structural and tectonic evolution of the eastern cayman trough caribbean sea from seismic reflection data the eastern cayman trough preserves a record of the late cretaceous to paleogene caribbean history that is largely affected by neogene strike slip tectonics of the current plate boundary we conducted an analysis of seismic data within the eastern cayman trough based upon single and multichannel seismic reflection profiles collected during the seacarib ii cruise in 1987 and the casis cruise in 1992 these data show that the basement of the eastern cayman trough can be divided into four domains from east to west with distinct morphologic and sedimentary character and inferred older to younger ages 1 a province of rifted mesozoic continental crust exhibiting seven parallel horst blocks striking northeast southwest 2 a continent ocean transition bet een provinces 1 and 3 that exhibits seamounts small hills and sedimentary basins 3 an eocene oceanic crust with rough basement but smoother relief than the rifted crust basement trends are roughly north south and oblique to the northwest trend in domain 1 and 4 the northern jamaica slope which forms an east west trending slope with northward dipping strata that flank the three deeper water domains of the cayman trough the domains are interpreted to be the product of the eocene east west opening of the cayman trough as a pull apart basin in a left lateral strike slip setting closure of the 1100 km of eocene and younger oceanic crust of the cayman trough places the fault block province adjacent to the belize margin of central america restoration of normal faults in the fault block province places an additional 190 km of left lateral offset along the cayman trough a neogene phase of transpression has reactivated structures in the four domains along with on land structures described by previous authors in jamaica the proximity of the eastern margin of the cayman trough to petroliferous continental rocks in central america suggests an improved possibility of hydrocarbon potential unfortunately s diment thicknesses of less than 1 km probably are not conducive to hydrocarbon formation

trace metal geochemistry of remote rivers in the canadian arctic archipelago abstract trace metals are essential micronutrients for phytoplankton as well as useful tracers of biogeochemical processes in aquatic systems the largest arctic rivers are known to play an important role in the cycling of trace metals in the arctic ocean however these systems account for little more than half of arctic freshwater discharge leaving a major gap in our understanding of the trace metal geochemistry from smaller river systems this is especially problematic for rivers draining the arctic coastal margins as these continuous permafrost systems are anticipated to be particularly sensitive to climate change this study presents the first observations of dissolved and particulate trace metal concentrations and lead isotopes in 14 rivers in the canadian arctic archipelago caa dissolved concentrations of aluminum iron manganese nickel copper zinc cadmium and lead display clear spatial variability in their distributions small rivers located in the central islands of the caa have remarkably low concentrations of these trace metals while the rivers draining the southern continental landmass have higher values this geographic variability in dissolved metal concentrations reflects both differences in bedrock geology and the south north environmental gradients in the archipelago we extrapolate these findings to estimate the dissolved trace metal concentrations for other rivers draining the caa based on their geographic location elemental ratios measured in the suspended particulate matter in several rivers indicates a significant enrichment of nickel copper zinc and lead over the crustal composition in particular lead isotope composition shows an extremely large range varying from the highly radiogenic tree river 206pb 207pb 1 5121 in the south to the relatively unradiogenic glacier river 206pb 207pb 1 0153 in the central caa lack of correlation between the pb isotopic composition and pb enrichment suggests pb is derived from within the watershed this work presents the first observations of dissolved and particulate trace metal concentrations in small coastal draining rivers from the caa an important first step in developing a baseline against which to evaluate future change in the high arctic

angular velocities of nubia and somalia from continuous gps data implications on present day relative kinematics abstract this study focuses on the break up of the african tectonic plate into separate nubian and somalian blocks based on recent global positioning system gps data a new unique velocity field has been obtained by processing all available observations of permanent gps stations on africa since 1996 the quantity and distribution of the stations and the length of the time series of observations exceed that of previous studies by a considerable margin allowing one to derive a reliable estimate of the differential motion between the nubia and somalian plates which are considered as a single african block in the prevailing global tectonic plate models the estimated relative pole of rotation of somalia with respect to nubia is located at 54 8 s 37 0 e with magnitude 0 069 ma implying distinct opening in the ethiopian rift of magnitude 7 mm year and azimuth n94 e whereas in southeastern south africa this value is reduced to 2 mm year in almost the same direction this is in accordance with some of the independent geological and geophysical tectonic models of the nubia somalia plate boundary region however the spatial density of the current tracking network is still not optimal to establish the exact location of the entire somalia nubia plate boundary in particular the possible branch east of lake victoria and heading towards the mozambique channel is impossible to confirm or reject at this moment

extension and subsidence adjacent to a weak continental transform an example from the rukwa rift east africa the rukwa rift is a 300 km long half graben basin that lies along the central part of a 1000 km long continental transform in the east african rift the basin contains carboniferous to quaternary sedimentary strata 11 km thick within the basin maximum extension has been directed nearly normal to the border fault even though this border fault has been dominated by dextral strike slip however extension and subsidence in the rukwa rift are not explained by releasing bend or oblique extension fault geometries we interpret the orientation of the extension as a local stress rotation symptomatic of a low friction weak strike slip border fault structural and morphologic features suggest that an along strike contrast in the frictional strength of the border fault controls the location of this extension subsidence and extension normal to the border fault in the rukwa rift occur along a weak transform fault segment as an along strike accommodation of drag and local shortening against an adjacent strong segment thus three dimensional strain is accommodated differently along the strike of the border fault as a function of the frictional strength of the fault zone

modeling of surface deformation in volcanic areas the 1970 1972 and 1982 1984 crises of campi flegrei italy campi flegrei is a densely inhabited volcanic area within a caldera 12 14 km in diameter immediately west of naples italy in 1970 1972 and in 1982 1984 campi flegrei experienced considerable ground surface deformation producing a bulge about 3 5 m high at its peak in the two inflation episodes the point of maximum uplift did not change coinciding with the caldera center about which the displacements exhibited radial symmetry the 1982 1984 uplift was accompanied by considerable seismic activity gravity changes have been interpreted as reflecting the occurrence of a subvertical magmatic intrusion volcanological petrological and geophysical data point to the existence of a shallow magma chamber just beneath the center of the caldera we assume that the observed surface displacements are the response of an essentially elastic medium to a pressure increase in the magma chamber static deformation is calculated by using a finite element method assuming axial symmetry around a vertical axis through the caldera center the role played by various components of the model geometry boundary conditions elastic properties is analyzed it is shown that models assuming uniform elasticity are inadequate therefore the major volcanotectonic features as well as the influence of temperature and pressure on the elastic properties are taken into account the results of various more complex models are presented it is suggested that a progressively fractured zone whose size and shape depend also on the possible occurrence of magmatic intrusions may explain the observed surface displacements and the other data collected at campi flegrei it is suggested that the 1970 1972 uplift was possibly accompanied by larger scale changes in the stress field

electrical resistivity tomography revealing the internal structure of monogenetic volcanoes 1 eruptive activity of individual monogenetic volcanoes usually lasts a few days or weeks however their short lifetime does not always mean that their dynamics and structure are simple monogenetic cones construction is rarely witnessed from the beginning to the end and conditions for observing their internal structure are hardly reached we provide high resolution electrical resistivity sections 10 m electrode spacing of three monogenetic cones from northeastern spain comparing our results to geological observations to interpret their underground continuation the 100 m maximum depth of exploration provides information on almost the entire edifices highlighting the relationships between strombolian and hydromagmatic deposits in two multiphase edifices a main observation is a column of distinct resistivity centered on the puig d adri volcano which we interpret as the eruptive conduit this method can provide valuable information on the past volcanic dynamics of monogenetic volcanic fields which has real implications for the forecast of future activity

a horizontal crack in a layered structure satisfies deformation for the 2004 2006 uplift of campi flegrei 1 sources responsible for volcanic unrest produce characteristic surface deformation given a sufficient number of distributed observation points inversion is the preferred procedure for retrieving the source parameters of location and volume or pressure change most often the solutions have been for point sources embedded in a homogeneous half space recent work indicates that layered structures particularly those with soft superficial layers significantly perturb the deformation pattern compared with that for the homogeneous medium we apply the methods of l crescentini and a amoruso to data for the most recent mini uplift in the campi flegrei caldera and show that models using a homogeneous medium cannot adequately fit all the data incorporating a layered structure appropriate for campi flegrei allows a significantly better fit avoiding characteristic discrepancies which are revealed by a synthetic test failure to use such structure results in incorrect source parameters possibly leading to misleading geophysical interpretations

