irregular recurrence of paleoearthquakes along the central garlock fault near el paso peaks california 1 new investigations at the el paso peaks paleoseismic site have refined and extended the record of paleoearthquakes for the central garlock fault event evidence in the form of buried fissures scarps folds and upward terminations has allowed us to identify six well resolved earthquakes designated as events w u r q k and f within the last 7000 years the exposures that we excavated did not reveal additional evidence for three poorly resolved events reported by mcgill and rockwell 1998 evidence for event y identified in the previous study was reexamined and found not to be a paleoearthquake radiocarbon dates of detrital charcoal combined with a method of interpolating the event ages with revised sedimentation rates provide our preferred constraints on the timing of faulting events the most recent surface rupturing earthquake event w occurred between a d 1450 and 1640 the penultimate event u occurred between a d 675 and 950 event r which was unrecognized in the previous study occurred between a d 250 and 475 event q occurred relatively shortly before event r between a d 25 and 275 event k occurred between 3340 and 2930 b c the oldest identified paleoearthquake event f occurred between 5300 and 4670 b c the event ages indicate that earthquake recurrence is highly irregular at the el paso peaks site with individual preferred intervals ranging from as little as 215 years to as many as 3300 years the irregular recurrence of surface rupturing earthquakes along the central garlock fault may be related to temporal and spatial clustering of earthquakes proposed for faults in the eastern california shear zone

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

impact of riser reconstructions on estimation of secular variation in rates of strike slip faulting revisiting the cherchen river site along the altyn tagh fault nw china abstract slip rates are heavily contested for many of the first order strike slip faults within the indo asian collision zone rates determined geodetically are generally lower than those reported using reconstructions of offset landforms and it is unclear if this discrepancy reflects true secular variation in slip history systematic errors in interpretation or both here i examine the methods used to derive slip rates from reconstructions of displaced fluvial risers and show that such rates are subject to potentially important uncertainties that have largely been overlooked review of published data demonstrates that the slip rate can vary by a factor of 1 2 to 5 for the same site depending on whether the reconstruction uses the age of the upper or lower terrace for the initiation of riser offset to reduce this epistemic uncertainty i have developed six geomorphic indices that can be used to identify the most accurate end member reconstruction 1 comparison of riser offset with inset channel width 2 similarity of riser and tread displacements 3 morphological analysis of the scarp profile 4 riser deflection in plan view 5 diachroneity of terrace abandonment and 6 whether riser crests or bases yield the slip vector without the use of these geomorphic observations the epistemic uncertainty associated with current methods for determining slip rate from offset fluvial risers is likely to be so large that there is no resolvable discrepancy between the gps and geologic rates within the indo asian collision zone application of three of these indices to new field mapping of the cherchen he river site 86 4 e along the central altyn tagh fault yields a revised slip rate of 9 4 2 3 mm yr equivalent within error to the rates previously derived from gps and paleoseismic studies although reinterpretation of published data from the sulamu tagh site 87 4 is consistent with this revised rate additional work is needed to reconcile this result with some of the rates reported near aksay 94 e

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

constancy of geologic slip rate along the central garlock fault implications for strain accumulation and release in southern california summary we present new slip rate estimates for the central garlock fault the incised edge of an alluvial fan deposit with a 10be cosmogenic radionuclide age of 13 3 5 9 1 1 ka is offset 70 7 m yielding a slip rate of 5 3 1 0 2 5 mm yr 1 a stream thalweg that is deeply incised into this surface is offset a lesser amount 58 4 m providing the lower bound for this rate climate considerations however suggest that the deep incision of this thalweg may have occurred at a younger date specifically at the end of the younger dryas period at 11 5 ka or at the onset of a summer monsoon rainfall pattern at 8 10 ka if the deep incision was related to one of these climate events then the resulting slip rate would be 5 1 0 3 and 6 6 1 2 mm yr 1 respectively all of the slip rates are consistent with previous geologic slip rates most of which suggest a latest pleistocene holocene slip rate of 5 7 mm yr 1 these geologic slip rates however contrast markedly with much slower at most half as fast short term rates of elastic strain accumulation constrained by geodesy the new slip rate thus adds to a growing body of evidence indicating that the garlock fault is experiencing a period of transient lack of strain accumulation in which the lower crust and mantle beneath the fault is deforming at a rate that is much slower than its long term average rate these observations suggest that the garlock fault experiences two modes of strain accumulation the current slow mode in which strain accumulates very slowly along the fault and fast mode during which the fault must store and release elastic strain energy at much faster rates than the long term average to account for the relatively rapid geologic slip rates measured along the central part of the fault

transtensional model for the sierra nevada frontal fault system eastern california active strike slip and normal faults along the eastern margin of the sierra nevada primarily accommodate northwestward translation of the sierra nevada central valley i e sierran microplate with respect to stable north america strike slip faults bordering the eastern sierran microplate are subparallel to small circles about the sierra nevada north american euler pole normal faults of the sierra nevada frontal fault system strike 45 clockwise of the small circle trajectories and exhibit well defined left stepping en echelon patterns consistent with formation in dextral transcurrent regime major graben bordering the northeastern sierran microplate are located in regions where the locus of range front deformation steps abruptly eastward in a releasing geometry relative to sierra nevada north american motion crustal shortening occurs at the northern end of the sierran microplate where a component of northwest dextral shear steps westward in a left restraining geometry across the sierran crest to the sacramento valley kinematic inversions of earthquake focal mechanisms from the walker lane belt bordering the eastern sierra nevada indicate that seismogenic deformation primarily is characterized by horizontal shearing and oblique crustal thinning directions of macroscopic dextral shear inferred from the inversions are subparallel to the trajectories of small circles about the sierra nevada north american euler pole normal faulting along most of the eastern sierran range front thus appears to primarily accommodate microplate translation rather than sierran uplift or regional basin and range extension

