earthquake ground motion estimation using strong motion records a review of equations for the estimation of peak ground acceleration and response spectral ordinates abstract engineering seismology is the link between earth sciences and engineering the main input of engineering seismology in engineering design are loading conditions which must satisfy certain conditions regarding their level and frequency of occurrence during the lifetime of a structure one method for estimating these loading conditions is through equations based on strong ground motion recorded during previous earthquakes these equations have a handful of independent parameters such as magnitude and source to site distance and a dependent parameter such as peak ground acceleration pga or spectral acceleration and the coefficients in the equation are usually found by regression analysis this review examines such equations in terms of data selection accelerogram processing techniques of the strong motion records used to construct the equations the characterisation of earthquake source travel path and local site used and regression techniques employed to find the final equations it is found that little agreement has been reached in the past 30 years of ground motion estimation relation studies workers have chosen their techniques based on the available data which varies greatly with geographical region also it is noted that there is a need to include more independent parameters into ground motion estimation equations if the large uncertainties associated with such equations are to be significantly reduced the data required to do this is unfortunately scarce

new insights into the subglacial and periglacial hydrology of vatnajokull iceland from a distributed physical model we apply a time dependent distributed glaciohydraulic model tovatna jo kull ice cap iceland aiming to determine the large scale subglacial drainage structure theimportance of basallyderivedmeltwater theinfluence ofapermeable glacierbedand vatnajo kull s discharge contribution to major rivers in iceland the model comprisestwo coupled layersthatrepresentthesubglacialhorizonperchedona subsurfaceaquifer inthe western sector and bedrock in the eastern sector to initialize and drive the simulations we use digital elevation models of the ice surface and bed the1999 2000 measured mass balance and an estimate of subglacial geothermal heat fluxes the modelled subglacial flow field differs substantially from that derived by hydraulic potential calculations and the corresponding distribution of basal effective pressure shows a strong correlation between low effective pressure and surge prone areas in northeastern and southern sectors of vatnajo kull simulations suggest that geothermally derived basal melt may account for upto 5 of the annualglacial discharge and buried aquifers may evacuate up to 30 ofsubglacialwater time dependenttestsyieldestimatesoftheglacialdischargecomponent in various outlet rivers and suggest a possible seasonal migration of subglacial hydraulic divides this study of present dayvatnajo kull hydrology formsthe starting point for inves tigationsof its future evolution

mud volcanism in the gulf of cadiz results from the ttr 10 cruise a new deep water mud volcano field between 2000 and 3500 m water depth was discovered in the deep south portuguese margin as well as several new mud volcanoes in the south spanish and western moroccan margins of the gulf of cadiz during the ttr 10 training through research unesco ioc cruise in july august 2000 this work followed the discovery of a large mud volcano field in the gulf of cadiz first investigated during the ttr 9 cruise gardner 2001 geophys res lett 28 339 342 kenyon et al 2000 ioc technical series no 56 the discoveries were made based on a seamap side scan sonar mosaic and multibeam bathymetry seabeam collected in the area by the naval research laboratory nrl washington dc usa in 1992 kindly released for this purpose single channel seismics long range side scan sonar okean tv controlled grab hull mounted 3 5 khz profiler and coring were used to investigate several seafloor features observed on the side scan sonar imagery in the south iberia spanish and moroccan margins of the gulf of cadiz which were confirmed to be mud volcanoes the typical structures related to fluid venting in the gulf of cadiz are essentially represented by conical mud volcanoes with diameters ranging from several tens of meters to 4 km and heights that can reach 200 m some of these structures appear to be aligned along major conjugate ne sw and nw se trending faults that can be identified on the side scan sonar imagery the new field discovered in the south portuguese margin is the deepest in the gulf of cadiz area and includes three new mud volcanoes bonjardim olenin and carlos ribeiro which seem to be quite active with near surface gas hydrate occurrence and a high saturation in h2s and hydrocarbon gases mainly methane in the mud breccia and overlying pelagic sediments gas hydrates were recovered from the bonjardim mud volcano an intensely gassified mud breccia with one fragment of semi consolidated claystone with a thin bituminous veneer at the surface was recovered from the carlos ribeiro mud volcano the fauna recovered consists mainly of pogonophoran worms belonging to several species and undetermined species of foraminifera three new mud volcanoes were also discovered in the nw moroccan margin rabat student and jesus baraza these show a richer fauna that includes several species of molluscs polychaetes pogonophoran worms crustaceans echinoderms and some fragments of dead coral madrepora and lophelia carbonate crusts were recovered from the student mud volcano the ginsburg mud volcano discovered during the previous ttr 9 cruise was revisited and gas hydrates recovered once again a new mud volcano was also discovered in the spanish margin tasyo where evidence was found of coral build ups on the hard substratum of the mud volcanic edifice

kinematics of the western africa eurasia plate boundary from focal mechanisms and gps data summary the western mediterranean displays a complex pattern of crustal deformation distributed along tectonically active belts developed in the framework of slow oblique plate convergence we used earthquake and global positioning system gps data to study the present day kinematics and tectonics of the africa eurasia plate boundary in this region crustal seismicity and focal mechanisms analysed in terms of seismic moment release and seismic deformation outline the geometry of major seismic belts and characterize their tectonics and kinematics continuous gps data have been analysed to determine euler vectors for the nubian and eurasian plates and to provide the global frame for a new mediterranean gps velocity field obtained by merging continuous and campaign observations collected in the 1991 2005 time span gps velocities and displacements predicted by the nubia eurasia rotation pole provide estimates of the deformation accommodated across the tectonically active belts the rather simple deformation occurring in the atlantic region characterized by extension about perpendicular to the middle atlantic and terceira ridges and right lateral motion along the gloria transform fault turns into a complex pattern of deformation occurring along broader seismic belts where continental lithosphere is involved our analysis reveals a more complex fragmentation of the plate boundary than previously proposed the roughly e w trending mainly compressive segments i e southwestern iberia northern algeria and southern tyrrhenian where plate convergence is largely accomodated across rather localized deformation zones and partially transferred northward to the adjacent domains i e the algero balearic and tyrrhenian basins are interrupted by regions of more distributed deformation i e the rif alboran betics tunisia libya and eastern sicily or limited seismicity i e the strait of sicily which are characterized by less homogeneous tectonics regimes mainly transcurrent to extensional in correspondence of the observed breaks tectonic structures with different orientation interfere and we find belts with only limited deformation i e the high and middle atlas the tunisian atlas and the offshore tunisia libya belt that extends from the plate boundary into the nubian plate along pre existing tectonic lineaments our analysis suggest that the sicilian pelagian domain is moving independently from nubia according to the presence of a right lateral and extensional decoupling zone corresponding to the tunisia libya and strait of sicily deformation zone despite the space variability of active tectonic regimes plate convergence still governs most of the seismotectonic and kinematic setting up to the central aeolian region in general local complexities derive from pre existing structural features inherited from the tectonic evolution of the mediterranean region on the contrary along calabria and the apennines the contribution of the subducted ionian oceanic lithosphere and the occurrence of microplates i e adria appear to substantially modify both tectonics and kinematics finally gps data across the gibraltar arc and the tyrrhenian calabria domain support the hypothesis that slab rollback in these regions is mostly slowed down or stopped

quantifying temporal changes in gully erosion areas with object oriented analysis abstract mapping gully systems and quantifying their changes over time are essential for implementing soil conservation measures the aim of this study is to analyze the changes in the gully systems in the context of land management image analysis of remotely sensed data in combination with field verification has proven to be a good and practical approach for mapping gully features over large areas given the variability in gully size shape and occurrence recent work has shown object based image analysis also termed as object oriented analysis ooa to be superior to pixel based methods for the identification and characterization of gullies this study presents an improved procedure to map gully features one that has been extended to assess and quantify erosion area dynamics in addition to the convention of using suitable topographic and spectral thresholds in the method the use of contrast and edge filter information and process knowledge of erosion by overland flow was incorporated in the rule set to help recognize potential gullies in ikonos 2 and geoeye 1 data changes in the area enclosed by the gully system boundary estimated for three different sub watersheds sw1 sw2 and sw3 observed over a period of eight years ranged from moderate 11 in sw2 and 21 in sw1 to a very high increase 91 in sw3 however the changes seen in gully system density were much higher than the changes in the area enclosed by the gully system boundary 81 104 and 109 in the respective sws the complex gully systems were better identified semi automatically than was possible by manual digitization in particular the finer edges of the gully systems which in turn led to better quantification of changes in the gully systems the study also determined that the rule set developed for gully feature extraction is more sensitive to the spatial resolution of the imagery used than the quality or resolution of the digital terrain model and its derivatives determining suitable segmentation parameters selecting appropriate object features for the classification the thresholds used retain the trial error aspects in this analysis this limits its application to a regional scale the rule set developed is generic and transferable to other region imagery with adaptation the rule set will be made available on our website www itc nl ooa group

the quest for the africa eurasia plate boundary west of the strait of gibraltar the missing link in the plate boundary between eurasia and africa in the central atlantic is presented and discussed a set of almost linear and sub parallel dextral strike slip faults the swim1 faults that form a narrow band of deformation over a length of 600 km coincident with a small circle centred on the pole of rotation of africa with respect to eurasia was mapped using a new swath bathymetry compilation available in the area offshore sw portugal these faults connect the gloria fault to the rif tell fault zone two segments of the plate boundary between africa and eurasia the swim faults cut across the gulf of cadiz in the atlantic ocean where the 1755 great lisbon earthquake m 8 5 8 7 and tsunami were generated providing a new insight on its source location

relationship of the presence of a non calcareous clay loam horizon to dem attributes in a gently sloping area abstract the initial objective of this study was to identify relationships between terrain attributes and soil cover over a loessic flat area covering a limestone plateau the second objective was to determine those energy factors flow path solar radiation wind intensity which could improve the understanding of morphology and soil genesis we describe 341 field observations taken over 1600 ha of an experimental area used for monitoring the water and nitrate supply in the petite beauce region 100 km to the southwest of paris for each observation several soil variables were encoded one was the presence of a non calcareous clay loam nccl horizon relief is very smooth in this region mean slope around 0 5 the main terrain attributes were derived from a digital elevation model dem at 20 20 m and assigned to the pedological observations a multiple logistic regression was used to analyse the relationship between the nccl horizon and terrain attributes special statistics were used for aspect because of the circular nature of this variable the results show a strong relationship between the presence of nccl horizon and slope gradient and slope aspect while hydrological parameters are not correlated with this horizon the mean angle of the aspect frequency of the nccl horizon was calculated and compared to the mean angles of wind direction and solar radiation balance there is a small difference between wind direction and aspect frequency of the nccl horizon this result confirms the role of wind in the spatial pattern of soils further data are required to better understand the combination of several factors role of vegetation and the age of the reshaping

natural cf4 and sf6 on earth the occurrence of cf4 and sf6 in natural fluorites caf2 is reported contents are found to be typically 200 2000 ppt mass for cf4 and 50 100 ppt mass for sf6 cf4 and sf6 were also detected in granites where fluorite is an accessory mineral cf4 and sf6 thus possess a large reservoir in the continental crust that by degassing can sustain natural atmospheric background levels of 40 ppt mole and up to 0 01 ppt mole respectively the article also discusses how natural sf6 may cause interference in hydrological tracer studies

