Swell Effect Correction of Sub-bottom Profiler Data with Weak Sea Bottom Signal

Abstract

A 3.5 kHz or chirp sub-bottom profiling survey is widely used in the marine geological and engineering purpose exploration. However, swells in the sea degrade the quality of the survey data. The horizontal continuity of profiler data can be enhanced and the quality can be improved by correcting the influence of the swell. Accurate detection of sea bottom location is important in correcting the swell effect. In this study, we tried to pick sea bottom locations by finding the position of crossing a threshold of the maximum value for the raw data and transformed data of envelope or energy ratio. However, in case of the low-quality data where the sea bottom signals are not clear due to sea wave noise, automatic sea bottom detection at the individual traces was not successful. We corrected the mispicks for the low quality data and obtained satisfactory results by picking a sea bottom within a range considering the previous average of sea bottom, and excluding unreliable big-difference picks. In case of trace by trace picking, fewest mispicks were found when using energy ratio data. In case of picking considering the previous average, the correction result was relatively satisfactory when using raw data.

A case study on swell correction of Chirp sub-bottom profiler (SBP) data using multi-beam echo sounder (MBES) data

“…Swell effect corrections are divided into two steps, consisting of sea-bottom detection and subsequent swell suppression. In order to effectively remove the swell, accurate sea-bottom detection on the seismic dataset is important (Lee et al, 2015). One method of sea-bottom detection is based on the cross-correlation scheme, which recognizes the sea-bottom at the point of maximum crosscorrelation between the seismic source signal and the reflected signal trace (Kim et al, 2003).…”