deformation processes adjacent to active faults examples from eastern california 1 major seismogenic faults are embedded within narrow zones of inelastic off fault deformation ofd where both distributed displacement and modification of rock properties occur active distributed displacement may affect slip rate estimates seismic energy radiation and geodynamic models this study addresses the role of ofd in the displacement history and mechanical behavior of seismogenic faults by multisite study of deformed geologic features adjacent to 30 60 km long active strike slip faults of 10 km of dextral displacement in the mojave desert eastern california we find that distributed displacement accommodates 0 to 25 of the total displacement over zones of one to two kilometers width displacement occurs mostly within 100 200 m of faults and decreases nonlinearly away from the main fault we show evidence for distributed displacement through simple shear in the form of parallel secondary faults and progressive deformation of linear markers adjacent to the calico fault we also find evidence for shear via rotation and progressive fragmentation adjacent to the harper lake fault analysis of block dimensions show that blocks tend to decrease in size toward faults and that cumulative length of secondary faults is longer than the main fault by at least a factor of 10 based on crosscutting relationships and the relationship of ofd to geophysically imaged compliant zones around active faults we argue that distributed displacement is an active process and suggest that zones of diminished rigidity near faults may be at least in part driven by secondary faulting during the rupture propagation along the main fault

statistical analysis of the frequency of eruptions at furnas volcano sao miguel azores abstract furnas volcano is one of three major volcanic centres on the island of sao miguel acores both furnas and fogo have displayed violent explosive activity since the island was first occupied in the early 15th century ad there is concern that future volcanic activity will not only cause major economic losses but will also result in widespread mortality and it is for these reasons that a major programme of hazard assessment has been undertaken on furnas the present study is part of this programme and involves both the general statistical modelling of the record of historic eruptions and more specifically develops a technique for determining the rate of volcanic eruptions an important parameter in the poisson probability model

late quaternary slip rates across the central tien shan kyrgyzstan central asia 1 slip rates across active faults and folds show that late quaternary faulting is distributed across the central tien shan not concentrated at its margins nearly every intermontane basin contains neogene and quaternary syntectonic strata deformed by holocene north south shortening on thrust or reverse faults in a region that spans two thirds of the north south width of the central tien shan slip rates on eight faults in five basins range from 0 1 to 3 mm yr fault slip rates are derived from faulted and folded river terraces and from trenches radiocarbon optically stimulated luminescence and thermoluminescence ages limit ages of terraces and aid in their regional correlation monte carlo simulations that sample from normally distributed and discrete probability distributions for each variable in the slip rate calculations generate most likely slip rate values and 95 confidence limits faults in basins appear to merge at relatively shallow depths with crustal scale ramps that underlie mountain ranges composed of pre cenozoic rocks the sum and overall pattern of late quaternary rates of shortening are similar to current rates of north south shortening measured using global positioning system geodesy this similarity suggests that deformation is concentrated along major fault zones near range basin margins such faults separated by rigid blocks accommodate most of the shortening in the upper crust index terms 8107 tectonophysics continental neotectonics 9320 information related to geographic region asia 8010 structural geology fractures and faults

slip rate of the calico fault implications for geologic versus geodetic rate discrepancy in the eastern california shear zone 1 long term 10 5 years fault slip rates test the scale of discrepancy between infrequent paleoseismicity and relatively rapid geodetic rates of dextral shear in the eastern california shear zone ecsz the calico fault is one of a family of dextral faults that traverse the mojave desert portion of the ecsz its slip rate is determined from matching and dating incised pleistocene alluvial fan deposits and surfaces displaced by fault slip a high resolution topographic base acquired via airborne laser swath mapping aids in identification and mapping of deformed geomorphic features the oldest geomorphically preserved alluvial fan unit b is displaced 900 200 m from its source at sheep springs wash in the northern rodman mountains this fan deposit contains the first preserved occurrence of basalt clasts derived from the pipkin lava field and overlies quaternary conglomerate deposits lacking these clasts the 40 ar 39 ar dating of two flows from this field yields consistent ages of 770 40 ka and 735 9 ka an age of 650 100 ka is assigned to this fan deposit based on these ages and on the oldest cosmogenic 3 he exposure date of 653 20 ka on a basalt boulder from the surface of unit b this assigned age and offset together yield a mid pleistocene to present average slip rate of 1 4 0 4 mm yr ayounger fan surface unit k records 100 10 m of dextral displacement and preserves original depositional morphology of its surface granitic boulders and pavement samples from this surface yield an average age of 56 4 7 7 ka after taking into account minimal cosmogenic inheritance of granitic clasts the displaced and dated k fans yield a slip rate of 1 8 0 3 mm yr distributed deformation of the region surrounding the fault trace if active could increase the overall displacement rate to 2 1 0 5 mm yr acceleration of slip rate from an average of 1 4 mm yr prior to 50 ka to 1 8 mm yr since 50 ka is possible though a single time averaged slip rate of 1 6 0 2 mm yr satisfies the data these rates are faster than any other paleoseismic or long term slip rate yet determined for other dextral faults in the mojave desert and imply that fault slip rates and earthquake productivity are heterogeneous across this portion of the ecsz total displacement across the calico fault diminishes northward as shear is distributed into folding and sinistral faults in the calico mountains this pattern is consistent with an approximately threefold drop in geologic slip rate as the calico fault steps over onto the blackwater fault and demonstrates the significance of fault interaction for understanding the pattern of present day strain accumulation in the ecsz

