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Our main research areas are seismic modeling, wave equation migration velocity analysis (WEMVA) and full waveform inversion (FWI). In this page we give short introductions to the different areas. To make the text easy to read, and not require too much background knowledge, the most technical details are leaved out.

The purpose of a seismic modeling (or seismic stimulation) is a process where computers are used to simulate how seismic waves propagate through the Earth. The results from the simulations are used to understand how seismic waves in a real experience behave and propagate. Other motivations for performing seismic modeling are for instance the fact that seismic modeling is a major part of several algorithms which purpose is to give detailed images of the subsurface based on real data collected from for instance a seismic survey.

The starting point for the modeling is to find a mathematical equation which describes the wave phenomenon in interest. Two standard equations are the acoustic wave equation (AWE) and the elastic wave equation (EWE). The major difference between these two equations is that the latter includes shear waves in addition to pressure waves which the former equation describes. In that sense, the latter equation is physically more correct since it includes more true physics. On the other hand, the EWE is more complex than the AWE, and thus needs more computer resources.

The next point is to transform the mathematical equation into a “language” which the computer understand. There exist several useful methods to do this, where the two most popular maybe are the finite difference method and the finite element method. Once the equation is transformed into computer language, one is able to simulate a seismic wave inside a medium.

The final step for the setup of a seismic modeling is the construction of a model of the medium one is interested in. This model is used as input for the modeling software.

An important observation of seismic modeling is that it is impossible to simulate wave propagation phenomena which are identical to the one observed in nature. This fact is due to the principle that when performing modeling several approximations are necessary; i.e the mathematical equations involved in the modeling are not able to describe all physical phenomena occurring in a real wave propagation. In addition, when transforming the equation to computer language several approximations are used. However, the most important wave phenomena are described by the equation and the software, and are not too far away from the one observed in nature.

Below is the result of estimating the velocity model from synthetic data using Wave equation Migration Velocity Analysis (WEMVA) based on reverse-time migration (right). The true velocity model is displayed on the left.

The image below shows the result of Full-Waveform Inversion (FWI) using the WEMVA velocity model as an initial guess.

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