Seismic Monitoring of the Sacramento Basin Using Dark Fiber and Distributed Acoustic Sensing (DAS)

Abstract

We use a pre-existing fiber optic cable, previously installed as part of a telecommunication network that is currently not in use (so resource called dark fiber) and distributed acoustic sensing (DAS) techniques to develop seismic processing approaches to identify and map local microseismic events within the Sacramento Basin. We use this high-density passive seismic dataset to investigate the optimal pre-processing strategies and techniques to identify small natural tectonic events recorded by the fiber while excluding the more common anthropogenic seismic sources, such as cars driving along highways. We further evaluate the virtual seismometer method (VSM), which is a seismic interferometric technique that is very sensitive to the source parameters (location, mechanism and magnitude) and to the earth structure in the source region. VSM provides a precise estimate of the Green’s function between two seismic sources by cross-correlating waveforms generated by each source and recorded at the same geophones. Here, we will demonstrate the capability of VSM using fiber datasets. The ultimate aim here is to transform this type of data collection and processing techniques into products useful for basin-scale geothermal system characterization and subsurface mapping.