two mode ionospheric response and rayleigh wave group velocity distribution reckoned from gps measurement following mw 7 8 nepal earthquake on 25 april 2015 the coseismic induced ionospheric total electron content tec perturbations were analyzed following the mw 7 8 nepal earthquake 28 147 n 84 708 e depth 15 km that occurred on 25 april 2015 at 06 11 26 utc the ionospheric response is due to both the modes i e shock acoustic waves slow mode and rayleigh wave induced fast mode the continuous global positioning system gps data at about 60 sites from various gps networks have been used in the present study all the sites within epicentral distance of 2400 km and 70 170 azimuth recorded the rayleigh wave induced tec response while the sites within 400 2200 km in the same azimuth recorded the response from both the modes the maximum coseismic induced peak to peak tec amplitude is 1 2 total electron content unit 1 tecu 1016 el m 2 from hodochron plot the apparent rayleigh wave velocity has been determined as 2400 m s on the average and the acoustic wave velocity as 1180 m s both these waves being discernible beyond 1200 km of epicentral distance as also evident from hodochron plot and wavelet spectrographs we reckoned the rayleigh wave group velocities using ionospheric response at selected radial pairs of stations and validated the ionospheric response distribution seen mainly depending on the epicentral distance satellite geometry directivity of radiation pattern and the upper crustal heterogeneity this study highlights the characteristics of ionospheric response consequent to the 2015 nepal earthquake

ionospheric disturbances of the 2007 bengkulu and the 2005 nias earthquakes sumatra observed with a regional gps network 1 we studied ionospheric disturbances associated with the two large earthquakes in sumatra indonesia namely the 2007 bengkulu and the 2005 nias earthquakes by measuring the total electron contents tec using a regional network of global positioning system gps receivers we first focus on coseismic ionospheric disturbances cids of the bengkulu earthquake mw 8 5 they appeared 11 16 min after the earthquake and propagated northward as fast as 0 7 km s consistent with the sound speed at the ionospheric f layer height resonant oscillation of tec with a frequency of 5 mhz continued for at least 30 min after the earthquake the largest aftershock mw 7 9 also showed clear cids similar to the main shock a cid propagating with the rayleigh wave velocity was not observed possibly because the station distribution did not favor the radiation pattern of the surface waves this earthquake which occurred during a period of quiet geomagnetic activity also showed clear preseismic tec anomalies similar to those before the 2011 tohoku oki earthquake the positive and negative anomalies started 30 60 min before the earthquake to the north and the south of the fault region respectively on the other hand we did not find any long term tec anomalies within 4 5d ays before the earthquake co and preseismic ionospheric anomalies of the 2005 nias earthquake mw 8 6 were however masked by strong plasma bubble signatures and we could not even discuss the presence or absence of cids and preseismic tec changes for this earthquake

very short term earthquake precursors from gps signal interference based on the 2013 nantou and rueisuei earthquakes taiwan abstract we set up a gps network with 17 continuous gps cgps stations in southwestern taiwan to monitor real time crustal deformation we found that systematic perturbations in gps signals occurred just a few minutes prior to the 2013 nantou ml 6 5 and rueisuei ml 6 4 earthquakes in taiwan the anomalous pseudorange readings were several millimeters higher or lower than those in the background time period these systematic anomalies were found as a result of interference of gps l band signals by electromagnetic emissions ems prior to the mainshocks the ems may occur in the form of harmonic or ultra wide band radiation and can be generated during the formation of mode i cracks at the final stage of earthquake nucleation we estimated the directivity of the likely em sources by calculating the inner product of the position vector from a gps station to a given satellite and the vector of anomalous ground motions recorded by the gps the results showed that the predominant inner product generally occurred when the satellite was in the direction either toward or away from the epicenter with respect to the gps network our findings suggest that the gps network may serve as a powerful tool to detect very short term earthquake precursors and presumably to locate a large earthquake before it occurs nevertheless a direct measurement of ems at the site of the gps array is required in future studies to confirm this hypothesis

silicic volcanism at an off axis geothermal field in the mariana trough back arc basin an abyssal hill site with localized high heat flow on the 3 m y old west flank of the active ridge in the mariana trough has sets of oblique fault scarps mapped by multi beam transits and clusters of 50 to 1 000 m diameter domes examined with a deep tow survey some of the domes including small 20 to 30 m high rocky knobs encrusted with manganese oxide crop out through the sediment cover but despite heat flow evidence that they are sites of hydrothermal discharge these bedrock features are fundamentally different from the hydrothermal mounds found on some mid ocean ridges dredging one dome recovered a rhyodacite pumice that we believe erupted at a depth of 2 600 3 600 m within the basin the siliceous rock may be an extreme differentiate of a tholeiitic magma but a more likely origin is partial melting of the basin s sedimentary fill

three dimensional distribution of ionospheric anomalies prior to three large earthquakes in chile using regional global positioning system gps networks we studied three dimensional spatial structure of ionospheric total electron content tec anomalies preceding three recent large earthquakes in chile south america i e the 2010 maule mw8 8 the 2014 iquique mw8 2 and the 2015 illapel mw8 3 earthquakes both positive and negative tec anomalies with areal extent dependent on the earthquake magnitudes appeared simultaneously 20 40 minutes before the earthquakes for the two mid latitude earthquakes 2010 maule and 2015 illapel positive anomalies occurred to the north of the epicenters at altitudes 150 250 km the negative anomalies occurred further to the north at higher altitudes 200 500 km this lets the epicenter the positive and negative anomalies align parallel with the local geomagnetic field which is a typical structure of ionospheric anomalies occurring in response to positive surface electric charges

geology of a vigorous hydrothermal system on the endeavour segment juan de fuca ridge a high precision high resolution geologic map explicitly documents relationships between tectonic features and large steep sided sulfide sulfate silica deposits in the vigorously venting endeavour hydrothermal field near the northern end of the juan de fuca ridge water depth in the vent field varies from 2220 to 2200 m location of the most massive sulfide structures appears to be controlled by intersections of ridge parallel normal faults and other fracture fissure sets that trend oblique to and perpendicular to the overall structural fabric of the axial valley the fractured basaltic substrate is primarily composed of well weathered pillow and lobate flows as presently mapped the field is about 200 by 400 m on a side and contains at least 15 large 1000 m3 sulfide edifices and many tens of smaller commonly inactive sulfide structures the larger sulfide structures are also the most vigorously venting features in the field they are commonly more than 30 m in diameter and up to 20 m in height actively venting sulfide structures in the northern portion of the field stand higher and are more massive than active structures in the southern portion of the field which tend to be slightly to distinctly smaller maximum venting temperatures of 375 c are associated with the smaller structures in the southeastern portion of the field highest temperature venting fluids from the more massive structures in the northern portion of the field are consistently 20 30 c lower hydrothermal output from individual active sulfide features varies from no flow in the lower third of the edifice to vigorous output from fracture controlled black smoker activity near the top of the structures a different type of high temperature venting takes place from the upper sides of the structures in the form of overflow from fully exposed quiescent pools of buoyant 350 c vent water trapped beneath overhanging sulfide sulfate silica ledges or flanges these flanges are attached to the upper outer walls of the large sulfide edifices two types of diffuse venting in the endeavour field include a lower temperature 8 15 c output through colonies of large tubeworms and 25 50 c vent fluid that seems to percolate through the tops of overhanging flanges the large size and steep walled nature of the these structures evidently results from sustained venting in a mature hydrothermal system coupled with dual mineral depositional mechanisms involving vertical growth by accumulation of chimney sulfide debris and lateral growth by means of flange development

directivity and apparent velocity of the coseismic ionospheric disturbances observed with a dense gps array abstract coseismic disturbances in ionosphere have been observed after recent thrust earthquakes off the pacific coast of japan with a dense global positioning system array positive pulses in electron content as large as several times 10 15 electrons m 2 and as long as 4 5 min emerge 10 min after earthquakes and propagate horizontally with apparent velocity of 1 km s close to the sound velocity at the ionospheric height they may have been excited by coseismic uplifts of the sea surface initially as upward propagating compressive pulses of atmosphere which were gradually refracted to propagate horizontally in ionosphere the propagation has strong north south asymmetry and interaction between the movements of charged particles in acoustic waves and geomagnetic fields might have selectively attenuated the northward propagating disturbances

ionospheric electron enhancement preceding the 2011 tohoku oki earthquake 1 the 2011 march 11 tohoku oki earthquake mw9 0 caused vast damages to the country large events beneath dense observation networks could bring breakthroughs to seismology and geodynamics and here i report one such finding the japanese dense network of global positioning system gps detected clear precursory positive anomaly of ionospheric total electron content tec around the focal region it started 40 minutes before the earthquake and reached nearly ten percent of the background tec it lasted until atmospheric waves arrived at the ionosphere similar preseismic tec anomalies with amplitudes dependent on magnitudes were seen in the 2010 chile earthquake mw8 8 and possibly in the 2004 sumatra andaman mw9 2 and the 1994 hokkaido toho oki mw8 3 earthquakes but not in smaller earthquakes

