oceanography in the kattegat and skagerrak over the past 8000 years in the kattegat between sweden and denmark a large number of cores containing holocene seafloor deposits were investigated stratigraphically sedimentological biostratigraphical and chronostratigraphical variables were especially emphasized palynological and foraminiferal analyses indicate several changes in the oceanographic circulation system in the skagerrak kattegat during the holocene radiocarbon datings and pollen analyses suggest that these changes occurred at 8000 4000 2000 between 1000 and 500 and 300 years b p compilation of stratigraphical data from the region suggests that at about 8000 years b p the english channel opened and the southern jutland current was formed this had a major influence on the skagerrak but only a marginal effect can be traced in the kattegat the major components of the present circulation system in the kattegat skagerrak were established about 4000 years b p and the subsequent changes in the circulation pattern and the inflow outflow system that developed at approximately 2000 500 and 300 years b p are variants of these

green s functions of coseismic strain changes and investigation of effects of earth s spherical curvature and radial heterogeneity summary a set of green s functions is presented for calculating the coseismic strain caused by four independent seismic sources in a spherically symmetric non rotating perfectly elastic and isotropic snrei earth model corresponding expressions are derived assuming that the seismic sources are located at the polar axis the proper combination of these expressions allows calculation of the coseismic strain components resulting from an arbitrary seismic source at any earth position calculations of strain components are made for the near field resulting from the four independent sources at a depth of 32 km inside the 1066a earth model results agree well with those calculated for a half space earth model thus confirming the validity of the theory presented in this research a case study is performed and earth model effects are investigated furthermore this paper investigates effects of spherical curvature and the stratified structure of the earth in computing coseismic strain changes curvature effects are small for three types of seismic sources but extremely large for the horizontal tensile opening on the vertical fault plane because a general coseismic deformation comprises four independent solutions the large curvature effect on the horizontal tensile opening source contributes to the general result effects of earth s stratified structure are large for all depths and epicentral distances they reach a discrepancy greater than 30 per cent almost everywhere and 100 per cent in a very far field results show that effects of crustal structure mainly exist in the near field they do not affect results for a far field

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

a spatial temporal analysis of the development of a log spiral shaped embayment with the use of semi annual data collected from may 1985 to may 1995 this study assesses the evolution of a log spiral shaped embayment at the northeast beach located at canada s southernmost promontory the emplacement of stone breakwaters initiated scour of the shoreline and the embayment which developed thereafter adjusted to reflect changes in lake levels and naturally occurring variance in wave and sediment dynamics each of the 21 recorded measurements of the embayment configuration is assessed for characteristics of log spiral morphology the results demonstrate that logarithmic spiral curves fit the 21 recorded embayment configurations very closely the significant parameters and statistics associated with each log spiral curve show that no heteroschedacity of variance is present among the residuals and only one significant autocorrelation is observed the appropriateness of the log spiral fits is verified by the coefficients of determination which with the exception of the november 1988 dataset are all over the required value of 0 98 both the spiral angle and the radius show decreasing trends through time and the graphical plots illustrate only minor fluctuations after may 1991 these results suggest that the embayment may have shifted from some form of quasi equilibrium condition to approach a state of dynamic equilibrium the persistence of the logarithmic spiral configuration through time supports the findings of other investigators who claim that the log spiral planform represents the equilibrium embayment shape that might be expected on the flank of a breakwater system 1997 john wiley sons ltd

