persistent scatterer interferometric synthetic aperture radar for crustal deformation analysis with application to volcan alcedo galapagos 1 while conventional interferometric synthetic aperture radar insar is a very effective technique for measuring crustal deformation almost any interferogram includes large areas where the signals decorrelate and no measurement is possible persistent scatterer ps insar overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms existing ps methods have been very successful in analysis of urban areas where stable angular structures produce efficient reflectors that dominate background scattering however man made structures are absent from most of the earth s surface furthermore existing methods identify ps pixels based on the similarity of their phase history to an assumed model for how deformation varies with time whereas characterizing the temporal pattern of deformation is commonly one of the aims of any deformation study we describe here a method for ps analysis stamps that uses spatial correlation of interferogram phase to find pixels with low phase variance in all terrains with or without buildings prior knowledge of temporal variations in the deformation rate is not required for their identification we apply stamps to volcan alcedo where conventional insar fails because of dense vegetation on the upper volcano flanks that causes most pixels to decorrelate with time we detect two sources of deformation the first we model as a contracting pipe like body which we interpret to be a crystallizing magma chamber the second is downward and lateral motion on the inner slopes of the caldera which we interpret as landsliding

qualitative effects of local geology on damage pattern september 1997 registered the onset of a seismic sequence striking the umbria marche region central italy in which earthquakes up to intensity ix caused widespread damage with respect to villages settled in an intermountain basin near the epicentral area the resulting damage pattern is investigated to give a better understanding of future local ground motion sensitivity macroseismic data are collected and compared with the surface geology of 26 villages and hamlets within a restricted area among these 26 settlements seven individual groups of different geological conditions are discernible showing a gradual variation to the damage severity the greatest damage occurred within the basin in villages settled close to border faults significant damage also occurred at locations on the contact between fan debris with bedrock or alluvium in support of models existing in literature these observations show that strong shaking can be generated at the edge of basins

the shallow plumbing system of rabaul caldera a partially intruded ring fault the floor of rabaul caldera experiences complex deformation as revealed both in the geological and historical record as well as through recent systematic monitoring the observed deformation pattern has been modelled previously as being caused by tumescent strain above one or more point sources at shallow levels within the caldera block or as a response of the caldera structure to deeper sources of deformation here two dimensional finite element modelling is used to re interpret the pre 1994 eruption deformation data demonstrating that the observed pattern may have been caused by dykes located in sectors of the ring fault system as delimited by seismicity both a pressurised ring structure and a pair of arcuate sources are modelled maximum compressional stress results in a central position within the encompassed block and a moat like feature forms offset outwards from the intersection of the azimuth of the modelled deformation sources and the free surface the modelled deformation generally fits well with the observed movements that the shallow ring dyke appears not to be complete existing as two discrete arcuate dykes helps to explain observed changes in the indicated tilt directions through time changing areas of relative down warping offset outwards from the seismically active ring structure and north south oriented structural up doming south of matupit the distribution of thermal anomalies and the lack of evidence for shallow central caldera intrusions can also be explained by this scenario associated normal faulting above these dykes and or the stress regime generated by simultaneous intrusions into opposite sides of the ring fault are proposed to explain the apparent inward dip of the intrusions at very shallow levels leading to the eruptive sites being offset outwards from the seismic zone a conceptual model is proposed to try to explain the general behaviour of the caldera between 1971 and the eruption of 1994

h v spectral ratios and array techniques applied to ambient noise recorded in the colfiorito basin central italy the colfiorito basin is a small intramountain depression in the southern section of the northern apennine chain that is filled with quaternary alluvial deposits the presence of soft alluvial deposits has significantly influenced the level of local damage that was caused by two major earthquakes m l 5 6 and 5 8 belonging to the swarm that started in september 1997 to verify the effects of the basin structure on the predominant frequency of seismic motion ambient noise measurements were carried out in the colfiorito basin during two experiments in may and july of 2002 the horizontal to vertical spectral ratios hvsrs were calculated for data collected at four profiles in the basin array techniques were applied to determine the wave types that composed the noise to estimate their apparent velocity and azimuth of propagation and to calculate a velocity dispersion curve from which a velocity depth structure was derived the data analysis shows a high amplification in the hvsr at low frequency this feature is common to most of the sites including the reference site and it is interpreted as being due to weather disturbances the peak frequencies of the spectral ratio calculated at the sites located in the center of the basin coincide with the theoretically estimated resonance frequencies the array averaged hvsr calculated for the array located in the middle of the plain has a pronounced peak at 0 9 hz this corresponds to the peak of the amplification function calculated on the basis of the velocity model deduced from the dispersion analysis the hvsr method is instead unsuitable for the prediction of the resonance frequencies of sediments in the sites where strong lateral variations of basement topography are present we measured apparent velocities in the range of 0 3 0 8 km sec by applying f k methods to array recordings these values are compatible with the predominance of surface waves in the noise as also confirmed by polarization analysis both rayleigh and love waves are present in the background seismic noise the results obtained by applying the spatial autocorrelation method to the vertical component of the ground motion recorded at a 240 m wide circular array deployed in the middle of the basin revealed the presence of rayleigh waves and f k methods combined with polarization techniques revealed the presence of polarized love waves the wave field analysis indicates two main propagation directions the first is around n100 e in the frequency band of 1 0 2 0 hz this radiation can be interpreted as being generated at the east southeast step borders of the basin the second main direction is around n300 e in the frequency band of 2 0 3 0 hz its source may be a 180 m deep depression located at the southwest corner of the basin

the 1997 umbria marche italy earthquake sequence a first look at the main shocks and aftershocks a long sequence of earthquakes six with magnitudes between 5 and 6 struck central italy starting on september 26 1997 causing severe damages and loss of human lives the seismogenic structure consists of a nw se elongated fault zone extending for about 40 km the focal mechanisms of the largest shocks reveal normal faulting with ne sw extension perpendicular to the trend of the apennines consistently with the quaternary tectonic setting of the internal sector of the belt and with previous earthquakes in adjacent regions preliminary data on the main shocks and aftershocks show that extension in this region of the apennines is accomplished by normal faults dipping at low angle 40 to the southwest and confined in the upper 8 km of the crust these normal faults might have reactivated thrust planes of the pliocene compressional tectonics the aftershock distribution and the damage patterns also suggest that the three main shocks ruptured distinct 5 to 15 km long fault segments adjacent and slightly offset from one another

