an outline of the plate tectonics of china china is principally a part of the eurasian plate but the margins of the indian and philippine sea plates are involved in the himalayas and in the coastal range of taiwan respectively within the eurasian plate the cathaysian paleoplate is separated from the angaraian paleoplate by the junggar hegen suture which contains paleozoic ophiolites and rare blueschists the three microplates of the cathaysian paleoplate consist of precambrian cratons and or phanerozoic accretionary fold belts these coalesced precambrian cratons record at least six stages of intense orogeny before cratonization the paleozoic to cenozoic accretionary fold belts of china can be correlated with similar events now found in west pacific andean and atlantic type active continental margins ophiolites occupying many of these tectonic zones provide evidence for the age and igneous history of oceanic crust formed during the paleozoic to cenozoic the presence of blueschist in some of these chinese sutures reveals evidence of large scale subduction and tectonic exhumation during consolidation of the eurasian plate cenozoic collision of the eurasian and indian plates produced deformation and uplift of the himalayas strongly influencing the tectonics of western china in contrast mesozoic tertiary evolution of eastern china is typical basin range geology similar to that of the western united states which included development of deep sedimentary basins along with calc alkaline plutonic and volcanic activity associated with crustal thinning and high heat flow the complicated tectonic evolution of china is greatly illuminated by the presence of ophiolites and blueschists in proterozoic to tertiary convergent boundaries these petrotectonic assemblages provide evidence of an extremely mobile history of plate movement in china

western hellenic subduction and cephalonia transform local earthquakes and plate transport and strain abstract focal parameters of local earthquakes in the region of the ionian islands of western greece are constrained with a temporary dense array of three component seismographs operated jointly offshore and onshore seismic deformation is documented to be confined to the east of the n20 e striking steep continental slope west of cephalonia island the right lateral cephalonia transform fault ctf inferred from large earthquakes the pre apulian continental material appears to be only deforming east of the transform fault where it is in upper plate position to the hellenic subduction east of the transform fault the transmission velocity tomography from local earthquakes compared in depth section with a previous marine reflection profile provides evidence in support of a shallow landward dipping boundary around 12 km deep under the ionian islands along which they may override the lower plate on either side of this interface local earthquakes occur with different focal mechanisms in support with its interpretation as the interplate under cephalonia island reverse faulting deforms the upper plate along nw se structures which may also be affected by left lateral bookshelf faulting small earthquakes show normal faulting along the western coast of cephalonia and its extension 20 km ssw the trace of the ctf as inferred from the occurrence of the large strike slip earthquakes another group of normal fault earthquakes locates in the lower plate from under cephalonia to zante just outboard of a possible change of interplate dip suggested from reflection seismics landward under the islands these normal fault earthquakes appear to coincide in position with that of the load imposed by the upper plate transported over them rather than occurring in an outer rise outboard the plate boundary and trench as observed in other subductions and attributed to the control by the flexural bending of the lower plate under the pull of the sinking slab interpretation has to consider several peculiar features of plate interaction in western greece with respect to a steady state model for major subduction zones in particular a fast deformation of the upper plate in front of an orogenically overthickened crust and of the southwestward push of extruding anatolia its transport which is the cause of the migration of the plate boundary rather than the roll back of a slab which has been proposed to be detached possibly a flat and ramp shape of the interplate the geometrical complexity of the shear limit across the ctf between subduction and collision and the nearby variation of the nature of the foreland crust

earthquake mechanisms of the adriatic sea and western greece implications for the oceanic subduction continental collision transition summary we present 21 focal solutions magnitude 5 5 reliably computed by body wave modelling for the western hellenic arc from yugoslavia to the southern peloponnese mechanisms located within the aegean show normal faulting the t axis trending n s in the centre and parallel to the active boundary in the external part mechanisms associated with the keffalinia fault are consistent with dextral strike slip motion reverse mechanisms located along the active boundary are remarkably consistent and do not depend on the nature of the active boundary continental collision or oceanic subduction the consistency in azimuth of the slip vectors and of the gps velocity relative to africa all along the active boundary suggests that the deformation is related to the same motion the discrepancy between seismic energy release and the amount of shortening confirms that the continental collision is achieved by seismic slip on faults but the oceanic subduction is partially aseismic the northward decrease in velocity between continental collision and oceanic subduction suggests the continental collision to be a recent evolution of the active subduction

application of satellite magnetic anomaly data to curie isotherm mapping a boundary condition on temperature at depth in the continental crust can in principle be obtained by mapping of the curie isotherm where it forms the base of the magnetic crust an approach to mapping magnetic crustal thickness using satellite magnetic anomaly data is described because magnetic crustal thickness is small with respect to satellite altitude inversion of the anomaly data yields magnetization models expressing regional variations in the vertical integral of magnetization this parameter is inversely correlated with regional heat flow in the western united states suggesting that areas of low apparent magnetization are areas of thin magnetic crust resulting from a shallow curie isotherm for a simple model of a uniformly magnetized magnetic crust or intra crustal layer curie depth is linearly related to apparent magnetization if the relation can be calibrated by two or more curie depth estimates regional apparent curie isotherm configuration can be mapped in an alternative approach a family of curie depth models can be computed using assumed magnetization values in each case the curie depth configuration is used as a boundary condition in a thermal model that model is selected which gives a heat flow distribution best fitting observations conductive heat flow models for a traverse across the rio grande rift using a finite element technique and for a map grid using a one dimensional thermal model approximation are given as examples

evidence for transform faulting in the ionian sea the cephalonia island earthquake sequence of 1983 accurate locations of aftershocks of the january 17 1983 ms 7 0 main shock in the ionian islands have been determined as well as fault plane solutions for this main shock and its largest aftershock which are interpreted as a right lateral strike slip motion with a thrust component on a fault striking in about a ne sw direction

