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Bahuguna, Ashish, and Arjun Sil. "Comprehensive Seismicity, Seismic Sources and Seismic Hazard Assessment of Assam, North East India." Journal of Earthquake Engineering 24, no. 2 (April 11, 2018): 254–97. http://dx.doi.org/10.1080/13632469.2018.1453405.
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Chandan Dey, Santanu Baruah, Bijit Kr Choudhury, Timangshu Chetia, Sowrav Saikia, Antara Sharma, and Manoj K Phukan. "Living with Earthquakes: Educating masses through earthquake awareness: North East (NE) India perspective." Annals of Geophysics 64, no. 3 (July 23, 2021): SE330. http://dx.doi.org/10.4401/ag-8479.
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Earthquake is one of the most frightening and destructive phenomena of nature. The northeast India region, as well as its adjoining South-Asian neighbours including Myanmar and Bangladesh, is tectonically and seismically most active. The region categorized under the highest level of seismic hazard potential: Zone V, of the seismic zonation map of India, has experienced nearly 22 large (M ≥7.0) and two great earthquakes (M S ∼ 8.7) in the past 130 years. All these earthquakes caused wide-spread damage over the region. In the recent past, with rapid urbanization combined with a significant population rise as compared to those times when these great/large earthquakes occurred, the seismic vulnerability index has increased manifold. The situation demands widespread dissemination of seismic hazard and preparedness information via community engagement and highlighting on potentially tragic consequences of earthquakes by conducting extensive mock drill exercises & earthquake awareness programmes. In this paper, the role and efforts of the statuary bodies in the region, such as National Disaster Management Authority (NDMA) and CSIR – Northeast Institute of Science and Technology (NEIST) and societal program of Academy of Scientific and Innovative research, to mitigate and minimize seismic hazard by extensive dissemination of earthquake information, via scientific scenario and impact assessment, is holistically compiled.
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Borah, Niranjan, and Abhishek Kumar. "Probabilistic seismic hazard analysis of the North-East India towards identification of contributing seismic sources." Geomatics, Natural Hazards and Risk 14, no. 1 (December 27, 2022): 1–38. http://dx.doi.org/10.1080/19475705.2022.2160662.
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Joshi, A., Kapil Mohan, and R. C. Patel. "A deterministic approach for preparation of seismic hazard maps in North East India." Natural Hazards 43, no. 1 (April 21, 2007): 129–46. http://dx.doi.org/10.1007/s11069-007-9112-7.
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Tirmizi, Osman, Shuhab D. Khan, Sara Mirzaee, and Heresh Fattahi. "Hazard Potential in Southern Pakistan: A Study on the Subsidence and Neotectonics of Karachi and Surrounding Areas." Remote Sensing 15, no. 5 (February 26, 2023): 1290. http://dx.doi.org/10.3390/rs15051290.
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Coastal communities in deltaic regions worldwide are subject to subsidence through a combination of natural and anthropogenic processes. The city of Karachi in southern Pakistan is situated along the diffuse western boundary of the tectonically active Indian Plate, making it more susceptible to natural subsidence processes from plate motion-related deformational events such as earthquakes and faulting. Karachi has a dense population of over 16 million people, and determining the rate of subsidence and extent of neotectonic activity is crucial for mitigating seismic hazards. Excessive abstraction of groundwater and extensive groundwater use in irrigation are some of the anthropogenic contributions to subsidence in the area. A combination of the lack of historical data and few previous studies of the area make it difficult to determine the rate and extent of deformation in this region. We present an analysis of subsidence and neotectonic activity in Karachi and its surrounding areas using Interferometric Synthetic Aperture Radar (InSAR) timeseries techniques. The InSAR results for satellite LOS velocity change in both ascending and descending Sentinel-1 tracks indicate subsidence in key residential and industrial areas. Further decomposition into two dimensions (east–west and vertical) quantifies subsidence in these areas up to 1.7 cm per year. Furthermore, InSAR data suggest the presence of an active north–east dipping listric normal fault in North Karachi that is confirmed in the shallow subsurface by a 2D seismic line. Subsidence is known to cause the reactivation of faults, which increases the risk of damage to infrastructure.
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Raghu Kanth, S. T. G., and Sujit Kumar Dash. "Deterministic seismic scenarios for North East India." Journal of Seismology 14, no. 2 (April 24, 2009): 143–67. http://dx.doi.org/10.1007/s10950-009-9158-y.
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Pallavi, Ranjit Das, Sandeep Joshi, Claudio Meneses, and Tinku Biswas. "Advanced Unified Earthquake Catalog for North East India." Applied Sciences 13, no. 5 (February 22, 2023): 2812. http://dx.doi.org/10.3390/app13052812.
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Northeast India is one of the world’s most seismically active regions. The event data included in this research for the period 1737–2012 is mostly obtained from worldwide database agencies such as ISC, NEIC, and GCMT. Historical seismicity is collected from published and unpublished documents and some earthquake events are collected from the Indian Meteorological Department Bulletins. As the Mw scale is developed and validated in the southern California region and overestimates the smaller magnitude earthquakes, therefore, recent literature suggested an improved version of the seismic moment magnitude scale (Mwg) applicable for the entire globe considering both long- and short-period frequency-spectra using modern instrumental data. To update the earthquake catalog of Northeast India, we prepared empirical relationships between different magnitudes to Mwg using robust statistical General Orthogonal Regression. A procedure is also suggested for converting different earthquake sizes towards seismic moment scale. The Magnitude of Completeness (Mc) and the Gutenberg–Richter (GR) recurrence parameter values for the declustered homogenized catalog in four time periods, namely 1737–1963, 1964–1990, 1964–2000, and 1964–2012, have been computed. Our analysis suggests that the use of the Mwg scale improves seismicity parameters ‘b’ up to 30%, ‘a’ up to 17%, and ‘Mc’ up to 18% for the Northeast India region. A complete unified earthquake catalog in terms of advanced seismic moment magnitude scale could help understand seismicity and earthquake engineering studies of the region.
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Haerifard, S., H. Jarahi, M. Pourkermani, and M. Almasian. "Seismic Hazard Assessment at Esfaraen‒Bojnurd Railway, North‒East of Iran." Geotectonics 52, no. 1 (January 2018): 151–56. http://dx.doi.org/10.1134/s0016852118010041.
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Carlton, Brian, Andy Barwise, and Amir M. Kaynia. "Seismic Hazard Assessment for a Wind Farm Offshore England." Geotechnics 2, no. 1 (January 6, 2022): 14–31. http://dx.doi.org/10.3390/geotechnics2010002.
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Offshore wind has become a major contributor to reducing global carbon emissions. This paper presents a probabilistic seismic hazard analysis for the Sofia Offshore Wind Farm, which is located about 200 km north-east of England in the southern North Sea and will be one of the largest offshore wind farms in the world once completed. The seismic source characterization is composed of two areal seismic source models and four seismic source models derived using smoothed gridded seismicity with earthquake catalogue data processed by different techniques. The ground motion characterization contains eight ground motion models selected based on comparisons with regional data. The main findings are (1) the variation in seismic hazard across the site is negligible; (2) the main source controlling the hazard is the source that includes the 1931 Dogger Bank earthquake; (3) earthquake scenarios controlling the hazard are Mw = 5.0–6.3 and R = 110–210 km; and (4) the peak ground accelerations on rock are lower than for previous regional studies. These results could help guide future seismic hazard assessments in the North Sea.
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Rizzo, Paul C., N. R. Vaidya, E. Bazan, and C. F. Heberling. "Seismic Hazard Assessment in the Southeastern United States." Earthquake Spectra 11, no. 1 (February 1995): 129–60. http://dx.doi.org/10.1193/1.1585806.
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Comparisons of response spectra from near and far-field records to those estimated by attenuation functions commonly used in evaluating seismic hazards show that these functions provide reasonable results for near-field western North American sites. However, they estimate relatively small motions for far-field eastern North American sites, which is contrary to the empirical evidence of the 1886 Charleston and 1988 Saguenay Earthquakes. Using the 1988 Saguenay records scaled for magnitude, and several western North American records scaled to account for the slower attenuation in the east, we have developed deterministic median and 84th percentile, 5 percent damped response spectra to represent ground motions from a recurrence of the 1886 Charleston Earthquake at a distance between 85 to 120 km. The resulting 84th percentile spectrum has a shape similar to, but is less severe than, the USNRC Regulatory Guide 1.60 5 percent damped spectrum tied to a peak ground acceleration of 0.2g.
