the influence of fluid sensitive dispersion and attenuation on avo analysis summary analysis of seismic data suggests that hydrocarbon deposits are often associated with higher than usual values of attenuation but this is generally ignored during amplitude versus offset avo analysis the effect can be modelled with equivalent medium theory based on the squirt flow concept but the excess attenuation is associated with strong velocity dispersion consequently when we study reflections from the interface between such an equivalent medium and an elastic overburden we find that the reflection coefficient varies with frequency the impact of this variation depends on the avo behaviour at the interface class i reflections tend to be shifted to higher frequency while class iii reflections have their lower frequencies amplified we calculate synthetic seismograms for typical models using the reflectivity method for materials with frequency dependent velocities and attenuations and find that these effects are predicted to be detectable on stacked data two field data sets show frequency anomalies similar to those predicted by the analysis and we suggest that our modelling provides a plausible explanation of the observations

digital elevation model resolution effects on terrain attribute calculation and quantitative soil landscape modeling the accuracy of digital elevation models dem and dem derived products depends on several factors including the horizontal resolution and vertical precision at which the elevation data are represented and the source of the elevation data this accuracy becomes increasingly important as we extend the use of dem data for spatial prediction of soil attributes our objective was to compare terrain attributes and quantitative soil landscape models derived from grid based dem represented at different horizontal resolutions 10 and 30 m represented at different vertical precisions 0 1 and 1 m and acquired from different sources decreasing the horizontal resolution of the field survey dem produced lower slope gradients on steeper slopes steeper slope gradients on flatter slopes narrower ranges in curvatures larger specific catchment areas in upper landscape positions and lower specific catchment areas values in lower landscape positions overall certain landscape features were less discernible on the 30 m dem than on the 10 m dem decreased vertical precision produced a large proportion of points with zero slope gradient and zero slope curvature and a large number of steeply sloping and more highly curved areas differences among dem from different sources were more significant with less accurate representation of depressions and drainage pathways with the usgs dem as compared to the field survey dem empirical models developed from different dem included similar predictive terrain attributes and were equally successful in predicting a horizon depth ahd in the validation data set

sources of spatial complexity in two coastal plain soil landscapes abstract the spatial pattern of soils and soil properties in soil landscapes is considered here as a function of 1 systematic variation along catenas or associated with spatial patterns of soil forming factors and 2 local pseudo random variations associated with local disturbances or small unobserved variations in soil forming factors the problem is approached at two study sites in the u s atlantic coastal plain using algebraic graph theory and the spectral radius of the soil adjacency matrix as a measure of complexity the matrix is constructed based on the observed spatial contiguity of soil taxa and soil factor sequences sfs are defined for each site based on systematic soil variation associated with variations in parent material topography sandy surface thicknesses and secondary podzolization the spectral radii of the networks described by the adjacency graphs are compared to those associated with the maximum for a graph of the same size and the maximum associated with control entirely by variations in soil forming factors at the clayroot study site which is entirely cropland complexity of the adjacency matrix is less than the maximum that could be accounted for by the four identified sfs due to redundant information in the sfs the littlefield site by contrast has a spectral radius greater than here where about half the site is forested the contingent variation is likely associated with effects of individual trees on soil morphology the utility of the adjacency analysis is in identifying whether soil heterogeneity is likely associated with sfs or with contingent factors not captured in sfs

thermotectonic history of the chiplakot crystalline belt in the lesser himalaya kumaon india constraints from apatite fission track thermochronology abstract fission track ages and confined track length distribution of apatite samples separated from the chiplakot crystalline belt ccb of the lesser himalayan crystalline lhc zone located to the south of the main central thrust mct munsiari thrust mt in kumaon india have been determined ages from the ccb along the kali and darma valleys fall in two distinct groups in the northern part of the ccb the ages range from 9 8 0 6 to 7 6 0 6 ma with a weighted mean of 9 6 0 1 ma while in the southern part the ages vary from 17 9 0 9 to 12 9 1 1 ma with a weighted mean of 14 1 0 1 ma the bimodal distribution of track lengths indicates that the ages are mixed ages rather than simple cooling ages the apatite fission track aft ages and already published structural data of the ccb suggest a complex erosional denudation history within the upper 3 4 km of the crust of the ccb the ages further indicate that the ccb was thrust into place earlier than the middle miocene i e at the time of development of the mct since then these rocks have remained within the upper 3 km of crust and were affected by only moderate to slow erosion and exhumation these results have important implications for the tectonic evolution of the lhc zone to the south of the mct mt the exhumation of the lhc zone in different parts of the himalaya was not uniform in the kumaon himalaya it was not controlled as in the himachal himalaya by any major tectonic event since it was thrust over the lesser himalayan meta sedimentary lhms zone and underwent moderate to slow erosion and exhumation

landforms as extended composite phenotypes biotic influences on geomorphology and vice versa are ubiquitous this paper explores whether landforms may be extended composite phenotypes of biota based on four criteria process form relationships between biota and landforms evolutionary synchrony selective pressure via ecosystem engineering and niche construction and positive feedback benefitting the engineer organism s coral reefs peat bogs biomantles insect mounds grassland soils salt marshes mangrove swamps and some vegetation dependent sand dune types clearly meet these criteria karst landforms meandering rivers and tree uprooting pit mound systems meet the first three criteria but positive feedback to engineer organisms has not been established research in biogeomorphology will surely identify other extended phenotypes implications are that biological evolution will continue to drive landscape metamorphosis the appearance of new landform types and presumably the disappearance of extended phenotypes associated with extinct species independently of extended phenotypes tightly coupled geomorphological ecological interactions such as coevolution and biogeomorphic forms of ecosystem engineering and niche construction are common the toposphere encompassing earth s landforms is partly a biotic construct some elements would be present in an abiotic world but the toposphere would not exist in anything resembling its contemporary state without a biosphere this raises important questions with respect to earth system evolution the bio litho atmo hydro topo and pedospheres coevolve at the global scale major biotic events have driven revolutions in the other spheres but the atmosphere and the global hydrological system seem to have been relatively steady state at the global scale the toposphere and pedosphere have not this suggests that perhaps landforms and soils provide the major mechanisms or degrees of freedom by which earth responds to biological evolution landforms and soils may thus be the voice of the biosphere as it authors planetary change even if clear biotic signatures are lacking copyright 2015 john wiley sons ltd

spatiotemporal variation in exhumation of the crystallines in the nw himalaya india constraints from fission track dating analysis abstract during himalayan orogeny coeval thrusting along the main central munsiari thrust mct mt and extension along the south tibetan detachment system stds are widely responsible for rapid exhumation of the higher himalayan crystalline hhc zone apatite and zircon fission track data along the kaliganga and darma valleys in the kumaon himalaya serve to document the shallow bedrock exhumation history of the hhc taking into account sample location within the hhc with respect to the mct mt the apatite fission track aft data sets along the darma 1 0 0 1 to 2 8 0 3 ma and kaliganga 1 4 0 2 to 2 4 0 3 ma which are sharing same structural setting and rock types and being separated by 40 km show very similar patterns of exhumation histories since plio quaternary in the kumaon himalaya data sets along darma and kaliganga are very similar to data set of adjacent traverse 50 km away along the goriganga valley studied by patel and carter 2009 whole data sets within the hhc in kumaon himalaya provide clear evidence for plio quaternary tectonic activity along the vaikrita thrust vt precipitation in this region exerts a strong influence on erosional surface processes fluvial erosional unloading along the himalaya is focused on the high mountainous region of the hhc where the orographic barrier forces out the maximum percentage of annual rainfall ft cooling ages reveal coincidence between rapid erosion and exhumation that is focused in a 25 30 km wide sector of the hhc rather than covering the entire orogen similarity of aft age pattern and exhumation rates along all three major traverses goriganga darma and kaliganga indicates that the region has been experiencing constant rate of crustal uplift and erosion since long time comparison of fission track ages from the kumaon himalaya with other segments of the nw himalaya shows spatiotemporal variation in exhumation it is described due to the development of local structures such as dome window in jammu and kashmir and himachal himalayas and quaternary active thrusting along the vt and mct mt in the garhwal kumaon himalaya

