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A probabilistic seismic hazard assessment has been carried out along the continental section of the Cameroon volcanic line (CVL) in West Africa. We compiled a catalogue of local earthquakes from different sources and homogenize the magnitudes to moment magnitude (Mw). The seismicity of the CVL is concentrated around Mount Cameroon the active volcano and diffuse on the rest. Three seismic source zones were identified: one in Mount Cameroun, the second NE of the volcano in the grabens of Kumba-Tombel, and the third seismic source corresponds to West Cameroon horst. The recurrence model is that of Gutenberg and Richter, ZMAP software was used to decluster the catalogue and to determine seismic parameters for each source zone. To calculate the hazard, we choose two ground motion prediction equations, and to account for uncertainties, a logic tree approach was implemented using CRISIS software. We estimated the peak ground acceleration (PGA) for eleven cities spread along the CVL, for return period (RP) 475 and 2475 years. The results show that for RP 475 years, Buea, located at the foot of Mount Cameroon, has a PGA of 10% g. This value decreases as one moves away from Buea. The seismic hazard was also calculated for the period of 0.2s. Uniform hazard spectra for RP 475 and 2475 years are plotted for three cities, each chosen in one of the seismic source zone. For each city and RP, the spectral acceleration increases with the period, up to around 0.1s, and then it decreases as the period increases. [ABSTRACT FROM AUTHOR]

In the context of assessing seismic hazard, accurately predicting ground motion stands out as a crucial task. Achieving precision in ground motion modeling proves valuable in revealing the actual pattern, even when faced with insufficient data on soil structure, provided there is precise information about the seismic source. This study introduces a methodology for calculating local- and near-field ground motion, expressed in peak ground acceleration (PGA) and intensity values. The deterministic approach is employed, incorporating source characteristics and one-dimensional (1D) site effects. For the chosen test area, the Ismayilli-Shamakhi region on the southeastern slope of the Greater Caucasus in Azerbaijan, two seismic scenarios are investigated: the 1902 Shamakhi earthquake (magnitude M = 6.8) and the November 25, 2000 Baku-Caspian earthquake (two shocks with moment magnitude Mw = 6.08 and 6.18). Different soil types are considered to validate the proposed methodological procedures. The analysis involves the computation of peak ground acceleration motion for two scenario earthquakes: a local-field event with M = 6.8 and a near-field event with Mw = 6.5, representing the average magnitude of the 2000 Baku-Caspian earthquake. The computed peak ground acceleration values are then used to derive intensities. Notably, the 1902 Shamakhi earthquake and the 2000 Baku-Caspian earthquake exhibit similar trends on surface PGA values. The local-field scenario estimates PGA values ranging from 77 to 328 gal, corresponding to MSK-64 scale intensity levels of VII-IX. The near-field scenario, with PGA values ranging from 28 to 62 gal, aligns with MSK-64 intensity levels of VI–VII. In the final assessment, the amplification factor in the study area varies between 0.55 and 0.83. The seismic hazard level is identified as high in the southern and southeastern regions, particularly in areas with soft shallow and medium-depth soils, indicating a high potential for ground motion amplification. [ABSTRACT FROM AUTHOR]

In this research, we have compiled a catalogue of the worst tsunami earthquakes that caused destruction and losses in the northern coastal region of Egypt. Variability in seismic source parameters reflects the level of cognitive uncertainty that exists because most of these destructive tsunamis, if not all, occurred in the pre-instrumental period. We also synthesized a set of hypothetical tsunamis constrained by seismotectonic knowledge of the area of influence to embrace the uncertainty. We also collected the topo-bathymetry information available to make a simulation on the scale of the Egyptian north coast. The multiple scenarios were computed considering references and hypothetical scenarios, and results were presented in maps and tables for wave heights, inundation depth, and estimated arrivals. Comparisons were made between the results calculated in this study and those from previous studies. These were done to identify and measure the reasons for the difference and similarities. The results may contribute to developing risk reduction strategies and a national early warning system. Variability in tsunami intensity measures is prepared for the hypothetical scenarios due to the difference in the fault's magnitude, location, and geometry. Also, for the first time, temporally based scenarios the sea-level rise and delta sinking were considered in order to highlight the importance of multi-risk analysis for the region of interest. The insight on incorporating other hazards of the temporal resolution indicates a significant increase in inundated areas and wave height. Therefore, proper and detailed estimation of multi-hazard maps for the coastal region of the Nile Delta is highly required to protect the ongoing sustainable development and protect the people and their assets. [ABSTRACT FROM AUTHOR]

As part of a feasibility study for a potential electronuclear power plant in Tunisia, a new seismic catalogue and a new seismic source model have been proposed, for Tunisia and adjacent areas. These findings are used in this study to evaluate the seismic hazard for two selected nuclear power plant sites: Marsa-Douiba in the north and Skhira in the southeast. The investigations and the assessment are conducted at a regional scale. The location of these sites and the choice of a regional review extent allow us to consider the entire Tunisian territory as the study area and also to conduct the hazard evaluation at a 'national level'. In this study, a probabilistic seismic hazard analysis is performed using the R-CRISIS software, and a logic tree is developed to capture uncertainties related to the characterisation of both seismic sources and ground-motion. First, a hazard map of Tunisia for the return period of 475 years is generated to compare it with the ones obtained within previous studies. Then, the 10,000-year return period is considered, and the recommendations of the International Atomic Energy Agency are applied to determine the uniform hazard spectrums and perform disaggregation for the selected sites. [ABSTRACT FROM AUTHOR]

Earthquake Monitoring Center (EMC) at Sultan Qaboos University (SQU) initiated evaluating the seismic hazard in the Sultanate of Oman in 2009. EMC has produced the first probabilistic and deterministic seismic hazard maps for Oman in 2012 and 2013, respectively. In the current study, the probabilistic seismic hazard assessment (PSHA) is revisited to provide an updated assessment of the seismic actions on the Sultanate. The present study has several advantages over its predecessor: using an updated homogeneous earthquake catalogue, recently developed seismic source model; inclusion of epistemic uncertainties for the source models, recurrence parameters, maximum magnitude, and more recent and applicable ground-motion prediction equations (GMPEs). Epistemic uncertainties were treated using a combination of the best available databases within a properly weighted logic tree framework. Seismic hazard maps in terms of horizontal peak ground acceleration (PGA) and 5% damped spectral accelerations (SA) at the bedrock conditions (VS = 760 m/s) for 475- and 2475-year return periods were generated using the classical Cornell-McGuire approach. Additionally, uniform hazard spectra (UHS) for the important population centers are provided. The results show higher values at the northern parts of the country compared to the hazard values obtained in the previous study. [ABSTRACT FROM AUTHOR]