cause of the rupture and distribution of broken submarine carbonate chimneys in the gulf of cadiz southwestern spain abstract during the 2000 and 2001 r v cornide de saavedra cruises a vast field of hydrocarbon derived carbonate chimneys was discovered and sampled along the cadiz contourite channel and guadalquivir diapiric ridge photographs taken on board using an underwater camera revealed a spectacularly high density of pipe like chimneys lying on the sea floor though some of them were also found protruding from muddy sediment the major axes of the fallen chimneys which can be as long as 1 m exhibit a regular spatial distribution showing a conspicuous nw se trend furthermore their basal morphology shows a characteristic angular breakage associated to a flexo traction process both the uniform distribution of the major axis and the basal morphology of the chimneys imply that the cause of the rupture could be related either to strong bottom sea currents or to inertia forces associated with oscillatory ground motion due to seismic shaking the preferential orientation of the broken chimneys their mechanical properties the geological and topographical conditions of the area in relation to seismic ground motion amplification and the flow speed of the mediterranean outflow water mow along the cadiz contourite channel suggest that the most probable cause of the chimneys rupture was an earthquake the minimum magnitude of this seismic event is estimated to be more than 7 0 the causative fault being located directly under the chimney field or as far as 30 60 km away the chimneys rupture took place between ca 5 ka to present

influence of glacier advance on the development of the multipart riffeltal rock glacier central austrian alps the multipart riffeltal rock glacier located in a tributary valley of the kaunertal tyrol austria is investigated to enlarge the knowledge about spatial and temporal development of rock glaciers in and at the margins of pro glacial areas and to get a better understanding of glacier rock glacier interactions the subject of interest consists of a complex system of two adjacent rock glacier tongues and various superposed lobes with differing ages origin and root zones and therefore diverse development to determine the reasons for their diverging development the internal structure and permafrost occurrence on and in the surrounding area of the rock glacier were studied by application of geomorphological mapping geophysical methods and measurement of the basal temperature of the winter snow cover bts permafrost modelling was performed on the basis of bts data and land surface parameters derived from a high resolution airborne laser scanning als digital elevation model dem additionally the als data were used to measure vertical and horizontal changes of the rock glacier surface between 2006 and 2012 glacier rock glacier interactions during and since the little ice age lia are evident for the development of the studied rock glacier a geomorphic map gives important information about the connection between glacial advance or retreat and permafrost or ground ice occurrence the combination of all information helps in the analysis of diverse kinematic action of neighbouring rock glacier tongues copyright 2014 john wiley sons ltd

the contourite depositional system of the gulf of cadiz a sedimentary model related to the bottom current activity of the mediterranean outflow water and its interaction with the continental margin the present paper is mostly a synthesis of work conducted on the continental margin of the gulf of cadiz using a broad database collected by several cruises and projects supported by the spanish research council and the nrl and naval oceanographic office usa including bathymetry sidescan sonar imagery seismic profiles sediment cores submarine photographs and physical oceanographic data these data have enabled us to establish a detailed understanding of the morphologic development of the margin its pliocene and quaternary stratigraphy and a full characterization of the contourite depositional system cds generated by the mediterranean outflow water mow the northern margin of the gulf of cadiz shows the following distinct features a an active compressive framework where the cadiz allocthonous unit provides an unstable substratum for late miocene pliocene and quaternary sedimentation b a relative lack of submarine canyons except in the western area of the algarve margin c a very broad continental slope that lacks a marked continental rise d a middle slope dominated by along slope processes driven by the mow which has generated a complex cds during the pliocene and quaternary and e an irregular lower slope and abyssal plain region dominated by down slope processes that is partly detached from an upper slope source region the cds is composed of both depositional and erosive features the main depositional features are characterised by sedimentary wave fields sedimentary lobes mixed drifts plastered drifts elongated mounded and separated drifts and sheeted drifts the main erosive features are contourite channels furrows marginal valleys and moats these various depositional and erosive features have a specific location along the margin and their detailed distribution is essential to understand the present and past interaction of the mow with the middle slope based on this distribution five morphosedimentary sectors have been identified within the cds which from east to west are 1 proximal scour and sand ribbons 2 overflow sedimentary lobe 3 channels and ridges 4 active contourite drifts and 5 submarine canyons the development of the cds has been controlled in general by the pliocene and quaternary environmental and paleoceanographic changes and by the morphology of the margin but in detail the development of each of these sectors is related to systematic deceleration of the mow as it flows westwards to the interaction with the margin bathymetry and to the effects of coriolis force our comprehensive sedimentary model for the cds defines the gulf of cadiz margin as a mixed contourite turbidite system with a detached combined drift fan morphology this is different from many other contourite influenced margins where the contourite processes are dominant on the middle slope and separated from the down slope processes which are characteristic on the lower slope and abyssal plains

vast fields of hydrocarbon derived carbonate chimneys related to the accretionary wedge olistostrome of the gulf of cadiz we report the first discovery and sampling of vast fields of hydrocarbon derived carbonate chimneys along the gulf of cadiz continental slope at depths between 500 and 1200 m a large variety of carbonate chimneys more than 200 samples were recovered from four different areas named the diasom tasyo gbf guadalquivir basin and esf east moroccan fields observations from an underwater camera revealed a spectacular high density of pipe like chimneys some of them longer than 2 m lying over the sea floor and some protruding from muddy sediment local fissures and alignment of isolated chimneys were also observed suggesting that their distribution is controlled by fault planes chimneys collected show a wide range of morphological types spiral cylindrical conical mushroom like and mounded with numerous nodule protuberances and ramified fluid channelways the chimneys are mainly composed of authigenic carbonates ankerite fe bearing dolomite and calcite with abundance of iron oxides forming agglomerates of pseudo pyrite framboids n 18 o isotopic values vary from 0 7 to 5 5x whereas n 13 c values indicate that chimney carbonates are moderately depleted in 13 c ranging from 346x to 320x pdb interpreted as formed from a mixture of deep thermogenic hydrocarbons and shallow biogenic methane these vast fields of carbonate chimneys imply new considerations on the importance of hydrocarbon fluid venting in the gulf of cadiz and moreover on the active role of the olistostrome accretionary wedge of the gibraltar arc b 2003 elsevier science b v all rights reserved

relationships between compressional wave and shear wave velocities in clastic silicate rocks new velocity data in addition to literature data derived from sonic log seismic and laboratory measurements are analyzed for clastic silicate rocks these data demonstrate simple systematic relationships between compressional and shear wave velocities for water saturated clastic silicate rocks shear wave veloci ty is approximately linearly related to compressional wave velocity and the compressional to shear velocity ratio decreases with increasing compressional velocity laboratory data for dry sandstones indicate a nearly constant compressional to shear velocity ratio with rigidity approximately equal to bulk modulus ideal models for regular packings of spheres and cracked solids exhibit behavior similar to the observed water saturated and dry trends for dry rigidity equal to dry bulk modulus gassmann s equations predict velocities in close agreement with data from the water saturated

eastern segment of the azores gibraltar line central eastern atlantic an oceanic plate boundary with diffuse compressional deformation new seismic reflection images across the eastern segment of the azores gibraltar line west of the collisional area between the african and iberian plates have revealed a complex pattern of compressional deformation involving the mesozoic oceanic lithosphere the compressional deformation developed in a region of slow plate convergence and is diffused at different lithospheric levels across an area spanning 200 km from the gorringe ridge to the seine plain the convergence between the african and iberian plates has been active since tertiary time and our results indicate that no subduction zone exists across this part of the plate boundary

dating large infrequent earthquakes by damaged cave deposits the long term recurrence patterns of past earthquakes are of considerable consequence for hazard assessments and have implications for earthquake physics we introduce a rigorously dated record of earthquakes from an extensive number of well preserved pre seismic and postseismic precipitates from caves located off the dead sea transform we dated events directly at the paleoseismic contact by means of a novel correlation method with the oxygen isotope record of the speleothems recovered in one of the caves within the 185 k y covered we dated 38 seismite samples these stem from 13 18 earthquakes with a mean recurrence interval of 10 14 k y we show that the deformational events dated in the study caves complement independent near fault paleoseismic records by tem poral correlation with the earthquakes recorded therein this opens up a significant new avenue of earthquake research that will provide precise dating and observational con straints on large infrequent earthquakes

surface and bed topography of trapridge glacier yukon territory canada digital elevation models and derived hydraulic geometry measurements of ice thickness and surface elevation are prerequisite to many glaci ological investigations a variety of techniques has been develo ped for inter pret ation of these data including means of constructing regularly gridded digital eleva tion models dem s for use in numcrical studies here we present a simple yet stati sti cally sound method for processing ice pe netr ating radar data and descr ibe a tech nique for interpol ating these data onto a regular grid dems generatcd fort rapridge glacier yukon territory canada are used to derive geometric quantities lhal give pre liminary insights into the underlying basin scale hydrol ogical syste m this simple geo metric analysis suggests that at low water press ures a dendrilic drainage netw ork exists that evolves into a uniaxial morphology as water pressure approaches notation these pre dictions are compared to hydraulic connection probabilities based on bore hole drilling

a seismic reflection and gloria study of compressional deformation in the gorringe bank region eastern north atlantic seismic reflection and gloria side scan sonar data obtained on rrs charles darwin cruise cd64 reveal new information on the styles of deformation in the gorringe bank region at the eastern end of the azores gibraltar plate boundary previous studies suggest that gorringe bank was formed by the overthrusting of a portion of the african plate upon the eurasian plate the new seismic data show however that the most intensely deformed region is located south of gorringe bank on the northern flanks of a nw se trending submarine ridge which includes the ampere and coral patch seamounts the deformation is expressed as long wavelength up to 60 km large amplitude up to 800 m folds in the sediments and underlying acoustic basement which in places are associated with one or more reverse faults and as a fabric of short wavelength folds up to 3 km with a ne trend in contrast the same sedimentary units when traced beneath the flanking plains are undeformed except for some faults with a small throw 30 m some of which offset the seafloor gloria data show that recent deformation is broadly distributed over the region structural trends rotate from 45 in the west to 70 in the east of the region nearly perpendicular to the nw verging plate motion vectors as determined from plate kinematic models flexure modelling suggests that a portion of gorringe bank has loaded 152 ma oceanic lithosphere and that a maximum of 50 km of shortening has occurred at gorringe bank since the mid miocene our observations support a model in which there is no single plate boundary in the region rather that the deformation is distributed over a 200 330 km wide zone

influence of the drainage network identification method on geomorphological properties and hydrological response the influence of the method of identification of the drainage network on its geomorphological characteristics and on its hydrological response is analysed blue lines photo interpreted networks and networks generated from digital elevation models dems by an automatic algorithm are compared with field observations for two small alpine catchments the comparisons are carried out in quantitative terms by using several geomorphological indices and functions and by calculating the hydrological response of the networks as represented by their geomorphologic instantaneous unit hydrograph giuh the results show that the effect of the identification method on the geomorphological indices and on the hydrological response is significant and that the threshold area for channel initiation is not constant moreover the available data show a poor correlation between local slope and threshold area finally the influence of the threshold area on the shape of the giuh is larger when the residence time on the hillslopes is of the same order as the residence time in the network in the opposite case the variability of the flow velocity along the network seems to play an important role 1997 john wiley sons ltd

identification of peneplains by multi parameter assessment of digital elevation models the concept of peneplains has existed since the end of the nineteenth century typical peneplains are elevated geomorphological features with a low relief surface on top they may be tilted due to tectonic activity or intersected by evolving erosion until now neither a standardized definition for peneplains nor an established procedure to identify and quantify well preserved peneplains as prominent landforms existed at present the global availability of homogeneous digital elevation models dems provides an accurate characterization of the morphology of the earth surface in this study a new numerical dem based fuzzy logic approach is presented for the delineation of peneplains solely from a morphological perspective the approach is based on a morphometric analysis of the 90 arcsec shuttle radar topography mission srtm dem four critical parameters are employed which are implemented within a geographic information system gis the parameters for the correct and unambiguous description of a flat top mountain are i slope ii curvature iii terrain ruggedness index and iv relative height the approach was developed using a test area in the central tibetan plateau which is characterized by representative and well preserved peneplains and for which additional field data were collected in order to verify the method peneplains were delineated in different regions with various geological settings for which potential peneplains were already described in the literature the results from the appalachian mountains andes massif central and new zealand confirm the robustness of the proposed approach copyright 2015 john wiley sons ltd

