self driven mode switching of earthquake activity on a fault system theoretical results based on two different modeling approaches indicate that the seismic response of a fault system to steady tectonic loading can exhibit persisting fluctuations in the form of self driven switching of the response back and forth between two distinct modes of activity the first mode is associated with clusters of intense seismic activity including the largest possible earthquakes in the system and frequency size event statistics compatible with the characteristic earthquake distribution the second mode is characterized by relatively low moment release consisting only of small and intermediate size earthquakes and frequency size event statistics following a truncated power law the average duration of each activity mode scales with the time interval of a large earthquake cycle in the system the results are compatible with various long geologic paleoseismic and historical records the mode switching phenomenon may also exist in responses of other systems with many degrees of freedom and nonlinear dynamics 1999 elsevier science b v all rights reserved

the evolution of regional seismicity between large earthquakes 1 we describe a simple model that links static stress coulomb modeling to the regional seismicity around a major fault unlike conventional coulomb stress techniques which calculate stress changes we model the evolution of the stress field relative to the failure stress background seismicity is attributed to inhomogeneities in the stress field which are created by adding a random field that creates local regions above the failure stress the inhomogeneous field is chosen such that when these patches fail the resulting earthquake size distribution follows a gutenburg richter law immediately following a large event the model produces regions of increased seismicity aftershocks where the overall stress field has been elevated and regions of reduced seismicity where the stress field has been reduced stress shadows the high stress levels in the aftershock regions decrease due to loading following the main event combined with the stress shadow from the main event this results in a broad seismically quiet region of lowered stress around the epicenter pre event seismicity appears as the original stress shadows finally fill as a result of loading the increase in seismicity initially occurs several fault lengths away from the main fault and moves inward as the event approaches as a result of this effect the seismic moment release in the region around the future epicenter increases as the event approaches synthetic catalogues generated by this model are virtually indistinguishable from real earthquake sequences in california and washington

evaluation of the results for an intermediate term prediction of the 8 january 2006 mw 6 9 cythera earthquake in the southwestern aegean during the past few decades the critical earthquake model which is based on observations concerning accelerating seismic deformation and concepts of the critical point dynamics has been proposed by various seismologists as a useful tool for intermediate term earthquake prediction a refined approach of this model has been previously applied to search for preshock critical regions in the southern aegean using all available data until the middle of 2002 a critical region corre sponding to a large mainshock had been identified papazachos et al 2002a b in the southwestern part of the aegean near the cythera island the predicted in 2002 parameters for this ensuing earthquake are u 36 5 n k 22 7 e for the epicental geographic coordinates with a model uncertainty of 120 km focal depth 100 km moment magnitude m 6 9 0 5 and origin time tc 2006 4 2 0 the generation of the strong cythera earthquake on 8 january 2006 with m 6 9 epicenter coordinates u 36 2 n and k 23 4 e and a focal depth of h 65 km satisfies this intermediate term prediction the region where significant macroseismic effects were anticipated from the predicted mainshock cythera south peloponnesus west crete and west cyclades corresponds to the area where damage by the 8 january 2006 strong earthquake has been observed the verification of this prediction is strong evidence that the intermediate term prediction of strong earthquakes is potentially feasible but additional forward testing of the model is needed to validate this result

earthquake activity related to seismic cycles in a model for a heterogeneous strike slip fault we investigate the evolution of seismicity within large earthquake cycles in a model of a discrete strike slip fault in elastic solid the model dynamics is governed by realistic boundary conditions consisting of constant velocity motion of regions around the fault static kinetic friction and dislocation creep along the fault and 3d elastic stress transfer the fault consists of brittle parts which fail during earthquakes and undergo small creep deformation between events and aseismic creep cells which are characterized by high ongoing creep motion this mixture of brittle and creep cells is found to generate realistic aftershock sequences which follow the modified omori law and scale with the mainshock size furthermore we find that the distribution of interevent times of the simulated earthquakes is in good agreement with observations the temporal occurrence however is magnitude dependent in particular the small events are clustered in time whereas the largest earthquakes occur quasiperiodically averaging the seismicity before several large earthquakes we observe an increase of activity and a broadening scaling range of magnitudes when the time of the next mainshock is approached these results are characteristics of a critical point behavior the presence of critical point dynamics is further supported by the evolution of the stress field in the model which is compatible with the observation of accelerating moment release in natural fault systems

formation and effects of alternate bars major river regulation works have often resulted in alternate bar formation experimental work is described which provides more information on this phenomenon alternate bar formation is closely associated with meandering inferring that alternate bar formation is caused by flow induced periodic disturbances of the horizontal velocity profile based on these considerations a criterion has been developed which defines the upper limit of alternate bar formation and this has been satisfactorily compared to other formation criteria and experimental data the lower limit is given by the initiation of bedload transport a simple relation between slope channel width and grain size is then deduced to indicate whether for a given channel alternate bars can develop for any discharge this relation takes into account armoring effects another equation is proposed to predict the scour depth resulting from alternate bar formation such scour often induces costly river maintenance works finally some interesting results on flow resistance hav been found leading to a tentative equation for the intermediate roughness range

icequakes coupled with surface displacements for predicting glacier break off a hanging glacier at the east face of weisshorn switzerland broke off in 2005 we were able to monitor and measure surface motion and icequake activity for 25 days up to 3 days prior to the break off the analysis of seismic waves generated by the glacier during the rupture maturation process revealed four types of precursory signals of the imminent catastrophic rupture 1 an increase in seismic activity within the glacier 2 a change in the size frequency distribution of icequake energy 3 a modification in the structure of the waiting time distributions between two successive icequakes and 4 a correlation between the seismic activity and the log periodic oscillations of the surface velocities superimposed on the global acceleration of the glacier during the rupture maturation analysis of the seismic activity led us to identify two regimes a stable phase with diffuse damage and an unstable and dangerous phase characterized by a hierarchical cascade of rupture instabilities where large icequakes are triggered

accelerated preshock deformation of broad regions in the aegean area twenty four regions where accelerating deformation has been observed for a few decades before corresponding strong m 6 0 7 5 mainshocks are identified in the broader aegean area to a first approximation these preshock regions have elliptical shapes and the radius r in km of a circle with an area equal to the corresponding ellipse is related to the moment magnitude m of the mainshock by the equation log r 0 42 m 0 68 the dimension of each preshock region is about seven to ten times larger than the rupture zone fault length of the corresponding mainshock the time variation of the cumulative benioff strain was satisfactorily fitted by a power law relation which is predicted by statistical physics if the mainshock to which accelerating strain rates leads is considered as a critical point the duration t in years of the accelerating benioff strain release period is given by the relation log t 5 94 0 75 log s r where s r is the mean benioff strain rate release per year for 104 km2 in the preshock region calculated by the complete available data m 5 2 for the entire instrumental period 1911 1998 the importance of identifying and investigating such regions for better understanding the dynamics of the active part of the lithosphere as well as for earthquake prediction and time dependent seismic hazard assessment is discussed