uranium and barium cycling in a salt wedge subterranean estuary the influence of tidal pumping abstract the contribution of submarine groundwater discharge sgd to oceanic metal budgets is only beginning to be explored here we demonstrate that biogeochemical processes in a northern florida subterranean estuary ste significantly alter u and ba concentrations entering the coastal ocean via sgd tidal pumping controlled the distribution of dissolved metals in shallow beach groundwater hourly observations of intertidal groundwaters revealed high u and low ba concentrations at high tide as a result of seawater infiltration into the coastal aquifer during ebb tide u decreased and ba increased due to freshwater dilution and more importantly biogeochemical reactions that removed u and added ba to solution u removal was apparently a result of precipitation following the reduction of u vi to u iv a significant correlation between ba and dissolved organic carbon doc in shallow beach groundwaters implied a common source likely the mineralization of marine particulate organic matter driven into the beach face by tidal pumping in deeper groundwaters where the labile organic matter had been depleted ba correlated with mn we estimate that net sgd fluxes were 163 and 1660 mol m 1 d 1 for u and ba respectively or 1 and 8 mol m 2 d 1 if a 200 m wide seepage area is considered our results support the emerging concept that subterranean estuaries are natural biogeochemical reactors where metal concentrations are altered relative to conservative mixing between terrestrial and marine endmembers these deviations from conservative mixing significantly influence sgd derived trace metal fluxes

the 1997 umbria marche italy earthquake sequence relationship between ground deformation and seismogenic structure a field survey performed during the 1997 umbria marche earthquake sequence led us to recognize ground and pavement ruptures associated with the three largest shocks mw 5 7 the ruptures are concentrated in narrow bands that in part are on and near previously mapped high angle normal faults the geometry of the ground deformation is consistent with the ne trending extension indicated by cmt focal solutions of the mainshocks the distribution of aftershocks suggests that the three mainshocks occurred on 40 sw dipping normal faults geological investigations modelling of expected coseismic elevation changes and seismic data suggest that the surface deformation is not the direct result of primary rupture of faults at depth

fluxes of water and solute in a coastal wetland sediment 2 effect of macropores on solute exchange with surface water abstract we investigated interactions between sediment physical structure and solute transport in an intertidal coastal wetland two distinct pore size classes in the sediment were identified macropores had effective diameters greater than 100 m and a normalized volume of 5 matrix pores had effective diameters smaller than 100 m and were the volumetrically dominant pore size class 95 we found that infiltration and evaporation driven water fluxes were segregated between macropores and matrix pores respectively which had the effect of enhancing diffusive effluxes of chloride from the sediment to surface water chloride was highly concentrated relative to seawater in matrix porewater but was comparatively dilute in macropores concentration differences in pore size classes declined with depth until indistinguishable below 10 cm the segregated chloride distribution can be explained if recharge to the sediment occurred by downward infiltration in macropores and discharge occurred by an upward flux in matrix pores to satisfy evapotranspiration without disturbance by the downward infiltration flux in macropores upward advection of chloride in matrix pores and evapoconcentration increased chloride concentrations in matrix pores to a level well above the concentration in seawater the resulting high concentrations of chloride in matrix pores induced a large diffusive efflux of chloride into surface water that was sufficient to balance new input of chloride by infiltration of seawater in macropores 0 085 mmol cl cm 2 day transport models that were constrained by water balance measurements at the field site explained both the exponential form of the vertical distribution of chloride in matrix pores and the rate of change in storage of chloride in sediment porewater over a 1 month period we conclude that segregation of water and solute fluxes in two pore size classes strongly influences sediment salinity of coastal wetlands which has direct bearing on primary productivity of dominant vegetation and on exchange of dissolved nutrients and contaminants between intertidal wetlands and open water

on the characteristics of local geology and their influence on ground motions generated by the loma prieta earthquake in the san francisco bay region california strong ground motions recorded at 34 sites in the san francisco bay region from the loma prieta earthquake show marked variations in characteristics dependent on crustal structure and local geological conditions peak horizontal acceleration and velocity inferred for sites underlain by rock generally occur on the transverse component of motion they are consistently greater with lower attenuation rates than the corresponding mean value predicted by empirical curves based on previous strong motion data theoretical amplitude distributions and synthetic seismograms calculated for 10 layer models suggest that bedrock motions were elevated due in part to the wide angle reflection of s energy from the base of a relatively thin 25 km continental crust in the region characteristics of geologic and geotechnical units as currently mapped for the san francisco bay region show that average ratios of peak horizontal acceleration velocity and displacement increase with decreasing mean shear wave velocity ratios of peak acceleration for sites on soil alluvium fill bay mud are statistically larger than those for sites on hard rock sandstone shale franciscan complex spectral ratios establish the existence of predominant site periods with peak amplifications near 15 for potentially damaging levels of ground motion at some sites underlain by alluvium and fill bay mud average spectral amplifications inferred for vertical and the mean horizontal motion are respectively 1 1 for sites on the franciscan complex kjf 1 4 1 5 for sites on mesozoic and tertiary rocks tmzs 2 1 2 0 for sites on the santa clara formation qts 2 3 2 9 for sites on alluvium qal and 2 1 4 0 for sites on fill bay mud qaf qhbm these mean values are not statistically different at the 5 significance level from those inferred from previous low strain data analyses suggest that soil amplification and reflected crustal shear energy were major contributors to levels of ground motion sufficient to cause damage to vulnerable structures at distances near 100 km in the cities of san francisco and oakland

detailed evaluation of site response estimation methods across and along the sedimentary valley of volvi euro seistest using records from the euro seistest area near thessaloniki greece we studied empirically the amplification effects of a sedimentary valley one of the main advantages of this site is the very detailed knowledge of the near subsurface structure due to exhaustive geophysical and geotechnical measurements and data analyses jongmans et al 1998 the uniqueness of the seismological data set is the very dense network 31 stations were installed perpendicular and parallel to the valley axis with minimum interstation distances of 250 m the mean ampli fications along both axes estimated from 13 local events were imaged using the traditional spectral ratio technique variations of the mean amplifications due to the choice of different data subsets were tested by the use of up to 89 local events supplemented by four teleseismic events offering good low frequency resolution results obtained using the traditional spectral ratio technique were compared with results from a generalized inversion technique the h v ratio technique a coda wave technique and nakamura s technique advantages and disadvantages of each method are outlined especially from a practical point of view

the seismic coda site effects and scattering in alluvial basins studied using aftershocks of the 1986 north palm springs california earthquake as source arrays abstract we use single station recordings of widely distributed earthquake sources to identify heterogeneities in the earth9s crust that scatter energy into the early part of the observed s wave codas we assume that ray theory accurately describes the propagation of body waves from the earthquake sources to the scatterers but we assume no propagation mechanism between the scatterers and the seismic station a grid of hypothetical scatterers is assumed to cover the earth9s surface and the strength of each scatterer is determined by an iterative inversion method our data are recordings of aftershocks of the 1986 north palm springs earthquake recorded at a seismic station in the coachella valley smp and at a station in the morongo valley smc the technique is applied separately to each horizontal component of motion at each station we identify a particular spot at the northwest edge of the quaternary alluvium in the coachella valley that scatters waves into the s coda observed at smp 8 km distant in the valley the geologic structure that causes the strong scattering seems to be the basin edge structure rather than the mountainous terrain 3 km farther west the early coda at smc is dominated by scattering within a few kilometers of smc either in the basin itself or in the morongo valley fault zone this study shows that laterally propagating waves are sometimes observable in the early coda casting doubt on the use of 1 d techniques for estimating site responses the northwest edge of the coachella valley seems to be an especially strong scatterer of incident waves if other basins have similar loci of strong scattering perhaps these places can be identified using microearthquake seismograms and used to predict strong ground motions in the basins

