discrete plio pleistocene phases of tilting and counterclockwise rotation in the southeastern aegean arc rhodos greece early pliocene formation of the south aegean left lateral strike slip system the island of rhodos represents an uplifted block in the largely submerged southeastern aegean forearc it has a complex history of subsidence uplift and counterclockwise rotation during the plio pleistocene in response to the interplay between large scale geodynamic processes in this paper we present a new chronostratigraphic framework for the continental pliocene apolakkia basin of southwestern rhodos we combine these time constraints with recently published chronostratigraphic data from the marine plio pleistocene basins of northeastern rhodos to reconstruct rotational and vertical motions our palaeomagnetic results identify two rotation phases for rhodos c 10 9 6 counterclockwise ccw rotation between 3 8 and 3 6 ma and c 17 6 ccw rotation since 0 8 ma between these phases rhodos tilted to the se drowning the southeastern coast to a depth of 500 600 m between 2 5 and 1 8 ma then to the nw which resulted in the re emergence of the drowned relief between 1 5 and 1 1 ma we relate the rotations of rhodos to incipient formation of the south aegean sinistral strike slip system and the foundering of the rhodos basin the previously shown absence of messinian evaporites in the deep marine rhodos basin in combination with the 3 8 ma onset of ccw rotation of rhodos constrains the onset of the formation of the south aegean strike slip system between 5 3 and 3 8 ma the formation of this strike slip system is probably related to the interplay of oblique collision between the southeastern aegean region and the northward moving african plate the westward motion of anatolia gravitational spreading of the overthickened aegean lithosphere and the recently postulated southwestward retreat of the african subducted slab along a subduction transform edge propagator fault

seismicity and active tectonics at coloumbo reef aegean sea greece monitoring an active volcano at santorini volcanic center using a temporary seismic network the volcanic center of santorini island is the most active volcano of the southern aegean volcanic arc dense seismic array consisting of fourteen portable broadband seismological stations has been deployed in order to monitor and study the seismo volcanic activity at the broader area of the santorini volcanic center between march 2003 and september 2003 additional recordings from a neighbouring larger scale temporary network cycnet were also used for the relocation of more than 240 earthquakes recorded by both arrays a double difference relocation technique was used in order to obtain optimal focal parameters for the best constrained earthquakes the results indicate that the seismic activity of the santorini volcanic center is strongly associated with the tectonic regime of the broader southern aegean sea area as well as with the volcanic processes the main cluster of the epicenters is located at the coloumbo reef a submarine volcano of the volcanic system of santorini islands a smaller cluster of events is located near the anydros islet aligned in a ne sw direction running almost along the main tectonic feature of the area under study the santorini amorgos fault zone in contrast the main santorini island caldera is characterized by the almost complete absence of seismicity this contrast is in very good agreement with recent volcanological and marine studies with the coloumbo volcanic center showing an intense high temperature hydrothermal activity in comparison to the corresponding low level activity of the santorini caldera the high resolution hypocentral relocations present a clear view of the volcanic submarine structure at the coloumbo reef showing that the main seismic activity is located within a very narrow vertical column mainly at depths between 6 and 9 km the focal mechanisms of the best located events show that the cluster at the coloumbo reef is associated with the kameni coloumbo fracture zone which corresponds to the western termination of the major ene wsw santorini amorgos fault zone stress tensor inversion of the available fault plane solutions from coloumbo reef as well as existing neotectonic fault information from ne santorini coloumbo peninsula suggests that the ne santorini coloumbo faults belong to a single rupture system with a 30 rotation of the local stress field with respect to the nnw sse regional extension field of the southern aegean sea the observed change of the fault plane solutions shows that local conditions at the coloumbo submarine volcano area control the observed faulting pattern

