1:45 PM - 3:15 PM
[SVC33-P09] A research on variations in source wavelet and on reduction of source effects in the seismograms among the rounds of airgun shootings
Keywords:Structure evolution, Aira Caldera, Controlled seismic source, Volcano monitoring
The second pilot experiment of the Time-lapse Seismic Volcano Monitoring (TSVM) and the application of the source effect reduction in the rounds are presented. Stable source waveform is essential to detect any changes in subsurface structure in depth in controlled source seismology. Keeping source waveform constant is highly required to run the seismic rounds successfully. The reduction of the effect due to source wavelet variation is necessary before inspection of structure evolution because source wavelet effects on appearance of seismogram, significantly.
The first pilot experiment of TSVM was performed across the Aira Caldera with using airgun in irrigation reservoir, Sumiyoshi-ike which locates on the northwest of the caldera on 2020. According to the first experiment, it is confirmed that the source waveform from the device is controlled by some operation parameters, such as chamber size, tow depth, and operation pressure of shooting. However, because an irrigation reservoir is operating for agricultural purposes, water level depends upon cultivation phases and upon precipitation. The same water level is not always promised among each experiment round, and water level difference can cause some change in source waveform as Liu et al. (2021) reported previously. Therefore, it is necessary to accept that change in source waveform is unavoidable and to prepare the method to reduce source effect due to the different source condition in TSVM.
The second pilot experiment has done on December 2022 at the same configuration with the previous experiment. The same chamber size, the same tow depth or the same clearance distance to the water bottom are applied under the same operation pressure at the same place in the reservoir at the experiment, and only water level differed by 0.5 m. The chamber size was selected at 1050 cui due to its efficiency and favorite flat frequency component generated in the previous experiment. We got 575 shots in the same tow depth and 317 shots in the same clearance distance with the previous experiment. Actual variation of both source wavelet and far-field seismograms, and the result of the source effect reduction on the seismograms is presented.The second pilot experiment of the Time-lapse Seismic Volcano Monitoring (TSVM) and the application of the source effect reduction in the rounds are presented. Stable source waveform is essential to detect any changes in subsurface structure in depth in controlled source seismology. Keeping source waveform constant is highly required to run the seismic rounds successfully. Source waveform can vary due to some uncontrollable parameters through the rounds of airgun shooting at the station. The reduction of the effect due to source wavelet variation is necessary before inspection of structure evolution because source wavelet effects on appearance of seismogram, significantly.
The first pilot experiment of TSVM was performed across the Aira Caldera with using airgun in irrigation reservoir, Sumiyoshi-ike which locates on the northwest of the caldera on 2020. According to the first experiment, it is confirmed that the source waveform from the device is controlled by some operation parameters, such as chamber size, tow depth, and operation pressure of shooting. However, because an irrigation reservoir is operating for agricultural purposes, water level depends upon cultivation phases and upon precipitation. The same water level is not always promised among each experiment round, and water level difference can cause some change in source waveform as Liu et al. (2021) reported previously. Therefore, it is necessary to accept that change in source waveform is unavoidable in sustaining seismic experiment rounds for the volcano monitoring, and to prepare the method to reduce source effect due to the different source condition in TSVM.
The second pilot experiment has done on December 2022 at the same configuration with the previous experiment. The same chamber size, the same tow depth or the same clearance distance to the water bottom are applied under the same operation pressure at the same place in the reservoir at the experiment, and only water level differed by 0.5 m. The chamber size was selected at 1050 cui due to its efficiency and favorite flat frequency component generated in the previous experiment. We got 575 shots in the same tow depth and 317 shots in the same clearance distance with the previous experiment. Actual variation of both source wavelet and far-field seismograms, and the result of the source effect reduction on the seismograms is presented. This project is funded by Nuclear Reguration Agency (NRA), Japan.
The first pilot experiment of TSVM was performed across the Aira Caldera with using airgun in irrigation reservoir, Sumiyoshi-ike which locates on the northwest of the caldera on 2020. According to the first experiment, it is confirmed that the source waveform from the device is controlled by some operation parameters, such as chamber size, tow depth, and operation pressure of shooting. However, because an irrigation reservoir is operating for agricultural purposes, water level depends upon cultivation phases and upon precipitation. The same water level is not always promised among each experiment round, and water level difference can cause some change in source waveform as Liu et al. (2021) reported previously. Therefore, it is necessary to accept that change in source waveform is unavoidable and to prepare the method to reduce source effect due to the different source condition in TSVM.
The second pilot experiment has done on December 2022 at the same configuration with the previous experiment. The same chamber size, the same tow depth or the same clearance distance to the water bottom are applied under the same operation pressure at the same place in the reservoir at the experiment, and only water level differed by 0.5 m. The chamber size was selected at 1050 cui due to its efficiency and favorite flat frequency component generated in the previous experiment. We got 575 shots in the same tow depth and 317 shots in the same clearance distance with the previous experiment. Actual variation of both source wavelet and far-field seismograms, and the result of the source effect reduction on the seismograms is presented.The second pilot experiment of the Time-lapse Seismic Volcano Monitoring (TSVM) and the application of the source effect reduction in the rounds are presented. Stable source waveform is essential to detect any changes in subsurface structure in depth in controlled source seismology. Keeping source waveform constant is highly required to run the seismic rounds successfully. Source waveform can vary due to some uncontrollable parameters through the rounds of airgun shooting at the station. The reduction of the effect due to source wavelet variation is necessary before inspection of structure evolution because source wavelet effects on appearance of seismogram, significantly.
The first pilot experiment of TSVM was performed across the Aira Caldera with using airgun in irrigation reservoir, Sumiyoshi-ike which locates on the northwest of the caldera on 2020. According to the first experiment, it is confirmed that the source waveform from the device is controlled by some operation parameters, such as chamber size, tow depth, and operation pressure of shooting. However, because an irrigation reservoir is operating for agricultural purposes, water level depends upon cultivation phases and upon precipitation. The same water level is not always promised among each experiment round, and water level difference can cause some change in source waveform as Liu et al. (2021) reported previously. Therefore, it is necessary to accept that change in source waveform is unavoidable in sustaining seismic experiment rounds for the volcano monitoring, and to prepare the method to reduce source effect due to the different source condition in TSVM.
The second pilot experiment has done on December 2022 at the same configuration with the previous experiment. The same chamber size, the same tow depth or the same clearance distance to the water bottom are applied under the same operation pressure at the same place in the reservoir at the experiment, and only water level differed by 0.5 m. The chamber size was selected at 1050 cui due to its efficiency and favorite flat frequency component generated in the previous experiment. We got 575 shots in the same tow depth and 317 shots in the same clearance distance with the previous experiment. Actual variation of both source wavelet and far-field seismograms, and the result of the source effect reduction on the seismograms is presented. This project is funded by Nuclear Reguration Agency (NRA), Japan.