stochastic synthesis of earthquake catalogs a model of earthquake occurrence is proposed that is based on results of statistical studies of earthquake catalogs we assume that each earthquake generates additional a probability that depends on time as t 1 this assumption together with one regarding the independence of branching events on adjacent branches of the event tree is sufficient to permit the generation of complete catalogs of earthquakes that have the same time magnitude statistical properties as real earthquake catalogs if is about 0 5 the process generates sequences that have statistical properties similar to those for shallow earthquakes many well known relations are reproduced including the magnitude frequency law omori s law of the rate of aftershock and foreshock occurrence the duration of a recorded seismic event versus its magnitude the self similarity or lack of scale of rate of earthquake occurrence in different magnitude ranges etc a value of closer to 0 8 or 0 9 seems to simulate the statistical properties of intermediate and deep shocks a formula for seismic risk prediction is proposed and the implications of the model for risk evaluation are outlined the possibilities of the determination of long term risk from real or synthetic catalogs that have the property of self similarity are dim

pre seismic electromagnetic phenomena in the framework of percolation and fractal theories abstract understanding the electromagnetic response to geodynamic processes occurring in the earth s upper crust in particular pre seismic and seismic processes is a challenging task in modern geophysics there is increasing evidence that seismo electromagnetic sem phenomena are difficult to describe quantitatively by linear models using averaged parameters of the medium such as electrical and hydraulic conductivities because the upper crust is highly inhomogeneous at all scales porous and can be fully or partially water saturated the most natural way to describe its parameters is via fractal theoretic and percolation theoretic models recent studies indicate that the electrokinetic effect is the most likely driving mechanism for the various types of sem signals here we considered the hydraulic electric and electrokinetic conductances of a porous water saturated medium as a function of porosity and moisture content utilizing a percolation fractal approach we show that the electric conductivity and electrokinetic current in such a medium are both proportional to c 2 and c 2 where c and c are the critical values of porosity and moisture content respectively this behavior admits the possibility of a relatively large change in the respective electric and electrokinetic parameters due to a small change in the mechanical strain field this is significant because it may account for the appearance of some types of sem signals at large distances from the earthquake origin which is the main deficiency of most models indeed the anticipated strain changes related to pre earthquake processes is usually very small except near the focal area the expected averaged electromagnetic response also would be very small unless a local underground water system exists not necessarily near the focal area but which is close to critical point s we discuss the conditions under which electrotelluric and geomagnetic variations can accompany mechanical disturbances in the earth s crust

precursors to the kalapana m 7 2 earthquake the kalapana hawaii earthquake of november 1975 had a rupture length of 40 to 50 km and was located on the south flank of the active volcano kilauea the source mechanism was dip slip normal faulting on a plane dipping 20 degrees to the se with the greatest principal stress oriented in that direction and accumulated by volcanic intrusions into kilauea s rifts the source area of the 1975 earthquake was subject to intensive geological and geophysical research for many years before this earthquake because of its proximity to the volcano we studied the distribution of epicenters for small earthquakes from 1962 to 1975 seven seismographs located within 3 km of the aftershock area had been in operation for 3 to 10 years before the mainshock and geodetic triangulations and trilaterations in the source area had been carried out repeatedly since 1914 we found that precursory changes occurred throughout most of the rupture area but in two distinctly different patterns in the larger outer anomalous area the seismicity rate was decreased by 50 during the 3 8 years before the mainshock in addition several geodetic lines indicated anomalous strain release during this time within two inner areas the seismicity remained high then increased shortly before the mainshock in one of the inner areas a p wave travel time delay of 0 2 s could be detected which began about 3 5 years before the mainshock within the other inner anomalous area geodetic strain was accumulating until the first half of 1975 when 3 5 10 4 strain 35 bars was released aseismically by contrast the outer anomalous volume was experiencing strain softening from 1970 1971 on we interpret these observations as indicating that strain softening by fault creep in the outer anomalous area transferred stress into two major asperities locked portions of the fault a velocity decrease and foreshocks were observed in one asperity and high stress accumulation in the other implying that dilatancy of the crust probably occurred our model is qualitatively supported by the independent evidence of strong motion records which show that the kalapana earthquake was a complex multiple rupture we conclude that the kalapana earthquake was preceded by a preparatory process which lasted 3 8 0 3 years and which had dimensions of 45 10 km covering approximately the aftershock area

a systematic spatiotemporal test of the critical point hypothesis for large earthquakes 1 the critical point hypothesis for large earthquakes predicts two different precursory phenomena in space and time an accelerating moment release and the growth of the spatial correlation length the objective of this work is to investigate both methods with respect to their predictive power a systematic statistical test based on appropriate random earthquake catalogs allows to quantify the correlations of a precursory pattern with the subsequent mainshock activity the analysis of target earthquakes in california since 1960 with magnitudes m mcut reveals that these correlations increase systematically with growing mcut and correlations at greater than 95 confidence are observed for mcut 6 5 in the case of the spatial correlation length in particular the seismicity patterns are found to be significantly correlated with each of the largest earthquakes m 7 0 individually the acceleration of the moment release has a similar trend but is less significant

accelerating seismic crustal deformation in the southern aegean area a region of intense accelerating seismic crustal deformation has been identified in the southwestern part of the hellenic arc broader area of cythera island the identification is performed using a detailed parametric grid search of the broader southern aegean area for accelerating energy release behavior the identified region has similar properties with past preshock critical regions which have been identified for strong mainshocks in the aegean area based on such observations which suggest that this region is at a critical state that can lead to a critical point that is to the generation of a mainshock an estimation is made of the possible epicenter coordinates magnitude and origin time of this oncoming large m 7 0 earthquake the estimation procedure is validated on the basis of retrospective analysis of strong events in the aegean area as well as by appropriate application on synthetic random catalogs these results the existence of similar observations of accelerating seismic deformation in eastern part of southern aegean and independent information on the time distribution of large earthquakes m 6 8 for the whole southern aegean indicate that the generation of strong earthquakes in this area in the next few years must be considered as very probable

precursory seismic quiescence seventeen cases of precursory seismic quiescence to mainshocks with magnitudes fromml 4 7 toms 8 0 are summarized the amount of rate decrease ranges from 45 to 90 the significance of these changes varies between 90 and 99 99 the assumption that the background rate is approximately constant is fulfilled in most crustal volumes studied all quiescence anomalies seem to have abrupt beginnings and the rate during the anomalous period is fairly constant the duration of the precursors ranges from 15 to 75 months and it is not clear what factors determine that time at least three successful predictions have been based on seismic quiescence these cases have shown that mainshocks can be predicted based on quiescence but they have also shown that the interpretation of the data in real time is difficult and nonunique if a false alarm is defined as a period of quiescence with a significance level larger than a precursory quiescence in the same tectonic area then we estimate based on searches in four areas that the false alarm rate may be on the order of 50 failure to predict may be expected in perhaps 50 of mainshocks even in carefully monitored areas quiescence cannot be used as a precursor in tectonic environments with low seismic activity most characteristics of the phenomenon are still poorly defined but data exist which probably permit at least a doubling of the presently available data on case histories

