potential and gravity changes raised by point dislocations summary we derive expressions in closed form which give the gravity potential changes caused by point dislocations they enable us to evaluate coseismic changes in surface gravity and geoid height numerical simulation shows that a great earthquake could cause a geoid height change of order 1 m

post processing removal of correlated errors in grace data 1 gravity fields produced by the gravity recovery and climate experiment grace satellite mission require smoothing to reduce the effects of errors present in short wavelength components as the smoothing radius decreases these errors manifest themselves in maps of surface mass variability as long linear features generally oriented north to south i e stripes the presence of stripes implies correlations in the gravity field coefficients here we examine the spectral signature of these correlated errors and present a method to remove them finally we apply the filter to a model of surface mass variability to show that the filter has relatively little degradation of the underlying geophysical signals we seek to recover

gravity changes due to the sumatra andaman and nias earthquakes as detected by the grace satellites a reexamination summary in this paper we study the geoid changes caused by the sumatra andaman earthquake 2004 december 26 and the nias earthquake 2005 march 28 using data from the gravity recovery and climate experiment grace satellites new is that we explore the possibility to separate the effects of the sumatra andaman and nias earthquakes based on correlation analysis we investigate the separability of the sumatra andaman and nias signals and the feasibility of separating the non seismic linear trend from the time dependent post seismic relaxation effect as input data we use 76 months of global geopotential coefficients from the gfz release 4 rl04 of grace data to suppress unphysical artefacts in grace data striping the grace coefficients are smoothed with an anisotropic decorrelation filter model parameters are estimated through a bayesian approach we compare our results with geophysical models of both earthquakes calculated based on the viscoelastic gravitational dislocation theory the slip models used are inverted from gps measurements our findings indicate that the inversion of grace data for the sumatra andaman effect will contain significant signal from the nias earthquake and will benefit from removing the modelled nias effect from the data comparing grace measurements to geophysical models reveals significant differences we suggest how the gps calibrated models may be improved to better fit the grace data in the first months after the earthquake we also find evidence for a fast process in the andaman sea possibly due to aseismic slip similar phenomena were observed in previous studies

observing coseismic gravity change from the japan tohoku oki 2011 earthquake with goce gravity gradiometry the japan tohoku oki earthquake 9 0 mw of 11 march 2011 has left signatures in the earth s gravity field that are detectable by data of the gravity field recovery and climate experiment grace mission because the european space agency s esa satellite gravity mission gravity field and steady state ocean circulation explorer goce launched in 2009 aims at high spatial resolution its measurements could complement the grace information on coseismic gravity changes although time variable gravity was not foreseen as goal of the goce mission we modeled the coseismic earthquake geoid signal and converted this signal to vertical gravity gradients at goce satellite altitude we combined the single gradient observations in a novel way reducing the noise level required to detect the coseismic gravity change subtracted a global gravity model and applied tailored outlier detection to the resulting gradient residuals furthermore the measured gradients were along track filtered using different gradient bandwidths where in the space domain gaussian smoothing has been applied one year periods before and after earthquake occurrence have been compared with the modeled gradients the comparison reveals that the earthquake signal is well above the accuracy of the vertical gravity gradients at orbital height moreover the obtained signal from goce shows a 1 3 times higher amplitude compared with the modeled signal besides the statistical significance of the obtained signal it has a high spatial correlation of 0 7 with the forward modeled signal we conclude therefore that the coseismic gravity change of the japan tohoku oki earthquake left a statistically significant signal in the goce measured gravity gradients

coseismic and postseismic deformation of the 2011 tohoku oki earthquake constrained by grace gravimetry 1 spaceborne gravimetry data from the gravity recovery and climate experiment grace are processed using spatio spectral slepian localization analysis enabling the high resolution detection of permanent gravity change associated with both coseismic and postseismic deformation resulting from the great 11 march 2011 mw 9 0 tohoku oki earthquake the grace observations are then used in a geophysical inversion to estimate a new slip model containing both coseismic slip and after slip the grace estimated moment for the total slip up to the end of july 2011 is estimated as 4 59 0 49 1022 n m equivalent to a composite mw of 9 07 0 65 if the moment for the tohoku oki main shock is assumed to be 3 8 1022 n m the contribution from the after slip is estimated to be 3 0 1021 12 8 1021 n m in good agreement with a postseismic slip model inverted from gps data we conclude that grace data provide an independent constraint to quantify co and post seismic deformation for the tohoku oki event

imaging and observing the electrical moho abstract defining the depth to the base of the crust is of profound importance for understanding and developing theories of the secular variation of our planet including crustal formation and evolution since its discovery 100 year ago the seismic moho is almost ubiquitously used as the crust mantle boundary reference laboratory studies on crustal and mantle rocks suggest that there should be a concomitant step lie change in electrical conductivity an electric moho emoho at the crust mantle boundary we examine resolution properties of electrical and electromagnetic methods for imaging and observing an emoho for three generic models one to represent the archean one for the proterozoic and the third for the phanerozoic we show that in all three cases given the existence in most localities of a conducting lower crust compared to the upper crust and upper lithospheric mantle the problem is difficult and at the edge and often beyond confident resolution for some highly unusual localities however the lower crust is more resistive than the underlying upper mantle and in those cases it is possible to resolve an emoho but very high quality data are required examples of emoho observations around the globe are discussed focussing on the results from a site on the southwestern part of the slave craton northwestern canada

electrical resistivity cross section across northern part of saurashtra region an insight to crystallized magma and fluids abstract saurashtra region forms the western part of the deccan volcanic province dvp in india and is bounded by the cambay rift basin crb in the east narmada rift basin nrb in the south and kachchh rift basin krb in the north this region is uplifted due to different stages of inter continental breakup madagascar india seychelles india different stages of rifting reactivation of fault zones and deccan volcanism the major portion of saurashtra region is covered by deccan basalts underlain by mesozoic sediments detailed magnetotelluric mt and long period magnetotelluric lmt soundings have been carried out in the northern part of saurashtra with an aim to bring out the geoelectrical configuration of different basins jamnagar jasdan and cambay along the profile 2d inversion carried out for different modes transverse electric te transverse magnetic mode tm and te tm independently the inversion of different modes shows distinct electrical signatures due to the 3d nature of the data we have considered the tm mode of interpretation because it is less prone to 3d distortions the final model represents large scale heterogeneities in the crust due to the presence of different resistive and conductive blocks high conductive lithosphere denotes the thermal influx of the mantle material to the base of the crust exchange of heat with the lower crust during basaltic magmatic underplating released carbonate fluids and or dehydration of minerals resulting in high conductivity anomalies a prominent conductive feature on the east side of the profile at upper crustal depths may be due to partial melts associated with mafic ultra mafic intrusions related to the reunion plume activity different resistive blocks in conjunction with seismic tomography studies represent recrystallized older precambrian crust that forms the uplifted blocks of jamnagar jasdan and western part of cambay basins

coseismic gravity changes of the 2010 earthquake in central chile from satellite gravimetry 1 the first map of coseismic changes in gravity and geoid height has been drawn using the data from the gravity recovery and climate experiment grace satellites for the 2004 sumatra andaman earthquake here we present the second case of coseismic gravity change observation by satellite gravimetry i e the change caused by an interplate thrust earthquake that occurred on 27 february 2010 in central chile mw 8 8 gravity showed a negative jump with the largest drop of 5 gal on the back arc side the observed changes agree with those calculated assuming the realistic earth and fault parameters inferred from coseismic displacements of global positioning system gps stations gravity in this area shows large seasonal and inter annual variability and postseismic gravity changes could be isolated only by carefully removing hydrological signals

crustal dilatation observed by grace after the 2004 sumatra andaman earthquake we report the detection of an earthquake by a space based measurement the gravity recovery and climate experiment grace satellites observed a 15 microgalileo gravity change induced by the great december 2004 sumatra andaman earthquake coseismic deformation produces sudden changes in the gravity field by vertical displacement of earth s layered density structure and by changing the densities of the crust and mantle grace s sensitivity to the long spatial wavelength of gravity changes resulted in roughly equal contributions of vertical displacement and dilatation effects in the gravity measurements the grace observations provide evidence of crustal dilatation resulting from an undersea earthquake

interseismic strain accumulation measured by gps in the seismic gap between constitucion and concepcion in chile the concepcion constitucion area 35 37 s in south central chile is very likely a mature seismic gap since no large subduction earthquake has occurred there since 1835 three campaigns of global positioning system gps measurements were carried out in this area in 1996 1999 and 2002 we observed a network of about 40 sites including two east west transects ranging from the coastal area to the argentina border and one north south profile along the coast our measurements are consistent with the nazca south america relative angular velocity 55 9 n 95 2 w 0 610 ma discussed by vigny et al 2008 this issue which predicts a convergence of 68 mm year oriented 79 n at the chilean trench near

