a framework for karst ecohydrology ecohydrology can be defined as the science of integrating hydrological and biological processes over varied spatial and temporal scales there exists in karst a strong and direct interaction between the circulation and storage of groundwater and surface water these fluxes in turn affect the spatial distribution of organisms in these habitats because of the fact that the appearance storage and circulation of water in karstified areas is significantly different from other more homogenous and isotropic terrains karst ecohydrology should develop original methods and approaches at the same time traditional approaches are also very useful large karst underground geomorphological patterns occur in many sizes and varieties ranging from a few meters long or deep to very large the deepest being deeper than 1km and longer than hundreds of kilometres in this article special attention is paid to ecohydrological functions of karst underground features caves pits conduits etc which play a crucial dual role in 1 hydrology and hydrogeology of water circulation and storage and 2 ecology of many rare and endangered species differences in morphology hydrology hydrogeology and climate have resulted in a range of different environments which provide the opportunity for the coexistence of different species the role of the epikarst and vadose zones as well as caves in ecohydrological processes is discussed the importance of the flood factor in karst ecology is analysed the aim of this article is to move forward the discussion among different disciplines to promote and develop a conceptual framework for karst ecohydrology

subsurface flow in a soil mantled subtropical dolomite karst slope a field rainfall simulation study abstract soil and epikarst co evolve resulting in complex structures but their coupled structural effects on hydrological processes are poorly understood in karst regions this study examined the plot scale subsurface flow characteristics from an integrated soil epikarst system perspective in a humid subtropical cockpit karst region of southwest china a trench was excavated to the epikarst lower boundary for collecting individual subsurface flows in five sections with different soil thicknesses four field rainfall simulation experiments were carried out under different initial moisture conditions dry and wet and rainfall intensities 114 mm h 1 high and 46 mm h 1 low on average the soil epikarst system was characterized by shallow soil overlaying a highly irregular epikarst surface with a near steady infiltration rate of about 35 mm h 1 the subsurface flows occurred mainly along the soil epikarst interface and were dominated by preferential flow the subsurface flow hydrographs showed strong spatial variability and had high steady state coefficients 0 52 and 0 36 for high and low rainfall intensity events irregular epikarst surface combining with high vertical drainage capacity resulted in high threshold rainfall depths for subsurface flows 67 mm and 263 mm for initial wet and dry conditions respectively the above results evidenced that the irregular and permeable soil epikarst interface was a crucial component of soil epikarst architecture and consequently should be taken into account in the hydrological modeling for karst regions

role of permeability and storage in the initiation and propagation of natural hydraulic fractures 1 joint sets within sedimentary basins are commonly interpreted to have formed by tensile failure in conditions where pore fluid pressure was elevated such tensile fractures are inferred to be a part of the process that relieves high fluid pressure by locally increasing rock permeability in spite of the importance of this feedback mechanism the detailed mechanics of hydraulic fracture genesis remain poorly understood we describe the results of both experimental and numerical studies of hydraulic fracture genesis on the basis of an experimental protocol that combines rock extension with elevated pore fluid pressure such that the hydraulic fracture criterion is met in the sample interior this is achieved by simultaneously dropping both minimum stress and external pore fluid pressure inducing a large fluid pressure drop between the sample interior and its ends poroelastic modeling suggests that the pore fluid pressure is highest close to but not at the sample ends and is locally maintained at levels that meet the hydraulic fracture criterion for up to 50 s application of this experimental protocol to an impure sample of sandstone resulted in the generation of several hydraulic fractures subparallel to the maximum principal stress fracturing did not occur in a drained test on the same sample demonstrating that the elevated pore fluid pressure was critical to fracture formation to better understand the experimental results we explore the role of rock permeability and storage on fracture processes using a numerical model that directly couples a lattice boltzmann model for fluid mechanics with a discrete element model for solid mechanics like the experiment the numerical simulations produced opening mode fractures when operated to replicate the conditions of the experiment fractures preferentially occur in portions of the model inferred to be mechanically weak local fluid pressure gradients strongly influence the state of stress in the solids and thereby fracture growth increasing the model permeability increases fracture propagation rate decreases sample deformation and increases fracture spacing sample deformation increases and fracture spacing decreases with increasing overpressure it appears that bulk forcing of the solid via fluid seepage forces is important in fracture genesis explaining the key roles of permeability and diffusivity in the hydrofracture process

propagation velocity of a natural hydraulic fracture in a poroelastic medium the propagation rate of a natural hydraulic fracture is limited by the rate that fluid flows from the saturated rock into the void space created by fracture growth unlike induced hydraulic fractures natural hydraulic fractures can not be modeled by specifying rates of fracture growth or fluid flow into the fracture as boundary conditions numerical solutions of the governing equations for natural hydraulic fracture growth in a poroelastic medium indicate that growth rates are primarily controlled by the hydraulic conductivity the storage sp and the initial flaw length 2 o computationally more efficient models which partially and completely decouple material stresses from fluid pressures give similar results results for several rock types indicate that although the rate of fracture propagation is limited by fluid flow fracture growth still accelerates results are generalized in dimensionless plots of fracture length versus time for various values of the dimensionless parameter 1 gsp where g is the shear modulus and is the drained poisson s ratio

