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Characterizing the subsurface structure is an important parameter for the improvement of seismic hazard assessment. Due to the tectonic complexity of the earth, some deep fractures do not reach the earth’s surface and are not detectable with visual analysis. Therefore, the lack of knowledge of faults and fractures can result in disasters, especially in urban planning. Many geophysical methods can be used to estimate subsurface structure characterization. However, a more reliable method is required to assess seismic hazards and reduce potential damage in metropolitan areas without destroying buildings and structures. This paper aims to identify hidden faults and structures using shear wave velocity sections. To do this, surface wave dispersion curve was extracted from the vertical component of microtremor array recording using the spatial autocorrelation (SPAC) method in two profiles and 13 array stations (perpendicular to the altitudes) to obtain shear wave velocity structure (Vs) in the west of Mashhad, northeast of Iran. The results of shear wave velocity profiles (Vs) indicate sudden changes in the thickness of sediments. This can be related to the displacement of a normal fault in this area causing the bottom rock to fall and an increase in the alluvial thickness in the central part of the plain. The velocity in the floor rock is 2000 meters per second in this area. According to the surface outcrops and water wells data, its material is slate and Phyllite metamorphic rocks that are exposed in the adjacent heights. Besides, the seismic profile results were well consistent with electrical resistance data and well logs indicating that the tool array method is flexible, non-invasive, relatively fast, and effective for urban areas with satisfactory accuracy.

A comprehensive understanding of the internal structure and construction of a geomechanical formation model play an important role in developing and using geothermal resources. Formation models help in identifying the channel and cycling modes of the heat flow. Due to urban sprawl and development, constructing a formation model of geothermal resources based on data from traditional geophysical methods is challenging. The microtremor survey method (MSM) is adopted to obtain critical information in Jimo, which is famous for rare seawater geothermal resources in China. Three microtremor survey lines are deployed to identify subsurface structures up to 2 km into the ground. Dispersion curves of Rayleigh waves with frequencies from 0.4 to 10 Hz are extracted using the spatial autocorrelation method. An empirical equation is adopted to obtain the apparent shear wave (S-wave) velocity of each survey point and to plot the apparent S-wave velocity sections. The obtained sections reveal the development of two interacting faults, which form a channel for the heat-flow cycle. Two conceptual models are established to depict the formation and cycling modes of seawater geothermal resources in Jimo, based on the results and analysis. Our model will help verify the geothermal system and scientifically guide the development of unique geothermal resources. Moreover, the developed model verifies that MSM is effective and dependable for identifying fracture zones and strata.

On 28th July 2018, a massive landslide occurred in a mountainous area in Northern Thailand. The landslide after ten days of heavy rainfall generated the movement of uphill mountain soil into the populated village. This study presents a comprehensive failure analysis of local rainfall-induced landslides based on topographical and geological information. Rainfall measurement data were gathered from two rainfall stations close to the study area. The rainfall records show that the total monthly rainfalls in 2018 were significantly higher than the average monthly rainfalls over the past decade. Site investigation started with an unmanned aerial photogrammetric survey to generate a digital elevation model. Then, dynamic probing test, microtremor survey, and electrical resistivity survey were carried out along undisturbed soils beside the failed slope to evaluate the thickness of the soft soil cover on top of the rock basement. During the site survey, residual soil samples were collected to determine engineering properties in the laboratory. Finally, a slope stability analysis was performed to assess the landslide hazard based on the results of aerial photogrammetric survey, field exploration, and laboratory tests. The slope stability analysis and rainfall records revealed that the Huay Khab landslide was mainly caused by an increase in the water content of residual soils due to the prolonged rainfall which led to a sharp decrease in the shear strength. This leads to the conclusion that the proposed landslide investigation program could be used to assess the potential of landslide failure due to prolonged rainfall on a local scale.

