| 张渤地震带及邻区近震体波成像及孕震环境分析 |
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| 引用本文： | 杨歧焱,吴庆举,盛艳蕊,高家乙,宋键,邸龙.张渤地震带及邻区近震体波成像及孕震环境分析[J].地球物理学报,2018,61(8):3251-3262. |
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| 作者姓名： | 杨歧焱 吴庆举 盛艳蕊 高家乙 宋键 邸龙 |
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| 作者单位： | 1. 河北地质大学勘查技术与工程学院, 石家庄 050031;2. 中国地震局地球物理研究所, 北京 100081;3. 河北省地震局, 石家庄 050021;4. 河南省地震局, 郑州 450016 |
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| 基金项目： | 河北地质大学博士科研启动基金（BQ2017027），地震科技星火计划项目（XH17006Y）和国家自然科学基金（41474074，41674094）共同资助. |
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| 摘 要： | 针对张渤地震带深部孕震构造环境和地幔岩浆对地壳底侵作用的问题，本文充分收集了华北地区区域数字地震台网176个固定台站记录到的观测数据，应用近震体波层析成像方法，获得了华北地区地壳的P波三维速度结构和VP/VS波速比.依据VP/VS波速比能反映岩石物理性质和流变学特征的特性，并结合人工地震测深剖面、大地电磁测深、地球化学等成果，讨论了张渤地震带的孕震环境和动力学机制等问题.研究结果显示：张渤地震带强震位于高低速异常分界线附近或偏向高速体一侧，震源体下方均存在广泛的低速异常分布，据此推测这些低速异常的存在可能与流体有关，同时也揭示出张渤地震带地震主要分布在上地壳，从震源深度分布及地壳物性结构分析上地壳具有发震的构造背景，也有发震的物性基础，是一个易震层和多震层.张渤地震带地壳内部在20 km下方存在偏高的波速比特征，这些可能反映了在该区域内中、上地壳幔源物质的侵入和热状态的岩体在横向上的变化，可能是地幔岩浆长期底侵作用的结果.由于深部幔源物质的侵入，使得地壳深部流体的供给量增加，在地壳发震层下长期存在的流体会影响断裂带的结构，降低断裂带的强度，使区域应力场发生变化从而导致断裂带上应力的集中，进而引发地震发生.
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| 关 键 词： | 地震走时 层析成像 波速比 张渤地震带 |
| 收稿时间： | 2017-09-21 |
Regional seismic body wave tomography and deep seismogenic environment beneath Zhangbo seismic belt and its adjacent area |
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| YANG QiYan,WU QingJu,SHENG YanRui,GAO JiaYi,SONG Jian,DI Long.Regional seismic body wave tomography and deep seismogenic environment beneath Zhangbo seismic belt and its adjacent area[J].Chinese Journal of Geophysics,2018,61(8):3251-3262. |
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| Authors: | YANG QiYan WU QingJu SHENG YanRui GAO JiaYi SONG Jian DI Long |
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| Institution: | 1. Hebei GEO University, Shijiazhuang 050031, China;2. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;3. Earthquake Administration of Hebei Province, Shijiazhuang 050021, China;4. Earthquake Administration of Henan Province, Zhengzhou 450016, China |
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| Abstract: | This study focused on the deep seismo-tectonic environment and mantle magma underplating of the Zhangbo (Zhangjiakou-Bohai) seismic belt in North China. We fully collected the observational data recorded by 176 permanent stations of the regional digital seismograph network in North China, and applied the body wave tomography method to obtain the three-dimensional P-wave velocity structure and VP/VS of the crust in North China, which permits to infer the physical features and rheological characteristics of rock. Combined with the artificial seismic sounding profiles, magnetotelluric and geochemistry surveys, some issues such as the seismogenic environment and dynamic mechanism of the Zhangbo seismic belt are addressed. Results show that the major earthquakes in the Zhangbo seismic belt are typically located near the high-low-velocity anomaly boundary or on the high-velocity side. There are a wide range of low-velocity anomalies beneath the source bodies, which are speculated to be associated with the presence of fluid. Our results also reveal the major earthquakes in the Zhangbo seismic belt are mainly distributed in the upper crust. Based on the depth distribution of hypocenters and the physical structure analysis, we suggest the upper crust has tectonic setting and the physical properties for generation of earthquakes. There is a high velocities ratio below 20 km within the crust in the Zhangbo seismic which may reflect the intrusion of mantle-derived materials in the middle-upper crust and lateral thermal changes of the rock mass in the region, which could be related to long-term under plating of mantle magma. Due to the invasion of deep mantle source material and increase of the supply of deep fluid in the crust, the long-term existence of fluid under the crustal seismogenic layer will affect the structure of the fault zone and reduce its strength, thus changing the regional stress field, leading to the strain concentration on the fault zone, which triggers earthquakes in this area. |
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| Keywords: | Seismic Travel time Tomography VP/VS wave velocity ratio Zhangbo seismic belt |
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