scaling laws between seismo electric magnetic fields and earthquake magnitude the mechanisms generating the charges potentials and abnormal electromagnetic radiation that accompany earthquakes have been discussed based on observational theoretical and laboratory studies in particular over the last few decades we previously conducted stick slip tests using precut granite cores with a contact electrode on the sample side and proposed that surface charges released from charge trapping centres on sheared asperities are a possible source of the above mentioned charges or potentials here we discuss seismo electric and magnetic fields formed by the surface charges and derive their scaling laws with the earthquake magnitude at a distance according to our model detectability of these fields at a point on the ground surface depends strongly on wet dry condition at a fault zone sheared asperities

note on a possible origin for seismic electrical signals abstract a physical model is suggested that can explain the generation of seismic electric signals observed in greece it also explains a number of experimental facts for example why these signals 1 propagate at large distances and 2 are detected only in certain sensitive regions

evaluation and interpretation of thirteen official van telegrams for the period september 10 1986 to april 28 1988 abstract all the thirteen official earthquake prediction telegrams sent by van researchers during september 10th 1985 to april 28th 1988 based on seismic electric signals ses observations were examined against seismic data the first four telegrams pertaining to the m s 6 0 kalamata earthquake and its aftershocks were all failures of the remaining nine telegrams five were complete failures because there was no earthquakes with m 4 in the candidate areas within 11 d after the telegram even when some events occured after the telegram correlation with prediction was either non unique or the error in magnitude was too large in seven cases earthquakes with a magnitude comparable to that of predicted events took place in the candidate areas just before the related telegrams without any ses contrary to van s assertion of one to one correspondence between ses and earthquakes

simultaneous seismic and magnetic measurements in the low noise underground laboratory lsbb of rustrel france during the 2001 january 26 indian earthquake since the decommission of the underground launching control room of the ground based component of the french nuclear missile system the whole installation has been turned into a cross disciplinary underground laboratory the lsbb is a unique low noise underground laboratory because of its initial military conception and its location in the regional park of luberon far from large cities industry and heavy traffic the deepest point is 500 m below the surface at this depth a huge and non conventional shielded cylindrical capsule is installed with no metal 1268 m 3 in volume with a residual electromagnetic noise lower than 2 ft hz 1 2 above 10 hz as a result fluctuations of the earth s magnetic field under 10 hz can be recorded at a very low noise level with a low t c squid 3 d magnetometer taking advantage of the main gallery topology a broad band underground seismic array has been deployed since 2001 an analysis of data recorded simultaneously by the seismic underground array and by the magnetometer sensors during the indian earthquake of 2001 january 26 is presented evidence of a magnetic field perturbation induced by the seismic waves at teleseismic distance 6250 km is supported by a polarization analysis of seismic and magnetic signals spectral analysis shows specific frequency bands of perturbation related to physical processes such as ground water flow acceleration within the mountain structure

additional evidence on some relationship between seismic electric signals ses and earthquake focal mechanism abstract investigating the period 1983 1994 for western greece a possible correlation between the selectivity characteristics of the ses seismic electric signals of the van method and earthquake parameters has been reported by uyeda et al uyeda s al damegh k s dologlou e nagao t 1999 some relationship between van seismic electric signals ses and earthquake parameters tectonophysics 304 41 55 they found that the earthquake source mechanism changed from largely strike slip type to thrust type at the end of 1987 and this coincided with a shift in the ses sensitive site from pirgos pir to ioannina ioa van station here we report the results for the period january 1 2002 july 25 2004 during which the ses sensitive site of pir became again active after a 10 year period of quiescence this activation was followed by strike slip earthquakes on august 14 2003 and march 17 2004 with magnitude 6 4 and 6 5 respectively in the hellenic arc which provides additional evidence on the correlation reported by uyeda et al the ses activities recorded at pir have been discriminated from artificial noise by employing the natural time domain analysis introduced recently

directional properties of van s ses and ulf mt signals at ioannina greece abstract in order to examine the validity of the earthquake prediction technique developed in greece by van varotsos alexopoulos and nomicos and elucidate the underlying physical processes we performed a magnetotelluric mt recording of the ulf band 3 200 s in the vicinity of van s sensitive station ioannina ioa by comparing mt electric field of ionospheric or magnetospheric origin electric field of lightning origin and van s seismic electric signals ses the following facts were revealed 1 the mt electric field always varies in the ene wsw direction indicating existence of significant electrical conductivity contrast near the site 2 the lightning electric field orientation is somewhat more scattered but still holds the same preferred direction as that of the mt electric field the scatter is larger for larger lightning field probably due to closer location of lightning stroke to the station and or due to no linear saturation of the recording signals 3 the ses electric field orientation is even more scattered than that of the lightning origin these observations suggest that the sources of the ses are in the neighborhood of the station it is still unclear how the ses associated with distant earthquakes are emitted from the sources near the ioa station

a telemetric system for measuring electrotelluric variations in greece and its application to earthquake prediction abstract a detailed description of the telemetric system that records variations in the earth s electrical field from sixteen field stations in greece is presented each field station measures potential differences between eight pairs of electrodes inserted into the ground in two orthogonal directions n s and e w two techniques have been applied the first one is real time where the field station takes the information digitizes it and transmitts it via telephone line to a central station in athens which decodes the information offsets it automatically and displays on chart recorders the small variations in the telluric current the resolution of the system is 0 1 mv for a total gain of 200 the second technique uses dataloggers where the information is digitized and stored in the datalogger memory the central station has a commercial personal computer which communicates with the datalogger takes the information via a standard telephone line and plots the recordings every 4 h the data are stored in compressed mode on a tape back up streamer for future reference the system works unattended

anomalous pre seismic transmission of vhf band radio waves resulting from large earthquakes and its statistical relationship to magnitude of impending earthquakes summary to confirm the relationship between anomalous transmission of vhf band radio waves and impending earthquakes we designed a new data collection system and have documented the anomalous vhf band radio wave propagation beyond the line of sight prior to earthquakes since 2002 december in hokkaido northern japan anomalous vhf band radio waves were recorded before two large earthquakes the tokachi oki earthquake mj 8 0 mj magnitude defined by the japan meteorological agency on 2003 september 26 and the southern rumoi sub prefecture earthquake mj 6 1 on 2004 december 14 radio waves transmitted from a given fm radio station are considered to be scattered such that they could be received by an observation station beyond the line of sight a linear relationship was established between the logarithm of the total duration time of anomalous transmissions te and the magnitude m or maximum seismic intensity i of the impending earthquake for m4 m5 class earthquakes that occurred at depths of 48 54 km beneath the hidaka mountains in hokkaido in 2004 june and 2005 august similar linear relationships are also valid for earthquakes that occurred at different depths the relationship was shifted to longer te for shallower earthquakes and to shorter te for deeper ones numerous parameters seem to affect te including hypocenter depths and surface conditions of epicentral area i e sea or land this relationship is important because it means that pre seismic anomalous transmission of vhf band waves may be useful in predicting the size of an impending earthquake

