isopach pattern of the lower cambrian zabriskie quartzite death valley region california nevada how useful in tectonic reconstructions new thickness measurements of the lower cambrian zabriskie quartzite indicate an original isopach pattern much less regular than once supposed and thus less useful as an indicator of the magnitude of lateral slip on the death valley fault system but within a wide range of possible restorations the isopachs conform with the locations of proterozoic highlands and basins the zabriskie quartzite being mature laterally persistent and unlike the underlying formations devoid of evidence of rifting apparently records the beginning of the passive stage of the developing cordilleran miogeocline

geology of panamint valley saline valley pull apart system california palinspastic evidence for low angle geometry of a neogene range bounding fault geological studies support the interpretation that northern panamint valley and saline valley southeast california form paired pull apart basins on opposite sides of the right slip hunter mountain fault zone eight to ten km of late cenozoic net slip can be established on the hunter mountain fault zone palinspastic reconstruction of northern panamint valley indicates that the valley was formed by movement on a shallow crustal low angle normal fault of 0 15 degree west dip during the last 3 0 ma this interpretation appears to contradict the notions that little extension is accomodated in the uppermost crust by low angle faulting and that the most recent extension in the basin and range province is accomodated exclusively by high angle faulting saline valley however is interpreted to have formed by extension on closely spaced rotated planar normal faults thus within one geometric system of paired pull apart basins extension appears to have been accommodated in the shallow crust in two different ways

geophysical character of the proposed eastern extension of the garlock fault and adjacent areas eastern california a geophysical investigation was conducted over kingston wash in eastern california to determine if the garlock fault extends east of the death valley fault zone beneath the wash as had been proposed by davis and burchfiel the geophysical data reveal magnetic and gravity lineaments that trend northwest n80 w across the wash geologic data from adjacent outcrops suggest that the geophysical lineament represents a left lateral strike slip fault the lineament is thus interpreted to be a part of the garlock fault which extends 25 to 30 km eastward from the death valley fault the eastern extension passes south of the southern salt spring hills and north of the silurian hills the length of the proposed garlock fault beyond the death valley fault requires recalculation of the amount of extension in the basin range terrain of southern death valley in light of the additional length extension on the order of 100 is implied for the region

penetration electric fields at the nightside dip equator associated with the main impulse of the storm sudden commencement of 8 july 1991 1 the geomagnetic storm sudden commencement ssc of 8 july 1991 was reported wilson et al 2001 to be characterized by a reduction enhancement of x component at midlatitudes in the noon midnight sector in the 1 hour period after its start at 1636 ut this distinctive feature is seen even after accounting for the effects of the chapman ferraro current by subtracting the step like increase of x h component at low latitude stations on the same magnetic meridian from the midlatitude data we present evidence to show that over the same 1 hour period after the start of the ssc on 8 july 1991 an eastward electric field disturbance peak value 1 2 mv m grew up and decayed at the premidnight dip equator the eastward electric field evidenced at the nightside dip equator is interpreted as the signature of the penetration of the dawn to dusk electric field associated with an enhancement of region 1 field aligned currents facs driven by the solar wind the negative disturbance in the h x component at midlatitudes in the noon sector is explained as the magnetic effect of facs that carry the large scale electric fields from the magnetosphere to the polar ionosphere as well as the disturbance of polar origin type 2 ionospheric currents excited by the large scale electric field

imaging the structure of a large scale tid using isr and tec data 1 here we present north american observations of the 3 dimensional structure of large scale traveling ionospheric disturbances tids that affected the low and mid latitude ionosphere during the stormtime period of october 1 2 2002 using tec data from the american network of dual frequency gps receivers we are able to examine the effect of the tids on the background tec and thus image their horizontal scales incoherent scatter radar data from the arecibo observatory give information on the vertical structure of the disturbances the meridional and zonal structure of the tids are explored by computing the tec perturbation a method which has a resolution of a fraction of a tec unit the technique is effective in mapping the global structure of large scale disturbances as the lower latitude perturbations can be examined at the same time as the higher latitude sources the method may prove valuable in studying the formation and propagation of tids

estimating daytime vertical exb drift velocities in the equatorial f region using ground based magnetometer observations 1 the daytime equatorial electrojet is a narrow band of enhanced eastward current flowing in the 100 to 120 km altitude region within 2 latitude of the dip equator a unique way of determining the daytime strength of the electrojet is to observe the difference in the magnitudes of the horizontal h component between a magnetometer placed directly on the magnetic equator and one displaced 6 to 9 degrees away the difference between these measured h values provides a direct measure of the daytime electrojet current and in turn the magnitude of the vertical exb drift velocity in the f region ionosphere this paper discusses a recent study that has established the quantitative relationship between the vertical exb drift velocity in the ionospheric f region and the daytime strength of the equatorial electrojet in the south american west coast longitude sector

crustal extension and magmatic processes cocorp profiles from death valley and the rio grande rift new crustal scale information on the interaction between normal faulting and magmatic activity is provided by recent cocorp deep seismic reflection profiles in death valley california and by reprocessing of the cocorp data from the socorro area of the rio grande rift new mexico the most striking feature on the seismic sections from these areas is a prominent subhorizontal series of reflectors at mid crustal depth previous studies have suggested that thin tabular magma bodies lie within the mid crustal reflective zones in addition because they are traced without apparent offset beneath faults both mapped at the surface and interpreted from the cocorp data these mid crustal horizons are here inferred to be detachments or zones of tectonic decoupling upper crustal cenozoic faults do not appear to penetrate deeper than 15 km in death valley and 13 km in the rio grande rift in death valley these faults are relatively planar with moderate dips 20 to 35 and appear to bound large basement rocks one such zone of normal faults can be traced from the magma body inferred at 15 km depth beneath central death valley to the surface location of a 690 000 yr old basaltic cinder cone listric and low to moderate angle normal faults are evident on the reprocessed new mexico data and constitute the structural component of upper crustal extension in particular a listric master fault traceable to depths as great as 13 km is inferred to underlie the albuquerque basin unlike the death valley data no faults are observed to merge with the socorro magma body per se rather subhorizontal to moderately west dipping packages of reflections are imaged between the base of the faulted upper crust 13 km depth and the mid crustal magma body about 20 km depth the middle crust marks a major rheological boundary between the faulted upper crust and a ductile lower crust extending by penetrative flow and intrusion events seen in the middle and lower crust are generally subhorizontal and prominent layering is observed a band of reflections attributed to the crust mantle boundary is evident on most seismic sections the upper mantle appears seismically transparent on some of the profiles the events attributed to the base of the crust are the deepest in a series of strong and continuous reflections at least one of which is a layer of magma this association supports the suggestion that magmatic intrusions are a probable cause for the high reflectivity observed in the deep crust of many extensional terranes

the death valley turtlebacks reinterpreted as miocene pliocene folds of a major detachment surface determining the origin of extension parallel folds in metamorphic core complexes is fundamental to understanding the development of detachment faults an excellent example of such a feature occurs in the death valley region of california where a major undulatory detachment fault is exposed along the well known turtleback antiformal surfaces of the black mountains in the hanging wall of this detachment fault are deformed strata of the copper canyon formation new age constraints indicate that the copper canyon formation was deposited from 6 to 3 ma the formation was folded during deposition into a se plunging syncline with an axial surface coplanar with that of a synform in the underlying detachment this relation suggests the turtlebacks are a folded detachment surface formed during large scale extension in an overall constrictional strain field the present more planar black mountains frontal fault system may be the result of out stepping of a normal fault system away from an older detachment fa

theoretical effects of geomagnetic activity on low latitude ionospheric electric fields 1 the influence of geomagnetic activity on middle and low latitude thermospheric winds and ionospheric electric fields is investigated using model results from the national center for atmospheric research thermosphere ionosphere electrodynamics general circulation model model runs are made for different levels of geomagnetic activity model results show that the equatorward ionospheric currents produced by disturbance winds develop positive charge accumulation at low latitudes that maximizes in the premidnight sector the local time of maximum electric potential perturbation depends significantly on universal time so that the local time of reversal of the equatorial zonal perturbation electric field varies with longitude by 2 to 3 hours depending on the intensity of geomagnetic activity the westward perturbation electric field in the postsunset period indicates that stronger geomagnetic activity will produce a lower driven height of the evening f region after geomagnetic activity ceases model results show that the zonal disturbance winds can last for many days in the postrecovery period while the meridional disturbance winds decay more rapidly the long lasting zonal winds through the pedersen currents they drive help maintain meridional disturbance potential drops that decay much more slowly than the zonal disturbance potential drops after the activity ceases

