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Recent major seismic events, such as the Chi-Chi (1999) and the Wenchuan (2008) earthquakes occurred in Taiwan and China, have offered a variety of case histories on the performance of structures subjected to reverse faulting–induced deformation. A novel faulting mitigation method has recently been proposed, introducing a soft deformable wall barrier in order to divert the fault rupture away from the structure. This can be materialized by constructing a thick diaphragm-type soil bentonite wall (SBW) between the structure and the fault rupture path. The paper investigates the key parameters in designing such a SBW, aiming to mitigate the fault rupture hazard on shallow foundations. The paper employs a thoroughly validated finite element analysis methodology to explore the efficiency of a weak SBW barrier in protecting slab foundations from large tectonic deformation due to reverse faulting. A dimensional analysis is conducted in order to generalize the validity of the derived conclusions. The dimensionless formulation is then used to conduct a detailed parametric study, exploring the effect of SBW thickness w / H , depth H SBWl /H, and shear strength τ soil / τ SBW , as well as the bedrock fault offset h/H , foundation surcharge load q / ρgB , and fault outcrop location s/B . It is shown that the wall thickness, depth, and shear strength should be designed on the basis of the magnitude of the bedrock fault offset, the location of the fault relative to the structure, and the shear strength of the soil. The efficiency of the weak barrier is improved using lower strength and stiffness material compared to the alluvium. A simplified preliminary design methodology is proposed, and presented in the form of a flowchart. [ABSTRACT FROM AUTHOR]

It is well known that coseismic landslides are likely to occur under stronger shaking at shorter epicentral distance under the effects of topography and amplification of shaking together with such local geology as rock and soil types. However, this paper addresses a different issue that is the role of faults played in the triggering of landslides, both coseismic and non-seismic, and the long-term slope instability that lasts for decades or centuries after devastating earthquakes. Experiences during and after gigantic landslides are important to understand what happens in and around faults. Noteworthy is that there are cases in which slope instability starts after earthquakes and lasts for some time along surface manifestation of faults, whether or not they are the causative fault. Another important issue is the recovery of stability in shallow parts of slopes. Experiences in Japan, Taiwan and China suggest that a few decades is needed for this re-stabilization. Discussion is further made of geologically generated ground water pressure that is another causative mechanism of landslides. Thus, further field study is encouraged to promote slope hazard assessment. • Long-term slope instability after major earthquakes was studied by introducing examples in the past. • Compound effects of earthquake and rainfall on slope instability are presented. • Continuous slope instability along major tectonic lines is discussed. • Landslides triggered by abnormal ground water pressure are touched upon. • The concepts of process zone and geopressure should be investigated in more details. • The studied cases suggest the importance of more geological/geomorphological studies for understanding the landslide hazards in tectonically active regions of the world. [ABSTRACT FROM AUTHOR]

The objective of this paper is to identify the first mode ground period Tg, at each interesting site along Taiwan High Speed Rail (THSR) route, and further, to determine the site-dependent design response spectrum for particular sites with Tg larger than 1 s. In this paper, a linear model of shear wave propagating in a multi-layered half-space is developed to identify the first mode ground period Tg of an interesting site on the basis of the field bore hole data. Furthermore, for each one of the strong ground motion observation stations within the Chiayi-Tainan area, the first mode ground period Tg was identified by either coda waves or pre-event ambient vibrations from the seismograms. In addition, the site-specific parameter Cv in defining the normalized response spectrum was also determined based on the observed strong ground motions at the specified observation station, and hence the empirical function between Tg and Cv can be regressed for this interesting area. Therefore, for a particular site along THSR route within the Chiayi-Tainan area, the site-specific parameter Cv can be determined from the regressed empirical function by the identified first mode ground period Tg, and further, used to develop the site-dependent design response spectrum. [Copyright &y& Elsevier]

Many earthquake empirical models were developed based on the statistics in the past. However, it is commonly seen that a non-local model was applied to a local study without any adjustment. In this paper, a new algorithm using maximum likelihood estimation (MLE) to adjust a non-local model for local applications was presented, including a case study assessing the probability of major earthquake occurrences in Taipei. Specifically, considering the fault length of 36 km and slip rate of 2 mm/yr, it suggests the Sanchiao (or Shanchiao) fault could induce a major earthquake with magnitude M w 7.14±0.17, based on a non-local model integrated with limited local data using the MLE algorithms. [ABSTRACT FROM AUTHOR]