submarine volcanoes along the aegean volcanic arc abstract the aegean volcanic arc has been investigated along its offshore areas and several submarine volcanic outcrops have been discovered in the last 25 years of research the basic data including swath bathymetric maps air gun profiles underwater photos and samples analysis have been presented along the four main volcanic groups of the arc the description concerns i paphsanias submarine volcano in the methana group ii three volcanic domes to the east of antimilos volcano and hydrothermal activity in southeast milos in the milos group iii three volcanic domes east of christiana and a chain of about twenty volcanic domes and craters in the kolumbo zone northeast of santorini in the santorini group and iv several volcanic domes and a volcanic caldera together with very deep slopes of several volcanic islands in the nisyros group the tectonic structure of the volcanic centers is described and related to the geometry of the arc and the neotectonic graben structures that usually host them the ne sw direction is dominant in the santorini and nisyros volcanic groups located at the eastern part of the arc where strike slip is also present whereas nw se direction dominates in milos and methana at the western part where co existence of e w disrupting normal faults is observed the volcanic relief reaches 1100 1200 m in most cases this is produced from the outcrops of the volcanic centers emerging usually at 400 600 m depth and ending either below sea level or at high altitudes of 600 700 m on the islands hydrothermal activity at relatively high temperatures observed in kolumbo is remarkable whereas low temperature phenomena have been detected in the santorini caldera around kameni islands and in the area southeast of milos in methana and nisyros hydrothermal activity seems to be limited in the coastal areas without other offshore manifestations

tectonostratigraphic models of the alpine terranes and subduction history of the hellenides abstract the tectonostratigraphy of the hellenic terranes is related to their paleogeodynamic and paleogeographic evolution which comprises three major stages i continental rifting in the northern margin of gondwana characterised by volcanosedimentary complexes of late paleozoic triassic ii continental drifting and contemporaneous oceanic opening of tethyan basins in between the continental terranes during triassic paleogene with shallow water carbonate platforms on the continental terranes and ophiolite suites interlayered with pelagic sediments within the tethyan basins iii accretion of the tectonostratigraphic terranes with docking along the active european margin characterised by flysch melange sedimentation along the trenches from early jurassic to neogene two tectonostratigraphic models can be distinguished one for the continental terranes carbonate platforms and another for the oceanic basins the duration of each geodynamic stage for each terrane is obtained from the chronology of the tectonostratigraphic facies change the general trend is younger ages observed in the southern terranes and older ages towards the northern terranes the two alternative tectonostratigraphic models are applied in the two groups of terranes and the chronology of the geodynamic paleogeographic stages is estimated the hellenic subducted slab as shown in the seismic tomographic images is correlated to the terrane paleogeography using the estimated widths and the average subduction rates the upper 1700 km of the slab correspond to the three southern more external terranes whereas the remainingpart of the slab may represent the other more internal terranes a palinspastic model of the hellenides is presented taking into account the chronology of each stage for every terrane obduction of ophiolites over the southern platforms is observed in all four oceanic basins blueschist exhumation formation of core complexes and tectonic windows through extensional detachments occur after micro collision of continental terranes platforms and their isostatic uplift within the upper plate after their detachment from the subducting slab

the santorini volcanic complex and its relation to the stratigraphy and structure of the aegean arc greece abstract the santorini complex is the most active volcano of the southern aegean volcanic arc its relationship to the surrounding area was examined by using a dense set of seismic reflection profiles three seismic units were recognized in the surrounding area unit a consists of generally strong subparallel continuous reflectors into which two subunits a1 and a2 were distinguished that are unconformable in the upper slopes and the shelves and conformable at lower sectors the age of unit a which consists mainly of volcaniclastic sediments is considered quaternary unit b consists of faulted and slightly folded strong continuous reflectors that pinch out at lower basin margin sectors than unit a its age is mainly pliocene its sediments are probably terrigenous and it was deposited in the basins at the early and middle stages of their formation finally unit c represents the acoustic mainly metamorphic basement the dominant tectonic structure in the area is the ne sw trending normal faults superimposed on earlier e w normal faults the santorini complex includes one caldera at santorini and one crater at columbus about 7 km to the northeast the caldera of santorini consists of four deep basins depth from 290 to 390 m the columbus volcano has a well defined crater with a single basin depth 500 m and was formed in 1650 a d by an underwater explosion the start of volcanic activity of santorini which initiated in the early pleistocene and continues up until today may be related to the change in the normal fault orientation from e w to ne sw and to the unconformity between units a and b

