computational simulation of seepage instability problems in fluid saturated porous rocks potential dynamic mechanisms for controlling mineralisation patterns abstract pore fluid flow associated with seepage instabilities can play an important role in controlling large mineralisation patterns within the upper crust of the earth to demonstrate this process two kinds of seepage instability problems in fluid saturated porous rocks are considered in this paper the first kind of seepage instability problem is caused by the temperature induced buoyancy of pore fluid so that it can be called the buoyancy driven seepage instability problem while the second kind of seepage instability problem is caused by chemical dissolution reactions that are commonly encountered in the upper crust of the earth so that it can be called the chemical dissolution driven seepage instability problem after the mathematical governing equations of and computational methods for these two kinds of seepage instability problems are introduced two numerical examples are used to elucidate how and why these two kinds of seepage instabilities can provide favorable places for the formation of large mineralisation patterns within the upper crust of the earth the related computational simulation results have demonstrated that 1 the convective pore fluid flow caused by the buoyancy driven seepage instability not only can dissolve minerals at the lower part of the upper crust but also can transport the dissolved minerals from the lower part to the upper part of the upper crust resulting in large mineralisation patterns near the surface of the earth s upper crust 2 the chemical dissolution driven seepage instability in fluid saturated porous rock can provide some favorable places such as finger like channels created by porosity enhancement in the porous rock for the formation of large mineralisation patterns within the upper crust of the earth

ground motion prediction equations in the san jacinto fault zone significant effects of rupture directivity and fault zone amplification we present a new set of ground motion prediction equations gmpes for horizontal peak ground acceleration peak ground velocity and 5 damped pseudo spectral acceleration psa developed for the san jacinto fault zone sjfz area besides using these equations to quantify seismic shaking in the area the results allow us to examine the physics and local properties controlling the observed ground motions the analyzed dataset includes 30 000 observations from 800 events spanning a magnitude range of 1 5 m 6 0 and recorded by up to 140 stations at epicentral distances ranging from essentially zero to 150 km the local gmpe is developed for the sjfz by applying classical regression techniques with predictive variables that include first distance and magnitude and then site characteristics rupture directivity and fault zone amplification the significance of these effects is determined by measuring the uncertainty reduction of the gmpe due to each factor the results show that in contrast to many regional studies traditional site characteristic has a relatively minor effect on peak amplitudes in our study area however rupture directivity is a significant factor controlling the amplitudes of ground motion even for small events the dense seismic network and newly developed directivity tool enable us to extract efficiently directivity effects with statistical significance using the ground motion dataset during the regression analysis process the obtained rupture directivities are consistent with the main focal mechanism orientations and surface trace orientations known from other studies and predictions for bimaterial ruptures in the trifurcation area of the sjfz fault zone amplification is a second important factor showing strong impact on the peak ground motion values with increasing role for the lower frequency range 10 hz examined in the 5 damped psa values we also observe signatures of large amplitude variances which indicate additional source related control on the distribution of amplitudes besides rupture directivity for aftershocks close in time and location to the m l 5 1 earthquake of march 2013 using the full set of records we present the most complete set of gmpes for the sjfz area including a higher amplitude prediction for regions in the direction of rupture

the observed north atlantic meridional overturning circulation its meridional coherence and ocean bottom pressure abstractanalyses of meridional transport time series from the rapid climate change meridional overturning circulation rapid moc array at 26 n and from argo float and altimetry data at 41 n reveal that at semiannual and longer time scales the contribution from the western boundary dominates the variability of the north atlantic meridional overturning circulation moc defined as the transport in the upper 1000 m of the ocean because the variability of the western boundary contribution is associated with a geostrophic overturning it is reflected in independent estimates of transports from gradient of ocean bottom pressure obp relative to and below 1000 m on the continental slope of the western boundary at three nominal latitudes 26 39 and 42 5 n time series of western meridional transports relative to and below 1000 m derived from the obp gradient or equivalently derived from the transport shear profile exhibit approximately the same phase relationship between 26 and 39 42 5 n as the wes

the relationship between u s east coast sea level and the atlantic meridional overturning circulation a review scientific and societal interest in the relationship between the atlantic meridional overturning circulation amoc and u s east coast sea level has intensified over the past decade largely due to 1 projected and potentially ongoing enhancement of sea level rise associated with amoc weakening and 2 the potential for observations of u s east coast sea level to inform reconstructions of north atlantic circulation and climate these implications have inspired a wealth of model and observation based analyses here we review this research finding consistent support in numerical models for an antiphase relationship between amoc strength and dynamic sea level however simulations exhibit substantial along coast and intermodel differences in the amplitude of amoc associated dynamic sea level variability observational analyses focusing on shorter generally less than decadal timescales show robust relationships between some components of the north atlantic large scale circulation and coastal sea level variability but the causal relationships between different observational metrics amoc and sea level are often unclear we highlight the importance of existing and future research seeking to understand relationships between amoc and its component currents the role of ageostrophic processes near the coast and the interplay of local and remote forcing such research will help reconcile the results of different numerical simulations with each other and with observations inform the physical origins of covariability and reveal the sensitivity of scaling relationships to forcing timescale and model representation this information will in turn provide a more complete characterization of uncertainty in relevant relationships leading to more robust reconstructions and projections

