the effect of hydrogeological conditions on variability and dynamic of groundwater recharge in a carbonate aquifer at local scale summary groundwater recharge in fractured karstic aquifers is particularly difficult to quantify due to the rock mass s heterogeneity and complexity that include preferential flow paths along karst conduits the present study s major goals were to assess how the changes in lithology as well as the fractured karst systems influence the flow mechanism in the unsaturated zone and to define the spatial variation of the groundwater recharge at local scale the study area is located within the fractured carbonate western mountain aquifer yarkon taninim west of the city of jerusalem at the ein karem ek production well field field monitoring included groundwater level observations in nine locations in the study area during years 1990 2014 the measured groundwater level series were analyzed with the aid of one dimensional dual permeability numerical model of water flow in variably saturated fractured porous media which was calibrated and used to estimate groundwater recharge at nine locations the recharge values exhibit significant spatial and temporal variation with mean and standard deviation values of 216 and 113 mm year respectively based on simulations relationships were established between precipitation and groundwater recharge in each of the nine studied sites and compared with similar ones obtained in earlier regional studies simulations show that fast and slow flow paths conditions also influence annual cumulative groundwater recharge dynamic in areas where fast flow paths exist most of the groundwater recharge occurs during the rainy season 60 80 from the total recharge for the tested years while in locations with slow flow path conditions the recharge rate stays relatively constant with a close to linear pattern and continues during summer

catchment scale surface water groundwater connectivity on china s loess plateau abstract thick loess deposits up to 200 m deep and a large unsaturated zone up to 100 m below the soil surface complicate the interactions between surface water and groundwater in china s loess plateau especially in catchments characterized by tableland gully topography in this region in the heihe watershed electrical conductivity ec chloride cl concentrations and stable water isotope data d and 18 o obtained during dry and wet seasons in the period of 2012 2014 are used to determine the relationship between surface water and groundwater ec and cl concentrations are found to be unsuitable for analyzing the relationship between surface water and groundwater in this watershed due to the impacts of chemical weathering the stable water isotope data indicate a gaining surface water system i e groundwater and gully runoff both recharge streamflow further groundwater appears to dominate the hydrologic cycle in the watershed therefore water resources management on china s loess plateau should pay more attentions to groundwater protection

some comparisons between mining induced and laboratory earthquakes although laboratory stick slip friction experiments have long been regarded as analogs to natural crustal earthquakes the potential use of laboratory results for understanding the earthquake source mechanism has not been fully exploited because of essential difficulties in relating seismographic data to measurements made in the controlled laboratory environment mining induced earthquakes however provide a means of calibrating the seismic data in terms of laboratory results because in contrast to natural earthquakes the causative forces as well as the hypocentral conditions are known a comparison of stick slip friction events in a large granite sample with mining induced earthquakes in south africa and canada indicates both similarities and differences between the two phenomena the physics of unstable fault slip appears to be largely the same for both types of events for example both laboratory and mining induced earthquakes have very low seismic efficiencies eta tau a bar tau where a is the apparent stress and bar tau is the average stress acting on the fault plane to cause slip nearly all of the energy released by faulting is consumed in overcoming friction in more detail the mining induced earthquakes differ from the laboratory events in the behavior of as a function of seismic momentm0 whereas for the laboratory events 0 06 independent ofm0 depends quite strongly onm0 for each set of induced earthquakes with 0 06 serving apparently as an upper bound it seems most likely that this observed scaling difference is due to variations in slip distribution over the fault plane in the laboratory a stick slip event entails homogeneous slip over a fault of fixed area for each set of induced earthquakes the fault area appears to be approximately fixed but the slip is inhomogeneous due presumably to barriers zones of no slip distributed over the fault plane at constant bar tau larger events correspond to larger a as a consequence of fewer barriers to slip if the inequality a bar tau 0 06 has general validity then measurements of a ea m0 where is the modulus of rigidity andea is the seismically radiated energy can be used to infer the absolute level of deviatoric stress at the hypocenter

dynamic modeling of slow slip coupled with tremor 1 we theoretically study the generation mechanism of slow slip in a dynamical framework assuming a fault in a fluid saturated thermoporoelastic medium the fluid flow is taken into consideration dynamic slip is assumed to create pores and cause shear heating on the fault key parameters in the modeling are su and su the nondimensional parameter su represents the relative dominance of the effect of pore creation on the fluid pressure change over that of shear heating while su is associated with the dominance of fluid flow effect over the effect of shear heating our calculation shows that we have to assume su 1 and relatively small values for su to simulate rupture speed that is negligibly small compared to the shear wave velocity although this was also found in our former paper our new finding here is the simulation of slow slip coupled with tremor we find that frozen slip is reactivated sporadically because the fluid inflow triggered by the pore creation elevates the fluid pressure on the fault the slip reactivation actually occurs if su is smaller than a threshold such sporadic reactivation of slips can be a model for slow slip coupled with tremor we also show that the moment evolution curves are categorized into two separate groups when su 0 1 one of them represents slow slips while the other represents ordinary earthquakes

a model to simulate recharge processes of karst massifs the recharge processes have been evaluated for two karst massifs of southern italy the mt terminio and mt cervialto characterized by wide endorheic areas the annual mean recharge has been estimated by geographic information system gis tools from regression of annual mean values of different ground elevated rain gauges and thermometers the recharge has been distinguished for endorheic areas and the other areas of spring catchment and the ratio between the output spring and input rainfall has been also estimated recharge coefficient the annual recharge has been used to calibrate a daily scale model which allows to estimate the amount of effective rainfall which is retained as soil moisture the amount reaching the water table recharge s s and the amount of rainfall which develops the runoff and leaves the catchment all these amounts vary through the hydrological year in function of soil moisture deficit and daily rainfall intensity the model allows estimating the recharge conditions through the hydrological year and it is a useful tool for water management copyright 2014 john wiley sons ltd

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

use of s wave attenuation from perforation shots to map the growth of the stimulated reservoir volume in the marcellus gas shale abstract water filled fractures stimulated by hydraulic fracturing will severely attenuate s waves by comparing the p and s wave amplitudes generated from perforation shots in the marcellus gas shale one can infer the existence and constrain the location of stimulated hydraulic fractures the waveforms of the perforation shots in unstimulated gas shale are first analyzed to define the prestimulation radiation pattern then the change of perforation shot s wave waveform is examined for information about the development of hydraulic fractures s wave attenuation validates the existence of offstage hydraulic fractures and the invasion of treatment fluid from another neighbor stage this method might have potential use in designing an active seismic survey to more effectively monitor hydraulic fracture stimulation beyond the current microseismic mapping techniques

groundwater storage changes in the tibetan plateau and adjacent areas revealed from grace satellite gravity data abstract understanding groundwater storage gws changes is vital to the utilization and control of water resources in the tibetan plateau however well level observations are rare in this big area and reliable hydrology models including gws are not available we use hydro geodesy to quantitate gws changes in the tibetan plateau and surroundings from 2003 to 2009 using a combined analysis of satellite gravity and satellite altimetry data hydrology models as well as a model of glacial isostatic adjustment gia release 5 grace gravity data are jointly used in a mascon fitting method to estimate the terrestrial water storage tws changes during the period from which the hydrology contributions and the gia effects are effectively deducted to give the estimates of gws changes for 12 selected regions of interest the hydrology contributions are carefully calculated from glaciers and lakes by icesat 1 satellite altimetry data permafrost degradation by an active layer depth ald model soil moisture and snow water equivalent by multiple hydrology models and the gia effects are calculated with the new ice 6g c vm5a model taking into account the measurement errors and the variability of the models the uncertainties are rigorously estimated for the tws changes the hydrology contributions including gws changes and the gia effect for the first time we show explicitly separated gws changes in the tibetan plateau and adjacent areas except for those to the south of the himalayas we find increasing trend rates for eight basins 2 46 2 24 gt yr for the jinsha river basin 1 77 2 09 gt yr for the nujiang lancangjiang rivers source region 1 86 1 69 gt yr for the yangtze river source region 1 14 1 39 gt yr for the yellow river source region 1 52 0 95 gt yr for the qaidam basin 1 66 1 52 gt yr for the central qiangtang nature reserve 5 37 2 17 gt yr for the upper indus basin and 2 77 0 99 gt yr for the aksu river basin all these increasing trends are most likely caused by increased runoff recharges from melt water and or precipitation in the surroundings we also find that the administrative actions such as the chinese ecological protection and construction project help to store more groundwater in the three rivers source region and suggest that seepages from the endorheic basin to the west of it are a possible source for gws increase in this region in addition our estimates for gws changes basically confirm previous results along afghanistan pakistan north india and bangladesh and clearly reflect the excessive use of groundwater our results will benefit the water resource management in the study area and are of particular significance for the ecological restoration in the tibetan plateau

