hydrogeologic factors affecting acid neutralization in cadwell creek watershed west central massachusetts cadwell creek in west central massachusetts like many new england watersheds is underlain by crystalline metamorphic bedrock with glacial till serving as the main unconfined aquifer groundwater hydrology and chemistry were monitored in a network of 10 wells low air equilibrated ph lpar 4 7 5 4 low alkalinity near 0 mg l 1 caco3 and low conductivity 23 34 mhos occur in the groundwater in the downstream parts of the watershed where hydraulic gradients are steep and groundwater residence times are short about 3 months on the other hand the headwater areas are typified by low hydraulic gradients and slower groundwater velocities with correspondingly higher air equilibrated groundwater ph 7 0 7 4 alkalinity up to 26 mg l 1 and higher conductivity 32 71 mhos therefore even in this supposedly acid sensitive terrain groundwater is neutralized if mineral water contact time is sufficiently long here 1 year because some 70 of cadwell creek base flow originates as shallow groundwater in the lower reaches of the watershed the stream is very acidic most of the year only during late summer when deeper base flow from headwater sources prevails does the ph and alkalinity of the streamwater rise appreciably

dislocation models of interseismic deformation in the western united states 1 the gps derived crustal velocity field of the western united states is used to construct dislocation models in a viscoelastic medium of interseismic crustal deformation the interseismic velocity field is constrained by 1052 gps velocity vectors spanning the 2500 km long plate boundary zone adjacent to the san andreas fault and cascadia subduction zone and extending 1000 km into the plate interior the gps data set is compiled from u s geological survey campaign data plate boundary observatory data and the western u s cordillera velocity field of bennett et al 1999 in the context of viscoelastic cycle models of postearthquake deformation the interseismic velocity field is modeled with a combination of earthquake sources on 100 known faults plus broadly distributed sources models that best explain the observed interseismic velocity field include the contributions of viscoelastic relaxation from faulting near the major plate margins viscoelastic relaxation from distributed faulting in the plate interior as well as lateral variations in depth averaged rigidity in the elastic lithosphere resulting rigidity variations are consistent with reduced effective elastic plate thickness in a zone a few tens of kilometers wide surrounding the san andreas fault saf system primary deformation characteristics are captured along the entire saf system eastern california shear zone walker lane the mendocino triple junction the cascadia margin and the plate interior up to 1000 km from the major plate boundaries

hydrogeochemical cycling and chemical denudation in the fort river watershed central massachusetts an appraisal of mass balance studies the fort river watershed in central massachusetts receives precipitation with a composition similar to that in hubbard brook new hampshire yet the average stream water chemistry is substantially different showing higher ph and tds this is largely a function of bedrock and surficial geology and chemical differences among small streams within the fort river watershed are apparently controlled by the composition and thickness of the prevailing surficial cover the surficial deposits determine groundwater and surface water flow paths thereby affecting the resultant contact time with mineral matter and the chemistry of the runoff despite the rural setting over 95 of the annual sodium and chloride in the streams comes from road salt after correcting for this factor cation denudation rates are about equal to those at hubbard brook however silica removal is occurring at a rate more than 30 greater in the fort river when climatic conditions in hubbard brook and fort river are normalized weathering rates appear consistently higher in the fort river reflecting differences in weathering processes i e cation exchange and silicate breakdown and hydrogeology because of uncertainties in mechanisms of cation removal from watersheds the silica denudation rate may be a better index of weathering intensity

near station topographic masses correction for high accuracy gravimetric prospecting the expanding role of gravity prospecting in mineral and hydrocarbon exploration as well as seismic and volcanic risk studies will be related to its ability to provide high resolution anomalies to achieve this goal it is necessary to consider the errors resulting from the topographic corrections in particular near station effects such errors are relevant not only for severe topographies but also for relatively flat surfaces involving microgravity applications and large scale surveys indeed the errors introduced by low resolution digital elevation models can be of the same order of magnitude as the anomalies of interest this basic fact is demonstrated by tests on synthetic models the results of this analysis are summarized in an intuitive graph that can be used to estimate what near station topographic resolution is necessary for a specific survey for the vulcano island test site in southern italy we also compare results obtained using three different representations of the topographic surface with different horizontal resolutions and vertical precisions one from existing photogrammetric data the second from a digitized map and the third from a very high resolution laser scanning system among the three methods laser scanning is shown to obtain the highest resolution topographic reconstructions in the shortest time some weaknesses of the laser scanning methodology are discussed and we suggest ways of overcoming them

influence of the earthquake cycle and lithospheric rheology on the dynamics of the eastern california shear zone the eastern california shear zone is bounded by the high heat flow region of the basin and range province and the low heat flow region of the sierra nevada block this difference in thermal state influences the rheology of the lower crust upper mantle resulting in a viscosity contrast between the two regions we analyze the effect of such a contrast on the kinematics and dynamics of the shear zone with numerical models this viscosity contrast drives asymmetric strain accumulation in the upper crust producing an asymmetric surface velocity field an additional consequence of this strain pattern is the potential for asymmetric co seismic displacement during an earthquake

constancy of geologic slip rate along the central garlock fault implications for strain accumulation and release in southern california summary we present new slip rate estimates for the central garlock fault the incised edge of an alluvial fan deposit with a 10be cosmogenic radionuclide age of 13 3 5 9 1 1 ka is offset 70 7 m yielding a slip rate of 5 3 1 0 2 5 mm yr 1 a stream thalweg that is deeply incised into this surface is offset a lesser amount 58 4 m providing the lower bound for this rate climate considerations however suggest that the deep incision of this thalweg may have occurred at a younger date specifically at the end of the younger dryas period at 11 5 ka or at the onset of a summer monsoon rainfall pattern at 8 10 ka if the deep incision was related to one of these climate events then the resulting slip rate would be 5 1 0 3 and 6 6 1 2 mm yr 1 respectively all of the slip rates are consistent with previous geologic slip rates most of which suggest a latest pleistocene holocene slip rate of 5 7 mm yr 1 these geologic slip rates however contrast markedly with much slower at most half as fast short term rates of elastic strain accumulation constrained by geodesy the new slip rate thus adds to a growing body of evidence indicating that the garlock fault is experiencing a period of transient lack of strain accumulation in which the lower crust and mantle beneath the fault is deforming at a rate that is much slower than its long term average rate these observations suggest that the garlock fault experiences two modes of strain accumulation the current slow mode in which strain accumulates very slowly along the fault and fast mode during which the fault must store and release elastic strain energy at much faster rates than the long term average to account for the relatively rapid geologic slip rates measured along the central part of the fault

chemical weathering of silicate rocks in aldan shield and baikal uplift insights from long term seasonal measurements of solute fluxes in rivers abstract a reassessment of available information from the russian hydrological survey on long term seasonal measurements of water suspended matter and dissolved major element discharges in 30 small and large watersheds draining acid silicate rocks granites gneisses quartzites shales of the aldan shield and baikal uplift was combined with new data on river water chemistry for three granitic watersheds in order to calculate the fluxes of elements due to chemical weathering in accord with data on world rivers a positive correlation between chemical erosion rate and runoff is observed the majority of cations are removed during summer monsoon the spring flood yields 10 20 of the annual flux and the winter season accounts for only 5 15 the mean multi annual flux of total dissolved solid which is largely dominated by ca 60 80 on the siberian craton is comparable with that of temperate zones but higher than that of the canadian shield for similar runoff values rock composition and annual temperatures important element recycling due to litter degradation and weathering acceleration via organic ligands produced by abundant vegetation over permafrost soils is invoked to explain these results

avtis a novel millimetre wave ground based instrument for volcano remote sensing during may and june 2004 we tested a novel millimetre wave ground based dual mode radar and radiometer on soufriere hills volcano montserrat avtis all weather volcano topography imaging sensor has an active radar mode designed to image the distance to lava domes on volcanoes whose summits are commonly obscured by persistent cloud such as soufriere hills volcano the passive radiometer mode can be employed to measure the surface temperature of the imaged topography in its current form avtis can be deployed by two people and takes 50 min to acquire a 20 5 scene at 0 1 increments during the fieldwork period the lava dome was not growing and only the radar mode was used the data recorded indicate that the maximum distance imaged was about 3800 m combining datasets acquired from different viewpoints can potentially provide a full 3d topographic model the accuracy and completeness of this reconstruction are reduced by two factors firstly relatively small grazing angles of the ground based line of sight rendered incised valleys invisible secondly methods currently used to orient the instrument limit the accuracy of the resulting topographic information nevertheless valuable information on new topographic surfaces was obtained in an area north of the lava dome where a valley has been infilled by deposits and in the amphitheatre created by the giant collapse event of july 2003

