changes in antarctic bottom water properties in the western south atlantic in the late 1980s data collected in 1988 1989 as part of the south atlantic ventilation experiment have been combined with the historical database to study the circulation and water mass variability of the abyssal water in the argentine basin a map of potential temperature at 4000 m used as an indication of geostrophic shear defines a south and western intensified crescent shaped abyssal recirculation within this recirculation and its northward extension to the brazil basin antarctic bottom water aabw properties have undergone two modifications during the 1980s 1 the water mass cooled 0 05 c and freshened 0 008 in salinity ratio on surfaces of constant density 2 the densest layer of aabw was altered to less dense water through mixing or advection out of the study area this water mass change does not appear to have affected the flow pattern data collected in 1983 and 1988 to the north in the brazil basin show penetration of the freshwater mass in the deep western boundary current to between 18 s and 10 s indicating very rapid propagation of the anomaly from the argentine basin into the brazil basin as a deep western boundary current it is suggested that open ocean convective events within the weddell sea contributed to the change in aabw documented here

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

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

partial melting zones in the crust in southern tibet from magnetotelluric results magnetotelluric studies in southern tibet along a north south traverse 200 km long crossing the yarlung zangbo suture zone near lhasa have enabled us to construct a two dimensional model in which layers of anomalously high conductivity exist at depths shallower than 33 km the electrical properties of these layers are different on the two sides of the suture zone we show here that the most plausible explanation of the high conductivity is the existence of partial melting zones in the upper part rather than the lower part of a crust 70 km thick this represents a powerful constraint for thermo mechanical models of continental collisions

freshening drives contraction of antarctic bottom water in the australian antarctic basin antarctic bottom water aabw in the australian antarctic basin has become fresher and lighter since the late 1960s with largest changes observed near the sources of aabw the volume of aabw with neutral density n 28 30 kg m 3 decreased by 50 between 1969 1971 and 2008 2012 thinning at a rate of 100 m per decade contraction of dense aabw was balanced primarily by expansion of water lighter than n 28 15 kg m 3 prior to 1995 and by inflation of less dense classes of aabw after 1995 oxygen concentrations remained unchanged in the densest aabw and increased on neutral surfaces for aabw with n 28 31 kg m 3 between 1995 and 2011 2012 consistent with continued ventilation over this time period the observed changes in potential temperature salinity density volume and oxygen of aabw can be accounted for by freshening of the source waters but cannot be explained by changes in formation rate alone key points freshening drives contraction of antarctic bottom water aabw aabw has contracted by about 50 and thinned more than 100 m per decade since 1970 small increase in oxygen on isopycnals suggests continued ventilation of aabw 2014 american geophysical union all rights reserved

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

on the difficulty of detecting streaming potentials generated at depth in order to investigate how a streaming potential coefficient measured in the laboratory at a typical scale of 10 cm can be incorporated into a field model with a typical scale of 1 to 10 km we measured the electric field induced by water flows forced at 150 m depth through a 10 m wide granite fractured zone the water flows were obtained by pumping cyclically 10 m of water from a borehole that cut the fractured zone at depth and contemporaneously reinjecting it into another borehole located 50 m away after one day a steady state fluid flow regime was reached with pumping cycles lasting 45 minutes indicating a hydraulic conductivity of 10 5 m s 1 and a specific storage coefficient of 3 25 10 6 m 1 the expected self potential at the surface was an anomaly with two maxima of opposite sign and 2 v amplitude each both located 160 m away from the middle of the borehole heads the signal being divided by two 500 m away from the middle of the borehole heads in agreement with wurmstich and morgan 1994 instead we observed an electrical signal of 8 mv midway between the borehole heads and smaller than 5 mv 33 m away from the borehole heads the discrepancy observed between the data and the model can be explained by fluid flow leakages that occurred close to the water table head represented about 20 of the total water flow and activated smaller but closer electric sources this experiment thus illustrates the practical difficulty of detecting streaming potentials generated at depth it shows in particular that in fractured zones and hence in the vicinity of a major active fault small water flows located distantly from an energetic targeted source but close to some of the electrodes of the network can sometimes drastically distort the shape of the expected anomaly models of possible electrical earthquake precursors therefore turn out to be more speculative than expected

