Bengkulu city, located in the western part of Sumatra, is characterized by the prevalence of alluvial deposits. In certain areas, local site effects on soft alluvial sediments such as clay, sand, silt, mud, and gravel can amplify ground movements caused by significant seismic waves. Consequently, a comprehensive site effect study was conducted with closer measurement points to establish a more detailed seismic microzonation. In order to evaluate how the soil reacts to seismic activity, the HVSR method is performed to analyze the ambient soil noise within the study area. Field measurements reveal variations in the predominant frequency (ranging from 0.4 to 16.5 Hz), HVSR amplification (ranging from 0.3 to 12.3), and Kg distribution (ranging from 0.02 to 239.26), respectively. Furthermore, the PGA Kanai method was utilized to estimate soil shear strain (GSS) in the study area, using data from the 2000 Bengkulu-Enggano Earthquake (Mw 7.9) and the 2007 Bengkulu-Mentawai Earthquake (Mw 8.4). The analysis indicated a consistent distribution of Kg values with GSS and PGA values, alongside Modified Mercalli Intensity (MMI) values, exhibiting correlation coefficients greater than 0.9. This suggests that Bengkulu City faces a moderate to high vulnerability to severe damage from earthquakes. The closer examination of HVSR data at finer measurement points aids in identifying exposure to new hazards and contributes valuable insights for formulating regional planning policies centered on disaster risk reduction and enhancing existing strategies in Bengkulu City.

Installing strong ground motion measuring devices in existing structures is significant for earthquake engineering and building safety to monitor whether the structures can be damaged or not. This study determined with different spectral ratio methods the dominant vibration period and amplification characteristics of both the structure and the ground from earthquake and noise records and compared the results. For this purpose, online- monitored accelerometer devices were placed on the top floor of a 5-story public building that was improved in 2008, on the ground where it was built, and on the rock approximately 1 km away from this building. MASW measurement was taken to determine the ground class of the area where the accelerometer device was installed on the ground right next to the building. Many earthquake records of different distances and magnitudes were obtained by the fixed devices located in the building, on the ground, and the rock. Spectral ratio methods were applied to the recorded earthquakes according to the reference station method and horizontal/vertical ratio methods according to the single station method. In addition to the analyses applied to the earthquake records, noise measurements were taken at night on the building floors and ground, and these measurements were evaluated according to the horizontal/vertical spectral ratio method and floor spectral ratio methods. As a result of all the analyses, the amplifications, dominant frequencies, and damping ratio of the building and the ground were determined, and the interference status of the building and the ground was examined. As a result, it was observed that the dominant frequency of the building, the spectral ratio amplification, and the damping ratio values of the building were approximately the same by using different spectral ratio methods for earthquake and noise data. In addition, there was a slight increase in the building's dominant period as a result of earthquakes that occurred at different times.

The Mining Palace, established by King Carlos III of Spain in 1792, is a neoclassical architectural wonder in Mexico. Unfortunately, like many historical monuments and buildings in Mexico City, ground subsidence has led to structural damage. In the case of the Mining Palace, this subsidence has caused the buildings in the palace to lean. Our team used ambient noise techniques, electrical resistive tomography, and ground penetration radar to investigate the subsoil conditions. We also conducted seismic noise measurements to identify the vibration frequencies of various structural elements and buildings within the palace. Our research revealed significant lateral variation in geophysical properties due to the compacting of a soft clay layer, water infiltration, and the weight of certain structural elements. We found that the fundamental frequencies measured, both in the subsoil and the building, are not too close, indicating that Soil Structure Interaction effects are absent.

Bhaktapur, lying in the Kathmandu Basin, suffered damages during the 2015 Gorkha Earthquake, potentially exacerbated by local site effects. This research addresses the lack of site response study on Suryabinayak Municipality, located in the southern part of Bhaktapur district. Horizontal to Vertical Spectral Ratio (HVSR) and Floor Spectral Ratio (FSR) methods were employed to determine the fundamental frequencies of soil deposits at 241 free field stations and 20 Reinforced Concrete (RC) isolated buildings respectively. The fundamental frequency of soil deposits varies from 0.27 Hz to 10.00 Hz. Higher frequencies were noted near the basin edges, attributed to shallow sediment deposits, whereas a lower frequencies prevailed towards the basin centre due to an increase in sediment thickness. Out of 20 buildings studied, 7 are highly susceptible to soil-structure resonance as the frequency disparity between building and free-field is less than 15%. This research not only quantified the frequency distribution and soil-structure resonance likelihood but also established a correlation between building height and its fundamental frequency. A significant correlation is observed with a coefficient of determination (R2) value of 60.64% and 83.36% in the longitudinal and transverse directions respectively. The study's results can be endorsed to mitigate seismic hazards, build seismic-resilient structures, and maintain historical monuments.