seasonal study of d18o and d13c in living stained benthic foraminifera from two swedish fjords in a previous 16 month seasonal study on living stained benthic foraminifera from two fjords on the swedish west coast it was reported that foraminifera proliferated in response to phytodetritus input the strongest response came from the opportunistic species stainforthia fusiformis in this study our objective was to find out if that phytodetritus input resulted in a change in the carbon isotopic composition of the foraminiferal tests we also wanted to examine if variations in salinity and temperature due to seasonality or deep water exchanges were reflected in the 18o values from s fusiformis that were obtained from the havstens fjord 20 m and the gullmar fjord 119 m during the 16 month study we developed a time series of 18o and 13c after the spring blooms in the havstens and the gullmar fjord decreases of about 0 2 to 0 3 in the foraminiferal 13c values were noted in the gullmar fjord after the autumn blooms decreases of the same order were also noted comparing the havstens and the gullmar fjord we found a 1 difference in both 13c and 18o we attribute this to hydrographic differences between the two fjords using calculated values of 18o together with the measured ones we noticed that s fusiformis in the gullmar fjord seems to calcify close to equilibrium with respect to the oxygen isotopes during autumn water temperatures were relatively high in the havstens fjord and foraminiferal abundance in the fjord was also high after a phytodetritus input but the measured 18o values do not reflect these higher temperatures this apparently contradictory combination of results might be explained by a varying 18o composition of the water during the year which counterbalances the temperature effect

global displacements caused by point dislocations in a realistic earth model we define dislocation love numbers h nm ij l nm ij k nm ij l nm t ij and green s functions to describe the elastic deformation of the earth caused by a point dislocation and study the coseismic displacements caused in a radially heterogeneous spherical earth model we derive spherical harmonic expressions for the shear and tensile dislocations which can be expressed by four independent solutions a vertical strike slip a vertical dip slip a tensile opening in a horizontal plane and a tensile opening in a vertical plane we carry out calculations with a radially heterogeneous earth model 1066a the results indicate that the dominating deformations appear in the near field and attenuate rapidly as the epicentral distance increases the shallower the point source the larger the displacements both the earth s curvature and vertical layering have considerable effects on the deformation fields especially the vertical layering can cause a 10 difference at the epicentral distance of 0 1 as an illustration we calculate the theoretical displacements caused by the 1964 alaska earthquake m w 9 2 and compare the results with the observed vertical displacements at 10 stations the results of the near field show that the vertical displacement can reach some meters the far field displacements are also significant for example the horizontal displacements u can be as large as 1 cm at the epicentral distance of 30 0 5 cm at about 40 magnitudes detectable by modern instrument such as satellite laser ranging slr very long baseline interferometry vlbi or global positioning system gps globally the displacement u r caused by the earthquake is larger than 0 25 mm

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

green s functions for post seismic strain changes in a realistic earth model and their application to the tohoku oki m w 9 0 earthquake based on a spherically symmetric self gravitating viscoelastic earth model we derive a complete set of green s functions for the post seismic surface strain changes for four independent dislocation sources strike slip dip slip and horizontal and vertical tensile point sources the post seismic surface strain changes caused by an arbitrary earthquake can be obtained by a combination of the above green s functions the post seismic surface strain changes in the near field agree well with the results calculated by the method in a half space earth model wang et al in comupt geosci 32 527 541 2006 which verifies our green s functions with an increase in the epicentral distance the effect of the curvature on both the co and post seismic strain changes clearly increases revealing the importance of our spherical theory for far field calculations next we use our green s functions to simulate the post seismic surface strain changes that were caused by the viscoelastic relaxation of the mantle over the 6 year period after the tohoku oki mw 9 0 earthquake based on continuous global positioning system gps observations around honshu island of japan northeastern china south korea and the russian far east we also deduce the post seismic strain changes caused by the tohoku oki mw 9 0 earthquake overall the distributions of the calculated and gps derived strain changes agree well each other finally we compare the relative error between the observed and simulated strain changes over the 3 0 4 5 year period after the earthquake in both the near and far field we find that the relative errors decrease as the epicentral distance increases which validates our green s functions for research in the far field

some insights into topographic elastic and self gravitation interaction in modelling ground deformation and gravity changes in active volcanic areas surface displacements and gravity changes due to volcanic sources are influenced by medium properties we investigate topographic elastic and self gravitation interaction in order to outline the major factors that are significant in data modelling while elastic gravitational models can provide a suitable approximation to problems of volcanic loading in areas where topographic relief is negligible for prominent volcanoes the rough topography could affect deformation and gravity changes to a greater extent than self gravitation this fact requires the selection depending on local relief of a suitable model for use in the interpretation of surface precursors of volcanic activity we use the three dimensional indirect boundary element method to examine the effects of topography on deformation and gravity changes in models of magma chamber inflation deflation topography has a significant effect on predicted surface deformation and gravity changes both the magnitude and pattern of the geodetic signals are significantly different compared to half space solutions thus failure to account for topographic effects in areas of prominent relief can bias the estimate of volcanic source parameters since the magnitude and pattern of deformation and gravity changes depend on such effects

