Nepal, a landlocked country in the Himalayan region, was struck by a devastating earthquake of magnitude Mw 7.8 on 25th April, 2015. The major earthquake destroyed millions of structures and caused immense loss of life. Unfortunately, only a few seismic stations recorded the earthquake, presenting a challenge for understanding the observed non-uniform structural damage in the region. In this study, synthetic ground motions are generated at the bedrock level using the stochastic finite fault method. The ground motions are later estimated at the surface level using the equivalent linear site response analysis program, using soil profiles from 9 borehole locations from the Kathmandu basin. The key characteristics of the synthetic strong ground motions are tabulated and analyzed. Peak ground accelerations (PGA) at bedrock in the region range from 0.064 g to 0.09 g. Remarkably, the Kankali site (BH6) exhibits the highest outcrop acceleration response, with bedrock and outcrop PGAs measuring 0.083 g and 0.170 g, respectively. Observations indicate that soil profiles experience their greatest amplification ratio within the frequency range of 1.2 Hz-7.3 Hz. Plots of response spectra for the synthetic ground motions are derived and compared with the provisions of the Nepal's seismic design code. The key characteristics of strong ground motions and observations from the derived response spectra correlate well with the available reports of structural damage in the earthquake. These observations provide valuable insights into seismic vulnerability and soil behavior that is crucial for seismic hazard assessment and engineering design considerations.

The seismic response characteristics of the Yellow River terrace are crucial, as it is one of the key human activity areas. Seismic response characteristics of Yellow River terrace stations in Ningxia were analyzed using strong-motion earthquake records from seismic observations in the Loess Plateau and corresponding station data, employing the Horizontal-to-Vertical Velocity Response Spectrum Ratio method. The seismic vulnerability coefficient (Kg) was computed, and the bedrock depth was estimated. The results indicate that the spectral ratio curves of the Yellow River terrace can be classified into three types: single-peak, multi-peak, and ambiguous-peak types. The predominant period of the terraces ranges from 0.12 to 1.22 s, and the amplification factor ranges from 2.87 to 10.29. The calculated Kg values range from 2.09 to 63.24, and the bedrock depth ranges from 10.68 to 168.11 m. The site's predominant period, amplification factor, high Kg values, and deep bedrock depths can significantly impact seismic design, potentially leading to greater damage during earthquakes. Based on the predominant period, Kg values, and bedrock depth, the seismic vulnerability of Yinchuan is assessed to be high.

An earthquake event with a moment magnitude of 7.7 took place in Pazarc & imath;k (Kahramanmara & scedil;, T & uuml;rkiye) on February 6, 2023. Approximately 9 hours after this event, another powerful earthquake event in Elbistan (Kahramanmara & scedil;) with a moment magnitude of 7.6 occurred. This study reports the level of devastation in Kahramanmara & scedil;, Hatay, and Ad & imath;yaman cities of T & uuml;rkiye that were heavily affected. Mainly, the characteristics of the recorded input motions at the affected areas and their spectral accelerations at different sites (possessing different soil classes) along with the design values are evaluated. Moreover, soft-weak story failures and pancake collapses of buildings are discussed together with strong column-weak beam philosophy. The influence of site effect on the input motions and, therefore, on the structural damages is highlighted, too.

This study investigates the influence of the soil-structure interaction (SSI) on the seismic performance of structures, focusing on the effects of foundation size, soil type, and superstructure height. While the importance of SSI is well recognized, its impact on structural behavior under seismic loads remains uncertain, particularly in terms of whether it reduces or amplifies structural demands. A simplified dynamic model, incorporating both the mechanical behavior of the soil and structural responses, is developed and validated to analyze these effects. Using a discrete element approach and the 1940 El Centro earthquake for validation, the study quantitatively compares the response of soil-interacting structures to those with fixed bases. The numerical results show that larger foundation blocks (20 m x 20 m and 30 m x 30 m) increase the seismic response values across all soil types, causing the structure to behave more like a fixed-base system. In contrast, reducing the foundation size to 10 m x 10 m increases the flexibility of structures, particularly buildings built on soft soils, which affects the displacement and acceleration response spectra. Softer soils also increase natural vibration periods and extend the plateau region in regard to spectral acceleration. This study further finds that foundation thickness has a minimal impact on spectral displacement, but structures on soft soils show more than a 15% reduction in spectral displacement (SD) compared to those on hard soils, indicating a dampening effect. Additionally, increasing the building height from 7 to 21 m results in a more than 20% decrease in SD for superstructures with natural vibration periods exceeding 2.4 s, while taller buildings with longer natural vibration periods exhibit opposite trends. Structures built on soft soils experience larger foundation-level displacements, absorbing more seismic energy and reducing earthquake accelerations, which mitigates structural damage. These results highlight the importance of considering SSI effects in seismic design scenarios to achieve more accurate performance predictions.

The April 2010 earthquake (Mw = 7.2), which occurred about 40 km to the southeast of the city of Mexicali, Mexico, caused significant damage to buildings. To improve knowledge of the seismic response of the soil due to the occurrence of earthquakes, a response spectrum at 5% damping was calculated. A comparison between the spectral ordinates obtained in this study and the spectra proposed by the regulations of the Federal Electricity Commission (CFE for its acronym in Spanish) in its seismic design for civil works manual, which is currently used as the design standard throughout the country, was made. We calculated response spectra using records from the April 2010 earthquake and a stratigraphic profile of the city to calculate a transfer function. We first corrected the records for site effect due to stations being over sedimentary soil, and then used them as Green functions to perform a numerical simulation of propagation through the stratigraphic profile to obtain a simulated surface record from which response spectra were calculated. Additionally, ambient seismic noise was measured at the same site to get the dominant period (To). We observed that the transfer function was similar to the spectral quotient up to 5 Hz and that To calculated in both ways gave similar values. The comparison suggests that the design spectrum of the CFE regulation can be considered as a representative spectrum for Mexicali for periods greater than 1.3 s, but not for the zone of short periods.

Slopes have a significant impact on the ground motion characteristics, which can aggravate the damage degree of building structures during a strong earthquake. However, many studies have focused on the design response spectra under flat site conditions and fewer researchers have investigated the impact of slope topography on the design response spectra. In this study, the numerical simulation is used to obtain the seismic response of slopes and the differential evolution algorithm is used to obtain the standardized response spectra of the acceleration time histories along the ground surface behind the slope crest. The impacts of slope height (H), slope gradient (i), average shear wave velocity in the top 30 m (VS30) and distance from the slope crest (x) on the characteristic parameters of the design response spectra are then investigated. The results show that H, i, VS30 and x have a little influence on the normalized second inflection point period (mean(Tg/Tg,ff)) but a great influence on the normalized plateau value (mean(alpha max/alpha max,ff)). Specifically, both mean(Tg/Tg,ff) and mean(alpha max/alpha max,ff) show a trend from increasing first to decreasing and stabilizing finally as x increases; the mean(alpha max/alpha max,ff) shows an increasing trend as H increases, but a decreasing trend as i or VS30 increases. Finally, to provide some guidance for the seismic design of building structures near slopes, two approximate relationships are proposed: (1) between mean(Tg/Tg,ff) and x, and (2) between mean(alpha max/alpha max,ff) and H, i, VS30, x. The main innovation of this paper is that the relationship between the characteristic parameters of the design response spectra and the slope site characteristic parameters is clearly summarized and quantified for the first time.