a geochemical and geophysical reappraisal to the significance of the recent unrest at campi flegrei caldera southern italy volcanic unrest at calderas involve complex interaction between magma hydrothermal fluids and crustal stress and strain campi flegrei caldera cfc located in the naples italy area and characterised by the highest volcanic risk on earth for the extreme urbanisation undergoes unrest phenomena involving several meters of uplift and intense shallow micro seismicity since several decades despite unrest episodes display in the last decade only moderate ground deformation and seismicity current interpretations of geochemical data point to a highly pressurized hydrothermal system we show that at cfc the usual assumption of vapour liquid coexistence in the fumarole plumes leads to largely overestimated hydrothermal pressures and accordingly interpretations of elevated unrest by relaxing unconstrained geochemical assumptions we infer an alternative model yielding better agreement between geophysical and geochemical observations the model reconciles discrepancies between what observed 1 for two decades since the 1982 84 large unrest when shallow magma was supplying heat and fluids to the hydrothermal system and 2 in the last decade compared to the 1980 s unrest the post 2005 phenomena are characterized by much lower aquifers overpressure and magmatic involvement as indicated by geophysical data and despite large changes in geochemical indicators our interpretation points out a model in which shallow sills intruded during 1969 1984 have completely cooled so that fumarole emissions are affected now by deeper co2 richer magmatic gases producing the modest heating and overpressure of the hydrothermal system our results have important implications on the short term eruption hazard assessment and on the best strategies for monitoring and interpreting geochemical data this article is protected by copyright all rights reserved

earthquakes in the davie ridge madagascar region and the southern nubian somalian plate boundary the largest earthquake sequence mb up to 6 4 and m0 up to 5 1018 nm to have struck eastern africa within the past 60 years occurred in may and june of 1985 off the coast of the tanzania mozambique border the epicenters are located on the northern extension of the davie ridge a prominent north south trending bathymetrie feature accompanied by distinct gravity anomalies a joint hypocenter location of the 14 largest events in this sequence appears as a cluster of epicenters with no apparent lineation al teleseismic distances p and sh waves generated by the two largest events of this sequence have nearly identical waveforms on the long period records of the worldwide standard seismograph network a formal inversion of the data shows a pure normal faulting mechanism on nodal planes striking slightly west of north at least two point sources are necessary to model each event one at a depth of 40 10 km and the other at about 20 5 km on a regional scale normal faulting seems to characterize the scattered seismicity throughout the region between madagascar and the eastern arm of the east african rift zone even though oceanic lithosphere dominates part of the region and no topographic expression of a rift system can be identified since normal faulting events of up to 25 5 km deep also characterize the scattered seismicity west of the topographic expression of the western arm of the rift zone at about the same latitude we propose that the southern termination of the nubian somalian plate boundary consists of a diffuse zone of east west extension up to 2000 km wide

fluid flow in the resurgent dome of long valley caldera implications from thermal data and deep electrical sounding abstract temperatures of 100 c are measured at 3 km depth in a well located on the resurgent dome in the center of long valley caldera california despite an assumed 800 c magma chamber at 6 8 km depth local downflow of cold meteoric water as a process for cooling the resurgent dome is ruled out by a peclet number analysis of temperature logs these analyses reveal zones with fluid circulation at the upper and lower boundaries of the bishop tuff and an upflow zone in the metasedimentary rocks vertical darcy velocities range from 10 to 70 cm a 1 a 21 km long geoelectrical profile across the caldera provides resistivity values to the order of 10 0 to 10 3 m down to a depth of 6 km as well as variations of self potential interpretation of the electrical data with respect to hydrothermal fluid movement confirms that there is no downflow beneath the resurgent dome to explain the unexpectedly low temperatures in the resurgent dome we challenge the common view that the caldera as a whole is a regime of high temperatures and the resurgent dome is a local cold anomaly instead we suggest that the caldera was cooled to normal thermal conditions by vigorous hydrothermal activity in the past and that a present day hot water flow system is responsible for local hot anomalies such as hot creek and the area of the casa diablo geothermal power plant the source of hot water has been associated with recent shallow intrusions into the west moat the focus of planning for future power plants should be to locate this present day flow system instead of relying on heat from the old magma chamber

importance of structural history in the summit area of stromboli during the 2002 2003 eruptive crisis inferred from temperature soil co2 self potential and electrical resistivity tomography the 2002 2003 eruptive crisis of stromboli volcano in the aeolian islands raised the question of how to assess the stability of the flanks of this volcanic edifice during such a crisis to provide a response to this question we analyzed a detailed fluid flow mapping plus the reiteration of a profile located in the vicinity of the active vents using the self potential method temperature data soil gas co2 measurements and electric resistivity tomography coupling the interpretation of these methods that are sensitive to the flow of gas and water in the ground indicates the position of areas of mechanical weakness in addition they can be used to monitor the change in the discharge of fluids associated with these features before and during the 2002 2003 eruptive crisis our results emphasize the importance of old structural boundaries such as the large fossa crater in the development of the new set of fractures observed during the 2002 2003 eruptive crisis between october 2002 and january 2003 the use of co2 soil gas technique evidenced an increase in the discharge of co2 outside the large fossa crater boundaries along the failure boundary of the southern sciara del fuoco area self potential and temperature measurements made before the 2002 2003 eruptive crisis reveal significant changes along the main structural boundaries of the fossa area the development of these anomalies is interpreted as an increase of the permeability of the structure from may 2000 to may 2002 between january 2003 and march 2003 the reiteration of self potential temperature and co2 measurements shows an increase of fluid discharge along weakness planes located inside the large fossa crater boundary they evidence no change outside this structural boundary the importance of the large fossa crater boundary in controlling the deformation and fluid flow from january to march 2003 has been attested by the development of the fractures inside the large fossa crater boundary and also with a network of electrooptical distance measurement stations located inside and outside this ancient crater this multidisciplinary approach to fluid flow assessment before and during an eruptive crisis is complementary to geodetic measurements of the deformation of the edifice it demonstrates for the first time the powerful potential of combining electrical resistivity tomography self potential temperature and soil co2 measurements in assessing the position of the planes of mechanical weakness in a volcanic edifice

denudational and thermal history along a transect across the lambert graben northern prince charles mountains antarctica derived from apatite fission track thermochronology 1 the denudational history along a transect across the western margin of the lambert graben northern prince charles mountains east antarctica is quantified on the basis of thermal history modeling of apatite fission track data from four vertical profiles early cretaceous paleogeothermal gradients estimated from the fission track data increase from 19 c km 1 50 km west of the rift margin to 29 c km 1 within the immediate vicinity of the western master fault two discrete phases of enhanced denudation during the phanerozoic are inferred for the western rift margin the first occurred during the early paleozoic with minimum denudation of between 1 6 and 5 0 km which is broadly coeval with initial rifting and the major period of permo triassic sedimentation within the lambert graben the formation of the graben was related to the formation of the ancestral gamburtsev mountains due to variscan compression and substantial crustal thickening of the east antarctic craton the second phase of denudation commenced in the early cretaceous with estimated amounts ranging between 1 0 and 4 5 km generally increasing toward the rift margin with the maximum total denudation occurring 20 km west of the western master fault of the graben the early cretaceous phase of denudation was probably related to tectonic reactivation of the earlier permo triassic rift during the initial separation of the indian and antarctic sector of gondwana

time lapse ert monitoring of an injection withdrawal experiment in a shallow unconfined aquifer toquantifyperformanceof3dtime lapseelectricalresistivity tomography ert a sequential injection withdrawal experiment was designed for monitoring the pump and capture remediation of a conductive solute in an unconfined alluvial aquifer prior information is incorporated into the inversion procedure via regularization with respect to a reference model according to threeprotocols 1independentregularizationinvolvingasingle reference model 2 background regularization involving a referencemodelobtainedviainversionofpreinjectiondata and3 time lapseregularizationinvolvinganevolvingreferencemodel obtained via inversion of data from previous experimental stages emplacementandsequentialwithdrawalofthesoluteisclearly imaged for all protocols time lapse regularization results in greater amounts of model structure while providing significantcomputationalsavings ert estimatedelectricalconductivity is used to predict solute concentration and solute mass in the aquifer at any experimental stage we are able to estimate total solute mass in the aquifer with a maximum accuracy of 60 85 depending on regularization protocol and survey geometry wealsoestimatethewithdrawnsolutemassforeveryexperimentalstagethechangeinmassbetweenexperimentalstages withdrawn mass estimates are more reliable than total mass estimates and do not exhibit systematic underprediction or dependence on regularization protocol withdrawn mass estimates areaccurateforchangesinmassbelow2 4 kgofpotassiumbromide kbr for horizontal and vertical dipole dipole surveys respectively estimating the withdrawn solute mass does not require background subtraction and thus does not require backgrounddata

