|
| | Abstract | | The DAS uses backscattering of laser light caused at any point along the optical fiber. Although DAS is very useful because it could provide very dense and distributed seismic records along 20 km distance, the quality of data and comparison of waveforms to ones by conventional geophone have been not well-known. According to Schlumberger, their DAS measures the strain rate parallel to the fiber elongation in contrast to geophone measuring the particle motion of displacement. To confirm the physical quantity of DAS measurement in real field study, we carried out experiments using DAS and three-component seismometers at the same location. We used 100-m-long three optical fibers at 20 cm depth, one hundred 4.5 Hz vertical geophones at every meter and 18 units of low-freq. 3C seismometers. The 4-days experiment was carried out in September 2017. Using two natural earthquakes we compared the calculated strain rate using horizontal components of the seismometers to DAS records. The comparison of S-wave phases shows surprisingly nice fitting to each other. The phase to phase fitting suggests we can compare theoretical strain records and observed ones. |
|
|
|
| |
|