关键词: 红河断裂带, 重力变化, 重力反演, 质量迁移, 深部变形

Abstract: Surface geological and deep geophysical exploration research have shown the northern and middle Red river fault zone’s (RRF) present crustal structure and deformation has significant lateral differences. In order to detect it’s material migration characteristics, we analyze and extract gravity changes caused by vertical surface movement, surface water circulation, denudation, and GIA effects based on gravity data of RRF from 2013 to 2019. Results indicate that the recent gravity change of RRF has segmental characteristics: The average rate of gravity change in north, middle, and middle-south section is -0.39±1.30, 0.16±1.57, 0.29±1.25μGal/yr, the north section is bounded by RRF, with negative change in eastern and positive change in western, gravity change rate increases with 3.1 ±0.55μGal/yr.100km from the western to eastern, reflecting the process of deep material flow cross the RRF -meet the Lancang-river rigid block-mass accumulation under the background of material flow eastward in the Qinghai-Tibet Plateau; gravity change rate of middle section is lower than that on both sides , Reflecting the deep control of RRF; the middle-south section is the junction area between the Indochina / Sichuan-Yunnan rhomboid and South China block, it’s positive gravity change trend reflects mutual lateral compression and material accumulation between blocks. The results of moho deformation based on gravity changes and crustal structure model shows that deformation rates of the north, middle, and middle-south section are -0.06, 1.36, and 0.32 cm/yr; the moho in north section gradually changes from sinking to uplifting from eastern to western; the middle section shows uplifting in eastern and sinking in western; the middle-south section’s deformation rate is lower and differences between two sides is also small; deformation rate in RRF is significantly lower than that in both sides, which shows a strong boundary control effect on deep crustal deformation. The results provide new constraint for the study of fault activity and strong earthquakes background at southeastern margin of Tibetan Plateau.

Key words: Red river fault, Gravity change, Gravity inverse, Mass migration, Deep deformation