present day crustal deformation and geodetic strain in the vicinity of dholavira harappan civilization site kachchh western part of the indian plate abstract to understand the geodynamics in the vicinity of dholavira a harappan civilization site hcs in kachchh western india gps data from 2009 to 2015 were processed and analyzed tectonically this part of northern kachchh is in the influence of island belt fault ibf and allah bund fault abf and is seismically one of the most active intra plate regions of india the motion with respect to indian plate is used for the estimation of deformation and strain rate while fault associated slip rate has been estimated by inverse modeling of observed site motions the analysis reveals that the abf deforms with an average rate of 1 8 mm yr however the segmented ibf has a maximum deformation rate of 2 9 mm yr towards the pachham island and minimum towards the khadir island the computation discloses a maximum seismic moment m0 of 2 1 1024 dyne cm in this part which corresponds to an earthquake of mw 6 0 the calculated maximum strain of 0 04 micro strain year is low but significant in the intra plate region the postseismic deformation after the mw 7 7 2001 bhuj earthquake is estimated to be low in this part the reverse along with strike slip motion of faults builds up stress in the area and accumulating more strain

miocene nne directed extensional unroofing in the menderes massif southwestern turkey structural investigations in the central part of the menderes massif odemio kiraz submas sif reveal the presence of a large scale low angle extensional shear zone with a top to the n ne shear sense regional ductile deformation was accompanied by the intrusion of two syntectonic granodiorites that have been dated with the 40 ar 39 ar method one hornblende isochron age of 19 5 1 4 ma and two biotite plateau ages of 13 1 0 2 and 12 2 0 4 ma respectively constrain that extension was already active in the early miocene successive tectonic denudation of the odemio kiraz submassif resulted in the formation of a n dipping detachment fault in which ductile fabrics were severely reworked by cataclasis under decreasing temperature syntectonic neogene sediments currently exposed along the southern margin of the gediz graben were deposited in the hanging wall of the extensional fault system and were tectonically emplaced onto the cataclasites during progressive exhumation minor rotation c 15 caused southward tilting of the sediments ongoing nne directed extension created a steep normal fault that truncates the detachment fault and constitutes the southern boundary fault of the gediz graben

india and sunda plates motion and deformation along their boundary in myanmar determined by gps using a regional gps data set including 190 stations in asia from nepal to eastern indonesia and spanning 11 years we update the present day relative motion between the indian and sundaland plates and discuss the deformation taking place between them in myanmar revisiting measurements acquired on the main boundary thrust in nepal it appears that points in southern nepal exhibit negligible deformation with respect to mainland india including these points using a longer time span than previous studies and making an accurate geodetic mapping in the newest reference frame allows us to refine the present day indian motion our results confirm that the current motion of india is slower than predicted by the nuvel 1a model and in addition our india eurasia motion is significantly 5 mm yr slower than previous geodetic determinations this new indian motion combined with a refined determination of the sundaland motion gives way to a relative india sunda angular velocity of 20 2 n 26 1 e 0 370 myr in itrf2000 predicting a relative motion of 35 mm yr oriented n10 at the latitude of myanmar there the sagaing fault accommodates only 18 mm yr of right lateral strike slip only half of the shear component of motion we present two models addressing how and where the remaining deformation may occur a first model of distributed deformation implies convergence on the arakan subduction the northern continuation of the now famous sumatra andaman trench and wrench faulting in the arakan wedge the second model uses localized deformation where deformation observed west of the sagaing fault is entirely due to elastic loading on a faster and oblique arakan subduction 23 mm yr this latter model predicts that a major earthquake of mw 8 5 may occur every century on this segment of the subduction

miocene rise of the shillong plateau and the beginning of the end for the eastern himalaya abstract a common feature of convergent plate boundaries is the self organization of strain exhumation and topography along discrete arcuate boundaries deviations from this geometry can represent first order changes in stress applied at a plate boundary that must affect how strain is partitioned within the interior of an orogen the simplicity of the himalayan fold and thrust belt seen along its central portion breaks down along the eastern extremity of the arc where the 400 km long shillong plateau has developed this change in strain partitioning affects nearly 25 of the arc and has not previously been considered to be important to the orogen s development new low temperature thermochronometry data suggest this structure initiated in mid to late miocene time significantly earlier than was previously estimated from the sedimentary record alone development of the shillong plateau may be linked to a number of kinematic changes within the himalayan and burman collision zones that occur at the same time these events include the onset of e w extension in central tibet eastward expansion of high topography of the tibetan plateau onset of rotation of crustal fragments in southeastern tibet and re establishment of eastward subduction beneath the indo burman ranges we suggest that the coincidence of these tectonic events is related to the dismemberment of the eastern himalayan arc signifying a change in regional stress applied along the india eurasia burma plate boundaries discrepancies between vertical long term faulting rates and geodetically derived far field convergence rates suggest that the collisional boundary in the eastern himalayan system may be poorly coupled due to introduction of oceanic and transitional crust into the eastern plate boundary the introduction of dense material into the plate boundary late in the orogen s history may explain regional changes in the strain field that affect not only the himalaya but also the deformation field more than 1000 km into the tibetan plateau

