organized structures in subsurface bubble clouds langmuir circulation in the open ocean observations of the movement and distribution of subsurface bubbles reveal the structure of coherent motions near the ocean surface the measurements were obtained in the open ocean from a freely drifting self contained acoustical instrument equipped with side scan sonar dual frequency echo sounders and ambient sound recording systems the bubble clouds are organized into long narrow plumes aligned with the wind consistent with windrows caused by langmuir circulations they have widths of about 3 to 5 m and lengths up to 100 m with multiple scales coexisting their mean separation depends upon wind speed below 5 m s 1 mean spacings were about 5 m increasing to 10 m when winds exceeded 10 m s 1 the maximum depth to which the plumes were observed to penetrate depended to some extent on wind speed with the greatest penetrations of 12 m occurring at the highest wind speeds 13 m s 1 however the time averaged depth of observed bubble plume penetration bears only a weak dependence on wind speed whenever winds exceeded 5 m s 1 a mean penetration depth of 6 m was observed associated with these bubble plumes were maximum downward velocities of about 0 06 m s 1 these speeds were detected at 8 m depth in the center of the plumes magnitudes decreased to zero near the surface and horizontally toward the boundaries of the plumes

seismicity of the aegean and surrounding area abstract seismicity parameters based on instrumental and historical data are given for 36 seismic sources of shallow earthquakes and for 6 seismic sources of intermediate depth earthquakes in the aegean and surrounding area 34 n 43 n 18 e 30 e these parameters are of two categories parameters of the first category are useful for seismic hazard evaluation a and b values of the frequency magnitude relation maximum earthquake magnitude number of shocks larger than certain magnitude per year while parameters of the second category are proper for describing the spatial distribution of seismicity mean return period most probable magnitude in a certain time period moment rate shallow seismicity is highest along the convex side of the hellenic arc but close to the coast ionian islands south peloponnesus south of crete south of karpathos and rhodos in central greece patraikos corinthiakos evoikos gulfs thessalia and along a seismic belt which includes the northwestern anatolia fault zone the northernmost part of the aegean sea and the serbomacedonia zone the intermediate depth seismic activity is distributed in two parts of the benioff zone which dips from the convex side eastern mediterranean to the concave side aegean sea of the hellenic arc the one part shows a low dip angle and includes earthquakes with focal depths between 70 km and 100 km this part has a high seismicity earthquake magnitudes up to 8 0 and is situated below the inner slope of the sedimentary part of the hellenic arc eastern peloponnesus north of crete rhodos based on the fact that this part of the benioff zone is a continuation of the seismic zone of shallow earthquakes along the hellenic arc and that both zones have the same seismicity it is concluded that they constitute a continuous seismic belt on which coupling occurs between the subducted eastern mediterranean lithosphere and the overthrusted aegean lithosphere the other inner part of the benioff zone shows low seismicity maximum earthquake magnitude up to 7 1 with earthquakes of focal depths between 100 km and 180 km it dips at a mean angle of 38 below the volcanic arc of the southern aegean sea and is the result of the subduction of the front part of the eastern mediterranean lithosphere without coupling with the aegean lithosphere

back arc extension in the scotia sea the nature of back arc extension in the east scotia sea is re examined with the use of an enlarged geophysical data set well developed oceanic magnetic lineations confirm that the present spreading episode started about 8 ma ago that spreading is asymmetric and that the total rate increased from 50 to 70 m m a about 1 5 ma ago most of the currently active south sandwich volcanic island arc lies upon ocean floor only 6 8 m a old and generated at the current spreading ridge subsequent extension has not modified the curvature of the arc east west magnetic lineations of miocene age in the central scotia sea and contemporaneous low k arc tholeiites dredged from the eastern south scotia ridge discovery bank indicate a regime of coupled subduction and back arc extension preceding that occurring now a speculative model involving a series of collisions of parts of this earlier discovery trench with ridge crest sections of the south american antarctic plate boundary explains the transformation of this earlier regime into the present self contained sandwich plate regime the considerable small scale variability observed in the back arc region may be seen as an inevitable consequence of the action of the ridge trench collision mechanism the entire scotia sea could have formed by a similar kind of back arc extensional modification of the south american antarctic plate boundary

subduction influence on magma supply at the east scotia ridge despite a spreading rate of 65 70 km ma 1 the east scotia ridge has along most of its length a form typically associated with slower rates of sea floor spreading this may be a consequence of cooler than normal mantle upwelling which could be a feature of back arc spreading at the northern end of the ridge recently acquired sonar data show a complex rapidly evolving pattern of extension within 100 km of the south sandwich trench new ridge segments appear to be nucleating at or near the boundary between the south american and scotia sea plates and propagating southwards supplanting older segments the most prominent of these north of 56 30 s has been propagating at a rate of approximately 60 km ma 1 for at least 1 ma and displays a morphology unique on this plate boundary a 40 km long axial high exists at the centre of this segment forming one of the shallowest sections of the east scotia ridge beneath it seismic reflection profiles reveal an axial magma chamber or amc reflector similar to those observed beneath the east pacific rise and valu fa ridge simple calculations indicate the existence here of a narrow 1 km wide body of melt at a depth of approximately 3 km beneath the sea floor from the topographic and seismic data we deduce that a localised mantle melting anomaly lies beneath this segment rates of spreading in the east scotia sea show little variation along axis hence the changes in melt supply are related to the unique tectonic setting in which the south american plate is tearing to the east perhaps allowing mantle flow around the end of the subducting slab volatiles released from the torn plate edge and entrained in the flow are a potential cause of the anomalous melting observed a southward mantle flow may have existed beneath the axis of the east scotia ridge throughout its history

potential earthquake risk estimations by application of a simulation process abstract potential earthquake risks are defined here in terms of the annual probability of exceeding a peak ground acceleration level at the free surface of a site potential earthquake risks in israel were estimated by shapira 1981 1982 by considering the apparent seismicity of the region during the last 145 years in this paper a simulation process has been applied in order to examine the reliability of previous estimations and to provide another general tool for earthquake risk evaluation a relatively simple monte carlo procedure was developed and has been used for estimating as an example the potential earthquake risk in jerusalem israel the estimated probabilities obtained by the simulation procedure are for all practical purposes similar to the apparent probabilities previously determined by the author however a re evaluation of the potential earthquake risks in israel will be required when an attenuation equation based on local and regional acceleration measurements has been developed