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Rahman, T., L. Ricky, and Chhangte. "Estimation of probabilistic seismic hazard for Aizawl city in North Eastern India (NEI)." IOP Conference Series: Earth and Environmental Science 491 (July 8, 2020): 012028. http://dx.doi.org/10.1088/1755-1315/491/1/012028.
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Drogreshka, Katerina, Jasmina Najdovska, and Dragana Chernih-Anastasovska. "SEISMIC ZONES AND SEISMICITY OF THE TERRITORY OF THE REPUBLIC OF NORTH MACEDONIA." Knowledge International Journal 31, no. 3 (June 5, 2019): 669–74. http://dx.doi.org/10.35120/kij3103669d.
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According to all sources of data available to the Seismological Observatory the seismic activity in the Republic of North Macedonia is mainly tectonic, with the exception of weak collapse earthquakes. This seismic activity is caused by its affiliation to the Mediterranean area of the Alpine-Himalayan orogeny belt. Epicentral areas belong to the three main seismic zones, West-Macedonian seismic zone, Vardar seismic zone and East-Macedonian seismic zone. Three secondary seismic zones, transverse to the main seismic zones, are also defined. Each of these zones is characterized by а specific time and space distribution of earthquake locations, with frequent seismic microactivity, lot of minor to light earthquakes and very rare moderate to major earthquakes. Observed seismic activity on the territory of the Republic of North Macedonia has a main role for the evaluation of the seismic hazard of the specific territory.
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Kumar, Susheel, and Nitin Sharma. "The seismicity of central and north-east Himalayan region." Contributions to Geophysics and Geodesy 49, no. 3 (September 1, 2019): 265–81. http://dx.doi.org/10.2478/congeo-2019-0014.
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Abstract The Himalayan range extends upto 2400 km arc from Indus river valley in the west to Brahmaputra river valley in the east of India. Due to distinct geological structures of Himalayan seismic belt, seismicity in Himalaya is inhomogeneous. The inhomogeneity in seismicity is responsible for a number of seismic gaps in the Himalayan seismic belt. Thus Iin the present study, we proposed the study of spatial and temporal evolution of seismicity in entire central and north-east Himalayan region by using Gutenberg-Richter relationship. A detailed study on the behavior of natural seismicity in and around the seismic gap regions is carried out. The study region is segmented in four meridional regions (A) 80°E to 83.5°E, (B) 83.5°E to 87.5°E, (C) 87.5°E to 90°E and (D) 90°E to 98°E along with a fixed latitude belt. The homogeneous catalogue with 3 ≤ Mb ≤ 6.5 is used for the spatial and temporal analysis of seismicity in terms of b-value. It is find out that pockets of lower b-values are coinciding over and around stress accumulated regions. The observed low b-value before occurrence of the Nepal earthquake of 25th April, 2015 supports the argument of impending occurrence of moderate to large magnitude earthquake in Sikkim and north-east Himalayan region in future.
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Farman, Mustafa Shakir, and AbdulMuttalib Isa Said. "Updated Probabilistic Seismic Hazard Assessment for Iraq/2018." Civil Engineering Journal 4, no. 7 (July 30, 2018): 1610. http://dx.doi.org/10.28991/cej-0309199.
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Recently, Iraq has experienced an unprecedented seismic activity, specifically, near the east boundary with Iran which reveals the need to re-evaluate the seismic hazard at this region. This study consists of two phases. The first is collecting the earthquake records covering the recent events till the end of November 2017 including the 12 November 2017 (7.3Mw) earthquake, and applying data processing to get the net data for independent events for the study area which were more than 4300 of net main earthquakes of Mw ≥ 4 and were used in the second phase. The second phase is applying the PSHA method by dividing the study area into a grid of small cells of size 0.5 0.5°and the hazard parameters were calculated at the center of each of these grid cells then, converting the final results to contours over the study area. It is found that the values increases towards the east-northeast and north due to the continued tectonic boundary convergence between the Arabian, Iranian and Turkish plates which produces intense earthquake activity. The design spectral acceleration at 0.2 and 1.0 seconds found to be 0.33, 0.17, 0.47, 0.25, 0.71, 0.35 g for Basra, Baghdad and Erbil, respectively. The comparison between the PGA values from this study and from the seismic hazards maps from Iraqi seismic codes of 1989, 1997 and 2016, for return periods of 475 and 2475 years, reveals the continued increase with time which reveals the need to updating the seismic hazard maps continuously.
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SHUKLA, H. P., R. S. DATTATRAYAM, and A. K. BHATNAGAR. "Seismicity of region around dams in North West India." MAUSAM 63, no. 2 (December 16, 2021): 261–74. http://dx.doi.org/10.54302/mausam.v63i2.1399.
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The collision of Indian and Eurasian continents caused large scale deformation and high seismicityof vast areas of both continents in the geological history. The North-West portion of the Himalayan arc which is lyingunder the rupture zones of Kangra earthquake of 1905, Uttarkashi earthquake of 1991 and Chamoli earthquake in 1999,has experienced many earthquakes of magnitude 6 and above. The region of North-West India between 30.0º - 35.0ºNorth and 73.0º - 79.0º East is, therefore, under intense investigations by various scientists since the origin of theHimalayas. India Meteorological Department had opened thirteen seismic observatories in early sixties for monitoringof earthquake activities in and around Bhakra, Pong, Pandoh dams in Punjab / Himachal Pradesh and Salal dam inJ&K on specific demand of the dam authorities. These observatories have recorded the earthquakes occurred in thisregion having magnitude even less than 2. The data collected for the last two decades is very useful for the scientiststo investigate seismicity and tectonics of the Himalayas. The present study could locate the regions which areseismically most active and also the region of seismic gap. Thus present study confirms association of seismic activityin the region with two major fault systems called Main Boundary Thrust (MBT) and Main Central Thrust (MCT).Comparative seismic activity within 100 km from each dam, reveal that most active region was around Pong followed byPandoh, Bhakra and Salal dams. The temporal variation of b-values for the whole period also shows that low b-valueanomalies are usually followed by large earthquakes of M > 5.5. No definite conclusions could be drawn with regard tothe relationship between the observed seismic activity around the dam sites with the corresponding water levelfluctuations in the reservoirs.
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Reddy, M. V. Ravi Kishore, Supriya Mohanty, and Rehana Shaik. "Seismic Performance of Soil-Ash and Soil-Ash-Foundation System." International Journal of Geotechnical Earthquake Engineering 11, no. 1 (January 2020): 45–70. http://dx.doi.org/10.4018/ijgee.2020010103.
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In this study, a 3D seismic response of soil deposit, soil-ash deposit and soil-ash-foundation system was investigated. Homogeneous sand deposit of 80m × 9m × 20m was initially analyzed. A pond ash layer is on top of the sand deposit with varying thicknesses and the efficiency of the pond ash layer on the sand deposit was evaluated for its best suitability. The optimum sand-ash deposit overlain by a shallow foundation has been analysed under the excitation of the Nepal (Mw:7.8) and North East India earthquake (Mw:7.5). A seismic response analysis was performed using finite element software PLAXIS3D. The finite element model adopted for the present study has been validated using 1D nonlinear ground response analysis programs. e.g. DEEPSOIL and Cyclic1D. Results of the response analysis have been determined in terms of acceleration, displacement, excess pore pressure, and excess pore pressure ratio. It was observed that, the sand-pond ash-foundation system experienced liquefaction when excited under the Nepal earthquake motion whereas it is safe against the North East India earthquake.
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Syaifuddin, Firman, Amien Widodo, and Dwa Desa Warnana. "Surabaya earthquake hazard soil assessment." E3S Web of Conferences 156 (2020): 02001. http://dx.doi.org/10.1051/e3sconf/202015602001.
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The vulnerability of land in an area to earthquake ground motions is one of the factors causing damage caused by the earthquakes. The city of Surabaya, which is crossed by two active fault segments, needs an assessment to reduce the risk of being affected by an earthquake that might occur. The aims of this study are (1) to find out the distribution of Seismic Site Classes, (20 to know the distribution of the value of Seismic Amplification, and (3) to know the potential of liquefaction in the city of Surabaya. Surabaya city, which is geologically dominated by alluvium deposits, consists of soft soil (SE) and medium (SD) sites based on N-SPT30 and Vs30 data. The level of soil amplification against earthquakes ranging from 1 to 4. This occurs because the physical properties of the Surabaya City soil layer are dominated by alluvium deposits. Regions with more than 2 amplification values are located around the coastline on the North and East coasts of Surabaya City. Based on the potential liquefaction index value, Surabaya City is included in the region with a high potential for liquefaction with a potential liquefaction index value of more than 5.
