Construction and application of preprocessing technology for passive source ocean bottom seismometer data

The passive source Ocean Bottom Seismometer (OBS) survey is one of the important methods for the study of deep structure in the oceanic area. Affected by many factors such as ocean current, rugged seafloor, seabed temperature and pressure environment in the deployment area, the OBS data have been facing such problems as uncertainty of attitude, clock drift and horizontal azimuth deviation. Based on the characteristics of domestic OBS hardware and its observation data, this study constructs a preprocessing technology for the three critical data correction steps of instrument attitude, clock time, and horizontal azimuth. The instrument attitude correction scheme is constructed through the characteristics of the hardware design. The time correction technology is proposed from the combination of the characteristics of crystal oscillator and the cross-correlation method of ambient noise. Horizontal azimuth correction is conducted based on two technical approaches: minimization of tangential component of P-wave energy and principal component analysis of P-wave. The above-mentioned preprocessing technology system has achieved excellent results in the data preprocessing of passive source OBS data acquired in the Sulawesi Sea. The results of time-frequency analysis of ambient noise level and seismic signal show that the preprocessing technology can effectively improve the quality of passive source OBS data which could lay a solid foundation for further scientific research.