andean rolling mosses gather on stone pavements geoecology of grimmia longirostris hook in a high periglacial paramo abstract rolling mosses of grimmia longirostris hook were studied in paramo piedras blancas a high andean area in venezuela using a geoecological research framework focused on interactions between geomorphic ecological and soil processes spatial patterns of mosses were analyzed downslope from granitic outcrops on three slopes at 4445 4480 m elevation fragments from epilithic mosses on the apex outcrops were the source of other mosses distance of moss transport below rocks was measured at all sites mosses on the gentlest 4 34 m long slope were censused along a belt transect on 17 contiguous quadrats density of moss growth forms stone size percent of bare soil cover and surface soil properties were determined surface clast morphology and profile characteristics of a periglacial stone pavement at the slope base were also examined mosses on this site included four growth forms epilithic mosses on outcrops mobile rolling moss balls epilithic mosses on loose clasts and unattached elongated mosses moss balls density 0 87 mosses m2 lay on upper transect plots over bare soils 92 cover disturbed by needle ice soils here contained 43 51 fine grains 0 063 mm and 2 9 5 9 organic matter this made them exceptionally prone to ice segregation and needle ice formation lower transect plots showed 78 100 stone cover cobbles and blocks but little exposed soil mosses attached to loose clasts were exceedingly abundant 31 m2 on this section unattached elongated mosses often resting along boundaries between adjacent stones were also common 5 5 m2 the basal stone pavement showed a shallow 7 cm rock veneer over a 24 cm thick profile with exceptionally fine soil up to 83 2 fine grains 8 6 organic matter a conceptual developmental model emphasizing the close linkages among the spatial distribution of mosses patterns of surface clasts and characteristics of soils and stone pavements is proposed i stones and mosses are transported downhill by needle ice and other frost agents moss fragments gradually assume a globular shape forming rolling moss balls ii when these reach the stones and pavements on the basal slope they cannot be transported any further and remain immobile iii some mosses come to rest along boundaries between stones and develop into unattached elongated mosses or iv they may become gradually attached to cobbles on the stone pavement clasts with epilithic mosses can continue moving toward the basin floor v some mosses become fragmented and provide a source of elongated mosses or remain partially attached to clasts stone pavements develop by a combination of rock accumulation following needle ice transport rock upheaving and sorting by ground frost slope runoff and downward soil illuviation

mountain geomorphology a theoretical framework for measurement programmes abstract ten distinctive mountain geomorphic systems identified on the basis of structural elements and spatial scale are considered questions and approaches to measurement programmes that are most appropriate to each system are discussed with the aid of illustrative examples from the literature

channel change fluvial geomorphology and river engineering the case of the afon trannon mid wales the afon trannon a gravel bed river in mid wales with a catchment area of 72 km2 has recently been the subject of an engineering flood protection scheme following the enlargement and grading of the channel lateral instability has produced considerable problems of maintenance geomorphological investigations are described which attempt to pinpoint the lessons of the scheme historical studies of floodplain sediments and channel change indicate firstly an initially rather stable channel but secondly a considerable early history of channelization which may still have repercussions for system stability this early channelization has now been modified in the recent scheme contemporary field study by survey and sediment tracing using the magnetic technique indicates the present instability of the sediments in a meandering channel given a trapezoidal cross section and varied banks low flow adjustments are as important as flood adjustments in the lower straightened reach lessons for engineering schemes include the desirability of assessing erosion risk by rapid cheap field techniques and historical investigations and the consideration of more ecologically acceptable channel designs

the seismogenic thickness of the southern california crust the average seismogenic thickness measured from the surface down to maximum depth of earthquake rupture for the southern california crust is 15 0 km 1 2 1 1 km we determine the seismogenic thickness using the depth distribution of the seismic moment release of 19 years of seismicity we calibrate the depth distribution of moment release from background seismicity by comparing the maximum depth of rupture during moderate to large magnitude earthquakes to the premainshock background seismicity of the respective mainshock region the calibration shows that the depth above which 99 9 of the moment release of background seismicity occurs reliably estimates the maximum depth of rupture during moderate to large earthquakes locally the seismogenic thickness is highly variable ranging from less than 10 km in the salton trough to greater than 25 km at the southwestern edge of the san joaquin valley similarly the seismogenic thickness along the major strike slip faults can vary significantly along strike changes in seismogenic thickness along strike do not correspond to the mapped surface segmentation of the major southern california strike slip fault systems in the future such estimates of the seismogenic thickness can be used to refine existing seismic hazard estimates for southern california

biogeomorphic relationships between slope processes and globular grimmia mosses in haleakala s crater maui hawai i abstract globular mosses were found in haleakala s crater maui at five locations between 2175 and 2725 m the highest altitude site with abundant epilithic mosses growing on alkali olivine basalt outcrops and a large mossball population was studied mossballs form when moss cushions are dislodged from rocks but continue growing unattached to substrate detachment agents include rainsplash desiccation wind frost and disturbance by birds dark rumped petrels that burrow nests under outcrops or by goats when loosened moss polsters are transported down steep 26 34 slopes by different geomorphic processes including frost mainly needle ice activity runoff and wind mossballs contained two species grimmia trichophylla grev and grimmia torquata drumm growing separately or commingled weight size and various shape indices were determined for 260 specimens shape and size were correlated larger mosses become less spheroidal because heavier specimens are less disturbed by needle ice remaining immobile for increasingly longer time periods thus becoming flattened distance of downslope transport from source rockwalls was measured for 330 specimens 83 shifted 100 cm but only 5 had moved 200 839 cm heavier mossballs moved short distances thus 88 of all biomass remained within 200 cm from outcrops substrate soils were compared with those within globoids surface site soils were much coarser than mossball grains twelve substrate samples had on average 21 3 gravel 2 mm 6 1 fines 0 063 mm and 2 1 organic matter in contrast 12 mossballs contained this area is frequently subjected to freezing temperatures while fog interception from incoming tradewinds contributes significant moisture amounts to precipitation ground disturbance by frost activity seemed significant needle ice grows frequently on this slope as evidenced by widespread presence of miniature sorted stripes striated soils fine earth flags below stones gaps around stones and fine soil raised patches observed during multiple visits biogeomorphic interactions between mossballs and substrate at haleakala are briefly discussed from the perspective of self organized criticality and interpreted to represent a self replicating moss dispersal system dependent on slope geomorphic processes

high resolution fault displacement mapping from three dimensional seismic data evidence for dip linkage during fault growth abstract detailed mapping using high resolution three dimensional seismic data has revealed a number of sub horizontal anomalies in the distribution of vertical displacement throw on the planes of growth faults in the gulf of mexico recognition of these anomalies is highly sensitive to the interval at which the fault displacements are sampled because they represent local decreases in throw which are confined to small discrete parts of the fault planes the distribution of the anomalies is inconsistent with model displacement fields of quasi elliptical concentric contours and is therefore incompatible with models of fault growth by uniform slip distribution and radial tip line propagation an alternative model is proposed whereby the evolution of a fault plane is established by the propagation and linkage of precursor fault segments in the dip direction dip linkage overlap and linkage of fault tips in the dip direction results in relay structures that are sub parallel to fault strike and therefore displacement minima that are sub horizontal on normal and thrust faults however since they are orthogonal to the main slip direction on the fault these structures have a low preservation potential and are therefore unlikely to be well resolved on cross sectional seismic profiles

using rare earth elements to monitor sediment sources from a miniature model of a small watershed in the three gorges area of china abstract understanding soil erosion processes at different landscape positions is important in order to predict and control watershed soil losses rare earth elements rees can be used to trace eroded soil sources but their efficacy may be soil dependent we constructed a miniature watershed model of a small watershed located in the three gorges area of china and used oxides of eight rees to trace the erosion of a purple soil the miniature watershed was divided into eight regions containing a different landform type as a potential sediment source a different ree was applied in each region redistributions of the rees under three successive simulated rainfall events with intensities of 1 0 1 5 or 2 0 mm min 1 were examined the percentage contribution from each region to the total soil loss from the watershed fluctuated relative to landform type during the three rainstorms contributions from the lower main gully decreased before stabilizing while those from the upper main gully increased before decreasing and those from other sources all increased before stabilizing overall the contribution of the gully system comprising main and branch gullies was greater than that of the slopes contributions from the gully system tended to decrease with increases in rainfall intensity and rainstorm duration while those from the slopes increased a comparison of the calculated and actual soil loss masses indicated that the accuracy of the ree tracing method was less for the coarse textured purple soil than those previously found for fine textured soils the increased errors likely due to the assumption used in the calculation that there is no particle size selectivity during erosion needs to be addressed this pilot study provided a technical reference for the use of rees in monitoring sediment sources from a natural watershed and a theoretical basis for soil conservation in the three gorges area

