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Very Large Scale Finite Difference Modeling of Seismic Wavesby Submitted to the Department of Earth, Atmospheric, and Planetary Sciences on September 21, 1994 in partial fulfillment of the requirements for the degree of Master of Scienc} ABSTRACT
In this thesis we develop a method for solving very large scale seismic wave
propagation problems using an out of core finite difference approach. We implement
our method on a parallel computer using special memory management techniques based
on the concepts of pipelining, asynchronous I/O, and dynamic memory allocation. We
successfully apply our method for solving a 2-D Acoustic Wave equation in order
to show its utility and note that it can be easily extended to solve 3-D Acoustic
or Elastic Wave equation problems. We use second order finite differencing operators
to approximate the 2-D Acoustic Wave equation. The system is implemented using
a distributed-memory/message-passing approach on an nCUBE 2 parallel computer
at MIT’s Earth Resources Laboratory. We use two test cases, a small (256
X 256 grid) constant velocity model and the Marmousi velocity model (751 X 2301
grid). We conduct several trials- with varying memory sizes and number of nodes-
to fully evaluate the performance of the approach. In analyzing the results we
conclude that the performance is directly related to the number of nodes, memory
size, and bandwidth of the I/O- subsystem. We demonstrate that is feasible
and practical to solve very large scale seismic wave propagation problems with
current computer technologies by using advanced computational techniques. We compare
two versions of the system, one using asynchronous I/O and the other using synchronous
I/O, to show that better results can be obtained with the asynchronous version
with pipelining and overlapping of I/O with computations. Return to Theses Return to ERL Home Updated: {June, 1999}
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