scotia sea tectonics from high resolution satellite gravity the release of altimetric data from the geosat geodetic mission by the us navy 1 is leading to a much improved understanding of tectonics in the southern ocean a region in which remoteness and adverse physical conditions have limited the acquisition of geophysical data by research ships the scotia sea is an outstanding example of back arc spreading which is revealed in some detail by free air gravity anomaly maps derived from the latest release of data acquired south of 30 s 2 sea surface height data for this region have been reduced to a grid of free air gravity anomalies and are illustrated here by means of colour shaded relief and contour maps the new data confirm the existence of a number of inactive spreading ridges within the scotia sea and surrounding small basins the amplitudes and wavelengths of gravity anomalies over these ridges conform in general to the expected relationship with spreading rate except in the central scotia sea where a proposed miocene slow spreading ridge appears to have left no clear signature the spreading ridge axis in the east scotia sea comprises seven or more segments separated by small mainly sinistral offsets and exhibits a median valley with depths of 200 1000 m that is reflected in free air lows of 10 40 mgal near both its northern and southern termini the gravity signature of the ridge becomes less distinct with a less pronounced axial low the northernmost segments of the ridge are displaced in a right lateral sense by a feature which appears to represent a southward migrating non transform offset whereas the process of spreading in drake passage and the east scotia sea was comparable to mid ocean ridges that in the central scotia sea may have been disorganized as observed in some western pacific back arc basins

measurements of turbulence in the upper ocean mixing layer using autosub abstract the rate of dissipation of turbulent kinetic energy has been measured with airfoil probes mounted on an autonomous vehicle autosub on constant depth legs at 2 10 m below the surface in winds up to 14 m s 1 the observations are mostly in an area limited by fetch to 26 km where the pycnocline depth is about 20 m at the operational depths of 1 55 15 9 times the significant wave height hs and in steady winds of about 11 6 m s 1 when the wave age is 11 7 17 2 dissipation is found to be lognormally distributed with a law of the wall variation with depth and friction velocity breaking waves leaving clouds of bubbles in the water are detected ahead of the autosub by a forward pointing sidescan sonar and the dissipation is measured when the clouds are subsequently reached bands of bubbles resulting from the presence of langmuir circulation are identified by a semiobjective method that seeks continuity of band structure recognized by both forward and sideways pointing sidescan sonars the times

the role of seismicity models in probabilistic seismic hazard estimation comparison of a zoning and a smoothing approach summary seismic hazard estimations are compared using two approaches based on two different seismicity models one which models earthquake recurrence by applying the truncated gutenbergrichter law and a second one which smoothes the epicentre location of past events according to the fractal distribution of earthquakes in space woo 1996 the first method requires the definition of homogeneous source zones and the determination of maximum possible magnitudes whereas the second method requires the definition of a smoothing function our results show that the two approaches lead to similar hazard estimates in low seismicity regions in regions of increased seismic activity on the other hand the smoothing approach yields systematically lower estimates than the zoning method this epicentre smoothing approach can thus be considered as a lower bound estimator for seismic hazard and can help in decision making in moderate seismicity regions where source zone definition and estimation of maximum possible magnitudes can lead to a wide variety of estimates due to lack of knowledge the two approaches lead however to very different earthquake scenarios disaggregation studies at a representative number of sites show that if the distributions of contributions according to source site distance are comparable between the two approaches the distributions of contributions according to magnitude differ reflecting the very different seismicity models used the epicentre smoothing method leads to scenarios with predominantly intermediate magnitudes events 5 m 5 5 while the zoning method leads to scenarios with magnitudes that increase with the return period from the minimum to the maximum magnitudes considered these trends demonstrate that the seismicity model used plays a fundamental role in the determination of the controlling scenarios and ways to discriminate between the most appropriate models remains an important issue

aeration due to breaking waves part i bubble populations abstract the population of bubbles produced by breaking waves in 10 m winds of up to 12 m s 1 is analyzed using calibrated images from a vertical pencil beam sonar system placed on the seabed near the dutch coast the structure in the images is parameterized and the volumetric bubble backscatter is inverted to yield bubble concentrations data were obtained at three acoustic frequencies with inversion effected by prescribing a bubble spectrum with two free variables leaving a redundant measurement to test the robustness of the model median concentrations may in this way be obtained up to the sea surface measurements are multiply regressed on wind and dominant wave variables bubbles penetrate to a depth of about a factor of 6 1 times the significant wave height hs where is the wave age or ratio of dominant wave phase speed to wind speed the measured mean bubble radius decreases weakly with depth unless waves are gently sloping at about 5 m 1 at 0 4 m the mean radius ranges from 30 to 80

seismic risk of circum pacific earthquakes i strain energy release commonly used earthquake whole process frequency magnitude and strain energy magnitude laws are merged to obtain an analytic expression for an upper bound magnitude to regional earthquake occurrencem3 which is expressed primarily in terms of the annual maximum magnitudem1 and the magnitude equivalent of the annual average total strain energy releasem2 values ofm3 are also estimated graphically from cumulative strain energy release diagrams both methods are illustrated by application to the high seismicity of the circum pacific belt using duda s 1965 data and regionalisation values ofm3 obtained analytically with their uncertainties are in agreement with those obtained graphically empirical relations are then obtained betweenm1 m2 andm3 which could be of general assistance in regional seismic risk considerations if they are found to be of a universal nature for instance m3 andm2 differ by one magnitude unit in subregions of the circum pacific

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

the surface rupture and slip distribution of the 17 august 1999 izmit earthquake m 7 4 north anatolian fault the 17 august 1999 izmit earthquake occurred on the northern strand of the north anatolian fault zone the earthquake is associated with a 145 km long surface rupture that extends from southwest of duzce in the east to west of hersek delta in the west detailed mapping of the surface rupture shows that it consists of five segments separated by releasing step overs herein named the hersek karamursel golcuk izmit sapanca lake sapanca akyazi and karadere segments from west to east respectively the hersek segment which cuts the tip of a large delta plain in the western end of the rupture zone has an orientation of n80 the n70 80 e trending karamursel golcuk segment extends along the linear southern coasts of the izmit gulf between karamursel and golcuk and produced the 470 cm maximum displacement in golcuk the northwest southeast striking golcuk normal fault between the karamursel golcuk and izmit sapanca segments has 2 3 m maximum vertical displacement the maximum dextral offset along the izmit sapanca lake segment was measured to be about 3 5 m and its trend varies between n80 e and east west the sapanca akyazi segment trends n75 85 w and expresses a maximum displacement of 5 2 m the karadere segment trends n65 e and produced up to 1 5 m maximum displacement the karadere and sapanca akyazi segments form fan shape or splaying ruptures near their eastern ends where the displacement also diminished

