importance of a stochastic distribution of floods and erosion thresholds in the bedrock river incision problem 1 fluvial erosion of bedrock occurs during occasional flood events when boundary shear stress exceeds a critical threshold to initiate incision therefore efforts to model the evolution of topography over long timescales should include an erosion threshold and should be driven by a stochastic distribution of erosive events however most bedrock incision models ignore the threshold as a second order detail in addition climate is poorly represented in most landscape evolution models so the quantitative relationship between erosion rate and measurable climatic variables has been elusive here we show that the presence of an erosion threshold when combined with a well constrained probabilistic model of storm and flood occurrence has first order implications for the dynamics of river incision in tectonically active areas first we make a direct calculation of the critical shear stress required to pluck bedrock blocks for a field site in new york second we apply a recently proposed stochastic threshold bedrock incision model to a series of streams in california with known tectonic and climatic forcing previous work in the area has identified a weak relationship between channel gradient or relief and rock uplift rate that is not easily explained by simpler detachment limited models the results with the stochastic threshold model show that even low erosion thresholds which are exceeded in steep channels during high frequency flood events fundamentally affect the predicted relationship between gradient and uplift rate in steady state rivers in a manner consistent with the observed topography this correspondence between theory and data is however nonunique models in which a thin alluvial cover may act to inhibit channel incision in the low uplift rate zone also provide plausible explanations for the observed topography third we explore the broader implications of the stochastic threshold model to the development of fluvial topography in active tectonic settings we suggest that continued field applications of geomorphic models including physically meaningful thresholds and stochastic climate distributions are required to advance our knowledge of interactions among surficial climatic and crustal processes

late pleistocene braided rivers of the atlantic coastal plain usa abstract infrared landsat imagery band 4 clearly reveals braided river patterns on late pleistocene terraces of unglaciated rivers in the atlantic coastal plain of the southeastern united states a region that presently exhibits meandering patterns that have existed throughout the holocene these pleistocene braided patterns provide a unique global example of river responses to late quaternary climate changes in an unglaciated humid subtropical region at 30 35 north latitude detailed morphological and chronological results are given for the oconee altamaha river valley in georgia and for the pee dee river valley in south carolina including 15 optically stimulated luminescence osl dates and four radiocarbon dates correlative examples are drawn from additional small to large rivers in south and north carolina osl and radiocarbon 14 c dates indicate distinct braiding at 17 30 ka within oxygen isotope stage 2 ois 2 and braiding probably existed at least during parts of ois 3 and possibly ois 4 back to ca 70 ka the chronology suggests that braiding is the more common pattern for the late quaternary in the southeastern united states braided terraces appear to have been graded to lower sea levels and are onlapped by holocene floodplain deposits up to 10 60 km from the coast the braiding probably reflects the response of discharge and sediment yield to generally cooler and drier paleoclimates which may have had a pronounced runoff season sedimentation of eolian dunes on the braid plains is coeval with braiding and supports the conclusion of dry soils and thin vegetation cover during the late pleistocene our chronological data contribute to a body of literature indicating that reliable osl age estimates can be obtained from quartz rich bed load sand from braided rivers based on good correlations with both radiocarbon dates from braided fluvial sediment and osl dates from stratigraphically correlative eolian sand

predicted bounds on peak global mean sea level during marine isotope stages 5a and 5c abstract estimates of marine isotope stage mis 5c and 5a global mean sea level gmsl based on marine terraces and coastal indicators range from 15 37 m and 9 30 m below present respectively tectonic displacement and glacial isostatic adjustment gia complicate efforts to refine this range we revisit this issue using numerical predictions of post glacial sea level change and updated estimates of site specific tectonic signals based upon these predictions laurentide and cordilleran peripheral bulge dynamics and variations in the gravitational effect of these ice masses dominate the gia signal along the east and west coasts of north america published compilations suggest that mis 5 sea level indicators extending from virginia to the caribbean lie on the outer flank of the peripheral bulge while those along a transect from oregon to baja california sit on the inner flank of the bulge our gia modeling reconciles these data by adopting a significantly weaker i e lower viscosity upper mantle in analyzing data on the pacific coast relative to the atlantic an inference supported by seismic tomography we present a sensitivity analysis that compares the observed elevation of globally distributed high stand markers to a suite of gia simulations that vary the earth model and gmsl from the last interglaciation mis 5e 130 115 ka to 70 ka we conclude that gmsl peaked at 8 5 4 6 m 1 during mis 5a and 9 4 5 3 m during mis 5c a more restrictive analysis yields slightly wider bounds corresponding to 10 5 5 5 m and 11 1 6 6 m respectively

a mechanistic model for river incision into bedrock by saltating bed load 1 abrasion by bed load is a ubiquitous and sometimes dominant erosional mechanism for fluvial incision into bedrock here we develop a model for bedrock abrasion by saltating bed load wherein the wear rate depends linearly on the flux of impact kinetic energy normal to the bed and on the fraction of the bed that is not armored by transient deposits of alluvium we assume that the extent of alluvial bed cover depends on the ratio of coarse sediment supply to bed load transport capacity particle impact velocity and impact frequency depend on saltation trajectories which can be predicted using empirical functions of excess shear stress the model predicts a nonlinear dependence of bedrock abrasion rate on both sediment supply and transport capacity maximum wear rates occur at moderate relative supply rates due to the tradeoff between the availability of abrasive tools and the partial alluviation of the bedrock bed maximum wear rates also occur at intermediate levels of excess shear stress due to the reduction in impact frequency as grain motion approaches the threshold of suspension measurements of bedrock wear in a laboratory abrasion mill agree well with model predictions and allow calibration of the one free model parameter which relates rock strength to rock resistance to abrasive wear the model results suggest that grain size and sediment supply are fundamental controls on bedrock incision rates not only by bed load abrasion but also by all other mechanisms that require bedrock to be exposed in the channel bed

a framework of holocene and late pleistocene environmental change in eastern iran inferred from the dating of periods of alluvial fan abandonment river terracing and lake deposition abstract we review studies of the holocene and late pleistocene stratigraphy of eastern iran to infer past changes in the environment within this presently arid region we build a scenario of widespread and presumably climatically driven evolution of the landscape through the holocene six sites covering a 10 range in latitude indicate a regional abandonment of alluvial fan surfaces at 10 3 ka with the younger 9 ka end of this age range supported by several of the best constrained studies incision of rivers into the fan surfaces has occurred in discrete stages in the early to mid holocene 9 7 ka leading to the formation of flights of river terraces detailed records of lakebed deposition in the presently arid interior of iran are rare though the available data indicate lake highstand conditions at

ability of a global three dimensional model to locate regional events 1 we assess the ability of a global three dimensional 3d seismic model of the crust and upper mantle cub2 0 to locate seismic events using regional travel time data alone epicentral distances 20 assessments are based on a ground truth gt database comprising nearly 1000 uncommonly well located events which occur in 23 event clusters across eurasia and north africa groomed p and pn arrival time data observed at regional distances from individual events and 1000 empirical phase path anomalies produced from event clusters evidence is presented that supports the conversion of the shear velocities vs in cub2 0 to compressional velocities vp in the upper mantle using the thermoelastic properties of an assumed mantle composition rather than traditional empirical scaling relationships two principal results are presented first this 3d vp model fits the empirical p and pn phase path anomalies very well in both pattern and absolute level second location assessments demonstrate that intrinsic regional location accuracy is 5 km using the 3d vp model and 10 km using the 1d model ak135 these findings highlight the importance of gt databases in assessing regional travel time models and establish that a global 3d vs model together with vp inferred from it provides a solid basis on which to build improvements in regional location capabilities

reconciliation of sea level observations in the western north atlantic during the last glacial cycle abstract a south to north gradient of increasing marine isotope substage mis 5a 80 ka bp sea level has been recorded across the caribbean and surrounding region relative to present mis 5a sea levels range from 19 m to more than 3 m between barbados haiti the bahamas florida bermuda and the us atlantic coast in contrast no gradient in sea level is observed for the last interglacial period mis 5e 128 118 ka bp at tectonically stable localities in the same region with deposits generally lying several metres above present we demonstrate here that these controversial observations are reconciled by taking into account the isostatic response of the earth to glacial loading and unloading a fundamental effect that is commonly overlooked in the interpretation of sea level observations from different locations to define a global sea level curve furthermore the observed gradient can be used to place constraints on earth rheology and is an important indicator of the behaviour of the north american ice sheets during the last glacial cycle

channel changes in badlands stripping of the vegetation and soil from a 13 hectare site in virginia underlain by coastal plain sediments created a rapidly evolving badland topography two types of channels developed 1 sand bed alluvial channels were graded to transport the bed material load supplied from slope erosion with available runoff but they also generally eroded their beds slowly and 2 steeper bedrock floored channels incised rapidly in bedrock channels the erosion rate was proportional to the 4 9ths power of drainage area and the 2 3rds power of gradient these exponents are consistent with a model in which the erosion rate is proportional to the bed shear during high flows due to rapid mass wasting and reduced runoff the alluvial channels became as much as 50 steeper during the winter than the summer with an attendant yearly cycle of winter aggradation and summer entrenchment the gradients their seasonal variability and their downstream hydraulic geometry were consistent with the predictions of total load transport formulas for sand beds and high loads the hydraulic geometry of alluvial channels in the virginia badlands were similar to that on the morrison formation in the western united states

