Reacquainting the Structural Characteristics of Pull-Apart Basins Based on Simulations with Wet Clay

Abstract

A pull-apart basin (PAB) is a releasing zone constrained by strike–slip faults. A PAB partly appears as a unique basin type typically dominated by the basin sidewall and cross-basin faults. However, the structural characteristics of different subsidiary faults derived from strike–slip motions are currently poorly understood in PABs. Under the control of different bend strike–slip faults, this study examines the formation and evolution of PABs reconstructed from wet clay with high water content (68%) as the experimental material. It was reported that (1) a PAB shows the single asymmetric half-graben architecture in the profile and rhombus in the plane, regardless of the bend type of the strike–slip fault; (2) the subsidiary fault area density increases with increasing fault displacement in PABs and might be impacted by the nature of the wet clay; (3) as the strike–slip fault displacement increases, the subsidiary fault number initially increases and then begins to decrease with large fault formation; and (4) T-faults are the most numerous faults in PABs, followed by Riedel shear faults. R′- and P-shear faults account for a small proportion and are unstable. The proportion of Riedel shear faults gradually decreases from the underlapping strike–slip faults to the overlapping strike–slip faults, accompanied by an increase in the corresponding R′-shear faults. The primary control factor affecting the proportion of subsidiary faults is the stress component. Re-recognition of subsidiary faults in the PABs is significant for interpreting strike–slip faults and the study of hydrocarbon migration.