Geophysical Sensing in Environmental Applications: Efficient Numerical SimulationsEPA Grant Number: R825225
Title: Geophysical Sensing in Environmental Applications: Efficient Numerical Simulations
Investigators: Liu, Qing-Huo
Institution: Duke University
Current Institution: New Mexico State University - Main Campus
EPA Project Officer: Hahn, Intaek
Project Period: November 21, 1996 through September 20, 2001
Project Amount: $500,000
RFA: Exploratory Research - Early Career Awards (1996) RFA Text | Recipients Lists
Research Category: Early Career Awards
Description:The objective of this research is to develop efficient forward and inverse techniques to model electromagnetic and acoustic problems in environmental geophysical sensing. Specifically, fast forward and inverse computer models will be developed for electrical resistance tomography (ERT), electromagnetic induction (EMI), radio imaging methods (RIM), surface seismic reflection, and borehole seismic imaging measurements in three-dimensional inhomogeneous media.
In environmental geophysical sensing, electromagnetic and acoustic sensors are used on the earth's surface or in boreholes to probe the complex underground medium. The interpretation of these important measurements remains a challenging problem because of the complex interaction of waves with the underground medium. Simulating realistic three-dimensional models encountered in these problems can easily exceed the capacity of any modern supercomputer if conventional methods are used. Therefore, there is a pressing demand for more efficient forward and inverse techniques. These forward and inverse solutions are also critical in processing the collected data and in computer-aided design of new measurement systems.
For time-harmonic electromagnetic problems, including those for ERT, EMI, and RIM systems, special methods such as numerical mode-matching techniques and spectral-domain techniques will be explored to solve large three-dimensional forward problems. These techniques will allow one to solve much larger problems than conventional finite-difference and finite-element methods. For transient electromagnetic and acoustic problems, new absorbing boundary conditions for finite-difference methods with nonuniform grids will be developed to solve wave propagation problems efficiently.
The ultimate goal of this program is to solve the nonlinear inverse problems, i.e., to infer the material properties from a set of measured data. The coupling between efficient forward solutions and the inverse algorithms is critical for these large-scale inverse problems.
This research will significantly advance the capability of simulating large-scale forward and inverse electromagnetic and acoustic problems in environmental geophysical sensing. The computer programs developed can be used to enhance the understanding of complicated wave interactions in the underground medium, and to improve the interpretation and processing capability of electromagnetic and acoustic measurements in complex environments.
With the fast and accurate modeling programs, researchers will be able to provide useful information regarding underground objects, leaks, and discontinuities in a timely manner. With the modeling capability, remediation of waste sites will become much better, safer, and less costly.