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Nath, S. K., M. D. Adhikari, S. K. Maiti, N. Devaraj, N. Srivastava, and L. D. Mohapatra. "Earthquake scenario in West Bengal with emphasis on seismic hazard microzonation of the city of Kolkata, India." Natural Hazards and Earth System Sciences 14, no. 9 (September 25, 2014): 2549–75. http://dx.doi.org/10.5194/nhess-14-2549-2014.
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Abstract. Seismic microzonation is a process of estimating site-specific effects due to an earthquake on urban centers for its disaster mitigation and management. The state of West Bengal, located in the western foreland of the Assam–Arakan Orogenic Belt, the Himalayan foothills and Surma Valley, has been struck by several devastating earthquakes in the past, indicating the need for a seismotectonic review of the province, especially in light of probable seismic threat to its capital city of Kolkata, which is a major industrial and commercial hub in the eastern and northeastern region of India. A synoptic probabilistic seismic hazard model of Kolkata is initially generated at engineering bedrock (Vs30 ~ 760 m s−1) considering 33 polygonal seismogenic sources at two hypocentral depth ranges, 0–25 and 25–70 km; 158 tectonic sources; appropriate seismicity modeling; 14 ground motion prediction equations for three seismotectonic provinces, viz. the east-central Himalaya, the Bengal Basin and Northeast India selected through suitability testing; and appropriate weighting in a logic tree framework. Site classification of Kolkata performed following in-depth geophysical and geotechnical investigations places the city in D1, D2, D3 and E classes. Probabilistic seismic hazard assessment at a surface-consistent level – i.e., the local seismic hazard related to site amplification performed by propagating the bedrock ground motion with 10% probability of exceedance in 50 years through a 1-D sediment column using an equivalent linear analysis – predicts a peak ground acceleration (PGA) range from 0.176 to 0.253 g in the city. A deterministic liquefaction scenario in terms of spatial distribution of liquefaction potential index corresponding to surface PGA distribution places 50% of the city in the possible liquefiable zone. A multicriteria seismic hazard microzonation framework is proposed for judicious integration of multiple themes, namely PGA at the surface, liquefaction potential index, NEHRP soil site class, sediment class, geomorphology and ground water table in a fuzzy protocol in the geographical information system by adopting an analytical hierarchal process. The resulting high-resolution surface consistent hazard, liquefaction and microzonation maps are expected to play vital roles in earthquake-related disaster mitigation and management of the city of Kolkata.
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Coman, Cristina, and Sanda Manea. "Landslides Hazard Assessment Using Different Approaches." Mathematical Modelling in Civil Engineering 13, no. 2 (June 27, 2017): 1–16. http://dx.doi.org/10.1515/mmce-2017-0004.
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AbstractRomania represents one of Europe’s countries with high landslides occurrence frequency. Landslide hazard maps are designed by considering the interaction of several factors which, by their joint action may affect the equilibrium state of the natural slopes. The aim of this paper is landslides hazard assessment using the methodology provided by the Romanian national legislation and a very largely used statistical method. The final results of these two analyses are quantitative or semi-quantitative landslides hazard maps, created in geographic information system environment. The data base used for this purpose includes: geological and hydrogeological data, digital terrain model, hydrological data, land use, seismic action, anthropic action and an inventory of active landslides. The GIS landslides hazard models were built for the geographical area of the Iasi city, located in the north-east side of Romania.
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Chakraborty, K., P. P. Mondal, M. Chabukdhara, and S. Sudhakar. "Forest fire scenario and challenges of mitigation during fire season in North East India." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-8 (November 27, 2014): 27–33. http://dx.doi.org/10.5194/isprsarchives-xl-8-27-2014.
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Forest fires are a major environmental problem in North East Region (NER) with large tracts of forest areas being affected in every season. Forest fires have become a major threat to the forest ecosystems in the region, leading to loss of timber, biodiversity, wildlife habitat and loss to other natural resources. Studies on forest fire have reported that about 50% of forest fire in the country takes place in NE region. The forest fire in NER is anthropogenic in nature. The forest fire hazard map generated based on appropriate weightage given to the factors affecting fire behavior like topography, fuel characteristic and proximity to roads, settlements and also historical fire locations helped to demarcate the fire prone zones. Whereas, during fire season the weather pattern also governs the fire spread in the given area. Therefore, various data on fuel characteristics (land use/land cover, forest type map, forest density map), topography (DEM, slope, aspect) proximity to settlement, road, waterbodies, meteorological data from AWS on wind speed, wind direction, dew point have been used for each fire point to rank its possible hazard level. Near real time fire location data obtained from MODIS/FIRMSwere used to generate the fire alerts. This work demonstrates dissemination of information in the form of maps and tables containing information of latitude and longitude of fire location, fire occurrence date, state and district name, LULC, road connectivity, slope and aspect, settlements/water bodies and meteorological data and the corresponding rating of possibility of fire spread to the respective fire control authorities during fire season.
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Chetia, Timangshu, Saurabh Baruah, Chandan Dey, Sangeeta Sharma, and Santanu Baruah. "Probabilistic Analysis of Seismic Data for Earthquake Forecast in North East India and its Vicinity." Current Science 117, no. 7 (October 10, 2019): 1167. http://dx.doi.org/10.18520/cs/v117/i7/1167-1173.
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Williams, Jack N., Luke N. J. Wedmore, Åke Fagereng, Maximilian J. Werner, Hassan Mdala, Donna J. Shillington, Christopher A. Scholz, et al. "Geologic and geodetic constraints on the magnitude and frequency of earthquakes along Malawi's active faults: the Malawi Seismogenic Source Model (MSSM)." Natural Hazards and Earth System Sciences 22, no. 11 (November 7, 2022): 3607–39. http://dx.doi.org/10.5194/nhess-22-3607-2022.
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Abstract. Active fault data are commonly used in seismic hazard assessments, but there are challenges in deriving the slip rate, geometry, and frequency of earthquakes along active faults. Herein, we present the open-access geospatial Malawi Seismogenic Source Model (MSSM; https://doi.org/10.5281/zenodo.5599616), which describes the seismogenic properties of faults that formed during ongoing east African rifting in Malawi. We first use empirically derived constraints to geometrically classify active faults into section, fault, and multifault seismogenic sources. For sources in the North Basin of Lake Malawi, slip rates can be derived from the vertical offset of a seismic reflector that dated lake cores indicate is 75 ka. Elsewhere, slip rates are constrained from advancing a systems-based approach that partitions geodetically derived rift extension rates in Malawi between seismogenic sources using a priori constraints on a regional strain distribution and a hanging wall flexural extension in magma-poor continental rifts. Slip rates are then combined with source geometry and empirical scaling relationships to estimate earthquake magnitudes and recurrence intervals, and their uncertainty is described from the variability in logic tree outcomes used in these calculations. Sources in the MSSM are 5–269 km long, which implies that large-magnitude (Mw 7–8) earthquakes may occur in Malawi. However, low slip rates (0.05–2 mm yr−1) mean that the frequency of such events will be low (recurrence intervals of ∼103–104 years). We also find that, for 9 out of 11 faults in Lake Malawi's North Basin, differences in the slip rates, when estimated independently from the geodetic data and the offset seismic reflector, are not statistically significant. The MSSM represents an important resource for investigating Malawi's increasing seismic risk and provides a framework for incorporating active fault data into seismic hazard assessment elsewhere in the East African Rift and other tectonically active regions.
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Kulkarni, Swapnil. "Seismic Analysis of Building Resting on Sloping Ground." International Journal for Research in Applied Science and Engineering Technology 9, no. VII (July 15, 2021): 1340–52. http://dx.doi.org/10.22214/ijraset.2021.36647.
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In India, for example, the north-east states. The scarcity of plain ground in hilly areas compels construction activity on sloping ground resulting in various important buildings such as reinforced concrete framed hospitals, colleges, hotels and offices resting on hilly slopes. The behavior of buildings during earthquake depends upon the distribution of mass and stiffness in both horizontal and vertical planes of the buildings. Various models were analyzed using staad pro. after all result and comparison it is found that buildings with set back and step back patterns give more stable pattern during earthquake.
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Petterson, Michael, Sonam Wangchuk, and Norgay Konchok. "A multiple natural hazard analysis, SECMOL College region, near Leh, Ladakh, North India, with applications for community-based DRR." Disaster Prevention and Management: An International Journal 29, no. 3 (November 19, 2019): 287–312. http://dx.doi.org/10.1108/dpm-02-2019-0064.