alkane and pah depositional history sources and fluxes in sediments from the fraser river basin and strait of georgia canada hydrocarbon data for dated sediment cores from fraser basin lakes and the strait of georgia in canada reveal a pristine pre industrial background that remains unaltered in modern sediments far from human activities these pristine sediments contain polycyclic aromatic hydrocarbons pahs from combustion natural forest and prairie fires and alkanes and pahs from weathering of soils containing vascular plant remains and natural petroleum hydrocarbons and algal production at other locations examined however these natural loadings have been augmented over the past century by hydrocarbons from petroleum the combustion of liquid oil gasoline and solid coal wood fuels and from processing of wood either directly from disturbed land and slash burning or indirectly through pulp mill effluent although contamination is clearest where there are nearby human activities alkane profiles pah distributions and alkane unresolved complex mixtures suggest a widespread contamination from petroleum combustion products from human activities can also be identified although with less source specificity than with the petroleum products regional emissions from anthropogenic combustion processes appear to support modern pah increases within the fraser river basin and there is little evidence of inputs from global emissions principal components analysis using the new centred log ratio normalisation procedure to normalise data discriminates well between pahs entering lakes from runoff or the atmosphere and pah formed diagenetically within lake sediments as well as between combustion and petroleum pahs

location of the nubia somalia boundary along the southwest indian ridge the northern boundary between the nubian west african and somalian east african plates is marked by the existence of the east african rift which is the locus of roughly east west stretching due to the separation of these plates south of 20 s any expression of deformation or seismicity due to the relative motion of these two presumably distinct plates vanishes or is extremely subtle although the boundary must continue until it intersects another plate boundary until recently there were no observational limits on the location of that intersection and the recent limits were very broad being thousands of kilometers wide here from an analysis of the locations of the old edge of magnetic anomaly 5 which is over 11 ma seafloor we show that the main locus of deformation between nubia and somalia near the southwest indian ridge over the past 11 m y can be no wider than a few hundred kilometers from 100 km west of the du toit fracture zone to 50 km east of the andrew bain fracture zone complex deformation is most likely concentrated along a closely spaced set of several fracture zones known collectively as the andrew bain fracture zone complex which is only 100 km wide the displacement along the nubia somalia boundary over the past 11 m y is 23 km 6 km 95 confidence limits indicating a displacement rate of 2 mm yr much slower than typical rates of seafloor spreading and subduction but comparable to that along the owen fracture zone and dalrymple trough which separate the arabian plate from the indian plate and along the azores gibraltar line which separates the eurasian plate from the nubian plate

evidence for motion between nubia and somalia along the southwest indian ridge the east african rift marks the northern boundary of the nubian west african and somalian east african plates and has formed by horizontal stretching due to the separation of these plates1 south of 20 s any expression of deformation or seismicity due to the relative motion of these two distinct plates vanishes although the boundary must continue until it intersects another plate boundary the nearest such boundary is that of the antarctic plate marked by the southwest indian ridge but previous analyses of plate motion data have indicated no significant difference between nubia antarctica and somalia antarctica motion2 3 here we show using a large compilation of plate motion data that nubia antarctica motion does differ from somalia antarctica motion and we determine a relative angular velocity of the two plates that has compact confidence limits our analysis places the pole of rotation near to the southern limit of african seismicity implying that the southern part of the nubian somalian plate boundary is a diffuse zone of convergence up to 2 mm yr 1 whereas up to 6 mm yr 1 of separation is accommodated across the east african rift about half the separation rate of the slowest mid ocean ridge

evidence for high frequency cyclic fault activity from high resolution seismic reflection survey rukwa rift tanzania a high resolution seismic survey of the rukwa rift has imaged the upper 300 m of the pliocene holocene section the sediments are characterized by aggradational deposition in shallow lacustrine conditions that episodically dried out overall the reflection package expands northeastwards towards the lupa fault half graben bounding fault isopach maps for nine intervals 6 m to 65 m thick show four periods of marked expansion of the section towards the lupa fault interpreted to represent times of fault activity or infilling of fault created topography during the early stage of fault quiescence there are three periods of little or much reduced expansion interpreted to represent infilling of the accommodation space between the lake floor and the lake surface during periods of fault inactivity cyclicity of such high frequency has not been widely reported for faults which penetrate the crust the periods of activity show remarkably similar displacement patterns with no lateral migration of the main depocentre implying that seismic and aseismic slip has persistently clustered in the same parts of the fault identification of high frequency fault cyclicity has implications for sequence stratigraphy in tectonically active areas since there is a tendency to assume faults do not have cyclic effects on the scale of tens of thousands of years

multisensory satellite observations of the expansion of the batagaika crater and succession of vegetation in its interior from 1991 to 2018 on site monitoring in large areas located in inaccessible regions can be difficult and costly thus remote sensing is an essential tool for mapping and monitoring changes in such regions therefore this paper describes long term multisensory satellite observations of the expansion of the batagaika crater in northern siberia and natural succession of vegetation in its interior from 1991 to 2018 landsat 5 tm landsat 7 etm landsat 8 oli tirs imageries were mainly used as a data source for analyses although sentinel 2a imagery and dem image from aster satellite were also employed for calculating a vegetation index and expansion in the crater area the observations were conducted in years 1991 2018 and were made in a summer season the results reveal that the crater area increased by almost three times during these 27 years and that the fastest expansion took place between 2010 and 2014 with 22 7 increment the analysis of elevation of the crater revealed that in 2018 its maximum depth was ca 70 m and that depth was decreasing towards its north east tail additionally the satellite imagery of land surface temperature which is a driving force of crater expansion was visualized for chosen hot days within the time frame 2010 2018 the study of temporal and spatial changes in ndvi spatial distributions inside the crater revealed also a high rate of the succession of vegetation which may reduce melting of permafrost inside the batagaika crater and its further expansion

subsurface structure of the solfatara volcano campi flegrei caldera italy as deduced from joint seismic noise array volcanological and morphostructural analysis 1 the joint application of different seismological techniques for seismic noise analysis and the results of a volcanological and morphostructural survey have allowed us to obtain a detailed and well constrained image of the shallow crustal structure of the solfatara volcano campi flegrei caldera italy horizontal to vertical spectral ratios inversion of surface wave dispersion curves and polarization analysis provided resonance frequencies and peak amplitudes shear wave velocity profiles and polarization pattern of coherent ambient noise these results combined in a unique framework indicate that the volcanic edifice is characterized by lateral and vertical discontinuities and heterogeneities in terms of shear wave velocity lithological contrasts and structural setting the interpretation of the seismological results with the volcanological and morphostructural constraints supports the hypothesis that the volcano has been characterized by a complex and intense activity with the alternation of constructive and destructive phases during which magmatic and phreatomagmatic explosions built a complex tuff cone later reworked by atmospheric agents and altered by hydrothermal activity the differences in the velocity structure between the central and eastern parts of the crater have been interpreted as resulting from a possible eastward migration of the eruptive vent along the deformational features affecting the area and to the presence of viscous lava and lithified tuff bodies within the feeding conduits which are buried under a covering of reworked materials of variable thickness the observed fault and fracture systems partially inherited from regional structural setting and exhumed during volcanism and ground deformation episodes also seems to strongly control wave propagation affecting the noise polarization properties

ion concentrations in ice wedges an innovative approach to reconstruct past climate variability abstract for atmospheric gases and aerosols snow and ice provide a useful archive of paleoenvironmental history in the northern hemisphere this archive has been largely limited to greenland ice but promising pioneering work has been done recently using chronology of an ice wedge in barrow northern alaska here we investigate past aerosols at the same ice wedge sampling site reconstructing the sea ice fluctuations in the adjacent beaufort sea during the bolling allerod ba and younger dryas yd periods we confirm the integrity of methanesulfonate ion ms concentrations in the biws as marine proxies and then find that the ice wedge has a high ms concentration through the beginning coldest yd periods the high ms concentration indicates that even during the coldest yd periods 12 900 12 700 yrbp the near shore region in the alaskan beaufort sea near barrow may not have been completely filled by permanent sea ice

time dependent volcano source monitoring using interferometric synthetic aperture radar time series a combined genetic algorithm and kalman filter approach 1 modern geodetic methods allow continuous monitoring of deformation fields of volcanoes the acquired data contribute significantly to the study of the dynamics of magmatic sources prior to during and after eruptions and intrusions in addition to advancing the monitoring techniques it is important to develop suitable approaches to deal with deformation time series here we present test and apply a new approach for time dependent nonlinear inversion using a combination of a genetic algorithm ga and a kalman filter kf the ga is used in the form presented by shirzaei and walter 2009 and the kf implementation now allows for the treatment of monitoring data as a full time series rather than as single time steps this approach provides a flexible tool for assessing unevenly sampled and heterogeneous time series data and explains the deformation field using time consistent dislocation sources following synthetic tests we demonstrate the merits of time consistent source modeling for interferometric synthetic aperture radar insar data available between 1992 and 2008 from the campi flegrei volcano in italy we obtained multiple episodes of linear velocity for the reservoir pressure change associated with a parabolic surface deformation on the volcano these data may be interpreted via differential equations as a linear flux to the shallow reservoir that provides new insight into how both the shallow and deep reservoirs communicate beneath campi flegrei the synthetic test and case study demonstrate the robustness of our approach and the ability to track and monitor the source of systems with complex dynamics it is applicable to time dependent optimization problems in volcanic and tectonic environments in other tectonic environments in other areas and allows understanding of the spatiotemporal extent of a physical process in quantitative manner

