regional geologic and petrologic framework for iron oxide apatite rare earth element and iron oxide copper gold deposits of the mesoproterozoic st francois mountains terrane southeast missouri usa this paper provides an overview on the genesis of mesoproterozoic igneous rocks and associated iron oxide apatite ioa rare earth element iron oxide copper gold iocg and iron rich sedimentary deposits in the st francois mountains terrane of southeast missouri usa the st francois mountains terrane lies along the southeastern margin of laurentia as part of the eastern granite rhyolite province the province formed during two major pulses of igneous activity 1 an older early mesoproterozoic ca 1 50 1 44 ga episode of volcanism and granite plutonism and 2 a younger middle mesoproterozoic ca 1 33 1 30 ga episode of bimodal gabbro and granite plutonism the volcanic rocks are predominantly high silica rhyolite pyroclastic flows volcanogenic breccias and associated volcanogenic sediments with lesser amounts of basaltic to andesitic volcanic and associated subvolcanic intrusive rocks the iron oxide deposits are all hosted in the early mesoproterozoic volcanic and volcaniclastic sequences previous studies have characterized the st francois mountains terrane as a classic a type within plate granitic terrane however our new whole rock geochemical data indicate that the felsic volcanic rocks are effusive derivatives from multicomponent source types having compositional similarities to a type within plate granites as well as to s and i type granites generated in an arc setting in addition the volcanic hosted ioa and iocg deposits occur within bimodal volcanic sequences some of which have volcanic arc geochemical affinities suggesting an extensional tectonic setting during volcanism prior to emplacement of the ore forming systems the missouri iron orebodies are magmatic related hydrothermal deposits that when considered in aggregate display a vertical zonation from high temperature magmatic hydrothermal ioa deposits emplaced at moderate depths 1 2 km to magnetite dominant ioa veins and iocg deposits emplaced at shallow subvolcanic depths the shallowest parts of these systems include near surface iron oxide only replacement deposits surficial epithermal sediment hosted replacement deposits synsedimentary ironstone deposits and mn rich exhalite deposits alteration associated with the ioa and iocg mineralizing systems of the host volcanic rocks dominantly produced potassic with lesser amounts of calcic and sodic rich mineral assemblages no deposits are known to be hosted in granite implying that the mineralizing systems were operative during a relatively short postvolcanic period yet prior to intrusion of the granitoids companion studies in this special issue on mineral chemistry stable isotopes and iron isotopes suggest that the magnetite within the ioa deposits formed from high temperature fluids of magmatic or magmatic hydrothermal origin however the data do not discriminate between a magmatic hydrothermal source fluid exsolved from an fe rich immiscible liquid or an fe rich silicate magma mineral chemical fluid inclusion and stable isotope data from these new studies record the effects of metasomatic fluids that interacted with crustal reservoirs such as volcanic rocks or seawater

three dimensional numerical simulation of fully coupled groundwater flow and land deformation in unsaturated true anisotropic aquifers due to groundwater pumping 1 a hydrogeomechanical numerical model is presented to evaluate three dimensional groundwater flow and land deformation in unsaturated true anisotropic aquifers due to groundwater pumping this multidimensional numerical model is developed on the basis of the fully coupled poroelastic governing equations for saturated unsaturated groundwater flow in deforming true anisotropic geologic media and the galerkin finite element method a series of true anisotropic aquifers which comprise variously tilting layers respectively and a corresponding isotropic aquifer which is composed of a geometrically averaged equivalent isotropic material are simulated for the purpose of comparison the numerical simulation results show that true anisotropy has significant effects on the spatial distributions and temporal changes of hydraulic head and displacement vector such effects of true anisotropy are caused by the uneven partitioning of the hydraulic pumping stress between the vertical and horizontal directions in both groundwater flow and solid skeleton deformation fields this directionally uneven partitioning of the hydraulic pumping stress results from both the differences in hydraulic and mechanical properties among the principal axes and the discordance between the global coordinate axes and the principal axes

tomographic images of the el asnam fault zone and the evolution of a seismogenic thrust related fold the p wave velocity structure of the upper 9 km of the el asnam algeria fault zone the site of the ms7 3 earthquake october 10 1980 is obtained by inverting arrival times from 310 selected aftershocks computed crustal structure and relocation of aftershocks yield new insight on the structural geology of the area and help to clarify the evolution of fault related folding and the complexity of the rupture episodes during the el asnam earthquake the correlation between tomograms and geologic structures observed at the surface and inferred at depth delineates local heterogeneities of the upper crust there is evidence for distinct large scale structural trends consisting of two main thrusts with antithetic reverse faults seismic tomography provides reasonable constraints on the el asnam fault related fold geometry pointing out a complex preexisting structure along which the rupture evolution is controlled by the heterogeneous crust we propose that the main shock originated along an inverted normal fault bordering the pre neogene basement lateral lithologic heterogeneities obtained by seismic tomography reflect the fault segmentation and geometrical discontinuities along strike in agreement with the tectonic pattern

mathematical model for regional land subsidence due to pumping 1 integrated aquifer subsidence equations based on vertical displacement only a mathematical model for regional land subsidence has been developed by employing terzaghi s concept of effective stress and assuming vertical solid compressibility only first the groundwater mass conservation equation in a compressible aquifer is developed for a three dimensional space assuming that the problem justifies an assumption of a thin aquifer relative to horizontal lengths of interest this equation is then integrated over the aquifer s thickness taking into account the conditions on top and bottom surfaces bounding the aquifer the result is the commonly used aquifer flow equation in terms of averaged piezometric head by introducing a relationship between changes in averaged piezometric head and corresponding changes in aquifer thickness a single equation is obtained in terms of land subsidence the development is carried out for a single and a multi layered confined aquifer and for a phreatic one an example is given of the application of the equation in radial coordinates describing land subsidence in a hypothetical six layered aquifer

a coupled one dimensional viscoelastic plastic model for aquitard consolidation caused by hydraulic head variations in aquifers accurate and practical calculation of aquitard consolidation is required for a reliable analysis of land subsidence caused by groundwater overexploitation in a multilayered aquifer system because aquitards are generally more compressible than aquifers are this study proposes a coupled one dimensional viscoelastic plastic consolidation model that considers the combined effect of changes in soil parameters and body force to simulate aquitard consolidation caused by hydraulic head variations in neighbouring aquifers the proposed model uses variable total stress and simultaneously solves hydraulic head and vertical soil displacement the constitutive relation based on the voigt model with different elastic moduli of the spring in normally consolidated and overconsolidated soils is used to describe the viscoelastic plastic deformation mechanism of aquitards in addition the proposed model considers the combined effect of variations in hydraulic conductivity elastic moduli and body force on the calculation of aquitard consolidation three hypothetical scenarios with various hydraulic head variations in aquifers are used to examine the coupled one dimensional viscoelastic plastic consolidation model the results show that neglecting plasticity and viscosity of soil causes aquitard consolidation to be respectively underestimated and overestimated in addition ignoring body force variation underestimates aquitard consolidation whereas neglecting soil parameters variation overestimates aquitard consolidation two real case scenarios are also studied to further demonstrate the applicability of the coupled one dimensional viscoelastic plastic consolidation model copyright 2015 john wiley sons ltd

a new view of italian seismicity using 20 years of instrumental recordings in this paper we show the seismicity of the past 20 years that occurred in italy and surrounding regions hypocentral locations have been obtained by using p and s wave arrival times from the ingv national and several regional permanent seismic networks more than 48 000 events selected from an original data set of about 99 780 are used to reconstruct the most complete seismic picture of the italian region so far the seismicity distribution allows inference on seismotectonics of this complex region of subduction versus continental collision our results clearly reveal the geometry of the adria and the ionian subduction and a continuous normal fault belt in the upper crust following the apennines mountain range the depth of the seismogenic layer is computed from the cut off of seismicity at depth and shows large variations along and across the seismic active regions earthquakes are generated by the different velocity of slab retreat and the subsequent asthenospheric upwelling d 2004 elsevier b v all rights reserved

earthquake locations and three dimensional crustal structure in the coyote lake area central california previous work on the simultaneous inversion method has been improved and extended to incorporate iterative solution for earthquake locations and laterally heterogeneous structure approximate ray tracing and parameter separation are important elements of the improved method application of the method to p wave arrival time data recorded by stations of the u s geological survey central california network yields a three dimensional model for the velocity structure of the upper crust in an area encompassing the rupture zone of the coyote lake earthquake of august 1979 very strong correlations between the velocity model and the geology and gravity and magnetic anomalies are observed improved estimates of the locations of earthquakes in the study area are also determined the relocation of explosions indicates epicentral accuracies of the order of a kilometer or better based on the revised hypocentral locations it is concluded that the san andreas fault is vertical in this area with no actual offset between the epicenters and the fault trace in contrast the calaveras has two or more active fault surfaces one nearly vertical and another dipping 75 to the northeast

