http://localhost:8081/jspui/handle/123456789/26 Wed, 02 Jul 2025 07:27:31 GMT 2025-07-02T07:27:31Z http://localhost:8081/jspui/handle/123456789/15543 Title: DYNAMIC BEHAVIOUR OF BATTER PILES AND PILE GROUPS Authors: M, Bharathi Abstract: Batter piles (also known as inclined or raker piles) are often used for supporting bridges, offshore structures, transmission line towers, etc., where the horizontal load per pile may exceed the capacity of vertical pile. During the past seismic events, batter piles have shown both beneficial and detrimental effects. Several researchers have discussed and debated on the virtues and drawbacks of batter piles which further helped in understanding their response in a better manner. A number of documents are available on the seismic performance of batter pile groups based on controlled tests on scaled laboratory models. The primary objective of the present study is to examine the dynamic behaviour of bored cast in-situ batter piles and pile groups in the field conditions. In this thesis, extensive field investigations along with finite element (FE) models are discussed in detail to understand the dynamic response of batter piles and pile groups. This research comprises four major components: (a) dynamic pile load tests on single vertical and batter piles; (b) dynamic pile load tests on vertical and batter pile groups; (c) 3D finite element analysis of single piles and pile groups and (d) measurement of dynamic pile load test induced vibration in adjacent building and its finite element analysis. In the initial phase, the behaviour of bored cast in-situ reinforced concrete (RC) six single piles: (a) single vertical pile (B0); (b) vertical pile with an under-ream bulb (B0U1); (c) 10° batter pile (B10); (d) 10° batter pile with an under-ream bulb (B10U1); (e) 20° batter pile (B20); and (f) 20° batter pile with an under-ream bulb (B20U1), subjected to lateral and vertical dynamic loading is examined experimentally. All these six piles are subjected to dynamic load generated by an oscillator motor assembly firmly mounted on top of the pile cap. In each direction, the piles are subjected to six different intensity of force levels (varied in the form of eccentricity of the oscillating mass). In addition, four different RC pile groups consisting of: (a) three vertical piles (3VG); (b) three 20° batter piles (3BG); (c) four vertical piles (4VG); and (d) four 20° batter piles (4BG), are also constructed by bored cast in-situ method and tested for five different intensity of force levels. Further, the effect of lateral loading direction on the dynamic responses of these piles and pile groups is also explored. The dynamic response of piles and pile groups is recorded in real time using piezoelectric accelerometers placed at appropriated location on the pile cap. From the recorded dynamic response, the variation in resonant frequency, peak displacement, induced strain etc., is obtained and discussed in detail. Numerical investigations are also performed to evaluate the behaviour of batter piles and pile groups subjected to dynamic loading using 3D FE models. Appropriate loading and dynamic boundary conditions, element sizes and lateral extents of the model are used to develop 3D FE iv models. The material properties of both soil and pile are considered similar to the experimental investigation test site. The effect of loading direction, intensity of exciting force level, material nonlinearity etc., are explored in detail. In addition, an attempt is also made to understand the bending moment profiles of batter piles through a hybrid modelling approach. The developed 3D FE models reasonably replicate the experimental findings. Thus, the model developed could also be used for other parametric studies which are not experimentally feasible. The effect of pile-soil modulus ratios (Ep/Es) on the dynamic response of batter piles is also examined using 3D FE model. When dynamic tests are conducted on pile groups, the vibrations propagated through the soil mass to the adjacent structure. These vibrations are measured at the source and at different floor levels (including ground floor and roof) of the adjacent building, in the form of acceleration and velocity time histories. The response obtained through the experiment is also compared with 2D FE analyses of the integrated building-pile group-soil system. The estimated vibration responses in terms of peak ground acceleration (PGA), peak ground velocity (PGV), pseudospectral acceleration (PSA) and predominant frequencies (f) are compared with the permissible limits recommended in the relevant standards and codes of practice. Sat, 01 Jun 2019 00:00:00 GMT http://localhost:8081/jspui/handle/123456789/15543 2019-06-01T00:00:00Z http://localhost:8081/jspui/handle/123456789/15471 