the mw 6 3 2003 lefkada earthquake greece and induced stress transfer changes abstract a large earthquake of magnitude mw 6 3 occurred on 14 august 2003 nw of the lefkada island which is situated at the ionian sea western greece the source parameters of this event are determined using body wave modeling the focal depth was found equal to 9 km the constrained focal mechanism revealed dextral strike slip motion 15 80 and 170 the duration of the source time function was 8 s and the seismic moment 2 9 1025 dyn cm the earthquake occurred close to the northern end of the kefallinia transform fault where the 1994 moderate event and its aftershock sequence were also located the epicentral distribution of the 2003 aftershock sequence revealed the existence of two clusters the first one is located close to the epicentral area of the mainshock while the second southern close to the northwestern coast of the kefallinia island a gap of seismicity is observed between the two clusters the length of the activated zone is approximately 60 km the analysis of data revealed that the northern cluster is directly related to the mainshock while the southern one was triggered by stress transfer caused by the main event

toward mapping surface deformation in three dimensions using insar 1 one of the limitations of deformation measurements made with interferometric synthetic aperture radar insar is that an interferogram only measures one component of the surface deformation in the satellite s line of sight we investigate strategies for mapping surface deformation in three dimensions by using multiple interferograms with different imaging geometries geometries for both current and future missions are evaluated and their abilities to resolve the displacement vector are compared the north component is always the most difficult to determine using data from near polar orbiting satellites however a satellite with an inclination of about 60 120 would enable all three components to be well resolved we attempt to resolve the 3d displacements for the 23 october 2002 nenana mountain alaska earthquake the north component s error is much larger than the signal but proxies for eastward and vertical motion can be determined if the north component is assumed negligible inversions of hypothetical coseismic interferograms demonstrate that earthquake model parameters can be well recovered from two interferograms acquired on ascending and descending tracks

asperity break after 12 years the mw6 4 2015 lefkada greece earthquake the mw6 4 earthquake sequence of 2015 in western greece is analyzed using seismic data multiple point source modeling nonlinear slip patch and linear slip inversions reveal a coherent rupture image with directivity toward the southwest and several moment release episodes reflected in the complex aftershock distribution the key feature is that the 2015 earthquake ruptured a strong asperity which was left unbroken in between two large subevents of the mw6 2 lefkada doublet in 2003 this finding and the well analyzed cephalonia earthquake sequence of 2014 provide strong evidence of segmentation of the major dextral cephalonia lefkada transform fault ctf being related to extensional duplex transform zones we propose that the duplexes extend farther to the north and that the ctf runs parallel to the western coast of lefkada and cephalonia islands considerably closer to the inhabited islands than previously thought generally this study demonstrates faulting complexity across short time scales earthquake doublets and long time scales seismic gaps

warm ocean is eroding west antarctic ice sheet 1 satellite radar measurements show that ice shelves in pine island bay have thinned by up to 5 5 m yr 1 over the past decade the pattern of shelf thinning mirrors that of their grounded tributaries the pine island thwaites and smith glaciers and ocean currents on average 0 5 c warmer than freezing appear to be the source the synchronised imbalance of the inland glaciers is the result of reduced lateral and basal tractions at their termini and the drawdown of grounded ice shows that antarctica is more sensitive to changing climates than was previously considered

geophysical interpretation of the magnetic anomalies of china derived from magsat data the ambiguities about geophysical implications based on the correlation of scalar magnetic anomalies and geological features were investigated a method was developed to convert scalar magnetic anomalies into a map of the lateral variations of magnetic susceptibility of the lithosphere this map is directly correlated with the causative sources the method is based on spherical harmonic analysis of lateral variations seen on the scalar magnetic anomaly map and those of the lithospheric magnetic susceptibility the harmonic coefficients are related through the fundamental causality relationship governing a magnetized body and its associated scalar magnetic anomaly the main features of the resulting magnetic susceptibility anomalies are outlined

the ivrea zone as a model for the distribution of magnetization in the continental crust magnetic properties of the principal lithologies of the ivrea zone of northern italy have been measured maficultramafic granulite facies rocks and amphibolites from the granulite amphibolite facies transition zone are highly magnetic with susceptibilities greater than 0 5 10 3 cgs saturation magnetization values greater than 90 10 3 emu cm and curie points between 570 and 580 c the magnetic phase is magnetite all other lithologies are moderately to weakly magnetic the magnetic mafic granulites are thick and laterally continuous and thus would make an appropriate deep crustal source for long wavelength magnetic anomalies in regions typified by low to average geothermal gradients

slip distribution of the 2015 lefkada earthquake and its implications for fault segmentation this work was partially supported by the uk natural environmental research council nerc through ne k011006 1 ne p008828 1 and the centre for the observation and modelling of earthquakes volcanoes and tectonics comet ga 13 m 031 http comet nerc ac uk

crustal structure of the churchill superior boundary zone between 80 and 98 w longitude from magsat anomaly maps and stacked passes a modeling technique using spherical shell elements and equivalent dipole sources has been applied to magsat signatures at the churchill superior boundary in manitoba ontario and ungava a large satellite magnetic anomaly 12 nt amplitude on pogo and magsat maps near the churchill superior boundary was found to be related to the richmond gulf aulacogen the averaged crustal magnetization in the source region is 5 2 a m 1 stacking of the magnetic traces from magsat passes reveals a magnetic signature 10 nt amplitude at the churchill superior boundary in an area studied between 80 w and 98 w modeling suggests a steplike thickening of the crust on the churchill side of the boundary in a layer with a magnetization of 5 a m 1 signatures on aeromagnetic maps are also found in the source areas for both of these satellite anomalies