earthquake clusters in southern california i identification and stability 1 we use recent results on statistical analysis of seismicity to present a robust method for comprehensive detection and analysis of earthquake clusters the method is based on nearest neighbor distances of events in space time energy domain the method is applied to a 1981 2011 relocated seismicity catalog of southern california having 111 981 events with magnitudes m 2 and corresponding synthetic catalogs produced by the epidemic type aftershock sequence etas model analysis of the etas model demonstrates that the cluster detection results are accurate and stable with respect to 1 three numerical parameters of the method 2 variations of the minimal reported magnitude 3 catalog incompleteness and 4 location errors application of the method to the observed catalog separates the 111 981 examined earthquakes into 41 393 statistically significant clusters comprised of foreshocks mainshocks and aftershocks the results reproduce the essential known statistical properties of earthquake clusters which provide overall support for the proposed technique in addition systematic analysis with our method allows us to detect several new features of seismicity that include 1 existence of a significant population of single event clusters 2 existence of foreshock activity in natural seismicity that exceeds expectation based on the etas model and 3 dependence of all cluster properties except area on the magnitude difference of events from mainshocks but not on their absolute values the classification of detected clusters into several major types generally corresponding to singles burst like and swarm like sequences and correlations between different cluster types and geographic locations is addressed in a companion paper

observational constraints on the fracture energy of subduction zone earthquakes we relate seismologically observable parameters such as radiated energy seismic moment rupture area and rupture speed to the dynamics of faulting to achieve this objective we computed the radiated energy for 23 subduction zone earthquakes recorded between 1992 and 2001 most of these earthquakes have a magnitude m w 7 5 but we also included some smaller m w 6 7 well studied subduction zone earthquakes and six crustal earthquakes we compiled static stress drop estimates for these 29 earthquakes from literature and used a slip weakening model to determine the radiation efficiency of these earthquakes we also determined the rupture speed of these earthquakes from literature from fracture mechanics fracture energy and hence radiation efficiency can be related to the rupture speed the radiation efficiencies estimated from the partitioning of energy as given by the slip weakening model are consistent with the rupture speed estimated for these earthquakes most earthquakes have radiation efficiencies between 0 25 and 1 and are hence efficient in generating seismic waves but tsunami earthquakes and two deep earthquakes the 1994 bolivia and the 1999 russia china border earthquakes have very small radiation efficiencies 0 25 and hence dissipate a large amount of energy during faulting we suggest that differences in the radiation efficiencies of different types of earthquakes could be due to fundamental differences in their rupture mechanics in deep events the energy is probably dissipated in thermal processes in the fault zone while it is possible that the morphology of the trench causes large energy dissipation during the rupture process of tsunami earthquakes

decadal shift of nao linked interannual sea level variability along the u s northeast coast abstractrecent studies have linked interannual sea level variability and extreme events along the u s northeast coast nec to the north atlantic oscillation nao a natural internal climate mode

modeling the effect of stratification on cemented layer formation in sulfide bearing mine tailings abstract reactive transport simulations have been applied to investigate possible effects of stratification on the potential of sulfide bearing mine tailings to form protective cemented layers the simulations are based on characteristic strata found at a german tailings site including sulfide enriched heavy mineral layers mica enriched silt layers and homogeneously mixed layers the simulated secondary phases jarosite gypsum amorphous ferric arsenate amorphous fe hydroxide alunite amorphous silica and kaolinite are similar to those observed in the field using scanning electron microscope analyses of cemented layers it has been observed that the pore area becomes disconnected if the porosity is decreased to values below 15 which would indicate a strong decrease in permeability stratification was found to play a crucial role in cemented layer formation cemented layers are absent or insignificant in systems with a homogeneous distribution of fe bearing sulfides they are extensively developed in systems with a an arsenopyrite rich layer or b a mica enriched layer situated immediately below an fe sulfide enriched layer the modeling results have clearly demonstrated that the key processes operating in scenario a are very different from the key processes in scenario b in scenario a the oxidation of arsenopyrite is followed by the precipitation of amorphous ferric arsenate which can be solely responsible for significant pore reduction in scenario b the presence of a large amount of reactive aluminosilicates e g biotite and ca bearing plagioclase immediately below the fe sulfide rich layer appears to be crucial key processes are extensive formation of acid rock drainage ard followed by enhanced ph driven weathering of aluminosilicates resulting in the accumulation of secondary phases directly below the fe sulfide rich layer in both scenarios a cemented layer is formed that effectively retards the further downward movement of the oxidation front the presented details on the role of stratification in the formation of cemented layers could be considered in the construction of mining heaps as a possible measure to stimulate natural attenuation