SUMMARY The applicability of rotational seismology to the general wavefield of microtremors is theoretically demonstrated based on a random process model of a 2-D wavefield. We show the effectiveness of taking the rotations (i.e. spatial differentiation) of microtremor waveforms in separating the Rayleigh and Love waves in a wavefield where waves are simultaneously arriving from various directions with different intensities. This means that a method based on rotational seismology (a rotational method) is capable of separating Rayleigh and Love waves without adopting a specific array geometry or imposing a specific assumption on the microtremor wavefield. This is an important feature of a rotational method because the spatial autocorrelation (SPAC) method, a conventional approach for determining phase velocities in microtremor array surveys, requires either the use of a circular array or the assumption of an isotropic wavefield (i.e. azimuthal averaging of correlations is required). Derivatives of the SPAC method additionally require the assumption that Rayleigh and Love waves are uncorrelated. We also show that it is possible to apply a rotational method to determine the characteristics of Love waves based on a simple three-point microtremor array that consists of translational (i.e. ordinary) three-component sensors. In later sections, we assume realistic data processing for microtremor arrays with translational sensors to construct a theoretical model to evaluate the effects of approximating spatial differentiation via finite differencing (i.e. array-derived rotation, ADR) and the effects of incoherent noise on analysis results. Using this model, it is shown that in a short-wavelength range compared to the distance for finite differencing (e.g. $\lambda < 3h$, where $\lambda $ and $h$ are the wavelength and distance for finite differencing, respectively), the leakage of unwanted wave components can determine the analysis limit. It is also shown that in a long-wavelength range (e.g. $\lambda > 3h$), the signal intensity gradually decreases, and thus the effects of incoherent noise increase (i.e. the signal-to-noise ratio, SNR decreases) and determine the analysis limit. We derive the relation between the SNR and wavelength. Although the analysis results quantitatively depend on the array geometry used for finite differencing, the qualitative understanding supported by mathematical expressions with a physically clear meaning can serve as a guideline for the treatment of data obtained from ADR.

This study conducted microtremor testing along six survey lines that cross three typical earth fissures in the Datong basin to determine the dynamic response characteristics of earth fissure sites with regard to the Fourier amplitude spectrum, response spectrum, and Arias intensity. The results show the following. (1) The predominant frequency of an earth fissure site is mainly affected by the thickness and the shear wave velocity of the soil layer and is minimally effected by the presence of an earth fissure. (2) Earth fissures have a pronounced amplification effect on dynamic response. Fourier amplitude, response acceleration, and Arias intensity are high near an earth fissure and decrease with an increase in distance from the earth fissure, tending toward stability at a distance of 20 m. (3) The area that is seriously affected by this amplification is within 6–8 m of an earth fissure, and the general affected area is farther out than this, to a distance of 25 m. (4) New construction should be avoided in an area affected by the amplification, and existing buildings in general and seriously affected areas need to be reinforced to increase their seismic fortification intensity.

Padang is the capital of West Sumatra Province, close to three earthquake sources such as the Megathrust Zone, the Mentawai Fault, and the Great Sumatra Fault on the mainland. Due to the fact that the impact of the earthquake can create a tsunami event in the future, the government needs to prepare shelters for vertical evacuation. About 65 existing buildings have been selected as vertical evacuation buildings, but there is no clear information on their seismic performance. This research proposes a complete assessment of the existing RC building by considering soil characteristics such as the predominant period and Vs30 from microtremor observations. A selected 3 stories of a school building located in the earthquake red zone (Vs30 1.5s), less than 1 Km far from the shoreline, was considered in this paper. Based on the seismic index evaluation of the building, the X direction is smaller than the seismic demand (0.8) for the first and second floors (unsatisfactory). For the first, second and third floor, the Y direction has a larger seismic index than the seismic demand. Therefore, the performance is satisfactory for the first to the third story. Based on the required inspection, the building is unsatisfactory for the X-direction. Therefore, it needs to be strengthened. We propose a re-size of the RC for the building column to improve the ductility. The proposed size for the column is 50 x 60 cm. From the re-seismic evaluation, a satisfactory seismic index for the X and Y direction can be obtained.

We attempted a comprehensive site response study of Garhwal-Kumaun Himalaya in the Central seismic Gap (CSG) using the data collected from 97 strong motion, microtremor and broadband stations. Site...

The geotechnical industry has widely adopted the refraction microtremor shear-wave velocity measurement technique, which is accepted by building authorities for evaluation of seismic site class around the world. Clark County and the City of Henderson, Nevada, populated their Earthquake Parcel Map with over 10,000 site measurements for building code enforcement, made over a 3-year period. 2D refraction microtremor analysis now allows engineers to image lateral shear-wave velocity variations and do passive subsurface imaging. Along with experience at a basic level, the ability to identify the “no energy area” and the “minimum-velocity envelope” on the slowness-frequency (p-f) image helps practitioners to assess the quality of their ReMi data and analysis. Guides for grading (p-f) image quality, and for estimating depth sensitivity, velocity-depth tradeoffs, and depth and velocity resolution also assist practitioners in deciding whether their refraction microtremor data will meet their investigation objectives. Commercial refraction microtremor surveys use linear arrays, and a new criterion of 2.2% minimum microtremor energy in the array direction allows users to assess the likelihood of correct results. Unfortunately, any useful and popular measurement technique can be abused. Practitioners must follow correct data collection, analysis, interpretation, and measurement procedures, or the results cannot be labeled “refraction microtremor” or “ReMi” results. We present some of the common mistakes and provide solutions with the objective of establishing a “best practices” template for getting consistent, reliable models from refraction microtremor measurements.

