N) t ^ SAND-74-0252 SAND74-0252 Unlimited Release A80006098

Free-Field Ground Motion Induced by Underground Explosions

William R. Perret, Robert C. Bass

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sr 1004-DF(2-74) SAND74-0252 Unlimited Release Printed February 1975

FREE-FIELD GROUND MOTION INDUCED BY UNDERGROUND EXPLOSIONS

William R. Perret Robert C. Bass Underground Physics Division Sandia Laboratories Albuquerque. NM 87115

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™sponsore^ 'TLd by Xthe Umt^Sfst:terGo=e'nt°Ul M ^^^^^^ ^^^^^^

theii «-Pl<'y»^'"°;e" employe" makes any subcontractors, °' *V^" ^^P/^ssumes any legal warranty, «'

infringe privately owned rights.

ABSTRACT

Free-field ground motion induced by 60 contained underground nuclear explosions and one underground chemical explosion detonated by the U.S. Atomic Energy Commission at the and elsewhere was measured, and data from recorded motion have been collated and analyzed for effects of geologic environment on attenuation of the motion. These data include those derived from hydrodynamic, nonlinear, and linear response of the rock. This study involved nearly 1100 peak stress sind motion data, of which 116 were of stress and particle velocities from within the hydrodynamic response region and the remainder were accelerations, particle velocities, and displacements from the nonlinear and beginning of the linear response regions. Data from the latter two regions included 183 in a dry alluvium environment, 198 in dry tuff, 215 in wet tuff, and 425 in hard rock, i. e,, granite, salt, dolomite, and similar sedimentaries.

Log-linear regression of these data normalized to explosive energy release equivalent to that of one kiloton of TNT for each motion parsimeter in each environment indicate such facts as no differentiation between dry alluvium, dry tuff, wet tuff, or granite, in particle velocities in the hydrodynamic response regime where stress is attenuated as the inverse

BisTR!Eur>::.; 2. 96-power of distance from the source and particle velocity as the inverse 1. 87-power. Scaled accelerations are generally represented by two-branched attenuation in both the nonlinear and linear domains, but except for dry alluvium this appears to bec