dichotomy in mode propagation of coseismic ionospheric disturbance observations from 11 april 2012 indian ocean earthquake the ionosphere response to the great intraplate indian ocean earthquake of 11 april 2012 mw 8 6 and its largest aftershock mw 8 2 is analyzed using gps aided total electron content tec measurements data from the dense gps networks sugar sumatran gps array and the permanent andaman nicobar array formed the near field observations at distances 250 1200 km from the epicenter stations such as iisc dgar and few others provided measurements over 2000 km from the epicenter the coseismic ionospheric disturbances cids with a propagation velocity of 930 1262 m s equals the speeds of the shock acoustic waves arrive within 10 18 min after the earthquake occurrence the observed phenomenon of cid splitting into two modes north and south of the epicenter is akin to the well documented effects of anisotropy on wave propagation closer to the epicenter to its south the propagation velocity of cid is 1 km s and farther southeast of the network the velocity reduces to 500 600 m s in contrast toward andaman in the north the cid propagation velocity increases to 2 3 5 km s the zenith angle of the line of sight between the gps receiver and satellite appears to influence the amplitude of the tec fluctuations the anomalous azimuthal variation of the rayleigh wave radiation pattern best explains the observed n s asymmetry of cid

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

from sumatra 2004 to tohoku oki 2011 the systematic gps detection of the ionospheric signature induced by tsunamigenic earthquakes the recent tsunamigenic earthquake in tohoku 11 march 2011 strongly affirms one more time after the sumatra event 26 december 2004 the necessity to open new paradigms in oceanic monitoring detection of ionospheric anomalies following the sumatra tsunami demonstrated that ionosphere is sensitive to the tsunami propagation observations supported by modeling proved that tsunamigenic ionospheric anomalies are deterministic and reproducible by numerical modeling via the ocean neutral atmosphere ionosphere coupling mechanism in essence tsunami induces internal gravity waves propagating within the neutral atmosphere and detectable in the ionosphere most of the ionospheric anomalies produced by tsunamis were observed in the far field where the tsunami signature in the ionosphere is clearly identifiable in this work we highlight the early signature in the ionosphere produced by tsunamigenic earthquakes and observed by gps measuring the total electron content close to the epicenter we focus on the first hour after the seismic rupture we demonstrate that acoustic gravity waves generated at the epicenter by the direct vertical displacement of the source rupture and the gravity wave coupled with the tsunami can be discriminated with theoretical support we illustrate the systematic nature of those perturbations showing several observations nominally the ionospheric perturbation following the tsunamigenic earthquakes in sumatra on 26 december 2004 and 12 september 2007 in chile on 14 november 2007 in samoa on 29 september 2009 and the recent catastrophic tohoku oki event on 11 march 2011 based on the analytical description we provide tracks for further modeling efforts and clues for the interpretation of complex and thus often misleading observations the routine detection of the early ionospheric anomalies following the rupture highlights the role of ionospheric sounding in the future ocean monitoring and tsunami detection

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

ionospheric remote sensing of the denali earthquake rayleigh surface waves 1 using the global positioning system we have detected ionospheric disturbances associated with the long period rayleigh waves from the 2002 denali earthquake ms 7 9 the dense california gps networks allowed us to map the ionospheric perturbations and to compute the group velocity with a high spatial resolution above the pacific coasts due to a low sampling rate a large error in the velocity determination remains nonetheless it demonstrates that bi static remote sensing measurements of seismic waves with gps networks can be performed monostatic measurements with a dedicated satellite could possibly be used to record in the ionosphere surface waves originating from large earthquakes such a space based remote sensing of the local group velocity of rayleigh surface waves would effectively complement the seismic networks for high resolution global tomography of the earth s lithosphere

