passive seismic reflection interferometry a case study from the aquistore co2 storage site saskatchewan canada abstractseismic reflection interferometry has recently been tested in a few resource exploration applications we have evaluated passive seismic interferometry results for data from the aquistore co2 storage site saskatchewan canada with the objective of testing the method s ability to image the subsurface geology and its potential for time lapse imaging we analyzed passive seismic data recorded along two perpendicular geophone lines for two time periods that include 23 days in june 2014 and 13 days in february 2015 beam forming analysis showed that a nearby power plant is the dominant source of ambient noise we retrieved virtual shot gathers not only by correlating long noise panels 1 h for both recording periods but also by correlating shorter noise panels 10 s from two days of each recording period we applied illumination diagnosis to the noise panels from the two chosen days for each period to help suppress the surface waves comparisons of the common midpoints stacked sections resulting

concrete dams as seismic imaging sources 1 we obtained noise correlation functions ncf in northern montana from broadband data that include p and s wave first arrivals and short period surface waves for frequencies extending to nearly 15 hz at offsets of 5 17 km using ambient resonant vibrations of a concrete gravity arch dam as seismic source a seismograph operated close to the dam acted as a virtual source with a compact autocorrelation function making it feasible to use short duration cross correlation time windows to obtain a larger number of ncf stacks with impulsive high frequency body wave first arrivals from recording durations of a single day to several weeks

developing earth models with full waveform inversion exploration in more geologically complex areas requires new methodologies in its quest to answer these new challenges the oil and gas industry has moved from ray based imaging to finite difference wave equation migration to achieve better subsurface descriptions of target zone and reservoirs notable in this progression is the movement from ray traced kirchhoff algorithms through one way wave equation methods to use the acoustic two way wave equation

magmatic evolution of a volcano studied by 230th 238u disequilibrium and trace elements systematics the etna case age determinations of several lava flows from etna through 230th 238u disequilibrium internal isochrons yield a precise chronology of the volcano s history for the last 200 000 years and emphasize the main episodes in the formation of this huge complex strato volcano study of 230th232th 0 initial ratios of lavas together with their trace element compositions yields a consistent model of magmatic evolution implying the existence for 200 000 years of a deep reservoir of alkalic magma periodically mixed with magmas of tholeiitic affinity these short periods of mixing appear to be related to the formation of the large calderas of etna in addition to these processes affecting the deep reservoir fractional crystallization also occurred in more superficial levels of the volcanic edifice thereby yielding several series of differentiation of relatively short duration as for its geochemistry etna s volcanism is of oceanic type but with its own characteristics and in a peculiar geodynamic context at the edge of the african plate

finite difference modeling experiments for seismic interferometry in passive seismic interferometry new reflection data can be retrieved by crosscorrelating recorded noise data the quality of the retrieved reflection data is among others dependent on the duration and number of passive sources present during the recording time the source distribution and the source strength to investigate these relations we set up several numerical modeling studies to carry out the modeling in a feasible time we design a finite difference algorithm for the simulation of long duration passive seismic measurements of band limited noise signatures in the subsurface novel features of the algorithm include the modeling of thousands of randomly placed sources during one modeling run the modeling experiments explore the dependency relation between the retrieved reflections and source signature length source positions number of sources and source amplitude variations from these experiments we observed that the positions of the passive sources and the length of the source signals are of direct influence on the quality of the retrieved reflections random amplitude variations among source signals do not seem to have a big impact on the retrieved reflections

evolution of the etna volcano information from the southern wall of the valle del bove caldera abstract the greater part of etna can be regarded as a complex strato shield volcano constructed from the overlapping products of several centres of trachy basaltic activity the valle del bove is a horse shoe shaped caldera 8 km long and 5 km wide cut into the eastern flanks of etna the caldera is one of the few areas on the volcano where historic eruptions have not obscured the products of pre historic centres of activity and these are well exposed in the cliff walls surrounding the caldera examination of these older volcanics provides important information on the eruptive style and internal plumbing of the etna volcano during pre historic times and suggests that both were significantly different from the present day much of the southern wall of the valle del bove represents a surviving portion of the trifoglietto ii volcano the largest pre historic centre of activity a stratigraphy is constructed for the southern wall the trifoglietto ii lavas and pyroclastics rest unconformably upon the eroded remnants of an older centre and are themselves overlain by the products of younger centres all the lavas exposed in the southern wall are of alkalic affinity and comprise a trachybasaltic suite ranging from hawaiite to benmoreite variation in the chemistry of the lavas can be explained by their differentiation at high levels in the crust from a more basic magma of alkali olivine basalt hawaiite composition an anomalous trend in the tio 2 content of the trifoglietto ii lavas may be explained by the fractionation of kaersutite ti rich amphibole a study has been made of the numerous dykes exposed in the walls of the valle del bove the alignments of which parallel trends which are important on etna at the present time it is proposed that the initial opening of the valle del bove occurred sometime between 20 000 and 10 000 y b p as a result of a phreatic or phreato magmatic explosion near the base of the eastern flank of trifoglietto ii this is visualised as triggering a slope failure and resulting in the destruction of much of the centre by a catastrophic landslide this mechanism has much in common with the explosive eruptions which produced both the bandai san japan caldera in 1888 and the mount st helens caldera in may 1980

sediment transport by dry ravel 1 dry ravel is a general term that describes the rolling bouncing and sliding of individual particles down a slope and is a dominant hillslope sediment transport process in steep arid and semiarid landscapes during fires particles can be mobilized by the collapse of sediment wedges that have accumulated behind vegetation on a daily basis particles may be mobilized by bioturbation and by small landslides experiments on a dry ravel flume indicate that a basic expression of the momentum equation predicts the distance traveled by particles propelled down a rough surface this equation is further elaborated to produce a nonlinear slope dependent transport equation for dry ravel that represents the rate at which sediment crosses a contour width of slope sediment traps installed on two hillslope transects near santa barbara california measured the flux from dry ravel initiated by bioturbation and the data support the form of the equation additionally a physical model based on the infinite slope stability analysis is proposed for the initiation of dry ravel by landsliding the analytical result from this model is supported by experiments and field data reported by others

alluvial fans on volcanic islands a morphometric perspective sao vicente cape verde abstract the distribution morphology and development of volcanic island alluvial fans are investigated using sao vicente from the cape verde volcanic chain east central atlantic ocean this is a tectonically and volcanically inactive dryland setting comprising an eroded plio pleistocene composite volcano overlying a submarine shield volcano we mapped 228 alluvial fans quantifying fan f and catchment c morphological properties area a gradient g relief r length l fans and catchments of varying size and gradient are distributed around the island coastal margins 6 and along interior valley sides 94 regression results i e ve ve slopes of best fit lines conformed to broader fan research but with weak correlations and coefficient exponent values outside or at the lower end of values reported from non volcanic settings analysis of fan area and gradient vs catchment area regression residuals revealed fans were dominated by small steep gradient 28 and large low gradient forms 39 fan building space is a fundamental control specifically linked to volcano structure but with interplay between rock strength base level and climate fans around the volcanic edifice flanks are uncommon due to steep flank slopes where flank margin fans occur they are typically small and steep forms due to marine erosion fans along flank incised valleys are common large low gradient fans are associated with a major volcanic rift aligned valley structure with extensive erosion into altered and weathered edifice core lithologies small steep gradient fans are associated with edifice flank valleys steeper and narrower valley forms reflect incision into stronger lithologies of the composite volcano flanks restricting fan building space fans located within the volcano central depression are amongst the largest and lowest gradient types building into the eroded and unconfined edifice core space coalescence apex toe incision toe erosion and catchment stream channel backfilling displayed by most fans suggest landscape erosion dominates during more arid periods e g interglacials with the dryland setting generating limited sediment and insufficient flood runoff for transport and fan deposition fan building likely occurs during wetter periods linked to quaternary climate variability quaternary eustatic variations are relevant for the volcano edifice margins where sea level changes control fan building space and erosion

geometric and kinematic variations along the active pernicana fault implication for the dynamics of mount etna ne flank italy abstract geological and structural analyses and ground deformation measurements performed along the eastern portion of the pernicana fault system and its splay segments allow the structural setting and the kinematic behaviour of the fault to be defined in addition the interrelationship between the deformation style of fault segments and the variations of the volcanic pile thickness along the fault strike are investigated using detailed sedimentary basement data brittle deformation dominates the n105 fault segment where the volcanic pile is more than 200 m thick with the development of a well defined fault plane characterised by main left lateral kinematics the transtensive deformation of the n105 fault is partitioned eastward at rocca campana to a main n120 segment here this segment crosses a culmination of the sedimentary basement close to vena village where the deformation pattern of the thin volcanic pile less than 100 m thick is influenced by the more ductile behaviour of the basement generating local short structures with different orientation and kinematics in the southern block of the fault on the northern one short e w trending faults show left lateral displacements with a minor reverse component on south dipping planes this kinematics is related to the oblique orientation of the n120 segment with respect to the seaward motion of the ne flank of etna on the whole the compressive component of the deformation affecting the n120 segment of the pernicana fault system generates a positive flower structure

long term uplift rate of the etna volcano basement southern italy based on biochronological data from pleistocene sediments the eastern flank of mt etna volcano rests on pleistocene marine sediments which unconformably cover the apenninic maghrebian chain units a quantitative biostratigraphic analysis was carried out based on the calcareous nannofossil content of the pleistocene deposits outcropping along the s and ne periphery of the volcano sediments were constrained to the mnn19e and mnn19f biozones deposited from 1 2 to 0 589 ma according to the depth of deposition and the present altitude of the pleistocene succession uplift rates are estimated between 1 1 and 1 7 mm yr 1 for the northeastern sector of the etna edifice and between 0 36 and 0 61 mm yr 1 for the southern one this inhomogeneous long term uplift rate affecting the etna region probably results from a buried thrust below the northern flank of etna which is related to the post tortonian geodynamic evolution of ne sicily

seismic exploration scale velocities and structure from ambient seismic noise 1 hz the successful surface waves retrieval in solid earth seismology using long time correlations and subsequent tomographic images of the crust have sparked interest in extraction of subsurface information from noise in the exploration seismology subsurface information in exploration seismology is usually derived from body wave reflections 1 hz which is challenging for utilization of ambient noise we use 11 h of noise recorded in the sirte basin libya first we study the characteristics of the noise we show that the bulk of the noise is composed of surface waves at frequencies below 6 hz some noise panels contain nearly vertically traveling events we further characterize these events using a beamforming algorithm from the beamforming we conclude that these events represent body wave arrivals with a fairly rich azimuthal distribution having body wave arrivals in the noise is a prerequisite for body wave reflections retrieval we crosscorrelate and sum the recorded ambient noise panels to retrieve common source gathers following two approaches using all the noise and using only noise panels containing body wave arrivals likely to contribute to the reflections retrieval comparing the retrieved gathers with active seismic data we show that the two way traveltimes at short offsets of several retrieved events coincide with those of reflections in the active data and thus correspond to apexes of reflections we then compare retrieved stacked sections of the subsurface from both approaches with the active data stacked section and show that the reflectors are consistent along a line the results from the second approach exhibit the reflectors better