an analysis of geophysical experiments to test newton s law of gravity signals reported as evidence for a non newtonian fifth force at a north carolina television tower and elsewhere can be explained in a conventional way by postulating small density variations underground the assumptions employed in earlier analyses which pointed to a failure of the inverse square law are examined and found to be difficult to justify

seismic hazard assessment and mitigation in india an overview the indian subcontinent is characterized by various tectonic units viz himalayan collision zone in north indo burmese arc in north east failed rift zones in its interior in peninsular indian shield and andaman sumatra trench in south east indian territory during the last about 100 years the country has witnessed four great and several major earthquakes soon after the occurrence of the first great earthquake the shillong earthquake m w 8 1 in 1897 efforts were started to assess the seismic hazard in the country the first such attempt was made by geological survey of india in 1898 and since then considerable progress has been made the current seismic zonation map prepared and published by bureau of indian standards broadly places seismic risk in different parts of the country in four major zones however this map is not sufficient for the assessment of area specific seismic risks necessitating detailed seismic zoning that is microzonation for earthquake disaster mitigation and management recently seismic microzonation studies are being introduced in india and the first level seismic microzonation has already been completed for selected urban centres including jabalpur guwahati delhi bangalore ahmadabad dehradun etc the maps prepared for these cities are being further refined on larger scales as per the requirements and a plan has also been firmed up for taking up microzonation of 30 selected cities which lie in seismic zones v and iv and have a population density of half a million the paper highlights the efforts made in india so far towards seismic hazard assessment as well as the future road map for such studies

u pb sims dating of synkinematic granites timing of core complex formation in the northern anatolide belt of western turkey secondary ion mass spectrometry sims u th pb dating of magmatic zircon from the synkinematic egrigoz and koyunoba granites and a leucogranite dyke dates core complex formation in the northern anatolide belt of western turkey at 24 19 ma the granites intrude into the footwall of the simav detachment and are strongly elongated in the nne direction parallel to tectonic transport on the detachment although large parts of the granites are undeformed localized mylonitic to ultramylonitic deformation occurs directly beneath the simav detachment and preserves evidence of progressive deformation from ductile to brittle conditions oscillatory zoned rims of long prismatic zircon from the egrigoz and koyunoba granites yield identical and well constrained intrusion ages of 20 7 0 6 ma and 21 0 0 2 ma whereas inherited grains range from palaeoproterozoic 2972 13 ma to neoproterozoic 653 6 ma to 500 5 ma in age a leucogranite dyke yields an intrusion age of 24 4 0 3 ma with inherited neoproterozoic 640 7 ma to 511 6 ma grains our data in conjunction with published 40 ar 39 ar biotite ages indicate very rapid cooling greater than c 200 c ma 1 for the granites during and after synkinematic emplacement

low seismicity in the bhutan himalaya and the stress shadow of the 1897 shillong plateau earthquake abstract the seismicity of the bhutan himalaya region is generally low as compared to its adjoining himalayan segments the topography in the region is slightly subdued and different from the neighbouring central nepal region low seismicity in the region may possibly be due to the postulated low convergence rate in the bhutan himalaya difference in subsurface structures or the aseismic nature of the region we suggest that the lower seismicity in the bhutan himalaya may also be due to stress change caused by the great 1897 shillong plateau earthquake as the low seismicity region of the bhutan himalaya coincides with the stress shadow of the earthquake

granitoid rocks of the southern menderes massif southwestern turkey field evidence for tertiary magmatism in an extensional shear zone recent field campaign in the southern menderes massif in southwestern turkey revealed that the so called core of the massif comprises two distinct types of granitoid rocks an orthogneiss traditionally known as augen gneisses and leucocratic metagranite where the latter is intrusive into the former and the structurally overlying cover schists these differ from one another in intensity of deformation degree of metamorphism and kinematics the orthogneiss display penetrative top to the n nne fabrics formed under upper amphibolite facies conditions during the eocene main menderes metamorphism mmm whereas foliation and stretching lineation exists in the leucocratic metagranites but are not strongly developed the leucocratic metagranites show evidence of syn to post emplacement deformation in a series of weakly developed top to the s ssw fabrics formed under lower greenschist facies conditions leucocratic metagranite bodies occur all along the augen gneiss schist contact in the southern menderes massif they are emplaced as sheet like bodies into country rocks previously deformed and metamorphosed during a top to the n nne alpine orogeny along a ductile extensional shear zone located between orthogneisses and metasediments which was possibly active during emplacement the data presently available indicate that emplacement and associated ductile extensional deformation occurred during late oligocene early miocene time these results confirm previous contentions that there are tertiary granites in this part of the menderes massif

oblique convergence and slip partitioning in the nw himalaya implications from gps measurements we report gps measurements of crustal deformation across the kashmir himalaya we combined these results with the published results of gps measurements from the karakoram fault system and suggest that in the kashmir himalaya the motion between the southern tibet and india plate is oblique with respect to the structural trend we estimated this almost north south oblique motion to be 17 2 mm yr which is partitioned between dextral motion of 5 2 mm yr on the karakoram fault system and oblique motion of 13 6 1 mm yr with an azimuth of n198 e in the northwest southeast trending kashmir himalayan frontal arc thus the partitioning of the india southern tibet oblique motion is partial in the kashmir himalayan frontal arc however in the neighboring nepal himalaya there is no partitioning the entire india southern tibet motion of 19 20 mm yr is arc normal and is accommodated entirely in the himalayan frontal arc the convergence rate in the kashmir frontal himalaya is about 25 less than that in the nepal himalayan region however here the karakoram fault system accommodates about 20 of the southern tibet and indian plate convergence and marks the northern extent of the nw himalayan arc sliver the kaurik chango rift a north south oriented seismically active cross wedge transtensional fault appears to divide the sliver in two parts causing varying translatory motion on the karakoram fault on either side of the kaurik chango rift

