coastal uplift on active normal faults the eliki fault greece the eliki fault forms part of a system of major normal fault segments that borders the southern margin of the gulf of corinth half graben radiocarbon dating of elevated marine fossils reveals broadly uniform holocene coastal uplift at a time averaged rate of 1 5 mm yr both along the eliki fault and in the transfer zone that separates it from the neighbouring fault segment coseismic uplift increments are considered to account for only a minor part of the 6 m of emergence recorded here in the last 3000 years reappraisal of shoreline data from the perachora peninsula at the eastern end of the gulf of corinth indicates a similar though less rapid 0 7 mm yr pattern of uniform holocene emergence as these holocene coastal records embody both coseismic and interseismic deformation they can be used to characterise long term tectonic strain

extensional tectonics of northwestern macedonia greece since the late miocene tectonic field studies in the florina ptolemais basin northwestern greece were carried out in an attempt to define the regional stress tensors in selected areas affected by neogene and quaternary faulting using recently proposed quantitative methods the analysis allows us to distinguish two extensional phases in the area a late miocene pliocene one with a ne sw average direction of extension and a pleistocene recent one with a nw se direction of extension we conclude that the principal stress axes 2 and 3 were interchanged in passing from one phase to the other these results are reasonably consistent with results of studies carried out in other parts of the aegean area especially the south aegean back arc domain

footwall uplift associated with late jurassic normal faulting in the northern north sea tilted fault blocks in the north sea show varying degrees of erosion such footwall erosion is predicted by the domino model of extension in which rigid fault blocks rotate as extension proceeds profiles of three north sea fields snorre brent and heather are analysed to estimate the amount of uplift that accompanied late jurassic normal faulting and these estimates are compared with the footwall uplift predicted by the domino model agreement between observed and predicted uplift is excellent varying from 1 km at snorre to c 100 m at heather for a given amount of extension large fault blocks tend to be bounded by large faults and to show a greater degree of erosion the brent province of the northern north sea is an area of prolific hydrocarbon discoveries almost all of the major oil fields occur in tilted fault blocks which were formed by late jurassic extension and subsequently buried by cretaceous tertiary thermal subsidence badley et al 1988 marsden et al 1990 the crests of the tilted blocks are typically eroded or degraded with varying amounts of middle lower jurassic and upper triassic section removed this footwall erosion is commonly ascribed in the literature to pre rifting doming ziegler 1982 heterogeneous stretching coward 1986 local transpression beach 1985 or even regional compression frost 1987 the purpose of this paper is to show that the uplift and degradation is a direct consequence of the late jurassic normal faulting and fault block rotation the degree of uplift is related in a simple way to the size across strike of

variations in the crustal structure beneath western turkey summary we use teleseismic receiver functions to investigate the crustal structure at two locations in westernturkey using seismic data recorded on small arrays of temporary broad band seismographs the results from these analyses are compared with receiver function results from the gdsn station anto on the anatolian plateau in central turkey the crust is 30 km thick in the region of western turkey where active normal faulting reveals present day extension in the upper crust and alkali basaltic volcanism reveals recent extension within the subcrustal lithosphere the crust is 34 km thick further east where crustal extension is still evident but less pronounced in the anatolian plateau which is not currently extending the crust is 38 km thick the level of extension estimated from these measurements of crustal thickness implies a b factor of 1 2 this value agrees with the amount of extension estimated in the upper crust from the integrated seismic strain rate b factor of 1 3 from surface faulting b factor of 1 25 and from the amount of extension in the subcrustal lithosphere estimated from the volcanism b factor 2 all indicating that the extension is approximately uniformly distributed vertically throughout the lithosphere the moho transition in this region appears to thin slightly as the degree of extension increases westwards

