on the summer poleward coastal current off sw mexico 1 for the first time on the basis of direct observations june 2003 and june 2005 the characteristics of the summer time coastal poleward current off sw mexico are reported only the surface evidence of this coastal current has previously been described from ship drift compilations in june 2003 the current was 90 180 km wide 400 m deep with speed 0 3 ms 1 and transport 4 sv 1 sv 106 m3 s 1 in june 2005 its width was 90 km it was 250 300 m deep with mean speed 0 15 m s 1 and transport 2 5 sv california current water ccw and equatorward flow were found further offshore mesoscale eddies significantly affected the coastal current and transported ccw into the coastal zone

p wave velocity anisotropy related to sealed fractures reactivation tracing the structural diagenesis in carbonates abstract fracture properties are important in carbonate reservoir characterization as they are responsible for a large part of the fluid transfer properties at all scales it is especially true in tight rocks where the matrix transfer properties only slightly contribute to the fluid flow open fractures are known to strongly affect seismic velocities amplitudes and anisotropy here we explore the impact of fracture evolution on the geophysical signature and directional v p anisotropy of fractured carbonates through diagenesis for that purpose we studied a meter scale parallelepiped quarry block of limestone using a detailed structural and diagenetic characterization and numerous v p measurements the block is affected by two en echelon fracture clusters both being formed in opening mode mode 1 and cemented but only one being reactivated in shear we compared the diagenetic evolution of the fractures which are almost all 100 filled with successive calcite cements with the p wave velocities measured across this meter scale block of carbonate which recorded the tectonic and diagenetic changes of a south provence sedimentary basin we found that a directional v p anisotropy magnitude as high as 8 16 correlates with the reactivated fractures cluster dip angle which is explained by the complex filling sequence and softer material present inside the fractures that have been reactivated during the basin s tectonic inversion we show that although a late karstification phase preferentially affected these reactivated fractures it only amplified the pre existing anisotropy due to tectonic shear we conclude that v p anisotropy measurements may help to identify the fracture sealing opening processes associated with polyphased tectonic history the anisotropy being independent of the current stress state this case shows that velocity anisotropies induced by fractures resulted here from a cause that is different from how these features have often been interpreted selective reactivation of sealed fractures clusters rather than direction of currently open ones

correlation scales objective mapping and absolute geostrophic flow in the california current the spatial covariances of the time dependent density and geostrophic velocity fields off southern california are determined from a unique set of repeated hydrographic observations 44 cruises made by the california cooperative oceanic fisheries investigations from 1984 to 1994 the covariances and objective analysis are used to combine direct velocity observations from shipboard acoustic doppler current profiler adcp measurements made on a recent survey october 1993 with hydrographic observations the analysis reduces ageostrophic noise in the adcp velocities by smoothing and enforcing horizontal nondivergence additionally the velocities are mapped over scales that are dynamically consistent with the hydrography maximum surface geostrophic flow in the california current in october 1993 is about 35 cm s 1 50 larger than that estimated assuming a 500 m level of no motion absolute flow at 500 m is o 10 cm s 1 and indicates that the surface eddy field penetrates through the thermocline uncertainty in the geostrophic reference calculated from the adcp measurements is of o 4 cm s 1 the velocity residual objectively analyzed minus raw adcp estimates exhibits smaller correlation scales than the geostrophic flow

the 2010 yushu earthquake triggered landslide hazard mapping using gis and weight of evidence modeling the yushu county qinghai province china april 14 2010 earthquake triggered thousands of landslides in a zone between 96 20 32 9 e and 97 10 8 9 e and 32 52 6 7 n and 33 19 47 9 n this study examines the use of geographic information system gis technology and bayesian statistics in creating a suitable landslide hazard zone map of good predictive power a total of 2 036 landslides were interpreted from high resolution aerial photographs and multi source satellite images pre and post earthquake and verified by selected field checking before a final landslide inventory map of the study area could be established using gis software the 2 036 landslides were randomly partitioned into two subsets a training dataset which contains 80 1 628 landslides for training the model and a testing dataset 20 408 landslides twelve earthquake triggered landslide associated controlling parameters such as elevation slope gradient slope aspect slope curvature topographic position distance from main surface ruptures peak ground acceleration distance from roads normalized difference vegetation index distance from drainages lithology and distance from all faults were obtained from variety of data sources landslide hazard indices were calculated using the weight of evidence model the landslide hazard map was compared with training data and testing data to obtain the success rate and predictive rate of the model respectively the validation results showed satisfactory agreement between the hazard map and the existing landslide distribution data the success rate is 80 607 and the predictive rate is 78 855 the resulting landslide hazard map showed five classes of landslide hazard i e very high high moderate low and very low the landslide hazard evaluation map should be useful for environmental recovery planning and reconstruction work

evaluation of different machine learning models for predicting and mapping the susceptibility of gully erosion abstract gully erosion constitutes a serious problem for land degradation in a wide range of environments the main objective of this research was to compare the performance of seven state of the art machine learning models svm with four kernel types bp ann rf and brt to model the occurrence of gully erosion in the kashkan poldokhtar watershed iran in the first step a gully inventory map consisting of 65 gully polygons was prepared through field surveys three different sample data sets s1 s2 and s3 including both positive and negative cells 70 for training and 30 for validation were randomly prepared to evaluate the robustness of the models to model the gully erosion susceptibility 12 geo environmental factors were selected as predictors finally the goodness of fit and prediction skill of the models were evaluated by different criteria including efficiency percent kappa coefficient and the area under the roc curves auc in terms of accuracy the rf rbf svm brt and p svm models performed excellently both in the degree of fitting and in predictive performance auc values well above 0 9 which resulted in accurate predictions therefore these models can be used in other gully erosion studies as they are capable of rapidly producing accurate and robust gully erosion susceptibility maps gesms for decision making and soil and water management practices furthermore it was found that performance of rf and rbf svm for modelling gully erosion occurrence is quite stable when the learning and validation samples are changed

hydromechanical behavior of a deformable rock fracture subject to normal stress lbl 12297 preprint to be published in the journal of geophysical research hydromechanical behavior of a deformable rock fracture subject to normal stress y w tsang and p a witherspoon january 1981 two week loan copy this is a library circulating copy which may be borrowed for two weeks for a personal retention copy call tech info diu is ion ext 6782 prepared for the u s department of energy under contract w 7405 eng 48

gis based support vector machine modeling of earthquake triggered landslide susceptibility in the jianjiang river watershed china abstract support vector machine svm modeling is based on statistical learning theory it involves a training phase with associated input and target output values in recent years the method has become increasingly popular the main purpose of this study is to evaluate the mapping power of svm modeling in earthquake triggered landslide susceptibility mapping for a section of the jianjiang river watershed using a geographic information system gis software the river was affected by the wenchuan earthquake of may 12 2008 visual interpretation of colored aerial photographs of 1 m resolution and extensive field surveys provided a detailed landslide inventory map containing 3147 landslides related to the 2008 wenchuan earthquake elevation slope angle slope aspect distance from seismogenic faults distance from drainages and lithology were used as the controlling parameters for modeling three groups of positive and negative training samples were used in concert with four different kernel functions positive training samples include the centroids of 500 large landslides those of all 3147 landslides and 5000 randomly selected points in landslide polygons negative training samples include 500 3147 and 5000 randomly selected points on slopes that remained stable during the wenchuan earthquake the four kernel functions are linear polynomial radial basis and sigmoid in total 12 cases of landslide susceptibility were mapped comparative analyses of landslide susceptibility probability and area relation curves show that both the polynomial and radial basis functions suitably classified the input data as either landslide positive or negative though the radial basis function was more successful the 12 generated landslide susceptibility maps were compared with known landslide centroid locations and landslide polygons to verify the success rate and predictive accuracy of each model the 12 results were further validated using area under curve analysis group 3 with 5000 randomly selected points on the landslide polygons and 5000 randomly selected points along stable slopes gave the best results with a success rate of 79 20 and predictive accuracy of 79 13 under the radial basis function of all the results the sigmoid kernel function was the least skillful when used in concert with the centroid data of all 3147 landslides as positive training samples and the negative training samples of 3147 randomly selected points in regions of stable slope success rate 54 95 predictive accuracy 61 85 this paper also provides suggestions and reference data for selecting appropriate training samples and kernel function types for earthquake triggered landslide susceptibility mapping using svm modeling predictive landslide susceptibility maps could be useful in hazard mitigation by helping planners understand the probability of landslides in different regions

tidal current ellipses in a three dimensional baroclinic numerical model of the gulf of california using a numerical model of the circulation of the gulf of california a description of the tidal ellipses parameters is given the best modeled constituents are those of the semidiurnal band while those of the diurnal band are underestimated in general tidal ellipse semimajor axes for the diurnal and semidiurnal bands increase from south to north with a maximum in the archipelago area the annual and semiannual components are largest in the southern part the eccentricity of the internal tide is larger than the barotropic tide but in general the currents are mostly rectilinear with no preferred sense of rotation it is found that the barotropic currents are more energetic than the baroclinic currents the most energetic component is the barotropic m2 component followed by the ssa s2 and sa harmonics for the internal currents the energy levels of the m2 ssa and sa harmonics are about the same and are much larger than the rest of the constituents

