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Dieren en planten

Water en land

Mens en Milieu

Prospecting methods   Seismic studies   
Seismic vessel, Marijke de Boer

Seismic studies

Sound fibrations are reflected differently by the various layers in the earth's crust. Geologists use this principle to map the earth's structure. This seismic research can be compared to determining the depth of a well by shouting into it. The tremors caused by the voice in the air in the well reflect off of the bottom and the walls, producing an echo after a short period of time. The depth of the well can be determined from this amount of time.

  • Seismic research under water

    Airguns are used during seismic studies in the sea, rivers, canals and lakes. Shock waves are created by exploding compressed air under the water surface. The reflected tremors which have passed through the rock layers are registered by very sensitive hydrophones floating on the water surface. The hydrophones are placed in plastic cables and towed behind a ship. The results of the measurements are recorded on board, after which the data are processed using computers to produce a seismogram. By interpreting the information, geologists can form a picture of the depth, thickness and formation of the rock layers and their development.
    In order to study the Wadden Sea seismically, approximately 10,000 explosions are necessary. Because gas and oil is much more intensively searched for in the North Sea, many more explosions have been need there up till now.

  • Environmental effects from seismic studies

    Seismic studies at sea are particularly disturbing due to the loud explosions. However since dynamite is not used, there is no release of dangerous materials. Because just about the entire Dutch section of the Continental Plate (NCP) has already been charted, it is expected that the intensity of the seismic studies will soon end in this area.