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

sediment sorting and beach erosion along a coastal foreland magnetic measurements in point pelee national park ontario canada abstract in situ and laboratory based magnetic measurements were made on sand samples from the beach on the eastern side of point pelee national park ppnp in northwestern lake erie in order to examine both the composition and spatial distribution of magnetic minerals magnetic remanence measurements on bulk and particle size fractions showed that the magnetic properties were dominated by multidomain ferrimagnetic grains probably magnetite and or maghemite particle size specific measurements on different grain size fractions showed that the

gravity changes from a stress evolution earthquake simulation of california 1 the gravity signal contains information regarding changes in density at all depths and can be used as a proxy for the strain accumulation in fault networks a stress evolution time dependent model was used to create simulated slip histories over the san andreas fault network in california using a linear sum of the gravity signals from each fault segment in the model via coseismic gravity green s functions a time dependent gravity model was created the steady state gravity from the long term plate motion generates a signal over 5 years with magnitudes of 2 gal the current limit of portable instrument observations moderate to large events generate signal magnitudes in the range of 10 to 80 gal well within the range of ground based observations the complex fault network geometry of california significantly affects the spatial extent of the gravity signal from the three events studied

a gravity gradient method for characterizing the post seismic deformation field for a finite fault summary gravity gradients are an effective method for delineating the extent of subsurface density anomalies the change in subsurface density contrasts due to the seismic deformation gives rise to detectable gravity changes via the dilatational gravity signal or bouguer anomaly solutions for the corresponding gravity gradients of these signals are developed for a vertical strikeslip fault gravity gradient solutions exhibit similar spatial distributions as those calculated for coulomb stress changes reflecting their physical relationship to the stress changes the signals magnitudes of the order of 10 4 e are beyond the resolution of typical exploration instruments improvements to superconducting gravity gradiometers are necessary for gravity gradients to be used as a viable method for the observation of the stress field changes over large spatial scales

depth correlated benthic faunal quantity and infaunal burrow structures on the slopes of a marine depression in the northern part of the kattegat western sweden a series of marine depressions remain since the last glaciation one of these the well oxygenated alkor deep is about 3 km long and 800 m wide and with a depth of 138 m random depth stratified sampling was made along four transects on the slopes including benthic macrofauna 0 1 m2grab samples and sediment profile imaging a significant positive correlation was found between depth and the faunal variables abundance and biomass deposit feeders such as maldane sarsi heteromastus filiformis andabra alba were among the dominants and may have been supported by down slope advected organic material in many images pockets and extensive burrows were seen in the sediment that appeared to be constructed by the crustaceans calocaris macandreae and maera loveni the ecological significance of their irrigation of the sediment is discussed due to the faunal activity deep down in the sediments of the slopes the mean apparent redox potential discontinuity rpd was found as deep as between 8 0 and 11 3 cm depth and rpd was significantly positively correlated with water depth on the slopes there appears to be a balance between the input of organic material and the capacity of the benthic organisms to assimilate that carbon

a model for the exchange of water and salt between the baltic and the skagerrak abstract a model for the exchange of salt and water between the baltic and the sea the skagerrak is presented because of strong inter basin interactions in the baltic entrance area the model must include the kattegat and the belt sea these are modeled by horizontally homogeneous two layer sub models the most prominent dynamical properties of the sub models are wind driven entrainment flows and rotational baroclinic hydraulic controls the model is driven by a meteorologically forced barotropic transport qh calculated from the freshwater supply to the baltic qf and the sea level fluctuations in the kattegat and turbulent entrainment flows coupled to the wind speed w and in the belt sea also to the barotropic transport the most important bathymetric features of the basins are included the model equations are integrated numerically for a test period of 1 years the stratification in the kattegat as well as in the belt sea is quite well predicted it is found that approximately one half of

