late pleistocene chronology of sediments from the yermak plateau and uncertainty in dating based on geomagnetic excursions the yermak plateau is one of several regions in the arctic ocean where paleomagnetism yields controversial results despite low sedimentation rates late pleistocene paleomagnetic excursions have b

mom analysis of dipole antennas in crosshole borehole radar and field experiments in this paper we propose a method of moments mom analysis that includes the borehole effects on crosshole borehole radar and we verify that the mom represents the crosshole borehole radar data correctly we derive the far field approximation of an electric field radiated by an electric point source in this derivation we assume that the point source is in a cylindrically layered medium while the observed electric field is in another cylindrically layered medium the equations that are derived are used as a transfer function to connect the two impedance matrices one for the transmitting antenna and the other one for the receiving one in these matrices the influence of the scattered field by the borehole is included completely we conducted field experiments in granite with a controlled borehole medium in order to investigate the influence of the borehole in this paper we estimated the relative amplitude and the group delay of the received signals between the water filled borehole case and the air filled borehole case this paper showed that the estimated amplitude and delay depend on the frequency and that the proposed mom could predict these frequency dependencies

is the central arctic ocean a sediment starved basin abstract numerous short sediment cores have been retrieved from the central arctic ocean many of which have been assigned sedimentation rates on the order of mm ka implying that the arctic basin was starved of sediments during plio pleistocene times a review of both shorter term sedimentation rates through analysis of available sediment core data and longer term sedimentation rates through estimates of total sediment thickness and bedrock age suggests that cm ka scale rates are pervasive in the central arctic ocean this is not surprising considering the physiographic setting of the arctic ocean being a small land locked basin since its initial opening during early cretaceous times we thus conclude that the central arctic ocean has not been a sediment starved basin either during plio pleistocene times or during pre pliocene times rigorous chronstratigraphic analysis permits correlation of sediment cores over a distance of 2600 km from the northwestern amerasia basin to the northwestern eurasia basin via the lomonosov ridge using paleomagnetic biostratigraphic and cyclostratigraphic data

the vertical propagation of disturbances triggered by seismic waves of the 11 march 2011 m9 0 tohoku earthquake over taiwan in this paper concurrent colocated measurements of seismometers infrasonic systems magnetometers hf cw high frequency continuous wave doppler sounding systems and gps receivers are employed to detect disturbances triggered by seismic waves of the 11 march 2011 m9 0 tohoku earthquake no time delay between colocated infrasonic i e super long acoustic waves and seismic waves indicates that the triggered acoustic and or gravity waves in the atmosphere or seismo traveling atmospheric disturbances stads near the earth s surface can be immediately activated by vertical ground motions the circle method is used to find the origin and compute the observed horizontal traveling speed of the triggered infrasonic waves the speed of about 3 3 km s computed from the arrival time versus the epicentral distance suggests that the infrasonic waves i e stads are mainly induced by the rayleigh waves the agreements in the travel time at various heights between the observation and theoretical calculation suggest that the stads triggered by the vertical motion of ground surface caused by the tohoku earthquake traveled vertically from the ground to the ionosphere with speed of the sound in the atmosphere over taiwan

magnetostratigraphic data from late quaternary sediments from the yermak plateau arctic ocean evidence for four geomagnetic polarity events within the last 170 ka of the brunhes chron summary palaeomagnetic investigations of two sediment cores recovered from rv polarstern near the eastern slope of the yermak plateau sites ps 1533 and ps 2212 reveal convincing evidence for four polarity events of the earth s magnetic field during the last 170 ka a comprehensive rock magnetic study of the sediments proved that fine grained magnetite is the principal carrier of the remanent magnetization no changes in magneto mineralogy across the polarity transitions in the sediments investigated were found calcareous nannofossil biostratigraphy ams 14c accelerated mass spectrometry and oxygen isotope data and 10be and 230th stratigraphies yielded age ranges of 24 29 ka for the mono lake event 34 43 ka for the laschamp event 72 86 ka for the norwegian greenland sea event and 118 128 ka for the blake event two reverse polarity samples at the base of core ps 2212 3 kal are interpreted as the termination of the biwa i event 171 181 ka the events exhibit full inversion of inclination in both cores the data suggest that the transition process of the earth s magnetic field during such polarity events requires some 1 ka