field observations of geological effects triggered by the january february 2014 cephalonia ionian sea greece earthquakes abstract on jan 26 and feb 3 2014 cephalonia island ionian sea greece was struck by two strong shallow earthquakes noa local magnitudes ml5 8 and ml5 7 respectively the earthquakes ruptured two sub parallel strike slip faults with right lateral kinematics during both earthquakes ground shaking phenomena such as liquefaction road failures rock falls small medium size landslides and stonewall failures were widespread all over the western part of the island no primary fault surface ruptures were observed however one patch of the rupture of the second event may have nearly reached the surface because of the abundance of surface cracks with cm size offsets mapped in the field in north paliki peninsula liquefaction phenomena were mainly triggered in reclaimed lands in the waterfront areas of argostoli and lixouri inducing structural damages to quays sidewalks and piers we also present evidence for liquefaction induced ground disruption in the recently constructed marina of argostoli which is situated at the opposite eastern shore to the town

geodetic evidence for low coupling on the hellenic subduction plate interface we develop a block model for the aegean and surrounding areas constrained by global positioning system gps in order to investigate the degree of coupling on the hellenic subduction interface i e the fraction of the motion across the plate boundary accommodated by elastic strain accumulation we use previously published models and seismicity to define the geometry of the interface separating the down going nubian slab from the overriding aegean this model provides a good fit to the gps observations for the 200 000 km2 aegean block the wrms of the residual velocities is 1 4 mm yr for 80 gps velocity estimates approximately the 95 level of the gps velocity uncertainties we investigate the degree of coupling on the seismically active plate interface the hellenic trench splay fault believed to be the source of the 365 ad great crete earthquake and tsunami and the kephalonia transform fault by comparing the modeled gps residual velocity field for a range of coupling values the gps observations are almost insensitive to coupling on the kephalonia transform fault because of the vertical dip of the fault that creates interseismic deformation only close to the fault where few gps sites exist the absence of resolvable shortening of the leading edge of the aegean plate precludes coupling of more than 0 2 20 of the full nubia aegean convergence rate on the modeled plate interface because of the shallow dip of the plate interface and trench splay fault and high rate of convergence if these boundaries were fully coupled high elastic strain rates would be expected to extend well into the overriding aegean plate based on our preferred value for the degree of coupling 0 1 and assuming characteristic earthquake behavior we estimate a recurrence time for great earthquakes with slip similar to that for the 365 crete event of 5700 8300 yr consistent with the absence of subsequent great earthquakes on this segment of the subduction zone

the cephalonia transform fault and its extension to western lefkada island greece the central area of the ionian islands is dominated by the existence of a major tectonic structure called the cephalonia transform fault ctf its main part cephalonia segment has been identified by previous work based on the spatial distribution of earthquake foci fault plane solutions of strong earthquakes active tectonics structural studies and geodetic measurements this part cephalonia segment which exhibits strike slip motion with a thrust component strikes in a northeast direction dips to the southeast and has a length of 90 km in the present paper information concerning new fault plane solutions orientation of isoseismals sea bottom topography and recent gps results are used to further check the properties of this southern part of the ctf and to explore its northeastward prolongation to lefkada island it is shown that the ctf is extended to the western coast of lefkada this northern branch lefkada segment of the ctf which is also characterized by strike slip motion with a thrust component strikes in a north northeast direction dips to the east southeast and has a length of 40 km these two segments of the ctf form a major kinematic boundary where the slip rate is 2 3 cm yr

regional magnetic anomaly constraints on continental breakup continental lithosphere magnetic anomalies mapped by the magsat satellite are related to tectonic features associated with regional compositional variations of the crust and upper mantle and crustal thickness and thermal perturbations these continental scale anomaly patterns when corrected for varying observation elevation and the global change in the direction and intensity of the geomagnetic field show remarkable correlation of regional lithospheric magnetic sources across rifted continental margins when plotted on a reconstruction of pangea accordingly these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans

the 2003 december 26 bam earthquake iran mw 6 6 aftershock sequence summary from 2003 december 29 to 2004 january 30 a dense seismological network of 23 stations was installed in the epicentral area of the 2003 december 26 bam earthquake to study the aftershock seismicity we select the 331 earthquakes recorded at a minimum of 10 stations with rms less than 0 1 s and uncertainties less than 1 km to infer the precise geometry of the seismicity in the fault region we also process the data with the double difference technique to confirm the results the aftershock cluster is 25 km long trends north south and is located 5 km west of the bam baravat escarpment exactly beneath the observed surface breaks at depth aftershocks are concentrated between 6 and 20 km beneath the upper layer of relatively low velocity that experienced the maximum slip and they dip slightly westward the southernmost part of the aftershock cluster is narrow and defines the rupture zone that is likely the bam baravat fault at depth however it is unlikely that it is connected at surface to the bam baravat escarpment but more likely to the co seismic ruptures south of bam on the contrary the distribution of the northernmost aftershocks spread into a more complex pattern which is consistent with a northward propagation of the rupture along the fault plane the focal mechanisms are consistent with right lateral strike slip faulting on n s trending faults parallel to the bam baravat escarpment

seismicity and geodynamics of western peloponnese and central ionian islands insights from a local seismic deployment abstract the tectonic setting of western peloponnese and central ionian islands greece is characterized by the subduction of the oceanic african plate beneath the aegean micro plate the transition from subduction to continental collision in northwestern greece is accommodated by the right lateral cephalonia transform fault in this work we exploit the recordings of a temporary seismic network composed of 15 stations operating from july 2016 until may 2017 to investigate the complex deformation of this region our local network fills in a major observational gap in one of the most tectonically active regions of the hellenic arc we detected and located more than 1200 local earthquakes and constrained five 1d optimum local velocity models the relocated seismicity including the aftershock sequence that followed the october 2018 mw 6 7 earthquake offshore zakynthos and associated focal mechanisms constrained for the major earthquakes point out a complex crustal deformation we propose a clockwise rotation of the ionian akarnania block accommodated by major marginal strike slip fault zones that appear segmented along their strike additionally left lateral motion is observed on the kyllini cephalonia fault along a north west direction finally the seismicity recorded in north cephalonia offshore myrtos and fiskardo suggests that the cephalonia transform fault is a large deformation zone where secondary wnw striking sinistral strike slip faults occur