dynamic modeling of slow earthquakes based on thermoporoelastic effects and inelastic generation of pores 1 we numerically simulate features of slow earthquakes to understand their generation mechanism in the framework of dynamic modeling their typical features will be that the fault rupture velocity and stress drop are markedly lower than those of ordinary earthquakes we assume a fault in a thermoporoelastic medium taking account of fluid flow and inelastic creation of pores on the fault this paper is an extension of our studies published in the work of suzuki and yamashita 2006 2007 2008 in which a nondimensional parameter su was shown to play a critical role in dynamic fault rupture the parameter su represents the dominance of the effect of inelastic pore creation over that of frictional heating under the condition of no fluid flow however it can be shown that su plays an important role even if the fluid flow is considered in the present study we successfully simulate slow fault rupture growth and low stress drop which characterize the slow earthquakes critical ingredients of our modeling are assumptions of 1 su considerably larger than assumed for the simulation of ordinary earthquakes 2 fluid flow into the inelastically created pores and 3 initial shear stress significantly smaller than assumed for the simulation of ordinary earthquakes the assumption of a large value of su corresponds to that of a slip resistant and low stress drop zone the fluid inflow can promote the fault rupture in the slip resistant zone

understanding of slip weakening and strengthening in a single framework of modeling and its seismological implications 1 we theoretically study dynamic fault slip taking account of thermoporoelastic effects including inelastic porosity change the porosity on the fault is assumed to increase inelastically with increasing fault slip we find in the analysis of a 1d fault model that qualitative nature of system behavior is controlled by a single nondimensional parameter su a quantity proportional to the increase rate of inelastic porosity divided by the thickness of shear heating zone the change of value of su is found to cause slip weakening as well as slip strengthening it is reported in some studies that the radiation efficiency estimated seismologically exceeds unity for some earthquakes which contradicts its definition this paradox can be solved if we assume a relatively large su value for these earthquakes

fracture controlled fluid circulation and dissolutional weathering in sinkhole prone carbonate rocks from central italy abstract fractures karstic cavities and calcite precipitates are analysed on mesozoic carbonate strata from the cornicolani mountains central italy to quantify the relationships between fractures and related karstic cavities and to infer the fracture controlled fluid pathways the study area is characterized by active sinkholes and other karstic caves which are among the deepest ones in the world results show a clear control of fractures on the process of dissolutional weathering and therefore on the fluid circulation a model is proposed in which two different modes of dissolutional weathering coexist i a mode of diffuse weathering consisting in the dissolutional enlargement of closely spaced joints and bedding surfaces this process affects the strata situated at depths of up to 5 m ii a mode of more concentrated weathering active along highly permeable fault damage zones at depths of at least 70 m these processes are mostly connected with the shallow circulation of calcite dissolving meteoric waters and are controlled by the disparity of permeability between the fault damage zones and the surrounding jointed strata some calcite precipitates along the studied fault damage zones may be connected with a dissolutional process operated by waters that interacted with the adjacent quiescent volcanic district such calcite dissolving waters and the presence of high permeable fault damage zones along which the waters may ascent are probably the cause for the development of some of the deep sinkholes along faults in the study area

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

bacteria biomass and carbonic anhydrase activity in some karst areas of southwest china abstract to determine the role of microbes in karst processes it is necessary to investigate the ecological distribution and characteristics of soil microorganisms in karst areas in this paper a preliminary study was carried out in two different karst areas of southwest china nongla and the guilin yaji karst experimental site guangxi soil samples from 10 20 cm in depth were analyzed for the number of bacteria and the predominant bacteria were identified analysis showed that the amount of soil bacteria correlated highly with characteristics of the karst ecosystems including their different geochemical environments and vegetation the predominance of azotobacteraceae colonies showed that the soil fertility of both types of karst areas may be improving also the origin of carbonic anhydrase ca which could accelerate karst processes was explored the ca producing bacteria were screened and activities of extracellular and intracellular ca were measured obvious differences existed in intracellular and extracellular ca activities of soil bacteria between the two karst ecosystems with different vegetation conditions this suggests that the activity of ca from soil bacteria in the two different karst areas was also correlated with karst ecosystem characteristics including their different geochemical environments and vegetation features

geologic influence on groundwater salinity drives large seawater circulation through the continental shelf observations of offshore freshened groundwater and saline groundwater discharge along continental shelves have important implications for water resources ecosystem function and the composition of the ocean but they cannot be explained by basic theory we show that these independent observations are linked and result from processes that drive variable density groundwater flow through the spatial heterogeneity that is ubiquitous in geologic formations we use lithologic data to develop geostatistical models that mimic the architecture of coastal aquifers simulation of groundwater flow and salt transport through these random realizations shows that heterogeneity produces spatially complex subsurface salinity distributions that extend tens of kilometers offshore even at steady state the associated density gradients drive high saline groundwater circulation rates that cannot be predicted by equivalent homogeneous models results suggest that these phenomena may be common along continental shelves potentially altering estimates of ocean chemical budgets and impacting coastal water management for future generations

the seismic efficiency of the 1999 chi chi taiwan earthquake 1 on september 20 1999 the ms7 6 chi chi earthquake ruptured the chelungpu fault in central taiwan in this work the seismic efficiency which is the ratio of seismic radiation energy es to strained energy e of the earthquake is estimated the value of e estimated from the slip distribution inferred by dominguez et al 2003 is 3 208 1024 ergs based on this value the calculated from es measured from near field seismograms and from near field and teleseismic data are 0 137 and 0 262 respectively the two values do not seem to agree with the 0 06 hypothesis proposed by mcgarr 1994 from the es calculated from two es ms laws 0 049 and 0 019 which fit the hypothesis however the two laws could underestimate es

detecting the flow relationships between deep and shallow aquifers in an exploited groundwater system using long term monitoring data and quantitative hydrogeology the acque albule basin case rome italy five years of hydrogeological monitoring and field activities performed in the complex hydrogeological system of the acque albule basin aab were conducted to define the hydrogeological setting the relationship between deep and shallow aquifers and a conceptual groundwater flow model of this exploited area using conventional quantitative techniques the basin which is located close to rome italy on the west side of the apennine chain and just north of the colli albani volcano subsided after development of a north south fault system about 115 000 y bp the aab experiences intense hydrothermal activity which has produced a large travertine deposit 80 m thick the travertine deposit constitutes a fractured aquifer that is the final destination of more than 5 m3 s 1 of water and is strongly dewatered by quarry activities the complex hydrogeology of this basin was investigated revealing two main hydraulically connected aquifers one thermalised and partly confined into the limestone bedrock and one unconfined in the travertine the two aquifers are separated by a non continuous clayey aquiclude the hydrogeological survey and geological characterisation contributed to the development of the groundwater flow conceptual model analysis and comparison of the monitored levels highlighted the pattern of flow between the deep and shallow parts of the flow system copyright 2012 john wiley sons ltd