evidence of debris flow occurrence after wildfire in upland catchments of south east australia abstract numerous reports of flash floods mud torrents and landslides in burnt landscapes of south east australia were only recently linked to debris flows and recognised as a significant process that warrant more detailed investigation this paper provides a systematic documentation of high magnitude erosion events after wildfire in south east australia focusing on small

time lapse seismic performance of a sparse permanent array experience from the aquistore co2 storage site abstracta sparse areal permanent array of buried geophones was deployed at the aquistore co2 storage site in saskatchewan canada the purpose of this array is to facilitate 4d seismic monitoring of co2 that is to be injected to the deep subsurface use of a sparse buried array is designed to improve the repeatability of time lapse data and to economize the monitoring effort prior to the start of co2 injection two 3d dynamite seismic surveys were acquired in march 2012 and may 2013 using the permanent array the objective of acquiring these data was to allow an assessment of the data repeatability and overall performance of the permanent array a comparison of the raw data from these surveys and with a conventional high resolution 3d vibroseis survey demonstrated that 1 the signal to noise ratio for the buried geophones was increased by 6 7 db relative to surface deployed geophones and by an additional 20 db for dynamite relative to a vibroseis source 2 the use of buried sensors and sources at this

fluvial sediment transport in response to moderate storm flows following chaparral wildfire ventura county southern california chaparral wildfire has a profound effect on erosion and sedimentation in southern california the wheeler fire in july 1985 burned the entire basin of a tributary drainage area 2 14 km 2 of the north fork of matilija creek near ventura california after the fire fine gravel was delivered to the channel by the process of dry ravel dry particle by particle sliding of debris under the force of gravity at a rate of 0 29 m 3 km 2 month the first winter flow 2 1 m 3 s following the fire deposited 550 m 3 of fine gravel in the 270 m study reach near the mouth of the tributary at least 90 of this fine gravel was derived from colluvium delivered by dry ravel processes from hillslopes near the channel the second winter flow 2 5 m 3 s eroded the channel to the pre fire thalweg a reduction in particle size and critical shear stress associated with deposition of small gravel following the fire allowed these moderate magnitude flows to transport large volumes of sediment deposits of two debris flows were identified in the tributary basin radiocarbon dating of these deposits gives dates of 1045 95 yr b p for the older deposit and between 295 35 and 385 84 yr b p for the younger deposit these dates indicate that the recurrence interval of large debris flows in the study basin is at least an order of magnitude greater than the recurrence interval of fire in the area

illuminating wildfire erosion and deposition patterns with repeat terrestrial lidar erosion following a wildfire is much greater than background erosion in forests because of wildfire induced changes to soil erodibility and water infiltration while many previous studies have documented post wildfire erosion with point and small plot scale measurements the spatial distribution of post fire erosion patterns at the watershed scale remains largely unexplored in this study lidar surveys were collected periodically in a small first order drainage basin over a period of 2 years following a wildfire the study site was relatively steep with slopes ranging from 17 to 30 during the study period several different types of rain storms occurred on the site including low intensity frontal storms 2 4 mm h 1 and high intensity convective thunderstorms 79 mm h 1 these storms were the dominant drivers of erosion erosion resulting from dry ravel and debris flows was notably absent at the site successive lidar surveys were subtracted from one another to obtain digital maps of topographic change between surveys the results show an evolution in geomorphic response such that the erosional response after rain storms was strongly influenced by the previous erosional events and pre fire site morphology hillslope and channel roughness increased over time and the watershed armored as coarse cobbles and boulders were exposed the erosional response was spatially nonuniform shallow erosion from hillslopes 87 of the study area contributed 3 times more sediment volume than erosion from convergent areas 13 of the study area however the total normalized erosion depth volume area was highest in convergent areas from a detailed understanding of the spatial locations of erosion we made inferences regarding the processes driving erosion it appears that hillslope erosion is controlled by rain splash for detachment and overland flow for transport and quasi channelized erosion with the sites of highest erosion corresponding to locations with the lowest roughness by contrast in convergent areas we found erosion caused by overland flow soil erosion was locally interrupted by immobile objects such as boulders bedrock or tree trunks resulting in a patchy erosion network with increasing roughness over time

ambient seismic noise eikonal tomography for near surface imaging at valhall the permanent ocean bottom array at the valhall field in norway provides an excellent source of passive seismic data to test what might be accomplished with seismic interferometry the array was installed in 2003 kommedal et al 2004 and data can be recorded for long periods in all weather conditions the subsurface structure is well known both from numerous wells and from seismic imaging during periods without active seismic acquisition at valhall there is abundant passive energy in the data over a wide range of fre quencies

incipient sediment motion across the river to debris flow transition sediment transport in mountain channels controls the evolution of mountainous terrain in response to climate and tectonics and presents major hazards to life and infrastructure worldwide despite its importance we lack data on when sediment moves in steep channels and whether movement occurs by rivers or debris flows we address this knowledge gap using laboratory experiments on initial sediment motion that cross the river to debris flow sediment transport transition results show that initial sediment motion by river processes requires heightened dimensionless bed shear stress or critical shields stress with increasing channel bed slope by as much as fivefold the conventional criterion established for lowland rivers beyond a threshold slope of 22 the channel bed fails initiating a debris flow prior to any fluvial transport and the critical shields stress within the debris flow regime decreases with increasing channel bed slope combining theories for both fluvial and debris flow incipient transport results in a new phase space for sediment stability with implications for predicting fluvial sediment transport rates mitigating debris flow hazards and modeling channel form and landscape evolution

the valle del bove mount etna its origin and relation to the stratigraphy and structure of the volcano abstract the valle del bove is a major horseshoe shaped depression some 5 km in diameter and over 1000 m deep carved into the eastern flank of mount etna volcano the origin of the valle del bove has been a subject of debate for over a century but recent models relate it to the collapse of the ancient trifoglietto ii centre of etna either by caldera collapse or phreatomagmatic explosive activity careful morphological analysis shows the valle del bove to have formed after the post trifoglietto ii ellittico and leone centres and therefore to be considerably younger than the trifoglietto ii centre it has also been argued that the pyroclastic deposits that occur on the flanks of the volcano in close spatial relationship with the valle del bove were produced by the same event these pyroclastics are divided on the basis of age and composition into two groups the upper and lower tephra deposits the stratigraphy petrology and radiocarbon date of the lower tephra deposits indicate a trifoglietto ii age at least 20 000 years before the formation of the valle del bove the upper tephra deposits have a strong phreatomagmatic character and are closest in age to the valle del bove there is no evidence however to link them with its formation morphological study shows the valle del bove to consist of a series of coalescing scallops indicative of formation by landsliding the material removed by slope failure and subsequent fluvial transport followed a valley to the coast where it forms a fan shaped accumulation the chiancone consisting of volcaniclastics of fluvial and mudflow origin it is argued that the valle del bove did not result from simple caldera collapse but formed from a series of collapses caused by gravitational slope failure the chiancone is considered to be the product of this collapse

the 18 7 ka phreatomagmatic flank eruption on etna italy relationship between eruptive activity and sedimentary basement setting this paper documents a phreatomagmatic flank eruption that occurred 18 700 100 a bp on the lower north eastern slope of etna during the ellittico volcano activity which produced fall and surge deposits this type of eruption is connected to a sedimentary basement ridge at etna the interaction between the rising magma and the shallow groundwater hosted in the volcanic pile overlying the impermeable sediments resulted in phreatomagmatic instead of strombolian activity three eruptive phases are distinguished based on field and analytical data i an explosive phreatomagmatic opening ii a main phase producing coarse lithic rich fallout and a strombolian deposit and iii the final pulsating surge forming phase the discovery of this phreatomagmatic flank eruption which occurred at lower altitude raises important issues for previous hazard assessments at etna

applications in geomorphology abstract geomorphology is a pure science with the goal of understanding earth surface processes and landscape evolution and it is also an applied science with the goal of addressing the needs of society with many new high resolution methods of depicting topography and much improved numerical dating geomorphologists are working on problems involving rates of surface processes landscape evolution and applications to areas of concern to society that were impossible to address a few decades ago some of the areas of enquiry where geomorphology has been applied include natural hazards landslides floods earthquakes and tsunamis ecosystem management site anthropology land use planning engineering geology expert witness testimony and hazard reduction assessment and perception how people perceive and respond to potential hazards how their vulnerability can increase their risk and how preparedness and response can be improved depends as much on the social sciences as on physical science

an example of river pattern evolution produced during the lateral growth of a central polygenic volcano the case of the alcantara river system mt etna italy abstract analysis of numerous geognostic soundings and geophysical investigation data indicates the presence of a wide depression identifiable as the ancient valley of the alcantara river below the northern flank of mt etna surface and subsurface data were used to reconstruct the complex stratigraphic succession filling the paleo alcantara valley consisting of superimposed lava flows interlayered with thick lentiform clastic bodies the evolution of the alcantara river system was defined with reference to the different phases of growth of mt etna the first correlation between volcanic activity and the drainage system refers to the initial phases of alkaline volcanism 170 100 ka during this period the southern watershed of the paleo alcantara valley acted as a morphological barrier to the products of the various volcanoes which gradually grew in the sector now occupied by the valle del bove the paleo alcantara riverbed was sporadically invaded by lava flows generated by peripheral activity of the central edifice a radical modification of the hydrographic pattern of the region began about 45 40 ka as a consequence of the growth of the ellittico volcano the main eruptive centre of the etnean edifice the gradual expansion of this volcano led over a period between about 30 and 25 ka to the northward deviation of the paleo alcantara riverbed the consequent erosion of a section of the watershed with the adjacent hydrographic basin of the paleo s paolo river resulted in the capture of the latter from then on the hydrographic pattern of the area gradually took on the characteristics it has today a water circulation system developed within the thick volcanic pile filling the paleo alcantara valley with the formation of an aquifer which is today one of the most important hydro structures of the whole volcanic edifice and is in part exploited in the eastern side of sicily

