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Finite-Element Simulations of Earthquakes

Citation

Aagard, Brad Thomas (2000) Finite-Element Simulations of Earthquakes. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechThesis:04292016-090209111

Abstract

This thesis discusses simulations of earthquake ground motions using prescribed ruptures and dynamic failure. Introducing sliding degrees of freedom led to an innovative technique for numerical modeling of earthquake sources. This technique allows efficient implementation of both prescribed ruptures and dynamic failure on an arbitrarily oriented fault surface. Off the fault surface the solution of the three-dimensional, dynamic elasticity equation uses well known finite-element techniques. We employ parallel processing to efficiently compute the ground motions in domains containing millions of degrees of freedom.

Using prescribed ruptures we study the sensitivity of long-period near-source ground motions to five earthquake source parameters for hypothetical events on a strike-slip fault (Mw 7.0 to 7.1) and a thrust fault (Mw 6.6 to 7.0). The directivity of the ruptures creates large displacement and velocity pulses in the ground motions in the forward direction. We found a good match between the severity of the shaking and the shape of the near-source factor from the 1997 Uniform Building Code for strike-slip faults and thrust faults with surface rupture. However, for blind thrust faults the peak displacement and velocities occur up-dip from the region with the peak near-source factor. We assert that a simple modification to the formulation of the near-source factor improves the match between the severity of the ground motion and the shape of the near-source factor.

For simulations with dynamic failure on a strike-slip fault or a thrust fault, we examine what constraints must be imposed on the coefficient of friction to produce realistic ruptures under the application of reasonable shear and normal stress distributions with depth. We found that variation of the coefficient of friction with the shear modulus and the depth produces realistic rupture behavior in both homogeneous and layered half-spaces. Furthermore, we observed a dependence of the rupture speed on the direction of propagation and fluctuations in the rupture speed and slip rate as the rupture encountered changes in the stress field. Including such behavior in prescribed ruptures would yield more realistic ground motions.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:earthquake, ground motion, earthquake simulations, wave propagation, earthquake rupture
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Civil Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Hall, John F.
Thesis Committee:
  • Hall, John F. (chair)
Defense Date:13 October 1999
Other Numbering System:
Other Numbering System NameOther Numbering System ID
EERL99-03
Funders:
Funding AgencyGrant Number
NSF FellowshipUNSPECIFIED
Southern California Earthquake CenterUNSPECIFIED
CaltechUNSPECIFIED
Record Number:CaltechThesis:04292016-090209111
Persistent URL:http://resolver.caltech.edu/CaltechThesis:04292016-090209111
Related URLs:
URLURL TypeDescription
http://resolver.caltech.edu/CaltechEERL:1999.EERL-99-03Related DocumentTechnical Report EERL 99-03 in CaltechAUTHORS
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9690
Collection:CaltechTHESIS
Deposited By: Kathy Johnson
Deposited On:29 Apr 2016 16:54
Last Modified:29 Apr 2016 16:54

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