the exploitation of state of the art digital terrain databases and combined or satellite only earth gravity models for the estimation of the crust mantle interface over oceanic regions summary thepredictionofthegeometryofcharacteristiccrustalinterfaces suchasbathymetryormoho can be carried out efficiently by applying well tested estimation procedures the computation of the gravity response at the earth s surface of a characteristic density layer in the earth s interior in combination with the statistical tool of least squares collocation have been proven to be a flexible and useful prediction tool especially at regions with lack in primary crustal observations toinvestigatethecontributionofrecentlyreleaseddigitalterraindatabasestothis estimation procedure we use the one minute global elevation databases gebco and topo14 using the combined earth gravity model egm2008 and recently released goce only models we produce the observed grid of gravity anomalies over two test areas in the indian and the atlantic oceans the estimation procedure is based on a two layer model of the upper crust and is driven mainly by the definition and quality of the involved covariance functions the application leads to independent and much denser estimations of the crust mantle interface over these regions in comparison with the available moho information provided by global databasessuchascrust2 0 apartfromthedirectcomparisonbetweentheobtainedsolutions a further assessment was carried out in terms of computing the corresponding isostatic effects on the available regional altimeter data

physical properties and state of the crust and upper mantle of the eastern mediterranean sea deduced from geophysical data abstract by evaluating the geophysical information available for the eastern mediterranean sea ems a crustal thickness map and some conclusions as to the nature of the crustal type were drawn it was found that the ionian abyssal plain is floored by an oceanic type of crust which is 14 km thick and covered by sediments of the order of 8 km thick the herodotus abyssal plain in the levantine sea is floored by a crust 22 km thick and covered by sediments ranging between 10 and 15 km thick the eastern mediterranean rise extending more or less continuously from the apulian plateau to rhodes and the south of the antalya basin is of a thickness ranging between 28 and 34 km the thickness of its sedimentary cover is of the order of 10 km the borders of the eastern mediterranean sea are built up of thick continental crust for example the hellenides of western greece range between 40 and 44 km thick and western turkey has a similar crustal thickness the crust of sicily also exceeds 40 km whereas the southern and eastern borders of the ems are approximately 30 32 km thick tectonically the northern border of the ems is built up of active continental margins defined by the calabrian hellenic and cyprus antalya arcs whereas the southern border represents a passive continental margin controlled mainly by subsidence and stretching to the east the dead sea megashear limits the area the deep basins of the eastern mediterranean sea are tectonically controlled by subsidence and partial stretching the mediterranean ridge or rise is still an area of dispute regarded by some authors as a subsiding continental fragment and separated from the hellenic arc by the hellenic trench whereas others consider it to be a zone of crustal shortening thickened mainly by thrusting both the western and southwestern borders of the mediterranean rise and the hellenides are controlled by compressional processes similar to those deforming the calabrian arc the stravo and pliny trenches to the east southeast border of the hellenic arc are partly affected by strike slip movements various plate tectonic models of the area have been proposed by several authors though the complexity of the deformation hardly permits reliable reconstructions the lack of reliable paleomagnetic information and the absence of linear magnetic anomalies do not favour the application of plate tectonic concepts vertical processes due to the uprising of lithothermal systems below the hellenic and calabrian arcs may also be regarded as the driving force controlling the present day deformation

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

drainage systems and the development of normal faults an example from pleasant valley nevada abstract drainage systems in regions of active extension contain information about fault zone structure and development and particularly about the lateral growth of individual fault segments that is difficult to obtain by more conventional means such as the dating of sedimentary material we investigate drainage fault interaction in pleasant valley nevada where a large normal faulting earthquake occurred in 1915 we find geomorphological evidence for a propagation increase in length of several km at both ends of one of the 1915 fault segments at one end we estimate the propagation rate to be about 50 m per earthquake this estimate is uncertain but is within the range predicted by theoretical models of fault growth drainage along the axes of half graben in this region may be influenced by the spacing of tilted fault blocks the highest valleys are also the narrowest whether the axial streams succeed in reaching lower neighbouring sinks depends on whether sedimentation rates are able to keep basins filled to the levels of the basement highs that separate half graben of opposite polarity a knowledge of modern drainage fault interactions may help predict drainage systems and the position of potential syn rift reservoir sediments in older extensional terrains where fault configurations but not facies distributions are known from seismic reflection surveys

