monofractal and multifractal approaches in investigating scaling properties in temporal patterns of the 1983 2000 seismicity in the western corinth graben greece abstract much recent work has been focused on understanding the statistical properties of time occurrence series of earthquakes investigating into the patterns of seismic sequences reveals evidence of scaling features in temporal behavior this is shown in the clustering properties of seismicity of the western corinth graben greece from 1983 to 2000 power law behavior has been found by means of allan factor analysis and fourier spectra for the earthquake sequence with consistent values for the scaling exponents that decrease with the threshold magnitude the analysis of the temporal variation of the scaling exponent performed with different threshold magnitudes reveals an enhancing of the clusterization in correspondence to larger events the multifractal analysis of the temporal distribution of the events has shown a decrease of the intermittent character with the threshold magnitude

characterization of seafloor pockmark seepage of hydrocarbons employing fractal a case study from the western continental margin of india here we apply quantitative technique to describe the seafloor seepages based on the multibeam backscatter and bathymetric investigations to characterize the pockmark morphology the variable seafloor backscatter strength for coarser seafloor sediments are related to the diagenesis derived from biodegraded seepages in this regard box counting method is used to estimate fractal dimension for backscatter imagery data of 398 blocks these blocks are further sub grouped into six classes depending on the spread of pockmark related seepages the study area lies 102 km west off marmagao along the central west coast of india which contains pre dominantly 70 gas charged sediments comparison between the estimated self similar fractals reveals that there is approximately 97 correlation between the box dbox and information dinfo dimensions box dimension derived fractal dimension values suggest that the seepages are more along the fault trace in deeper waters in comparison to sparsely distributed shallow water seepages besides this poor seepage is confined within the smooth to moderately rough seafloor it is established that the high backscatter strength along the upper slope of the pockmark region having higher fractal dimensions reflects multifractal behavior of seepage distribution entire area indicates patchy seepage patterns as supported by estimated fractal values showing intermittent fluctuations which emphasizes non linear behavior estimated self organizing criticality soc parameters for six representative blocks reveal that the nature of pockmark fault trace sediment nature coupled with slumping of pockmark s wall sediment movement due to bottom currents are controlling the dynamic balance in the area seepage system further our study emphasizing the multifractal behavior of seepage blocks clearly depicts the drift in the seepage pattern

seismicity normal faulting and the geomorphological development of the gulf of corinth greece the corinth earthquakes of february and march 1981 three major destructive earthquakes of m s 6 7 6 4 6 4 occurred in the eastern part of the gulf of corinth in february and march 1981 associated normal faulting was observed on both the north and the south sides of the gulf examination of teleseismic local seismic surface faulting and geomorpbological data suggests that the first and second of these shocks activated major north dipping normal faults these faults control the topography and bathymetry and are related to the recent uplift and subsidence of the coastline it is probable that the first earthquake occurred on a faultwhich outcrops underwater and the second on a fault which is visible on land it appears that the third shock activated an antithetic normal fault dipping southwards on the north side of the gulf and that the overall structure of the gulf of corinth graben is asymmetric the northern antithetic fault clearly demonstrates the geomorphological changes associated with developing young normal faulting in addition we suggest that observations of recent coastline movement provide a powerful tool for identifying major active fault systems and predicting their historical role in the paleogeography of an area

1 fβ fluctuations and self similarity in earthquake dynamics observational evidences in southern italy abstract recently it has been determined that many statistical features of earthquakes are scale invariant with universal values for exponents the analysis of scaling laws has led to the development of a wide variety of physical models of seismogenesis involving nonlinear dynamics and it can be used to better characterize the seismicity pattern in this work the presence of scale invariance properties in the seismicity of a selected area of the southern appennine chain is revealed 1 f fluctuations are detected from the analysis of earthquake sequences using the counting statistics and at the spatial scale a self similar structure in the epicentre aggregate is determined by the estimation of its fractal dimension finally correlations between temporal exponent fractal dimension and b value variations are described

