闫成国^1,,
曹井泉¹,
陈宇坤¹,
刘保金²,
高武平¹,
姬计法²,
张文朋¹,
酆少英²
1. 天津市地震局, 天津 300201
2. 中国地震局地球物理勘探中心, 郑州 450002

基金项目: 天津市科技重大专项"地震风险预警技术及服务产品研发与应用"项目（18ZXAQSF00110），国家自然科学基金（41772123）及天津市"十二五"蓟运河断裂探测项目（津发改投资647号）共同资助


详细信息

作者简介: 闫成国, 男, 1982年生, 硕士, 高级工程师, 主要从事地震地质、活动构造的研究工作.E-mail:yanchg2004@163.com

中图分类号: P315

收稿日期:2020-05-11
修回日期:2020-11-06
上线日期:2020-12-05

Fine crustal structures of Zhangjiakou—Bohai tectonic zone in Tianjin area revealed by a deep seismic reflection profile

YAN ChengGuo^1,,
CAO JingQuan¹,
CHEN YuKun¹,
LIU BaoJin²,
GAO WuPing¹,
JI JiFa²,
ZHANG WenPeng¹,
FENG ShaoYing²
1. Tianjin Earthquake Agency, Tianjin 300201, China
2. Geophysical Prospecting Center, China Earthquake Administration, Zhengzhou 450002, China


MSC: P315

--> Received Date: 11 May 2020
Revised Date: 06 November 2020
Available Online: 05 December 2020


摘要
摘要:穿过天津地区张渤带的长86 km、NE向深地震反射剖面揭示了该区清晰的地壳精细结构图像和断裂的深浅构造特征，为研究张渤地震构造带的深部孕震环境和构造模式提供了地震学证据，对探讨晚中生代以来华北裂陷盆地的深部动力学过程及演化具有重要意义.结果表明，天津地区张渤带地壳以结晶基底反射T_G为界，分为上下两部分；上地壳反射波组丰富，分层特征明显，界面起伏形态清楚，清晰地刻画出冀中坳陷新生代沉积分层、箕状沉积凹陷的底界、潮白河断裂、蓟运河断裂及丰台—野鸡坨断裂的几何结构；地壳内部结晶基底（T_G）至Moho之间，显示出近于"反射透明"的地震波场特征，无明显震相，这与华北其他地区的深地震反射剖面结果明显不同；地壳厚度为30.0~34.5 km，总体变化趋势为中段地壳厚而南北端相对较薄，Moho在横向上显示出明显的不均匀和横向间断特征，在Moho被错断处存在两个明显的反射事件R_A和R_C，R_A可能是软流圈热物质上涌的侧向残留物，叠层状反射震相R_C则表现出壳幔过渡带特征；剖面揭示了2条错断Moho的超壳深大断裂（F_D1和F_D2）和9条上地壳断裂，深大断裂应是软流圈热物质上涌，造成上地幔隆起而形成的，上地壳断裂与地壳垂直运动及侧向引张力有关；超壳深断裂（F_D1和F_D2）为本区深部热物质的上涌与能量交换提供了通道，而与之对应的地壳浅部断裂（F₃和F₉），则为能量调整提供了可能的条件，断裂邻近区域可能是未来发生强震的地区，值得注意.
关键词: 张渤构造带/
深地震反射剖面/
地壳精细结构/
深断裂

Abstract:A NE-trending deep seismic reflection profile with 86 km long across the Zhangjiakou-Bohai tectonic zone in Tianjin area was completed in 2018. This profile reveals the fine crustal structure image and the tectonic features of the faults in this tectonic zone. It provides new seismic evidence for the research on the deep seismogenic environment and tectonic patterns of the Zhangjiakou-Bohai tectonic zone. These results are of great significance for the discussion on the deep dynamic and evolutionary process of the North China rift basin since the Late Mesozoic. According to this study, the crust of the Zhangjiakou-Bohai tectonic zone in Tianjin area is divided into the upper part and the lower part based on the reflection T_G of the crystalline basement. The reflection wave groups in the upper part of the crust are abundant and present obvious layers. The clear ups and downs of the interfaces clearly depict the Cenozoic sedimentary layers of the Jizhong depression, the bottom boundary of the "dustpan shaped" sedimentary depression, and also the geometry of the Chaobaihe, Jiyunhe and Fengtai-Yejituo faults. On the contrary, there has no distinct seismic phase in the area between the crystalline basement (T_G) and the Moho surface, which has great differences from the results of other parts of North China. The crustal thickness ranges from 30.0 to 34.5 km, and the crust in the middle segment is thicker than both the north and south segments. The Moho surface presents prominent inhomogeneity and discontinuity in the transverse direction, and there are two obvious reflection events, R_A and R_C, at the area where the Moho surface is offset. The R_A may be the lateral residue of the upwelling of the asthenosphere. The laminated reflection seismic phase of R_C presents characteristics of the crust-mantle transition zone. This profile reveals 2 deep faults offset the Moho surface (F_D1 and F_D2) and 9 upper crust faults. The deep faults should be caused by the uplift of the upper mantle resulted from the asthenosphere. The upper crust faults are related to the vertical movement and lateral tension of the upper crust. The deep faults (F_D1 and F_D2) provide a channel for the energy exchange and upwelling of deep thermal materials in this area. The corresponding shallow crustal faults (F₃ and F₉) provide possible conditions for energy adjustment. Therefore, the adjacent areas of these faults should be paid attention to for the occurrence of strong earthquakes in the future.
Key words:Zhangjiakou-Bohai tectonic zone/
Deep seismic reflection profile/
Crustal fine structure/
Deep fault



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