monazite dating of granitic gneisses and leucogranites from the kerala khondalite belt southern india implications for late proterozoic crustal evolution in east gondwana two stages of granitic magmatism occurred during the pan african evolution of the kerala khondalite belt kkb in southern india granitic gneisses were derived from porphyritic granites which intruded prior to the main stage of deformation and peak metamorphism subsequently leucogranites and leucotonalites formed during fluid absent melting and intruded the gneiss sequences monazites from granitic gneisses leucogranites and a leucotonalite were investigated by conventional u pb and electron microprobe dating in order to distinguish the different stages of magma emplacement u pb monazite dating yielded a wide range of ages between 590 520 ma which are interpreted to date high grade metamorphism rather than magma emplacement the results of this study indicate that the kkb experienced protracted heating 50 ma at temperatures above 750 800 c during the pan african orogeny the tectonometamorphic evolution of the study area is comparable to southern madagascar which underwent a similar sequence of events earlier than the kkb the results of this study further substantiate previous assertions that the timing of high grade metamorphism in east gondwana shifted from west to east during the late proterozoic

upper holocene sea level changes in the west saronic gulf greece abstract along the peloponnesian coast of the saronic gulf and on the coast of aegina and poros islands submerged coastal geomorphological features related directly with submerged ancient coastal constructions indicate three distinct sea levels submerged tidal notches incised on the carbonate basement beachrocks formed in the intertidal zone and archaeological indicators such as the ancient harbour installations in kenchreai and epidaurus and on aegina island the extended coastal buildings and constructions in agios vlasis psifta and palaiokastro methana and vagionia on poros island are used to determine the age and magnitude of submersion and the extent of the upper holocene marine transgression by the correlation of geomorphological historical and archaeological indications three distinct sea levels were identified at 3 30 0 15 m 0 90 0 15 m and 0 55 0 05 m initial change in sea level occurred definitely after ad 400 100 the intermediate change is dated between ad 1586 and 1839 and the most recent change after 1839 sea transgression followed a long period of sea level stability which lasted at least 2200 years from the middle bronze age to the late roman period

postseismic and interseismic displacements near a strike slip fault a two dimensional theory for general linear viscoelastic rheologies 1 we present an analytic solution for the deformation near an infinite strike slip fault in an elastic layer overlying a linear viscoelastic half space the theory is valid for any linear viscoelastic rheology and any earthquake sequence this is a generalization of the work of j c savage and colleagues which only holds for models with a uniform shear modulus maxwell viscoelastic lower half space and periodic rupture recurrence we demonstrate the theory for models of an elastic layer over a maxwell standard linear solid burgers and triviscous half space for each of these models we calculate example postseismic displacements interseismic displacements in a periodic earthquake sequence and interseismic displacements for a nonperiodic earthquake sequence our solution is for a simple geometry however the model presents an elegant tool to explore the evolution of displacements for relatively complex rheologies and rupture recurrence histories

surficial patterns of debris flow deposition on alluvial fans in death valley ca using airborne laser swath mapping data debris flows are a common event in mountainous environments they often possess the greatest potential for destruction of property and loss of lives in these regions delimiting the spatial extent of potential damage from debris flows relies on detailed studies of the location of depositional zones current research indicates debris flow fans have two distinct depositional zones however the two zones were derived from studies containing detailed analyses of only a few fans high resolution airborne laser swath mapping alsm data is used to calculate profile curvature and surface gradient on 19 debris flow fans on the eastern side of death valley the relationship between these parameters is assessed to 1 identify if debris flow fans are accurately represented by two depositional zones and 2 to assess how these terrain parameters relate to one another at the individual fan scale the results show at least three zones of deposition exist within the sampled fans these zones do not hold consistent when individual fan morphometry is analyzed in conjunction with localized fan surface gradients fans with consistently shallower gradients exhibit numerous depositional zones with more subtle changes in profile curvature steeper gradient fans exhibit significantly fewer zones with more pronounced local changes in profile curvature the surface complexity of debris flow fans is evident from these analyses and must be accounted for in any type of hazard studies related to these features