measurement of field saturated hydraulic conductivity on fractured rock outcrops near altamura southern italy with an adjustable large ring infiltrometer up to now field studies set up to measure field saturated hydraulic conductivity to evaluate contamination risks have employed small cylinders that may not be representative of the scale of measurements in heterogeneous media in this study a large adjustable ring infiltrometer was designed to be installed on site directly on rock to measure its field saturated hydraulic conductivity the proposed device is inexpensive and simple to implement yet also very versatile due to its large adjustable diameter that can be fixed on site it thus allows an improved representation of the natural system s heterogeneity while also taking into consideration irregularities in the soil rock surface the new apparatus was tested on an outcrop of karstic fractured limestone overlying the deep murge aquifer in the south of italy which has recently been affected by untreated sludge disposal derived from municipal and industrial wastewater treatment plants the quasi steady vertical flow into the unsaturated fractures was investigated by measuring water levels during infiltrometer tests simultaneously subsurface electrical resistivity measurements were used to visualize the infiltration of water in the subsoil due to unsaturated water flow in the fractures the proposed experimental apparatus works well on rock outcrops and allows the repetition of infiltration tests at many locations in order to reduce model uncertainties in heterogeneous media

spatial analysis of soil hydraulic conductivity in a tropical rain forest catchment the topography of first order catchments in a region of western amazonia was found to exhibit distinctive recurrent features a steep straight lower side slope a flat or nearly flat terrace at an intermediate elevation between valley floor and interfluve and an upper side slope connecting interfluve and intermediate terrace a detailed survey of soil saturated hydraulic conductivity ksat depth relationships involving 740 undisturbed soil cores was conducted in a 0 75 ha first order catchment the sampling approach was stratified with respect to the above slope units exploratory data analysis suggested fourth root transformation of batches from the 0 0 1 m depth interval log transformation of batches from the subsequent 0 1 m depth increments and the use of robust estimators of location and scale the ksat of the steep lower side slope decreased from 46 to 0 1 mm h over the overall sampling depth of 0 4 m the corresponding decrease was from 46 to 0 1 mm h on the intermediate terrace from 335 to 0 01 mm h on the upper side slope and from 550 to 0 015 mm h on the interfluve a depthwise comparison of these slope units led to the formulation of several hypotheses concerning the link between ksat and topography

preuplift joints in granites evidence for subcritical and postcritical fracture growth this study relates to jointing in granite that took place in the crust before uplift thus offering an insight into paleo fracture processes our investigation reveals a unique set of joints within granite of the south bohemian pluton exposed in the borsov quarry southeast of prague in the czech republic these joints occur in close proximity and exhibit a great variety of fracture surface morphologies the joints in the borsov granite may be divided into four groups based on fractographic features 1 partial mirror planes without fringes 2 mirror planes rimmed by en echelon fringes 3 complex en echelon fringes and 4 hackled fringes on the basis of theoretical experimental and fractographic data obtained in outcrops we have constructed a curve for the change in crack velocity v as a function of the stress intensity factor k i and we have plotted the various joints in the borsov granite on this curve the spread of the joints along the curve indicates that the joints terminated under widely different physical conditions possibly responding to repeated extensional events and different fracture mechanisms hence a new quantitative method of joint classification is introduced such a great variety of fractographic features is unknown from joint sets that occur in a single quarry in sedimentary rock because their formation always relates to a particular fracture mechanism we argue that the joints in the borsov granite formed before uplift in a fluid enriched environment while the granite responded to diverse local effective stress conditions

erratum to locating magma reservoirs using insar and petrology before and during the 2011 2012 cordon caulle silicic eruption earth planet sci lett 395 2014 254 266

when interflow also percolates downslope travel distances and hillslope process zones copyright 2014 john wiley sons ltd introduction in hillslopes with soils characterized by deep regoliths such as ultisols oxisols and alfisols interflow occurs episodically over impeding layers near and parallel to the soil surface such as low conductivity b horizons e g newman et al 1998 buttle andmcdonald 2002 du et al in review till layers mcglynn et al 1999 bishop et al 2004 hardpans mcdaniel et al 2008 c horizons detty and mcguire 2010 and permeable bedrock tromp van meerveld et al 2007 as perched saturation develops within and above these impeding but permeable horizons flow moves laterally downslope but the perched water also continues to percolate through the impeding horizon to the unsaturated soils and saprolite below perched water and solutes will eventually traverse the zone of perched saturation above the impeding horizon and then enter and percolate through the impeding horizon in such flow situations only lower hillslope segments with sufficient downslope travel distance will deliver water to the riparian zone within the time scale of a storm farther up the slope lateral flow within the zone of perched saturation will act mainly to shift the point of percolation location where a water packet leaves the downslope flow zone in the upper soil layer and enters the impeding layer down the hillslope from the point of infiltration in flatter parts of the hillslope or in areas with little contrast between the conductivities of the upper and impeding soil layers lateral flow distances will be negligible from darcy s law we can estimate the downslope travel distance for quasi steady state conditions within the saturated layer assuming boussinesq slope parallel flow above the restrictive layer and normal flow perpendicular to the slope through the restrictive layer to unsaturated soils below figure 1 using a downslope flow vector we must employ an orthogonal normal vector and avoid harr s 1977 mistake of adding non orthogonal and non independent gradient vectors in calculating flow directions weassume that each layer is isotropic and the impeding layer is saturated or nearly so and drains freely to an unsaturated layer below pressure head equals zero at the base of the impeding layer we assume diffuse porosity within the impeding layer so percolation is not restricted to randomly spaced discontinuities with these assumptions generally applicable to hillslopes with deep regoliths and a low conductivity layer paralleling the soil surface we will calculate downslope travel distances for reasonable combinations of slopes conductivities and impeding layer thicknesses evaluate these distances with respect to typical slope lengths map the downslope travel distances on watersheds with soil and slope conditions matching these assumptions and discuss how couplingboussinesq downslope flow and percolation affect our understanding of the potential zonation of lateral flow processes