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Purpose This paper places a college at the centreof a multi-hazard assessment (earthquake, flood and landslide). The college is within a less studied, rural area of Ladakh, North India. Research focusses on a case study (Students Educational and Cultural Movement of Ladakh (SECMOL) College), close to Leh, Ladakh, and extends to incorporate/apply thinking from/to the wider Ladakh region. The approach adopted, centring on the hazard assessment of a single entity/local area, allows a rapid uptake of hazard recommendations within a college environment planning to continue its existence for decades ahead. A sister paper (Petterson et al., 2019) documents the active involvement of college staff and students in the principles of geohazard assessment and the development of student-centric hazard assessments of the college and their home village. SECMOL is a self-sufficient, alternative, college, organised along strong environmentally sustainable principles. The paper aims to discuss these issues. Design/methodology/approach This work has adopted different strategies for different hazards. Fieldwork involved the collection of quantitative and qualitative data (e.g. shape and size of valleys/river channels/valley sides, estimation of vegetation density, measurement of sediment clasts, angle of slopes, assessment of sediment character, stratigraphy of floodplains and identification of vulnerable elements). These data were combined with satellite image analysis to: define river catchment character and flood vulnerability (e.g. using the methodology of Collier and Fox, 2003), examine catchment connectivity, and examine landslip scars and generic terrain analysis. Literature studies and seismic database interrogation allowed the calculation of potential catchment floodwater volumes, and the collation of epicentre, magnitude, depth and date of seismic events, together with recent thinking on the return period of large Himalayan earthquakes. These data were used to develop geological-seismic and river catchment maps, the identification of vulnerable elements, and disaster scenario analyses. Findings This research concludes that SECMOL, and much of the Ladakh region, is exposed to significant seismic, flood and landslide hazard risk. High magnitude earthquakes have return periods of 100s to c. 1,000 years in the Himalayas and can produce intense levels of damage. It is prudent to maximise earthquake engineering wherever possible. The 2010 Leh floods demonstrated high levels of devastation: these floods could severely damage the SECMOL campus if storms were centred close by. This study reveals the connectivity of catchments at varying altitudes and the potential interactions of adjacent catchments. Evacuation plans need to be developed for the college. Northern ridges at SECMOL could bury parts of the campus if mobilised by earthquakes/rainfall. Slope angles can be lowered and large boulders moved to reduce risk. This work reinforces recommendations that relate to building quality and urban/rural planning, e.g. using spatial planning to keep people away from high-risk zones. Practical implications The frequency of hazards is low, but potential impacts high to very high. Hazard mitigation actions include engineering options for hazardous slopes, buildings to be earthquake-proofed, and evacuation management for large floods. Originality/value Methodologies undertaken in this research are well-tested. Linkages between disciplines are ambitious and somewhat original. The application of this work to a specific college centre site with the capacity to rapidly take up recommendations is novel. The identification of catchment inter-connectivity in this part of Ladakh is novel. This work complements a sister paper (Petterson et al., 2019) for community aspects of this study, adding to the novelty value.
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., Malsawmtluanga, Vabeihmo Ch, Lalduhawmi Rebecca, and Malsawmtluangi . "Morphometric analysis of relative tectonic activity in the upper parts of Tlawng river watershed in Lunglei, Mizoram, India." Disaster Advances 14, no. 10 (September 25, 2021): 15–22. http://dx.doi.org/10.25303/1410da1522.
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The State of Mizoram in India is geologically located within the Indo Burmese Wedge (IBW) of the Indo Burmese Arc (IBA). The state is a landlocked state domestically bordered by Tripura in the north-west, Assam in the north and Manipur to its north-east. It shares international boundaries with Bangladesh to its west and Myanmar in the east. This region is amongst the most seismically active regions of the world and numerous seismic activities had occurred in the past. The high seismicity of the region of North East India is attributed to plate tectonics and is lying in the plate boundary region where numerous active faults are present. To assess the tectonic activities in the upper parts of the Tlawng river watershed in Lunglei of Mizoram, morphotectonic parameters including Basin elongation ratio (Re), Drainage basin asymmetry factor (Af), Transverse topographic symmetry factor (T), Bifurcation ratio (Rb), Hypsometry integral (HI), Mountain front sinuosity (Smf), Channel sinuosity (S), Ratio of valley floor width to valley height (Vf) and Stream length gradient index (SL) were used and the study revealed that the present Lunglei is tectonically active.
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Kozacı, Özgür, and Erhan Altunel. "Characteristics of the North Anatolian Fault at the eastern end of Marmara seismic gap based on multidisciplinary field evidence." Geophysical Journal International 229, no. 3 (January 28, 2022): 1785–803. http://dx.doi.org/10.1093/gji/ggac022.
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SUMMARY The northern branch of the North Anatolian Fault (NAF) is the primary source of the greatest natural hazard for the Marmara Megapolis and specifically the İstanbul Metropolitan area. The Sea of Marmara section of the NAF is a ∼125-km-long seismic gap bound by the M7.4 1912 Mürefte earthquake rupture in the west and M7.4 1999 İzmit earthquake rupture in the east. Terminations of these ruptures define the length of the seismic gap in the Marmara Sea and consequently the magnitude and rupture extent of the expected large magnitude earthquake. The Hersek Peninsula is the last location where the NAF can be studied on land before it enters the Sea of Marmara. In addition, it is a geologically key location for the western termination of the M7.4 İzmit surface rupture. This study integrates high-resolution onshore and offshore data from Hersek Peninsula and its vicinity in İzmit Bay to assess the seismic hazard for the Marmara region. Detailed geological and geomorphic mapping, palaeoseismic trenching, geophysical and geotechnical subsurface data and archeoseismologic investigations demonstrate that the 1999 İzmit earthquake surface rupture died off east of the Hersek Peninsula due to structural complexity of the NAF at this location and the most recent earthquake to rupture the surface at Hersek Peninsula was the historical 1509 CE event. A restraining bend and bifurcation of the NAF at Hersek Peninsula suggests that this location might be a persistent asperity forming a surface rupture segmentation point at least since Pleistocene. Surface ruptures documented in palaeoseismic trenches north of the Hersek Lagoon and an offset 6th century East Roman aqueduct; however, suggests that this section of the NAF has ruptured the surface multiple times in the past and is highly likely to rupture again during the expected Marmara earthquake. The aqueduct; which crosses the surface trace of the NAF, is offset 14 ± 1 m and yields 13.6 ± 1 mm yr–1 dextral slip rate indicating that the northern branch of the NAF accrues and releases the majority of the stress between Eurasia and Anatolian block in the Marmara region. If the ∼125-km-long seismic gap between the 1912 and 1999 ruptures fail during a single event the expected Marmara earthquake can reach M7.4.
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Gasperini, Luca, Massimiliano Stucchi, Vincenzo Cedro, Mustapha Meghraoui, Gulsen Ucarkus, and Alina Polonia. "Active fault segments along the North Anatolian Fault system in the Sea of Marmara: implication for seismic hazard." Mediterranean Geoscience Reviews 3, no. 1 (March 2021): 29–44. http://dx.doi.org/10.1007/s42990-021-00048-7.
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AbstractA new analysis of high-resolution multibeam and seismic reflection data, collected during several oceanographic expeditions starting from 1999, allowed us to compile an updated morphotectonic map of the North Anatolian Fault below the Sea of Marmara. We reconstructed kinematics and geometries of individual fault segments, active at the time scale of 10 ka, an interval which includes several earthquake cycles, taking as stratigraphic marker the base of the latest marine transgression. Given the high deformation rates relative to sediment supply, most active tectonic structures have a morphological expression at the seafloor, even in presence of composite fault geometries and/or overprinting due to mass-wasting or turbidite deposits. In the frame of the right-lateral strike-slip domain characterizing the North Anatolian fault system, three types of deformation are observed: almost pure strike-slip faults, oriented mainly E–W; NE/SW-aligned axes of transpressive structures; NW/SE-oriented trans-tensional depressions. Fault segmentation occurs at different scales, but main segments develop along three major right-lateral oversteps, which delimit main fault branches, from east to west: (i) the transtensive Cinarcik segment; (ii) the Central (East and West) segments; and (iii) the westernmost Tekirdag segment. A quantitative morphometric analysis of the shallow deformation patterns observed by seafloor morphology maps and high-resolution seismic reflection profiles along the entire basin allowed to determine nature and cumulative lengths of individual fault segments. These data were used as inputs for empirical relationships, to estimate maximum expected Moment Magnitudes, obtaining values in the range of 6.8–7.4 for the Central, and 6.9–7.1 for the Cinarcik and Tekirdag segments, respectively. We discuss these findings considering analyses of historical catalogues and available paleoseismological studies for the Sea of Marmara region to formulate reliable seismic hazard scenarios.
