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Tortum Lake, in Turkey, which is a natural feature and a large landslide barrier lake, was formed due to a natural landslide disaster. In this context, areas with the potential to create landslides in Tortum Lake and the waterfall region are identified and displaced with zoning. Microtremor horizontal-to-vertical spectral ratio method and seismic refraction studies were used, and by considering the results, the areas with high landslide potential were determined. It aims to choose an effective study area by determining the areas with high landslide capability and revealing the boundaries of the geotechnical project. Areas with high landslide potential were compared with those where landslides have happened, and it showed that this method can be used for determining sliding risk before it happens. Results showed that regions with low VS30, combined with the slope, create the potential for landslides. Afterward, when the map of ground amplification values obtained from the microtremor data was reviewed, it was found that the physical properties of areas with high ground amplification values would be the same as those of areas with low VS30 values. When these two maps are reviewed, it is observed that areas with low VS30 values and high ground amplification values are in the same locations as those with high sliding potential. The correct determination of the geotechnical project work area is important both to draw attention to the right area to be designed and to avoid wasting unnecessary time and money on unnecessary areas. [ABSTRACT FROM AUTHOR]

Wilayah Kemiling yang terletak di Kota Bandar Lampung sering kali mengalami gempa lokal dengan magnitudo kecil. Gempa ini terjadi secara berulang dan dirasakan di daerah Kemiling dan sekitarnya. Hal tersebut dapat menimbulkan kekhawatiran bagi warga dan dapat merusak bangunan. Fokus utama pada studi ini adalah untuk memahami bagaimana karakteristik tanah dan indeks kerentanan seismik di daerah tersebut. Untuk meminimalisir dampak kerusakan akibat gempa, perlu dilakukan mikrozonasi pada wilayah rawan gempa. Parameter mikrozonasi yang digunakan untuk mengetahui karakteristik tanah antara lain amplifikasi (A0), frekuensi natural (f0), indeks kerentanan seismik (Kg), periode dominan (T0), dan kecepatan gelombang geser hingga kedalaman 30 meter (VS30). Sebanyak 65 titik pengukuran mikrotremor telah diukur di Kecamatan Kemiling dan sekitarnya meliputi kota Bandar Lampung, Kecamatan Gedong Tataan, dan Kecamatan Natar. Pada penelitian ini digunakan analisis metode Horizontal to Vertical Spectral Ratio (HVSR) dan didapatkan bahwa frekuensi natural berkisar antara 0,5-31,47 Hz, periode dominan 0,03-2,0 sekon, amplifikasi 0,76-7,67 kali penguatan, indeks kerentanan seismik 0,05-76,31, dan VS30 49,61-777,80 m/s. Hasil penelitian menunjukkan bahwa wilayah barat daya hingga utara Kemiling memiliki risiko kerentanan yang lebih tinggi dibandingkan wilayah lainnya dengan tipe tanah berupa tanah lunak. Oleh karena itu, diperlukan tindakan mitigasi yang tepat, termasuk pengembangan rencana mitigasi risiko, pemantauan lanjutan, dan keterlibatan aktif masyarakat dalam perencanaan darurat.

The development of geothermal energy has received extensive attention because of global energy scarcity and environmental pollution. The Tangquan area is in the north of the Yangtze fold belt, and the lack of magmatic rock development has resulted in a low-temperature type of geothermal reservoir. There are sporadic hot springs and cold springs exposed in the study area, but the uncertain deep geological structure, unknown geothermal reservoir formation mechanism, and lack of detailed exploration data seriously restrict the exploration and development of geothermal resources in the area. Filling underground faults with water can significantly reduce electrical resistivity, while traps filled with warm water can cause a decrease in S-wave velocity. Thus, a new integrated geophysical method, including the controlled source audio-frequency magnetotelluric (CSAMT) and microtremor methods, is applied for geothermal exploration in the region. The combination of CSAMT and microtremor methods can determine thermal-controlled and water-conducting structures more effectively and locate geothermal storage more accurately. The source, channel, storage, and cover of regional geothermal reservoir formation are analyzed using geophysical and geological data. That is, the regional NE- and NW-trending faults are explained as thermal-controlled and water-conducted structures, respectively. The deep Sinian Dengying Formation supplies a heatand water-bearing space. The tectonic intersection area, especially the tensional fault zone, is found to be closely related to the existence of geothermal reservoirs, which is well verified by later drilling results. Finally, a geothermal reservoir model is established to comprehensively understand the distribution of geothermal energy in the region. [ABSTRACT FROM AUTHOR]

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Determining the characteristics of ground motions in a wide period range of 0.1 to 10 seconds is crucial for seismic risk assessment. Eskişehir province, with a population of approximately one million and a developing industry is a high seismic risk region despite its relatively low seismic activity due to rapid urbanization. Determining seismic velocities and bedrock depths is important for reducing urbanization and earthquake risks. This study was conducted to obtain this information. The research, supported by 7 and 8 network measurements performed at 15 different points in total in 2017 and 2018, allowed the determination of the Vs structure up to depths of 600-700 m using microtremor measurements with the single-station Horizontal/Vertical spectral ratio (H/V) method and network measurements with the SPAC (Spatial Autocorrelation) method. The data obtained were used to create a subsurface depth model using inverse solution methods. Engineering bedrock was detected at depths of 100-250 m and velocities of 500-800 m/s for shallow sections using small and large network/array measurements in the middle of the Eskişehir plain. S-wave velocities ranging from 1100 m/s in the west to 1800 m/s in the east and seismological bedrock at an average depth of 600-800 m were determined. Microtremor studies show bedrock depths that deepen from west to east and south to north, reaching 800 m at the deepest point. The Vs velocity of the seismological bedrock obtained from surface wave dispersion curves varies between 1200- 1800 m/s. In conclusion, detailed geological and geophysical analyses are of vital importance for seismic risk assessments and hazard analyses in the Eskişehir basin and similar areas. The critical role of local ground effects, i.e., ground motion amplifications, in seismic damage analysis was once again emphasized by this study. [ABSTRACT FROM AUTHOR]