normal mode simulation of prompt elastogravity signals induced by an earthquake rupture as soon as an earthquake starts the rupture and the propagation of seismic waves redistribute masses within the earth this mass redistribution generates in turn a long range perturbation of the earth gravitational field which can be recorded before the arrival of the direct seismic waves the recent first observations of such early signals motivate the use of the normal mode theory to model the elastogravity perturbations recorded by a ground coupled seismometer or gravimeter complete modelling by normal mode summation is challenging due to the very large difference in amplitude between the prompt elastogravity signals and the direct p wave signal we overcome this problem by introducing a two step simulation approach the normal mode approach enables a fast computation of elastogravity signals in layered self gravitating earth models the fast and accurate computation of gravity perturbations indicates instrument locations where signal detection may be achieved and may prove useful in the implementation of a gravity based earthquake early warning system

a new model for the dynamic evolution of chinese lithosphere continental roots plume tectonics abstract chinese continental lithosphere comprises three tectonic domains 1 eastern china a region characterized by rifting extensional basins and voluminous basaltic volcanism 2 central china a plexus of cratonic terrains with low heat flow 40 50 mw m2 including the tarim erdos and yangtze blocks welded by pre cenozoic orogenic belts and 3 western china a region comprising the qinghai tibet himalaya orogen the relatively thin crust 35 km and lithosphere 70 km of eastern china is believed to reflect mantle upwelling while near normal crust 45 km and thickened lithosphere 200 km in central china suggest a mantle lithosphere root resembling those inferred for the kaapvaal and siberian cratons thickened crust 70 km and lithosphere 150 km in western china reflect the advanced development of an orogen root the lower density and relative buoyancy of central cratonic mantle roots appear to have contributed to the long term tectonic stability of the central chinese lithospheric blocks in contrast gravitational instability produced by thickening of the denser western chinese lithosphere and the resulting subsidence and eventual delamination of orogenic roots are believed to have led to postorogenic extensional collapse although the geological relationships suggest compressional forces caused both mountain building and orogen root development extensional stress resulting from gravitational collapse is believed to have induced lithospheric and crustal thinning with concomitant reduction of topography the term continental roots plume tectonics has been adopted to describe the configuration and dynamic condition of subcontinental lithosphere and upper mantle beneath china accordingly it is proposed that supracrustal tectonic forms represent the surface expressions of and responses to deep continental roots plume tectonics while the prevailing view is that the western orogenic belt is not genetically related to eastern continental rifting such a relationship is inherent to the continental roots plume tectonics model it is further proposed that the formation of orogenic lithosphere roots triggered eastward extrusion of the asthenosphere along the 400 km depth mantle interface and in response to subduction at the eastern margin produces plume like upwelling beneath eastern china we suggest that processes involved in continental roots plume tectonics are directly responsible for the formation and evolution of the eurasian supercontinent

evidence of sea level rise at the early ostionan coralie site gt 3 c ad 700 grand turk turks and caicos islands abstract soil and sediment analyses were conducted on samples from the early ostionan coralie site c ad 705 60 on grand turk turks and caicos islands the earliest dated settlement site in the bahama islands the focus of these analyses was a sand layer mantling archaeological features discovered on a buried land surface the tapering wedge shaped configuration of the sand body prompted the hypothesis that it was deposited by water either a storm surge or a more gradual rise in sea level this hypothesis was tested using soil morphological descriptions particle size distribution analysis and grain characteristics contents of organic carbon and total phosphorus and identification of invertebrate organisms found in the soil samples a fining upward trend in particle size round and rolled grain shapes and a rich shallow water micro invertebrate infauna indicated a gradual marine transgression over the site as opposed to either a catastrophic storm event or aeolian deposition these results explain the incremental inland shift of settlement activity over time at coralie

a network of superconducting gravimeters detects submicrogal coseismic gravity changes with high resolution continuous gravity recordings from a regional network of superconducting gravimeters we have detected permanent changes in gravity acceleration associated with a recent large earthquake detected changes in gravity acceleration are smaller than 10 8 meters seconds 2 1 micro galileo about 10 9 times the surface gravity acceleration and agree with theoretical values calculated from a dislocation model superconducting gravimetry can contribute to the studies of secular gravity changes associated with tectonic processes

crustal structures revealed from a deep seismic reflection profile across the solonker suture zone of the central asian orogenic belt northern china an integrated interpretation abstract the solonker suture zone is one of the most important tectonic boundaries in the southeastern part of the central asian orogenic belt caob an 630 km long reflection seismic profile across this suture was recently completed by the chinese sinoprobe project the processed seismic data show clear crustal structures and provide new constraints on the tectonic and crustal evolution models the moho is delineated as a relatively flat boundary between a strongly reflective lower crust and a transparent mantle at a depth of 40 45 km 14 5 s two way travel time which is in agreement with the refraction data recorded along the same profile in a broad view the profile images an orogen that appears bivergent with and approximately centered on the solonker suture zone the southern portion of this profile is dominated by a crustal scale cratonward propagating fold and thrust system that formed during the late permian and triassic through collision and subsequent convergence in a post collisional stage the major thrust faults are truncated by mesozoic granitoid plutons in the upper crust and by the moho at the base of the crust this geometry suggests that the moho was formed after the thrusting event the northern portion of the profile although partially obliterated by post collisional magmatic bodies shows major south dipping folding and thrusting bands of layered reflectors immediately overlying the moho are interpreted as basaltic sills derived from the mantle episodic mafic underplating may have occurred in this region giving rise to post collisional magmatic events and renewal of the moho a few mantle reflectors are also visible the overall geometry of these mantle reflectors supports the tectonic models that the southern orogen manchurides experienced south directed subduction and the northern orogen altaids underwent north directed subduction prior to collision along the solonker suture zone

ellipsoidal correction in grace surface mass change estimation the earth s shape is much closer to an ellipsoid than a sphere the commonly used spherical approximation in mass change inversion is expected to cause bias by the spherical harmonic sh solutions from gravity recovery and climate experiment grace especially in high latitude regions where significant present day ice losses occur this bias or ellipsoidal correction reaches up to 8 from the evaluation by simulations based on synthetic mass change rate models further evaluation using 14 plus years of grace monthly sh solutions from april 2002 to december 2016 indicates that the ellipsoidal correction is also noticeable in the total mass change time series over polar regions before and after the ellipsoidal correction the estimated linear rates from mass change time series differ by 4 3 4 7 5 2 5 7 and 6 6 for five selected regions over greenland antarctic peninsula ap amundsen sea embayment ase alaska glacier and svalbard islands respectively although with amplitudes likely below the current grace s uncertainty level these differences are consistently negative over the five regions this indicates that the spherical approximation leads to systematic underestimation for polar mass change rates thus the ellipsoidal correction needs to be considered for more precise mass recovery with grace sh solutions it also depends on spatial scales of mass change signals the smaller the spatial scale the larger the correction to more reliably estimate high latitude surface mass changes by grace sh solutions the ellipsoidal correction is recommended especially for ice loss signals over polar regions

topographic effects on coseismic gravity change for the 2011 tohoku oki earthquake and comparison with grace we estimate gravity changes due to coseismic horizontal deformation and inclined bathymetry referred to as topographic effects in this study associated with the 2011 tohoku oki earthquake using a layered half space dislocation model as an approximation we represent inclined topography with ramp body models in the near field of the earthquake and calculate topographic effects from both an inclined seafloor and moho the moho effect partly compensates that from the seafloor an additional contribution comes from seawater column variations as the sloped seafloor moves trenchward topographic effects are first order contributions to coseismic gravity changes for the 2011 tohoku oki earthquake after 300 km gaussian smoothing comparable to the spatial resolution of the gravity recovery and climate experiment grace topographic effects create a dominantly negative gravity pattern with amplitudes up to 1 1 gal for oceanic areas surrounding the epicenter there are discrepancies between model predictions 10 4 to 6 9 gal and grace observations 10 1 to 1 7 gal errors in the adopted fault slip model and difficulties in separating coseismic and postseismic deformation may contribute to these but topographic effects currently neglected in dislocation models are also responsible topographic effects ought to be included in coseismic fault slip and related gravity modeling for the 2011 tohoku oki earthquake and similar events in regions of steep topography