relating the hydraulic properties of a fractured rock mass to seismic attributes theory and numerical experiments numerical experiments are conducted to establish how the properties of a seismic signal are related to the hydraulic properties of a fractured rock mass a hybridized reflectivity method is developed and used to compute a 1d synthetic seismogram for a geologic section which consists of a series of layers with one of the layers consisting of fractures seismic attributes notably instantaneous amplitude frequency and bandwidth are computed for a reflected seismic energy from a fractured zone with known distribution of fracture parameters fracture length aperture and spacing the permeability of the fractured zone is computed using a discrete fracture model the synthetic seismogram is computed using the modified displacement discontinuity model mdd which accounts for fracture opening and finite lengths of fractures a significant correlation is established between the seismic attributes and fractured rock mass permeability all the seismic attributes tend to increase with increase in permeability the correlation is significant enough to establish a meaningful empirical relation between seismic attributes and fracture permeability

landslide occurrence as a response to land use change a review of evidence from new zealand abstract vegetation cover is an important factor influencing the occurrence and movement of rainfall triggered landslides and changes to vegetation cover often result in modified landslide behaviour however it is difficult to relate the occurrence of landslides directly to variations in land use especially in some european countries in contrast new zealand provides a good opportunity to investigate geomorphic responses to anthropogenic land cover changes before european settlers first arrived in the 1840s hilly regions were only marginally influenced by human activity the maoris new zealand s first settlers lived largely on coastal plains or near lakes and rivers they influenced general vegetation cover only through localized burning practices in contrast european settlers moved into the back country and converted extensive hill areas from native forest and bush to pasture this reduced the strength of the regolith and rendered the slopes more susceptible to landslides pulses of natural sedimentation in the pre european period have been related to volcanic activity climatic variability including changes in frequency of cyclonic storms and wind erosion and fluvial erosion following forest fires initiated either by volcanic eruptions or lightning strikes since european deforestation began sediment production has largely been determined by landslide events on unstable slopes thousands of landslides were triggered by high magnitude low frequency climatic events during storms with estimated return periods in excess of 50 years in contrast low magnitude high frequency rainfall events have caused gully and channel erosion examples from different parts of new zealand indicate changes in sediment generating processes following land use modifications after deforestation landslides have contributed significantly to sediment sequences in depositional basins such as lakes swamps estuaries coastal wetlands and the nearshore and offshore zones of continental platforms

application of lidar and discriminant analysis to determine landscape characteristics for different types of slope failures in heavily vegetated steep terrain horseshoe run watershed west virginia abstract a landslide inventory map was created for horseshoe run watershed west virginia using high resolution topographic data obtained from airborne lidar a total of 152 landslides were remotely mapped and classified as planar slides rotational slumps debris flows debris fans debris slides and active slopes based on morphologic characteristics interpreted from lidar derived shaded relief maps with field verification at several locations seven landscape variables were calculated for the watershed from the high resolution 0 5 m topographic data elevation slope angle slope aspect distance from roads distance from streams plan curvature and profile curvature statistical analyses were conducted to determine the mean and standard deviations for each variable and corresponding slope failure type discriminant analyses were conducted on the different types of failed slopes with a maximum 86 accuracy level to determine which landscape characteristics contribute to each type of landslide results from the discriminant analyses indicate that statistically significant differences exist between the failure classes mapped within the watershed and that slope angle slope aspect and landscape curvature are important variables influencing the type of process the results from this study have important implications for predicting where certain types of slope failures may occur based on landscape characteristics

seasonal gyres in the northern gulf of california abstract the circulation pattern in the northern gulf of california based on drifting buoys and hydrographic observations can be explained using the results of a linear two layer primitive equations model forced at the annual frequency by the pacific ocean wind stress and heat flux through the surface the modeled surface circulation consists of a cyclonic gyre from june to october and an anticyclonic gyre from december to april both located in the central region of the northern gulf of california which includes angel de la guarda island the maximum intensities of the gyres occur in august and february respectively with values of surface velocities of 65 cm s 1 in agreement with the observations and very low opposite velocities in the bottom layers may and november are transition months in which both gyres can be observed finally in june july or december january the growing gyre is still connected with the rest of the gulf of california through the narrows between tiburon island san este

geomorphic studies of landslides in the tully valley new york implications for public policy and planning on april 27 1993 a large landslide in the tully valley onondaga county ny destroyed three houses and resulted in the evacuation of four others it also triggered a loss of potable drinking water for about 15 homes north of the slide area and affected a total of 20 ha of land in the 7 years following this slide several studies have been conducted by federal and state environmental agencies and by local universities the goal of these investigations has been to determine what caused this slide document the history of past landslides in the region and establish whether future slides are likely to occur this paper reports on the results of these investigations and examines their effect on the tully valley community

sst thermohaline structure and circulation in the southern gulf of california in june 2004 during the north american monsoon experiment 1 the thermohaline structure circulation and heat fluxes in the gulf of california entrance during june 2004 are described based on conductivity temperature depth and lowering acoustic doppler current profiler data collected in a 14 day survey supported by satellite data the avhrr images show extensive mesoscale structures in the region the most striking being 1 a cool filament extending from the california current domain and 2 a warm intrusion along the mainland shelf on the warm side of the thermal front created by the cool filament there was a strong current flowing into the gulf with speeds up to 0 70 ms 1 in the surface this current which the sst images suggest was associated with a decaying eddy carried 6 sv into the gulf associated with the second structure there was an ingoing coastal current on the mainland shelf with weak surface currents but with speeds 0 25 ms 1 at its core between 70 and 200 m this coastal current transported 2 sv into the gulf the two ingoing currents appear to join inside the gulf forming a very strong speeds 0 40 0 80 ms 1 narrow 30 km coastal current between the surface and 500 m depth changes in the thermohaline structure of the upper layers observed by repeat sampling of three cross sections were dominated by advection however it was found that the advective heat flux is very variable in space and time for the period of observation it was estimated that the lateral heat input was 4 8 3 0 105 wm 2 as estimated with ladcp currents and 5 7 2 20 105 wm 2 with geostrophic velocities

estimating suppression of eddy mixing by mean flows particle and tracer based estimates of lateral diffusivities are used to estimate the suppression of eddy mixingacrossstrongcurrents particlesandtracersare advectedusingavelocityfieldderivedfromseasurface height measurements from the south pacific in a region west of drake passage this velocity field has been used in a companion paper to show that both particle and tracer based estimates of eddy diffusivities are equivalent despite recent claims to the contrary these estimates of eddy diffusivities are here analyzed to show 1 that the degree of suppression of mixing across the strong antarctic circumpolar current is correctly predicted by mixing length theory modified to include eddy propagation along the mean flow and 2 that the suppressioncan beinferredfromparticletrajectoriesby studyingthestructureofthe autocorrelationfunction of the particle velocities beyond the first zero crossing these results are then used to discuss how to compute lateral and vertical variations in eddy diffusivities using floats and drifters in the real ocean

characteristics of the displacement of a landslide with shallow sliding surface in a heavy snow district of japan the displacement of a landslide with shallow sliding surface in a heavy snow district was automatically monitored for over 4 years by a newly developed displacement gauge meteorological properties meltwater and or rainfall mr water equivalent of snow and other factors were simultaneously observed pore water pressure was monitored but only for a limited period of time since the displacement of the landslide was too large statistical analyses showed that maximum daily displacements of each year were observed not in snow melting periods but immediately before or at the beginning of a snow cover period there are three types of annual variation pattern with peaks in mid november to mid december mid april and mid july the variation pattern of displacement from the beginning of march to the beginning of june showed the least total displacement of those three types therefore snow cover is likely to affect the displacement of a landslide detailed investigation of the landslide displacement during snow cover periods showed that the rate of displacement slowed as the snow cover deepened meaning a decrease in mr and increase in water equivalent of snow the displacement ratio for the unit antecedent mr effect during snow cover periods dropped when the snow started to accumulate on the ground in all 4 years the reduction was likely attributable to snow load since it was found to have a negative logarithmic relation with the water equivalent of snow changes in pore water pressure and the relationship between pore water pressure and displacement during the snow cover periods differed from those in the other periods therefore the displacement of a landslide that has a shallow sliding surface in a snowy region was considered to be affected by snow accumulation conditions especially water equivalent of snow

aragonite saturation and ph variation in a fringing reef are strongly influenced by oceanic conditions seasonal variations of the co2 system in seawater for coral reefs are often controlled by both chemical biological processes and by regional oceanographic features in combination with the residence time of adjacent water this study reports the seasonal variability of the co2 system along a year though dissolved inorganic carbon and ph measurements in cabo pulmo a fringing reef from the mexican pacific two conditions were found on the reef summer with the presence of tropical surface water tsw characterized by high temperature lower dic levels and a higher aragonite saturation arag and winter with gulf of california water gcw when the opposite occurred this seasonal variation was due to the horizontal advection of two surface water masses gulf of california water during winter and tropical surface water the rest of the year as a result of the ocean circulation at the entrance of the gulf of california therefore the reef is significantly influenced by open ocean waters where the depth is less than 20 m the seasonal variability in arag between months with the presence of gcw and tsw is one of the largest ranges reported in coral reefs arag 0 5 units our results suggest that the reef community cannot modify the aragonite or ph of incoming ocean water this might be the case in other fringing reefs where the use of ocean acidification forecast models is suitable