time resolved study of charge generation and propagation in igneous rocks electrical resistivity changes ground potentials electromagnetic em and luminous signals preceding or accompanying earthquakes have been reported many times in addition to ground uplift and tilt and other parameters however no concept exists that would tie these diverse phenomena together into a physically coherent model using low to medium velocity impacts to measure electrical signals with microsecond time resolution it is observed that when gabbro and diorite cores are impacted at relatively low velocities 100 m s highly mobile charge carriers are generated in a small volume near the impact point they spread through the rocks causing electric potentials exceeding 400 mv em and light emission as the charge cloud spreads the rock becomes momentarily conductive when a granite block is impacted at higher velocity 1 5 km s the propagation of the p and s waves is registered through the transient piezoelectric response of quartz after the sound waves have passed the surface of the granite block becomes positively charged suggesting the same charge carriers as observed during the low velocity impact experiments expanding from within the bulk during the next 2 3 ms the surface potential oscillates indicating pulses of electrons injected from ground and contact electrodes the observations are consistent with positive holes e g defect electrons in the o2 sublattice traveling via the o 2p dominated valence band of the silicate minerals the positive holes propagate as charge clouds rather than as classical em waves before activation they lay dormant in form of electrically inactive positive hole pairs php chemically equivalent to peroxy links o3x oo xo3 with x si4 al3 etc phps are introduced into the minerals by way of hydroxyl o3x oh which all nominally anhydrous minerals incorporate when crystallizing in h2o laden environments the fact that positive holes can be activated by low energy impacts and their attendant sound waves suggests that they can also be activated in the crust by microfractures during the dilatancy phase depending on where in the stressed rock volume the charge carriers are activated they will form rapidly moving or fluctuating charge clouds that can account for earthquake related electrical signals and em emission wherever such charge clouds intersect the surface high fields are expected causing electric discharges and earthquake lights

1 fα fluctuations in geoelectrical signals observed in a seismic area of southern italy abstract recent studies have shown that many natural systems display temporal fluctuations with long range power law correlations suggesting a fractal geometry of the underlying dynamical system four geoelectrical time series measured in a seismic area of southern italy are investigated by means of spectral tools in order to evidence the existence of power law correlations results show the scaling behaviour for all the signals recorded pointing to the presence of fractal features expressing a long term correlation with scaling exponents which indicate stabilizing mechanisms furthermore our findings suggest an observational evidence of correlations between the variation of parameters describing the temporal fluctuations of geoelectrical signals and earthquakes that occurred in the area investigated

a new approach to investigate the correlation between geoelectrical time fluctuations and earthquakes in a seismic area of southern italy we propose a new approach to investigate the possible correlation between electrical signals and earthquakes good correlation has been found between the spectral power law exponent of geoelectrical signals and the hurst exponent of the seismicity of the area investigated a tendency of both parameters to converge toward unity typical of self organized critical dynamics is evident before the occurrence of the major event recorded in the area during the observation period

can electromagnetic disturbances related to the recent great earthquakes be detected by satellite magnetometers abstract on december 26 2004 the world s fourth largest earthquake since 1900 and the largest since the 1964 prince william sound alaska earthquake occurred off the west coast of northern sumatra with a magnitude of 9 3 on march 28 2005 another event of magnitude 8 7 took place in the same region the december 26 2004 earthquake has prompted scientists to investigate possible electromagnetic signatures of this event using ground magnetic observations iyemori et al iyemori t et al 2005 geomagnetic pulsations caused by the sumatra earthquake on december 26 2004 geophys res lett 32 l20807 doi 10 1029 2005gl024083 have suggested that a 3 6 min long geomagnetic pulsation observed shortly after this event was generated by the earthquake they have speculated that a 30 s magnetic pulsation was also caused by the earthquake here for the first time champ satellite magnetic and electron density data are examined to find out if electromagnetic signatures which are possibly related to these recent megathrust earthquakes are observed in satellite magnetic data we have shown that some specific features are observed after the two earthquakes with periods of about 16 and 30 s our results favor an external source origin for the 30 s pulsation moreover after more than 1 h champ magnetic data indicate the existence of a feature characterized by the same parameters duration amplitude and frequency content which could be associated with each earthquake respectively further investigations are required in order to answer the question of whether these signals can be associated with earthquakes and to assign their possible usefulness with respect to earthquake development