subaerial river bank erosion processes and their interaction with other bank erosion mechanisms on the river arrow warwickshire uk river bank erosion occurs primarily through a combination of three mechanisms mass failure fluvial entrainment and subaerial weakening and weathering subaerial processes are often viewed as preparatory processes weakening the bank face prior to fluvial erosion within a river basin downstream process domains occur with subaerial processes dominating the upper reaches fluvial erosion the middle and mass failure the lower reaches of a river the aim of this paper is to demonstrate that a subaerial processes may be underestimated as an erosive agent and b process dominance has a temporal as well as spatial aspect bank erosion on the river arrow warwickshire uk was monitored for 16 months december 1996 to march 1998 using erosion pins variations in the rate and aerial extent of erosion are considered with reference to meteorological data throughout the first 15 months all erosion recorded was subaerial resulting in up to 181 mm a 1 of bank retreat compared with 13 to 27 mm a 1 reported by previous researchers while the role of subaerial processes as preparatory is not contended it is suggested that such processes can also be erosive the three bank erosion mechanisms operate at different levels of magnitude and frequency and the river arrow data demonstrate this thus the concept of process dominance has a temporal as well as spatial aspect particularly over the short time periods often used for studying processes in the field perception of the relative efficacy of each erosive mechanism will therefore be influenced by the temporal scale at which the bank is considered with the advent of global climate change both these magnitude frequency characteristics and the consequent interaction of bank erosion mechanisms may alter it is therefore likely that recognition of this temporal aspect of process dominance will become increasingly important to studies of bank erosion processes copyright 2001 john wiley sons ltd

downdip segmentation of strike slip fault zones in the brittle crust outcrop scale field evidence from the southern san jacinto fault zone in southern california indicates that bedding parallel slip may be an important mechanism for transferring and accommodating slip within strike slip fault zones that cut across heterogeneous stratigraphy steeply dipping strike slip fault segments exposed in conglomeratic sandstones abruptly terminate at weaker shale layers where slip occurs on bedding parallel planes cross sections of fault related seismicity within the southern san jacinto fault zone reveal that events generally cluster within tabular steeply dipping fault parallel streaks that are limited in extent in the downdip direction the depths of the downdip terminations of shallow streaks tend to be roughly coincident with the depths of the updip terminations of deeper streaks these configurations define stepover geometries that range in character from sharp to diffuse the examples described herein provide evidence that downdip segmentation within strike slip fault zones may be common over a wide range of scales

applicability of rare earth element oxides as a sediment tracer for coarse textured soils a leaching experiment using a mixture of five ree oxides and gravelly sandy loam soils was conducted to examine the applicability of the ree oxides as a sediment tracer for coarse textured soils the experiment showed little leaching of the oxides and an enrichment of various size classes of soil particles with the oxides which reflected the strong binding capability of the ree oxides with the gravelly sandy loam soils it also showed that the ree oxides preferentially bound with small size classes of soil particles the preferential binding of the ree oxides with fine materials will cause the overestimation of the soil loss from a given area i e tagged with a given ree if aggregates are broken down during sediment transport and clay materials are preferentially delivered and if the soil loss is computed by analyzing the ree concentrations in the whole sediment to address the non uniform binding issue the method based on measuring the ree concentrations for four particle size groups was tested the potential error of the method was evaluated by comparing the soil loss that would be computed in the case that the particle size distribution was shifted to the smallest particle size class within a particle size group and in the case that no sediment sorting occurred the result showed that the method would produce a potential error of approximately 4 in the estimation of the total soil loss when sediment sorting occurred the non uniform binding of the oxides does not preclude the use of the ree oxides on the coarse textured soils in the presence of non uniform binding of the oxides but adjustments in the technique are required for an accurate estimation of soil loss using the ree technique

particle sorting due to off road vehicle traffic in a high andean paramo summary in the paramo de piedras blancas venezuelan andes unrestricted access by off road vehicles orv s within the past 10 years has caused widespread soil damage by generating numerous tire tracks pebbles and vagant lichens thamnolia vermicularis have been sharply segregated in the vicinity of the tracks both are concentrated in the elongated depressions creating an unusual type of sorted stripes materials migrate to tire tracks due to frequent ground frost and formation of needle ice a ubiquitous geomorphic agent of this high paramo lichens also have been concentrated in the tracks by wind activity the role of needle ice in transporting pebbles to hollow depressions is discussed and illustrated with other examples of recent patterned ground from this paramo

the orientation of sorted stripes in the maritime subantarctic marion island the orientation of sorted stripes developed in glacial deposits on marion island is examined this study confirms earlier reports of preferential occurrence of sorted stripes on windward slopes however sorted stripes were also found to occur on low angle leeward slopes mechanisms for the orientation of sorted stripes by wind action are discussed copyright 2001 john wiley sons ltd

parallel fault strands at 9 km depth resolved on the imperial fault southern california 1 precision relocation of hundreds of small earthquakes occurring along the imperial fault in southern california during the last two decades reveals parallel steaks of seismicity at 9 km depth these strands are spaced about 0 5 km apart within a 2 km wide zone of earthquakes near the brittle ductile transition between the shallow locked part of the fault and a creeping zone at depth these results suggest that the lower crustal shear zone below the imperial fault site of major earthquakes in 1940 and 1979 must be at least two kilometers wide

aspects of the crustal structure of the western mojave desert california from seismic reflection and gravity data seismic and gravity data taken along line 1 of the 1982 consortium for continental reflection profiling cocorp mojave desert survey n s profile 30 km long have been used to characterize the upper crust north of the san andreas fault in the western mojave block of southern california consortium for continental reflection profiling seismic reflection data were reprocessed to emphasize the upper 5 seconds two way travel time the resultant common depth point cdp sections provided starting models for generating a refined geologic cross section using a combination of ray tracing forward modeling and gravity interpretation the forward modeling was used to validate the existence of faults and constrain their dips the gravity data were used to refine the overall model particularly in poor data areas on the cdp sections gravity data taken along three nearby profiles parallel to primary line of section were also used to determine the structural trend results from the first two seconds indicate the presence of a series of ene striking reverse faults beneath the late tertiary and quaternary sedimentary cover of the western mojave the faults dip northward and offset the sediment basement interface the largest such feature has an apparent throw of 1 8 km and exhibits a subtle scarp at the earth s surface suggesting holocene displacement the orientation of these faults although not an instantaneous representation of the present day stress field is consistent with nnw compression across the western mojave block and wnw striking san andreas fault as determined from nearby focal mechanisms and in situ stress measurements the faults also appear to be closing small sedimentary basins in the mojave block which may have formed during an earlier extensional phase similar to what is happening on a much larger scale in the los angeles basin to the south of the san andreas fault reflections between 2 and 5 s coupled with the local geology and gravity modeling are consistent with the presence of the pelona rand schist in the subsurface beneath the western mojave the upper surface of the schist i e vincent rand thrust equivalent rises southward toward the san andreas fault where it is displaced vertically up to the south at least 5 km along the e w trending hitchbrook fault such that the schist crops out between the hitchbrook and subparallel san andreas to the south the same structure may exist beneath the tehachapi mountains with the roles of the hitchbrook and san andreas faults played by the north and south branches of the garlock fault respectively the rising or arching of the basement toward the san andreas fault and toward the garlock is not only reflected in the geology and topography local to these faults in many places but is also generally observed on seismic reflection profiles in the vicinity of these faults in the western mojave furthermore the arching is also consistent with a strong component of fault normal compression

developing equations to explore relationships between aggregate stability and erodibility in ultisols of subtropical china abstract a soil aggregate represents a key soil structural unit that influences several physical soil properties such as water infiltration runoff and erosion the relationships between soil aggregate stability and interrill and rill erodibility are critical to process based erosion prediction models yet remain unclear likely due to the difficulty of distinguishing between interrill and rill eroded sediment during the erosion process this study was designed to partition interrill and rill erosion rates and relate them to the aggregate stability of ultisols in subtropical china six kinds of rare earth elements rees were applied as tracers mixed with two cultivated soils developed over quaternary red clay or shale at six slope positions soil aggregate stability was determined by the le bissonnais lb method simulated rainfall of three intensities 60 90 and 120 mm h 1 was applied to a soil plot 2 25 m long 0 5 m wide 0 2 m deep at three slope gradients 10 20 and 30 for a duration of 30 min after runoff initiation the results indicated that rill and interrill erosion rates in the soil developed over shale were considerably greater than those in the soil developed over quaternary red clay equations using an aggregate stability index a s to replace the erodibility factor of interrill and rill erosion in the water erosion prediction project wepp model were constructed after analysing the relationships between estimated and measured rill and interrill erosion data the results show that these equations based on a s have the potential to improve methods for assessing interrill and rill erosion erodibility synchronously for subtropical ultisols by using an ree tracing method

sorted stripes on sub antarctic kerguelen island observations of sorted stripes at nine different localities on sub antarctic kerguelen island are presented the study sites range from 25 600 m above sea level and are of varying aspect it is found that there is a strong relationship between stripe orientation and the wind direction to the extent that at one locality stripes were orientated across a slope stripe width was seen to increase with altitude and in addition the coarse stripe was dominant at lower elevations and the fine stripe at higher elevations at one site a secondary set of stripes was observed to occur within the fine stripe of a primary larger set on a trachyte plug there was evidence of lateral squeezing in the formation of the stripes a number of minor observations pertaining to the possible mechanism of stripe formation are given

