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

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Ngôn ngữ: eng

Ký hiệu phân loại: 333.9 Other natural resources

Thông tin xuất bản: Washington, D.C. : Oak Ridge, Tenn. : United States. National Nuclear Security Administration ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2018

Mô tả vật lý: Size: p. 2020-2036 : , digital, PDF file.

Bộ sưu tập: Metadata

ID: 260273

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.
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