We investigated the applicability of miniature microtremor arrays with a radius of a few meters or less to shallow surveys (up to a few tens of meters). It is shown that the upper limit wavelength normalized by the seismometer separation distance s that is analyzable by a miniature array does not depend on the observation instrument as long as the instrument has a self‐noise level that is sufficiently lower than the microtremor intensities; however, it generally depends on the average S‐wave velocity of the ground. This means that a miniature array is useful at soft‐soil sites but not hard‐soil sites. A statistical study in central Japan showed that the penetration depth by a miniature array with s = 1 m ranges from 6 to 12 m; specifically, the depth exceeds 12 m in one quarter of the cases but remains below 6 m in one quarter of the cases. This large variation is due to the variation in the average S‐wave velocity. A miniature array should thus be used in combination with a larger array with an s value of several meters to 20 m. In urbanized areas with high industrial activity, where the microtremor wavefield is likely isotropic, these arrays can be replaced by a linear array. In environments with extremely low signal‐to‐noise ratios, a less efficient zero‐crossing method should be applied to the larger array. An appropriate observation strategy should be selected for a given geoenvironment. Field examples show that our strategy enables efficient and feasible dense surveys. Plain Language Summary: A microtremor array survey is a non‐destructive, passive method for subsurface exploration. Because such a survey is also easy to conduct and cost‐effective, it is widely used for seismic hazard assessments. It is expected that the benefits can be extended to lunar and planetary exploration. We demonstrate that a miniature microtremor measurement device with a radius of a few meters or less can be used for shallow surveys. The performance of the miniature measurement device does not depend on the observation instrument. This device is effective at soft‐soil sites but not hard‐soil sites. To increase survey feasibility, miniature measurement devices should be used in combination with a larger measurement device. In ground environments with extremely low signal‐to‐noise ratios, larger measurement devices and somewhat less efficient methods must be applied. It is important to select an observation strategy that is appropriate for a given geological environment considering the balance between the efficiency and feasibility of a shallow survey. Key Points: The applicability of a miniature array with a radius of a few meters or less to shallow surveys is reviewed and summarizedThe applicability of a miniature array depends on the average S‐wave velocity of the ground but not on the observation instrumentIllustrative field examples of our strategy, which enables a dense survey to obtain a shallow two‐dimensional velocity section, are shown [ABSTRACT FROM AUTHOR]

On September 28, 2018, a 7.5 Richter magnitude earthquake struck the Palu City neighborhood of Petobo. The tectonic activity along the Palu-Koro fault generated this earthquake, which resulted in soil liquefaction. The purpose of this study is to use microtremor measurements at 33 distinct places to investigate the properties of the soil layer after liquefaction. The obtained data was then evaluated utilizing Horizontal to Vertical Spectral Ratio (HVSR) methodologies such as Ground Shear Strength (GSS), amplification factor, and vulnerability index to determine the soil layer's properties and susceptibility. The dominant frequency ranges from 0.19 to 4.75 Hz, while the dominant period ranges from 0.21 to 5.17 seconds, according to the measurement results. According to these measurements, the silt layer varies between 5 and 30 m. GSS values in the 10-4 to 10-2 range indicate that soil cracking, subsidence, liquefaction, landslides, and compaction are likely. The soil vulnerability and amplification index values range from 2.36 to 4.37, respectively. These values show the potential level of danger, which might be low, medium, high, or extremely high. Peak ground acceleration varied from 299.52 to 301.52 gals, suggesting high to extremely high danger levels. The microzonation map created for this study is considered to be a useful resource for training disaster mitigation approaches and facilitating infrastructure development planning in the region.

Abstract This technical report explains details on the results of the investigation to build a subsurface structural model and a selection of earthquake data at the target site of the blind prediction exercise for “The 6th International Association of Seismology and Physics of the Earth’s Interior/International Association of Earthquake Engineering International Symposium on the Effect of Surface Geology on Seismic Motion (ESG6).” The selection process of the target site in the Kumamoto Plain, Japan, in ESG6 was explained with a historical review of the blind prediction tests in the previous ESG conferences. We have collected existing subsurface structural and earthquake data and conducted geophysical and geotechnical surveys in and around the target site to generate important velocity structure and the earthquake data used in the blind test. Microtremor data were obtained in triangular arrays ranging in side lengths from 1 to 962 m, and active surface wave data were derived along a 36-m line at the site. These data were provided for the prediction of a subsurface structural model in the first step of the blind prediction exercise. We also conducted a velocity logging in a borehole to a bottom depth of 39 m at the site and laboratory tests of soil samples from the borehole. We constructed a velocity profile of the shallow and deep sedimentary layers from a combination of the geophysical and geotechnical data at the site, and validated it by comparing the characteristics of the ground motion data from the moderate event. This “preferred velocity model” was provided as a standard model to the participants in the second and third steps of the blind prediction test to predict the earthquake ground motions of a moderate event and the mainshock of the 2016 Kumamoto earthquake. Graphical Abstract

S-wave velocity (Vs) profile or time averaged Vs to 30 m depth (VS30) is indispensable information to estimate the local site amplification of ground motion from earthquakes. We use a horizontal-to-vertical spectral ratio (H/V) of seismic ambient noise to estimate the Vs profiles or VS30. The measurement of H/V is easier, compared to active surface wave methods (MASW) or microtremor array measurements (MAM). The inversion of H/V is non-unique and it is impossible to obtain unique Vs profiles. We apply deep learning to estimate the Vs profile from H/V together with other information including site coordinates, deep bedrock depths, and geomorphological classification. The pairs of H/V spectra (input layer) and Vs profiles (output layer) are used as training data. An input layer consists of an observed H/V spectrum, site coordinates, deep bedrock depths, and geomorphological classification, and an output layer is a velocity profile. We applied the method to the South Kanto Plain, Japan. We measured MASW, MAM and H/V at approximately 2300 sites. The pairs of H/V spectrum together with their coordinates, geomorphological classification etc. and Vs profile obtained from the inversion of dispersion curve and H/V, compose the training data. A trained neural network predicts Vs profiles from the observed H/V spectra with other information. Predicted Vs profiles and their VS30 are reasonably consistent with true Vs profiles and their VS30. The results implied that the deep learning could estimate Vs profile from H/V together with other information.

AbstractBhaktapur, 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.

