the density contrast at the mohorovicic discontinuity summary the compilation of new global mohorovicic moho topographic data enables us to estimate the density contrast between the crust and mantle assuming that this contrast is constant the minimization of the external gravitational potential induced by the earth s topographic masses and the moho discontinuity gives the value of 0 28 gcm 3 for the density jump at the moho under the continental areas for the oceanic areas where the information about the moho depths is unavailable or poor the procedure has not been applied

sinking cities in indonesia alos palsar detects rapid subsidence due to groundwater and gas extraction abstract we use interferometric synthetic aperture radar insar time series analysis of alos l band sar data to resolve land subsidence in western indonesia with high spatial and temporal resolution the data reveal significant subsidence in nine areas including six major cities at rates up to 22 cm year land subsidence is detected near lhokseumawe in medan jakarta bandung blanakan pekalongan bungbulang semarang and in the sidoarjo regency the fastest subsidence occurs in highly populated coastal areas particularly vulnerable to flooding we correlate the observed subsidence with surface geology and land use despite the fact that subsidence is taking place in compressible deposits there is no clear correlation between subsidence and surface geology in urban areas we find a correlation between rapid patchy subsidence and industrial land use and elsewhere with agricultural land use this suggests that the subsidence is primarily caused by ground water extraction for industrial and agricultural use respectively we also observe subsidence associated with exploitation of gas fields near lhokseumawe and in the sidoarjo regency a continuation of these high rates of subsidence is likely to put much of the densely populated coastal areas below relative sea level within a few decades

seismic tomography of the colorado rocky mountains upper mantle from crest lithosphere asthenosphere interactions and mantle support of topography abstract the crest experiment colorado rocky mountains experiment and seismic transects integrated the earthscope usarray transportable array with portable and permanent stations to provide detailed seismic imaging of crust and mantle properties beneath the highest topography region of the rocky mountains inverting approximately 14 600 p and 3600 s wave arrival times recorded at 160 stations for upper mantle v p and v s structure we find that large v p perturbations relative to ak135 of 7 and v s variations of 8 take place over very short approaching tens of kilometers lateral distances highest heterogeneity is observed in the upper 300 km of the mantle but well resolved low velocity features extend to the top of the transition zone in portions of these images the previously noted low velocity upper mantle aspen anomaly is resolved into multiple features the lowest v p and v s velocities in the region are found beneath the san juan mountains which is clearly distinguished from other low velocity features of the northern rio grande rift taos latir region aspen region and below the never summer mountains we suggest that the san juan anomaly and a similar feature below the taos latir region of northern new mexico are related to delamination and remnant heat and melt beneath these sites of extraordinarily voluminous middle cenozoic volcanism we interpret a northeast southwest grain in velocity structure that parallels the colorado mineral belt to depths near 150 km as being reflective of control by uppermost mantle proterozoic accretionary lithospheric architecture further to the north and west the wyoming province and northern colorado plateau show high velocity features indicative of thick 150 km preserved archean and proterozoic lithosphere respectively overall we interpret the highly heterogeneous uppermost mantle velocity structure beneath the southern rocky mountains as reflecting interfingered chemical proterozoic lithosphere that has been is currently being replaced and modified by upwelling asthenosphere low velocity features resolved here indicate that this process may be sourced as deeply as the top of the mantle transition zone at 410 km one driving mechanism for this is upper mantle interaction between upwelling hydration induced partial melt and destabilized downwelling lithosphere in the deeper upper mantle tomographic imaging of mantle seismic velocity and crustal thickness results and modeling from the crest experiment indicate that the highest elevations of the colorado rocky mountains are substantially supported by the mantle and strong correlations between low velocity mantle and thin crust high topography are noted across the region this along with rich upper mantle seismic heterogeneity suggests that mantle buoyancy and dynamics are central to present day topographic support and recent geomorphic evolution of the region

deep mantle forces and the uplift of the colorado plateau 1 we introduce a quantitative model of global mantle convection that reconstructs the detailed motion of a warm mantle upwelling over the last 30 ma towards the interior of the southwestern usa from observed present day mantle heterogeneity the onset and evolution of uplift in the central basin and range province and colorado plateau during this time is determined by tracking the topographic swell due to this mantle upwelling we show that 1 the extension and basaltic volcanism post 25 ma in the central basin and range coincides with the arrival and eastward progression of this upwelling and 2 dynamic uplift of the southern colorado plateau totaling about 1 km transpired in the last 20 ma since 10 ma the center of uplift continued northeastward from the southwestern rim of the plateau consistent with a young grand canyon model and eastward sweep of magmatism in the western colorado plateau

evidence of the present relative land stability of venice italy from land sea and space observations 1 the city of venice is very vulnerable to loss in surface elevation as a result of subsidence and eustacy because of its small elevation above sea level the alarm of the scientific community related to this persistent problem is increasing because of the forecasts of sea level rise caused by global warming in order to evaluate the present relative subsidence of venice a study has been performed by combining high precision leveling satellite radar interferometry sri and tide gauge measurements the analysis of the most recent data points out with an unprecedented detail the present ground stability of the city

separating natural and anthropogenic vertical movements in fast subsiding areas the po plain n italy case the geological and the anthropogenic components of vertical movement act on different time scales millions to thousands years and hundreds to tens of years respectively this peculiarity has been used in order to separate the factors controlling sea level changes in the po plain area the component due to long term geological processes is calculated from stratigraphic data commercial wells and seismic lines adding to this long term component the contribution of pleistocene deglaciation obtained from analytical models an estimate of the total natural component of vertical velocities is obtained the validity of these values is confirmed by comparison with velocities obtained from archaeological data and detailed palynological and paleontological analyses the anthropogenic components can be inferred by comparison between the total natural vertical velocities we calculate and vertical velocities obtained from other data sets two applications are proposed using tide gauge records and geodetic data respectively

correlation of geoid and depth anomalies over the agulhas plateau abstract correlations of geoid anomalies with bathymetry are an important source of information in the compensation of submarine features we have used this technique to constrain models of the density structure of the lithosphere beneath the agulhas plateau south of africa we explain the correlation in terms of a two layer airy isostatic model the plateau is compensated in part by crustal thickening and in part by an underlying layer of anomalously low density mantle the anomalous mantle layer extends to a depth of about 50 km and has a density 1 2 lower than normal mantle crustal thickening alone is insufficient to explain the observed correlation between bathymetry and the geoid the anomalous mantle region may be the source for the excessive volumes of basalt which have intruded and thickened the crust of the plateau there is strong evidence that depleted mantle rock is lighter than undepleted mantle rock a similar model may hold for the walvis ridge

topography the geoid and compensation mechanisms for the southern rocky mountains the southern rockies of colorado are anomalously high elevations greater than 2800 m topographically rough implying active uplift and underlain by significant low velocity anomalies in the upper mantle that suggest an intimate relationship between mantle geodynamic processes and the surface topography the region is in isostatic equilibrium i e near zero free air gravity anomaly however the poor correlation between the high topography and crustal thickness makes the application of simple compensation models e g pure heiskanen or pratt hayford problematic knowledge of how the current topography of the rockies is isostatically compensated could provide constraints on the relative role of sublithospheric buoyancy versus lithospheric support here we evaluate the geoid and its relationship to the topography using the geoid to elevation ratio gtr in the spatial domain and the admittance in the frequency domain to constrain the mechanism of compensation we separate the upper mantle geoid anomalies from those with deeper sources through the use of spherical harmonic filtering of the egm2008 geoid we exploit the fact that at wavelengths greater than the flexural wavelength where features are isostatically compensated the geoid topography ratio can be used to estimate the depth of compensation and the elastic thickness of the lithosphere the results presented below indicate that the main tectonic provinces of the western united states have moderate geoid topography ratios between 3 5 and 5 5 m km 3 9 for the southern rockies 4 25 for the colorado plateau and 5 2 for the northern basin and range suggesting shallow levels of isostatic compensation in terms of the elastic thickness of the lithosphere our results indicate an elastic thickness of less than 20 km these value support the notion that a major portion of the buoyancy that has driven uplift resides at depths less than 100 km and that upper mantle processes such as small scale convection may play a significant role in the buoyant uplift of the southern rockies as well as other actively uplifting areas of the western united states further support for this hypothesis is provided by high coherence for the geoid topography relationship for nearly all wavelengths between 50 and 1000 km

teleseismic travel time anomalies and deep crustral structure in central australia summary teleseismic travel times have been recorded along two lines of instruments traversing the amadeus basin and southern arunta block of central australia for the purpose of examining the deep crustal and upper mantle structure underlying these features pronounced differential travel times approaching 1 5 s and with major azimuthal variation have been recorded most of the useful observations originated from events to the north japan marianas and to the east fiji tonga at epicentral distances of 40 65d a few observations of southerly azimuth events macquarie ridge and south sandwich islands were also recorded the inferred structure beneath the basin and block exhibits major lateral variations the essential aspects of which are 1 a zone of relatively high velocity material dipping steeply northwards such that the continuation of its southern edge to the surface coincides approximately with a mylonitic shear zone known as the redbank deformed zone 2 a steeply dipping zone of relatively low velocity material immediately to the south of this shear zone and partly underlying the high velocity zone if the travel times are interpreted in terms of an undulating moho variations in moho depth of 20 km occur over horizontal distances of less than 50 km with relatively shallow moho depths occurring immediately to the north of the redbank deformed zone such an interpretation is consistent with the gravity anomalies observed across the geological structures the inferred structure is out of hydrostatic equilibrium and departures from local isostasy approach 150 mpa these stress differences must have persisted during the 300 ma following the alice springs orogeny that led to the present crustal structure evidence in the form of the surface topography and seismicity suggests that some stress relaxation has occurred and still is occurring but not at the shear zone itself at the time of the orogeny the structure may have been close to isostatic equilibrium but as erosion took place complete local rebound did not occur either because horizontal compressive forces still operated or because the strength of the lithosphere increased with time

