a microearthquake study of the mygdonian graben northern greece during march and april 1984 a temporary network of 29 portable stations was operated in the region of the mygdonian graben near thessaloniki northern greece where a destructive earthquake ms 6 5 had occurred in the summer of 1978 during a period of six weeks we recorded 540 earthquakes with magnitudes ranging from 0 2 to 3 0 from this set of data 254 events are selected which according to us have a precision in epicenter and depth better than 1 5 km a total of 54 single event focal mechanisms have been determined the seismicity and focal mechanisms show a rather complex pattern there are no clear individual faults but the e w and nw se striking zones show n s extension zones striking nne ssw show dextral strike slip motion but nw se zones with sinistral strike slip are also observed in the center of the graben where the 1978 earthquake was located we observe several thrust mechanisms distributed in two groups showing either nw se or e w compression these earthquakes seem to be located 2 km above the earthquakes showing normal mechanisms the mean direction of the t axes found from the focal mechanisms trends n15 and dips sub horizontal we propose a model for the formation and evolution of a complex graben system comprising several stages in the initial stage the deformation occurs along pre existing nw se or nne ssw faults with normal or strike slip movements in the second stage a new e w trending group of normal faults is formed over the ancient fault network these new faults have a direction perpendicular to the mean t axis and accommodate better the actual state of stress at this stage the initial faults adjust to the deformation produced by the e w trending new faults and may constitute geometric barriers to the evolution of the new normal faults

magnitude scaling of early warning parameters for the mw 7 8 tocopilla chile earthquake and its aftershocks we studied the correlation between the final event magnitude and four parameters obtained from the early portion of p and s phases for a set of high quality subduction events these relationships are used in the framework of earthquake early warning systems for real time magnitude estimation the investigated parameters are thelow pass filteredpeakdisplacement pd theintegralofthevelocitysquared iv2 and the predominant and characteristic periods p and c we created a dataset from the continuous records of the first twoweeks following the 14 november 2007 mw 7 8 tocopilla chile earthquake the dataset includes 69 events with magnitudes greater than 4 among them the main event mw 7 8 the main aftershocks of mw 6 7 occurred on november 15 and 4 events with magnitudegreater than 6 the low pass filtered pd readonshortp phaseands phasewindowsiswellcorrelated withthefinalmagnitude confirming previous results indeed when examining 2 s timewindows of pwaves we didnotobserveanysaturationeffectformagnitudesgreaterthan6 5 however thereisa slope change in the regression curve a similar result is obtained from the integral of squared velocity computed over short windows around p and s waves the character istic and predominant periods are correlated with magnitudes up to mw 6 but they clearly do not scale with the magnitude for the stronger events our observations offer insight into the feasibility of an early warning system in chile

seismic evidence for an earthquake nucleation phase near source observations show that earthquakes initiate with a distinctive seismic nucleation phase that is characterized by a low rate of moment release relative to the rest of the event this phase was observed for the 30 earthquakes having moment magnitudes 2 6 to 8 1 and the size and duration of this phase scale with the eventual size of the earthquake during the nucleation phase moment release was irregular and appears to have been confined to a limited region of the fault it was characteristically followed by quadratic growth in the moment rate as rupture began to propagate away from the nucleation zone these observations suggest that the nucleation process exerts a strong influence on the size of the eventual earthquake

gravity wave and orographic wave activity observed around the antarctic and arctic stratospheric vortices by the cosmic gps ro satellite constellation 1 polar stratospheric gravity wave activity is studied using data from the constellation observing system for meteorology ionosphere and climate cosmic global positioning system radio occultation gps ro waves with vertical wavelengths of 2 to 15 km are considered the temperature variance 2 is used as a measure of wave activity and is studied on isentropic surfaces large intermittent orographic wave activity is identified during austral spring 2007 above the patagonian andes and the antarctic peninsula where 2 in the stratosphere increases by up to a factor of 5 for periods of 5 days to a few weeks the 2 are also investigated in equivalent latitudes to allow a direct comparison with the changing vortex structure the october 2007 2 inside the antarctic vortex boundary region at 400 600 k is one and a half times that outside the vortex this region of enhanced 2 descends in time and is not observed during the decay of the arctic vortex during the boreal winter of 2006 2007 orographic wave activity is observed above scandinavia and greenland an analysis of the 400 k and the 450 k levels in both hemispheres shows a strong relationship between enhanced 2 and the location of the vortex edge suggesting that the waves observed are propagating poleward and are guided to higher altitudes by the vortex the line of sight of the occultations shows a preference for north south alignment indicating that cosmic favors the detection of orographic waves above the north south oriented mountain ranges considered here

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

aftershocks of the june 20 1978 greece earthquake a multimode faulting sequence abstract a 10 station portable seismograph network was deployed in northern greece to study aftershocks of the magnitude m b 6 4 earthquake of june 20 1978 the main shock occurred in a graben about 25 km northeast of the city of thessaloniki and caused an east west zone of surface rupturing 14 km long that splayed to 7 km wide at the west end the hypocenters for 116 aftershocks in the magnitude range from 2 5 to 4 5 were determined the epicenters for these events cover an area 30 km east west by 18 km north south and focal depths ranges from 4 to 12 km most of the aftershocks in the east half of the aftershock zone are north of the surface rupture and north of the graben those in the west half are located within the boundaries of the graben composite focalmechanism solutions for selected aftershocks indicate reactivation of geologically mapped normal faults in the area also strike slip and dip slip faults that splay off the western end of the zone of surface ruptures may have been activated the epicenters for four large m 4 8 foreshocks and the main shock were relocated using the method of joint epicenter determination collectively those five epicenters form an arcuate pattern convex southward that is north of and 5 km distant from the surface rupturing the 5 km separation along with a focal depth of 8 km average aftershock depth or 16 km neis main shock depth implies that the fault plane dips northward 58 or 73 respectively a preferred nodal plane dip of 36 was determined by b c papazachos and his colleagues in 1979 from a focal mechanism solution for the main shock if this dip is valid for the causal fault and that fault projects to the zone of surface rupturing a decrease of dip with depth is required

observation and modeling of gravity wave propagation through reflection and critical layers above andes lidar observatory at cerro pachon chile a complex gravity wave event was observed from 04 30 to 08 10 utc on 16 january 2015 by a narrow band sodium lidar and an all sky airglow imager located at andes lidar observatory alo in cerro pachon 30 25 s 70 73 w chile the gravity wave packet had a period of 18 35 min and a horizontal wavelength of about 40 50 km strong enhancements of the vertical wind perturbation exceeding 10 m s 1 were found at 90 km and 103 km consistent with nearly evanescent wave behavior near a reflection layer a reduction in vertical wavelength was found as the phase speed approached the background wind speed near 93 km a distinct three layered structure was observed in the lidar data due to refraction of the wave packet a fully nonlinear model was used to simulate this event which successfully reproduced the amplitudes and layered structure seen in observations the model results provide dynamical insight suggesting that a double reflection occurring at two separate heights caused the large vertical wind amplitudes while the three layered structure in the temperature perturbation was a result of relatively stable regions at those altitudes the event provides a clear perspective on the filtering processes to which short period small scale gravity waves are subject in mesosphere and lower thermosphere

hypocenter locations in finite source rupture models we use a database of more than 80 finite source rupture models for more than 50 earthquakes m w 4 1 8 1 with different faulting styles occurring in both tectonic and subduction environments to analyze the location of the hypocenter within the fault and to consider the correlation between hypocenter location and regions of large slip rupture in strike slip and crustal dip slip earthquakes tends to nucleate in the deeper sections of the fault subduction earthquakes do not show this tendency ratios of the hypocentral slip to either the average or the maximum slip show that rupture can nucleate at locations with any level of relative displacement rupture nucleates in regions of very large slip d 2 3 d max in only 16 of the events in regions of large slip 1 3 d max d d max in 35 of the events and in regions of low slip d 1 3 d max in 48 of the events these percentages significantly exceed the percentages of fault area with very large 7 and large 28 slip ruptures that nucleate in regions of low slip however tend to nucleate close to regions of large slip and encounter a zone of very large slip within half the total rupture length applying several statistical tests we conclude that hypocenters are not randomly located on a fault but are located either within or close to regions of large slip

