a model of sea level rise caused by ocean thermal expansion abstract warming of the atmosphere as a result of an increased concentration of greenhouse gases is expected to lead to a significant rise is global sea level we present estimates of the component of this sea level rise caused by thermal expansion of the ocean these estimates are based on the idea that the upper layers of the main gyres of the ocean are ventilated by the subduction of water at higher latitudes and its subsequent equatorward and downward flow into the main thermocline along surfaces of constant density in this mechanism heat enters the ocean by an advection process rather than by vertical diffusion as in previous estimates of the component of sea level rise that is caused by thermal expansion after the heat initially enters the subtropical gyres by subduction it is then redistributed to preserve gradients of the depth integrated pressure field by an adjustment involving low vertical mode baroclinic waves estimates of historical sea level rise based on this simple ventilation sch

simulation of co seismic secondary fracture displacements for different earthquake rupture scenarios at the proposed nuclear waste repository site in forsmark simulation of co seismic secondary fracture displacements for different earthquake rupture scenarios at the proposed nuclear waste repository site in forsmark

sea level rise a review of recent past and near future trends global mean sea level is a potentially sensitive indicator of climate change global warming will contribute to worldwide sea level rise slr from thermal expansion of ocean water melting of mountain glaciers and polar ice sheets a number of studies mostly using tide gauge data from the permanent service for mean sea level bidston observatory england have obtained rates of global slr within the last 100 years that range between 0 3 and 3 mm yr 1 with most values concentrated between 1 and 2 mm yr 1 however the reliability of these results has been questioned because of problems with data quality and physical processes that introduce a high level of spatial and temporal variability sources of uncertainty in the sea level data include variations in winds ocean currents river runoff vertical earth movements and geographically uneven distribution of long term records crustal motions introduce a major source of error to a large extent these can be filtered by employing palaeo sea level proxies and geophysical modelling to remove glacio isostatic changes ultimately satellite geodesy will help resolve the inherent ambiguity between the land and ocean level changes recorded by tide gauges future sea level is expected to rise by 1 m with a best guess value of 48 cm by the year 2100 such rates represent an acceleration of four to seven times over present rates local land subsidence could substantially increase the apparent slr for example louisiana is currently experiencing slr trends nearly 10 times the global mean rate these recently reduced slr estimates are based on climate models that predict a zero to negative contribution to slr from antarctica most global climate models gcms indicate an ice accumulation over antarctica because in a warmer world precipitation will exceed ablation snow melt however the impacts of attritional processes such as thinning of the ice shelves have been downplayed according to some experts furthermore not all climate models are in agreement opposite conclusions may be drawn from the results of other gcms in addition the west antarctic ice sheet is potentially subject to dynamic and volcanic instabilities that are difficult to predict because of the great uncertainty in slr projections careful monitoring of future sea level trends by upgraded tide gauge networks and satellite geodesy will become essential finally because of the high spatial variability in crustal subsidence rates wave climates and tidal regimes it will be the set of local conditions especially the relative sea level rise rather than a single global mean sea level trend that will determine each locality s vulnerability to future slr

low frequency and broad band source models for the 2009 l aquila italy earthquake summary the 2009 l aquila italy earthquake mw 6 3 produced an unprecedented number of seismological records for a normal faulting event and hence represents an important case study of damaging moderate magnitude earthquakes occurring in densely inhabited areas we have investigated the source process of the 2009 l aquila earthquake in both the low and broad band frequency ranges by analysing the teleseismic and strong motion data a low frequency 0 5 hz source model has been determined by waveform inversion of teleseismic and near field strong motion data yielding slip distributions with a major asperity located about 8 km southeast of the hypocentre the broad band 0 2 10 hz source characteristics were estimated using the empirical green s function method providing the strong motion generation area of about 42 km2 located southeast of the hypocentre below the village of onna this coincides with the location of the asperity from the inversion analysis indicating that the low frequency and broad band ground motions produced during the earthquake were generated at similar locations on the fault plane the position of the strong motion generation area also correlates well with the distribution of observed macroseismic mcs intensities reported by ingv the maximum macroseismic intensities of ix x were reported southeast of the epicentre with an intensity of x measured in onna the source properties of the 2009 l aquila mainshock reveal the estimated size of the strong motion generation area to be in agreement with predictions made using empirical source scaling relation for inland crustal earthquakes implying a stress drop of approximately 10 mpa this further indicates that the 2009 l aquila earthquake involved a stress drop similar to that of previously recorded earthquakes in the central and southern apennines

sea level variations induced by heating and cooling an evaluation of the boussinesq approximation in ocean models in this paper a sigma coordinate ocean model is modified to remove the commonly used boussinesq approximation so that the effect of thermal expansion is exactly included in the basic equations in order to cope with the seasonal heating cycle and the detection of climate change through variation in sea level height tests are performed to evaluate the differences between boussinesq and non boussinesq calculations under different heating and cooling conditions and different model domains for an idealized case of a flat bottom shallow ocean basin without wind forcing simulations of a warm eddy show that the non boussinesq dynamics have only a minor effect on the baroclinic current field however vertically averaged velocities though small compared with the baroclinic velocities are cyclonic for the boussinesq calculation and anticyclonic for the non boussinesq calculation the results indicate that global or closed basin boussinesq models should be able to simulate most of the observed steric sea level changes on seasonal or climate timescales when corrected by a spatially uniform time dependent factor calculated from the volume averaged density change the seasonal variation of the globally averaged sea level calculated from climatological data is small about 1 cm variations in steric sea level in regional models both boussinesq and non boussinesq may differ from those of global models owing to the unknown transport across their boundaries associated with the local heating and cooling a spatially uniform time dependent correction similar to that associated with thermal expansion is proposed to account for transport across open boundaries of regional models variations of sea level obtained from a boussinesq model of the atlantic ocean approximate the seasonal signal due to the heating cooling cycle of each hemisphere as observed by satellite altimeter data

role of the atmospheric and oceanic circulation in the tropical pacific sst changes a coupled climate model is used to explore the response of the tropical sea surface temperature sst to positive sst anomalies in the global extratropics the main model results here are consistent with previous numerical studies in response to prescribed sst anomalies in the extratropics the tropical ssts rise rapidly and reach a quasi equilibrium state within several years and the tropical subsurface temperatures show a slow response the annual mean hadley cell as well as the surface trades are weakened the weakened trades reduce the poleward ekman transports in the tropical ocean and furthermore lead to anomalous positive convergences of heat transport which is the main mechanism for maintaining the tropical pacific sst warming the process of an extratropical influence on the tropics is related to both the atmospheric and oceanic circulations the intertropical convergence zone itcz moves southward and eastward in the pacific corresponding to a reduction of the hadley circulation and walker circulation at the same time convective precipitation anomalies are formed on the boundary of the climatological itcz while the climatological mean convections centered in the southeast asia region are suppressed the largely delayed response of the tropical subsurface temperature cannot be explained only by the strength change of the subtropical cells stcs but can be traced back to the slow changing of subsurface temperature in the extratropics in the extratropical oceans warming and freshening reduce the surface water density and the outcropping lines of certain isopycnal layers are moved poleward this poleward movement of outcropping lines can weaken the positive temperature anomalies or even lead to negative anomalies on given isopycnal layers displayed on time dependent isopycnal layers positive subsurface temperature anomalies are present only in the region after subduction and are subsequently replaced by negative temperature anomalies in the deep tropics regions the noticeable features of the density compensation of temperature and salinity indicate that diapycnal processes play an important role in the equatorward transport of the temperature and salinity anomalies from the midlatitude

