Prediction of the intensity of earthquake-induced motions at the ground surface attracts extensive attention from the geoscience community due to the significant threat it poses to humans and the built environment. Several factors are involved, including earthquake magnitude, epicentral distance, and local soil conditions. The local site effects, such as resonance amplification, topographic focusing, and basin-edge interactions, can significantly influence the amplitude-frequency content and duration of the incoming seismic waves. They are commonly predicted using site effect proxies or applying more sophisticated analytical and numerical models with advanced constitutive stress-strain relationships. The seismic excitation in numerical simulations consists of a set of input ground motions compatible with the seismo-tectonic settings at the studied location and the probability of exceedance of a specific level of ground shaking over a given period. These motions are applied at the base of the considered soil profiles, and their vertical propagation is simulated using linear and nonlinear approaches in time or frequency domains. This paper provides a comprehensive literature review of the major input parameters for site response analyses, evaluates the efficiency of site response proxies, and discusses the significance of accurate modeling approaches for predicting bedrock motion amplification. The important dynamic soil parameters include shear-wave velocity, shear modulus reduction, and damping ratio curves, along with the selection and scaling of earthquake ground motions, the evaluation of site effects through site response proxies, and experimental and numerical analysis, all of which are described in this article.

The presence of frozen soil layers leads to stratification in soil stiffness, thereby influencing the dynamic response of pile foundations in seasonally frozen soil regions. This study investigated the dynamic response of pile-soil interaction (PSI) systems in such regions. A reduced-scale (1/10) model of a pile group with an elevated cap in railway bridges was subjected to shake-table testing. During these tests, measurements were taken of soil and pile accelerations, displacement time histories, and pile strain. The acceleration amplification factor (AMF) and response spectrum of the soil and pile foundation were analyzed based on these data. Additionally, the pile-soil interaction and the dynamic shear stress-strain relationship of the soil were investigated. The experiment indicated that the presence of a frozen soil layer alters the energy dissipation order of the pile-soil interaction system. This leads to a weakened dynamic response of the pile foundation. Furthermore, the seasonally frozen soil layer acts as a filter for high-frequency ground motion, thereby mitigating resonance between ground motion and the pile foundation, ensuring the protection of the pile foundation. However, the significant stiffness contrast induced by the seasonally frozen soil can pose a threat to structural safety under increasing peak ground acceleration (PGA). As PGA increases, there is a transition from linear to nonlinear interaction between the pile and soil, initially affecting the unfrozen soil layer, then the frozen-unfrozen transition layer, and ultimately impacting the seasonally frozen soil layer.

The earthquakes in Pazarc & imath;k (Mw 7.7) and Elbistan (Mw 7.6), occurring along the East Anatolian Fault Zone (EAFZ) on February 6, 2023, caused significant damage and destruction to the built environment within the affected area. In this study, the preliminary site investigations were conducted in the G & ouml;lba & scedil;& imath; district, where the impacts of both earthquakes were severely felt, offering scientifically valuable information regarding the soil damage. Comprehensive liquefaction analyses were performed using the geotechnical laboratory test data on soil specimens collected from the G & ouml;lba & scedil;& imath; district. These analyses confirmed the liquefaction-induced ground failures observed immediately after the two earthquakes. Furthermore, microzonation data collected in the G & ouml;lba & scedil;& imath; district were consolidated, and seismic site response analyses were conducted. Simulations showed that local soils in the region could amplify seismic waves by a factor of two. Utilizing the calculated Peak Ground Acceleration (PGA) and amplification factors, GIS-based distribution maps of the entire area were developed. These maps serve as practical resources for practitioners and local planners, aiding in spatial settlement decisions and urban transformation planning. They contribute significantly to enhancing the understanding of earthquake hazards in the region.

Our study introduces a methodology to improve large-scale seismic damage assessment by incorporating site-specific fragility curves, considering soil-structure interaction (SSI) and site amplification (SAmp) effects. The proposed method proposes an enhanced building exposure model, using publicly available data and the open-source OpenQuake Engine software. The objective is to determine whether a more refined approach incorporating SSI and SAmp can impact the final damage calculation. We evaluate our approach by estimating the damage distribution for the Thessaloniki 1978 earthquake scenario using the actual building stock of Thessaloniki. We present several maps with aggregated damages at different levels to investigate the spatial variability of SSI and SAmp, and their influence on the resulting damages. Our estimated physical damages have been compared with those obtained using approaches from the existing literature. Apparently, using an updated building exposure model to assess damages makes any comparison with past observed damages challenging. Nevertheless, incorporating SSI and SAmp in large-scale damage assessment can provide valuable support for strategic decision-making in cities and improve the accuracy of the expected loss assessment due to a seismic event.

On 15 January 2023, a shallow, moderate earthquake with a magnitude (Mw) of 4.7 and a depth of one kilometer struck the northern part of Leyte Island in the central Philippines. Originating along the northern Leyte segment of the Philippine Fault, a well-established creeping fault, the earthquake caused significant geologic, structural, and socio-economic impacts despite its low magnitude. Probable surface rupture and landslides were reported, leading to a comprehensive field investigation. Our investigation revealed an similar to 8 km discontinuous surface rupture along the northern Leyte segment of the Philippine Fault, with a maximum left-lateral displacement of 2 cm. This was the first documented occurrence of such a phenomenon associated with an earthquake of a magnitude less than 6, particularly along a creeping fault segment. The maximum ground shaking felt was reported on the PHIVOLCS Earthquake Intensity Scale (PEIS) to be VI (very strong), equivalent to a Modified Mercalli Intensity (MMI) of VI along the fault strike. However, strong motion accelerographs recorded a peak ground acceleration (PGA) of 0.407 g, equivalent to PEIS VIII (very destructive), attributed to local site amplification influenced by subsurface geology. In the area where the local site amplification occurred, limited liquefaction was observed on marshlands with recent and alluvial deposits. Two landslides were observed in the mountainous area west of the fault. Structural damages were noted in areas with PEIS VI intensity and areas transected by the surface rupture. Despite the earthquake's low magnitude, the event documented significant impacts, including surface ruptures, liquefaction, landslides, and severe structural damage. The peculiarities of this event are attributed to the shallowness of the earthquake source, and local site conditions, including geology, geomorphology, and soil properties, contributed to the severity of the impacts. Moderate in size, this earthquake emphasizes the importance of documenting moderate-sized earthquakes as a tool and guide for medium- and long-term earthquake risk assessment and resiliency.