migration of activity within normal fault systems examples from the quaternary of mainland greece abstract we examine five areas of mainland greece where active extension occurs on sub parallel systems of normal faults and where geomorphological and stratigraphic evidence indicates that the faulting has migrated basinwards into the original hanging walls in several cases within the late quaternary by comparing fault slip rates estimated from geomorphological data with current extension rates known from geodetic measurements it appears that the newest faults can account for effectively all the present day motions fault migration of this sort is easy to recognize in young systems close to sea level because vertical movements of footwalls and hanging walls are obvious and reveal which faults are currently most active but is less easy to confirm away from reliable reference levels or in older terrains with poorer time resolution it is probably more common than is appreciated and has a profound effect on syn rift sedimentation and erosion patterns fault migration is probably an inevitable consequence of the interplay between stresses generated by the fault related topography and the ultimate strength of major faults it is likely to be further encouraged in places where lower crustal flow or rotations about a vertical axis are important however it is not clear why migration should preferentially occur into the hanging walls as observed in central greece

normal faulting in the upper continental crust observations from regions of active extension abstract observations of present day normal faulting in regions of active continental extension may be helpful when interpreting the geological record in older extensional basins the most obvious manifestation of active extension is normal faulting in earthquakes earthquake foci are mostly confined to the upper seismogenic continental crust whose thickness imposes a scale on the observed deformation large earthquakes move faults with lengths similar or large compared with the thickness of the seismogenic layer large seismogenic normal faults on the continents appear to be restricted to a dip range of around 30 60 dips significantly gentler than 20 have not been observed in fault plane solutions of large earthquakes large seismographic normal faults are approximately planar in cross section and cut through the base of the upper seismogenic layer rotating about a horizontal axis as they move a reasonable estimate of the regional extension can often be made from the dip of the large normal faults and the tilt of the blocks they bound the domino model such faults are rarely continuous for more than 15 20 km but commonly change strike or step in an en echelon fashion this segmentation may occur on a scale controlled by the thickness of the seismogenic layer and is an important influence on sedimentation and drainage these observations are common to large seismogenic normal faults from a variety of tectonic settings and suggest that the kinematics of normal faulting may not be strongly influenced by the forces responsible for the extension which can vary widely in nature and magnitude small earthquakes which move faults that are small compared with the seismogenic layer thickness show no simple pattern and often can be interpreted as internal deformation of blocks bounded by large faults in some places the seismogenic basement faults do not reach the surface but are decoupled from the sedimentary cover by layers of weak lithology faults in the sedimentary cover may be strongly curved in cross section requiring their hangingwalls to deform internally estimating extension from such faults is not straightforward and requires a knowledge of the hangingwall deformation estimates made in this way are often very non unique and prone to large errors we postulate that the thickness of the seismogenic upper crust controls both the maximum length of large normal fault segments along strike and the maximum size of blocks that can rotate coherently about a horizontal axis

tectonics of the neoproterozoic southern granulite terrain south india geological correlations between south india and adjacent gondwana fragments are hampered by the lack of a coherent structural framework for india s southern granulite terrain sgt this paper is an attempt at delineating its large scale geometry and neoproterozoic kinematics and tectonics the basic regional pattern is that of a high grade gneissic layering produced during several deformation stages grouped as d1 which became refolded during two regionally separated phases of upright folding d2a nnw trending d2b ne trending and reworked in e to ese trending zones of increased strain d3 of these the palghat cauvery shear zone pcsz which marks the boundary between archaean terrains in the north and proterozoic belts in the south may represent a major crustal shear zone whereas the achankovil zone az is better considered as a high strain zone characterized by flattening with a reverse component d1 structures developed close to the peak of pan african high grade metamorphism d2a and d2b occurred on the retrograde path partly at supersolidus and partly at subsolidus conditions d3 high strain zones show subsolidus textures in view of the general clockwise nature with a clear decompressional component of all published p t paths we propose that d2 d3 occurred during partial exhumation of the terrain correlations with madagascar are weakened as the az is no longer considered a major crustal shear zone whereas correlations with sri lanka are strengthened by the presence of a similar syntactical bend possibly produced by an indentor