Various geological disasters, such as landslides and ground movements, occur annually in Srimulyo Village, Malang District, with varying levels of damage. Ground movements can affect structures built above, causing sinking, cracking, and collapse. Research into landslides and ground movements triggered by vibrations is generally conducted using the microtremor method, which has proven effective. This study uses the microtremor method to map the soil condition that is potentially prone to movement or landslides based on the observed soil vulnerability index. Data was collected using a TDL 303s Digital Portable Seismograph instrument; the measurement points were established in the form of a grid distributed across the research area, with a recording duration of approximately 45 minutes at each point. The analysis technique utilizes the Horizontal Vertical Spectrum Ratio (HVSR) based on the Fast Fourier Transform (FFT) principle. The study’s results found that the research location’s seismic vulnerability index varies between 6.5 and 16.5. Areas with high seismic vulnerability index values, specifically those with Kg>11.5, are scattered on the west, south, and southeast sides of the research location. Based on field observations, these areas are dominated by relatively thick sediment layers, leading to lower dominant frequency values and higher amplification values; consequently, the seismic vulnerability index in the southern region is also high. [ABSTRACT FROM AUTHOR]

Using microtremor data from the Wangjiayan landslide in Beichuan (Southwest China), we applied the horizontal-to-vertical spectral ratio (HVSR) method to evaluate the associated seismic effect. The results show the following: (1) The microtremor spectrum characteristics of the Wangjiayan landslide are significant, and the HVSR curves feature multiple peaks and fluctuate significantly in the high-frequency band, suggesting contributions from the underlying stratigraphic structure, overburden thickness, and topography. (2) The predominant frequencies of the landslide crown, the landslide bedding, and the landslide main body appear at 2.75, 3.79, and 3.61–4.06 Hz, with corresponding peak amplification factors of 3.44, 2.45, and 2.34–2.48. The amplification effect tends to intensify as the elevation of the microtremor measurement points rises gradually. (3) Microtremor directional characteristics are evident at the crown of the Wangjiayan landslide, with significant directivity ranging from 80 to 110°, including the main slide direction of the landslide at 80°. (4) The preferential orientation of the joints in the Wangjiayan landslide area ranges from 70 to 100°, coinciding with the significant directivity of the microtremors at the landslide crown, which indicates that the tectonic stress induced by the Yingxiu–Beichuan fault may have a particular promoting effect on the formation of the Wangjiayan landslide. The results serve as an additional reference for researching the triggering mechanism of the Wangjiayan landslide and provide technical support for investigating the seismic effect of old landslides. [ABSTRACT FROM AUTHOR]

Although Gümüşhane province is a quiet region in terms of seismicity, it is under earthquake danger due to its proximity to the NAFZ. Therefore, it is of great importance to reveal the local site effects in the central district of Gümüşhane province, which is in a rapid and intense construction process. For this purpose, the predominant frequency (or period), horizontal to vertical spectral ratio (HVSR) defining the amplification potential and S-wave velocity (VS30) values, which are important parameters in the detection of site effects, were calculated by applying the HVSR and multichannel surface wave analysis (MASW). The predominant frequencies determined for the investigation area from microtremor data collected at a single station vary between 1.21-13.40 Hz, dominant periods between 0.07-0.82 sec, amplification potential values between 1.12-9.76 and VS30 values between 300.2-677.2 m/sec. Additionally, using the calculated VS30 values, soil classification was defined for the investigation area according to TBDY (2018), NEHRP (2020) and Eurocode-8 (2004). Using the measurement parameters obtained from HVSR and MASW methods, microzonation maps of the predominant frequency, predominant period, amplification potential risk and VS30 values of the study area were created. According to these maps, it was seen that the high predominant frequency and low predominant period regions in the central district of Gümüşhane province had low magnification potential and high VS30 values. With this study, it has been concluded that the ground parameters obtained from different geophysical methods for the central district of Gümüşhane province are in good harmony with each other and with the geological structure of the region. With this study, it has been concluded that the site effect parameters obtained from different geophysical methods for the central district of Gümüşhane province are in good harmony with each other and with the geological structure of the region. ing that pending at employer. please check into it and confirm my request [ABSTRACT FROM AUTHOR]

Bhaktapur city, one of the historical cities of Nepal, is among the old settlements within Kathmandu Valley that were frequently devastated during major earthquakes. Historical evidence clearly states the high seismic vulnerability of Bhaktapur. So, this study characterizes the free field of the Bhaktapur district in terms of periods. For this, the horizontal to vertical (H/V) technique was used to determine the predominant period of the study area, measuring microtremor data at 200 m × 200 m spacing in the core city area, whereas 400 m × 400 m spacing of measurement was done at the outskirts of the city with rare settlement. The spatial distribution map of the predominant period is prepared with the period obtained from 609 measuring points. The map shows that the predominant period ranges from 0.1 to 4 s and then categorized into four different zones—A (0.10–0.6 s), B (0.6–1.0 s), C (1.0–1.7 s), and D (1.7–4.0 s). The central parts of the study areas are spotted with longer periods (1.7–4.0 s), where the density of the dweller is high. The structural period of 28 reinforced concrete buildings was also determined to understand the level of danger of the buildings due to soil-structure resonance. The predominant period of the buildings ranges from 0.12 to 0.42 s. The possibility of soil structure resonance condition is higher for six buildings, medium for two buildings, and low for the rest of the buildings. The results can be applied to urban planning, seismic hazard mitigation, conservation, and restoration of heritage monuments. [ABSTRACT FROM AUTHOR]

Bengkulu City in Indonesia is one of the areas prone to earthquakes, yet it has developed increasingly in the last five years. One of the prospective areas in Bengkulu City, called Singaran Pati, is located close to the Dendam Tak Sudah Lake, a natural tropical lake. This research aims to interpret geological characteristics for the spatial plan development in the study area. Microtremor measurement and site investigation are implemented to observe the geophysical and geological characteristics of the study site. Inversion analysis using Monte Carlo simulated annealing is conducted to generate a shear wave velocity profile. Based on the shear wave velocity, the identified bedrock surface is illustrated in a 3D geological model. A simple analysis of the natural period to estimate allowable structural building storeys is also performed. Results show that the depth of the bedrock surface is around 4.5–147 m. The study area is dominantly categorised as Site Classes C and D. Low- to medium-rise buildings are appropriate to construct based on the geophysical and geotechnical information. The findings can provide preliminary guidelines on geotechnical and geological information for the seismic site conditions in the study area in Bengkulu City. [ABSTRACT FROM AUTHOR]

