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The effectiveness of the tuned mass damper inerter (TMDI) in reducing the vibration of building structures under site-specific earthquake excitation is investigated. The site is Guwahati, Assam, which lies in the most severe seismic intensity zone in India. In this paper, the optimization of the TMDI design parameters is carried out for the site-specific input derived for the building site by a modulated Clough-Penzien (C-P) spectrum fitted to the power spectral density function obtained from a strong motion model of the site. All possible topologies of the TMDI, with one terminal of the inerter being connected to the damper mass attached to the top storey of the example buildings, and the other terminal being connected to any other floor, are investigated. The structure-TMDI system is analyzed both in the frequency-domain and in the time-domain. A numerical study is conducted with two example building structures. Optimization of design parameters of the TMDI is carried out using the technique of simulated annealing in the frequency-domain using the site-specific modulated Clough-Penzien spectrum as input. The performance of the optimal TMDI cases is evaluated by subjecting the example structures to 10 site-specific synthetically generated accelerograms. Results indicate that the TMDI is superior to the TMD for all topologies of the TMDI in case of the 3-storieed structure; and for topologies of the TMDI in which the inerter spans more than 4 floors for the 8-storied structure, with improved reductions in top-floor displacement, acceleration, and stroke length. [ABSTRACT FROM AUTHOR]

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

Exposure to extreme shocks in early life is found to have a lasting impact in adulthood. Exploiting the variation in exposure measured by age and intensity of an earthquake, we evaluate the impact of a 7.7 MW earthquake in Gujarat, India, on the health stock of children who were in utero or below three years. Using the India Human Development Survey data from 2004–05 and earthquake intensity data, we find an affected girl child to be shorter by at least 2.5 cm at the age of 3–6 years. The earthquake seems to have destroyed the household infrastructures and health facilities, affecting the expecting mothers and newborn children. The households using services to meet nutritional needs of children and pregnant women seem to be least affected. Our findings recommend faster reconstruction activities and highlight the importance of universal healthcare and nutritional delivery services to mitigate the impacts of early-life shocks. [ABSTRACT FROM AUTHOR]

The Shore Temple in Mahabalipuram (Tamil Nadu, Southern India) exists since the late 7th century. Historical sources suggest that it was built on an island in honour of the gods Vishnu and Shiva. A former bridge over the canal, which separated the island from the mainland, and a seawall, which protected the shore from the waves are dysfunctional now, as they are located too high above the present day sea level. A holy well, part of the temple complex, reaches down to the modern freshwater lens. We suggest that about 1 m uplift occurred after the construction of the temple, the canal and the seawall, but before the construction of the well. This event during the reign of King Rajasimhan in the early 8th century most likely was caused by an earthquake of magnitude M > 6.5 that led to the uplift of the island. There are thick walls of a ruined masonry building in the former, sand-filled canal, tilted in various directions. These are evidence for liquefaction of subsoil, caused by a second earthquake of intensity IX-X. The east coast of India has remained prone to destructive earthquakes: archaeoseismology proves to be useful tool which can help to identify these areas. [ABSTRACT FROM AUTHOR]

The earthquakes have the most dominating societal and economic impact on the built environment. The earthquakes in an intraplate region are infrequent but often damaging. The uncontrolled urban growth in cities due to population explosion and migration makes it necessary to assess seismic hazards in an active region. It provides parameters for seismic safety and helps in disaster mitigation. The Kachchh Rift Basin (KRB) of western India is a seismically active intraplate region where many damaging earthquakes have occurred in the past (Mw 7.8 in 1819, Mw 7.6 in 2001). The KRB hosts many economic corridors and ports. Though the region has been put in a category with highest seismic hazard, the entire region is not prone to high hazards. The primary objective of the study is to integrate major attributes that influence seismic hazard on a GIS platform and prepare a multi-criteria-based hazard map by multi-criteria decision process named as analytical hierarchy process (AHP) developed by Saaty. In this study, the information about some of the attributes like peak ground acceleration (PGA), geology and geomorphology, and tsunami hazard is taken from published literature, whereas shear wave velocity to 30 m depth (Vs)30 and amplification factor were obtained through empirical relationships. The integration of these different attributes was performed, and weights were assigned depending on their contribution to the seismic hazard. The multi-criteria approach reveals that the southwestern part comprising of Kachchh mainland has a low hazard as compared to central and northern parts and almost 1 million people and around 0.18 million houses are exposed to moderate to high hazard. Large swaths of land are prone to liquefaction hazard. The corridor comprising of Bhuj, Bhachau and Rapar needs seismic microzonation. This macro level hazard map will be beneficial for the urban planners and government authorities to decide the areas, where seismic microzonation or site-specific studies are required that would help in mitigating earthquake disasters in the future. [ABSTRACT FROM AUTHOR]

