Centrifuge and Numerical Modeling of Normal Fault-Rupture Propagation in Clay with and without a Preexisting Fracture

Abstract

Over the last few decades, extensive research has been conducted to investigate fault-rupture propagation induced by faulting through uncemented soil. While it has long been realized that many natural soils are cemented, relatively few publications have been devoted to investigating fault-rupture propagation in cemented soil. Moreover, preexisting fracture in soil may be reactivated during earthquakes, and its influence on fault-rupture propagation is not fully understood. In this study, three centrifuge model tests are reported on investigating fault-rupture propagation induced by normal faulting in uncemented clay and cemented clay with and without a preexisting fracture. Preliminary numerical analyses of the centrifuge tests are also carried out to study the mechanism of fault-rupture propagation in these three ground conditions. Ground deformation was dominated by a shear mechanism in uncemented clay, and a shear zone along the projection of the bedrock-fault plane was observed. On the other hand, a bending deformation mechanism was identified at the ground surface in cemented clay with and without a preexisting fracture. In the presence of cementation, two main ruptures were observed, where one initiated at the cemented ground surface and propagated downward toward the center of the cemented clay, whereas the other initiated at the bedrock fault and propagated upward. The presence of a fracture in cemented clay was found to initiate a fault rupture at the tip of the preexisting fracture.