the 2004 parkfield earthquake test of the electromagnetic precursor hypothesis 1 a controversy has existed for 30 years concerning the possibility of earthquake prediction using electromagnetic precursors long term electromagnetic monitoring prior to during and after the m6 0 earthquake at parkfield california on 28 september 2004 now provides a definitive test of this hypothesis during the earthquake our instruments recorded clearly documented electrical signals from an earthquake impulsive changes of up to 2 5 mv at an electrode located 250 m from the rupture zone followed by a transient decay lasting at least 3 1 4 hours similar signals 1 5 mv were recorded with the only two m 5 aftershocks but their transient decays lasted for only 17 min these signals are unambiguously a result of the earthquake and can be useful in studies of fluid flow in faults a major current topic in earthquake physics patterns in the distribution of transient voltages differ from static stress changes but are consistent with a small coseismic pressure drop on the fault and fluid flow inward signals at a distance of 1 km from the fault are less than 1 mv and are statistically no different from zero in our analysis transient voltages for the aftershocks have opposite polarity from those recorded with the main shock and are again maximal close to the fault suggesting subsequent outward flow from the fault finally there is no evidence of any precursory signal strongly calling into question previously suggested signals preceding smaller or more distant earthquakes

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

study of directivity effect on electromagnetic emissions in the hf band as earthquake precursors preliminary results on field observations abstract this work focuses on the use of electromagnetic emissions em in the hf band as a warning event for earthquakes em at hf components 41 mhz and 46 mhz were monitored and recorded from eight field stations in greece and correlated with seismological events directivity effect raised since em emissions at specific station locations were correlated to earthquake events from prescribed regions em recordings during 1999 were used and by visual inspection were associated to most of the earthquake events greater than 5r using these observations a novel algorithm based on the ratio of short term to long term signal average together with a prediction rules set derived from 1999 s em emissions study were developed to combine results from several field stations performance of the system was promising but was dependent on the geographic area of interest overall performance for earthquakes events of magnitude greater than 5 7 r was 75 of seismic events were correctly predicted by em activity while 25 were not predicted

seismic electric signals ses and earthquakes a review of an updated van method and competing hypotheses for ses generation and earthquake triggering abstract electromagnetic phenomena are sometimes associated with seismic events but earthquake prediction using seismic electric signals ses has not been seriously considered since the early 1990s there are several causes 1 false alarms that have created panics in greece and 2 a strong critique of the varotsos alexopoulos nomicos van method used there an updated van method that includes time series analysis has made successful medium range predictions and short range predictions when coupled with seismic time series analysis four types of potential mechanisms to create precursory ses relying on deformation effects temperature effects ore mineral movement or groundwater variation are reviewed data relevant to each are insufficient to favor a single mechanism records of the number of false positive and missed events for an updated van method have not been well maintained false positives appear to be abundant and render the method unusable co seismic groundwater fluctuations are addressed and two novel hypotheses of earthquake trigger mechanism are also presented ionospherically induced electric and resultant magnetic fields to weaken rock thereby causing failure and volatiles liberated from minerals additionally promoting rock failure recommendations for further study are included

electric field polarization around ioannina van station greece inferred from a resistivity mapping abstract in the summer of 1997 we made a bipole dipole mapping survey around ioannina station of van varotsos alexopoulos and nomicos where detection of the pre seismic electric signal ses has been repeatedly reported since we had found the characteristic directional properties of the electric field in the previous study the present study was aimed to examine it by investigating the shallow electric structure around the station the apparent resistivity tensor was derived from two sets of measured voltages at each receiver position from a rough sketch of the resistivity tensor distribution we found that the electric field was enhanced along the direction parallel to the trend of the basin at receivers located in the conductive basin and perpendicular to it at receivers in the resistive mountainside conductance distribution models with thin plates were constructed by using the measured voltages the results showed that the van station is located on the resistive portion near the contact between the conductive and the resistive part furthermore we simulated the apparent resistivity tensor near the van station on the inferred conductance distribution model although the directional property similar to those of magnetotelluric mt and lightning electric field was not reproduced there we found that the electric field polarization is affected by heterogeneous structure not only around receivers but also around the source

the application of the magnetotelluric impedance tensor to earthquake prediction research in greece continuous short period 0 1 3600 s measurements of the magnetotelluric field components were conducted simultaneously at two sites in greece for a period of 5 weeks the estimation of the impedance tensor elements from 8 hr windows of recorded data at each station is found to describe the local electromagnetic induction with great accuracy the computation of the residual electric field obtained as the difference between the observed and estimated inductive part of the electric fields clearly improves the detection of any local electric field anomaly this method was used in an attempt to detect precursory sci smic electrical signals ses that have been reported to precede earthquakes in greece the results indicate the success of this method in resolving ambiguities about the nature of the reported ses i e whether it has an external or internal source although during the recording period no large earthquake occurred five with a magnitude of between ml 4 0 and ml 4 3 occurred within a radius of 150 km from one of the stations the magnetotelluric recordings and the computed residual electric fields for the time intervals reported to contain the ses precursors to these events were analysed in some detail in two of the cases it was found that the sources could not be related to earthquake processes in the other three cases the nature of the source of the suspected ses although electric could not be established with certainty these results indicate that for earthquakes of small magnitude ml 4 3 or of large epicentral distance r 100 km the detection of a ses is extremely difficult

the effect of geological anisotropies on the detectability of seismic electric signals abstract the detectability of seismic electric signals was examined in relation to the geological anisotropies both at the large scale of geotectonics and neotectonics and at the smaller scale of electric stations the distribution of the detected seismic events in the cases of the ioannina and assiros stations showed a strong dependence upon the geotectonic zonation and especially upon the ophiolite suture zones of north pindos and almopia axios vardar the major neotectonic transcurrent faults did not show an important effect keratea station and especially point a on a granitic dyke showed an extraordinary detectability independant of the geotectonic zonation attributed to the local anisotropy and to its connecton with batholiths at depth within the aegean paleo volcanic arc of upper miocene age

aspects on the origin of the precursory magnetic anomalies of the mw 6 4 aquila earthquake an anomalous behaviour of the scaling exponent derived from the detrended fluctuation analysis dfa of the time series of low frequency variations of the horizontal and vertical magnetic field components has been recently reported as being observed 2 months prior to the mw 6 3 earthquake on 6 april 2009 close to l aquila city italy here we suggest a possible physical explanation of this effect based on the experience from similar measurements in greece in particular for example we compare these observations associated with aquila earthquake with the ones of the mw 6 6 earthquake on 13 may 1995 at kozani grevena greece where both magnetic field variations and seismic electric signals ses were recorded almost 1 month before the latter earthquake anomalous variations in both electric and magnetic field were detected the time series of that were analysed by means of dfa and led to an exponent close to unity similarly the calculated dfa exponent for the aquila earthquake time series of the anomalous magnetic field variations 2 months before the main shock was also found close to unity these results could imply that in the case of aquila according to the maxwell s laws one should expect to observe simultaneously with the magnetic signal an associated ses activity provided that an appropriate station to monitoring the earth s electric field variations in the same area was available hence it seems that similar underlying non linear dynamic processes in mechanical and as well as electromagnetic sense with features of criticality dominated in both pre focal areas

