Temporal Variations in Seismic Velocity via Ambient Noise Interferometry: Application to Wastewater Injection and Induced Seismicity

Session: Mechanisms of Induced Seismicity: Pressure Diffusion, Elastic Stressing and Aseismic Slip [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

The town of Greeley, Colorado, situated in a previously aseismic segment of the Front Range, has experienced low-magnitude earthquakes since 2014. These events have been linked to the injection of oil and gas-derived waste water into the basal sandstone units of the Denver Basin (Yeck et al., 2016; Brown et al., 2017.) In response to the initial widely felt M 3.2 earthquake in 2014, the University of Colorado Boulder rapidly installed seismometers in the region that remained in place through 2019. In this study, we investigate changes in upper crustal relative seismic velocity (dv/v) over the past six years. Seismic velocity variations are determined by calculating daily ambient noise cross-correlations using the Python package MSNoise (Lecocq et al. 2014.) Velocity variations have been observed in studies in other regions and have been associated with volcanic activity, geothermal deformation, groundwater fluctuation, and other processes that alter media over short timespans. We explore whether the pattern of velocity changes correlates with the temporal evolution of injection, pore pressure, and seismicity. We compare the velocity changes with the record of monthly injection volumes at nearby Class II wastewater disposal sites obtained from the Colorado Oil and Gas Conservation Commission. One issue that is addressed is how reliably localized subsurface changes (~ 5 square kilometers) can be resolved with a regional-scale seismic network. Our results may provide insight into the use of ambient noise interferometry as an additional, low-cost analysis for continuous monitoring networks.

Presenting Author: Thomas M. Clifford

Authors