a comparison of stream bank erosion processes on forested and moorland streams in the balquhidder catchments central scotland stream bank erosion rates measured over a two year period on a moorland and a forested stream in the institute of hydrology s balquhidder paired catchments in central scotland were compared bank erosion rates are generally higher on the mainstream of the moorland catchment and highest in wintger on both streams bank erosion is correlated with the incidence of frost minimum temperatures measured on stream banks of the forested stream were an average of 3 7 c higher than on stream banks both outside the forest and on the moorland stream this makes the incidence of frost on forested stream banks half as frequent volumes of material eroded from the mainstreams were combined with bulk density measurements and it is estimated that erosion of the mainstream banks is contributing 1 5 and 7 3 per cent of the sediment yield of the forested and moorland catchments respectively analysis of the vertical distribution of erosion on the banks of both streams suggests an undercutting mechanism which is more pronounced in the moorland stream the influence of trees on bank erosion and possible implications for the management of forest streams are discussed 1997 by john wiley sons ltd

a conceptual model for determining soil erosion by water current estimates of rates of soil erosion by water derived from plots are incompatible with estimates of long term lowering of large drainage basins traditional arguments to reconcile these two disparate rates are awed the ux of sediment leaving a speci ed area cannot be converted to a yield simply by dividing by the area because there is no simple relationship between ux and area here we develop an approach to the determination of erosion rates that is based upon the entrainment rates and travel distances of individual particles the limited available empirical data is consistent with the predictions of this approach parameterization of the equations to take account of such factors as gradient and sediment supply is required to proceed from the conceptual framework to quantitative measurements of erosion however our conceptual model solves the apparent paradox of the sediment delivery ratio resolves recent discussion about the validity of erosion rates made using usle erosion plots and potentially can reconcile erosion rates with known lifespans of continents our results imply that previous estimates of soil erosion are fallacious copyright 2004 john wiley sons ltd

fault relays bends and branch lines abstract branch lines between normal faults and their sub parallel splays mapped from 3d seismic reflection data show a range of forms from straight lines to closed loops the different geometries are interpreted as representing stages in the failure of relay zones and in the progressive replacement of fault tip lines with fault branch lines the geometries of these normal fault branch lines are similar to those for thrusts previously inferred from limited two dimensional data the orientation of the axis of a relay and its associated bends relative to a fault slip direction is identified as an important control on the structures developed within the relay neutral restraining and releasing bends can each occur on any fault type normal reverse and strike slip but data bias is a major factor in determining which bend geometry is most often observed with each fault type on normal faults the initial relay zone geometry controls the dominant branch line orientation and the same control is likely on branch lines associated with the other modes of faulting a review of the relay geometries and strains occurring with all three modes of faulting highlights the role of the orientation of the mechanical anisotropy of a bedded sequence relative to the orientations of fault surface and slip directions this relative orientation determines how the relay strain is accommodated and hence the degree of hard linkage and development of branch lines

preliminary experiments to assess the effectiveness of magnetite powder as an erosion tracer on the loess plateau abstract soil water erosion monitoring is essential for long term soil conservation and ecological restoration on the loess plateau region of china traditional approaches such as runoff plots and water weirs in a watershed provide reliable spatially averaged soil erosion data but cannot validate process based erosion prediction models for dynamic soil erosion evaluation erosion tracer techniques are capable of quantitatively determining spatial distribution of soil erosion ideal tracers are expected to provide highly contrasting values compared with background ones and be analyzed efficiently and acquired cost effectively in this laboratory study magnetite powder was selected as an erosion tracer to test the tracer was implanted into loessial soils from the loess plateau using a wet soil tracer mixing procedure the effectiveness of magnetite powder as an erosion tracer was evaluated in aspects of basic magnetic features between the tracer and soils distribution under different soil aggregate sizes mobility along soil profiles and detachment of tracer labeled loessial soils by shallow surface flow along a slope results showed that magnetite powder was bound tightly to loessial soil aggregates with no noticeable vertical mobility under long term leaching conditions and almost synchronous detachment with the eroded soils furthermore the tracer is an inexpensive tracer approximately 0 08 us kg 1 which has higher magnetic susceptibility over two or three orders of magnitude than ordinary soils and high sensitivity of analysis

pleistocene brawley and ocotillo formations evidence for initial strike slip deformation along the san felipe and san jacinto fault zones southern california abstract we examine the pleistocene tectonic reorganization of the pacific north american plate boundary in the salton trough of southern california with an integrated approach that includes basin analysis magnetostratigraphy and geologic mapping of upper pliocene to pleistocene sedimentary rocks in the san felipe hills these deposits preserve the earliest sedimentary record of movement on the san felipe and san jacinto fault zones that replaced and deactivated the late cenozoic west salton detachment fault sandstone and mudstone of the brawley formation accumulated between 1 1 and 0 6 0 5 ma in a delta on the margin of an arid pleistocene lake which received sediment from alluvial fans of the ocotillo formation to the west southwest our analysis indicates that the ocotillo and brawley formations prograded abruptly to the east northeast across a former mud dominated perennial lake borrego formation at 1 1 ma in response to initiation of the dextral oblique san felipe fault zone the 25 km long

tracing sediment movement in interrill overland flow on a semi arid grassland hillslope using magnetic susceptibility experiments were undertaken to determine the feasibility of tracing sediment movement in interrill overland flow crushed magnetite was introduced as a source line 10 cm wide by 8 m long on a runoff plot 18 m wide by 29 m long located in southern arizona initial magnetic susceptibilities along this source line and along three transects located 0 25 2 95 and 5 m downslope of the source line were measured movement of the magnetite in response to three rainfall simulation experiments was monitored during the first two experiments overland flow discharge was sampled at miniature flumes located along two cross sections on the plot downslope of the source line and at a supercritical flume at the plot outlet magnetic susceptibilities along the source line and transects were measured after all three experiments results show that the magnetite moves very early in the experiments and that it reaches one of the flumes 2 m downslope of the source line in 3 min most of the tracer moves a very short distance 29 7 per cent is deposited within 25 cm of the source line and only 2 2 per cent is deposited 2 95 m away the deposition rate appears to decrease exponentially away from the source line very little magnetite is recorded in the flow through the miniature flumes in general it makes up less than 1 per cent of the total sediment load no temporal pattern in these percentages is observed magnetite appears to be an effective tracer of sediment movement in interrill overland flow though its higher density than natural soil may affect its detachment and transport

bedload entrainment travel lengths step lengths rest periods studied with passive iron magnetic and active radio tracer techniques this paper reports results from bedload transport investigations with active radio and passive iron magnetic tracers in the lainbach a step pool mountain river in bavaria southern germany the spatial distributions of the iron tracers after flood events can be best described by exponential or gamma distributions there is some indication of a tendency of size selective transport of the iron tracers but there is also a considerable amount of scatter in the correlations between weight size and travel length owing to the masking influence of other variables such as the shape of the particles and different positions in the river bed the experiments with artificial magnetic tracers showed that elongated pebbles rods had the longest mean transport distance platy ones discs remained relatively close to the starting points the particles from the pool showed the greatest transport lengths and a 100 per cent chance of being eroded the pebble transmitter system petsy consists of transmitters implanted into individual pebbles a computerized receiver a stationary antenna system with an antenna switchboard and a data logging system the particles do not move continuously but in a series of transport steps and non movement intervals a single value for a given size class is not adequate to describe the critical conditions of entrainment under natural circumstances a probability approach is much more suitable the critical unit discharges total discharge divided by active channel width along the measuring reach are dependent on river bed morphology in the steps bedload needs higher unit discharges to be entrained once entrained the transport of bedload is stochastic in nature and the single particle transport is controlled by the step lengths and the duration of rest periods the distributions of both parameters can be approximated by exponential functions applying the stochastic concept proposed by einstein the mean values of the random variables step length and duration of rest period measured with the petsy technique were used for the simulation of spatial distributions of bedload particles from point sources more field and laboratory data are needed to include varying flow and roughness conditions with tracers representing different particle characteristics

splash and wash dynamics an experimental investigation using an oxisol abstract limited data are available in the literature on the partitioning of interrill erosion into splash and wash components laboratory rainfall simulation experiments were conducted on an oxisol at 5 10 and 20 slopes at a constant rainfall intensity rainwash was separated from front splash and lateral splash using a novel experimental design results indicate that output of sediment from the 0 18 m 2 erosion plots was dominated by splash with a geometric mean aggregate diameter gmad similar to that of the original soil the most easily detached aggregate size by splash was 500 to 1000 m i e coarse sand sized aggregates wash was dominated by aggregates with a gmad significantly finer than the soil matrix and this reflected the limited energy available to transport coarse aggregates detached by splash wash and splash sediment flux and the runoff coefficient increased significantly with slope angle peak front splash was associated with a different dimensionless water depth dwd for each slope angle as slope angle increased the dwd at peak output increased from 0 to 0 4 at 5 and from 1 4 to 1 7 at 20 time trends of front splash output for 5 and 10 slopes were similar to those presented in the literature however data for the 20 slopes were more complicated with a series of pulses related to periodic migrating waves of wash sediment superimposed on the general pattern these migrating bedload waves are interesting in that they seem analogous to those documented in the fluvial environment at steady or even decreasing discharge data indicate that front splash flux exceeded wash transport on all slopes tested these data reflect the boundary conditions of the experiment but may be applicable under certain field situations such as on short steep furrow side slopes

