a heating process of kuchi erabu jima volcano japan as inferred from geomagnetic field variations and electrical structure since august 2000 we have recorded the total intensity of the geomagnetic field at the summit area of kuchi erabu jima volcano where phreatic eruptions have repeatedly occurred a time series analysis has shown that the variations in the geomagnetic field since 2001 have a strong relationship to an increase in volcanic activity these variations indicate thermal demagnetization of the subsurface around the presently active crater the demagnetization source for the early variations until summer 2002 was estimated at about 200 m below sea level for the variations since 2003 the source was modeled on the basis of the expansion of a uniformly magnetized ellipsoid the modeling result showed that the source is located at 300 m above sea level beneath the crater we carried out an audio frequency magnetotelluric survey with the aim of obtaining a relation between the demagnetization source and the shallow structure of the volcano a two dimensional inversion applied to the data detected two good conductors a shallow thin one which is restricted to a region around the summit area while the other extends over the edifice at depths between 200 and 800 m these conductors are regarded as clay rich layers with low permeability which were assumed to be generated through hydrothermal alteration the demagnetization source for the early variations was possibly located at the lower part of the deep conductor and the source after 2003 lies between the two conductors where groundwater is considered to be abundant based on these results as well as on seismological geodetic and geochemical information we propose a heating process of the kuchierabu jima volcano in the initial stage high temperature volcanic gases supplied from the deep seated magma remained temporarily at the level around the lower part of the less permeable deep conductor since the ascent path had not yet been established then when the pathway developed as a result of repeated earthquakes it became possible for a massive flux of volcanic gases to ascend through the conductor the high temperature gases reached the aquifer located above the conductor and the heat was efficiently transported to the surrounding rocks through the groundwater as a consequence an abrupt increase of the gas flux and di ffusion of the heat through the aquifer occurred and the high temperature zone expanded since the high temperature zone is located beneath another conductor which acts as caprock we assume that the energy of the phreatic explosion is accumulated there

fault generated mountain fronts in southeast spain geomorphologic assessment of tectonic and seismic activity abstract tectonic activity of se spain is evaluated through the application of a general morphometric analysis over 17 different mountain fronts the selected fronts are distributed along the two most prominent crustal scale structures of the mediterranean sector of spain the eastern betic shear zone ebsz and the valencia trough geomorphic indexes used in this study are mountain front sinuosity index smf and valley floor width ratio vf this work is largely based on the smf vf regression analysis of the studied fronts together with previous available data from sw usa the development of mountain fronts in both different lithologies and tectonic contexts enabled characteristic morphometric signatures for different activity scenarios tectonic activity classes to be obtained this study thus indicates that variations of mountain front geomorphology triggered by different styles of faulting can be detected by morphometric analysis it is demonstrated that discrete uplift rates of 0 15 0 08 m ka are sufficient to keep relatively low smf values down to 1 4 in active fronts class 1 taking into account the reported uplift rates and preliminary palaeoseismic data for some of the class 1 studied fronts recurrence periods for surface rupture events can be theoretically bracketed for se spain recurrence periods for class 1 fronts could theoretically range between 10 000 and 12 500 years for maximum slip conditions and 1750 and 2600 years for minimum slip conditions inactive fronts class 3 develop under uplift rates down to 0 03 m ka and tested recurrence intervals for rupture events range between 25 000 and 50 000 years class 2 fronts of intermediate characteristics and activity display uplift rates between 0 07 and 0 03 m ka

eruption mechanism as inferred from geomagnetic changes with special attention to the 1989 1990 activity of aso volcano abstract geomagnetic changes associated with the volcanic activity of aso volcano were detected with a dense network of continuously recording proton precession magnetometers during the period from june 1989 to june 1990 magnetic date clearly indicate that changes in the magnetization within the volcano are most probably caused by temperature changes this activity can be divided into five stages which are characterized by magnetization and demagnetization of the volcano these magnetic changes with durations of a few months are definitely correlated with some typical volcanic events at the crater as well as the volcanic tremor activity the demagnetization stage appears when the vent is covered by a water pool or the volcanic activity is enhanced the magnetization stage follows the opening of a vent and several large explosions which make the vent permeable the source of magnetic changes lies at a depth of about 200 m below the crater rim in the southwestern part of the active crater magnetic moments responsible for observed magnetic changes at stages 1 2 and 4 are 3 4 5 2 and 2 2 wbm respectively the corresponding source volume is estimated as a single sphere of radius 40 50 m or a spherical shell of 100 m or so an effective mechanism of rapid heating cooling exists which is ascribed to the interaction of groundwater and superheated vapor i e a shallow hydrothermal system this hydrothermal system driven by the surface cap of the vent controls every feature of the eruptions at the final outlet of aso volcano

nonstationary analysis of geomagnetic time sequences from mount etna and north palm springs earthquake 1 volcanomagnetic and or seismomagnetic effects are geomagnetic variations generated before eruptions and or seismic events our aim is to analyze geomagnetic time series to detect the volcanomagnetic and or seismomagnetic effects among a number of other variations two advanced signal processing techniques are proposed to analyze the geomagnetic time series the first technique called continuous wavelet transform singularity analysis cwtsa is based on the continuous wavelet transform the second called time variant statistical analysis of nonstationary signals tvans is based on a time varying adaptive algorithm recursive least squares both techniques are very effective in detecting the geomagnetic variations at the time instants likely linked to volcanic and or seismic activity the application of these methodologies to geomagnetic time sequences respectively recorded on mount etna during the volcanic activity of 1981 and in north palm springs during the seismic events of 8 july 1986 yields a good correspondence between events detected by both techniques and volcanic end seismic events the statistical significance of geomagnetic time series was also assessed to verify the obtained results from cwtsa and tvans it was defined at significance level of 95 in the wavelet power spectrum for the difference of the geomagnetic time series aiming at distinguishing the most significant events when they are upon this one

synthesis of the quaternary in the almeria littoral neotectonic activity and its morphologic features western betics spain a sequence of marine and continental quaternary episodes is established as are their interrelationships the zone s tectonics have in most cases remained active to the present and control the factors all the tyrrhenian levels containing strombus bubonius are affected by the many faults that cross the lateral fringe and continue onto the shelf among these are the loma del viento fault n120 e a normal fault with certain leftward characteristics the el alquian faults n140 160 e which coincide according to several authors bousquet 1979 with the surface feature of a great dextral deep accident and the carboneras fault or the serrata fault n40 45 e left strike slip fault given the varying behaviour of the shoreline we have chosen to divide it into four sectors campo de dalias el alquian cabo de gata mojacar garrucha and campo de nijar serrata due to its geographical location no marine continental relationships exist in the latter a chart has been made in an attempt to synthesize the most significant stratigraphic genetic and tectonic characteristics of each sector lastly the influence of tectonics on the distribution and heights of the quaternary shorelines is clearly shown in a chart of the transgressive maxima of the tyrrhenian episodes

possible electrokinetic origin of large magnetic variations at la fournaise volcano abnormal time variations of the geomagnetic field related to volcanic activity have been reported for several decades1 10 two main candidates have been considered for the source mechanism of these volcanomagnetic variations piezomagnetism and electro kinetic effects we considered both of these mechanisms in our attempts to interpret the most spectacular volcanomagnetic variations observed on piton de la fournaise volcano reunion island 11 but now new analysis of the latest data which covers a time span of more than three years leads us to think that water circulation is the main agent of the strong magnetic signals observed on the volcano in addition to the signals that we correlated with the volcano activity11 12 longer period components also exist as shown here with amplitudes and characteristics that have not been reported before we propose that these magnetic variations are generated by electrokinetic effects in which case the water circulation system into this massif would be a sensor for detecting stress changes linked to the volcano activity