stable oxygen and carbon isotope information on the establishment of a new opportunistic foraminiferal fauna in a swedish skagerrak fjord basin in 1979 1980 significant faunal changes reported fromrecent coastal environments which are not directly influenced by urban and industrial impact are rarely seen in gullmar fjord on the swedish west coast a significant foraminiferal fauna change occurred in connectionwith severe low oxygen conditions that evolved in thewinter of 1979 1980 a foraminiferal fauna marked by common skagerrak kattegat species which had previously characterised the deep fjord basin was replaced by the opportunistic low oxygen tolerant species stainforthia fusiformis williamsson to study this phenomenon further we performed stable oxygen and carbon isotope analyses on the indicator species itself s fusiformis both on specimens from sediment cores representing approximately the last 85 years and on living stained individuals taken from a transect across the deep fjord basin our purpose was to detail how and why s fusiformis came to dominate the fauna the oxygen isotope results suggest that salinities and temperatures in the deep basin have been relatively constant over the last c 85 years while the carbon isotopes show a significant change towards more negative values in association with the faunal shift of 1979 1980 the combined results from both the cores and the surface sediments suggest that s fusiformis did not inhabit the deep basin until 1980 before then almost all specimens of s fusiformis were small sized and their carbon isotope values suggest they were re deposited shallow water specimens that had been transported down to the central deep basin as part of a suspension load after a major faunal extinction in 1979 1980 s fusiformis of all sizes suddenly appeared in large numbers and their carbon isotopic values were similar to the signal from registered in the recent living fauna within the deep basin this suggests that the opportunistic s fusiformis established itself in the deep basin as a consequence of the severe low oxygen event and the faunal crash of the previously dominating skagerrak kattegat fauna less

viscoelastic displacement and gravity changes due to point magmatic intrusions in a gravitational layered solid earth summary we present a method for the computation of time dependent geodetic and geophysical signatures deformation potential and gravity changes due to magmatic intrusions in a layered viscoelastic gravitational medium this work is an extension of a deformation model previously developed to compute effects due to volcanic loading in an elastic gravitational layered media the model assumes a planar earth geometry useful for near field problems and consists of welded elastic and viscoelastic layers overlying a viscoelastic half space every layer can either be considered elastic or viscoelastic the intrusion treated as a point source can be located at any depth in any of the layers or in the half space several examples of theoretical computations for different media are also presented we have found that in line with previous results obtained by other authors introducing viscoelastic properties in all or part of the medium can extend the effects displacements gravity changes etc considerably and therefore lower pressure increases are required to model given observed effects the viscoelastic effects seem to depend mainly on the rheological properties of the layer zone where the intrusion is located rather than on the rheology of the whole medium we apply our model to the 1982 1984 uplift episode at campi flegrei modelling simultaneously the observed vertical displacement and gravity changes the results clearly show that for a correct interpretation of observed effects it is necessary to include the gravitational field in the anelastic theoretical models this factor can change the value and pattern of time dependent deformation as well as the gravity changes explaining cases of displacement without noticeable gravity changes or vice versa cases with uplift and incremental gravity values and other cases the combination of displacement and gravity changes is found to be especially effective in constraining the possible characteristics of the magmatic intrusion as well as the rheology of the medium surrounding it

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

surface potential and gravity changes due to internal dislocations in a spherical earth ii application to a finite fault summary we present a numerical formulation for computing elastic deformations caused by a dislocation on a nite plane in a spherically symmetric earth it is based on our previous work for a point dislocation sun okubo 1993 the formulation enables us to compute the displacement potential and gravity changes due to an earthquake modelled as spatially distributed dislocations as an application of the nite fault dislocation theory we make a case study of the theoretical and observed gravity changes the computed results are in excellent agreement with the observed gravity changes during the earthquake the gravity changes in the near eld can reach some 100 gal which can be easily detected by any modern gravimeter in the far eld they are still signi cantly large jdgj 10 gal within the epicentral distance h 1 gal within h 0 1 gal within h 0 01 gal globally we also calculate the geoid height changes caused by the 1964 alaska earthquake and by the same earthquake with revised parameters and an assumed barrier we nd that the earthquake should have caused geoid height changes as large as 1 5 cm

