Superficial S-Wave Velocity and Damping Factor Model Determined by the Masw Measurement in the Grenoble Sedimentary Basin

Abstract eng:
In order to understand and predict earthquake ground motions at high frequencies, it is necessary to evaluate a superficial S-wave velocity structure. In the Grenoble basin, several geotechnical and geophysical surveys have been carried out for estimating the deep velocity structure. However, the superficial velocity profiles have not been obtained in enough detail for allowing reliable numerical predictions of ground motion for frequencies above 1 Hz. Therefore, we have applied the MASW technique using the High-Resolution method to estimate S-wave velocity structure at the uppermost 50 meters of sedimentary layers. The estimated S-wave velocity structure by the genetic inversion algorithm indicates that the soft soil sediment (less than Vs 400-500 m/s) is more deeply deposit in the middle-east of Grenoble than in other areas. Finally, we made a 3D S-wave velocity model for the uppermost layers that will be used for high frequency ground motion predictions in the Grenoble sedimentary basin. Moreover, we proposed a method for determining quality factors of superficial layers by using MASW recording data. The quality factors of S-waves determined by waveform inversion are about 15 within a frequency range from 5 to 50 Hz. We also discuss on the usefulness of joint inversion between a fundamental mode and higher modes.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket