source scaling relationship for m 4 6 8 9 earthquakes specifically for earthquakes in the collision zone of taiwan we investigated the source scaling of earthquakes mw 4 6 8 9 mostly from the taiwan orogenic belt and made a global compilation of source parameters to examine the scaling self similarity finite fault slip models 12 dip slip and 7 strike slip using mainly dense strong motion data and teleseismic data from taiwan were utilized seven additional earthquakes m 7 were included for further ex amination of scaling of large events we determined the effective length and width for the scaling study was m0 l 2 and m0 l 3 for the events less than and larger than the seismic moment of 10 20 nm respectively regardless of the fault types suggesting a nonself similar scaling for small to moderate events and a self similar scaling for large events although the events showed variation in stress drops with the exception of three events with high stress drops most of the events had stress drops of 10 100 bars the observed bilinear relation is well explained by the derived magnitude area equation of shaw 2009 when we considered only events with stress drops of 10 100 bars and a seismogenic thickness of 35 km the bilinear feature of the regressed magnitude area scaling holds for ruptured areas up to about 1000 km 2 for our seismogenic thickness of 35 km for the events having rupture areas larger than that the average slip becomes proportional to the rupture length the distinct high stress drop events from blind faults in the western foothill of taiwan yield local high peak ground accelerations pgas when compared to the next generation attenuation model regardless of the relative small magnitudes of these events the high pgas give the region higher seismic hazard potential and thus require special attention for seismic hazard mitigation

wind drag coefficient over first year sea ice in the bering sea profiles of relative wind speed and temperature were collected from four levels over rough sea ice in the marginal ice zone of the bering sea and used to compute surface wind drag coefficients based upon 138 profiles for near constant ice conditions northeast winds of 3 15 m s 1 and near neutral stability the mean near neutral 10 m drag coefficient was 0 00309 0 00049 this is among the largest drag coefficients measured for neutral atmospheric conditions over sea ice sixty five percent of the variance of this estimate is explained by orientation of the ice floe to the wind an additional 5 of the variance is explained by wind speed dependence provided that diabatic atmospheric stability over the bering sea ice pack is well correlated with low wind speed the significant ice advecting wind stress on the ice is determined from the neutral value of the drag coefficient a function of ice roughness length alone the ice forecaster thus may use remote measurements or estimates of wind speed and surface roughness to assess the wind component of ice advection

rupture kinematics of the 2005 mw 8 6 nias simeulue earthquake from the joint inversion of seismic and geodetic data the 2005 mw 8 6 nias simeulue earthquake was caused by rupture of a portion of the sunda megathrust offshore northern sumatra this event occurred within an array of continuous global positioning system gps stations and produced measurable vertical displacement of the fringing coral reefs above the fault rupture thus this earthquake provides a unique opportunity to assess the source character istics of a megathrust event from the joint analysis of seismic data and near field static co seismic displacements based on the excitation of the normal mode data and geodetic data we put relatively tight constraints on the seismic moment and the fault dip where the dip is determined to be 8 to 10 with corresponding moments of 1 24 10 22 to 1 00 10 22 n m respectively the geodetic constraints on slip distribution help to eliminate the trade off between rupture velocity and slip kine matics source models obtained from the inversion of various combinations of the teleseismic body waves and geodetic data are evaluated by comparing predicted and observed long period seismic waveforms 100 500 sec our results indicate a rela tively slow average rupture velocity of 1 5 to 2 5 km sec and long average rise time of up to 20 sec the earthquake nucleated between two separate slip patches one beneath nias and the other beneath simeulue island the gap between the two patches and the hypocentral location appears to be coincident with a local geological disrup tion of the forearc coseismic slip clearly tapers to zero before it reaches the trench probably because the rupture propagation was inhibited when it reached the accre tionary prism using the models from joint inversions we estimate the peak ground velocity on nias island to be about 30 cm sec an order of magnitude slower than for thrust events in continental areas this study emphasizes the importance of util izing multiple datasets in imaging seismic ruptures

strike slip earthquakes on quasi vertical transcurrent faults inferences for general scaling relations the recent occurrence of several large strike slip earthquakes provides the opportunity to review and complement available data on the scaling of seismic moment mo with length of rupture l for large earthquakes depending on their tectonic setting and mechanism for strike slip earthquakes on quasi vertical transcurrent faults the mo versus l relation has a significant change of slope around mo 0 6 0 8 1020 n m and for larger earthquakes mo scales linearly with l this is compatible with models where slip is controlled by the width of the fault also it appears to be easier to categorize large earthquakes by their mechanism strike slip on vertical transcurrent fault versus pure thrust normal than their tectonic setting interplate intraplate

changes to the dispersive characteristics of soils along an evolutionary slope sequence in the vera badlands southeast spain implications for site stabilisation abstract in dispersive marls near vera badland gullies are eroding into a previously stable matorral covered landscape this relatively recent activity was probably triggered by minor climatic or land use change in this landscape calvo cases and harvey earth surface processes and landforms 21 1996 725 argued that new gully head slopes with differing aspect represent a sequence of progressive erosion using this interpretation as a basis slope surface materials were explored for evidence of material chemical stabilisation by sampling along profiles positioned centrally on those slopes the extent to which the inferred geomorphic sequence is paralleled by progressive changes in site geochemistry is considered crusts and subsoils differ significantly in terms of ph and sodium adsorption ratio sar but not calcium content the crust is thus distinctive but not calcic rather the ph differences suggest a process involving an organic agent probably algae slope position was an important discriminant taking sar alone differences between crusts and subsoils were not significant at the slope base but increased in significance with distance up the profile considering differences between the three profiles the middle profile had significantly higher sar values both in the crust and at depth than the other profiles whereas late slope subsoils and crusts taken alone are not dispersive sar the potential stabilisation of this type of badland soil and surface is finally considered whereas harvey harvey a m 1982 the role of piping in the development of badlands and gully systems in southeast spain in bryan r yair a eds badland geomorphology and piping geobooks norwich pp 317 335 argues that site morphology suggests that geomorphological instability increases through time the soil sequence suggests decreases in material dispersivity and consequently surface autostabilisation it is concluded that the concept of badland stabilisation needs further clarification

liquid and plastic limits of clayey organic c rich mountain soils role of organic matter and mineralogy abstract the soil liquid ll and plastic limit pl and their difference pi plasticity index are physical properties related with the soil mechanical behavior determined on the

contribution of radar interferometry to a two step inversion of the kinematic process of the 1992 landers earthquake we study the rupture process of the 1992 landers earthquake to limit the trade off between slip amplitude and rupture time that affects solutions using only seismological data we adopt a two step approach we first constrain the slip distribution and its uncertainty by independent geodetic data to recover in the second step the temporal details of the rupture propagation the first step consists of an inversion of interferometric data and global positioning system measurements both independently and together to constrain slip distribution on a three segment fault model along both strike and dip direction we use a genetic algorithm to test the uniqueness of the solution and a least squares formulation to find the model which best fits the data we conclude from the results of these geodetic inversions that interferometric data are rich enough to access the slip distribution in the case of the landers earthquake since the surface deformations are more sensitive to shallow slip in our configuration the slip amplitude is better resolved near the surface than at depth the resulting slip distribution is in agreement with geological observations at the surface and confirms the heterogeneous nature of the landers earthquake most of the slip occurs at shallow depths on the homestead valley fault second segment with a maximum value of around 7 m another high slip zone is observed on the johnson valley fault first segment at 8 km depth in the second step we invert strong motion data with the a priori final slip amplitude and its uncertainty deduced from geodetic data to constrain the time history of the rupture process this second step emphasizes a strong variation of the temporal development of the earthquake fast rupture front velocities appear within high slip zones and the rupture slows when it encounters a resistance along the fault on average the rupture front propagates with velocities close to the s wave velocity and terminates about 20 s after initiation the large variations in both slip amplitude and rupture velocity suggest that the rupture process is better described by successively breaking asperities than by a pulse propagating with constant velocity

the causes of piping in a set of abandoned agricultural terraces in southeast spain this study aims to identify some of the factors contributing to the piping process in abandoned terraces in seven sites located in the murcia region southeast spain the local landscape has the appearance of badland geomorphology possessing deep valleys which until the 1970s were terraced and cultivated the terraces have now been abandoned to the piping process the research focuses on the relationship between the size and position of pipes and the physical and geochemistry properties of the local highly dispersive marl lithology and the extent to which the reworking of the materials for terrace cultivation has exacerbated piping erosion morphologically the terracing in the stream beds has resulted in a series of gentle benches separated by steeper risers with variable drop riser height a series of flat infiltration surfaces result and because the resculpting produces a reduced bulk density infill with enhanced throughflow infiltrating water is forced along steep hydraulic gradients to a low outfall at the base of the riser paralleling studies of land levelling and terrace abandonment in similar materials elsewhere piping in the study area is shown to be closely related to the physical and chemical characteristics of the materials its sodicity and dispersive character considerable differences in structure texture mineralogical composition and material s surface crust and subsoil geochemical properties emerged from site signature plots and these results suggest that agricultural processes affect the dispersive character of the crust materials presumably because agricultural activity increases the buffering effect of organic acids on the dispersed clay this is supported by the observation that on the one site that was levelled but not used for agriculture a stable organically distinct crust like the abandoned agricultural sites has not formed the changes to the material s aggregate stability and bulk density properties when terracing occurs is examined but insufficient evidence is available from the data collected to unpick the causes of aggregate stability changes in the study plots the way in which differences between crust and subsoil enhance infiltration is discussed and the role of the terrace drop in influencing hydraulic gradients and pipe development is illustrated a possible index to describe the relationship between evacuated material volumes and the controlling parameters discussed above is tested it is concluded that terracing which is intended as a conservation practice has in dispersive materials actually enhanced piping leading to the abandonment of farming

morphological analysis and erosion rate evaluation in badlands of radicofani area southern tuscany italy abstract since 1988 geomorphologic research based on field surveys and photo geological analysis has been conducted in southern tuscany italy in areas characterised by very rapid morphological evolution in the area outcrop pliocene marine claystones uplifted during the quaternary up to 750 m above sea level now undergoing intense erosion processes leading to considerable badlands formation morphodynamic analysis conduced by direct and indirect measurements in a sample area were taken in order to quantify the erosion rate in badland areas the torrente piantrafolla sample area was chosen as representative of the study area it was most recently monitored during the period nov 2000 feb 2004 at this time morphographic and morphometric analyses carried out in selected measurement stations located on slopes identified gravity as the main morphogenetic process responsible for slope shaping the calanchi badland areas are characterised by constant and rapid shrinking of their edges resulting from landslides which occur in autumn and winter as a consequence of intense rainstorms selected measurement stations indicate an erosion rate value range from 5 to 7 5 cm y the comparison between 1976 and 1994 digital elevation models dem obtained from photogrammetric restitution indicated a mean erosion rate of about 5 cm y in a nineteen year period this value considerably higher than the values measured in other italian basins indicate a very rapid evolution of the slopes due mainly to small earth flows inside calanchi badlands

relationships among rainfall runoff and suspended sediment in a small catchment with badlands abstract the araguas catchment of the central spanish pyrenees has been monitored since 2004 to study weathering erosion and the hydrological and sediment response to rainfall events in order to understand the hydromorphological dynamics of a badland area in a relatively humid environment this small catchment 0 45 km2 shows highly active processes of physical and chemical weathering related to seasonal variations in temperature and moisture erosion and sediment transport are widely studied in badlands within mediterranean environments because they represent the dominant sediment source to obtain information about suspended sediment and discharge a gauging station was installed within the araguas catchment during the summer of 2005 the aim of this work is to determine the relationships among rainfall runoff and suspended sediment in this badland area towards this goal we analyze the relationships between suspended sediment concentration and discharge during rainfall events from a hydrological viewpoint the araguas catchment reacts to all rainfall events with torrential flow being the most characteristic hydrological response the results obtained between october 2005 and april 2007 reveal extremely high concentrations of suspended sediment with values frequently exceeding 100 g l 1 and reaching a maximum of 1200 g l 1 three different types of hysteretic loops were observed clockwise 22 events 28 counter clockwise 27 events 34 and figure eight 12 events 15 moreover 23 of events were classified as complex hysteretic loops and removed from the analysis due to their complexity clockwise hysteretic floods are characterized by their long duration and the highest hydrological and sedimentological responses counter clockwise hysteretic floods are characterized by their short duration and moderate hydrological and sediment responses finally figure eight hysteretic floods are related to multiple peaks in suspended sediment coinciding with oscillations in discharge associated with the highest rainfall intensities within each event and moderate hydrological and sediment responses

paradoxical pseudotachylyte fault melt outside the seismogenic zone abstract fault generated melt pseudotachylyte is an established indicator of palaeoseismic faulting the existing consensus that frictionally induced melting occurs within the classic seismogenic zone contrast the contention over how pseudotachylyte forms within the ductile regime central to this issue is whether all pseudotachylyte originates as pressure dependent frictional melt along slip surfaces or if pressure independent processes have roles in its formation propagation of high velocity slip into deeper crustal levels provides a satisfactory explanation for pseudotachylyte at depth but does not of itself rationalize earthquake nucleation outside the classic seismogenic zone pseudotachylyte from the minas fault zone nova scotia canada is used to demonstrate the formation and preservation of fault related melt under lower crustal conditions microstructures retain evidence of intense dislocation glide with minimal climb and ductile disaggregation of the host the latter are consistent with intracrystalline deformation in the peierls stress controlled glide regime it remains unclear whether the crystal plasticity serves only as a precursory stage to rupture and high velocity slip or is itself responsible for both instability and the thermal transient there are similarities between accelerating plastic slip leading to rupture and aseismic creep bursts tremor that emphasize the mechanistic complexity of deep faulting and the need to extend consideration beyond that of a simple brittle ductile response the occurrence of tremor bursts fall within the depth range of paradoxical pseudotachylyte and provides a circumstantial link between active tectonics and the geologic record that merits examination

surface rupture effects on earthquake moment area scaling relations empirical earthquake scaling relations play a central role in fundamental studies of earthquake physics and in current practice of earthquake hazard assessment and are being refined by advances in earthquake source analysis a scaling relation between seismic moment m0 and rupture area a currently in use for ground motion prediction in japan features a transition regime of the form m0 a2 between the well recognized small self similar and very large w model earthquake regimes which has counterintuitive attributes and uncertain theoretical underpinnings here we investigate the mechanical origin of this transition regime via earthquake cycle simulations analytical dislocation models and numerical crack models on strike slip faults we find that even if stress drop is assumed constant the properties of the transition regime are controlled by surface rupture effects comprising an effective rupture elongation along dip due to a mirror effect and systematic changes of the shape factor relating slip to stress drop based on this physical insight we propose a simplified formula to account for these effects in m0 a scaling relations for strike slip earthquakes

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

slip length scaling in large earthquakes the role of deep penetrating slip below the seismogenic layer coseismic slip is observed to increase with earthquake rupture length for lengths far beyond the length scale set by the seismogenic layer the observation when interpreted within the realm of static dislocation theory and the imposed limit that slip be confined to the seismogenic layer implies that earthquake stress drop increases as a function of rupture length for large earthquakes and hence that large earthquakes differ from small earthquakes here a three dimensional elastodynamic model is applied to show that the observed increase in coseismic slip with rupture length may be satisfied while maintaining a constant stress drop across the entire spectrum of earthquake sizes when slip is allowed to penetrate below the seismogenic layer into an underlying zone characterized by velocity strengthening behavior is this deep coseismic slip happening during large earthquakes we point to a number of additional associated features of the model behavior that are potentially observable in the earth these include the predictions that a substantial fraction on the order of one third of the total coseismic moment is due to slip below the seismogenic layer and that slip below the seismogenic layer should be characterized by long rise times and a dearth of high frequency motion

thirty years of studies on badlands from physical to vegetational approaches a succinct review the scientific subjects addressed in the research into badlands since the publication of bryan and yair s book bryan r b and yair a editors 1982 badland geomorphology and piping geo books norwich 408 pp are briefly analysed with a steadily increasing number of papers per year attention to some aspects such as runoff generation piping and the role of lithology and soils varied whereas the percentage of studies on erosion rates increased steadily over time vegetation was not a subject of research in early papers as most of the papers dealing with vegetation were rather descriptive and published in local or limited diffusion media which contrasts with the present situation when about 40 of papers published in international journals about badlands address some aspect of vegetation however the growth in the attention paid to vegetation and erosion rates was not linked to any increase in papers dealing with badland reclamation badlands are now seen as a group of systems with some common features but diverse dynamics depending mainly on climatic and lithological drivers more attention should be paid in the future to investigating the evolution of these landforms over time mostly through modelling studies whereas emerging technologies foster detailed analyses that were not possible formerly although some badland areas determine on and off site environmental issues others are spots of landscape diversity that merit protection rather than reclamation

scaling of fault parameters for continental strike slip earthquakes the long standing conflict between the predictions of elastic dislocation models and the observation that average coseismic slip increases with rupture length is resolved with application of a simple displacement depth function and the assumption that the base of the seismogenic zone does not result from the onset of viscous re laxation but rather a transition to stable sliding in a medium that remains stressed at or close to failure the resulting model maintains the idea of self similarity for earth quakes across the entire spectrum of earthquake sizes