drop shape and erosivity part ii splash detachment transport and erosivity indices the relevance of drop shape for erosivity was tested for different combinations of drop sizes and fall heights for all test combinations together the introduction of the observed drop shape in erosivity parameters only produces minor improvements in the relation between erosivity and detachment and transport by splash this result is attributed to the dominance of oblate shapes in high velocity conditions using small fall heights and low fall velocities as in many rainfall simulators and drop tests it is shown that prolate drops produce a splash detachment which is 2 to 3 times higher than that produced by drops with an oblate shape at impact as drop production in rainulators or for aggregate stability drop tests may result in more or less uncontrolled variations of drop shape it is concluded that in addition to other test conditions drop shape should be specified moreover it is noted that the erosive capability of prolate drops can explain partly the high splash erosion amounts below vegetation

postglacial geomorphic development of the dinosaur provincial park badlands alberta experimental studies concerning current geomorphic processes and erosion rates in the badlands of dinosaur provincial park alberta have not explained the unusual extent of badland development or prominent nonstructural near horizontal surfaces that occur in the park two of these surfaces result from spillway development associated with wisconsin deglaciation and the extent of badland development is associated with major spillway concentration and exposure of highly erodible cretaceous strata a third surface is associated with erosion caused by locally generated runoff all surfaces are blanketed with aeolian sands and silts deposited around 5500 bp which profoundly affected the hydrology of the area and water and sediment discharge from the badlands to the red deer river subsequent stripping of the aeolian cover by streams along with piping and tunnel erosion has reexposed vulnerable cretaceous strata and restored the high erosion rates now observed in these badlands

effects of silt clay content on the susceptibility of river banks to subaerial erosion abstract the aim of this paper is to demonstrate how subaerial processes vary with the silt clay content of river bank soil and to consider this variation in the context of erosion observed in the field in particular spatial and temporal variations in erosion interactions with other bank erosion processes and the implications for bank morphology are explored a number of soil blocks of known silt clay content were subjected to a series of freeze thaw and drying wetting cycles changes in the dimensions of the soil blocks were recorded and the mass of soil eroded from each block together with maximum size of eroding aggregates were measured limitations to this methodology are acknowledged including a limited ability to replicate the forces to which a river bank may be subject restrictions imposed by the available equipment in producing temperature and humidity cycles which reflect those occurring in the field and issues of scale the results indicate that river banks with high silt clay contents are the most susceptible to erosion by subaerial processes high susceptibility may influence spatial variations in bank erosion processes and rates including downstream changes in the effectiveness and significance of subaerial erosion a vertical zoning of processes on a river bank is recognised whereby the upper part of the bank is subject to subaerial erosion and the lower part to fluvial erosion given that a high silt clay content tends to indicate increased susceptibility to subaerial erosion but increased resistance to fluvial erosion this vertical zoning may have implications for bank morphology

particle tracking in ideal faulted blocks using 3d co ordinate geometry abstract this article performs particle material point tracking for ideal brittle faults with translational and rotational slip components the fault planes are considered to be planar and step like in separate cases in the latter case the hangingwall block is considered to behave ductilely for a specific choice of the three cartesian co ordinate axes dip slip fault will change two out of the three ordinates of any point in the faulted block that moves a strike slip faulting can change one out of the three ordinates on the other hand whatever be the orientation of the orthogonal co ordinate axes an oblique slip fault of any dip amount and a purely rotational fault with dip 0 90 alter all the three ordinates except the pivot point in the latter case as expected oblique slip faulting modifies the co ordinates of the shifted material points depending on both i the pitch of stretching lineation and ii the dip of the fault plane

applying a three dimensional velocity model waveform cross correlation and cluster analysis to locate southern california seismicity from 1981 to 2005 we compute high precision earthquake locations using southern california pick and waveform data from 1981 to 2005 our latest results are significantly improved compared to our previous catalog by the following 1 we locate events with respect to a new crustal p and s velocity model using three dimensional ray tracing 2 we examine six more years of waveform data and compute cross correlation results for many more pairs than our last analysis and 3 we compute locations within similar event clusters using a new method that applies a robust fitting method to obtain the best locations satisfying all the differential time constraints from the waveform cross correlation these results build on the relocated catalogs of hauksson and shearer 2005 and shearer et al 2005 and provide additional insight regarding the fine scale fault structure in southern california and the relationship between the san andreas fault saf and nearby seismicity in particular we present results for two regions in which the seismicity near the southern saf seems to align on dipping faults

interrill soil erosion processes on steep slopes abstract to date interrill erosion processes are not fully understood under different rainfall and soil conditions the objectives are to 1 identify the interrill erosion regime and limiting process under the study condition 2 characterize the interactive effects of rainfall intensity and flow depth on sediment transport competency and mode and 3 develop a lumped interrill erosion model a loess loam soil with 39 sand and 45 silt was packed to flumes and exposed to simulated rainfall a complete factorial design with three factors was used which included rainfall intensity 48 62 102 149 and 170 mm h 1 slope gradient 17 6 26 8 36 4 46 6 and 57 7 and slope length 0 4 0 8 1 2 1 6 and 2 m rain splash sediment discharge in runoff and flow velocity were measured results showed that rainfall intensity played a dual role not only in detaching soil materials but also in enhancing sediment transport sediment transport was the process limiting interrill erosion rate under the study condition two major sediment transport modes were identified rainfall driven rolling creeping and flow driven rolling sliding the relative importance of each mode was largely determined by flow depth the competence of the flow in transporting sediment decreased downslope as flow depth increased due to increased dissipation of raindrop energy the optimal mean flow depth for the maximal interrill erosion rates was

straightening of the northern san jacinto fault california as seen in the fault structure evolution of the san jacinto valley stepover abstract we investigate a releasing stepover between the casa loma and claremont strands of the northern san jacinto fault zone to evaluate the late quaternary structural evolution of the fault zone and to assess the likelihood of a rupture jumping across the stepover our new cone penetration test cpt and trench observations along the claremont fault at mystic lake indicate that the main strand of the claremont fault has jumped nearly a half kilometer westward into the san jacinto releasing stepover during the late quaternary multiple faults are inferred from the cpt data within a small sag at the northeast side of the stepover that cuts through younger stratigraphy to the west of the basin bounding fault near mystic lake previous seismic reflection data also suggest the presence of a young fault that cuts basin strata beneath the middle of mystic lake farther west of our study area numerous tectono geomorphic features observed in satellite and light detection and ranging digital elevation model lidar dem imagery are interpreted to delineate the location of the currently active faults including a zone of faults that cut across the basin from the northern end of the casa loma fault to the claremont fault seismicity observations suggest the presence of many faults within the stepover zone finally new paleoseismic data from the mystic lake site suggest that some late holocene earthquakes may have jumped the stepover all of these observations suggest that the san jacinto stepover which has been used as the primary basis for segmenting the northern san jacinto fault zone is being bypassed and that the fault zone may now be capable of larger earthquakes than previously expected

determining the origins and history of sedimentation in an underground river system using natural and fallout radionuclides abstract natural and anthropogenic radionuclides were used to characterize the source of sediment reaching the underground river in the karst system at jenolan new south wales australia it was found that the relationship between 226 ra and 232 th concentrations in both spatially averaged soil samples and transported sediments distinguished between two of the most likely source subcatchments sedimentary sequences collected from within the underground system showed that contemporary deposition was made up of an equal mixture of sediment from these two sources however at least three earlier deposition periods were also identifiable each with different relative contributions from the source catchments the first appearance of 137 cs in the sedimentary sequence and correlations with historical information provided a chronology for these changes and it is concluded that the contemporary phase was initiated in the early 1950s most probably by forestry activities this work demonstrates that natural radioactivity can be used as a tracer of the origins of sediment providing an important new approach to problems in sediment supply transport and deposition

seismic imaging of the alpine fault near inchbonnie new zealand 1 the transpressive alpine fault is the boundary between the pacific and australian plates across the south island of new zealand earthquakes on the alpine fault and related structures pose a serious risk to many urban centers including the city of christchurch although it is a major feature on satellite images the alpine fault is a difficult target for surface studies along much of its length it mostly traverses densely forested and mountainous terrain and where it occurs in the lowlands it is usually covered by recent sediments to investigate the alpine fault at a rare accessible location inchbonnie we have acquired high resolution seismic reflection data along five 380 1200 m long lines images produced from these data reveal a glacially overdeepened valley containing a thick sequence of diverse glacigenic sediments that have been disrupted by three en echelon strands of the principal alpine fault and several secondary fault strands based on their seismic facies the sedimentary sequence is interpreted to comprise basal lacustrine beds overlain successively by alluvial colluvial deposits that possibly include the remnants of large landslides deltaic fan units and braided river gravels whereas the principal alpine fault strands disrupt the entire post glacial sedimentary section and likely offset basement at depths up to 400 m most of the secondary faults either merge with the principal fault strands at shallow depths or are surficial features limited to the sedimentary section

incipient motion conditions for single rock fragments in simulated rill flow laboratory experiments using simulated tilting rill channels with different bed roughnesses have been conducted to determine hydraulic conditions for incipient motion of single rock fragments lying on rill beds these threshold conditions can be described by a modified shields entrainment parameter m and relative depth z adjusted for rill conditions the negative relation found between m and z also fits steep stream channel data collected by other investigators plots of the classical shields entrainment parameter versus both relative depth and relative particle size also showed clear negative trends special care has been taken to avoid false relations that can arise between compound parameters this occurs when the latter are not independent from each other because of their definitions