aromatic hydrocarbon biomarkers in terrestrial organic matter of devonian to permian age abstract this paper presents the results of a detailed study on the occurrence and distribution of alkylnaphthalenes and alkylphenanthrenes in 39 coal and sediment samples from the late palaeozoic containing predominantly terrestrial organic matter most of the samples represent the euramerian flora realm and originate from locations beyond the variscan front in eastern northern and central europe i e especially england and the moscow basin the samples are of relatively low maturity 0 32 to 1 80 rr and consist mainly of mixtures of type iii and ii kerogen quantification of the c0 to c4 naphthalenes and the c0 to c4 phenanthrenes showed that these compound classes were highly abundant in all samples aromatic hydrocarbon maturity parameters in general are in good agreement with measured vitrinite reflectance values 1 2 7 trimethylnaphthalene an assumed diagenetic product of oleanane type biomarkers was present in all investigated samples this observation provides evidence that oleanane type lipids were biosynthesised by organisms predating the evolution of angiosperms or that assumed formation pathways for 1 2 7 trimethylnaphthalene are insecure 1 2 8 trimethylphenanthrene was significantly enriched in samples from the permian and the one sample from the devonian investigated in this study the precursor s of 1 2 8 trimethylphenanthrene therefore may have been produced by organisms which were least abundant in the carboniferous depositional environments represented by our samples

monitoring and modelling hydrothermal fluid emission at la solfatara phlegrean fields italy an interdisciplinary approach to the study of diffuse degassing discharge of hydrothermal fluids at la solfatara is one of the many pieces of evidence testifying to the level of activity and the potential danger characterizing the volcanic complex of the phlegrean fields recent measurements of diffuse degassing shed light on the unexpected magnitude of this process and prompted further research to improve our understanding of the hydrothermal system feeding the surface phenomenon at la solfatara in this work we first present new data on co2 diffuse degassing that were collected during a campaign in july 2000 and confirm previous measurements of the degassing rate these data together with other information on subsurface structures and conditions provided the necessary constraints to perform physical modelling of the hydrothermal fluid circulation at la solfatara numerical simulations describe the ascent and evolution of a hot multi phase and multi component fluid composed of water and carbon dioxide through a homogeneous porous medium when certain system properties and conditions are used this model reproduces some of the main features which characterize the natural system including the energy budget associated with the ascent and condensation of hot fluids and the development of a single phase gas region whose existence was inferred from independent chemical data further simulations investigated the effects associated with changes in rock properties and fluid injection rates results showed that an increase in the permeability at shallow depth may have an important influence on the system conditions and fluid discharge they imply that surface phenomena accompanied by very high temperatures at shallow depths may survive long after deep feeding has ceased

architecture and temporal variations of a terrestrial co2 degassing site using electric resistivity tomography and self potential the hartousov mofette field in nw bohemia czech republic is characterized by strong co2 degassing from the lithospheric mantle in a test survey using electrical resistivity tomography we observed changes over time in the subsurface structure beneath heavily co2 degassing spots to depths of about 40 m and compared them to co2 gas flux and soil gas mappings from previous studies changes in the electrical resistivity were measured between september 2012 and october 2013 at irregular intervals and highlight large variations in the resistivity distribution where the co2 degassing was strongest 56 103 g m 2 day 1 indicating a fluid induced change of properties of the underlying clayey sediments positive and negative anomalies in the electric self potential parallel to the erts can be found where co2 degassing occurs which indicates varying ascent or descent of fluids within these spots some degassing spots seem not to be actively degassing continuously over time which can also be observed by other studies in the same area we suggest that future gas mappings are accompanied by methods that observe the state of fluid systems at subsurface over time e g electric resistivity tomography and self potential

imaging high stage river water intrusion into a contaminated aquifer along a major river corridor using 2 d time lapse surface electrical resistivity tomography the hanford 300 area is located adjacent to the columbia river in south central washington state usa and was a former site for nuclear fuel processing operations waste disposal practices resulted in persistent unsaturated zone and groundwater contamination the primary contaminant of concern being uranium uranium behavior at the site is intimately linked with river stage driven groundwater river water exchange such that understanding the nature of river water intrusion into the 300 area is critical for predicting uranium desorption and transport in this paper we use time lapse electrical resistivity tomography ert to image the inland intrusion of river during high stage conditions we demonstrate a modified time lapse inversion approach whereby the transient water table elevation is explicitly modeled by removing regularization constraints across the water table boundary this implementation was critical for producing meaningful imaging results we inverted approximately 1200 data sets 400 per line over 3 lines using high performance computing resources to produce a time lapse sequence of changes in bulk conductivity caused by river water intrusion during the 2011 spring runoff cycle over approximately 125 days the resulting time series for each mesh element was then analyzed using common time series analysis to reveal the timing and location ofmore river water intrusion beneath each line the results reveal non uniform flows characterized by preferred flow zones where river water enters and exits quickly with stage increase and decrease and low permeability zones with broader bulk conductivity break through curves and longer river water residence times the time lapse ert inversion approach removes the deleterious effects of changing water table elevation and enables remote and spatial continuous groundwater river water exchange monitoring using surface based ert arrays under conditions where groundwater and river water conductivity are in contrast less

geology and geophysics of the rukwa rift east africa exploration in the rukwa rift using gravity and seismic reflection surveys fieldwork and drilling has defined the structure and stratigraphy of the basin in greater detail than any other part of the western rift the stratigraphy comprises precambrian basement karroo sandstones shales and coals upper miocene red beds and miocene recent lacustrine and fluvial sediments during miocene recent rifting the greatest sediment input apparently came from axial fluvial systems flowing from the northwest and southeast the southwestern area experienced alternating shallow lacustrine and fluviodeltaic conditions during the miocene recent cenozoic age rift structures have a dominant nw se and a subordinate n s trend the nw se trend tends to follow a precambrian basement and later karroo structural trend ne sw seismic lines indicate up to 10 km extension of the tertiary section in a direction oblique to the probable e w regional extension direction in the southeastern portion of the basin both karroo and tertiary quaternary sediments expand into the lupa fault zone reaching thicknesses of up to 3 and 7 km respectively tertiary quaternary sediment thicknesses decrease northwestward accompanied by a decrease in the amount of extension and a broadening of the basin as extension is transferred to the lake tanganyika rift

electrical resistivity tomography imaging of the near surface structure of the solfatara crater campi flegrei naples italy we describe the results from an electrical resistivity tomography ert survey performed inside the solfatara crater located in the central part of the campi flegrei cf composite caldera the solfatara volcano represents the most active zone within the cf area in terms of hydrothermal manifestations and local seismicity eight dipole dipole ert lines have been measured with the aim of deducing a 3d resistivity model for the upper 80 m beneath the solfatara the results have allowed classification of the shallow structure below the crater into a low resistivity lr class up to about 4 m an intermediate resistivity ir class from 5 m up to 50 m and a high resistivity hr class from 60 m onward in order to solve the ambiguities arising in the interpretation of the nature of these bodies a comparison has been done between the 3d ert model and the co2 flux soil temperature and gravity maps over the same area by combining all of these parameters the whole lr body has been ascribed to a water dominated geothermal basin and the hr body to a steam gas dominated reservoir finally the ir class has been interpreted as a widespread background situation with intermediate character where volatiles and condensates can coexist in the same volumes at variable percentages coherently with the resistivity variation within this class since fluid dynamics in the solfatara crater change rapidly ert surveys repeated in the future are expected to be of great help in monitoring possible pre eruptive changes as well as in better following evolution of the local geothermal system

