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1.
Errors in expected human losses due to incorrect seismic hazard estimates   总被引：8，自引：4，他引：4  
Seismic hazard maps are constructed by extrapolating from the frequency of small earthquakes, the annual probability of large, infrequent, earthquakes. Combining the potential contribution from all seismically active volumes, one calculates the peak ground acceleration with a probability to be exceeded by 10?% in 50?years at any given point. The consequential risk, the losses to be expected, derives from the damage the calculated shaking causes to buildings, and the impact on occupants due to collapsing structures. We show that the numbers of fatalities in recent disastrous earthquakes were underestimated by the world seismic hazard maps by approximately two to three orders of magnitude. Thus, seismic hazard maps based on the standard method cannot be used to estimate the risk to which the population is exposed due to large earthquakes.  相似文献   

2.
The development of the new seismic hazard map of metropolitan Tehran is based on probabilistic seismic hazard computation using the non-Poisson recurrence time model. For this model, two maps have been prepared to indicate the earthquake hazard of the region in the form of iso-acceleration contour lines. They display the non-Poisson probabilistic estimates of peak ground accelerations over bedrock for 10 and 63 % probability of exceedance in 50 years. To carry out the non-Poisson seismic hazard analysis, appropriate distributions of interoccurrence times of earthquakes were used for the seismotectonic provinces which the study region is located and then the renewal process was applied. In order to calculate the seismic hazard for different return periods in the probabilistic procedure, the study area encompassed by the 49.5–54.5°E longitudes and 34–37°N latitudes was divided into 0.1° intervals generating 1,350 grid points. PGA values for this region are estimated to be 0.30–0.32 and 0.16–0.17 g for 10 and 63 % probability of exceedance, respectively, in 50 years for bedrock condition.  相似文献   

3.
The present study presents a review on the progressive development of the seismic zonation map of India both from official agencies and also from independent individual studies. The zonation map have been modified and updated regularly with the occurrence of major destructive earthquakes over the years in the Indian subcontinent with the addition of new data. This study discusses the criteria chosen for the progressive zonation and the major earthquakes that were responsible for retrospection of the earlier published maps. The seismic zonation maps of India have also been prepared by various independent workers by adopting different approaches to achieve the purpose of the zonation. Despite the endeavors from various sources to provide a solution for the problem of earthquake hazards in India, there were many limitations on the zonation map as it gives the picture at a regional scale mostly on the bedrock level without addressing the local site conditions. But nevertheless, the seismic zonation map gives basic guidelines for any region to know the hazard scenario and if any city or urban population is under threat from seismic point of view, further site specific seismic microzonation may be carried out. In the International scenario, the Global Seismic Hazard Assessment Program (GSHAP) in 1999 prepared a hazard map for world in terms of peak ground acceleration (PGA) with a 10% probability of exceedance in 50 years, but it turned out to be an underestimation of the hazard parameter when compared with the observed PGA. To tackle the problem of seismic hazards, there was a need to have a detail study on the local site conditions in terms of its geological, geophysical and geotechnical properties. With the advent of better instrumentation and knowledge on the mechanics of earthquakes, it was possible to identify zones of hazards at a local level and this gives rise to the study of seismic microzonation. Seismic microzonation work has been carried out in India in some of the strategic important mega cities and industrial build up that has the potential of being damaged from future earthquakes, as has been shown in the past. Though the microzonation map is not the final output map, as it can still be updated at later stage with more input data, it does provide a more realistic picture on the site specific seismic hazard.  相似文献   

