thrust fault growth and segment linkage in the active ostler fault zone new zealand abstract thrust faulting is a fundamental mode of crustal deformation yet many of the key geometrical attributes of thrust faults and the controls on fault rupture growth and linkage remain poorly resolved numerous surface rupturing thrust faults cut through upper quaternary glacial outwash terraces within the ostler fault zone an active thrust system in the southern alps new zealand we use these deformed marker surfaces to define the three dimensional deformation field associated with their surface expression and to map displacement and length on 40 fault segments displacement transfer across two fault segment arrays occurs in distinctly different styles in one displacement is transferred between en echelon fault segments to produce a smooth linear displacement gradient in the other large scale folding and a population of small faults transfer displacement between two non overlapping fault segments with a residual displacement minimum within the transfer zone size distribution of fault segment length and maximum displacement follow a power law scaling relationship maximum displacement d max scales linearly with and represents 1 of segment trace length l d max l data from the segments of the ostler fault zone display similar scaling to a global fault dataset this similarity is surprising given that the observed displacements along the ostler fault represent only 20 ky of slip on fault segments that are likely to be many times older

strain partitioning in the northern walker lane western nevada and northeastern california abstract paleomagnetic studies constrain both the kinematics and the timing of neogene intracontinental strain in the walker lane of northwestern nevada northeastern california the northwest trending walker lane is a zone of complex faulting and dextral offset along the boundary between the sierra nevada and the basin and range here an extensive tertiary volcanic section provides a paleomagnetic test for vertical axis rotation the 25 1 ma nine hill tuff covered the two structural domains of northern walker lane and parts of the adjacent provinces in the northernmost domain the pyramid lake domain the nine hill tuff is unrotated or rotated slightly counter clockwise in contrast nine hill tuff is rotated 35 44 clockwise in the northeastern part of the adjacent carson domain usable exposures of the tuff are lacking elsewhere in the carson domain but 9 13 ma basalts record 37 51 clockwise vertical axis rotation these basalts were sampled at three sites encompassing the n s length of the carson domain younger basalts from the carson domain show smaller clockwise rotations the paleomagnetic studies show that the deformation in the northern walker lane is partitioned into domains dominated by translation rotation and extension dextral slip along the walker lane is accommodated primarily by northwestward translation in the pyramid lake domain and by clockwise vertical axis rotation in the carson domain some neogene extension is also accommodated in the walker lane but most of it is occurring to the west of the walker lane along the edge of the sierra nevada comparison of paleomagnetic results from rocks of different ages constrains the timing of the present deformation regime in the walker lane the similar rotations recorded in 25 ma and 9 13 ma rocks indicates that virtually all of the rotation in the carson domain occurred after the eruption of the 9 13 ma basalts smaller rotations recorded in younger rocks constrain rotation rate

geomorphic constraints on listric thrust faulting implications for active deformation in the mackenzie basin south island new zealand 1 deformed fluvial terraces preserved over active thrust related folds record the kinematics of folding as fault slip accumulates on the underlying thrust in the mackenzie basin of southern new zealand the kinematics revealed by folded fluvial terraces along the active ostler and irishman creek fault zones are inconsistent with traditional models for thrust related folding in which spatially uniform rock uplift typically occurs over planar fault ramps instead warped and tilted terraces in the mackenzie are characterized by broad continuous backlimbs and abrupt forelimbs and suggest folding through progressive limb rotation by relating this pattern of surface deformation to the underlying thrust with a newly developed simple geometric and kinematic model we interpret both faults as listric thrusts rooted at depth into gently dipping planar fault ramps constraints on the model from detailed topographic surveying of deformed terraces ground penetrating radar over active fault scarps and luminescence dating of terrace surfaces suggest slip rates for the ostler and irishman creek faults of 1 1 1 7 mm yr and 0 5 0 7 mm yr respectively the predicted depth of listric faulting for the ostler fault 0 7 0 2 0 1 km and the irishman creek fault 1 3 0 5 0 1 km generally agrees with geophysical estimates of basin depth in the mackenzie and suggests control of preexisting basin architecture on the geometry of active thrusting despite the potential effects of changes in fault curvature and hanging wall internal deformation the methodology presented here provides a simple tool for approximating the kinematics of surface deformation associated with slip along listric or curviplanar thrust faults