tsunamigenic seismogenic structures neotectonics sedimentary processes and slope instability on the southwest portuguese margin tectonically active structures prone to cause devastating earthquakes and tsunamis e g the lisbon 1755 earthquake were investigated during the unesco ioc training through research 10 ttr 10 cruise on the southwest portuguese continental margin using single channel seismic profiles a 3 5 khz hull mounted sea bottom profiler 10 khz okean long range side scan sonar 30 khz oretech deep towed side scan sonar and a high resolution deep towed sea bottom profiler these data allowed the definition of new active faults and the establishment of morphological criteria for the classification of active faults in the study area landslides associated with the activity of a major tectonic structure the marques de pombal fault and other areas with clear signs of mass wasting phenomena were mapped a slope to basin sedimentary system comprising 21 sedimentary ridges up to 20 km long was mapped and described it was found that the sediments are mainly transported into the deep basins by mass transport processes across the steepest fault scarps forming a channel levee system while gravitational slides slumps dominate the shallower slopes the sedimentary ridges with an elevation of 40 50 m 50 60 ms twt above the seafloor are imaged on the high resolution seismic profiles as an alternation of high and low amplitude reflectors it is shown that the pereira de sousa fault its plateau and the principes de avis plateau are experiencing uplift according to sedimentary and morphological criteria

object based gully system prediction from medium resolution imagery using random forests abstract erosion in particular gully erosion is a widespread problem its mapping is crucial for erosion monitoring and remediation of degraded areas in addition mapping of areas with high potential for future gully erosion can be used to assist prevention strategies good relations with topographic variables collected from the field are appropriate for determining areas susceptible to gullying image analysis of high resolution remotely sensed imagery hri in combination with field verification has proven to be a good approach although dependent on expensive imagery automatic and semi automatic methods such as object oriented analysis ooa are rapid and reproducible however hri data are not always available we therefore attempted to identify gully systems using statistical modeling of image features from medium resolution imagery here aster these data were used for determining areas within gully system boundaries gsb using a semi automatic method based on ooa we assess if the selection of useful object features can be done in an objective and transferable way using random forests rf for prediction of gully systems at regional scale here in the sehoul region near rabat morocco moderate success was achieved using a semi automatic object based rf model out of bag error of 18 8 besides compensating for the imbalance between gully and non gully classes the procedure followed in this study enabled us to balance the classification error rates the user s and producer s accuracy of the data with a balanced set of class showed an improved accuracy of the spatial estimates of gully systems when compared to the data with imbalanced class the model over predicted the area within the gsb 13 27 but its overall performance demonstrated that medium resolution satellite images contain sufficient information to identify gully systems so that large areas can be mapped with relatively little effort and acceptable accuracy

evidence for crustal degassing of cf4 and sf6 in mojave desert groundwaters dissolved tetrafluoromethane cf4 and sulfur hexafluoride sf6 concentrations were measured in groundwater samples from the eastern morongo basin emb and mojave river basin mrb located in the southern mojave desert california both cf4 and sf6 are supersaturated with respect to equilibrium with the preindustrial atmosphere at the recharge temperatures and elevations of the mojave desert these observations provide the first in situ evidence for a flux of cf4 from the lithosphere a gradual basin wide enhancement in dissolved cf4 and sf6 concentrations with groundwater age is consistent with release of these gases during weathering of the surrounding granitic alluvium dissolved cf4 and sf6 concentrations in these groundwaters also contain a deeper crustal component associated with a lithospheric flux entering the emb and mrb through the underlying basement the crustal flux of cf4 but not of sf6 is enhanced in the vicinity of local active fault systems due to release of crustal fluids during episodic fracture events driven by local tectonic activity when fluxes of cf4 and sf6 into mojave desert groundwaters are extrapolated to the global scale they are consistent within large uncertainties with the fluxes required to sustain the preindustrial atmospheric abundances of cf4 and sf6

a palaeoseismological and geoarchaeological investigation of the eliki fault gulf of corinth greece abstract palaeoseismological and morphotectonic analyses enable us to define a 400 m wide actively deformed zone associated with the active eliki normal fault central greece bounded on the south by a second order fault and on the north by a composite and prominent fault scarp this scarp is further analysed by trenching based on colluvium stratigraphy displacement of distinct horizons and deposition of sedimentary layers three faulting events have been identified along four fault strands affecting unconsolidated sediments in the trench the two younger events with throws of 0 93 and 1 37 m respectively the third event with a throw of 0 44 m and the penultimate 373 bc event suggest a variable seismic history the entire alluvial plain of the kerynitis and vouraikos rivers which cross the eliki fault has subsided at a rate of 1 4 mm year resulting in the burial of the late hellenistic roman occupation horizons under 3 m of fluvial and colluvial sediments in places extension in the broader area is accommodated by the seismically active eliki and egion faults structural and palaeoseismological analysis of those two faults indicates that they accommodate 1 5 mm year or about 10 of the geodetically estimated extension of up to 13 mm year

crustal architecture and tectonic evolution of the gulf of cadiz sw iberian margin at the convergence of the eurasian and african plates 1 the gulf of cadiz located at the southwestern iberian margin is characterized by widespread seismicity compressional and strike slip fault plane solutions and by a large elongated positive free air gravity anomaly the gulf of cadiz gravity high gcgh multichannel seismic profiles across and along gcgh together with bathymetric and gravity data allow us to study in detail the tectonic architecture and crustal structure of the gulf of cadiz the upper shelf and slope of the gulf of cadiz includes the main structural domains of the betic fold and thrust belt in the middle part of the gulf the paleozoic basement crops out on the shallow guadalquivir bank and is associated with the largest signature of the gcgh whereas toward the outer part of the gulf the basement deepens progressively a large nw se normal fault and conjugate ne sw faults define a prominent basement high associated with the gcgh modeling of the gcgh suggests localized crustal thinning of 10 km along the central part of the gulf of cadiz probably generated during the mesozoic rifting episode between the iberian and african plates concentric wedges of fold and thrust belts and large allochthonous masses were emplaced in the gulf of cadiz during the neogene compressional phase the final emplacement of these units becomes progressively young from the se pre early langhian toward the foreland in the nw late tortonian seafloor surface ruptures pockmarks and submarine landslides provide evidence of active faulting in the gulf of cadiz to accommodate the present day convergence between the african and eurasian plates previously extensional faults have probably been reactivated and inverted at depth as suggested by the intermediate depth seismicity

holocene earthquake record offshore portugal sw iberia testing turbidite paleoseismology in a slow convergence margin the sw margin of the iberian peninsula hosts the present day boundary between the eurasian and african plates convergence 4 5 mm yr is accommodated through a wide deformation zone characterized by moderate magnitude seismic activity this zone has also been the source of the most important seismic events in western europe such as the 1755 lisbon earthquake and tsunami and 1969 horseshoe earthquake despite efforts to identify active seismogenic structures in the gulf of cadiz in the last ten years little is known about its paleoseismic history the turbidite paleoseismology approach was applied for the first time in a low rate convergent margin to determine the recurrence interval of large earthquake events that occurred in sw iberia during the holocene four sediment cores collected at strategically located sites offshore portugal i e tagus abyssal plain infante don henrique basin and horseshoe abyssal plain reveal that these deep sea basins preserve a record of episodic deposition of turbidites in the sw iberian margin excluding special climatic events earthquakes are the most likely triggering mechanism for synchronous widely spaced distributed turbidites during the holocene when the sea level was relatively stable age correlation together with textural mineralogical physical properties and geochemical signatures of the new cores complemented by pre existing multicores and gravity cores reveals a total of 7 widespread turbidite events for the holocene precise dating of the most recent turbidite event e1 based on

archeological and pedological evidence for large prehistoric earthquakes in the new madrid seismic zone central united states prehistoric liquefaction features have been identified by careful observation of their structural and stratigraphic relations to native american occupation horizons and their subtle soil characteristics the ages of these liquefaction features have been estimated from radiocarbon dating of wood associated with the features and native american artifacts found within bounding occupation horizons at three sites near blytheville arkansas in the central part of the new madrid seismic zone one sand blow crater formed between a d 800 and 1400 two sand blow deposits formed between a d 800 and 1670 and three possibly four sand dikes formed since 4035 b c where not found in association with native american occupation horizons and artifacts prehistoric liquefaction features can be difficult to distinguish from features that formed during the great new madrid earthquakes of a d 1811 and 1812 this raises the possibility that prehistoric liquefaction features may have been misinterpreted during previous studies in the area nevertheless a paleoearthquake chronology is beginning to emerge for the new madrid seismic zone our findings are consistent with paleoseismological studies in the northern part of the seismic zone and suggest a recurrence interval of hundreds of years for earthquakes large enough to induce liquefaction in this region m 6 4 by mapping the age distribution of liquefaction features a more accurate assessment of the long term earthquake potential of the region will be possible

mediterranean undercurrent sandy contourites gulf of cadiz spain abstract the pliocene quaternary pattern of contourite deposits on the eastern gulf of cadiz continental slope results from an interaction between linear diapiric ridges that are perpendicular to slope contours and the mediterranean undercurrent that has flowed northwestward parallel to the slope contours and down valleys between the ridges since the late miocene opening of the strait of gibraltar coincident with the northwestward decrease in undercurrent speeds from the strait there is the following northwestward gradation of sediment facies associations 1 upper slope facies 2 sand dune facies on the upstream mid slope terrace 3 large mud wave facies on the lower slope 4 sediment drift facies banked against the diapiric ridges and 5 valley facies between the ridges the southeastern sediment drift facies closest to gibraltar contains medium fine sand beds interbedded with mud the adjacent valley floor facies is composed of gravelly shelly coarse to medium sand lags and large sand dunes on the valley margins compared to this the northwestern drift contains coarse silt interbeds and the adjacent valley floors exhibit small to medium sand dunes of fine sand further northwestward sediment drift grades to biogenous silt near the faro drift at the portuguese border because of the complex pattern of contour parallel and valley perpendicular flow paths of the mediterranean undercurrent the larger scale bedforms and coarser grained sediment of valley facies trend perpendicular to the smaller scale bedforms and finer grained contourite deposits of adjacent sediment drift facies the bottom current deposits of valleys and the contourites of the cadiz slope intervalley areas are distinct from turbidite systems the valley sequences are not aggradational like turbidite channel levee complexes but typically exhibit bedrock walls against ridges extensive scour and fill into adjacent contourites transverse bedform fields and bioclastic lag deposits both valley and contourite deposits exhibit reverse graded bedding and sharp upper bed contacts in coarse grained layers low deposition rates and a regional pattern of bedform zones textural variation and compositional gradation the surface sandy contourite layer of 0 2 1 2 m thickness that covers the gulf of cadiz slope has formed during the present holocene high sea level because high sea level results in maximum water depth over the gibraltar sill and full development of the mediterranean undercurrent the late pleistocene age of the mud underlying the surface sand sheet correlates with the age of the last sea level lowstand and apparent weak mediterranean undercurrent development thus the cyclic deposition of sand or mud layers and contourite or drape sequences appear to be related to late pliocene and quaternary sea level changes and mediterranean water circulation patterns since its pliocene origin the contourite sequence has had low deposition rates of

dating groundwater with trifluoromethyl sulfurpentafluoride sf5cf3 sulfur hexafluoride sf6 cf3cl cfc 13 and cf2cl2 cfc 12 1 a new groundwater dating procedure using the transient atmospheric signal of the environmental tracers sf5cf3 cfc 13 sf6 and cfc 12 was developed the analytical procedure determines concentrations of the four tracers in air and water samples sf5cf3 and cfc 13 can be used to date groundwaters in some environments where the cfcs and sf6 have previously failed because these new tracers have increasing atmospheric input functions no known terrigenic source and are believed to be stable under reducing conditions sf5cf3 has a dating range from 1970 to modern the mixing ratio mole fraction in north american air has increased from the detection limit of 0 005 parts per trillion ppt to the 2006 mole fraction of about 0 16 ppt no evidence was found for degradation of sf5cf3 in laboratory anaerobic systems the solubility of sf5cf3 was measured in water from 1 to 35 c groundwater samples that contained large amounts of terrigenic sf6 did not contain terrigenic sf5cf3 cfc 13 is a trace atmospheric gas with a dating range in groundwater of about 1965 to modern cfc 13 has been used primarily in very low temperature refrigeration thus groundwater environments are less likely to be contaminated with nonatmospheric sources as compared to other widely used cfcs because of the low solubility of sf5cf3 and cfc 13 in water an excess air correction must be applied to the apparent ages the new dating procedure was tested in water samples from wells and springs from maryland virginia and west virginia

