断裂下方出现岩石圈地幔缺口,可能与岩石圈拆沉有关,推测中地壳高速体可能是热物质通过岩石圈薄弱位置上涌后在壳内冷却形成的结晶物.(3)大别山和苏鲁地体早期可能是同生构造,受扬子板块俯冲、郯庐断裂带的走滑活动以及古太平洋板块俯冲等因素控制,造成现今岩石圈深部结构的差异.(4)研究区内的主要地质体表现出各自不同的地震活动性,地震分布总体呈现出北多南少的特征,且地震主要发生在高、低速过渡带或高速异常区域.郯庐断裂带中段郯城下方的地震在纵向上呈高角度条带状展布,最大震源深度接近25 km,表明断裂面在深部可能存在高倾角发育.Dabie-Sulu orogenic belt is an important collisional mountain belt in eastern China.Detailed lithospheric velocity model is essential for better comprehension of the tectonic evolution and geodynamic processes in this region.The earthquake catalog data recorded by the China Digital Seismic Network from 2008 to 2021 are collected in this study,including the waveform data of 103 self-managed stations in Jiangsu,Anhui and Henan provinces.We also assembled the Rayleigh surface wave dispersion data for the period of 8~70 s in this area,and the joint inversion method of body wave and surface wave data is employed to determine the Vp and Vs models with horizontal grid intervals of 0.5°×0.5°.Additionally,the earthquakes were relocated by joint inversion.This research obtained the following results:(1)The crustal velocity models in Dabie and Sulu orogenic belts exhibit a similar pattern of convex upwards and concave downwards.Both high and low-velocity anomalies exist in the middle crust,but the lithosphere thickness of the Sulu orogen is relatively thinner.(2)The lithospheric mantle gaps on the south side of the Xiangfan-Guangji fault,the Xiaotian-Mozitan fault and the Jiashan-Xiangshui fault are likely related to the lithosphere delamination.We suggest that the high-velocity anomalies in the middle crust probably are the products of crystallization of upwelling mantle materials through the lithosphere weak zones.(3)The Dabie Mountain and the Sulu terrane may have shared a common tectonic origin,yet the differences in their current lithospheric mantle could result from the subduction of the Yangtze plate,the strike-slip motion of the Tan-Lu fault zone,and the subduction of the Paleo-Pacific plate.(4)Main geological bodies show distinct seismic activities,with a general trend of higher seismicity in the north than in the south,and earthquakes mainly occur in the transition zone between high and low velocities or in high velocity anomaly areas.The earthquakes beneath Tancheng in the central segment of Tan-Lu fault zone

关 键 词：大别—苏鲁造山带 体波面波联合反演 岩石圈三维速度结构 郯庐断裂带中南段 地震重定位 

分 类 号：P315[天文地球—地震学]