constraining the late pleistocene history of the laurentide ice sheet by dating the missinaibi formation hudson bay lowlands canada abstract well dated paleorecords from periods prior to the last glacial maximum lgm are important for validating models of ice sheet build up and growth however owing to glacial erosion most late pleistocene records lie outside of the previously glaciated region which limits their ability to inform about the dynamics of paleo ice sheets here we evaluate new and previously published chronology data from the missinaibi formation a pleistocene aged deposit in the hudson bay lowlands hbl canada located near the geographic center of the laurentide ice sheet lis available radiocarbon ams 44 conventional 36 amino acid n 13 uranium thorium u th n 14 thermoluminescence tl n 15 and optically stimulated luminescence osl n 5 data suggest that an ice free hbl may have been possible during parts of marine isotope stage 7 mis 7 ca 243 000 to ca 190 000 yr bp mis 5 ca 130 000 to ca 71 000 yr bp and mis 3 ca 29 000 to ca 57 000 while mis 7 and mis 5 are well documented interglacial periods the development of peat forest bed and fluvial deposits dating to mis 3 n 20 radiocarbon dates 4 tl dates 3 osl dates suggests that the lis retreated and remained beyond or somewhere within the boundaries of the hbl during this interstadial ice sheet models approximate the margin of the lis to southern ontario during this time which is 700 km south of the hbl therefore if correct our data help constrain a significantly different configuration and dynamicity for the lis than previously modelled we can find no chronological basis to discount the mis 3 age assignments however since most data originate from radiocarbon dates lying close to the reliable limit of this geochronometer future work on dating the missinaibi formation using other geochronological methods e g u th osl is necessary in order to confirm the age estimates and strengthen the boundaries of the lis during this period

the vertical separation of mainshock rupture and microseismicity at qeshm island in the zagros fold and thrust belt iran we investigate the depth and geometry of faulting within a cluster of buried reverse faulting earthquakes that struck qeshm island in the zagros fold and thrust belt over a four year period between november 2005 and july 2009 of particular interest is our observation that there was a vertical separation between the largest two earthquakes mw 5 8 and 5 9 which ruptured the lower parts of a 10 km thick sedimentary cover and microseismicity recorded by a local network after the first mw 5 8 event which was concentrated within the underlying basement at depths of 10 20 km although measured in different ways the largest three earthquakes using radar interferometry moderate sized events with teleseismically recorded long period waveforms and the microseismicity using data from a local seismic network we used consistent velocity and elastic parameters in all our modelling and the observed vertical separation is robust and resolvable we suggest that it reflects the influence of the proterozoic hormuz salt a weak layer at the base of the sedimentary cover across which rupture failed to propagate because the full thickness of the seismogenic layer failed to rupture during the largest earthquakes in the sequence the lower unruptured part may constitute a continued seismic hazard to the region considering the rarity of earthquakes larger than mw 6 2 in the zagros simply folded belt we suggest that the hormuz salt forms an important regional barrier to rupture not just a local one finally we note that buried faulting involved in the largest earthquakes is almost perpendicular to the trend of an anticline exposed at the surface immediately above them this suggests that locally faulting and folding are decoupled probably along a weak layer of marls or evaporites in the middle part of the sedimentary cover

the laurentide and innuitian ice sheets during the last glacial maximum the late wisconsinan advance of the laurentide ice sheet started from a middle wisconsinan interstadial minimum 27 30 14 c ka bp when the ice margin approximately followed the boundary of the canadian shield ice extent in the cordillera and in the high arctic at that time was probably similar to present ice advanced to its late wisconsinan stage 2 limit in the northwest south and northeast about 23 24 14 c ka bp and in the southwest and far north about 20 21 14 c ka bp in comparison to some previous reconstructions of ice extent our current reconstruction has substantially more late wisconsinan ice in the high arctic where an innuitian ice sheet is generally acknowledged to have existed in the atlantic provinces where ice is now thought to have extended to the continental shelf edge in most places and on eastern baffin island where ice probably extended to the fiord mouths rather than to the fiord heads around most of the ice margin the late wisconsinan maximum ice extent either exceeded the extent of earlier wisconsinan advances or it was similar to the early wisconsinan advance ice marginal recession prior to 14 14 ck a bp occurred mainly in deep water and along the southern terrestrial fringe however heinrich event 1 probably drew down the entire central ice surface at 14 5 14 c ka bp sufficiently to displace the labrador sector outflow centre 900 km eastward from the coast of hudson bay the onset of substantial ice marginal recession occurred about 14 14 c ka bp in the northwest southwest and south but not until about 10 11 14 c ka bp in the northeast and in the high arctic thus the period of maximum ice extent in north america generally encompasses the interval from b24 21 to 14 14 c ka bp or considerably longer than the duration of the lgm defined as occurring during a period of low global sea level as well as during a time of relative climate stability b18 14 c ka bp the interval of advance of much of the laurentide ice sheet to its maximum extent between b27 14 c ka bp and b24 14 c ka bp coincides with a suggested interval of rapid fall in global sea level to near lgmlevels r 2001 elsevier science ltd all rights reserved

quaternary fluvial history of the delaware river new jersey and pennsylvania usa the effects of glaciation glacioisostasy and eustasy on a proglacial river system abstract fluvial glacial and estuarine deposits in the delaware valley record the response of the delaware river to glaciation sea level change and glacioisostasy during the quaternary incision following an early pleistocene glaciation created the present valley which is inset into a pliocene strath and fluvial plain middle and upper pleistocene and holocene deposits were laid down in this inset valley estuarine terraces in the lower valley and bayshore at 20 m probably marine isotope stage mis 11 8 m mis 5e and 3 m mis 5a or c and a fluvial deposit that correlates to offshore mis 3 marine deposits at 20 m are at elevations consistent with glacioisostatic models successive incisions during lowstands in the middle and late pleistocene lengthened deepened and narrowed the channel in the lower valley and shifted the channel westward in delaware bay during mis 2 glaciation from 25 to 18 ka the delaware was diverted to the hudson shelf valley by glacioisostatic tilting most glacial sediment was trapped in fluvial lacustrine valley fills north of the terminal moraine incision of the valley fill was accomplished during the early stage of rebound between 17 and 12 ka drainage to the delaware shelf was restored between 15 and 13 ka as the forebulge collapsed during incision multiple postglacial terraces formed where the valley was perpendicular to rebound contours and so was steepened and elevated northward and a single terrace formed where the valley paralleled the contours and there was no differential elevation or steepening about 65 of the original volume of mis 2 glacial sediment remains in the main valley and most of the eroded volume is in the channel in the lower valley beneath holocene estuarine fill little glacial sediment reached the delaware or hudson shelf overbank deposition on the lower postglacial terrace and modern floodplain spans the holocene the volume of holocene sediment in the estuary and bay yields a basinwide denudation rate of about 20 m my

a theoretical model for fluvial channel response time during time dependent climatic and tectonic forcing and its inverse applications the fluvial response time dictates the duration of fluvial channel adjustment in response to changing climatic and tectonic conditions however when these conditions vary continuously the channel cannot equilibrate and the response time is not well defined here i develop an analytical solution to the linear stream power model of fluvial incision that predicts the channel topography as a function of time dependent climatic and tectonic conditions from this solution a general definition of the fluvial response time emerges the duration over which the tectonic history needs to be known to evaluate channel topography this new definition is used in linear inversion schemes for inferring climatic or tectonic histories from river long profiles the analytic solution further reveals that high frequency climatic oscillations such as milankovitch cycles are not expected to leave significant fingerprints on the long profiles of fluvially incised detachment limited rivers

refining the laurentide ice sheet at marine isotope stage 3 a data based approach combining glacial isostatic simulations with a dynamic ice model abstract while glacial geologic records track the retreat history of the laurentide ice sheet constraints on the ice sheet build up history are more elusive as the laurentide ice sheet expanded to its maximum extent at the last glacial maximum 26 ka it erased most evidence of previous glaciations however an increasing number of dated non glacial deposits point to a relatively confined laurentide ice sheet during marine isotope stage 3 mis 3 60 26 ka suggesting rapid ice growth rates leading to the last glacial maximum in this study we demonstrate that predictions of relative sea level change due to glacial isostatic adjustment involving a late and rapid growth of the laurentide ice sheet are consistent with sea level bounds associated non glacial deposits of mis 3 age in canada we also run a simple dynamic ice model that adopts the paleotopography generated from the glacial isostatic adjustment simulation and show that using accumulation rates similar to that of the present day arctic rapid glaciation rates starting at mid mis 3 44 ka are predicted

epicentre accuracy based on seismic network criteria summary we establish reliable and conservative estimates for epicentre location accuracy using data that are readily available in published seismic bulletins a large variety of seismic studies rely on catalogues of event locations making proper assessment of location uncertainty critical event location and uncertainty parameters in most global regional and national earthquake catalogues are obtained from traditional linearized inversion methods using a 1 d earth model to predict traveltimes reported catalogue uncertainties are based on the assumption that error processes are gaussian zero mean and uncorrelated unfortunately these assumptions are commonly violated leading to the underestimation of true location uncertainty especially at high confidence levels we find that catalogue location accuracy is most reliably estimated by station geometry we make use of two explosions with exactly known epicentres to develop local network location 0 2 5 accuracy criteria using monte carlo simulations of network geometry we find that local network locations are accurate to within 5 km with a 95 per cent confidence level when the network meets the following criteria 1 there are 10 or more stations all within 250 km 2 an azimuthal gap of less than 110 3 a secondary azimuthal gap of less than 160 and 4 at least one station within 30 km to derive location accuracy criteria for near regional 2 5 10 regional 2 5 20 and teleseismic 28 91 networks we use a large data set of exceptionally well located earthquakes and nuclear explosions beyond local distances we find that the secondary azimuthal gap is sufficient to constrain epicentre accuracy and location error increases when the secondary azimuthal gap exceeds 120 when station coverage meets the criterion of a secondary azimuth gap of less than 120 near regional networks provide 20 km accuracy at the 90 per cent confidence level while regional and teleseismic networks provide 25 km accuracy at the 90 per cent confidence level