uncertainties in slip rate estimates for the mission creek strand of the southern san andreas fault at biskra palms oasis southern california this study focuses on uncertainties in estimates of the geologic slip rate along the mission creek strand of the southern san andreas fault where it offsets an alluvial fan t2 at biskra palms oasis in southern california we provide new estimates of the amount of fault offset of the t2 fan based on trench excavations and new cosmogenic 10be age determinations from the tops of 12 boulders on the fan surface we present three alternative fan offset models a minimum a maximum and a preferred offset of 660 m 980 m and 770 m respectively we assign an age of between 45 and 54 ka to the t2 fan from the 10be data which is significantly older than previously reported but is consistent with both the degree of soil development associated with this surface and with ages from u series geochronology on pedogenic carbonate from t2 described in a companion paper by fletcher et al this volume these new constraints suggest a range of slip rates between 12 and 22 mm yr with a preferred estimate of 14 17 mm yr for the mission creek strand of the southern san andreas fault previous studies suggested that the geologic and geodetic slip rate estimates at biskra palms differed we find however that considerable uncertainty affects both the geologic and geodetic slip rate estimates such that if a real discrepancy between these rates exists for the southern san andreas fault at biskra palms it cannot be demonstrated with available data

holocene slip rates along the owens valley fault california implications for the recent evolution of the eastern california shear zone one of the largest historical earthquakes in california occurred in 1872 along the owens valley fault located along the western margin of the eastern california shear zone new paleoseismic and optically stimulated luminescence data are the first to bracket the timing of the pre 1872 rupture to between 3 3 0 3 and 3 8 0 3 ka these data yield an earthquake recurrence interval between 4100 and 3000 yr under the assumption of uniform return and indicate a holocene slip rate between 1 8 0 3 and 3 6 0 2 mm yr our data are broadly consistent with a model proposed for the space time evolution of the eastern california shear zone our holocene slip rate estimates for the owens valley fault are slower than present day slip rates determined from elastic half space models of geodetic data this discrepancy is reduced by using the recurrence interval estimated here and a viscoelastic model of geodetic data or by including geologic slip rates from adjacent faults

comparison of geodetic and geologic data from the wasatch region utah and implications for the spectral character of earth deformation at periods of 10 to 10 million years the wasatch fault and adjacent fault zones provide an opportunity to compare present day deformation rate estimates obtained from space geodesy with geologic displacement rates over at least four temporal windows ranging from the last millennium up to 10 myr the three easternmost gps sites of the basin and range geodetic network bargen at this latitude define a 130 km wide region spanning three major normal faults extending east west at a total rate of 2 7 0 4 mm yr with an average regional strain rate estimated to be 21 4 nstrain yr about twice the basin and range average on the wasatch fault the vertical component of the geologic displacement rate is 1 7 0 5 mm yr since 6 ka 0 6 mm yr since 130 ka and 0 5 0 7 mm yr since 10 ma however it appears likely that at the longest timescale rates slowed over time from 1 0 to 1 4 mm yr between 10 and 6 ma to 0 2 to 0 3 mm yr since 6 ma the cumulative vertical displacement record across all three faults also shows time variable strain release ranging from 2 to 4 mm yr since 10 ka to 1 mm yr averaged over the past 130 kyr conventional earthquake recurrence models reid type behavior would require an accordingly large variation in strain accumulation or loading rate on a 10 kyr timescale for which there appears to be no obvious geophysical explanation alternatively seismic strain release given a wide range of plausible constitutive behaviors for frictional sliding may be clustered on the 10 kyr timescale resulting in the high holocene rates with comparatively low uniform strain accumulation rates on the 100 kyr timescale wallace type behavior the latter alternative combined with observations at the million year timescale and the likelihood of a significant contribution of postseismic transients implies maxima of spectral amplitude in the velocity field at periods of 10 myr variations in tectonic loading 10 kyr clustered strain release and of 100 years postseismic transients if so measurements of strain accumulation and strain release may be strongly timescale dependent for any given fault system

paleoseismology and global positioning system earthquake cycle effects and geodetic versus geologic fault slip rates in the eastern california shear zone published slip rates for the owens valley fault zone in eastern california based on geodetic data and elastic half space models 5 7 mm yr are faster than longer term geologic rates 2 3 mm yr we use global positioning system data spanning the central owens valley a more realistic rheological model with an elastic upper crust over a viscoelastic lower crust and upper mantle and paleoseismic data from adjacent faults to show that this difference could reflect earthquake cycle effects we estimate a long term rate 2 1 0 7 mm yr and earthquake recurrence interval 2750 350 1000 yr from the geodetic data both in agreement with independent geologic estimates