the butte valley and layton well thrusts of eastern california distribution and regional significance the butte valley and layton well thrusts are major structural features in two adjacent mountain ranges west of southern death valley the butte valley thrust in the southern panamint range underlies most of the range and emplaces proterozoic rocks over strata as young as jurassic in age the layton well thrust to the southwest in the slate range has been interpreted to have proterozoic rocks juxtaposed on rocks as young as jurassic suggesting that the butte valley thrust and the layton well thrust might be correlative new information indicates that the allochthonous rocks of the layton well thrust are mesozoic in age and are not likely part of the same allochthon as that above the butte valley thrust in addition the butte valley thrust cuts sharply downward to the north and west across lower plate paleozoic strata suggesting that the fault roots beneath the layton well thrust the layton well thrust probably belongs to the east sierran thrust system and thus would be in the upper plate of the butte valley thrust

the equatorial electrojet during geomagnetic storms and substorms the climatology of the equatorial electrojet during periods of enhanced geomagnetic activity is examined using long term records of ground based magnetometers in the indian and peruvian regions equatorial electrojet perturbations due to geomagnetic storms and substorms are evaluated using the disturbance storm time dst index and auroral electrojet ae index respectively the response of the equatorial electrojet to rapid changes in the ae index indicates effects of both prompt penetration electric field and disturbance dynamo electric field consistent with previous studies based on f region equatorial vertical plasma drift measurements at jicamarca the average response of the equatorial electrojet to geomagnetic storms dst 50 nt reveals persistent disturbances during the recovery phase which can last for approximately 24 h after the dst index reaches its minimum value this after storm effect is found to depend on the magnitude of the storm solar euv activity season and longitude

first observations of poleward large scale traveling ionospheric disturbances over the african sector during geomagnetic storm conditions this paper presents first observations of poleward traveling ionospheric disturbances tids during strong geomagnetic conditions over the african sector by analyzing different data sets we have observed both positive and negative ionospheric responses during the storm period of 08 10 march 2012 considering the african region as a whole three longitudinal sectors were strategically selected to establish the entire regional response on both sides of the geomagnetic equator results show poleward shift in peak total electron content tec enhancements depletions at different times which are associated to large scale tids the observed phenomena are linked to the global ionospheric response and electrodynamics the understanding has been established using data from international gnss service receiver network radio occultation electron density profiles derived e b drift measurements from magnetometer observations and regional ground based and satellite data contrary to other related studies generated regional tec perturbation maps were not enough to show obvious directions of the large scale tids due to insufficient data over the northern hemispheric part of the african sector there appears to be a switch between positive and negative storm phases during the same storm period especially in the southern hemisphere part of the african region where enough data were available however a detailed analysis revealed that the positive storm phase corresponded to the expansion of the equatorial ionization anomaly eia toward some parts of midlatitude regions and possibly with the contribution from low latitude electrodynamics associated to equatorial electrojet while the other part recorded a negative storm phase due to storm induced changes from the auroral origin we have observed a simultaneous occurrence of both poleward and equatorward propagating tids over the african sector during the same geomagnetic storm period our results show that short lived large scale tids are possibly launched by the equatorial electrojet while the eia expansion contributes through modulation to the poleward propagation of the disturbances temporal variation of tec perturbations on a storm day over the entire african sector showed the existence of large scale tids during the main and recovery phases which can travel poleward up to 20 latitude the amplitudes of the tids have range 2 total electron content unit 1 tecu 1016 el m 2 period of 2 h and virtual velocities of 250 59 750 95 m s in midlatitude regions and up to 990 65 m s within the eia region

terrestrial heat flow in the malawi rifted zone east africa implications for tectono thermal inheritance in continental rift basins abstract rift basins show the widest range of heat flow values compared to passive continental margins and intracratonic sag basins elevated heat flow is often used to infer asthenospheric upwelling or subsurface magmatic activity for magma assisted rifts despite the lack of surface volcanism for magma poor rifts it is possible that magmatic bodies will be present at lower and mid crustal levels but yet to breach the surface thus necessitating consideration of heat flow from tectono thermal inheritance in addition to more recent magmatism we use aeromagnetic data to investigate the terrestrial heat flow distribution in the malawi rifted zone mrz in east africa defined as the neogene malawi rift and surrounding permo triassic karoo rift basins we use the two dimensional power density spectrum technique to estimate the curie point depth cpd geothermal gradient and heat flow beneath the mrz our results reveal predominance of shallow cpds 18 20 km high geothermal gradients 29 32 c km and elevated heat flow 70 82 mw m 2 within the karoo rift basins along the malawi rift geothermal gradient 25 27 c km and heat flow 60 66 mw m 2 are generally lower except pronounced high heat flow 70 82 mw m 2 at the rungwe volcanic province rvp in the north and at the central rift segment where the rift overprints karoo rift basins the surrounding cratonic blocks show deeper cpds 24 27 km lower geothermal gradients 22 24 c km and lower heat flow 53 63 mw m 2 we interpret that the elevated heat flow in the karoo rift basins are related to residual heat flow from the permo triassic rifting phase replenished by later jurassic cretaceous diking events apart from the thermal anomaly beneath the rvp which is due to neogene magmatism other important targets for geothermal explorations in the mrz are the residual thermal anomalies in the karoo rift basins we infer that in areas of active magma poor rifting pronounced heat flow may not only occur in regions of asthenospheric upwelling but may concentrate in the ancient magmatic rift segments our findings have implications for crustal stretching tectono thermal inheritance and geothermal energy potentials in east africa and other segments of magma poor rifting

rolling hinge or fixed basin a test of continental extensional models in death valley california united states two models are typically offered to explain severe continental extensional tectonism low angle detachment faults with alloch thonous sedimentary basins above a crustal rolling hinge or differential displacement on systems of distinct deeply rooted normal faults with in place sedimentary basins structural and stratigraphic relationships between the badwater turtleback and the adjacent furnace creek basin in death valley provide a test of these contrasting models there ductile extensional deformation of basement rock at the badwater turtleback coincided with brittle extensional deformation and local uplift in the adjacent furnace creek basin between 13 and 18 ma in the furnace creek basin crustal extension of this age is evident as 1 greater fault density and offset in pre 13 ma rocks relative to post 13 ma rocks and 2 the presence of laterally variable sedimentary breccias and conglomerates which indicate a syndepositional paleotopographic high this high is approximately on line with the likely projection of an early badwater turtleback fault the surface expression of the turtleback mylonites these relationships indicate that the badwater turtleback and furnace creek basin were contiguous prior to 13 ma and that the basin formed in place relative to the black mountains basement these findings support arguments for extension in the death valley area by distinct deeply rooted fault zones rather than by a rolling hinge detachment fault

a high resolution seismic reflection refraction study of the chugach peninsular terrane boundary southern alaska we present results from a high resolution seismic refraction analysis of the shallow approximately 2 km crustal structure along the 107 km long trans alaska crustal transect chugach reflection line in southern alaska and a comparison with laboratory measurements of field samples the refraction analysis includes the two dimensional interpretation of several thousand first and secondary arrival travel times digitized from 1024 channel split spread common shot gathers the velocity model derived from this analysis better defines the location and geometry of terrane boundaries than does the normal incidence reflection section and agrees well with surface mapping of lithologies furthermore the model predicts travel times within 100 ms of the reflection times recorded from the base of the quaternary on the chugach reflection section thicknesses of quaternary deposits with velocities between 1 1 and 2 0 km s correlate inversely with the quantity of observed lower crustal reflections on the chugach section suggesting that the presence or absence of these sediments in sufficient thickness exerted primary control on the quality of the deeper portion of the section there is a significant velocity contrast between crystalline rocks across the border ranges fault 5 0 versus 5 6 km s the major contact between the chugach and peninsular terranes in agreement with laboratory measurements of field specimens in the peninsular terrane the modeling indicates that an unnamed fault delimiting the southern flank of the copper river basin dips steeply northward at 50 and has about 1300 m of vertical offset laboratory measurements document a maximum velocity anisotropy of 20 for phyllitic schists of the valdez group in the chugach terrane in agreement with the observed e w strike and near vertical dip of the valdez group we determined a significant 14 velocity anisotropy for ray paths oriented n s versus ne sw

simultaneous pure and simple shear the unifying deformation matrix abstract any simultaneous combination of finite simple shear and finite pure shear is a linear transformation which can be expressed as a single transformation matrix for two dimensions the matrix is upper triangular with an off diagonal term called the effective shear strain is a simple function of the pure and simple shear components for three dimensions a simultaneous combination of thrusting in the x direction thrusting in the y direction and a wrench in the x direction in addition to 3 orthogonal components of coaxial strain can also be represented by a 3 3 upper triangular matrix here three off diagonal terms xy x y and y z occur xy is a simple function of the horizontal coaxial strain values and thrusting in the x direction yz depends on the coaxial strain components in the y and z directions and the thrusting in the y direction while xz is related to all six strain components the matrix also allows for volume change either homogeneously or preferentially in a single direction a method of decomposing the deformation matrix into a series of incremental deformation matrices where each incremental deformation records the same kinematic vorticity number as the finite deformation is shown the orientation and magnitude of the finite strain ellipsoid ellipse is easily and accurately found at any increment during the deformation

