the quaternary geology of the labrador shelf the regional distribution of glacial and postglacial sediments on the labrador shelf was mapped by medium and high resolution seismics and shows a succession of tills that extend to the continental shelf edge at approximately 600 m the uppermost of these tills is less laterally extensive and does not occur on the labrador shelf bank tops in water depths less than 160 m we infer that the last glacial episode was less extensive than the preceding ones glaciomarine stratified silts and postglacial muds are found overlying the upper till in the deep basins that separate the banks the upper till glaciomarine silts and postglacial muds are interpreted to constitute one complete deglacial cycle radiocarbon age determination suggests this deglacial sequence began at approximately 20 000 years bp on the northernmost labrador shelf and hudson strait seismic evidence indicates a late glacial readvance locally deposited a till that overlies the glaciomarine sediments associated with the last glacial advance

horizontal crustal motion in the central and eastern mediterranean inferred from satellite laser ranging measurements four campaigns to acquire satellite laser ranging slr measurements at sites in the mediterranean region have been completed these measurements to the lageos satellite made largely by mobile systems cover a time span beginning in november 1985 and ending in june 1993 the range data from 18 sites in the central and eastern mediterranean have been simultaneously analyzed with data acquired by the remainder of the global laser tracking network estimates of horizontal motion were placed into a regional northern europe fixed kinematic reference frame uncertainties are on the order of 5 mm yr for sites having at least four occupations by mobile systems and approach 1 mm yr for permanently located sites with long histories of tracking the resulting relative motion between sites in the aegean exhibit characteristics of broadly distributed pattern of radial extension but at rates that are about 50 larger than those implied from studies of seismic strain rates based on seismicity of magnitude 6 or greater or across the region the motion estimated for sites in turkey exhibit velocity components associated with the westward motion of the anatolian block relative to eurasia these results provide a present day snapshot of ongoing deformational processes as experienced by the locations occupiedmore by slr systems less

gps measurements of current crustal movements along the dead sea fault 1 a network of 11 continuous gps stations was constructed in israel between 1996 and 2001 to monitor current crustal movements across the dead sea fault dsf analysis of the gps measurements with respect to the itrf2000 reference frame yields time series of daily site positions containing both secular and seasonal variations horizontal secular variations station velocities are evaluated with respect to the main tectonic element in the region the dsf we use six velocity vectors west of the dsf to define the itrf2000 pole of the sinai sub plate and rotate the velocity field for all stations into the sinai reference frame srf the velocity vectors reveal that 1 relative station movements are less than 4 mm yr 2 the nine stations located west of the dsf show no statistically significant motion with respect to the srf and 3 the two stations located in the golan heights katz and elro and a station in damascus syria udmc show 1 7 2 8 mm yr northward motion with respect to sinai indicating a left lateral motion along the dsf using locked fault models we estimate the current slip rate across the dsf as 3 3 0 4 mm yr if we exclude the northern sites elro and udmc which are located adjacent to the compressional jog of mount hermon our estimate increases to 3 7 0 4 mm yr the calculated itrf2000 sinai eurasia and nubia poles and a published pole for arabia allow us to calculate the current relative plate motion of sinai arabia and sinai nubia

plate tectonic framework for the october 9 1996 cyprus earthquake we determine the centroid depths for the mw 6 8 october 9 1996 cyprus earthquake and its largest after shock to 32 and 27 km respectively by modeling p and sh waveforms these depths are consistent with shallow subduction as the african plate west of cyprus penetrates beneath the anatolian plate we calculate the pole of rotation between anatolia and africa and determine their relative motion the result indicates that along the cyprean arc convergence between the african and anatolian plate in agreement with the observed seismicity decreases from west to east the northeasterly striking nodal plane is suggested as the plane on which the cyprus earthquake ruptured since its strike agrees well with the derived plate motion vector the faulting geometry suggests the emergence of a strike slip tear fault within the african plate separating the continental eratosthenes seamount south of cyprus from the oceanic african lithosphere that subducts west of cyprus

