Dissertations / Theses on the topic 'Earthquake catalogue'

Il lavoro di ricerca ha avuto in oggetto la quantificazione probabilistica della pericolosità sismica lungo la rotta di una condotta per il trasporto di crudo nel Golfo del Bengala. L’esito dell’analisi è stato espresso in termini di spettri di risposta elastici medi dell’accelerazione orizzontale e in presenza di deviazione standard, riferiti a cinque periodi di ritorno (Tr =95, 225, 475, 975 e 2475 anni). Inoltre, due mappe di pericolosità sismica riferite all’accelerazione di picco orizzontale e all’accelerazione spettrale di periodo T=0.2 sec sono state prodotte per il territorio del Bangladesh e le regioni circostanti. L’analisi è stata eseguita secondo il metodo classico di Cornell-McGuire e introducendo in aggiunta un lineamento tettonico per il quale è stato applicato il modello del terremoto caratteristico. Un catalogo degli eventi sismici è stato compilato per un’area estesa circondante la condotta, consultando numerose fonti internazionali e regionali, riferito al periodo 1663-2012. I dati del catalogo sono stati successivamente sottoposti a un processo di rimozione delle repliche, omogeneizzazione, rimozione degli eventi dipendenti (precursori e repliche) e analisi di completezza. Differenti scenari tettonici presenti nell’area di studio sono stati considerati per la selezione di opportune relazioni di attenuazione. Un approccio ad albero logico, costituito da cinquantadue rami è stato adottato per tenere conto dell’incertezza epistemica. L’analisi dei valori degli spettri di accelerazione ha evidenziato un cambiamento considerevole del livello di pericolosità in diversi punti della condotta, specie per elevati periodi di ritorno (Tr= 975 e 2475 anni), giustificando la necessità di uno studio specifico lungo la rotta. Inoltre, le mappe di pericolosità ottenute hanno riportato valori molto maggiori rispetto a quelli indicati in letteratura, portando alla conclusione che gli studi probabilistici precedenti sottostimano la pericolosità sismica per la maggior parte dei distretti del Bangladesh.
The scope of the study was to perform the probabilistic seismic hazard assessment (PSHA) along the route of an offshore pipeline for the transport of oil in the Bay of Bengal. The outcome of the seismic hazard analysis is given in terms of horizontal median uniform hazard spectra and plus and minus one sigma for five return periods (i.e., Tr= 95, 225, 475, 975, and 2475 years), in correspondence of four selected sites of the pipeline route. In addition, two seismic hazard maps for horizontal peak acceleration and spectral acceleration at T=0.2 sec with 475 year-return period are provided, extending in Bangladesh and neighbourhood regions. PSHA was performed as per classical Cornell-McGuire approach, and introducing in addition a tectonic lineament for which the model of “characteristic earthquake” was applied. A comprehensive earthquake catalogue was produced for a large area surrounding the pipeline, consulting numerous international and local sources, spanning the period 1663-2012 A.D. Processing of the data of the catalogue was performed, consisting in removing of duplicate events, homogenising, declustering, and analysis of completeness periods for different magnitude ranges. Different tectonic environments within the study area were accounted for in the selection of appropriate ground-motion prediction equations. A logic-tree framework constituted by 52 branches was adopted in the computation for taking into account epistemic uncertainties. The analysis of the values of UHSs at different selected sites has pointed out the change of the level of hazard along the route of the pipeline, justifying the need for performing a specific hazard assessment along it. Moreover, the comparison of the hazard maps whit those available in literature, has showed higher values of hazard in the performed study, which leads to consider that for most districts of Bangladesh the earlier probabilistic hazard analyses underestimate the seismic hazard considerably.