The Samos (Sisam) Island earthquake of October 30, 2020 (11:51:25 UTC, Mw = 7.0, ML = 6.6, depth = 12 km) was a major earthquake with an epicenter in the Aegean Sea, ~ 10 km north of Samos Island and ≥ 40 km from the Aegean region of Turkey. The main stages of this study were the analysis of the aftershock regime of the earthquake, the correlation of this regime with the kinematics and the determination of seismic wave propagation and aftershock duration. In the subsequent 2 months, there were 4783 aftershock earthquakes (1.0 ≤ ML ≤ 5.3) within the earthquake's deformation zone. The cause of the mainshock was an E-W oriented normal faulting, and showed seismotectonic behavior compatible with the active tectonics of western Anatolia. According to the epicenter map of the aftershocks, the October 30, 2020, Samos earthquake process resulted in crust deformation over a total geographical area of 75 km × 41 km. The results of the seismic source propagation showed that there was no spatially or temporally correlated advance in dominant energy release observed around the mainshock hypocenter. A stable decay of aftershock activity was observed from the spatial and temporal analyses of the aftershocks that occurred within 2 months of the mainshock event. Moreover, with the proposed method of this study using the completeness plane technique to estimate the duration of aftershock activity allowed aftershocks to be estimated to last for ~ 2 years. For validation, this method was applied to two previous earthquakes with different faulting mechanisms. [ABSTRACT FROM AUTHOR]

The frequency-magnitude distributions of earthquakes are used in this study to estimate the earthquake hazard parameters for individual earthquake source zones within the Mainland Southeast Asia. For this purpose, 13 earthquake source zones are newly defined based on the most recent geological, tectonic, and seismicity data. A homogeneous and complete seismicity database covering the period from 1964 to 2010 is prepared for this region and then used for the estimation of the constants, a and b, of the frequency-magnitude distributions. These constants are then applied to evaluate the most probable largest magnitude, the mean return period, and the probability of earthquake of different magnitudes in different time spans. The results clearly show that zones A, B, and E have the high probability for the earthquake occurrence comparing with the other seismic zones. All seismic source zones have 100 % probability that the earthquake with magnitude ≤6.0 generates in the next 25 years. For the Sagaing Fault Zone (zones C), the next Mw 7.2-7.5 earthquake may generate in this zone within the next two decades and should be aware of the prospective Mw 8.0 earthquake. Meanwhile, in Sumatra-Andaman Interplate (zone A), an earthquake with a magnitude of Mw 9.0 can possibly occur in every 50 years. Since an earthquake of magnitude Mw 9.0 was recorded in this region in 2004, there is a possibility of another Mw 9.0 earthquake within the next 50 years. [ABSTRACT FROM AUTHOR]

Despite our understanding of the different mechanisms of man-made earthquakes, their short-term prediction and prevention is yet to be attained. In the present study, we propose an integrated four-step approach to predict and prevent man-made earthquakes or reduce their chance of occurrence. Our four-step approach includes locating the highly anomalous zones of microseismic emission (MSE) that result from the stress-deformed state inside a geological formation and often represents the "seismic nuclei" for impending earthquakes, monitoring the variations and dynamics of the anomalous MSE zones over a period of one lunar month, inducing a creep-discharging of the MSE zones using a vibroseis seismic source at the ground surface, and monitoring the same MSE zones following the creep-discharge to determine whether the stress-deformed state was released and the chance of potential earthquake occurrence has been eliminated or reduced. The proposed full four-step approach has never implemented at one single location. Nevertheless, these steps have been tested separately at different sites and have proven successful. We propose conducting the full four-step approach at various locations of potential man-made earthquake activities around the world including the state of Oklahoma in the USA. [ABSTRACT FROM AUTHOR]

A sequence of small-to-moderate terrifying earthquakes occurred in the northern part of the State of Kuwait on November 15, 2019. These earthquakes have certainly been recorded by the Kuwait National Seismological Network (KNSN), where the magnitudes of the earthquakes ranged from 0.8 to 4.1 having focal depths ranging from 2 to 15 km. This sequence of the earthquakes continued to occur for 2 days in a row, where a total of 56 earthquakes were recorded. The objective of this work is to use the available data to determine the seismic source characterizations including fault plane solutions and stress pattern in the vicinity of earthquake sequence area. Detecting and recording the digital waveform of these earthquakes by the KNSN have given us an opportunity to analyze the data of these earthquakes using waveform inversion, focal mechanism, and stress inversion techniques. Using the waveform inversion method, the seismic moment (Mo) and moment magnitudes (Mw) of the two largest earthquakes in this sequence were determined to be 0.1532E+16 and 0.9578E+15 equivalent to Mw 4.1 and 3.9, respectively. The focal mechanism solution of all earthquakes of this sequence indicated that the type of fault was normal faulting with strike-slip component and took a northeast-southwest (NE-SW) direction, and seemingly being compatible with the structure setting of the region and also the direction of earthquakes sequence clustering. Using the multiple inverse method (MIM), the mean stress difference was essentially calculated and found to be 0.549 and sigma1 axis = 76.3/38.0 and sigma3 axis = 189.6/26.9. The acquired results give a clear picture about the structure of the region and may be used later to get acquainted with the type of earthquakes, whether they are of tectonic type, triggered, or induced. [ABSTRACT FROM AUTHOR]

The formation velocity is an important factor affecting the precise location of microseismic source. The establishment of elastic wave velocity model in the monitoring area to satisfy the requirements for precise location of seismic source has been a technical problem for the mine microseismic monitoring. Based on the assumption of horizontal layered medium condition, a new velocity model inversion method has been proposed. According to the concept of equal difference time surface, the first arrival travel time difference between the measured points and datum points is investigated on the basis of the observation point of first arrival travel time duration placed in the middle in the observational network. The minimal difference (double time difference) between the measured first arrival time difference and the calculated first arrival time difference is taken as the constraint condition, and the objective function is constructed to solve the velocity model. The DIRECT fast search algorithm with global optimization characteristics is applied to solve the objective function. This method is used to carry out the trial treatment for the mine microseismic model data and the measured data. The results show that the stratified velocity model under the horizontal layered medium can be obtained by his method using the microseismic data of known seismic source, with a better adaptability to different monitoring systems. Through the test for the actual data of "well-ground" joint microseismic monitoring, the velocity model obtained by the method in this paper can get more accurate location of the seismic source. [ABSTRACT FROM AUTHOR]

The outcomes of this study are necessary to assess seismic hazard in Kuwait. The noticeable increase in urban development and construction of tall structures and skyscrapers highlights the importance of seismic risk analysis and the creation of a unified seismic code for Kuwait. This paper can be considered as an initial step through the assessment and deaggregation of seismic hazards in Kuwait. To achieve this purpose, a complete seismic catalog for Kuwait and the active Zagros Seismic Belt has been created containing all the available historical and instrumental earthquakes, unified in magnitude and foreshocks and aftershocks removed. Alternative seismotectonic models were built basing on structural geological situation, seismicity and focal mechanisms. The recurrence parameters along with the maximum expected earthquake from all seismic sources were basically estimated. Appropriate ground motion prediction relation within a logic tree formulation was fundamentally used in creating seismic hazard maps. A state-of-the-art probabilistic approach is used in this study to produce hazard maps at 75, 475, 975, and 2475 years return periods (equivalent to 50%, 10%, 5%, and 2%, respectively, probability of exceedance in 50 years) at the PGA, 0.1, 1 and 4 s spectral periods. The hazard maps were computed using a spacing grid of 0.1° × 0.1° across the Kuwait area. Uniform hazard spectra and deaggregation of seismic hazard have been established for the governorates of Kuwait. Additionally, a sensitivity analysis was performed for theses governorates to reduce uncertainties in the seismotectonic source models, predictive ground motion equation and maximum expected earthquake magnitude. These results with vulnerability index are essential components for seismic risk analysis in Kuwait. [ABSTRACT FROM AUTHOR]

