reassessment of the rifting process in the western corinth rift from relocated seismicity the seismic activity in the western part of the corinth rift greece over the period 2000 2007 monitored by a dense network of three component stations is analysed in terms of multiplets and high precision relocation using double difference techniques this detailed analysis provides new insights into the geometry of faults at depth the nature and the structure of the active zone at 6 8 km depth previously interpreted as a possible detachment and more generally into the rifting process the seismicity exhibits a complex structure strongly varying along the rift axis the detailed picture of the seismic zone below the rift indicates that its shallower part at depths of 6 8 km is 1 1 5 km thick with a complex microstructure and that its deeper part at depths of 9 12 km gently dipping to the north 10 20 is 0 1 0 3 km thick with a microstructure consistent with the general slope of the structure although the nature of this seismic zone remains an open question the presence of seismicity beneath the main active area the strong variability of the structure along the rift over short distances and the complex microstructure of the shallower part revealed by the multiplet analysis are arguments against the hypothesis of a mature detachment under the rift this active zone more likely represents a layer of diffuse deformation the geometry of the mapped active faults is not well defined at depth as no seismicity is observed between 0 and 4 km except for the aigion fault rooting in the seismic layer at 6 km depth with a dip of 60 a distinct cloud of seismicity may be associated with the antithetic kalithea fault on which the 1909 fokis earthquake m s 6 3 may have occurred the link between the 1995 rupture m s 6 2 and the faults known at the surface has been better constrained as the relocated seismicity favours a rupture on an offshore blind fault dipping at 30 rather than on the deeper part of the east helike fault consequently the 1995 event is expected to have decreased the coulomb stress on the east helike fault to explain these seismic observations along with the geodetic observations a new mechanical model for the rifting process in this region is proposed involving non elastic mostly aseismic uniform ns opening below the rift axis coupled with the downward and northward growth of a yet immature detachment the reported gps rates would mainly result from this deep silent source and the seismicity would reveal the detachment position not yet connected to the ductile lower crust in such a model the strong fluctuations of microseismicity would result from small strain instabilities undetected by continuous gps and possibly related to pore pressure transients

comparison of frequency of occurrence of earthquakes with slip rates from long term seismicity data the cases of gulf of corinth sea of marmara and dead sea fault zone summary in this article through the comparison of knowledge relating to historical earthquakes with the understanding of present day earthquake mechanics and overall gps slip rates in the eastern mediterranean region it has been possible to obtain an idea of how frequently large earthquakes may be expected in some parts of the region it has also been possible to make an assessment from these early events of slip rates over a long period of time for the gulf of corinth in greece the marmara sea in turkey and the dead sea fault system as well as deriving long term magnitude frequency relations for these same regions it has been demonstrated that slip rates calculated from historical data are in general comparable to those calculated from gps measurements and field observations while the size of historical earthquakes and their uncertainty can be quantified this permits a more reliable estimation of the long term hazard the calculation of which is the concern of the engineering seismologist it has also been shown that in most cases large earthquakes are less frequent when they are estimated from long term data sets rather than from the instrumental period making the notion of recurrence time and of hazard assessment questionable this study focuses on some of the few areas in the world for which long term macroseism information exists and which facilitate this kind of analysis

the quaternary evolution of the gulf of corinth central greece coupling between surface processes and flow in the lower continental crust abstract the gulf of corinth in central greece is an active normal fault zone with particularly clear evidence of isostatic footwall uplift constrained by quaternary marine terraces and hanging wall subsidence and sedimentation it is bounded to the south by a pliocene to early pleistocene sedimentary basin which is now eroding into the gulf previous work has suggested that the relief across this region has increased dramatically since the early pleistocene due to the isostatic response to increased rates of footwall erosion and hanging wall sedimentation it is indeed assumed here that incision accompanying the draw down of global sea level at 0 9 ma during the first major pleistocene glaciation initiated the erosion of the basin south of the gulf of corinth and so abruptly increased the sedimentation rate in the gulf the resulting transient thermal and isostatic response to these changes is modelled with the subsiding depocentre and eroding sediment source coupled by flow in the lower continental crust the subsequent enhancement of relief involving an increase in bathymetry from near zero to 900 m and 500 m of uplift of the eroding land surface in the sediment source is shown to be a direct consequence of this change the model is sensitive to the effective viscosity of the lower crust and can thus resolve this parameter by matching observations a value of 6 1019 pa s is indicated suggesting a viscosity at the moho no greater than 1018 pa s similar transient topographic effects caused by increased rates of sedimentation and erosion are likely to be widespread within the geological record suggesting that this coupling process involving flow in the weak lower crust may be of major geological and geomorphological importance

tsunamigenic sources in an active european half graben gulf of corinth central greece abstract the gulf of corinth is an active half graben dissecting the mainland of greece along an east west axis the gulf is well known for its intense seismic activity and its rapid extension rates however published historical catalogues reveal that the gulf of corinth is also the site of frequent and relatively destructive tsunami occurrences this paper presents a comparative study of the potential of probable tsunami sources in the gulf of corinth by referring to published offshore geology data coseismic seafloor displacement along offshore faults and submarine mass failures are the active tsunamigenic sources the paper applies easy to use empirical and semi empirical equations that estimate the generated tsunami wave height just over the source area building upon the most probable worst case scenarios for both coseismic fault displacement and submarine mass failure generated tsunamis the tsunami potential of its case is explored a maximum probable 6 7 m w offshore earthquake would produce a rupture on the seafloor surface with a maximum displacement of 0 66 to 1 08 m in height in the gulf of corinth the tsunami which would be generated by the seafloor displacement would have a wave height of the same magnitude as the seafloor displacement furthermore existing evidence of submarine mass failures that took place over the last 3000 years in the eastern part of the corinth gulf had and would have the potential of generating tsunamis with a maximum wave height of 1 04 and 4 04 m and maximum wave length of 4 52 and 6 25 km

sediment accumulation patterns and fine scale strata formation on the waiapu river shelf new zealand abstract multiple sediment transport and reworking processes influence fine cm scale strata formation and long term accumulation on the waiapu river shelf new zealand gravity cores collected during two cruises in august 2003 and may 2004 were analyzed using 7 be and 210 pb geochronologies bulk carbon 13 c x radiographs and grain size to investigate sediment mixing and accumulation patterns the presence of 7 be on the inner and mid shelf regions 210 pb accumulation rates revealed that the middle to outer shelf 50 130 m acted as fine sediment repositories on longer time scales excess 210 pb accumulation rates were high with an area weighted average of 1 1 0 1 cm yr and ranging between 0 2 and 3 5 cm yr yet were localized such that only an estimated 23 ranging between 17 and 38 of the fluvial load was retained on the shelf between 40 and 200 m depths over the last 80 to 100 yr sediments not retained on the shelf were either transported to deeper waters or along the shelf beyond the sampling area several cores collected from the high sediment accumulation zone on the middle to outer shelf exhibited non steady state excess 210 pb profiles suggesting that multiple transport processes influenced fine scale strata formation layers of low excess 210 pb activity and predominantly terrestrial 13 c and c n values were likely formed during floods when sediments were rapidly deposited and buried on the shelf these event layers were sufficiently thick up to 20 cm such that all or a portion of the initial flood layer immediately transited through the surface mixing layer ensuring preservation in the sediment record sediments inter bedded with these event layers reflected a relatively marine source indicating either that they were not deposited rapidly or were significantly bioturbated a gradient of physical and biological mixing signatures extending radially from the waiapu river mouth suggested that high background accumulation rates and flood deposits negatively impacted the preservation of biological structures and enhanced preservation of event produced beds