dipolar self potential anomaly associated with carbon dioxide and radon flux at syabru bensi hot springs in central nepal the syabru bensi hot springs are located at the main central thrust mct zone in central nepal high carbon dioxide and radon exhalation fluxes reaching 19 kg m a2 d a1 and 5 bq m a2 s a1 respectively are associated with these hot springs making this site a promising case to study the relationship between self potential and fluids gas and water exhalation along a fault zone a high resolution self potential map covering an area of 100 m by 150 m that surrounds the main gas and water discharge spots exhibits a dipolar self potential anomaly with a negative peak reaching a180 mv at the main gas discharge spot the positive lobe of the anomaly reaching 120 mv is located along the terraces above the main gas and water discharge spots several electrical resistivity tomograms were performed in this area the resistivity tomogram crossing the degassing area shows a dipping resistive channel interpreted as a fracture zone channeling the gas and the hot water we propose a numerical finite difference model to simulate the flow pattern in this area with the constraints imposed by the electrical resistivity tomograms the self potential data the position of the gas vents and hot water discharge area this study provides insights on the generation of electrical currents associated with geothermal circulation in a geodynamically active area a necessary prerequisite to study using self potentials a possible modulation of the geothermal circulation by tectonic activity citation byrdina s et al 2009 dipolar self potential anomaly associated with carbon dioxide and radon flux at syabru bensi hot springs in central nepal

east african rift system offset age and tectonic significance of the tanganyika rukwa malawi intracontinental transcurrent fault zone abstract the 1000 200 km tanganyika rukwa malawi fractures area is shown to be a right lateral intracontinental transform zone belonging to the east african rift system using the results carried out from complementary techniques remote sensing field structural analysis and k ar isotopic dating it appears that tectonics in this area have acted at different times the oldest being at 2000 1400 m y the youngest being still active today and are mainly due to the reactivation of nw se structures the area consists mainly of large nw se en echelon dextral transcurrent faults along which the southern tanganyika rukwa and northern malawi troughs are opening ne sw transverse faults showing a curved horizontal shape end these troughs axially eocene to recent volcanic activity is associated with the intersection of the northeastern main nw se transcurrent fracture the livingstone fault

strain accommodation by slow slip and dyking in a youthful continental rift east africa continental rifts begin and develop through repeated episodes of faulting and magmatism but strain partitioning between faulting and magmatism during discrete rifting episodes remains poorly documented in highly evolved rifts tensile stresses from far field plate motions accumulate over decades before being released during relatively short time intervals by faulting and magmatic intrusions1 2 3 these rifting crises are rarely observed in thick lithosphere during the initial stages of rifting here we show that most of the strain during the july august 2007 seismic crisis in the weakly extended natron rift tanzania was released aseismically deformation was achieved by slow slip on a normal fault that promoted subsequent dyke intrusion by stress unclamping this event provides compelling evidence for strain accommodation by magma intrusion in addition to slip along normal faults during the initial stages of continental rifting and before significant crustal thinning

adventive hydrothermal circulation on stromboli volcano aeolian islands italy revealed by geophysical and geochemical approaches implications for general fluid flow models on volcanoes on march 15th 2007 a paroxysmal explosion occurred at the stromboli volcano this event generated a large amount of products mostly lithic blocks some of which impacted the ground as far as down to 200 m a s l about 1 5 km far away from the active vents two days after the explosion a new vapour emission was discovered on the north eastern flank of the volcanic edifice at 560 m a s l just above the area called nel cannestra this new vapour emission was due to a block impact in order to investigate the block impact area to understand the appearance of the vapour emission we conducted on may 2008 a multidisciplinary study involving electrical resistivity tomography ert ground penetrating radar gpr self potential sp co2 soil diffuse degassing and soil temperature surveys this complementary data set revealed the presence of an anomalous conductive body probably related to a shallow hydrothermal level at about 10 15 m depth more or less parallel to the topography it is the first time that such a hydrothermal fluid flow with a temperature close to the water boiling point 76 c has been evidenced at stromboli at this low elevation on the flank of the edifice the ert results suggest a possible link between 1 the main central hydrothermal system of stromboli located just above the plumbing system feeding the active vents with a maximum of subsurface soil temperature close to 90 c and limited by the neostromboli summit crater boundary and 2 the investigated area of nel cannestra at 500 m a s l a buried eruptive fissure active 9 ka ago in parallel sp and co2 soil diffuse degassing measurements suggest in this sector at slightly lower elevation from the block impact crater a magmatic and hydrothermal fluid rising system along the n41 regional fault a complementary ert profile on may 2009 carried out from the neostromboli crater boundary down to the block impact crater displayed a flank fluid flow apparently connected to a deeper system the concept of shallow hydrothermal level have been compared to similar ert results recently obtained on mount etna and la fossa cone of vulcano this information needs to be taken into account in general fluid flow models on volcanoes in particular peripheral thermal waters as those bordering the north eastern coast of stromboli could be contaminated by hydrothermal and magmatic fluids coming from regional faults but also from the summit

native sulfur sulfates and sulfides from the active campi flegrei volcano southern italy genetic environments and degassing dynamics revealed by mineralogy and isotope geochemistry abstract we investigated sulfur bearing minerals from the campi flegrei caldera southern italy in relation to the increase of hydrothermal activity phenomena since 2006 aimed at providing insights into the volcanic system dynamics mineral encrustations and muds were sampled between 2013 and 2015 at the long standing degassing crater of the solfatara tuff cone and its recently restless north eastern pisciarelli slope deep seated sulfides were further separated from two drill cores agip s mofete boreholes 1500 m and 2695 m depth the mineral assemblage and texture of sampled encrustations were determined by x ray diffraction optical and scanning electron microscopy and x ray microanalysis by energy dispersive spectrometry native sulfur and alunite dominate among the newly formed mineral phases other minerals are mostly alunogen and locally pickeringite potassium alum hematite and pyrite mereiterite and amarillite sporadically occur the mud pools are rich in gypsum potassium alum and pyrite quartz and argillic phases locally with analcime are dispersed in the outcropping rocks 34 s values were determined for shallow subsurface native sulfur 5 5 to 0 0 and alunite 1 7 to 0 2 as well as for the deep seated pyrite 3 3 to 7 4 in the depth range 1500 2695 m 18 o values were measured for shallow native alunite 4 2 to 7 0 pisciarelli alunite was finally analyzed for its 87 sr 86 sr ratio and 143 nd 144 nd ratios 0 707517 6 and 0 512459 6 respectively textural and isotopic data constrain the genesis of alunite at the expense of k feldspars through rock alteration by hydrothermal fluids we suggest that the caldera is a low sulfidation system hosting acid sulfate deposits in its active degassing area the acid sulfate environment developed on an argillitic facies that thins outwards and is characteristic for steam heated and magmatic steam environments these environments developed in relation to the fractured settings that facilitates the gas emissions from deeper levels and the meteoric infiltration from surface to depth newly determined 34 s data are lower than previously published values suggesting a progressive decrease in the sulfur isotopic composition through time at least since 1956 the isotopic variation is associated with a lowering of the so 2 h 2 s ratio and the widening of the surface of co 2 degassing in the absence of significant changes in the average co 2 flux values and in the carbon and helium isotope compositions native sulfur and sulfates move from sulfur isotope equilibrium to disequilibrium we ascribe this transition to enhanced so 2 scrubbing due to a high rock permeability that facilitates a faster gas ascent rate in the shallow crust

electromagnetic outline of the solfatara pisciarelli hydrothermal system campi flegrei southern italy abstract we describe the results from a combined controlled source audio magnetotelluric csamt and natural source magnetotelluric mt survey carried out in the solfatara pisciarelli s p area located in the central part of the campi flegrei cf composite caldera west of naples southern italy the s p area represents the most active zone within the cf caldera in terms of hydrothermal manifestations and local seismicity since 1969 the cf caldera is experiencing ground deformation seismicity and geochemical fluid changes which are particularly evident in the s p area a 1 km long nearly w e directed csamt mt profile crossing the fumarole field was carried out in the s p area with the aim of deducting a resistivity model of the structural setting of the hydrothermal system in the first 3 km depth an interpretation of the modelled section across the profile is given in this paper taking advantage from already existing seismic gravity and geochemical data in the same area three well distinct zones have been outlined the first zone is a very shallow electrically conductive body localized beneath the westernmost segment of the profile which within a short distance of about 100 m dips westwards from near surface down to some hundred metres in depth mostly accounting for the very low resistivity 1 10 m and the exceedingly high values of v p v s 4 this shallow zone has been ascribed to a water saturated high pressurized geothermal reservoir the second zone which has been localized below the west central portion of the csamt mt transect appears as a composite body made up of a nearly vertical plumelike structure that escapes at about 2 25 km depth from the top edge of the east side of a presumably horizontal platelike body the plumelike structure rises up to the free surface in correspondence of the fumarole field whereas the platelike structure deepens at least down to the 3 km of maximum exploration depth the combined interpretation of resistivity 50 100 m body wave velocity ratio v p v s 3 and geochemical data indicates that the plumelike portion can likely be associated with a steam gas saturated column and the platelike portion with a high temperature 300 c over pressurized gas saturated reservoir finally the third zone which has been localized beneath the eastern half of the transect from about 1 2 km down to about 3 km of depth is also characterized by very low resistivity values 1 10 m jointly interpreted with seismic v p v s 0 g cm 3 data this last electrically conductive structure appears to be associated with a hydrothermally mineralized clay rich body