rupture directivity of small earthquakes at parkfield 1 theoretical modeling of strike slip ruptures along a bimaterial interface suggests that earthquakes initiating on the interface will have a preferred rupture direction we test this model with 450 small earthquakes 2 3 exhibiting southeast rupture characteristics some spatial and temporal variability in rupture directivity is also apparent we observe a higher proportion of northwest directivity ruptures following the 2004 m 6 parkfield earthquake which ruptured toward the northwest our results are generally consistent with the preferred southeast rupture directivity model but suggest that directivity is likely due to several contributing factors

observations inferences and mechanisms of the atlantic meridional overturning circulation a review this is a review about the atlantic meridional overturning circulation amoc its mean structure temporal variability controlling mechanisms and role in the coupled climate system the amoc plays a central role in climate through its heat and freshwater transports northward ocean heat transport achieved by the amoc is responsible for the relative warmth of the northern hemisphere compared to the southern hemisphere and is thought to play a role in setting the mean position of the intertropical convergence zone north of the equator the amoc is a key means by which heat anomalies are sequestered into the ocean s interior and thus modulates the trajectory of climate change fluctuations in the amoc have been linked to low frequency variability of atlantic sea surface temperatures with a host of implications for climate variability over surrounding landmasses on intra annual timescales variability in amoc is large and primarily reflects the response to local wind forcing meridional coherence of anomalies is limited to that of the wind field on interannual to decadal timescales amoc changes are primarily geostrophic and related to buoyancy anomalies on the western boundary a pacemaker region for decadal amoc changes is located in a western transition zone along the boundary between the subtropical and subpolar gyres decadal amoc anomalies are communicated meridionally from this region amoc observations as well as the expanded ocean observational network provided by the argo array and satellite altimetry are inspiring efforts to develop decadal predictability systems using coupled atmosphere ocean models initialized by ocean data

north atlantic sea level and circulation summary monthly sea levels from an extensive array of north atlantic tide gauges 26 50 n are examined the spatial scale of the sea level variations and the reasons for them are discussed one application of such a study is clearly in the design of a tide gauge network for monitoring eustatic changes of sea level the spatial scale of the sea level changes is large there is a coherent sealevel signal which can be traced along the eastern boundary of the north atlantic from newlyn 50 n to tenerife 28 n there are also two distinct groupings of tide gauges along the western boundary separated by cape hatteras the contribution of local air pressure and wind stress is quantified at each gauge through multiple regression techniques and the gains are then interpreted in terms of recent theoretical and numerical modelling studies for example the gains suggest that the wind forced boundary current along the nova scotian shelf is trapped to within about 16 km of the coast the influence of local meteorology cannot account for the large scale modes of variability the coherent signal along the eastern boundary is correlated with changes in the sverdrup transport of the north atlantic and hence the large scale wind field the two modes on the western boundary appear to be related to baroclinic boundary current variations the newlyn sea level record is finally corrected for some of the above effects to illustrate the utility of such a residual series in the identification of eustatic changes and vertical crustal movement

precipitation in pores a geochemical frontier the purpose of this article is to review some of the recent research in which geochemists have examined precipitation of solid phases in porous media particularly in pores a few nanometers in diameter nanopores while this is a review it is actually more forward looking in that the list of things about this phenomenon that we do not know or cannot control at this time is likely longer than what we do know and can control for example there are three directly contradictory theories on how to predict how precipitation proceeds in a medium of varying pore size as will be discussed below the confusion on this subject likely stems from the complexity of the phenomenon itself one can easily clog a porous medium by inducing a rapid homogeneous precipitation directly from solution or have limited precipitation occur that does not affect permeability or even porosity substantially it is more difficult to engineer mineral precipitation in order to obtain a specific outcome such as filling all available pore space over a targeted area for the purposes of contaminant sequestration however breakthrough discoveries could occur in the next five to ten years that enhance our ability to predict robustly and finely control precipitation in porous media by understanding how porosity and permeability evolve in response to system perturbations these discoveries will likely stem at least in part from advances in our ability to 1 perform and interpret x ray neutron scattering experiments that reveal the extent of precipitation and its locales within porous media anovitz and cole 2015 this volume and 2 utilize increasingly powerful simulations to test concepts and models about the evolution of porosity and permeability as precipitation occurs steefel et al 2015 this volume a further important technique to isolate specific phenomena and understand reactivity is also microfluidics cell

co2 injectivity in saline aquifers the impact of non darcy flow phase miscibility and gas compressibility a key aspect of co2 storage is the injection rate into the subsurface which is limited by the pressure at which formation starts to fracture hence it is vital to assess all of the relevant processes that may contribute to the pressure increase in the aquifer during co2 injection building on an existing analytical solution for immiscible and spatially varying non darcy flow this paper presents a mathematical model that accounts for combined effects of non darcy flow phase miscibility and gas compressibility in radial two phase displacements results show that in low permeability formations when co2 is injected at high rates non darcy simulations forecast better displacement efficiency compared to flow under darcy conditions this will have a positive effect on the formation co2 storage capacity this however comes at the cost of increased well pressures more favorable estimations of the pressure buildup are obtained when co2 compressibility is taken into account because reservoir pressures are reduced due to the change in the gas phase properties also non darcy flow results in a significant reduction in halite precipitation in the near well region with a positive effect on co2 injectivity in the examples shown non darcy flow conditions may lead to significantly different pressure and saturation distributions in the near well region with potentially important implications for co2 injectivity