internal structure of sst features in the central gulf of california abstract closely spaced xbt and ctd data were used to study the sub surface structure of features observed in satellite avhrr sea surface temperature sst images of the gulf of california gc such as fronts jets and gyres the lowest ssts in the gc are found around the midriff islands and especially over the sills because of strong mixing from tidal currents and breaking internal waves this minimum sst area is limited to the south and north by sharp sst fronts which frequently show convolutions gyres and filaments a vertical section of temperature along the gulf length shows that about 300 km south of the sills the isotherms begin to spread out in the vertical reducing stratification the thermocline isotherms begin surfacing about 100 km south of the sill forming the sst minimum area which has a maximum temperature difference of 6 c with waters to the south and a horizontal sst gradient of 0 05 c km 1 the evolution and subsurface structure of a cool filament apparently originated as an instability of the sst front was intensely sampled satellite images show that its head advanced due south at about 0 5 ms 1 along the edge of a pool of warm surface water about 110 km in diameter the thermocline below the warm pool was raised at its edge and some isotherms reached the surface producing the cool filament the tilt of the temperature salinity and density isolines at the edge of the warm pool produced a geostrophic jet adjacent to the cool filament and just inside the warm pool with maximum speed 0 5 ms 1 and extending down to 80 m the filament lasted about 10 days its width was 30 km and it reached a maximum length of 120 km the volume transport of the jet in the top 100 m was around 0 7 sv

detection of gas hydrates in faults using azimuthal seismic velocity analysis vestnesa ridge w svalbard margin accepted for publication in journal of geophysical research solid earth copyright 2020 american geophysical union further reproduction or electronic distribution is not permitted

open ocean regimes of relative dispersion as two fluid particles separate in time the entire spectrum of eddy motions is being sampled from the smallest to the largest scales in large scale geophysical systems for which the earth rotation is important it has been conjectured that the relative diffusivity should vary respectively as d2 and d4 3 for distances respectively smaller and larger than a well defined forcing scale of the order of the internal rossby radius with d the r m s separation distance particle paths data from a mid latitude float experiment in the central part of the north atlantic appear to support these statements partly two particles initially separated by a few km within two distinct clusters west and east of the mid atlantic ridge statistically dispersed following a richardson regime d2 t3 asymptotically for r m s separation distances between 40 and 300 km in agreement with a d4 3 law at early times and for smaller separation distances an exponential growth in agreement with a d2 law was briefly observed but only for the eastern cluster with an e folding time around 6 days after a few months or separation distances greater than 300 km the relative dispersion slowed down naturally to the taylor absolute dispersion regime

seasonal variation of geostrophic velocity and heat flux at the entrance to the gulf of california mexico 1 the divergence of the surface heat flux in the gulf of california is driven by the exchange of waters with the pacific ocean castro et al 1994 to estimate these exchanges geostrophic velocities and heat fluxes were computed from nine sections of closely spaced conductivity temperature depth stations across the entrance to the gulf of california between 1992 and 1999 the mean geostrophic velocity was composed of two alternating cores of inflow and outflow the two cores that were adjacent to either coast were broader and contained the highest inflow 0 40 m s and outflow 0 25 m s velocities supporting the general idea of inflow along sinaloa and outflow along baja california bc during winter and spring the baroclinic outflow usually occurred near bc and the baroclinic inflow occurred either through the center of the section and or along the sinaloa coast both inflow and outflow cores were 45 km wide and extended deeper than 700 dbar summer and fall showed a more complex pattern with alternating cores of inflow and outflow but with inflow along sinaloa on all cruises during may the inflow was mainly in the center of the section while outflow was concentrated along bc the heat transport associated with the geostrophic flow was calculated and compared with estimates derived from surface heat budgets for the gulf castro et al 1994 both the geostrophic flow and heat transport exhibited for the first empirical orthagonal function mode a strong seasonal signal with the maximum amplitude in may and the minimum amplitude in late october a seasonal fit to the net heat transport had an amplitude of 50 1012 w and phase of 133 days in good agreement with other authors further validating the geostrophic velocity estimates the heat added to subtracted from the pacific ocean accelerates decelerates alongshore currents and appears to propagate 10 westward as a rossby wave

a brief survey of gis in mass movement studies with reflections on theory and methods this paper surveys the evolution and progress of landslide studies with particular reference to the use of geographic information systems gis in setting the agenda for research the article begins with a critical discussion of the mass movement classification problem and notes that it has been thornier and more complex than it has for many other types of extreme natural phenomena the evolution of slope instability studies is charted from its descriptive field based origins to recent higher levels of understanding on the one hand there has been a shift from static to dynamic modelling of slope processes using digital simulation and computer graphics while on the other hand automated cartography gis and remote sensing have enabled regional studies at last to predominate over site based ones however gis often tends to favour inductive study design and so does the continuing emphasis on classification the low level of insight generated by inductive studies has inhibited the development of more interdisciplinary frameworks for study it has also proved difficult to reorient landslide studies to tackle slope instability problems with greater sensitivity to the stakeholders needs finally although social administrative political cultural and perceptual aspects of landslides have been neglected there are signs of a new interest in these important aspects

gis techniques and statistical models in evaluating landslide hazard geographical information systems gis and numerical cartography may greatly facilitate the development and use of statistical models for the assessment of regional landslide hazard from a small drainage basin located in central italy relevant geological and geomorphological factors were collected and processed by applying gis technology in particular modules were used which both generate high fidelity digital terrain models and automatically partition the terrain into main slope units the resulting information was then analysed by discriminant analysis which enabled landslide hazard and risk to be evaluated in each slope unit although not lacking drawbacks the method proved to be a feasible and cost effective approach to landslide susceptibility assessment and mapping

delineating fracture zones using surface tunnel surface seismic data p s and s p mode conversions a surface tunnel surface seismic experiment was conducted at the aspo hard rock laboratoryto study the seismic response of major fracture systems intersecting the tunnel a newly developedthree com

statistical analysis of the surface circulation in the california current system using satellite tracked drifters abstract a kinematic description of the surface circulation in the southern california current system is presented using the statistics of the 7 11 month long trajectories of 29 satellite tracked mixed layer drifters the drifters were released north of 30 n and traveled southward at an average speed of 3 4 cm s 1 along baja california through an inhomogeneous field of mesoscale eddies of 15 cm s 1 rms variability lagrangian and eulerian statistics of the variations about this mean southward drift are computed the drifter ensemble mean lagrangian decorrelation time scale is 4 5 days and the lagrangian decorrelation space scale is 40 50 km the computation of dispersion of single particles about the mean drift shows that the theory of diffusion by homogeneous random motion taylor s theory describes these dispersive motions well ensemble mean diffusivities of about 4 107 cm2 s 1 are found on a 200 200 km2 spatial average single partial diffusivities are found to be proportional to the kinetic ene

hypocenter migration as an explanation for temporal changes in coda q in the 1993 earthquake swarm near the norris lake community georgia qc coda q and b value exhibit systematic temporal variations on a scale of months and hours the long term monthly variations correlate with the swarm s growth and decay examination of the hypocenters demonstrates that q is a strong function of hypocenter and the temporal variations of q reflect a systematic migration of hypocenters the b value appears to vary in this swarm because the method of magnitude determination is dependent on qc throughout the duration of the swarm the active areas migrated from a high qc area eastward to a low qc area variations of qc over periods of hours were explained by a shifting ofhypocenters between high and low qc areas significant changes in qc occur for hypocenters that are separated by distances 10 km the nonuniform fractal distribution of relative scattering coefficients plays a major role in determining the spatial dependence of q by using forward coda modeling on the distribution of relative scattering coefficients derived for this earthquake swarm we can reproduce seismic coda with the same spatial dependence on q as found in the earthquakes throughout the swarm the relative locations of earthquakes associated with different q values and our ability to model different q values from a known distribution of relative scattering coefficients confirm that the migration of hypocenters and not a temporal change in attenuation properties determines the temporal variation of qc observed during the norris lake community earthquake swarm

effect of coastal trapped waves and wind on currents and transport in the gulf of california subsurface pressure ssp observations from stations inside and outside of the gulf of california gc are used to analyze the relationship between low frequency currents temperature and transport inside the gc and intraseasonal coastal trapped waves ctws which propagate poleward along the coast toward the gc correlation functions and coherences of ssp stations were consistent with intraseasonal ctws splitting in two at the mouth of the gulf one part enters the gulf propagates around the gulf and eventually toward the mouth and another part that appears to jump the mouth of the gulf and travels poleward along the west coast of the peninsula the correlation and coherence estimates of ssp at manzanillo with currents showed that downwelling ctws generated along gulf current anomalies toward the head of the gulf at the mainland shelf of the mouth whereas at ballenas channel sill san lorenzo sill these waves generated current anomalies toward the mouth near the surface bottom at the san lorenzo sl sill downwelling ctws increased the near bottom 400 m temperature and reduced the bottom transport of deep fresher and colder water that flows toward the head of the gulf cross calibrated multiplatform winds were used to investigate their relationship with currents the first empirical orthogonal function of the along gulf wind stress showed that wind blowing toward the head of the gulf generated a reduction of bottom transport toward the head of the gulf through the sl sill and intensified surface geostrophic current fluctuations toward the head of the gulf there was also significant correlation between inflow bottom transport and outflow surface geostrophic velocities averaged across the gulf consistent with the exchange pattern for the northern gulf