rapid changes of glacial climate simulated in a coupled climate model abrupt changes in climate termed dansgaard oeschger and heinrich events have punctuated the last glacial period approximately 100 10 kyr ago but not the holocene the past 10 kyr here we use an intermediate complexity climate model to investigate the stability of glacial climate and we find that only one mode of atlantic ocean circulation is stable a cold mode with deep water formation in the atlantic ocean south of iceland however a warm circulation mode similar to the present day atlantic ocean is only marginally unstable and temporary transitions to this warm mode can easily be triggered this leads to abrupt warm events in the model which share many characteristics of the observed dansgaard oeschger events for a large freshwater input such as a large release of icebergs the model s deep water formation is temporarily switched off causing no strong cooling in greenland but warming in antarctica as is observed for heinrich events our stability analysis provides an explanation why glacial climate is much more variable than holocene climate

constraints on the pleistocene chronology of sediments from the lomonosov ridge 1 despite its importance in the global climate system age calibrated marine geologic records reflecting the evolution of glacial cycles through the pleistocene are largely absent from the central arctic ocean this is especially true for sediments older than 200 ka three sites cored during the integrated ocean drilling program s expedition 302 the arctic coring expedition acex provide a 27 m continuous sedimentary section from the lomonosov ridge in the central arctic ocean two key biostratigraphic datums and constraints from the magnetic inclination data are used to anchor the chronology of these sediments back to the base of the cobb mountain subchron 1215 ka beyond 1215 ka two best fitting geomagnetic models are used to investigate the nature of cyclostratigraphic change within this chronology we show that bulk and mineral magnetic properties of the sediments vary on predicted milankovitch frequencies these cyclic variations record glacial and interglacial modes of sediment deposition on the lomonosov ridge as evident in studies of ice rafted debris and stable isotopic and faunal assemblages for the last two glacial cycles and were used to tune the age model potential errors which largely arise from uncertainties in the nature of downhole paleomagnetic variability and the choice of a tuning target are handled by defining an error envelope that is based on the best fitting cyclostratigraphic and geomagnetic solutions

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

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

vertical midscale ionospheric disturbances caused by surface seismic waves based on irkutsk chirp ionosonde data in 2011 2016

a comparison of different magnetic methods for determining the relative grain size of magnetite in natural materials some results from lake sediments abstract a new rapid method for identifying relative grain size variations in magnetic involves the parameter anhysteretic susceptibility arm i e specific arm obtained in a 1 oe steady field which is particularly sensitive to the single domain sd and small pseudo single domain psd grains of the finer magnetite fraction a second parameter low field susceptibility is relatively more sensitive to the coarser magnetite fraction larger psd and smaller multidomain md grains we can then obtain a measure of the ratio of coarse to fine grain magnetite for large numbers of samples by plotting arversus a simple idealized model based on sized magnetite samples is proposed to explain the use of the armversus plot for detecting relative grain size changes in the magnetic content of natural materials the sediments of three lakes that contain magnetite or a similar magnetic carrier and have a wide range of values of arm and are used to test the model the model is used to interpret the magnetic variations observed and the interpretations are supported by high field hysteresis measurements of the same sediments the combination of the high field hysteresis method of day et al 1 and the arm vs method is a powerful technique allowing the rapid identification of both the relative grain size and domain state for large numbers of samples containing magnetite the armvs method should be used as an intial means of identifying distinct groups of samples the high field hysteresis method should then be applied to a few representative samples from each group to confirm the initial interpretation