the environmental seismic intensity scale esi 2007 in greece addition of new events and its relationship with magnitude in greece and the mediterranean preliminary attenuation relationships abstract the environmental seismic intensity esi scale has been officially released in 2007 and is based on the quantification of earthquake environmental effects due to its quantitative nature the scale improves the process of assessing macroseismic intensities particularly in the epicentral area of those cases in which sole traditional intensity scales prove to be ineffective following a large number of publications that applied this relatively newly established scale there is some need for parametrization this is because this intensity scale can offer new insights to seismic hazard assessment and has the potential to reduce the uncertainties that stem from traditional macroseismic scales this study has three main goals firstly to enrich and compile an esi 2007 database from earthquakes in greece by adding 4 new events secondly to extract a relationship between magnitude and the esi 2007 for greece and the mediterranean thirdly to offer a preliminary estimate of how the intensity attenuates with distance after developing a code in python language to assist this process the esi 2007 scale was applied in the 1995 ms 6 6 kozani grevena earthquake the 1978 mw 6 5 thessaloniki earthquake the historic 1894 atalanti earthquake sequence m 6 4 and m 6 8 and the 365ad event in crete m 8 4 these events were selected because they have well documented and extensive co seismic effects including primary and secondary surface ruptures rockfalls landslides and liquefaction phenomena for the kozani earthquake extracted results were correlated with sar interferograms in order to provide a complete and high spatial resolution of the ground deformation both the kozani grevena and the thessaloniki events produced a maximum intensity ix on the esi 2007 scale the atalanti earthquake produced a maximum intensity x and the 365ad crete earthquake a maximum intensity xii overall the esi 2007 scale compares fairly well with the traditional macroseismic scales except for some villages in the kozani grevena epicentral area where due to the poor quality of buildings existing scales overestimated the intensity by one degree compared to the esi 2007 it is interesting to note that both for greece and the mediterranean area a strong correlation exists between mw and the esi 2007 scale in particular the following relationships between the mw and the esi scale have been extracted i for greece io esi 2007 3 1427 exp 0 1643mw and ii for the mediterranean io esi 2007 3 3543exp 0 1557mw however more events and more data regarding the intensity distributions are required to establish the intensity attenuation with distance

a model for a seismic computerized alert network in large earthquakes damaging ground motions may occur at large epicentral distances because of the relatively slow speed of seismic waves it is possible to construct a system to provide short term warning as much as several tens of seconds of imminent strong ground motions from major earthquakes automated safety responses could be triggered by users after receiving estimates of the arrival time and strength of shaking expected at an individual site although warning times are likely to be short for areas greatly damaged by relatively numerous earthquakes of moderate size large areas that experience very strong shaking during great earthquakes would receive longer warning times

a global view of stratospheric gravity wave hotspots located with atmospheric infrared sounder observations 1 the main aim of this study is to find and classify hotspots of stratospheric gravity waves on a global scale the analysis is based on a 9 year record 2003 to 2011 of radiance measurements by the atmospheric infrared sounder airs aboard nasa s aqua satellite we detect gravity waves based on 4 3 m brightness temperature variances our method focuses on peak events i e strong gravity wave events for which the local variance considerably exceeds background levels we estimate the occurrence frequencies of these peak events for different seasons and time of day and use the results to find local maxima or hotspots in addition we use airs radiances at 8 1 m to simultaneously detect convective events including deep convection in the tropics and mesoscale convective systems at middle latitudes we classify the gravity wave sources based on seasonal occurrence frequencies for convection but also by means of time series analyses and topographic data our study reproduces well known hotspots of gravity waves e g the andes and the antarctic peninsula however the high horizontal resolution of the airs observations also allows us to locate numerous mesoscale hotspots which are partly unknown or poorly studied so far most of these mesoscale hotspots are found near orographic features like mountain ranges coasts lakes deserts or isolated islands this study will help to select promising regions and seasons for future case studies of gravity waves

travel times of pn waves in the aegean and surrounding area summary based on accurately located 23 very shallow earthquakes h 1 14 km in northern and central greece by portable networks of seismic stations and by the joint epicentre method the travel times of the p waves from the foci of these earthquakes to the sites of 54 permanent stations in the balkan region have been determined the travel times of p waves in the central and eastern part of the area eastern greece south eastern yugoslavia the aegean sea bulgaria southern romania western turkey fit a straight line very well with the p velocity equal to 7 9 f 0 1 km s on the contrary the travel times of p waves to stations in the western part of the area albania western greece do not fit this curve because the p waves travelling to these stations are delayed by more than 1 s due to the thicker crust under the dinarides hellenides mountain range time delays for p waves have been calculated for each permanent station in the balkan area with respect to the mean travel time curve of these waves in the central and eastern part of the area corrections of the travel times for these delays contribute very much to the improvement of the accuracy in the location of the shallow earthquakes in the aegean and surrounding area

s wave attenuation in the crust in northern greece abstract the attenuation of shear waves in the crust is estimated for frequencies between 1 5 and 12 0 hz by applying a single station method based on the rate of decay of the s wave to coda wave amplitude ratio with distance the data used come from local earthquakes that occurred in the thessaloniki area northern greece during the period 1983 through 1989 and were recorded by the telemetered network of the geophysical laboratory of the university of thessaloniki the q s values obtained are 115 244 477 and 755 for 1 5 3 0 6 0 and 12 0 hz respectively these values are very close to the coda q values estimated for the same area using the s to s single scattering model for lapse times between 30 and 100 sec but they are higher than the coda q values for lapse times between 10 and 30 sec the estimated q s is found to be strongly frequency dependent proportional to f 0 91 which is very close to the frequency dependence of the coda q

a gravity wave climatology for antarctica compiled from challenging minisatellite payload global positioning system champ gps radio occultations 1 the seasonal geographical and altitudinal dependence of gravity wave activity in the lower stratosphere over antarctica is presented gravity wave activity is estimated by calculating potential energy ep from radio occultation profiles obtained by the challenging minisatellite payload global positioning system champ gps experiment significant seasonal variation of wave activity is observed smaller wave activity in summer is attributed to waves with small phase velocities experiencing critical level filtering at other times of the year when wave activity is large less filtering occurs and the strong background wind is likely to cause doppler shifting of waves to longer vertical wavelengths which can reach larger amplitudes before saturating relationships between gravity wave activity and geographic location indicate that topography is a strong source for wave activity especially over the antarctic peninsula however wind rotation in this area was found to reduce the wave energy in summer at certain altitudes a strong enhancement of wave energy is observed at the edge of the polar vortex again reduced critical level filtering and doppler shifting in the area of the jet are likely to be major causes for this finding possible limitations to this study due to observational filtering are discussed

deterministic ground motion scenarios for engineering applications the case of thessaloniki greece abstract in this article we present a deterministic study to estimate seismic ground motions expected in urban areas located near active faults the purpose was to generate bedrock synthetic time series to be used as seismic input into site effects evaluation analysis and loss estimates for the urban area and infrastructures of thessaloniki northern greece two simulation techniques a full wave method to generate low frequency seismograms 1 hz were used to compute time series associated with four different reference earthquakes having magnitudes from 5 9 to 6 5 and located within 30 km of thessaloniki the propagation medium and different source parameters were tested through the modeling of the 1978 thessaloniki earthquake m 6 5 moreover two different nucleation points were considered for each fault in order to introduce additional variability in the ground motion estimates between the two cases the quasi unilateral rupture propagation toward the city produces both higher median peak ground acceleration pga and peak ground velocity pgv values and higher variability than bilateral ones conversely the low frequency ground motion that is peak ground displacement pgd is slightly influenced by the position of the nucleation point and its variability is related to the final slip distribution on the faults of the reference earthquakes and to the location of the sites with respect to the nodal planes of the radiation pattern to validate our deterministic shaking scenarios we verified that the synthetic peak ground motions pga and pgv and spectral ordinates are within one standard deviation of several ground motion prediction equations valid for the region at specific sites we combined the low and high frequency synthetics to obtain broadband time series that cover the entire frequency band of engineering interest 0 25 hz the use of synthetic seismograms instead of empirical equations in the hazard estimates provides a complete evaluation of the expected ground motions both in frequency and time domains including predictions at short distances from the fault 0 10 km and at periods larger than 2 3 sec