Near-surface diffractors are one of the problems in land seismic exploration. They can scatter the surface wave energy emanating from the seismic source and contaminate the signal received by seismic receivers. The scattered energy from the near-surface diffractors manifests itself on seismic shot gathers as strong hyperbolic events, called diffractions, masking the weakly reflected body waves. Diffractions present complications to most of surface-wave suppression schemes, especially when they have been scattered by scatterers outside the receiver line. Different methods have been used to eliminate diffractions from seismic data, including geophone arrays, filtering, and inverse scattering. Each of those methods has its own limitations. In this study, we present processing algorithms to map and attenuate near-surface diffractors of surface waves in seismic shot gathers. The mapping algorithm is based on semblance measurements and time-offset relations, while the attenuation algorithm is based on the least-square fitting of a source wavelet. The algorithms are applied on synthetic data from two different models. The first model has three near-surface diffractors, while the second model has three clusters of near-surface diffractors. Each cluster consists of three near-surface diffractors with a different geometry for each cluster. The results show that the proposed algorithms are successful in locating and attenuating most near-surface diffractors, except when the separation between individual diffractors is below the wavelength of the diffracted surface wave. [ABSTRACT FROM AUTHOR]

The province of Isparta is located in the southwest of Turkey and is in a seismically active belt. Many moderate and large earthquakes that occurred in the historical and instrumental periods in the region caused severe losses of life and property. This study aims to calculate the probabilistic seismic hazard analysis (PSHA) of Isparta province, which has the potential to produce earthquakes with magnitudes of six or more due to its active tectonics. It also aims to obtain peak ground acceleration (PGA) maps. A comprehensive and homogeneous data set of Mw≥4 for the period between 1900 and March 2021 was used in the analysis. The estimation of the seismic hazard parameters was based on the Poisson method, and the peak ground acceleration values corresponding to the recurrence period of 475 years were obtained by using two different attenuation relationships. The PGA maps of both attenuation relationships were visualized in the GIS environment. The highest PGA was obtained as 0.52 g from Akkar and Çağnan formula and 0.63 g from Kalkan and Gülkan formula in the Yalvaç district, located in the north of Isparta province. [ABSTRACT FROM AUTHOR]

The objective of this paper was to develop the soil surface seismic hazard maps for the proposed site of Nasser New City, West Assiut, based on probabilistic seismic hazard assessment, mainly in terms of the mean peak ground acceleration (PGA) and spectral acceleration (SA) values. Assessment of soil surface seismic hazard maps is required for disaster preparedness, risk, and hazard mitigation decisions for the study area. To carry out this assessment, soil profile is defined based on soil shear wave velocity that is global Vs30 of USGS. These velocities are converted to site classification based upon the National Earthquake Hazards Reduction Program (NEHRP) guidelines. A seismic hazard evaluation with level hazard 10% probability of exceedance in 50 years in terms of 5% damped peak ground acceleration and spectral acceleration was carried out, PGA and SA values at bedrock, at 0.1, 0.5, 1.0, and 2.0 s spectral period, were calculated at central part of Nasser New City. Using site amplification factors corresponding to various site classes based on Vs30, spatial variation of SA at spectral periods 0.1, 0.5, 1.0, and 2.0 s for 475 years as return period is demonstrated as maps. Results of this work are important for civil engineering purposes, land use planning, and resistant structure design for earthquake. [ABSTRACT FROM AUTHOR]

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A significant amount of energy is released from sub-surface during an earthquake which is caused by seismotectonic activity. The occurrences of earthquake and its distribution pattern are necessary to correlate with concentrated and deviated energy in the sub-surface for better understanding the seismotectonic activity. Hence, the main aim of the present research is to develop hierarchical sub-surface energy anomaly index and its significant on seismotectonic activity by geospatial analysis of the seismic cluster zone and active tectonic signature through geoinformatics for Lower Tista sub-basin, India. In the present research, sub-surface energy has been quantified and threshold energy has been computed to estimate sub-surface energy anomaly in various hierarchical order. Also, the hierarchical sub-surface energy anomaly index has been computed and compared with the seismic cluster zone, seismotectonic activity, and geological formation. The analysis shows that the north and central part of the study region along Rathong chhu, Kalet Khola and Great rangit micro basin denotes as HSEAI Class V which represents low intensity earthquake with clustered concentration and includes in least to weak shaking anomaly zone. This zone is located in the fringe of greater and lesser Himalayan sequence along Main central thrust and inside Ramgarh thrust of lesser Himalayan sequence. It suggests higher energy concentrated and released through micro earthquakes along the active thrust with less energy anomaly. The southern part of the study region in quaternary surface adjacent to Himalayan foothills along Lish, Gish, Chel, and Dharala micro basin denotes as HSEAI Class II which are not resemble with any recent earthquakes and lies on least intensity sub-surface energy anomaly zone. This region intersects the frontal thrust and adjoins with Gish fault and Tista lineament which is presently not in active even though higher energy is concentrated in the sub surface. It suggests the energy anomaly is less even though energy accumulated in the sub-surface which signifies the energy concentrated in the sub-surface but not yet released. It predicts the energy may release with the displacement of thrust in future with higher magnitudes. [ABSTRACT FROM AUTHOR]

The Eastern Anatolia Observatory (DAG), to accommodate a 4-m telescope, is under construction in the city of Erzurum at Karakaya Peak of the Palandöken Mountain Range. Owing to the vulnerability of the telescope and its optical components to earthquakes and the high demand for pointing accuracy for quality astronomical observations, the seismic hazard needs to be reliably determined before any design and construction work begins. A relevant rectangular zone, extending 250 km from the observatory in each direction, is selected as the study area. Then, the seismic hazard at the DAG site is estimated by using the probabilistic hazard analysis method. Using different magnitude scales, several earthquake catalogues are recompiled by converting them into a uniform moment magnitude (Mw) scale, and the seismic sources that could affect the study area are determined. The results are aggregated for epistemic uncertainties using the logic-tree method. Finally, peak ground acceleration (PGA) values are obtained for two recurrence periods corresponding to two different design levels (operating basis and design basis earthquakes) using two different ground motion attenuation models. The disaggregation of the seismic hazard permits association of the PGA estimates with various faults. Disaggregation also provides source information for synthetic ground motion generation. Effects of rupture directivity and topographical amplification are discussed. [ABSTRACT FROM AUTHOR]

In 2016, an earthquake with a magnitude of Mw 7.1 occurred at 01:25 JST (16:25 UTC on April 15, 2016) on April 16, 2016, popularly known as the Kumamoto, Japan, earthquake, following the earthquake with a magnitude of Mw 6.1 that occurred on April 14, 2016, at 21:26 JST (12:26 UTC on April 14, 2016). This was one of the largest earthquakes to occur since the deployment of the Kyoshin network (K-NET) and Kiban-Kyoshin network (KiK-net) after the 1995 Hyogo-ken Nanbu event. In the present study, the 2016 Kumamoto, Japan, earthquake has been simulated using the modified hybrid technique. Out of 53 recorded stations located in the Kyushu region, simulations have been performed at 28 recordings using the modified hybrid technique. Earlier, this technique was independent of site response functions and the high-frequency decay parameter (kappa (κ)). In this study, these two important factors have been introduced. With the help of the selected model, simulated accelerograms and their corresponding Fourier and response spectra for each site have been generated. Later, parameters like duration, PGA, Fourier, and response spectra have been compared with the observed ones at different stations. It was found that the observed PGA at the closest station, KMMH16, located at an epicentral distance of 7 km, was 1155 cm/s2, while the simulated value was 1217 cm/s2. Other frequency domain parameters are very well matched with the observed data at other sites. These studies can help in seismic hazard analysis and in designing earthquake-resistant buildings. [ABSTRACT FROM AUTHOR]