geochronological framework of mesozoic volcanic rocks in the great xing an range ne china and their geodynamic implications abstract mesozoic volcanic rocks are widespread throughout the great xing an range ne china however precise data constraining the exact eruption ages are limited especially for those from the southern great xing an range which severely hampers our understanding of the petrogenesis and geodynamics of these rocks in this paper we report precise in situ la icpms zircon u pb age measurements for these volcanic rocks volcanic rocks in the southern great xing an range were divided into four units from bottom to top namely the manketouebo manitu baiyingaolao and meiletu formations the previous studies suggested that these volcanic rocks were mainly formed in the late jurassic our data demonstrate that the manketouebo formation erupted during late jurassic to early cretaceous time whereas the other formations are all of cretaceous age the southern great xing an range age dataset along with recently obtained precise ages for volcanic rocks from the northern great xing an range indicate that mesozoic volcanism throughout the great xing an range commenced in late jurassic but peaked during the cretaceous they formed under an extensional tectonic setting which resulted from closure of the mongol okhotsk ocean and subsequent orogenic collapse the globally elevated mantle temperature in cretaceous may provided thermal contributions to the generation of the volcanisms

coseismic slip of the 2010 mw 8 8 great maule chile earthquake quantified by the inversion of grace observations abstract the 27 february 2010 mw 8 8 maule chile earthquake ruptured over 500 km along a mature seismic gap between 34 s and 38 s the concepcion constitucion gap where no large megathrust earthquakes had occurred since the 1835 mw 8 5 event notable discrepancies exist in slip distribution and moment magnitude estimated by various models inverted using traditional observations such as teleseismic networks coastal river markers tsunami sensors global positioning system gps and interferometric synthetic aperture radar insar we conduct a spatio spectral localization analysis based on slepian basis functions of data from gravity recovery and climate experiment grace to extract coseismic gravity change signals of the maule earthquake with improved spatial resolution 350 km half wavelength our results reveal discernible differences in the average slip between the grace observation and predictions from various coseismic models the sensitivity analysis reveals that grace observation is sensitive to the size of the fault but unable to separate depth and slip here we assume the depth of the fault is known and simultaneously invert for the fault plane area and the average slip using the simulated annealing algorithm our grace inverted fault plane length and width are 429 6 km 146 5 km respectively the estimated slip is 8 1 1 2 m indicating that most of the strain accumulated since 1835 in the concepcion constitucion gap was released by the 2010 maule earthquake

expected improvements in determining continental hydrology ice mass variations ocean bottom pressure signals and earthquakes using two pairs of dedicated satellites for temporal gravity recovery 1 the gravity recovery and climate experiment mission has demonstrated the ability to quantify global mass variations at large spatial scales with monthly to sub monthly temporal resolution future missions of this type taking advantage of improved measurement technologies will be limited by temporal aliasing errors we suggest the addition of a second pair of satellites to reduce these errors using an optimized mission architecture consisting of a polar pair of satellites coupled with a lower inclined pair of satellites 72 both in 13 day repeating orbits we quantify the expected scientific improvements that having two pairs of satellites will provide over one pair numerical simulations to spherical harmonic degree 100 are run over one full year analysis using empirical orthogonal functions reveals that two satellite pairs determine annual mass variations in small basins which are undetected using one pair of satellites averaging kernels are used to show that two satellite pairs offer an 80 reduction in the level of error in determining mass variations in 53 hydrological basins and 12 greenland basins over the year after standard grace post processing techniques have been applied to the one pair solutions it is seen that two satellite pairs with no post processing still offer a 25 75 improvement in determining the mass variations spatiospectral localization analysis is used to show increased spatial resolution and higher signal to noise ratios in recovering hydrology in the amazon river basin ocean bottom pressure signals in the southeast pacific basin and a simulated earthquake signal representative of the 2010 maule chile earthquake

imaging the continental upper mantle using electromagnetic methods abstract the internal structure of the continental lithosphere holds the key to its creation and development and this internal structure can be determined using appropriate seismic and electromagnetic methods these two are complementary in that the seismic parameters usually represent bulk properties of the rock whereas electrical conductivity is primarily a function of the connectivity of a minor constituent of the rock matrix such as the presence of a conducting mineral phase e g carbon in graphite form or of a fluid phase e g partial melt or volatiles in particular conductivity is especially sensitive to the top of the asthenosphere generally considered to be a region of interconnected partial melt knowledge of the geometry of the lithosphere asthenosphere boundary is important as this boundary partially controls the geodynamic processes that create modify and destroy the lithosphere accordingly collocated seismic and electromagnetic experiments result in superior knowledge than would be obtained from using each on its own this paper describes the state of knowledge of the continental upper mantle obtained primarily from the natural source magnetotelluric technique and outlines how hypotheses and models regarding the development of cratonic lithosphere can be tested using deep probing electromagnetic surveying the resolution properties of the method show the difficulties that can be encountered if there is conducting material in the crust examples of data and interpretations from various regions around the globe are discussed to demonstrate the correlation of electromagnetic and seismic observations of the lithosphere asthenosphere boundary also the observations from laboratory measurements on candidate mineralogies representative of the mantle such as olivine are presented

time variability of the earth s gravity field hydrological and oceanic effects and their possible detection using grace the grace satellite mission scheduled for launch in 2001 is designed to map out the earth s gravity field to high accuracy every 2 4 weeks over a nominal lifetime of 5 years changes in the gravity field are caused by the redistribution of mass within the earth and on or above its surface grace will thus be able to constrain processes that involve mass redistribution in this paper we use output from hydrological oceanographic and atmospheric models to estimate the variability in the gravity field i e in the geoid due to those sources we develop a method for constructing surface mass estimates from the grace gravity coefficients we show the results of simulations where we use synthetic grace gravity data constructed by combining estimated geophysical signals and simulated grace measurement errors to attempt to recover hydrological and oceanographic signals we show that grace may be able to recover changes in continental water storage and in seafloor pressure at scales of a few hundred kilometers and larger and at timescales of a few weeks and longer with accuracies approaching 2 mm in water thickness over land and 0 1 mbar or better in seafloor pressure

improved constraints on seismic source parameters of the 2011 tohoku earthquake from grace gravity and gravity gradient changes a new approach of using only the north component of gravity change from gravity recovery and climate experiment grace data reveals that a substantially higher spatial resolution of the observed seismic deformation following the 2011 tohoku earthquake is achievable at 333 km or longer here we show that grace observed north component of gravity change 17 6 1 1 gal and the corresponding gravity gradient change e g txz at 1 25 0 09 meotvos agree well with seismic gps model predictions localized slepian spectrum analysis further confirms that the grace gravity and gravity gradient changes agree well with seismic model spectra and have powers up to the limit of the grace solution complete to spherical harmonic degree 60 using the gravity observations for the fault parameter inversion via simulated annealing algorithm we show that the estimated slip orientation and centroid location are different from gps seismic solutions and potentially due to the additional offshore constraint from grace data

coseismic and post seismic signatures of the sumatra 2004 december and 2005 march earthquakes in grace satellite gravity s u m m a r y the grace satellite mission has been measuring the earth s gravity field and its temporal variations since 2002 april although these variations are mainly due to mass transfer within the geofluid envelops they also result from mass displacements associated with phenomena including glacial isostatic adjustment and earthquakes however these last contributions are difficult to isolate because of the presence of noise and of geofluid signals and because of grace s coarse spatial resolution 400 km half wavelength in this paper we show that a wavelet analysis on the sphere helps to retrieve earthquake signatures from grace geoid products using a wavelet analysis of grace geoids products we show that the geoid variations caused by the 2004 december m w 9 2 and 2005 march m w 8 7 sumatra earthquakes can be detected at grace resolution the 2004 december earthquake produced a strong coseismic decrease of the gravity field in the andaman sea followed by relaxation in the area affected by both the andaman 2004 and the nias 2005 earthquakes we find two characteristic timescales for the relaxation with a fast variation occurring in the vicinity of the central andaman ridge we discuss our coseismic observations in terms of density changes of crustal and upper mantle rocks and of the vertical displacements in the andaman sea we interpret the post seismic signal in terms of the viscoelastic response of the earth s mantle the transient component of the relaxation may indicate the presence of hot viscous material beneath the active central andaman basin

the influence of gravity on the displacement field produced by fault slip we calculated surface displacements produced by a synthetic megathrust earthquake using two spherical layered elastic dislocation models which differ only in that one model accounts for the coupling between elasticity and gravity and the other does not we show that including gravity perturbs the displacement field differently in the near medium and far fields as a result slip inversions based on an earth model without gravity cannot simultaneously fit the near medium and far field displacements generated using a forward model including gravity this suggests that the spatially systematic misfits between observations and dislocation predictions seen in the literature arise at least in part because these studies are based on models that neglect gravity although the magnitude of the far field displacements is small compared to those of the near field our slip inversions show the most improvement when we both up weight the far field observations and use a physically consistent model in the inversion

