Details

Autor(en) / Beteiligte

• Lindsey, Nathaniel J.
• Martin, Eileen R.
• Dreger, Douglas S.
• Freifeld, Barry
• Cole, Stephen
• James, Stephanie R.
• Biondi, Biondo L.
• Ajo‐Franklin, Jonathan B.

Titel

Fiber‐Optic Network Observations of Earthquake Wavefields

Ist Teil von

• Geophysical research letters, 2017-12, Vol.44 (23), p.11,792-11,799

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2017

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Our understanding of subsurface processes suffers from a profound observation bias: seismometers are sparse and clustered on continents. A new seismic recording approach, distributed acoustic sensing (DAS), transforms telecommunication fiber‐optic cables into sensor arrays enabling meter‐scale recording over tens of kilometers of linear fiber length. We analyze cataloged earthquake observations from three DAS arrays with different horizontal geometries to demonstrate some possibilities using this technology. In Fairbanks, Alaska, we find that stacking ground motion records along 20 m of fiber yield a waveform that shows a high degree of correlation in amplitude and phase with a colocated inertial seismometer record at 0.8–1.6 Hz. Using an L‐shaped DAS array in Northern California, we record the nearly vertically incident arrival of an earthquake from The Geysers Geothermal Field and estimate its backazimuth and slowness via beamforming for different phases of the seismic wavefield. Lastly, we install a fiber in existing telecommunications conduits below Stanford University and show that little cable‐to‐soil coupling is required for teleseismic P and S phase arrival detection. Plain Language Summary A new seismic recording technology, called distributed acoustic sensing (DAS), turns common telecommunications fiber‐optic cables into a very long (tens of kilometers) array of single‐component seismometers. We catalog and analyze earthquake observations from three different DAS experiments and demonstrate some of the possibilities of using this technology for earthquake seismology. We compare DAS records with a conventional seismometer and then show how the array style response of DAS enables recording of additional information such as the direction of the seismic energy. We also install a fiber in a typical telecommunications conduit below Stanford University, as opposed to directly burying the fiber in soil, and show that main seismic waves are still detected despite the hypothesized decrease in coupling between the fiber and the ground. Key Points Distributed acoustic sensing (DAS) transforms fiber optics into dense seismic arrays (1 sensor/meter) using laser scattering Earthquake observations indicate that DAS and seismometer sensitivity is similar at 0.8‐1.6 Hz Fiber installed in telecommunication conduit shows sensitivity to propagating seismic waves