the significance of various sediment magnetic mineral fractions for tracing sediment sources in killimicat creek abstract the mineral magnetic properties of sediment are increasingly being used to determine the sources of sediment and associated nutrients and contaminants in drainage basins this study was undertaken to measure the relative contributions of the magnetic mineral components in sediment i e components associated with surface bound fe the heavy mineral fraction and as inclusions in particles to determine the extent to which they represent the bulk of the sediment deposited channel sediment samples from the tributaries and downstream reach at the first major confluence in the headwaters of killimicat creek new south wales were sieved to separate 6 particle size fractions and the mineral magnetic properties measured to determine the relative contribution of sediment from the smaller tributary basin the finest sand component 63 125 m was then separated into light and heavy mineral fractions and magnetic measurements made on each fraction magnetic parameter data from the 63 125 m fraction measured before density separation show a dominance of sediment 70 12 derived from the smaller tributary basin measurements of the light sediment fraction give a similar result 73 13 the proportion of the heavy mineral fraction delivered from the smaller tributary is 78 38 the light mineral fraction of all of the samples were treated with hcl to remove surface bound fe and subsequent magnetic measurements show that 41 94 of the mass specific magnetic susceptibility is attributable to magnetic minerals associated with surface bound fe the heavy mineral component while 60 is associated with sediment particles rather than the discrete heavy mineral component

multi year tracking of sediment sources in a small agricultural watershed using rare earth elements rare earth elements rees have been successfully used as a sediment tracer but the ree technique has never been used for studying sediment sources for a multi year period a nearly four year field experiment was conducted on a small agricultural watershed near coshocton oh usa to assess the applicability of the ree technique for a multi year period and to evaluate the relative contributions of sediment sources in the watershed tracer depletion and tracer enrichment ratio ratio of the tracer concentrations in sediment to the concentrations in the soil in the areas of application were evaluated to examine the applicability and accuracy of the technique a minimum of 91 per cent of the mass of the applied elements was still available on any individual morphological element at the end of the experimental period the tracer enrichment ratio varied from 0 4 to 2 3 and it was not significantly related to time the relative contributions of six morphological elements within the watershed were evaluated as proportions to total sediment yield the relative contribution of the lower channel was significantly increased as a function of the amount of sediment yield while that of the lower backslope was significantly decreased the relative contribution of the lower channel significantly decreased as a function of cumulative sediment yield while the contributions of the shoulder and the upper backslope significantly increased our results showed that the ree technique can be used to track sediment sources for a relatively long period with two limitations or potential sources of error associated with a selective depletion of tracers and a contamination of downslope areas with tagged sediments from upslope areas copyright 2006 john wiley sons ltd

fault systems of the 1971 san fernando and 1994 northridge earthquakes southern california relocated aftershocks and seismic images from larse ii we have constructed a composite image of the fault systems of the m 6 7 san fernando 1971 and northridge 1994 california earthquakes using industry reflection and oil test well data in the upper few kilometers of the crust relocated aftershocks in the seismogenic crust and larse ii los angeles region seismic experiment phase ii reflection data in the middle and lower crust in this image the san fernando fault system appears to consist of a decollement that extends 50 km northward at a dip of 25 from near the surface at the northridge hills fault in the northern san fernando valley to the san andreas fault in the middle to lower crust it follows a prominent aseismic reflective zone below and northward of the main shock hypocenter interpreted upward splays off this decollement include the mission hills and san gabriel faults and the two main rupture planes of the san fernando earthquake which appear to divide the hanging wall into shingle or wedge like blocks in contrast the fault system for the northridge earthquake appears simple at least east of the larse ii transect consisting of a fault that extends 20 km southward at a dip of 33 from 7 km depth beneath the santa susana mountains where it abuts the interpreted san fernando decollement to 20 km depth beneath the santa monica mountains it follows a weak aseismic reflective zone below and southward of the main shock hypocenter the middle crustal reflective zone along the interpreted san fernando decollement appears similar to a reflective zone imaged beneath the san gabriel mountains along the larse i transect to the east in that it appears to connect major reverse or thrust faults in the los angeles region to the san andreas fault however it differs in having a moderate versus a gentle dip and in containing no mid crustal bright reflections

fingerprinting suspended sediment sources in the catchment of the river ouse yorkshire uk statistically verified composite fingerprints and a multivariate mixing model have been employed to establish the main sources of the suspended sediment transported through the lower non tidal reaches of the river ouse and one of its main tributaries the river wharfe during the period 1994 1997 in the case of the suspended sediment samples collected from the river ouse the load weighted mean contributions from uncultivated topsoil cultivated topsoil and channel bank sources were estimated to be c 25 38 and 37 respectively while for the river wharfe these sources contributed c 70 4 and 23 respectively c 4 was derived from woodland topsoil suspended sediment samples collected during higher flows evidenced a greater contribution from channel banks than samples collected during lower flows source materials were also differentiated according to the three main geological source areas carboniferous permian and triassic and jurassic and their load weighted mean contributions were estimated to be c 24 41 and 35 for the river ouse and c 91 9 and 0 there are no jurassic rocks in this catchment for the river wharfe respectively when suspended sediment samples from tributary streams were used to characterize each geological source area the equivalent results for the river ouse were c 30 46 and 24 considering the three main tributaries that contribute to the river ouse the load weighted mean contributions from the rivers swale ure and nidd were estimated to be 82 15 and 3 respectively these values have been compared with estimates of the relative magnitude of the annual suspended sediment loads of these three rivers for the years 1995 and 1996 derived from continuous monitoring of discharge and turbidity differences between the two sets of results are ascribed to the different periods of record involved and to the timing of suspended sediment sampling relative to the overall storm hydrograph and thus the degree to which the available samples are representative of the overall suspended sediment flux although a number of limitations must be recognized the fingerprinting approach to source ascription is seen as providing valuable information regarding suspended sediment sources in the study catchments copyright 1999 john wiley sons ltd

detachment and transportation of loose sediments by raindrop splash summary laboratory experiments on sediments ejected by splash consisted of two parts quantities ejected and mean projected distances were measured since the splash tray was 100 cm long and 20 cm wide and since both measurements were made on a receiving screen of one square metre it was obvious that only part of the translocated sediment was caught it was subject to serious doubt that the measured distances were representative for all sediment translocated if it is stated that the ejected sediment is distributed according to an exponential function around any point of impact located on the tray and if by definition tray and rainfall are perfectly homogeneous the ratio of the true to the measured distance and the ratio of the caught to the translocated sediment are only a function of the exponent of the real function the apparent distance being also a function of this exponent is thus the only factor needed to solve the two questions hence all empirical data were transformed into true data

earthquake focal mechanisms in the eastern transverse ranges and san emigdio mountains southern california and evidence for a regional decollement earthquake focal mechanisms obtained from p wave first motions are presented for the eastern transverse ranges and the san emigdio mountains in southern california the former region shows a predominance of strike slip faulting whereas quaternary faults in the region show thrust motion we suggest that the observed strike slip mode of deformation cannot continue indefinitely without the occurrence of more thrust faulting fault deformation in the san emigdio mountains inferred from focal mechanisms is in accord with displacements across quaternary faults in the area this study and a search of the literature has yielded 19 mechanisms with shallow dipping nodal planes previous workers have interpreted such mechanisms as evidence for a regional decollement if such a regional decollement exists these data give some indication of its regional extent slip directions inferred from the focal mechanisms with shallow dipping nodal planes show some regional consistency but this pattern cannot be entirely explained with current tectonic models a comparison of the stress drop of an event having a shallow dipping nodal plane with an event with steeper planes gave inconclusive results

seasonal changes in the sediment flux on steep hillslopes in a humid diurnal frost environment mountain hillslopes are generally shaped by a combination of various types of sediment transport processes e g surface erosion soil creep and dry ravel which can occur simultaneously in the same area since sediment transport is generally affected by multiple microclimatic factors such as heavy rainfall and changes in ground temperature the types of predominant sediment transport processes vary by season we conducted field observations in the southern japanese alps in the period from 2009 to 2013 using sediment traps and time lapse cameras to investigate the seasonal changes in the type and flux of hillslope sediment transport on steep mountains in which both rainfall and diurnal freeze thaw triggered sediment transport in winter and early spring sediment transport via diurnal freeze thaw soil creep and dry ravel was highly active whereas rainfall induced soil creep and selective transport by overland flow were active in summer and autumn when precipitation is abundant average sediment flux of 0 033 and 0 074 kg m 1 day 1 respectively sediment flux was spatially variable and was affected by the form of the slope sediment flux on the concave slope was higher than on the ridge shaped slope during both freeze thaw and rainfall periods sediment flux on an old landslide exceeded that in second growth forest regardless of the slope shape temporal changes in the sediment flux were not completely synchronized among monitoring plots and were affected by slope shape grain size and episodic sediment supply events such as release of sediment from woody debris copyright 2016 john wiley sons ltd