coseismic deflection change of the vertical caused by the 2011 tohoku oki earthquake mw 9 0 summary this paper presents a scheme to compute coseismic deflection change and presents a set of green s functions for four independent dislocation sources to compare the theoretical deflection changes with the grace observed ones the dislocation love numbers are truncated and the green s functions are computed with application of a gaussian filter using this computing scheme the modelled coseismic geoid and deflection changes can be compared directly with the grace observed ones numerical computation and comparison show that the computing scheme is valid and efficient and that it can obviate much unnecessary computing time for high degree love numbers this study further examines the problem of sea water correction to modelled geoid and deflection changes because it is an important and necessary step to compare the modelled results with grace observed deformations as an application of the dislocation theory and the computing scheme described as a result of this study we consider the 2011 tohoku oki earthquake mw 9 0 using three different fault slip models using the fault models we compute the coseismic geoid and deflection changes for an area around japan considering sea water corrections results indicate that the coseismic geoid and deflection changes can be detected clearly by grace observation and the coseismic geoid change is not sensitive to the fault slip models the three slip models yield identical coseismic geoid changes whereas the coseismic deflection changes are very sensitive to the fault slip models because the modelled deflection changes indicate pretty large difference especially for the e w component these behaviours provide us a new and useful approach to invert seismic faults using grace observed deflection changes as constraints

fine crustal structure and deformation beneath the great xing an ranges caob revealed by deep seismic reflection profile abstract a crustal seismic reflection profile across the great xing an ranges gxar was recorded in 2011 revealed features of crustal structure and deformation at the eastern margin of the central asian orogenic belt caob the reliability of crust and upper mantle image was improved by rigorous regulations of seismic data acquisition and a series of special procedures for seismic data processing the diversiform seismic reflection fabrics within deep crust to mantle transition zone twt two way time 12 14 s approximately 36 42 km beneath gxar reflects the complicated products of tectonic and magmatic interaction of lower crustal and mantle components during evolution of gxar preliminary processing result shows the contact relationship of the gxar and adjacent basins we can identify lots of curved reflection phases from volcanic rock and opposite moho reflection events this scenario may suggest multi times tectonic transformation from contraction to extension presumably its cause of formation reflects the comprehensive dynamic action of the mongolia okhotsk tectonic system and the circum pacific tectonic system

a late glacial holocene palaeoecological record from pye lake on the eastern shore of nova scotia canadageological survey of canada contribution 20080395 pollen and chironomid analyses and radiocarbon dating at pye lake on the eastern shore of nova scotia are used to outline the vegetation and climatic history of the area the coast was deglaciated prior to 12 200 14c bp 14 300 cal bp and herbaceous tundra vegetation invaded the area midge inferred maximum summer surface water temperatures in the lake ranged between 9 and 11 c subsequent gradual warming to 18 c by 10 800 14c bp 12 725 cal bp favoured the migration of a variety of herbaceous and shrub taxa into the region rapid cooling to 10 c saw vegetation revert to herbaceous tundra communities this interval related to the younger dryas cold interval of the north atlantic and europe lasted until 10 000 14c bp 11 630 cal bp the climate then warmed again to conditions similar to those that prevailed immediately before onset of younger dryas cooling further warming saw successive tree species migrate into the area until by the mid holocene the forests contained most of the taxa preva

general formulations of global co seismic deformations caused by an arbitrary dislocation in a spherically symmetric earth model applicable to deformed earth surface and space fixed point summary based on the authors previous work co seismic deformations for a spherical symmetric earth model are summarized and reformulated unified expressions presented herein accommodate physical deformations displacement potential gravity geoid and strain changes the corresponding green s functions are derived by combining spheroidal and toroidal deformations sign errors in previous publications are corrected in these new formulas these expressions are developed basically for a deformed earth surface because most traditional geodetic measurements are performed on the terrain surface however through development of space geodetic techniques such as the satellite gravity missions co seismic gravity changes can be detected from space in this case the above dislocation theory e g the co seismic gravity change cannot be applied directly to the observed data because the data do not include surface crustal deformation the free air gravity change correspondingly the contribution by the vertical displacement part must be removed from the traditional expressions for this purpose we present the corresponding expressions applicable to space observations some numerical technical problems are discussed in addition a smoothing technique is necessary to damp the high frequency contribution so that the theory can be applied reasonably global co seismic deformations caused by the 2004 sumatra andaman earthquake m9 3 are studied as an application of the new green s function that earthquake caused a global deformation detected by gps strain metres and even a satellite gravity mission these global deformations are calculated based on the derived green s functions and the seismic wave derived earth model a segment summation scheme is used considering the slip distribution on a limited fault plane the results are useful for interpreting observed deformations especially those in the far field the earthquake reveals global co seismic deformations and effects of spherical curvature and the earth s layered structure comparisons between results for a spherical earth mode and a half space model show a large discrepancy at an epicentral distance of about 1000 km implying that effects of spherical curvature and layer structure are considerably large in addition the theoretical results are compared with the real observed strain steps horizontal displacements and gravity changes caused by that earthquake good agreement validates the results of the current theoretical work finally we discuss the application the above theory to the grace data through several case studies

the value of non pollen palynomorphs in interpreting paleoecological change in the great basin nevada usa non pollen palynomorphs npps are identifiable microfossils that survive chemical digestion during pollen extraction and appear in pollen slides they represent important proxies and indicators of environmental change that can be integrated with pollen studies of landscape history npps have been widely studied in europe since the 1970s and regularly included in paleoecological studies whereas in the united states only the most common npps have been routinely tallied the aim of this study is to contribute to the validation of the use of npps in the reconstruction of landscape history we analyzed npps in modern and fossil sediment samples from stonehouse meadow located in spring valley in the eastern part of central nevada we present a total of 64 modern and fossil npps with images and morphological descriptions given for all previously unknown npps and a selection of the most important known npps the comparison of pollen and npps in the fossil sediments improves our interpretation of the ecological changes of the last 8000 yr

long and short term postseismic gravity changes of megathrust earthquakes from satellite gravimetry using monthly satellite gravimetry data we studied time variable gravity field after three m9 class earthquakes the 2004 sumatra andaman 2010 chile maule and 2011 tohoku oki earthquakes the observations showed that the gravity typically 1 decreases coseismically 2 continues to decrease for a few months and 3 increases over a longer period therefore postseismic gravity changes have two components with different time constants and polarities the mechanisms of short and long term postseismic gravity changes are not as clear as coseismic changes at the moment but might be explained to some extent with afterslip and the maxwell viscoelasticity respectively these two components are difficult to discriminate with surface velocity measurements because the forearc area moves trenchward at both stages they appear in different polarities in gravity making satellite gravimetry a unique tool to separate them

source parameter inversion for recent great earthquakes from a decade long observation of global gravity fields we quantify gravity changes after great earthquakes present within the 10 year long time series of monthly gravity recovery and climate experiment grace gravity fields using spherical harmonic normal mode formulation the respective source parameters of moment tensor and double couple were estimated for the 2004 sumatra andaman earthquake the gravity data indicate a composite moment of 1 2 1023 n m with a dip of 10 in agreement with the estimate obtained at ultralong seismic periods for the 2010 maule earthquake the grace solutions range from 2 0 to 2 7 1022 n m for dips of 12 24 and centroid depths within the lower crust for the 2011 tohoku oki earthquake the estimated scalar moments range from 4 1 to 6 1 1022 n m with dips of 9 19 and centroid depths within the lower crust for the 2012 indian ocean strike slip earthquakes the gravity data delineate a composite moment of 1 9 1022 n m regardless of the centroid depth comparing favorably with the total moment of the main ruptures and aftershocks the smallest event we successfully analyzed with grace was the 2007 bengkulu earthquake with m0 5 0 1021 n m we found that the gravity data constrain the focal mechanism with the centroid only within the upper and lower crustal layers for thrust events deeper sources i e in the upper mantle could not reproduce the gravity observation as the larger rigidity and bulk modulus at mantle depths inhibit the interior from changing its volume thus reducing the negative gravity component focal mechanisms and seismic moments obtained in this study represent the behavior of the sources on temporal and spatial scales exceeding the seismic and geodetic spectrum

gravitational gradient changes following the 2004 december 26 sumatra andaman earthquake inferred from grace summary it has been demonstrated that the gravity recovery and climate experiment grace spaceborne gravimetry data are capable of observing coseismic gravity changes resulting from great earthquakes such as the 2004 december 26 sumatra andaman event mw 9 1 9 3 here we show for the first time that refined deformation signals from the 2004 december 26 sumatra andaman earthquake mw 9 1 9 3 together with the 2005 march 28 nias earthquake mw 8 6 can be revealed by deriving the full gravitational gradient tensor from grace monthly gravitational field the grace inferred coseismic gravitational gradient changes agree well with coseismic slip model predictions since the high frequency contents in gravitational field variation can be amplified by deriving the gravitational gradients the grace derived coseismic gravitational gradient changes clearly delineate the fault lines locate significant slips and better define the extent of the coseismic deformation