The region of Garhwal is one of the most seismically active areas in India. Many destructive earthquakes have occurred there in the past. The current seismic activity in Garhwal is also high. The region is characterized by a high population density; therefore, in choosing ways to develop it, protecting the population and reducing material damage from expected strong seismic events are of utmost urgency. The solution primarily requires using various antiseismic measures during construction, which are selected based on the characteristics of seismic treatments. The purpose of this research is to assess the seismic hazard and seismic treatments in some settlements of Garhwal. To solve this problem, data obtained in previous stages of studies in Western Himalaya are interpreted once again. In particular, the results of geological and geophysical and structural and geological studies have made it possible to reveal the main seismogenerating structures and determine their characteristics. The analysis of the data on strong ground motions in the epicenter areas of the Dharamsala (April 26, 1986, Mw = 5.5), Uttarkashi (October 20, 1991, Mw = 6.8), and Chamoli (March 28, 1999, Mw = 6.5) earthquakes and the study of the attenuation patterns of ground accelerations in the Garhwal region have enabled us to estimate the expected maximum magnitudes, focal depths, and source mechanisms of the earthquakes. A regional model of seismic source zones (SSZs) is proposed. Using the results of seismological and seismotectonic studies, the parameters of ground motions during the maximum credible earthquakes are estimated, such as peak ground accelerations, spectra and durations of vibrations, and the seismic-effect value in the seismic intensity scale points for some settlements in Garhwal. [ABSTRACT FROM AUTHOR]

This paper aims to improve the site classification scheme and amplification factors for the Indian Seismic Code. The present code IS 1893 (1):2016 ignores the amplification of effective peak ground acceleration due to the existence of soft soil layers. This results in lower design spectral accelerations on soil sites compared to those adopted by codes in other nations. 124 well documented sites from India are considered for ground response analysis using the equivalent linear procedure of DEEPSOIL. Time histories recorded from India and abroad are made spectrum compatible with the Type I spectra of Indian code, corresponding to all the seismic intensities with Effective Peak Ground Acceleration of 0.1 g, 0.16 g, 0.24 g and 0.36 g. Statistical methods are used to construct mean, mean plus standard deviation and mean minus standard deviation response spectra and amplification factors for the sites considered. Before the statistical analysis, each amplification factor curve is normalized with the effective site period (Tg) which exhibits a "characteristic peak at values of T/Tg not far from 1". Normalized acceleration response spectra as well as period dependent soil amplification factors and equations are proposed for the new classification system. It is observed that the stratigraphy, impedance contrast, sediment thickness and site period play an important role in determining the soil amplification factors and therefore, should be considered in the future site classification schemes of the Indian Seismic Code. [ABSTRACT FROM AUTHOR]

Earthquakes in the Indo-Burmese arc occur due to interaction of India and Sunda plates along the Indo-Burmese Wedge and Sagaing Fault. Majority of the moderate to major magnitude earthquakes in the Indo-Burmese Wedge occur within the Indian slab and very few of them occur on the plate interface. Earthquakes within the wedge are rare and the 22 June 2020 earthquake of magnitude 5.5 (Mw) on the India-Myanmar border in Mizoram, India, at shallow depth is probably one such earthquake. The earthquake caused moderate damage (maximum intensity VIII on MSK scale) in remote border villages (Vaphai and Chawngtui) with sparse population without any fatality. The earthquake did not seem to be related with the Mat Fault, which was transverse to the north-south trending wedge, as various estimates of mainshock and the region of maximum damage was ~20 km northeast of the surface trace of the Mat Fault. It appeared to be associated with almost north-south oriented Churachandpur Mao Fault (CMF) with dextral slip which mapped extensively and monitored geodetically in the neighbouring regions of Manipur and Nagaland to the north. Occurrence of this shallow depth earthquake may imply that some segment of the CMF might be seismically active, unlike in the north, where it appears to be predominantly aseismic. This implies that the seismic hazard along the CMF may vary along its length. [ABSTRACT FROM AUTHOR]