The North Anatolian Fault Zone (NAFZ), which produced the 1999 Golcuk-Izmit earthquake, extends in three branches in the Marmara Region and causes a significant earthquake hazard. This study consists of processing and analysing data from three stations (TUBI, MER1 and DUMT) that are part of the IGS and MAGNET (Marmara Permanent GPS Network) network and are situated close to the epicentre of the Golcuk-Izmit earthquake. By analysing the time series generated from three daily solutions (TUBI, DUMT and MER1 stations), the displacements due to the earthquake were computed (17 August 1999). When GPS processing on 15–16 August 1999, especially for the Golcuk-Izmit earthquake, is examined, it is possible to interpret this situation as a precursor of the earthquake, as a result of the examination of the data obtained from the process of 15 and 16 August 1999. On August 17, 1999, the movement at the TUBI, DUMT and MER1 points before the earthquake was 2–6 cm while it was computed on average 38–86 cm during and after the earthquake. The earthquake clearly had substantial impact on the horizontal components on 17 Aug 1999. The horizontal coordinates of TUBI, DUMT and MER1 stations have changed by around 49–87 cm, and the height components have changes by around 14–137.10 cm based on the time series of coordinate discrepancies. [ABSTRACT FROM AUTHOR]

The frequency–magnitude distribution (b-value) and upper bound magnitude to Gumbel's third asymptotic distribution (ω-value) for the seismicity of the Pamir–Hindu Kush region from March 1949 to December 2018 is analyzed. The seismicity analysis includes an earthquake catalogue of M ≥ 3.0 extracted from National Earthquake Information Center (NEIC), USGS database which displays distribution of the earthquakes (declustered) in the study area. The study area has been divided into sub-zones that include the Hindu Kush, South Pamir, Central Pamir, and North Pamir. The b- and ω-values of the entire region, zones, and cross-sections have been estimated to understand the implications of variations in seismicity among the different parts. Considerable variations in the b- and ω-values are identified with b and ω ranging from 0.99 to 1.47 and 6.20 to 8.27 respectively. According to this study, the seismic zones of Hindu Kush and North Pamir correspond to a "low b-values" and a "very high ω-values" which are associated with the main tectonic features. [ABSTRACT FROM AUTHOR]

A power plant is an essential structure that powers various sectors of the economy. It is vital to ensure the safety of such structures from natural hazards like earthquakes. The probabilistic seismic hazard analysis (PSHA) is the most advanced method of estimating earthquake hazards and risks. PSHA is the standard method for making site-specific, earthquake-resistant designs for important structures like a power plant. In the present study, the PSHA has been carried out for a power plant site in Chittagong using the latest available information on seismicity in the region. An updated earthquake catalog homogenized in uniform moment magnitude scale was prepared for the region. Seismicity analysis was carried out, and the seismicity parameters for the region were estimated from the frequency magnitude distribution plot. The peak ground acceleration (PGA) and the spectral acceleration at the bedrock for 10% and 2% probability of exceedance within 50 years were evaluated using different source models and attenuation relations in a logic tree framework. The site was characterized based on the soil investigation data from 31 boreholes, and amplification factors considering the local geology (SPT-N values) were obtained through ground response analysis. Subsequently, the surface level peak ground acceleration was estimated and depicted as hazard contour maps. The power plant site was observed to have a large spatial variation of seismic hazard at different locations. [ABSTRACT FROM AUTHOR]

Anti-seismic devices are employed to implement the best performance of the structures under earthquakes. In this paper, semi-active tuned mass dampers (SA-TMDs) are studied by considering several combinations of variable friction forces and external disturbances. The variable damping model is used, where the goal consists in estimating the external actions to find the best friction force for system dampening. In particular, general, sinusoidal, and Gaussian dynamic loadings are considered. To obtain the response of the structure and dampers, several numerical solutions have been implemented. Probabilistic and determines analyses have been also developed to study different damper characteristics. Results show that a SA-TMD can reduce the structure displacements up to ~ 70.0% indicating a good performance in controlling different oscillations. This technology not only preserves the integrity of a structure mitigating its vibrations but also improves the life of occupants and their safety and comfort. This is beneficial from the perspective of practical application, and it is an advancement with respect to this theme. [ABSTRACT FROM AUTHOR]

Electrical resistivity and seismic refraction geophysical methods have been used to investigate the competence of the near-surface soil at the proposed College of Engineering, Mountain Top University's permanent site, Makogi-Oba, Ogun State, Nigeria, with a view to determining its suitability for construction purposes. The techniques adopted were the 2D electrical resistivity tomography, 1D vertical electrical sounding, 2D seismic refraction tomography, and the multi-channel analysis of surface wave (MASW). The 2D ERT was first conducted, and this was followed by the vertical electrical sounding at some selected points on the 2D ERT profiles. This was followed by the seismic refraction tomography survey before the multi-channel analysis of surface waves was finally done. The 2D electrical resistivity imaging delineated between three to four geoelectric layers which were interpreted as the clayey topsoil, a clayey-sand/sand layer, a low-resistivity clay, and a bottom clayey-sand/sand layer. The maximum depth probed was 49.7 m. The vertical electrical sounding delineated four geoelectric layers which were interpreted as thin clayey topsoil, a clay layer, a clayey-sand/sand layer, and a bottom clay layer. From the vertical electrical soundings, topsoil resistivity and depth ranged from 12 to 51 ohm-m and 0.4 to 0.8 m respectively, second layer resistivity and depth ranged from 3 to 7 ohm-m and 1.5 to 5.2 m respectively, and third layer resistivity and depth ranged from 13 to 163 ohm-m and 1.6 to 9.1 m respectively. The fourth layer resistivity varied between 3 and 46 ohm-m. Though just relatively competent, the third layer is the most competent layer delineated and depth to this layer ranged between 2.2 and 5.6 m. On the seismic tomography models, only two distinct layers were delineated with the discrimination property being the degree of consolidation of the earth materials. Seismic compressional wave velocity, shear wave velocity, bulk density, compressibility, bulk modulus, shear modulus, and rock-mass quality within the first layer ranged between 511 and 1500 ms−1, 175 and 185 ms−1, 1474 and 1929 kgm−3, 0.5661 × 10−9 and 1.0254 × 10−9 Pa, 0.90146 × 109 and 1.69657 × 109 Pa, 49.95 and 55.36 MPa, and 0.001026 and 0.01 respectively. Within the second layer, seismic compressional wave velocity, shear wave velocity, bulk density, compressibility, bulk modulus, shear modulus, and rock-mass quality ranged between 1042 and 1750 ms−1, 190 and 245 ms−1, 1761 and 2005 kgm−3, 0.1925 × 10−9 and 0.4438 × 10−9 Pa, 2.1096 × 109 and 5.09943 × 109 Pa, 65.16 and 107.62 MPa, and 0.003484 and 0.01778 respectively. The seismic tomography and MASW results confirmed that the top geoacoustic layer is loosely consolidated while the underlying layer is a more consolidated earth material which is predominantly clay. Based on the geoelectric and geoacoustic parameters, any competent material could not be established within the subgrade soils. The clayey-sand/sand layer delineated as the third layer on the VES is recommended for laboratory geotechnical testing to determine if it can support light to medium engineering structures. [ABSTRACT FROM AUTHOR]