hydrogeochemical processes in an arid region of europe almeria se spain abstract in the lower andarax river basin 3 aquifer units have been defined namely the carbonate aquifer the deep aquifer and the detrital aquifer which between them contain a wide variety of water types identification of hydrogeochemical processes has been performed by studying a series of ionic ratios comprising the principal constituents together with b and li cl vs so4 cl vs mg cl vs li b vs li among the processes detected the circulation of groundwaters with high concentrations of so4 was found to have significant effects moreover in the coastal region naturally occurring processes related to the flushing of saline waters from sediments of marine origin occur in conjunction with others clearly of human origin that are related to saltwater intrusion a further factor is the entry from overlying deposits of waters with a high saline content this salinity is related to the flushing of sediments of marine origin the use of b and li together enables waters in which salinity is related to seawater to be distinguished from others in which salinity is related to evaporitic layers or to thermal areas the concentration of li is directly related to water temperature while that of b is greater in the most saline sectors of gypsiferous and or seawater origin

internal heating and thermal constraints on the mantle we have carried out numerical simulations to study the average temperature and thermal structure of an internally heated mantle it is found that in an incompressible mantle the hottest parts are localized in regions of slow flow in the middle and upper mantle whereas in a compressible mantle they occur over laterally extensive regions near the core mantle boundary cmb for chondritic concentrations of heat producing elements hpe s the average thermal conductivity in the mantle must be high to avoid heating the core and the temperature of the cmb tcmb is low to avoid large scale melting the mantle may have been extensively molten in the archaean

the potential influence of radiative heat transfer on the formation of megaplumes in the lower mantle abstract recent seismic tomographic models have revealed broad low velocity anomalies in the lower mantle beneath africa and the central pacific which suggest a break in the symmetry between hot and cold regions in lower mantle dynamics we have considered the possible impact from radiative heat transfer which can be described by a nonlinear temperature dependent coefficient in the thermal conductivity in 2d numerical simulations results for rayleigh numbers up to 106 show a strong stabilizing influence from radiative heat transfer on mantle upwellings and the production of extremely hot thermal anomalies in the interior this nonlinearity is responsible for producing a strong attractor in the mantle convective system which greatly simplifies its time dependent dynamics the possible link of the simplified lower mantle time dependent dynamics with polar wander is discussed the main point here is that slow time dependence of the huge anomalies in the lower mantle can be the main mechanism controlling long term rotational dynamics

inferring the viscosity and the 3 d density structure of the mantle from geoid topography and plate velocities summary in a dynamic earth mantle mass heterogeneities induce gravity anomalies surface velocities and surface topography these lateral density heterogeneities can be estimated on the basis of seismic tomographic models recent papers have described a realistic circulation model that takes into account the observed plate geometry and is able to predict the rotation vectors of the present plates the relationship between the surface observables and the heterogeneities is sensitive to the viscosity stratification of the mantle here we use this model combined with a generalized least squares method in order to infer the viscosity profile of the earth from the surface observations and to get some new insight into the 3 d density structure of the mantle the computed radial viscosity profile presents a continuous increase of more than two orders of magnitude the asthenosphere has a viscosity close to 2 x lo2 pa s no sharp discontinuity is requested at the upper lower mantle interface the largest viscosity 7 x 10 pas is reached in the middle of the lower mantle at greater depth approaching the core mantle boundary the viscosity decreases by one order of magnitude the model suggests that the well known degree 2 and order 2 anomaly in the transition zone of the upper mantle is merely the signature of the slabs it also slightly increases the degree 2 and order 0 in the lower mantle and decreases it in the upper mantle in other words the inversion requests a hotter lower mantle beneath the equator and a colder upper mantle at the same latitudes

mapping ground subsidence induced by aquifer overexploitation using advanced differential sar interferometry vega media of the segura river se spain case study differential sar interferometry dinsar is a remote sensing technique with the well proven ability to monitor ground deformations in this work we have applied an advanced dinsar technique the coherent pixels technique cpt to study subsidence phenomena due to the excessive pumping of groundwater in the vega media of the segura river se spain from 1993 to the present the settlement map retrieved with dinsar shows settlement of up to 8 cm at some points of the study area and has been compared with other data provided by ground instruments to analyse the relationship with ground deformation a correlation has been observed between these measurements and the observations from on site testing of piezometric groundwater fluctuations and borehole extensometric settlement however the distribution of damaged buildings well points and basements does not show a clear relationship with measured subsidence values because the occurrence of damage also depends on the structural state of the buildings and the characteristics of their foundations in addition the distribution of pumping wells is not indicative of the distribution of the volume of water withdrawal which is the real conditioning factor of piezometric level changes it can be concluded that the results obtained provide very useful spatial and temporal data about this phenomenon in an urban area at a low cost the data can be used for forecasting purposes and helps to define zones with future ground settlement problems if the same conditions are repeated this technique has also allowed the monitoring of ground subsidence in the vega media of segura river for a period 1993 1995 where no instrument information was available

syn tectonic sedimentation in a neogene strike slip basin containing a stacked gilbert type delta se spain abstract the pliocene sedimentation in the cerro blanco ei barranquete subbasin cbb subbasin that forms part of the larger almeria nijar carboneras basin anc basin is controlled by a releasing overstep and a restraining zone in the ne trending serrata strike slip fault zone the sedimentary development of this subbasin can be considered in three stages of a fault kinematic model during stage i a wave influenced shoaling zone was present in front of an emergent serrata cape to the ne with a basin to the sw and w uplift of the shoaling zone in a restraining n080e trending cerro blanco fault zone cb fault zone is evidenced by the following syn tectonic sedimentary phenomena a a rotational unconformity towards the nw b four deepening pulses in the shallow water zone c massflow deposits originating from a near coastal zone possibly triggered by tectonic pulses during stage ii the uplifted zone became increasingly shallow and finally emerged quartz pebbles in the sediments that indicate a land connection between the serrata cape and the metamorphic basement in the north differentiate this stage from the previous one prograding shoreline deposits marked the outbuilding of the serrata cape towards the sw an episodically subsiding zone due to a releasing overstep between the sinistral n040e trending nw serrata boundary fault nwsb fault and b fault during stage ila is indicated by a southwestward outbuilding fandelta during this stage there was only one depocentre during stage ilb the depocentre of the subsiding zone split up this shifting of depocentres is explained according to the releasing overstep model by an increase of the overlap between the nwsb fault and the b fault during stage iii the cbb subbasin became continental and was inverted as demonstrated by its present day relief the area was severely faulted by n040e trending r and y shears on a metre scale which led to an estimated cumulative sinistral displacement of 2 km since fandelta deposition the present day activity of the nwsb fault is shown by sinistrally deflected stream courses and pressure ridges

non adiabaticity in mantle convection seismic observations indicate that earth s lower mantle is homogeneous as revealed by smooth depth variations of the bulk sound velocity and bullen s inhomogeneity parameter being close to one here we show with 3d spherical convection simulations that it should also be non adiabatic because a significant proportion of mantle heat sources is internal the computer simulations predict non adiabaticity of 100 300 degrees for the lower mantle geotherm with 1 01 implying that the temperature drop across the core mantle boundary exceeds 1000 degrees

volcanomagnetic effects observed on piton de la fournaise volcano reunion island 1985 1987 a permanent network of four to six telemetered magnetic stations has been installed on piton de la fournaise volcano in october 1985 and 1986 eight eruptive sequences have occurred since then some of which affected only the summit whereas others affected the whole massif volcanomagnetic variations are observed with each of these volcanic events the geomagnetic field intensity is measured simultaneously every minute at each station with a precision of 0 25 nt nanotesla the main results are the following volcanomagnetic variations observed with eruptions have amplitudes of several nanoteslas to more than 10 nt with characteristic time durations ranging from l min or less to several months a good correlation between the magnetic variations recorded at the different stations is observed spatial and temporal properties of the volcanomagnetic field appear to be controlled by the features of the eruptions several days before the beginning of the december 1985 march july november december 1986 and january 1987 eruptions changes in the intensity differences are observed with amplitudes of a few nanoteslas up to 5 nt at stations located close to the active part of the rift zone variations are also observed in the most remote stations for larger eruptions in march 1986 november december 1986 and january 1987 correlations between magnetic variations ground deformations and seismic activity have been observed for the december 1985 march 1986 november december 1986 and january 1987 events three main mechanisms could account for the observed volcanomagnetic variations piezomagnetic effects electrokinetic effects and electrical resistivity changes since variations in the stress field in the surroundings can modify the induced and natural magnetizations of magnetized rocks the circulation of water through the interconnected pore network microcracks faults aquifers and also the electrical resistivity of geological structures through the modification of the properties of the pore network

