seismic risk in turkey the aegean and the eastern mediterranean the occurrence of large magnitude earthquakes summary the file of turkish seismicity developed by kandilli observatory istanbul for earthquakes to 1970 is extended here up to 1978 using 1sc and pde data entries into this file are maintained on the surface wave magnitude scale m and conversion of body wave magnitude mb to m has been carried out where necessary using a formula derived for turkish earthquakes completeness analysis suggests that magnitudes m 4 5 may be used for statistical evaluation of seismic risk this file is analysed by a range of methods to provide a suite of risk forecasts forecasting results from least squares and maximum likelihood estimates of the whole process gutenberg richter cumulative frequency law of earthquake magnitude occurrence and from the part process of gumbel s first extreme value distribution all show small systematic differences in forecasts but all three methods lead to magnitude forecasts which fall well within the range of standard deviation however these forecasts are obtained by subdividing turkish seismicity in a cellular manner and many of these cells show curvature of the earthquake frequency magnitude distribution curve concave with respect to the origin gumbel s third asymptotic distribution of extreme values is chosen as an appropriate statistical description approximate upper bounds o to earthquake surface wave magnitude occurrence are evaluated and estimates of largest magnitudes expected over an interval of 75yr are forecast with uncertainties values of w are asymptotic uncertain and theoretically correspond to infinite return periods strain energy release diagrams are then invoked to estimate empirically the large magnitude m which is equivalent to the total strain energy which may be accumulated in a region this equivalent magnitude m is consistently less than w and there is a finite waiting time typically ranging from about 15 to 70 yr during which the energy equivalent to m3 may be accumulated

seismic slip deficit in the southwestern forearc of the hellenic subduction zone abstract the seismic coupling and the spatiotemporal distribution of seismicity on the presumed rupture surface of the 365 a d m w 8 3 0 2 crete event at the shallow plate contact of the hellenic subduction zone hsz southwest of crete is investigated the maximum cumulative average seismic slip u seis on the rupture surface is estimated for different time periods using historic and instrumental seismicity catalogs and utilizing a formula that incorporates empirical relations linking rupture area and average slip of an event to its moment magnitude m w events above the completeness magnitude of the catalog are incorporated by summation while events below are taken account of by integrating over the extrapolated frequency magnitude distribution using a truncated gutenberg richter relation estimates of u seis for the time intervals 0 1999 1500 1999 and 1964 2006 using historic and instrumental catalogs suggest a considerable seismic slip deficit when compared with the total slip expected from the temporal extrapolation of geodetic measurements this suggests a recent weakly coupled plate contact and a total slip predominantly accommodated aseismically despite the 365 a d event high seismic activity up to magnitudes of about m w 6 is found accompanying the aseismic slip at the plate contact investigations of the seismicity distribution hint at a spatial variability of the seismic energy release in the western forearc of the hsz activity in the proximity of the 365 a d epicenter is observed to be an order of magnitude larger than toward the northwest between crete and peloponnese this spatiotemporal variability of the seismic energy release and seismic coupling suggests that subregions of the plate contact undergo alternating periods of locking followed by intermediate magnitude events and aseismic sliding thus the behavior of significant portions of the plate contact southwest of crete may be described as conditionally stable

variation of seismic coupling with slab detachment and upper plate structure along the western hellenic subduction zone abstract the western hellenic subduction zone is characterized by a trenchward velocity of the upper plate in the ionian islands segment complete seismic coupling is achieved as is predicted by standard plate tectonic models in which there is no slab pull force because the slab has broken off the moderate local seismic moment rate relates to a shallow downdip limit for the seismogenic interface this characteristic may be attributed to the ductility of the lower crust of the upper plate which allows a decollement between the upper crust of the overriding plate and the subducting plate farther south a deeper downdip limit of the seismogenic interface is indicated by thrust faulting earthquakes which persist much deeper in western crete a correspondingly larger downdip width of this seismogenic zone is consistent with the suggested larger maximum magnitude of earthquakes here however since the seismic moment release rate seems to be moderate in the peloponnese and western crete like in in the ionian islands this seismically active interface cannot maintain complete seismic coupling across its larger downdip width a cause may be the lateral addition of overweight to the part of the slab still attached in crete by the free fall of its part that has broken off from the surface further north this increased slab pull reduces the compressive normal stress across the seismogenic interface and thus causes partial seismic coupling in its shallower part however the width of this part may provide an additional area contributing to slip in large earthquakes which may nucleate deeper on stick slip parts of the interface hints at anomalies in structure and seismicity which need to be resolved may relate to the present location of the edge of the tear in the slab