a comparison of the gis based landslide susceptibility assessment methods multivariate versus bivariate the purpose of this study is to evaluate and to compare the results of multivariate logical regression and bivariate landslide susceptibility methods in geographical information system gis based landslide susceptibility assessment procedures in order to achieve this goal the asarsuyu catchment in nw turkey was selected as a test zone because of its well known landslide occurrences interfering with the e 5 highway mountain pass

geographical variability of the first baroclinic rossby radius of deformation global 1 83 18 climatologies of the first baroclinic gravity wave phase speed c1 and the rossby radius of deformation l1 are computed from climatological average temperature and salinity profiles these new atlases are compared with previously published 5 83 58 coarse resolution maps of l1 for the northern hemisphere and the south atlantic and with a 1 83 18 fine resolution map of c1 for the tropical pacific it is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5 15 owing to seemingly minor computational errors geographical variations in the new high resolution maps of c1 and l1 are discussed in terms of a wkb approximation that elucidates the effects of earth rotation stratification and water depth on these quantities it is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and l1 at any particular location in the world ocean this is rationalized from consideration of the wkb approximation

seismically induced landslide displacements a predictive model newmark s model for predicting earthquake induced landslide displacements provides a simple way to predict the coseismic displacements affecting a sliding mass subject to earthquake loading in this model seismic slope stability is measured in terms of critical acceleration which depends on the mechanical soil properties pore pressure distribution and slope geometry the triggering seismic forces are investigated in terms of energy radiation from the source propagation and site effects based on 190 accelerometric recordings from 17 italian earthquakes with magnitudes between 4 5 and 6 8 the method is based on the calibration of relations having the general form of an attenuation law that relates the energy of the seismic forces to the dynamic shear resistances of the sliding mass to propagate the expected landslide displacements as an inverse function of the distance from the fault rupture the amount of displacement computed through these relations provides a criterion to predict the occurrence of slope failures finally maps showing in a deterministic and a probabilistic way the potential of seismically induced landslide displacements are displayed as a tool to provide seismic landslide scenarios and earthquake induced landslide hazard maps respectively

oceanic turbulence and stochastic models from subsurface lagrangian data for the northwest atlantic ocean the historical dataset provided by 700 m acoustically tracked floats is analyzed in different regions of the northwestern atlantic ocean the goal is to characterize the main properties of the mesoscale turbulence and to explore lagrangian stochastic models capable of describing them the data analysis is carried out mostly in terms of lagrangian velocity autocovariance and cross covariance functions in the gulf stream recirculation and extension regions the autocovariances and cross covariances exhibit significant oscillatory patterns on time scales comparable to the lagrangian decorrelation time scale they are indicative of sub and superdiffusive behaviors in the mean spreading of water particles the main result of the paper is that the properties of lagrangian data can be considered as a superposition of two different regimes associated with looping and nonlooping trajectories and that both regimes can be parameterized using a simple first order lagrangian stochastic model with spin parameter v the spin couples the zonal and meridional velocity components reproducing the effects of rotating coherent structures such as vortices and mesoscale eddies it is considered as a random parameter whose probability distribution is approximately bimodal reflecting the distribution of loopers finite v and nonloopers zero v this simple model is found to be very effective in reproducing the statistical properties of the data

topographic controls on evolution of shallow landslides in pastoral wairarapa new zealand 1979 2003 abstract this study aims to identify topographic influence on shallow landslides and their evolution during 1979 2003 in the pastoral lower north island new zealand landslide affected sites were mapped from aerial photographs and an aster satellite image the two landslide maps were overlaid in a geographic information system arcgis to detect the changes that have taken place in landslide affected areas the change map and the landslide distribution maps were overlaid with three topographic layers of slope gradient slope position and slope aspect that had been derived from a digital elevation model in arcgis the overlay analysis revealed that landslides affected area increased from 23 75 ha in 1979 to 110 97 ha in 2003 the distribution of landslide affected sites is inversely correlated with slope gradient but positively with slope position northern aspects are the most vulnerable to landsliding containing about 78 of the total affected sites moderate slope gradients suffered the most severe landsliding in the lower to middle slopes the overall magnitude and frequency of landsliding is also related to northern and eastern octants on the moderate slope gradients in the low to moderate slope positions although the same topographic setting is conducive to landsliding in both 1979 and 2003 the rate of landsliding varies with topographic setting hence topography is critical not only to landsliding but also to the evolution of sites already affected by landslides such an understanding over large spatial scales is possible only with the use of multitemporal remote sensing data and gis that are able to speed up data collection and analysis

tidal dissipation and stratification in the gulf of california the effect of tidal mixing upon the distribution of stratification and sea surface temperature sst in the gulf of california is studied by direct observation and by numerical modeling data from conductivity temperature depth surveys made in september and december of 1986 are used to describe the distribution of stratification and sst a vertically integrated finite differences numerical model was used to obtain the geographical distribution of available turbulent kinetic energy tke from the m2 tide the following three areas were found to be strongly affected by tidal mixing the shallow coastal area at the head of the gulf the shelf south of tiburon island and the area of the midgulf archipelago the first two are vertically well mixed and are therefore similar to other shelf sea frontal areas dissipation occurs all around the islands of the archipelago and the sills are foci of the most intense tidal dissipation stratification in this area was reduced with respect to the background but complete vertical mixing does not occur therefore the strong sst fronts that occur in this area do not mark the boundary between well mixed and stratified water the simpson hujiter criterion simpson and hunter 1974 for stratification and frontal position produced 2 75 crit 3 0 for the frontal position in the shallow northern gulf this value of crit is larger than in other shelf sea fronts which may be due to horizontal advection which is not included in the criterion we found that the effect of advection may be of the same order of magnitude as that of buoyancy flux in the area over the sills criti the available tke is not enough to produce complete mixing over the 400 m of water over the sills

ocean currents across the entrance to the gulf of california observations of transport and currents in april may and december 1992 and january 1993 were made across the entrance to the gulf of california with an acoustically tracked dropsonde flow was into the gulf along sinaloa and out of the gulf along baja california the transports were 5 10 sv and the currents were deep with 10 cm s 1 flow extending to depths greater than 1000 m the currents were intensified in the upper 300 m geostrophic flows compared well with observed currents when smoothed to 2 3 times the rossby radius salinity in the upper 300 m was higher on the baja california side of the gulf indicating modification of subtropical subsurface waters within the gulf as well as the presence of surface and near surface gulf waters the salinity minimum associated with california current waters at 50 m had narrow cores that can be resolved only with closely spaced conductivity temperature depth casts mass and heat fluxes for the upper 300 m were estimated as 280 t s 1 and 0 1 1012 w in may and 170 t s 1 and 2 0 1012 w in december

a numerical simulation of the two and three dimensional lagrangian circulation in the northern gulf of california the surface circulation in the northern gulf of california is dominated by a cyclonic gyre during summer and an anticyclonic gyre during winter the associated 3d lagrangian circulation is calculated and compared with that detected by surface floats by inhibiting vertical advection in a three dimensional 3d numerical model in general the 3d circulation follows the same horizontal paths as in the two dimensional 2d case but with vertical excursions along the trajectories however in some areas especially those close to the coasts which represents 20 of the study area the vertical displacements cause the paths of both cases with and without vertical advection to differ considerably thus resulting in different destinations for the particles this finding is of relevance for the fate of larvae or contaminants in the area which so far had been studied on the basis of 2d results alone

probabilistic landslide susceptibility and factor effect analysis the susceptibility of landslides and the effect of landslide related factors at penang in malaysia using the geographic information system gis and remote sensing data have been evaluated landslide locations were identified in the study area from interpretation of aerial photographs and from field surveys topographical and geological data and satellite images were collected processed and constructed into a spatial database using gis and image processing the factors chosen that influence landslide occurrence were topographic slope topographic aspect topographic curvature and distance from drainage all from the topographic database lithology and distance from lineament taken from the geologic database land use from landsat thermatic mapper tm satellite images and the vegetation index value from spot hrv high resolution visible satellite images landslide hazardous areas were analyzed and mapped using the landslide occurrence factors employing the probability frequency ratio method using the all factors to assess the effect of these factors each factor was excluded from the analysis and its effect verified using the landslide location data as a result all factors had relatively positive effects except lithology on the landslide susceptibility maps in the study area

spatial distribution of relative scattering coefficients determined from microearthquake coda a coda envelope inversion technique is developed to image the three dimensional spatial distribution of relative scattering coefficients the technique is applied to the norris lake community georgia earthquake swarm of 1993 the relative scattering coefficient is the ratio of the scattering coefficient to a regionally determined average used to normalize the coda amplitudes the inversion problem was solved using the algebraic reconstruction technique art with the relative scattering coefficient constrained to positive values although coda envelope inver sion is based on the theory for single scattering we show that it may with a correction factor be used to characterize the distribution of relative scattering coefficients when multiple scattering contributes significantly to the coda the coda envelope inversion for the norris lake community earthquake swarm revealed a highly nonuniform distribution of relative scattering coefficients the zones of strong scattering are correlated with the hypocenters and areas of rough topography moreover at shallow depths the relative scattering coefficients are frequency dependent with scattered energy increasing with frequency we interpret this frequency dependence to imply that open fractures less than 250 m in length are responsible for strong scattering in the coda of these shallow earthquakes at greater depths scattering is independent of frequency and probably relates to velocity layering a strong reflecting layer was identified at or below 7 km which is consistent with the thrust plain identified in the georgia cocorp reflection lines the inhomogeneous distribution of scattering strength obtained in this study argues strongly against the observation based as sumption that the scattering structures are uniformly distributed in the crust