intense foreshocks and a slow slip event preceded the 2014 iquique mw 8 1 earthquake the subduction zone in northern chile is a well identified seismic gap that last ruptured in 1877 the moment magnitude mw 8 1 iquique earthquake of 1 april 2014 broke a highly coupled portion of this gap to understand the seismicity preceding this event we studied the location and mechanisms of the foreshocks and computed global positioning system gps time series at stations located on shore seismicity off the coast of iquique started to increase in january 2014 after 16 march several mw 6 events occurred near the low coupled zone these events migrated northward for 50 kilometers until the 1 april earthquake occurred on 16 march on shore continuous gps stations detected a westward motion that we model as a slow slip event situated in the same area where the mainshock occurred

the 1978 earthquake sequence near thessaloniki northern greece summary this paper presents a detailed study of teleseismically and locally recorded foreshocks and aftershocks of the 1978 thessaloniki earthquake sequence and discusses the relations between the locations and mechanisms of these shocks and the three dimensional geometry of faulting in the source region sixteen teleseismically recorded events were relocated using a relative relocation method and positioned geographically using the accurate locally determined location of the largest aftershock all these shocks had depths shallower than 15 km the spatial distribution of the foreshocks showed that the activity was initiated at the central part of the epicentral region progressed westwards and for about 20 days clustered in the region of the imminent mainshock no teleseismically recorded foreshock was located west of the mainshock location in less than 1 hr after the mainshock large aftershocks occurred west of it and in later stages spanned the entire western part of the epicentral region no teleseismically recorded aftershocks were located east of the mainshock locally recorded aftershocks were accurately located and provided a more detailed picture of the seismic deformation they occurred at depths between 3 and 12 km and in three distinct clusters separated by well defined gaps the largest foreshock on may 23 had a moment of 5 6 1024dyne cm and a mean displacement of 31cm the mainshock on june 20 had a moment of 5 2 1025dyne cm a strain drop of 4 0 10 5 static stress drop of 12 bar and a mean displacement of 64 cm these values are for one of the two possible interpretations of the aftershock distribution which suggests that the largest earthquakes of the sequence occurred on two different but adjacent fault segments the first event 1 on may 23 occurred along the central fault segment and was followed 28 days later by the second event 2 on june 20 along a western fault segment finally 61 days later another smaller earthquake event 3 occurred along another fault east of event 1

anisotropic radiation modelling of macroseismic intensities for estimation of the attenuation structure of the upper crust in greece a method is suggested for the analysis of macroseismic intensity data in order to accurately determine an average attenuation structure of the upper part of the crust in an area the method is based on a model which assumes that the observed intensities depend on source properties radiation pattern size focal depth geometrical spreading and anelastic attenuation the method is applied to 13 008 intensity values observed in corresponding sites of greece and grouped in 4228 groups according to their spatial clustering in order to diminish observational errors and site effects an average intensity attenuation coefficient c 0 0039 0 0016 corresponding to a quality factor q 350 140 is determined for the upper 20 km of the crust in this area this value is relatively low in good agreement with the relatively high heat flow and high seismic activity of this area a byproduct of the present study is the determination for each earthquake of a macroseismic focal depth and of a macroseismic size which is strongly correlatted with both the earthquake s magnitude and its seismic moment determined by independent methods

coda waves a review the analysis and interpretation of coda waves have received increasing attention since the early seventies in the past few years interest in this subject has spread worldwide and the study of high frequency seismic coda waves has become a very important seismological topic as a conclusion of the studies accomplished in this time coda waves are considered the result of scattering processes caused by heterogeneities acting on seismic waves p ands waves play a particularly important role in this interaction the process introduces an attenuation which added to the intrinsic absorption gives the observed apparent attenuation therefore coda waves constitute a thumbprint left by the heterogeneities on the seismograms coda waves offer decisive information about the mechanism of how scattering and attenuation take place this review describes coda waves in detail and summarizes the work done in this subject to 1986 the relation between coda waves and attenuation in the context of research on seismic scattering problems is stressed particular attention has been given to the application of coda waves to estimate source and medium parameters the state of the art of the temporal variations of coda wave shape and the possible use of these variations as an earthquake precursor also are presented care has been taken to introduce the statistical models used to deal with the heterogeneities responsible for scattering

gravity waves above the andes detected from gps radio occultation temperature profiles jet mechanism 1 a significant wave activity wa in the upper troposphere and lower stratosphere mainly during winter was detected at midlatitudes in the southern hemisphere 30 40s above the andes range from an analysis of global positioning system radio occultation gps ro temperature profiles retrieved by champ challenging minisatellite payload and sac c satelite de aplicaciones cientificas c low earth orbit leo satellites between may 2001 and february 2006 the possible main gravity wave sources in this region are i orographic forcing ii geostrophic adjustment and iii deep convection the available vertical resolution of gps ro soundings does not rule out any of these alternatives based on satellite imaginary the wa enhancements cannot be attributed to deep convection events inertia gravity waves igws could be generated after a geostrophic adjustment process following a perturbation of the zonal jet situated above the andes mountains by mountain waves mws the monthly wa intensity follows the zonal wind velocity strength according to its seasonal variability at jet altitudes as the gps leo lines of sight are roughly meridionally aligned and the morphology of the andes at middle latitudes is predominantly north south it was possible to detect mws as well as igws from gps ro temperature profiles this characteristic does not apply for other mountain range alignments from the analysis of a numerical simulation at the time and location of a single ro event with very strong wa two main modes of oscillation with horizontal wavelength around 40 and 200 km were identified the first one is attributed to a mw and the second one to an igw

gravity wave characteristics in the southern hemisphere revealed by a high resolution middle atmosphere general circulation model abstractgravity wave characteristics in the middle to high latitude southern hemisphere are analyzed using simulation data over 3 yr from a high resolution middle atmosphere general circulation model without using any gravity wave parameterizations gravity waves have large amplitudes in winter and are mainly distributed in the region surrounding the polar vortex in the middle and upper stratosphere while the gravity wave energy is generally weak in summer the wave energy distribution in winter is not zonally uniform but it is large leeward of the southern andes and antarctic peninsula linear theory in the three dimensional framework indicates that orographic gravity waves are advected leeward significantly by the mean wind component perpendicular to the wavenumber vector results of ray tracing and cross correlation analyses are consistent with this theoretical expectation the leeward energy propagation extends to several thousand kilometers which explains part of the gravity wave distribution aro

comment on earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records by aldo zollo maria lancieri and stefan nielsen an early warning system should determine the loca tion and magnitude of an earthquake as rapidly as possiblein order to broadcast an alarm to regions that will undergosevere ground shaking it was recently claimed by zollo etal 2006 that earthquake size could be determined fromonly the first 2 seconds of p or s wave strong motion data this represents a fraction of the rupture time for larger m 7 events using this relatively short amount of data themethod of analysis was to find the peak ground displace ment pgd which was reported to scale with earthquakemagnitude such rapid information would play an importantand much needed role in an earthquake early warning eew system here we perform a similar analysis onstrong motion data from the kik net and k net arrays injapan and find no compelling evidence that the peak grounddisplacement during the first couple of seconds of p wave isrelated to the eventual size of a large earthquake