estimating permeability from field measurements of seismic attenuation in fractured chalk broadband 100 4000 hz cross hole seismic data have been acquired at a borehole test site where extensive hydrological investigations have previously been performed including in situ estimates of permeability the rock type is homogeneous chalk and fractures and bedding planes have been identified from well logs high values of seismic attenuation q 22 27 33 were observed over a 10 m depth interval where fracture permeability values of 20 50 darcy had been recorded an attempt has been made to separate the attenuation due to scattering and intrinsic mechanisms the estimated values of intrinsic attenuation q 31 43 71 have been reproduced using a number of current theories of seismic wave propagation and fluid flow induced seismic attenuation in cracked and fractured media a model that considers wavelength scale pressure gradients is the preferred attenuation mechanism model parameters were obtained from the hydro geological and seismic data however we conclude that it is not possible to use seismic q to measure rock permeability remotely principally because of the inherent uncertainties arising from model parameterisations

divergent evolution and the spatial structure of soil landscape variability abstract the spatial structure of soil variability at the landscape scale was examined on adjacent geomorphic surfaces dating from 80 to 200 ka in eastern north carolina the purpose was to determine whether there is evidence at broader scales distances of 102 104 m for the divergent evolution observed in the field at very detailed scales distances of 100 102 m the state probability function spf which measures spatial dependence for categorical environmental data along a transect was applied to soil series mapped at a 1 24 000 scale the older talbot terrace and younger pamlico terrace surfaces showed distinctly different patterns of spatial variability the range of spatial dependence was shorter on the older surface about 200 vs 300 m and the spf was higher at any given distance indicating more variability the spf for the pamlico surface also indicates a periodicity related to fluvial dissection of the landscape which is not readily detectable on the talbot transect despite its greater degree of dissection the results confirm earlier field studies which suggest that pedogenesis is marked by divergence whereby differences in initial conditions or local perturbations persist and increase to produce a more variable soil cover

soil deepening by trees and the effects of parent material abstract in some cases biomechanical effects of individual trees may locally deepen or thicken regolith especially in relatively shallow soils this biogeomorphic ecosystem engineering phenomenon is at least partly contingent on the geological setting the purpose of this research was to gain further insight into the biogeomorphic phenomenon and to assess the relative importance of biomechanical and geological effects earlier studies in the ouachita mountains of arkansas showed that individual trees locally thicken the regolith via mechanisms associated with root penetration of bedrock however that work was conducted mainly in areas of strongly dipping and contorted rock where joints and bedding planes susceptible to root penetration were thought to be common and accessible this project extended the research to the cumberland plateau region of kentucky where flat level bedded sedimentary rocks are dominant soil depth beneath trees was compared to that of non tree sites by measuring depth to bedrock beneath rotted tree stumps and at adjacent sites with 1 0 m while soil thickness beneath stumps was greater in the ouachita mountains compared to the kentucky sites in both regions soils beneath stumps are significantly deeper than adjacent soils further there were no statistically significant differences in the difference between stump and adjacent sites between the two regions this suggests the local deepening effects of trees occur in flat bedded as well as steeply dipping lithologies

impacts of old comparatively stable treethrow microtopography on soils and forest dynamics in the northern hardwoods of michigan usa abstract uprooting represents a key disturbance process in forests forming pit mound microtopography which can then dramatically impact pedogenesis and the forest ecology at our study sites in northern michigan where well drained sandy spodosols dominate pit mound microtopography tends to persist for millennia because of its persistence the influence of this type of microtopography is greater here than in most forests in that respect our sites represent an end member along a continuum of forest soil disturbance by uprooting we studied post uprooting pedogenesis at 14 dated pit mound pairs mapped and characterized the pit mound topography over 2 8 ha the soils below within 317 soil profiles and the trees above to better understand the complex interactions among this type of disturbance regime and forest dynamics we used a pair correlation function and chi square test approach to study the relationships between treethrow features and the living trees at one of these sites soil variability as affected by microtopography was studied using geostatistics pit mound microtopography here covers 17 of the surface and are generally randomly distributed across the forest floor mounds are more prominent features of the forest floor than are pits pits infill with sediment and litter obscuring them whereas mounds persist for millennia in the sandy sediment because runoff is limited and litter forms a protective armor treethrow features had volumes of roughly 214 225 m3 ha and on average each uprooting event translocated 0 6 m3 of soil about 0 8 m laterally and 0 1 0 2 m vertically areas of the pit mound features did not differ between slope aspects supporting an idea that on the gentle slopes of the study sites uprooting does little to affect the movement of sediment downslope the exceptional longevity of the treethrow features is probably a factor in the statistical randomness with which treethrow features are distributed on the forest floor as footprints of many uprooting events are interlaced across the forest floor as reported elsewhere soil development was accelerated in pits leading to increasingly greater differences in soil development between pits and mounds over time and illustrating the concept of locally divergent pedogenesis in older pits the abnormally thick soil profiles extent so far below the depth of rooting that they are unlikely to be disturbed by future uprooting events on the coarser spatial scale of the forest stand uprooting decreased the ranges and increased the sills of spatial autocorrelation for o e and bhs horizon thicknesses the effect of treethrow dynamics on soil characteristics was greatest and statistically most significant for e horizon thicknesses where the range was decreased from 13 m to 10 m whereas the maximal level of semivariance sill increased by 42 all tree species preferred treethrow mounds to pits or undisturbed microsite for regeneration especially acer saccharum

dynamic pedogenesis new views on some key soil concepts and a model for interpreting quaternary soils abstract inasmuch as soils are open systems and rarely if ever achieve equilibrium with their environments it is philosophically sound to view all soils as expressing varying levels of polygenesis as that term has been redefined soil genesis and resultant morphology may then be viewed in a comprehensive framework of soil evolution that consists of two linked pathways one developmental and the other regressive that reflect interactions of both exogenous and endogenous vectors vectors are factors processes and conditions of pedogenesis following this philosophy a model of pedogenesis is framed in an evolutional paradigm that emphasizes the integrated effects of dynamic and passive pedogenic vectors in directing pathways and in controlling rates of soil genesis through time the dynamic vectors include energy and mass fluxes frequencies of soil wetting and drying water table dynamics organisms feedback processes and pedoturbation the passive vectors include parent materials soil chemical environment stability of geomorphic surfaces and various evolved soil properties and conditions accessions both sets of vectors vary spatially and the dynamic vectors more so than passive vectors fluctuate through time the model is expressed as s f d p dd dt dd dt where s is the state of the soil or degree of profile evolution d is the set of dynamic vectors p is the set of passive vectors and dd dt and dp dt denote change through time t the model helps explain the apparent minimal development and regressed character of some old soils and the rapid and strong development of some young ones