Earthquake early warning (EEW) has been implemented in several regions around the world. However, because of natural randomness and uncertainty, false alarm and missed alarm can be expected in EEW. The key scope of this study is to evaluate the reliability of an on-site EEW in Taiwan, by testing the system's algorithm with 17,836 earthquake data from 1999 to 2013. The analysis shows that the on-site EEW system, empirically speaking, should have a false-alarm probability of 2.5%, and a missed-alarm probability of 14.1%. Considering missed alarm should be more critical to EEW, a new algorithm that could reduce the system's missed-alarm occurrences to 6% is also discussed in this paper. [ABSTRACT FROM AUTHOR]

During an earthquake, buildings are analysed dynamically without any consideration of their neighbouring structures and usually this also neglects the influence of surficial rotational ground motion. Population growth and increased land costs have increased the spatial density of buildings in urban areas. This closer proximity of buildings to one another leads to more complex interactions between buildings and the surficial seismic ground motion field that includes both horizontal and rotational components. To address these issues, this paper explores the Structure-Soil-Structure Interaction (SSSI) between a pair of buildings, including the surficial horizontal and rotational ground motions. A reduced-order parametric model of this complex system is proposed. Ground accelerogram data recorded from the 6-DOF sensor SINAPS@ Kefalonia (Greece) post-seismic experiment and the SMART-1 array in Taiwan were employed. This extensive parametric study analyses over six million system/ground motion cases. Results suggest that the rotational ground motion can affect the seismic response when the SSSI is considered, producing an additional amplification of acceleration responses of certain structures. The impact of the rotational ground motion depends principally on the fundamental natural period of the building, and the SSSI depends mainly on the frequency ratio (here Ω b) between the buildings. • The influence of the rotational ground motion depends principally on the fundamental natural period of building 1. • The importance of the SSSI depends mainly on the frequency ratio between the buildings. • The maximum response total acceleration of building 1 is almost double that estimated from just using a simple SSI model. [ABSTRACT FROM AUTHOR]

Abstract: Site classification is an important procedure for a reliable site-specific seismic hazard assessment. On the other hand, the site conditions at strong-motion stations are essential for accurate interpretation and analysis of the recorded ground motion data obtained from different regions of the world. For some countries with insufficient data on the subsurface geological settings, the required site condition information is not available. This paper presents a new and efficient approach for site classification based on artificial neural networks (ANN) along with a selected set of representative horizontal to vertical spectral ratio (HVSR) curves for four site classes. The nonlinear nature of ANN and their ability to learn in a complex environment make it highly suitable for function approximation and solving complicated engineering problems. Two types of radial basis function (RBF) neural networks, namely, probabilistic neural networks (PNN) and generalized regression neural networks (GRNN) were chosen in this study, as no separate training phase is required, rendering them particularly suitable for site classification. The proposed approach has been tested using data of the Chi-Chi, Taiwan, earthquake (Mw=7.6) recorded from 87 stations at which the site conditions are known. Analyses show that both the PNN and the GRNN perform very well with similar accuracy in estimating site conditions, with successful rates of 78% and 75%, respectively. [Copyright &y& Elsevier]

Abstract: The destructive 1999 Chi–Chi earthquake (Mw 7.5) was the largest inland earthquake in Taiwan in the 20th century. Several observations witness the non-linear seismic soil response in sediments during the earthquake. In fact, large settlements as well as evidence of liquefaction attested by sand boils and unusual wet ground surface were observed at some sites. In this paper, we present a seismic response simulation performed with CyberQuake software on a site located within the Chang-Hwa Coastal Industrial Park during the 1999 Chi–Chi earthquake in Taiwan. A non-linear multi-kinematic dynamic constitutive model is implemented in the software. Computed NS, EW and UP ground accelerations obtained with this model under undrained and two-phase assumptions, are in good agreement with the corresponding accelerations recorded at seismic station TCU117, either for peak location, amplitudes or frequency content. In these simulations, liquefaction occurs between depths 1.3 and 11.3m, which correspond to the observed range attested by in place penetration tests and other liquefaction analyses. Moreover, the computed shear wave velocity profile is very close to post-earthquake shear wave velocity profile derived from correlations with CPT and SPT data. Finally, it is shown that in non-linear computations, even though a 1D geometry is considered, it is necessary to take into account the three components of the input motion. [Copyright &y& Elsevier]

Abstract: A series of ground vibration measurements were carried out during the executions of dynamic compaction (DC) at an industrial site. This site is near the seashore of central Taiwan and was a reclaimed land formed by hydraulic fill. The measured data included vibrations induced by standard and different tamping energies of DC. The vibrations of ground with several shallow isolation trenches were also measured. This paper presents the various vibration characteristics including waveform, Fourier spectrum, response spectrum, and amplitude attenuations with distance. The influences of tamping energy and isolation trench on ground vibration are also displayed. [Copyright &y& Elsevier]