coupled hydromechanical thermochemical processes in rock fractures the behavior of rock fractures under various coupled processes is reviewed under seven broad categories 1 hydromechanical processes 2 thermohydrologic processes 3 hydrochemical processes 4 thermohydromechanical processes 5 thermohydrochemical processes 6 hydromechanical chemical processes and 7 thermomechanical hydrochemical processes the state of the art and possible directions of further research in these coupled processes are discussed rock fracture behaviors considered include not only dilation closure shear and joint propagation but also changes in flow permeability and chemical sorption and retardation capabilities these properties are of critical concern in practical considerations of the rock mass as a medium to store and isolate chemical and radioactive wastes investigations of coupled processes in two fracture systems and multifracture systems are identified as important areas for future research the need to consider coupled processes in borehole testing procedures involving rock fractures is emphasized

teleconnection between the atlantic meridional overturning circulation and sea level in the mediterranean sea abstractthe mediterranean sea can be viewed as a barometer of the north atlantic ocean because its sea level responds to oceanic gyre scale changes in atmospheric pressure and wind forcing rela

wind induced interannual variability of sea level slope along shelf flow and surface salinity on the northwest atlantic shelf in this study we examine the importance of regional wind forcing in modulating advective processes and hydrographic properties along the northwest atlantic shelf with a focus on the nova scotian shelf nss gulf of maine gom region long term observational data of alongshore wind stress sea level slope and along shelf flow are analyzed to quantify the relationship between wind forcing and hydrodynamic responses on interannual time scales additionally a simplified momentum balance model is used to examine the underlying mechanisms our results show significant correlation among the observed interannual variability of sea level slope along shelf flow and alongshore wind stress in the nss gom region a mechanism is suggested to elucidate the role of wind in modulating the sea level slope and along shelf flow stronger southwesterly northeastward winds tend to weaken the prevailing southwestward flow over the shelf building sea level in the upstream newfoundland shelf region whereas weaker southwesterly winds allow stronger southwestward flow to develop raising sea level in the gom region the wind induced flow variability can influence the transport of low salinity water from the gulf of st lawrence to the gom explaining interannual variations in surface salinity distributions within the region hence our results offer a viable mechanism besides the freshening of remote upstream sources to explain interannual patterns of freshening in the gom

the sea level budget along the northwest atlantic coast gia mass changes and large scale ocean dynamics sea level rise and decadal variability along the northwestern coast of the north atlantic ocean are studied in a self consistent framework that takes into account the effects of solid earth deformation and geoid changes due to large scale mass redistribution processes observations of sea and land level changes from tide gauges and gps are compared to the cumulative effect of gia present day mass redistribution and ocean dynamics over a 50 year period 1965 2014 gia explains the majority of the observed sea level and land motion trends as well as almost all interstation variability present day mass redistribution resulting from ice melt and land hydrology causes both land uplift and sea level rise in the region we find a strong correlation between decadal steric variability in the subpolar gyre and coastal sea level which is likely caused by variability in the labrador sea that is propagated southward the steric signal explains the majority of the observed decadal sea level variability and shows an upward trend and a significant acceleration which are also found along the coast the sum of all contributors explains the observed trends in both sea level rise and vertical land motion in the region as well as the decadal variability the sum of contributors also explains the observed acceleration within confidence intervals the sea level acceleration coincides with an accelerating density decrease at high latitudes

potential signatures of damage related radiation from aftershocks of the 4 april 2010 mw 7 2 el mayor cucapah earthquake baja california mexico abstract we observe enhanced high frequency radiation of p waves from aftershocks of the 4 april 2010 m w 7 2 el mayor cucapah baja california earthquake that may reflect isotropic radiation generated by rock damage in the source regions to eliminate path radiation pattern and site effects we use spectral ratios of four pairs of collocated events with similar size and focal mechanism that occurred within short time intervals less than 24 hrs and were recorded at the same stations the p p and the s s spectral ratios calculated for the selected pairs of events show that events with similar size may have differences of high frequency radiation up to a factor of 4 at 10 hz and up to a factor of 10 at 4 hz for p and s waves respectively to evaluate the differences between p and s wave energy radiated at high frequencies we calculate the p p s s ratio of the ratios at high frequencies f 1 5 hz in a band for which the signal to noise ratio is adequate since the pairs of used events have approximately the same size the ratio of ratios is expected to be near unity we observed high p p s s spectral ratios at high frequencies f 6 hz up to a factor of 9 which may reflect isotropic radiation associated with rock damage to find additional possible signatures of rock damage we evaluate changes of coda q using the same data the results show small change of q for a doublet located on the laguna salada fault however for the doublets located south of the sierras el mayor cucapah where there was no surface rupture before the sequence changes of q at 5 hz by a factor of about 3 indicate significant temporal variations of rock properties along the source receiver path