4.
Estimation of seismic hazard in Gujarat region, India   总被引：1，自引：1，他引：0  
The seismic hazard in the Gujarat region has been evaluated. The scenario hazard maps showing the spatial distribution of various parameters like peak ground acceleration, characteristics site frequency and spectral acceleration for different periods have been presented. These parameters have been extracted from the simulated earthquake strong ground motions. The expected damage to buildings from future large earthquakes in Gujarat region has been estimated. It has been observed that the seismic hazard of Kachchh region is more in comparison with Saurashtra and mainland. All the cities of Kachchh can expect peak acceleration in excess of 500?cm/s2 at surface in case of future large earthquakes from major faults in Kachchh region. The cities of Saurashtra can expect accelerations of less than 200?cm/s2 at surface. The mainland Gujarat is having the lowest seismic hazard as compared with other two regions of Gujarat. The expected accelerations are less than 50?cm/s2 at most of the places. The single- and double-story buildings in Kachchh region are at highest risk as they can expect large accelerations corresponding to natural periods of such small structures. Such structures are relatively safe in mainland region. The buildings of 3?C4 stories and tall structures that exist mostly in cities of Saurashtra and mainland can expect accelerations in excess of 100?cm/s2 during a large earthquake in Kachchh region. It has been found that a total of 0.11 million buildings in Rajkot taluka of Saurashtra are vulnerable to total damage. In Kachchh region, 0.37 million buildings are vulnerable. Most vulnerable talukas are Bhuj, Anjar, Rapar, Bhachau, and Mandvi in Kachchh district and Rajkot, Junagadh, Jamnagar, Surendernagar and Porbandar in Saurashtra. In mainland region, buildings in Bharuch taluka are more vulnerable due to proximity to active Narmada-Son geo-fracture. The scenario hazard maps presented in this study for moderate as well as large earthquakes in the region may be used to augment the information available in the probabilistic seismic hazard maps of the region.  相似文献   

5.
The assessment of local site effects on seismic ground motions is of great importance in earthquake engineering practice. Several destructive earthquakes in the past have demonstrated that the amplification of ground motion and associated damage to structures due to local site conditions is a significant consideration in earthquake hazard analysis. A recent paper published in this journal highlights the hazard posed by earthquakes in the megacity of Kolkata in India due to its seismic and geological settings. The seismic hazard assessment study speculates that the deep alluvial deposit in the city may increase the seismic hazard probably due to the amplification of the seismic energies. This paper focuses on the seismic response studies of the various soil strata (i.e. for local subsurface conditions) obtained from various construction sites in the city for predicted earthquake. It is very well recognized that site response studies (a part of seismic microhazard zonation for urban areas) are the first step towards performance-based foundation design or seismic risk analysis and mitigation strategy. One of the problems for carrying out site-specific study in Kolkata is the lack of recorded strong motion data in the city. Hence, this paper outlines a methodology to carry out site-specific study, where no strong motion data or seismic data are available. The methodology uses wavelet-based spectrum compatibility approach to generate synthetic earthquake motions and equivalent linear method for seismic site response analysis. The Mega City of Kolkata has been considered to explain the methodology. Seismic hazard zonation map by the Bureau of Indian Standards classifies the City of Kolkata as moderate seismic zone (Zone III) with a zone factor 0.16. On the other hand, GSHAP(Global Seismic Hazard Assessment Program) map which is based on 10% probability of exceedance in 50 years specifies a maximum peak ground acceleration (PGA) of 1.6 m/s2 (0.163 g) for this region. In the present study, the seismic response has been carried out based on GSHAP. The results of the analysis indicate the amplification of ground motion in the range of 4.46–4.82 with the fundamental period ranging from 0.81 to 1.17 s. Furthermore, the maximum spectral accelerations vary in the range of 0.78–0.95 g.  相似文献   

6.
The Himalayas are one of very active seismic regions in the world where devastating earthquakes of 1803 Bihar–Nepal, 1897 Shillong, 1905 Kangra, 1934 Bihar–Nepal, 1950 Assam and 2011 Sikkim were reported. Several researchers highlighted central seismic gap based on the stress accumulation in central part of Himalaya and the non-occurrence of earthquake between 1905 Kangra and 1934 Bihar–Nepal. The region has potential of producing great seismic event in the near future. As a result of this seismic gap, all regions which fall adjacent to the active Himalayan region are under high possible seismic hazard due to future earthquakes in the Himalayan region. In this study, the study area of the Lucknow urban centre which lies within 350 km from the central seismic gap has been considered for detailed assessment of seismic hazard. The city of Lucknow also lies close to Lucknow–Faizabad fault having a seismic gap of 350 years. Considering the possible seismic gap in the Himalayan region and also the seismic gap in Lucknow–Faizabad fault, the seismic hazard of Lucknow has been studied based on deterministic and the probabilistic seismic hazard analysis. Results obtained show that the northern and western parts of Lucknow are found to have a peak ground acceleration of 0.11–0.13 g, which is 1.6- to 2.0-fold higher than the seismic hazard compared to the other parts of Lucknow.  相似文献   

