Rapid Surface Deployment of a DAS System for Earthquake Hazard Assessment

Distributed acoustic sensing (DAS) is a relatively new technology used in many geophysical applications. The versatility, high spatiotemporal resolution, and sensitivity to surface waves make DAS ideal for rapid deployment surveys such as earthquake-aftershock monitoring and hazard assessment. However, these applications usually rely on trenched cable installations that are time consuming and cost-prohibitive to deploy, or on existing telecommunication fibers that are limited in spatial coverage. To examine the potential of untrenched surface deployments, we acquired DAS data in continuous mode for one hour on a rapidly deployed fiber array composed of six parallel linear subsections directly on the surface with different fiber-ground contact conditions. We applied ambient interferometry and adopted a simplified method to determine the average shear-wave velocity of the top 30 m (VS30). Our methodology resulted in robust VS30 estimates for each surface deployment subsection that are consistent with collocated 1-m-deep trenched cables. The implications of these findings support DAS as a viable method for noninvasive-deployment surface surveys for rapid earthquake hazard and damage assessment.