earthquakes and archaeology abstract this article examines the use of archaeological evidence for the assessment of historical earthquakes in the eastern mediterranean region and middle east long before the advent of modern seismology we ask the questions when and where have large earthquakes happened in the past how can this evidence contribute to our scientific understanding of earthquake activity is it possible on literary and archaeological grounds to distinguish between earthquake damage and damage from other causes it is found that archaeological evidence for an earthquake is not always clear or unambiguous and that there is a need for collaboration between archaeologists historians geologists engineering seismologists and workers in other disciplines to evaluate the traces of earthquakes in excavations both for understanding their effects at the site and for the information they can provide about the nature of the earthquake implicated

saturation regions in catchments and their relations to soil and topographic properties abstract criteria are derived for the existence of saturated areas on draining hillslopes in natural catchments these are given in terms of soil transmissivity the hillslope gradient and its wetness state characterised by the baseflow discharge from the catchment analyses are made for idealised hillslopes with uniform soils to obtain expression for the width of the saturated zone the size of saturated zones on undulating hillslopes with gradiational soils is shown to depend strongly on topographic convergence or divergence the effects of soil transmissivity hillslope geometry and drainage flux density are lumped into a dimensionless parameter whose value determines the location of seepage boundaries on slopes of specified geometry scaling relations for seepage area in catchments of different size are shown to be generally nonlinear and depend primarily on local hillslope gradients relative predictions of seepage zone size are confirmed by observed hydrographs from three catchments with different physical characteristics

simulations of strong ground motion in sw iberia for the 1969 february 28 ms 8 0 and the 1755 november 1 m 8 5 earthquakes ii strong ground motion simulations summary this is the second paper of a series of two concerning strong ground motion in sw iberia due to earthquakes originating from the adjacent atlantic area the aim of this paper is to use the velocity model that was proposed and validated in the companion paper for seismic intensity modelling of the 1969 m s 8 0 and 1755 m 8 5 8 7 earthquakes first we propose a regression to convert simulated values of peak ground velocity pgv into modified mercalli intensity mmi in sw iberia and using this regression we build synthetic isoseismal maps for a large m s 8 0 earthquake that occurred in 1969 based on information on the seismic source provided by various authors we show that the velocity model effectively reproduces macroseismic observations in the whole region we also confirm that seismic intensity distribution is very sensitive to a small number of source parameters rupture directivity fault strike and fault dimensions then we extrapolate the method to the case of the great m 8 5 8 7 1755 earthquake for a series of hypotheses recently proposed by three authors about the location of the epicentral region the model involving a subduction

momentum and energy balance of the mediterranean outflow field data taken in the gulf of cadiz have been analyzed to describe some aspects of the momentum and energy balance of the mediterranean outflow a crucial component of the momentum balance is the total stress entrainment stress and bottom drag which has been estimated from a form of the bernoulli function evaluated from density and current observations for the first 60 km west of the camarinal sill the outflow was confined within a narrow channel on the continental shelf at about 70 km downstream the outflow crossed over the shelf slope break and began to descend the continental slope the buoyancy force increased substantially and the outflow underwent a geostrophic adjustment albeit one heavily influenced by mixing and dissipation the current direction turned 90 degrees to the right at a near inertial rate in this region the estimated geostrophic velocity greatly underestimated the actual current and the estimated curvature rossby number was about 0 5 current speeds were in excess of 1ms 2 1 and the total stress was as large as 5 pa the entrainment stress estimated independently from property fluxes reached a maximum of about 1 pa or considerably smaller than the inferred bottom stress by about 130 km downstream the current was aligned approximately along the local topography the current amplitude and the estimated stress were then much less about 0 3 m s21 and 0 3 pa the entrainment stress was also very small in this region well downstream of the strait this slightly damped geostrophic flow continued on to cape st vincent where the outflow began to separate from the bottom bottom stress thus appears to be a crucial element in the dynamics of the mediterranean outflow allowing or causing the outflow to descend more than a kilometer into the north atlantic in the regions of strongest bottom stress the inferred drag coefficient was about 2 2 12 3 10 23 depending upon which outflow speed is used in the usual quadratic form entrainment stress was small by comparison to the bottom stress but the entrainment effect upon the density anomaly was crucial in eroding the density anomaly of the outflow the observed entrainment rate appears to follow roughly a critical internal froude number function

object based gully feature extraction using high spatial resolution imagery abstract gully erosion is responsible for a substantial amount of soil loss and is generally considered an indicator of desertification hence mapping these gully features provides essential information needed on sediment production identification of vulnerable areas for gully formation land degradation and environmental and socio economical effects this paper investigates the use of object oriented image analysis ooa to extract gully erosion features from satellite imagery using a combination of topographic spectral shape geometric and contextual information obtained from ikonos and geoeye 1 data a rule set was developed and tested for a semi arid to sub humid region in morocco the percentage of gully system area indicated negligible overestimations between the reference area and the ooa area in two sub watersheds 0 03 and 1 77 we also observed that finer gully related edges within the complex gully systems were better identified semi automatically than was possible by manual digitization suggesting higher detection accuracy ooa based gully mapping is quicker and more objective than traditional methods and is thus better suited to provide essential information for land managers to support their decision making processes and for the erosion research community

closure of the africa eurasia north america plate motion circuit and tectonics of the gloria fault we examine the closure of the current plate motion circuit between the african north american and eurasian plates to test whether these plates are rigid and whether the gloria fault is an active transform fault we also investigate the possible existence of microplates that have been previously proposed to lie along these plate boundaries and compare the predicted direction of motion along the african eurasian plate boundary in the mediterranean with the direction of slip observed in earthquakes from marine geophysical data we obtain 13 transform fault azimuths and 40 3 m y average spreading rates 34 of which are determined from comparison of synthetic magnetic anomaly profiles to 140 observed profiles slip vectors from 32 earthquake focal mechanisms further describe plate motion detailed magnetic surveys north of iceland provide 11 rates in a region where prior plate motion models had few data magnetic profiles north of the azores triple junction record a rate of 24 mm yr 4 mm yr slower than used by prior models gloria and sea beam surveys accurately measure the azimuths of seven transform faults our plate motion model fits six of the seven within 2 two transform faults surveyed by gloria side scan sonar lie near famous area transform faults a and b and give azimuths 13 clockwise of them because recent studies show that short offset transforms such as transforms a and b are in many places oblique to the direction of plate motion we exclude azimuths from transforms with less than 35 km offset the best fitting and closure enforced vectors fit the data well except for a small systematic misfit to the slip vectors on right lateral slipping transforms slip vectors tend to be a few degrees clockwise of plate motion and mapped fault azimuths whereas on left lateral slipping transforms slip vectors tend to be a few degrees counterclockwise of plate motion and mapped fault azimuths we search the long eurasia north america boundary for evidence of an additional plate but find no systematic misfits to the data in particular if a spitsbergen plate exists and moves relative to eurasia its motion is less than 3 mm yr an africa eurasia euler vector determined by adding the eurasia north america and africa north america euler vectors is consistent with the gloria fault trend and with slip vectors from eastern azores gibraltar ridge focal mechanisms a small circle centered at the africa eurasia closure enforced pole fits the trace of the gloria fault the model in which closure was enforced predicts 4 mm yr slip across the azores gibraltar ridge and west northwest convergence near gibraltar 45 more oblique than suggested by a recent model based on compressive axes of focal mechanisms moreover our model predicts directions of plate motion that agree well with northwest trending slip vectors from thrust earthquakes between gibraltar and sicily because closure enforced vectors fit the data nearly as well as the best fitting vectors we conclude that the data are consistent with a rigid plate model and with the gloria fault being a transform fault

gully position characteristics and geomorphic thresholds in an undisturbed catchment in northern australia gullying is a significant process in the long term dynamics and evolution of both natural and rehabilitated i e post mining landscapes from a landscape management perspective it is important that we understand gully initiation and development as it is well recognized that catchment disturbance can result in the development of gullies that can be very difficult to rehabilitate this study examines gully position using geomorphic statistics relating to features such as depth width and length in a catchment undisturbed by european activity in the northern territory australia the results demonstrate that gullying occurs throughout the catchment and that a slope area threshold does not exist and that gully position broadly follows the catchment area slope relationship simple relationships relating catchment area and slope to gully depth width and length provide poor results despite these relationships having been found to apply for ephemeral gullies in cropland the results suggest that gully initiation thresholds are low as a result of an enhanced fire regime a threshold model for gully position that uses catchment area and slope to switch between gully and hillslope was evaluated and found broadly to capture gully position copyright 2006 john wiley sons ltd

computer assisted terrain sketch mapping that considers the geomorphological features in a loess landform abstract in geography a terrain sketch map is necessary to understand the features and internal structures of a landscape due to its ability to depict key information in a geographical scene using as few lines as possible previous computer drawn sketch maps have focused on the artistic effect rather than on depicting terrain features and landform structures and thus they differ considerably from hand drawn sketch maps by geographers or geologists this study develops a dem based method for terrain sketch mapping that considers the typical feature descriptions of a loess landform and the visual hierarchy expression in line with the law of visual perspective the method was tested with experiments on two landforms of chinese loess plateau based on digital elevation models dem with a horizontal resolution of 5 m in the developed method first typical terrain features including the visual outline shoulder line gully and flow lines are extracted from the dem second the map is divided into three visual levels in accordance with the data extension and viewing point then terrain feature lines are assigned to different visual levels finally the visual outlines in the distant view are generalized following the law of visual perspective results are assessed through a questionnaire with specialists experts and students non experts the sketch map was able to characterise loess landforms and is somewhat similar to traditional hand drawn maps the generalisation method realises the near and distant view characteristics of a sketch map which are detailed and simplified respectively the results of the questionnaire also showed that our method presents terrain morphology and geographical scene more accurately and reliably than a hand drawn sketch map

recognition of earthquake related damage in archaeological sites examples from the dead sea fault zone abstract archaeological structures that exhibit seismogenic damage expand our knowledge of temporal and spatial distribution of earthquakes afford independent examination of historical accounts provide information on local earthquake intensities and enable the delineation of macroseismic zones they also illustrate what might happen in future earthquakes in order to recover this information we should be able to distinguish earthquake damage from anthropogenic damage and from other natural processes of wear and tear the present paper reviews several types of damage that can be attributed with high certainty to earthquakes and discusses associated caveats in the rare cases where faults intersect with archaeological sites offset structures enable precise determination of sense and size of slip and constrain its time among the characteristic off fault damage types i consider horizontal shifting of large building blocks downward sliding of one or several blocks from masonry arches collapse of heavy stably built walls chipping of corners of building blocks and aligned falling of walls and columns other damage features are less conclusive and require additional evidence e g fractures that cut across several structures leaning walls and columns warps and bulges in walls circumstantial evidence for catastrophic earthquake related destruction includes contemporaneous damage in many sites in the same area absence of weapons or other anthropogenic damage stratigraphic data on collapse of walls and ceilings onto floors and other living horizons and burial of valuable artifacts as well as associated geological palaeoseismic phenomena such as liquefaction land and rock slides and fault ruptures additional support may be found in reliable historical accounts special care must be taken in order to avoid circular reasoning by maintaining the independence of data acquisition methods