seismotectonics of the sinai subplate the eastern mediterranean region summary we define the sinai subplate from a seismotectonic perspective as a distinct component in the plate tectonics of the eastern mediterranean region this is based on the tectonic characteristics of a comprehensive listing of all ml 4 recorded seismicity in the region during the 20th century on newly calculated and recalculated fault plane mechanisms of first p wave arrivals and on published solutions based on waveform inversion of broad band data the low seismicity level and scarcity of strong events in the region required a thorough search for useful data and a careful examination of the reliability of the focal solutions we gathered all available records of first p wave onsets from the iss and isc bulletins and the local seismic networks altogether we were able to calculate 48 new focal mechanisms and 33 recalculated ones of events that occurred during the years 1940 1992 with the increasing number of teleseismic and regional broad band stations in the later years we added 37 solutions based on teleseismic and regional waveform inversions of events that occurred during 1977 2001 these mechanisms enabled us to examine the seismotectonic character of the sinai subplate the strike and rake directions of the calculated mechanisms usually reflect the geometry and the large scale type of deformation observed along the boundaries of the sinai subplate the dead sea transform the cypriot arc convergent zone and the suez rift nevertheless along each of these boundaries we found anomalous solutions that attest to the complexity of the deformation processes along plate margins earthquakes along the dead sea transform exhibit mainly sinistral transtension and transpression reflecting its leaky manner and local change in the transform geometry the presence of other unexpected mechanisms near the transform however reflects the heterogeneous deformation it induces around as expected thrust mechanisms along the cypriot arc mirror its convergent nature and typical curved geometry transtension and transpressional solutions in the eastern segment of the arc reflect the sinistral shear motion between anatolia and sinai there however shear mechanisms found between cyprus and the eratosthenes seamount pose a problem regarding its collision process most intriguing of all are ml 4 thrust and shear solutions found in the gulf of suez they are associated with predominantly normal mechanisms within a rift zone and therefore constitute a unique phenomenon yet to be deciphered

pacific offshore record of plinian arc volcanism in central america 2 tephra volumes and erupted masses 1 sediment gravity cores collected from the pacific seafloor offshore central america contain numerous distal ash layers from plinian type eruptions at the central american volcanic arc dating back to more than 200 ka in part 1 of this contribution we have correlated many of those ash layers between cores and with 26 tephras on land the marine ash layers cover areas of up to 106 km2 in the pacific ocean and represent a major fraction 60 90 of the erupted tephra volumes because the pacific coast lies within a few tens of kilometers downwind from the volcanic arc combining our own mapping efforts on land and published mapping results with our marine data yields erupted volumes of all major tephras along the arc that range from 1 to 420 km3 recalculated to erupted magma mass the widespread tephras account for 65 of the total magma output at the arc complementing our tephra data with published volumes of the arc volcanic edifices and volcano ages we calculate the long term average magma eruption rates for each volcano moreover we use incompatible element variations to calculate the cumulate masses that were fractionated during variable degrees of differentiation this yields a minimum estimate of long term average magma production rate at each volcano because intrusives without surface expression and losses by erosion are not accounted for peak magma production rates increase from costa rica to guatemala but there is considerable scatter within each region and large differences even between neighboring volcanoes