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

latest aspects of earthquake prediction in greece based on seismic electric signals ii abstract since 1983 continuous monitoring of the electrotelluric field has been carried out using an array of measuring stations located at various sites in greece the basic physical properties of the transient changes seismic electric signals ses in the electrotelluric field that are forerunners of earthquakes were first described six years ago since then a large body of data has been collected resulting in new insight into various aspects of the method the present paper reviews the latest developments in ses based earthquake prediction and describes the current procedures used to predict the epicenter and magnitude of an impending earthquake a detailed list of the predictions officially issued in greece during the past 3 years january 1 1987 november 30 1989 is also given public warnings were issued well before the most destructive seismic activity

tectonoelectric zonation in the hellenic arc abstract the electrical apparent resistivities were measured by means of the magnetotelluric effect at twenty sites in greece and in two directions e w and n s in most of the sites ew differs considerably from ns these results allow the following three zones to be distinguished 1 1 an external zone along western greece with ew ns 2 2 an intermediate zone along the main mountain chain in continental greece where ns ew and 3 3 an internal zone in the northern aegean where ew ns the above resistivity zones are compared to data from geotectonic neotectonic seismotectonic and in situ stress measurements which all show a similar geometry of zonation almost parallel to the active hellenic arc

comments on the results obtained in greece by the van method of seismic prediction abstract emissions of electromagnetic waves before great earthquakes have been observed many times in the past for example the observation at a distance of 10000 km of a radio emission on 18 mhz 6 days before the great chilean earthquake of may 1960 the main features of the van method for predicting earthquakes are described explanation are suggested for 1 1 the predictability of earthquakes and of their focal zone 2 2 the propagation of the telluric currents 3 3 the remarkable sensitivity of the keratea station and 4 4 the directivity effect and the shadow zone

electric potential changes prior to shear fracture in dry and saturated rocks electric potential changes before shear rupture were measured using darley dale sandstone quartz rich and icelandic basalt quartz free on both dry specimens and in the presence of pore fluid we find that electric potential changed markedly just prior to dynamic rupture in dry and saturated sandstones and saturated basalt but we did not detect precursory signals in dry basalt the absence of signals in dry basalt provides strong evidence that the piezoelectric effect and electrokinetic effect are dominant sources for precursory signals moreover we find that the amplitude of the precursory signals due to electrokinetic effect in saturated sandstone were as large as the coseismic signals we propose that this signal is caused by accelerating evolution of dilatancy as cracks grow in the rock before rupture resulting in water flow into the dilatant region with an electric current produced concurrently

dicing with earthquakes the van group have been publicizing claims to be predicting earthquakes since 1981 their predictions of two basic parameters of earthquakes magnitude and location are very loosely constrained most van magnitude predictions are below 5 7 ms with a tolerance of 0 7 ms the uncertainty range spanned by a predicted magnitude is so enveloping that such forecasts cannot be viewed as plainly successful in terms of van s claims to spatial resolution these if successful might constrain the linear dimension of the source region of a magnitude 8 0 ms earthquake but do not adequately constrain a magnitude as large as 7 5 ms not only do van need to refine the tolerances in their magnitude and location predictions before careful judgements can be made but it is also necessary to provide an unambiguous statement of the prediction hypothesis used in relation to a pre published and communally archived dataset of complete seismic electric signal occurrences similar to seismological station bulletins

dielectric properties of granodiorite partially saturated with water and its correlation to the detection of seismic electric signals abstract transient electric signals emitted prior to earthquake occurrence are recorded at certain sites in the earth s crust termed sensitive these field observations enforce the laboratory investigation of the dielectric response of rocks forming these localities the dielectric relaxation of granodiorite rock coming from such a sensitive locality keratea greece reveals through complex impedance spectroscopy that the activation volume for relaxation of this rock is negative that so far has been reported only rarely this result however supports a theoretical model on the pre seismic electric signals and is likely to be correlated with the sensitivity of the site and hence with the selectivity

on the origin of electrotelluric disturbances prior to an earthquake in kalamata greece abstract a long distance 200 km electromagnetic signal occured at keratea near athens few days prior to the september 13th 1986 kalamata earthquake we suggest an explanation based on the fact that long range stress occuring before an earthquake should create local electrical potential gradients in heterogeneous ground at great distances this could be a general explanation for the origin of electrical telluric signals appearing before an earthquake

a note on the prediction of the september 13 1986 strong earthquake in kalamata southwest peloponnesus greece abstract a comparison between the observed focal parameters of the september 13 1986 kalamata greece strong shock and the predicted ones shows that the prediction was quite successful as far as time of occurrence location and focal depth are concerned the discrepancy between the observed m s 6 2 and predicted m s 6 5 7 6 magnitude is attributed to the use of old seismological information and the lack of systematic observation of non seismic earthquake precursors precursors of this type observed by local people before some recent greek shocks including the kalamata earthquake indicate that their systematic monitoring could substantially contribute toward earthquake prediction in greece assuming the random model the probability that the kalamata earthquake occurred in the specified target area by chance is 0 65

geoelectric signals in china and the earthquake generation process we present original apparent resistivity records for stations located in the chinese provinces of hebei and sichuan along with seismicity patterns fault maps and limited hydrologic data these records are part of a 30 year database of geoelectric signals that have been recorded in china by a nationwide network of more than 100 stations set up by the state seismological bureau of the people s republic of china the database includes the time period during which the m 7 8 1976 tangshan and m 7 2 1976 songpan earthquakes occurred resistivity data recorded in and around the epicentral region of the tangshan event show coherent changes both temporal and in areal distribution years and months before and after the earthquakes a regional change in water table occurred more than 3 years prior to the tangshan earthquake the resistivity and water table signals appear to correlate in the 2 to 3 year period prior to the earthquake rainfall records from the region around tangshan extending to the cities of beijing and tianjin do not appear to account for the resistivity changes regional seismicity and active fault patterns in north china indicate that deformation occurs mainly along the borders of large tectonic blocks the source region for the geoelectric signals appears to lie within a large shear zone at the edge of a tectonic block undergoing rotation the tangshan epicentral area is thus only part of a larger zone of deformation we suggest that dilational strain associated with the opening of fractures may lower resistivity and water table for shallow crustal depths such as those monitored by the chinese geoelectric network dilation and resistivity changes are expected to begin at stress levels well below the peak values of the seismic cycle our study suggests that in some cases the areal extent of geoelectric signals may be significantly larger than that of the eventual earthquake source dimension the chinese geoelectric database offers an opportunity to improve our understanding of possible geoelectric precursors to earthquakes