temporal evolution of surface rupture deduced from coseismic multi mode secondary fractures insights from the october 8 2005 mw 7 6 kashmir earthquake nw himalaya abstract detailed rupture fracture analyses of some of the well studied earthquakes have revealed that the geometrical arrangement of secondary faults and fractures can be used as a geological tool to understand the temporal evolution of slip produced during the mainshock the october 8 2005 mw 7 6 kashmir earthquake nw himalaya surface rupture provides an opportunity to study a complex network of secondary fractures developed on the hanging wall of the fault scarp the main fault scarp is clearly thrust type rupture length is 75 5 km and the overall trend of the rupture is nw se we present the results of our detailed structural mapping of secondary faults and fractures at 1 100 scale on the hanging wall of the southern end of the rupture in the vicinity of the sar pain secondary ruptures can be broadly classified as two main types 1 normal faults and 2 right lateral strike slip riedel fractures the secondary normal faults are nw se striking with a maximum 3 3 meter vertical displacement and 2 5 meter horizontal displacement estimated total horizontal extension across the secondary normal faults is 3 1 3 5 we propose that the bending moment and coseismic stress relaxation can explain the formation of secondary normal faults on the hanging wall of the thrust fault the strike slip riedel fractures form distinct sets of tension t and shear fractures r r y with right lateral displacement field observations revealed that the riedel fractures t cut the secondary normal faults in addition there is kinematic incompatibility and magnitude mismatch between the secondary normal faults and strike slip riedel fractures the cross cutting relationship geometric and magnitude incoherence implies a temporal evolution of slip from dip to strike slip during the mainshock faulting the interpretation is consistent with the thrust fault plane solution with minor right lateral strike slip component

lidar observations of gravity wave activity and arctic stratospheric vortex core warming measurements of stratospheric thermal structure and gravity wave activity have been obtained with a rayleigh lidar in the canadian high arctic at eureka 80 n 86 w during five recent winters the observations reveal that an annual late december warming of the upper stratosphere occurred in the polar vortex core and was sustained through the winter increased gravity wave activity was detected in the vortex jet during the warming that these two phenomena developed in parallel suggests they are related it is proposed that increased gravity wave momentum deposition above the jet maximum forced flow into the vortex core where it descended and warmed adiabatically

temporal and spatial variation on coda q 1 associated with the north palm springs earthquake of july 8 1986 a temporal and spatial change of codaq 1 associated with the occurrence of the north palm springs earthquake of july 8 1986 was studied by using 242 small local earthquakes in the vicinity of the mainshock we found that the codaq 1 of earthquakes which occurred before the mainshock was significantly higher than that of the aftershocks in the mainshock area while the codaq 1 for the surrounding area remained almost constant throughout 1986 codaq 1 was determined separately for the lapse time windows of 10 to 20 sec and 15 to 40 sec for the period from 1981 to 1987 the result for the time window 10 to 20 sec showed a peak in codaq 1 before the time of mainshock at all frequencies the peak appeared earlier at lower frequencies there was no significant change in codaq 1 for the time window 15 to 40 sec probably because the change was restricted to a small area

hypothetical real time gnss modeling of the 2016 mw 7 8 kaikōura earthquake perspectives from ground motion and tsunami inundation predictionhypothetical real time gnss modeling of the 2016 mw 7 8 kaikōura earthquake

site effects in the city of thessaloniki greece estimated from acceleration data and 1d local soil profiles abstract in this study the site effects on seismic ground motion in the city of thessaloniki greece are estimated by applying experimental methods on acceleration data and theoretical modeling the technique of standard spectral ratio ssr is applied to a reference station located on rock while the horizontal to vertical spectral ratio hvsr technique is applied to earthquake records entire record length including p and s waves as well as on noise recordings in addition the ssr method is also applied to the vertical components the results from all methods are compared in terms of resonant frequencies and amplification levels the fundamental resonant frequency is identified by all methods while the average amplification level is generally underestimated when the hvsr technique is used an attempt is made to correlate the site amplifications computed in this study with the observed macroseismic intensities reported at the same sites for the 20 june 1978 earthquake a relation of the form i b log s s f is derived where i is the intensity increment with respect to the intensity of the reference station and ssr is the mean amplification factor obtained at each station using the ssr technique for a certain frequency band in the numerical approach we construct complete strong motion synthetics using the modal summation method for the p sv waves up to frequencies of 10 hz as input four point sources are used located at different distances and azimuths from the stations ratios of response spectra of the local 1d over the regional 1d synthetic seismograms are calculated the obtained mean spectral amplifications are compared with those derived from experimental data and the two sets are found to be consistent at most stations

geodetic constraints on the fault pattern of the 1978 thessaloniki northern greece earthquake ms 6 4 summary repeated measurement of a 110 km long high precision spirit levelling traverse indicates that between 1958 and 1978 about 25 cm of subsidence occurred along a distance of 30 km in the mygdonian quaternary graben near thessaloniki northern greece observed displacements are significant against random and systematic errors and most are unrelated to near surface effects and can be assigned to the 1978 thessaloniki destructive earthquakes the available data do not permit a formal inversion but an elastic dislocation analysis indicates that the main shock of the seismic sequence ms 6 4 was probably associated with a ne dipping wnw trending blind normal fault marking the southwestern margin of the mygdonian graben in agreement with seismological and structural data there also exists evidence for incipient faulting in the central southern part of the mygdonian graben

earthquake magnitude calculation without saturation from the scaling of peak ground displacement gps instruments are noninertial and directly measure displacements with respect to a global reference frame while inertial sensors are affected by systematic offsets primarily tilting that adversely impact integration to displacement we study the magnitude scaling properties of peak ground displacement pgd from high rate gps networks at near source to regional distances 10 1000 km from earthquakes between mw6 and 9 we conclude that real time gps seismic waveforms can be used to rapidly determine magnitude typically within the first minute of rupture initiation and in many cases before the rupture is complete while slower than earthquake early warning methods that rely on the first few seconds of p wave arrival our approach does not suffer from the saturation effects experienced with seismic sensors at large magnitudes rapid magnitude estimation is useful for generating rapid earthquake source models tsunami prediction and ground motion studies that require accurate information on long period displacements

a modeling study of stratospheric waves over the southern andes and drake passage abstractlarge amplitude stratospheric gravity waves over the southern andes and drake passage as observed by the atmospheric infrared sounder airs on 8 9 august 2010 are modeled and studied using a deep 0 70 km version of the coupled ocean atmosphere mesoscale prediction system coamps model the simulated tropospheric waves are generated by flow over the high central andes ridge and the patagonian peaks in the southern andes some waves emanating from patagonia propagate southeastward across drake passage into the stratosphere over a horizontal distance of more than 1000 km the wave momentum flux is characterized by a tropospheric maximum over patagonia that splits into two comparable maxima in the stratosphere one located directly over the terrain and the other tilting southward with altitude using spatial ray tracing techniques and flow conditions derived from the numerical simulation the authors find that waves that originate from the high ridge in the central andes are absorbed by a critica

thessaloniki s detailed microzoning subsurface structure as basis for site response analysis the city of thessaloniki is located in northern greece close to a large seismogenic area and it has experienced several destructive earthquakes during the present century in this paper we focus on the definition of the subsurface structure of the city from a site response analysis perspective the paper presents together with a summary of geology and seismicity the results of a large scale geophysical and geotechnical survey in order to determine and validate geometry and dynamic properties of the main soil formations the synthesis and combination of recent results regarding the dynamic properties with those obtained from the elaboration of a large database of classical geotechnical tests led to the design of a detail geotechnical map and of various 1 d profiles 2 d cross sections and 3 d thematic maps for the main soil formations these soil profiles and maps are oriented to site effect studies and provide a comprehensive picture easily adapted to geographic information systems gis for planning and design purposes moreover the results of this study were correlated with macroseismic observations reported in many earlier published microzonation studies of thessaloniki these comparative observations revealed the complexity of surface geology of the urban area a fact which is expected to provoke additional amplification with respect to 1 d resonance