appropriate boundary conditions for modeling very long earthquakes and physical consequences we have studied two sets of models to find appropriate boundary conditions for the theoretical modeling of very long earthquakes i e those for which the length l is much larger than the width w of the rectangular aftershock area and the resulting physical consequences in the first set we study the conventional rectangular crack model for l w 2 and 4 i e the stress drop is confined to a rectangular region and there is no rupture outside this region w model in the second set of models which is suggested by geologic data we constrain the stress drop to a rectangular zone seismogenic layer but we do not have any constraint on the rupture above and below this layer the applied stress in this region above and below the seismogenic layer is taken to be exactly equal to the yield stress of the material so that no stress drop occurs when it yields this implies that the material on either side of the seismogenic layer is shearing aseismically just before the earthquake occurs and also implies that the material in these regions is purely plastic the major conclusion of our work is that the second set of models the rupture propagates dynamically for some distance into these nonbrittle zones above and below the seismogenic layer this result is supported by geological evidence and also by recent seismic evidence that moments of some large earthquakes increase with increasing wavelength at very long periods the slip in large parts of these zones is found to be nonnegligible the slip is still confined to a finite width which may be considered as an effective width but this width is larger than the width of the seismogenic brittle layer this effective width increases as the length of the region of stress drop increases and may be larger than this length for long faults thus for the second set of models the aftershock area would underestimate the actual rupture area the moment and the slip at the center for the second set of models are larger than for the first set for the same l w ratio of the stress drop region even if we assume that there is no radiated energy from the regions above and below the seismogenic zone for l w 2 the duration of slip at interior points on the fault for the two models are the same but for l w 4 the duration of slip at a given interior point is much larger for the second set of models however the particle velocity during this added time of slip for the second class of models is small and almost constant so that at least for l w up to 4 this difference may not be significant for strong ground motion near such a fault the rise times and slips at any interior point of the fault is mainly width controlled for the first set of models and mainly controlled by the length of the elastic region or the effective width for the latter set since longer faults are observed to have larger slips than shorter ones of the same width the first set of models would predict that stress drops increase with rupture length for the same fault width however this observation can be explained by the second set of models even for constant stress drops for the second set of models we find that a fault twice the length of another has much less than double the slip for the same average stress drop we suggest that both classes of models studied are realistic models of earthquake sources but for different cases

badland dynamics in the central pyrenees temporal and spatial patterns of weathering processes the genesis and development of badlands is controlled by bedrock lithology topography and climate the development of badlands in the central spanish pyrenees is favoured by the presence of marls and a climate with a marked seasonality the combination of these factors results in active hydrosedimentological processes the aim of the present work was to study the dynamics of badlands in the central pyrenees with a focus on the temporal and spatial patterns of the dominant weathering processes the study area was a small mountain catchment and we focussed on the continuous observation of a number of physical parameters that control regolith development and weathering processes samples collected from different depths at sites with different aspects enabled temporal comparisons of the factors involved in the development of surface regolith that can be considered as indicators of the weathering of the marls these indicators were then related to environmental variables moisture and temperature atterberg limits were established and related to moisture content to explain slope dynamics and related processes finally analyses of carbonate content were performed in the laboratory the results validate the employed methodology supporting our description of weathering processes the established chronological sequence and the relation of these processes to climatic and topographic parameters the results obtained since january 2004 show that the chosen indicators are sensitive to seasonal dynamics variations in temperature and water supply and slope aspect the development and dynamics of regolith on north facing slopes is more active than that on south facing slopes freeze thaw is the main weathering process on north facing slopes while south facing slopes are dominated by the development of crusts associated with wetting drying processes washing effects and lower temperatures upon north facing slopes mean that the dissolution of carbonates is more pronounced in such areas compared with south facing slopes especially within the upper layers of the regolith copyright 2006 john wiley sons ltd

impact of physico chemical soil properties on erosion features in the aliano area southern italy abstract this study has been carried out on three pairs of clayey silt slopes which are examples of typical badlands near aliano southern italy these show features of erosion which are common to se exposed clayey silt rocks outcropping in the same area after mineralogical geochemical and grain size analyses these slopes were compared with the se exposed adjacent ones having however a different erosive action and a partially vegetated covering was found pedological analyses show a clear development of soil horizons where the slope is rich in organic matter and this is wholly consistent with the presence of vegetation a comparison between the eroded substrates and non eroded substrates showed that the former have higher 16 m the grain size also distinguishes crusts from substrates the latter having higher fractions tds ph sar and ps are parameters which distinguish the eroded from the non eroded sides of the slopes on average the eroded substrates have ph sar and ps values higher than the non eroded ones the esp values of the eroded slopes are slightly higher than those of the non eroded ones up to now the relations between ph tds sar ps and esp have been considered as descriptors of dispersivity however an improvement can be made regarding the predictability of diagrams such as esp tds when taking mineralogical composition into consideration the crusts are less dispersive than the eroded substrates and the non eroded ones show the same feature as crusts this suggests that the most severely weathered part of a slope tends to reach a stable condition when a strong decrease in sar ps and esp occurs this study shows that the erosion mechanism involves morphological and geographic exposure climatic elements as well as grain size mineralogy chemistry and the exchange processes of soil

a rare great earthquake on an oceanic fossil fracture zone first motion solution found in this study and has a strike consistent with the fracture zone north of the bend the southern fault plane with strike 178 d ip 54 and rake 65 has a strike consistent with the portion of the fracture zone to the south of the bend and has a dip which can be explained by the style of deformation that the region is undergoing the centroid moment tensor solution of the broad band model is calculated and found to be consistent with the region of low misfit in mantle wave solution space the broad band solution has a moment of 1 53 10 21 nm mw 8 1 again consistent with the mantle wave data slip propagated bilaterally with an approximate rupture velocity of 3k ms 1 80 per cent of local shear wave speed the rupture front is less well resolved to the south of the epicentre than to the north the majority 75 per cent of moment originated from slip on the northern fault the broad band data requires significant slip below the oceanic moho with as much as 70 per cent of moment due to slip in the brittle uppermost mantle in the preferred model

multiple cmt source analysis of the 2004 sumatra earthquake while it is agreed that the great sumatra earthquake of december 26 2004 was among the largest earthquakes of the past century there has been disagreement on how large it was which part of the fault ruptured and how the rupture took place we present a centroid moment tensor cmt analysis of the earthquake in which multiple point sources are used in the inversion to mimic a propagating slip pulse the final model consists of five point sources with the southernmost sources accounting for the majority of the moment release the presumed fault planes of the southern sources strike northwest while those in the north strike northeast consistent with the geometry of the subduction trench slip on the fault is found to be more oblique in the north than in the south the inversion with five sources leads to a moment magnitude for the sumatra earthquake of m w 9 3 consistent with estimates from long period normal mode amplitudes

rheological evolution of a pseudotachylyte bearing deep crustal shear zone in the western canadian shield abstract crustal scale continental strike slip fault systems are typically thought to be thermally segregated into an upper seismogenic expression and a lower zone of ductile deformation likely extending into the lower crust the ability of the lower crust to sustain stress is fundamental to understanding the mechanical behavior of the lithosphere yet significant debate exists regarding the strength of the ductile crust the cora lake shear zone in the western churchill province of the canadian shield is a 4 7 km wide zone of granulite to upper amphibolite facies mylonite which hosts synkinematic pseudotachylyte suggesting a locally strong lower crust kilometer scale mapping suggests that the shear zone localized at a major lithological and terrane boundary with the pseudotachylyte network centered within the ca 1 km wide more intensely deformed finer grained ultramylonitic core in this contribution we use optical petrography and electron backscatter diffraction to describe microstructure across a transect of the cora lake shear zone by combining these observations with grain size piezometry experimental flow laws and regional pressure temperature paths we conclude that stress amplification from a relatively common type of km scale lithological heterogeneity and cooling history is the most reasonable explanation for the deep crustal pseudotachylyte

possibility of biases in the estimation of earthquake recurrence and seismic hazard from geologic data abstract aseismic deformation is an integral part of the earthquake process and may lead to systematic biases in the estimation of earthquake size recurrence and attendant strong ground motions in seismic hazard analyses founded on the geologic description of the locations lengths and slip rates of active faults observations are reviewed and presented to suggest that large earthquakes systematically rupture to increasingly greater depths below the seismogenic layer and that the portion of slip on faults accommodated by aseismic processes may be inversely related to the length of rupture expected to occur on them if so the expected seismic moment per unit area of earthquakes on mapped faults may be systematically overestimated as a function of rupture length when derived from regressions of seismic moment and aftershock area and estimates of seismic moment rate derived from geologic measures of fault offset might be systematically overestimated as an inverse function of the length of rupture expected to recur on a fault