source dynamic parameters of four greek earthquakes and a possible correlation with the lead times of their precursor seismic electric signals abstract since 1982 eighteen telemetric stations in greece have continuously been recording variations in the telluric field transient changes of the telluric field called seismic electric signals ses have been observed simultaneously at some stations from several hours to several days before an earthquake the lead time t of the ses which is the time difference between the occurrence of the earthquake and the ses varies between 6 h and 4 days four large earthquakes m 5 3 6 4 which occurred in 1983 in the cephalonia region in greece showed clear ses with lead times falling into two groups i and ii of several hours and a few days respectively for the four events we studied p wave spectra of the ume swedish seismological station at a teleseismic distance of 26 both short and long period instruments were employed brune s model 1970 was used to calculate source dimensions and relative values of other source dynamic parameters two groups of high and low stress drop were found events with lead times of group i show high stress drop while events with lead times of group ii show low stress drop the relative values of stress drop differ by a factor of 4 between the two groups high and low while within each group they exhibit only a small scatter the largest relative seismic moment m 0 is found for the largest event the three other events with comparable magnitudes have similar seismic moments the same relation was found for the radiated energy e s

anomalous behaviors of geomagnetic diurnal variations prior to the 2011 off the pacific coast of tohoku earthquake mw9 0 there have been many reports on ultra low frequency ulf electromagnetic phenomena associated with earthquakes in a very wide frequency range in this study unusual behaviors of geomagnetic diurnal variations prior to the 2011 off the pacific coast of tohoku earthquake mw9 0 have been reported ratios of diurnal variation range between the target station esashi esa which is about 135 km from the epicenter and the remote reference station kakioka kak about 302 km distant to the epicenter have been computed the results of 10 day running mean of the ratios showed a clear anomaly exceeding the statistical threshold in the vertical component about 2 months before the mega event this anomaly is unique over a 3 year background and the further stochastic test indicates that this anomaly is unlikely a random anomaly which is highly suggestive of correlation with the mega event the original records of geomagnetic fields of the esa station also exhibit continuous anomalous behaviors for about 10 days in the vertical component approximate 2 months prior to the mw9 0 earthquake

periodic variations in the earth s electric field as earthquake precursors results from recent experiments in greece abstract the results obtained during an extensive investigation of the variations in the earth s electric field at three tectonically active areas in greece and their relation to the occurrence of earthquakes are described in all three cases a 24 h periodic oscillation of the earth s electric field was observed prior to large imminent earthquakes one of which was the september 13th 1986 measuring ms 6 2 r earthquake which devastated the city of kalamata finally two physical processes which could explain the above phenomenon are proposed

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

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

on the anomalous changes of seismicity and geomagnetic field prior to the 2011 mw 9 0 tohoku earthquake abstract in xu et al 2013 it has just been reported that approximately 2 months prior to the m w 9 0 tohoku earthquake that occurred in japan on 11 march 2011 anomalous variations of the geomagnetic field have been observed in the vertical component at a measuring station about 135 km from the epicenter for about 10 days 4 14 january 2011 here we show that this observation is in striking agreement with independent recent results obtained from natural time analysis of seismicity in japan in particular this analysis has revealed that an unprecedented minimum of the order parameter fluctuations of seismicity was observed around 5 january 2011 thus pointing to the initiation at that date of a strong precursory seismic electric signals activity accompanied by the anomalous geomagnetic field variations starting from this date natural time analysis of the subsequent seismicity indicates that a strong main shock was expected in a few days to one week after 08 40 lt on 10 march 2011

melting of forsterite mg2sio4 up to 15 gpa the melting curve of forsterite has been studied by static experiment up to a pressure of 15 gpa forsterite melts congruently at least up to 12 7 gpa the congruent melting temperature is expressed by the kraut kennedy equation in the following form tm k 2163 1 3 0 v0 v v0 where the volume change with pressure was calculated by the birch managhan equation of state with the isothermal bulk modulus k0 125 4 gpa and its pressure derivative k 5 33 the triple point of forsterite mg2sio4 liquid will be located at about 2600 c and 20 gpa assuming that congruent melting persists up to the limit of the stability field of forsterite the extrapolation of the previous melting data on enstatite and periclase indicates that the eutectic composition of the forsterite enstatite system should shift toward the forsterite component with increasing pressure and there is a possibility of incongruent melting of forsterite into periclase and liquid at higher pressure although no evidence on incongruent melting has been obtained in the present experiment

laboratory measurements anomalous 0 1 0 5 hz streaming potential under geochemical changes implications for electrotelluric precursors to earthquakes streaming potentials resulting from flow of various salt solutions in rock were measured on saturated sediments fontainebleau sandstones the streaming potential v was found to be proportional to the driving pore pressure p pulses of amplitude 15 40 mv in the frequency range of 0 1 to 0 5 hz were observed when the conductivity of the injected water was decreased and the fluid flow rate was relatively low corresponding to a darcian velocity of 17 to 30 cm h the amplitudes of these pulses are 47 to 133 of the corresponding steady components of the v values such geochemically induced effects may possibly be responsible for the frequency signals from 0 1 to 0 5 hz that were sometimes observed before an earthquake

some relationship between van seismic electric signals ses and earthquake parameters abstract a possible correlation between ses seismic electric signals of the van method characteristics and earthquake parameters is investigated for the period january 1 1983 december 31 1994 for western greece during this period there were total of 55 earthquakes of mb 5 0 in the region of the so called selectivity maps of the ioannina ioa and pirgos pir van stations cmt solutions are available for 29 of these earthquakes eighteen were preceded by ses at ioa and eleven at pir none of them was preceded by simultaneous ses at both stations the main results are as follows 1 the direction of the ses vector at ioa is correlated with the focal position of predicted earthquakes although nearby earthquakes often have ses with dissimilar vector directions 2 the ses of all nine thrust events of the 29 earthquakes were observed at ioa but their vector direction was not unique 3 eleven earthquakes in the zone west of kefallinia to peloponese preceded by ses at pir were of the strike slip type with varying degrees of normal component the vector direction of ses at pir for these earthquakes was predominantly westward 4 the source mechanism changed from largely strike slip type to thrust type in the above zone at the end of 1987 and this coincided with a shift in the sensitive site from pir to ioa indicating a possible correlation between the source mechanism and selectivity characteristics of van stations