seismicity of the cyprus region we have used a combination of macroseismic and instrumental techniques to re evaluate the seismicity of cyprus and the surrounding region for the period 1890 1900 we identified 56 events which we believe to have a surface wave magnitude ms of 4 5 or greater early events are located by felt effects alone and macroseismic information is used to improve the location of many later events we find the broad pattern of seismicity follows that given by standard listings an area of weak seismicity to the north west of cyprus in the gulf of antalia includes intermediate depth events as are found in the hellenic arc to the west a gap of reduced activity separates this activity from that of the main region of cyprus where we could find no evidence for sub crustal foci there appears to be no present seismological connection along the presumed plate boundary to the north east to the junction of the east anatolian fault and the extension of the dead sea rift system we find a much greater level of activity in the first part of this century than is given in the standard listings such as that of the isc up to 1963 we identified 47 events of ms 4 5 compared with only 10 given in the isc files recent improved station coverage locates more events in the region but these have not been of large magnitude and the moment release in recent decades has been appreciably less than earlier in the century for the events in our list the total moment release is 2 7x 1019 nm with 75 of this originating in the main cyprus region we reaffirm the danger of uncritical use of standard earthquake listings for tectonic interpretation and in particular for hazard evaluation in areas such as this where neither the historical nor the instrumental seismicity record is complete

the florence rise the western bend of the cyprus arc the florence rise is a submarine feature extending from the island of cyprus in the southeast to the anaximander mountains which form the northwestern end of the cyprus arc south of western turkey the eastern florence rise includes a topographic high near cyprus while its central domain displays relatively low relief most of the major elements of relief appear to be bounded by faults in the light of new geophysical data an underlying core ridge likely made of pre pliocene nappes emplaced from the north separates relatively undeformed sediments to the northeast from actively shearing sediments and seismic basement to the southwest a dextral arc parallel wrench zone at least 15 km wide has created a lineated seafloor texture and accompanying flower structures within the central florence rise apparent riedel type conjugate shears within this system cut across the florence rise and mark changes in the relief along the arc several mud volcanoes are observed within the wrench zone and along associated faults indicating that overpressuring at depth is relieved by these faults there is no evidence for any typical subduction along this arcuate trend which is considered to act as the present boundary between the african and anatolian aegean plates in contrast both the nature of faulting and the morphology of the florence rise seem to indicate some degree of transpressional coupling between the two plates even though they appear disconnected by a tectonic boundary in the form of a major shear zone

seismicity of the eastern mediterranean region perspective from the sinai subplate we conducted a comprehensive study of the seismicity of the eastern mediterranean and examined its relation to the regional plate tectonics based on various published catalogs we have constructed a new list of ml 4 earthquakes which were recorded during the years 1900 1991 and represents most of the seismic moment released in the area over this period b values are 1 02 1 0 and 1 07 for the whole sinai subplate the dead sea transform and the cypriot arc respectively seismic efficiency of the dead sea transform is very low about 7 stressing the role of aseismic deformation in that plate border most of the major and moderate events ml 5 occur in belts associated with the geologically documented borders of the sinai subplate the cypriot convergent arc in the north the dead sea transform in the east and the rift of suez in the southwest the latter like the gulf of eilat aqaba was considered aseismic during the first half of the century the northwestern border however could not be delineated low level activity appears within the subplate especially north of latitude 32 n reflecting the breakdown of this part of sinai as it approaches the cypriot convergence zone though most of the seismic moments tend to concentrate along the subplate borders some moderate activity spreads out in wide belts which reflect the complexity of deformation accompanying motion along the subplate borders

tectonic significance of the eratosthenes seamount a continental fragment in the process of collision with a subduction zone in the eastern mediterranean ocean drilling program leg 160 abstract one of the objectives of odp leg 160 in the eastern mediterranean sea april may 1995 was concerned with the study of processes of genesis and incipient collision of an inferred crustal fragment the eratosthenes seamount with the active margin of the eurasian plate to the north represented by southern cyprus the upper part of the eratosthenes seamount i e upper several hundred metres was found to include both shallow and deep water carbonates dating back to early cretaceous time shallow water platform carbonate deposition similar to that of the onshore levant continental margin to the east i e part of the north african plate was followed by submergence to bathyal depths 1000 m in the late cretaceous to middle eocene punctuated by depositional and tectonic hiatuses tectonic uplift approximately 1 km was followed by shallow water carbonate deposition in the early miocene the platform was exposed during the messinian desiccation crisis during the early pliocene the platform subsided to bathyal depths associated with localised accumulation of limestone debris flows subsidence accelerated in the late pliocene early pleistocene reaching a present day maximum depth of ca 2500 m deformation of the eratosthenes seamount i e subsidence and high angle faulting resulted from crustal flexure induced by southward overthrusting of the cyprus active margin tectonic subsidence of the eratosthenes seamount was approximately synchronous with rapid surface uplift of the over riding plate the troodos ophiolite of southern cyprus this uplift is explained in terms of incipient collision of an eratosthenes continental fragment with a subduction trench coupled with the effects of diapiric protrusion of serpentinite located within the core of the troodos ophiolite the eratosthenes drilling thus documented a modern analogue of subduction collisional processes leading to accretion of continental fragments and carbonate platforms in orogenic belts