ree patterns nd sm and u pb ages of the metamorphic rocks of the diagorou darbani greenstone belt liptako sw niger implication for birimian palaeoproterozoic crustal genesis

holocene turbidites record earthquake supercycles at a slow rate plate boundary ongoing evidence for earthquake clustering calls for records of numerous earthquake cycles to improve seismic hazard assessment especially where recurrence times overstep historical records we show that most turbidites emplaced at the africa eurasia plate boundary off west algeria over the past 8 k y correlate across sites fed by independent sedimentary sources requiring a regional trigger correlation with paleoseismic data inland and ground motion predictions support that m 7 earthquakes have triggered the turbidites the bimodal distribution of paleo events supports the concepts of earthquake supercycles and rupture synchronization between nearby faults 13 paleo earthquakes underpin clusters of 3 6 events with recurrence intervals of 300 600 yr separated by periods of quiescence of 1 6 k y without major events on other faults over the study area this implies broad phases of strain loading alternating with phases of strain release our results suggest that fault slip rates are time dependent and call for revising conventional seismic hazard models

along strike changes in the structural evolution over a brittle detachment fault example of the pleistocene corinth patras rift greece abstract the patras corinth and northern saronic gulfs occupy a 200 km long n120 trending pleistocene rift zone where peloponnese drifts away from mainland greece the axes of patras and corinth basins are 25 km apart and linked by two transfer fault zones trending n040 the older one defines the western slope of panachaikon mountain and the younger one limits the narrow rion patras littoral plain between these two faults the ca 4 km thick rion patras series dips 20 30 ssw it is part of the patras gulf synrift deposits which pile in an asymmetric basin governed by a fault dipping ca 25 35 nne located in the southern gulf of patras mapping of this fault to the east in northern peloponnese shows that it is an inactive north dipping low angle normal fault 0 to 30 n called the northern peloponnese major fault npmf the structural evolution of the npmf was different in the gulfs of patras and corinth in the gulf of patras it is still active in northern peloponnese footwall uplift and coeval southward tilting flattened the fault and locked its southern part steeper normal faults formed north of the locked area connecting the still active northern part of the npmf to the surface after several locks the presently active normal faults psathopyrgos aigion helike trend along the southern shore of the gulf of corinth this migration of faults caused the relative 25 km northward shift of the corinth basin and the formation of ne sw trending transfer faults between the corinth and patras gulfs

the structures stratigraphy and evolution of the gulf of corinth rift greece summary a multichannel seismic and bathymetry survey of the central and eastern gulf of corinth goc greece reveals the offshore fault geometry seismic stratigraphy and basin evolution of one of earths most active continental rift systems active right stepping en echelon north dipping border faults trend ese along the southern gulf margin significantly overlapping along strike the basement offsets of three akrata derveni sithas and xylocastro are linked the faults are biplanar to listric typically intermediate angle 35 in the centre and 45 48 in the east near the surface but decreasing in dip and or intersecting a low or shallow angle 15 20 in the centre and 19 30 in the east curvi planar reflector in the basement major s dipping border faults were active along the northern margin of the central gulf early in the rift history and remain active in the western gulf and in the subsidiary gulf of lechaio but unlike the southern border faults are without major footwall uplift much of the eastern rift has a classic half graben architecture whereas the central rift has a more symmetric w or u shape the narrower and shallower western gulf that transects the 40 km thick crust of the hellenides is associated with a wider distribution of overlapping high angle normal faults that were formerly active on the peloponnesus peninsula the easternmost sector includes the subsidiary gulfs of lechaio and alkyonides with major faults and basement structures trending ne e w and nw the basement faults that control the rift architecture formed early in the rift history with little evidence other than the vrachonisida fault along the northern margin in the marine data for plan view evolution by subsequent fault linkage several have maximum offsets near one end crestal collapse graben formed where the hanging wall has pulled off the steeper onto the shallower downdip segment of the derveni fault the dominant strikes of the corinth rift faults gradually rotate from 090 120 in the basement and early rift to 090 100 in the latest rift reflecting a 10 rotation of the opening direction to the 005 presently measured by gps the sediments include a locally 1 5 km thick early rift section and a late rift section also locally 1 5 km thick that we subdivide into three sequences and correlate with seven 100 ka glacio eustatic cycles the gulf depocentre has deepened through time currently 700 mbsl as subsidence has outpaced sedimentation we measure the minimum total horizontal extension across the central and eastern gulf as varying along strike between 4 and 10 km and estimate full values of 6 11 km the rift evolution is strongly influenced by the inherited basement fabric the regional nnw structural fabric of the hellenic nappes changes orientation to ese in the parnassos terrane facilitating the focused north south extension observed offshore there the basement penetrating faults lose seismic reflectivity above the 4 14 km deep seismogenic zone multiple generations and dips of normal faults some cross cutting accommodate extension beneath the goc including low angle 15 20 interfaces in the basement nappes the thermally cool forearc setting and cross orogen structures unaccompanied by magmatism make this rift a poor analogue and unlikely precursor for metamorphic core complex formation

quaternary tectonics in the gulf of patras western greece abstract air gun seismic and 3 5 khz profiling data from the gulf of patras western greece show that it is occupied by a small asymmetric graben with several geometric similarities to the larger scale graben in the gulf of corinth to the east major listric faulting characterizes the southern flank of the graben whilst the northern flank represents an associated rollover structure affected by antithetic and synthetic faulting the present phase of subsidence is of holocene age but buried growth faults suggest earlier subsidence in the gulf the average rate of subsidence through the holocene is estimated to be 10 mm year the gulf of patras graben together with the gulf of corinth graben and the megara basin represent a continuous system of wnw ese trending grabens in a broad zone of intense seismicity within the aegean domain individual grabens are offset and are interconnected by ne sw trending fault systems

