利用地震层析成像数据修正中国西北地区莫霍界面深度  

CORRECTION TO THE MOHO DISCONTINUITY DEPTH OF THE NORTHWESTERN CHINA USING THE DATA OF SEISMOLOGIC TOMOGRAPHY

作　　者：许萍[1] 傅容珊[1] 黄建平[1] 戴志阳[1] 查显杰[1] 

机构地区：[1]中国科学技术大学地球和空间科学学院,中国合肥230026

出　　处：《地震学报》2005年第6期598-604,共7页Acta Seismologica Sinica

基　　金：中国科学院创新项目(KZCX3-SW-131)和国家自然科学基金(40274033)资助.

摘　　要：考虑到地壳和上地幔密度异常对地表重力的影响,本文提出了修正单纯利用重力资料 反演地壳厚度的算法．该算法利用地震层析成像结果推算出地壳和上地幔密度异常分布,然 后计算由此分布引起的地表重力异常,再从观测布格重力异常中扣除上述密度异常引起的重 力效应,最后在地壳均衡假设的基础上顾及到对反演参考深度的修正,直接反演区域地壳厚 度．本文利用胥颐等地震层析成像的数据,修正了中国西北地区莫霍界面的深度．结果表明, 该区域地壳和上地幔密度异常引起的地表重力异常值为—60×1O-5m／s2～30×10-5m／s2． 与直接使用布格重力异常反演地壳厚度相比较,该密度异常对该区域莫霍界面将产生约6 km 的修正．本方法使得利用重力数据反演地壳厚度在理论上更为完备,实际应用中也比较可 行,为更进一步逼近莫霍界面的真实形态提供了一种途径．Considering the influence of the density anomaly of the crust and upper mantle on the gravity, this paper provides a new arithmetic to inverse the crustal thickness. Applying the result of seismologic tomography, we calculate the lateral density heterogeneity of the crust and upper mantle and the gravity anomalies resulted from such lateral density heterogeneity, and then subtract gravity anomalies caused by mentioned density anomalies from observed Bouguer anomalies. Finally in view of the correction to the initial crustal thickness grounded on the hypothesis of isostasy, inverse the regional crustal thickness. Using the data of seismic tomography offered by Xu Yi et a!, we inverse the Moho depth beneath northwestern China and obtain the gravity anomalies on the surface of the earth is -60×10 ^-5 m/s^2-30×10 ^-5 m/s^2. Compared with the result inverseddirectly using Bouguer anomalies, this method can bring correction of 6 km to the Moho depth. And when we inverse the thickness of the crust using the data of gravity, it will be further mature in theory, be feasible in practice and provide a new arithmetic for us to understand the conformation of the Moho.

关 键 词：地震层析成像 傅立叶变换 布格重力异常 莫霍界面 

分 类 号：P315.726[天文地球—地震学]