terrestrial and gps measurements of deformation across the taupo back arc and hikurangi forearc regions in new zealand geodetic measurements of deformation across the taupo back arc and hikurangi forearc regions of new zealand are derived from global positioning system gps measurements made in 1990 and 1991 and triangulation observations made in the 1920s 1950s and 1970s the gps horizontal coordinate differences have precisions of 5 6 mm and the triangulation observations have precisions of 0 7 1 2 arc sec these different kinds of observation allow simultaneous estimation of strain parameters and single epoch coordinates for a total of 184 stations at 68 of which gps observations were made under the assumption that no shift of the scale or orientation of the gps reference frame is embodied in the data from 13 gps stations within the taupo volcanic zone tvz common to the 1990 and 1991 surveys the rotational dilatational and shear components of the deformation rate tensor within the tvz can be estimated for that 1 year interval the principal extension rate from 1990 to 1991 is 0 21 0 09 10 6 yr 68 confidence at an azimuth of 124 13 corresponding to 8 4 mm yr extension over 40 km neither the orthogonal principal extension rate 0 02 0 03 10 6 yr nor the rotation rate 0 06 0 04 rad yr is significant the dilatation rate of 0 23 0 09 10 6 yr is therefore produced by uniaxial extension the data from 75 stations distributed from behind the back arc region and well into the forearc region which were surveyed in at least two of the triangulation or gps epochs between the 1920s and 1991 allow the spatial variation of the shear components of the deformation rate tensor to be estimated the maximum engineering shear rates lie in the range 0 1 0 2 10 6 yr within the tvz and maintain these values with similar orientations in the forearc region to the east the western and southern margins of active extension are reasonably well determined by changes in orientation and magnitude of the shear component these results provide confirmation of the previously less well determined deformation field and in comparison with subduction models indicate that the surface deformation is reflecting variation from north to south of coupling of the subduction plate interface and that both trench suction and gravitational collapse probably contribute to the extension in the forearc region

source model for the mw 6 7 23 october 2002 nenana mountain earthquake alaska from insar 1 the 23 october 2002 nenana mountain earthquake mw 6 7 occurred on the denali fault alaska to the west of the mw 7 9 denali earthquake that ruptured the same fault 11 days later we used 6 interferograms constructed using radar images from the canadian radarsat 1 and european ers 2 satellites to determine the coseismic surface deformation and a source model data were acquired on ascending and descending satellite passes with incidence angles between 23 and 45 degrees and time intervals of 72 days or less modeling the event as dislocations in an elastic half space suggests that there was nearly 0 9 m of right lateral strike slip motion at depth on a near vertical fault and that the maximum slip in the top 4 km of crust was less than 0 2 m the nenana mountain earthquake increased the coulomb stress at the future hypocenter of the 3 november 2002 denali earthquake by 30 60 kpa

strike slip kinematics in central and eastern iran estimating fault slip rates averaged over the holocene 1 according to gps measurements the right lateral shear between central iran and afghan blocks amounts to 16 mm yr a model based on very long term estimates of fault rates suggests the current shear originated about 5 ma ago and has been accommodated by strike slip faulting limited to the western 2 mm yr gowk nayband fault and eastern 14 mm yr sistan system fault edges of the lut block we have used high resolution spot5 pixel size 2 5 m images to measure recent cumulative offsets and estimate slip rates over shorter time periods that average several seismic cycles only recent offsets a few tens of meters have been found along the anar fault inside the central iran plateau and along the sistan faults east of the lut the offset morphologies postdate the last incision of the network and are most probably of holocene age 12 2 ka the corresponding slip rates range between 0 5 0 75 mm yr 1 75 2 5 mm yr 1 5 mm yr 1 2 5 mm yr for the anar east neh west neh and asagie fault respectively these estimates suggest the gps shear rate across the lut may not extrapolate over the holocene they also indicate strike slip faulting is not confined to the lut edges but also occurs in central iran suggesting the ongoing strike slip tectonics might have originated between 8 and 22 ma ago earlier than considered previously and consistent with observations in ne iran

holocene slip rate on the gowk strike slip fault and implications for the distribution of tectonic strain in eastern iran we provide the first quantitative estimate of the holocene slip rate on the gowk strike slip fault in eastern iran the main active strand of the fault cuts lakebed sediments within the south golbaf pull apart basin numerous channels incised into the palaeolake surface are displaced right laterally by 30 5 m at the fault radiocarbon dating of two terrestrial wood fragments constrains the lake desiccation at a maximum of 7 9 0 1 cal ka bp from which we estimate a minimum slip rate for the gowk fault of 3 8 0 7 mm yr22121 this estimate indicates that the gowk fault is one of the most important structures in the accommodation of regional tectonic strain in eastern iran the gowk fault has generated five destructive earthquakes in the past 30 yr at a minimum rate of 3 8 0 7 mm yr22121 the average interval between earthquakes assuming that the fault typically fails in events involving 223c3 m of slip will be 6602013960 yr the southern 223c90 km of the gowk fault the sarvestan segment has no record of historical earthquakes and constitutes a considerable remaining hazard in this region our estimated rate is consistent with geodetic measurements of deformation across the same area and hence suggests that the slip rate on the gowk fault has been constant since at least 223c8 ka ago determining whether or not holocene and late quaternary variations in slip rate occur in general across eastern iran requires similar quantitative studies of fault slip rate across the major faults of eastern iran

the 2006 march 25 fin earthquakes iran insights into the vertical extents of faulting in the zagros simply folded belt summary we investigate the depth of faulting and its connection with surface folding in the zagros simply folded belt of iran our focus is a sequence of earthquakes mw 5 7 5 5 5 2 5 0 4 9 that struck the fin region in the south eastern simply folded belt on 2006 march 25 modelling ground displacements measured with radar interferometry we find that either n or s dipping model reverse faults can reproduce the observed fringe patterns despite the uncertainty in fault orientation we can constrain the vertical extents of rupture to between a top depth of 5 6 km and a bottom depth of 9 10 km consistent with the 8 km centroid depth of the largest earthquake we suggest that the faulting ruptured the thick competent group of paleozoic and mesozoic conglomerates and platform carbonates which makes up the lower part of the sedimentary cover the rupture probably terminated within the precambrian hormuz salt at its base and the cretaceous gurpi marls at its top these mechanically weak layers act as barriers to rupture separating faulting within the competent group from deformation in the layers above and below the pattern of coseismic surface uplift is centred on the common limb of the fin syncline and guniz anticline but is oblique by 20 to the trend of these open symmetric whaleback folds and also overlaps a section of the fin syncline axis these observations suggest that locally surface folding is decoupled from the underlying reverse faulting although the fin syncline and guniz anticline are symmetric structures some other nearby folds show a strong asymmetry with steep or overturned southern limbs consistent with growth above n dipping reverse faults this suggests that the simply folded belt contains a combination of forced folds and detachment folds we also investigate the distribution of locally recorded aftershocks in the weeks following the main earthquakes most of these occurred at depths of 10 30 km with a particularly high concentration of events at 20 25 km these aftershocks therefore lie within the crystalline basement rather than the sedimentary cover and are vertically separated from the main rupture this study confirms earlier suggestions that earthquakes of mw 5 6 are capable of being generated within the thick competent group of paleozoic and mesozoic sediments as well as in the basement below the hormuz salt formation

reassessment of earthquakes 1900 1999 in the eastern mediterranean and the middle east summary we have reappraised locations and surface wave magnitudes of earthquakes this century in the eastern mediterranean and the middle east between 10 and 44 n and 18 and 70 e the results are presented in an improved parametric catalogue of shallow earthquakes h 40 km large enough ms 6 0 to be of interest in seismotectonics and earthquake engineering a considerable number of early events of 6 ms 7 2 not included in other catalogues have been identified and their magnitudes assessed we find that iss isc locations are systematically shifted by 10 30 km to the north or northeast of their macroseismic epicentres also we derived a regional average relationship between log m0 and ms we show that the correlation of magnitude with epicentral intensity is very weak as is expected and a source of error in frequency relations

rapid late pleistocene incision of atlantic passive margin river gorges the direct and secondary effects of rapidly changing climate caused large rivers draining the atlantic passive margin to incise quickly into bedrock beginning about 35 000 years ago measured in samples from bedrock fluvial terraces 10 beryllium shows that both the susquehanna and potomac rivers incised 10 to 20 meter deep gorges along steep convex lower reaches during the last glacial cycle this short lived pulse of unusually rapid down cutting ended by 13 000 to 14 000 years ago the timing and rate of downcutting are similar on the glaciated susquehanna and unglaciated potomac rivers indicating that regional changes not simply glacial meltwater initiated incision

water load definition in the glacio hydro isostatic sea level equation abstract models of glacio hydro isostatic rebound and the concomitant sea level change have been progressively improved over the past three decades recently the procedures used by the group at the australian national university anu for the hydro isostatic component of the theory have been questioned quat sci rev 21 2002 409 although the details of the anu group s procedures have not been published because they are mainly computational in nature rather than representing significant conceptual advances because of this criticism we set out here in detail the procedures that have been used for the treatment of the migration of shorelines as sea levels rise and fall the effect of retreat and advancing grounded ice on shelves and shallow seas and the transitions from grounded to floating ice and vice versa we conclude that there is no basis for the criticism that these formulations and their implementation provide a high resolution and complete description of both sea level change and of the estimates of volumes of ice exchanged with the oceans the results from this formulation are confirmed by the entirely independent analyses of milne et al quat sci rev 21 2002 361 and mitrovica and milne geophys j int 2002 submitted for publication who conclude that our formulation is significantly more accurate than the procedure advocated by peltier science 265 1994 195 rev geophys 36 1998a 603 geophys res lett 25 1998b 3955

