promotion of graphite formation by tectonic stress a laboratory experiment summary graphitization of less ordered hexagonal carbon was studied under in situ pressure and temperature conditions on anthracite black shale and a synthetic calcite anthracite mixture at upper greenschist facies conditions anthracite exhibited a continuous loss of volatiles in the temperature range from 100 cu p to850 c 9 9 weight per cent at 450 c as detected by differential thermal analysis dta and thermo gravimetry tg energy dispersive x ray diffraction edx revealed a broad amorphous 002 graphite reflection while after p t treatment nearly perfect crystallized graphitic carbon was detected the electrical conductivity was measured at the same time in the frequency range from 0 7 up to 100 khz as a function of time the bulk resistivity was decreased by about three orders in magnitude at constant pressure and temperature conditions 0 7 gpa 450 c while the complex response exhibited a continuous decrease of the imaginary part of the impedance quasi metallic conduction now dominated the charge transport application of pressure strain temperature and time caused an increase in ordering and the degree of interconnection of the formerly randomly oriented carbon sheets the experimental results are an approach towards the explanation of the abundant occurrence of crystalline graphite observed in overthrusts and nappe structures which are distinguished by high conductivity structures

the use of vertical wind shear versus helicity in interpreting supercell dynamics a series of idealized simulations of supercell storms are presented for environments representing straight through circular hodographs to clarify the character of the storm dynamics over the large spectrum of hodograph shapes commonly observed the primary emphasis is on comparing and contrasting recent theories of supercell dynamics based on updraft shear interactions storm relative environmental helicity sreh and beltrami flow solutions to help clarify the degree to which each theory can represent the essential storm dynamics one of the particular questions being addressed is whether storm dynamics are significantly different for straight versus curved hodographs which has become a point of some controversy over recent years in agreement with previous studies the authors find that the physical processes that promote storm maintenance rotation and propagation are similar for all hodograph shapes employed and are due primarily to nonlinear interactions between the updraft and the ambient shear associated with the localized development of rotation on the storm s flank significant correlations between the updraft and vertical vorticity are also observed across the shear spectrum and in agreement with predictions of linear theories associated with sreh this correlation increases for increasing hodograph curvature however storm steadiness and propagation must already be known or inferred for such concepts to be applied thus limiting the applicability of this theory as a true predictor of storm properties tests of the applicability of beltrami solutions also confirm reasonable agreement for purely circular hodographs for which the analytical solutions are specifically designed however analysis of the model results indicates that the terms ignored for such solutions representing the nonlinear effects associated with storm rotation are more significant than those retained over most of the hodograph spectrum which severely limits the general applicability of such analyses

ground based velocity track display gbvtd analysis of w band doppler radar data in a tornado near stockton kansas on 15 may 1999 abstract on 15 may 1999 a storm intercept team from the university of oklahoma collected high resolution w band doppler radar data in a tornado near stockton kansas thirty five sector scans were obtained over a period of approximately 10 min capturing the tornado life cycle from just after tornadogenesis to the decay stage a low reflectivity eye whose diameter fluctuated during the period of observation was present in the reflectivity scans a ground based velocity track display gbvtd analysis of the w band doppler radar data of the stockton tornado was conducted results and interpretations are presented and discussed it was found from the analysis that the axisymmetric component of the azimuthal wind profile of the tornado was suggestive of a burgers rott vortex during the most intense phase of the life cycle of the tornado the temporal evolution of the axisymmetric components of azimuthal and radial wind as well as the wavenumber 1 2 and 3 angular harmonics of the azimuthal wind are a

observed and numerically simulated structure of a mature supercell thunderstorm abstract through the interactive use of doppler radar analyses and a three dimensional numerical storm simulation the detailed structure of a supercell tornadic storm is analyzed this storm named the del city storm occurred in central oklahoma on 20 may 1977 the storm exhibits certain important features which are essential to maintaining its longevity and which promote the storm s transition to its tornadic phase these features are strongly influenced by the rotational character of the storm separates the precipitation from the updraft and which orients the resulting downdrafts to which reinforce low level convergence along the gust front and sustain the storm analyses of air parcel and rain trajectories within the storm provide a detailed visualization of this internal structure these trajectories reveal that air parcels rising through the cyclonically rotating updraft actually turn anticyclonically with height owing to the influence of the storm relative environmental wind field downdraft traj

magnetic and electric fields associated with changes in high pore pressure in fault zones application to the loma prieta ulf emissions we determined the electric and magnetic fields generated during failure of faults containing sealed compartments with pore pressures ranging from hydrostatic to lithostatic levels exhumed fault studies and strain measurement data limit the possible size of these compartments to less than 1 km in extent rupture of seals between compartments produces rapid pore pressure changes and fluid flow and may create fractures that propagate away from the high pressure compartment along the fault face nonuniform fluid flow results from pressure decrease in the fracture from crack generated dilatancy partial blockage by silica deposition and clearing as pressure increases a direct consequence of this unsteady fluid flow may be associated transient magnetic signals caused by electrokinetic piezomagnetic and magnetohydrodynamic effects models of these processes for fault geometries with 1 km high pressure compartments show that electrokinetic effects are several orders of magnitude larger than the other mechanisms the electrokinetic signals produced by this unsteady flow are comparable in magnitude and frequency to the magnetic signals observed prior to the ml 7 1 loma prieta earthquake of october 18 1989 provided fracture lengths are less than 200 m

a theory for strong long lived squall lines abstract we study herein the mechanics of long lived line oriented precipitating cumulus convection squall lines using two and three dimensional numerical models of moist convection these models used in juxtaposition enable us to address the important theoretical issue of whether a squall line is a system of special long lived cells or whether it is a long lived system of ordinary short lived cells our review of the observational literature indicates that the latter is the most consistent paradigm for the vast majority of cases but on occasion a squall line may be composed of essentially steady supercell thunderstorms the numerical experiments presented herein show that either type of squall line may develop from an initial line like disturbance depending on the magnitude and orientation of the environmental shear with respect to the line with shallow shear oriented perpendicular to the line a long lived line evolves containing individually short lived cells our analysis of this type o