fluid transport properties in sediments and their role in large slip near the surface of the plate boundary fault in the japan trench abstract fluid transport properties such as permeability and porosity are significant parameters that affect earthquake generation we measured the transport properties of shallow sediments sampled around the plate boundary near the japan trench during iodp expedition 343 at confining pressures up to 40 mpa the permeabilities of samples from the shallow plate boundary fault were very low at 10 20 m 2 equivalent to a hydraulic diffusivity of 10 10 m 2 s 1 permeability and porosity in the core of the fault zone at the plate boundary were lower than those in the immediately overlying sediments and the surrounding intact sediment suggesting that the plate boundary fault can act as a barrier for fluid flow low permeability and high pore compressibility in the shallow plate boundary fault create a strong potential for dynamic fault weakening due to fluid pressurization with frictional heating even when the initial shear stress is low our investigation supports the hypothesis that thermal pressurization on the fault plane helped facilitate the extremely large slip in the shallow part of the subduction zone during the tohoku earthquake as the fault zone has a lower permeability than the surrounding sediments and a higher clay content pore pressure generation at depth by dehydration of clay minerals can explain formation of the shallow strong patch on the fault more reasonably than continuous fluid influx from the subducting oceanic crust which does not affect pore pressure at depth in the fault zone although there are many possible mechanisms of fault weakening thermal pressurization can act relatively efficiently as slip begins even at shallow depths therefore our results support the role of thermal pressurization in shallow slip during the tohoku earthquake

influence of pyroclastic soil on epikarst formation a test study in southern italy terra nova 00 1 6 2010 abstract epikarst formation in the southern apennines italy was hypothesized to be significantly influenced by diffuse rainwater infiltration through soil of pyroclastic origin multidisciplinary investigations were carried out at an experimental field site to test this hypothesis at this site other factors influencing epikarst formation can be assumed invariant a direct relationship was observed between soil thickness and epikarst thickness this relationship supports the hypothesis that the pyroclastic soil plays a significant role in governing epikarst evolution and thickening the sandy loam texture and the high hydraulic conductivity of the soil allow easy rainwater infiltration therefore causing a diffuse interaction between percolation water and the soil medium and spatially homogeneous recharge within the aquifer system the soil contains a large accumulation of organic carbon and considerable co2 production results from the activity of autochthonous microorganisms belonging to different genera

unusual behaviour of epikarst in the acqua dei faggi carbonate aquifer southern italy hydrogeological and geophysical investigations demonstrated the existence of an epikarstic zone in a carbonate aquifer of southern italy about 10 m thick nevertheless the hydrogeological behaviour of the epikarst is different from that schematized by several authors in the test site the contrast in permeability at the bottom of the epikarst does not cause retention of percolation and storage of water in a perched temporary aquifer within the uppermost portion of the carbonate medium because of the high fracture density and good interconnection of openings within the underlying limestone the percolation is diffuse also below the epikarstic zone as well as the groundwater flow the funnelling effect into larger shafts does not play an important role on the hydrogeological behaviour of the aquifer

rupture dynamics with energy loss outside the slip zone 1 energy loss in a fault damage zone outside the slip zone contributes to the fracture energy that determines rupture velocity of an earthquake a nonelastic two dimensional dynamic calculation is done in which the slip zone is modeled as a fault plane and material off the fault is subject to a coulomb yield condition in a mode 2 crack like solution in which an abrupt uniform drop of shear traction on the fault spreads from a point coulomb yielding occurs on the extensional side of the fault plastic strain is distributed with uniform magnitude along the fault and it has a thickness normal to the fault proportional to propagation distance energy loss off the fault is also proportional to propagation distance and it can become much larger than energy loss on the fault specified by the fault constitutive relation the slip velocity function could be produced in an equivalent elastic problem by a slip weakening friction law with breakdown slip dc increasing with distance fracture energy g and equivalent dc will be different in ruptures with different initiation points and stress drops so they are not constitutive properties they are determined by the dynamic solution that arrives at a particular point peak slip velocity is however a property of a fault location nonelastic response can be mimicked by imposing a limit on slip velocity on a fault in an elastic medium

modeling the influence of epikarst evolution on karst aquifer genesis a time variant recharge boundary condition for joint karst epikarst development 1 the epikarst a zone of increased weathering near the land surface determines the distribution of recharge to a karst aquifer in both space and time it links climatic and near surface geological conditions with the karstification of a limestone aquifer defining both the hydraulic and the chemical boundary conditions for the development of the karst system realistic modeling of the epikarst is therefore a prerequisite for the simulation of karst aquifer genesis a conceptual model of the joint karst epikarst evolution is presented in this paper an epikarst module is developed and implemented in a numerical continuum discrete conduit flow model for karst genesis which accounts for the joint evolution of the epikarst and the main karstic conduit network under unconfined conditions the influence of epikarst genesis on the evolution of the underlying karst aquifer is investigated in four scenarios it is found that only the interaction of epikarst and initial heterogeneity in the underlying carbonate rock leads to the development of a dendritic cave system if no heterogeneity in the initial conduit network or in the recharge distribution is included maze type caves develop

nonlinear effects of temperature fluid pressure and inelastic porosity on dynamic fault slip and fault tip propagation emergence of slip strengthening and pulse like fault slip 1 we theoretically study dynamic faulting taking account of thermoporoelastic effects including inelastic porosity change the porosity is assumed to increase with increasing fault slip we first derive the analytical solutions for the changes of fluid pressure temperature and fault slip assuming 1 d fault model as found in our previous study the evolution of these quantities is controlled by a single nondimensional parameter su a quantity proportional to the rate of increase in inelastic porosity multiplied by the thickness of shear heating zone if we assume that temperature elevation remains below the melting temperature of fault rocks su is found be close to zero or greater than unity our 2 d simulation shows that pulse like slip appears when su is greater than unity which is a necessary consequence of the emergence of slip strengthening while slip weakening caused by thermal pressurization arises when su is close to zero the applied shear stress is entirely released when su is close to zero while it is released only partially when su is greater than unity so that the latter will be more reasonable according to seismological observations the fault tip stress increases significantly with the fault extension in classical singular fault model in contrast the fault tip stress is only weakly dependent on the size of extending fault in our model when su is greater than unity so that the fault growth is more vulnerable to spatial perturbation of model parameters our present study indicates the importance of slip strengthening for the understanding of dynamic faulting

microseismicity beyond dots in a box introduction this special section of geophysics is a consequence of a very successful seg workshop titled microseismicity beyond dots in a box the workshop was held 22 october 2010 following the seg annual meeting that was held in denver more than 120 people attended the meeting and nine oral papers and 22 posters were presented small microseismic events or acoustic emissions occur naturally and a result of anthropogenic influences in reservoirs sudden stress release leads to elastic rock failure which serves as an effective seismic source these microearthquakes may be the result of production or hydraulic stimulation but they also may be a consequence of natural tectonic activity they are usually detectable using only sensitive sensors and after careful data processing such passive seismic monitoring has been used in mining settings for more than 100 years but its application in petroleum setting is relatively new as such it is a rapidly advancing field of technology where the challenges are manifold and span issues associated with data acquisition processing and interpretation much can be learned from methods and case studies developed for microseismic monitoring in volcanological geothermal and mining settings but one of the key advantages in oilfield monitoring is that a great deal is ordinarily already known about the reservoir comparatively good velocity models exist and production or injection information is available the same is obviously not true for a volcano the microearthquake or microseismic event location is useful in itself clusters of events delineate faults and fracturing highlighting reactivation or the generation of new zones of failure this has been very effective in helping assess the efficacy of hydraulic stimulation i e frac monitoring longer term monitoring will no doubt provide an early warning system for detecting top seal leakage and fault reactivation in co 2 sequestration projects for example until

nonlinear thermoporoelastic effects on dynamic earthquake rupture 1 in this study we theoretically examine thermohydraulic effects on dynamic earthquake rupture we first derive the system of governing equations assuming a thermoporoelastic medium and then conduct numerical calculations based on these equations nonlinear feedback between changes in temperature fluid pressure and fault slip are shown to play an important role in rupture dynamics for example these feedbacks produce a longer duration of fault slip than that predicted by the classical griffith crack model assumed in an elastic medium deviation of our results from those of the griffith crack model increases with increased thickness of the heated fault zone the feedback effects also produce slip weakening behavior and gradual slip onset the slip weakening distance increases with increased rate of fluid outflow from the heated fault zone our simulations demonstrate that smaller events record smaller static stress drops consistent with seismological observations this relationship occurs because ongoing fault slip tends to result in increased fluid pressure our simulations also indicate that scaling relationships between small and large earthquakes are complicated by thermohydraulic effects