stress drop heterogeneity within tectonically complex regions a case study of san gorgonio pass southern california in general seismic slip along faults reduces the average shear stress within earthquake source regions but stress drops of specific earthquakes are observed to vary widely in size to advance our understanding of variations in stress drop we analysed source parameters of small magnitude events in the greater san gorgonio area southern california in san gorgonio the regional tectonics are controlled by a restraining bend of the san andreas fault system which results in distributed crustal deformation and heterogeneous slip along numerous strike slip and thrust faults stress drops were estimated by fitting a brune type spectral model to source spectra obtained by iteratively stacking the observed amplitude spectra the estimates have large scatter among individual events but the median of event populations shows systematic statistically significant variations we identified several crustal and faulting parameters that may contribute to local variations in stress drop including the style of faulting changes in average tectonic slip rates mineralogical composition of the host rocks as well as the hypocentral depths of seismic events we observed anomalously high stress drops 20 mpa in a small region between the traces of the san gorgonio and mission creek segments of the san andreas fault furthermore the estimated stress drops are higher below depths of 10 km and along the san gorgonio fault segment but are lower both to the north and south away from san gorgonio pass showing an approximate negative correlation with geologic slip rates documenting controlling parameters of stress drop heterogeneity is important to advance regional hazard assessment and our understanding of earthquake rupture processes

source pulse enhancement by deconvolution of an empirical green s function observations of the earthquake source time function are enhanced if path recording site and instrument complexities can be removed from seismograms assuming that a small earthquake has a simple source its seismogram can be treated as an empirical green s function and deconvolved from the seismogram of a larger and or more complex earthquake by spectral division when the deconvolution is well posed the quotient spectrum represents the apparent source time function of the larger event this study shows that with high quality locally recorded earthquake data it is feasible to fourier transform the quotient and obtain a useful result in the time domain in practice the deconvolution can be stabilized by one of several simple techniques in this paper the method is implemented and tested on high quality digital recordings of aftershocks of the jan 9 1982 miramichi new brunswick earthquake in particular seismograms from a jan 17 aftershock 017 13 33 gmt local mag 3 5 exhibit path or site effects which complicate the determination of source parameters after deconvolution the apparent far field source of this event is a simple pulse in displacement with duration 0 07 second for both p and s

does the mid atlantic united states sea level acceleration hot spot reflect ocean dynamic variability 1 to test a hypothesized faster than global sea level acceleration along the mid atlantic united states i construct a gaussian process model that decomposes tide gauge data into short term variability and longer term trends and into globally coherent regionally coherent and local components while tide gauge records indicate a faster than global increase in the rate of mid atlantic u s sea level rise beginning 1975 this acceleration could reflect either the start of a long term trend or ocean dynamic variability the acceleration will need to continue for 2 decades before the rate of increase of the sea level difference between the mid atlantic and southeastern u s can be judged as very likely unprecedented by 20th century standards however the difference is correlated with the atlantic multidecadal oscillation north atlantic oscillation and gulf stream north wall indices all of which are currently within the range of past variability

a simple model of the decadal response of the ocean to stochastic wind forcing abstract a simple linear model is used to estimate the decadal response of the extratropical ocean to wind stress forcing assuming a flat bottom a mean state at rest and no dissipation the barotropic fields are governed by a time dependent sverdrup balance the baroclinic ones by the long rossby wave equation the ocean is bounded by a coast in the east and a radiation condition is used in the west at each frequency the baroclinic response consists of a forced response plus a rossby wave generated at the eastern boundary for zonally independent forcing the response propagates westward at twice the rossby phase speed the wind stress is assumed to be stochastic with a white frequency spectrum so the model represents the continuous excitation of the ocean interior by the weather fluctuations the model predicts the shape and level of the frequency spectra of the oceanic pressure field and their variation with longitude and latitude the baroclinic response is spread over a continuum of frequencies

mechanisms underlying recent decadal changes in subpolar north atlantic ocean heat content the subpolar north atlantic spna is subject to strong decadal variability with implications for surface climate and its predictability in 2004 2005 spna decadal upper ocean and sea surface temperature trends reversed from warming during 1994 2004 to cooling over 2005 2015 this recent decadal trend reversal in spna ocean heat content ohc is studied using a physically consistent observationally constrained global ocean state estimate covering 1992 2015 the estimate s physical consistency facilitates quantitative causal attribution of ocean variations closed heat budget diagnostics reveal that the spna ohc trend reversal is the result of heat advection by midlatitude ocean circulation kinematic decompositions reveal that changes in the deep and intermediate vertical overturning circulation cannot account for the trend reversal but rather ocean heat transports by horizontal gyre circulations render the primary contributions the shift in horizontal gyre advection reflects anomalous circulation acting on the mean temperature gradients maximum covariance analysis mca reveals strong covariation between the anomalous horizontal gyre circulation and variations in the local wind stress curl suggestive of a sverdrup response results have implications for decadal predictability