the collision complex of the north scotia ridge single channel and multichannel seismic reflection profiles of the north scotia ridge trending west east off southernmost south america show the north side to consist of a wedge of deformed sediments resting on a planar layered sequence relative movement of the ridge northward toward the falkland plateau has resulted in deformation and uplift of the near surface sediment layers of the falkland trough to form an accretionary wedge these sediments are 1 to 3 s of two way travel time in thickness and lie above a well defined reflector whose velocity at the northern part of the trough is 3 6 km s the deeper layers extend to depths in places greater than 9 0 s of two way travel time beneath the north slope without any significant deformation the deepest observed reflector is associated with a 5 9 km s basement the deformed pile of sediments or collision zone of the north scotia ridge is similar to that observed at other active compressive plate boundaries

the seismic parameter b of the frequency magnitude relation and its association with the geological zones in the area of greece abstract the parameter b of the frequency magnitude relation has been accurately calculated for each of the 21 seismic zones into which the aegean and surrounding area 34 n 43 n 18 e 30 e has been divided on the basis of several seismotectonic criteria these 21 seismic zones have been geographically separated into three a b c groups regions according to the values of the parameter b the outer region a is characterized by a relatively high value 1 03 the middle region b by an intermediate value 0 84 and the innermost region c by a low value 0 60 the boundaries of these three groups of zones almost coincide with the boundaries of well known geological zones this observation is interpreted in terms of mechanical heterogeneity of the material and of structural and stress conditions in the area

rupture zones in the aegean region rupture zones of strong shallow earthquakes can be investigated by field observations of surface fault traces sf accurate location of spatial clusters of aftershocks or other small earthquakes cl reliable fault plane solutions fp and information on the spatial distribution of sites with high i viii macroseismic intensities ma the validity of these four techniques was successfully tested by comparing the results of their application to several cases of strong shallow earthquakes these techniques were then applied to spatially define the rupture zones of 150 strong m 6 0 shallow earthquakes in the aegean and surrounding area the type of faulting was determined for all these zones by the use of reliable fault plane solutions which are available for this area the orientation of most of these rupture fault zones is in good agreement with the presently acting stress field with some exceptions which are attributed to the rupture of pre existing faults the tectonic implications of these zones are discussed 1999 elsevier science b v all rights reserved

small scale spatial variation of the stress field in the back arc aegean area results from the seismotectonic study of the broader area of mygdonia basin n greece abstract in the present work a detailed seismotectonic study of the broader area of the mygdonia basin n greece is performed digital data for earthquakes which occurred in the broader mygdonia basin and were recorded by the permanent telemetric network of the geophysical laboratory of the aristotle university of thessaloniki during the period 1989 1999 were collected and fault plane solutions for 50 earthquakes which occurred in the study area were calculated with a modified first motions approach which incorporates amplitude and radiation pattern information fault plane solutions for the 3 main shocks of volvi 23 05 78 m w 5 8 and 20 06 78 m w 6 5 and arnaia 04 05 95 m w 5 8 events and the 1978 aftershock sequence were additionally used moreover data from two local networks established in the mygdonia basin were also incorporated in the final dataset determination of the stress field was realized by the use of the method of gephart and forsyth gephart j w forsyth d w 1984 an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence jour geophys res v 89 no b11 p 9305 9320 for the stress tensor inversion and the results were compared with independent estimates based on the calculation of the average moment tensor papazachos c b kiratzi a a 1992 a formulation for reliable estimation of active crustal deformation and its application to central greece geophys j int 111 424 432 the obtained stress results show a relatively good agreement between the two approaches with differences in the azimuth of the dominant extension axis of the order of 10 furthermore comparison with independent information for the mean stress axes provided by the study of kinematics on neotectonic faults mountrakis d kilias a tranos m thomaidou e papazachos c karakaisis g scordilis e chatzidimitriou p papadimitriou e vargemezis g aidona e karagianni e vamvakaris d skarlatoudis a 2003 determination of the settings and the seismotectonic behavior of the main seismic active faults of northern greece area using neotectonic and seismological data earthquake planning and protection organisation oasp in greek shows a similar agreement with typical misfit of the order 10 the stress inversion method was modified in order to select one or both nodal planes of the focal mechanism which corresponds to the true fault plane of the occurred earthquakes and was able to select a single fault plane in the majority of examined cases using this approach the obtained fault plane rose diagrams are in agreement with results from various neotectonic studies moreover several secondary active fault branches were identified which are still not clearly observed in the field

the skyros earthquake mw 6 5 of 26 july 2001 and precursory seismicity patterns in the north aegean sea the rupture zone of the m w 6 5 earthquake of 26 july 2001 in the north aegean sea nas is oriented northwest southeast and occupies the southwestern part of the seismic zone of nas the motion indicates reverse faulting with a significant sinistral strike slip component a review of the past nas seismicity reveals that in the last 150 yr the seismicity is strongly clustered in time with 14 out of 15 pre 2001 events being members of a cluster only the 1912 earthquake is an isolated event this implies that the probability of the 2001 earthquake being the first member of a new time cluster is 0 93 which is the probability for the next nas strong earthquake to occur within a time interval equal to the mean interarrival time of cluster events 2 9 2 06 yr the distribution of the earthquake rupture zones and the position of the 2001 event suggest that the next event may rupture one of the unruptured parts of nas to the northeast of the 2001 earthquake

a catalogue of seismicity in greece and the adjacent areas for the twentieth century a magnitude homogeneous earthquake catalogue spanning the twentieth century has been assembled for greece and adjacent areas data assemblage had to consider all of the common magnitude scales mw ms mb and ml including ml ath of the national observatory of athens noa fourteen different correlation equations between magnitude scales were considered in order to approach magnitude homogeneity in the final catalogue this catalogue contains an estimate of both mw and ms for each earthquake and the actual reported values of mb ms mw and ml the final catalogue includes 5198 earthquakes after having been truncated at 4 mw to eliminate large numbers of patchily reported microearthquakes these 5198 earthquakes during 1900 1999 are within the area 33 438n 18 30 998e focal depths 1 0 215 km and magnitude range 4 0vmwv7 7 the surface wave magnitude ms is always estimated for each earthquake to facilitate application of the catalogue to seismic hazard assessment since seismic attenuation laws are more often expressed in terms of ms rather than mw alongside this new catalogue the data of papazachos and papazachou for the period 550 bc 1899 then provide a full picture of the known seismicity of greece d 2004 elsevier b v all rights reserved

