Abstract: The acquisition of paleostress data has always been a key and difficult problem in the field of tectonics and crustal dynamics. Previous findings show that the distribution of dykes and the alignment of volcano vents can indicate the direction of major principal stresses during the volcanic eruption period. The extension direction of underground dyke is generally parallel to the linear arrangement direction of vent and both of them give the direction of maximum horizontal principal stress in this period. This law has similar mechanical principle to hydraulic fracturing. Vent alignment survey method is a kind of geostress inversion method based on volcanic linear mode. In this paper theoretical basis of vent alignment survey method and the linear model of volcanic array are introduced. Based on the panchromatic high-resolution remote sensing image and digital elevation model(DEM)data in the Tengchong area, combining the geological exploration data about lithologic distribution of igneous rocks and the past research results of volcanic activities in the area, the research divides the volcanoes in this area, according to the age of volcanic eruption, into Holocene, late Pleistocene, early Pleistocene and Pliocene. Nakamura model was established based on the morphological characteristics and spatial distribution of the crater, and volcanic eruption period to evaluate the linear degree of the volcano in different age, and to carry out inversion of the paleostress field of the four volcanic eruption periods in Tengchong area. The reliability of the inversion results is evaluated according to Paulsen's data reliability assessment system. The data from inverting the paleostress of each show that maximum horizontal principal stress directions in the early Pleistocene period and late Pleistocene period are 39° and 37° respectively and reliability grades of inverted paleostress results in the two eras all belong to grade B; Inverted paleostress results in Holocene and Pliocene are not reliable because of the poor linearity of volcanic arrangement. The geostress direction determined by the vent alignment survey method is fairly consistent with the current geostress field obtained by the focal mechanism solution and the anelastic strain recovery(ASR method)and matches the tectonic history of Tengchong area since Neogene. The research findings demonstrate that the vent alignment survey method is an effective paleostress inversion method. The application of this method in the paleostress inversion of the Tengchong volcanic area is of important reference significance for the study of paleostress field in other volcanic areas in China.

Key words: volcanoes in Tengchong area, vent alignment survey method, linear alignment, paleostress inversion, in-situ stress orientation

摘要： 古地应力数据的获取一直以来是构造地质学和地壳动力学领域中的重点和难点问题，研究表明火山岩脉的分布和火山口的线性排列可以较好地反映火山喷发时期的主应力方向。文中以腾冲地区全色高分辨率卫星遥感图像和数字高程模型数据（DEM）为基础，结合前人对该区域地质构造、火山活动的研究成果和地质勘查资料，将火山口排列调查法应用于腾冲地区不同时期的古地应力研究中，分别对腾冲地区新近纪以来各个火山喷发时期的古地应力场进行了反演。反演得到的古地应力场数据显示：早更新世和晚更新世的最大水平主应力方向分别为39°和37°；根据Paulsen可靠度评估体系评估得出2时期地应力反演结果的可靠度等级均为B级。利用火山口排列调查法反演所得的地应力方向与通过震源机制解和非弹性应变恢复等方法得到的现今区域地应力场方向基本一致，与腾冲地区新近纪以来构造历史反映的地应力变化状况相吻合。研究结果表明，火山口反演调查法是一种有效的古地应力反演方法，此方法在腾冲火山地区古地应力反演中的应用对中国其它火山地区古地应力场研究具有重要的借鉴意义。

关键词: 腾冲火山群, 火山口排列调查法, 线性排列, 古地应力反演, 地应力方向