eddy properties in the california current system 1 eddy detection and tracking algorithms are applied to both satellite altimetry and a high resolution dx 5 km climatological model solution of the u s west coast to study the properties of surface and undercurrent eddies in the california current system eddy properties show remarkable similarity in space and time and even somewhat in polarity summer and fall are the most active seasons for undercurrent eddy generation while there is less seasonal variation at surface most of the eddies have radii in the range of 25 100 km sea level anomaly amplitudes of 1 4 cm and vorticity normalized by f amplitudes of 0 025 0 2 many of the eddies formed near the coast travel considerable distance westward with speeds about 2 km day consistent with the effect anticyclones and cyclones show equatorward and poleward displacements respectively long lived surface eddies show a cyclonic dominance the subsurface california undercurrent generates more long lived anticyclones than cyclones through instabilities and topographic coastline effects in contrast surface eddies and subsurface cyclones have much more widely distributed birth sites the majority of the identified eddies have lifetimes less than a season eddies extend to 800 1500 m depth and have distinctive vertical structures for cyclones and anticyclones eddies show high nonlinearity rotation speed higher than propagation speed and hence can be efficient in transporting materials offshore

seasonal surface connectivity in the gulf of california abstract a three dimensional numerical model is used to study seasonal connectivity in the gulf of california from the eulerian velocity fields of the model particle trajectories were calculated for the 12 months of the year using an advection diffusion scheme connectivity was quantified for twelve gulf provinces with different dynamic circulation characteristics being defined by the eulerian velocity field strong or weak coastal currents eddies and areas of mixing and exchange retention occurred for 9 12 months of the year in the upper gulf eddy and sonora regions of the northern gulf because of the gulf wide eddy circulation which implies high potential for the auto recruitment of larvae in this province high retention was also found on the peninsula side of the southern gulf in association with weaker residual currents again implying potential for self recruitment in contrast low retention was observed on the mainland side of the central and southern gulf from which particles are exported to many areas by the faster residual currents enhancing the potential for recruitment of distant coastal species empirical orthogonal function analyses revealed a strong annual and semiannual evolution in accordance with the strong seasonality of the gulf dynamics

characterisation of a landslide fissure pattern by integrating seismic azimuth tomography and geotechnical testing in order to characterise the fissure field provoked by the super sauze mudslide south french alps in the surface material we conducted a seismic survey and compared the resulting p wave tomogram to surface observations and cone penetrometer tests the first results show that the distribution of the p wave velocities correlates well with the fissure parameters i e density depth and thickness estimated from digital photographs and field observations in addition one finds good agreement between the p wave velocity distribution and the material resistances interpolated from the penetrometer tests indicating a probable physical relationship the results of our study demonstrate that seismic azimuth tomography is efficient for characterising fissure systems with the main advantage of the method lying in the integration capacity of wave propagation compared to local mechanical tests provided that the correlation between p wave velocity and fissure characteristics are confirmed at other sites this technique could be the basis for future and more systematic studies of high hazard zones related to landslides copyright 2011 john wiley sons ltd

summer generation of the southern gulf of california eddy train 1 ocean color and sea surface temperature satellite observations show the existence of a series of anticyclonic eddies along the axis of the southern gulf of california sgoc to investigate the summer generation of these eddies a regional version of the hybrid coordinate ocean model hycom has been configured for the goc and has been nested inside the global model a suite of experiments using the nested goc model was developed and used to isolate the effects of the local wind and the effects of the oceanic remote forcing on the generation of the sgoc eddies the results indicate that the local wind is not essential for the generation of these eddies rather it is the oceanic remote forcing in the sgoc the monthly variability of the currents and sea surface height is mainly due to the deterministic near coastal poleward eastern boundary currents pebc the interaction of the pebc with the topographic irregularities the capes at topolobampo and cabo lobos and the ridges extending offshore from the entrance of the san lorenzo and sinaloa rivers generates the sgoc eddies the northward upper ocean transport induced by the pebc includes two maximums one in may june and the other in december during the summers of 1999 and 2004 the pebc were intensified by the arrival of equatorially originated downwelling coastally trapped waves ctws which contributed to the generation of the sgoc eddies the summer 2004 ctw increased the northward upper ocean transport by 2 sv this particular ctw was measured by several tide gauges located along the coast

effects of fractures on seismic wave velocity and attenuation the effects of fractures on the seismic velocity and attenuation of a rock are investigated using theoretical results and experimental data fractures in a rock mass influence the traveltimes and amplitudes of seismic waves that have propagated through them the displacement discontinuity model recently employed in fracture investigations is modified to describe the effect of fractures on seismic wave velocity and attenuation this new model the modified displacement discontinuity model mdd is formulated in a way analogous to transmission line analysis the fractures are treated as transmission lines for the passage of seismic waves the mdd takes into consideration realistic fracture parameters which include the fracture length the fractional area of a fracture surface in contact and the nature of the infilling material a single fracture of varying geometric and material properties is shown to affect dramatically the transmission properties of a propagating waveform and hence the seismic velocity and attenuation these effects have been shown to result in a frequency dependent velocity and attenuation the sensitivity of the fracture parameters to seismic wave velocity and attenuation was investigated and interesting results were obtained fracture parameters used in designing experimental models consisting of synthetically manufactured cracks were fed into the mdd and a well known crack model hudson s model for comparison velocities as a function of the incident wave angle were obtained from both numerical models and were compared with the results from the experimental modelling for p waves the mdd model results show better agreement with those of the experimental model for all crack densities investigated than those from hudson s model

elastic wave propagation in media with parallel fractures and aligned cracks a model of parallel slip interfaces simulates the behaviour of a fracture system composed of large closely spaced aligned joints the model admits any fracture system anisotropy triclinic the most general monoclinic orthorhombic or transversely isotropic and this is specified by the form of the 3 3 fracture system compliance matrix the fracture system may be embedded in an anisotropic elastic background with no restrictions on the type of anisotropy to compute the long wavelength equivalent moduli of the fractured medium requires at most the inversion of two 3 3 matrices when the fractures are assumed on average to have rotational symmetry transversely isotropic fracture system behaviour and the background is assumed isotropic the resulting equivalent medium is transversely isotropic and the effect of the additional compliance of the fracture system may be specified by two parameters in addition to the two isotropic parameters of the isotropic background dilute systems of flat aligned microcracks in an isotropic background yield an equivalent medium of the same form as that of the isotropic medium with large joints i e there are two additional parameters due to the presence of the microcracks which play roles in the stress strain relations of the equivalent medium identical to those played by the parameters due to the presence of large joints thus knowledge of the total of four parameters describing the anisotropy of such a fractured medium tells nothing of the size or concentration of the aligned fractures but does contain information as to the overall excess compliance due to the fracture system and its orientation as the aligned microcracks which were assumed to be ellipsoidal with very small aspect ratio are allowed to become non fiat i e have a growing aspect ratio the moduli of the equivalent medium begin to diverge from the standard form of the moduli for flat cracks the divergence is faster for higher crack densities but only becomes significant for microcracks of aspect ratios approaching 0 3

surface drifter pair spreading in the north atlantic 1 this study examines spreading of surface drifter pairs deployed as part of the clivar mode water dynamic experiment climode project in the gulf stream region the spreading is resolved at hourly resolution and quantified by relative dispersion and finite scale lyapunov exponents at scales from 1 3 km to 300 500 km the dispersion follows richardson s law indicating stirring by eddies comparable in scale to the pair separation distance at larger scales the spreading becomes a random walk described by a constant diffusivity the behavior from 1 3 km to the local deformation radius is inconsistent with the enstrophy cascade of 2 d quasigeostrophic turbulence to test various hypotheses for this result drifter pair spreading is examined for pairs that were not launched together pairs deployed in the eastern subtropical north atlantic and climode pairs subsampled to daily temporal resolution our results indicate the presence of significant energy at the submesoscale in the gulf stream region which flattens the wave number spectrum and dominates surface stirring at this scale range results in the less energetic subtropical eastern atlantic are more equivocal

shear wave propagation in jointed rock state of stress the mechanical characteristics and orientation of joints determine the behaviour of rock masses including the strength the stiffness and all forms of conduction and diffusion furthermore the preferential orientation of joints renders the medium anisotropic in turn these properties affect the velocity and damping of propagating elastic waves the purpose of this study is to investigate the propagation of long wavelength shear waves through a rock mass with open joints filled with softer gouge and subjected to low confinement these conditions are selected in view of near surface geophysical characterisation studies for geotechnical engineering applications such as foundations tunnels and slopes experimental data are gathered with a slender column made of discrete elements with gouge material in the joints the column is excited in the first torsional vibration mode to gather accurate measurements of velocity and damping for wave propagation direction normal to the joints data are analysed with m