cohesive strengthening of fault zones during the interseismic period an experimental study 1 there is widespread evidence indicating that faults regain a portion of their strength during the interseismic period here we present experiments designed to understand and quantify the interseismic cohesive strengthening resulting from fluid rock reactions in fault zones the triaxial experiments consisted of fracturing cores of fontainebleau sandstone under dry conditions forming a localized shear failure zone stage 1 the specimens were then reacted hydrothermally under isostatic conditions allowing the fault damage zone to compact consolidate and strengthen stage 2 following reaction the specimens were then reloaded to failure under nominally dry conditions so that the increase in cohesive strength of the fault could be measured stage 3 experiments show that cohesion increase is positively correlated to temperature and pore pressure during reaction after 6 hours of reaction at the highest temperatures 927 c and pore pressures 200 mpa cohesion increases by as much as 35 mpa microstructural examination of the specimens showed that the gouge particles within the fault compacted and cemented together exhibiting textures typical of pressure solution and that fractures in the surrounding damage zone had healed a theoretical treatment of the data was conducted using these experiments in combination with results on time dependent changes in fault cohesion presented by tenthorey et al 2003 we find that the rate controlling process in our experiments has an activation energy q of approximately 70 kj mol 1 we use this information to develop a model for time dependent cohesive strengthening in fault zones within the continental seismogenic regime we conclude that significant cohesive strengthening of fault zones can occur during the interseismic period of medium to large earthquakes given the presence of reactive pore fluids

fluidization and melting of fault gouge during seismic slip identification in the nojima fault zone and implications for focal earthquake mechanisms 1 the record of physical processes that occur during seismic slip events is well preserved in fault rocks from the active nojima fault in japan the fault rocks formed at about 3 km depth and comprise thin alternating layers of very fine gouge and pseudotachylyte derived from granite each layer is thinner than a few millimeters and corresponds to one seismic slip event the very thin slip zone width suggests that some mechanisms of slip weakening operated and our studies of the fault rocks suggest that fluidization and melting of gouge were particularly important fluidized and nonfluidized gouges were distinguished using the detection probability of fragmented counterparts method it is known from granular material science that the phase transition from a grain friction regime to fluidization of granular materials can occur only by a very small decrease in volume fraction of solid grains once fluidization occurs the frictional resistance decreases abruptly to nearly zero even before thermal pressurization reaches its extreme state when fault gouge is melted frictional resistance is governed by the viscosity of melt which depends mainly on temperature chemical composition h2o concentration and the volume fraction of unmelted grains for each pseudotachylyte layer we estimated the temperature of melt using various temperature indices and measured volume fraction of unmelted grains we synthesized these data to reconstruct the change in viscosity during seismic slip events the melt viscosity is very high 107 9 pas during initial melting due to the combined effect of low temperature 750 800 c and large volume fraction of solid grains thus seismic slip is inevitably restrained instantaneously once this mechanical barrier is overcome the viscosity reduces continuously and dramatically as slip increases at 1000 c the viscosity reduces to 104pas and eventually to 10pas at 1280 c thus stress drops almost completely and rupturing tends to run away

snowmelt infiltration and storage within a karstic environment vers chez le brandt switzerland summary even though karstic aquifers are important freshwater resources and frequently occur in mountainous areas recharge processes related to snowmelt have received little attention thus far given the context of climate change where alterations to seasonal snow patterns are anticipated and the often strong coupling between recharge and discharge in karst aquifers this research area is of great importance therefore we investigated how snowmelt water transits through the vadose and phreatic zone of a karst aquifer this was accomplished by evaluating the relationships between meteorological data soil water content vadose zone flow in a cave 53 m below ground and aquifer discharge time series data indicate that the quantity and duration of meltwater input at the soil surface influences flow and storage within the soil and epikarst prolonged periods of snowmelt promote perched storage in surficial soils and encourage surficial lateral flow to preferential flow paths thus in karstic watersheds overlain by crystalline loess a typical pedologic and lithologic pairing in central europe and parts of north america soils can serve as the dominant mechanism impeding infiltration and promoting shallow lateral flow further hydrograph analysis of vadose zone flow and aquifer discharge suggests that storage associated with shallow soils is the dominant source of discharge at time scales of up to several weeks after melt events while phreatic storage becomes import during prolonged periods without input soils can moderate karst aquifer dynamics and play a more governing role on karst aquifer storage and discharge than previously credited overall this signifies that a fundamental understanding of soil structure and distribution is critical when assessing recharge to karstic aquifers particularly in cold regions

strike slip fault propagation cleavage in carbonate rocks the mattinata fault zone southern apennines italy disjunctive spaced solution cleavage in carbonate rocks is genetically associated with the propagation of the left lateral strike slip mattinata fault in the gargano promontory italy typical cleavage development is restricted within the 200 300 mwide fault zone which is bounded by virtually unfractured wall rocks the cleavage consists of sub parallel solution surfaces which are often reactivated as sheared solution planes geometrical and kinematic relationships exist between the fault and the associated cleavage planes thus 1 cleavage fault intersection lines lie parallel to the fault and the sheared cleavage rotational axes and 2 the cleavage fault angle is almost constantly equal to 408 a model for the development of the mattinata fault is proposed in which the cleavage surfaces are interpreted as fault propagation deformations cleavage nucleates as solution planes at the front of the advancing fault as the result of stress concentration in this region two distinct time sequential processes are shown to operate during the fault propagation 1 typical millimetre to centimetre spaced solution surfaces form in the distal tip zone of the advancing fault plane 2 as the tip advances the fault plane breaks through the cleavage as minor shear displacements reactivate some of these nascent surfaces these observations may prove useful in understanding mechanisms for fault controlled enhanced reduced permeability and fluid pathways 1999 elsevier science ltd all rights reserved

validating the kagis black box gis based model in a mediterranean karst aquifer case of study of mela aquifer se spain this research was funded by the spanish ministry of science and innovation projects cgl2013 48802 c3 3 r and cgl2015 69773 c2 1 p and by the university of alicante projects gre15 19 and gre17 12

hydraulic testing and modelling of a low angle fracture zone at finnsjon sweden abstract the hydraulic characteristics of a gently dipping fracture zone in crystalline rock at the finnsjon test site in sweden are described the information is derived from single hole injection tests of different packer spacings including very detailed tests in 0 11 m sections in a few borehole segments in addition detailed hydraulic interference tests were performed by pumping in different parts of the zone and monitoring pressure changes in multiple section observation boreholes the results of the hydraulic testing show that the fracture zone is composed of two to five thin highly conductive subzones in the boreholes the uppermost subzone is consistently located close to the upper boundary of the major zone and can be correlated over several hundreds of metres there is evidence of both lateral and vertical hydraulic anisotropy along the zone the interference tests show that the fracture zone is delimited by semi permeable boundaries probably constituted by steeply dipping fracture zones the results of the hydraulic testing are used to simulate the pressure responses obtained in the observation boreholes by numerical modelling

hydrogeological behaviour of some fault zones in a carbonate aquifer of southern italy an experimentally based model complex flow circulation patterns are likely to be present in fault controlled groundwater flow systems such as carbonate aquifers nevertheless not much information is available for faults in carbonates and their hydrogeological behaviour is often neglected in conceptual and numerical models the understanding of this aspect of subsurface fluid flow has been improved in a carbonate aquifer where hydrogeological investigations at site scale demonstrated the existence of fault zones that act as barriers the hydraulic conductivity of the fault core is as low as that of siliciclastic rocks that represent the regional aquitard of the carbonate aquifer despite the lower permeability the fault zones allow a significant groundwater flowthrough and a good interdependence of piezometric heads upgradient and downgradient of the faults because of this discontinuous heterogeneity the aquifer looks like a basins in series system where seasonal springs can be detected along some fault zones as a function of groundwater level fluctuations