Title: FINITE-DIFFERENCE MODELLING OF 3D BASIN EFFECTS ON GROUND MOTION CHARACTERISTICS Authors: Kamal Abstract: The 2D13D basins play a major role in amplification of ground motion level and generation of different seismic phases. The various physical phenomena occurring in a basin during an earthquake are responsible for the significant spatial variation of ground motion characteristics. The presence of very large population-density as well as city-density in the basins worldwide stimulated this research work. The different aspects of basin effects on ground motion characteristics and damage pattern include the physical phenomenon like single and double resonances (Romo and Seed 1986; Stone et al., 1987; Narayan et al., 2002), basin-generated surface (BGS) waves (Kawase. 1996: Graves et al.. 1998: Pitarka et al., 1998). subsurface basement focusing (Gao et al.. 1996: Davis et al.. 2000: Booth et al.. 2004; Narayan and Kumar. 2012: 2014a), complex mode transformation of the basin-transduced surface waves - (Kawase. 1993; Narayan 2010; 2012a: Narayan and Kumar, 2014b) and site-city-interaction (Gueguen et al.. 2002: Kham et al., 2006: Semblat et al., 2008; Sahar et al., 2015). Furthermore, realistic quantification of basin effects on the ground motion characteristics requires an efficient numerical method since analytical solutions are not possible. The incorporation of frequency-dependent damping in the time-domain numerical simulation of basin is very much essential since the BGS-waves are highly affected by the sediment-damping (Day and Minster, 1984; Emmerich and Korn, 1987; Kristek and Moczo, 2003). The quantification of characteristics of the BGS-waves in a basin is very important since the flat layer response are generally inadequate to explain the observed damages in 3D basins (Hatyarna et al., 1995: Kawase, 1996; Graves et al., 1998; Pitarka et al., 1998; Bakir et al., 2002). The BGS-waves develop very large differential ground motion which can adversely affect long-span lifelines such as pipelines, bridges and communication transmission systems (1-lather et al.. 2008). Generally, the damage surveys and numerical simulations reveal that the BGS-waves cause intense damage in a bandwidth parallel to and at some distance frorn the basin-edge (Pitarka et al., 1998; Narayan, 2005). This may be due to 2D nature of most of the basins, where damage survey have been carried out. The extensive literature reviews associated with the basin effects on the characteristics of the BGS-waves revealed that nobody has studied the effects of circular basins like intracratonic basins (e.g. Michigan basin and Congo basin) and impact crater basins (e.g. Sudbury basin and Arizona basin) on the characteristics of BGS-waves. Now, question arise in the mind, what will be the effects of circular basin on the characteristics of BGS-waves propagating towards the centre of circular-basin and associated spatial variation of ground motion? Further, whether there may be focusing of the BGS-wave or not and if it is happening whether focusing will be a frequency dependent or not. Furthermore, it appears that nobody has documented the effects of azimuth of the incident body waves on the characteristics of the BGS-waves for an azimuthal range of 0-360° (Oprsal et al., 2005). In order to fulfil the above identified gaps as well as to find out the answers to the aforesaid questions, the viscoelastic seismic responses of the various considered circular basin models have been computed along different arrays and analysed. The research works have been divided in two parts. The first part of the thesis describes the development of an efficient 3D viscoelastic finite-difference (FD) algorithm for incorporating the frequency-dependent damping in the time-domain simulations. The second part of the thesis describes the effects of various parameters like shape-ratio, geometry of sediment basement interface (GSBI), size and the sediment rheology of the semi-sphericai (SS-) basin on the characteristics of the BGS-waves and associated spatial variations of amplitude amplification. average spectral amplification (ASA) and differential ground motion (DGM). The effects of azimuthal angle of the incident body waves on the characteristics of the BGS-waves are also studied in details. In order to show the importance of 3D basin simulations as well as to help in improving the level of seismic microzonation of an area which has already been carried out based on ID response of sediment deposit, average aggravation factors (AAF) have been computed. Due to the lack of suitable earthquake records across the intracralonic and impact crater circular basin, sediment data as well as the basin basement geometry, validation of the simulated characteristics of the BGS-waves in the circular basin could not become possible - and only parametric studies could be carried out. An excellent correlation between the computed phase-velocities for the S- and P-waves using the FD responses of an unbounded viscoelastic homogeneous medium with the same computed analytically using the Futterman's relations (1962) and the GMB-EK rheological model (Emmerich and Korn. 1987) revealed the accuracy of implementation of frequency-dependent damping in the developed 3D viscoelastic FD program. Furthermore, the almost frequency-independent inferred nature of the computed quality factors also supports the above conclusion (McDonal et. al.,1958: Kristek and Moczo. 