electrical conductivity and carbon in metamorphic rocks of the yukon tanana terrane alaska electrical conductivity of a water saturated quartz mica garnet schist collected from a surface outcrop near the denali fault zone in the yukon tanana terrane of east central alaska increases slightly with pressure to about 200 mpa this behavior is unlike that exhibited by other yukon tanana samples or by most rocks from other locations detailed petrographic examination of the sample revealed the presence of a stringer of carbonaceous material generally less than 10 m thick enclosed in and intergrown with one of the muscovite layers and extending for about 2 cm along the foliation the stringer is probably responsible for the anomalous conductivity change with pressure making the sample the first for which anomalous electrical conductivity behavior can be attributed to carbon associated with a specific feature the carbonaceous stringer together with its host muscovite layer are deformed and broken around a rotated garnet porphyroclast the deformation was accommodated by plastic deformation of quartz and therefore occurred in the ductile regime under conditions at least equivalent to greenschist facies metamorphism we interpret the textural relations to indicate that the carbonaceous material was formed by fluid deposition in a fracture formed within the muscovite layer possibly during the main phase of metamorphism and deformation and that the mica and carbon stringer were then deformed by the noncoaxial deformation responsible for rotation of the garnet porphyroclasts together the facts that the deformation resulting in garnet rotation was ductile and that the garnet rotation disrupted the stringer demonstrate that the carbonaceous stringer was present at depth i e 10 km brittle deformation on the microscopic scale is observed to have broken the connectivity of the carbon stringer explaining in part why the rock does not exhibit anomalously high conductivity at 0 1 mpa 1 atm pressure the brittle deformation is interpreted to have been caused by unloading due to uplift the observations indicate that carbonaceous material may exert a primary control on crustal electrical conductivity because it may be present as interconnected arrays in grain boundaries or microfractures or in megascopic throughgoing fractures

syngenetic thin graphite rich horizons in lower crustal rocks from the serre san bruno calabria italy and implications for the nature of high conducting deep crustal layers abstract in order to better understand the nature of deep crustal high electrical conductivity we studied the electrical properties of a tilted section of a former lower continental crust exposed in the calabrian arc of the alpine apennine mountain system geoelectric field measurements and impedance measurements on rock samples showed that these high grade metamorphic rocks are generally highly resistive as expected for crystalline electrolytically conducting rocks of low porosity this holds for graphite free metabasites as well as for metapelites which generally contain accessory up to 3 biogenic graphite in the form of isolated grains clearly as an exception a group of thin stratiform black horizons with thicknesses of 1 15 cm within the metapelitic series was detected by means of self potential sp measurements rock samples from these horizons exhibit high quasi metallic bulk conductivities of up to 50 s m 0 02 m in agreeement with up to 20 syngenetic graphite forming a network of interconnected streaks or crack fillings the high amount of carbon most probably originates from organic matter of c org rich black shales relative enrichment of the low mobility graphitic matter compared to the carbon content of the assumed protoliths may have been due to pressure solution and partial melting during prograde metamorphism without major contribution of a fluid phase resulting in isolated graphite flakes although enriched graphite in this form has little effect on electrical conductivity for the calabrian black horizons microscopic analyses make conceivable that in a further decisive step isolated graphite grains were mechanically smeared to continuous pathways during uplift by shearing producing hereby the observed graphitic network which is needed to generate high conductivity as c org rich black shales are common members of sedimentary sequences throughout the earth s history good conductors of this type may be expected in the continental crust at any depth depending on tectonic and metamorphic history with the exception of magmatic protoliths regarding the extremely high conductivity of the meta black shale samples containing syngenetic sheared graphite a total thickness of a few meters of such rocks is sufficient to explain magnetotelluric high conductivity anomalies in the deep crust

mixed layer illite smectite as a paleotemperature indicator in the amethyst vein system creede district colorado usa ordered illite smectite is the most abundant and widespread product of argillic alteration associated with the oligocene epithermal ag pb zn cu au amethyst vein system southwest colorado hydrothermal illite smectites exhibit all reichweite from 1 to 3 and span the composition range from about 25 to about 3 illite the composition and reichweite of illite smectite vary smoothly with distance from the amethyst vein with increasing distance from the vein percent illite and the reichweite decrease when composition temperature relationships of illite smectite from modern geothermal systems are applied to the fossil amethyst system isotherms describing the thermal regime at the time of argillization can be estimated temperatures near 240 c appear to have existed near the amethyst vein these temperatures agree with homogenization temperatures obtained from fluid inclusions in vein minerals the most distal illite smectites sampled about 260 m from the vein indicate temperatures near 110 c estimated thermal gradients are on the order of 0 4 to 1 c per meter although illite smectite composition and structure vary systematically with distance from the amethyst vein there are no systematic trends associated with the numerous smaller veins and veinlets in the hanging wall of the system this indicates that temperatures of both wallrock and the fluids in all but the major amethyst vein were nearly the same during clay formation apparently the hydrothermal system had reached a fairly steady mature thermal state at the time of argillization

electric lithosphere of the slave craton the archean slave craton in northwestern canada is an ideal natural laboratory for investigating lithosphere formation and evolution and has become an international focus of broad geoscientific investigation following the discovery of economic diamondiferous kimberlite pipes three deep probing magnetotelluric surveys have recently been carried out on the craton using novel acquisition procedures the magnetotelluric responses reveal an unexpected and remarkable anomaly in electrical conductivity collocated with the kimberlite field that is modeled as a spatially confined upper mantle region of low resistivity 30 m at depths of 80 100 km and is interpreted to be due to dissolved hydrogen or carbon in graphite form this geophysically anomalous upper mantle region is also spatially coincident with a geochemically defined ultradepleted harzburgitic layer the tectonic processes that emplaced this structure are possibly related to the lithospheric subduction and trapping of overlying oceanic mantle at 2630 2620 ma

finestructure of the del city edmond tornadic mesocirculation abstract interrelationships among severe thunderstorm wind flow tornado parent circulation and tornado are examined with dense single and dual doppler radar observations from the del city edmond oklahoma storm of 20 may 1977 beginning with tornadogenesis rising inflow air from right hand quadrants and subsiding air from a developing downdraft on the storm s rear are wrapped in a large spiral pattern about the tornado the updraft appears to drive the tornado while the downdraft appears to form as entrained environmental air concentrated by the intensifying parent circulation is cooled evaporatively

