laboratory simulation of clast abrasion brewer paul lewin j 2002 laboratory simulation of clast abrasion earth surface processes and landforms 27 pp 145 164 rae2008

self driven mode switching of earthquake activity on a fault system theoretical results based on two different modeling approaches indicate that the seismic response of a fault system to steady tectonic loading can exhibit persisting fluctuations in the form of self driven switching of the response back and forth between two distinct modes of activity the first mode is associated with clusters of intense seismic activity including the largest possible earthquakes in the system and frequency size event statistics compatible with the characteristic earthquake distribution the second mode is characterized by relatively low moment release consisting only of small and intermediate size earthquakes and frequency size event statistics following a truncated power law the average duration of each activity mode scales with the time interval of a large earthquake cycle in the system the results are compatible with various long geologic paleoseismic and historical records the mode switching phenomenon may also exist in responses of other systems with many degrees of freedom and nonlinear dynamics 1999 elsevier science b v all rights reserved

clast shape analysis and clast transport paths in glacial environments a critical review of methods and the role of lithology the reconstruction and tracing of transport paths in glaciated and other environments have a long tradition in the earth sciences we here present a dataset of clast shape samples from a worldwide selection of glaciated mountain environments in order to assess the reliability of this approach overall and the role of lithology on the performance of clast shape measurements in particular our findings demonstrate that the widely used ra c40 co variance approach is applicable to 63 of the 19 catchments investigated while the alternative rwr c40 approach is more widely applicable to 75 of these catchments a systematic assessment of mixing of lithologies at the catchment scale demonstrates that such mixing leads to pronounced overlaps between different control envelopes that had previously been separated thereby removing the discriminatory power of the method mixing of similar lithologies between different catchments shows an even more extreme loss of discriminatory power which strongly suggests that lithology plays a primary role in determining clast shape and that catchment specific processes are superimposed systematic analysis of the dataset also shows that nearly all catchments apart from two can be grouped into two types type i relates to sites in lesser mountain ranges and is characterised by dominantly blocky forms in the subglacial realm highlighting significant reworking processes type ii sites are dominantly in high mountain environments and characterised by a high similarity between subglacial and fluvial control envelopes this indicates that although reworking may be pronounced it is not necessarily effective enough to remove the platy shape that most likely results from extraglacial and supraglacial inputs our study highlights the potential of clast shape analysis as a tool that allows generic processes to be identified between catchments thereby enabling an understanding of debris cascades in glaciated mountain environments we finish with recommendations for ensuring that future clast shape studies are robust reproducible and comparable between different sites

the gutenberg richter or characteristic earthquake distribution which is it abstract paleoearthquake and fault slip rate data are combined with the cit usgs catalog for the period 1944 to 1992 to examine the shape of the magnitude frequency distribution along the major strike slip faults of southern california the resulting distributions for the newport inglewood elsinore garlock and san andreas faults are in accord with the characteristic earthquake model of fault behavior the distribution observed along the san jacinto fault satisfies the gutenberg richter relationship if attention is limited to segments of the san jacinto that are marked by the rupture zones of large historical earthquakes or distinct steps in fault trace the observed distribution along each segment is consistent with the characteristic earthquake model the gutenberg richter distribution observed for the entirety of the san jacinto may reflect the sum of seismicity along a number of distinct fault segments each of which displays a characteristic earthquake distribution the limited period of instrumental recording is insufficient to disprove the hypothesis that all faults will display a gutenberg richter distribution when averaged over the course of a complete earthquake cycle but given that 1 the last 5 decades of seismicity are the best indicators of the expected level of small to moderate size earthquakes in the next 50 years and 2 it is generally about this period of time that is of interest in seismic hazard and engineering analysis the answer to the question posed in the title of the article at least when concerned with practical implementation of seismic hazard analysis at sites along these major faults appears to be the characteristic earthquake distribution

controlled moraine development and debris transport pathways in polythermal plateau icefields examples from tungnafellsjokull iceland a modern landsystems analogue for plateau icefield glaciation is presented based upon tungnafellsjokull in the arid cold interior of iceland landform mapping and intensive clast form analysis on three separate forelands occupied during the little ice age reveal variability in the morphology of moraines and the degree of clast modification which is interpreted as a function of the complex interplay between a the efficacy of glacial erosion b passive versus active debris transfer mechanisms and c the volume of debris provision for ice marginal freeze on mechanisms a steep outlet bounded by rockwalls produced a landform assemblage and debris transport signature typical of valley glaciers whereas two unconfined outlets produced a landform sediment imprint typical of polythermal conditions this comprises subglacial bedforms relating to the initiation of warm based ice by strain heating below icefalls at the plateau edge terminating at arcs of ice cored controlled moraine representative of frozen snout conditions patterns in clast form data on the unrestricted forelands reflect the characteristics of glacier dynamics and thermal regimes at the margin of a plateau icefield where bedrock steps of sufficient size to initiate strain heating and bedrock abrasion and plucking are located only a short distance from the marginal freeze on conditions of a snout creating debris rich folia and controlled moraine additional englacial debris may well have been carried to the glacier margin through the development of ogives and englacial thrusting at the base of the icefall thereby explaining the occurrence of striae on clasts that have otherwise been little modified by glacial abrasion copyright 2010 john wiley sons ltd

a note on adding viscoelasticity to earthquake simulators abstract here i describe how time dependent quasi static stress transfer can be implemented in an earthquake simulator code that is used to generate long synthetic seismicity catalogs most existing seismicity simulators use precomputed static stress interaction coefficients to rapidly implement static stress transfer in fault networks with typically tens of thousands of fault patches the extension to quasi static deformation which accounts for viscoelasticity of earth s ductile lower crust and mantle involves the precomputation of additional interaction coefficients that represent time dependent stress transfer among the model fault patches combined with defining and evolving additional state variables that track this stress transfer the new approach is illustrated with application to a california wide synthetic fault network