outward dipping ring fault structure at rabaul caldera as shown by earthquake locations the locations of a large number of earthquakes recorded at rabaul caldera in papua new guinea from late 1983 to mid 1985 have produced a picture of this active caldera s structural boundary the earthquake epicenters form an elliptical annulus about 10 kilometers long by 4 kilometers wide centered in the southern part of the rabaul volcanic complex a set of events with well constrained depth determinations shows a ring fault structure that extends from the surface to a depth of about 4 kilometers and slopes steeply outward from the center of the caldera this is the first geophysical data set that clearly outlines the orientation of an active caldera s bounding faults this orientation however conflicts with the configuration of many other calderas and is not in keeping with currently preferred models of caldera formation

ground motion amplification geology and damage from the 1989 loma prieta earthquake in the city of san francisco main shock and aftershock accelerograms from the loma prieta earthquake sequence are analyzed to study relative ground amplification at sites in the city of san francisco main shock spectra are estimated for those stations that recorded only aftershocks by comparing their records to those from stations that recorded both the ratios of the spectra with respect to a stable bedrock station located at fort mason show distinct spectral shapes that are strongly correlated with the rock type underlying the site earthquake damage is quantified using estimates of the modified mercalli intensity at the recording sites and safety tags issued by the city of san francisco building department these intensities are compared with ground amplification in three frequency bands and with the intensities at the same sites from the 1906 san francisco earthquake there is sufficient correlation to show that site amplification is one of the controlling factors in damage distribution

advective transport affecting metal and nutrient distributions and interfacial fluxes in permeable sediments abstract our laboratory flume experiments demonstrate that advective porewater flows produce biogeochemical reaction zones in permeable sediments leading to specific and reproducible complex patterns of fe mn and nutrients oxygenated water forced into the sediment when boundary flows were deflected by protruding sediment structures generated distinct zones of nitrification and ferric iron precipitation this inflow was balanced by ammonium rich porewater ascending from deeper sediment layers thereby creating an anoxic channel where dissolved fe2 and mn2 could reach the surface between the zones of ferric iron precipitation and fe2 upwelling a layer with increased manganese oxide and solid phase fe ii concentrations formed indicating redox reaction between these components the establishment of topography on the previously smooth sediment surface reversed the net interfacial flux of solutes while the smooth control core was found to be a sink for metals and nutrients the sediment with mounds acted as a source for these substances our experiments show that in sandy sediment with an oxidised surface layer reduced metal species can be released to the water column by flow topography interactions we conclude that advective transport processes constitute an important process controlling biogeochemical zonations and fluxes in permeable sea beds

holocene geologic history of a transform margin estuary elkhorn slough central california abstract elkhorn slough is california s second largest estuary and the united states first estuarine sanctuary it occupies the western reaches of elkhorn valley a relic river valley eroded by drainage pouring out of the santa clara and or great valley of california into monterey bay during the early pleistocene during the mid late pleistocene elkhorn valley was tectonically truncated from its headwaters by right lateral movement along the san andreas fault during the last glacial maximum 16 18 10 3 years before present b p local drainage in elkhorn valley incised a stream channel at least 29 m below present day sea level as its base level was progressively lowered with the ensuing holocene sea level rise marine waters invaded this incised channel floored with non marine sandy gravels creating a high energy tidal inlet at the mouth of elkhorn slough approximately 8000 years b p as sea level continued to rise the main channel of elkhorn slough became filled by an estuarine fining upward sequence characterized by progressively shallower lower energy deposits a quiet water estuary considerably larger than the present day elkhorn slough existed approximately 3000 years b p as the slough was slowly filling salt marshes developed along its landward margins and have progressively advanced toward the center of the slough during the past 5000 years historical records indicate numerous natural changes in the elkhorn slough vicinity in the mid 1850s a d elkhorn slough was a minor tributary to the much larger pajaro salinas river system which shared a common entrance to the pacific ocean north of moss landing in 1909 winter storms modified the course of the salinas river to its present location south of moss landing while elkhorn slough persisted as a tributary to the old salinas river channel construction of jetties at the moss landing harbor in 1946 provided a direct link between the pacific ocean and elkhorn slough at this time salt marshes began to retreat from the axis of elkhorn slough as it evolved into its present form as a relatively stable estuarine embayment had the jetties not been installed elkhorn slough would have likely evolved into a freshwater wetland and eventually into a dry alluvial valley within 2000 years the future fate of elkhorn slough will undoubtedly be controlled by relative sea level changes sediment supply and human activities

trace element cycling in a subterranean estuary part 1 geochemistry of the permeable sediments abstract subterranean estuaries are characterized by the mixing of terrestrially derived groundwater and seawater in a coastal aquifer subterranean estuaries like their river water seawater counterparts on the surface of the earth represent a major but less visible hydrological and geochemical interface between the continents and the ocean this article is the first in a two part series on the biogeochemistry of the subterranean estuary at the head of waquoit bay cape cod ma usa the pore water distributions of salinity fe and mn establish the salt and redox framework of this subterranean estuary the biogeochemistry of fe mn p ba u and th will be addressed from the perspective of the sediment composition a second article will focus on the groundwater and pore water chemistries of fe mn u and ba three sediment cores were collected from the head of waquoit bay where the coastal aquifer consists of permeable sandy sediment a selective dissolution method was used to measure the concentrations of p ba u and th that are associated with amorphous hydr oxides of iron and manganese and crystalline fe and mn hydr oxides the deeper sections of the cores are characterized by large amounts of iron hydr oxides that are precipitated onto organic c poor quartz sand from high salinity pore waters rich in dissolved ferrous iron unlike fe hydr oxides which increase with depth the mn hydr oxides display midcore maxima this type of vertical stratification is consistent with redox controlled diagenesis in which mn hydr oxides are formed at shallower depths than iron hydr oxides p and th are enriched in the deep sections of the cores consistent with their well documented affinity for fe hydr oxides in contrast the downcore distribution of ba especially in core 3 more closely tracks the concentration of mn hydr oxides even though mn hydr oxides are 200 300 times less abundant than fe hydr oxides in the cores mn hydr oxides are known to have an affinity for ba which is many orders of magnitude greater than iron hydr oxides hence the downcore distribution of ba in fe hydr oxide rich sediments is most probably controlled by the presence of mn hydr oxides u is enriched in the upper zones of the cores consistent with the formation of highly reducing near surface sediments in the intertidal zone at the head of the bay hence the recirculation of seawater through this type of subterranean estuary coupled with the abiotic and or biotic reduction of soluble u vi to insoluble u iv leads to the sediments acting as a oceanic net sink of u these results highlight the importance of permeable sediments as hosts to a wide range of biogeochemical reactions which may be impacting geochemical budgets on scales ranging from coastal aquifers to the continental shelf