new insights into crustal structure cenozoic magmatism co2 degassing and seismogenesis in the southern apennines and irpinia region from local earthquake tomography we present high resolution vp and vp vs models of the southern apennines italy computed using local earthquakes recorded from 2006 to 2011 with a graded inversion scheme that progressively resolves the crustal structure from the large scale of the apennines belt to the local scale of the normal fault system high vp bodies defined in the upper crust and midcrust under the external apennines are interpreted as extensive mafic intrusions revealing anorogenic magmatism episodes that broadened on the adriatic domain during paleogene under the mountain belt a low vp region annular to the neapolitan volcanic district indicates the existence of a thermal fluid anomaly in the midcrust coinciding with a shallow moho and diffuse degassing of deeply derived co2 in the belt axial zone low vp vs gas pressurized rock volumes under the apulian carbonates correlate to high heat flow strong co2 dominated gas emissions of mantle origin and shallow carbonate reservoirs with pressurized co2 gas caps we hypothesize that the pressurized fluid volumes located at the base of the active fault system influence the rupture process of large normal faulting earthquakes like the 1980 mw6 9 irpinia event and that major asperities are confined within the high vp apulian carbonates this study confirms once more that preexisting structures of the pliocene apulian belt controlled the rupture propagation during the irpinia earthquake the main shock broke a 30 km long ne dipping seismogenic structure whereas delayed ruptures both the 20 s and the 40 s subevents developed on antithetic faults reactivating thrust faults located at the eastern edge of the apulian belt

evaluating the hydraulic and transport properties of peat soil using pore network modeling and x ray micro computed tomography abstract micro scale properties of peat pore space and their influence on hydraulic and transport properties of peat soils have been given little attention so far characterizing the variation of these properties in a peat profile can increase our knowledge on the processes controlling contaminant transport through peatlands as opposed to the common macro scale or bulk representation of groundwater flow and transport processes a pore network model pnm simulates flow and transport processes within individual pores here a pore network modeling code capable of simulating advective and diffusive transport processes through a 3d unstructured pore network was developed its predictive performance was evaluated by comparing its results to empirical values and to the results of computational fluid dynamics cfd simulations this is the first time that peat pore networks have been extracted from x ray micro computed tomography ct images of peat deposits and peat pore characteristics evaluated in a 3d approach water flow and solute transport were modeled in the unstructured pore networks mapped directly from ct images the modeling results were processed to determine the bulk properties of peat deposits results portray the commonly observed decrease in hydraulic conductivity with depth which was attributed to the reduction of pore radius and increase in pore tortuosity the increase in pore tortuosity with depth was associated with more decomposed peat soil and decreasing pore coordination number with depth which extended the flow path of fluid particles results also revealed that hydraulic conductivity is isotropic locally but becomes anisotropic after upscaling to core scale this suggests the anisotropy of peat hydraulic conductivity observed in core scale and field scale is due to the strong heterogeneity in the vertical dimension that is imposed by the layered structure of peat soils transport simulations revealed that for a given solute the effective diffusion coefficient decreases with depth due to the corresponding increase of diffusional tortuosity longitudinal dispersivity of peat also was computed by analyzing advective dominant transport simulations that showed peat dispersivity is similar to the empirical values reported in the same peat soil it is not sensitive to soil depth and does not vary much along the soil profile

pressure change and surface expansion in salt marshes due to tidal inundation infiltration of water across the surface water interface of a marsh in areas flooded due to tides has been known to cause swelling of sediments the sudden tidal inundation in an unflooded soil creates a head gradient at the surface of the unsaturated soil above the water table when water infiltrates into the soil under this gradient the suction head in the unsaturated domain decreases and the pore pressure in the saturated zone increases with time resulting in swelling of highly compressible marsh soils a one dimensional mathematical model which consists of a mass conservation equation quasi static equilibrium equations stress strain relations for an assumed perfectly elastic solid matrix and a variable total stress expression has been employed to obtain a numerical solution for pore pressure change and swelling due to tidal inundation numerical results are presented graphically at the spatial and temporal points of interest for a constant depth of ponding of water at the marsh surface resulting from tidal inundation results show that swelling of soil is primarily governed by the initial head gradient across the marsh surface water interface

applying the relative hypocentre location approach where was the 1980 november 23 irpinia earthquake the purpose of this work is to evaluate under what conditions it is feasible and with what accuracy it is possible to locate the nucleation point of a large earthquake given the availability of aftershocks located with high precision by the deployment of a local network we experiment with several approaches and apply them lo the location of the epicentre of the 1980 november 23 irpinia earthquake mw 6 9 first we use local pg phases selected to optimize the azimuthal coverage obtaining a well constrained location with a small statistical error which typically underestimates the true hypocentre uncertainty we then exploit the relative location technique obtaining stable almost coincident solutions under three conditions 1 using multiple independent master events to derive an average epicentre 2 fitting simultaneously the larger data set for all available master events using a forward approach 3 conducting an a priori evaluation of the statistics of station and master events to separate model uncertainties and improve the statistical accuracy of the relative locations moreover only by introducing station statistics can we achieve the desired accuracy of 1 km in constraining the rupture nucleation point of this large earthquake and we show that the application of the relative location technique to uncleaned unweighted data for a single master event provides only a crude epicentre with a confidence ellipse deceivingly smaller than the true hypocentre uncertainty the revised epicentre for the 1980 november 23 irpinia earthquake 48 803 n 15 302 e validates the class of multidisciplinary reconstructions of the source process such as the model of valensise et al 1989 based on the hypocentre of westaway jackson 1987 and is shifted by almost 13 km to the nw of the epicentre recently proposed by westaway 1992

resistivity based monitoring of biogenic gases in peat soils 1 biogenic free phase gas fpg formation was induced in a peat block dimensions 0 28 0 21 0 21 m extracted from a peatland in maine electrical resistivity er surface deformation and methane ch4 flux from the peat surface was monitored over a 48 day period during which the temperature remained constant at 21 1 c er measurements were made on 5 vertical electrode arrays each containing 20 electrodes spaced at 0 01 m intervals surface deformation was monitored using 30 elevation rods equally spaced across the surface of the block and average ch4 flux from the peat surface estimated by integration of measurements obtained with a portable gas detector over a 20 min time period pore water conductivity was recorded at three depths 0 06 0 09 and 0 15 m at a single point in the block er measurements were inverted for the ratio resistivity change relative to a background data set and corrected for changes in pore fluid conductivity permitting an estimate of equivalent change in gas content assuming 1 insignificant surface conduction 2 porosity changes estimated from peat surface expansion and 3 an archie saturation exponent n of 1 3 based on results from a parallel block experiment the resistivity ratios reveal a pattern of fpg evolution consistent with surface deformation and ch4 flux data during the first part of the experiment approximately the first 24 days a gradual buildup in fpg within a layer 4 6 cm below the peat surface water table occurs concurrent with modest surface deformation and low ch4 fluxes in contrast during the latter half of the experiment approximately 25 48 days a complex pattern of more pronounced gas buildup and release at multiple depths occurs concurrent with large rates of surface deformation and higher ch4 fluxes the experiment demonstrates that er monitoring is a viable geophysical technology for imaging and monitoring biogenic gas fluxes in peat soils here the resistivity clearly shows that fpg is preferentially generated in layers about 0 04 0 06 m below the peat surface and that the buildup of gas is spatially nonuniform even in a relatively small peat block furthermore the experimental results suggest that factors other than temperature and atmospheric pressure must control biogenic gas accumulation and release as the method is readily deployable at the field scale possibly in an autonomous monitoring mode resistivity measurements may permit significant improvements in understanding of carbon gas generation and release from northern peatlands

chemical dilation and the dual porosity of humified bog peat abstract hydrochloric acid and calcium and sodium chloride salt solutions were passed through humified bog peat cores of 1 m length to determine values for the material properties governing solute transport hydraulic conductivity effective porosity and dispersivity chloride passed through the bulk peat cores about twice as fast as predicted from chloride breakthrough curves measured by selective ion probes inserted into the peat 30 cm downgradient from the source with continued experimentation chloride dispersion increased chloride also passed through the peat up to 12 times slower than predicted by conservative advection the retardation of the chloride fronts the faster bulk transport and the asymmetry of the breakthrough curves all indicate that humified bog peat is a dual porosity medium solutes both move preferentially through active macropore spaces and diffuse into dead pore space in the peat matrix neither the effective porosity nor the dispersivity of the peat could be precisely determined from the breakthrough curves because the hydraulic conductivity and discharge rates through the peat increased as much as five times when the chloride tracer solutions passed through the cores in initial experiments the shapes of the breakthrough curves were generally consistent with dispersivities of the order of centimeters similar to that observed for granular soils at the same length scale meters whereas they flattened considerably during later experiments suggesting dispersivities in the range of tens of centimeters we hypothesize that the interaction of the chloride tracer solutions with organic acid functional groups may cause macropores to dilate and micropores to close off