joint seismic tomography for bulk sound and shear wave speed in the earth s mantle high quality p and s travel times are now available from careful reprocessing of data reported to international agencies a restricted data set has been extracted for which comparable ray coverage is achieved for p and s and used for a joint inversion to produce a three dimensional model for shear and bulk sound velocities represented in terms of 2 2 cells and 18 layers in depth through the mantle about 106 times for each of p and s are combined to produce 312 549 summary rays for each wave type linearizing about the ak135 reference model 583 200 coupled tomographic equations are solved using an iterative partitioned scheme clear high resolution images are obtained for both bulk sound speed and shear wavespeed the bulk and shear moduli have differing sensitivity to temperature and mineral composition and so the images of the two velocity distributions help to constrain the nature of the processes which produce the variations different heterogeneity regimes can be recognised in the upper mantle the transition zone most of the lower mantle and the lowermost mantle in the upper mantle many features can be explained by thermal effects but in some orogenic zones e g western north america the opposite sense of the bulk sound and shear wave speed variation requires compositional effects or volatiles to outweigh any thermal effects in the lower mantle pronounced narrow structures which may represent remnant subduction are most marked in shear the level of large scale variations in bulk sound speed compared to shear diminishes with depth in the lower mantle reaching a minimum near 2000 km below this depth the variability of both wave speeds increases near the core mantle boundary the variations of the two wave speeds show little concordance suggesting the presence of widespread chemical heterogeneity

volcanomagnetic signals during the recent popocatepetl mexico eruptions and their relation to eruptive activity abstract an interdisciplinary approach correlating magnetic anomalies with composition of the ejecta in each eruption as well as with seismicity was used to study the effect of magmatic activity on the local magnetic record at popocatepetl volcano located 65 km southeast of mexico city eruptions began on december 1994 and have continued with dome growth and ash emissions since then the tlamacas tla geomagnetic total field monitoring station located 5 km away from popocatepetl s crater was installed in december 1997 in order to detect magnetic anomalies induced by this activity spatial correlation and weighted difference methods were applied to detect temporal geomagnetic anomalies using tla s record and the teoloyucan magnetic observatory as a reference station weighted differences were applied to cancel the effects of non vulcanogenic external field variations magnetic anomalies over a 2 year time span were classified into four types correlating them with geochemical seismic and visual monitoring of the volcanic activity magnetic anomalies are believed to be caused by magma injection and gas pressure build up which is sensitive to vent morphology and clearing during eruption although some anomalies appear to be thermally related changes in the stress field are very important most magnetic anomalies are short time signals that reverse to baseline level decreasing anomalies 0 5 to 6 8 nt precede eruptions by 1 8 days the presence of a mafic magmatic component was determined by mineral examination and silica and magnesium analyses on the ejecta from the 1997 1999 eruptions whole rock analyses ranged from dacitic 65 sio 2 to andesitic 57 sio 2 with 2 6 6 mgo the higher mgo lower silica samples contain forsteritic olivine fo90 sio 2 does not increase and mgo does not increase with time suggesting ascent of small magma pulses which are consistent with the magnetic data

the importance of radiative heat transfer on superplumes in the lower mantle with the new post perovskite phase change abstract a new post perovskite phase has been identified recently from both x ray observations and first principles calculations this novel phase change occurs at a depth about 200 km above the core mantle boundary for temperatures of around 2800 k using a two dimensional extended boussinesq model we have studied the dynamical consequences of this deep mantle phase transition on mantle convection with particular emphasis on the effects on lower mantle plume structures we have employed a depth dependent viscosity with a viscosity maximum in the mid lower mantle and two phase transitions one at 670 km depth and the other at a depth of 2650 km the phase transition at 670 km is endothermic while we have examined both exothermic and endothermic possibilities for the new phase transition our results show the following situations favorable for the development of superplumes 1 endothermic phase transition for both constant and radiative thermal conductivities and 2 exothermic phase transition and radiative thermal conductivity smaller unstable plumes are found for exothermic phase transition and constant thermal conductivity extremely high lateral temperature increases exceeding 1500 degrees are found inside the lower mantle plume for constant thermal conductivity this lateral temperature contrast is mitigated by the presence of radiative thermal conductivity in order for superplumes to prevail in the lower mantle with a deep exothermic phase change we must invoke some form of radiative thermal conductivity for stabilizing and promoting large upwellings with a width exceeding at least 500 km strong lateral heterogeneities in both the seismic velocity and density fields can be produced in the plumes and the surrounding mantle for this new phase transition with a large clapeyron slope close to 10 mpa k

layered convection with an interface at a depth of 1000 km stability and generation of slab like downwellings abstract we investigate the stability of hypothetical layered convection in the mantle and the mechanisms how the downwelling structures originating in the lower layer are generated the stability is studied by means of numerical simulations of the double diffusive convection in a 2d spherical model with radially dependent viscosity we demonstrate that the stability of the layering strongly depends not only on the density contrast between the layers but also on the heating mode and the viscosity profile in the case of the classical boussinesq model with an internally heated lower layer the density contrast of about 4 between the compositionally different materials is needed for the layered flow to be maintained the inclusion of the adiabatic heating cooling in the model reduces the temperature contrast between the two layers and thus enhances the stability of the layering in this case a density contrast of 2 3 is sufficient to preserve the layered convection on a time scale of billions of years the generation of the downwelling structures in the lower layer occurs via mechanical or thermal coupling scenarios if the viscosity dependent on depth and average temperature at each depth is considered the low viscosity zone develops at a boundary between the two convecting layers which suppresses mechanical coupling then the downwelling structures originating in the lower layer develop beneath upper layer subductions thus resembling continuous slab like structures observed by seismic tomography

lithological control of land subsidence induced by groundwater withdrawal in new urban areas granada basin se spain multiband dinsar monitoring ground subsidence in the southeastern border of the granada basin se spain has been studied using remote sensing techniques over the last decades the region has experienced a huge urban expansion which has caused a substantial increase in water supply requirements water needs are exclusively met by groundwater by means of numerous pumping wells which exploit a confined detrital aquifer of alluvial fan deposits with a heterogeneous facies distribution a general piezometric level decline up to 50 m has been recorded in the aquifer during the past 30 years that has induced the generation of a subsiding area with oval shape oriented wnw ese just where the new urban areas and pumping wells are located subsidence has been monitored by exploiting synthetic aperture radar sar images from envisat 2003 2009 and cosmo skymed 2011 2014 a new approach which combines a dinsar and small area persistent scatterer interferometry psi analysis has been applied obtaining a good accuracy regarding temporal and spatial dimension of the subsidence envisat data 2003 2009 reveal subsidence rates up to 10 15 mm year and cosmo skymed 2011 2014 values slightly lower up to 10 mm year temporal variations in the subsidence velocity are in accordance with the rainfall pattern and piezometric fluctuations in the aquifer the sector with highest rates of subsidence does not correspond to the area with more intense groundwater exploitation but to the area with greater presence of clays in the confining layer of the aquifer there is a clear lithological control in the spatial distribution of the ground subsidence this work integrates detailed geological and hydrogeological data with differential sar interferometry monitoring with the aim to better understand subsidence processes in detrital aquifers with small scale heterogeneity copyright 2016 john wiley sons ltd

