Abstract

This work reports the results of an accelerometer monitoring aimed at revealing the seismic response ofhillslopes in the town of Qiaozhuang, in Qingchuan County, near the north-eastern end of the fault ruptured duringthe 2008Mw7.9Wenchuan earthquake in Sichuan Province. Serious damage and slope failures were inducedby this earthquake in the town center and on the hills in the peri-urban zone. This suggested the possible occurrenceof amplification phenomena. Five accelerometer stations were emplaced at two topographic reliefs to investigatetheir response to ground motion during the last part of the Wenchuan seismic sequence. About 50aftershocks were recorded, whose magnitude (ML) varied between 1.2 and 5.5 and epicentral distance rangedfroma fewto 90 km. The accelerometer records provided evidence of directional amplification,whichwas investigatedby analyzing the polar diagrams of normalized Arias intensity (Ia) and the horizontal to vertical spectralratios (HVSR). Evidence of the anisotropic dynamic response and site specific resonance frequencies was obtainedfor both topographic reliefs.However, the ground shakingmaximaorientations differed depending on the local geological setting: in one casethey were transversal and in the other case sub-parallel to the relief elongation.No preferential direction of maximum shaking was observed at the site in the valley. Furthermore, evidence ofresonance was derived from the calculation of spectral ratio between the sites on the slope and those at thefoot of the hills. The resonancewasmore pronounced at higher elevations,which suggested a possible occurrenceof topographic amplification. Resonance frequencies were lower (3-5 Hz) on the smaller hill consisting of subverticallylayered phyllites and higher (up to 7 Hz) on the larger hill made mainly of limestones, whereas an oppositerelation between resonance frequency and hill size could be expected from a purely topographic effect.This and the presence of amplification factors larger than 2 suggest that, in addition to topographic effects,local geology also played a significant role in differentiating the site response.

Autore Pugliese

• Wasowski Janusz

Tutti gli autori

• Luo Y.; Del Gaudio V.; Huang R.; Wang Y.; Wasowski J.

Titolo volume/Rivista

Engineering geology

Anno di pubblicazione

2014

ISSN

0013-7952

ISBN

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Numero di citazioni Wos

Nessuna citazione

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Settori ERC

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Codici ASJC

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