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

attenuation of coda waves in northern greece the single scattering model has been applied for the estimation of codaq values for local earthquakes that occurred in northern greece during the period 1983 1989 and recorded by the telemetered network of the geophysical laboratory of the university of thessaloniki codaq estimations were made for four frequency bands centered at 1 5 hz 3 0 hz 6 0 hz and 12 0 hz and for the lapse time windows 10 20 sec 15 30 sec 20 45 sec 30 60 sec and 50 100 sec the codaq values obtained show a clear frequency dependence of the formq c q 0 f n whileq 0 andn depend on the lapse time window q 0 was found equal to 33 andn equal to 1 01 for the time window of 10 to 20 sec while for the other windowsq 0 increased from 60 to 129 withn being stable close to 0 75 this lapse time dependence is interpreted as due to a depth dependent attenuation the high attenuation and the strong frequency dependence found are characteristic of an area with high seismicity in agreement with studies in other seismic regions

magnitude versus faults surface parameters quantitative relationships from the aegean region historical and seismotectonic data from the broader aegean region have been collected and all possible information relative to ground deformation associated to earthquakes that hit the area have been re evaluated all events associated to co seismic surface faulting have been selected and further investigated while geomorphologic and geological criteria have been used to recognise and characterise the seismogenic faults associated to these morphogenic earthquakes sensu bull inqua 16 1993 24 in particular in order to perform seismic hazard analyses we compiled a list of all earthquakes where the surface rupture length srl the maximum vertical displacement mvd or the average displacement ad is available we thus obtained reliable values of these source parameters for 36 earthquakes of which 26 occurred during the 20th century 6 in the 19th century and the 3 remaining earlier magnitude versus srl and mvd has been compiled for estimating empirical relationships the calculated regression equations are ms 0 90 log srl 5 48 and ms 0 5 9log mvd 6 75 showing good correlation coefficients equal to 0 84 and 0 82 respectively co seismic fault rupture lengths and especially maximum displacements in the aegean region have systematically lower values than the same parameters worldwide but are similar to those of the eastern mediterranean middle east region the envelopes of our diagrams are also calculated and discussed for estimating the worst case scenario furthermore for all investigated seismogenic structures based on several geological criteria we measured the geological fault length gfl which is the total length of the neotectonic faults showing cumulative recent activity we then compared srl with gfl and their ratio shows a clear bimodal distribution with a major peak at 0 8 1 0 indicating that about 50 of the investigated earthquakes ruptured almost the entire fault length while a second peak around the value of 0 5 is clearly related to a segmentation process of longer neotectonic structures further implications of this distribution are also discussed eventually from the distribution of gfl versus magnitude we also infer an important geological threshold for the occurrence of morphogenic earthquakes at about 5 5 degrees

rayleigh raman lidar observations of gravity wave activity from 15 to 70 km altitude over syowa 69 s 40 e the antarctic the potential energy of gravity waves gws per unit mass ep at altitudes of 15 70 km has been examined from temperature profiles obtained by a rayleigh raman rr lidar at syowa station 69 s 40 e from may 2011 to october 2013 with the exception of the summer months the gws with ground based wave periods longer than 2 h and vertical wavelengths between 1 8 and 16 km were extracted from the temperature profiles ep was larger in winter than in spring and fall although in 2012 at altitudes below 30 km ep was larger in spring than in winter and fall ep increased with a mean scale height of 11 3 km ep profiles showed a local maximum at an altitude of 20 km and a minimum at 25 km in almost every month which has not been reported by previous studies observed by radiosondes the values of ep in october of 2012 were smaller at 35 60 km and larger at 20 35 km than those in october of 2011 and 2013 this difference in the ep profile is most probably caused by different seasonal variations of zonal winds the larger and smaller ep values seem to be observed both below and above the altitude at which the zonal wind speed reached 0 m s 1 this result suggests that wind filtering of gravity waves with small phase speeds is significantly important in early spring

what is the source of the stratospheric gravity wave belt in austral winter abstractduring austral winter and away from orographic maxima or hot spots stratospheric gravity waves in both satellite observations and interim european centre for medium range weather forecasts ecmwf re analysis era interim data reveal enhanced amplitudes in a broad midlatitude belt extending across the southern ocean from east of the andes to south of new zealand the peak latitude of this feature slowly migrates poleward from 50 to 60 s wave amplitudes are much weaker across the midlatitude pacific ocean these features of the wave field are in striking agreement with diagnostics of baroclinic growth rates in the troposphere associated with midlatitude winter storm tracks and the climatology of the midlatitude jet this correlation suggests that these features of the stratospheric gravity wave field are controlled by geographical variations of tropospheric nonorographic gravity wave sources in winter storm tracks spontaneous adjustment emission from the midlatitude winter jet frontogenesi

earthquake magnitude scaling using seismogeodetic data 1 the combination of gps and strong motion data to estimate seismogeodetic waveforms creates a data set that is sensitive to the entire spectrum of ground displacement and the full extent of coseismic slip in this study we derive earthquake magnitude scaling relationships using seismogeodetic observations of either p wave amplitude or peak ground displacements from five earthquakes in japan and california ranging in magnitude from 5 3 to 9 0 the addition of the low frequency component allows rapid distinction of earthquake size for large magnitude events with high precision unlike accelerometer data that saturate for earthquakes greater than m 7 to 8 and is available well before the coseismic displacements are emplaced these results though based on a limited seismogeodetic data set support earlier studies that propose it may be possible to estimate the final magnitude of an earthquake well before the rupture is complete

magnitude estimation using the first three seconds p wave amplitude in earthquake early warning 1 pd is the peak amplitude of displacement in the first three seconds after the arrival of the p wave we investigated the attenuation of pd with the hypocentral distance r in southern california as a function of magnitude m and obtained the following relationship log pd 3 463 0 729 m 1 374 log r 0 305 given an earthquake location determined by the p wave arrival times at stations close to the epicenter this relationship can be used to define a so called pd magnitude of earthquakes our result shows that for earthquakes in southern california the pd magnitudes agree with the catalog magnitudes with a standard deviation of 0 18 for events less than magnitude 6 5 therefore pd is a robust measurement for estimating the magnitudes of earthquakes and has practical application in earthquake early warning systems citation wu y m and l zhao 2006 magnitude estimation using the first three seconds p wave amplitude in earthquake early warning geophys res lett 33 l16312 doi 10 1029 2006gl026871

gravity waves over antarctica and the southern ocean consistent momentum fluxes in mesoscale simulations and stratospheric balloon observations stratospheric balloons from the vorcore campaign have provided a unique description of the gravity wave field in the lower stratosphere above antarctica and the southern ocean during the austral spring of 2005 mesoscale simulations are carried out to analyze further the gravity wave field first the realism of the simulated waves is assessed by comparison to the observations a satisfactory overall agreement is found but different behaviour is noted for orographic waves overestimation in the simulations relative to the observations and non orographic waves underestimation second the gravity wave field is analyzed in more detail than was possible from observations alone it is necessary to distinguish and quantify orographic and non orographic waves separately orographic waves are larger and more intermittent yet affect only a limited geographical region hence although orographic sources stand out as hot spots for gravity waves their contribution to momentum fluxes entering the stratosphere is comparable to or smaller than the contribution of non orographic sources a diagnostic for intermittency the gini coefficient is proposed it clearly marks the distinction between orographic and non orographic sources intermittencies of 0 8 and 0 5 respectively sensitivity to resolution is quite small regarding the spatial structure of the gravity wave field but is significant for the amplitudes the momentum flux values increase by 2 when the horizontal resolution is doubled and possible biases of both simulations and observations are discussed nonetheless the good agreement between observations and simulations and the complementary information on the biases of each dataset promises that in the future these different estimates of gravity wave momentum fluxes may converge copyright 2012 royal meteorological society