optically stimulated luminescence dating supports central arctic ocean cm scale sedimentation rates 1 this paper presents new results from optically stimulated luminescence osl dating on a sediment core raised from the crest of the lomonosov ridge in the central arctic ocean there has been much debate about dating sediment cores from the central arctic ocean and by using an independent absolute dating technique we aim to test whether or not relatively fast cm scale ka sedimentation rates were typical of arctic s pleistocene depositional mode on the basis of mainly paleomagnetic reversal stratigraphy many previous studies suggest mm scale ka sedimentation rates a common feature in these studies is that the first down core paleomagnetic negative inclination is consistently interpreted as the brunhes matuyama boundary at about 780 ka our osl dating results indicate that this assumption is not generally valid and that the first encountered negative inclination represents younger age excursions within the brunhes chron implying reinterpretation of many published core studies where paleoenvironmental reconstructions have been made for the central arctic ocean our dating results furthermore corroborates a correlation of the uppermost 2 3 m of the lomonosov ridge cores to a well dated core located off the barents kara sea margin that in turn is correlated to cores in the fram strait valuable information on the paleoceanographical evolution in the arctic ocean from mis 6 to the holocene is given through this correlation of records from the central arctic ocean to records off the eurasian continental margin

geologic time series from deep sea sediments time scales and distortion by bioturbation abstract in order to evaluate the time and frequency domain characteristics of geologic time series obtained from deep sea sediments two important problems must be considered first an accurate time scale must be established for the sediment records to be studied an accurate time scale is a basic requirement for such techniques as spectral and cross spectral analysis secondly the distortion of a geologic time series by sedimentation processes such as bioturbation must be considered if inferences are to be made about the mechanisms controlling climatic and oceanographic processes reflected in the geologic record recently it has been suggested that the periodic components in paleoclimatic records which can be related to variations in the earth s orbital parameters can be used as a means for providing very detailed control for late pleistocene sediment sections a time scale is estimated by tuning an individual frequency component in a climate record to an orbital parameter the tuning procedure commonly uses the technique of bandpass filtering which removes all frequency components except the one equivalent to an orbital parameter and then adjusting the geologic time scale so that the filtered record and orbital record align since bandpass filtering will produce a periodic record from any data set a question is raised as to the circularity of this tuning approach a series of numerical experiments using synthetic time series are used to determine if the tuning of a geologic record artificially induces improved correlation and increased periodic character in a climatic record these experiments indicate that the tuning does not artificially induce these effects thus it is suggested that the careful use of orbital tuning provides a powerful means of defining a geologic time scale the degree to which bioturbation distorts a paleoclimatic record is studied by comparing the spectra of oxygen isotopic records obtained from cores with sedimentation rates ranging from 1 to 12 cm 1000 yr 1 it is shown that the systematic change in the variance spectra of these records that is predicted by models of bioturbation cannot be observed for sedimentation rates greater than 2 cm 1000 yr 1 this can be explained in part if bioturbation is a function of sedimentation rates if this is the case then bioturbation must proceed to depth of tens to hundreds of centimeters however it seems likely that the degree to which bioturbation alters the climate signal preserved in deep sea sediment cores has been overestimated

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

rayleigh wave signature in ionograms induced by strong earthquakes 1 after the magnitude 9 0 earthquake off the pacific coast of tohoku near the east coast of honshu japan which occurred on 11 march 2011 an unusual multiple cusp signature mcs was observed in ionograms at three ionosonde stations across japan to investigate the general characteristics of mcss we examined ionograms obtained during the period 1957 to 2011 from five ionosonde stations in japan after earthquakes with a seismic magnitude of 8 0 or greater a total of 43 such earthquakes occurred after 1957 as recorded in the database of the united states geological survey mcss were observed in 8 of 43 earthquakes allowing us to investigate the specific conditions of mcs appearance the appearance of mcss at different epicentral distances exhibits traveling characteristics at a velocity of 4 0 km s which is in the range of rayleigh waves there is a 7 min offset in delay time after the earthquake at each epicentral distance in the travel time diagram this offset is consistent with the propagation time of acoustic waves from the ground to the ionosphere launched by rayleigh waves mcss in ionograms provide a snapshot of vertical disturbances induced by a wave because the sweep time for the whole ionospheric echo traces is much shorter than the propagation time of acoustic waves the vertical scale of the disturbances is 10 30 km which corresponds to an acoustic wave period of 20 50 s at ionospheric heights