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

diffuse emission of organic trace gases from the flank and crater of a quiescent active volcano vulcano aeolian islands italy 1 volcanoes discharge a range of inorganic major gas species e g h2o co2 so2 and co not only during eruptions but also during quiescent phases through fumarolic and diffuse degassing in their craters and on their flanks the emission of organic trace gases from volcanoes is similarly not expected to be restricted to discrete fumarolic gas discharges alone to test this hypothesis we have sampled soil gas emissions for organic compounds and determined co2 fluxes along a profile extending from the vegetated base of the active la fossa cone vulcano island italy over the unvegetated volcanic flank and up into the crater rim and base and then continuing over fumarolic areas the results indicate that the majority of volatile organic compounds in the soil gas show significant increases in concentration toward the crater and fumaroles and that diffuse emissions contribute significantly to the volcanic halocarbon source strength emissions of the halocarbon cfc 11 ccl3f correlate well with soil co2 fluxes measured on site r2 0 89 slope 1 42 0 1 and both increase toward the crater and fumaroles other ozone depleting substances were found in concentrations significantly above those found in field and system blanks including ch3br ch3cl ch3i c2h5br and chlorinated benzenes abundances ranged from upper pptv to ppmv for example the maximum observed cfc 11 concentrations were 1200 pptv in diffuse emissions and 3700 pptv in dry fumarolic gas average dry air is 268 pptv on the basis of these results the natural volcanic source strength of halocarbon emissions to the atmosphere requires reevaluation and in some cases correction to higher values global average fumarolic and diffuse halocarbon source strengths were estimated and scaled to known global volcanic fumarolic and diffuse co2 flux data among these were cfc 11 8 56 4 7 10 6 tg y 1 ch3br 0 98 0 47 10 6 tg y 1 chcl3 94 9 27 6 10 6 tg y 1 and ccl4 3 41 1 0 10 6 tg y 1

lagrangian observations of meddy formation during a mediterranean undercurrent seeding experiment mediterranean eddies meddies play an important role in maintaining the temperature and salinity distributions in the north atlantic but relatively little is known about their early life histories including where how often and by what mechanism they form a major field program called a mediterranean undercurrent seeding experiment has been carried out to directly observe meddy formation and the spreading pathways of mediterranean water into the north atlantic between may 1993 and march 1994 49 rafos floats were deployed sequentially in the mediterranean undercurrent south of portugal and tracked acoustically for up to 11 months the float deployments were accompanied by high resolution xbt sections across the undercurrent nine meddy formation events were observed in the float trajectories six near cape st vincent at the southwestern corner of the iberian peninsula and three near the estremadura promontory along the western portuguese continental slope meddy formation thus occurs where the continental slope turns sharply to the right when facing in the downstream direction of the undercurrent after conditionally sampling the float dataset to identify floats that were well seeded in the undercurrent the authors have estimated a meddy formation rate of 15 20 meddies per year the timescale for meddy formation at cape st vincent was found to be 3 7 days shorter than previous estimates based on the volume of larger meddies meddies were observed to form most frequently when the speed of the mediterranean undercurrent was relatively fast the meddy formation process at cape st vincent resembles the conceptual model of e a d asaro whereby anticyclonically rotating eddies are formed by separation of a frictional boundary layer with negative relative vorticity at a sharp corner comparison of the relative vorticity in the anticyclonic shear zone of the undercurrent and that of the newly formed meddies shows that much of the anticyclonic relative vorticity in meddies can be accounted for by the horizontal shear in the undercurrent this confirms earlier work suggesting that the classical mechanism for the generation of submesoscale coherent vortices by collapse and geostrophic adjustment of a weakly stratified fluid injected into a stratified ocean may not be the principle mechanism at work in the formation of meddies at cape st vincent

quantitative analysis of land surface topography land surface topography significantly affects the processes of runoff and erosion a system which determines slope aspect and curvature in both the down slope and across slope directions is developed for an altitude matrix also the upslope drainage area and maximum drainage distance are determined for every point within the altitude matrix a fortran 66 program performs the analysis

the giant chaotic body in the atlantic ocean off gibraltar new results from a deep seismic reflection survey abstract the central eastern atlantic continental slope and parts of the horseshoe and seine plains west of the gibraltar arc are occupied by a seismically chaotic body this paper reports new deep seismic reflection data that allows a first assessment of the three dimensional geometry of the body and discussion of its evolution the seismically chaotic body is huge in area and volume and complex in origin comprising mainly gravity deposits debris flows olistostromes in the northern sector and tectonic melanges in the southern where the body forms part of a south verging accretionary prism related to africa iberia convergence submarine extension of the rifian system of n africa the northern part up to several tens of thousands of cubic kilometers in volume results from the superposition of a few endoolistostromes probably of miocene age centripetally discharged onto the eastern horseshoe plain and adjacent slope from structural highs generated during the late miocene paroxismal phase of iberia africa convergence submarine flows were triggered along regional continuous slopes up to 100 km in length their volume largely exceeds previously reported marine occurrences of gravity flow deposits the outstanding examples of which occur in intraplate settings hot spots old passive margins at the boundaries lateral or frontal ramps of the southern tectonic melange complex smallscale olistostromes of pliocene age also occur recalling the so called precursory olistostromes of collisional chains the gravity and tectonic structures occur in a convergent plate setting with low shortening rates and their eventual fate will be incorporation with disruption in a collisional chain their volume and extent appear comparable to those that can be calculated for huge chaotic units in orogens such as the argille scagliose liguride complex of the apennines in which disrupted olistostromes and tectonic melanges coexist

reefs of the deep the biology and geology of cold water coral ecosystems coral reefs are generally associated with shallow tropical seas however recent deep ocean exploration using advanced acoustics and submersibles has revealed unexpectedly widespread and diverse coral ecosystems in deep waters on continental shelves slopes seamounts and ridge systems around the world advances reviewed here include the use of corals as paleoclimatic archives and their biogeological functioning biodiversity and biogeography threats to these fragile long lived and rich ecosystems are mounting the impacts of deep water trawling are already widespread and effects of ocean acidification are potentially devastating

influence of the atlantic inflow and mediterranean outflow currents on late quaternary sedimentary facies of the gulf of cadiz continental margin abstract the late quaternary pattern of sedimentary facies on the spanish gulf of cadiz continental shelf results from an interaction between a number of controlling factors that are dominated by the atlantic inflow currents flowing southeastward across the cadiz shelf toward the strait of gibraltar an inner shelf shoreface sand facies formed by shoaling waves is modified by the inflow currents to form a belt of sand dunes at 10 20 m that extends deeper and obliquely down paleo valleys as a result of southward down valley flow a mid shelf holocene mud facies progrades offshore from river mouth sources but atlantic inflow currents cause extensive progradation along shelf toward the southeast increased inflow current speeds near the strait of gibraltar and the strong mediterranean outflow currents there result in lack of mud deposition and development of a reworked transgressive sand dune facies across the entire southernmost shelf at the outer shelf edge and underlying the mid shelf mud and inner shelf sand facies is a late pleistocene to holocene transgressive sand sheet formed by the eustatic shoreline advance the late quaternary pattern of contourite deposits on the spanish gulf of cadiz continental slope results from an interaction between linear diapiric ridges that are oblique to slope contours and the mediterranean outflow current flowing northwestward parallel to the slope contours and down valleys between the ridges coincident with the northwestward decrease in outflow current speeds from the strait there is the following northwestward gradation of contourite sediment facies 1 upper slope sand to silt bed facies 2 sand dune facies on the upstream mid slope terrace 3 large mud wave facies on the lower slope 4 sediment drift facies banked against the diapiric ridges and 5 valley facies between the ridges the southeastern sediment drift facies closest to gibraltar contains medium fine sand beds interbedded with mud the adjacent valley floor facies is composed of gravelly shelly coarse to medium sand lags and large sand dunes on the valley margins by comparison the northwestern drift contains coarse silt interbeds and the adjacent valley floors exhibit small to medium sand dunes of fine sand because of the complex pattern of contour parallel and valley perpendicular flow paths of the mediterranean outflow current the larger scale bedforms and coarser grained sediment of valley facies trend perpendicular to the smaller scale bedforms and finer grained contourite deposits of adjacent sediment drift facies radiocarbon ages verify that the inner shelf shoreface sand facies sedimentation rate 7 1 cm kyr mid shelf mud facies maximum rate 234 cm kyr and surface sandy contourite layer of 0 2 1 2 m thickness on the cadiz slope 1 12 cm kyr have deposited during holocene time when high sea level results in maximum water depth over the gibraltar sill and full development of the atlantic inflow and mediterranean outflow currents the transgressive sand sheet of the shelf and the mud layer underlying the surface contourite sand sheet of the slope correlate respectively with the late pleistocene sea level lowstand and apparent weak mediterranean outflow current

residence time mineralization processes and groundwater origin within a carbonate coastal aquifer with a thick unsaturated zone this study aims at establishing groundwater residence times identifying mineralization processes and determining groundwater origins within a carbonate coastal aquifer with thick unsaturated zone and lying on a granitic depression a multi tracer approach major ions sio2 br ba sr2 18o 2h 13c 3h ne ar combined with a groundwater residence time determination using cfcs and sf6 allows defining the global setting of the study site a typical mineralization conditioned by the sea sprays and the carbonate matrix helped to validate the groundwater weighted residence times from using a binary mixing model terrigenic sf6 excesses have been detected and quantified which permits to identify a groundwater flow from the surrounding fractured granites towards the lower aquifer principally the use of cfcs and sf6 as a first hydrogeological investigation tool is possible and very relevant despite the thick unsaturated zone and the hydraulic connexion with a granitic environment

morphotectonic characterization of major bathymetric lineaments in gulf of cadiz africa iberia plate boundary insights from analogue modelling experiments abstract new high resolution multi beam bathymetry data allowed the recognition of several bathymetric lineaments ca 100 km long trending wnw ese in seafloor sediments of the gulf of cadiz offshore sw iberia the interpretation of multi channel mcs profiles crosscutting these lineaments showed that they are controlled by underlying deep seated faults which have endured a polyphase reactivation history to get insights on the recent tectonic evolution of these structures we performed two sets of analogue modelling experiments assuming 1 right lateral strike slip basement faulting and coupled passive shearing affecting an overlying soft cover and 2 low angle transpressive deformation along a narrow shear band overlying the fault our results show a good correlation between the experimentally obtained structural patterns and the natural morphotectonic lineaments allowing the use of some of the observed natural features as strain gauges based on this we conclude that the study lineaments correspond to the bathymetric expression of ongoing dextral wrenching reactivation of wnw ese pre existing faults and we estimate the age of this tectonic reactivation as being ca 1 8 ma i e form late pliocene to present day these characteristics agree with the most recent kinematic models derived from geodetic observations indicating that present day convergence between nubia and iberia is subparallel to the newly identified lineaments and occurs at a 4 mm yr rate

geodetic measurements of crustal deformation in the western mediterranean and europe geodetic measurements of crustal deformation over large areas deforming at slow rates 5 mm yr over more than 1000 km such as the western mediterranean and western europe are still a challenge because 1 these rates are close to the current resolution of the geodetic techniques 2 inaccuracies in the reference frame implementation may be on the same order as the tectonic velocities we present a new velocity field for western europe and the western mediterranean derived from a rigorous combination of 1 a selection of sites from the itrf2000 solution 2 a subset of sites from the european permanent gps network solution 3 a solution of the french national geodetic permanent gps network rgp and 4 a solution of a permanent gps network in the western alps regal the resulting velocity field describes horizontal crustal motion at 64 sites in western europe with an accuracy on the order of 1 mm yr or better its analysis shows that central europe behaves rigidly at a 0 4 mm yr level and can therefore be used to define a stable europe reference frame in that reference frame we find that most of europe including areas west of the rhine graben the iberian peninsula the ligurian basin and the corsica sardinian block behaves rigidly at a 0 5 mm yr level in a second step we map recently published geodetic results in the reference frame previously defined geodetic data confirm a counterclockwise rotation of the adriatic microplate with respect to stable europe that appears to control the strain pattern along its boundaries active deformation in the alps apennines and dinarides is probably driven by the independent motion of the adriatic plate rather than by the africa eurasia convergence the analysis of a global gps solution and recently published new estimates for the african plate kinematics indicate that the africa eurasia plate motion may be significantly different from the nuvel1a values in particular geodetic solutions show that the convergence rate between africa and stable europe may be 30 60 slower than the nuvelia prediction and rotated 10 30 counterclockwise in the mediterranean