complex multifault rupture during the 2016 mw 7 8 kaikōura earthquake new zealand the 2016 moment magnitude m w 7 8 kaik ura earthquake was one of the largest ever to hit new zealand hamling et al show with a new slip model that it was an incredibly complex event unlike most earthquakes multiple faults ruptured to generate the ground shaking a remarkable 12 faults ruptured overall with the rupture jumping between faults located up to 15 km away from each other the earthquake should motivate rethinking of certain seismic hazard models which do not presently allow for this unusual complex rupture pattern science this issue p eaam7194 1 1 lookup doi 10 1126 science aam7194

lithological properties and weathering response on badland hillslopes rills and rill networks are important geomorphological features in clay rich badland areas rill network geometry varies with climate and topography but the lithological properties are also critical rill systems on mudrock and sandstone in alberta badlands were studied to examine progressive changes in material properties as smectite rich mudrocks and sandstones undergo weathering and the impact of seasonal changes in precipitation patterns three plots with well developed rill systems on each unit were examined in may 2001 and 2003 geometric properties were determined along a dense grid and surface and subsurface samples were analyzed for texture crust structure sem mineralogical composition xrd content of major elements xrf aggregate stability and moisture content the rill width depth ratio decreased from 2001 to 2003 on mudrock rill networks the popcorn crust found in 2001 changed to a thin dense crust in 2003 2001 materials had higher na and ca concentrations and the 2003 materials have higher al k concentrations unweathered mudrock shards were subjected to incremental weathering in controlled laboratory conditions depending on moisture input different crust types developed on materials after 10 wetting drying cycles material responded to different amounts of precipitation by alteration from swelling to dispersion

quantitative study of piping processes in badland areas of the ebro basin ne spain abstract in the ebro basin piping is an ubiquitous erosion process in badland areas occurring in two main situations on slopes of exposed tertiary clays and in recently incised silty clay holocene valley fill sediments the quantitative importance of the main factors controlling piping processes in those conditions was obtained by statistical analysis based on multiple and stepwise regressions piping erosion is strongly related to a high sodium absorption ratio sar which favours clay dispersion however the statistical analysis indicates that the chemical characteristics and the physical chemical behaviour are a necessary condition but are not sufficient on their own to develop piping processes on the slopes piping is controlled by the physical and chemical properties of the material such as the dispersion index the granulometric fraction smaller than 4 m ph and crack density in the valley fill sediments piping is mainly controlled by the sulphate concentration in the water extract from saturated paste which is also associated with high sar values and the dispersion index in both geomorphic situations piping is always related to high crack density and high topographic gradient

geochronological position of badlands and geomorphological patterns in the guadix baza basin se spain abstract the guadix baza basin is one of a number of intramontane depressions located within the betic cordillera se spain where the geological and geomorphological evolution is controlled by tectonic activity the basin ceased to be closed after capture by the atlantic network when five main land systems developed late pleistocene geological evolution basically consisted of erosional modelling when badlands were deeply incised in highly erodible materials marls and silts three travertine platforms and several palaeolithic sites were used to determine that this main incision period fell within a 115 000 48 000 yr range there are few signs of geomorphological evolution of this basin in the last 48 000 yr based on these geomorphological data and soil development tectonic uplift of the basin probably played a secondary role in its evolution and climatic conditions in southern iberia in the 144 000 48 000 yr period were more humid and variable than later

crustal earthquake instability in relation to the depth variation of frictional slip properties recent stability studies using constitutive relations of the type found by dieterich ruina and others to describe frictional slip of rocks in the laboratory have provided a new explanation of the depth cutoff of shallow crustal earthquakes the class of friction laws discussed has the property that the sliding stress depends on normal stress temperature slip rate and slip history for sliding at a fixed slip rate v and fixed environment e g normal stress temperature etc the shear strength evolves toward a steady state value ss v stability analysis show that for d ss v dv 0 velocity strengthening implies stable steady state sliding at least for a broad class of constitutive laws more fully described in the paper experiments by dieterich and by tullis and weeks on westerly granite with mature sliding surfaces indicate that d ss v dv is negative at room temperature whereas higher temperature experiments by stesky show that d ss v dv becomes positive above approximately 300 c therefore in the case of the earth where temperature increases with depth the above observations seem to suggest that the depth cutoff of crustal earthquake activity can be understood in terms of the variation of the frictional response with depth from a regime with d ss v dv 0 this is not inconsistent with but rather refines the suggestion by sibson and others that the depth cutoff is due to a transition from brittle friction to ductile flow further our results show definitively that the shallow depth confinement of seismicity is compatible with a model in which deformation is localized to a fault zone extending well below the seismogenic depth the depth confinement does not require a model showing transition to a zone of broadly distributed creep flow beneath the seismogenic zone following mavko a two dimensional quasi static strike slip fault model is analyzed but using different numerical procedures and a depth variation of frictional properties based on the laboratory data mentioned above and the lachenbruch sass depth variation of temperature for the san andreas fault the resulting predictions of such features as the confinement of crustal earthquakes to shallow depths the development of locked patches the recurrence time for the seismic cycle the seismic stress drop and displacement etc are generally in agreement with the observed characteristics of large scale strike slip earthquakes along the san andreas fault calculations based on the laboratory data predict for example that stick slip nucleates around 5 7 km that large seismic motion occurs around the nucleation depth and above but diminishes gradually to zero at 13 15 km depths that rapid postseismic creep occurs over another 3 4 km depth and that at greater depths steady slip consistent with the average plate velocity is only modestly perturbed by the earthquakes occurring above the most uncertain parameter is the slip weakening distance l for evolution of fault surface state we illustrate how features of the predicted earthquake cycles vary with l over the range for which calculations are feasible

on the scaling of slip with rupture length for shallow strike slip earthquakes quasi static models and dynamic rupture propagation we explore whether observations of average surface rupture properties among strike slip earthquakes reflect the underlying mechanics we compare the observed relationship between average slip and rupture length for 27 surface ruptures 18 plate boundary earthquakes and 9 away from transform plate boundaries with predictions from two families of uniform stress drop models purely elastic models with a rupture limiting locking depth predict a nonlinear relationship while a quasidynamic model with no locking depth predicts a linear relationship we explore whether observations of fault slip at the earth s surface distinguish which if either of these two families of models may be favored we find that the data provide insufficient constraints to rule out either a linear or a nonlinear relationship this might arise from uncertainties in the observations or from reasonable but unrecoverable variations in locking depths and uniform stress drops among earthquakes we advance an alternative interpretation that the complexity among the observations is consistent with dynamic rupture models featuring spatially varying stress drops

resolution of fault slip along the 470 km long rupture of the great 1906 san francisco earthquake and its implications data from all available triangulation networks affected by the 1906 earthquake have been combined to assess the trade off between slip resolution and its uncertainty and to construct a conservative image of coseismic slip along the rupture because of varying network aperture and station density slip resolution is very uneven although slip is determined within uncertainties of 1 0 m along 60 of the fault constraints are poor on the remaining mostly offshore portions of the rupture slip decreases from maxima of 8 6 and 7 5 m at shelter cove and tomales bay to 4 5 m near mount tamalpais and 2 7 m at loma prieta the geodetically derived slip distribution is in poor agreement with estimates based on analysis of s wave seismograms probably because these waves register only 20 30 of the total seismic moment obtained from longer period surface waves consideration of a range of fault geometries for 1906 slip near loma prieta indicates right lateral motions lie between 2 3 and 3 1 m these values are considerably greater than the 1 5 m of measured surface slip on which several assessments of high earthquake hazard for this fault segment were based this factor along with the absence of 1989 slippage where 1906 surface slip was used to make the forecasts casts doubt on some claims of success in predicting the 1989 m 6 9 loma prieta earthquake

earthquake scaling fault segmentation and structural maturity abstract slip and length measurements on earthquakes suggest large stress drop variability we analyze an extended set of slip length measurements for large earthquakes m 6 to seek for the possible origin s of this apparent variability we propose that such variability arises from earthquakes breaking a variable number of major fault segments that number depends on the strength of the inter segment zones which itself depends on the structural maturity of the faults we propose new d max l parameterizations based on that idea of multiple segment ruptures in such parameterizations each broken segment roughly scales as a crack while the total multi segment rupture does not stress drop on individual segments is roughly constant only varying between 3 5 to 9 mpa the slight variation that is still observed depends on fault structural maturity more mature faults have lower stress drops than immature ones the new d max l functions that we propose reduce uncertainties with respect to available relationships they thus provide a more solid basis to estimate seismic hazard by integrating fault properties revealed by geological studies

