The Burst-Like Behavior of Aseismic Slip on a Rough Fault: The Creeping Section of the Haiyuan Fault, China

摘要

Recent observations suggesting the influence of creep on earthquakes nucleation and arrest are strong incentives to investigate the physical mechanisms controlling how active faults slip. We focus here on deriving generic characteristics of shallow creep along the Haiyuan fault, a major strike-slip fault in China, by investigating the relationship between fault slip and geometry. We use optical images and time series of Synthetic Aperture Radar data to map the surface fault trace and the spatiotemporal distribution of surface slip along the creeping section of the Haiyuan fault. The fault trace roughness shows a power-law behavior similar to that of the aseismic slip distribution, with a 0.8 roughness exponent, typical of a self-affine regime. One possible interpretation is that fault geometry controls to some extent the distribution of aseismic slip, as it has been shown previously for coseismic slip along active faults. Creep is characterized by local fluctuations in rates that we define as creep bursts. The potency of creep bursts follows a power-law behavior similar to the Gutenberg-Richter earthquake distribution, whereas the distribution of bursts velocity is non-Gaussian, suggesting an avalanche-like behavior of these slip events. Such similarities with earthquakes and lab experiments lead us to interpret the rich dynamics of creep bursts observed along the Haiyuan fault as resulting from long-range elastic interactions within the heterogeneous Earth's crust.