福建地区地壳三维P波速度结构与构造含义  

3D P-WAVE VELOCITY STRUCTURE OF CRUST IN FUJIAN AREA AND ITS TECTONIC IMPLICATIONS

作　　者：李强[1,2] 吴建平[1] LI Qiang;WU Jian-ping(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Fujian Earthquake Agency,Fuzhou 350003,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]福建省地震局,福州350003

出　　处：《地震地质》2023年第4期970-986,共17页Seismology and Geology

基　　金：国家自然科学基金(42104091)。

摘　　要：福建地区经历了复杂的构造演化过程,多期构造变化所形成的巨量侵入-火山岩在该区域广泛出露。文中利用1999-2021年福建地震台网的观测报告,并融合周边省份的部分数据,挑选出了3203个地震,其中包括76423条绝对到时数据,389021条P波相对到时数据。采用双差地震层析成像方法获得了福建地区地壳三维P波速度的精细结构,横向分辨率为0.25°。除闽西北地块外,其他区域可被检测板较好恢复。研究结果表明:1)闽西南地块在15~25km深度普遍呈现相对低速特征,结合区域地质背景、前人的接收函数结果及大地电磁测深数据等分析认为,该低速特征并非由部分熔融或韧性剪切带所致,主要是由于区域地壳更富含石英成分引起的;2)闽东地块的中下地壳存在2个相对低速异常体,且与地表大地热流异常相对高值区对应;3)福安-南靖断裂带在中下地壳对该区域的地壳速度分布具有一定的控制作用,进一步证实其是区域内的一条深大断裂带。The Fujian area is located tectonically at the southeastern margin of the South China continent,which consists of three sub-blocks,the northwest Fujian block,the southwest Fujian block and the east Fujian block.This region is the forefront of the interaction between the Eurasian plate and the Philippine Sea plate.Geologically,the Fujian area has undergone a complex tectonic evolution process,and the huge intrusive-volcanic rocks formed by multi-stage tectonic changes were widely exposed in this region.Since the inversion of the crustal three-dimensional P-wave velocity structure was important for understanding the tectonic evolution process and the deep seismogenic environment in the region,a lot of research work has been carried out in Fujian area,including seismic body wave tomography,ambient noise surface wave tomography and artificial seismic profiles.Although some important features of the crustal velocity structure in this region had been obtained by natural seismic body wave or ambient noise surface wave imaging,the grid lateral resolution was relatively poor(generally above 0.5°horizontally),which made it difficult to constrain effectively the detailed features of the fault zone velocity structure in this region.For example,the Fu'an-Nanjingfault zone,as an important fault zone in the region,which controlled the magmatic intrusion activities before the Mesozoic,the features of its deep velocity structure have been rarely revealed.Although the resolution of artificial seismic profiles was high,it covered a relatively limited detection range in this region.In this paper,3203 natural local earthquakes were selected using the observation reports of Fujian seismic network from 1999 to 2021 and integrating some data from neighboring provinces,which includes both 76423 absolute arrival time data and 389021 P-wave relative arrival time data from131 seismic stations.The test results of checkboard showed that the northwest Fujian block had poor recovery at all depths due to the limited internal seismic ray coverag

关 键 词：福建地区 双差层析成像 速度结构 福安-南靖断裂带 

分 类 号：P315.2[天文地球—地震学]