triggered slip observations of the 17 august 1999 izmit turkey earthquake using radar interferometry we use synthetic aperture radar interferometry insar to map the displacement field of the 17 august 1999 izmit earthquake which largely conforms to that predicted for an elastic upper crust we determine the earthquake source parameters and show that slip continues farther west than the mapped fault ruptures we also show that additional sub surface displacements occurred on parallel strands of the north anatolian fault zone we argue that this was caused by changes in static stress accompanying the mainshock or by the dynamic release of regional stresses

opening history of powell basin antarctic peninsula the opening of powell basin was part of the regional response to n55 w relative plate motion of south america away from antarctica which led to the formation of drake passage during the eocene and oligocene restoration of microplates around the basin using gridded magnetic anomalies from its margins illustrates the pre break up continuity of the pacific margin anomaly magnetic high associated with a mesozoic arc batholith newly compiled magnetic anomaly data over the powell basin show subdued linear seafloor spreading type anomalies these are used together with marginal and regional geology to constrain the opening history of the basin magnetic reversal modelling suggests that slow spreading in powell basin probably occurred between 29 7 ma and 21 8 ma following rifting of mesozoic continental crust with associated break up volcanism a simple two phase model for the rotation of the south orkney microcontinent away from the antarctic peninsula accounts for the pattern of magnetic reversals recorded in powell basin and for the structure of its margins

thessaloniki gerakarou fault zone tgfz the western extension of the 1978 thessaloniki earthquake fault northern greece and seismic hazard assessment abstract active faulting and seismic properties are re investigated in the eastern precinct of the city of thessaloniki northern greece which was seriously affected by two large earthquakes during the 20th century and severe damage was done by the 1759 event it is suggested that the earthquake fault associated with the occurrence of the latest destructive 1978 thessaloniki earthquake continues westwards to the 20 km long thessaloniki gerakarou fault zone tgfz which extends from the gerakarou village to the city of thessaloniki this fault zone exhibits a constant dip to the n and is characterised by a complicated geometry comprised of inherited 100 trending faults that form multi level branching tree like fault geometry along with nne to ne trending faults the tgfz is compatible with the contemporary regional n s extensional stress field that tends to modify the pre existing nw se tectonic fabric prevailing in the mountainous region of thessaloniki both the 1978 earthquake fault and tgfz belong to a ca 65 km long e w trending rupture fault system that runs through the southern part of the mygdonia graben from the strymonikos gulf to thessaloniki this fault system here called thessaloniki rentina fault system trfs consists of two 17 20 km long left stepping 100 trending main fault strands that form underlapping steps bridged by 8 10 km long ene wsw faults the occurrence of large m 6 0 historical earthquakes in 620 677 and 700 a d demonstrates repeated activation and therefore the possible reactivation of the westernmost segment the tgfz could be a major threat to the city of thessaloniki changes in the coulomb failure function cff due to the occurrence of the 1978 earthquake calculated out in this paper indicate that the tgfz has been brought closer to failure a convincing argument for future seismic hazard along the tgfz

kernel estimation methods for seismic hazard area source modeling in probabilistic seismic hazard analysis the representation of seismic sources by area zones is a standard means of data reduction however where the association between seismicity and geology is complex as it is in many tectonic regimes the construction of zone geometry may become contentiously subjective and ambiguities may end up being resolved through appeal to the nonscientific rule of conservatism or pragmatism although consideration of alternative zonations within a logic tree framework provides a channel for some of the uncertainty it does not address the fundamental validity of the zonation procedure itself in particular neither the minimal assumption of uniform seismicity within a zone nor the euclidean geometry of a zone accord with the fractal spatial distribution of seismicity and the magnitude insensitivity of zonation ignores the spatial extent and correlations of different sized earthquakes an alternative procedure for area source modeling avoids euclidean zones and is based statistically on kernel estimation of the activity rate density inferred from the regional earthquake catalog the form of kernel is governed by the concepts of fractal geometry and self organized criticality with the bandwidth scaling according to magnitude in contrast with zonal models for intraplate regions the kernel estimation methodology makes provision for moderate earthquakes to cluster spatially while larger events may migrate over sizeable distances

comment on ambient and transient bubble spectral densities in quiescent seas and under spilling breakers by herman medwin and nigel d breitz medwin and breitz 1989 presented a series of very interesting measurements of near surface oceanic bubbles their data obtained at a depth of 25 cm below the sea surface under wind velocities of 12 15 m s 1 were compared with those of baldy s 1988 obtained in a laboratory tank at depths of 25 and 30 cm below the mean water level under a wind velocity of 14 m s i despite very different experimental conditions generally existing in the field and laboratory tanks the spectra of bubble densities obtained in these two studies were suggested by medwin and breitz to be in apparently excellent agreement they went on to state that as bubble densities depend only on the wind speed and not on the wave height the laboratory and field data at a similar water depth under the same wind velocity are directly comparable we will demonstrate below that the bubble data cannot be compared on the basis of wind speed alone and that the apparent agreement can be explained if the wave conditions were included in the comparison the field therefore the wind friction velocity in baldy s 1988 experiment may even be higher than the value estimated by medwin and breitz 1989 in fact baldy 1988 reported that the bubble population increased by a factor of ten when the wind velocity varied from 11 to 14 m s taking all these together we see that the bubble population measured by baldy should be about 1 to 2 orders of magnitude greater than those by medwin and breitz because there is a general similarity of the bubble size spectrum baldy and bourguel 1987 baldy 1988 hwang et al 1990 the wind stress dependence of the global population is expected to be applicable to the bubble size spectrum as the bubble population is merely an integration of its spectral density over a certain size range it becomes clear then that the nearly identical size spectra of medwin and breitz and of baldy as reported by medwin and breitz cannot be interpreted as an agreement the spectra densities shown in figure 7 of medwin and breitz are off by a factor of 2 from those shown in their figure 6 the former are correct h medwin personal communication 1990

