SAGA - Scientific Computing with Algebraic and Generative Abstractions

SeisMod - Seismic simulator

The seismic simulator SeisMod was developed in close cooperation with the Department of earth science, University of Bergen. SeisMod is built using the Sophus software library. This gave a remarkable flexibility, so that 6 different versions have been developed catering for different requirements of the geophysical model and execution time behaviour. All the codes are available for SGI Cray and SUN Ultra platforms. The versions are motivated by the vastly different computing times needed for computing the models, depending on the complexity of the rock models. Assuming isotropic rocks (seismic properties are independent of direction) then the equations will contain many identical terms, and the computation may be simplified accordingly. More complicated equations are needed if we allow anisotropy. The case of transverse isotropy means that the seismic waves will meet the corresponding property of spin, so the seismic waves will not propagate with the same velocity in the different directions of the media.

The following figures illustrate these differences. The simulation represents a 1km by 1km uniform 2-dimensional rock model. The seismic wave was initiated by a pulse lasting about 10ms at the center of the model. In the transverse isotropic cases we also see a clear separation between the faster moving p-waves, which spin, and the slower moving s-waves.

Pulse initiated
Figure 1: Isotropic case, seismic wave 25ms after the pulse started.

Isotropic waves
Figure 2: Isotropic case, seismic waves 100ms after the pulse started.

Transverse isotropic waves
Figure 3: Transverse isotropic case with vertical axis of symmetry, seismic waves 100ms after the pulse started.

Transverse isotropic waves in folded 
sediments
Figure 4: Transverse isotropic case with the axis of symmetry curved in the rock, seismic waves 100ms after the pulse started.

All these different versions actually boil down to how we may implement the tensor level of the system. Thus three versions of the tensor module corresponds to these three cases. Furthermore, any of these may freely be combined with a parallel implementation of the problem grid, giving 6 versions of the program.

SeisMod also includes a poroelastic version, treating porous rock as a two-component medium: the hard rock with oil and water. This is implemented as a modification of the application layer in Sophus, and it can be combined with any of the other 6 implementations, giving a total of 12 simulation programs. Each of these versions handles a specific combination of rock properties and sequential or parallel execution.

SeisMod and a rock modelling tool (VelRock) are available, also for commercial use. Contact with a geophysical consulting company can be made on request.



These pages last updated 2010-11-15 1999-2010 Magne Haveraaen, University of Bergen, Norway.
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