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Radziminovich, Ya, N. Gileva, A. Seredkina, and V. Melnikova. "DZHIRGA EARTHQUAKE on April 27, 2014, Mw=4.9, КР=13.3, I0=7 (Northern Baikal Region)." Earthquakes in Northern Eurasia, no. 23 (December 15, 2020): 307–16. http://dx.doi.org/10.35540/1818-6254.2020.23.31.
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We consider the April 27, 2014, Mw=4.9 Dzhirga earthquake, occurred within the north-eastern end of the Barguzin Depression. The event is the second one by energy level in the study area for the period of instrumental observations. The earthquake was followed by an aftershock sequence of 75 weak shocks recorded till the end of the year. The focal mechanism was determined from surface wave records from 13 digital broadband seismic stations of the IRIS networks. The obtained solution demonstrates the normal fault kinematics with both nodal planes striking north-east that corresponds to the regional fault pattern. The focal depth is estimated equal to 19 km. The maximum observed intensity was 5 points on the MSK-64 scale at the epicentral distance of 13 km. The Dzhirga earthquake analysis made it possible to fill in the lack of seismological information about the study area. The data obtained can be used for refinement of seismic hazard assessment of the north of the Barguzin Basin.
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Stewart, Jonathan P., Grace A. Parker, Gail M. Atkinson, David M. Boore, Youssef M. A. Hashash, and Walter J. Silva. "Ergodic site amplification model for central and eastern North America." Earthquake Spectra 36, no. 1 (January 2, 2020): 42–68. http://dx.doi.org/10.1177/8755293019878185.
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The United States Geological Survey national seismic hazard maps have historically been produced for a reference site condition of VS30 = 760 m/s. For other site conditions, site factors are used, which heretofore have been developed using ground motion data and simulations for shallow earthquakes in active tectonic regions. Research results from the Next Generation Attenuation–East (NGA-East) project, as well as previous and contemporaneous related research, demonstrate different levels of site amplification in central and eastern North America (CENA) as compared to active regions. We provide recommendations for modeling of ergodic site amplification in CENA based primarily on research results from the literature. The recommended model has three additive terms in natural logarithmic units. Two describe linear site amplification: an empirically constrained VS30-scaling term relative to a 760 m/s reference and a simulation-based term to adjust site amplification from the 760 m/s reference to the CENA reference of VS = 3000 m/s. The third term is a nonlinear model that is described in a companion document. All median model components are accompanied by epistemic uncertainty models.
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Kayal, J. R., and Dapeng Zhao. "Three-dimensional seismic structure beneath Shillong Plateau and Assam Valley, Northeast India." Bulletin of the Seismological Society of America 88, no. 3 (June 1, 1998): 667–76. http://dx.doi.org/10.1785/bssa0880030667.
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Abstract Northeast India is bounded by the Himalayan arc to the north and the Burmese arc to the east. The Shillong Plateau and Assam Valley lie at the boundary zone of the two arcs. Three microearthquake surveys were conducted in this area from 1984 to 1986. We have applied a tomographic method to about 2800 high-quality P- and S-wave arrival times from 364 local earthquakes that were recorded in the magnitude range 2.0 to 4.0 by 22 temporary seismic stations during the surveys to determine the 3D velocity structure of the crust and upper mantle in this region. The result reveals significant lateral heterogeneities in the study area. The tomographic images obtained in this study are compatible with the major tectonic features such as active faults and seismicity trends.
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Goulet, Christine A., Yousef Bozorgnia, Nicolas Kuehn, Linda Al Atik, Robert R. Youngs, Robert W. Graves, and Gail M. Atkinson. "NGA-East Ground-Motion Characterization model part I: Summary of products and model development." Earthquake Spectra 37, no. 1_suppl (July 2021): 1231–82. http://dx.doi.org/10.1177/87552930211018723.
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In this article, we present an overview of the research project NGA-East, Next Generation Attenuation for Central and Eastern North America (CENA), and summarize the key methodology and products. The project was tasked with developing a new ground motion characterization (GMC) model for CENA. The final NGA-East GMC model includes a set of 17 median ground motion models (GMMs) for peak ground acceleration and velocity (PGA, PGV) and response spectral ordinates for periods ranging from 0.01 to 10 s. The NGA-East GMMs are applicable to horizontal components of ground motions on very hard rock, for the moment magnitude range of 4.0–8.2, and distances of up to 1500 km. The aleatory standard deviations of GMMs are also provided for site-specific analysis (single-station standard deviation) and for general probabilistic seismic hazard analyses (PSHA) applications (ergodic standard deviation). In addition, adjustment factors are provided for source depth and hanging-wall effects, as well as for hazard computations at sites in the Gulf Coast Region. During the course of the project, several innovative technologies were developed and implemented to increase the transparency and repeatability of the GMC building process. This involved expanding on a set of candidate median GMMs to define and capture an appropriate range of epistemic uncertainty in ground motions. We also developed a new approach for modeling the aleatory variability that was completely independent of the median GMMs. The development made extensive use of the CENA database but also borrowed data from other parts of the world when relevant and led to an integrated suite of models. Through this repeatable process, epistemic uncertainty could be quantified more objectively than before, relying less on expert opinion. The NGA-East project went through a comprehensive Seismic Senior Hazard Analysis Committee (SSHAC) Level 3 peer review process before its release.
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McNab, Fergus, R. Alastair Sloan, and Richard T. Walker. "Simultaneous orthogonal shortening in the Afghan-Tajik Depression." Geology 47, no. 9 (July 16, 2019): 862–66. http://dx.doi.org/10.1130/g46090.1.
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Abstract The Afghan-Tajik Depression is a sedimentary basin in the Alpine-Himalayan mountain chain. It is traversed by series of north-south arcuate folds, suggesting that the basin is undergoing east-west compression. A second set of folds in the south of the depression runs east-west, crosscutting those trending north-south. We present results from teleseismic body waveform inversion and depth phase modeling for five recent earthquakes, and from detailed mapping of structures related to active faulting based on satellite imagery and topographic data. We argue that both sets of folds are active and that deformation is vertically partitioned, with north-south compression accommodated on east-west–trending thrust faults within the basement, and east-west compression accommodated on north-south–trending thrust faults above a detachment within the basin fill. The observation that orthogonal shortening can be accommodated simultaneously in this way has several important implications. Juxtaposed orthogonal fold systems identified in the geological record may not require temporally separate events, particularly in gravity-driven fold-and-thrust belts in foreland-basin settings. Pervasive detachment may limit the size of potential earthquakes by preventing single events from rupturing the entire seismogenic layer. However, it may also disguise geomorphic signatures of faulting and interseismic strain accumulation within the lower layer, hindering accurate seismic hazard assessment and regional tectonic interpretations.
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YADAV, Abhishek, Suresh KANNAUJIYA, Prashant Kumar CHAMPATI RAY, Rajeev Kumar YADAV, and Param Kirti GAUTAM. "Estimation of crustal deformation parameters and strain build-up in Northwest Himalaya using GNSS data measurements." Contributions to Geophysics and Geodesy 51, no. 3 (September 28, 2021): 225–43. http://dx.doi.org/10.31577/congeo.2021.51.3.2.
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GPS measurements have proved extremely useful in quantifying strain accumulation rate and assessing seismic hazard in a region. Continuous GPS measurements provide estimates of secular motion used to understand the earthquake and other geodynamic processes. GNSS stations extending from the South of India to the Higher Himalayan region have been used to quantify the strain build-up rate in Central India and the Himalayan region to assess the seismic hazard potential in this realm. Velocity solution has been determined after the application of Markov noise estimated from GPS time series data. The recorded GPS data are processed along with the closest International GNSS stations data for estimation of daily basis precise positioning. The baseline method has been used for the estimation of the linear strain rate between the two stations. Whereas the principal strain axes, maximum shear strain, rotation rate, and crustal shortening rate has been calculated through the site velocity using an independent approach; least-square inversion approach-based triangulation method. The strain rate analysis estimated by the triangulation approach exhibits a mean value of extension rate of 26.08 nano-strain/yr towards N131°, the compression rate of –25.38 nano-strain/yr towards N41°, maximum shear strain rate of 51.47 nano-strain/yr, dilation of –37.57 nano-strain/yr and rotation rate of 0.7°/Ma towards anti-clockwise. The computed strain rate from the Baseline method and the Triangulation method reports an extensive compression rate that gradually increases from the Indo-Gangetic Plain in South to Higher Himalaya in North. The slip deficit rate between India and Eurasia Plate in Kumaun Garhwal Himalaya has been computed as 18±1.5 mm/yr based on elastic dislocation theory. Thus, in this study, present-day surface deformation rate and interseismic strain accumulation rate in the Himalayan region and the Central Indian region have been estimated for seismic hazard analysis using continuous GPS measurements.