east pacific rise 8 10 30 n evolution of ridge segments and discontinuities from seamarc ii and three dimensional magnetic studies magnetic bathymetric and seamarc ii side scan sonar data from the ridge flanks adjoining the overlapping spreading center osc at 9 03 n on the east pacific rise epr are used to establish the evolution of this ridge axis discontinuity and adjacent ridge segments within the past 2 4 m y a three dimensional inversion for magnetization shows the discontinuity evolved from one of small offset 2 km to an 8 km offset osc within the past approximately 1 0 m y the osc has left a v shaped discordant zone indicating an average southward migration of 42 km m y since the beginning of anomaly 2 time 1 8 m y the west flank discordant zone consists of discrete abandoned overlap basins bounded by highly magnetized ridge tips with anomalous lineations while the east flank discordant zone is a broad swath of high magnetization anomalous lineations and greater depths kinematic modelling indicates that southward migration has not been steady but has been accomplished by a series of episodic propagation events with rates ranging from 500 mm yr ridge tips have been abandoned at intervals of approximately 50 000 100 000 years both by linkage of neighboring ridge segments and by self decapitation magnetic modelling suggests rotations of overlap basins of 25 consistent with predictions of kinematic modelling orientation of magnetic isochrons indicate a 3 6 counterclockwise change in pacifie cocos plate motion within the past 1 m y assuming orthogonal spreading throughout this time although the discontinuity currently located at 9 03 n existed prior to this change in plate motion its growth into a right stepping 8 km offset osc may be causally related to this change the current configuration of intratransform spreading within the siqueiros has developed since onset of the brunhes anomaly 0 73 m y possibly in response to this recent counterclockwise change in plate motion in addition to the osc there is evidence for several small discontinuities offsetting the ridge during anomaly 2 time which have since migrated along the ridge and vanished an axial magnetization high is observed along the crest of the epr change in the magnitude of the axial magnetization high or shifts in its location relative to the bathymetric axis coincide with several devals within the area magnetization maxima are found at ridge transform intersections and the osc these highs may reflect presence of highly fractionated feti basalts erupted from magma chambers with restricted supply located adjacent to both large and short offset ridge axis discontinuities discrete magnetization highs are found off axis adjacent to clipperton and siqueiros fracture zones indicating that production of feti basalts at ridge transform intersections is episodic magnetizations are higher north of clipperton than south of it possibly reflecting a long lived starvation in magma supply north of clipperton and more abundant supply to the south most seamounts within the area have the same magnetization polarity as surrounding seafloor indicating that seamount formation occurs near the ridge axis the exceptions lie near magnetic reversal boundaries and are consistent with seamount formation as close as 10 km from the ridge axis few pronounced magnetization highs are associated with seamounts indicating that the magnetized source layer is no thicker beneath them than surrounding seafloor or that seamount basalts are substantially less magnetic than normal mid ocean ridge basalts

ionospheric holes made by ballistic missiles from north korea detected with a japanese dense gps array 1 a dense array of global positioning system gps receivers is a useful tool to study ionospheric disturbances here we report observations by a japanese gps array of ionospheric holes i e localized electron depletion they were made by neutral molecules in exhaust plumes e g water of ballistic missiles from north korea taepodong 1 and 2 launched on 31 august 1998 and 5 april 2009 respectively negative anomaly of electron density emerged 6 min after the launches in the middle of the japan sea and extended eastward along the missile tracks by comparing the numerical simulation of electron depletion and the observed change in ionospheric total electron content we suggest that the exhaust plumes from the taepodong 2 second stage effused up to 1 5 1026 water molecules per second the ionospheric hole signature was used to constrain the taepodong 2 trajectory together with other information e g coordinates of the launch pad time and coordinates of the first stage splashdown and height and time of the second stage passage over japan the taepodong 2 is considered to have reached the ionospheric f region in 6 min flown above northeastern japan 7 min after the launch and crashed to the pacific ocean without attaining the first astronautical velocity the ionospheric hole in the 1998 taepodong 1 launch was much less in size but it is difficult to compare directly the thrusts of the two missiles due to uncertainty of the taepodong 1 trajectory

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

hydrothermal sulfide and oxide deposits on seamounts near 21 n east pacific rise hydrothermal deposits were sampled by submersible from the calderas and summit benches of two seamounts 20 and 30 km west of the east pacific rise at 21 n the deposits document a wide variety of off axis hydrothermal activity including samples from the interiors of seafloor sulfide deposits in contrast to most mid ocean ridge deposits sulfide deposits on green seamount are rich in si fe and cu are poor in zn and contain abundant quartz sulfide chimneys grew by quenching of hydrothermal fluids and deposition of walls of colloform pyrite marcasite zn sulfide and minor galena whereas coarse grained pyrite and chalcopyrite were deposited at higher temperatures 250 c in chimney interiors as chimney walls grew outward into sea water increased temperatures in the inner walls resulted in recrystallization to pyrite and deposition of pyrite and chalcopyrite in pore space cooling in the outer portions of chimneys caused deposition of opal at temperatures of about 80 170 c as chimneys coalesced and opal rich material was heated in the interiors of sulfide edifices opal was recrystallized to chalcedony and quartz faulting has exposed the interiors of sulfide deposits where further recrystallization and deposition of chalcopyrite and quartz occurred at temperatures of 230 320 c clogging of chimneys changes in flow paths and cooling of the deposits led to the deposition of late mixed layer illite smectite iron sulfides fe poor sphalerite opal and barite the sulfide deposits formed over a time span of at least 140 000 to 70 000 yr ago probably coincident with caldera and pit crater formation the ages of the sulfide deposits provide constraints on the last volcanic and tectonic activity and they also suggest that it took a maximum of 260 000 yr for the seamount to reach its present height red seamount is presently hydrothermally active and deposits consisting predominantly of amorphous fe oxyhydroxide are forming on small pillow cones in the caldera at temperatures of 10 15 c hydrothermal nontronite deposits capped by mn oxide crusts cover much of the southern summit bench of red seamount and formed at temperatures of around 30 c iron rich talc and sulfide grains in nontronite provide evidence of former high temperature activity and suggest that a sulfide deposit is present nearby

statistical analysis of an ionospheric parameter as a base for earthquake prediction 1 this paper is related to the use of ionospheric density variations to tentatively predict earthquakes the results of this statistical analysis are presented as a function of various parameters the ion density was recorded by the low altitude satellite demeter during more than 6 years and a search for anomalies was automatically conducted with the complete data set in a second time a software checked if each anomaly could correspond to an earthquake the search was conducted at less than 1500 km from the anomaly positions and until 15 days after the anomaly time the earthquakes have been classified depending on their magnitude depth and position below the sea or inland this attempt to predict earthquakes of course generates a lot of false alarms and wrong detections nevertheless it is shown that the number of good detections increases with the magnitude of the earthquakes in average the number of perturbations is higher the day of the earthquake and then smoothly decreases for the days before earthquakes below the sea are better detected there are seismic areas close to the south atlantic magnetic anomaly and at high latitudes where the number of natural perturbations is too important to expect a high number of good detections finally when there are several perturbations corresponding to a single earthquake it is possible to combine their positions to have a better estimation of the location of the future epicenter however uncertainties about the time and the magnitude are large

growth history of hydrothermal black smoker chimneys hollow mineral spires known as black smoker chimneys precipitate around 350 c jets of hydrothermal fluid spouting from the sea floor on the east pacific rise epr at 21 n refs 1 2 i describe and discuss here the formation of mineral zoning across the walls of these structures throughout two major growth phases a sulphate dominated stage and a sulphide replacement stage during the sulphide replacement stage at least four distinct sulphide mineral zonation sequences develop across chimney walls from interior to exterior the apparently successive formation of these sulphide zonation sequences is attributed to evolution of radial thermal and chemical gradients accompanying the gradual thickening and sealing of black smoker chimney walls

accretion and oxidation of a superfast spread axial melt lens tims and sims zircon analyses of the iodp hole 1256d gabbros abstract iodp hole 1256d penetrates a complete section of upper oceanic crust spread from the east pacific rise at a full rate of up to 220 mm yr here we present u pb zircon data from hole 1256d gabbroic rocks using isotope dilution thermal ionization mass spectrometry id tims and secondary ion mass spectrometry sims three gabbro samples yielded th corrected weighted mean 206pb 238u sims dates of 15 03 0 14 ma 15 13 0 35 ma and 15 23 0 12 ma an id tims th corrected weighted mean 206pb 238u date of 15 191 0 040 ma from the first of the three samples provides verification and refinement of the timing of magmatism the u pb dates agree with the predicted age of the crust based on marine magnetic anomalies suggesting the gabbros most likely formed by intrusion and crystallization at or near the ridge axis zircons from two of the studied samples have anomalously high th u ratios likely reflecting oxidation of u prior to or during zircon crystallization the elevated o2 of late stage melts in the axial melt lens may be related to progressive crystallization assimilation of hydrothermally altered sheeted dikes and gabbros and or contamination of the melt lens by seawater derived saline brines

ionospheric plasma response to m w 8 3 chile illapel earthquake on september 16 2015 the lithosphere and the atmosphere ionosphere continuously exchange energy through various coupling mechanisms in particular the earth surface displacement caused by earthquakes volcanoes and tsunamis can manifest as ionospheric plasma perturbations we investigate the coseismic induced ionospheric total electron content tec perturbations following the m w 8 3 illapel thrust earthquake that occurred on september 16 2015 the continuous global positioning system gps data at 48 sites from centro sismologico nacional and international gnss service gps networks have been used in this study the nearest gps site recorded the ionospheric response 10 min after the occurrence of this earthquake the maximum vertical coseismic induced tec amplitude is 1 4 tecu and the perturbations are pronounced in the northern region of the epicenter and confined to less than 1500 km radius the average horizontal acoustic wave velocity has been determined as 1260 m s we also observed acoustic resonance recorded by prn 12 at 4 3 mhz corresponding to the first overtone of acoustic mode and lasting for about 30 min in this study we present characteristics of gps derived ionospheric plasma perturbations following illapel earthquake

volcanic growth faults and the origin of pacific abyssal hills the topographic features known as abyssal hills characterize 30 of the ocean floor and yet their origin has been the subject of vigorous debate for over 40 years submersible based investigations show that pacific abyssal hills are created on the flanks of the east pacific rise as horsts and grabens which lengthen with time hills are bounded on one side by ridge facing scarps produced by normal faulting and on the other by more gentle slopes produced by volcanic growth faulting

correlation analysis for preseismic total electron content anomalies around the 2011 tohoku oki earthquake we can observe the changes of total electron content tec in ionosphere by analyzing the data from global navigation satellite systems gnss satellites up to now preseismic tec anomalies have been reported in several papers however they are not so clear as coseismic tec anomalies and their analysis methods have some problems for practical earthquake prediction one factor making it difficult to detect tec anomalies is large noises in tec data nonnegligible tec disturbances are caused by many natural mechanisms to overcome this difficulty we propose correlation analyses between one gnss station and gnss stations surrounding it first we model tec time series over a few hours using polynomial functions of time second we calculate prediction errors as the departure of the tec time series from the models over time scale of a few minutes and define it as the tec anomaly third we calculate the correlation between anomaly of one gnss station and those at the surrounding stations although such a correlation method has long been used for radio communications in particular for spread spectrum communications and very long baseline interferometry to increase signal to noise ratio it has not been widely applied for tec analysis as a result of our method we demonstrate that the correlation analysis can detect preseismic anomalies about 1 h before the 2011 tohoku oki earthquake on 11 march mw 9 0 20 min before the foreshock on 9 march and 40 min before the aftershock on 7 april mw 7 3