kinematics of the southern walker lane belt and motion of the sierra nevada block california deformation in the southern walker lane belt region of the southwestern great basin accommodates significant portions of both pacific north america transform motion and basin and range extension apparent kinematic inconsistencies between geodetic and fault slip data in this region have made it difficult to understand the nature of the interaction between these deformation processes and to infer the regional kinematics we model the kinematics of this region in a manner that enforces kinematic consistency and includes fault geometry and slip rate data global positioning system gps survey data and very long baseline interferometry very long baseline array vlbi vlba site velocity data a model is found that is consistent with the set of available data and this model differs significantly from prior models for the region our model has the sierra nevada block which bounds the western margin of the great basin moving n50 w 5 at 12 7 1 5 mm yr with only minor amounts of counterclockwise rotation left lateral slip on the western garlock fault is a consequence of the relatively great westerly component of sierra nevada velocity we also find that the basin and range extension east of our study area occurs at a rate of about 2 5 mm yr which is slower than the rate in the central great basin

transient strain accumulation and fault interaction in the eastern california shear zone satellite synthetic aperture radar interferometry reveals transient strain accumulation along the blackwater little lake fault system within the eastern california shear zone the surface strain map obtained by averaging eight years 1992 2000 of earth resource satellite ers radar data shows a 120 km long 20 kmwide zone of concentrated shear between the southern end of the 1872 owens valley earthquake surface break and the northern end of the 1992 landers earthquake surface break the observed shear zone is continuous through the garlock fault which does not show any evidence of left lateral slip during the same time period a dislocation model of the observed shear indicates right lateral slip at 7 6 3 mm yr on a vertical fault below 5 km depth a rate that is two to three times greater than the geologic rates estimated on northwest trending faults in the eastern mojave area this transient slip rate and the absence of resolvable slip on the garlock fault may be the manifestation of an oscillatory strain pattern between interacting conjugate fault systems

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

large magnitude transient strain accumulation on the blackwater fault eastern california shear zone we investigate the quaternary slip rate for the blackwater fault eastern california shear zone through mapping and geochronology of offset volcanic rocks basalt flows of the black mountains support the presence of faulting at 3 77 0 11 ma 1 8 0 1 km of subsequent slip and a well constrained long term slip rate of 0 49 0 04 mm yr total slip diminishes northward evidenced by a 0 3 1 8 km offset of a 7 23 1 07 ma dacite flow in the black hills and fault termination in the lava mountains 5 km short of the garlock fault slow long term slip rate together with sparse evidence for holocene rupture contradict predictions of rapid slip rate from tectonic geodesy these results support the conclusion that as much as 95 of geodetic strain accumulation across the blackwater fault and thus from 1 to 6 mm yr of geodetic strain measured across the eastern california shear zone is a transitory phenomenon discrepant geologic and geodetic results may indicate an increased near term seismic hazard but merit caution for interpretation of fault slip rates from geodesy alone

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

present day kinematics of the eastern california shear zone from a geodetically constrained block model we use global positioning system gps data from 1993 2000 to determine horizontal velocities of 65 stations in eastern california and western nevada between 35 and 37 n we relate the geodetic velocities to fault slip rates using a block model that enforces path integral constraints over geologic and geodetic time scales and that includes the effects of elastic strain accumulation on faults locked to a depth of 15 km the velocity of the sierra nevada block with respect to nevada is 11 1 0 3 mm yr with slip partitioned across the death valley 2 8 0 5 mm yr panamint valley 2 5 0 8 mm yr and airport lake owens valley 5 3 0 7 4 6 0 5 mm yr faults the western mojave block rotates at 2 1 0 8 my clockwise with 3 7 0 7 mm yr of left lateral motion across the western garlock fault we infer 11 2 mm yr of right lateral motion across the mojave region of the eastern california shear zone

integration of chang e 1 imagery and laser altimeter data for precision lunar topographic modeling lunar orbital imagery and laser altimeter data are two major data sources for lunar topographic modeling most of the previous work has processed imagery and laser altimeter data separately usually though there are inconsistencies between the topographic models derived from them this paper presents an endeavor to integrate the chang e 1 imagery and laser altimeter data for consistent and precision lunar topographic modeling a combined adjustment model for the chang e 1 imagery and laser altimeter data is developed in which the participants are the laser altimeter points image exterior orientation eo parameters and tie points collected from the stereo images a weighting scheme is designed for the participants in the adjustment and a local surface constraint is imposed to improve the adjustment performance the output of the combined adjustment is the refined image eo parameters and laser ground points experimental results using the chang e 1 data in the apollo 15 and 16 landing site areas show that the proposed combined adjustment approach can reduce the misregistrations between the imagery and the laser altimeter data by a maximum of 1 18 pixels in image space the japanese selenological and engineering explorer selene laser altimeter data at the apollo 15 and 16 landing site areas are employed for comparison analysis small shifts between the selene and chang e 1 laser altimeter data were found the topography derived from chang e 1 data after the combined adjustment shows a relatively consistent trend with the topography determined by the selene laser altimeter data