a viscoelastic earthquake simulator with application to the san francisco bay region earthquake simulation on synthetic fault networks carries great potential for characterizing the statistical patterns of earthquake occurrence i present an earthquake simulator based on elastic dislocation theory it accounts for the effects of interseismic tectonic loading static stress steps at the time of earthquakes and postearthquake stress readjustment through viscoelastic relaxation of the lower crust and mantle earthquake rupture initiation and termination are determined with a coulomb failure stress criterion and the static cascade model the simulator is applied to interacting multifault systems one a synthetic two fault network and the other a fault network representative of the san francisco bay region the faults are discretized both along strike and along dip and can accommodate both strike slip and dip slip stress and seismicity functions are evaluated over 30 000 yr trial time periods resulting in a detailed statistical characterization of the fault systems seismicity functions such as the coefficient of variation and a and b values exhibit systematic patterns with respect to simple model parameters this suggests that reliable estimation of the controlling parameters of an earthquake simulator is a prerequisite to the interpretation of its output in terms of seismic hazard

coseismic deformation from earthquake faulting on a layered spherical earth summary a method for calculating the static displacement field following earthquake faulting in a layered spherical earth is presented at shallow levels the earth s layering is characterized by sharp jumps in bulk and shear moduli at the conrad discontinuity and the moho and is therefore important to consider when evaluating crustal deformation the solution to the equations of static equilibrium is represented as a superposition of spheroidal and toroidal components that each depend on spherical harmonic degree and the moment tensor a method that has recently been applied to the problem of wave propagation on a layered spherical earth is here applied to the static deformation field by representing the point source in terms of discontinuities in the displacement stress vector the green s function for a particular source geometry is derived directly numerical tests are presented to verify the accuracy of the method and to illustrate the effects of sphericity and layering on the calculated deformation fields the effect of sphericity is generally less than about 2 per cent of maximum deformation within 100 km of an earthquake source at crustal depths comparisons between the deformation calculated on a spherical homogeneous earth and spherical layered earth show that up to 20 per cent errors would be introduced if the earth s layered structure were ignored the effect of layering is strongest for sources with a strong horizontal slip component

stress diffusion along rupturing plate boundaries an analysis is made of viscoelastic lithosphere asthenosphere coupling in the time dependent redistribution of stress along plate boundaries or other seismic lineaments following great earthquakes the study is based on a generalization by rice of elsasser s model of stress diffusion in which general elastic plane stress deformations are allowed in lithospheric plates which are coupled in an elementary way to a maxwellian viscoelastic asthenosphere solutions are developed which describe the large scale quasistatic distribution of thickness averaged in the lithosphere at or near stationary or travelling rupture zones modeled here by either crack like zones of fixed stress drop or dislocation type slip zones sudden ruptures shed load onto the asthenosphere which is gradually transferred back to the lithosphere by a slow relaxation process the spatial and temporal characteristics of the predicted stress alterations suggest a significant role of lithosphere asthenosphere coupling effects in triggering interactions of great earthquakes patterns of prolonged aftershock activity and the breaking of barriers or gaps by time dependent stressing

debris transport in a temperate valley glacier haut glacier d arolla valais switzerland hambrey m j goodsell becky glasser n f 2005 debris transport in a temperate valley glacier haut glacier d arolla valais switzerland journal of glaciology 51 172 pp 139 146

sedimentary facies of a glacially influenced continental succession in the pennsylvanian jericho formation galilee basin australia recent work on the late palaeozoic ice age in eastern australia has shown the joe joe group in the eastern galilee basin queensland to be of critical importance as it is one of few records of pennsylvanian glacial activity outside south america this paper presents detailed sedimentological data from which the late palaeozoic environment of the region is reconstructed and which consequently allows for robust comment on the broader gondwanan glaciation the jericho formation in the lower joe joe group was deposited in an active extensional basin in lacustrine to fluvial environments during the mid namurian to early stephanian the region experienced a cool climate during this time and polythermal mountain or valley type glaciers periodically advanced into the area from highlands to the north east the jericho formation preserves a suite of proglacial to terminal glacial facies that is characterized by massive and stratified diamictites deposited from debris flows massive and horizontally laminated conglomerates and sandstones deposited from hyperconcentrated density flows laminated siltstones with outsized clasts and interlaminated siltstone conglomerate deposited through ice rafting into lakes and sedimentary dykes and breccias deposited through overpressurization of groundwater beneath permafrost non glacial facies are dominated by fluvial sandstones and lacustrine overbank siltstones the glacigenic rocks of the jericho formation are confined to discrete packages recording three separate glacial advances during the latest namurian to late westphalian this arrangement is consistent with the temporal distribution of glacigenic rocks from around the remainder of australia and gondwana which supports the theory that glacial deposits occurred in discrete intervals the joe joe group is a key succession in the world in this context as at this time eastern australia provides the only unequivocal evidence of a namurian westphalian glaciation outside south america the continuous record of sedimentation through the pennsylvanian and early permian is indicative of significant warming between glacial intervals which is difficult to reconcile with the development of long lived cold based ice sheets across the supercontinent 2007 the authors journal compilation