Precursors related to seismicity patterns are probably the most promising phenomena for short-term earthquake forecasting, although it remains unclear if such forecasting is possible. Foreshock activity has often been recorded but its possible use as indicator of coming larger events is still debated due to the limited number of unambiguously observed foreshocks. Seismicity data which is inadequate in volume or character might be one of the reasons foreshocks cannot easily be identified. One method used to investigate the possible presence of generic seismicity behavior preceding larger events is the aggregation of seismicity series. Sequences preceding mainshocks chosen from empirical data are superimposed, revealing an increasing average seismicity rate prior to the mainshocks. Such an increase could result from the tendency of seismicity to cluster in space and time, thus the observed patterns could be of limited predictive value. Randomized tests using the empirical catalogues imply that the observed increasing rate is statistically significant compared to an increase due to simple clustering, indicating the existence of genuine foreshocks, somehow mechanically related to their mainshocks. If network sensitivity increases, the identification of foreshocks as such may improve. The possibility of improved identification of foreshock sequences is tested using synthetic data, produced with specific assumptions about the earthquake process. Complications related to background activity and aftershock production are investigated numerically, in generalized cases and in data-based scenarios. Catalogues including smaller, and thereby more, earthquakes can probably contribute to better understanding the earthquake processes and to the future of earthquake forecasting. An important aspect in such seismicity studies is the correct estimation of the empirical catalogue properties, including the magnitude of completeness (Mc) and the b-value. The potential influence of errors in the reported magnitudes in an earthquake catalogue on the estimation of Mc and b-value is investigated using synthetic magnitude catalogues, contaminated with Gaussian error. The effectiveness of different algorithms for Mc and b-value estimation are discussed. The sample size and the error level seem to affect the estimation of b-value, with implications for the reliability of the assessment of the future rate of large events and thus of seismic hazard.
Οι προσεισμοί αποτελούν τα πλέον υποσχόμενα πρόδρομα φαινόμενα για τη βραχυπρόθεσμη πρόγνωση των σεισμών, παρόλο που παραμένει άγνωστο το αν μια τέτοια πρόγνωση είναι εφικτή. Η χρήση της προσεισμικής δραστηριότητας ως ένδειξη ενός επερχόμενου μεγάλου σεισμού είναι αμφιλεγόμενη, κυρίως λόγω του περιορισμένου πλήθους των προσεισμών, γεγονός που πιθανά οφείλεται στην ανεπαρκή καταγραφή σεισμικών δεδομένων. Η άθροιση σεισμικών σειρών είναι μια μέθοδος που εφαρμόζεται προκειμένου να μελετηθεί η πιθανή παρουσία ενός γενικευμένου μοτίβου σεισμικότητας πριν από ισχυρούς σεισμούς. Η υπέρθεση σεισμικών ακολουθιών που προηγήθηκαν των κυρίων σεισμών αναδεικνύει μια αυξανόμενη μέση δραστηριότητα πριν από τους κύριους σεισμούς. Μια τέτοια συμπεριφορά θα μπορούσε να προκύψει και από την εγγενή τάση των σεισμών να ομαδοποιούνται χωρικά και χρονικά, με αποτέλεσμα τα παρατηρούμενα μοτίβα να έχουν περιορισμένη προγνωστική αξία. Τυχαιοποιημένοι έλεγχοι των πραγματικών δεδομένων υποδηλώνουν ότι ο παρατηρούμενος αυξανόμενος ρυθμός είναι στατιστικά σημαντικός σε σύγκριση με τη μεταβολή που οφείλεται στη γένεση απλών συστάδων σεισμών, αναδεικνύοντας την ύπαρξη προσεισμών αιτιολογικά συσχετιζόμενων με τους κύριους σεισμούς. Μια ενδεχόμενη αύξηση της ευαισθησίας των σεισμικών δικτύων πιθανά να συμβάλει στην αποτελεσματικότερη αναγνώριση των προσεισμών. Η