Response spectra for the deep sediment-filled Rhone Valley in the Swiss Alps

Abstract We present numerical modeling of earthquake ground motion for various profiles across the Swiss Rhone Valley and characterize the seismic response in terms of spectral acceleration. First, we evaluate the relative amplification of 2D with respect to 1D response. Then, we show how the selected bedrock spectrum influences the response spectra of the valley sites. Particular attention is paid to how the internal sediment structure and the often weakly constrained Q-factor shape the seismic response. Results obtained for the different profiles are compared with reference spectra (Swiss building code and Eurocode 8) and for one profile with recorded data as well. From this comparison, we infer that the surficial layer strongly influences spectral acceleration values between 0.1 and 1 s. The total thickness of sediments significantly affects the seismic response at longer periods around the fundamental period of the studied valley sections between 1.8 and 3.6 s.

[1]  Kim B. Olsen,et al.  A comparison of observed and simulated site response in the Rhône valley , 2008 .

[2]  Donat Fäh,et al.  Probabilistic seismic hazard assessment of Switzerland: best estimates and uncertainties , 2009 .

[3]  Peter Suhadolc,et al.  Application of numerical wave-propagation techniques to study local soil effects: The case of Benevento (Italy) , 1994 .

[4]  Donat Fäh,et al.  Earthquake Catalogue of Switzerland (ECOS) and the Related Macroseismic Database , 2003 .

[5]  C. Frischknecht,et al.  Toward Seismic Microzonation—2-D Modeling and Ambient Seismic Noise Measurements: The Case of an Embanked, Deep Alpine Valley , 2005 .

[6]  Donat Fäh,et al.  A combined inversion of Rayleigh wave dispersion and 2-D resonance frequencies , 2007 .

[7]  D. Fäh,et al.  The 1946 magnitude 6.1 earthquake in the Valais: site-effects as contributor to the damage , 2009 .

[8]  D. Giardini,et al.  Predictive ground motion scaling in Switzerland: Best estimates and uncertainties , 2005 .

[9]  Enrique Alarcón,et al.  The direct boundary element method: 2D site effects assessment on laterally varying layered media (methodology) , 2004 .

[10]  D. Giardini,et al.  2D Resonances in Alpine Valleys Identified from Ambient Vibration Wavefields; 13th World Conference on Earthquake Engineering; Proceedings of the 13th WCEE; , 2004 .

[11]  Donat Fäh,et al.  Reconstructing the damage field of the 1855 earthquake in Switzerland: historical investigations on a well-documented event , 2006 .

[12]  P. Bard,et al.  The two-dimensional resonance of sediment-filled valleys , 1985 .

[13]  P. Heitzmann,et al.  Deep Structure of the Swiss Alps: Results of NRP 20 , 1997 .

[14]  Pierre-Yves Bard,et al.  The seismic response of sediment-filled valleys. Part 2. The case of incident P and SV waves , 1980 .

[15]  Roberto Paolucci,et al.  Assessment of Seismic Site Effects in 2-D Alluvial Valleys Using Neural Networks , 2000 .

[16]  Kim B. Olsen,et al.  Site Amplification in the Los Angeles Basin from Three-Dimensional Modeling of Ground Motion , 2000 .

[17]  Julian J. Bommer,et al.  Criteria for Selecting and Adjusting Ground-Motion Models for Specific Target Regions: Application to Central Europe and Rock Sites , 2006 .

[18]  S. Vahdani,et al.  Response of the Tarzana strong motion site during the 1994 Northridge earthquake , 2002 .

[19]  Donat Fäh,et al.  Two-dimensional resonances in Alpine valleys identified from ambient vibration wavefields , 2006 .

[20]  T. Sasatani.  Seismic Wave Propagation in a Stratified Half-Space , 1985 .

[21]  Donat Fäh,et al.  Analysis of three-component ambient vibration array measurements , 2008 .

[22]  Enrique Alarcón,et al.  The use of direct boundary element method for gaining insight into complex seismic site response , 2005 .

[23]  J. Bommer,et al.  Prediction of elastic displacement response spectra in Europe and the Middle East , 2007 .

[24]  D. Giardini,et al.  Identifying 2D Resonance in Microtremor Wave Fields , 2003 .

[25]  Stefano Parolai,et al.  Site-specific response spectra from the combination of microzonation with probabilistic seismic hazard assessment—An example for the Cologne (Germany) area , 2007 .

[26]  D. Fäh,et al.  The Valais earthquake of December 9, 1755 , 2004 .

[27]  D. Fah.  Evaluating site effects in areas of low seismicity , 2006 .

[28]  Donat Fäh,et al.  Array measurements of S‐wave velocities from ambient vibrations , 2004 .

[29]  Paolo Franchin,et al.  Seismic risk evaluation of RC bridge structures , 2003 .