geoelectric structure of the proterozoic wopmay orogen and adjacent terranes northwest territories canada magnetotelluric mt soundings were made along a transect in northern canada crossing the proterozoic wopmay orogen fort simpson basin and adjacent parts of the slave craton and the nahanni terrane the results are used to define the geoelectric structure and constrain the crustal and lithospheric structure and evolution across the wopmay orogen geoelectric strikes at crustal depths average n34 e and are interpreted to be related to transcurrent faulting that occurred during late distal collisions at the western margin of the orogen weak two dimensionality in the fort simpson basin is interpreted to be due to the sedimentary rocks in the basin at longer periods geoelectric strikes across the wopmay orogen rotate from n43 e at uppermost mantle penetration to n62 e at a depth of 100 km the uppermost mantle strikes are interpreted to be due to ductile shearing linked to the transcurrent faulting in the overlying crust the deeper strikes may be caused by shearing at the base of the present day lith

a numerical simulation of cyclic mesocyclogenesis abstract a three dimensional nonhydrostatic numerical model the advanced regional prediction system is used to study the process of cyclic mesocyclogenesis in a classic supercell thunderstorm during the 4 h simulation the storm s mesocyclone undergoes two distinct occlusions with the beginning of a third indicated at the end of the simulation the occlusion process exhibits a period of approximately 60 min and is qualitatively similar in each case initial midlevel 3 7 km mesocyclogenesis proceeds according to the classic picture that is via tilting of streamwise environmental vorticity the development of an evaporatively driven rear flank downdraft rfd signals the beginning of the occlusion process the developing rfd wraps cyclonically around the mesocyclone causing the gust front to surge outward simultaneously the occluding mesocyclone rapidly intensifies near the surface trajectory analyses demonstrate that this intensification follows from the tilting and stretching of near ground

carbon deposition during brittle rock deformation changes in electrical properties of fault zones and potential geoelectric phenomena during earthquakes 1 to investigate potential mechanisms for geoelectric phenomena accompanying earthquakes we have deformed hollow cylinders of sioux quartzite to failure in the presence of carbonaceous pore fluids and investigated the resulting changes in electrical conductivity and carbon distribution samples were loaded at room temperature or 400 c by a hydrostatic pressure at their outer diameter increasing pressure at a constant rate to 290 mpa pore fluids consisted of pure co co2 and ch4 and a 1 1 mixture of co2 and ch4 each with pore pressures of 2 0 to 4 1 mpa failure occurred by the formation of mode ii shear fractures transecting the hollow cylinder walls radial resistivities of the cylinders fell to 2 9 to 3 1 m m for co tests and 15 2 to 16 5 m m for co2 ch4 tests compared with 23 m m for dry undeformed cylinders carbonaceous fluids had no discernable influence on rock strength on the basis of mapping using electron microprobe techniques carbon occurs preferentially as quasi continuous films on newly formed fracture surfaces but these films are absent from preexisting surfaces in those same experiments the observations support the hypothesis that electrical conductivity of rocks is enhanced by the deposition of carbon on fracture surfaces and imply that electrical properties may change in direct response to brittle deformation they also suggest that the carbon films formed nearly instantaneously as the cracks formed carbon film deposition may accompany the development of microfracture arrays prior to and during fault rupture and thus may be capable of explaining precursory and coseismic geoelectric phenomena

microscopic scale conductivity as explanation of magnetotelluric results from the alps of western switzerland summary recent mt soundings carried out in the penninic alps of valais have shown the presence of a very good outcropping conductor extremely high conductivity was attributed to the presence of graphite to verify this assumption the electrical properties of borehole black shales were measured under simulated physical conditions electrical frequency hydrostatic confining pressure internal fluid pressure temperature these measurements showed that under all physical conditions electrical frequency in the 0 005 200 hz interval hydrostatic confining pressure up to 39 mpa internal fluid pressure up to 23 mpa temperature up to 180 uc one of the samples studied was very conductive resistivity less than 2 vm under all physical conditions interestingly despite similar macroscopic aspect other samples from a nearby borehole were found to be only slightly conductive chemical mineralogical and petrographic investigations revealed that the enhanced electrical conductivity is mostly due to textural characteristics such as grain size and carbon film distribution at the grain boundaries rather than to chemical differences

carbon enhanced electrical conductivity during fracture of rocks changes in electrical resistance during rock fracture in the presence of a carbonaceous atmosphere have been investigated using nugget sandstone and westerly granite the experiments were performed in an internally heated gas pressure vessel with a load train that produced strain rates between 10 6 and 10 5 s 1 samples were deformed at temperatures of 354 to 502 c and pressures of 100 to 170 mpa in atmospheres of ar or mixtures of 95 co2 with 5 co or 5 ch4 compositions that are well within the field of graphite stability at the run conditions in experiments using nugget sandstone resistance reached a minimum value when the maximum temperature was achieved and good electrode contact was made the resistance then increased as the experiment continued probably due to dry out of the sample a change in the oxidation state of the fe oxide associated with the cement or destruction of current bearing pathways at approximately 200 mpa end load the rock sample failed plots of load and resistance versus time show several interesting features in one experiment for example as the end load reached about 175 mpa resistance stopped increasing and remained fairly constant for a period of approximately 0 5 hour during loading the end load displayed small decreases that were simultaneous with small decreases in resistance when the end load and the displacement indicated rock failure resistance decreased dramatically from 150 m to 100 m in a single experiment the westerly granite also showed a decrease in resistance during dilatancy the nature and distribution of carbon in the run products were studied by electron microprobe and time of flight secondary ion mass spectroscopy top sims carbon observed by mapping with the former is clearly observed on micro cracks that based on the microtexture are interpreted to have formed during the deformation the tof sims data confirm the electron probe observations that carbon is present on fracture surfaces these observations and experimental results lead to the hypothesis that as microfractures open in the time leading up to failure along a fracture carbon is deposited as a continuous film on the new reactive mineral surfaces and this produces a decrease in resistance subsequent changes in resistance occur as connectivity of the initial fracture network is altered by continued deformation such a process may explain some electromagnetic effects associated with earthquakes

mobile x band polarimetric doppler radar observations of the 4 may 2007 greensburg kansas tornadic supercell abstracton 4 may 2007 a supercell produced an ef 5 tornado that severely damaged the town of greensburg kansas volumetric data were collected in the greensburg storm by the university of massachusetts x band mobile polarimetric doppler radar umass x pol for 70 min 10 tornadoes were detected this mobile doppler radar dataset is one of only a few documenting an ef 5 tornado and the supercell s transition from short track cyclic tornado production mode 1 to long track tornado production mode 2 using bootstrap confidence intervals it is determined that the mode 2 tornadoes moved in the same direction as the supercell vault in contrast the mode 1 tornadoes moved to the left with respect to the vault from polarimetric data collected in this storm the authors infer the presence of large oblate drops high zdr high hv in the forward flank and surrounding some of the tornadoes the authors speculate that the weak echo column wec in the greensburg tornado which extended above 10 km agl