neoproterozoic alkaline magmatism at sivamalai southern india abstract the sivamalai alkaline complex lies at the southern margin of the cauvery shear system that separates the archaean and proterozoic domains of the southern granulite terrain in india u pb tims dating of zircon from a pegmatitic syenite sample in the complex yields a concordant age of 590 2 1 3 2 ma which is interpreted to date the intrusion of the alkaline rocks a lower concordia intercept at 168 210 ma defined by two grains with high common lead may indicate post magmatic disturbances due to recrystallisation which is also evident in the cl images of the zircons epma dating of monazite from a post kinematic pegmatite which intrudes the crystalline basement hosting the alkaline rocks yields an age of 478 29 2 ma and provides a lower bracket for the main phase of tectonism in this part of the southern granulite terrain the pan african high grade metamorphism and ductile deformation has thus most likely affected the alkaline rocks this is supported by the presence of a metamorphic foliation and extensive recrystallisation textures seen in the rocks the major and trace element concentrations measured on selected samples reveals the presence of both enriched and depleted rock types the enriched group includes ferrosyenite and nepheline syenite while the depleted group has only nepheline syenites the trace element depletion of some nepheline syenites is interpreted to be a result of fractional crystallization involving the removal of accessory phases like zircon titanite apatite and allanite

mechanics of continental rift architecture continental rifts are long narrow features bounded on one or both sides by normal faults along which several kilometers of displacement has occurred resulting in deep rift valleys that form sedimentary basins continental rifts all share the same geometrical features they have widths that are characteristic of the region in which they form they are predominantly asymmetric and they are segmented along axes at a length scale that is also characteristic of the region we describe a very simple mechanical model to explain these three features the rift initiates with the formation of a conjugate set of normal faults that intersect at the center of the seismogenic layer one of these becomes the boundary fault system the other the failed conjugate fault being offset by the former becomes locked early in the rifting history hence an asymmetric graben is formed which is the basic building block of rifts the failed conjugate fault has distinctive properties that allow it to be easily distinguished from other faults examples of these faults from the tanganyika and malawi rifts show excellent agreement with predictions about their positions with respect to the boundary fault system and their net displacement and slip history the width of the asymmetric graben is a simple function of seismogenic thickness the net displacement on the boundary fault system is limited by the resistive friction and the flexural restoring force we calculate this limiting boundary fault system displacement and using the displacement length scaling law for normal faults suggest that this controls the along axis segmentation length both maximum fault slip and segmentation length are functions of the seismogenic thickness and the effective elastic thickness of the crust these calculations agree very well with observations of segmentation from the african rifts and the maximum length of range fronting normal faults in nevada

the dzhungarian fault late quaternary tectonics and slip rate of a major right lateral strike slip fault in the northern tien shan region the dzhungarian strike slip fault of central asia is one of a series of long nw se right lateral strike slip faults that are characteristic of the northern tien shan region and extends over 300 km from the high mountains into the kazakh platform our field based and satellite observations reveal that the dzhungarian fault can be characterized by three 100 km long sections based on variation in strike direction through morphological analysis of offset streams and alluvial fans and through optically stimulated luminescence dating we find that the dzhungarian fault has a minimum average late quaternary slip rate of 2 2 0 8 mm yr and accommodates n s shortening related to the india eurasia collision this shortening may also be partly accommodated by counterclockwise rotation about a vertical axis evidence for a possible paleo earthquake rupture indicates that earthquakes up to at least mw 7 can be associated with just the partitioned component of reverse slip on segments of the central section of the fault up to 30 km long an event rupturing longer sections of the dzhungarian fault has the potential to generate greater magnitude earthquakes mw 8 however long time periods e g thousands of years are expected in order to accumulate enough strain to generate such earthquakes