a close ridge small scale atmospheric flow field and its influence on snow accumulation the rough steep and complex terrain in the alpine environment causes a variety of flow patterns such as blocking speed up or flow separation which influence precipitation snow deposition and ultimately snow distribution on the ground cloud terrain interactions flow particle interactions and snow transport affect snow accumulation patterns but the relative importance of these processes is not fully understood in particular in complex mountainous terrain a unique combination of measurements and model simulations is used in a local case study during a two day snowfall event to demonstrate the current understanding of snow accumulation in very steep alpine terrain doppler wind lidar measurements show an eddy like structure on the leeward side of the sattelhorn ridge in the dischma valley near davos switzerland which could partly be replicated by advanced regional prediction system arps flow simulations snow deposition measurements with a terrestrial laser scanner tls show a complex deposition pattern which is only partially captured by alpine3d deposition simulations driven by the arps flow fields this shows that additional processes such as avalanches may play a role or that a more refined simulation of flow or flow particle interactions is required to fully understand snow distribution in very steep mountainous terrain

uniqueness of geological correlations an example from the death valley extended terrain the northern death valley furnace creek fault zone is a major northwest trending fault system in the death valley region but the magnitude of offset and its significance to extensional tectonism in the region are controversial stratigraphic data have provided first order constraints on offset across the fault zone but offer limited resolution previous correlations of mesozoic thrust faults across the fault zone have relied on regional stratigraphic trends to fingerprint structurally similar thrust plates we show that a northeast trending mesozoic backfold within the predominantly east directed fold and thrust belt was probably continuous from the southern panamint range california to the belted range nevada the relative position of this antithetic structure allows uniquely compatible correlations of three mesozoic structures between two range blocks across the northern death valley furnace creek fault zone independent of stratigraphic arguments the offset structures have geometric properties of size vergence order and spacing that indicate a probability less than 10 4 of the mesozoic orogen identically repeating this structural suite in two unrelated places reconstruction of these correlative structures indicates 68 4 km n48 w 6 w of apparent dextral offset between the cottonwood and funeral mountains in general agreement with previous estimates based on stratigraphic observations but of substantially higher precision this reconstruction and the restoration of a 30 km separation between the funeral and grapevine mountains indicated by offset segments of the backfold suggest a simple pre extensional geometry for the mesozoic orogen in the death valley region consistent with observations from unextended blocks and analogous to that of the cordilleran orogen at the latitude of calgary alberta

seismic depth imaging of normal faulting in the southern death valley basin motivated by the need to image faults to test cenozoic extension models for the death valley region of the western basin and range province an area of strong lateral velocity variations we examine the geometry of normal faulting in southern death valley by seismic depth imaging we analyze cocorp death valley line 9 to attain an enhanced image of shallow fault structure to 2 5 km depth previous work used standard seismic processing to infer normal faults from bed truncations displacement of horizontal reflectors and diffractions we obtain a detailed velocity model by nonlinear optimization of first arrival times picked from shot gathers examine the unprocessed data for fault reflections and use a kirchhoff prestack depth imaging procedure to handle lateral velocity variations and arbitrary dips properly fault plane reflections reveal the listric true depth geometry of the normal fault at the black mountains range front in southern death valley this is consistent with the concept of low angle ex

three dimensional model of the late cenozoic history of the death valley region southeastern california the accumulation of a large database on the timing and kinematics of late cenozoic deformation in the death valley region of southeastern california indicates a complex three dimensional history on the basis of paleogeographic reconstructions we suggest the system was initiated as a localized pull apart between two conjugate strike slip faults the garlock and furnace creek faults and evolved into a system characterized by distributed transtension related to the eastern california shear zone our reconstructions differ from previous models in the incorporation of significant vertical axis rotations of a number of crustal blocks to explain paleomagnetic data from the region the model may resolve 1 a long standing problem of the eastern termination of the garlock fault which is explained here as a complex system of splays that initially terminated in the pull apart between the furnace creek and garlock systems and 2 the complex architecture of the black mountains which is explained here in terms of initial extreme attenuation between the garlock and furnace creek systems with overprinting by a fold and normal fault system that operated simultaneously as a result of distributed transtension this model suggests much of the displacement field is taken up in rotations and translations and the actual crustal thinning in our model is relatively small 50 66 of original thickness

paleogeographic reconstruction of the death valley extended region evidence from miocene large rock avalanche deposits in the amargosa chaos basin california large rock avalanche deposits are extremely useful tools in paleogeographic and tectonic reconstructions these deposits are large 0 1 km3 semicoherent snapshots of source area that were emplaced instantaneously in a sedimentary basin a rock avalanche deposit with a known age in a sedimentary basin requires the restoration of that basin to a position adjacent to the rock avalanche source area at the time of emplacement the miocene sedimentary section of the amargosa chaos and sperry hills basins in the southern death valley region contains deposits of large rock avalanches from both spatially and temporally separated source terranes the rock avalanche deposits in the amargosa chaos basin require the restoration of the basin to within 10 km of the kingston range prior to 7 8 ma west derived alluvial fan sediments in this basin can be confidently tied to the southern panamint mountains with early east derived alluvial fan sediments pre 7 8 ma tied to the kingston range moreover the pre 7 8 ma stratigraphy of the amargosa chaos basin is equivalent to the pre 7 8 ma stratigraphy of the miocene sedimentary section in the sperry hills prior to 7 8 ma the amargosa chaos and sperry hills basins were both parts of a larger sedimentary basin sedimentologic constraints on the geometry of the amargosa chaos basin indicate that throughout its history it was a half graben opening along a west dipping normal fault with substantial vertical relief in the uplifted footwall evidence for this topography exists in the form of multiple large rock avalanche deposits derived from footwall bedrock the axis of this basin trends northwest with the active basin bounding normal fault on the northeast margin at 7 8 ma the extension direction in the southern death valley region changed from southwest to northwest younger sediments including three younger rock avalanche deposits record the motion of the amargosa chaos basin away from the sperry hills basin top to the northwest displacement of 30 km along the amargosa detachment system is required between 7 8 ma and 4 9 ma between the sperry hills basin and the location of amargosa chaos basin in the southern black mountains continued post 4 9 ma northwest directed extension is required between the amargosa chaos basin and the southern panamint mountains in addition 15 km of right lateral slip on the southern portion of the grand view fault is required from 7 8 to 3 ma to move the sperry hills basin away from its pre 7 8 ma position adjacent to the kingston range

ionospheric electron content within the equatorial f 2 layer anomaly belt this paper describes some new results on the day to day behavior of the location of the equatorial anomaly in the columnar electron content the measurements were made from a unique network of stations covering dip latitudes from 0 n to 25 n during the period in 1975 1976 near sunspot minimum when the ats 6 satellite was visible from india the latitudinal distribution of the total electron content on a particular day was found to depend only on the strength of the electrojet current as determined by the difference of the horizontal magnetic field at stations on the magnetic equator and another outside the equatorial electrojet rather than on the horizontal magnetic field measured only at the equatorial station during magnetically disturbed periods the presence or absence of the anomaly was also found to depend only upon the strength of the electrojet current the varying electrojet current that is the equatorial electric field is very effective in moving the ionization to the anomaly latitudes of 15 20 but the columnar electron content over the magnetic equator remains relatively constant

interannual persistence of the seasonal snow cover in a glacierized catchment knowledge of the spatial snow distribution and its interannual persistence is of interest for a broad spectrum of issues in cryospheric sciences in this study snow depths derived from airborne laser scanning are analyzed for interannual persistence of the seasonal snow cover in a partly glacierized mountain area 36 km2 at the end of five accumulation periods the snow covered area varied by 16 of its temporal mean mean snow depth of the total area ranged by a factor of two 1 31 2 58 m with a standard deviation of 0 42 m interannual correlation coefficients of snow depth distribution were in the range 0 68 0 84 of the investigated area 75 was found to be interannually persistent the remaining area showed variable snow cover from year to year caused by occasional avalanches and changes in surface topography as a result of glacier retreat snow cover underwent a change from a homogeneous distribution on the former glacier surface to a more heterogeneous snow cover in the recently deglaciated terrain a geostatistical analysis shows interannual persistence in scaling behavior of snow depth in ice free terrain with scale break distances at 20 m scale invariant behavior of snow depth is indicated over 100 m on smooth glacier surfaces