gravity isostasy and andean crustal shortening between latitudes 30 and 35 s we started the work by analyzing an e w crustal section at 33 s latitude which extends from the western chilean trench crosses the andean belt and goes inland into argentina a two layer gravity seismic model was prepared here it provided a maximum moho depth of 62 km beneath the andean axis this model is consistent with a one layer standard crustal model with normal thickness t 33 km and densities of 2 9 g cm3 and 3 3 g cm3 for the crust and the upper mantle respectively then we analyzed the andean isostatic behaviour on four andean gravimetric sections at latitudes of 30 32 33 and 35 s based on one layer simple models these results show antiroots near the chilean trench and crustal thickenings beneath the andean belt which locate the moho discontinuity at depths of 70 km at 30 s 65 km at 32 and 33 s and 57 km at 35 s from the crustal gravimetric models the following provisional charts for the sector were prepared and compared 1 topography 2 bouguer gravity 3 isostatic corrections 4 moho contours these charts are consistent with each other and they point out that the compensation of the andean belt trends approximately to isostasy in the airy concept other results also confirm this 1 the remarkable decrease of the isostatic anomalies in each of the analyzed sections as regards the bouguer anomalies and 2 the relationships between the exceeding areas and the corresponding crustal root areas which are consistent with the airy numerical relations as to the perfect isostatic equilibrium thus the bouguer anomalies are mainly controlled by the m discontinuity finally shortenings in the andean sector were fixed based on the crustal thicknesses found from gravity inversion these are 150 km at 30 s decreasing southwards and reaching only 90 km at 35 s these shortenings explain the cenozoic andean uplift without requiring other mechanisms such as magmatic intrusions

the passive and active nature of ocean heat uptake in idealized climate change experiments the influence of ocean circulation changes on heat uptake is explored using a simply configured primitive equation ocean model resembling a very idealized atlantic ocean we focus on the relative importance of the redistribution of the existing heat reservoir due to changes in the circulation and the contribution from anomalous surface heat flux in experiments in which the surface boundary conditions are changed we perform and analyze numerical experiments over a wide range of parameters including experiments that simulate global warming and others that explore the robustness of our results to more general changes in surface boundary conditions we find that over a wide range of values of diapycnal diffusivity and southern ocean winds and with a variety of changes in surface boundary conditions the spatial patterns of ocean temperature anomaly are nearly always determined as much or more by the existing heat reservoir redistribution than by the nearly passive uptake of temperature due to changes in the surface boundary conditions calculating heat uptake by neglecting the existing reservoir redistribution which is similar to treating temperature as a passive tracer leads to significant quantitative errors notably at high latitudes and secondarily in parts of the main thermocline experiments with larger circulation changes tend to produce a relatively larger magnitude of existing reservoir redistribution and a faster growing effective heat capacity of the system the effective heat capacity is found to be sensitive to both vertical diffusivity and southern ocean wind

deterministic ground motion scenarios for engineering applications the case of thessaloniki greece abstract in this article we present a deterministic study to estimate seismic ground motions expected in urban areas located near active faults the purpose was to generate bedrock synthetic time series to be used as seismic input into site effects evaluation analysis and loss estimates for the urban area and infrastructures of thessaloniki northern greece two simulation techniques a full wave method to generate low frequency seismograms 1 hz were used to compute time series associated with four different reference earthquakes having magnitudes from 5 9 to 6 5 and located within 30 km of thessaloniki the propagation medium and different source parameters were tested through the modeling of the 1978 thessaloniki earthquake m 6 5 moreover two different nucleation points were considered for each fault in order to introduce additional variability in the ground motion estimates between the two cases the quasi unilateral rupture propagation toward the city produces both higher median peak ground acceleration pga and peak ground velocity pgv values and higher variability than bilateral ones conversely the low frequency ground motion that is peak ground displacement pgd is slightly influenced by the position of the nucleation point and its variability is related to the final slip distribution on the faults of the reference earthquakes and to the location of the sites with respect to the nodal planes of the radiation pattern to validate our deterministic shaking scenarios we verified that the synthetic peak ground motions pga and pgv and spectral ordinates are within one standard deviation of several ground motion prediction equations valid for the region at specific sites we combined the low and high frequency synthetics to obtain broadband time series that cover the entire frequency band of engineering interest 0 25 hz the use of synthetic seismograms instead of empirical equations in the hazard estimates provides a complete evaluation of the expected ground motions both in frequency and time domains including predictions at short distances from the fault 0 10 km and at periods larger than 2 3 sec

nonlinear dynamic failure process of tunnel fault system in response to strong seismic event strong earthquakes and faults have significant effect on the stability capability of underground tunnel structures this study used a 3 dimensional discrete element model and the real records of ground motion in the wenchuan earthquake to investigate the dynamic response of tunnel fault system the typical tunnel fault system was composed of one planned railway tunnel and one seismically active fault the discrete numerical model was prudentially calibrated by means of the comparison between the field survey and numerical results of ground motion it was then used to examine the detailed quantitative information on the dynamic response characteristics of tunnel fault system including stress distribution strain vibration velocity and tunnel failure process the intensive tunnel fault interaction during seismic loading induces the dramatic stress redistribution and stress concentration in the intersection of tunnel and fault the tunnel fault system behavior is characterized by the complicated nonlinear dynamic failure process in response to a real strong seismic event it can be qualitatively divided into 5 main stages in terms of its stress strain and rupturing behaviors 1 strain localization 2 rupture initiation 3 rupture acceleration 4 spontaneous rupture growth and 5 stabilization this study provides the insight into the further stability estimation of underground tunnel structures under the combined effect of strong earthquakes and faults

decovalex iii bmt3 benchpar wp4 the thermo hydro mechanical responses to a glacial cycle and their potential implications for deep geological disposal of nuclear fuel waste in a fractured crystalline rock mass a number of studies related to past and on going deep repository performance assessments have identified glaciation deglaciation as major future events in the next few hundred thousand years capable of causing significant impact on the long term performance of the repository system benchmark test 3 bmt3 of the international decovalex iii project has been designed to provide an illustrative example that explores the mechanical and hydraulic response of a fractured crystalline rock mass to a period of glaciation the primary purpose of this numerical study is to investigate whether transient events associated with a glacial cycle could significantly influence the performance of a deep geological repository in a crystalline shield setting a conceptual site scale tens of kilometres hydro mechanical hm model was assembled based primarily on site specific litho structural hydrogeological and geomechanical data from the whiteshell research area in the canadian shield with simplification and generalization continental glaciological modelling of the laurentide ice sheet through the last glacial cycle lasting approximately 100 000 years suggests that this site was glaciated at about 60 ka and between about 22 5 and 11 ka before present with maximum ice sheet thickness reaching 2500 m and maximum basal water pressure head reaching 2000m the ice sheet drainage model was scaled down to generate spatially and temporally variable hydraulic and mechanical glaciated surface boundary conditions for site scale subsurface hm modelling and permafrost modelling under extreme periglacial conditions permafrost was able to develop down to the assumed 500 m repository horizon two and three dimensional coupled hm finite element simulations indicate during ice sheet advance there is rapid rise in hydraulic head high transient hydraulic gradients and high groundwater velocities 2 3 orders of magnitude higher than under nonglacial conditions surface water recharges deeper than under nonglacial conditions upon ice sheet retreat the gradients reverse fracture zone network geometry interconnectivity and hydraulic properties significantly influence flow domain response residual elevated heads are preserved for 10 000s in the low diffusivity rock and no hydraulic jacking or shear failure occurs at depth it was found that transient coupled modelling is necessary to capture the essence of glacial effects on performance assessment model dimensionality also significantly affects simulated results

