Ares J. Rosakis Ares J. Rosakis
Theodore von Kármán Professor of Aeronautics and Mechanical Engineering

Research Interests

Laboratory Earthquakes
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Collaborators: H. Kanamori and N. Lapusta, Caltech; J. R. Rice, Harvard; M. Bouchon, Grenoble, France; S. Das, Oxford, UK. Students/Post Docs: Michael Mello and Harsha S. Bhat, Caltech

imageThe goal of the this work is to create model laboratory experiments mimicking the dynamic shear rupture process associated with natural earthquakes. Such experiments are used to observe new physical phenomena and to also create benchmark comparisons with existing analytical analysis and field observations. The experiments use high-speed photography, photoelasticity, and laser velocimetry as diagnostics. The fault systems are simulated using two photoelastic plates (Homalite) held together by friction. The far field tectonic loading is simulated by pre-compression and the triggering of dynamic rupture (spontaneous nucleation) is achieved by suddenly dropping the normal stress in a small region by disintegrating a thin wire.

The fault forms an acute angle with the compression axis to provide the shear driving force necessary for continued rupturing. We investigate the characteristics of rupture, such as rupture speed, rupture mode, associated ground motion under various conditions such as tectonic load and interface roughness. Both homogeneous and bimaterial interfaces (abutted by both elastic and damaged medium) are investigated.

Some of the key outcomes from this project are:

  1. First laboratory evidence for supershear earthquake ruptures.
  2. Laboratory Evidence for Bi-Lateral rupture in a bimaterial interface, contrary to theoretical predictions.
  3. Explanation of the 1999 Izmit earthquake that went supershear only on one side of the fault.
  4. First laboratory verification of conditions that generate pulse-like and crack-like ruptures.
  5. Experiments on rupture in a damaged medium showed yet another mechanism for generating asymmetric ruptures.
  6. Verification of unique ground motion signatures associated with supershear ruptures.

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Division of Engineering & Applied Science
California Institute of Technology

Caltech    last update: 05/31/2016