We use morphometric and geomorphic approaches in order to evaluate the relative active tectonic index (IAT) of the SW Cameroon Atlantic Coast, including the active Cameroon Volcanic Line (CVL). We determine the linear, areal, relief morphometric parameters and geomorphic indices of 53 drainage basins from the Digital Elevation Model (DEM, 30 m) using Geographic Information System (GIS) interpretive techniques coupled with available geological and field data. The results of the landscape analysis reveal significant variations of the morphometric parameters and geomorphic indices within the study area. The linear (~ 67.92%), areal (~ 94.34%), and relief (~ 86.84%) morphometric parameters, as well as the geomorphic indices (~ 84.91%), indicate a strong structural control. The longitudinal river and normalized stream profiles display complex, stepped, and uneven shapes with knickpoints (Kps). These results highlight the dominance of the tectonic control over the lithological variations and differential erosion. From the IAT values, the area is subdivided into very high (~ 18.87%), high (~ 54.72%), moderate (~ 22.64%), and low (~ 3.77%) tectonic classes. The high-to-very high tectonic activity (~ 73.59%) proves that the SW Cameroon Atlantic Coast is tectonically unstable due to mantle dynamism, CVL activity, and differential erosion. [ABSTRACT FROM AUTHOR]

We compared shear wave velocity (Vs) profiles from multichannel analysis of surface waves (MASW) to downhole Vs profiles measured in 10 boreholes in central Illinois to evaluate the reliability of the MASW Vs profiles measured in glacial deposits. The Vs profiles from the two methods were compared by calculating multiple statistical parameters, including average difference, average relative difference, relative standard deviation, and correlation coefficient resulting in overall average values of 71 m/s, 17%, 17%, and 79%, respectively. Such comparisons showed that the MASW-derived Vs profiles compare fairly well with Vs profiles acquired by downhole logging and that the MASW method provides reliable Vs measurements for mapping subsurface geology in the glacial deposits. We also used the data to investigate the effect of the rapid change in lithology with depth and the number of layers of the initial model input to MASW inversion on the reliability of the measured MASW Vs measurements. The lithologic heterogeneity did not have a significant effect on the MASW-derived Vs measurements. However, using an initial model input to MASW inversion with fewer number of layers has generally improved the accuracy of the MASW Vs measurements. [ABSTRACT FROM AUTHOR]

The seismotectonic activity in Northeastern Egypt is intimately related to the active tectonic structures (mainly faults) which deform the region and induce intraplate seismicity. The present contribution is a new attempt to integrate structural, remote sensing, and seismic data, and implement a reliable geospatial analysis to investigate and assess the nature of the relation between tectonic structures and seismotectonic activity in the Cairo–Suez district which is an active seismic source zone in Northeastern Egypt. The achieved remote sensing and GIS-based geospatial analysis introduces valuable information on the frequency, orientation, and density of investigated tectonic fault trends. The spatial distribution of earthquakes epicenters which recorded during the period (1997–2016) with magnitude (ML ≥ 3.0) is evidently interrelated with the detected tectonic trends, and normal faulting with subordinate shear component is the most focal mechanisms indicated from the analyzed seismic events. The depth analysis of the studied earthquakes suggests a "hard linkage" between the major rift-boundary faults in the northern Gulf of Suez rift and the tectonic trends in the southern domain of the Cairo–Suez district, and thus indicates seismic activity on relatively deeper crustal levels. Most of the studied earthquakes have occurred on the WNW–ESE to NW–SE oriented faults in predominantly extensional to transtensional stress regime, which indicating the WNW to NW tectonic trend as an active fault trend. The intraplate seismotectonic activity in Northeastern Egypt is highly controlled by two active tectonic boundaries, the Red Sea–Gulf of Suez rift and Aqaba–Dead Sea transform (to the east) and the Pelusium Shear System (PSS, to the west). Any reliable hypothetical model explaining the seismotectonic setting in such region would consider the Cairo–Suez district as a large transfer zone transmitting the "far-field" stresses northwestward to the PSS with an effective mechanism keeping the within-plate WNW–ESE, NW–SE, and E–W tectonic trends highly prone to rejuvenation and seismic rupture. [ABSTRACT FROM AUTHOR]

Overlying key strata are regarded as plane-strained beams sandwiched by the soft rock strata in the up and down directions, and are considered elastic media. Based on the theory of the elastic foundation beam, the distribution of energy accumulation and fracture positions before and after the fracture of overlying key strata are derived, and the energy release of fractures in each stratum is calculated. To investigate the impact damage to a roadway owing to the breaking of the key stratum, panel 5312 of Jining No. 3 coal mine is taken as an example. FLAC 3D software was applied to simulate a rock burst on the roadway when the seismic source was located at the overlying key strata and different energy was released. It is shown that the side of the roadway near the working face had a high concentration of vertical stress in the coal, and the dynamic load increment generated by the source broke the static load state and triggered the rock burst. After the burst damage, the decrease in the vertical stress in the coal explained the source of the kinetic energy. With a horizontal deformation velocity of the roadway's surrounding rocks of 1.5 m/s as the limit, the critical energy value for the burst failure caused by the fracture of each key stratum was determined. [ABSTRACT FROM AUTHOR]

The Lombok island is a part of the Sunda Arc, tectonically controlled by the subduction system of the Indo-Australian Plate in the southern part and the Flores thrust in the northern part. A sequence of major earthquakes consisting of Mw 5.9–6.9 struck in July–August 2018 and generated massive loss and damage in the Lombok and neighboring regions. In the current study, we analyzed the seismicity clustering of this series of shallow earthquakes including the seismic data from 2009 to 2021. We applied the logarithmic transformation of the nearest-neighborhood distance (log10η) for the seismic data within the domain of space (magnitude), time (magnitude), and depth (magnitude). The combined relationship between these factors has been estimated, which showed that the seismicity in Lombok island was prominently unimodal and indicated the existence of a single type of statistically distributed earthquake. These relationships also point out a contribution of space, time, and depth of around 32.410%, 54.447%, and 13.143%, respectively. Later, we utilized the Welch power spectrum analysis for log10η and analyzed the performance and complexity of the seismicity. The analysis clearly showed the highest peak that was corresponding to the frequency of series earthquake distribution from 25 July to 8 August 2018. [ABSTRACT FROM AUTHOR]

We use machine learning to identify spatial clusters of earthquakes, besides using multi-criteria decision-making models (MCDM) to estimate earthquake vulnerability in the Himalayan seismo-tectonic zone. Seismicity data from the USGS catalogue having 7687 earthquakes indicate eight active source zones or clusters of earthquakes. The earthquake clusters located in the eastern Himalayas are relatively larger in areal extent than those in the western Himalayas. The vulnerability was assessed using two MCDM models, i.e. fuzzy analytical hierarchy process (AHP) and fuzzy technique for order preference by similarity to ideal solution (TOPSIS). Twenty-six parameters were utilised to estimate physical, societal, geotechnical and structural vulnerabilities and integrated earthquake vulnerability map. The results show that more than 50% of the population residing in the region are relatively highly vulnerable due to earthquakes, ~ 25.81% are moderately vulnerable, and ~ 23.44% have low to very low vulnerability. Identifying the most active source zones and estimating vulnerability could be extremely useful for hazard mitigation in the Himalayan region. [ABSTRACT FROM AUTHOR]