Underground space utilization is becoming increasingly essential for modern metropolitan cities such as Singapore. Mapping a soil/rock interface using traditional borehole investigation methods is expensive and difficult, owing to the numerous physical constraints within a built-up city. Boreholes are often far apart, resulting in many unforeseen ground conditions during subsequent excavation. Geophysical methods are sometimes employed as possible alternatives for fast, economical, and efficient bedrock surveys. The goal of this study is to investigate the practical details of applying microtremor array measurement (MAM) as a non-invasive surface wave survey for mapping soil/rock interfaces in Singapore. Critical configurations in field data acquisition are examined, and practical recommendations for array construction are provided. In addition, 30 in situ MAM tests are carried out for two major geological formations in Singapore. From the results, a standard shear wave velocity (Vs) of 500 m/s is found to be suitable for interpreting the soil/rock interface, for the Bukit Timah Granite and Jurong formations. However, the method does not predict well when soft Kallang formation deposits are present. Other limitations are also discussed in the later parts of this paper. Conclusions and practical recommendations are discussed, providing constructive guidance to the industry. The proposed Vs-based method and associated guidelines and limitations can be used to create a digital geological database and are especially useful for rock profiling in an urban environment.

Microtremor Horizontal to Vertical spectral ratio technique, also known as the Nakamura’s method is growing in status for site response analysis. 500 locations in RAJUK area (1530 km2) have been selected for microtremor observations. Microtremor data have been compiled and studied to estimate the predominant resonance frequency and H/V peak amplitude following the SESAME (2004) guideline. Finally, seismic vulnerability index of site soil using Nakamura’s technique has been determined from predominant resonance frequency and H/V peak amplitude parameter. The calculated seismic vulnerability index for the studied 500 locations varies between 0.16 and 7.28. The low seismic vulnerability index (Kg) value means that the areas are relatively stiff and underlain by substantial deposit of sediments. The relatively higher Kg values are spread in the soft alluvial deposit areas. The areas with high Kg values are considered as fragile zones that may initiate significant damage to infrastructure situated in those areas during an earthquake.

Lombok Island is an active seismic area in Indonesia potentially hit by an earthquake due to located between two earthquake generators from the south and the North. Several large earthquakes rocked Lombok, an earthquake with a magnitude of 6.4 on July 29, 2018, and 7.0 on August 5, 2018. This study aims to determine the characteristics of the local site effect based on the dominant frequency value ( ), soil amplification ( ), sediment layer thickness (d), , dominant period (T 0 ), and seismic vulnerability index ( ) and to comprehend the soil class (site class) based on the thickness of the sediment layer (d), and in the North Lombok region. The data used is secondary data from microtremor signal recordings in North Lombok Regency in 2018. Data processing used Geopsy software, and microtremor data were analyzed using the HVSR method. From processing the HVSR data, the dominant frequency value about (0.8 - 18) Hz, amplification value (1.7 – 9.7), dominant period value (0.05 – 1.2) seconds, seismic vulnerability index value (0.4 – 71) , and the value of in the study area (20.05 – 287.04) m/s. Based on microtremor analysis, the local site effect indicates that alluvium rocks caused stronger earthquake vibrations and more damage. Whereas the Kalibabak and Lekopiko formations caused fewer earthquake vibrations and less wear. Based on the dominant period and , area study classify as Site Class IV class E and Site Class III class D Copyright © 2021 IPR . All rights reserved.

This research proposes a relationship between two methods such as a numerical approach by conducting a microtremor array observation and field survey by using the seismic cone penetration test unit (SCPTu). A database of shear-wave velocity (Vs) measurements was established using the microtremor array technique and seismic cone penetration test unit (SCPTu) on high-quality samples of rock and soft soil in Padang city, Indonesia. The study also demonstrates that the Vs values obtained from the different methods are consistent with the microtremor array technique. This technique may thus be deemed a valuable tool, as it can be used in engineering practice with confidence. Comparison of the Vs for different soils at the first layer between the microtremor array observation results and the SCPTu results exhibited the microtremor array method is unable to determine the Vs at the layer where its Vs changes dramatically, such as at the same layer as station UNP at 2 to 3.5m deep.