natural remanent magnetization acquisition in bioturbated sediment general theory and implications for relative paleointensity reconstructions we present a general theory for the acquisition of natural remanent magnetizations nrm in sediment under the influence of a magnetic torques b randomizing torques and c torques resulting from interaction forces dynamic equilibrium between a and b in the water column and at the sediment water interface generates a detrital remanent magnetization drm while much stronger randomizing torques may be provided by bioturbation inside the mixed layer these generate a so called mixed remanent magnetization mrm which is stabilized by mechanical interaction forces during the time required to cross the surface mixed layer drm is lost and mrm is acquired at a rate that depends on bioturbation intensity both processes are governed by a mrm lock in function the final nrm intensity is controlled mainly by a single parameter that is defined as the product of rotational diffusion and mixed layer thickness divided by sedimentation rate this parameter defines three regimes 1 slow mixing 10 with mrm acquisition and full drm randomization and 3 intermediate mixing because the acquisition efficiency of drm is larger than that of mrm nrm intensity is particularly sensitive to in case of mixed regimes generating variable nrm acquisition efficiencies this model explains 1 lock in delays that can be matched with empirical reconstructions from paleomagnetic records 2 the existence of small lock in depths that lead to drm preservation 3 specific nrm acquisition efficiencies of magnetofossil rich sediments and 4 some relative paleointensity artifacts

infrasound from earthquakes 1 infrasonic signals have been observed from 31 earthquakes by arrays of microphones operated by the los alamos national laboratory between 1983 and 2003 the properties of the signals are presented signal amplitudes corrected for propagation and distance show a relation with seismic magnitude the variance in the relation is understood primarily in terms of the uncertainties or errors in the ground motion deduced from an independent data set and the stratospheric winds which strongly influence signal propagation signal durations can extend over many minutes a relation is found between signal duration and magnitude to understand this we propose a model in which regions distant from the epicenter are excited by seismic surface waves the surface motion of these regions in turn produces signals which precede or follow the signals from the epicenter analysis failed to detect signals from 56 earthquakes during the observation period predicted signal to noise ratios for these earthquakes indicated that the signals would have been too weak for detection

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

glacial history and paleoceanography of the southern yermak plateau since 132 ka bp abstract the southern yermak plateau yp is situated at the entrance to the arctic ocean in the narrow marginal ice zone miz between the polar and arctic fronts north west of svalbard a gravity core jm10 02gc has been analysed in order to reconstruct paleoceanographic conditions and the movement of the sea ice margin as well as the glacier ice conditions of the svalbard barents sea ice sheet sbis during the last interglacial glacial cycle the distribution of planktic and benthic foraminifera planktic and benthic oxygen and carbon isotopes and variations in ice rafted debris ird has been investigated the sediment core covers the time interval from the marine isotope stage mis 6 5e transition termination ii c 132 ka bp to the early holocene during termination ii tii the sbis retreated and the sea ice margin was in distal position whereas during mis 5 to mis 4 the sea ice margin was close to the core site several core intervals interpreted as representing mis 5e mis 5c mis 5a mis 3 and mis 1 were barren of calcareous microfossils whereas the intervals representing mis 4 and mis 2 were characterised by high productivity hp of planktic and benthic foraminifera these glacial hp zones were associated with the open water conditions resulting from the advection of atlantic water aw and retreat of the sea ice margin the barren zones during mis 5 mis 3 and mis 1 resulted from the proximity of the sea ice margin whereas during mis 2 the likely cause was an advance of the sbis