itrax description and evaluation of a new multi function x ray core scanner a new automated multi function core scanning instrument named itrax has been developed that records optical radiographic and elemental variations from sediment half cores up to 1 8 m long at a resolution as fine as 200 m an intense micro x ray beam focused through a flat capillary waveguide is used to irradiate samples to enable both x radiography and x ray fluorescence xrf analysis data are acquired incrementally by advancing a split core via a programmable stepped motor drive through the flat rectangular section x ray beam traditional xrf determination of element composition in sediments provides high quality data but it takes a considerable time and normally consumes gram quantities of material that is often only available in limited quantities the itrax core scanner non destructively collects optical and x radiographic images and provides high resolution elemental profiles that are invaluable for guiding sample selection for further destructive detailed sampling this paper presents a description of the construction characteristics and capabilities of the itrax system high resolution itrax data obtained from sediment cores are also presented and compared with results from traditional wavelength dispersive xrf analysis at lower resolution finally some recent technical developments linked to the second generation itrax are presented

deciphering hemipelagites from homogenites through anisotropy of magnetic susceptibility paleoseismic implications sea of marmara and gulf of corinth abstract in closed marine basins and large lakes gravity re depositional processes often result in specific turbidites with two abruptly separated layers a coarse graded lower term and an upper homogenous fine grained term an additional mixed term generally occurs in between indicating to and from particle displacements the later ones are related to oscillating bottom currents responsible for a high increase of the fine fraction segregation within the reworked wasted mass the whole sedimentary event is the association homogenite turbidite hmtu which specific a settling condition area here characterized through anisotropy of magnetic susceptibility ams homogenites s magnetic foliation appears anomalously high with respect to their expected state of compaction and strikingly higher than hemipelagites s values we applied this approach to late pleistocene holocene sediments from the sea of marmara and from the gulf of corinth grain size and other magnetic parameters related to mineralogy are added to better assess the granular array influence on ams as hmtu is considered as often related to earthquake triggering and tsunami seiche effects ams appears as a useful tool for subaqueous paleoseismic investigations first it may evidence the signature of paleo earthquakes second it permits to decipher hemipelagic intervals which are inferred to represent the time elapsed between two successive reworking events

active faulting at the western tip of the gulf of corinth greece from high resolution seismic data abstract the gulf of corinth is one of the fastest spreading intra continental rifts on earth gps data indicate that the rift is currently opening in a nne ssw direction with a rate of extension reaching up to 16 mm yr 1 in its westernmost part although the rest of the offshore rift has been well studied the western tip of the rift is still poorly explored we present an accurate map of submarine faults in this area based on two high resolution seismic reflection surveys single channel sparker in the eastern part of the studied area the sedimentary infill is affected by the known north eratini south eratini and west channel faults further to the west the seafloor is mostly flat and is bounded to the north by the normal south dipping trizonia fault to the north the shallower part of the gulf shows to the east a diffuse pattern of normal and strike slip deformation which is replaced to the west by a 7 5 km long se striking strike slip fault zone called the managouli fault zone to the westernmost tip of the gulf in the nafpaktos basin two fault sets with different strikes are encountered the one with a ne sw strike exhibits a clear strike slip component the western tip of the gulf of corinth is the only part of the corinth rift where convincing evidence for strike slip movement has been found this fault pattern is likely related to the complex deformation occurring at the diffuse junction at the western tip of the rift between three crustal blocks continental greece peloponnese and the ionian island akarnania block

intrabasin paleoearthquake and quiescence correlation of the late holocene dead sea 1 a comprehensive multisite paleoseismic archive of the late holocene dead sea basin past 2500 years is established by constructing two age depth chronological models of two sedimentary sections exposed at the retreating shores of the modern dead sea two new paleoseismic study sites studied are the ein feshkha nature reserve outcrop located at the northern part of the basin and close to an active underwater transverse fault and the east ze elim gully outcrop at the southern part of the basin age depth regression models are calculated for these sections based on atmospheric radiocarbon ages of short lived organic debris calibrated with a bayesian model the uncertainties on individual model ages are smaller than 100 years the new chronological records are compared to a laminae counting study of the ein gedi core migowski et al 2004 located at the central dead sea basin the ein feshkha outcrop yielded the largest number of seismites in the studied time interval n 52 while lower numbers of seismites are recovered from the ze elim outcrop and ein gedi core n 15 and 36 respectively the seismites show no strong dependence on the limnological sedimentological conditions in the particular sampling sites they coappear in both shallow and deep water environments and in different sedimentary facies during time intervals when the chronologies are comparable it appears that the number of seismites is significantly larger in the northern part of the basin ein gedi and ein feshkha seismic quiescence intervals are apparent at all three sites from 2nd 4th century a d and at 500 150 b c at ze elim and ein gedi several synchronous seismites appear in all sections termed here the intrabasin seismites ibs among them 1927 1293 1202 1212 749 551 419 and 33 a d and 31 and mid 2nd century b c the recurrence time of the ibs from the 2nd century b c to the 14th century a d is 200 years compared with 100 years for all earthquakes on a diagram of epicentral distance versus magnitude historic earthquakes that are correlated with ibs plot in a field of high local intensity the farther and stronger ibs earthquakes require lower local intensities to be recorded this study demonstrates that a painstaking effort is still needed for unraveling the seismic history of the dead sea basin the results also indicate that such a study will likely be highly rewarding

contrasting modes of shelf sediment dispersal off a high yield river waiapu river new zealand abstract recent studies of continental margins suggest that small high yield rivers are capable of generating shelf sediment gravity flows an idea that fundamentally alters our understanding of material flux from the continents to the ocean discharge measurements indicate that the waiapu river north island new zealand reaches hyperpycnal concentrations 36 kg m 2 on a yearly basis this study contrasts shelf edge basins with a broad trough along the shelf edge off the waiapu river testing whether there is evidence that shelf sediment gravity flows propagate to topographic lows observations and measurements through geochemical and sedimentological analyses of sediment cores em1002 swath bathymetry and chirp sub bottom profiles suggest differing transport modalities on the outer shelf in general a southern trough shaped region exhibits high terrigenous inputs and non steady state 210pb profiles whereas the northern basins contain steady state 210pb profiles and increased marine influence sediment gravity flows dominate accumulation in the southern region whereas within the northern portion surface plume sedimentation is indicated overall this study suggests that sediment gravity flows could be bypassing the northern basins perhaps a result of oceanographic influences and bathymetric steering as they seek a more direct route across the shelf

a palaeoseismological and geoarchaeological investigation of the eliki fault gulf of corinth greece abstract palaeoseismological and morphotectonic analyses enable us to define a 400 m wide actively deformed zone associated with the active eliki normal fault central greece bounded on the south by a second order fault and on the north by a composite and prominent fault scarp this scarp is further analysed by trenching based on colluvium stratigraphy displacement of distinct horizons and deposition of sedimentary layers three faulting events have been identified along four fault strands affecting unconsolidated sediments in the trench the two younger events with throws of 0 93 and 1 37 m respectively the third event with a throw of 0 44 m and the penultimate 373 bc event suggest a variable seismic history the entire alluvial plain of the kerynitis and vouraikos rivers which cross the eliki fault has subsided at a rate of 1 4 mm year resulting in the burial of the late hellenistic roman occupation horizons under 3 m of fluvial and colluvial sediments in places extension in the broader area is accommodated by the seismically active eliki and egion faults structural and palaeoseismological analysis of those two faults indicates that they accommodate 1 5 mm year or about 10 of the geodetically estimated extension of up to 13 mm year