characteristics of recessional moraines at a temperate glacier in se iceland insights into patterns rates and drivers of glacier retreat icelandic glaciers are sensitive to climate variability on short term timescales owing to their north atlantic maritime setting and have been undergoing ice marginal retreat since the mid 1990s recent patterns rates and drivers of ice frontal retreat at skalafellsjokull se iceland are examined using small scale recessional moraines as a geomorphological proxy these small scale recessional moraines exhibit distinctive sawtooth planform geometries and are constructed by a range of genetic processes associated with minor ice margin re advance including i combined push squeeze mechanisms ii bulldozing of pre existing proglacial material and iii submarginal freeze on remote sensing investigations and lichenometric dating highlight sequences of annually formed recessional moraines on the northern and central parts of the foreland conversely moraines are forming on a sub annual timescale at the southeastern skalafellsjokull margin using annual moraine spacing as a proxy for annual ice margin retreat rates imrrs we demonstrate that prominent periods of glacier retreat at skalafellsjokull are coincident with those at other icelandic outlet glaciers as well as those identified at greenlandic outlet glaciers analysis of imrrs and climate data suggests summer air temperature sea surface temperature and the north atlantic oscillation have an influence on imrrs at skalafellsjokull with the glacier appearing to be most sensitive to summer air temperature on the basis of further climate data analyses we hypothesise that sea surface temperature may drive air temperature changes in the north atlantic region which in turn forces imrrs the increase in sea surface temperature over recent decades may link to atmospheric driven variations in north atlantic subpolar gyre dynamics

trends of grain sizes on gravel bars in the rio chagres panama abstract we examined the trends of grain sizes along the upper 414 km 2 of the mountainous rio chagres drainage basin in panama gravel bars were sampled along 40 km of the rio chagres and five major tributary streams using a transect pebble count of median diameter lithology and clast rounding although previous investigators have found that downstream fining can be obscured by inputs of colluvial sediment and other local controls in mountain drainages we decided to examine the trends of grain sizes along a tropical mountain river where rapid weathering and high capability of transport might be capable of overriding the input effects of colluvium specifically we tested the hypotheses that downstream fining would be present as a result of selective sorting and that weak felsic particles would decrease in size preferentially to strong mafic particles because of abrasion statistical analyses reveal a weak downstream decrease of sediment size on gravel bars along the study reach of the rio chagres with a sternberg diminution coefficient for felsic and mafic grains of 0 013 and 0 017 respectively felsic clasts have thicker weathering rinds and become rounded downstream faster than mafic particles but tumbling mill tests of abrasion show no significant differences in rate of mass loss in relation to lithology and downstream decreases in grain size are similar between lithologies dividing the study reach into six sub reaches bounded by major tributary junctions we further tested the hypothesis that downstream trends in fining might be obscured at the basin scale by sediment input from tributaries but that trends in grain sizes might be more visible at the reach scale between tributaries we did not find any consistent trends in grain size between tributaries stream width appears to assert a local control on grain size coarse particles are associated with narrow channel reaches whereas smaller particles are associated with wide channel reaches

glacial remobilization cycles as revealed by lateral moraine sediment bodalsbreen glacier foreland western norway the proglacial area of bodalsbreen glacier in western norway contains nine moraine ridges formed at the maximum of the little ice age ad 1755 and during the subsequent glacier retreat ad 1767 2000 the frontal moraines are composed of a sandy diamicton whereas the lateral ones consist of only boulder sized clasts without any matrix these lateral moraines seemingly are composed of a very high proportion of mature clasts a notion supported by detailed clast roundness and shape analyses furthermore there is evidence for a decline in clast maturity between the outer older three and the inner younger three moraine ridges this decline is interpreted as a change from recycled to freshly plucked clasts thus the more mature clasts in the outer moraines are thought to consist of sediment that has been recycled in the glacial system whereas the less mature clasts on the inner moraine ridges comprise younger glacially freshly plucked material the holocene glacial history of the study area with a

san francisco bay area earthquake simulations a step toward a standard physical earthquake model earthquakes in california s san francisco bay area are likely to be more strongly affected by stress interaction than earthquakes in any other place in the world because of the region s closely spaced subparallel distribution of faults i believe therefore that meaningful quantification of earthquake probability and hazard in the bay area can be made only with the guidance provided by physically based and regionwide earthquake models that account for this interaction this article represents a first step in developing a standard physical earthquake model for the san francisco bay area through realistic 3000 year simulations of earthquakes on all of the area s major faults these simulations demonstrate that a standard physical earthquake model is entirely feasible they illustrate its application and they blueprint its construction a standard physical earthquake model provides the mechanism to integrate fully the diverse disciplines within the earthquake research community as a platform for data utilization and verification a physical earthquake model can employ directly any earthquake property that is measurable in the field or in the laboratory to tune and test its seismicity products as a platform for probability forecasts a physical earthquake model can supply rational estimates of every imaginable earthquake statistic while simultaneously satisfying all slip and earthquake rate constraints as a platform for hazard analysis a physical earthquake model can compute earthquake shaking intensity from first principles by convolving a full suite of rupture scenarios with site specific dislocation green s functions physical earthquake models have advanced greatly in the last decade simulations of earthquake generation and recurrence are now sufficiently credible that such calculations can begin to take substantial roles in scientific studies of earthquake probability and hazard manuscript received 9 march 1999