evidence of fluid flow in microfractures in geopressured shales petrographic and microprobe analyses of geopressured shales from the oligocene frio formation brazoria county texas provide direct evidence of hydraulic fracturing and significant fluid flow in the shales the optical continuity of the fracture margins and their higher al si ratios indicate that the fracture margins have undergone more complete alteration of smectite to illite than the interiors of the fracture blocks crosscutting relationships between calcium sulfate and the organic material that fills the fractures indicate that calcium sulfate was emplaced before the organic material and thus was precipitated in the subsurface the calculated fracture permeabilities of the shales on the order of 10 13 m2 are similar in magnitude to that of he frio sandstone reservoirs which suggests that these fractured shales could support flow comparable to that in the sandstones fracture fill deposits or collapse could in turn reduce this flow in addition the more extensive alteration of the fracture margins suggests that fluid in these shales flowed preferentially through the microfractures rather than through the matrix

physicochemical models of effusive rhyolitic eruptions constrained with insar and dem data a case study of the 2011 2012 cordon caulle eruption abstract the 9 month long 2011 2012 eruption of cordon caulle southern andes chile is the best instrumentally recorded rhyolitic eruption to date and the first time that the effusion of a rhyolitic flow has been observed in detail we use interferometric synthetic aperture radar insar with time lapse digital elevation models dems and numerical models to study the dynamics of coupled magma reservoir deflation and lava effusion insar recorded 2 2 2 5 m of subsidence after the first three days of the eruption which can be modeled using a spheroidal magma reservoir at a depth of 5 km 20 km long and with a pressure drop of 20 30 mpa the source is elongated in the nw se direction and its large dimensions imply a large plumbing system active throughout the eruption and spanning neighboring volcanoes with a slight change in the geometry halfway through the effusive phase tandem x and pleiades dems record the extrusion of both the rhyolitic lava flow and the intrusion of a shallow laccolith around the eruptive vent after the third day of the eruption with a total volume of 1 45 km3 dre the laccolith was emplaced during the first month of the eruption during both the explosive and effusive stages of the eruption both the reservoir pressure drop and the extruded volume time series follow quasi exponential trends and can be explained by a model that couples the reservoir pressure decrease time and pressure dependent variations in the magma properties inside of the reservoir and conduit flow this model predicts both the temporal evolution and amplitude of both time series during the effusive phase and a magma compressibility of 10 10 pa 1 half the reported compressibility of the magma of the sub plinian explosive phase further we estimate that the reservoir contained 1 3 wt dissolved h2o at the onset of lava effusion with no exsolved co2 and h2o in the reservoir throughout the effusive phase this implies that the magma was significantly degassed after the explosive phase the remaining volatiles in the magma after the explosive stage might have caused magma fragmentation consistent with the hybrid explosive effusive style observed during the waning of the eruption

a simple model of flow patterns in overpressured sedimentary basins with heat transport and fracturing overpressure zones in sedimentary basins are defined as sediments where the fluid pore pressure is substantially higher than hydrostatic chief among the causes for the formation of overpressure is the rapid deposition of low permeablity sediments so that compaction and dewatering are inhibited this results in the support of the overlying material in part by the fluid rather than by grain to grain contact many overpressure zones also have associated geothermal anomalies whereby the geotherms are hotter than normal in this paper we present a one dimensional model of overpressure generation and dissipation with hydraulic fracture the fluid flow is coupled to the fluid temperature field and to the motion of the solid sediment matrix compacted coordinates are introduced to decouple the fluid velocity and temperature from the solid matrix velocity using a maximum sedimentation rate of 1 km myr 1 and a hydraulic conductivity at the top of the layer equal to 5 10 12 m s 1 3 km of partially compacted sediment are deposited in 5 myr generating an overpressure of 0 81 of the lithostatic pressure at the bottom of the sediment layer an undercompaction of 19 relative to normally compacted sediment is developed at a final depth of 3 66 km by the end of sedimentation dissipation of the overpressure takes place on a timescale of the order of 40 myr the equilibrium temperature generates thermal gradients in excess of 38 c km 1 at shallow depths fast sedimentation rate and high permeability in the fractured state favor oscillating behavior and propagation of fracture waves overpressure zones may constitute a proximal source of hydrothermal fluids for the genesis of ore deposits in sedimentary basins

the role of the subcutaneous zone in karst hydrology abstract the subcutaneous zone is the upper weathered layer of rock beneath the soil but above the permanently saturated phreatic zone it is of particular hydrological importance in karst because of its high secondary permeability arising from the considerable chemical solution in this zone however corrosional enlargement of fissures diminishes with depth thus permeability decreases in the same direction with the result that percolation is inhibited except down widened master joints and faults storage of water consequently occurs in this zone particularly after storms the upper surface of this suspended saturated layer in the subcutaneous zone is defined by a perched water table which slopes towards points of rapid vertical percolation the potential induces lateral water movement converging on the most permeable areas such as beneath dolines leakage from the subcutaneous store sustains slow percolation in the vadose zone cross correlation of rainfall with percolation rates in caves in new mexico u s a and new zealand reveal response lags of 2 14 weeks with no apparent relationship to depth below the surface other percolation sites show no correlation with rainfall interpreted as being a consequence of considerable friction in tight fissure networks the recognition of storage and rapid as well as very slow percolation from the subcutaneous zone requires re interpretation of the components of hydrographs from karst springs and of some conceptual models of karst aquifers the importance of subcutaneous storage in sustaining baseflow discharge at some sites must be recognised as must the contribution of subcutaneous water to flood hydrographs methods of estimating the volumes of subcutaneous and phreatic components of karst spring flood hydrographs are presented the paper concludes with a discussion of the significance of subcutaneous hydrologic processes for an understanding of karst geomorphology the desirability of explaining karst landform evolution in terms of hydrologic processes is stressed