submarine earthquake geology along the north anatolia fault in the marmara sea turkey a model for transform basin sedimentation abstract the submerged portions of the north anatolia fault system beneath the marmara sea were studied with high resolution multibeam bathymetry subbottom profiling and sediment cores the major objectives were to learn about the seismic and tectonic history of the fault from the stratigraphic record at a scale similar to paleoseismic studies on land and to develop tools for submarine earthquake geology that can be applied to fault controlled basins in general we focused on holocene sediment in several marmara sea basins of different sizes the approach was to test whether 1 the depocenters of the larger basins contain a record of all historic ms 7 earthquakes within the marmara sea region 2 the small transform basins record earthquakes that rupture through them 3 vertical and strike slip holocene deformation can be quantified and 4 the effects of an earthquake generally includes both primary structural features due to rupture of the sea floor such as strata offset scarps and tilting as well as secondary effects due to shaking such as mass wasting and gravitational flows we found evidence of earthquakes that we correlate with historic events in 181 ad 740 ad 1063 ad 1343 ad 1509 ad 1766 ad 1894 ad and 1912 ad the geologic evidence is primarily from those basins adjacent to the rupture as inferred from historic data this suggests that coseismic deformation of the sea floor along the rupture is a critical factor in the sedimentary record we propose a qualitative sedimentation model that relates this coseismic deformation to mass wasting of the slope scour of the basin floor seiche motions and homogenite deposition frequent earthquake activity sheds sediments from the flanks contributes to the much thicker sediment on the basin floor and decreases the likelihood of sediment failures in response to normal marine gravity driven processes the surveying techniques and approaches used have therefore the potential of documenting earthquake ruptures of fault segments and to extend the earthquake record far before the known history thus improving hazard evaluations and the fundamental understanding of earthquake process

a comparison of geodetic and finite strain pattern in the aegean geodynamic implications abstract a comparison of the active strain pattern of the aegean constrained by global positioning system measurements and the oligo miocene finite strain field shows some striking similarities in terms of direction and rates of extension the geometry of extension at crustal scale is also very similar with north dipping normal faults connecting near the brittle ductile transition to shallow north dipping shear zones this pattern of extension is not significantly modified by the recent extrusion of the motion of anatolia and aegea the persistence over more than 25 myr of the same pattern of extension suggests that the cause for extension resides within the aegean lithosphere gravitational collapse allowed by extensional boundary conditions after 30 ma slab retreat is the primary cause for post orogenic extension in the aegean and western anatolia

bridging onshore and offshore present day kinematics of central and eastern mediterranean implications for crustal dynamics and mantle flow we present a new kinematic and strain model of an area encompassing the calabrian and hellenic subduction zones western anatolia and the balkans using haines and holt s 1993 method we derive continuous velocity and strain rate fields by interpolating geodetic velocities including recent gps data in the balkans relative motion between stable eurasia and the western aegean sea is gradually accommodated by distributed n s extension from southern balkans to the eastern corinth gulf so that the westward propagation of the north anatolian fault naf throughout continental greece or peloponnesus is not required we thus propose that the naf terminates in north aegean and that n s extension localized in the corinth gulf and distributed in southern balkans is due to the retreat of the hellenic slab the motion of the hyblean plateau apulia peninsula south adriatic sea ionian basin and sirte plain can be minimized by a single rigid rotation around a pole located in the sirte plain compatible with the opening the pelagian rifts 2 2 5 mm yr and seismotectonics in libya we interpret the trenchward ultraslow motion of the calabrian arc 2 2 5 mm yr as pure collapse the calabrian subduction being now inactive in the absolute plate motion reference frame our modeled velocity field depicts two toroidal crustal patterns located at both ends of the hellenic subduction zone clockwise in nw greece and counter clockwise in western anatolia we suggest the nw greece toroidal pattern is the surface expression of a slab tear and consequent toroidal asthenospheric flow

submarine and coastal sediment failure triggered by the 1995 ms 6 1 r aegion earthquake gulf of corinth greece on june 15th 1995 a locally destructive earthquake of magnitude ms 6 1 on the richter scale occurred offshore 7 5 km nne of the town of aegion in the western gulf of corinth greece an offshore survey using 3 5 khz subbottom profiling system and a remote operated vehicle rov has shown that the earthquake caused small sized subaerial to submarine sediment failure in at least four sites in three fan delta deposits the rododafni the eliki and the tolofonas the fan deltas were located within a radius of about 9 km from the epicentre the areal size of the four sediment failure sites ranged from 2 104 m2 to 6 105 m2 whilst the volume of the failed masses ranged from 4 103 to 3 106 m3 the sediment deformation types identified at the failure sites consist of ground cracking rotational slides elongated slides sediment gravity flows and extrusion of mixtures of water and sand sand boils the sediment failure in the four sites affected the upper 5 6 m of well layered holocene topset and foreset fan delta deposits the failure occurred on slopes ranging from 0 2 to 23 and the slip planes were all bedding planes which have a gradient from 0 2 to 21 the dominant instability mechanism that caused the sediment failure in the rododafni and eliki fan deltas is considered to be liquefaction of a shallow sub surface horizon the liquefaction was caused by elevated pore pressure enhanced perhaps by the presence of gas resulting from the cyclic loading induced by the earthquake the liquefied layer is assumed to have temporarily provided a failure surface for sliding to take place on and caused movement of sand that was ejected onto the surface in the tolofonas fan delta the causative mechanism in the case of the multi block rotational slide is considered to be deformation of the underlying sediments caused by remoulding and or liquefaction while in the case of the elongated slide it is considered to be the result of a combination of shear stress increase and or strength degradation of the unconsolidated sediment both of these conditions could have been generated during the cyclic loading resulting from the aegion earthquake the study of historical documents reveals that sediment failure like those described above have also occurred at least four times during the past 2500 years in the same locations therefore it is suggested that they could be repeated in the future by any earthquake event with a magnitude greater than 6 r depending upon the proximity of the site to the earthquake epicentre