7.
A method of seismic zonation based on the deterministic modeling of rupture planes is presented. Finite rupture planes along identified lineaments are modeled in the Uttarakhand Himalaya based on the semi empirical technique of Midorikawa (Tectonophysics 218:287–295, 1993). The expected peak ground acceleration thus estimated from this technique is divided into different zones similar to zones proposed by the Bureau of Indian standard, BIS (Indian standards code of practice for earthquake-resistant design of structures, 2002). The proposed technique has been applied to Kumaon Himalaya area and the surrounding region for earthquakes of magnitude M > 6.0. Approximately 56000 km2 study area is classified into the highest hazard zone V with peak accelerations of more than 400 cm/s2. This zone V includes the cities of the Dharchula, Almora, Nainital, Haridwar, Okhimath, Uttarkashi, Pithorahargh, Lohaghat, Munsiari, Rudraprayag, and Karnprayag. The Sobla and Gopeshwar regions belong to zone IV, where peak ground accelerations of the order from 250 to 400 cm/s2 can be expected. The prepared map shows that epicenters of many past earthquakes in this region lie in zone V, and hence indicating the utility of developed map in defining various seismic zones.  相似文献   

8.
According to the latest UNFA Report on state of world population 2007, unleashing the potential of urban growth by 2030, the urban population will rise to 5 billion or 60?% of the world population. Liquefaction in urban areas is dangerous phenomenon, which cause more damage to buildings and loss of human lives. Chennai, the capital city of the State Tamil Nadu in India, is one of the densely populated cities in the country. The city has experienced moderate magnitude earthquakes in the past and also categorized under moderate seismic hazard as per the Bureau of Indian Standards (BIS in Criteria for earthquake resistant design of structures; Bureau of Indian Standards, New Delhi, 1893 2001). A study has been carried out to evaluate the liquefaction potential of Chennai city using geological and geomorphological characteristics. The subsurface lithology and geomorphological maps were combined in the GIS platform for assessing the liquefaction potential. The liquefaction hazard broadly classified into three categories viz., liquefaction likely, possible and not likely areas. Mainly, the liquefaction likely areas spread along the coastal areas and around the river beds. The rest of the areas are liquefaction not likely and possible. The present map can be used as first-hand information on regional liquefaction potential for the city, and it will be help to the scientists, engineers and planners who are working for future site-specific studies of the city.  相似文献   

9.
This study presents the future seismic hazard map of Coimbatore city, India, by considering rupture phenomenon. Seismotectonic map for Coimbatore has been generated using past earthquakes and seismic sources within 300 km radius around the city. The region experienced a largest earthquake of moment magnitude 6.3 in 1900. Available earthquakes are divided into two categories: one includes events having moment magnitude of 5.0 and above, i.e., damaging earthquakes in the region and the other includes the remaining, i.e., minor earthquakes. Subsurface rupture character of the region has been established by considering the damaging earthquakes and total length of seismic source. Magnitudes of each source are estimated by assuming the subsurface rupture length in terms of percentage of total length of sources and matched with reported earthquake. Estimated magnitudes match well with the reported earthquakes for a RLD of 5.2% of the total length of source. Zone of influence circles is also marked in the seismotectonic map by considering subsurface rupture length of fault associated with these earthquakes. As earthquakes relive strain energy that builds up on faults, it is assumed that all the earthquakes close to damaging earthquake have released the entire strain energy and it would take some time for the rebuilding of strain energy to cause a similar earthquake in the same location/fault. Area free from influence circles has potential for future earthquake, if there is seismogenic source and minor earthquake in the last 20 years. Based on this rupture phenomenon, eight probable locations have been identified and these locations might have the potential for the future earthquakes. Characteristic earthquake moment magnitude (M w ) of 6.4 is estimated for the seismic study area considering seismic sources close to probable zones and 15% increased regional rupture character. The city is divided into several grid points at spacing of 0.01° and the peak ground acceleration (PGA) due to each probable earthquake is calculated at every grid point in city by using the regional attenuation model. The maximum of all these eight PGAs is taken for each grid point and the final PGA map is arrived. This map is compared to the PGA map developed based on the conventional deterministic seismic hazard analysis (DSHA) approach. The probable future rupture earthquakes gave less PGA than that of DSHA approach. The occurrence of any earthquake may be expected in near future in these eight zones, as these eight places have been experiencing minor earthquakes and are located in well-defined seismogenic sources.  相似文献   