πιθανότητα μιας τέτοιας βελτίωσης ελέγχεται με τη χρήση συνθετικών δεδομένων τα οποία προκύπτουν υπό προϋποθέσεις ως προς τη σεισμική διαδικασία. Οι επιπλοκές που μπορεί να προκύψουν από την παρουσία σεισμικότητας υποβάθρου και των μετασεισμικών ακολουθιών διερευνώνται αριθμητικά, με γενικευμένες περιπτώσεις και σενάρια που βασίζονται σε πραγματικά δεδομένα. Οι κατάλογοι που περιλαμβάνουν μικρότερους και επομένως περισσότερους σεισμούς μπορούν πιθανώς να συμβάλουν στην καλύτερη κατανόηση των σεισμικών διεργασιών και στη μελλοντική πρόγνωση των σεισμών. Σημαντική πτυχή σε τέτοιες μελέτες αποτελεί η σωστή εκτίμηση των ιδιοτήτων των σεισμικών καταλόγων, όπως είναι το μέγεθος πληρότητας και η παράμετρος b. Η επίδραση των σφαλμάτων των μεγεθών που υπάρχουν στους σεισμικούς καταλόγους στην εκτίμηση των προαναφερθέντων ιδιοτήτων ερευνάται χρησιμοποιώντας συνθετικά μεγέθη στα οποία ενυπάρχουν κανονικώς κατανεμημένα σφάλματα. Κατά τη διερεύνηση της αποτελεσματικότητας των διαφόρων μεθόδων που χρησιμοποιούνται για την εκτίμηση του μεγέθους πληρότητας προκύπτει ότι το μέγεθος του δείγματος και του σφάλματος των μεγεθών μπορούν να επηρεάσουν την εκτίμηση της παραμέτρου b, με επιπτώσεις στην εκτίμηση του ρυθμού των μελλοντικών ισχυρών σεισμών και την αξιολόγηση του σεισμικού κινδύνου.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1986.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Bibliography: leaves 262-269.
by Jozef Frans Maria Van Dyck.
Ph.D.

A strategy for relocating earthquakes in a catalog is presented. The strategy is based on the argument that the distribution of the earthquake events in a catalog is reasonable a priori information for earthquake relocation in that region. This argument can be implemented using the method of maximum likelihood for arrival time data inversion, where the a priori probability distribution of the event locations is defined as the sum of the probability densities of all events in the catalog. This a priori distribution is then added to the standard misfit criterion in earthquake location to form the likelihood function. The probability density of an event in the catalog is described by a Gaussian probability density. The a priori probability distribution is, therefore, defined as the normalized sum of the Gaussian probability densities of all events in the catalog, excluding the event being relocated. For a linear problem, the likelihood function can be approximated by the joint probability density of the a priori distribution and the distribution of an unconstrained location due to the misfit alone. After relocating the events according to the maximum of the likelihood function, a modified distribution of events is generated. This distribution should be more densely clustered than before in general since the events are moved towards the maximum of the posterior distribution. The a priori distribution is updated and the process is iterated. The strategy is applied to the aftershock sequence in southwest Iceland after a pair of earthquakes on 29th May 2008. The relocated events reveal the fault systems in that area. Three synthetic data sets are used to test the general behaviour of the strategy. It is observed that the synthetic data give significantly different behaviour from the real data.

The document contains the catalog of earthquakes in Vogtland /West Bohemia within the period of 2008/10/19 -to- 2009/03/16. The events were recorded by a seismic mini-array operated by the Institute of Earthsciences, University of Postdam.
Das Dokument enthält einen Katalog von Erdbeben im Vogtland/Westböhmen im Zeitraum 2008/10/19 -bis- 2009/03/16. Die Erdbeben wurden mit Hilfe eines seismologischen Miniarrays, welches vom Institut für Geowissenschaften, Universität Potsdam, aufgestellt wurde, registriert.