origin of the ahead of tsunami traveling ionospheric disturbances during sumatra tsunami and offshore forecasting the presence of ionospheric disturbances associated with sumatra 2004 tsunami that propagated ahead of tsunami itself has previously been identified however their origin remains unresolved till date focusing on their origin mechanism we document these ionospheric disturbances referred as ahead of tsunami travelling ionospheric disturbances atids using tec data from gps aided geo augmented navigation gagan gps receivers located near the indian east coast we first confirm the atids presence in tec that appear 90 minutes ahead of the arrival of tsunami at the indian east coast we propose here a simulation study based on tsunami atmospheric ionospheric coupling that considers tsunamigenic acoustic gravity waves agws to excite these disturbances we explain the atids generation based on the dissipation of transverse mode of the primary agws the simulation corroborates the excitation of atids with characteristics similar to the observations therefore we offer an alternative theoretical tool to monitor the offshore atids where observations are either rare or not available and could be potentially important for the tsunami early warning

a palaeomagnetic approach to the origin of the black sea summary available palaeomagnetic data for the circum black sea region are reviewed with the object of evaluating the geodynamical evolution of the black sea jurassic data from the south of the stara planina forebalkan zone south of the moesian platform in bulgaria which was then part of the east european platform place the region at about 39 latitude while the pontides the northernmost tectonic unit of turkey were at a lower latitude 10 15 palaeomagnetic investigations on upper cretaceous magmatic rocks sampled in different parts of the srednogorie tectonic unit southern boundary of the stara planina forebalkan indicate that the region was at 39 palaeolatitude during the upper cretaceous while the pontides had moved northward to 23 palaeolatitude since early cretaceous time the great caucasus domain of the ussr was welded to eurasia by coniacian time and had a palaeolatitude of 36 calculated palaeopole positions for the above mentioned geological times for the pontides fit well with the african palaepoles but largely deviate from the eurasian ones taken together these observations indicate that the pontides were not part of eurasia instead they were separated from the east european platform by the early mesozoic tethys this conclusion does not favour the rifted back arc hypothesis for the formation of the black sea during cretaceous time as suggested by some researchers adamia et al 1977 hsii et al 1977 sengor yilmaz 1981

discriminating the tectonic and non tectonic contributions in the ionospheric signature of the 2011 mw7 1 dip slip van earthquake eastern turkey 1 it has previously been suggested that ionospheric perturbations triggered by large dip slip earthquakes might offer additional source parameter information compared to the information gathered from land observations based on 3d modeling of gps and glonass derived total electron content signals recorded during the 2011 van earthquake thrust intra plate event mw 7 1 turkey we confirm that coseismic ionospheric signals do contain important information about the earthquake source namely its slip mode moreover we show that part of the ionospheric signal initial polarity and amplitude distribution is not related to the earthquake source but is instead controlled by the geomagnetic field and the geometry of the global navigation satellite system satellites constellation ignoring these non tectonic effects would lead to an incorrect description of the earthquake source thus our work emphasizes the added caution that should be used when analyzing ionospheric signals for earthquake source studies

ionospheric signature of surface mine blasts from global positioning system measurements sources such as atmospheric or buried explosions and shallow earthquakes are known to produce infrasonic pressure waves in the atmosphere because of the coupling between neutral particles and electrons at ionospheric altitudes these acoustic and gravity waves induce variations of the ionospheric electron density the global positioning system gps provides a way of directly measuring the total electron content in the ionosphere and therefore of detecting such perturbations in the upper atmosphere in july and august 1996 three large surface mine blasts 1 5 kt each were detonated at the black thunder coal mine in eastern wyoming as part of a seismic and acoustic monitoring experiment we deployed five dual frequency gps receivers at distances ranging from 50 to 200 km from the mine and were able to detect the ionospheric perturbation caused by the blasts the perturbation starts 10 to 15 min after the blast lasts for about 30 min and propagates with an apparent horizontal velocity of 1200 meters per second its amplitude reaches 3 x 10 exp 14 el per square meters in the 7 3 min period band a value close to the ionospheric perturbation caused by the m 6 7 northridge earthquake the small signal to noise ratio of the perturbation can be improved by slant stacking the electron content time series recorded by the different gps receivers taking into account the horizontal propagation of the perturbation the energy of the perturbation is concentrated in the 200 to 300 second period band a result consistent with previous observations and numerical model predictions the 300 second band probably corresponds to gravity modes and shorter periods to acoustic modes respectively using a 1 d stratified velocity model of the atmosphere we show that linear acoustic ray tracing fits arrival times at all gps receivers we interpret the perturbation as a direct acoustic wave caused by the explosion itself this study shows that even relatively small subsurface events can produce ionospheric perturbations that are above the detection threshold of the gps technique by sensing derivative signals which can be detected over a relatively broad region it appears that gps might be particularly useful for source characterization within the first acoustic quiet zone where infrasound would probably be ineffective this suggests that dual frequency gps monitoring could contribute to comprehensive nuclear test ban treaty verification