three dimensional models of deformation near strike slip faults we use three dimensional elastic models to help guide the kinematic interpretation of crustal deformation associated with strike slip faults deformation of the brittle upper crust in the vicinity of strike slip fault systems is modeled with the assumption that upper crustal deformation is driven by the relative plate motion in the upper mantle the driving motion is represented by displacement that is spectied on the bottom of a 15km thick elastic upper crust everywhere except in a zone of finite width in the vicinity of the faults which we term the shear zone stress free basal boundary conditions are specified within the shear zone the basal driving displacement is either pure strike slip or strike slip with a small oblique component and the geometry of the fault system includes a single fault several parallel faults and overlapping en echelon faults we examine the variations in deformation due to changes in the width of the shear zone and due to changes in the shear strength of the faults in models with weak faults the width of the shear zone has a considerable effect on the surficial extent and amplitude i c1 j l c i rl l b blhi aill i srizcxi ld 3 rr ij i n flail 3il i dilitiiiat df ti ijtluii clicili c i i zor tz a j t s ii acmes strong fault lnnlds havs lnore luc tlixd dxz a ac tip of tne faults and the deformation is partly distributed outside the fault zone the dimensions of large basins along strike slip faults such as the rukwa and dead sea basins and the absence of uplift around pull apart basins fit models with weak faults better than models with strong faults our models also suggest that the length to width ratio of pull apart basins depends on the width of the shear zone and the shear strength of the faults and is not constant as previously suggested we show that pure strike slip motion can produce tectonic features such as elongate half grabens along a single fault rotated blocks at the ends of parallel faults or extension perpendicular to overlapping en echelon faults which can be misinterprete d to indicate a regional component of extension zones of subsidence or uplift can become wider than expected for transform plate boundaries when a minor component of oblique motion is added to a system of parallel strike slip faults

an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence the orientations of fault planes and slip directions indicated by a population of earthquake focal mechanisms can be used to determine best fit regional principal stress directions and r 2 1 3 1 a measure of relative stress magnitudes under the assumption of uniform stress in the source region this analysis allows for the possibility that failure occurs on preexisting zones of weakness of any orientation in the inversion we perform a grid search of stress models to find the one which requires the smallest total rotation of all the fault planes that is needed to match the observed and predicted slip directions the method allows for errors in orientations of both the fault planes and slip directions we have an objective means for identifying the more likely of the two possible fault planes from each focal mechanism relative to a given stress model thus we do not face the problem of ambiguity of nodal planes which plagues other analyses of this kind by using a grid search of stress models rather than a linearization scheme we are able to perform a realistic error analysis and thus establish confidence limits for the preferred regional stresses the method can be used to investigate possible stress inhomogeneities during earthquake sequences by analyzing subsets of the data population the technique has been applied to 76 events from the san fernando earthquake sequence for which we have found best fit stresses plunge and azimuth 1 7 187 2 27 281 3 62 84 and r 0 65 the average misfit between this stress model and all the data is about 8 and all but eight of the aftershocks have misfits of less than 20 these values are considerably less than the uncertainty of the focal mechanism determinations therefore significant stress inhomogeneities are not required by the data our analysis does not support the suggestion of a change in stresses during the aftershock sequence as proposed by others on the basis of an apparent change in focal mechanisms

african stress pattern from formal inversion of focal mechanism data abstract the kinematic models and the associated orientation of extensional stress of the east african rift system have been subjected to much debate since a long time in the past decades the proposed models relied on the interpretation of the overall rift geometry geological fault slip data and the few focal mechanisms available these models generally suffer of a poor time control and an underestimation of the possible changes in the stress field and geodynamic regime with time and space in the recent years there has been a significant increase in the number of focal mechanisms available for the entire rift system and it is now possible to estimate the present day stress field in relative detail based on seismotectonic data alone we compile 347 focal mechanism data from the global harvard cmt catalogue and various other sources and grouped 332 of them in 24 distinct regions boxes on the basis of their geographical proximity kinematic homogeneity and tectonic setting for each box and for the same data set reduced stress tensors have been obtained by formal stress inversion using both the tensor program delvaux sperner 2003 and the slick method michael 1984 1987 both inversion methods show in comparable results in terms of horizontal stress axes orientations and tectonic stress regimes which stem for the robustness of the approach the obtained stress pattern reflects a complex interaction between 1st order effects as different driving forces including plate boundary forces and 2nd and 3rd order effects as gravitational potential of topography intra lithospheric processes and the influence of structural heterogeneities of the rift structures the evidence present in the stress orientations of the 2nd and 3rd order stress pattern as the variations in the horizontal stress axes along the axis of the rift are of particular interest as they were not yet captured or shown in earlier numerical models of the stress field additional sources of tectonic forces in supplement to the gravitational potential energy forces as considered in the earlier models are necessary to explain the observed patterns

geophysical and hydrogeological experiments from a shallow hydrothermal system at solfatara volcano campi flegrei italy response to caldera unrest 1 integration of high resolution geophysical and hydrogeological investigations at solfatara volcano campi flegrei italy allowed us to 1 image the shallow and intermediate subsurface to the crater 2 elucidate patterns in the shallow subsurface degassing and 3 refine and upgrade volcano monitoring strategies for this dynamic area our results show that the subsurface to the crater can be divided roughly into two zones a dry outcropping layer overlying a horizon saturated by hydrothermal fluids within this saturated zone intersections of dominant nw and ene striking structural lineaments act as preferential escape conduits for the fluids which generate high microseismic noise amplitudes in the southeastern part of the crater hydrogeological data suggest an uprising of the isotherms below solfatara crater and a marked increment of fluid degassing over the last 40 years sudden variations of both seismic noise level and noise cycling are positively correlated with early stages of ground inflation during the ad 2000 uplift we believe therefore that monitoring of seismic noise can be used for upgrading early warning strategies in this sector of the campi flegrei volcanic system

unrest at campi flegrei a contribution to the magmatic versus hydrothermal debate from inverse and finite element modeling 1 we present results from the modeling of ground deformation and microgravimetric data recorded at campi flegrei in order to assess the causative phenomena of caldera unrest between 1981 and 2001 we find that residual gravity changes during ground uplift 1982 1984 are indicative of mass changes in a hybrid of magmatic and hydrothermal sources during deflation between 1985 and 2001 the inversion of gravity residuals for a single source does not provide convincing results we then performed the joint inversion of gravity and deformation data for multiple spherical sources and refined source parameters by finite element modeling in order to mitigate against limitations of the analytical solutions the data recorded during inflation and rapid deflation may be best explained by mass and pressure changes in a deep magmatic source at about 5 km depth and a shallow 2 km deep hydrothermal source both sources contribute equally to the gravity changes observed between 1982 and 1984 the contemporary uplift appears to be mainly caused by the shallow source the subsequent deflation is dominated by a pressure decrease in the hydrothermal source the magmatic source contributes chiefly to the observed gravity changes pressure and density variations within multiple shallow seated hydrothermal sources provide acceptable fits to the deflation and accompanying gravity changes recorded since 1988 these shallow level dynamics also appear to trigger spatially and temporarily random short term reversals of the overall mode of ground subsidence since 1985 our analysis does not support the idea of magmatic contributions to these short lived periods of inflation

velocity anisotropy observed in wellbore seismic arrivals combined effects of intrinsic properties and layering a method of estimating velocity anisotropy by the t p inversion of seismic traveltimes observed in a multidepth and offset vsp experiment is developed in the method a set of seismic traces observed at afixed depth in the wellbore are transformed to the t p domain incidence angle dependent interval velocities are extracted from the resulting curves using coherency measures after accounting for the effects of the overlaying layers to test the method we obtained seismic records from a shallow borehole drilled through a flat lying sedimentary sequence one depth interval that consists of a homogeneous bioturbated shale is nearly isotropic a second interval characterized by an alternation of thin 1 m sands and shales displays an anisotropy of 15 withvelocitiesincreasingfromthenearvertical 0 308 to the oblique 30 8 0 558 angles of incidence oblique velocities were always larger the observation thattheshale sanddepthintervaldisplayingthegreatest anisotropy also is the most heterogeneous in the sonic logs suggests that the thin layering produces the anisotropy the theoretical vertical to horizontal velocity anisotropy for this interval computed assuming isotropic layering is 14 2 comparing this theoretical value to the vertical to oblique value obtained over a smaller range of incidence angles indicates that the theoretical valueistoosmall thisdiscrepancyispossiblybecauseof the intrinsic anisotropy of the shale layers themselves that is not considered in the theoretical calculations

