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

spatial and temporal constancy of seismic strain release along an evolving segment of the pacific north america plate boundary abstract three new slip rates from the death valley fish lake valley dvflv fault contribute to an exceptionally detailed record of lateral rate variations on this 300 km long system from south to north these three new sites are south mud canyon cucomongo canyon and indian creek slip rates were determined by combining offsets measured with 1 m resolution airborne lidar data with 10be cosmogenic nuclide surface exposure and optically stimulated luminescence ages from displaced alluvial fans the offset fans date to 17 4 2 3 ka at south mud canyon 39 3 ka at cucomongo canyon and 6 3 1 8 ka at indian creek yielding slip rates of 2 1 0 5 0 4 mm yr 6 1 1 3 1 0 mm yr and 2 2 0 8 0 6 mm yr respectively at indian creek the holocene 6 ka and late quaternary 70 ka slip rates are the same within uncertainty suggesting temporal constancy of seismic strain release along the northern dvflv fault zone over these time spans when combined with slip rates determined in earlier companion studies these results show that the late quaternary slip rate decreases northward and southward from the central part of the fault as slip is transferred onto north trending zones of distributed normal faulting towards the northeast and southwest of the central zone of rapid deformation this complex pattern of strain accommodation may reflect structural evolution towards a straighter structurally simpler zone of dextral shear that locally utilizes well established dextral faults that are linked where necessary by nascent zones of deformation summation of the rates of all major faults in the eastern california shear zone ecsz at the 37 n latitude of red wall canyon in northern death valley shows that the cumulative geologic rate of 8 5 10 mm yr is indistinguishable from the 9 mm yr geodetic rate although the cumulative rate on the major faults of the ecsz is slower to the north and south this probably reflects more distributed deformation in these areas rather than transient strain accumulation these results demonstrate the importance of obtaining multiple slip rates to effectively document the behavior of any fault system especially in studies of seismic hazard assessment and comparisons of geologic and geodetic rate data

joint earthquake source inversions using seismo geodesy and 3 d earth models a joint earthquake source inversion technique is presented that uses insar and long period teleseismic data and for the first time takes 3 d earth structure into account when modelling seismic surface and body waves ten average source parameters moment latitude longitude depth strike dip rake length width and slip are estimated hence the technique is potentially useful for rapid source inversions of moderate magnitude earthquakes using multiple data sets unwrapped interferograms and long period seismic data are jointly inverted for the location fault geometry and seismic moment using a hybrid downhill powell monte carlo algorithm while the insar data are modelled assuming a rectangular dislocation in a homogeneous halfspace seismic data are modelled using the spectral element method for a 3 d earth model the effect of noise and lateral heterogeneity on the inversions is investigated by carrying out realistic synthetic tests for various earthquakes with different faulting mechanisms and magnitude mw 6 0 6 6 synthetic tests highlight the improvement in the constraint of fault geometry strike dip and rake and moment when insar and seismic data are combined tests comparing the effect of using a 1 d or 3 d earth model show that long period surface waves are more sensitive than long period body waves to the change in earth model incorrect source parameters particularly incorrect fault dip angles can compensate for systematic errors in the assumed earth structure leading to an acceptable data fit despite large discrepancies in source parameters three real earthquakes are also investigated eureka valley california 1993 may 17 mw 6 0 aiquile bolivia 1998 february 22 mw 6 6 and zarand iran 2005 may 22 mw 6 5 these events are located in different tectonic environments and show large discrepancies between insar and seismically determined source models despite the 40 50 km discrepancies in location between previous geodetic and seismic estimates for the eureka valley and aiquile earthquakes the seismic data are found to be compatible with the insar location a 30 difference in strike between insar and seismic derived source models is also resolved when taking 3 d earth structure into account in the analysis of the eureka valley earthquake the combination of both insar and seismic data further constrains the dip for the zarand earthquake and in all cases the seismic moment is more robustly constrained in the joint inversions than in the individual data set inversions unmodelled lateral heterogeneities in earth and the models could partly explain some of the observed source parameter discrepancies related to the seismic data the authors 2014 published by oxford university press on behalf of the royal astronomical society

stability metastability and elastic properties of a dense silica polymorph seifertite 1 dense silica polymorphs with sixfold coordinated si have been found in snc and lunar meteorites and may be important minerals for silica rich components in the lower mantle however the stable crystal structure in the lower mantle and properties of dense silica remain controversial under stable heating and quasi hydrostatic stress conditions we found that the cacl2 type undergoes a phase transition to the pbo2type seifertite at 130 140 gpa and 2500 k our data suggest that this phase transition occurs at a greater depth than the perovskite postperovskite transition in the lowermost mantle the molar volume measured at 1 bar is the smallest among the reported silica polymorphs therefore having the highest calculated density and in excellent agreement with recent first principles calculations the greater molar volume of seifertite found in the shergottite meteorite and previous experiments supports a metastable synthesis of the phase outside its stability field our data combined with the hugoniots of silica polymorphs also rule out the possibility of the formation of seifertite in the meteorite within its stability field we found very little change in bulk sound speed across the cacl2 type seifertite transition if shear wave velocity decreases at the transition to seifertite as suggested by some computational studies this silica transition may provide an alternative explanation for the discontinuities with a shear wave velocity decrease found at depths greater than the d discontinuity

quaternary faulting in queen valley california nevada implications for kinematics of fault slip transfer in the eastern california shear zone walker lane belt new geologic map tectonic geomorphologic and terrestrial cosmogenic nuclide tcn geochronologic data document the geometry style kinematics and slip rates on late quaternary faults within the queen valley california nevada area these data provide important insight into the kinematics of fault slip transfer from the dextral white mountains fault zone northward into the mina defl ection queen valley is an 16 kmlong ne trending basin bounded to the south by the white mountains and underlain by four major pleistocene to holocene alluvialfan surfaces four different fault types and orientations cut and offset all but the youngest surfaces 1 the normal slip queen valley fault which consists of a set of ne striking nw and se dipping normal fault scarps that cut across the se side of the valley and offset all but the youngest surfaces 2 discontinuous ne striking sinistral faults exposed on the north side of the valley 3 the nw striking dextral coyote springs fault which merges into 4 a set of e w striking thrust faults measured offsets across normal fault scarps developed within 10 be tcn dated surfaces yield minimum late pleistocene horizontal extension rates of 0 1 0 3 mm yr documented fault geometries and slip orientations across queen valley suggest that fault slip transfer models such as the extensional displacement transfer block rotation and simple shear models within the dextral fault system proposed for the eastern california shear zone walker lane belt are not applicable to this part of the mina defl ection rather dextral fault slip is transferred by both a restraining westward step and a releasing eastward step restraining and releasing bends have been extensively documented at a range of scales in strike slip fault tectonic settings globally and they have been simulated in analog models thus it is not surprising to document both within the 630 km long dextral shear zone that makes up the northern eastern california shear zone walker lane belt our results combined with published slip rates for the dextral white mountain fault zone and the eastern sinistral coaldale fault suggest that transfer of dextral slip into the mina defl ection is partitioned into three different components horizontal extension along the queen valley fault thrust faulting that merges into the dominantly dextral slip along the coyote springs fault and dominantly sinistral slip along the coaldale fault a velocity vector diagram of fault slip partitioning across queen valley predicts a small component of contraction across the coyote springs and western coaldale faults contraction across the mina defl ection is consistent with global positioning system data an observed reduction in late pleistocene fault slip rates at the northern end of the eastern california shear zone and across the southwestern part of the mina defl ection may be explained by distribution of slip across a much broader zone than generally thought