on the reported ionospheric precursor of the 1999 hector mine california earthquake 1 using global positioning system gps data from sites near the 16 oct 1999 hector mine california earthquake pulinets et al 2007 identified anomalous changes in the ionospheric total electron content tec starting one week prior to the earthquake pulinets 2007 suggested that precursory phenomena of this type could be useful for predicting earthquakes on the other hand and in a separate analysis afraimovich et al 2004 concluded that tec variations near the epicenter were controlled by solar and geomagnetic activity that were unrelated to the earthquake in an investigation of these very different results we examine tec time series of long duration from gps stations near and far from the epicenter of the hector mine earthquake and long before and long after the earthquake while we can reproduce the essential time series results of pulinets et al we find that the signal they identified as being anomalous is not actually anomalous instead it is just part of normal global scale tec variation we conclude that the tec anomaly reported by pulinets et al is unrelated to the hector mine earthquake

modelling of the total electronic content and magnetic field anomalies generated by the 2011 tohoku oki tsunami and associated acoustic gravity waves summary in this work numerical simulations of the atmospheric and ionospheric anomalies are performed for the tohoku oki tsunami 2011 march 11 the tsunami atmosphere ionosphere tai coupling mechanism via acoustic gravity waves agws is explored theoretically using the tai coupled model for the modelled tsunami wave as an input the coupled model simulates the wind density and temperature disturbances or anomalies in the atmosphere and electron density magnetic anomalies in the f region of the ionosphere also presented are the gps total electron content tec and ground based magnetometer measurements during the first hour of tsunami and good agreements are found between modelled and observed anomalies at first within 6 min from the tsunami origin the simulated wind anomaly at 250 km altitude and tec anomaly appear as the dipole shaped disturbances around the epicentre then as the concentric circular wave fronts radially moving away from the epicentre with the horizontal velocity 800 m s 1 after 12 min followed by the slow moving horizontal velocity 250 m s 1 wave disturbance after 30 min the detailed vertical horizontal propagation characteristics suggest that the anomalies appear before and after 30 min are associated with the acoustic and gravity waves respectively similar propagation characteristics are found from the gps tec and magnetic measurements presented here and also reported from recent studies the modelled magnetic anomaly in the f region ionosphere is found to have similar temporal variations with respect to the epicentre distance as that of the magnetic anomaly registered from the ground based magnetometers the high frequency component 10 min of the simulated wind tec and magnetic anomalies in the f region develops within 6 7 min after the initiation of the tsunami suggesting the importance of monitoring the high frequency atmospheric ionospheric anomalies for the early warning these anomalies are found to maximize across the epicentre in the direction opposite to the tsunami propagation suggesting that the large atmospheric ionospheric disturbances are excited in the region where tsunami does not travel

ionospheric anomalies immediately before mw7 0 8 0 earthquakes recent observations suggested that ionospheric anomalies appear immediately before large earthquakes with moment magnitudes mw of 8 2 or more do similar phenomena precede smaller earthquakes here we answer this question by analyzing vertical total electron contents vtec observed near the epicenters before and after 32 earthquakes with mw7 0 8 0 using data from nearby global navigation satellite systems stations to detect anomalies we defined the reference curves to fit the observed vtec and considered the departure from the curves as anomalies in estimating the reference curves we excluded time windows prescribed for individual earthquakes considering mw possibly affected by earthquakes we validated the method using synthetic vtec data assuming both preseismic coseismic and postseismic anomalies out of the 32 mw7 0 8 0 earthquakes eight earthquakes showed possible preseismic anomalies starting 10 20 min before earthquakes for earthquakes of this mw range we can observe preseismic ionospheric changes probably when the background vtec is large say 50 tecu total electron content unit 1 tecu 1016 el m 2 or more

apparent ionospheric total electron content variations prior to major earthquakes due to electric fields created by tectonic stresses growing evidence for ionospheric signatures of impending earthquakes comes from electron content measurements along slanted paths from gps satellites to multiple ground stations located up to 500 km away from the epicenters these slant total electron content stec measurements deviate from the classic u shape pattern starting about 40 min to over an hour before major earthquakes unlike other naturally occurring stec fluctuations at midlatitudes we show here that these earthquake induced deviations are simultaneous over a wide geographical area and do not propagate thereby indicating a ground based origin prior to the 11 march 2011 tohoku oki earthquake mw 9 0 the deviations were as much as 10 of the undisturbed stec we argue that such deviations must be due to an electric field forced rise or fall of the main ionosphere with little change in the vertical electron density profile hence apparent is used in the title we show how stress related underground electric fields penetrate to 80 km altitude above which penetration to the main ionosphere easily occurs with magnitudes high enough to create stec variations comparable to those observed since many thousands of gps receivers exist worldwide our theory suggests the possibility of early warning systems that could provide 10 to 20 min notice prior to large earthquakes after allowing time for signal processing this theory for prequake induced stec fluctuations also explains the ground based ulf magnetic field data acquired by fraser smith et al 40 min prior to the loma prieta earthquake

spacecraft observations of electromagnetic perturbations connected with seismic activity 1 results of a statistical study of intensity of vlf electromagnetic waves observed in the vicinity of earthquakes are presented a unique set of data obtained by the micro satellite demeter altitude of about 700 km nearly sun synchronous orbit and a robust two step data processing has been used in the first step all the measured data are used to construct a map of electromagnetic emissions containing a statistical description of wave intensity at a given point of the satellite orbit under given conditions in the second step the intensity measured close to earthquakes is analyzed using the statistical distribution of background intensity obtained in the first step the changes of wave intensity caused by seismic activity are investigated and their statistical significance is evaluated altogether more than 2 5 years of satellite data have been analyzed and about 9000 earthquakes with magnitudes larger than or equal to 4 8 that occurred all over the world during the analyzed period have been included in the study it is shown that during the night there is a statistically significant decrease by 4 6 db of the measured wave intensity shortly 0 4 hours before an intense surface depth less than or equal to 40 km earthquake

preearthquake anomalous ionospheric signatures observed at low mid latitude indian station delhi during the year 2015 to early 2016 preliminary results we have analyzed five major earthquake events measuring greater than 6 on richter scale m 6 that occurred during the year 2015 to early 2016 affecting indian region ionosphere using f 2 layer critical parameters f o f 2 h m f 2 obtained using digisonde from a low mid latitude indian station delhi 28 6 degrees n 77 2 degrees e 19 2 degrees n geomagnetic latitude 42 4 degrees n dip normal day to day variability occurring in ionosphere is segregated by calculating f 2 layer critical frequency and peak height variations delta f o f 2 h m f 2 from the normal quiet time behavior apart from computing interquartile range we find that the ionospheric f 2 region across delhi by and large shows some significant perturbations 3 4 days prior to these earthquake events resulting in a large peak electron density variation of similar to 200 these observed perturbations indicate towards a possibility of seismo ionospheric coupling as the solar and geomagnetic indices were normally quiet and stable during the period of these events it was also observed that the precursory effect of earthquake was predominantly seen even outside the earthquake preparation zone as given by dobrovolsky et al 1979 the thermosphere neutral composition o n 2 as observed by global ultraviolet imager across delhi during these earthquake events does not show any marked variation further the effect of earthquake events on ionospheric peak electron density is compared to the lower atmosphere meteorological phenomenon of 2015 sudden stratospheric warming event

m w dependence of the preseismic ionospheric electron enhancements ionospheric electron enhancement was reported to have occurred 40 min before the 2011 tohoku oki mw9 0 earthquake japan by observing total electron content tec with global navigation satellite systems receivers their reality has been repeatedly questioned due mainly to the ambiguity in the derivation of the reference tec curves from which anomalies are defined here we propose a numerical approach based on akaike s information criterion to detect positive breaks sudden increase of tec rate in the vertical tec time series without using reference curves we demonstrate that such breaks are detected 25 80 min before the eight recent large earthquakes with moment magnitudes mw of 8 2 9 2 the amounts of precursory rate changes were found to depend upon background tec as well as mw the precursor times also showed mw dependence and the precursors of intraplate earthquakes tend to start earlier than interplate earthquakes we also performed the same analyses during periods without earthquakes to evaluate the usefulness of tec observations for short term earthquake prediction

effects of rayleigh taylor instability and ionospheric plasma bubbles on the global navigation satellite system signal abstract ionospheric disturbances induced by various natural e g earthquakes volcanic eruption thunderstorms meteorite showers solar eclipses or anthropogenic e g nuclear explosions launching of space shuttles processes can be detected through change in total electron content tec in the f layer these ionospheric perturbations can be captured by worldwide expanding geodetic gnss networks mainly during the day time when the solar radiation ionizes the air molecules however during post sunset period strong ionospheric irregularities known as equatorial plasma bubbles epbs develop due to the classical configuration for the rayleigh taylor r t instability that diffracts navigation and communication signals here we use various instances of ionospheric disturbances triggered by natural processes e g earthquakes and volcanic eruption in the recent decade to investigate the spatiotemporal and seasonal effects of ionospheric irregularities on the gnss signals our study suggests that in the low latitudinal region e g sumatra mexico such ionospheric irregularities can mask the ionospheric perturbations due to the higher production rate of epbs hence detection of such co seismic tec anomaly becomes difficult however in the high latitudinal region e g iceland alaska due to the lower production rate of epbs ambient ionospheric irregularities are insignificant and hence coseismic tec anomalies can be captured even during night time we argue that the production rate of epbs further depends upon seasonal and longitudinal parameters on the globe