bubble clouds and the dynamics of the upper ocean this is a review of turbulence in the upper ocean close to the sea surface particularly of the information that has been obtained from sonar observations of bubble clouds produced by breaking wind waves these clouds provide tracers of the turbulent motions and are important especially at high wind speeds in the process of air sea gas transfer the observations of bubble clouds are here related to other measurements of turbulence particularly to direct measurements of currents and temperatures in lakes or at sea and to laboratory studies some novel observations of bubble clouds and breaking waves their frequency and relation to langmuir circulation are presented there is now emerging a pattern of clues that point to the dominance of breaking surface gravity waves as a source of turbulence to a depth below the surface of 0 04 to 0 2 times the wavelength of the dominant breaking waves although the effect of swell has yet to be clarified the relative depth appears to increase with increasing values of w 1 c where w10 is the wind speed and c the phase speed of the dominant waves below this region the generation of turbulence may be dominated by shear stress or convection here turbulence is generally similar to that in the atmospheric boundary layer there are however coherent motions on the scale of the mixing layer that persist for periods of a few minutes to an hour or so to which the transport of a large part of the momentum and heat fluxes can be attributed and which strongly affect the dispersion of buoyant particles or bubbles these motions deserve special study to establish their contribution to heat and momentum transport and hence to determine if or when they should be specifically represented in models of the upper ocean devised for example to describe the dispersion of passive and non passive tracers or the air sea transfer of gases

terrane motion by strike slip faulting of forearc slivers forearc slivers bounded by a trench and an active strike slip fault occur in about 50 of modern subduction zones analysis of earthquake slip vectors indicates that modern sliver terranes typically migrate at rates of 1 2 cm yr tertiary transport of some forearc slivers by 1000 km or more is therefore expected as a consequence of normal subduction active arc parallel strike slip faulting occurs whenever interplate coupling is strong and convergence is somewhat oblique strike slip rate increases with greater convergence obliquity

structure and variability of langmuir circulation during the surface waves processes program a cooperative multiplatform field experiment was conducted in the eastern north pacific during february and march of 1990 as part of the surface waves processes program swapp one of the experimental objectives was to investigate langmuir circulation so that its role in the evolution of the oceanic surface boundary layer could be better understood the concurrent use of different observational techniques ranging from simple surface drifters to complex doppler sonar systems resulted in new information about langmuir circulation structure and variability estimates of langmuir cell spacing indicated that a broad range of scales from about 2 to 200 m was excited during periods of strong surface forcing and that the energy containing scales evolved with time estimates of cell spacing based on doppler velocities from a surface scanning sonar directed crosswind showed this scale evolution but estimates based on backscattered intensity did not this was attributed to the fact that the intensity based estimates were only indirectly related to circulation strength the near surface convergent velocities from the sonar were used to form an objective quantitative measure of the temporal variations in langmuir circulation strength as expected the circulation strength increased dramatically during strong wind events however circulation strength and wind stress did not decrease simultaneously and langmuir circulation was detectable for up to a day after abrupt reductions in wind stress energy from the surface wave field which decayed more slowly than the wind was apparently responsible for maintaining the circulation the variation of circulation strength was found to be better related to u us than to u where u is the friction velocity is the wind stress and us is the surface wave stokes drift this scaling is consistent with wave current interaction theories of langmuir cell generation

macrobubble clouds produced by breaking wind waves a laboratory study 1 clouds of large air bubbles produced by breaking wind waves have been studied in a laboratory tank temporal evolutions of these macrobubble clouds including their length scales aspect ratios area scales and velocities are presented the bubble concentration and void ratio within the cloud are also found the initial downwind velocity of the cloud is about one half but can reach about two thirds the phase velocity of the breaking wave the maximum penetrating depth of the cloud is about one half the breaking wave height all these geometric and kinematic characteristics of the cloud are also associated with those of the breaking wave

an alternative approach to probabilistic seismic hazard analysis in the aegean region using monte carlo simulation abstract the aegean is the most seismically active and tectonically complex region in europe damaging earthquakes have occurred here throughout recorded history often resulting in considerable loss of life the monte carlo method of probabilistic seismic hazard analysis psha is used to determine the level of ground motion likely to be exceeded in a given time period multiple random simulations of seismicity are generated to calculate directly the ground motion for a given site within the seismic hazard analysis we explore the impact of different seismic source models incorporating both uniform zones and distributed seismicity a new simplified seismic source model derived from seismotectonic interpretation is presented for the aegean region this is combined into the epistemic uncertainty analysis alongside existing source models for the region and models derived by a k means cluster analysis approach seismic source models derived using the k means approach offer a degree of objectivity and reproducibility into the otherwise subjective approach of delineating seismic sources using expert judgment similar review and analysis is undertaken for the selection of peak ground acceleration pga attenuation models incorporating into the epistemic analysis greek specific models european models and a next generation attenuation model hazard maps for pga on a rock site with a 10 probability of being exceeded in 50 years are produced and different source and attenuation models are compared these indicate that greek specific attenuation models with their smaller aleatory variability terms produce lower pga hazard whilst recent european models and next generation attenuation nga model produce similar results the monte carlo method is extended further to assimilate epistemic uncertainty into the hazard calculation thus integrating across several appropriate source and pga attenuation models site condition and fault type are also integrated into the hazard mapping calculations these hazard maps are in general agreement with previous maps for the aegean recognising the highest hazard in the ionian islands gulf of corinth and hellenic arc peak ground accelerations for some sites in these regions reach as high as 500 600 cm s 2 using european nga attenuation models and 400 500 cm s 2 using greek attenuation models

delineation of seismic sources in probabilistic seismic hazard analysis using fuzzy cluster analysis and monte carlo simulation abstract determination of seismic sources is the first step in probabilistic seismic hazard analysis psha however this step especially in low seismic regions is often controversial in conventional psha procedure determination of seismic sources is merely based on the subjective judgments of experts and in many cases there are great differences among proposed seismic models in a specific region as a result one important source of uncertainty in psha is due to determination of seismic sources in this article by combination of fuzzy clustering analysis and monte carlo simulation an objective method for determination and probabilistic modeling of seismic sources is presented by clustering spatial locations of earthquakes it is possible to specify the extent of each seismic source in an objective way a cluster quality index is used to identify the optimum number of clusters the density and spread of events in each cluster determines the geometrical shape of seismic sources moreover in this article a method is proposed to construct spatial probability density functions pdfs of earthquake locations based on the results of fuzzy clustering analysis the spatial pdf of earthquakes can be used for the generation of synthetic events in monte carlo simulation the azarbaijan region with its varied seismotectonics and generally high seismicity is used as an important area of seismicity in which to develop and demonstrate the application and capability of fuzzy clustering analysis in specifying seismic sources the psha is performed for the city of tabriz and a comprehensive comparison is made between the results of conventional psha ordinary monte carlo hazard analysis and the proposed method the results indicate there is an objective relationship between observed seismicity and seismotectonic evidences in the region moreover the distribution of synthetic events is highly correlated with the observed seismicity seismotectonic and geological information of the region