alternating marine and lacustrine sedimentation during late quaternary in the gulf of corinth rift basin central greece abstract the gulf of corinth in central greece has a maximum depth of about 900 m and is separated from the open sea by the rion strait with a sill depth of 62 m marked by an extensive submarine terrace during eustatic sea level lowstands the gulf of corinth was a lake under lacustrine conditions stratified sediments accumulated in the deep water basins and turbid underflows from rivers eroded the basin slopes as the sea level rose marine waters flooded the gulf and deltas prograded across the shelves in shallow water areas two key reflectors termed z and x are terrace surfaces commonly erosional which mark the base of the overlying deltaic sequences in deep water basins z and x mark the top of the acoustically stratified sediments interpreted as lacustrine turbidites reflectors y and w mark the base of these stratified intervals and overlie acoustically transparent sections similar to the holocene section the last lacustrine conditions in the gulf z to y were during isotopic stage 2 and terminated about 12 000 yr ago age estimates based on sedimentation rates suggest that the x to w interval corresponds to the stage 4 lowstand of sea level in the western gulf of corinth shoreline transgressive surfaces corresponding to minor transgressions in stage 5 and to major transgression at the end of stage 6 are recognised this seismic stratigraphy permits a detailed interpretation of the history of the gulf of corinth in the past hundred thousand years it also provides a general model for sedimentation in rift basins in which marine and lacustrine sediments alternate

fluidization of buried mass wasting deposits in lake sediments and its relevance for paleoseismology results from a reflection seismic study of lakes villarrica and calafquen south central chile abstract a dense grid of very high resolution seismic profiles on lake villarrica provides a quasi 3d view on intercalated lenses of low amplitude reflections which are connected by acoustic wipe out patches and fractures to an underlying voluminous mass wasting deposit the lenses are interpreted as being created by earthquake triggered liquefaction in this buried mass wasting deposit and subsequent sediment fluidization and extrusion at the paleo lake bottom these sediment volcanoes are mapped in detail they have a rather uniform circular geometry and show a linear relationship between apparent width and maximum thickness on a seismic section the largest sediment volcanoes are up to 80 m wide and 1 9 m thick their slope angles designate a syn to post depositional sagging of most sediment volcanoes sediment volcano detection and mapping from nearby lake calafquen further strengthen the revealed geometrical relationships locally some of the sediment fluid escape structures extend to a higher position in the stratigraphy which points to a polyphase escape process associated with multiple multi century spaced strong earthquakes thickness and morphology of the source layer seem to exert a dominant control in the production of sediment fluid extrusions this study shows that reflection seismic profiling allowed recognizing 4 different seismic events in the studied stratigraphic interval which are evidenced by mass wasting deposits and or fluidization features

a comparison of the sedimentary records of the 1960 and 2010 great chilean earthquakes in 17 lakes implications for quantitative lacustrine palaeoseismology seismically induced event deposits embedded in the sedimentary infill of lacustrine basins are highly useful for palaeoseismic reconstructions recent well documented great megathrust earthquakes provide an ideal opportunity to calibrate seismically induced event deposits for lakes with different characteristics and located in different settings this study used 107 short sediment cores to investigate the sedimentary impact of the 1960 mw 9 5 valdivia and the 2010 mw 8 8 maule earthquakes in 17 lakes in south central chile i e lakes negra lo encanado aculeo vichuquen laja villarrica calafquen pullinque pellaifa panguipulli neltume rinihue ranco maihue puyehue rupanco and llanquihue a combination of image analysis magnetic susceptibility and grain size analysis allows identification of five types of seismically induced event deposits i mass transport deposits ii in situ deformations iii lacustrine turbidites with a composition similar to the hemipelagic background sediments lacustrine turbidites type 1 iv lacustrine turbidites with a composition different from the background sediments lacustrine turbidites type 2 and v megaturbidites these seismically induced event deposits were compared to local seismic intensities of the causative earthquakes eyewitness reports post earthquake observations and vegetation and geomorphology of the catchment and the lake megaturbidites occur where lake seiches took place lacustrine turbidites type 2 can be the result of i local near shore mass wasting ii delta collapse iii onshore landslides iv debris flows or mudflows or v fluvial reworking of landslide debris on the contrary lacustrine turbidites type 1 are the result of shallow mass wasting on sublacustrine slopes covered by hemipelagic sediments due to their more constrained origin lacustrine turbidites type 1 are the most reliable type of seismically induced event deposits in quantitative palaeoseismology because they are almost exclusively triggered by earthquake shaking moreover they most sensitively record varying seismic shaking intensities the number of lacustrine turbidites type 1 linearly increases with increasing seismic intensity starting with no lacustrine turbidites type 1 at intensities between v and vi and reaching 100 when intensities are higher than vii combining different types of seismically induced event deposits allows the reconstruction of the complete impact of an earthquake

sedimentary impacts of recent moderate earthquakes from the shelves to the basin floor in the western gulf of corinth abstract in seismically active areas long term records of large earthquakes are indispensable to constrain reccurence patterns of large earthquakes in the western corinth rift one of the most active areas in europe in terms of seismicity data about ancient earthquakes are still insufficient despite historical records covering the last two millenia and several studies in onshore paleoseimology in this paper we test the use of offshore sediments from the gulf of corinth to identify sediment failures and tsunamis that have been triggered by historical earthquakes two shelves 40 100 m deep one sub basin 180 m and the basin floor 330 m have been sampled by short gravity cores the cores were analyzed in order to identify and characterize event deposits the age control has been provided by 137cs and 210pb activity measurements showing that the cores represent 2 to 4 centuries of sedimentation in each site sandy event deposits are interbeded in the muddy hemipelagic sedimentation the age of event deposits has been compared to the record of historical earthquakes using new and published macroseismic data this comparison shows temporal coincidence of some event deposits and documented earthquakes with a macroseismic intensity vii in the area e g in 1861 ce 1888 ce and 1909 ce in nearshore shallow water settings the record of event deposits does not exactly fit with the historical record of large earthquakes because too few event deposits are present this may be due to the absence of sediment failures or to a lower preservation of the deposits in such settings in the deepest site in the basin floor the correspondence is better a sandy turbidite probably corresponds to each large earthquake since 1850 ce except one aseismic sediment density flow that occurred at the end of the 20th century surprisingly the ms 6 2 june 15 1995 aigion earthquake is only possibly recorded in one nearshore site on the aigion shelf in the form of a tsunami back wash flow deposit this study showed that moderate earthquakes m 5 8 6 5 can significantly impact marine sediments regarding the evaluation of seismic hazard in the area the basin floor is proposed as a promising site for long term paleoseismology in the gulf of corinth while shallower settings need to be considered more carefully