stratosphere perturbed by the 2011 mw9 0 tohoku earthquake this study examined the formosat 3 cosmic radio occultation soundings of total electron content in the ionosphere from 150 to 550 km and refractivity index in the lower atmosphere from 0 to 60 km after during the 2011 mw9 0 tohoku earthquake tsunami the refractivity index observations show the first evidence of the tohoku earthquake tsunami induced vertical oscillations in the lower atmosphere the atmospheric oscillations with vertical wavelength ranging from 0 5 to 8 km and from 10 to 40 km respectively appear in the stratosphere and ionosphere after the earthquake onset the short vertical wavelengths suggest that the oscillations are the atmospheric oscillatory tail due to the wavefront of the earthquake tsunami the radio occultation technique is a tool for detecting the atmospheric waves induced by earthquake or some other sources plain language summary it has been well known that the sudden uplift of the earth s surface due to earthquake tsunami significantly disturbs the upper atmosphere and ionosphere however the evidence of earthquake tsunami induced waves in the lower atmosphere is insufficient due to the lack of observation supporting here the formosat 3 cosmic f3 c radio occultation refractivity index is for the first time to capture the tohoku earthquake induced vertical oscillations at the stratosphere altitudes from 30 to 40 km the results in this study not only shed lights on understanding of earthquake tsunami waves perturbing the whole atmosphere but also suggest that the radio occultation technique can benefit to the earthquake tsunami warning system

giant ionospheric disturbances excited by the m9 3 sumatra earthquake of 26 december 2004 1 an mw 9 3 earthquake originated in the indian ocean off the western coast of northern sumatra at 00 58 53 universal time ut on 26 december 2004 two giant ionospheric disturbances at 01 19 and 04 10 ut are observed by a network of digital doppler sounders in taiwan the first disturbance excited mainly by rayleigh waves which consists of a packet of short period doppler shift variations results in vertical ionospheric fluctuations with a maximum velocity of about 70 m s and displacement of about 200 m the second disturbance in a w shaped pulse propagating at a horizontal speed of 360 70 m s is attributable to coupling of the atmospheric gravity waves agw excited by broad crustal uplift together with the following big tsunami waves around the earthquake source zone the accompanying ionosonde data suggest that the agw in the atmosphere may have caused the ionosphere to move up and down by about 40 km

origin of apparent magnetic excursions in deep sea sediments from mendeleev alpha ridge arctic ocean 1 arctic deep sea sediments often record intervals of negative inclination of natural remanence that are tens of centimeters thick implying magnetic excursions with durations of tens of thousand years that far exceed excursion durations estimated elsewhere and the lack of tight age control usually provides excessive freedom in the labeling of arctic excursions fortuitous variations in sedimentation rate have been invoked to explain the amplified excursions alternating field demagnetization of natural remanent magnetization nrm of sediment cores 08jpc 10jpc 11jpc and 13jpc recovered by the healy oden trans arctic expedition in august 2005 hotrax05 to the mendeleev alpha ridge yields apparent magnetic excursions in sediments deposited in the brunhes chron thermal demagnetization of the nrm however implies multiple magnetization components with negative inclination components usually unblocked below 350 c analysis of isothermal remanent magnetization acquisition curves from magnetic extracts indicates two magnetic coercivity components superimposed on one another magnetic experiments conducted under high and low temperatures show features that are characteristic for titano magnetite and titanomaghemite presence of the two magnetic phases is further confirmed by elemental mapping on a scanning electron microscope equipped for x ray energy dispersive spectroscopy eds and by high resolution x ray diffraction xrd it is unlikely that anomalously thick intervals of negative inclination in these brunhes aged sediments are caused by unusual behavior of the magnetic field in the arctic area we therefore attribute low and negative nrm inclinations in these cores to partially self reversed chemical remanent magnetizations apparently carried by titanomaghemite and acquired during the oxidation of detrital titano magnetite grains the high ti contents and high oxidation states indicated by eds and xrd data provide the conditions required for partial self reversal by ionic reordering during diagenetic maghemitization and this process appears to have affected all hotrax05 cores collected from the mendeleev alpha ridge

