Shear wave velocity (Vs) is an essential parameter for soil strength and mechanical properties of rocks. Twenty profiles of multichannel analysis of surface waves (MASW), five microtremor measurements, and two geotechnical boreholes have been conducted at the King Saud University site. According to the National Earthquake Hazards Reduction Program classification, the results indicated three distinct layers. The first layer is comprised of silty sand with gravel and thickness ranges of 4-14 m of shear wave velocity (Vs) from 400 to 760 m/s, indicating site C class; the second layer features highly weathered limestone where Vs varies between 760 and 1500 m/s refers B class, while the third layer consists of compact/massive limestone where Vs varies from 1500 to 3500 m/s representing site A class. The bedrock varies in depth from south to north, showing the shallowest depth in the central zone. Moreover, the estimated shear wave velocity and bedrock depth from microtremor measurements agree with MASW results. These results specified distinct weak zones at depths ranging from 2 to 25 m through the study area, emphasizing potential geotechnical concerns associated with these weak zones. Integrating shear wave velocity and microtremor measurements is crucial for advancing sustainable urban development by providing more informed design choices considering local soil conditions. This highlights the significance of geophysical techniques in supporting sustainable development initiatives.

Seismic Site Characterization involves the qualitative assessment of top-soil properties that have the capability of amplifying the generated earthquake ground motions. The geotechnical properties of topsoil refer to the top 30m subsurface profile which plays a vital role in seismic microzonation and Ground Response Analysis (GRA) studies. Among various geotechnical parameters, shear-wave velocity (Vs) of the top 30 m subsurface is mainly linked to seismic site characterization and amplification studies. The average shear-wave velocity of the top 30 m subsurface, Vs(30), has been used for seismic site classification in accordance with the National Earthquake Hazard Reduction Program (NEHRP) and various building codes. In this study, an attempt has been made to retrieve the geospatial variation of average shear-wave velocity for Coimbatore city using the active Multichannel Analysis of Surface Waves (MASW) test which is one of the non-destructive geophysical tests. To retrieve the spatial distribution of shear-wave velocity (Vs), the test was carried out at 35 locations in the vicinity of important structures, schools, colleges, and hospitals within the city. The seismic records have been acquired in the field and analyzed using the winMASW software. From the one-dimensional MASW test, the study area has an average Vs(30) in the range of 640 m/s to 909 m/s and has been classified as site-class BC (soft rock) according to NEHRP standards. These test results have been validated using the collected SPT bore log data from various locations, including 40 sites in the vicinity of the conducted MASW tests. The site-specific correlation between the shear-wave velocity (Vs) and the corrected SPT N- Value, N1(60), and between Vs and shear modulus (G) have been developed for Coimbatore city with a regression coefficient of 0.79 and 0.83 respectively. From the fundamental site period map, the study area has a site period in the range of 0.1 to 0.2 s, which indicates that 1to 2- storey buildings that are densely distributed throughout the city may lead to damage in case of probable future earthquakes. This study bridges the connectivity from the evaluated bedrock acceleration using the Seismic Hazard Analysis (SHA) and provides insights for evaluating surface acceleration using GRA studies.

This study introduces a simplified analytical method to extract shear wave velocity profiles from seismic waves evoked by explosives, providing a time-efficient solution to the conventional Multichannel Analysis of Surface Waves (MASW) method. Controlled ammonium nitrate emulsion explosions were used at five research sites throughout Thailand with different geological conditions to capture ground motion data through a 16-geophone array during field investigations. This direct analysis evaluates surface wave arrival times in real-time while implementing elastic theory-derived empirical factors for analysis. The proposed method delivers results that match MASW-derived profiles yet require fewer complex procedures and shows Vs30 variations from 4.43 to 38.33%. The simplified method delivered the most accurate results in areas displaying gradual soil property transitions and showed reduced precision when dealing with abrupt soil type or mechanical property shifts. The new method transforms petroleum exploration seismic data into geotechnical applications by delivering dependable shear wave velocity profiles with lower complexity and using fewer resources. It is specifically valuable for limited-budget engineering projects or difficult-to-access locations.

The S-wave velocity (Vs) is a valuable parameter for assessing the mechanical properties of subsurface materials for geotechnical purposes. Seismic surface wave methods have become prominent for estimating near-surface Vs models. Researchers have proposed methods based on passive seismic signals as efficient alternatives to enhance depth of investigation, lateral resolution and reduce field effort. This study presents the Multichannel Analysis of Surface Waves (MASW) utilizing Common Virtual Source Gathers (CVSGs) derived from seismic ambient noise cross-correlations, based on Ambient Noise Seismic Interferometry concepts. The method is applied to passive data acquired with an array of receivers at the Paranoa earth dam in Brasilia, Brazil, to construct a pseudo-2D Vs image of the massif for interpretation. Our findings showcase the adopted processing flow and combination of methods as an effective approach for near-surface Vs estimation, demonstrating its usability also for large earth dam embankments.

The Nilufer district experienced the most recent urbanization among the central districts of Bursa in South Marmara region with the completion of rapid construction. Since 358 BCE, many destructive earthquakes were reported on the branches of the North Anatolian Fault (NAF) which caused extensive damage to buildings and loss of life near Bursa city. Besides some studies conducted to define the soil behavior in the vicinity of Bursa, a seismic hazard study in Nilufer is still lacking. We, therefore, carried out a microzonation study including the following steps. First, an earthquake hazard analysis was conducted and the peak ground acceleration (PGA) values were determined for an expected earthquake. In the next step, MASW (Multi-Channel Analysis of Surface Wave) measurements conducted at 54 points in 28 neighbourhoods of Nilufer district were evaluated. Soil mechanical parameters were determined at 11 boreholes to assess the liquefaction potential. It was found that almost half of the study area suffers from low damage considering only the vulnerability index (Kg) index, which depends on the site effect. Therefore, in addition to the Kg values, we created a microzonation map using the results of soil liquefaction, settlement, changes in groundwater level, and the average values of spectral acceleration. The study area is classified by four damage levels changing from low to high. Using only the Kg index could not quantify the potential damage level in the study area, thus we showed that the districts of Altinsehir, Hippodrome, Urunlu and Alaaddinbey, Ertugrul, 29 Ekim, 23 Nisan, Ahmetyesevi and Minarelicavus were identified at potentially high-risk damage zones. The results of this study clearly showed that considering the Kg index, which depends only on the local site effect, may lead to inadequate damage values.

