4 cm Portable Active Seismic Source (PASS) for Meter- to Kilometer-Scale Imaging and Monitoring of Subsurface Structures

Abstract

Abstract We have developed a minimal Portable Active Seismic Source (PASS) system for imaging and monitoring geological formations. Stacking of the signals continuously generated by the PASS enhances the signal-to-noise ratio, allowing the use of a small seismic source to explore and monitor areas with poor accessibility. The small size and low cost of the PASS allow its deployment in many places to continuously monitor geological formations, including reservoirs, with high spatial resolution. The PASS generates chirp signals with a wide frequency range, which is configurable to suit the imaging or monitoring target. Here we report applications of our PASS on a riverbank and, in combination with a distributed acoustic sensing (DAS) array, on a tailings embankment in a mining area. With its dense array of DAS receivers, the PASS-DAS system shows promise for high-resolution and low-cost monitoring applications. The chirp signals from our PASS unit (4 cm diameter motor), generated by eccentric rotation of a mass <10 g with a frequency range of 20–60 Hz, propagated a horizontal distance of >900 m. We also recorded temporal variations of seismic velocity and attenuation associated with rainfall events and ice formation. These field experiments demonstrate that the PASS can be used to rapidly and inexpensively image sites with limited access, such as mountainous and extraterrestrial environments, and for monitoring embankments, landslides, and geothermal or CO2 storage reservoirs.