seismic and mineralogical structures of the lower mantle from probabilistic tomography 1 one of the most powerful approaches for understanding the 3 d thermo chemical structure of the lower mantle is to link tomographic models with mineral physics data this is not straightforward because of strong trade offs between thermal and chemical structures and their influence on seismic structures they can be reduced by mapping simultaneously perturbations of wave speeds and density anomalies and by the quantitative assessment of the accuracy and uniqueness of seismic and mineralogical data here we present new tomographic maps of low order even degree seismic structures which are an improvement on earlier models they satisfy constraints from body wave surface wave and normal mode data simultaneously thereby enhancing the spatial resolution furthermore the seismic structure at a given location is represented by a probability density function pdf which takes into account the uncertainty and non uniqueness of the solution due to modeling and data restrictions following a robust statistical procedure we fit heterogeneity of wave speeds and density from hypothetical thermo chemical models to those of our tomographic maps we thereby constrain lateral variations of temperature as well as iron silica and post perovskite concentration in terms of pdfs our work shows that large scale chemical variations are likely everywhere in the lower mantle in most of the d region post perovskite is most abundant in the circum pacific belt but near the core its lateral variation is more complex furthermore post perovskite concentration trades off with the amplitudes of temperature and silicate variations but not with their lateral distribution this might be the reason why temperature and silicate variations appear not constrained by our data in the lowermost few hundred km of the mantle

constraints on the presence of post perovskite in earth s lowermost mantle from tomographic geodynamic model comparisons abstract lower mantle tomography models consistently feature an increase in the ratio of shear wave velocity v s to compressional wave velocity v p variations and a negative correlation between shear wave and bulk sound velocity v c variations these seismic characteristics also observed in the recent sp12rts model have been interpreted to be indicative of large scale chemical variations other explanations such as the lower mantle post perovskite ppv phase which would not require chemical heterogeneity have been explored less constraining the origin of these seismic features is important as geodynamic simulations predict a fundamentally different style of mantle convection under both scenarios here we investigate to what extent the presence of ppv explains the observed high v s v p ratios and negative v s v c correlation globally we compare the statistical properties of sp12rts with the statistics of synthetic tomography models derived from both thermal and thermochemical models of 3 d global mantle convection we convert the temperature fields of these models into seismic velocity structures using mineral physics lookup tables with and without ppv we account for the limited tomographic resolution of sp12rts using its resolution operator for both v s and v p structures this allows for direct comparisons of the resulting velocity ratios and correlations although the tomographic filtering significantly affects the synthetic tomography images we demonstrate that the effect of ppv remains evident in the ratios and correlations of seismic velocities we find that lateral variations in the presence of ppv have a dominant influence on the v s v p ratio and v s v c correlation which are thus unsuitable measures to constrain the presence of large scale chemical variations in the lowermost mantle to explain the decrease in the v s v p ratio of sp12rts close to the cmb our results favour a ppv bearing cmb region which has implications for the stability field of ppv in the earth s mantle

pacific north america plate motions new results from very long baseline interferometry expansion and densification of the very long baseline interferometry vlbi network by the nasa crustal dynamics project continues to clarify details of pacific north america motions in this paper i construct for the first time rigid plate tectonic models based purely on space geodetic data construction of vlbi plate models has the advantages of averaging the bias and errors of individual site velocities making failures in the rigid plate assumption easy to document and allowing the consistency of specified plate models to be quantified against the vlbi data set as a whole vlbi based rigid plate models vm2 and vm3 obtained by fitting vector velocities of 10 sites in the stable interiors of the north america and pacific plates reveal a misfit of vlbi observations and rm2 minster and jordan 1978 predictions significant at the 99 confidence level nuvel l demets et al 1990 reproduces the velocities of these 10 sites far better than rm2 and offers a fit to the data which is statistically indistinguishable from vm2 and vm3 by including velocities of 16 additional stations in the deforming plate margin vm2 and vms can resolve all four terms vpn total pacific north america motion vsa san andreas slip ve w path integrated deformation east and west of the san andreas in the vector equation characterizing pacific north america plate boundary deformation vpn vsa ve vw for several points along the san andreas without reference to a global plate model geological or local geodetic measurements or restrictions on distributed shear in most cases instantaneous vlbi determined rates agree with geologically based estimates mapped to point c 36 0 n 120 6 w in central california vm2 gives vpn c 46 8 1 4 mm yr n36 2 w vsa c 38 6 1 3 mm yr n36 2 w and ve c 8 2 1 3 mm yr n34 7 w vlbi substantially eliminates vw c the component of the san andreas discrepancy west of c although a few millimeters per year of right lateral strike slip on offshore faults can not be rejected at point d 34 1 n 117 0 w in southern california vm2 returns vsa d 25 0 1 1 mm yr n52 3 w ve d 8 8 1 1 mm yr n25 8 w and vw d 13 3 1 6 mm yr n21 5 w vw d is accommodated west of the san andreas to the channel islands the azimuth of san andreas slip suggests that the transverse ranges north of los angeles are absorbing 8 1 mm yr of compression perpendicular to the trend of the fault

surface slip during large owens valley earthquakes data sets and expanded results contributing to this study are available in the supporting information the earthscope southern and eastern california lidar project available online at http opentopo sdsc edu involved data acquisition and processing for the plate boundary observatory pbo by ncalm http www ncalm org unavco operates the pbo for earthscope http www earthscope org supported by the national science foundation ear 0350028 and ear 0732947 funding for this study was provided by the southern california earthquake center scec project 12140 the geological society of america graduate student research fund the community foundation of san bernardino county and the western washington university geology department we thank g seitz m price and k morgan for assistance in the field and s bacon j arrowsmith r weldon k scharer j unruh c madden madugo and d haddad for helpful discussions constructive reviews by d schwartz r briggs e schermer d clark and one anonymous reviewer substantially improved the paper we also thank the staff at the uc white mountain research center for facilitating this work any use of trade firm or product names is for descriptive purposes only and does not imply endorsement by the u s government

mapping spherical seismic into physical structure biases from 3 d phase transition and thermal boundary layer heterogeneity summary earth s mantle is to a very good first approximation spherically symmetric with lateral deviations in seismic velocities and density of only a few per cent this observation has led to the common assumption that average radial seismic models reflect the mantle s average physical structure we test this assumption by using a set of dynamically generated mantle structures and comparing seismic velocities for the average radial physical state with laterally averaged seismic velocities the thermal and thermochemical dynamic circulation models are earth like in terms of convective vigour thermal structure and geographical pattern of heterogeneity we find that in general averaged seismic structure is not distinguishable from the seismic structure of the physical average within the uncertainty bounds of seismic reference models an exception is near phase boundaries where phase boundary topography broadens the averaged seismic jump relative to the discontinuity at physical reference conditions in an inversion for 1 d seismic structure where narrow discontinuities are imposed these biases may map into a lower jump and substantially stronger velocity gradients above and below the interface than are actually present other small biases in averaged structure occur in thermal boundary layers including those that form above chemical piles these biases are caused by large lateral variations in temperature not compositional variability

a doubling of the post perovskite phase boundary and structure of the earth s lowermost mantle a new model of the deep earth allows geophysicists to measure variations in earth s temperature near the boundary between the rocky mantle and core using a recently discovered phase change in the lowest part of the earth s mantle where atoms rearrange themselves in crystals under extreme pressure and temperature the model also explains odd features of this part of the mantle such as patchy regions that reflect seismic waves generated by large earthquakes and inferences of dense partial melting combined with observations the results imply very large variations in temperature providing further evidence for circulation of material throughout the earth s mantle the thermal structure of the earth s lowermost mantle the d layer spanning depths of 2 600 2 900 kilometres1 is key to understanding the dynamical state and history of our planet earth s temperature profile the geotherm is mostly constrained by phase transitions such as freezing at the inner core boundary or changes in crystal structure within the solid mantle that are detected as discontinuities in seismic wave speed and for which the pressure and temperature conditions can be constrained by experiment and theory a recently discovered phase transition at pressures of the d layer2 3 4 is ideally situated to reveal the thermal structure of the lowermost mantle where no phase transitions were previously known to exist here we show that a pair of seismic discontinuities observed in some regions of d can be explained by the same phase transition as the result of a double crossing of the phase boundary by the geotherm at two different depths this simple model can also explain why a seismic discontinuity is not observed in some other regions and provides new constraints for the magnitude of temperature variations within d