dating geomorphologic surfaces using cosmogenic 3he cosmogenically produced 3he in rocks can be used to date geomorphologic surfaces using the late pleistocene bonneville flood event the subsequent development of the provo shoreline and associated volcanic rocks a production rate of 432 atoms g yr in olivine is determined for 38 56 n latitude present geomagnetic latitude 46 5 at 1445 m altitude integrated over the last 14 400 years measurements of cosmogenic helium in flood deposits on river scoured surfaces and lava flows show that it is possible to date directly large scale events such as volcanic eruptions and catastrophic floods olivine and pyroxene are both satisfactory minerals for cosmogenic dating by the 3he method however in most cases plagioclase and quartz are unsuitable because they do not quantitatively retain helium isotopes in their lattices

current sierra nevada north america motion from very long baseline interferometry implications for the kinematics of the western united states we use geodetic measurements from very long baseline interferometry to estimate the motion of the sierra nevadan microplate which is composed of the sierra nevada and the great valley the motion of the sierra nevadan microplate relative to the north american plate is described by a right handed rotation of 0 61 m y about lat 32 n long 128 w this euler pole lies only 10 southwest of the sierra nevadan microplate and predicts a significant counterclockwise rotation about a local vertical axis it further predicts a velocity of the eastern edge of the sierra nevada at 38 0 n 119 3 w relative to stable north america of 11 1 mm yr toward n36 3 w quoted uncertainties are plus or minus one standard error which accounts for about one fourth of the velocity between the pacific and north american plates and is 25 clockwise of many prior estimates the velocity nearly parallels the boundary between the sierra nevada and the great basin which implies that current motion within the great basin results in a rotational noncoaxial deformation we use this velocity to estimate how motion is distributed across the broad deforming zone taking up pacific north america plate motion we find that the vector sum of strike slip along the san andreas fault and motion of the sierra nevada relative to stable north america taken up by deformation within the great basin differs little from the pacific north america plate velocity the difference can be described at 36 n along the san andreas fault by a vector of 6 mm yr directed toward n20 w this vector resolves into components of 5 mm yr parallel to the fault and 2 mm yr perpendicular to the fault with 95 confidence intervals of 0 to 10 mm yr and 1 to 5 mm yr respectively the component perpendicular to the fault is several times smaller than found in prior studies and places a small upper bound on fault perpendicular shortening we conclude that motion previously inferred to be taken up by deformation other than strike slip along the san andreas fault or deformation within the great basin is much smaller than previously thought

evolution of the bonneville shoreline scarp in west central utah comparison of scarp analysis methods and implications for the diffusion model of hillslope evolution abstract wave cut pluvial shoreline scarps are ideal natural experiments in hillslope evolution because the ages of these scarps are often precisely known and because they form with a range of heights alluvial textures and microclimates i e orientation previous work using midpoint slope methods on pluvial scarps in the basin and range concluded that scarp evolution is nonlinear and microclimatically controlled the purpose of this study was to further examine the influence of scarp height texture and microclimate in an attempt to calibrate a nonlinear model of scarp evolution to do this over 150 profiles of the bonneville shoreline in the adjacent snake and tule valleys west central utah were collected and analyzed by fitting the entire scarp profile to diffusion equation solutions taking into account uncertainty in the initial scarp angle in contrast to previous studies this analysis revealed no evidence for nonlinearity or microclimatic control to understand the reason for this discrepancy we undertook a systematic study of the accuracy of each scarp analysis method the midpoint slope inverse method was found to yield biased results with systematically higher diffusion ages for young tall scarps the slope offset method is unbiased but has limited resolution because it requires many scarp profiles to yield a single diffusion age a method that incorporates the full scarp profile and uncertainty in the initial scarp angle was found to be the most accurate technique the application of the full scarp method to the bonneville shoreline supports the use of a linear diffusion model for scarps up to 20 m in height scarp orientation had no discernable effect on diffusivity values soil texture was found to have a weak but significant inverse relationship with diffusivity values

last glacial maximum and holocene lake levels of owens lake eastern california usa abstract stratigraphic investigations of fluvio deltaic and lacustrine sediments exposed in stream cuts quarry walls and deep trenches east of the sierra nevada in owens valley near lone pine california have enabled the reconstruction of pluvial owens lake level oscillations age control for these sediments is from 22 radiocarbon 14 c dates and the identification and stratigraphic correlation of a tephra which when plotted as a function of age versus altitude define numerous oscillations in the level of pluvial owens lake during the latest pleistocene and early holocene we have constructed a lake level altitude curve for the time interval 27 000 cal yr bp to present that is based on the integration of this new stratigraphic analysis with published surface stratigraphic data and subsurface core data pluvial owens lake regressed from its latest pleistocene highstands from 27 000 to 15 300 cal yr bp as recorded by 15 m of down cutting of the sill from the altitudes of 1160 to 1145 m by 11 600 cal yr bp the lake had dropped 45 m from the 1145 m sill this lowstand was followed by an early holocene transgression that attained a highstand near 1135 m before dropping to 1120 m at 7860 7650 cal yr bp that had not been recognized in earlier studies the lake then lowered another 30 m to shallow and near desiccation levels between 6850 and 4300 cal yr bp fluvial cut and fill relations north of lone pine and well preserved shoreline features at 1108 m indicate a minor lake level rise after 4300 cal yr bp followed by alkaline and shallow conditions during the latest holocene the new latest quaternary lake level record of pluvial owens lake offers insight to the hydrologic balance along the east side of the southern sierra nevada and will assist regional paleoclimatic models for the western basin and range