geomagnetic field for 0 3 ka 1 new data sets for global modeling 1 paleomagnetic and archeomagnetic records are used in both regional and global studies of earth s magnetic field we present a description and assessment of five newly compiled data sets also used in the companion paper by korte et al 2009 to produce a series of time varying spherical harmonic models of the geomagnetic field for the last 3000 years data are drawn from our compilation of lake sediment records and from the online database geomagia50v2 the five selections are available from the earthref digital archive at http earthref org cgi bin erda cgi n 944 data are grouped according to the source of material and we conducted separate assessments of reliability for archeomagnetic artifacts and lava flows the arch3k dat data set and for sediments sed3k dat the overall number of data is 55 greater than in previous compilations constrained data sets were selected using different criteria for each group winnowing of archeological data was based on uncertainties supplied by the original data providers the lake sediment data assessment relied on preassigned age uncertainties and one or more of the following comparisons with archeomagnetic data from the same region regional consistency among several lakes and consistency with global archeomagnetic models we discuss relative merits of a larger unconstrained data set or a smaller possibly more reliable one the constrained data sets eliminate a priori up to 35 of the available data in each case and rely on potentially subjective assessments of data quality given the limited data available our analyses indicate that iterative rejection of a small number 1 1 5 of outlying data during global field modeling is a preferable approach specific regional comparisons among the models and data support the conclusion that korte et al s outlier free cals3k 3 model based on all available measurements from sediments and archeological artifacts currently provides the best global representation of the 0 3 ka field the arch3k 1 model provides a better fit to the denser european archeomagnetic data and may be better in that region

slip rates on the helike fault gulf of corinth greece new evidence from geoarchaeology palaeoseismological and archaeological analysis of a trench enabled us to estimate the holocene slip rates on the east helike fault flanking the south western gulf of corinth we recognized two major fault strands within the trench the north fault controls a succession of three colluvial wedges and the deposition of a 2 7 m thick sedimentary sequence the south fault controls the deposition of a 2 9 m thick brownishred colluvium based on colluvial stratigraphy radiocarbon dating of the sediments suggests that the slip rate was c 0 3 mm yr 1 from 10 250 to c 1400 bp when it increased dramatically to c 2 0 mm yr 1 after a strong earthquake event near 1400 bp the faster slip rate evidently increased the sedimentation rate

why earthquake hazard maps often fail and what to do about it abstract the 2011 tohoku earthquake is another striking example after the 2008 wenchuan and 2010 haiti earthquakes of highly destructive earthquakes that occurred in areas predicted by earthquake hazard maps to be relatively safe here we examine what went wrong for tohoku and how this failure illustrates limitations of earthquake hazard mapping we use examples from several seismic regions to show that earthquake occurrence is typically more complicated than the models on which hazard maps are based and that the available history of seismicity is almost always too short to reliably establish the spatiotemporal pattern of large earthquake occurrence as a result key aspects of hazard maps often depend on poorly constrained parameters whose values are chosen based on the mapmakers preconceptions when these are incorrect maps do poorly this situation will improve at best slowly owing to our limited understanding of earthquake processes however because hazard mapping has become widely accepted and used to make major decisions we suggest two changes to improve current practices first the uncertainties in hazard map predictions should be assessed and clearly communicated to potential users recognizing the uncertainties would enable users to decide how much credence to place in the maps and make them more useful in formulating cost effective hazard mitigation policies second hazard maps should undergo rigorous and objective testing to compare their predictions to those of null hypotheses including ones based on uniform regional seismicity or hazard such testing which is common and useful in similar fields will show how well maps actually work and hopefully help produce measurable improvements there are likely however limits on how well hazard maps can ever be made because of the intrinsic variability of earthquake processes

late holocene evolution of the east eliki fault gulf of corinth central greece abstract trench stratigraphy and morphotectonic analysis was used to examine the recent evolution of the helike eliki plain and eliki fault the entire alluvial plain of the kerynites and vouraikos rivers which cross the eliki fault has subsided at rate of 1 4 mm yr resulting in the burial of the late hellenistic roman occupation horizons under 3 m of fluvial and colluvial sediments along the eastern segment of the eliki fault five trenches have been excavated and their 5000 yr old fluvial and colluvial deposits have been studied in association with the fault strand imprinted on them the kerynites river crosses at high angle the eliki fault and appears to be sensitive in tectonic movements related with the eliki fault sedimentation in the alluvial plain and the fluvial geomorphology of the kerynites river is important for understanding the fault evolution and the burial of the ancient 4th century bc helike city the kerynites river course highlights breaching deformation is the more likely to connect east and west eliki fault segments and that postseismic deformation is a significant mechanism for stress accommodation for part of the west end of the gulf of corinth

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

event driven deltaic sedimentation on a low gradient low energy shelf the brazos river subaqueous delta northwestern gulf of mexico abstract the brazos river delta is located in the northwestern gulf of mexico sedimentation on the brazos river subaqueous delta has been largely understudied swath bathymetry data collected across the subaqueous delta reveals a noticeable asymmetry with much deeper water depths and greater cross shelf slopes along the eastern up drift side of the delta than along the western down drift side end member sampling reveals that brazos river derived sediment is red red brown or brown in color exhibits increased bulk density and is enriched in calcium a function of carbonate rich areas of the watershed whereas the gulf of mexico inner shelf muds are gray to black and have a relatively lower calcium content analyses of a series of 33 submersible vibra cores collected across the subaqueous delta reveal alternating beds of brazos river derived sediment and gulf of mexico shelf dominated sediment excess 210pb geochronologies of select cores reveal that sediment accumulation has been a combination of fluvial flood event deposition and deposition of remobilized sediment from the proximal shelf and older portions of the delta rather than steady state accumulation because the brazos river is susceptible to local climatic cycles fluvial flood events that create the event layers are intermittent between prolonged periods where marine processes drive accumulation results also show that the primary depocenter of the subaqueous delta has migrated southwestward over time and the erosion of earlier depocenters and proximal shelf sediment has contributed to accumulation on the delta over the past 50 years the subaqueous delta has reached an equilibrium where flood event beds can be completely remobilized within a year and net accumulation approximates relative sea level rise this study highlights relatively rapid clinoform migration due to natural and anthropogenic changes to the system and demonstrates subaqueous delta growth through a combination of direct fluvial and marine derived sediment input

a late holocene record of environmental changes from the aliki lagoon egion north peloponnesus greece abstract aliki lagoon is a small lagoon located on the micro tidal south coast of the gulf of corinth greece the sediments of the lagoon recovered in three cores provide a record of late holocene environmental change including tectonic subsidence tsunami layers and change in local vegetation and sedimentation four periods of rapid environmental changes were identified over a 5000 yr long record these date from about 4700 3000 2500 and 2000 yr bp each change is linked to activity on the egion fault a deepening of the lagoonal bottom and a rise in relative sea level six tsunami events are recorded and have been caused by earthquakes on the egion fault three events 4700 3000 and 2500 bp eliki fault 2350 40 yr bp and two more distal fault ruptures the vegetation history and pollen zones are similar to those recognised by jahns vegetation hist archaebot 2 1993 187 on the argive plain 100 km southeast of the lagoon five successive sedimentological configurations are established in relation to the time frame provided by the tectonic activity 1 crevasse splay 2 fresh to brackish water marsh 3 and 4 brackish to hypersaline blind lagoon and 5 brackish to hypersaline blind lagoon or brackish open lagoon