delineation of shallow seismic source zones using k means cluster analysis with application to the aegean region the selection of specific uniform seismic source zones for use in probabilistic seismic hazard analysis is often controversial recognizing that a consistent approach to source model development is not always possible as the information available relating to geology and seismotectonics can vary from region to region the k means algorithm for hierarchical cluster analysis can be used to partition regions based on observed seismicity the aegean incorporating greece albania former yugoslav republic of macedonia f y r o m southern bulgaria and western turkey with its varied seismotectonics and generally high seismicity is used as an important area of seismicity in which to develop and demonstrate the application of k means two types of algorithm are considered the first is a point source k means that can be used to partition a catalogue of earthquake hypocentres the second is a novel line source development of the algorithm appropriate in seismology as these are analogues for the traces of active faults which is then applied to a catalogue of known fault ruptures in the aegean the common problems of the k means methodology are also addressed ensemble analyses are used to identify better choices of initial estimates for the cluster centres a cluster quality index is used to identify the optimum number of clusters and its robustness assessed when considering different subsets of the observed earthquake catalogue an alternative approach is also implemented monte carlo seismic hazard analysis is used to compare models with different numbers of clusters with the observed seismicity of the 20th century considerable variation is found in the optimum number of clusters identified either by the quality index or by stochastic seismic hazard analysis ultimately the k means partitions of seismicity are developed into source models and their representation of aegean seismotectonics assessed the result is that models containing between 20 and 30 clusters emerge as the most appropriate in capturing the spatial variation in hypocentral distribution and fault type in the aegean

motion of the scotia sea plates earthquake data from the scotia arc to early 2002 are reviewed in the light of satellite gravity and other data in order to derive a model for the motion of plates in the scotia sea region events with magnitude greater than or equal to5 which occurred on or near the boundaries of the scotia and sandwich plates and for which centroid moment tensor cmt solutions are available are examined the newer data fill some of the previous sampling gaps along the boundaries of the scotia and sandwich plates and provide tighter constraints on relative motions variations in the width of the brunhes anomaly on evenly spaced marine magnetic profiles over the east scotia ridge provide new estimates of scotia sandwich plate spreading rates since there are no stable fracture zones in the east scotia sea the mean azimuth of sea floor fabric mapped by sidescan is used to constrain the direction of spreading 18 newrate estimates and four azimuths from the east scotia ridge are combined with 68 selected earthquake slip vectors from the boundaries of the scotia sea in a least squares inversion for the best fitting set of euler poles and angular rotation rates describing the present day motions of the scotia and sandwich plates relative to south america and antarctica our preferred model tlp2003 gives poles that are similar to previous estimates except for scotia plate motion with respect to south america which is significantly different from earlier estimates predicted rates of motion also differ slightly our results are much more robust than earlier work we examine the implications of the model for motion and deformation along the various plate boundaries with particular reference to the north and south scotia ridges where rates are obtained by closure

coseismic and postseismic fault slip for the 17 august 1999 m 7 5 izmit turkey earthquake we use global positioning system gps observations and elastic half space models to estimate the distribution of coseismic and postseismic slip along the izmit earthquake rupture our results indicate that large coseismic slip reaching 5 7 meters is confined to the upper 10 kilometers of the crust correlates with structurally distinct fault segments and is relatively low near the hypocenter continued surface deformation during the first 75 days after the earthquake indicates an aseismic fault slip of as much as 0 43 meters on and below the coseismic rupture these observations are consistent with a transition from unstable episodic large earthquakes to stable fault creep sliding at the base of the seismogenic zone

earthquake clustering and energy release of the african arabian rift system the earthquakes associated with continental deformation are spatially and temporally variable and are fundamental in understanding fault activity and seismogenic hazards we conduct kk means cluster analysis on seismicity in the african arabian rift systems to create the first computationally objective analysis of the pattern of earthquakes we use seismic moment to compute spatial variations in maximum credible earthquake mcred and likely time to the next major release of seismic energy our best fit model has 32 clusters of 100 400 km 100 400 km in length with cluster size decreasing northward along the rift and cluster boundaries correlating with major structural segmentation of the rift mcred varies between mwmw 5 2 and 7 4 across the whole dataset with the highest values estimated in portions of the rift where the majority of extension is accommodated by seismogenic failure

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

dynamical processes of transfer at the sea surface abstract this review describes the dynamical processes of transport from and immediately below the sea surface particularly those which involve convergence and the separation of flow and which result in the renewal of surface water at horizontal scales ranging from millimeters to hundreds of meters turbulence at or near the sea surface derives from several processes breaking waves and the bubbles they may produce precipitation and spray langmuir circulation and thermal convection and turbulence which is internally generated by shear interest in the subject derives from the requirements to predict air sea fluxes of heat momentum and gases to develop climate models to interpret satellite images of the sea surface including those of ship wakes and to predict upper ocean structure including mixing layer depth in models of phytoplankton blooms and acoustic propagation the general effect of subsurface turbulence on the sea surface and the effects of surfactants is described and each process is discussed in turn laboratory experiments and theoretical studies have contributed particularly to the understanding of the interaction of vortices and turbulence with the surface and to the consequences of breaking waves they point to the development of instability in the flow ahead of steep waves carrying parasitic capillary waves which may contribute to the onset of flow separation on the leading face of the waves and the development of a rotor or roller below the wave crest shown most clearly in the pattern of streamlines in a frame of reference moving forward with the wave the conditions near the flow separation line on the wave surface ahead of the rotor may be similar to those produced by vortices approaching a free surface detailed observation of breaking waves at sea is lacking but some progress has been made using acoustics to detect the clouds of subsurface bubbles formed by the larger breakers and the depth to which they penetrate the possible importance of three dimensional effects in breaking waves is discussed and a conjectural sketch of the surface flow field and the surface separation and reattachment pattern following a plunging breaker is described recent observations show elevated levels of turbulence close to the sea surface the depth of the layer in which this occurs is shown to be consistent with information derived from sonar studies of the depth of bubble clouds the observed frequency of breaking waves and laboratory observations of breaking waves rain is known to knock down the sea reducing the frequency and intensity of breaking waves the precise mechanics of the phenomena are uncertain but an enhancement of near surface turbulence and the damping of short surface gravity waves has been observed in laboratory experiments langmuir circulation temperature ramps and convection all associated with coherent structures are processes which mix the upper ocean although their relative importance is unknown connections between studies with quite disparate motivations are found to help provide descriptions of the upper ocean processes and estimates of the time scale of surface renewal associated with each of the processes identified many quantities being transferred across the sea surface appear to be transported by dynamical processes of scale much smaller than that of the dominant surface waves although their subsequent diffusion in the mixing layer may be strongly influenced by the larger scale processes further careful measurements in the laboratory and at sea are required to quantify the fluxes associated with the processes and to relate them to external parameters such as wind speed