identifying space time clustering properties of the 1983 1997 irpinia basilicata southern italy seismicity abstract the fractality of the earthquake sequence 1983 1997 of irpinia basilicata southern italy one of the most seismically active regions of the mediterranean area has been analysed by temporal and spatial fractal tools the fractal exponent estimated by the allan factor method characterises the time clustering behaviour of the set of earthquakes while the correlation dimension d c calculated by means of the correlation integral method gives information on the space clustering behaviour of the sequence of seismic events analysing the variations of both the parameters we recognised the presence of a strong space time clusterisation associated with the major events that occurred in the investigated area

scaling characteristics of local geomagnetic field and seismicity at etna volcano and their dynamics in relation to the eruptive activity abstract the evolution of scaling characteristics of the local geomagnetic field and of the seismicity at etna volcano is studied in relation to the strong eruptive activity occurred here from 2000 to 2002 scaling laws are found in the hourly time variability of magnetic data and in the seismicity pattern the scaling exponents suggest the presence of persistent temporal fluctuations clear links between the dynamics of the measured data and the eruptive volcanic episodes are revealed fractal dimensions of seismicity seem to be always correlated to the beginning of main eruptive events while strong alterations of the dynamics of the local magnetic field take place only when the eruptive fractures opened very close to the magnetic sites

ultrasonic velocity and anisotropy of hydrocarbon source rocks an experimental study of the physical properties of black kerogen rich shales also including maturation analysis scanning electron microscope sem observations and physical modeling revealed fairly peculiar petrophysical parameters specifically these rocks have very low porosity and density but most importantly both p and s ultrasonic velocities normal to bedding are extremely low whereas they are much higher parallel to bedding giving rise to a strong anisotropy even at high confining pressures we found that these parameters primarily reflect kerogen content microstructure and maturation level of these rocks we found also that microcracks inferred from ultrasonic velocity measurements occur only in mature shales these microcracks are parallel to the bedding plane and further enhance strong intrinsic anisotropy notably at low effective pressure our results show that on a small scale kerogen rich shales are transversely isotropic rocks and can be effectively modeled using the thin laye

analysis of site effects in magnetotelluric data by using the multifractal detrended fluctuation analysis abstract we investigated the multifractal structure of magnetic field h measured by magnetotelluric stations installed at three different sites in taiwan characterized by different site conditions magnetotelluric data include three components of the magnetic field h we applied the multifractal detrended fluctuation analysis mf dfa to magnetic magnitude time series evaluated as the l2 norm our findings point out to a significant discrimination among these data in terms of multifractal characteristics of the signals indicating a strong influence of the environmental settings of the measurement sites on the temporal fluctuations of magnetic field h such results highlight the usefulness of the mf dfa in discriminating dynamics in observational time series of magnetotellurics

the nucleation and rupture process of the 1981 gulf of corinth earthquakes from deconvolved broad band data summary source parameters of the largest three normal faulting earthquakes ms6 6 6 3 6 4 in the 1981 gulf of corinth greece sequence are determined using deconvolved broad band data recorded by arrays and single stations and a 2 d finite source model such a model enables the spatial extent rupture velocity and stress drop of the earthquakes to be determined and geological observations of surface slip can be included as a further constraint on the waveform modelling all three earthquakes were shallow lo km with low stress drops 30 bars and exhibited source complexity the correspondence between the complexity of the earthquake sources and that of the mapped fault breaks implies that the segmentation of surface faulting in greece is representative of faulting at depth tiny initial pulses which correlate across the arrays are seen in the seismograms from the gulf of corinth earthquakes at most stations these initial subevents 1 per cent of the total moment are interpreted as the breaking of small asperities which initiated the main rupture and are used to constrain the attenuation correction t 0 2 s