tectonic connection of the hellenic and cyprus arcs and related geotectonic elements abstract the cyprus arc system forms part of a well defined presently active plate boundary and is a critical area for understanding the evolution of the eastern mediterranean sea the available seismic reflection profiles are utilised in order to establish the nature and origin of the main tectonic features of the arc which include 1 a the cyprus trench displaying evidence of underthrusting and morphostructural features typical of subduction zones 2 b the pytheus trench associated with right lateral strike slip movement and connecting the western end of the cyprus trench to the strabo trench sector of the hellenic trench system 3 c a predominantly transtensional fault zone connecting the easternmost part of the cyprus trench via the baer bassit overthrust zone in syria to the dead sea transform fault system 4 d a zone of complex deformation involving thrust and transform elements running from the misis mountains of southeast turkey through the kyrenia range in cyprus to the gulf of antalya and transected by roughly n s major shears notably the cape gelidonya anaximander mountains strike slip zone which appears to form the western boundary of the present active system of the cyprus arc the nature of the shallow structures associated with the cyprus arc is consistent with a geotectonic model involving some post miocene rotation of the south anatolian cyprus block probably induced by escape dynamics resulting from continent continent collision in eastern turkey and the development of the maras triple junction in southeastern turkey the alternation of plate boundary sectors respectively characterised by thrusting and strike slip displacement suggests that the shallow crust in this part of the eastern mediterranean is in a compartmented and relatively brittle state allowing accumulated boundary stresses to be accommodated largely by displacements and deformation along secondary features

seismic images at the convergence zone from south of cyprus to the syrian coast eastern mediterranean abstract multichannel seismic profiles from cruise 5 of the r v akademik nikolaj strakhov provide the first deep seismic reflection images and extensive coverage south and east of cyprus five nw se trending seismic lines cross an area of active continental collision main tectonic structures are the eratosthenes seamount collision zone the hecateaus rise and the latakia larnaca ridge systems the levantine basin extends to the south all over the area the data required careful processing due to the low fold coverage the reverberatory character of the signal and the strong multiple energy the seismic results clearly image the thick sedimentary sequence of the levantine basin this basin is observed to terminate abruptly at the junction with the hecateaus rise south of cyprus to the east and north the deformation appears to be partitioned along two separated structures next to the latakia and larnaca ridges they correspond to major oblique fault systems

seismotectonics of the cyprian arc summary the cyprian arc forms the plate boundary between the anatolian plate in the north and the nubian and sinai plates in the south we examine the tectonic setting and seismic activity along the arc in light of new geodetic studies indicating relative ne sw plate motions across the arc the first order tectonic variations are determined by the arc s geometry the eastern arc oriented subparallel to relative motion is dominated by transcurrent tectonism the western arc is oriented almost normal to relative plate motion and is subjected to convergent processes variations in the level and depth of seismic activity along the western arc suggest that the northwestern section of the arc represents a subduction boundary whereas the southeastern section represents a collision boundary the two tectonic domains of the western arc are separated by a ne sw trending tear fault which produces large earthquakes such as the mw 6 8 1996 paphos earthquake we compare the geometrically similar cyprian and hellenic arcs and find significant differences in the rate direction and type of convergence across the two arcs the hellenic arc is subjected mainly to subduction whereas the shorter cyprian arc is subjected to subduction collision and transcurrent tectonic processes