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

volcano tectonic evolution of the polygenetic kolumbo submarine volcano santorini aegean sea abstract here we show for the first time the 3d structural evolution of an explosive submarine volcano by means of reflection seismic interpretation four to five vertically stacked circular and cone shaped units consisting mainly of volcaniclastics build the kolumbo underwater volcano which experienced its first eruption 70 ka ago and its last explosive eruption 1650 ad 7 km ne of santorini volcano southern aegean sea the summed volume of volcaniclastics is estimated to range between 13 22 km3 the entire kolumbo volcanic complex has a height of 1 km and a diameter of 11 km all volcaniclastic units reveal the same transparent reflection pattern strongly suggesting that explosive underwater volcanism was the prevalent process growth faults terminate upwards at the base of volcaniclastic units thus representing a predictor to an eruption phase similarities in seismic reflection pattern between kolumbo and near by volcanic cones imply that the smaller cones evolved through explosive eruptions as well hence the central aegean sea experienced several more explosive eruptions 23 than previously assumed thus justifying further risk assessment however the eruption columns from the smaller volcanic cones did not reach the air and consequently no sub aerial pyroclastic surge was created the anydros basin that hosts kolumbo volcanic field opened incrementally nw to se and parallel to the pliny and strabo trends during four major tectonic pulses prior to the onset of underwater volcanism

tectono stratigraphic evolution through successive extensional events of the anydros basin hosting kolumbo volcanic field at the aegean sea greece abstract the structural evolution of the south aegean sea is little explored due to the lack of marine seismic data our present day understanding is mainly based on some island outcrops and gps measurements in this study we discuss the rather incremental opening of the anydros basin in the pliocene during six major tectonic pulses and the subsequent basin fill processes by interpreting seismic data and derived time isochore maps between the active pulses basin floor tilting persisted on a much lower rate seismic data illustrate the depositional processes in the emerging anydros basin the observation of onlap fill strata divergent reflection pattern moat channels and contourite drifts imply that deposition was controlled by turbidity and contour currents as well as the tilting basin floor the metamorphic attico cycladic basement shows a rise that aligns along an nw se directed axis crossing anydros island this axis marks a structural change of the santorini amorgos ridge and thus represents a major structural boundary dip angles of ne sw trending major faults like the santorini amorgos fault indicate normal faulting to be the superior mechanism forming the present horst and graben environment hence the area is likely to be in a state of nw se directed extensional stresses forming the asymmetric graben structure of anydros secondary fault clusters strike the same direction but show much steeper dip angles possibly indicating strike slip movement or resulting from deformational stresses along the hinge zones of the normal faults the majority of the faults we discovered are located in the area of earthquake clusters which is another indication of recent faulting ring faults around kolumbo submarine volcano result from caldera collapse and mark the diameter of the magma chamber approximately to 20 km

the 1956 greek tsunami recorded at yafo israel and its numerical modeling floating type tidal gauge installed in the port of yafo israel the tsunami was triggered by an earthquake in the aegean sea on 9 july 1956 this paper presents a retrieval of tsunami waves from the record at the first stage of the study an attempt had been undertaken to reproduce the 1956 tsunami assuming a coseismic nature of its generation source although these simulations resulted in tsunami waves with their amplitude close to that obtained from the record measured at yafo they did not contain significant spectral energy components with periods of 15 min as appear in the spectra of 1956 tide gauge records when landslide movement triggered by the main shock and or by the largest aftershock is suggested as a source of these tsunami waves the spectra of the resulted marigram obtained in the proximity to yafo contain harmonics with frequencies very close to those measured this corroborates the landslide nature of the tsunamigenic source responsible for generation of higher frequency relative to the tidal waves energy components the peak periods determined via spectral analysis of the recent tide gauge records 1 year and longer in the absence of tsunami events vary from 50 to 60 min similar periods have been revealed in a special numerical study dealing with longwave propagation toward the coast of israel thus confirming that their origin is related to continental shelf resonance these resonance periods differ significantly from those found for the 1956 tsunami

