利用接收函数方法重建丽江—小金河断裂及其邻区的地壳结构

To reconstruct the crustal structure of Lijiang-Xiaojinhe fault and its surrounding area by the receiver function

造山作用和岩浆作用等会使Moho面形态及壳内物质组分发生改变.复杂的地质构造会使经典H-k扫描的结果产生偏差.在经典H-k扫描的基础上发展了接收函数地壳平均P波、S波速度扫描技术,理论模型测试表明,该方法具有较高的稳定性和可靠性.我们将该方法应用在丽江—小金河断裂及其邻区,结果显示在Moho面倾斜、地壳各向异性的情况下有很好的应用潜力.结果表明:丽江—小金河两侧的地壳厚度存在明显差异,北侧地壳厚度在45~57 km,南侧地壳厚度在54~60 km,且在峨眉山大火成岩省内带的东北地壳厚度达到最大,超过60 km;丽江小金河周边地区的k值为1.6~2.0,横向分布不均匀;峨眉山大火成岩省喷发时,上涌的岩浆在峨眉山大火成岩省内带东北缘的地壳底部形成了底侵层,这使得该区域Moho面倾角超过20°,地壳较厚且k值较高.

Mountain-building and magmatic activities can cause changes in the morphology and composition of the Moho and crustal materials.Complex geological structures can lead to deviations in the results of classic H-kstackingmethod.In this paper,we developed a receiver function crustal average P-wave and S-wave velocity scanning technique based on the classic H-k stackingmethod.,and theoretical model tests showed that this method has high stability and reliability.We applied this method to the Lijiang-Xiaojinhe fault and its surrounding area,and the results showed that this method has great potential for application in situations where the Moho is inclined and the crustal anisotropy is present.Our study showed that there is a significant difference in crustal thickness between the two sides of the Lijiang-Xiaojinhe fault,with the crustal thickness on the northern side ranging from 45 km to 57km and on the southern side ranging from 54 km to 60 km.In addition,there is a maximum crustal thickness value exceeding 60km on the northeastern margin of the Emeishan large igneous province.The k values in the Lijiang-Xiaojinhe area range from 1.6 to 2.0,indicating strong regional variability.The results of this paper show that due to the activity of the mantle plume during the eruption of the large igneous province,the underplating layer is formed in the northeastern margin of the inner belt of the Emeishan large igneous province,which makes the crust in this area thicker,the k value is larger,and the Moho inclination angle exceeds 20°.