estimating the propagation characteristics of large scale traveling ionospheric disturbances using ground based and satellite data 1 in this article the propagation characteristics of large scale traveling ionospheric disturbances ls tids are estimated during the geomagnetic storm periods of 14 16 may 2005 and 25 27 september 2011 over south africa one and two gps arrays have been independently considered for the storms of 15 may 2005 and 26 september 2011 respectively the average periods of dominant modes 2 5 3 5h in the time series data were determined by applying wavelet analysis on both ionosonde and gps data the consideration of diurnal gps total electron content tec variability from receivers along three different longitude sectors showed a time shift in tec enhancement with increasing latitude the first indication of equatorward motion of the traveling ionospheric disturbances tids the statistical method based on gps radio interferometry employed shows that these tids were mostly propagating nearly equatorward for both storm periods which is consistent with the existing literature about storm induced tids on storm days tid horizontal velocities have been determined in the range of 200 500m s the analysis of diurnal tec response from different stations confirmed that the positive storm effect observed on 15 may 2005 was a result of the large scale tids of wavelength 4000 km on the other hand the estimated wavelengths of ls tids on 26 september 2011 were 2400 3400km between 10 and 17 ut a time lag is observed between the times at which enhancements in tec ionosonde fof2 and hmf2 data are revealed and this has been attributed to the passage of the tid

curie point depths of the island of kyushu and surrounding areas japan as part of a comprehensive nationwide evaluation of geothermal resources for japan the first of the curie point depth maps covering the island of kyushu has been prepared the map was created by inverting gridded regional aeromagnetic data two satisfactory algorithms were developed to invert the gridded data based upon a distribution of point dipoles the first algorithm estimates x0 y0 and z0 the coordinates of the centroid of the distribution by computing a least squares fit to the radial frequency of the fourier transform the second algorithm estimates centroid depth only by computing a least squares fit to the squared amplitude of the frequency estimates the average depth to the top zt of the collection of point dipoles was estimated by a variation of the second algorithm the depth to the bottom of the dipoles inferred curie point depth is zb 2z0 zt the depth estimates are hand contoured to produce the final map the curie point depth map is then compared to regional geology and heat

inhomogeneous precipitation distribution and snow transport in steep terrain 1 the inhomogeneous snow distribution found in alpine terrain is the result of wind and precipitation interacting with the snow surface over topography we introduce and explain preferential deposition of precipitation as the deposition process without erosion of previously deposited snow and thus in absence of saltation a numerical model is developed describing the relevant processes of saltation suspension and preferential deposition the model uses high resolution wind fields calculated with a meteorological model arps the model is used to simulate a 120 h snow storm period over a steep alpine ridge for which snow distribution measurements are available the comparison to measurements shows that the model captures the larger scale snow distribution patterns and predicts the total additional lee slope loading well however the spatial resolution of 25 m is still insufficient to capture the smaller scale deposition features observed the model suggests that the snow distribution on the ridge scale is primarily caused by preferential deposition and that this result is not sensitive to model parameters such as turbulent diffusivity drift threshold or concentration in the saltation layer

on the role of isostasy in the evolution of normal fault systems the footwalls of west dipping normal faults that separate the west central colorado plateau from the basin and range province record at least 5 7 km and perhaps as much as 15 20 km of west side up neogene uplift with an axis just 10 20 km west of undeformed plateau strata the uplift is expressed as folding and steep faulting in pre tertiary cratonic and disconformably overlying neogene strata forming a basement cored anticline and coincident topographic high on the western margin of the plateau the authors interpret the uplift as a nonelastic response of the crust to buoyancy forces accompanying the tectonic denudation of the plateau margin profound isostatically driven deformation of the footwalls of major normal faults may be common in extensional terrains calling into question several assumptions fundamental to existing models of the evolution of normal fault systems

the black mountains turtlebacks rosetta stones of death valley tectonics the black mountains turtlebacks expose mid crustal rock along the western front of the black mountains as such they provide keys to understanding the tertiary structural evolution of death valley and because of the outstanding rock exposure they also provide valuable natural laboratories for observing structural processes there are three turtlebacks the badwater turtleback in the north the copper canyon turtleback and the mormon point turtleback in the south although important differences exist among them each turtleback displays a doubly plunging antiformal core of metamorphic and igneous rock and a brittle fault contact to the northwest that is structurally overlain by miocene pleistocene volcanic and or sedimentary rock the turtleback cores contain mylonitic rocks that record an early period of top southeastward directed shear followed by top northwestward directed shear the earlier formed mylonites are cut by and locally appear concurrent with 55 61 ma pegmatite we interpret these fabrics as related to large scale basement involved thrust faults at the turtlebacks now preserved as areally extensive metamorphosed basement over younger cover contacts the younger and far more pervasive mylonites record late tertiary extensional unroofing of the turtleback footwalls from mid crustal depths available geochronology suggests that they cooled through 300 8c at different times 13 ma at badwater 6 ma at copper canyon 8 ma at mormon point at mormon point and copper canyon turtlebacks these dates record cooling of the metamorphic assemblages from beneath the floor of an 11 ma tertiary plutonic complex collectively these relationships suggest that the turtlebacks record initiation of ductile extension before 14 ma followed by injection of a large plutonic complex along the ductile shear zone ductile deformation continued during extensional uplift until the rocks cooled below temperatures for crystal plastic deformation by 6 8 ma subsequent low angle brittle fault slip led to final exposure of the igneous and metamorphic complex the turtleback shear zones can constrain models for crustal extension from map view as well as cross sectional perspectives in map view the presence of basement involved thrust faults in the turtlebacks suggest the black mountains were a basement

curie point depth estimates from aeromagnetic data from death valley and surrounding regions california aeromagnetic data were analyzed to determine the curie point depth cpd by power density spectral and three dimensional inversion methods within and surrounding death valley in southern california we calculated the cpd for 0 5 regions using 2d power density spectral methods and found that the cpds varied between 8 and 17 km however the 0 5 region may average areas that include shallow and deep cpds and because of this limitation we used the 3d inversion method to determine if this method may provide better resolution of the cpds the final 3d model indicates that the depth to the bottom of the magnetic susceptible bodies varies between 5 and 23 km even though both methods produced roughly similar results the 3d inversion method produced a higher lateral resolution of the cpds the shallowest cpds occur within the central and southern death valley panamint valley coso geothermal field and the tecopa hot springs region deeper 15 km cpds occur over outcropping granitic and precambrian lithologies in the panamint range grapevine mountains black mountains and the argus range the shallowest cpd occurs within the central death valley over a possible seismically imaged magma body and slightly deeper values occur within the panamint valley southern death valley and tecopa hot springs the shallow cpd values suggest that partially molten material may also be found in these latter regions the cpd computed heat flow values for the region suggest that the entire area has high heat flow values 100 mw m 2 on the other hand locally extremely high values 200 mw m 2 occur within the panamint valley the southern and central death valley and tecopa hot springs region these locally high heat flow values may be related to midcrustal magma bodies but additional geophysical experiments are needed to determine if the magma bodies exist

extensional tectonics in the death valley area california transport of the panamint range structural block 80 km northwestward in the hypothesis presented here the panamint range is a structural block that was detached during late cenozoic time from underlying rocks that now form the black mountains and was transported tectonically an estimated 80 km to the northwest transport occurred along a single low angle westward dipping detachment fault or perhaps along a system of such faults the estimate of 80 km of transport distance is based on the apparent right lateral offset of late precambrian and paleozoic facies and thickness trends along the furnace creek fault zone that bounds the detached block on the northeast the death valley turtleback surfaces are considered to be gigantic mullions related to the detachment surface

simultaneous storm time equatorward and poleward large scale tids on a global scale we report on the first simultaneous observations of poleward and equatorward traveling ionospheric disturbances tids during the same geomagnetic storm period on a global scale while poleward propagating tids originate from the geomagnetic equator region equatorward propagating tids are launched from the auroral regions on a global scale we use total electron content observations from the global navigation satellite systems to show that these tids existed over south american african and asian sectors the american and african sectors exhibited predominantly strong poleward tids while the asian sector recorded mostly equatorward tids which crossed the geomagnetic equator to either hemisphere on 9 march 2012 however both poleward and equatorward tids are simultaneously present in all three sectors using a combination of ground based magnetometer observations and available low latitude radar julia data we have established and confirmed that poleward tids of geomagnetic equator origin are due to ionospheric electrodynamics specifically changes in e b vertical drift after the storm onset