high benthic fertility and taphonomy of foraminifera a case study of the skagerrak north sea abstract the skagerrak basin is a deep water extension of the north sea it is of particular interest as an analogue for past epicontintal shelf basins because it presents environmental contrasts with the adjacent shelf seas in this study the distribution patterns of benthic foraminifera have been used to infer taphonomic and oceanographic processes only by separating living from dead assemblages is it possible to interpret taphonomic changes the transport of foraminiferal tests to the danish slope is inferred from the presence there of dead exotic tests whose provenance is considered to be from the south the abundance of detrital organic matter on the danish slope is likewise inferred to be sourced from the same direction thus the danish slope is interpreted to be a depositional sink apart from transport another taphonomic process is the dissolution of calcareous tests this is clearly demonstrated both by the fragility of some tests as viewed under the microscope and by the disparity between the composition of the living and dead factor associations in the deep basin in particular the two predominantly calcareous living associations are replaced by a single predominantly agglutinated dead association due to carbonate dissolution the danish slope of the skagerrak basin is demonstrated to be an area of high benthic fertility this is based on the high density of living stained benthic foraminifera comparable with that of the mississippi delta particularly the abundance of stainforthia fusiformis an opportunistic species and tubular agglutinated forms the fertility is linked with the high abundance of particulate organic matter here previous regional studies have focused on total living plus dead distributions of 100 or 125 m sized foraminifera these factor assemblages are distinct from the 63 m living and dead associations described here

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

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

anchor ice formation and ice rafting in southwestern lake michigan u s a abstract anchor ice i e ice attached to the bed in a lake stream or ocean is common in the nearshore zone of southwestern lake michigan during winter lacustrine anchor ice has at least four distinct morphologies and was observed on sand pebble and boulder substrates in water depths to 4 m the limit of diving traverses the maximum depth of anchor ice formation may be much greater anchor ice is released from the lake bed on mornings following formation events released floating anchor ice carries sediment to the water surface this sediment is ice rafted along shore and offshore under the influence of prevailing winds we estimate that 0 85 m3 of sand per meter of beach is being removed from the nearshore zone of southwestern lake michigan by anchor ice annually melting ice drops this sand in deep water far from shore this is a significant loss of sand from the sediment starved nearshore zone of southwestern lake michigan

effects of earth s lateral inhomogeneous structures on coseismic gravity changes based on the perturbation method we present a new method to study the effects of earth s laterally inhomogeneous structures on coseismic gravity changes caused by dislocations within a 3 d heterogeneous spherical earth model we describe this method by six independent dislocations a vertical strike slip two vertical dip slips perpendicular to each other and three tensile openings on three perpendicular planes we derived the calculation formulae for the six independent dislocations a combination of the six independent dislocations is useful to compute the effects on coseismic gravity changes resulting from an arbitrary seismic source at an arbitrary position

surface coseismic gravity changes caused by dislocations in a 3 d heterogeneous earth summary this study describes an examination of surface gravity changes caused by dislocations within a 3 d heterogeneous earth this new theory is described using six independent dislocations a vertical strike slip two vertical dip slips perpendicular to each other and three tensile openings on three perpendicular planes a combination of the six independent dislocations is useful to compute coseismic gravity changes resulting from an arbitrary seismic source at an arbitrary position based on the 3 d lateral inhomogeneous p wave velocity model we deduce the 3 d density and s wave velocity models using the relation of karato finally numerical computations are performed for a location south of japan 30 n 135 e we calculate the coseismic gravity changes resulting from the six independent dislocations for source depths of 100 300 and 637 km respectively numerical results show that the maximum 3 d effect varies concomitantly with the dislocation type and the source depth for seismic problems the effect of elastic parameter is dominant

