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 Citation Map 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 Beresnev, I. A. Articles by Field, E. H. Search for Related Content GeoRef GeoRef Citation

Stochastic finite-fault modeling of ground motions from the 1994 Northridge, California, earthquake. II. Widespread Nonlinear response at soil sites

Department of Geological & Atmospheric Sciences Iowa State University, 253 Science I, Ames, Iowa 50011-3212beresnev{at}iastate.edu
Department of Earth Sciences Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canadagma{at}ccs.carleton.ca
EES-4, MS D-443 Los Alamos National Laboratory, Los Alamos, New Mexico 87545johnson{at}seismo5.lanl.gov
Department of Earth Sciences University of Southern California, Los Angeles, California 90089-0740field{at}usc.edu

Abstract

On average, soil sites behaved nonlinearly during the M 6.7 1994 Northridge, California, earthquake. This conclusion follows from an analysis that combines elements of two independent lines of investigation. First, we apply the stochastic finite-fault simulation method, calibrated with 28 rock-site recordings of the Northridge mainshock, to the simulation of the input motions to the soil sites that recorded this event. The calibrated model has a near-zero average bias in reproducing ground motions at rock sites in the frequency range from 0.1 to 12.5 Hz.

The soil sites selected are those where there is colocation of strong-motion accelerographs and temporary instruments from the Northridge aftershock observation network. At these sites, weak-motion amplification functions based on numerous aftershock records have been empirically determined, in three separate investigations reported in the literature. These empirical weak-motion amplification factors can be applied to the simulated input rock motions, at each soil site, to determine the expected motions during the mainshock (i.e., neglecting nonlinearity). These expected motions can then be compared to the actual recordings during the mainshock.

This analysis shows that the recorded strong-motion spectra are significantly over-estimated if weak-motion amplifications are used. The null hypothesis, stating that the inferred differences between weak- and strong-motion amplifications are statistically insignificant, is rejected with 95% confidence in the frequency range from approximately 2.2 to 10 Hz. On average, the difference between weak- and strong-motion amplifications is a factor of 2. Nonlinear response at those soil stations for which the input peak acceleration exceeded 150 to 200 cm/sec² contributes most to this observed average difference. These findings suggest a significant nonlinear response at soil stations in the Los Angeles urban area during the Northridge mainshock. The effect is consistent with the increase in damping of shear waves at high levels of strain, which is well known from geotechnical studies of soil properties.

This article has been cited by other articles:

				C. Wu, Z. Peng, and D. Assimaki Temporal Changes in Site Response Associated with the Strong Ground Motion of the 2004 Mw 6.6 Mid-Niigata Earthquake Sequences in Japan Bulletin of the Seismological Society of America, December 1, 2009; 99(6): 3487 - 3495. [Abstract] [Full Text] [PDF]

				P. Gu and Y. K. Wen A Record-Based Method for the Generation of Tridirectional Uniform Hazard-Response Spectra and Ground Motions Using the Hilbert-Huang Transform Bulletin of the Seismological Society of America, October 1, 2007; 97(5): 1539 - 1556. [Abstract] [Full Text] [PDF]

				Stochastic Finite-Fault Modeling of Ground Motions from the 1999 Chi-Chi, Taiwan, Earthquake: Application to Rock and Soil Sites with Implications for Nonlinear Site Response Bulletin of the Seismological Society of America, August 1, 2003; 93(4): 1691 - 1702.

				Ground Motions at Memphis and St. Louis from M 7.5-8.0 Earthquakes in the New Madrid Seismic Zone Bulletin of the Seismological Society of America, April 1, 2002; 92(3): 1015 - 1024.

				Stochastic Simulation of Strong-Motion Records from the 15 April 1979 (M 7.1) Montenegro Earthquake Bulletin of the Seismological Society of America, April 1, 2002; 92(3): 1095 - 1101.

				Empirical Evidence for Acceleration-Dependent Amplification Factors Bulletin of the Seismological Society of America, March 1, 2002; 92(2): 761 - 782.

				Nonlinearity at California Generic Soil Sites from Modeling Recent Strong-Motion Data Bulletin of the Seismological Society of America, March 1, 2002; 92(2): 863 - 870.

				Two Mw 4.8 Cerro Prieto, Baja California, Mexico, Earthquakes on 1 June and 10 September 1999: Strong-Motion Observations Bulletin of the Seismological Society of America, December 1, 2001; 91(6): 1456 - 1470.

				Inversion of Strain-Dependent Nonlinear Characteristics of Soils Using Weak and Strong Motions Observed by Borehole Sites in Japan Bulletin of the Seismological Society of America, April 1, 2001; 91(2): 365 - 380.

				J. H. Steidl Site Response in Southern California for Probabilistic Seismic Hazard Analysis Bulletin of the Seismological Society of America, December 1, 2000; 90(6B): S149 - S169. [Abstract] [Full Text] [PDF]

				Y. Lee and J. G. Anderson Potential for Improving Ground-Motion Relations in Southern California by Incorporating Various Site Parameters Bulletin of the Seismological Society of America, December 1, 2000; 90(6B): S170 - S186. [Abstract] [Full Text] [PDF]

				S. Hartzell, S. Harmsen, A. Frankel, and S. Larsen Calculation of broadband time histories of ground motion: Comparison of methods and validation using strong-ground motion from the 1994 Northridge earthquake Bulletin of the Seismological Society of America, December 1, 1999; 89(6): 1484 - 1504. [Abstract] [PDF]

				C. W. Scrivner and D. V. Helmberger Finite-difference modeling of two aftershocks of the 1994 Northridge, California, earthquake Bulletin of the Seismological Society of America, December 1, 1999; 89(6): 1505 - 1518. [Abstract] [PDF]

				G. Cultrera, D. M. Boore, W. B. Joyner, and C. M. Dietel Nonlinear soil response in the vicinity of the Van Normal Complex following the 1994 Northridge, California, earthquake Bulletin of the Seismological Society of America, October 1, 1999; 89(5): 1214 - 1231. [Abstract] [PDF]

				I. A. Beresnev and G. M. Atkinson Stochastic finite-fault modeling of ground motions from the 1994 Northridge, California, earthquake. I. Validation on rock sites Bulletin of the Seismological Society of America, December 1, 1998; 88(6): 1392 - 1401. [Abstract] [PDF]