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

ionospheric disturbances triggered by the 11 march 2011 m9 0 tohoku earthquake 1 an earthquake of magnitude 9 0 occurred near the east coast of honshu tohoku area japan producing overwhelming earth surface motions and inducing devastating tsunamis which then traveled into the ionosphere and significantly disturbed the electron density within it hereafter referred to as seismotraveling ionospheric disturbances stids the total electron content tec derived from nationwide gps receiving networks in japan and taiwan is employed to monitor stids triggered by seismic and tsunami waves of the tohoku earthquake the stids first appear as a disk shaped tec increase about 7 min after the earthquake occurrence centered at about 200 km east of the epicenter near the west edge of the japan trench fast propagating disturbances related to rayleigh waves quickly travel away from the epicenter along the main island of japan with a speed of 2 3 3 3 km s accompanied by sequences of concentric circular tec wavefronts and followed by circular ripples close to a tsunami speed of about 720 800 km h that travel away from the stid center these are the most remarkable stids ever observed where signatures of rayleigh waves tsunami waves etc simultaneously appear in the ionosphere

ionospheric response to earthquakes of different magnitudes larger quakes perturb the ionosphere stronger and longer recently it has been shown that the ionosphere is capable of showing images of seismic fault shortly after an earthquake this gives rise to the idea of retrieval of seismic information from ionospheric observations as the first step toward such inversion here we study distinctive features of ionospheric response to shallow earthquakes both submarine and inland of moment magnitudes mw7 2 9 1 using gps measurements of the ionospheric total electron content we show that 1 the amplitude of coseismic total electron content variations in the near field is larger after more powerful earthquakes and 2 stronger earthquakes m 7 9 are in general characterized by a longer negative phase in coseismic perturbations

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

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

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

two mode long distance propagation of coseismic ionosphere disturbances 1 using gps total electron content tec measurements we analyzed ionosphere response to the great kurile earthquake of 4 october 1994 high spatial resolution of the japanese dense array of gps receivers geonet provided us the unique opportunity to observe the evolution of coseismic ionospheric disturbances cid which propagated for more than 1800 km away from the epicenter plotting a traveltime diagram for the cid and using an array processing technique within the approximation of a spherical cid wavefront we observed a phenomenon of cid separation into two modes and we found that characteristics of the cid depend on the distance from the epicenter the maximum of the cid amplitude was observed at 500 km from the epicenter within the first 600 700 km the cid propagation velocity was about 1 km s which is equal to the sound speed at the height of the ionospheric f layer starting from 600 to 700 km out from the epicenter the disturbance seems to divide into two separate perturbations with each propagating at a different velocity about 3 km s for the one and about 600 m s for the other apparently the tec response in the far field of the cid source is a mixture of signals that further splits into two modes because of the difference in their velocities our observations are in good agreement with the results of space time data processing in the approximation of a spherical wavefront of cid propagation