solidus and liquidus profiles of chondritic mantle implication for melting of the earth across its history abstract we investigated the melting properties of a synthetic chondritic primitive mantle up to core mantle boundary cmb pressures using laser heated diamond anvil cell melting criteria are essentially based on the use of x rays provided by synchrotron radiation we report a solidus melting curve lower than previously determined using optical methods the liquidus curve is found between 300 and 600 k higher than the solidus over the entire lower mantle at cmb pressures 135 gpa the chondritic mantle solidus and liquidus reach 4150 150 k and 4725 150 k respectively we discuss that the lower mantle is unlikely to melt in the d layer except if the highest estimate of the temperature profile at the base of the mantle which is associated with a very hot core is confirmed therefore recent suggestions of partial melting in the lowermost mantle based on seismic observations of ultra low velocity zones indicate either 1 a outer core exceeding 4150 k at the cmb or 2 the presence of chemical heterogeneities with high concentration of fusible elements our observations of a high liquidus temperature as well as a large gap between solidus and liquidus temperatures have important implications for the properties of the magma ocean during accretion not only complete melting of the lower mantle would require excessively high temperatures but also below liquidus temperatures partial melting should take place over a much larger depth interval than previously thought in addition magma adiabats suggest very high surface temperatures in case of a magma ocean that would extend to more than 40 gpa as suggested by siderophile metal silicate partitioning data such high surface temperature regime where thermal blanketing is inefficient points out to a transient character of the magma ocean with a very fast cooling rate

fan surface evidence for debris flow avulsion controls and probabilities saline valley california debris flow fans form by shifts of the active channel termed avulsions field and experimental evidence suggest that debris flow avulsions may be induced by depositional lobes that locally plug a channel or super elevation of the channel bed above the surrounding fan surface by analogy to fluvial fans to understand debris flow avulsion processes we differentiate between these controls by quantifying the spatial distribution of debris flow lobe and channel dimensions along with channel bed super elevation on nine debris flow fans in saline valley california usa channel beds are generally super elevated by 2 5 channel depths above the fan surface and locally by more than 7 channel depths thereby substantially exceeding super elevation on fluvial fans depositional lobe thickness and channel depth decrease with distance from the fan apex although both are highly variable across the fans median channel depths roughly correspond to the 50 75th percentiles of lobe thicknesses while minimum channel depths roughly correspond to the 10 25th percentiles in contrast the thicknesses of lobes that have triggered avulsions roughly equal local channel depths and are on average twice as thick as the local median lobe thickness the spatial correspondence between avulsion locations and thick lobe deposits and the lack of correlation with channel bed super elevation leads us to infer that avulsions on these fans are mostly caused by thick lobes forming channel plugs although results may vary with climatic and tectonic setting our findings indicate that avulsion hazard assessment on populated fans should include mapping and monitoring of channel depths relative to typical deposit thicknesses on a given fan

variation in wind speed and surface shear stress from open floor to porous parallel windbreaks a wind tunnel study as vegetative windbreaks become established on a large scale in agricultural ecosystems understanding the influence of windbreak networks on the momentum budget of the atmospheric boundary layer becomes important the authors conducted a wind tunnel experiment to study the variation of wind speed profile and surface shear stress of wind flow passing from an open surface to another with parallel windbreaks five spacing l 5 10 15 20 30 h wherein h is the windbreak height windbreak arrays with moderate porosity aerodynamic porosity alpha 0 501 were used in the experiments both near floor and over array wind speed measurements showed that airflow will approach equilibrium state behind a special windbreak of the array varying from 4th to 9th windbreak when the spacing change from 30 to 5 h within the range of l h values investigated arrays with narrower spacing cause higher friction velocity and roughness length which were up to 2 26 and nearly 100 times those observed over open floor respectively a semiempirical momentum budget model is developed on the arrayed surface to estimate windbreak drag and shear stress on the protected floor windbreak drag accounts for more than 80 of shear stress on the arrayed surface and the shear stress on protected floor is less than 20 when l h 40 based on the model estimation the sum of the two estimated components agrees well with the estimates obtained from over array wind profiles

distributed extensional deformation in a zone of right lateral shear implications for geodetic versus geologic rates of deformation in the eastern california shear zone walker lane 1 the eastern california shear zone ecsz walker lane belt represents an important evolving component of the pacific north america plate boundary geodetic data suggest the northern ecsz is accumulating dextral shear at a rate of 9 3 mm a more than double the total measured late pleistocene rate at 37 5 n at this latitude the silver peak lone mountain splm extensional complex plays an important role in accommodating and transferring slip among the strike slip and normal faults of the ecsz and walker lane to better understand the recent geodynamic evolution of this region we determined late pleistocene extension rates for the clayton valley fault zone one of a series of down to the northwest normal faults comprising the splm using geologic mapping differential gps fault scarp surveys and cosmogenic nuclide geochronology extension rates along the clayton valley fault zone are time invariant at 0 1 0 1 to 0 3 0 1 mm a depending on fault dip since 137 ka when combined with other published fault slip rates at this latitude the cumulative late pleistocene geologic slip rate is 3 3 to 5 2 mm a this rate is lower than both the geodetic rate of dextral shear and other long term slip rate budgets in the northern ecsz our results suggest that deformation in clayton valley is spread across a diffuse set of normal faults and that not all of the deformation is recorded in the surficial geology we suggest that the low cumulative geologic slip rate in the northern ecsz may be a result of this distributed extension which can cause long term rates of deformation to be significantly underestimated

fluvial archive of peculiar avulsive fluvial patterns in the largest quaternary intracratonic basin of tropical south america the bananal basin central brazil abstract the bananal basin is the most important intracratonic quaternary sedimentary basin of south america and preserves a good record of the paleohydrological conditions of central brazil at the cerrado amazon ecotone this area is currently a large tropical plain seasonally flooded by rainfall and water table saturation that can be classified as a seasonal wetland this paper presents a geological and geomorphological analysis supported with geochronological dating aiming to reconstruct the pleistocene environmental history of the bananal basin the basin was filled by the sediments sourced by the araguaia mortes fluvial system the deposits belong to the araguaia formation which covers 106 000 km 2 of the bananal basin tl and osl chronologies of the araguaia formation show that sedimentation started at least in the middle pleistocene mis 7 but aggradation and avulsion processes were important in the lower middle pleniglacial between 70 5 ka and 34 0 4 6 ka mis 4 and 3 and in the upper pleniglacial between 24 5 3 1 and 17 2 2 3 ka mis 2 river avulsions were more intense in the lower bananal basin bananal island region remarkably we did not record ages between 17 ka and 10 ka although avulsion seems to have been more active in the past the abandonment by the araguaia of a channel belt now occupied by the underfit javaes river indicates that avulsion is still active the avulsion processes are mainly related to palaeohydrological changes although present day seismic activity is also recorded additional data is needed to generate a more detailed scenario for the older middle pleistocene deposits the data is remarkable however because it is the first middle pleistocene record described in a large alluvial tropical system in brazil the fluvial record is temporally in agreement with records from other large brazilian fluvial systems such as the amazon and parana basins the bananal plain however is unique because of its particular style of sedimentation and geomorphologic processes that generated a mega scale anabranching like complex pattern of paleochannels presently occupied by underfit streams

exhumation of the inyo mountains california implications for the timing of extension along the western boundary of the basin and range province and distribution of dextral fault slip rates across the eastern california shear zone 1 new geologic mapping tectonic geomorphologic 10be terrestrial cosmogenic nuclide and u th he zircon and apatite thermochronometric data provide the first numerical constraints on late cretaceous to late quaternary exhumation of the inyo mountains and vertical slip and horizontal extension rates across the eastern inyo fault zone california the east dipping eastern inyo fault zone bounds the eastern flank of the inyo mountains a prominent geomorphic feature within the western basin and range province and eastern california shear zone u th he zircon and apatite thermochronometry yield age patterns across the range that are interpreted as indicating 1 two episodes of moderate to rapid exhumation associated with laramide deformation during the late cretaceous early tertiary 2 development of a slowly eroding surface during a prolonged period from early eocene to middle miocene 3 rapid cooling exhumation and initiation of normal slip along the eastern inyo fault zone accommodated by westward tilting of the inyo mountains block at 15 6 ma and 4 rapid cooling exhumation and renewed normal slip along the eastern inyo fault zone at 2 8 ma fault slip continues today as indicated by fault scarps that cut late pleistocene alluvial fan surfaces the second episode of normal slip at 2 8 ma also signals onset of dextral slip along the hunter mountain fault yielding a pliocene dextral slip rate of 3 3 1 0 mm a where a is years summing this dextral slip rate with estimated dextral slip rates along the owens valley death valley and stateline faults yields a net geologic dextral slip rate across the eastern california shear zone of 9 3 2 2 1 4 to 9 8 1 4 1 0 mm a