velocity and attenuation anisotropy implication of seismic fracture characterizations recent observations from several walkaround walkaway and 3d vsps from various parts of the world have shown that anisotropy symmetry directions or fracture orientations estimated from traveltime or velocity anisotropy do not necessarily agree with symmetry directions from amplitude or attenuation analysis we have also consistently found that attenuation anisotropy in reservoir intervals is generally stronger than in overburdens we argue in this article that instead of reconciling the differences between various attributes we should try to understand the mechanisms and use the difference in velocity and attenuation anisotropy which may contain additional information about subsurface fracture systems

frequency dependent anisotropy due to meso scale fractures in the presence of equant porosity fractured rock is often modelled under the assumption of perfect fluid pressure equalization between the fractures and equant porosity this is consistent with laboratory estimates of the characteristic squirt flow frequency however these laboratory measurements are carried out on rock samples which do not contain large fractures we consider coupled fluid motion on two scales the grain scale which controls behaviour in laboratory experiments and the fracture scale our approach reproduces generally accepted results in the low and high frequency limits even under the assumption of a high squirt flow frequency we find that frequency dependent anisotropy can occur in the seismic frequency band when larger fractures are present shear wave splitting becomes dependent on frequency with the size of the fractures playing a controlling role in the relationship strong anisotropic attenuation can occur in the seismic frequency band the magnitude of the frequency dependence is influenced strongly by the extent of equant porosity with these results it becomes possible in principle to distinguish between fracture and microcrack induced anisotropy or more ambitiously to measure a characteristic fracture length from seismic data

permeability effects on the seismic response of gas reservoirs summary in this work we analyse the role of permeability on the seismic response of sandstone reservoirs characterized by patchy gas water saturation we do this in the framework of johnson s model which is a generalization of white s seminal model allowing for patches of arbitrary geometry we first assess the seismic attenuation and velocity dispersion characteristics in response to wave induced fluid flow to this end we perform an exhaustive analysis of the sensitivity of attenuation and velocity dispersion of compressional body waves to permeability and explore the roles played by the johnson parameters t and s v which characterize the shape and size of the gas water patches our results indicate that within the typical frequency range of exploration seismic data this sensitivity may indeed be particularly strong for a variety of realistic and relevant scenarios next we extend our analysis to the corresponding effects on surface based reflection seismic data for two pertinent models of typical sandstone reservoirs in the case of softer and more porous formations and in the presence of relatively low levels of gas saturation we observe that the effects of permeability on seismic reflection data are indeed significant these prominent permeability effects prevail for normal incidence and non normal incidence seismic data and for a very wide range of sizes and shapes of the gas water patches for harder and less porous reservoirs the normal incidence seismic responses exhibit little or no sensitivity to permeability but the corresponding non normal incidence responses show a clear dependence on this parameter again especially so for low gas saturations the results of this study therefore suggest that for a range of fairly common and realistic conditions surface based seismic reflection data are indeed remarkably sensitive to the permeability of gas reservoirs and thus have the potential of providing corresponding first order constraints

finite difference simulations of seismic scattering implications for the propagation of short period seismic waves in the crust and models of crustal heterogeneity synthetic seismograms produced by the finite difference method are used to study the scattering of elastic and acoustic waves in two dimensional media with random spatial variations in seismic velocity the results of this study provide important insights about the propagation of short period 5 the self similar medium is characterized by a scattering q that is constant with frequency whereas theory predicts that the apparent q in an exponential medium is proportional to frequency these alternative models of crustal heterogeneity can thus be tested by improved measurements of the frequency dependence of crustal q at frequencies greater than about 1 hz assuming that scattering is responsible for most of the attenuation at these frequencies measurements of the time decay of the synthetic coda waves clearly show that the single scattering model of coda decay is not appropriate in the presence of moderate amounts of scattering attenuation scattering q 200 in these cases q values derived from the coda decay rate using the single scattering theory do not correspond to the transmission q of the medium the cross correlation of synthetic waveforms observed for an array of receivers along the free surface is observed to be dependent on the correlation distance of the medium the self similar random medium proposed here for the crust produces waveform variations at high frequencies 15 30 hz similar to those reported for actual small scale seismic arrays with apertures of hundreds of meters

modelling and analysis of attenuation anisotropy in multi azimuth vsp data from the clair field anisotropic variations in attenuation are of interest since they can give information on the fracture system and may be more amenable to measurement than absolute attenuation values we examine methods for detecting changes in relative attenuation with azimuth from vsp data and validate the techniques on synthetic data analysis of a multi azimuth walkaway vsp data set from a fractured hydrocarbon reservoir indicates that such azimuthal variations in p wave attenuation are observable the effects are localized in the reservoir and analysis allows the prediction of a fracture strike direction which agrees with geological information the observed effects can be modelled under reasonable assumptions which suggests the validity of the link between the anisotropic attenuation and the fracturing

modelling frequency dependent seismic anisotropy in fluid saturated rock with aligned fractures implication of fracture size estimation from anisotropic measurements measurements of seismic anisotropy in fractured rock are used at present to deduce information about the fracture orientation and the spatial distribution of fracture intensity analysis of the data is based upon equivalent medium theories that describe the elastic response of a rock containing cracks or fractures in the long wavelength limit conventional models assume frequency independence and cannot distinguish between microcracks and macrofractures the latter however control the fluid flow in many subsurface reservoirs therefore the fracture size is essential information for reservoir engineers in this study we apply a new equivalent medium theory that models frequency dependent anisotropy and is sensitive to the length scale of fractures the model considers velocity dispersion and attenuation due to a squirt flow mechanism at two different scales the grain scale microcracks and equant matrix porosity and formation scale fractures the theory is first tested and calibrated against published laboratory data then we present the analysis and modelling of frequency dependent shear wave splitting in multicomponent vsp data from a tight gas reservoir we invert for fracture density and fracture size from the frequency dependence of the time delay between split shear waves the derived fracture length matches independent observations from borehole data

t matrix approach to shale acoustics summary the t matrix approach of quantum scattering theory is used here to place many long wavelength equivalent medium approximations for porous composites polycrystals and cracked media on a common footing and to indicate their limitations but also to derive some new results based on two point statistics in this way we have obtained an insight into the difficult problem of elastic inclusions at finite concentrations which is of foremost relevance when estimating the effective material parameters of porous cracked shales involving stacks of more or less horizontally aligned clay platelets mixed together with more rounded silt minerals and with fluid filling the spaces a rather involved perturbative analysis of the effects of interactions between or structural correlations among the various inclusions minerals and cavities making up a real shale of hexagonal symmetry was performed in an attempt to obtain a better match between theoretical predictions based on a combination of coherent and optical potential approximations and experimental results recovered from ultrasonic wave speeds for the effective elastic stiffness tensor for the particular data set considered in this study the t matrix approach was able to match the data better than the approach of hornby et al but the match was not completely satisfactory further progress in theoretical shale modelling may come from a better knowledge of the elastic properties of pure clay minerals a more detailed knowledge of the microstructure of shales the incorporation of constraints obtained from comparisons between theoretical predictions and experimental results as well as a continuing development of the t matrix approach numerical results also for the effect of bedding parallel microcracks on the elasticity of such a real shale have value in illustrating the importance of taking into account the effects of spatial distribution when trying to deal with non dilute mixtures of highly contrasting material properties