an alternative view of the bayesian probabilistic prediction of strong shocks in the hellenic arc abstract a bayesian discrete distribution as developed by ferraes 1985 is applied to predict the inter arrival times for strong shocks in the hellenic arc on the basis of nine samples of shocks with seismotectonic locations very different from those used by ferraes the results suggest an alternative view of the bayesian probabilistic prediction of strong earthquakes in the hellenic arc and can be summed up as follows 1 a maximum final bayesian probabilities of various inter arrival times in a given seismotectonic segment are very dependent on the data set used and particularly on its time length 2 b when using this method to determine the time intervals during which large shocks are to be expected in the western and eastern hellenic arcs it is very difficult to estimate intervals of less than a decade the determination of the occurrence time even in the long term sense remains the major problem in the prediction of these shocks 3 c bayesian probabilities in conjunction with seismicity observations indicate that large intermediate depth earthquakes in the hellenic arc are long overdue shocks of this sort can be expected to occur in the next few years it is also pointed out that although bayesian type predictions may be useful for engineering purposes they are not a suitable basis for making specific predictions or taking special precautions

the bayesian probabilistic prediction of strong earthquakes in the hellenic arc abstract the bayesian probability theory in conjunction with the poisson process model is used to develop a bayesian discrete distribution to estimate or predict the inter arrival times tj for strong earthquakes in the hellenic arc the bayesian posterior probabilities may be computed from the relationship p t r m t r e t r 1 e t r j 1 m t j e t j 1 e t j where p t r m is the conditional probability of the event tr given that an earthquake of magnitude m has occurred the bayesian discrete analysis is performed first by using the poisson process to determine the prior probability distribution for tj and the likelihood function we can imagine the random earthquake experiment involved in the application of bayes theorem to earthquake prediction to be a two stage experiment the first stage was initiated a long time ago when the real time arrival dates of strong earthquakes were first recorded the second stage was initiated in 1935 when the earthquake magnitude scale was introduced by richter 1935 in southern california richter probably never thought that this measure of the earthquake magnitude then will be an experiment designed to give us information about the outcome of the earthquake inter arrival times the first stage the earthquake data analyzed in this study have been taken from the earthquake catalog for the hellenic arc prepared by ambraseys 1981 the discrete bayesian analysis suggests determining the most likely outcomes for the length of earthquake inter arrival times by using some maximum values of the final bayesian probabilities the following inferences concerning future strong earthquake occurrences in the hellenic arc area may be drawn 1 1 our western northwestern zone is a seismic region which approximately coincides with the region studied by wyss and baer therefore we agree with the geographic location of the expected earthquake forecasted by wyss and baer 1981 2 2 using probability theory bayes theorem poisson process we concluded that a period of strong earthquake activity is expected to occur in the same geographic location during the decade 1992 2002 this conclusion supports ambraseys conclusion however it should be noted that our conclusion indicates that the period of strong earthquake activity will occur anyway a decade later than predicted by wyss and baer

multiple asperity model for earthquake prediction large earthquakes often occur as multiple ruptures reflecting strong variations of stress level along faults dense instrument networks with which the volcano kilauea is monitored provided detailed data on changes of seismic velocity strain accumulation and earthquake occurrence rate before the 1975 hawaii 7 2 mag earthquake during the 4 yr of preparation time the mainshock source volume had separated into crustal volumes of high stress levels embedded in a larger low stress volume showing respectively high and low stress precursory anomalies