the motion and active deformation of india measurements of surface displacements using gps constrain the motion and deformation of india and india eurasia plate boundary deformation along the himalaya the gps velocities of plate interior sites constrain the pole of the angular velocity vector of india with respect to eurasia to lie at 25 6 1 0 n 11 1 9 0 e approximately 6 west of the nuvel 1a pole of 3 ma plate motion the angular rotation rate of 0 44 0 03 myr 1 is 14 slower than the long term rate of 0 51 myr 1 insignificant velocities between plate interior sites indicate that the exposed indian plate is stable to within 7 10 9 yr 1 the observed contraction vector across the himalaya 20 mm yr veers from n20 e in the northwest himalaya to n25 w in east nepal consistent with east west extension of southern tibet

the greenland gravitational constant experiment an airy type geophysical experiment was conducted in a 2 km deep hole in the greenland ice cap at depths between 213 m and 1673 m to test for possible violations of newton s inverse square law the experiment was done at dye 3 the location of a distant early warning line radar dome and the site of the deepest of the greenland ice sheet program gisp drill holes gravity measurements were made at eight depths in 183 m intervals with a lacoste romberg borehole gravity meter prior to the experiment the borehole gravity meter was calibrated with an absolute gravity meter and the wireline depth rinding system used in the borehole logging was calibrated in a vertical mine shaft against a laser geodimeter the density of the ice in the region was calculated from measurements taken from ice cores obtained from earlier drilling observations ice penetrating radar was employed in order to correct the gravity data for the topography of the ice rock interface surface gravity observations were made to assess the extent to which density variations in the sub ice rock could affect the vertical gravity gradient the locations of the gravity observation points were determined with a combination of gps recording first order leveling and edm surveying an anomalous variation in gravity totaling 3 87 mgal 3 87 10 5 m s2 in a depth interval of 1460 m was observed this may be attributed either to a breakdown of newtonian gravity or to unexpected density variations in the rock below the ice

convergence across the northwest himalaya from gps measurements 1 horizontal velocities of 26 global positioning system gps stations in the northwest himalayan region provide new constraints on the partitioning of india eurasia convergence and elastic strain accumulation about the locked main frontal thrust mft the northwest striking karakorum fault slips at 11 4 mm yr and contributes to east west extension of southern tibet and westward motion of the northwest himalaya towards nanga parbat rather than playing a role in eastward extrusion of tibet crustal shortening across the himalaya occurs within a zone centered about 100 km north of the siwalik foothills and the mft model inversions of the gps data indicate that the mft is locked over a width of 100 km comparison with geologic mft slip rate estimates suggests that this zone is building up a slip deficit at a rate of 14 1 mm yr and will eventually fail in future great earthquakes

rigid indian plate constraints from gps measurements abstract we analyze gps data from 26 sites located on the indian plate and along its boundary the large spatial coverage of the indian plate by these sites and longer data duration helped us in refining the earlier estimates of the euler pole for the indian plate rotation our analysis suggests that the internal deformation of the indian plate is very low

strong seismic coupling underneath garhwal kumaun region nw himalaya india abstract no great earthquake has occurred in the garhwal kumaun region of nw himalaya in the past 500 years or more we report results of continuous gps measurements from 28 sites from the region to suggest that the convergence rate in this part of the himalaya is about 18 mm yr which is leading to strain accumulation in the region the main himalayan thrust mht in the frontal part of the himalaya under the outer and southern lesser himalaya is strongly coupled for a width of about 85 km the midcrustal ramp where earthquakes of himalayan seismic belt occur exhibits low coupling strong coupling on the mht beneath the outer and lesser himalaya is homogeneous except in the very shallow updip part of the mht subduction of sediments of the indo gangetic plains or the delhi hardwar ridge does not seem to influence coupling a high rate of strain accumulation which has continued for more than 500 years on a strongly coupled mht makes this one of the most earthquake vulnerable segments of the himalayan arc

locked and loading megathrust linked to active subduction beneath the indo burman ranges it is unclear whether subduction is still active beneath the indo burman mountain range analyses of gps measurements from this region reveal a locked megathrust fault implying that subduction is active and could generate a large earthquake

