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Replication of apparent nonlinear seismic response with linear wave propagation models
1U.S. Bureau of Reclamation, Box 25007 D-8330, Denver, CO 80225, USA.
Science (New York, N.Y.)
|March 26, 1999
Summary
Ground motion amplification in sediment can appear nonlinear but is explained by linear wave propagation through random 3D crustal variations. This finding is crucial for accurate seismic loading predictions in earthquake engineering.
Area of Science:
- Seismology
- Earthquake Engineering
- Geophysics
Background:
- Understanding ground-motion amplification by sediment is vital for predicting seismic loadings.
- Observed amplifications during the Northridge earthquake showed apparent nonlinear behavior, with weaker aftershocks causing larger effects than the mainshock.
Purpose of the Study:
- To investigate the mechanisms behind observed ground-motion amplification by sediment.
- To determine if linear wave propagation can explain apparent nonlinear sediment responses.
Main Methods:
- Earthquake simulations using empirical impulse responses.
- Elastic finite-difference calculations incorporating random three-dimensional (3D) crustal velocity variations.
Main Results:
- Linear wave propagation through random 3D velocity variations successfully explains observed ground-motion amplifications.
- This model also reproduces the log-normal dispersion of peak ground motions.
Conclusions:
- Apparent nonlinear sediment responses can be attributed to linear wave propagation in heterogeneous media.
- Deterministic models are insufficient for quantifying near-source ground motion scaling and dispersion.
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