near surface vortex structure in a tornado and in a sub tornado strength convective storm vortex observed by a mobile w band radar during vortex2 abstractas part of the second verification of the origins of rotation in tornadoes experiment vortex2 field campaign a very high resolution mobile w band doppler radar collected near surface 200 m agl observations in an ef 0 tornado near tribune kansas on 25 may 2010 and in sub tornado strength vortices near prospect valley colorado on 26 may 2010 in the tribune case the tornado s condensation funnel dissipated and then reformed after a 3 min gap in the prospect valley case no condensation funnel was observed but evidence from the highest resolution radars in the vortex2 fleet indicates multiple sub tornado strength vortices near the surface some with weak echo holes accompanying doppler velocity couplets using high resolution doppler radar data the authors document the full life cycle of sub tornado strength vortex beneath a convective storm that previously produced tornadoes the kinematic evolution of these vortices from genesis to decay is investigated via ground based velocity

measurement and analysis of dissolution patterns in rock fractures 1 nuclear magnetic resonance imaging nmri is applied to noninvasively measure flow and dissolution patterns in natural rough walled water saturated halite fractures three dimensional images of water density and flow velocity acquired with nmri allow quantification of the developing fracture morphology and flow patterns the flow patterns are correlated strongly to the local apertures and the large scale wall roughness the correlations of the dissolution patterns to the fracture morphology flow patterns and mineralogical composition of the rock matrix are a function of the overall dimensionless damkohler number at high damkohler numbers the dissolution patterns are dominated by the flow structure in addition at high damkohler numbers buoyancy stratified flow becomes important in such cases the dissolution patterns also depend on the orientation and elevation of the fracture walls resulting in preferential upward dissolution at low damkohler numbers the dissolution patterns depend mainly on the mineralogical composition of the rock matrix these findings suggest that coupled flow and dissolution processes are much more complex and unpredictable than commonly assumed even under simplified conditions

lithospheric geometry of the wopmay orogen from a slave craton to bear province magnetotelluric transect 1 two dimensional inversions of lithospheric probing magnetotelluric mt data at a total of 20 sites acquired along an approximately east west 300 km long profile across the wopmay orogen in the northwest territories canada provide electrical resistivity models of the boundary between the archean slave craton and the adjacent proterozoic bear province an analysis of distortion effects and structural dimensionality indicates that the mt responses are primarily one dimensional or only weakly two dimensional with a depth independent geoelectric strike angle of n32 e consistent with regional structural geology the regional scale model generated from the longer period responses from all of the sites along the profile reveals significant lateral variations in the lithospheric mantle resistive cratonic roots are imaged to depths of 200 km beneath both the slave craton and the hottah terrane of the bear province these are separated by a less resistive region beneath the great bear magmatic zone which is speculatively interpreted as a consequence of a decrease in the grain size of olivine in the wopmay mantle caused by localized shearing compared to its neighboring cratonic roots focused two dimensional models from higher frequency responses at sites on specific sections of the profile reveal the resistivity structure at crustal depths beneath the region these suggest that the root of the slave craton crosses beneath the wopmay orogen and that the wopmay fault zone does not penetrate into the lower crust a comparison of these results with those obtained during the lithoprobe project farther south shows striking along strike variations in the conductivity structure associated with the wopmay orogen

latest aspects of earthquake prediction in greece based on seismic electric signals ii abstract since 1983 continuous monitoring of the electrotelluric field has been carried out using an array of measuring stations located at various sites in greece the basic physical properties of the transient changes seismic electric signals ses in the electrotelluric field that are forerunners of earthquakes were first described six years ago since then a large body of data has been collected resulting in new insight into various aspects of the method the present paper reviews the latest developments in ses based earthquake prediction and describes the current procedures used to predict the epicenter and magnitude of an impending earthquake a detailed list of the predictions officially issued in greece during the past 3 years january 1 1987 november 30 1989 is also given public warnings were issued well before the most destructive seismic activity

the dependence of numerically simulated convective storms on vertical wind shear and buoyancy abstract the effects of vertical wind shear and buoyancy on convective storm structure and evolution are investigated with the use of a three dimensional numerical cloud model by varying the magnitude of buoyant energy and one directional vertical shear over a wide range of environmental conditions associated with severe storms the model is able to produce a spectrum of storm types qualitatively similar to those observed in nature these include short lived single cells certain types of multicells and rotating supercells the relationship between wind shear and buoyancy is expressed in terms of a nondimensional convective parameter which delineates various regimes of storm structure and in particular suggests optimal conditions for the development of supercell type storms applications of this parameter to well documented severe storm cases agree favorably with the model results suggesting both the value of the model in studying these modes of convection as well as the value of this representation i

electric field patterns as seismic precursors in this paper we report the results of two and a half years of measurements of the ground electric field at the pacific coast of mexico the analysis of the voltage itself does not show any distinguishable feature that could be correlated to earthquakes fourier analysis however gives clear patterns of the electric field prior to the four ms w 6 earthquakes that occurred in the zone during the time interval considered

analysis of hot fluid infiltration in fractured granite by fluid inclusion study abstract the la peyratte granite deux sevres france is crosscut by veins of hydrothermal origin petrographie analysis shows that most of these veins were sealed by phengite crystals during a single hydrothermal event one of these veins 300 m width was chosen for detailed investigations of fluid inclusions inside the wall rock a thermal gradient was determined 335 c inside the vein to 260 c at 11 mm inside the wall rock theoretical modelling shows that the thermal gradient cannot originate from a permanent heat source continuous flow but from a variable one pulsed regime the modelling is based on a periodic function for simplifying the calculations in this case the fluid residence time 0 5 h must be short compared to the period 1 d in order to fit the measured thermal gradient the thermal gradient was established during a period of time long enough for alteration mineral reactions to proceed it disappeared when the vein was sealed it was then that the fluid inclusions were trapped at homogenization temperatures