crustal structure in the area of the 2002 molise earthquake clues for the evolution of the southern apennines the apennines is a mountain belt with paired extension and compression that are explained by the subduction and delamination of the ionian adria lithosphere during the belt formation the adria crust is flexed downward and then incorporated into the wedge after peeling off along some weak level whose origin is still discussed in southern apennines this process seems to have stopped at about 0 7 ma by the development of a tear in the subducting lithosphere and consequent extension that spread along the mountain range seismological data acquired after the 2002 mw 6 0 molise strike slip earthquake yield modeling the structure of the adria crust as congealed close to the leading edge of the belt tomography images show inverted normal faults within the sedimentary cover apulian units fault inversion incomplete close to the compressional front testifies for a final squeezing of the entire previously flexed apulian continental margin pronounced high vp and low vp vs anomalies are observed at depth greater than 12 km and undoubtfully attributed to heterogeneities of the basement solving the long lasting contention on the nature of similar high speed bodies observed beneath the apennines beneath these bodies we observe a strong reflectivity suggesting the presence of a fluid filled layer in the middle lower crust that may act as a decoupling level in the apennines tectonics the deep fluids are also favoring the rupture of strike slip earthquakes like those that occurred in 2002 and the intermediate depth seismicity diffused in the apulian region

upper crustal tomographic images of the amiata vulsini geothermal region central italy we computed the three dimensional p wave velocity structure of the upper crust beneath the adjacent amiata and vulsini quaternary volcanoes central italy inverting local earthquake arrival times we used 676 selected earthquakes out of more than 3000 in the m range 1 5 4 0 located between 1977 and 1992 by two contiguous microseismic networks operated by ente nazionale energia elettrica to monitor three geothermal areas namely latera torre alfina and mount amiata the resolving capability of the data set has been verified both with a priori synthetic tests and an a posteriori analysis of the resolution matrix we find a 40 25 7 h km3 crustal volume where we can resolve details as small as 2 to 4 km our analysis is favored by numerous geological and geophysical data collected for geothermal exploration these independent data give us specific constraints for both choosing a starting model and interpreting tomographic results we find high velocity anomalies in the upper 3 km of the crust beneath latera torre alfina and mount amiata geothermal fields related to uplifted limestone units the lateral extension of limestone units is defined by the three dimensional velocity pattern a negative anomaly clearly identifies the radicofani graben a plio quaternary depression filled with low velocity clayey sediments between 1 and 3 km depth a sharp gradient between high velocities 6 9 km s in the northern region and lower velocities in the southern one is recovered at 7 km depth this feature may indicate the transition between the tuscan province uplifted metamorphic crust and thickened carbonate series of the latium province

crustal and uppermost mantle structure in italy from the inversion of p wave arrival times geodynamic implications summary in this paper we present a 3 d image of the p wave velocity structure in the crust and uppermost mantle beneath italy obtained by inverting p wave arrival times of crustal earthquakes we used about 48000 arrival times at stations close to the epicentres within 200 km to mitigate the eiects of both reading errors and intrinsic complexity for long distance ray paths due to the scale of heterogeneities in the earth structure beneath italy whereas two of the inverted layers located in the lower crust and beneath the moho are well resolved by the data the upper crustal layer has regions of relatively poor resolution beneath the central apennines due to the sparse station spacing we made several attempts varying the moho geometry to obtain reliable and stable results without introducing too complex and unconstrained ap rioriinformation one of the most important results is the discovery of low velocity anomalies at 38 km depth beneath the northern apenninic and calabrian arcs which we interpret as subducted crustal material of the adriatic and ionian lithospheres in the lower crust beneath the entire apennines a pronounced low velocitybelt is present suggesting high temperatures in front of the bent adriatic lithosphere based on our results and on those previously obtained from seismic tomography we propose amodel for the geodynamic evolution of the apenninic system in which the present day scenario re ects lateral heterogeneities in the subducting ionian oceanic and adriatic continental lithosphere

deformation effects of porosity variation on soil consolidation caused by groundwater table decline soil consolidation has been widely analyzed using the poroelastic theory as soil consolidation proceeds porosity variation leads to the changes in hydraulic conductivity young s modulus and body force however the combined deformation effect of porosity variation on soil consolidation is rarely examined in this study a poroelastic consolidation model used to simultaneously consider the changes in hydraulic conductivity young s modulus and body force was developed to investigate the combined deformation effect of porosity variation on soil consolidation caused by groundwater table decline the results indicate that the deformation effect of porosity variation on soil consolidation is negligible when the body force number is 0 01 soil displacement could be overestimated or underestimated if the combined deformation effect of porosity variation is not completely considered the misestimation of soil displacement increases as the body force number increases in addition the combined deformation effect of porosity variation also affects the transmission of pore water pressure therefore it could be concluded that a reliable analysis of soil consolidation must simultaneously account for the variations in hydraulic conductivity young s modulus and body force

hydraulic reversals and episodic methane emissions during drought cycles in mires reversals in hydraulic head and extensive methane losses were identified during a drought cycle from changes in hydraulic head and dissolved methane profiles in peat glacial lake agassiz peatlands northern minnesota united states during the summer 1990 drought regional groundwater discharged from the mineral soil underlying the peat to raised bogs concentrations of dissolved ch sub 4 in pore water showed that much of the peat column was supersaturated with respect to a reference standard of 1 atm partial pressure ch sub 4 by the summer of 1991 the severity of the drought lessened and the upper peat column was resaturated with precipitation derived water groundwater flow was then controlled by local precipitation driven recharge flow systems and the regional groundwater that was discharged affected only the peat immediately above the mineral soil peat interface in contrast during the summer of 1991 concentrations of dissolved ch sub 4 in pore water were all undersaturated with respect to 1 atm partial pressure ch sub 4 23 refs 5 figs

linearized inversion for fault rupture behavior application to the 1984 morgan hill california earthquake we present a technique to infer the rupture history of an earthquake from near source records of ground motion unlike most previous studies each point on the fault is assumed to slip only once when the rupture front passes with a spatially variable slip intensity in this parameterization the data are linearly related to slip intensity but nonlinearly related to rupture time we perform a linearized inversion for slip intensity and rupture time by iteratively perturbing an assumed starting model the inverse problem for the model perturbation is solved using a tomographic back projection technique smoothing and inequality constraints are applied to ensure that the resulting solution is stable and feasible asymptotic ray theory is used to calculate theoretical seismograms and partial derivatives with respect to model parameters in test cases with noisy synthetic data sets we found that it is possible to distinguish between rupture models having variable slip amplitude and models having variable rupture velocity provided the station coverage is adequate we apply the technique to recordings of the april 24 1984 morgan hill earthquake the results indicate that slip amplitude on the fault plane was extremely variable and that the rupture front did not propagate uniformly away from the hypocenter in particular rupture was delayed on a 12 km2 section of the fault approximately 14 km to the southeast of the hypocenter the rupture front surrounded the region which subsequently failed with a component of rupture propagation back toward the hypocenter similar behavior has been observed in dynamic rupture models with stress or strength inhomogeneities this segment of the fault ruptured with a large slip amplitude releasing 12 of the total seismic moment from 4 of the total area of the aftershock zone the surface trace of this section of the fault is characterized by a complex left step that could act to increase the normal stress acting across the fault however the distribution of aftershocks suggests that the fault at depth is simpler and that it may bend to the right in either case our rupture model suggests that this segment of the fault represents an asperity which initially resisted rupture but eventually ruptured massively we estimate the shear fracture energy for this earthquake to be 2 106 j m2

a new asymptotic method for the modeling of near field accelerograms we study high frequency radiation from a dislocation model of rupture propagation at the earthquake source we demonstrate that in this case all the radiation emanates from the rupture front and by a change of variables that at any instant of time the high frequency waves reaching an observer come from a line on the fault plane that we call isochrone an asymptotic approximation to near source velocity and acceleration is obtained that involves a simple integration along the isochrones for every time step it is shown that wave front discontinuities critical or stopping phases are radiated every time an isochrone becomes tangent to a barrier this leads to what we call the critical ray approximation which is given in a closed form the previous results are compared with discrete wavenumber synthetics obtained by bouchon 1982 for the gilroy 6 recording of the coyote lake earthquake of 1980 the fit between the asymptotic and full numerical method is extremely good the critical ray approximation permits the identification of different phases in bouchon s synthetics and the prediction of the behavior of the signal in the vicinity of their arrival time

the campania lucania southern italy earthquake of 23 november 1980 abstract we present the main seismological results of our study of the campania lucania earthquake of 23 november 1980 a complete set of far field and local data has been analysed from long period body waves data we determine the fault plane solution 1 140 1 60 2 75 2 54 a depth of 15 km and calculate a seismic moment of 6 1025 dyne cm and a source duration of 6 s from data of a local network deployed immediately after the event we determine aftershock locations they are aligned in a direction nw se that fit extremely well with the focal solution determined above we can choose as fault plane the plane striking 140 and dipping at 60 and the event is a normal event with a large component of left lateral strike slip the source area evaluated from this aftershock distribution 14 km 40 km is quite suitable for an earthquake of a seismic moment of 6 1025 dyne cm