climatic forcing of asymmetric orogenic evolution in the eastern cordillera of colombia new apatite fission track data paleoelevation estimates from paleobotany and recently acquired geological data from the eastern cordillera of colombia document the onset of increased exhumation rates in the northeastern andes at ca 3 ma the eastern cordillera forms an efficient orographic barrier that intercepts moisture laden winds sourced in the amazon lowlands leading to high rainfall and erosion gradients across the eastern flank of the range in contrast the drier leeward western flank is characterized by lower rates of deformation and exhumation in light of the geological evolution of the eastern cordillera the combination of these data sets suggests that the orographic barrier reached a critical elevation between ca 6 and ca 3 ma which ultimately led to protracted yet more focused erosion along the eastern flank sequentially restored structural cross sections across the eastern flank of the eastern cordillera indicate that shortening rates also have increased during the past 3 ma from fission track and structural cross section balancing we infer that accelerated exhumation led to increasing tectonic rates on the eastern flank creating a pronounced topographic and structural asymmetry in the eastern cordillera the tectonic and climatic evolution of this orogen thus makes it a prime example of the importance of climatic forcing on tectonic processes

geomorphic controls of soil spatial complexity in a primeval mountain forest in the czech republic abstract soil diversity and complexity is influenced by a variety of factors and much recent research has been focused on interpreting or modeling complexity based on soil topography relationships and effects of biogeomorphic processes we aimed to i describe local soil diversity in one of the oldest forest reserves in europe ii employ existing graph theory concepts in pedocomplexity calculation and extend them by a novel approach based on hypothesis testing and an index measuring graph sequentiality the extent to which soils have gradual vs abrupt variations in underlying soil factors and iii reveal the main sources of pedocomplexity with a particular focus on geomorphic controls a total of 954 soil profiles were described and classified to soil taxonomic units stu within a 46 ha area we analyzed soil diversity using the shannon index and soil complexity using a novel graph theory approach pairwise tests of observed adjacencies spectral radius and a newly proposed sequentiality index were used to describe and quantify the complexity of the spatial pattern of stus this was then decomposed into the contributions of three soil factor sequences sfs i degree of weathering and leaching processes ii hydromorphology and iii proportion of rock fragments six reference soil groups and 37 second level soil units were found a significant portion of pedocomplexity occurred at distances shorter than the 22 m spacing of neighbouring soil profiles the spectral radius an index of complexity of the pattern of soil spatial adjacency was 14 73 to which the individual sfs accounted for values of 2 0 8 0 and 3 5 respectively significant sequentiality was found for degree of weathering and hydromorphology exceptional overall pedocomplexity was particularly caused by enormous spatial variability of soil wetness representing a crucial soil factor sequence in the primeval forest moreover the soil wetness gradient was partly spatially correlated with the gradient of soil weathering and leaching suggesting synergistic influences of topography climate hydro geology and biomechanical and biochemical effects of individual trees the pattern of stony soils random in most respects resulted probably from local geology and quaternary biogeomorphological processes thus while geomorphology is the primary control over a very locally complex soil pattern microtopography and local disturbances mostly related to the effects of individual trees are also critical considerable local pedodiversity seems to be an important component of the dynamics of old growth mixed temperate mountain forests with implications for decreasing pedodiversity in managed forests and deforested areas

the role of trees in the geomorphic system of forested hillslopes a review abstract forested hillslopes form a special geoecosystem an environment of geomorphic processes that depend strongly on forest ecology including the growth and decay of trees changes in structure disturbances and other fluctuations hence the following various functions of trees are reviewed here their role in both biomechanical and biochemical weathering as well as their importance for the hillslope geomorphic subsystem and for transport of soil material via tree uprooting and root growth special attention is paid to tree uprooting a process considered the most efficient and most frequent biogeomorphological indicator of bio physical activity within forest in complex terrain trees have varied implications for soil formation in different environments boreal to tropical forests and altitudes in this paper an attempt has been made to emphasize how trees not only modulate geomorphic processes but also how they act as a direct or indirect agent of microrelief formation the most striking example of which being widespread and long lasting pit and mound microtopography based on the analyzed literature it seems that some problems attributed to forest ecology can have a fundamental effect on forested hillslope dynamics a relationship which points to the need for its integration and interpretation within the field of geomorphology the biology of individual trees has a key influence on the development of e g rock faces weathering front migration and changes in the soil biomantle within upper and lower forest belts additionally forms and sediments depend largely on the horizontal and vertical extent volume and structure of root systems as well as on active processes taking place in the root zone and rhizosphere furthermore although trees to a large extent stabilize slope surfaces their presence can also have a dual effect on slope stability due to tree uprooting a process which in some circumstances can trigger mass movements e g debris avalanches so far several attempts at quantifying the influence of trees on slopes have been made via the use of mathematical equations enabling researchers to calculate 1 the root plate volume of uprooted trees 2 the amount of soil displacement due to tree root growth and 3 rates of erosion sedimentation and soil creep in light of the reviewed literature the most urgent issue appears to be the need for a thorough study of the interactions and feedbacks occurring between trees and geomorphic systems e g soil mixing and biotransport by trees in different climate zones altitudes and time frames especially in terms of the development of forest ecosystems during the holocene

regolith properties under trees and the biomechanical effects caused by tree root systems as recognized by electrical resistivity tomography ert abstract following previous findings regarding the influence of vascular plants mainly trees on weathering soil production and hillslope stability in this study we attempted to test a hypothesis regarding significant impacts of tree root systems on soil and regolith properties different types of impacts from tree root system direct and indirect are commonly gathered under the key term of biomechanical effects to add to the discussion of the biomechanical effects of trees we used a non invasive geophysical method electrical resistivity tomography ert to investigate the profiles of four different configurations at three study sites within the polish section of the outer western carpathians at each site one long profile up to 189 m of a large section of a hillslope and three short profiles up to 19 5 m that is microsites occupied by trees or their remnants were made short profiles included the tree root zone of a healthy large tree the tree stump of a decaying tree and the pit and mound topography formed after a tree uprooting the resistivity of regolith and bedrock presented on the long profiles and in comparison with the short profiles through the microsites it can be seen how tree roots impact soil and regolith properties and add to the complexity of the whole soil regolith profile trees change soil and regolith properties directly through root channels and moisture migration and indirectly through the uprooting of trees and the formation of pit and mound topography within tree stump microsites the impact of tree root systems evaluated by a resistivity model was smaller compared to microsites with living trees or those with pit and mound topography but was still visible even several decades after the trees were windbroken or cut down the ert method is highly useful for quick evaluation of the impact of tree root systems on soils and regolith this method in contrast to traditional soil analyses offers a continuous dataset for the entire microsite and at depths not normally reached by standard soil excavations the non invasive nature of ert studies is especially important for protected areas as it was shown in the present study