seismo ionospheric observations modeling and backprojection of the 2016 kaikōura earthquake we processed global navigation satellite system gnss time series data to extract total electron content tec perturbations of the ionosphere caused by the kaik ura earthquake we used ray based modeling to infer which part of the earth s surface coupled significant energy from the solid earth into the atmosphere we compared modeled tec data with the observed time series data and determined that significant coupling occurred north northeast of the initial slip this work corroborates existing analysis made with geodetic and interferometric synthetic aperture radar insar data the tec data suggested that the initial rupture coupled some energy into the atmosphere but later surface displacements 60 s after the initiation caused more significant ionospheric perturbations using an array of gnss stations we were able to track the moveout of the acoustic wave through the ionosphere we used a method commonly used in seismological studies called backprojection to estimate the location of the source of the tec perturbation on earth s surface this is the first time that this method has been applied to tec data and the results are promising the backprojection results are slightly shifted in space from the known area of maximum uplift and we attribute this small discrepancy to the fact that we did not account for horizontal winds in the atmosphere nor the 3d heterogeneity of the real atmosphere in the travel time modeling

high resolution mapping of tec perturbations with the gsi gps network over japan two dimensional total electron content tec perturbations over japan are mapped with the geographical survey institute gsi gps network geonet gps earth observation network its spatial resolution is 0 15 latitude 0 15 longitude and temporal resolution is 30 seconds two dimensional tec observations with these high resolutions revealed spatial structures and temporal evolutions of traveling ionospheric disturbances tids in the nighttime mid latitude ionosphere on july 03 1997 a preliminary result of the tec perturbation mapping indicates that it would be a strong tool to investigate the ionospheric structures in detail coordinated observations with other ionospheric observation techniques such as incoherent scatter is radars airglow imagers and ionosondes are needed to clarify the vertical structure of the ionosphere

pattern and evolution of seismo ionospheric disturbances following the 2011 tohoku earthquakes from gps observations global positioning system gps has been widely used to sense crustal deformation and ionospheric anomalies particularly seismic ionospheric disturbances in march 2011 the earthquakes with magnitude of up to mw 9 occurred in tohoku near the east coast of honshu japan the gps earth observation network geonet in japan with more than 1200 continuously operating stations provides a unique opportunity to study the detailed seismic ionospheric disturbances in this paper the pattern and evolution of seismic ionospheric disturbances following the tohoku earthquakes are investigated by dense geonet data including amplitude propagation pattern direction speed and evolution maximal coseismic ionospheric disturbances are found with up to more than 4 tecu and the disturbance period is around 10 20 min the seismic ionospheric effects following the aftershocks are attenuated with the increase of the time and distance between the ionospheric pierce point and the epicenter of the main event which last more than 2 h seismic ionospheric disturbance detected by gps measurement is not only related to the main shock but also the giant aftershocks propagation velocities of the total electron content tec disturbance show a decrease when it spreads 400 600 km away from the epicenter in the north western direction where it is just near the west coast of japan furthermore the tec disturbance also has obvious directional features in the first half hour the tec disturbance in the southeast direction has the biggest amplitude while the dominant direction is changed to northwest tens of minutes later in addition signals with higher frequencies are existed in seismic tec variation at the epicenter region but do not appear in the far field

excitation of 4 min periodic ionospheric variations following the great sumatra andaman earthquake in 2004 1 periodic variations of the ionosphere were detected by ground based gps total electron content tec measurements after the sumatra andaman earthquake in 2004 the observational data showed that the 4 min periodic tec variations occurred 1 h after the earthquake and continued for longer than 4 h at the phkt station about 30 cycles of the 4 min periodic tec variations were observed from 0230 to 0430 ut the maximum peak to peak amplitude of the variations was about 0 6 total electron content unit tecu 1 tecu 1016 el m 2 around 0320 ut the frequency of these periodic variations was 3 9 mhz they were detected by the samp station in the northern sumatra and the phkt and bnkk stations in thailand with the signal from seven gps satellites prn 8 11 13 19 23 27 and 31 they were observed in a limited area from 4 n to 15 n in latitude and from 96 e to 101 e in longitude although the western boundary was not certain because of the limit of the observational field of view the amplitude of these tec variations showed the dependence on the zenith angle of the path between the gps receiver and satellite the amplitude had a maximum when the zenith angle was the smallest this could be caused by the vertical structure of the electron density variations this also suggested that the electrons were oscillating along the geomagnetic field the 4 min periodic tec variations were interpreted to be induced by the long lasting free oscillation of the atmosphere set up by the earthquake their long duration also indicates that they were generated by a nontransient process like resonance