sedimentary record of a tsunami during roman times bay of cadiz spain abstract historical data show that the gulf of cadiz has been exposed to destructive tsunamisduring at least the past 2000 yr the last tsunami was generated by the ad 1755 lisbon earthquake which affected the atlantic coasts of spain portugal and morocco today these littoral areas areintensely populated and the expected damage could be much greater tsunami studies are of greatimportance in helping to determine the recurrence interval of these events the presence of washover fan deposits on the inland margin of the valdelagrana spit bar cadiz spain indicates the occurrence of a high energy marine event ca 2300 cal yr bp historical geomorphological sedimentological palaeontological and geochronological data suggest that atsunami could have affected the area during roman times copyright 2002 john wiley sons ltd journal of quaternary science keywords tsunami deposits grain size palaeontology gulf of cadiz south spain introduction investigations of the geological records of past tsunamis arean important tool in helping to determine the recurrenceinterval of such events in a region these investigations arealso the only way of determining the prehistoric occurrenceand tsunami hazard in areas of infrequent seismic activity however at present it is dif cult to distinguish betweentsunami deposits and those laid down by other high energyevents such as a storm surge or hurricane recent work bygoff et al 2001 has helped to identify a series of diagnosticcriteria for tsunami deposits and research is underway tohighlight the differences between these and other high energyevents goff and chagu e goff in preparation j goff personalcommunication 2002 wave hydrodynamics the speci ccoastal setting morphology orientation availability and typeof sediments depositional environments tsunami magnitudeand tidal range are all factors that help to de ne the type andpreservation of tsunami deposits furthermore the ability todetermine the tsunamigenic source largely depends upon thepalaeoseismic and historical record e g goff et al 2001

random forests and evidential belief function based landslide susceptibility assessment in western mazandaran province iran in many parts of the world landslide susceptibility remains inadequately mapped due to the lack of both data and suitable methods for widespread implementation iran is one of those countries with extensive landslide problems with nearly 4900 large landslides occurring between 1993 and 2007 at the same time landslide susceptibility has not been assessed for the country random forest rf has recently been shown to be a suitable tool for such mapping in this study we further coupled the rf method with an evidential belief function ebf approach and tested the suitability for landslide susceptibility mapping for variable terrain and data conditions in the west of mazandaran province northern iran locations of earlier landslides were identified by interpreting aerial photographs and through extensive field surveys eleven conditioning factors were used in the rf model the spatial relationship between landslide occurrence and conditioning factors was then assessed using the data driven ebf model and ebf values paired to each map finally the ebf maps were used for running the rf model finally the efficiency of the rf ebf model was tested using the area under the curve to measure the success and prediction rates of the incorporated data this resulted in a success rate of 85 2 and a prediction rate of 81 8 the most important conditioning factors identified were lithology altitude distance from roads and land use respectively based on the overall assessment the combined rf and ebf approach was found to be objective and an applicable estimator that improves the predictive accuracy and controls for overfitting and thus useful for landslide susceptibility mapping at regional scales

poseidon s horses plate tectonics and earthquake storms in the late bronze age aegean and eastern mediterranean abstract in light of the accumulated evidence now published the oft denigrated suggestion that major earthquakes took place in the aegean and eastern mediterranean areas during the late 13th and early 12th centuries bc must be reconsidered a new study of earthquakes occurring in the aegean and eastern mediterranean region during the 20th century utilizing data recorded since the invention of seismic tracking devices shows that this area is criss crossed with major fault lines and that numerous temblors of magnitude 6 5 enough to destroy modern buildings let alone those of antiquity occur frequently it can be demonstrated that such major earthquakes often occur in groups known as sequences or storms in which one large quake is followed days months or even years later by others elsewhere on the now weakened fault line when a map of the areas in the aegean and eastern mediterranean region affected i e shaken by 20th centuryad earthquakes of magnitude 6 5 and greater and with an intensity of vii or greater is overlaid on robert drews map of sites destroyed in these same regions during the so called catastrophe near the end of the late bronze age it is readily apparent that virtually all of these lba sites lie within the affected high shaking areas while the evidence is not conclusive based on these new data we would suggest that an earthquake storm may have occurred in the late bronze age aegean and eastern mediterranean during the years 1225 1175bc this storm may have interacted with the other forces at work in these areas c 1200bc and merits consideration by archaeologists and prehistorians

earthquake induced rockfall hazard zoning abstract a methodology for quantitative probabilistic hazard zonation for earthquake induced rockfalls is presented and demonstrated in the area of friuli eastern italian alps affected by the 1976 mw 6 5 earthquake four rockfall datasets have been prepared both from historical data analysis and field surveys the methodology relies on a three dimensional hazard vector whose components include the rockfall kinetic energy the fly height and the annual frequency the values of the first two components are calculated for each location along the slope using the 3d rockfall runout simulator hy stone the rockfall annual frequency is assessed by multiplying the annual onset frequency by the simulated transit frequency the annual onset frequency is calculated through a procedure that combines the extent of unstable areas calculated for 10 different seismic hazard scenarios with different annual frequencies of occurrence and the magnitude relative frequency relationship of blocks as derived from the collected field data for each annual frequency of occurrence the unstable area is calculated as a function of morphometric and earthquake characteristics a series of discriminant analysis models using the rockfall datasets and dems of different resolution 1 and 10 m identified the controlling variables and verified the model robustness in contrast with previously published relationships we show that the slope curvature plays a relevant role in the computation of the unstable area

detecting himalayan glacial lake outburst floods from landsat time series abstract several thousands of moraine dammed and supraglacial lakes spread over the hindu kush himalayan hkh region and some have grown rapidly in past decades due to glacier retreat the sudden emptying of these lakes releases large volumes of water and sediment in destructive glacial lake outburst floods glofs one of the most publicised natural hazards to the rapidly growing himalayan population despite the growing number and size of glacial lakes the frequency of documented glofs is remarkably constant we explore this possible reporting bias and offer a new processing chain for establishing a more complete himalayan glof inventory we make use of the full seasonal archive of landsat images between 1988 and 2016 and track automatically where glofs left shrinking water bodies and tails of sediment at high elevations we trained a random forest classifier to generate fuzzy land cover maps for 2491 images achieving overall accuracies of 91 we developed a likelihood based change point technique to estimate the timing of glofs at the pixel scale our method objectively detected ten out of eleven documented glofs and another ten lakes that gave rise to previously unreported glofs we thus nearly doubled the existing glof record for a study area covering 10 of the hkh region remaining challenges for automatically detecting glofs include image insufficiently accurate co registration misclassifications in the land cover maps and image noise from clouds shadows or ice yet our processing chain is robust and has the potential for being applied on the greater hkh and mountain ranges elsewhere opening the door for objectively expanding the knowledge base on glof activity over the past three decades

mapping active faults offshore portugal 36 n 38 n implications for seismic hazard assessment along the southwest iberian margin swath bathymetry and acoustic backscatter data from the southwest iberian margin which hosts the present day boundary between the european and african plates reveal the surficial expression of several fault structures 100 km offshore of portugal high resolution and multichannel seismic reflection profiles collected perpendicular to these structures show folding and reverse faulting of the quaternary units suggesting present day tectonic activity successive submarine landslide deposits at the base of the scarps provide evidence of cyclic fault activity the location and dimension of these newly identified structures agree with the modeled source suggested for the a d 1755 lisbon earthquake and tsunami possibly the most destructive event in western europe during historical time these fault escarpments and deformed seafloor sediments associated with a cluster of shallow seismicity suggest that these thrusts are active and may pose a significant earthquake and tsunami hazard to the coasts of portugal spain and morocco

seismites an attempt at critical analysis and classification abstract the main types of seismites are reviewed following the proposed classification and are illustrated by our own case studies the large variety of seismites depends on the sedimentologic hydrodynamic and diagenetic characters of the deposits subject to seismic shocks on a given site generally different types of seismites cane be related to the same seismic event these peculiar but widespread sedimentary structures are not always univocal and may often be related to different causes therefore the structures discussed must necessarily be placed in a detailed geological context

natural fluorinated organics in fluorite and rocks results of measurements of fluorinated compounds in gasses extracted from igneous and metamorphic rocks are reported a new extraction method analogous to a pepper mill for geological samples is described it permits extraction at low temperatures and ensures a rapid transfer of extracted gases from active surfaces to cryogenic pre concentration loop values for cf4 cf3cl cf2cl2 cfcl3 chf3 sf6 and nf3 in fluorites granites basalts and other igneous and metamorphic rocks are reported it is proposed that trifluoroacetic acid tfa that was recently discovered in various environmental archives could also origin from similar geogenic sources

kinematics of the iberia maghreb plate contact from seismic moment tensors and gps observations the iberian peninsula and the maghreb experience moderate earthquake activity and oblique nw se convergence between africa and eurasia at a rate of 5 mm yr coeval extension in the alboran basin and a n35 e trending band of active left lateral shear deformation in the alboran betic region are not straightforward to understand in the context of regional shortening and evidence complexity of deformation at the plate contact we estimate 86 seismic moment tensors mw 3 3 to 6 9 from time domain inversion of near regional waveforms in an intermediate period band those and previous moment tensors are used to describe regional faulting style and calculate average stress tensors the solutions associated to the trans alboran shear zone show predominantly strike slip faulting and indicate a clockwise rotation of the largest principal stress orientation compared to the regional convergence direction 1 at n350 e at the n algerian and sw iberian margins reverse faulting solutions dominate corresponding to n350 e and n310 e compression respectively over most of the betic range and intraplate iberia we observe predominately normal faulting and wsw ene extension 3 at n240 e from gps observations we estimate that more than 3 mm yr of african nubian eurasian plate convergence are currently accommodated at the n algerian margin 2 mm yr in the moroccan atlas and 2 mm yr at the sw iberian margin 2 mm yr is a reasonable estimate for convergence within the alboran region while alboran extension can be quantified as 2 5 mm yr along the stretching direction n240 e superposition of both motions explains the observed left lateral transtensional regime in the trans alboran shear zone two potential driving mechanisms of differential motion of the alboran betic gibraltar domain may coexist in the region a secondary stress source other than plate convergence related to regional scale dynamic processes in the upper mantle of the alboran region as well as drag from the continental scale motion of the nubian plate along the southern limit of the region in the atlantic ocean the 3 5 mm yr westward motion of the gibraltar arc relative to intraplate iberia can be accommodated at the transpressive sw iberian margin while available gps observations do not support an active subduction process in this area

seismicity source mechanisms and tectonics of the azores gibraltar plate boundary abstract a study and partial revision of the seismicity and source mechanisms of earthquakes are presented for the oceanic plate boundary of eurasia and africa from the azores islands to the strait of gibraltar focal mechanisms of 36 earthquakes wave form modelling of 4 and seismic moments and dimensions of 28 have been calculated these results indicate that the boundary is divided into three sections with different characteristics the azores the central section and the east section the azores section has high seismicity of moderate magnitude and a low slip rate 0 76 cm yr the predominant mechanism is normal or transform faulting with horizontal tensions on average in a n25 e direction in the central section large earthquakes occur with strike slip right lateral motion along faults in an e w direction there is a high slip rate 3 39 cm yr the east section is of more complex nature large earthquakes also occur but the predominant mechanism is reverse faulting with a horizontal pressure axis in the n30 w direction resulting in underthrusting of africa from the slip vectors the pole of rotation for the african plate is located at 28 2 n 21 1 w nearer to the boundary than previous locations close to the continent there is a continuation in the ocean crust of some structural features of the iberian peninsula