soil hydraulic properties on the steep karst hillslopes in northwest guangxi china soil hydraulic properties such as soil infiltration rate and hydraulic conductivity are closely linked to runoff generation and infiltration processes but little is known about them on karst hillslopes the objectives of this paper were to investigate the change in soil stable infiltration rate q s and near saturated hydraulic conductivity k ns in different slope positions and to understand their relationship with rock fragment content and soil texture within the topsoil in subtropical karst regions of southwest china tension infiltrometers 20 cm in diameter were used to measure q s and k ns at pressure head of 20 mm on hillslopes 1 a disintegrated landslide failure and 2 an avalanche slope the change of q s and k ns was great and they mostly had a moderate variability with coefficient of variations cv between 0 1 and 1 0 in the different slope positions on average q s ranged from 0 43 to 4 25 mm min and k ns varied from 0 75 to 11 00 mm min these rates exceed those of most natural rainfall events confirming that overland flow is rare on karst hillslopes from bottom to top q s and k ns had a decrease increase decrease trend due to the presence of large rock outcrops 2 m in height on hillslope 1 but had an increasing trend on hillslope 2 with less complex landform they tended to increase with increase in total rock fragment content 5 250 mm within the topsoil as well as slope gradient on both hillslopes pearson correlation analysis suggested that higher coarse pebble 20 75 mm cobble 75 250 mm and sand 2 0 05 mm contents as well as total rock fragment content could significantly facilitate water infiltration into soils but higher clay 0 002 mm content could restrict water movement this result indicated that rock fragment sand and clay contents may remarkably affect water flow in the topsoil layers and should be considered in hydrological modeling on karst hillslopes in subtropical regions

hydraulic properties of karst fractures filled with soils and regolith materials implication for their ecohydrological functions abstract in regions with shallow soils underlain by fractured bedrock hydrological processes of substrate are no longer only limited to soil layers however ecohydrological functions of bedrock fractures especially those filled with different soil and regolith materials have not been fully understood in this study we aimed to evaluate water transport and supplying capacities of the filled fractures through investigating hydraulic properties and explore their dominant influencing factors three typical fractures a vertical one filled with fine textured soil vsf a vertical one filled with soil and regolith materials vsrf and a non vertical one filled with coarse textured soil nsf were selected from a large newly excavated trench on a karst hillslope of southwest china stratified samples of fracture fillings were collected to measure saturated hydraulic conductivity k s water retention curves and basic physicochemical properties additionally twenty soil profiles in different topographic locations in the same study area were also analyzed in order to support the results derived from the filled fractures all fractures exhibited extremely high k s 87 149 mm h 1 in surface soil 0 10 cm which allowed rapid infiltration of rainwater into subsurface subsurface water transport was smooth when underlying fracture fillings were loamy with relatively high k s about 10 mm h 1 like in nsf but was blocked when they were clayey with low k s 1 like in vsf and vsrf all fracture fillings had abilities to hold water and available water was the most in nsf which provided an extra water source for plant growth in shallow soil regions the ecohydrological functions of the filled fractures often depend on the properties and layering of fracture fillings which was supported by those obtained from the twenty soil profiles these results are helpful for better understanding of the ecohydrological processes and functions of fractures filled with different materials in karst regions

threshold relations in subsurface stormflow 2 the fill and spill hypothesis analysis of subsurface stormflow from 147 storms at the 20 m long trench in the panola mountain research watershed by tromp van meerveld and mcdonnell 2006a showed that there was a distinct 55 mm precipitation threshold for significant subsurface stormflow production this second paper in the series investigates the processes responsible for this threshold response we installed a dense spatial array of maximum rise crest stage gauges and recording wells on the hillslope and studied the temporal and spatial patterns of transient saturation at the soil bedrock interface and its relation to subsurface stormflow measured at the trench face results show that while transient groundwater developed on parts of the hillslope during events smaller than 55 mm it was not until more than 55 mm of rain fell before bedrock depressions on the hillslope were filled water spilled over microtopographic relief in the bedrock surface and the subsurface saturated areas became connected to the trench when connectivity was achieved the instantaneous subsurface stormflow rate increased more than fivefold compared to before the subsurface saturated areas were connected to the trench face total subsurface stormflow was more than 75 times larger when connectivity was achieved compared to when connectivity was not achieved the fill and spill hypothesis presented in this paper is a process explanation for the observed threshold behavior of tromp van meerveld and mcdonnell 2006a thereby linking patterns and processes

constructing a saturated hydraulic conductivity map of spain using pedotransfer functions and spatial prediction abstract currently most of the research focused on general pedotransfer functions ptfs has been generated under humid climatic conditions nevertheless this article proposes an estimation of pedotransfer functions for a great variety of climatic and physiographic conditions with a predominance of soils developed under semi arid conditions such as those occurring in spain the results obtained in spite of the variety of measuring methods of the variables used show that it is possible to estimate saturated hydraulic conductivity values for soils from sand content data these are compared with results obtained from the application of other authors ptfs this is an important support to the present attempts at establishing soil inference systems the ptfs obtained have increased the number of profile points in networks with saturated hydraulic conductivity data allowing the transformation of point data to a continuous saturated hydraulic conductivity surface to reach this goal three methods have been applied that of batjes inverse distance weight and kriging interpolation with the latter giving the best results finally a saturated hydraulic conductivity map with a spatial resolution of 1 1 km for the spanish part of the iberian peninsula has been generated the resulting map showed a good spatial fit after being compared with lithological distribution which confirms the applicability of the method for future hydrological applications