subtraction of the telluric inductive component from van measurements abstract in order to understand the role of electrical properties in the vicinity of van stations that have already been found to be appropriate for the collection of seismic electric signals ses a magnetotelluric mt investigation was carried out over of the entire van network we present preliminary mt results for two stations of the van telemetric network in continental greece a procedure was developed by which a real time subtraction of the telluric inductive component from the electric measurements can be made the resulting real time recording of the residual electric field allows a better identification of the ses such an example is presented for an ses that preceded a 5 5 magnitude earthquake in western greece

electric potential changes associated with slip failure of granite preseismic and coseismic signals electric potential changes were measured for stick slip events in granite samples with a three block direct shear arrangement at 8 mpa normal stress two electrodes were mounted on the left and right hand blocks and the electric potential difference between each electrode and the ground was measured with a high input impedance recording system of frequency range from dc to 100 hz as well as coseismic electric signals of about 1 5 v which appeared the moment of the dynamic slip event preseismic signals were detected just before the slip event the coseismic signal rises stepwise with opposite polarities at the two electrodes and exponentially decays with a time constant of e s where e is the permittivity and s is the conductivity of the rock sample we conducted a simple test of rapid stress drop without slipping and observed almost the same electric signal as the coseismic signal this suggests that the electric signal is generated by the piezoelectric effect we proposed a generation model based on the piezoelectric effect and the resultant relaxation process and obtained a theoretical frequency response which is in agreement with experimental data the preseismic signal appears about 2 3 s before the dynamic event with an amplitude of about 50 mv the local strains along two sliding surfaces were also measured to monitor the growth of the rupture nucleation zone when the growth of the rupture nucleation zone occurred on the left sliding surface a clear preseismic signal was detected at the electrode mounted on the left granite block when the growth occurred on the right hand surface a signal was detected at the electrode on the right block this shows that the preseismic electric signal is caused by stress change in the rupture nucleation zone these preseismic and coseismic signals were also detected with an antenna which was placed away from the sample surface

thermally stimulated currents in rocks ii abstract thermally stimulated currents have been observed in eight rock samples selected intentionally to represent the mean crustal stucture in greece for each sample we have determined the re orientation parameters o and hm from in the usual arrhenius expression o exp hm kt in this paper we indicate that for all rock samples investigated a linear connection exists between in o and hm

earthquake premonitory processes evolution of stresses and electric current generation the principles and assumptions of the earthquake premonitory and rebound theory are reviewed the theory based on a continuum model of fracturing processes the stress evolution equations describe the dynamic processes governing a continuous distribution of dislocations special attention is paid to the problem of electric current generation in a seismic source zone electric current is considered as reflecting the rate of polarization which is influenced by motion of the charge bearing dislocations the relationship between the current density and stress accumulation rate is derived

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

negative activation volume for dielectric relaxation in hydrated rocks abstract negative defect activation volumes are extremely rare in solids here we report for the first time that this holds in a couple of hydrated rocks for dielectric relaxation by exploring the complex impedance spectra at various pressures and temperatures the present findings mean that the relaxation time of the relevant relaxation mechanisms decreases upon increasing pressure thus it may become too short at higher pressure and hence lead to the emission of transient electric signals before fracture this may constitute the long standing laboratory confirmation for the explanation of the generation of electric signals prior to an earthquake as recently pointed out by uyeda et al tectonophysics 470 2009 205 213

measurements of electric potential variation by piezoelectricity of granite from laboratory experiments we observed that unloading stress on a piece of granite induced a pulsed electric potential variation which decays exponentially with a time constant ranging from 1 5 to 4 0 s the electric potential variation depends on the magnitude and the sustaining time of applied stress indicating that the variation is due to piezoelectricity and migration of bound charges that compensate the piezoelectric polarization an apparent piezoelectric coefficient of granite was obtained to be about 1 4 10 15 c n three orders of the magnitude smaller than that of a single crystal of quartz

subglacial sediments as a control on the onset and location of two siple coast ice streams west antarctica laterally continuous subglacial sediments are a necessary component for ice streaming in the modern onset regions of the ice streams draining the siple coast of west antarctica on the basis of new seismic data combined with previous results we present geophysical results from seismic reflection and refraction experiments in the upper reaches of ice streams c and d that highlight continuous sedimentary basins within and upstream of the current onset regions of both ice streams with streaming ice overlying these sedimentary packages the subglacial environment changes from no sediment to discontinuous sediment to continuous sediment cover along a longitudinal profile from the ice sheet to tributary c1b along this same profile we observe a speedup of ice flow and then full development of the ice stream tributary ice stream d flows above a thick sedimentary package with an uppermost low seismic velocity zone indicative of soft till and the upglacier and lateral extensions of ice stream d are tightly constrained by the extent of continuous sediments the inland termination of these sediments suggests that future migration of high velocity low shear stress ice flow in these regions appears unlikely

analysis of the electromagnetic field recorded in the friuli seismic zone northeast italy abstract some examples of unusual telluric activity were found during the italian polish magnetotelluric measurement campaign in the friuli seismic zone 1987 1988 the standard procedure for the elimination of the induction component from the telluric recordings and the calculation of the transfer functions were first applied however due to a high noise level in the observed telluric fields in the northern alpine region it appeared indispensable to develop new methods for the detection of any tectonically related component of the telluric field the common function defined as the average curve derived from two telluric stations and multiplied by the correlation coefficients moving window procedure allowed an increase in the telluric activity time changes of variances to be traced before and during seismic events in september 1987 and february 1988 another approach was based on the time frequency isoline calculations of the poynting vector of electromagnetic field positive isoline values opposite to the usual downward direction of this flux were discovered and correlated with a course of seismic activity some good results were found for the time intervals studied some considerations on a mechanism for the generation of an electric current in a zone of seismic preparation are discussed an accumulation of stress leads to an oriented motion of the charged charge bearing dislocations the mechanism consists of the formation of a kind of polarization current induced by the motion of these dislocations