This dissertation is a comprehensive summary of four papers on the development and application of new strategies for locating tremor and relocating events in earthquake catalogs. In the first paper, two new strategies for relocating events in a catalog are introduced. The seismicity pattern of an earthquake catalog is often used to delineate seismically active faults. However, the delineation is often hindered by the diffuseness of earthquake locations in the catalog. To reduce the diffuseness and simplify the seismicity pattern, a relocation and a collapsing method are developed and applied. The relocation method uses the catalog event density as an a priori constraint for relocations in a Bayesian inversion. The catalog event density is expressed in terms of the combined probability distribution of all events in the catalog. The collapsing method uses the same catalog density as an attractor for focusing the seismicity in an iterative scheme. These two strategies are applied to an aftershock sequence after a pair of earthquakes which occurred in southwest Iceland, 2008. The seismicity pattern is simplified by application of the methods and the faults of the mainshocks are delineated by the reworked catalog. In the second paper, the spatial distribution of seismicity of the Hengill region, southwest Iceland is analyzed. The relocation and collapsing methods developed in the first paper and a non-linear relocation strategy using empirical traveltime tables are used to process a catalog collected by the Icelandic Meteorological Office. The reworked catalog reproduces details of the spatial distribution of seismicity that independently emerges from relative relocations of a small subset of the catalog events. The processed catalog is then used to estimate the depth to the brittle-ductile transition. The estimates show that in general the northern part of the area, dominated by volcanic processes, has a shallower depth than the southern part, where tectonic deformation predominates. In the third and the fourth papers, two back-projection methods using inter-station cross correlations are proposed for locating tremor sources. For the first method, double correlations, defined as the cross correlations of correlations from two station pairs sharing a common reference station, are back projected. For the second method, the products of correlation envelopes from a group of stations sharing a common reference station are back projected. Back projecting these combinations of correlations, instead of single correlations, suppresses random noise and reduces the strong geometrical signature caused by the station configuration. These two methods are tested with volcanic tremor at Katla volcano, Iceland. The inferred source locations agree with surface observations related to volcanic events which occurred during the tremor period.

Low frequency earthquakes (LFEs) are detected at depths of 16-30 km on a 150 km section of the San Andreas Fault (SAF) centered at Parkfield, CA. The LFEs are divided into 88 families based on waveform similarity. In continuous families a burst of a few LFE events recurs every few days while episodic families experience essentially quiescent periods often lasting months followed by bursts of hundreds of events over a few days. The occurrence of LFEs has also been shown to be sensitive to extremely small (~1 kPa) tidal stress perturbations. However, the clustered nature of LFE occurrence could potentially bias estimates of tidal sensitivity. Here we re-evaluate the tidal sensitivity of LFE families on the deep San Andreas using a declustered catalog. Declustered LFE families are still highly sensitive to primarily right-lateral shear stress (RLSS) and to a lesser extent fault normal stress (FNS).

An accurate seismic hazard assessment can only be carried out if a homogeneous and sufficiently complete catalogue for the study area is available. Since the catalogue for southern Africa was last updated in the early 1990s for the Global Seismic Hazard Assessment Program (GSHAP), it is necessary that a new updated, homogeneous and complete earthquake catalogue be compiled that includes data acquired during the last two decades. The process of compiling the new earthquake catalogue for southern Africa (South Africa, Lesotho, Swaziland, Botswana, and Namibia) was done as part of the Global Earthquake Modelling (GEM) project. The data from published and unpublished sources, and databases from the South African National Seismograph Network (SANSN), Bulawayo (BUL), the Geological Survey of Botswana, the National Earthquake Information Centre (NEIC), the Advanced National Seismic System (ANSS), and the International Seismic Centre (ISC) were retrieved and evaluated. After the data from the different sources were merged, duplicates and induced earthquakes were removed. The catalogue was unified with all magnitude types converted to moment magnitude (MW). Unifying the southern African catalogue to one magnitude scale had multiple challenges, considering that the catalogue is mostly incomplete, and it was therefore not easy to derive relations between different magnitude scales. The question of which method and relations are most suitable for converting all magnitude scales to MW had to be addressed. To ensure that all the events are independent, several procedures were carried out to decluster the catalogue and most suitable method selected. The final catalogue includes all available events, i.e. historical, and instrumental events from 1690 to December 2011, excluding fore- and aftershocks and induced events. This catalogue has 920 events with MW ≥ 4 whereas GSHAP has only 100 events with MS ≥ 4 in the southern African region. The largest event in the final catalogue occurred in 1952 and is located in the Okavango Delta region in Botswana with magnitude MW = 6.7. The maximum likelihood method was used at each point on a grid covering the study area, to estimate the spatial distribution of the b-value and the activity rate. The maximum curvature method was used for estimating the spatial distribution of magnitude of completeness, which was also substantiated with the Gutenberg-Richter, time-scale and spatial-scale magnitude of completeness graphs.