10.
Seismic hazard studies were conducted for Gaziantep city in the South Anatolia of Turkey. For this purpose, a new attenuation relationship was developed using the data of Zaré and Bard and accelerations were predicted employing this new equation. Deterministic approach, total probability theorem and GIS methodology were all together utilized for the seismic assessments. Seismic hazard maps with 0.25° grid intervals considering the site conditions were produced by the GIS technique. The results indicated that the acceleration values by the GIS hazard modelings were matched with the ones from the deterministic approach, however, they were underestimated comparing with the total probability theorem. In addition, the GIS based seismic hazard maps showed that the current seismic map of Turkey fairly yields conservative acceleration values for the Gaziantep region. Therefore, the constructed GIS hazard models are offered as a base map for a further modification of the current seismic hazard map.  相似文献   

11.
A. Golara 《Natural Hazards》2014,73(2):567-577
Seismic hazard maps are widely used for engineering design, land-use planning, and disaster mitigation. The development of the new seismic hazard map of Iran with regard to the specification of Iranian high-pressure gas network is based on probabilistic seismic hazard analysis using the historical and new earthquakes data, geology, tectonics, fault activity, and seismic zone models in Iran. The map displays the probabilistic estimates of peak ground acceleration for the return period of 2,475 year (2 % probability in 50 years). The results presented in this study will provide the basis for the preparation of risk map, the estimation of insurance premiums, finding best paths for future pipelines, planning, and relocating lifeline facilities especially for interconnected infrastructures.  相似文献   

12.
Mumbai city, the economical capital of India, is located on the west coast of stable intra-plate continental region of Peninsular India which has an experience of significant historical earthquakes in the past. The city stood as the fourth most populous city in the world. Recent seismo-tectonic studies of this city highlighted the presence of active West coast fault and Chiplun fault beneath the Deccan basalt. In the present study, spatial variability of probabilistic seismic hazard for Mumbai region (latitudes of 18.85–19.35°N and longitudes of 72.80–73.15°E at a grid spacing of 0.05°) which includes Mumbai city, Suburban, part of Thane district and Navi Mumbai, in terms of ground motion parameters; peak horizontal acceleration and spectral acceleration at 1.0-s period for 2 and 10 % probability of exceedance in 50 years are generated. The epistemic uncertainty in hazard estimation is accounted by employing seven different ground motion prediction equations developed for worldwide shallow crustal intra-plate environments. Further, the seismic hazard results are deaggregated for Mumbai (latitude 18.94°N, longitude 72.84°E) to understand the relative contributions of earthquake sources in terms of magnitude and distance. The generated hazard maps are compared with the zoning specified by Indian seismic code (IS1893: Part 1 in Indian standard criteria for earthquake-resistant design of structures, Part 1—General provisions and buildings. Bureau of Indian Standards, New Delhi, India, 2002) for rocky site. Present results show an underestimation of potential seismic hazard in the entire study region by non-probabilistic zoning prescribed by IS1893: Part 1 with significantly higher seismic hazard values in the southern part of Navi Mumbai.  相似文献   

13.
Using 4.0 and greater magnitude earthquakes which occurred between 1 January 1900 and 31 Dec 2008 in the Sinop province of Turkey this study presents a seismic hazard analysis based on the probabilistic and statistical methods. According to the earthquake zonation map, Sinop is divided into first, second, third and fourth-degree earthquake regions. Our study area covered the coordinates between 40.66°– 42.82°N and 32.20°– 36.55°E. The different magnitudes of the earthquakes during the last 108 years recorded on varied scales were converted to a common scale (Mw). The earthquake catalog was then recompiled to evaluate the potential seismic sources in the aforesaid province. Using the attenuation relationships given by Boore et al. (1997) and Kalkan and Gülkan (2004), the largest ground accelerations corresponding to a recurrence period of 475 years are found to be 0.14 g for bedrock at the central district. Comparing the seismic hazard curves, we show the spatial variations of seismic hazard potential in this province, enumerating the recurrence period in the order of 475 years.  相似文献   