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

active faults and paleoseismicity in fennoscandia especially sweden primary structures and secondary effects abstract fennoscandia today a region of low to moderately low seismicity was at the time of deglaciation with rates of uplift on the order of tens of centimetres per year a region of very high seismicity and active tectonics this is evident both from primary fault structures and from secondary sedimentary and hard rock effects in the region around the epicentral areas the map of active faults in fennoscandia includes numerous structures previously not recognised despite this the recording of active faults and paleoseismic events is still in its initial phase much more data will surely accumulate in the near future

steric sea level variations during 1957 1994 importance of salinity 1 spatially averaged 50 s 65 n temperature and salinity changes in the 0 3000 m layer during the 1957 1994 period resulted in a sea level rise at a mean rate of about 0 55 mm per year about 10 of this rate is due to a decrease of the volume mean salinity the magnitude of total steric sea level tssl changes and the ratio of thermosteric and halosteric anomalies to tssl anomaly are nonuniform geographically salinity effects are critically important to the tssl changes in some regions of the ocean for example the thermosteric anomaly is nearly compensated by the halosteric anomaly in the subpolar north atlantic this fact will cause erroneous heat content estimates based on altimetric observations from space if a climatological salinity is assumed based on the present historical archive of salinity data a decrease in global mean salinity has occurred this increase of fresh water would cause sea level rise at a rate of 1 3 0 5 mm yr if the added water comes from sources other than floating sea ice

major earthquake at the pleistocene holocene transition in lake vattern southern sweden lake vattern sweden is within a graben that formed through rifting along the boundary between two precambrian terrains geophysical mapping and geological coring show that substantial tectonic movements along the lake vattern graben occurred at the very onset of the holocene this is evident from deformation structures in the soft sediment accumulated on the lake floor our interpretation of these structures suggests as much as 13 m of vertical tectonic displacements along sections of a 80 km long fault system if these large displacements are from one tectonic event lake vattern must have had an earthquake with seismic moment magnitudes to 7 5 in addition our geophysical mapping shows large landslides along sections of the steep lake shores pollen analysis of sediment infillings of some of the most prominent sediment deformation structures places this major seismic event at the younger dryas preboreal transition ca 11 5 ka we suggest that this event is mainly related to the rapid release of ice sheet load following the deglaciation this paleoseismic event in lake vattern ranks among the larger known intraplate tectonic events in scandinavia and attests to the significance of glacio isostatic unloading

how fast is rupture during an earthquake new insights from the 1999 turkey earthquakes we report that during the two devastating 1999 earthquakes in turkey rupture propagated over a large part of the nearly 200km long fault zone at supershear speed approaching 5km s we present observations and modeling which confirm the original inference of supershear rupture during the izmit earthquake and we show that supershear rupture also occurred during the duzce earthquake we show that the rupture velocity measured about 2 times the shear wave velocity is the value predicted by theoretical studies in fracture dynamics we look for clues to explain these observations

global and full depth ocean temperature trends during the early twenty first century from argo and repeat hydrography the early 21st century s warming trend of the full depth global ocean is calculated by combining the analysis of argo top 2000m and repeat hydrography into a blended full depth observing system the surface to bottom temperature change over the last decade of sustained observation is equivalent to a heat uptake of 0 72 0 09 w m 2 applied over the surface of the earth 90 of it being found above 2000m depth we decompose the temperature trend point wise into changes in isopycnal depth heave and temperature changes along an isopycnal spiciness to describe the mechanisms controlling the variability the heave component dominates the global heat content increase with the largest trends found in the southern hemisphere s extratropics 0 2000m highlighting a volumetric increase of subtropical mode waters significant heave related warming is also found in the deep north atlantic and southern ocean 2000m 4000m reflecting a potential decrease in deep water mass renewal rates the spiciness component shows its strongest contribution at intermediate levels 700m 2000m with striking localised warming signals in regions of intense vertical mixing north atlantic and southern oceans finally the agreement between the independent argo and repeat hydrography temperature changes at 2000m provides an overall good confidence in the blended heat content evaluation on global and ocean scales but also highlights basin scale discrepancies between the two independent estimates those mismatches are largest in those basins with the largest heave signature southern ocean and reflect both the temporal and spatial sparseness of the hydrography sampling

a note on the representation of steric sea level in models that conserve volume rather than mass this note discusses the representation of steric sea level in ocean circulation models changes in steric sea level are caused when changes in the density of the water column imply an expansion or contraction of the column models usually make the boussinesq approximation and conserve volume rather than mass and so do not properly represent expansion or contraction this means that although expansion contraction is included in the equation of state it is not accounted for by the model dynamics in this note we examine the equation governing the time evolution of the sea level displacement it is shown that requiring conservation of mass rather than volume introduces a new term to this equation a simple example is used to show the relationship of the new term to the surface buoyancy flux the equilibrium response to the new term has two parts one part consists of the goldsbrough and stommel gyres for which in the ocean interior vortex stretching due to the local expansion contraction of the water column is balanced by changes in planetary vorticity the other part corresponds to the inverse barometer the effect is to adjust sea level by a globally uniform but timevarying factor determined by the net expansion contraction of the global ocean since this correction is globally uniform it has no dynamical significance both the goldsbrough stommel gyres and the inverse barometer solution are missing from models as currently formulated this does not represent a serious error however if comparison is made with observations of sea level model calculated sea level should be adjusted by a globally uniform time varying factor determined by the net expansion contraction of the global ocean this would be important for assessing the likely rise in sea level in response to global warming

subduction and transport in the indian and pacific oceans in a 2 co2 climate abstract subduction water mass transformation and transport rates in the indo pacific ocean are diagnosed in a recent version of the canadian centre for climate modelling and analysis coupled model it is found that the subduction across the base of the winter mixed layer is dominated by the lateral transfer particularly within the relatively dense water classes corresponding to the densest mode and intermediate waters however within lighter densities including those characterizing the lighter varieties of mode waters the vertical transfer has a strong positive input to the net subduction the upper ocean volume transports across 30 n and 32 s are largest within the density classes that correspond to mode waters in the north pacific the buoyancy flux converts the near surface waters mostly to denser water classes whereas in the southern ocean the surface waters are transformed both to lighter and denser water classes depending on the density in response to a doubling of co2 the subduction tr

interannual and decadal temperature variability in the southwest pacific ocean between 1955 and 1988 abstract the spatial and temporal variability of the southwest pacific ocean is examined with the aim of describing the physical processes operating on interannual and decadal timescales the study takes advantage of a new temperature atlas of the upper 450 m of the southwest pacific ocean obtained from 40 000 bathythermograph profiles between 1955 and 1988 rotated principal components analysis was used to filter the important spatial and temporal scales of temperature variability in the data three different analyses are presented they include two intraocean analyses and a joint analysis of subsurface ocean temperature sea level pressure and surface winds the dominant el nino mode describes the large vertical excursions of the thermocline in the western tropical pacific in response to atmospheric forcing at a 3 6 month lag more importantly most of the retained modes outside of the equatorial region have time variations that correlate with el nino one ocean mode with a spatial pattern represen

conditions for flow in the continental crust 1 earthquake focal depth distributions and effective elastic thickness variations on the continents suggest that in old cold regions such as shields the lower continental crust can be stronger than the upper mantle and imply that the upper mantle can flow even when the lower crust does not however in other places substantial flow in the lower crust does occur particularly near extensional metamorphic core complexes we suggest that the lower crust only flows when its viscosity is significantly reduced either by heating from igneous intrusions or by the addition of water in both cases the important characteristics of the flow are a consequence of the limited time over which the viscosity reduction occurs the timescale is controlled either by conductive cooling of intrusions or by the separation of melt from its matrix which removes the water