morphology and development of selected badlands in southeast spain implications of climatic change four areas were selected to represent a range of processes characteristic of badland surfaces in southeast spain petrer and monnegre in alicante vera and tabernas in almeria at petrer rilling and swelling processes produce a deeply cracked surface drained by a finely textured network of shallow rills at monnegre piping and rilling are differentially developed on slopes ultimately controlled by basal incision at vera aspect controlled lichen and vegetation cover produce a sequence of badland development within which the relative importance of piping mass movement and rilling varies through the sequence at tabernas simple overland flow is the dominant process but aspect influences rill network density and badland evolution the factors controlling badland development can be grouped into those related to gross morphology to surface cover and runoff generation and to material properties these factors are effective over varying timescales implying that morphological response times differ among the selected badlands

m loga models and other curiosities abstract magnitude m log area a relations have been the focus of considerable research in the past two decades because of their importance in estimating moment magnitude m for earthquake probability calculations and seismic hazard analysis for m w there is a strong consensus for constant stress drop scaling for the larger earthquakes m 7 that dominate the moment balancing in continental crust the l model scaling employed by hanks and bakun 2002 2008 involves fault slip growing with fault length l when l w 15 km or so requiring that static stress drops increase with increasing fault slip constant stress drop representations of the same larger earthquake data such as shaw 2009 2013 require slip at depths significantly greater than w 15 km available evidence supports neither of these requirements leaving us perplexed as to how large earthquake ruptures initiate and propagate in continental crust deep slip m log a models that involve an unknown amount of seismic moment earthquake slip at unknown depths w are not appropriate for use in earthquake probability studies governed by shallow slip depths w seismic moment earthquake slip balancing such as those in california during the twenty first century

analysis of the relationship between seismic moment and fault length for large crustal strike slip earthquakes between 1977 92 we have used an uniform data set to determine the scaling relation between seismic moment m0 and fault length for 34 large crustal strike slip earthquakes in the period 1977 92 the seismic moments used were obtained by the centroid moment tensor analysis the aftershocks of each event were relocated in this study and the fault length estimated from their spatial extent for large events we find that in spite of some scatter in the data the trend of this uni form data set indicates that m0 c 2 our data set does not show any obvious change of slope around m0 6 8 x 102o n m as was seen in a previous non uniform data set in

the role of mineralogy geochemistry and grain size in badland development in pisticci basilicata southern italy mineralogical geochemical and grain size composition of soil and pore water chemistry parameters were characterized on both eroded south facing and non eroded north facing clayey silt slopes in the basilicata region southern italy only a few grain size parameters and clay mineralogy discriminate eroded from non eroded substrates compared with the latter the former have fractions of over 63 m and 1 4 m lower and fractions 4 63 m higher grain size characters of crusts did not discriminate with respect to substrate bulk rock mineralogy was not distinctive but the clay mineral assemblage shows that the eroded slope is enriched in kaolinite mixed layers illite smectite and chlorite whereas illite decreases although overlaps are common chemical data enable discrimination between eroded and non eroded slopes ph sar sodium adsorption ratio tds total dissolved salts and ps percentage of sodium are distinctive parameters for both eroded and non eroded slopes tds increases in depth in the non eroded slope whereas the maximum tds is just below the crust in the eroded one on average eroded substrates are higher in ph sar and ps than non eroded ones the esp exchangeable sodium percentage of the eroded slope has a higher value than the non eroded one crusts are less dispersive than eroded substrates and non eroded substrates behave as crusts this suggests that the portion of the slope most severely exposed to weathering tends to stabilize due to strong decreases in sar ps and esp several diagrams reported in the literature show similarly anomalous crust samples on eroded slopes compared with other samples coming from greater depths on eroded slopes in the present case study the exchangeable form of na characterizes crusts more than the soluble form this study describes the erosional mechanism which involves morphological and geographic exposure and climatic elements as well as grain size mineralogy chemistry and exchangeable processes of soils copyright 2006 john wiley sons ltd

features and evolution of slip structures in badlands areas se spain abstract slips are little known mud coated structures several centimeters thick produced by gravity driven flows on free vertical surfaces we have differentiated a sequence formed by three main morphologies mud drips slips and pseudo stalactites this study located in the badlands of the guadix and baza basins se spain suggests that formation of muddy morphologies on subvertical walls is determined by the physico chemical characteristics of colloidal suspensions slurries related to rainy periods and does not indicate any substrate decay multiple braided microchannels internally structured like irregular book pages are commonly found each formed by mudflows during rainy episodes these morphologies constitute a temporary sink of fine erosive materials they consist of scarcely sorted mixtures of heterogeneous matter of a detrital cohesive nature with low clay contents which inherit the features of the parent materials the current semiarid environmental conditions appear to favor conservation rather than development the differences observed in the slips of the guadix and baza basins can be determined by the different geomorphological evolution of the two basins and to a lesser extent by the properties of the slurries that fed the slips

clay mineralogy as a crucial factor in badland hillslope processes abstract comprehensive and important work has been done in understanding badland processes on both the big scale and more recently on smaller scale in order to understand the subtle differences between sites however most studies lack important information regarding clay mineralogy and their importance for weathering processes type and rate of weathering depend on material physico chemical properties climatic regimes and slope characteristics as weathering progresses the surface conditions change influencing erosion processes usually badland lithologies are reported as sodium rich highly dispersive materials but that is not invariably true the primary objective of this study is to show that clay minerals have an important role in defining surface and subsurface processes on badland hillslopes field studies conducted in dinosaur park badlands alberta canada chinguacousy badlands ontario canada and sestino badlands tuscany italy have shown that there are two dominant clay rich lithologies smectite rich and smectite poor mudrocks different surface crust and weathering profiles were observed on smectite rich mudrocks during two field years with distinct precipitation inputs after a dry fall winter season the popcorn surface was very well developed 2 3 cm the subsurface layer 10 15 cm thick overlaid the layer of smaller shards followed by the unweathered material after a very wet fall winter season the surface layer was denser and thinner 0 5 cm with wider cracks and a thin subsurface layer attached to the crust weathering profiles on smectite poor lithologies did not show any differences with variable climatic conditions a thin surface layer was composed of soft thin and small 0 5 0 3 0 1 cm shards a layer of larger shards overlying unweathered material was beneath it in order to better understand the described occurrences badland materials were monitored in controlled laboratory conditions during an incremental weathering experiment six samples of each material were subjected to 10 cycles of simulated rainfall which duration ranged 10 60 min very short rainfalls 10 20 min can cause swelling of clay minerals in smectite rich materials and formation of popcorn surface during drying periods during subsequent wetting drying periods the crust becomes flatter and denser and desiccation cracks become wider and deeper samples subjected to 50 and 60 min of rainfall showed maximum swelling after only one cycle of rainfall after this swift swelling samples became unstable and dispersive during subsequent wetting dispersion became dominant resulting in flatter surfaces thinner crust and narrower desiccation cracks smectite poor mudrocks appeared to be resistant to variable wetting and drying large shards broke down into smaller due to differential swelling of illite and chlorite once they were reduced to tiny flaky shards the surface became compacted the surface cracks served as the initial pathways for sediment and water movement knowing if the material is smectite rich or smectite poor can help in prediction of processes and the erosion rates the amount intensity and duration of precipitation will determine not only the rate of weathering but also the type of the weathered surface on smectite rich surfaces smectite poor materials appear to be more resistant to change in precipitation

effects of frictional heating on the thermal hydrologic and mechanical response of a fault the mechanical response of a fault zone during an earthquake may be controlled by the diffusion of excess heat and fluid pressures generated by frictional heating in this study we formulate a fault model which incorporates the effects of frictional heating on the thermal hydrologic and mechanical response of a small patch of the failure surface this model is used to examine the parameters that control the fault response and to determine their critical range of values where thermal pressurization is significant the problem has two time scales a characteristic slip duration and a characteristic time for thermal pressurization the slip duration is set by the fault geometry the characteristic time for thermal pressurization is set by the slip rate the friction coefficient and the thermal and hydraulic characteristics of the medium the response of the fault depends on the relative magnitude of these two times results suggest that the fault width and hydraulic characteristics of the fault zone and adjacent medium are the primary parameters controlling the mechanical response for earthquakes occurring across zones of low porous medium compressibility 10 9 pa 1 and permeability 10 18 m2 the characteristic time for thermal pressurization is small in this case frictional heating can cause fluid pressures to approach lithostatic values the shear strength to approach zero and the temperature rise to stabilize at a maximum value dependent on the pore dilatational and transport properties of the porous medium whether the patch acts as a barrier to slip or exhibits substantial strain weakening is dependent on the shear strain across the fault moderate slip events where shear strains exceed two cause substantial strain weakening and consequently large stress drops accelerations and displacements thus it is possible for the patch to act as a barrier for small earthquakes but not for large ones both the dynamic stress drop and total displacement decrease for zones with larger compressibility permeability or width if the compressibility or permeability exceeds 10 8 pa 1 or 10 14 m2 or the shear strain is less than one then the effects of frictional heating may be negligible and the fault will exhibit no strain weakening characteristics consequently the patch acts as barrier that halts or resists further fault motion extrapolation of these results suggests that spatial variations in fault width and hydraulic characteristics will cause a heterogeneous stress drop and fault slip over the failure surface explaining many of the features of active faulting e g barriers nonuniform slip rupture stoppage random ground accelerations strong motions and frequency magnitude relations