geological contributions extinct rift valleyson the nature of greenstone belts in the precambrian at present there is considerable speculation concerning the origin of greenstone belts they are compared with phanerozoic geosynclines fold belts modern island arcs or with the rift structures formed above subduction zones in marginal seas four stages in greenstone belt development can be determined 3 8 3 0 3 0 2 6 2 6 1 9 and 1 9 b y and younger sections of early greenstone belts contain all the essential features of the modern oceanic sequences their peculiarities are great thickness presence of jaspilites and scarce occurrence of very coarse clastics on the contrary the latter type of sediment is widespread in younger greenstone belts and in those of the last stage which are completely formed in continental environment whole rock chemistry of precambrian volcanics more than 1800 analyses all over the world confirms that alkali olivine basalts are absent till 1 9 b y and andesites are generally rare widespread type of early precambrian basalts are ol hy and q normative ones showing close similarity to typical abyssal tholeiites the presence of basaltic komatiites is not a unique petrochemical feature of volcanism in the early precambrian as one thinks now similar rocks have been found in phanerozoic rift zones there is no evidence suggesting significant shortening of initial crustal complexes and greenstone belts these data along with slight metamorphism and above features can only be explained by the formation of greenstone belts in rifting environment during the early stages 3 8 1 9 b y the thickness of the protocrust was not more than 10 20 km it allows us to understand the rare occurrence of intermediate volcanics at early stages of the earth s evolution in summary it is argued that in the early precambrian the spread of primitive oceanic lithosphere was not compensated by the consumption in subduction zones consequently plate tectonics cannot explain the formation of the crust in the early history of the earth

multi dimensional distribution of near field ionospheric disturbances produced by the 2015 mw7 8 nepal earthquake abstract ionospheric anomalies possibly associated with large earthquakes particularly coseismic ionospheric disturbances have been detected by global positioning system gps a large nepal earthquake with magnitude mw7 8 occurred on april 25 2015 in this paper we investigate the multi dimensional distribution of near field coseismic ionospheric disturbances cids using total electron content tec and computerized ionospheric tomography cit from regional gps observational data the results show significant ionospheric tec disturbances and interesting multi dimensional structures around the main shock regarding the tec changes coseismic ionospheric disturbances occur approximately 10 20 min after the earthquake northeast and northwest of epicentre the maximum ridge to trough amplitude of cids is up to approximately 0 90 tecu min propagation velocities of the tec disturbances are 1 27 0 06 km s and 1 91 0 38 km s it is believed that the ionospheric disturbances are triggered by acoustic and rayleigh waves tomographic results show that the three dimensional distribution of ionospheric disturbances obviously increases at an altitude of 300 km above the surrounding epicentre predominantly in the entire region between 200 km and 400 km significant ionospheric disturbances appear at 06 30 ut from tomographic images this study reveals characteristics of an ionospheric anomaly caused by the nepal earthquake