the 1994 sefidabeh eastern iran earthquakes revisited new evidence from satellite radar interferometry and carbonate dating about the growth of an active fold above a blind thrust fault in 1994 three shallow earthquakes of mw 6 occurred close together on blind thrusts near sefidabeh in eastern iran in an earlier study of the teleseismic waveforms the geomorphology and the faulting in the epicentral region it was suggested that these earthquakes were associated with the growth of a ridge above a blind thrust fault system whose activity could be detected by its effect on the surface drainage in this study we present a sar interferogram that precisely determines the location and amount of coseismic surface displacements showing that the earthquakes in the sefidabeh sequence probably occurred on en echelon fault segments associated with three stepping ridges we also present u th dates of 100 ka for lake deposits uplifted by the growing ridge from the cumulative dated uplift and knowledge of the surface displacements due to an earthquake sequence we estimate that 120 such events have occurred in the past 100 ka with an average recurrence interval of 830 yr and an average convergence rate of 1 5 mm yr 1 on the sefidabeh thrust each estimate has an uncertainty of a factor of two either way we argue that the sefidabeh fault originally formed by coalescence of many small fault segments and has grown in length at about 2 cm yr 1 in the past 100 ka though the coseismic surface deformation observed in the sar interferogram closely resembles folding the overall topography does not because of inherited topography associated with earlier geological deformation in spite of this the activity of the buried thrust fault can easily be detected by its effect on the surface drainage a significant lesson when interpreting landscapes that are not entirely due to the present day deformation

stress triggering in thrust and subduction earthquakes and stress interaction between the southern san andreas and nearby thrust and strike slip faults 1 we argue that key features of thrust earthquake triggering inhibition and clustering can be explained by coulomb stress changes which we illustrate by a suite of representative models and by detailed examples whereas slip on surface cutting thrust faults drops the stress in most of the adjacent crust slip on blind thrust faults increases the stress on some nearby zones particularly above the source fault blind thrusts can thus trigger slip on secondary faults at shallow depth and typically produce broadly distributed aftershocks short thrust ruptures are particularly efficient at triggering earthquakes of similar size on adjacent thrust faults we calculate that during a progressive thrust sequence in central california the 1983 mw 6 7 coalinga earthquake brought the subsequent 1983 mw 6 0 nunez and 1985 mw 6 0 kettleman hills ruptures 10 bars and 1 bar closer to coulomb failure the idealized stress change calculations also reconcile the distribution of seismicity accompanying large subduction events in agreement with findings of prior investigations subduction zone ruptures are calculated to promote normal faulting events in the outer rise and to promote thrust faulting events on the periphery of the seismic rupture and its downdip extension these features are evident in aftershocks of the 1957 mw 9 1 aleutian and other large subduction earthquakes we further examine stress changes on the rupture surface imparted by the 1960 mw 9 5 and 1995 mw 8 1 chile earthquakes for which detailed slip models are available calculated coulomb stress increases of 2 20 bars correspond closely to sites of aftershocks and postseismic slip whereas aftershocks are absent where the stress drops by more than 10 bars we also argue that slip on major strike slip systems modulates the stress acting on nearby thrust and strike slip faults we calculate that the 1857 mw 7 9 fort tejon earthquake on the san andreas fault and subsequent interseismic slip brought the coalinga fault 1 bar closer to failure but inhibited failure elsewhere on the coast ranges thrust faults the 1857 earthquake also promoted failure on the white wolf reverse fault by 8 bars which ruptured in the 1952 mw 7 3 kern county shock but inhibited slip on the left lateral garlock fault which has not ruptured since 1857 we thus contend that stress transfer exerts a control on the seismicity of thrust faults across a broad spectrum of spatial and temporal scales

cumulative right lateral fault slip rate across the zagros makran transfer zone role of the minab zendan fault system in accommodating arabia eurasia convergence in southeast iran the zendan minab zone is the transition zone between the zagros collision to the west and makran subduction to the east it is also linked to the north with the nayband gowk fault system that bounds the lut block to the east the total convergence rate between arabia and eurasia is estimated to range between 23 and 35 mm yr 1 in a nne trending direction the deformation through the minab zendan system is accommodated within two fault systems the western n160 e trending minab zendan fault system and the eastern north south sabzevaran jiroft fault system the study area is characterized by a well defined succession of quaternary deposit levels the age of these deposits was estimated by archaeological data regional palaeoclimate correlations and constrained by additional in situ10be dating in another paper in this study these deposits exhibit offsets both lateral and vertical that are evaluated by satellite image analysis and gps profiles thanks to offsets and ages the strike slip rates associated with the minab zendan and the sabzevaran jiroft fault systems are calculated to be 5 1 1 3 or 6 6 1 5 and 6 2 0 7 mm yr 1 respectively these results allow an evaluation of the velocity vector of the musandam peninsula oman with respect to the lut block of 11 4 2 0 or 12 9 2 2 mm yr 1 in a n10 15 e direction close to the gps estimates this study also constrains the in plane slip rates for each fault previous works indicate that the zagros accommodates only 10 mm yr 1 of shortening while 10 mm yr 1 should be accommodated by the alborz mountains in northern iran this last 10 mm yr 1 may be accommodated through the nayband gowk system and the east iranian ranges implying that the two fault systems constituting the zagros makran transfer zone have different geodynamic roles the western minab zendan fault system links the makran and zagros deforming zones whereas the northwestern jiroft sabzevaran fault system is transmitting the deformation to the nayband gowk system and then to the alborz ranges the presence of another such strike slip zone within the makran seems to indicate that the accommodation zone between the zagros and makran is wide of the order of 400 km we interpret this deformation pattern that accompanies the genesis of the immature transform zone by a flexure of the slab under the zagros makran transfer zone instead of a tear in the slab that may be expected to induce a sharper transition zone

the 2010 2011 south rigan baluchestan earthquake sequence and its implications for distributed deformation and earthquake hazard in southeast iran we investigate the source processes and tectonic significance of two earthquakes that occurred on 2010 december 20 mw 6 5 and 2011 january 27 mw 6 2 within a desert region south of the town of rigan se iran the two earthquakes which we refer to as the south rigan events occurred close to one another at the northern margin of the shahsavaran mountains a mainly volcanic chain in which the potential for active faulting has not previously been considered in detail surface displacements mapped using sar interferometry multiple event relocation analysis of epicentres body waveform modelling and field measurements of surface rupture together reveal that the 2010 december 20 earthquake involved an average of 1 3 m right lateral slip on a vertical fault trending 210 whereas the 2011 january 27 resulted from 0 6 m of slip on a conjugate left lateral fault striking 310 parallel to the trend of the shahsavaran mountains and confined within a zone of increased coulomb stress from the earlier main shock the main slip for the 2010 and 2011 main shocks failed to reach the surface though minor cracks and en echelon fissures were mapped following both events some of the surface cracks may have been enhanced during a period of minor afterslip in the days following the 2010 main shock using the insights gained from our investigation of the two south rigan earthquakes we perform a regional reconnaissance of the active faulting using spot5 2 5 m satellite imagery we show that distributed n s right lateral faulting is widely distributed north of the shahsavaran mountains we also show evidence for left lateral strike slip faulting parallel to the shahsavaran mountains with a component of extension in the east and shortening in the west which is likely to accommodate regional n s right lateral shearing by clockwise rotation about a vertical axis the distributed strike slip faulting is closely associated with the distribution of towns and villages and constitutes a continuing hazard to local populations

neogene rejuvenation of central appalachian topography evidence for differential rock uplift from stream profiles and erosion rates abstract the persistence of topography within ancient orogens remains one of the outstanding questions in landscape evolution in the eastern north american appalachians this question is manifest in the outstanding problem of whether topographic relief is in a quasi equilibrium state decaying slowly over many millennia or whether relief has increased during the late cenozoic here we present quantitative geomorphic data from the nonglaciated portion of the susquehanna river drainage basin that provide insight into these end member models analysis of channel profiles draining upland catchments in the northern valley and ridge appalachian plateau blue ridge and piedmont provinces reveals that a large number of streams have well defined knickpoints clustered at 300 600 m elevation but not systematically associated with transitions from weak to resistant substrate cosmogenic 10 be inventories of modern stream sediment indicate that erosion rates are spatially variable ranging from 5 30 m myr above knickpoints to 50 100 m myr below knickpoints overall channel gradients normalized for drainage area scale linearly with catchment averaged erosion rates collectively regionally consistent spatial relationships among erosion rate channel steepness and knickpoints reveal an ongoing wave of transient channel adjustment to a change in relative base level reconstructions of relict channel profiles above knickpoints suggest that higher rates of incision are associated with 100 150 m of relative base level fall that accompanied epierogenic rock uplift rather than a change to a more erosive climate or drainage reorganization channel response timescales imply that the onset of relative base level change predates 3 5 ma and may have begun as early as 15 ma we suggest that adjustment of the channel network was likely driven by changes in mantle dynamics along the eastern seaboard of north america during the neogene

fault slip distribution of the 1999 mw 7 1 hector mine california earthquake estimated from satellite radar and gps measurements we use a combination of satellite radar and gps data to estimate the slip distribution of the 1999 m w 7 1 hector mine earthquake a right lateral strikeslip earthquake that occurred on a northwest southeast striking fault in the southern california mojave desert the data include synthetic aperture radar interferograms insar from both ascending and descending orbits radar amplitude image offset fields sario for both ascending and descending azimuth directions and campaign gps observations from 55 stations provided by agnew et al 2002 we model the fault with nine segments derived from the field mapped fault rupture the sario data and aftershock locations we first estimate the dip of each fault segment as well as a single constant strike slip component across each segment resulting in an average dip of 83 to the northeast and slip of up to 5 6 m then we fix the optimal fault segment dip discretize the fault segments into 1 5 km 1 5 km patches and solve for the variable slip distribution using a nonnegative least squares method that includes an appropriate degree of smoothing our preferred solution has both right lateral strike slip and reverse faulting the estimated geodetic moment is 5 93 10 19 n m m w 7 1 similar to seismological estimates indicating that there are insignificant interseismic and postseismic deformation signals in the data we find strike slip displacements of up to 6 0 m and reverse faulting of up to 1 6 m with the maximum slip located just northwest of the epicenter most of the slip is concentrated northwest and south of the epicenter little slip is found on the northeastern branch of the fault the sario data and our modeling indicate that the amount and extent of surface fault rupture were underestimated in the field

