Ground motion response to an ML 4.3 earthquake using co-located distributed acoustic sensing and seismometer arrays

Journal Article · Sat Mar 17 00:00:00 EDT 2018 · Geophysical Journal International

DOI:https://doi.org/10.1093/gji/ggy102· OSTI ID:1429250

Wang, Herbert F. ^[1]; Zeng, Xiangfang ^[2]; Miller, Douglas E. ^[3]; Fratta, Dante ^[4]; Feigl, Kurt L. ^[5]; Thurber, Clifford H. ^[5]; Mellors, Robert J. ^[6]

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1. Department of Geoscience, University of Wisconsin–Madison, Madison, WI 53706, USA; University of Wisconsin-Madison
2. Department of Geoscience, University of Wisconsin–Madison, Madison, WI 53706, USA; State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China
3. Silixa Ltd, 230 Centennial Park, Centennial Avenue, Elstree, Hertfordshire WD63SN, UK; Earth Resource Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
4. Geological Engineering, Department of Civil and Environmental Engineering, University of Wisconsin–Madison, Madison, WI 53706, USA
5. Department of Geoscience, University of Wisconsin–Madison, Madison, WI 53706, USA
6. Atmospheric, Earth, and Energy Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA

The PoroTomo research team deployed two arrays of seismic sensors in a natural laboratory at Brady Hot Springs, Nevada in March 2016. The 1500 m (length) by 500 m (width) by 400 m (depth) volume of the laboratory overlies a geothermal reservoir. The surface Distributed Acoustic Sensing (DAS) array consisted of 8700 m of fiber-optic cable in a shallow trench, including 340 m in a well. The conventional seismometer array consisted of 238 three- component geophones. The DAS cable was laid out in three parallel zig-zag lines with line segments approximately 100 meters in length and geophones were spaced at approximately 60- meter intervals. Both DAS and conventional geophones recorded continuously over 15 days during which a moderate-sized earthquake with a local magnitude of 4.3 was recorded on March 21, 2016. Its epicenter was approximately 150-km south-southeast of the laboratory. Several DAS line segments with co-located geophone stations were used to compare signal-to-noise (SNR) ratios in both time and frequency domains and to test relationships between DAS and geophone data. The ratios were typically within a factor of five of each other with DAS SNR often greater for P-wave but smaller for S-wave relative to geophone SNR. The SNRs measured for an earthquake can be better than for active sources, because the earthquake signal contains more low frequency energy and the noise level is also lower at those lower frequencies. Amplitudes of the sum of several DAS strain-rate waveforms matched the finite difference of two geophone waveforms reasonably well, as did the amplitudes of DAS strain waveforms with particle-velocity waveforms recorded by geophones. Similar agreement was found between DAS and geophone observations and synthetic strain seismograms. In conclusion, the combination of good SNR in the seismic frequency band, high-spatial density, large N, and highly accurate time control among individual sensors suggests that DAS arrays have potential to assume a role in earthquake seismology.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Univ. of Wisconsin, Madison, WI (United States)
• Sponsoring Organization: Chinese Academy of Sciences; Ormat Technologies Inc., Reno, NV (United States); Silixa Ltd., Hertfordshire (United Kingdom); USDOE National Nuclear Security Administration (NNSA); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Geothermal Technologies Office (EE-4G); Univ. of Oregon, Eugene, OR (United States); Univ. of Texas, El Paso, TX (United States); Univ. of Utah, Salt Lake City, UT (United States)
• Grant/Contract Number: AC52-07NA27344; EE0006760
• OSTI ID: 1429250
• Alternate ID(s): OSTI ID: 1514806
• Report Number(s): LLNL-JRNL--745280; GJI-17-0894
• Journal Information: Geophysical Journal International, Journal Name: Geophysical Journal International Journal Issue: 3 Vol. 213; ISSN 0956-540X
• Publisher: Oxford University Press
• Country of Publication: United States
• Language: English

Related Subjects

60 signal-to-noise ratio
15 GEOTHERMAL ENERGY
47 OTHER INSTRUMENTATION
Distributed Acoustic Sensing (DAS)
Instrumentation
P waves
S waves
Seismic array
Seismic spectra
Seismograms
earthquake seismology
ground motion
particle velocity
strain