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Tremblay, Robert, and Gail M. Atkinson. "Comparative Study of the Inelastic Seismic Demand of Eastern and Western Canadian Sites." Earthquake Spectra 17, no. 2 (May 2001): 333–58. http://dx.doi.org/10.1193/1.1586178.
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The damage potential of earthquake ground motions compatible with site-specific 2% in 50 year uniform hazard spectra is compared at two North American sites in areas of moderate seismic hazard: Montreal, in the east, and Vancouver, along the west coast. For Vancouver, crustal, subcrustal and Cascadia subduction ground motion earthquake ensembles are considered. Nonlinear dynamic analyses of bi-linear single-degree-of-freedom oscillators exhibiting various ductility levels and damage laws were performed to determine R factors required to prevent structural collapse for each site and each system. Then, inelastic response parameters were computed for the general design case, wherein a prescribed R factor is used for a given system irrespective of tectonic region or structural period. The results show that the R factors vary with the ductility level, the damage law, the structural period, and the tectonic region. Neglecting the latter two dependencies in design, as is current practice, may lead to significant discrepancies in the level of protection achieved for different structures in different regions.
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Baskoutas, Ioannis, George Popandopoulos, and Prasanta Chingtham. "Temporal variation of seismic parameters in the western part of the India-Eurasia plate collision zone." Research in Geophysics 1, no. 1 (December 20, 2011): 3. http://dx.doi.org/10.4081/rg.2011.e3.
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We examined the temporal seismicity variation in the north-west Himalayas and the adjacent regions in relation to strong earthquake occurrences in the period 1970-2010. The aim was to promote seismic hazard assessment and to show the possibilities of strong earthquake forecasting by means of the FastBEE computer tool. The temporal variation of the seismicity is expressed in terms of three basic seismic parameters: the logarithm of the number of earthquakes logN, the seismic energy released in the mode logE2/3 and the b-value of the earthquake magnitude-frequency distribution expressed by the Gutenberg-Richter relation. Significant changes to relative mean values, forming consecutive relative minima and maxima, of the obtained temporal variation series of the seismicity parameters can be considered anomalies. These anomalies were investigated before strong (magnitude Mw≥5.6.) earthquake occurrences and were successfully correlated with 12 strong earthquakes. The mean time of the duration of the anomalies before the origin time of the impending earthquake were estimated to be equal to 3.3±1.3 years. We conclude that, in the region under study, the established correlations can be useful for the intermediate-term forecasting of strong earthquakes and that the continuous monitoring of the temporal evolution of seismicity by means of the FastBEE tool can contribute to the evaluation of the seismic hazard status in a target area. The available earthquake data and the results obtained indicate that after the beginning of 2006, the temporal variation of the seismicity does not present clear prognostic anomalies. This behavior is compatible with the absence of earthquakes with a magnitude of Mw 6.0 or more in the area examined.
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Güvercin, Sezim Ezgi, Hayrullah Karabulut, A. Özgün Konca, Uğur Doğan, and Semih Ergintav. "Active seismotectonics of the East Anatolian Fault." Geophysical Journal International 230, no. 1 (February 4, 2022): 50–69. http://dx.doi.org/10.1093/gji/ggac045.
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SUMMARY The East Anatolian Fault (EAF) is a 700-km-long left-lateral transform fault located between the Anatolian and Arabian plates. The proximity of the Euler Pole to the Arabia–Anatolia Plate boundary leads to rapid changes in plate velocity along the boundary, which is manifested by the decreasing slip rates from east (10 mm yr–1) to west (∼1–4 mm yr–1). The EAF displays heterogeneous seismicity patterns with seismic gaps, localized clusters and broad diffuse zones. In this study, in order to understand the origin of these complexities and quantify the seismic hazard along the EAF, we present an improved seismicity catalogue with more than 26 000 earthquakes and 160 focal mechanisms from regional moment tensor inversion between 2007 and 2020. The focal mechanisms and seismicity show that the EAF dips towards north and forms a well-defined plate boundary in the east between Palu and Çelikhan with almost pure left-lateral motion. Further west, the boundary becomes broader with activity along subparallel faults. Focal mechanisms show heterogeneous stress orientations in consistence with geodetically determined strain rate field. The stress orientations show a transition from strike-slip to extension towards the west of Çelikhan. Amongst all segments of EAF, the Pütürge segment, which holds the near-repeating earthquakes in the vicinity of the nucleation of the 2020 Mw 6.8 earthquake, is distinguished with its steady and high rate of seismicity. Further east, the neighbouring Palu segment is characterized by several distinct moderate earthquakes. We do not observe any change in the seismicity rate on these segments of the EAF following large earthquakes. In order to quantify the seismic hazard along the EAF, we calculate the recurrence time and maximum magnitude for each segment by using an extended seismicity catalogue of 150 yr including the large historical earthquakes and the geodetic strain rate. The results show ∼150 yr recurrence time with Mmax∼6.7–7.0 along the seismically active Palu and Pütürge segments on the east, while relatively silent western segments yield longer recurrence times; 237–772 for Pazarcık and 414–917 for Amanos segments with slightly larger magnitudes (Mmax ∼7–7.4). We infer that the seismicity patterns and strain-rate field along the EAF are shaped by several factors such as strong geometrical irregularities, heterogeneous coupling and complex plate motion leading to rapid change of fault slip rate.
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Islami, Kleidi, Giovanni Tecchio, and Claudio Modena. "Seismic Intervention and Dynamic Testing of an Arch Bridge." Applied Mechanics and Materials 105-107 (September 2011): 1159–64. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.1159.
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This work presents the dynamic tests on a retrofitted masonry arch bridge. The Gresal Bridge, located in the North-East of Italy, was highly exposed to seismic hazard, due to the slenderness of its high piers. A retrofit intervention has been carried out, and a new rc slab has been built under the pavement, anchored to the piers with high strength vertical ties and restrained at the abutments, to create a new resistance arrangement withstanding inertial forces. The dynamic behaviour has been initially assessed with numerical models comparing the response of the bridge before and after the repair, and has subsequently been tested by the Output-Only technique to detect the variation of the modal response induced by the strengthening intervention. The dynamic tests have shown the structure to be more rigid than expected and, after calibration, a good agreement to exist between the numerical frequencies and the experimental records captured on the retrofitted bridge.
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Orecchio, Barbara, Silvia Scolaro, Josep Batlló, Giancarlo Neri, Debora Presti, Daniel Stich, and Cristina Totaro. "New Results for the 1968 Belice, South Italy, Seismic Sequence: Solving the Long-Lasting Ambiguity on Causative Source." Seismological Research Letters 92, no. 4 (March 10, 2021): 2364–81. http://dx.doi.org/10.1785/0220200277.
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Abstract We present the first estimates of moment tensor solutions and probabilistic nonlinear hypocenter locations for the 1968 Belice earthquake sequence, which is the most relevant seismic activity occurred in western Sicily in historical times. This seismic phase, including six earthquakes with magnitude between 5 and 6.4, produced severe damages and fatalities in a sector of the Nubia–Eurasia plate margin, previously considered aseismic. Poorly constrained and often controversial hypocenter locations and focal mechanism solutions available from the literature have led to a long-lasting ambiguity on the possible causative source of the sequence, also having primary effects on the regional seismotectonic modeling and seismic hazard evaluations. The two main fault models proposed in the literature alternatively assigned a primary role to the north-northwest-trending Nubia–Eurasia plate convergence, causing thrust faulting on about east-trending structures or to the differential foreland retreat driving dextral strike-slip movements on about north–south-oriented faults. By focusing on the starting and the most energetic phase of the 1968 sequence, we computed the moment tensor solutions for three of the strongest earthquakes using digitized waveforms and a time-domain waveform inversion technique. Then, we also analyzed, by means of a Bayesian hypocenter location technique, the spatial distribution of the 1968 earthquakes. All the results indicate that the 1968 Belice sequence was characterized by predominant reverse faulting occurring on about east-to-northeast-trending structures, thus solving the dualism between models previously proposed in the literature. Our findings well agree both with the geodynamic framework governed by the Nubia–Eurasia north-northwest-trending convergence and with the geological reconstructions of the regional thrust front in the western Sicily area. The results of moment tensor estimations and nonlinear hypocenter locations furnishing an improved knowledge of the most relevant seismic activity of western Sicily also concur to better constraint the seismotectonic modeling of the region.