integrating 3 d seismic data field analogs and mechanical models in the analysis of segmented normal faults in the wytch farm oil field southern england united kingdom we propose a methodology for the analysis of normal fault geometries in three dimensional 3 d seismic data sets to provide insights into the evolution of segmented normal fault systems and to improve recovery efforts in fault controlled oil fields limited seismic resolution can obscure subtle fault characteristics such as segmentation and gaps in fault continuity that are significant for oil migration and thus accurate reservoir characterization detailed seismic data analyses that incorporate principles of normal fault mechanics however can reveal evidence of fault segmentation we integrate seismic attribute analyses outcrop analog observations and numerical models of fault slip and displacement fields to augment the use of 3 d seismic data for fault interpretation we applied these techniques to the wytch farm oil field in southern england resulting in the recognition of significant lateral and to a lesser extent vertical segmentation of reservoir scale faults slip maxima on fault surfaces indicate two unambiguous segment nucleation depths controlled by the lithological heterogeneity of the faulted section faults initiated preferentially in brittle sandstone and limestone units subsequent growth and linkage of segments predominantly in the lateral direction resulted in composite fault surfaces that have long lateral dimensions and multiple slip maxima reservoir compartmentalization is greatest at the level of prevalent segment linkages which corresponds at wytch farm with the predominant hydrocarbon producing unit the sherwood sandstone at relatively shallower depths fault segments are younger and less evolved resulting in a greater degree of segmentation with intact relay zones

linkage and evolution of conjugate strike slip fault zones in limestones of somerset and northumbria conjugate strike slip fault zones that cover metre scale areas at beadnell northumbria and kilve somerset were initiated as conjugate vein arrays early conjugate faults are linked by the propagation of one fault that eventually by passes the other fault a model for the development of strike slip faults is presented using fault and vein geometries and the position of damage zones with respect to the master faults as an indication of the propagation direction this model includes the evolution of networks from 1 the initial random development of vein arrays to 2 the isolated development of several unconnected conjugate fault segments that pass into vein arrays through 3 the intersection of a conjugate set of master faults and linkage with minor antithetic faults and the formation of new vein arrays with extensional geometries after a linked network of faults is established to 4 breaching of intersection points by dominant faults and finally 5 the propagation towards oversteps that are breached to form a through going fault the geometry of the active structures simplifies with time as strain is localised along the master fault but the complexities are preserved in the fault walls

gaining insights into interrill erosion processes using rare earth element tracers abstract increasing interest in developing process based erosion models requires better understanding of the relationships among soil detachment transportation and deposition the objectives are to 1 identify the limiting process between soil detachment and sediment transport for interrill erosion 2 understand the dynamic relationships between transport and deposition by tracking sediment fate with multiple tracers and 3 verify the effects of slope length on interrill soil erosion five rare earth element ree tracers were applied in five bands or segments to track sediment dynamics on a 10 4 4 m long uniform slope under simulated rainfall a silt loam soil with 8 clay and 87 silt was used six rain events were applied the first four with 60 mm h 1 and the last two with 90 mm h 1 sediment in runoff and deposition along the slope were measured results confirmed that interrill soil erosion was controlled by the transport process thus soil erodibility estimated with many interrill erosion models was actually sediment transportability as the slope length increased soil erosion rates initially increased and then decreased indicating that the upper section was dominated by erosion and the lower section by transport raindrop driven creeping prevailed in the upper section while flow driven rolling dominated in the lower section sediment influx from upslope clearly suppressed soil detachment downslope moreover the steady state sediment discharge from a segment was positively correlated to the amount of sediment deposited downslope from that segment implying that 1 re detachment transport and deposition occurred simultaneously in the system and 2 sediment was transported in a form of bedload mainly rolling or creeping on interrill areas sediment delivery ratios of each segment tended to slightly increase downslope suggesting the flow driven transport was more efficient than the raindrop driven transport the sequence of sediment discharged from different slope positions was inconsistent with the transport distance theory however interrill erosion processes vary with soil slope and rainfall properties and the findings here need to be verified in different conditions

hydraulics of interrill overland flow on a semi arid hillslope southern arizona parsons a j abrahams a d and luk s h 1990 hydraulics of interrill overland flow on a semi arid hillslope southern arizona j hydrol 117 255 273 simulated rainfall experiments were conducted on an 18 m wide by 35 m long runoff plot located in southern arizona by using a wide plot that extended from the divide to beyond the rill heads it was possible to examine the full range of lateral variability and downslope changes in interrill overland flow on a shrub covered semi arid piedmont hillslope the mean depth d mean velocity v and reynolds number re of overland flow were computed for two measured sections situated 12 5 and 21 m from the top of the plot at a section d vs re and v vs re relations show that increases in re are accomodated largely by increases in d these hydraulic relations are principally the result of resistance to flow increasing with re as overland flow spreads into new areas inasmuch as the maximum equilibrium discharge simulated in these experiments has a return period of about 7 yr increasing resistance to flow as re increases may be considered typical of most overland flow events on shrub covered piedmont hillslopes in southern arizona downslope hydraulic relations differ strikingly from at a section relations under equilibrium runoff conditions resistance to flow decreases rapidly as re increases permitting increases in re to be accomodated entirely by increases in v the decrease in resistance to flow is due to progressive downslope concentration of flow into fewer deeper threads under non equilibrium conditions downslope hydraulic relations may be quite different from those obtaining at equilibrium but resistance to flow always decreases downslope this is the result of low flows following pathways formed by higher flows that concentrate downslope analyses of overland flow hydraulics at the scale of interrill areas produce results that are quite different from those obtained from small plots a knowledge of the hydraulics at this scale is essential if models of interrill overland flow are to become more realistic and hence better predictors of runoff hydrographs and sediment yield

evidence for possible horizontal faulting in southern california from earthquake mechanisms we find that 36 of the 505 fault plane solutions m 3 0 1981 1990 in southern california have a nodal plane dipping no more than 30 with the assumption of the low angle nodal planes being the fault planes four cross sections are constructed to show the possible horizontal faults in the middle and upper crust more than half of these low angle faults are located within or adjacent to the transverse ranges the focal depths vary from 1 km in the southern end of the sierra nevada and the southwestern mojave desert to 20 km in the transverse ranges the slip directions are also diverse in general east west extensional movements are dominant in the boundary between the southern sierra nevada extending to the san emigdio mountains and the western mojave desert whereas north south compressional movements are dominant in the transverse ranges in the peninsular ranges and the salton trough both the slip directions and focal depths vary these features suggest that seismically active low angle faults in southern california may exist at different depths and slip in various directions our data do not support the existence of a regional scale seismically active detachment in southern california only in the western transverse ranges is there some suggestion of a large detachment surface at a depth of about 13 to 14 km

tracing sediment redistribution across a break in slope using rare earth elements experimentally determined spatial patterns of soil redistribution across a break in slope derived using 10 rare earth element ree oxides as sediment tracers are presented an erosion experiment was conducted using simulated rainfall within a laboratory slope model measuring 2 5 m wide by 6 m long with a gradient of 15 declining to 2 soil was tagged with multiple ree and placed in different locations over the slope and at the end of the experiment ree concentrations were measured in samples collected spatially a new method was developed to quantify the erosion and deposition depths spatially the relative source contributions to deposited sediment and the sediment transport distances particle size selectivity over an area of net deposition was also investigated by combining downslope changes in particle size distributions with changes in sediment ree composition within a flow pathway during the experiment the surface morphology evolved through upslope propagation of rill headcuts which gradually incised the different ree tagged zones and led to sediment deposition at the break in slope and the development of a fan extending over the shallow slope segment the spatial patterns in ree concentrations the derived erosion and deposition depths the relative source contributions to deposition zones and the sediment transport distances corroborate the morphological observations and demonstrate the potential of using ree for quantifying sediment transport processes

interactions between a cushion plant azorella selago and surface sediment transport on sub antarctic marion island on sub antarctic marion island cushions of the dominant vascular plant species azorella selago interact with the geomorphology of fellfield landscapes by affecting sediment distribution and ultimately terrace formation here to understand the consequences of azorella cushions for substrate movement and sorting we quantified the size and shape of azorella cushions and the grain size distribution of sediment surrounding these cushions using a combination of image analysis approaches results show that as cushions become larger they tend to become more elongated and grow more perpendicular to the slope mean and variance of grain size were greater upslope of azorella cushions while the number of particles was higher downslope of cushions although these differences were not significant at all sites studied differences between upslope and downslope particle sizes were however not related to cushion elongation or growth angle as had been expected the observed sediment partitioning is likely caused by a combination of frost related sediment transport and azorella cushions acting as sediment obstructions understanding these interactions between azorella cushions and the landscape is especially important in the light of recent warming and drying on the island as particle size affects soil properties such as water holding capacity and frost susceptibility

splash detachment runoff depth and soil cohesion summary a set of laboratory experiments has been carried out in order to investigate the importance of soil cohesion and the interference due to the depth of the surface runoff on the detachment rate of soil particles and aggregates experimental data show that the soil detachment rate decreases as the runoff depth increases this indicates that the detachment power of the raindrops is partially dispersed by the water layer an inverse relationship between soil detachment and soil cohesion has been confirmed nevertheless the grain size distribution must also be used in order to define soil detachability