velocity models for the highly extended crust of death valley california we employ nonlinear optimization to obtain shallow velocity structure from cocorp seismic reflection profiles in the highly extended death valley region california we also use group velocity analysis of regional earthquake surface waves that have traversed in and near the extended domain when compared with regional models for surrounding provinces our results show no evidence for significant uplift of the middle crust or removal of the upper crust we do not find fundamental upper crustal variations between regions proposed to have widely varying extensional histories these observations constrain previously proposed extensional mechanisms toward less than extreme amounts of extension

investigations of ground water flow associated with the saratoga warm springs and the tecopa hot springs near death valley california using magnetic and conductivity methods abstract electrical and ground magnetic surveys at saratoga springs and tecopa hot springs in the vicinity of death valley reveal intersecting faults that appear to control the spring locations faults striking east west and north south intersect at saratoga springs high electrical conductivity along imaged faults at saratoga springs implies shallow ground water channels between 5 and 20 m deep regions of high conductivity correlate with water saturated zones or clays gradients in magnetic and conductivity data at saratoga are interpreted as faults similarly northwest and northeast trending faults are inferred to intersect at isolated spring in tecopa valley our data suggest that ground water flow along deep structures allows water to be heated and could account for the water temperature of about 41 c at the springs at bath in tecopa valley however we hypothesize that cold water from the amargosa river percolates downward and mixes with hot water rising at the fault intersections the river water accounts for the lower water temperatures at saratoga and at the isolated spring as compared to the spring at bath in tecopa valley

a study of spectral methods of estimating the depth to the bottom of magnetic sources from near surface magnetic anomaly data summary based on a critical evaluation of several different spectral magnetic depth determination techniques on areally large synthetic layered and random magnetization models we recommend the following considerations in the usage of the methods as necessary prerequisites to successful bottom depth determinations 1 using windows with sufficient width to ascertain that the response of the deepest magnetic layer is captured and by verifying the spectra and computing the depth estimates with the largest possible windows 300 500 km 2 avoiding filtering to remove arbitrary regional fields accomplished by compiling magnetic anomalies derived from modern spherical harmonic degree 13 earth s main field models e g recent international geomagnetic reference field models igrf or comprehensive models cm 3 ascertaining the near circularity of the autocorrelation function to avoid analysing biased spectra containing strong anomaly trends and 4 avoid determining the slopes from the exponential low wavenumber part of the spectra in the cases of layered magnetization we also describe the details of the new spectral peak forward modelling method and discuss the conditions under which the method can lead to useful results we found that despite all these precautions in some cases the results can still be erroneous and therefore we recommend a critical evaluation of the results by modelling heat flow and taking into account seismic information on the crustal and lithospheric thicknesses and seismic velocities wherever possible in the southcentral us east of the rockies where the surface heat flow ranges between 40 and 65 mw m 2 w e obtained the magnetic bottom depth of 40 10 km using the approach of the forward modelling of the spectral peak this range is similar to the seismically derived crustal thickness of 45 50 km suggesting therefore that the entire crust may be magnetic in this region because of the uncertainties in the various heat flow contributing parameters such as the variations in thermal conductivity radiogenic heat and hydraulic regime we could not constrain the lithospheric thickness beyond an estimate ranging approximately from 100 to 200 km

sedimentology of the debris flow dominated warm spring canyon alluvial fan death valley california facies analysis of widely distributed exposures of the 32 6 km2 and 8 1 km long warm spring canyon fan central death valley shows that it has been built principally by debris flow deposits these deposits were derived from a mature panamint range catchment mostly underlain by precambrian mudrock quartzite and dolomite stacked clast rich and matrix supported debris flow lobes of slightly bouldery muddy pebble cobble gravel in beds 20 150 cm thick dominate the fan from apex to toe accounting for 75 98 of most exposures interstratified with the debris flows are less abundant 2 25 of cuts thinner 5 30 cm and more discontinuous beds of clast supported and imbricated pebble cobble gravel deposited by overland flows and gully flows this facies formed by the surficial fine fraction water winnowing of the debris flows primarily during recessional flood stage of the debris flow events two other facies associations make up a small part of the fan the incised channel tract consists of a 250 m wide clast supported ribbon of irregularly to thickly bedded boulder pebble cobble gravel nested within debris flow deposits this channel fill is oriented generally perpendicular to the panamint range front it formed by extensive erosion and winnowing of debris flows deposited within the incised channel into which all water discharge from the catchment is funnelled the limited presence of this facies only straddling the present incised channel indicates that this channel overall has maintained a consistent position on the fan except for slight lateral shifts some caused by strike slip offset fault offset temporarily closed the upper incised channel causing recessional debris flow mud to be ponded behind the dam the other local facies assemblage consists of subrounded to rounded moderately sorted pebble gravel in low angle cross beds that slope both basinwards and fanwards this gravel was deposited in beachface backshore and shoreface barrier spit environments that developed where lake manly impinged on the warm spring fan during late pleistocene time these deposits straddle headcuts into and were derived from erosion of the debris flow deposits wave energy sorted finer sediment from the shore zone concentrated coarser sediment and rounded the coarse to very coarse pebble fraction by selective reworking

storm and substorm causes and effects at midlatitude location for the st patrick s 2013 and 2015 events midlatitude locations are unique regions exposed to both geomagnetic storm and substorm effects which may be superposed on specific events imposing an extra handicap for the analysis and identification of the sources and triggers we study space weather effects at the midlatitude location of the iberian peninsula for the st patrick s day events in 2013 and 2015 we have been able to identify and separate storm and substorm effects on ground magnetometer data from san pablo toledo observatory during storm time revealing important contributions of the substorm current wedge on both events the analysis of these substorm local signatures have shown to be related to the production of effective geomagnetically induced currents and ionospheric disturbances as measured from global navigation satellite systems data at mad2 igs permanent station and not directly related to the storm main phase the whole sun to earth chain has been analyzed in order to identify the solar and interplanetary triggers in both events a high speed stream hss and a coronal mass ejections cme are involved though for 2015 event the hss has merged with the cme increasing the storm geoeffectiveness the enhancement of substorm geoeffectiveness is justified by the effects of the inclined magnetic axes of the sun and of the earth during equinox period

dynamic response of ionospheric plasma density to the geomagnetic storm of 22 23 june 2015 on 21 22 june 2015 three consecutive interplanetary shocks slammed into the earth s magnetosphere immediately after the third shock at 18 36 ut on 22 june marked by an exceptional sudden storm commencement with an amplitude of delta sym h similar to 106 nt a major geomagnetic storm commenced in the present study a multi instrument approach comprising observations data analysis and modeling is used to examine the global ionospheric response results show that enhanced storm time processes produced major total electron content tec variations at different latitudes longitudes and phases of the storm a closer inspection of the tec observations reveals strong longitudinal and hemispherical asymmetry in addition multiple equatorward and poleward propagating traveling ionospheric disturbances tids were detected in the tec data equatorward propagating tids are consistent with vertical neutral winds simulated from thermosphere ionosphere electrodynamics general circulation model however poleward tids were not reproduced in the model we find that a combination of driving processes including enhanced high latitude injection prompt penetration electric fields disturbance dynamo effect neutral winds and composition changes were acting at different stages of the storm

structure of the central death valley pull apart basin and vicinity from cocorp profiles in the southern great basin cocorp deep seismic reflection profiles in the vicinity of the central death valley pull apart basin in southeastern california provide three dimensional information on the subsurface of an active extensional terrane variations in the orientation and density of reflectors indicate that the crust and upper mantle of the region is divisible into three seismic zones which may represent regions of differing lithology rheology or both the reflections in the upper 5 s 15 km of the data have gentle to moderate dips between 5 and 10 s reflections are predominantly subhorizontal and below 10 s 30 km there are no notable reflections the boundaries between the above reflecting zones are marked by prominent reflecting horizons which are continuous throughout the survey region the observed reflection geometries resemble those predicted by the crustal model of the region proposed by wright and troxel 1973 on the basis of geological studies in addition many of the upper crustal reflectors can be traced directly to mapped features based on those correlations the upper reflecting zone 0 5 s is interpreted to be a region of brittle deformation with the various upper crustal reflectors interpreted as faults and basin sediments the reflecting horizon at the base of the upper zone appears to be the lower boundary of the faulted upper crustal blocks and it has been suggested that it locally includes partially molten rock the observed geometries and amplitudes of reflections from the lower crust 15 30 km depth or 5 10 s two way traveltime are consistent with the model of wright and troxel for a ductilely deformed and intruded lower crust the prominent reflecting horizon at the base of that zone is designated the reflection moho and the seismically transparent lowest zone appears to correspond to the upper mantle the seismic data define a zone of faults referred to here as the wingate wash fault zone which appears to form the southern boundary of the central death valley basin and also may have provided a conduit for the migration of magma from a mid crustal magma body to the surface the wingate wash fault zone appears to intersect the southern death valley fault zone and the frontal faults of the black mountains in the subsurface beneath the youngest volcanic edifice in the region those three fault zones appear to separate the panamint owlshead and black mountain upper crustal fault blocks from the available data a reconstruction of the possible fault block movements during the time of basin subsidence is presented that reconstruction suggests that the central death valley basin formed as a result of the combined down to the east rotation and northwest translation of the fault blocks in manner similar to that proposed by reches for other parts of the basin and range