the ionospheric anomalies prior to the m9 0 tohoku oki earthquake the gps total electron content tec data were used to investigate the ionospheric abnormal behaviors prior to the 2011 tohoku oki earthquake the observations show a significant enhancement in tec on march 8 2011 and during the same period the solar activity also has a large increase both an empirical model and a theoretical model were used to check whether the tec anomalies were entirely contributed by the increase in solar radiation the comparison between the observations and the simulation results shows that only the solar radiation enhancement was not enough to produce the observed significant tec enhancement it means that some additional mechanisms such as the per earthquake ionospheric disturbance or the geomagnetic activities may play a significant role in the significant tec enhancement on march 8 the temporal spatial distribution of the extreme tec enhancement within 30 days before the earthquake was particularly pursued it is found that the extreme enhancement was persistently located in the region adjacent to the epicenter and the magnetic conjugate point for a long time of 16 h in addition a geomagnetic disturbance with kp 4 occurred on march 7 therefore the significant tec enhancement on march 8 might be related to the m9 0 tohoku oki earthquake and the geomagnetic disturbance

chemostratigraphic reconstruction of biofacies molecular evidence linking cyst forming dinoflagellates with pre triassic ancestors new data from numerous detailed mass spectrometric studies have detected triaromatic dinosteroids in precambrian to cenozoic rock samples triaromatic dinosteroids are organic geochemicals derived from dinosterols compounds known in modern organisms to be the nearly exclusive widely occurring products of dinoflagellates we observed the ubiquitous occurrence of these dinosteroids in 49 late triassic through cretaceous marine source rocks and the absence of them in 13 permian carboniferous source rocks synergistic with the dinoflagellate cyst record however finding dinosteroids in lower paleozoic and precambrian strata presents challenging results for molecular paleontologists evolutionary biologists palynologists and especially for those concerned with the food web at various times of biological crisis other than the few species known as parasites and symbionts many other dinoflagellate species are important as primary producers the presence of precambrian to devonian triaromatic dinosteroids gives chemostratigraphic evidence of dinoflagellates or other organisms with similar chemosynthetic capabilities in rocks significantly older than the oldest undisputed dinoflagellate fossils dinoflagellate cysts from the middle triassic 240 ma and older than the putative silurian 420 ma dinocyst arpylorus antiquus calandra sargent from tunisia this systematic chemostratigraphic approach can shed light not only on lineages of dinoflagellates and their precursors but potentially on many other lineages especially bacteria algae plants and possibly some metazoans

statistical evidences of seismo ionospheric precursors applying receiver operating characteristic roc curve on the gps total electron content in china abstract evidence of the seismo ionospheric precursor sip is reported by statistically investigating the relationship between the total electron content tec in global ionosphere map gim and 56 m 6 0 earthquakes during 1998 2013 in china a median based method together with the z test is employed to examine the tec variations 30 days before and after the earthquake it is found that the tec significantly decreases 0600 1000 lt 1 6 days before the earthquake and anomalously increases in 3 time periods of 1300 1700 lt 12 15 days 0000 0500 lt 15 17 days and 0500 0900 lt 22 28 days before the earthquake the receiver operating characteristic roc curve is then used to evaluate the efficiency of tec for predicting m 6 0 earthquakes in china during a specified time period statistical results suggest that the sip is the significant tec reduction in the morning period of 0600 1000 lt the sip is further confirmed since the area under the roc curve is positively associated with the earthquake magnitude

detection and modeling of rayleigh wave induced patterns in the ionosphere 1 global positioning system gps allows the detection of ionospheric disturbances associated with the vertical displacements of most of the major shallow seismic events we describe a method to model the time and space distributions of rayleigh wave induced total electron content tec patterns detected by a dense gps array we highlight the conditions for which a part of the ionospheric pattern can be directly measured at teleseismic distance and above the epicenter in particular a satellite elevation angle lower than 40 is a favorable condition to detect rayleigh wave induced ionospheric waves the coupling between the solid earth and its atmosphere is modeled by computing the normal modes of the solid earth atmosphere system we show the dependency of the coupling efficiency on various atmospheric conditions by summation of the normal modes we model the atmospheric perturbation triggered by a given earthquake this shows that a part of the observation is a rayleigh induced radiation pattern and therefore characteristic of the seismic rupture through atmosphere ionosphere coupling we model the ionospheric perturbation after the description of the local geomagnetic field anisotropic effects we show how the observation geometry is strongly affecting the radiation pattern this study deals with the related data for two earthquakes with far field and near field observations using the japanese gps network geonet after the 12 may 2008 wenchuan earthquake china and after the 25 september 2003 tokachi oki earthquake japan respectively waveforms and patterns are compared with the observed tec perturbations providing a new step toward the use of ionospheric data in seismological applications

volcanism and metallogenesis of axial and off axial structures on the east pacific rise near 13 degrees n a fast spreading segment 12 cm yr super 1 of the east pacific rise near 12 degrees 50 n explored in detail by surface ship and manned submersible displays intense hydrothermal activity the rise crest about 1 500 m in width with a regional depth of 2 600 m is occupied at its center by an axial graben 1 3 titania alkali enriched olivine ti k basalts with high tio 2 1 4 and high alkali content na 2 o 3 0 k 2 o 0 3 occur on the southeastern seamount the fractionated tholeiites are believed to have been derived from primitive melts during differentiation which took place within a magma reservoir asymmetrical with respect to the axis of the graben which supplied both axial and off axial lava flows the ti k enriched basalts are believed to have been produced from an alkali enriched magmatic source

traveling ionospheric disturbances propagating ahead of the tohoku oki tsunami a case study we document two kinds of traveling ionospheric disturbances namely ctids co tsunami traveling ionospheric disturbances and atids ahead of tsunami traveling ionospheric disturbances related to the tohoku oki tsunami of 2011 march 11 they are referred to the disturbances that remain behind and ahead of the principal tsunami wave front respectively we first note their presence in a numerical experiment performed using a simulation code coupling the tsunami atmosphere and ionosphere this code uses the tsunami wavefield as an input and simulates acoustic gravity waves agws in the atmosphere and tids in the form of total electron content tec disturbance in the ionosphere the simulated tec reveals the excitation of ctids at about 2 tecu and atids at about 1 tecu representing up to 5 per cent disturbance over the ambient electron density and they arise from the dissipation of agws in the thermosphere a novel outcome is that during the tsunami passage between 6 and 12 of epicentral distance strong atids arrive 20 60 min ahead of the tsunami wave front covering 3 10 of distance from the tsunami location simulation results are compared with the far field observations using gnss satellites and confirm that atids are the first detected tec maximum occurring 20 60 min ahead of the tsunami arrival our simulation also confirms the presence of largest tec maximum representing ctids 10 20 min after the first tsunami wave atids reported in this study have characteristics that can be potentially used for the early warning of the tsunami

gps detection of ionospheric perturbations following the january 17 1994 northridge earthquake sources such as atmospheric or buried explosions and shallow earthquakes producing strong vertical ground displacements are known to produce pressure waves that propagate at infrasonic speeds in the atmosphere at ionospheric altitudes low frequency acoustic waves are coupled to ionospheric gravity waves and induce variations in the ionospheric electron density using global positioning system gps data recorded by the permanent gps network operating in southern california we computed ionospheric electron content time series for several days preceding and following the january 17 1994 mw 6 7 northridge earthquake we observe an anomalous signal beginning several minutes after the earthquake with time delays that increase with distance from the epicenter the signal frequency and phase velocity are consistent with results from numerical models of atmospheric ionospheric acoustic gravity waves excited by seismic sources as well as previous electromagnetic sounding results we believe that these perturbations are caused by the ionospheric response to the strong ground displacement associated with the northridge earthquake

recent progress in ionospheric earthquake precursor study in china a brief review abstract the study of ionospheric anomaly variation before large earthquakes has attracted the attention of geophysicists for many years this is primarily because ionospheric anomaly variation has been considered to constitute one possible method to identify earthquake precursors since china covers several major earthquake zones it is critical for chinese scientists to study possible ionospheric earthquake precursors in this report we provide a brief summary of recent progress in the study of ionospheric earthquake precursors mainly from chinese mainland researchers as well as some other scientists this report focuses on 1 some case studies of ionospheric abnormal behaviors before some great earthquakes around the world e g m7 9 wenchuan earthquake m9 0 tohoku oki earthquake m7 0 haiti earthquake and 2 some statistical characteristics of ionospheric anomalies before earthquakes including their temporal and spatial distributions and the relationship with the forthcoming earthquake the above mentioned studies may provide some new and beneficial insights for the future study of ionospheric earthquake precursors

chemical and thermal constraints on focussed fluid flow in the lower oceanic crust the mechanism of heat extraction from the lower oceanic crust near the ridge axis is poorly constrained despite its importance for understanding both the process of accretion of the plutonic complex and the mass fluxes associated with ridge hydrothermal systems we have investigated the role of zones of focussed fluid flow in the plutonic complex of the oman ophiolite in the near axis cooling of the oceanic crust lineaments identified on aerial photographs that occur at 1 km spacing show evidence for extensive hydrothermal fluid flow through regions 10 to 50 m wide fluid flow is initiated in these regions at 800 c and continues at least into the lower greenschist facies strontium isotope analyses indicate that the fluid flux through these zones is sufficient to transport a metasomatic front from the base of the sheeted dike complex to close to the moho computed minimum fluid fluxes to transport a metasomatic front through the focussed fluid flow zones are 1x108 kgm2 modeling of diffusive exchange of calcium from olivine to clinopyroxene indicates enhanced cooling rates adjacent to the focussed fluid flow zones heat fluxes estimated from the enhanced cooling rates are broadly consistent with the fluid fluxes determined from modeling the sr isotopic composition of samples from the focussed fluid flow zones the combination of independent estimates of the fluid and heat fluxes such as these can provide more rigorous constraints on the thermal history than either approach used in isolation our results show that focussed fluid flow could play a major role in the cooling in the lower oceanic crust significant focussed fluid flow in the lower oceanic crust has important implications for predicting the total mass flux associated with hydrothermal circulation at mid ocean ridges this is because fluids flowing through channels become chemically rock buffered at smaller fluid fluxes than those flowing pervasively through a rock mass thus if focussed fluid flow is an important mechanism of heat loss from the lower oceanic crust the chemical fluxes from ridge hydrothermal systems into the oceans may be smaller than currently thought