glacial isostatic adjustment as a control on coastal processes an example from the siberian arctic the geomorphology of the western siberian arctic coast represents a significant departure from the global trend of holocene delta formation by major rivers the ob and yenisei rivers in western siberia drain into the arctic ocean via estuaries 900 and 500 km long respectively eastern siberian rivers such as the lena indigirka and kolyma terminate at significant marine deltas we show that this spatial variation in coastal geomorphology can be explained by the glacial isostatic adjustment of the region the development and collapse of a peripheral bulge in western siberia associated with the glaciation and subsequent deglaciation of the eurasian ice sheets led to a distinct spatial variation in sea level change that continues to this day in particular since the marked decrease in global scale ice melting ca 7 ka our model predicts a sea level rise at the mouth of the ob river of 14 m compared to a rise of 6 m at the mouth of the lena river which ceased at 3 ka we propose that the enhanced sea level rise in the western siberian arctic associated with peripheral bulge subsidence has prevented the establishment of marine deltas at the mouths of the ob and yenisei rivers we conclude that regional variations in relative sea level change driven by glacial isostatic adjustment should be considered when interpreting large scale coastal morphology and deltaic stratigraphy which is normally assumed to correlate with eustatic fluctuations

fault slip in the 1997 manyi tibet earthquake from linear elastic modelling of insar displacements summary the mw 7 6 1997 manyi earthquake occurred in an area of central northern tibet where sparse vegetation coverage and a lack of human habitation provide excellent conditions for interferometric synthetic aperture radar insar studies we use coseismic pairs of radar images acquired by the esa ers 2 satellite to construct interferograms of the surface displacement field due to the earthquake the location and extent of the coseismic fault rupture are mapped using a combination of optical satellite imagery high resolution digital topography interferometric correlation and azimuth offset measurements in so doing we are able to relate prominent geomorphic features in the fault zone to bends in the fault using elastic dislocation models consistent with this mapped fault trace we then test a range of fault geometries and slip conditions to find the combination which best explains the insar displacements our favoured model contains a reversal in fault dip approximately halfway along its length occurring at the location of a restraining bend slip on this model fault is heterogeneous with two areas of peak slip of 7 m or greater and components of dip slip displacement which vary significantly along strike the success of this model in fitting the data implies that an observed asymmetry in the coseismic interferograms can be explained in terms of the local fault geometry rather than by using non linear elastic rheologies as suggested by earlier authors

active tectonics of the alpine himalayan belt between western turkey and pakistan summary over 80 new fault plane solutions combined with satellite imagery as well as both modern and historical observations of earthquake faulting are used to investigate the active tectonics of the middle east between western turkey and pakistan the deformation of the western part of this region is dominated by the movement of continental material laterally away from the lake van region in eastern turkey this movement helps to avoid crustal thickening in the van region and allows some of the shortening between arabia and eurasia to be taken up by the thrusting of continental material over oceanic type basement in the southern caspian mediterranean makran and black sea thus central turkey bounded by the north and east anatolian strike slip faults is moving west from the van region and overrides the eastern mediterranean at two intermediate depth seismic zones one extending between antalya bay and southern cyprus and the other further west in the hellenic trench the motion of northern iran eastwards from the van region is achieved mainly by a conjugate system of strike slip faults and leads to the low angle thrusting of iran over the southern caspian sea the seismicity of the caucasus shows predominantly shortening perpendicular to the regional strike but there is also some minor elongation along the strike of the belt as the causcasus overrides the caspian and black seas the deformation of the eastern part of this region is dominated by the shortening of iran against the stable borders of turkmenistan and afghanistan the north east direction of compression seen in zagros is also seen in north east iran and the kopet dag where the shortening is taken up by a combination of strike slip and thrust faulting large structural as well as palaeomagnetic rotations are likely to have occurred in ne iran as a result of this style of deformation north south strike slip faults in southern iran allow some movement of material away from the collision zone in ne iran towards the makran subduction zone where genuinely intermediate depth seismicity is seen within this broad deforming belt large areas such as central turkey nw iran azerbaijan central iran and the southern caspian appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200 300 km wide the motion of these blocks can usefully be described by poles of rotation the poles presented in this paper predict motions consistent with those observed and also predict the opening of the gulf of iskenderun ne of cyprus the change within the zagros mountains from strike slip faulting in the nw to intense thrusting in the se and the relatively feeble seismicity in se iran baluchistan this description also explains why the north south structures along the iran afghanistan border do not cut the east west ranges of the makran within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation even though motions at the surface may be concentrated on faults the evolution of fault systems within the active zones is controlled by geometric constraints such as the requirement that simultaneously active faults do not in general intersect many of the active processes discussed in this paper particularly large scale rotations and lateral movement along the regional strike are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them

the 2004 may 28 baladeh earthquake mw 6 2 in the alborz iran overthrusting the south caspian basin margin partitioning of oblique convergence and the seismic hazard of tehran we use teleseismic waveform analysis and locally recorded aftershock data to investigate the source processes of the 2004 baladeh earthquake which is the only substantial earthquake to have occurred in the central alborz mountains of iran in the modern instrumental era the earthquake involved slip at 10 30 km depth with a south dipping aftershock zone also restricted to the range 10 30 km which is unusually deep for iran these observations are consistent with co seismic slip on a south dipping thrust that projects to the surface at the sharp topographic front on the north side of the alborz this line is often called the khazar fault and is assumed to be a south dipping thrust which bounds the north side of the alborz range and the south side of the south caspian basin though its actual structure and significance are not well understood the lack of shallower aftershocks may be due to the thick pile of saturated overpressured sediments in the south caspian basin that are being overthrust by the alborz a well determined earthquake slip vector in a direction different from the overall shortening direction across the range determined by gps confirms a spatial separation partitioning of left lateral strike slip and thrust faulting in the alborz these strike slip and thrust fault systems do not intersect within the seismogenic layer on the north side though they may do so on the south the earthquake affected the capital tehran and reveals a seismic threat posed by earthquakes north of the alborz located on south dipping thrusts as well as by earthquakes on the south side of the range closer to the city

dynamic topography and long term sea level variations there is no such thing as a stable continental platform abstract globally uniform i e eustatic sea level trends with time scales approaching 100 myr have been inferred from both seismic and backstripping stratigraphic analysis at a small set of geographic sites that are presumed to lie on stable continental platforms and passive continental margins characterized by simple thermal subsidence histories e g the new jersey margin the western african margin we demonstrate using mantle flow simulations based on high resolution seismic tomography that both the new jersey margin and the conjugate western african margin have been subject to orders of 100 m of dynamic i e flow induced topography change over the last 30 myr we also show that the changing pattern of downwelling mantle flow associated with plate subduction is a significant contributor to the background eustatic sea level trend which is also of order 100 m during the 30 myr time window therefore late cenozoic variations of dynamic topography on these passive margin sites are comparable to the eustatic sea level changes and can partially mask the latter furthermore even if the observed trend could be accurately corrected for local dynamic topography variation the residual eustatic signal does not merely reflect changes in mean spreading rates at mid ocean ridges we conclude that the observed long term sea level variations at so called stable sites cannot be interpreted as eustatic moreover previous analyses that have used long term sea level trends as a proxy for spreading rates and geochemical fluxes must be revisited

active tectonics and late cenozoic strain distribution in central and eastern iran 1 right lateral shear between central iran and afghanistan is accommodated on n s right lateral strike slip faults surrounding the aseismic dasht e lut north of 34 n the right lateral shear is accommodated on left lateral faults that rotate clockwise about vertical axes little is known of the late tertiary and younger offsets and slip rates on the active fault systems results that are important for understanding the regional tectonics we use observations from satellite imagery to identify displaced geological and geomorphological markers which we use in conjunction with the overall morphology and orientation of the active fault systems to estimate the total cumulative right lateral shear estimates of cumulative fault movements from offset features and inferred vertical axis rotation of fault bounded blocks suggest that the late cenozoic strain is concentrated toward the eastern margin of iran along the sistan shear zone where bedrock offsets of at least 70 km are observed across the active faults the geomorphology of the deh shir anar and great kavir strike slip faults in central iran suggest that although little shortening is accommodated across this region they might still be active and hence capable of producing earthquakes present day activity on these faults in central iran would not be expected from distributions of instrumental and historical earthquakes although speculative the late tertiary strain distribution described in this paper is consistent with what we know of the present day rates of shear in eastern iran and provides a framework to which later more detailed work can be added

rapid laurentide ice sheet advance towards southern last glacial maximum limit during marine isotope stage 3 abstract marine isotope stage mis 3 58 28 ka is a period of intermediate global ice volume between mis 4 and the last glacial maximum of mis 2 here we report geologic evidence for southern laurentide ice sheet rapid growth to near its last glacial maximum extent after a period with limited ice in the southernmost hudson bay lowland a14c age on wood in lacustrine sediments interbedded with glacial tills in central eastern wisconsin dates a laurentide ice sheet advance southwards to an extent at least equivalent to at least its 17 ka deglacial limit by 39 1 0 4 ka this advance ended before 30 4 0 9 ka based on another 14c date on wood in lacustrine sediment overlying the till layers this advance is consistent with 14c ages from michigan and iowa and gulf of mexico runoff records that support a concurrent southern laurentide ice sheet advance we infer changes in north american ice volume using ice sheet model simulations from a large ensemble that are consistent with 14c data and gulf of mexico discharge constraints the simulations show the laurentide ice sheet growing from a volume equivalent to 25 30 m of global mean sea level gmsl before 40 ka to 40 45 m of gmsl at 40 ka and reaching 65 70 m gmsl by 30 ka consistent with glacial isostatic adjustment assessments of near to intermediate field sea level data we thus show from our terrestrial field data and ice sheet model simulations that an individual ice sheet can grow rapidly which has only been inferred previously for global ice volume from gsml records