linear and nonlinear computations of the 1992 nicaragua earthquake tsunami numerical computations of tsunamis are made for the 1992 nicaragua earthquake using different governing equations bottom frictional values and bathymetry data the results are compared with each other as well as with the observations both tide gauge records and runup heights comparison of the observed and computed tsunami waveforms indicates that the use of detailed bathymetry data with a small grid size is more effective than to include nonlinear terms in tsunami computation linear computation overestimates the amplitude for the later phase than the first arrival particularly when the amplitude becomes large the computed amplitudes along the coast from nonlinear computation are much smaller than the observed tsunami runup heights the average ratio or the amplification factor is estimated to be 3 in the present case when the grid size of 1 minute is used the factor however may depend on the grid size for the computation

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

tectono sedimentary development of an extensional basin the neogene megara basin greece the miocene pliocene to pleistocene succession exposed in the megara basin comprises a grossly coarsening upwards sequence at least 1 km thick the oldest strata exposed in the nw record the establishment of alluvial fans and axial streams these drained into a lacustrine environment subject to minor wave and possibly tidal action the lower part of the central basin fill is comprised of marls siltstones sandstones and conglomerates they record the pulsed infill of the predominantly freshwater lake megara by progradation of a network of shallow multichannel streams which drained a western hinterland containing ultrabasic rocks cherts and limestones frequent examples of large scale soft sediment deformation structures and stratigraphic thickening into hangingwall rolloven indicate active fault control of sedimentation the lake river interface featured gilbert deltas which were subject to periodic transgression by climatically controlled lake expansions the upper part of the pliocene basin fill largely comprises fluviatile gravels but with two important marine transgressional horizons and renewed calcareous mar1 deposition including a basinwide tufa horizon towards the top the overlying pleistocene alluvial clastics were deposited by a nw flowing system and thicken markedly into a major basin bounding fault deposition of these fluvial deposits was interrupted towards the top of the sequence by the rapid deposition of monomict limestone breccias of debris flow origins which are believed to mark a catastrophic event at some time in the late pleistocene c 1 ma the basin bounding faults became inactive and the entire basin fill was inverted in response to uplift in the footwall of the active major fault strand that bounds the se margin of the alkyonides gulf

geometry of continental normal faults seismological constraints teleseismic body waves from large earthquakes are used to study the downdip geometry of continental normal faults in the aegean waveform modeling techniques together with rigorous statistical tests are applied to put firm bounds on the amount of downdip curvature of these faults and the role of coseismic slip on a basal detachment synthetic modeling shows that good azimuthal station coverage and inclusion of sh waves are necessary to resolve fault curvature the data indicate ruptures of the aegean events occurred on planar faults extending across the entire brittle portion of the crust no seismogenic low angle detachment faulting at the base of the upper crust was detected for these events decoupling of the brittle upper crust from the plastic lower crust probably occurs aseismically in a ductile fashion

