The 3D model and growth pattern of the Longquan Shan fault zone in Sichuan basin, China: Implications for the potential earthquake rupture patterns

Abstract

The fault three-dimensional (3D) structure and growth pattern are fundamental features of an active fault, which provide basic parameters for seismic hazard analysis. The Longquan Shan Fault Zone (LQFZ) is a major active fault, stretching for 200 km in the Sichuan Basin, southwestern China. In this study, we obtain a new, detailed 3D structure model of the LQFZ based on 43 high-resolution seismic reflection profiles. We further quantify the fault heave distribution along the entire LQFZ to understand its growth pattern. We find that the LQFZ contains four major thrust faults and a shallow detachment layer. We obtain 106 displacement values from the seismic profiles and 1963 heave values from the 3D structure model. The heave distribution of the LQFZ contains multiple peaks, indicating that the LQFZ is formed through the linkage of multiple fault segments. The cumulative heave profile of the four faults seems like an isolation fault, which implies the LQFZ has grown coherently since its formation. The maximum displacement and fault length of the four thrust faults show a linear scaling relation, suggesting that the faults grow in a self-similar manner. We also analyze the potential earthquakes on the LQFZ based on the 3D fault model and the fault growth pattern.