Erzurum province is located close to two important faults, namely the North Anatolian Fault Zone and the East Anatolian Fault Zone. Additionally, numerous local faults such as the A & scedil;kale, Ba & scedil;k & ouml;y-Kandilli, Erzurum-Dumlu, Paland & ouml;ken, and Horasan-Narman Fault Zones could potentially trigger devastating earthquakes for Erzurum province. All these seismic hazard sources require a well-understanding of the soil dynamic properties in Erzurum province. The single-station microtremor method were carried out at 45 points to determine the Atat & uuml;rk University Central Campus-Erzurum soil dynamic parameters with this motivation. Seismic vulnerability index and seismic bedrock depth values were calculated with the help of empirical relations using the soil dominant frequency and soil amplification factor values calculated from the horizontal/ vertical spectral ratio method. The south-eastern region of the study area exhibits characteristics such as low soil dominant frequency values, high soil amplification factor values, elevated Kg values, and considerable engineering bedrock depth. This area is particularly vulnerable to potential earthquake damage due to its high sediment thickness and susceptibility to site effects. Notably, points three and four also demonstrate low soil dominant frequency values, coinciding with the locations of hospitals and administrative units. Therefore, it is imperative to intensify site effect investigations, especially using active sources of geophysical methods in these specific areas.

According to the Mexican National Seismological Service (SSN), about 25 % of Mexico's seismic activity is concentrated in the state of Oaxaca. Overtime, its population has suffered serious material damage and human losses. In the event of an earthquake, the rigidity of the subsoil beneath urban centers directly impacts the amount of damage to buildings and infrastructure. However, because damage is influenced by the soil seismic response and because there are as yet no updated site response studies that allow us to propose a seismic microzonation of the metropolitan area of Oaxaca, research of this type is very useful for educational and governmental institutions. In this study, seismic noise recording was carried out with broadband sensors to characterize the Horizontal to Vertical Spectral Ratio (HVSR). The main outcome of the study is a map representing the distribution of the seismic site response in the metropolitan area of the City of Oaxaca (ZMO). Furthermore, these results were correlated with the study area's soil type records.

The S-wave velocity (SWV) is a crucial parameter in seismic site characterization and seismic microzonation. In Varanasi city, we determined the shear wave velocity through a dual approach, employing joint inversion of microtremor array survey and the Horizontal to Vertical Spectral Ratio (HVSR) method. This combined analysis from two distinct methods enhances the reliability of our S-wave velocity model for the subsurface soil strata. To assess the S-wave velocity profile in shallow subsurface soil layers, we conducted forward and inverse modelling of geophysical data. This evaluation was cross-referenced with geotechnical borehole data to ensure accuracy. Microtremor measurements were conducted at 115 single stations and 12 array stations in the city. Joint modelling of HVSR and Rayleigh wave phase velocity dispersion provided insights into the site characteristics. Utilizing neighbourhood algorithms, we inverted dispersion curves from microtremor array measurements to obtain the S-wave velocity profile. The results were validated using geotechnical borehole data in the study area. The microtremor-derived S-wave velocity disclosed significant impedance contrasts in the topsoil layer, reaching a depth of approximately 12 m, with velocities ranging from 180 to 250 m/s. The second layer, extending to around 40-50 m, exhibited velocities between 300 and 400 m/s, while the bottom layer surpassed 600 m/s. Comparisons with SPT-derived S-wave velocity confirmed a well-correlated S-wave velocity profile for the top layer. The various methods converged to an average S-wave velocity of 360 m/s up to a depth of 50 m.

Two large earthquakes (Mw = 7.7 and Mw = 7.6) that occurred in Turkey on February 6, 2023, affected a very extent region and caused a lot of loss of life and property. This paper presents preliminary results from geophysical measurements (Seismic Refraction Tomography-SRT, Multi-Channel Surface Wave Analysis-MASW and Microtremor-MT) on eight profiles in four provinces (Kahramanmaras, Hatay, Malatya, Gaziantep) to understand the relationship between subsurface properties and the destruction that occurs immediately after earthquakes. By analyzing the geophysical data, the dynamic-elastic properties of ground and the soil classification according to Vs30 were determined. It is generally understood that the near-surface (= similar to 15-20 m) have a very porous/fractured structure. Soil classes were defined as ZD (Malatya-1, Hatay-1 and Kahramanmaras-1) and ZC (Malatya-2, Hatay-2, Gaziantep-1,2 and Kahramanmaras-2). In addition, by evaluating the information of strong ground motion station closest to the measurement profiles, it is observed that the PGA values versus epicenter distances are higher at stations in the zone parallel to the direction of both faults than those in the perpendicular zones. This leads directivity effect in the propagation of earthquake waves. The results indicate that one of the basic reasons for the damages is that the earthquake-ground-structure relationship has not been fully and accurately reflected in building designs. Therefore, future researches involving more geophysical data and PGA values will provide more information about the structural, physical and geotechnical properties of subsurface and definitive results.