long term monitoring of ulf electromagnetic fields at parkfield california 1 electric and magnetic fields in the 10 4 1 0 hz band were monitored at two sites adjacent to the san andreas fault near parkfield and hollister california from 1995 to 2007 a data window 2002 2005 enclosing the 28 september 2004 m6 parkfield earthquake was analyzed to determine if anomalous electric or magnetic fields or changes in ground conductivity occurred before the earthquake the data were edited removing intervals of instrument malfunction leaving 875 days in the 4 year period frequent spikelike disturbances were common but were not more frequent around the time of the earthquake these were removed before subsequent processing signal to noise amplitude spectra estimated via magnetotelluric processing showed the behavior of the ultralow frequency fields to be remarkably constant over the period of analysis these first order plots make clear that most of the recorded energy is coherent over the spatial extent of the array three main statistical techniques were employed to separate local anomalous electrical or magnetic fields from the dominant coherent natural fields transfer function estimates between components at each site were employed to subtract the dominant field and look deeper at the residual fields the data were decomposed into principal components to identify the dominant coherent array modes and the technique of canonical coherences was employed to distinguish anomalous fields which are spatially broad from anomalies which occur at a single site only and furthermore to distinguish anomalies present in both the electric and magnetic fields from those present in only one field type standard remote reference apparent resistivity estimates were generated daily at parkfield a significant seasonal component of variability was observed suggesting local distortion due to variations in near surface resistance in all cases high levels of sensitivity to subtle electromagnetic effects were demonstrated but no effects were found that can be reasonably characterized as precursors to the parkfield earthquake

an alternative approach to reveal critical behaviour in the case of the mw 6 3 aquila earthquake an independent approach based on a power law relation interconnecting the lead time of precursory signals and the stress drop of forthcoming earthquake confirms the reported evidence that the observed magnetic field anomaly and consequently according to maxwell s laws electric field anomaly prior to mw 6 3 aquila earthquake in 2009 exhibit features of criticality precisely by inserting the data from aquila earthquake in this power law we get an exponent 0 329 which is in excellent agreement with previously found ones and falls within the range values 0 3 0 4 for critical exponents for fracture this fact implies that upon the initiation of the observed magnetic field anomaly and the associated electric signal prior to aquila earthquake the prefocal area enters into a critical stage where nonlinear dynamic processes typical behaviour of a system close to criticality prevail

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

anomalous electrotelluric residuals prior to a large imminent earthquake in greece abstract periodic anomalies period 24 h have been observed in the electrotelluric field prior to a large imminent earthquake in greece the periodic anomaly is modulated by an exponential term which implies that successive peaks increase toward the time of the impending earthquake it is shown that the amplitudes of the periodic variations are much bigger than those accompanying changes of the geomagnetic field

geoelectric potential changes possible precursors to earthquakes in japan whether electromagnetic precursors to earthquakes eqs exist is an important question not only for eq prediction but also for understanding the physical processes of eq generation slow transient geoelectric potential changes have been observed before several recent eqs in japan in most cases they appeared 1 19 days before the eqs and their duration and intensity were several minutes to 1 h and 1 2 mv 100 m the changes appeared before five of all six eqs with magnitude 5 that occurred within 20 km of our stations during the observation period changes were also detected at greater epicentral distances up to 75 km before two other eqs including one eq of magnitude 4 7 which was preceded by a signal simultaneously recorded at three widely separated stations these geoelectric potential changes have been distinguished through the following criteria from a multitude of other changes which were noise of various origins i the selected changes were proportional in amplitude to the length of the recording station s short 100 m dipoles and were simultaneously detected also on long 1 10 km dipoles when the latter were in operation ii no such changes occurred during the observation period that were not followed by eqs although the eq precursory nature of these geoelectric potential changes is admittedly unproven it seems that the present results warrant continued serious research into the occurrence generation and transmission of these signals and their possible causal relationship to eqs

characteristics of electromagnetic noise in the ioannina region greece a possible origin for so called seismic electric signal ses the study of electromagnetic noise in the ioannina region nw greece shows the existence of long transient electric signals duration 10 s without measurable correlated magnetic signals as is the case for seismic electric signal ses observed in the van network of short term earthquake prediction our signals have an artificial origin and are emitted by different kinds of transmitters implanted in the ioannina region this origin can be clearly ascertained from simultaneous observation at stations in direct sight of the transmitters of four electromagnetic components two electric and two magnetic in a broad band of frequencies 10 3 10 hz relying on these observations it is proposed that the april 18 and 19 1995 electric signals interpreted by the van group as ses precursors to the may 13 kozani earthquake are due to some transmitter located far to the north of the ioa station of the van network the transmitters of this area would be of digital type as is increasingly common in radio telecommunication networks we believe that careful studies of electromagnetic noise in a broad range of frequencies should precede lengthy discussions of the statistical significance of recorded signals

a model for the influence of local inhomogeneities on the magnetotelluric variations at two van stations in greece abstract the magnetotelluric impedance tensor has been measured for the stations thiva and loannina of the van network in greece a model is suggested that can explain the distortion of the tensor by near surface structure if a 3 d near surface local structure and a 1 d regional one are considered the values calculated for the ratio ew ns are in reasonable agreement with the experimental ones the calculated values for the strike direction are 40 and 15 for thiva and ioannina respectively these values are comparable to the experimental ones of 40 5 and 15 5

convection current generated prior to rupture in saturated rocks laboratory experiments were performed to study the generation mechanism of electric signals during deformation and rupture of rock with the focus on the effects of pore water movement we have developed a triaxial apparatus that is specially designed for this purpose within the framework of the international frontier program on earthquake research of the institute of physical and chemical research riken this apparatus can deform a rock specimen that is electrically isolated from the surroundings at a very slow strain rate using a cylindrical specimen of intact rock inada granite makabe granite muroto gabbro and fujieda sandstone saturated with distilled water we carried out triaxial deformation tests under a constant pore pressure at room temperature during a deformation test we continuously measured the electric current generated in the specimen in addition local strains pore pressure and pore fluid movement from the intensifier were recorded at a sampling frequency up to 1 khz the volume change due to dilatancy was obtained from the average of the local strain measurements at four positions we found that the convection current flowed before the main fracture showing good correlation with the dilatancy rate and the water flow rate the current density of the signal was about 1 ma m2 this result demonstrated that the electric current is caused by an electrokinetic effect due to the water flow associated with accelerating evolution of dilatancy before the fracture

reply to comment on seismomagnetic effects from the long awaited 28 september 2004 m 6 0 parkfield earthquake by m j s johnston y sasai g d egbert and r j mueller by p varotsos and s uyeda the comment by varotsos and uyeda 2008 vu hereafter does not have much to do with our article which reports electromagnetic data and their implications prior to during and following the 2004 m 6 parkfield earthquake eq in fact our article did not include any extensive discussion of the possible flaws in the seismic electric signal ses approach to eq prediction the four main points vu discuss in their comment are from a summary sentence in the introduction that is preceded by the phrase controversy about these ses results exists because 1 2 4 where 1 4 are the specific points that vu list we respond to each of these points in the following discussion a final comment made by vu concerns our observation that ses type signals are not seen in the data that we have we could have provided more detailed evidence about the lack of ses in the months preceding the earthquake but see little point in including long data plots that show nothing note that all of these data are freely available from the northern california earthquake data center ncedc www ncedc org last accessed october 2007 in our article we presented null results from sites above the parkfield eq rupture without extrapolating to the conclusion that sess do not exist anywhere in fact park et al 2007 report additional data from 10 20 km lines over the entire region that also show no evidence for ses type signals preceding the parkfield eq such signals were also not seen in 16 yr of previous monitoring with these lines park 1991 1997 furthermore no signals were seen in 2 yr of data on 10 km lines both along and within the fault and orthogonal to the fault a little farther to the north johnston 1989 to suggest that all of these observations resulted from an