using the radium quartet to quantify submarine groundwater discharge and porewater exchange abstract the specific ingrowth rates of different radium isotopes make them valuable tracers to distinguish processes occurring at different temporal scales here we demonstrate the use of the radium quartet 223ra 224ra 226ra and 228ra to differentiate flows of submarine groundwater discharge and porewater exchange to a coastal embayment alfacs bay nw mediterranean sea based on the assumption that these processes occur on different time scales in order to evaluate the seasonal dynamics of groundwater and porewater inputs to the bay we conducted three seasonal samplings at alfacs bay during which samples for ra isotopes were collected from bay waters groundwater springs porewaters and irrigation channels activities of short lived ra isotopes in the bay showed a strong seasonality e g average 224ra activities in summer 32 dpm 100 l 1 up to 4 times higher than in winter 8 dpm 100 l 1 in contrast the activities of the long lived ra isotopes were fairly constant throughout the year e g activities of 226ra were 16 and 14 dpm 100 l 1 in summer and winter respectively the relatively short exposure to sediments of recirculation fluxes resulted in porewaters significantly enriched in short lived ra isotopes relative to the long lived ones e g 224ra 1100 1300 dpm 100 l 1 226ra 17 99 dpm 100 l 1 whereas coastal groundwaters were enriched in all the ra isotopes e g 224ra 120 150 dpm 100 l 1 226ra 200 400 dpm 100 l 1 the distinct signatures of different sources allowed us to construct seasonal ra mass balances to estimate both groundwater discharge which ranges from 40 60 103 m3 d 1 in summer to 310 200 103 m3 d 1 in winter and porewater exchange fluxes ranging from 1200 120 103 m3 d 1 in summer to 270 40 103 m3 d 1 in winter whereas the seasonal variability of groundwater inputs is likely governed by the terrestrial hydraulic gradient a qualitative evaluation of the drivers of porewater exchange suggested that the strong seasonality of the seawater recirculation inputs is likely mediated by seasonal cycles on the activity of benthic infauna ra isotopes are thus valuable tracers to differentiate fluxes of both submarine groundwater discharge and porewater exchange allowing a more accurate evaluation of the fluxes of freshwater and solutes to coastal ecosystems as well as their implications for coastal biogeochemical cycles

high density macroseismic survey in urban areas part 2 results for the city of rome italy high density macroseismic surveys were carried out in rome following both the 14 october 1997 m w 5 6 i 0 viii mcs and the 26 march 1998 m w 5 3 i 0 vi vii mcs umbria marche central italy earthquakes the aim of the work was to investigate the relationship between intensity and local geology for the modern urban area of rome an issue yet to be examined in contemporary times intensity data for both earthquakes were correlated with near surface geology the results show a statistically significant amplification in holocene alluvial deposits in particular we found one degree of difference in mcs intensity between hard rock and recent alluvium formations furthermore the distribution of the earthquake effects in alluvium filled valleys was studied as a function of the shape ratio h l of the alluvial basins in the tiber river valley higher effects were found to be concentrated within a 150 m wide band along the bedrock alluvium surface contact suggesting the occurrence of an edge effect surprising results were observed in the minor alluvial valleys which displayed the strongest effects in terms of shaking the narrowest valleys width

active tectonics in the central apennines and possible implications for seismic hazard analysis in peninsular italy abstract the central apennines fault system cafs of peninsular italy overprints earlier structures of a neogene fold and thrust belt and includes segments characterized by diffuse seismicity distributed within a nnw sse trending zone 50 60 km wide the system has been analysed by means of morphotectonic and structural analysis of exposed active fault segments the resulting fault structure consists of an interconnecting network of roughly n s trending left lateral strike slip segments and mostly nw se oriented transtensional to normal faults evidence for recent activity of cafs structures is provided by faulted middle pleistocene holocene deposits including 30 40 ka old pyroclastites and 40 ka old palustrine sediments fresh scarps in both bedrock and late quaternary continental deposits and decametric lateral offsets locally affecting the post wurmian drainage pattern of the area the regional stress field responsible for the development and evolution of the cafs as inferred from fault slip data is characterized by a nw se compression and by a ne sw extension the cafs pattern and its present day kinematics have been related to left lateral strike slip motion on north south trending crustal faults the existence of deep seated strike slip faults in the central apennines has implications for seismic hazard analysis motion along these structures suggests in fact that coseismic surface faulting is distributed and that cumulative displacements include normal transtensional and strike slip components the seismogenic potential of cafs structures can therefore be best described by multiple rupture models and be better analysed in terms of partial contributions of lower rank features constituting congruent structural associations within the system

comparison of four numerical models for simulating seepage from salt marsh sediments a boundary integral equation method biem model and three differently formulated finite element method fem models were implemented to explore the spatial and temporal patterns in marsh pore water seepage that each generated the biem model is based on the laplace equation coupled to a dynamic free surface condition that assumes that as the water table changes the aquifer instantaneously loses or gains an amount of water equal to the change in head times the specific yield the fem models all implement a simplified richards equation that allows gradual desaturation or resaturation and thus flow in both the saturated and unsaturated zones of the aquifer two of the fem models are based on the governing equation for the usgs model sutra and thus take into account fluid and aquifer compressibility one of these was modified to take into account the effect of tidal loading on the total stress which is assumed to be constant in the derivation of the original version of sutra the third fem model assumes that neither the fluid or aquifer matrix is compressible so that changes in storage are due solely to changes in saturation the unmodified sutra model generated instantaneous boundary fluxes that were up to two orders of magnitude greater and spatially more uniform than those of the other models the fem model without compressibility generated spatial and temporal patterns of the boundary fluxes very similar to those produced by the biem model the sutra model with the tidal stress modification gave fluxes similar in magnitude to the biem and no compressibility models but with distinctly different distributions in space and time these results indicate that accurate simulation of seepage from marsh soils is highly sensitive to aquifer compressibility and to proper formulation of the effect of tidal loading on the total stress in the aquifer they also suggest that accurate simulation may require total stress correction not only for tidal loading but for changes in the water table as well finally to aid the development of methods for the measurement of compressibility we present a schematic pore scale model to illustrate the factors that may govern the compressibility of marsh soils