evaluation of fully coupled strata deformation and groundwater flow in response to longwall mining a finite element poroelastic model is presented to evaluate fully coupled strata deformation and groundwater flow resulting from underground longwall mining in variably saturated fractured geologic media through an equivalent porous elastic continuum representation the explicit coupling between the groundwater flow field and the solid skeleton deformation field is achieved by simultaneously solving the governing equations for groundwater flow and solid skeleton deformation the implicit coupling between these two fields is also accomplished by considering the effects of both unsaturated water flow and solid skeleton deformation on the hydraulic properties such as water content and hydraulic conductivity in addition to the implicit coupling caused by unsaturated water flow the other implicit coupling caused by solid skeleton deformation is also important because it may produce hydraulic heterogeneity and anisotropy in a geologic medium affecting the groundwater flow field even when the system is in a fully saturated condition a physically based constitutive model is proposed to account for the deformation strain dependencies of porosity and saturated hydraulic conductivity of the fractured media to evaluate the impacts of longwall mining and to understand their hydrogeomechanical nature the numerical model is applied to a well documented case study with satisfactory results although the numerical simulation results presented in this paper will not apply to all underground longwall mines because of differences in site specific hydrogeological and geomechanical settings the methodology described herein may find some useful applications in many longwall mining projects

aftershocks of the campania lucania italy earthquake of 23 november 1980 abstract the result of a study of 1130 aftershocks of the 1980 campania lucania earthquake are presented the data were collected primarily with a dense array of portable smoked drum seismographs deployed in the epicentral region a few days after the main shock tests performed on subsets of the data to establish the location accuracy are described in detail and epicentral maps and cross sections are presented and discussed one hundred and sixty well constrained fault plane solutions using upward traveling rays are presented the distribution of aftershocks forms an elongate cloud which does not define a plane this is not because the events are poorly located a subset of events located with epicentral errors of less than 1 km and depth errors less than 2 km forms a similar cloud to the complete aftershock set the aftershock mechanisms are very varied some are similar to the main event but many differ profoundly these include events on shallow or vertical planes and thrust events the latter include some events which require contraction in the direction in which the main event indicates extension the aftershocks of all mechanisms are intermixed in space in such a way that no simple system of faults can explain them a model to explain the aftershocks and the lack of surface ruptures in the main event is offered it is proposed that the main shock cuts between two aseismic detachment surfaces and that the aftershocks are a consequence of the complicated deformation that such a geometry demands whatever interpretation is adopted the results are a challenge to the commonly accepted view that aftershocks even approximately define simple fault planes or that aftershock mechanisms replicate the mechanism of the main shock defects in interpretations of the main shock and aftershocks process arise largely from a lack of information about the geometry of structures at depth in the epicentral region suitable deep reflection profiles could help to resolve this problem

free phase gas processes in a northern peatland inferred from autonomous field scale resistivity imaging the mechanisms that control free phase gas fpg dynamics within peatlands and therefore estimates of past present and future gas fluxes to the atmosphere remain unclear electrical resistivity imaging eri is capable of autonomously collecting three dimensional data on the centimeter to tens of meter scale and thus provides a unique opportunity to observe fpg dynamics in situ we collected 127 3 d eri data sets as well as water level soil temperature atmospheric pressure and limited methane flux data at a site in a northern peatland over the period july august 2013 to improve the understanding of mechanisms controlling gas releases at a hitherto uncaptured field scale our results show the ability of eri to image the spatial distribution of gas accumulation and infer dynamics of gas migration through the peat column at high i e hourly temporal resolution furthermore the method provides insights into the role of certain mechanisms previously associated with the triggering of fpg releases such as drops in atmospheric pressure during these events buoyancy driven gas release primarily occurs in shallow peat as proposed by the shallow peat model releases from the deeper peat are impeded by confining layers and we observed a large loss of fpg in deep peat that may likely represent a rupture event where accumulated fpg escaped the confining layer as suggested by the deep peat model negative linear correlations between water table elevation and resistivity result from hydrostatic pressure regulating bubble volume although these variations did not appear to trigger fpg transfer or release

structure of peat soils and implications for water storage flow and solute transport a review update for geochemists abstract global peatlands are a valuable but vulnerable resource they represent a significant carbon and energy reservoir and play major roles in water and biogeochemical cycles peat soils are highly complex porous media with distinct characteristic physical and hydraulic properties pore sizes in undecomposed peat can exceed 5 mm but significant shrinkage occurs during dewatering compression and decomposition reducing pore sizes the structure of peat soil consists of pores that are open and connected dead ended or isolated the resulting dual porosity nature of peat soils affects water flow and solute migration which influence reactive transport processes and biogeochemical functions advective movement of aqueous and colloidal species is restricted to the hydrologically active or mobile fraction of the total porosity i e the open and connected pores peat may attenuate solute migration through molecular diffusion into the closed and dead end pores and for reactive species also through sorption and degradation reactions slow diffusion limited solute exchanges between the mobile and immobile regions may give rise to pore scale chemical gradients and heterogeneous distributions of microbial habitats and activity in peat soils while new information on the diversity and functionalities of peat microbial communities is rapidly accumulating the significance of the geochemical and geomicrobial study on peat stands to benefit from a basic understanding of the physical structure of peat soils in this paper we review the current knowledge of key physical and hydraulic properties related to the structure of globally available peat soils and briefly discuss their implications for water storage flow and the migration of solutes this paper is intended to narrow the gap between the ecohydrological and biogeochemical research communities working on peat soils

crustal earthquake instability in relation to the depth variation of frictional slip properties recent stability studies using constitutive relations of the type found by dieterich ruina and others to describe frictional slip of rocks in the laboratory have provided a new explanation of the depth cutoff of shallow crustal earthquakes the class of friction laws discussed has the property that the sliding stress depends on normal stress temperature slip rate and slip history for sliding at a fixed slip rate v and fixed environment e g normal stress temperature etc the shear strength evolves toward a steady state value ss v stability analysis show that for d ss v dv 0 velocity strengthening implies stable steady state sliding at least for a broad class of constitutive laws more fully described in the paper experiments by dieterich and by tullis and weeks on westerly granite with mature sliding surfaces indicate that d ss v dv is negative at room temperature whereas higher temperature experiments by stesky show that d ss v dv becomes positive above approximately 300 c therefore in the case of the earth where temperature increases with depth the above observations seem to suggest that the depth cutoff of crustal earthquake activity can be understood in terms of the variation of the frictional response with depth from a regime with d ss v dv 0 this is not inconsistent with but rather refines the suggestion by sibson and others that the depth cutoff is due to a transition from brittle friction to ductile flow further our results show definitively that the shallow depth confinement of seismicity is compatible with a model in which deformation is localized to a fault zone extending well below the seismogenic depth the depth confinement does not require a model showing transition to a zone of broadly distributed creep flow beneath the seismogenic zone following mavko a two dimensional quasi static strike slip fault model is analyzed but using different numerical procedures and a depth variation of frictional properties based on the laboratory data mentioned above and the lachenbruch sass depth variation of temperature for the san andreas fault the resulting predictions of such features as the confinement of crustal earthquakes to shallow depths the development of locked patches the recurrence time for the seismic cycle the seismic stress drop and displacement etc are generally in agreement with the observed characteristics of large scale strike slip earthquakes along the san andreas fault calculations based on the laboratory data predict for example that stick slip nucleates around 5 7 km that large seismic motion occurs around the nucleation depth and above but diminishes gradually to zero at 13 15 km depths that rapid postseismic creep occurs over another 3 4 km depth and that at greater depths steady slip consistent with the average plate velocity is only modestly perturbed by the earthquakes occurring above the most uncertain parameter is the slip weakening distance l for evolution of fault surface state we illustrate how features of the predicted earthquake cycles vary with l over the range for which calculations are feasible

effects of body force on transient poroelastic consolidation due to groundwater pumping by applying linear poro elasticity theory the body force effect on steady soil consolidation i e settlement caused by constant water table depression due to groundwater pumping was investigated the result shows that when the soil is soft or thick or both neglecting the body force effect can lead to severe underestimation of soil displacement and incremental effective stress however the transient response of soil consolidation was not analyzed in addition the water table depression due to groundwater pumping in fact varies with time in this study the body force effect on transient consolidation of soil subjected to variable water table depression is further examined a poroelastic consolidation numerical model is developed herein to conduct this examination

40ar 39ar geochronology of mafic rocks from the granite rhyolite terrane of southeastern missouri abstract the predominant 1480 ma granites and rhyolites of the st francois mountains southeastern missouri are intruded by mafic rocks a 40 ar 39 ar study of some of these the skrainka mafic group indicates an age of 1240 ma significantly younger than the host rocks significantly older than grenville keweenawan age and close to the age of similar rocks in labrador

source mechanisms of twenty six large shallow earthquake ms 6 5 during 1980 from p wave first motion and long period rayleigh wave data source mechanisms of 26 large shallow earthquakes are determined in terms of a double couple point source with a correction for the nondirectional part of source finiteness by using p wave first motions and long period rayleigh wave spectra recorded on wwssn ida and gdsn networks the combined use of both data sets allows us to determine the double couple mechanism uniquely in most cases constrained linear moment tensor inversion m xz m yz 0 correctly determines the strike of the fault but fails to estimate the dip and underestimates the scalar moment all thrust events along the deep sea trenches analyzed in this study show nodal planes which dip perpendicular to the trench axis at an angle shallower than 45 the fit to data of the double couple inversion is comparable to that of the constrained moment tensor inversion using the phase spectra of surface waves we can detect a slow source process with an accuracy of about 10 to 20 sec