shear wave imaging from traffic noise using seismic interferometry by cross coherence we apply the cross coherence method to the seismic interferometry of traffic noise which originates from roads and railways to retrieve both body waves and surface waves our preferred algorithm in the presence of highly variable and strong additive random noise uses cross coherence which uses normalization by the spectral amplitude of each of the traces rather than crosscorrelation or deconvolution this normalization suppresses the influence ofadditive noise and overcomes problems resulting from amplitudevariations among input traces by using only the phase information and ignoring amplitude information the method effectively removes the source signature from the extracted response and yields a stable structural reconstruction even in the presence of strong noise this algorithm is particularly effective where the relative amplitude among the original traces is highly variable from trace to trace we use the extracted reflected shear waves from the traffic noise data to construct a stackedandmigratedimage andweusetheextractedsurfacewaves love waves to estimate the shear velocity as a function of depth this profile agrees well with the interval velocity obtained from the normal moveout of the reflected shear waves constructed by seismic interferometry these results are useful in a wide range of situations applicable to both geophysics and civil engineering

sources of debris flow material in burned areas abstract the vulnerability of recently burned areas to debris flows has been well established likewise it has been shown that many if not most post fire debris flows are initiated by runoff and erosion and grow in size through erosion and scour by the moving debris flow as opposed to landslide initiated flows with little growth to better understand the development and character of these flows a study has been completed encompassing 46 debris flows in california utah and colorado in nine different recently burned areas for each debris flow progressive debris production was measured at intervals along the length of the channel and from these measurements graphs were developed showing cumulative volume of debris as a function of channel length all 46 debris flows showed significant bulking by scour and erosion with average yield rates for each channel ranging from 0 3 to 9 9 m 3 of debris produced for every meter of channel length with an overall average value of 2 5 m 3 m significant increases in yield rate partway down the channel were identified in 87 of the channels with an average of a three fold increase in yield rate yield rates for short reaches of channels up to several hundred meters ranged as high as 22 3 m 3 m debris was contributed from side channels into the main channels for 54 of the flows with an average of 23 of the total debris coming from those side channels rill erosion was identified for 30 of the flows with rills contributing between 0 1 and 10 5 of the total debris with an average of 3 debris was deposited as levees in 87 of the flows with most of the deposition occurring in the lower part of the basin a median value of 10 of the total debris flow was deposited as levees for these cases with a range from near zero to nearly 100 these results show that channel erosion and scour are the dominant sources of debris in burned areas with yield rates increasing significantly partway down the channel side channels are much more important sources of debris than rills levees are very common but the size and effect on the amount of debris that reaches a canyon mouth is highly variable

predicting the probability and volume of postwildfire debris flows in the intermountain western united states empirical models to estimate the probability of occurrence and volume of postwildfire debris flows can be quickly implemented in a geographic information system gis to generate debris flow hazard maps either before or immediately following wildfires models that can be used to calculate the probability of debris flow production from individual drainage basins in response to a given storm were developed using logistic regression analyses of a database from 388 basins located in 15 burned areas located throughout the u s intermountain west the models describe debris flow probability as a function of readily obtained measures of areal burned extent soil properties basin morphology and rainfall from short duration and low recurrence interval convective rainstorms a model for estimating the volume of material that may issue from a basin mouth in response to a given storm was developed using multiple linear regression analysis of a database from 56 basins burned by eight fires this model describes debris flow volume as a function of the basin gradient aerial burned extent and storm rainfall applications of a probability model and the volume model for hazard assessments are illustrated using information from the 2003 hot creek fire in central idaho the predictive strength of the approach in this setting is evaluated using information on the response of this fire to a localized thunderstorm in august 2003 the mapping approach presented here identifies those basins that are most prone to the largest debris flow events and thus provides information necessary to prioritize areas for postfire erosion mitigation warnings and prefire management efforts throughout the intermountain west

oxygen isotope composition of natural waters in the mt etna area oxygen isotopes of both rainwater and groundwater samples from mt etna were used to obtain information on recharge areas flow paths and the origin of wet air masses oxygen isotope composition was determined in rainwater samples collected for a period of 3 years october 1997 october 2000 in 11 rain gauges distributed along the flanks of mt etna from sea level to 2900 m of altitude values ranged from 213 8 to 1 9 the lowest values being measured at higher altitudes and or during cooler periods for rain gauges located from sea level up to 1000 m altitude volume weighted values defined an isotopic gradient of 22 7 km which is in the range observed in the mediterranean area higher altitude gauges yielded a much lower gradient 2 0 6 km probably due to the fact that vapour condensing at higher altitudes was mixed with an 18 o rich volcanic component deriving from the huge vapour output of the summit craters the oxygen isotope composition of about 210 groundwater samples collected all around the volcano ranged from 2 9 3 to 2 5 0 the higher values measured on the eastern flank indicated that recharge occurs at lower altitudes on this flank the low variability 0 30 0 65 of the monthly values gathered from 14 groundwater sampling points over a period of 2 years indicates that the groundwater system is isotopically well mixed some long term trends may be explained by variations in annual recharge due to the prevalent isotope composition of wet air masses q 2004 elsevier b v all rights reserved

empirical models to predict the volumes of debris flows generated by recently burned basins in the western u s abstract recently burned basins frequently produce debris flows in response to moderate to severe rainfall post fire hazard assessments of debris flows are most useful when they predict the volume of material that may flow out of a burned basin this study develops a set of empirically based models that predict potential volumes of wildfire related debris flows in different regions and geologic settings the models were developed using data from 53 recently burned basins in colorado utah and california the volumes of debris flows in these basins were determined by either measuring the volume of material eroded from the channels or by estimating the amount of material removed from debris retention basins for each basin independent variables thought to affect the volume of the debris flow were determined these variables include measures of basin morphology basin areas burned at different severities soil material properties rock type and rainfall amounts and intensities for storms triggering debris flows using these data multiple regression analyses were used to create separate predictive models for volumes of debris flows generated by burned basins in six separate regions or settings including the western u s southern california the rocky mountain region and basins underlain by sedimentary metamorphic and granitic rocks an evaluation of these models indicated that the best model the western u s model explains 83 of the variability in the volumes of the debris flows and includes variables that describe the basin area with slopes greater than or equal to 30 the basin area burned at moderate and high severity and total storm rainfall this model was independently validated by comparing volumes of debris flows reported in the literature to volumes estimated using the model eighty seven percent of the reported volumes were within two residual standard errors of the volumes predicted using the model this model is an improvement over previous models in that it includes a measure of burn severity and an estimate of modeling errors the application of this model in conjunction with models for the probability of debris flows will enable more complete and rapid assessments of debris flow hazards following wildfire

rill erosion in natural and disturbed forests 2 modeling approaches 1 as forest management scenarios become more complex the ability to more accurately predict erosion from those scenarios becomes more important in this second part of a two part study we report model parameters based on 66 simulated runoff experiments in two disturbed forests in the northwestern u s the 5 disturbance classes were natural 10 month old and 2 week old low soil burn severity high soil burn severity and logging skid trails in these environments the erosion rates were clearly detachment limited and the rill erodibility parameters calculated from four hydraulic variables increased by orders of magnitude the soil shear stress based erodibility parameter kr was 1 5 10 6 s m 1in the natural plots 2 0 10 4 s m 1 in the high soil burn severity plots and 1 7 10 3 s m 1 in the skid trail plots kr values for the low soil burn severity plots had negative sign the erodibility value for the skid trail plots fell within ranges reported for tilled agricultural fields and also for forest roads the kr values decreased as erosion occurred in the plots and therefore should not be a constant parameter the stream power produced the largest r2 value 0 41 when hydraulic predictors and the sediment flux were log transformed but none of the four hydraulic variables soil shear stress stream power unit stream power and unit length shear force explained much of the variability in sediment flux rates across the five levels of disturbance when evaluated in the linear form of the erosion models under consideration

the role of debris supply conditions in predicting debris flow activity debris flow frequency and magnitude were determined for 33 basins in southwest british columbia basins were first classifiedaseitherweathering limitedortransport limitedusingadiscriminantfunctionbasedondebris contributingarea an area weighted terrain stability number and drainage density multiple regression was used to predict magnitude peak discharge frequency and activity frequency times magnitude within each group of basins model performance was improved by stratifying the total sample of debris flow basins into weathering and transport limited groups explained varianceincreasedbyanaverageof15percentinthetransport limitedsample indicatingthatsedimentsupplyconditionsin themoreactivebasinsarefundamentalinpredictingdebrisflowactivity anindependenttestoftheregressionmodelswith 11basinsyieldedgenerallygoodresultsfordebrisflowmagnitudeandpeakdischarge predictionofdebrisflowfrequency provedproblematicalinweathering limitedbasins themethodsdevelopedhereprovideestimatesofdebrisflowattributes in basins for which few data on past events are available copyright 1999 john wiley sons ltd

runoff generated debris flows observations and modeling of surge initiation magnitude and frequency 1 runoff during intense rainstorms plays a major role in generating debris flows in many alpine areas and burned steeplands yet compared to debris flow initiation from shallow landslides the mechanics by which runoff generates a debris flow are less understood to better understand debris flow initiation by surface water runoff we monitored flow stage and rainfall associated with debris flows in the headwaters of two small catchments a bedrock dominated alpine basin in central colorado 0 06 km2 and a recently burned area in southern california 0 01 km2 we also obtained video footage of debris flow initiation and flow dynamics from three cameras at the colorado site stage observations at both sites display distinct patterns in debris flow surge characteristics relative to rainfall intensity i we observe small quasiperiodic surges at low i large quasiperiodic surges at intermediate i and a single large surge followed by small amplitude fluctuations about a more steady high flow at high i video observations of surge formation lead us to the hypothesis that these flow patterns are controlled by upstream variations in channel slope in which low gradient sections act as sediment capacitors temporarily storing incoming bed load transported by water flow and periodically releasing the accumulated sediment as a debris flow surge to explore this hypothesis we develop a simple one dimensional morphodynamic model of a sediment capacitor that consists of a system of coupled equations for water flow bed load transport slope stability and mass flow this model reproduces the essential patterns in surge magnitude and frequency with rainfall intensity observed at the two field sites and provides a new framework for predicting the runoff threshold for debris flow initiation in a burned or alpine setting