preseismic ionospheric anomalies detected before the 2016 kumamoto earthquake on 15 april 2016 the kumamoto earthquake mw 7 3 occurred in japan with no warning signals global navigation satellite system gnss receivers provide useful information on disturbances in the ionosphere by calculating the changes in total electron content tec which is the number of electrons in the ionosphere here we show our recently proposed correlation analysis of tec data which can detect the preseismic ionospheric anomalies from the public gnss data our method detected the ionospheric anomaly several tens of minutes before the 2016 kumamoto earthquake near its epicenter furthermore we gave an indicator to distinguish between the preseismic tec anomalies and the medium scale traveling ionospheric disturbances mstids by calculating the anomalous area rates these results support the hypothesis for existence of the preceding phenomena before large earthquakes

challenges in the detection of ionospheric pre earthquake total electron content anomalies peta for earthquake forewarning various studies have investigated the link between seismic activity and ionospheric precursory phenomena many of these retrospective case studies have supported the existence of pre earthquake ionospheric anomalies by examining past earthquake events using a variety of analytical methods based on existing methodologies however the conversion of a retrospective analysis to a prospective forewarning scenario is not a straightforward process the obstacles to its potential adoption stem mainly from assumptions made during data analysis and interpretation in this study several parameters pertaining to existing approaches for the detection of these ionospheric anomalies are highlighted and discussed in particular ionosphere total electron content tec a detailed examination is conducted to understand the roles that each of these parameters play in the detection process and the consequent difficulties when adopting them in a prospective analysis these issues include accounting for variations in ionosphere characteristics owing to different measurement platforms e g ground and space based observations and statistical methods e g standard deviation envelopes used in detecting anomalies furthermore the necessity of excluding space weather contributions in the underlying tec fluctuations poses a challenge in determining the validity of observed ionospheric anomalies the notion of an earthquake preparation zone is also evaluated in the context of the ionosphere along with its implications in a forewarning scenario these issues need to be addressed in current research in order to enable its possible application in earthquake forewarning

coseismic ionospheric disturbance of the large strike slip earthquakes in north sumatra in 2012 mw dependence of the disturbance amplitudes we studied ionospheric responses to the 2012 april 11 mw8 6 north sumatra earthquake using total electron content tec measurements with the regional global navigation satellite system gnss network this earthquake ruptured the oceanic lithosphere off the indian ocean coast of north sumatra and is known as the largest strike slip earthquake ever recorded coseismic ionospheric disturbances cid with rapid tec enhancement of a few tec units propagated northward with a speed of acoustic waves 1 km s resonant atmospheric oscillation with a frequency 4 mhz have been found as monochromatic oscillation of tec lasting for an hour after the main shock and the largest aftershock we compared cid amplitudes of 21 earthquakes worldwide with moment magnitudes mw 6 6 9 2 they roughly obeyed a law such that cid amplitude increases by two orders of magnitude for the mw increase of three the 2012 north sumatra earthquakes slightly deviated negatively from the trend possibly reflecting their strike slip mechanisms i e small vertical crustal movements for their magnitudes

on the co seismic ionospheric disturbances cids in the rapid run ionosonde observations over allahabad following mw 7 8 nepal earthquake on april 25 2015

manifestations of hydrothermal discharge from young abyssal hills on the fast spreading east pacific rise flank spectacular black smokers along the mid ocean ridge crest represent a small fraction of total hydrothermal heat loss from ocean lithosphere previous models of measured heat flow suggest that 40 50 of oceanic hydrothermal heat and fluid flux is from young seafloor 0 1 5 ma on mid ocean ridge flanks despite evidence that ridge flank hydrothermal flux affects crustal properties ocean chemistry and the deep sea biosphere few ridge flank vent sites have been discovered we describe the first known seafloor expressions of hydrothermal discharge from tectonically formed abyssal hills flanking a fast spreading ridge seafloor manifestations of fluid venting from two young east pacific rise abyssal hills 0 1 ma at 10 20 n 103 33 2 w 0 5 ma at 9 27 n 104 32 3 w include fault scarp hydrothermal mineralization and macrofauna fault scarp flocculations containing hyperthermophilic microbes and hilltop sediment mounds and craters possibly created by fluid expulsion these visible features can be exploited for hydrothermal exploration of the vast abyssal hill terrain flanking the mid ocean ridge and for access to the subseafloor biosphere petrologic evidence suggests that abyssal hills undergo repeated episodes of transitory fluid discharge possibly linked to seismic events and that fluid exit temperatures can be briefly high enough to transport copper 250 c

secular and environmental constraints on the occurrence of dinosterane in sediments abstract the distribution patterns of sedimentary a ring methylated steranes have changed markedly over geological time although dinosterane and its isomer 24 ethyl 4 methylcholestane have been tentatively identified in three proterozoic rock units they are either not detectable or occur in low abundance relative to 3 methyl steranes throughout most of the palaeozoic between permian and middle triassic times 260 220 ma ago 4 methyl sterane abundances in marine sediments increased markedly the presence of dinosterane in some middle triassic marine sediments is contemporaneous with the appearance of fossil cysts of uncontested dinoflagellate affinity 4 methyl steranes including dinosterane or their precursor sterenes and sterols then show a continuous presence often in high abundance in marine sediments from the late triassic through to the present day assemblages of 4 methyl steranes and their precursors but with dinosterane absent or in low relative abundance are often the predominant steroids in lacustrine sediments in the cainozoic dinosterane appears to arise predominantly from marine dinoflagellates and as a consequence is a useful biological marker for mesozoic and cainozoic marine organic matter the isomer 24 ethyl 4 methylcholestane is likely to have multiple origins although its very high abundance in tertiary lacustrine sediments and oils compared to older materials suggests that dinoflagellates could also be the source in these cases

preseismic ionospheric electron enhancements revisited 1 possible enhancement of ionospheric total electron content tec immediately before the 2011 tohoku oki earthquake mw9 0 has been reported by heki 2011 critical responses to it often come in two stages they first doubt the enhancement itself and attribute it to an artifact second when they accept the enhancement they doubt the significance of the enhancement among natural variability of space weather origin for example kamogawa and kakinami 2013 attributed the enhancement to an artifact falsely detected by the combined effect of the highly variable tec under active geomagnetic condition and the occurrence of a tsunamigenic ionospheric hole here we closely examine the time series of vertical tec before and after the 2011 tohoku oki earthquake we first demonstrate that the tsunami did not make an ionospheric hole and next confirm the reality of the enhancement using data of two other sensors ionosonde and magnetometers the amplitude of the preseismic tec enhancement is within the natural variability and its snapshot resembles to large scale traveling ionospheric disturbances however distinction could be made by examining their propagation properties similar tec anomalies occurred before all the m 8 5 earthquakes in this century suggesting their seismic origin

plate tectonics piecing together rifts earth s crust is formed where tectonic plates rift apart and upwelling magma solidifies disparate observations from rifts beneath the oceans and on land provide insights into the dynamics of rifting and opportunities for synthesis

surface water changes recorded in late quaternary marine sediments of the ulleung basin east sea japan sea abstract in order to reconstruct past sea surface temperature sst and salinity sss in the east sea japan sea this study investigated the oxygen isotopic composition of the planktonic foraminifer globigerina bulloides and the degree of unsaturation of alkenones in bulk sediments of core ty99pc18 recovered from the southeastern part of the ulleung basin east sea between 11 and 15 cal kyr bp the surface waters were 2 4 c cooler than today the surface salinity was 12 lower during 14 15 cal kyr bp than today then increased after 14 cal kyr bp but remained lower during 11 14 cal kyr bp than present values between 14 and 15 cal kyr bp the northern east china sea surface waters were likely to be greatly diluted by fresh water discharge from land and coastal waters would have flowed into the east sea through the korea strait during 11 14 cal kyr bp the southern input waters most likely changed from fresh water influenced coastal water to open ocean water the increased salinity probably enhanced active deep water convection at that time during 7 11 cal kyr bp the surface waters were warmer 1 c and more saline 1 3 than today indicating that the warm and saline kuroshio current became stronger and that one of its branches flowed into the east sea during this time interval the cold 2 c and less saline waters 1 at 3 6 cal kyr bp may indicate a suppression of the kuroshio current the sst and sss values are close to the present values at about 3 cal kyr bp suggesting that the physiological conditions of the east sea approached that of the present at this time

detecting multiple surface waves excited by the 2011 tohoku oki earthquake from geonet observations abstract multiple surface waves circling the earth excited by the 2011 m w 9 0 tohoku oki earthquake were well recorded by both global and regional broadband bb seismometer networks in this study we explore the ability of kinematic solutions of global positioning system gps observations from geonet to reveal the phases of multiple surface waves even though multipath effects and common mode errors are not reduced the wave packages of g 2 g 3 of love waves and r 2 r 3 of rayleigh waves are clearly identified from the raw gps displacement time series in the 100 500 s periods which show great coherency with bb seismograms in both amplitude and time the arrival times of these wave packages tally with the synthetic value by the group velocities from the global dispersion model we consider that kinematic solutions of continuous gps measurement can act as a supplementary tool for studying global surface wave dispersion