Local soil effect plays an essential role in estimating of earthquake damage that occurs on the existing structures and in the planning and design of the new structures. One of the most critical steps in determining the earthquake design characteristics of a region is related with determining the behavior of the layers that form the soil in that region under cyclic stresses that develop because of earthquakes. Kütahya Dumlupınar University central campus needs constant new construction as the student potential increases each year in addition to the existing building stock. For this reason, data have been collected by using microtremor at 36 points and Multichannel Analysis of Surface Waves (MASW) at 4 points to determine the mechanical and physical characteristics of soil. Data being collected by the single station microtremor method were evaluated by means of horizontal-vertical spectral ratio technique, and the dominant vibration frequency values were evaluated, and the shear wave velocities (Vs30) up to a depth of 30 m were obtained by evaluating the data collected with MASW method. By establishing the relationship of the parameters obtained from both methods with the geological units, the results about the soil characteristics of the study zone were revealed. In accordance, the middle and northwest parts of the study area were composed of rock units when compared to the southeast part, and this boundary was controlled by an antithetic fault. [ABSTRACT FROM AUTHOR]

On September 28, 2018, a 7.5 Richter magnitude earthquake struck the Palu City neighborhood of Petobo. The tectonic activity along the Palu-Koro fault generated this earthquake, which resulted in soil liquefaction. The purpose of this study is to use microtremor measurements at 33 distinct places to investigate the properties of the soil layer after liquefaction. The obtained data was then evaluated utilizing Horizontal to Vertical Spectral Ratio (HVSR) methodologies such as Ground Shear Strength (GSS), amplification factor, and vulnerability index to determine the soil layer's properties and susceptibility. The dominant frequency ranges from 0.19 to 4.75 Hz, while the dominant period ranges from 0.21 to 5.17 seconds, according to the measurement results. According to these measurements, the silt layer varies between 5 and 30 m. GSS values in the 10-4 to 10-2 range indicate that soil cracking, subsidence, liquefaction, landslides, and compaction are likely. The soil vulnerability and amplification index values range from 2.36 to 4.37, respectively. These values show the potential level of danger, which might be low, medium, high, or extremely high. Peak ground acceleration varied from 299.52 to 301.52 gals, suggesting high to extremely high danger levels. The microzonation map created for this study is considered to be a useful resource for training disaster mitigation approaches and facilitating infrastructure development planning in the region. [ABSTRACT FROM AUTHOR]

This technical report explains details on the results of the investigation to build a subsurface structural model and a selection of earthquake data at the target site of the blind prediction exercise for "The 6th International Association of Seismology and Physics of the Earth's Interior/International Association of Earthquake Engineering International Symposium on the Effect of Surface Geology on Seismic Motion (ESG6)." The selection process of the target site in the Kumamoto Plain, Japan, in ESG6 was explained with a historical review of the blind prediction tests in the previous ESG conferences. We have collected existing subsurface structural and earthquake data and conducted geophysical and geotechnical surveys in and around the target site to generate important velocity structure and the earthquake data used in the blind test. Microtremor data were obtained in triangular arrays ranging in side lengths from 1 to 962 m, and active surface wave data were derived along a 36-m line at the site. These data were provided for the prediction of a subsurface structural model in the first step of the blind prediction exercise. We also conducted a velocity logging in a borehole to a bottom depth of 39 m at the site and laboratory tests of soil samples from the borehole. We constructed a velocity profile of the shallow and deep sedimentary layers from a combination of the geophysical and geotechnical data at the site, and validated it by comparing the characteristics of the ground motion data from the moderate event. This "preferred velocity model" was provided as a standard model to the participants in the second and third steps of the blind prediction test to predict the earthquake ground motions of a moderate event and the mainshock of the 2016 Kumamoto earthquake. [ABSTRACT FROM AUTHOR]

Abstract We investigated the applicability of miniature microtremor arrays with a radius of a few meters or less to shallow surveys (up to a few tens of meters). It is shown that the upper limit wavelength normalized by the seismometer separation distance s that is analyzable by a miniature array does not depend on the observation instrument as long as the instrument has a self‐noise level that is sufficiently lower than the microtremor intensities; however, it generally depends on the average S‐wave velocity of the ground. This means that a miniature array is useful at soft‐soil sites but not hard‐soil sites. A statistical study in central Japan showed that the penetration depth by a miniature array with s = 1 m ranges from 6 to 12 m; specifically, the depth exceeds 12 m in one quarter of the cases but remains below 6 m in one quarter of the cases. This large variation is due to the variation in the average S‐wave velocity. A miniature array should thus be used in combination with a larger array with an s value of several meters to 20 m. In urbanized areas with high industrial activity, where the microtremor wavefield is likely isotropic, these arrays can be replaced by a linear array. In environments with extremely low signal‐to‐noise ratios, a less efficient zero‐crossing method should be applied to the larger array. An appropriate observation strategy should be selected for a given geoenvironment. Field examples show that our strategy enables efficient and feasible dense surveys.