present day crustal motion around the pamir plateau from gps measurements abstract we have used geodetic techniques to improve constraints on the crustal motion of the pamir plateau three campaigns of global position system data acquisition between 2011 and 2015 demonstrate that in association with the india asia collision a complex pattern of crustal motion exists in the pamir plateau in a north south direction from the indian plate to the hazak block the crust has absorbed 35 mm yr of shortening of which 35 is distributed around the hindu kush region 12 mm yr and another 35 is taken up around the alai valley also 12 mm yr global position system measurements also show 5 mm yr of shortening between the pamir plateau and the tajik basin whereas between the pamir and the tarim basin an 10 mm yr extension rate is observed with respect to the stable eurasian plate the pamir rotates counterclockwise at a rate of 1 822 myr 1 with an euler pole positioned about the west end of the tajik basin 37 03 0 74 n 65 89 0 12 e the strain rate field calculated from global position system velocities reveals that the crustal motion is consistent with localized deformation around the hindu kush and the alai valley the latter representing a zone with strong shallow seismic activity

elastic thickness structure of the andaman subduction zone implications for convergence of the ninetyeast ridge abstract we use the bouguer coherence morlet isostatic response function technique to compute the spatial variation of effective elastic thickness te of the andaman subduction zone the recovered te map resolves regional scale features that correlate well with known surface structures of the subducting indian plate and the overriding burma plate the major structure on the india plate the ninetyeast ridge ner exhibits a weak mechanical strength which is consistent with the expected signature of an oceanic ridge of hotspot origin however a markedly low strength 0

the 40ar 39ar age of extensional ductile deformation and granitoid intrusion in the northern menderes core complex implications for the initiation of extensional tectonics in western turkey the simav detachment fault in the northern part of menderes core complex in western turkey separates cover sequence rocks with brittle deformation from high grade metamorphic core rocks and young granitoid intrusions the timing of shear zone formation and the intrusion of syn tectonic granitoids is constrained by 40ar 39ar geochronology on muscovite from mylonitic gneiss and biotite from the egrigoz granitoid 40ar 39ar data indicate that mylonitic deformation occurred at 22 86 0 47 ma whilst the cooling age of the granitoid is 20 19 0 28 ma the intrusion and cooling of the egrigoz granitoid occurred between 23 20 ma these data demonstrate that extensional deformation in the northern menderes core complex began before early miocene times and represents an early stage in the tertiary extensional tectonics of western turkey

plateau pop up in the great 1897 assam earthquake the great assam earthquake of 12 june 1897 reduced to rubble all masonry buildings within a region of northeastern india roughly the size of england and was felt over an area exceeding that of the great 1755 lisbon earthquake1 hitherto it was believed that rupture occurred on a north dipping himalayan thrust fault propagating south of bhutan2 3 4 5 but here we show that the northern edge of the shillong plateau rose violently by at least 11 m during the assam earthquake and that this was due to the rupture of a buried reverse fault approximately 110 km in length and dipping steeply away from the himalaya the stress drop implied by the rupture geometry and the prodigious fault slip of 18 7 m explains epicentral accelerations observed to exceed 1g vertically and surface velocities exceeding 3 m s 1 ref 1 this quantitative observation of active deformation of a pop up structure confirms that faults bounding such structures can penetrate the whole crust plateau uplift in the past 2 5 million years has caused the indian plate to contract locally by 4 2 mm yr 1 reducing seismic risk in bhutan but increasing the risk in northern bangladesh

evidence of interseismic coupling variations along the bhutan himalayan arc from new gps data although the first order pattern of present day deformation is relatively well resolved across the himalayas irregular data coverage limits detailed analyses of spatial variations of interseismic coupling we provide the first gps velocity field for the bhutan himalaya combined with published data these observations show strong east west variations in coupling between central and eastern bhutan in contrast with previous estimations of first order uniform interseismic coupling along the himalayan arc we identify significant lateral variations in western and central bhutan the fully coupled segment is 135 155 km wide with an abrupt downdip transition whereas in eastern bhutan the fully coupled segment is 100 120 km wide and is limited updip and downdip by partially creeping segments this is the first observation of decoupling on the upper ramp along the himalayan arc with important implications for large earthquake surface rupture and seismic hazard

low deformation rate in the koyna warna region a reservoir triggered earthquake site in west central stable india abstract we analyse nine years of gps measurements of crustal deformation from the koyna warna region within the stable india plate the koyna warna region experienced a strong earthquake on 10 december 1967 m 6 3 that is considered to have been induced by the impoundment of the koyna reservoir and the continuing earthquake activity in the region is considered to be associated with the koyna and warna reservoirs the earthquakes occur in a very small region of 30 10 km2 in two well defined seismic zones the nne ssw trending koyna seismic zone and the nnw sse trending warna seismic zone these zones are characterised by predominantly left lateral strike slip motion and normal motion respectively in 2003 we initiated campaign mode gps measurements in the region analysis of the gps data collected over nine years indicate low to moderate deformation rate

spatial distribution of earthquake potential along the himalayan arc abstract to determine the spatial distribution of earthquake potential along the active himalayan arc we utilize gps measurements and earthquake data we derive horizontal velocity field and 2 d strain rates from a new set of 41 regional gps stations along with 446 published velocities we convert these strain rate tensors to geodetic moment rate build up within 24 contiguous segments and compare to the seismic moment rate release derived from a reassessed earthquake catalog of 900 years the geodetic to seismic moment rate ratio an indicator of stored strain energy varies from below unity to more than 50 in different segments the estimated geodetic moment rate ranges from 1 7 1018 nm yr to 10 2 1018 nm yr whereas the seismic moment rate ranges from 3 7 1016 nm yr to 5 1 1019 nm yr this variation between the geodetic and seismic moment rate corresponds to a moment deficit rate of 1 15 1017 nm yr to 7 97 1018 nm yr along various segments of the study region the above moment deficit rate provides an equivalent earthquake potential of magnitude 5 7 8 2 in different segments specifically the higher earthquake potential mw 8 0 corresponds to the segments in the central seismic gap and the northeast part of himalaya whereas the lower earthquake potential mw