transient deformation in california from two decades of gps displacements implications for a three dimensional kinematic reference frame our understanding of plate boundary deformation has been enhanced by transient signals observed against the backdrop of time independent secular motions we make use of a new analysis of displacement time series from about 1 000 continuous global positioning system gps stations in california from 1999 to 2018 to distinguish tectonic and nontectonic transients from secular motion a primary objective is to define a high resolution three dimensional reference frame datum for california that can be rapidly maintained with geodetic data to accommodate both secular and time dependent motions to this end we compare the displacements to those predicted by a horizontal secular fault slip model for the region and construct displacement and strain rate fields over the past 19 years california has experienced 19 geodetically detectable earthquakes and widespread postseismic deformation we observe postseismic strain rate variations as large as 1 000 nstrain year with moment releases equivalent up to an mw6 8 earthquake we find significant secular differences up to 10 mm year with the fault slip model from the mendocino triple junction to the southern cascadia subduction zone the northern basin and range and the santa barbara channel secular vertical uplift is observed across the transverse ranges coastal ranges sierra nevada as well as large scale postseismic uplift after the 1999 mw7 1 hector mine and 2010 mw7 2 el mayor cucapah earthquakes we also identify areas of vertical land motions due to anthropogenic natural and magmatic processes finally we demonstrate the utility of the kinematic datum by improving the accuracy of high spatial resolution 12 day repeat cycle sentinel 1 interferometric synthetic aperture radar displacement and velocity maps

paleolithospheric structure revealed by continental geoid anomalies abstract lithospheric geoid anomalies record changes in elevation and potential energy experienced by continental lithosphere estimates of local isostatic equilibration and potential energy in tandem with lithosphere related geoid anomalies can be used to estimate paleolithospheric thickness providing a clearer understanding of how and why continental topography is developed we employ several simplifying assumptions about the crustal and mantle lithosphere density and structure and readily acknowledge that our results are therefore first order approximations to predict the pre orogenic structure of the lithosphere at the outset we emphasize that while this approach does not provide an exhaustive evaluation of the deformation mechanism it does serve to quantify the relative role played by the variations in the crustal and upper mantle components of the lithosphere in this way we are able to use independent measurement of lithospheric geoid anomalies current post orogenic elevation and lithospheric structure and paleoelevation information to estimate topographic development and structural support over time application of this technique to the southwestern united states indicates that the uplift of the colorado plateau is the result of processes in both the crust and mantle lithosphere and that the lithosphere of the pre orogenic southern basin and range was thinned relative to the northern basin and range and colorado plateau although we use the southwestern u s as an example this method can help constrain uplift mechanisms for any region for which the structure and geoid anomaly of the modern lithosphere is well understood

the isostatic compensation of the colorado plateau basin and range transition zone in central utah abstract the western margin of the colorado plateau in central utah is similar in tectonic style to the adjacent basin and range province and appears to be a transition between the two provinces it is important to understand the isostatic compensation of the topography the source of the associated gravity anomalies and the regional mechanical structure since these variations can be linked to the mechanism controlling the uplift of the colorado plateau and adjacent regions in this paper the isostatic response function admittance function technique is used to study the isostatic compensation of the colorado plateau basin and range transition zone in central utah and determine the applicability of this technique in the study of small geologically complex areas the observed admittance determined from the topography and free air gravity anomaly had small errors for the long wavelength estimates small nearly zero phase angles and high coherence this suggests that most of the energy in the power spectrum of the free air anomaly is correlated with the gravity fields of the topography and its compensation the residual gravity anomaly based on the observed admittance is small except in the region of the wasatch front where the presence of a fairly symmetric high low high trend suggests compensated crustal or lithospheric structures not correlated to the topography the observed admittance function is compared to three simple isostatic models a surface loaded continuous elastic plate a subsurface loaded continuous elastic plate and a pratt model of local compensation it was found that the best fit elastic plate models defined similar results in spite of differing assumptions as to the form of the loading these models both had best fit effective flexural rigidities of 10 20 nm and moho depths of approximately 35 km the calculated residual gravity anomalies based on these models are nearly identical to the residual anomaly of the pratt model with a compensation depth of 65 km the residual anomaly of all three models reproduced the trends and magnitude of the residual anomaly based on the observed admittance it is suggested that this local compensation is due to subsurface laterally varying thermal density anomalies these results differ from previous isostatic rebound studies of ancient lake bonneville which give larger magnitude effective flexural rigidities these differences can possibly be attributed to differing time scales of loading between lake bonneville and the long term thermal loading of the basin and range extension and associated volcanism or the overall simplicity of the considered models care should be exercised in the interpretation of admittance functions determined across transition zones between adjacent tectonic provinces depths of compensation and flexural rigidities can represent averaged values all additional geophysical and geologic information should be considered in the interpretations

compensation of swells and plateaus in the north pacific no direct evidence for mantle convection at intermediate and long wavelengths the ratio of geoid height to topography is sensitive to the depth and mode of compensation a low geoid topography ratio 8 m km in conjunction with a poor correlation between geoid height and topography is evidence of mantle convection after subtracting a reference geoid from the observed geoid previous studies have found a regular pattern of geoid highs and lows with a characteristic wavelength of 3000 4000 km since these geoid highs and lows were poorly correlated with topography and resulted in very high geoid topography ratios 10 20 m km they were believed to reflect the planform of mantle convection we show that the regular pattern of geoid highs and lows is an artifact caused by truncating the reference geoid at spherical harmonic degree 10 since the geoid spectrum is red the residual geoid is dominated by degree 11 when the harmonics of the reference geoid are rolled off gradually the regular pattern of geoid highs and lows disappears in the northeast pacific the new residual geoid reflects the lithosphere age offsets across the major fracture zones in the northwest pacific the residual geoid corresponds to isostatically compensated swells and plateaus we have calculated the geoid topography ratio for 10 swells and plateaus and have found a range of compensation depths the highest geoidaopography ratio of 5 5 m km occurs on the flanks of the hawaiian swell intermediate ratios occur in four areas including the midway swell these intermediate ratios reflect a linear combination of the decaying thermal swell and the increasing volume of airy compensated seamounts low geoid topography ratios occur over the remaining five areas e g emperor seamounts reflecting the absence of a thermal swell our findings do not support the hypothesis that the planform of mantle convection is evident in the geoid we see only indirect evidence of thermal plumes reheating the lower lithosphere

comment on recent subsidence of the venice lagoon from continuous gps and interferometric synthetic aperture radar by y bock s wdowinski a ferretti f novali and a fumagalli

evolutionary aspects of lithosphere discontinuity structure in the western u s 1 we have produced common conversion point ccp stacked ps and sp receiver function image volumes of the moho and lithosphere asthenosphere boundary lab beneath the western united states using transportable array data the large image volumes and the diversity of tectonic environments they encompass allow us to investigate evolution of these structural discontinuities the moho is a nearly continuous topographic surface whereas the lab is not and the seismic images show a more complex expression the first order change in lab depth in the western u s occurs along the cordilleran hingeline the former laurasian passive margin along the southwestern precambrian north american terranes the lab is about 50 deeper to the east of the hingeline than to the west with most of the increase in lab thickness being in the mantle lithosphere we infer that the moho and the lab are late mesozoic or cenozoic everywhere west of the hingeline modified during farallon subduction and its aftermath between the hingeline and the rocky mountain front the lab and to a lesser extent the moho have been partially reset during the cenozoic by processes that continue today seismicity and recent volcanism in the interior of the western u s are concentrated along gradients in crustal and or lithospheric thickness for example the hingeline and the eastern edge of the coastal volcanic magmatic terranes to us this suggests that lateral gradients in integrated lithospheric strength focus deformation similarly areas conjectured to be the sites of convective downwellings and associated volcanism are located along gradients in regional lithosphere thickness

apennines subduction related subsidence of venice italy 1 the foreland regional monocline related to the northern apennines subduction can be followed from the po basin to the friuli region italy at least 240 km north eastward in seismic reflection profiles of the po basin and of the northern adriatic sea the dip of the regional monocline gradually decreases from about 22 to close to 0 pleistocene sediments onlap and pinchout to the northeast venice is located on a segment of the active monocline dipping about 1 8 to the southwest in sediments around the venice area the 1 43 ma limit is in the 960 1500 m depth range indicating a long term subsidence rate of about 0 7 1 0 mm yr therefore a significant part of the natural component of the town subsidence is related to the north eastward retreat of the adriatic subduction the subduction related downflexure affects the whole of the po plain basin and part of the southern alps where it opposes to the general uplift related to orogenesis

inflation rate of the colli albani volcanic complex retrieved by the permanent scatterers sar interferometry technique 1 we analyzed 99 ers sar images of the colli albani volcano using the permanent scatterers technique we retrieved the average surface displacement velocities for over 100 000 scatterers for the period 1993 2000 showing that present deformation is concentrated in the area of most recent volcanic activity with rates up to 2 6 mm yr in the satellite line of sight we inverted the observed deformation using several analytical solutions for volcanic sources in an elastic half space the best fit is obtained with two mogi sources aligned in a n s direction at 5 and 7 km depth beneath the western flank of the volcano

geoid anomalies and the structure of continental and oceanic lithospheres geoid anomalies in the wavelength range corresponding to spherical harmonies 6 to 30 are used to bring new constraints on the deep structure of the continental lithosphere on the nature of upper mantle seismic anomalies and on the thermal evolution of the oceanic lithosphere for the shallow lithospheric density anomalies considered here the geoid anomaly is shown to follow approximately the moment law derived from isostasy by a procedure of least squares inversion the geoid over old cratons is found to be equal to that over relatively young 50 myr oceanic lithosphere the oceanic geoid as a function of age follows the expected linear trend with flattening at old ages these results are independent of the degree at which the spherical harmonics are truncated if the tectosphere consisted only of a thick thermal boundary layer marked geoid lows with an amplitude larger than 20 m should be present over cratons in disagreement with the present observation the predicted geoid agrees with the observations if the negative density anomalies associated with a depleted peridotitic layer are present to the bottom of the lithosphere this analysis of the geoid confirms the petrological inferences that the deep roots observed seismically in the top upper mantle form a chemically differentiate reservoir the density of these cold roots is similar to that of mantle material elsewhere because the increase in density resulting from their lower temperature is largely balanced by the decrease in density caused by their depletion analysis in wavelength range corresponding to harmonics 6 to 30 in the oceans confirms that the geoid flattens at old ages and thus supports the view that an important amount of heat is transferred at the base of the lithosphere by small scale convection

