Fujian Earthquake Agency
Xiamen Institute of Marine Earthquake, China Earthquake Administration

位于中国大陆东南缘的福建地区是东南沿海的一个活动构造带，有着复杂的形成和演化历史。为了认识该区浅部地壳结构和基底构造特征，利用福建地区4条NE向深地震测深测线的Pg波走时数据，使用有限差分层析成像方法，获得了4条剖面上部地壳的精细速度结构，揭示了该区上部地壳速度结构的横向变化、基底构造以及断裂浅部特征。4条剖面速度介于4 700 ~6 100 m/s，自西向东速度变化逐渐增强，构造单元边界两侧基底速度横向变化明显；4条剖面结晶基底界面埋深介于1.0~6.0 km，由北往南有所加深，基底面的起伏与构造凸起和凹陷对应；闽西北隆起带的上部结构速度整体偏高且界面埋深较浅，与变质基底有关；闽西南拗陷带的上部地壳结构高低速变化明显且界面形态呈深浅间隔变化，与该区的断陷盆地和拗陷与隆起交错的地质构造相对应；东南沿海中生代岩浆带的上部地壳速度高、变化大，表明华南大陆东部所受的构造活动强于西部。剖面经过的NW向断裂带都切割基底，与该区的地质构造和构造变形的主方向一致，反映了受古太平洋板块NW向的俯冲−碰撞挤压作用。研究成果为获得东南沿海重要的NW向构造深浅关系提供浅部地震学证据。

The Fujian region, located along the southeastern margin of the Chinese continent, constitutes an active tectonic belt along the coastal area in southeast China, with complex formation and evolution histories. To understand the characteristics of upper crustal structures and basement structures in the Fujian, this study collected the Pg travel time data from four NE-trending deep seismic sounding (DSS) survey lines in the region. Employing finite-difference tomography, this study obtained the fine-scale velocity structure of the upper crust along the four profiles, revealing the lateral variations in the upper crustal velocity structure, basement structures, and shallow fault characteristics in the region. Key findings are as follows: (1) The velocities along the four profiles range between 4700 and 6100 m/s, gradually increasing from west to east. They exhibit noticeable lateral variations in basement velocities on either side of tectonic unit boundaries. (2) The burial depth of crystalline basement interface along the four profiles varies between 1.0 and 6.0 km, deepening from north to south. The undulations in the basement surface correspond to the structural uplifts and depressions. (3) The upper structures in the uplift zone in northwest Fujian exhibit overall high velocities and shallow burial depths, which are related to the metamorphic basement. (4) Regarding the upper crust in the depression zone in southwest Fujian, its structures exhibit significant variations velocities, and its interface morphology displays alternating patterns of deep and shallow parts. These correspond to the geological structures characterized by fault basins and depressions interlacing with uplifts in the region. (5) The upper crust of the Mesozoic magmatic zone along the coastal area in southeast China exhibits high and greatly varying velocities, indicating that stronger tectonic activity in the eastern part of South China Continent compared to its western part; (6) The NW-trending fault zone where the DSS profiles pass through cut through the basement, showing dominant strikes consistent with those of the geological structures and tectonic deformations in Fujian. This finding reflects the NW-directed subduction-collision compression from the Paleo-Pacific Plate. These findings provide shallow seismic evidence for obtaining significant depth relationships of NW-trending structures along the coastal area in southeast China.

国家自然科学基金项目(41474701)；中国地震局地震行业科研专项项目(201508015)；中国地震局地震科技星火计划项目(XH19024Y)

李培，任丛荣，李海艳，等. 福建地区上部地壳结构深地震测深探测研究[J]. 煤田地质与勘探，2023，51(12)：93−105.

LI Pei，REN Congrong，LI Haiyan，et al. Revealing the upper crustal structure in the Fujian region using deep seismic profiling[J]. Coal Geology & Exploration，2023，51(12)：93−105.