hydrological changes and vertical crustal deformation in south india inference from grace gps and absolute gravity data abstract monsoon rainfall over indian subcontinent causes large hydrological changes that deform the earth on varied time scale the seasonal hydrological mass changes are in the range of 20 50 cm of equivalent water height over southern india which causes vertical deformation of 1 2 cm we compare the deformation computed from grace mass signal with that of height changes from continuous gps data from two locations in south india and find that the amplitude and phases of seasonal vertical deformation derived from both gps and grace are consistent indicating that hydrological effects are major cause of periodic deformation in the region this supports the earlier deduction that grace data can be utilized to remove hydrological effects from gps data high precision absolute gravity values measured near the gps location and groundwater levels measured in the boreholes corroborate the space based observations of hydrological changes and vertical deformation gps and grace data also indicate inter annual variation caused due to rainfall variability signifying that hydrological effects must be removed before deriving any long term vertical deformation trend

estimates of interseismic deformation in northeast india from gps measurements abstract estimates of interseismic deformation in northeastern india based on gps measurements at eight permanent stations 2003 2006 and six campaign sites 1997 2006 are presented here the euler pole of rotation of indian tectonic plate in itrf2000 determined from the present data set is located at 51 7 0 5 n 15 1 1 5 e with angular velocity of 0 469 0 01 myr 1 the results show that there is a statistically insignificant present day active deformation within the shillong plateau and in the foreland spur north of the plateau in the brahmaputra valley convergence rate of the northeastern gps sites with respect to the igs station lhasa along baselines that are normal to the himalayan arc in this region is 16 0 5 mm yr this represents the arc normal indo eurasian convergence rate across the northeastern boundary similar to arc normal convergence rates determined in central nepal along the himalayan arc however unlike central nepal in the arunachal himalaya the 16 mm yr shortening is distributed between the lesser as well as higher and tethyan himalayas baselines between sites on the indo burmese fold and thrust belt ibftb and shillong plateau indicate variations in the shortening rate from 1 5 mm yr on the tripura mizoram salient trs south of the plateau to 6 mm yr in the imphal recess ir to the east and 8 mm yr in naga salient ns to the northeast this suggests that the deformation in the ibftb is segmented into n s blocks along e w transverse zones exhibiting dextral slip between ns ir and sinistral slip between ir and trs baselines between the ibftb sites also show 10 0 6 mm yr convergence pointing to the existence of an active transverse zone between aizawl and imphal

earthquake occurrence processes in the indo burmese wedge and sagaing fault region abstract earthquakes in the indo burmese wedge and sagaing fault regions occur in response to the partitioning of the india sunda motion along these two distinct boundaries under the accretionary wedge of the indo burmese arc majority of the earthquakes occur in the depth range of 30 60 km and define an eastward gently dipping seismicity trend surface that coincides with the indian slab the dip of the slab steepens in the east direction and earthquakes occur down to a depth of 150 km though the slab can be traced up to the 660 km discontinuity although these features are similar to a subduction zone the nature of the earthquakes and our analysis of their focal mechanisms suggest that these earthquakes are of intra slab type which occur on steep plane within the indian plate and the sense of motion implies a northward relative motion with respect to the sunda plate thus these earthquakes and the stress state do not support active subduction across the indo burmese arc which is also consistent with the relative motion of india sunda plates the absence of inter plate earthquakes lack of evidence of the occurrence of great earthquakes in the historical records and non seismogenic nature of the plate interface under the accretionary wedge suggest that seismic hazard due to earthquakes along the plate boundary may be relatively low however major intra slab earthquakes at shallow and intermediate depths may still cause damage in the sediment filled valley regions of manipur and cachar in india and chittagong and sylhet regions of bangladesh in the sagaing fault region earthquakes occur through dextral strike slip motion along the north south oriented plane and the stress state is consistent with the plate motion across the sagaing fault

revisiting the 1991 uttarkashi and the 1999 chamoli india earthquakes implications of rupture mechanisms in the central himalaya abstract the central himalaya has attracted much attention due to its potential to host a great earthquake an inference based on the history of earthquakes and the geodetic slip estimates the largest and earliest historically documented earthquake in the central himalaya occurred in 1803 m 7 7 near uttarkashi on its western part much before the great event of 1934 mw 8 2 located farther to the east both of which were felt severely in the gangetic plain south of the mountain front the seismotectonic model by seeber and armbruster 1981 predicts that large great earthquakes originate on the main himalayan thrust mht and their ruptures propagate southward to the main frontal thrust mft the rupture of the april 25 2015 mw 7 8 gorkha nepal earthquake however was southeast directed with a southwest directed slip and its mw 7 3 aftershock on may 12 also showed a similar slip direction post 2015 we revisited the 1991 uttarkashi mw 6 7 and the 1999 chamoli mw 6 5 earthquakes in india both of which had originated on the mht flat but show ssw directed slips as reported in this study ruptures of both these earthquakes fell short of reaching the mft just as the historically documented 1803 earthquake but their shaking effects were felt in the southern plains these observations compel us to conclude that the varying rupture modes exhibited by the himalayan earthquakes are controlled primarily by the geometry of the flat ramp flat system