contribution of glacier melt to sea level rise since ad 1865 a regionally differentiated calculation the contribution of glacier melt including the greenland ice sheet to sea level change since ad 1865 is estimated on the basis of modelled sensitivity of glacier mass balance to climate change and historical temperature data calculations are done in a regionally differentiated manner to overcome the inhomogeneity of the global distribution of glaciers a distinction is made between changes in summer temperature and in temperature over the rest of the year our best estimate of the ice melt in the period 1865 1990 in terms of sea level change equivalent is 5 7 cm 2 7 cm for glaciers and 3 0 cm for the greenland ice sheet additional calculations show that simpler methods like using annual or even global mean temperature anomaly give estimates that differ by up to 55 consequently a regionally differentiating approach is advised for making projections of glacier melt with gcm output

sea level change due to oscillations in seafloor spreading rate abstract we present a theory for divergent seafloor spreading which predicts that transient surges in spreading rate would cause geodynamic sea level rise rates approximately equal to the transient surge velocity at the ridge crest multiplied by the aspect ratio of the spreading plate i e a surge velocity of 3 cm yr acting on a plate thickness 100 km and width 3000 km would produce a geodynamic sea level rise rate of 1 mm yr this rate is geologically significant and it is suggested that the calving of ice by flotation due to geodynamic sea level rise may feedback positively on a thermal sea level rise and provide a mechanism whereby plate tectonics can actually drive climatic change the theory depends on the assumption that plate motion is governed by thermally driven ridge push forces balanced by frictional drag at the base of the plate

melting of ice shelves and the mass balance of antarctica we calculate the present ice budget for antarctica from measurements of accumulation minus iceberg calving run off and in situ melting beneath the floating ice shelves the resulting negative mass balance of 469 gt year 1 differs substantially from other recent estimates but some components are subject to high temporal variability and budget uncertainties of 20 50 annual accumulation from an earlier review is adjusted to include the antarctic peninsula for a total of 2144 gt year 1 an iceberg production rate of 2016 gt year 1 is obtained from the volume of large icebergs calculated from satellite images since 1978 and from the results of an international iceberg census project ice shelf melting of 544 gt year 1 is derived from physical and geochemical observations of meltwater outflow glaciological field studies and modeling of the sub ice ocean circulation the highest melt rates occur near ice fronts and deep within sub ice cavities run off from the ice sheet surface and from beneath the grounded ice is taken to be 53 gt year 1 less than half of the negative mass balance need come from the grounded ice to account for the unattributed 0 45 mm year 1 in the ipcc best estimate of the recent global sea level rise

supershear rupture on multiple faults for the mw 8 6 off northern sumatra indonesia earthquake of april 11 2012 1 we perform a back projection method to image the rupture propagation and short period energy release of the 2012 off northern sumatra earthquake mw8 6 using hi net data recorded in japan the results show a complex pattern of four conjugate faults over about 180 sec there is a striking correspondence between the lengths and orientations of our rupture pattern with the distribution of aftershocks each of the first three stages of the rupture corresponds to a clear lineation in the aftershocks with lengths of 200 to 400 km rupture speeds for several of the fault segments were very high about 5 km s and exceed the local s wave velocity this is the first example of an oceanic earthquake with supershear rupture speed

upper mantle structure in the south central chilean subduction zone 30 to 36 s 1 regional p and s wave travel time data were used to obtain three dimensional seismic tomography models for vp vs and vp vs above the subducting slab in central chile and argentina in this region there is an abrupt change from a normal subduction geometry south of 33 s to a flat subduction geometry to the north we find low vp low vs and high vp vs ratios in the southern half of our study area directly beneath the modern active volcanic arc which we interpret as localized pockets of melt in the northern half of our study area above where the subducting nazca plate flattens at 100 km depth we find low vp high vs and low vp vs ratios these unusual results point to a lack of melt or hydrated mineralogies such as serpentine both of which are characterized by high vp vs values the only mantle rocks that have low vp vs and high vs are mg rich compositions such as dehydrated serpentinite or orthopyroxenite we suggest that significant portions of the mantle overlying the flat slab consist of orthopyroxenite formed by a transient fluxing of silica rich fluids such fluids may have come from sediments that were subducted during the initiation of flat subduction at this latitude at 10 ma this would imply that the hydration of mantle material above a flat slab can be a transient phenomenon which leaves little residual free water behind but significantly alters the mantle chemistry

generation mechanism of spiciness anomalies an ogcm analysis in the north atlantic subtropical gyre oceanic teleconnections between the low and midlatitudes are a key mechanism to understanding the climate variability spiciness anomalies density compensated anomalies have been shown to transport temperature and salinity signals when propagating along current streamlines in the subtropical gyres of the atlantic and pacific oceans the generation mechanism of spiciness anomalies in the north atlantic subtropical gyre is investigated using an analytical model based on the late winter subduction of salinity and temperatureanomalies along isopycnal surfaces the keystone ofthis approachisthe change ofthe coordinates frame from isobaric to isopycnic surfaces suited for subduction problems the isopycnal nature of spiciness anomalies and the use of a linear density equation allows for the analytical model to depend only upon surface temperature and salinity anomalies the mean thermocline currents and the surface density ratio this model clarifies and above all quantifies the mechanism by which surface temperature and salinity anomalies are modulated by density ratios to produce fully different isopycnal temperature and salinity anomalies

earthquake triggering by static and dynamic stress changes 1 in this study we aim to understand the effect of static and dynamic stress changes in promoting earthquake failures on secondary faults toward this goal we solve the equation of motion of a spring slider dynamic system including inertia and using rate and state dependent constitutive laws we separately investigate the dynamic response of this fault analog system to a sudden stress change represented either as a stress step or as a stress pulse which are used to model permanent static and transient dynamic stress perturbations the induced earthquake failure does not occur immediately at the application of the coseismic stress change but it is delayed in time we define this time interval as the triggering delay for a given stress perturbation we analyze the dependence of triggering delays on different system conditions and constitutive parameters our results clearly show that the effects of static and dynamic stress changes are quite different while a static stress change is able to advance as well as to delay an induced instability depending on its sign a dynamic stress pulse is only able to promote a nearly instantaneous failure provided its amplitude is positive and large enough with respect to the direct effect of friction in other words dynamic stress changes can only cause nearly instantaneous failures without any relevant triggering delay these results should be considered in interpreting the seismicity rate changes caused by large earthquakes at least as long as seismic events are interpreted as sliding instabilities obeying rate and state dependent friction laws

control of mode and intermediate water mass properties in drake passage by the amundsen sea low the evolutionof the physical properties of subantarctic mode water samw and antarctic intermediate water aaiw in the drake passage region is examined on time scales down to intraseasonal within the 1969 2009 period both samw and aaiw experience substantial interannual to interdecadal variability significantly linked to the action of the amundsen sea low asl in their formation areas observations suggest that the interdecadal freshening tendency evident in samw over the past three decades has recently abated while aaiw has warmed significantly since the early 2000s the two water masses have also experienced a substantial lightening since the start of the record examination of the mechanisms underpinning water mass property variability shows that samw characteristics are controlled predominantly by a combination of air sea turbulent heat fluxes cross frontal ekman transport of antarctic surface waters and the evaporation precipitation balance in the subantarctic zone of the southeast pacific and drake passage while aaiw properties reflect air sea turbulent heat fluxes and sea ice formation in the bellingshausen sea the recent interdecadal evolution of the asl is consistent with both the dominance of the processes described here and the response of samw and aaiw on that time scale