use of long period surface waves for rapid determination of earthquake source parameters 2 preliminary determination of source mechanisms of large earthquakes ms 6 5 in 1980 an inversion method for fast retrieval of earthquake source parameters developed earlier has been applied to 28 large m s 6 5 shallow earthquakes which occurred in 1980 rayleigh waves recorded by the ida international deployment of accelerographs network were used for the analysis for very shallow events the inversion is ill conditioned and two of the moment tensor elements m zx and m zy are unresolvable of the 28 events a solution is obtained for 25 with the constraints m zx m zy 0 although these constraints limit the solution to be either vertical strike slip or 45 dip slip the method provides a useful first approximation to the mechanism solution for deeper events all of the elements of the moment tensor can be determined after the seismograms have been retrieved the solution can be obtained in 10 min for most events the method would be adequate for preliminary cataloging purposes

hydrological hotspots in blanket peatlands spatial variation in peat permeability around a natural soil pipe 1 measurements were made of the hydraulic conductivity k of peat around a natural soil pipe in a blanket bog this is the first investigation of decimeter scale variability in both vertical k and horizontal k in blanket peats which were found to be higher than indicated by previous research this information suggests that it may be appropriate to reconsider i the spatial sampling strategies employed to investigate subsurface flow in blanket peatlands and ii how field data are used to parameterize flow models critically there was spatial structure in the heterogeneity with a wedge of high k peat directly above the pipe forming a hydrological conduit between near surface peat and the perennially flowing pipe there was also significantly greater horizontal k parallel to the pipe s orientation compared with horizontal k perpendicular to the pipe determinations of the triaxial anisotropy of k undertaken for the first time in peat soils revealed substantial directional variations in k the k around the pipe peat interface was investigated however sample length dependency of k for peat samples precluded the investigation of a hypothesized low k skin around the pipe

three dimensional earthquake locations and upper crustal structure of the sannio matese region southern italy abstract the sannio matese region is one of the most seismically active regions of italy and has been struck by large historical earthquakes at present the area is characterized by low magnitude background seismicity and small seismic sequences following m 4 main events in this paper we show vp and vp vs models and 3d locations for a complete set of earthquakes occurring in the period 1991 2001 we observe a significant crustal heterogeneity with large scale east verging high vp fault related folds stacked by the pliocene compression the relocated earthquakes cluster along a 70 east dipping nw striking plane located at the border of the high vp thrust units normal fault earthquakes related to the young and active extension occur within these high vp zones interpreted as high strength material we expect large future earthquakes to occur within these high vp zones actually characterized by low magnitude seismicity at their borders

mathematical model for regional land subsidence due to pumping 2 integrated aquifer subsidence equations for vertical and horizontal displacements a mathematical model for regional subsidence due to pumping from an aquifer is developed on the basis of biot s work on coupled three dimensional consolidation following biot s work on threedimensional consolidation with coupling between mass conservation and equilibrium equations a mathematical model for regional subsidence due to pumping from an aquifer is developed by averaging the three dimensional model over the thickness of the aquifer and assuming conditions of plane stress both vertical land subsidence and horizontal displacements as functions of plane coordinates and time can be estimated by solving the model equations for a given confined or leaky confined aquifer an analytical solution is presented for the special case of a single well pumping from an infinite homogeneous isotropic aquifer the solution provides estimates of changes in averaged over the vertical values of piezometric head vertical subsidence and horizontal displacement the results indicate that under the conditions of the studied case of radial flow the solution for piezometric head is identical to the one obtained by noncoupled models furthermore half the volume strain is produced by vertical subsidence while the other half by the horizontal displacement hence the vertical subsidence is only approximately half the value obtained in noncoupled models which neglect horizontal displacement a numerical example demonstrates these conclusions

structural control on fault geometry example of the grevena ms 6 6 normal faulting earthquake in this paper we present a three dimensional velocity structure of the kozani grevena region a relatively low seismicity area of the western margin of the internal hellenides which was struck by a ms 6 6 earthquake on may 13 1995 p wave arrival times from 656 aftershocks are inverted to resolve the velocity structure of the upper 12 km of the crust the 1995 ruptured fault dheskati fault lies at the southeastern end of a 35 km long normal fault the servia fault the crustal heterogeneities identified by tomography help to constrain the geometry and structure of the 1995 fault and the rupture evolution during the mainshock the aftershocks and the velocity structure define a fault dipping 35 toward nw which from 5 km depth splays upward into two nearly parallel shallow faults the slip during the mainshock and the aftershocks all were concentrated along the deeper portion of the fault while the limited slip observed at the surface occurred on the northern of the two shallower splays the paleochori fault it appears that the lithological heterogeneities of the shallow crust are responsible for the splaying of the main fault upward our work stresses the importance of crustal structure in determining fault geometry and segmentation and rupture evolution

numerical simulation of the noordbergum effect resulting from groundwater pumping in a layered aquifer system abstract numerical simulations were carried out to investigate the so called noordbergum effect i e reverse water level fluctuation resulting from groundwater withdrawal two specific cases were analyzed a three layer aquifer system composed of two permeable aquifers separated by a semi impermeable aquitard and a corresponding single layer aquifer system composed of an equivalent lumped material in the numerical simulation of the layered aquifer system the noordbergum effect is observed during the early time period of pumping in the overlying aquitard and unpumped aquifer while the underlying aquifer is pumped in contrast the numerical simulation results of the lumped aquifer system do not show such a reverse water level fluctuation throughout the entire domain these results strongly suggest that the noordbergum effect can be explained by the difference in poroelastic responses of the layered heterogeneous and lumped homogeneous aquifer systems to the hydraulic pumping stress the noordbergum effect is caused by two mechanisms a faster mechanical propagation deformation of the pumping stress than its hydraulic propagation drawdown from the pumped aquifer into the adjacent aquitard and unpumped aquifer due to relatively lower hydraulic conductivity of the aquitard and a mechanical amplification excessive compression in the lower part of the relatively soft aquitard however the pumping stress is evenly distributed throughout the entire domain of the lumped aquifer system without such mechanisms since it has homogeneous hydraulic and mechanical properties

simulating vertical flow in large peatlands ground water flow simulations are used to evaluate the importance of three parameters on vertical flow in peatlands regional slope permeability of the mineral soil underlying the peat and peatland topography our results indicate that the extent of vertical ground water flow in peatlands is primarily controlled by mineral soil permeability local ground water flow cells that form under small water table mounds at bog domes can drive peat pore water into permeable mineral soil however when peat forms over low permeability mineral soil vertical movement of peat pore water becomes negligible and lateral flow of water in the upper portion of the peat column dominates the peatland hydrology this effect is not due to the low permeability of humified peat layers as is commonly assumed in many peatland studies field data from the hudson bay lowland canada and the glacial lake agassiz peatlands of northern minnesota confirm the validity of these models these results are relevant in settings other than peatlands where relief is low and small topographic mounds exist

the rupture process of the 1980 irpinia italy earthquake from the inversion of strong motion waveforms abstract the distribution of slip and the behaviour of rupture propagation during the 23rd november 1980 irpinia earthquake ms 6 9 was investigated by analysing strong motion accelerograms the rupture was assumed to develop on a two dimensional purely normal fault whose geometry was constrained by geologic and geodetic data and by the aftershock space distribution theoretical seismograms have been computed using the isochron approach with a spatially variable slip intensity the asymptotic ray theory is used to evaluate the far field green functions the rupture model was updated following a trial and error approach the fit of observed waveforms with synthetic seismograms allowed several peculiarities in the rupture history to be pointed out the source model resulting from the solution of the forward waveform modelling was then used as starting model for the inversion of ground velocities therefore we performed a linearized inversion for slip velocity and rupture times on the fault by iteratively perturbing the assumed starting model the inverse problem is solved by means of a tomographic back projection technique the inferred source model shows a bilateral rupture which does not propagate uniformly away from the hypocentre the rupture velocity and the slip distribution on the fault plane are rather variable the solution confirms the shallow dislocation gap in the central part of the fault suggested by the behaviour of the surface rupture the results indicate that the rupture propagated northwestward along a further fault fragment for which no surface evidence is observed the aftershocks occurred mostly inside of or near to the edges of the source areas of maximum co seismic slip

groundwater surface water interaction between an esker aquifer and a drained fen summary groundwater discharge from an esker aquifer to a fen was studied to understand relevant hydrological processes for groundwater surface water interaction in an esker peatland hillslope piezometric levels of the peat layer and esker sand layer were continuously monitored and compared to climate data groundwater exfiltration points were spatially mapped and related to peat depth the study showed a clear interaction between fen surface water and sand esker groundwater although the hydraulic conductivity of peat was low and the peat depth thick in the artesian aquifer beneath the fen the piezometric head showed a clear response to precipitation and evapotranspiration wetting of the peat is rapidly seen as pressure increase in the confined aquifer this provides new information on hydraulics of wetlands found in aquifer discharge areas groundwater exfiltrated through thick peat layers in vertical preferential point discharges demonstrating how double porosity provides flow through the peat layer with low hydraulic conductivity in the peat matrix the pipe flow channels were found in the deep peat area in the transition zones from deep peat to shallow peat diffuse seepage through the ditch bottom was found where ditches cut into the sand layer increased discharge through the ditch bed reduced the flow resistance at the aquifer boundary which can lower the groundwater level in the esker the results show new processes in the groundwater discharge zone that are useful for groundwater modelling and policy development for future groundwater protection