unexpected earthquake hazard revealed by holocene rupture on the kenchreai fault central greece implications for weak sub fault shear zones this work forms part of the nercand esrc funded project earthquakes without frontiers and was partly funded by the nerc grant looking inside the continents from space

basinward migration of rift border faults implications for facies distributions and preservation potential basinward migration of half graben footwall margins occurs throughout the active aegean extensional province and has significant implications for facies distributions and preservation potential in synrift fills worldwide recognition of this phenomenon is particularly important for predicting the preservation and distribution of hydrocarbon reservoirs in rift basins using an example from the gediz graben of western turkey it is shown that basinward migration of footwall margins exhumes proximal facies of lateral sedimentary systems severely limiting their preservation potential and providing a ready source of easily erodible material this in turn leads to the generation of extensive footwall derived depositional systems which frequently displace axial drainage systems toward the hanging wall dip slope

direct geological evidence for prior earthquakes on the 1981 corinth fault central greece we present the preliminary results of geomorphic and trench investigations at the eastern end of a scarp produced by the 1981 corinth earthquake sequence at this site the 1981 rupture produced average vertical displacements of 0 6 0 7 m maximum 1 3 m that in part occurred along a cumulative scarp which displaces the fan surface by up to 5 m based on this cumulative scarp displacing the holocene fan surface we estimate a vertical slip rate of 1 mm yr that translates to 1 mm yr n s extension we found evidence for two individual pre 1981 earthquakes which occurred on the basis of preliminary radiocarbon dating on two paleosols shortly after a d 590 and a d 1295 each of these events produced a vertical displacement ranging between 0 5 and 1 2 m hence comparable to the 1981 scarp height this suggests that coseismic slip may have been characteristic at this location over the past three seismic cycles following this hypothesis and assuming a periodic strain release a maximum recurrence interval of 700 yr is calculated these results indicate that the 1981 surface breaking faults accommodate only part of the regional extension deduced from the geodetic measurements

the geometrical evolution of normal fault systems abstract the purpose of this paper is to examine the kinematic behaviour of normal fault systems and see what general conditions govern their geometrical evolution we pay particular attention to seismological and surface data from regions of present day active normal faulting as the instantaneous three dimensional geometry at the time of fault movement is better known in active regions than in areas where the faults are now static most normal faults are concave upward or listric this shape can be produced by geometric constraints either because the faults reactivate curved thrusts or because they must be curved to accommodate rotations another effect which will produce curved faults is the variation of rheology with depth brittle failure at shallow depths produces less fault rotation than does distributed creep in the lower part of the crust an important geometric feature of normal faulting is the uplift of the footwall the amount of such uplift is related not only to the elastic properties of the lithosphere but also to the throw and dip of the fault a striking feature of active normal faults is that they occur in groups in which all the faults dip in the same direction this behaviour arises because the faults cannot intersect if they do one must cease to be active the rotation which such fault systems produce reduces the dip of the faults until a new steeply dipping fault is formed once a new fault cuts pre existing faults the earlier faults become locked and a new set of faults must propagate rapidly across the whole region involved many of these geometric constraints also apply to thrust faulting