The Indian subcontinent has a history of overwhelming earthquakes. The main cause for the high frequency and intensity of the earthquakes is that the Indian plate is driving into Asia at a rate of approximately 50 mm/year in north-east direction. Geographical statistics of India shows that almost 54% of the land is susceptible to earthquakes. In this paper, we analyzed the trend of earthquakes that occurred during 2000-2019 in Indian continent by the method of moving averages and fitting the curve to the past data. Here, the past behavior of seismic events of different magnitudes and fatalities due to this natural hazard during last two decades has been discussed. [ABSTRACT FROM AUTHOR]

Spatial variation of seismic b -value is estimated in the Indo-Myanmar subduction zone of northeast (NE) India using the homogeneous part of earthquake catalogue (1996–2015), recorded by International Seismological Center (ISC), consisting of 895 events of magnitude M W  ≥ 3.9. The study region is divided into 1° × 1° square grids and b-values are estimated at each grid by maximum likelihood method. In this study, the b-value varies from 0.75 to 1.54 in the region. Significant variation of low b-value in the respective location may indicate high stress accumulation in that region. Spatial variation reveals intermediate b -value anomalies around the epicenter of the M w  = 6.7 Manipur earthquake which occurred on 3rd January at 23:05 UTC (4 January 2016 at 04:35 IST). The variations of b-values are also estimated with respect to depth. The low b -value associated with the depth range ∼15–55 km, which may imply crustal homogeneity and high stress accumulation in the crust. Since, NE India lies in the seismic zone V of the country; this study can be helpful to understand seismotectonics in the region. [ABSTRACT FROM AUTHOR]

Assumptions about regional earthquake hazard in the Bay of Bengal and the frequency of such events were brought into question by the 26 December 2004 Indian Ocean earthquake and tsunami. An initial element of earthquake risk management is to quantify the hazard, and catalogues of past events are a major contribution to that effort. We have developed a new comprehensive catalogue of earthquakes with a felt intensity occurring before 31 December 1899 and of magnitude of four and above for instrumentally recorded events from 1 January 1900 using all available sources. Between 810BC and 2012, we find that 562 earthquakes were experienced in the Bay of Bengal and Bangladesh. Unsurprisingly, data on events become increasingly scarce the further back in time the catalogue extends and significant conflicts and discrepancies are identified for events listed in different sources. Nonetheless, our new data catalogue provides a useful foundation upon which further archival research may build in order to develop a richer understanding of regional earthquake hazard. [ABSTRACT FROM AUTHOR]

A moderate earthquake of local magnitude 6.4 occurred in Sonitpur Assam, India on April 28, 2021. Although the earthquake occurred in India, Bhutan suffered considerable damage to structures and infrastructures, especially in the eastern districts. Due to inherent vulnerabilities of Bhutanese residential buildings, encapsulated in rural stone masonry and rammed earth construction, widespread damages were reported in many districts although the shaking was moderate only. We report the damage mechanisms observed in buildings and infrastructures and juxtapose the mechanisms with seismic vulnerability of Bhutanese residential buildings using analytical and empirical approaches. Finite element analysis is performed to validate the failure mechanisms. Intensity map for the earthquake is constructed based on the damage description and vulnerability curve is derived for rural stone masonry building class using the damage data of 2009, 2011, and 2021 earthquakes. The sum of observations and analyses highlights that the Bhutanese residential buildings are likely to be damaged considerably even by moderate shaking, and their capacities are expected to be far exceeded by strong shaking. • Seismic vulnerability of Bhutanese vernacular stone masonry is reported. • Seismic vulnerability is presented using observed damage mechanisms. • Empirical seismic vulnerability curve is derived using damage data. • Analytical fragility functions for Bhutanese vernacular stone masonry are created. [ABSTRACT FROM AUTHOR]