moment and duration of shallow earthquakes from love wave modelling for regional distances abstract love waves from five earthquakes in southwest germany italy yugoslavia greece and algeria as recorded at the broadband grafenberg array in eastern bavaria are modelled in detail using an extended reflectivity method the focal mechanisms are taken from the literature or determined from long period wwnss data the theoretical double couple moment function used for modelling increases smoothly during the risetime t from zero to the seismic moment m0 t and m0 are determined by matching the observed and theoretical love wave seismograms in the long period wwnss frequency band t is approximately equal to the rupture duration values from 1 4 to 20 s are found seismic moments generally agree within a factor of about two with those found by other authors from larger data sets the earthquakes in southwest germany and greece were simple events and can be modelled very well by one double couple in the case of the other earthquakes the theoretical love wave seismograms are too short for these earthquakes there is some independent evidence for a multiple event nature this evidence is condensed into source models consisting of two or three double couples representing separate and complete sub earthquakes which then explain the observations quite well in the case of the algerian earthquake the long love wave duration may also be due to complications in structure along the wavepath across the mediterranean and the alps the present results show that accurate love wave modelling for a single station at regional distance from an epicentre is a reliable method for estimation of seismic moment and rupture duration use of a digitally recording station with large dynamic range allows events over a large magnitude interval to be studied the grafenberg array is well suited for such an investigation of european and north african earthquakes

the irpinia italy 1980 earthquake detailed analysis of a complex normal faulting a detailed analysis of near source strong motion and leveling data together with the results of teleseismic waveform modeling by westaway and jackson 1987 and aftershock studies by deschamps and king 1984 allows a satisfactory kinematic description of the complex normal faulting associated with the magnitude ms 6 9 november 23 1980 irpinia earthquake southern italy the three main rupture episodes starting at about 0 20 and 40 s are here associated with better constrained source parameters than in previous studies we first evaluated the triggering time for the 11 closest accelerometers by using the well recorded 40 s strong motion phases this gave the absolute time and location of the dominant episodes of faulting the first rupture propagated mainly toward the northwest on a ne dipping normal fault at a mean velocity close to 3 km s for about 20 km and continued 15 km further on smaller subfaults it was associated with surface breakage in the southeastern part the second rupture started from the southeastern end of the first rupture about 18 s after it and propagated about 20 km toward the southeast on a low angle normal fault dipping 20 ne it was associated with secondary faulting on steeper planes reaching the surface the third and last episode at 39 s nucleated near the first hypocenter at shallower depth and the rupture possibly propagated on a 10 to 15 km long normal fault striking se antithetic to the first activated fault a clear correlation appears between the strength of the geological formations and the existence of surface breakage and shallow aftershock activity

viscosity effect on consolidation of poroelastic soil due to groundwater table depression in this study the viscosity effect on consolidation of poroelastic soil due to groundwater table depression is examined a viscoelastic consolidation numerical model is developed to conduct this examination by nondimensionalizing the governing equations the viscosity number that depends on hydraulic conductivity viscous moduli and thickness of soil is obtained to represent the viscosity effect on consolidation of poroelastic soil the case of clay stratum sandwiched between sandy strata subjected to sudden and gradual groundwater table depressions is used to investigate the importance of viscosity effect to poroelastic consolidation the results show that the displacement and pore water pressure of clay stratum are strongly related to the viscosity effect the overestimation of soil displacement will occur if the viscosity effect is neglected hence the viscosity effect needs to be considered in modeling consolidation of poroelastic soil under groundwater table depression

a mathematical model for regional land subsidence due to pumping 3 integrated equations for a phreatic aquifer a mathematical model is developed for the areal distribution of drawdown land subsidence and horizontal displacements due to groundwater pumping from a deformable phreatic aquifer this paper is a continuation of earlier works published by the authors bear and corapcioglu 1981a b on the subject of regional land subsidence due to pumping in confined and leaky aquifers all the basic assumptions underlying these previous works are also valid here however in this case the same methodology is extended to the case of a phreatic aquifer the main additional feature in the present paper is that due to the decline of the water table the total stress at points within the flow domain changes continuously following the development of a three dimensional mathematical model consisting of a mass conservation equation quasi static equilibrium equations and stress strain relations for an assumed perfectly elastic solid matrix a regional horizontal two dimensional model is derived by averaging the three dimensional model over the vertical thickness of the aquifer taking into account the continuous variation in total stress as a result of water table fluctuations the separation of an initially coinciding phreatic surface which serves as the upper boundary of the aquifer and a surface consisting of a set of solid particles during the lowering of the water table and the compaction of the aquifer has been incorporated into the averaging procedure an analytical solution is given for the case of a single pumping well the solution which is expressed in terms of the classical well function for a confined aquifer but with a modified storativity provides estimates of drawdown vertical subsidence and horizontal displacement the displacements for a sample problem are compared with those of a confined aquifer under similar conditions the results indicate that under the conditions of the studied case of radial flow vertical and horizontal displacements due to pumping from a phreatic aquifer with the same discharge rate would be less than those of a confined one furthermore the same averaging procedure is extended for a system of phreatic and leaky confined aquifers and for the unsaturated zone above the water table an additional change in total stress is obtained in terms of moisture content of the zone above the phreatic surface

tomographic inversion of local earthquake data from the hengill grensdalur central volcano complex iceland parameters is generally low however a quantitative analysis of resolution provides an unambiguous assessment of well resolved volumes within the better resolved regions of the model the averaging volumes are 1 2 km and 2 4 km in vertical and horizontal extent respectively results of tomographic inversion image three distinct bodies of anomalously high velocity two of these extend from near the surface to a depth of about 3 km these high velocity volumes are located directly beneath the surface expressions of the extinct grensdalur volcano and the extinct husmuli basalt shield the third high velocity structure occurs in the depth range of 3 4 km but does not extend to the surface these three high velocity bodies are interpreted to be solidified magmatic intrusions relatively low velocities underlay limited portions of the trace of the present accretionary axis and a low velocity body is imaged in the roots of the active hengill volcano the volume of lower velocities located beneath the surface expression of the hengill volcano is interpreted to be a region of partial melt

three dimensional velocity structure in northern california coast ranges from inversion of local earthquake arrival times abstract the three dimensional p wave velocity structure in the upper crust in the northern california coast ranges from santa rosa to ukiah is obtained by simultaneous inversion of local earthquake and refraction travel time data for velocity and hypocentral parameters in this region where there are lateral heterogeneities the three dimensional inversion provides important results not found in two dimensional refraction studies the medium is parameterized with velocities at the intersections gridpoints of a nonuniform three dimensional grid travel times are calculated with approximate ray tracing along arcuate paths which are reasonable for lateral distances less than 45 km inversions with 5 to 10 and 2 to 3 km gridspacing achieved 80 per cent decreases in data variance the inversion with 2 to 3 km gridspacing reduced the rms residual level to approximately the level of timing error anomalously low velocities to at least 6 km depth are found along the maacama and healdsburg rodgers creek hrc fault zones the low velocity region is widest at the en echelon junction of the maacama and hrc fault zones low velocities are associated with the clear lake basin where there is a thick sequence of volcanics interbedded with sedimentary deposits there is a high velocity body located southeast of the geysers between the maacama and collayomi fault zones which may be associated with igneous intrusives or high grade metamorphism related to an underlying inferred partial melt body modeled in previous teleseismic travel time studies there is some indication in the vapor dominated geothermal reservoir of lower velocities relative to surrounding water saturated rock as has been shown in some laboratory experiments hypocenter locations obtained in the inversion show little variation from hypocenters obtained through inversion for one dimensional velocity model and station corrections for the inversion with 2 to 3 km gridspacing however some groups of events become more tightly clustered

three dimensional p velocity structure in the region of the ms 6 9 irpinia italy normal faulting earthquake abstract we have calculated the three dimensional velocity structure in the epicentral region of the 1980 irpinia southern italy earthquake using thurber s inversion technique for hypocenter and velocity parameters particular care was given to the evaluation of the resolution of the models because of the poor reading accuracy of the analog stations operating at that time we analyzed the averaging vector for each node of the model in order to estimate the degree of smearing within the final tomographic image this approach is suitable for determining the best parametrization to use i e the minimum grid spacing and for evaluating the region where the computed velocities are meaningful the results show that the main rupture occurred along a sharp nw se trending velocity contrast which probably reflects a crustal discontinuity the velocity variations along the fault probably due to lithological heterogeneities account for the complex character of this earthquake based on the velocity distribution at depth the secondary rupture that started about 40 s after the mainshock is interpreted to be the result of reactivation of an old thrust as a normal fault

from velocity and attenuation tomography to rock physical modeling inferences on fluid driven earthquake processes at the irpinia fault system in southern italy we retrieve 3 d attenuation images of the crustal volume embedding the fault system associated with the destructive ms 6 9 1980 irpinia earthquake by tomographic inversion of t measurements a high qp anomaly is found to be correlated with the 1980 fault geometry while the qs model shows regional scale variations related to the ne edge of the uplifted pre tertiary limestone an upscaling strategy is used to infer rock properties such as porosity consolidation type of fluid mixing and relative saturation percentage at 8 10 km fault depth we constrain the porosity and consolidation in the ranges 4 5 and 5 9 respectively with the possible fluid mixes being both brine co2 and ch4 co2 the consolidation parameter range indicates high pore pressures at the same depths these results support the evidence for a fracture system highly saturated in gases and a seismicity triggering mechanism at the fault zone which is strongly controlled by fluid induced pore pressure changes