viscoelastic coupling model of the san andreas fault along the big bend southern california the big bend segment of the san andreas fault is the 300 km long segment in southern california that strikes about n65 w roughly 25 counterclockwise from the local tangent to the small circle about the pacific north america pole of rotation the broad distribution of deformation of trilateration networks along this segment implies a locking depth of at least 25 km as interpreted by the conventional model of strain accumulation continuous slip on the fault below the locking depth at the rate of relative plate motion whereas the observed seismicity and laboratory data on fault strength suggest that the locking depth should be no greater than 10 to 15 km the discrepancy is explained by the viscoelastic coupling model which accounts for the viscoelastic response of the lower crust thus the broad distribution of deformation observed across the big bend segment can be largely associated with the san andreas fault itself not subsidiary faults distributed throughout the region the working group on california earthquake probabilities 1995 in using geodetic data to estimate the seismic risk in southern california has assumed that strain accumulated off the san andreas fault is released by earthquakes located off the san andreas fault thus they count the san andreas contribution to total seismic moment accumulation more than once leading to an overestimate of the seismicity for magnitude 6 and greater earthquakes in their type c zones

chemical weathering of silicate rocks in karelia region and kola peninsula nw russia assessing the effect of rock composition wetlands and vegetation this study is aimed at assessing the effect of factors including lithology forest peatland coverage dissolved organic carbon and vegetation on chemical fluxes and concentrations of major elements in rivers the mean annual element concentrations and dissolved fluxes of acid and basic rock dominated watersheds of the karelia region and kola peninsula nw russia have been estimated from the chemical composition of river water samples collected in the summers of 1996 2000 and from annual discharge and chemical composition data of 16 watersheds collected from 1961 to 1975 the mean annual flux corrected for atmospheric input varies from 0 5 to 5 6 t km2 y and is dominated by alkali metals for the kola alkaline rocks and by calcium for the karelian granito gneisses the pure granitic and pure basaltic river chemical denudation rates in the baltic shield are 0 33 and 2 3 t km2 y respectively the cationic and silica fluxes of both granitic and basaltic watersheds are comparable with those of other boreal regions having similar runoff compositions and climate the cationic flux of the rivers is positively correlated with the basic rock fraction of the watershed whereas the dissolved organic carbon flux increases with the increasing peatland fraction the chemical composition of the river water is controlled by bedrock dissolution during dry periods and by plant litter degradation and washout of organic debris from the topsoil horizon during wet periods taking account the chemical composition of the plant litter and the biological turnover intensity it was estimated that the plant litter degradation in kola and karelia regions provides 10 40 of total annual dissolved riverine element flux

new formulae for estimating lava flow volumes at mt etna volcano sicily a new data set of etna lava flows erupted since 1868 has been compiled from eight topographic maps of the volcano published at intervals since then volumes of 59 flows or groups of flows were measured from topographic difference maps most of these volumes are likely to be considerably more accurate than those published previously we cut the number of flow volumes down to 25 by selecting those examples for which the volume of an individual eruption could be derived with the highest accuracy this refined data set was searched for high correlations between flow volume and more directly measurable parameters only two parameters showed a correlation coefficient of 70 or greater planimetric flow area a 70 and duration of the eruption d 79 if only short duration 18 days flows were used flow length cubed l3 had a correlation coefficient of 98 using combinations of measured parameters much more significant correlations with volume were found dh had a correlation coefficient of 90 h is the hydrostatic head of magma above the vent and 92 where w is mean width and e is the degree of topographic enclosure and a combination of the two 97 these latter formulae were used to derive volumes of all eruptions back to 1868 to compare with those from the complete data set values determined from the formulae were on average lower by 16 dh 7 and 19

studying monogenetic volcanoes with a terrestrial laser scanner case study at croscat volcano garrotxa volcanic field spain erosional processes natural or anthropogenic may partly destroy the relatively small sized volcanic edifices characteristic of monogenetic volcanic zones leaving their internal structure well exposed nevertheless the study of these outcrops may be extremely challenging due to restricted accessibility or safety issues digital representations of the outcrop surface have been lately used to overcome such difficulties data acquired with terrestrial laser scanning instruments using light detection and ranging technology enables the construction of such digital outcrops the obtained high precision 3 d terrain models are of greater coverage and accuracy than conventional methods and when taken at different times allow description of geological processes in time and space despite its intrinsic advantages and the proven satisfactory results this technique has been little applied in volcanology related studies here we want to introduce it to the volcanological community together with a new and user friendly digital outcrop analysis methodology for inexperienced users this tool may be useful not only for volcano monitoring purposes but also to describe the internal structure of exposed volcanic edifices or to estimate outcrop erosion rates that may be helpful in terms of hazard assessment or preservation of volcanic landscapes we apply it to the croscat volcano a monogenetic cone in the la garrotxa volcanic field catalan volcanic zone ne spain quarrying of which leads to a perfect view of its interior but restricts access to its uppermost parts croscat is additionally one of the most emblematic symbols of the la garrotxa volcanic field natural park and its preservation is a main target of the park administration

stateline fault system a new component of the miocene quaternary eastern california shear zone the eastern california shear zone is an active north northwest trending zone of intraplate right lateral shear that absorbs 25 of pacific north america relative plate motion the stateline fault system sfs which includes several previously recognized discontinuously exposed quaternary structures along the california nevada border is in this paper defined as a continuous 200 km long zone of active dextral shear that includes from south to north the mesquite pahrump and amargosa valley segments recognition of this system expands the known extent of the eastern california shear zone 50 km to the east northeast from its traditionally recognized boundary along the death valley fault system proximal volcanic and rock avalanche deposits offset across the mesquite segment of the sfs indicate 30 4 km of slip on this structure since 13 1 0 2 ma this offset is an order of magnitude larger than previous estimates across this section of the sfs but it is consistent with larger offsets previously proposed for the central and northern sections the total offset and averaged slip rate since mid miocene time 2 3 0 35 mm yr are similar to those of other major faults across this portion of the basin and range which from east to west include the death valley panamint valley hunter mountain and owens valley fault systems however in contrast to these faults the average post mid miocene slip rate on the sfs is approximately twice that estimated from present day geodetic observations and an order of magnitude greater than estimates of average post mid pleistocene slip rates this discrepancy between long term short term and geodetically derived slip rates differs from other geologic geodetic slip rate discrepancies in the eastern california shear zone where geodetic slip rates are significantly faster than both long term and short term geologic slip rates this suggests that either the slip rate on the sfs has diminished over time such that the system is an abandoned strand of the relatively young eastern california shear zone or that the present day slip rate represents a transient period of slow slip such that strands of the shear zone must accommodate a complex spatial and temporal distribution of slip

lava flow volume and morphology from digitised contour maps a case study at mount etna sicily abstract the volume and morphology of a lava flow field can be measured by mapping and comparing the topography before and after lava emplacement contour maps are a widely available source of topographic data containing a record of the geomorphological changes at volcanoes due to lava emplacement this paper explores the use of 1 25 000 scale digitised contour maps for mapping two lava flows of diverse eruption history and morphology at mount etna sicily we find that subtracting dems created from these maps gives a good representation of volume and shape for thicker lava flows 10 m mean thickness in the case of the 1983 lava flow however thinner