formulation of coseismic changes in earth rotation and low degree gravity field based on the spherical earth dislocation theory in this paper we present analytical formulas to compute the coseismic earth rotation change polar motion and length of day and low degree gravity field change based on a spherical dislocation theory using the preliminary reference earth model and our formulas we calculate coseismic changes in earth s rotation and low degree stokes coefficients caused by the four largest earthquakes since 1960 the results verify that the present method is consistent with previous studies but the method cannot be verified by the observations a case study on the 2011 tohoku oki earthquake mw 9 0 indicates that the coseismic earth rotation change depends on the magnitude and source parameters and results show a difference between a point source and finite fault model we also investigate the effect of seawater redistribution on coseismic earth rotation change but the effect is small and can be neglected

study on co seismic energy losses from hypocenter to ocean bottom for sumatra earthquake 2004 using 3 d crustal deformation model our co seismic grace gravity data level 2 rl 05 data product gx og 2 gsm for sumatra earthquake 2004 is obtained by differencing monthly gravity field average for november 2004 from that of january 2005 and band pass filtering 17 30 degrees and orders in spectral domain here we propose an 11 layered 3 d thrust fault gravity model based on several co seismic rupture models in literature previously we have covered the 3 d modelling details and its inferences like slip rate seismic moment momentum etc in our published literature further we extend the inferences through our model for this case study here we have estimated the layer wise energy distribution by undertaking two types energy loss one is spherical spreading and second absorption with constrained by literature we have computed layer wise energy loss equivalent energy differential pressure slip rate ultimate slip and work done the computed differential pressure and work done for sumatra earthquake 2004 are 1 7552 108 n m2 and 1 657 1018 j respectively we also estimated the absorption coefficient calculated absorption coefficients from our model to honour the slip rate of sumatra earthquake 2004 the differential pressure is estimated for ocean bottom and sea level surface the volumetric analysis is also provided for entire 3 d body layer wise using excess mass of our model the computed differential pressure indeed corresponds to an area pulse at ocean bottom that led to a tsunami generation

improved source parameter constraints for five undersea earthquakes from north component of grace gravity and gravity gradient change measurements abstract the innovative processing of gravity recovery and climate experiment grace data using only the north component of gravity change and its corresponding gravity gradient changes allows the enhancement of the spatial resolution for coseismic deformation signals here we report the study of five undersea earthquakes using this technique the 2004 sumatra andaman earthquake the 2007 bengkulu earthquake the 2010 maule chile earthquake the 2011 tohoku earthquake and the 2012 indian ocean earthquakes by using the high spherical harmonic degree up to degree 96 data products and the associated grace data processing techniques the retrieved north component of gravity change is up to 34 1 4 gal for the 2004 sumatra andaman earthquake which illustrates by far the highest amplitude of the coseismic signal retrieved from satellite gravimetry among previous studies we creatively apply the localized spectral analysis as an efficient method to empirically determine the practical spherical harmonic truncation degree by combining least squares adjustment with the simulated annealing algorithm point source parameters are estimated which demonstrates the unique constraint on source model from grace data compared to other data sources for the 2004 sumatra andaman earthquake grace data produce a shallower centroid depth 9 1 km as compared to the depth 28 3 km from gps data for the 2011 tohoku earthquake the grace estimated centroid location is southwest of the gps seismic solutions and the slip orientation is about 10 clockwise from the published gps seismic slip models we concluded that these differences demonstrate the additional and critical offshore constraint by grace on source parameters as compared to gps seismic data

pollen analysis of core ds7 1sc dead sea showing intertwined effects of climatic change and human activities in the late holocene the dead sea sediment holds the archives of a complex relationship between ever changing nature and ancient civilisations here the detailed pollen analyses of core ds7 1sc off ein gedi are presented for the first time the record covers the last 2500 years the facies changes from halite when no freshwater flows in the dead sea to laminites when rainfall provides sufficient inflow for the jordan and subsidiary rivers a couple of times through the record the pollen diagram supported by the facies change shows a wetter roman byzantine period which allowed intensive arboriculture and a wetter period at the end of the xixth and beginning of the xxth centuries the latter in good relation with historical and instrumental data based on radiocarbon chronologies on several pollen diagrams along the western dead sea shore the transition to drier climates and the transition to pastoralism are suggested to take place between a few decades before the islamic period and close to this transition a high resolution palynological study of the individual laminae forming the laminites aragonite and gypsum in the summer versus detritics in winter confirms the seasonal character of the laminae but throws a note of caution as for their regular annual character

variations in the earth s oblateness during the past 28 years 1 analysis of satellite laser ranging slr data indicates that the earth s dynamic oblateness j2 has undergone significant variations during the past 28 years the dominant signatures in the observed variations in j2 are 1 a secular decrease with a rate of approximately 2 75 10 11 yr 1 2 seasonal annual variations with a mean amplitude of 2 9 10 10 3 significant interannual variations with timescales of 4 6 years and 4 a variation with period of 21 years and an amplitude of 1 4 10 10 with minimum in december 1988 two large interannual variations are related to the strong el nino southern oscillation events during the periods of 1986 1991 and 1996 2002 and it appears that another interannual cycle may have started in late 2002 the superposition of the decadal variation on the interannual signal makes the j2 fluctuation appear to be anomalously large during the 1996 2002 period contemporary models of the mass redistributions in the atmosphere ocean and surface water can explain a major part of the 4 to 6 year fluctuations however the cause of the decadal variation remains unknown

the crustal accretion history and tectonic evolution of the ne china segment of the central asian orogenic belt abstract the basement rocks in parts of ne china constitute a khondalitic sequence of sillimanite and garnet bearing gneisses hornblende plagioclase gneiss and various felsic paragneisses zircon u pb dating of garnet sillimanite gneiss samples from the erguna xing an jiamusi and khanka blocks indicates that high grade metamorphism occurred at 500 ma evidence from detrital zircons in paleozoic sediments from the songliao block also indicates the former presence of a 500 ma component this uniformity of u pb ages across all crustal blocks in ne china establishes a 1300 km long late pan african khondalite belt which we have named the ne china khondalite belt this indicates the blocks of ne china were amalgamated prior to 500 ma contrary to current belief one scenario is that this amalgamated terrane had a tectonic affinity to the siberia craton once forming part of the late pan african 500 ma sayang baikal orogenic belt extensively developed around the southern margin of the siberia craton this belt was the result of collision between currently unidentified terranes with the southeastern angara anabar province at about 500 ma where the rocks were deformed and metamorphosed to granulite facies it appears likely that at sometime after 450 ma the combined ne china blocks rifted away from siberia and moved southward to form what is now ne china the combined block collided with the north china craton along the solonker xar moron changchun suture zone at 230 ma rather than in the end permian as previously thought local rifting at the eastern extremity of the developing central asian orogenic belt caob resulted in the splitting away of the jiamusi khanka bureya blocks however this was only transient and sometime between 210 and 180 ma these were re united with the caob by the onset of pacific plate subduction which has dominated the tectonic evolution of the region since that time

the location and evolution of the tectonic boundary between the paleoproterozoic jiao liao ji belt and the longgang block northeast china abstract in this paper we discuss the location nature and evolution of the tectonic boundary between the jiao liao ji belt and the longgang block northeast china the boundary in terms of paleogeography which involves a study of the liaohe group or tectonics employing non seismic geophysical data e g gravity data and magnetotelluric soundings existing geological data and the differences in physical properties between the jiao liao ji belt and the longgang block we clarified the spatial distribution of the tectonic boundary and characterized the geological bodies at different depths on either side of the boundary we analyzed the most recently updated bouguer gravity anomaly gravity magnetic and electrical profile data as well as comprehensive data on the physical properties of the rocks in the research area thus providing information on the geological nature of the boundary at deep levels the results indicate that during the early period of formation of the jiao liao ji belt a basin controlling boundary fault developed that constituted the original tectonic boundary between the jiao liao ji belt and the longgang block this fault extended from shuangtaling to sandaoling lian shanguan dawanggou balidianzi and erhulai to guaimozi following a roughly east west trend most previous studies have considered that the liaohe group which extends from benxi city to benxi county and huanren county is the paleo geographic boundary of the jiao liao ji belt