thrusting and back thrusting as post emplacement kinematics of the almora klippe insights from low temperature thermochronology abstract crystalline klippen over the lesser himalayan sequence lhs in the kumaon and garhwal regions of nw himalaya are the representative of southern portion of the main central thrust mct hanging wall these were tectonically transported over the juxtaposed thrust sheets berinag tons and ramgarh of the lhs zone along the mct these klippen comprise of nw se trending synformal folded thrust sheet bounded by thrusts in the south and north in the present study the exhumation histories of two well known klippen namely almora and baijnath and the ramgarh thrust sheet in the kumaon and garhwal regions vis a vis himalayan orogeny have been investigated using apatite fission track aft ages along a 60 km long orogen perpendicular transect across the almora klippe and the ramgarh thrust sheet 16 aft cooling ages from the almora klippe and 2 from the ramgarh thrust sheet have been found to range from 3 7 0 8 to 13 2 2 7 ma and 6 3 0 8 to 7 2 1 0 ma respectively from lhs meta sedimentary rocks only a single aft age of 3 6 0 8 ma could be obtained three aft ages from the baijnath klippe range between 4 7 0 5 and 6 6 0 8 ma aft ages and exhumation rates of different klippen show a dynamic coupling between tectonic and erosion processes in the kumaon and garhwal regions of nw himalaya however the tectonic processes play a dominant role in controlling the exhumation thrusting and back thrusting within the almora klippe and ramgarh thrust sheet are the post emplacement kinematics that controlled the exhumation of the almora klippe combining these results with the already published aft ages from the crystalline klippen and the higher himalayan crystalline hhc the kinematics of emplacement of the klippen over the lhs and exhumation pattern across the mct in the kumaon and garhwal regions of nw himalaya have been investigated

effects of incomplete parameterization on full wavefield viscoelastic seismic data for petrophysical reservoir properties in inversion of viscoelastic full wavefield seismic data the choice of model parameterization influences the uncertainties and biases in estimating seismic and petrophysical parameters using an incomplete model parameterization results in solutions in which the effects of missing parameters are attributed erroneously to the parameters that are included incompleteness in this context means assuming the earth is elastic rather than viscoelastic the inclusion of compressional and shear wave quality factors qp and qs in inversion gives better estimates of reservoir properties than the less complete elastic model parameterization qp and qs are sensitive primarily to fluid types and saturations the parameter correlations are sensitive also to the model parameterization as noise increases in the viscoelastic input data the resolution of the estimated parameters decreases but the parameter correlations are relatively unaffected by modest noise levels

geomorphic edge effects in response to abiotic and anthropogenic disturbances in forest ecosystems of the gorce mountains western carpathians abstract in the present paper we report on the only known example of a hummocky meadow in poland the area of the hala dluga in the gorce mountains is a hotspot of complex geomorphic edge effects that have been widely studied in relation to human impacts and forest disturbances applying an interdisciplinary approach we aimed to study the geomorphic activity in edge conditions between two contrasting ecosystems a high mountain meadow and a forest several methods were applied geomorphic mapping radiocarbon dating soil analysis geomorphometry wood anatomy and investigations of historical maps these methods enabled us to reconstruct the history of the hala dluga over the past ca 300 years and to evaluate geomorphic activity and soil dynamics in this area the treethrow pit mound microtopography hummocky meadow buckelwiese of this area was formed under forest conditions but due to long term human impacts linked to sheep grazing and mowing was preserved as a distinct topography for at least 100 years while this topography was still clearly visible in the 1950s when it was first reported it is currently gradually disappearing under trees that have formed a belt around the study area soils of the study site were disturbed by tree uprooting with many key features identified during the soil profile analysis spots of coarse partly oriented sandstone fragments in pits patches of organic matter in the metamorphic b horizon and a large number of root remnants and pieces of charcoal in different parts of treethrow mounds and pits we suggest a non linear or even polygenetic soil evolution due to altered vegetation and disturbance regimes the evaluation of wood remnants revealed that the majority of uprooted tree species were picea abies l h karst and larix decidua mill we conclude that in the gorce mountains geomorphic edge effects can form hotspots of geomorphic activity driven by human impacts natural disturbances and the specific hydrological regime in the highest parts of the massif

the squirt flow mechanism macroscopic description we introduce a poroelasticity model that incorporates the two most important mechanisms of solid fluid interaction in rocks the biot mechanism and the squirt flow mechanism this combined biot squirt bisq model relates compressional velocity and attenuation to the elastic constants of the drained skeleton and of the solid phase porosity permeability saturation fluid viscosity and compressibility and the characteristic squirt flow length squirt flow length is a fundamental rock property that does not depend on frequency fluid viscosity or compressibility and is determined experimentally we find that the viscoelastic response of many sandstones is dominated by the squirt flow component of the bisq mechanism and that the viscoelastic properties of these rocks can be expressed through a single dimensionless parameter omega r 2 kappa where omega is angular frequency r is the characteristic squirt flow length and kappa is hydraulic diffusivity the biot mechanism alone does not give an adequate explanation of the observed velocity dispersion and attenuation and the viscoelastic behavior of many sandstones

pedodiversity and global soil patterns at coarse scales with discussion several algorithms for analyzing the diversity of the world pedosphere are reviewed and employed special emphasis has been laid on indices based on the theory of information we study the diversity and distribution of major soil groups by continents and climatic zones on the basis of data compiled by the fao at the scale i 5 000 ooo major soil group distribution model relationships on a world level seem to follow more equitable patterns than those established for biocenoses and soil patterns at fine scales at a continental level the pedosphere s diversity is characterized by similarities rather than differences differences in diversity by climatic zones are more marked evenness pielou s index and diversity shannon s index tend to be greater in the climatic zones of intermediate latitudes than in circumequatorial and circumboreal latitudes the climatic zones closest to the poles could be the planet s most uniform soil patterns at small scales mountain areas in general achieve the highest pedorichness and lowest values of diversity global soil pattern distribution was also analyzed using multivariate techniques at a continental level it is possible for the structure of the global pedosphere to be determined by the continent s geological tectonic and climatic histories soil patterns of different climatic zones are linked in a very well defined latitudinal gradient

time dependent factors of soil and weathering mantle diversity in the humid tropics and subtropics a concept of soil self development and denudation abstract time dependent processes are the most important factor contributing to diversity of the soil and weathering mantle swm in the humid tropics and subtropics two models of swm self development in time are proposed and exemplified by soil chronosequences on tropical volcanic islands in the pacific ocean and in the humid subtropics on the east coast of the black sea the first derived from basic ash parent material lacking phyllosilicates is an eutric regosol vitric andosol mollic andosol chromic luvisol humic ferralsol sequence the second formed on basic material rich in phyllosilicates is a leptosol regosol ferrallic cambisol haplic nitisol stagnic acrisol sequence each component of these chronosequences contributes to swm diversity in time and space and to the complexity of the soil cover patterns the swm denudation model is exemplified by a stagnic acrisol haplic nitisol eutric cambisol lithic leptosol chronosequence on eroded hills and terraces of the east coast of the black sea temporal and spatial changes in soil properties texture chemistry mineralogy are examined in all three swm chronosequences

inherited vs acquired complexity in east texas weathering profiles complexity in weathering profiles may reflect variability in the parent material and or complex feedback relationships within regolith weathering systems because regolith formation modifies or destroys the parent material it is difficult to determine the extent to which variability in the weathering profile is inherited as opposed to created by the weathering processes the state probability function spf designed to model the spatial pattern of transitions in system states is applied to complex weathering profiles formed in glauconitic materials in east texas to address this issue the weathering profile is remarkably complex with units ranging from unweathered parent material to highly modified weathering products similar to those found in the bt horizons of the overlying rhodic paleudalf there is a very general vertical sequence with more weathered material near the top and less weathered material near the bottom however the pattern is quite irregular highly weathered units are found everywhere except at the base of the study section and much less developed units are found throughout though the spf indicates a high degree of spatial complexity the value never approaches or exceeds that which would be expected in a random vertical sequence of weathering horizons variation inherited from the parent material would produce spf values greater than that for a random sequence the complex patterns in the east texas regolith are thus attributable primarily to feedbacks within the weathering system and indicate that the complexity is dominantly acquired whatever anisotropy there may have been in the parent material has been magnified and overprinted by complex interactions within the weathering system