superficial simplicity of the 2010 el mayor cucapah earthquake of baja california in mexico the geometry of faults is usually thought to be more complicated at the surface than at depth and to control the initiation propagation and arrest of seismic ruptures the fault system that runs from southern california into mexico is a simple strike slip boundary the west side of california and mexico moves northwards with respect to the east however the m w 7 2 2010 el mayor cucapah earthquake on this fault system produced a pattern of seismic waves that indicates a far more complex source than slip on a planar strike slip fault here we use geodetic remote sensing and seismological data to reconstruct the fault geometry and history of slip during this earthquake we find that the earthquake produced a straight 120 km long fault trace that cut through the cucapah mountain range and across the colorado river delta however at depth the fault is made up of two different segments connected by a small extensional fault both segments strike n130 e but dip in opposite directions the earthquake was initiated on the connecting extensional fault and 15 s later ruptured the two main segments with dominantly strike slip motion we show that complexities in the fault geometry at depth explain well the complex pattern of radiated seismic waves we conclude that the location and detailed characteristics of the earthquake could not have been anticipated on the basis of observations of surface geology alone

mapping an earthquake induced landslide based on uav imagery case study of the 2015 okeanos landslide lefkada greece abstract on november 17 2015 07 10 utc an earthquake of mw 6 5 induced slope failures mainly at the western part of the island of lefkada ionian sea greece the most characteristic one is the okeanos site deep seated landslide near village athani that affected the man made environment part of the site including a dirt road moved downwards along the coastal cliff and a luxury hotel suffered heavy damage the goal of this study is to map in detail the okeanos landslide and to provide relevant quantitative data i e structural data and volume of both the accumulated and removed material in order to achieve this a comparison between pre earthquake and post earthquake point clouds generated from aerial imagery and uav acquired photos took place using structure from motion the steep coastal cliff site was surveyed in detail even in areas that are difficult to approach results from this study show that the total landslide area covers a surface of 36 000 m2 while a removed volume of 93 000 m3 of landslide material was evaluated using change detection techniques in addition fieldwork and survey data revealed that the sliding surface was a pre existing fault surface upon which the geological material moved downwards the coastal cliff the sliding surface dips west and is exposed along a 115 m long and 25 30 m high section scarp as a conclusion this study underlines the importance of a thorough geological study in order to identify landslide prone areas prior to any building activity and shows that a uav survey is capable to provide adequate information during a post earthquake field survey for co seismic landslide mapping and modeling

fault plane modelling of the 2003 august 14 lefkada island greece earthquake based on the analysis of envisat sar interferograms abstract on 2003 august 14 a mw 6 2 earthquake occurred offshore the lefkada island in the eastern ionian sea one of the most seismically active areas in europe the earthquake caused extended damages in the island and a number of ground failures especially along the north western coast seven ascending envisat asar images are used to process six co seismic interferograms the roi pac package is used for interferogram generation with the srtm dem applied in a two pass method the formation of the co seismic pairs is limited due to the existence of one pre seismic image only dense vegetation is covering the island which is an obstacle in getting good coherence since c band images are used nevertheless ground deformation of 56 mm two fringes in the line of sight of the satellite is detected in all six co seismic interferograms by inversion of the data from the observed fringes a best fitting model of the activated fault is calculated assuming a dislocation in an elastic half space the inferred fault is a pure dextral strike slip fault dipping 59 5 eastward 16 2 km long and 10 2 km wide it is located north of the fault of the mw 6 5 2015 november 17 earthquake and a 10 15 km gap remains between the two faults the 2003 fault does not reach the surface and its upper edge is at a depth of 3 5 1 km no evidence is found of slip south of the lefkada island as suggested by some seismological studies

initial scalar magnetic anomaly map from magsat a scalar magnetic anomaly map between 50 geographic latitude was derived from magsat data acquired during the november 1979 to june 1980 mission lifetime separation of anomaly fields from core and external fields was accomplished utilizing techniques developed for pogo data mayhew 1979 langel et al 1980 comparison with a similar map from pogo data shows that the basic anomaly patterns are essentially reproducible except in a few regions such as the atlantic and pacific at latitudes south of 15 increased resolution due to a lower measurement altitude is evident in the magsat map

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 two fault model of the 2003 leucas aegean arc earthquake based on topological inversion of gps data the fault pattern of the 2003 m w 6 2 leucas lefkada lefkas earthquake at the northwest edge of the aegean arc an area of very high seismicity rates was modeled using global positioning system gps data the rupture process of this earthquake is a matter of debate because of the complexities in the aftershock distribution and in the waveforms of the mainshock as well as the kinematics of the area are not well understood especially the characteristics of the cephalonia kefalonia keffalinia transform fault and its relationship with major discordant active thrusts representing the tectonic fabric of western greece our analysis was based on the topological inversion topinv algorithm which uses a deterministic hypergrid search to identify one or more clusters of n dimensional points around the true solution of the system of observation equations from these clusters optimal estimators of the variables defining okada type faults and their variance covariance matrices are computed as statistical moments and results are validated by minimum mean misfits faulting of the 2003 seismic sequence was approximated by two stepping essentially strike slip segments with a separation of 10 km this pattern is in agreement with fault rupture models based on inversion of seismological data and their main difference is a thrust component in the major segment well constrained by interferometric synthetic aperture radar and gps observations of uplift this thrust component may reflect either postseismic evaporite salt controlled slip or uncertainties in the inversion models the 2003 and other seismic sequences among them the 1953 m 7 2 cephalonia catastrophic earthquakes that were associated with major uplift seem to confirm previous views for an 100 km wide shear zone superimposed on compression along the edges of the aegean arc online material description of analytical inversion methodology the topological inversion algorithm topinv including a figure showing projection of hypergrids on planes