uncertainties in slip rate estimates for the mission creek strand of the southern san andreas fault at biskra palms oasis southern california this study focuses on uncertainties in estimates of the geologic slip rate along the mission creek strand of the southern san andreas fault where it offsets an alluvial fan t2 at biskra palms oasis in southern california we provide new estimates of the amount of fault offset of the t2 fan based on trench excavations and new cosmogenic 10be age determinations from the tops of 12 boulders on the fan surface we present three alternative fan offset models a minimum a maximum and a preferred offset of 660 m 980 m and 770 m respectively we assign an age of between 45 and 54 ka to the t2 fan from the 10be data which is significantly older than previously reported but is consistent with both the degree of soil development associated with this surface and with ages from u series geochronology on pedogenic carbonate from t2 described in a companion paper by fletcher et al this volume these new constraints suggest a range of slip rates between 12 and 22 mm yr with a preferred estimate of 14 17 mm yr for the mission creek strand of the southern san andreas fault previous studies suggested that the geologic and geodetic slip rate estimates at biskra palms differed we find however that considerable uncertainty affects both the geologic and geodetic slip rate estimates such that if a real discrepancy between these rates exists for the southern san andreas fault at biskra palms it cannot be demonstrated with available data

the volume and shape of the 1991 1993 lava flow field at mount etna sicily the 1991 1993 lava flow is the most voluminous flow erupted at mount etna sicily in over 300 years estimates of the volume obtained by various methods range from 205 106 m3 tanguy 1996 to over 500 106 m3 barberi et al 1993 this paper describes the results of an electronic distance measurement edm based field survey of the upper surface of the 1991 1993 flow field undertaken in 1995 the results were digitised interpolated and converted into a digital elevation model and then compared with a pre eruption digital elevation model constructed from a 1 25 000 contour map of the area based on 1989 aerial photographs our measurements are the most accurate to date and show that the 1991 1993 lava flow occupies a volume of 231 29 106 m3

holocene slip rates along the owens valley fault california implications for the recent evolution of the eastern california shear zone one of the largest historical earthquakes in california occurred in 1872 along the owens valley fault located along the western margin of the eastern california shear zone new paleoseismic and optically stimulated luminescence data are the first to bracket the timing of the pre 1872 rupture to between 3 3 0 3 and 3 8 0 3 ka these data yield an earthquake recurrence interval between 4100 and 3000 yr under the assumption of uniform return and indicate a holocene slip rate between 1 8 0 3 and 3 6 0 2 mm yr our data are broadly consistent with a model proposed for the space time evolution of the eastern california shear zone our holocene slip rate estimates for the owens valley fault are slower than present day slip rates determined from elastic half space models of geodetic data this discrepancy is reduced by using the recurrence interval estimated here and a viscoelastic model of geodetic data or by including geologic slip rates from adjacent faults

paleoseismology and global positioning system earthquake cycle effects and geodetic versus geologic fault slip rates in the eastern california shear zone published slip rates for the owens valley fault zone in eastern california based on geodetic data and elastic half space models 5 7 mm yr are faster than longer term geologic rates 2 3 mm yr we use global positioning system data spanning the central owens valley a more realistic rheological model with an elastic upper crust over a viscoelastic lower crust and upper mantle and paleoseismic data from adjacent faults to show that this difference could reflect earthquake cycle effects we estimate a long term rate 2 1 0 7 mm yr and earthquake recurrence interval 2750 350 1000 yr from the geodetic data both in agreement with independent geologic estimates

chemical weathering in two adirondack watersheds past and present day rates rates of chemical weathering in two forested adirondack watersheds were determined from mineral and elemental depletion trends in soil profiles and from input output budgets based on precipitation and surface water chemistry long term rates of weathering have averaged about 500 to 600 eq ha yr for both watersheds since the glaciers retreated from the region about 14 000 yr ago present day denudation rates average 1679 eq ha yr in the panther lake watershed and only 198 eq ha yr in the woods lake watershed mineral weathering reactions in both watersheds involve primarily the dissolution of plagioclase potassium feldspar and hornblende mass balance calculations however indicate that hornblende weathers in disproportionately large amounts in the panther lake watershed relative to its abundance in soils and till cation exchange in the glacial till mantling the panther lake watershed may also play an important role in controlling surface water chemistry in the basin in the panther lake watershed the current rate of weathering which is about a factor of 3 greater than the long term average may reflect a recent adjustment for higher hydrogen ion fluxes brought about by acid deposition the capacity of the thick till deposits in the panther lake watershed to neutralize acidity is ultimately reflected by the circum neutrality of panther lake in the woods lake watershed the soils and thin till deposits cannot effectively neutralize current acid loadings and therefore woods lake is acidic with a ph below 5

the influence of loading by lavas on the siting of volcanic eruption vents on mt etna abstract until now it has been considered that the positioning of magma conduits dykes and eruption sites on mt etna is controlled by stresses set up by regional tectonism it is also likely that gravitational stresses have some influence on the subsurface path taken by etnean magmas prior to eruption an additional effect discussed here is based mainly on convincing field evidence gathered over a number of years it is proposed that fracturing of the surface and changes in the stress pattern due to loading by recent lava flows may strongly influence the siting of eruptions detailed field observations are presented showing that cracks and fumaroles have consistently appeared round the edges of recent lava flows and that these cracks are sometimes later used by erupting lavas eruption statistics indicate that since 1970 50 of new eruptive vents have appeared within 80 m of a recent flow edge and field measurements show that downward flexure is still occurring at the edges of lava flows more than sixteen years old simple theoretical modelling indicates that this effect is strongest at the surface with gravitational and regional tectonic control of eruption sites dominating at progressively deeper levels

photogrammetric monitoring of lava dome growth during the 2009 eruption of redoubt volcano abstract the 2009 eruption of redoubt volcano alaska began with a phreatic explosion on 15 march followed by a series of at least 19 explosive events and growth and destruction of at least two and likely three lava domes between 22 march and 4 april on 4 april explosive activity gave way to continuous lava effusion within the summit crater we present an analysis of post 4 april lava dome growth using an oblique photogrammetry approach that provides a safe rapid and accurate means of measuring dome growth photogrammetric analyses of oblique digital images acquired during helicopter observation flights and fixed wing volcanic gas surveys produced a series of digital elevation models dems of the lava dome from 16 april to 23 september the dems were used to calculate estimates of volume and time averaged extrusion rates and to quantify morphological changes during dome growth effusion rates ranged from a maximum of 35 m 3 s 1 during the initial two weeks to a low of 2 2 m 3 s 1 in early summer 2009 the average effusion rate from april to july was 9 5 m 3 s 1 early rapid dome growth was characterized by extrusion of blocky lava that spread laterally within the summit crater in mid to late april the volume of the dome had reached 36 10 6 m 3 roughly half of the total volume and dome growth within the summit crater began to be limited by confining crater walls to the south east and west once the dome reached the steep north sloping gorge that breaches the crater growth decreased to the south but the dome continued to inflate and extend northward down the gorge effusion slowed during 16 april 1 may but in early may the rate increased again this rate increase was accompanied by a transition to exogenous dome growth from mid may to july the effusion rate consistently declined the decrease is consistent with observations of reduced seismicity gas emission and thermal anomalies as well as declining rates of geodetic deflation or inflation these trends suggest dome growth ceased by july 2009 the volume of the dome at the end of the 2009 eruption was about 72 10 6 m 3 more than twice the estimated volume of the largest dome extruded during the 1989 1990 eruption in total the 2009 dome extends over 400 m down the glacial gorge on the north end of the crater with a total length of 1 km width of 500 m and an average thickness of 200 m

chemical weathering in granitic environments abstract factors controlling chemical weathering in granitic environments are deduced using an extensive database from the literature based on a transition state theory model we evaluated the effects on chemical weathering of runoff temperature and ph the dependence between temperature and runoff and chemical weathering is complicated by other factors such as the presence depth of soil cover soil cover favors chemical weathering when it is thin and rich in weatherable minerals in contrast it reduces chemical weathering when is thick and poor in primary minerals processes that increase the contact time and the surface of the water rock interactions such as physical denudation increase chemical weathering rates in granitic environments the effect of temperature can be quantified assuming an apparent activation energy value of 48 7 kj mol to describe chemical weathering of silica in granitic crystalline environment under high runoff conditions

