Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Imhof, M. G. Articles by Toksöz, M. N. Search for Related Content GeoRef GeoRef Citation

Scattering from Tunnels near Sources and their Effect on Seismic Signatures of Explosions

Department of Geological Sciences
4044 Derring Hall (0420)
Virginia Tech
Blacksburg, VA 24061-0420
(M.G.I.)

Earth Resources Laboratory
Department of Earth, Atmospheric, and Planetary Sciences
Massachusetts Institute of Technology
Cambridge, MA 02139
(M.N.T.)

Explosions often take place in complexes with chambers, shafts, and tunnels used for access and instrumentation. Cavities and tunnels have a very large impedance contrast relative to the surrounding material and might act as strong scatterers of seismic waves. They represent secondary sources with different radiation patterns and different distance dependencies than the primary waves. The characterization of the primary events is made more difficult by these secondary signals.

We used the 2D multiple multipole (MMP) method to calculate seismograms and radiation patterns for linearized, effective sources near heterogeneities such as cavities. We examined the effects of distance between source and a scatterer, the effect of a regular arrangement of cavities and the location of the source therein, and the effect of different source mechanisms for a particular L-shaped geometry representing a large tunnel with a source in a side-drift. Depending on the 2D configuration of cavities, we obtained peak-amplitude ratios of S to P waves ranging from 5 to 70%.

Seismograms recorded during the nonproliferation experiment (NPE) show strong azimuthal variations in waveforms and amplitudes. Near the NPE source, there was a large complex of tunnels and cavities. For an idealized 2D geometry, we calculated synthetic seismograms. The early arrivals on the synthetics compared fairly well to the observations, especially if near-receiver heterogeneities are included to couple radial (P) and transverse (S) components. Around the arrival of near-source generated S waves, the envelopes are roughly similar. Because our models are oversimplified, that is, 2D, we do not conclude that near-source scattering causes the near-source generated S waves. Rather, we believe that one cannot exclude near-source heterogeneities, for example, cavities, as a possible cause of near-source generated S waves.

This article has been cited by other articles:

				The Effect of Synchronized Multiple-Cavity Sources on Seismic Radiation Bulletin of the Seismological Society of America, August 1, 2002; 92(6): 2381 - 2390.