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Article: Interpretation of seismic vertical amplification observed at an array site

TitleInterpretation of seismic vertical amplification observed at an array site
Authors
Issue Date2000
PublisherSeismological Society of America. The Journal's web site is located at http://www.bssaonline.org
Citation
Bulletin Of The Seismological Society Of America, 2000, v. 90 n. 2, p. 275-285 How to Cite?
AbstractStrong ground motions were recorded at Port Island, Kobe, by a borehole array during the 1995 Hyogo-ken Nanbu (Kobe) earthquake. These records indicate that, while the horizontal peak accelerations were reduced as seismic waves traveling from the bottom to the surface, motions in the vertical direction were significantly amplified at the surface, with peak value of 1.5 to 2 times larger than the horizontal components. Some studies have discussed local site effects on the horizontal motions, whereas the available study on the vertical amplification is limited. In this article, we present a possible mechanism to explain the observed vertical amplification in detail. We consider that the observed large vertical amplification is mainly associated with incomplete saturation of near-surface soils, which causes substantial amplification of P waves but does not affect the propagation of S waves. Based on the concept of homogeneous pore fluid and Biot's theory of two-phase media, we discuss the characteristics of P-wave velocity, Poisson's ratio and degree of saturation in shallow soil layers, and show evidence of incomplete saturation of near-surface soils at the array site. We analyze a simple model to theoretically investigate the effects of saturation on vertical-motion amplification. The results show that the degree of saturation may produce substantial influence on the amplification, both amplitude and frequency content. Using a solid-fluid coupled finite element procedure, we perform a simulation of the observed vertical motions at the array site by including the effects of saturation. The results demonstrate the mechanism of large amplification caused by incomplete saturation of near-surface layers. The present study indicates that vertical-component motions may significantly be affected by pore-water saturation of soils, suggesting that we may need to carefully examine the condition of saturation in the study of vertical site amplification.
Persistent Identifierhttp://hdl.handle.net/10722/150157
ISSN
2015 Impact Factor: 2.311
2015 SCImago Journal Rankings: 2.068
References

 

DC FieldValueLanguage
dc.contributor.authorYang, Jen_US
dc.contributor.authorSato, Ten_US
dc.date.accessioned2012-06-26T06:01:54Z-
dc.date.available2012-06-26T06:01:54Z-
dc.date.issued2000en_US
dc.identifier.citationBulletin Of The Seismological Society Of America, 2000, v. 90 n. 2, p. 275-285en_US
dc.identifier.issn0037-1106en_US
dc.identifier.urihttp://hdl.handle.net/10722/150157-
dc.description.abstractStrong ground motions were recorded at Port Island, Kobe, by a borehole array during the 1995 Hyogo-ken Nanbu (Kobe) earthquake. These records indicate that, while the horizontal peak accelerations were reduced as seismic waves traveling from the bottom to the surface, motions in the vertical direction were significantly amplified at the surface, with peak value of 1.5 to 2 times larger than the horizontal components. Some studies have discussed local site effects on the horizontal motions, whereas the available study on the vertical amplification is limited. In this article, we present a possible mechanism to explain the observed vertical amplification in detail. We consider that the observed large vertical amplification is mainly associated with incomplete saturation of near-surface soils, which causes substantial amplification of P waves but does not affect the propagation of S waves. Based on the concept of homogeneous pore fluid and Biot's theory of two-phase media, we discuss the characteristics of P-wave velocity, Poisson's ratio and degree of saturation in shallow soil layers, and show evidence of incomplete saturation of near-surface soils at the array site. We analyze a simple model to theoretically investigate the effects of saturation on vertical-motion amplification. The results show that the degree of saturation may produce substantial influence on the amplification, both amplitude and frequency content. Using a solid-fluid coupled finite element procedure, we perform a simulation of the observed vertical motions at the array site by including the effects of saturation. The results demonstrate the mechanism of large amplification caused by incomplete saturation of near-surface layers. The present study indicates that vertical-component motions may significantly be affected by pore-water saturation of soils, suggesting that we may need to carefully examine the condition of saturation in the study of vertical site amplification.en_US
dc.languageengen_US
dc.publisherSeismological Society of America. The Journal's web site is located at http://www.bssaonline.orgen_US
dc.relation.ispartofBulletin of the Seismological Society of Americaen_US
dc.titleInterpretation of seismic vertical amplification observed at an array siteen_US
dc.typeArticleen_US
dc.identifier.emailYang, J:junyang@hkucc.hku.hken_US
dc.identifier.authorityYang, J=rp00201en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1785/0119990068-
dc.identifier.scopuseid_2-s2.0-0034121717en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0034121717&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume90en_US
dc.identifier.issue2en_US
dc.identifier.spage275en_US
dc.identifier.epage285en_US
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridYang, J=35605258800en_US
dc.identifier.scopusauthoridSato, T=7406984636en_US

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