Lombok Island and its surrounding is an area that has a high seismicitys level because it is located in the Eastern Sunda Arc. Tectonically, Lombok Island located between the Indo-Australia plate collision zone with Eurasia in the south and the fult of the backarc Bali-Flores in the north. This research’s purposed to determine the distribution of vulnerability index and peak ground acceleration value are used to determine the GSS value, so mapping of potential damage areas could be done. The microtremor data taken on 32 observation points distributed in Lombok Island. Microtremor data is analysed using Horizontal to Vertical Spectral Ratio (HVSR) method to get seismic vulnerability index (Kg) and dominant period. Determination of Peak Ground Acceleration (PGA) value using data from the MASE Stasion measurement results based on earthquake events on August 5, 2018. Seismic vulnerability index and peak ground acceleration value are used to determine the GSS value. Determination of potential damage area using analysis of the dominant period, seismic vulnerability indexs and Ground Shear Strain values. The results of this research showed that seismic vulneribility index value in research area is about 0,029 sekon to 1,360 sekon, seismic vulneribility index value is about 0,56 to 189,92 and GSS value is about 2,52 x 10-5 to 8,46 x 10-3. The results show that the light damage dominated in East Lombok Districts, the moderate damage is on Mataram City and it dominated in West Lombok Districts. The heavy damage present in the most parts of West Lombok Districts.

Microtremor measurements are used for preliminary site effect of the Quaternary sediments of Varanasi in Indo-Gangatic plain, which is being planned as a Smart City of India. We evaluated site effects using single and arrays Microtremor measurements at various sites in the Varanasi City, Uttar Pradesh, India. At City, H/V spectral ratios using microtremor measurements indicate fundamental frequency range 0.37–0.63 Hz, corresponds amplification 5 to 14 times. This indicates that the deep thickness of the upper soft soil at about several hundreds of meters. Such huge amount of sediments deposition sources could be associated with fluvial rivers system in the area and sediment drain from Himalaya. The average peak frequency (~0.5) may reflect the Quaternary-Tertiary boundary. Microtremor array measurements at two sites were taken using circular arrays (30 and 60 m) which consists of three recording stations on the circumference of circle and one in the centre of circle. The Phase velocity dispersion of Rayleigh wave is calculated from array using SPAC method, and a 1-D shear wave velocity structure is determined by means of inversion processes. The top layers up to 50 m show shear velocities between 280 and 320 m/s and the velocities of underneath layer vary between 1500 and 1600 m/s till 100 m of depth. These results from the present study would be useful for future planning purposes as well as risk management and to reduce severity of earthquake effects in the study area.

The measurement of site amplification of microtremors is an important tool for evaluating seismic hazard at local and regional level. The H/V spectral ratio (HVSR) method is applied to estimate the amplification of ground motion at resonance frequency. The fundamental resonance frequency is estimated at 8 different sites in study region and shows the maximum vulnerability of the site to the earthquakes. This frequency ranges between a minimum of 2.8 Hz to a maximum of 9.3 Hz. The thickness of the sediments below the surface of recording sites is calculated using the empirical relationship that comes out to be in a particular range of 9.5 m–33.1 m above the bed rock. The sedimentary thickness and the resonance frequency clearly matched with geological setting of the study area. The observation shows a slow reduction in the thickness of the sediments and increase in the resonance frequency from South-western part to North-eastern part of the study region. The results show that most of the sites are highly vulnerable to seismic risks with high amplification of seismic waves in the area. Thus, current study provides a deep insight in to the seismic hazard of the Sikkim region with a clear emphasis on the site amplification and the sedimentary cover for the region.