significance of interdune deposits and bounding surfaces in aeolian dune sands bounding surfaces and interdune deposits provide keys for detailed interpretations of the development shape type wavelength and angle of climb of aeolian bedforms as well as overall sand sea conditions current alternate interpretations of bounding surfaces require very different but testable models for sand sea deposition two perpendicular traverses of jurassic entrada sandstone utah reveal relations among cross strata first order bounding surfaces and horizontal strata these field relations seem explicable only as the deposits of downwind migrating climbing enclosed interdune basins horizontal strata and dune bodies consisting of superimposed smaller crescentic dunes cross stratified deposits a 1 7 km traverse parallel to the palaeowind direction provides a time transgressive view showing continuous cosets of cross strata first order bounding surfaces and interdune deposits climbing downwind at an angle of a few tenths of a degree changes occur in the angle of climb cross strata structure and interdune deposits these reflect changes in depositional conditions through time a 1 5 km traverse perpendicular to the palaeowind direction provides a view at an instant in geological time showing first order bounding surfaces and interdune deposits forming flat laterally discontinuous lenticular bodies the distribution of interdune sedimentary structures in this traverse is very similar to that of some modern interdune basins such as those on padre island texas hierarchies of bounding surfaces in an aeolian deposit reflect the bedform development on an erg the presence of three orders of bounding surfaces indicates dune bodies consisting of smaller super imposed dunes the geometry of first order bounding surfaces is a reflection of the shape of the inter dune basins second order bounding surfaces originate by the migration of the superimposed dunes over the larger dune body and reflect individual dune shape and type third order bounding surfaces are reactivation surfaces showing stages in the advance of individual dunes the presence of only two orders of bounding surfaces indicates simple dunes modern and entrada interdune deposits show a wide variety of sediment types and structures reflecting deposition under wet damp and dry conditions interdune deposits are probably the best indicators of overall erg conditions and commonly show complex vertical sequences reflecting changes in specific depositional conditions

flexural cantilever models of extensional subsidence in the munster basin sw ireland and old red sandstone fluvial dispersal systems

seismic hazard evaluation for specific seismic regions of the world tsapanos t m and burton p w 1991 seismic hazard evaluation for specific seismic regions of the world tectonophysics 194 153 169 seismic hazard is estimated for fifty of the most seismically active countries of the world using the technique of gumbel s third asymptotic distribution of extreme values and hazard maps are produced for this purpose a catalogue of 9700 earthquakes with magnitudes m 2 5 5 has been compiled and earthquakes in the time period 1898 1985 are examined here an equal area grid point mesh of about 5 o latitude x 5 o longitude is chosen to represent the local seismicity this cell size corresponds approximately to the area of romania which is the smallest country examined the results estimate the most probable maximum magnitude for a time period of 85 years which exceeds magnitude 7 for all fifty of the cellular seismic regions and the contour maps and tables show its spatial variation and rank the countries in terms of overall relative seismic hazard the maps effectively produce a brief seismic hazard atlas

surface fault traces fault plane solution and spatial distribution of the aftershocks of the september 13 1986 earthquake of kalamata southern greece a shallow earthquake ofms 6 2 occurred in the southern part of the peloponnesus 12 km north of the port of the city of kalamata which caused considerable damage the fault plane solution of the main shock geological data and field observations as well as the distribution of foci of aftershocks indicate that the seismic fault is a listric normal one trending nne ssw and dipping to wnw the surface ruptures caused by the earthquake coincide with the trace of a neotectonic fault which is located 2 3 km east of the city of kalamata and which is related to the formation of messiniakos gulf during the pliocene quaternary tectonics field observations indicate that the earthquake is due to the reactivation of the same fault

strontium and carbon isotope stratigraphy of the llandovery early silurian implications for tectonics and weathering abstract a high resolution 87sr 86sr curve and paired 13c carbonate organic data set is generated for the llandovery series from the ikla drill core in estonia a 13c carbonate curve is also presented from the pancake range in nevada observed 87sr 86sr values in the ikla drill core are at a minimum in the early llandovery rhuddanian stage 0 7079 to 0 7080 and then trend to more radiogenic ratios in the basal part of the telychian stage an 87sr 86sr high near 0 7084 is observed in the telychian at the top of the studied section the range of values is in general agreement with the data from previous sample sets of brachiopods and conodonts recovered from localities in north america and europe that record a rising trend in the 87sr 86sr ratio throughout the llandovery from approximately 0 7080 to 0 7084 the major increase in the 87sr 86sr ratio during the late llandovery may be due to weathering of radiogenic source rocks that were uplifted during early silurian continent continent collisions the sr rise potentially coincides with the occurrence of an unusually thick sequence of k bentonite beds representing large magnitude ash falls in the early telychian a previously documented negative 13c excursion in marine carbonates in the lower telychian interval of the ikla core is quasi synchronous with the increase in 87sr 86sr our new organic matter 13c data from the ikla core confirm that this negative 13c carbonate excursion is not a result of diagenesis furthermore a negative 13c excursion in carbonates from the early telychian portion of the pancake range section in nevada seems to confirm the global scope of this carbon cycle perturbation

