用四维反演方法研究地震活动的深部环境

STUDY ON DEEP TECTONIC BACKGROUND OF EARTHQUAKE ACTIVITY BY USING THE 4D INVERSIONAL METHOD

摘要:

导出了用重力和水准重复测量资料反演地壳界面密度和垂直形变随时间变化的四维反演公式,并对甘肃河西地区(包括祁连山地区)和滇西北地区的重力和水准重复测量资料进行了计算.根据计算结果,分析了2个地区莫霍面密度变化速率和垂直形变速率与地震的关系.结果表明,甘肃河西地区和滇西北地区莫霍面密度大规模减小和莫霍面大范围隆起可作为1年尺度的地震预报的深部判据.地震往往发生在莫霍面隆起区与沉降区、密度减小区与增长区的过渡地带.

Abstract:

The 4D model is used to invert dynamic variation for crustal density and vertical deformation from the data of gravity measurement and leveling survey.The inverse formulae are derived.Using the formulae, data of gravity measurement and leveling survey in the Hexi region of Gansu province and northwestern Yunnan province are computed, for study on variations of the lower crustal interface density and vertical deformation of Moho surface with time.Relationship between the variations and moderate-strong earthquakes in the two regions is analysed.The results show that density of lower crustal interface reduced on a large scale and upheaval of a wide range of Moho surface in the two regions may be a geophysical criterion in crustal depth for earthquake prediction in one year.Strong earthquakes often occur in regions that are located between upheaval and subsidence of the Moho surface or density reduction and density increase of the interface.