some isostatic and thermal consequences of the vertical strain geometry in convergent orogens abstract the thermal and isostatic consequences of continental deformation particularly surface elevation horizontal buoyancy forces and metamorphism in the crust depend to a considerable extent on the way in which strain is distributed between the crust and the mantle lithosphere 1 since these vertical strains may be strongly decoupled by processes such as convective thinning or detachment of the lower thermal boundary layer 2 with the extent of this decoupling varying in space and time in an orogen 3 it is useful to parameterise the vertical strain on the scale of the crust c and lithosphere 1 respectively we illustrate this parameterisation by considering the thermal and isostatic consequences of a number of c 1 paths which may develop during the convergent deformation of a thermally stabilised lithosphere three qualitatively distinct c 1 paths in orogens are distinguished on the extent of decoupling between vertical strains in the crust and mantle lithosphere type 1 paths involve no decoupling so the vertical strain in the lithosphere is homogeneous for a given c type 1 paths result in relatively low surface elevation and low intermediate metamorphic temperatures appropriate for the development of glaucophane schist and barrovian metamorphic assemblages type 2 paths allow decoupling due to processes such as convective thinning of the mantle lithosphere on the orogenic timescale but only after considerable initial lithospheric thickening type 2 paths lead to relatively high surface elevations for a given c and intermediate to high metamorphic temperatures only after the mantle lithosphere is thinned the increase in potential energy associated with mantle lithospheric thinning resulting in an increase in buoyancy forces by as much as 10 13 nm 1 will quickly terminate convergent deformation with the result that metamorphic heating will postdate the thickening deformation and may induce extensional collapse of the orogen type 3 paths involve efficient mantle lithosphere thinning as the crust thickens with a consequence being particularly the possibility of relatively high metamorphic temperatures during active crustal thickening for a given driving force convergent deformation along a type 3 path will be terminated at relatively small c providing an appropriate setting for the development of high t low p metamorphic assemblages

land subsidence in central mexico detected by alos insar time series abstract massive groundwater extraction is common throughout mexico and is well known to result in land subsidence however most land subsidence surveys focus on one single city mainly mexico city and thus fail to reveal the regional extent of the problem here we use 2007 2011 interferometric synthetic aperture radar insar time series analysis of alos data to resolve land subsidence in the entire central mexico region we identify land subsidence in 21 areas including 17 cities linear vertical rates over 30 cm yr are observed in mexico city while in the other locations rates of 5 10 cm yr are detected we define 3 main categories of subsidence using the averaged velocity maps in conjunction with previously published structural surface geology and land use mapping 1 rapid large scale subsidence 2 rapid local scale subsidence and 3 slow patchy subsidence the correlation between subsidence and land use confirms that groundwater extraction mainly for agricultural and urban activities is the main cause of land subsidence we observe that the boundaries of the subsiding areas are typically characterized by high velocity gradients often coinciding with pre existing faults motion on these faults being driven by water extraction rather than by tectonic activity regional surveys of this type are necessary to understand the spatial and temporal evolution of land subsidence to constrain the distribution and connectivity of water bearing units and ultimately to reach better hazard mitigation plans

on the use of quasi static deformation to understand reservoir fluid flow deformation above a producing reservoir provides a valuable source of information concerning fluid flow and flow properties quasi static deformation occurs when the displacements are so slow that we may neglect inertial terms in the equations of motion we present a method for inferring reservoir volume change and flow properties such as permeability from observations of quasi static deformation such displacements may represent surface deformation such as tilt leveling interferometric synthetic aperture radar insar or bathymetry observations or subsurface deformation as inferred from time lapse seismic surveys in our approach the equation for fluid flow in a deforming reservoir provides a mapping from estimated fractional volume changes to reservoir permeability variations if the reservoir behaves poroelastically over the interval of interest all the steps in this approach are linear thus the inference of reservoir permeability from deformation data becomes a linear inverse problem in an application to the wilmington oil field in california we find that observed surface displacements obtained by leveling and insar are indeed compatible with measured reservoir volume fluxes we find that the permeability variations in certain layers coincide with fault block boundaries suggesting that in some cases faults are controlling fluid flow at depth

quantitative evidence that compaction of holocene sediments drives the present land subsidence of the po delta italy 1 deltas are highly dynamic coastal systems that over the last few decades have generally experienced a substantial area loss caused by trapping of river sediments in upland drainage basins as well as land subsidence due to natural and anthropogenic causes a major example is the po delta in the mediterranean in northeastern italy this area has experienced as much as 3 m of land subsidence from the 1930s to the 1970s primarily because of the extraction of gas bearing waters however present subsidence rates are largely unknown and the ground settlement is supposedly controlled by natural long term deep processes we have combined radar interferometric point target analysis ipta with previous geomorphological investigations on aerial satellite images and seismic surveys and geochronological data from core samples and geomechanical in situ tests to assess the current sinking of the delta and to understand the processes controlling the vertical movement the high density of the measurable point targets more than 15 000 allows characterization of the spatial variation in the vertical land motions vlm ranging from 1 to 15 mm yr we find that subsidence rates are significantly correlated with the age of highly compressible holocene deposits that compose the shallowest 30 40 m of the sedimentary sequence a typical log type consolidation equation applicable at the scale of the entire delta has been obtained we conclude that the consolidation of late holocene sediments is the major cause of the present land subsidence in the po river delta this finding has significant impact on the understanding of many other modern deltas that were formed in the lower holocene epoch

tectonic geomorphometrics of the western united states speculations on the surface expression of upper mantle processes the topography of the western united states provides a classic field laboratory for investigations of the relationship between surface features and sub crustal dynamic processes the interpretation of recently collected high resolution seismic images of the upper mantle beneath the central colorado rocky mountains substantiates the notion that much of the high elevation coincides with thin or attenuated continental crust with respect to predicted airy crustal thicknesses necessitating topographic support by anomalously buoyant mantle this is highly suggestive that broad scale topographic features may be correlated with buoyancy variations in the upper mantle in an attempt to sharpen our understanding of the underlying geodynamics we evaluate the correlation between the surface topographic character and data sets that provide information about density variations indicative of buoyancy in the upper mantle including the lithospheric geoid upper mantle seismic velocity anomalies and crustal lg q our general conclusion is that mantle buoyancy is driving differential surface uplift throughout the western united states and this driver of topography is manifested by measureable anomalies in the topographic roughness at short wavelengths tens of kilometer and elevated spectral power in the topography at longer several hundred kilometers wavelengths a provocative conclusion is that the long recognized physiographic provinces of the colorado plateau rocky mountains and rio grande rift are also neotectonic provinces that are related to convective processes and related buoyancy in the upper mantle

small scale convection at the edge of the colorado plateau implications for topography magmatism and evolution of proterozoic lithosphere the colorado plateau of the southwestern united states is characterized by a bowl shaped high elevation late neogene quaternary magmatism at its edge large gradients in seismic wave velocity across its margins and relatively low lithospheric seismic wave velocities we explain these observations by edge driven convection following rehydration of colorado plateau lithosphere a rapidly emplaced cenozoic step in lithosphere thickness between the colorado plateau and adjacent extended rio grande rift and basin and range province causes small scale convection in the asthenosphere a lithospheric drip below the plateau is removing lithosphere material from the edge that is heated and metasomatized resulting in magmatism edgedriven convection also drives margin uplift giving the plateau its characteristic bowl shape the edge driven convection model shows good consistency with features resolved by seismic tomography

preliminary data from valle giumentina pleistocene site abruzzo central italy a new approach to a clactonian and acheulian sequence abstract valle giumentina is a pleistocene open air site in central italy abruzzo nine archaeological layers occur in the last 25 m of a 70 m thick sedimentary sequence in the 1950s the various archaeological layers were attributed to the clactonian acheulian and levalloisian traditions recent multidisciplinary fieldwork and studies 2012 2016 acquired new archaeological chronostratigraphical and paleoenvironmental data this contribution presents the preliminary results of the ongoing excavation of layer 42 alb this is a paleosol located at 4 m depth at the top of a lacustrine deposit directly below the coarse deposits associated with the last major erosive event faunal remains consisted essentially by cervus elaphus the lithic series is characterized by a specific flake production system only a part of the block is reduced and platforms and surfaces are not prepared several methods are used including the ssda systeme par surfaces de debitage alternees backed flakes are frequent numerous blanks are transformed by intensive or marginal retouch functional objectives are multiple as shown by different tool structures and use wear traces valle giumentina 42 alb is a butchery site used briefly but frequently during warmer substages occurring during an overall cold period the clactonian industry of valle giumentina is often considered as simple or expedient we demonstrate its real technical complexity and its functional significance comparisons are made with other european sites

disruptive influences of residual noise network configuration and data gaps on insar derived land motion rates using the sbas technique abstract the interferometric synthetic aperture radar insar small baseline subset sbas technique can be applied to land with varying deformation magnitudes ranging from mm yr to tens of cm yr sbas defines a network of interferograms that is limited by temporal and spatial baseline thresholds that are often applied arbitrarily or in apparently subjective ways in the literature we use simulated sar data to assess 1 the influence of residual noise and sbas network configuration on insar derived deformation rates and 2 how the number of interferograms and data gaps in the time series may further impact the estimated rates this leads us to an approach for defining a sbas network based on geodetic reliability theory represented by the redundancy number r number simulated insar datasets are generated with three subsidence signals of linear rates plus sinusoidal annual amplitudes of 2 mm yr plus 2 mm 20 mm yr plus 5 mm and 100 mm yr plus 10 mm contaminated by gaussian residual noise bounded within 2 2 mm 5 5 mm and 10 10 mm corresponding to standard deviations of approximately 0 5 mm 1 5 mm and 3 0 mm respectively the influence of data gaps is investigated through simulations with percentages of missing data ranging from 5 to 50 that are selected 1 randomly across the 4 year time series and 2 for three month windows to represent the northern winter season where snow cover may cause decorrelation these simulations show that small deformation rates are most adversely affected by residual noise in some extreme cases the recovered trends can be contrary to the signal i e indicating uplift when there is simulated subsidence we demonstrate through simulations that the r number can be used to pre determine the reliability of sbas network design indicating the r values between 0 8 and 0 9 are optimal r numbers less than 0 3 can deliver erroneous rates in the presence of noise commensurate with the magnitude of deformation finally the influence of data gaps is not as significant compared to other factors such as a change in the number of interferograms used although the blocks of winter gaps in the sbas network show a larger effect on the rates than gaps at random intervals across the simulated time series