2003). The analysis of the computed responses of the semi-circular (SC) and semi-spherical (SS) basins for the different polarizations of the incident plane S-wave front along different arrays revealed that both the Rayleigh and Love waves are generated at each point of a basin-edge. Further, a simple combination of the incident plane S-wave front with a particular polarization and the SS-basin made it possible to study the effects of azimuthal angle of the incident body wave on the characteristics of the BGS-waves in a azimuthal range of 03600. It was inferred that the amplitudes of Rayleigh and Love waves depend on the amplitude of component of the incident body wave within and transverse to a plane which is normal to the basin-edge. Based on the findings of the research work, it may be suggested that there should be parameters like azimuth. focal mechanism and angle of incidence of body wave, shape of basin, location, sediment and rock rheology in an empirical relation for predicting the amplitude of BGS-waves in the components normal and parallel to the basin-edge (Joyner. 2000: Somerville et al.. 2004). The matching of the obtained lowest frequency content in the BGS-waves with the lowest resonance frequency (F0) of the SS-basin corroborates with the finding of Bard and Bouchon (1980a&b) and Narayan (2005). The observed increase of amplitude of the BGS-waves towards to the centre of the SS-basin, even in the presence of sediment-damping and the dispersion of the BGS-waves may be attributed to the focusing of the BGS- waves. Furthermore, it is concluded that the focusing of the BGS-waves in the SS-basin is frequency- - dependent. The obtained level of ASA/DGM is comparable in both the SC- and SS-basins near the basin-edge but the difference is increasing towards the centre of basins. It is also concluded that the focusing and trapping of the BGS-wave in the SS-basin is more sensitive to the impedance contrast as compared to the sediment-damping. The analysis of responses of the SS-basin with different basin shape ratio revealed a decrease of ASA with the decrease of basin shape ratio due to (I) decrease of frequency bandwidth of the BGS-waves and (2) decrease of spectral amplitudes of the BGS-waves due to an increase of phase velocity. It is inferred that the spatial variation of characteristics of the BGS-waves was highly controlled by the geometry of sediment-basement interface. The obtained ID AAF in the Sc- and SS-basins clearly reflects the inadequacy of 1 D response of a 2D/3D basin. It is recommended to compute the AAF using the same components of ground motion as that of the incident body wave to conservatively aggravate the ground motion to incorporate the 3D basin-effects in the seismic microzonation where it has already been carried out using 1 D response of the soil column. The findings of this research work calls for a special attention during the seismic hazard assessment in the intracratonic and impact crater circular basins. Wed, 01 Jul 2015 00:00:00 GMT http://localhost:8081/jspui/handle/123456789/15471 2015-07-01T00:00:00Z http://localhost:8081/jspui/handle/123456789/15147 Title: SEISMIC HAZARD ASSESSEMENT USING EXTREME VALUE STATISTICS Authors: Chhavi Abstract: Seismic Hazard Assessment (SHA) depends on detailed knowledge of physical processes, tectonic set up, comprehensive and qualitative data sets, understanding of internal structure of earth and various mathematical and statistical modelling. The mathematical models of SHA vary with region to region. In the Himalayan arc, a uniform pattern of stress accumulation and its subsequent release has never been observed. The seismicity patterns follow these processes, sporadically as well as spatially, resulting in seismically very active regions as well as seismic gaps, which continuously accumulate stresses over a long period without any release. Generally, in a typical SHA practice, the inadequacy of the dataset used along with the unaccountability for the physical processes are the key reasons for impractical results. Moreover, a sensitive treatment of the prepared