distribution timing and causes of andean deformation across south america the andean orogeny in south america has lasted over 100 ma it comprises the peruvian incaic and quechuan phases the nazca and south american plates have been converging at varying rates since the palaeocene the active tectonics of south america are relatively clear from seismological and global positioning system gps data horizontal shortening is responsible for a thick crust and high topography in the andes as well as in se brazil and patagonia we have integrated available data and have compiled four fault maps at the scale of south america for the mid cretaceous late cretaceous palaeogene and neogene periods andean compression has been widespread since the aptian the continental margins have registered more deformation than the interior for the peruvian phase not enough information is available to establish a tectonic context during the incaic phase strike slip faulting was common during the quechuan phase crustal thickening has been the dominant mode of deformation to investigate the mechanics of deformation we have carried out 10 properly scaled experiments on physical models of the lithosphere containing various plates the dominant response to plate motion was subduction of oceanic lithosphere beneath continental south america however the model continent also deformed internally especially at the margins and initial weaknesses

variation of the mean sea level from topex poseidon data variations of the 10 day averaged sea level extracted from topex poseidon t p altimeter data are examined from october 1992 to february 1995 data are corrected from instrumental drifts and recent precise orbit and ocean tide corrections are used when data from the less accurate first eight cycles are excluded and atmospheric pressure effects are not corrected the 10 day mean sea level varies by 5 0 mm rms its variations can be described by a 4 1 1 mm yr drift a small annual signal of 2 7 mm amplitude and a residual signal of 3 5 mm rms amplitude and gaussian statistics close to formal error estimates the mean sea level rise is difficult to explain by drifts of geophysical corrections though the case for the wet tropospheric correction and that for the orbit are uncertain pressure effects should be corrected relative to the global pressure averaged over the ocean the latter shows a seasonal signal of 1 cm amplitude and apparent fluctuations of 30 to 70 day periods these fluctuations could result from errors in the atmospheric pressure fields but they seem to be mostly related to large regional pressure evolutions evidence is also found for a sampling effect by the t p orbit of pressure signals at shorter than 10 day periods pressure effects on sea level are then assumed to be an inverse barometer relative to 10 day global atmospheric pressure over the ocean which allows analysis of the geographical repartition of the mean sea level evolution due to other effects the mean sea level rise is comparable in the northern 4 2 2 5 mm yr and southern 3 7 1 9 mm yr hemispheres it seems mostly related to interannual variations of the tropical ocean 41 of the global signal and of the northern hemisphere subtropical gyres 30 of the global signal residual noise on these regional values seems inversely proportional to the square root of the number of data points in each area the hemispheric seasonal pressure variation relative to the globally averaged pressure over the ocean is less than 3 mm amplitude in our calculation it is implicitely assumed that it induces a small interhemispheric water mass exchange the amplitudes of the seasonal hemispheric sea level variations are 27 and 18 mm in the northern and southern hemispheres respectively these amplitudes are very close to being inversely proportional to the ocean surface in each hemisphere the maxima of sea level in these hemispheres are reached in the last weeks of september and march respectively at subpolar latitudes semiannual components are observed in each hemisphere which are consistent with those of sea surface temperature

seismic moment ratio of aftershocks with respect to main shocks the empirical bath s law indicates that the earthquake process is self similar and provides an opportunity to estimate the magnitude of the largest aftershock subsequent to a main shock however the analysis of this relation is limited to a small magnitude range and also depends on the aftershock selection rules as an alternative we analyze in this paper the cumulative seismic moment of aftershocks relative to the main shock moment because i it is a physical quantity that does not only take the largest aftershock into account ii background activity can be considered and as a result estimations are less affected by selection rules and iii the effects of the catalog cut off magnitude can be corrected what leads to larger magnitude range for the analysis we analyze the global preliminary determination of epicenters u s geological society catalog combined with centroid moment tensor focal mechanisms and find that the seismic moment release of aftershocks is on average approximately 5 of the main shock seismic moment we show that the results can be well fitted by simulations of the epidemic type aftershock sequence model in particular we test whether simulations constrained by predictions of the static stress triggering model proposing a break of self similarity due to the finite seismogenic width are in agreement with observations our analysis shows that the observed dependency on the main shock magnitude as well as systematic variations with the main shock fault plane solution can be both explained by the constraints based on the static stress triggering

simulating earthquake rupture and off fault fracture response application to the safety assessment of the swedish nuclear waste repository abstract to assess the long term safety of a deep repository of spent nuclear fuel upper bound estimates of seismically induced secondary fracture shear displacements are needed for this purpose we analyze a model including an earthquake fault which is surrounded by a number of smaller discontinuities representing fractures on which secondary displacements may be induced initial stresses are applied and a rupture is initiated at a predefined hypocenter and propagated at a specified rupture speed during rupture we monitor shear displacements taking place on the nearby fracture planes in response to static as well as dynamic effects as a numerical tool we use the 3dimensional distinct element code 3dec because it has the capability to handle numerous discontinuities with different orientations and at different locations simultaneously in tests performed to benchmark the capability of our method to generate and propagate seismic waves 3dec generates results in good agreement with results from both stokes solution and the compsyn code package in a preliminary application of our method to the nuclear waste repository site at forsmark southern sweden we assume end glacial stress conditions and rupture on a shallow gently dipping highly prestressed fault with low residual strength the rupture generates nearly complete stress drop and an m w 5 6 event on the 12 km 2 rupture area of the 1584 secondary fractures 150 m radius with a wide range of orientations and locations relative to the fault a majority move less than 5 mm the maximum shear displacement is some tens of millimeters at 200 m fault fracture distance

global sea level change determination and interpretation the notion of sea level rise brings to the popular mind the specter of deep inundation of coastal regions one pictures skyscrapers emerging from the waters like so many sleeping flamingos standing in the shallows of a lake of course if all of the world s ice sheets suddenly melted or collapsed this vision would apply to new york city and its coastal counterparts but there is a general consensus that such a calamity is not an immediate threat houghton et al 1990 the actual situation for the recent historical past and near future appears to be more benign but with nonetheless extremely significant even devastating impacts due to erosion and flooding of coastal areas

the electric moho since mohorovicic1 discovered a dramatic increase in compressional seismic velocity at a depth of 54 km beneath the kulpa valley in croatia the moho has become arguably the most important seismological horizon in earth owing to its role in defining the crust mantle boundary it is now known to be a ubiquitous feature of the earth being found beneath both the continents and the oceans and is commonly assumed to separate lower crustal mafic rocks from upper mantle ultramafic rocks electromagnetic experiments conducted to date however have failed to detect a corresponding change in electrical conductivity at the base of the crust although one might be expected on the basis of laboratory measurements2 here we report electromagnetic data from the slave craton northern canada which show a step change in conductivity at moho depths such resolution is possible because the slave craton is highly anomalous exhibiting a total crustal conductance of less than 1 siemens more than an order of magnitude smaller than other archaean cratons we also found that the conductivity of the uppermost continental mantle directly beneath the moho is two orders of magnitude more conducting than laboratory studies on olivine would suggest inferring that there must be a connected conducting phase