global positioning system detection and energy estimation of the ionospheric wave caused by the 13 july 2003 explosion of the soufriere hills volcano montserrat 1 volcanic explosions or shallow earthquakes are known to trigger acoustic and gravity waves that propagate in the atmosphere at infrasonic speeds at ionospheric heights coupling between neutral particles and free electrons induces variations of electron density detectable with dual frequency global positioning system gps measurements using gps data collected in the caribbean we identified an ionospheric perturbation after a major volcanic explosion at the soufriere hills volcano montserrat lesser antilles on 13 july 2003 spectral analysis reveals peaks centered at 1 and 4 mhz similar to those in previous observations and consistent with theory suggesting both gravity and acoustic wave components we retrieve a horizontal velocity of 624 m s for the acoustic component which implies upward propagation at 33 consistent with ray tracing results we model the acoustic wave using an n wave pressure source at ground level combined with ray tracing to propagate the neutral pressure wave this accounts for the dispersive characteristics of the atmosphere while conserving total acoustic energy plasma velocity is derived from neutral velocity using a finite difference solution of the magnetohydrodynamic momentum equation the continuity equation for charge densities is used to compute corresponding electron density variations which are then numerically integrated along satellite to receiver line of sights simultaneously accounting for the satellite displacements we minimize the misfit between observed and model waveforms to estimate a total acoustic energy release of 1 53 x 10 10 j for the primary explosion event at soufriere hills volcano associated with the peak dome collapse this method can be applied to any explosion of sufficient magnitude provided gps data are available at near to medium range from the source

vertical structure of the ionospheric response following the m w 7 9 wenchuan earthquake on 12 may 2008 the response of the vertical ionospheric electron density structure to the mw 7 9 wenchuan earthquake on 12 may 2008 was recorded by the formosat 3 cosmic f3 c radio occultation ro precise orbit determination pod total electron content tec the horizontal propagation characteristics of the seismo traveling ionospheric disturbances were identified by combining ground based global navigation satellite system gnss tec data and ro tec data the postseismic ionospheric infrasound wavefront with wavelength of around 80 km at altitude of 150 350 km was scanned vertically by an individual ro tec profile a large amount of tec profiles around the epicenter from 0000 to 1200 ut provide evidence of continental earthquake induced vertical oscillations that lasted in the ionosphere for several hours ro observed vertical perturbations appear on both the southward and northward sides of the epicenter the vertical structure of the ionospheric oscillations with wavelength ranging from 10 to 80 km increased with altitude between 230 and 650 km

concentric waves and short period oscillations observed in the ionosphere after the 2013 moore ef5 tornado 1 we detected clear concentric waves and short period oscillations in the ionosphere after an enhanced fujita scale ef 5 tornado hit moore oklahoma u s on 20 may 2013 using dense wide coverage ionospheric total electron content tec observations in north america these concentric waves were nondispersive with a horizontal wavelength of 120 km and a period of 13 min they were observed for more than 7 h throughout north america tec oscillations with a period of 4 min were also observed to the south of moore for more than 8 h a comparison between the tec observations and infrared cloud image from the goes satellite indicates that the concentric waves and short period oscillations are caused by supercell induced atmospheric gravity waves and acoustic resonances respectively this observational result provides the first clear evidence of a severe meteorological event causing atmospheric waves propagating upward in the upper atmosphere and reaching the ionosphere

parameters of seismic source as deduced from 1 hz ionospheric gps data case study of the 2011 tohoku oki event following the first time ionospheric imaging of a seismic fault here we perform a case study on retrieval of parameters of the extended seismic source ruptured during the great m9 0 tohoku oki earthquake using 1 hz ionospheric gps data from the japanese network of gps receivers geonet and several gps satellites we analyze spatiotemporal characteristics of coseismic ionospheric perturbations and we obtain information on the dimensions and location of the sea surface uplift seismic source we further assess the criterion for the successful determination of seismic parameters from the ionosphere the detection is possible when the line of sights from satellites to receivers cross the ionosphere above the seismic fault region besides we demonstrate that the multisegment structure of the seismic fault of the tohoku oki earthquake can be seen in high rate ionospheric gps data overall our results show that under certain conditions ionospheric gps derived tec measurements could complement the currently working systems or independent ionospherically based system might be developed in the future