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

60 k y record of extension across the western boundary of the basin and range province estimate of slip rates from offset shoreline terraces and a catastrophic slide beneath lake tahoe deformation across three major fault strands within the lake tahoe basin has been mapped by using a novel combination of high resolution seismic chirp airborne laser and acoustic multibeam derived bathymetry and deep and shallow water sediment cores submerged erosional terraces of late pleistocene age 19 2 6 1 8 ka record vertical de formation across fault strands that ranges between 10 and 15 m offset of 10 m is observed across the southern part of the west tahoe fault avalanche deposits from the catastrophic mckinney bay slide ca 60 ka are offset across the stateline fault by at least 21 25 m the submerged shoreline terraces and debris avalanche provide marker beds with which to constrain the extensional history of the region for the past 60 k y this history is then used to assess the future seismic hazard of the region data on deformation across these two important marker beds combined with chronological control from 14 c and optically stimulated luminescence measurements yield an estimate of extension across the lake tahoe basin that is 0 4 0 5 mm yr on the basis of these measurements there exists the potential for a large seiche wave generating m7 earthquake every 3 k y late pleisto cene and holocene vertical deformation rates within the tahoe basin are characteristic of basin and range faulting and place the tahoe basin within the western limits of the extensional basin and range province

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

active transtensional boundary zone between the western great basin and sierra nevada block western u s cordillera the walker lane and northern part of the eastern california shear zone form a boundary zone accommodating differential motion between the sierra nevada and western great basin within the boundary zone global positioning system velocities show a westward increase from 2 3 mm yr in the central great basin to 14 mm yr in the sierra nevada and a clockwise rotation from west northwest to northwest in the same region incremental extensional strain axes recorded by earthquake focal mechanisms and fault slip inversion show an east to west counterclockwise rotation of 50 from parallel with the velocity field in the central great basin to nearly orthogonal to the velocity field along the eastern flank of the sierra nevada unlike plane strain deformation within the central great basin the progressive deviation between the orientation of extension axes and the velocity field in the boundary zone is a product of nonplane strain the boundary zone records active constriction formed in conditions varying from wrench dominated to extension dominated transtension

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

late quaternary activity along the lone pine fault eastern california the lone pine fault is a north trending secondary break of the owens valley fault zone 1 4 km west of lone pine california this fault forms an east facing scarp as much as 6 5 m high across an abandoned outwash fan of the tioga latest pleistocene glaciation the fault experienced large right lateral and smaller vertical displacement during the 1872 owens valley earthquake knowledge of the character and amount of slip at this site in and before 1872 is necessary for evaluations of earthquake hazard near owens valley and may help us to understand earthquakes along other parts of the eastern front of the sierra nevada and in the great basin scarp profiles indicate a 1 to 2 m component of dip slip in 1872 thus three 1872 type earthquakes could have created the scarp this number of events is also indicated by desert varnish patterns on boulders in the fault scarp by scarp morphology and by sediments near the fault horizontal offset of a relict channel on the fan is 12 to 18 m 3 earthquakes horizontal offset of a younger debris flow is 10 to 12 m apparently 2 earthquakes average horizontal offset for each earthquake including that of 1872 is 4 to 6 m the age of the fan surface is bracketed by a 21 ka shoreline of former lake owens and by the time of abandonment of the fan about 10 ka an average recurrence interval for 3 earthquakes is 5 000 to 10 500 yr the average recurrence interval combined with the average oblique offset for each event of 4 3 to 6 3 m gives an average late quaternary slip rate of 0 4 to 1 3 mm yr for the lone pine fault if we add the average horizontal slip component for the lone pine fault to the 1872 horizontal slip reported for the adjacent main owens valley trace of 2 7 to 4 9 m the combined 1872 horizontal slip component for the owens valley fault zone is approximately between 7 and 11 m a large value the associated horizontal slip rate for the owens vallev fault zone is 0 7 to 2 2 mm yr