a petrographic study of phyllic alteration superimposed on potassic alteration the sibert porphyry deposit rhone france zoned wallrock alteration surrounds each phyllic vein three zones distinguished 1 a nearest wallrock zone where the preexisting minerals except quartz are wholly transformed into muscovite 2 an intermediate wallrock zone where the alteration intensity decreases 30 of the rock is replaced by white micas and 3 a farthest wallrock zone where a small proportion of preexisting biotites and plagioclases recrystallizes less than 10 of the primary minerals recrystallize modified journal abstract

a magnetotelluric investigation of the san andreas fault at carrizo plain california high quality wide band magnetotelluric data were collected along two profiles crossing the san andreas fault at carrizo plain california for crustal imaging as part of the san andreas deep drilling project two dimensional inversions of the data indicate that the upper crustal part of the san andreas fault does not appear here as an anomalously conductive zone additionally a broad resistive zone under the temblor mountains east of the fault suggests resistive crystalline or metamorphic rocks may be present here as opposed to the more conducting franciscan assemblage contradicting the generally accepted geologic model

carbonaceous matter in peridotites and basalts studied by xps sali and leed abstract carbonaceous matter in peridotite xenoliths and basalt from the hualalai volcano in a basalt glass collected directly from an active lava lake on the east rift of kilauea in garnet and diopside megacrysts from the jagersfontein kimberlite and in gabbros from the stillwater and bushveld complexes has been studied by x ray photoelectron spectroscopy xps thermal desorption surface analysis by laser ionization sali and low energy electron diffraction leed the basalt and two of the four xenoliths from hualalai and both jagersfontein megacrysts yielded trace quantities 10 nanomoles of organic compounds on heating to 700 c organics were not detected in the rocks from the layered intrusions and neither carbonaceous matter nor organics were detected in the glass from the lava lake where detected organics appear to be associated with carbonaceous films on microcrack surfaces carbonaceous matter exists as films less than a few nm thick and particles up to 20 m across both of which contain elements expected to be present in significant quantities in magmatic vapors namely si alkalis halogens n and transition metals leed studies suggest that the carbonaceous films are amorphous the data suggest two possible mechanisms for the formation of the organics one is that they are a product of abiotic heterogeneous catalysis of volcanic gas on new chemically active mineral surfaces formed by fracturing during cooling alternatively organics may have been assimilated into the volcanic gases prior to eruption and then deposited on cracks formed during eruption and cooling in any case there is no evidence to suggest that the organics represent laboratory or field biogenic contamination

doppler radar observations of anticyclonic tornadoes in cyclonically rotating right moving supercells abstractsupercells dominated by mesocyclones which tend to propagate to the right of the tropospheric pressure weighted mean wind on rare occasions produce anticyclonic tornadoes at the trailing end of the rear flank gust front more frequently mesoanticyclones are found at this location most of which do not spawn any tornadoes in this paper four cases are discussed in which the formation of anticyclonic tornadoes was documented in the plains by mobile or fixed site doppler radars these brief case studies include the analysis of doppler radar data for tornadoes at the following dates and locations 1 24 april 2006 near el reno oklahoma 2 23 may 2008 near ellis kansas 3 18 march 2012 near willow oklahoma and 4 31 may 2013 near el reno oklahoma three of these tornadoes were also documented photographically in all of these cases a strong mesocyclone i e vortex signature characterized by azimuthal shear in excess of 5 10 3 s 1 or a 20 m s 1 change in doppler velocity over 5 km

the owl horn radar signature in developing southern plains supercells abstract during spring 2001 in the southern plains a recurring hitherto undocumented reflectivity signature that the authors have called the owl horn signature because the radar reflectivity pattern resembles the profile of the great horned owl was observed on a mobile x band radar display the reflectivity signature was always located at the rear side of a developing supercell spanned the entire rear side of the storm and was always seen on low level plan position indicator ppi scans it lasted on the order of only 5 10 min and was not an artifact of the radar a study of the owl horn signature was undertaken using the tracking radar echoes by correlation technique trec to estimate the wind field trec has previously been applied to clear air and hurricane environments and to the internal motions of severe storms but not to their evolution the characteristics of the signature are presented and then through the application of trec to the radar reflectivity data doppler wind data were no

earthquake predictions issued in greece by seismic electric signals since february 6 1990 abstract the present paper describes the results of all official predictions that were issued on the basis of seismic electric signals recorded in greece during the period feb 6 1990 may 31 1991 they amount to four cases of activities multiple events in two cases the predictions were also submitted for publication to tectonophysics before the beginning of the corresponding seismic activities while in a third case the prediction was announced during an international conference held in japan also before the occurrence of the earthquake after the submission of the manuscript a number of earthquakes occurred during the period up to may 31 1992 they are summarized along with their predictions in appendix 1

results of ultra low frequency magnetic field measurements during the guam earthquake of 8 august 1993 we report the results of measurements of ultra low frequency magnetic noise during a large earthquake ms 7 1 at guam of 8 august 1993 depth 60 km the ulf observing system is located in the guam island about 65 km from the epicenter several distinct features of this analysis are summarized 1 we have proposed rather sophisticated statistical analyses monthly mean standard deviation in order to estimate the wave intensity and polarization i e ratio z h 2 a comparison between the ulf wave activity and kp is useful in distinguishing between the space geomagnetic pulsations and non space emissions 3 then the use of the ratio z h is found to be of essential importance in discrimating the emissions presumably of seismic origin from space plasma waves 4 the statistical analysis of the temporal evolution of this ratio has yielded that it shows a broad maximum only about one month before the earthquake and this suggests that the emissions during this period are very likely to be magnetic precursors 5 the temporal variation of z component is similar to that for the loma prieta earthquake such that it shows a broad maximum ten days two weeks before the earthquake and another increase a few days before the earthquake 6 the emissions presumably associated with the earthquake are of noise like nature and their main frequency is 0 02 0 05 hz with maximum intensity 0 1 nt

the relationship between overshooting tops in a tornadic supercell and its radar observed evolution abstractthis is a study of a tornadic supercell in kansas on 14 may 2018 in which data of relatively high spatiotemporal resolution from a mobile polarimetric x band doppler radar were integrate