the seismic sequence of january february 2014 at cephalonia island greece constraints from sar interferometry and gps this article has been accepted for publication in geophysical journal internationa 2015 published by oxford university press on behalf of the royal astronomical society all rights reserved

properties of the 2003 lefkada ionian islands greece earthquake seismic sequence and seismicity triggering on 14 august 2003 lefkada island central ionian was strongly af fected by an mw 6 2 earthquake a dense temporary seismic network was installed one day after and accurately located hundreds of aftershocks that defined in detail the main rupture as well as the activity distribution in the neighboring fault segments the main rupture occupied the northwestern part of the coastline and trends north northeast south southwest in agreement with regional tectonics regional network locations were appropriately calibrated using the local network data allowing the relocation of the mainshock and strong m 4 5 or larger aftershocks during the first day intense aftershock activity took place up to 40 km beyond the southern end of the main rupture theoretical static stress changes from the mainshock give a preliminary explanation for the aftershock distribution aside from the main rupture as well as triggering of seismicity in the nearby kefalonia fault providing evidence for future seismic hazard ensuing from this fault

spatial correlation of aftershock locations and on fault main shock properties 1 we quantify the correlation between spatial patterns of aftershock hypocenter locations and the distribution of coseismic slip and stress drop on a main shock fault plane using two nonstandard statistical tests test t1 evaluates if aftershock hypocenters are located in low slip regions hypothesis h1 test t2 evaluates if aftershock hypocenters occur in regions of increased shear stress hypothesis h2 in the tests we seek to reject the null hypotheses h0 aftershock hypocenters are not correlated with 1 low slip regions or 2 regions of increased shear stress respectively we tested the hypotheses on four strike slip events for which multiple earthquake catalogs and multiple finite fault source models of varying accuracy exist because we want to retain earthquake clustering as the fundamental feature of aftershock seismicity we generate slip distributions using a random spatial field model and derive the stress drop distributions instead of generating seismicity catalogs we account for uncertainties in the aftershock locations by simulating them within their location error bounds our findings imply that aftershocks are preferentially located in regions of low slip u umax and of increased shear stress 0 in particular the correlation is more significant for relocated than for general network aftershock catalogs however the results show that stress drop patterns provide less information content on aftershock locations this implies that static shear stress change of the main shock may not be the governing process for aftershock genesis

new evidence of a meridional current system in the equatorial ionosphere an interesting variation in the geomagnetic d component has been found by analysis of the magsat data characteristics of this variation are that it appears everyday on the low latitude duskside and is antisymmetric about the dip equator negative in the northern hemisphere that the magnitude from 5 to 25 nt depends upon the geographic longitude and altitude and that no corresponding change can be seen on the ground magnetic data the change suggests a meridional current system in the equatorial ionosphere produced in association with the electrojet current along the dip equator this effect should be taken into account in the study of geomagnetic anomaly of internal origin with the magsat data

crustal velocity and strain rate fields in italy and surrounding regions new results from the analysis of permanent and non permanent gps networks summary we present a new geodetic velocity solution for italy and the surrounding areas obtained from an analysis of continuous and survey mode global positioning system observations collected between 1991 and 2002 we have combined local regional and global networks into a common reference frame velocity solution providing a new detailed picture of the regional scale deformation field in the central mediterranean our velocity estimates are computed with respect to a new stable eurasian reference frame constraining the kinematics of the greater african eurasian plate boundary system in the study area we provide strain rate values for the main seismotectonic districts which are in good agreement with the seismic deformation inferred from earthquake focal mechanisms the southern tyrrhenian area calabria the apennines the southeastern alps the southern dinarides and the albanides display deformation rates at the order of 20 30 nanostrain yr 1 the corsica sardinia block moves according to eurasian plate motions and there is no indication that the opening of the tyrrhenian is still active the pelagian and sicilian domains are separated by a northwest southeast discontinuity the sicily channel rifted area and marginally significant relative motion between the pelagian plateau and the african plate is also observed the southern tyrrhenian is affected by north south compression and accommodates up to 50 per cent of the africa eurasia relative plate motion whereas the calabrian arc exhibits 2 mm yr 1 northwest southeast extension the observed deformation pattern suggests the presence of a major approximately north south tectonic discontinuity separating the sicilian and calabrian domains an extensional boundary observed along peninsular italy coincides with the distribution of seismogenic faults along the axis of the apennines this boundary separates a tyrrhenian and an adriatic domain with diverging velocities orientated north nnw ward and northeastward respectively the apennines are extending perpendicularly to the chain axis at rates of less than 3 mm yr 1 and only in the outer northern apennines indications of active shortening are observed insignificant deformation is observed in the western po plain and the western alps while the central and eastern alps display north south shortening the eastern adriatic domain is shortening perpendicular to the dinaric front with strain rates increasing from north to south the locus of collision between the aegean balkan system and the adriatic and ionian domains is marked by the kephalonia fault system which accommodates up to 20 1 mm yr 1 of right lateral motion the deformation pattern observed in the peri adriatic domain is well described by a counter clockwise rotation of the adriatic microplate around a pole located in the western alps

