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安徽气枪实验固定台层析成像初步结果
张云鹏 王宝善 王伟涛 徐逸鹤
中国地震局地球物理研究所地震观测与地球物理成像重点实验室, 北京市民族大学南路5号 100081
摘要:
为探索气枪震源在探测区域性地壳结构中的应用, 2015年10月10~20日在长江马鞍山-安庆段开展气枪流动激发实验(安徽实验),在20个固定点定点激发2973炮,中间流动激发1872炮,由周边109个固定台、700个流动台(包括11条测线)进行接收。为获取郯庐断裂带南端较为精细的地壳速度结构,本文利用安徽气枪实验中采集到的固定台数据进行初至P波震相拾取,对20个气枪源、52个台站、335个震相进行体波层析成像,验证了利用气枪震源进行体波层析成像的可行性,并得到了P波速度结构的一些初步结果:①利用大容量气枪震源可进行三维体波层析成像;②15km深度的成像结果显示出大区域高低速异常区的清晰轮廓,即从研究区中心向外整体呈现出低-超低-低-高的分布特征,与地质构造背景相关,具有显著的横向不均匀性;③秦岭-大别造山带显示出高速异常,与其深部超高压变质岩相对应,而长江中下游地区整体呈现低速异常,与其特殊的成矿背景相对应。
关键词:  郯庐断裂带南端  大容量气枪  震相拾取  体波层析成像
DOI:
分类号:
基金项目:
Preliminary Results of Tomography from Permanent Stations in the Anhui Airgun Experiment
Zhang Yunpeng, Wang Baoshan, Wang Weitao, and Xu Yihe
Key Laboratory of Seismic Observation and Geophysical Imaging, Institute of Geophysics, CEA, Beijing 100081, China
Abstract:
In order to explore the ability of airgun sources in imaging the crustal structure, we conducted an experiment along the Yangzte River at the section from Ma’ anshan to Anqing using an offshore airgun source (referred as the Anhui Airgun Experiment). During the experiment, the airgun source was fired 2973 times at 20 multiple shot points, while 109 permanent stations and 700 temporary stations (11 profiles) were used to record the signal. For 20 multiple shot points, we picked up 335 P-wave arrivals at 52 permanent stations. Then we obtained the P-wave velocity structure of the crust beneath the southern tip of the Tan-Lu fault. The preliminary result of P-wave velocity structure confirms the possibility of 3D body wave imaging using large volume airgun sources. The imaged velocity heterogeneity at a depth of 15km is correlated to the geological settings. High velocity anomaly beneath the Qinling-Dabie orogenic belt could be explained by the ultrahigh-pressure metamorphic rocks in the deep region, while the low velocity anomaly at the Yangtze River region may correspond to the special background of mineralization.
Key words:  Southern tip of the  Tancheng-Lujiang fault  Large volume airgun  Phase picking  Body-wave tomography