the influence of edifice slope and substrata on volcano spreading gravitational volcano spreading is caused by flow of weak substrata due to volcanic loading and is now a process known to affect many edifices the process produces extension in the upper edifice evidenced by graben and normal faults and compression at the base seen in strike slip faults and thrusts where spreading is identified host volcanoes have a range of fault densities variable rift and graben shapes and different degrees of structural asymmetry previous studies have suggested a link between edifice shape and structure and the proportion of brittle to ductile material in the substrata or lower edifice we study this link using refined sand cone analogue models standing on a brittle ductile sand silicone substrata two scenarios have been investigated the first mainly represents oceanic volcanoes with a ductile layer within the edifice type i where there is an outer ductile free surface the second represents most continental volcanoes that have ductile substrata type ii we apply the model results to natural examples and develop quantitative relationships between slope brittle ductile ratio fault density spreading rate and structural style displacement fields calculated from stereophotogrammetry show significant differences between different slope models we find that more faults are produced when the cone is initially steeper or when the brittle substratum is thinner however the effect of the brittle layer dominates over that of slope the strike slip movements are found to be an essential feature in the spreading mechanism and the graben are in fact transtensional features strike slip and graben faults make a conjugate flower pattern the structures produced are well organised for type ii edifices but they are poorly organised for type i models type i models represent good analogues for oceanic volcanoes that are commonly affected by large slumps bounded by an extensional zone and lack of well formed sector graben the well observed connection between oceanic volcano rifts and large landslide slumps is confirmed to be a consequence of spreading

transient deterministic shallow landslide modeling requirements for susceptibility and hazard assessments in a gis framework abstract application of transient deterministic shallow landslide models over broad regions for hazard and susceptibility assessments requires information on rainfall topography and the distribution and properties of hillside materials we survey techniques for generating the spatial and temporal input data for such models and present an example using a transient deterministic model that combines an analytic solution to assess the pore pressure response to rainfall infiltration with an infinite slope stability calculation pore pressures and factors of safety are computed on a cell by cell basis and can be displayed or manipulated in a grid based gis input data are high resolution 1 8 m topographic information derived from lidar data and simple descriptions of initial pore pressure distribution and boundary conditions for a study area north of seattle washington rainfall information is taken from a previously defined empirical rainfall intensity duration threshold and material strength and hydraulic properties were measured both in the field and laboratory results are tested by comparison with a shallow landslide inventory comparison of results with those from static infinite slope stability analyses assuming fixed water table heights shows that the spatial prediction of shallow landslide susceptibility is improved using the transient analyses moreover results can be depicted in terms of the rainfall intensity and duration known to trigger shallow landslides in the study area

sediment availability on burned hillslopes 1 erodibility describes the inherent resistance of soil to erosion hillslope erosion models typically consider erodibility to be constant with depth this may not be the case after wildfire because erodibility is partly determined by the availability of noncohesive soil and ash at the surface this study quantifies erodibility of burned soils using methods that explicitly capture variations in soil properties with depth flume experiments on intact cores from three sites in western united states showed that erodibility of fire affected soil was highest at the soil surface and declined exponentially within the top 20 mm of the soil profile with root density and soil depth accounting for 62 of the variation variation in erodibility with depth resulted in transient sediment flux during erosion experiments on bounded field plots material that contributed to transient flux was conceptualized as a layer of noncohesive material of variable depth dnc this depth was related to shear strength measurements and sampled spatially to obtain the probability distribution of noncohesive material as a function of depth below the surface after wildfire in southeast australia the initial dnc ranged from 7 5 to 9 1 mm which equated to 97 117 mg ha 1 of noncohesive material the depth decreased exponentially with time since wildfire to 0 4 mm or 5 mg ha 1 after 3 years of recovery the results are organized into a framework for modeling fire effects on erodibility as a function of the production and depletion of the noncohesive layer overlying a cohesive layer

characterization of shallow geology by high frequency seismic noise tomography summary to study the applicability of the passive seismic interferometry technique to near surface geological studies seismic noise recordings from a small scale 2 d array of seismic stations were performed in the test site of nauen germany rayleigh wave green s functions were estimated for different frequencies a tomographic inversion of the traveltimes estimated for each frequency from the green s functions is then performed allowing the laterally varying 3 d surface wave velocity structure below the array to be retrieved at engineering geotechnical scales furthermore a 2 d s wave velocity cross section is obtained by combining 1 d velocity structures derived from the inversion of the dispersion curves extracted at several points along a profile where other geophysical analyses were performed it is shown that the cross section from passive seismic interferometry provides a clear image of the local structural heterogeneities that are in excellent agreement with georadar and geoelectrical results such findings indicate that the interferometry analysis of seismic noise is potentially of great interest for deriving the shallow 3 d velocity structure in urban areas

predicting sediment delivery from debris flows after wildfire abstract debris flows are an important erosion process in wildfire prone landscapes predicting their frequency and magnitude can therefore be critical for quantifying risk to infrastructure people and water resources however the factors contributing to the frequency and magnitude of events remain poorly understood particularly in regions outside western usa against this background the objectives of this study were to i quantify sediment yields from post fire debris flows in southeast australian highlands and ii model the effects of landscape attributes on debris flow susceptibility sediment yields from post fire debris flows 113 294 t ha 1 are 2 3 orders of magnitude higher than annual background erosion rates from undisturbed forests debris flow volumes ranged from 539 to 33 040 m3 with hillslope contributions of 18 62 the distribution of erosion and deposition above the fan were related to a stream power index which could be used to model changes in yield along the drainage network debris flow susceptibility was quantified with a logistic regression and an inventory of 315 debris flow fans deposited in the first year after two large wildfires total burned area 2919 km2 the differenced normalised burn ratio dnbr or burn severity local slope radiative index of dryness ai and rainfall intensity from rainfall radar were significant predictors in a susceptibility model which produced excellent results in terms identifying channels that were eroded by debris flows area under curve auc 0 91 burn severity was the strongest predictor in the model auc 0 87 when dnbr is used as single predictor suggesting that fire regimes are an important control on sediment delivery from these forests the analysis showed a positive effect of ai on debris flow probability in landscapes where differences in moisture regimes due to climate are associated with large variation in soil hydraulic properties overall the results from this study based in the southeast australian highlands provide a novel basis upon which to model sediment delivery from post fire debris flows the modelling approach has wider relevance to post fire debris flow prediction both from risk management and landscape evolution perspectives

studying co2 storage with ambient noise seismic interferometry a combined numerical feasibility study and field data example for ketzin germany seismic interferometry applied to ambient noise measurements allows the retrieval of the seismic response between pairs of receivers we studied ambient noise seismic interferometry ansi to retrieve time lapse reflection responses from a reservoir during co2 geologic sequestration using the case of the experimental site of ketzin germany we applied ansi to numerically modeled data to retrieve base and repeat reflection responses characterizing the impedances occurring at the reservoir both with and without the injection of co2 the modeled data represented global transmission responses from band limited noise sources randomly triggered in space and time we found that strong constraints on the spatial distribution of the passive sources were not required to retrieve the time lapse signal as long as sufficient source location repeatability was observed between the base and the repeat passive survey to illustrate the potential of the technique ansi was applied to three days of passive field data recorded in 2012 at ketzin comparison with the modeled results illustrated the potential to retrieve key reflection events using ansi on field data from ketzin this study supports the idea that the geologic setting and characteristics of ambient noise at ketzin may be opportune to monitor co2 sequestration

reconstruction of subsurface structure from ambient seismic noise an example from ketzin germany summary passive seismic interferometry is a new promising methodology for seismic exploration interferometry allows information about the subsurface structure to be extracted from ambient seismic noise in this study we apply the cross correlation technique to approximately 25 hr of recordings of ambient seismic noise at the ketzin experimental co2 storage site germany common source gathers were generated from the ambient noise for all available receivers along two seismic lines by cross correlation of noise records this methodology isolates the interstation green s functions that can be directly compared to active source gathers we show that the retrieved response includes surface waves refracted waves and reflected waves we use the dispersive behaviour of the retrieved surface waves to infer geological properties in the shallow subsurface and perform passive seismic imaging of the subsurface structure by processing the retrieved reflected waves

critical shear stress for erosion of cohesive soils subjected to temperatures typical of wildfires received 26 february 2004 revised 15 september 2004 accepted 5 november 2004 published 22 january 2005 1 increased erosion is a well known response after wildfire to predict and to model erosion on a landscape scale requires knowledge of the critical shear stress for the initiation of motion of soil particles as this soil property is temperature dependent a quantitative relation between critical shear stress and the temperatures to which the soils have been subjected during a wildfire is required in this study the critical shear stress was measured in a recirculating flume using samples of forest soil exposed to different temperatures 40 550 c for 1 hour results were obtained for four replicates of soils derived from three different types of parent material granitic bedrock sandstone and volcanic tuffs in general the relation between critical shear stress and temperature can be separated into three different temperature ranges 275 c which are similar to those for water repellency and temperature the critical shear stress was most variable 1 0 2 0 n m 2 for temperatures 2 0 n m 2 between 175 and 275 c and was essentially constant 0 5 0 8 n m 2 f or temperatures 275 c the changes in critical shear stress with temperature were found to be essentially independent of soil type and suggest that erosion processes in burned watersheds can be modeled more simply than erosion processes in unburned watersheds wildfire reduces the spatial variability of soil erodibility associated with unburned watersheds by eliminating the complex effects of vegetation in protecting soils and by reducing the range of cohesion associated with different types of unburned soils our results indicate that modeling the erosional response after a wildfire depends primarily on determining the spatial distribution of the maximum soil temperatures that were reached during the wildfire

underestimation of body waves and feasibility of surface wave reconstruction by seismic interferometry interferometry is an approach to extract the green s function between two receivers as if the virtual source is at one of the receiver locations the green s function which is the response to an impulsive source accounts for the wave propagation in the medium between the two receivers it is commonly thought that green s function estimates obtained from interferometry accurately represent the full green s function but this is not always the case in fact the accuracy of the retrieved green s function which consists of the surface and body waves is in practice restricted by the limited distribution of the sources of field fluctuations we demonstrate the importance of adequate source distribution for the accuracy of the retrieved green s function using examples from interferometry applications in these examples sources are controlled as in exploration seismology or uncontrolled as in crustal seismology