glacis geometry as a geomorphic marker of recent tectonics the guadix baza basin south spain abstract the guadix baza basin occupies 4000 km 2 and constitutes the largest intramontane basin of the betic cordillera southern spain it has a well preserved geomorphic surface a glacis which started to be eroded when the basin conditions changed from endorheic to exorheic taking into account its large preserved surface area more than 1200 km 2 and its pre deformational geometry this geomorphic surface is a useful marker of recent deformation combining geological and geomorphological data and high resolution dem topographic profiles of the glacis have been produced to estimate vertical displacements caused by active compression and extension structures these structures have produced relative vertical displacements of up to 100 m from the late middle pleistocene to the present assuming an age for the glacis of between 205 and 600 ka it has been possible to estimate long term minimum and maximum vertical rates of the activity of normal faults and folds using this geomorphic surface as a marker vertical slip rates range from 0 07 to 0 49 mm year for the main active normal faults and vertical folding rates range from 0 05 to 0 17 mm year for several active folds these long term vertical slip and folding rates are in accordance with other values previously estimated in other sectors of the betic cordillera when present detailed geomorphic study of recent glacis is an excellent tool for evaluating active tectonics over large regions

aftershock zones of large shallow earthquakes fault dimensions aftershock area expansion and scaling relations summary we determine the aftershock areas from relocated hypocentres for 64 dip slip and eight strike slip earthquakes in the period 1977 1996 together with those for three recent earthquakes the 1998 antarctic plate earthquake the 1999 izmit turkey earthquake and the 2000 wharton basin earthquake we also include the data for 27 strike slip earthquakes from pegler das 1996 we find that the location of the hypocentre is essentially random along strike for both strike slip and dip slip earthquakes subduction zone earthquakes appear to initiate more frequently towards the down dip edge of the fault whereas the non subduction zone dip slip earthquakes do not have any preferred depth of initiation the aftershock zones of subduction zone earthquakes often expand substantially along strike and up dip but far less in the down dip direction whereas those for non subduction zone earthquakes do not expand significantly in either the up or the down dip direction subduction zone thrust earthquakes have larger and more numerous aftershocks than earthquakes in all other tectonic settings for strikeslip earthquakes we find that slip increases at least linearly with length for dip slip earthquakes we find that the ratio of length to width increases systematically with length for lengths 40 km indicating that there is some restriction on fault width slip is found to be proportional to length over the moment range 10 17 nm m0 3r10 21 nm

cyclic ductile and brittle deformation related to coseismic thrust fault propagation structural record at the base of a basement nappe preveli crete 1 the structural record at the base of a basement nappe preveli nappe crete greece thrust upon sedimentary rocks is investigated aimed on understanding mechanisms which result in decoupling of the thrust sheet from its original substratum we identify several superimposed deformation stages each with characteristic structural style and indications of episodic deformation at initially high differential stress the final stage involves formation of a matrix supported breccia transected by pseudotachylytes comprising the lowermost 30 m of the nappe brecciation and pseudotachylyte formation occurred in a single event and structures were not modified afterward complete induration of breccia and composition of phengite crystallized during devitrification of pseudotachylytes place the sequence of events into the middle crust we propose a model relating episodic deformation and cyclic stress history to propagation of a thrust fault in a limited number of seismic events terminal brecciation and frictional fusion record passage of the fault front beneath the site of observation and decoupling of the thrust sheet absence of discernible further deformation is consistent with negligible basal friction during transport as a nappe brecciation and pseudotachylyte formation mark the switch from a history of repeated coseismic loading and postseismic stress relaxation in the plastosphere driven by seismic events on the approaching thrust fault to passive transport with deformation localized in a weak thrust plane for a sequence of superimposed ductile to brittle structures our model provides an alternative to progressive cooling and exhumation concomitant with deformation over millions of years

badlands in marl lithologies a field guide to soil dispersion subsurface erosion and piping origin gullies abstract field scientists studying badland processes in mediterranean and semi arid climates require assurances that the material in which gullies are presented is not dispersive a dispersive context means first infiltration rates may be radically changing in very short periods due to swelling and deflocculation of clays second surface crusts could be the result of translocation of sodium into subsurface positions third rills may be formed or at least exacerbated by shallow subsurface erosion fourth large gullies with substantial up channel headcuts including so called bank gullies may have formed because subsurface pipes have collapsed and fifth that network connectivity and evolution may be principally internal being effected by subsurface pipe capture network integration and most importantly the bulk of the sediment moving around in the landscape is not being lost from the surface this paper presents a decision support tool to assist the effective diagnosis of a landscape s principal genetic process suite the soil s behaviour in response to its geochemistry in marls with high exchangeable sodium percentages esps is outlined in simple terms with minimum use of laboratory or field chemical investigations using examples the paper then presents a simple set of form indicators that can be used in the field to diagnose the possibility that subsurface process are dominating landscape erosion surface crust character ephemeral rills and large subsurface tunnel settings are explained and classified in a final section the geomorphological implications of piping in gullied landscapes are explored by reference to the literature on connectivity

self consistent earthquake fault scaling relations update and extension to stable continental strike slip faults using seismic moment m length l data for stable continental region scr faults augmented by data not included in previous studies this article reassesses and confirms the bilinear scaling relation for the dip slip faults of leonard 2010 furthermore using the new data i propose a separate bilinear relation for estimating magnitude from surface rupture length there are now a small number of scr strike slip earthquakes for which the fault dimensions have been estimated i use these to constrain a trilinear scaling relation for this class of fault for the four fault types interplate dip slip interplate strike slip scr intraplate dip slip and scr intraplate strike slip the scaling relations for the 10 permutations of m d l w and a are given

spatial and temporal distribution of slip for the 1992 landers california earthquake we have determined a source rupture model for the 1992 landers earthquake m w 7 2 compatible with multiple data sets spanning a frequency range from zero to 0 5 hz geodetic survey displacements near field and regional strong motions broadband teleseismic waveforms and surface offset measurements have been used explicitly to constrain both the spatial and temporal slip variations along the model fault surface our fault parameterization involves a variable slip multiple segment finite fault model which treats the diverse data sets in a self consistent manner allowing them to be inverted both independently and in unison the high quality data available for the landers earthquake provide an unprecedented opportunity for direct comparison of rupture models determined from independent data sets that sample both a wide frequency range and a diverse spatial station orientation with respect to the earthquake slip and radiation pattern in all models consistent features include the following 1 similar overall dislocation patterns and amplitudes with seismic moments of 7 to 8 10 26 dyne cm seismic potency of 2 3 to 2 7 km 3 2 very heterogeneous unilateral strike slip distributed over a fault length of 65 km and over a width of at least 15 km though slip is limited to shallower regions in some areas 3 a total rupture duration of 24 sec and an average rupture velocity of 2 7 km sec and 4 substantial variations of slip with depth relative to measured surface offsets the extended rupture length and duration of the landers earthquake also allowed imaging of the propagating rupture front with better resolution than for those of prior shorter duration strike slip events our imaging allows visualization of the rupture evolution including local differences in slip durations and variations in rupture velocity rupture velocity decreases markedly at shallow depths as well as near regions of slip transfer from one fault segment to the next as rupture propagates northwestward along the multiply segmented fault length the rupture front slows as it reaches the northern limit of the johnson valley landers faults where slip is transferred to the southern homestead valley fault an abrupt acceleration is apparent following the transfer this process is repeated and is more pronounced as slip is again passed from the northern homestead valley fault to the emerson fault although the largest surface offsets were observed at the northern end of the rupture our modeling indicates that substantial rupture was also relatively shallow less than 10 km in this region

simulating badland erosion with kineros2 in a small mediterranean mountain basin vallcebre eastern pyrenees abstract the ca l isard catchment 1 32 km 2 a sub basin of the vallcebre experimental catchments yields large amounts of sediments about 580 mg km 2 year 1 that are produced in relatively small but very active eroded areas badlands several lines of evidence suggest that there is a delay between sediment production caused by intense summer rainstorms and sediment transport occasioned by the main floods produced by large precipitation events following wet antecedent conditions first a calibration validation exercise was carried out with sediment yield data obtained using containers provided with slot divisors in a badlands micro catchment 1240 m 2 then the model was applied to the main badlands areas in the ca l isard sub catchment for a 4 year period and the simulated sediment yields were compared with the records at the gauging station the test was performed with the generalized likelihood uncertainty estimation glue approach for assessing the uncertainty associated with model predictions which assumes that many parameter sets can give acceptable simulations the results demonstrated the capacity of kineros2 to simulate badland erosion although it showed limited robustness a clear temporal mismatch between erosion and sediment transport and the relevance of sediment stores in the catchment were confirmed while the total weights of sediment were generally under predicted the limited suitability of the area used for calibration or the role of sediment sources not simulated in the approach may account for this shortcoming