The Kachchh paleo-rift basin of western India which recently experienced Mw 7.6, 26th January 2001 Bhuj earthquake, is one of the most active and vulnerable intra-cratonic zones in the world categorized as seismic zone V, i.e. having potential to produce earthquakes of intensity IX or higher. We analysed the geodetic and seismic principal strain rates to reveal the seismic hazard potential of the Kachchh paleo-rift basin. The geodetic strain rates are calculated from the reported surface motion in the region using a modified least-square inversion scheme that utilizes distance and spatial coverage dependent weight factor on the uncertainty in the plate motion to get a reliable estimate of principal strain rates and their orientations at regular grid nodes. An optimal weighting factor yields a mean rate of compression of ~ − 16 ± 6 nano strain/yr towards north-northeast in the region. The seismic strain rates are estimated based on fault plane solutions of the significant past earthquakes (Mw ≥ 2.5) of the region using the Kostrov formulations. The seismic strain rate and stress inversion estimate indicate that the region released elastic strain at an average rate of ~ − 85 nano strain/yr towards north-south in the past 350 years. A composite analysis of the geodetic and seismic strain rates indicates 900–3000 years of recurrence interval of major (Mw 7.8–8) earthquakes in the region. Our analysis indicates a high rate of strain build-up on the reactivated major faults in the region that have the potential to generate devastating (Mw ≥6) earthquakes. [Display omitted] • A high rate of tectonic compression with a mean strain build-up rate of ~ 16 nano strain/yr towards NNE is obtained. • Three major earthquakes in past 350 years contribute >98% in measure of average seismic strain rate of ~85 nano strain/yr. • 5°-40° change in orientation of both (geodetic & seismic) principal strain rates axes show a rather complex tectonic zone. • Composite analysis of geodetic and seismic strain rates yields a recurrence period of >1000 years for Mw >7.5 earthquakes. • Zones with higher strain build-up compared to strain release rate have higher probability to produce next >Mw 6 earthquakes. [ABSTRACT FROM AUTHOR]

A relative in-depth review of current earthquake loss estimation software packages are given and compared in this paper. A simple and user-friendly tool for quick seismic risk assessment has been developed for Indian condition using spectrum-based, micro-level-based ground motion attenuation relation. The attenuation relation used here defines a suitable hazard scenario with moment magnitude and location of the earthquake as parameters. A comparison of losses using the proposed software with other open-source software tools has been carried using two case studies situated at different location of India, covering different building typologies. It is observed that the losses estimated by the proposed tool found to be less than the losses estimated by other two tools based on macroseismic intensity and PGA approach. The variation in the loss estimates results mainly from the lack of correlation between the different definitions of seismic hazard and different vulnerability models. [ABSTRACT FROM AUTHOR]

The Talala (Sasangir) area in the Saurashtra region of Gujarat, western India, is experiencing tremors since 2001. The swarm type of earthquake activity in 2001, 2004, and every year from 2007 onward has occurred after the monsoon and lasted 2-3 months each time. In 2007 some 200 shocks (largest M 5.0) and in 2011 about 400 shocks down to M1 are well recorded with 1-2 km location error. The focal depths are about 2-10 km and shocks are accompanied by blast-like subterranean sounds. The epicenter (21.09 N 70.45E, focal depth: 5 km from location program, 3 km from MTS) of the October 20, 2011 mainshock occurred about 12-km WNW of Talala town or 8-km SSW of the 2007 M 5.0 earthquake epicenter. The epicentral trends deciphered from local earthquake data indicate two ENE trends (Narmada trend) for about 50 km length and a conjugate 15-km-long NNW trend (Aravali trend). The focal mechanisms by moment-tensor analysis of full wave forms of two 2007 events of M 4.8 and 5.0 and the 2011 event of M 5.1 indicate rupture along either of the two trends. The ENE trends follow a gravity low between the gravity highs of Girnar mounts. Seismic reflections also indicate a fault in the area named Girnar Fault. Most of Saurashtra region including the Talala area is covered by Deccan Trap Basalt forming plateaus and conical ridges. There is no major fault within Saurashtra Peninsula though it is believed to have major faults along the boundaries that are non-seismic. The intensity of the October 20, 2011 Talala earthquake is estimated to be 6.5 in MM scale while isoseismals of 6, 5, and 4 and felt distance give M 5.1 based on Johnston's 1994 empirical regressions. The source parameters of the 2011 Talala earthquake are estimated using data from 14 broadband seismograph stations. Estimated seismic moment, moment magnitude, stress drop, corner frequency, and source radius are found to be 10 N-m, 5.1, 1.6 MPa, 1.3 Hz, and 2,300 m, respectively. The b and p values are obtained to be low, being 0.67 and 0.71, respectively. PGA of 35 cm/sec is noted and the decay rate of acceleration has been estimated from strong motion data recorded at 5 stations with epicentral distances ranging from 32 to 200 km. [ABSTRACT FROM AUTHOR]