an apparent shear zone trending north northwest across the mojave desert into owens valley eastern california strain rates measured at four geodetic networks in eastern california situated between northern owens valley and transverse ranges along a small circle drawn about the pacific north america pole of rotation are remarkably consistent each exhibits 0 14 mu rad yr simple right lateral engineering shear strain accumulation across the local vertical plane tangent to the small circle local faults e g owens valley garlock helendale traversing these networks are not as closely aligned with the vertical planes of maximum shear strain accumulation as is the local tangent to the small circle a fifth network slightly east of the small circle shows no significant strain accumulation thus a shear zone trending n35 degree w from near the eastern end of the big bend of the san andreas fault to northern owens valley is indicated by these data this corresponds to the eastern california shear zone proposed on geological evidence by dokka and travis the shear zone carries approximately 8 mm yr of the pacific north america relative plate motion from the san andreas fault north northwest across the mojave desert into owens valley and the northern basin and range province the shear zone observed at the surface may be a manifestation of a through going subcrustal fault

new kinematic models for pacific north america motion from 3 ma to present i evidence for steady motion and biases in the nuvel 1a model we use velocities derived from 2 4 5 years of continuous gps observations at 21 sites on the pacific and north american plates along with a subset of the nuvel 1a data to examine the steadiness of pacific north america motion since 3 16 ma the transfer of baja california to the pacific plate and the magnitude of biases in the nuvel 1a estimate of pacific north america motion we find that pacific north america motion has remained steady since 3 16 ma but at rates significantly faster than predicted by nuvel 1a in the vicinity of baja california our gps derived model and recent seafloor spreading rates in the southern gulf of california both indicate that the nuvel 1a model underestimates pacific north america rates by 4 2 mm yr 1 steady pacific north america motion since 3 16 myr and increasing seafloor spreading rates since 3 58 myr in the gulf of california imply that pacific north america motion was partitioned between seafloor spreading in the gulf of california and decelerating slip along faults in or offshore from the baja peninsula

modeling of postseismic relaxation following the great 1857 earthquake southern california abstract repeated first order triangulation measurements made from 15 monuments in central and southern california are used to explore the structure of the crust and upper mantle beneath southern california as well as to estimate the distribution of slip during the great 1857 earthquake the monuments are divided into two subnetworks with repeated observations covering the respective time intervals from 1884 to 1923 and from 1898 to 1923 the angle changes occurring within these times are modeled as a sum of two contributions postseismic displacements following the 1857 earthquake and plate tectonic loading the postseismic displacements have been calculated using a elastic viscoelastic coupling model that for any fault geometry yields the exact displacements on a spherically stratified earth the southern california crust and upper mantle are modeled as an upper elastic plate underlain by a viscoelastic asthenosphere for several different combinations of structural parameters inversions are performed for the slip distribution of the 1857 earthquake in general the best fits to the data are achieved with a triangular slip distribution an elastic plate thickness of 16 km a crustal thickness of 16 to 33 km and a mantle viscosity of 0 4 to 0 8 10 19 pa s although these inversions identify the best rheological models they lead to observed residuals that are inconsistent with a normally distributed data set a preferred model of slip is constructed that accounts for the budget of total slip during the earthquake cycle and satisfies a normally distributed data set the preferred slip distribution is similar in shape to the mapped surface slip distribution but is greater in amplitude by a factor of 1 5 to 2 in addition the san jacinto fault which has no known surface slip associated with the 1857 earthquake is inferred to have accommodated 1 to 3 m of slip during the 1857 earthquake and appears to be the favored site for tectonic strain accumulation since 1857 inferred fault slip exceeding known surface slip implies either unrecognized secondary faulting or a slip deficit at the surface relative to the slip at depth

strain accumulation in owens valley california 1974 to 1988 strain accumulation observed over the 1974 to 1988 interval in a 25 by 100 km aperture trilateration network spanning owens valley is adequately described by a strain rate that is uniform in space and time the tensor strain rate components referred to a coordinate system with the 2 axis directed n18 w parallel to the trend of the valley and the 1 axis n72 e are 11 0 042 0 014 strain yr 12 0 058 0 007 strain yr and 22 0 002 0 014 strain yr quoted uncertainties are standard deviations and extension is reckoned positive across the 25 km breadth of the network this amounts to 1 0 0 3 mm yr extension normal to the axis of the valley 2 9 0 4 mm yr right lateral shear across the axis and no extension parallel to the axis if the measured strain accumulation is attributed to slip on the deeper section of the owens valley fault with the uppermost 10 km of the fault locked the observed right lateral deformation would imply about 7 mm yr right lateral slip on the buried fault much greater than the geologic estimate of 2 0 5 mm yr right lateral secular slip beanland and clark 1994 nor is the observed uplift profile across the valley consistent with continuing normal slip on just the deep segment of the owens valley fault normal slip at depth on the sierra frontal fault also seems to be required the observed deformation across owens valley apparently implies processes more complicated than those represented by the conventional model of strain accumulation along a throughgoing fault

present day kinematics of the eastern california shear zone from a geodetically constrained block model we use global positioning system gps data from 1993 2000 to determine horizontal velocities of 65 stations in eastern california and western nevada between 35 and 37 n we relate the geodetic velocities to fault slip rates using a block model that enforces path integral constraints over geologic and geodetic time scales and that includes the effects of elastic strain accumulation on faults locked to a depth of 15 km the velocity of the sierra nevada block with respect to nevada is 11 1 0 3 mm yr with slip partitioned across the death valley 2 8 0 5 mm yr panamint valley 2 5 0 8 mm yr and airport lake owens valley 5 3 0 7 4 6 0 5 mm yr faults the western mojave block rotates at 2 1 0 8 my clockwise with 3 7 0 7 mm yr of left lateral motion across the western garlock fault we infer 11 2 mm yr of right lateral motion across the mojave region of the eastern california shear zone

runout analysis of a large rockfall in the dolomites italian alps using lidar derived particle sizes and shapes lidar data were used to quantify and analyse a rockfall event which occurred in 2003 in the western dolomites italian alps in addition to previously existing airborne laserscanning als data high resolution terrestrial laserscanning tls data were collected by using the original point clouds the volume axial ratio and runout length of single boulders as well as the surface roughness in the runout zone of the rockfall were derived the total volume of the rockfall event of approximately 10 000 m was estimated by a reconstruction of the pre event surface at the detachment zone the analysis of the laser scanning data of the accumulation zone revealed a power law scaling for boulder volumes larger than 8 m the dependence of runout length on boulder volume is complex it is moderated by particle sphericity in addition we used als and tls data to derive the spatial distribution of surface roughness on the talus cone tls allow for more accurate roughness mapping than als data but for most applications the point density of als data seems to be sufficiently high to derive measures of roughness different sampling approaches for plane fitting on the scale of 5 m did not show significant effects besides the computational time the results of our analyses provide important perspectives for rockfall modelling and process understanding with potential applications in both applied natural hazards and pure geomorphological research copyright 2012 john wiley sons ltd

lidar monitoring of mass wasting processes the radicofani landslide province of siena central italy abstract the radicofani basin stretching about 30 km nw se is an intra central apennine basin connected to pliocene pleistocene extensional tectonics it consists of an early to middle pliocene succession including essentially shelf pelites in the radicofani area province of siena tuscany region morphodynamic processes are very frequent with widespread badlands and rapidly evolving mudflows in order to evaluate the general instability of the radicofani area geological and geomorphological surveys were carried out the 1954 1990 and 2003 aerial surveys allowed a comparison of the changes in the various morphological aspects of the study area which suggested an increase in slope instability with time a new complex translational landslide evolving into mudflows activated during the winter of 2003 was monitored using an experimental system based on terrestrial lidar light detection and ranging and gps global positioning system technologies this system allowed the monitoring of the morphologic and volumetric evolution of the landslide a comparison of the monitoring data of october 2004 june 2005 may 2006 and may 2007 points out that the evolution is characterised by the sliding of displaced materials a volume of about 1300 m 3 of materials was removed during the period 2004 2005 300 m 3 for 2005 2006 and 400 m 3 for 2006 2007 the greater initial mass movement probably reflects a greater static imbalance during the early period of landslide movement and increased rainfall therefore the proposed monitoring system methodology allows the numerical evaluation of the landslide morphological evolution and to validate the landslide evolution model based on geological and geomorphological field surveys