active deformation and seismic potential in the serbomacedonian zone northern greece abstract the seismic potential in the central part of the serbomacedonian geological zone n greece is examined for 1 the lateral distribution of the rupture zones of the 1902 1932 and 1978 large shocks and 2 the potential stress drop stored in the area of these three shocks the distribution of rupture zones defines an area trending sse nnw and the whole length of the area examined has been ruptured since 1902 in the area of the 1902 and 1932 large earthquakes the slip accumulated is enough to generate more large shocks

occurrence patterns of large earthquakes in the seismic zones along the hellenic arc occurrence patterns of large shallow and intermediate depth earthquakes in the seismic zones along the hellenic arc have been investigated it is shown that throughout this active region the earthquakes tend to occur in a rather systematic manner at each time period earthquakes occur within a discrete activated segment of the arc these occurrence patterns are considered to offer an insight into identifying where large earthquakes are expected to occur in the future

seismicity of the hellenic subduction zone in the area of western and central crete observed by temporary local seismic networks temporary local seismic networks were installed in western crete in central crete and on the island gavdos south of western crete respectively in order to image shallow seismically active zones of the hellenic subduction zone more than 4000 events in the magnitude range between 0 5 and 4 8 were detected and localized the resulting three dimensional hypocenter distribution allows the localization of seismically active zones in the area of western and central crete from the mediterranean ridge to the cretan sea furthermore a three dimensional structural model of the studied region was compiled based on results of wide angle seismics surface wave analysis and receiver function studies the comparison of the hypocenter distribution and the structure has allowed intraplate and interplate seismicity to be distinguished high interplate seismicity along the interface between the subducting african lithosphere and the aegean lithosphere was found south of western crete where the interface is located at about 20 to 40 km depth an offset between the southern border of the aegean lithosphere and the southern border of active interplate seismicity is observed in the area of crete the offset varies laterally along the hellenic arc between about 50 and 70 km a southwards dipping zone of high seismicity within the aegean lithosphere is found south of central crete in the region of the ptolemy trench it reaches from the interface between the plates at about 30 km depth towards the surface in comparison the aegean lithosphere south of western crete is seismically much less active including the region of the ionian trench intraplate seismicity within the aegean plate beneath crete and north of crete is confined to the upper about 20 km between 20 and 40 km depth beneath crete the aegean lithosphere appears to be seismically inactive in western crete the southern and western borders of this aseismic zone correlate strongly with the coastline of crete

high precision gravity observations on crete greece abstract the position of crete within the hellenic arc trench system is important for understanding the tectonics and geodynamics of the area in 1983 1984 a high precision network of 52 reoccupied gravity stations was established on crete for studies of vertical crustal movement and the detection of precursory phenomena associated with a large magnitude earthquake m 7 forecase just northwest of crete first by wyss and baer 1981 the standard deviation of the network adjustment is 0 045 and 0 065 g u for 1983 and 1984 respectively after applying a newly developed adjustment algorithm there were not statistically significant gravity changes for the stations of the network during its remeasurement in 1984 however there were differences at some stations of more than twice the level of their standard error stations established along the sedimentary basins of east and central crete such as perama heraklio and lerapetra grabens have a tendency to subsidence perama cheliana tymbaki stavraki have subsided from 37 22 to 72 23 mm on the other hand nearly all stations established on horsts tend to show uplift malia chania and heraklio airport were uplifted from 58 20 to 65 29 mm these elevation change values were obtained using the bouguer gravity gradient of 0 2 g u mm almost all the stations west of rethymno have a tendency for uplift regardless of their tectonic setting it is argued that the gravity data provide initial evidence that present day earth movements are consistent with longer term tectonic observations of uplift in western crete the occurrence of a strong shallow earthquake m 6 3 just offshore and west of crete between 1983 and 1984 may have been associated with this movement

