Ocean Bottom Seismometers (OBS) are seismometers designed to record earthquakes and micro-vibrations induced by other crustal tectonic events on the seabed. Compared with land seismometers, ambient vibration on the ocean floor rises and decays rapidly, with amplitude differences exceeding 20 times. Such ambient vibration originates from the ocean and is positively correlated with wind and wave conditions. OBS features complex structure, large volume and high cost; deployment and recovery operations are relatively complicated. Deploying ocean bottom seismometers enables recording of foreshocks and microseismic activities that are difficult to observe on land, facilitates research on regional variations in Earth’s structure, and serves as the most powerful tool for measuring seismic activity and characteristics near trenches and mid-ocean ridges.
These receivers must possess wide frequency bandwidth, large dynamic range, high sampling rate, stable performance under low signal-to-noise ratio, and good coupling with the seabed. Computers are adopted to conduct 3D tomographic inversion imaging based on body wave and surface wave records using teleseismic travel-time residuals and local earthquake data to solve image recognition problems, generating pseudo-color images of seabed stratigraphic structures. The imaging scale depends on array aperture, while accuracy is related to the number of array elements and array geometry. Based on seabed stratigraphic structures, sediment thickness, source rock distribution and trap conditions can be determined to evaluate hydrocarbon resources and guide subsequent exploration activities. Additionally, OBS can be applied to analyze marine engineering geological conditions, identify unstable seabed zones and prevent geological disasters.
Our company has developed float-sink short-period ocean bottom seismometers and float-sink broadband ocean bottom seismometers. In 2016, cable-type and buried ocean bottom seismometers adaptable to various marine seismic observation modes were developed to promote the advancement of marine seismic observation technology in China.
The figure below shows the field test of our ocean bottom seismometers in the South China Sea.