In this recent study, six different hybrid soft computing techniques namely artificial neural networks-artificial bee colony (ANN-ABC), artificial neural networks-ant colony optimization (ANN-ACO), artificial neural networks-ant lion optimizer "ANN-ALO", artificial neural networks-imperialist competitive algorithm (ANN-ICA), artificial neural networks-shuffled complex evolution (ANN-SCE), and artificial neural networks-teaching–learning-based optimization (ANN-TLBO) were used to evaluate the liquefaction probability of soil based on reliability analysis. To compare the accuracy of the presented prediction models, a reliability index, score analysis, and error matrix have been carried out, in addition to construction of Taylor diagram and REC curve to demonstrate the relative performances of various models used in present study. While all of the given approaches could efficiently predict the probability of liquefaction, ANN-ALO has been found to give the best prediction effectiveness. It is found that the performances of the other five hybrid models are very similar; although, ANN-ALO (R2 = 0.682 for training and R2 = 0.723 for testing) hybrid model comprehensively outperforms them. The error parameters reported by various machine learning models such as ANN-ABC (R2 = 0.680 for training and R2 = 0.701 for testing), ANN-ACO (R2 = 0.674 for training and R2 = 0.713 for testing), ANN-ICA (R2 = 0.681 for training and R2 = 0.720 for testing), ANN-SCE (R2 = 0.656 for training and R2 = 0.702 for testing), and ANN-TLBO (R2 = 0.675 for training and R2 = 0.713 for testing) have been found to be lying in the acceptable range and hence considered reliable. Therefore, developed models can also be utilized as a valid model for predicting the probability of liquefaction for very complicated real-world earthquake engineering challenges, according to the findings of the present study. [ABSTRACT FROM AUTHOR]

Small strain dynamic properties of soil are the primary input parameter in seismic ground response analysis studies. This study examines the small strain shear modulus (Gmax) and damping ratio (ξ) using bender element (BE) tests on subsoil samples along with evaluation of liquefaction potential (sandy soil) using well-accepted cyclic resistance ratio relationship collected from a railway construction site at Agartala, North Eastern (NE) state of India. The objective of this study is to develop a database and empirical relationship on dynamic properties of Agartala soil which may help to carry out future site-specific seismic hazard studies of Agartala city and other regions with similar soil properties. Experimental results indicate that shear wave velocity (Vs), Gmax, and ξ vary within a wide range such as 60.61 to 234.64 m/s, 5.3 to 104.6 MPa, and 8.9 to 22.1%.respectively depending upon the type of soil and a closed form empirical equations are proposed to calculate Gmax for different types of soil. Besides, a validation study also highlights well agreement of results on Vs obtained through experimental measurement and field in situ-based relationship. Finally, higher liquefaction susceptibility of the study area is reported based on calculated liquefaction potential index (LPI). [ABSTRACT FROM AUTHOR]

Nearly 108-km lengths of Mersin shores are composed of natural beaches. The region is located between major tourist centers. In the future, this region is thought to be built with a great number of tourist facilities. Turkey's largest seaport, Ataş refinery (Mersin International Port) is located in Mersin. Recently, Mersin is becoming of great importance to Turkey as the latter plans to construct its second nuclear power plant in the region. Therefore, as nuclear power plants are built to withstand environmental hazards, it is very important to analyze the seismic risk of the areas where the nuclear power plant will be constructed. The region is located between the East Anatolian Fault Zone and Center Anatolian Fault Zone. Based on the Turkey Earthquake Regions Map, Mersin is divided into second-, third-, and fourth-degree earthquake regions. In this study, we sampled earthquakes of magnitude of 4.0 or greater between 01 Jan 1900 and 31 Dec 2010 in the area; seismic hazard of Mersin province was estimated with probabilistic and statistical methods. The study area was selected as the coordinates between 36.03° and 37.42° North and 32.57° and 35.16° East. On the study area, different scaled magnitude values in the last 110 years converted to a common scale (Mw) and earthquake catalog was re-compiled and also seismic sources that may affect the area was determined. In this study, the seismic hazards of the region were obtained using the methods of probability and statistics. This study used three different attenuation relationships. Using the attenuation relationships suggested by Boore et al. (Seismol Res Lett 68(1):128-153, ) and Kalkan and Gülkan (Earthquake Spectra 20:1111-1138, ), the largest ground acceleration which corresponds to a recurrence period of 475 years was found as 0.08-0.09 g and Akkar and Çağnan (Bull Seismol Soc Am 100 6:2978-2995, ), 0.04 g for bedrock at the central district. When computing for seismic hazard curves, Mut district appears to have a greater seismic hazard compared with other districts. Moreover, according to the attenuation relationships, seismic hazard curves corresponding to a recurrence period of 475 years were obtained for the Mersin Central, Mut, Erdemli, Çamlıyayla, and Tarsus districts. [ABSTRACT FROM AUTHOR]

The Gutenberg-Richter parameters (a and b), fractal dimension (DC), and relationships between these parameters are calculated for different regions of the North of Central-East Iran Blocks (NCEIB). The whole examined area (between 34°-36° N and 55°-61° E) is divided into 55 equal square grids. Both the a and b values for the frequency-magnitude distribution (FMD) and DC are investigated simultaneously from 55 equal square grids. By using the completeness earthquake dataset for earthquakes of the instrumental period from 1976 to 2015, it is concluded that calculated values of a, b, and DC imply variations of seismotectonic stress. The most vulnerable regions for occurrence of the large earthquakes in the NCEIB are considering the computed lowest b values and the highest DC values. The relationships among DC-b and DC-(a/b) are used to classify the level of earthquake hazards for individual seismic source zones, in which the calibration curves illustrate a positive correlation among the DC and b values (Dc = 0.609 b − 0.008) and also a positive correlation among the DC and a/b ratios (Dc = 0.069 a/b + 0.215) having similar regression coefficients (R2 = 0.80 to 0.87) for both regressions. It is observed that the relationship among a/b and DC may be used for evaluation of seismicity and earthquake hazard assessment because of the high value for correlation coefficients and limited scattering of the calculated parameters. [ABSTRACT FROM AUTHOR]

A study was performed by equivalent linear 1D ground response analysis to obtain the influence of local soil sites in altering induced bedrock ground response for Kathmandu. Different types of soil with their dynamic soil behavior were modelled. Three input ground motions, namely, Gorkha earthquake, Loma Gilroy earthquake, and Kobe earthquake, were selected to perform the ground response analysis. The result shows higher value of amplification for Gorkha earthquake, 2015, as compared to other input motions. For the locations comprising of clay soil deposit, the amplification in terms of peak ground acceleration (PGA) was observed to be higher for all studied input ground motions. The amplitude amplification in terms of PGA, peak ground velocity (PGV), peak ground displacement (PGD), profile plot, and response spectra were mapped with the input of Gorkha earthquake, 2015. Also, the spectral acceleration results of specific sites were compared with recommended design spectra of Indian Standard seismic code (IS 1893 2016) and Nepal Building code (NBC 105 2020) by considering soft soil and very soft soil as per IS 1893 2016 and NBC 105 2020, respectively, for 5% damping ratio. From this study, the peak spectral acceleration for various locations of Kathmandu valley were estimated to be 0.41 to 1.26 g. Moreover, for the regions comprising of shallow bedrock, spectral acceleration was obtained to be higher for lower period of vibration, and if the bedrock is at higher depth, spectral acceleration was higher for longer period of vibration. [ABSTRACT FROM AUTHOR]