subsidence rates in the po plain northern italy the relative impact of natural and anthropogenic causation abstract the central eastern po plain in northern italy is a rapidly subsiding sedimentary basin that hosts about 30 of the italian population and 40 of italy s total productive activities subsidence rates range from 0 to 70 mm year the maximum occurring in synclinal areas at the po delta and near bologna the minimum located at the top of buried probable tectonically active anticlines mirandola ferrara we show that modern subsidence is at least an order of magnitude higher than due solely to long term natural processes this implies that most subsidence in the po plain has been induced by human activities as previously noted we suggest that the main factor controlling modern subsidence is water withdrawal which was particularly intense during the second half of the 20th century coinciding with accelerating economic growth we also evaluate the impact of rapid subsidence on floods in low areas by comparing subsidence velocity maps with flood maps this shows that there is a clear cut correlation between flood frequency and rapid subsidence in contrast few floods occurred in low subsidence areas which generally correspond with the top of buried anticlines we finally note that the anthropic caused increase in subsidence has now greatly increased the potential for additional floodings

instabilities from phase transitions and the timescales of mantle thermal evolution we have investigated the effects of mantle phase transitions on the earth s thermal evolution by numerical modelling our results show that the tendency of layering grows with increasing vigor of convection a self consistent model which couples the convective dynamics of the mantle to the secular cooling of the core is constructed for a temperature dependent effective viscosity we found that the thermal history of the earth is characterized by two timescales one is associated with layered convection in the early period which is followed by a transition period with dramatic overturns as the rayleigh number decreases sufficiently low whole mantle convection prevails and a faster cooling timescale ensues

profiles of the bullen parameter from mantle convection modelling the state of adiabaticity in the mantle can be assessed by using the bullen parameter profile derived from seismology we have employed the extended boussinesq convection models in a cartesian 2 d domain to extract the bullen parameter as a function of depth in both base heated and internally heated configurations and for both constant and variable thermal conductivity we also studied models with depth dependent thermal expansivity our results show that the values of the bullen parameter for a rayleigh number of 10 6 lie close to one with sometimes excursions out to 0 9 and 1 1 they are sensitive to the mode of heating and the depth dependences of the thermal expansivity and changes of thermal conductivity we obtained a subadiabatic geotherm above the lower boundary layer in all the models with constant thermal expansivity but a decrease of thermal expansivity with depth can result in a subadiabatic geotherm below the upper boundary layer thus the profiles of the bullen parameter have a definite potential of being useful in constraining the physical parameters and flow structures associated with mantle convection fl 2000 elsevier science b v all rights reserved

el nino induced onshore transport in the california current during 1982 1983 persistent 9 month large scale positive temperature 3 4 c negative salinity 0 1 0 3 and positive dissolved oxygen 0 5 1 ml l subsurface anomalies characterize the el nino induced onshore transport in the california current during 1982 83 these anomalies characteristic diagrams and sign reversals in the salinity and oxygen anomalies are consistent only with enhanced onshore transport of subarctic water from the offshore california current onshore transport excludes poleward propagating kelvin waves as a generation mechanism for the 1982 83 californian el nino the data however support the conclusion simpson 1983 that an anomalous basinwide atmospheric circulation produced the californian el nino

lower mantle dynamics with the post perovskite phase change radiative thermal conductivity temperature and depth dependent viscosity the new post perovskite phase near the core mantle boundary has important ramifications on lower mantle dynamics we have investigated the dynamical impact arising from the interaction of temperature and depth dependent viscosity with radiative thermal conductivity up to a lateral viscosity contrast of 10 4 on both the ascending and descending flows in the presence of both the endothermic phase change at 670 km depth and an exothermic post perovskite transition at 2650 km depth the phase boundaries are approximated as localized zones we have employed a two dimensional cartesian model using a box with an aspect ratio of 10 within the framework of the extended boussinesq approximation our results for temperature and depth dependent viscosity corroborate the previous results for depth dependent viscosity in that a sufficiently strong radiative thermal conductivity plays an important role for sustaining superplumes in the lower mantle once the post perovskite phase change is brought into play this aspect is especially emphasized when the radiative thermal conductivity is restricted only to the post perovskite phase these results revealed a greater degree of asymmetry is produced in the vertical flow structures of the mantle by the phase transitions mass and heat transfer between the upper and lower mantle will deviate substantially from the traditional whole mantle convection model streamlines revealed that an overall complete communication between the top and lower mantle is difficult to be achieved 2005 elsevier b v all rights reserved

normal mode and free air gravity constraints on lateral variations in velocity and density of earth s mantle with the use of a large collection of free oscillation data and additional constraints imposed by the free air gravity anomaly lateral variations in shear velocity compressional velocity and density within the mantle dynamic topography on the free surface and topography on the 660 km discontinuity and the core mantle boundary were determined the velocity models are consistent with existing models based on travel time and waveform inversions in the lowermost mantle near the core mantle boundary denser than average material is found beneath regions of upwellings centered on the pacific ocean and africa that are characterized by slow shear velocities these anomalies suggest the existence of compositional heterogeneity near the core mantle boundary

layered convection induced by phase transitions we report a systematic study on the conditions under which an endothermic phase transition can enforce layered convection two dimensional numerical calculations of convection in a domain containing a divariant phase change were performed in the framework of the extended boussinesq approximation i e considering the effects of adiabatic gradient latent heat and frictional heating in the energy equation we find that the critical value of the negative clapeyron slope which must be surpassed in order to induce layered convection decreases in magnitude with increasing rayleigh number ra in the range 104 ra 2 106 near the critical clapeyron slope vacillations between double and single layer convection or strongly leaking double layer convection are possible the breakdown into layers is influenced very little by the latent heat release but depends solely on the phase boundary deflection caused by lateral temperature differences the value of the critical clapeyron slope also seems little affected by the width of the transition zone or by its depth a possible superplastic rheology within the transition zone would tend to favor layered convection scaling the model results to the 670 km discontinuity in the earth s mantle as a possible endothermic phase boundary we estimate the critical clapeyron slope to be in the range of 4 to 8 mpa k 40 to 80 bar k the possibility that the spinel perovskite periclase transition is within this range appears to be remote but certainly cannot be neglected

simultaneous inversion for 3 d variations in shear and bulk velocity in the mantle until recently most of the seismic tomographic modeling has been addressing the question of lateral heterogeneity either in p or s wave velocities the s wave velocity variations are larger and hence provide stronger signal on long period waveforms the direct p travel times being the first arrivals on the other hand are most frequently reported in the international seismological centre isc bulletins in mineral physics experiments the variation in bulk velocity is more often measured to better understand the differences between vp and vp patterns and better link the results from mineral physics to those of seismic tomography we formulate the inverse problem in terms of relative perturbations in the shear velocity vs 12 and bulk sound velocity v k 12 we use a large data set which consists of waveforms waveform derived travel times and travel times from the isc bulletins the earthquakes are relocated using corrections for lateral heterogeneity the events which cannot be reliably determined are discarded the model is defined as spherical harmonics to degree 12 horizontally and as chebyshev polynomials to order 13 radially for both shear and bulk sound velocity the inversion is performed under smoothness constraint the resolution tests and bootstrapping analysis indicate that the model is well recovered particularly at long wavelength the results indicate a much larger variability of shear than bulk sound velocity the model explains observations well the most intriguing result obtained in this study is that the variations in shear velocity and bulk sound velocity are negatively correlated in the lowermost mantle the explanation is not very clear from the mineral physics point of view it is not unlikely that this could be explained in terms of thermal variation even though we are unwilling to rule out the possibility of large wavelength compositional variations