long term accelerating foreshock activity may indicate the occurrence time of a strong shock in the western hellenic arc abstract in the decades prior to the occurrence of the 1899 ms 6 6 and 1947 ms 7 0 main shocks in the western hellenic arc wha the rate of occurrence of foreshocks ms 5 2 within a radius of 100 km around the epicenters can generally be said to have accelerated after a long period of very low foreshock activity stage i the process culminates in a final rapid acceleration of foreshocks some months before the main shocks stage ii while the last two months are quiescent stage iii these three stages are in good correspondence with the three stages of crustal deformation and several precursors to the main shock as predicted by the dilatancy model the data fit very well power law equations similar to those found for short term foreshocks of ordinary earthquakes and those associated with the creation of artificial lakes the position of the rupture zones of past wha strong shocks implies that the eastern part of the segment is the most probable location for the next strong shock in the arc a process of accelerating seismic activity similar to that which preceded the 1899 and 1947 shocks has been under way since 1966 around this part of the segment a comparison between changes in the power law curves for the earlier earthquakes and the one now expected indicates that the latter is now 3 8 months overdue assuming that the long term accelerating foreshock activity is a seismotectonic peculiarity of the wha segment i suggest that the preparation of the next rupture in the wha has entered a highly mature stage and that there will very probably be an earthquake in this area within the next few months

kinematics and deformation of central and southwestern greece from historical triangulation data and implications for the active tectonics of the aegean abstract changes in the coordinates of 38 stations 32 of which were common to three historical triangulation surveys 1889 1905 1927 1930 and 1950 1970 in central greece were computed based on conventional adjustment techniques and the assumption of a nearly fixed baseline length some of the calculated coordinate changes are significant against the a posteriori network adjustment errors and are likely to indicate tectonic motions consistent with those deduced from geological and geophysical data and other geodetic studies comparison of the first survey network with gps data more explicitly the historical geodetic data confirm the rotational character of the deformation in the area but they show that the strain pattern is likely to have changed after 1930 between 1890 and 1930 strain was changing smoothly as if no strain discontinuities existed while the peloponnesus was under contraction from the northeast probably reflecting accommodation of strain from the arc significant left lateral shear in the gulf of corinth and n s extension in the whole of the study area were observed only after 1930 estimates of strain are consistent with those deduced from comparison of historical triangulation and gps data corrected for the scale error that exists in the terrestrial geodetic data in greece and estimates of strain from seismological data the change in the kinematic pattern after 1930 seems to be confirmed by changes in the shear strain computed directly from changes in observed angles between stations and from changes in the seismicity rates such changes although not unusual in the geological record are not easy to explain but may reflect elastic rebound effects in area with an extremely complicated tectonic fabric or hysteresis in the accommodation of e w compression from the arc by n s stretching

tectonic significance of silurian magmatism in the canadian appalachians new u pb ages for granites from the new brunswick part of the canadian appalachians indicate that 90 of the undeformed felsic plutons are silurian and not devonian as previously thought silurian igneous and sedimentary assemblages were recently recognized throughout the canadian appalachians although the petrogenetic types of magmas as well as the grades of metamorphism and deformation vary widely our data support proposed tectonic models that suggest relatively continuous subduction and orogenic activity in the canadian appalachians from middle ordovician to middle devonian time

triassic sediments of the inner moray firth scotland early rift deposits patterns of triassic sedimentation in the inner moray firth are examined in the light of a new model of continental rift sedimentation that has been developed in the tertiary to recent rifts of east africa the major tectonic control during the trias was the great glen fault to the northwest which can be shown to have been moving in dip slip fashion at this time the structure of the firth appears to have resembled the simple half graben that makes up the great east african rift system deposits both thicken and get finer towards the fault sediments found in off shore wells are dominated by laminated fine sand and silty clay with sporadic evaporites similar sequences are characteristic of or associated with ephemeral lakes in modern semi arid continental rift settings no alluvial fans have been detected close to the faulted margin again this is consistent with general patterns of sedimentation against boundary faults in the kenyan rift the coarsest sedimentary sequences in the moray firth are on the unfaulted margin to the south around burghead they consist of fluviatile lake shore and aeolian deposits the fluvial sediments show evidence of tectonically induced cycles of sedimentation which are interpreted in terms of waves of detritus working down the drainage system beds dominated by pebbly horizontal laminae and reminiscent of steep straight and shallow ephemeral streams alternate with troughed sands of deeper more sinuous but equally ephemeral rivers these are the coarsest sediments of the unfaulted margin of the basin however the lack of thick conglomerate sheets which are a feature of east african sequences at equivalent positions within the rift basin suggests only small scale fault activity and a relatively subdued topography during triassic times this is supported by evidence of extensive calichification during the rhaetic which produced a top trias marker horizon found throughout the inner moray firth