joint inversion of observed gravity and gps baseline changes for the detection of the active fault segment at the red river fault zone summary methods for the determination of active fault segments by inversion of temporal gravity and gps global positioning system baseline changes are presented in this paper a numerical test is performed for estimating four types of fault movement models from simulated gravity changes with random noise results of the numerical test show clearly the possibility of detecting fault movement from observed gravity changes based on this work active segments of the red river fault zone rrfz are investigated by inversion of observed gravity changes from 1985 november to 1988 november and gps baseline changes from 1988 august to 1991 october both separately and jointly the results from the joint inversion indicate an active segment of the red river fault characterized by right lateral strike slip 1 0 0 2 m with a length of 232 3 km a width of 6 3 km a dip angle of 100 5 80 5 ne a depth of 10 1 km and a strike direction of 169 2 se these characteristics of the detected active segment at the rrfz agree with those of geological investigations and seismic activity in the area estimated horizontal displacements at the rrfz indicate that drastic movements are concentrated on the northern segment whereas the southern segment of the fault is relatively stable the estimated fault slip rate along strike at the red river fault is 8 11 mm yr 1 larger than the geological estimate of 6 mm yr 1 which implies that the rrfz is presently active the results obtained in this research support previous interpretations that the fault movements at the rrfz are mainly a result of the collision of the indian and the eurasian plates

first detection of absolute gravity change caused by earthquake unequivocal coseismic gravity change was detected for the first time by absolute gravimetry the measurements were done just one day before and only 7 days after a m6 1 earthquake m6 1 the absolute gravity change was 6 microgal significantly larger than the observational error of about 1 microgal of particular interest is that the observed spatial gravity variations agree remarkably well with those expected from an elastic dislocation model constructed on displacement data alone the result strongly encourages us to perform a simultaneous inversion of both gravity and displacements to have better insight of earthquakes

coseismic displacements caused by point dislocations in a three dimensional heterogeneous spherical earth model summary we present a method to study the coseismic displacements caused by point dislocations in a 3 d heterogeneous spherical earth model specifically first we express the solutions by the sum of unperturbed displacements on a spherically symmetric earth model and the effects of the earth s laterally inhomogeneous structures 3 d effect then we deliberately decompose the 3 d effect into two contributions the effect of seismic sources and the effect of the earth s lateral increments which are obtainable respectively by perturbation of seismic source functions and perturbation of equilibrium equation next we present new formulations for six point seismic sources a vertical strike slip two vertical dip slips perpendicular to each other and three tensile openings on three perpendicular planes a combination of the six dislocations is useful to compute the 3 d effect resulting from an arbitrary seismic source at an arbitrary position finally based on a 3 d earth model we calculate the coseismic displacements resulting from three types of point dislocations results show that the maximum 3 d effect on coseismic displacements which varies concomitantly with the dislocation type and the source depth is about 1 2 per cent of the corresponding unperturbed solutions among those parameters the effect due to the heterogeneities in s wave velocity is biggest

relation of dislocation love numbers and conventional love numbers and corresponding green s functions for a surface rupture in a spherical earth model summary this study was undertaken to complete the dislocation theory presented by sun et al for a spherical earth model with special treatment of coseismic deformations for a surface rupture the previous theory is valid only for inner sources but the coseismic deformations for a surface rupture source remain unsolved therefore this study deals with the special case of coseismic deformations for a surface rupture dislocation for this purpose we first derive the relation between the dislocation love numbers and the conventional love numbers that is the tidal press and shear love numbers based on the okubo reciprocity theorem then we derive the corresponding green s functions for coseismic displacement potential geoid gravity and strain changes using okubo asymptotic solutions finally we present numerical results of those green s functions for four independent seismic sources then we discuss the computation of coseismic deformations at the singular point epicentre as a case study the computations of the coseismic deformations caused by the 2011 tohoku oki earthquake mw 9 0 with considering the new green s functions as a constrain validates the theoretical model established in this study

source parameters of the bhuj earthquake india of january 26 2001 from height and gravity changes 1 height and gravity measurements observed along a profile across the epicentral area before and after the january 26 2001 mw 7 6 bhuj earthquake show a maximum uplift of 1 57 0 5 m and a corresponding gravity change of 393 18 gal a best fit single dislocation model inverted from the height changes using non linear optimization methods indicates that the high slip rupture was well contained in the aftershock zone and likely did not break to depths shallower than 10 km source parameters arrived in the present study agree well with those provided by seismic inversions and the distribution of aftershocks gravity data over the epicentral area are well modeled by the preferred model however a strong influence of shallow hydrological processes is inferred for three sites two located on the banni plains whose mean gravity change 280 gal suggests a total mass redistribution of as much as 2 9 mt