Macroseismic data in the form of felt reports of earthquake shaking is vital to seismic hazard assessment, especially in view of the relatively short period of instrumental recording in many countries. During the early 1990s, a very detailed examination of historical earthquake records held in the State Government archives and the Public Library of South Australia was carried out by myself. This original work resulted in the compilation of a list of just over 460 earthquakes in the period prior to seismic network recording, which commenced in 1963, The majority of these events had escaped mention in any previous publication on South Australian seismicity and seismic risk. This historical earthquake research, including the production of a large number of isoseismal maps to enable earthquake quantification in terms of magnitude and location, appears to have been the only study of its kind in South Australia performed so comprehensively, and resulted in the most extensive list available. After 20 years, it still stands as the definitive list of historical earthquake events in the state. The incorporation of these additional historical events into the South Australian Earthquake Catalogue maintained by the SA Department of Primary Industries and Resources had the potential to raise the previous listing of just 49 pre-instrumental events to 511 earthquakes, and to extend it back another 46 years to 1837. Some of the major events have been formally included in the South Australian Earthquake Catalogue. However, for many events, there was insufficient information and/or time to finalise the source parameters due to the onerous task of manually trawling through historical records and newspapers for felt reports. With the advent of the information age, researching historical newspapers and records is now a feasible undertaking. As an example, I recovered reports of an additional 110 previously unrecognised events during the first 50 years of colonisation from digitised South Australian newspapers, recently made available on the National Library of Australia’s website called TROVE. This was done in a relatively short period of time and now the South Australian Historical Earthquake List incorporating these events comprises some 679 entries. This thesis builds upon and consolidates the work that was commenced 20 years ago. By doing so, it proposes the establishment of flexible and convenient computerized processes to maintain well into the future an increasingly accurate record of historical earthquakes in South Australia. This work may also provide a model for the ongoing development of historical earthquake records in other states and territories of Australia.
Thesis (M.Phil.) -- University of Adelaide, School of Chemistry and Physics, 2013

博士
國立中正大學
地震研究所暨應用地球物理研究所
97
This thesis aims to better understand earthquake occurrences of Taiwan in terms of three aspects. These aspects include (1)detection of a scaling law in spatial-temporal distribution of earthquakes, (2)verification of differences of the scaling law after a medium earthquake occurrence, and (3)investigation of temporal correlation of earthquake distribution by using Diffusion Entropy Analysis. The first aspect examines the feasibility of applying a unified scaling law to earthquakes, comparing the difference of this law between earthquake time sequences and declustered ones, and comparing the variances of the law from different geological settings. The second aspect uses another scaling law which was created by rescaling the conditional probability density function with seismic rates. The last one analyzes the time distribution of inter-cluster earthquakes with various time units to infer the correlation of earthquake occurrences, and compare of real earthquake sequences with the synthetic ones. The results of the first study show that no matter how cell size and cut-off magnitude change, a very similar pattern symbolizing the scaling law would be produced. After declustering, an apparent indicator of the characteristics of aftershocks disappears, and the indicator corresponding to the main shock remains almost the same. In addition, the scaling laws obtained from four different sub-regions, although are slightly different from each other, all show to be of a similar scaling law. The second study demonstrates that after the occurrence of a median earthquake, the magnitude of earthquake seems to be independent, but the waiting time seems to be dependent, on the history contained in the seismic catalogs. The results of the third study show that there is a positive temporal correlation when the event time series is sampled by a time unit ranging from 120 to 1800 minutes. In the range of the time units, a two-slope feature in the determination of scaling exponent in DEA are observed, and the scenario is demonstrated by the simulations of a synthetic earthquake sequence generated by the Copying Mistake Map model. Our simulation suggests that the earthquake sequence may consist of a randomness sequence and a correlated sequence, and the latter contributes to the correlation observed in our analysis.