infrasonic sounds excited by seismic waves of the 2011 tohoku oki earthquake as visualized in ionograms after the m 9 0 tohoku oki earthquake in 2011 strong deformation of ionogram echo traces forming multiple cusp signatures mcss were observed at three stations 790 1880 km from the epicenter the vertical structure of the ionospheric disturbances was determined by true height analysis and compared with broadband seismograph records at stations close to the ionosondes these ionospheric disturbances were caused by vertically propagating acoustic waves excited by the up down ground motion of seismic waves numerical simulations have shown that acoustic waves with a period of 15 40 s and amplitude of order 1 mm s at the ground level were sufficient to create mcss as sharp as those observed these acoustic wave parameters are consistent with the seismic records if the motion of the air mass on the ground level is assumed to be the same as the ground motion the travel time diagram of the seismic records along the line connecting the epicenter and ionosondes showed that the first mcs ionogram detected at each station was caused by p waves while the others were caused by rayleigh waves

terrigenous events and climate history of the sophia basin arctic ocean periods of enhanced terrigenous input to the ocean s basins of the north atlantic have been reported for the last glacial period we present a set of new sediment cores recovered from the sophia basin north of svalbard which exhibit widespread ice rafted debris layers reflecting enhanced terrigenous input throughout the last 200 ka b p their consistent stratigraphic position sedimentological character high sedimentation rate and geochemical characteristic point to synchronously deposited layers which we name terrigenous input events ties owing to their higher densities they generate excellent reflectors for sediment penetrating acoustic devices and prominent acoustic layers in the imagery of sedimentary structures therefore ties can be used for regional acoustic stratigraphy each of the events can be linked to major glacial activity on svalbard however the early weichselian glaciation is not recorded as a tie and in agreement with other work might not have occurred on svalbard as a major glacial advance to the shelf break nonsynchronous timing of western and northern sources on svalbard points against sea level induced iceberg discharge events

arctic ocean deep sea record of northern eurasian ice sheet history the sediment composition of deep sea cores from the central arctic ocean the fram strait and the yermak plateau was analyzed for several parameters to reconstruct the history of marine paleoenvironment and terrestrial glaciation in the last 200 000 years layers with high amounts of coarse terrigenous ice rafted debris ird and often high contents of smectite were deposited during extensive glaciations in northern eurasia when ice sheets reached the northern continental margins of the barents and kara seas and discharged icebergs into the arctic ocean intercalated layers with relatively low ird and smectite contents but abundant planktic foraminifers in the coarse fraction were deposited during periods of atlantic water inflow to the arctic ocean and seasonally open waters leads in a sea ice cover with only few icebergs in the arctic ocean high ird contents in the sediments reflect the presence of ice sheets on the kara and barents seas shelves and the hinterland during the entire oxygen isotope stage 6 ca 190 130 ka in substage 5b ca 90 80 ka at the stage boundary 5 4 around 75 ka and in late stage 4 early stage 3 ca 65 50 ka these results are in excellent correlation with those from recent field work in northern scandinavia european russia siberia and on the shelves relatively low amounts of ird in central arctic ocean sediments from the late weichselian glacial maximum ca 24 18 ka correlate well with the recent reconstruction of a very limited eastern ice sheet extension during this time oxygen and carbon isotope records of planktic foraminifers from the analyzed sediment cores show a number of prominent excursions which can be interpreted as evidence for freshwater events in the arctic ocean the synchroneity of freshwater events and ird input suggests a common source strongest events were associated with deglaciations of the barents and kara seas after the ice sheets had blocked the outflow of large rivers for several millennia the outflow of freshwater from large ice dammed lakes occurred at ca 130 80 75 and 52 ka freshwater events in the central arctic ocean during the last deglaciation ca 18 ka were relatively small compared to the previous events this indicates that during most of the late weichselian glacial maximum a river outflow from northern siberia to the arctic ocean was possible atlantic water inflow to the arctic ocean and seasonally open waters in the ice leads occurred during the interglacials ofoxygen isotope stage 1 and substage 5e during several interstadials stage 3 substages 5a and 5c and to a lesser degree within stadials and glacials stages 2 4 and 6 with the exception ofthe interglacials these periods were times ofstrong ice growth on the continents as revealed by terrestrial data the coincidence suggests that open waters in the arctic ocean and the nordic seas were an important moisture source in addition to more southerly sources which fostered the growth of ice sheets on northern eurasia