The S-wave Fourier amplitude spectra from the strong-motion network data in the Himachal region of the northwest Himalaya are used to estimate site amplification and 5-wave attenuation (Q&bgr;). For this analysis, 60 three-component records were used from eight earthquakes with magnitudes ranging from M 3.4 to 5.4, recorded at 13 stations over a hypocentral distance range of R = 9-48 km. The characteristics of the site amplification are analyzed using horizontal-to-vertical (H/V) Fourier spectral ratios of the S phase of the time history. The average amplification is close to unity except in a narrow frequency range of 2-4 Hz. The overall behavior of the H/V ratio is consistent with local geological conditions of the study region. The 5-wave quality factor Q(f) is estimated as 103f0.66 for 0.2 ≤ f ≤ 20 Hz, and the validity is checked by computing path attenuation functions derived from the new Q(f). The estimated Q(f)is also compared with results from previous studies of Q for the Himalayan region. [ABSTRACT FROM AUTHOR]

The M6.9 Sikkim Earthquake of 18 September 2011 caused widespread devastation in the state and adjoining areas from disrupting the road network to damaging structures of commercial, public, and religious values. This event presented another opportunity to further the understanding of earthquake risk of the affected region as well as of the North-Eastern Himalayan region, which have similar patterns of seismicity, built environment and construction practices. The general pattern of damage to structures, landslides, rockfalls, etc. was consistent with the shaking associated with this event. However, collapses of many buildings and damages to structures were disproportionate to the observed intensity of shaking, primarily due to poor compliance with seismic codes, inferior quality of raw materials and shoddy workmanship. Consequently, the seismic risk in the region is growing at an alarming pace with increasing inventory of vulnerable construction. The current event provides a preview of what is likely to happen in the event of a larger earthquake which the Himalayan region has witnessed in the past. This article discusses the construction practice in Sikkim Himalayas and their seismic performance in the recent earthquake, highlighting the vulnerability of inventories and suggests steps to mitigate the seismic risk for future events. [ABSTRACT FROM AUTHOR]

The 1300-km rupture of the 2004 interplate earthquake terminated at around 15° N, in the northernmost segment of the Andaman-Nicobar subduction zone. This part of the plate boundary is noted for its generally lower level seismicity, compared with the southern segments. Based on the Global Centroid Moment Tensor (CMT) and National Earthquake Information Center (NEIC) data, most of the earthquakes of Mw ≥4.5 prior to 2004 were associated with the Andaman Spreading Ridge (ASR), and a few events were located within the forearc basin. The 2004 event was followed by an upward migration of hypocenters along the subducting plate, and the Andaman segment experienced a surge of aftershock activity. The continuing extensional faulting events, including the most recent earthquake (10 August 2009; Mw 7.5) in the northern end of the 2004 rupture, suggest the reduction of compressional strain associated with the interplate event. The style of faulting of the intraplate events before and after a great plate boundary earthquake reflects the relative influences of the plate-driving forces. Here we discuss the pattern of earthquakes in the Andaman segment before and after the 2004 event to appraise the spatial and temporal relation between large interplate thrust events and intraplate deformation. This study suggests that faulting mechanisms in the outer-ridge and outer-rise regions could be indicative of the maturity of interplate seismic cycles. [ABSTRACT FROM AUTHOR]