upper crustal structure of the benevento area southern italy fault heterogeneities and potential for large earthquakes summary the benevento region is part of the southern apennines seismogenic belt which experienced large destructive seismic events both in historical and in recent times the study area lies at the northern end of the irpinia fault which ruptured in 1980 with a ms 6 9 normal faulting event which caused about 3000 casualties the aims of this paper are to image lateral heterogeneities in the upper crust of the benevento region and to try to identify the fault segments that are expected to generate such large earthquakes this work is motivated by the recognition that lithological heterogeneities along major fault zones inferred from velocity anomalies reflect the presence of fault patches that behave differently during large rupture episodes in this paper we define the crustal structure of the benevento region by using the background seismicity recorded during 1991 and 1992 by a local seismic array these data offer a unique opportunity to investigate the presence of structural discontinuities of a major seismogenic zone before the occurrence of the next large earthquake the main result that we obtained is the delineation of two nw trending high velocity zones hvzs in the upper crust beneath the matese limestone massif these high velocities are interpreted as high strength regions that extend for 30 40 km down to at least 12 km depth the correspondence of these hvzs with the maximum intensity regions of historical earthquakes 1688 ad 1805 ad suggests that these anomalies delineate the extent of two fault segments of the southern apenninic belt capable of generating m 6 5 7 earthquakes the lateral offset observed between the two segments from tomographic results and isoseismal areas is possibly related to transverse right lateral faults

calderas in the precambrian terrane of the st francois mountains southeastern missouri precambrian igneous rocks in the st francois mountains of southeastern missouri consist of silicic volcanic rocks mostly ash flow tuff which crop out mostly in the western and southwestern part of the region and epizonal granitic plutons which are mostly exposed in the northeastern part of the area these relations suggest that the exposures in the northeast are of a somewhat deeper part of the crust and that rocks there are now exposed because of west southwesterly tilting and beveling by erosion in the eastern st francois mountains the occurrence of a thick rhyolitic ash flow tuff grassy mountain ignimbrite and its distribution relative to a large high silica pluton butler hill granite suggest that the ash flow is the principal eruptive material of a caldera the butler hill caldera and that butler hill granite is the frozen magma chamber that was originally beneath it structural relations indicate that butler hill granite was emplaced into the volcanic rocks of the caldera during resurgent doming four small low silica plutons silvermine stono knoblick and slabtown granites are distributed peripherally to the butler hill granite and are interpreted as ring plutons emplaced along the ring fracture of the caldera or along arcuate intracaldera faults after resurgent doming and emplacement of butler hill granite more than 3 km of silicic volcanic rocks occupy a basinal structure in the western st francois mountains these rocks lie with angular unconformity upon up domed older rocks of the butler hill caldera along an arcuate zone of megabreccia and disturbed structure on the western margin of the older caldera this feature is interpreted as the topographic wall of a second caldera which lies to the west the occurrence of the thick taum sauk rhyolite stratigraphically about 3 km higher than the rocks involved in the megabreccias may indicate that there was yet another caldera formed in this western part of the st francois mountains

peat porewaters have contrasting geochemical fingerprints for groundwater recharge and discharge due to matrix diffusion in a large northern bog fen complex abstract although northern peatlands represent a globally significant reservoir for carbon considerable uncertainty exists concerning solute transport systems within large 1000 km 2 peat deposits we therefore delineated geochemical gradients linked to groundwater recharge and discharge along a 6 km transect within the 1200 km 2 red lake peatland of northwestern minnesota we used ratios of ca mg and 87 sr 86 sr to distinguish discharge of calcareous groundwater 1 4 and 0 7155 respectively to the peatland from the mineral substratum along a topographic gradient from a bog crest downslope to an internal fen water track and bog islands in contrast the stable isotopes of the porewaters 18 o from 12 8 to 7 8 show that the active pore spaces in these peat profiles have been flushed by recharge from the near surface peat we hypothesize that back diffusion of groundwater derived solutes from the peat matrix to active pore spaces has allowed the geochemical signal from paleo hydrogeologic discharge to persist into the current regime of dilute recharge this effect has not been observed previously on the landform scale and has important implications for carbon cycling in peatlands

source complexity of the 1980 southern italian earthquake from the analysis of strong motion s wave polarization strong motion records from 23 november 1980 earthquake in irpinia basilicata southern italy recorded less than 59 km to the source show strong s wave phases coherent up to 10 hz at more distant stations the signal is only coherent up to 5 hz even when recordings contain signal up to 10 hz hodogram plots of the coherent signal in the 5 to 10 hz range show lissajous figures of sh and sv waves radiated by the nearest point with strong seismic radiation by the terminations of the rupture or by other relatively compact features the largest acceleration recorded at the sturno station is due to high frequency pulses radiated by a source south of the station and 25 km from the epicenter hodogram plots of low frequencies show polarizations due to the propagation of the large scale rupture along the fault lissajous figures help to discriminate p and s arrivals and reveal their direction of propagation on the basis of this kind of analysis it is confirmed that the 1980 irpinia basilicata earthquake ml 6 5 was composed of three main sub events at 0 sec 19 sec and 39 sec in relative time the first and second events broke the same structure striking nw there is also evidence of bilateral propagation the third event broke a second smaller structure also striking nw and placed very close to the alignment of the previous ones

speculations on the geometry of the initiation and termination processes of earthquake rupture and its relation to morphology and geological structure earthquake initiation and termination processes are commonly described in terms of barriers and asperities barriers fall into two classes geometric barriers are associated with places where the orientation of a failure surface changes and relaxation barriers where stress is low because aseismic creep processes outpace tectonic loading geometric barriers fall into conservative and nonconservative subgroups according to whether finite fault motion can proceed without the creation of new structures or whether it demands the creation of new faulting or void space the multiple faulting or fragmentation associated with some nonconservative barriers can disrupt fault planes and form asperities by means of selected examples it is shown that a description in terms of these barriers can help one to visualise the processes of earthquake rupture and its relation to the geological environment

quantitative investigations of the missouri gravity low a possible expression of a large late precambrian batholith intersecting the new madrid seismic zone analysis of gravity and magnetic anomaly data helps characterize the geometry and physical properties of the source of the missouri gravity low an important cratonic feature of substantial width about 125 km and length 600 km filtered anomaly maps show that this prominent feature extends nw from the reelfoot rift to the midcontinent rift system geologic reasoning and the simultaneous inversion of the gravity and magnetic data lead to an interpretation that the gravity anomaly reflects an upper crustal 11 km thick batholith with either near vertical or outward dipping boundaries considering the modeled characteristics of the batholith structural fabric of missouri and relations of the batholith with plutons and regions of alteration a tectonic model for the formation of the batholith is proposed the model includes a mantle plume that heated the crust during late precambrian and melted portions of lower and middle crust from which the low density granitic rocks forming the batholith were partly derived the batholith called the missouri batholith may be currently related to the release of seismic energy in the new madrid seismic zone earthquake concentrations occur at the intersection of the missouri batholith and the new madrid seismic zone three qualitative mechanical models are suggested to explain this relationship with seismicity

vp and vp vs images in the mw 6 0 colfiorito fault region central italy a contribution to the understanding of seismotectonic and seismogenic processes 1 in 1997 the umbria marche apennines central italy was struck by a series of moderate magnitude normal faulting earthquakes accompanied by a prolonged sequence of aftershocks seismological analysis revealed a 40 km long nw trending structure composed by several low angle normal fault segments in this paper we present the three dimensional 3 d vp and vp vs structure of the fault zone determined by the inversion of p and s wave arrival times from 1982 aftershocks the high resolution tomographic images reveal strong heterogeneity along and across the fault zone and allow us along with the 3 d location of earthquakes to define the fault geometry at depth and to improve our understanding on the seismotectonics of this part of the northern apennines thrust and fold belt the relocated aftershocks suggest that the main ruptures occurred on planes slightly steeper than previously hypothesized and at depths shallower than those evidenced by 1 d locations we find that the preexisting structure which developed during the neogene compressional tectonics plays an important role in the earthquake generation and rupture evolution of the normal faulting events we propose that the main shocks whose hypocenters are all located at 6 km depth originated along a shallow decollement of the meso cenozoic cover thrust over the metamorphic basement geometrical discontinuities and lateral steps along the inherited structures control the lateral fault extent and determine fault segmentation this study offers a good example of how lithological heterogeneities and the complexity of the upper crust structure strongly affect the faulting process