fractals in geology and geophysics the definition of a fractal distribution is that the number of objectsn with a characteristic size greater thanr scales with the relationn r d the frequency size distributions for islands earthquakes fragments ore deposits and oil fields often satisfy this relation fractals were originally introduced by mandelbrot to relate the length of a coastline to the length of the measuring stick this application illustrates a fundamental aspect of fractal distributions scale invariance the requirement of an object to define a scale in photographs of many geological features is one indication of the wide applicability of scale invariance to geological problems scale invariance can lead to fractal clustering geophysical spectra can also be related to fractals these are self affine fractals rather than self similar fractals examples include the earth s topography and geoid

probabilities of activation of seismic faults in critical regions of the aegean area summary properties of the accelerating seismic crustal deformation pattern and of the intermediateterm seismic quiescence pattern have been combined to identify faults in the aegean area 34 n 43 n 19 e 30 e that have a considerable probability of generating strong earthquakes m 6 4 during the next 5 yr period eight groups of such faults have been identified and the probability of each fault being activated during this time period has been estimated three of these groups are located in southern greece hellenic arc two in central greece east central greece ionian islands two in northwestern turkey and one in the area of the borders of albania greece and the former yugoslav republic of macedonia the importance of these results for intermediate term seismic hazard assessment is discussed

identification of seismic precursors before large earthquakes decelerating and accelerating seismic patterns 1 a useful way of understanding both seismotectonic processes and earthquake prediction research is to conceive seismic patterns as a function of space and time the present work investigates seismic precursors before the occurrence of an earthquake it does so by means of a methodology designed to study spatiotemporal characteristics of seismicity in a selected area this methodology is based on two phenomena the decelerating moment release dmr and the accelerating moment release amr as they occur within a period ranging from several months to a few years before the oncoming event the combination of these two seismic sequences leads to the proposed decelerating accelerating moment release damr earthquake sequence which appears as the last stage of loading in the earthquake cycle this seismic activity appears as a foreshock sequence and can be supported by the stress accumulation model sam the damr earthquake sequence constitutes a double seismic precursor identified in space and time before the occurrence of an earthquake and can be used to improve seismic hazard assessment research in this study the developed methodology is applied to the data of the 1989 loma prieta california the 1995 kobe japan and the 2003 lefkada greece earthquakes the last part of this study focuses on the application of the methodology to the ionian sea western greece and forecasts two earthquakes in that area

an observational test of the origin of accelerating moment release before large earthquakes 1 a progressive increase of seismic activity distributed over a wide region around a future earthquake epicenter is termed accelerating moment release amr this phenomenon has been observed in several studies over the last 15 years although there is no consensus about the physical origin of the effect in a recent hypothesis known as the stress accumulation sa model the amr is thought to result from the last stage of loading in the earthquake cycle in this view the increasing seismicity is due to minor stress release as the whole region becomes sufficiently stressed for the major event to occur the stress accumulation model makes specific predictions about the distribution of events in an amr sequence because the amr is predicted to be a result of loading on the main fault the precursory activity should be concentrated in the positive lobes of the far field stresses calculated by a backslip dislocation model of the main shock to test this model amr is first found in optimal circular regions around the epicenters of each of the m w 6 5 earthquakes in central and southern california since 1950 a backslip dislocation model is then used to determine which of the precursory events occur in the regions predicted by stress accumulation amr is shown to occur preferentially in the lobes of the backslip stress field predicted by the stress accumulation model

physical properties of the variations of the electric field of the earth preceding earthquakes ii determination of epicenter and magnitude abstract as reported in the preceding paper a transient change of the electric field of the earth seismic electric signal hereafter called ses appears many hours before an earthquake eq by measuring this change in a given direction and dividing it with a suitable relative effective resistivity one obtains a quantity that reflects the current density in this direction measurements in two directions e w and n s give the relative signal intensity jrel at the station under consideration by measuring jrel at a number of stations and considering that it attenuates according to a 1 r law the epicenter can be determined with an accuracy usually around 100 km once the epicenter has been determined the product jrel r can be evaluated so that the magnitude m can be estimated by resorting to an empirical log jrel r versus m plot the uncertainty of m is around 0 5 units following sobolev 1975 and for the statistics to be beyond any doubt predictions were officially documented before the eq occurrence for 23 earthquakes with a magnitude equal or greater than ms 5 0 two events were missed the present method is compared to other electrical methods used in china japan and soviet union a number of problems concerning the origin of the effect its directivity and the attenuation with distance remain open for further studies

stress reorientation and lurr implication for earthquake prediction using lurr after reviewing the problems associated with the current implementation of the lurr theory we suggest that taking account of stress field complexity and stress reorientation may resolve these problems by introducing the concept of maximum faulting orientation mfo we propose a new approach for calculating lurr results presented for the case of the northridge earthquake provide encouragement for the stress reorientation explanation and the new approach

evolving towards a critical point a review of accelerating seismic moment energy release prior to large and great earthquakes there is growing evidence that some proportion of large and great earthquakes are preceded by a period of accelerating seismic activity of moderate sized earthquakes these moderate earthquakes occur during the years to decades prior to the occurrence of the large or great event and over a region larger than its rupture zone the size of the region in which these moderate earthquakes occur scales with the size of the ensuing mainshock at least in continental regions a number of numerical simulation studies of faults and fault systems also exhibit similar behavior the combined observational and simulation evidence suggests that the period of increased moment release in moderate earthquakes signals the establishment of long wavelength correlations in the regional stress field the central hypothesis in the critical point model for regional seismicity is that it is only during these time periods that a region of the earth s crust is truly in or near a self organized critical soc state such that small earthquakes are capable of cascading into much larger events the occurrence of a large or great earthquake appears to dissipate a sufficient proportion of the accumulated regional strain to destroy these long wavelength stress correlations and bring the region out of a soc state continued tectonic strain accumulation and stress transfer during smaller earthquakes eventually re establishes the long wavelength stress correlations that allow for the occurrence of larger events these increases in activity occur over longer periods and larger regions than quiescence which is usually observed within the rupture zone of a coming large event the two phenomena appear to have different physical bases and are not incompatible with one another