significance of preferential flow at the rock soil interface in a semi arid karst environment abstract in many semi arid environments the surface materials are frequently characterized by thin soils and large proportions of bare rock both of which are expected to considerably influence infiltration and groundwater recharge processes in this study small plot scale irrigation experiments in combination with dye tracer application as well as real time and subsequent soil moisture measurements and soil particle size analysis were conducted to investigate the significance of preferential flow at the rock soil interface large scale assessments of soil depth and surface type distribution were used to upscale the findings of the irrigation experiments to the scale of a complete hillslope and further to estimate percolation properties of a hypothetical rainfall event the two experimental plots were each located in the west bank mountains close to ramallah each irrigation experiment was designed with 50 mm of precipitation applied on an area of 1 m 2 during the course of ca 2 5 h each irrigation plot had a surface share of approximately 50 rock outcrop and 50 soil surface percolation properties were investigated by subsequent soil moisture measurements at high spatial resolution on vertical soil profiles on the irrigated plot dye tracer application on the rock outcrop during the sprinkling allowed for tracking of resulting outcrop runoff in the subsurface the soil depth survey included 2100 measurement points on 7 transects which allowed the estimation of local soil depth distribution results of the irrigation experiments showed that precipitation induced runoff from rock outcrops continued below ground as preferential flow along the rock soil interface while water from the soil surface percolated mainly vertically and much more homogeneously this was evident from the high density soil moisture measurements as well as from the dye tracer patterns outcrop runoff percolated faster and to greater depths than water infiltrating directly from the soil surface thus possessing a greater potential for groundwater recharge

role of epikarst in near surface hydrological processes in a soil mantled subtropical dolomite karst slope implications of field rainfall simulation experiments epikarst exerts a strong control on run off generation in karst regions but it is still unclear in karst regions our study aimed to demonstrate the effect of epikarst on near surface hydrological processes in a subtropical cockpit karst region of southwest china using plot scale rainfall simulation experiments with different rainfall intensities low and high and antecedent moisture conditions dry and wet a trench excavated to the epikarst lower boundary allowed identification of flow pathways in the entire soil epikarst architecture system thus facilitating the water balance calculations using a conceptual model with the assumption of a two stage hydrological evolution more than 70 of the total rainfall water moved vertically through the shallow soil layer and then was redistributed by the epikarst as subsurface flow occurring on the soil epikarst interface depression filling on epikarst surface water held by epikarst and deep percolation epikarst water regulation capacity defined as the sum of depression filling on epikarst surface water held by epikarst epikarst seepage flow and deep percolation was 58 mm wet antecedent condition and 223 mm dry antecedent condition total run off from the soil epikarst system was dominated by saturated subsurface flow showing a threshold process controlled by epikarst storage capacity storing as much as 181 mm of rainfall water under dry antecedent condition our study proved that despite the epikarst being relatively poorly developed and covered by a soil mantle it still exerted a strong influence on near surface hydrological processes and thus should be adequately considered in future modelling of water recharge and depletion dynamics in this integrated soil epikarst system copyright 2015 john wiley sons ltd

fracturing processes due to temperature and pressure nonlinear waves propagating in fluid saturated porous rocks a model is proposed of rock deformation fracturing in the subsurface of hydrothermal systems in response to deep fluid rock temperature and pore fluid pressure perturbations carried upward by hot and pressurized fluid fronts since during these episodes of unrest one also has to take into account that rock parameters can evolve a model of fluid diffusivity change as a function of pore fluid pressure is described through reformulating the linear thermoporoelastic equations rock deformation fracturing is thus thought of as being associated with migration of thermomechanical nonlinear waves which travel upward associated with an increase in concurrent fluid diffusivity on dynamical grounds it is assumed that on the boundary of the two superimposed horizons the overlying rock suddenly starts rupturing caused by the arrival of supercritical water from below which drives up a pore fluid pressure excess in this connection the purpose of this analysis is to investigate the general evolution of the subsurface pressure and temperature fields assuming that the original signal is itself strong enough to generate fracturing processes of the overburden rock on its arrival a general formulation provides evidence of nonlinear thermal waves compensated waves and residual pressure burgers waves that can be found for every value of the system parameters a mechanical analogy is also presented which is treated analytically and numerically allowing one to gain intuitive insight into such complex phenomena a characteristic of these nonlinear processes is that the resulting timescales of the order of years for the case of the campi flegrei and the izu peninsula can be particularly small corresponding to quick hyperthermal phenomena during the filtrating movement of fluid toward the earth s surface

spatial variability of saturated hydraulic conductivity in shallow macroporous soils in a forested basin field single ring infiltrometer and laboratory constant head parameter measurements of saturated hydraulic conductivity kh were used in combination to examine macropore effects on kh in shallow forest soils in a small basin in southern ontario canada soil matrix kh generally decreased with depth for hillslope podzols and stream valley gleysols differences in average maximum and minimum matrix kh were observed between soil types with lowest values occurring in the valley gleysols bulk profile kh assumed to include the effects of macropores had no apparent spatial pattern within a given soil type and mean bulk kh did not differ between soil types kh of macroporous soil was similar to matrix hydraulic conductivities for the porous hillslope podzols however it could be several orders of magnitude greater than the minimum matrix kh observed at a given site for the gleysols this difference increased with total profile thickness geostatistical analyses revealed anisotropic distributions of both bulk and matrix kh in the basin with the maximum and minimum directions of spatial correlation being parallel and normal to the stream valley respectively degree of anisotropy and scale of spatial dependence were lower for bulk kh relative to the minimum matrix kh values

mechanism for joint saturation in mechanically layered rocks an example from southern israel abstract over 700 joint spacings were measured along a 190 m scanline within a single limestone bed of the turonian gerofit formation southern israel by investigating joints belonging to a single systematic set confined to a bed of uniform thickness one can factor out the major influences of bed thickness lithology and mechanical properties on joint set development joint spacing distributions and fracture spacing ratios fsr vary dramatically along the length of the scanline and correlate directly with throughgoing fracture zones belonging to the same tectonic stress regime regions cross cut by fracture zones display narrower median joint spacings fsr of 1 3 and unimodal joint spacing distributions where fracture zones are absent joint spacings have wider medians fsr of 0 8 and multimodal distributions because fracture zones most likely represent areas of high strain and laboratory experiments demonstrate a systematic decrease in fracture spacing with increasing strain regions of the bed cross cut by fracture zones are likely at a more advanced stage of joint set development and hence closer to saturation than other regions joint saturation in the gerofit formation may be achieved by a shift in scale from single layer to multi layer jointing as the development of throughgoing joints prevents the formation of additional bedding confined joints