petrofabric p wave anisotropy and seismic reflectivity of high grade tectonites abstract ji s salisbury m h and hanmer s 1993 petrofabric p wave anisotropy and seismic reflectivity of high grade tectonites tectonophysics 222 195 226 in order to understand seismic anisotropy and its influence on the reflectivity of lower crustal fault zones we have undertaken experimental measurements of p wave velocities up to 600 mpa for 20 granulite and upper amphibolite facies mylonites from the snowbird tectonic zone canada the rocks whose composition ranges from ultramafic to felsic have experienced extremely large ductile strain it is found that the amphibolitic mylonites exhibit significant vp anisotropy 6 13 at 600 mpa whereas the pyroxene bearing granulite facies mylonites and the quartz or feldspathic tonalitic granitic and diatexitic mylonites are quasi isotropic in order to constrain interpretation of the measured vp properties microstructural analyses have been systematically performed in the samples studied it is shown that the interaction between feldspar and quartz or pyroxene and the absence of amphibole cause anisotropy in the granulite facies mylonites to be low the amphibolitic mylonites are strongly anisotropic because of a large volume fraction of hornblende with strong lpo 001 lineation and 100 foliation the anisotropy pattern in the amphibolitic mylonites is consistently orthorhombic vp x vp y vp z where x is parallel to stretching lineation y is normal to the lineation in the foliation plane and z is normal to the foliation plane but the anisotropy pattern in the mica rich mylonites is transversely isotropic vp x vp y vp z if sufficiently large volumes of the crust display such patterns this difference may be an important indicator for kinematic analysis in the middle to lower crust using modern seismic techniques the study demonstrates that while seismic reflectivity is strongly lithology controlled fabric induced anisotropy can both enhance and decrease seismic reflectivity hence the discontinuity of seismic reflections along ductile shear zones in the lower crust is not necessarily indicative of the discontinuity of the shear zones but may indicate changes in composition or metamorphic grade

the elastic anisotrophy of shales shales constitute about 75 of the clastic fill sedimentary basins and have a decisive effect on fluid flow and seismic wave propagation because of their low permeability and anisotropic microstructure the elastic stiffnesses of a shale with partially oriented clay particles is expressed in terms of the coefficients w sub lmn in an expansion of the clay particle orientation distribution function in generalized legendre functions application is made to the determination of the anellipticity of shales for transverse isotrophy the anellipticity quantifies the deviation of the p wave slowness curve from an ellipse and is shown to depend on a single coefficient w sub 400 in the expansion of the clay particle orientation distribution function if w sub 400 is small the anellipticity may be neglected as is apparently the case for a near surface late tertiary shale studied by winterstein and paulson strongly aligned clay particles result in a positive value of w sub 400 and a positive anellipticity in agreement with the majority of the field measurements however less well ordered shales could have a significantly positive second moment w sub 200 but only a small positive or even negative value of w sub 400 for such shales the anellipticity would be small or negative despite amore preferred alignment of clay particles in the bedding plane numerical examples of clay particle orientation distribution functions leading to zero or negative anellipticity are given less

earthquakes as self organized critical phenomena a cellular automation model with threshold elements previously proposed by bak et al 1988 which generates 1 f noise and self organizes into a critical state is studied as a model for earthquake occurrence the model explains some of fractal features of earthquakes such as the power law distribution of the size of the earthquake the model is modified so that every earthquake may trigger aftershocks the modified trigger model explains other fractal features of earthquakes such as the power law decay of aftershock frequency and the power law decay of aftershock frequency and the power law correlation of the hypocenter distribution