surface faulting in the southern italian campania basilicata earthquake of 23 november 1980 the campania basilicata earthquake of 23 november 1980 was the largest ms 6 9 and most destructive earthquake that has occurred in this region of southern italy for over 100 years killing more than 3 000 people the consensus among seismologists geologists and earthquake engineers who have studied1 10 this event is in keeping with previous italian earthquakes that it did not produce faulting at the surface this has led to the establishment of a number of models2 3 11 13 requiring an unusual tectonic setting for the southern apennines however on a recent visit to the epicentral region of the earthquake may 1984 we discovered more than 10 km of surface faulting that is consistent with focal mechanisms for this event based on first motion polarities2 4 5 12 and long period waveform studies14 16 which show that it involved normal faulting with one nodal plane dipping at 60 towards the north east our observations of this the first well documented earthquake fault break to be reported in italy suggest that the deformation associated with earthquakes in the southern apennines takes place in the upper 10 15 km of the earth s crust on steep planar normal faults which break the surface as is widely observed in other areas of active extension outside italy

a faulting model for the 1979 imperial valley earthquake by comparing synthetic particle velocities with the near source strong motion data we have constructed by trial and error a faulting model for the 1979 imperial valley earthquake the calculation of the synthetic seismograms takes into account the vertical inhomogeneity of the elastic parameters in the imperial valley and the spatial variation of the slip rate parameters on the fault plane the independent slip rate parameters are 1 the strike slip rate amplitude 2 the dip slip rate amplitude 3 the duration that slip rate is nonzero the rise time of the slip function and 4 the rupture time which determines when the slip rate is initiated our faulting model has the following principal features 1 faulting occurred on the imperial fault and on the brawley fault rupture on the brawley fault being triggered by rupture on the imperial fault 2 the imperial fault is a plane 35 km long and 13 km wide with a strike of 323 measured clockwise from north and a dip of 80 ne the brawley fault is a 10 km long and 8 km wide plane with a strike of 360 and a dip of 90 3 faulting on the imperial fault is primarily right lateral strike slip with a small component of normal dip slip in the sediments at its northern end the larger strike slip rates are generally confined between depths of 5 and 13 km with maximum values of about 1 0 m s the duration varies on the fault with a maximum of 1 9 s which is considerably shorter than the total time for the rupture to take place 4 the rupture velocity on the imperial fault is highly variable locally it exceeds the shear wave velocity and in one instance the compressional wave velocity the average rupture velocity though is less than the shear wave velocity 5 although the slip on the brawley fault contributes only about 4 of the total moment it greatly affects the ground motion at nearby stations 6 the total seismic moment is 6 7 1018 n m where the imperial fault contributes 6 4 1018 n m and the brawley fault contributes 2 7 1017 n m in the process of trying almost 300 faulting models we found that given the elastic parameters of the medium the synthetic seismograms were most sensitive to the specification of the rupture time although the slip rate amplitudes are linearly related to the data the rupture time and the duration are not the parameterization of the nonlinear variables has a strong effect on the generation of synthetic seismograms from a finite fault

peat deformation and biogenic gas bubbles control seasonal variations in peat hydraulic conductivity the hydraulic conductivity k of peat beneath the water table varies over short annual periods biogenic gas bubbles block pores and reduce k and seasonal changes in the water table position cause peat deformation altering peat pore size distribution although it has been hypothesized that both processes reduce k during warm dry summer conditions temporal variations in k under field conditions have been explained previously by peat volume changes strain alone we determine the effect of both controls on k by monitoring changes in gas content strain and k within a poor fen over the growing season k decreased by an order of magnitude in the near surface peat 0 3 0 7 m this reduction is more strongly correlated with providing the first field based evidence that biogenic gas bubbles reduce k in the deeper peat 0 7 1 3 m k is correlated principally with strain however causality is uncertain because of multicollinearity between strain and to mitigate for multicollinearity we took advantage of a peatland drainage experiment where the water table was artificially dropped at the beginning of the growing season reducing correlations between strain and remained the primary cause of k variations just beneath the water table at a depth of 0 5 0 7 m although further down through the peat profile 0 7 1 2 m changes in k were controlled by strain we suggest that the larger pore structure of the poorly decomposed peat just below the water table is impacted less by volume changes than that of the more decomposed peat at depth however within this poorly decomposed peat k is reduced by the high gas contents that result from higher rates of methane production copyright 2012 john wiley sons ltd

unsaturated hydraulic properties of sphagnum moss and peat reveal trimodal pore size distributions in ombrotrophic peatlands the moisture content of the vadose zone acrotelm controls oxygen diffusion rates redox state and the turnover of organic matter whether peatlands act as sinks or sources of atmospheric carbon thus relies on variably saturated flow processes the richards equation is the standard model for water flow in soils but it is not clear whether it can be applied to simulate water flow in live sphagnum moss transient laboratory evaporation experiments were conducted to observe evaporative water fluxes in the acrotelm containing living sphagnum moss and a deeper layer containing decomposed moss peat the experimental data were evaluated by inverse modeling using the richards equation as process model for variably saturated flow it was tested whether water fluxes and time series of measured pressure heads during evaporation could be simulated the results showed that the measurements could be matched very well providing the hydraulic properties are represented by a suitable model for this a trimodal parametrization of the underlying pore size distribution was necessary which reflects three distinct pore systems of the sphagnum constituted by inter intra and inner plant water while the traditional van genuchten mualem model led to great discrepancies the physically more comprehensive peters durner iden model which accounts for capillary and noncapillary flow led to a more consistent description of the observations we conclude that the richards equation is a valid process description for variably saturated moisture fluxes over a wide pressure range in peatlands supporting the conceptualization of the live moss as part of the vadose zone

three dimensional finite difference simulation of fault dynamics rectangular faults with fixed rupture velocity we analyze three dimensional finite difference solutions for a simple shear crack model of faulting to determine the effects of fault length and width on the earthquake slip function the fault model is dynamic with only rupture velocity fault dimensions and dynamic stress drop prescribed the numerical solutions are accurate for frequencies up to 5 hz and are combined with asymptotic results for shear cracks in order to characterize the slip function at higher frequencies near the hypocenter the slip velocity exhibits a square root singularity whose intensity increases with hypocentral distance at distances greater than the fault width w growth of the velocity intensity ceases and the slip function becomes nearly invariant with distance along the fault length closed form expressions are developed for the dependence of static slip s slip rise time tr and slip velocity intensity v on fault geometry along the center line of a long narrow fault at hypocentral distances exceeding w these expressions reduce to s w tr 0 5 w vr and v w 2 vr where is the dynamic stress drop the shear modulus and vr the rupture velocity the numerical results imply that uniform dislocation kinematic earthquake models in which slip is represented by a ramp time function will underpredict high frequency ground motion relative to low frequency ground motion a further implication of the numerical solutions is that the nature of inelastic processes at the advancing edge of a long fault will depend on fault width but will be independent of rupture length

ground surface response to continuous compaction of aquifer system in tehran iran results from a long term multi sensor insar analysis abstract most of the developed groundwater basins in iran are subject to land subsidence hazards resulting from the over extraction of groundwater several areas in tehran the capital city and a provincial center in north central iran have been reported to be subsiding at different rates in this study we present the results of an interferometric synthetic aperture radar insar time series analysis of tehran using different sar data between 2003 and 2017 by constructing more than 400 interferograms derived from 39 envisat asar c band 10 alos palsar l band 48 terrasar x x band and 64 sentinel 1 c band sar datasets we compile displacement time series from interferometric observations using the small baseline sb technique our analysis identifies 3 distinct subsidence features in tehran with rates exceeding 25 cm yr in the western tehran plain approximately 5 cm yr in the immediate vicinity of tehran international airport and 22 cm yr in the varamin plain to the southeast of tehran city the temporal pattern of land subsidence which is dominated by a decreasing trend generally follows the regional decline in groundwater level which suggests that anthropogenic processes caused by excessive groundwater extraction are the primary cause of land subsidence integrating a decadal time series of subsidence constructed from multi sensor insar with in situ observations suggests that inelastic and permanent compaction dominates the main deformation regime of the tehran aquifer and the ratio between elastic and inelastic deformation is approximately 0 4 a geological analysis indicates that the shape of the subsidence bowl in the western tehran plain does not follow the trend of major mapped faults in the region in contrast the subsidence bowl in varamin is controlled by the pishva fault which suggests that either this fault acts as a hydrologic barrier to the groundwater flow in this region or that the differences in sediment thickness causes the discontinuity in land subsidence

three dimensional numerical simulation of fully coupled groundwater flow and land deformation due to groundwater pumping in an unsaturated fluvial aquifer system a series of three dimensional numerical simulations using a hydrogeomechanical numerical model is performed to analyze and predict fully coupled groundwater flow and land deformation due to groundwater pumping in an unsaturated fluvial aquifer system which has irregular lateral boundaries the aquifer system is composed of a loam layer underlain by a sand layer on bedrock a steady state numerical simulation is performed first to obtain initial spatial distributions of pressure head hydraulic head and groundwater flow velocity before groundwater pumping and its results are illustrated and validated reasonably with respect to field measurements of hydraulic head a transient state numerical simulation is then performed to obtain spatial and temporal distributions of pressure head hydraulic head groundwater flow velocity and land displacement vector during groundwater pumping and its results are also illustrated and validated reasonably with respect to field measurements of both hydraulic head and vertical displacement these numerical simulation results show that hydrogeomechanical numerical modeling can be a useful tool for analyzing and predicting long term groundwater level fluctuation and land deformation due to groundwater pumping in actual three dimensional aquifer systems