evidence of high energy events in the geological record mid holocene evolution of the southwestern donana national park sw spain abstract four phases are distinguished in the mid holocene evolution of the southwestern donana national park sw spain based on the multidisciplinary study of sediments in drill cores in the oldest phase 5500 5400 cal years bp a coastal brackish lagoon occupied the central part of the study area partly enclosed by the donana spit and limited by fluvial levees an evolution from subtidal to intertidal conditions characterized the areas located close to the inner side of the donana spit during the same phase the following phase 5400 5200 cal years bp is characterized by a high energy event tsunami which caused the breakthrough of the donana spit and the creation of new littoral strands in the inner areas in the first period of the third phase 5200 4200 cal years bp estuarine infilling was probably the dominant process with the accumulation of phyllosilicate rich clays in the lagoon bed this was followed by a renewed phase of instability 4200 4100 cal years bp indicated by the presence of fine storm lain deposits and thicker probably tsunami induced shelly deposits the last phase 4100 3700 cal years bp comprises a an infilling period with a diminution of the marine influence and b two new high energy events which caused the erosion of the donana spit and the creation of new cheniers in the last 7000 years the comparison of these results with a revision of both geological and historical records has revealed the occurrence of twenty tsunamis at least during this period in portugal and southern spain evidences of these high energy events are washover fans bioclastic coarse sized layers within salt marsh deposits or the presence of giant boulders and pebbles the determination of the recurrence period is very difficult owing to the very scarce data although our data and other authors do not discard a possible periodicity of 2000 years for a cycle of two events separated by 300 400 years

alluvial gully erosion an example from the mitchell fluvial megafan queensland australia considerable attention has been focused on the role of gullies as a contributor to contemporary sediment loads of rivers in australia in southern australia rapid acceleration of hillslope gully erosion has been widely documented in the post european period last 200 years in the northern australian tropics however gully erosion processes operating along alluvial plains have not been well documented and can differ substantially from those gullies eroding into colluvium on hillslopes aerial reconnaissance surveys in 2004 along 13 500 km of the main stem rivers that drain into the gulf of carpentaria goc identified extensive areas of alluvial lands that have been impacted by a pervasive form of gully erosion more detailed remote sensing based mapping within the 31 000 km2 mitchell river fluvial megafan has identified that active gullying into alluvium occupies 0 4 129 km2 of the lower mitchell catchment these alluvial gullies are concentrated along main drainage channels and their scarp heights are highly correlated to the local relief between the floodplain and river thalweg while river incision into the megafan since the pleistocene has developed the relief potential for erosion other factors such as floodplain hydrology soil dispersibility and vegetation also influence the distribution of gullies in this paper we present a conceptual model of alluvial gullies and contend that they represent a distinct end member in the continuum of gully forms that have been described in the geomorphic literature an understanding of the processes driving this form of alluvial gullying can only be gained when they are differentiated from widely described colluvial hillslope gully models and theories we present evidence of type examples of alluvial gullying in the mitchell and through analysis of their distribution and morphology at different scales highlight some of the key mechanisms that are potentially initiating these features and driving their expansion copyright 2009 john wiley sons ltd

soft sediment deformation structures interpreted as seismites in lacustrine sediments of the prebetic zone se spain and their potential use as indicators of earthquake magnitudes during the late miocene lacustrine formations of late miocene age in the prebetic area se spain show several types of deformational structures that are interpreted as seismites they are present in both marginal and deep lacustrine facies seismites formed in marginal lake environments comprise sand dikes pillows and intruded and fractured gravels in deep lacustrine facies the seismites are represented by pseudonodules mushroom like silts protruding into laminites mixed layers disturbed varved lamination and loop bedding the measured orientations of these structures are consistent with the orientations of the main faults limiting the basins showing that their origin is clearly related to the tectonic stress field that prevailed in the region during the late miocene the magnitudes of the earthquakes that deformed the sediments have been estimated after published data from both ancient and recent lake deposits accumulated in tectonic active regions elsewhere a rank of earthquake magnitudes with two end members i e the lowest magnitudes recorded by loop bedding in laminites and the highest magnitudes represented by intruded and fractured gravels is proposed

predictive modeling of bedrock outcrops and associated shallow soil in upland glaciated landscapes abstract identifying the areal extent of bedrock outcrops and shallow soils has important implications for understanding spatial patterns in vegetation composition and productivity stream chemistry gradients and hydrologic and soil properties of landscapes manual methods of delineating bedrock outcrops and associated shallow soils are still commonly employed but they are expensive to implement over broad areas and often limited by representation of polygon units few studies have automated the delineation of bedrock outcrops these focused on delineation approaches in landscapes with rapidly eroding hillslopes and sparse vegetation the objectives of this study were to assess the accuracy of visually interpreting high resolution relief maps for locating bedrock outcrops and associated shallow soil boss

a review of the physical oceanography of the mediterranean outflow abstract the physical oceanography of the mediterranean sea is reviewed with particular emphasis on the mediterranean outflow in the gulf of cadiz in this region the dense mediterranean water forms a high velocity bottom current that interacts strongly with the sea floor the major energy source for the plume comes from the release of potential energy as the plume descends the continental slope and the major energy sink is work against bottom stress which is as large as 4 pa where the plume begins to descend the continental slope in this region the current makes a nearly inertial turn that would otherwise appear to be steered by the underlying topography the mediterranean plume entrains the overlying north atlantic central water and thereby loses much of its density anomaly the mixed mediterranean water becomes neutrally buoyant in the lower portion of the north atlantic thermocline near cape st vincent there are then two preferred transport modes having somewhat different temperature and salinity whose distinct characteristics can be found far into the open north atlantic the temperature salinity and volume of the mediterranean water in the strait of gibraltar and in the gulf of cadiz appear to be roughly constant since modern measurements have been made the estimated westward transport of mediterranean water has gone down considerably as direct measurement techniques have been applied a recent estimate is that the westward transport of pure mediterranean water is only about a half a sv 1 sv 106 m3 s 1 the transport of mixed mediterranean water in the western gulf of cadiz is larger by about a factor of three or four because of the entrainment of north atlantic water

tectonic activity as a significant source of crustal tetrafluoromethane emissions to the atmosphere observations in groundwaters along the san andreas fault abstract tetrafluoromethane cf 4 concentrations were measured in 14 groundwater samples from the cuyama valley mil potrero and cuddy valley aquifers along the big bend section of the san andreas fault system safs in california to assess whether tectonic activity in this region is a significant source of crustal cf 4 to the atmosphere dissolved cf 4 concentrations in all groundwater samples but one were elevated with respect to estimated recharge concentrations including entrainment of excess air during recharge c r e 30 fmol kg 1 h 2 o indicating subsurface addition of cf 4 to these groundwaters groundwaters in the cuyama valley contain small cf 4 excesses 0 1 9 times c r e which may be attributed to an in situ release from weathering and a minor addition of deep crustal cf 4 introduced to the shallow groundwater through nearby faults cf 4 excesses in groundwaters within 200 m of the safs are larger 10 980 times c r e and indicate the presence of a deep crustal flux of cf 4 that is likely associated with the physical alteration of silicate minerals in the shear zone of the safs extrapolating cf 4 flux rates observed in this study to the full extent of the safs 1300 km 20 100 km suggests that the safs potentially emits 0 3 1 10 1 kg cf 4 yr 1 to the earth s surface for comparison the chemical weathering of 7 5 10 4 km 2 of granitic rock in california is estimated to release 0 019 3 2 10 1 kg cf 4 yr 1 tectonic activity is likely an important and potentially the dominant driver of natural emissions of cf 4 to the atmosphere variations in preindustrial atmospheric cf 4 as observed in paleo archives such as ice cores may therefore represent changes in both continental weathering and tectonic activity including changes driven by variations in continental ice cover during glacial interglacial transitions

looking for clues to paleoceanographic imprints a diagnosis of the gulf of cadiz contourite depositional systems a new morphosedimentary map of the gulf of cadiz is presented showing the contourite depositional system on the gulf s middle slope this map is constructed from a broad da tabase provided by the spanish research council and the u s naval research laboratory our map shows that this contourite depositional system comprises five morphosedimentary sectors 1 proximal scour and sand ribbons 2 overflow sedimentary lobe 3 channels and ridges 4 contourite deposition and 5 submarine canyons the gulf of cadiz con tourite depositional system stems directly from the interaction between mediterranean out flow water and the seafloor its morphosedimentary sectors are clearly related to the sys tematic deceleration of the mediterranean outflow waters westward branches bathymetric stress on the margin and the coriolis force the slope s depositional system can be consid ered as a mixed contourite and turbidite system i e a detached combined drift and fan

earthquake magnitude frequency epicentral distance and soft sediment deformation in sedimentary basins abstract empirical equations available for earthquake magnitude frequency and the maximum epicentral distance of liquefied sites versus magnitude are combined with the characteristic instantaneous sediment deposition rate at a station in a sedimentary basin to form a model for the local stratigraphic frequency of earthquake induced soft sediment deformation structures both the style of sedimentation and the characteristics of the earthquake source combine to determine the pattern of incidence of the structures in a basin the model is probably most directly applicable to the geodynamic interpretation of fluvial basins in which substantial volumes of readily liquefied sands accumulate at high local short term rates

large scale mapping of gully affected areas an approach integrating google earth images and terrain skeleton information abstract the gully erosion process poses a threat to the ecological environment land management and agronomic productivity although current studies on gully feature mapping conducted at hill slope or catchment scales have yielded good performances the approach for large scale gully affected areas mapping is still challenging this study demonstrates a novel approach inspired by the relationship between gully distribution and surface runoff the google earth ge images and aster gdem were applied to explore the feasibility of open data source in large scale gully mapping the ge images were used for the initial classification based on object based image analysis and random forest model the drainage network obtained from the digital elevation model was generated as the terrain skeleton which controls the gully bodies the rule sets for removing commission and omission errors were developed based on the spatial relationship between the segments and drainage networks the experiment was conducted at one of the most serious erosion regions in the loess plateau with an area of 154 000 km2 owing to the novel integration strategy of image and topographic features the mapping results prove the approach extracts gully affected areas efficiently with acceptable accuracy overall accuracy is 78 80 even within the complex gully zone compared with visual interoperation the proposed approach provides a potential tool to erosion research community that could also be of interest to geomorphologists and policy makers

geologic and topographic controls on fast flow in the laurentide and cordilleran ice sheets ice streams are fast flowing arteries which play a vital role in the dynamics and mass balance of present day ice sheets although not fully understood fast flow dynamics are intimately coupled with geologic topographic thermal and hydrologic conditions of the underlying bed these are difficult observables beneath contemporary ice sheets hindering elucidation of the processes which govern ice streaxn behavior for past ice sheets the problem is antithetic geologic evidence of former ice streams exists but spatim and temporal histories are uncertain however detailed knowledge of bed geology and topography is available in many places we take advantage of this information to compile terrain characteristics relevant to fast flow dynamics in the laurentide and cordilleran ice sheets using seed points where fast flowing wisconsinan ice has been geologically inferred discriminant analysis of a suite of north american geologic and topographic properties yields a concise measure of ice bed coupling strength our analysis suggests that the interior plains and continental shelf regions of north america have low basal coupling relative to areas of variable relief or exposed bedrock in the cordillera and on the canadian shield we conclude that the interior plains and continental shelves are both topographically and geologically predisposed to large scale basal flows i e ice streaxns or surge lobes this result holds independent of whether the mechanism of fast flow is sediment deformation or decoupled sliding over the bed

the use of distinct disciplines to investigate past earthquakes abstract the investigation of past earthquakes can be approached in many different ways with a large variety of methods and techniques this is mainly due to the complexity of this natural phenomenon in both its genetic aspects and consequential ones in the present note we briefly analyse the peculiarities of instrumental seismology historical seismology archaeoseismology and earthquake geology but especially we emphasise the major differences among these four distinct approaches in order to better define and clearly separate these disciplines in terms of appropriate tools to be applied and possible outcomes to be expected an alternative point of view is proposed based on the source of information and not on a chronological distribution as commonly accepted in the literature although multidisciplinarity is a common approach for investigating past earthquakes each one of the discussed disciplines has its own peculiarities advantages and limitations and researchers should be aware of this