碩士
國立臺灣大學
地質科學研究所
96
This study collected 1130 regional centroid moment tensor (CMT) solutions, which were obtained by the Institute of Earth Sciences, Academia Sinica for earthquakes occurred in the Taiwan region in 1995-2005 by inverting the BATS broadband waveforms, to characterize their statistic properties and tectonic implications. The moment magnitude ranges from 3.3 to 7.1 in this catalog with a complete magnitude (Mc) of ~4.0 and the b-value of 0.921. Predominant thrusting events(42.92％) are common in the colliding boundary, fold-and-thrusting belt, and subducting interface, whereas the normal faulting(4.51％) presents mainly in the Okinawa Trough, northern Hoping Basin, and the eastern Central Range. To evaluate the robustness of BATS CMT solutions, this study compares 96 CMT solutions in common between BATS and GCMT catalogs. Results show that the BATS solutions are well constrained for events with misfit < 0.5, which are roughly comparable to solutions of GCMT with moment error < 0.2. The BATS Mw is generally less than GCMT Mw by an average of ~0.17. This is very likely due to the insufficient quality of solutions in GCMT catalog for small earthquakes. For obtaining more robust solutions in the future, the uncertain of epicenter location, velocity model and station coverage must be improved by new techniques such like location searching, 3-D Green’s function. Horizontal seismic strain directions, which are shown in terms of well constrained BATS CMT dataset, agree well with the surface geodetic GPS observations. Seismic strain rate along the Costal Range is ~1E-7/yr, which is about one order of magnitude smaller than the one derived from GPS measurements. This study applies Michael’s method (1984) to invert the stress tensor for obtaining the seismic stress field in the Taiwan region. Finally, we take advantage of these results to delineate the seismogenic structures associated with tectonic processes around Taiwan. Our results provide seismological constraints on the mode of deformation and stress field in the Taiwan region.

Tee present research focuses on seismic hazard studies for the states of Tripura and Mizoram in the North-East India with taking into account the complex sesismotectonic characteristics of the region. This area is more prone to earthquake hazard due to complex subsurface geology, peculiar topographical distribution, continuous crustal deformation due to the under thrusting of Indian and the Eurasian plates, a possible seismic gap, and many active intraplate sources identified within this region. The study area encompasses major seismic source zones such as Indo Burmese Range (IBR), Shillong Plateau (SP), Eastern Himalayan arc (EH), Bengal Basin (BB), Mishmi Thrust (MT) and Naga Thrust (NT). Five historical earthquakes of magnitude Mw>8 have been listed in the study area and 15 events of magnitude Mw>7 have occurred in last 100 years. Indian seismic code BIS-1893-2002 places the study area with a high level of seismic hazard in the country (i.e. seismic zone V). More than 60% of the area is hilly steep-terrain in nature and the altitude varies from 0 to 3000 meters. Recent works have located a seismic gap, known as the Assam gap since 1950 between the EH, SP, and IBR with the Eurasian plate. Various researchers have estimated the return period, and a large size earthquake is expected in this region any time in future. The area is also highly prone to liquefaction, since rivers in Tripura (Gomati, Howrah, Dhalai, Manu, Bijay, Jeri, Feni) and the rivers in Mizoram (Chhimtuipui, Tlawng, Tut, Tuirial and Tuivawl etc.) are scattered throughout the study area where soil deposits are of sedimentary type. In 2011, both the states together have experienced 37 earthquakes (including foreshocks and aftershocks) with magnitudes ranging from 2.9 to 6.9. Of these events, there were 23 earthquakes (M>4) of magnitudes M6.4 (Feb 4th 2011), M6.7 (March 24th 2011), M6.9 (Sept.18th 2011), M6.4 (October 30th 2011), M6.9 (Dec 13th 2011), M5.8 (Nov 21st 2011), M5 (Aug 18th 2011), M4.9 (July 28th 2011), M4.6 (Dec 15th 2011), M4.6 (Jan 21st 2011), M4.5 (Dec 9th 2011), M4.5 (Oct 21th 2011), M4.5 (Oct 17th 2011), M4.5 (Sept 18th 2011), M4.3 (Oct 10th 2011), M4.3 (Sept 22nd 2011), M4.3 (April 4th 2011), M4.2 (Sept 9th 2011), M4.2 (Sept 18th 2011), M4.1 (April 29th 2011), M4.1 (Feb 22nd 2011), M4 (June 9th 2011), and M4 (Dec 2nd 2011) which occurred within this region [source: IMD (Indian Metrological