warming of the global ocean spatial structure and water mass trends abstractthis study investigates the multidecadal warming and interannual to decadal heat content changes in the upper ocean 0 700 m focusing on vertical and horizontal patterns of variability these results support a nearly monotonic warming over much of the world ocean with a shift toward southern hemisphere warming during the well observed past decade this is based on objectively analyzed gridded observational datasets and on a modeled state estimate besides the surface warming a warming climate also has a subsurface effect manifesting as a strong deepening of the midthermocline isopycnals which can be diagnosed directly from hydrographic data this deepening appears to be a result of heat entering via subduction and spreading laterally from the high latitude ventilation regions of subtropical mode waters the basin average multidecadal warming mainly expands the subtropical mode water volume with weak changes in the temperature salinity s relationship known as spice variability howeve

evidence for and implications of self healing pulses of slip in earthquake rupture dislocation time histories of models derived from waveforms of seven earthquakes are discussed in each model dislocation rise times the duration of slip for a given point on the fault are found to be short compared to the overall duration of the earthquake 10 however in many crack like numerical models of dynamic rupture the slip duration at a given point is comparable to the overall duration of the rupture i e slip at a given point continues until information is received that the rupture has stopped propagating alternative explanations for the discrepancy between the short slip durations used to model waveforms and the long slip durations inferred from dynamic crack models are 1 the dislocation models are unable to resolve the relatively slow parts of earthquake slip and have seriously underestimated the dislocations for these earthquakes 2 earthquakes are composed of a sequence of small dimension short duration events that are separated by locked regions barriers 3 rupture occurs in a narrow self healing pulse of slip that travels along the fault surface evidence is discussed that suggests that slip durations are indeed short and that the self healing slip pulse model is the most appropriate explanation a qualitative model is presented that produces self healing slip pulses the key feature of the model is the assumption that friction on the fault surface is inversely related to the local slip velocity the model has the following features high static strength of materials kilobar range low static stress drops in the range of tens of bars and relatively low frictional stress during slip less than several hundreds of bars it is suggested that the reason that the average dislocation scales with fault length is because large amplitude slip pulses are difficult to stop and hence tend to propagate large distances this model may explain why seismicity and ambient stress are low along fault segments that have experienced large earthquakes it also qualitatively explains why the recurrence time for large earthquakes may be irregular

moment tensor inversion of ground motion from mining induced earthquakes trail mountain utah a seismic network was operated in the vicinity of the trail mountain mine central utah from the summer of 2000 to the spring of 2001 to investigate the seismic hazard to a local dam from mining induced events that we expect to be triggered by future coal mining in this area in support of efforts to develop ground motion prediction relations for this situation we inverted ground motion recordings for six mining induced events to determine seismic moment tensors and then to estimate moment magnitudes m for comparison with the network coda magnitudes m c six components of the tensor were determined for an assumed point source following the inversion method of mcgarr 1992a which uses key measurements of amplitude from obvious features of the displacement waveforms when the resulting moment tensors were decomposed into implosive and deviatoric components we found that four of the six events showed a substantial volume reduction presumably due to coseismic closure of the adjacent mine openings for these four events the volume reduction ranges from 27 to 55 of the shear component fault area times average slip radiated seismic energy computed from attenuation corrected body wave spectra ranged from 2 4 105 to 2 4 106 j for events with m from 1 3 to 1 8 yielding apparent stresses from 0 02 to 0 06 mpa the energy released for each event approximated as the product of volume reduction and overburden stress when compared with the corresponding seismic energies revealed seismic efficiencies ranging from 0 5 to 7 the low apparent stresses are consistent with the shallow focal depths of 0 2 to 0 6 km and rupture in a low stress low strength regime compared with typical earthquake source regions at midcrustal depths

warming and circulation change in the eastern south pacific ocean deep ocean temperature salinity and dissolved oxygen observations in the eastern south pacific ocean collected during the late austral fall in 1995 are compared with observations made there 28 years earlier during the same season and similar el nino southern oscillation phase warming observed above 800 m at 43 s reflects the production of warmer subantarctic mode water in recent decades warming observed above 1600 m at 28 s is due to downward isotherm displacement and southward movement of water masses by 100 200 km as revealed by joint analysis of temperature and oxygen data such changes would be expected for a weaker subtropical gyre in the south pacific an observed oxygen decrease between about 1800 m and 2900 m at 28 s may indicate enhanced southward boundary current flow at mid depths off chile

fennoscandian earthquakes whole crustal rupturing related to postglacial rebound local and regional earthquake locations provide seismic evidence that large shield earthquakes have occurred in northern fennoscandia these paleoearthquakes with fault lengths of up to 160 kilometers and average displacements of up to 15 meters were triggered by nonisostatic compressive stresses caused by the removal of the ice at the end of the last deglaciation the fennoscandian faults were probably formed by single events that ruptured through most of the crust the largest event moment magnitude mw 8 2 was larger than other known stable continent earthquakes outside failed rifts or extended crust

coupled pattern analysis of sea surface temperature and topex poseidon sea surface height abstract though thermal effects dominate steric changes in sea level the long period contribution of thermal expansion to sea level is uncertain nerem et al found that a global map of sea surface temperature sst trends and a corresponding map of topex poseidon derived sea surface height ssh trends were strongly correlated this result is explored with a coupled pattern analysis cpa between five years of global sst and ssh which allows for matching of modes of common temporal variability the dominant mode found is an annual cycle that accounts for nearly all 95 3 of the covariance between the fields and has a strong sst ssh spatial correlation 0 68 the spatial correlation is strong in both the atlantic 0 80 and the pacific 0 70 good temporal and spatial agreement between the ssh and sst fields for the primary seasonal mode suggests that a robust regression between fields may have some physical significance with respect to thermal expansion and that the regression coefficient might be

southwest pacific ocean water mass changes between 1968 69 and 1990 91 abstract water mass changes are estimated in the southwest pacific ocean by comparing a meridional hydrographic section along 170 w between 60 s and the equator occupied in 1968 69 during the southern cross cruise and again in 1990 during a noaa climate and global change cruise another comparison is made using a hydrographic section along 35 s between the date line and 169 w occupied in 1969 during usns eltanin cruise 40 and again in 1991 during a mapkiwi cruise the most robust change consists of cooling and freshening on isopycnals with peak differences exceeding 1 0 c 0 25 pss at the base of the subtropical thermocline the cooling and freshening starts above the stratification minimum of the subantarctic mode water and persists to below the salinity minimum of the antarctic intermediate water amplitudes are largest at 48 s near where these water masses subduct and decay toward 20 s near the axis of the subtropical gyre this change is likely the result of surface warming and or freshening

surficial geology indicates early holocene faulting and seismicity central sweden in sweden knowledge of the location and timing of glacially induced faulting and seismicity is critical to effective engineering of a long term nuclear disposal facility to improve understanding and modeling of the complex ice induced and tectonic stresses associated with glacially induced faulting field studies detailing the location and timing of movement of such structures are required although the fault has not been confirmed in the bedrock multi proxy surficial geologic evidence indicates that the recently discovered scarp in bollnas is such a structure machine excavated trenches across the scarp reveal landsliding down the scarp and in one location faulted and vertically offset fine grained glacial sediments the presence of water escape structures in trenches excavated on a topographic high strongly suggests a co seismic origin derived from earthquake magnitudes 5 5 numerous landslides in till exist in the region as well four slopes with landslides were examined in detail and the factors of safety for these slopes indicate stable conditions and suggest a seismic trigger basal radiocarbon dates from peat bogs located stratigraphically above the landslides provide minimum limiting ages for the co seismic landslides the oldest date indicates sliding prior to 10 180 calendar years before the present the proposed bollnas fault is 400 km south of the so called lapland fault province to date it is the southernmost confirmed glacially induced fault in sweden the results of this study are consistent with existing modeling results that indicate fault instability in this region of central sweden following deglaciation