time series analysis of lava flux we have applied time series analytical techniques to the flux of lava from an extrusive eruption tilt data acting as a proxy for flux are used in a case study of the may august 1997 period of the eruption at soufriere hills volcano montserrat we justify the use of such a proxy by simple calibratory arguments three techniques of time series analysis are employed spectral spectrogram and wavelet methods in addition to the well known 9 hour periodicity shown by these data a previously unknown periodic flux variability is revealed by the wavelet analysis as a 3 day cycle of frequency modulation during june july 1997 though the physical mechanism responsible is not clear such time series analysis has potential for other lava flux proxies at other types of volcanoes

block rotation and termination of the hosgri strike slip fault california from three dimensional map restoration the hosgri fault is located immediately offshore of south central california and is part of the transform boundary between the pacific and north american plates this fault terminates to the southeast into east trending folds and reverse separation faults of the western transverse ranges our new structure contour maps of deformed horizons show a spatial relationship between faulting and folding consistent with right lateral slip restoration of these digital maps quantifies post miocene right lateral slip across the southern hosgri fault to be 3 5 km this slip is absorbed by folding thrust overlap and clockwise vertical axis rotation of elongate blocks between strands of the fault the restored part of a block located to the east has rotated 8 clockwise extrapolating this restored rotation to the 50 km block length produces an estimate of 7 km of dextral shear for a total including the 3 5 km fault slip of 10 5 km of post miocene displacement our three dimensional approach precludes interpretations for reverse slip on the hosgri fault and is not consistent with models for more than 80 km of late cenozoic right lateral fault slip

right lateral displacements and the holocene slip rate associated with prehistoric earthquakes along the southern panamint valley fault zone implications for southern basin and range tectonics and coastal california deformation the n20 w trending panamint valley fault zone is linked to the n60 w trending hunter mountain strike slip fault and the saline valley fault system which represents one of the three major fault systems accommodating active crustal extension in the southern great basin a 25 km long zone of fault scarps along the southern panamint valley fault zone is recognized as the surface rupture zone associated with the most recent prehistoric earthquake the displacement associated with the most recent event determined through six detailed topographic maps of offset features is 3 2 0 5 m and a number of larger offsets in range of 6 7 m and 12 m are also observed if the larger displacements represent respectively two and three events each of 3 m then the fault zone appears to be associated with a characteristic earthquake which we estimate from the length of the rupture zone and the displacement to be between ms 6 5 and 7 2 the holocene slip rate is 2 36 0 79 mm yr is determined from the displacement of two alluvial features whose maximum age is estimated from pluvial shorelines assuming a characteristic earthquake model the recurrence interval is between 860 and 2360 years the holocene slip rate appears to be similar to the 4 million year slip rate of 2 2 7 mm yr determined from the hunter mountain fault which we suggest reflects the relatively constant tectonics in this region over the last 4 million years we further speculate that this supports the san andreas discrepancy in that the holocene slip rate of the san andreas fault probably represents its very long term several ma slip rate the total slip vector of the southern panamint valley fault system is oriented toward n35 w making this a predominantly strike slip fault in conjunction with the n60 w orientation of the hunter mountain strike slip fault we suggest that the displacement vector for the southern great basin is toward the nw consistent with results from vlbi data rather than wnw as determined by combining vlbi and geological data this in turn suggests that the coastal california deformation component involves respectively less shortening and more strike slip displacement perpendicular and parallel to the san andreas fault than is currently proposed

morphology of basaltic lava channels during the mt etna september 2004 eruption from airborne laser altimeter data 1 the morphological features of active lava channels acquired over mt etna by means of airborne laser altimeter data are presented the data were acquired on 16th september 2004 using an optech altm 3033 laser altimeter the flight height was about 2000 m above ground during the flight the lava erupted from the eastern part of the mt etna summit area flowed into the valle del bove the measured morphologic features are channel width wc flow width wf levee height hl flow thickness tf and channel depth dc the main lava flow shows a well developed channel with levees the average measured values for the morphologic features of this flow are wc 16 m wf 52 m hl 7 m tf 5 m and dc 2 m the wc parameter shows linear increase from about 7 m near the vent up to about 25 m close to the front 1600 m in length

coastal cliff monitoring and analysis of mass wasting processes with the application of terrestrial laser scanning a case study of rugen germany abstract an active landslide affecting a composite sea cliff section of the island of rugen germany was investigated and monitored using terrestrial laser scanning biannual surveys were performed from 2006 to 2011 high resolution scans were used to delineate landslide extensions monitor the spatial and temporal changes and evaluate the processes of mass wasting along the cliff section between may 2006 and may 2011 the multi temporal analysis documents a strong landward progression of the landslide that resulted in an increase in the planimetric area by 32 in the same period 9365 m 3 of soil volume has been removed primarily due to rainfall triggered surface runoff erosion and the resulting slumping this volume loss correlates with the preferential erosion of weak and unconsolidated sediments building up the major part of the cliff face this produced a maximum cliff top retreat of 17 32 m with an average retreat rate of 3 46 m yr 1 the quantification of the mass wasting processes and cliff top retreat demonstrates the substantial effect of local cliff lithology on slope stability and supports a prognosis of the near future development of the landslide furthermore the absence of local wave attack indicators or human activity highlights the major role of subaerial processes in the erosion of the sea cliff these results can be transferred to cliff locations in the urbanised cliff top area nearby that currently suffer similar cliff erosion processes and episodic events of large cliff top retreats the study therefore provides reliable data for the local authorities in charge of hazard assessment and planning and implementation of adaptive countermeasures

sector collapse forming at casita volcano nicaragua catastrophic sector collapse occurs when a volcano becomes structurally unable to support its own load one process particularly capable of weakening the edifice is hydrothermal activity it can produce high pore pressures and alter strong rock to clays alteration can extend progressively over long periods 100 yr allowing deformation to develop slowly before collapse an important finding is that structures produced by such deformation are recognizable and could permit collapse prediction we present the case of casita nicaragua where hydrothermal activity has been weakening the edifice core causing flank spreading altering original constructional shape and steepening flank slopes one side is slumping outward producing a crescentic scar with a basal bulge we identify this feature as the site of a potential sector collapse with conditions ripe for failure

surface movements of emplaced lava flows measured by synthetic aperture radar interferometry lava flows continue to move after they have been emplaced by flow mechanisms this movement is largely vertical and can be detected using differential synthetic aperture radar sar interferometry there are three main components to this motion 1 movement of surface scatterers resulting in radar phase decorrelation 2 measurable subsidence of the flow surface due to thermal contraction and clast repacking and 3 time dependent depression of the flow substrate these effects act in proportion to the thickness of the lava flow and decay with time although there is a time lag before the third component becomes significant we explore these effects using sar data from the ers satellites over the etna volcano sicily phase decorrelation on young thick a a lava flows persists for a few years and probably results from surface block rotations during flow contraction maximum measured subsidence rates of the 1991 1993 lava flow over a period of 70 days are about 0 7 mm day 1 but are potentially greater in areas of data decorrelation these rates fall to 2 7 10 2 mm day 1 after about 20 years in flows about 50 m thick sooner for thinner flows comparison with measured subsidence rates on kilauean lava lakes suggests that thermal contraction only accounts for about one third of the observed subsidence the remaining motion is thought to come from surface clast repacking during cooling and from creep mechanisms in the flow substrate measurements of postemplacement surface movement provide new constraints on the thermomechanical properties of lava flows and have cautionary implications for the interpretation of interferometric sar data of volcanoes 2001 american geophysical union

integration of radar interferometry and laser scanning for remote monitoring of an urban site built on a sliding slope the alpine village of lamosano belluno italy located near a wide and active landslide has been seriously threatened by ground instabilities since 1960 in this paper the results obtained by two different remote monitoring techniques synthetic aperature radar interferometry and three dimensional laser scanner imaging planned for lamosano hazard assessment are presented both techniques compare images taken at different times to map and classify changes that occurred on the imaged scenario the radar and laser data are gathered at the same dates with about ten month temporal separation the displacements measured separately by each of the two techniques highlight a similar sliding motion on the lamosano village area providing a good validation to each other and contributing to the definition of the village instability hazard