reassessment of earthquakes 1900 1999 in the eastern mediterranean and the middle east summary we have reappraised locations and surface wave magnitudes of earthquakes this century in the eastern mediterranean and the middle east between 10 and 44 n and 18 and 70 e the results are presented in an improved parametric catalogue of shallow earthquakes h 40 km large enough ms 6 0 to be of interest in seismotectonics and earthquake engineering a considerable number of early events of 6 ms 7 2 not included in other catalogues have been identified and their magnitudes assessed we find that iss isc locations are systematically shifted by 10 30 km to the north or northeast of their macroseismic epicentres also we derived a regional average relationship between log m0 and ms we show that the correlation of magnitude with epicentral intensity is very weak as is expected and a source of error in frequency relations

historical and pre historical tsunamis in the mediterranean and its connected seas geological signatures generation mechanisms and coastal impacts abstract the origin of tsunamis in the mediterranean region and its connected seas including the marmara sea the black sea and the sw iberian margin in the ne atlantic ocean is reviewed within the geological and seismotectonic settings of the region a variety of historical documentary sources combined with evidence from onshore and offshore geological signatures geomorphological imprints observations from selected coastal archeological sites as well as instrumental records eyewitnesses accounts and pictorial material clearly indicate that tsunami sources both seismic and non seismic e g volcanism landslides can be found in all the seas of the region with a variable tsunamigenic potential local regional and basin wide tsunamis have been documented an improved map of 22 main tsunamigenic zones and their relative potential for tsunami generation is presented from west to east the most important tsunamigenic zones are situated offshore sw iberia in the north algerian margin in the tyrrhenian calabria and messina straits in the western and eastern segments of the hellenic arc in the corinth gulf of central greece in the levantine sea offshore the dead sea transform fault and in the eastern side of the marmara sea important historical examples including destructive tsunamis associated with large earthquakes are presented the mean recurrence of strong tsunamis in the several basins varies greatly but the highest event frequency 1 96 years is observed in the east mediterranean basin for most of the historical events it is still unclear which was the causative seismic source and if the tsunami was caused by co seismic slip by earthquake triggered submarine landslides or by a combination of both mechanisms in pre historical times submarine volcanic eruptions i e caldera collapse massive pyroclastic flows volcanogenic landslides and large submarine landslides caused important tsunamis although little is known about their source mechanisms we conclude that further investigation of the tsunami generation mechanisms is of primary importance in the mediterranean region inputs from tsunami numerical modeling as well as from empirical discrimination criteria for characterizing tsunami sources have been proved particularly effective for recent well documented aseismic landslide tsunamis e g 1963 corinth gulf 1979 cote d azur 1999 izmit bay 2002 stromboli volcano since the tsunami generation mechanisms are controlled by a variety of factors and given that the knowledge of past tsunami activity is the cornerstone for undertaking tsunami risk mitigation action future interdisciplinary research efforts on past tsunamis are needed

the 1956 earthquake and tsunami in amorgos greece summary we conduct a comprehensive study of the amorgos greece earthquake and tsunami of 1956 july 09 the largest such event in the aegean sea in the 20th century systematic relocation of the main shock and 34 associated events defines a rupture area measuring 75 40 km the use of the preliminary determination of focal mechanism algorithm resolves the longstanding controversy about the focal geometry of the event yielding a normal faulting mechanism along a plane dipping to the southeast which expresses extensional tectonics in the back arc behind the hellenic subduction zone the seismic moment of 3 9 10 27 dyn cm is the largest measured in the past 100 yr in the mediterranean basin a quantitative database of 68 values of tsunami run up was built through the systematic interview over the past 5 yr of elderly eyewitness residents of 16 aegean islands and the turkish coast of asia minor it confirms values of up to 20 m on the southern coast of amorgos 10 m on astypalaia and up to 14 m on the western coast of folegandros 80 km to the west of the epicentre these values largely in excess of the inferred seismic slip at the source and their concentration along isolated segments of fault are incompatible with the generation of the tsunami by the seismic dislocation and require an ancillary source in the form of a series of landslides triggered by the earthquake and or its main aftershocks a model confirmed by hydrodynamic simulations using both the dislocation source and models of landslide sources