generation of microcracks by dynamic shear rupture and its effects on rupture growth and elastic wave radiation laboratory and field observations suggest that dynamically propagating earthquake faults generate a large number of tensile microcracks in their vicinity which will contribute to the formation of fault zones intense interactions are expected to occur between such microcracks and a dynamically propagating fault which will complicate the fault growth near field seismic waves will also be affected by the generation of microcracks we numerically study how such tensile microcracks are generated and how dynamic growth of a macroscopic shear rupture and near field elastic waves are affected by the distribution of generated microcracks it is essential to consider a large number of microcracks in such studies so that it is impractical to consider each microcrack individually from the viewpoint of computation time and memory we overcome this difficulty by representing the microcrack distribution by anisotropic properties of the overall elastic coefficients on the basis of hudson s 1980 study our simulations show that the decrease in the microcrack density is approximated well by a logarithmic function of the distance from the rupture plane microcracks on the dilational side of the rupture plane are shown to make larger angles to the rupture plane than on the compressive side these are consistent with field and laboratory observations it is also shown that dynamically generated microcracks tend to reduce the rupture tip shear stress this implies that the dynamic growth of a shear rupture is more decelerated when microcracks are generated than when the shear rupture is isolated in an isotropic and homogeneous medium if the dynamic rupture growth is arrested suddenly an abrupt expansion of the distribution zone of microcracks is shown to occur near the arrested rupture tip aftershocks are expected to cluster in this zone because of the shear stress enhancement there and the high density of distributed microcracks which facilitates aftershock occurrence due to dynamic coalescence of microcracks our simulations also show that the component of radiated displacement waves perpendicular to the rupture plane is much more affected by the generation of microcracks than the parallel component

physical modeling investigation of rainfall infiltration in steep layered volcanoclastic slopes abstract infiltration processes in layered slopes can be strongly affected by the different hydraulic properties of the soils constituting the layers with potential downslope flow diversion that can have effects on slope stability as well as on runoff generation and groundwater recharge in this respect volcanoclastic soil covers represent a typical example as layers with strongly contrasting textures are deposited during the various eruptive phases in this paper the results of a transient infiltration test carried out in a densely instrumented physical model of a layered volcanoclastic sloping cover are presented the soil cover was constituted by a layer of gravelly pumices interbedded between two layers of finer ashes sandy loams even with such an extreme contrast in texture capable of significantly delaying the advancement of infiltration through the layer of pumices flow diversion occurred only temporarily at the interface between the upper layer of ashes and the pumices in fact although a long lasting intense rainfall was applied into an initially dry soil profile the downslope diverted water volume in form of a subsurface runoff was just a small fraction of the total applied rainfall in fact the accumulation of water above the upper edge of the pumices responsible of the subsurface runoff soon led to the establishment of a large water potential gradient which redirected the infiltrating flow through the pumices and stopped the downslope flow diversion

hydro geomorphological modelling of ash fall pyroclastic soils for debris flow initiation and groundwater recharge in campania southern italy abstract carbonate mountain ranges surrounding volcanic centers in the campania region of southern italy are covered by discontinuous ash fall pyroclastic deposits of variable thicknesses the cover thickness and stratigraphy are relevant to hydrological controls on both rainfall induced landslides and groundwater recharge to improve understanding of the hydrologic regimes within the pyroclastic soil mantle a hydrological monitoring station was installed upslope of a debris flow source area in the sarno mountains monitoring results demonstrate consistently unsaturated conditions strong seasonal and inter annual variations in pressure head and delayed and damped dynamics at different depths related to rainfall and evapotranspiration patterns frequencies of recorded pressure head time series were analyzed to quantify the seasonal hydrological regime of the cover as a whole as well as variations within individual soil horizons for the whole ash fall pyroclastic soil cover variable seasonal frequencies of pressure head were recognized exceeding landslide alert and groundwater recharge threshold values analysis of frequencies for individual soil horizons showed a strongly delayed timing determining in winter and summer an opposite hydrological behavior between the shallowest and deepest soil horizons a model that accounts for topographic variations in cover thickness and these hydrological regimes is proposed to quantify hydro geomorphological controls on debris flows triggering and groundwater recharge the model is based on the estimation of ash fall pyroclastic soil thickness along slopes by the total thickness fallen in a given area and an inverse relationship with slope angle allowing the assessment at the distributed scale over peri volcanic mountainous areas moreover it links the spatially variable thicknesses of ash fall pyroclastic soils to the amount of soil water storage allowing the assessment of frequency of hydrological conditions leading to debris flow initiation and groundwater recharge

quasi static fault slip on an interface between poroelastic media with different hydraulic diffusivity a generation mechanism of afterslip 1 we theoretically study the generation mechanism of afterslip assuming a two dimensional in plane fault on a bimaterial interface that separates poroelastic half spaces with different hydraulic diffusivities the deformation is assumed to be quasi static our study shows that the coseismic faulting triggers quasi static fault tip growth effectively because of positive feedback between the evolving fault slip and fluid pressure buildup a similar study was made by yamashita 2007 but he assumed the difference to be only in the biot willis coefficient and undrained and drained poisson s ratios a comparison with the model of yamashita 2007 shows that the diffusivity contrast is much more effective for the generation of afterslip we also find that the fault tip is likely to extend unilaterally in the direction of slip in the medium of higher diffusivity the duration of fault growth is longer for a larger diffusivity contrast we find a scaling relationship in which the moment released by the quasi static fault extension is approximated well by a linear function of the duration of fault growth this is largely different from the expectations from a 2 d classical dynamic fault model the moment is proportional to the square of duration of fault growth if the classical fault model is assumed

soil water balance in an unsaturated pyroclastic slope for evaluation of soil hydraulic behaviour and boundary conditions flowslides in granular soils pose a major threat to life and the environment their initiation in unsaturated soils is regulated by rainfall infiltration which reduces the matric suction and hence shear strength analysis of such phenomena is of strategic importance especially when it aims to mitigate landslide risk by means of early warning systems ewss in this framework physically based models need to reproduce the hydro mechanical behaviour of the slopes through numerical analyses whose main uncertainty concerns the hydraulic conditions at the boundaries of the studied domain and hydraulic conductivity functions of unsaturated soils hence consummate knowledge of both these factors is absolutely necessary for efficient predictions in this paper hydraulic boundary conditions and hydraulic conductivity functions are investigated at the scale of the slope through an application of soil water balance based on in situ monitoring at the test site of monteforte irpino southern italy meteorological data matric suction and soil water content measurements were collected over four years at the test site the soil water balance was analysed on a seasonal time scale with regard to the whole pyroclastic cover resting on the steep limestone substratum infiltration and runoff are estimated interaction between the soil cover and the substratum is investigated and the hydraulic conductivity functions operative at the site scale are defined

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

contribution of correlation and spectral analyses to the regional study of a large karst aquifer charente france the purpose of the study is to demonstrate that correlation and spectral analyses can contribute to the regional study of a large karst aquifer an example is presented for the la rochefoucauld karst aquifer charente france different types of spatially distributed time series provide valuable spatio temporal information for the karst aquifer the available time series consist of the spring flow rates the flow rates at different locations in sinking streams the piezometric levels the electrical conductivity and temperature of the water the atmospheric pressure and the precipitation the analysis of the flow rates at the springs shows that the aquifer empties very slowly and has a large storage capacity hydrodynamic links were established between three of the four rivers flowing on the aquifer and the springs the results also demonstrate the important spatial heterogeneity of the aquifer and indicate that the most rapid flow occurs in the northern part of the aquifer hourly piezometric and electrical conductivity time series indicate that the transmissivity of the aquifer varies when some conductive channels become desaturated during the low water period the delays between the distributed recharge and the piezometric level between the localized river input and the flow rates at the springs and between the electrical conductivities in rivers and the main spring provide information on the travel times in the aquifer the observation of earth tides and barometric effects indicate that this apparently unconfined aquifer has a confined behaviour