analysis of surface wind and roughness length evolution with fetch using a combination of airborne lidar and radar measurements 1 a combination of surface wind speed sws and sea state variables derived from quasi simultaneous airborne lidar and radar measurements made in the framework of the flux etat de mer et teledetection en condition de fetch variable fetch experiment is used to analyze the evolution of surface roughness length neutral drag coefficient and friction velocity coefficient with fetch in the first hundred kilometers offshore over the gulf of lion western mediterranean the study focuses on the tramontane mistral event documented in the afternoon of 24 march 1998 particular attention is given to sws derived from nadir lidar measurements the sws retrieval methodology developed and validated for open ocean conditions by flamant et al 1998 has been modified to account for the specificity of the coastal mediterranean environment complex mixture of continental and maritime aerosol turbid productive waters the lidar derived sws evolution with fetch observed on 24 march 1998 in the afternoon was validated against in situ and remote sensing measurements made from a buoy a ship as well as from the spaceborne altimeter topex the spatial variability in sws observed with the airborne lidar was controlled by the structure of the wake regions downstream of the massif central and the maritime alps delimiting the longitudinal extension of the mistral and was influenced by swell resulting from the action of a steady northeasterly flow coming from the ligurian sea in connection with intense alpine lee cyclogenesis these findings were supported by the other measurements it is further shown that based on a formulation of the dimensionless roughness dependance with wave age airborne lidar and radar measurements can be combined to provide insight into the evolution with fetch of roughness length neutral drag coefficient and friction velocity four distinct sea state regimes over a distance of 100 km could be identified from the remotely sensed variables obtained with this novel approach in connection with atmospheric forcing the dependance of lidar radar derived drag coefficient with lidar derived sws for the four regimes was found to be remarkably consistent with the relationship derived from the buoy measurements finally lidar radar derived friction velocities were found in good agreement with the buoy and in situ aircraft measurements

an apparent shear zone trending north northwest across the mojave desert into owens valley eastern california strain rates measured at four geodetic networks in eastern california situated between northern owens valley and transverse ranges along a small circle drawn about the pacific north america pole of rotation are remarkably consistent each exhibits 0 14 mu rad yr simple right lateral engineering shear strain accumulation across the local vertical plane tangent to the small circle local faults e g owens valley garlock helendale traversing these networks are not as closely aligned with the vertical planes of maximum shear strain accumulation as is the local tangent to the small circle a fifth network slightly east of the small circle shows no significant strain accumulation thus a shear zone trending n35 degree w from near the eastern end of the big bend of the san andreas fault to northern owens valley is indicated by these data this corresponds to the eastern california shear zone proposed on geological evidence by dokka and travis the shear zone carries approximately 8 mm yr of the pacific north america relative plate motion from the san andreas fault north northwest across the mojave desert into owens valley and the northern basin and range province the shear zone observed at the surface may be a manifestation of a through going subcrustal fault

tectonic controls on late cenozoic strike slip faulting volcanism and landscape development in the mojave desert california recent studies of the late cenozoic tectonics of the mojave desert block suggest that strain is regionally heterogeneous and has been partitioned into six domains that are separated by major strike slip faults and extensional zones tectonic rotation of these domains as well as their internal deformation by strike slip faulting have occurred as the result of broadly distributed regional right shear sixty five kilometers of total right slip is reckoned to have occurred along faults of the southern half of the province between the helendale and granite mountains faults the broad network of faults of the mojave along with kinematically and temporally similar strike slip faults of the death valley region furnace creek and southern death valley fault zones constitute a regional through going zone of right shear named the eastern california shear zone ecsz this zone of intracontinental shear also likely includes the walker lane belt of western nevada because of its physical connection to faults the southern portion of the san andreas fault system the ecsz must have also accommodated a portion of pacific north american transform motion in addition to imparting the strong nw structural grain to the region the tectonic regime has had a profound effect on neogene paleogeography andmore has apparently facilitated local magmatism faulting and block rotations have created a series of structurally controlled basins and uplifts of many geometries extension in several basins has also been accompanied by young basaltic magmatism these include surface flows such as at mt pisgah shield volcano and subsurface dike emplacement beneath troy lake less

debris flow volume quantile prediction from catchment morphometry estimation of the volumes of potential future debris flows is a key factor in hazard assessment and mitigation worldwide however there are few catchments for which detailed volume frequency information is available we 1 reconstructed volume frequency curves for 10 debris flow catchments in saline valley california usa from a large number of well preserved unmodified surficial flow deposits and 2 assessed the correlations between lobe volume quantiles and a set of morphometric catchment characteristics we found statistically significant correlations between lobe volume quantiles including median and maximum and catchment relief length planimetric distance from the fan apex to the most distant point along the watershed boundary perimeter and melton ratio relief divided by the square root of catchment area these findings show that it may be possible to roughly estimate debris flow lobe volume quantiles from basic catchment characteristics that can be obtained from globally available elevation data this may assist in design volume estimation for debris flow catchments where past flow volumes are otherwise unknown

late quaternary denudation death and panamint valleys eastern california abstract late quaternary denudation rates are constrained from alluvial fans and tributary watersheds in central death and panamint valleys preliminary results suggest that the denudation rate is in part a function of the mean watershed elevation rainfall increases semi logarithmically with higher elevation to about 2500 m where it becomes limited by the regional average maximum moisture content of the air mass the fan volumes show a power law relation to the watershed areas the fan volumes ranged from about 250 000 to 4000 km 3 and the watershed areas range from about 60 000 to 2000 km 2 the upper limit of the denudation rates estimated from small death valley fans restricted to the east side of the basin along the black mountain frontal scarp range between about 0 03 to 0 18 mm yr the maximum is made by assuming most of the clastic accumulation in these fans followed the last highstand of lake manly around 24 000 yr which is the least conservative condition the upper limit of the denudation rates from the panamint fans range from 0 04 to 0 20 mm yr assuming the accumulation mainly postdates ois 4 60 000 yr or ois 2 20 000 yr based on the presence or absence of inset shorelines from the last glacial pluvial maximum the greater denudation rate associated with the higher mean watershed elevations can mainly be attributed to the greater rainfall at higher elevation denudation rates are about a third or less of the neogene dip slip rates reported from nearby active faults consistent with relief increasing during dryer periods

acceleration and evolution of faults an example from the hunter mountain panamint valley fault zone eastern california article i nfo we present new space geodetic data indicating that the present slip rate on the hunter mountain panamint valley fault zone in eastern california 5 0 0 5 mm yr is significantly faster than geologic estimates based on fault total offset and inception time we interpret this discrepancy as evidence for an accelerating fault and propose a new model for fault initiation and evolution in this model fault slip rate initially increases with time hence geologic estimates averaged over the early stages of the fault s activity will tend to underestimate the present day rate the model is based on geologic data total offset and fault initiation time and geodetic data present day slip rate the model assumes a monotonic increase in slip rate with time as the fault matures and straightens the rate increase follows a simple rayleigh cumulative distribution integrating the rate time path from fault inception to present day gives the total fault offset 2010 elsevier b v all rights reserved

