5:15 PM - 7:15 PM
[STT42-P08] Deep well seismic observation using existing optical fiber cable for measurement and DAS-VSP analysis
Keywords:Deep observation well, Optical sensor, Existing optical fiber cable for measurement, DAS, DAS seismogram, DAS-VSP analysis
In the 3000m-class deep observation well of NIIGATA INSTITUTE OF TECHNOLOGY, development and test observation of the optical hybrid observation system has been performed. The optical hybrid observation system consists of a 3-components optical seismometer and DAS (Distributed Acoustic Sensing). Optical seismometers are installed at surface and high-temperature and high-pressure environment at depth of 1977m (Pressure: approx. 20MPa, Temperature: approx. 105°C) in February 2022. DAS measurement using dark fiber in existing measurement cable have started in July 2023, and a number of DAS seismograms (dynamic strain variation) are observed.
In order to verify whether DAS-VSP (vertical seismic profile) analysis is possible or not using observed DAS seismograms, a cross-correlation analysis was performed. The DAS interrogator is ONYX manufactured by SINTELA. The gauge length is 6.38m, measurement interval is 3.19m and sampling interval is 1 millisecond. This report focuses on aftershocks of the 2024 Noto Peninsula earthquake that occurred from January 18 to June 17, 2024 (>137E, >M4; 19 earthquakes). First, from each DAS seismogram, the initial part of P-wave (4 sec) and S-wave (5 sec) were extracted. Next, a cross-correlation analysis was performed with the oscillation point set at deep (No.600; depth of 1898m), and the receiver point as a shallower point (No.599 to 10) for 19 earthquakes. Finally, the cross-correlation functions for each receiving point were stacked.
The results showed that observed DAS seismograms contribute to DAS-VSP analysis (see figures below). This suggests that DAS-VSP analysis may be possible from DAS seismograms at other observation points that use optical measurement cable.
In order to verify whether DAS-VSP (vertical seismic profile) analysis is possible or not using observed DAS seismograms, a cross-correlation analysis was performed. The DAS interrogator is ONYX manufactured by SINTELA. The gauge length is 6.38m, measurement interval is 3.19m and sampling interval is 1 millisecond. This report focuses on aftershocks of the 2024 Noto Peninsula earthquake that occurred from January 18 to June 17, 2024 (>137E, >M4; 19 earthquakes). First, from each DAS seismogram, the initial part of P-wave (4 sec) and S-wave (5 sec) were extracted. Next, a cross-correlation analysis was performed with the oscillation point set at deep (No.600; depth of 1898m), and the receiver point as a shallower point (No.599 to 10) for 19 earthquakes. Finally, the cross-correlation functions for each receiving point were stacked.
The results showed that observed DAS seismograms contribute to DAS-VSP analysis (see figures below). This suggests that DAS-VSP analysis may be possible from DAS seismograms at other observation points that use optical measurement cable.