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Rost, S., G. A. Houseman, A. W. Frederiksen, D. G. Cornwell, M. Kahraman, S. Altuncu Poyraz, U. M. Teoman, et al. "Structure of the northwestern North Anatolian Fault Zone imaged via teleseismic scattering tomography." Geophysical Journal International 227, no. 2 (July 10, 2021): 922–40. http://dx.doi.org/10.1093/gji/ggab265.
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SUMMARY Information on fault zone structure is essential for our understanding of earthquake mechanics, continental deformation and seismic hazard. We use the scattered seismic wavefield to study the subsurface structure of the North Anatolian Fault Zone (NAFZ) in the region of the 1999 İzmit and Düzce ruptures using data from an 18-month dense deployment of seismometers with a nominal station spacing of 7 km. Using the forward- and back-scattered energy that follows the direct P-wave arrival from teleseismic earthquakes, we apply a scattered wave inversion approach and are able to resolve changes in lithospheric structure on a scale of 10 km or less in an area of about 130 km by 100 km across the NAFZ. We find several crustal interfaces that are laterally incoherent beneath the surface strands of the NAFZ and evidence for contrasting crustal structures either side of the NAFZ, consistent with the presence of juxtaposed crustal blocks and ancient suture zones. Although the two strands of the NAFZ in the study region strike roughly east–west, we detect strong variations in structure both north–south, across boundaries of the major blocks, and east–west, parallel to the strike of the NAFZ. The surface expression of the two strands of the NAFZ is coincident with changes on main interfaces and interface terminations throughout the crust and into the upper mantle in the tomographic sections. We show that a dense passive network of seismometers is able to capture information from the scattered seismic wavefield and, using a tomographic approach, to resolve the fine scale structure of crust and lithospheric mantle even in geologically complex regions. Our results show that major shear zones exist beneath the NAFZ throughout the crust and into the lithospheric mantle, suggesting a strong coupling of strain at these depths.
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Devaraj, Deepa, R. Ramkrishnan, T. Prabu, Sreevalsa Kolathayar, and T. G. Sitharam. "Synthesis of Linear JTFA-Based Response Spectra for Structural Response and Seismic Reduction Measures for North-East India." Journal of Earthquake and Tsunami 14, no. 06 (August 8, 2020): 2050023. http://dx.doi.org/10.1142/s1793431120500232.
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North-East India (NEI) has a long history of devastating earthquakes due to the complicated tectonic setting of the region. A shortage of sufficient recorded time-histories from the region calls for a synthesis of accelerograms for dynamic analyses. In this study, a novel Joint Time-Frequency Analysis (JTFA) technique is adopted for the synthesis of accelerograms, considering the non-stationary behavior of earthquake waves. JTFA is used for analyzing the signals in a joint time and frequency domain to better understand its characteristics and synthesize signals without compromising its inherent characteristics like frequency content and amplitude. Synthetic accelerograms are developed using JTFA techniques for different magnitude and distance ranges between 5 to 6.8 and 0–480[Formula: see text]km and response spectra are developed. Synthesized generalized accelerograms and their response spectra are compared with actual signals in the same magnitude-distance ranges and were found to match. A comparison of the frequency contents of actual and synthetic signals was also carried out using Fourier Transforms and spectrograms (SPs) and was found to be in good agreement. Further, a comparative study of various earthquake reduction measures for NEI is carried out for a scenario earthquake using the synthesized data, and the best suitable structural input for the region is recommended.
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Abdullah, Saquib, Santanu Misra, R. Sarvesha, and Biswajit Ghosh. "Resurfacing of deeply buried oceanic crust in Naga Hills Ophiolite, North-East India: Petrofabric, microstructure and seismic properties." Journal of Structural Geology 139 (October 2020): 104141. http://dx.doi.org/10.1016/j.jsg.2020.104141.
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Barman, Prakash, Jagat Dwipendra Ray, Ashok Kumar, J. D. Chowdhury, and Kahsyap Mahanta. "Estimation of present-day inter-seismic deformation in Kopili fault zone of north-east India using GPS measurements." Geomatics, Natural Hazards and Risk 7, no. 2 (November 25, 2014): 586–99. http://dx.doi.org/10.1080/19475705.2014.983187.
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Cox, Randel Tom, Robert D. Hatcher, Steven L. Forman, Ronald Counts, James Vaughn, Eric Gamble, Jacob Glasbrenner, Kathleen Warrell, Narayan Adhikari, and Sean Pinardi. "Synthesis of Recent Paleoseismic Research on Quaternary Faulting in the Eastern Tennessee Seismic Zone, Eastern North America: Implications for Seismic Hazard and Intraplate Seismicity." Bulletin of the Seismological Society of America 112, no. 2 (January 11, 2022): 1161–89. http://dx.doi.org/10.1785/0120210209.
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ABSTRACT Causes of intraplate seismicity remain a great unsolved problem, in contrast with plate-boundary seismicity. Modern seismicity records frequent seismic activity in plate-boundary seismic zones, but in fault zones where seismic activity is not frequent, plate boundary or intraplate, resolution of prehistoric earthquake activity is critical for estimating earthquake recurrence interval and maximum expected magnitude. Thus, documenting prehistoric earthquakes is crucial for assessing earthquake hazard posed to infrastructure, including nuclear reactors and large dams. The ∼400 km long eastern Tennessee seismic zone (ETSZ), United States, is the third most active seismic zone east of the Rocky Mountains in North America, although the largest recorded ETSZ earthquake is only Mw 4.8. Ironically, it is the least studied major eastern U.S. seismic zone. Recent ETSZ field surveys revealed an 80 km long, 060°-trending corridor containing northeast-striking Quaternary thrust, strike slip, and normal faults with displacements ≥1 m. It partially overlaps a parallel trend of seismicity that extends 30 km farther southwest, suggesting this active faulting zone may extend ∼110 km within part of the ETSZ. Near Dandridge, Tennessee, a thrust fault in French Broad River alluvium records two earthquakes in the last 40,000 yr. About 50 km southwest near Alcoa, Tennessee, a thrust fault cuts Little River alluvium and records two earthquakes between 15,000 and 10,000 yr ago. About 30 km farther southwest at Vonore, Tennessee, a thrust fault displaces bedrock ≥2 m over colluvium, and alluvium is normal faulted >2 m. This corridor, just west of the Blue Ridge escarpment, overlies a steep gradient in midcrustal S-wave velocities, consistent with a basement fault at hypocentral depths. The corridor faults may be connected to a basement fault or localized coseismic faults above a blind basement fault. Our current data suggest at least two Mw≥6.5 surface rupturing events in the last 40,000 yr.
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Farajpour, Zoya, and Shahram Pezeshk. "A ground-motion prediction model for small-to-moderate induced earthquakes for Central and Eastern United States." Earthquake Spectra 37, no. 1_suppl (June 6, 2021): 1440–59. http://dx.doi.org/10.1177/87552930211016014.
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This study presents a new ground motion model (GMM) for small-to-moderate potentially induced earthquakes for Central and Eastern United States (CEUS). We used a hybrid empirical model as the base model, which was developed and calibrated for tectonic events in Central and Eastern North America (CENA) as part of the Next-generation Attenuation-East (NGA-East) project. We calibrated the base model using a comprehensive database of potentially induced ground motions with smaller magnitudes and shallower depths than tectonic earthquakes, excluding all earthquake events and stations within the Gulf Coast region. We determined the model functional form coefficients using a mixed-effect regression procedure. The proposed GMM is derived for the peak ground acceleration and response-spectral ordinates at periods ranging from 0.01 to 10.0s, moment magnitudes ranging from 3.0 to 5.8, and hypocentral distances up to 200km. The performance of the proposed GMM is evaluated through a set of comprehensive residual analyses. Furthermore, we compared the proposed GMM with recently published GMMs with the observed data for CEUS. The proposed GMM could apply in long-term and short-term US Geological Survey National Seismic Hazard Maps and for the hazard evaluation of induced seismicity.