measurements with an automatically recording inverted echo sounder aries and the bubble clouds abstract we report here analysis of the first observations with a new instrument aries designed to record the acoustic backscatter from bubble clouds at several levels below the surface of the ocean the instrument is deployed on a subsurface mooring and records internally data has been analysed from deployments of aries for one week in the irish sea and for periods of 4 and 9 weeks near the edge of the uk continental shelf during periods in which meteorological data waves and near surface temperatures and on occasion currents were being recorded by other instruments the results while being generally similar to earlier measurements in coastal waters show that the bubble clouds are more intense having greater acoustic scattering cross per unit volume mv and extend on average deeper into the water column a simple model accounting for the shape of the clouds their advection through the sonar beam and their decay through bubbles returning to the surface or through their gas dissolving int

a new seismic hazard model for new zealand we present a new probabilistic seismic hazard analysis psha for new zealand an important feature of the analysis is the application of a new method for the treatment of historical distributed seismicity data in psha the psha uses the seismicity recorded across and beneath the country to define a three dimensional grid of a values i e parameter a of a gutenberg richter distribution log n yr a bm in which n yr is the number of earthquakes per year recorded inside each grid cell equal to or greater than magnitude m parameter b and the limiting maximum cutoff magnitude of the gutenberg richter distribution are defined from the surrounding region 14 crustal and 23 subcrustal seismotectonic zones are defined for the country and then smoothed across the boundaries of the zones the methodology therefore combines the modern method of defining continuous distributions of seismicity parameters frankel 1995 frankel et al 1996 with the traditional method of defining large area sources and the associated seismicity parameters e g algermissen et al 1990 the methodology provides a means of including deep subduction zone seismicity in a psha preserves the finer scale spatial variations of seismicity rates across a region avoids the undesirable edge effects produced in the traditional method when adjacent area sources enclose areas of significantly different seismicity rates and also enables parameters most reliably defined at a regional scale parameter b and maximum cutoff magnitude of a gutenberg richter distribution and slip type to be incorporated into the psha the psha combines the modeled seismicity data with geological data describing the location and earthquake recurrence behavior of 305 active faults and new attenuation relationships for peak ground acceleration and spectral acceleration developed specifically for new zealand different attenuation expressions are used for crustal and subduction zone earthquakes the resulting psh maps for a 150 year return period show the highest hazard to occur in the center and southwest of the country in the areas of highest historical crustal and deep subduction zone seismicity in contrast the longer return period maps 475 and 1000 year return period show the highest hazard to occur from the southwest to northeast ends of the country along the faults that accommodate the majority of the motion between the pacific and australian plates the maps are currently being used to revise new zealand s building code which has previously been based on pshas that did not explicitly include individual faults as earthquake sources manuscript received 10 april 2001

segmentation of the sumatran fault segmentation of the sumatran fault is discerned using an analytical approach in which a k means algorithm partitions earthquakes into clusters of seismicity along the fault clusters are tessellated into segment zones from which segment lengths and maximum credible magnitude are estimated decreasing the depth of seismicity sampled from 70 to 60 to 50 km reduces interaction with deeper seismicity and results from the k means algorithm initially suggest that the fault has k 14 16 and 16 clusters respectively after inspection it becomes clear that the optimum number of clusters is 16 the 16 cluster model developed into zones generates segment lengths ranging from 22 to 196 km and maximum earthquake potentials in the range of mw 6 5 7 8 the sumatran fault is dominated by eight great central segments distributed approximately symmetrically about lake maninjau these central fault segments dominate the hazard which is less in the far north because segments are shorter

second order moment of central california seismicity 1969 1982 the second order moment cross correlation function of earthquakes in the u s geological survey central california catalog between 1969 and 1982 was calculated with respect to a magnitude threshold m 4 0 over interevent distances up to 80 km and interevent times up to 320 days the statistical procedure results in a representation of the spatial temporal structure of the catalog associated with m 4 0 earthquakes and is capable of revealing patterns too weak to be detected in the space time distribution of seismicity for individual earthquake sequences a method is introduced for identifying aftershocks based on a physical two parameter model of the earthquake interaction process the results show that the aftershock process dominates the second order moment and may even obscure the statistical expression of a precursory process a concentration of foreshocks within 15 km and 3 days of m 4 0 main shocks exhibits an apparent migration toward the main shock loci with velocity 2 6 5 3 km d this concentration may be related to an observed tendency for m 4 0 events to cluster auto correlate over this interevent range with the identified aftershocks removed the residual catalog is poissonion in space and time when two m 4 0 earthquakes occur within 80 km and 40 days of each other aftershock productivity appears to be relatively enhanced in the earlier sequence this suggests that aftershock populations are not solely dependent on their main shocks and that unusually productive aftershock sequences may be predictors of future moderate earthquakes

enhanced magma supply at the southern east scotia ridge evidence for mantle flow around the subducting slab abstract bathymetric and seismic data show that the southernmost segment of the east scotia ridge segment e9 is anomalous in its curved plan form and in the presence of a large axial volcanic ridge avr spreading commenced only within the past 1 million years on this segment which appears to have propagated both northward and southward the presence of a caldera at the summit of the avr indicates that a shallow magma chamber of limited extent existed recently beneath the ridge eruption from this magma chamber probably within the past 0 1 million years may have led to the formation of the avr itself careful examination of seismic reflection profiles suggests that small pockets of magma may still exist beneath the avr magmatism on segment e9 may be enhanced as a result of the flow of shallow mantle around the southern end of the subducting slab beneath the south sandwich arc in a manner similar to that proposed for the northern end this mantle probably carries a slightly enriched hotspot signature and is affected by volatiles released from the edge of the slab both tending to increase the supply of magma to the back arc spreading centre

a monte carlo approach to seismic hazard analysis abstract we have developed a monte carlo methodology for the estimation of seismic hazard at a site or across an area this method uses a multitudinous resampling of an earthquake catalog perhaps supplemented by parametric models to construct synthetic earthquake catalogs and then to find earthquake ground motions from which the hazard values are found large earthquakes extrapolated from a gutenberg richter recurrence relation and characteristic earthquakes can be included in the analysis for the ground motion attenuation with distance the method can use either a set of observed ground motion observations from which estimates are randomly selected a table of ground motion values as a function of epicentral distance and magnitude or a parametric ground motion attenuation relation the method has been tested for sites in new england using an earthquake catalog for the northeastern united states and southeastern canada and it yields reasonable ground motions at standard seismic hazard values this is true both when published ground motion attenuation relations and when a dataset of observed peak acceleration observations are used to compute the ground motion attenuation with distance the hazard values depend to some extent on the duration of the synthetic catalog and the specific ground motion attenuation used and the uncertainty in the ground motions increases with decreasing hazard probability the program gives peak accelerations that are comparable to those of the 1996 u s national seismic hazard maps the method can be adapted to compute seismic hazard for cases where there are temporal or spatial variations in earthquake occurrence rates or source parameters

