HR: 0800h
AN: S41A-0959    [Abstracts]
TI: Representations of the Radiated Energy in Earthquakes
AU: * Rivera, L
EM: luis@sismo.u-strasbg.fr
AF: EOST-IPGS, 5, rue Rene Descartes, Strasbourg, 67084 France
AU: Kanamori, H
EM: hiroo@gps.caltech.edu
AF: Seismological Laboratory California Institute of Technology, 1200E Blvd, Pasadena, CA 91125 United States
AB: We investigate the representation of the radiated energy, $E_R$, in earthquakes. The radiated energy, $E_R$, is estimated in seismology from either far-field seismic waves or the stress and displacement on the fault plane. Although $E_R$ comes from the entire volume of the Earth, it can be expressed as an integral over the fault plane. However, the integrand cannot be given a simple physical meaning such as the radiated energy density on the fault plane. The stress on the fault plane changes rapidly during a seismic rupture. Although the energy radiated by this process is not included in the estimate of $E_R$ in a simplified practice in seismology, it is correctly included in the expression of $E_R$ in the standard seismological practice. Using the representation theorem, we can express $E_R$ as a surface integral over the fault plane, with the integrand containing the slip function on the fault plane. However, the integrand at a point depends on not only the slip function at the point, but also the slip functions everywhere on the fault plane. Thus, the simple method in which $E_R$ is estimated by summation of the local energy flux on the fault plane does not yield a correct estimate. In view of occasional confusions on these issues in the literature, we address in this paper 1) the physical meaning of the surface integral in the expression of $E_R$, 2) the effect of rapid changes in stress on the fault plane on the seismological estimate of $E_R$, and 3) the difficulty in estimating $E_R$ using a local energy flux on the fault plane.
DE: 7260 Theory and modeling
DE: 5104 Fracture and flow
DE: 7203 Body wave propagation
DE: 7209 Earthquake dynamics and mechanics
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2004 AGU Fall Meeting