complex normal faulting in the apennines thrust and fold belt the 1997 seismic sequence in central italy a long sequence of moderate magnitude earthquakes 5 m 6 struck central italy in september and october 1997 at the end of the sequence a year later the seismogenic area extends for about 60 km along the apennines the analysis of historical seismicity suggests that this seismic sequence filled a 700 year gap in this portion of the chain other historical sequences in the same area are characterized by prolonged seismic release on adjacent fault segments probably due to the in volvement of shallow and complex structures inherited by the compressive tectonics the distribution of seismicity and the fault plane solutions show that the extension in this region is accomplished by normal faults dipping at relatively low angles 40 to the southwest the focal mechanisms of the largest shocks reveal normal faulting with extension perpendicular to the apenninic chain northeast southwest consistently with the quaternary tectonics of the internal sector of the northern apen nine belt and with previous earthquakes in adjacent regions three mainshocks oc curred on distinct 5 to 10 km long fault segments adjacent and slightly offset be tween each other high quality aftershock locations show that seismicity is confined within the sedimentary mesozoic cover in the upper 8 km of the crust and that most of the aftershocks are shallower than the largest shocks which nucleated at 6 km depth faults evidenced by aftershock locations have a planar geometry and show increased complexity toward the surface most of the aftershock focal mechanisms are dominated by normal faulting several strike slip events occurred at shallow depths reactivating portions of pre existing thrust planes that segment the normal fault system the spatiotemporal evolution of seismicity shows a peculiar migration of hypocenters along the strike of the main faults with multiple ruptures and the activation of fault segments before the occurrence of the main rupture episodes

advective pore water input of nutrients to the satilla river estuary georgia usa abstract in situ benthic flux measurements pore water nutrient profiles water column nutrient distributions sediment grain size distributions and side scan sonar observations suggest that advective transport of pore waters may be a major input pathway of nutrients into the satilla river estuary coastal georgia usa in situ benthic chamber incubations demonstrate the occurrence of highly variable but occasionally very large sea floor fluxes of silicate phosphate and ammonium locally occurring benthic microbial mineralization of organic matter as estimated by s35 sulphate reduction rate measurements is insufficient to support these large fluxes we hypothesize that the observed interlayering of permeable sandy sediments with fine grained organic rich sediments in the estuary provides conduits for advective transport of pore water constituents out of the sediments because permeable layers may extend significant distances beneath the salt marsh the large fluxes observed may be supported by remineralization occurring over large areas adjacent to the estuary advective transport may be induced by pressure gradients generated by a variety of processes including landward recharge by meteoric or rain waters if sand layers extend far enough into the maritime coastal lands alternatively tidal variations across the salt marsh sediment surface may hydraulically pump water through the sediment system because these fluxes appear to be concentrated into small layers this source may be a significant input of nutrients to the estuary even if permeable sandy layers comprise a very small proportion of the seabed

site effects as inferred from damage severity observation a long seismic sequence affecting the umbria marche region central italy started on september 26 1997 earthquakes with intensities up to ix mcs caused diffused damage over a large area the resulting damage pattern is investigated for villages settled in an intermountain basin near the epicentral area macroseismic data are collected and compared with the surface geology for 15 villages and hamlets within a restricted area among these 15 settlements six individual groups are discernable showing a gradual variation of the damage severity such abrupt damage variation inside a relatively small area is influenced by modest scale lithological transitions in particular major effects occurred in those villages settled in the sedimentary basin close to border faults safest sites resulted to be those settled on bedrock and on the alluvial plane far from the edge these observations support models existing in literature which claim that edge effects and the generation of diffracted waves in soft basins can contribute to a stronger shaking

flow induced uptake of particulate matter in permeable sediments we demonstrate the fast transfer of suspended particles from the boundary layer into the upper strata z 2 x 10 l l m2 incubated in a laboratory flume increased pressure up and downstream of small mounds z 2 5 cm drove water 5 5 cm into the core carrying suspended particles 1 pm to 2 2 cm sediment depth within 10 h simultaneously decreased pressure at the downstream slope of the protrusions drew pore fluid from deeper layers z 5 10 cm to the surface in the sediment friction reduced the velocity of the particulate tracers resulting in size fractionation and layers of increased particle concentration ripple topography 0 8 2 8 cm high enhanced interfacial particle 1 pm flux by a factor 2 3 when compared to a level control core the pathways of the particle and solute tracers below a sediment ripple are explained with a source sink model that describes the pore flow velocity field our results suggest that bedform induced interfacial flows are important for the uptake of particulate organic matter into permeable shelf sediments

distribution of ground motion intensity inferred from questionnaire survey earthquake recordings and microtremor measurements a case study in christchurch new zealand during the 1994 arthurs pass earthquake the areal distribution of seismic ground motion intensity in the city of christchurch new zealand during the 1994 arthurs pass earthquake ml 6 6 was evaluated using an intensity questionnaire together with local site amplifications inferred from seismic recordings and microtremors in order to estimate the intensity in parts of the city where no intensity data were available intensity data were compared to relative levels of shaking determined from both weak motion and microtremor recordings weak ground motion amplification factors were determined using ratios of ground accelerations at five sediment sites with respect to a rock site microtremor amplification factors were determined from horizontal to vertical spectral ratios at a 1 km spacing throughout the city a positive correlation between weak motion and microtremor amplification factors allowed extrapolation of microtremor amplification to estimated mm intensity emmi emmi ranged from 3 to 6 and was consistent with the questionnaire intensity and geological conditions and showed detailed information on the areal distribution of ground motion intensity in the city

using the radium quartet for evaluating groundwater input and water exchange in salt marshes the fluxes of 226ra half life 1600 years and 228ra half life 5 7 years from the north inlet salt marsh to the sea are much larger than can be supported by decay of their th parents in the surface marsh sediments these fluxes are sustained almost entirely by groundwater flow through the marsh an average groundwater flow of approximately 10 cm3 cm 2 day 1 is indicated if the groundwater activities we have measured are representative the fluxes of 223ra half life 11 4 day and 224ra half life 3 6 day are factors of 22 and ten more than those expected from the flux of 226ra groundwater also sustains most of the flux of the short lived isotopes the measured ra activity ratio pattern in the marsh creeks matches the groundwater signature but is distinct from the pattern of the parent thorium isotopes in the sediment we present a model to explain the anomalous distribution pattern of these isotopes despite their large throughput the inventories of desorbable 226ra and 228ra in the top 15 cm sediment layer are very low nevertheless the activities of 226ra and 228ra in the porewaters are large indicating a low distribution coefficient 10 for radium and a short retention time 10 days in the surface sediment layer we surmise that groundwater flow may be a significant source of radium isotopes in the waters of shallow estuaries and coastal margins this source must be recognized while considering mass balance of any tracer be it radium nutrients other metals or 18o

modelling the effect of salinity on radium desorption from sediments abstract the desorption of the four naturally occurring radium isotopes 223 ra 224 ra 226 ra and 228 ra from estuarine sediments is investigated these isotopes are created within sediments by the radioactive decay of insoluble thorium parents due to competition from other ions for the occupation of adsorption sites on the sediment grains radium desorption is a function of salinity a model is developed to describe radium desorption as it is affected by salinity grain size and sediment concentration it is shown that to model the desorption of radium for a particular sediment requires the estimation of two independent parameters one of these parameters is the concentration of radium available for exchange on the sediment the other depends on major ion and radium exchange coefficients desorption experiments performed on sediments from the bed of the bega river australia are used to validate the model and to evaluate the parameters needed for model application

