Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Velocity and attenuation structure of very shallow soils; evidence for a frequency-dependent Q

Luca Malagnini
Velocity and attenuation structure of very shallow soils; evidence for a frequency-dependent Q
Bulletin of the Seismological Society of America (October 1996) 86 (5): 1471-1486

Abstract

The importance of a detailed knowledge of the shear-wave velocity structure in the very shallow depth was recently stressed in strong ground motion studies. In this article, we investigate the 1D velocity and attenuation structure of the very shallow coverage of a sediment-filled valley by using surface waves from a small explosive source, recorded along a 65-m-long linear array. The group and phase velocity dispersion curves are obtained from the analysis of the multi-channel recordings and inverted for the velocity structure. The velocity model obtained in this way is then used as a new starting model for a waveform inversion process, in which both compressional- and shear-wave velocities are iteratively adjusted, obtaining a significative improvement of the fit between data and synthetics. The Q structure is investigated by using the technique described in Malagnini et al. (1995). The velocity is kept fixed, and the reference frequency for the computation of causal Q is put at 10 Hz, due to the high-frequency content of the recorded waveforms. The resulting Q values in the upper layer (Q (sub P) = Q (sub S) = 9 in the first 20 m in depth) are higher than those previously observed at 1 Hz in the same site (Q (sub P) = Q (sub S) = 2 in the first 22 m in depth), suggesting, at least in the investigated case, a frequency-dependent attenuation structure for soft-soil coverages.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 86
Serial Issue: 5
Title: Velocity and attenuation structure of very shallow soils; evidence for a frequency-dependent Q
Author(s): Malagnini, Luca
Affiliation: Istituto Nazionale di Geofisica, Rome, Italy
Pages: 1471-1486
Published: 199610
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 43
Accession Number: 1997-008916
Categories: Engineering geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
N36°30'00" - N47°30'00", E06°30'00" - E19°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 199703
Close Modal

or Create an Account

Close Modal
Close Modal