The sand deposit in Central Western Taiwan typically contained significant amounts of fines. The assessment of liquefaction potential using the simplified procedure often involved adjustment in field test results to account for the effects of fines. The available fines content (FC) adjustment methods are highly empirical and may lead to very different conclusions. The need and/or level of FC adjustment should be justified based on cyclic behavior of sand and its relationship with fines. This study made an attempt to provide that reference information for a silty sand commonly found in Central Western Taiwan. A series of isotropic consolidation, undrained monotonic and cyclic triaxial tests were conducted on reconstituted Mai Liao Sand (MLS) with various FCs and densities. Concurrent shear wave velocities were measured using bender elements in some of the cyclic triaxial tests. This paper describes the geological background, the laboratory tests and their implications in the assessment of liquefaction potential for MLS. [Copyright &y& Elsevier]

The current simplified methods for assessing soil liquefaction potential use a deterministic safety factor in order to judge whether liquefaction will occur or not. However, these methods are unable to determine the liquefaction probability related to a safety factor. An answer to this problem can be found by reliability analysis. This paper presents a reliability analysis method based on the popular Seed''85 liquefaction analysis method. This reliability method uses the empirical acceleration attenuation law in the Taiwan area to derive the probability density distribution function (PDF) and the statistics for the earthquake-induced cyclic shear stress ratio (CSR). The PDF and the statistics for the cyclic resistance ratio (CRR) can be deduced from some probabilistic cyclic resistance curves. These curves are produced by the regression of the liquefaction and non-liquefaction data from the Chi-Chi earthquake and others around the world, using, with minor modifications, the logistic model proposed by Liao [J. Geotech. Eng. 114 (1988) 389]. The CSR and CRR statistics are used in conjunction with the first order and second moment method, to calculate the relation between the liquefaction probability, the safety factor and the reliability index. Based on the proposed method, the liquefaction probability related to a safety factor can be easily calculated. The influence of some of the soil parameters on the liquefaction probability can be quantitatively evaluated. [Copyright &y& Elsevier]

This paper presents a derivation of attenuation relations of Arias intensity for various site conditions based on the strong-motion data recorded in the 1999 Chi-Chi Taiwan earthquake. The data are from the mainshock and three large aftershocks with stations in the footwall area and in the area away from the fault. At each station, Arias intensity is computed from two horizontal acceleration time histories. The Arias intensity data are separated into four groups according to site classes assigned to recording stations. For each site class, the attenuation relation of Arias intensity is derived using a two-step regression analysis method. The attenuation relations established in this study can be used to estimate Arias intensity from a rupture of a thrust fault for sites in the footwall area or in the area away from the fault. [Copyright &y& Elsevier]

In the early morning (1:47 Taiwan time) of September 21, 1999, the largest earthquake of the century in Taiwan (Mw=7.6, ML=7.3) struck this island country. The earthquake killed more than 2400 people and caused great destruction to buildings, bridges, dams, highways, and railways. One of the causes for heavy damages to the structures is soil liquefaction and ground settlement during the earthquake. In this paper, investigation of soil liquefaction and case histories of liquefaction are presented. Three CPT-based simplified methods, the Robertson method, the Olsen method, and the Juang method, are examined using the case histories derived from the Chi-Chi earthquake. The results of the comparison show that the Juang method is more accurate than the two methods in predicting liquefaction potential of soils based on the cases derived from the Chi-Chi earthquake, although all three methods are quite comparable in accuracy. [Copyright &y& Elsevier]

This paper presents a generalized reduced-order nonlinear model subjected to multi-support seismic excitation. The hysteretic, nonlinear, relationship of piers is phenomenologically captured by a calibrated Bouc-Wen model. This generalized reduced-order model is benchmarked against legacy physical experimental tests performed at the University of Bristol. A deterministic approach using real spatiotemporal ground motions recorded at the SMART-1 array, Taiwan, is employed as an alternative to a stochastic methodology used in current provision codes. This is so that the influence of nonlinearity and ground motion aleatory and epistemic effects are fully captured. Incremental Dynamic Analysis (IDA) is then performed to identify the performance levels at which this system transitions from elastic to inelastic behaviour. A parametric study is then performed to explore the effect of the spatial variability of the ground motion while bridge alignment, valley profile and ground motion intensity are modified. Results indicate that bridges over shallow valleys with a central rise are prone to significant analysis errors if multi-support excitation is not employed. • A generalized reduced-order nonlinear model of a multi-span bridge under asynchronous excitation is proposed. • Hysteretic behavior of piers is facilitated by a generalized Bouc-Wen model. • The effect of certain valley profiles on bridge responses to the spatial variability of ground motions is significant. [ABSTRACT FROM AUTHOR]