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See detail2D dynamic studies combined with the surface curvature analysis to predict Arias Intensity amplification
Torgoev, Almazbek ULg; Havenith, Hans-Balder ULg

in Journal of Seismology (2016)

A 2D elasto-dynamic modelling of the pure topographic seismic response is performed for six models with a total length of around 23.0 km. These models are reconstructed from the real topographic settings ... [more ▼]

A 2D elasto-dynamic modelling of the pure topographic seismic response is performed for six models with a total length of around 23.0 km. These models are reconstructed from the real topographic settings of the landslide-prone slopes situated in the Mailuu-Suu River Valley, Southern Kyrgyzstan. The main studied parameter is the Arias Intensity (Ia, m/sec), which is applied in the GIS-based Newmark method to regionally map the seismically-induced landslide susceptibility. This method maps the Ia values via empirical attenuation laws and our studies investigate a potential to include topographic input into them. Numerical studies analyse several signals with varying shape and changing central frequency values. All tests demonstrate that the spectral amplification patterns directly affect the amplification of the Ia values. These results let to link the 2D distribution of the topographically amplified Ia values with the parameter called as smoothed curvature. The amplification values for the low-frequency signals are better correlated with the curvature smoothed over larger spatial extent, while those values for the high-frequency signals are more linked to the curvature with smaller smoothing extent. The best predictions are provided by the curvature smoothed over the extent calculated according to Geli’s law. The sample equations predicting the Ia amplification based on the smoothed curvature are presented for the sinusoid-shape input signals. These laws cannot be directly implemented in the regional Newmark method, as 3D amplification of the Ia values addresses more problem complexities which are not studied here. Nevertheless, our 2D results prepare the theoretical framework which can potentially be applied to the 3D domain and, therefore, represent a robust basis for these future research targets. [less ▲]

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See detailInitiation of earthquake-induced slope failure: influence of topographical and other site specific amplification effects
Havenith, Hans-Balder ULg; Vanini, M.; Jongmans, D. et al

in Journal of Seismology (2003), 7(3), 397-412

Increased structural damage caused by earthquakes on hilltops and along ridges has often been related to amplification of ground motion due to the presence of topography. However, comparison between ... [more ▼]

Increased structural damage caused by earthquakes on hilltops and along ridges has often been related to amplification of ground motion due to the presence of topography. However, comparison between observations and numerical modeling has shown that amplification is only partly dependent on the prominent surface morphology. Strong effects are also induced by soft layers, such as weathered rock material or colluvium, covering the topographies. Numerous seismically triggered landslides are reported to occur in the same materials that are likely to amplify ground motions. Therefore, it can be suspected that ground motion dynamics significantly contribute to the observed slopes failures. This potential relationship is the subject of the present case study, the Ananevo rockslide in the northeastern Tien Shan mountains. The survey included geophysical prospecting, earthquake recordings and structural analyses of the rock fabric. On the basis of the field data, observed amplification effects could be related to the local geological conditions and particularly to the surface morphology and to the presence of low-velocity layers-deeply weathered rocks-on the top of the bedrock. Surface layer- and topography-dependent amplification has also been studied numerically by 2D and 3D finite element modeling of ground motion dynamics. The present paper focuses on additional effects that may be induced by the presence of a fault zone and of the landslide scarp. Further, observed and computed ground motion dynamics are connected with slope failure susceptibility: 2D numerical simulations reveal that strain localization is closely related to wave amplification in surficial low-velocity layers, particularly below convex surface morphologies. [less ▲]

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See detailProbabilistic PGA and Arias Intensity maps of Kyrgyzstan (Central Asia)
Abdrakhmatov, K.; Havenith, Hans-Balder ULg; Delvaux, Delphine ULg et al

in Journal of Seismology (2003), 7(2), 203-220

New probabilistic seismic hazard and Arias Intensity maps have been developed for the territory of the Kyrgyz Republic and bordering regions. Data were mainly taken from the seismic catalogue of ... [more ▼]

New probabilistic seismic hazard and Arias Intensity maps have been developed for the territory of the Kyrgyz Republic and bordering regions. Data were mainly taken from the seismic catalogue of Kyrgyzstan and partly from the world seismic catalogue. On the base of seismicity and active tectonics, seismic zones were outlined over the area. For these, Gutenberg-Richter laws were defined using mainly instrumental data, but regarding also historical events. Attenuation of acceleration inside the target area could not be determined experimentally since existing strong motion data are insufficient. Therefore, empirical laws defined for other territories, principally Europe and China, were applied to the present hazard computations. Final maps were calculated with the SEISRISKIII program according to EUROCODE8 criteria, i.e. for a period of 50 years with 90% probability of non-exceedance. For long-term prediction, 100 years maps with 90% probability of non-exceedance have been developed. The procedure used for seismic hazard prediction in terms of PGA (Peak Ground Acceleration) was also applied to Arias intensities in order to be able to define regional seismogenic landslide hazard maps. [less ▲]

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