Detection of the active segment at the Red River Fault Zone by inversion of observed gravity changes

Abstract

A method for determining fault movement models by inversion of temporal gravity changes at a fault zone is presented in this paper. To demonstrate the validity of the method, a numerical test is performed for estimating four types of fault movement models from simulated gravity changes with random noise. Results from the numerical test show the possibility of detecting fault movement models from gravity changes. Based on this work, the active segment at the Red River Fault Zone (RRFZ) is investigated by inversion of observed gravity changes in the area (November 1985 to November 1990). The inverted results from the gravity changes of segments between points indicate an active segment at the Red River fault, characterized by right-lateral strike slip (1.7 ± 0.2 m), with a length of 237.6 km ±6.1, a width of 13.3 ± 4.0 km, a dip-angle of 83.0 ° ± 3.0 °, a depth of 13.1 ± 3.1 km, and a strike direction of 157.7 ° ± 3.0 ° (SE). These characteristics of the detected active segment at the RRFZ are in agreement with those from geological investigations, and from the inversion of observed GPS baseline changes in the area, and imply that the current fault movements at the Red River fault may belong to the inherited structural movements.