bayesian imaging of the 2000 western tottori japan earthquake through fitting of strong motion and gps data summary we image the rupture process of the 2000 western tottori earthquake m w 6 6 through fitting of strong motion and gps data we consider an observational network consisting of 18 strong motion and 16 gps stations located within three fault lengths from the epicentre we assume a planar fault and compute green s functions for a 1 d velocity model the earthquake rupture is described as a shear dislocation parameterized in terms of peak slip velocity rake angle rupture time and rise time defined on a regular grid of nodes on the fault surface and derived at inner points through bilinear interpolation our inversion procedure is based on a bayesian approach the solution of the inverse problem is stated in terms of a posterior probability density function pdf representing the conjunction of prior information with information contained in the data and in the physical law relating model parameters with data inferences on model parameters are thus expressed in terms of posterior marginal pdfs due to the non linearity of the problem we use a markov chain monte carlo mcmc method based on the metropolis algorithm to compute posterior marginals except for a few cases posterior marginals do not show a gaussian like distribution this prevents us from providing a mean model and from characterizing uncertainties in terms of standard deviations only resolution on each single parameter is analysed by looking at the difference between prior and posterior marginal pdfs posterior marginals indicate that the best resolved feature is a major slip patch peak value of 311 140 cm located between the hypocentre and the top edge of the fault centered at a depth of 4 5 km this shallow slip patch is triggered about 3 s after the earthquake nucleated and required about 4 s to reach its final slip value the presence of this shallow slip patch is common to all previous studies in contrast to some previous studies we do not identify any significant slip 1 m at the bottom of the fault we also compare inferences from both strong motion and gps data with inferences derived from strong motion data only in both cases the shallow slip patch is identified at other locations the main effect of the gps data is in reducing the probability associated with high values of slip gps data reduce the presence of spurious fault slip and therefore strongly influence the resulting final seismic moment

approach to estimating the maximum depth for glacially induced hydraulic jacking in fractured crystalline rock at forsmark sweden hydraulic jacking is a significant dilation of a fracture that occurs when the pore pressure within it exceeds the sum of the fracture s normal stress and tensile strength this phenomenon may occur during a glacial period because of changes in hydraulic and mechanical boundary conditions since hydraulic jacking may alter flow patterns and the transport capacity of the rock mass its possible effects on the long term performance of a nuclear waste repository should be considered we develop an approach to assess glacially induced hydraulic jacking in fractured crystalline rock and establish bounding estimates of the maximum jacking depth for the swedish nuclear fuel and waste management company s skb repository site at forsmark the pore pressure is estimated using mechanically uncoupled two dimensional poroelastic continuum models with hydraulic and mechanical conditions based on skb s reconstruction of the weichselian glaciation at this site 120 0kab p for warm based conditions the water pressure at the ice bed interface is set at 98 of the mechanical load whereas for glacial conditions with extensive proglacial permafrost the corresponding water pressure is set at a lower annual average value we demonstrate that the pore pressure within the uppermost kilometer of rock is mainly governed by the water pressure at the ice bed interface and that the mechanical impact of the ice load on the pore pressure is sufficiently small to be ignored given the current and estimated future stress conditions at forsmark hydraulic jacking is mainly of concern for subhorizontal fractures i e it is sufficient to consider situations when the pore pressure exceeds the vertical stress we conclude that hydraulic jacking at forsmark will be confined to the uppermost 200m of the rock mass

the baltic shield earthquakes abstract the baltic shield area is a low seismicity area with few seismic events exceeding m l 4 since 1979 dense regional seismic networks have been in operation and have allowed accurate location including focal depths and fault plane solutions of more than 200 earthquakes in the range m l 0 6 4 5 the location of the southern sweden seismicity shows that a long part of the protogine zone the border between the younger western and older eastern crustal rocks marks a change in seismic activity the focal depths of the earthquakes indicate three seismically different crustal layers upper crust 0 13 km in northern sweden 0 18 km in southern sweden middle crust down to 35 km and the seismically quiet lower crust the gutenberg b value is smaller for the middle crust than for the upper crust the fault plane solutions show that strike slip is dominant along the tornquist line the southwestern border of the baltic shield area normal faulting occurs in northern sweden reverse faulting is more common than normal faulting the stresses released by the earthquakes show a remarkable consistency considering the small sizes of the earthquakes the data are consistent with a n60w direction of the regional principal compression supporting the view that the baltic shield seismicity is related to plate tectonic processes rather than to uplift the spatial distribution of the baltic shield seismicity is consistent with a model in which the earthquakes are considered as sudden breakdowns of asperities of normally stably sliding faults aseismic sliding is estimated to be more than 20 000 times more extensive than seismic sliding the rate at which southern sweden presently deforms horizontally is estimated to be 1 mm yr

elastic stress relaxation a mechanism for opposite sense of secondary faulting with respect to a major fault abstract the motion along a major fault perturbs the local stress field and produces numerous secondary fractures among these the secondary fractures that have the opposite sense of motion with respect to the main fault are particularly intriguing for example the right lateral reverse motion of the ms 7 1 loma prieta earthquake of 18 october 1989 produced a series of left lateral normal fractures located in a narrow zone about 1 km in widt subparallel to the trace of the san andreas fault through a rigorous inversion of geodetic data associated with the earthquake that allowed the slip to vary on the rupture surface we studied the origin of the left lateral normal fractures by comparing the location orientation and slip sense of the observed fractures with the perturbed elastic stress field calculated from the estimated slip distribution of the earthquake the perturbed state of stress at the earth s surface is complex and the greatest principal stress changes from horizontal to vertical the area of left lateral tensile state of stress coincides with that of the observed left lateral normal fractures the magnitudes of the induced fault normal tensile stresses of 60 120 bars and left lateral fault parallel shear stresses of 0 4 bars in the area are large enough to produce the ground failures thus the observed left lateral normal fractures adjacent to the san andreas fault are interpreted to be related to coseismic elastic stress relaxation the same mechanism can also be used to explain the normal faulting in the upthrown blocks of the thrust faults which produced the 1980 el asnam algeria and the 1968 tokachi oki japan earthquakes

crustal deformation of the andean foreland at 31 30 s argentina constrained by magnetotelluric survey abstract twenty five new long period magnetotelluric sites near 31 5 s were collected in a west east profile this profile and the previous one aligned with and adjacent to the eastern end have been merged to form a single profile of more than 700 km long extending from the precordillera to the chaco pampean plain the geotectonic scenario is characterized by a modern flat subduction zone of the nazca plate located at a depth of around 120 km and clearly defined by the distribution of earthquake hypocenters recorded by local and regional networks a bulge shape at 68 5 w with an anomalous dip to the west is observed within this segment the smooth slab deformation might result from the restriction on eastward motion due to the presence of an electrically resistive zone the magnetotelluric model shows that this thick zone of increased resistivity is found from shallow crustal levels to upper mantle depths the bulge geometry allows hot fluids and volatiles to rise from the deeper asthenospheric wedge and reach the lower crust reducing its viscosity and letting it flow the zones of low resistivity in the lower crust show spatial correlation with the areas of foreland deformation from precordillera to the sierras pampeanas and may also suggest a ductile regime shear zones reactivated by cenozoic faulting must necessarily have their roots in the levels of the ductile lower crust associated to conductive channels the zone where the lower crust is closer to the surface coincides with the areas of greatest structural relief and erosion the interface between the folded ductile lower crust and the brittle upper crust might act as the main level of decollement of the bordering structures between the precordillera sierra de pie de palo and the sierras pampeanas in addition the geometry of the interface might be conditioning the vergence of those structures