Landslides with a shallow and complex bedrock layer, where bedrock topography affects the stability of the slide, are a widespread phenomenon. The current methods for evaluating such landslides include conventional in situ methods and array-based geophysical methods. However, these methods are not capable of characterizing the complete spatial extent of the bedrock layer cost-effectively and are difficult to conduct for steep slopes. Therefore, in this study, microtremor horizontal to vertical spectral ratio (MHVSR) is proposed as an effective tool when used in conjunction with other methods to improve our understanding of the landslide. In this study, the method is used to make a tight grid of MHVSR measurements within the landslide. Using this method, a 3D image of bedrock topography can be created over a larger spatial extent to reveal the potential critical landslide zones. This method is employed for two active landslides that have recently experienced considerable movements. Using the MHVSR, several bowl-shaped features were detected in the bedrock layer, which were not detected using conventional invasive in situ methods. These features play a key role in landslide behavior as they can trap water and create a fully saturated soft zone within the critical slide. Missing such key features in the geologic model of the landslide can lead to errors in the slope stability models and cost overruns in rehabilitation efforts. The grid pattern MHVSR method used in this study offers a simple, rapid, and cost-effective tool for landslide site characterization for sites with shallow and complex bedrock topography.

SUMMARYWe examine the potential of frequency-dependent Rayleigh wave ellipticity, derived from microtremors, for the investigation of heterogeneous subsurface structure. Based on numerical simulation, we analyse the effects of interference waves in microtremors, primarily the various propagation directions of the Rayleigh waves, linear polarization waves and white noise, on the ellipticity frequency-dependent estimation of the Rayleigh waves. A data processing scheme to separate the Rayleigh waves from the interference waves is proposed and verified by synthetic data. We performed a field experiment in the mountainous areas of Southwest China to show that the ellipticity frequency dependence of Rayleigh waves in the period range of 0.05–5 s can be estimated from the microtremor records with the proposed data processing scheme. In addition, the method is feasible for investigating lateral heterogeneity within the top several hundred metres in the mountain regions. The study also reveals that the features of the ellipticity anomaly of a local heterogeneity are related to the propagation directions of the Rayleigh waves, and to reduce the ambiguity of the anomaly, the propagation direction of the waves picked for the ellipticity estimation should be consistent with (along or opposite to) that of the survey line. Then, to eliminate the effects of the phase differences due to the propagation direction, or time, the ellipticity for each location should be estimated by a single event rather than multiple events from the derived Rayleigh wave arrivals.

Seismic surveys were performed using a novel application of combined active and passive surface wave methods to evaluate the integrity of levees protecting islands in the Sacramento–San Joaquin Delta, California, USA, from flooding. Delta islands have been undergoing rapid subsidence during the past century due to farming practices that have led to the loss of a surficial peat layer. A large earthquake on any one of several active faults in the region could cause multiple levee failures and extensive flooding in the Delta. Surface wave surveys were carried out along the crest of levees using the active method (2D multichannel analysis of surface waves) and along the base of levees using the passive method (microtremor array method). This allowed 2D seismic S‐wave velocity (VS) profiles to be prepared for each site by combining shallow data from the active survey along the crown of the levee with deeper data from a passive survey along the toe of the levee. TheseVS profiles reveal a low‐velocity peat layer beneath the levee body that was confirmed by geotechnical borehole logs. Lateral variability of the levee was evaluated using average velocity to the base of the levee versus along‐levee distance.

To investigate the sediment structures within the Tangshan earthquake region in North China, we developed an effective and inexpensive method for reliably detecting the thickness of Quaternary sediments by using converted waves from local, small earthquakes recorded by a dense seismic array. From January to March 2017, we deployed 145 three-component seismographs with inter-station distances ranging between 1 and 4 km throughout the Tangshan earthquake region. Tens of local events with magnitudes between ML 0.1 and ML 2.4 were adequately recorded by the Tangshan dense seismic array and were accurately relocated. A synthetic seismogram analysis clearly showed that the travel-time differences between direct S and Sp converted waves or between direct P and Ps converted waves were almost linearly correlated with the sediment thicknesses, providing tight constraints on the basement depth. With this method, we generated a sediment thickness map of the Tangshan earthquake region. Overall, the measurements from the local converted wave method are consistent with those of previous microtremor horizontal-to-vertical spectral ratio studies. The sediment thicknesses indicate that the subsurface sedimentary structure throughout the Tangshan earthquake region has experienced significant transformations over time, partially controlled by the NE–SW-trending Tangshan Fault. The obtained sediment thickness map provides beneficial information for ensuring the safe construction of infrastructure in Tangshan city and can serve as an important model for simulating earthquake strong ground motions in the Tangshan earthquake region. Our study suggests that the proposed simple and efficient method of using converted waves could be applied to other populous plains or basins with high seismic activity and could be used to determine the general characteristics of the sediment structures in a given study area.

