利用地震成像技术研究我国首个国际认可的陨石坑  

Study on the crater of first international recognition in China using seismic tomography

作　　者：樊计昌[1] 刘明军[1] 韩艳杰 海燕[1] 赵成斌[1] 

机构地区：[1]中国地震局地球物理勘探中心,郑州450002 [2]河南省地震局,郑州450016

出　　处：《地球物理学进展》2016年第5期1895-1901,共7页Progress in Geophysics

基　　金：国家自然科学基金项目(41174078;41474077)资助

摘　　要：20世纪80年代起,辽宁省岫岩县境内的一个环形构造由中国科学家从地质、地球化学推断为陨石撞击坑,后经地质钻探进行了证实.但该环形构造的深部整体特征仍有待用地震勘探方法来确认.为了对该环形构造的深部有个整体认识,利用三维地震成像方法首次对岫岩坑的地震波折射数据进行了研究,获得了该坑的三维速度结构.结果表明:该撞击坑从地表到深度100 m的速度层对应坑内上部107 m厚的湖泊相沉积物,深度100 m到300 m的速度层对应坑内下部厚度为188 m的角砾岩堆积透镜体.大约250 m深处的波阻抗界面与地质钻孔的260 m深处的陨石冲击分界面相对应.深度300 m到650 m的低速度层可能对应角砾岩堆积透镜体下面的下元古界变质岩系的程度较低的撞击裂隙层.坑中心深度约700 m周围以及向下出现的7.0 km/s以上的高波速可能是陨石撞击时所产生的高温高压使表层岩石达到熔融状态,改变了围岩的性质,致使围岩速度升高.Since the 1980s, Chinese scientists based on geological and geochemical evidence infer that a circular structure in Xiuyan county of Liaoning province is the meteorite crater, which was confirmed by the geological drilling. But the deep-seated overall structural characteristic of the crater is yet to be confirmed by seismic exploration method. The 3D velocity structure of the crater has been obtained by using seismic refraction data through 3D seismic tomography in order to obtain the whole deep-seated structure. The results show that the velocity layer from the surface to the depth of 100 m within the crater corresponds to the upper 107 m thick lake sediments, and the velocity layer from the depth of 100 m to 300 m corresponds to the lower 188 m thick breccia accumulation lens. The wave impedance interface about 250 m deep corresponds to the meteorite impact interface confirmed by geological drilling in the 260 m deep. The low velocity layer from the depth of 300 m to 700 m corresponds to the broken Lower Proterozoic metamorphic rock layer with less impacting. Because the meteorite impact produces high temperature and high pressure, melts the surface layer rock, changes nature of the surrounding rock, and elevates velocity of surrounding rock, therefor, there is more than 7.0 km/s high velocity from the depth of 700 m to the deeper.

关 键 词：岫岩陨石撞击坑 三维地震成像 地震波走时 速度结构 

分 类 号：P631[天文地球—地质矿产勘探]