complex subduction and small scale convection revealed by body wave tomography of the western united states upper mantle abstract new high resolution p and s wave tomography of the united states upper mantle from the pacific coast to the great plains reveals strong multi scale heterogeneity closely correlated with tectonic and magmatic activity we invert teleseismic travel time residuals from the earthscope transportable array and more than 1700 additional temporary and permanent stations for 3 d velocity perturbations to a depth of 1000 km the inversion uses recent advances in western u s crust models to better isolate the mantle component of travel time residuals and frequency dependent 3 d sensitivity kernels to map travel time residuals measured in multiple frequency bands into velocity structure in addition to separate v p and v s models we jointly invert the two datasets for v p v s perturbations by imposing a smoothness constraint on the ln v s ln v p field the joint inversion helps us identify regions where partial melt is probable the amplitude of v p v s and v p v s variations is greatest in the upper 200 km of the mantle and the form of velocity anomalies suggests a provincially heterogeneous lithosphere and the occurrence of widespread small scale convection partially molten mantle is inferred beneath yellowstone and the eastern snake river plain srp the salton trough and the clear lake volcanic field the inferred depth extent of partial melt is consistent with a generally hydrated upper mantle and elevated temperatures beneath the eastern srp and yellowstone despite continuous subduction since the cretaceous the distribution of sub lithospheric high velocity anomalies is dissected similar to other recent studies based on our new tomography models western u s geologic history and plate tectonic reconstructions we infer patchy and incomplete removal of the flat subducting laramide slab and slab tearing associated with eocene accretion in the northwestern u s

analysis of surface deformations over the whole italian territory by interferometric processing of ers envisat and cosmo skymed radar data abstract interferometric processing of series of data acquired over time by synthetic aperture radar sar satellites makes it possible to measure millimetric deformations typically due to landslides subsidence and earthquake or volcanic phenomena and to monitor the stability of terrain and infrastructures despite the unique capability to observe very large areas this technology has been typically applied to the analysis of relatively small sites or specific geophysical phenomena in this work we present the first application of this technology to a national scale project which required the processing through advanced persistent scatterer interferometry psi techniques of about 20 000 sar images acquired from 1992 to 2014 over the whole italian territory by the ers envisat and cosmo skymed satellites the obtained results provide a huge database of surface deformation measurements covering the last 20 years and the whole italian territory which represents an extremely useful and pioneering service for geo hazards mapping and prevention

models of isostatic and dynamic topography geoid anomalies and their uncertainties knowledge of the dynamic topography at earth s surface caused by sublithospheric density contrasts would provide crucial constraints on models of mantle dynamics we calculate global models of this dynamic topography by subtracting from the observed topography estimates of the topography caused by assumed isostatically compensated density variations in the crust the oceanic lithosphere and the continental tectosphere we also calculate the isostatic geoid anomaly that would result from these compensated near surface density anomalies because there is controversy about the thermal structure of old oceanic lithosphere we investigate two models of the cooling of the oceanic lithosphere half space and plate and calculate the effect of each on the inferred dynamic topography peak amplitudes of dynamic topography from sublithospheric sources expanded to spherical harmonic degree 6 are approximately 1 km we estimate the uncertainties in the calculated dynamic topography and geoid by combining the errors in the data and systematic errors to obtain the spectral coefficients of the fields we use weighted least squares inversions the calculated dynamic topography arising from sublithospheric sources residual geoid and errors associated with these fields can be used in studies of mantle dynamics

a tectonic redefinition of the southern rocky mountains abstract the southern rocky mountains of the western united states physiographically defined and described by n m fenneman nearly 60 yrs ago are tectonically redefined and extended they are shown to constitute the crestal range of a mammoth continental arch like feature here named the alvarado ridge its axis trends south from casper wyoming at least as far south as el paso texas beyond which the ridge begins to lose morphological identity maximum elevations along the crest of the ridge exceed 4 2 km the summit ranges are bordered on either side by gently sloping rises that extend outward for at least 1300 km falling to elevations of less than 400 m modest rift structures along the ridge axis continue beyond the southern terminus of the mountains before playing out a major sediment filled axial graben exists over the southern two thirds of the ridge but equivalent parts of it farther north were stripped of their neogene fill by erosion in the headwaters areas of the colorado and north platte rivers the maximum elevation of earlier laramide mountains in this area has been estimated to have been no more than 2 km in colorado half that of the present range related topography was nearly obliterated by erosion prior to late eocene time lateral stream planation produced a southeast sloping major late eocene erosion surface across the region that had what was probably an isostatically adjusted average maximum elevation of less than 900 m present day elevations and relief on the ridge crest are the result of steep crestal normal faulting pronounced block uplift and regional arching with extensional strain limited to an axial corridor less than 200 km wide this episode of mountain building began in middle miocene time 17 to 12 ma culminating in latest miocene and early pliocene time between 7 and 4 ma ago debris from the newly elevated range the southern rocky mountains sensu lato was shed along the full length of the neogene alvarado ridge down parts of both rises as well as into its medial graben the uplifted and tilted east rise the great plains ramp has an extensive aggradational cover that spread eastward to distances of 700 km and more in middle miocene to earliest pliocene time its fluviatile lacustrine and eolian sediments are undergoing dissection today but a sufficient portion remains to define the unmodified profile of the east rise as well as the original length of the ridge it is coincidentally similar in configuration and scale to the west rise of the mid atlantic ridge the topography of the crestal mountain ranges on both structures is also remarkably similar the southern rocky mountains are as high as the alps but are not the product of lithospheric compression and crustal thickening rather they reflect profound epeirogenic uplift driven by lithospheric thinning and accompanied by extensional strain and differential vertical jostling along the crest of the ridge

recent subsidence of the venice lagoon from continuous gps and interferometric synthetic aperture radar 1 coastal regions are increasingly affected by larger storms and rising sea level predicted by global warming models aggravating the situation in the city of venice where tidal induced seasonal flooding coupled with natural and anthropogenic subsidence have been perennial problems in light of accelerated efforts to protect venice from the rise in sea level we assess land subsidence in the venice lagoon over the last decade through a combined analysis of gps position time series from 2001 55 to 2011 00 for four stations installed by the magistrato alle acque di venezia and thousands of observations of insar permanent scatterers using radarsat 1 images from 2003 3 to 2007 85 we determine that the northern lagoon subsides at a rate of 2 3 mm yr whereas the southern lagoon subsides at 3 4 mm yr the city of venice continues to subside at a rate of 1 2 mm yr in contrast to geodetic studies in the last decade of the 20th century suggesting that subsidence has been stabilized the gps results indicate a general eastward tilt in subsidence and that the natural subsidence rate related to the retreat of the adriatic plate subducting beneath the apennines is at least 0 4 0 6 mm yr our combined gps and insar analysis demonstrates high spatial resolution in the vertical direction with a precision of 0 1 0 2 mm yr with respect to a global reference frame continued efforts to secure the city of venice from flooding must also take into account the significant local and regional subsidence rates as well as the expected rise in sea level

assessing short and long time displacements in the venice coastland by synthetic aperture radar interferometric point target analysis 1 the venice lagoon in italy is a unique environment vulnerable to loss in surface elevation relative to the mean sea level we present detailed synthetic aperture radar sar interferometric analyses on persistent point targets for the historical center of venice the tourist area of sottomarina and the zennare farmland close to the southern lagoon edge the selected areas are characterized by different degrees of development and our analyses show the remarkable capability of sar interferometric point target analysis ipta to map land displacement rates in densely urbanized zones and to detect movement information on isolated structures with a mm year accuracy a detailed analysis of the time series from 1992 to 2000 provided by ipta shows that the vertical component of the measured displacements are the superposition of a short timescale generally seasonal movement on the order of 1 cm that is likely related to the fluctuation of environmental variables temperature piezometric head in the aquifer system underlying the lagoon sea lagoon water level and a long term ground deformation associated with building construction the geomorphology of the area and the human development of natural resources if venice is confirmed to be generally stable significant long term subsidence on the order of 4 mm year is detected at the sottomarina coastland the highest displacement rates of up to 8 10 mm year are recorded in the farmland bounding the lagoon margin where the movements are found to be highly site specific

sar monitoring of progressive and seasonal ground deformation using the permanent scatterers technique spaceborne differential radar interferometry has proven a remarkable potential for mapping ground deformation phenomena e g urban subsidence volcano dynamics coseismic and postseismic displacements along faults as well as slope instability however a full operational capability has not been achieved yet due to atmospheric disturbances and phase decorrelation phenomena these drawbacks can often be at least partially overcome by carrying out measurements on a subset of image pixels corresponding to natural or artificial stable reflectors permanent scatterers ps and exploiting long temporal series of interferometric data this approach allows one to push the measurement precision very close to its theoretical limit in the order of spl sim 1 mm for c band european remote sensing ers like sensors in this paper the detection of both time uniform and seasonal deformation phenomena is addressed and a first assessment of the precision achievable by means of the ps technique is discussed results highlighting deformation phenomena occurring in two test sites in california are reported fremont in the southern bay area and san jose in the santa clara valley

geodetic control on recent tectonic movements in the central mediterranean area abstract during the neogene and quaternary the western mediterranean geodynamics was apparently dominated by the nearly eastward migration of the apenninic arc and the associated opening spreading of the back arc basin tyrrhenian sea however during the last 5 my the collision of the arc with the apulian platform led to a dramatic change in the tectonic setting of the area as geological processes require a long period of time to register the displacements of the different blocks it is indispensable to take into account the present day motion given by space geodesy data analysis in order to better constrain the geological models geodetic motions were derived from global positioning system gps satellite laser ranging slr and very long baseline interferometry vlbi observations collected from different networks all the geodetic solutions have been computed and combined at the centre of space geodesy cgs at matera italy the geodetic results show a nne motion of the adriatic plate with a small component of counter clockwise rotation in good agreement with the geological and geophysical observations in the southern tyrrhenian area the lengthening of the matera cagliari baseline should imply that convergence cannot be considered as the driving mechanism for the apenninic subduction process the estimated motion of noto is in quite good agreement with the estimated motion of the african plate

improving deformation models by discounting transient signals in geodetic data 2 geodetic data stress directions and long term strain rates in italy

exploiting uavsar for a comprehensive analysis of subsidence in the sacramento delta abstract the sacramento san joaquin delta like other heavily engineered deltas throughout the world has undergone substantial subsidence since the late 1800s when the natural estuary was leveed to form islands today islands within the delta have subsided to the point where most lie below mean sea level long term sustainability of the delta requires reversal of subsidence but spatially comprehensive maps of subsidence have not been available to inform and monitor remediation reported here is the first spatially dense map of recent subsidence rates across the delta based on synthetic aperture radar interferometry and constrained by gnss observations the analysis uses a temporally dense and spatially overlapping set of data acquired by the uninhabited aerial vehicle sar uavsar sensor in 2009 2015 on average the delta is subsiding by 9 2 4 4 mm yr with high variability even at the sub island scale including peak subsidence of 160 4 4 mm yr occurring just inland of the levee of the westernmost island and average subsidence of 11 mm yr along the planned path of water conveyance tunnels through the delta the results are compared to local sea level rise slr measured at a tidal gauge in san francisco bay to show that subsidence is currently the dominant contributor to local relative sea level rise rslr by nearly a factor of five based on recently measured and modeled acceleration of slr subsidence in the delta is likely to dominate rslr until the middle of the 21th century