earthquake catalogue is another prerequisite for precise estimation of the seismic hazard, which is lengthy and cumbersome. It is thus of paramount importance to use statistical methods that analyse as closely as possible the range of large return period earthquake events in the Himalaya and best describe the seismicity pattern in seismic gap and also required statistical model that well described the seismicity of low seismic region. For this purpose, various earthquake recurrence models have been applied in seismically different regions and then are examined in the light of damaging earthquakes. To capture the realistic behaviour of large return period events the Extreme Value Statistics (EVS) is better alternative. The Extreme Value Distribution (EVD) is based on yearly maximum event, whereas the Generalized Pareto Distribution (GPD) select those events which cross a specified threshold value. The Pareto, Truncated Pareto, and Tapered Pareto are the special cases of the GPD and Gumbel Type I, Type II and Type III are the types of EVD. To perform the EVD and GPD the entire Himalayan region has been divided into five seismogenic source zones (SSZs). Estimated probabilities of earthquakes occurrence using Pareto, Truncated Pareto and Tapered Pareto distribution have also been compared with the Modified Gutenberg-Richter (G-R) and the Characteristics recurrence distribution. Statistical analysis shows that the Tapered Pareto distribution better describes seismicity in all SSZs in comparison to other distributions. The annual probability of earthquake occurrence have been re-examined using two models: Gumbel Type I and Type III distributions and then compared with Modified G-R distribution and found that Gumbel Type I provides highest probability while Modified G-R estimates lowest probability and Gumbel Type III distribution also better defines seismicity in comparison to usual distributions for all SSZs. To look into the effects of such modelling on strong ground motion, the Probabilistic Seismic Hazard Assessment has been ii carried out for the Himalaya. It has been observed that Peak Ground Acceleration (PGA) estimated using Tapered Pareto were relatively higher than the Modified G-R distribution which reveal that the data is incomplete in the range of the large earthquake and not well captured by classical method. Similar trend have been shown by Gumbel Type III i.e. PGA values are relatively higher for Gumbel Type III. Uniform PGA contour maps have been prepared using Tapered Pareto and Gumbel Type III for an exposure time of 50 years for 90% and 98 % confidence level and these contour maps are very close to realistic observations. In low seismicity area where a comprehensively complete catalogue of earthquake events is not available and standard models fail to capture the seismicity, EVD is better alternative for SHA and requires only the annual maximum events and no treatment of earthquake catalogue is prerequisite. To test the applicability of EVD, an attempt has been made for SHA in South India and divided into four SSZs. The Gumbel Type I method has capabilities of reliably deducing the G-R parameters. Parameters of Gumbel Type I have been estimated using two plotting position formulas given by Gumbel (1958) and Bury (1999), respectively. In the present analysis, probabilities of earthquakes occurrences of magnitude Mw ⩾ 4.0 have been estimated and well match with the observed data. Thus, models can be considered as a simplified method to evaluate the SHA at low seismicity area. To understand the seismicity pattern of discordant seismicity of Himalaya, three types of regions have been considered namely: North-West Himalayan, the Garhwal Himalaya and the Nepal. The seismicity parameters have been revisited using Constant Moment release model which is based on strain rate data. Probability of earthquake occurrence with time has compared with Constant Seismicity model assuming Poissonian Distribution. From the comparing the results of above stated two models in North-West region, it has been observed that Constant Moment release model predict the higher occurrence rate of earthquake as compared to Constant Seismicity model, which implies that either the occupied accumulated stress is not being unconfined in the form of earthquakes or the compiled earthquake catalogue is insufficient. Similar trend has been observed for Seismic Gap area but with lesser difference reported from both methods. However, for the Nepal region, the estimated seismicity by the two methods has been found to be relatively less when estimated using Constant Moment Release model which implies that the in Nepal region accumulated strain is releasing in the form of large earthquake occurrence event. To further investigate the effect of