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Abstract Morphological characteristics of slopes determine the predominant frequency，which may amplify the incident seismic wave of the same or similar frequency range，thereby increase the slope dynamic response，and even trigger landslides. The microtremors and seismic observations were carried out in the adits along the Shiziliang slope surface in the meizoseismal area of Wenchuan earthquake(Ms 8.0). The spectral ratios of horizontal to vertical component from the microtremor and the seismic records of 3 aftershocks were analyzed and the spectral characteristic curves were obtained. It was found that the minimum predominant frequency occurred at the slope crest. The PGA amplification decreased initially and then increased with the elevation，exhibiting a concave shape. The biggest PGA amplification reached 1.25 at the slope crest. The phenomenon of the low predominant frequency corresponding to the high PGA amplification at the top of slope may be related to the ratio of slope height to the wavelength of incident wave. The ratio was 0.2 when the PGA amplification reached the maximum value. To further investigate the morphological amplification effect on spectral characteristics，dynamic analysis was performed using the finite difference software FLAC by inputting the waves of multiple frequencies from the seismic acceleration records at Wolong station during Wenchuan earthquake(Ms 8.0). 3 different angles of inclination were assumed for the slope being simulated. The calculated predominant frequencies of the slopes with different angles of inclination were found to be the same，which were verified by the results from inputting Ricker wavelets of different mono-frequencies. This indicated that the slope angle had no effect on the predominant frequency.
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Received: 11 March 2014
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2015, Vol. 34 