evaluation of topographic effects in remotely sensed data abstract remotely sensed data are generally analyzed assuming flat terrain as the spectral signature of the ground depends upon the orientation of the surface slope the topography has to be considered for efficient radiometric corrections in mountainous regions in this paper we present a modelization of the atmospheric downward radiance at the ground level which gives us the relative contributions of the direct solar beam and of the diffused radiation for different atmospheric turbidities and different solar incidence angles lastly we estimate the influence of the topography on these contributions to show up which effects can be neglected

electric field patterns as seismic precursors in this paper we report the results of two and a half years of measurements of the ground electric field at the pacific coast of mexico the analysis of the voltage itself does not show any distinguishable feature that could be correlated to earthquakes fourier analysis however gives clear patterns of the electric field prior to the four ms w 6 earthquakes that occurred in the zone during the time interval considered

mechanisms of seismic quiescences in the past decade there have been major advances in understanding the seismic cycle in terms of the recognition of characteristic patterns of seismicity over the entire tectonic loading cycle the most distinctive types of patterns are seismic quiescences of which three types can be recognized post seismic quiescence which occurs in the region of the rupture zone of an earthquake and persists for a substantial fraction of the recurrence time following the earthquake intermediate term quiescences which appear over a similar region and persist for several years prior to large plate rupturing earthquakes andshort term quiescences which are pronounced lulls in premonitory swarms that occur in the hypocentral region hours or days before an earthquake although the frequency with which intermediate term and short term quiescences precede earthquakes is not known and the statistical significance of some of the former has been challenged there is a need if this phenomena is to be considered a possibly real precursor to consider physical mechanisms that may be responsible for them the characteristic features of these quiescences are reviewed and possible mechanisms for their cause are discussed post seismic quiescence can be readily explained by any simple model of the tectonic loading cycle as due to the regional effect of the stress drop of the previous principal earthquake the other types of quiescence require significant modification to any such simple model of the possibilities considered only two seem viable in predicting the observed phenomena dilatancy hardening and slip weakening intermediate term quiescences typically occur over a region equal to or several times the size of the rupture zone of the later earthquake and exhibit a relationship between the quiescence duration and size of the earthquake they thus involve regional hardening or stress relaxation and agree with the predictions of the dilatancy diffusion theory short term quiescences on the other hand are more likely explained by fault zone dilatancy hardening and or slip weakening within a small nucleation zone because seismicity is a locally relaxing process seismicity should follow a behaviour known in rock mechanics as the kaiser effect in which only a very slight increase in strength due to dilatancy hardening or decrease in stress due to slip weakening is required to cause quiescence this is in contrast to other precursory phenomena predicted by dilatancy which require large dilatant strains and complete dilatancy hardening

a proposed method for locating the critical region of a future earthquake using the critical earthquake concept using the critical point concept and extending bowman s idea of critical earthquake we develop an intersecting circle method to locate the critical region a simulation check shows that this method is effective in finding a given critical region we selected several real cases from new zealand and china and used this method to find the critical regions before the occurrence of large earthquakes the result shows that this method is valid for detecting a critical region and the epicenter of mainshock might be in the critical region

load unload response ratio and accelerating moment energy release critical region scaling and earthquake prediction the main idea of the load unload response ratio lurr is that when a system is stable its response to loading corresponds to its response to unloading whereas when the system is approaching an unstable state the response to loading and unloading becomes quite different high lurr values and observations of accelerating moment energy release amr aer prior to large earthquakes have led different research groups to suggest intermediate term earthquake prediction is possible and imply that the lurr and amr aer observations may have a similar physical origin to study this possibility we conducted a retrospective examination of several australian and chinese earthquakes with magnitudes ranging from 5 0 to 7 9 including australia s deadly newcastle earthquake and the devastating tangshan earthquake both lurr values and best fit power law time to failure functions were computed using data within a range of distances from the epicenter like the best fit power law fits in amr aer the lurr value was optimal using data within a certain epicentral distance implying a critical region for lurr furthermore lurr critical region size scales with mainshock magnitude and is similar to the amr aer critical region size these results suggest a common physical origin for both the amr aer and lurr observations further research may provide clues that yield an understanding of this mechanism and help lead to a solid foundation for intermediate term earthquake prediction

evidence of bias in estimations of earthquake size magnitudes of earthquakes determined using traditional methods show systematic deviations dependent on tectonic setting from accurate estimates of earthquake size magnitudes are overestimated for most of the continental earthquakes underestimated for mid oceanic ridges and differences of varying sign are obtained for subduction zones this is important in evaluating the seismic risk or consideration of effects such as the seismic versus aseismic strain release as seismic moments determined from magnitudes can be wrong by as much as a factor of four

precursory accelerating seismic crustal deformation in the northwestern anatolia fault zone abstract we present the results of a systematic search for the identification of accelerating seismic crustal deformation in the broader northern aegean area and in northwestern turkey we found that accelerating seismic deformation release expressed by the generation of intermediate magnitude earthquakes is currently observed in nw turkey on the basis of the critical earthquake model and by applying certain constraints which hold between the basic quantities involved in this phenomenon it can be expected that this accelerating seismic activity may culminate in the generation of two strong earthquakes in this area during the next few years the estimated epicenter coordinates of the larger of these probably impending earthquakes are 39 7 n 28 8 e its magnitude is 7 0 and its occurrence time tc 2003 5 the second strong event is expected to occur at tc 2002 5 with a magnitude equal to 6 4 and epicenter coordinates 40 0 n 27 4 e the uncertainties in the calculated focal parameters for these expected events are of the order of 100 km for the epicenter 0 5 for their magnitude and 1 5 years for their occurrence time

acoustic emission experiments of rock failure under load simulating the hypocenter condition a series of acoustic emission ae experiments of rock failure have been conducted under cyclic load in tri axial stress tests to simulate the hypocenter condition the specimens are loaded by the combined action of a constant stress intended to simulate the tectonic loading and a small sinusoidal disturbance stress analogous to the earth tide induced by the sun and the moon each acoustic emission signal can indicate the occurrence time location and relative magnitude of the damage micro crack in the specimen the experimental results verified some precursors such as lurr load unload response ratio and aer accelerating energy release before macro fracture of the samples a new parameter the correlation between the ae and the load has been proposed to describe the loading history on the eve of some strong earthquakes the correlation between the benioff strain and the coulomb failure stress cfs decreases similar to the variation of lurr prior to strong earthquakes

random stress and earthquake statistics spatial dependence summary we calculate the 3 d stochastic rotations of focal mechanisms disorientations caused by stresses arising from the presence of many small random point defects that may surround the tip of an earthquake fault these random stresses can be shown to be distributed according to a cauchy distribution as a consequence the next episode of fracture of a fault cannot be planar the disorientation of focal mechanisms of these new rupture episodes is closely approximated by a rotational cauchy distribution as observed previously the geometry of fault systems for natural earthquakes is consistent with these observations since it too can be modelled by the cauchy distribution these observations indicate how the 3 d rupture process in rocks and other materials can be modelled we also calculate distributions of disorientations caused by a uniformly random 3 d rotation of sources these distributions are governed by symmetry properties of earthquake focal mechanisms to take into account the source symmetry we compare the cauchy distribution which is due to influence of random stresses to the distributions caused by random rotations

