An ocean-bottom seismometer (OBS) is a seismometer that is designed to record the earth motion under oceans and lakes from man-made sources and natural sources.
An ocean-bottom seismometer goes over the side of R/V Oceanus in early 2001, off Barbados. It will record long-period, low-frequency seismic waves for up to a year before the ship returns to retrieve the instrument. (Photo by John Whitehead, Woods Hole Oceanographic Institution)
Image: Ocean Bottom seismometer
This shows a P wave (red) converting into an S wave (blue), with the P wave having the ability to travel through the ocean and reflect back down off of the surface into the seismometer. This creates water multiples that do not exist when the seismometer has free-air above it.
A seismometer is an instrument that responds to ground noises and shaking such as caused by quakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The output of such a device—formerly recorded on paper or film, now recorded and processed digitally—is a seismogram. Such data is used to locate and characterize earthquakes, and to study the internal structure of Earth.
Kinemetric seismograph.
Basic horizontal-motion seismograph. The inertia of the round weight tends to hold the pen still while the base moves back and forth.
Replica of Zhang Heng's seismoscope Houfeng Didong Yi
Milne horizontal pendulum seismometer. One of the Important Cultural Properties of Japan. Exhibit in the National Museum of Nature and Science, Tokyo, Japan.