lagrangian observations of the circulation in the northern gulf of california argos drifters deployed in the northern gulf of california in september 1995 showed the presence of a cyclonic gyre while a second deployment in march 1996 revealed an anticyclonic gyre a circulation pattern consisting of a seasonally reversing gyre had been proposed before on the basis of satellite images geostrophic calculations and numerical models but so far no direct observations have been made to test its existence in september the gyre was cyclonic baroclinic very well defined stable and strong its mean speed and rotation time were 0 3 m s21 and 7 days in march the gyre had the same mean speed but it was anticyclonic and displaced to the northwest of the summer position the march gyre has barotopic and baroclinic characteristics but the observed speeds are stronger than in numerical simulations these data and a data bank analysis suggest that the summer gyre is a persistent summer feature but the winter spring situation remains ill defined and requires further research

an expert knowledge based approach to landslide susceptibility mapping using gis and fuzzy logic this paper presents an expert knowledge based approach to landslide susceptibility mapping in an effort to overcome the deficiencies of data driven approaches the proposed approach consists of three generic steps 1 extraction of knowledge on the relationship between landslide susceptibility and predisposing factors from domain experts 2 characterization of predisposing factors using gis techniques and 3 prediction of landslide susceptibility under fuzzy logic the approach was tested in two study areas in china the kaixian study area about 250 km 2 and the three gorges study area about 4600 km 2 the kaixian study area was used to develop the approach and to evaluate its validity the three gorges study area was used to test both the portability and the applicability of the developed approach for mapping landslide susceptibility over large study areas performance was evaluated by examining if the mean of the computed susceptibility values at landslide sites was statistically different from that of the entire study area a z score test was used to examine the statistical significance of the difference the computed z for the kaixian area was 3 70 and the corresponding p value was less than 0 001 this suggests that the computed landslide susceptibility values are good indicators of landslide occurrences in the three gorges study area the computed z was 10 75 and the corresponding p value was less than 0 001 in addition we divided the susceptibility value into four levels low 0 0 0 25 moderate 0 25 0 5 high 0 5 0 75 and very high 0 75 1 0 no landslides were found for areas of low susceptibility landslide density was about three times higher in areas of very high susceptibility than that in the moderate susceptibility areas and more than twice as high as that in the high susceptibility areas the results from the three gorge study area suggest that the extracted expert knowledge can be extrapolated to another study area and the developed approach can be used in large scale projects results from these case studies suggest that the expert knowledge based approach is effective in mapping landslide susceptibility and that its performance is maintained when it is moved to a new area from the model development area without changes to the knowledge base c 2014 elsevier b v all rights reserved

mixing structures in the mediterranean sea from finite size lyapunov exponents 1 we characterize horizontal mixing and transport structures in the surface circulation of the mediterranean sea as obtained from a primitive equation circulation model we calculate the finite size lyapunov exponents fsles of the velocity data set which give a direct measure of the local stirring by proper election of the fsle parameters we focus on the mesoscale structures locating a number of vortices embedded in an intricate network of high stretching lines these lines control transport in the system at the edge of the vortices a dense tangle of line intersections appears identifying strong mixing the spatial distribution of fsles averaged over one year allows to classify areas in the mediterranean basin according by their mixing activity the space average of fsles on selected geographical regions gives a measure for quantifying and comparing the mixing seasonal variability

spatial structure of anticyclonic eddies in the algerian basin mediterranean sea analyzed using the okubo weiss parameter abstract three algerian eddies open sea big anticyclonic eddies in the algerian basin western mediterranean sea are studied in detail using altimetric and in situ data to characterize their spatial structure we make use of the okubo weiss parameter which allows to separate the flow into vorticity dominated and deformation dominated regions the application of this parameter to geostrophic velocity fields obtained from sea level anomaly maps show that the observed eddies have a spatial structure in close resemblance to that found in coherent vortices of two dimensional turbulence these eddies appear to have a rather coherent vorticity dominated core region surrounded by an outer region dominated by deformation with a very complicated and variable in time structure this analysis is also applied to ctd data collected across three eddies sampled between 1997 and 1998 from these data eddy cores are equivalently defined as the interior region enclosed by the maximum of azimuthal velocity and are consistent with the horizontal structures seen in sla maps the distinction between the core and the outer region circulation cell is particularly important to understand the role of transport and stirring of properties associated to eddies as illustrated by the observed salinity structure some selected sst images and drifter trajectories the core is characterized by very small isopycnal salinity gradients while the surrounding cell is characterized by a strong slope of isohalines with respect to isopycnals persistent stagnation points are observed around the eddy and correspond to regions of high values of deformation with respect to vorticity these regions allow analyzing characteristic patterns seen in the corresponding sst images in addition drifters trajectories exhibit very different behavior when crossing such regions

heterogeneities and diagenetic control on the spatial distribution of carbonate rocks acoustic properties at the outcrop scale abstract carbonate rocks are characterized by a high heterogeneity of their properties at the outcrop scale that results from complex interactions between sedimentary diagenetic and fracturing processes here we show acoustic p wave velocity measurements conducted step by step on three decameter scale outcrop surfaces in cretaceous carbonate rocks with contrasted heterogeneities two shallow water highly fractured cassis and low fractured calissanne carbonates and one basin highly compacted grignantes p wave measurements were compared to outcrop geology and with plug porosity p wave velocity laboratory measurements and a thin section study results show a strong scale dependence of p wave velocities which always are lower at the decimeter scale than at the plug scale vp in situ versus vp plug large discrepancies 2000 m s highlight the signature of large heterogeneities open fractures stylolithes and lower discrepancies in situ distribution follows the dip of the ripple foresets which are controlling grain sorting and porosity in calissanne outcrop the near isotropic vp are explained by an early intense fracturing and cementation in cassis outcrop and the strong horizontal anisotropy with a hole effect behavior on variograms highlights the late re opening of multiple intervals of compaction bands in grignantes these results illustrate that the early diagenesis coupled to fracture or stylolithe reactivation opening are two key processes that explain the outcrop scale p wave velocity distribution anisotropy in carbonates

use of multifractal seismic waveform parameters to characterize the hydraulic properties of fractured media numerical experiments summary the multifractal characteristics of seismic waveforms that have propagated through fractured media were studied using numerical experiments the study suggests that multifractal waveform parameters i e information dimension correlation dimension curvature and range indices bear correlations with the hydraulic properties of the fractured media the characteristic waveform parameters were estimated from a multifractal analysis of 1 d synthetic seismograms generated using a variation of the reflectivity method waveforms from fractured zones were obtained by a superposition of reflections from horizontal fractures with a varying distribution of fracture length aperture and spacing the constructive and destructive interferences of the composite reflections from the fractures in the fractured layer result in waveforms that possess multifractal attributes the characteristic parameters extracted from the waveforms are shown here to correlate with the hydraulic properties of the fractured rockmass which include the fracture permeability the discontinuity index and the fracture density parameter

surface circulation in the gulf of california in summer from surface drifters and satellite images 2004 2006 surface drifters released in the gulf of california between june 2004 and august 2006 are used to describe the surface circulation in late spring and summer in the june to september mean there was a poleward coastal current on the shelf and slope of the mainland side of the gulf with mean speed 0 3 m s it reached the northern gulf and joined the cyclonic circulation typical of this zone in summer in the western half of the southern gulf the drifters presented recirculating currents that are due to mesoscale eddies that appear to dominate the surface circulation in summer in june 2004 the coastal current presented an enhancement event with mean speed around 0 60 m s and maximum 0 80 m s it took 20 days for a particular drifter to travel the 1000 km from the gulf entrance to the head this strengthening of the coastal current was apparent in chlorophyll a and sst satellite images the drifters following closely the intrusion of warm chlorophyll poor surface water from outside the gulf the drifters and the satellite images suggest that the current enhancement event lasted less than a month this mesoscale event was linked with a mesoscale remote forcing in the tropical pacific coast and with a mesoscale local forcing of the wind these events seem to occur every year and are probably important in carrying organisms and properties from the entrance to the whole length of the gulf

surface dispersion in the gulf of california abstract surface dispersion is measured in the gulf of california by means of argos drifters released along this semi enclosed elongated basin first basic one particle statistics lagrangian scales absolute dispersion and diffusion coefficients are estimated along and across the gulf absolute dispersion shows a nearly ballistic regime during the lagrangian time scale t 2 where t is time during the subsequent 30 days absolute dispersion enters a random walk regime t along the gulf while being saturated across the basin due to the lateral boundaries secondly the analysis is extended to two particle statistics relative dispersion between pairs of drifters and finite scale lyapunov exponents fsle relative dispersion is nearly exponential in both directions during the first few days though evidence is not conclusive during the subsequent 30 days it grows as t 1 5 along the gulf while being saturated across the basin again it is shown that relative dispersion along the gulf is proportional to t 3 where t represents a shifted time that depends on the initial separation of the particles this form of the richardson regime is consistently measured for particles that are sufficiently separated 30 km or more the richardson regime is verified with the fsle for particle separations ranging from 30 to 140 km approximately the obtained dispersion properties are discussed in terms of the main circulation features within the basin such as mesoscale vortices that occupy the width of the gulf these structures might retain buoys during days or weeks thus preventing or delaying further displacements and therefore affecting the particle dispersion the vortices are also an important mechanism to translate particles across the gulf between the peninsula and the continent thus promoting the saturation of dispersion along this direction

