Location
San Diego, California
Presentation Date
30 Mar 2001, 1:30 pm - 3:30 pm
Abstract
The largest available strong-motion recording (PGA=0.35g), least affected by topography, structural response and/or soil-structure interaction, is investigated for possible nonlinear site response during the M, 5.9 Athens earthquake of 7 September 1999. Smoothed horizontal-to-vertical spectral ratios (HVSR) are calculated in subsequent overlapping 3.5-s windows, thus covering a wide range of excitation levels. Mean HVSR curves are computed for a so-called “weak-“ and “strong-“ motion range (mean horizontal ground acceleration in window, MGA<=10.2 cm/s/s and >=20.5 cm/s/s). The two curves have similar shape, with the “strong” curve visibly shifted toward lower frequencies relative to the “weak” one; the dominant site resonance occurs at 4.0 Hz (0.25 s) and 4.7 Hz (0.21 s), respectively. Linear correlation analysis shows that the resonance frequency, f0, and MGA are significantly correlated (t=-0.661). We attribute this behaviour to the degradation of the sediment shear modulus (nonlinearity). Our results, combined with indications that sediment sites in the near-fault area were exposed to ground shaking well above PGA=0.35 g during the earthquake of 7 September 1999, imply that these sites exhibited considerable nonlinear response.
Department(s)
Civil, Architectural and Environmental Engineering
Meeting Name
4th International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics
Publisher
University of Missouri--Rolla
Document Version
Final Version
Rights
© 2001 University of Missouri--Rolla, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Document Type
Article - Conference proceedings
File Type
text
Language
English
Recommended Citation
Dimitriu, P.; Anastasiadis, A.; Theodulidis, N.; and Klimis, N., "Nonlinear Site Response During the 7 September 1999 Athens, Greece, Earthquake (MW 5.6)" (2001). International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. 23.
https://scholarsmine.mst.edu/icrageesd/04icrageesd/session03/23
Included in
Nonlinear Site Response During the 7 September 1999 Athens, Greece, Earthquake (MW 5.6)
San Diego, California
The largest available strong-motion recording (PGA=0.35g), least affected by topography, structural response and/or soil-structure interaction, is investigated for possible nonlinear site response during the M, 5.9 Athens earthquake of 7 September 1999. Smoothed horizontal-to-vertical spectral ratios (HVSR) are calculated in subsequent overlapping 3.5-s windows, thus covering a wide range of excitation levels. Mean HVSR curves are computed for a so-called “weak-“ and “strong-“ motion range (mean horizontal ground acceleration in window, MGA<=10.2 cm/s/s and >=20.5 cm/s/s). The two curves have similar shape, with the “strong” curve visibly shifted toward lower frequencies relative to the “weak” one; the dominant site resonance occurs at 4.0 Hz (0.25 s) and 4.7 Hz (0.21 s), respectively. Linear correlation analysis shows that the resonance frequency, f0, and MGA are significantly correlated (t=-0.661). We attribute this behaviour to the degradation of the sediment shear modulus (nonlinearity). Our results, combined with indications that sediment sites in the near-fault area were exposed to ground shaking well above PGA=0.35 g during the earthquake of 7 September 1999, imply that these sites exhibited considerable nonlinear response.