inverted barometer contributions to recent sea level changes along the northeast coast of north america regional sea level sl changes reflect dynamic and isostatic ocean effects recent works have interpreted accelerated and extreme sl changes along the northeast coast of north america primarily in terms of dynamic changes however dedicated study of isostatic changes related to surface atmospheric pressure loading the inverted barometer ib effect has been lacking this investigation uses five different atmospheric pressure products to analyze the influence of the ib effect on annual mean sl from tide gauge records the ib effect explains 25 of interannual sl variance and accounts for 50 of the magnitude of a recent extreme event of sl rise along atlantic canada and new england estimated ib effects also amount to 10 30 of recent multidecadal sl accelerations over the mid atlantic bight and southern new england these findings reiterate the need for careful estimation and removal of isostatic effects for studies of dynamic sl

on the relationship between the meridional overturning circulation alongshore wind stress and united states east coast sea level in the community earth system model large ensemble

annual sea level changes on the north american northeast coast influence of local winds and barotropic motions abstractunderstanding the relationship between coastal sea level and the variable ocean circulation is crucial for interpreting tide gauge records and projecting sea level rise in this study annual sea level records adjusted for the inverted barometer effect from tide gauges along the north american northeast coast over 1980 2010 are compared to a set of data assimilating ocean reanalysis products as well as a global barotropic model solution forced with wind stress and barometric pressure correspondence between models and data depends strongly on model and location at sites north of cape hatteras the barotropic model shows as much if not more skill than ocean reanalyses explaining about 50 of the variance in the adjusted annual tide gauge sea level records additional numerical experiments show that annual sea level changes along this coast from the barotropic model are driven by local wind stress over the continental shelf and slope this result is interpreted in the light of a simple dynamic

wind forced interannual variability of the atlantic meridional overturning circulation at 26 5 n the observed atlantic meridional overturning circulation amoc at 26 5 n shows interannual variability consisting of an increase from early 2004 to late 2005 and a following downtrend which reaches a minimum in the winter of 2009 2010 these interannual amoc fluctuations are dominated by changes in the upper mid ocean geostrophic flow except during the winter of 2009 2010 when the anomalous wind driven ekman transport also has a significant contribution the physical mechanisms for the interannual changes of the amoc are proposed and evaluated in a two layer model while the ekman transport is linked to the north atlantic oscillation nao the anomalous geostrophic transport involves the oceanic adjustment to surface wind forcing in particular the intensification and weakening of the southward interior geostrophic flow is modulated by the internal rossby wave adjustment to the surface wind forcing the gulf stream on the other hand is controlled by both topographic waves along the us coast and westward propagating planetary waves our study suggests that a large part of the observed amoc interannual variability at 26 5 n can be explained by wind driven dynamics

a sea change in our view of overturning in the subpolar north atlantic to provide an observational basis for the intergovernmental panel on climate change projections of a slowing atlantic meridional overturning circulation moc in the 21st century the overturning in the subpolar north atlantic program osnap observing system was launched in the summer of 2014 the first 21 month record reveals a highly variable overturning circulation responsible for the majority of the heat and freshwater transport across the osnap line in a departure from the prevailing view that changes in deep water formation in the labrador sea dominate moc variability these results suggest that the conversion of warm salty shallow atlantic waters into colder fresher deep waters that move southward in the irminger and iceland basins is largely responsible for overturning and its variability in the subpolar basin

investigating uncertainties in empirical green s function analysis of earthquake source parameters i use a well recorded earthquake sequence to investigate the uncertainties of earthquake stress drops calculated using an empirical green s function egf approach the earthquakes in the largest m 2 1 repeating sequence targeted by the san andreas observatory at depth safod parkfield california are recorded by multiple borehole stations and have simple sources well constrained stress drops and abundant smaller earthquakes to use as egfs i perform three tests to estimate quantitatively the likely uncertainties to arise in less optimal settings i use egf earthquakes with a range of cross correlation values and separation distances from the main earthquakes the stress drop measurements decrease by a factor of 3 as the quality of the egf assumption decreases a good egf must be located within approximately one source dimension of the large earthquake with high cross correlation i subsample the large number of measurements for the main earthquakes to investigate the expected stress drop uncertainties in studies where fewer stations or egfs are available if only one measurement is available the uncertainties are likely to be at least 50 the uncertainties decrease to 20 with five or more measurements using multiple egfs is a good alternative to multiple stations to investigate the effects of limited frequency bandwidth i recalculate the corner frequencies after progressively decimating the sample rate decreasing the high frequency limit of the bandwidth decreases the estimate of the corner frequency and stress drop the corner frequency may be underestimated if it is within a factor of 3 of the maximum frequency of the signal

