Quick Search:    advanced search

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

This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal 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 REINKE, R. E. Articles by STUMP, B. W. Search for Related Content GeoRef GeoRef Citation

Stochastic geologic effects on near-field ground motions in alluvium

AIR FORCE WEAPONS LABORATORY/NTESG KIRTLAND AIR FORCE BASE,, NEW MEXICO 87117-6008
SOUTHERN METHODIST UNIVERSITY DEPARTMENT OF GEOLOGICAL SCIENCES, DALLAS, TEXAS 75275

Abstract

Analysis of accelerograms recorded at the 20 m range from a buried 5-lb detonation in alluvium revealed wide (as large as 20 dB in the amplitude modulus of the Fourier transform) variations in response for frequencies above 35 Hz. Additional experiments were performed which ruled out source asymmetry or instrumental irregularity as the cause of these variations. The observations suggest that scattering by geologic inhomogeneity is responsible for the frequency-dependent spatial variability in ground motion. A thorough understanding of the physical processes responsible for this variability requires that a quantitative relationship be established between the subsurface material property information and the observed ground motion characteristics. An attempt was made to do this using available standard penetration test data from the test bed where the initial experiment was detonated. Autocorrelations of the blow count data from the standard penetration test were computed and compared with theoretical exponential and Gaussian distributions. The exponential distribution with a scale length between 2.0 and 3.0 m best matches the data. Assuming the Born approximation, a scale length of 2.0 to 3.0 m implies that significant scattering should occur above 10 Hz. The recorded ground motions are, however, coherent out to about 35 Hz, suggesting a scale length on the order of 0.5 to 1.0 m, which is beyond the resolution of the standard penetration test technique. This scale length is, however, not unreasonable in light of the general geologic characteristics of the test area.

This article has been cited by other articles:

				Possibility of Spatial Variation of High-Frequency Seismic Motions due to Random-Velocity Fluctuation of Sediments Bulletin of the Seismological Society of America, February 1, 2000; 90(1): 48 - 65.

				S. BLAKESLEE and P. MALIN High-frequency site effects at two Parkfield downhole and surface stations Bulletin of the Seismological Society of America, April 1, 1991; 81(2): 332 - 345. [Abstract] [PDF]