Rapid visual screening technique has been resorted to for assessing seismic vulnerability and risk in the Himalayan township of Mussoorie that falls in Zone IV of the Earthquake Zoning Map of India. Damage during an earthquake in this zone is expected to reach MSK intensity VIII. A total of 3344 structures in 11 residential wards of the town were surveyed in the field. Data collected in the field were analysed under GIS environment which suggests that a total of 615 (18%) buildings show high probability of Grade 5 damage and very high probability of Grade 4 damage class. The economic loss likely to be incurred is estimated to be of the order Rs 238.85 crore in the township of Mussoorie alone. Modest estimates suggest that 369 persons might sustain grievous injuries in this event. The study highlights the fact that some of the lifeline buildings are under severe threat and are required to be retrofitted or replaced on priority basis. [ABSTRACT FROM AUTHOR]

The south Indian state of Tamil Nadu in the peninsular shield is a zone of low to moderate seismic activity with a sparse historical record of significant earthquakes. The current intensity-based zoning adopted by the Indian seismic code stipulates an effective peak ground acceleration (PGA) of either 0.10 or 0.16g for different parts of the state, for the maximum considered earthquake (MCE), and the service life of a structure. In the current study, probabilistic seismic hazard contour maps for Tamil Nadu and the union territory of Pondicherry, in terms of the ground-motion parameters, PGA and spectral accelerations, at 0.1, 0.5, and 1.0 sec for 2%, 5%, and 10% probabilities of exceedance in a 50 yr period, have been produced. Hazard computations have been performed over a grid of sites covering the territory at an interval of 0.2°. A comprehensive earthquake catalog has been compiled for the region extending between 2 and 20.7° N latitude and 68 and 88° E longitude and spanning ~950 yrs. The hazard maps are produced by suitably accounting for epistemic uncertainty in the hazard computations within a logic-tree framework incorporating parameters such as different probabilistic hazard analysis methods (classical Cornell-McGuire and zone-free approaches), catalog completeness estimation methods, maximum cutoff magnitude, and ground-motion predictive equations for shallow crustal intraplate environments. The hazard maps are compared to the zoning prescribed by the seismic code. The current estimations show that the potential seismic hazard in considerable parts of the state is underestimated by the broad zoning adopted by the Indian Standards. [ABSTRACT FROM AUTHOR]

A comprehensive, consistently interpreted new catalog of felt intensities for India (Martin and Szeliga, 2010, this issue) includes intensities for 570 earthquakes; instrumental magnitudes and locations are available for 100 of these events. We use the intensity values for 29 of the instrumentally recorded events to develop new intensity versus attenuation relations for the Indian subcontinent and the Himalayan region. We then use these relations to determine the locations and magnitudes of 234 historical events, using the method of Bakun and Wentworth (1997). For the remaining 336 events, intensity distributions are too sparse to determine magnitude or location. We evaluate magnitude and location accuracy of newly located events by comparing the instrumental- with the intensity-derived location for 29 calibration events, for which more than 15 intensity observations are available. With few exceptions, most intensity-derived locations lie within a fault length of the instrumentally determined location. For events in which the azimuthal distribution of intensities is limited, we conclude that the formal error bounds from the regression of Bakun and Wentworth (1997) do not reflect the true uncertainties. We also find that the regression underestimates the uncertainties of the location and magnitude of the 1819 Allah Bund earthquake, for which a location has been inferred from mapped surface deformation. Comparing our inferred attenuation relations to those developed for other regions, we find that attenuation for Himalayan events is comparable to intensity attenuation in California (Bakun and Wentworth, 1997), while intensity attenuation for cratonic events is higher than intensity attenuation reported for central/eastern North America (Bakun et al., 2003). Further, we present evidence that intensities of intraplate earthquakes have a nonlinear dependence on magnitude such that attenuation relations based largely on small-to-moderate earthquakes may significantly overestimate the magnitudes of historical earthquakes. [ABSTRACT FROM AUTHOR]