tectonics and sedimentation in the gulf of corinth and the zakynthos and kefallinia channels western greece abstract single channel seismic reflection profiling data are presented from the gulf of corinth and from the continental margin outside the gulf of patras different tectonic styles are exhibited in the two regions the gulf of corinth is occupied by a complex asymmetrical graben structure with major faults trending nearly perpendicular to the local tectonic zones of the internal hellenides the gulf is interpreted to have formed during the quaternary in response to approximately north south extensional stress the deep floor of the gulf is underlain by a sequence of turbidites up to 1 km thick affected by normal growth faulting that extends up to the sea floor the sea areas inside the ionian islands of zakynthos and kefallinia zakynthos and kefallinia channels occupy a broad structural depression that trends parallel to the local tectonic zones of the external hellenides and is situated on the continental side of the strophades continental margin rise the channels contain local nw se trending structural basins zakynthos and kefallinia basins whose geometry is controlled by reverse faults or thrusts with associated diapirism in triassic evaporites hydra bank is interpreted as a tilted fault block with a diapiric core and its faulted western margin can be traced into the zone of thrusting and diapirism in southeast kefallinia at the boundary between the ionian and pre apulian paxos zones of the external hellinides the zakynthos and kefallinia structural basins are filled with a variety of sediments including prodeltaic deposits in front of the modern delta complex of the acheloos river slumped masses and debris flow deposits and in the zakynthos basin occasional turbidites the boundary separating zones of extensional and compressional focal mechanisms for shallow earthquakes crosses the gulf of patras the inner part of which exhibits wnw ese trending graben tectonics apparently related to the gulf of corinth tectonic province onshore neotectonic studies around the gulf of patras are required in order to understand the nature and cause of the westward tectonic transition from wnw ese graben structures in the gulfs of corinth and patras to nw se oriented zones of subsidence with associated compressional tectonics and diapirism in the zakynthos and kefallinia channels

time clustering properties of seismicity in the etna region between 1874 and 1913 time properties of seismic activity of the etna volcano italy from 1874 to 1913 are investigated by fractal dimension analysis period selection was due to the interesting volcanic and seismic activity which had occurred within this time interval a catalogue was adopted revised by the reexamination of historical sources and with the addition of new material time evolution of the temporal fractal dimension dt calculated on a 40 seismic events moving window revealed the following correlations with the eruptive processes long term fractal dimension variations are due to the magma rise from the depth mid term variations are closely related to stress conditions at the volcano edifice and short term variations are induced by the onset of eruption the spatial localisation of data allowed interpretation of seismic activity in relation to the main structural systems outcropping on the volcano edifice and in the surrounding areas

forecasting where larger crustal earthquakes are likely to occur in italy in the near future a forecast of future occurrences of larger m 5 9 crustal earthquakes in italy is made on the basis of historic and instrumental seismicity and following a seismotectonic regionalization recently derived on the basis of geological evidence combined with earthquake epicenters and focal mechanisms completeness problems in the seismic catalog allow one to study only 20 regions out of 58 large crustal seismicity within each seismogenic region is modeled as either a periodic gauss process or a random poisson process according to the experimental coefficient of variation of the series of past occurrences in each region return times are estimated directly from the series of m 4 5 earthquakes if they are sufficient in number or from the gutenberg richter law applied to lower magnitude seismicity m 4 5 otherwise the immediate probability of an m 5 9 crustal seismic event is esti mated to be very low in all regions except southeastern sicily and appennino abrnz zese in the near future next 20 yr the estimated probability is high above 65 also in the appennino forlivese and naso capo d orlando regions in addition to detailed seismic risk reevaluations these regions represent the best bet for a program of intensive monitoring to gather a record of the process of strain accumulation and seismic release

intermittent type temporal fluctuations in seismicity of the irpinia southern italy region we present a new approach to investigate the temporal fluctuations of seismicity in terms of intermittency as the underlying dynamical mechanism for the variability of seismic activity analyzing the 1983 1997 irpinia southern italy seismicity we base our analysis on the multifractal formalism combined with the estimate of the correlation codimension our findings show that the seismic activity of the area investigated is strongly intermittent and the degree of intermittency lowers if aftershock clusters associated to the larger events are removed