preferential flow occurs in unsaturated conditions copyright 2011 john wiley sons ltd because it commonly generates high speed high volume flow with minimal exposure to solid earthmaterials preferential flow in the unsaturated zone is a dominant influence in many problems of infiltration recharge contaminant transport and ecohydrology by definition preferential flow occurs in a portion of a medium that is a preferred part whether a pathway pore or macroscopic subvolume there are many possible classification schemes but usual consideration of preferential flow includes macropore or fracture flow funneled flow determined by macroscale heterogeneities and fingered flow determined by hydraulic instability rather than intrinsic heterogeneity that preferential flow is spatially concentrated associates it with other characteristics that are typical although not defining it tends to be unusually fast to transport high fluxes and to occur with hydraulic disequilibrium within the medium it also has a tendency to occur in association with large conduits and high water content although these are less universal than is commonly assumed predictive unsaturated zone flow models in common use employ several different criteria for when and where preferential flow occurs almost always requiring a nearly saturated medium a threshold to be exceeded may be specified in terms of the following i water content ii matric potential typically a value high enough to cause capillary filling in a macropore of minimum size iii infiltration capacity or other indication of incipient surface ponding or iv other conditions related to total filling of certain pores yet preferential flow does occur without meeting these criteria my purpose in this commentary is to point out important exceptions and implications of ignoring them some of these pertain mainly to macropore flow others to fingered or funneled flow and others to combined or undifferentiated flow modes

short slip duration in dynamic rupture in the presence of heterogeneous fault properties recent studies of strong motion data consistently show that the risetime duration of slip at particular locations on the fault is significantly shorter than the overall rupture duration the physical explanation for this observation and its implications have become central issues in earthquake source studies two classes of mechanisms have been proposed to explain short risetimes one explanation is that velocity weakening frictional behavior on the fault surface causes the fault to self heal this possibility is suggested by rate dependent friction observed in laboratory experiments and by some two dimensional dynamic numerical simulations of earthquake rupture it has recently been demonstrated however that the velocity dependence of friction observed in the laboratory is too weak to cause faults to self heal an alternative explanation for short risetimes is that spatially heterogeneous fault strength e g barriers limit the slip duration in this paper we investigate this second explanation for short risetimes by constructing a three dimensional dynamic rupture model for the 1984 morgan hill california earthquake mw 6 2 using a kinematic model previously obtained from waveform inversion of strong motion data we assume velocity independent friction and a critical stress fracture criterion and derive a dynamic model specified by the spatial distribution of dynamic stress drop and strength excess that reproduces the slip and rupture time of the kinematic model the slip velocity time functions calculated from this dynamic model are then used in a subsequent inversion to fit the strong motion data by alternating between dynamic and kinematic modeling we obtain a dynamic model that provides an acceptable fit to the recorded waveforms in this dynamic model the risetime is short over most of the fault which is attributable entirely to the short scale length slip stress drop heterogeneity required by the strong motion data a self healing mechanism such as strongly velocity dependent friction is not required to explain the short risetimes observed in this earthquake

focusing of elastic waves for microseismic imaging microseismic events generate compressive waves and shear waves which can be recorded at receivers we present a theory that shows how elastic p and s waves separately backpropagate to the original source location these refocused p and s wavefields are free of singularities we also demonstrate a technique that enhances the ability to image the spatial focus for each wave type using elastic waves the improved spatial focus obtained is achieved in a velocity model for which the interface boundaries are approximate but where the mean slowness is correct deconvolution designs a signal to be rebroadcasted from the receivers using only the waves recorded at each receiver such that the wavefield has an optimal temporal focus at the source location we demonstrate theoretically and numerically that improved temporal focusing of elastic waves leads to improved spatial focusing for each wave type this proposed technique only involves a simple preprocessing step to the recorded data and its cost is hence negligible compared to the total cost of microseismic imaging

source process of the 1997 yamaguchi japan earthquake analyzed in different frequency bands a set of source rupture models for the 1997 yamaguchi japan earthquake are constructed using an inversion analysis of strong motion data synthetic green functions and empirical green functions egf are adopted for a low frequency band and a high frequency band respectively slip zones in the high frequency models correspond to the edge of the large slip zones of low frequency models in space and to the rupture onset in time the calculated slip stress relations show that the stress decrease rate is more rapid in the high frequency models and that there is little slip at a constant stress level in all the models

radiation efficiency and apparent stress of small earthquakes in a south african gold mine 1 nine triaxial borehole accelerometers were installed within 200 m along a 2650 m deep haulage tunnel in the mponeng gold mine in south africa we analyzed the high sample rate recordings 15 khz to determine source parameters of small earthquakes in the mine to study the source processes we carried out multiple time window waveform inversions for five larger events 0 8 m 1 4 that occurred within 150 m of the stations from the inversion results we could determine the fault planes for all five events and estimate the range of rupture speed we can conclude that rupture speeds were faster than 2 5 km s 65 of the shear wave velocity the radiation efficiency is written as a function of the rupture speed and becomes greater with increasing rupture speed this study indicates that radiation efficiencies of small earthquakes in the south african gold mine are almost equal to those of larger natural earthquakes we also calculated radiated seismic energies and static stress drops of the five events to investigate their apparent stresses apparent stresses of the five events were from 1 to 10 mpa and static stress drops were 1 to 20 mpa we found that the source parameters rupture speed apparent stress radiation efficiency and static stress drop did not largely differ from values for larger natural earthquakes this suggests that the dynamic rupture processes of these small events were similar to those of the larger natural earthquakes

response of a fractured bedrock aquifer to recharge from heavy rainfall events abstract climate change is predicted to lead to an increased frequency of high intensity rainfall events the impact on groundwater resources particularly in areas of fractured bedrock aquifer systems requires knowledge of how recharge is affected in this study the response of a fractured bedrock aquifer to heavy rainfall events is characterized the study area is the gulf islands a temperate region in british columbia canada of the 14 provincial observation wells with hourly groundwater level data only three showed pronounced responses to heavy rain events and were analyzed in detail a detailed analysis at one well suggests rises in groundwater level were better correlated to all rain events than exclusively heavy rain during summer the strength of the correlation decreased as the rainfall intensity increased solution of the green ampt equation for rainfall events of varying magnitude indicated that an increase in rainfall intensity leads to more surface ponding and overland flow thus the occurrence of more frequent heavy rain events in the future may result in lower net recharge thermal infrared images in seepage areas and the 18 o and 2 h composition for precipitation and seepage suggest rapid seepage responses to heavy rain events and rapid seepage dissipation rates the overall rapid response of the fractured bedrock was advantageous for studying the response of the system to heavy rain events

global depletion of groundwater resources 1 in regions with frequent water stress and large aquifer systems groundwater is often used as an additional water source if groundwater abstraction exceeds the natural groundwater recharge for extensive areas and long times overexploitation or persistent groundwater depletion occurs here we provide a global overview of groundwater depletion here defined as abstraction in excess of recharge by assessing groundwater recharge with a global hydrological model and subtracting estimates of groundwater abstraction restricting our analysis to sub humid to arid areas we estimate the total global groundwater depletion to have increased from 126 32 km3 a 1 in 1960 to 283 40 km3 a 1 in 2000 the latter equals 39 10 of the global yearly groundwater abstraction 2 0 6 of the global yearly groundwater recharge 0 8 0 1 of the global yearly continental runoff and 0 4 0 06 of the global yearly evaporation contributing a considerable amount of 0 8 0 1 mm a 1 to current sea level rise