thermohydrological conditions and silica redistribution near high level nuclear wastes emplaced in saturated geological formations evaluation of the thermohydrological conditions near high level nuclear waste packages is needed for the design of the waste canister and for overall repository design and performance assessment most available studies in this area have assumed that the hydrologic properties of the host rock are not changed in response to the thermal mechanical or chemical effects caused by waste emplacement however the ramifications of this simplifying assumption have not been substantiated we have studied dissolution and precipitation of silica in liquid saturated hydrothermal flow systems including changes in formation porosity and permeability using numerical simulation we compare predictions of thermohydrological conditions with and without inclusion of silica redistribution effects two cases were studied namely a canister scale problem and a repository wide thermal convection problem and different pore models were employed for the permeable medium fractures with uniform or nonuniform cross sections we find that silica redistribution in water saturated conditions does not have a sizeable effect on host rock and canister temperatures pore pressures or flow velocities

formation dry out from co2 injection into saline aquifers 1 effects of solids precipitation and their mitigation f ormation d ry o ut from co 2 i njection into s aline a quifers p art 1 e ffects of s olids p recipitation and their m itigation karsten pruess 1 and nadja muller 2 earth sciences division lawrence berkeley national laboratory university of california berkeley ca 94720 shell international exploration and production b v exploratory research rijswijk the netherlands abstract injection of co 2 into saline aquifers may cause formation dry out and precipitation of salt near the injection well which may reduce formation porosity permeability and injectivity this paper uses numerical simulation to explore the role of different processes and parameters in the salt precipitation process and to examine injection strategies that could mitigate the effects the main physical mechanisms affecting the dry out and salt precipitation process include 1 displacement of brine away from the injection well by injected co 2 2 dissolution evaporation of brine into the flowing co 2 stream 3 upflow of co 2 due to gravity effects buoyancy 4 backflow of brine towards the injection point due to capillary pressure gradients that oppose the pressure gradient in the co 2 rich gas phase and 5 molecular diffusion of dissolved salt the different mechanisms operate on a range of spatial scales co 2 injection at constant rate into a homogeneous reservoir with uniform initial conditions is simulated in 1 d radial geometry to resolve multi scale processes by taking advantage of the similarity property i e the evolution of system conditions as a function of radial distance r and time t depends only on the similarity variable r 2 t simulations in 2 d vertical cross sections are used to examine the role of gravity effects we find that counterflow of co 2 and brine can greatly increase aqueous phase salinity and can promote substantial salt precipitation even in formations with low dissolved solids salt precipitation can accentuate effects of gravity override we find that injecting a slug of fresh water prior to commencement of co 2 injection can reduce salt precipitation and permeability loss near the injection well

reactive geothermal transport simulations to study the formation mechanism of an impermeable barrier between acidic and neutral fluid zones in the onikobe geothermal field japan two types of fluids are encountered in the onikobe geothermal reservoir one is neutral and the other is acidic ph 3 it is hypothesized that acidic fluid might be upwelling along a fault zone and that an impermeable barrier might be present between the acidic and neutral fluid zones we carried out reactive geothermal transport simulations using toughreact xu and pruess 1998 and 2001 to test such a conceptual model mn rich smectite precipitated near the mixing front and is likely to form an impermeable barrier between regions with acidic and neutral fluids

the persistence of directivity in small earthquakes abstract we derive a simple inversion of peak ground acceleration pga or peak ground velocity pgv for rupture direction and rupture velocity and then test this inversion on the peak motions obtained from seven 3 5 m 4 1 earthquakes that occurred in two clusters in november 2002 and february 2003 near san ramon california these clusters were located on two orthogonal strike slip faults so that the events share the same approximate focal mechanism but not the same fault plane three earthquakes exhibit strong directivity but the other four earthquakes exhibit relatively weak directivity we use the residual pgas and pgvs from the other six events to determine station corrections for each earthquake the inferred rupture directions unambiguously identify the fault plane for the three earthquakes with strong directivity and for three of the four earthquakes with weak directivity the events with strong directivity have fast rupture velocities 0 63 v 0 87 the events with weak directivity either rupture more slowly 0 17 v 0 35 or bilaterally the simple unilateral inversion cannot distinguish between slow and bilateral ruptures adding a bilateral rupture component degrades the fit of the rupture directions to the fault planes by comparing pgas from the events with strong and weak directivity we show how an up dip rupture in small events can distort the attenuation of peak ground motion with distance when we compare the rupture directions of the earthquakes to the location of aftershocks in the two clusters we find than almost all the aftershocks of the three earthquakes with strong directivity occur within 70 of the direction of rupture

rupture directivity of microearthquake sequences near parkfield california 1 the direction of propagation is an important factor that affects the pattern of ground motion generated by an earthquake characterizing factors favoring a potential rupture propagation direction is thus an important task here we analyze the earthquake directivity of repeating earthquake sequences located on the san andreas fault near parkfield california all earthquakes of a sequence have very similar waveforms and have overlapping surface ruptures we show that subtle variations of the transfer function between earthquakes of a common sequence can be interpreted as a change of apparent rupture duration relative apparent rupture durations are computed for all pairs of events at all available stations and for each sequence we invert these measurements to obtain an estimation of the apparent rupture duration for each individual event of the sequence relative to a reference event variation of apparent rupture duration with azimuth attests for the rupture directivity we show that the majority of analyzed microearthquakes presents a rupture in the south east direction we also show that on a given repeating sequence most earthquakes tend to show the same rupture direction