long wavelength p wave and s wave propagation in jointed rock masses field data suggest that stress level and joint condition affect shear wave propagation in jointed rock masses however thestudyoflong wavelengthpropagationinajointedrock mass is challenging in the laboratory and limited data are available under controlled test conditions long wavelength p wave and s wave propagation normal to joints using an axially loaded jointed column device reproduces a range of jointconditions theeffectsofthenormalstress loadinghistory joint spacing matched surface topography i e joint roughness joint cementation e g after grouting joint opening and plasticity of the joint filling on the p wave and s wavevelocitiesandons waveattenuationarenotable the ratio vp vs in jointed rock masses differs from that found in homogeneous continua the concept of poisson s ratio as a functionof vp vsisunwarranted and vp vscanbeinterpreted in terms of jointed characteristics analytic models that consider stress dependent stiffness and frictional loss in joints as well as stress independent properties of intact rocks can model experimental observations properly and extract joint properties from rock mass test data thus joint propertiesandnormalstresshaveaprevalentroleinpropagationvelocityandattenuationinjointedrockmasses

statistical analysis for assessing shallow landslide susceptibility in south tyrol south eastern alps italy abstract this paper conducts a statistical analysis to determine shallow landslide susceptibility in an approximately 7500 km2 region of the south eastern alps south tyrol italy the study applies the weight of evidence wofe method which is useful in determining landslide susceptibility in large areas with complex geological and geomorphological settings the statistical analysis and landslide susceptibility mapping are based on 882 past landslides three geometric topographic factors and two anthropogenic factors which are the most relevant landslide predisposing factors the quality of the proposed model particularly the fitting performance was assessed the landslide database was divided into a training set to obtain the model and a validation set to estimate the model quality the results show that the developed susceptibility model predicts an acceptable percentage 75 of landslides therefore the model can be useful and reliable for land planners and decision makers also due to its cost effectiveness ratio

probability maps of landslide reactivation derived from tree ring records pra bellon landslide southern french alps probability maps of landslide reactivation are presented for the pra bellon landslide located in the southern french alps based on results obtained with dendrogeomorphic analysis spatiotemporal patterns of past landslide activity was derived from tree ring series of 403 disturbed mountain pine trees growing in the landslide body in total 704 growth disturbances were identified in the samples indicating 22 reactivation phases of the landslide body between 1910 and 2011 the mean return period was 4 5 years given the spatiotemporal completeness of the reconstruction probabilities of landslide reactivation were computed and illustrated using a poisson distribution model and for 5 20 50 and 100 years probability of landslide reactivation is highest in the central part of the landslide body and increases from 0 13 for a 5 year period to 0 94 for a 100 year period conversely probabilities of reactivation are lower at its margins the proposed method differs from conventional approaches based on statistical analyses or physical modeling that have demonstrated to have limitations in the prediction of spatiotemporal reactivation of landslides our approach is in contrast based on extensive data on past landslides and therefore allowed determination of quantitative probability maps of reactivation derived directly from the frequency of past events this approach is considered a valuable tool for land managers in charge of protecting and forecasting people and their assets from the negative effects of landslides as well as for those responsible for land use planning and management it demonstrates the reliability of dendrogeomorphic mapping that should be used systematically in forested shallow landslides

direction dependence of fracture compliance induced by slickensides abstractthe effect of a fracture on seismic wave propagation can be represented in terms of the normal and shear fracture compliance in many studies fractures are assumed to have no preferential orientation for slip along the fracture plane however examination of fractures found in recovered cores or in exposed outcrops shows irregularities such as hackles or slickensides which are formed in the direction of joint fault propagation these irregularities represented as sawtooth ridges can be expected to facilitate movement in a particular direction more than the opposite direction in a way that depends on the height and shape of the irregularities as a result fractured rocks should exhibit a different compliance for shear in one direction compared with shear in the opposite orientation we used numerical modeling to offer a critical assessment of this phenomenon by directly calculating the change in normal and shear compliance in the presence of hackles the effect of the geometry of the hackles

experimental studies on the effects of fracture on the p and s wave velocity propagation in sedimentary rock calcarenite del salento abstract experimental studies were carried out in laboratory in order to investigate the effects of fracture on compressional p wave and shear s wave velocity propagation and therefore the relations between seismic properties and rock mass parameters the discontinuity index i d fracture density parameter c linear fracture parameter and the rock quality designation rqd were used to describe the rock mass parameters these parameters are analyzed and then related to the seismic properties four vertical aligned fractures were created on an intact calcarenite block 0 6 m long 0 4 m thick and 0 4 m width by sawing the measures were carried out in four different blocks of cacarenite having the same physical properties and in four different phases in first block the fractures were filled with air in the second block the fractures were filled with terra rossa in third block the fractures were filled with wet terra rossa and in the fourth block the fractures were filled with clay the test results were statistically analysed using the method of least squares regression and polynomial relationships with high correlation coefficient were found between the fractured rock parameters and p wave s wave velocities and v p v s ratio the investigations suggest that the p wave and s wave velocities decrease with increasing the fracture parameters while the v p v s ratio increases with decreasing the fracture parameters furthermore the results of the experimental studies were applied on the seismic refraction tomography data acquired in a great measurements campaign undertaken in the adriatic salentina coast south italy in order to monitor the coastal erosion the geophysical results using the polynomial relationships between the fractured rock parameters and p wave velocity are in good agreement with the geomorphological and geological results

gis based landslide susceptibility mapping for the 2005 kashmir earthquake region abstract the m w 7 6 october 8 2005 kashmir earthquake triggered several thousand landslides throughout the himalaya of northern pakistan and india these were concentrated in six different geomorphic geologic anthropogenic settings a spatial database which included 2252 landslides was developed and analyzed using aster satellite imagery and geographical information system gis technology a multi criterion evaluation was applied to determine the significance of event controlling parameters in triggering the landslides the parameters included lithology faults slope gradient slope aspect elevation land cover rivers and roads the results showed four classes of landslide susceptibility furthermore they indicated that lithology had the strongest influence on landsliding particularly when the rock is highly fractured such as in shale slate clastic sediments and limestone and dolomite moreover the proximity of the landslides to faults rivers and roads was also an important factor in helping to initiate failures in addition landslides occurred particularly in moderate elevations on south facing slopes shrub land grassland and also agricultural land were highly susceptible to failures while forested slopes had few landslides one third of the study area was highly or very highly susceptible to future landsliding and requires immediate mitigation action the rest of the region had a low or moderate susceptibility to landsliding and remains relatively stable this study supports the view that 1 earthquake triggered landslides are concentrated in specific zones associated with event controlling parameters and 2 in the western himalaya deforestation and road construction contributed significantly to landsliding during and shortly after earthquakes

relationships among compressional wave attenuation porosity clay content and permeability in sandstones anelastic attenuation is the process by which rocks convert compressional waves into heat and thereby modify the amplitude and phase of the waves understanding the causes of compressional wave attenuation is important in the acquisition processing and interpretation of high resolution seismic data and in deducing the physical properties of rocks from seismic data we have measured the attenuation coefficients of compressional waves in 42 sandstones at a confining pressure of 40 mpa equivalent to a depth of burial of about 1 5 km in a frequency range from 0 5 to 1 5 mhz the compressional wave measurements were made using a pulse echo method in which the sample 5 cm diameter 1 8 cm to 3 5 cm long was sandwiched between perspex lucite buffer rods inside the high pressure rig the attenuation of the sample was estimated from the logarithmic spectral ratio of the signals corrected for beam spreading reflected from the top and base of the sample the results show that for these samples compressio

mechanisms for vertical nutrient transport within a north atlantic mesoscale eddy abstract prompted by observational evidence for an enhanced source of surface nutrients within an anticyclonic eddy in the ne atlantic we investigate vertical transport processes that may produce such a phenomenon for the eddy investigated the dominant mechanism is found to be ageostrophic circulation resulting from a perturbation of the circular flow of the eddy this can produce upwelling velocities of order 10 m d 1 ekman pumping due to wind stress on the eddy also produces upwelling within but on a smaller scale of 0 5 m d 1 there is no evidence that self propagation of the eddy leads to an enhanced nutrient flux by displacement upwards of nutrient laden deeper isopycnals over the core of the eddy deeper winter mixing within the eddy relative to the surroundings however may contribute to the elevated nutrient levels

three dimensional connectivity in the gulf of california based on a numerical model abstract quantifying connectivity is useful for understanding the exchange and trapping of some tracers such as fish larvae and nutrients in the gulf of california connectivity studies have been limited to certain periods and regions the current study investigated the connectivity among 17 areas defined by the presence of eddies and weak or strong flows as obtained from a three dimensional non linear baroclinic model the particles were released into the water column and advected for 28 days using an advection diffusion scheme the results revealed a seasonal connectivity pattern in the northern region particle trapping was greater during the cyclonic circulation period june to september compared with the anticyclonic period november to march this high retention was due to both the presence of a cyclonic eddy in the central portion of the region and the intense northwestward flow off the coast of sonora retentions were low for the large island region due to the intense exchange between the northern and southern regions east of angel de la guarda island the transport occurred predominantly towards the northwest due to the nearly permanent deep flow in that direction and to a branching of the surface flow among the large islands during the anticyclonic period and the northwestward low during the cyclonic period in the peninsular and central areas of the southern region retentions were high due to weak flows and the presence of eddies respectively the greatest retention and low dispersion of particles in practically all of the provinces were recorded during the transition periods of the circulation