sedimentology of latero frontal moraines and fans on the west coast of south island new zealand exposures through the lgm latero frontal moraine loops at sites along the west coast of south island new zealand reveal a depositional environment that was dominated by the progradation of steep fronted debris flow fed fans manifest in crudely stratified to massive diamictons arranged in sub horizontal to steeply dipping clinoforms and containing discontinuous bodies of variably sorted stratified sediment lfa 1 the fans were constructed by debris covered glaciers advancing over outwash plains as recorded by well stratified and horizontally bedded gravels sands and diamicts lfa 0 the ice contact slopes of the fans are offlapped by retreat phase deposits in the form of glacilacustrine depo centres lfa 2 which record the existence of moraine dammed lakes interdigitation of lake rhythmites and subaerial to subaqueous sediment gravity flow deposits documents intense debris flow activity on unstable moraine fan surfaces glacier readvances in all catchments are documented by glacitectonic disturbance and localized hydrofracturing of lfa 2 followed by the emplacement of schist dominated debris flow fed fans lfa 3 inside and over the top of the earlier latero frontal moraine fan loops contorted and disturbed bedding in lfa 3 reflects its partial deposition in supraglacial positions clast lithologies in lfas 1 and 3 reveal that two distinct transport pathways operated during moraine construction with an early period of latero frontal fan construction involving mixed lithologies and a later period of ice contact supraglacial fan construction dominated by schist lithologies from the mountains these two periods of deposition were separated by a period of moraine abandonment and paraglacial reworking of ice contact slopes to produce lfa 2 the occurrence of lfa 3 at all sites indicates that the glacier readvance phase responsible for its deposition was not localized or glacier specific and involved the transfer of large volumes of schist possibly due to rock slope failures onto glacier surfaces the absence of any sediment that could be unequivocally classified as subglacial till reflects the dominance of debris flow and glacifluvial processes in latero frontal moraine construction in this hyper humid west coast setting

younger dryas glacial landsystems in north west scotland an assessment of modern analogues and palaeoclimatic implications abstract by explicitly linking process to form landsystem models developed in modern environments provide powerful tools for the reconstruction of past environments from the sedimentological and geomorphological record some landform characteristics however may originate by more than one process equifinality so although a particular depositional model may fit the data it is not necessarily the correct one here we critically examine the use of modern analogues to interpret glacial landforms focusing on hummocky moraine a distinctive landform association consisting of numerous sharp crested moraine mounds and ridge fragments which occurs on many valley floors in upland britain detailed studies of examples of younger dryas age in the north west highlands of scotland show that they represent ice contact fans which have been affected to varying degrees by ice push and subglacial deformation and that they formed at active oscillating ice margins the sedimentological data are inconsistent with an origin by englacial thrusting as has been proposed for similar moraines elsewhere in upland britain on the basis of morphological criteria comparison with modern glacial landsystems shows that although aspects of hummocky moraines in the study area have close modern counterparts none provides an exact analogue in all respects this may reflect the distinctive climate of western scotland during the younger dryas estimates of mean july temperatures in the younger dryas in scotland based on chironomid assemblages are c 8 c at sea level when combined with reconstructed equilibrium line altitudes for contemporaneous glaciers these estimates indicate mean annual precipitation totals in the range of 2358 337 mm yr 1 at sea level in nw scotland c 26 higher than present day values the implied heavy snowfall suggests that glaciers in western scotland during the younger dryas were of high activity type unlike modern glaciers in svalbard for example high glacier velocities and high winter precipitation would suppress permafrost development despite low mean annual temperatures the climatic environment also favoured rapid oscillations of glacier margins during both glacier build up and retreat phases climatic factors combined with the availability of large quantities of subglacial debris led to the development of distinctive glacial landsystems which may have no direct modern analogue

modeling of periodic great earthquakes on the san andreas fault effects of nonlinear crustal rheology we analyze the cycle of great earthquakes along the san andreas fault with a finite element numerical model of deformation in a crust with a nonlinear viscoelastic rheology the viscous component of deformation has an effective viscosity that depends exponentially on the inverse absolute temperature and nonlinearly on the shear stress the elastic deformation is linear crustal thickness and temperature are constrained by seismic and heat flow data for california the models are for anti plane strain in a 25 km thick crustal layer having a very long vertical strike slip fault the crustal block extends 250 km to either side of the fault during the earthquake cycle that lasts 160 years a constant plate velocity p 2 17 5 mm yr 1 is applied to the base of the crust and to the vertical end of the crustal block 250 km away from the fault the upper half of the fault is locked during the interseismic period while its lower half slips at the constant plate velocity the locked part of the fault is moved abruptly 2 8 m every 160 years to simulate great earthquakes the results are sensitive to crustal rheology models with quartzite like rheology display profound transient stages in the velocity displacement and stress fields the predicted transient zone extends about 3 4 times the crustal thickness on each side of the fault significantly wider than the zone of deformation in elastic models models with diabase like rheology behave similarly to elastic models and exhibit no transient stages the model predictions are compared with geodetic observations of fault parallel velocities in northern and central california and local rates of shear strain along the san andreas fault the observations are best fit by models which are 10 100 times less viscous than a quartzite like rheology since the lower crust in california is composed of intermediate to mafic rocks the present result suggests that the in situ viscosity of the crustal rock is orders of magnitude less the rock viscosity determined in the laboratory

gravitational viscoelastic postseismic relaxation on a layered spherical earth viscoelastic relaxation of a ductile asthenosphere underlying a purely elastic plate is a strong candidate process for explaining anomalous rates of crustal deformation observed following large earthquakes the nongravitational treatment of pollitz 1992 which is valid on a global scale and includes the effects of compressibility is here extended to permit the calculation of gravitational viscoelastic relaxation for a specified spherically layered viscoelastic rheology following an earthquake in an elastic layer the simple approximations we adopt make the resulting treatment particularly suitable for near field calculations for an asthenosphere with a maxwell rheology the effect of gravitational coupling is manifested only many relaxation times after the earthquake as obtained by previous investigators its effect is generally to speed up the long wavelength component of the relaxation process and attenuate the overall vertical displacement pattern several subtle features common to the relaxation behavior from several different fault types thrust rift and strike slip are identified the effect of gravitational coupling on horizontal displacements is consistent with flexure of the upper elastic plate driven by the corresponding effects on the vertical displacement stress diffusion away from the source region generally exhibits pulse like behavior which is dispersive in both space and time if the asthenosphere is confined to a relatively narrow channel then the dispersion branches governing relaxation are radically altered and stress diffusion effects far from the coseismic rupture zone exhibit a complicated time dependence reflecting the competing tendencies of toroidal and spheroidal mode relaxation