The Underpass at Yogyakarta International Airport (YIA) is in the Temon District, Kulon Progo Regency, Yogyakarta Province, Indonesia. The YIA has become one of the focal points for national infrastructure development and economic growth. Based on historical seismic activity, YIA and its vicinity are characterized by high levels of seismic activity. However, the data and information available regarding this matter are notably limited. This research aims to assess the soil vulnerability in the vicinity of the YIA Underpass. The soil vulnerability assessment is conducted by measuring microtremors and groundwater levels. The microtremor data is processed using the Horizontal-to-Vertical Spectral Ratio (HVSR) method with geopsy software and guidelines provided by Site Effects Assessment Using Ambient Excitations (SESAME). The research findings reveal that the study area exhibits a high seismic hazard potential, as evidenced by the seismic vulnerability index (Kg), which is more than 20. The interpretation of the HVSR curve indicates that the study area is characterized by a low dominant frequency (f0) ranging from 0.214 to 0.289 Hz, along with varying shear wave velocities. Based on the stress-corrected shear wave velocity (Vs1), point U01 is more likely to liquefy than U05 and U07 as Vs1 in some soil layers is less than 215 m/s. This analysis indicates that the study area is susceptible to earthquake hazards due to thick soil deposit layers and shallow groundwater levels. [ABSTRACT FROM AUTHOR]

On February 6th 2023 two major earthquakes struck southeast Turkey, M7.7 Kahramanmaras and M7.6 Elbistan, respectively. Unfortunately, due to the impact of these catastrophic events more than 50 000 casualties and 35 000 collapsed buildings have been reported since then. The aim of the study is to demonstrate preliminary site response analysis and assessment of re-liquefaction potential of sites which have been affected by the earthquakes - especially the cities of Iskenderun and Golbasi. Both site-specific areas have clear evidences of liquefaction and lateral spreading events which imply the focus of the presented paper. A series of geophysical MASW and microtremor tests have been performed in order to determine shear wave velocities up to depth of 30 m as well as the fundamental natural frequency of the soil deposits. Moreover, samples have been collected from sand and silt ejecta in order to evaluate some basic physical properties - grain-size curves, specific gravity and plasticity parameters. On the basis of the obtained data seismic classification of the investigated sites according to current design codes has been made and in-depth distance to relatively stiff layer has been assumed. For the sake of evaluating risk of re-liquefaction the widely-used simplified stress-based approach to triggering assessment has been adopted considering some rules of the thumb (e.g., sieve analysis and plasticity properties evaluation). Lastly, post-liquefaction reconsolidation settlement and lateral displacement have been determined in terms of future earthquakes. [ABSTRACT FROM AUTHOR]

The northern part of Pemalang City consists of Quaternary deposits, having the potential for earthquake amplification effect. This amplification effect amplifies the ground shaking because of an earthquake (the local site effect) that has the potential to cause damage. This study investigated the amplification factor from the HVSR curve of microtremor measurements due to soil response based on ground shear strain, the risk level of the earthquake based on peak ground acceleration (PGA), and earthquake intensity. The microtremor data from five locations in Pemalang were used to calculate the amplification factor and predominant frequency. The damaging earthquake parameters around Java during 2010-2020 were used to calculate the PGA. The microtremor data were processed using the HVSR method, and PGA was calculated using the Kanai equation. The HVSR result shows that Pemalang has an amplification factor ranging from 6.23 to 19.59 and ground shear strain varying between 0.86 x 10-4 and 6.67 x 10-4, which shows that Pemalang only experiences the vibration when an earthquake occurs. The PGA results using the Kanai equation (19.71-54.56 gal) were included in the low vulnerability category, and MMI earthquake intensity (3.08-4.70) was included in the felt earthquake category (II SIG BMKG scale). Therefore, the amplification factor from the HVSR curve of microtremor measurement, ranging from 6.23 to 19.59, showed low soil response and low-risk vulnerability based on the damaging earthquake parameter around Java during 2010-2020. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to present the damage features of masonry structures and engineering seismology studies after the 19–22 November 2021 Köprüköy earthquakes (Mw 5.1 and Mw 4.7). The masonry structures damaged near the epicenter have been examined. Damages have been detected that such as vertical cracks in the walls of the masonry structures, out-of-plane bending of the walls, splits in the joints of the walls, and separation of the floors from the elements such as walls and roofs. The fact that the structures in the region do not receive an engineering service and that they are constructed without complying with the relevant earthquake regulations are thought to cause such damage. The damage in Topçu village of Köprüköy district in Erzurum is more than in other settlements. Microtremor measurements have been applied in Topçu Village to investigate dynamic soil features. The soil amplification factor and soil predominant period have been obtained ~ 6.8 and ~ 1.3 s for the first measurement and ~ 9.4 and ~ 1.3 s for second location, respectively. Also, Vs30, bedrock depth, vulnerability index, and shear strain parameters have been calculated using some empirical relations. High bedrock depth and low Vs30 values are obtained for both measurements. The vulnerability index and shear strain values also indicate that the vulnerability of the soil is high. In order to remain in the safe zone for structures in a possible future earthquake, it has been suggested that it should comply with the earthquake-soil-structure relationship and should be designed in accordance with the earthquake regulation standard. [ABSTRACT FROM AUTHOR]

To accurately explore distribution of a historical small coal mine goaf in Hami, Xinjiang, integrated application of microtremor and transient electromagnetic is used for goaf exploration researching. This work use different physical properties data into lithology, use microtremor exploration to determine the goaf position and use transient electromagnetic exploration identify goaf water. Two methods can complement each other, verify each other, and effectively reduce the wrong results of single geophysical method. Which also provides a reference for the selection and application of geophysical exploration means in small mine goaf exploration.

Abstract We present the 1D subsoil structure and local site effects at KUMA strong ground motion station in Kumamoto City, Japan. We analyze data from a field campaign conducted in the framework of the Blind Prediction BP1 test of the 6th IASPEI/IAEE International Symposium: Effects of Surface Geology on Seismic Motion. In parallel with other participants of the BP1 test, we process data from passive and active source measurements aiming to determine the shear-wave velocity, Vs, structure and the site response at KUMA station. Passive measurements are associated to five microtremor arrays. In each array, seven seismometers have been deployed in a common-center triangle shape, recording microtremors simultaneously for 1 to 2 h. The vertical component of microtremors was analyzed using the spatial autocorrelation (SPAC) method. Cross-correlation coefficients were computed for all station pairs available for each array. By fitting the average SPAC’s coefficients to the first-kind zero-order Bessel function, J0, and assuming that microtremors primarily comprise fundamental mode Rayleigh waves, phase velocity dispersion curves were determined. Phase velocity values for frequencies > 15 Hz were obtained from data of a close-by active source geophone profile. We integrated the data with those of the passive measurements and obtained an experimental phase velocity dispersion curve. The resulting curve shows low velocity variation, from 150 to 200 m/s, in the surface layers, whereas significant dispersion appears in frequencies below 2.5 Hz. By inverting this curve, we achieved to determine the 1D shear-wave velocity structure at KUMA station. Site response characteristics were determined by applying the Horizontal-to-Vertical-Spectral-Ratios method. Significantly amplified peaks in the frequency range between 0.3 to 1.5 Hz dominate HVSR spectral ratios. These peaks correspond to resonant frequencies of soils and originate from different impedance contrasts within the substratum of the site. Graphical Abstract

