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Probabilistic Liquefaction Analysis Using Standard Penetration Test

Kamel Filali, Badreddine Sbartai

Studia Geotechnica et Mechanica

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2022

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Vol. 44, nr 2

162--174

EN

The Youd etal liquefaction resistance curves developed in 2001 to characterize the cyclic resistance of soil based on SPT test are the most used in the context of the Seed and Idriss simplified procedure as a deterministic model. These curves were developed from a modified database of Seed etal. in 1985 with the assumption that the actual peak shear stress (τd) induced at depth h is always less than that predicted by the simplified procedure (τr) of Seed and Idriss (rd= τd/τr<1). By using a suite of equivalent linear site response analyses to adjust the dynamic and the simplified shear stress at depth h, Filali and Sbartai showed in 2017 that the dynamic peak shear stress for some earthquakes is greater than the simplified peak shear stress (rd>1). As in this case, the assumption of the simplified procedure is not verified, Filali and Sbartai have proposed a corrector factor (RC) in the range where rd>1 to adjust the deformable and rigid body. In this paper, we will present a probabilistic study for the evaluation of the liquefaction potential using a database based on SPT measurement compiled after the Chi-Chi Taiwan earthquake, in which the cyclic stress ratio is evaluated using the proposed corrector factor. The objective of this study is to present a probabilistic shape of the cyclic resistance ratio (CRR) curves based on the original simplified method of Seed and Idriss and the corrected version and a new formulation for computing the probability of liquefaction.

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The improvement of the earthquake and microseismic Horizontal-to-Vertical Spectral Ratio (HVSR) in estimating site efects

Sarmadi Mohammad Ali, Heidari Reza, Mirzaei Noorbakhsh, Siahkoohi Hamid Reza

Acta Geophysica

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2021

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Vol. 69, no. 4

1177--1188

EN

The horizontal-to-vertical spectral ratio (HVSR) has been widely used to calculate near-surface site efects including funda mental resonance frequency and soil amplifcation. In this study, we investigated the features of HVSR in order to assess the reliability of this method. The main premise of Nakamura (1989; Nakamura, Y., 2000. Clear identifcation of fundamental idea of Nakamura’s technique and its applications. In: Proceedings of the 12th World Conference on Earthquake Engineer ing. Auckland, New Zealand.) HVSR method is to assume there are little to no amplifcation or de-amplifcation of motion recorded by the vertical component. In this study, we disregarded this assumption and used diferent proposed spectral ratios of earthquake accelerograms to examine and evaluate the accuracy of the HVSR technique. In addition, to increase the accuracy of the results, near-surface attenuation parameter Kappa (K), as an important spectral decay parameter which has infuence on the site efects, has been incorporated in proposed spectral ratios. The efciency of proposed spectral ratios was evaluated using 3948 accelerograms (Includes surface and borehole stations) of 496 earthquakes from 18 KiK-net accelerometery stations of the two regions of Japan with moment magnitudes ranging from 3 to 5. The two selected areas have diferent geological characteristics and diferent site efects parameters. According to the results, The HVSR method is under-determined at stations where the waves are mainly amplifed as they pass through the site. Moreover, in a single sta tion by calculating the amplifcation value on the vertical component, Site efects measurements obtained from surface and borehole data along with classical HVSR technique have a lower mean absolute error than those obtained by using HVSR technique alone.

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Study of Site Effect at Seismic Station Located in Undermined Area of Karviná Region (Czech Republic)

Lednicka M., Kalab Z.

Acta Geophysica

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2016

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Vol. 64, no. 5

1715--1730

EN

The Karviná region is well known as an area with an intensive mining induced seismicity. The local geological pattern, especially subsurface sedimentary layers, belongs to one of the most important factors that influence the amplification of seismic effect on the surface. In order to investigate the amplification effect, there are used methods of spectral ratio that enable to analyse records of vibrations. In the present study, two methods, signed as SSR (standard spectral ratio) and HVSR (horizontal to vertical spectral ratio), were used for the site effect evaluation. The analysis was performed in the populated Doubrava locality where high seismic loading on the surface due to mining induced seismicity is documented.

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Influence of attenuation and site on microearthquakes’ spectra in Shillong region, of northeast, India: A case study

Biswas R., Baruah S., Bora D.

Acta Geophysica

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2013

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Vol. 61, no. 4

886--904

EN

We examine the influence of attenuation and site on the spectra of microearthquakes having origin within the Shillong region. The ratios of spectral amplitudes at lower and higher frequencies are measured for three different stations at varying epicentral distances to estimate Q value for both P- and S-wave in near and sub-surface layer. The average estimates of QP and QS are found to be 178 and 195. The ratio of QS to QP emerges to be greater than unity in major parts of the Shillong area, suggesting dominance of dry crust prevailing in Shillong region. The variation in corner frequencies for these spectra is inferred to be characteristics of the site. Besides, the disparity in spectral content with reference to hard rock site yields the inference that the incoming seismic signals get amplified considerably while traversing from southern part to northeastern part of Shillong, best outlined at 2 to 5 Hz, which is well corroborated by the existing lithology.