extensional failure and hydraulic valving at minas da panasqueira portugal evidence from vein spatial distributions displacements and geometries abstract at panasqueira portugal exceptional exposure and demonstrable vein connectivity allow robust characterisation of brittle elastic failure mechanisms in intrusive related environments extensional failure was driven by cycles of fluid injection hydraulic valving and vein growth under conditions with v 1 and differential stress

episodic fluid expulsion from geopressured sediments numerical simulation of fluid explusion from geopressured sediments using a one dimensional finite difference model shows that large volumes of fluid can be transported through a fractured seal during short lived 100 year expulsion events in this model abnormal fluid pressures are maintained by an impermeable seal when the fluid pressure exceeds 85 of the lithostatic pressure a vertical fracture opens in the seal providing a permeable pathway from the geopressured sediments into the overlying section fluid pressure in the seal decreases as fluid flows through the fracture closing the fracture as sediments in the seal compact once the fracture closes the seal remains impermeable until fluid flowing from deeper in the section increases fluid pressure to the fracture criteria a process that takes 10 000 500 000 years fractures emplaced in relatively incompressible seals such as compacted and or cemented sediments remain open for 20 50 years fluid fluxes through the seal integrated over the life of these events are 1 5 107 kg m2 and temperatures in the overlying sediments are increased by 5 20 c these temperature anomalies decay to less than half their original value in 300 years suggesting that the thermal anomalies observed in wells that are attributed to fluid expulsion formed in response to a very recent or currently active event

recent unrest 2002 2015 imaged by space geodesy at the highest risk chilean volcanoes villarrica llaima and calbuco southern andes abstract villarrica llaima and calbuco volcanoes are the most active and dangerous volcanoes in the southern andes and we use interferometric synthetic aperture radar insar observations from multiple satellites ers 2 envisat alos radarsat 2 cosmo skymed terrasar x sentinel 1a and alos 2 to constrain ground deformation that spans episodes of unrest and eruption at all three volcanoes between 2002 and 2015 we find episodes of ground deformation at each volcano which we invert using analytic elastic half space models to make some of the first geophysical inferences about the source depths of potential magma chambers at llaima we interpret that the vei 2 april 3 2009 eruption was preceded by 6 15 cm of precursory ground uplift one month before from a source 5 km below the surface on the western side of the edifice the vei 2 march 3 2015 villarrica eruption was followed by a short lived uplift of 5 cm in the se part of the volcano from a source depth of 6 km the vei 4 april 22 23 2015 calbuco eruption produced 12 cm of coeruptive subsidence from a source depth 8 11 km and offset 2 km s from the summit importantly we do not find clear evidence that the january 1 2008 the march 3 2015 and april 22 2015 eruptions at llaima villarrica and calbuco volcanoes were preceded by either transient or continuous ground uplift there are several possible explanations for the lack of precursory deformation at each volcano it is possible that any precursory deformation occurred only hours before the eruption e g at calbuco pre eruptive inflation was canceled by co eruptive subsidence as we inferred happened during the april 2009 llaima eruption the pre eruptive deformation was too small to be detectable in areas with persistent topography correlated phase delays pressurized source are deep or that open vent volcanoes like villarrica and llaima do not pressurize at all three volcanoes x and c band interferograms decorrelate in a few weeks due to vegetation snow and ice and have persistent atmospheric phase delays that we find cannot be reliably removed with available global weather models the low number of sar acquisitions therefore makes it challenging to reliably measure unaliased deformation we recommend a multi satellite observing strategy with short repeat periods frequently acquired high resolution digital elevation models and with acquisitions during every satellite overflight that may improve the temporal resolution of measurements

micromechanical modeling of cracking and failure in brittle rocks dynamic micromechanical models are used to analyze crack nucleation and propagation in brittle rock models of rock are created by bonding together thousands of individual particles at points of contact the feasibility of using these bonded particle models to reproduce rock mechanical behavior is explored by comparing model behavior to results from actual laboratory tests on different rock types the behavior of two granite models are examined in detail to study cracking and failure patterns that occur during compressional loading because discontinuum models are being used the rock models are free to crack and break apart under stress such that the micromechanics of cracking can be examined stress waves are allowed to propagate outward from each crack and it is shown that these dynamic waves significantly affect the rock behavior as the peak stress in the modeled rock is approached and many of the bonds are close to breaking a passing wave from a nearby crack is sufficient to break more bonds this causes clusters of cracks to be created and then eventual macroscopic shear failure occurs as these clusters connect to bisect the sample the failure patterns observed in the granite models are similar to those observed in actual laboratory tests