end of winter snow depth variability on glaciers in alaska a quantitative understanding of snow thickness and snow water equivalent swe on glaciers is essential to a wide range of scientific and resource management topics however robust swe estimates are observationally challenging in part because swe can vary abruptly over short distances in complex terrain due to interactions between topography and meteorological processes in spring 2013 we measured snow accumulation on several glaciers around the gulf of alaska using both ground and helicopter based ground penetrating radar surveys complemented by extensive ground truth observations we found that swe can be highly variable 40 difference over short spatial scales tens to hundreds of meters especially in the ablation zone where the underlying ice surfaces are typically rough elevation provides the dominant basin scale influence on swe with gradients ranging from 115 to 400 mm 100 m regionally total accumulation and the accumulation gradient are strongly controlled by a glacier s distance from the coastal moisture source multiple linear regressions used to calculate distributed swe fields show that robust results require adequate sampling of the true distribution of multiple terrain parameters final swe estimates comparable to winter balances show reasonable agreement with both the parameter elevation relationships on independent slopes model climate data set 9 36 difference and the u s geological survey alaska benchmark glaciers 6 36 difference all the glaciers in our study exhibit substantial sensitivity to changing snow rain fractions regardless of their location in a coastal or continental climate while process based swe projections remain elusive the collection of ground penetrating radar gpr derived data sets provides a greatly enhanced perspective on the spatial distribution of swe and will pave the way for future work that may eventually allow such projections

numerical modeling of blowing and drifting snow in alpine terrain in mountainous regions snow transport due to wind significantly influences snow distribution and as a result avalanche danger a physically based numerical two layer model is developed to simulate blowing and drifting snow in alpine terrain one layer describes the driving wind field and the transport in suspension the description is based on the atmospheric boundary layer equations using an e model for the turbulent closure the second layer describes the transport due to saltation including erosion and deposition of snow here conservation equations for mass and momentum are formulated for the mixture of snow and air particle trajectory calculations are used to parameterize quantities characterizing the saltation layer both layers are mutually coupled by boundary conditions a two way coupling between particles and airflow is taken into account comparisons between simulation results and field measurements around an alpine crest show encouraging results

observations and simulations of quasiperiodic ionospheric oscillations and large scale traveling ionospheric disturbances during the december 2006 geomagnetic storm 1 a numerical simulation was performed to investigate quasiperiodic ionospheric oscillations that were observed with periods of 4 5 h by the ionosonde network okinawa yamagawa kokubunji and wakkanai in japan during the 15 december 2006 magnetic storm this simulation used the coupled magnetosphere ionosphere thermosphere cmit 2 0 model the cmit model reproduced the main characteristics of the observed ionospheric oscillations although it remains a challenging task to simulate the observations in a quantitative sense term analysis of the ion continuity equation demonstrated that the ionospheric oscillations in this event were mainly induced by the disturbed neutral winds which were associated with the large scale thermospheric circulation and traveling atmospheric disturbances tads during the storm the tads simulated from the model were then compared with those observed by the gps earth observation network geonet in japan to validate the simulation results a prominent northward propagating large scale traveling ionospheric disturbance lstid during daytime seen by the geonet total electron content tec data was captured by the cmit model two southward lstids observed by geonet gps network were also reproduced by the cmit model however the model gave faster phase speeds for the southward propagating lstid occurred during 0620 0800 ut and the northward propagating lstid furthermore the model missed the lstid seen in the tec perturbation data during 0140 0220 ut finally both observations and simulations showed a strong hemispheric asymmetry for the tad propagation that occurred during 0000 0400 ut which may be associated with the hemispheric asymmetry of the change of joule heating at high latitude

electrical conductivity images of quaternary faults and tertiary detachments in the california basin and range comparison of an electrical resistivity section derived from magnetotelluric mt data to a geologic section extending eastward from the sierra nevada near latitude 36 20 n shows that the crust is dominated by steeply dipping conductive features that correlate with active strike slip faults while there is a subhorizontal conductor at a depth 20 km beneath some of the profile it is broken by vertical structures associated with the active strike slip faults the continuous subhorizontal anomalies in the lower crust typically observed in extensional regions are therefore absent in the resistivity section the present day strike slip tectonic regime as indicated by geodetic data in this part of the basin and range is not producing features that could be inferred to indicate subhorizontal shear zones resulting from lateral crustal flow during extension because the miocene tectonic regime resulted in the formation of metamorphic core complexes and thus was accompanied by such flow the present regime appears to represent a fundamental transition in the mode of crustal deformation in the region a serendipitous result of our study was the identification on resistivity sections of carbonate aquifers in the upper crust comparison of resistivities from the mt section to measured fluid resistivities from springs and boreholes suggests that the aquifers must be heterogeneous with more saline brines occupying the deepest portions of the carbonates

snow avalanche formation 1 snow avalanches are a major natural hazard endangering human life and infrastructure in mountainous areas throughout the world in many countries with seasonally snow covered mountains avalanche forecasting services reliably warn the public by issuing occurrence probabilities for a certain region however at present a single avalanche event cannot be predicted in time and space much about the release process remains unknown mainly because of the highly variable layered character of the snowpack a highly porous material that exists close to its melting point the complex interaction between terrain snowpack and meteorological conditions leading to avalanche release is commonly described as avalanche formation it is relevant to hazard mapping and essential to short term forecasting which involves weighting many contributory factors alternatively the release process can be studied and modeled this approach relies heavily on snow mechanics and snow properties including texture while the effect of meteorological conditions or changes on the deformational behavior of snow is known in qualitative or semiquantitative manner the knowledge of the quantitative relation between snow texture and mechanical properties is limited but promising developments are under way fracture mechanical models have been applied to explain the fracture propagation and micromechanical models including the two competing processes damage and sintering have been applied to explain snow failure there are knowledge gaps between the sequence of processes that lead to the release of the snow slab snow deformation and failure damage accumulation fracture initiation and fracture propagation simultaneously the spatial variability that affects damage fracture initiation and fracture propagation has to be considered this review focuses on dry snow slab avalanches and shows that dealing with a highly porous media close to its melting point and processes covering several orders of scale from the size of a bond between snow grains to the size of a mountain slope will continue to be very challenging

instruments and methods simulating complex snow distributions in windy environments using snowtran 3d we present a generalized version of snowtran 3d version 2 0 that simulates wind related snow distributions over the range of topographic and climatic environments found globally this version includes three primary enhancements to the original liston and sturm 1998 model 1 an improved wind sub model 2 a two layer sub model describing the spatial and temporal evolution of friction velocity that must be exceeded to transport snow the threshold friction velocity and 3 implementation of a three dimensional equilibrium drift profile sub model that forces snowtran 3d snow accumulations to duplicate observed drift profiles these three sub models allow snowtran 3d to simulate snow transport processes in variable topography and different snow climates in addition snowtran 3d has been coupled to a high resolution spatially distributed meteorological model micromet to provide more realistic atmospheric forcing data micromet distributes data precipi tation wind speed and direction air temperature and relative humidity obtained from meteorological stations and or atmospheric models located within or near the simulation domain snowtran 3d has also been coupled to a spatially distributed energy and mass balance snow evolution modeling system snowmodel designed for application in any landscape and climate where snow is found snowtran 3d is typically run using temporal increments ranging from 1 hour to 1 day horizontal grid increments ranging from 1 to 100 m and time spans ranging from individual storms to entire snow seasons

regional gravity studies in southeastern california western arizona and southern nevada bouguer gravity anomaly low pass and band pass maps of southeastern california western arizona and southern nevada are analyzed to determine regional crustal structure based on 100 250 km band pass wavelength filtering of the bouguer anomaly map a low amplitude gravity maximum is associated with the highly extended terrane along the colorado river region of california arizona and nevada two crustal models constructed using bouguer gravity anomaly data and constrained by geological mapping aeromagnetic data and seismic refraction data are consistent with the dome shaped midcrustal lens of probable dioritic composition centered under the whipple mountains proposed by mccarthy et al 1989 although other models are not precluded this midcrustal lens extends from the western edge of the colorado river extensional corridor to east of the buckskin and hualapai mountains in arizona dioritic material is exposed in various mountain ranges in the colorado river extensional corridor and may be part of the source of the gravity maximum that is associated with each range