these two models in seismic gap, PSHA has been carried out for Uttrakhand Himalaya, which is located in central seismic gap of Himalaya. The annual iii occurrence rates of earthquake have been estimated by Constant Seismicity and Constant Moment release models and Uniform hazard contours for PGA have been obtained for an exposure time of 50 years for 90% and 98 % confidence level. The patterns have been depicted by the PGA contours, which are fairly regular with the major seismotectonic features. In this study, various types of magnitude recurrence models have been applied according to seismotectonic environments. The seismic hazard vis-à-vis the model applicable for a region has been interpreted in terms of the physical process of earthquake occurrence. The fitting of different distribution models for estimating the probability of earthquake occurrence in seismically varying seismic source zones is informative and useful from an engineering point of view, and most certainly from a SHA perspective. The following are the primary outputs of this research work: 1. The application of Constant Seismicity and Constant Moment rate approaches for SHA has revealed discordant patterns of strain release in terms of earthquakes in the Himalaya. In Constant Seismicity model, the occurrence of large earthquake event is not represented well which restrains this model from reflecting the real physical process. The accumulated energy in the region can be released in the form of either a single large earthquake or many small to medium scale earthquakes depending on the tectonic environment of the region. The present study concludes that the Constant Moment Release model is a better alternative to understand the earthquake occurrence in the region where it is necessary to compensate the lowering of 𝑀𝑚𝑎𝑥 by increasing rate of small to moderate earthquakes. 2. In North-West region, the total seismicity rate estimated using Constant Moment release is observed to be 55.67% higher than those obtained by Constant Seismicity model, which reflects that accumulated strain is not released fully by the past earthquakes. This indicates that accumulated strain is compensated either by other tectonic activities like locking or perhaps the earthquake catalogue itself is insufficient and incomplete. 3. The annual occurrence of earthquakes using Constant Moment release rate model is 71% higher than those estimated by Constant Seismicity rate model for all magnitude ranges in Garhwal Himalaya region. If it’s true and Garhwal Himalaya region being in central seismic gap which has experienced relatively lesser seismicity compared to the North-West region, the accumulated energy budget indicates that a major earthquake is ready to strike in the Garhwal Himalaya seismic gap region. 4. In the Nepal region the total seismicity (𝑀𝑚𝑖𝑛) computed using Constant Seismicity model is found to be 78% higher than those estimated using Constant Moment Release model iv which shows that the maximum part of accumulated energy has been released from large earthquake occurrence. 5. The use of EVS has well captured the behaviour of seismicity for larger events whereby Tapered Pareto and Gumbel Type III models were observed to best fitted with the observational data to the lower range of magnitudes as well. 6. It has been proven that for low seismicity regions like South India the methods using Gumbel Type I distribution may be used successfully. Synthetic catalogue can be prepared using relationship of Gumbel parameters to G-R parameters for low seismic area. 7. One of the main conclusions is that the differences in the estimated probabilities using the different distributions has definite bearing on the ultimate results of SHA exercises, and hence it is recommended to use different statistical models that best fit in the seismogenic source zones in an area. Fri, 01 Feb 2019 00:00:00 GMT http://localhost:8081/jspui/handle/123456789/15147 2019-02-01T00:00:00Z http://localhost:8081/jspui/handle/123456789/15146 Title: SEISMICALLY INDUCED LANDSLIDE HAZARD ANALYSES FOR LOWER INDIAN HIMALAYA Authors: Nath, Ritu Raj Abstract: The entire Himalayan arc is recognized as a global hotspot for landslide and seismic events; which may be ascribed to the orogeny processes that had formed the Himalaya. Every year landslides and related natural disaster events claim many lives and destroy property, infrastructure, and the environment of the Himalaya. It is estimated that Himalayan landslides kill 1 person/100 sq. km per year and average losses due to Himalayan landslides is more than USD 1 million/year. Given the great relief, high seismicity, active tectonism, high volume of precipitation, and wide variety of rock and sediment types; landslides seem ubiquitous in the Himalaya and is perhaps