synchronization and scale in geomorphic systems abstract geomorphic systems consist of coupled subsystems with traits of small world networks swn characterized by tightly connected clusters of components with fewer connections between the clusters geomorphic systems based on scale hierarchies often exhibit a connected caveman small world network ccswn structure swns are efficient for linking a large number of components with a relatively small number of links but effects of ccswn structure on synchronization and scale linkage have not been examined synchronization is analyzed via graph theory and applied to 1 relationships among three levels of form process interaction in stream channels 2 hierarchical relationships of weathering systems at scales from weathering profiles to landscapes and 3 interactions in fluviokarst systems at the scale of flow processes and of landscape evolution relationships among system components are represented as simple unweighted graphs the largest eigenvalue of the adjacency matrix spectral radius reflects the critical coupling strength required to synchronize the system the second smallest eigenvalue of the laplacian of the adjacency matrix algebraic connectivity is a measure of the synchronizability in all examples both are much less than the maximum for networks of the same number of nodes the sparseness of the networks is the major contributor to the low synchronization but the specific pattern of connections wiring is also significant where ccswn structures arise naturally they help explain how geomorphic effects are transmitted between disparate scales in the absence of obvious scale linkage where ccswns are an option for representation of geomorphic systems in models and data structures they will not improve scale linkage despite the efficiency of swns in other respects methods developed here can be applied to evaluating alternative spatial data structures or mapping strategies which either increase synchronization supporting a lumping or aggregation approach or decrease synchronization indicating disaggregation or splitting into scale hierarchies

p wave seismic attenuation by slow wave diffusion effects of inhomogeneous rock properties recent research has established that the dominant p wave attenuation mechanism in reservoir rocks at seismic frequencies is because of wave induced fluid flow mesoscopic loss the p wave induces a fluid pressure difference at mesoscopic scale inhomogeneities larger than the pore size but smaller than the wavelength typically tens of centimeters and generates fluid flow and slow diffusion biot waves continuity of pore pressure is achieved by energy conversion to slow p waves which diffuse away from the interfaces in this context we consider a periodically stratified medium and investigate the amount of attenuation and velocity dispersion caused by different types of heterogeneities in the rock properties namely porosity grain and frame moduli permeability and fluid properties the most effective loss mechanisms result from porosity variations and partial saturation where one of the fluids is very stiff and the other is very compliant such as a highly permeable sandstone at shallow depths saturated with small amounts of gas around 10 saturation and water grain and frame moduli variations are the next cause of attenuation the relaxation peak moves towards low frequencies as the background permeability decreases and the viscosity and thickness of the layers increase the analysis indicates in which cases the seismic band is in the relaxed regime and therefore when the gassmann equation can yield a good approximation to the wave velocity

seismic wave attenuation and dispersion resulting from wave induced flow in porous rocks a review one major cause of elastic wave attenuation in heterogeneous porous media is wave induced flow of the pore fluid between heterogeneities of various scales it is believed that for frequencies below 1 khz the most important cause is the wave induced flow between mesoscopic inhomogeneities which are large compared with the typical individual pore size but small compared to the wavelength various laboratory experiments in some natural porous materials provide evidence for the presence of centimeter scale mesoscopic heterogeneities laboratory and field measurements of seismic attenuation in fluid saturated rocks provide indications of the role of the wave induced flow signatures of wave induced flow include the frequency and saturation dependence of p wave attenuation and its associated velocity dispersion frequency dependent shear wave splitting and attenuation anisotropy during the last four decades numerous models for attenuation and velocity dispersion from wave induced flow have been developed with varying degrees of rigor and complexity these models can be categorized roughly into three groups according to their underlying theoretical framework the first group of models is based on biot s theory of poroelasticity the second group is based on elastodynamic theory where local fluid flow is incorporated through an additional hydrodynamic equation another group of models is derived using the theory of viscoelasticity though all models predict attenuation and velocity dispersion typical for a relaxation process there exist differences that can be related to the type of disorder periodic random space dimension and to the way the local flow is incorporated the differences manifest themselves in different asymptotic scaling laws for attenuation and in different expressions for characteristic frequencies in recent years some theoretical models of wave induced fluid flow have been validated numerically using finite difference finite element and reflectivity algorithms applied to biot s equations of poroelasticity application of theoretical models to real seismic data requires further studies using broadband laboratory and field measurements of attenuation and dispersion for different rocks as well as development of more robust methods for estimating dissipation attributes from field data

toward one meter resolution in 3d seismic high resolution 3d hr3d seismic data are important for hydrocarbon exploration of shallow reservoirs site characterization and geohazard assessments the goal of this contribution is to identify and quantify the parameters to increase the resolution of hr3d seismic data to meter scale the main acquisition parameters controlling the resolution of the collected data are the spectrum of the seismic source source receiver offset range and trace density an evolution to one meter scale resolution of 3d seismic will rely on combining a reproducible seismic source with high frequencies up to at least 600 hz a high uniform trace density of more than 4 million traces per square kilometer and an offset range shorter than approximately 200 m the resulting 3d seismic data volume will reach meter scale resolution for water and target depths of less than 600 m the proposed hr3d system will be suitable for 3d and 4d characterization of seabed properties and shallow stratigraphy the identification of geohazards and hydrocarbon leakage and monitoring the environmental impact of offshore activities the p cable 3d system is an excellent starting point for achieving one meter scale resolution due to its flexible and tight meter scale shot and receiver spacing

equivalent medium representation of fractured rock a similarity may be found between various approaches for determining the effects of parallel fractures or aligned cracks on seismic wave propagation at wavelengths that are long compared with the scale length of the cracks fractures can be modeled using an empirical linear slip condition however natural fracture surfaces can also be simulated directly as planar distributions of small isolated areas of slip cracks model 1 or conversely as planar distributions of imperfect interfacial contacts model 2 an alternative is plane surfaces separated by thin continuous layers of viscous fluid or a soft material model 3 we present analytic expressions for the fracture compliances for these three models and using these analytic results compute the effective compliances and stiffnesses of the fractured material as a result it is possible to relate the measured compliances or stiffnesses directly to the statistics of the microstructural details of a fracture given appropriate a priori information on the fracture surfaces the results for model 1 are equivalent to a volume distribution of cracks as studied by hudson 1980 1981 for small crack density the results for model 2 are basically the same as those given by white 1983 for a packing of spheres and finally the results for model 3 are in agreement with those given by backus 1962 for combinations of two constituent layers these results can be extended to the case of nonaligned fractures and to allow for fluid flow between cracks and into a porous matrix rock finally it is shown that the ratio of the normal to shear fracture compliance is a good indicator of the properties of the fracture infill

signatures of divergence and self organization in soils and weathering profiles abstract complex system behaviors such as self organization are difficult to address in geology system evolution often cannot be directly observed and in geology models and theory must be reconciled with field evidence however self organization can be addressed within the historical interpretive paradigm by applying a measure of the degree of self organization of geologic features using standard interpretive methods to determine the nature of changes and determining whether those changes result in an increase or decrease in organization in this way stable non self organizing convergent development can be distinguished from unstable chaotic self organizing divergent development kolmogorov entropy k entropy was used as a measure of the self organization of soil profiles in eastern north carolina in general the profiles are low in k entropy indicating a generally high level of predictability and information in the vertical arrangement of pedogenetic horizons as a broad generality the study p