mesoscale eddies in the southern gulf of california during summer characteristics and interaction with the wind stress 1 the hydrodynamic characteristics of mesoscale eddies of the southern gulf of california are described from observations made in august 2004 vertical profiles to 1000 m were made with a conductivity temperature depth ctd probe with dissolved oxygen and fluorescence sensors and a lowered acoustic doppler profiler the four sampled eddies were aligned along the gulf axis and had alternating sense of rotation the okubo weiss parameter was used to calculate the eddy core radii and it also revealed that the current field of almost all the sampled area was eddy dominated the mean radii of the eddy cores varied between 32 and 36 km maximum surface velocities were 0 4 0 5 m s the anticyclonic eddies were 500 700 m deep while the cyclones were 450 500 m deep the depression of the isolines associated with the anticyclonic eddies was 100 m at depths between 200 and 400 m however the thermocline pycnocline which spanned from 20 to 75 m was domed by 10 m the cyclonic eddies lifted the isolines by 70 m at depths above 500 m but the isolines were flat above 60 m this suggests that different dynamics operate in the layer above the strong and shallow pycnocline in particular the wind stress curl can affect circulation and pycnocline topography and therefore the patterns that appear in chlorophyll satellite images in our case the eddies were detectable in those images because of the chlorophyll enhanced streamers along their edges and for anticyclones probably because the chlorophyll maximum found at 40 50 m depth was domed following the pycnocline

transport properties in the adriatic sea as deduced from drifter data abstract the surface transport properties in the adriatic sea a semienclosed subbasin of the mediterranean sea have been studied using a drifter dataset in the period december 1994 march 1996 three main points have been addressed first the exchange between southern and northern regions and between deep and coastal areas have been studied focusing on the role of topography a significant cross topography or cross shelf exchange has been found probably due to the direct wind forcing and to the influence of stratification that isolates the surface flow from bottom effects especially in the open sea second a lagrangian transport model with parameters derived from the data has been implemented simulated particles have been compared with drifter data with positive results the model is found to be able to reproduce reality with good approximation except for a specific advective event during the late summer season finally the residence timescale t that is the average time spent by a surface parti

magmatic processes in the alaska subduction zone by combined 3 d b value imaging and targeted seismic tomography 1 we combine two complementary seismological methods to study the deep roots of arc volcanism in the alaskan subduction zone targeted seismic body wave tomography and imaging of the relative size distribution b value of earthquakes for the tomography we apply a staggered inversion scheme starting with the minimum 1 d velocity model progressing to a 3 d velocity model inversions are based on traveltime data from about 5500 events 1971 2002 with approximately 100 000 p and 50 000 s high quality arrivals allowing us to resolve the 3 d velocity field on a 20 20 km grid for the b value imaging we have introduced a new 3 d sampling approach to map the b values on surfaces in the wadati benioff zone wbz our b value study is based on 12 474 relocated events of magnitude of completeness 2 4 and depth 40 km we observe anomalously high b values at depths around 100 km appearing locally concentrated beneath active subduction volcanoes we believe that these zones are associated with dehydration of the slab and subsequent magma generation the analysis of vp vs ratios likewise shows indications of the presence of fluids significantly higher vp vs ratios rising in columns from the top of the wbz at 100 km depth below active volcanic centers on the basis of the joint interpretation we propose that our images track fluids from their genesis at 100 km depth at the top of the subducting plate to the bottom of the crust below volcanoes

comparison of landslide susceptibility based on a decision tree model and actual landslide occurrence the akaishi mountains japan abstract this paper proposes a statistical decision tree model to analyze landslide susceptibility in a wide area of the akaishi mountains japan the objectives of this study were to validate the decision tree model by comparing landslide susceptibility and actual landslide occurrence and to reveal the relationships among landslide occurrence topography and geology landslide susceptibility was examined through ensemble learning with a decision tree decision trees are advantageous in that estimation processes and order of important explanatory variables are explicitly represented by the tree structures topographic characteristics elevation slope angle profile curvature plan curvature and dissection and undissection height and geological data were used as the explanatory variables these topographic characteristics were calculated from digital elevation models dems the objective variables were landslide occurrence and reactivation data between 1992 and 2002 that were depicted by satellite image analysis landslide susceptibility was validated by comparing actual data on landslides that occurred and reactivated after the model was constructed between 2002 and 2004 this study revealed that from 2002 to 2004 landslides tended to occur and reactivate in catchments with high landslide susceptibility the landslide susceptibility map thus depicts the actual landslide occurrence and reactivation in the akaishi mountains this result indicates that the decision tree model has appropriate accuracy for estimating the probabilities of future landslides the tree structure indicates that landslides occurred and reactivated frequently in the catchments that had an average slope angle exceeding ca 29 and a mode of slope angle exceeding 33 which agree well with previous studies a decision tree also quantitatively expresses important explanatory variables at the higher order of the tree structure

quantifying bedrock fracture patterns within the shallow subsurface implications for rock mass strength bedrock landslides and erodibility 1 the role of bedrock fractures and rock mass strength is often considered a primary influence on the efficiency of surface processes and the morphology of landscapes quantifying bedrock characteristics at hillslope scales however has proven difficult here we present a new field based method for quantifying the depth and apparent density of bedrock fractures within the shallow subsurface based on seismic refraction surveys we examine variations in subsurface fracture patterns in both fiordland and the southern alps of new zealand to better constrain the influence of bedrock properties in governing rates and patterns of landslides as well as the morphology of threshold landscapes we argue that intense tectonic deformation produces uniform bedrock fracturing with depth whereas geomorphic processes produce strong fracture gradients focused within the shallow subsurface additionally we argue that hillslope strength and stability are functions of both the intact rock strength and the density of bedrock fractures such that for a given intact rock strength a threshold fracture density exists that delineates between stable and unstable rock masses in the southern alps tectonic forces have pervasively fractured intrinsically weak rock to the verge of instability such that the entire rock mass is susceptible to failure and landslides can potentially extend to great depths conversely in fiordland tectonic fracturing of the strong intact rock has produced fracture densities less than the regional stability threshold therefore bedrock failure in fiordland generally occurs only after geomorphic fracturing has further reduced the rock mass strength this dependence on geomorphic fracturing limits the depths of bedrock landslides to within this geomorphically weakened zone

ocean color observations of eddies during the summer in the gulf of california 1 using seawifs ocean color satellite images collected during 1997 2001 a series of eddies have been observed in the gulf of california these eddies are not clearly seen in the summertime sea surface temperature images the surface circulation between the midriff islands and the mouth of the gulf appears to be dominated by this series of eddies that have an alternating sense of rotation an eddy pair is observed to extend from cabo lobos in each of the three years suggesting that the eddies are topographically locked the formation mechanism of the eddies remains unknown however we suspect the most likely mechanism includes baroclinic instabilities along the coast produced by interactions between coastally trapped waves and local wind driven currents

surface relative dispersion in the southwestern gulf of mexico abstractsurface dispersion properties in the southwestern gulf of mexico are studied by using a set of 441 drifters released during a 7 yr period and tracked for 2 months on average the drifters have a drogue below the surface ekman layer so they approximately follow oceanic currents this study follows two different approaches first two particle or pair statistics are calculated relative dispersion and finite scale lyapunov exponents fsles relative dispersion estimates are consistent with theoretical dispersion regimes of two dimensional turbulence an exponential growth during the first 3 days a richardson like regime between 3 and 20 days in which relative dispersion grows as a power law in time and standard dispersion linear growth for longer times the fsles yield a power law regime for scales between 10 and 150 km but do not detect an exponential regime for short separations less than 10 km robust estimates of diffusivities based on both relative dispersion and fsles are provided

transmission of seismic waves across single natural fractures fractures and other nonwelded contacts are important mechanical and hydrological features of rock masses their effects on seismic wave propagation can be modeled as a boundary condition in the seismic wave equation seismic stress is continuous across such a boundary but seismic particle displacement and seismic particle velocity are not the complete solutions for seismic wave reflection conversion and transmission across a displacement and velocity discontinuity between two half spaces with different densities and elastic properties are derived for all angles of the incident wave the ratio between the seismic stress across this boundary and the seismic particle displacement and velocity are described by a specific stiffness and a specific viscosity respectively a displacement discontinuity results in frequency dependent reflection and transmission coefficients and a frequency dependent group time delay the velocity discontinuity results in frequency independent coefficients and zero delay results of laboratory experiments on compressional and shear wave transmission across three different natural fractures in a quartz monzonite are described measurements were made at different effective stresses under dry and saturated conditions at room temperature it is shown that the effect of these fractures on the spectral amplitudes for compressional and shear pulses transmitted across these fractures are described well by a displacement discontinuity for compressional pulses under dry and saturated conditions and by a combined displacement and velocity discontinuity for shear wave pulses under dry and saturated conditions values of specific stiffness and specific viscosity vary between fractures and increase with increasing effective stress as does the static specific stiffness of these fractures changes in the spectral amplitudes of transmitted pulses are also analyzed in terms of attenuation using the seismic quality factor q which is found to be a function of frequency