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Han, X., Y. Li, J. Du, X. Zhou, C. Xie, and W. Zhang. "Rn and CO<sub>2</sub> geochemistry of soil gas across the active fault zones in the capital area of China." Natural Hazards and Earth System Sciences Discussions 2, no. 2 (February 20, 2014): 1729–57. http://dx.doi.org/10.5194/nhessd-2-1729-2014.
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Abstract. The present work is proposed to investigate the spatiotemporal variations of soil gas Rn and CO2 across the active faults in the capital area of China, for the understanding of fault activities and the assessment of seismic hazard. A total of 342 soil gas sampling sites were measured twice in 2011 and 2012 along seven profiles across four faults. The results of soil gas surveys show that in each profile, due to the variation of gas emission rate, the concentrations of Rn and CO2 changed in the vicinity of faults. Spatial distributions of Rn and CO2 in the study areas were different from each other, which was attributed to soil types affecting the existence of Rn and CO2. Compared with 2011 soil gas survey, the increases of Rn and CO2 concentrations in 2012 were related to the enhancement of seismic activities in the capital area of China. Our results indicate that special attention for seismic monitoring should be paid to Xinbaoan-Shacheng Fault and the north east segment of Tangshan Fault in the future.
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Ulysse, Sophia, Dominique Boisson, Valmy Dorival, Kelly Guerrier, Claude Préptit, Léna Cauchie, Anne-Sophie Mreyen, and Hans-Balder Havenith. "Site Effect Potential in Fond Parisien, in the East of Port-au-Prince, Haiti." Geosciences 11, no. 4 (April 12, 2021): 175. http://dx.doi.org/10.3390/geosciences11040175.
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In the frame of a Belgo-Haitian cooperation project (PIC 2012–2016), a study of the local seismic hazard was performed in Fond Parisien, an area located on the foothills of the “Massif de la Selle”, along the easternmost portion of the Enriquillo Plantain Garden Fault (EPGF). The H/V Spectral Ratio (HVSR) technique was applied to study the resonance frequency of the target areas and the azimuth of the wave field. The amplification factors were estimated using Standard Spectral Ratios obtained from earthquakes recorded by a temporary seismic network. Using the Multichannel Analysis of Surface Waves method, the seismic properties of the shallow layers were investigated. Then, the results were compared to local Electrical Resistivity Tomography data. These results highlight, in the central part of Fond Parisien, an E-W zone of low velocities ranging from 200 m/s to 450 m/s and low resistivities between 1 Ωm and 150 Ωm, due both to tectonic folding of the rocks and to the presence of sediment filling in the eastern part. The latter is marked, in most of its sites, by resonances at one or more frequencies ranging from 0.7 Hz to 20 Hz. Infiltration and storage of brackish water in the underground layers also contribute to the low resistivity values. With the noise HVSR data, we also evidenced a significant influence of the EPGF on the main orientation of the seismic wavefield as in the vicinity of this fault, the azimuths are parallel to the orientation of the fault. Overall, the results also show greater potential for site effects in the block formed by the sedimentary basin and strong amplification of the seismic ground motion for the sites bordering the basin to the north and west. We interpret the amplification in the north and south-west as probably originating from topographic irregularities locally coupled with sediment deposits, while in the center of the western part, the site effects could be explained by the presence of folds and related weakened and softened rocks. By the integration of several geophysical methods, we could distinguish areas where it is possible to build more safely. These zones are located in the northern part and encompass Quisqueya Park and neighboring areas as well as the village “La Source” in the southern part. In the rest of Fond Parisien, i.e., in the more central and eastern parts, buildings should be erected with caution, taking into account the nearby presence of the EPGF and the influence of fine sediments on the amplification of the seismic motion.
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Kumari, Sangeeta, A. P. Singh, Uma Shankar, Birender Pratap, and Arun Kumar Gupta. "Study of Local Site Conditions for Seismic Hazard Assessment at the BHU Campus, Varanasi, North India, using Ambient Noise Measurements." Journal of the Geological Society of India 98, no. 11 (November 15, 2022): 1531–40. http://dx.doi.org/10.1007/s12594-022-2208-6.
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Sharma, Antara, Santanu Baruah, Davide Piccinini, Sowrav Saikia, Manoj K. Phukan, Monisha Chetia, and J. R. Kayal. "Crustal seismic anisotropy beneath Shillong plateau - Assam valley in North East India: Shear-wave splitting analysis using local earthquakes." Tectonophysics 717 (October 2017): 425–32. http://dx.doi.org/10.1016/j.tecto.2017.08.027.
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Talukder, Mohammad Kamruzzaman, Philippe Rosset, and Luc Chouinard. "Reduction of Bias and Uncertainty in Regional Seismic Site Amplification Factors for Seismic Hazard and Risk Analysis." GeoHazards 2, no. 3 (September 3, 2021): 277–301. http://dx.doi.org/10.3390/geohazards2030015.
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Site amplification factors in National Building Codes are typically specified as a function of the average shear wave velocity over the first 30 m (Vs30) or site class (A, B, C, D and E) for defined ranges of Vs30 and/or ranges of depth to bedrock. However, a single set of amplification factors may not be representative of site conditions across the country, introducing a bias in seismic hazard and seismic risk analyses. This is exemplified by significant differences in geological settings between East and West coast locations in North America. Western sites are typically characterized by lower impedance contrasts between recent surface deposits and bedrock in comparison to Eastern sites. In North America, site amplification factors have been derived from a combination of field data on ground motions recorded during West Coast earthquakes and numerical models of site responses that are meant to be representative of a wide variety of soil profiles and ground motions. The bias on amplifications and their impact on seismic hazards is investigated for the Montreal area, which ranks second for seismic risks in Canada in terms of population and hazard (PGA of 0.25 g for a 2475 years return period). Representative soil profiles at several locations in Montreal are analyzed with 1-D site response models for natural and synthetic ground motions scaled between 0.1 to 0.5 g. Since bedrock depths are typically shallow (<30 m) across the island, bedrock shear wave velocities have a significant influence on the impedance contrast and amplifications. Bedrock shear wave velocity is usually very variable due to the differences in rock formations, level of weathering and fracturing. The level of this uncertainty is shown to be greatly decreased when rock quality designation (RQD) data, common information when bore hole data are logged, is available since it is highly correlated with both shear and compression wave velocities. The results are used to derive region-specific site amplification factors as a function of both Vs30 and site fundamental frequency and compared to those of the National Building Code of Canada (2015). The results of the study indicate that there are large uncertainties associated with these parameters due to variability in soil profiles, soil properties and input seismic ground motions. Average and confidence intervals for the mean and for predictions of amplification factors are calculated for each site class to quantify this uncertainty. Amplifications normalized relative to class C are obtained by accounting for the correlation between site class amplifications for given ground motions. Non-linearity in the analysis of equivalent linear 1-D site response is taken into account by introducing the non-linear G/Gmax and damping ratios curves. In this method, it is assumed that the shear strain compatible shear modulus and damping ratio values remains constant throughout the duration of the seismic excitation. This assumption is not fully applicable to a case when loose saturated soil profile undergo heavy shaking (PGA > 0.3 g). In this study, all simulations with input motion PGA >0.3 g have been performed by using the EL method instead of the NL method considering that cohesive soils (clay and silt) at Montreal sites are stiff and cohesionless soils (sand and gravel) are considerably dense. In addition, the field and laboratory data required to perform NL analyses are not currently available and may be investigated in future works.
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Behzadafshar, Katayoun. "Study on frequency content of provided strong ground motion in West Azerbaijan and East Azerbaijan." Ukrainian Journal of Ecology 7, no. 4 (December 25, 2017): 340–48. http://dx.doi.org/10.15421/2017_125.
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<p>This study aims to better reveal the characteristics of the assessed ground motion in west and east Azerbaijan. Due to existence of happened great earthquakes and large number of potential seismic sources in North-West of Iran which is located in junction of Alborz and Zagros seismotectonic provinces, it is an interesting area for seismologists. Considering to population and existence of large cities like Tabriz, Ardabil and Orumiyeh which play crucial role in industry and economy of Iran, authors decided to focus on study of frequency content of strong ground motion to achieve ground acceleration in different frequencies indicate critical frequencies in the studied area. in this study have been applied is professional industrial software which has been written in 2009 and provided by authors; Because This applied software can cover previous software weak points very well. Obtained hazard maps illustrate that maximum accelerations will be experienced in North West to South East direction which increased by frequency reduction from 100 Hz to 10 Hz then decreased by frequency reduce (to 0.25 Hz). Maximum acceleration will be occurred in the basement in 10 Hz.</p>