statistical significance of minimum of the order parameter fluctuations of seismicity before major earthquakes in japan in a previous publication the seismicity of japan from 1 january 1984 to 11 march 2011 the time of the m9 tohoku earthquake occurrence has been analyzed in a time domain called natural time chi the order parameter of seismicity in this time domain is the variance of chi weighted for normalized energy of each earthquake it was found that the fluctuations of the order parameter of seismicity exhibit 15 distinct minima deeper than a certain threshold 1 to around 3 months before the occurrence of large earthquakes that occurred in japan during 1984 2011 six out of 15 of these minima were followed by all the shallow earthquakes of magnitude 7 6 or larger during the whole period studied here we show that the probability to achieve the latter result by chance is of the order of 10 5 this conclusion is strengthened by employing also the receiver operating characteristics technique

measuring multifractality in seismic sequences abstract we investigated the multifractal structure of the interevent times between successive earthquakes that occurred in umbria marche which is one of the most seismically active areas of central italy we used the multifractal detrended fluctuation analysis mf dfa which permits detection of multifractality in nonstationary series analyzing the time evolution of the multifractal behaviour of the seismic sequence a loss of multifractality during the aftershocks is revealed

the seismicity geomorphology and structural evolution of the corinth area of greece in the eastern gulf of corinth geological structure is closely reflected in the topography in the 1981 corinth earthquakes ground deformation accentuated existing geomorphological patterns we explore the relationship between seismicity and landforms in space and time the area examined extends beyond the epicentral region of the 1981 events and its evolution is traced over the last 40000 years to understand the relation between deep and superficial structures we discuss processes that occurred in the 1981 earthquakes and go on to propose that surface faulting appears only above linear faults at depth that move in earthquakes with magnitudes m s greater than six where faults at depth intersect or bend the faulting becomes distributed and prim ary faulting does not reach the surface here the surface manifestation of faulting at depth is surface folding and secondary faulting such regions are identified in maps of the eastern gulf of corinth evidence for the evolution of the fault systems is provided by eyewitness accounts of shoreline changes following the recent earthquakes historical and archaeological data pertaining to old sea levels and 14 c dates for molluscs collected from fossil shorelines the results of these studies broadly confirm an earlier view of j a jackson et al earth planet sci lett 57 377 397 1982 that motion has shifted from faulting south of the city of corinth to faulting in the perachora peninsula but the transfer is not complete areas lying between the two fault systems have moved up and down in historical and archaeological times indicating that both systems are still active the evidence for activity of the northern system points to a repeat time of 300 years for earthquakes com parable with those of 1981 the work discussed in this paper suggests that some of the features previously described as m arine terraces are fault controlled continental surfaces furtherm ore beach deposits at a num ber of different levels long regarded as successive shorelines are in fact contemporaneous the critical ages were obtained by radiocarbon dating of shell carbonate a technique which yields dependable results if applied to samples which have been carefully selected and pretreated palaeontological dating of the terraces in contrast is found to be misleading because the faunas are environm entally controlled and consequently diachronous

the squirt flow mechanism macroscopic description we introduce a poroelasticity model that incorporates the two most important mechanisms of solid fluid interaction in rocks the biot mechanism and the squirt flow mechanism this combined biot squirt bisq model relates compressional velocity and attenuation to the elastic constants of the drained skeleton and of the solid phase porosity permeability saturation fluid viscosity and compressibility and the characteristic squirt flow length squirt flow length is a fundamental rock property that does not depend on frequency fluid viscosity or compressibility and is determined experimentally we find that the viscoelastic response of many sandstones is dominated by the squirt flow component of the bisq mechanism and that the viscoelastic properties of these rocks can be expressed through a single dimensionless parameter omega r 2 kappa where omega is angular frequency r is the characteristic squirt flow length and kappa is hydraulic diffusivity the biot mechanism alone does not give an adequate explanation of the observed velocity dispersion and attenuation and the viscoelastic behavior of many sandstones