theory and application of the day plot mrs ms versus hcr hc 2 application to data for rocks sediments and soils 1 new theoretical curves relating the hysteresis parameters mrs ms and hcr hc for single domain sd superparamagnetic sp pseudo single domain psd and multidomain md grains and their mixtures are applied to published data for natural materials the day plot of mrs ms versus hcr hc has been used to crudely classify samples into box like sd psd and md or sometimes incorrectly md sp regions with arbitrary boundaries new type curves for md psd sd md and sd sp grains and mixtures permit more subtle and precise modeling the predicted md trend and its junction with the psd trend are observed in two data sets for magnetite spherules from carbonate rocks and for temperature varying hysteresis results spanning the verwey transition the latter data are the basis of a suggested new method for pinpointing the psd md threshold size selected data for pottery clays soils and paleosols generally follow sd md type curves and indicate intermediate size psd magnetite with narrow to broad size distributions a lake sediment section with known grain size progression tracks in the predicted sense along the sd md trend selected data for glaciomarine and pelagic sediments are also generally compatible with sd md trends examples of remagnetized carbonate rocks submarine basaltic glasses and glassy rims of pillow basalts all follow predicted sp sd or sp psd mixing curves with a large range in volume fraction of sp grains 0 75 but a narrow range of sp particle sizes 10 2 nm larger sp grains spanning the range to sd size 25 30 nm are absent for unknown reasons oceanic dolerites gabbros and serpentinized peridotites in some cases fall in a novel region of the day plot parallel to but below magnetite sd md mixing curves

first ionospheric images of the seismic fault slip on the example of the tohoku oki earthquake 1 1hz gps measurements from the japanese gps network geonet allowed to retrieve information on the seismic fault of the great m9 0 tohoku oki earthquake from the ionosphere total electron content tec measurements the first arrival of the tec perturbation was registered 464 seconds after the earthquake 140 km on the east from the epicenter within next 45 seconds the distribution of ionospheric points imaged a rectangular area 37 39 39 28 n 142 8 143 73 e which coincides with the area of the coseismic crustal uplift from this source region the coseismic ionospheric perturbation further propagated at 1 3 1 5 km s such velocity values are 30 40 higher than previously reported for acoustic waves it is likely that we observed shock acoustic waves propagating at supersonic speed and having blown all the electrons available between the ground and the height of detection this fact is coherent with registration of the first arrival of perturbation 464 sec after the earthquake that is generally speaking too short time for a regular acoustic wave to reach the ionosphere our findings show that the real time gps monitoring of seismo active areas could inform about the parameters of coseismic crustal displacements and can be subsequently used for short term tsunami warnings in the case of the 03 11 2011 earthquake the first ionosphere perturbations were registered 17 minutes before the tsunami arrived on the east coast of honshu

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

surface waves of the 2011 tohoku earthquake observations of taiwan s dense high rate gps network 1 surface waves generated by the 2011 mw 9 0 tohoku japan earthquake were recorded by both the high rate gps and broadband seismic stations in taiwan in this study we investigate the precision of high rate gps displacements and estimate the feasibility of using gps for seismology study in taiwan one hertz observations of 210 continuous gps stations in taiwan and neighboring islands were processed using a precise point positioning technique to estimate the absolute epoch by epoch positions generated by the tohoku earthquake modified sidereal filtering was used to correct for near daily periodical variations of high rate position time series that may be influenced by multipath effects and a band pass filter was used to remove noises from marginal frequencies for all the 210 stations the gps precision after modified sidereal filtering improved from 8 2 to 7 4 mm in the horizontal and from 19 5 to 12 7 mm in the vertical components except for about 20 of the data with large position errors after applying the band pass filter in the teleseismic frequency band 0 008 0 08 hz excluding 54 stations with noisy data 156 continuous gps stations were selected surface wave displacements derived from both high rate gps and broadband seismometers are highly consistent and the correlation coefficients are enhanced by a band pass filter 0 008 0 08 hz from 0 85 to 0 95 in the horizontal and from 0 58 to 0 85 in the vertical components we consider continuous gps can be used as an alternative approach to study characteristics of surface wave propagation in taiwan