Landslides are one of the natural disasters that frequently occur in Indonesia and can result in loss of life, property, and environmental damage. Semaka Subdistrict, Tanggamus Regency, Lampung Province, is located in a landslide-prone area. The aim of this research is to analyze the geological characteristics and soil layer dynamics for landslide mitigation in the Semaka area. This study uses a scoring method based on three parameters: slope inclination, sediment thickness, and peak ground acceleration (PGA), to determine site class and create a landslide-prone zone map in the Semaka region. Microtremor data is analyzed using the Horizontal to Vertical Spectrum Ratio (HVSR) method. The obtained data represents ground vibrations as a function of time, with a dominant frequency range in the Semaka area between 2.18 and 13.48 Hz and sediment thickness ranging from 10 to 80 meters. The maximum PGA values range from 100 to 600 gal. The seismic sources used in the PGA map are from the subduction zone and Semangko Fault. Based on the slope values, geological factors such as sediment thickness, and PGA values, the villages of Sedayu and Sukaraja are identified as the areas most susceptible to landslides. The findings of this research are expected to enhance landslide control measures in the Semaka region.

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We present the 1D subsoil structure and local site effects at KUMA strong ground motion station in Kumamoto City, Japan. We analyze data from a field campaign conducted in the framework of the Blind Prediction BP1 test of the 6th IASPEI/IAEE International Symposium: Effects of Surface Geology on Seismic Motion. In parallel with other participants of the BP1 test, we process data from passive and active source measurements aiming to determine the shear-wave velocity, Vs, structure and the site response at KUMA station. Passive measurements are associated to five microtremor arrays. In each array, seven seismometers have been deployed in a common-center triangle shape, recording microtremors simultaneously for 1 to 2 h. The vertical component of microtremors was analyzed using the spatial autocorrelation (SPAC) method. Cross-correlation coefficients were computed for all station pairs available for each array. By fitting the average SPAC's coefficients to the first-kind zero-order Bessel function, J0, and assuming that microtremors primarily comprise fundamental mode Rayleigh waves, phase velocity dispersion curves were determined. Phase velocity values for frequencies > 15 Hz were obtained from data of a close-by active source geophone profile. We integrated the data with those of the passive measurements and obtained an experimental phase velocity dispersion curve. The resulting curve shows low velocity variation, from 150 to 200 m/s, in the surface layers, whereas significant dispersion appears in frequencies below 2.5 Hz. By inverting this curve, we achieved to determine the 1D shear-wave velocity structure at KUMA station. Site response characteristics were determined by applying the Horizontal-to-Vertical-Spectral-Ratios method. Significantly amplified peaks in the frequency range between 0.3 to 1.5 Hz dominate HVSR spectral ratios. These peaks correspond to resonant frequencies of soils and originate from different impedance contrasts within the substratum of the site. [ABSTRACT FROM AUTHOR]

The 2006 Yogyakarta earthquake, with a magnitude of Mw 6.3, caused significant damage primarily on the west side of the Opak River. The Opak River area encompasses formations that exhibit distinct responses to seismic wave propagation. Formations consisting of unconsolidated and young sedimentary materials tend to experience wave amplification during seismic events. This study aims to investigate the seismic wave characteristics within each formation unit using microtremor measurements. The seismic wave parameters analyzed include dominant frequency, amplification factor, shear wave velocity, weathered layer thickness, seismic vulnerability index, and lithology based on N-SPT data. The study utilized 190 microtremor data sets and 7 N-SPT data sets. The microtremor data was processed using the Horizontal to Vertical Spectral Ratio Nakamura method, while the shear wave velocity data was processed using the Imai and Tonouchi approach. The findings revealed higher amplification factors in areas dominated by unconsolidated sedimentary materials and young formations. Quaternary formations are dominated by unconsolidated sedimentary material composed of sand, silt, clay, and breccia. Formations with a tertiary age are composed of more complex lithologies such as breccia-tuff, dacite tuff, andesitic tuff, volcanic breccias, lavas, siltstone, sandstone, and conglomerate. These conditions make Quaternary formations have seismic parameter characteristics such as lower dominant frequency, higher amplification factor, thicker sediment layer thickness, and higher seismic vulnerability index compared to Tertiary formations. Quaternary formations correlate with damage to buildings after the Yogyakarta earthquake, with an average shear wave velocity character of 279-293.67 m/s, and are in a zone with a vulnerability index >20. Tertiary formations demonstrated higher seismic resistance compared to Quaternary formations, indicating their relative stability. [ABSTRACT FROM AUTHOR]

Peak Ground Acceleration (PGA) is a crucial factor in infrastructure planning, particularly in the context of constructing the Jogja-Bawen Toll Road in Magelang Regency. However, there is a lack of comprehensive research on the optimal PGA value for this region. This research addressed this gap by analyzing two significant earthquake scenarios, namely the Bantul and Yogyakarta earthquakes, with magnitudes of 6.3 Mw and 7.44 Mw, respectively. Three methods were employed for this analysis, namely the Indonesian seismic code, Kanno (2006), and Fukushima (1990) attenuations, as well as microtremor measurements. The PGA value generated by the seismic code ranges from 0.348-0.380g. For the 6.3 Mw earthquake scenario, the Kanno attenuation results in a PGA range of 0.115-0.181g, the Fukushima attenuation yielded 0.082-0.114g, and the microtremor measurements indicated 0.036-0.092g. In the case of the 7.44 Mw earthquake scenario, the Kanno attenuation generated a PGA range of 0.202-0.265g, the Fukushima attenuation produced 0.052g-0.062g, and the microtremor measurements indicated 0.036g-0.088g. The result showed that the PGA value derived from the seismic code is relatively higher because it considered various earthquake models and magnitudes. Meanwhile, the PGA value obtained from microtremor measurements was smaller due to the consideration of site class and site-specific amplification factors at the study site. [ABSTRACT FROM AUTHOR]