tectonics and sedimentation in the gulf of corinth and the zakynthos and kefallinia channels western greece abstract single channel seismic reflection profiling data are presented from the gulf of corinth and from the continental margin outside the gulf of patras different tectonic styles are exhibited in the two regions the gulf of corinth is occupied by a complex asymmetrical graben structure with major faults trending nearly perpendicular to the local tectonic zones of the internal hellenides the gulf is interpreted to have formed during the quaternary in response to approximately north south extensional stress the deep floor of the gulf is underlain by a sequence of turbidites up to 1 km thick affected by normal growth faulting that extends up to the sea floor the sea areas inside the ionian islands of zakynthos and kefallinia zakynthos and kefallinia channels occupy a broad structural depression that trends parallel to the local tectonic zones of the external hellenides and is situated on the continental side of the strophades continental margin rise the channels contain local nw se trending structural basins zakynthos and kefallinia basins whose geometry is controlled by reverse faults or thrusts with associated diapirism in triassic evaporites hydra bank is interpreted as a tilted fault block with a diapiric core and its faulted western margin can be traced into the zone of thrusting and diapirism in southeast kefallinia at the boundary between the ionian and pre apulian paxos zones of the external hellinides the zakynthos and kefallinia structural basins are filled with a variety of sediments including prodeltaic deposits in front of the modern delta complex of the acheloos river slumped masses and debris flow deposits and in the zakynthos basin occasional turbidites the boundary separating zones of extensional and compressional focal mechanisms for shallow earthquakes crosses the gulf of patras the inner part of which exhibits wnw ese trending graben tectonics apparently related to the gulf of corinth tectonic province onshore neotectonic studies around the gulf of patras are required in order to understand the nature and cause of the westward tectonic transition from wnw ese graben structures in the gulfs of corinth and patras to nw se oriented zones of subsidence with associated compressional tectonics and diapirism in the zakynthos and kefallinia channels

geodetic investigation of the 13 may 1995 kozani grevena greece earthquake the ms 6 6 13 may 1995 kozani grevena earthquake struck a region of low historical seismic activity which includes a 10 year old triangulation network in northern greece after the earthquake monuments from this network were occupied with gps to measure co seismic displacements inversion of the co seismic displacement field to yield a source mechanism is achieved by use of a hybrid simplex monte carlo method which requires no a priori constraints the model focal mechanism agrees well with the global cmt solution and locally observed aftershocks but implies a significantly higher scalar moment than do seismological or sar interferometry studies and has a longer fault length than the model based on sar interferometry

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

on the role of isostasy in the evolution of normal fault systems the footwalls of west dipping normal faults that separate the west central colorado plateau from the basin and range province record at least 5 7 km and perhaps as much as 15 20 km of west side up neogene uplift with an axis just 10 20 km west of undeformed plateau strata the uplift is expressed as folding and steep faulting in pre tertiary cratonic and disconformably overlying neogene strata forming a basement cored anticline and coincident topographic high on the western margin of the plateau the authors interpret the uplift as a nonelastic response of the crust to buoyancy forces accompanying the tectonic denudation of the plateau margin profound isostatically driven deformation of the footwalls of major normal faults may be common in extensional terrains calling into question several assumptions fundamental to existing models of the evolution of normal fault systems

rupture process of large earthquakes in the northern mexico subduction zone the cocos plate subducts beneath north america at the mexico trench the northernmost segment of this trench between the orozco and rivera fracture zones has ruptured in a sequence of five large earthquakes from 1973 to 1985 the jan 30 1973 colima event m s 7 5 at the northern end of the segment near rivera fracture zone the mar 14 1979 petatlan event m s 7 6 at the southern end of the segment on the orozco fracture zone the oct 25 1981 playa azul event m s 7 3 in the middle of the michoacan gap the sept 19 1985 michoacan mainshock m s 8 1 and the sept 21 1985 michoacan aftershock m s 7 6 that reruptured part of the petatlan zone body wave inversion for the rupture process of these earthquakes finds the best earthquake depth focal mechanism overall source time function and seismic moment for each earthquake in addition we have determined spatial concentrations of seismic moment release for the colima earthquake and the michoacan mainshock and aftershock these spatial concentrations of slip are interpreted as asperities and the resultant asperity distribution for mexico is compared to other subduction zones the body wave inversion technique also determines the moment tensor rate functions but there is no evidence for statistically significant changes in the moment tensor during rupture for any of the five earthquakes an appendix describes the moment tensor rate functions methodology in detail

lithosphere dynamics and continental deformation the unifying theme in this section is the remarkable weakness of major faults i will consider the diverse new evidence for weakness and the evidence for high pore pressure localized in faults as a fundamental cause with this background one can better understand why faults remain active even after large rotations with respect to stress i will look at large neogene 23 7 million year old rotations about horizontal axes in the basin and range province and about vertical axes along the pacific margin recent developments will be summarized from studies of neogene tectonics neotectonics in california alaska and the mississippi embayment in the context of a weak north american stress field that results mainly from topographic forces to close i will present new geophysical studies relevant to the continuing controversy over whether the basic structure of the north american mantle lithosphere was altered by an early tertiary episode of flat subduction