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

tsunamigenic ionospheric hole 1 traveling ionospheric disturbances generated by an epicentral ground sea surface motion ionospheric disturbances associated with rayleigh waves as well as post seismic 4 minute monoperiodic atmospheric resonances and other period atmospheric oscillations have been observed in large earthquakes in addition a giant tsunami after the subduction earthquake produces an ionospheric hole which is widely a sudden depletion of ionospheric total electron content tec in the hundred kilometer scale and lasts for a few tens of minutes over the tsunami source area the tsunamigenic ionospheric hole detected by the tec measurement with global position system gps was found in the 2011 m9 0 off the pacific coast of tohoku the 2010 m8 8 chile and the 2004 m9 1 sumatra earthquakes this occurs because plasma is descending at the lower thermosphere where the recombination of ions and electrons is high through the meter scale downwelling of sea surface at the tsunami source area and is highly depleted due to the chemical processes

ionospheric disturbances infrasound waves over the czech republic excited by the 2011 tohoku earthquake 1 a train of large amplitude infrasound wave packets was observed by multipoint continuous doppler sounding system in the ionosphere over the czech republic on 11 march 2011 it is shown that these infrasound wave packets originated from vertical motion of the ground surface that was caused by arrival of seismic waves generated by the strong tohoku earthquake the infrasound wave packets were observed in the ionosphere at heights of 210 220 km about 9 min after the detection of corresponding wave packets on the ground which is consistent with the calculated time for vertically propagating infrasound waves absolute values of cross correlation coefficients between ionospheric and ground measurements are typically higher than 0 9 for two wave packets 0 98 the individual wave packets recorded on the ground have different observed horizontal velocities and correspond to different types of seismic waves a comparison of vertical velocities of ground motion with oscillation velocities of air particles in the ionosphere indicates that almost 1 10 of the infrasound energy flux excited at the ground reached the altitudes of 210 220 km for wave periods longer than 30 s estimates of sound attenuation are performed it is also shown that it is necessary to consider the value of electron density gradient at the reflection height of the sounding radio wave and air plasma compression owing to the infrasound wave to get reasonable estimates of oscillation velocities of air particles from doppler shift frequencies

ionospheric disturbances induced by a missile launched from north korea on 12 december 2012 1 ionospheric disturbances caused by a missile launched from north korea on 12 december 2012 were investigated by using the gps total electron content tec the spatial characteristic of the front edge of v shaped disturbances produced by missiles and rockets was first determined considering the launch direction and the height of estimated ionospheric points at which gps radio signal pierces the ionosphere the missile passed through the ionosphere at heights of 391 425 and 435 km at 0056 30 0057 00 and 0057 30 ut respectively the observed velocities of the missile were 2 8 and 3 2 km s at that time which was estimated from the traveling speed of the front edge of v shaped disturbances westward and eastward v shaped disturbances propagated at 1 8 2 6 km s the phase velocities of the westward and eastward v shaped disturbances were much faster than the speed of acoustic waves reported in previous studies suggesting that sources other than acoustic waves may have played an important role furthermore the plasma density depletion that is often observed following missile and rocket launches was not found this suggests that the depletion resulting from the missile s exhaust was not strong enough to be observed in the tec distribution in the topside ionosphere

ionospheric disturbances in the vicinity of the chelyabinsk meteoroid explosive disruption as inferred from dense gps observations the paper describes results of studying effects of total electron content tec variations triggered by the chelyabinsk meteoroid airburst as inferred from unique data of a dense gps network located around the final part of the meteoroid atmospheric path well pronounced tec disturbances with an average period of about 10 min and amplitude of 0 07 0 5 tecu total electron content unit 1 tecu 1016 el m 2 were detected these disturbances were initiated by an ionospheric source activated about 5 6 min after the airburst the disturbance velocity damping with time and distance from the airburst was revealed using a gps interferometric technique several modes of tec disturbances with propagation velocities ranging from 250 to 660 m s were distinguished through the distance time diagram analysis the estimated position of ionospheric source of tec disturbances is shifted 36 km southwestward from the airburst which is most likely to be associated with the conjoint influence of tec data errors damping and anisotropy of tid propagation velocity

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