2010 maule earthquake slip correlates with pre seismic locking of andean subduction zone analysis of seismic data and global positioning system gps observations from the region around the site of the recent magnitude 8 8 maule earthquake in chile have been combined with modelling of the andean subduction zone to build up a detailed image of the event the earthquake occurred at a seismic gap part of the fault that has not experienced a major earthquake since 1835 and it seems to have released most of the stress accumulated since that time the observations suggest that coseismic slip heterogeneity at the scale of single asperities and therefore the seismic potential of future great earthquakes might be anticipated by geodetic observations these authors show evidence for a high coherence between the slip distribution inferred from the 2010 maule earthquake chile and the patchwork of interseismic locking distribution derived from global positioning system observations during the previous decade their work suggests that coseismic slip heterogeneity at the scale of single asperities should indicate the seismic potential of future earthquakes which thus might be anticipated by geodetic observations the magnitude 8 8 maule chile earthquake of 27 february 2010 ruptured a segment of the andean subduction zone megathrust that has been suspected to be of high seismic potential1 2 3 4 5 6 it is the largest earthquake to rupture a mature seismic gap in a subduction zone that has been monitored with a dense space geodetic network before the event this provides an image of the pre seismically locked state of the plate interface of unprecedentedly high resolution allowing for an assessment of the spatial correlation of interseismic locking with coseismic slip pre seismic locking might be used to anticipate future ruptures in many seismic gaps6 7 8 9 10 11 12 given the fundamental assumption that locking and slip are similar this hypothesis however could not be tested without the occurrence of the first gap filling earthquake here we show evidence that the 2010 maule earthquake slip distribution correlates closely with the patchwork of interseismic locking distribution as derived by inversion of global positioning system gps observations during the previous decade the earthquake nucleated in a region of high locking gradient and released most of the stresses accumulated in the area since the last major event in 1835 two regions of high seismic slip asperities appeared to be nearly fully locked before the earthquake between these asperities the rupture bridged a zone that was creeping interseismically with consistently low coseismic slip the rupture stopped in areas that were highly locked before the earthquake but where pre stress had been significantly reduced by overlapping twentieth century earthquakes our work suggests that coseismic slip heterogeneity at the scale of single asperities should indicate the seismic potential of future great earthquakes which thus might be anticipated by geodetic observations

subionospheric vlf signal perturbations possibly related to earthquakes a likely vlf subionospheric signal effect related to seismic activity was first reported by hayakawa et al 1996a b in association with the great kobe earthquake we have analyzed similar data during periods around 10 other great earthquakes magnitude m 6 in order to understand the main features of such an effect the following characteristics emerged from our analysis the effect appears as a transient oscillation with a 5 to 10 day period which is initiated a few days before a large earthquake and decays over a few days to weeks after it it is mainly related to crustal earthquakes it appears when resonant atmospheric oscillations with periods in a range of 5 11 days exist before the earthquake the seismic influence on the vlf signal is probably explained by the generation of long period gravity waves during the earthquake process and their intensification at heights of 70 90 km

coseismic crustal deformation from the 1994 hokkaido toho oki earthquake monitored by a nationwide continuous gps array in japan using a brand new nationwide continuous gps array we monitored coseismic displacements from the october 4 1994 hokkaido toho oki kurile islands earthquake mjma 8 1 based on 2 week time series of site coordinates of 21 gps stations we present a coseismic deformation field of whole hokkaido within 1 cm precision for example the station at nemuro 170 km west of the epicenter moved 44 cm to the east and subsided 10 cm even stations in southern hokkaido 600 km apart from the epicenter moved a few cm horizontally toward the epicenter we compare the gps result with displacements calculated from two preliminary models assuming fault planes parallel or perpendicular to the kurile trench since the observed were far field displacements on land both models can explain the gps result

detection of ruptures of andaman fault segments in the 2004 great sumatra earthquake with coseismic ionospheric disturbances 1 near field coseismic perturbations of ionospheric total electron content tec caused by direct acoustic waves from focal regions can be observed with global positioning system gps they appear 10 15 min after the earthquake with typical periods of 4 5 min and propagate as fast as 1 km s toward directions allowed by ambient geomagnetic fields ionospheric disturbance associated with the 2004 december 26 great sumatra andaman earthquake was recorded with nine continuous gps receiving stations in indonesia and thailand here we explore the possibility to constrain the rupture process of the earthquake with the observed ionospheric disturbances we assumed linearly distributed point sources along the zone of coseismic uplift extending 1300 km from sumatra to the andaman islands that excited acoustic waves sequentially as the rupture propagate northward by 2 5 km s tec variations for several satellite receiver pairs were synthesized by simulating the propagation of acoustic waves from the ground to the ionosphere and by integrating the tec perturbations at intersections of line of sights and the ray paths the tec perturbations from individual point sources were combined using realistic ratios and the total disturbances were compared with the observed signals prescribed ratios based on geodetically inferred coseismic uplifts reproduced the observed signals fairly well similar calculation using a rupture propagation speed of 1 7 km s degraded the fit suppression of acoustic waves from the segments north of the nicobar islands also resulted in a poor fit which suggests that ruptures in the northern half of the fault were slow enough to be overlooked in short period seismograms but fast enough to excite atmospheric acoustic waves coseismic ionospheric disturbance could serve as a new indicator of faulting sensitive to ruptures with timescale up to 4 5 min

gradual reduction in ionospheric f 2 region before the 2013 lushan earthquake contributed to the forthcoming earthquake or solar activity ionospheric anomalies before earthquakes during geomagnetic quiet conditions have been extensively discussed due to the importance of earthquake prediction however because of the high variability of ionosphere a real caution should be adopted before attributing the observations to seismo ionospheric precursors sips in an investigation of contradictory results in ionospheric variation before 2013 lushan earthquake we examine the ionospheric variation versus solar activity in order to assess the influence of solar activity of 27 day periodicity on ionospheric variation a quadratic regression model is developed by using the data of f2 layer critical frequency fof2 in april of 2008 2014 using the model ionospheric variation before the 2013 lushan earthquake is analyzed the results show that fof2 was strongly correlated with solar activity index f10 7 and had a low correlation with the remaining by eliminating the contribution of solar radiation which indicates that the gradual reduction in fof2 before the earthquake was contributed to the variation of solar radiation rather than the forthcoming earthquake

lithosphere atmosphere ionosphere coupling laic model an unified concept for earthquake precursors validation abstract the paper presents a conception of complex multidisciplinary approach to the problem of clarification the nature of short term earthquake precursors observed in atmosphere atmospheric electricity and in ionosphere and magnetosphere our approach is based on the most fundamental principles of tectonics giving understanding that earthquake is an ultimate result of relative movement of tectonic plates and blocks of different sizes different kind of gases methane helium hydrogen and carbon dioxide leaking from the crust can serve as carrier gases for radon including underwater seismically active faults radon action on atmospheric gases is similar to the cosmic rays effects in upper layers of atmosphere it is the air ionization and formation by ions the nucleus of water condensation condensation of water vapor is accompanied by the latent heat exhalation is the main cause for observing atmospheric thermal anomalies formation of large ion clusters changes the conductivity of boundary layer of atmosphere and parameters of the global electric circuit over the active tectonic faults variations of atmospheric electricity are the main source of ionospheric anomalies over seismically active areas lithosphere atmosphere ionosphere coupling laic model can explain most of these events as a synergy between different ground surface atmosphere and ionosphere processes and anomalous variations which are usually named as short term earthquake precursors a newly developed approach of interdisciplinary space terrestrial framework istf can provide also a verification of these precursory processes in seismically active regions the main outcome of this paper is the unified concept for systematic validation of different types of earthquake precursors united by physical basis in one common theory

regard a new gnss based real time finite fault modeling system for geonet the short period seismometer based magnitude saturation problem especially for events with magnitude 8 can be improved by a real time global navigation satellite system gnss positioning technique which has enabled rapid estimation of a finite fault model for a large earthquake without any saturation a new real time fault modeling system based on the gnss earth observation network geonet is developed and is under experimental operation in japan in this paper we present the newly developed system regard the real time geonet analysis system for rapid deformation monitoring which consists of real time gnss positioning automatic detection of coseismic displacement by the event and quasi real time finite fault model inversion routines the performance of the automatic event detection system is tested through experimental real time operation based on geonet data for two months furthermore we also test the reliability of the finite fault model inversion routines using real raw gnss data observed for past large earthquakes the 2003 tokachi oki earthquake moment magnitude mw 8 3 the 2011 tohoku earthquake mw 9 0 and the 2011 off ibaraki earthquake mw 7 7 a simulated 1707 hoei type nankai trough earthquake mw 8 7 is also tested the real time experimental operation shows that real time gnss positioning is precise enough to detect all the tested earthquakes and the inversion results demonstrate that the regard can reliably estimate the earthquake size and its extent within 3 min after the origin time these results suggest that the regard system will complement the seismometer based magnitude determination system

ionospheric tec modelling for earthquakes precursors from gnss data abstract in present study we measured the total electron content tec variation in the ionosphere from global navigation satellite system gnss data which might have been induced by earthquakes in the himalayan region the results were analysed with other inducing factors geomagnetic storm and solar flare affecting tec in order to constraint the causative factor the study has been performed to understand a relationship between ionospheric electron content and earthquakes occurrences with special emphasis on himalayan region and provides information on spatio temporal variation of tec from gnss observation stations vis a vis prominent earthquakes of the region the results indicate that the ground based gnss gps observations show the deviation in vertical total electron content vtec in ionosphere few days prior to the seismic event as evident from our two continuously operating reference stations cors as well as from cors of unavco data centre ionospheric perturbation has also been observed in case of low magnitude earthquakes mw 4 9 in present study whenever recording station lies very close to the epicentre tec variation is found to increase as the epicentre distances decreases in case of mw 7 8 2015 nepal earthquake the tec variation is found to increase by 15 20 tec unit recorded at station separated by 60 km apart this may provide us the avenue for epicentre detection as tec concentration was found to increase as we move closer to the epicentre tec variations mostly high tec have been observed during a period of 0 8 days prior to 4 earthquakes 1st april 2015 pipalkoti earthquake 4 9mw 25th april 2015 nepal earthquake 7 8mw 26 april 2015 6 7mw and 12th may 2015 7 3mw nepal earthquakes significant low tec values were also observed before 13 14 days prior to first two earthquake events overall the study has revealed that low tec followed by couple of high tec values correlate well with the seismic events in himalayan region

a long term seismic quiescence before the 2004 sumatra mw 9 1 earthquake the 2004 sumatra m w 9 1 earthquake was preceded by a seismic quiescence that began 13 years before the mainshock an earthquake catalog created by the international seismological centre is analyzed in the study area 80 110 e 10 s 20 n between 1964 and 2004 including 1153 earthquakes shallower than 100 km with body wave magnitude of 5 0 m b 6 7 a detailed analysis of the earthquake catalog using a gridding technique zmap shows the quiescent area is located between 3 and 6 n which covers the southeastern part of the focal area including the rupture initiation point of the 2004 sumatra earthquake the observed spatial pattern of quiescence can be explained by stress perturbation due to a long term slow slip located on the deeper edge of the mainshock fault which is predicted by a numerical simulation based on a laboratory derived friction law although the quiescence is not significant statistically it may still be considered unlikely that such an anomalous quiescence would occur at almost the same time and location as other long term anomalies reported in the previous studies including decreases in b value and tidal triggering

