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Induced Dynamic Nonlinear Ground Response at Garner Valley, California

Center for Earthquake Research and Information, University of Memphis, 3876 Central Ave, Suite 1, Memphis, Tennessee 38152-3050

Paul Bodin

Pacific Northwest Seismic Network, Department of Earth Sciences, University of Washington, Box 351310, Seattle, Washington 98195-7010

Charles A. Langston

Center for Earthquake Research and Information, University of Memphis, 3876 Central Ave, Suite 1, Memphis, Tennessee 38152-3050

Fred Pearce

Earth Resources Laboratory, Massachusetts Institute of Technology, Boston, Massachusetts 02139

Joan Gomberg

U.S. Geological Survey, University of Washington, Seattle, Washington 98195-1310

Paul A. Johnson

Geophysics Group, Los Alamos National Laboratory, Mail Stop D443, Los Alamos, New Mexico 87545

Farn-Yuh Menq

Department of Civil Engineering, University of Texas at Austin Geotechnical Center, 301 E. Dean Keeton ECJ 9.227, Austin, Texas 78712

Thomas Brackman

Center for Integrative Natural Science and Mathematics, Northern Kentucky University, Highland Heights, Kentucky 41099

We present results from a prototype experiment in which we actively induce, observe, and quantify in situ nonlinear sediment response in the near surface. This experiment was part of a suite of experiments conducted during August 2004 in Garner Valley, California, using a large mobile shaker truck from the Network for Earthquake Engineering Simulation (NEES) facility. We deployed a dense accelerometer array within meters of the mobile shaker truck to replicate a controlled, laboratory-style soil dynamics experiment in order to observe wave-amplitude-dependent sediment properties. Ground motion exceeding 1g acceleration was produced near the shaker truck. The wave field was dominated by Rayleigh surface waves and ground motions were strong enough to produce observable nonlinear changes in wave velocity. We found that as the force load of the shaker increased, the Rayleigh-wave phase velocity decreased by as much as 30% at the highest frequencies used (up to 30 Hz). Phase velocity dispersion curves were inverted for S-wave velocity as a function of depth using a simple isotropic elastic model to estimate the depth dependence of changes to the velocity structure. The greatest change in velocity occurred nearest the surface, within the upper 4 m. These estimated S-wave velocity values were used with estimates of surface strain to compare with laboratory-based shear modulus reduction measurements from the same site. Our results suggest that it may be possible to characterize nonlinear soil properties in situ using a noninvasive field technique.

This article has been cited by other articles:

				Z. Lawrence, P. Bodin, and C. A. Langston In Situ Measurements of Nonlinear and Nonequilibrium Dynamics in Shallow, Unconsolidated Sediments Bulletin of the Seismological Society of America, June 1, 2009; 99(3): 1650 - 1670. [Abstract] [Full Text] [PDF]