14.
This article presents probabilistic seismic hazard analyses of northern Pakistan region carried out to produce macro-seismic hazard maps for the region that define new regional ground motion design parameters for 95-, 475-, 975- and 2475-year return period earthquakes as regional contour maps and horizontal uniform hazard at important cities. The Cornell–McGuire approach (Cornell in Bull Seismol Soc Am 58(05):1583–1606, 1968; McGuire in FORTRAN computer program for seismic risk analysis. US Geological Survey, Open file Report, 76-6768, 1976) is used to carry out the analyses at 0.1° rectangular grid. The seismotectonic model of the region used in analysis consists of shallow and deep area zones differentiated based on the focal depths of the earthquakes. Earthquake catalogue compiled and used in the analysis is a composite catalogue composed of 19,373 events. Ground motion prediction equations (GMPEs) used are calibrated using goodness-of-fitness measures and visual inspection with local strong motion data. Epistemic uncertainty in the GMPEs is taken into account through the logic tree approach. Comparison of ground motions due to deep earthquakes is made for the first time for the region. The comparison between ground motion due to shallow and deep earthquakes indicates that the seismic hazard would be underestimated if the deep earthquakes are excluded. Ground motion values obtained in this study considering all the earthquakes suggest ground motions are dominant towards the north east of the region. The proposed study indicates that the ground motion hazard values suggested by the current Building Code of Pakistan underestimate the seismic hazard. Final results of this study are in close agreement with the recent studies on the region.  相似文献   

15.
The Indian subcontinent is characterized by various tectonic units viz., Himalayan collision zone in North, Indo-Burmese arc in north-east, failed rift zones in its interior in Peninsular Indian shield and Andaman Sumatra trench in south-east Indian Territory. During the last about 100 years, the country has witnessed four great and several major earthquakes. Soon after the occurrence of the first great earthquake, the Shillong earthquake (M w: 8.1) in 1897, efforts were started to assess the seismic hazard in the country. The first such attempt was made by Geological Survey of India in 1898 and since then considerable progress has been made. The current seismic zonation map prepared and published by Bureau of Indian Standards, broadly places seismic risk in different parts of the country in four major zones. However, this map is not sufficient for the assessment of area-specific seismic risks, necessitating detailed seismic zoning, that is, microzonation for earthquake disaster mitigation and management. Recently, seismic microzonation studies are being introduced in India, and the first level seismic microzonation has already been completed for selected urban centres including, Jabalpur, Guwahati, Delhi, Bangalore, Ahmadabad, Dehradun, etc. The maps prepared for these cities are being further refined on larger scales as per the requirements, and a plan has also been firmed up for taking up microzonation of 30 selected cities, which lie in seismic zones V and IV and have a population density of half a million. The paper highlights the efforts made in India so far towards seismic hazard assessment as well as the future road map for such studies.  相似文献   

16.
Probabilistic seismic hazard analysis (PSHA) is carried out for the archaeological site of Vijayapura in south India in order to obtain hazard consistent seismic input ground-motions for seismic risk assessment and design of seismic protection measures for monuments, where warranted. For this purpose the standard Cornell-McGuire approach, based on seismogenic zones with uniformly distributed seismicity is employed. The main features of this study are the usage of an updated and unified seismic catalogue based on moment magnitude, new seismogenic source models and recent ground motion prediction equations (GMPEs) in logic tree framework. Seismic hazard at the site is evaluated for level and rock site condition with 10% and 2% probabilities of exceedance in 50 years, and the corresponding peak ground accelerations (PGAs) are 0.074 and 0.142 g, respectively. In addition, the uniform hazard spectra (UHS) of the site are compared to the Indian code-defined spectrum. Comparisons are also made with results from National Disaster Management Authority (NDMA 2010), in terms of PGA and pseudo spectral accelerations (PSAs) at T = 0.2, 0.5, 1.0 and 1.25 s for 475- and 2475-yr return periods. Results of the present study are in good agreement with the PGA calculated from isoseismal map of the Killari earthquake, \({\hbox {M}}_{\mathrm{w}} = 6.4\) (1993). Disaggregation of PSHA results for the PGA and spectral acceleration (\({\hbox {S}}_{\mathrm{a}}\)) at 0.5 s, displays the controlling scenario earthquake for the study region as low to moderate magnitude with the source being at a short distance from the study site. Deterministic seismic hazard (DSHA) is also carried out by taking into account three scenario earthquakes. The UHS corresponding to 475-yr return period (RP) is used to define the target spectrum and accordingly, the spectrum-compatible natural accelerograms are selected from the suite of recorded accelerograms.  相似文献   