rifting and shallow dipping detachments clues from the corinth rift and the aegean the corinth rift is superimposed on the hellenic nappe stack that formed at the expense of the apulian continental crust above the subducting african slab extension started in the pliocene and the major steep normal faults that control the geometry of the present day rift were born very recently some 600 kyr ago only they root into a shallow dipping zone of microseismicity recorded near the base of the upper crust the significance of this seismogenic zone is debated considering the northward dip of the zone of microseismicity the depth of microearthquakes and their focal mechanisms we observe a strong similarity with the northern cycladic detachments in terms of expected pressure temperature conditions and kinematics we herein show 1 that the formation of the corinth rift can be considered a part of a continuum of extension that started some 30 35 ma in the aegean and that was recently localised in a more restricted area 2 that the present day structure and kinematics of the corinth rift can be explained with a series of decollements relayed by steeper ramps that altogether formed a mechanically weak crustal scale detachment and 3 that the deformation fluid behaviour and metamorphic features seen in the northern cycladic metamorphic core complexes can be good analogues of the processes at work below the corinth rift

the january 2010 efpalio earthquake sequence in the western corinth gulf greece abstract the january 2010 efpalio earthquake sequence provides some key elements to enhance our view on the western corinth gulf tectonics the sequence lasted almost six months and included two mw 5 strong events both exhibiting normal faulting along e w trending planes this paper attempts to construct a unified seismotectonic model of the sequence jointly interpreting earthquake locations moment tensors and slip inversions in terms of the possible activated fault planes previous studies have connected the prevailing microseismic activity to a major low angle north dipping structure under the corinth gulf and the efpalio sequence favors such a general trend moreover it clearly shows the significance of the shallow activity so far less recognized and possibly connected to the relatively steep faults outcropping on the northern coast the first 18 january 2010 mw 5 event had almost no on fault aftershocks and most likely it occurred on a 55 south dipping nodal plane the early off fault aftershocks formed two clusters roughly e w trending both of which are connected with normal faulting cross sections revealed that the northernmost cluster is connected with a north dipping structure where the second 22 january 2010 mw 5 event occurred in addition the very shallow parts of the faults

the record of historic earthquakes in lake sediments of central switzerland deformation structures in lake sediments in central switzerland can be attributed to strong historic earthquakes the type and spatial distribution of the deformation structures reflect the historically documented macroseismic intensities thus providing a useful calibration tool for paleoseismic investigations in prehistoric lake sediments the swiss historical earthquake catalogue shows four moderate to strong earthquakes with moment magnitudes of mw 5 7 to mw 6 9 and epicentral intensities of i0 vii to i0 ix that affected the area of central switzerland during the last 1000 years these are the 1964 alpnach 1774 altdorf 1601 unterwalden and 1356 basel earthquakes in order to understand the effect of these earthquakes on lacustrine sediments four lakes in central switzerland sarner see lungerer see baldegger see and seelisberg seeli were investigated using high resolution seismic data and sediment cores the sediments consist of organicand carbonate rich clayey to sandy silts that display fine bedding on the centimeter to millimeter scale the sediments are dated by historic climate and environmental records 137 cs activity and radiocarbon ages deformation structures occur within distinct zones and include large scale slumps and rockfalls as well as small scale features like disturbed and contorted lamination and liquefaction structures these deformations are attributed to three of the abovementioned earthquakes the spatial distribution of deformation structures in the different lakes clearly reflects the historical macroseismic dataset lake sediments are only affected if they are situated within an area that underwent groundshaking not smaller than intensity vi to vii we estimate earthquake size by relating the epicentral distance of the farthest liquefaction structure to earthquake magnitude this relationship is in agreement with earthquake size estimations based on the historical dataset d 2004 elsevier b v all rights reserved

geometry and slip rate of the aigion fault a young normal fault system in the western gulf of corinth the aigion fault is one of the youngest major normal faults in the gulf of corinth greece with an immature displacement profile based on geometry slip rate and comparison with regional faults we estimate the fault system length at 10 km we find the slip rate of the fault system is 3 5 1 mm yr decreasing to 2 5 0 7 mm yr close to its eastern tip complex fault geometry and displacement profiles on the shelf east of aigion are consistent with the latter as the eastern tip location analysis of slip on this fault system and the established fault to the south western eliki fault suggests that slip was transferred rapidly but not homogeneously between the two faults during the period of contemporaneous activity together with a lack of evidence of lateral propagation at the eastern fault tip in the last 10 13 k y we suggest that the fault developed and established its current length rapidly within its 200 300 k y history these results contribute to our understanding of the process of northward fault migration into the rift and the development of new normal faults

slope failures and stability analysis of shallow water prodeltas in the active margins of western greece northeastern mediterranean sea sediment instabilities are common on the prodeltas of the seismically active continental margins of western greece sediment failures on the low angle 0 5 2 prodelta slopes manifest themselves as successions of peripheral rotational block slumps restricted to the foresets of the late highstand systems tract hst the individual slump blocks are about 80 150 m long and are bounded by growth faults acting as curved slip planes that extend to a mean depth of 10 15 m below seafloor shear planes develop in the lower part of muddy and or gas charged hst foresets deeper basal transparent muddy layers of the early hst bottomset together with the late pleistocene transgressive systems tract sequences tst are mostly unaffected on the steeper 2 6 fan delta slopes of the western gulf of corinth debris flows and avalanches with a significant retrogressive component dominate slope destabilisation sediment cores taken from landslide scarps and slide planes penetrated gas bubble releasing sediments thereby indicating that failure planes are in the late hst foresets upper part of the early hst bottomsets gas charged zone the foresets of the hst prodelta deposits display high water content 30 80 low bulk density 1 4 1 9 g cm 3 and relatively low values of undrained shear strength 3 20 kpa the water content of the hst distal muddy bottomsets is relatively higher 50 110 and bulk density relatively lower 1 3 1 7 g cm 3 with low values of shear strength 2 10 kpa the shear strength of the gas releasing sediment layer displays lower values 2 9 kpa relative to the overlying post failure muddy sediments of the late 100 300 years slope stability was calculated using the normalised soil parameter nsp method under undrained conditions for normally consolidated prodelta sediments this analysis indicates that instabilities could be induced by critical earthquake ground accelerations of 26 6 29 6 g for the hst foresets and 12 4 14 1 g for the basal transparent layer belonging to the early hst bottomsets consequently the early hst bottomsets has to be considered a potentially unstable layer since the regional peak ground accelerations pgas for the next 50 years are expected to range from 19 to 30 g moreover our results show that new glide planes in the prodeltaic sediment bodies of the seismically active continental margins of western greece will likely develop from the gas charged sediments of the lower part of the hst foresets to the upper part of early hst bottomsets