forward and inverse modelling of gravity revealing insight into crustal structures of the eastern alps abstract the crustal structure of the eastern alps is less known than that of the western alps as participants of the european geotraverse and particular swiss projects investigated the alpine crust there recently the eastern alps were subject to seismic research which was conducted in the context of the german austrian and italian transalp project the 3d modelling of the density structure which is presented in this paper belonged to a series of piggy back projects which were closely accomplished using the seismic reflection studies we present a combined gravity seismic interpretation which is based on the results of both older deep seismic profiles and the new transalp profile special emphasis was laid on geologic and tectonic information which served as model constraints for near surface structures a 3d forward modelling of both the bouguer gravity field and the geoidal undulations provides in depth insight into the lithosphere and considers the constraints due to the uncertainties of used constraints particularly in depths of the eastern alpine moho an inversion technique complemented this study and provided insight into the shape and density contrast at the crust mantle interface the modelling indicates that the bouguer gravity field in the eastern alps is mainly caused by two sources the density contrast at the crust mantle boundary 350 kg m3 and the density inhomogeneities in the upper 10 km of the crust which contributes to the overall gravity field by amounts of approximately 30 10 5 m s2 the results of the forward and inverse modelling produced a shallower crust mantle boundary in the southern adriatic area in comparison with the northern part and differs from the seismic findings of the transalp group to some extent this observation and observable mismatch in the long wavelength model and the observed geoidal undulations point to density inhomogeneities in sub crustal and even sub lithospheric depths these deep seated inhomogeneities should have a substantial bearing on the isostatic balance of the eastern alps

constraints on yield strength in the oceanic lithosphere derived from observations of flexure summary the wavelength and amplitude of outer rises seaward of sub duction zones and arches surrounding islands and seamounts are used to parameterize flexure profiles in terms of the moment and curvature at the first zero crossing the data show the clear age dependence in the mechanical thickness of the lithosphere up to 60 100myr saturation of moment at large curvature is interpreted in terms of a depth dependent yield strength for the lithosphere using relations adopted from laboratory experiments of rock deformation a comparison of theoretical curves with observed moments indicates that old oceanic lithosphere has no long term strength below about 40 km depth with no difference between 100 and 165 myr old crust moderate axial loading forces 200 mpa can explain most variations in the moment curvature observations except in the case of the kuril trench which appears anomalous given the age of the crust regional tension causes greater variability in moment as compared to regional compression because of the greater slope in the brittle failure envelope under tension the observations point to a lithosphere weaker than the prediction from experimental deformation of rocks of the possible weakening mechanisms elevated pore fluid pressure on faults does not predict the correct age dependence and is incompatible with earthquake focal mechanisms our favoured explanation is that the activation energy q appropriate for ductile flow at geological strain rates is lower than the values derived from laboratory extrapolations of dry olivine data taken at high temperatures if recent oceanic geotherms are reliable q in the lower lithosphere must be lower than 100kcal mol 1 the method used here is most appropriate for trench profiles with curvatures greater than 10 7m 1 for lower curvatures such as along seamount profiles small errors in the curvature estimate cause large changes in rheological parameters

persistent scatterer interferometry analysis of ground deformation in the po plain piacenza reggio emilia sector northern italy seismo tectonic implications

western u s upper mantle structure regional three dimensional inversions of upper mande p wave velocity structure are created from teleseismic p wave travel time residuals recorded by many of the high density high frequency regional arrays operated within the western united states these inversions are adjusted to a global international seismic centre reference and merged to obtain an image of the upper mantle beneath western united states the p wave velocities in the upper mantle are slow on average and the structure is very heterogeneous where resolution is good coherent upper mantle structures are imaged that extend as deep as 200 km the juan de fuca and gorda slabs which penetrate to greater depths are exceptions and deviate from the average velocity at a given depth by as much as 4 lateral resolution of these structures usually is very good although the magnitude of the actual seismic variations is probably greater than that imaged the long wavelength part of the imaged mantle structure defines coherent elongate features with wavelengths of 200 500 km within 250 km of the pacific coast these structures have a wavelength of 250 km and trend parallel to the surface physiography and young tectonic structures beneath the continental interior where use is made of additional seismic studies to infer average structure in regions of poor teleseismic data coverage structures have a wavelength of 500 km and trend northeasterly this northeast orientation is discordant with young tectonic structures but aligns with young volcanic activity

itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters 1 unlike the past international terrestrial reference frame itrf versions where global long term solutions were combined the itrf2005 uses as input data time series weekly from satellite techniques and 24 h session wise from very long baseline interferometry of station positions and daily earth orientation parameters eops the advantage of using time series of station positions is that it allows to monitor station non linear motion and discontinuities and to examine the temporal behavior of the frame physical parameters namely the origin and the scale the itrf2005 origin is defined in such a way that it has zero translations and translation rates with respect to the earth center of mass averaged by the satellite laser ranging slr time series spanning 13 years of observations its scale is defined by nullifying the scale and its rate with respect to the very long baseline interferometry vlbi time series spanning 26 years of observations the itrf2005 orientation at epoch 2000 0 and its rate are aligned to the itrf2000 using 70 stations of high geodetic quality the estimated level of consistency of the itrf2005 origin at epoch 2000 0 and its rate with respect to the itrf2000 is respectively 0 1 0 8 5 8 mm and 0 2 0 1 1 8 mm yr along the x yand z axis we estimate the formal errors on these components to be 0 3 mm and 0 3 mm yr we believe that this low level of agreement between the two frame origins is most probably due to the poor slr network geometry and its degradation over time the itrf2005 combination involving 84 co location sites revealed a scale inconsistency of 1 ppb 6 3 mm at the equator at epoch 2000 0 and 0 08 ppb yr between the slr and vlbi long term solutions as obtained by the stacking of their respective time series possible causes of this inconsistency may include the poor slr and vlbi networks and their co locations local tie uncertainties systematic effects and possible inconsistent model corrections used in the data analysis of both techniques for the first time of the itrf history the itrf2005 rigorous combination provides self consistent series of eops including polar motion from vlbi and satellite techniques and universal time and length of day from vlbi only a velocity field of 152 sites with an error less than 1 5 mm yr is used to estimate absolute rotation poles of 15 tectonic plates that are consistent with the itrf2005 frame this new absolute plate motion model supersedes and significantly improves that of the itrf2000 which involved six major tectonic plates citation altamimi z x collilieux j legrand b garayt and c boucher 2007 itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters j geophys res 112 b09401

geoid height versus topography for oceanic plateaus and swells oceanic plateaus and swells are a major component of the seafloor topography yet they remain among the most poorly understood features this is especially true of the oceanic plateaus which show large variations in crustal thickness to determine the depth and mode of compensation for 53 of the largest plateaus and swells we analyzed the relationship between geoid height and topography in polygonal areas containing each feature both geoid height and topography were first band pass filtered 400 km i 4000 km to isolate the signal associated with local compensation from flexural and deep mantle signals the ratio of geoid height to topography was then determined by fitting a straight line to the data except for nine of the smaller features there is a high correlation between geoid height and topography that is positive in accordance with airy and thermal compensation models eighteen features have high geoid topography ratios that cannot be explained by the airy compensation model of crustal thickening these features thermal swells are partially supported by thermal buoyancy forces in the lower half of the lithosphere the ratios are highest for active hot spot swells and decay with the thermal age of the swell to values consistent with airy compensation of the enduring volcanic edifice the remaining features plateaus have lower geoid topography ratios in agreement with the airy compensation model those plateaus with average height greater than 4 km are thought to be continental fragments the shorter plateaus tend to be volcanic features modified continental plateaus presumably small fragments of extended and intruded continental margin crust cluster around heights of n3 km overlapping the range associated with oceanic plateaus since the origin of many plateaus is poorly understood this global geoid topography analysis provides a new technique for comparing the deep structure of oceanic plateaus and swells

joint seismic geodynamic and mineral physical constraints on three dimensional mantle heterogeneity implications for the relative importance of thermal versus compositional heterogeneity summary the joint interpretation of seismic and geodynamic data requires mineral physical parameters linking seismic velocity to density perturbations in the earth s mantle the most common approach is to link velocity and density through relative scaling or conversion factors r s dln dlnv s however the range of possible r s values remains large even when only considering thermal effects we directly test the validity of several proposed depthdependent conversion profiles developed from mineral physics studies for thermally varying properties of mantle materials the tests are conducted by simultaneously inverting shear wave traveltime data and a diverse suite of convection related constraints interpreted with viscous flow response functions of the mantle these geodynamic constraints are represented by surface spherical harmonic basis functions up to harmonic degree 16 and they consist of the global free air gravity field tectonic plate divergences dynamic surface topography and the excess ellipticity of the core mantle boundary cmb the tests yield an optimum 1 d thermal r s profile that is generally compatible with all considered data with the exception of the dynamic surface topography that is most sensitive to the shallow upper mantle this result is not surprising given that cratonic roots are known to be compositionally distinct from the surrounding ambient mantle moreover it is expected that the temperature dependence of the thermal r s in the upper mantle is significant due to the temperature dependence of seismic attenuation or q therefore a simple 1 d density velocity relationship is insufficient to address this problem we obtained independent estimates of the first order correction factors to the selected r s profile within the cratonic roots and in the ambient thermal upper mantle these correction factors defined as r s lnv s are highly negative within the cratons signifying considerable compositional buoyancy this result confirms that the negative buoyancy associated with the low temperatures in the cratons is significantly counteracted by the composition induced positive buoyancy resulting in near neutral buoyancy of the cratonic roots within the ambient upper mantle the correction factors are found to be positive which is consistent with the expected behaviour of the r s relationship in thermally varying upper mantle material we obtain a significantly greater reconciliation of the global gravity anomalies and dynamic surface topography when applying these laterally varying corrections compared to a simple 1 d r s relationship inversion for a fully 3 d r s relationship reveals secondary effects including additional compositional variation within the cratonic roots and the deep mantle superplume structures we estimate the relative magnitude of the thermal and compositional non thermal contributions to mantle density anomalies and conclude that thermal effects dominate shear wave and density heterogeneity throughout the non cratonic mantle we also demonstrate the potential pitfalls of scaling a purely seismically derived model to obtain density rather than performing a true joint inversion to obtain velocity and density simultaneously