The Kocaeli region, located in the eastern Marmara near the North Anatolian Fault Zone, is well known as a zone of high seismic hazard due to its proximity to major fault zones and high seismic risk due to the dense distribution of critical industrial facilities in the area. The region experienced two major earthquakes in 1999 in Kocaeli (Mw = 7.4) and Duzce (Mw = 7.1). This study performs site-specific probabilistic and deterministic seismic hazard analyses at 14 sites in the Kocaeli basin. The multi-mode spatial autocorrelation, a modification to the original SPAC method, is performed to obtain the velocity profiles at the selected 14 sites. The updated method used here employs array-based measurement of seismic ambient noise and measures Rayleigh-wave velocity dispersion from which a one-dimensional shear-wave velocity profile is obtained using a series of small arrays of seismometers. In addition to the array data, the horizontal to vertical spectral ratios from the central stations of the array is used. After obtaining the velocity profiles at each site, site-specific seismic hazard analyses are performed. Probabilistic seismic hazard analysis results are compared to the design spectra from Turkey's current and previous seismic design codes. Analyses are also repeated with reference engineering bedrock conditions to investigate the contribution of site conditions to the seismic hazard. Numerical results of the study indicate the high seismic hazard in the region and highlight the significance of using local parameters in seismic hazard analyses. [ABSTRACT FROM AUTHOR]

Microtremor and geoelectrical resistivity surveys have been conducted in areas where the April 10, 2021, earthquake of 6.1 Mw caused the most damage. Wirotaman Village, Malang Regency, was one of the regions with the most extensive damage. This study aims to investigate the seismic vulnerability and subsurface conditions that result in severe damage at the research location. This study's Horizontal to Vertical Spectral Ratio Analysis (HVSR) curve was derived from the recorded microtremor signal in the frequency domain. The frequency parameter and amplification factor obtained from the curve are used to determine the seismic vulnerability index. In addition, a geoelectrical resistivity study with a dipoledipole configuration was conducted at the site with the most extensive damage. The results of this study show the correlation between the results of the HVSR curve analysis and geoelectrical resistivity in determining the seismic vulnerability of an area. The results indicated that the high seismic vulnerability index value ranged from Kg = 12.0 to 18.0, with the most severe damage concentrated in the Southwest at SA 05 and SA 06. Based on the results of the geoelectrical survey, information was obtained that several points of damage to buildings at SA 05 (red circle) were on the same line, where this condition was associated with the possibility of new faults at that location. This microtremor and geoelectric resistivity investigation reveals thick sedimentary deposits with a high seismic vulnerability index and low resistivity. This study's findings can be utilized as a guide for micro zonation studies in research areas. This research contributes to the surrounding community in the form of disaster mitigation, where construction must avoid local fault positions that have been found to reduce the level of damage when natural geological disasters occur. [ABSTRACT FROM AUTHOR]

Desa Jati Mulyo berada di Kecamatan Dendang Kabupaten Tanjung Jabung Timur yang didominasi oleh gambut sehingga rentan terhadap penurunan muka tanah. Penelitian ini bertujuan untuk mengetahui tingkat kerentanan tanah serta distribusi nilai parameter mikrotremor. Pengukuran dilakukan menggunakan seismograf MAE A6000S sebanyak 36 titik yang tersebar di Desa Jati Mulyo. Analisis data mikrotremor menggunakan metode HVSR (Horizontal to Vertical Spectral Ratio) dengan menggunakan perangkat lunak Geopsy menghasilkan nilai parameter frekuensi alami (f0) dan amplifikasi (A0), selanjutnya perhitungan dilakukan untuk menentukan nilai indeks kerentanan seismik (Kg). Hasil penelitian menunjukkan rentang nilai frekuensi natural area penelitian berkisar antara 0,57 Hz hingga 9,12 Hz. Kemudian nilai faktor amplifikasi berada diantara rentang 1,87 hingga 7,54 dan nilai indeks kerentanan sesimik berada diantara rentang 0,80 hingga 33,44. Berdasarkan Hasil Penelitian, terdapat 3 zona kerentanan seismik pada daerah penelitian, yaitu zona rendah, zona sedang dan zona tinggi. Daerah penelitian di dominasi oleh zona tinggi yang mana hampir seluruhnya tersebar di kawasan penelitian. Hal ini dikarenakan wilayah penelitian merupakan endapan aluvial yang tertutup lahan gambut, maka terdapat bahaya penurunan muka tanah yang tinggi dan dan berpotensi terjadi kerusakan akibat gempabumi.

Abstract The study used data acquired by the ESG6 Blind Prediction Step BP1 Working Group for purposes of facilitating a comparison of interpretation methods for obtaining shear-wave velocity profiles (Vs) from array observations of microtremor (passive seismic) noise. This work uses the direct-fitting MMSPAC method and the krSPAC method on passive seismic data supplied from four seven-station nested triangular arrays with apertures ranging from 1 to 962 m, located within Kumamoto City, Japan. The data allow a useful frequency range of 38 Hz down to 0.3 Hz, giving depth sensitivities from 2 m to > 1000 m. Results are presented as a seven-layer model which has time-averaged shear wave velocities for top 30 m and 300 m of V s30 = 189 m/s and V s300 = 584 m/s, respectively. HVSR spectra show two significant peaks at 1.2 and 0.35 Hz which are indicative of major Vs contrasts at depths 26 m and 750 m. The MMSPAC method (and its krSPAC variant) also proved viable on one asymmetric array where four of the seven stations were corrupted by incoherent low-frequency noise. Indications of a lateral variation in Vs could be detected due to the non-concentric geometry of the four arrays, and also from variations in HVSR spectra at stations of the largest array. Further analysis in step 4 of the blind trials, making use of geological data and a Preferred model supplied to participants, showed apparent discrepancies between the Preferred and our BP1 model for the upper 40 m where a supplied PS log appears to be inconsistent with geological data and the blind BP1 model. At low frequencies 0.5–2.5 Hz dispersion data and the BP1 model suggest that use of the Rayleigh effective mode is superior to use of the fundamental mode in deducing the Vs model at depths below 100 m. The method of direct fitting of model and observed SPAC spectra used in MMSPAC also enabled the use of a bandwidth 0.5–38 Hz for interpretation, which is a wider bandwidth than that achieved by other participants for use of passive seismic data alone. Graphical Abstract

