Stanford University

Geophysics Sem. -Dr. Ajo-Franklin: Exploring Subsurface w/ Distributed Acoustic Sensing & Dark Fiber

Thursday, May 9, 2019 12:00 PM
Mitchell 350/372
Faculty/Staff, Students, Alumni/Friends, Members
Geophysics Department

Speaker: Dr. Jonathan Ajo-Franklin; Staff Scientist at Lawrence Berkeley National Laboratory 

Exploring the Subsurface with Distributed Acoustic Sensing & Dark Fiber

“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. More recent datasets include fiber transects in the Mojave (Ft. Irwin) and offshore cable data acquired near Monterey, CA. We demonstrate 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.

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