uranium lead isotopic ages from the sierra nevada batholith california this study provides new information on the timing and distribution of mesozoic magmatic events in the sierra nevada batholithic complex chiefly between 36 and 37 n latitude u pb ages have been determined for 133 zircon and 7 sphene separates from 82 samples of granitoid rocks granitoid rocks in this area range in age from 217 to 80 m y triassic intrusions are restricted to the east side of the batholith jurassic plutons occur south of the triassic plutons east of the sierra nevada as isolated masses within the cretaceous batholith and in the western foothills of the range cretaceous plutons form a continuous belt along the axis of the batholith and occur as isolated masses east of the sierra nevada no granitic intrusions were emplaced for 37 m y east of the sierra nevada following the end of jurassic plutonism however following emplacement of the eastern jurassic granitoids regional extension produced a fracture system at least 350 km long into which the dominantly mafic calc alkalic independence dike swarm was intruded 148 m y ago the dike fractures probably represents a period of regional crustal extension caused by a redistribution of the regional stress pattern accompanying the nevadan orogeny intrusion of cretaceous granitic plutons began in large volume about 120 m y ago in the western sierra nevada and migrated steadily eastward for 40 m y at a rate of 2 7 mm y this slow and constant migration indicates remarkably uniform conditions of subduction with perhaps downward migration of parent magma generation or a slight flattening of the subduction zone such steady conditions could be necessary for the production of large batholithic complexes such as the sierra nevada the abrupt termination of plutonism 80 m y ago may have resulted from an increased rate of convergence of the american and eastern pacific plates and dramatic flattening of the subduction zone u pb ages of the giant forest alaskite sequence in sequoia national park are all in the range 99 3 m y indicating a relatively short period of emplacement and cooling for this nested group of plutons u pb ages of a mafic inclusion and its host granodiorite indicate that both were derived from a common source or that the mafic inclusion was totally equilibrated with the granodioritic magma comparison of isotopic ages determined by different methods such as zircon u pb sphene u pb hornblende k ar and biotite k ar suggests that zircon u pb ages generally approximate the emplacement age of a pluton however some plutons probably contain inherited or entrained old zircons and the zircons of some samples are disturbed by younger thermal and metamorphic events the ages reported here are consistent with u pb age determinations previously made on granitic rocks to the north stern et al 1981 the age distribution of granitic belts determined here is in general agreement with those established by k ar dating evernden and kistler 1970 but does not differentiate the five epochs of plutonism determined in their study

strain accumulation in owens valley california 1974 to 1988 strain accumulation observed over the 1974 to 1988 interval in a 25 by 100 km aperture trilateration network spanning owens valley is adequately described by a strain rate that is uniform in space and time the tensor strain rate components referred to a coordinate system with the 2 axis directed n18 w parallel to the trend of the valley and the 1 axis n72 e are 11 0 042 0 014 strain yr 12 0 058 0 007 strain yr and 22 0 002 0 014 strain yr quoted uncertainties are standard deviations and extension is reckoned positive across the 25 km breadth of the network this amounts to 1 0 0 3 mm yr extension normal to the axis of the valley 2 9 0 4 mm yr right lateral shear across the axis and no extension parallel to the axis if the measured strain accumulation is attributed to slip on the deeper section of the owens valley fault with the uppermost 10 km of the fault locked the observed right lateral deformation would imply about 7 mm yr right lateral slip on the buried fault much greater than the geologic estimate of 2 0 5 mm yr right lateral secular slip beanland and clark 1994 nor is the observed uplift profile across the valley consistent with continuing normal slip on just the deep segment of the owens valley fault normal slip at depth on the sierra frontal fault also seems to be required the observed deformation across owens valley apparently implies processes more complicated than those represented by the conventional model of strain accumulation along a throughgoing fault

slip rate of the western garlock fault at clark wash near lone tree canyon mojave desert california the precise tectonic role of the left lateral garlock fault in southern california has been controversial three proposed tectonic models yield significantly different predictions for the slip rate history orientation and total bedrock offset as a function of distance along strike in an effort to test these models we present the first slip rate estimate for the western garlock fault that is constrained by radiocarbon dating a channel referred to here as clark wash incised into a latest pleistocene alluvial fan has been left laterally offset at least 66 6 m and no more than 100 m across the western garlock fault indicating a left lateral slip rate of 7 6 mm yr 95 confidence interval of 5 3 10 7 mm yr using dendrochronologically calibrated radiocarbon dates the timing of aggradational events on the clark wash fan corresponds closely to what has been documented elsewhere in the mojave desert suggesting that much of this activity has been climatically controlled the range front fault located a few hundred meters northwest of the gar lock fault has probably acted primarily as a normal fault with a holocene rate of dip slip of 0 4 0 7 mm yr the record of prehistoric earthquakes on the garlock fault at this site though quite possibly incomplete suggests a longer interseismic interval 1200 2700 yr for the western garlock fault than for the central garlock fault the relatively high slip rate determined here indicates that the western and central segments of the garlock fault show similar rates of movement that are somewhat faster than rates inferred from geodetic data the high rate of motion on the western garlock fault is most consistent with a model in which the western garlock fault acts as a conjugate shear to the san andreas fault other mechanisms involving extension north of the garlock fault and block rotation at the eastern end of the fault may be relevant to the central and eastern sections of the fault but they cannot explain a high rate of slip on the western garlock fault

coulomb stress evolution in a diffuse plate boundary 1400 years of earthquakes in eastern california and western nevada usa diffuse plate boundaries are characterized by deformation distributed over a wide area in a complex network of active faults and by relatively low strain rates these characteristics make it difficult to understand the spatial and temporal distribution of seismicity the area east of the sierra nevada between longitudes 121 degrees w and 116 degrees w is part of a diffuse plate boundary at least 17 major surface rupturing earthquakes have happened here in the last 1400 years our purpose is to determine whether these events influence each other or whether they are randomly distributed in time and space we model the evolution of coseismic and postseismic coulomb failure stress changes delta cfs produced by these earthquakes and we also model interseismic stresses on the entire fault network our results show that 80 of the earthquake ruptures are located in areas of combined coseismic and postseismic delta cfs 0 2 bar this relationship is robust as shown by the control tests that we carried out using random earthquake sequences we also show that the fish lake valley pyramid lake and honey lake faults have accumulated 45 37 and 27 bars respectively of total delta cfs i e coseismic postseismic interseismic in the last 1400 years such values are comparable to the average stress drop in a major earthquake and these three faults may be therefore close to failure

right lateral displacements and the holocene slip rate associated with prehistoric earthquakes along the southern panamint valley fault zone implications for southern basin and range tectonics and coastal california deformation the n20 w trending panamint valley fault zone is linked to the n60 w trending hunter mountain strike slip fault and the saline valley fault system which represents one of the three major fault systems accommodating active crustal extension in the southern great basin a 25 km long zone of fault scarps along the southern panamint valley fault zone is recognized as the surface rupture zone associated with the most recent prehistoric earthquake the displacement associated with the most recent event determined through six detailed topographic maps of offset features is 3 2 0 5 m and a number of larger offsets in range of 6 7 m and 12 m are also observed if the larger displacements represent respectively two and three events each of 3 m then the fault zone appears to be associated with a characteristic earthquake which we estimate from the length of the rupture zone and the displacement to be between ms 6 5 and 7 2 the holocene slip rate is 2 36 0 79 mm yr is determined from the displacement of two alluvial features whose maximum age is estimated from pluvial shorelines assuming a characteristic earthquake model the recurrence interval is between 860 and 2360 years the holocene slip rate appears to be similar to the 4 million year slip rate of 2 2 7 mm yr determined from the hunter mountain fault which we suggest reflects the relatively constant tectonics in this region over the last 4 million years we further speculate that this supports the san andreas discrepancy in that the holocene slip rate of the san andreas fault probably represents its very long term several ma slip rate the total slip vector of the southern panamint valley fault system is oriented toward n35 w making this a predominantly strike slip fault in conjunction with the n60 w orientation of the hunter mountain strike slip fault we suggest that the displacement vector for the southern great basin is toward the nw consistent with results from vlbi data rather than wnw as determined by combining vlbi and geological data this in turn suggests that the coastal california deformation component involves respectively less shortening and more strike slip displacement perpendicular and parallel to the san andreas fault than is currently proposed

normal mode and free air gravity constraints on lateral variations in velocity and density of earth s mantle with the use of a large collection of free oscillation data and additional constraints imposed by the free air gravity anomaly lateral variations in shear velocity compressional velocity and density within the mantle dynamic topography on the free surface and topography on the 660 km discontinuity and the core mantle boundary were determined the velocity models are consistent with existing models based on travel time and waveform inversions in the lowermost mantle near the core mantle boundary denser than average material is found beneath regions of upwellings centered on the pacific ocean and africa that are characterized by slow shear velocities these anomalies suggest the existence of compositional heterogeneity near the core mantle boundary