The main aim of this research focuses on the seismo-geodetic data integration to identify the origin-time of seismic precursors through the ionospheric total electron content (TEC) parameter. The case study concerns the moderate-sized earthquake (Mw = 5.7) that occurred in Ain Témouchent-northwestern Algeria on December 22, 1999. The adopted approach is to reproduce the Global Positioning System (GPS)_TEC time-series signal in order to identify large-amplitude electron density perturbations in the ionized layer of the Earth’s atmosphere. Thus, we propose an analytical and interpretive method to identify the seismo-ionospheric precursor occurrence time of the polarized signal during the earthquake preparation phase. For this purpose, the use of geodetic data derived from signal processing of dual-frequency permanent ground-based GPS/Global Navigation Satellite Systems (GNSS) receivers allowed us to identify ionospheric disturbances preceding the triggering of the mainshock. Furthermore, modeling the time occurrence of aftershocks revealed a strong correlation exists between the seismo-ionospheric precursors and the main aftershocks. Space geodesy techniques integrated into seismic networks achieve valuable enhancement to reinforce the Earthquake and Tsunami Early Warning System. [ABSTRACT FROM AUTHOR]

Applying the equivalent medium method, a dynamic constitutive equation of rock with three-dimensional geo-stress is constructed by modifying the Kelvin-Voigt model, and a theoretical model of stress wave propagation through a three-dimensional geo-stressed rock is proposed. Based on the theory of one-dimensional stress wave propagation, the wave equation of the theoretical model is derived, and the analytical formulas of the stress wave propagation velocity, spatial attenuation coefficient and response frequency are obtained by using harmonic solution. Based on stress wave propagation experimental, the proposed theoretical model is verified by comparing the experimental and theoretical results. Based on the validated theoretical model, the effects of three-dimensional geo-stress on stress wave propagation velocity, spatial attenuation coefficient and response frequency are studied by using the parametric study. The results show that the proposed model of stress wave propagation can effectively study the propagation of stress wave in three-dimensional geo-stressed rock. Three-dimensional geo-stress varies the level of a rock porosity and damage, which makes the rock have different equivalent modulus, and then affects the stress wave propagation characteristics. Moreover, the initial porosity, initial elastic modulus, viscosity coefficient of a rock and vibration frequency have significant influence on the stress wave propagation velocity, spatial attenuation coefficient and response frequency. [ABSTRACT FROM AUTHOR]

A magnetotelluric (MT) station was installed in the northern part of Algeria in December 2014 with the aim of investigating any electromagnetic phenomena related to crustal activities. Significant changes in the five channels of the MT signal amplitude were observed during a sequence of minor to light earthquakes that occurred in the vicinity of the MT station. We applied the singular spectral analysis (SSA) method to the recorded magnetotelluric time series in order to discriminate the co-seismic electromagnetic signals. In particular, we investigated the reconstructed components extracted from the telluric and magnetic field components. Based on the obtained results, the co-seismic electric signal can be found in the third reconstructed component for the two electric field components. On the other hand, the three magnetic components do not present the same results after the application of the SSA technique, where the co-seismic magnetic signal can be found in different reconstructed components. In this work, the adopted analysis method has shown its ability to clearly detect co-seismic electromagnetic signals in the magnetotelluric time series. The primary goal of this work is to implement an effective algorithm for detecting clearly co-seismic electromagnetic signals. [ABSTRACT FROM AUTHOR]

This paper reports for the first time a detailed structural evolution, the emplacement, and geomorphological controls of groundwater seepage phenomenon in the Maloney Ridge Keffi, Central Nigeria. The series of NNW-SSE and E-W ductile compressional regimes that affected the Precambrian tectono-metamorphic basement rocks created antiformal and synformal structures whose eastern outer skins have been eroded from the Precambrian to recent. The Maloney Ridge crest whose 020° axis has been thrust northwards by a possible two-stage vertical reverse faulting (the first of which is consistent with the axis of the ridge, and the second, along an E-W plane) resulted in averagely 20° plunges in the stretching/mineral lineation preserved as augens, slightly mylonitic quartz ribbons, and stretched xenoliths in the gneisses with trends concordant with the metamorphic 020° planes of foliation. Later NW-SE and E-W ductile-cum-brittle shears and fractures development preserved sets of NW-SE and E-W dipping and vertical fractures, many of which have been filled with late-stage magmatic quartzofeldspathic veins and beryl-bearing pegmatites in line with the regional Pan-African fabric of Central Nigeria. Detailed analyses of the fractures around Tudun Amama northern section of the Ridge, the epicenter of the seepage distribution which increases vertically and outward along a centrally warped horizontal collection plane which intercepts the rising water table during the 3 months of monitoring, led to the development of a model that shows that there exist along the axis of the ridge a direct geomorphological and structural relationship with these seepages. The geomorphological depression at that section of the ridge could be an earlier dip-slip structural failure that reached deeper levels and so justifying the higher concentration of the seepages at that section of the ridge. We conclude that, contrary to the general assumption that the area and especially the ridge is unproductive in terms of groundwater, systematic targeting of these intercepting fractures which are deep enough to intercept the fluctuating water table level can result in good yielding boreholes. Sections of roads adjoining such portions along the ridge which have been stubborn in terms of failures will require engineering designs to handle such problems. [ABSTRACT FROM AUTHOR]

The Jammu region is located in the Northwestern Himalayas, which has been hit by moderate to large magnitude earthquakes regularly, including the deadliest 2005 Kashmir earthquake in Muzzafarabad. In this study, deterministic and probabilistic seismic hazard assessment of the Jammu region was carried out based on a logic tree framework. Within a 350-km radius of the Jammu, all potential seismic sources were identified, and an updated earthquake catalogue was prepared, spanning the years 1520 AD to 2020 AD. In DSHA, a hybrid scenario is developed using two independent earthquake scenarios. Three declustering algorithms with four GMPEs for active shallow crustal and Himalayan region clubbed to form a hybrid model for PSHA. Peak ground acceleration and peak spectral acceleration at 0.2 s and 1.0 s were estimated for 2% and 10% probability of exceedance in 50 and 100 years. For rock site conditions, the seismic hazard curves and uniform hazard response spectrum are presented for ten main cities of the Jammu region. This area shows the peak ground acceleration (PGA) variation between 0.08 and 0.66 g with maximum hazard in the southwestern part comprising of districts of Poonch, Rajouri, and Jammu, and parts of Reasi. IS-1893 (2016) suggested 0.24 g for a 2% probability of exceedance in 50 years which is significantly higher than PGA predicted in the present study. The hazard values will be useful for the designing of structural elements of infrastructure projects in this region. [ABSTRACT FROM AUTHOR]