low frequency magnetic field measurements near the epicenter of the ms 7 1 loma prieta earthquake the authors report the results of measurements of low frequency magnetic noise by two independent monitoring systems prior to the occurrence of the m sub s 7 1 loma prieta earthquake of 17 october 1989 their measurements cover 25 narrow frequency bands in the more than six decade frequency range 0 01 hz 32 khz with a time resolution varying from a half hour in the ulf range 0 01 10 hz to one second in the elf vlf range 10 hz 32 khz the ulf system is located near corralitos about 7 km from the epicenter the elf vlf system is located on the stanford campus about 52 km from the epicenter analysis of the elf vlf system is located on the stanford campus about 52 km from the epicenter analysis of the elf vlf data has revealed no precursor activity that they can identify at this time however the ulf data have some distinctive and anomalous features first a narrow band signal appeared in the range 0 05 0 2 hz around september 12 and persisted until the appearance of the second anomalous feature which consisted of a substantial increase in the noise background starting on 5 october and covering almost the entire frequency range of the ulf system third there was an anomalousmore dip in the noise background in the range 0 2 5 hz starting one day ahead of the earthquake finally and perhaps most compelling there was an increase to an exceptionally high level of activity in the range 0 01 0 5 hz starting approximately three hours before the earthquake there do not appear to have been any magnetic field fluctuations originating in the upper atmosphere that can account for this increase further while the systems are sensitive to motion seismic measurements indicate that there were no significant shocks preceding the quake thus the various anomalous features in the data and in particular the large amplitude increase in activity starting three hours before the quake may have been magnetic precursors less

the role of disseminated calcite in the chemical weathering of granitoid rocks accessory calcite present at concentrations between 300 and 3000 mg kg 1 occurs in fresh granitoid rocks sampled from the merced watershed in yosemite national park ca usa loch vale in rocky mountain national park co usa the panola watershed ga usa and the rio icacos puerto rico calcite occurs as fillings in microfractures as disseminated grains within the silicate matrix and as replacement of calcic cores in plagioclase flow through column experiments using de ionized water saturated with 0 05 atm co2 produced effluents from the fresh granitoid rocks that were dominated by ca and bicarbonate and thermodynamically saturated with calcite during reactions up to 1 7 yr calcite dissolution progressively decreased and was superceded by steady state dissolution of silicates principally biotite mass balance calculations indicate that most calcite had been removed during this time and accounted for 57 98 of the total ca released from these rocks experimental effluents from surfically weathered granitoids from the same watersheds were consistently dominated by silicate dissolution the lack of excess ca and alkalinity indicated that calcite had been previously removed by natural weathering the extent of ca enrichment in watershed discharge fluxes corresponds to the amounts of calcite exposed in granitoid rocks high ca na ratios relative to plagioclase stoichiometries indicate excess ca in the yosemite loch vale and other alpine watersheds in the sierra nevada and rocky mountains of the western united states this ca enrichment correlates with strong preferential weathering of calcite relative to plagioclase in exfoliated granitoids in glaciated terrains in contrast ca na flux ratios are comparable to or less than the ca na ratios for plagioclase in the subtropical panola and tropical rio icacos watersheds in which deeply weathered regoliths exhibit concurrent losses of calcite and much larger masses of plagioclase during transport limited weathering these results indicate that the weathering of accessory calcite may strongly influence ca and alkalinity fluxes from silicate rocks during and following periods of glaciation and tectonism but is much less important for older stable geomorphic surfaces

integrated teleseismic studies of the southern alberta upper mantle this paper presents results from a teleseismic experiment conducted across the hearne province in south central alberta data from an array of nine portable broad band seismographs deployed along a 500 km nw se array have been supplemented with recordings from two canadian national seismograph network stations p wave delay times from 293 earthquakes have been inverted for upper mantle velocity structure below the array the recovered model reveals high velocities beneath much of the southern hearne province to depths of 200 250 km which are interpreted as deep seated lithospheric structure contrary to recent tectonic models these results suggest that the hearne lithosphere has remained intact in particular it appears unlikely that evidence for extensive lower crustal melting derives from lithospheric delamination however the results admit the possibility that high mantle conductivity as revealed in magnetotelluric studies originates through small volumes of connected hydrous minerals or other c

a double moment multiple phase four class bulk ice scheme part ii simulations of convective storms in different large scale environments and comparisons with other bulk parameterizations abstract part i of this study described a detailed four class bulk ice scheme 4ice developed to simulate the hydro meteor profiles of convective and stratiform precipitation associated with mesoscale convective systems in part ii the 4ice scheme is incorporated into the goddard cumulus ensemble gce model and applied without any tuning to two squall lines occurring in widely different environments namely one over the pica ocean in the global atmospheric research program s garp atlantic tropical experiment gate and the other over a midlatitude continent in the cooperative huntsville meteorological experiment cohmex comparisons were made both with earlier three class ice formulations and with observations in both cases the 4ice scheme interacted with the dynamics so as to resemble the observations much more closely than did the model runs with either of the three class ice parameterizations the following features were well simulated in the cohmex case a lack of stratiform rain at the s

generation of ulf electromagnetic emissions by microfracturing microfracturing electrification is discussed as a possible explanation of ulf electromagnetic emissions observed before and after earthquakes using a space time simple model of microfracture progression it is possible to compare theoretical results and observed results with special reference to the intensity spectrum and temporal development of ulf magnetic field variations

coupled interaction of earthquake nucleation with deep earth gases a possible mechanism for seismo electromagnetic phenomena summary the mechanisms of seismo electromagnetic phenomena remain largely unexplained to address this issue we introduce a fault model that takes account of a coupled interaction between earthquake nucleation and deep earth gases this interaction causes a negatively electrified gas flow due to an exo electron attachment reaction as the gases pass through fractured asperities this transient activity may be regarded to be a pressure impressed electric current generator in the model the current and frequency are formulated as functions of earthquake parameters the estimated current is sufficient to explain the seismic electromagnetic signals observed at ground level a physical model of how current generation is coupled with ionospheric electromagnetic disturbances is explained in terms of magnetic induction coupling for strong offshore earthquakes which may provide a plausible explanation of observed ionospheric electron enhancement prior to some recent offshore earthquakes the model also suggests that geomagnetic observations close to an epicentre of a strong offshore earthquake may provide an effective means of detecting clear and identifiable precursor signals