teleseismic magnetic effects tmds of 2011 tohoku earthquake 1 anomalous magnetic variations were observed by ground magnetometers in east asia area after the 2011 tohoku earthquake some earlier reports showed that the seismo magnetic variations have obvious amplitude around the epicenter we emphasis here that the variations can still be notable at stations 2000 4000 km away from epicenter and we define it as teleseismic magnetic disturbances tmds tmds appear about 8 min later after the arrival of seismic rayleigh waves at teleseismic distances and propagate at a horizontal velocity of 3 9 0 1 km s the wave like tmds last for no longer than 10 min and have a main period of 2 1 3 3 min tmds are not generated by direct effects of processes in focal area crust or tsunami waves instead their properties consist with the rayleigh wave model of seismo ionospheric disturbances hence we conclude that the tmds are the magnetic manifestation of seismotraveling ionospheric disturbances stids generated by the interaction between the ionosphere and atmosphere through acoustic waves launched by traveling rayleigh waves our findings contribute to the knowledge of seismo electromagnetic effects in the atmosphere ionosphere system and further our understanding of couplings between various spheres of the earth

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

arctic ocean glacial history while there are numerous hypotheses concerning glacial interglacial environmental and climatic regime shifts in the arctic ocean a holistic view on the northern hemisphere s late quaternary ice sh

ionospheric f2 region perturbed by the 25 april 2015 nepal earthquake seismic waves can be detected in the earth s atmosphere and ionosphere however their impacts on ionospheric electron density ne structures near the altitude of peak ne hmf2 have not yet been fully determined due to the lack of sufficient observations sampled in the vertical direction here we apply a ground based global positioning system gps receiving network in asia as well as the space based gps occultation experiment on board the formosat 3 cosmic f3 c satellite to vertically scan the ionospheric ne structures which were perturbed by the magnitude mw7 8 nepal earthquake that occurred on 25 april 2015 the f3 c altitudinal ne profiles show that the nepal earthquake induced air perturbations penetrate into the ionosphere at supersonic speeds of approximately 800 m s and change the ne structure by 10 near hmf2 the vertical scale of the ne perturbation is 150 km while the hmf2 is uplifted by more than 30 km within 1 min those results reveal that the earthquake induced ground displacement should be considered as a significant force that perturbs the vertical ne structure of the ionosphere

mineral magnetic properties of artificial samples systematically mixed from haematite and magnetite summary detailed rock magnetic investigations were carried out on a set of samples with defined ratios of haematite and magnetite the measured parameters provide a reference for interpreting common rock magnetic parameters in investigations of sediments the contribution of haematite to the magnetic fraction must exceed 95 wt of the magnetic fraction when mixed with magnetite in order to visibly influence grain size and coercitivity indicative magnetic parameters coercivity of remanence bcr and coercive force bc do not change in the same way with increasing haematite content which results in a peak bcr bc value at around 99 5 wt haematite variations in haematite content can be ignored when interpreting most rock magnetic parameters especially grain size indicative parameters for samples where haematite contents range from 0 to 98 wt the s ratio is still the most sensitive parameter for estimating the relative amount of haematite in magnetite haematite mixtures a combination of s ratio the saturation isothermal remanent magnetization divided by the low field magnetic susceptibility sirm lf and bcr is the most effective way to identify haematite in natural samples our results agree with literature data and fill the gap between results obtained either from pure magnetite or haematite with comparable grain sizes