the mw6 5 17 november 2015 lefkada greece earthquake structural interpretation by means of the aftershock analysis the 2015 mw6 5 lefkada main shock occurred at the south western part of lefkada island greece less than 2 years after the occurrence of a doublet along the western part of the nearby kefalonia island paliki peninsula on 25 01 2014 with mw6 1 and 03 02 2014 with mw6 0 and 12 years after the 2003 mw6 2 main shock that struck the northwestern part of lefkada island the four failed dextral strike slip fault segments belong to the kefalonia transform fault zone ktfz the major active boundary that bounds from the west the area of central ionian islands namely lefkada and kefalonia it is associated with several known historical earthquakes and is considered the most hazardous area in the greek territory the ktfz fault segments are characterized by high slip rates of the order of tens of millimeters per year with maximum earthquake magnitudes up to 6 7 for lefkada and 7 2 for kefalonia fault zone respectively the double difference location technique was employed for relocating the aftershocks revealing a seismogenic layer extending from 3 to 16 km depth and multiple activation on well defined fault planes with strikes that differ than the main rupture and dips either to east or to west this implies that strain energy was not solely released on a main fault only but on secondary and adjacent fault segments as well the reliable definition of their geometry forms the basis for the structural interpretation of the local fault network the aftershock spatial distribution indicates three main clusters of the seismic activity along with activation of smaller faults to an extent of more than 50 km a northeasterly striking cluster is observed to the north of the main shock epicenter with a remarkable aftershock density the central cluster is less dense than the previous one with an epicentral alignment in full accordance with the strike provided by the main shock centroid moment tensor solution and is considered as the main rupture with a length of 17 km the third cluster encompassing a large number of aftershocks is located in the offshore area between lefkada and kefalonia islands with a ne sw epicentral alignment alike the first cluster the northeast southwest striking secondary faults positioned obliquely and in continuation of the main fault segment reveal that the ktfz is being deformed in a complex tectonic setting the presence of faults with this geometry implies strain partitioning and sheds light to new components necessary to be taken into account in the seismic hazard assessment stress transfer models of the m 6 0 main shocks were investigated and the calculated static stress changes may well explain their sequential occurrence static stress changes due to the 2015 coseismic slip were also calculated with the main objective of exploring the aftershock occurrence pattern and it was found as the driving mechanism that triggered the vast majority of the off fault aftershocks

fault model for the 2015 leucas aegean arc earthquake analysis based on seismological and geodetic observations the 17 november 2015 m w 6 6 earthquake in leucas leukas lefkas or lefkada island in the ionian sea western aegean arc was modeled using teleseismic long period p and sh waveforms and global positioning system gps slip vectors detailed fault modeling in this region characterized by intense seismicity and deformation rates usually assigned to the cephalonia transform fault is a challenge because of the unfavorable observation system to overcome this problem we independently analyzed seismological and geodetic data and then jointly evaluated the results the adopted model indicates that the 2015 earthquake can be assigned to a shallow strike slip fault with a minor component of thrusting along the southwest coasts of leucas and with relatively high slip for the area additionally mostly low angle fault solutions satisfying geodetic observations were identified but were not further investigated the preferred fault model permits recognition that recent m w 6 0 earthquakes in the area some marked by extreme peak ground accelerations are associated with a string of strike slip or oblique slip occasionally overlapping fault segments with variable characteristics along or close to the west coasts of leucas and cephalonia keffalinia kefalonia islands whereas the catastrophic 1953 m w 7 2 cephalonia and other previous major earthquakes were associated with thrust faulting electronic supplement 1 table of the global positioning system gps derived displacements and figures of p wave first motion polarities comparison of earthquake source parameters gps time series 2d projections of geodetic solutions the variance covariance matrix of the geodetic solution and the geodetic variable slip model 1 http www bssaonline org lookup suppl doi 10 1785 0120160080 dc1

transition from collision to subduction in western greece the katouna stamna active fault system and regional kinematics transition from subduction to collision occurs in western greece and is accommodated along the downgoing plate by the kefalonia right lateral fault that transfers the hellenic subduction front to the apulian collision front here we present an active tectonic study of aitolo akarnania western greece that highlights how such a transition is accommodated in the overriding plate based on new multi scale geomorphic and tectonic observations we performed an accurate active fault trace mapping in the region and provide evidence for active normal and left lateral faulting along the katouna stamna fault ksf a 65 km long nnw striking fault system connecting the amvrakikos gulf to the patras gulf we further show that the cenozoic hellenide thrusts located west of the ksf are no longer active either in field observation or in gps data leading us to propose that the ksf forms the northeastern boundary of a rigid ionian islands akarnania block iab cosmic ray exposure measurements of 10be and 36cl were performed on a quaternary alluvial fan offset along the ksf 50 m left lateral offset a maximum abandonment age of 12 14 ka for the alluvial fan surface can be determined giving an estimated ksf minimum geological left lateral slip rate of 4 mm year 1 in agreement with high gps slip rates 10 mm year 1 despite this high slip rate the ksf is characterized by subdued morphological evidence of tectonic activity a gypsum breccia bedrock and a low level of seismicity suggesting a dominantly creeping behavior for this fault finally we discuss how the iab appears to have been progressively individualized during the pleistocene younger than 1 5 ma

native iron in the continental lower crust petrological and geophysical implications lower crustal granulite xenoliths recovered from a kimberlite pipe in western africa contain native iron fe 0 as a decomposition product of garnet and ilmenite magnetic measurements show that less than 0 1 percent by volume of iron metal is present data from geothermometry and oxygen geobarometry indicate that the oxide and metal phases equilibrated between iron wustite and magnetite wustite buffers which may represent the oxidation state of the continental lower crust and the depleted lithospheric upper mantle ferromagnetic native iron could be stable to a depth of approximately 95 kilometers and should be considered in the interpretation of long wavelength static magnetic anomalies

engineering geological mapping of earthquake induced landslides in south lefkada island greece evaluation of the type and characteristics of the slope failures a moderate shallow depth earthquake mw 6 5 occurred onshore lefkada island on november 17 2015 with the focal depth estimated at 11 km the seismic fault is a near vertical strike slip fault running along the western coast part of the cephalonia transform fault landslides and ground cracks were mainly reported at the western part of the island inducing structural damages high severity slope failures occurred at egremnoi and gialos areas that both are located at coastal regions this study aims to investigate the engineering geological conditions at these areas and assess the characteristics and physical quantities e g type area m2 and volume m3 of the instabilities to achieve this engineering geological mapping was implemented in egremnoi and gialos area aiming to a classify the geological units mapped on the heavily damaged areas and b to correlate them with the type of slope failures furthermore type and dimensions of slope failures were evaluated to estimate the total volume of the mass movement all the data originated from the engineering geological mapping have been digitized and rasterized at 5 m grid spacing using the arc info gis software to perform a newmark s sliding block analysis the outcome arisen by this analysis is that the generated by the earthquake peak ground acceleration at these areas should be at least 0 45 g to trigger these kinds of slope failures