digital terrain modelling a review of hydrological geomorphological and biological applications the topography of a catchment has a major impact on the hydrological geomorphological and biological processes active in the landscape the spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques many geographic information systems are being developed that store topographic information as the primary data for analysing water resource and biological problems furthermore topography can be used to develop more physically realistic structures for hydrologic and water quality models that directly account for the impact of topography on the hydrology digital elevation models are the primary data used in the analysis of catchment topography we describe elevation data sources digital elevation model structures and the analysis of digital elevation data for hydrological geomorphological and biological applications some hydrologic models that make use of digital representations of topography are also considered

neogene through quaternary tectonic reactivation of sw iberian passive margin southwest portugal the gulf of cadiz and morocco are under the potential threat of natural hazards linked to seismicity and tsunami generation we report the results of two multi channel seismic mcs surveys carried out in 1992 and 1998 along the continental margin and oceanic crust of sw iberia this mcs data set shows the evidence of the compressional deformation which involves both the continental and the oceanic crust of the study area the area of deformation extends from the southern border of the tagus abyssal plain to the seine abyssal plain encompassing the continental margin of sw portugal most of the structures observed are probably related to a mid miocene phase of africa europe plate convergence in this paper we discuss the recent advances on the identification of the tectonic structures that are still active and that may generate great earthquakes and tsunamis the tectonic structures identified are located respectively at the guadalquivir bank along the eastern border of the horseshoe abyssal plain and along the southern continental slope of sw portugal

water masses and circulation in the western alboran sea and in the straits of gibraltar abstract some new elements of alboran sea circulation and water masses in close connection with flows through the straits of gibraltar are presented a general description is given of water masses found in 1981 during mediprod iv cruise from the gulf of cadiz to the gulf of lions followed by a brief review of the conditions found in the straits of gibraltar based on 1981 and 1961 observations the hydrological structure vertical and horizontal and surface and bottom currents typical of the western alboran sea are analysed we present some detailed observations about vertical currents in the deep waters near the straits and finally we analyse the characteristics of the mediterranean overflow through the straits our conclusions in part confirm those of bryden and stommel 1982 and in part shed light on the general pattern of the mediterranean currents entering the alboran sea from the east however considering the suggestion of stommel bryden and mangelsdorf 1973 that the deep currents in the interior of the western mediterranean basin are basically controlled by a bernoulli flow induced by the intense currents in the straits and the weak vertical stratification in the mediterranean we suggest that an interaction of a large scale circulation pattern and the topography of the alboran basin which is much shallower than the western mediterranean basin may play a major role in controlling hydraulically the deep mediterranean waters overflow a detailed water mass analysis of 1981 data and comparison with previous data revealed a time and space variability in the mediterranean waters the scales of this variability are unknown but the s variations make it difficult to make assumptions as to the depth of origin of the deep waters found in the alboran sea which flow into the atlantic ocean over the gibraltar sill

rapid development and infilling of a buried gully under cropland central belgium abstract analysis of contemporary and past gully erosion and infilling processes allowed to reconstruct the long term evolution of a permanent gully system under cropland an active and a buried gully under cropland were investigated the recent sediment deposits within the active gully adjacent to the buried gully showed that the recent gully was filling in at a mean rate of 6 4 cm a 1 in the buried gully several erosion and deposition phases could be identified and the type of deposited sediments revealed a complex infilling history charcoal pottery and brick fragments of different sizes were found at all depths of the gully infilling their age indicates that the first gully incised after the midst of the 17th century most probably in the second half of the 18th century or the early 19th century gully morphology and analogy with the processes in the recent gully indicate that the buried gully filled in rapidly overall five cycles of cut and fill occurred in 350 years or less and four cycles even within little less than a few decades indicating that gully development and infilling under cropland can be very rapid processes

tetrafluoromethane in the deep north pacific ocean 1 dissolved tetrafluoromethane cf4 has been measured for the first time in the north pacific ocean surface water collected during calm weather is near equilibrium with the modern atmosphere deep water isolated from atmospheric exchange for centuries is near equilibrium with the preindustrial atmosphere after accounting for an expected 5 addition of this low solubility gas due to air injection during high latitude deep water formation these results strongly suggest that dissolved cf4 is conservative in seawater and that the oceanic imprint of anthropogenic increases in atmospheric cf4 can be used as a time dependent tracer of ocean ventilation and subsurface circulation processes although the continental lithosphere is a source of natural atmospheric cf4 we find no evidence of an oceanic lithospheric cf4 input into deep pacific waters the estimated upper limit of a potential oceanic lithospheric cf4 flux to the global atmosphere is on the order of 4 of that from the continental lithosphere

stress on the mediterranean outflow plume part ii turbulent dissipation and shear measurements abstract bottom and interfacial stresses on the mediterranean outflow plume are estimated using vertical profiles of turbulent dissipation and velocity collected in the gulf of cadiz turbulent dissipation is high throughout the plume with a local minimum often present near the plume nose depth of maximum downstream velocity bottom stresses are estimated by applying a log layer model to the dissipation measurements the dissipation measurements are also divided by plume scale vertical shear from the horizontal velocity profiles to construct profiles of stress within the plume the mean stress estimates in the bottom layer agree well with those calculated in the log layer from the dissipation measurements alone the bottom layer means are slightly larger than those of the interfacial layer the maximum stresses in each layer are uncertain since they depend on the ill defined shape of the stress profiles within the plume dissipation derived stress estimates in the log layer and those from dissipation

new insights on speleoseismology the geothermal gradient and heat flow values in caves for the study of active faults abstract normally in paleoseismology the study of the tectonic slip rate is performed in trenches on the fault scarp or by the estimation of fault movements from the geomorphic features in this work we have carried out a paleoseismic analysis of the benis fault located in southeast spain combined with a geothermal analysis inside a deep cave related to the fault 350 m thus we have estimated the last earthquake magnitude and time of occurrence from evidence of ceiling collapse and displaced carbonate blocks inside a cave which is developed across the fault the magnitude was obtained from the application of the empirical relationship of the fault parameters and coseismic vertical displacement yielding a value ranging between m 5 9 and m 6 5 moreover we dated this paleoearthquake by the paleontological record of a lynx pardinus spelaea with an age of 65 18 ka bp additionally we have measured the thermal profile of the benis cave 350 m of depth from single rock point temperature measurements during 2 years the temperature profile shows three different parts inside the cave the shallow heterogeneous thermal zone till 50 m depth the homogeneous thermal zone 150 m till with constant temperature and the hetero thermal deep zone deeper than 150 m and till the deepest zone 350 m furthermore we have estimated the vertical geothermal gradient 1 85 c 100 m for the deepest zone 150 290 m the temperature increases with depth showing a reverse thermal profile in comparison with normal gradients in deep caves finally we have calculated the heat flux of 0 46 mwm 2

seismotectonics of the ibero maghrebian region abstract a study of the seismotectonics of the ibero maghrebian region is presented as deduced from main geological features seismicity and focal mechanism data the hypocentral distribution of shallow intermediate depth and deep earthquakes is analyzed the direction of the stress distribution is inferred from the focal mechanism of 24 selected events a seismotectonic framework summarizing these results together with the main geological features shows that a nw se general direction of horizontal compressive stresses is present in the region with a localized zone of horizontal tensions in the betics and the alboran sea the presence of intermediate depth and deep earthquakes is tentatively explained as caused by two consecutive processes of subduction

extraction of multi scale landslide morphological features based on local g i using airborne lidar derived dem abstract for automatic landslide detection landslide morphological features should be quantitatively expressed and extracted high resolution digital elevation models dems derived from airborne light detection and ranging lidar data allow fine scale morphological features to be extracted but noise in dems influences morphological feature extraction and the multi scale nature of landslide features should be considered this paper proposes a method to extract landslide morphological features characterized by homogeneous spatial patterns both profile and tangential curvature are utilized to quantify land surface morphology and a local gi statistic is calculated for each cell to identify significant patterns of clustering of similar morphometric values the method was tested on both synthetic surfaces simulating natural terrain and airborne lidar data acquired over an area dominated by shallow debris slides and flows the test results of the synthetic data indicate that the concave and convex morphologies of the simulated terrain features at different scales and distinctness could be recognized using the proposed method even when random noise was added to the synthetic data in the test area cells with large local gi values were extracted at a specified significance level from the profile and the tangential curvature image generated from the lidar derived 1 m dem the morphologies of landslide main scarps source areas and trails were clearly indicated and the morphological features were represented by clusters of extracted cells a comparison with the morphological feature extraction method based on curvature thresholds proved the proposed method s robustness to dem noise when verified against a landslide inventory the morphological features of almost all recent 10 years landslides were extracted this finding indicates that the proposed method can facilitate landslide detection although the cell clusters extracted from curvature images should be filtered using a filtering strategy based on supplementary information provided by expert knowledge or other data sources

do norwegian deep water coral reefs rely on seeping fluids hundreds of large coral reefs up to 45 m high exist a on the continental shelf and b on morainic threshold ridges in fjords of northern mid and southwest norway they occur in water depths between 400 and 40 m and contain a large variety of megafauna the most common frame building coral is lophelia pertusa l the oldest reef found to date is 8600 calendar years old determined by radiocarbon dating of buried lophelia skeleton even though many of these reefs have been known to science for over 200 years there is as yet no viable and unifying hypothesis to explain their existence in deep cool waters other than perhaps the hydraulic theory presented by the author in 1990 it states that primary producers mainly bacteria are locally formed and concentrated at reef locations due to seepage of light hydrocarbons mainly methane on the continental shelf and nutrient rich groundwater in the fjords the hydraulic theory is supported by the following topographic reflection seismic and geochemical indicators for the continental shelf reefs a seaward dipping sedimentary permeable strata enhanced acoustic seismic reflectors adjacent pockmark craters locally elevated light hydrocarbon sediment content locally elevated seawater methane content for the fjord reefs b threshold morainic substratum rather than adjacent hardrock substratum sub surface dipping sedimentary layers h2s smell of near surface sediment samples these indicators or reef associated observations have been documented by german british and norwegian researchers over the last 10 15 years however all the listed indicators do not necessarily occur at each of the respective shelf and fjord reef locations simultaneously

using hilltop curvature to derive the spatial distribution of erosion rates 1 erosion rates dictate the morphology of landscapes and therefore quantifying them is a critical part of many geomorphic studies methods to directly measure erosion rates are expensive and time consuming whereas topographic analysis facilitates prediction of erosion rates rapidly and over large spatial extents if hillslope sediment flux is nonlinearly dependent on slope then the curvature of hilltops will be linearly proportional to erosion rates in this contribution we develop new techniques to extract hilltop networks and sample their adjacent hillslopes in order to test the utility of hilltop curvature for estimating erosion rates using high resolution 1 m digital elevation data published and new cosmogenic radionuclide analyses in the feather river basin california suggest that erosion rates vary by over an order of magnitude 10 to 250 mm kyr 1 hilltop curvature increases with erosion rates allowing calibration of the hillslope sediment transport coefficient which controls the relationship between gradient and sediment flux having constraints on sediment transport efficiency allows estimation of erosion rates throughout the landscape by mapping the spatial distribution of hilltop curvature additionally we show that hilltop curvature continues to increase with rising erosion rates after gradient limited hillslopes have emerged hence hilltop curvature can potentially reflect higher erosion rates than can be predicted by hillslope gradient providing soil production on hilltops can keep pace with erosion finally hilltop curvature can be used to estimate erosion rates in landscapes undergoing a transient adjustment to changing boundary conditions if the response timescale of hillslopes is short relative to channels