effects of frictional heating on the thermal hydrologic and mechanical response of a fault the mechanical response of a fault zone during an earthquake may be controlled by the diffusion of excess heat and fluid pressures generated by frictional heating in this study we formulate a fault model which incorporates the effects of frictional heating on the thermal hydrologic and mechanical response of a small patch of the failure surface this model is used to examine the parameters that control the fault response and to determine their critical range of values where thermal pressurization is significant the problem has two time scales a characteristic slip duration and a characteristic time for thermal pressurization the slip duration is set by the fault geometry the characteristic time for thermal pressurization is set by the slip rate the friction coefficient and the thermal and hydraulic characteristics of the medium the response of the fault depends on the relative magnitude of these two times results suggest that the fault width and hydraulic characteristics of the fault zone and adjacent medium are the primary parameters controlling the mechanical response for earthquakes occurring across zones of low porous medium compressibility 10 9 pa 1 and permeability 10 18 m2 the characteristic time for thermal pressurization is small in this case frictional heating can cause fluid pressures to approach lithostatic values the shear strength to approach zero and the temperature rise to stabilize at a maximum value dependent on the pore dilatational and transport properties of the porous medium whether the patch acts as a barrier to slip or exhibits substantial strain weakening is dependent on the shear strain across the fault moderate slip events where shear strains exceed two cause substantial strain weakening and consequently large stress drops accelerations and displacements thus it is possible for the patch to act as a barrier for small earthquakes but not for large ones both the dynamic stress drop and total displacement decrease for zones with larger compressibility permeability or width if the compressibility or permeability exceeds 10 8 pa 1 or 10 14 m2 or the shear strain is less than one then the effects of frictional heating may be negligible and the fault will exhibit no strain weakening characteristics consequently the patch acts as barrier that halts or resists further fault motion extrapolation of these results suggests that spatial variations in fault width and hydraulic characteristics will cause a heterogeneous stress drop and fault slip over the failure surface explaining many of the features of active faulting e g barriers nonuniform slip rupture stoppage random ground accelerations strong motions and frequency magnitude relations

fluid pressurization due to frictional heating on a fault at a permeability contrast 1 frictional heating on a fault plane causes pore fluids to pressurize when the permeability of the fault zone materials is sufficiently low fluid pressure on the fault can approach the normal stress though it can never be exceeded due to the feedback between pore pressure and frictional strength however if slip occurs at a boundary between materials of different permeabilities such as fault gouge and a damage zone the highest pressure develops within a few millimeters of the fault in the lower permeability material rather than at the fault surface the pressure increase off the fault can reach or exceed the normal stress given a large enough permeability contrast because there is no direct feedback between this pressure and the frictional heating at the fault surface high fluid pressures off the fault might result in the slip shifting into the lower permeability material where the frictional strength has been reduced

understanding of dynamic earthquake slip behavior using damage as a tensor variable microcrack distribution orientation and mode and secondary faulting 1 the importance of the damage effect on dynamic earthquake slip behavior is clarified using the damage tensor variable dynamic mode ii faults that are embedded in damage inducing media are assumed to relate to damage effects this study confirms that the rupture velocity for spontaneous fault tip growth in the damage medium is reduced being slightly smaller than rupture velocities observed for classical elastic material inelastic energy loss resulting in damage is relatively small but nonnegligible to the accumulated fracture energy two framework parameters employed in this study determine microcrack orientations and modes of microcracks and provide information on deviations in microcrack distribution between isotropic and nonisotropic ones spatial microcrack distribution patterns in isotropic and homogeneous systems are strongly dependent on a parameter related to the damage creation criterion when considering secondary faulting two apparently different behaviors pulverization and branch development are understood in a single framework which gives a new insight into fault zone formation the present results show that damage effect must be treated as a tensor variable rather than a scalar one as employed in many previous studies

non permanent shallow halocline in a fractured carbonate aquifer southern italy summary we carried out hydrogeological geophysical hydrochemical isotopic and molecular biological investigations in a fractured carbonate aquifer in southern italy to verify if prolonged variations in groundwater salinity with depth can be due to mixing processes between fresh infiltration water and groundwater all investigations revealed the formation of a non permanent halocline at the experimental site whose thickness and shape varies over time variations in thickness and shape are influenced by infiltration processes three main types of electrical conductivity ec profiles were found during the research period in the high flow period the ec profile consisted of a transition layer and a nearly homogeneous higher salinity groundwater layer and no mixed layer was observed a nearly homogeneous mixed layer was detected in the low flow period excluding the late recession when the ec profile was characterized by a higher salinity groundwater layer and a negligible transition layer the ec profile through the transition layer was approximately symmetric and linear probably due to a velocity shear across this layer the velocity shear was probably caused by the difference in opening porosity detected between the upper and lower carbonate bedrock through geophysical investigations the investigated phenomenon is due to water that infiltrates very close to the observation well in fact a the isotopic composition of the lower salinity groundwater layer in early recharge 2007 2008

heterogeneous distribution of the dynamic source parameters of the 1999 chi chi taiwan earthquake 1 the spatial and temporal distribution of the stress on the fault plane of the 1999 chi chi taiwan earthquake is calculated from kinematic inversion results using a three dimensional finite difference method for solving the elastodynamic equations we analyze the relations between stress and slip for all grid positions on the fault and use these relations to infer the friction law for the rupture the dynamic source parameters were also determined our results show that for most of the points on the fault the relation between stress and slip was consistent with the slip weakening law during the rupture process especially for those points with large slip however consistency with the velocity weakening law is not clear from the observed relation between stress and slip velocity the distributions of the dynamic parameters on the fault are very heterogeneous the peak value of the static stress drop is 35 mpa in general high stress drop occurred in the areas with large slip the estimated strength excesses are generally small suggesting that the tectonic shear stress had reached the level of the fault strength before the main shock the slip weakening distance dc and the fracture energy gc are proportional to the final slip the aftershock activity correlates with the spatial distribution of dynamic source parameters usually the aftershocks near the fault plane are concentrated in regions with small or negative static stress drop and there were few aftershocks in regions which had large values of critical slip weakening distance dc

spatial and temporal distribution of slip for the 1992 landers california earthquake we have determined a source rupture model for the 1992 landers earthquake m w 7 2 compatible with multiple data sets spanning a frequency range from zero to 0 5 hz geodetic survey displacements near field and regional strong motions broadband teleseismic waveforms and surface offset measurements have been used explicitly to constrain both the spatial and temporal slip variations along the model fault surface our fault parameterization involves a variable slip multiple segment finite fault model which treats the diverse data sets in a self consistent manner allowing them to be inverted both independently and in unison the high quality data available for the landers earthquake provide an unprecedented opportunity for direct comparison of rupture models determined from independent data sets that sample both a wide frequency range and a diverse spatial station orientation with respect to the earthquake slip and radiation pattern in all models consistent features include the following 1 similar overall dislocation patterns and amplitudes with seismic moments of 7 to 8 10 26 dyne cm seismic potency of 2 3 to 2 7 km 3 2 very heterogeneous unilateral strike slip distributed over a fault length of 65 km and over a width of at least 15 km though slip is limited to shallower regions in some areas 3 a total rupture duration of 24 sec and an average rupture velocity of 2 7 km sec and 4 substantial variations of slip with depth relative to measured surface offsets the extended rupture length and duration of the landers earthquake also allowed imaging of the propagating rupture front with better resolution than for those of prior shorter duration strike slip events our imaging allows visualization of the rupture evolution including local differences in slip durations and variations in rupture velocity rupture velocity decreases markedly at shallow depths as well as near regions of slip transfer from one fault segment to the next as rupture propagates northwestward along the multiply segmented fault length the rupture front slows as it reaches the northern limit of the johnson valley landers faults where slip is transferred to the southern homestead valley fault an abrupt acceleration is apparent following the transfer this process is repeated and is more pronounced as slip is again passed from the northern homestead valley fault to the emerson fault although the largest surface offsets were observed at the northern end of the rupture our modeling indicates that substantial rupture was also relatively shallow less than 10 km in this region

chemical and isotopic δ18o δ2h δ13c 222rn multi tracing for groundwater conceptual model of carbonate aquifer gran sasso infn underground laboratory central italy summary a hydrochemical and isotope study was conducted on the drainage waters of an underground laboratory located inside the gran sasso massif central italy the study was expected to improve the conceptual model of groundwater circulation at the base of an over 1000 thick unsaturated zone in the gran sasso partitioned karst aquifer this lithostratigraphically and tectonically complex aquifer is typical of africa europe thrust and fold collision belt in the mediterranean area in this case investigations on water rock interactions during recharge in complex aquifers overlaid by a thick unsaturated zone have been made thanks to the strategic location of the gran sasso underground laboratories located in the core of a huge carbonate aquifer knowledge of the local basic hydrogeological setting was the starting point for a detailed hydrogeochemical and isotopic study which was carried out at the aquifer scale and at the fine scale in the underground laboratories the water rock interaction processes were investigated both spatially and in temporal sequences analysing recharge waters and groundwater in the underground laboratories by multitracing techniques including major ions and 18o 2h and 13c stable isotopes use of 222rn provides information on transit time in the aquifer processes proved to be typical of carbonate rocks with clear influence of vertical movement of water on chemical physical parameters through the unsaturated zone conversely in the saturated zone these processes proved to be dominantly affected by local geological structural conditions a conceptual model with dual flow velocity is proposed directly related to the local geological structural setting 222rn decay enables to calculate an effective velocity of around 10 m day for the fracture network through the sequence of less permeable dolomites and underlying limestone lag time between recharge and chemical changes in the saturated zone testifies to an effective velocity of about 35 m day for fast flow through recent and active extensional faults