patterns and average rates of late neogene recent uplift of the betic cordillera se spain abstract the facies distribution in the sedimentary units infilling a series of neogene basins has been used to reconstruct the relief generation and uplift across the internal zone of the betic cordillera in southern spain uplift amounts and average rates can be estimated using the current elevation of the outcrops of well dated deposits indicative of ancient sea level positions coral reefs and coastal conglomerates record the initial development of emergent betic relief during the langhian continental and marginal marine deposits indicate the existence of a large island centred on the present sierra nevada sierra de los filabres chain by the end of the middle miocene the precursor of the sierra nevada sierra de los filabres chain originally part of this large island remained emerged whilst the surrounding areas were re invaded by the sea during the early tortonian at the end of the tortonian the inland basins granada and guadix basins became continental while the sierras de la contraviesa sierra de gador and sierra alhamilla emerged separating the alboran basin from the alpujarra tabernas and sorbas basins which became narrow passages of the mediterranean sea in contrast the sierra cabrera emerged during the late messinian suggesting a progressive uplift from west to east of the sierras south of the sierra nevada sierra de los filabres chain during the pliocene only the low areas closest to the present day coast remained as marine basins and progressively emerged throughout this stage the highest average uplift rate recorded is 280 m ma for the sierra de gador although the average uplift rates of upper neogene coastal marine rocks since depositon have maximum values of approximately 200 m ma most of the uplift of the betic mountains took place before the early pliocene the recorded uplift of neogene rocks was highest at the margins of western sierra nevada where peaks higher than 3000 m occur the average rates of uplift were lower to the east of this major relief the main sierras and depressions in the present day landscape correspond respectively to the emergent land in which uplift was concentrated and to the marine basins that existed before the final emergence of the region the altitude of the sierras reflects the time at which they became emergent the highest mountains being the first to rise above sea level

the non adiabatic nature of mantle convection as revealed by passive tracers abstract we have investigated the state of adiabaticity in mantle flows by using a lagrangian tracer technique to map out the thermal state of parcels in both downwelling and upwelling flows in mantle flush events the model baed on a core cooling boundary condition has two major phase transitions and a temperature dependent viscosity the temperature histories of the first tracers that enter into the lower mantle during a flushing event reveal a superadiabatic increase of up to 700 k due to conduction and viscous dissipation the lateral temperature anomalies in the deep lower mantle monitored by the tracers can exceed 1000 k the cold sinking anomalies follow a superadiabatic path and are heated up according to the time history of the flush event the time history of the rising parcels is strongly influenced non adiabatically by the two phase transitions in the upper mantle with only a small segment in the upper mantle below the surface where the parcels are found to be invariably slightly superadiabatic following a major flush event the horizontally averaged temperature profiles display strong subadiabaticity in the deep mantle and superadiabaticity in the transition zone during this time the mean temperature profiles do not follow an adiabat anywhere the concept of adiabaticity may have limited applications in strongly time dependent mantle convection with phase transitions where major overturns take place from time to time

predominance of long wavelength heterogeneity in the mantle analysis of travel time anomalies of long period shear waves recorded by the global digital seismographic network indicates that mantle heterogeneities which probably reflect patterns of mantle convection occur most prominently on length scales greater than about 6 000 km when projected onto a two dimensional map at the earth s surface models of mantle convection will need to be able to produce a similar power spectrum

quantification of vertical movements in the eastern betics spain by comparing levelling data comparison of precision levelling data carried out at diverent times is a technique that allows the quantification of recent vertical movements we used the precision levelling data from the instituto geografico nacional of spain to improve our understanding of the recent tectonic evolution of some areas in the southeastern iberian peninsula eastern betics where significant deformation has occurred during the last century the resulting movements are presented in recent vertical movement profiles profiles with significant movements are discussed taking into account the geologic and seismic features of each zone these profiles are alicante albacete alicante almeria larva near jaen almeria and almeria el palo near malaga the results obtained point to the existence of important tectonic deformation rates near the main tectonic structures crossing the profiles the main tectonic anomalies expressed in constant rates of vertical velocity are a 2 mm year step near the ene wsw trending valldigna jumilla fault zone between alicante and albacete a 0 9 mm year step located in the nne ssw trending cocon terreros fault zone between murcia and almeria a subsidence of about 1 5 mm year of the almeria basin zone that can be related to nw se and e w faults a step of 1 mm year related to the ene wsw trending guadahortuna fault between granada and jaen a 1 mm year step associated with the ene wsw trending cadiz alicante fault zone near the granada area and a 1 4 mm year step related to the tectonic activity of the nw se and ne sw trending system of faults that avect the iberian coast of the alboran sea almeriaa nd granada zone the anomalies related to the ene wsw to e w trending structures are associated with reverse faults whereas the anomalies related to the faults oriented in a ne sw or nw se direction are associated with strike slip faults with a normal component of vertical movement these movements are consistent with the present day betics stress tensor determined with diverent methodologies such as the focal mechanism analysis and microstructural and geomorphological studies that indicate the existence of a maximum horizontal compression in a nnw sse direction together with a perpendicular extension if we consider the rates of vertical deformation to be constant in time and if we consider that all the accumulated stress results in big earthquakes m 6 0 with no ductile deformation an estimate of the minimum return periods for major earthquakes can be made the return periods which range between 500 and 1200 years depending on the zone should be regarded as new information in the assessment of seismic hazard these values are in agreement with those deduced from the seismic catalogues of the areas where there is suycient information 2000 elsevier science b v all rights reserved

identification of potential subsidence related to pumping in the almeria basin se spain ground subsidence of detrital deposits in the almer ia basin se spain was studied using the remote sensing technique of differential interferometry sar dinsar this basin is one of the most arid in europe receiving an average rainfall of 250 mm per year over the last 60 years the region has experienced an enormous agricultural and urban expansion whose water demand has been largely supplied from groundwater leading to the current situation of overexploitation of water resources this paper outlines the likely relationship between groundwater abstraction and subsidence to this end 34 ers and envisat images taken between 2003 and 2009 were analysed to estimate ground surface deformations and hence compared with water table variations measured in a number of piezometers in the basin the analysis shows a clear parallelism between the variations in piezometric level and deformation of the ground surface in addition the zones of greatest subsidence coincide with those areas where groundwater abstractions are concentrated subsidence over the examined period varies from 10 to 30 mm with extreme values as high as 50 mm which translates to a rate of between 1 7 and 5 mm year reaching maximum rates of 8 mm year at some points given such subsidence rates damage to urban infrastructures are for the moment incipient

radar interferometry techniques for the study of ground subsidence phenomena a review of practical issues through cases in spain subsidence related to multiple natural and human induced processes affects an increasing number of areas worldwide although this phenomenon may involve surface deformation with 3d displacement components negative vertical movement either progressive or episodic tends to dominate over the last decades differential sar interferometry dinsar has become a very useful remote sensing tool for accurately measuring the spatial and temporal evolution of surface displacements over broad areas this work discusses the main advantages and limitations of addressing active subsidence phenomena by means of dinsar techniques from an end user point of view special attention is paid to the spatial and temporal resolution the precision of the measurements and the usefulness of the data the presented analysis is focused on dinsar results exploitation of various ground subsidence phenomena groundwater withdrawal soil compaction mining subsidence evaporite dissolution subsidence and volcanic deformation with different displacement patterns in a selection of subsidence areas in spain finally a cost comparative study is performed for the different techniques applied

geological and hydrogeological environment in tianjin with potential geohazards and groundwater control during excavation this paper discusses the geological and hydrogeological features of quaternary deposits in tianjin as well as the geohazards related to groundwater hydrology in this region the soft soil deposits comprising silt sand silty clay and clay are composed of four aquifer groups in the first aquifer group one phreatic aquifer and two confined aquifers have relationships with underground construction in the urban area these three aquifers are separated by two aquitards and collectively form a multi aquifer system during geotechnical construction potential geohazards present are related to the groundwater which include water in rushing quicksand and piping hazards to prevent the aforementioned geohazards dewatering is conducted however groundwater pumping may result in large settlements of the surrounding ground to reduce pumping induced settlement the dewatering waterproofing system has been adopted according to the characteristics of the subsoil excavation depth and the surrounding environment the dewatering system can be divided into five patterns in the first four patterns when pumping is conducted in the excavation pit the groundwater head in the adjacent aquifers outside the pit decreases due to the leakage effect of the aquitards located between the aquifers in the fifth pattern waterproof curtain has cut off the aquifers completely and dewatering in the pit cannot result in settlement around excavation pit to avoid geohazards related to groundwater hydrology countermeasures recommended include construction of an effective waterproof curtain selection of a reasonable excavation dewatering pattern and withdrawal of required groundwater