Probabilistic seismic hazard analysis (PSHA) is nowadays the more complete analysis method to estimate the seismic input for structural analysis. However, it is strongly influenced by seismogenic parameters and attenuation equations. Here PSHA using empirical Green's functions (EGFs) with 2 + 2 variables is carried out, which, as proposed, are related to each other through the moment magnitude. This combination, already known as "physically based PSHA (pb-PSHA)," is an approach that should be disseminated since it could provide a good alternative in countries where the seismogenic zones and/or attenuation equations are not well established. The proposed model, using differential equations, is based on a linear fault, random/periodic/impulsive/linear source functions, and punctual hypocenter. Results are shown in terms of new seismic parameters, specific return periods, and ground accelerations. The studied country is Portugal since it appears to the authors that no study has been published about pb-PSHA for Portugal. In this sense, the model could be of importance for hazard analyses to incentivize more research on the earthquake source physics. [ABSTRACT FROM AUTHOR]

This study highlights the 2D rupture propagation of 2005 M7.6 Kashmir earthquake. Beamforming and multi signals classification (MUSIC) back projection techniques are applied on the recorded seismic waves of teleseismic seismometers to model the rupture propagation of 2005 M7.6 Kashmir earthquake. These techniques are robust enable to model propagated rupture extents and rupture phases as the event data is available with the teleseismic seismometers. The imaging of the 2005 M7.6 Kashmir earthquake source propagation with beamforming technique shows three phases of rupture propagation of 10, 10, and 25 s with the velocity of 0, 2.2, and 1.9 km/s respectively. While resolving the rupture propagation with MUSIC, it is observed that rupture propagated 26 and 14 s covering distance of 50 and 31 km respectively. Both techniques confirm the bidirectional rupture propagation with various velocities and time. Both the rupture speed and duration vary due to both applied technique resolutions. Our findings are quite consistent with the published slip models of the Kashmir earthquake. The modeling of 2005 Kashmir earthquake propagation provides key information about the mechanics of Bagh-Balakot Thrust, western Himalaya side. [ABSTRACT FROM AUTHOR]

Resonance in the soil increases the earthquake force applied to buildings and can lead to serious damage to structures. Due to the importance of the resonance in soil for structural design, this study attempted to clarify the effect of earthquake signals' nonlinear dynamic properties on soil resonance. This objective was accomplished by generating an artificial soil profile using DEEPSOIL software, which contained 16 layers and had a shear wave velocity (m/s) of 987.025696004126. Ten common strong ground motion records were applied to a soil profile. First, resonance in the soil was investigated in response to the application of ten ground motions. Subsequently, the nonlinear dynamic properties of the earthquake acceleration time series were investigated, and the relationship between the earthquake signals' nonlinear dynamic properties and the resonance in the soil was evaluated. The results indicated that ground motions with symmetrical or right tail multifractal singularity spectrum curves triggered resonance probability in soil. Ground motions with a mono-scale structure raised the likelihood of resonance in soil more than motions with a multifractal structure. The soil resonance probability was augmented by long memory and the anti-correlated behavior of the ground motions. The findings suggest that in the case of structural design, when assessing the risk of resonance in the soil, the only ground motions considered should be those having at least one condition of the mono-scale structure or multifractal structure with symmetrical- or right-tail singularity spectrum. [ABSTRACT FROM AUTHOR]

There is a limited number of published data regarding the tectonic style of the foreland of the Bitlis-Zagros Suture Zone in southeast Turkey. Particularly, the relationship between buried thrust faults and blind thrusts is unclear. The location from where the subsurface data of this paper was obtained lies 40 km north of Diyarbakır, and this data has provided an opportunity to define blind thrust related folding and discuss its relationship with the buried thrust faults determined by the earlier work. The 3D land seismic reflection data were recorded for hydrocarbon exploration where the top of the Hoya Formation is defined. The folding of Hoya Formation is interpreted to be related to the blind thrust and back thrust. During the interpretation, the attribute modules of the current seismic interpretation software were used, of which the Fault Likelihood and Automatic Fault Interpretation (AFI) attributes have especially been beneficial. The blind thrust related folding defined in this paper has no surface expressions unlike its counterparts related to the Ergani-Silvan and Mardin blind thrust zones located in the north and south, respectively. The depth and location of the blind thrusts and related structures defined in this paper suggest that they are younger than the buried thrusts and may represent the continuation of the Ergani-Silvan blind thrust. [ABSTRACT FROM AUTHOR]

Data collection and classification for earthquake damage to tunnels and the analysis of the influencing factors are important for the anti-seismic design of tunnels. The first purpose of this review is to briefly review the seismic damage types of mountain tunnels from the perspectives of both the tunnel body and the tunnel portal. Then, damage influencing factors for mountain tunnels are explored from the perspectives of earthquake parameters, geology conditions, and tunnel structure characteristics. Finally, some suggestions are made to reduce the earthquake disasters of mountain tunnels. It is believed that this study will contribute to the earthquake disaster control and prevention design of future mountain tunnels. At the same time, it can always remind us that the tunnel earthquake disaster cannot be ignored and requires continuous in-depth research. [ABSTRACT FROM AUTHOR]

Uttarakhand, a state located in the seismically active western Himalayas (India), has witnessed several high magnitude earthquakes in the past. It falls under zones IV (severe) and V (very severe) as per the seismic code of India. The region has several major hydroelectric and infrastructural projects that are presently operational and in the planning stages. Therefore, it is necessary to determine the area expected to be affected by the seismic activity in this region. The seismic hazard assessment of the study area was conducted using the Cornell–McGuire approach. A comprehensive earthquake catalog was prepared considering all the earthquakes occurrences within a 300-km radius of the study area. The catalog was declustered and homogenized into a single-moment magnitude scale considering different region-specific conversion relationships. The study area was divided into ten discrete seismogenic source zones. These source zones were modeled as separate area sources. For each of these zones, seismicity parameters were evaluated using the earthquake catalog and tectonic framework. The hazard assessment at the bedrock level was carried out by combining regional and global attenuation models in a logic tree architecture. The seismic hazard at the surface level was evaluated based on suitable site amplification factors determined for different site classes using shear velocity in the top 30 m (VS30) obtained from the topographic gradient. The results were presented in terms of Arias intensity and peak ground acceleration (PGA) hazard maps for 2% and 10% probability of exceedance in 50 years. The analysis observed that 80 % of the study area is highly vulnerable to seismic hazards, including landslides/rockslides. The predicted ground motion intensity in this study will aid in the safe design of structures and the proper planning of important infrastructure projects. [ABSTRACT FROM AUTHOR]

Earthquake ground motion model is an essential part of seismic hazard assessment. The model consists in several empirical ground motion prediction equations (GMPEs) that are considered to be applicable to the given region. When the recorded ground motion data are scarce, numerical modeling of ground motion based on available seismological information is widely used. We describe results of stochastic simulation of ground motion acceleration records for western Saudi Arabia. The simulation was performed using the finite fault model and considering peak ground acceleration and amplitudes of spectral acceleration at natural frequencies 0.2 and 1.0 s. Based on the parameters of the input seismological model that were accepted in similar previous studies, we analyze influence of variations in the source factor (stress drop) and in the local attenuation and amplification factors (kappa value, crustal amplification). These characteristics of the model are considered as the major contributors to the ground motion variability. The results of our work show that distribution of simulated ground motion parameters versus magnitude and distance reveals an agreement with the GMPEs recently used in seismic hazard assessment for the region. Collection of credible information about seismic source, propagation path, and site attenuation parameters using the regional ground motion database would allow constraining the seismological model and developing regional GMPEs. The stochastic simulation based on regional seismological model may be applied for generation of ground motion time histories used for development of analytical fragility curves for typical constructions in the region. [ABSTRACT FROM AUTHOR]