high radiogenic heat production in the kerala khondalite block southern granulite province india in situ radioelemental k u and th analysis and heat production estimates have been made at 59 sites in the kerala khondalite block kkb of the southern granulite province sgp of india together with the in situ analyses on granulites and gneisses previously reported from 28 sites and heat production estimated from the published geochemical analyses on granites and syenites of the kkb the new data set allows good characterization of heat production for the major granulite facies rocks and granitoids of the kkb garnet biotite gneisses are characterized by high levels of th and u with mean values of 60 and 3 ppm respectively khondalites leptynites and charnockites have slightly lower levels of th 23 20 and 22 ppm respectively and u 2 9 2 4 and 0 9 ppm respectively the mean k u th abundances for the granites leucogranites and granitic gneisses ranges from 3 9 to 4 3 2 6 to 4 3 ppm 22 to 50 ppm respectively and for the syenites 4 8 2 ppm and 5 7 ppm mean radiogenic heat production values for garnet biotite gneiss khondalite leptynite and charnockite are 5 5 2 7 2 4 and 2 2 w m 3 respectively for the granites leucogranites granitic gneisses and syenites it is 2 6 3 4 4 6 and 1 4 w m 3 respectively heat production of granulite facies rocks which are the most abundant rocks in kkb correlate well with th but less with u suggesting that variation is caused by th and u bearing accessory minerals such as monazite and zircon the high heat production of the kkb granulites are in contrast to the low heat production of the late archaean granulites of the northern block nb of the sgp which are highly depleted in radioelements and also the granulites of madurai block mb that have higher radioelemental abundances than in the granulites of the nb the high heat production of the kkb granulites could be due to the nature of protoliths and or metasomatism associated with neoproteroic to pan african alkaline magmatic activity represented by alkali granite and syenite carbonatite emplacements and emplacement of pegmatites

weak ductile shear zone beneath a major strike slip fault inferences from earthquake cycle model constrained by geodetic observations of the western north anatolian fault zone gps data before and after the 1999 izmit duzce earthquakes on the north anatolian fault zone turkey reveal a preseismic strain localization within about 25 km of the fault and a rapid postseismic transient using 3 d finite element calculations of the earthquake cycle in an idealized model of the crust comprising elastic above maxwell viscoelastic layers we show that spatially varying viscosity in the crust can explain these observations depth dependent viscosity without lateral variations can reproduce some of the observations but cannot explain the proximity to the fault of maximum postseismic velocities a localized weak zone beneath the faulted elastic lid satisfactorily explains the observations if the weak zone extends down to midcrustal depths and the ratio of relaxation time to earthquake repeat time ranges from 0 005 to 0 01 for weak zone widths of 24 and 40 km respectively in the weakened domain and greater than 1 0 elsewhere corresponding to viscosities of 1018 0 3 pa s and greater than 1020 pa s models with sharp weak zone boundaries fit the data better than those with a smooth viscosity increase away from the fault implying that the weak zone may be bounded by a relatively abrupt change in material properties such a change might result from lithological contrast grain size reduction fabric development or water content in addition to any effects from shear heating our models also imply that viscosities inferred from postseismic studies primarily reflect the rheology of the weak zone and should not be used to infer the mechanical properties of normal crust

paleoseismicity of the 1981 corinth earthquake fault seismic contribution to extensional strain in central greece and implications for seismic hazard we present paleoseismological trenching results for the active skinos fault which ruptured the surface on the alkyonides gulf basin margin in the 1981 gulf of corinth earthquake sequence three trenches expose evidence of up to six previous events which are comparable to the 1981 deformation in terms of size and geometry vertical displacement produced by the 1981 earthquake ranged from 0 45 to 1 3 m at the bambakies fan trench sites decreasing towards the eastern fault tip east of the trenches trench 1 reveals two previous events with vertical displacements between 0 5 and 1 2 m since 390 a d trench 2 reveals five or six previous events but these are not dated trench 3 reveals four previous events since 670 a d vertical displacements associated with interpreted paleoearthquakes at the trench sites are 1 2 m the recurrence interval on the skinos fault is estimated to average 330 years however significant variation in recurrence interval is allowed by the available radiometric dates average vertical displacement rates derived from the trenches are in the range 0 7 2 5 mm yr a similar long term average vertical displacement rate of 1 2 2 3 mm yr is estimated for the lifespan of the basin bounding fault this equates to a horizontal seismic strain contribution of 2 5 mm yr from the skinos fault this local seismic strain rate overlaps within error with geodetically determined velocities across the alkyonides gulf assumed to represent uniform deep crustal strain thus seismic deformation on the basin bounding fault system may take up the major part of extension across the basin and aseismic strain is not necessitated by the data if correct this would imply that geodetically determined strain rates may be used as a proxy for potential seismic moment release in seismic hazard analyses for this region