new aspects on the interconnection between precursory seismic electric signal lead time and geodynamics in the northern aegean sea new insights on the deformation process of a confined region in the northern aegean sea corroborates the claims that the observed long lead times of the precursory seismic electric signals of the two largest earthquakes which occurred within the last 15 years in the area are attributed to specific geodynamics possible underlying physics are also discussed

identifying long range correlated signals upon significant periodic data loss abstract when monitoring geophysical parameters data from segments that are contaminated by noise may have to be abandoned this is the case for example in the geoelectrical field measurements at some sites in japan where high noise due mainly to leakage currents from dc driven trains prevails almost during 70 of the 24 hour operational time we show that even in such a case the identification of seismic electric signals ses which are long range correlated signals may be possible if the remaining noise free data are analyzed in natural time along with detrended fluctuation analysis dfa

possible correlation between geoelectric potential change in izu oshima island and the earthquake swarm off the east izu peninsula japan abstract since may 1987 we have monitored the geoelectric potential change in izu oshima island using three long span dipoles and ntt nippon telegraph and telephone corporation facilities occasionally anomalous potential changes which were different from those induced by geomagnetic variations have been observed their possible correlation with nearby seismic activity has been examined with the result that the daily number of appearances of one type of anomalous potential change increased shortly before m 5 events in all three earthquake swarms that have occurred since 1987 in the area off the east izu peninsula whether or not this correlation is valid and useful for prediction purpose is still not certain

enhancement of seismic electric signals using magnetotellurics abstract during two field studies carried out in greece in 1986 and 1987 1988 electric precursors superimposed on the telluric field and the time dependence of the magnetotelluric apparent resistivity were studied using the magnetotelluric method applied in the frequency band of 0 00028 0 5 hz the recognition of any transient electric signal in the telluric field was improved by reducing the main part of the magnetotelluric induction by making use of a residual electric field the residual field is defined as the difference between the measured electric field and the field which is calculated by multiplying the measured magnetic field with the magnetotelluric impedance tensor in concordance with a previous study this method is shown to be rather effective one conclusion from our study is that it is practical to employ the residual field method in a continuous daily analysis within an earthquake prediction research experiment we have demonstrated that suspected electric transients are revealed as anomalies of non magnetic origin after a careful analysis in three cases significant transient electric signals were classified as suspected seismic electric signals they were clearly resolved on the residual field and all correlated well in time with three earthquakes occurring close to the stations during the time of recording

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

the critical behaviour of a power law between preseismic electric signals and earthquakes of different mechanism in greece and japan the consistency of the critical exponent in the power law relation between the stress drop of the earthquake and the lead time of the precursory seismic electric signal is checked using new data from the recent m w 4 9 earthquake of strike slip mechanism that occurred on 12 november 2013 in northern evia island greece and the megathrust m w 9 0 tohoku earthquake on 11 march 2011 in japan for the first case the derived exponent is in excellent agreement with previous ones obtained from all non thrust events analysed by the author and matches the value of critical exponent for fracture on the other hand the megathrust tohoku earthquake follows the behaviour of all thrust events studied by the author and thus the calculated exponent significantly deviates from this critical value the different behaviour between non thrust and thrust type events could be attributed to the fact that thrust mechanism earthquakes usually occur in collision or subduction zones which are characterised by high accumulation of strain however a larger number of thrust events are required in order to obtain reliable results and shed light in the above experimental findings

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

statistical evaluation of the ses predictions issued in greece alarm and success rates earthquake prediction based on continuous measurements of the electric field of the earth has been systematically carried out by varotsos and co workers in greece predictions were issued by telegrams to greek authorities statistical evaluation of these predictions was made by comparing telegram prediction information with earthquake parameters determined by the us geological survey the space time domain selected for this evaluation was 20 24 e 36 41 n from january 1987 to june 1989 successfully predicted earthquakes are defined here as those that occurred within 22 days of the prediction within 100 km of the predicted epicenter and with a magnitude difference predicted minus true rot greater than 0 7 twelve predictions were issued for earthquakes with expected ms 5 3 following our criteria ten were successful two were not the magnitudes of the predicted earthquakes varied from 4 1 to 5 5 for earthquakes with mb usgs 5 0 the ratio of the predicted to the total number of earthquakes is 6 12 50 and the success rate of the prediction is also 612 50 with a probability gain of a factor of 4 with a confidence level of 99 8 the possibility of this success rate being explained by a random model of earthquake occurrence taking into account a regional factor which includes high seismicity in the prediction area can be rejected for earthquakes with mb usgs 4 5 a statistical significance could not be obtained because of the large number of small earthquakes

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

streaming potential and permeability of saturated sandstones under triaxial stress consequences for electrotelluric anomalies prior to earthquakes the streaming potential due to fluid circulation in rock was measured on saturated sediments fontainebleau sandstones the electrokinetic coupling coefficient which is the ratio of the streaming potential and the excess pore pressure is proportional to the fluid resistivity additionally for a fluid conductivity of 10 3 s m the electrokinetic coupling coefficient varies from 10 to 6642 mv 0 1 mpa for sample permeability in the range of permeabilities from 0 15 10 15 to 1220 10 15 m2 the different values of the electrokinetic coupling coefficient have been explained by the effect of increasing surface conductivity which becomes nonnegligible compared to fluid conductivity for low permeability when the sample is deformed under triaxial stress up to failure the vertical permeability along the principal stress drops by about 0 20 0 1 mpa when failure occurs the typical variation of the electrokinetic coupling coefficient is a large increase beginning with the onset of the localization of the shear band at about 75 of the yield stress and stopping at the failure this increase of the electrokinetic coupling coefficient is due to an increase of potential in the shear zone when new surfaces are created and connected possible consequences of our results are given concerning the electrical fields which could appear during the preparation of an earthquake it is shown that in some cases self potential anomalies reported in the deformed zone preceding an earthquake occurrence could be due to an increase of the electrokinetic coupling coefficient from 75 of the yield stress to rupture in the vicinity of one of the electrodes any variation of fluid resistivity or permeability in the vicinity of one electrode could change the electrokinetic coupling coefficient inducing a surface electrokinetic potential anomaly in regard to the interpretation of the electrokinetic effect which occurs at large distance from the epicenter a larger electrokinetic potential anomaly could be measured between electrodes situated along a vertical fluid flow for instance in a shallow borehole an electrokinetic potential anomaly up to 30 mv for a fluid conductivity of 0 01 s m and a rock permeability of 10 12 m2 could be observed with a change of the underground water table level as slight as 50 cm 50 mbar moreover if the permeability between the electrodes is increased by a factor of 8 103 the electrokinetic coupling coefficient could be enhanced by a factor up to 650