the effects of dem resolution and neighborhood size on digital soil survey terrain characteristics such as slope gradient slope aspect profile curvature contour curvature computed from digital elevation model dem are among the key inputs to digital soil surveys based on geographic information systems gis these terrain attributes are computed over a neighborhood spatial extent the objective of this research was to investigate the combined effect of dem resolution and neighborhood size on digital soil surveys using the soil landscape inference model solim approach the effect of neighborhood size and dem resolution on digital soil survey was examined through computing the required terrain attributes using different neighborhood sizes from 3 to 54 m for 3 6 9 12 18 and 27 m resolution dem these attributes were then compiled and used to digitally map soils using the solim approach field work completed on a hillslope in dane county wi in the summer of 2003 was used to validate each of the solim derived soil surveys for accuracy the results of the soil survey validations suggest that there is a range of neighborhood sizes that produces the most accurate results for a given resolution dem this range of neighborhood sizes however varies from landscape to landscape when the soils on a gently rolling landscape were mapped the neighborhood sizes that produced the most accurate results ranged from about 33 48 m when soils on short steep backslope positions were mapped the neighborhood size values that produced the most accurate results range from about 24 36 m this paper also shows that it is not always the highest resolution dem that produces the highest accuracy knowing which dem resolution and neighborhood size combinations produce the most accurate digital soil surveys for a particular landscape will be extremely useful to users of gis based soil mapping applications

sensitivity of three component 3d finite difference elastic seismic modeling to inclusion parameters in hti and tti media with high inclusion density parameters associated with the presence of inclusions cracks or vugs significantly influence seismic responses the t matrix method is used to define approximate anisotropic effective elastic stiffness tensors for media with inclusions this allows 3d three component eighth order staggered grid finite difference modeling to simulate the seismic responses of anisotropic media with high inclusion density various aspect ratios spatial distributions and orientations of inclusions and fluid content the model parameters are chosen to represent aligned inclusions ranging from vertical cracks to vugs in a carbonate reservoir encased in clastics the magnitude of anisotropy increases with increasing inclusion density for p and s waves cracks in a high velocity carbonate reduce the stiffnesses and correspondingvelocities this results in smaller contrasts with the surrounding lower stiffness clastics and hence smaller reflection coefficients s wave splitting and the anisotropy of vp vs are clearly

seismic attenuation effects of pore fluids and frictional sliding seismic wave attenuation in rocks was studied experimentally with particular attention focused on frictional sliding and fluid flow mechanisms sandstone bars were resonated at frequencies from 500 to 9000 hz and the effects of confining pressure pore pressure degree of saturation strain amplitude and frequency were studied observed changes in attenuation and velocity with strain amplitude are interpreted as evidence for frictional sliding at grain contacts since this amplitude dependence disappears at strains and confining pressures typical of seismic wave propagation in the earth we infer that frictional sliding is not a significant source of seismic attenuation in situ partial water saturation significantly increases the attenuation of both compressional p and shear s waves relative to that in dry rock resulting in greater p wave than s wave attenuation complete saturation maximizes s wave attenuation but causes a reduction in p wave attenuation these effects can be interpreted in term

tectonic and climatic significance of a late eocene low relief high level geomorphic surface colorado new paleobotanical data suggest that in the late eocene the erosion surface which capped the front range colorado was 2 2 3 3 km in elevation which is similar to the 2 5 km present elevation of surface remnants this estimated elevation casts doubt on the conventional belief that the low relief geomorphic surface was formed by lateral planation of streams to a base level not much higher than sea level and that the present deeply incised canyons must represent neogene uplift of colorado description of the surface calculations of sediment volume and isostatic balance and fluvial landsculpting models demonstrate that while the high elevation of the erosion surface was due to tectonic forces its smoothness was mostly a result of climatic factors a sediment balance calculated for the front range suggests that from 2 to 4 km of material were eroded by the late eocene consistent with fission track ages this amount of erosion would remove a significant portion of the 7 km of laramide upper crustal thickening isostatic modeling implies that the 2 2 3 3 km elevation was most likely created by lower crustal thickening during the laramide a numerical model of fluvial erosion and deposition suggests a way that a late eocene surface could have formed at this high elevation without incision a humid climate with a preponderance of small storm events will diffusively smooth topography and is a possible mechanism for formation of low relief high level surfaces paleoclimate models suggest a lack of large storm events in the late eocene because of cool sea surface temperatures in the equatorial region return to a drier but stormier climate post eocene could have caused the incision of the surface by young canyons by this interpretation regional erosion surfaces may represent regional climatic rather than tectonic conditions

is land use change a cause of loss of pedodiversity the case of the mazzarrone study area sicily abstract anthropogenic soils created ex novo by land use change in large scale farming are from a pedogenetic point of view catastrophic events that bring the soils to time zero and change the natural pattern of the soilscape remarkably in some cases the quantitative aspects of pedodiversity of a soilscape in south east sicily where some types of soils in recent decades have suffered a consistent reduction due to the transformations by large scale farming are considered the evolution of pedodiversity over a 53 year period 1955 to 2008 is examined using a dedicated statistical method and a space time model based on markov analysis and cellular automata in order to predict the evolution of the soilscape pattern in the next 42 years i e until 2050 soil subgroups using the usda soil taxonomy and a classification proposal were considered and the following indices were used richness shannon s diversity index simpson diversity index modified simpson s diversity index shannon s evenness index simpson s evenness index and modified simpson s evenness index these indices measured over time show quantitatively a decrease in pedodiversity that highlights the effect of the human intervention in modifying the natural order of the soilscape

pedodiversity and pedogenesis in zayandeh rud valley central iran abstract a geomorphic hierarchical downscaling method was used to decompose the forms and processes forming the landscapes and their subdivisions in the main region of zayandeh rud valley the purpose of this study was to determine the degree of soil heterogeneity and to check if k entropy would be a good measure of soil evolution soil diversity analyses were performed considering soil families as individuals of soil entities in each geomorphic or taxonomic category level pedodiversity indices were used to follow the trend of soil and landscape evolution the relationships between k entropy shannon diversity index and pedo richness versus increasing area were analyzed to find out the effects of soil landscape evolution on complexity of soil patterns in different geomorphic surfaces entropy age relationship was studied to check the pedogenetic pathways responsible for soil landscape evolution the soil diversity increases as geomorphic and taxonomic hierarchy levels decrease the diversity indices were high when the sequence of soil horizons in a homogeneous family was also investigated an increase in k entropy of soil and landscape during time confirms the hypothesis of soil divergence evolution whereby differences in initial conditions or local perturbations and dynamic instability appear to have produced more variable soils and landscapes in the study area

nonequilibrium regolith thickness in the ouachita mountains abstract interpretations of regolith and soil thickness in the context of landscape evolution are typically based on the notion that thickness is controlled by the interaction of weathering rates and erosion and tuned to topography on sideslopes of the ouachita mountains arkansas however there is a high degree of local spatial variability that is largely unrelated to topography this indicates nonequilibrium in the sense that there is no evidence of a balance between rates of weathering and removal as is postulated in some conceptual models in geomorphology and pedology johnson s soil thickness model is applied as an alternative to interpret local variations in regolith thickness at the study sites regolith thickness is not generally related to slope curvature elevation or pedogenic development in the solum this indicates that variability in thickness is related chiefly to processes and controls acting in the lower regolith below the solum the primary controls of variability are local lithol