seismotectonic evidence of an active normal fault beneath thessaloniki greece during 3 weeks in 1985 we operated a dense network of portable seismological stations around the city of thessaloniki in northern greece where a destructive earthquake had occurred in 1978 we recorded 282 microearthquakes with magnitudes ranging between 0 2 to 3 0 and we computed 22 fault plane solutions the experiment was designed to map the stress pattern west of the 1978 shock and to study the asvestohorio fault around this fault located near thessaloniki mercier et al 1983 observed a few cracks during the 1978 shock the seismicity shows the same scattered pattern seen through the whole chalkidiki region we observe also a dense cluster around asvestohorio but this cluster is probably related to explosions in nearby mines after filtering the data from possible explosions we found evidence of seismic activity the earthquakes are dipping toward the ne suggesting that the asvestohorion fault is active the fault plane solutions do not help in defining the geometry of the fault but the p and t axes are consistent with the regional stress pattern

on the frequency dependence of q in the kalamata south greece region as obtained from the analysis of the coda of the aftershocks of the kalamata 1986 earthquake

application of real time gps to earthquake early warning 1 we explore the use of real time high rate gps displacement data for earthquake early warning using 1 hz displacement waveforms from the april 4 2010 mw 7 2 el mayor cucapah earthquake we compare these data to those provided by the broadband velocity and accelerometer instrumentation of the southern california seismic network the unique information provided by the gps based displacement timeseries is the permanent static displacement using a simple algorithm that can be applied in real time we extract the static offset shortly after the s wave arrival around the time of the observed peak shaking at the same site and before shaking at more distant locations these data can be used as they become available to provide a robust estimate of the earthquake magnitude which ranges from 6 8 to 7 0 in this case we therefore conclude that real time high rate gps can provide a useful and independent assessment of earthquake magnitude for the purpose of earthquake early warning and real time earthquake information systems in general including tsunami warning systems

atmospheric teleconnections involving the southern ocean 1 i review the characteristic patterns of low frequency interannual and subdecadal variation in atmospheric circulation over the southern hemisphere sh extratropics and their climatic associations e g temperature precipitation winds sea surface temperatures ssts and sea ice conditions for the southern ocean the considerable spatial and temporal limitations of the observational database have strongly conditioned the pace of our understanding of sh teleconnections particularly for the pacific sector where the tropical el nino southern oscillation enso exerts a dominant influence an enso signal appears in the intensity interannual variations of the amundsen sea mean low pressure asl jet streams and long waves these variations comprise the so called pacific south america psa teleconnection patterns of low frequency variability in sh circulation that are mostly extratropical in origin but which can interact with enso are dominated by the zonally symmetric high latitude mode or antarctic oscillation aao the aao involves an alternation of atmospheric mass between middle and high southern latitudes a zonally asymmetric mode of wave number 1 is represented by an oscillation in pressure height between australian and south american sectors depicted by a trans polar circulation index a significant wave number 2 oscillation in the coupled atmosphere ocean ice system or antarctic circumpolar wave acw has a similar periodicity to enso and is strongest in the pacific sw atlantic sectors atmospheric teleconnections involving the southern ocean including those to enso show evidence of recent changes and the climatic implications of these are discussed

saturated gravity wave spectra measured with balloons in mendoza argentina spectral results from a sounding of temperature and wind velocity between 11 9 and 23 1 km performed with an open type stratospheric balloon near the andes mountains are reported the use of this kind of balloons and high performance instruments allowed to attain better spatial resolution around 2 5 meters during the descent than previous results and other sounding techniques this high resolution permitted to study the complete interval of altitude data in three consecutive subintervals below around and above the tropopause each of these subintervals shows different saturation characteristics some differences have been found with the general pattern of power spectral densities reported by different theories a large amplitude wave of around 1 8 km and possibly originated in the mountain relief is clearly observed in the temperature vertical and shear wind velocity components

earthquake magnitude estimation from early radiated energy 1 from inspection of a large set of japanese events we investigate the scaling of the early radiated energy inferred from the squared velocity integral iv2 with the final magnitude of the event we found that the energy can only discriminate whether the event has a magnitude larger or smaller than 5 8 and in the latter case it can allow for real time magnitude estimation however by normalizing iv2 for the rupture area the initial slip scales with the magnitude between 4 m 7 following the expected scaling laws we show that the ratio between the squared peak displacement and iv2 is a proxy for the slip following the same scaling but it can be directly derived from the data without any assumption on the rupture area the scaling relationship between initial slip and magnitude can be used for early warning applications when integrated in a probabilistic evolutionary approach

depth dependent seismic attenuation in the granada zone southern spain abstract coda q estimates for the granada basin southern spain are obtained by analyzing earthquakes occurring within or close to the borders of this area the data set is composed of 54 earthquakes with local magnitudes ranging between 2 2 and 4 0 and with epicentral distances to the nearest station smaller than 10 km a single scattering process is assumed coda q values obtained show a clear dependence on frequency according to the relationship q q o f n where n ranges from 0 81 to 0 89 after removing the main site effects and discussing the possible multiple scattering influence the lapse time dependence is interpreted as due to attenuation variations with depth this result agrees with the variation of coda q obtained by using different sets of events with increasing hypocentral depth ranges

application of real time gps to earthquake early warning in subduction and strike slip environments 1 we explore the application of gps data to earthquake early warning and investigate whether the coseismic ground deformation can be used to provide fast and reliable magnitude estimations and ground shaking predictions we use an algorithm to extract the permanent static offset fromgps displacement time series and invert for theslip distribution on the fault plane which is discretized into a small number of rectangular patches we developed a completely self adapting strategy in which the initial fault plane model is built based on a quick approximate magnitude estimation and is then allowed to increase in size based on the evolutionary magnitude estimation resulting from the slip inversion two main early warning outputs are delivered in real time magnitude and the along strike extent of the rupture area these are finally used to predict the expected ground shaking due to the finite source we tested the proposed strategy by simulating real time environments for three earthquakes for themw9 0 2011 tohoku oki earthquake our algorithm provides the first magnitude estimate of 8 2 at 39 s after the origin time and then gradually increases to 8 9 at 120 s the estimated rupture length remains constant from the outset at 360 km for the mw 8 3 2003 tokachi oki earthquake the initial magnitude estimate is 8 5 at 24 s and drops to 8 2 at 40 s with a rupture length of 290 km finally for the mw 7 2 2010 el mayor cucapah earthquake the magnitude estimate is 7 0 from the outset with a rupture length of 140 km the accuracy of the ground shaking prediction using the gps based magnitude and finite extent is significantly better than existing seismology based point source approaches this approach would also facilitate more rapid tsunami warnings

generation of mesoscale gravity waves in upper tropospheric jet front systems abstract multiply nested mesoscale numerical simulations with horizontal resolution up to 3 3 km are performed to study the generation of mesoscale gravity waves during the life cycle of idealized baroclinic jet front systems long lived vertically propagating mesoscale gravity waves with horizontal wavelengths 100 200 km are simulated originating from the exit region of the upper tropospheric jet streak in a manner consistent with past observational studies the residual of the nonlinear balance equation is found to be a useful index in diagnosing flow imbalance and predicting wave generation the imbalance diagnosis and model simulations suggest that balance adjustment as a generalization of geostrophic adjustment is likely responsible for generating these mesoscale gravity waves it is hypothesized that through balance adjustment the continuous generation of flow imbalance from the developing baroclinic wave will lead to the continuous radiation of gravity waves

