Building and calibrating seismic velocity models with gOcad

@inproceedings{SüssRM2000,
 abstract = { In the frame of integrated hazard risk assessment of sedimentary basins regional velocity models are needed for multiple applications :
- Time/depth conversion of seismic profiles for structural interpretation,
- forward modelling of wave propagation in lithosphere scale models,
- precise relocation of earthquakes.
It is the goal to approach these very different applications using only one unified seismic velocity model. Using GOCAD a regional 3D velocity model in the Los Angeles Basin California was derived from stacking velocities of reflection seismic profiles. The model was subsequently calibrated using available sonic logs from exploration and production wells. Additionally, the top of the basement was included.
Statistic relations of velocities and other surveyed properties in wells are used to extend the model into regions where no direct measurements of velocities are available. A mapping technique was applied where no geophysical, but only geologic parameters (depth, stratigraphic thickness, stratigraphic depth, etc.) are available. In addition, a simple background model was derived that is based on a classic Log(Depth)/Log(Velocity) relationship. 
The flexibility of GOCAD allows to parametise many different topologies and thus to transfer the velocity model to multiple applications. Based on the statistic framework, given by GOCAD, probabilistic synthetic velocity models can be derived, integrating regional, as well as local boundary conditions.
The current workflow includes :
- Import, conversion, and manual filtering;
- derivation of a statistic background model;
- calculation of intermediate velocity models in time and depth;
- calculation of a velocity volume using different approaches;
- time/depth conversion of stacking velocities or well-log velocities;
- time/depth conversion of seismic profiles;
- export of seismic velocities models to other applications (Simulators, Photoshop-plugin, etc.).
This type of velocity models opens a new wide range of modeling approaches for seismic hazard risk assessment ranging from worst case estimations to multiple even probable solutions based on th current knowledge. },
 author = { Süss, M. Peter AND Shaw, John H. },
 booktitle = { 20th gOcad Meeting },
 month = { "june" },
 publisher = { ASGA },
 title = { Building and calibrating seismic velocity models with gOcad },
 year = { 2000 }
}