the major present-day process shaping the landscape. With ingress of roads and other heavy constructions like dams and hydro power plants in this fragile mountain chain, the overall risk of landslide hazard increases manifold. This necessitates an accurate and updated landslide hazard zonation (LHZ) for the Himalayan belt, based on which future landuse pattern can be envisaged. LHZ is a scientific practice of predicting the spatial distribution of landslides over a region which is determined as a function of landslide occurrence and various landslide related factors. Considering the high incidences of landslide disasters and their long term socio-economic impact, national guidelines are drafted to guide the activities envisaged for mitigating landslide risk through Landslide Hazard Zonation (LHZ) mapping. The classical approach of LHZ mapping is based on examination of various static landslide causative factors with occasional inclusion of triggering factors like rainfall and earthquakes. As the positive correlation between seismicity and landslide occurrence had become more and more prominent, the classical approaches got changed; and a paradigm shift has been observed in LHZ studies of-late. More emphasis is now given on comprehending the occurrence and mechanism of seismically induced landslides due to the complexity and enormity of such events. There have been several earthquakes in the Himalayan region viz. Chamoli earthquake (Mw-6.8), Kashmir earthquake (Mw-7.6), Sikkim earthquake (Mw-6.9), Nepal earthquake (Mw-7.8), which caused widespread landslide events. In fact, in many cases, losses due to seismically induced landslides have been more than those caused directly due to shaking. Out of the all earthquake related casualties, which are not caused directly by ground shaking, approximately 70% may be attributed to landslides. In this context, LHZ studies considering earthquakes as main triggering factor is a time bound priority for the Himalayan region. However, a critical review of the existing literature reveals that there is a paucity of macro-scale, regional level studies quantifying the role of seismicity in LHZ mapping for the Himalayan arc in general, and the lower Himalayan belt in particular. An endeavour has been iv made in this research work to carry out LHZ mapping under both static and seismic conditions for a part of lower Indian Himalaya. The research work has been carried out in three phases: (a) in the first phase, the study area's present scenario of landslide susceptibility under static conditions is assessed using statistical method of LHZ mapping; (b) in the second phase, suitable method for carrying out seismically induced LHZ mapping is formulated; and (c) in the third phase, LHZ maps of the study area are prepared under different seismic conditions to quantify the role of seismicity in landslide occurrence and spatial distribution in the study area. The study area encompasses approximately 12,350 sq. km.; with estimated population of more than 15 lakhs as per the 2011 India census. Several important and thickly populated cities of Uttarakhand and Himachal Pradesh are located in the study area. Geologically, the study area exhibits a complex and heterogeneous amalgamation of fifteen formations from different ages'. The study area falls in Zone IV as per IS 1893(Part I): 2016, indicating that the whole study area is seismically very active. The area caters three major thrusting systems of the Himalayan arc: Main Frontal Thrust (MFT), Main Boundary Thrust (MBT) and a portion of Main Central Thrust (MCT), along with numerous transverse lineaments. In the first phase, eight static landslide causative parameters are identified for the study area. A comprehensive landslide inventory has been prepared, which is the primary step in LHZ mapping and data has been extracted from various sources. The prepared landslide inventory is used for proximity analyses to establish correlation between landslide activities and various causative parameter. Information Value method, one of the widely used statistical methods of LHZ mapping, has been applied to prepare the initial LHZ map of the study are under static causative parameters. The prepared LHZ map has identified almost 37% of the total study area as the zones of high to very high landslide susceptibility. Different statistical methods, which are widely used for landslide susceptibility assessment, generally lack in incorporating seismic indicators. This may be attributed to the paucity of sufficient earthquake induced landslide inventories, which is attributed to the rarity of an extreme earthquake event. Moreover, the conventional studies correlating earthquake magnitude and landslide distribution, types and coverage area drew criticism from