when faults communicate viscoelastic coupling and earthquake clustering in a simple two fault system 1 3 d finite element models of a simplified northern and southern san andreas type fault system are presented with the goal of better understanding how great earthquakes m 7 5 on one major segment of a fault can affect the earthquake cycle on another colinear fault segment separated from the first by an asesimically creeping segment we find that the earthquake cycles of the two seismogenic fault segments become coupled as the lower crustal viscosity and or the fault separation distance are decreased further models with a 10 30 difference in relative fault breaking strengths exhibit a bi modal distribution of repeat times for each fault resulting in earthquakes that appear clustered in time

distribution of glaciofluvial sediment within and on the surface of a high arctic valley glacier marthabreen svalbard marthabreen is a 7 8km long valley glacier in sw spitsbergen the glacier is partially covered by a layer of angular debris derived from rockfall in its accumulation area pierced in places by pinnacles and ridges of glaciofluvial sediment these concentrations of glaciofluvial sediment fall into three categories 1 debris pinnacles 2 longitudinal sediment dykes 3 longitudinal ridge accumulations debris pinnacles are slabs of sediment predominantly sands gravels and cobbles elevated to the glacier surface along thrusts longitudinal sediment dykes are low 1m high ridges of sorted sand and gravels which are not associated with penetrative ice structures their occurrence downglacier of sediment dykes and debris pinnacles suggests that they originate as supraglacial or englacial channels or tunnels filled by sediment derived from the dykes or thrusts the presence of large quantities of glaciofluvial sediment on the surface of marthabreen does not imply englacial water flow at high levels within the glacier but is related to ice deformational processes such as thrusting and folding of debris rich stratification copyright 1999 john wiley sons ltd

earthquake cycle fault zones and seismicity patterns in a rheologically layered lithosphere we study the coupled evolution of earthquakes and faults in a model consisting of a seismogenic upper crust governed by damage rheology over a viscoelastic substrate the damage rheology has two types of functional coefficients 1 a generalized internal friction separating states associated with material degradation and healing and 2 damage rate coefficients for positive degradation and negative healing changes the evolving damage modifies the effective elastic properties of material in the upper crust as a function of the ongoing deformation this simulates the creation and healing of fault systems in the upper seismogenic zone in addition to the vertically averaged thin sheet approximation we introduce a green function for three dimensional elastic half space for the instantaneous component of deformation the formulation accounts in an internally consistent manner for evolving deformation fields evolving fault structures aseismic energy release and spatiotemporal seismicity patterns these developments allow us to simulate long histories of crustal deformation and to study the simultaneous evolution of regional earthquakes and faults for various model realizations to focus on basic features of a large strike slip fault system we first consider a simplified geometry of the seismogenic crust by prescribing initial conditions consisting of a narrow damage zone in an otherwise damage free plate for this configuration the model generates an earthquake cycle with distinct interseismic preseismic coseismic and postseismic periods model evolution during each period is controlled by a subset of physical properties which may be constrained by geophysical geodetic rock mechanics and seismological data in the more generic case with a random initial damage distribution the model generates large crustal faults and subsidiary branches with complex geometries the simulated statistics depend on the space time window of the observational domain the results indicate that long healing timescale h describing systems with relatively long memory leads to the development of geometrically regular fault systems and the characteristic frequency size earthquake distribution conversely short h relatively short memory leads to the development of a network of disordered fault systems and the gutenberg richter earthquake statistics for intermediate values of h the results exhibit alternating overall switching of response from periods of intense seismic activity and the characteristic earthquake distribution to periods of low seismic activity and gutenberg richter statistics

high precision 40ar 39ar age of the gas emplacement into the songliao basin the problem of determining an exact isotopic age of hydrocarbon emplacement is complex because minerals suitable for dating with common isotopic methods are often lacking in the sedimentary domain however the igneous quartz from the cretaceous volcanic rocks that host the gas reservoir in the songliao basin northeastern china contains abundant secondary fluid inclusions with high concentrations of k and high partial pressures of methane trapped during gas emplacement quartz with abundant k rich fluid inclusions provides an excellent closed system well suited for 40 ar 39 ar dating three igneous quartz samples were measured by stepwise crushing to release the inclusion based argon gas all three samples yielded well defined isochrons with ages in close agreement precisely constraining the gas emplacement at 42 4 0 5 ma 2 below the daqing oil field in the songliao basin extending possible gas reservoirs from the upper cretaceous to the middle eocene