long term earthquake clustering summary we analyse statistically the long term properties of several instrumental earthquake catalogues complete catalogues exhibit both short and long term clustering for earthquakes of all depth ranges after accounting for the effect of short term clustering we find that in residual declustered catalogues long term clustering not periodicity characterizes the occurrence of all earthquakes shallow intermediate and deep the degree of clustering in residual catalogues is the same for earthquakes in different depth ranges circumstantial evidence indicates that the long term v ariation of seismicity is governed by a power law temporal distribution as in short term clustering it is scale invariant the fractal dimension of an earthquake set on the time axis is of the order of 0 8 0 9 therefore mainshock occurrence is closer to a stationary poisson process than standard aftershock sequences of shallow earthquakes

velocity anisotropy and attenuation of shale in under and overpressured conditions the seismic velocity and attenuation of fully saturated shales were measured for the first time under overpressured conditions using the ultrasonic reflection technique shale cores from naturally overpressured horizons in the north sea were tested in the laboratory at confining and pore pressures relevant to in situ conditions a single frequency tone burst pulse wave was used to determine the seismic wave velocities and quality factors of the shale samples with errors less than 0 3 and 0 1 db cm respectively at a frequency of 0 75 mhz sample length changes with varying confining and pore pressure were measured and the pore pressure equilibration time was monitored for each sample the anisotropy of the seismic attributes vp vs qp and qs was determined over a range of differential pressures from 5 to 60 mpa with respect to the predominant foliation the ultrasonic velocity data followed a transversely isotropic pattern depending on the direction of wave propagation with respect to the laminations the poisson s ratio was found to rise by 5 as the shale material progressed from a normally pressured to an overpressured state the quality factor q characteristics were interpreted in terms of pore geometry and connectivity as well as the directional permeability of the transversely isotropic shale material the results were converted to bulk and shear loss modulus defects and a positive bulk loss was observed for waves propagating perpendicular to the lamination plane even above differential pressures of 20 mpa this indicates different levels of biot flow and squirt flow attenuation mechanisms acting within the shale structure depending on the wave propagation and vibration directions

the strain pattern in the western hellenic arc deduced from a microearthquake survey summary than loo0 earthquakes recorded during 7 weeks in 1986 in the peloponnese and surrounding areas show shallow seismicity spread over a wide area bounded by the hellenic trench the highest level in the energy release is for clusters located along the hellenic trench where changes in the morphology are seen a few clusters are also observed as at the intersection between the gulf of corinth and the gulf of patras near the lake trikhonis or between kythira and crete in the peloponnese the shallow earthquakes do not define single faults but are diffusely distributed a higher concentration and a deepening of the foci within the whole crust towards the west seem to reflect a higher strain rate there fault plane solutions exhibit a scattered pattern for earthquakes shallower than 11 km but for earthquakes deeper than 11 km they show some consistency in the orientation of p t and b axes gently dipping nodal planes are seen all over the peloponnese with the conjugate vertical plane striking in various directions and with no consistency in the sense of motion these earthquakes are located between 8 and 18 km deep and could reflect a decoupling between the lower and the upper crust reverse faulting is seen in the gulf of kefallinia and the western peloponnese the p axes trend ne sw to e w normal faulting is seen in the gulf of corinth and in central peloponnese with the t axes trending n s and in the southern peloponnese where the t axes trend nw se the deformation over the western hellenic arc revealed by fault plane solutions of earthquakes with depth between 11 and 40 km appears to be the superposition of two phenomena first throughout the aegean crustal extension with orientation roughly parallel to the trench dominates with crustal shortening and subduction along the aegean arc superimposed on this is a more local effect of the collision between the aegea and apulia which seems to induce horizontal compression roughly perpendicular to the aegean arc west of the peloponnese and epirus the compression due to this decays eastward at a distance comparable with the width of the collision zone the deepening of the brittleductile transition is likely to be due to an increase of the strain field towards the ionian islands