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

u series evidence for widespread reef development in shark bay during the last interglacial field observations and u series ages reveal that shark bay western australia wa has been inundated by the sea on at least three occasions during the late pleistocene holocene resulting in a succession of marine deposits around the bay the exact age of these deposits has until now been problematic due to a lack of reliable and accurate age data this study reports 16 new u series coral dates from emergent reef deposits around shark bay and point to an extended period of coral reef development during the peak of the last interglacial marine isotope stage mis 5e this is attributed to enhancement of marine circulation within the reaches and basins a result of higher sea levels and an absence of major sill and bank structures stromatolites are absent from the geological record within shark bay until the late holocene suggesting that sea levels and marine sedimentary processes that have operated during the present sea level highstand are unique to this period there is little direct evidence of fossil reef development occurring during interglacials of the middle late pleistocene mis 9 11

the tectono sedimentary evolution of the lechaion gulf the south eastern branch of the corinth graben greece abstract the gulf of corinth is the second most active continental rift in the world and thus a much studied natural laboratory for analyzing details of rift history a new detailed offshore seismic survey combined with previously acquired data in its least studied part the lechaion gulf shed light on the tectono sedimentary evolution of the eastern end of the corinth rift this study shows that i the lechaion gulf is the submerged northern part of the onshore corinth nemea basin ii they are both bounded to the south by the north dipping klenia and kenchreai faults which are considered at present inactive iii both the corinth nemea basin and the lechaion gulf were formed at around between 3 6 and 4 ma bp middle to late pliocene at the same time with the megara basin and iv the lechaion gulf was submerged and took its present shape at around between 0 7 and 1 7 ma bp at the same time with the gulf of corinth and the alkyonides gulf furthermore sequence stratigraphy interpretation of seismic profiles from the lechaion gulf revealed i a total post alpine sediment thickness of almost 3 km below the lechaion gulf ii at least 400 m of sediments accumulated during the last 245 ka corresponding to a mean sedimentation rate of 1 m ka for the last 245 ka and 2 3 m ka for the holocene and iii differential vertical movement in the order of 4 5 km between the bedrock under the lechaion gulf and the adjacent mountains yields an accumulative average slip rate of 0 9 m ka or less over the last 4 ma therefore for estimating more accurately the slip rates the uplift rates the extensional rates and the earthquake recurrence interval over the eastern end of the corinth rift the presently mentioned tectono sedimentary evolution of the lechaion gulf must be taken into consideration

late pleistocene and holocene sea level change in greece and south western turkey a separation of eustatic isostatic and tectonic contributions summary sea level change during late pleistocene and holocene times is a combination of eustatic isostatic and tectonic contributions in the central mediterranean sea region of greece and western turkey the isostatic components are important due to the changing gravitational potential of the earth the readjustment of the crust upon the removal of the large ice sheets and the addition of the meltwater into the oceans including the mediterranean changes in relative sea level due to these glacio hydro isostatic adjustments have reached amplitudes of 1 mm yr 1 during the last few thousand years a model for the isostatic contribution to sea level change including the movement of shorelines due to the combined eustatic isostatic changes is developed based on earth model and ice sheet parameters estimated from sea level observations from other areas comparisons of this model with observations of sea level change permit rates of vertical movement to be estimated for late holocene time allowance for the isostatic factors makes a significant difference to these rates the plains of argolis lakonia messinia and navarine in the southern peloponnese for example appear to be tectonically stable on time scales of a few thousand years and longer consistent with the position of the last interglacial shoreline close to the present day sea level the observations here of a rising sea level are largely the consequence of the glacio hydro isostasy and not of a long term tectonic process crete as a whole is subject to tectonic uplift but at variable rates and forms part of an arcuate zone of uplift extending from rhodes and karpathos in the east to kithera in the west at rates that locally exceed 4 mm yr 1 the southern shore of the gulf of corinthos is also subject to uplift at rates approaching 1 5 mm yr 1 these isostatically corrected estimates for the past few thousand years are in agreement with longer term estimates based on the position of the last interglacial shoreline only on the perachora peninsula do the tectonic rates over these two time intervals appear to be in disagreement with the late holocene rates being much higher than the long term rates