genesis stability and preservation potential of large lateral moraines of alpine valley glaciers towards a unifying theory based on findelengletscher switzerland abstract lateral moraines are prominent features of glaciated landscapes in high mountain environments and key landforms in glacier and palaeoclimatic reconstructions yet compared to smaller moraines they have been little studied and several aspects are not well understood we here present detailed sedimentological results from the lateral moraines of findelengletscher in sw switzerland to gain new insights into the formation of these landforms the lateral moraines studied here stand up to 140 m above the valley floor are over 3 km long and strongly asymmetrical in cross profile with distal slopes between 29 and 36 and proximal slopes that are commonly 41 64 but locally reach angles of up to 80 recorded lithofacies comprise loose clast and matrix supported stratified diamicts and intercalated sorted sediments in the distal slopes and near the crestline overconsolidated matrix supported massive and weakly stratified diamicts and streaked out sorted sediment lenses in the core and proximal slopes and partly intercalated dark brown layers overlain by loose and consolidated diamicts exposed in near vertical walls in the proximal flank these are interpreted as supraglacial debris flow units with intercalated fluvial wash horizons glaciotectonised and subglacial traction till with boudinaged and streaked out sediment lenses and palaeosoils overlain by sediment produced by overtopping of the former moraine surface during a subsequent advance of the glacier clast shape analysis and process observations reveal that the dominant mode of transport is subglacial and glaciofluvial and that the main mode of sediment delivery to the moraines is by debris flows after the material has been transferred from the bed via englacial debris bands and meltout at the surface this differs from previous studies that found that a supraglacial source was dominant sedimentary structures clast fabric and process observations during the 1979 1980 readvance of findelengletscher strongly suggest that proximal layers of reworked pre existing sediments and or basal traction zone till have been plastered onto the moraine core in several locations causing a high degree of overconsolidation and strongly clustered fabric eigenvalues s 1 0 94 with clustering parallel to the moraine crestline this suggests that a combination of basal lateral drag and lateral plastering produces the observed proximal stability and ensures a high preservation potential we develop a conceptual model that describes alpine lateral moraines as structurally complex landforms that do not just record a single event as often surmised and we discuss implications for palaeo glacier reconstruction and the application of numerical dating methods

evidence for a landslide origin of new zealand s waiho loop moraine the waiho loop moraine has been interpreted as evidence for younger dryas cooling in southern new zealand but recent dating and climatological studies have questioned this idea a detailed analysis of the sedimentology of the moraine suggests it was formed after a large landslide onto the franz josef glacier triggered a glacial surge independent of climate forcing

development of sediment landform associations at cold glacier margins dry valleys antarctica hambrey m j fitzsimons s j 2010 development of sediment landform associations at cold glacier margins dry valleys antarctica sedimentology 57 3 857 882 michael hambrey is corresponding author sponsorship marsden fund of new zealand university of otago research committee nerc grant no ner a s 2000 01256

implications of fault slip rates and earthquake recurrence models to probabilistic seismic hazard estimates abstract increasingly fault slip rates are being used to constrain earthquake recurrence relationships for site specific probabilistic seismic hazard ground motion assessments this paper shows the sensitivity of seismic hazard assessments to variations in recurrence models and parameters that incorporate fault slip rates two models are considered to describe the partitioning of the slip rate or seismic moment rate into various magnitude earthquakes an exponential magnitude distribution and a characteristic earthquake distribution assuming an exponential distribution the activity rate n m 0 is constrained by the upper bound magnitude m u the b value for the region and the fault slip rate s for a given s variations in m u and b value have significant effects on recurrence and computed hazard depending on whether the assumption is made that the seismicity rate is constant or the moment rate is constant there is increasing evidence that the characteristic earthquake model is more appropriate for individual faults than the exponential magnitude distribution based on seismicity data from areas having repeated large earthquakes a generalized recurrence density function is developed and the resulting recurrence relationship requires only m u b value and s a comparison of the recurrence relationships from this model with the historical seismicity and paleoseismicity data on the wasatch and san andreas faults shows a good match the computed hazard based on the characteristic earthquake model differs from that obtained for the exponential model as a function of the fault to site distance and the acceleration level one check on the recurrence models using slip rate is to compare over large regions activity rates based on seismicity data and slip rate data such a comparison in the western transverse ranges shows a reasonable match for both the exponential and characteristic earthquake models in the moderate to large magnitude range

the glacial sedimentology and geomorphological evolution of an outwash head moraine dammed lake south island new zealand extensive exposures through the glacial landforms around southern lake pukaki new zealand comprise seven lithofacies lfs 1 7 lfs 1 3 are grouped together as lfa 1 pukaki member and record pulsed subaqueous grounding line fan progradation cohesionless debris flows underflow activity and rhythmite deposition by suspension settling iceberg rafting of dropstones and pulsed traction current activity localized disturbance of these deposits by glacitectonic deformation and multi generational hydrofracture fills records minor readvances by the glacier snout and the emplacement of a glacitectonite lf 4 derived from cannibalization of glacilacustrine sediments lfs 4 6 are grouped together as lfa 2 twizel member and record direct glacigenic deposition of glacitectonite lf 4 subglacial traction till lf 5 and supraglacially dumped boulder rubble lf 6 stratigraphic relationships between lfa 1 with lfa 2 record the oscillatory behaviour of the former tasman glacier snout when it formed a calving margin in a proglacial and locally supraglacial lake dammed by a glacitectonically disturbed outwash head and lateral moraine ridges this is entirely consistent with the landform sediment record of its coeval terrestrial margins where flutings and push moraines are diagnostic of active temperate glacier recession from a glacially overridden outwash head the latter being recorded by the vertically stacked sub horizontally bedded and coarse grained gravels of lf 7 waitaki member previous proposals that late pleistocene lake damming was initiated by an ice cored moraine arc appear unfounded because the glacilacustrine deposits only lie above the altitude of the outwash head lateral moraine arc in locations where they have been glacitectonically compressed alternatively it is proposed that the overdeepened subglacial topography was produced by the construction of an outwash head leading to a glacilacustrine sediment sink which operates at times when the expanded tasman glacier actively retreats from the outwash head apex the changing landsystem imprint related to the shrinkage of the tasman glacier records spatio temporal landsystem change involving evolution from a coupled landsystem to a moraine dammed to an uncoupled landsystem

