long period variations in gravity field caused by mantle anelasticity a numerical perturbation approach is used to assess the effect of mantle anelasticity on the earth s zonal response coefficient the zonal geopotential coefficient j2 and the orbital node of geodetic satellites the theoretical predictions are used to compare solutions of elastic ocean tide models and tides observed by geodetic satellites for mr m m ssa and s a the discrepancies between the satellite observed tides and the solution from schwiderski and recent altimetric ocean tide models can be partly explained by the predicted effect of mantle anelasti city at mf and m m frequencies approximately 80 of the observed semiannual variation in 2 by geodetic satellites can be attributed to the tidal deformation from anelasticity and from the classical equilibrium ocean the predicted for the 18 6 year tide was computed for an earth with an anelastic mantle and a nonequilibrium ocean the range of the lower and upper bounds of for the 18 6 year tide is from 0 345 to 0 377 in amplitude and from 6 o to 3 o in phase with preferred amplitude of 0 365 and phase of 0 o8

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

quantitative relations of seismic source parameters and a classification of earthquakes abstract relations between earthquake parameters moment m0 fault area s fault length l and width w stress drop time characteristics and magnitudes and faulting type dip slip ds and strike slip ss are quantitatively analyzed using a dataset of 240 events m 5 the analysis is carried further toward an earthquake systematization by introducing earthquake classes the results are 1 1 l w 2 1 for ds l w 2 30 for ss and l w 3 7 for giant m0 1029 dyne cm earthquakes respectively 2 2 log m0 1 5 log s 22 2 s in km2 and tentatively log m0 2 45 log s 17 49 for ds and ss and giant earthquakes respectively 3 3 the large scatter of data in m0 s dependences is the result of the combined effect of the variation in and l w 4 4 the concept of constant is replaced by variable to explain the large variations in relations between m0 s l and w for both ds and ss earthquakes and partly between body and surface wave magnitudes low intermediate and high stress drop gd 30 30 60 and 60 bar respectively earthquakes are defined 5 5 a relation of reciprocity exists between seismic slip fault length and width and stress drop 6 6 a saturation of s for some very large earthquakes is suggested from the interpretation of actual data on m0 s l w etc 7 7 the total source duration tsd increases with m0 in relation with earthquake type and tentatively log m0 2 16 log tsd 24 50 holds for ds earthquakes 8 8 log m0 1 5 mm 16 1 holds for mm brune engen mantle wave magnitude 8 5 8 75 9 9 more magnitudes of shorter or longer period on both body and surface wave basis are useful in constraining significant earthquake features 10 10 low and high frequency earthquakes can be distinguished using the gutenberg richter relation ms mb as a reference relation or a relation between ms and mmaxb 11 11 aki s similarity conditions are extended by adding two more conditions as to express more specifically four basic features geometry deformation frequency and time of the earthquake source 12 12 a reference earthquake is defined by criteria consistent with the similarity conditions 13 13 on this basis and in view of nonsimilarity of earthquakes in their totality a scheme for earthquake classification is proposed

periodicity of the earth electric precursor before strong earthquakes abstract data on the anomalous behaviour of the earth electrical potential before strong earthquakes are compared the data are taken from two different locations in the balkan seismic region the existence of an approximately 24 h anomalous impulse variation of the potential with a maximum amplitude just before an approaching earthquake is pointed out the variation starts to occur a few days before the main shock and coincides with the maximum of the last impulse

growth of greenland ice sheet interpretation an observed 0 23 m year thickening of the greenland ice sheet indicates a 25 to 45 excess ice accumulation over the amount required to balance the outward ice flow the implied global sea level depletion is 0 2 to 0 4 mm year depending on whether the thickening is only recent 5 to 10 years or longer term 100 years if there is a similar imbalance in the northern 60 of the ice sheet area the depletion is 0 35 to 0 7 mm year increasing ice thickness suggests that the precipitation is higher than the long term average higher precipitation may be a characteristic of warmer climates in polar regions

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

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

seismic electric signals from displacement of charged dislocations abstract one possible mechanism for the generation of seismic electric signals is the displacement of segments of charged dislocations responding to changes in the applied stress using information available from the study of simpler ionic crystals a crude estimate is made of the voltage that could be generated from large blocks of the earth s crust during a pre earthquake stress adjustment within the many uncertainties of critical parameters the results are consistent with the magnitudes of precursor signals that have been observed in greece

real time detection of anomalous geoelectric changes abstract aiming at an accurate and quick detection of anomalous changes of the electric field so that we can detect tectonic signals we developed observation methods for use both on land and on the ocean floor with these observation methods that is observation on land using electrodes and the underground cables of the nippon telegraph and telephone company and on the ocean floor using the power feeding arrangement of the ocean bottom seismograph of the japan meteorological agency we can obtain more reliable data than those from ordinary observation methods using these data we further developed two techniques of analysis in real time which are based on a statistical model eliminating components induced by the variations of the geomagnetic field and or the movement of the seawater for both cases the geomagnetic field at the kakioka magnetic observatory and or the seawater level data observed on the ocean floor were used as associated data the predominant induced component in the variation of the geoelectric field is almost completely separated in the cases of the geoelectric field in the mito region and on the ocean floor owing to the characteristic periodicity of the monopolar variation of noise in the numazu region in spite of the large amplitude of the noise mainly due to the leak current of the d c electric trains in the original data from the numazu region the noises were considerably separated with these methods into the induced component part or tidal component part with these methods consequently the detectability of anomalous changes was improved about ten times and about five times in the cases of the geoelectric field in the mito region and on the ocean floor and in the case of the geoelectric field in the numazu region respectively

efficiency test of earthquake prediction around thessaloniki from electrotelluric precursors abstract since the completion of the network in january 1983 the electric field of the earth has been continuously monitored at four sites near thessaloniki the capital of northern greece from the present study and from previous investigations by similar measurements in greece it is evident that transient changes of the electrotelluric field occur prior to earthquakes the analysis of these electric forerunners leads in many cases to a successful prediction of the epicentral area the magnitude and the time of the impending event predictions prior to regional earthquakes are issued and documented with telegrams from november 1983 until the end of may 1984 twelve earthquakes m l 3 5 occurred in the vicinity of thessaloniki ten of these were predicted and warnings given by telegram whereas two smaller seismic events were missed two additional predictions were unsuccessful independent of their magnitudes predicted events took place within a time window of 6 hrs to 6 days after the observations of the electrotelluric anomalies the accuracy of the predicted epicenters in eight cases is better than 100 km which corresponds roughly to the mean distance between the electric stations magnitude estimates deviate by less than 0 5 magnitude units from the seismically observed ones considering the two largest earthquakes it is shown that the probability of making each of these predictions by chance is of the order of 10 2

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

a study of anomalous underground electric field variations associated with a volcanic eruption continuous measurements of vertical subsurface geoelectric fields in the frequency range dc 0 6 hz and 1 3 khz vlf are reported anomalous field variations of the ulf band are observed a few days prior to and a month after a minor volcanic eruption of mt mihara the variations displayed essentially distorted pulses rising sharply initially gradually decreasing and then suddenly falling off the electric field variations also seem to extend to the vlf band it is felt that the anomalous electric field variations were caused by electrokinetic phenomena induced by variations of hydrothermal circulation around the crater or by variations of crack density due to volcanic activity

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

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

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

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

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

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