Eight thousand three hundred thirty-nine intensity observations have been evaluated for earthquakes that occurred on the Indian subcontinent and surrounding plate boundaries from the seventeenth century to the present. They characterize 570 earthquakes, more than 90% of which occurred in the past two centuries. The electronic supplement to this article lists these data using European Macroseismic Scale (EMS-981 intensities with their geographic coordinates. We summarize these data graphically in the form of a spatially averaged intensity map for the subcontinent, a map that emphasizes the features of many previously published earthquake hazard maps for the Indian plate, but which more faithfully depicts regional amplification and attenuation. We also estimate the probable return time for future damaging shaking in five of India's largest cities. [ABSTRACT FROM AUTHOR]

Seismicity in Himalayas is much in evidence. Historical records reveal that devastating earthquakes have been a regular feature of the entire Himalayan system. Besides providing knowledge of what happened in the past these historical records hold clues that might be of great significance for assessing risk potential associated with seismicity. Earthquakes cause tremendous loss to life and property all around the world every year. The amount of loss in terms of life, property and the disruption of key infrastructure and facilities has been rising continuously. Although there are no strong evidences that suggest a rise in seismic activities, the increasing population concentration in seismically sensitive zones has raised the degree of human vulnerability to such events underscoring the need for their study. Historical records on seismicity show that a large number of earthquakes have occurred in the western Himalayan state of Himachal Pradesh since times immemorial. An evaluation of the location and distribution of earthquakes in the study area and the potential human population which may be vulnerable has been carried out. Historic seismicity in Himachal Pradesh from has been studied from the ancient period to the beginning of 21st century. Defining where the vulnerable population resides is one of the key questions for disaster mitigation and prevention policies. The vulnerable population with respect to seismicity in the state has been mapped based on information from ancient Indian literature, historical archives, books, memoirs and catalogues prepared by various scholars and organizations and the patterns of population concentration. The results underline that very high seismic zones coincide with the areas of high population concentration and these are the areas in need of effective intervention and specific action for reducing the impact of this disaster. [ABSTRACT FROM AUTHOR]

In this article point source seismological model is used to model the available strong-motion accelerograms in northeastern India. Key seismic parameters such as Quality factor (Q-value), kappa factor (&kappa0), site amplification, and stress drop are derived from the strong-motion data. A total of 111 three-component records coming from seven earthquakes with magnitudes ranging from Mw 5.2 to 7.2 are used in obtaining the source and path parameters. The Q-value of the Indo-Burma tectonic domain, which is a subduction zone, is obtained as 431ƒ0.7. For the Bengal basin-Shillong plateau region the Quality factor is estimated as 224ƒ0.93. The kappa factors for vertical and horizontal components are obtained as 0.013 and 0.033 for soft rock type sites. For firm ground sites κ0 is estimated as 0.025 for vertical and 0.041 for horizontal components, respectively. The site amplification functions for soft rock and firm ground conditions are found from the horizontal-to-vertical ratio. The obtained stress drops of the seven events lie between 128 and 282 bars. The source parameters obtained in this study provide a useful framework for working out ground-motion relations in northeastern India. [ABSTRACT FROM AUTHOR]

Abstract  We study source characteristics of two small, local earthquakes which occurred in Delhi on 28 April 2001 (Mw3.4) and 18 March 2004 (Mw2.6). Both earthquakes were located in the heart of New Delhi, and were recorded in the epicentral region by digital accelerographs. The depths of the events are 15 km and 8 km, respectively. First motions and waveform modeling yield a normal-faulting mechanism with large strike-slip component. The strike of one of the nodal planes roughly agrees with NE–SW orientation of faults and lineaments mapped in the region. We use the recordings of the 2004 event as empirical Green’s functions to synthesize expected ground motions in the epicentral region of a Mw5.0 earthquake in Delhi. It is possible that such a local event may control the hazard in Delhi. Our computations show that a Mw5.0 earthquake would give rise to PGA of ~200 to 450 gal, the smaller values occurring at hard sites. The estimate of corresponding PGV is ~6 to 15 cm/s. The recommended response spectra, Sa, 5% damping, for Delhi, which falls in zone IV of the Indian seismic zoning map, may not be conservative enough at soft sites for a postulated Mw5.0 local earthquake. [ABSTRACT FROM AUTHOR]