active tectonics of the alpine himalayan belt between western turkey and pakistan summary over 80 new fault plane solutions combined with satellite imagery as well as both modern and historical observations of earthquake faulting are used to investigate the active tectonics of the middle east between western turkey and pakistan the deformation of the western part of this region is dominated by the movement of continental material laterally away from the lake van region in eastern turkey this movement helps to avoid crustal thickening in the van region and allows some of the shortening between arabia and eurasia to be taken up by the thrusting of continental material over oceanic type basement in the southern caspian mediterranean makran and black sea thus central turkey bounded by the north and east anatolian strike slip faults is moving west from the van region and overrides the eastern mediterranean at two intermediate depth seismic zones one extending between antalya bay and southern cyprus and the other further west in the hellenic trench the motion of northern iran eastwards from the van region is achieved mainly by a conjugate system of strike slip faults and leads to the low angle thrusting of iran over the southern caspian sea the seismicity of the caucasus shows predominantly shortening perpendicular to the regional strike but there is also some minor elongation along the strike of the belt as the causcasus overrides the caspian and black seas the deformation of the eastern part of this region is dominated by the shortening of iran against the stable borders of turkmenistan and afghanistan the north east direction of compression seen in zagros is also seen in north east iran and the kopet dag where the shortening is taken up by a combination of strike slip and thrust faulting large structural as well as palaeomagnetic rotations are likely to have occurred in ne iran as a result of this style of deformation north south strike slip faults in southern iran allow some movement of material away from the collision zone in ne iran towards the makran subduction zone where genuinely intermediate depth seismicity is seen within this broad deforming belt large areas such as central turkey nw iran azerbaijan central iran and the southern caspian appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200 300 km wide the motion of these blocks can usefully be described by poles of rotation the poles presented in this paper predict motions consistent with those observed and also predict the opening of the gulf of iskenderun ne of cyprus the change within the zagros mountains from strike slip faulting in the nw to intense thrusting in the se and the relatively feeble seismicity in se iran baluchistan this description also explains why the north south structures along the iran afghanistan border do not cut the east west ranges of the makran within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation even though motions at the surface may be concentrated on faults the evolution of fault systems within the active zones is controlled by geometric constraints such as the requirement that simultaneously active faults do not in general intersect many of the active processes discussed in this paper particularly large scale rotations and lateral movement along the regional strike are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them

gps constraints on africa nubia and arabia plate motions summary we use continuously recording gps cgps and survey mode gps sgps observations to determine euler vectors for relative motion of the african nubian arabian and eurasian plates we present a well constrained eurasia nubia euler vector derived from 23 igs sites in europe and four cgps and three sgps sites on the nubian plate 0 95 4 8 n 21 8 4 3 e 0 06 0 005 myr 1 we see no significant 1m m yr 1 internal deformation of the nubian plate the gps nubian eurasian euler vector differs significantly from nuvel 1a 21 0 4 2 n 20 6 0 6 e 0 12 0 015 myr 1 implying more westward motion of africa relative to eurasia and slower convergence in the eastern mediterranean the arabia eurasia and arabia nubia gps euler vectors are less well determined based on only one cgps and three sgps sites on the arabian plate the preliminary arabia eurasia and arabia nubia euler vectors are 27 4 1 0 n 18 4 2 5 e 0 40 0 04 myr 1 and 30 5 1 0 n 25 7 2 3 e 0 37 0 04 myr 1 respectively the gps arabia nubia euler vector differs significantly from nuvel 1a 24 1 1 7 n 24 0 3 5 e 0 40 0 05 myr 1 but is statistically consistent at the 95 per cent confidence level with the revised euler vector reported by chu gordon based on a re evaluation of magnetic anomalies in the red sea 31 5 1 2 n 23 0 2 7 e 0 40 0 05 myr 1 the motion implied in the gulf of aqaba and on the dead sea fault dsf by the new gps nubia arabia euler vector i e ignoring possible sinai block motion and possible internal plate deformation grades from pure left lateral strike slip in the gulf and on the southern dsf with increasing compression on the central and northern dsf with relative motion increasing from 5 6 to 7 5 mm yr 1 1m m yr 1 from south to north along the northern dsf i e north of the lebanon restraining bend motion is partitioned between 6 1m m yr 1 left lateral motion parallel to the fault trace and 4 1m m yr 1 faultnormal compression relative motions on other plate boundaries including the anatolian and aegean microplates derived from the gps euler vectors agree qualitatively with the sense of motion indicated by focal mechanisms for large crustal earthquakes m 6 where data are available on fault slip rates on plate bounding faults north anatolian fault east anatolian fault dead sea fault red sea rift they are generally lower than but not significantly different from the full plate motion estimates suggesting that the majority of relative plate motion is accommodated on these structures