western united states extension how the west was widened abstract cenozoic extension in the western united states presents a complex interrelation of extension volcanism and plate boundary tectonics that defeats simple notions of active or passive rifting forces driving extension can originate at plate boundaries through basal traction basal normal forces or from buoyancy forces internal to the crust and lithospheric mantle the latter two are most responsible for driving extension where it is observed in the basin and range the complex evolution of the northern basin and range probably represents removal or alteration of mantle lithosphere interacting with buoyancy stored in the crust in contrast crustal buoyancy forces combined with a divergent plate boundary between about 28 and 16 ma to drive extension in the southern basin and range the central basin and range most likely extended as a result of boundary forces external to itself but arising from buoyancy forces elsewhere in the western united states

lithospheric flexure and gravity anomalies at proterozoic plate boundaries in the canadian shield abstract proposed proterozoic sutures in the canadian shield show paired positive and negative gravity anomalies previous interpretations ascribe the negative anomaly to an increase in crustal thickness of the older province towards the suture and the positive to increased density and thickness of the younger province here the asymmetrical negative anomaly is interpreted to be the result of flexure of the older lithosphere as it is thrust under the younger more buoyant plate the absence of any visual correlation between topography and observed gravity over suture zones suggests the presence of subsurface loads which are thought to be the primary sources for the related positive gravity anomalies two dimensional modelling of suture anomalies has resulted in the following estimates for elastic plate thicknesses in the canadian shield 60 km for the slave plate and 75 120 125 km for the cape smith labrador and grenville areas of the superior province flexural rigidities at sutures increase with the age of the lithosphere when loaded supporting previous results obtained in oceans and mountain ranges

lithospheric gravitational potential energy and past orogenesis implications for conditions of initial basin and range and laramide deformation gravitational body forces i e buoyancy forces have come to be seen as critical to the evolution of orogens nevertheless constraining the role of body forces in specific geologic scenarios is made difficult by the substantial number of poorly constrained physical parameters needed to fully relate forces to deformation by separating the calculation of buoyancy forces from the calculation of the resulting deformation models based on relatively simple descriptions of the lithosphere can yield geologically useful constraints among these are the importance of paleoelevation in driving syn and postcontractional extension and in localizing contractional strain although such phenomena have been considered in more complex models of continental deformation the simpler analysis presented here clearly establishes first order limits on lithospheric structures and paleoelevations consistent with buoyancy driven deformation in the early cenozoic great basin of the western united states we show that the low elevations inferred in much of the geologic literature are inconsistent with a body force origin for observed extensional tectonism east of the colorado plateau localization of laramide deformation coincides with pre laramide subsidence of the western interior seaway this subsidence prestressed the lithosphere making the southern rocky mountains the weak link in responding to regional compressional stress

observational constraints on models of the hawaiian hot spot swell a detailed analysis of the topography and geoid associated with the hawaii emperor seamount chain reveals that while geoid topography ratios are high over the southeastern part of the chain they fall off with distance away from the current hot spot location the topographic expression of the swell has two maxima near the intersections between the seamount chain and the murray and molokai fracture zones respectively both geoid and topography rapidly decrease westward of the intersection with the murray fracture zone it appears that the region of the pacific plate between the two fracture zones has been more susceptible to reheating and hot spot penetration than elsewhere along the chain alternatively the observed pattern may be indicative of time variation in the strength of the hawaiian hot spot

the role of gravitational potential energy in active deformation in the southwestern united states in orogenic belts intrinsic buoyancy and extrinsic boundary forces act on the continental lithosphere determining the relative importance of these forces is fundamental to understanding the dynamics of continental deformation in the western united states estimates of gravitational potential energy show that given available constraints on rheology buoyancy forces are sufficient to produce the wide variety of rates and styles of observed deformation including absence of deformation this underscores the importance of gravitational potential energy for deformation in orogenic belts

space geodesy subsidence and flooding in new orleans a subsidence map of the city offers insight into the failure of the levees during hurricane katrina

vertical land motion and relative sea level changes along the coastline of brest france from combined space borne geodetic methods abstract in spite of the recent advances and the current perspectives of satellite radar altimetry to reach the coastline and monitor coastal sea level changes this space borne technology remains geocentric by essence in contrast the quantity that matters for coastal management and society is relative sea level that is the sea level relative to the land as measured by conventional tide gauges however two important issues are associated with the use of tide gauges first supplemental information is required to separate vertical land motion from ocean climate signals in tide gauge records and hence to understand the causes of future coastal sea level changes and their relative importance this can be provided by space borne geodetic techniques for instance installing a permanent global positioning system gps antenna at the tide gauge second vertical land motion can show local spatial patterns which limits the spatial validity of the point wise information at the gps station using interferometry synthetic aperture radar insar and high precision gps data the above mentioned limitations were addressed in the case study of brest france our findings show that over the past decades brest and its surroundings are overall stable in agreement with the geological setting except for the embankment areas of the commercial and military harbours the gps calibrated insar results were then further combined with geocentric satellite radar altimetry data to obtain relative sea level trends along the brest coastline with an unprecedented high spatial resolution of 200 m our approach is applicable beyond the case study of brest especially in coastal areas where tide gauge data are not available provided satellite data are

dynamics of slow moving landslides from permanent scatterer analysis high resolution interferometric synthetic aperture radar insar permanent scatterer data allow us to resolve the rates and variations in the rates of slow moving landslides satellite to ground distances range changes on landslides increase at rates of 5 to 7 millimeters per year indicating average downslope sliding velocities from 27 to 38 millimeters per year time series analysis shows that displacement occurs mainly during the high precipitation season during the 1997 1998 el nino event rates of range change increased to as much as 11 millimeters per year the observed nonlinear relationship of creep and precipitation rates suggests that increased pore fluid pressures within the shallow subsurface may initiate and accelerate these features changes in the slope of a hill resulting from increases in the pore pressure and lithostatic stress gradients may then lead to landslides

a new project to monitor land subsidence in the northern venice coastland italy the paper deals with the implementation of a levelling and global positioning system gps network to control land subsidence in the coastal area north of the venice lagoon about 480 km of levelling lines with 527 benchmarks 45 of which suited for differential gps measurements were established in 2004 a complete survey of the net was carried out in 2004 soon after its establishment the 2004 records have been compared with previous scattered data obtained by the use of levelling surveys dgps and sar interferometry the results show a trend in land settlement that increases from the lagoon margin to the north and jeopardize the venice coastland groundwater withdrawals for domestic agricultural and health spas uses peat oxidation of reclaimed marshlands for farming natural consolidation of the holocene deposits and tectonics of the pre quaternary basement are the causes of land subsidence in the study area since most of the area lies below the mean sea level and on account of the expected sea level rise due to global change a detailed monitoring of land displacements in the near future will be of paramount importance to plan necessary works for coastland protection

high nonlinear urban ground motion in manila philippines from 1993 to 2010 observed by dinsar implications for sea level measurement abstract in coastal low lying urban areas vertical ground motions can significantly exacerbate the hazards related to sea level rise however their spatial extent their temporal evolution and even sometimes their existence are often poorly known this study aims to monitor variable urban ground motion uplift and subsidence from 1993 to 2010 in the metropolitan area of manila philippines because high subsidence rates have been reported in this city in previous studies conventional differential sar interferometry dinsar was applied with an adapted stacking procedure to the archive of ers and envisat satellite images to produce surface deformation velocity maps for different periods the results showed that the city is locally affected by vertical ground motions on the order of 15 cm yr moreover the spatio temporal evolution of the ground motion phenomena is highly nonlinear these results are in good agreement with previous studies focused on groundwater use in manila and in the marikina fault valley suggesting a plausible interpretation of the processes causing surface motion incidentally the ground motions are affecting the locations of several geodetic instruments including a tide gauge with sea level records starting in 1902 two permanent gps global positioning system stations and a doris doppler orbitography and radiopositioning integrated by satellite station a major implication of those large and locally variable ground motions is that they impede the use of the nearby gps and doris data to correct the tide gauge records and to derive robust sea level trends associated with climate change

decoding the origins of vertical land motions observed today at coasts in recent decades geodetic techniques have allowed detecting vertical land motions and sea level changes of a few millimetres per year based on measurements taken at the coast tide gauges on board of satellite platforms satellite altimetry or both global navigation satellite system here contemporary vertical land motions are analysed from january 1993 to july 2013 at 849 globally distributed coastal sites the vertical displacement of the coastal platform due to surface mass changes is modelled using elastic and viscoelastic green s functions special attention is paid to the effects of glacial isostatic adjustment induced by past and present day ice melting various rheological and loading parameters are explored to provide a set of scenarios that could explain the coastal observations of vertical land motions globally in well instrumented regions predicted vertical land motions explain more than 80 per cent of the variance observed at scales larger than a few hundred kilometres residual vertical land motions show a strong local variability especially in the vicinity of plate boundaries due to the earthquake cycle significant residual signals are also observed at scales of a few hundred kilometres over nine well instrumented regions forming observation windows on unmodelled geophysical processes this study highlights the potential of our multitechnique database to detect geodynamical processes driven by anthropogenic influence surface mass changes surface loading and glacial isostatic adjustment and tectonic activity including the earthquake cycle sediment and volcanic loading as well as regional tectonic constraints future improvements should be aimed at densifying the instrumental network and at investigating more thoroughly the uncertainties associated with glacial isostatic adjustment models

land subsidence in houston correlated with flooding from hurricane harvey abstract hurricane harvey caused unprecedented flooding and socioeconomic devastation in eastern texas with high winds elevated storm tide and record rainfall the flooded area is mapped using the radar backscattering difference between sentinel 1a b satellite acquisitions spanning the event which provides a snapshot of standing water at the time of image acquisition we find vast areas outside of designated flood hazard zones are overwhelmed furthermore we map pre cyclone land subsidence using multitemporal interferometric processing of large sar datasets acquired by advanced land observation satellite alos and sentinel 1a b satellites we find that subsidence of up to 49 mm yr and 34 mm yr during the alos jul 2007 jan 2011 and sentinel 1a b dec 2015 to aug 2017 acquisition periods affect various parts of houston galveston area we conclude that 85 of the flooded area subsided at a rate 5 mm yr we suggest that subsidence affected flood severity by modifying base flood elevations and topographic gradients supported by the chi square test of independence this work highlights the importance of incorporating insar measurements of land subsidence in flood resilience strategies