transtensional deformation in the lake tahoe region california and nevada usa dextral transtensional deformation is occurring along the sierra nevada great basin boundary zone sngbbz at the eastern edge of the sierra nevada microplate in the lake tahoe region of the sngbbz transtension is partitioned spatially and temporally into domains of north south striking normal faults and transitional domains with conjugate strike slip faults the normal fault domains which have had large holocene earthquakes but account only for background seismicity in the historic period primarily accommodate east west extension while the transitional domains which have had moderate holocene and historic earthquakes and are currently seismically active primarily record north south shortening through partitioned slip the upper crust in this region undergoes overall constrictional strain major fault zones within the lake tahoe basin include two normal fault zones the northwest trending tahoe sierra frontal fault zone tsffz and the north trending west tahoe dollar point fault zone most faults in these zones show eastside down displacements both of these fault zones show evidence of holocene earthquakes but are relatively quiet seismically through the historic record the northeast trending north tahoe incline village fault zone is a major normal to sinistral oblique fault zone this fault zone shows evidence for large holocene earthquakes and based on the historic record is seismically active at the microearthquake level the zone forms the boundary between the lake tahoe normal fault domain to the south and the truckee transition zone to the north several lines of evidence including both geology and historic seismicity indicate that the seismically active truckee and gardnerville transition zones north and southeast of lake tahoe basin respectively are undergoing north south shortening in addition the central carson range a major north trending range block between two large normal fault zones shows internal fault patterns that suggest the range is undergoing north south shortening in addition to east west extension a model capable of explaining the spatial and temporal partitioning of slip suggests that seismic behavior in the region alternates between two modes one mode characterized by an east west minimum principal stress and a north south maximum principal stress as at present in this mode seismicity and small scale faulting reflecting north south shortening concentrate in mechanically weak transition zones with primarily strike slip faulting in relatively small magnitude events and domains with major normal faults are relatively quiet a second mode occurs after sufficient north south shortening reduces the north south shmax in magnitude until it is less than sv at which point sv becomes the maximum principal stress this second mode is then characterized by large earthquakes on major normal faults in the large normal fault domains which dominate the overall moment release in the region producing significant east west extension

pleistocene lake outburst floods and fan formation along the eastern sierra nevada california implications for the interpretation of intermontane lacustrine records berin d i owen l a finkel r c clemmens s 2006 pleistocene lake outburst floods and fan formation along the eastern sierra nevada california implications for the interpretation of intermontane lacustrine records quaternary science reviews 25 2729 2748 sponsorship national science foundation grant ear 0207245

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

interpretation of biological and environmental changes across the neoproterozoic cambrian boundary developing a refined understanding of the radiation and preservational record of early multicellular organisms

high frequency holocene glacier fluctuations in new zealand differ from the northern signature understanding the timings of interhemispheric climate changes during the holocene along with their causes remains a major problem of climate science here we present a high resolution 10be chronology of glacier fluctuations in new zealand s southern alps over the past 7000 years including at least five events during the last millennium the extents of glacier advances decreased from the middle to the late holocene in contrast with the northern hemisphere pattern several glacier advances occurred in new zealand during classic northern warm periods these findings point to the importance of regional driving and or amplifying mechanisms we suggest that atmospheric circulation changes in the southwest pacific were one important factor in forcing high frequency holocene glacier fluctuations in new zealand

continuous gps measurements of contemporary deformation across the northern basin and range province we have acquired and analyzed data from the northern basin and range nbar continuous gps network since july 1996 the rms residual with respect to the best fitting lines through the individual station position estimates is 2 3 mm in the horizontal and 6 10 mm in the vertical after the first 395 days of operation uncertainties in horizontal velocity estimates are 1 2 mm yr 1 relative motion among nbar sites located in eastern nevada and in utah is small but east west extension is significant assuming uniform strain accumulation across the whole network the relative motion observed across the wasatch fault zone is 2 2 mm yr east west relative motions among stations in western nevada and california in contrast are dominated by northwest right lateral shear we infer an integrated deformation across the northern basin and range of 11 2 mm yr northwest these rates are consistent with previous geodetic measurements our gps velocity estimates however reveal a possibly abrupt transition from east west extension in eastern nevada and utah to right lateral shear in western nevada this transition is roughly coincident with the central nevada seismic belt and is consistent with the right oblique focal mechanisms of the 1954 dixie valley and fairview peak earthquakes the transition also appears to correlate spatially with a transition in upper mantle structure

