The accurate prediction of site effects is closely related to the quality of the seismic site characterization. Furthermore, increasingly probabilistic design procedures require not only a single seismic velocity profile, but a suite of profiles that rigorously accounts for epistemic and aleatory uncertainties. The quantification of these uncertainties is particularly important for non-invasive site characterization techniques that require inversion, such as surface wave methods, as the non-uniqueness of the derived velocity profiles depends on the uncertainties of the experimental data, which are dependent on the type and number of non-invasive measurements as well as the site's geologic setting. This work expands upon previous efforts to develop shear wave velocity (Vs) profile’s whose corresponding uncertainty is consistent with that of the experimental data and that rigorously address the non-uniqueness in the inverse problem. In particular, this work addresses three key points. First, how experimental data from multiple active-source and/or passive-wavefield surface wave arrays can be statistically combined to quantify site-specific aleatory uncertainty. Second, how multiple inversion parameterizations can and should be used to quantify epistemic uncertainty in the inverse problem. Third, how site-specific statistical models can be derived from non-invasive site characterization efforts as an alternative to existing Vs randomization techniques commonly used in practice. These advances are demonstrated at the Garner Valley Downhole Array (GVDA) site located in southern California. As a result of this study, new uncertainty-consistent shear and compression wave velocity profiles have been produced at the GVDA site for use in future forward and backward prediction efforts.

Coastal ports are important transportation hubs connecting sea and land, not only important nodes of international trade and logistics, but also an important part of national economic development and national defense security. China's coastal ports are usually located near the earthquake zone. Therefore, it is necessary to investigate their ground motion characteristics to ensure the safety and reliability of the coastal ports. In seismic response problems, the presence of transverse isotropic soil results in different stiffness and damping characteristics in different directions, directly affecting the dynamic response characteristics of the soil. In this study, a finite element numerical analysis with equivalent nonlinear soil model is established to study the effect. As an example, the soil dynamic parameters in Yangshan Port were calibrated by a series of bending element, resonance column and dynamic triaxial tests. The influences of transverse isotropy on the PGA and response spectrum are studied. The seismic characteristics under different seismic intensities were analyzed, and a standard design response spectrum considering anisotropic soil layers was provided. The results can be used to improve the seismic design of coastal ports and provide a scientific basis for the seismic safety evaluation of existing ports.

Site effect is an important topic in earthquake engineering and seismic risk analyses. It is widely acknowledged that during the vertical propagation of the seismic waves, this phenomenon generally contributes to amplification of the resulting surface ground motion with respect to the local stratigraphy, surface topography, impedance contrast, and the mechanical properties of the surficial sediments This may lead to significant variation of the seismic shaking and structural damage at short distances. The standard procedure in the site-specific seismic hazard analysis is to evaluate the site effects using local amplification factors (AFs) or dynamic site response simulations. The common indicator of the variety of site conditions is the time-averaged shear wave velocity of the en first 30 m (Vs₃₀). However, Vs₃₀ alone may often not be sufficient to adequately assess the site effects and it is often combined with the fundamental vibration period (T_nat). The Saguenay Lac-Saint-Jean region (SLSJ) is characterized with moderate seismic activity and a typical Quaternary stratigraphy consisting of stiff glacial sediments at the base, soft post-glacial Laflamme Sea sediments and more recent alluvial planes. Important impedance contrast exists between the crystalline bedrock and the overlying surficial deposits. In this study, we analyse the site dynamic response through 1D linear and nonlinear simulations using representative soil profiles and earthquake motions. Typical parameters are evaluated to develop amplification functions for the region.

The Geotechnical Information DB System (called GeoInfo) in South Korea distributes a large volume of geotechnical survey results conducted at various construction sites. The geotechnical survey includes Standard Penetration Test (SPT) and collocated geophysical tests such as downhole and suspension logging tests. The previous study collected those test results and developed an N-Vs model based on regression, and it was confirmed that the developed model followed general trends of N-Vs well across wide range of N values. However, when compared to the N-Vs model proposed in Japan, the Korean model estimates a higher Vs than one from Japan model at the same N value. To figure out the reason of difference, this study conducted a residual analysis on the N-Vs models proposed in South Korea, centering on the geologically diverse Busan region, specifically the Nakdonggang delta and erosion basins. The findings emphasize the intrinsic correlation between geological attributes and the efficacy of N-Vs relations. A primary insight highlighted the importance of considering geological attributes when enhancing N-Vs relations.

This paper aims to present an experimental investigation on the unsaturated dynamic parameters of two types of soil i.e. sand and silt. These dynamic parameters are compared with emphasis on the influence of matric suction on the variations of small-strain shear modulus and damping ratio. Seven bender element and resonant column tests were performed on saturated and unsaturated specimens. The soils used in this study were Firoozkooh sand (No. 161) and non-plastic Firoozkooh silt. For this purpose, an unsaturated triaxial cell equipped with a set of bender elements and an unsaturated resonant column have been used. All specimens had an initial void ratio of 0.7 and were tested in various matric suctions under a mean net stress of 50 kPa. For applying and controlling of the matric suction, the axis translation technique and water head control (WHC) methods have been implemented. The obtained results from both bender element and resonant column tests, implied that there was a significant impact of matric suction on the shear modulus of the tested soils. The shear modulus of the tested sand started from the fully saturated state and increased to reach its maximum value around and between the Air-Entry value (AEV) and the Residual value (RV), then decreased and remained approximately constant with increase of matric suction; whereas, the shear modulus of the non-plastic silt continuously increased with increasing the matric suction. Also, the output data indicated that for the silt specimens, the damping ratio decreased with the increasing matric suction while in the sand specimens, noticeable variations of damping ratio with the matric suction occurred around and between the AEV and Residual value (RV). In addition, the values of shear modulus measured by the bender element tests were slightly higher than those obtained by resonant column tests.

This study employs dynamic centrifuge testing and numerical modeling to assess the seismic response of a soft soil profile. The soil profile comprises a 23.4 m thick layer of lightly overconsolidated kaolinite clay overlying a 2.3 m dense sand layer. The centrifuge model underwent strong base shaking, and accelerations, pore pressures, and settlements were recorded at various depths. These experimental results are then compared to those obtained from a nonlinear dynamic analysis using the finite difference program FLAC. The clay layer is represented using the PM4Silt (Plasticity Model for Silt) constitutive model, calibrated based on laboratory test data. The numerical model yields reasonable predictions of accelerations at various depths, though it exhibits less nonlinearity compared to the centrifuge test. Pore pressures in the shallow clay layer match well between the physical and numerical models, but the simulation overpredicts pressures at greater depths. Despite some discrepancies between the experimental data and numerical results, the study demonstrates that numerical modeling, with appropriate calibration, can adequately replicate the seismic response of soft clay soil layers.

Recent seismic events have renewed interest in assessing near-fault ground motions, where the role of vertical ground acceleration was revealed to be significant. Geotechnical studies on near-fault effects are still lacking; specifically, although numerical studies have been performed, experimental tests on large-scale models are not yet available in the literature. This paper presents the outcomes of an experimental project to improve our understanding of the vertical earthquake component for near-source conditions and its propagation on the uppermost soil layers. Specifically, the experimental campaign aims to identify the dynamic response of an ideal soil column to vertical accelerations. Particular attention is devoted to the amplification amount of the vertical input motion. The research results confirm the importance of the near-fault effects and provide valuable tools for studying the soil response under vertical actions.