integration of horizontal well geological data into reservoir descriptions rotliegende sandstone lancelot area southern north sea lancelot guinevere and excalibur are rotliegende group gas fields that were developed mainly by horizontal drilling horizontal well geological data from these fields are interpreted and integrated with vertical well data to evaluate the target zone and enhance the reservoir description lateral variations in reservoir quality and eolian facies are interpreted in a horizontal core borehole images and conventional electric logs are used to identify facies record the lateral extent and orientation of eolian dune cross bed sets characterize diagenetic trends and locate fractures through the uncored horizontal well sections the cored interval consists of gently dipping medium grained dune base strata separated by a set boundary from moderately steeply dipping fine grained dune top sediments permeability varies with grain size and is therefore greater in the dune base than the dune top in this cored section the main facies in the horizontal wells as a whole are of eolian dune interdune and fluvial to marine reworked eolian origin comparison of facies in horizontal and vertical wells defines reservoir units in the upper part of the formation that show large scale mound and intermound infilling geometries reflecting relic dune field geomorphology comparison of the lateral extents and heights of eolian cross bed sets and patterns of foreset bed dip vector swing suggest that the sets are strongly trough shaped in copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received may 25 1995 revised manuscript received march 6 1996 final acceptance august 14 1996 2robertson research international limited llandudno north wales ll30 1sa united kingdom current address robertson blackwatch ltd netherton business centre fetternear kemnay inverurie aberdeenshire ab1 5lx united kingdom 3mobil north sea limited 3 6 clements inn london wc2a 2eb united kingdom we thank mobil north sea ltd brabant oilex ltd and robertson research international ltd for permission to publish this paper we thank the following people for their helpful discussions peter corbett richard wood john ebbern peter lucas rob crossley and carl watkins and aapg referees peter hutchinson neil hurley and roy nurmi whose critical reviews helped improve the organization of the paper the opinions expressed and any misconceptions however are entirely ours

spatio temporal microseismicity clustering in the cretan region abstract spatio temporal clustering of microseismicity in the central forearc of the hellenic subduction zone in the area of crete is investigated data for this study were gathered by temporary short period networks which were installed on the islands of crete and gavdos between 1996 and 2004 the similarity of waveforms is quantified systematically to identify clusters of microseismicity waveform similarities are calculated using an adaptive time window containing both the p and s wave onsets the cluster detection is performed by applying a single linkage approach clusters are found in the interplate seismicity as well as in the intraplate seismicity of the continental crust in the region of the transtensional ptolemy structure the majority of the clusters are off the southern coast of crete in a region of elevated intraplate microseismic activity within the aegean plate clusters in the gavdos region are located at depths compatible with the plate interface while cluster activity in the region of the ptolemy trench is distributed along a nearly vertical structure throughout the crust extending down to the plate interface most clusters show swarm like behaviour with seismic activity confined to only a few hours or days without a dominant earthquake and with a power law distribution of the interevent times for the largest cluster precise relocations of the events using travel time differences of p and s waves derived from waveform cross correlations reveal migration of the hypocenters this cluster is located in the region of the ptolemy trench and migration occurs along the strike of the trench at 500 m day relocated hypocenters as well as subtle differences in the waveforms suggest an offset between the hypocenters and thus the activation of distinct patches on the rupture surface the observed microseismicity patterns may be related to fluids being transported along the plate interface and escaping towards the surface in zones of crustal weakness ptolemy structure triggering swarm like cluster activity along its way