the messinian salinity crisis past and future of a great challenge for marine sciences forty years after the image of the mediterranean transformed into a giant salty lake was first conceived the fascinating history of the messinian salinity crisis msc still arouses great interest across a large and diverse scientific community early outcrop studies which identified severe palaeoenvironmental changes affecting the circum mediterranean at the end of the miocene were followed by investigations of the marine geology during the 1950s to 1970s these were fundamental to understanding the true scale and importance of the messinian event now after a long period of debate over several entrenched but largely untested hypotheses a unifying stratigraphic framework of msc events has been constructed this scenario is derived mainly from onshore data and observations but incorporates different perspectives for the offshore and provides hypotheses that can be tested by drilling the deep mediterranean basins the msc was an ecological crisis induced by a powerful combination of geodynamic and climatic drivers which had a great impact on the subsequent geological history of the mediterranean area and on the salinity of the global oceans these changed the mediterranean s connections with both the atlantic ocean and the freshwater paratethyan basins causing high amplitude fluctuations in the hydrology of the mediterranean the msc developed in three main stages each of them characterized by different palaeoenvironmental conditions during the first stage evaporites precipitated in shallow sub basins the msc peaked in the second stage when evaporite precipitation shifted to the deepest depocentres and the third stage was characterized by large scale environmental fluctuations in a mediterranean transformed into a brackish water lake the very high resolution timescale available for some late miocene intervals in the mediterranean makes it possible to consider environmental variability on extremely short time scales including in some places annual changes despite this fundamental questions remain some of which could be answered through new cores from the deepest mediterranean basins improvements in seismic imaging and drilling techniques over the last few decades make it possible to plan to core the entire basinal messinian succession for the first time the resulting data would allow us to decipher the causes of this extreme environmental change and its global scale consequences

eastern mediterranean surface water temperatures and d18o composition during deposition of sapropels in the late quaternary 0indices and d 18 o of planktonic foraminifer calcite d 18 ofc across late pleistocene sapropel intervals show that d 18 ofc decreased between 1 and 4 6 and sst increased between 0 7 and 6 7 c maximal d 18 oseawater depletion of eastern mediterranean surface waters at the transition is between 0 5 and 3 0 and in all but one case exceeded the depletion seen in a western mediterranean core the depletion in d 18 oseawater is most pronounced at sapropel bases in agreement with an initial sudden input of monsoon derived freshwater most sapropels coincide with warming trends of sst the density decrease by initial freshwater input and continued warming of the sea surface pooled fresh water in the surface layer and prohibited deep convection down to ageing deep water emplaced during cold and arid glacial conditions an exception to this pattern is glacial sapropel s6 its largest d 18 oseawater depletion 3 is almost matched by the depletion in the western mediterranean sea and it is accompanied by surface water cooling following an initially rapid warming phase a second period of significant isotopic depletion is in isotope stage 6 at the 150 kyr insolation maximum while not expressed as a sapropel due to cold sst it is in accord with a strengthened monsoon in the southern catchment index terms 1055 geochemistry organic geochemistry 1620 global change climate dynamics 3309 4267 oceanography general paleoceanography 9604 information related to geologic time cenozoic keywords mediterranean sea sapropels sea surface temperatures oxygen isotopes quaternary citation emeis k c et al eastern mediterranean surface water temperatures and d 18 o composition during deposition of sapropels

sediment instability and slumping in the southern aegean sea and the case history of the 1956 tsunami the aegean and ionian seas in greece and adjacent regions constitute the most tsunamigenic areas in europe the most recent large tsunami was a 20 m high wave that generated on 9 july 1956 in the amorgos basin south aegean sea in association with a ms 7 5 earthquake we first present new evidence for sea floor sediment instability from bathymetric shallow and intermediate penetration seismic profiles and a number of gravity cores second we investigate the generation mechanism of the 1956 large tsunami the determination of the mean repeat time of the minimum seismic ground acceleration required for slump triggering of sediment masses showed that in particular south aegean basins like the argolikos and amorgos ones the mean recurrence of massive sediment slumping ranges between 50 and 100 years in other basins however it is around or more than 500 years in the southern amorgos basin a large scale sediment slump has been identified this was probably triggered by the 1956 mainshock and or its aftershock of ms 7 2 that occurred in the slump source area 13 min after the mainshock the generation of the 1956 tsunami is attributed to the combined action of a reactivated large normal fault to the south of the amorgos island and to the occurrence of the large sediment slump

