Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published October 1994 | Published
Journal Article Open

Theoretical Rayleigh and Love Waves from an Explosion in Prestressed Source Regions


Expressions and synthetics for Rayleigh and Love waves generated by theoretical tectonic release models are presented. The multipole formulas are given in terms of the strengths and time functions of the source potentials. This form of the Rayleigh and Love wave expressions is convenient for separating the contribution to the Rayleigh wave due to the compressional and shear-wave source radiation and the contribution of the upgoing and downgoing source radiation for both Rayleigh and Love waves. Because of the ease of using different compression and shear-wave source time functions, these formulas are especially suited for sources for which second- and higher-order moment tensors are needed to describe the source, such as the initial value cavity release problem. A frequently used model of tectonic release is a double couple superimposed on an explosion. Eventually, we will compare synthetics of this and more realistic models in order to determine for what dimensions of the tectonic release model this assumption is valid and whether the Rayleigh wave is most sensitive to the compressional or shear-wave source history. The pure shear cavity release model is a double couple with separate P- and S-wave source histories. The time scales are proportional to the source region's dimension and differ by their respective body-wave velocities. Thus, a convenient way to model the effect of differing shot point velocities and source dimensions is to run a suite of double-couple source history calculations for the P- and SV-wave sources separately and then sum the different combinations. One of the more interesting results from this analysis is that the well-known effect of vanishing Rayleigh-wave amplitude as a vertical or horizontal dip-slip double-couple model approaches the free surface is due to the destructive interference between the P- and SV-wave generated Rayleigh waves. The individual Rayleigh-wave amplitudes, unlike the SH-generated Love waves, are comparable in size to those from other double-couple orientations. This has important implications to the modeling of Rayleigh waves from shallow dipslip fault models. Also, the P-wave radiation from double-couple sources is a more efficient generator of Rayleigh waves than the associated SV wave or the P wave from explosions. The latter is probably due to the vertical radiation pattern or amplitude variation over the wave front. This effect should be similar to that of the interaction of wave-front curvature with the free surface.

Additional Information

© 1994 Seismological Society of America. Manuscript received 12 February 1990. This research was supported by the Defense Advanced Research Projects Agency (DARPA) of the U.S. Department of Defense and was monitored in part by the Air Force Office of Scientific Research under Contract Number F49620-83-C-0025 and the Air Force Geophysics Laboratory under Contract Numbers F19628-85-K-0017 and F19628-87-K-0028. In addition, while at the Center of Seismic Studies, DGH and CBA received support from DARPA through the Defense Supply Service-Washington under Contract Number MDA903-84-C-0020. Contribution Number 4841, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California. Extensive revisions were made by DGH while at the Earth Resources Laboratory, Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology and the Air Force Phillips Laboratory, Geophysics Directorate, Earth Science Division under support of the Air Force Office of Scientific Research through Grant Number F49620-93-1-0221.

Attached Files

Published - 1410.full.pdf


Files (2.4 MB)
Name Size Download all
2.4 MB Preview Download

Additional details

August 20, 2023
August 20, 2023