sensitivity analysis of seismic hazard for western liguria north western italy a first attempt towards the understanding and quantification of hazard uncertainty abstract the use of logic trees in probabilistic seismic hazard analyses often involves a large number of branches that reflect the uncertainty in the selection of different models and in the selection of the parameter values of each model the sensitivity analysis as proposed by rabinowitz and steinberg rabinowitz n steinberg d m 1991 seismic hazard sensitivity analysis a multi parameter approach bull seismol soc am 81 796 817 is an efficient tool that allows the construction of logic trees focusing attention on the parameters that have greater impact on the hazard in this paper the sensitivity analysis is performed in order to identify the parameters that have the largest influence on the western liguria north western italy seismic hazard the analysis is conducted for six strategic sites following the multi parameter approach developed by rabinowitz and steinberg rabinowitz n steinberg d m 1991 seismic hazard sensitivity analysis a multi parameter approach bull seismol soc am 81 796 817 and accounts for both mean hazard values and hazard values corresponding to different percentiles e g 16 ile and 84 ile the results are assessed in terms of the expected pga with a 10 probability of exceedance in 50 years for rock conditions and account for both the contribution from specific source zones using the cornell approach cornell c a 1968 engineering seismic risk analysis bull seismol soc am 58 1583 1606 and the spatially smoothed seismicity frankel a 1995 mapping seismic hazard in the central and eastern united states seismol res lett 66 8 21 the influence of different procedures for calculating seismic hazard seismic catalogues epicentral parameters source zone models frequency magnitude parameters maximum earthquake magnitude values and attenuation relationships is considered as a result the sensitivity analysis allows us to identify the parameters with higher influence on the hazard only these parameters should be subjected to careful discussion or further research in order to reduce the uncertainty in the hazard while those with little or no effect can be excluded from subsequent logic tree based seismic hazard analyses

the 17 august 1999 izmit earthquake on 17 august 1999 an earthquake of magnitude 7 4 shook northwestern turkey details on the earthquake9s characteristics and effects across northwestern turkey are provided and are put in the historical context of previous earthquakes in the region the earthquake was the seventh in a series of earthquakes migrating westwards along the north anatolian fault since 1939 information on historical earthquakes modeling and estimates of the slip rate along the fault indicate that the location and severity of the earthquake should not have come as a surprise

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

time independent and time dependent seismic hazard in greece based on seismogenic sources abstract an improved procedure is followed to assess time independent andtime dependent hazard for 144 broad sites cities towns villages of greece in termsof expected macroseismic intensities at each one of these sites in this procedureseveral new results are taken into account source parameters based on new researchwork on seismicity and on other relative information new regionalization and im proved seismicity data parameters and anisotropic radiation at the seismic source anew relation for the attenuation of macroseismic intensities and the effect of localconditions site effects on the strong ground motion analytic relations and tables determined by this procedure permit the reliableassessment of time independent hazard in terms of macroseismic intensity in mmscale peak horizontal ground acceleration and velocity at each one of these 144sites and at any probability level time dependent hazard has been also assessed for these 144 broad sites in greece in terms of the probability for the occurrence of strong ground motion with macro seismic intensity i vii in mm scale at each one of these sites during the period1996 2010 comparison of the assessed time dependent hazard with observed ma croseismic intensities of the period 1950 1995 indicates that the time dependentmodel gives very reasonable results introduction

optical measurements of small deeply penetrating bubble populations generated by breaking waves in the southern ocean bubble size distributions ranging from 0 5 to 125 m radius were measured optically during high winds of 13 m s 1 and large scale wave breaking as part of the southern ocean gas exchange experiment very small bubbles with radii less than 60 m were measured at 6 9 m depth using optical measurements of the near forward volume scattering function and critical scattering angle for bubbles 80 the bubble size distributions generally followed a power law distribution with mean slope values ranging from 3 6 to 4 6 the steeper slopes measured here were consistent with what would be expected near the base of the bubble plume bubbles likely stabilized with organic coatings were present for time periods on the order of 10 100 s at depths of 6 9 m here relatively young seas with an inverse wave age of approximately 0 88 and shorter characteristic wave scales produced lower bubble concentrations shallower bubble penetration depths and steep bubble size distribution slopes conversely older seas with an inverse wave age of 0 70 and longer characteristic wave scales produced relatively higher bubble concentrations penetrating to 15 m depth larger bubble sizes and shallower bubble size distribution slopes when extrapolated to 4 m depth using a previously published bubble size distribution our estimates suggest that the deeply penetrating small bubbles measured in the southern ocean supplied 36 of the total void fraction and likely contributed to the transfer and supersaturation of low solubility gases

multivariate statistical analysis for the assessment of groundwater quality under different hydrogeological regimes multivariate statistical analysis has been widely used for hydrogeochemical characterization of groundwater quality in this study hydrochemical data from three hydrological basins were used and two methods factor and cluster analyses were applied the first area is the coastal area of eastern thermaikos gulf where groundwater is influenced by seawater intrusion and geothermal fluids the other two areas are the inland basins of gallikos and perdikas in which agricultural and industrial activities constitute the main anthropogenic pollution sources of groundwater initially the aforementioned methods were applied for each area separately and resulted in a different number of significant factors and clusters while the natural and anthropogenic influences were spatially determined in each area additionally factor and cluster analyses were applied coupling data from all areas therefore five clusters and three major factors were determined distinguishing the hydrochemical processes and impacts from anthropogenic activities in more detail it is worth mentioning that the application of cluster analysis in the coupled groundwater samples of all studied areas resulted beneficially in the most hydrochemically complex area salinization dominates in the coastal area while in gallikos and perdikas basins high concentrations of no3 occur mainly due to agricultural activities and small livestock units the numerous hydrochemical samples are identified as the main issue for the higher discretization and reliability of the second approach nevertheless this study is associated with a number of limitations of multivariable statistical analysis regarding extreme concentrations of cl and na this issue stimulates further research in overcoming and understanding these drawbacks