long term earthquake prediction in the hellenic trench arc system abstract data concerning seismic sequences which have occurred in the hellenic trench sedimentary arc tectonic system have been used to investigate the time variation of the difference d 1 between the magnitude of the main shock and that of the largest aftershock the data are well fitted by an harmonic function with period of 29 years for both the western seismic zone ionian islands s peloponnesus w crete and the south southeastern zone crete karpathos rhodos it has been observed that the largest earthquakes in both zones are associated with low values of the d 1 t function based on these observations we suggest that a strong seismic activity with earthquakes of m 7 0 will break out soon in the hellenic trench arc system the largest of these earthquakes are expected between 1983 and 1987 a quiescence in seismicity which started fifteen years ago in the southern part of the western zone also indicates the generation of a very strong earthquake in this area during the next five years or so

comments on preseismic quiescence before large earthquakes in the aegean and surrounding area by karakaisis et al 1987 commentaire et reponse a l article de karakaisis g f panagiotopoulos d g krimnianiotou m ch papazachos b c 1987 ann geophysicae 5b 2 155 160

the seismology of greece abstract a review and a bibliography are given of the seismological literature for the area of greece in the period from 1950 up to the present time the aim is to incorporate all aspects of seismology starting with instrumental installations passing on to earthquake catalogues statistics and effects and ending up with structural properties and seismotectonics the purpose is to provide a service to every geophysicist who has an interest in this tectonically complex area and particularly to the numerous researchers engaged in geophysical expeditions to greece

intermediate term earthquake prediction in the area of greece application of the algorithm m8 the 3 strongest earthquakes m 7 0 which have occurred since 1973 in the area of greece were preceded by a specific increase of the earthquake activity in the lower magnitude range this activation is depicted by algorithm m8 this algorithm of intermediate term earthquake prediction was originally designed for diagnosis by times of increased probability tips of the strongest earthquake m 8 0 worldwide keilis borok andkossobokov 1984 at present the algorithm is retrospectively tested for smaller magnitudes in different seismic regions keilis borok andkossobokov 1986 1988 a tip refers to a time period of 5 years and an area whose linear size is proportional and several times larger than that of the incipient earthquake source altogether the tips diagnosed by the algorithm m8 in the area of greece occupy less than 20 and the times of expectation tes about 10 of the total space time domain considered also there is a current tip for the southeastern aegean sea and 1988 1992 it may specify the long term prediction given inwyss andbaer 1981a b

times of increased probability of earthquakes of ml 5 5 in greece diagnosed by algorithm m8 an attempt is made to explore the possibility of identifying the times of increased probability tips of occurrence of earthquakes with ml 5 5 by premonitory intermediate term seismic activation in lower magnitude ranges as defined in the algorithm m8 a tip refers to a 5 year period and an area whose length is several times greater than that of an incipient earthquake this algorithm has been already tested retrospectively for the strongest earthquakes of magnitude greater than or equal to 7 0 which have occurred in greece since 1973 in the present study the same algorithm is also applied retrospectively by considering smaller earthquakes of local magnitude ml greater than or equal to 5 5 the obtained results show that ten out of eleven events with m 5 5 which took place in greece and surrounding region from january 1 1977 till december 31 1990 occurred within the tips diagnosed by the algorithm m8 retrospectively only the thessaloniki earthquake of june 20 1978 did not occur within tip the m8 algorithm failed in four cases namely those that occurred in regions for which our catalogue was not complete altogether the tips occupy less than 25 and times expectation about 8 of the total space time considered there is also a current tip started at the end of 1986 or at the beginning of 1987 for the south southwestern part of thehellenic arc indicating that this area deserves particular attention if the algorithm m8 works reliably then this tip will be filled by the end of 1992 this result by no means constitute the definitive earthquake prediction but merely outline a territory for more detailed and comprehensive analysis

seismic quiescence in the western hellenic arc may foreshadow large earthquakes south of crete the seismicity rate was constant in space and time between 1950 and 1978 but in the western hellenic trench the rate was the same as that south of crete until 1962 whereupon it decreased by 80 we now suggest that the anomaly constitutes a warning of large earthquakes within the coming decade