experimental constraints on bar migration through bends implications for meander wavelength selection the bed of an initially straight channel often deforms into a series of migrating alternate bars that can cause bank erosion and the development of periodic planform curvature which is often expressed as a meandering channel trace the planform curvature in turn leads to topography similar to alternate bars but stationary with respect to the meander the migration of alternate bars over this steady topography may lead to interactions influencing meander initiation and wavelength selection we studied these interactions in flume channels with bends of various lengths and angles and having various width to depth ratios in channels whose wavelength was equal to the length of bars in straight channels nearly eight channel widths bars migrated through sine generated channels with angles up to 10 the critical bend angle was smaller for channels of longer wavelength and smaller width to depth ratio migration was nonuniform and bars temporarily stalled when in phase with the curvature induced topography leading to amplification of the topography flow against an opposing bank can lead to such a strong boundary shear stress divergence that migration of the bars is prevented because sediment that otherwise would have led to bar migration is scoured from the bar front we propose that the amplification of bar pool topography in bends where free alternate bars are stalled enhances scour of the bank which leads to selection of a meander wavelength equal to that of the alternate bars

electro magnetic earthquake bursts and critical rupture of peroxy bond networks in rocks abstract we propose a mechanism for the low frequency electromagnetic emissions and other electromagnetic and electric phenomena which have been associated with earthquakes the mechanism combines the critical earthquake concept and the concept of crust acting as a charging electric battery under increasing stress the electric charges are released by activation of dormant charge carriers in the oxygen anion sublattice called peroxy bonds or positive hole pairs php where a php represents an o 3 x oo yo 3 with x y si 4 al 3 i e o in a matrix of o 2 of silicates we propose that php are activated by plastic deformations during the slow cooperative build up of stress and the increasingly correlated damage culminating in a large critical earthquake recent laboratory experiments indeed show that stressed rocks form electric batteries which can release their charge when a conducting path closes the equivalent electric circuit we conjecture that the intermittent and erratic occurrences of em signals are a consequence of the progressive build up of the battery charges in the earth crust and of their release when crack networks percolate through the stressed rock volumes providing a conductive pathway for the battery currents to discharge em signals are thus expected close to the rupture either slightly before or after that is when percolation is most favored the proposed mechanism should be relevant for the broader understanding of fractoemissions

precursory seismic activation and critical point phenomena in this paper we relate the behavior of seismicity prior to a characteristic earthquake to the excitation in proximity to a spinodal instability we illustrate the spinodal instability as the upper limit of superheated water prior to a steam explosion we draw an analogy between the steam explosion and a characteristic earthquake and show that the power law activation associated with the spinodal instability is essentially identical to the power law increase in benioff strain observed prior to characteristic earthquakes we find that theory and actual data give very similar results

case 23 nomination of precursory seismic quiescence as a significant precursor several cases of extremely strong quiescences have been investigated in great detail and it was found that they are statistically highly significant and that they cannot be reasonably explained by catalog heterogeneity several additional cases of quantitatively measured quiescence have been documented the method of measuring quiescence has progressed from using visual means to using a quantitative approach and the understanding of the noise sources has significantly advanced during the last few years therefore i feel that quiescence is a real phenomenon and the method to detect it has matured to a point that is acceptable for the list of significant precursors although considerably more work needs to be done to understand this parameter and its role in the earthquake generation process

currently active regions of decelerating accelerating seismic strain in central asia 1 accelerating preshock seismic strain in a broad critical region and decelerating preshock seismic strain in a narrower seismogenic region constitute a model for intermediate term prediction of strong main shocks an effort is made in the present work for a forward test of the decelerating accelerating seismic strain d as model by identifying such patterns and estimating the corresponding probably ensuing strong main shocks m 7 0 in central asia 20 n 45 n 42 e 105 e five such patterns have been identified and the origin time magnitude and epicentral geographic coordinates of each of the corresponding main shocks have been estimated predicted model uncertainties of the estimated time magnitude and space parameters of these probably ensuing main shocks as well as appropriate statistical tests against a standard gutenberg richter seismicity distribution are also presented to allow a future objective evaluation of the model s efficiency for intermediate term earthquake prediction

atmospheric corrections to satellite radiometric data over rugged terrain radlometnc measurements from satelhtes m the solar portmn of the electromagnetic spectrum can be converted to measurements of surface eratance over rugged terrain the satelhte image must be precisely registered to a terrain data set for small areas a first order polynomial mterpolatmn scheme is generally satisfactory for the geometric rectlficatmn if there are saturated plxels a nearest neighbor procedure is used for the mterpolated satellite radiance nmnbers otherwise a cublc convolutmn algorithm is used path radiance and path transmittance are calculated wlth a simple spectral model whmh reqmres an estimate of the water vapor and aerosol content of the atmosphere

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

linear and nonlinear dynamics in electrical precursory time series implications for earthquake prediction abstract the time dynamics of geoelectrical precursory time series has been investigated using autoregressive models the approach used here allows us to obtain information on the geophysical system producing the electrical phenomena in seismic active areas when the only information about the time series comes from the time series themselves it is based on two forecasting approaches the global autoregressive approximation and the local autoregressive approximation the first approach views the data as a realization of a linear stochastic process whereas the second approach considers the data points as the results of a deterministic process supposedly nonlinear the comparison of the predictive skills of the two techniques is a strong test to distinguish between low dimensional chaos and random dynamics our findings give us insight in the inner dynamics of the geophysical process under study an estimate of the number of degrees of freedom of the dynamical system governing the electrical phenomena is obtained the stochastic nature of the electrical precursory signals has been highlighted and the possible implications for the earthquake prediction problem are discussed the processed time series are geoelectrical measurements recorded by an automatic station located in tito southern italy which is one of the most seismic areas of the mediterranean region we found that the global linear approach is superior to the local one and the physical system governing the phenomena of electrical nature is characterized by a large number of degrees of freedom the results are confirmed by the presence of rich scaling properties in the power spectra of the processed electrical signals