rare earth element oxides for tracing sediment movement the development of soil conservation plans and evaluation of spatially distributed erosion models require knowledge of rates of soil loss and sedimentation on different landscape elements and slope positions characterization of soil erosion rates and patterns within watersheds is important for the understanding of erosion processes and landscape evolution experimental data that show spatial translocation of soil on slopes are limited a method for obtaining spatially distributed information on sediment movement employing rare earth element ree oxides is proposed five ree oxides in powder form were uniformly mixed with the soil on different parts of a 10 slope in a 4 4 m soil bed particle translocation was measured during eight simulated rainfalls at 60 mm h 1 intensity a laser scanner was utilized to obtain digital elevation models dems of the soil surface that were used as the reference data to compare with the tracer method ree concentration in soil and runoff samples was determined by inductively coupled plasma mass spectrometry icp ms erosion rates for different slope positions estimated from ree concentrations correlated with those calculated from the dems with relative differences for different slope sections of 4 40 the enrichment ratio for this type of tracer was 1 7 the amount of sediment produced on different parts of the slope varied with the greatest erosion occurring on the upper middle part of the slope the experiment showed that the multi element tracer method provided a satisfactory way to study soil erosion distribution on a uniform slope d 2003 elsevier b v all rights reserved

the concept of transport capacity in geomorphology the notion of sediment transport capacity has been engrained in geomorphological and related literature for over 50 years although its earliest roots date back explicitly to gilbert in fluvial geomorphology in the 1870s and implicitly to eighteenth to nineteenth century developments in engineering despite cross fertilization between different process domains there seem to have been independent inventions of the idea in aeolian geomorphology by bagnold in the 1930s and in hillslope studies by ellison in the 1940s here we review the invention and development of the idea of transport capacity in the fluvial aeolian coastal hillslope debris flow and glacial process domains as these various developments have occurred different definitions have been used which makes it both a difficult concept to test and one that may lead to poor communications between those working in different domains of geomorphology we argue that the original relation between the power of a flow and its ability to transport sediment can be challenged for three reasons first as sediment becomes entrained in a flow the nature of the flow changes and so it is unreasonable to link the capacity of the water or wind only to the ability of the fluid to move sediment secondly environmental sediment transport is complicated and the range of processes involved in most movements means that simple relationships are unlikely to hold not least because the movement of sediment often changes the substrate which in turn affects the flow conditions thirdly the inherently stochastic nature of sediment transport means that any capacity relationships do not scale either in time or in space consequently new theories of sediment transport are needed to improve understanding and prediction and to guide measurement and management of all geomorphic systems

crustal scale transcurrent fault development in a weak layered crust from an integrated geophysical research carboneras fault zone eastern betic cordillera spain new magnetotelluric and receiver transfer function studies provide insights from the upper to the lower crust of the eastern betic cordillera which is deformed by large folds normal faults and a major transcurrent left lateral fault the carboneras fault zone cfz receiver function analysis determines a nnw dipping moho reaching 20 that increases in depth from 20 km south of the cfz up to 34 km in the sierra de los filabres in addition seismic discontinuities determined in the upper crust are interpreted as major contacts between metamorphic complexes that are detached and folded the mt inversion model reveals a conductive zone also representing a crustal seismic discontinuity associated with the alpujarride nevado filabride contact and fitting the n vergent geometry of the sierra alhamilla antiform a small flexure at moho coincides with the cfz as revealed by the bouguer anomaly trend in agreement with the receiver function results moreover the bahr strike and tipper angle at the stations placed closest to the cfz clearly reveal the continuity of the cfz at least down to approximately 15 km in depth crossing all the detected crustal discontinuities up to the moho the lack of a clear moho offset associated with the carboneras fault supports the idea that some large strike slip faults tend to accommodate the deformation by a broadening fault zone at lower crustal levels its nucleation could occur at the base of a thin crust where melting processes critically reduced the lithospheric strength during the late miocene to then propagate upward reaching the topographic surface northward the lithosphere comprised moderately larger strength and the crustal discontinuities favored the development of larger folds with kilometric amplitude instead of strike slip faults since the late miocene

tracing movements of topsoil by magnetic measurements two case studies an array of magnetic measurements is used to trace the occurrence of magnetically enhanced topsoil in two different environmental settings the first is a cultivated slope section where the results confirm that movements of topsoil have occurred but that identification of specific erosional processes is problematic the second is a lake catchment system where measurements on soils and sediments allow a partial reconstruction of soil movements from different sources over the last 200 y the study highlights both the need to analyse the magnetic mineralogies of different particle size fractions and the difficulties that may be encountered in trying to discriminate between topsoil and subsoil material on the basis of demagnetization parameters alone

stratigraphic record of pleistocene faulting and basin evolution in the borrego badlands san jacinto fault zone southern california sedimentary rocks in the borrego badlands southern california contain a record of pleistocene crustal deformation during initiation and evolution of the san jacinto fault zone we used detailed geologic stratigraphic and paleomagnetic analysis to determine the age and geometry of the deposits and reconstruct the history of fault controlled sedimentation in this area the base of the 300 to 500 m thick ocotillo formation is a paraconformity to abrupt conformable contact that records a brief hiatus followed by rapid progradation of coarse alluvial sediment over lacustrine facies of the borrego formation at 1 05 0 03 ma this coincides with regional scale progradation of ocotillo formation sand and gravel and appears to record initiation of strike slip faults in the southwestern salton trough at ca 1 1 ma thickness trends clast compositions paleocurrents and distribution of paleosols provide evidence for initiation of the east coyote mountain fault at ca 1 05 ma followed by onset of nne ward basin tilting obliquely toward the santa rosa segment of the clark fault at ca 1 0 ma stratigraphic omission of the ocotillo formation and progressively older units southwest of the coyote creek fault beneath the fonts point sandstone provides evidence that tilting to the northnortheast was related in part to growth of the san felipe anticline during deposition of the ocotillo formation map and stratigraphic data suggest that the coyote creek fault in the western borrego badlands postdates ocotillo deposition and thus appears to have propagated southeast into the study area at ca 0 6 ma the fonts point sandstone is a thin sheetlike alluvial deposit that records the end of deposition and onset of transpressive deformation in the borrego badlands the base of the fonts point sandstone changes from a conformable contact in a narrow belt southeast of the inspiration point fault where it is dated at 0 6 0 02 ma to an angular unconformity on the folded ocotillo formation northwest of the fault the pattern of stratal truncation records initiation of the inspiration point fault at ca 0 6 ma this coincides with a major structural reorganization in the san jacinto fault zone that initiated the modern phase of north south shortening and erosion in the southwestern salton trough

the effect of spatial variability in overland flow on the downslope pattern of soil loss on a semiarid hillslope southern arizona summary in this study we investigate the relation between soil loss and slope length in an interrill portion of a gentle plan planar semiarid hillslope in southern arizona simulated rainfall experiments were conducted on an 18 m wide by 35 m long runoff plot the upper end of which coincided with the hillslope divide sediment loads were measured at two cross sections s1 and s2 located 12 5 and 21 m respectively downslope from the divide from these data section soil losses under equilibrium runoff conditions were computed average section soil loss was found to increase from the divide to s1 and to decrease from s1 to s2 to explain this downslope pattern of soil loss a simulation model was developed for soil detachment by raindrop impact and sediment removal by overland flow at a cross section input data for the model consist of overland flow depths and velocities measured at closely spaced points along a cross section the model was applied to three cross sections located at 3 3 12 5 and 21 m downslope from the divide and predicted a downslope pattern of soil loss similar to that observed the success of the model suggests that in the interrill portions of a wide range of gentle arid and semiarid hillslopes downslope patterns of soil loss are controlled in large part by downslope changes in across slope distributions of overland flow depth and velocity

investigating source areas of eroded sediments transported in concentrated overland flow using rare earth element tracers rare earth element oxides reos have excellent potential for use as tracers in erosion studies using laboratory and field experiments we aimed to develop and test a simple application method for spreading reos and to use reos to determine the source of sediment to concentrated overland flow paths tracks left by farm machinery tramlines in fields act as concentrated flow paths delivering a large amount of surface runoff and entrained sediment to the field boundary however little is known regarding where this sediment is sourced from two field experiments were conducted to investigate this one looking at whether sediment is entrained from different points along the length of the tramline and one looking at the area over which sediment is entrained from either side of a tramline results from leaching tests and rainfall simulations clearly demonstrated the potential of this method for tracing sediment there was very little movement of reos through the soil profile and they were transported with sediment in overland flow in the field experiment a large proportion of the sediment transported in the tramline originated within the first metre either side of it however the total area over which eroded sediment collects and flows into the tramline is potentially large with small amounts of sediment eroded from the between 4 and 6 m being transported in the tramline reos have an excellent potential for use as a tracer of soil erosion they provide a quick and cheap method of identifying sources of eroded sediments and have good potential for use in determining erosion rates