Department), India]. The earthquake (M6.9) that occurred on Sept. 18th 2011 is known as the Sikkim earthquake, and it caused immense destruction including building collapse, landslides, causalities, disrupted connectivity by road damages and other infrastructural damages in Sikkim state as well as the entire North-East India. In the cities of Agartala and Aizawl of Tripura and Mizoram, construction of high rise building is highly restricted by the Government. Being the capital city, many modern infrastructures are still pending for growth of the city planning. Although many researchers have studied and reported about the status of seismicity in North-East Region of India, very few detailed studies have been carried out in this region except Guwahati, Sikkim and Manipur where almost the whole of the study area is highly vulnerable to severe shaking, amplification, liquefaction, and landslide. From the available literature, no specific study exists for Tripura and Mizoram till date. In the present research, seismic hazard assessment has been performed based on spatial-temporal distribution of seismicity and fault rupture characteristics of the region. The seismic events were collected from regions covering about 500 km from the political boundary of the study area. The earthquake data were collected from various national and international seismological agencies such as the IMD, Geological Survey of India (GSI), United State Geological Survey (USGS), and International Seismological Centre (ISC) etc. As the collected events were in different magnitude scales, all the events were homogenized to a unified moment magnitude scale using recent magnitude conversion relations (region specific) developed by the authors for North-East Region of India. The dependent events (foreshocks and aftershocks) were removed using declustering algorithm and in total 3251 declustered events (main shocks) were identified in the study area since 1731 to 2011. The data set contains 825 events of MW < 4, 1279 events of MW from 4 to 4.9, 996 events MW from 5 to 5.9, 131 events MW from 6 to 6.9, 15 events MW from 7 to 7.9 and 5 events MW ≥8. The statistical analysis was carried out for data completeness (Stepp, 1972). The whole region was divided into six seismic source zones based on the updated seismicity characteristics, fault rupture mechanism, size of earthquake magnitude and the epicentral depth. Separate catalogs were used for each zone, and seismicity parameters a and b were estimated for each source zone and other necessary parameters such as mean magnitude (Mmean), Mmax, Mmin, Mc and recurrence periods were also estimated. Toposheets/vector maps of the study area were collected and seismic sources were identified and characterized as line, point, and areal sources. Linear seismic sources were identified from the Seismotectonic atlas (SEISAT, 2000) published by the GSI, in addition to the source details collected from available literature and remote sensing images. The SEISAT map contains 43 maps presented in 42 sheets covering entire India and adjacent countries with 1:1million scale. Sheets representing the features of the study area were scanned, digitized and georeferenced using MapInfo 10.0 version. After this, tectonic features and seismicity events were superimposed on the map of the study area to prepare a Seismotectonic Map with a scale of 1:1million. In seismic hazard assessment, a state of art well known methodologies (deterministic and probabilistic) was used. In deterministic seismic hazard analysis (DSHA) procedure, hazard assessment is based on the minimum distance between sources to site considering the maximum magnitude occurred at each source. In hazard estimation procedure a lot of uncertainties are involved, which can be explained by probabilistic seismic hazard analysis (PSHA) procedure related to the source, magnitude, distance, and local site conditions. The attenuation relations proposed by Atkinson and Boore (2003), and Gupta (2010) are used in this analysis. Because in this region two type activities are mostly observed, regions such as SP, and EH are under plate boundary zone whereas IBR is under subduction process. These equations (GMPEs) were validated with the observed PGA (Peak ground acceleration) values before use in the hazard evaluation. The hazard curves for all six major sources were prepared and compiled to get the total hazard curve which represents the cumulative hazard of all