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

energy flux model of seismic coda separation of scattering and intrinsic attenuation a new model of seismic coda is presented based on the balance between the energy scattered from the direct wave and the energy in the seismic coda this energy flux model results in a simple formula for the amplitude and time decay of the seismic coda that explicitly differentiates between the scattering and intrinsic anelastic attenuation of the medium this formula is valid for both weak and strong scattering and implicitly includes multiple scattering the model is tested using synthetic seismograms produced in finite difference simulations of wave propagation through media with random spatial variations in seismic velocity some of the simulations also included intrinsic dissipation the energy flux model explains the coda decay and amplitude observed in the synthetics for random media with a wide range of scattering q in contrast the single scattering model commonly used in the analysis of microearthquake coda does not account for the gradual coda decay observed in the simulations for media with moderate or strong scattering attenuation scattering q less than or equal to 150 the simulations demonstrate that large differences in scattering attenuation cause only small changes in the coda decay rate as predicted by the energy flux model the coda decay rate is sensitive however more to the intrinsic q of the medium the ratio of the coda amplitude to the energy in the direct arrival is a measure of the scattering attenuation thus analysis of the decay rate and amplitude of the coda can in principle produce separate estimates for the scattering and intrinsic q values of the crust we analyze the coda from two earthquakes near anza california intrinsic q values determined from these seismograms using the energy flux model are comparable to coda q values found from the single scattering theory the results demonstrate that coda q values are at best measures of the intrinsic attenuation of the lithosphere and are unrelated to the scatteing q less

seismicity focal mechanisms and tectonics in the last four years there has been a tremendous increase in the detail of tectonic processes reported in the typical seismotectonic study new data from many local and regional networks of seismographs established during the previous four year period plus the now routine application of improved hypocentral location procedures long period body wave modelling and moment tensor inversion using digitally recorded data have increased resolution of both the hypocentral location and the nature of the faulting process consequently research emphasis has been on local tectonics or those aspects of regional and global tectonics requiring high resolution i briefly describe below some of the highlights of these studies

early magnitude and potential damage zone estimates for the great mw 9 tohoku oki earthquake the mw 9 0 2011 tohoku oki earthquake has reopened the discussion among the scientific community about the effectiveness of earthquake early warning for large events a well known problem with real time procedures is the parameter saturation which may lead to magnitude underestimation for large earthquakes here we measure the initial peak ground displacement and the predominant period by progressively expanding the time window and distance range to provide consistent magnitude estimates m 8 4 and a rapid prediction of the potential damage area this information would have been available 35 s after the first p wave detection and could have been refined in the successive 20 s using data from more distant stations we show the suitability of the existing regression relationships between early warning parameters and magnitude provided that an appropriate p wave time window is used for parameter estimation we interpret the magnitude under estimation as a combined effect of high pass filtering and frequency dependence of the main radiating source during the rupture process

a premonitory pattern of earthquakes in northern greece on 20 june 1978 at 20 h 03 min 23 s an earthquake of surface wave magnitude 6 5 occurred in the migdonian basin between the lagada and volvi lakes and 26 km from thessaloniki the main shock was preceded by a seismic sequence which started on 8 may the largest earthquake of that sequence occurred on 23 may and had a surface wave magnitude of 5 8 the long duration of this sequence before the main shock of 20 june had tremendous psychological effects on the whole country greek seismologists were in a difficult position during that time 8 may 20 june especially after the earthquake of 23 may when pressed to state whether these earthquakes were foreshocks or aftershocks long lasting seismic sequences with earthquakes of magnitude 6 are common in the aegean area because these sequences are sometimes followed by large earthquakes it is important to see whether the latter can be predicted the may june 1978 seismic sequence provided the opportunity for testing hypotheses about statistical properties which it has been suggested could distinguish between foreshocks and aftershocks this particular sequence has been investigated extensively1 4 and more accurate data are available than for any other sequence around greece focal mechanism studies5 6 and field observations2 showed that the largest earthquakes of the sequence were produced by horizontal extension in a nearly north south direction and that the main rupture occurred on a normal fault which strikes almost east west and dips to the north the fault length of the main shock of 20 june was estimated7 to be 32 km accurate determination of earthquake foci using portable seismographs showed that the earthquakes of this sequence were shallow h 17 km while the distribution of the epicentres had a very clear east west elongation4 5 a migration of the seismic activity from east to west has also been observed between 8 may and 14 july we investigate here the time variation of the average magnitude and the frequency of all the shocks with m 3 0 of this sequence the time variations of these seismic parameters are examined in connection with the distribution of well determined epicentres of 38 earthquakes with m 4 3 in order to search for any premonitory pattern of the 23 may and 20 june major earthquakes

earth science is earthquake rupture deterministic reply rydelek and horiuchi 1 present an analysis of earthquakes in japan whose magnitudes m ranged from 6 0 to 8 0 they determine pmax the peak predominant period for p wave arrival for the five nearest hi net seismic network stations and plot the event averaged pmax versus magnitude they find no statistically significant trend in their data

historical and recent large megathrust earthquakes in chile abstract recent earthquakes in chile 2014 mw 8 2 iquique 2015 mw 8 3 illapel and 2016 mw 7 6 chiloe have put in evidence some problems with the straightforward application of ideas about seismic gaps earthquake periodicity and the general forecast of large megathrust earthquakes in northern chile before the 2014 iquique earthquake 4 large earthquakes were reported in written chronicles 1877 1786 1615 and 1543 in north central chile before the 2015 illapel event 3 large earthquakes 1943 1880 1730 were reported and the 2016 chiloe earthquake occurred in the southern zone of the 1960 valdivia megathrust rupture where other large earthquakes occurred in 1575 1737 and 1837 the periodicity of these events has been proposed as a good long term forecasting however the seismological aspects of historical chilean earthquakes were inferred mainly from old chronicles written before subduction in chile was discovered here we use the original description of earthquakes to re analyze the historical archives our interpretation shows that a priori ideas like seismic gaps and characteristic earthquakes influenced the estimation of magnitude location and rupture area of the older chilean events on the other hand the advance in the characterization of the rheological aspects that controlled the contact between nazca and south american plate and the study of tsunami effects provide better estimations of the location of historical earthquakes along the seismogenic plate interface our re interpretation of historical earthquakes shows a large diversity of earthquakes types there is a major difference between giant earthquakes that break the entire plate interface and those of mw 8 0 that only break a portion of it

shallow structure and recent evolution of the aegean sea a synthesis based on continuous reflection profiles abstract a dense grid of continuous seismic reflection profiles partly calibrated with drilling results has allowed construction of a structural outline of the entire aegean sea in the north aegean we observe a clear difference between the thickly sedimented northern margin basins and the steep slopes of the trough margin of the southern north aegean the trough itself comprises a series of separate tectonic depressions resulting from an apparent transtensional motion the central aegean consists of a complex tectonic puzzle caused by the prevailing extension incipient strike slip faulting sub parallel to the north aegean trough trend may however affect its eastern anatolian domain three main structural areas characterize the southern aegean comparable structural directions cut across this chiefly extensional basin but one fault system may be prevailing over the others depending on the area the central cretan sea results from the interaction of at least two distinct extensions these were superimposed on previous mostly e w structural trends generated during the inception of the southern hellenic subduction and led to the present day predominant sw ne trending extension as a hypothesis we propose that the overall late miocene present evolution of the aegean sea is directly dependent on two geodynamic processes to the southeast of the area collision between arabia and turkey leads to the lateral westward expulsion of the aegean continental crust and to the west hellenic subduction is still active

rayleigh lidar observations of gravity wave activity in the winter upper stratosphere and lower mesosphere above davis antarctica 69 s 78 e 1 gravity wave activity in the upper stratosphere and lower mesosphere uslm is investigated using temperature data retrieved from a rayleigh lidar at davis antarctica 69 s 78 e during the 2007 and 2008 winters the temporal and height variabilities of waves with ground based periods greater than 2 h and vertical wavelengths between 4 km and 20 km are analyzed stratospheric gravity wave potential energy per unit mass shows a weaker correlation with stratospheric winds at davis than that reported in the arctic gravity waves dissipate above 40 km during winter while there is no dissipation in the autumn mesosphere a separate analysis of gravity waves with ground based periods of 2 6 h revealed lower dissipation in the winter mesosphere the seasonal cycle of gravity wave activity is evident throughout the uslm with peak activity observed during winter the gravity wave potential energy and vertical wavenumber power spectral density at davis are similar to that recorded at other high latitude sites