structure from motion photogrammetry a low cost effective tool for geoscience applications abstract high resolution topographic surveying is traditionally associated with high capital and logistical costs so that data acquisition is often passed on to specialist third party organisations the high costs of data collection are for many applications in the earth sciences exacerbated by the remoteness and inaccessibility of many field sites rendering cheaper more portable surveying platforms i e terrestrial laser scanning or gps impractical this paper outlines a revolutionary low cost user friendly photogrammetric technique for obtaining high resolution datasets at a range of scales termed structure from motion sfm traditional softcopy photogrammetric methods require the 3 d location and pose of the camera s or the 3 d location of ground control points to be known to facilitate scene triangulation and reconstruction in contrast the sfm method solves the camera pose and scene geometry simultaneously and automatically using a highly redundant bundle adjustment based on matching features in multiple overlapping offset images a comprehensive introduction to the technique is presented followed by an outline of the methods used to create high resolution digital elevation models dems from extensive photosets obtained using a consumer grade digital camera as an initial appraisal of the technique an sfm derived dem is compared directly with a similar model obtained using terrestrial laser scanning this intercomparison reveals that decimetre scale vertical accuracy can be achieved using sfm even for sites with complex topography and a range of land covers example applications of sfm are presented for three contrasting landforms across a range of scales including an exposed rocky coastal cliff a breached moraine dam complex and a glacially sculpted bedrock ridge the sfm technique represents a major advancement in the field of photogrammetry for geoscience applications our results and experiences indicate sfm is an inexpensive effective and flexible approach to capturing complex topography

inference of multiple earthquake cycle relaxation timescales from irregular geodetic sampling of interseismic deformation abstract characterizing surface deformation throughout a full earthquake cycle is a challenge due to the lack of high resolution geodetic observations of duration comparable to that of characteristic earthquake recurrence intervals 250 10 000 years here we approach this problem by comparing long term geologic slip rates with geodetically derived fault slip rates by sampling only a short fraction 0 001 0 1 of a complete earthquake cycle along 15 continental strike slip faults geodetic observations provide snapshots of surface deformation from different times through the earthquake cycle the timing of the last earthquake on many of these faults is poorly known and may vary greatly from fault to fault assuming that the underlying mechanics of the seismic cycle are similar for all faults geodetic observations from different faults may be interpreted as samples over a significantly larger fraction of the earthquake cycle than could be obtained from the geodetic record along any one fault alone as an ensemble we find that geologically and geodetically inferred slip rates agree well with a linear relation of 0 94 0 09 to simultaneously explain both the ensemble agreement between geologic and geodetic slip rate estimates with observations of rapid postseismic deformation we consider the predictions from simple two layer earthquake cycle models with both maxwell and burgers viscoelastic rheologies we find that a two layer burgers model with two relaxation timescales is consistent with observations of deformation throughout the earthquake cycle whereas the widely used two layer maxwell model with a single relaxation timescale is not suggesting that the earthquake cycle is effectively characterized by a largely stress recoverable rapid postseismic stage and a much more slowly varying interseismic stage