crustal deformation in the central ionian islands greece results from dgps and dinsar analyses 1995 2006 abstract ground deformation studies based on differential gps dgps and differential interferometric sar dinsar analyses have been conducted in the seismically active area of the central ionian islands local gps networks were installed in cephallonia 2001 and zakynthos 2005 the cephallonian network has been remeasured five times and zakynthos once as of july 2006 the studies have yielded detailed information regarding both local and regional deformations that are occurring in the area for lefkas island dinsar analysis march to september 2003 revealed 56 mm of uplift in the central and western parts and is attributed to the august 2003 earthquake mw 6 3 that occurred offshore to the west synthetic dinsar modelling of the magnitude and extent of deformation is consistent with the seismologically deduced parameters for the ruptured segment along the lefkas transform fault subsidence for cephallonia island dinsar analysis 1995 to 1998 indicated ground deformation up to 28 mm located in small sections of the island further interferometric analysis for the period 2003 to 2004 encompassing the occurrence of the lefkas earthquake in august 2003 indicated 28 mm of uplift in the northern part while during the next two years 2004 to 2005 further uplift of at least 56 mm had taken place at the western and northern part of the island dgps measurements for the period 2001 to 2006 revealed a clockwise rotation of the island with respect to a centrally located station on aenos mt the horizontal component of deformation generally ranged from 6 to 34 mm with the largest values at the western and northern parts of the island considering the vertical deformation two periods are distinguished the first one 2001 to 2003 is consistent with anticipated motions associated with the main geological and tectonic features of the island the second one 2003 to 2006 has been tentatively attributed to dilatancy in which relatively small uplift 20 40 mm occurred along the southern and southeastern parts of the island while larger magnitudes 50 mm happened at the western part paliki peninsula these large magnitudes of uplift over an extended area 50 km in conjunction with an accelerated benioff strain determined from the analysis of the seismicity in the broader region are consistent with dilatancy this effect commenced some time after 2003 and is probably centered in the area between zakynthos and cephallonia if this interpretation is correct it may foreshadow the occurrence of a very strong earthquake s sometime during 2007 to 2008 in the above designated region

new observational information on the precursory accelerating and decelerating strain energy release recent reliable data are used to study the behavior of seismic activity before 46 strong shallow earthquakes m 6 0 which correspond to five complete samples of mainshocks these samples include 6 mainshocks m 6 0 7 1 that occurred in western mediterranean since 1980 17 mainshocks m 6 0 7 2 which occurred in the aegean greece and surrounding area since 1980 5 mainshocks m 6 4 7 5 that occurred in anatolia since 1980 12 mainshocks m 6 0 7 3 that occurred in california since 1980 and 6 mainshocks m 7 0 8 3 that occurred in japan since 1990 in all 46 cases a similar precursory seismicity pattern is observed specifically it is observed that accelerating benioff strain square root of seismic energy release caused by preshocks occurs in a broad circular region critical region with a radius about eight times larger than the fault length of the mainshock in agreement with results obtained by various research groups during the last two decades however in a much smaller circular region seismogenic region with a radius about four times the fault length the corresponding preshock strain decelerates with the time to the mainshock the time variation of the strain follows in both cases a power law but the exponent power is smaller than unit m 0 3 in the case of the accelerating preshock strain and larger than unit m 3 0 in the case of the decelerating preshock strain predictive properties of this decelerating in accelerating out strain model are expressed by empirical relations the possibility of using this model for intermediate term earthquake prediction is discussed and the relative model uncertainties are estimated

snow distribution melt and surface water inputs to the soil in the mountain rain snow transition zone summary the timing magnitude and spatial distribution of snow cover and the resulting surface water inputs swi are simulated at a small catchment located in the rain snow transition zone of southwest idaho usa a physically based snow model is run on this 1 5 ha study catchment which has an elevation range of 1600 1645 masl the catchment is divided into relatively steep mean slope angle of 21 degrees northeast and southwest facing hill slopes by an ephemeral stream that drains to the southeast swi are fundamental controls on soil moisture streamflow generation groundwater recharge and nutrient cycling although the timing of melt events is similar across the basin southwest facing slopes receive smaller magnitude and more frequent swi from mid winter snow melt while the northeast facing slope receives greater swi during the spring three spatial patterns are observed in the modeled swi time series 1 equal between slopes 2 majority of swi on southwest facing slopes and 3 majority of swi on northeast facing slopes although any of these three spatial patterns can occur during the snow season four emergent swi patterns emerge through the melt season 1 near uniform 2 controlled by topographic differences in energy fluxes 3 transitional and 4 controlled by snow distribution rain on snow ros events produce similar swi between the northeast and southwest facing slopes with the difference being attributed primarily to snow distribution turbulent fluxes dominate the snowpack energetics in four of the five rain on snow events and advective fluxes from precipitation are greater than 17 during the 2 rain on snow events in december and january net radiation fluxes dominate spring melt events variations in the method used to distribute precipitation may result in large differences in total precipitation to the basin

an analytic method for radiometric correction of satellite multispectral scanner data the problem of radiometric correction of multispectral scanner data is posed as the problem of determining an intrinsic reflectance factor characteristic of the surface material being imaged and invariant to topography position of the sun atmosphere and position of the viewer a scene radiance equation for remote sensing is derived based on an idealized physical model of image formation the scene radiance equation is more complex for rugged terrain than for flat terrain since it must model slope aspect and elevation dependent effects scene radiance is determined by the bidirectional reflectance distribution function brdf of the surface material and the distribution of light sources the sun is treated as a collimated source and the sky is treated as a uniform hemispherical source the atmosphere is treated as an optically thin horizontally uniform layer the limits of this approach are reviewed using results obtained with landsat mss images and a digital terrain model dtm of a test site near st mary lake british columbia canada new results based on regression analysis are described for the st mary lake site previous work is extended to take advantage of explicit forest cover data and to consider numeric models of sky radiance the calculation of sky irradiance now takes occlusion by adjacent terrain into account the results for st mary lake suggest that the cosine of the incident solar angle and elevation are the two most important correction terms skylight and inter reflection from adjacent terrain however also are significant

mean flow and turbulence around a laboratory spur dike the three dimensional turbulent flow field around a spur dike in a plane fixed bed laboratory open channel was studied experimentally using a microacoustic doppler velocimeter mean and turbulence characteristics in all three spatial directions were evaluated at upstream and downstream cross sections near the dike results showed that the primary flow separated in both lateral and vertical directions two counter rotating flow circulations consisting of the lateral and vertical velocity components originated at the dike section downstream of the dike the circulation in the flow separation zone is stronger than the one in the contracted primary flow zone the maximum bed shear stresses estimated using reynolds stresses is about three times as large as the mean bed shear stress of incoming flow

critical point theory of earthquakes observation of correlated and cooperative behavior on earthquake fault systems 1 the critical point theory for earthquakes was originally proposed to explain the scaling relations observed in earthquakes including the gutenberg richter frequency magnitude relation and the omori s law for aftershocks in this model main shocks their foreshocks and aftershocks are all associated with the formation of a correlated cooperative spatial region with high stress until now only indirect evidence of the existence of these correlated regions has been reported here in this paper we present observations and analyses that allow us to directly map the high stress spatially correlated regions preceding four major earthquakes i e the 1992 landers california 1995 kobe japan 1999 chi chi taiwan and 1999 hector mine california earthquakes we therefore conclude that the locations and extent of large main shocks and their immediate aftershocks can be determined from seismicity data taken prior to the main shocks and provide additional evidence in support of the critical point theory for earthquakes