tertiary granitoids of rhodope northern greece magmatism related to extensional collapse of the hellenic orogen abstract many granites that occur in orogenic belts such as the himalaya the hercynides or caledonides are thought to result from anatexis of the lower parts of over thickened thrust stacked crustal units just preceding termination of the orogenic cycle numerous tertiary granitoids occur in the rhodope zone of northern greece and adjacent regions of bulgaria a belt regarded as an eastern extension of the alpine system these granites could also be regarded as syn or late tectonic crustal melts in that some have been emplaced as sheet like bodies along major alpine thrust planes and show a strong marginal foliation parallel to the pervasive alpine compressional fabrics in detail however the geochemistry of the granitoids their timing and relationships with country rocks suggest they have been emplaced in an extensional regime that is related to the collapse of the hellenic orogen and more particularly to the crustal thinning that the aegean region has suffered since the mid tertiary rather than being products of crustal thickening it is suggested that their petrogenesis is related to the elevation of thermal gradients during the extensional phase which initiated thermal breakdown of hydrous minerals in the lithosphere and lower crust that had existed metastably during compression and the subduction of cool ocean lithosphere beneath the region in the late mesozoic early tertiary

gps derived crustal deformation analysis of kachchh zone of 2001 m7 7 earthquake western india abstract in this study we present the first estimates of crustal deformation using the time series 2009 2015 from gps network of gujarat gng comprising 10 gps continuous and 5 campaign mode stations in the seismically active kachchh region the gps data were processed using gamit globk glorg software and results reveal very low amount of intra plate deformation in this part of the indian plate international terrestrial reference frame itrf velocity of sites deduced in this study indicates 46 51 mm yr of motion with one sigma uncertainty a maximum of 3 0 0 5 mm yr of deformation has been estimated in the kachchh region however estimated strain rate from the velocity field indicates a maximum strain of 5 nano strain yr our results indicate deformation of a weak zone where earthquakes may trigger due to the combination of local as well as regional stress the analysis of strain tensors near the major fault systems kmf khf swf and gf indicates strike normal compression in the area the low rate of deformation derived in the present study is important to understand the seismic hazard level in this part of the indian intra plate

complete tertiary exhumation history of the menderes massif western turkey an alternative working hypothesis the main exhumation of the menderes massif western turkey occurred along an originally n dipping datca kale main breakaway fault that controlled depositions in the kale and the gokova basins during the oligocene early miocene interval the isostatically controlled upward bending of the main breakaway fault brings the lower plate rocks to the surface in the early miocene e w trending n and s dipping graben bounding faults fragmented the exhumed dome shaped massif the development of half grabens by rolling master fault hinges has allowed further exhumation of the central menderes massif after the pliocene high angle normal faults cut all of the previous structures this model suggests that the menderes massif is a single large metamorphic core complex that has experienced a two stage exhumation process

postseismic deformation following the 2015 mw7 8 gorkha nepal earthquake new gps data kinematic and dynamic models and the roles of afterslip and viscoelastic relaxation we report global positioning system gps measurements of postseismic deformation following the 2015 mw7 8 gorkha nepal earthquake including previously unpublished data from 13 continuous gps stations installed in southern tibet shortly after the earthquake we use variational bayesian independent component analysis vbica to extract the signal of postseismic deformation from the gps timeseries revealing a broad displacement field extending 150 km northward from the rupture kinematic inversions and dynamic forward models show that these displacements could have been produced solely by afterslip on the main himalayan thrust mht but would require a broad distribution of afterslip extending similarly far north this would require the constitutive parameter a b to decrease northward on the mht to 0 05 mpa an extreme sensitivity of creep rate to stress change and seems unlikely in light of the low interseismic coupling and high midcrustal temperatures beneath southern tibet we conclude that the northward reach of postseismic deformation more likely results from distributed viscoelastic relaxation possibly in a midcrustal shear zone extending northward from the seismogenic mht assuming a shear zone 5 20 km thick we estimate an effective shear zone viscosity of 3 10 3 10 pa s over the first 1 12 postseismic years near field deformation can be more plausibly explained by afterslip itself and implies a b 0 5 1 mpa consistent with other afterslip studies this near field afterslip by itself would have re increased the coulomb stress by 0 05 mpa over 30 of the gorkha rupture zone in the first postseismic year and deformation further north would have compounded this reloading