major and trace elements δ13c and polycyclic aromatic hydrocarbons in the late pleistocene ice wedges a case study of batagay yedoma central yakutia abstract we studied the ionic composition of ice the content of suspended and dissolved trace and major elements in ice values of 13 and the composition of pahs of inclusions in the late pleistocene syngenetic ice wedges of the batagay yedoma for the first time the complex geochemical study of batagay megaslump was carried out the ice of the upper and lower complex of different ages was studied mineralisation of the late pleistocene ice wedges of batagay yedoma ranges from 66 56 to 424 8 mg l 1 from ultrafresh to desalinated the ionic composition of the ice is bicarbonate calcium and corresponds to snow formed under the influence of continental air masses the proportion of ca contained in dissolved form is not more than 20 30 as for the other elements the proportion of mg k na al fe mn sr ba in suspended form is greater than 90 the content of trace elements in inclusions in ice wedges and soils is equal which confirms the pedogenic origin of the inclusions in ice according to our data values of 13 in lipids of the pedogenic material in ice decrease with depth the lowest values values of 13 less than 30 were observed in the ice wedge of the upper complex at a depth of 7 4 8 6 m the increase of 13c values of lipids from pedogenic material in ice wedges with depth is due to the landscape change from grassland ecosystems to forest ecosystems and may also be influenced by the increased frequency of fires that occurred during the transition to forest ecosystems and the disappearance of large herbivores

monitoring active fumaroles through time lapse electrical resistivity tomograms an application to the pisciarelli fumarolic field campi flegrei italy abstract volcanoes are usually monitored through observations of many physical and chemical phenomena in the most dangerous cases as the one of the campi flegrei caldera italy great amount of data are collected both in discrete or continuously and regularly stored however how to transform such mass of data in a deeper understanding of the volcano dynamics is still an open question dissimilar information are in fact always hard to compare but just integrating all the available knowledge hazardous events could be prevented in a reliable way fluids as water and gasses mobilized in the subsoil by the heat induced by deep magmatic sources are widely recognized as the first engine of similar occurrences and the volcanic gas emissions represent together with the seismic activity one of the most considered precursors at the same time the electrical geophysical methods are the most applied in order to detect and characterize the fluid patterns in the subsoil so the integration of geoelectrical and geochemical observations should represent one of the most pursued approach in volcanoes monitoring on the contrary standard way to compare such data has been not yet codified the ert tomograms capability to individuate that parts of the subsoil where gasses cumulate is well understood in literature however we look for indications about its proficiency in associating the electrical resistivity changes relative to these zones once compared to the geochemical time series to deep related contributes distinguishing them from the seasonal ones the electrical signature of the fluid patterns reconstructed through a time lapse ert approach could be of relevance to better characterize the volcanic phenomena and their origins in this paper a first test of ert and geochemical time series integration was performed to enhance the understanding of the pisciarelli fumarolic field evolution now the most active area in the whole campi flegrei caldera

structure and stratigraphy of the rukwa rift abstract combining recently acquired multifold seismic data with well and gravity information and field mapping a comprehensive picture of the structure and stratigraphy of the rukwa rift has emerged the rukwa rift lies between the tanganyika and nyasa malawi rifts in the western branch of the east african rift system in southwest tanzania the rukwa rift is a nw trending half graben basin that is 350 km long and 40 km wide unlike the neighboring tanganyika and nyasa rifts there is no evidence of half graben polarity reversals in the rukwa rift the nw trending boundary fault system lies on the northeastern side of the basin and comprises a series of listric faults most internal faults also show listric forms and trend n s oblique to the boundary fault the basal sedimentary section is the permo triassic karroo sequence this is overlain by the red bed sandstone sequence in which both mesozoic and tertiary fauna have been found the cenozoic lake bed sequence is the highest unit and covers nearly all of the present basin sediment thicknesses commonly reach 7 km and attain a maximum of 12 km at the southeastern end of the basin the lake bed sequence is the thickest unit in the main depocentre but the karroo sequence is often the thickest unit on the shoaling side of the half graben the rukwa rift is here interpreted to have evolved as a strike to oblique slip pull apart basin based on numerous indications of nw trending strike slip faulting

geodynamic significance of the trm segment in the east african rift w tanzania active tectonics and paleostress in the ufipa plateau and rukwa basin abstract the tanganyika rukwa malawi trm rift segment in western tanzania is a key sector for understanding the opening dynamics of the east african rift system ears in an oblique opening model it is considered as a dextral transfer fault zone that accommodates the general opening of the ears in an nw se direction in an orthogonal opening model it accommodates pure dip slip normal faulting with extension orthogonal to the rift segments and a general e w extension for the entire ears the central part of the trm rift segment is well exposed in the ufipa plateau and rukwa basin within the paleoproterozoic ubende belt it is also one of the most seismically active regions of the ears we investigated the active tectonic architecture and paleostress evolution of the ufipa plateau and adjacent rukwa basin and in order to define their geodynamic role in the development of the ears and highlight their pre rift brittle tectonic history the active fault architecture fault kinematic analysis and paleostress reconstruction show that the recent to active fault systems that control the rift structure develop in a pure extensional setting with extension direction orthogonal to the trend of the trm segment two pre rift brittle events are evidenced an older brittle thrusting is related to the interaction between the bangweulu block and the tanzanian craton during the late pan african early paleozoic it was followed by a transpressional inversion during the early mesozoic this inversion stage is the best expressed in the field and caused dextral strike slip faulting along the fault systems that now control the major rift structures it has been erroneously interpreted as related to the late cenozoic ears which instead is characterized by pure normal faulting our third and last stress stage

electrical resistivity tomography study of taal volcano hydrothermal system philippines taal volcano 311 m in altitude is located in the philippines 14 n 121 e and since 1572 has erupted 33 times causing more than 2 000 casualties during the most violent eruptions in march 2010 the shallow structures in areas where present day surface activity takes place were investigated by dc resistivity surveys electrical resistivity tomography ert lines were performed above the two identified hydrothermal areas located on the northern flank of the volcano and in the main crater respectively due to rough topography deep valleys and dense vegetation most measurements were collected using a remote method based on a laboratory made equipment this allowed retrieval of information down to a depth of 250 m erts results detail the outlines of the two geothermal fields defined by previous self potential co2 soil degassing ground temperature and magnetic mapping harada et al japan acad sci 81 261 266 2005 zlotnicki et al bull volcanol 71 29 49 2009a phys chem earth 34 294 408 2009b hydrothermal fluids originate mainly from inside the northern part of the main crater at a depth greater than the bottom of the crater lake and flow upward to the ground surface furthermore water from the main crater lake infiltrates inside the surrounding geological formations the hydrothermal fluids outlined by gas releases and high temperatures cross the crater rim and interact with the northern geothermal field located outside the main crater

normal vs strike slip faulting during rift development in east africa the malawi rift kinematic analysis of neogene and quaternary faults demonstrates that the direction of extension in the malawi rift rotated from east northeast to southeast rift development commenced with the formation of half grabens bounded by northwest north and northeast striking normal faults owing to slightly oblique rifting the northwest striking faults in the northernmost rift segment show a small dextral oblique slip component whereas north and northeast oriented faults in the central part of the rift display a sinistral oblique slip component this first event resulted in block faulting and basin subsidence which is largely responsible for the present day basin morphology of lake malawi a major change in fault kinematics occurred because of rotation of the extension direction and permutation of the principal compressive and intermediate axes the structural pattern inherited from the first rifting phase was no longer suitably oriented to accommodate extensional deformation and strike slip faulting assumed a major role the strike slip regime amplified uplift of basement ridges within the rift in regions of local transpression but it also created alluvial basins because of local transtension this new kinematic style is compatible with the recent seismicity older faults that show mainly the first deformational increment are restricted to the outermost parts of the rift toward the center the faults depict an increase in strike slip components of movement suggesting deformation propagation toward the rift center which results in a narrowing of the active rift environments with time