are long tide gauge records in the wrong place to measure global mean sea level rise ocean dynamics land motion and changes in earth s gravitational and rotational fields cause local sea level change to deviate from the rate of global mean sea level rise here we use observations and simulations of spatial structure in sea level change to estimate the likelihood that these processes cause sea level trends in the longest and highest quality tide gauge records to be systematically biased relative to the true global mean rate the analyzed records have an average twentieth century rate of approximately 1 6 mm yr but based on the locations of these gauges we show that the simple average underestimates the twentieth century global mean rate by 0 1 0 2 mm yr given the distribution of potential sampling biases we find that 1 probability that observed trends from the longest and highest quality tide gauge records are consistent with global mean rates less than 1 4 mm yr

on the stability of isostatically compensated mountain belts the formation of convergent mountain belts is invariably accompanied by an increase in gravitational potential energy due to part of the work done by the forces driving convergence the evolution of potential energy stored in an orogen is dependent on 1 the density structure 2 the thermal evolution and 3 the way convergent deformation is partitioned between crust and mantle lithosphere it is now well recognized that this increase in potential energy associated with the mountain building process raises the possibility that significant extension or collapse may accompany the relaxation of the forces driving convergence provided the lithosphere is thermally weakened e g england 1987 in this paper we evaluate the stability of isostatically compensated mountain belts under the assumption that the strength of continental lithosphere is governed by a combination of frictional sliding and creep processes using the brace goetze model for the rheology of the lithosphere the reference lithosphere defined to be in potential energy and isostatic balance with the mid ocean ridges changes with different thermal parameters of the lithosphere the instantaneous extensional strain rate for thermally mature mountain belts is calculated by balancing the horizontal buoyancy force stored in the mountain belts measured relative to the reference state with the vertically integrated strength of the lithosphere for initial strengths spanning the probable natural range it is shown that horizontal buoyancy forces arising in isostatically balanced mountain belts are sufficiently large to induce the collapse at significant rates greater than a few times 10 16 s 1 and leading to significant finite extension providing the moho temperatures exceed about 650 700 c a condition only likely to be attained if the mantle lithosphere has not been thickened to the same extent as the overlying crust consequently processes that thin the mantle lithosphere as a consequence of convergent deformation such as the convective instability of a thickened lower thermal boundary layer greatly increase the possibility of collapse the calculations presented here suggest that near complete destruction of the mountain system by extensional collapse may be possible if such processes can reduce total lithospheric thickening to less than half the contemporary crustal thickening i e fl fc 2 where fl and fc are the lithospheric and crustal thickening factors

on the gravitational potential of the earth s lithosphere the mean potential energy of the lithosphere is useful for defining the tectonic reference state trs of the earth and can be used to constrain the ambient state of stress in the plates in the absence of external forces applied at the base or along plate boundaries a lithospheric column with the potential energy of the trs would remain undeformed thus the difference between the potential energy of a lithospheric column and the trs determines whether the column is in an extensional joeutral or compressional state of stress we evaluate and intraplate variations about this mean using a simple first order lithospheric density model this model assumed that the continental geotherm is linear and density variations below a depth of 125 km have negligible influence on and is consistent with observed geoid anomalies across continental margins is estimated to be 2 379 1014 n m 1 which is equivalent to the potential energy of both near sea level continental lithosphere 160 to 220 m for an assumed crustal density c in the range 2800 2700 kg m 3 and cooling oceanic lithosphere at a depth of 4 3 km with the exception of eurasia which has anomalously high mean potential energy 2 383 1014 n m 1 the mean potential energies of the continental plates are nearly identical to the global mean the mean potential of the oceanic plates was found to be a strong function of the mean age of the oceanic lithosphere both the global and plate mean potential energies are relatively insensitive to a wide range in c the potential of the mid ocean ridges 2 391 1014 n m 1 is greater than the global mean which is consistent with the divergent nature of the ridges elevated continental lithosphere with a height of about 70 m has an equivalent potential energy to suggesting that in the absence of external forces continental regions will be in a slightly extensional state of stress the importance of our potential energy formulation is substantiated by the strong correlation between the torque poles associated with the potential energy distributions and the observed plate velocity poles for the south american nazca indo australian and pacific plates

evidence for shallow isostatic compensation of the southern rocky mountains from rayleigh wave tomography in the past decade seismologists have found that the topography in colorado correlates with seismic velocities in the upper mantle not with crustal thickness and postulated that isostatic compensation of the southern rocky mountains takes place largely in the mantle to test the validity of this hypothesis we use rayleigh wave phase and amplitude data recorded in the rocky mountain front passcal experiment to obtain crustal thickness and shear wave structure in the crust and upper mantle the thickest crust in the model is beneath one of the two most elevated regions the san juan volcanic field the other most elevated region in central colorado the sawatch range is underlain by crust of anomalously low velocity the seismically defined mantle lithosphere is thicker beneath the great plains than beneath the colorado plateau and is largely absent beneath the southern rocky mountains but the correlation of topography with mantle velocities is weaker than the correlation with crustal anomalies we construct a model that matches the observed bouguer gravity anomaly primarily with variations in crustal thickness and density by assuming that density anomalies are proportional to the observed velocity anomalies the anomalous mantle may also contribute to maintaining regional isostasy in colorado but its contribution may be much less important than the crust

lithospheric thickness jumps at the s atlantic continental margins from satellite gravity data and modelled isostatic anomalies abstract isostatic equilibrium is a good approximation for passive continental margins in these regions geoid anomalies are proportional to the local dipole moment of density depth distributions which can be used to constrain the amount of oceanic to continental lithospheric thickening lithospheric jumps we consider a five or three layer 1d model for the oceanic and continental lithosphere respectively composed of water a sediment layer both for the oceanic case the crust the mantle lithosphere and the asthenosphere the mantle lithosphere is defined by a mantle density which is a function of temperature and composition due to melt depletion in addition a depth dependent sediment density associated with compaction and ocean floor variation is adopted we analyzed satellite derived geoid data and after filtering extracted typical averaged profiles across the western and eastern passive margins of the south atlantic they show geoid jumps of 8 1 m and 7 0 m for the argentinian and african sides respectively together with topography data and an averaged crustal density at the conjugate margins these jumps are interpreted as isostatic geoid anomalies and yield best fitting crustal and lithospheric thicknesses in a grid search approach five parameters are systematically varied namely the thicknesses of the sediment layer the oceanic and continental crusts and the oceanic and the continental mantle lithosphere the set of successful models reveals a clear asymmetry between the south africa and argentine lithospheres by 15 km preferred models predict a sediment layer at the argentine margin of 3 6 km and at the south africa margin of 1 2 5 km moreover we derived a linear relationship between oceanic lithosphere sediment thickness and lithospheric jumps at the south atlantic margins it suggests that the continental lithospheres on the western and eastern south atlantic are thicker by 45 70 and 60 80 km than the oceanic lithospheres respectively

the minimum depth of compensation of topographic masses summary based on the recently compiled crustal thickness data it is shown that the airy heiskanen model of compensation only partly compensates the surface topographic masses to fit the external gravitational potential induced by the surface topography the pratt hayford concept of compensation has also to be considered employing the dynamical flattening of the earth the minimum depth of compensation has been estimated to be of the order of 100 150 km this means that the topographic masses are compensated throughout the earth s lithosphere at least

southern california permanent gps geodetic array spatial filtering of daily positions for estimating coseismic and postseismic displacements induced by the 1992 landers earthquake the june 28 1992 m w 7 3 landers california earthquake was the first earthquake to be surveyed by a continuously operating global positioning system gps array the coordinate time series of seven sites are evaluated for station displacements during an interval of 100 days centered on the day of the earthquake we employ a new spatial filtering technique that removes common mode errors from the coordinate time series this approach provides precise estimates of site specific displacements compared to the cumbersome method of analyzing baselines between pairs of stations all sites indicate significant coseismic horizontal displacements of 5 65 mm with uncertainties of 1 2 mm horizontal displacements are in general agreement with elastic dislocation models in particular for sites closer to the epicenter vertical displacements range from 13 to 7 mm with uncertainties of 2 4 mm the observed vertical displacements in all cases show 5 10 mm more subsidence than expected from geodetic and seismic geologic models significant postseismic horizontal displacements totaling 6 2 mm 10 20 of the coseismic displacement are detected at the three sites closest to the epicenter these displacements are modeled as a short term exponential relaxation with a decay time of 22 10 days superimposed on a longer term linear interseismic trend scaling the observed coseismic and postseismic displacements at one of the sites with the distance to the epicenter provides a measure of site strain which agrees well with the direction and magnitude determined from more precise laser strain meter data the time series do not show any detectable preseismic displacements

mapping regional land displacements in the venice coastland by an integrated monitoring system abstract an original integrated monitoring method is designed to infer an accurate and reliable figure of regional land displacements in coastal areas where the presence of internal waters wetlands farmlands urban and industrial centers usually reduces the efficiency of single ground based and satellite based measuring techniques five different methods i e spirit leveling differential global positioning system dgps continuous gps cgps interferometric synthetic aperture radar insar and interferometric point target analysis ipta are integrated into a subsidence integrated monitoring system sims to overcome the limits characterizing each technique the sims has been used over the past decade to provide a new image of the land displacements in the venice region the result exhibits a resolution never obtained before the central lagoon including the city of venice shows a general stability while the northern and southern lagoon extremities and their related catchment sectors sink with serious rates averaging 3 to 5 mm year the sinking rates increase up to 10 15 mm year in the coastland south of the lagoon relatively small uplifts less than 1 mm year are observed at the alpine foothills and in a wide area comprised between the euganean hills and the lagoon the observed land displacements have been associated to the geological features of the study region i e tectonics seismicity differential consolidation of the middle upper pleistocene and holocene deposits and to anthropogenic activities such as land reclamation and groundwater withdrawal