accelerating seismicity of moderate size earthquakes before the 1999 chi chi taiwan earthquake testing time prediction of the self organizing spinodal model of earthquakes summary seismic activation of moderate size earthquakes for the 1999 chi chi taiwan earthquake has been found a self organizing spinodal sos model can explain some observations concerning seismic activation but the equal time durations of the mid and precursory periods during an earthquake cycle conjectured in the original published sos model have not been supported in this case the chi chi test presented here shows unequal time durations of the mid and precursory periods of an earthquake cycle this in turn makes the possibility of time prediction of a characteristic earthquake impossible in the context of the sos model in addition comparisons with numerical simulations of the sliding block model suggest the change in the system s stiffness is a potential mechanism of seismic activation

a renormalization group approach to the stick slip behavior of faults we treat a fault as an array of asperities with a prescribed statistical distribution of strengths when an asperity fails the stress on the failed asperity is transferred to one or more adjacent asperities for a linear array the stress is transferred to a single adjacent asperity and for a two dimensional array to three adjacent asperities using a renormalization group rg method we investigate the properties of a scale invariant hierarchical model for the stochastic growth of fault breaks through induced failure by stress transfer an extrapolation to arbitrarily large scales shows the existence of a critical applied stress at which the solutions bifurcate at stresses less than the critical stress virtually no asperities fail on a large scale and the fault is locked above the critical stress asperity failure cascades away from the nucleus of failure we interpret this catastrophic failure as an earthquake and it corresponds to the transition from stick to slip behavior on the fault thus the stick slip behavior of most faults can be attributed to the distribution of asperities on the fault we propose our stochastic mechanism as an alternative to the traditional hypotheses for the stick slip behavior of faults a major advantage of our approach is the inclusion of scale invariance thus the observed frequency magnitude relation for seismicity is a natural consequence of our basic hypothesis

a physical model for the precursory magnetic anomalies of the m5 4 alum rock and m6 0 parkfield earthquakes here we propose an alternative physical model based on the concept of criticality for the explanation of the observed magnetic signals prior to the m6 0 parkfield and the m5 4 alum rock earthquakes motivated by an analogous experience from major earthquakes in greece where both magnetic field variations and seismic electric signals were also recorded few weeks before the main shock we suggest that in all these cases similar dynamic processes characterized by critical behaviour should govern the corresponding pre focal areas when the relevant precursory signals emerged

seismic quiescence precursor to the 1983 kaoiki ms 6 6 hawaii earthquake a remarkable seismicity rate decrease of 65 per cent occurred in most of the aftershock volume 2 4 yr before the 1983 kaoiki ms 6 6 main shock if the background seismicity rate 1978 to mid 1981 is extrapolated to the time of the main shock more than 300 earthquakes of ml 1 8 are missing because of the quiescence subvolumes measuring 5 5 km on a side and located within the aftershock zone showed seismicity rate decreases ranging from 0 to 90 per cent the volume of no change had dimensions of approximately 10 3 km it contained the main shock hypocenter and was located near the center of the 10 km radius aftershock area the seismic quiescence in different subvolumes of the aftershock volume surrounding this central nonquiet zone varied somewhat in starting time amount of rate decrease and statistical significance according to the standard deviate z test the reported rate decrease is the most pronounced example of precursory quiescence defined to date the seismicity pattern before the 1983 kaoiki shock conformed to the quiescence hypothesis proposed on the basis of the precursors to the 1975 hawaii main shock no quiescence was observed within the immediate surrounding of the hypocenter while strong rate decreases occurred in most of the rest of the main shock source volume it is thus hypothesized that major asperities which contain high stress levels and from which main ruptures can emanate may be recognizable as volumes of constant seismicity rate within surrounding volumes of quiescence provided that decreases of seismicity rate as a function of time can be defined quantitatively

physical properties of the variations of the electric field of the earth preceding earthquakes i abstract in an earlier paper we described the physical properties of the preseismic transient variations in the electrotelluric field the present letter clarifies a few points that were not properly emphasized in our previous publications furthermore recent results like that of the destructive kalamata earthquake on september 13 1986 indicate that the duration of a preseismic electric signal may reach considerably high values lasting up to several hours

earthquake rupture as a critical point consequences for telluric precursors abstract earthquakes are related to rupture phenomena in complex statistical systems of cracks we first review some available information suggesting that rupture in earthquakes is a critical point the consequences of this hypothesis on several phenomena are then discussed in particular we focus our attention on a simple theory of electroseismic activity based on mechano electrical transduction effects such as the piezoelectric or the pressure induced polarization effect the neighbourhood of the rupture threshold is characterized by a specific response which could correspond to telluric wave activity observed as precursors of earthquakes

local scour at sloped wall spur dike like structures in alluvial rivers the effect of side slope on the prediction of the maximum local scour depth around sloped wall spur dike like structures has been investigated using two existing prediction methods where slope factors were considered the first one was developed from experimental data and is empirical in nature while the second one was developed using an analytical treatment by considering the flow concentration in the restricted region of scour hole both of the above approaches are applicable for clear water scour with the aid of the analytical model the slope factors for the empirical formulas have been extrapolated for milder side slopes the results of the above two methods together with the maximum measured local scour depth around a spur dike like structure in an alluvial river have been compared and discussed with particular emphasis on the effect of side slope on estimates of the maximum local scour depth

predictive modeling of the seismic cycle of the greater san francisco bay region the seismic cycle for the san francisco bay region is synthesized by a model combining the pre and post 1906 seismic histories the long term acceleration of seismic release seismic moment benioff strain release or event count in the seismic cycle and the shorter term accelerations preceding the larger earthquakes within that cycle are modeled using an empirical predictive technique called time to failure analysis in which rate of seismic release is proportional to an inverse power of the remaining time to failure the exponent of time to failure in the accelerating sequences appears to be scale invariant and the length of the full cycle is estimated at 269 50 years the 1989 loma prieta earthquake which is the culmination of the first subcycle in the present long term seismic cycle should have been predictable with an uncertainty of 2 years in time and 0 5 in magnitude although the specific location at loma prieta was not predictable by this technique if our model is correct and if the loma prieta earthquake is the culmination of a subcycle the san francisco bay region should be entering a relatively long 20 50 years period of seismic quiescence above magnitude 6 a great earthquake such as the 1906 san francisco event would appear to be more than a century in the future