temporal and spatial patterns of biological community development at nascent deep sea hydrothermal vents 9 50 n east pacific rise the april 1991 discovery of newly formed hydrothermal vents in areas of recent volcanic eruption between 9 45 n and 9 52 n on the east pacific rise provided a unique opportunity to follow temporal changes in biological community structure from the birth of numerous deep sea hydrothermal vents in march l992 dsv alvin was used to deploy an on bottom observatory the biologic geologic transect to monitor faunal succession along a 1 37 km segment of the axial summit caldera between 9 49 61 n and 9 50 36 n depth 2520 m photo and videographic documentation of megafaunal colonization and chemical analyses of diffuse hydrothermal fluids associated with many of these developing communities within the transect were performed in march 1992 december 1993 october 1994 and november 1995 photographic and chemical time series analyses revealed the following sequence of events in low temperature venting areas 1 immediately following the 1991 eruption hydrogen sulfide and iron concentrations in diffuse fluids were extremely high 1 mmol kg 1 and microbially derived material blanketed active areas of venting in the form of thick microbial mats 2 mobile vent fauna e g amphipods copepods octopods and galatheid and brachyuran crabs and non vent fauna e g nematocarcinid shrimp proliferated in response to this increased biological production 3 within 1 yr of the eruption areal coverage of microbial mat was reduced by 60 and individuals of the vestimentiferan tube worm tevnia jerichonana settled gregariously in areas where diffuse flow was most intense 4 two years after the eruption maximum levels of h2s decreased by almost half from 1 90 to 0 97 mmol kg 1 and dense thickets of the vestimentiferan riftia pachyptila dominated vent openings previously inhabited by tevnia jerichonana 5 three years after the eruption maximum hydrogen sulfide levels declined further to 0 88 mmol kg 1 and mussels bathymodiolus thermophilus were observed on basaltic substrates 6 four years after the eruption galatheid crabs and serpulid polychaetes increased in abundance and were observed close to active vent openings as maximum hydrogen levels decreased to 0 72 mmol kg 1 also by this time mussels had colonized on to tubes of riftia pachyptila 7 between 3 and 5 yr after the eruption there was a 2 to 3 fold increase in the number of species in the faunal assemblages in the absence of additional volcanic tectonic disturbance we predict that mytilid and vesicomyid bivalves will gradually replace vestimentiferans as the dominant megafauna 5 10 yr following the eruption we also anticipate that the abundance of suspension feeders will decline during this period while the abundance of carnivores will increase we hypothesize that the above series of events 1 7 represents a general sequence of biological successional changes that will occur at newly formed low temperature deep sea hydrothermal vents along the northern east pacific rise and contiguous ridge axes megafaunal colonization at deep sea hydrothermal vents is considered to be the consequence of an intimate interaction of the life history strategies of individual species physical oceanographic processes and the dynamic hydrothermal environment our observations indicate that the successful sequential colonization of dominant megafaunal vent species from tevnia jerichonana to riftia pachyptila to bathymodiolus thermophilus also may be strongly influenced by temporal changes in geochemical conditions additional evidence demonstrating the close link between diffuse vent flux fluid geochemistry and faunal succession included the rapid death of several newly formed biological assemblages coincident with abrupt changes in the geochemical composition of the venting fluid and the local refocusing or cessation of vent flow these correlations suggest that future models of faunal succession at hydrothermal vents along intermediate to fast spreading mid ocean ridges should consider not only the interplay of species specific life history strategies community productivity and physical oceanographic processes but also the influence of changing geochemical conditions on the sequential colonization of megafaunal species

is an ionospheric electron enhancement preceding the 2011 tohoku oki earthquake a precursor 1 heki 2011 reported that the tec gradually enhanced from 40 minutes before the 2011 m9 0 off the pacific coast of tohoku earthquake tohoku eq to the time when the co seismic acoustic wave reached the ionosphere and the tec immediately recovered at the normal state this paper shows an alternative interpretation of total electron content tec variation in the ionosphere associated with the tohoku eq our interpretation is that a tsunamigenic ionospheric hole a wide depletion of the tec occurred after the co seismic acoustic wave reached the ionosphere and gradually recovered at the normal state with several tens of minutes kakinami et al 2012 the difference between heki 2011 and kakinami et al 2012 is attributed to the reference curves of the tec to extract the ionospheric variations the former is given by the least squares fitting curve of the eq day data excluding an expected precursor period while the latter is given by the data of the similar orbit of global positioning system gps satellite on another day the results suggest that variation of slant tec is explained by the depletion of tec due to tsunami rather than the precursory enhancement

gnss ionospheric seismology recent observation evidences and characteristics abstract the detail and nature of earthquakes are still challenging from traditional technique observations e g seismometers and strong motion accelerographs nowadays the ionospheric total electron content tec can be obtained from ground based global navigation satellite systems gnss and space borne gnss radio occultation which can be used to investigate the seismo ionospheric disturbances and may provide insights on the earthquake in this paper gnss ionospheric seismology is presented and reviewed including methods observation results and characteristics case studies of the 2008 wenchuan earthquake and 2011 japan earthquake are presented using ground based gnss observations significant co post seismic ionospheric anomalies are found from continuous gnss observations near the epicenters showing that the seismic ionospheric total electron content tec disturbances were derived mainly from the main shock the detailed pattern and evolution of the ionospheric disturbance are revealed by denser gnss observations some simulations explore the nature of the ionospheric perturbation highlighting that acoustic gravity waves are generated close to the epicenter and that surface rayleigh waves and tsunamis generate in the atmosphere ionosphere acoustic and gravity waves respectively these waves are induced by solid earth ocean and atmosphere coupling at the ground or ocean interface with the atmosphere propagating upward until the ionosphere create strong perturbation in plasma density and plasma velocity

coupled interaction of earthquake nucleation with deep earth gases a possible mechanism for seismo electromagnetic phenomena summary the mechanisms of seismo electromagnetic phenomena remain largely unexplained to address this issue we introduce a fault model that takes account of a coupled interaction between earthquake nucleation and deep earth gases this interaction causes a negatively electrified gas flow due to an exo electron attachment reaction as the gases pass through fractured asperities this transient activity may be regarded to be a pressure impressed electric current generator in the model the current and frequency are formulated as functions of earthquake parameters the estimated current is sufficient to explain the seismic electromagnetic signals observed at ground level a physical model of how current generation is coupled with ionospheric electromagnetic disturbances is explained in terms of magnetic induction coupling for strong offshore earthquakes which may provide a plausible explanation of observed ionospheric electron enhancement prior to some recent offshore earthquakes the model also suggests that geomagnetic observations close to an epicentre of a strong offshore earthquake may provide an effective means of detecting clear and identifiable precursor signals

tec anomalies assessment for earthquakes precursors in north eastern india and adjoining region using gps data acquired during 2012 2018 abstract a total of 160 earthquakes in north east indian region and surroundings were analysed for earthquake precursor detection using gps based total electron content tec estimation in the ionosphere tec is very sensitive to short term disturbances of a geomagnetic storm solar flares and seismic activities in the present study tec in the ionosphere was measured using dual frequency signals from five gps based continuously operating reference stations system cors installed in north eastern states of india the abnormality in tec variations was observed by constructing boundary limits using statistical method the values crossing the limits being the anomaly the results for mw 5 earthquakes such as mw 5 5 kohima earthquake july 14 2012 mw 6 8 myanmar earthquake november 11 2012 and mw 5 6 kokrajhar earthquake june 28 2015 covering north east india suggest tec anomaly 10 days 12 days and 13 days prior to the events analysis of 160 earthquakes suggests that the rate of success in tec based anomaly detection for earthquake precursor increases with increase in magnitude of the earthquakes in average mw 6 earthquakes could be fully detectable rate of success with reference to cors were also computed and was found in the order of cherrapunjee meghalaya madankamdev assam mohanpur agartala mawtawar meghalaya khanapara assam therefore present investigations confirmed tec anomalies prior to earthquakes and present the expected rate of success making it imperative to set up an automated system for real time monitoring of tec for earthquake precursor detection and appropriate forewarning in near future

the evolution of middle america and the gulf of mexico caribbean sea region during mesozoic time a plate tectonic model for the evolution of middle america and the gulf of mexico caribbean sea region is presented the model which is based upon the existence of the mojave sonora megashear incorporates into the triassic pangea reconstruction three microplates between north and south america thus avoiding the overlap of the bullard fit these plates are the yaqui bounded on the north by the mojave sonora megashear the east and west maya plates bounded on the north by the mexican volcanic zone and on the south by a predecessor of the motagua fault zone and the chortis plate parts of guatemala and honduras during late jurassic time as north america split away from europe africa and south america shear with left lateral sense of displacement occurred along the transform faults that bounded the micro plates if 800 km of left lateral displacement along the mojave sonora megashear 300 km along the mexican volcanic belt and 1 300 km along a proto motagua megashear are restored and if yucatan and cuba are rotated to fit against northern south america then 1 a curvilinear belt of late paleozoic rocks that show lithologic as well as paleontologic similarities extends across the reconstruction and links outcrops in texas eastern mexico nuclear central america and colombia 2 a mediterranean like sea is delineated that was a precursor of most of the present gulf of mexico 3 correlation is implied between the distinctive quartzose san cayetano formation of cuba and the caracas and juan griego groups of venezuela geometric constraints suggest that probably shear initially occurred along the mexican volcanic zone near the end of the middle jurassic subsequently probably about 160 m y ago displacements that total 800 km began along the mojave sonora megashear contemporaneously yucatan and fragments of pre cretaceous rocks that compose parts of central and western cuba migrated northward toward their present positions rotation of yucatan was facilitated by considerable displacement along the proto motagua zone and along a zone that is probably coincident with the modern salina cruz fault accumulation of widespread major salt units of late jurassic callovian to early oxfordian age in the gulf basin probably occurred contemporaneously with the arrival of these blocks at their present positions clastic units that interfinger with some of the youngest salt units and rim the gulf of mexico have not recorded major recognized translations since their accumulation clockwise rotation of south america and the chortis plate occurred during early cretaceous time this movement which was manifested by subduction of jurassic ocean floor against the previously rifted precursor of the island of cuba and under parts of hispaniola and puerto rico is recorded by circum caribbean orogeny abrupt changes in the relative motions between north and south america during late cretaceous time may have resulted in extension and outpourings of basalt upon the jurassic rocks of the ocean floor of the venezuelan basin west of beata ridge sea floor spreading formed the colombian basin related subduction occurred as the chortis plate including part of central america the nicaraguan rise and southeastern cuba was sutured against the maya east plate along the present motagua fault and cayman trench our model is constrained by published geologic data the relative positions of north and south america from atlantic sea floor magnetic anomalies and the requirement that the major transform faults be compatible with the poles of rotation for the appropriate relative motions between north and south america paleomagnetic data from middle america are sparse but do not conflict with the predicted motions of some of the microplates especially chortis