The dataset provided in this paper includes the lateral vibration data obtained by on-site vibration tests on an 18-story timber-concrete hybrid building, which was completed in 2017 and is located within the University of British Columbia campus in Vancouver, Canada. Aiming at evaluating vibration properties such as natural periods, damping ratios, and mode shapes, microtremor measurement (i.e., ambient vibration test) and human-powered excitation tests were conducted from March 27th to 29th, 2023. Lateral velocity data of the building were collected using eight servo velocity sensors, type VSE-15D, and a data acquisition system, type SPC-52, composed of an A/D converter and a DC amplifier. The voltage data picked up by the sensors was first converted to digital data and then transferred to the hard disk drive in a laptop through Ethernet. In the microtremor measurements, the lateral vibration in the longitudinal and the transverse directions of the test building were measured with three types of locations of the sensors in order to evaluate the vibration behavior along the height of the building and its torsional behavior. The human-powered excitation tests were carried out by pushing walls by eight persons in accordance with the fundamental frequency in the transverse direction, aiming at obtaining larger amplitude than with microtremor. The dataset is useful to deepen the understanding of the dynamic properties of tall timber-concrete hybrid buildings and encourage reasonable structural design and health monitoring of tall mass timber buildings.

A microtremor survey based on ground surface data acquisition was used to identify and characterize the karst area of Cerme Cave, Yogyakarta, Indonesia, from the entrance to the exit of the cave. The entrance and exit of the cave are used as tie-in points because the characteristics of the two locations can be directly observed. Parameters used in this study include ground vibration amplification, shear wave velocity, and Poisson’s ratio. The presence of cavities can be characterized by a relatively strong contrast between these physical parameters and their surroundings. The exit of the cave, which can be considered as a sinkhole, has a dominant frequency of 3.2 to 4.6 Hz, which is relatively higher than that of the surrounding area. At the entrance of Cerme Cave, which has a large cavity, a small ground vibration amplification was detected, less than 0.1. The entrance and exit of the cave also exhibit a low shear wave propagation velocity of less than 350 m/s. The presence of a subsurface fluvial channel in Cerme Cave can be characterized by a high Poisson’s ratio of 0.4–0.5, a gain value of less than 0.1, and a shear wave velocity of less than 350 m/s.

As a widespread geological hazard, the disaster development process of earth fissures is irreversible and difficult to control, which seriously affects the construction and safe operation of engineering facilities. However, few clear conclusions and special regulations have been given regarding the influence of earth fissures on the dynamic response characteristics of a site and earthquake prevention and disaster reduction measures. Therefore, the microtremor was used instead of earthquake motions to reveal the dynamic response of a site with fissures. The earth fissures in the Taiyuan Basin, which exhibit a large amount of activity, were used as representative examples. In order to reveal the dynamic response from several aspects, four methods, including the Fourier spectrum, the horizontal-to-vertical spectral ratio (HVSR), the response acceleration, and the Arias intensity, were employed. The results show that the spectrum peaks increase sharply at an earth fissure and return to a stable value approximately 20–25 m away from the fissure, indicating that the earth fissures have an amplification effect on the dynamic response of the site. Additionally, a greater amplification occurs on the hanging wall of the earth fissure. The influence range of the dynamic response of site can be divided into four areas. Suggestions on the seismic fortification intensity and setback distances were also proposed. After ground motion finite element simulation, the amplification effect of seismic response at the earth fissure site has been further confirmed. The amplification mechanism was summarized as the coupling of the changes in the soil properties caused by earth fissure activity, the catadioptric effect of the earth fissure interface, and the multiple amplifications caused by secondary fissures. [ABSTRACT FROM AUTHOR]

Any public infrastructure has a set service life limit. In the Indonesian case, the public building has a 50-year design life. This paper presents a performance assessment of a multiple-story building in Aceh-Indonesia. A multi-story Faculty of Engineering Universitas Syiah Kuala building was used in this study. This multi-story building structure has been used for more than 24 years since it was built in 1998. This structure is 29.4 m long, 13 m wide, and 14.4 m tall in geometric terms. This study reveals how this three-story building behaves, including displacement, base shear, and structure performance level per ASCE 41-17 criteria. The processes in this study are broken down into various stages, including pushover analysis and comparing the building's current natural frequency. ETABS software was used to model building structures. According to the study, the building's performance is still more or less similar to the initial plan. Pushover in the X-direction (Push X) is believed to be immediate occupancy (IO), and pushover in the Y-direction (Push Y) is believed to be life safety (LS). The pushover analysis results for Push X suggested that the structure is safe and retains rigidity. Push Y indicated minor damage within the life safety category after a service life of 24 years. This pushover analysis indicated that the structure has reduced its rigidity, making it less able to resist further displacement. Based on the base shear, which experiences a displacement that is significantly greater than the estimate at the original planning stage, it is known that stiffness decreases. [ABSTRACT FROM AUTHOR]

This paper presents the effects of waste tires, water content, and relative density on the soil dominant frequency based on experiment. Cylindrical molds with a diameter of 30 cm and height of 50 cm are prepared to understand the effects of these materials. The molds are filled with sand at different relative densities (60% and 80%). In addition, samples are prepared by adding waste tire particles at different rates (0%, 0.5%, 1%, and 2%) to the sand to achieve different relative densities and water contents (0%, 5%, 10%, and 15%). The soil dominant frequency and horizontal/vertical (H/V) amplitude are determined using the microtremor technique by measuring each cylinder for 60 min using a broadband seismometer. Microtremor data are analyzed using the H/V spectral ratio (Nakamura) method. The experimental result shows that the waste tire particles added to the sand decrease the H/V amplitude. The most suitable environment features a relative density of 60%, which is achieved using 1% waste tires and 0% water content. Meanwhile, the most suitable environment has been achieved using 0% water content and 0.5% waste tire ratio for 80% relative density. Using the prepared composite material with waste tires as an additive on the soil may reduce the destructive effects of earthquakes. [ABSTRACT FROM AUTHOR]