论文部分内容阅读
根据西昌附近的丽江-新市镇爆炸地震测深剖面,提取了三分量记录中的横波信息,并导出了该地区的地壳、上地幔弹性结构。结果表明:三分量记录剖面中可分辨出7个反射横波和两个横波首波,把地表至上地幔顶部110 km分成7层,上地壳为三层,底层是8—10 km的低速层;下地壳为两层,莫霍面的深度为50—53 km;莫霍面之下是17—25 km的低速上地幔和28—30 km的高速上地幔.当把测线分成四段分析时,发现该区的弹性特点在横向和垂向上都有明显变化,上地壳有三个块体:丽江-金河程海块体,金河程海-昭觉块体,昭觉-新市镇块体。下地壳有两个块体:丽江-安宁河块体,安宁河-新市镇块体。上地幔顶部为一个块体。此外,根据弹性参数和岩石类型的关系作如下推测:由地表到3—5 km除局部地区存在基性、超基性岩浆岩之外,多数地区为沉积岩所覆盖。由此至14—20 km属于正常的花岗岩或变质岩层。由此到22—27 km可能在构造运动中经历了增压、增温的岩石破裂、破碎过程,形成了现今的低速、低弹性和低密度层。27—40 km的区域可能经历了花岗岩—片麻岩的变质作用。由此到50—53 km的莫霍面可能是麻粒岩—玄武岩的变质层或纯玄武岩层。由莫霍面到76—80 km的上地幔,可能是现今的高温、低压区,76—110 km的区域可能是高压.低温的上地幔。
According to the sounding profiling section of the Lijiang-Xinquzhen earthquake near Xichang, the shear wave information in the three-component record was extracted and the crustal and upper mantle elastic structures in the area were derived. The results show that seven reflection shear waves and two shear waves can be distinguished in the three-component recording profile. The top 110 km of the upper mantle are divided into seven layers, the upper crust is three layers and the bottom is low velocity layer of 8-10 km. The crust is two layers with a depth of 50-53 km on the Moho and a low-velocity upper mantle of 17-25 km beneath the Moho and a high-velocity upper mantle of 28-30 km.When the survey line is divided into four sections, It is found that the elastic characteristics of this area have obvious changes both horizontally and vertically. There are three blocks in the upper crust: Lijiang-Jinhe Chenghai block, Jinhe Chenghai-Zhaojue block, Zhaojue-Xinzhen block . The lower crust has two blocks: Lijiang - Anning River block, Anning River - New Town block. The top of the upper mantle is a block. In addition, based on the relationship between elastic parameters and rock types, it is speculated as follows: from the earth’s surface to 3-5 km, most areas are covered by sedimentary rocks, except for the basic and ultrabasic magmatic rocks in some areas. From this to 14-20 km belong to the normal granite or metamorphic rock. As a result, 22-27 km may have undergone turbulent and warming rock-breaking and crushing during the tectonic movement, forming today’s low-velocity, low-elastic and low-density layers. The 27-40 km area may have undergone granitic-gneiss metamorphism. As a result, the Moho of 50-53 km may be a metamorphic or pure basalt layer of granulite-basalts. From the Moho to the upper mantle of 76-80 km, it may be today’s high-temperature and low-pressure region, and the region of 76-110 km may be a high-pressure, low-temperature upper mantle.