the structure of tornadoes near attica kansas on 12 may 2004 high resolution mobile doppler radar observations abstract the university of massachusetts w and x band mobile doppler radars scanned several tornadoes at close range in south central kansas on 12 may 2004 the detailed vertical structure of the doppler wind and radar reflectivity fields of one of the tornadoes is described with the aid of boresighted video the inside wall of a weak echo hole inside the tornado was terminated at the bottom as a bowl shaped boundary within several tens of meters of the ground doppler signatures of horizontal vortices were noted along one edge in the lowest 500 m of the tornado the vertical structure of doppler velocity displayed significant variations on the 100 m scale near the center of the tornado a quasi horizontal radial bulge of the weak echo hole at 500 600 m agl dropped to about 400 m above the ground and was evident as a weak echo band to the south of the tornado it is suggested that this feature represents echo weak material transported radially outward by a vertical circulation significant vertical

error propagation in electromagnetic transfer functions what role for the magnetotelluric method in detecting earthquake precursors summary whether electromagnetic precursors exist is a contentious issue that should be considered in the context of the focal depth and epicentral distance at which earthquakes nucleate and with due regard to externally driven changes in the electromagnetic fields recorded at the earth s surface if high frequency electromagnetic signals are generated by earthquakes then these signals may not be detectable because of attenuation occurring between the focal depth of the earthquake and the earth s surface this is particularly true in seismotectonic regions e g subduction zones where saline fluids including seawater raised heat flow and partial melts often lead to enhanced conductivities a technique for examining temporal variations in magnetotelluric mt spectra is presented which i considers both non inductive and inductive parts of the mt transfer function ii allows electromagnetic skin depths and adjustment distances to be calculated iii takes account of error propagation in the transfer functions and and iv acknowledges possible nonearthquake sources of observed variations in transfer functions and their errors data processing tends to eliminate non stationary electromagnetic disturbances of the source field hence the method is more suited to detecting hypothesized changes in subsurface conductivity than short lived electromagnetic bursts the technique is applied to mt data from seismotectonic regions in new zealand mt ruapehu the andes western cordillera and the mediterranean montecristo island and to a culturally quiet control site situated on a stable craton in central australia we demonstrate that the mt method can resolve apparent conductivity changes of the order of a few percent over 48 hr time intervals and give thresholds for other interval lengths comparison of the results obtained from seismotectonic regions with those from central australia and consideration of external source field effects highlight how temporal variations of electromagnetic fields might be speciously interpreted as earthquake precursors

graphite ch4 h2o co2 equilibria at low grade metamorphic conditions equilibrium calculations and published phase equilibria are used to show that at temperatures below 400 c and pressures above 300 bar the fluids coexisting with graphite in the c o h system consist either of co2 h2o mixtures or ch4 h2o mixtures bulk fluid compositions consisting of ch4 h2o will unmix to methane rich fluid and h2o rich liquid at temperatures below about 325 c compositions on the co2 h2o join will unmix only at temperatures below about 275 c oxygen fugacity in the ch4 h2o graphite three phase region is fixed at constant p and t and approximately equal to that of the quartz magnetite fayalite assemblage in the co2 h2o graphite three phase region oxygen fugacity is about three orders of magnitude greater from the end stages of diagenesis to temperatures of 300 c and possibly 400 c in salt rich systems many metamorphic rocks may contain ch4 h2o fluids rather than co2 h2o mixtures thus metamorphic reactions involving carbonate minerals would involve ch4 graphite and h2o rather than co2 the immiscibility between ch4 and h2o could result in the common occurrence of methane natural gas in low grade metamorphic terrains

a magnetotelluric profile across the german deep drilling project ktb area two and three dimensional modeling results previous interpretations of magnetotelluric data from the vicinity of the german deep drilling project ktb revealed two major structures a midcrustal layer of increased conductivity and large regional extent and a highly anisotropic upper crust nevertheless a satisfactory combination of both structures explaining all measurements has not yet been achieved mostly due to incomplete and qualitatively poor data simplified superposition of both structures could not yield an explanation of the observations on the basis of a carefully processed new data set we apply different modeling approaches to verify the existence of both structures models calculated with a two dimensional modeling program which allows for general anisotropy as well as a full three dimensional code show that an anisotropic upper crust is overlaying a regional east west striking high conductivity structure nevertheless this continuous conductive midcrustal layer with a conductance decreasing from north to south must be replaced by a quasi anisotropic one at least in the region of the ktb the final model may still be oversimplified considering the complexity of the true but unknown geology in this particular area but it demonstrates which major electrically effective structures could be resolved

unstable graphite films on grain boundaries in crustal rocks abstract the origin of high electrical conductive anomalies in the lower crust is a long standing and controversial problem although it has been proposed that saturated saline water or partial melt increases electrical conductivity graphite film has also been recognized as a potential cause of high conductivity since the discovery of fine graphite films on the grain boundaries of high grade metamorphic rocks to investigate the stability of graphite film on grain boundary of silicate minerals under lower crustal conditions electrical conductivity of graphite film on synthetic grain boundaries of quartz bicrystals was measured by means of impedance spectroscopy at 1 gpa and up to 1200 k in a multianvil apparatus at first heating the electrical conductivity of the thin graphite film with thickness less than 100 nm was initially very high but decreased with time during annealing under high temperature conditions 1000 k the conductivity of a thin carbon film rapidly decreases and approaches the quartz conductivity this indicates that graphite film on a grain boundary between two quartz crystals is not stable at high temperatures optical microscopic observation of the run products suggested a disconnected feature of graphite on a quartz grain boundary disconnection of graphite film can be caused by higher interfacial energy between graphite and silicate minerals than that of the grain boundary energy therefore a thin graphite film is not a likely candidate to account for high conductivity anomalies in the middle and lower continental crust

high resolution mobile doppler radar observations of cyclic mesocyclogenesis in a supercell abstract on 15 may 2003 two ground based mobile doppler radars scanned a supercell that moved through the texas panhandle and cyclically produced mesocyclones the two radars collected data from the storm during a rapid cyclic mesocyclogenesis stage and a more slowly evolving tornadic period a 3 cm wavelength radar scanned the supercell continuously for a short time after it was cyclic but close to the time of tornadogenesis a 5 cm wavelength radar scanned the supercell the entire time it exhibited cyclic behavior and for an additional 30 min after that the volumetric data obtained with the 5 cm wavelength radar allowed for the individual circulations to be analyzed at multiple levels in the supercell most of the circulations that eventually dissipated moved rearward with respect to storm motion and were located at distances progressively farther away from the region of rear flank outflow the circulations associated with a tornado did not move nearly as far rearward relative to the storm the mean