In this study, shallow seismic surveys, including seismic refraction, Multichannel Analysis of Surface Waves (MASW), Refraction Microtremor (ReMi), and Microtremor measurements were conducted to estimate site characterization at 26 strong-motion stations of AFAD (Disaster and Emergency Management Presidency) in the province of Hatay, situated in one of the most seismically active regions in southern Turkey. The Horizontal to vertical spectral ratio (HVSR) technique was applied, using smoothed Fourier spectra derived from a long duration series to determine dominant frequency values at different amplification levels. Shear wave velocity up to 30 m of the ground was detected with MASW analysis. In the ReMi analysis, up to 80 m was reached with a corresponding average of 650 m/s shear wave velocity. The shear wave velocities estimated by the MASW method up to 30 m were compared with those found by the ReMi method, and they were observed to be very compatible. The province of Hatay was classified according to Vs30 based NEHRP Provisions, Eurocode-8, the Turkish Building Earthquake Regulation (TBDY-2018), and Rodriguez-Marek et al. (2001). The shear-wave velocity (Vs30), Horizontal to Vertical ratio’s (H/V) peak amplitude, dominant period, and site class of each site were determined. The H/V peak amplitudes range between 1.9 and 7.6, while the predominant periods vary from 0.23 sec to 2.94sec in the study area. These results are investigated to explain the consistency of site classification schemes.

Boulders are spheroidal and weathered rock fragments that exist in softly weathered granite strata. Boulders can cause severe damage to the cutter heads of shield machines and can even lead to the failure of shield tunneling during the excavation of metro tunnels in granite strata. However, there is no effective method to safely and rapidly cope with this problem on a large scale. This study proposes a method to detect and to pretreat boulders during shield tunneling within granite strata. The detection method is a combination of microtremor surveying and supplementary drilling exploration to ensure both rapid, large-scale detection and high detection accuracy. Based on the microtremor survey results, principles of interpretation are developed to predict the presence of boulders and evaluate the safety status of shield tunneling. Furthermore, the predicted boulders are precisely confirmed by supplementary drilling exploration. After the boulder locations are detected, a combined surface drilling and preblasting technique are adopted to pretreat the boulders. This method was successfully applied in the shield tunneling of Fuzhou Metro Line 5 in China. The application shows that this method is effective for the prediction and pretreatment of boulders during shield tunneling. The prediction of boulders has high accuracy. The preblasting of boulders improves the tunneling efficiency, which significantly reduces the total thrust and torque on the cutter head, and markedly increases the tunneling speed.

One of the developing areas in Bengkuku City, Indonesia is the downstream of Muara Bangkahulu River. Therefore, this study aims to present an investigation of the local site and analysis of ground response in this area. Geophysical measurements were adopted in this research using multichannel analysis of surface wave and microtremor. Furthermore, field measurements were processed to interpret the characteristics of the ground surface, such as shear wave velocity (Vs) profiles, time-averaged shear wave velocity for the first 30 m depth (Vs30), and site classifications. The results show that the study area is categorised into Site Classes C and D. Also, the loose sedimentary soils exist at shallow depth and tend to be more vulnerable to undergo seismic phenomenon, which includes liquefaction and ground amplification. Generally, the results are expected to provide a better understanding of geophysical characteristics and earthquakes, which will help the local government to compose a spatial plan on the basis of seismic hazard mitigation.