deformation in response to landscape evolution during glacial cycles on the u s atlantic passive margin abstract elevations of pleistocene highstand formations that lie across the south carolina and northern georgia coastal plain lie well above those of reconstructed past sea levels this discrepancy has been attributed to some combination of tectonics glacial isostatic adjustment and or deviations in estimated ocean volumes derived from the marine 18 o record to reconcile these anomalous elevations we combine a landscape evolution model with models of coupled ice sheet sea level and solid earth deformation along the southern u s atlantic passive margin to estimate erosion deposition and corresponding isostatic response since marine isotope stage mis 11 410 ka we find that along shore changes in modeled paleo shoreline elevations are similar to measured elevations along 100s of kilometers up to 10 m of shoreline uplift since mis 11 may be attributed to isostatic feedback in response to sediment redistribution

global analysis of the stream power law parameters based on worldwide 10be denudation rates abstract the stream power law expressed as e kamsn where e is erosion rate lt 1 k is an erodibility coefficient t 1l 1 2m a is drainage area l 2 s is channel gradient l l and m and n are constants is the most widely used model for bedrock channel incision despite its simplicity and limitations the model has proved useful for topographic evolution knickpoint migration palaeotopography reconstruction and the determination of rock uplift patterns and rates however the unknown parameters k m and n are often fixed arbitrarily or are based on assumptions about the physics of the erosion processes that are not always valid which considerably limits the use and interpretation of the model in this study we compile a unique global data set of published basin averaged erosion rates that use detrital cosmogenic 10be these data n 1457 enable values for fundamental river properties to be empirically constrained often for the first time such as the concavity of the river profile m n ratio or concavity index the link between channel slope and erosion rate slope exponent n and substrate erodibility k these three parameters are calculated for 59 geographic areas using the integral method of channel profile analysis and allow for a global scale analysis in terms of climatic tectonic and environmental settings in order to compare multiple sites we also normalize n and k using a reference concavity index m n 0 5 a multiple regression analysis demonstrates that intuitive or previously demonstrated local scale trends such as the correlation between k and precipitation rates do not appear at a global scale our results suggest that the slope exponent is generally 1 meaning that the relationship between erosion rate and the channel gradient is nonlinear and thus support the hypothesis that incision is a threshold controlled process this result questions the validity of many regional interpretations of climate and or tectonics where the unity of n is routinely assumed

fault identification for buried strike slip earthquakes using insar the 1994 and 2004 al hoceima morocco earthquakes summary the 1994 m w 6 0 and 2004 m w 6 5 al hoceima earthquakes are the largest to have occurred in morocco for 100 yr and give valuable insight into the poorly understood tectonics of the area bodywave modelling indicates the earthquakes occurred on near vertical strike slip faults with the nodal planes oriented nw se and ne sw distinguishing between the primary fault plane and auxiliary planes using either geodetic or seismic data is difficult due to the spatial symmetry in deformation fields and radiation pattern of moderately sized buried strikeslip earthquakes preliminary studies using aftershock locations and surface observations have been unable to identify the orientation of the primary fault plane for either earthquake conclusively we use radar interferometry and aftershock relocation of the earthquake sequence to resolve the ambiguity for the 2004 earthquake inverting the interferograms for a uniform slip model based either of the two potential nodal planes results in similar misfits to the data however the ne sw best fit fault plane has an unrealistically high fault slip to length ratio and we conclude the nw se striking nodal plane is the primary fault plane and slip was right lateral we carry out tests on synthetic data for a buried strike slip earthquake in which the orientation of the fault plane is known a priori independent of geometry missing data and correlated noise models produced assuming the auxiliary plane to be the fault plane have very high fault slip to length ratios the 1994 earthquake had a smaller magnitude and comparisons of model misfits and slip to length ratios do not conclusively indicate which of the nodal planes is the primary fault plane nonetheless the insar data provides valuable information by improving the accuracy of the earthquake location by an order of magnitude we carry out a multiple event relocation of the entire earthquake sequence including aftershocks making use of the absolute locations for the 1994 and 2004 main shocks from our insar study the aftershock locations are consistent with a nw se orientated fault plane in 2004 and suggests that the 1994 earthquake occurred on a ne sw fault perpendicular to the fault which ruptured in 2004 previous tectonic models of the area proposed a bookshelf model of block rotation with nne ssw left lateral faults this model requires modification to accommodate the observation of right lateral slip on a nw se fault plane for the 2004 earthquake and we prefer to interpret the fault orientations as due to a zone of distributed shear with a right lateral fault striking at 115 and conjugate clockwise rotating left lateral faults striking at 25

regolith production and transport at the susquehanna shale hills critical zone observatory part 2 insights from meteoric 10be 1 regolith mantled hillslopes are ubiquitous features of most temperate landscapes and their morphology reflects the climatically biologically and tectonically mediated interplay between regolith production and downslope transport despite intensive research few studies have quantified both of these mass fluxes in the same field site here we present an analysis of 87 meteoric 10be measurements from regolith and bedrock within the susquehanna shale hills critical zone observatory ssho in central pennsylvania meteoric 10be concentrations in bulk regolith samples n 73 decrease with regolith depth comparison of hillslope meteoric 10be inventories with analyses of rock chip samples n 14 from a 24 m bedrock core confirms that 80 of the total inventory is retained in the regolith the systematic downslope increase of meteoric 10be inventories observed at ssho is consistent with 10be accumulation in slowly creeping regolith 0 2 cm yr 1 regolith flux inferred from meteoric 10be varies linearly with topographic gradient determined from high resolution light detection and ranging based topography along the upper portions of hillslopes at ssho however regolith flux appears to depend on the product of gradient and regolith depth where regolith is thick near the base of hillslopes meteoric 10be inventories at the north and south ridgetops indicate minimum regolith residence times of 10 5 3 7 and 9 1 2 9 ky respectively similar to residence times inferred from u series isotopes in ma et al 2013 the combination of our results with u series derived regolith production rates implies that regolith production and erosion rates are similar to within a factor of two on ssho hillcrests

glacially influenced late pleistocene stratigraphy of a passive margin new jersey s record of the north american ice sheet abstract glacial isostasy and the sediment supply changes associated with the waxing and waning of ice sheets have dramatic effects on the stratigraphy of adjacent continental shelves in ancient stratigraphic records the glacial influences on such deposits could be difficult to recognize because of the removal of coeval terrestrial glacial deposits by erosion this study illustrates the effects of the laurentide ice sheet on a basin near its maximum limit the new jersey continental shelf analysis of 1600 km of geopulse uniboom minisparker and airgun profiles reveals four depositional sequences that have a maximum thickness of 75 m near the shelf edge sequences i and iv correspond to the major glacial interglacial sea level changes at marine isotope chron mic 6 5e and 2 1 whereas sequences ii and iii reflect smaller scale sea level fluctuations during chrons 4 3c and 3b 3a respectively sequences i and iv are characterized by relatively thick low stand to early transgressive deposits near the shelf edge formed during times of increased sediment supply but are thin and discontinuous across much of the shelf reflection horizons in these units deepen northward in the northern half of the study area due to collapse of a peripheral bulge that formed at the margin of the laurentide ice sheet the hudson river moved from a more southerly drainage pattern to the modern hudson shelf valley position possibly under the influence of the advancing peripheral bulge sequences ii and iii are largely preserved within a broad mid shelf swale likely created by the migration of an ancestral hudson river and their thickness implies much higher sedimentation rates during chrons 4 and 3 than seen today if the terrestrial glacial record was eroded the increased rates of sedimentation during the pleistocene dominance of sediments derived from northern new england and northward tilting of strata could be interpreted as a result of uplift of a northern source area the unusually high frequency of the relative sea level oscillations 20 kyr the concentration of sediment supply during low stands and early transgressions and the correspondence of sea level change with climatic change could be used to infer their relationship to a nearby ice sheet geologists studying deposits formed during times of widespread continental glaciation should consider possible glacial influences on the stratigraphy of mid latitude deposits even in the absence of sediments directly deposited by ice

implications of sediment flux dependent river incision models for landscape evolution 1 developing a quantitative understanding of the factors that control the rate of river incision into bedrock is critical to studies of landscape evolution and the linkages between climate erosion and tectonics current models of long term river network incision differ significantly in their treatment of the role of sediment flux we analyze the implications of various sediment flux dependent incision models for large scale topography in an attempt 1 to identify quantifiable and diagnostic differences between models that could be detected from topographic data or from the transient responses of perturbed systems and 2 to explain the apparent ubiquity of mixed bedrock alluvial channels in active orogens although certain forms of the various models can be discarded as inconsistent with morphological data we find that the relative intrinsic concavity indices of detachment and transport limited systems defined herein largely dictate whether the various models can be tied to distinctive steady state morphologies preliminary data suggest that no such diagnostic differences may exist and other methods must be developed to test models accordingly we develop and explore differences in the scaling behavior of topographic relief and the extent of detachment versus transport limited channels as a function of rock uplift rate that may allow discrimination among various models further we explore potentially diagnostic differences in the rates and patterns of transient channel response to changes in rock uplift rate in addition to general differences between detachment and transport limited systems our analysis identifies an interesting hysteresis in landscape evolution hybrid channels at the threshold between detachment and transport limited conditions are expected to act as detachment limited systems in response to an increase in rock uplift rate or base level fall and as transport limited systems in response to a decrease in rock uplift rate especially during postorogenic topographic decline the analyses presented set the stage for field studies designed to test quantitatively the various river incision models that have been proposed