palynological records of red tide producing species in canada past trends and implications for the future abstract increases in red tides and other harmful algal blooms habs during the past 50 yr on both the atlantic and pacific coasts of canada suggest that global scale factors such as climate change and increased international shipping trade are the driving forces because the historical record is too short to understand the long term dynamics of habs the holocene history of harmful phytoplankton species was examined using ultra high resolution studies annual to decadal scale of dinoflagellate cysts as a proxy for red tide production paleoecological transfer functions were then applied to the cyst assemblage data to determine correlations with changes in sea surface temperature and salinity pacific records were obtained from varved marine sediments in saanich inlet british columbia and in the santa barbara basin off california comparison of annual cyst production and historical plankton data provides cyst theca ratios from which the magnitude of past bloom size can be evaluated the 10 500 yr pacific record clearly shows that the largest blooms correspond to cysts of protoceratium reticulatum and gonyaulax spinifera during the early holocene sporadic blooms of potentially toxic alexandrium spp lingulodinium polyedrum and gymnodinium spp also occurred from ca 7000 to 5000 yr bp and more frequently from ca 2000 to 3000 yr bp individual holocene blooms were up to 10 times larger than in the historical record but they almost always occurred sequentially without overlap of red tide species in pre historical times the bloom cycles started and stopped abruptly in 10 yr or less and they persisted for about 100 1000 yr in contrast the variability and near concurrence of species blooms in the modern past 60 yr record is unmatched in the past and suggests disequilibrium of the natural ecosystem structure atlantic records from la have and emerald basins on the scotian shelf are less precise because bioturbation limits time resolution to ca 25 yr however cyst abundances of cf alexandrium protoceratium reticulatum gonyaulax spinifera and lingulodinium polyedrum were also an order of magnitude larger in the early holocene where they correspond to a summer sea surface warming of 2 5 c lesser peaks also appear during the past 2000 yr where they apparently correspond to a slight increase in winter temperature there is no evidence of much lower salinity that would support stronger stratification the similarity of pre industrial age cyst records of red tide histories in the oceanographically different pacific and atlantic regions of canada indicates that climate change including surface temperature and storminess is the main driving force stimulating blooms this implies that habs will reoccur regardless of efforts to limit spreading however reduced pollution may decrease the hab diversity thereby stabilizing the population dynamics and increasing the predictability of bloom occurrences

petrology and isotopic geochemistry of dawsonite bearing sandstones in hailaer basin northeastern china abstract the co2 gas reservoir sandstones in the hailaer basin contain abundant dawsonite and provide an ideal laboratory to study whether any genetic relationship exists between dawsonite and the modern gas phase of co2 the origins of dawsonite and co2 in these sandstones were studied by petrographic and isotopic analysis according to the paragenetic sequence of the sandstones dawsonite grew later than co2 charging at 110 85 ma the dawsonite 18o value is 7 4 smow and the calculated 18o values of the water present during dawsonite growth are from 11 4 to 9 2 smow this combined with the nahco3 dominated water linked to dawsonite growth suggests meteoric water being responsible for dawsonite growth the 13c values of gas phase co2 and the ratios of 3he 4he of the associated he suggest a mantle magmatic origin of co2 rich natural gas in hailaer basin dawsonite 13c values are 5 3 to 1 5 average 3 4 and the calculated 13c values of co2 gas in isotopic equilibrium with dawsonite are 11 4 to 7 3 these c isotopic values are ambiguous for the dawsonite c source from the geological context the timing of events together with formation water conditions for dawsonite growth dawsonite possibly grew in meteoric derived water atmospherically derived co2 maybe or at least the dominant c source for dawsonite it seems that there are few relationships between dawsonite and the modern gas phase of co2 in the hailaer basin

late mesozoic calc alkaline volcanism of post orogenic extension in the northern da hinggan mountains northeastern china abstract late mesozoic calc alkaline volcanism in the northern da hinggan mountains ndhm ne china exhibits geochemical and sr nd isotopic characteristics similar to those of cenozoic calc alkaline volcanism in the basin and range province usa whole rock k ar dating results show that these volcanic sequences were erupted during 138 116 ma composed of basaltic andesites trachyandesites group 1 hornblende andesites trachytes group 2 and rhyolite lavas group 3 they are characterized by low mgo contents 4 20 lile lree enrichment and significant nb ta depletion as well as a little depleted to slightly enriched nd and weakly enriched sr isotopic ratios group 1 initial 87sr 86sr 0 70502 0 70572 nd t 0 78 to 0 91 group 2 initial 87sr 86sr 0 70497 0 70518 nd t 0 86 to 1 26 group 3 initial 87sr 86sr 0 70510 0 70635 nd t 0 41 to 0 25 the systematic variations in major and trace elements homogeneous sr nd isotope data and temporal consistency among three volcanic groups indicate that they were derived from a similar mantle source metasomatized by fluids related to the closure of the paleo asian and or mongolia okhotsk oceans and were produced through different degrees of fractional crystallization of the primary melts group 1 basaltic rocks were formed through removal of olivine and pyroxene of the primary melts while group 2 trachytes which contain the lowest lree contents e g la 24 28 ppm and relatively less enriched sr and higher nd isotope ratios were generated after removal of a few percent of lree rich minerals such as hornblende clinopyroxene and apatite of melts like group 1 group 3 rhyolite lavas exhibiting the highest abundances of strongly incompatible elements such as rb and k moderate lree contents e g la 28 53 ppm as well as apparently negative eu and sr anomalies represent the final crystallized products following a plagioclase predominant fractionation of melts like group 2 the low mgo contents and evolved affinities of the volcanic rocks imply that beneath the ndhm there existed many crustal magma reservoirs throughout the eruption episodes in which mantle derived primary melts had experienced intense differentiation these facts in combination with the contemporaneous basin and range tectonic regime suggest that the extensive calc alkaline volcanism in the ndhm was attributed to post orogenic diffuse extension rather than either an upwelling mantle plume or mesozoic oceanic plate subduction

late quaternary pollen transport processes western north atlantic data from box models cross margin and n s transects abstract surface pollen assemblages in coastal and neritic sediments of the western north atlantic compare well with eastern north american vegetation zones and late quaternary pollen in marginal marine sediments clearly correlate with changes in terrestrial vegetation and paleoclimates in contrast offshore assemblages are strongly affected by differential adaptation of pollen to long distance transport by wind and water marine pollen transport processes were studied by measuring air and water inputs to a coast shelf box model and by study of surface samples from cross margin transects in three different climatic and oceanographic regions at approximately 38 45 and 55 n latitude the box model shows that aerial transport is the main process by which pollen moves across the continental margin off nova scotia two clear seabed distribution patterns were found betula quercus and herb pollen decrease rapidly offshore in abundance grains per cubic centimetre and in relative abundance percentage pinus and picea have abundance peaks on the continental margin but percentages increase further offshore distributions of the main pollen and spore taxa were compared for late wisconsinan glacial oxygen isotopic stage 2 12 28 ka terminal pleistocene 10 12 ka and holocene sediments at 5 continental margin and 3 deep sea sites the largest changes were found in percentages of pinus picea and herb pollen during the late wisconsinan glacial and terminal pleistocene intervals at subpolar latitudes these data can be related to shifts in paleo vegetation winds and hydrology that accompany global climate change

lithospheric electrical structure between the erguna and xing an blocks evidence from broadband and long period magnetotelluric data abstract the central asian orogenic belt caob is the largest accretionary orogen on earth and its evolution has been controversial for a long time northeast china and adjacent regions form the eastern portion of the caob which is an important area for exploring the tectonic evolution of both the northeast asia and the caob the erguna and xing an blocks are two micro blocks in the west of northeast china the magnetotelluric mt method can study subsurface electrical structures a dense broadband and long period magnetotelluric mt profile across the collision belt of the two blocks has been completed based on the results of data analysis a three dimensional 3 d resistivity model of the crust and upper mantle has finally been obtained the mt results show that the derbugan fault is not a suture zone whereas the xinlin xiguitu fault is considered the boundary of the erguna and xing an blocks by westward subduction the conductive bodies in the middle lower crust of the erguna and xing an blocks may have been formed in an extensional environment and imply that the crust is weak the collision belt includes a prominent high conductivity anomaly from the lower crust to the upper mantle and indicates the existence of mantle upwelling associated with probable delamination

storms and shoreline retreat in the southern gulf of st lawrence abstract storms play a major role in shoreline recession on transgressive coasts in the southern gulf of st lawrence gsl southeastern canada long term relative sea level rise off the north shore of prince edward island has averaged 0 3 m century over the past 6000 years 0 2 m century over 2000 years this has driven long term coastal retreat at mean rates 0 5 m a but the variance and details of coastal profile response remain poorly understood despite extensive sandy shores sediment supply is limited and sand is transferred landward into multidecadal to century scale storage in coastal dunes barrier washover deposits and flood tidal delta sinks charlottetown tide gauge records show mean relative sea level rise of 3 2 mm a 0 32 m century since 1911 a further rise of 0 7 0 4 m is projected over the next 100 years when differenced from tidal predictions the water level data provide a 90 year record of storm surge occurrence combined with wind wave hindcast and sea ice data this provides a catalogue of potentially significant coastal storms we also document coastal impacts from three recent storms of great severity in january and october 2000 and november 2001 digital photogrammetry 1935 1990 and shore zone surveys 1989 2001 show large spatial and temporal variance in coastal recession rates weakly correlated with the storm record in part because of wave suppression or coastal protection by sea ice large storms cause rapid erosion from which recovery depends in part on local sand supply but barrier volume may be conserved by washover deposition barrier shores with dunes show high longshore and interdecadal variance with extensive multidecadal healing of former inlet and overwash gaps this reflects recovery from an episode of widespread overwash prior to 1935 possibly initiated by intense storms or groups of storms in the latter half of the 19th century with evidence from the storms of 2000 2001 this points to the importance of storm clustering on scales of weeks to years in determining erosion vulnerability as well as the need for a long term large scale perspective in assessing coastal stability the expected acceleration in relative sea level rise together with projections of increasing storm intensity and greatly diminished winter ice cover in the southern gsl implies a significant increase in coastal erosion hazards in future

