Stick-Slip Induced Source Ground Vibration in Sheared Granular Fault

Date: 4/25/2019

Time: 11:30 AM

Room: Elliott Bay

The devastating potential of earthquake to society calls for a thorough understanding of earthquake source physics and dynamics. Stick-slips in sheared granular fault, as being the laboratory equivalent of natural earthquakes, are intensively studied in recent years. In these existing studies, numerous attentions have been paid to the kinematics and mechanics of the granular gouge, with few detailed results being reported regarding the response of confining plates to the stick-slips. Since the motion of the plates is analogous to the ground vibration in fault blocks, investigating the stick-slip induced ground vibration in sheared granular fault is necessary for unveiling the complex mechanism of earthquakes and may also shed light on the prediction of ground shaking and determination of hazard for future earthquakes.

Here, a two‑dimensional implementation of the combined finite‑discrete element method (FDEM), which merges the finite element method (FEM) and the discrete element method (DEM), is used to explicitly simulate a sheared granular fault system. In the FDEM model, the deformation of plates and particles is simulated using the FEM formulation while particle‑particle and particle‑plate interactions are modeled using DEM‑derived techniques. The results demonstrate that during the stick phases, both plates move at an approximately constant velocity in the direction of shearing. Whereas when slip occurs, the bottom of the upper plate bounces to the right and the top of the lower plate resets towards left. As the normal load increases, the plates are more vibrant during slips when the model is subjected to larger normal loads. Additionally, for all the normal load scenarios, the x-velocities at the sensor points during slips could be three orders larger than that during the stick phases. The simulations not only reveal the behavior of stick‑slip dynamics in granular fault gouge, but also demonstrate the capabilities of FDEM for studying stick‑slip type behavior of granular fault gouge system.

Presenting Author: Ke Gao

Authors