Tropical cyclones are one of the most intense weather hazards over east coast of India and create a lot of devastation through gale winds and torrential floods while they cross the coast. So an attempt is made in this study to simulate track and intensity of tropical cyclone "Fanoos", which is formed over the Bay of Bengal during 5-10 December 2005 by using mesoscale model MM5. The simulated results are compared with the observed results of India Meteorological Department (IMD); results show that the cumulus parameterization scheme, Kain-Fritsch (KF) is more accurately simulated both in track and intensity than the other Betts-Miller (BM) and Grell Schemes. The reason for better performance of KF-1 scheme may be due to inclusion of updrafts and downdrafts. The model could predict the minimum Central Sea Level Pressure (CSLP) as 983 hPa as compared to the IMD reports of 984 hPa and the wind speed is simulated at maximum 63 m/s compared to the IMD estimates of 65 m/s. Secondly "Fanoos" development from the lagrangian stand point in terms of vertical distribution of Potential Vorticity (PV) is also carried out around cyclone centre. [ABSTRACT FROM AUTHOR]

In the absence of strong motion records, ground motion during the 26th January, 2001 Kutch, India earthquake, has been estimated by analytical methods. A contour map of peak ground acceleration (PGA) values in the near source region is provided. These results are validated by comparing them with spectral response recorder data and field observations. It is found that very near the epicenter, PGA would have exceeded 0.6 g. A set of three aftershock records have been used as empirical Green's functions to simulate ground acceleration time history and 5% damped response spectrum at Bhuj City. It is found that at Bhuj, PGA would have been 0.31 g–0.37 g. It is demonstrated that source mechanism models can be effectively used to understand spatial variability of large-scale ground movements near urban areas due to the rupture of active faults. [ABSTRACT FROM AUTHOR]

A 2-D subcrustal velocity model for the central Indian continental lithosphere has been derived by travel time and relative amplitude modeling of a digitally normalized analog seismic record section of the Hirapur-Mandla DSS profile, using a ray-tracing technique. Some prominent wave groups with apparent velocities slightly higher than the Moho reflection phase (PMP) are identified on the normalized record sections assembled with a reduction velocity of 6 km s−1. We interpret these phases as the wide-angle reflections from subcrustal lithospheric boundaries. Comparison of synthetic seismograms with the observed record section shows that the observed phases cannot be explained either by multiples or by the P-to-S converted phase (PMS) from the Moho. Subcrustal velocity models either with a velocity increase or with a single low velocity layer (LVL) also do not provide a satisfactory fit. We infer that a subcrustal velocity model with two alternate LVLs (velocity 7.2 km s−1), separated by a 6-km thick high velocity layer (velocity 8.1 km s−1), can satisfy both the observed travel times and amplitudes. The prominent reflection phases are modeled at depths of 49, 51, 57 and 60 km. It is inferred that the subcrustal lithosphere in the central Indian region has a lamellar structure with varying structural and mechanical properties. The alternating LVLs, occurring at relatively shallow depths below Moho, may be associated with the zones of weakness and lower viscosity suggesting continued mobility, with a possible thermal source in the upper mantle. This explains the source of observed high heat flow values in the central Indian region. [ABSTRACT FROM AUTHOR]

This comment raises some scientific concerns regarding one of a recent publications in Quaternary International entitled “Macroseismic intensity assessment of 1885 Baramulla Earthquake of northwestern Kashmir Himalaya, using the Environmental Seismic Intensity scale (ESI 2007)” by Amad et al., 2013 (Article in Press). The authors have allegedly re-evaluated the historical reports of the 1885 Baramulla Earthquake of NW Kashmir by conducting extensive field investigations on those sites where environmental effects from the historical earthquake were reported. Thus, both primary (surface rupture) and secondary effects were studied and an ESI intensity of X was estimated for the epicentral area. However, the presented primary effects, on which the core of the contribution stands, are taken from Neve, 1928 and Jones, 1885 (cited in the prose) and provided secondary effects are not supported by any evidence(s). In my opinion the authors have not produced any new evidence to contradict or support the historical data. [ABSTRACT FROM AUTHOR]