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

a hectare of fresh striations on the arkitsa fault central greece abstract some large new exposures of active normal faults in central greece reveal polished surfaces that could represent as many as 50 increments of co seismic slip the slip surfaces are nearly two dimensional with the slip vector aligned down the axes of corrugations and undulations however small but regular changes in slip vector between top and bottom of the exposure and a regular asymmetry of the polishing on corrugations may be related to block rotations about a vertical axis and show how the slip vector changes with time

the 1995 grevena northern greece earthquake fault model constrained with tectonic observations and sar interferometry after the 1995 grevena ms 6 6 event in northern greece we mapped the earthquake fault break in detail the surface break is small 8 12 km long 4 cm slip compared to the moment release of the event however the morphologic and tectonic study of the active faults in the field and using the spot satellite imagery suggests that the earthquake ruptured part of a much larger fault system including interconnecting segments we used sar interferometry of the satellite ers 1 imagery to characterize the coseismic displacement field this shows a kidney shaped zone of subsidence reaching 30 cm flanked by an uplift zone reaching 5 cm we reproduce this field using dislocations in an elastic half space and our observations of the fault system this requires 1 m slip from 4 to 15 km depth on a main normal fault segment dipping nnw our preliminary model includes significant ne dipping scissors faulting at the eastern end of the rupture clearly seen in the interferograms

a block model of distributed deformation by faulting it is clear from palaeomagnetic evidence that large and hitherto unexpected rotations about a vertical axis are common in regions of distributed continental deformation we propose a simple two dimensional model to illustrate how fault movement and block rotation within a zone of distributed deformation may be related to the relative motion of the rigid plates that bound the zone one surprizing feature of this model is that the component of strike slip motion on the faults within the deforming zone is in the opposite sense to the strike slip component across the zone as a whole thus slip vectors within the zone are not the same as that between the bounding rigid plates in contrast to deformation at oceanic plate boundaries examples of active fault geometries similar to those of our model can be seen in greece iran and the western usa

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

uplifted marine terraces in davao oriental province mindanao island philippines and their implications for large prehistoric offshore earthquakes along the philippine trench abstract we conducted systematic mapping of holocene marine terraces in eastern mindanao island philippines for the first time raised marine platforms along the 80 km long coastline of eastern davao oriental province are geomorphic evidence of tectonic deformation resulting from the westward subduction of the philippine sea plate along the philippine trench holocene coral platforms consist of up to four terrace steps t1 1 5 m t2 3 6 m t3 6 10 m and t4 8 12 m amsl from the lowest to highest respectively terraces are subhorizontal exposing cemented coral shingle and eroded coral heads while terrace risers are 1 3 m high radiocarbon ages 8080 4140 cal yr bp reveal that erosional surfaces were carved onto the holocene transgressive reef complex which grew upward until 8000 years ago the maximum uplift rate is 1 5 mm yr based on the highest holocene terrace at

early earthquakes in the kozani area northern greece abstract a cursory examination of the as yet incomplete crudely known and not easily quantifiable seismic history of northern greece suggests an episodic seismic activity of medium magnitude events similar to that of other parts in the balkans and a lack of any evidence in the historical records of large earthquakes in the region this is consistent with the lack of continuity of faults in central greece with few segments being demonstrably continuous for longer than about 20 to 25 km my examination of primary sources also shows that for the period investigated it is not possible to assign reliably location and magnitude to historical earthquakes in this region