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

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

back arc extension in the southern andes a review and critical reappraisal the interpretation that the mafic rocas verdes green rocks complex of the southern andes represents part of the uplifted floor of a late jurassic to early cretaceous back arc basin has proved particularly useful in understanding the geological evolution of the southern andes the north scotia ridge and the antarctic peninsula clear field evidence of the back arc setting of the 9rocas verdes gabbro sheeted dyke pillow lava ophiolitic assemblages has encouraged fruitful petrological and geochemical comparison with mid ocean ridge and marginal basin basalts other onshore ophiolite complexes and archaean greenstone belts uncertainty still surrounds estimates of the original width and depth of the basin as well as the proportion of new mafic crust compared with relict sialic crust in the basin floor these questions are unresolved owing mainly to the considerable lower cretaceous turbiditic basin infill and the effects of mid cretaceous compressional deformation while the field relations clearly indicate that the rocas verdes basin is not an older piece of ocean floor trapped behind a volcanic arc it is not yet clear whether the basin is directly subduction related or falls in the category of back arc leaky transforms like the proto gulf of california or apparent rip off features like the andaman sea

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

identification and analysis of electromagnetic signals in greece the case of the kozani earthquake van prediction an electric station was installed in july 1993 4 5 km away from the van station of ioannina and recorded in the following two years a number of anomalous signals including those of april 18 and 19 1995 interpreted by the van group as seismic electric signals precursors to the may 13 kozani earthquake west macedonia a magnetic station was also installed and clearly recorded the magnetic components of the same events the amplitude shape characteristic pattern and duration magnetic characteristics and polarisation of the anomalous signals suggest that they are generated by artificial industrial sources

seismomagnetic effects from the long awaited 28 september 2004 m 6 0 parkfield earthquake precise measurements of local magnetic fields have been obtained with a differentially connected array of seven synchronized proton magnetometers located along 60 km of the locked to creeping transition region of the san andreas fault at parkfield california since 1976 the m 6 0 parkfield earthquake on 28 september 2004 occurred within this array and generated coseismic magnetic field changes of between 0 2 and 0 5 nt at five sites in the network no preseismic magnetic field changes exceeding background noise levels are apparent in the magnetic data during the month week and days before the earthquake or expected in light of the absence of measurable precursive deformation seismicity or pore pressure changes obser vations of electric and magnetic fields from 0 01 to 20 hz are also made at one site near the end of the earthquake rupture and corrected for common mode signals from the ionosphere magnetosphere using a second site some 115 km to the northwest along the fault these magnetic data show no indications of unusual noise before the earthquake in the ulf band 0 01 20 hz as suggested may have preceded the 1989 ml 7 1 loma prieta earthquake nor do we see electric field changes similar to those suggested to occur before earthquakes of this magnitude from data in greece uni form and variable slip piezomagnetic models of the earthquake derived from strain displacement and seismic data generate magnetic field perturbations that are con sistent with those observed by the magnetometer array a higher rate of longer term magnetic field change consistent with increased loading in the region is apparent since 1993 this accompanied an increased rate of secular shear strain observed on a two color edm network and a small network of borehole tensor strainmeters and increased seismicity dominated by three m 4 5 5 earthquakes roughly a year apart in 1992 1993 and 1994 models incorporating all of these data indicate increased slip at depth in the region and this may have played a role in the final occurrence of the 28 september 2004 m 6 0 parkfield earthquake the absence of electric and magnetic field precursors for this and other earthquakes with m 5 7 3 elsewhere in the san andreas fault system indicates useful prediction of damaging earthquakes seems unlikely using these electromagnetic data

electromagnetic signals generated in the solid earth by digital transmission of radio waves as a plausible source for some so called seismic electric signals abstract claims by the van group varotsos p alexopoulos k 1984 physical properties of the variations of the electric field of the earth preceding earthquakes i tectonophysics 110 73 98 and later works to have developed a short term earthquake prediction technique in greece continue to arouse contentious debates claims of success in using geoelectrical precursors to predict earthquakes are criticized and defended 1998 letters phys today 51 6 15 100 great debates in seismology the van method of earthquake prediction 1998 eos 79 573 580 this is partly because of the unknown origin of the so called seismic electric signals ses precursors their particular characteristics are not those of the usual electromagnetic noise cultural noise or of the natural electromagnetic field magnetotelluric field in this paper we show that transient electric signals looking like ses can be generated by digital transmitters of the radio telecommunication network such signals have been observed in different regions of the world including greece and vietnam their characteristics have been analyzed in a broad band of frequencies 10 3 103 hz in the ioannina greece site which is considered as the most sensitive area of the van network it is concluded that some of the signals recorded at this site and identified as ses are probably of artificial origin and that the criteria used by the van group are not sufficient to guarantee that the so called ses are not man made without an extended and thorough study of the ambient electromagnetic noise in a broad band of frequencies and better information about the electrical properties of the deep structure beneath the monitoring station earthquake predictions issued on the basis of signals recorded by the van network are of dubious significance