rifting of africa and pattern of mantle convection beneath the african plate abstract the mesozoic and cenozoic tectonic setting of the african continent is characterized by an extensional stress regime as is evident from the evolution of the west central and east african rift systems the opening of the indian and atlantic oceans and the development of tethys domain as well as from the results of geophysical investigations the most prominent feature of the bouguer gravity anomaly map of africa is a great belt of negative bouguer anomalies which extends across the entire african continent from ethiopia in the east to benguela in the west in conjunction with the red sea spreading zone this belt appears to encircle a centre in cameroon it probably corresponds to a distinct zone of lithospheric thinning and extension the entire african continent is characterized by higher than normal elevations it is located inside the african residual geoid high earthquake fault plane solutions confirm the extensional character of the present tectonic regime of eastern and southern africa where normal faulting predominates the average orientation of t axes is n s in south africa nw se in zambia mozambique and madagascar e w in kenya and ethiopia and ne sw in the red sea region from north to south the orientation of t axes rotates systematically in a clockwise sense by 130 and describes a radial pattern centred on equatorial west africa this indicates that the african lithosphere has been subject to continent wide radial extension around a hypothetical west african spreading centre referred to as the african spreading centre a asc a which coincides with the geographical centre of the african plate shear traction exerted by the convecting mantle on the base of the lithosphere is considered to be a major driving force of plate movements in the case of africa the continent wide regularities in the pattern of lithospheric extension the elevated position of the continent as well as the evolution of the mid oceanic ridge system surrounding africa provide distinct boundary conditions for the pattern of large scale mantle flow beneath the african plate it is proposed that relatively warm and less dense mantle material rises below africa forming a single mega plume or a number of plumes at the base of the african lithosphere the ascending material diverges and flows radially away from the centre of ascent corresponding to the asc a this ascending flow forms part of a very large mantle convection cell which occupies the eurafrican hemisphere the descending branch of this convection cell is located at a distance of 80 90 from the asc a the mid oceanic ridges surrounding the african continent are located between the upwelling and the downwelling branches of this convection cell at a distance of 50 60 from the asc a upper mantle flow below the sea floor spreading axes is uni directional and horizontal and is directed away from the asc a

new sedimentary structures in seismites from sw tanzania evaluating gas vs water escape mechanisms of soft sediment deformation seismite horizons are abundant in cretaceous sandstones of the rukwa rift basin southwestern tanzania diverse morphologies of soft sediment deformation are preserved including two new unusual sedimentary structures herein referred to as 1 balloon shaped inflation structures and 2 surface fractures with linked sandstone splays this original description of new sedimentary structures contributes to the growing catalogue of seismically induced deformation features their unusual morphologies bring to the forefront an important though seldom touched upon question of how to differentiate between gas and water escape in soft sediment deformation features the recognition of the spectrum of soft sediment deformation structures contained in strata and their deformational mechanisms is important because it permits the differentiation between triggering mechanisms particularly seismic activity and can constrain such events spatially and temporally we interpret the surface fractures and linked sandstone splays to reflect a high gas effusion rate formed by the release of high pressure gas followed by a limited expulsion of water the balloon shaped inflation structures reflect lower gas effusion rates due to expulsion of lower pressure gas that did not breach the cretaceous surface seal when these gas pulses did breach the paleosurface they formed gas discharge pits these seismogenic structures are consistent with deposition of cretaceous strata in the rukwa rift during periods of active carbonatite volcanism seismicity and possibly hot spring activity this documentation serves as an important data point for the re examination of the classification scheme of soft sediment deformation structures as primarily water escape structures to accommodate for the genesis of some secondary sedimentary features by gas escape

geochemistry of the active layer and near surface permafrost mackenzie delta region northwest territories canada the soluble ion content of the active layer and near surface permafrost was determined at 41 sites in the mackenzie delta region northwest territories canada in delta soils ca2 and mg2 are the dominant soluble cations but the quantity and relative abundance of na increase with proximity to the beaufort sea coast soils beneath frequently flooded surfaces are ion rich in comparison with ground above the level of decadal flooding within a terrain type near surface permafrost soil solute concentrations are similar between paired cores spaced 1 m apart but at greater distances cores spaced 3 13 m apart solute concentrations are significantly different comparatively low soil solute concentrations in old upland surfaces near inuvik may be a result of progressive removal of soluble materials from the active layer and permafrost during periods of deeper thaw in sandy silt alluvium solutes excluded during downward freezing may accumulate at the base of the active layer and be sequestered by a ris

pan arctic patterns in black carbon sources and fluvial discharges deduced from radiocarbon and pah source apportionment markers in estuarine surface sediments 1 a pan arctic geospatial picture of black carbon bc characteristics was obtained from the seven largest arctic rivers by combining with molecular combustion markers polycyclic aromatic hydrocarbons and radiocarbon 14c analysis the results suggested that the contribution from modern biomass burning to bc ranged from low in the yukon 8 and lena 5 rivers to high in the yenisey river 88 the mackenzie river contributed almost half of the total arctic fluvial bc export of 202 kton a 1 kton 109 g with the five russian arctic rivers contributing 10 36 kton a 1 each the 14c based source estimate of fluvially exported bc to the arctic ocean weighted by the riverine bc fluxes amount to about 20 from vegetation biofuel burning and 80 from 14c extinct sources such as fossil fuel combustion and relict bc in uplifted source rocks combining these pan arctic data with available estimates of bc export from other rivers gave a revised estimate of global riverine bc export flux of 26 103 kton a 1 this is twice higher than a single previous estimate and confirms that river export of bc is a more important pathway of bc to the oceans than direct atmospheric deposition

tectonic evolution of the cuvette centrale zaire the cuvette centrale central basin of zaire is an infra cambrian to recent basin with up to 9 km of sedimentary section basin subsidence can be largely explained by a postulated late proterozoic failed rift and subsequent thermal relaxation seismic reflection profiles and well data reveal a palaeozoic development of the basin punctuated by two regional deformational episodes one in the early palaeozoic late cambrian and a second in the late palaeozoic late permian triassic both episodes result from ne sw contraction with the late palaeozoic episode being largely a reactivation of the early palaeozoic structures the timing of the two deformations correlates with collisional events at continental margins some distance from the congo basin in the early palaeozoic the deformation appears to be related to the late stages of the west congolian fold and thrust belt and coincides regionally with the pan african event sensu stricto the late palaeozoic deformation coincides with collisional tectonics along the southern margin of gondwana and the generation of the cape and sierra ventana foldbelts it is postulated that in both the early and late palaeozoic africa and gondwana experienced widespread intracontinental deformation generated by distant collisional processes much as central asia is experiencing today

recent seismicity of the east african rift system and its implications abstract the seismicity of the east african rift system and southern red sea is studied here location of earthquake epicenters in east africa shows that there is a seismicity gap in space and time between the main ethiopian rift system and the eastern rift however distribution of earthquake epicenters together with the energy mapping suggest a continuity of seismic activity or stress field from the main ethiopian rift system to the western rift system via the southernmost rifts of ethiopia in general except for some earthquakes which occurred at different complex tectonics regions mechanisms of earthquakes studied here show dominantly normal faulting suggesting that the rift system is an extensional zone on the continent the presence of greater focal depth earthquakes to the southern part of the rift system may indicate that softer materials at a shallower depth are present in afar and neighboring regions than in the remaining part of the east african rift system this interpretation is supported by other geophysical studies low electrical resistivity and gravity data performed in afar it is also supported by low and high stress drops found for the northern part afar depression and southern part of the east african rift system respectively

three dimensional electrical resistivity tomography of the solfatara crater italy implication for the multiphase flow structure of the shallow hydrothermal system the solfatara volcano is the main degassing area of the campi flegrei caldera characterized by 60 years of unrest assessing such renewal activity is a challenging task because hydrothermal interactions with magmatic gases remain poorly understood in this study we decipher the complex structure of the shallow solfatara hydrothermal system by performing the first 3 d high resolution electrical resistivity tomography ert of the volcano the 3 d resistivity model was obtained from the inversion of 43 432 resistance measurements performed on an area of 0 68 km2 the proposed interpretation of the multiphase hydrothermal structures is based on the resistivity model a high resolution infrared surface temperature image and 1 136 soil co2 flux measurements in addition we realized 27 soil cation exchange capacity cec and ph measurements demonstrating a negligible contribution of surface conductivity to the shallow bulk electrical conductivity hence we show that the resistivity changes are mainly controlled by fluid content and temperature the high resolution tomograms identify for the first time the structure of the gas dominated reservoir at 50 m depth that feeds the bocca grande fumarole through a 10 m thick channel in addition the resistivity model reveals a channel like conductive structure where the liquid produced by steam condensation around the main fumaroles flows down to the fangaia area within a buried fault the model delineates the emplacement of the main geological structures mt olibano solfatara crypto dome and tephra deposits it also reveals the anatomy of the hydrothermal system especially two liquid dominated plumes the fangaia mud pool and the pisciarelli fumarole respectively

long term tir imagery processing for spatiotemporal monitoring of surface thermal features in volcanic environment a case study in the campi flegrei southern italy the tir monitoring system was partially funded by the 2000 2006 national operating programme and by the italian civil protection department in the framework of the 2004 2006 agreement with the istituto nazionale di geofisica e vulcanologia