| 宁化-大田-惠安地壳构造与速度结构特征 |
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| 引用本文： | 蔡辉腾, 金星, 王善雄, 李培, 陈伟. 宁化-大田-惠安地壳构造与速度结构特征[J]. 地球物理学报, 2016, 59(1): 157-168, doi: 10.6038/cjg20160113 |
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| 作者姓名： | 蔡辉腾 金星 王善雄 李培 陈伟 |
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| 作者单位： | 福建省地震局, 福州 350003 |
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| 基金项目： | 国家自然科学基金项目(41474071),地震行业科研专项(2015419015)联合资助. |
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| 摘 要： | 福建地处欧亚大陆东南缘,新构造活动强烈,区内北东向断裂带异常发育,是华南震区中、强地震活动的频发区.为深入认识我国东南沿海地壳上地幔速度结构特征及其深部构造背景,福建省地震局联合中国地震局地球物理勘探中心于2010年至2012年在福建陆域实施由18次人工爆破、四条北西向原生纵测线和四条北东向集成纵测线构成的三维人工地震测深实验.本文对该实验中以北西-南东走向近似垂直穿过政和-海丰断裂的宁化-大田-惠安深地震测深测线数据进行处理解释,采用地震射线走时正演构建了该剖面二维地壳速度模型.结果显示,沿剖面地壳厚度由西向东逐渐减薄,其西北侧地壳厚约31.8 km,东南侧地壳厚达28.4 km.剖面上地壳P波速度从5.90 km·s-1逐渐增加至6.20 km·s-1,上地壳厚度横向变化不大,厚度在16~17 km左右,但是下地壳厚度由西向东减薄较为明显.地壳以政和-海丰断裂为界,东西两段具有明显不同的速度结构,呈西段速度偏低、东段速度较高的特性,且西段在上下地壳分界面下方存在一个低速层.研究表明,剖面不同区段呈现出的速度结构差异与该区大地构造单元的划分基本吻合,剖面解释结果和以往远震接收函数研究结果均印证了作为闽西南坳陷带和闽东火山断陷带分界线的政和-海丰断裂是一条切割至下地壳底部的深大断裂.
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| 关 键 词： | 深地震测深 二维地壳速度结构 政和-海丰断裂 福建中部 |
| 收稿时间： | 2015-02-13 |
| 修稿时间： | 2015-08-17 |
The crust structure and velocity structure characteristics beneath Ninghua-Datian-Hui'an |
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| CAI Hui-Teng, JIN Xing, WANG Shan-Xiong, LI Pei, CHEN Wei. The crust structure and velocity structure characteristics beneath Ninghua-Datian-Hui'an[J]. Chinese Journal of Geophysics (in Chinese), 2016, 59(1): 157-168, doi: 10.6038/cjg20160113 |
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| Authors: | CAI Hui-Teng JIN Xing WANG Shan-Xiong LI Pei CHEN Wei |
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| Affiliation: | Earthquake Administration of Fujian Province, Fuzhou 350003, China |
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| Abstract: | Fujian located on the southeast edge of the Eurasia Plate has a strong neo-tectonic activity with anomalous development of the NE-oriented fault zone within the region, which is also the frequent area of moderate and strong seismic activities in South China seismic region. In order to understand better the velocity structure characteristics of crust and upper mantle and its deep tectonic background in southeast coast of China, the 3-D artificial seismic sounding experiments were carried out through 18 explosions, four NW-oriented original and four NE-oriented integrated longitudinal survey lines conducted by Earthquake Administration of Fujian Province in coordination with Geophysical Exploration Center of China Earthquake Administration in Fujian land during years 2010 and 2012. And the 2-D crust velocity model of this profile is built based on the interpretations of the survey lines of deep seismic sounding beneath Ninghua-Datian-Hui'an which nearly goes vertically through the Zhenghe-Haifeng fault along the NW-SE.Since artificial seismic sounding experiment bears definite source parameters, seismic waveforms of high SNR and reliable phase data, it is a chief method to obtain the deep crust velocity structure with high precision. The data interpretation process is as follows:(1) pre-process the waveform data to improve SNR so as to further identify and pick up phases of different wave sets;(2) conduct the ray tracing and calculate the theoretical travel time, constantly improving models to attain the best fitting state of theoretical travel time and observational travel time.Results show that the crust thickness gradually decreases from the west to the east along the profile, with the crust thickness 31.8 km in the northwest and 28.4 km in the southeast. And the P-wave velocity of upper crust along the profile gradually increases from 5.90 km·s-1 to 6.20 km·s-1 with minor lateral variations in the upper crust thickness that varies from 16 km to 17 km, but the thickness of lower crust largely decreases from the west to the east. The Zhenghe-Haifeng fault as the boundary, the eastern and western sections of its crust have distinct velocity structures with characteristics of relatively low velocity in the west and high velocity in the east. Besides, there is a low velocity layer underneath the interface between the upper and lower crust in the western section, and the low velocity position bears some corresponding relations with the two moderate strong earthquakes in this area.The study indicates that the velocity structure difference presented in different sections of profile roughly coincides with the division of geotectonic units in this area. Thus both the interpretation results of the profile and previous teleseismic receiver function results confirm the fact that as the boundary between the depression zone in southwest Fujian and volcanic rift zone in eastern Fujian, the Zhenghe-Haifeng is a deep fault cutting to the bottom of lower crust. |
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| Keywords: | Deep seismic sounding 2-D crust velocity model Zhenghe-Haifeng fault Central region of Fujian |
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