reply to comment by klump et al on noble gases and stable isotopes in a shallow aquifer in southern michigan implications for noble gas paleotemperature reconstructions for cool climates 1 in their comment klump et al 2006 hereinafter referred to as kbk make three main points concerning hall et al 2005 1 that the model of excess air that accounts for fractionation via the mechanism of diffusive loss should have produced significant changes from normal isotopic ratios 2 the suggestion that the presence of excess he in the gas phase in the unsaturated zone is incorrect and 3 the observed offset in noble gas temperatures ngts from measured ground temperature can be explained by locking in noble gas concentrations during the annual snow melt point 3 which is by far the most relevant portion of the comment deserves most of our attention in this reply it is important to note up front that the model as suggested in kbk is completely unworkable for the site studied in the work of hall et al 2005 kbk note that more data would resolve some of the unresolved issues from hall et al 2005 but this is true for any preliminary study

the winter 1991 1992 earthquake sequence at cephalonia island western greece properties of the earthquake sequence of the 23 january 1992 5 8 ms earthquake in cephalonia island western greece are investigated the parameter b in the frequency magnitude relation is found equal to 1 084 while the decay parameter p of the time distribution of the aftershock sequence is found equal to 0 991 the principal parameters method is applied to the aftershock sequence and the average strikes of n156 e 20 and n61 e 10 were obtained denoting also very small dips the major strike which resulted from the aftershock epicentre distribution was nw se similar to miocene neogene basins on cephalonia island

fault modelling of the early 2014 m6 earthquakes in cephalonia island w greece based on gps measurements abstract modelling of ground deformation was performed based on gps measurements that were collected in the western part of cephalonia paliki peninsula which had experienced two moderate magnitude earthquakes in early 2014 both events of magnitudes mw 6 1 jan 26 and mw 5 9 feb 3 had the same right lateral character of motion with a small thrust component but different focal depth of 16 km and 5 km respectively the gps results show large amplitudes of displacement in both horizontal 6 40 cm and vertical 8 15 cm components in the vicinity of paliki for the period 2010 2014 which is attributed primarily to those earthquakes various scenarios of activated faults were considered to model the observed ground deformation that was associated with those events the most plausible case that accounts for a realistic and best fit approximation of the measured displacement vectors has a solution of two activated faults of ssw nne trending direction that are separated by a small offset consistent with the lack of surface exposure of the seismogenic faults the best fit model assumes two easterly dipping fault planes at burial depths of 0 8 km and 0 5 km and at angles of 72 and 65 respectively the gps deduced models clearly resolved the plane ambiguities associated with the focal mechanism solutions of the two major events a small normal fault component along the upper part of the fault planes should be considered to further improve the best fit approximation of the observed vertical deformation it was also found that a non negligible deformational component from aftershocks is inherent in the observed data mainly from paliki

source characteristics of the 2015 mw6 5 lefkada greece strike slip earthquake we present a kinematic slip model from the inversion of 1 hz gps strong motion and interferometric synthetic aperture radar insar data for the 2015 mw6 5 lefkada greece earthquake we will show that most of the slip during this event is updip of the hypocenter 10 7 km depth with substantial slip 0 5 m between 5 km depth and the surface the peak slip is 1 6 m and the inverted rake angles show predominantly strike slip motion slip concentrates mostly to the south of the hypocenter and the source time function indicates a total duration of 17 s with peak moment rate at 6 s we will show that a 65 dipping geometry is the most plausible due to a lack of polarity reversals in the insar data and good agreement with coulomb stress modeling aftershock locations and regional moment tensors we also note that there was an 20 cm peak to peak tsunami observed at one tide gauge station 300 km away from the earthquake we will discuss tsunami modeling results and study the possible source of the amplitude discrepancy between the modeled and the observed data at far field tide gauges

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

scalar magnetic anomalies of canada and northern united states derived from magsat data the total magnetic field of the earth over canada and the northern united states is sampled along individual orbits passes of the magnetometer satellite magsat on the basis of data extracted from the magsat chronicle tapes the main magnetic field at a given sample point is calculated using the main field model by langel et al 1982a and then subtracted from the sampled value the external magnetic field contribution is partially removed by a quadratic function fitted to each individual pass the resulting magnetic residuals are resampled at 55 by 55 km grid points on an equal area projection and subsequently contoured the dawn passes yield a magnetic map that is different than the dusk passes implying that the remaining external magnetic field component has a dawn dusk asymmetry the component is further suppressed by applying a band pass filter in the frequency domain the magnetic anomaly map derived by averaging the dawn and the dusk band pass filtered maps shows the main features seen on the aeromagnetic maps of canada and the united states the map also shows that the appalachian and the cordilleran orogens and the grenville superior suture zone are magnetically low regions whereas the craton basins such as the michigan the thelon and the ne british columbia basin are magnetically high areas