chemical and physical weathering in new zealand s southern alps monitored by bedload sediment major element composition abstract the haast and clutha rivers drain opposing flanks of new zealand s southern alps major element analyses of grain size fractions 2 1 mm 1 mm 355 m 355 63 m and 2 o 5 concentrations in all river sediment suggests that most cao is bound in a combination of phosphate bearing minerals such as apatite along with other heavy mineral phases with similar hydrodynamic properties e g epidote chemical index of alteration cia values for grain size fractions from both rivers are similar haast 54 63 clutha 49 61 and do not systematically vary with grain size or sample location al 2 o 3 cao na 2 o k 2 o a cn k relationships suggest that cia values are controlled by albite muscovite mixing rather than feldspar weathering both a cn k relationships and modal mineralogical calculations from clutha river samples indicate progressive downstream attrition of muscovite from coarser to finer grain size fractions in contrast haast river sediments display less variable normative muscovite concentrations and no downstream enrichment depletion trends the haast and clutha watersheds have drastically different sediment yields but the similarity of sediments from both rivers indicates that there is minimal climatic control on the weathering intensity of fluvial sediments rather bedload geochemistry is controlled primarily by mechanical breakdown of lithic fragments and subsequent preferential attrition of muscovite albite quartz the geochemical signature of mechanical attrition and hydrodynamic winnowing is more developed in clutha river samples because of longer sediment residence time within its fluvial system these findings suggest that high standing island hsi fluvial sedimentary evolution is characterized by the dominance of physical weathering processes and the absence of silicate chemical weathering signatures

statistical physics approach to understanding the multiscale dynamics of earthquake fault systems 1 earthquakes and the faults upon which they occur interact over a wide range of spatial and temporal scales in addition many aspects of regional seismicity appear to be stochastic both in space and time however within this complexity there is considerable self organization we argue that the occurrence of earthquakes is a problem that can be attacked using the fundamentals of statistical physics concepts of statistical physics associated with phase changes and critical points have been successfully applied to a variety of cellular automata models examples include sandpile models forest fire models and particularly slider block models these models exhibit avalanche behavior very similar to observed seismicity a fundamental question is whether variations in seismicity can be used to successfully forecast the occurrence of earthquakes several attempts have been made to utilize precursory seismic activation and quiescence to make earthquake forecasts some of which show promise

crustal deformation in great california earthquake cycles periodic crustal deformation associated with repeated strike slip earthquakes is computed for the following model a depth l h extending downward from the earth s surface at a transform boundary between uniform elastic lithospheric plates of thickness h is locked between earthquakes it slips an amount consistent with remote plate velocity vpl after each lapse of earthquake cycle time tcy lower portions of the fault zone at the boundary slip continuously so as to maintain constant resistive shear stress the plates are coupled at their base to a maxwellian viscoelastic asthenosphere through which steady deep seated mantle motions compatible with plate velocity are transmitted to the surface plates the coupling is described approximately through a generalized elsasser model we argue that the model gives a more realistic physical description of tectonic loading including the time dependence of deep slip and crustal stress buildup throughout the earthquake cycle than do simpler kinematic models in which loading is represented as imposed uniform dislocation slip on the fault below the locked zone parameters of the model are chosen to fit seismic and geologic constraints and the apparent time dependence of surface strain rates along presently locked traces of the 1857 and 1906 san andreas ruptures we fix vpl 35 mm yr tcy 160 years and l 9 11 km based on earthquake nucleation depths the geodetic data are then found to be described reasonably within the context of a model that is locally uniform along strike and symmetric about a single san andreas fault strand by lithosphere thickness h 20 30 km and elsasser relaxation time tr 10 16 years we therefore suggest that the asthenosphere appropriate to describe crustal deformation on the earthquake cycle time scale lies in the lower crust and perhaps crust mantle transition zone and has an effective viscosity between about 2 1018 and 1019 pa s depending on the thickness assigned to the asthenospheric layer predictions based on the chosen set of parameters are also consistent with data on variations of contemporary surface strain and displacement rates as a function of distance from the 1857 and 1906 rupture traces although the fit is degraded by asymmetry relative to the fault and by slip on adjacent fault strands

the influence of rock mass strength on glacial valley cross profile morphometry a case study from the southern alps new zealand the erosional morphology in the vicinity of the main divide of the southern alps and fiordland new zealand appears to be a product of the interaction between alpine fault induced tectonic processes rock mass strength of the uplifted and eroded bedrock and the processes acting to denude the developing mountain landscape the magnitude of the effects of glacial erosion on the landscape is directly controlled by the size and physical properties of the glaciers whilst the form of the trough is a direct consequence of the rock mass strength rms properties of the slope rock realistic models of development of the cross profile shape of glacial valleys must take into consideration the rms properties of the eroded substrate

a revised approach to discriminating sediment transport histories in glacigenic sediments in a temperate alpine environment a case study from fox glacier new zealand clast shape measurements have developed into a standard method for reconstructing the transport histories of sediments in glacial environments the majority of studies use the ra c40 covariance approach with some researchers routinely including clasts of varying lithologies within their samples the corollary is that variable lithological properties may control clast form and roundness rather than debris transport mechanisms despite this the role of lithology on clast shape in glacial environments has rarely been analysed furthermore some studies have reported difficulties in using the ra c40 co variance plot in discriminating clasts that have undergone subglacial transport and clasts that have been modified by fluvial activity results from a glacierized valley in a temperate alpine setting indicate that detailed analysis of clast shape where samples are of uniform lithology although time consuming is a useful tool in the investigation of deposits in glaciated environments copyright 2012 john wiley sons ltd