crustal gravitational potential energy change and subduction earthquakes crustal gravitational potential energy gpe change induced by earthquakes is an important subject in geophysics and seismology for the past forty years the research on this subject stayed in the stage of qualitative estimate in recent few years the 3d dynamic faulting theory provided a quantitative solution of this subject the theory deduced a quantitative calculating formula for the crustal gpe change using the mathematic method of tensor analysis under the principal stresses system this formula contains only the vertical principal stress rupture area slip dip and rake it does not include the horizontal principal stresses it is just involved in simple mathematical operations and does not hold complicated surface or volume integrals moreover the hanging wall vertical moving up or down height has a very simple expression containing only slip dip and rake the above results are significant to investigate crustal gpe change commonly the vertical principal stress is related to the gravitational field substituting the relationship between the vertical principal stress and gravitational force into the above formula yields an alternative formula of crustal gpe change the alternative formula indicates that even with lack of in situ borehole measured stress data scientists can still quantitatively calculate crustal gpe change the 3d dynamic faulting theory can be used for research on continental fault earthquakes it also can be applied to investigate subduction earthquakes between oceanic and continental plates subduction earthquakes hold three types a crust only on the vertical up side of the rupture area b crust and seawater both on the vertical up side of the rupture area c crust only on the vertical up side of the partial rupture area and crust and seawater both on the vertical up side of the remaining rupture area for each type we provide its quantitative formula of the crustal gpe change we also establish a simplified model called crw model as follows for type b and type c subduction earthquakes if the seawater average depth on the vertical up side of the rupture area is less than a tenth of the hypocenter depth then take the approximation that the seawater above the continental plate is replaced by the upper crustal material of the continental plate the formula of quantitative calculating the crustal gpe change is also provided for this model finally for 16 september 2015 mw 8 3 illapel chile earthquake we apply crw model and obtain the following results the crustal gpe change is equal to 1 8 1019 j and the hanging wall vertical moving up height is 1 9 m with respect to the footwall we believe this paper might be the first report on the quantitative solution of the crustal gpe change for this subduction earthquake our results and related method will be helpful in research into the earthquakes in peru chile subduction zone and the andean orogeny in short this study expounds a new method for quantitative determining the crustal gpe change caused by subduction earthquakes which is different from other existing methods

slip distribution of the february 27 2010 mw 8 8 maule earthquake central chile from static and high rate gps insar and broadband teleseismic data 1 the shallow depth underthrust earthquake of february 27 2010 mw 8 8 ruptured the subduction plate interface in central chile between 34 s and 38 s we retrieve the spatial and temporal distribution of slip during this mega earthquake through a joint inversion of teleseismic records insar and high rate gps hrgps data additionally our model is shown to agree with broadband surface waves rupture initiated at about 32 km depth and propagated bilaterally resulting in two main slip zones located ssw and nne of the hypocenter nucleation did not take place within or at the edge of one of these main asperities but in between during the first 30s slip propagated predominantly southwards later on the rupture evolved more slowly and more symmetrically eventually the northern asperity became predominant with maximum slip reaching about 20 m most of the seismic moment was released within 110s a relatively short time explained by the bilateral propagation the overall average rupture velocity is 2 6 km s but propagation occurred initially faster towards the south 3 2 km s large slip did not reach the trench a result consistent with the moderate size of the tsunami down dip rupture stopped at about 50 km depth in agreement with the lower limit of the locked zone inferred by ruegg et al 2009 from pre seismic gps data

slow postseismic recovery of geoid depression formed by the 2004 sumatra andaman earthquake by mantle water diffusion 1 earthquakes are accompanied with mass redistributions and cause changes in gravity field and shape of geoid an equipotential surface coincident with the mean sea surface such coseismic changes were detected by satellite gravimetry after the 2004 sumatra andaman earthquake but little has been known on what happens on geoid after the earthquake here we report slow postseismic recovery of coseismic geoid depression from satellite measurements this cannot be explained with simple afterslip or viscous relaxation of maxwellian upper mantle it suggests the relaxation of coseismic dilatation and compression by the diffusion of supercritical h2o abundant in the upper mantle such a self healing system of coseismic geoid undulations a brand new role of water in mantle would significantly reduce the amount of permanent shifts of the earth s rotation axis by earthquakes

coseismic gravity changes of the 2011 tohoku oki earthquake from satellite gravimetry 1 the massive tohoku oki earthquake of a moment magnitude mw of 9 0 occurred on 11 march 2011 off the pacific coast of the northeastern japan the mass redistribution in and around the focal region associated with this earthquake was studied using the gravity changes detected by gravity recovery and climate experiment grace satellite after the 2004 sumatra andaman and the 2010 central chile maule earthquakes the present study presents the third case of clear detection of coseismic gravity changes by grace the observed gravity changes were dominated by decrease over the back arc region of 7 gal or less this reflects to a large extent coseismic crustal dilatation of the landward plate they agree well with the changes calculated with the green s function for the realistic earth using fault parameters inferred from coseismic crustal movements the spatial patterns of the gravity changes of these earthquakes are very similar because they are all shallow angle reverse faulting at convergent plate boundaries we found linear relationship between gravity decreases and seismic moments

the lithosphere structure of the great xing an range in the eastern central asian orogenic belt constrains from the joint geophysical profiling abstract the great xing an range is characterized by a complex crustal history involving the successive development of several paleozoic to mesozoic tectonic domains a set of new different geophysical data including deep seismic reflection profile seismic refraction wide angle reflection profile and magnetotelluric survey were conducted recently to establish the lithosphere structure and geodynamic framework of the great xing an range and adjacent basins results based on the interpretation of the integrated geophysical data include the discovery of the crocodile style assembly fabric of the songnen and xing an blocks the intrusion of the great xing an range continental crust into the songnen block while the mantle lithosphere of the songnen block beneath the xing an block the great xing an range experienced the delamination and the underplating which is very common in the eastern part of central asian orogenic belt the building of the great xing an range could divide into two phases a the crustal shortening and overlapping resulted from the compression between the songnen and xing an blocks in late devonian to early carboniferous b the vertical building by the upwelling and underplating of the magmas in mesozoic and cenozoic

what drove late mesozoic extension of the northern china mongolia tract the northern china mongolia tract exhibited a tectonic transition from contractional to extensional deformation in late mesozoic time late middle to early late jurassic crustal shortening is widely thought to have resulted from collision of an amalgamated north china mongolia block and the siberian plate but widespread late late jurassic early cretaceous extension has not been satisfactorily explained by existing models some prominent features of the extensional tectonics of the northern china mongolia tract are 1 late jurassic voluminous volcanism prior to early cretaceous large magnitude rapid extension 2 overlapping in time of contractional deformation in the yinshan yanshan belt with development of extensionrelated basins in the interior of the northern china mongolia tract and 3 widespread occurrence of alkali granitic plutonism extensional basins and metamorphic core complexes in the early cretaceous a new explanation is advanced in this study for this sequence of events the collision of amalgamated north china mongolia with siberia led to crustal overthickening of the northern china mongolia tract and formation of a high standing plateau subsequent breakoff at depth of the north dipping mongol okhotsk oceanic slab is suggested as the main trigger for late mesozoic lithospheric extension of that tract slab breakoff resulted in mantle lithospheric stretching of the adjacent northern china mongolia tract with subsequent ascent of hot asthenosphere and magmatic underplating at the base of the crust collectively these phenomena triggered gravitational collapse of the previously thickened crust leading to late late jurassic early cretaceous crustal extension and importantly coeval contraction along the southern margin of the plateau in the yinshan yanshan belt the proposed model provides a framework for interpreting the spatial and temporal relationships of distinct processes and reconciling some seemingly contradictory phenomena such as the synchronous extension of northerly terranes during major contraction in the neighboring yanshan yinshan belt d 2003 elsevier b v all rights reserved