cosmogenic 10be and 36cl geochronology of offset alluvial fans along the northern death valley fault zone implications for transient strain in the eastern california shear zone the northern death valley fault zone ndvfz has long been recognized as a major right lateral strike slip fault in the eastern california shear zone ecsz however its geologic slip rate has been difficult to determine using high resolution digital topographic imagery and terrestrial cosmogenic nuclide dating we present the first geochronologically determined slip rate for the ndvfz our study focuses on the red wall canyon alluvial fan which exposes clean dextral offsets of seven channels analysis of airborne laser swath mapping data indicates 297 9 m of right lateral displacement on the fault system since the late pleistocene in situ terrestrial cosmogenic 10 be and 36 cl geochronology was used to date the red wall canyon fan and a second correlative fan also cut by the fault beryllium 10 dates from large cobbles and boulders provide a maximum age of 70 22 20 ka for the offset landforms the minimum age of the alluvial fan deposits based on 36 cl depth profiles is 63 8 ka combining the offset measurement with the cosmogenic 10 be date yields a geologic fault slip rate of 4 2 1 9 1 1 mm yr 1 whereas the 36 cl data indicate 4 7 0 9 0 6 mm yr 1 of slip summing these slip rates with known rates on the owens valley hunter mountain and stateline faults at similar latitudes suggests a total geologic slip rate across the northern ecsz of 8 5 to 10 mm yr 1 this rate is commensurate with the overall geodetic rate and implies that the apparent discrepancy between geologic and geodetic data observed in the mojave section of the ecsz does not extend north of the garlock fault although the overall geodetic rates are similar the best estimates based on geology predict higher strain rates in the eastern part of the ecsz than to the west whereas the observed geodetic strain is relatively constant

kinematics of present crust and mantle flow in southern california in the southern california region published geologic studies of prehistoric fault offsets yield at least 81 rates of slip covering various periods of time chiefly since the opening of the gulf of california these rates together with the known geometries of active faults are used to constrain a hand fit block model for present horizontal velocity of the crust the assumptions employed are that these rates apply to the present that the blocks are internally rigid down to the greatest depth of earthquakes and that the over all pacific north american plate motion is correctly given by global models the resulting model fits 67 data within their uncertainties 10 more with a small discrepancy 1 mm yr and fails to accommodate only 4 data 2 of which are inconsistent with other data nominal precision is good 3 mm yr but accuracy and uniqueness are both suspect because many block boundaries are questionable despite its many local defects this model suggests four reliable regional conclusions first the rate of shortening on the south side of the transverse ranges varies from 6 to 14 mm yr increasing eastward which implies an unrecognized seismic hazard unless the motion is taken up by folding or fault creep second the pattern of block rotation rates is quite different from the pattern of rotations shown by tertiary paleomagnetic declinations which implies some major pliocene reorganization of blocks third the great bend left step of the plate boundary fault system in the transverse ranges appears to be straightening gradually by a 3 m y clockwise rotation relative to both plates finally if it is assumed that plate shortening has been occurring at this bend since the early pliocene and that crust and upper mantle velocities are similar then this model predicts mantle lithosphere downwelling to at least 250 km depth beneath the transverse ranges this prediction is consistent with upper mantle seismic velocity structure

neotectonics and quaternary geology of the hunter mountain fault zone and saline valley region southeastern california abstract the hunter mountain fault zone strikes northwesterly is right lateral strike slip and kinematically links the northern panamint valley fault zone to the southern saline valley fault zone the most recent displacement of the fault is recorded in the offset of holocene deposits along the entire length of the fault zone right lateral offsets of drainage channels within grapevine canyon reach up to 50 to 60 m initial incision of the offset channels is interpreted on the basis of geomorphic and climatic considerations to have occurred approximately 15 ka the 50 to 60 m of offset during 15 ka corresponds to a right lateral fault slip rate of 3 3 4 0 mm year within grapevine canyon further to the north along the nelson range front the fault is composed of two sub parallel fault strands and the fault begins to show an increased normal component of motion a channel margin that is incised into a holocene surface that is between 10 and 128 ka in age is offset 16 20 m which yields a broad minimum bound on the lateral slip rate of 0 125 2 0 mm year the best preserved single event displacements recorded in holocene deposits range from 1 5 to 2 5 m in addition to faulting within grapevine canyon and the main rangefront fault along the southwest edge of saline valley there also exist normal fault strands within the valley that strike northeasterly and towards eureka valley the northeasterly striking normal faults in the valley appear to be actively transferring dextral slip from the hunter mountain fault zone north and east onto the furnace creek fault zone separations on northerly trending normal faults within saline valley yield estimates of slip rates in the hundredths of millimeters per year

gypsum a joint tomographic model of mantle density and seismic wave speeds 1 gypsum is a 3 d model of mantle shear wave s speeds compressional wave p speeds and density the model is developed through simultaneous inversion of seismic body wave travel times p and s and geodynamic observations while using realistic mineral physics parameters linking wave speeds and density geodynamic observations include the global free air gravity field divergence of the tectonic plates dynamic topography of the free surface and the flow induced excess ellipticity of the core mantle boundary gypsum is built with the philosophy that heterogeneity that most closely resembles thermal variations is the simplest possible solution models of the density field from earth s free oscillations have provided great insight into the density configuration of the mantle but are limited to very long wavelength solutions alternatively scaling higher resolution seismic images to obtain density anomalies generates density fields that do not satisfy geodynamic observations the current study provides a 3 d density model for the mantle that directly satisfies geodynamic and seismic observations through a joint seismic geodynamic inversion process notable density field observations include high density piles at the base of superplume structures supporting the general results of past normal mode studies however we find that these features are more localized and have lower amplitude than past studies would suggest when we consider both fast and slow seismic anomalies in gypsum we find that p and s wave speeds are strongly correlated throughout the mantle however we find a low correlation of fast s wave zones in the deep mantle 1500 km depth with the corresponding p wave anomalies suggesting a systematic divergence from simplified thermal effects in ancient subducted slab anomalies the cratonic lithosphere and d regions are shown to have strong compositional signatures however we argue that temperature variations are the primary cause of p wave speed s wave speed and density anomalies throughout most of the mantle

simultaneous inversion for 3 d variations in shear and bulk velocity in the mantle until recently most of the seismic tomographic modeling has been addressing the question of lateral heterogeneity either in p or s wave velocities the s wave velocity variations are larger and hence provide stronger signal on long period waveforms the direct p travel times being the first arrivals on the other hand are most frequently reported in the international seismological centre isc bulletins in mineral physics experiments the variation in bulk velocity is more often measured to better understand the differences between vp and vp patterns and better link the results from mineral physics to those of seismic tomography we formulate the inverse problem in terms of relative perturbations in the shear velocity vs 12 and bulk sound velocity v k 12 we use a large data set which consists of waveforms waveform derived travel times and travel times from the isc bulletins the earthquakes are relocated using corrections for lateral heterogeneity the events which cannot be reliably determined are discarded the model is defined as spherical harmonics to degree 12 horizontally and as chebyshev polynomials to order 13 radially for both shear and bulk sound velocity the inversion is performed under smoothness constraint the resolution tests and bootstrapping analysis indicate that the model is well recovered particularly at long wavelength the results indicate a much larger variability of shear than bulk sound velocity the model explains observations well the most intriguing result obtained in this study is that the variations in shear velocity and bulk sound velocity are negatively correlated in the lowermost mantle the explanation is not very clear from the mineral physics point of view it is not unlikely that this could be explained in terms of thermal variation even though we are unwilling to rule out the possibility of large wavelength compositional variations

electronic spin transitions in iron bearing mgsio3 perovskite the electronic spin state of iron in perovskites with the chemical composition mg0 9375fe0 0625sio3 mg0 8750fe0 1250sio3 and mg0 9375fe0 0625si0 9375fe0 0625o3 have been determined at 0 k and various pressures between 40 160 gpa using ab initio methods the results indicate that ferric iron exhibits a wide range of spin transition pressures between about 60 160 gpa while ferrous iron has a much narrower span between about 130 145 gpa in general the lowest spin transition pressures are associated with the most energetically favorable substitution configurations where iron atoms are closest together the effect of spin state on calculated elastic properties is found to be small c 2006 elsevier b v all rights reserved