short term post wildfire dry ravel processes in a chaparral fluvial system abstract dry ravel the transport of sediment by gravity transfers material from steep hillslopes to valley bottoms during dry conditions following wildfire dry ravel greatly increases in the absence of vegetation on hillslopes thereby contributing to sediment supply at the landscape scale dry ravel has been documented as a dominant hillslope erosion mechanism following wildfire in chaparral environments in southern california however alteration after initial deposition is not well understood making prediction of post fire flood hazards challenging the majority of big sycamore canyon burned during the may 2013 springs fire leaving ash and a charred layer that covered hillslopes and ephemeral channels dry ravel processes following the fire produced numerous deposits in the hillslope channel transition zone field data focus on 1 deposition from an initial post wildfire dry ravel pulse and 2 subsequent alteration of dry ravel deposits over a seven month period between september 2013 and april 2014 we quantify geomorphic responses in dry ravel deposits including responses during the one small winter storm that generated runoff following the fire field measurements document volumetric changes after initial post wildfire deposition of sediment derived from dry ravel erosion and deposition mechanisms that occurred within dry ravel deposits situated in the hillslope channel transition zone included 1 mobilization and transport of a portion or the entire deposit by fluvial erosion 2 rilling on the surface of the unconsolidated deposits 3 deposition on deposits via continued hillslope sediment supply and 4 mass wasting that transfers sediment within deposits where surface profiles are near the angle of repose terrestrial lidar scanning point clouds were analyzed to generate profiles quantifying depth of sediment erosion or deposition over remaining dry ravel deposits after the first storm season this study contributes to the understanding of potential effects of wildfire on fine sediment delivery to fluvial systems in chaparral ecosystems

time dependent deformation of the eastern flank of mt etna after slip or viscoelastic relaxation abstract major results of post intrusive gps monitoring of the 5 months encompassing and following the onset of 2002 03 mt etna eruption are presented and discussed here the overall ground deformation pattern is characterized by a time dependent relaxation function we evaluated two different parametrizations of relaxation functions each one linked to a different relaxation process i viscoelastic relaxation and ii after slip mechanism the former indicated that the process occurred within a weak layer characterized by viscosity values ranging between 7 1 1014 pa s and 1 3 1015 pa s the latter evidenced that frictional processes occurred beneath a layer of velocity strengthening having a thickness with values ranging between 0 4 km and 1 7 km either model may explain the observed time dependent deformation both from the statistical point of view and the comparison with geologic and seismic information although we are unable to favour one model rather than the other these results indicate that the mechanism responsible for the observed post intrusive deformation occurs within a sliding zone located inside the clayey sedimentary basement

comparing models of debris flow susceptibility in the alpine environment abstract debris flows are widespread in val di fassa trento province eastern italian alps where they constitute one of the most dangerous gravity induced surface processes from a large set of environmental characteristics and a detailed inventory of debris flows we developed five models to predict location of debris flow source areas the models differ in approach statistical vs physically based and type of terrain unit of reference slope unit vs grid cell in the statistical models a mix of several environmental factors classified areas with different debris flow susceptibility however the factors that exert a strong discriminant power reduce to conditions of high slope gradient pasture or no vegetation cover availability of detrital material and active erosional processes since slope and land use are also used in the physically based approach all model results are largely controlled by the same leading variables overlaying susceptibility maps produced by the different methods statistical vs physically based for the same terrain unit of reference grid cell reveals a large difference nearly 25 spatial mismatch the spatial discrepancy exceeds 30 for susceptibility maps generated by the same method discriminant analysis but different terrain units slope unit vs grid cell the size of the terrain unit also led to different susceptibility maps almost 20 spatial mismatch maps based on different statistical tools discriminant analysis vs logistic regression differed least less than 10 hence method and terrain unit proved to be equally important in mapping susceptibility model performance was evaluated from the percentages of terrain units that each model correctly classifies the number of debris flow falling within the area classified as unstable by each model and through the metric of roc curves although all techniques implemented yielded results essentially comparable the discriminant model based on the partition of the study area into small slope units may constitute the most suitable approach to regional debris flow assessment in the alpine environment

fire related sedimentation events on alluvial fans yellowstone national park u s a abstract we document initiation and flow processes deposit facies and geomorphic effects of forest fire related sedimentation on small alluvial fans in yellowstone national park brief intense convective storm precipitation on steep basins burned in the 1988 fires produced sedimentation events involving a variety of depositional processes on fans over the course of all documented events flows on fans progressed from higher to lower sediment concentration events were often dominated by either debris flows or relatively sediment poor streamflow processes in some events however flows ranging a over wide spectrum of sediment concentration produced significant fan deposits debris flows were generated by progressive sediment bulking involving pervasive surface runoff and rill erosion on st ep upper basin slopes followed by deep incision as flows progressed down channels debris flow deposits show a marked decline in thickness and coarse gravel content downfan often with extensive distal gravel poor facies we recognized a relatively minor percentage of noncohesive debris flow and hyperconcentrated flow facies with sorting and stratification intermediate between muddy debris flow and streamflow facies these were deposited where dilute flows bulked with coarse sediment by eroding channel alluvium or earlier deposits of the event below incised fan channels streamflows expanded as sheetfloods which prograded lower fans with distally fining deposits basins 3 km2 typically produced streamflow events on fans but sediment texture and availability on slopes and in channels are primary factors determining flow processes on fans of smaller basins burned soil surfaces provided abundant silt and clay for debris flow generation but because soil surface sediment was stripped and or compacted over time the lack of available fines resulted in dominance of streamflow processes in later events

particle friction angles in steep mountain channels sediment transport rates in steep mountain channels are typically an order of magnitude lower than predicted by models developed for lowland rivers one hypothesis for this observation is that particles are more stable in mountain channels due to particle particle interlocking or bridging across the channel width this hypothesis has yet to be tested however because we lack direct measurements of particle friction angles in steep mountain channels here we address this data gap by directly measuring the minimum force required to dislodge sediment pebbles to boulders and the sediment weight in mountain channels using a handheld force gauge at eight sites in california with reach averaged bed angles ranging from 0 5 to 23 and channel widths ranging from 2 m to 16 m we show that friction angles in natural streams average 68 and are 16 larger than those typically measured in laboratory experiments which is likely due to particle interlocking and burial results also show that larger grains are disproportionately more stable than predicted by existing models and that grains organized into steps are twice as stable as grains outside of steps however the mean particle friction angle does not vary systematically with bed slope these results do not support systematic increases in friction angle in steeper and narrower channels to explain the observed low sediment transport rates in mountain channels instead the spatial pattern and grain size dependence of particle friction angles may indirectly lower transport rates in steep narrow channels by stabilizing large clasts and channel spanning steps which act as momentum sinks due to form drag

constraining age and volume of lava flow invasions of the alcantara valley etna volcano italy new insights from paleomagnetic dating and 3d magnetic modeling abstract the alcantara river marks the northern border of etna volcano and along its ne sector it forms a narrow nw se elongated valley that is carved in the mts peloritani sedimentary sequences the valley has been invaded by several lava flows during the growth of the main bulk of the stratovolcano edifice in the past 60 ky ellittico and mongibello volcanoes in this paper we have constrained the age of the main lava flows forming the valley floor and reconstructed the length and volume of the main lava flow that impacted this area through a multidisciplinary approach integrating stratigraphic and aeromagnetic data analysis together with new paleomagnetic and 14c dating the new age determinations showed that the evolution of the present day geological and hydrographic setting of the valley was mainly conditioned by a few flank eruptions that occurred in the lower n flank of etna during the activity of the mongibello volcano in particular between 13 9 and 9 7 ka bp the valley floor was filled by the so called alcantara lava flow for its entire length up to the river mouth reaching a maximum length of about 24 km later two other flank eruptions producing the so called mt dolce and solicchiata lava flows occurred at 9 1 7 2 and 7 3 7 2 ka bp respectively covering the eruptive fissure and the proximal portion of the alcantara lava field and generated the most recent northward shift of the riverbed finally 3d magnetic modeling allowed us to calculate the total on and off shore volume of the alcantara lava flow as 1 km3 a value comparable to those of the long lasting historical eruptions of etna conversely the 24 km length reached by this lava flow is anomalously high when compared to lava flows of the past 15 ky likely because its emplacement occurred within the valley floor preventing any possibility of lateral expansion

post fire thin debris flows sediment transport and numerical modelling the creation of a hydrophobic layer in the soil during res in semi arid environments inhibits the in ltration of rainfall this leads to increased rates of runoff and associated sediment transport when the hydrophobic layer is deposited beneath the soil surface a perched water table develops which may cause thin 1 2 cm hillslope failures that are distinguishable from features caused by rilling and sheet ow evidence for these failures was observed after a re near santa barbara california the amount of sediment eroded from some hillslopes was substantial with 290 kg of sediment per metre width of hillslope delivered to the valley oor the mechanics of these failures are examined with a numerical model that incorporates a stability analysis with subsurface ow routing along a typical hillslope pro le the model correctly predicts the location of the failures as well as the rainfall amount necessary to trigger them copyright 2003 john wiley sons ltd

post wildfire landscape change and erosional processes from repeat terrestrial lidar in a steep headwater catchment chiricahua mountains arizona usa abstract flooding and erosion after wildfires present increasing hazard as climate warms semi arid lands become drier population increases and the urban interface encroaches farther into wildlands we quantify post wildfire erosion in a steep initially unchannelized 7 5 ha headwater catchment following the 2011 horseshoe 2 fire in the chiricahua mountains of southeastern arizona using time lapse cameras rain gauges and repeat surveys by terrestrial laser scanner we quantify the response of a burned landscape to subsequent precipitation events repeat surveys provide detailed pre and post rainfall measurements of landscape form associated with a range of weather events the first post fire precipitation led to sediment delivery equivalent to 0 017 m of erosion from hillslopes and 0 12 m of erosion from colluvial hollows volumetrically 69 of sediment yield was generated from hillslope erosion and 31 was generated from gully channel establishment in colluvial hollows processes on hillslopes included erosion by extensive shallow overland flow formation of rills and gullies and generation of sediment laden flows and possibly debris flows subsequent smaller rain events caused ongoing hillslope erosion and local deposition and erosion in gullies winter freeze thaw led to soil expansion likely related to frost heaving causing a net centimeter scale elevation increase across soil mantled slopes by characterizing landscape form the properties of near surface materials and measuring both precipitation and landscape change we can improve our empirical understanding of landscape response to environmental forcing this detailed approach to studying landscape response to wildfires may be useful in the improvement of predictive models of flood debris flow and sedimentation hazards used in post wildfire response assessments and land management and may help improve process based models of landscape evolution

the virtual refraction useful spurious energy in seismic interferometry seismic interferometry is rapidly becoming an established technique to recover the green s function between receivers but practical limitations in the source energy distribution inevitably lead to spurious energy in the results instead of attempting to suppress all such energy we use a spurious wave associated with the crosscorrelation of refracted energy at both receivers to infer estimates of subsurface parameters we named this spurious event the virtual refraction illustrated by a numerical two layer example we found that the slope of the virtual refraction defines the velocity of the faster medium and that the stationary phase point in the correlation gather provides the critical offset with the associated critical time derived from the real shot record this approach includes all of the necessary information to estimate wave speeds and interface depth without the need of inferences from other wave types