slip rates on the fish springs fault owens valley california deduced from cosmogenic 10be and 26al and soil development on fan surfaces long term deformation along the fish springs fault in owens valley california is recorded by offset landforms including a previously dated cinder cone 39 ar 40 ar 314

evidence of power law flow in the mojave desert mantle studies of the earth s response to large earthquakes can be viewed as large rock deformation experiments in which sudden stress changes induce viscous flow in the lower crust and upper mantle that lead to observable postseismic surface deformation laboratory experiments suggest that viscous flow of deforming hot lithospheric rocks is characterized by a power law in which strain rate is proportional to stress raised to a power n refs 2 3 most geodynamic models of flow in the lower crust and upper mantle however resort to newtonian linear stress strain rate relations here we show that a power law model of viscous flow in the mantle with n 3 5 successfully explains the spatial and temporal evolution of transient surface deformation following the 1992 landers and 1999 hector mine earthquakes in southern california a power law rheology implies that viscosity varies spatially with stress causing localization of strain and varies temporally as stress evolves rendering newtonian models untenable our findings are consistent with laboratory derived flow law parameters for hot and wet olivine the most abundant mineral in the upper mantle and support the contention that at least beneath the mojave desert the upper mantle is weaker than the lower crust

elevated shear zone loading rate during an earthquake cluster in eastern california we compare geodetic velocity to geologic fault slip rates to show that tectonic loading was doubled across the eastern california shear zone ecsz during a cluster of major earthquake activity new slip rates are presented for six dextral faults that compose the ecsz in the central mojave desert these rates were determined from displaced alluvial fans dated with cosmogenic 10 be and from a displaced lava flow dated with 40 ar 39 ar we find that the sum geologic mojave ecsz slip rate 6 2 1 9 mm yr is only half the present day geodetically measured velocity of 12 2 mm yr these rates account for cumulative fault slip and geodetic observations that span the 60 km wide shear zone therefore this difference cannot be attributed to postseismic relaxation redistribution of tectonic loading over the earthquake cycle at a regional scale suggests that earthquake clustering may be enhanced via feedback with weakening of ductile shear zones

riser diachroneity lateral erosion and uncertainty in rates of strike slip faulting a case study from tuzidun along the altyn tagh fault nw china 1 at late quaternary timescales offset fluvial terrace risers are among the most common landforms used to determine rates of strike slip faulting although diachroneity in the age of riser segments on opposite sides of the fault has been noted previously an unexplored source of uncertainty associated with deriving slip rates from these markers centers on quantifying the size of the displacement uncertainty such diachroneity introduces to evaluate the impact of riser diachroneity we investigated the tuzidun site 37 73 n 86 72 e along the cherchen he reach of the active central altyn tagh fault the east bank of the channel is flanked by a left laterally offset terrace riser while the measured offset is 54 3 m geochronologic measurements and analysis of riser topography indicate that the downstream riser segment formed between 6 0 0 8 ka and 5 7 0 4 ka while the upstream riser segment may have been laterally refreshed as recently as 0 5 0 2 ka a valley wall on the west bank of the channel places a maximum limit of 38 6 m on the amount of possible lateral erosion of the upstream riser this bound in turn limits the total offset since formation of the downstream riser to range from 54 3 to 89 7 m together these observations bracket the millennial altyn tagh fault slip rate to range from 9 0 1 3 to 15 5 1 7 mm a 1 more generally this investigation shows that the observed riser displacement does not necessarily correlate with the age of either riser segment downstream or upstream of the fault in cases where one segment is displaced while the other is subjected to lateral erosion if this diachroneity goes undetected erroneous slip rate measurements are likely to result

chronology of glaciations in the sierra nevada california from 10be surface exposure dating abstract we use 10 be surface exposure dating to construct a high resolution chronology of glacial fluctuations in the sierra nevada california most previous studies focused on individual glaciated valleys whereas our study compares chronologies developed throughout the range to identify regional patterns in the timing of glacier response to major climate changes sites throughout the range indicate last glacial maximum retreat at 18 8 1 9 ka 2 that suggests rather consistent changes in atmospheric variables e g temperature and precipitation throughout the range the penultimate glacial retreat occurred at ca 145 ka our data suggest that the sierra nevada landscape is dominated by glacial features deposited during marine isotope stage mis 2 and mis 6 deposits of previously recognized glaciations between circa 25 and 140 ka e g mis 4 tenaya early tahoe cannot be unequivocally identified the timing of sierra nevada glacial retreat correlates well with other regional paleoclimate proxies in the sierra nevada but differs significantly from paleoclimate proxies in other regions our dating results indicate that the onset of lgm retreat occurred several thousand years earlier in the sierra nevada than some glacial records in the western us