sources. Evaluation of PGA, Sa (0.2s and 1.0s) parameters at bedrock level were estimated considering a grid size of 5 km x 5 km, and spectral acceleration values corresponding to a certain level of probability (2% and 10%) were done to develop uniform hazard spectrum (UHS) for both the cities (Agartala and Aizawl). To carry out the seismic microzonation of Agartala and Aizawl cities, a detailed study using geotechnical and geophysical data has been carried out for site characterization and evaluation of site response according to NEHRP (National Earthquake Hazard Response Program) soil classifications (A, B, C, D, and E-type). Seismic site characterization, which is the basic requirement for seismic microzonation and site response studies of an area. Site characterization helps to have the idea about the average dynamic behavior of soil deposits, and thus helps to evaluate the surface level response. A series of geophysical tests at selected locations have been conducted using multichannel analysis of surface waves (MASW) technique, which is an advanced method to obtain direct shear wave velocity profiles from in situ measurements for both the cities. Based on the present study a major part of Agartala city falls under site class D, very few portions come under site class E. On the other hand, Aizawl city comes under site class C. Next, a detailed site response analysis has been carried out for both the cities. This study addresses the influence of local geology and soil conditions on incoming ground motion. Subsurface geotechnical (SPT) and geophysical (MASW) data have been obtained and used to estimate surface level response. The vulnerable seismic source has been identified based on DSHA. Due to the lack of strong motion time history of the study area, synthetic ground motion time histories have been generated using point source seismological model (Boore 2003) at bedrock level based on fault rupture parameters such as stress drop, quality factor, frequency range, magnitude, hypocentral distance etc. Dynamic properties such as the shear modulus (G) and damping ratios (ζ) have been evaluated from the soil properties obtained from SPT bore log data collected from different agencies such as PWD (Public works Department), and Urban Development Dept. of the State Government, in situ shear wave velocity has been obtained from MASW survey in different locations, and following this, a site response analysis has been carried out using SHAKE-2000 to calculate the responses at the ground surface in combination of different magnitudes, distances and epicentral depth for a particular site class. An amplification factor was estimated as the ratio of the PGA at the ground surface to the PGA at bedrock level, a regression analysis was carried out to evaluate period dependant site coefficients, and hence, the period dependant hazard impact on the ground surface could be calculated to obtain the spatial variation of PGA over the study area. Further, liquefaction potential of the site (Agartala) was also evaluated using available SPT bore log data collected and using presently estimated surface level PGA. The results are presented in the form of liquefaction hazard map representing as a Factor of safety (FS) against liquefaction with various depths such as 1.5m, 10m, and 15m respectively. It has been seen that Agartala city shows highly prone to liquefaction even up to 15 m depth. Hence, site specific study is highly recommended for implementing any important project. The liquefaction hazard assessment could not be conducted for the Aizawl city because of non availability of the SPT-N data, however, the city stands on hills/mountains, and therefore, such a study is not applicable in this area. Further, seismic microzonation maps for both the cities have been prepared considering Analytical Hierarchy Process (AHP) which support to the Eigen value properties of the system. Two types of hazard maps have been developed, one using deterministic and another using the probabilistic seismic microzonation maps. These maps can be directly used as inputs for earthquake resistant design, and disaster mitigation planning of the study area. However, an investigation has also been made in forecasting a major earthquake (Mw>6) in North-East India using several probabilistic models such as Gamma, Weibull and lognormal models. IBR and EH show a high probability of occurrences in the next 5 years (i.e. 2013-2018) with >90% probability.