the recurrence interval of post fire debris flow generating rainfall in the southwestern united states abstract in the southwestern united states post fire debris flows commonly initiate during short bursts of intense rainfall to date the frequency of the rainfall rates has not been quantified here we combine an existing database of debris flow occurrences and corresponding peak storm intensities with a geospatial library of rainfall recurrence interval ri information and climate type to determine the distribution of the estimated frequencies of the rainfall associated with 316 observed post fire debris flows in the southwestern united states our results indicate that a majority 77 of the observed debris flows were triggered by rainfall intensities with ri less than 2 years climatic and geographic differences in ri were evident in our analysis debris flows in most of the analyzed climates within california colorado and new mexico were primarily associated with 1 year or less ri intensities whereas debris flows in arid portions of arizona colorado and utah tended to be generated during storms greater than 2 year ri event consequence as defined by the impact on downstream communities and infrastructure was not directly related to ri as very destructive debris flows were initiated at a wide range of ri intensities our results highlight that post fire debris flow initiation can be expected during common rainstorms in the southwestern united states therefore emergency management plans and risk mitigation efforts must focus on both extreme and frequent rainstorms

sediment storage by vegetation in steep bedrock landscapes theory experiments and implications for postfire sediment yield 1 mechanistic models for sediment transport on hillslopes are needed for applications ranging from landscape evolution to debris flow hazards progress has been made for soil mantled landscapes however little is known about sediment production and transport in bedrock landscapes that often maintain a patchy soil mantle even though slopes exceed the angle of repose herein we investigate the hypothesis that patchy soil cover is stable on steep slopes due to local roughness such as vegetation dams that trap sediment upslope to quantify local sediment storage we developed a new theory and tested it against tilt table experiments results show that trapped sediment volume scales with the cube of dam width where the dam width is less than about fifty grain diameters particle force chains appear to enhance stability resulting in greater trapped volumes and sediment pile slopes that exceed the angle of repose trapped volumes are greatest for hillslopes that just exceed the friction slope and are independent of hillslope gradient for gradients greater than about twice the friction slope for neighboring dams spaced less than about five grain diameters apart grain bridging results in a single sediment pile that is larger than the sum of individual piles this work provides a mass conserving framework for quantifying sediment storage and nonlocal transport in bedrock landscapes results may explain the rapid increase in sediment yield following wildfire in steep terrain in the absence of rainfall as sediment dams are incinerated particles become gravitationally unstable and move rapidly downslope as dry ravel

stratigraphic constraints for explosive activity in the past 100 ka at etna volcano italy the pyroclastic deposits of etna have been correlated over the whole volcanic edifice for the first time allowing the construction of a continuous record of tephra producing events which extends from approximately 100 ka to the present in this interval five main periods of explosive activity have been identified a 100 ka strombolian to subplinian activity b 80 to 100 ka plinian benmoreitic activity c 16 to 80 ka strombolian to subplinian from basaltic to mugearitic activity d 15 5 to 15 ka plinian benmoreitic activity accompanying the caldera forming eruptions of the ellittico volcano and e the most recent 13 ka basaltic explosive activity of strombolian and subplinian type of the present edifice that also includes the 122 b c plinian eruption this study results in a semi quantitative and in some cases quantitative definition of the intensity and chronology of the explosive activity at etna moreover this work gives a new significance to the volcanic hazards of etna a volcano generally considered to be the site of gentle effusive eruptions

empirical synthesis of time asymmetrical green functions from the correlation of coda waves we demonstrate the existence of long range field correlations in the seismic coda of regional records in alaska the cross correlations between the different components of coda records at two points are measured for a set of distant earthquakes remarkably while individual correlations have a random character the correlations averaged over source and time exhibit deterministic arrivals that obey the same symmetry rules as the green tensor between the two points in addition the arrival times of these waves coincide with propagating surface waves between the two stations thus we propose to identify the averaged correlation signals with the surface wave part of the green tensor we observe the causal and anticausal parts of the green function however we find experimentally that amplitudes at positive and negative times are not equal we explain this observation by the long lasting anisotropy of the diffuse field we show that the flux of energy coming from the source can still dominate the late coda and result in nonsymmetric cross correlations when the distribution of earthquakes is not isotropic around the stations the extraction of green functions from coda waves allows new types of measurements with seismic waves along paths between stations that could not be obtained with the waves produced by earthquakes

a model for fire induced sediment yield by dry ravel in steep landscapes sediment flux from hillslopes to channels commonly increases following wildfires with implications for the carbon cycle river habitats and debris flow hazards although much of this material is transported via dry ravel existing ravel models are not applicable to hillslopes with gradients greater than the angle of repose which can constitute the majority of mountainous terrain to fill this knowledge gap we develop a continuity model for sediment storage by vegetation dams on steep hillslopes to predict sediment yields following wildfire the maximum volume of sediment stored prior to wildfire is set to be a function of vegetation density the capacity of plants to impound sediment and the contributing hillslope area time is required after fire to establish vegetation and replenish hillslope sediment storage which introduces vegetation regrowth rate soil production rate and fire recurrence interval as important variables that affect ravel yield model results for the san gabriel mountains california predict that sediment yield can increase by several orders of magnitude following fire these results are consistent with field data of ravel yield 30 mm per contributing area of hillslope in 5 months we collected following the 2009 station fire as well as postfire sediment flux recorded by 93 debris basins in contrast to previous work our model shows that heightened postfire sediment yields can be explained by a change in hillslope sediment storage independent of major changes in the soil production rate and landscape form over geomorphic timescales

high resolution lithospheric imaging with seismic interferometry in recent years there has been an increase in the deployment of relatively dense arrays of seismic stations the availability of spatially densely sampled global and regional seismic data has stimulated the adoption of industry style imaging algorithms applied to converted and scattered wave energy from distant earthquakes leading to relatively high resolution images of the lower crust and upper mantle we use seismic interferometry to extract reflection responses from the coda of transmitted energy from distant earthquakes in theory higher resolution images can be obtained when migrating reflections obtained with seismic interferometry rather than with conversions traditionally used in lithospheric imaging methods moreover reflection data allow the straightforward application of algorithms previously developed in exploration seismology in particular the availability of reflection data allows us to extract from it a velocity model using standard multichannel data processing methods however the success of our approach relies mainly on a favourable distribution of earthquakes in this paper we investigate how the quality of the reflection response obtained with interferometry is influenced by the distribution of earthquakes and the complexity of the transmitted wavefields our analysis shows that a reasonable reflection response could be extracted if 1 the array is approximately aligned with an active zone of earthquakes 2 different phase responses are used to gather adequate angular illumination of the array and 3 the illumination directions are properly accounted for during processing we illustrate our analysis using a synthetic data set with similar illumination and source side reverberation characteristics as field data recorded during the 2000 2001 laramie broad band experiment finally we apply our method to the laramie data retrieving reflection data we extract a 2 d velocity model from the reflections and use this model to migrate the data on the final reflectivity image we observe a discontinuity in the reflections we interpret this discontinuity as the cheyenne belt a suture zone between archean and proterozoic terranes

reflection images from ambient seismic noise one application of seismic interferometry is to retrieve the impulse response green s function from crosscorrelation of ambient seismic noise various researchers show results for retrieving the surface wave part of the green s function however reflection retrieval has proven more challenging we crosscorrelate ambient seismic noise recorded along eight parallel lines in the sirte basin east of ajdabeya libya to obtain shot gathers that contain reflections we take advantage of geophone groups to suppress part of the undesired surface wave noise and apply frequency wavenumber filtering before crosscorrelation to suppress surface waves further after comparing the retrieved results with data from an active seismic exploration survey along the same lines we use the retrieved reflection data to obtain a migrated reflection image of the subsurface

unravelling the processes controlling gas emissions from the central and northeast craters of mt etna abstract we measured volcanic gas emissions from the northeast crater nec and central crater cc of mount etna on 21st july 2008 and 3rd and 31st august 2009 using a novel lightweight open path fourier transform infrared spectrometry op ftir in active mode with a portable infrared lamp contemporaneously we measured the so2 flux of the total gas emission released by the combined summit craters 14 km downwind and the so2 flux emitted by the nec measured at the summit combining these data we determined the flux of the major volcanic components h2o co2 so2 hcl and hf emitted individually from cc and nec craters the results reveal similar so2 hcl ratios but distinct co2 so2 ratios 1 3 and 10 9 for nec and cc respectively and an order of magnitude greater co2 flux from the cc compared with the nec a simple model in which the nec branches from a central feeding conduit at a depth of 2 km can reproduce these observations we highlight that in such a system short term variations in co2 so2 ratios at each crater can occur due to minor variations in the magma gas flux entering each conduit at the branch without an overall change in magma supply co2 so2 variations measured at individual craters may therefore be unrepresentative of the volcanic system and require cautious interpretation monitoring of the total co2 and so2 fluxes emitted from each crater is on the contrary an optimal monitoring strategy and can be achieved using a combination of co2 so2 instruments and so2 imaging cameras

feasibility of virtual source reflection seismology using interferometry for mineral exploration a test study in the lalor lake volcanogenic massive sulphide mining area manitoba canada approximately 300 hours of ambient noise data were recorded on a grid of receivers covering an area of 4 km2 over the lalor mine canada to test the capability of seismic interferometry to image ore deposits in the crystalline rock environment underground mining activities create the main source of ambient noise in the area alongside the ambient noise survey a larger three dimensional active source seismic survey was also acquired and used to evaluate the interferometry results power spectral density calculations show random ambient noise with a frequency range of 2 hz 35 hz a beamforming analysis identified body waves arriving from the west northwest pointing towards the mine and surface waves propagating from the northeast the calculated virtual shot gathers retrieved by cross correlating ambient noise at all receivers were processed following both two dimensional and three dimensional approaches using a sequence similar to the one applied to the activesource three dimensional data the dip moveout stacked section reveals a number of events similar to those observed on the processed active seismic sections in particular the passive seismic interferometry method is capable to partly image shallowly dipping reflections but did not produce convincing images of steeply dipping reflections dip moveout stacked sections obtained with different cross correlation time windows indicate that the strength and number of reflections generally increase with longer noise records however a few reflections at depth show reduced coherency with longer noise time windows the passive seismic interferometry results over the lalor mining area are encouraging but image quality of the passive survey is lower than the acquired active three dimensional survey at the area future ambient noise surveys with longer offsets shorter receiver spacing and wider azimuth distribution are needed in crystalline rock environment to address the potential of the method for mineral exploration