researchers due to limitations of the dataset used and the regional and characteristic biasness associated with earthquake events. Such scenarios become exaggerated for the Himalayan region, where not until recently, much attention have been paid to seismically induced landslide hazard zonation. Most of the LHZ studies carried out for the Himalayan belt considered static landslide causative factors only; and the few studies that did consider earthquake scenarios, are concentrated around the Chamoli earthquake, Sikkim earthquake and Nepal earthquake. All v these earthquakes, in-spite-of having originated in the Himalaya only, differ significantly from one another in terms of their characteristics. Thus, it is understood that any statistical method derived from earthquake induced landslide inventory developed for a particular earthquake event may not be adequate enough for a different tectonic set up. Alternatively, Map combination method of LHZ mapping has been used in this research work where, probabilistically generated peak ground acceleration (PGA) is considered as landslide triggering seismic factor. The biggest advantage of this method is that various landslide causative parameters (static as well as triggering) can be incorporated as thematic layers, which are assigned a weight depending upon their perceived control on landslide occurrence. The weights of various thematic layers are numerically integrated to generate the LHZ map. However, the subjectivity in weight assignment procedure is the main limitation in this method. To address this issue, a landslide susceptibility scale is developed for the study area statistically, which is used to assign the weights of various thematic classes. Information Value method, Frequency Ratio method and Fuzzy Cosine Amplitude Methods are correlated to develop the susceptibility scale, which is further used for multi-hazard integration. The LSZ map prepared using the developed scale, is compared with other LSZ maps prepared using statistical methods for performance evaluation of the developed susceptibility scale. The developed susceptibility scale has produced better results for the study area. Use of probabilistic PGA values as landslide triggering factor in LHZ mapping has a distinct advantage: it eliminated the regional and characteristic biasness associated with an single earthquake, which increases the applicability of the method. The predicted PGAs are not from a single event, but rather represents the stress deformation expected in the region. Moreover application of PSHA in LHZ allows incorporation of seismotectonic environment (in terms of faults and lineaments) of a bigger area (R~300 km) which would likely to produce earthquakes in the study area, and recorded past seismicity. A detailed PSHA study has been carried out for the study area. The results of PSHA is discussed in terms of expected PGA for five scenario earthquakes with return periods of 10, 50, 100, 225 and 475 years. Consideration of the entire range of earthquake sizes quantifies the impact and implications of seismicity in landslide hazard comprehensively. Assignment of weights to different earthquake scenarios is a difficult task in LHZ mapping. There is no statistical correlation available to quantify the size of a scenario earthquake with landslide spatial distribution. Therefore a new method has been implemented in this research work to assign the weights objectively. The method, which is based on the normalized PGA values of different scenario earthquakes, could portray the relative importance vi of different earthquake size on LHZ mapping effectively. Five LHZ maps of the study area are prepared under seismic conditions to understand the role and impact of seismicity in landslide occurrence and their spatial distribution in the lower Himalaya. It is observed that for an earthquake scenario with 475 years return period, almost 51% of the total area falls under very high landslide hazard. This is a significant outcome of the study, which highlights the consideration of seismicity in LHZ mapping for the Himalayan arc. The results of the research work shows that in case of moderate to great earthquakes, there is paradigm shift of hazard zones from very low towards very high. Based on the results, the present study concludes that inclusion of earthquake scenarios will enhance the understanding of landslide hazard with a more pragmatic vision, especially for seismically active mountainous belts like the Himalaya. The LHZ maps prepared for the scenario earthquakes with 225 years and 475 years return period will be of practical use for implementing frame works for risk mitigation and disaster response. Sat, 01 Jun 2019 00:00:00 GMT http://localhost:8081/jspui/handle/123456789/15146 2019-06-01T00:00:00Z