tidally regulated chemical fluxes across the sediment water interface in elkhorn slough california evidence from a coupled geochemical and hydrodynamic approach measurements of four ra isotopes ba mn u and dissolved nutrients were used in concert with hydrodynamic modeling to reveal a large tidally regulated sediment surface water exchange within elkhorn slough an estuary in monterey bay california hydrologic and oceanographic data from in situ sensors and geophysical surveys of estuarine bottom sediments were integrated with the chemical measurements to develop ra flux boundary conditions for a three dimensional hydrodynamic transport model of the estuary sediment and surface water exchange is the dominant source of ra isotopes within this system this process occurs without significant fresh terrestrial groundwater discharge a number of known solute transport and pore water flushing mechanisms can explain the 224ra input including diffusion evaporative transport bioirrigation and inundation and drainage of borrows and macropores the 226ra results suggest that some of these mechanisms or others are capable of mobilizing ra from deeper sediments the sediments supplying this flux may cover an area as large as the entire intertidal zone primarily salt marsh to a depth of 1 2 cm in addition the ra delivery to the estuary appears to be temporally regulated by the tidal inundation of the salt marsh and subsequent drainage through tidal creek channels these results illustrate the importance of the intertidal zone as a flowpath in the estuarine water cycle and the tidal phase lag that results when solute from this zone is transported into the estuary this process is essential to understanding estuarine biogeochemical budgets of elements with significant sedimentary sources among marine environments estuaries stand out for their high biologic productivity numerous societal functions and hydrologic and chemical complexity because of their complexity and variability estuaries are also challenging environments to study and even more so to predict large tidal excursions temporally variable freshwater inputs and stratification can confound efforts to relate water chemistry to anything but the largest features e g riverine inputs mixing processes and thus net tidal exchange are spatially and temporally variable in many estuaries uncles 2002 making it difficult to predict chemical exchange with the sea the complex morphology of intertidal salt marshes and mudflats results in irregularly flushed areas where evaporation and stagnation can alter the salinity trace element and nutrient chemistry of intertidal water such water is ultimately remixed back into the main estuary influencing surface water chemistry sediment pore waters also possess distinct chemical characteristics and can influence surface water chemistry through a variety of exchange processes huettel et al 1998 charette and sholkovitz 2006 in shelf sands intertidal sand flats and other permeable sediments the dominant solute exchange mechanism is pressure induced advection created by the interaction of currents waves

rupture directivity of the major shocks in the 1997 umbria marche central italy sequence from regional broadband waveforms we derive the relative moment rate function for the main shocks in the fall 1997 central italy seismic sequence mw 5 7 6 0 5 6 by applying an empirical green function method by using three conveniently placed broad band mednet stations we obtain clear source time functions indicating directivity effects for all of the three earthquakes with southeastward rupture propagation for the two southernmost events and an opposite direction for the other and largest one taking a simple source model forward modeling is utilized for determining fault parameters such as length rupture propagation velocity and direction and slip distribution

using ra isotopes to examine transport processes controlling benthic fluxes into a shallow estuarine lagoon measurements of the benthic flux of four naturally occurring radium isotopes in a shallow lagoon in the bega river estuary has provided information on the types and rates of transport processes operating in the lagoon sediments the measurement techniques included ra mass budgets of the lagoon ra fluxes into benthic chambers and modelling of the pore water and solid phase ra profiles in a sediment core the sediment profile of 210pb and the solid phase and pore water profiles of the longer lived ra isotopes 228ra half life 5 7 years and 226ra half life 1600 years indicate bioturbation to a depth of 10 cm a diffusion bioturbation model has been used to assess the relative importance of molecular diffusion and bioturbation as transport processes controlling the benthic flux of ra the flux of the shortest lived isotope 224ra half life 3 7 days is not significantly enhanced by bioturbation and its flux is consistent with diffusion controlled release however bioturbation enhances the 228ra flux by a factor of more than two over the flux due to molecular diffusion alone modelled pore water profiles and flux calculations are consistent with a bioturbation time scale between 0 5 and 2 years the measured benthic flux of 226ra is much greater than can be accounted for by the modelled profile and may be due to slow 226ra desorption from the sediment variable sediment accumulation rates or groundwater flow based on 226ra pore water and flux measurements at the time of this study groundwater flow has an upper limit of 0 3 cm d 1

linking regional sources and pathways for submarine groundwater discharge at a reef by electrical resistivity tomography 222rn and salinity measurements 1 submarine groundwater discharge sgd is an important component of the hydrologic cycle connecting terrestrial to marine environments sgd in fringing reefs and its consequences on biogeochemistry and ecology remain mostly unexplored the 222rn activity and salinity of seawater indicate a substantial groundwater contribution throughout most of the 20 km2 studied tropical reef in pangasinan philippines over 30 km of electrical resistivity profiles with a penetration depth of 12 5 m shows widespread zones within the reef that are much more resistive than porous reef rocks or sediment saturated with typical seawater some discrete resistive areas are located close to where seawater has 222rn peaks and where geologic lineaments are likely located suggesting that these are preferential pathways for fresher groundwater discharging to the reef sgd at the site could be a major ecological factor connecting the reef to the subsurface environment which in turn may lead to connections to land

imaging the complex geometry of a magma reservoir using fem based linear inverse modeling of insar data application to rabaul caldera papua new guinea we test an innovative inversion scheme using green s functions from an array of pressure sources embedded in finite element method fem models to image without assuming an a priori geometry the

some thoughts on the use of insar data to constrain models of surface deformation noise structure and data downsampling repeat pass interferometric synthetic aperture radar insar provides spatially dense maps of surface deformation with potentially tens of millions of data points here we estimate the actual covariance structure of noise in insar data we compare the results for several independent interferograms with a large ensemble of gps observations of tropospheric delay and discuss how the common approaches used during processing of insar data affects the inferred covariance structure motivated by computational concerns associated with numerical modeling of deformation sources we then combine the data covariance information with the inherent resolution of an assumed source model to develop an efficient algorithm for spatially variable data resampling or averaging we illustrate these technical developments with two earthquake scenarios at different ends of the earthquake magnitude spectrum for the larger events our goal is to invert for the coseismic fault slip distribution for smaller events we infer the hypocenter location and moment we compare the results of inversions using several different resampling algorithms and we assess the importance of using the full noise covariance matrix