global ice volume during mis 3 inferred from a sea level analysis of sedimentary core records in the yellow river delta abstract estimates of global ice volume during the glacial phase of the most recent ice age cycle are characterized by significant uncertainty reflecting the relative paucity of geological constraints on sea level relevant to this time interval for example during the middle stages of marine isotope stage 3 published estimates of peak global mean sea level gmsl relative to the present range from 25 m to 87 m the large uncertainty in gmsl at mis 3 has significant implications for estimates of the rate of ice growth in the period leading to the last glacial maximum 26 ka we refine estimates of global ice volume during mis 3 by employing sediment cores in the bohai and yellow sea that record a migration of the paleoshoreline at 50 37 ka through a transition from marine to brackish conditions in particular we correct relative sea level at these sites for contamination due to glacial isostatic adjustment using a sea level calculation that includes a gravitationally self consistent treatment of sediment redistribution and compaction and estimate a peak global mean sea level of 38 7 m during the interval 50 37 ka with suitable sedimentary core records the approach described herein can be extended to refine existing constraints on global ice volume across the entire glacial period

glacial hydrology and erosion patterns a mechanism for carving glacial valleys article i nfo article history most glacial erosion models assume that erosion rates are proportional to ice sliding velocity while recent studies have shown that water plays a major role in modulating sliding velocities the impact it might have on erosion rates is still unclear here we incorporate subglacial hydrology into a glacial erosion model that is based on a sliding rule our results explicitly highlight that adding subglacial hydrology has profound impacts on the temporal and spatial patterns of glacial erosion first it suggests that erosion might mainly occur during melting seasons when subglacial water pressure is large and effective pressure is low i e before the channels fully develop and reduce the water pressure at the ice bedrock interface which promotes sliding and erosion second the distribution of erosion is bimodal with a peak at the equilibrium line altitude and as we demonstrate enhanced erosion at much lower altitudes within the ablation area where water due to melting abounds this has important implications because it explains why glacial erosion can simultaneously

active faulting and seismicity of the dasht e bayaz region eastern iran summary the dasht e bayaz left lateral strike slip fault system in ne iran ruptured over a length of ca 120 km during two earthquakes in 1968 and 1979 we constrain source parameters of the 1968 august 31 dasht e bayaz and 1979 november 27 khuli buniabad earthquakes by analysing long period body wave seismograms both earthquakes involved complex rupture processes with at least two subevents in each case coseismic surface ruptures and cumulative scarps in alluvium indicate fault segmentation on numerous short ca 20 km long strands with small pull aparts between them the earthquake subevents seen in the seismograms probably relate to this segmentation the total cumulative offset on the fault system is estimated at ca 4 5 km this is small compared to the total amount of late tertiary deformation expected in this part of iran and indicates that the dasht e bayaz fault may be relatively young distributed strike slip faulting is widespread in the region and there are indications that the dasht e bayaz fault is evolving from several short faults that are coalescing these results are important not only for understanding of the regional tectonics but for the development and evolution of strike slip faults in general

solutions of the stream power equation and application to the evolution of river longitudinal profiles 1 erosion by bedrock river channels is commonly modeled with the stream power equation we present a two part approach to solving this nonlinear equation analytically and explore the implications for evolving river profiles first a method for non dimensionalizing the stream power equation transforms river profiles in steady state with respect to uniform uplift into a straight line in dimensionless distance elevation space second a method that tracks the upstream migration of slope patches which are mathematical entities that carry information about downstream river states provides a basis for constructing analytical solutions slope patch analysis explains why the transient morphology of dimensionless river profiles differs fundamentally if the exponent on channel slope n is less than or greater than one and why only concave up migrating knickpoints persist when n 1 at migrating knickpoints slope patches and the information they carry are lost a phenomenon that fundamentally limits the potential for reconstructing tectonic histories from bedrock river profiles stationary knickpoints which can arise from spatially varying uplift rates differ from migrating knickpoints in that slope patches and the information they carry are not lost counterparts to migrating knickpoints called stretch zones are created when closely spaced slope patches spread to form smooth curves in distance elevation space these theoretical results are illustrated with examples from the california king range and the central apennines

seismotectonic rupture process and earthquake hazard aspects of the 2003 december 26 bam iran earthquake summary the catastrophic 2003 m w 6 6 bam earthquake in southern iran attracted much attention and has been studied with an abundance of observations from synthetic aperture radar teleseismic seismology aftershock studies strong ground motion geomorphology remote sensing and surface field work many reports have focused on the details of one or other data type producing interpretations that either conflict with other data or leave questions unanswered this paper is an attempt to look at all the available data types together to produce a coherent picture of the coseismic faulting in 2003 and to examine its consequences for active tectonics and continuing seismic hazard in the region we conclude that more than 80 per cent of the moment release in the main shock occurred on a near vertical right lateral strike slip fault extending from the city of bam southwards for about 15 km with slip of up t o2mb utmostly restricted to the depth range 2 7 km analysis of the strong ground motion record at bam is consistent with this view and indicates that the extreme damage in the city can be attributed at least in part to the enhancement of ground motion in bam because of its position at the end of the northward propagating rupture little of the slip in the main shock reached the earth s surface and more importantly aftershocks reveal that 12 km vertical extent of a deeper part of the fault system remained unruptured beneath the coseismic rupture plane at depths of 8 20 km this may represent a substantial remaining seismic hazard to the reconstructed city of bam we believe that some oblique reverse slip up to 2 m and less than 20 per cent of the released seismic moment occurred at a restricted depth of 5 7 km on a blind west dipping fault that projects to the surface at the bam baravat escarpment an asymmetric anticline ridge that is the most prominent geomorphological feature in the area this fault did not rupture significantly at shallow levels in 2003 and it may also represent a continuing seismic hazard widespread distributed surface ruptures north of the city are apparently unrelated to substantial slip at depth and may be the result of enhanced ground motion related to northward propagation of the rupture the faulting at bam may be in the early stages of a spatial separation partitioning between the reverse and strike slip components of an oblique convergence across the zone such a separation is common on the continents though in this case the slip vectors between the two faults differ only by 20 as a substantial strike slip component remains on the obliquereverse fault the bam earthquake is one in a series of large earthquakes involving faulting along the western edge of the lut desert in addition to the unruptured parts of the faults near bam itself continuing and substantial hazard is represented by unruptured neighbouring faults particularly blind thrusts along the jebel barez mountains to the south and strike slip faulting at sarvestan to the west

present day crustal deformation and plate kinematics in the middle east constrained by gps measurements in iran and northern oman summary a network of 27 gps sites was implemented in iran and northern oman to measure displacements in this part of the alpine himalayan mountain belt we present and interpret the results of two surveys performed in 1999 september and 2001 october gps sites in oman show northward motion of the arabian plate relative to eurasia slower than the nuvel 1a estimates e g 22 2m m yr 1 at n8 5 e instead of 30 5 mm yr 1 at n6 e at bahrain longitude we define a gps arabia eurasia euler vector of 27 9 0 5 n 19 5 1 4 e 0 41 0 1 myr 1 the arabia eurasia convergence is accommodated differently in eastern and western iran east of 58 e most of the shortening is accommodated by the makran subduction zone 19 5 2m m yr 1 and less by the kopet dag 6 5 2m m yr 1 west of 58 e the deformation is distributed in separate fold and thrust belts at the longitude of tehran the zagros and the alborz mountain ranges accommodate 6 5 2m m yr 1 and 8 2m m yr 1 respectively the right lateral displacement along the main recent fault in the northern zagros is about 3 2m m yr 1 smaller than what was generally expected by contrast large rightlateral displacement takes place in northwestern iran up to 8 mm yr 1 the central iranian block is characterized by coherent plate motion internal deformation 2m m yr 1 sites east of 61 e show very low displacements relative to eurasia the kinematic contrast between eastern and western iran is accommodated by strike slip motions along the lut block to the south the transition zone between zagros and makran is under transpression with right lateral displacements of 11 2m m yr 1

influence of glacial isostatic adjustment on river evolution along the u s mid atlantic coast abstract long term river evolution depends partly on crustal deformation which shapes the topography crossed by rivers on glacial timescales ice sheet growth and decay can produce crustal vertical motion of 10 mm yr resulting from the solid earth s adjustment to variations in ice and water loads comparable to tectonically driven rates in the most rapidly uplifting mountains on earth this process of glacial isostatic adjustment gia can influence river courses and drainage basins substantially particularly near former ice margins we explore the extent to which gia influenced the evolution of rivers along the united states east coast during the last glacial cycle we compute gravitationally self consistent gia responses that incorporate recent constraints on the laurentide ice sheet history through the last glacial build up phase and we connect the predicted variations in topography to abrupt changes in river dynamics recorded in the hudson delaware susquehanna and potomac rivers from 40 ka to present to the extent that increases in sediment transport capacity imply increases in river incision rate the gia driven changes in slope and drainage area are consistent with episodes of erosion and sedimentation observed in the hudson delaware and potomac rivers but inconsistent with the observed accelerated river incision in the susquehanna river at 30 14 ka these analyses add to a growing body of evidence showing that gia strongly influences river evolution over millennial timescales