soil creep the driving factors evidence and significance for biogeomorphic and pedogenic domains and systems a critical literature review abstract soil and regolith creep have been analyzed for at least the last 140 years using many methodological configurations and temporal and spatial scales the general concept of creeping soil and its mechanism first proposed by w m davis and g k gilbert at the end of the 19th century evolved since the 1940s towards theoretical models and precise short and long term field measurements this fruitful epoch continued with results enhanced at the turn of the 20th century by the application of new research methods e g radiometry and a redefinition of the term soil creep to encompass the sum of stochastic shallow subsurface and near surface processes causing net downslope movement of soil or regolith simultaneously another possibility of creep detection was noticed in dendrochronology and since the 1970s in the formally defined discipline of dendrogeomorphology indirect evaluations of creep activity were performed based on tree ring analyses of bent trees this method found many followers but was also heavily criticized as imprecise and lacking in evidence of which kind of tree trunk curvature e g pistol butt like deformation s shape curvature could be ascribed to creep movement from the beginning soil creep was associated with the activity of living organisms on hillslopes however this aspect of creep studies has never been fully developed in spite of the solid foundations and directions of potential studies pointed out by charles darwin at the end of the 19th century in this paper we focus on the historical context of soil creep studies and highlight forest ecosystems as probably the most active environment of biogenic creep mainly due to tree uprooting and other biomechanical effects of living and dead trees root channel infilling tree root mounding etc that are a factors in biotransport in the final sections the position of biogenic creep in the structure of biogeomorphic systems is discussed in relation to such important conceptual frameworks as the biogeomorphic ecosystem biogeomorphic feedback window and ecosystem engineering we also describe several hypotheses that should be carefully tested in the future and propose several research methods that have the ability to further our knowledge about soil creep radiometry laser scanning and soil micromorphology

needle ice formation induced frost heave and frost creep a case study through photogrammetry at stelvio pass italian central alps abstract needle ice growth is one of the more widespread and easily visible but less studied climate related processes shaping soil evolution surface dynamics and ecosystem changes in the alpine environments here we show the results of the monitoring of needle ice development at four plots located at 2670 m a s l close to the stelvio pass in the italian central alps during 2016 needle ice formation and evolution with time was monitored through the photogrammetric technique of the structure from motion sfm our monitoring data included also quantitative measurements of some selected physical and climatic parameters like air temperature ground temperature and ground water content at depths of 2 and 5 cm our data demonstrate that needle ice can develop with a relatively low ground water content 13 2 at a relatively high minimum ground temperature 0 3 c and with a low cooling rate the total frost heave seems to be related to the abundance of fine material although we couldn t demonstrate it statistically the absence of statistically significant relationships between frost heave and frost creep could be probably due to the importance of the observed needle ice toppling and the possible sliding of the clasts during the melting phases

relay zones between mesoscopic thrust faults in layered sedimentary sequences abstract we examine the geometry formation and destruction of relay zones in well bedded sedimentary sequences containing thrust fault segments with maximum observed displacements of 0 64 8 m contractional extensional and neutral relay zones are distinguished based on the stepping sense of the interacting fault segments and the orientation of the associated fault slip vectors large displacement gradients 0 17 1 0 in relay zones are mainly accommodated by folding with aggregate displacements maintained across segment boundaries and a significant component of the fault slip converted to fold related shortening folds in contractional relay zones verge in the direction of hanging wall motion with the steeper limb defining a parallelogram shaped zone between thrusts fault segment lengths are established after minimal displacement and folds in relay zones grow between segments as displacement accrues on the thrusts with increasing displacement upper and lower thrust tip lines in contractional and extensional relay zones are fixed at stratigraphic boundaries while the lateral thrust tip lines may propagate in a strike parallel direction upper and lower tip lines may eventually propagate to bypass relay zones that formed early in the fault growth history contractional relay zones remain intact at higher displacements than extensional relay zones

soil moisture and texture controls of selected parameters of needle ice growth needle ice was grown in the laboratory to determine the limits of soil moisture and texture on the growth of needle ice as the percentage of fines in the soil increases the lower limit of soil moisture required for growth decreases and may be defined by a linear boundary the efficiency of conversion of soil water to needle ice in soil samples used peaked at about 16 per cent soil fines contrary to expectations the finer textured soils produced significantly thicker ice crystals quantity of soil lifted by needle ice was related to ice height the ice mass to atmospheric void ratio soil texture and moisture and soil surface roughness however no definite quantitative relationships could be determined a test to determine if needle ice is selective in the grain sizes of particles lifted suggested no selectivity

the source of sediment transported by raindrop induced saltation summary the movement of particles traveling by raindrop induced saltation from 5 equally long segments on bare planar slopes 0 8 m to 20 m in length inclined at 5 was simulated under 100 mm h 1 rain with drops of 2 7 mm in size initially the sediment discharges were dominated by material detached from near the downstream boundary but as time progressed the dominant source moved upslope as particles detached in the upslope areas contributed to the sediment discharge on the 20 m long slope the top 4 m long slope segment was the dominant contributor to the discharge at the steady state this result is consistent with the relative degree of protection against detachment provided by the shallow flows in that segment however on the 4 m long slope although the uppermost 0 8 m long segment had the highest potential for detachment the capacity to transport material from that segment was restrictive and the dominant source at the steady state occurred further down the slope the results of the simulations indicate that if the slope is divided into a number of equally long segments the segment contributing to the greatest source of the sediment discharged by raindrop induced saltation at the steady state moves down the slope as slope length is reduced

solute release and sediment entrainment on microcatchments in the dinosaur park badlands alberta canada abstract this paper first considers the uptake of solutes and entrainment of sediments in runoff generated by simulated rainstorms on different badland surfaces then properties of the regolith materials related to solute uptake are described and studied in a number of simple laboratory experiments field and laboratory results are in close agreement runoff solute and sediment uptake are profoundly influenced by the large amounts of sodium montmorillonite present in the regolith shale surfaces although responding late to rainfall release increasing amounts of sediment and solutes sodium and sulphate as they swell and increase in erodibility on other surfaces low rates of rainfall acceptance are caused by the secretion of montmorillonite gels and there is a gradual decrease in solute and sediment concentration as accumulated salts are flushed from the surface the effect of the chemistry of the simulated rainfall on the experimental results is examined it is considered possible to characterize the pattern of solute and sediment uptake on the different badland surfaces and to apply this information to the identification of runoff sources in mesoscale drainage basins and to the routing of storm runoff

linking environmental regimes space and time interpretations of structural and functional connectivity connectivity as a concept has been increasingly part of discussions or explanations in hydrology geomorphology and ecology we address recent critiques of this approach by demonstrating how a refinement which distinguishes structural connectivity from functional connectivity can be used to explain patterns observed in very different environmental systems these systems are found in linkages between surface and subsurface flowpaths and the hyporheos in the river don a temperate river channel in yorkshire uk in surface and subsurface fluxes in agricultural land in the uk and in vegetation and surface conditions in a degrading environment at the sevilleta lter site in the semi arid southwest usa first we demonstrate long term geological and structural controls mediated by in channel processes second human organization of landscape elements is a significant control on runoff and erosion so that similar events can produce very different responses and vice versa third linkages between the removal of grass vegetation and runoff and erosion produce non linear and path dependent feedbacks which control the subsequent degradation of the landscape making the process difficult to reverse as a result of these studies we argue that even in cases where connectivity cannot be directly quantified at least at present this limitation does not prevent the concept from being a useful heuristic device for exploring responses of complex systems furthermore this result implies that an increasing need exists for disciplinary connectivity to investigate such systems

error in polygon overlay processing of geomorphic data predictive models for calculating sediment yield and discharge require accurate areal data such models may be unrealistic when using digitized data given the potential error involved in compiling and digitizing thematic polygon maps the estimation of boundary variability for digitized polygon maps of a 0 34 km2 area of badlands in dinosaur provincial park alberta shows the effects of positional errors introduced during mapping and digitizing processes polygon overlay of maps of surface features and slopes produced high frequencies of very small polygons and some unlikely combinations of slopes and surface features and decreased reliability in areal measurements in the composite map at an epsilon band width of 0 7 m a reasonable estimate of boundary variability 31 7 per cent of the resultant overlaid map can be considered unreliable

segmentation of fault networks determined from spatial clustering of earthquakes 1 we present a new method of data clustering applied to earthquake catalogs with the goal of reconstructing the seismically active part of fault networks we first use an original method to separate clustered events from uncorrelated seismicity using the distribution of volumes of tetrahedra defined by closest neighbor events in the original and randomized seismic catalogs the spatial disorder of the complex geometry of fault networks is then taken into account by defining faults as probabilistic anisotropic kernels the structure of those kernels is motivated by properties of discontinuous tectonic deformation and by previous empirical observations of the geometry of faults and of earthquake clusters at many spatial and temporal scales combining this a priori knowledge with information theoretical arguments we propose the gaussian mixture approach implemented in an expectation maximization em procedure a cross validation scheme is then used that allows the determination of the number of kernels which provides an optimal data clustering of the catalog this three step approach is applied to a high quality catalog of relocated seismicity following the 1986 mount lewis ml 5 7 event in california it reveals that events cluster along planar patches of about 2 km2 i e comparable to the size of the main event the finite thickness of those clusters about 290 m suggests that events do not occur on well defined and smooth euclidean fault core surfaces but rather that there exist a deforming area and a damage zone surrounding faults which may be seismically active at depth finally we propose a connection between our methodology and multiscale spatial analysis based on the derivation of a spatial fractal dimension of about 1 8 for the set of hypocenters in the mount lewis area consistent with recent observations on relocated catalogs