carbonaceous material in metamorphosed carbonate rocks from the waits river formation ne vermont and its effect on electrical conductivity the relations among electrical conductivity and graphite content metamorphic grade and fluid rock interaction are investigated for a suite of regionally metamorphosed graphitic carbonate rocks from the waits river formation ne vermont graphitization was complete by the lowest grade of metamorphism attained in the area 450 c and 450 mpa in low grade rocks graphite occurs as inclusions within calcite and along grain boundaries and in medium grade rocks it concentrates near porphyroblasts in neither suite does graphite form interconnected networks average reduced carbon abundances are 4400 and 2800 ppm for the low and medium grade rocks respectively high grade rocks are almost void of graphite except for one specimen the 13c values were determined for graphite and carbonates and 18o values were determined for the carbonates and silicate residues there is no change in isotopic values between low and medium grade rocks in contrast high grade rocks show marked decreases in 13c and 18o values of 4 compared to low and medium grade rocks both isotopic analyses and graphite depletion in high grade rocks were caused by influx of large quantities of magmatic water during peak metamorphism electrical conductivity was measured in the laboratory on representative specimens rocks with high carbon content 7000 ppm from both the low and high grade zones display almost an order of magnitude higher electrical conductivity than expected from their fluid content alone graphite does not form an interconnected network in these rocks yet it combines with the saline fluids to significantly increase electrical conductivities

thermal diffusivity of igneous rocks at elevated pressure and temperature thermal diffusivity measurements of seven igneous rocks were made to temperatures of 400 sup 0 c and pressures of 200 mpa the measuring method was based on the concept of cylindrical symmetry and periodic heat pulses the seven rocks measured were westerly rhode island granite climax stock nevada quartz monzonite pomona washington basalt atikokan ontario canada granite creighton ontario canada gabbro east bull lake ontario canada gabbro and stripa sweden granite the diffusivity of all the rocks showed a positive linear dependence on inverse temperature and excluding the east bull lake gabbro showed a linear dependence on quartz content quartz content varied from 0 to 31 by volume diffusivity in all cases rose or remained steady with increasing confining pressure the pressure effect was strongest at lowest pressures and vanished by levels between 10 and 100 mpa depending on rock type the pressure effect measured as a percentage change in diffusivity is stronger in the four rocks of granite composition than in the three of basaltic composition our results agree well with existing thermal diffusivity measurements at atmospheric pressure

petrophysical model of deep electrical conductors graphite lining as a source and its disconnection due to uplift petrophysical information including stress release data recently made available for low porosity 0 1 0 4 crystalline rocks has been used to develop a broken conductor model that may explain the origin of enhanced electrical conductivity of the intermediate to lower continental crusts of shields and its disappearance when the rocks are uplifted average pore size and pore density of their fluid flow paths are 0 1 0 4 m and 1 400 m respectively the model assumes that these paths are filled or lined with interconnected electrical conducting minerals such as graphite resulting in the rocks having resistivities as low as 40 to 800 m in situ graphite film thicknesses required to produce these resistivities are 5 20 nm 50 200 a the model also assumes that electrical conducting paths break up during uplift due to stress release resulting in a poorly conducting rock petrophysical data of granites and observations from deep drill holes suggest a porosity increase of the order of 3 from an uplift of 10 km or more however the newly formed pore space would fill with deposits or intruded material so that surface rock porosities would not be much larger than at depth electrical resistivities of rock samples containing disconnected grain boundary graphite presently exposed by the kapuskasing uplift of the canadian shield are in the range of 3000 12000 m for the direction of foliation these values are 10 100 times larger than the estimates for similar rocks containing interconnected graphite but are 10 100 times smaller than usually observed in the canadian shield for similar rocks absent of grain boundary graphite these observations are in good agreement with the results predicted by the broken conductor model for an uplift of 10 km or more if a gross linear relationship is assumed between crack porosity and uplift for the upper 10 km of the crust

the genesis of severe long lived bow echoes abstract a series of idealized simulations using a nonhydrostatic cloud model is used to investigate the genesis of bow echoes a bow shaped system of convective cells that is especially noted for producing long swaths of damaging surface winds it is hypothesized that severe long lived bow echoes represent a dynamically unique form of mesoconvective organization being produced for a restricted range of environmental conditions including a convective available potential energy cape of at least 2000 m2 s2 and vertical wind shears of at least 20 m s 1 over the lowest 2 5 5 km agl the key structural features include a 40 100 km long bow shaped segment of convective cells with a strong rear inflow jet extending to the leading edge of the bow at 2 3 km agl and cyclonic and anticyclonic eddies referred to as bookend vortices on the northern and southern flanks of the bowed segment respectively this structure characteristically develops three to four hours into the lifetime of a convective system a

ultra low frequency magnetic field measurements in southern california during the northridge earthquake of 17 january 1994 measurements of ultra low frequency ulf magnetic field fluctuations by two independent monitoring systems in southern california were in progress during january 1994 when the moderately large m6 7 northridge earthquake occurred on 17 january our two measuring systems are located at table mountain on the other side of the san gabriel mountains and at a distance of 81 km from the epicenter and at pinon flat south of palm springs and at a distance of 206 km from the epicenter both systems operated well throughout the month and without interruption due to the earthquake as a result of the occurrence of a moderate magnetic storm on 11 january which was followed by a period of enhanced ulf magnetic activity that persisted until after the time of the earthquake the sensitivity of our measurements throughout california was reduced for roughly a week before the earthquake took place nevertheless no large signals that could be associated with the earthquake were evident at any time except for the usual co seismic shaking response of the detectors subsequent removal of the upper atmosphere signals from the table mountain measurements using the measurements from the more distant pinon flat location as reference essentially left no significant residual thus assuming that ulf magnetic fields were produced by the earthquake their amplitudes were too small to produce obvious increases in the ulf background noise at 81 km from the epicenter which is in agreement with our earlier estimate of a range of about 100 km for the ulf magnetic field fluctuations observed prior to the m7 1 loma prieta earthquake these results imply that a network of conventional magnetic field detectors spaced less than 100 km apart would be required to detect ulf magnetic field fluctuations prior to earthquakes with magnitudes greater than 7 under the same conditions superconducting magnetic field gradiometers could offer greater sensitivity and range