the 2003 lefkada earthquake field observations and preliminary microzonation map based on liquefaction potential index for the town of lefkada abstract a strong earthquake mw 6 2 occurred offshore the island of lefkada or lefkas on august 14 2003 the maximum intensity has been evaluated io viii ems at lefkada municipality while vi to vii intensities were evaluated at many other villages of the island the offshore nne ssw oriented strike slip right lateral fault was activated by the main shock this fault is the northern termination of the cephalonia transform fault the most characteristic macroseismic effects were extensive typical ground failures like rock falls soil liquefactions subsidence densification ground cracks and landslides these macroseismic effects are remarkably similar to those reported from some historical lefkada shocks e g 1704 1914 ms 6 3 and 1948 ms 6 5 sand boils and ground fissures with ejection of mud were observed at the seaside of the town of lefkada and in the villages of nydri and vassiliki in situ soil profiles are obtained based mainly on borings after the earthquake boreholes records with spt values standard penetration test are obtained and the simplified procedure originally developed by seed and idriss was employed to evaluate the liquefaction resistance of soils the results indicated that the silty sandy layer which lies beneath the artificial fill in the coastal zone in lefkada town had liquefied during the 14 august earthquake an attempt was also made to establish a preliminary microzonation map for lefkada town using the data from liquefaction potential index analyses our map was validated by the occurrence of liquefaction phenomena inside the town

the 2003 bam iran earthquake rupture of a blind strike slip fault a magnitude 6 5 earthquake devastated the town of bam in southeast iran on 26 december 2003 surface displacements and decorrelation effects mapped using envisat radar data reveal that over 2 m of slip occurred at depth on a fault that had not previously been identified it is common for earthquakes to occur on blind faults which despite their name usually produce long term surface effects by which their existence may be recognised however in this case there is a complete absence of morphological features associated with the seismogenic fault that destroyed bam

the november 17th 2015 lefkada greece strike slip earthquake field mapping of generated failures and assessment of macroseismic intensity esi 07 abstract on november 17 2015 a strong shallow earthquake mw 6 5 occurred on the island of lefkada along a n20 5 e east dipping strike slip fault with right lateral sense of slip the event triggered environmental effects that were mainly mapped at the western part of the island while moving towards the eastern part the severity of the earthquake induced failures decreased the most characteristic geological effects that were triggered by the earthquake were slope failures including rock falls rock slides and landslides the spatial density of the failures follows an exponential increase with slope angle and decreases for values larger than 55 small size liquefaction phenomena such as sand craters and ejection of fine grained sand through ground cracks were documented at the coastal area of vassiliki the epicentral intensity was assessed based on the definitions of environment seismic intensity scale as viii esi 07 and the macroseismic epicenter viii up to ix was located at the coastal area of egremnoi west of athani village south lefkada in addition comparing the severity of earthquake induced failures on the main road network triggered by the 2003 and 2015 events it is concluded that the behavior of the protection measures such as fences and walls could be generally characterized as satisfactory on the contrary the similarity of the structural failures triggered by the 2003 event with the ones triggered by the 2015 earthquake documented at the port of vassiliki indicates that the post 2003 constructed port facilities failed to guarantee the functionality of the port of vassiliki

uplift of tibetan plateau a history of the elevation and crustal thickness of the tibetan plateau since the continental collision at 45 ma has been computed using a kinematic model based on plate tectonic reconstructions and conservation of crustal volume in our reconstructions the indochina block was attached to the southern margin of eurasia before being extruded to the southeast as evidenced by the opening of the south china sea this opening affected the mass input into tibet so that tibet did not uplift to an elevation higher than 1 km until early miocene when spreading of the south china sea ceased the model then gives a steady rise of tibet from middle miocene to its present elevation

3d crustal structure from local earthquake tomography around the gulf of arta ionian region nw greece during summer of 1995 local seismicity was recorded in the area around the gulf of arta in northwestern greece by a dense temporary seismic network of the 441 local events observed at 37 stations 232 well locatable events with a total of 2776 p phase readings were selected applying the criteria of a minimum of 6 p observations and an azimuthal gap less than 180 this data set is used to compute a minimum 1d velocity model for the region several tests are conducted to estimate model stability and hypocenter uncertainties leading to the conclusion that relative hypocenter location accuracy is about 500 m in latitude and longitude and 1 km in depth the minimum 1d velocity model serves as initial model in the non linear inversion for three dimensional p velocity crustal structure by iteratively solving the coupled hypocenter velocity problem in a least squares sense careful analysis of the resolution capability of our data set outlines the well resolved features for interpretation the resulting 3d velocity model shows generally higher average crustal velocities in the east and the well resolved area of the eastern gulf of arta exhibits a homogeneous velocity around 6 km s for the whole upper crust a pronounced north south trending zone of low velocities in the upper 5 10 km is observed in the area of the katouna fault zone kfz at greater depths below 10 km the kfz is underlain by high velocity material e w profiles suggest a horst graben structure associated with the kfz

coseismic deformation field observations and seismic fault of the 17 november 2015 m 6 5 lefkada island greece earthquake abstract on november 17 2015 07 10 07 utc a strong shallow mw6 5 earthquake occurred on the island of lefkada along a strike slip fault with right lateral sense of slip the event triggered widespread environmental effects at the south and western part of the island while the intensity and severity of these earthquake induced deformations is substantially decreased towards the eastern part of the island relocation of seismicity and inversion of geophysical gps insar data indicate that the seismic fault runs parallel to the west coast of lefkada along the aegean apulia plate boundary the fault plane strikes n20 5 e and dips to east with an angle of about 70 5 coseismic deformation was measured in the order of tens of centimeters of horizontal motion by continuous gps stations of noanet the noa gps network and by insar sentinel 1 a image pairs a coseismic uniform slip model was produced from inversion of insar data and permanent gps stations the earthquake measured mw 6 5 using both the geodetic moment produced by the slip model as well as the pgd relation of melgar et al 2015 grl in the field we observed no significant vertical motion of the shoreline or surface expression of faulting this is consistent with the predictions of the model the interferograms show a large decorrelation area that extends almost along all the western coast of lefkada this area correlates well with the mapped landslides the 2003 2015 pattern of seismicity in the ionian sea region indicates the existence of a 15 km seismic gap offshore nw cephalonia