late orogenic crustal extension in the northern menderes massif western turkey evidence for metamorphic core complex formation the simav metamorphic core complex of the northern menderes massif western turkey consists of a plutonic tertiary and metamorphic precambrian core footwall separated from an allochthonous cover sequence hanging wall by a low angle ductile to brittle extensional fault zone i e detachment fault the core rocks below the detachment fault are converted into mylonites with a thickness of a few hundred metres two main deformation events have affected the core rocks the first deformational event d1 was developed within the precambrian metamorphic rocks the second event d2 associated with the tertiary crustal extension includes two distinct stages stage one is the formation of a variably developed ductile mylonitic deformation d2d in metamorphic and granitic core rocks under greenschist facies conditions the majority of the mylonites in the study area have foliations that strike nnw to nne and dip sw to se stretched quartz and feldspar grains define the mineral lineation trending sw ne direction and plunging gently to sw the kinematic indicators indicate a top to ne sense of shear stage two formation of brittle deformation d2b that affected all core and cover rocks d2b involves the development of cataclasites and high angle normal faults an overall top towards the north sense of shear for the ductile mylonitic fabrics in the core rocks is consistent with the n s regional extension in western turkey

the 2016 mw 6 7 imphal earthquake in the indo burman range a case of continuing intraplate deformation within the subducted slab the 2016 m w 6 7 imphal earthquake is one of the largest and instrumentally well recorded seismic events to have occurred on the segment of the indo burman plate boundary where indian and burman plates converge in a roughly northeast direction similar to 3 4 cm yr this segment of the plate boundary has not generated any great earthquakes in the documented history but is noted for its complex intraslab deformation arc parallel compression and slip partitioning with the continental strike slip sagaing fault previous studies have noted a mix of faulting styles and hypocentral distribution indicating the inherent complexities within this segment based on the teleseismic moment inversion of 88 p and sh waveforms from 70 global broadband seismic stations we use the source model of the 2016 earthquake to corroborate the continuing intraslab deformation the earthquake is sourced at a depth of 55 km where the dip of the slab changes to similar to 50 degrees with the p axis oriented in the north northeast south southwest direction our analysis of azimuths and plunges of p axes of 214 earthquakes m w 4 5 global centroid moment tensor is consistent with this trend previous studies have noted two distinct types of intraplate earthquakes along this segment shallower events 25 75 km due to arc parallel bending and the deeper ones 90 150 km in response to slab pull interplate seismicity is almost absent and the potential for great earthquakes seems much lower compared with the rest of the eastern india plate boundary

gps measurements of present day convergence across the nepal himalaya the high elevations of the himalaya and tibet result from the continuing collision between india and asia which started more than 60 million years ago1 4 from geological and seismic studies of the slip rate of faults in asia5 it is believed that approximately one third of the present day convergence rate between india and asia 58 4mmyr 1 is responsible for the shortening uplift and moderate seismicity of the himalaya great earthquakes also occur infrequently in this region releasing in minutes the elastic strain accumulated near the boundary zone over several centuries and accounting for most of the advance of the himalaya over the plains of india the recurrence time for these great earthquakes is determined by the rate of slip of india beneath tibet which has hitherto been estimated indirectly from global plate motions6 from the slip rates of faults in asia7 8 from seismic productivity9 and from the advance of sediments on the northern ganges plain10 here we report geodetic measurements using the global positioning system gps of the rate of contraction across the himalaya which we find to be 17 52 2 mm yr 1 from the form of the deformation field we estimate the rate of slip of india beneath tibet to be 20 5 2 mmyr 1 strain sufficient to drive one or more great himalayan earthquakes with slip similar to that accompanying the magnitude 8 1 bihar nepal 1934 earthquake may currently be available in western nepal

intraplate deformation of the indian subcontinent 1 while deformation at the earth s surface primarily occurs along tectonic plate boundaries major earthquakes have shaken regions deep within continental interiors three of the largest m 7 5 historic intraplate earthquakes occurred within the indian subcontinent suggesting the possibility of significant intraplate deformation we consider surface velocities determined from new gps data collected at 29 continuous gps stations and 41 survey mode gps stations in india between 1995 and 2007 to find a north south shortening rate of 0 3 0 05 nanostrain yr 1 which may be accommodated by 2 1 mm yr of more localized convergence across central india southward motions at 4 7 mm yr of sites on the shillong plateau in northeast india reflect rapid shortening and high earthquake hazard associated with active thrust faults bounding the plateau the width and magnitude of the elastic strain accumulation field across the himalaya varies little from 76 90 longitude but the strain is more broadly distributed and convergence rates are higher along the eastern 200 km of the range

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

kinematics and strain rates of the eastern himalayan syntaxis from new gps campaigns in northeast india abstract newly acquired gps data along transects across himalaya in eastern himalayan syntaxis ehs reveal a clockwise rotation of rigid micro plate comprising part of brahmaputra valley ne himalaya and northern myanmar that rotates about a pole located at 14 5 n 100 8 e at an angular rate of 1 75 0 12 myr the ehs is being torn off from the main indian plate as a rigid block around which the kinematic clockwise rotation of tibetan gps sites toward the sichuan yunnan region occurs in the eurasia fixed frame the residual velocity field of the newly acquired data estimated after removing the rotation that minimizes the gps rates around ehs show a clear ne motion of the ehs sites indentation of the rigid indian plate into a less rigid area of the eurasian plate the most extensive ehs zones of compression and shortening are in the direction of indenter convergence with average values ranging between 50 100 nanostrain year along the frontal segment of ehs from nw to se the shortening rate is reduced from the local maximum value of 160 to 80 nanostrain year thus indicating a possibly locked fault patch of mishmi or lohit thrusts the southernmost part of segment activated during the large 1950 assam earthquake mw 8 6 an elastic block model was invoked to infer the average slip rates of sections around ehs and to estimate an average locking depth of 15 km the slip rate perpendicular to the locked sector of ehs reaches 32 4 mm year and permits to roughly infer a recurrence time of 200 year for an earthquake as energetic as the 1950 assam event