lithosphere structure and upper mantle characteristics below the bay of bengal the oceanic lithosphere in the bay of bengal bob formed 80 120 ma following the breakup of eastern gondwanaland since its formation it has been affected by the emplacement of two long n s trending linear aseismic ridges 85oe and ninetyeast and by the loading of ca 20 km of sediments of the bengal fan here we present the results of a combined spatial and spectral domain analysis of residual geoid bathymetry and gravity data constrained by seismic reflection and refraction data self consistent geoid and gravity modeling defined by temperature dependent mantle densities along a n s transect in the bob region revealed that the depth to the lithosphere asthenosphere boundary lab deepens steeply from 77 km in the south to 127 km in north with the greater thickness being anomalously thick compared to the lithosphere of similar age beneath the pacific ocean the geoid topography ratio gtr analysis of the 85 e and ninetyeast ridges indicate that they are compensated at shallow depths effective elastic thickness te estimates obtained through admittance coherence analysis as well as the flexural modeling along these ridges led to the conclusions i 85 e ridge was emplaced in off ridge environment te 10 15 km ii the higher te values of 25 km over the afanasy nikitin seamount ans reflect the secondary emplacement of the seamount peaks in off ridge environment iii that the emplacement of the ninetyeast ridge north of 2 n occurred in an off ridge environment as indicated by higher te values 25 30 km furthermore the admittance analysis of geoid and bathymetry revealed that the admittance signatures at wavelengths 800 km are compensated by processes related to upper mantle convection

understanding the subsidence process of a quaternary plain by combining geological and hydrogeological modelling with satellite insar data the acque albule plain case study abstract this paper focuses on a multidisciplinary study carried out in an urban area affected by subsidence and related structural damages the study area is located about 20 km east of rome italy and is characterised by relevant groundwater exploitation for various purposes as well as by the presence of compressible soils immediately below the ground level extensive processing at different scales of sar satellite images ers and envisat provided by esa in the frame of a cat 1 project by means of a dinsar technique was performed the time histories of ground displacements have been analysed in combination with a detailed geological setting of the study area and with the hydrogeological changes occurred in the last decades as the response to the anthropic stress based on a large piezometric dataset this comprehensive dataset allowed us to describe the space and time distributions of the subsidence process the spatial pattern and deformation rate change is attributed to the following causes i the changes in the groundwater levels due to the intensification of mine exploitation requiring dewatering operations and ii the distribution and thickness of recent compressible deposits specifically it is derived that the groundwater level variations drive the timing of subsidence triggering over the area whereas the local geological conditions control the magnitude of the deformation process

southern california permanent gps geodetic array error analysis of daily position estimates and site velocities we analyze time series of daily positions estimated from data collected by 10 continuously monitoring global positioning system gps sites in southern california during the 19 month period between the june 28 1992 mw 7 3 landers and january 17 1994 mw 6 7 northridge earthquakes each time series exhibits a linear tectonic signal and significant colored noise spectral power at frequencies in the range 5 yr 1 to 0 5 d 1 is dominated by white noise or possibly fractal white noise and is several orders of magnitude higher than what would be expected from random walk noise in this short period range attributed by others to geodetic monument motions estimating a single slope for the time series power spectra suggests fractal white noise processes with spectral indices of about 0 4 site velocity uncertainties assuming this fractal white noise model are 2 4 times larger than uncertainties obtained assuming a purely white noise model a combination white noise plus flicker noise spectral index of 1 model also fits the data and suggests that the velocity uncertainties should be 3 6 times larger than for the white noise model we cannot adequately distinguish between these two noise models nor can we rule out the possibility of a random walk signal at the lowest frequencies these questions await the analysis of longer time series in any case reducing the magnitude of low frequency colored noise is critical and appears to be best accomplished by building sites with deeply anchored and braced monuments otherwise rate uncertainties estimated from continuous gps measurements may not be improved significantly compared to those estimated from infrequent campaign mode measurements

3d joint inversion modeling of the lithospheric density structure based on gravity geoid and topography data application to the alborz mountains iran and south caspian basin region abstract we present a 3d algorithm to obtain the density structure of the lithosphere from joint inversion of free air gravity geoid and topography data based on a bayesian approach with gaussian probability density functions the algorithm delivers the crustal and lithospheric thicknesses and the average crustal density stabilization of the inversion process may be obtained through parameter damping and smoothing as well as use of a priori information like crustal thicknesses from seismic profiles the algorithm is applied to synthetic models in order to demonstrate its usefulness a real data application is presented for the area of northern iran with the alborz mountains as main target and the south caspian basin the resulting model shows an important crustal root up to 55 km under the alborz mountains and a thin crust ca 30 km under the southernmost south caspian basin thickening northward to the apsheron balkan sill to 45 km central and nw iran is underlain by a thin lithosphere ca 90 100 km the lithosphere thickens under the south caspian basin until the apsheron balkan sill where it reaches more than 240 km under the stable turan platform we find a lithospheric thickness of 160 180 km

variety and origin of magmas on shatsky rise northwest pacific ocean 1 shatsky rise consists of thick 30 km maximum basaltic crust with various geochemical compositions geochemistry data indicate that four magma types exist on the plateau namely normal low ti high nb and u1349 types the normal type is the most abundant in volume and appears on all three large edifices of the plateau tamu ori and shirshov massifs composition of the normal type is similar to normal mid ocean ridge basalt n morb composition but with slight relative enrichment of the more incompatible elements the low ti type is distinguished from the normal type basalt by slightly lower ti content at a given mgo composition of the high nb type is characterized by distinctively high contents of incompatible trace elements u1349 type basalts are composed of more primitive and depleted compositions compared with the others the normal type basalts constitute 94 of the lava units of the oldest tamu massif and non normal types i e the other three types basalts comprise 57 on the younger ori massif implying that geochemical compositions may have become heterogeneous with time petrological examination demonstrates that compositions of the normal low ti and high nb type basalts evolved through fractional crystallization of olivine plagioclase and augite in shallow magma chambers 200 mpa model calculations of immobile trace elements estimate that the normal type basalt can be formed by 15 melting of a depleted mantle source in the presence of residual garnet this degree of melting is similar to n morb but the larger effect of residual garnet during petrogenesis implies that a greater depth of melting

geoid height versus topography for a plume model of the hawaiian swell abstract we use a three dimensional variable viscosity convection model of a stationary plume beneath a drifting lithosphere to study the factors that control the geoid to topography ratio gtr of the hawaiian swell the rate of melting in the plume is predicted using a batch melting parameterization and the melt is assumed to migrate to the surface where it builds a volcanic edifice equivalent to the hawaiian island chain viscous stresses elastic deformation of the lithosphere and optionally the volcanic material deposited on the ocean floor are included in the calculation of surface topography and the corresponding geoid the derivation of the gtr from the model imitates methods that have previously been used to estimate the observed gtr for the hawaiian swell the first method we use here is that of marks and sandwell j geophys res 96 1991 8045 8055 which applies bandpass filters to retain only wavelengths from 400 to 4000 km as most characteristic of the swell topography and geoid and the gtr is estimated from the slope of the regression line of geoid versus topography another group of methods analyzes the data along profiles drawn across the hotspot swell and eliminates the unwanted signals e g the volcanic islands and the flexural moat around them by cutting out parts of the sections the gtr is then calculated from curves which best fit the topography and geoid profiles on the swell flanks only in our plume model when the effects of the volcanic surface loading are included marks and sandwell s method yields 4 4 m km for the gtr while profile fitting on the swell flanks gives 7 8 5 m km ignoring the volcanic load leads to 7 8 m km in all processing methods the observed gtr for the hawaiian swell has been reported to lie between 4 and 5 m km analysis of the data processing methods shows that the applied bandpass filters cannot completely remove the signal due to the volcanic edifice and lithospheric flexure and this causes apparent gtrs around 4 m km the pure swell model containing no volcanic load on the surface demonstrates that the hawaiian swell may have a proper gtr near 7 m km

static and dynamic support of western united states topography article history accepted 7 october 2013 available online 31 october 2013 editor p shearer isostatic and dynamic models of earth s surface topography can provide important insights into the driving processes of tectonic deformation we analyze these two estimates for the tectonically active western united states using refined structural models derived from earthscope usarray for the crust use of recent moho depth measurements and crustal density anomalies inferred from passive source seismology improve isostatic models however seismically determined lithospheric thickness variations from lithosphere asthenosphere boundary lab maps and lithospheric and mantle density anomalies derived from heat flow or uppermost mantle tomography do not improve isostatic models substantially perhaps this is a consequence of compositional heterogeneity a mismatch between thermal and seismological lab and structural complexity caused by smaller scale dynamics the remaining non isostatic dynamic component of topography is large topography anomalies include negative residuals likely due to active subduction of the juan de fuca plate and perhaps remnants of formerly active convergence further south along the margin our finding of broad scale positive residual topography in the basin and range substantiates previous results implying the presence of anomalous buoyancy there which we cannot fully explain the colorado plateau does not appear dynamically anomalous at present except at its edges many of the residual topography features are consistent with predictions from mantle flow computations this suggests a convective origin and important interactions between vigorous upper mantle convection and intraplate deformation

reply to comment by p teatini et al on recent subsidence of the venice lagoon from continuous gps and interferometric synthetic aperture radar 1 unlike most published scientific comments the comment submitted by p teatini l tosi and t strozzi on bock et al 2012 does not dispute the scientific merits of our study but rather reinforces its approach and main results regarding venice subsidence their main points appear to be that our study 1 did not cite the two last papers that they published tosi et al 2010 teatini et al 2012a 2 received considerable attention worldwide for a rather small level of subsidence 3 used a methodology that is not original 4 misrepresented some of their earlier work and 5 published uncertainties that were too optimistic

terrasar x reveals the impact of the mobile barrier works on venice coastland stability land subsidence and eustacy concurred to make the relative sea level in venice italy 23 cm higher over the last century in order to protect the city and its lagoon environment from increased flooding a series of mobile barriers are under construction at the three inlets of lido malamocco and chioggia connecting the adriatic sea to the inner water body since 2003 work has been proceeding with the reinforcement and extension of the existing jetties and the construction of breakwaters harbors and a small island within the lido inlet we detected significant local settlements of a few centimeters between march 2008 and january 2009 at the three inlets induced by the construction works through an interferometric analysis of 30 satellite radar images acquired by the new german terrasar x mission on a more regional scale we observe that the city of venice and the other major urban settlements on the lagoon littorals are not impacted by subsidence during this period the very high spatial resolution of 3 m and the short repeat time interval of 11 days of terrasar x enable the investigation of displacements with an unprecedented observed level of details opening new perspectives to geodynamic s research and civil engineering sectors for the monitoring of large infrastructures with potential vulnerability to terrain motion