the terraces of corinth gerrce a detailed record of eustatic sea level variations during the last 500 000 years abstract between corinth and xylokastro 20 marine terraces reflect the interaction of the northern peloponnese uplift and the global eustatic sea level fluctuations during the last 500 000 years correlation of the terraces with oxygen isotope records in deep sea cores allowed accurate dating of these fossilized transgressive shorelines curves of altitude versus age have been plotted they show a regular decrease of the uplift rate and a frequent return of the sea level very close to the present day one not only during the interglacial periods 5 7 9 11 13 but also during glacial periods 3 1 3 3 6 8 the alternative would be to suppose very complicated and highly improbable vertical movements of the substratum to explain the regularity of the curves the rhythm of these high sea levels is around 20 30 ka since at least 330 000 years ago

geodetic estimate of seismic hazard in the gulf of korinthos the recent 15 june 1995 m0 6 0 1018 n m aigion earthquake in the western gulf of korinthos has focussed attention on the seismic hazard of the region although there have been few large earthquakes in the region during this century the historical record suggests that there may have been many large earthquakes there in the interval 1750 1900 we present geodetic data that give estimates of the rate of extension of the gulf of korinthos during this century and which suggest that less than half of the elastic strain in the central and western gulf of korinthos has been released by earthquakes during this century in contrast the seismic and geodetic strains in the eastern gulf of korinthos are in agreement with each other if the discrepancy between seismic and geodetic strains in the western gulf of korinthos that has accumulated during this century is removed in earthquakes the moment release will be equivalent to several ms 6 5 earthquakes

characteristics and consequences of flow in the lower crust in some places there is strong evidence that the lower continental crust has flowed so as to smooth out variations in crustal thickness caused by differential crustal extension or shortening in order to better understand the processes involved we investigate the behavior of a fluid layer over a fluid half space to see how such a system responds to the deformation of its upper and lower boundaries this simple system can be used to study both the decay of crustal thickness contrasts and the behavior of a thin lithospheric sheet the changing response of the system to variations in density and viscosity contrasts and to different boundary conditions imposed on the fluid interface can easily be studied analytically the most important results are that variations in crustal thickness on a wavelength of a few times the thickness of the flowing channel will decay quickest and that large lateral variations in crustal thickness cause the fluid to develop a steep front which may cause a topographic step above it at the earth s surface deformation within the channel will be principally by simple shear the clear association of lower crustal flow with regions of thickened crust and magmatic activity suggests that both can reduce the viscosity of the lower crust to levels at which flow can occur the smoothing of crustal thickness contrasts leads to differential vertical motions and is thus a method by which substantial tilting can occur without faulting this differential uplift may be responsible for rotating and exhuming some of the detachment faults in metamorphic core complexes in the basin and range province of the western united states it is also a method of causing structural inversion in basins that does not require the reactivation of normal faults as thrusts or reverse faults

the may 17 1992 earthquakes in southeastern philippines 1 two large earthquakes q1 and q2 occurred off the eastern coast of mindanao along the philippine trench on may 1992 during these events the southeastern coasts of the island experienced one strong ground shaking and suffered from one set of tsunamis waves to investigate this phenomenon teleseismic body wave inversions and tsunami waveform analysis were undertaken for the quakes correlation of simulation results and field observations show that q1 was the most probable source of the damaging tsunami wave results also imply that the relation between the q1 and q2 that may have ruptured the southern and northern portion of the one day aftershock area respectively furthermore closer examination of the philippine trench indicates the presence of a bend in between the events that could have prevented the q1 to rupture in just one big event