possible lithosphere atmosphere ionosphere coupling effects prior to the 2018 mw 7 5 indonesia earthquake from seismic atmospheric and ionospheric data abstract in this study we analyse lithosphere atmosphere ionosphere coupling laic effects to identify some phenomena that could possibly be linked to the preparation phase of the mw 7 5 earthquake occurred in indonesia on september 28th 2018 by investigating the eight months preceding the seismic event first we find a seismic acceleration that started two months before the mainshock then studying some physical properties of the atmosphere skin temperature total column water vapor and aerosol optical thickness we find two increases of atmospheric anomalies about 6 and 3 7 months before the mainshock and the latter one is very promising as a candidate for seismic related phenomena furthermore we investigate ionospheric disturbances by analysing the swarm and for the first time china seismo electromagnetic satellite cses magnetic and electron density data during quiet geomagnetic time from different techniques we find interesting anomalies concentrated around 2 7 months before the mainshock on august 19th 2018 swarm and cses showed an enhancement of the electron density during night time we critically discuss the possibility that such phenomenon can be a possible pre seismic induced ionospheric effect finally we performed a cumulative analysis using all detected anomalies as a test case for a possible chain of physical phenomena that could happen before the earthquake occurrence with this study we support the usefulness to collect and store large earth ground and satellite observational dataset that in the future could be useful to monitor in real time the seismic zones to anticipate earthquakes although nowadays there is no evidence about useful prediction capabilities

two dimensional simulation of ionospheric variations in the vicinity of the epicenter of the tohoku oki earthquake on 11 march 2011 1 unusual ionospheric variations were observed in the m9 0 tohoku oki earthquake on 11 march 2011 among various kinds of features in the ionosphere significant depletion of total electron content tec near the epicenter was observed after the earthquake although previous studies have suggested that the coseismic ionospheric variations are associated with atmospheric perturbation caused by vertical displacement of the sea surface the mechanism of the tec depletion has not been fully understood in this paper a two dimensional nonlinear nonhydrostatic compressible atmosphere ionosphere model is employed to investigate the ionospheric variations in the vicinity of the epicenter the simulation results reveal that an impulsive pressure pulse produced by a sudden uplift of the sea surface leads to local atmospheric expansion in the thermosphere and that the expansion of the thermosphere combined with the effect of inclined magnetic field lines in the ionosphere causes the sudden tec depletion above the epicenter region

organic walled microfossils of possible dinoflagellate affinity from the lower permian of sonora northwest mexico abstract shallow water carbonates from the lower permian of sonora northwest mexico have yielded small organic walled microfossils that show several features characteristic of dinoflagellates the oldest unequivocal dinoflagellate fossils however presently known come from the middle triassic earlier reports of microfossils with possible dinoflagellate affinity from the paleozoic and neoproterozoic together with dinoflagellate specific biomarkers found in early cambrian rocks and molecular phylogenetic analyses suggest the presence of an intermediate stage of evolution or protodinoflagellate group in pre mesozoic times

mapping the fluid flow of the mariana mounds ridge flank hydrothermal system pore water chemical tracers we present a conceptual model of fluid circulation in a ridge flank hydrothermal system the mariana mounds the model is based on chemical data from pore waters extracted from piston cores and from push cores collected by deep sea research vessel alvin in small meter sized mounds situated on a local topographic high these mounds are located within a region of heat flow exceeding that calculated from a conductive model and are zones of strong pore water upflow we have interpreted the chemical data with time dependent transport reaction models to estimate pore water velocities in the mounds themselves pore water velocities reach several meters per year to kilometers per year within about 100 m from these zones of focused upflow velocities decrease to several centimeters per year up to tens of centimeters per year a larger area of low heat flow surrounds these heat flow and topographic highs with upwelling pore water velocities less than 2 cm yr in some nearby cores downwelling of bottom seawater is evident but at speeds less than 2 cm yr downwelling through the sediments appears to be a minor source of seawater recharge to the basaltic basement we conclude that the principal source of seawater recharge to basement is where basement outcrops exist most likely a scarp about 2 4 km to the east and southeast of the study area

alkenone temperature estimates for the east sea during the last 190 000 years abstract the late quaternary records of alkenone based sea surface temperature sst from a core located in the western margin of the east sea japan sea showed that the estimated temperature fluctuated greatly the variability being consistent with orbital scale global climate records during the period of marine isotope stage mis 6 the alkenone temperatures were low 7 10 c whereas during mis 5 5 the temperature increased rapidly up to 21 c during the entire period of mis 5 the temperature decreased from 21 c to 13 c then the temperature fluctuated between 10 c and 15 c during miss 4 and 3 after that it continued to fluctuate between 15 c and 17 c variation in the east sea sst is considered to be closely related to changes in the east asian monsoon system and seawater transport by the tsushima warm current the glacial surface cooling could be associated with the strong winter monsoon and or weakened summer monsoon in east asia during the glacial period when the sea level was low the influx of warm water was restricted and this might have enhanced the lowering of the surface temperature these conditions most likely caused significant changes in surface water circulation a basin scale cyclonic gyre might have occurred in the east sea without the development of the subpolar front during the interglacial period the surface warming seems to be related to the intensified summer monsoon system the high stand of the sea level and climate change most likely caused the development of cyclonic and anti cyclonic gyres in the north and south respectively and the subpolar front in the central part of the sea

the size and duration of the sumatra andaman earthquake from far field static offsets the 26 december 2004 sumatra earthquake produced static offsets at continuously operating gps stations at distances of up to 4500 kilometers from the epicenter we used these displacements to model the earthquake and include consideration of the earth s shape and depth varying rigidity the results imply that the average slip was 5 meters along the full length of the rupture including the approximately 650 kilometer long andaman segment comparison of the source derived from the far field static offsets with seismically derived estimates suggests that 25 to 35 of the total moment release occurred at periods greater than 1 hour taking into consideration the strong dip dependence of moment estimates the magnitude of the earthquake did not exceed mw 9 2

the 25 april 2015 nepal earthquake investigation of precursor in vlf subionospheric signal we present a critical analysis of the observations and interpretation of vlf sub ionospheric measurements related to the main nepal gorkha earthquake which occurred on april 25 2015 mw7 8 and its major aftershock on may 12 2015 mw7 3 the vlf narrowband signal used is from nwc 19 8 khz vlf transmitter located in australia and recorded at allahabad lat 25 41 n long 81 93 e allahabad is located very close 360 km to these earthquake eq epicenters two widely used analysis viz 1 terminator time and 2 night time fluctuation techniques are applied to extract seismic related effects in the nwc narrowband vlf data the terminator time analysis yields statistically significant shifts of 45 and 26 minutes respectively in evening terminator time in the nwc vlf amplitude signal one day before both the earthquakes the nighttime fluctuation method shows a consistent statistically significant increase in three parameters one day before the earthquake the observed terminator time and nighttime fluctuation shifts were associated with these earthquakes only after scrutinizing possible contributions from other potential sources such as solar activity other earthquakes on the signal path meteorological disturbances such as lightning activity wind speed temperature etc along the transmitter receiver great circle path the vlf sub ionospheric signal analysis results unambiguously point towards the presence of seismically excited atmospheric gravity waves agws during these major earthquakes and their important role in providing the coupling between the seismic source region and overlying ionosphere

effects of the legacy of axial cooling on partitioning of hydrothermal heat extraction from oceanic lithosphere the predicted and observed heat flux across the seafloor these methods have assumed a dynamic steady state thermal system we show that this assumption is not warranted and leads to an incorrect partitioning of hydrothermal circulation between ridge axes and flanks to more accurately estimate hydrothermal heat loss on ridge axes and flanks we consider the spatial and temporal extent and vigor of axial hydrothermal circulation in calculating hydrothermal heat extraction axial fluid circulation perturbs the thermal state of oceanic lithosphere for 5 ma after that circulation ceases reducing the hydrothermal heat extraction on ridge flanks we find 30 of hydrothermal heat extracted on axis 10 extractednearaxis fromendofaxialhydrothermalcirculationto1ma and 60 extracted from lithosphere 1 ma

geomagnetic dependence of ionospheric disturbances induced by tsunamigenic internal gravity waves summary a series of ionospheric anomalies following the sumatra tsunami has been recently reported in the literature these anomalies show the signature in the ionosphere of tsunami generated internal gravity waves igw propagating in the neutral atmosphere over the ocean all these anomalies observed in the total electron content tec measured by gps or altimeters show geographical heterogeneity in the perturbed tec amplitude and suggest a dependence on geomagnetic latitude this latitudinal dependence has been taken into account in the previous 3 d modelling used for the interpretation of the tec topex and jason data here we present an accurate description of the ocean atmosphere ionosphere coupling method and focus on the properties of the propagation of tsunamigenic igw in the neutral atmosphere and their interaction with the ionospheric plasma the analytical dependence on the geomagnetic field in the neutral plasma coupling discussed in detail and quantitative modelling is used to describe the propagation of a simple tsunami wave at the global scale what emphasize the role of geomagnetic field within the neutral plasma coupling at the equatorial and mid latitude regions the results presented here in terms of electron density and tec variations show a strong geometric dependance involving the magnetic field inclination and the propagative direction of the tsunami if the strongest electron density and tec perturbations are located around 15 0 and 15 north the structure and amplitude of the modelled perturbation changes in the two