mobility of continental mantle evidence from postseismic geodetic observations following the 1992 landers earthquake the crust around the rupture zone of the 1992 landers earthquake has continued to deform in the years following the earthquake at rates 3 times greater than pre earthquake rates we use a combination of global positioning system gps and synthetic aperture radar insar data collected during a 3 year epoch following the earthquake in order to investigate postseismic mechanisms responsible for the high transient velocities in order to maximize the potential signal from viscoelastic relaxation we evaluate and model postseismic relaxation following the first few months of documented accelerated deformation the combination of gps and insar data allows us to establish viscoelastic relaxation of the lower crust and upper mantle as the dominant postseismic process and to discriminate among possible viscoelastic models the data particularly require the presence of a highly ductile uppermost mantle beneath the central mojave domain with temperature between the wet and dry basalt solidus this is consistent with independent seismic and geochemical inferences of a regionally warm uppermost mantle further consideration of seismic velocity variations in conjunction with faulting patterns within the mojave desert suggests that the primary faulting characteristics of the mojave desert namely the pervasive late cenozoic deformation within the eastern california shear zone versus the near absence of faults in the western mojave domain are controlled by the rheology of the uppermost mantle

strain accumulation across the eastern california shear zone at latitude 36 30 n the motion of a linear array of monuments extending across the eastern california shear zone ecsz has been measured from 1994 to 1999 with the global positioning system the linear array is oriented n54 e perpendicular to the tangent to the local small circle drawn about the pacific north america pole of rotation and the observed motion across the ecsz is approximated by differential rotation about that pole the observations suggest uniform deformation within the ecsz strike n23 w 26 nstrain yr 1 extension normal to the zone and 39 nstrain yr 1 simple right lateral shear across it with no significant deformation in the two blocks the sierra nevada mountains and southern nevada on either side the deformation may be imposed by right lateral slip at depth on the individual major fault systems within the zone if the slip rates are death valley furnace creek fault 3 2 0 9 mm yr 1 hunter mountain panamint valley fault 3 3 1 6 mm yr 1 and owens valley fault 6 9 1 6 mm yr 1 however this estimate of the slip rate on the owens valley fault is 3 times greater than the geologic estimate

comparison of gully erosion estimates using airborne and ground based lidar on santa cruz island california abstract gully erosion removes comparatively large volumes of soil from small areas it is often difficult to quantify the loss of soil because the footprint of individual gullies is too small to be captured by most generally available digital elevation models dems such as the usgs national elevation dataset airborne lidar light detection and ranging has the potential to provide the required data density but an even newer class of ground based sensors may provide better local resolution at lower cost in this study we compared digital elevation models produced by airborne and ground based lidar systems with ground based geomorphic and geodetic survey data to determine their utility in quantifying volumetric soil loss due to gully erosion in a heavily degraded watershed 7 55 10 2 km 2 on southwestern santa cruz island in southern california volumetric estimates of the eroded sediment were produced by comparing the lidar derived dems of the gully system to a modeled pre erosion surface average point densities were significantly higher for the ground based lidar system and provided more detailed information however its limited scanning footprint and side looking orientation presented serious challenges in collecting continuous data from deeply incised gullies making the airborne system preferable for this type of investigation and likely for most applications where heavy topographic shadowing is prevalent

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

characterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital topographic data 1 range front alluvial fan deposition in arid environments is episodic and results in multiple fan surfaces and ages these distinct landforms are often defined by descriptions of their surface morphology desert varnish accumulation clast rubification desert pavement formation soil development and stratigraphy although quantifying surface roughness differences between alluvial fan units has proven to be difficult in the past high resolution airborne laser swath mapping alsm digital topographic data are now providing researchers with an opportunity to study topography in unprecedented detail here we use alsm data to calculate surface roughness on two alluvial fans in northern death valley california we define surface roughness as the standard deviation of slope in a 5 m by 5 m moving window comparison of surface roughness values between mapped fan surfaces shows that each unit is statistically unique at the 99 confidence level furthermore there is an obvious smoothing trend from the presently active channel to a deposit with cosmogenic 10be and 36cl surface exposure ages of 70 ka beyond 70 ka alluvial landforms become progressively rougher with age these data suggest that alluvial fans in arid regions smooth out with time until a threshold is crossed where roughness increases at greater wavelength with age as a result of surface runoff and headward tributary incision into the oldest surfaces

response to the comment by w h schwarz et al on joint determination of 40k decay constants and 40ar 40k for the fish canyon sanidine standard and improved accuracy for 40ar 39ar geochronology by p r renne et al 2010

spatial variations in slip rate along the death valley fish lake valley fault system determined from lidar topographic data and cosmogenic 10be geochronology 1 the death valley fish lake valley fault zone dv flvfz is a prominent dextral fault system in the eastern california shear zone ecsz combining offset measurements determined with lidar topographic data for two alluvial fans with terrestrial cosmogenic nuclide 10be ages from the fan surfaces yields a late pleistocene slip rate of 2 5 to 3 mm yr for the northern part of the dv flvfz in fish lake valley these rates are slower than the late pleistocene rate determined for the system in northern death valley indicating that slip rates decrease northward along this major fault zone when summed with the slip rate from the white mountains fault the other major fault in this part of the ecsz our results suggest that either significant deformation is accommodated on structures east of fish lake valley or that rates of seismic strain accumulation and release have not remained constant over late pleistocene to holocene time