epistemic uncertainty in california wide synthetic seismicity simulations abstract the generation of seismicity catalogs on synthetic fault networks holds the promise of providing key inputs into probabilistic seismic hazard analysis for example the coefficient of variation mean recurrence time as a function of magnitude the probability of fault to fault ruptures and conditional probabilities for foreshock mainshock triggering i employ a seismicity simulator that includes the following ingredients static stress transfer viscoelastic relaxation of the lower crust and mantle and vertical stratification of elastic and viscoelastic material properties a cascade mechanism combined with a simple coulomb failure criterion is used to determine the initiation propagation and termination of synthetic ruptures it is employed on a 3d fault network provided by steve ward unpublished data 2009 for the southern california earthquake center scec earthquake simulators group this all california fault network initially consisting of 8000 patches each of 12 square kilometers in size has been rediscretized into patches each of 1 square kilometer in size in order to simulate the evolution of california seismicity and crustal stress at magnitude m 5 8 resulting synthetic seismicity catalogs spanning 30 000 yr and about one half million events are evaluated with magnitude frequency and magnitude area statistics for a priori choices of fault slip rates and mean stress drops i explore the sensitivity of various constructs on input parameters particularly mantle viscosity slip maps obtained for the southern san andreas fault show that the ability of segment boundaries to inhibit slip across the boundaries e g to prevent multisegment ruptures is systematically affected by mantle viscosity

catastrophic landslides glacier behaviour and moraine formation a view from an active plate margin the influence of large bedrock landslides rock avalanches on the behaviour of glaciers is incompletely recognised here we present an example from an active tectonic margin in south island new zealand where large earthquakes leave a significant imprint on glacial records we demonstrate that terminal moraines on the western side of the southern alps record both ordinary i e climate driven and landslide initiated glacial advances following consideration of the processes involved in rock avalanche initiated moraine construction we suggest ways of determining the nature of the advance that built the terminal moraine the implications of these observations are important in breaking the conventional linkage of individual terminal moraines with climate forcing

absence of cooling in new zealand and the adjacent ocean during the younger dryas chronozone as the climate warmed at the end of the last glacial period a rapid reversal in temperature the younger dryas yd event briefly returned much of the north atlantic region to near full glacial conditions the event was associated with climate reversals in many other areas of the northern hemisphere and also with warming over and near antarctica however the expression of the yd in the mid to low latitudes of the southern hemisphere and the southwest pacific region in particular is much more controversial here we show that the waiho loop advance of the franz josef glacier in new zealand was not a yd event as previously thought and that the adjacent ocean warmed throughout the yd

reconstructing the transport history of glacigenic sediments a new approach based on the co variance of clast form indices abstract two indices are used to describe the aggregate shape and roundness characteristics of glacially transported clasts the c40 index the percentage of clasts with c a ratios 0 4 and the ra index the percentage of very angular and angular clasts in a sample analysis of the between and within sample co variance of these indices provides a powerful tool for discriminating actively and passively transported clasts in glacigenic deposits use of these indices is illustrated in an analysis of the form characteristics of clasts from lateral and frontal moraines at storbreen jotunheimen these fall between those of actively transported clasts in basal till low c40 and ra values and those of unmodified frost weathered clasts high c40 and ra values both indices decline down moraine within sample analyses of clast shape demonstrates that these aggregate clast form gradients reflect changes in the relative proportions of actively and passively transported debris on the moraines rather than progressive modification of actively transported clasts these analyses also indicate that actively transported clasts form the dominant component of the moraines particularly near the former glacier terminus further applications of the approach developed here are suggested

earthquake recurrence in simulated fault systems we employ a computationally efficient fault system earthquake simulator rsqsim to explore effects of earthquake nucleation and fault system geometry on earthquake occurrence the simulations incorporate rate and state dependent friction high resolution representations of fault systems and quasi dynamic rupture propagation faults are represented as continuous planar surfaces surfaces with a random fractal roughness and discontinuous fractally segmented faults simulated earthquake catalogs have up to 106 earthquakes that span a magnitude range from m4 5 to m8 the seismicity has strong temporal and spatial clustering in the form of foreshocks and aftershocks and occasional large earthquake pairs fault system geometry plays the primary role in establishing the characteristics of stress evolution that control earthquake recurrence statistics empirical density distributions of earthquake recurrence times at a specific point on a fault depend strongly on magnitude and take a variety of complex forms that change with position within the fault system because fault system geometry is an observable that greatly impacts recurrence statistics we propose using fault system earthquake simulators to define the empirical probability density distributions for use in regional assessments of earthquake probabilities

large earthquake cycles and intermittent criticality on heterogeneous faults due to evolving stress and seismicity 1 we analyze evolving stress and seismicity generated by three realizations of a discrete model of a strike slip fault in a three dimensional 3 d elastic half space using five functions of stress and five functions of seismicity the first model f has realistic dynamic weakening static minus dynamic frictions the second fc has zero critical dynamic weakening and the third sys is constrained to produce only system size events the results for model f show cyclical development saturation and destruction of fluctuations and long range correlations on the fault punctuated by the system size events the development stage involves evolution of stress and seismicity to distributions having broad ranges of scales evolution of response functions toward scale invariant behavior increasing seismicity rate and event sizes and increasing hypocenter diffusion most functions reach asymptotically stable values around 2 3 of the cycle and then fluctuate until one event cascades to become the next large earthquake in model fc the above evolution is replaced by scale invariant statistical fluctuations while in model sys the signals show simple cyclic behavior the results suggest that large earthquake cycles on heterogeneous faults with realistic positive dynamic weakening are associated with intermittent criticality produced by spontaneous evolution of stress heterogeneities toward a critical level of disorder having a broad range of scales the stress evolution and development of large earthquake cycles may be tracked with seismicity functions