magnetic measurements on la soufriere volcano guadeloupe lesser antilles 1976 1984 a re examination of the volcanomagnetic effects observed during the volcanic crisis of 1976 1977 abstract during the seismovolcanic crisis of 1976 1977 at la soufriere on guadeloupe a magnetic network of 12 reference markers was set up measurements of the intensity of the earth s magnetic field carried out up to once a day at each marker showed volcano magnetic variations of several nanoteslas nt the variations at certain markers were more or less concealed by transient magnetic variations due to anomalies in conductivity as early as 1978 measurements were resumed and a telemetering network was coupled with the network of reference markers to which 4 new markers were added a detailed study of conductivity anomalies was carried out on the entire volcano contrasts in conductivity linked to the existence of a superficial conducting surface on a ssw nne axis located south of the volcano caused a great lack of homogeneity in the field variations measured at the surface variations greater than about 10 nt appeared in the difference in intensity of the earth s magnetic field between two stations no long term magnetic variation was observed between 1978 and 1984 on the network of markers the accuracy of measurements of volcanic effects was at best 2 nt measurements carried out on the telemetering network during the night refined these results since their accuracy was 1 nt the only significant volcanic crisis between 1978 and 1984 5 7 january 1981 seems to be observed by telemetering stations all the measurements carried out in periods of volcanic inactivity make it possible to re examine the crisis of 1976 1977 though volcanomagnetic effects over short periods cannot be accurately determined variations with a time constant of several weeks were present over the entire volcano these variations were as high as 7 8 nt in remote stations and they can be linked to the three major phases of eruptive activity at la soufriere during the crisis of 1976 1977

multiband psinsar and long period monitoring of land subsidence in a strategic detrital aquifer vega de granada se spain an approach to support management decisions abstract this work integrates detailed geological and hydrogeological information with psi data to obtain a better understanding of subsidence processes detected in the detrital aquifer of the vega de granada se spain during the past 13 years ground motion was monitored by exploiting sar images from the envisat 2003 2009 cosmo skymed 2011 2014 and sentinel 1a 2015 2016 satellites psinsar results show an inelastic deformation in the aquifer and small land surface displacements up to 55 mm the most widespread land subsidence is detected during the envisat period 2003 2009 which coincided with a long dry period in the region the highest displacement rates recorded during this period up to 10 mm yr were detected in the central part of the aquifer where many villages are located for this period there is a good correlation between groundwater level depletion and the augmentation of the average subsidence velocity and slight hydraulic head changes

magnetic features of the magmatic intrusion that occurred in the 2007 eruption at stromboli island italy significant changes in the local magnetic field marked the resumption of eruptive activity at stromboli volcano on february 27 2007 after differential magnetic fields were obtained by filtering out external noise using adaptive filters and seasonal thermal noise using temperature data we identified step like changes of 1 4 nt coincident with the opening of eruptive fissures in the upper part of the sciara del fuoco the magnetic variations detected at two stations are closely related to the propagation of a shallow ne sw magmatic intrusion extending beyond the summit craters area these observations are consistent with those calculated using piezomagnetic models in which stress induced changes in rock magnetization are produced by the magmatic intrusion no significant magnetic changes were observed when the first fractures opened along the ne crater rim indeed the stress induced magnetization caused by this magmatic activity is expected to be too low because of the structural weakness and or thermal state of the summit area the continuous long term decay characterizing the post eruptive magnetic pattern can be related to a time dependent relaxation process a maxwell rheology was assumed and the temporal evolution of the piezomagnetic field was evaluated this allowed us to estimate the rheological properties of the medium in particular an average viscosity ranging between 1016 and 1017 pa s was a relaxation time of about 38 days

geodynamical implications from the correlation of surface geology and seismic tomographic structure abstract we have investigated the relationship between the lateral seismic structure in the mantle and the geological features associated with major mantle upwellings the oceanic ridge system and hotspots using the technique of correlation analysis we have identified that these features extend quite deeply into the mantle to a depth of around 1300 km this finding is surprising for the ridges because it indicates that the style of upwelling is rather active and is somewhat two dimensional in character the confidence level of the correlation between ridges and slow seismic regions is maintained at a level of greater than 90 to a depth of 1300 km this is followed by a sharp decrease to 50 at 1700 km a similar correlation pattern is found for the hotspots in both cases the correlation maxima lie close to a depth of 1000 km where remnants of old slabs have recently been revealed by correlation analysis these findings suggest that dynamical processes at a depth of around 1000 km can be linked with surface tectonic activity this correlation disappears at a depth of around 1500 1700 km certain features of the surface tectonic pattern can again be recognized around a depth of 2000 km and in the deepest mantle where major hotspot plumes and the remnant old lithosphere are the dominant features there may be some dynamical relationship between the ridge system and the two megaplumes we have proposed a physical mechanism based on viscous heating within megaplumes to explain the two peaks in the correlation between the hotspots and the seismic heterogeneities

bullen s parameter η a link between seismology and geodynamical modelling valuable information concerning the style of mantle density stratification can be gleaned from the spatial distribution of bullen s parameter by means of numerical modelling of 2 d cartesian convection and by monitoring this with the 2 d field of the local bullen s parameter values which were obtained by post processing the convection results we show that the local adiabaticity is seriously influenced by the presence of an endothermic phase transition at 670 km depth in this situation the upper mantle suffers much more from non adiabatic effects than the lower mantle we have also employed the 3 d distributions of density and seismic velocities from the model of ishii and tromp based on free oscillation observations and constructed 3 d local bullen s parameter for a spherical earth in the lower mantle we find that there is a striking similarity in the range of magnitudes of the local bullen s parameter calculated from convection and those inferred from the splitting of seismic free oscillations the morphologies of subadiabatic regions in the deep mantle under africa and the central pacific would suggest a thermal chemical nature of the superplumes their vertical extent is limited to around 400 km above the core mantle boundary cmb underneath the icelandic area in the north atlantic such an subadiabatic region in the deep mantle above the cmb cannot be discerned we conclude that the mantle is not as adiabatic as has commonly been held fl 2002 elsevier science b v all rights reserved

using probabilistic seismic tomography to test mantle velocity density relationships we use a neighborhood algorithm to explore the fit to long period seismic data of a wide variety of long wavelength mantle models this approach to the global tomographic inverse problem yields probability distributions for seismic velocities density and related properties as functions of depth such distributions can be robust even when individual models are not and allow us to test several assumptions about the earth that have long been enforced a priori in inversions in particular we are able to test the paradigm ofdeep mantle heterogeneity that is dominantly thermal in origin producing velocity and density perturbations that are well correlated and have relative amplitudes given by nlnb nlnvs 6 0 5 our distributions show that such relationships are unlikely and even though the results are consistent with recent best fitting models from damped seismic inversions they demonstrate that many specific properties ofsuch models are not robust the data clearly f density perturbations that are poorly or negatively correlated with velocity heterogeneity and have amplitudes several times larger yielding nlnb nlnvs s 1 0 than damped inversions allow these characteristics are most pronounced in the upper mantle transition zone and the base ofthe lower mantle suggesting layered convection the negative density velocity correlations f at these depths imply dominantly chemical heterogeneity while the likelihood ofrelatively high amplitude density variations suggests that variable iron content is an important component ofthis heterogeneity these results which we show to be consistent with independent gravity constraints represent a profound change in the interpretation of seismic constraints in addition the distributions show that even though best fitting density models from recent inversions or our sampling are consistent with the data most specific properties of such models are not robust this implies that it is more appropriate to use seismic model distributions rather than individual models to make geodynamic and geochemical inferences