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

chronology of tectonic geomorphic and volcanic interactions and the tempo of fault slip near little lake california new geochronologic and geomorphic constraints on the little lake fault in the eastern california shear zone reveal steady modest rates of dextral slip during and since the mid to late pleistocene we focus on a suite of offset fluvial landforms in the pleistocene owens river channel that formed in response to periodic interaction with nearby basalt flows thereby recording displacement over multiple time intervals overlap between 40 ar 39 ar ages for the youngest intracanyon basalt flow and 10 be surface exposure dating of downstream terrace surfaces suggests widespread channel incision during a prominent outburst flood through the little lake channel at ca 64 ka older basalt flows flanking the upper and lower canyon margins indicate localization of the owens river in its current position between 212 14 and 197 11 ka coupled with terrestrial light detection and ranging lidar and digital topographic measurements of dextral offset the revised little lake chronology indicates average dextral slip rates of at least 0 6 0 7 mm yr and 4 to 10 5 yr despite previous geodetic observations of relatively rapid interseismic strain along the little lake fault we find no evidence for sustained temporal fluctuations in slip rates over multiple earthquake cycles instead our results indicate that accelerated fault loading may be transient over much shorter periods 10 1 yr and perhaps indicative of time dependent seismic hazard associated with eastern california shear zone faults

late pleistocene slip rate along the owens valley fault eastern california 1 the owens valley fault zone ovf is one of the primary structures accommodating dextral shear across the eastern california shear zone ecsz previous estimates of the holocene slip rate along this structure rely on paleoseismic data and yield rates 2 3 times lower than those implied by geodetic velocities using displaced lava flows along the flank of crater mountain we present the first estimate of slip rate along the ovf during the late pleistocene subsurface characterization of the flow margin using a ground penetrating radar gpr allows for relatively precise determination of dextral displacement and terrestrial cosmogenic 36cl exposure ages of samples from the flow surface yield slip rates between 2 8 4 5 mm yr over the past 55 80 kyr our results suggest either that paleoseismic slip rate estimates underestimate the long term slip rate or that rates of strain release have not been steady during the latter part of the quaternary

faulted terrace risers place new constraints on the late quaternary slip rate for the central altyn tagh fault northwest tibet the active left lateral altyn tagh fault defines the northwestern margin of the tibetan plateau in western china to clarify late quaternary temporal and spatial variations in slip rate along the central portion of this fault system 85 90 e we have more than doubled the number of dated offset markers along the central altyn tagh fault in particular we determined offset age relations for seven left laterally faulted terrace risers at three sites kelutelage yukuang and keke qiapu spanning a 140 km long fault reach by integrating surficial geologic mapping topographic surveys total station and tripod light detection and ranging t lidar and geochronology radiocarbon dating of organic samples 230 th u dating of pedogenic carbonate coatings on buried clasts and terrestrial cosmogenic radionuclide exposure age dating applied to quartz rich gravels at kelutelage which is the westernmost site 37 72 n 86 67 e two faulted terrace risers are offset 58 3 m and 48 4 m and formed at 6 2 6 1 ka and 5 9 3 7 ka respectively at the yukuang site 38 00 n 87 87 e four faulted terrace risers are offset 92 12 m 68 6 m 55 13 m and 59 9 m and formed at 24 2 9 5 ka 6 4 5 0 ka 5 1 3 9 ka and 24 2 6 4 ka respectively at the easternmost site keke qiapu 38 08 n 88 12 e a faulted terrace riser is offset 33 6 m and has an age of 17 1 2 2 ka the displacement age relationships derived from these markers can be satisfied by an approximately uniform slip rate of 8 12 mm yr however additional analysis is required to test how much temporal variability in slip rate is permitted by this data set

late cenozoic history and slip rates of the fish lake valley emigrant peak and deep springs fault zones nevada and california several well dated stratigraphic markers permit detailed assessment of the temporal and spatial variation in slip rates along the interconnected faults of the fish lake valley emigrant peak and deep springs fault zones in west central nevada and east central california right lateral motion on the fish lake valley fault zone apparently began ca 10 ma 11 9 8 2 ma associated extensional faulting probably began ca 5 ma 6 9 4 ma and resulted in the opening of fish lake valley and deep springs valley the long term lateral slip rate for the fish lake valley fault zone since about 10 ma is 5 mm yr 3 12 mm yr our preferred lateral slip rate for the central most active part of the fish lake valley fault zone decreased from about 6 to 3 mm yr from the late miocene to the early pleistocene increased to about 11 mm yr during the middle pleistocene and decreased to about 4 mm yr during the late pleistocene extension may account for some of the change in lateral slip rate during the pliocene the large increase in lateral slip rate during the middle pleistocene is circumstantially linked to an increase in vertical slip rates on the fish lake valley and deep springs fault zones at about the time of the eruption of the bishop ash 0 76 ma vertical slip rates along the three fault zones are also related to fault strike vertical rates are highest on north striking faults and approach zero on northwest striking faults the long lived slip history of the fish lake valley fault zone fits a tectonic model in which the death valley furnace creek fish lake valley fault system is integrated with right lateral shear on faults of the central walker lane and the eastern california shear zone to accommodate part of the pacific north american relative plate motion our research demonstrates that the fish lake valley fault zone accounts for about half the rate of 10 12 mm yr of pacific north american plate boundary shear accommodated within the basin and range province between about lat 37 and 38 n