anelastic earth structure from the coherency of the ambient seismic field 1 cross correlation of the ambient seismic field is now routinely used to measure seismic wave travel times however relatively little attention has been paid to other information that could be extracted from these signals in this paper we demonstrate the relationship between the spatial coherency of the ambient field and the elastodynamic green s function in both time and frequency domains through measurement of the frequency domain coherency as a function of distance we sequentially recover phase velocities and attenuation coefficients from these measurements we generate 1 d shear wave velocity and attenuation models for southern california the ambient field measurements of attenuation and the exceptional path coverage that results from the many possible interstation measurements allow us to extend q estimates over a range of frequencies that has previously been difficult to analyze using earthquake data measurements from paths that cross major sedimentary basins show both lower wave speeds and lower quality factors than other paths as expected our results indicate that there is a wealth of information available in the spatial coherency of the ambient seismic field

imaging and monitoring of the shallow subsurface using spatially windowed surface wave analysis with a single permanent seismic source abstractdevelopment of shallow subsurface monitoring systems is important for monitoring the ground stability of shallow formation and also for conventional deep seismic monitoring because with cu

retrieval of local surface wave velocities from traffic noise an example from the la barge basin wyoming abstract in regions where active source seismic exploration is constrained by limitations of energy penetration and recovery cost and logistical concerns or regulatory restrictions analysis of natural source seismic data may provide an alternative in this study we investigate the feasibility of using locally generated seismic noise in the 2 6 hz band to obtain a subsurface model via interferometric analysis we apply this technique to three component data recorded during the la barge passive seismic experiment a local deployment in south western wyoming that recorded continuous seismic data between november 2008 and june 2009 we find traffic noise from a nearby state road to be the dominant source of surface waves recorded on the array and observe surface wave arrivals associated with this source up to distances of 5 kms the orientation of the road with respect to the deployment ensures a large number of stationary points leading to clear observations on both in line and cross line virtual source receiver pairs this results in a large number of usable interferograms which in turn enables the application of standard active source processing methods like signal processing common offset stacking and traveltime inversion we investigate the dependency of the interferograms on the amount of data on a range of processing parameters and on the choice of the interferometry algorithm the obtained interferograms exhibit a high signal to noise ratio on all three components rotation of the horizontal components to the radial transverse direction facilitates the separation of rayleigh and love waves though the narrow frequency spectrum of the surface waves prevents the inversion for depth dependent shear wave velocities we are able to map the arrival times of the surface waves to laterally varying group and phase velocities for both rayleigh and love waves our results correlate well with the known geological structure we outline a scheme for obtaining localized surface wave velocities from local noise sources and show how the processing of passive data benefits from a combination with well established exploration seismology methods we highlight the differences with interferometry applied to crustal scale data and conclude with recommendations for similar deployments

application of the virtual refraction to near surface characterization at the boise hydrogeophysical research site seismic interferometry is a relatively new technique to estimate the green s function between receivers spurious energy not part of the true green s function is produced because assumptions are commonly violated when applying seismic interferometry to field data instead of attempting to suppress all spurious energy we show how spurious energy associated with refractions contains information about the subsurface in field data collected at the boise hydrogeophysical research site by forming a virtual shot record we suppress uncorrelated noise and produce a virtual refraction that intercepts zero offset at zero time these two features make the virtual refraction easy to pick providing an estimate of refractor velocity to obtain the physical parameters of the layer above the refractor we analyse the cross correlation of wavefields recorded at two receivers for all sources a stationary phase point associated with the correlation between the reflected wave and refracted wave from the interface identifies the critical offset by combining information from the virtual shot record the correlation gather and the real shot record we determine the seismic velocities of the unsaturated and saturated sands as well as the variable relative depth to the water table finally we discuss how this method can be extended to more complex geologic models

the occurrence of mt barca flank eruption in the evolution of the nw periphery of etna volcano italy geological surveys tephrostratigraphic study and 40ar 39ar age determinations have allowed us to chronologically constrain the geological evolution of the lower nw flank of etna volcano and to reconstruct the eruptive style of the mt barca flank eruption this peripheral sector of the mt etna edifice corresponding to the upper simeto valley was invaded by the ellittico volcano lava flows between 41 and 29 ka ago when the mt barca eruption occurred the vent of this flank eruption is located at about 15 km away from the summit craters close to the town of bronte the mt barca eruption was characterized by a vigorous explosive activity that produced pyroclastic deposits dispersed eastward and minor effusive activity with the emission of a 1 1 km long lava flow explosive activity was characterized by a phreatomagmatic phase followed by a magmatic one the geological setting of this peripheral sector of the volcano favors the interaction between the rising magma and the shallow groundwater hosted in the volcanic pile resting on the impermeable sedimentary basement this process produced phreatomagmatic activity in the first phase of the eruption forming a pyroclastic fall deposit made of high density poorly vesicular scoria lapilli and lithic clasts conversely during the second phase a typical strombolian fall deposit formed in terms of hazard assessment the possible occurrence of this type of highly explosive flank eruption at lower elevation in the densely inhabited areas increases the volcanic risk in the etnean region and widens the already known hazard scenario

characterizing the primary material sources and dominant erosional processes for post fire debris flow initiation in a headwater basin using multi temporal terrestrial laser scanning data abstract wildfire dramatically alters the hydrologic response of a watershed such that even modest rainstorms can produce hazardous debris flows relative to shallow landslides the primary sources of material and dominant erosional processes that contribute to post fire debris flow initiation are poorly constrained improving our understanding of how and where material is eroded from a watershed during a post fire debris flow requires 1 precise measurements of topographic change to calculate volumetric measurements of erosion and deposition and 2 the identification of relevant morphometrically defined process domains to spatially constrain these measurements of erosion and deposition in this study we combine the morphometric analysis of a steep small 0 01 km 2 headwater drainage basin with measurements of topographic change using high resolution 2 5 cm multi temporal terrestrial laser scanning data made before and after a post fire debris flow the results of the morphometric analysis are used to define four process domains hillslope divergent hillslope convergent transitional and channelized incision we determine that hillslope divergent and hillslope convergent process domains represent the primary sources of material over the period of analysis in the study basin from these results we conclude that raindrop impact induced erosion ravel surface wash and rilling are the primary erosional processes contributing to post fire debris flow initiation in the small steep headwater basin further work is needed to determine 1 how these results vary with increasing drainage basin size 2 how these data might scale upward for use with coarser resolution measurements of topography and 3 how these results change with evolving sediment supply conditions and vegetation recovery

assessment of 4d seismic repeatability and co2 detection limits using a sparse permanent land array at the aquistore co2 storage site abstracttwo 3d time lapse seismic surveys were acquired in 2012 and 2013 at the aquistore co2 storage site prior to the start of co2 injection using these surveys we determined the background time lapse noise at the site and assessed the feasibility of using a sparse areal permanent receiver array as a monitoring tool applying a standard processing sequence to these data we adequately imaged the reservoir at 3150 3350 m depth evaluation of the impact of each processing step on the repeatability revealed a general monotonic increase in similarity between the data sets as a function of processing the prestack processing sequence reduced the normalized root mean squared difference nrms from 1 13 between the raw stacks to 0 13 after poststack time migration the postmigration cross equalization sequence further reduced the global nrms to 0 07 a simulation of the changes in seismic response due to a range of co2 injection scenarios suggested that co2 was detectable within the reservoir at the aquistor

strengthening the virtual source method for time lapse monitoring time lapse monitoring is a powerful tool for tracking subsurface changes resulting from fluid migration conventional time lapse monitoring can be done by observing differences between two seismic surveys over the surveillance period along with the changes in the subsurface differences in the two seismic surveys are also caused by variations in the near surface overburden and acquisition discrepancies the virtual source method monitors below the time varying near surface by redatuming the data down to the subsurface receiver locations it crosscorrelates the signal that results from surface shooting recorded by subsurface receivers placed below the near surface for the mars field data redatuming the recorded response down to the permanently placed ocean bottom cable obc receivers using the virtual source method allows one to reconstruct a survey as if virtualsources were buried at the obc receiver locations and the medium above them were a homogeneous half space separating the recorded wavefields

modeling the effects of eruptive and seismic activities on flank instability at mount etna italy 1 the identification and evaluation of trigger mechanisms for volcano flank instabilities and or collapse represent a key issue for risk assessment in densely populated volcanic areas as well as in long distance settings particularly in case of island or coastal volcanoes here we address quantitatively the effects of external seismic and inner magmatic forcing on the stress strain state associated to flank instabilities at mount etna sicily southern italy by means of a 2 d finite difference method numerical modeling modeled seismic actions include strong near field strong far field and low magnitude near field earthquakes magmatic actions consider the inner pressure changes induced by energetic lava fountains in the summit crater area and subvertical and oblique dike ascent below the summit area model results are validated in light of available monitoring data and recent eruptive activity numerical results show that the main strain effects are produced by high magnitude near field earthquakes expected return time of 103 yrs and by vertical uprise of a magma dike below the volcano summit area maximum displacements in the order of tens of centimeters may involve the summit area up to some 106 m3 m over some kilometers laterally stress releases up to 107 pa may affect a limited portion of the magmatic conduit thus favoring major effusive flank eruptions major catastrophic events such as volcano flank collapse should not be expected by applying either individually or combined the aforementioned actions

storm rainfall conditions for floods and debris flows from recently burned areas in southwestern colorado and southern california abstract debris flows generated during rain storms on recently burned areas have destroyed lives and property throughout the western u s field evidence indicate that unlike landslide triggered debris flows these events have no identifiable initiation source and can occur with little or no antecedent moisture using rain gage and response data from five fires in colorado and southern california we document the rainfall conditions that have triggered post fire debris flows and develop empirical rainfall intensity duration thresholds for the occurrence of debris flows and floods following wildfires in these settings this information can provide guidance for warning systems and planning for emergency response in similar settings debris flows were produced from 25 recently burned basins in colorado in response to 13 short duration high intensity convective storms debris flows were triggered after as little as six to 10 min of storm rainfall about 80 of the storms that generated debris flows lasted less than 3 h with most of the rain falling in less than 1 h the storms triggering debris flows ranged in average intensity between 1 0 and 32 0 mm h and had recurrence intervals of two years or less threshold rainfall conditions for floods and debris flows sufficiently large to pose threats to life and property from recently burned areas in south central and southwestern colorado are defined by i 6 5 d 0 7 and i 9 5 d 0 7 respectively where i rainfall intensity in mm h and d duration in hours debris flows were generated from 68 recently burned areas in southern california in response to long duration frontal storms the flows occurred after as little as two hours and up to 16 h of low intensity 2 10 mm h rainfall the storms lasted between 5 5 and 33 h with average intensities between 1 3 and 20 4 mm h and had recurrence intervals of two years or less threshold rainfall conditions for life and property threatening floods and debris flows during the first winter season following fires in ventura county and in the san bernardino san gabriel and san jacinto mountains of southern california are defined by i 12 5 d 0 4 and i 7 2 d 0 4 respectively a threshold defined for flood and debris flow conditions following a year of vegetative recovery and sediment removal for the san bernardino san gabriel and san jacinto mountains of i 14 0 d 0 5 is approximately 25 mm h higher than that developed for the first year following fires the thresholds defined here are significantly lower than most identified for unburned settings perhaps because of the difference between extremely rapid runoff dominated processes acting in burned areas and longer term infiltration dominated processes on unburned hillslopes