review of earth science research using terrestrial laser scanning abstract the application of advanced remote sensing technologies including terrestrial laser scanning tls to the earth sciences has increased rapidly in the last two decades improving the spatial and temporal resolution of data terrestrial laser scanning units have evolved into a common tool in studies of spectral and structural geology seismology natural hazards geomorphology and glaciology special consideration of the advantages and limitations of tls in each of these fields is discussed in depth in the context of important work published in each field the workflow used in a tls survey is crucial to the success of the survey and field specific earth science workflows are therefore also discussed products based on tls data such as triangulated irregular networks tin and digital surface models dsm are commonplace tools throughout the earth sciences and the use of these tools to measure slip distributions fault geometries aeolian transport river bed morphologies and flows and other research problems is expanded on where appropriate the review concludes with a discussion of recent trends in tls instrument development and their potential impact on the use of tls in the earth sciences in the future

monitoring coastal change using terrestrial lidar the paper describes recent applications by the british geological survey bgs of the technique of mobile terrestrial light detection and ranging lidar surveying to monitor various geomorphological changes on english coasts and estuaries these include cliff recession landslides and flood defences and are usually sited at remote locations undergoing dynamic processes with no fixed reference points advantages disadvantages and some practical problems are discussed the role of gps in laser scanning is described

tree damage and surface displacement the 1931 m 8 0 fuyun earthquake trees often suffer damage during large earthquakes due to shaking and rupturing of the ground surface from associated faults the damage may result in temporary asymmetric growth and reduction in the width of annual growth rings observation of tree displacement and tree ring analysis of the circle shrub sabina pseudosabina on the fuyun fault zone in northwest china reveals dextral displacement as much as 10 8 m along the surface rupture located near the epicenter of the 1931 m 8 fuyun earthquake tree ring analysis indicates a sharp change in ring width in 1931 rings of 1931 1934 are much narrower in width than those formed immediately before 1931 and after 1934 no obvious abnormalities in average temperature or rainfall during 1931 1934 were recorded the results of ring analysis and the displacement of trees indicate that the sharp change of tree ring width and the maximum displacements of 10 15 m near the epicentral area were generated by surface rupturing in the 1931 m 8 0 fuyun earthquake

pattern and rates of faulting in the central nevada seismic belt and paleoseismic evidence for prior beltlike behavior the central nevada seismic belt cnsb is a concentration of historical 1915 1932 1954 surface faulting in the western basin and range province forming a linear nearly continuous 300 km long rupture zone previous results are integrated in this study with new paleoseismic and exploratory trenching data from the historical zones to look for evidence of older similar beltlike patterns or elevated slip rates that could indicate whether the cnsb is a zone of focused long term crustal strain the data show that the continuous rupture belt produced by the seven earthquakes occurring between 1915 and 1954 is unique in the available paleoseismic record at the 1954 fairview peak fault the lack of prehistorical faulting in deposits containing the wilson creek bed 19 tephra eliminates the possibility of an identical seismic belt in the past 35 4 ka our studies also show that the faults have net slip rates ranging from a low of 0 09 mm yr on the fairview peak fault to a high of 0 7 mm yr on the 1932 cedar mountain fault these are considered moderate to low rates that are similar to most late quaternary faults in the western basin and range province a space time comparison shows that the paleoseismic histories for these multiple rupture zones are diverse and the number and timing of events in each of the zones indicate that there is little evidence for older contemporaneous ruptures of these same faults based on these results we reach several conclusions regarding the longer term holocene behavior of the cnsb although paleoseismic data preclude an older identical rupture belt among the historical zones consideration of associated holocene faults within the greater cnsb region indicates that several similar but not identical beltlike rupture patterns are plausible during the past 13 ka although each requires seismic gaps in the along strike pattern although long term strain represented by density of young faults does appear to increase from east to west into the cnsb the slip rate data demonstrate that the cnsb is not a belt of concentrated or elevated crustal strain compared with areas that extend west to the sierra nevada the increase in the distribution of holocene fault activity from east to west into the cnsb is consistent with a marked increase in the 1992 2002 gps velocity field at the latitude of the 1954 rupture sequence however a comparison of the geologic rates across the belt at this same latitude indicates that the extension rates 0 59 1 37 mm yr are systematically lower than both the campaign and continuous gps rates 2 20 3 13 mm yr by factors of 2 5 these discrepancies may be due to postseismic strain or to some form of off fault deformation we conclude that the results of our study of fault behavior in the cnsb best support the belt migration model proposed by wallace 1987 for the western basin and range province in which temporal tectonic pulses are believed to migrate regionally activating different beltlike combinations of late quaternary faults in an as yet unknown pattern of migration

quantitative assessment for the rockfall hazard in a post earthquake high rock slope using terrestrial laser scanning abstract geometric information and discontinuity characterization of rock masses are the key aspects of the analysis of the evolution and failure mechanisms of rockfalls with the advantageous use of terrestrial laser scanning tls the accurate three dimensional 3d spatial information of rock slopes can be obtained without contact by conducting a fuzzy k means algorithm in this study the automatic identification of discontinuity sets is achieved and dominant occurrences of rock mass discontinuities in each local region can be acquired in great detail this automatic identification method permits the user to visually identify the discontinuity sets and acquire their spacial distribution features e g occurrences spacings trace lengths and their geometric compounding relationships at the same time based on the shortest distance sd algorithm and the surface to plane volume calculation algorithm the distributions shapes volumes and scars of the rockfalls can be accurately detected over the monitored time interval these methods are able to provide adequate investigations and quantitative assessment for the rockfall failure mechanisms and evolutions of the hongshiyan post failure rock slope after the 2014 ludian earthquake the topography of the landslide surface mechanical properties scales and the structural features of the discontinuities have a significant effect on the failure mechanisms distributions and volumes of rockfalls the main failure mechanisms of the rockfall investigated in this rock slope can be divided into plane failure wedge failure and toppling failure the plane and wedge failures mainly occurred in the landslide surface while the toppling failures are mainly observed along the edge of the post failure slope which is obviously responded by preferred discontinuities the reverse dip stratified structure characteristics and the excavation disturbances during the recovering and slope treatment stage induce numerous progressive and continuous failures of rockfalls the results are beneficial for the design and optimization of rockfall treatments

the assessment of chemical weathering rates within an upland catchment in north east scotland a study has been made of weathering in glendye an upland catchement of heather moorland underlain mainly by granite with some gneiss in north east scotland the concentrations of a range of elements and ions in precipitation and river water were measured over a twelve month period the total input and output of each element or ion was calculated the resulting balances show net outputs of all species except hydrogen ion large net outputs of silicon 38 5 kg ha 1 a 1 and bicarbonate 48 kg ha 1 a 1 indicate considerable chemical weathering a large net output of chloride 32 kg ha 1 a 1 indicates the importance of dry deposition of oceanic aerosols when this is allowed for the rate of output of elements due to weathering is si ca na mg k fe al these results were compared with the abundance of elements in bedrock and differential weathering ratios calculated these are compared with data from the hubbard brook study in new hampshire in both cases calcium is by far the most mobile element the relative importance of the atmosphere and of chemical weathering as sources of each element was calculated and the results compared with those of a study at wet sleddale in the lake district similar patterns emerge in both cases

nonlinear strain buildup and the earthquake cycle on the san andreas fault two contrasting models of the earthquake deformation cycle on strike slip faults predict significant temporal declines in shear strain rate near the fault accompanied by a progressive broadening of the zone of deformation adjacent to it in the thin lithosphere model transient deformation results from flow in the asthenosphere due to stress relaxation following faulting through most or all of the lithosphere for an earth model with a thick elastic lithosphere plate thickness depth of seismic slip transient motions are due to postearthquake aseisrnic slip below the coseismic fault plane data from the san andreas fault indicate a long term temporal decrease in strain rate that persists for at least 30 years and may extend through the entire earthquake cycle observations support a cycle long rate decrease and a temporal spreading of the deformation profile only if movement cycles on the northern and southern locked sections of the fault are basically similar if so the usually lower strain rates and broader deformation zone currently observed on the southern san andreas represent a later evolutionary stage of the northern locked section where a great earthquake is a more recent occurrence although the data allow some extreme models to be discarded no sufficiently strong constraints exist to decide between the thin and thick lithosphere models regardless of the appropriate model the geodetic observations themselves indicate that strain buildup is sufficiently nonlinear to cause significant departures from recurrence estimates based on linear strain accumulation and the time predictable model