mean sea level variability along the northeast american atlantic coast and the roles of the wind and the overturning circulation the variability in mean sea level msl during 1950 2009 along the northeast american atlantic coast north of cape hatteras has been studied using data from tide gauges and satellite altimetry and information from the liverpool hadley centre lhc ocean model thereby providing new insights into the spatial and temporal scales of the variability although a relationship between sea level and the overturning circulation can be identified an increase of approximately 1 5 cm in msl for a decrease of 1 sv in overturning transport it is the effect of the nearshore wind forcing on the shelf that is found to dominate the interannual sea level variability in particular winds are found to be capable of producing low frequency changes in msl accelerations in a narrow coastal band comparable to those observed by the tide gauges evidence is presented supporting the idea of a common mode of spatially coherent low frequency msl variability both to the north and south of cape hatteras and throughout the northwest atlantic which is associated with large spatial scale density changes from year to year

signature of the atlantic meridional overturning circulation in sea level along the east coast of north america in this letter we examine the relationship between the north atlantic meridional overturning circulation moc and sea level sl along the east coast of north america in the eddy permitting ocean model occam we find a distinctive topography following pattern of sl variability in the western north atlantic that is closely linked with the changing strength of the moc with a 2 cm drop in sl along the us east coast corresponding to a 1sv increase in the moc we find a similar pattern of sl variability in the altimetry record and show that this meridionally coherent sl mode dominates interannual sl variability at tide gauges along the north american east coast between 40 50n hence we conclude that north american coastal sea level may indeed be a useful indicator of moc variability on interannual timescales allowing an observationally based estimate of the likely range of interannual moc fluctuations to be determined citation bingham r j and c w hughes 2009 signature of the atlantic meridional overturning circulation in sea level along the east coast of north america geophys res lett 36 l02603 doi 10 1029 2008gl036215

reconstruction of rocks petrophysical properties as input data for reservoir modeling the worldwide increasing energy demand triggered studies focused on defining the underground energy potential even in areas previously discharged or neglected nowadays geological gas storage co2 and or ch4 and geothermal energy are considered strategic for low carbon energy development a widespread and safe application of these technologies needs an accurate characterization of the underground in terms of geology hydrogeology geochemistry and geomechanics however during pre feasibility study stage the limited number of available direct measurements of reservoirs and the high costs of reopening closed deep wells must be taken into account the aim of this work is try to overcome these limits proposing a new methodology to reconstruct vertical profiles from surface to reservoir base of i thermal capacity ii thermal conductivity iii porosity and iv permeability through integration of well log information petrographic observations on inland outcropping samples and flow and heat transport modelling as case study to test our procedure we selected a deep structure located in the medium tyrrhenian sea italy obtained results are consistent with measured data confirming the validity of the proposed model notwithstanding intrinsic limitations due to manual calibration of the model with measured data this methodology represents a useful tool for reservoir and geochemical modellers that need to define petrophysical input data for underground modelling before the well reopening this article is protected by copyright all rights reserved

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

reactive transport modeling in fractured rock a state of the science review abstract the field of reactive transport modeling has expanded significantly in the past two decades and has assisted in resolving many issues in earth sciences numerical models allow for detailed examination of coupled transport and reactions or more general investigation of controlling processes over geologic time scales reactive transport models serve to provide guidance in field data collection and in particular enable researchers to link modeling and hydrogeochemical studies in this state of science review the key objectives were to examine the applicability of reactive transport codes for exploring issues of redox stability to depths of several hundreds of meters in sparsely fractured crystalline rock with a focus on the canadian shield setting a conceptual model of oxygen ingress and redox buffering within a shield environment at time and space scales relevant to nuclear waste repository performance is developed through a review of previous research this conceptual model describes geochemical and biological processes and mechanisms materially important to understanding redox buffering capacity and radionuclide mobility in the far field consistent with this model reactive transport codes should ideally be capable of simulating the effects of changing recharge water compositions as a result of long term climate change and fracture matrix interactions that may govern water rock interaction other aspects influencing the suitability of reactive transport codes include the treatment of various reaction and transport time scales the ability to apply equilibrium or kinetic formulations simultaneously the need to capture feedback between water rock interactions and porosity permeability changes and the representation of fractured crystalline rock environments as discrete fracture or dual continuum media a review of modern multicomponent reactive transport codes indicates a relatively high level of maturity within the yucca mountain nuclear waste disposal program reactive transport codes of varying complexity have been applied to investigate the migration of radionuclides and the geochemical evolution of host rock around the planned disposal facility through appropriate near and far field application of dual continuum codes this example demonstrates how reactive transport models have been applied to assist in constraining historic water infiltration rates interpreting the sealing of flow paths due to mineral precipitation and investigating post closure geochemical monitoring strategies natural analogue modeling studies although few in number are also of key importance as they allow the comparison of model results with hydrogeochemical and paleohydrogeological data over geologic time scales