seismic electric signals an additional fact showing their physical interconnection with seismicity abstract natural time analysis reveals novel dynamical features hidden behind time series in complex systems by applying it to the time series of earthquakes we find that the order parameter of seismicity exhibits a unique change approximately at the date s at which seismic electric signals ses activities have been reported to initiate in particular we show that the fluctuations of the order parameter of seismicity in japan exhibits a clearly detectable minimum approximately at the time of the initiation of the ses activity observed by uyeda and coworkers almost two months before the onset of the volcanic seismic swarm activity in 2000 in the izu island region japan to the best of our knowledge this is the first time that well before the occurrence of major earthquakes anomalous changes are found to appear almost simultaneously in two independent datasets of different geophysical observables geoelectrical measurements seismicity in addition we show that these two phenomena are also linked closely in space

tectonic leakage of fault bounded aquifers subject to non isothermal recharge a mechanism generating thermal precursors to seismic events abstract the thermal consequences of flow transients generated by deformation induced leakage at fault zones intersecting confined aquifers have been examined using a simple analytical model the recharge of the aquifer is assumed to take place by vertical infiltration through the confining layers the energy equation relevant in this case has been derived by evaluating enthalpy fluxes associated with lateral and vertical components of fluid flows as well as that due to volume changes in the permeable layer generated by deformation induced alterations in the hydraulic head results of numerical simulations indicate that thermal transients arise during the stress build up period when the infiltrating fluids mix with those in the aquifer but relatively rapid return to equilibrium conditions occur as soon as the leakage is cut off the model is thus capable of reproducing the characteristic features of thermal precursors found in observational records according to model results the growth of thermal perturbation as well as the time for attaining steady state conditions is proportional to the recharge rate the magnitude of the perturbation is related to the thermal gradients in the confining layers but permeability contrast between the confining layer and the aquifer also plays a significant role the model results also indicate that precursory signals are likely to be significant only in areas close to the fault plane where tectonic leakage has a direct influence on the hydraulic head of the aquifer if the fault plane is sensitive to deformation the tectonic leakage rate may undergo substantial changes in response to changing stress patterns and this in turn may easily lead to abrupt and substantial changes in the local thermal regime some of the transient thermal anomalies observed in records of temperatures in boreholes in tectonically active areas have characteristics similar to those predicted by the deformation induced leakage model examples are presented illustrating model fits to thermal transients identified as precursors to seismic events in firjusa turkmenistan didiweli georgia and izu peninsula japan the possibility of obtaining complementary information on processes responsible for fluid flow during pre seismic periods is pointed out it appears that the occurrence of thermal anomalies associated with small scale tectonic deformation may not be uncommon its detection depends on availability of suitable boreholes and of the facilities for monitoring of temperatures using high precision sensors over periods comparable to local recurrence periods of earthquakes

patterns of criticality in the recent seismic activity in the vicinity of athens greece new data from the mw 5 4 earthquake on 17 november 2014 in the vicinity of athens and its seismic electric signal ses precursor confirm patterns of criticality in the pre seismic region during the last preparatory phase in detail the stress drop of the main shock and the lead time of the associated ses are interconnected through a power law with an exponent a 0 327 falling in the range of critical exponents for fracture we note that this exponent is derived from a large amount of data and successfully passes the z score statistical test this fact supports the hypothesis that upon the emission of the ses the pre focal area enters a critical stage where nonlinear dynamic processes dominate

a three year continuous sample of officially documented predictions issued in greece using the van method 1987 1989 abstract copies of all officially documented predictions issued in greece using the van method for the period 1987 1989 are presented a correlation between these predictions and earthquakes is attempted selectivity maps based on experimental data are drawn and the selectivity effect with relation to some earthquake source parameters is commented upon finally the quality of the predictions for large earthquakes is discussed

electrotelluric forerunners to earthquakes in kamchatka abstract electrotelluric field etf data observed at shipunski station spn kamchatka were studied in detail for a period of 10 months from august 1982 to june 1983 during this time interval seven large earthquakes m 5 5 took place in the vicinity of cape shipunski within 180 km of the spn station a large earthquake m 5 7 took place on november 14 1982 this event was preceded by a period of seismic quiescence of about 3 months and it took place at an epicentral distance of 74 km from spn in the oceanic part of the lithosphere a striking change in the electrotelluric potential etp data for november 8 is observed 6 days before the occurrence of the earthquake the change in the etp is about 200 mv km at a signal to noise ratio of roughly 4 the independent parallel line at spn reveals the same anomalous etp change thus excluding instrumental and or electrode effect the possibility of a local source can be excluded after consideration of electric power sources in the area on the other hand the etf anomaly is rather similar to anomalies observed in greece prior to the kefallina earthquake of january 17 1983 the etf data are correlated with geomagnetic recordings from a station at petropavlovsk prt located about 90 km from cape shipunski from the correlation of the two fields we conclude that the changes in the geomagnetic field cannot produce the sudden changes in the electric field if the electric conductivity is constant spectral analysis of the etf data shows that the anomalies contain predominant periods of 24 h 12 h 8 h and 6 h thus resembling the typical main spectral components of geomagnetic field changes in spite of the apparent independent behaviour of the electric and geomagnetic fields during the anomalous period we propose that electromagnetic induction is the primary cause of the electric anomaly accompanied by rapid changes in the transfer functions between the two fields this means changes in the electromagnetic induction after large rapid changes of the resistivity in the fractured zone of the forthcoming earthquakes initiated by the percolation of an interstitial fluid at a critical state of the fracturing process

the van method contradictory and misleading results since 1981 we reexamine the van telegrams available to us in terms of the seismological data observed in the candidate region before and after the relevant telegram for the time period 1981 1985 the correlations are random earthquakes of any magnitude from an extremely low threshold i e m 2 5 at very short distances i e a few kilometers to large magnitudes i e m 7 0 at very large distances i e 500 km or even teleseismic events i e the iran earthquake of 1981 at a distance of about 2000 km were correlated by van with apparent ses on the basis of the occurrence of an earthquake anywhere from italy to aegean sea and from albania to crete island and usually based on telegrams exchanged between the van researchers from 1986 onwards the van telegrams were restricted mostly to the area of western greece which has the highest seismicity in europe by analyzing all of the van telegrams available to us we conclude that in no case was a mainshock predicted whenever the reported van correlation seems to be satisfactory the correlated event was either an aftershock or the correlation was not unique meaning that any of several earthquakes in the same focal region could be arbitrarily correlated with the telegram