trace element cycling in a subterranean estuary part 2 geochemistry of the pore water abstract submarine groundwater discharge sgd is an important source of dissolved elements to the ocean yet little is known regarding the chemical reactions that control their flux from sandy coastal aquifers the net flux of elements from sgd to the coastal ocean is dependent on biogeochemical reactions in the groundwater seawater mixing zone recently termed the subterranean estuary this paper is the second in a two part series on the biogeochemistry of the waquoit bay coastal aquifer subterranean estuary the first paper addressed the biogeochemistry of fe mn p ba u and th from the perspective of the sediment composition of cores charette et al charette m a sholkovitz e r hansell c m 2005 trace element cycling in a subterranean estuary part 1 geochemistry of the permeable sediments geochim cosmochim acta 69 2095 2109 this paper uses pore water data from the subterranean estuary along with bay surface water data to establish a more detailed view into the estuarine chemistry and the chemical diagenesis of fe mn u ba and sr in coastal aquifers nine high resolution pore water groundwater profiles were collected from the head of the bay during july 2002 there were non conservative additions of both ba and sr in the salinity transition zone of the subterranean estuary however the extent of sr release was significantly less than that of its alkaline earth neighbor ba pore water ba concentrations approached 3000 nm compared with 25 50 nm in the surface waters of the bay the pore water sr salinity distribution suggests a 26 elevation in the amount of sr added to the subterranean estuary the release of dissolved ba to the mixing zone of surface estuaries is frequently attributed to an ion exchange process whereby seawater cations react with ba from river suspended clay mineral particles at low to intermediate salinity results presented here suggest that reductive dissolution of mn oxides in conjunction with changes in salinity may also be an important process in maintaining high concentrations of ba in the pore water of subterranean estuaries in contrast pore water u was significantly depleted in the subterranean estuary a result of sgd driven circulation of seawater through reducing permeable sediments this finding is supported by surface water concentrations of u in the bay which were significantly depleted in u compared with adjacent coastal waters using a global estimate of sgd we calculate u removal in subterranean estuaries at 20 106 mol u y 1 which is the same order of magnitude as the other major u sinks for the ocean our results suggest a need to revisit and reevaluate the oceanic budgets for elements that are likely influenced by sgd associated processes

numerical inversion of deformation caused by pressure sources application to mount etna italy summary the interpretation of geodetic data in volcanic areas is usually based on analytical deformation models although numerical finite element fe modelling allows realistic features such as topography and crustal heterogeneities to be included the technique is not computationally convenient for solving inverse problems using classical methods in this paper we develop a general tool to perform inversions of geodetic data by means of 3 d fe models the forward model is a library of numerical displacement solutions where each entry of the library is the surface displacement due to a single stress component applied to an element of the grid the final solution is a weighted combination of the six stress components applied to a single elementsource the pre computed forward models are implemented in a global search algorithm followed by an appraisal of the sampled solutions after providing extended testing we apply the method to model the 1993 1997 inflation phase at mt etna documented by gps and edm measurements we consider four different forward libraries computed in models characterized by homogeneous heterogeneous medium and flat topographic free surface our results suggest that the elastic heterogeneities of the medium can significantly alter the position of the inferred source while the topography has minor effect

geodynamics of the yellowstone hotspot and mantle plume seismic and gps imaging kinematics and mantle flow abstract integration of geophysical and geological data show that the yellowstone hotspot resulted from a mantle plume interacting with the overriding north america plate a process that has highly modified continental lithosphere by magmatic and tectonic processes and produced the 16 17 ma 700 km long yellowstone snake river plain ysrp silicic volcanic system accessibility of the ysrp allowed large scale geophysical projects to seismically image the hotspot and evaluate its kinematic properties using geodetic measurements seismic tomography reveals a crustal magma reservoir of 8 to 15 melt 6 km to 16 km deep beneath the yellowstone caldera an upper mantle low p wave velocity body extends vertically from 80 km to 250 km beneath yellowstone but the anomalous body tilts 60 wnw and extends to 660 km depth into the mantle transition zone we interpret this conduit shaped low velocity body as a plume of up to 3 5 vp and 5 5 vs perturbation that corresponds to a 1 2 partial melt models of whole mantle convection reveal eastward upper mantle flow beneath yellowstone at relatively high rates of 5 cm yr that deflects the ascending plume into its west tilted geometry a geodynamic model of the yellowstone plume constrained by vp and vs velocities and attenuation parameters suggests low excess temperatures of up to 120 k corresponding to a maximum 2 5 melt and a small buoyancy flux of 0 25 mg s i e properties of a cool weak plume the buoyancy flux is many times smaller than for oceanic plumes nonetheless plume buoyancy has produced a 400 km wide 500 m high topographic swell centered on the yellowstone plateau contemporary deformation derived from gps measurements reveals sw extension of 2 3 mm yr across the yellowstone plateau one fourth of the total basin range opening rate which we consider to be part of basin range intraplate extension locally decadal episodes of subsidence and uplift averaging 2 cm yr characterize the 80 year yellowstone caldera monitored history and are modeled as hydrothermal magmatic sources moreover a recent episode 2004 2009 of accelerated uplift of the yellowstone caldera at rates up to 7 cm yr has been modeled as resulting from magmatic recharge of a 10 km deep sill at the top of the crustal magma reservoir regionally gravitational potential energy of the yellowstone swell drives the lithosphere southwest and downhill from the yellowstone plateau 400 km where it coalesces with basin range province wide westward extension based on the geometry and its assumed 660 km depth we extrapolate the plume source southwest to its original location at 17 ma and 600 km southwest and 200 km north of the ysrp importantly this location is beneath the southern part of the columbia plateau flood basalt field of the same age and implies that the yellowstone mantle plume may be the common source for both of these large volcanic fields our time progression model suggests that the original plume head rose vertically behind the juan de fuca plate but at 12 ma it lost the protection of the subducting plate from eastward mantle flow and encountered cooler thicker continental lithosphere becoming entrained in eastward upper mantle flow these results reveal that yellowstone plume plate processes have had a profound effect on late cenozoic geologic evolution and topography of a large part of the western u s

the effect of collapse structures on ground deformations in calderas ground deformations related to unrest episodes in calderas are generally interpreted like in other volcanic environments in terms of increased pressure within a magma chamber embedded in a continuous elastic medium in this framework the depth of the pressure source is inferred from the size of the deformed area this scheme works quite well for individual volcanoes for instance hawaiian shields where a good correspondence between inflation events and eruptive episodes has been observed ground deformation in calderas however show unusual features that are difficult to interpret within such a scheme because considerable positive deformation in the order of several meters and microfracturing i e intense seismicity may occur without eruptions altough the estimated depth for the magma source is sometime very shallow less than 1 2 km it has been recently suggested that the contact zones at the border of collapsed calderas could act as stress strain discontinuity zones and thus bias modeling results obtained for continuous elastic media we use both observations and theoretical modeling based on 3 d finite element techniques to show that ground deformations in collapsed calderas are strongly influenced by the caldera structure giving a new perspective in related geological and geophysical observations in such areas