reply on the comments of g a papadopoulos on the paper preseismic quiescence before large earthquakes in the aegean and surrounding area a considerable body of observations has been accumulated during the last decade relevant to the problem of long term earthquake prediction in the aegean and surrounding area by identifying precursory seismicity patterns much of this work concerns the effort to detect preseismic quiescence that is drop of the low magnitude seismicity rate in the seismogenic area of strong expected events by plotting the cumulative number of these small earthquakes as a function of time wyss baer 1981a b papazachos 1980 papazachos comninakis 1980 papadimitriou 1984 papadimitriou papazachos 1985a b papaioannou tsapanos papazachos 1987 in a recent paper from our laboratory which appeared in annales geophysicae karakaisis et al 1987 we made an effort to generalize the application of this method in the whole aegean and surrounding area 34 n 43 n 18 e30 e that is in an area which includes the aegean sea greece albania southern yugoslavia southern bulgaria and western turkey the paper consists of two main parts in the first part it has been shown that most of the earthquakes with mss7 0 which occurred in this area during the period 1947 1983 were preceded by a drop of the seismicity rate in rather broad areas around the epicentres of these earthquakes in the second part of our paper we made plots of the cumulative number of shocks for all seismic zones of this area these plots show that 11 of the shallow seismicity zones or parts of these zones and two zones of intermediate depth seismicity are at quiescence now on the basis of these observations and of other people s work on seismicity patterns in these zones we made the hypothesis that these zones may experience strong earthquakes it is pointed out in our paper that this work is of a rather qualitative character and further and more detailed studies are needed for quantitative results this can be facilitated by the establishment of a dense telemetric seismograph network in greece papadopoulos this issue claims that our results are of questionable validity because according to his opinion we applied an inappropriate method and we should have applied other quantitative methods that he suggests and because our data sample for each case is small furthermore he writes that we have overestimated the seismic potential of this area that is the number of the expected strong earthquakes in our paper is much larger than the number he calculates finally he accuses

greek tectonics and seismicity abstract the validity of existing tectonic models for the area of greece is examined in the light of the new recalculated parameters for earthquakes of the region makropoulos and burton 1981 relocated hypocentral positions are extracted from the catalogue to form radial and vertical distance depth cross sections centred on a reference point near the mid point of the aegean volcanic arc and these are used to form a three dimensional topography of the base of earthquake occurrence below 60 km isodepth maps are extracted from this topography as both three and two dimensional map presentations these maps reveal several significant features of deep seated tectonic processes in the region isodepths exceeding 150 km are seen in the northwest aegean and these are more closely linked to the sporadhes and gulf of thermaicos rather than the north aegean trough the 150 km isodepths are also seen in the northeast aegean straddling the dardanelles in the northeastern part of the peloponnesus gulf of saronikos and eastern gulf of corinth in the southern peloponnesus towards crete and extending from north of kos to south of rodos the largest extent of deepest activity is seen south of rodos and this continues towards southwest of turkey the subduction zone of the hellenic arc is clear but smooth benioff zones are not the norm and these data show that structural complexity is more readily observed it is concluded that none of the proposed tectonic models completely explain the observed activity over the whole area and rather than propose yet another model places where further work is still particularly necessary are identified

recent research on the physical aspects of earthquakes abstract recent developments in the field of physical aspects of earthquakes which encompasses in present day terminology the analysis of focal dynamics and of catastrophic effects of earthquakes are reviewed in particular individual sections of this review deal with the earthquake source effects of earthquakes on the ground the geographic and temporal distribution of earthquakes the characterization of seismic risk earthquake prediction and with the artificial release of earthquakes in this instance the review supplements earlier information by the author 1975 by new data published mainly between 1975 and 1984

distinctions and uses of stratification types in the interpretation of eolian sand abstract eolian and subaqueous cross strata cannot be distinguished reliably by many commonly cited criteria they can however generally be distinguished by the characteristics of their component types of stratification which represent processes of sorting and transport of the grain population on dunes eolian dune stratification types consist of grainflow cross strata grainfall laminae and wind ripple generated climbing translatent strata some of these types especially translatent strata have characteristics unique to the eolian realm these same stratification types are found to compose some ancient cross strata and their occurrence confirms the eolian interpretations of pans of the entrada jurassic navajo triassic jurassic and galesville cambrian formations a well as revealing emergent islands in the curtis formation jurassic previously considered to be totally marine in origin stratification types show a characteristic distribution on modern eolian dunes and differ in their relative abundances and structure on dunes of differing size and kind these same relations allow some estimates of the type shape and original height of ancient dune deposits as well as influencing the occurrences of surface features such as tracks and tipple forms the geological record of stratification types and other dune features is greatly affected however by the extent of the post depositional truncation of dunes