Current Research in EEPS Seminar – Dr. Jonathan Ajo-Franklin – Lawrence Berkeley National Laboratory
Title: Exploring the Subsurface with Distributed Acoustic Sensing & Dark Fiber
Abstract: “Dark Fiber” refers to the large number of fiber optic lines installed for telecommunication purposes but not currently utilized. With the advent of distributed acoustic sensing (DAS), these unused fibers have the potential to become a seismic sensing network with unparalleled spatial extent and density with applications to monitoring both natural seismicity as well as near-surface soil properties. We present results demonstrating the application of DAS to seismic monitoring on a variety of dark “networks of opportunity” including a 20 km run of telecommunications fiber between West Sacramento, CA and Woodland CA, part of the Dark Fiber Testbed maintained by the DOE’s ESnet user facility. We show that continuous DAS recording on such networks can be leveraged to generate both temporally-resolved near-surface velocity models using infrastructure ambient noise as well as detect local, regional, and teleseismic earthquakes with broadband fidelity. We also show preliminary results from recordings on offshore cables, demonstrating the potential for high-density seismic measurements in previously inaccessible regions.