structure and tectonics of the eastern cyprean arc abstract the geometry and nature of the eastern segment of the cyprean arc are little understood several hypotheses have been put forward to explain the tectonic situation there recent marine geophysical data for this region mapped several deep and shallow structural elements the most prominent element is a ridge the latakia ridge which extends from the syrian coast near latakia south westward to meet with an east west trending bathymetric escarpment east of the hecateus ridge the new seismic profiles suggest that these two elements mark the present plate boundary along the eastern cyprean arc the latakia ridge is a young and still active feature it was formed by southward migration of the plate boundary the ridge probably originated as a large thrust sheet which later when the convergence direction was changed became a zone of wrench faulting the ridge is still forming today and serves as a dam to the sediments north of it the wrench faulting activity is more pronounced in the eastern segment of the ridge

plate convergence in the cyprean arc abstract the cyprean arc is a part of the plate boundary between afro arabia and eurasia in the eastern mediterranean a re examination of the geophysical properties of the cyprean arc together with an analysis of multichannel seismic reflection profiles now available in the cyprean arc area provides a clearer view of the tectonic setting and processes in this region seismic activity and a gravity anomaly indicate that a northward subduction of oceanic material related to the african plate beneath the turkish plate is the mode of convergence along the western segment of the cyprean arc subduction is interrupted due to the collision of the eratosthenes seamount at the central segment of the cyprean arc which forms a zone of intense deformation the zone of deformation spreads away and disappears in the eastern segment of the cyprean arc no signs for deformation have been found in this portion either in the multichannel seismic reflection profiles in the seismicity or in the bathymetry the change in the mode of convergence and in the type of deformation along the cyprean arc is induced by crustal differences in the underthrusting plate interruption of subduction activity in one segment of the arc also affects the geometry of nearby segments and the processes over there

lithospheric boundaries and plate motions in the cyprus area abstract accurate location of earthquakes recorded by seismographs and reliable fault plane solutions of strong recent earthquakes are used to define the plate boundaries and the pattern of plate motion in cyprus and surrounding area spatial distribution of shallow h

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

a lower crustal event in the northeastern mediterranean the 1998 adana earthquake mw 6 2 and its aftershocks we analyse the main and aftershocks of the june 27 1998 adana earthquake using data from the short period cilician seismograph network in order to investigate the seismotectonics of the northeastern mediterranean region the mainshock is found to have a pure left lateral strike slip mechanism strike 50 dip 85 rake 10 mo 3 63 1018 nm the inferred strike direction of 50 n closely aligns with the surface trend of the goksun fault zone gfz the depth and size of the mainshock and the distribution of the aftershocks indicate that the rupture nucleated within the lower crust and did not extend to shallower zones this seismicity pattern indicates that these events are associated with actively interacting african and anatolian lithospheres in a strike slip manner at depth thus we propose that the southern segment of the gfz belongs to the diffuse africa anatolia plate boundary and plays a major role in the plate kinematics of the northeastern mediterranean