climate driven unsteady denudation and sediment flux in a high relief unglaciated catchment fan using 26al and 10be panamint valley california abstract environmental changes within erosional catchments of sediment routing systems are predicted to modulate sediment transfer dynamics however empirical and numerical models that predict such phenomena are difficult to test in natural systems over multi millennial timescales tectonic boundary conditions and climate history in the panamint range california are relatively well constrained by existing low temperature thermochronology and regional multi proxy paleoclimate studies respectively catchment fan systems present there minimize sediment storage and recycling offering an excellent natural laboratory to test models of climate sedimentary dynamics we used stratigraphic characterization and cosmogenic radionuclides crns 26al and 10be in the pleasant canyon complex pcc a linked catchment fan system to examine the effects of pleistocene high magnitude high frequency climate change on crn derived denudation rates and sediment flux in a high relief unglaciated catchment fan system calculated 26al 10be burial ages from 13 samples collected in an 180 m thick outcropping stratigraphic succession range from ca 1 55 0 22 ma in basal strata to ca 0 36 0 18 0 52 0 20 ma within the uppermost part of the succession the mean long term crn derived paleodenudation rate 36 8 mm kyr 1 is higher than the modern rate of 24 0 6 mm kyr from pleasant canyon and paleodenudation rates during the middle pleistocene display some high frequency variability in the high end up to 54 10 mm kyr the highest crn derived denudation rates are associated with stratigraphic evidence for increased precipitation during glacial pluvial events after the middle pleistocene transition post ca 0 75 ma suggesting 100 kyr milankovitch periodicity could drive the observed variability we investigated the potential for non equilibrium sedimentary processes i e increased landslides or sediment storage recycling to influence apparent paleodenudation rates end member mixing models suggest that a mixture of 50 low crn concentration sediment from landslides is required to produce the largest observed increase in paleodenudation rate the overall pattern of crn derived burial ages paleodenudation rates and stratigraphic facies suggests milankovitch timescale climate transitions drive variability in catchment denudation rates and sediment flux or alternatively that climate transitions affect sedimentary process regimes that result in measurable variability of crn concentrations in unglaciated catchment fan systems

tectonics of pliocene removal of lithosphere of the sierra nevada california pliocene ca 3 5 ma removal of dense eclogitic material under the sierra nevada has been proposed from variations in the petrology and geochemistry of neogene volcanic rocks and their entrained xenoliths from the southern sierra the replacement of eclogite by buoyant warm asthenosphere is consistent with present day seismologic and magnetotelluric observations made in the southern sierra a necessary consequence of replacing eclogite with peridotite is that mean surface elevations and gravitational potential energy both increase an increase in potential energy should increase extensional strain rates in the area if these forces are insuffi cient to signifi cantly alter pacifi c north american plate motion then increased extensional strain rates in the vicinity of the sierra must be accompanied by changes in the rate and style of deformation elsewhere changes in deformation in california and westernmost nevada agree well with these predictions existing geologic evidence indicates that a period of rapid uplift along the sierran crest of more than 1 km occurred between 8 and 3 ma most likely as a consequence of removal of lower lithosphere about this same time extensional deformation was initiated within 50 km of the eastern side of the sierra 5 3 ma and regional shortening began to produce the california coast ranges 5 3 ma we suggest that these events were induced by the 1 2 10 12 n m increase of gravitational potential energy generated by the sierran uplift evidence for pliocene uplift adjoining crustal extension and shortening in directly opposing parts of the coast ranges is found along nearly the entire length of the sierra nevada and implies that lithosphere was removed beneath all of the presentday mountain range the uplifted area lies between two large upper mantle high pwave velocity bodies under the south end of the san joaquin valley and the north end of the sacramento valley these high velocity bodies plausibly represent the present position of material removed from the base of the crust lithospheric removal may also be responsible for shifting of the distribution of transform slip from the san andreas fault system to the eastern california shear zone a prediction that awaits better defi ned slip histories on both faults overall the late cenozoic deformational history of the sierra nevada and vicinity illustrates that locally derived forces can infl uence deformation kinematics within plate boundary zones

on the likelihood of post perovskite near the core mantle boundary a statistical interpretation of seismic observations abstract recent experimental studies indicate that perovskite the dominant lower mantle mineral undergoes a phase change to post perovskite at high pressures however it has been unclear whether this transition occurs within the earth s mantle due to uncertainties in both the thermochemical state of the lowermost mantle and the pressure temperature conditions of the phase boundary in this study we compare the relative fit to global seismic data of mantle models which do and do not contain post perovskite following a statistical approach our data comprise more than 10 000 pdiff and sdiff travel times global in coverage from which we extract the global distributions of dln vs and dln vp near the core mantle boundary cmb these distributions are sensitive to the underlying lateral variations in mineralogy and temperature even after seismic uncertainties are taken into account and are ideally suited for investigating the likelihood of the presence of post perovskite a post perovskite bearing cmb region provides a significantly closer fit to the seismic data than a post perovskite free cmb region on both a global and regional scale these results complement previous local seismic reflection studies which have shown a consistency between seismic observations and the physical properties of post perovskite inside the deep earth

postperovskite phase transition and its geophysical implications 1 the stability of mg fe sio3 perovskite in the deep lower mantle has long been uncertain recently a phase transition from perovskite to postperovskite was discovered through a significant change in the x ray diffraction pattern at high pressure and high temperature conditions corresponding to the core mantle boundary region this phase transition was also confirmed by first principles calculations these suggest that mg fe sio3 postperovskite is the predominant mineral in the lowermost mantle called the d layer and phase transition from perovskite to postperovskite has significant geophysical implications for its nature and dynamics the postperovskite phase may account for the large seismic anomalies observed in the d region such as the d discontinuity s wave anisotropy and anticorrelation between the anomalies in s wave and bulk sound velocities in addition this phase transition is a strongly exothermic reaction it destabilizes the thermal boundary layer at the base of the mantle and should promote the formation of high temperature upwelling plumes

wind tunnel simulation of the three dimensional airflow patterns around shrubs 1 dunes formed around vegetation such as shrubs are common in arid and semiarid regions and some coastal regions understanding their dynamics requires insights into the airflow patterns around shrubs thus we analyzed the horizontal and vertical flow patterns around model shrubs using wind measurements obtained by particle image velocimetry in a scaled wind tunnel simulation flow patterns around shrubs were complicated by the presence of bleed flows and displaced flows below a critical shrub density between 0 05 and 0 08 bleed flow is dominant the flows separate in both horizontal and vertical planes when the shrub density equals or exceeds this critical density resulting in reverse cells in the lee of shrubs the horizontal reverse cells are characterized by two symmetrical opposing reverse eddies whereas the vertical reverse cells form a single eddy the positions of the reverse cells shift in response to changes in shrub density reflecting the interaction between bleed flow and reverse flow the parameters of horizontal reverse cells are functions of shrub density and wind velocity parameters of vertical reverse cells change mainly with respect to shrub density and vary only slightly with wind velocity the lengths of the horizontal and vertical reverse cells are correlated reflecting interactions between them field experiments on dune morphology will be required to relate these airflow patterns to dune development

interferometric synthetic aperture radar gps integration interseismic strain accumulation across the hunter mountain fault in the eastern california shear zone 1 the principal limitations of interferometric synthetic aperture radar insar to measure subtle long wavelength deformation are uncertainties associated with the satellite orbits we propose a method to remove orbital phase errors from the insar data by integrating insar and continuous gps time series we model the along track variation of the baseline errors as second order polynomials and estimate the coefficients using the continuous gps measurements we apply this method to a 600 km long region encompassing the basin and range and the eastern california shear zone comparison of the corrected insar velocities with independent gps data shows that this method removes the long wavelength insar errors the insar data reveal a region of sharp variation in the line of sight velocity across the hunter mountain fault we model the deformation as interseismic elastic strain accumulation across a strike slip fault the modeling suggests a fault slip rate of 4 9 0 8 mm yr and a locking depth of 2 0 4 km the shallow locking depth suggests that the hunter mountain fault is a transfer fault between low angle normal faults in the area