regolith behaviour and physical weathering of clayey mudrock as dependent on seasonal weather conditions in a badland area at vallcebre eastern pyrenees abstract studies on badland areas in the vallcebre basin pyrenees suggest that erosion rates are controlled by the weathering rate of mudrocks to obtain the temporal pattern of physical weathering and its control on the erosive processes monitoring of regolith temperatures at different aspect depth and lithology and periodical determination of regolith moisture and bulk density were carried out changes in surface regolith have also been monitored by means of photographic techniques using an especially designed tripod finally the hydrological and erosive response of the regolith trough the seasons were studied using rainfall simulations the results obtained support and confirm previous knowledge on the role of frost action in mudrock weathering and the role of subsequent regolith development and wetness status on infiltration and runoff generation these seasonal changes of behaviour are so important that they raise serious questions about the validity of observations or experiments carried out in only one season this work confirms that erosion processes are controlled by regolith formation during winter and regolith depletion by storm rainfall erosion during summer spring and early autumn it also raises important points about annual trends of infiltration and erodibility that should be used as guidelines for modelling runoff and sediment production

scaling relations of strike slip earthquakes with different slip rate dependent properties at depth abstract empirical observations suggest that earthquake stress drop is generally constant to investigate the effect of rupture width on earthquake scaling relations we analyze synthetic seismicity produced by a 3d vertical strike slip fault model using two different profiles of frictional slip rate behavior below the seismogenic zone within the rate and state framework a relatively abrupt transition of the a b profile from velocity weakening to strengthening at the base of the seismogenic crust produces increasing slip and stress drop with increasing event size choosing a smoother transition allows large earthquakes to propagate deeper leading to similar slip length scaling but constant stress drop scaling our numerical experiments support the idea that the maintenance of constant stress drop across the entire range of observed earthquake magnitudes may be achieved by allowing coseismic slip to rupture to depths below the seismogenic layer

slip distribution of the 1992 landers earthquake and its implications for earthquake source mechanics we use near source 10 to 164 km displacement seismograms to image the slip distribution and rupture history of the 28 june 1992 mw 7 3 landers california earthquake aftershock seismograms from similar distances are modeled to find the velocity model and frequency range 0 05 to 0 25 hz over which theoretical green s functions are most accurate and the measure of fit is used as an upper bound on theoretical error in the mainshock inversion we represent the rupture surface with three planar segments divided into 3 by 3 km elements extending from the surface to 18 km depth and solve for the slip distribution and the rupture time model that minimizes misfit to both recorded seismograms and mapped surface displacement in a least squares sense we investigate two faulting models one with a uniformly short 3 sec rise time everywhere on the fault surface and the other with a variable rise time 2 to 6 sec we perform sensitivity tests using synthetic data from a hypothetical earthquake to evaluate model resolution and solution stability in the sensitivity tests both fault models recover similar slip and rupture features but neither is capable of imaging details of the rise time for the landers earthquake we find an average rupture velocity of 2 5 km sec and use this average for a starting model in a linearized inversion for rupture time in our solutions of slip amplitude distribution the southernmost johnson valley fault segment has 20 of the total seismic moment 6 to 8 1019 n m with small displacements near the hypocenter the homestead valley segment contributes half of the moment with the largest slip amplitudes 25 to 35 km northwest of the hypocenter at 4 to 12 km depth and the camp rock emerson segment contributes the remaining moment with the largest slip amplitude 35 to 50 km northwest of the hypocenter in the shallow crust 9 km there is some evidence that the rupture front is delayed as it encounters high slip regions suggesting that prior to the mainshock these areas were further from failure owing either to greater strength or lower prestress

connectivity as a crucial determinant of badland morphology and evolution the way in which threshold behaviour landscape sensitivity and connectivity1 operate together at the meso and macro scale in badlands is initially considered from a theoretical energy utilisation perspective the argument is developed that intrinsic changes to process domain dominance can result in progressive shifts in process connectivity without the need to invoke external climatic or tectonic change from this premise a meso scale closed system model for the evolution of connected states in regionally isolated badlands is developed applicable to systems evolving towards a fixed base level within a less erosive host landscape the model shows how badlands disconnected from regional drainage can develop from a wide range of initial states into a convergent quasi equilibrium followed by a period of complex response as energy is dissipated across thresholds giving rise to a range of equifinal maximum entropy landscapes this classification is illustrated using a range of global badland examples longer term macro scale interruptions to this semi deterministic model of badland relief degradation are also considered from this longer term larger scale perspective it is argued that extrinsic changes to relative relief can be driven by base level changes tectonically isostatically or eustatically induced in which case the continuity and linkages of information within the system are modified by effects which move up through the system bottom up control macro scale climatic changes also alter connectivity by changing the power distribution of prevailing events and by causing long term changes in mean precipitation temperature and e p ratio which affect vegetation and therefore runoff resistance all across the landscape from this perspective longer term climatic change operates in a top down manner the interplay between these two larger scale controls will inevitably determine the pattern of connected states that the landscape experiences through time the top down and bottom up combinations that can lead to either rejuvenation and a return to the stages described for the closed system model or stabilisation enhanced phases of both morphological and geochemical stabilisation are discussed

geomorphological chemical and physical study of calanchi landforms in nw sicily southern italy abstract this work deals with an integrated geomorphological and chemical physical study of calanchi landforms in two sites ottosalme and catalfimo of nw sicily southern italy developed on dominant silty clay deposits the calanchi fronts are characterized by different morphological features and dominant geomorphic processes sharp knife edged ridges and concentrated water runoff dominate at ottosalme and smoother landforms affected by mass movements mud flows and translational slides prevail at catalfimo we focused on some geochemical and physical parameters such as ph total dissolved salts sodium adsorption ratio sar porosity plastic and liquid limits as possible causes of the above differences with special emphasis on their role in discriminating the behavior of peculiar microforms such as a weathered outer crust and the corresponding inner massive portion unweathered substrate our results show that the main chemical physical features of calanchi morphologies and microforms often display no clear correlations with respect to those reported in the existing literature pointing to a higher complexity of patterns and behaviors in particular all samples consist of dispersive material sar values 10 but a more plastic and liquid behavior at catalfimo can explain a higher occurrence of landslides and smoother morphology than at ottosalme higher sar values at ottosalme well explain the dominance of concentrated water erosion the chemical behavior of the studied microforms is better described by ph being alkaline with higher values in the inner substrate than the outer crust and appears to minimize the effects of all other parameters and their responses to other external controlling factors lower sar values in the crust suggest that clay dispersivity is not the prominent factor controlling its surface detachment and mobility downslope which is more likely promoted by its higher porosity and consequent water absorption than the inner portion with changes in the saturation state shear strength and water pressure

experimental study of the grain flow fluid mud transition in debris flows abstract we have performed a series of laboratory experiments that clarify the nature of the transition between fluid mud and grain flow behavior the surface velocity structure and the speed of the nose of debris flows in channels with semicircular cross sections were measured with several cameras and visual tracers while the mass flow rate was recorded using a load cell at the exit chamber other rheological tests were used to calculate independently the yield strength and matrix viscosity of the debris flow mixture shear rates were varied by nearly an order of magnitude for each mixture by changing the channel radius and slope shear rates were significantly higher than expected 6 55 s 1 given the modest slopes examined 10 7 15 2 the large values were primarily a result of the concentration of shear into narrow bands between a central nondeforming plug and the sidewall as a result the shear rate of interest was calculated by using the width of the shear band and the plug velocity as oppose

frequency domain inversion of strong motions application to the 1992 landers earthquake we present a frequency domain inversion in which the observed earthquake strong ground motions are used to constrain the space time dependence of slip on a fault green s functions are numerically evaluated and the parameters describing the rupture are the local slip rupture time and rise time these parameters are simultaneously evaluated without additional constraints this procedure allows for large variations in the local rupture velocity the june 28 1992 landers earthquake mw 7 3 offers an exceptional opportunity to apply this technique to a major strike slip event we model the rupture evolution including local differences in slip durations and variations in rupture velocity our final results are in good agreement with other inversion studies geodetic and surface observations the main discrepancies occurred at depth and at the end of the johnson valley fault we show that a relatively low resolution could be an explanation for these differences rupture velocity and slip are extremely heterogeneous both along strike and with depth a moment of 0 90 1020 n m was found the slip distribution shows that this event consists of a series of regions of high slip subevents separated by regions of relative low slip approximately 50 of the moment was released on the homestead valley fault in this region of large slip the rupture velocity inferred by our inversion is well constrained and is equal to 3 0 km s at depth and 2 5 km s near the surface our inversion favors the hypothesis that the duration of the slip at each point of the fault is of the order of the duration of rupture of each subevent