plausibility of long distance electrotelluric precursors to earthquakes a systematic analysis of the plausibility of different classes of models which could account for low frequency precursory electrotelluric signals observable at large distances from a large earthquake is carried out first we consider linear models for which either a stationary electrical field is generated by a current dipole in the source volume or a static deformation field results from a precursory strain in the source volume linearly inducing a streaming potential effect near the electrode in the former case only the conjunction of very favorable circumstances may lead to an electrical field larger than 10 mv km at more than 100 km with the constraint that no anomaly exceeds a few volts per kilometer in the source area it indeed requires a powerful electrical dipole current 104 a length 1 km which might be produced by a streaming potential effect associated with the connection of nonhydrostatic fluid reservoirs pore pressure difference up to 100 mpa a two dimensional channeling of the electrical currents from the source to the electrode area which would result from high conductivity horizontal layers and finally a local amplification factor of typically 100 near the electrodes which might be produced by a narrowing of the conductive channel for an elastic long distance interaction an electric field of 10 mv km at a distance 10 times the source length 100 km away from a m 6 earthquake requires a precursory deformation larger than the coseismic deformation if no strong local amplification is considered alternatively nonlinear models are proposed and discussed assuming that the crust is stuffed with small scale local instabilities fractures and nonhydrostatic fluid reservoirs among which a number are close to their instability threshold these instabilities may follow their own evolutionary process inducing sporadic fluid flow and hence streaming potential effect in the vicinity of the electrodes without any relation to a remote tectonic activity however these instabilities may be sensitive to very small changes in the stress field and hence be triggered by the elastic precursory deformation of a remote seismic source this requires that the precursory deformation near the instability is at least larger than the tidal strain 10 7 this necessary condition is met at a distance of up to 10 times the source dimension when the precursory strain source is only 10 of the coseismic deformation provided that the strain source is double the size of the seismic fault itself this model could account for the absence of self potential anomalies related to the earthquake itself as a large proportion of the available instabilities could have been swept away by the precursory strain furthermore with such a model a precursory strain in the source area could induce a detectable change in the background seismic activity over a vast area which may give a new interpretation of the times of increased probability observations for short distances the triggering of fluid instabilities by strain perturbation and the associated streaming potential effect may well be a promising model for explaining low frequency electric and magnetic precursors

parametric time series analysis of extreme events in earthquake electrical precursors abstract a statistical method to evaluate extreme events in earthquake precursory signals of electrical nature is proposed the occurrence probability of seismo electrical anomalies is computed by means of a parametric time series approach in order to avoid the influence of external noise a preliminary filtering of the electrical signals is performed in a second step an autoregressive model to describe the residual time series is suitably identified and fitted to the data finally parametric inference of extreme events is carried out on the basis of the selected model the performance of the technique has been evaluated by considering geoelectrical time series recorded by an automatic station located on the southern apennine chain italy this region was interested by the november 1980 irpinia basilicata earthquake and it is one of the most active areas of the mediterranean region finally a possible correlation between electrical anomalies and seismic events occurred in the area is discussed

fractals chaos self organized criticality and tectonics some geological structures have simple geometrical forms and can be analysed using deterministic equations examples include alluvial fans and many sedimentary basins but most geological structures are complex and appear to defy mathematical analyses yet in the complexity there is an order complex geological structures generally obey fractal statistics examples include topography distributions of earthquakes and faults and mineral deposits an unresolved question is whether the fractal order is simply the result of scale invariance or the result of governing equations that yield deterministic chaos in order to try to answer this question a variety of slider block models have been considered the stick slip behaviour of slider block models is a simple analogy to earthquakes a pair of slider blocks has been shown to behave chaotically models that use many slider blocks exhibit self organized criticality and generate fractal statistics similar to the statistics of regional seismicity

state vector a new approach to prediction of the failure of brittle heterogeneous media and large earthquakes the concept of state vector stems from statistical physics where it is usually used to describe activity patterns of a physical field in its manner of coarsegrain in this paper we propose an approach by which the state vector was applied to describe quantitatively the damage evolution of the brittle heterogeneous systems and some interesting results are presented i e prior to the macro fracture of rock specimens and occurrence of a strong earthquake evolutions of the four relevant scalars time series derived from the state vectors changed anomalously as retrospective studies some prominent large earthquakes occurred in the chinese mainland e g the m 7 4 haicheng earthquake on february 4 1975 and the m 7 8 tangshan earthquake on july 28 1976 etc were investigated results show considerable promise that the time dependent state vectors could serve as a kind of precursor to predict earthquakes

configurational entropy of critical earthquake populations we present an approach to describe the evolution of distributed seismicity by configurational entropy we demonstrate the detection of phase transitions in the sense of a critical point phenomenon in a 2d site percolation model and in temporal and spatial vicinity to the 1992 m7 3 landers earthquake in southern california our findings support the assumption of intermittent criticality in the earth s crust we also address the potential usefulness of the method for earthquake catalogue declustering

avalanching glacier instabilities review on processes and early warning perspectives avalanching glacier instabilities are gravity driven rupture phenomena that might cause major disasters especially when they are at the origin of a chain of processes reliably forecasting such events combined with a timely evacuation of endangered inhabited areas often constitute the most efficient action recently considerable efforts in monitoring analyzing and modeling such phenomena have led to significant advances in destabilization process understanding improving early warning perspectives the purpose of this paper is to review the recent progress in this domain three different types of instabilities can be identified depending on the thermal properties of the ice bed interface if cold 1 the maturation of the rupture is associated with a typical time evolution of surface velocities and passive seismic activity a prediction of the final break off is possible using these precursory signs for the two other types water plays a key role in the development of the instability if the ice bed interface is partly temperate 2 the presence of meltwater may reduce the basal resistance which promotes the instability no clear and easily detectable precursory signs are known in this case and the only way to infer any potential instability is to monitor the temporal evolution of the thermal regime the last type of instability 3 concerns steep temperate glacier tongues switching for several days weeks during the melting season into a so called active phase followed in rare cases by a major break off event although the prediction of such events is still far from being achievable critical conditions promoting the final instability can be identified

decelerating precursory seismicity in vrancea abstract preshock seismic excitation followed by seismic quiescence has been observed in the seismogenic region of strong shallow mainshocks the strain released by such preshocks is decelerating with the time to the mainshock and is fitted by a power law with a power value larger than unit this model is tested in the present work for the intermediate depth earthquakes of the vrancea region generated in an isolated seismogenic zone proper for such testing a backward application of this decelerating preshock strain model for the case of 4 3 1977 m 7 5 earthquake for which reliable data are available shows a good fit of the power law pattern to the seismic activity preceding the main shock the occurrence rate of recent intermediate depth shocks in vrancea indicates that this region is currently in a state of decelerating seismic deformation which may lead to the generation of a strong intermediate depth mainshock there at about the beginning of the third decade of the present century the respective uncertainties are unknown due to lack of previous relative studies