3:00 PM - 4:00 PM
[J08-P-03] Feasibility of the waveform analysis to the existing conventional wide-angle seismic survey data - Ocean Bottom Seismometer (OBS) and controlled-source seismic surveys in the Nankai subduction zone -
The OBS and controlled-source seismic survey is a powerful tool for imaging crustal structure beneath the seafloor. Conventionally, these data have been processed by traveltime analysis methods like a traveltime inversion, which provides us a large-scale crustal structure valuable for understanding the geodynamical processes oaccurring in the lithosphere.
In the traveltime analysis, we use arrival times only and do not utilize amplitude and phase. Therefore, if we could utilize the observed seismic waveform itself, we could extract more subseafloor information from the OBS survey data and might be able to image more detailed crustal structure.
Recently, new analysis methods utilizing the observed waveform, such as seismic interferometry, mirror imaging, and waveform inversion, have come into practical use. These modern waveform analysis methods enables us to image more detailed crustal structure than the conventional travletime analysis methods. However, to receive full benefits from these modern methods, we need to design seismic surveys to be optimal for waveform analysis, meaning dense OBS spacing.
To investigate the efficacy of the waveform analysis method for the existing conventional, actual OBS survey data, we applied these modern methods to a large number of OBS survey data obtained in the Nankai Trough subduction zone. These existing surveys were basically designed for travel-time analysis and OBS spacings were sparse (mostly 5 km). In addition, the data quality was not necessarily high because of narrow dynamic range of instruments. Despite these adverse conditions, we confirmed that these modern methods have a potential to extract detailed structural information, especially for the shallower part, from the existing sparse OBS survey data. In this talk, we are going to discuss the benefits and limitations of these waveform analysis methods to the conventional sparse OBS survey data.
In the traveltime analysis, we use arrival times only and do not utilize amplitude and phase. Therefore, if we could utilize the observed seismic waveform itself, we could extract more subseafloor information from the OBS survey data and might be able to image more detailed crustal structure.
Recently, new analysis methods utilizing the observed waveform, such as seismic interferometry, mirror imaging, and waveform inversion, have come into practical use. These modern waveform analysis methods enables us to image more detailed crustal structure than the conventional travletime analysis methods. However, to receive full benefits from these modern methods, we need to design seismic surveys to be optimal for waveform analysis, meaning dense OBS spacing.
To investigate the efficacy of the waveform analysis method for the existing conventional, actual OBS survey data, we applied these modern methods to a large number of OBS survey data obtained in the Nankai Trough subduction zone. These existing surveys were basically designed for travel-time analysis and OBS spacings were sparse (mostly 5 km). In addition, the data quality was not necessarily high because of narrow dynamic range of instruments. Despite these adverse conditions, we confirmed that these modern methods have a potential to extract detailed structural information, especially for the shallower part, from the existing sparse OBS survey data. In this talk, we are going to discuss the benefits and limitations of these waveform analysis methods to the conventional sparse OBS survey data.