an episode of rapid bedrock channel incision during the last glacial cycle measured with 10be we use 10 be to infer when how fast and why the susquehanna river incised through bedrock along the u s atlantic seaboard one of the world s most prominent and ancient passive margins although the rate at which large rivers incise rock is a fundamental control on the development of landscapes relatively few studies have directly measured how quickly such incision occurs either in tectonically active environments or along passive margins exposure ages of fluvially carved bedrock strath terraces preserved along the lower susquehanna river demonstrate that even along a passive margin large rivers are capable of incising through rock for short periods of time at rates approaching those recorded in tectonically active regions such as the himalayas over eighty samples collected along and between three prominent levels of strath terraces within holtwood gorge indicate that the susquehanna river incised more than 10 meters into the appalachian piedmont during the last glacial cycle beginning 36 ka incision rates increased dramatically and remained elevated until 14 ka the northern half of the susquehanna basin was glaciated during the late wisconsinan however similar rates and timing of incision occurred in the unglaciated potomac river basin immedi ately to the south the concurrence of incision periods on both rivers suggests that glaciation and associated meltwater were not the primary drivers of incision instead it appears that changing climatic conditions during the late pleistocene promoted an increase in the frequency and magnitude of flood events capable of exceeding thresholds for rock detachment and bedrock erosion thus enabling a short lived episode of rapid incision into rock although this study has constrained the timing and rate of bedrock incision along the largest river draining the atlantic passive margin the dates alone cannot explain fully why or by what processes this incision occurred however cosmogenic dating offers compelling evidence that episodes of rapid incision into bedrock are tied to glacial cycles and changes in global climate these results and the methods we employ provide valuable insights into the nature of bedrock channel incision not only along the susquehanna river and passive margins but also across a wide range of settings around the globe because river incision into bedrock transmits the effects of changing climate and tectonics through fluvial networks to hillslopes comprehending when where and why rivers incise has important implications for the evolution of land scapes

sediment and rock strength controls on river incision into bedrock recent theoretical investigations suggest that the rate of river incision into bedrock depends nonlinearly on sediment supply challenging the common assumption that incision rate is simply proportional to stream power our measurements from laboratory abrasion mills support the hypothesis that sediment promotes erosion at low supply rates by providing tools for abrasion but inhibits erosion at high supply rates by burying underlying bedrock beneath transient deposits maximum erosion rates occur at a critical level of coarse grained sediment supply where the bedrock is only partially exposed fine grained sediments provide poor abrasive tools for lowering bedrock river beds because they tend to travel in suspension experiments also reveal that rock resistance to fluvial erosion scales with the square of rock tensile strength our results suggest that spatial and temporal variations in the extent of bedrock exposure provide incising rivers with a previously unrecognized degree of freedom in adjusting to changes in rock uplift rate and climate furthermore we conclude that the grain size distribution of sediment supplied by hillslopes to the channel network is a fundamental control on bedrock channel gradients and topographic relief

the 2003 bam iran earthquake rupture of a blind strike slip fault a magnitude 6 5 earthquake devastated the town of bam in southeast iran on 26 december 2003 surface displacements and decorrelation effects mapped using envisat radar data reveal that over 2 m of slip occurred at depth on a fault that had not previously been identified it is common for earthquakes to occur on blind faults which despite their name usually produce long term surface effects by which their existence may be recognised however in this case there is a complete absence of morphological features associated with the seismogenic fault that destroyed bam

postglacial sea level change on a rotating earth first results from a gravitationally self consistent sea level equation we present and solve a gravitationally self consistent sea level equation which governs postglacial sea level variations on a spherically symmetric self gravitating viscoelastic and rotating earth we find that the inclusion of a glacio isostatically induced rotational excitation can significantly affect previous predictions of both present day sea level rates and postglacial sea level histories which were based on a theory that assumed a non rotating earth model to illustrate we consider present day sea level rates and tide gauge corrections along the us east coast and relative sea level curves in the far field of the late pleistocene ice sheets

insights into the 1968 1997 dasht e bayaz and zirkuh earthquake sequences eastern iran from calibrated relocations insar and high resolution satellite imagery summary the sequence of seismicity in the dasht e bayaz and zirkuh region of northeastern iran which includes 11 destructive earthquakes within a period of only 30 years forms one of the most outstanding examples of clustered large and intermediate magnitude seismic activity in the world we perform a multiple event relocation analysis with procedures to remove systematic location bias of 169 earthquakes most of which occurred in the period 1968 2008 to better image the distribution of seismicity within this highly active part of iran the geographic locations of the clustered earthquakes were calibrated by the inclusion of phase arrivals from seismic stations at short epicentral distances and also by matching the relative locations of the three largest events in the study to their mapped surface ruptures the two independent calibration methods provide similar results that increase our confidence in the accuracy of the distribution of relocated epicentres these calibrated epicentres combined with the mapping of faults from high resolution satellite imagery and from an insar derived constraint on fault location in one case allow us to associate individual events with specific faults and even with specific segments of faults to better understand the nature of the active tectonics in this region during the past four decades several previous assumptions about the seismicity in this region are confirmed 1 that the 1968 august 30 mw 7 1 dasht e bayaz earthquake nucleated at a prominent segment boundary and left step in the fault trace 2 that the 1968 september 11 mw 5 6 aftershock occurred on the dasht e bayaz fault at the eastern end of the 1968 rupture and 3 that the 1976 november 7 mw 6 0 qayen earthquake probably occurred on the e w left lateral avash fault we show in addition that several significant events including the 1968 september 1 and 4 mw 6 3 and 5 5 ferdows earthquakes the 1979 january 16 mw 6 5 and 1997 june 25 mw 5 9 boznabad events and the 1979 december 7 mw 5 9 kalat e shur earthquake are likely to have ruptured previously unknown faults our improved description of the faulting involved in the 1968 1997 earthquake sequence highlights the importance of rupturing of conjugate left and right lateral faults in closely spaced events or potentially even within a single earthquake as was likely the case at the eastern end of the 1979 november 27 mw 7 1 khuli buniabad main shock the high level of clustered seismic activity probably results from the simultaneous activity on left and right lateral faults an inherently unstable arrangement that must evolve rapidly the combination of high resolution satellite imagery and calibrated earthquake locations is a useful tool for investigating active tectonics even in the absence of detailed field observations

was the laurentide ice sheet significantly reduced during marine isotope stage 3 accurately reconstructing the paleogeography of the laurentide ice sheet lis during marine isotope stage 3 mis 3 ca 57 000 to ca 29 000 yr b p is critical for understanding glacial growth toward the last glacial maximum lgm refining sea level histories and studying the earth system response to rapid climate change events here we present a geochronological data set useful for testing hypotheses of global sea level and refining ice sheet configuration through this interval data n 735 span the entire mis 3 interval and consist of 14c determinations n 651 cosmogenic exposure ages n 52 and optically stimulated luminescence dates n 32 on that basis we hypothesize that the central region of the lis underwent a dramatic reduction in ice from ca 52 to 40 ka key to this hypothesis are geological records at sites in the hudson bay lowlands east central canada that suggest a marine incursion and development of terrestrial landscapes we show that these landscapes are consistent with recently published glacial isostatic adjustment predictions that include widespread deglaciation of the eastern labrador sector of the lis with ice buildup over the western keewatin sector at 42 ka ice growth from this minimum toward the lgm is likely to have been rapid the agreement between this data set and modeling predictions prompts the reassessment of key late pleistocene records including heinrich events loess deposition in the continental united states and sedimentological records from the gulf of mexico

coseismic slip model of the 2008 wenchuan earthquake derived from joint inversion of interferometric synthetic aperture radar gps and field data 1 we derived a coseismic slip model for the mw 7 9 2008 wenchuan earthquake on the basis of radar line of sight displacements from alos interferograms gps vectors and geological field data available interferometric synthetic aperture radar insar data provided a nearly complete coverage of the surface deformation along both ascending fine beam mode and descending orbits scansar to scansar mode the earthquake was modeled using four subfaults with variable geometry and dip to capture the simultaneous rupture of both the beichuan fault and the pengguan fault our model misfits show that the insar and gps data are highly compatible the combined inversion yields a 93 variance reduction the best fit model has fault planes that rotate from shallow dip in the south 35 to nearly vertical dip toward the north 70 our rupture model is complex with variations in both depth and rake along two major fault strands in the southern segment of the beichuan fault the slip is mostly thrust 13 m and occurred principally in the upper 10 km of the crust the rupture progressively transformed to right lateral strike slip as it propagated northeast with maximum offsets of 7 m our model suggests that most of the moment release was limited to the shallow part of the crust depth less than 10 km we did not find any shallow slip deficit in the slip depth distribution of this mixed mechanism earthquake aftershocks were primarily distributed below the section of the fault that ruptured coseismically

climatic control of bedrock river incision bedrock river incision drives the development of much of earth s surface topography and thereby shapes the structure of mountain belts and modulates earth s habitability through its effects on soil erosion nutrient fluxes and global climate although it has long been expected that river incision rates should depend strongly on precipitation rates quantifying the effects of precipitation rates on bedrock river incision rates has proved difficult partly because river incision rates are difficult to measure and partly because non climatic factors can obscure climatic effects at sites where river incision rates have been measured here we present measurements of river incision rates across one of earth s steepest rainfall gradients which show that precipitation rates do indeed influence long term bedrock river incision rates we apply a widely used empirical law for bedrock river incision to a series of rivers on the hawaiian island of kaua i where mean annual precipitation ranges from 0 5 metres to 9 5 metres ref 12 over 70 per cent of the global range and river incision rates averaged over millions of years can be inferred from the depth of river canyons and the age of the volcanic bedrock both a time averaged analysis and numerical modelling of transient river incision reveal that the long term efficiency of bedrock river incision across kaua i is positively correlated with upstream averaged mean annual precipitation rates we provide theoretical context for this result by demonstrating that our measurements are consistent with a linear dependence of river incision rates on stream power the rate of energy expenditure by the flow on the riverbed these observations provide rare empirical evidence for the long proposed coupling between climate and river incision suggesting that previously proposed feedbacks among topography climate and tectonics may occur