linear elastic fracture mechanics explains the past and present evolution of the aegean abstract geologically the deformation in the anatolian aegean region has been dominated by two processes the propagation of the north anatolian fault associated with the extrusion of the anatolian plateau and the north south stretching of the aegean we model gps data in the context of this understanding localised deformation zones are represented by dislocation elements which extend from the base of the lithosphere to the locking depth at the base of the seismogenic layer unlike other gps interpretations our models incorporate geological and seismological constraints to provide a robust description of the present day deformation of the anatolian aegean region we then show that the present day deformation observed by gps today is consistent with the continuation of the geological processes that started in the tertiary our approach is also consistent with the lithosphere preserving long term elastic strength and with the concepts of linear elastic fracture mechanics applying at a large scale

chronology of the pueblo viejo epithermal gold silver deposit dominican republic formation in an early cretaceous intra oceanic island arc and burial under ophiolite the pueblo viejo deposit production to 1996 166 t au 760 t ag is located in the dominican republic on the caribbean island of hispaniola and ranks as one of the largest high sulfidation acid sulfate epithermal deposits reserves in 2007 635 t au 3 648 t ag one of the advanced argillic ore bodies is cut by an inter mineral andesite porphyry dike which is altered to a retrograde chlorite illite assemblage but overprinted by late stage quartz pyrite sphalerite veins and associated low grade au ag zn cd hg in as se and te mineralization the precise tims u pb age 109 6 0 6 ma of the youngest zircon population in this dike confirms that the deposit is part of the early cretaceous los ranchos intra oceanic island arc intrusion related gold sulfide mineralization took place during late andesite dacite volcanism within a thick pile 200 m of carbonaceous sand and siltstones deposited in a restricted marine basin the high level deposit was shielded from erosion after burial under a late albian 109 100 ma ophiolite complex 8 km thick which was in turn covered by the volcano sedimentary successions 4 km of a late cretaceous early tertiary calc akaline magmatic arc estimates of stratigraphic thickness and published alunite illite and feldspar k ar ages and closure temperatures alunite 270 20 c illite 260 30 c k feldspar 150 c indicate a burial depth of about 12 km at 80 ma during peak burial metamorphism 300 c and 300 mpa the alteration assemblage kaolinite quartz in the deposit dehydrated to pyrophyllite temperature time relations imply that the los ranchos terrane then cooled at a rate of 3 4 c ma during slow uplift and erosion

determination of 137cs activities in surface sediments and derived sediment accumulation rates in thessaloniki gulf greece surficial and core samples collected from the eastern thessaloniki gulf located in the nw aegean sea were analyzed for their sedimentation rate and inventories of 137cs and 210pb the study of the spatial radionuclide dispersion in the specific region is essential for the assessment of marine pollution levels the sedimentation rates were calculated from the vertical distribution of 137cs and excess 210pb in the sediment cores the spatial distribution of 137cs was studied with respect to sediment characteristics such as the grain size of the sample and the organic carbon content the activity concentrations were measured by means of gamma ray spectrometry using hpge detector for 137cs and gross alpha counting using alpha counter for 210pb the average sedimentation rate along the sediment cores is characterized by a consistent pattern and varies from 0 18 0 02 to 0 22 0 03 cm year 1 the 137cs inventories varied from 205 15 to 602 39 bq m 2 while the 210pb inventories of the studied cores exhibited average value of 140 9 bq m 2 elevated 137cs activities were observed compared to certain mediterranean marine areas however they were lower than the reported values in the black sea

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

evaluation of tsunami impacts on shallow marine sediments an example from the tsunami caused by the 2003 tokachi oki earthquake northern japan abstract a combined approach of field geology and numerical simulation was conducted for evaluating the tsunami impacts on the shelf sediments the 2003 tokachi oki earthquake m 8 0 that occurred on 25 september 2003 off southeastern hokkaido northern japan generated a locally destructive tsunami maximum run up height of the tsunami waves reached 4 m above sea level in order to estimate the tsunami impacts on shallow marine sediments we compared pre and post tsunami marine sediments in water depths of 38 112 m in terms of grain size sedimentary structure and microfossil content decreases of fine fractions especially finer than very fine sand which led to coarsen the mean grain size were detected in the inner shelf of the northern part of the study area foraminiferal assemblages also changed in the coarsened sediments on the other hand the other shelf sediments largely unchanged or slightly fined we also simulated the tsunami wave velocity and direction and grain size entrained by the modeled tsunami the numerical simulation resulted in that the 2003 tsunami could transport very fine sand in water depths shallower than 45 95 m at the northern part of the study area this is comparable with the actual grain size changes after the tsunami had passed however some storms and tidal currents might also be possible to stir the surface sediments after the pre tsunami survey so we could not conclude that the grain size changes had been caused only by the tsunami nevertheless a combined approach of sampling and modeling was powerful for estimating the tsunami impacts under the sea

deltaic sedimentation and stratigraphic sequences in post orogenic basins western greece abstract post orogenic basin sediments in the gulfs of corinth patras and amvrakia on the western coast of greece occur in four tectonic settings 1 true graben 2 simple and complex half graben 3 shallow half graben associated with the high angel surface traces of thrust faults and 4 marginal depressions adjacent to graben in which sediment loading has occurred late quaternary facies distribution has been mapped in all three basins sea level changes interacting with the apparently fortuitous elevation of horsts at basin margins result in a complex alternation of well mixed marine stratified marine brackish and lacustrine facies organic carbon contents of muds are high in all but the well mixed marine facies basin margin slope is the most important determinant of facies distribution the steep slopes of the gulf of corinth half graben result in fan deltas which deliver coarse sediments in turbidity currents to the deep basin floor where gradients are reduced by marginal downwarping gulf of patras or on the gentle slopes of thrust related half graben gulf of amvrakia coarse sediments are trapped on the subaerial delta or the coastal zone and the fine sediment reaching the basin floor appears derived mainly from muddy plumes during winter floods

can turbidites be used to reconstruct a paleoearthquake record for the central sumatran margin turbidite paleoseismology aims to use submarine gravity flow deposits turbidites as proxies for large earthquakes a critical assumption being that large earthquakes generate turbidity currents synchronously over a wide area we test whether all large earthquakes generate synchronous turbidites and if not investigate where large earthquakes fail to do this the sumatran margin has a well characterized earthquake record spanning the past 200 yr including the large magnitude earthquakes in 2004 mw 9 1 and 2005 mw 8 7 sediment cores collected from the central sumatran margin in 2009 reveal that surprisingly few turbidites were emplaced in the past 100 150 yr and those that were deposited are not widespread importantly slope basin deposits preserve no evidence of turbidites that correlate with the earthquakes in 2004 and 2005 although recent flow deposits are seen in the trench adjacent slope basins and adjacent pairs of slope basin and trench sites commonly have different sedimentary records and cannot be correlated these core sites from the central sumatran margin do not support the assumption that all large earthquakes generate the widespread synchronous turbidites necessary for reconstructing an accurate paleoearthquake record