vertical variation of near saturated hydraulic conductivity in three soil profiles abstract hydraulic conductivity is an important parameter of water and solute transport in soils hydraulic conductivity is known to be highly variable in space but its dependence on soil horizonation has seldom been explored we measured the near saturated hydraulic conductivity of three soils located in the centre of france a neoluvisol a calcisol and a calcosol according to the referentiel pedologique using tension disc infiltrometry the reynolds and elrick s multipotential technique has been applied to the steady state infiltration kinetics measured at potentials 1 5 0 6 0 3 0 1 and 0 05 kpa to derive the hydraulic conductivity values each horizon of the three soil profiles has been characterised at least once at three locations 50 cm apart from each other on a flat surface prepared within the same access pit some horizons have been characterised on a second occasion in other access pits opened at nearly 10 m from the previous ones on average hydraulic conductivity values increased from 1 3 10 7 m s at 1 5 kpa to 2 5 10 6 m s at 0 3 kpa saturated hydraulic conductivity varied between 3 6 10 6 m s for the ploughed layer of the calcosol and 4 9 10 3 m s for the calcosol substrate c horizon the various horizons of the neoluvisol had hydraulic conductivity values which were not significantly different from each other except the ploughed layer which had lower hydraulic conductivity values than the underlying horizons the tilled layers of the calcisol and the calcosol also had lower hydraulic conductivity values than their respective underlying cambic horizons further the hydraulic conductivity of the tilled layer of the calcosol was lower than that of the tilled layers of the calcisol and the neoluvisol this difference was attributed to the effect of different tillage systems the calcosol being superficially tilled while the calcisol and neoluvisol were ploughed each year the structural s cambic horizons of the calcisol and calcosol had similar hydraulic conductivities but lower than their respective substrate limestone

effects of land use land cover and rainfall regimes on the surface runoff and soil loss on karst slopes in southwest china abstract surface runoff and soil loss from 2007 to 2010 related to land use and rainfall regimes in karst hill slopes in guizhou province southwest china were analyzed using the hierarchical clustering method sixty one rainfall events under the subtropical monsoon climate condition were classified into 5 types of rainfall regimes according to the depth maximum 30 min intensity and duration of rainfall in our study we first demonstrated that the amounts of surface runoff and soil loss on the karst hill slopes were very small compared to the non karst areas because the dual hydrological structure in the karst region including ground and underground drainage systems could influence the processes of rainfall recharge and runoff generation most rainfall water was transported underground through limestone fissures and fractures while little was in the form of surface runoff second the runoff and soil loss were affected by land use management and vegetation cover soil loss was intensified in a descending order to five types of land uses pastureland burned area cropland combination vegetation land young forestland third the runoff and soil loss exhibited remarkable variances among different rainfall regimes large runoff and soil loss were mainly created by heavy rainfall storms with a rainfall depth of more than 40 mm and a maximum 30 min rainfall intensity of over 30 mm h 1 in addition rainfall storms with large antecedent precipitations could also produce large runoff and soil loss these observations indicated that limestone fissures and fractures play important roles in surface runoff generation on karst limestone slopes due to their large storage capacity and high infiltration rate lastly the soil erosion risk in the karst pure limestone slope is quite high and should be paid particular attention especially in regards to over grazing because the soil loss created by a single heavy rainstorm in pastureland was 5 times the annual soil loss tolerance

rapid reinflation following the 2011 2012 rhyodacite eruption at cordon caulle volcano southern andes imaged by insar evidence for magma reservoir refill cordon caulle is a large fissural volcano that has erupted rhyodacitic magma of the same composition in its past three historical eruptions in 1921 1960 and 2011 2012 there was significant ground deformation observed before and during the 2011 2012 eruption here we use c and x band insar time series results to document post eruptive uplift up to 0 8 m between march 2012 and may 2015 with los rates up to 45 cm yr that have been largely aseismic along with subsidence in the 2011 2012 lava flow the 2012 uplift rate is one of the largest for silicic systems and was likely produced by the intrusion of 0 125 km3 of magma in the same tectonically controlled plumbing system that has been active during the historical eruptions nevertheless the uplift ended before the reservoir refilled with the erupted volume maybe due to a change in the pressure gradient produced by the 2011 2012 eruption

water source utilization by woody plants growing on dolomite outcrops and nearby soils during dry seasons in karst region of southwest china summary in the seasonally dry karst region of southwest china woodland vegetation is frequently associated with rocky outcrops we used stable isotope techniques to determine the water sources of two woody plant species the semideciduous tree rademachera sinica and the deciduous shrub alchornea trewioides across three surface types continuous and isolated dolomite outcrops as well as adjacent surfaces with soils main water sources for r sinica growing on the continuous outcrops shifted from deep water sources e g water in the saturated zone on march 23 2009 the late dry season of 2008 2009 to rainwater stored in rock fissures of the unsaturated zone on november 8 2009 the early dry season of 2009 2010 r sinica growing on nearby thin soils exhibited a similar shift of main water sources from deep water sources in the late dry season to shallow soil water 0 30 cm in the early dry season however they extracted deep water sources from the bottom of nearby outcrops rather than from deeper layers below the soil surface main water sources for r sinica growing on the isolated outcrops shifted from previous one to two months ago rainwater in the late dry season to the mixture of recent within the last one month and previous rainwater in the early dry season while using little or no deep water sources in contrast a trewioides growing on these two kinds of outcrops always relied on recent rainwater while those growing on soils always relied on shallow soil water the shift of water sources for tree species especially those growing on continuous rock outcrops and nearby soils may allow them to maintain normal transpiration throughout the year which increases the amount of evapotranspiration in the watershed and further enhances the water storage capacity of the study area

rock deformation and fracturing processes due to nonlinear shock waves propagating in hyperthermal fluid pressurized domains an analytical model for rock deformation and fracturing processes due to nonlinear waves of temperature and pressure and evolving with particularly large velocities in a fluid saturated rock over a hyperthermal aquifer is here discussed as in classical studies by rice and cleary 1976 mctigue 1986 and also bonafede 1991 and natale and salusti 1996 the upper fluid saturated matrix is considered homogeneous thermoelastic and isotropic in a one dimensional formulation as regards the nonlinear wave generation mechanism at the boundary between the two horizons the hot fluid from below is forced upward by a pressure gradient thus giving rise to strong pressure and temperature perturbations in such a context in order to schematize wave induced rock deformation and fracturing processes we assume a continuous temperature and pressure dependence of model parameters such as fluid diffusivity and thermal expansivity of the rock and fluid the solution we obtain is a strong shock wave corresponding to nonlinear fluid migration mechanisms in turn enhanced by the flow through the induced fractures in the overlying rock it has to be stressed that once such a process starts off it may be amplified and also may produce rather catastrophic behavior in the natural system this model essentially provides a theoretical tool for interpreting such geophysical effects in particular for volcanic complexes such as the rabaul caldera long valley caldera campi flegrei the island of vulcano or similar kinds of geological system