incorporating and reporting uncertainties in fault slip rates 1 quantitative slip rate estimates are essential to understanding crustal deformation processes and assessing seismic hazard computing slip rates requires two fundamental ingredients estimates of the age of an offset landforrn or deposit and displacement along the fault of interest because both of these measures contain uncertainty slip rates are inherently uncertain methods to compute and report slip rates have not been standardized and therefore slip rate data are presented inconsistently and are frequently ambiguous in particular slip rate uncertainty is often insufficiently characterized we present a rigorous probabilistic approach to computing and reporting intermediate to long term fault slip rates additionally we have developed freely available software that provides standard age and displacement uncertainty models we demonstrate the method using recent observations from the neodani and death valley fish lake valley fault zones and we compare slip rates determined using this approach with previously published results

modeling topographic and climatic control of east west asymmetry in sierra nevada glacier length during the last glacial maximum 1 glaciers draining westward from the sierra nevada divide california during the last glacial maximum lgm were 7 times longer than east draining glaciers we address the degree to which this difference may be attributed to the topographic asymmetry of the west tilted sierran block and the climate asymmetry resulting from orographic modification of pacific ocean storms we simulate kilometer scale glaciers within the 50 50 km kings canyon region of the southern sierra by employing a two dimensional numerical model that is driven by simple spatially variable climates and treats ice transport by deformation sliding and avalanching in numerical experiments we match simulated termini to lgm moraine positions to constrain the parameters of different climate scenarios the 38 km long lgm glacier in kings canyon was reproduced by a climate specified by an equilibrium line altitude ela of 3170 m a mass balance gradient of 0 01 m yr m and a maximum positive balance of 2 m yr this climate generates much shorter average 6 km long east draining glaciers that however overshoot the lgm moraines by 1 km roughly 97 of the e w difference in glacier lengths can therefore be attributed to topographic asymmetry alone a second experiment suggesting a 120 m higher ela of 3290 m east of the divide can explain the shorter east draining glaciers an experiment in which orographic precipitation is explicitly simulated and melt is prescribed using a positive degree day algorithm matches both kings canyon and the average east draining glacier length with an lgm climate that was 5 6 c cooler and 2 times wetter than the modern sierra nevada

active displacement transfer and differential block motion within the central walker lane western great basin velocities determined for 50 global positioning system sites within the central walker lane indicate differential motion among tectonic blocks forming a boundary zone between the great basin extensional province and the sierra nevada the velocity field is related to displacement transfer from the owens valley and furnace creek fault systems of east ern california to transtensional structures of the walker lane and extensional faults of the central nevada seismic belt block boundaries are sharp and appear to be inherited from pre tertiary crustal structure the block geometries exert strong influence on dif ferential displacements concentrated along boundaries as belts of divergent transcurrent and convergent motion the aggregate velocity accounts for about 25 of the relative motion between the pacific and north american plates about 5 mm yr of the motion is localized along the eastern margin of the sierra nevada whereas about 10 mm yr is stepped 100 km east along a belt of east northeast trending transtensional faults that merge with northwest trending transcurrent structures of the walker lane about 6 mm yr of the velocity field is transferred to north northeast trending extensional faults of the central nevada seismic belt the heterogeneous distribution of motions is consistent with partitioning of a regional velocity field formed by westward extension and n408w directed shear

slip rate variations on normal faults during glacial interglacial changes in surface loads geologic and palaeoseismological data document a marked increase in the slip rates of the wasatch fault and three adjacent normal faults in the basin and range province during the late pleistocene early holocene epochs the cause of this synchronous acceleration of fault slip and the subsequent clustering of earthquakes during the holocene has remained enigmatic although it has been suggested that the coincidence between the acceleration of slip and the shrinkage of lake bonneville after the last glacial maximum may indicate a causal relationship here we use finite element models of a discrete normal fault within a rheologically layered lithosphere to evaluate the relative importance of two competing processes that affect fault slip postglacial unloading the removal of mass which decreases the slip rate and lithospheric rebound which promotes faster slip we show that lithospheric rebound caused by regression of lake bonneville and deglaciation of adjacent mountain ranges provides a feasible mechanism for the high holocene rates of faulting in the wasatch region our analysis implies that climate controlled changes in loads applied to earth s surface may exert a fundamental control on the slip history of individual normal faults