17.
In recent years, Iraq has experienced an increase in seismic activity, especially, near the east boundary with Iran. Previous studies present their results in terms of PGA and for return periods of 500 years and less, and other studies not continued to include the whole PSHA process whereas some recent studies continued to include the whole PSHA process using earthquakes data till 2009 including dependent events. This study includes two main stages, the first is collecting the earthquakes records including the recent events till the end of March 2016 and applying data processing to get the net catalog to independent events. The second stage is applying the steps of PSHA method. Matlab programs have been built to execute these two stages and to convert the results of PSHA computations into contours of 5% damping PGA and spectral accelerations at 0.2 and 1.0 s for a return period of 2475 years, and for rock sites. Also, spectral acceleration against period has been presented for main cities. Also, the PGA map, for a return period of 475 years, has been plotted and then prepared together with similar maps of neighbor countries in one map for comparison. In general, this comparison indicates the similarity in behavior but, the values reveal a relative agreement and they are between Turkish and Iranian values.  相似文献   

18.
Antakya city is at risk because of strong earthquakes occurring in the area, and different soil conditions that can produce variation of the ground motion amplification. Microzonation of cities provides a basis for site-specific hazard analysis in urban settlements. In particular, seismic microzonation can be provided by means of detailed seismic assessment of the area, including earthquake recordings and geological studies. In this paper, we propose a preliminary microzonation map for the city of Antakya, based on the variation of the dominant periods and shear velocities of the sediments covering the area. The periods are retrieved from microtremor measurements conducted at 69 sites, using the horizontal-to-vertical spectral ratio technique. The results of microtremor analysis were compared with data obtained from refraction microtremor (ReMi) measurements at four profiles crossing the studied area. According to the classification of dominant periods, Antakya city can be divided into five zones, probably prone to different levels of seismic hazard. The shorter natural periods are in inner Antakya and both the sides of Asi River (i.e., northern and southern parts). The eastern and western parts of Antakya have maximum dominant periods. The V s 30 values were calculated by using the ReMi method along the profiles. Antakya city has V s 30 values in the range of category C of the national earthquake hazard reduction programme site classification.  相似文献   

19.
Iranian strong motion records as well as detailed conditions of their instrument sites and the characteristics of their causative seismic sources are compiled and processed. The dataset consists of 2286 three-component records from 461 Iranian earthquakes with at least two high-quality records having moment magnitude from 3.9 to 7.3. These records are about 20% of the Iranian database and are suitable for seismic hazard analysis and engineering applications. Perhaps for the first time in the literature, the distance to the surface projection of the fault is reported for a great number of records corresponding to earthquakes with M > 6.0. The raw accelerations are processed using the wavelet de-noising method. Having corrected and filtered these raw data, the pseudospectral accelerations are calculated for each of the three components of time series, separately. In addition to the ground motion parameters, a large and comprehensive list of metadata characterizing the recording conditions of each record is also developed. Moreover, careful revision of the characteristics of the earthquakes such as location, magnitude, style of faulting and fault rupture plane geometry, if available, is carried out using the best available information in a scientifically sound manner. Finally, we also focus on special ground motion records including records with peak ground acceleration (PGA) >300 cm/s2 and distances less than 30 km. These are “exceptional” records in the Iranian dataset and include less than 2% of the selected dataset.  相似文献   

20.
A comprehensive analytical as well as numerical treatment of seismological, geological, geomorphological and geotechnical concepts has been implemented through microzonation projects in the northeast Indian provinces of Sikkim Himalaya and Guwahati city, representing cases of contrasting geological backgrounds — a hilly terrain and a predominantly alluvial basin respectively. The estimated maximum earthquakes in the underlying seismic source zones, demarcated in the broad northeast Indian region, implicates scenario earthquakes of M W 8.3 and 8.7 to the respective study regions for deterministic seismic hazard assessments. The microzonation approach as undertaken in the present analyses involves multi-criteria seismic hazard evaluation through thematic integration of contributing factors. The geomorphological themes for Sikkim Himalaya include surface geology, soil cover, slope, rock outcrop and landslide integrated to achieve geological hazard distribution. Seismological themes, namely surface consistent peak ground acceleration and predominant frequency were, thereafter, overlaid on and added with the geological hazard distribution to obtain the seismic hazard microzonation map of the Sikkim Himalaya. On the other hand, the microzonation study of Guwahati city accounts for eight themes — geological and geomorphological, basement or bedrock, landuse, landslide, factor of safety for soil stability, shear wave velocity, predominant frequency, and surface consistent peak ground acceleration. The five broad qualitative hazard classifications — ‘low’, ‘moderate’, ‘high’, ‘moderate high’ and ‘very high’ could be applied in both the cases, albeit with different implications to peak ground acceleration variations. These developed hazard maps offer better representation of the local specific seismic hazard variation in the terrain.  相似文献   

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