a conceptual model of ocean heat uptake under climate change abstracta conceptual model of ocean heat uptake is developed as a multilayer generalization of gnanadesikan the roles of southern ocean ekman and eddy transports north atlantic deep water nadw formation and diapycnal mixing in controlling ocean stratification and transient heat uptake are investigated under climate change scenarios including imposed surface warming increased southern ocean wind forcing with or without eddy compensation and weakened meridional overturning circulation moc induced by reduced nadw formation with realistic profiles of diapycnal mixing ocean heat uptake is dominated by southern ocean ekman transport and its long term adjustment controlled by the southern ocean eddy transport the time scale of adjustment setting the rate of ocean heat uptake increases with depth for scenarios with increased southern ocean wind forcing or weakened moc deepened stratification results in enhanced ocean heat uptake in each of these experiments the role of diapycnal mixing in settin

the 2010 qinghai china earthquake a moderate earthquake with supershear rupture abstract from analyses using near field and teleseismic data we estimate the rupture speed of the 2010 qinghai china earthquake m w 6 9 comparisons of model calculations of the initiations to the observed near field seismogram at station yus indicate a fast supershear rupture propagation of about 5 0 km s from the teleseismic analyses using an envelope deconvolution method with an empirical green s function event two high frequency pulses are identified at 6 5 km and 41 8 km southeast of the epicenter indicating two subevents the location and timing of the high frequency events also show a supershear rupture velocity of 4 7 to 5 8 km s the supershear speed of the rupture likely contributed to the severe damage caused in the forward direction of the rupture toward the town of yushu

dynamic shear rupture interactions with fault bends and off axis secondary faulting 1 on the basis of elastodynamic stress fields for singular crack and nonsingular slip weakening models of propagating rupture we develop preliminary answers to such questions as follows if a rupturing fault is intersected by another providing a possible bend in the failure path when will stressing be consistent with rupture along the bend what secondary fault locations and orientations in a damaged region bordering a major fault will be stressed to failure by the main rupture stresses that could initiate rupture on a bend are shown to increase dramatically with crack speed especially near the limiting speed rayleigh for mode ii shear for mode iii whether a bend path once begun can be continued to larger scales depends on principal stress directions and ratios in the prestress field conditions should often be met in mode ii for which bend paths encouraged by stressing very near the rupture tip are discouraged by the larger scale stressing a basis for intermittent rupture propagation and spontaneous arrest secondary failure in the damage zone likewise increases markedly as the limiting speed is approached such may make the fracture energy much greater than for slip on a single surface the extent of secondary faulting is strongly affected by prestress directions and the ratio of residual to peak strength for mode ii prestress controls whether activation occurs primarily on the extensional side which we show to be the typical case or on the compressional side too natural examples are consistent with the concepts developed

postglacial rebound and sea level contributions to changes in the geoid and the earth s rotation axis summary the rate of change of the spherical harmonic degree 2 component of the earth s gravitational potential coa 20 and polar wander velocity are two signals which are sensitive to late pleistocene deglaciation current changes in sea level and deep mantle viscosity diierent load and earth models have been used in earlier papers to predict the component of these geophysical signals caused by the collapse of the last great ice sheets and recent melting of polar ice caps in this paper we present a systematic analysis of the dependence of the predictions on parameters of the ice and earth model we show that the key parameters of the ice model which govern the predictions are the mass the location of the centre of mass and the midpoint of the deglaciation phase of secondary importance is the length of the deglaciation phase and the mean ice load prior to the last glacial maximum these conclusions enable us to make a more robust inference of mantle viscosity than has been made before allowing for the uncertainties in the model of late pleistocene and present deglaciation as previous authors have shown the lower mantle viscosity is the most important rheological parameter and therefore thecoa 20 observation complements sea level observations which are primarily sensitive to lithospheric thickness and the viscosity of the upper part of the mantle using realistic constraints on the sizes locations and timing of deglaciation of the late pleistocene ice sheets and current changes in polar ice caps the observation of coa 20 is used to infer lower mantle viscosity as a function of the present rate of sea level change if the present rate of non steric sea level change is 1 mm yr 1 and that change has been occurring for less than 1000 years then the lower mantle viscosity satis es log10 glm 21 82 0 15 which is consistent with inferences drawn from recent sea level analyses and con rms other analyses of thecoa 20 observation if the polar wander signal is produced entirely by postglacial rebound and current sea level change no more than 20 per cent of the present contribution to global sea level change comes from greenland the above conclusions also hold if the density discontinuities at 420 and 670 km are modelled as phase boundaries rather than material chemical boundaries

evidence for fault lubrication during the 1999 chi chi taiwan earthquake mw7 6 the ground motion data of the 1999 chi chi taiwan earthquake exhibit a striking difference in frequency content between the north and south portions of the rupture zone in the north the ground motion is dominated by large low frequency displacements with relatively small high frequency accelerations the pattern is opposite in the south with smaller displacements and larger accelerations we analyze the fault dynamics in light of a fault lubrication mechanism using near field seismograms and a detailed rupture model the fault zone contains viscous material e g gouge in which pressure increases following the reynolds lubrication equation when the displacement exceeds a threshold lubrication pressure becomes high enough to widen the gap thereby reducing the area of asperity contact with less asperity contact the fault slips more smoothly suppressing high frequency radiation

aftershock triggering by complete coulomb stress changes 1 we examine the correlation between seismicity rate change following the 1992 m7 3 landers california earthquake and characteristics of the complete coulomb failure stress cfs changes cfs t that this earthquake generated at close distances the time varying dynamic portion of the stress change depends on how the rupture develops temporally and spatially and arises from radiated seismic waves and from permanent coseismic fault displacement the permanent static portion cfs depends only on the final coseismic displacement cfs diminishes much more rapidly with distance than the transient dynamic stress changes a common interpretation of the strong correlation between cfs and aftershocks is that load changes can advance or delay failure stress changes may also promote failure by physically altering properties of the fault or its environs because it is transient cfs t can alter the failure rate only by the latter means we calculate both cfs and the maximum positive value of cfs t peak cfs t using a reflectivity program input parameters are constrained by modeling landers displacement seismograms we quantify the correlation between maps of seismicity rate changes and maps of modeled cfs and peak cfs t and find agreement for both models however rupture directivity which does not affect cfs creates larger peak cfs t values northwest of the main shock this asymmetry is also observed in seismicity rate changes but not in cfs this result implies that dynamic stress changes are as effective as static stress changes in triggering aftershocks and may trigger earthquakes long after the waves have passed

formation mechanism for isopycnal temperature salinity anomalies propagating from the eastern south pacific to the equatorial region abstract equatorward propagation of temperature salinity or spiciness anomalies on an isopycnal surface emanating from the eastern subtropical south pacific and their formation mechanism are investigated based on a hindcast simulation with an eddy resolving quasi global ocean general circulation model because of density compensating meridional distributions of temperature and salinity the meridional density gradient is weak at the sea surface in the eastern subtropical south pacific with these mean fields cool sea surface temperature anomalies sstas can make the outcrop line of an isopycnal surface migrate equatorward more than 5 and induce warm and salty anomalies on the isopycnal surface subducted warm salty anomalies propagate to the equatorial region over approximately 5 yr and may influence equatorial isopycnal temperature salinity anomalies although the associated effects are unclear if these anomalies could further induce warm eastern equatorial sstas that are positively correlated wit