One dimensional seismic response analysis on the ground surface of the Non-Commercial Power Reactor (RDNK) site based on the mean uniform hazard spectrum (UHS) and disaggregation analysis has been conducted. The study’s objective was to perform an analysis on site-specific response spectra on the ground surface based on existing mean UHS and disaggregation data of the site that correspond to a 1,000 and 10,000 year return period of earthquakes in compliance with the national nuclear regulatory body requirements of Indonesia. Detailed site characterization was defined based on secondary data of a geotechnical drill-hole, seismic cross-hole, downhole data, and microtremor array data. The dynamic site characteristic analysis was presented along with strong motion selection and processing using two types of strong motion datasets. An investigation of strong motion selection, spectral matching, and scaling has been presented as an essential step in ground motion processing. One-dimensional equivalent linear analysis simulation was performed by computing the processed ground motions. A seismic design spectrum and ground surface response spectra from the two datasets of strong motion, both corresponding to a 10,000 and 1,000 year return period, are presented at the end of this study. This study has shown that in order to establish the appropriate seismic response design spectrum, site-specific data and seismic hazard analysis must be immensely considered., Jednodimenzionalna seizmička analiza na tlu u okolici nekomercijalnoga nuklearnog reaktora temeljena je na izučavanju srednjih, uniformnih spektara rizika te analizi dezagregacije tla. Analiza je načinjena na smjestištu koje je određeno svojim posebnim seizmičkim spektrom. Spomenute varijable izučavane su s obzirom na povratno razdoblje potresa od 1000 i 10 000 godina te su uspoređene s nacionalnim zakonodavstvom o sigurnosti nuklearnih postrojenja u Indoneziji. Analizirano područje detaljno je opisano iz sekundarnih podataka koji su obuhvatili geotehničke i sezimičke bušotinske podatke te mjerenja mikropotresa. Dinamička svojstva smjestišta predstavljena su usporedno s podatcima iz dvaju skupova mjerenja snažnih gibanja. Njihovo izučavanje spektralnom analizom te odabirom mjerenja opisano je kao temeljni korak u izučavanju gibanja tla. Jednodimenzionalna analiza načinjena je računalnom obradbom. Prikazani su seizmički i površinski spektri, za oba skupa podataka i oba povratna razdoblja. Pokazano je kako ove metode trebaju nužno biti korištene u analizi seizmičkoga rizika na smjestištima ove vrste.

The application of Rayleigh waves in geological prospecting and engineering has been widely tested and used as a new method of shallow seismic exploration. The previous method of surface wave inversion needed to calculate the corresponding phase velocity that satisfied the dispersion function. This process increases the computation amount and reduces the surface wave inversion efficiency. This paper proposes a method to solve the problem by using different definition methods of the objective function. The method greatly reduces the amount of computation while results in approximately equal results with traditional method. This cuts the inversion time to 1% of conventional methods and provides favorable conditions for multiple inversions to suppress multiple solutions. We set artificial initial parameters with linear constraints in our velocity increasing model test to accelerate the convergence rate of the target function and obtain accurate results quicker. Finally, this method is applied to the microtremor dispersion data with a strong disturbance, and the inversion results are consistent with the high-density electrical profile and geological survey data.

The present study aims mainly at investigating the site effect at the new Luxor city, Egypt, using microtremor measurements. Accordingly, 41 ambient noise recordings were implemented covering the investigated area in a reasonable manner with spacing nearly 1 km between each measurement station. The data were analyzed using Nakamura’s technique. The results show that; the investigated area exhibits low fundamental frequency values ranging between 0.28 - 0.47 Hz and its corresponding amplification factor values vary between 2.3 and 6.8. Consequently, the studied site is characterized by the presence of thick soft sediments overlying a hard bed rock. The seismic vulnerability index (Kg) was estimated, relying on the estimated fundamental frequency (F0) and amplification factor (A0), through the range between 11 and 95 across the mapped area. The obtained Kg values were noticed to be compatible with amplification level results. The central part of the investigated area reflects the higher Kg and A0 values.

Micromotion is the daily tiny vibration of the earth’s surface. Micromotional exploration can use the surface wave information of micro motion to study the shallow structure of underground media. In this study, we collected microtremor data at 68 stations in the Middle-Lower Yangtze Metallogenic Belt (MLYMB) and determined the resonant frequency and obtained the distribution of sedimentary thickness in this area by using H/V spectral ratio. According to the results of H/V, the sedimentary layer in the basin is thick, and the predominant frequency of the basin is 0.05 - 0.1 Hz. There are no obvious lateral changes in the impedance interface between bedrock and sedimentary layer in this area. The basement of Tongling, Anqing and Luzhou mining areas and their adjacent areas is Kongling-Dongling type basement, which is composed of a set of metamorphic core complex. The predominant frequency is 0.05 - 0.1 Hz. The sedimentary thickness gradually thinned from 3800 m in the west to 2100 m in the East. Moreover, this article used SPAC (spatial autocorrelation) method to obtain the S-wave velocity structure of the mining area near Luzong. The SPAC method reveals that the depth of the interface between the loose sediments and the volcanic rocks is about 600 m in the study area near the Luzhou mining area in the Middle-Lower Yangtze Metallogenic Belt, and the average depth of the interface between the volcanic rock section and the intrusive complex section is about 1000 m. The thickness of the intrusive rock is more than 2500 m. Tourmaline is developed in the interior of the intrusive rock, which may have better exploration value.