the 2013 earthquake swarm in helike greece seismic activity at the root of old normal faults the corinth rift in central greece has been studied extensively during the past decades as it is one of the most seismically active regions in europe it is characterized by normal faulting and extension rates between 6 and 15 mm yr 1 in an approximately n10e direction on 2013 may 21 an earthquake swarm was initiated with a series of small events 4 km southeast of aigion city in the next days the seismic activity became more intense with outbursts of several stronger events of magnitude between 3 3 and 3 7 the seismicity migrated towards the east during june followed by a sudden activation of the western part of the swarm on july 15th more than 1500 events have been detected and manually analysed during the period between 2013 may 21 and august 31 using over 15 local stations in epicentral distances up to 30 km and a local velocity model determined by an error minimization method waveform similarity based analysis was performed revealing several distinct multiplets within the earthquake swarm high resolution relocation was applied using the double difference algorithm hypodd incorporating both catalogue and cross correlation differential traveltime data which managed to separate the initial seismic cloud into several smaller densely concentrated spatial clusters of strongly correlated events focal mechanism solutions for over 170 events were determined using p wave first motion polarities while regional waveform modelling was applied for the calculation of moment tensors for the 18 largest events of the sequence selected events belonging to common spatial groups were considered for the calculation of composite mechanisms to characterize different parts of the swarm the solutions are mainly in agreement with the regional nne ssw extension representing typical normal faulting on 30 50 north dipping planes while a few exhibit slip in an nne ssw direction on a roughly subhorizontal plane moment magnitudes were calculated by spectral analysis of s waves yielding b values between 1 1 and 1 2 in their frequency magnitude distribution the seismic moment release history indicates swarm like activity during the first phase which could have acted as a preparatory stage for the second phase after 12 july that presented a more typical main shock aftershock behaviour the spatiotemporal analysis reveals that the swarm has occurred in a volume that is likely related with the extension at depth of the nne dipping pirgaki normal fault outcropping 8 km to the south the slow velocity of eastward migration of the epicentres during june implies triggering by fluids the situation appears different in the second phase of the sequence which was probably triggered by a build up of stress during the first one the relatively deep hypocentres of the 2013 swarm compared to the shallower seismic layer within the rift and their coincidence with the steeply dipping pirgaki fault favour an immature rift detachment model previous results from instrumental data indicate that approximately the same region had been activated during july august 1991 the availability of the dense permanent seismological network data thus allowed for a detailed analysis of this crisis a better understanding of its mechanical context and of the earlier events

cooling history of the puttetti alkali syenite pluton southern india abstract the puttetti alkali syenite pluton in southern india belongs to the suite of felsic magmatic intrusives emplaced during the late neoprotrozoic cambrian time during the final phase of amalgamation of the gondwana supercontinent in this study we evaluate the cooling history of this pluton based on various isotopic systems we present whole rock pb pb data on the syenite which yields an isochron age of 508 25ma three phlogopite separates from the syenite pluton give k ar ages of 454 0 9 0 448 5 8 9 and 445 6 8 8 ma indicating cooling age at temperatures of 415 c u pb analyses of zircons from this syenite yielded an age of 572 2 ma in a previous study with u pb closure temperatures 800 o c this age probably indicates the timing of emplacement of the puttetti pluton collectively we estimate from the isotopic age data and respective closure temperatures that the syenite body cooled at about 3 2 o c ma from about 800 o c to about 415 o c the markedly low cooling rate of the syenite pluton absence of chilled margin effects and common occurrence of pyroxene feldspar phlogopite and zircons megacrysts in the rock indicate that the host granulites were at high temperatures during the emplacement of the syenite magma the cooling history of puttetti syenite estimated in this study is closely comparable with the 3 4 o c ma cooling rate estimated for a granite pluton in a previous study from madagascar our study suggests protracted cooling rates for the late pan african intrusives emplaced within the gondwana crust with a long residence history in a hot crust bore they were exhumed to shallower levels