spatial variability of surface soil saturated hydraulic conductivity in a small karst catchment of southwest china soil saturated hydraulic conductivity ks is one of the most important parameters that determine soil water redistribution however it is little known in a karst area with thin discontinuous and rocky soils the purpose of this paper was to investigate the spatial variability of ks and its influencing factors in a small karst catchment with high heterogeneity in southwest china undisturbed surface 0 10 cm soil samples were collected with metal cylinders from an 80 m 80 m grid for measuring ks bulk density b non capillary porosity ncp and capillary porosity cp disturbed surface samples were taken with a shovel to measure soil organic carbon soc and rock fragment content rc environmental factors including topographical location slope and depression land use type forestland shrubland shrub grassland and farmland slope gradient slope exposure and elevation were investigated for each sampling point the results showed that ks value was relatively high 9 10 m d with a moderate variation and had a strong spatial dependence nugget sill value 0 06 ncp showed a very significantly p 0 05 but their interaction effects were significant this suggested that the influencing factors were more complex and they should be considered together in a karst area the mean ks value was the lowest in the forestland on the hillslope and in the farmland in the depression indicating where the surface runoff may appear easily such results could help to better understand the soil hydrological processes and contribute to the building of hydrological models in small karst catchments

spatial distribution of rock fragments on steep hillslopes in karst region of northwest guangxi china abstract rock fragments 5 mm in diameter at the soil surface and within the topsoil have a large effect on the intensity of various hydrologic and geomorphic processes however little information is available on the spatial distribution of rock fragments in subtropical regions the objective of this paper was to investigate the relationship between the spatial distribution of rock fragments and landforms on two different steep karst hillslopes in northwest guangxi southwest china on the first hillslope a disintegrated landslide failure with the presence of several large rock outcrops 2 m in height the spatial distribution of rock fragment cover had no obvious relationship with topographic position except that the mean cover percentage of small rock fragments 5 20 mm decreased from bottom to top on the second hillslope an avalanche slope without the presence of large rock outcrops the mean total rock fragment cover 5 600 mm increased from bottom 5 to top 21 with decreasing variability and rock fragments with various sizes 5 20 20 75 and 75 250 mm showed a similar increasing trend the mean total rock fragment cover increased linearly with slope gradient on the second hillslope and tended to increase and then decrease with gradient but their relationship was not obvious on the first hillslope this indicated that the spatial distribution of surface rock fragment cover had a close relationship with the presence of large rock outcrops and slope gradient however the median diameter d50 of the surface rock fragments had an increase decrease trend with slope gradient but there was no obvious relationship on both hillslopes with low overland flow therefore the dominant factor for the spatial distribution of rock fragment cover and size at the soil surface might not be soil erosion by water but slope gradient vegetation and geomorphologic condition of the slope the mean total volumetric rock fragment content 5 250 mm within the topsoil 10 20 cm thick increased linearly from bottom 16 to top 39 with slope gradient on the first hillslope and had a logarithmic increase from bottom 10 to top 27 with gradient on the second hillslope this suggested that rock fragment content within the topsoil was mostly controlled by slope gradient and topographic positions and had not a close relationship with the presence of large rock outcrops

the effect of vegetation on infiltration in shallow soils underlain by fissured bedrock abstract mean annual infiltration above the high level waste repository proposed to be sited at yucca mountain nevada has a large impact on assessments of repository performance ongoing investigations of infiltration processes have identified the relatively horizontal caprock environment above portions of the repository as a potentially large source of infiltrating waters due to shallow permeable soils above a moderately welded tuff with large soil filled fissures the combination of shallow soils and fissured bedrock allows rapid penetration of wetting pulses to below the rooting zone plant uptake can strongly reduce net infiltration in arid environments with high water storage capacity and despite the low water storage capacity there is a relatively high vegetation density in this environment the apparent discrepancy between high vegetation density and low water storage motivates the study of plant hydrologic interactions in this semiarid environment field observations were coupled with plant and landscape scale models to provide insight into plant hydrologic interactions several lines of evidence including i linear plant growth features observed on aerial photographs ii comparisons of plant cover within the fissured environment and comparable environments lacking fissures and iii direct excavations all suggest that the widely spaced soil filled fissures are conducive to plant growth even when fissures are buried at soil depths exceeding 30 cm results from a mechanistic simulation model for root growth into fissures suggest that the additional sheltered plant available soil water within fissures provides a competitive advantage for plant establishment therefore plants that germinate above a fissure are more likely to survive in turn developing linear features above fissures having established that plants preferentially root within soil filled fissures in the caprock environment a set of simulations were performed to examine the hydrologic consequence of plant roots within fissures at the landscape scale the response to three rainfall amounts was simulated for the largest storm fluxes at the fissure bottom peaked at 1 4 weeks after the storm when plant uptake was not active but were eliminated when fissures had active vegetation when plants were active within a fissure uptake eliminated net infiltration in the fissure regardless of the size of the storm two plant related mechanisms reduced total flux through the plant filled fissures i transpiration during fissure flow and ii wetting pulse retardation due to drier fissures prior to rain the first mechanism appears to be dominant in these simulations results suggest that transpiration may strongly limit net infiltration i e total deep percolation flux escaping the plant root zone significant infiltration can occur however when plants are dormant so that most infiltration would be expected to occur during winter