Shear-wave velocity is a soil mechanical property. It is the main cause of local ground-motion amplification, and it is responsible for a large amount of the damage. Therefore, it is crucial to investigate the soil characteristics down to bedrock to investigate the potential site effect. In this study, seven points in Ras Samadai area have been chosen to be investigated using Multichannel Analysis of Surface Waves (MASW) and Shallow Seismic Refraction (SSR) as active seismic methods. Furthermore, the Frequency-Wavenumber (f-k) and Horizontal-to-Vertical Spectral Ratio (HVSR) techniques were used as passive techniques to obtain the subsurface seismic velocity models and evaluate the site effect beneath the investigated points. The shallow and deep 1-D shear wave velocity models have been obtained at the chosen points using the MASW and f-k approaches. Furthermore, the research area is divided into three main layers based on the seismic refraction approach. At certain cross-sections, there are clear variations in the layers thickness resulting from faults effect. The HVSR method displays two different kinds of curves: flat and one peak curves, due to the variation in impedance contrast between the bedrock and the overlying soil. Moreover, the obtained vulnerability index (Kg) indicates that there is low level of hazards could happen in the study area. Finally, the 2-D lithological models are created to delineate the underground fault lines and displays the lateral variations in lithological composition. This information is useful for the seismic hazard analysis in terms of ground response prediction at ground surface and soil column.

The 2017 Pohang earthquake, with a moment magnitude (M) of 5.5, caused severe building damage and widespread liquefaction. In this study, we evaluate the applicability of ground response and liquefaction triggering analyses for the Pohang earthquake using deep shear wave velocity (VS) profiles. The VS profiles are obtained at Handong University and the Songdo Pine Forest by inverting the Rayleigh wave dispersion curves based on microtremor array measurements (MAM) and multi-channel analysis of surface waves (MASW). In onedimensional effective stress analyses for the two sites, we consider the uncertainty of the nonlinear soil properties for three cases and use 118 rock outcrop motions. At Handong University, the spectral accelerations of surface ground motions are larger than those of the current Korean design spectra with a return period of 500 years at the natural period of the damaged buildings. At the Songdo Pine Forest, for the Case 2, numerous ground motions result in the maximum pore water pressure ratio of 1 (i.e., liquefaction occurrence). Furthermore, we calculate the liquefaction potential index (LPI) values using the VS-based simplified method. To compute the cyclic stress ratio for depths, we utilize the peak ground accelerations estimated by ground response analyses and estimated by stress reduction factor (rd), respectively. The LPI values, based on the ground response analyses, range from 0 to 4, indicating minor or no damage, while the LPI value using the rd is zero. The results of the ground response and liquefaction triggering analyses are similar to the actual damage cases.

Dehradun lies in the intermontane Dun Valley in the Garhwal Sub Himalaya, which lies with the Main Boundary Thrust (MBT)- Himalayan Frontal Thrust (HFT) tectonic wedge with other intrawedge faults. These faults may rupture during a great earthquake and cause damage to the existing civil structures in the fault zone. Therefore, it is essential to characterise the active faults in and around Dehradun. We carried out 2D Shear wave velocity profiles across the Markanda Thrust, Rajban Fault, Bata Fault, Santaurgarh Thrust, Bhauwala Thrust, and Majhaun Fault at 18 sites using the Multichannel Analysis of Surface Wave (MASW) technique. The obtained shear wave velocity is further utilised to calculate geotechnical parameters like the average shear wave velocity (Vs(30)), soil stiffness, amplification factor, and predominant frequency. The weak, weathered or shear zones and dislocations are mapped in terms of a low shear wave velocity layer overlain by a high shear wave velocity layer at deeper depths near identified fault or thrust locations. The active fault/thrust zones in the Dun Valley have a shear wave velocity of 130 m/s to <1500m/s and consist of stiff soil to dense soils of class D to C as per the National Earthquake Hazard Reduction Programme (NEHRP) classification. This study contributes to a better understanding of the seismic characteristics of Dehradun and its surroundings, which is useful for earthquake mitigation studies.

The shallow seismic methods, including seismic refraction and 1D MASW, were used to investigate the shallow soil in the vicinity of five damaged building blocks in the village of El-Kalaheen. These building blocks exhibited structural problems including cracks, fissures and displacements between neighboring buildings. The results of both methods show that the shallow subsurface consists of two layers: a surface layer of loose sands, gravels, silts and clays and a compacted sandy clay layer that forms the bedrock in the area. The resulting seismic velocities were used to calculate the geotechnical parameters of the two layers, including Poisson's ratio, shear modulus, Young's modulus, material index and N-value. In addition, the shear wave velocities resulting from the 1D MASW method were used to calculate the average Vs30 in the site. The calculated values of the geotechnical parameters show a gradual increase in the competence of the upper layer from fairly competent and loose in the south of the area to competent and denser in the north. The geotechnical parameters of the bedrock also show an increase from moderately competent in the south to denser and more competent in the north. Possible zones of weakness are also observed in the southern part of the site. The calculated Vs30 indicates a site with stiff soil classification.

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.