kinematics of the eastern california shear zone evidence for slip transfer from owens and saline valley fault zones to fish lake valley fault zone late quaternary slip rates and satellite based geodetic data for the western great basin constrain regional fault slip distribution and evolution the geologic slip rate on the fish lake valley fault zone the northwest extension of the furnace creek fault zone increases northward from about 3 to 5 mm yr in agreement with modeled geodetic data the increase coincides with the intersections of the deep springs fault connected to the owens valley fault zone and of other faults connected to the saline valley fault the combined geologic and geodetic data suggest that 1 the northwest striking faults of the eastern california shear zone north of the garlock fault are connected by north to northeast striking normal faults that transfer slip in a series of right steps and 2 the amount and distribution of slip among the many faults of this broad complex plate boundary have changed through time

can we resolve 3d density heterogeneity in the lower mantle we reexamine the possibility of resolving 3d density structure in the mantle by performing test inversions using a dataset of well constrained degree 2 splitting coefficients we show that degree 2 in vs and vp can be resolved and confirm that dlnvs dlnvp 2 5 at depths 2000km indicating a chemical component to large scale heterogeneity models with positively correlated with vs in the deepest mantle fit the data at least as well as those in which density and velocities are anti correlated however some rough bounds on dln dlnvs can be inferred models obtained from geodynamic considerations are acceptable in contrast to models with large negative 0 6 dln dlnvs throughout the lower mantle the most robust feature is a marked increase in dln dlnvs at the top of the lower mantle reaching a maximum around 1500 km

surface and aerodynamic roughness in arid and semiarid areas and their relation to radar backscatter coefficient surface roughness is a key parameter for surface atmosphere exchanges of mass andenergy only a few field measurements have been performed in arid or semiarid areaswhere it is an important control of the aeolian erosion threshold an intensive fieldcampaign was performed in southern tunisia to measure the lateral cover lc and theaerodynamic roughness length z0 over 10 sites with different surface roughnesses lcwas determined by combining field measurements of the geometry of the roughnesselements and simple assumptions on their shapes z0was experimentally determined fromhigh precision wind velocity and air temperature profiles the resulting data were found tobe in good agreement with the existing relationships linking the geometric and theaerodynamic roughness this suggests that for natural surfaces z0can be estimated onthe basis of the geometric characteristics of the roughness elements this data set wasthen used to investigate the capabilities of radar backscatter coefficients s0 to retrieve lcand or z0 significant relationships were found between s0and both lcand z0 thesar ers data set is in agreement with the sir c slr data set from greeley et al 1997 on the basis of these two data sets including data from different arid and semiarid areas north africa south africa north america we propose an empirical relationship toretrieve z0using radar observations in the c band from operational sensors

tomographic filtering of geodynamic models implications for model interpretation and large scale mantle structure 1 the resolution operator r is a critical accompaniment to tomographic models of the mantle r facilitates the comparison between conceptual three dimensional velocity models and tomographic models because it can filter these theoretical models to the spatial resolution of the tomographic model we compute r for the tomographic model s20rts ritsema et al 1999 2004 and two companion models that are based on the same data but derived with different norm damping values the three models explain within measurement uncertainty s sks and s skks travel times equally well to demonstrate how artifacts distort tomographic images and complicate model interpretation we apply r to 1 a thermochemical and 2 an isochemical model of convection in the mantle that feature different patterns of shear velocity heterogeneity in the deep mantle if we assume that shear velocity heterogeneity is caused by temperature variations only r suppresses short wavelength structures removes strong velocity gradients and introduces artificial stretching and tilting of velocity anomalies temperature anomalies in the thermochemical model resemble the spatial extent of low seismic velocity anomalies and the shear velocity spectrum in the d region better than the isochemical model however the thermochemical model overpredicts the amplitude of shear velocity variation and places the african and pacific anomalies imperfectly we suspect that inaccurate velocity scaling laws and uncertain initial conditions control these mismatches extensive hypothesis testing is required to identify successful models

active faulting in the walker lane 1 deformation across the san andreas and walker lane fault systems accounts for most relative pacific north american transform plate motion the walker lane is composed of discontinuous sets of right slip faults that are located to the east and strike approximately parallel to the san andreas fault system mapping of active faults in the central walker lane shows that right lateral shear is locally accommodated by rotation of crustal blocks bounded by steep dipping east striking left slip faults the left slip and clockwise rotation of crustal blocks bounded by the east striking faults has produced major basins in the area including rattlesnake and garfield flats teels columbus and rhodes salt marshes and queen valley the benton springs and petrified springs faults are the major northwest striking structures currently accommodating transform motion in the central walker lane right lateral offsets of late pleistocene surfaces along the two faults point to slip rates of at least 1 mm yr the northern limit of northwest trending strike slip faults in the central walker lane is abrupt and reflects transfer of strike slip to dip slip deformation in the western basin and range and transformation of right slip into rotation of crustal blocks to the north the transfer of strike slip in the central walker lane to dip slip in the western basin and range correlates to a northward broadening of the modern strain field suggested by geodesy and appears to be a long lived feature of the deformation field the complexity of faulting and apparent rotation of crustal blocks within the walker lane is consistent with the concept of a partially detached and elastic brittle crust that is being transported on a continuously deforming layer below the regional pattern of faulting within the walker lane is more complex than observed along the san andreas fault system to the west the difference is attributed to the relatively less cumulative slip that has occurred across the walker lane and that oblique components of displacement are of opposite sense along the walker lane extension and san andreas contraction respectively despite the gross differences in fault pattern the walker lane and san andreas also share similarities in deformation style including clockwise rotations of crustal blocks leading to development of structural basins and the partitioning of oblique components of slip onto subparallel strike slip and dip slip faults

efficacy of the post perovskite phase as an explanation for lowermost mantle seismic properties constraining the chemical rheological and electromagnetic properties of the lowermost mantle d is important to understand the formation and dynamics of the earth s mantle and core to explain the origin of the variety of characteristics of this layer observed with seismology a number of theories have been proposed including core mantle interaction the presence of remnants of subducted material and that d is the site of a mineral phase transformation this final possibility has been rejuvenated by recent evidence for a phase change in mgsio3 perovskite thought to be the most prevalent phase in the lower mantle at near core mantle boundary temperature and pressure conditions here we explore the efficacy of this post perovskite phase to explain the seismic properties of the lowermost mantle through coupled ab initio and seismic modelling of perovskite and post perovskite polymorphs of mgsio3 performed at lowermost mantle temperatures and pressures we show that a post perovskite model can explain the topography and location of the d discontinuity apparent differences in compressional and shear wave models and the observation of a deeper weaker discontinuity furthermore our calculations show that the regional variations in lower mantle shear wave anisotropy are consistent with the proposed phase change in mgsio3 perovskite

slip rates and off fault deformation in southern california inferred from gps data and models 1 in southern california fault slip rate estimates along the san andreas fault saf and garlock fault from geodetically constrained kinematic models are systematically at the low end or lower than geologic slip rate estimates the sum of geodetic model slip rates across the eastern california shear zone is higher than the geologic sum however the ranges of reported model and geologic slip rate estimates in the literature are sufficiently large that it remains unclear whether these apparent discrepancies are real or attributable to epistemic uncertainties in the two types of estimates we further examine uncertainties in geodetically derived slip rate estimates on major faults in southern california by conducting a suite of inversions with four kinematic models long term rigid elastic block models constrained by the geologic slip rates cannot fit the present day gps derived velocity field deforming permanent off fault strain elastic block models and viscoelastic earthquake cycle block models constrained by geologic slip rates can fit the present day gps derived velocity field with 28 33 of the total geodetic moment rate occurring as distributed deformation off of the major faults models incorporating viscoelastic mantle flow predict systematically higher slip rates than purely elastic models on many of the major southern california faults with ranges of elastic viscoelastic 29 34 30 37 mm yr for the carrizo saf segment 20 24 20 32 mm yr for the mojave saf segment 14 17 18 22 mm yr for the coachella saf segment 13 19 14 22 mm yr for the san jacinto fault and 5 11 5 11 mm yr for the western garlock fault