effects of shear heating slip induced dilatancy and fluid flow on diversity of 1 d dynamic earthquake slip we theoretically study effects of thermal pressurization slip induced dilatancy and fluid flow on slip evolution assuming 1 d fault model we generalize the analysis made in our former papers by introducing an upper limit for the inelastic porosity evolution the expression for nondimensional parameter ta which is related to the upper limit is derived in the present paper we find that the parameter ta together with two nondimensional parameters su and su derived in our former papers completely determine the qualitative nature of system behavior once the initial condition is given for example changes in su and ta generate two qualitatively different slip behaviors both of which can be models for ordinary earthquake the slip is accelerated with time after experiencing an initial deceleration in one of them while the slip ceases after monotonic deceleration in the other the initial slip deceleration observed in the former case may be interpreted as a dynamic event preceding the main shock in seismological observations we mathematically derive the expression for the ranges of the nondimensional parameters in which the above two slip behaviors appear slow earthquakes are also modeled in the same framework and nonzero values of the nondimensional parameter su together with relatively large values of su and ta are found to contribute to the generation of such slow earthquakes the mathematical framework constructed here can be applied to understanding of some other natural phenomena such as a kind of reaction diffusion system

groundwater recharge assessment at local and episodic scale in a soil mantled perched karst aquifer in southern italy summary groundwater recharge assessment of karst aquifers at various spatial and temporal scales is a major scientific topic of current importance since these aquifers play an essential role for both socio economic development and fluvial ecosystems in this study groundwater recharge was estimated at local and episodic scales in a representative perched karst aquifer in a region of southern italy with a mediterranean climate the research utilized measurements of precipitation air temperature soil water content and water table depth obtained in 2008 at the acqua della madonna test area terminio mount karst aquifer campania region at this location the aquifer is overlain by ash fall pyroclastic soils the episodic master recession emr method an improved version of the water table fluctuation wtf method was applied to estimate the amount of recharge generated episodically by individual rainfall events the method also quantifies the amount of precipitation generating each recharge episode thus permitting calculation of the recharge to the precipitation ratio rpr on a storm by storm basis depending on the seasonally varying air temperature evapotranspiration and precipitation patterns calculated values of rpr varied between 35 and 97 among the individual episodes a multiple linear correlation of the rpr with both the average intensity of recharging rainfall events and the antecedent soil water content was calculated given the relatively easy measurability of precipitation and soil water content such an empirical model would have great hydrogeological and practical utility it would facilitate short term forecasting of recharge in karst aquifers of the mediterranean region and other aquifers with similar hydrogeological characteristics by establishing relationships between the rpr and climate dependent variables such as average storm intensity it would facilitate prediction of climate change effects on groundwater recharge the emr methodology could further be applied to other aquifers for evaluating the relationship of recharge to various hydrometeorological and hydrogeological processes

a fault constitutive relation accounting for thermal pressurization of pore fluid 1 the heat generated in a slip zone during an earthquake can raise fluid pressure and thereby reduce frictional resistance to slip the amount of fluid pressure rise depends on the associated fluid flow the heat generated at a given time produces fluid pressure that decreases inversely with the square root of hydraulic diffusivity times the elapsed time if the slip velocity function is crack like there is a prompt fluid pressure rise at the onset of slip followed by a slower increase the stress drop associated with the prompt fluid pressure rise increases with rupture propagation distance the threshold propagation distance at which thermally induced stress drop starts to dominate over frictionally induced stress drop is proportional to hydraulic diffusivity if hydraulic diffusivity is 0 02 m2 s estimated from borehole samples of fault zone material the threshold propagation distance is 300 m the stress wave in an earthquake will induce an unknown amount of dilatancy and will increase hydraulic diffusivity both of which will lessen the fluid pressure effect nevertheless if hydraulic diffusivity is no more than two orders of magnitude larger than the laboratory value then stress drop is complete in large earthquakes

answer to the comment on non permanent shallow halocline in a fractured carbonate aquifer southern italy by e petrella g naclerio a falasca a bucci p capuano v de felice and f celico j hydrol 373 2009 267 272

the effect of low permeability fault zones on groundwater flow in a compartmentalized system experimental evidence from a carbonate aquifer southern italy the hydrogeological behaviour of fault zones in carbonate aquifers is often neglected in conceptual and numerical models furthermore no information is available regarding the relationships between piezometric levels when significant compartmentalization occurs due to the occurrence of low flow fault zones the aim of this study was to refine the conceptualization of subsurface flow in faulted carbonate aquifers and to analyse relationships between sub basins within a compartmentalized aquifer system in southern italy the interactions between compartments that straddle low flow faults were investigated over four hydrologic years using a statistical approach to compare i the hydraulic heads within two wells located up and down gradient of tectonic discontinuities as well as ii the rainfall and piezometric levels the results of this study suggest that a set of barriers exists between the wells and therefore the total head loss observed between the wells approximately 80 m should be distributed across several aquitards with one aquitard exhibiting a relatively high permeability or low degree of integrity due to slight differences in permeability transient conditions in aquitards can occur over relatively short periods which is in agreement with the results of the statistical data analysis consequently rather than being caused by pure aquitards aquifer system compartmentalization likely results from slight differences in the permeability between lower permeability fault zones and adjacent higher permeability protoliths copyright 2014 john wiley sons ltd

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

assessment of doline geometry using geophysics on the quercy plateau karst south france in the protection of karstic aquifers the role played by dolines is of interest as these shallow structures can be preferential infiltration pathways for groundwater recharge in this study three depressions in south france orniac lot were identified and characterized using combined geophysical methods apparent conductivity mapping allows precise definition of dolines corresponding to topographic depressions it also reveals other dolines that are hidden by soil cover electrical resistivity and seismic refraction tomography provide detailed cross sections even though the dolines studied are close one to another they exhibit great variability in shape and content moreover time lapse data show that the most saturated regions are on the edges of the first doline such information helps to evaluate human impacts and forecast potential groundwater contamination

influence of depth focal mechanism and tectonic setting on the shape and duration of earthquake source time functions source time functions of 255 moderate to great earthquakes obtained from inversions of teleseismic body waves by tanioka and ruff 1997 and coworkers were compared in a systematic way they were scaled to remove the effect of moment and to allow the direct comparison and averaging of time function shape as well as duration time function durations picked by tanioka and ruff 1997 are proportional to the cube root of seismic moment if moments from the harvard centroid moment tensor catalog are used the average duration of scaled time functions is shorter and the average shape has a more abrupt termination for deeper events than shallower ones with a distinct change occurring at 40 km depth the complexity of the time functions as quantified by the number of subevents appears to decrease below 40 km depth furthermore among events shallower than 40 km the average duration of scaled time functions is shorter and their average shape has a more abrupt termination 1 for events with strike slip focal mechanisms compared to thrust events and 2 for the few thrust events associated with an intraplate setting compared to the majority associated with an interplate subduction boundary in each of these cases events in more technically and seismically active settings have a longer duration and a more gradual termination this can be interpreted in terms of lower stress drops and or slower rupture velocities at active plate boundaries suggesting that fault rheology depends on slip rate and may evolve as total fault slip accumulates furthermore differences in average time function shape and duration associated with different subduction zones suggest that differences exist in the rheology on the plate boundaries at the various subduction zones supporting data table is available via web browser or via anonymous ftp from ftp kosmos agu org directory append username anonymous password guest subdirectories in the ftp site are arranged by paper number information on seraching and submitting electronic supplements is found at http www agu org pubs esupp about html