three dimensional numerical modeling of slip rate variations on normal and thrust fault arrays during ice cap growth and melting 1 changes in the volumes of ice caps considerably alter the stress state of the lithosphere by generating a transient signal that is added to the tectonic background stress field these stress field changes in turn affect crustal deformation and in particular the slip behavior of existing faults here we use three dimensional finite element models to investigate how arrays of normal and thrust faults near a growing and subsequently melting ice cap are influenced in their slip evolution the results show that regardless of fault dip both types of faults experience a decrease in their slip rate during ice cap advance and an increase in their slip rate during ice cap retreat if they are located beneath the ice cap in contrast faults outside the ice cap that are loaded on their footwall or hanging wall only show the opposite pattern their slip rate increases during glacial loading and decreases during subsequent unloading if the load is located along strike of the fault that is at one of its tips the slip behavior of normal and thrust faults is different the normal fault shows a slip rate increase during unloading the thrust fault during loading our results explain the location and timing of deglaciation induced paleoearthquakes in scandinavia and the contrasting slip histories reported from normal faults in the basin and range province which are located at different positions relative to the former yellowstone ice cap more generally our findings imply that a uniform slip behavior of faults in formerly glaciated regions should not be expected

stream incision tectonics uplift and evolution of topography of the sierra nevada california abstract stream incision faulting thermochronologic and geobarometric data suggest that sierra nevada topography is a consequence of two periods of uplift stream incision of up to 1 km has occurred since 5 ma maximum eocene miocene incision was 150 m uplift of the sierra nevada westward tilting stream incision and east down normal and dextral faulting along the present eastern escarpment of the range began at 5 ma estimates of late cenozoic crestal rock uplift for different areas in the sierra nevada range from 1440 to 2150 m low summit erosion rates suggest that the rock uplift approximates the surface uplift of crestal summits tertiary stream gradients were lower than modern ones suggesting that the bottoms of the canyons have been uplifted in the late cenozoic and that the mean elevation of the sierra nevada has increased the elevation of pre cenozoic basement rocks above the base of tertiary paleochannels ranges from 1000 m in the south and

spatiotemporal patterns of fault slip rates across the central sierra nevada frontal fault zone abstract patterns in fault slip rates through time and space are examined across the transition from the sierra nevada to the eastern california shear zone walker lane belt at each of four sites along the eastern sierra nevada frontal fault zone between 38 and 39 n latitude geomorphic markers such as glacial moraines and outwash terraces are displaced by a suite of range front normal faults using geomorphic mapping surveying and 10 be surface exposure dating mean fault slip rates are defined and by utilizing markers of different ages generally 20 ka and 150 ka rates through time and interactions among multiple faults are examined over 10 4 10 5 year timescales at each site for which data are available for the last 150 ky mean slip rates across the sierra nevada frontal fault zone have probably not varied by more than a factor of two over time spans equal to half of the total time interval 20 ky and 150 ky timescales 0 3 0 1 mm year 1 mode and 95 ci at both buckeye creek in the bridgeport basin and sonora junction and 0 4 0 3 0 1 mm year 1 along the west fork of the carson river at woodfords data permit rates that are relatively constant over the time scales examined in contrast slip rates are highly variable in space over the last 20 ky slip rates decrease by a factor of 3 5 northward over a distance of 20 km between the northern mono basin 1 3 0 6 0 3 mm year 1 at lundy canyon site to the bridgeport basin 0 3 0 1 mm year 1 the 3 fold decrease in the slip rate on the sierra nevada frontal fault zone northward from mono basin is indicative of a change in the character of faulting north of the mina deflection as extension is transferred eastward onto normal faults between the sierra nevada and walker lane belt a compilation of regional deformation rates reveals that the spatial pattern of extension rates changes along strike of the eastern california shear zone walker lane belt south of the mina deflection extension is accommodated within a diffuse zone of normal and oblique faults with extension rates increasing northward on the fish lake valley fault where faults of the eastern california shear zone terminate northward into the mina deflection extension rates increase northward along the sierra nevada frontal fault zone to 0 7 mm year 1 in northern mono basin this spatial pattern suggests that extension is transferred from more easterly fault systems e g fish lake valley fault and localized on the sierra nevada frontal fault zone as the eastern california shear zone walker lane belt faulting is transferred through the mina deflection