the last climatic cycle at la grande pile vosges france a new pollen profile a new pollen diagram has been made from an old unanalyzed core from la grande pile gp xx correlations with the previous work of woillard 1975 1978 leads to the following conclusions the end of the eemian was marked by a minor climatic change prior to the melisey i stadial the ognon ii and ognon iii interstadials are not consistent and correspond to the level of reworking of mesophilous taxa during the last pleniglacial the limitations of the botanical interpretation of pollen spectra from the last pleniglacial are underlined lastly bruckenthalia and larix are identified for the first time at la grande pile the respective roles of these taxa following the eemian are additional arguments for correlating the st germain i and ii with the early weichsel interstadials in the north of middle europe

expanding extension subsidence and lateral segmentation within the santorini amorgos basins during quaternary implications for the 1956 amorgos events central south aegean sea greece abstract new bathymetric and seismic reflection data from the santorini amorgos tectonic zone in the southern cyclades have been analysed and a description of the morphology and tectonic structure of the area has been presented the basins of anhydros amorgos and santorini anafi have been distinguished together with the intermediate anhydros horst within the ne sw oriented santorini amorgos tectonic zone which has a length of 60 70 km and a width of 20 25 km the basins represent tectonic grabens or semi grabens bordered by the active marginal normal faults of santorini anafi amorgos ios anhydros and astypalaea the santorini anafi amorgos and ios marginal faults have their footwall towards the nw where alpine basement occurs in the submarine scarps and their hangingwall towards the southeast where the quaternary sediments have been deposited with maximum thickness of 700 m six sedimentary units 1 6 have been distinguished in the stratigraphic successions of the santorini anafi and the western anhydros basin whereas in the rest area only the upper four units 3 6 have been deposited this shows the expansion of the basin with subsidence during the quaternary due to ongoing extension in a northwest southeast direction growth structures are characterized by different periods of maximum deformation as this is indicated by the different sedimentary units with maximum thickness next to each fault transverse structures of northwest southeast direction have been identified along the santorini amorgos tectonic zone with distinction of the blocks segments of santorini anhydros kolumbo anhydros islet and amorgos recent escarpments with 7 9 m offset observed along the amorgos fault indicate that this was activated during the first earthquake of the 7 5 magnitude 1956 events whereas no recent landslide was found in the area that could be related to the 1956 tsunami

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

microseismic activity in the hellenic volcanic arc greece with emphasis on the seismotectonic setting of the santorini amorgos zone abstract the volcanic arc of the hellenic subduction zone with its four volcanic centers is of major relevance when evaluating the seismovolcanic hazard for the aegean region we present results from a 22 station temporary seismic network cycnet in the central hellenic volcanic arc hva cycnet recordings allow to analyze the level and spatio temporal evolution of microseismic activity in this region for the first time a total of 2175 events recorded between september 2002 and july 2004 are analyzed using statistical methods cluster analysis and relative relocation techniques we identify distinct regions with significantly varying spatio temporal behavior of microseismicity a large portion of the seismic activity within the upper crust is associated with the presence of islands representing horst structures that were generated during the major oligocene extensional phase in contrast the central part of the cyclades metamorphic core complex remains aseismic considering our magnitude threshold of 1 8 except one spot where events occur swarm like and with highly similar waveforms the highest activity in the study area was identified along the sw ne striking santorini amorgos zone within this zone the submarine columbo volcano exhibits strong temporal variations of seismic activity on a high background level this activity is interpreted to be directly linked to the magma reservoir and therein the migration of magma and fluids towards the surface ne of columbo where no volcanic activity has yet been reported we observe a similar seismicity pattern with small scaled activity spots that might represent local pathways of upward migrating fluids or even developing volcanic activity within this zone of crustal weakness in contrast the santorini and milos volcanic complexes do not show significant temporal variations and low to moderate background activity respectively relating our results to the distribution of historical earthquakes and the gps derived horizontal velocity field we conclude that the santorini amorgos zone is presently in the state of right lateral transtension reflecting a major structural boundary of the volcanic arc subdividing it into a seismically and volcanically quiet western and an active eastern part