faulting at mormon point death valley california a low angle normal fault cut by high angle faults new geophysical and fault kinematic studies indicate that late cenozoic basin development in the mormon point area of death valley california was accommodated by fault rotations three of six fault segments recognized at mormon point are now inactive and have been rotated to low dips during extension the remaining three segments are now active and moderately to steeply dipping from the geophysical data one active segment appears to offset the low angle faults in the subsurface of death valley

longitudinal differences of ionospheric vertical density distribution and equatorial electrodynamics 1 accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time season and magnetic activity is required to improve the operation of space based navigation and communication systems the vertical density distribution especially at low and equatorial latitudes is governed by the equatorial electrodynamics that produces a vertical driving force the vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground based global positioning system gps total electron content tec similarly the vertical drift which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low midlatitude region can be estimated using ground magnetometer observations we present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes the east african and west south american sectors chains of gps stations in the east african and west south american longitudinal sectors covering the equatorial anomaly region of meridian 37 e and 290 e respectively are used to reconstruct the vertical density distribution similarly magnetometer sites of african meridian b field education and research amber and intermagnet for the east african sector and south american meridional b field array samba and low latitude ionospheric sensor network lisn are used to estimate the vertical drift velocity at two distinct longitudes the comparison between the reconstructed and jicamarca incoherent scatter radar isr measured density profiles shows excellent agreement demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes similarly the comparison between magnetometer estimated vertical drift and other independent drift observation such as from vefi onboard communication navigation outage forecasting system c nofs satellite and julia radar is equally promising the observations at different longitudes suggest that the vertical drift velocities and the vertical density distribution have significant longitudinal differences especially the equatorial anomaly peaks expand to higher latitudes more in american sector than the african sector indicating that the vertical drift in the american sector is stronger than the african sector

folds with axes parallel to the extension direction an experimental study abstract experimental studies of single and multilayer folding have generally considered shortening of layers oriented perpendicular to the maximum extension direction x i e layers parallel to yz or in a more limited number of cases oblique layers still containing the intermediate y axis few experimental studies have considered the case where the extension direction x lies within the layer itself although in nature folds with axes parallel to x are quite commonly seen these folds have often been ascribed to passive rotation of fold axes during continued shear but it has been shown both theoretically and experimentally that active buckle folds can also develop with axes parallel to x single and multilayer analogue model experiments were performed on planar layers oriented initially perpendicular to the intermediate y axis and with the extension direction x lying within the layer itself all experiments were conducted in plane strain either in pure shear or simple shear paraffin waxes of different melting ranges were used as analogues for rocks with a power law rheology stress exponent around 2 3 with a viscosity ratio of ca 30 1 no measurable fold amplification was discernible for shortening of 36 or shear strain of 3 6 neither domed initial perturbations with circular sections parallel to the layer nor cylindrical perturbations elongate parallel to the initial stretching direction were significantly amplified only at much higher viscosity ratios ca 600 1 did active buckle folding develop this folding at high viscosity ratio was associated with flow of the matrix in the x direction around the layer developing a strong linear fabric parallel to x in the matrix immediately adjacent to the layer the development of this flow discontinuity between matrix and layer may be characteristic of active buckling of layers parallel to xz with fold axes parallel to x

mantle heterogeneity beneath eastern california from magnetotelluric measurements 1 a 300 km long magnetotelluric profile across the great valley sierra nevada and california basin and range reveals minimum resistivity differences of 1 order of magnitude at depths from moho at 30 35 km to depths greater than 200 km horizontal wavelengths of 25 km are seen for these changes at depths shallower than 100 km and the isabella high seismic wave speed anomaly is present in the section between depths of 100 and 200 km as a minimum tenfold resistivity increase a transformation from electrical resistivity to temperature and melt fraction using a petrological model and laboratory measurements reveals that partial melt is relatively uncommon and confined primarily to depths between 30 and 100 km the remainder of the observed resistivity variation is attributed to lateral variations in temperature predicted melt fractions match those inferred from miocene quaternary xenoliths but modeled temperatures are 200 c higher than inferred from thermobarometric analyses of the xenoliths possible causes for this discrepancy include an incorrect starting material for the petrological model exotic conductive phases higher conductivity due to oxidation state and or iron content and diffusion of ions through the solid matrix i show that hydrogen diffusion or higher oxygen concentrations are plausible explanation for the higher model temperatures less than 200 ppm h 106 si in olivine would increase the conductivity of the matrix sufficiently to allow temperatures inferred from the resistivity section to match those from the xenoliths a possible source of the hydrogen would be fragments of sinking metasomatized mantle lithosphere that melted during cenozoic delamination

death valley bright spot a midcrustal magma body in the southern great basin california a previously unrecognized midcrustal magma body may have been detected by cocorp deep seismic reflection profiles in the death valley region of the southern great basin high amplitude relatively broad band reflections at 6 s 15 km are attributed to partially molten material within a subhorizontal intrusion this bright spot extends laterally at least 15 km beneath central death valley a moderately dipping normal fault can be traced from the inferred magma chamber upward to a 690 000 yr old basaltic cinder cone the fault zone is inferred to have been a magma conduit during the formation of the cinder cone vertical variations in crustal reflection character suggest that the death valley magma body may have been emplaced along a zone of decoupling that separates a faulted brittle upper crust from a more ductile and or intruded lower crust the death valley bright spot is similar to reflections recorded by cocorp in 1977 in the rio grande rift where both geophysical and geodetic evidence support the inference of a tabular magma chamber at 20 km depth

mid and low latitude prompt penetration ionospheric zonal plasma drifts we have used ion drift observations from the de 2 satellite to determine the latitudinal variation and the temporal evolution of mid and low latitude prompt penetration zonal plasma drifts driven by magnetospheric electric fields our results indicate that sudden increases in convection lead to predominantly westward perturbation drifts which decrease equartorwards and have largest amplitudes in the dusk midnight sector the diurnal perturbation drift patterns shift to later local times with increasing storm time and decay to new quasi equilibrium values in about 2 hours as the ring current readjusts to the new polar cap potential the daily and latitudinal variations and temporal evolution of the de 2 prompt penetration drifts are generally in good agreement with predictions from the rice convection model although the experimental results show larger amplitudes and longer shielding time constants

geometry and subsurface lithology of southern death valley basin california based on refraction analysis of multichannel seismic data the shallow structure and subsurface lithology of southern death valley basin in eastern california were studied using refraction analysis of multichannel seismic reflection data acquired by cocorp two dimensional velocity models of the upper 3 km of southern death valley were derived from iterative fitting of first arrival travel times on common shot and common receiver gathers the structural basement beneath southern death valley defined by rocks having velocities greater than 4 0 km s is asymmetric and dips gently to the east where it is terminated by a steeply dipping fault which parallels the black mountain range front and has normal down to the west displacement numerous other faults that have normal components of displacement obliquely cross the seismic lines and indicate that the southern death valley basin formed from the divergent wrench system of the southern death valley fault zone

mountain snow distribution governed by an altitudinal gradient and terrain roughness 1 the heterogeneous mountain snow cover is challenging the eye and the analytical mind of the observer the snow distribution affects water resources natural hazards such as avalanches and ecology while a lot of recent research has helped to better understand this snow distribution and the processes that cause the heterogeneity it has not yet been possible to predict snow distribution satisfactorily on the basis of terrain parameters alone we present a model of the mean snow depth in topographic control units as a function of two terrain parameters the conventional elevation plus a fractal roughness parameter for this we used a unique data set of high resolution measurements of snow depth from an airborne laser scanner the model captures the heterogeneous snow distribution by merely analysing the terrain and the mean precipitation this unusually simple relationship holds for clusters of the snow depths of small topographical units by applying fractal analysis we describe the roughness of the terrain and use this parameter for the prediction of snow deposition rougher terrain holds less snow than smoother terrain this finding is important not only for avalanche warning or eco hydrological applications but also for reliably predicting how snow water storage may change in the light of the pronounced climate change already ongoing in mountain regions

