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Introduction

Geocap can compute sediment thickness data sets, based on seismic interpretations of the sediment base and the seafloor, and velocity information. The result of these computations can later be used for the sediment thickness calculations needed in UNCLOS Article 76.

The seabed and the base of the sediments can be interpreted from Seismic data as two horizons. The sediment thickness can be calculated as the vertical distance between these two interpretations. In order to do UNCLOS Article 76 sediment thickness calculations, we need to know the sediment thickness in meters. Normally a seismic line is interpreted with Two Way Travel (TWT) as the z coordinate. Two way travel time is the time it took for the sound signal to travel from the Seismic sound source, down to the reflector and back to hydrophone. This time is normally measured in milliseconds. We need to convert from TWT in milliseconds to depths in meters. This operation is called a "depth conversion".

In order to do a depth conversion, we need to know the velocity of the sound signal in the sediments. In the dept conversion process we can use a data type called a velocity profile. A velocity profile is a data set which consist of interval velocity information combined with the seismic interpretation for each horizon of a seismic line. The interval velocity stored in the velocity profile is the average velocity between two reflectors.

The first step in generating a sediment profile based on seismic interpretations is to generate a velocity profile from the interpretations and velocity information. Read about: Importing Velocities.

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