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Influence of the V (sub s) profiles beyond 30 m depth on linear site effects; assessment from the KiK-net data

Julie Regnier, Luis Fabian Bonilla, Etienne Bertrand and Jean-Francois Semblat
Influence of the V (sub s) profiles beyond 30 m depth on linear site effects; assessment from the KiK-net data
Bulletin of the Seismological Society of America (October 2014) 104 (5): 2337-2348


Site effects may be assessed using a standard soil classification parameter, V (sub S30) (the harmonic average shear-wave velocity in the first 30 m); however, this index does not account for the complexity of the velocity profile, especially its variability at depth. In the present study, in addition to V (sub S30) , we propose consideration of the gradient of the V (sub S) profile from 0 to 30 m depth, denoted B (sub 30) . A lower gradient value means low velocity increases with depth; a higher gradient indicates a rapid velocity increase with depth in the shallow layers. In addition, we consider the fundamental resonance frequency of the soil (f (sub 0) ), which has been shown to be a relevant parameter for site-effect assessment and which is obtained from the empirical site response. Using the Japanese KiK-net database, we analyze the variability of the V (sub S) profiles and the empirical borehole site responses of selected sites through the V (sub S30) , the velocity gradient B (sub 30) , and f (sub 0) . We select 289 sites for which the 1D linear numerical modeling is close to the empirical site response and a V (sub S) at the downhole station is greater than 1000 m/s. For a given V (sub S30) class, B (sub 30) , and f (sub 0) can be used to distinguish between two types of sites: deep sedimentary sites and sites with high velocity contrast at shallow depths. We find that, even if the gradient is calculated using shallow information, its use improves the site amplification characterization, compared to using only V (sub S30) , by reducing the intersite site-response variability. As expected, however, this improvement is limited for deep sedimentary sites. On the other hand, f (sub 0) is able to reduce the intersite response variability for deep sedimentary sites even though it is limited to specific V (sub S30) classes. Thus, the combined use of V (sub S30) , B (sub 30) , and f (sub 0) improves the assessment of linear site amplification.

ISSN: 0037-1106
EISSN: 1943-3573
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 104
Serial Issue: 5
Title: Influence of the V (sub s) profiles beyond 30 m depth on linear site effects; assessment from the KiK-net data
Affiliation: Centre d'Etudes et d'Expertise sur les Risques, l'Environnement, la Mobilite et l'Amenagement, DTer Mediterranee, Nice, France
Pages: 2337-2348
Published: 201410
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 52
Accession Number: 2014-091588
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
N30°00'00" - N45°00'00", E129°00'00" - E147°00'00"
Secondary Affiliation: Universite Paris-Est, FRA, France
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201447
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