palynological study of a mi kmaw shell midden northeast nova scotia canada before now no palynological studies were made on shell midden deposits in nova scotia despite a long history of archaeological research a test study of samples taken from the shell midden at maligomish indian island on the northumberland strait was conducted to determine if sufficient pollen fern and moss spores and other non pollen palynomorphs npp s including fungal remains algal spores could be recovered to allow interpretation of environmental conditions at the time of deposition several pollen processing methods were tested sieving and swirling chemical treatment with cold hcl 5 koh and brief exposure to 5 nh4oh and treatment with acetolysis solution we recovered variable amounts of pollen spores and npp s from samples taken at 3 5 cm 5 15 cm and 15 25 cm below surface abundant microcharcoal fragments prevented effective use of the swirling technique but sufficient palynomorphs were recovered by chemical treatments to allow assessment of down section changes in assemblages three radiocarbon ages from mya arenaria and crassostrea sp and measurements of sediment grain size moisture organic and inorganic carbon provide a framework for analysing palynological assemblage changes and context for interpreting differential palynomorph preservation despite some oxidation and microbial degradation of palynomorphs in the time interval ca 380 1600 cal yr bp the midden assemblages correlate with pollen zones from marine and lake core sites within ca 50 km of maligomish shifts in abundances of algal spores testate amoebae and aquatic plant pollen also indicate changes in depositional conditions during the time of midden use the study provides the first reference for archaeologists attempting to use palynology for analysis of samples from nova scotian shell bearing contexts

upper mantle rheology from grace and gps postseismic deformation after the 2004 sumatra andaman earthquake 1 mantle rheology is one of the essential yet least understood material properties of our planet controlling the dynamic processes inside the earth s mantle and the earth s response to various forces with the advent of grace satellite gravity measurements of mass displacements associated with many processes are now available in the case of mass displacements related to postseismic deformation these data may provide new constraints on the mantle rheology we consider the postseismic deformation due to the m w 9 2 sumatra 26 december 2004 and m w 8 7 nias 28 march 2005 earthquakes applying wavelet analyses to enhance those local signals in the grace time varying geoids up to september 2007 we detect a clear postseismic gravity signal we supplement these gravity variations with gps measurements of postseismic crustal displacements to constrain postseismic relaxation processes throughout the upper mantle the observed gps displacements and gravity variations are well explained by a model of visco elastic relaxation plus a small amount of afterslip at the downdip extension of the coseismically ruptured fault planes our model uses a 60 km thick elastic layer above a viscoelastic asthenosphere with burgers body rheology the mantle below depth 220 km has a maxwell rheology assuming a low transient viscosity in the 60 220 km depth range the grace data are best explained by a constant steady state viscosity throughout the ductile portion of the upper mantle e g 60 660 km this suggests that the localization of relatively low viscosity in the asthenosphere is chiefly in the transient viscosity rather than the steady state viscosity we find a 8 10 18 pa s mantle viscosity in the 220 660 km depth range this may indicate a transient response of the upper mantle to the high amount of stress released by the earthquakes to fit the remaining misfit to the grace data larger at the smaller spatial scales cumulative afterslip of about 75 cm at depth should be added over the period spanned by the grace models it produces only small crustal displacements our results confirm that satellite gravity data are an essential complement to ground geodetic and geophysical networks in order to understand the seismic cycle and the earth s inner structure

low degree gravity changes from grace earth rotation geophysical models and satellite laser ranging 1 several independent time series of variations c 21 s 21 and c 20 in earth s gravity field are compared for the period april 2002 to may 2007 we examine estimates from the gravity recovery and climate experiment grace earth rotation variations climate models and satellite laser ranging slr recently released grace solutions show significant improvement relative to earlier results especially for c 21 and s 21 at the annual period all estimates agree remarkably well and good correlation is found among time series at intraseasonal periods in general earth rotation values for c 21 and s 21 and slr values for c 20 agree best with grace estimates grace c 20 time series are contaminated by aliased ocean tide model errors slr c 21 and s 21 time series have been reported without an ocean pole tide opt correction and with an older solid earth pole tide sept model after correcting for opt and sept deficiencies slr c 21 and s 21 time series show improved agreement with other estimates

implications of postseismic gravity change following the great 2004 sumatra andaman earthquake from the regional harmonic analysis of grace intersatellite tracking data 1 we report gravity recovery and climate experiment grace satellite observations of coseismic displacements and postseismic transients from the great sumatra andaman islands thrust event mw 9 2 earthquake in december 2004 instead of using global spherical harmonic solutions of monthly gravity fields we estimated the gravity changes directly using intersatellite range rate data with regionally concentrated spherical slepian basis functions every 15 day interval we found significant step like coseismic and exponential like postseismic behavior in the time series of estimated coefficients from may 2003 to april 2007 for the spherical slepian functions after deriving coseismic slip estimates from seismic and geodetic data that spanned different time intervals we estimated and evaluated postseismic relaxation mechanisms with alternate asthenosphere viscosity models the large spatial coverage and uniform accuracy of our grace solution enabled us to clearly delineate a postseismic transient signal in the first 2 years of postearthquake grace data our preferred interpretation of the long wavelength components of the postseismic gravity change is biviscous viscoelastic flow we estimated a transient viscosity of 5 1017 pa s and a steady state viscosity of 5 1018 1019 pa s additional years of the grace observations should provide improved steady state viscosity estimates in contrast to our interpretation of coseismic gravity change the prominent postearthquake positive gravity change around the nicobar islands is accounted for by seafloor uplift with less postseismic perturbation in intrinsic density in the region surrounding the earthquake

lithospheric electrical structure of the great xing an range abstract in order to study the lithospheric structure and survey deep resources perspective of the great xing an range area a magnetotelluric sounding profile across the central great xing an range has been completed the profile starts from the eastern margin of the hailaer basin through the great xing an range to the western margin of the songliao basin an electrical structure model of the crust and the upper mantle was finally obtained after data processing qualitative analysis and 2d inversion of the observed data the electrical structure can be divided into three tectonic units the hailaer basin the great xing an range and the songliao basin which is consistent with the regional geology the research shows that 1 the high resistivity in the upper crust of the great xing an range may represent spatially multiple overlapping volcanic rocks in addition the low resistivity bodies in the middle lower crust may reflect hot and weak materials 2 the lower crust of the great xing an range may have experienced delamination 3 there is a lithospheric scale of west dipping structural transfer zone between the great xing an range and the songliao basin inferring that the songnen terrane firstly subducted to the xing an terrane then sutured in the form of soft collision and finally modified by volcanic activities later

simulating gravity changes in topologically realistic driven earthquake fault systems first results currently gps and insar measurements are used to monitor deformation produced by slip on earthquake faults it has been suggested that another method to accomplish many of the same objectives would be through satellite based gravity measurements the gravity recovery and climate experiment grace mission has shown that it is possible to make detailed gravity measurements from space for climate dynamics and other purposes to build the groundwork for a more advanced satellite based gravity survey we must estimate the level of accuracy needed for precise estimation of fault slip in earthquakes we turn to numerical simulations of earthquake fault systems and use these to estimate gravity changes the current generation of virtual california vc simulates faults of any orientation dip and rake in this work we discuss these computations and the implications they have for accuracies needed for a dedicated gravity monitoring mission preliminary results are in agreement with previous results calculated from an older and simpler version of vc computed gravity changes are in the range of tens of gal over distances up to a few hundred kilometers near the detection threshold for grace

central chile finally breaks chile is the site of some of the largest earthquakes in the world on average a magnitude 8 earthquake occurs there every 10 years or so these earthquakes take place in the subduction zone either as interplate ruptures at the interface between the south american and nazca plates or as intraplate events within the subducted nazca plate a few times in every century massive plate interface earthquakes break several hundred kilometers in a single shock this is what happened on 27 february 2010 when a major earthquake magnitude 8 8 occurred in the maule and biobio regions in central chile see the first figure this region had last experienced a major subduction earthquake in 1835 when darwin 1 visited the area as part of his voyage on the beagle his description of the earthquake inspired many seismologists and historians of chilean earthquakes 2 3

linking oceanic tsunamis and geodetic gravity changes of large earthquakes large earthquakes at subduction zones usually generate tsunamis and coseismic gravity changes these two independent oceanic and geodetic signatures of earthquakes can be observed individually by modern geophysical observational networks the gravity recovery and climate experiment twin satellites can detect gravity changes induced by large earthquakes while altimetry satellites and deep ocean assessment and reporting of tsunamis buoys can observe resultant tsunamis in this study we introduce a method to connect the oceanic tsunami measurements with the geodetic gravity observations and apply it to the 2004 sumatra mw 9 2 earthquake the 2010 maule mw 8 8 earthquake and the 2011 tohoku mw 9 0 earthquake our results indicate consistent agreement between these two independent measurements since seafloor displacement is still the largest puzzle in assessing tsunami hazards and its formation mechanism our study demonstrates a new approach to utilizing these two kinds of measurements for better understanding of large earthquakes and tsunamis