SCEC Award Number 16037 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Precision Tests of Stress Transfer Calculations in Earthquake Simulators
Name Organization
Michael Barall Invisible Software, Inc. Terry Tullis Brown University
Other Participants
SCEC Priorities 2e, 4e, 3f SCEC Groups CS, WGCEP, Simulators
Report Due Date 03/15/2017 Date Report Submitted 03/03/2017
Project Abstract
Most of the computational effort in an earthquake simulator goes into computing how slip on one part of a fault affects stresses on other parts of the fault. The simulator discretizes the fault system into a large number of fault elements, and uses Greens functions to determine how slip on some fault elements affects the stresses on all the fault elements. Because triangles can follow a curved surface without gaps while rectangles cannot, one intuitively expects that stress calculations performed with triangles should be more accurate than stress calculations done with rectangles. In a previous SCEC project, we performed accuracy tests for rectangular and triangular fault elements, on negatively-curved and positively-curved fault surfaces. Our surprising result was that triangles are not superior to rectangles. In this SCEC project, we expanded the number of test cases to include triangulations composed mainly of nearly-equilateral triangles (previously we used right triangles), to include both edge and screw dislocations (previously we only tested edge dislocations), and to include a cylindrical (zero-curvature) fault surface. For each test case, we measured three kinds of error: the error when a fault element acts as a dislocation source; the error when a fault element acts as a target; and the error in propagating a rupture from a slipping region into the immediately adjacent fault elements. These new tests confirm our previous results: triangles are not superior to rectangles. One or the other may be superior in a particular case, but, overall, rectangles perform as well as triangles.