Inferring friction and stress states from the angle between wing fractures and solution surfaces

Abstract

Wing fractures and solution surfaces formed in the vicinity of sliding fault tips are natural examples of mixed-mode fracture propagation. Classical fracture propagation models neglect the remote and crack frictional stresses and have limitations on estimating the kink angles of wing fractures from frictional interfaces under compression. Other methods, utilizing the cohesive end zone, improve the match with the field observations. However, limitations still exist for predicting the angles of wing fractures and solution surfaces simultaneously.We analyze the near-tip stress field including the non-singular terms to estimate the kink angles of wing fracture and solution surface. The estimated kink angles of wing fractures from closed fractures are smaller than the angles from open fractures, agreeing well with the experimental results. The introduced approach predicts that the greater the friction coefficient the smaller the kink angle. The predicted angle between a wing fracture and a solution surface varies between 90° and 141° depending on the remote stress ratio and the friction coefficient. From the published image of wing fractures and stylolites in limestone in Southern France, we were able to estimate the friction coefficient of the sliding faults and the relative magnitude of the horizontal stresses.