thermal and barometric constraints on the intrusive and unroofing history of the black mountains implications for timing initial dip and kinematics of detachment faulting in the death valley region california unroofing of the black mountains death valley california has resulted in the exposure of 1 7 ga crystalline basement late precambrian amphibolite facies metasedimentary rocks and a tertiary magmatic complex the 40ar 39ar cooling ages obtained from samples collected across the entire length of the range 55 km combined with geobarometric results from synextensional intrusions provide time depth constraints on the miocene intrusive history and extensional unroofing of the black mountains data from the southeastern black mountains and adjacent greenwater range suggest unroofing from shallow depths between 9 and 10 ma to the northwest in the crystalline core of the range biotite plateau ages from 13 to 6 8 ma from rocks making up the death valley turtlebacks indicate a midcrustal residence with temperatures 300 c prior to extensional unroofing biotite 40ar 39ar ages from both precambrian basement and tertiary plutons reveal a diachronous cooling pattern of decreasing ages toward the northwest subparallel to the regional extension direction diachronous cooling was accompanied by dike intrusion which also decreases in age toward the northwest the cooling age pattern and geobarometric constraints in crystalline rocks of the black mountains suggest denudation of 10 15 km along a northwest directed detachment system consistent with regional reconstructions of tertiary extension and with unroofing of a northwest deepening crustal section mica cooling ages that deviate from the northwest younging trend are consistent with northwestward transport of rocks initially at shallower crustal levels onto deeper levels along splays of the detachment the well known amargosa chaos and perhaps the badwater turtleback are examples of this splaying process considering the current distance of the structurally deepest samples away from moderately to steeply east tilted tertiary strata in the southeastern black mountains these data indicate an average initial dip of the detachment system of the order of 20 similar to that determined for detachment faults in west central arizona and southeastern california beginning with an initially listric geometry a pattern of footwall unroofing accompanied by dike intrusion progresses northwestward this pattern may be explained by a model where migration of footwall flexures occur below a scoop shaped hanging wall block one consequence of this model is that gently dipping ductile fabrics developed in the middle crust steepen in the upper crust during unloading this process resolves the low initial dips obtained here with mapping which suggests transport of the upper plate on moderately to steeply dipping surfaces in the middle and upper crust

axial directions of folds in rocks with linear planar fabrics abstract this paper examines the geological implications of an analysis of constraints on the orientation of fold axes in orthotropic materials we argue that rocks with penetrative linear and planar shape fabrics may have orthotropic anisotropic properties during deformation two forms of anisotropy rheological and structural could be potentially important in the control of fold axial directions we discuss a model of deformation of rocks with linear planar fabrics where in a single deformation event major fold axes need not be parallel to minor fold axes and neither need be perpendicular to the principal compressive stress direction geological and model examples of anistropic control on fold axial directions are given

are flat field snow depth measurements representative a comparison of selected index sites with areal snow depth measurements at the small catchment scale single or a limited number of point observations such as from index stations are commonly assumed to be representative for the snow cover of larger areas in many applications this study presents a systematic investigation of the relationship between point observations and areal mean snow depths ranging from the scale of tens of metres to entire catchments we analyse aerial snow depth information from four mountain regions in the european alps one in the spanish pyrenees and one in the canadian rocky mountains obtained from airborne laser scanning surveys this rich data set allowed to compare point values with snow cover statistics reflecting the real snow depth distribution of the investigation areas we present two contrasting approaches in order to assess the representativeness of typical flat field snow depth measurements in the first approach we define potential index stations based on topographic characteristics as commonly applied for snow cover monitoring stations the point observations of these index stations are then compared with the mean values in their vicinities we show that most of the index stations strongly overestimate the snow depth of the catchment and of their surrounding area at distances of several hundreds of metres results confirm the expectation that the larger the support area the smaller the difference to the mean of the complete catchment the second approach was to analyse topographic characteristics of all cells with snow depths that deviated less than 10 from the catchment mean it appears that these representative cells are rather randomly distributed and cannot be identified a priori in summary our results show large potential biases of index stations with respect to snow distribution and therefore also snow water equivalent copyright c 2014 john wiley sons ltd

evolution of extensional basins and basin and range topography west of death valley california neogene extension in the death valley region se california has produced a variety of sedimentary basins diachronous movements on an array of strike slip and normal fault systems have resulted in the uplift and preservation of older basins in modern ranges one of the best exposed of these is the nova basin on the western flank of the panamint mountains the nova basin includes over 2000 m of sedimentary and volcanic rocks deposited during denudation of the panamint mountains metamorphic core complex in late miocene early pliocene time the principal growth structure for the basin was the emigrant detachment which initiated and moved at a low angle modern panamint valley west of the range developed as a consequence of late pliocene recent kinematically linked movement on the right slip high angle hunter mountain fault zone and the low angle panamint valley detachment detailed mapping of the intersection between the emigrant and panamint valley detachments demonstrates that segments of the earlier system remained active during development of panamint valley and thus during development of modern basin and range topography as well these results indicate that large scale extension in the death valley region accommodated by movement on low to moderate angle normal fault systems and high angle strike slip fault systems is a continuing process basin and range topography in the panamint valley death valley area was generated at least in part by displacements on low angle detachments rather than high angle normal faults

sedimentary processes and facies of the waterlaid anvil spring canyon alluvial fan death valley california the anvil spring canyon fan of the panamint range piedmont in central death valley was built entirely by water flow processes as revealed by an analysis of widespread 2 to 12 m high stratigraphic cuts spanning the 9 7 km radial length of this 2 5 5 0 sloping fan two facies deposited from fan sheetfloods dominate the fan from apex to toe the main one 60 95 of cuts consists of sandy granular fine to medium pebble gravel that regularly and sharply alternates with cobbly coarse to very coarse pebble gravel in planar couplets 5 25 cm thick oriented parallel to the fan surface the other facies 0 25 of cuts comprises 10 to 60 cm thick wedge planar and wedge trough beds of pebbly sand and sandy pebble gravel in backsets sloping 3 28 both facies are interpreted as resulting from rare sediment charged flash floods from the catchment and were deposited by supercritical standing waves of expanding sheetfloods on the fan standing waves were repeatedly initiated enlarged migrated and then terminated either by gradually rejoining the flood or by more violent breakage and washout the frequent autocyclic growth and destruction of standing waves during an individual sheetflood resulted in the deposition of multiple coarse and fine couplet and backset sequences 50 250 cm thick across the active depositional lobe of the fan erosional intensity during washout of the standing wave determined whether early phase backset bed deposits or washout phase sheetflood couplet deposits were selectively preserved in a given cycle two minor facies are also found in the anvil fan pebble cobble gravel lags 0 20 of cuts are present above erosional scours into the sheetflood couplet and backset deposits they consist of coarse gravel concentrated through fine fraction winnowing of the host sheetflood facies by sediment deficient water flows this reworking occurred during recessional flood stage or from non catastrophic discharge during the long intervals between major flash floods this facies is common at the surface giving rise to a braided stream appearance however it is stratigraphically limited present as thin continuous to discontinuous beds or lenses that bound 50 to 250 cm thick sheetflood sequences the other minor facies of the anvil fan consists of clast supported and imbricated thickly stratified pebbly cobbly boulder gravel present in narrow radially aligned ribbons nested within sheetflood deposits this facies is interpreted as representing deposition in the incised channel of the fan a subenvironment characterized by greater flow competence resulting from maintained depth from channel wall confinement and by more frequent water flows and winnowing events caused by its direct connection with the catchment feeder channel

relation of deformation and multiple intrusion in the death valley extended region california with implications for magma entrapment mechanism the crystalline core of the black mountains crustal section death valley california exposes a tremendous volume of miocene plutonic rock intruded at a depth of 10 13 km few plutons were intruded above 10 km prior to unroofing by tectonic denudation in the eastern part of the core a brittle detachment fault separates predominantly miocene hanging wall strata from the midcrustal miocene 11 6 and 8 7 ma plutonic complex and early proterozoic basement in the west mylonitic lineations and foliations locally well developed within the 11 6 ma intermediate mafic willow spring pluton are cut by dikes which emanate from an 8 7 ma silicic plutonic complex the younger silicic complex throughout the crystalline core exhibits few ductile deformational structures published thermal and barometric studies from both plutonic bodies indicate similar midcrustal 10 13 km emplacement depths at ambient temperatures just above 300 c the significant difference in densities of these magmas argues against a density control for magma entrapment also the country rock above and below the plutonic complex contains no apparent differences from field observations that would suggest a change in density the depth of entrapment corresponds well with the expected depth for the crustal strength maximum determined from laboratory experiments the similar emplacement depths but contrasting styles of deformation of the two plutonic bodies further suggests that entrapment may have been controlled by a high strength barrier represented by the brittle ductile transition late hypabyssal intrusions and associated volcanism are linked to diachronous rapid unroofing of the range block all show a northwest progression paralleling the regional extension direction thus when migration of magma through the high strength barrier did occur it was apparently related to increased strain rates which allowed magma ascent by fracture exploitation rheological stratification of the crust may have played an important if not major role in trapping magmas in the middle crust in this area

the origin of large local uplift in extensional regions large localized uplift is commonly observed in continental regions undergoing extension these observations can be modelled by planar high angle normal faulting of an elastic upper crust overlying an inviscid lower crust isostasy provides the necessary driving force the model quantifies the role of flexural rigidity density variations in the crust and erosion and deposition of sediment