shear wave velocity anisotropy in sedimentary rocks a laboratory study a systematic laboratory study of shear wave velocity anisotropy in sedimentary rocks has been carried out as a function of both hydrostatic and uniaxial stress the presence of shear wave velocity anisotropy in sedimentary rocks was confirmed by transmitting a polarized shear wave in a rock sample and receiving a signal on an orthogonally polarized receiver the magnitude of the observed velocity anisotropy is dependent upon the magnitude and nature of the applied stress and the lithology of the rock sample shales exhibit significant velocity anisotropy independent of both uniaxial and hydrostatic stress which suggests the presence of preferentially aligned minerals sandstones also exhibit significant velocity anisotropy but the anisotropy is strongly dependent upon the stress hydrostatic stress was found to diminish the velocity anisotropy and uniaxial stress was found to enhance it this implies the presence of preferentially oriented cracks limestones exhibit weak velocity anisotropy these laboratory observations may be helpful in in situ identification of lithology

dynamic multifractality in earthquake time series insights from the corinth rift greece earthquake time series are widely used to characterize the main features of seismicity and to provide useful insights into the dynamics of the seismogenic system properties such as intermittency and non stationary clustering are common in earthquake time series such that multifractal concepts seem essential to describe the temporal clustering variability here we use a multifractal approach to study the time dynamics of the recent earthquake activity in the corinth rift the results indicate the degree of heterogeneous clustering and correlations acting at all time scales that suggest non poissonian behavior additionally the multifractal analysis in different time periods showed that the degree of multifractality exhibits strong variations with time which are associated with the dynamic evolution of the earthquake activity in the rift and the transition between periods of high and low seismicity

thermally induced brittle deformation in oceanic lithosphere and the spacing of fracture zones brittle deformation of oceanic lithosphere due to thermal stress is explored with a numerical model with an emphasis on the spacing of fracture zones brittle deformation is represented by localized plastic strain within a material having an elasto visco plastic rheology with strain softening we show that crustal thickness creep strength and the rule governing plastic flow control the formation of cracks the spacing of primary crack decreases with crustal thickness as long as it is smaller than a threshold value creep strength shifts the threshold such that crust with strong creep strength develops primary cracks regardless of crustal thicknesses while only a thin crust can have primary cracks if its creep strength is low for a thin crust the spacing of primary cracks is inversely proportional to the creep strength suggesting that creep strength might independently contribute to the degree of brittle deformation through finite versus zero dilatation in plastic strain associated and non associated flow rule results in nearly vertical and v shaped cracks respectively changes in the tectonic environment of a ridge system can be reflected in variation in crustal thickness and thus related to brittle deformation the fracture zone free reykjanes ridge is known to have a uniformly thick crust the australian antarctic discordance has multiple fracture zones and thin crust these syntheses are consistent with enhanced brittle deformation of oceanic lithosphere when the crust is thin and vice versa

multifractal patterns of seismicity spatial distribution of earthquake epicentres is investigated using a multifractal approach involving a whole spectrum of non integer dimensions of the set under consideration the multifractal approach allows to analyze not only geometrical characteristics of the spatial distribution but also intensities of seismicity at particular sites or probabilities of visiting particular sites by seismic events multifractal characteristics spectra of dimensions f and d q are calculated for three seismic regions pamir caucasus and california the functions f and d q contain information about concentration clustering properties and intermittency of spatial earthquake distribution