southern hemisphere extratropical gravity wave sources and intermittency revealed by a middle atmosphere general circulation model abstractsouthern hemisphere extratropical gravity wave activity is examined using simulations from a free running middle atmosphere general circulation model called kanto that contains no gravity wave parameterizations the total absolute gravity wave momentum flux mf and its intermittency diagnosed by the gini coefficient are examined during january and july the mf and intermittency results calculated from the kanto model agree well with results from satellite limb and superpressure balloon observations the analysis of the kanto model simulations indicates the following results nonorographic gravity waves are generated in kanto in the frontal regions of extratropical depressions and around tropopause level jets regions with lower higher intermittency in the july midstratosphere become more less intermittent by the mesosphere as a result of lower level wave removal the gravity wave intermittency is low and nearly homogeneous throughout the sh middle atmosphere during january this indicates t

iterative deconvolution of teleseismic p waves from the thessaloniki n greece earthquake of june 20 1978 teleseismic long period p waves from the june 20 1978 thessaloniki n greece earthquake ms 6 4 were modeled in an attempt to extract information about asperities or barriers on the fault plane the analysis is based on the inversion method of complex p waves developed by kikuchi and kanamori 1982 a far field source time function with a rise time of 2 sec and a process time of 5 sec is inferred corresponding to a source dimension of about 10 km when a rupture velocity of 2 km sec is assumed

a source study of the thessaloniki northern greece 1978 earthquake sequence summary the thessaloniki northern greece earthquake sequence appears to have occurred along faults forming a graben structure this graben situated in the border region between the serbomacedonian massif and the vardar zone is bounded to the south west by clearly exposed north west striking north east dipping normal faults relative hypocentre determinations fault plane solutions surface faulting and the aftershock distribution suggest that some of these faults have been reactivated during the 1978 earthquakes the source parameters of the mainshock mb 6 1 ms 6 4 were determined by computing body wave synthetic seismograms in the time domain and comparing them with the observed this modelling constrained the orientation of faulting determined by the p wave fault plane solution it also constrained the source depth to 6 mp 2 km similar depths were calculated by a relative relocation method for the other three large events of the sequence the dislocation time function required for the far field had a total duration of 9 mp 1 5 s the body wave moment was 5 2 mp 1 8 times 1025 dyne cm for a fault length of 35 km and a fault width of 17 km both estimated from the aftershock distribution the static stress drop was found to be 4 bar an accelerograph record of the mainshock shows two distinct events 3 4 s apart these two events were unresolved by the long period data in the far field but the unusually long duration of the mainshock time function suggests an overall slow energy release which probably occurred as a sequence of events close in space and time seismic energy released in this fashion can account for waveform complexities observed at some stations

11 years of rayleigh lidar observations of gravity wave activity above the southern tip of south america gravity wave gw activity is analyzed using temperature t data retrieved from a rayleigh lidar at rio gallegos argentina 51 6 s 69 3 w gw characteristics are derived from 302 nights of observations providing more than 1018 h of high resolution lidar data between 20 km and 56 km height from august 2005 to december 2015 t measurements are performed by a differential absorption lidar dial instrument this lidar was the southernmost outside antarctica until the end of 2017 rio gallegos is an exceptional place to observe large amplitude gw every lidar measurement is classified according to its relative position to the polar vortex the lidar measurements are compared with collocated sounding of the atmosphere using broadband emission radiometry saber and global positioning system radio occultation gps ro data the different instruments show different windows of the gw spectrum providing complementary observations in general the geometric mean of the specific gw potential energy pe is larger during winter and spring than during summer and autumn the largest geometric mean of pe is found inside the vortex and decreases monotonically at its edge outside it and when there is no vortex the same behavior is observed with satellite data on average it can be seen that lidar observations provide larger pe values than limb sounding measurements from a morlet continuous wavelet transform analysis 3 distinct modes are captured from saber and from gps ro data at the upper and lower stratosphere respectively in particular a systematic 3 5 4 years oscillation possibly related to el nino southern oscillation is observed

lidar observations of gravity wave activity in the middle atmosphere over davis 69 s 78 e antarctica a 16 month series of lidar measurements in the stratosphere and mesosphere lower thermosphere mlt region over davis station 69 s 78 e in antarctica is used to study gravity waves the unprecedentedly large number of observations totaling 2310 h allows us to investigate seasonal variations in gravity wave activity in great detail in the stratosphere the gravity wave potential energy density gwped is shown to have a large seasonal variation with a double peak in winter and minimum in summer we find conservative wave propagation to occur between 29 and 41 km altitude in winter as well as in summer whereas smaller energy growth rates were observed in spring and autumn these results are consistent with selective critical level filtering of gravity waves in the lower stratosphere in the mlt region the gwped is found to have a semiannual oscillation with maxima in winter and summer the structure of the winter peak is identical to that in the stratosphere suggesting that the gravity wave flux reaching the mlt region is controlled by the wind field near the tropopause level

structural analysis of recent and active faults and regional state of stress in the epicentral area of the 1978 thessaloniki earthquakes northern greece during spring and summer 1978 macedonia greece suffered damaging seismic activity during the two main shocks which occurred on may 23 mb 5 7 and june 20 mb 6 1 seismic open cracks and faults were formed in the epicentral area 25 km nne from thessaloniki they have been mapped and their kinematics analyzed these studies have shown that they result from the reactivation of existing faults of pleistocene recent and historical age and that the crust is stretching along a n s to nne ssw direction in that part of the north aegean principal stress directions have been computed from the slip vectors measured on recent neotectonic faults and seismic cracks and faults this computation utilizing a simple mechanical model homogeneous deformation through the addition of small and independent displacements of rigid blocks in a highly fractured body a striking feature of this analysis is that the tensional directions 3 deduced from seismic faulting and from recent neotectonic faulting are nearly the same they are compatible with the regional tension axis deduced from focal mechanisms of north aegean and with the focal mechanisms of the 1978 thessaloniki main shocks they are also compatible with in situ stress measurements in this region studies of superficial seismic faulting strongly support previous assumptions proposed from aftershock distribution the 1978 thessaloniki earthquakes resulted from reactivation of several different faults situated within the same ne dipping fault zone of upper eocene lower oligocene age and older separating the serbo macedonian massif from the peonias east vardar zone

three dimensional seismic attenuation structure beneath the aegean region and its tectonic implication abstract the three dimensional attenuation structure beneath the aegean sea and the surrounding regions is determined by inversion of seismic intensity data a large number of seismic intensity data have been accumulated in a uniform scale in the aegean region where the seismic activity is much higher than that of the other mediterranean regions nearly 7000 seismic intensity data from 50 earthquakes that have occurred in these regions are used to determine seismic attenuation structure and source acceleration of the earthquakes the resultant structure reveals a remarkable contrast of attenuation in the top layer depth 0 40 km low q is dominant in the aegean sea while high q is dominant in the surrounding land areas except for the southwestern turkey the low q regions correspond to areas of neogene quaternary grabens where the high seismicity of shallow earthquakes appears in the upper mantle high q zones corresponding to the subducting african plate dominate along the hellenic arc the irregular shape of high q zones might reflect the split or disintegration of the african slab some low q spots corresponding to the distribution of volcanoes exist along the volcanic arc the low q spots might correspond to diapirs causing the subduction volcanism

earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records 1 we show that the low pass filtered peak amplitudes of initial p and s wave seismic signals recorded in the vicinity of an occurring earthquake source correlates with the earthquake magnitude and may be used for real time estimation of the event size in seismic early warning applications the earthquake size can be therefore estimated using only a couple of seconds of signal from the p or s wave onsets i e while the rupture itself is still propagating and rupture dimension is far from complete we argue that dynamic stress release and or slip duration on the fault in the very early stage of seismic fracture scales both with the observed peak amplitude and with the elastic energy available for fracture propagation the probability that a fracture grows to a larger size should scale with the energy initially available citation zollo a m lancieri and s nielsen 2006 earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records geophys res lett 33 l23312 doi 10 1029 2006gl027795