dynamical consequences of depth dependent thermal expansivity and viscosity on mantle circulations and thermal structure the effects of both depth dependent thermal expansivity and depth dependent viscosity on mantle convection have been examined with two dimensional finite element simulations in aspect ratio ten boxes surface rayleigh numbers between 107 and 6 107 have been considered the effects of depth dependent properties acting singly or in concert are to produce large scale circulations with a few major upwellings the interior of the mantle is cooled by the many cold instabilities which are slowed down and eventually swept about by the large scale circulation the interior temperature of the mantle can be influenced by the trade off between depth dependent properties and internal heating for chondritic abundance of internal heating and depth dependent thermal expansivity the viscosity increase across the mantle can be no greater than a factor of around ten in order to keep the lower mantle adiabatic the thermal contrasts between the cold blobs and the surrounding mantle are strongly reduced by depth dependent properties whereas the lateral differences between the hot upwelling and the ambient lower mantle can be significant over several hundred degrees depth dependent properties also encourage the formation of a stronger mean flow in the upper mantle which may be important for promoting long term polar motions

can we resolve 3d density heterogeneity in the lower mantle we reexamine the possibility of resolving 3d density structure in the mantle by performing test inversions using a dataset of well constrained degree 2 splitting coefficients we show that degree 2 in vs and vp can be resolved and confirm that dlnvs dlnvp 2 5 at depths 2000km indicating a chemical component to large scale heterogeneity models with positively correlated with vs in the deepest mantle fit the data at least as well as those in which density and velocities are anti correlated however some rough bounds on dln dlnvs can be inferred models obtained from geodynamic considerations are acceptable in contrast to models with large negative 0 6 dln dlnvs throughout the lower mantle the most robust feature is a marked increase in dln dlnvs at the top of the lower mantle reaching a maximum around 1500 km

magnetic monitoring at merapi volcano indonesia abstract merapi volcano located 30 km north of the heavily populated city of yogjakarta java is one of the most active of the 129 volcanoes in indonesia about every 2 years a new phase of activity is observed depending on the past activity the unrest gives rise either to an endogenous dome which partly collapses in the southwest direction or to pyroclastic flows which travel as far as 15 km the 1990 1997 period has involved a plume emission on 30 august 1990 an extrusion on 20 january 1992 and a pyroclastic eruption on 22 november 1994 the intensity of the earth magnetic field has been measured simultaneously and digitally recorded at four stations since 1990 two overhauser magnetometers with resolution of 0 01 nt have been installed in the summit area to strengthen the volcano monitoring outstanding magnetic changes appear to correlate with volcanic activity three types of volcanomagnetic signals can be identified long term trends up to 15 nt with period 10 years medium term cyclic variations at most 3 nt in amplitude and with 1 2 years period and small events reaching 1 5 nt lasting a few months and associated with any remarkable volcanic activity merapi volcano began a new cycle of activity in 1995 leading to a dome growth in july 1996 and accompanied by 27 nuees ardentes in august the comparison between magnetic data seismicity and surface phenomena suggests that some long term trends of decade periods could be of thermomagnetic origin while mid term volcanomagnetic variations associated with the cycles of merapi activity could be of piezomagnetic origin short term variations of a few weeks duration less than 1 5 nt are well correlated with the 1995 1996 seismic activity

are mantle plumes adiabatic abstract the issue concerning the state of adiabaticity of mantle plumes has been examined in a cartesian two dimensional box with an aspect ratio of six we have investigated in the quasi steady state regime high rayleigh number convection with both depth dependent viscosity and thermal expansivity for both the boussinesq and the extended boussinesq approximations we have also assessed the influence of various forms of thermal conductivity and internal heating we have generalized the classical bullen s parameter equation from one dimension to multidimensions for assessing the local state of adiabaticity inside plumes and in their surroundings we have extracted from the local geotherms and the local thermodynamic properties the corresponding bullen s parameter profiles and the two dimensional maps portraying the state of adiabaticity in the mantle histograms characterizing the frequency of adiabaticity are also employed for quantification purposes in general superadiabatic thermal gradients are found inside the thick plume limbs and sometimes along the central part of the plume the centers of plume heads are subadiabatic or nearly adiabatic but the edges of the plume heads are strongly subadiabatic alternating strips of subadiabaticity and adiabaticity are found in the downwellings the ambient mantle outside the plumes is generally adiabatic and is sometimes perforated with islands of marked deviations from adiabaticity

compressible convection in a viscous venusian mantle finite element simulations of axisymmetric spherical shell compressible convection were carried out to investigate the effect of various surface boundary conditions in a venusian mantle we employed a thermal expansivity which decreased with depth a uniform viscosity an order of magnitude greater than the earth s and zero and chondritic quantities of internal heating as long as hot plumes from the core mantle boundary were strong the convection pattern was typical of that for variable flow that is it was characterized by steady upflowing regions unsteady collections of downflowtng plumes and large aspect ratio cells increases in the internal heating or the temperature t0 at the lop of the convecting layer weakened the hot plumes and therefore decreased the width of the cells a rigid surface increased the internal temperature and also decreased the widih of convection cells extensive regions of subadiabaticity were found in the mantle we compare our results with those for fully three dimensional convection under similar conditions schubert et al 1990

volcanomagnetic signals associated with the quasi continuous activity of the andesitic merapi volcano indonesia 1990 1995 abstract merapi volcano in java island indonesia is an andesitic stratovolcano which presents long periods of effusive activity during which an endogeneous dome is continuously growing the viscous lava dome gives rise to unstable blocks which collapse or turn into pyroclastic flows when the volcano does not exhibit any surface activity the overpressure within the volcano slowly increases depending on the quietness duration the unrest of the volcano can start with an explosive phase during which the former dome is partly destroyed magnetic variations of different time constant are observed during the 1990 1995 period which includes one gas plume emission on august 26 1990 and two eruptions on january 20 1992 and on november 22 1994 compared with other types of active volcanoes the observed volcanomagnetic variations are very small at the most a few nanoteslas nt to discriminate the variations associated with the global activity from the signals correlated with each unrest phase one has to dissociate the different time constant variations over the six year time span when long term trends are removed from the magnetic field in each station of the network an outstanding correlation between all the magnetic differences is emphasised the midterm variations point out 2 cycles of activity which fit the stress field evolution within the edifice leading to the 1992 and 1994 eruptions a new cycle has started in may 1995 in every identified cycle rapid volcanomagnetic signals are well associated with stress field changes may 1991 september 1991 february 1993 december 1993 some of the volcanomagnetic variations are short term precursory signals as the three months decrease up to 1 3 nt preceding the 1992 eruption the comparison between magnetic data seismicity and surface phenomena implies that the midterm volcanomagnetic variations associated with the cycles of merapi activity are of piezomagnetic origin

merapi volcano java indonesia and merapi type nuee ardente a particular nuee ardente type merapi type avalanche nuee has been defined at the merapi volcano because of its prominent role in the recent activity of the volcano gravity plays a significant role during the eruption

piezomagnetic fields due to an inclined rectangular fault in a viscoelastic half space an application to the 2002 2003 etna eruption summary time dependent piezomagnetic fields due to inclined rectangular faults embedded in a viscoelastic homogeneous half space were investigated a viscoelastic rheology of the surrounding medium was assumed to relate piezomagnetic changes at the surface to the stress field at depth the viscosity of the medium strongly influences time dependent stress changes especially in volcanic areas rocks near magmatic sources are considerably heated the presence of higher temperatures produces a lower effective viscosity in the crust making it necessary to consider its inelastic properties rocks no longer behave in a purely elastic manner but permanently deform because the viscosity is significantly lowered to determine the time dependent piezomagnetic fields in a viscoelastic medium we applied the correspondence principle to the analytical elastic solutions for dislocation sources among all the possible rheological models we investigated three cases in which the bulk modulus is purely elastic and the shear modulus relaxes as for i a maxwell solid ii a standard linear solid sls and iii a kelvin solid the piezomagnetic field completely vanishes after the relaxation process for a maxwell rheology whereas it is found to decrease over time and reach some finite offset values for sls and kelvin rheologies a real case study concerning the magnetic anomalies observed during the 2002 2003 mt etna eruption is also investigated post eruptive magnetic variations were in general agreement with a viscoelastic relaxation process of a sls rheology undergoing in the volcano edifice