three dimensional indirect boundary element method for deformation and gravity changes in volcanic areas application to teide volcano tenerife canary islands 1 most deformation models of volcanoes assume that the earth is a linear elastic isotropic and homogeneous half space although some volcanic areas are associated with significant relief we investigate the effects of topography on surface deformation and gravity changes caused by a magma intrusion in the earth s crust a three dimensional 3 d indirect boundary element method ibem that incorporates realistic topographic features is developed in order to perform this analysis our results show that the topography alters both the magnitude and pattern of the deformation and gravity signal as an example of realistic topography we consider a spherical source of dilatation located at 4 km depth below teide volcano summit tenerife canary islands in order to simulate the deformation and gravity changes that could be observed at tenerife if a hypothetical intrusion occurred in the volcanic system this approach gives a picture of the 3 d topographic effect at teide that can provide insight in order to improve the geodetic monitoring of the volcano

recent sediments and foraminiferal distribution in the skagerrak northeastern north sea abstract a number of bottom sediment samples from the skagerrak have been studied the surface sediment samples reflect the presence of three main sediment types with a fourth which occurs more scattered a selection of 50 samples was used for the study of the foraminifers of the 125 m fraction benthic foraminifers dominate the assemblages using factor analysis and the computer program cabfac the benthic foraminiferal data were reduced to five factors eight species have proven to be significant the factors benthic foraminiferal assemblages are dominated by bolivina cf b robusta elphidium excavatum cassidulina laevigata bulimina marginata melanis barleeanum globobulimina turgida and hyalines balthica respectively the first factors are clearly related to known hydrographic and bottom conditions

comparison of fault models of the 2008 wenchuan earthquake ms8 0 and spatial distributions of co seismic deformations article i nfo a proper slip fault model and a reasonable dislocation theory are necessary to compute and investigate co seismic deformations caused by the 2008 wenchuan earthquake ms8 0 to find such a model several comparisons are made of different dislocation theories seismic fault models and earth models results indicate that the fault model determined by combining gps and seismic waveform data is the best the spherical dislocation theory yields better results than that of a half space theory and the results obtained from a revised prem earth model are better than those from prem according to results of earlier investigations co seismic deformations such as the displacement geoid gravity and strain changes caused by the 2008 wenchuan earthquake ms8 0 are computed described and discussed results show that the earthquake generated considerable co seismic deformation in a large area around the epicenter the modeled deformations are applicable as a reference for other researchers to study inter structural inversion crustal deformation etc the effects of the curvature and layer structure are great moreover spherical dislocation theory is necessary for studying co seismic deformations caused by a large event

the impact of low ice cover on shoreline recession a case study from western point pelee canada abstract the western shore of point pelee national park ppnp in ontario canada exhibited high recession rates in the winter of 2005 2006 during the period 1959 2004 the western side of the park generally exhibited accretion attributed to longer duration of ice coverage during winter and favorable topography and sedimentary conditions in comparison to the eastern side compared to the winter of 2003 2004 changes in lake erie water levels winter wind regime and human made structures and interferences were negligible during 2004 2006 within the colchester to southeast shoal littoral cell in western lake erie where ppnp is located however the winter of 2005 2006 exhibited overall low ice cover conditions unlike the typical freeze up conditions in western lake erie the 2006 high recession rates on the western shore of point pelee are attributed to the low ice cover conditions in the winter of 2005 2006 while less than average ice cover does not in its own cause erosion in certain areas it increases the opportunity for sediment removal by waves by removing a significant source of protection during winter the episode illustrates the potential impacts of ice free and low ice cover winters on the western shore of point pelee and shores under similar conditions future climate change patterns are expected to result in shorter ice durations and more frequent ice free winters in the western basin of lake erie exposing western ppnp to wave action during the winter season and resulting in increased erosion the increased opportunity for shore erosion will negatively impact ecologically and economically viable spaces in ppnp