estimating the timing and location of shallow rainfall induced landslides using a model for transient unsaturated infiltration 1 shallow rainfall induced landslides commonly occur under conditions of transient infiltration into initially unsaturated soils in an effort to predict the timing and location of such landslides we developed a model of the infiltration process using a two layer system that consists of an unsaturated zone above a saturated zone and implemented this model in a geographic information system gis framework the model links analytical solutions for transient unsaturated vertical infiltration above the water table to pressure diffusion solutions for pressure changes below the water table the solutions are coupled through a transient water table that rises as water accumulates at the base of the unsaturated zone this scheme though limited to simplified soil water characteristics and moist initial conditions greatly improves computational efficiency over numerical models in spatially distributed modeling applications pore pressures computed by these coupled models are subsequently used in one dimensional slope stability computations to estimate the timing and locations of slope failures applied over a digital landscape near seattle washington for an hourly rainfall history known to trigger shallow landslides the model computes a factor of safety for each grid cell at any time during a rainstorm the unsaturated layer attenuates and delays the rainfall induced pore pressure response of the model at depth consistent with observations at an instrumented hillside near edmonds washington this attenuation results in realistic estimates of timing for the onset of slope instability 7 h earlier than observed landslides on average by considering the spatial distribution of physical properties the model predicts the primary source areas of landslides

geological and geomorphological evolution of the etna volcano ne flank and relationships between lava flow invasions and erosional processes in the alcantara valley italy abstract in this paper the interrelationships between volcanic activity and fluvial events in the alcantara valley are investigated based on the correlation between the stratigraphy of the ne flank of mt etna and subsurface data the geological and geomorphological evolutions of the valley are reconstructed new 1 10 000 scale geological mapping shows that the bulk of this sector of the volcano is made up of the ellittico volcano lava flows though they are widely covered by the products of the eruptive activity of the last 15 ka the present day morphological setting of the alcantara valley is the result of two main evolutionary phases initiated during the activity of the ellittico volcano only one lava flow invasion of the valley floor occurred in the first phase this phenomenon was followed by a long period of erosional processes leading to the entrenchment of the drainage pattern and the erosion of the ellittico lava flow about 20 25 ka ago an important change in the frequency of the lava flow invasions into the valley occurred associated with the final stage of the ellittico volcano activity marking the beginning of the second phase during this phase volcanic processes became predominant with respect to other morphogenetic processes in the alcantara valley lava flows coming from the ne flank of the ellittico volcano caused a radical modification of the morphological setting of this area even though only one lava flow emitted by an eruptive fissure located within the valley partially filled the riverbed during the eruptive activity of the last 15 ka the complete filling of the alcantara valley floor occurred in particular between 15 and 7 ka a lava flow originated from the mt moio scoria cone filled the valley floor for a distance of about 9 km following a short period of erosion an eruptive fissure located within the valley generated a 20 21 km long lava flow that was channelled along the full extent of the alcantara valley and stretches for about 3 km offshore in the ionian sea in the last 7 ka lava flows originating from the ne rift zone produced only temporary damming of the riverbed without any important contribution to the filling of the alcantara valley

quantifying sources of fine sediment supplied to post fire debris flows using fallout radionuclide tracers fine sediment supply has been identified as an important factor contributing to the initiation of runoff generated debris flows after fire however despite the significance of fines for post fire debris flow generation no investigations have sought to quantify sources of this material in debris flow affected catchments in this study we employ fallout radionuclides 137cs 210pbex and 239 240pu as tracers to measure proportional contributions of fine sediment 10 m from hillslope surface and channel bank sources to levee and terminal fan deposits formed by post fire debris flows in two forest catchments in southeastern australia while 137cs and 210pbex have been widely used in sediment tracing studies application of pu as a tracer represents a recent development and was limited to only one catchment the ranges in estimated proportional hillslope surface contributions of fine sediment to individual debris flow deposits in each catchment were 22 69 and 32 74 the greater susceptibility of 210pbex to apparent reductions in the ash content of channel deposits relative to hillslope sources resulted in its exclusion from the final analysis no systematic change in the proportional source contributions to debris flow deposits was observed with distance downstream from channel initiation points instead spatial variability in source contributions was largely influenced by the pattern of debris flow surges forming the deposits linking the tracing analysis with interpretation of depositional evidence allowed reconstruction of temporal sequences in sediment source contributions to debris flow surges hillslope source inputs dominated most elevated channel deposits such as marginal levees that were formed under peak flow conditions this indicated the importance of hillslope runoff and fine sediment supply for debris flow generation in both catchments in contrast material stored within channels that was deposited during subsequent surges was predominantly channel derived the results demonstrate that fallout radionuclide tracers may provide unique information on changing source contributions of fine sediment during debris flow events

the morphostructural setting of mount etna sedimentary basement italy implications for the geometry and volume of the volcano and its flank instability abstract the reinterpretation of more than 2500 subsurface data consisting of geoelectric and borehole prospecting undertaken at mount etna allows reconstructing the contour map of the sedimentary basement this reconstruction highlights a complex asymmetric topography due to the inhomogeneous long term updoming of the region and the interrelationship between the development of the drainage network and flank instability these different processes have produced a major morphological difference between the eastern sector characterised by a 17 km wide horseshoe shaped depression and the other flanks formed by palaeovalleys the origin of the wide horseshoe shaped depression can be attributed to the large scale flank instability processes involving the entire continental margin in the etna offshore this depression of the etna basement was generated by a series of coalescent landslides before the beginning of the eruptive activity of the timpe phase more than 220 ka ago this wide depression is the main cause of the flank instability that produced the gravitational slope failures of the valle del bove about 10 ka ago regarding mt etna s geometry we have estimated a total volume of about 532 km 3 that was emplaced during the past 330 ka resulting in an average rate of volcanic output of 0 0016 km 3 a the reconstruction of the temporal variation of the average eruptive rate highlights a drastic increase of volcanism during the last 100 ka in response to the gradual stabilization of the plumbing system in the etna region that led to the build up of the composite stratovolcano structure the data presented in this paper represent the state of knowledge of the sedimentary basement of etna which can be used for future studies aimed at developing a detailed understanding of the deep structure of the volcano s unstable flanks

the interaction of volcanic activity in quaternary times upon the evolution of the alcantara and simeto rivers mount etna sicily summary the interaction between volcanic and alluvial sequences is described for the alcantara and simeto valleys mount etna sicily this study provides valuable information on the stratigraphy for prehistoric lavas exposed on the lower western flanks of the volcano eight orders of terrace are recognised in the simeto valley the basal tholeiitic volcanics the oldest exposed lavas of etna are associated with terrace 7 of the simeto which is correlated with either the pre rianian nomentanan erosive phase or the early rianian stage of the pleistocene the earliest evidence of trachybasaltic volcanism in the simeto catchment occurs in terrace 4 which is considered to be of late maspinian age the oldest known volcanics in the north western part of the volcano are related to terrace 3 which is dated at around 20000 bp the alluvial deposits of these terraces provide a valuable sequence of italian quaternary sediments dating back over the last 300000 years the nature of these deposits is described and the probable conditions of their deposition considered the terraces in the upper part of the alcantara are quite different in their mode of formation from the lava capped cut and fill terraces of the simeto valley the current upper course of the alcantara river is considered to be quite youthful versilian in age and the terraces are bench features formed as the river cut down through the lava sequence

prediction of spatially explicit rainfall intensity duration thresholds for post fire debris flow generation in the western united states abstract early warning of post fire debris flow occurrence during intense rainfall has traditionally relied upon a library of regionally specific empirical rainfall intensity duration thresholds development of this library and the calculation of rainfall intensity duration thresholds often require several years of monitoring local rainfall and hydrologic response to rainstorms a time consuming approach where results are often only applicable to the specific region where data were collected here we present a new fully predictive approach that utilizes rainfall hydrologic response and readily available geospatial data to predict rainfall intensity duration thresholds for debris flow generation in recently burned locations in the western united states unlike the traditional approach to defining regional thresholds from historical data the proposed methodology permits the direct calculation of rainfall intensity duration thresholds for areas where no such data exist the thresholds calculated by this method are demonstrated to provide predictions that are of similar accuracy and in some cases outperform previously published regional intensity duration thresholds the method also provides improved predictions of debris flow likelihood which can be incorporated into existing approaches for post fire debris flow hazard assessment our results also provide guidance for the operational expansion of post fire debris flow early warning systems in areas where empirically defined regional rainfall intensity duration thresholds do not currently exist

comparison of soil infiltration rates in burned and unburned mountainous watersheds steady state infiltration measurements were made at mountainous sites in new mexico and colorado usa with volcanic and granitic soils after wildfires and at comparable unburned sites we measured infiltration in the new mexico volcanic soils under two vegetation types ponderosa pine and mixed conifer and in the colorado granitic soils under ponderosa pine vegetation these measurements were made within high severity burn areas using a portable infiltrometer with a 0 017 m 2 infiltration area and artificial rainfall rates ranging from 97 to 440 mm h 1 steadystate infiltration rates were less at all burned sites relative to unburned sites the volcanic soil with ponderosa pine vegetation showed the greatest difference in infiltration rates with a ratio of steady state infiltration rate in burned sites to unburned soils equal to 0 15 volcanic soils with mixed conifer vegetation had a ratio burned to unburned soils of at most 0 38 and granitic soils with ponderosa pine vegetation had a ratio of 0 38 steady state infiltration rates on unburned volcanic and granitic soils with ponderosa pine vegetation are not statistically different we present data on the particle size distribution at all the study sites and examples of wetting patterns produced during the infiltration experiments published in 2001 by john wiley sons ltd