impacts of human activities on recharge in a multilayered semiarid aquifer campo de cartagena se spain the development of intense agriculture in semiarid areas modifies intensity and spatial distribution of groundwater recharge by summing irrigation return flow to limited rainfall infiltration environmental tracers provide key information but their interpretation is complicated by more complex groundwater flow patterns in multilayered aquifers the real origin of the groundwater samples is hard to assess because of local mixing processes occurring inside long screened boreholes we use environmental tracers 14c 13c 2h 18o 3h to investigate the long term evolution of recharge in the five layer campo de cartagena aquifer in south eastern spain in addition to high resolution temperature loggings to identify the depth of origin of groundwater despite the complex background this methodology allowed a reliable interpretation of the geochemistry and provided a better understanding of the groundwater flow patterns the tritium method did not give good quantitative results because of the high variability of the recharge signal but remained an excellent indicator of recent recharge nonetheless both pre anthropization and post anthropization recharge regime could be identified and quantified by radiocarbon before the development of agriculture recharge varied from 17 mm year 1 at the mountain ranges to 6 mm year 1 in the plain whereas the mean annual rainfall is about 300 mm in response to the increase of agricultural activity recharge fluxes to the plain were amplified and nowadays reach up to 210 mm year 1 in irrigated areas these values are strengthened by global water budget and local unsaturated zone studies copyright 2013 john wiley sons ltd

extended boussinesq thermal chemical convection with moving heat sources and variable viscosity we have studied with an aspect ratio four box the thermal chemical convective evolution with strongly temperature and depth dependent viscosity and moving heat sources within the extended boussinesq framework in which both adiabatic and viscous heating are included and a depth dependent thermal expansivity is assumed in the equation of state our focus is to show how this type of mantle evolution with an averaged ra of 0 106 may develop with a linear chemical stratification and a uniformly hot mantle as an initial condition the effects of extended boussinesq and depth dependent thermal expansivity are to prevent the effective destruction of the chemical heterogeneities our results show that this initial condition would after the age of the earth lead to a lava lamp mode consisting of a thick chemically stratified and intensely internally heated layer with a thickness of around a quarter of the whole mantle thickness however in this isolated internally convecting layer exceedingly high temperatures greater than 4500 k would be reached in the deep mantle plumes can be launched from the top of this thick denser layer this lava lamp stage would give way to the formation of denser hill like structures at the core mantle boundary then upwellings with deep lower mantle origins can be induced by the interaction of the downwellings with the d layer our simulations show the possibility for some long range mass transfer interaction between these widely separated chemical hills promoted by the fast horizontal flow induced by the sinking currents along the low viscosity zone due to temperature dependent rheology at the core mantle boundary

geophysical inferences of thermal chemical structures in the lower mantle lateral variations of the temperature field in the lower mantle have been reconstructed using new results in mineral physics and seismic tomographic data we show that with the application of high pressure experimental values of thermal expansivity and of sound velocities the slow seismic anomalies in the lower mantle under the pacific and africa can be converted into realistically looking plume structures with large dimensions of 0 10 km the outer fringes of the plumes have an excess temperature of around 400 k in the core of the plumes are found tongue like structures with extremely high thermal anomalies these values can exceed 1200 k and are too high to be explained on the basis of thermal anomalies alone we suggest that these major plumes in the deep mantle may be driven by both thermal and chemical buoyancies or that enhanced conductive heat transfer may be important there

water and partial melting in mantle plumes inferences from the dissolved h2o concentrations of hawaiian basaltic magmas knowledge of dissolved h2o in primary kilauean magmas provides a constraint on h2o abundance in the deep mantle region that feeds the upwelling plume beneath hawaii given an h2o k2o mass ratio of 1 3 for basaltic glasses and melt inclusions from kilauea the mantle source is estimated to contain 450 190 ppm h2o this value is 3 times greater than that estimated for the mantle source for mid ocean ridge basalts consideration of oh solubility in olivine suggests that water undersaturated melting of the upwelling hawaiian plume probably begins at a depth of 250 km thus during plume ascent through most of the upper mantle water is partitioned between nominally anhydrous silicates and a small mass fraction of entrained hydrous silicate melt because water strongly influences the viscosity of olivine aggregates partial melting and melt extraction will have important effects on the rheology of the upwelling plume beneath hawaii

active faults seismicity and stresses in an internal boundary of a tectonic arc campo de dalias and nijar southeastern betic cordilleras spain abstract the betic rif cordilleras formed by the interaction of nw se convergence between the eurasian and african plates and the westward motion of their internal zones provide a good example of an active tectonic arc the campo de dalias and campo de nijar constitute outcropping sectors of neogene and quaternary rocks located in the southeastern border of the betic cordilleras and allow us to study the recent deformations developed in the internal border of this tectonic arc the main active faults with related seismicity representing a moderate seismic hazard associated to the southeastern betic cordilleras boundary include high angle nw se oriented normal faults that affect at least the upper part of the crust a main detachment located at 10 km depth and probably another detachment at 20 km as well seismite structures recent fault scarps with associated colluvial wedges that deform the drainage network and the alignment of the coastline indicate that the high angle faults have been active at least since the quaternary paleostresses determined from microfault analysis in quaternary deposits generally show an ene wsw trend of extension present day earthquake focal mechanisms include normal strike slip and reverse faulting normal and strike slip focal mechanisms generally indicate ene wsw extension and strike slip and reverse focal mechanisms are related to nnw sse compression the maximum horizontal compression has a consistently nnw sse trend the deep activity of detachments and reverse faults determines the nnw sse crustal shortening related to the eurasian african plate convergence at surface however the predominance of normal faults is probably produced by the increase in the relative weight of the vertical stress axis which in turn may be related to relief uplift and subsequent horizontal spreading the internal mountain front boundary of the betic cordilleras developed through the activity of a set of structures that is more complex than a typical external mountain front probably as a consequence of a vertical variable stress field that acted on previously deformed rocks belonging to the internal zone of the cordilleras

timing magma ascent at popocatepetl volcano mexico 2000 2001 abstract magnetic anomalies may be used to constrain magma ascent and are useful as precursors to eruptions especially when correlated with other geophysical and geochemical data in this paper we present multiparameter data on the magnetics dome morphology geochemistry and seismicity associated with the december 2000 january 2001 eruptions the largest of the recent eruptions at popocatepetl volcano a 6 month data period was studied in order to evaluate the precursors and post eruption processes several cycles of dome construction and destruction occurred from september 2000 through february 2001 in december large amplitude tremor associated with a higher effusion rate resulted in the formation of a large dome which filled the crater to within about 50 m of the lowest part of the crater rim seismic activity in december was marked by many volcanotectonic earthquakes and both high frequency and harmonic tremor on december 12 and 13 an increase in the tremor amplitude was followed by ash eruptions with 1 7 5 km high columns tremor amplitude increased again on december 15 and oscillated for the next four days activity remained high until the end of the month on january 22 an 18 km high plume produced ash and pumice fall to the east as well as pyroclastic flows and mudflows which reached 6 km from the crater the eruption left three concentric explosion pits partially destroying the december dome mixing of a mafic olivine bearing melt with a more evolved magma triggered the larger eruption on january 22 as can be seen from the higher mgo concentrations in some of the ejecta and the presence of a dark andesitic scoria with lower silica content and a white andesitic pumice with higher silica content precursory negative magnetic anomalies up to 5 nt 3 2 nt 5 nt 2 9 nt were associated with the ascent of the larger batches of magma which preceded the increases in seismicity before the december 2000 january 22 vei 3 4 eruptions no significant increases in seismicity were observed prior to the january 22 eruption except for a magnitude 2 4 earthquake on the day of the eruption there was however a 0 8 nt magnetic anomaly which lasted from january 10 to 12 and possibly to january 17 most of the magma ascended in three large batches and several smaller ones from october 22 through december 10 short lived crater domes with small volumes were formed at popocatepetl in september october and november 2000 and in march 2001 even the smaller negative anomalies from september to february were associated with the ascent of several batches of magma they preceded the increases observed in the seismicity and growth of a dome by several days