implications of shortening in the himalayan fold thrust belt for uplift of the tibetan plateau 1 recent research in the himalayan fold thrust belt provides two new sets of observations that are crucial to understanding the evolution of the himalayan tibetan orogenic system first u pb zircon ages and sm nd isotopic studies demonstrate that 1 greater himalayan medium to high grade metasedimentary rocks are much younger than true indian cratonic basement and 2 these rocks were tectonically mobilized and consolidated with the northern margin of gondwana during early paleozoic orogenic activity these observations require that greater himalayan rocks be treated as supracrustal material in restorations of the himalayan fold thrust belt rather than as indian cratonic basement in turn this implies the existence of greater himalayan lower crust that is not exposed anywhere in the fold thrust belt second a regional compilation of shortening estimates along the himalayan arc from pakistan to sikkim reveals that 1 total minimum shortening in the fold thrust belt is up to 670 km 2 total shortening is greatest in western nepal and northern india near the apex of the himalayan salient and 3 the amount of himalayan shortening is equal to the present width of the tibetan plateau measured in an arc normal direction north of the indus yalu suture zone this information suggests that a slab of greater indian lower crust composed of both indian cratonic lower crust and greater himalayan lower crust with a north south length of 700 km may have been inserted beneath the tibetan crust during the cenozoic orogeny we present a modified version of the crustal underthrusting model for himalayan tibetan orogenesis that integrates surface geological data recent results of mantle tomographic studies and broadband seismic studies of the crust and upper mantle beneath the tibetan plateau previous studies have shown that incremental mesozoic and early cenozoic shortening had probably thickened tibetan crust to 45 55 km before the onset of the main cenozoic orogenic event thus the insertion of a slab of greater indian lower crust with maximum thickness of 20 km tapering northward could explain the cenozoic uplift of the tibetan plateau the need for tibetan crust to stretch laterally as the greater indian lower crust was inserted may explain the widespread east west extension in the southern half of the plateau our reconstruction of the himalayan fold thrust belt suggests that indian cratonic lower crust of presumed mafic composition and high strength should extend approximately halfway across the tibetan plateau to the banggong suture from there northward we predict that the tibetan plateau is underlain by more felsic and therefore weaker lower crust of greater himalayan affinity two slab break off events are predicted by the model the first involved neotethyan oceanic lithosphere that foundered 45 35 ma and the second consisted of greater indian lithosphere most likely composed of greater himalayan material that delaminated and foundered 20 10 ma asthenospheric upwelling associated with the break off events may explain patterns of cenozoic volcanism on the tibetan plateau although the model predicts a northward migrating topographic front due solely to insertion of greater indian lower crust the actual uplift history of the plateau was complicated by early middle tertiary shortening of tibetan crust

explicit treatment of inheritance in dating depositional surfaces using in situ 10be and 26al we describe a new strategy for dating depositional landscape surfaces using in situ produced cosmogenic radionuclides crns that removes the complication of nuclide inheritance by clasts prior to depositon two amalgamated samples each consisting of 30 clasts one from the surface and one from a fixed depth in the subsurface constrain this crn inheritance and date the surface the inheritance may be used to estimate minimum exhumation rates and maximum transport times within the geomorphic system we test the technique using sup 10 be and sup 26 al to date the third fr3 of five terraces along the fremont river utah and the third wr3 of 15 along the wind river wyoming whereas effective ages based solely upon the surface samples yield 118 138 ka fr3 and 93 ka wr3 the subsurface samples reveal that inheritance accounts for 22 wr3 to 43 fr3 of the total crn concentration taking this into account yeilds terrace ages of nearly 61 81 ka for fr3 and nearly 67 76 ka for wr3 we explore the dependence of age estimates on the accumulation history of the terrace silt caps 22 refs 3 figs 1 tab

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

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

low quaternary slip rate reconciles geodetic and geologic rates along the altyn tagh fault northwestern tibet for more than two decades the slip rate along the active left slip altyn tagh fault of northwestern tibet has been disputed with millennial rates reported to be as much as three times faster than those determined geodetically this problem is significant because the total offset plate boundary length and age of the altyn tagh fault make it the most important single structure accommodating india asia convergence north of the himalayas here we show that the central altyn tagh fault slipped at only 14 9 mm a over the past 4 6 ka by tightly bracketing the age of a displaced fluvial terrace riser at yuemake 88 51 e 38 19 n this result contradicts previous latest quaternary rates and is consistent with those derived from geodetic paleoseismic and geologic measurements and thus resolves the long standing dispute over the latest quaternary slip rate along the longest active strike slip fault in tibet