global marine gravity field from the ers 1 and geosat geodetic mission altimetry satellite altimetry from the geosat and the ers i geodetic missions provide altimeter data with very dense spatial coverage therefore the gravity field may be recovered in great detail as neighboring ground tracks are very closely distributed cross track variations in the sea surface heights are extremely sensitive to sea surface variability to avoid errors in the gravity field caused by such effects sea surface variability needs to be carefully eliminated from the observations initially a careful removal of gross errors and outliers was performed and the tracks were fitted individually to a geoid model and crossover adjusted using bias and tilt subsequently sea surface heights were gridded using local collocation in which residual ocean variability was considered the conversion of the heights into gravity anomalies was carried out using the fast fourier transform fft in this process filtering was done in the spectral domain to avoid the so called orange skin characteristics comparison with marine gravity was finally carried out in three different regions of the earth to evaluate the accuracy of the global marine gravity field from ers 1 and geosat

seismicity and associated strain of central greece between 1890 and 1988 summary we examined the seismicity of central greece between 1890 and 1988 using macroseismic and instrumental data to ask two questions 1 does the seismicity of this period reveal all the major tectonic structures that are known to be active and 2 what are the likely strains associated with the seismicity over this period many known active structures have been effectively aseismic for the last hundred years and even the inclusion of all known large events earlier than 1890 reveals no activity associated with the ne coast of evia gulf of argos or graben ne of mt parnassos it is clear that even 100 years data are inadequate for either a reasonable assessment of seismic risk or for a confident estimation of maximum magnitude however we are aware of no earthquakes in central greece during the last 200 yr that were larger than ms 7 0 it is probable that the maximum magnitude is restricted by the maximum length of fault segments which appears to be around 15 20 km the earthquakes of ms 5 8 during 1890 1988 can account for a n s displacement of around 45 70 cm with maximum and minimum estimates a factor of two greater and smaller than this across part of a 1890 1900 triangulation network in central greece that was resurveyed in 1988 the contribution of smaller events may increase this displacement by about 50 per cent this cumulative seismic displacement is similar to that estimated from the geodetic work about 100 cm but a detailed comparison of the two sets of observations will be reported elsewhere a re evaluation of all the important earthquakes of 1890 1988 in central greece is presented in the appendix which summarizes information of use to both earth scientists and engineers

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

geometry and kinematics of active faults and their seismotectonic significance in the western corinth patras rift greece abstract the western part of the corinth patras rift is formed in an area which is being uplifted rifted domains have subsided relative to the adjacent areas in nw peloponnesus and sterea hellas but subsidence rates rarely exceed uplift rates extension is mainly accomplished by wnw trending active faults with lengths up to 25 km most of these faults show an along strike segmentation and often terminate against transfer faults displacement analysis along 170 mesoscopic faults and 36 mappable faults has been carried out to assess slip rates and to estimate the magnitudes and recurrence time intervals of earthquakes occurring along them earthquake magnitude ranges between 5 and 6 7 only eight faults appear to be capable of producing earthquake magnitudes larger than 6 recurrence times of these large earthquakes vary between 80 and 1690 years upper crustal deformation in the western corinth graben can be described by six large asymmetric grabens which are inferred to bottom out to a n dipping curved ramp the asymmetric shape of most wnw trending rifts in the hellenic peninsula including the corinth patras rift promotes the simple shear model of extension against the pure shear model in the upper crustal layer

observed correlations between aftershock spatial distribution and earthquake fault lengths we observe the spatial distributions of the magnitude of aftershocks following the six earthquakes of focal depth shallower than 20 km with magnitude more than 5 0 from 1983 to 1987 in japan the upper limit of the aftershock magnitude is examined as a function of the distance from mainshock hypocentre the observed spatial distributions of the upper limit are bimodal with a tendency of the upper limit to decrease as the distance from mainshock hypocentre increases moreover we observe the correlations between the aftershock spatial distribution and earthquake fault length we focus on the largest aftershocks in each of two aftershock sequences constituting the bimodal distribution the distances of the two largest aftershocks from the mainshock hypocentre are equal to the fault lengths of shallow earthquakes in japan and to the maximum earthquake fault lengths