nucleation and early seismic propagation of small and large events in a crustal earthquake model 1 earthquake nucleation and early seismic propagation are studied in a two dimensional strike slip fault model with depth variable properties the fault is governed by the dieterich ruina rate and state friction law we use an efficient and rigorous numerical procedure for elastodynamic analysis of earthquake sequences on slowly loaded faults developed by lapusta et al 2000 we find that for decreasing values of the characteristic slip distance of the friction law small events appear at the transition from the locked to creeping behavior toward the bottom of the seismogenic zone small and large events have very similar nucleation phases in our simulations here by nucleation phase we mean gradually accelerating aseismic slip in a small slowly expanding zone before the breakout of the dynamic seismically detectable event moment acceleration to which velocity seismograms are proportional in early stages of seismic propagation exhibits irregular fluctuations in the form of speedups and slowdowns in the moment release rate consistently with observations as reported by ellsworth and beroza 1995 our simulations show that such irregular moment acceleration can at least in part be due to the heterogeneous stress distribution imprinted on the fault by the arrest of previous small events and by stress concentrations at the borders of creeping regions and to partial arrest of the rupture in velocity strengthening fault regions which inhibit seismic slip index terms 7209 seismology earthquake dynamics and mechanics 7260 seismology theory and modeling 3220 mathematical geophysics nonlinear dynamics 7230 seismology seismicity and seismotectonics 3230 mathematical geophysics numerical solutions 8164 tectonophysics stresses crust and lithosphere keywords earthquake nucleation phase event clustering irregular moment release stress concentrations rate and state friction earthquake sequences

gully erosion impacts factors and control gully erosion attracts increasing attention from scientists as reflected by two recent international meetings poesen and valentin eds catena 50 2 4 87 564 li et al 2004 gully erosion under global change sichuan science technology press chengu china 354 pp this growing interest is associated with the increasing concern over off site impacts caused by soil erosion at larger spatial scales than the cultivated plots the objective of this paper is to review recent studies on impacts factors and control of gully erosion and update the review on dgully erosion and environmental change importance and research needst poesen et al 2003 catena 50 2 4 91 134 for the farmers the development of gullies leads to a loss of crop yields and available land as well as an increase of workload i e labour necessary to cultivate the land gullies can also change the mosaic patterns between fallow and cultivated fields enhancing hillslope erosion in a feedback loop in addition gullies tend to enhance drainage and accelerate aridification processes in the semi arid zones fingerprinting the origin of sediments within catchments to determine the relative contributions of potential sediment sources has become essential to identify sources of potential pollution and to develop management strategies to combat soil erosion in this respect tracers such as carbon nitrogen the nuclear bomb derived radionuclide 137 cs magnetics and the strontium isotopic ratio are increasingly used to fingerprint sediment recent studies conducted in australia china ethiopia and usa showed that the major part of the sediment in reservoirs might have come from gully erosion gullies not only occur in marly badlands and mountainous or hilly regions but also more globally in soils subjected to soil crusting such as loess european belt chinese loess plateau north america and sandy soils sahelian zone north east thailand or in soils prone to piping and tunnelling such as dispersive soils most of the time the gullying processes are triggered by

role of erosion processes on the morphogenesis of a semiarid badland area bardenas reales ne spain abstract bardenas reales badlands are located in the middle western sector of the ebro depression northern spain this consists of a big erosional depression with deeply dissected valley bounded by steep slopes labile argillaceous bedrock scarce high intensity rainfall and high temperatures make erosion the dominant morphogenetic process several erosion processes operate in the bardenas reales rilling gullying piping and mass movements the relative role played by these processes on the morphogenesis is largely controlled by physico chemical properties of the materials and climatic conditions precipitation distribution over the year controls the development of mass movements whereas regolith physical chemical properties favor piping gullying and rilling during the rainfall maxima soil erodibility in this area is clearly controlled by the sodium content and the presence of swelling clays these factors determine the distribution and appearance of piping processes cracking in holocene clay deposits devoid of swelling clays is related to high sodium content that confers a dispersive character clay dispersion causes loss of cohesion favoring piping in the rainfall maxima soil loss is significant and controlled by precipitation amount and maximum intensity conversely during periods of cyclonic rain erosion is scarce and mass movements are the dominant process in the slopes underlain by tertiary mudstones mud flows are frequent during the winter months in winter time when rains are of low intensity and evapotranspiration is limited infiltration through cracks is high consequently water content in the regolith may increase until the plastic limit is reached under these conditions and due to the high gradient of the slopes 34 shear strength is surpassed and the clay material is able to slide and flow

spatial variation of seismogenic depths of crustal earthquakes in the taiwan region implications for seismic hazard assessment abstract this paper presents the first whole taiwan scale spatial variation of the seismogenic zone using a high quality crustal seismicity catalog the seismicity onset and cutoff depths i e seismogenic depths are determined by the earthquake depth moment distribution and used to define the upper and lower boundaries of the seismogenic zone respectively together with the published fault geometries and fault area moment magnitude relations the depth difference in the onset and cutoff depths i e seismogenic thickness is used as the fault width to determine the moment magnitudes of potential earthquakes for the major seismogenic faults results show that the largest mw7 9 8 0 potential earthquake may occur along the changhua fault in western taiwan where the seismic risk is relatively high and seismic hazard mitigation should be a matter of urgent concern in addition the first motion focal mechanism catalog is used to examine the relation between the seismogenic depths and earthquake source parameters for crustal earthquakes 50 km the shallowest onset and cutoff depths are observed for normal and strike slip events respectively this observation is different from the prediction of the conventional continental rheology model which states that thrust events have the shallowest cutoff depth thus a more sophisticated rheology model is necessary to explain our observed dependence of the seismogenic depths on faulting types meanwhile for intermediate to large crustal mw 4 depth 50 km earthquakes thrust events tend to occur at the bottom region of the seismogenic zone but normal and strike slip events distribute at a large depth range

depositional processes in large scale debris flow experiments this study examines the depositional process and characteristics of deposits of large scale experimental debris flows to 15 m3 composed of mixtures of gravel to 32 mm sand and mud the experiments were performed using a 95 m long 2 m wide debris flow flume that slopes 31 following release experimental debris flows invariably developed numerous shallow 10 cm deep surges sediment transported by surges accumulated abruptly on a 3 runout slope at the mouth of the flume deposits developed in a complex manner through a combination of shoving forward and shouldering aside previously deposited debris and through progressive vertical accretion progressive accretion by the experimental flows is contrary to commonly assumed en masse sedimentation by debris flows despite progressive sediment emplacement deposits were composed of unstratified accumulations of generally unsorted debris hence massively textured poorly sorted debris flow deposits are not emplaced uniquely en masse the depositional

a composite source model of the 1994 northridge earthquake using genetic algorithms abstract the 17 january 1994 northridge earthquake m w 6 7 occurred on a buried thrust fault in the northwest los angeles metropolitan area we investigate the source process of this earthquake using the csmip strong motion records and a composite source model developed by zeng et al 1994a for realistic earthquake strong ground motion prediction our previous studies demonstrated the realism of the synthetic strong motions generated from the composite source model by comparing them with observed records from earthquakes in many areas of the world this article addresses an inverse study of the problem to find a specific composite source model for the northridge earthquake this is done by adjusting the location of a suite of composite subevents using genetic algorithms holland 1975 to best match the observed waveforms a test run of the genetic algorithm on synthetic data sets finds a very good convergence of the approach we reduce largely the intensive computation time by identifying subevents with major contribution to the waveform fit our result for the 1994 northridge earthquake indicates a complex earthquake rupture process with three large slip zones one at the hypocenter and the other two to the west of the hypocenter we then use this model to compute the high frequency strong motion velocity and acceleration the results show that the composite source model provides a very realistic broadband source description for the northridge earthquake

postseismic response of repeating aftershocks the recurrence intervals of repeating earthquakes on the san andreas fault in the loma prieta aftershock zone follow the characteristic 1 t decay of omori s law a model in which these earthquakes occur on isolated patches of the fault that fail in stick slip with creep around them can explain this observation in this model the recurrence interval is inversely proportional to the loading rate due to creep logarithmic velocity strengthening friction predicts 1 t decay in creep rate following the mainshock the time dependence of recurrence is inconsistent with a simple viscous constitutive relationship which predicts an exponential decay of loading rate thus our observations imply postseismic slip at seismogenic depth under a power law rheology the time dependence of postseismic deformation measured geodetically may be diagnostic of whether postseismic deformation is caused by creep or possible viscoelastic deformation at greater depths