postseismic deformation following the 1906 san francisco earthquake we have reevaluated triangulation data from northern california following the 1906 san francisco earthquake thereby increasing the temporal and spatial resolution of postseismic deformation following that event we have calculated uniform shear strain rates and average station velocities at point arena using data from 1906 1907 1929 1930 and 1973 1975 and for the point reyes petaluma arc using data from 1929 1930 1938 1939 and 1960 1961 with the addition of recent geodetic data we infer an effective relaxation time for long term postseismic deformation following the 1906 earthquake of 36 16 years the point arena data are satisfactorily fit with accelerated afterslip at depth along the san andreas fault plane for a 10 km deep 25 km wide afterslip zone the average slip rate between 1906 and 1930 is 11 2 cm yr between 1929 and 1975 it is 4 6 cm yr deformation in the point reyes petaluma arc is clearly asymmetric with respect to the trace of the san andreas fault especially between 1929 and 1939 after inverting for the range of acceptable accelerated deep afterslip and horizontal detachment models a detailed analysis using geologically reasonable geometries revealed that both model types have trouble explaining the spatial variations in the deformation field through time in particular accelerated deep afterslip models cannot reproduce the breadth of the observed deformation field to the northeast of the san andreas fault as a result more complex time varying deformation mechanisms are required to explain the point reyes petaluma arc observations

crustal deformation in great california earthquake cycles periodic crustal deformation associated with repeated strike slip earthquakes is computed for the following model a depth l h extending downward from the earth s surface at a transform boundary between uniform elastic lithospheric plates of thickness h is locked between earthquakes it slips an amount consistent with remote plate velocity vpl after each lapse of earthquake cycle time tcy lower portions of the fault zone at the boundary slip continuously so as to maintain constant resistive shear stress the plates are coupled at their base to a maxwellian viscoelastic asthenosphere through which steady deep seated mantle motions compatible with plate velocity are transmitted to the surface plates the coupling is described approximately through a generalized elsasser model we argue that the model gives a more realistic physical description of tectonic loading including the time dependence of deep slip and crustal stress buildup throughout the earthquake cycle than do simpler kinematic models in which loading is represented as imposed uniform dislocation slip on the fault below the locked zone parameters of the model are chosen to fit seismic and geologic constraints and the apparent time dependence of surface strain rates along presently locked traces of the 1857 and 1906 san andreas ruptures we fix vpl 35 mm yr tcy 160 years and l 9 11 km based on earthquake nucleation depths the geodetic data are then found to be described reasonably within the context of a model that is locally uniform along strike and symmetric about a single san andreas fault strand by lithosphere thickness h 20 30 km and elsasser relaxation time tr 10 16 years we therefore suggest that the asthenosphere appropriate to describe crustal deformation on the earthquake cycle time scale lies in the lower crust and perhaps crust mantle transition zone and has an effective viscosity between about 2 1018 and 1019 pa s depending on the thickness assigned to the asthenospheric layer predictions based on the chosen set of parameters are also consistent with data on variations of contemporary surface strain and displacement rates as a function of distance from the 1857 and 1906 rupture traces although the fit is degraded by asymmetry relative to the fault and by slip on adjacent fault strands

the application of a long range laser scanner for monitoring volcanic activity on mount etna abstract there is a requirement for rapid remote monitoring of ground deformation of volcanoes especially during eruptions a long range reflector less laser scanning instrument manufactured by riegl laser measurement systems was used on mount etna in october 2000 and its potential for monitoring ground surface changes associated with volcanic activity was evaluated the 3dlm lr1 scanner system can measure distances up to 2 km with an accuracy of 25 mm in typical conditions measurement rates range from 1 point per second at 2 km to 4 points per second at 10 m the system also records reflective intensity and this proved useful in distinguishing between different types of volcanic material cloud and gas obscured some measurements but the scanning nature of the instrument coupled with effective data filtering software allowed robust digital terrain models to be created

instabilities in the summit region of mount etna during the 1999 eruption during the 1999 eruption of mount etna sicily the summit of the volcano changed dramatically lavas erupted from a fissure on the southern flank of se cone formed a large compound flow field that buried a substantial part of the northern wall of valle del bove and the ground between there and se cone hot mass flow deposits formed on the eastern and western flanks of the chasm following a period of intense strombolian activity at the same time a new vent opened on the southern flank of se cone and there was a major rockfall from its summit seven weeks later part of the outer western rim of bocca nuova crater collapsed during another period of intense strombolian activity and lava emerged at a high effusion rate through the breached crater wall following a subsequent collapse of the bocca nuova crater rim a hot avalanche flowed a few hundred metres on top of the previous lava flow field similar deposits have been described on other volcanoes but their importance in the evolution of the summit of etna has not previously been recognised

application of a long range terrestrial laser scanner to a detailed rockfall study at vall de nuria eastern pyrenees spain abstract in this study we show the application of a long range terrestrial laser scanner tls to a detailed rockfall study in a test zone at vall de nuria located in the eastern pyrenees data acquisition was carried out using tls ilris3d the new generation of reflector less laser scanners with a high range accuracy and velocity of measurements eight scans were performed at 3 stations to acquire coordinates of almost 4 million points the results from the acquired data are a high accuracy digital elevation model dem and the reconstruction of the joint geometry the former is used for inventory of rockfalls and for more accurate rockfall simulation trajectories and velocities the latter allows us to model the geometry and volume of the source area in recent rockfalls our findings suggest that tls technology could be a tool of reference in rockfall studies in the near future

elevated shear zone loading rate during an earthquake cluster in eastern california we compare geodetic velocity to geologic fault slip rates to show that tectonic loading was doubled across the eastern california shear zone ecsz during a cluster of major earthquake activity new slip rates are presented for six dextral faults that compose the ecsz in the central mojave desert these rates were determined from displaced alluvial fans dated with cosmogenic 10 be and from a displaced lava flow dated with 40 ar 39 ar we find that the sum geologic mojave ecsz slip rate 6 2 1 9 mm yr is only half the present day geodetically measured velocity of 12 2 mm yr these rates account for cumulative fault slip and geodetic observations that span the 60 km wide shear zone therefore this difference cannot be attributed to postseismic relaxation redistribution of tectonic loading over the earthquake cycle at a regional scale suggests that earthquake clustering may be enhanced via feedback with weakening of ductile shear zones

mobility of continental mantle evidence from postseismic geodetic observations following the 1992 landers earthquake the crust around the rupture zone of the 1992 landers earthquake has continued to deform in the years following the earthquake at rates 3 times greater than pre earthquake rates we use a combination of global positioning system gps and synthetic aperture radar insar data collected during a 3 year epoch following the earthquake in order to investigate postseismic mechanisms responsible for the high transient velocities in order to maximize the potential signal from viscoelastic relaxation we evaluate and model postseismic relaxation following the first few months of documented accelerated deformation the combination of gps and insar data allows us to establish viscoelastic relaxation of the lower crust and upper mantle as the dominant postseismic process and to discriminate among possible viscoelastic models the data particularly require the presence of a highly ductile uppermost mantle beneath the central mojave domain with temperature between the wet and dry basalt solidus this is consistent with independent seismic and geochemical inferences of a regionally warm uppermost mantle further consideration of seismic velocity variations in conjunction with faulting patterns within the mojave desert suggests that the primary faulting characteristics of the mojave desert namely the pervasive late cenozoic deformation within the eastern california shear zone versus the near absence of faults in the western mojave domain are controlled by the rheology of the uppermost mantle

strain accumulation across the eastern california shear zone at latitude 36 30 n the motion of a linear array of monuments extending across the eastern california shear zone ecsz has been measured from 1994 to 1999 with the global positioning system the linear array is oriented n54 e perpendicular to the tangent to the local small circle drawn about the pacific north america pole of rotation and the observed motion across the ecsz is approximated by differential rotation about that pole the observations suggest uniform deformation within the ecsz strike n23 w 26 nstrain yr 1 extension normal to the zone and 39 nstrain yr 1 simple right lateral shear across it with no significant deformation in the two blocks the sierra nevada mountains and southern nevada on either side the deformation may be imposed by right lateral slip at depth on the individual major fault systems within the zone if the slip rates are death valley furnace creek fault 3 2 0 9 mm yr 1 hunter mountain panamint valley fault 3 3 1 6 mm yr 1 and owens valley fault 6 9 1 6 mm yr 1 however this estimate of the slip rate on the owens valley fault is 3 times greater than the geologic estimate