transient volcano deformation sources imaged with interferometric synthetic aperture radar application to seguam island alaska 1 thirty interferometric synthetic aperture radar insar images spanning various intervals during 1992 2000 document coeruptive and posteruptive deformation of the 1992 1993 eruption on seguam island alaska a procedure that combines standard damped least squares inverse methods and collective surfaces identifies three dominant amorphous clusters of deformation point sources predictions generated from these three point source clusters account for both the spatial and temporal complexity of the deformation patterns of the insar data regularized time series of source strength attribute a distinctive transient behavior to each of the three source clusters a model that combines magma influx thermoelastic relaxation poroelastic effects and petrologic data accounts for the transient interrelated behavior of the source clusters and the observed deformation basaltic magma pulses which flow into a storage chamber residing in the lower crust drive this deformational system a portion of a magma pulse is injected into the upper crust and remains in storage during both coeruption and posteruption intervals this injected magma degasses and the volatile products accumulate in a shallow poroelastic storage chamber during the eruption another portion of the magma pulse is transported directly to the surface via a conduit roughly centered beneath pyre peak on the west side of the island a small amount of this magma remains in storage during the eruption and posteruption thermoelastic contraction ensues this model made possible by the excellent spatial and temporal coverage of the insar data reveals a relatively simple system of interrelated predictable processes driven by magma dynamics

modelling of ground motion in the higashinada kobe area for an aftershock of the 1995 january 17 hyogo ken nanbu japan earthquake summary we model the ground motion from an aftershock of the 1995 january 17 hyogo ken nanbu kobe earthquake to investigate basin edge effects on wave propagation in higashinada ward downtown kobe point source finite difference seismograms calculated using a double couple solution and a 2 d basin structure are compared with the ground motion velocity seismograms recorded in a small station array deployed at sites within and outside the heavily damage zone in higashinada ward the comparison suggests that in the frequency range 0 1 2 hz that was analysed the observed spatial amplitude variation of the aftershock ground motion is attributable mainly to the basin edge effects we found that the basin edge effect caused by the superposition of the direct s wave and the basin edge diffracted waves amplified the ground motion in a narrow zone that is offset by about 0 7 km from the basin edge

unmasking the 1349 earthquake source southern italy paleoseismological and archaeoseismological indications from the aquae iuliae fault abstract the 9th september 1349 earthquake was one of the most catastrophic events experienced along the apennines at least three main shocks struck a vast area of the molise latium abruzzi regions and damage was even sustained by the distant monumental buildings of rome the southern most shock mw 6 7 occurred at the border between southern latium and western molise razing to the ground the towns of isernia venafro and cassino amongst others and devastating montecassino abbey as with other medieval catastrophic sequences e g in december 1456 mw 6 5 7 0 this earthquake has not yet been associated to any seismogenic source thus it still represents a thorn in the flesh of earthquake geologists we have here carried out a reappraisal of the effects of this earthquake and through an interpretation of aerial photographs and a field survey we have carried out paleoseismological analyses across a poorly known n130 normal fault that crosses the molise campania border this structure showed repeated surface ruptures during the late holocene the last one of which fits excellently with the 1349 event both in terms of the dating and the rupture dimension on the other hand archaeoseismic analyses have also indicated the faulting of an augustean aqueduct the amount of apparent offset of the aqueduct across the fault traces shows that there were other surface faulting event s during the roman high middle age period therefore in trying to ascertain whether these events were associated with known potentially of 346 ad or 848 ad or unknown earthquakes in the area it became possible that this 20 km long fault here named the aquae iuliae fault is characterized by high slip rates and a short recurrence time this is in agreement with both the similar behaviour of the neighbouring northern matese fault system and with recent gps analyses showing unexpectedly high extension rates in this area

three dimensional simulation of the near fault ground motion for the 1995 hyogo ken nanbu kobe japan earthquake abstract the 17 january 1995 hyogo ken nanbu earthquake is a typical example showing that the ground motions along basin edge faults can be very destructive in this study we simulate the near fault ground motion from this earthquake based on a kinematic fault model and a simplified 3d velocity structure of the kobe area the kinematic earthquake rupture and the wave propagation are modeled using a 3d finite difference method fdm our simulation identifies the basin edge effect as an important factor that influenced the ground motion amplification pattern in the kobe area we found that the coupling of the source directivity and basin edge effects causes impulsive ground motions with extremely high amplitude at periods greater than 1 sec and in a narrow zone offset less than 1 km from the basin edge the combination of these effects acted to create a fairly continuous band of amplification that extends about 30 km in an elongated zone parallel to the basin edge boundary in some areas localized site effects might have been as important as the abovementioned effects but they cannot explain the continuity of the extended east west zone of damage

detecting submarine groundwater discharge with synoptic surveys of sediment resistivity radium and salinity 1 a synoptic geophysical and geochemical survey was used to investigate the occurrence and spatial distribution of submarine discharges of water to upper nueces bay texas the 17 km survey incorporated continuous resistivity profiling measurements of surface water salinity temperature and dissolved oxygen and point measurements of dissolved ra isotopes the survey revealed areas of interleaving vertical fingers of high and low conductivity extending up through 7 m of bay bottom sediments into the surface water located within 100 m of surface salinity and dissolved ra maxima along with peaks in water temperature and lows in dissolved oxygen these results indicate either brackish submarine groundwater discharge or the leakage of oil field brine from submerged petroleum pipelines

salt marshes an important coastal sink for dissolved uranium abstract the global budget for marine uranium demands another geochemical sink other than deep sea systems and the coastal environment may host some or all of this missing sink in a previous paper sarin and church 1994 we have shown that some large subtidal estuaries are seasonal summer sinks at low salinities in this paper we show that intertidal salt marshes are even stronger sinks at all salinities if for somewhat different reasons uranium was sampled in dissolved and particulate fractions over several tidal cycles and seasons for a lower delaware bay salt marsh canary creek lewes delaware usa and uniquely during summer months the dissolved uranium is nonconservative moreover because uranium extraction is greater on higher tides and occurs over the entire salinity gradient this processing appears associated with surface of vegetated high marsh we hypothesize that either 1 uranium scavenging occurs during the process of tidal mixing and attendant flocculation of humic acids and iron oxides favoring this process is the presence of sulfonate complexes in salt marsh humic substances and iron coprecipitation during its extensive redox cycling in the salt marsh or 2 uranium extraction occurs at the marsh surface during extensive flooding of the salt marsh surface sediments favoring this process is the increase in sulfuric acidity at the summer salt marsh surface that could destabilize the tetracarbonate species of u vi the latter option is favored by both field observations of maximum removal at the surface during the spring and summer tide conditions and selective extraction of sediment phases where uranium is found as adsorbed and complexed forms in the ascorbate citrate and humic acid fractions respectively mass balance calculations show that under steady state conditions nearly two thirds of the uranium extracted from tidal waters is retained in the sediments while one third is exported as u enriched particles during ebbing tides independent confirmation of this balance comes from the measured accumulation rate of uranium buried at depth this represents the net inventory buried below the geochemically reactive surface responsible for the initial extraction and redistribution of uranium onto sediment or tidally exported phases extrapolated globally uranium burial in salt marshes alone or total marine wetlands including mangroves could comprise at least 10 and perhaps as much as 50 the total marine sink for uranium or on an area specific basis up to 50 times their marine areal extent