permeability dependence of seismic amplitudes can permeability be determined from seismic data this question has been around since maurice biot working for shell in the 1950s introduced the idea that seismic waves induce fluid flow in saturated rocks due to fluid pressure equilibration between the peaks and troughs of a compressional wave or due to grain accelerations in the case of a shear wave biot 1956 established a frequency dependent analytical relation between permeability and seismic attenuation however laboratory sonic log crosswell vsp and surface seismic have all demonstrated that biot s predictions often greatly underestimate the measured levels of attenuation dramatically so for the lower frequency measurements yet if an unresolved link truly exists between seismic amplitudes and permeability the potential benefit to the oil industry is enormous for this reason the department of energy doe brought together 15 participants from industry national laboratories and universities to concentrate for two days on whether permeability information is conceivably contained in and retrievable from seismic data the present article represents much of the workshop discussion which took place 5 6 december 2001 in berkeley california but is not strictly limited to it not all connections between hydrological and seismic properties are considered three dimensional seismic images and time lapse seismic monitoring are routinely used by reservoir engineers in constructing and constraining their reservoir model such imaging applications of seismic surveys to hydrological modeling are not discussed furthermore in fractured reservoirs it is reasonable to postulate that any locally determined seismic anisotropy defines a symmetry class for the geologic material that must also be satisfied by the permeability tensor neither are such material symmetry constraints discussed the focus here is only on whether the permeability of the rocks through which seismic waves propagate directly influences the decay of the wave amplitudes with distance key to addressing this question is an up to date discussion of the likely attenuation

sensitivity of 3d 3c synthetic seismograms to anisotropic attenuation and velocity in reservoir models abstractanisotropic attenuation in fluid saturated reservoirs with high fracture density may be diagnostic for reservoir characterization wave induced mesoscale fluid flow is considered to be the major cause of intrinsic attenuation at exploration seismic frequencies we perform tests of the sensitivity of anisotropic attenuation and velocity to reservoir properties in fractured hti media based on the mesoscale fluid flow attenuation mechanism the viscoelastic t matrix a unified effective medium theory of global and local fluid flow mechanisms is used to compute frequency dependent anisotropic attenuation and velocity for ranges of reservoir properties including fracture density orientation fracture aspect ratio fluid type and permeability the 3d 3c staggered grid finite difference anisotropic viscoelastic modeling with a crank nicolson scheme is used to generate seismograms using the frequency dependent velocity and attenuation computed by the viscoelastic t matrix a standard linear solid mo

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

influence of frequency and saturation on avo attributes for patchy saturated rocks abstractpartially saturated rocks are considered to be major sources of seismic wave velocity dispersion and attenuation in recorded real data from the physical description of partially saturated gas water and oil water reservoirs we use upscaling theories to compute an equivalent frequency dependent porous medium these homogenization methods are associated with mesoscale description of attenuation and dispersion coming from wave induced flow phenomena to compute wave propagation we use numerical codes in the frequency domain that allow us to take into account all the frequency dependent parameters without approximation or local time steps in this way the biot slow compressional wave is well modeled and its partially diffusive partially propagative behavior is completely considered the attenuation and dispersion of the waves in such media are coming partly from the wave mode conversion into diffusive slow waves not visible on seismograms but the amplitude of propagative p and s waves are mainl

plio plistocene in sequence thrust propagation along the main central thrust zone kumaon garhwal himalaya india new thermochronological data abstract the kumaon and garhwal himalayas nw india have similar geologic tectonic topographic and precipitation pattern however low temperature thermochronological age pattern varies significantly along the strike as well as across the strike of major faults here we interpret the new set of thermochronological age data across the strike of major faults namely vaikrita thrust vt munsiari thrust mt berinag thrust bt and the baijnath nappe along pindari valley in the kumaon garhwal himalaya in the present work 18 new apatite fission track aft ages of samples collected along a north south transect have been reported ages in the hanging wall of vt which range from 2 1 0 2 to 4 2 0 7 ma have been found to be becoming younger linearly with distance from north to the vt this trend crosses the vt with significant jump in ages in the south of the vt ages are lying between 0 3 0 1 and 3 9 0 8 ma and show linear variation with distance from the vt to bt no significant jump in ages across the mt is observed and the linear trend of younging southward is continuing till the bt the break and displacement in age pattern with youngest ages close to thrusts possibly indicate progressive late thrust movement it reflects sequential uplift and cooling towards the south from the vt to bt which is consistent with an in sequence style of thrust propagation we compare our new data to the published thermochronological data from its adjacent traverses along the goriganga and dhauliganga valleys 25 km away from the present traverse towards east and west respectively in the kumaon garhwal himalaya in order to understand potential along strike variations in the kinematics our observations indicate a dynamic coupling between tectonic and surface processes in the garhwal kumaon himalaya and support that the geometry of crustal scale faults and their associated kinematics control exhumation pathways of rocks

deterministic chaos and historical geomorphology a review and look forward the study of nonlinear dynamics in geomorphology has been dominated by analytical techniques derived largely from other fields ultimately however confronting nonlinear complexity requires problematizing from within a geomorphological context this paper focuses on deterministic chaos the major classes of techniques for detecting chaos in geomorphic systems are reviewed while the long time series most amenable to traditional methods of chaos detection are only occasionally available to geomorphologists there are methods for detecting chaos in spatial data including qualitative and categorical data many of these are similar to or are adaptations of familiar techniques for partitioning within and between unit variation and for identifying elementary uniform landscape units the manifestations of chaos in landforms and landscapes take the form of divergent vs convergent evolution increasing vs decreasing irregularity disproportionality vs proportionality of response to perturbations or initial variations and the lack of geographical consistency or commonality of response these also serve as criteria for distinguishing between achievement of a new steady state and unstable divergence in interpreting geomorphic changes study of nonlinear dynamics in earth science need not be dominated by theoreticians and modellers as complex nonlinear behaviors can be identified and diagnosed using the types of data observations and methods typically available to geomorphologists even more important is the need to further inform the study of nonlinear dynamics on the basis of field based geomorphology

modeling attenuation in reservoir and nonreservoir rock elastic waves attenuate in earth the number of wavelengths over which the amplitude decreases by a factor of ten is 0 733 q where q is the quality factor for vp 3 km s and frequency f 30 hz the wavelength vp f 0 1 km then for q 10 the amplitude decreases by a factor of 10 as the wave travels 0 733 q 0 733 km

fluid mobility and frequency dependent seismic velocity direct measurements the influence of fluid mobility on seismic velocity dispersion is directly observed in laboratory measurements from seismic to ultrasonic frequencies a forceddeformation system is used in conjunction with pulse transmission to obtain elastic properties at seismic strain amplitude 10 7 from 5 hz to 800 khz varying fluid types and saturations document the influence of pore fluids the ratio of rock permeability to fluid viscosity defines mobility which largely controls pore fluid motion and pore pressure in a porous medium high fluid mobility permits pore pressure equilibrium either between pores or between heterogeneous regions resulting in a low frequency domain where gassmann s equations are valid in contrast low fluid mobility can produce strong dispersion even within the seismic band here the low frequency assumption fails since most rocks in the general sedimentary section have very low permeability and fluid mobility shales siltstones tight limestones etc most rocks are not in the lowfrequency domain even at seismic frequencies only those rocks with high permeability porous sands and carbonates will remain in the low frequency domain in the seismic or sonic band