structural and geomorphological features of landslides in the bhutan himalaya derived from terrestrial laser scanning abstract this study presents data on landslides affecting the main west east transport corridor in the himalaya of eastern bhutan close to the main central thrust the study focuses on the extraction of structural and geometrical information from terrestrial laser scanning tls data utilising a case study landslide the namling landslide analyses of the tls data allow extraction of slide geometry discontinuity orientations and identification of the mode of failure the tls results are compared to a traditional engineering geological survey and prove to yield considerable added value and should form the basis of new approaches to geomorphological studies and site assessment macro scale geomorphological reconnaissance findings are outlined and interpreted within a conceptual model of the evolution of landslide features here termed hierarchical landsliding it is concluded that the nam ling landslide is indicative of deeper seated deformation and is not purely a function of road construction

detecting the development of active lava flow fields with a very long range terrestrial laser scanner and thermal imagery regular topographic surveys of active lava flows could provide significant insight into the development of flow fields but data of sufficient accuracy spatial extent and repeat frequency to quantify the processes involved have yet to be acquired here we report results from the use of a new very long range terrestrial laser scanner tls on active lavas at mount etna sicily the scanner proved capable of providing useful topographic data from volcanic terrain at ranges up to 3500 m with laser returns from ash covered slopes as well as from lava despite very low effusion rates 1 m3s 1 topographic changes associated with the emplacement and inflation of new flows and the inflation of a tumulus were detected irregular data spacing resulting from oblique views makes the interpretation of laser derived digital elevation models alone difficult but fusing topographic data with thermal images allows active flow features to be clearly visualized

use of a portable topographic mapping millimetre wave radar at an active lava flow a ground based millimetre wave radar avtis all weather volcano topography imaging sensor has been developed for topographic monitoring the instrument is portable and capable of measurements over ranges up to 7 km through cloud and at night in april and may 2005 avtis was deployed at arenal volcano costa rica in order to determine topographic changes associated with the advance of a lava flow this is the first reported application of mm wave radar technology to the measurement of lava flux rates three topographic data sets of the flow were acquired from observation distances of 3 km over an eight day period during which the flow front was detected to have advanced 200 m topographic differences between the data sets indicated a flow thickness of 10 m and a dense rock equivalent lava flux of 0 20 0 08 m3s 1

inference of multiple earthquake cycle relaxation timescales from irregular geodetic sampling of interseismic deformation abstract characterizing surface deformation throughout a full earthquake cycle is a challenge due to the lack of high resolution geodetic observations of duration comparable to that of characteristic earthquake recurrence intervals 250 10 000 years here we approach this problem by comparing long term geologic slip rates with geodetically derived fault slip rates by sampling only a short fraction 0 001 0 1 of a complete earthquake cycle along 15 continental strike slip faults geodetic observations provide snapshots of surface deformation from different times through the earthquake cycle the timing of the last earthquake on many of these faults is poorly known and may vary greatly from fault to fault assuming that the underlying mechanics of the seismic cycle are similar for all faults geodetic observations from different faults may be interpreted as samples over a significantly larger fraction of the earthquake cycle than could be obtained from the geodetic record along any one fault alone as an ensemble we find that geologically and geodetically inferred slip rates agree well with a linear relation of 0 94 0 09 to simultaneously explain both the ensemble agreement between geologic and geodetic slip rate estimates with observations of rapid postseismic deformation we consider the predictions from simple two layer earthquake cycle models with both maxwell and burgers viscoelastic rheologies we find that a two layer burgers model with two relaxation timescales is consistent with observations of deformation throughout the earthquake cycle whereas the widely used two layer maxwell model with a single relaxation timescale is not suggesting that the earthquake cycle is effectively characterized by a largely stress recoverable rapid postseismic stage and a much more slowly varying interseismic stage

fault slip rates effects of elastic heterogeneity on geodetic data and the strength of the lower crust in the salton trough region southern california 1 in southernmost california the salton trough sedimentary basin lies between the subparallel san jacinto and san andreas faults that together with the elsinore fault accommodate 80 of the 50 mm yr of pacific north american relative motion the slip rates on the san andreas and san jacinto faults have been a matter of recent debate and one source of uncertainty has been the influence of crustal strength heterogeneity due to elastically weak basin sediments on geodetic data to evaluate these effects we have modeled regional kinematics with elastic and viscoelastic finite element models that incorporate laterally and vertically varying crustal material properties we find that in general the effects of the sedimentary basin on surface deformation are relatively small and that to explain the geodetic velocity data the slip rate on the san andreas must be higher than that on the san jacinto fault consistent with traditional geologic estimates we also conclude that a relatively strong lower crust of viscosity 5 x 10 19 pa s exists in this region

chemical denudation and weathering mechanisms in central massachusetts u s a two small streams on opposite sides of the catchment of quabbin reservoir in west central massachusetts have very different chemical compositions table 1 cadwell creek which is underlain primarily by gneissic rocks has a thin surficial cover of sandy till yurerich et al 1989 shallow groundwater and interflow through the litter layer provide most runoff depressing the ph during high discharge events in mundberry brook schists and amphibolites are more prevalent in the watershed and the till contains a substantial volume of well neutralized groundwater storm events tend to flush this water into the stream channel consequently ph depressions are muted the quabbin catchment is dominated by this latter type of stream which apparently regulates the alkalinity in the reservoir the rate of chemical denudation for each stream as determined by mass export relative to precipitation input also shows some nota

late cenozoic history and slip rates of the fish lake valley emigrant peak and deep springs fault zones nevada and california several well dated stratigraphic markers permit detailed assessment of the temporal and spatial variation in slip rates along the interconnected faults of the fish lake valley emigrant peak and deep springs fault zones in west central nevada and east central california right lateral motion on the fish lake valley fault zone apparently began ca 10 ma 11 9 8 2 ma associated extensional faulting probably began ca 5 ma 6 9 4 ma and resulted in the opening of fish lake valley and deep springs valley the long term lateral slip rate for the fish lake valley fault zone since about 10 ma is 5 mm yr 3 12 mm yr our preferred lateral slip rate for the central most active part of the fish lake valley fault zone decreased from about 6 to 3 mm yr from the late miocene to the early pleistocene increased to about 11 mm yr during the middle pleistocene and decreased to about 4 mm yr during the late pleistocene extension may account for some of the change in lateral slip rate during the pliocene the large increase in lateral slip rate during the middle pleistocene is circumstantially linked to an increase in vertical slip rates on the fish lake valley and deep springs fault zones at about the time of the eruption of the bishop ash 0 76 ma vertical slip rates along the three fault zones are also related to fault strike vertical rates are highest on north striking faults and approach zero on northwest striking faults the long lived slip history of the fish lake valley fault zone fits a tectonic model in which the death valley furnace creek fish lake valley fault system is integrated with right lateral shear on faults of the central walker lane and the eastern california shear zone to accommodate part of the pacific north american relative plate motion our research demonstrates that the fish lake valley fault zone accounts for about half the rate of 10 12 mm yr of pacific north american plate boundary shear accommodated within the basin and range province between about lat 37 and 38 n

image based measurement of flux variation in distal regions of active lava flows 1 understanding the processes involved with the advance of lava flows is critical for improving hazard assessments at many volcanoes here we describe the application of computer vision and oblique photogrammetric techniques to visible and thermal images of active a flows in order to investigate distal flow processes at mount etna sicily photogrammetric surveys were carried out to produce repeated topographic data sets for calculation of volumetric lava flux at the flow fronts velocity profiles from a distal channel were obtained by rectification of a thermal image sequence and are used to investigate the rheological properties of the lava significant variations of the magma flux were observed and pulses of increased flux arrived within the flow front region on timescales of several hours the pulses are believed to be the distal result of more frequent flux changes observed in the vent region hence they reflect the importance of flow processes which are believed to cause the coalescence of flux pulses along the channel system as well as short period variations in effusion rate in considering advance processes for the individual flow fronts it must be assumed that they were fed by a highly unsteady flux which was volumetrically at least an order of magnitude lower than that observed near the vent