dynamic poroelasticity a unified model with the squirt and the biot mechanisms the velocities and attenuation of seismic and acoustic waves in rocks with fluids are affected by the two most important modes of fluid solid interaction 1 the biot mechanism where the fluid is forced to participate in the solid s motion by viscous friction and inertial coupling and 2 the squirt flow mechanism where the fluid is squeezed out of thin pores deformed by a passing wave traditionally both modes have been modeled separately with the biot mechanism treated in a macroscopic framework and the squirt flow examined at the individual pore level we offer a model which treats both mechanisms as coupled processes and relates p velocity and attenuation to macroscopic parameters the biot poroelastic constants porosity permeability fluid com pressibility and viscosity and a newly introduced microscale parameter a characteristic squirt flow length the latter is referred to as a fundamental rock property that can be determined experimentally we show that the squirt flow mechanism dominates the biot mechanism and is responsible for measured large velocity dispersion and attenuation values the model directly relates p velocity and attenuation to measurable rock and fluid properties therefore it allows one to realistically interpret velocity dispersion and or attenuation in terms of fluid properties changes e g viscosity during thermal enhanced oil recovery eor or to link seismic measurements to reservoir properties as an example of the latter transformation we relate permeability to attenuation and achieve good qualitative correlation with experimental data

geometry and kinematics of active faults and their seismotectonic significance in the western corinth patras rift greece abstract the western part of the corinth patras rift is formed in an area which is being uplifted rifted domains have subsided relative to the adjacent areas in nw peloponnesus and sterea hellas but subsidence rates rarely exceed uplift rates extension is mainly accomplished by wnw trending active faults with lengths up to 25 km most of these faults show an along strike segmentation and often terminate against transfer faults displacement analysis along 170 mesoscopic faults and 36 mappable faults has been carried out to assess slip rates and to estimate the magnitudes and recurrence time intervals of earthquakes occurring along them earthquake magnitude ranges between 5 and 6 7 only eight faults appear to be capable of producing earthquake magnitudes larger than 6 recurrence times of these large earthquakes vary between 80 and 1690 years upper crustal deformation in the western corinth graben can be described by six large asymmetric grabens which are inferred to bottom out to a n dipping curved ramp the asymmetric shape of most wnw trending rifts in the hellenic peninsula including the corinth patras rift promotes the simple shear model of extension against the pure shear model in the upper crustal layer

modelling the seismic attributes of overpressured siliciclastic rocks with a genetic annealing gan algorithm a genetic annealing gan algorithm is used to derive an empirical model which predicts compressional wave velocity values for overpressured siliciclastic rocks the algorithm involves non linear random searching and mutation techniques and its annealing component imposes a very strict control over the rate of convergence of the search this technique provides an alternative to the standard calculations involving the effective stress coefficient n the pore pressure is introduced into the model as an explicit variable and as part of an overpressure coefficient p p p c the ratio of pore to confining pressure empirical model derived data and known laboratory data are compared and their differences are shown to be within statistically acceptable error limits the empirical equation fits all under and overpressured data simultaneously irrespective of pore fluid pressure level with the same parameters it is used to predict seismic velocities very accurately for extreme levels of overpressure starting from normally pressured experimental data the model highlights the effect of pore pressure on the compressional wave velocity of fully saturated samples with different clay contents it can be used when the experimental data available are sparse and particularly when a prediction of material behaviour is necessary at specific pore fluid pressure and depth conditions

the evolution of the gulf of corinth greece an aftershock study of the 1981 earthquakes summary a preliminary study of the aftershocks of three earthquakes that occurred near to corinth greece in 1981 is combined with observations of the morphology and faulting to understand the evolution of the eastern gulf of corinth the well located aftershocks form a zone 60km long and 20km wide they do not lie on the main fault planes and are mostly located between the north dipping faulting on which the first two earthquakes occurred and the south dipping faulting associated with the third event a cluster of aftershocks also lies in the footwall of the eastern end of the south dipping fault of the third event morphologically it is observed that in the evolution of the eastern gulf of corinth antithetic faulting apparently predates the appearance of the main faulting at the surface this evolution can be explained by motion on a deep seated shallow angle aseismic normal fault a model based on such a fault also accounts for the aftershock distribution of the 1981 earthquakes