ductile brittle transition along the alasehir detachment fault and its structural relationship with the simav detachment fault menderes massif western turkey abstract western turkey has experienced extensional deformation since the tertiary an early phase of extensional deformation resulted in the formation of detachment faults in the northern part of the menderes massif the alasehir and simav detachment faults the footwalls of these two detachment faults are mid crustal level rocks the alasehir detachment fault developed in metamorphic rocks and in a syn extensional intrusion the salihli granodiorite the salihli granodiorite shows a gradual change from undeformed isotropic granodiorite to protomylonite mylonite and ultramylonite towards its upper structural levels the deformed granodiorite in turn grades into a cataclastic zone whose uppermost part is the alasehir detachment surface this gradual upward change from the undeformed granodiorite to a brittlely deformed detachment surface suggests that tertiary extension resulted in a ductile deformation at depth and the ductilely deformed granitoids were brought to shallower depths where they were brittlely deformed the metamorphic wall rocks of the intrusion are also mylonitized structurally upward a similar transition has also been found in the footwall of the simav detachment fault the upper part of which is also a cataclastic zone leading to the simav detachment fault separating the low grade metamorphic rocks and or non metamorphic rocks in its hanging wall from mainly high grade metamorphic rocks and syn tectonic granitoids in its footwall during ductile extension greenschist facies grade mylonitic deformation developed in the metamorphic rocks and the granitoids shear sense indicators along the two shear zones show top to n ne sense shear consistent with the regional cenozoic extension direction in western turkey available radiometric age data from the granitoids in the footwall of the two detachment faults suggest that the cenozoic extension in western turkey was initiated in oligocene to early miocene and the simav detachment fault is older than the alasehir detachment fault extensional features of these detachment faults suggest that the simav detachment fault characterise the earlier stage of the tertiary extensional tectonics of the menderes massif and later stage of this deformation resulted in the development of the alasehir detachment fault

spatial variation in the frequency magnitude distribution of earthquakes under the tectonic framework in the middle east abstract spatial variations of seismic energy released and b value over the middle east region are investigated based on a seismicity catalog from 1995 to 2007 the goal is to use these seismic parameters and based on other geodetic and geophysical observations such as gps measurements strain rate model fault distribution focal mechanism crustal model q model and gravity measurements etc to uncover spatial patterns that seem anomalous areas of high energy released cumulative seem to correspond to the areas of relatively high b values areas of high energy released and high b values seem to correspond very well with the location of continental collision where earthquake activities are high the divergent boundary between arabia and african plates and subduction zone at makran seem to correspond to low to moderate energy release northern pamir azerbaijan caucasus the lower part of zagros mountains eastern turkey owen fracture zone strait of bob el mandeb and south of the sulaiman shear zone seem to correspond to high cumulative energy released high strain rate high b values and high fault density while the central and eastern iran southern zagros northern pakistan gulf of aden alborz southwest of the caspian sea western caucasus and kopeh dagh seem to correspond with lower b values the cross section map for hindu kush shows general decreasing of the b values with depth however a region of high b value is observed underneath pamir at depths from 170 to 230 km this anomaly region can be due to dehydration of pamir crustal slab at depth

geophysical evidence for non newtonian gravity measurements of the variation of gravity with depth in mines and boreholes permit the densities of intervening rock strata to be inferred in the few cases in which reliable absolute values of density have been independently determined the calculations can be used to check the value of the newtonian gravitational constant g such large scale measurements of g are important because the validity of the inverse square law of gravity at short range is being questioned we have made such a series of measurements and have found four other data sets in the literature that suffice for the estimation of g we also report here a statistical analysis of 1 100 km2 of overlapping sea floor and sea surface gravity data from the gulf of mexico made available by exxon all these estimates of g give values that are higher than the conventional laboratory determined one while the possibilities of systematic errors in these data sets preclude a definite conclusion that newton s law of gravity fails at short range the strong circumstantial evidence suggests that well controlled large scale experiments on the inverse square law are urgently required

interseismic coupling on the main himalayan thrust we determine the slip rate and pattern of interseismic coupling on the main himalayan thrust along the entire himalayan arc based on a compilation of geodetic interferometric synthetic aperture radar and microseismicity data we show that convergence is perpendicular to the arc and increases eastwards from 13 3 1 7 mm yr to 21 2 2 0 mm yr these rates are comparable to geological and geomorphic estimates indicating an essentially elastic geodetic surface strain the interseismic uplift rate predicted from the coupling model closely mimics the topography suggesting that a small percentage of the interseismic strain is permanent we find that the fault is fully locked along its complete length over about 100 km width we don t find any resolvable aseismic barrier that could affect the seismic segmentation of the arc and limit the along strike propagation of seismic ruptures the moment deficit builds up at a rate of 15 1 1 10 19 n m yr for the entire length of the himalaya