An alternative formation mechanism for strike-slip fault in stable intracratonic basin

Abstract

The cratonic strike-slip fault is a kind of fault developed by strike-slip motion in relatively stable tectonic settings. Compared to strike-slip faults developed in an active tectonic settings, cratonic strike-slip faults have small-scale characteristics, weak activity and are difficult to identify without high-quality 3D seismic data. To date, there have been few in-depth investigations of this kind of strike-slip fault, leading to a poor understanding of its characteristics and genetic mechanisms. In this study, we extensively investigated the cratonic strike-slip faults discovered in recent years in the Ordos Basins of China via 3D seismic data, and conducted comparative analyses with similar features observed in other intracratonic basins and active tectonic settings. This study suggests that cratonic strike-slip faults have some special characteristics, such as small displacement and low maturity even when they have been active during several orogenic processes, vertical stratified structural style, and decoupling with the basin periphery structures in terms of trending direction and kinematics. This paper proposed an alternative formation mechanism for cratonic strike-slip faults. The cratonic strike-slip faults nucleate from fractures induced by regional compressive stress instead of being directly inherited from preexisting faults or basement faults. These fractures experience brittle shearing movement under various structural processes, such as plane-differential compression, oblique compression, block rotation, and finally evolve into long strike-slip faults. The development of cratonic strike-slip faults probably record the special stress transmission within the stable craton, the weak in-plane tectonic stresses in the intracratonic basin, which mainly operate at shallow depths. This formation mechanism can provide a new perspective for the understanding of brittle deformation on the earth's surface, and help to elucidate the occurrence of earthquake activity in stable blocks.