surface volume and gravity changes due to significant earthquakes occurred in central italy from 2009 to 2016 we have modelled the surface volume and gravity changes caused by four seismic events three mainshocks moment magnitude mw 6 0 5 9 6 5 occurred during the last seismic period started on 2016 august 24 in central italy and the 2009 april 6 l aquila earthquake mw 6 3 our calculations start from the source parameters estimated by the inversion of the largest dataset of interferometric synthetic aperture radar insar and global positioning system observations ever managed in italy after earthquake occurrences based on the half space elastic dislocation theory the vertical displacements modelled after the 2016 events allow to infer a substantial unbalance between the subsided and uplifted volumes in particular we detected 106 106 m3 of hangingwall subsidence against 37 106 m3 of footwall uplift that accounts for 74 of the total volume mobilization from the ratio between the footwall and total deformed volumes we have computed an average fault dip of 47 in line with the values retrieved by seismological methods the total gravity variations which affected the study area are of the order of 1 gal 1 gal 10 8 ms 2 in the far field and 170 gal in the near field the area affected within a gravity change of 1 gal is 140 km long and 57 km wide parallel to the apennines mountain chain the larger contribution is given by positive variations which account for the tensional style of deformation and larger subsided area the significant gravity variations modelled from the coseismic deformations point out the need to update our knowledge about the absolute gravity field in italy carrying out extensive measurements and to align italy to the recent international standards about national gravity and height networks international association of geodesy iag report commission 2 gravity field http www iag commission2 ch 2015

subsurface sediment profiles below point pelee indicators of postglacial evolution in western lake erie an extensive drilling program undertaken along the western barrier bar at point pelee national park ontario canada yielded considerable subsurface sediment data relevant to the nature and lateral geometry of sedimentary units below the point pelee foreland four major sedimentary units were identified a basal clay rich till a fine grained glaciolacustrine sand a medium grained sand unit subdivided into a poorly sorted shoreface sand and an aeolian dune sand derived from the shoreface sand and an organic marsh gyttja deposit the present study confirms the existence of a planar wave eroded till surface below the southern portion of point pelee at an elevation of approximately 164 m asl following this low water period in the basin lake levels rose abruptly to an elevation several metres above 172 m asl this resulted in erosion of the upper part of the glaciolacustrine sand during a later period of stable higher lake levels perhaps coinciding with the nipissing flood event about 4000 bp this resulted in a planar surface at approximately 169 5 m asl several radiocarbon dates on basal gyttja from the marsh averaging 3200 bp reflect a subsequent drop in levels to about 2n3 m below present levels though undated the initiation of shoreface and dune sand deposition is roughly coeval with the basal marsh deposits

oceanographic conditions in the deepest parts of the kattegat scandinavia revealed through recent benthic foraminifera and hydrography the kattegat has since the 1980s been subject to extensive investigations focusing on various aspects of the marine environment the most important reasons for this concentration of work are marine eutrophication periodically occurring oxygen deficiency in the bottom water and subsequent benthic mortality in this study a previously not discussed sill area separating two deep areas in the kattegat has been identified in the contexts of periodically occurring oxygen deficiency in the southern kattegat it is most relevant to study the environmental conditions in this area hydrographic data from the area inside and outside the sill area suggest that the deep water on both sides of the sill do communicate no evidence for stagnation in the deep area inside the sill was found in addition to hydrography data benthic foraminifera has been used as environmental tracers two characteristic benthic foraminiferal faunas have been defined one representing water depths exceeding 80 m and one representing shallower depths these faunas occur on both sides of the sill area two investigated deep depressions within the deep area inside the sill the alkor depth 138 m and poseidon depth 150 m are marked by a fauna that is identical with that in the so called kattegat trench this suggests that the depressions are not more stagnant if stagnant at all than the surrounding kattegat trench and the djupa rannan trench located outside the sill area the information generated in this study is essential for the understanding of the processes resulting in oxygen deficiency in the deep water of the southern kattegat