late cenozoic geodynamic evolution of eastern indonesia this paper presents an internally and globally consistent model of plate evolution in eastern indonesia from middle miocene to present time it is centered on the banda sea region located in the triple junction area between the pacific philippine australia and south east asia plates the geological and geophysical data available from indonesia were until recently insufficient to define a unique plate tectonic model in this paper the new data taken into account clearly restrict the possible interpretations owing to a great number of geological geophysical and geochemical studies the major plate boundaries the sunda banda subduction zone to the south the tarera aiduna fault zone and the seram thrust to the east and the sorong fault zone and molucca sea collision zone to the north are now clearly identified the age of the major tectonic structures is also better known geodetic measurements well constrain the present time plate kinematics we also consider the deformation history within eastern indonesia where numerous short lived microplates and their related microcontinents successively accreted to the asiatic margin moreover magnetic anomalies identification of the north and south banda sea basins allows a precise kinematic reconstruction of the back arc opening we used the plates software to test the coherency of our model presented as a series of 4 plate reconstruction maps from 13 ma to the present finally the origin of oceanic domains restored by our reconstruction is discussed

radar reflections from sedimentary structures in the vadose zone ground penetrating radar gpr is a suitable technique for imaging sedimentary structures in the vadose zone because small texture related capillary pressure variations lead to changes in water content and electromagnetic properties to study exactly how gpr reflections are generated by sedimentary structures gpr profiles of an aeolian sedimentary succession are combined with measurements of textural electromagnetic and water retention characteristics from a trench time domain reflectometry indicates that small variations in texture in the high angle dune sediment are associated with changes in water content synthetic modelling shows that these changes cause clear gpr reflections in an experimental approach to estimate the radar response of structures below the wave resolution i e features smaller than 4 variations in grain size distribution and porosity in a thin section were used to reconstruct water retention curves and impedance models of the thinly layered sediment synthetic radar records calculated from the impedance models show that reflections from the studied subcentimetre scale structures are composites of interfering signals although these low amplitude interfering signals will commonly be overprinted by more prominent reflections they may cause reflection patterns that change with frequency and do not represent primary bedding

formation and evolution of lateritic profiles in the middle amazon basin insights from radiation induced defects in kaolinite abstract the content of radiation induced defects rids in kaolinite samples originating from lateritic soils and continental detritic sediments of the middle amazon basin brazil is investigated using electron paramagnetic resonance the paleodose registered by kaolinites ranges from 80 to 900 kgy present day dose rates of radiation determined from the whole rock u and th content range between 4000 and 40 000 mgy ka in most samples u and th concentrations are correlated suggesting that u has not been remobilized by lateritization this observation is consistent with the fact that 80 of the total u content is incorporated in resistant minerals such as zircon and ti oxides the heterogeneous distribution of u observed by induced fission tracks mapping makes it possible to neglect the radiation contribution of the u decay chains in the dose rate calculation the interpretation of the measured content of rids in kaolinite is then performed using the calculated present day dose rate and assuming equilibrium in the radioactive decay chains for the sedimentary samples the amount of rids is broadly correlated to the dose rate and provides apparent absolute ages older than 20 ma the rid contents in kaolinites from the lateritic soils provide apparent ages ranging from 10 to 6 ma the high rid content of these lateritic kaolinites shows that their chemical isotopic and crystallographic properties are not representative of present day weathering conditions models assuming the dynamical equilibrium of kaolinites with local physical chemical conditions prevailing in lateritic soils are thus questionable alternatively our findings bring strong support for the use of the isotopic composition of kaolinites to decipher continental paleo climates

geodetic observations of the 2018 mw 7 5 sulawesi earthquake and its implications for the kinematics of the palu fault

applications of uthpb isotope systematics to the problems of radioactive waste disposal abstract concentrations of u th and pb and the isotopic composition of pb for whole rock samples of granitoids show 1 that open system behavior is nearly universal in the surface and near surface environment and 2 that elemental mobility is possible to depths of several hundred meters several identified or at least postulated factors that control u and or pb mobility include 1 the mineralogical sites for u and its daughter products 2 access of groundwater to these sites 3 the volume of circulating water and 4 the chemistry of the groundwater studies of granitic samples from peralkaline complexes in the arabian shield have shown that most samples lost less than 20 of their u during recent exposure to the near surface environment most of the u in these samples appears to be firmly bound in zircons in contrast most surface and shallow drill core samples of the granite of lankin dome granite mountains wyoming have lost 70 of their u most of the u in these samples is weakly bound in biotite and epidote family minerals the granite recovered during the illinois deep drill hole project stephenson county illinois is mineralogically similar to the granite of lankin dome but this granite lost radiogenic pb rather than u probably as a result of exposure to groundwater that had a markedly different chemistry from that in the granite mountains studies of the sherman granite wyoming and the gotemar granite southeastern sweden have shown that u and or pb mobility is greatest in and near fractured rock the greater mobility is interpreted to be the result of both a larger water rock ratio in the fractured rock and exposure to water over an increased surface area and consequently a greater number of uranium sites several types of geochemical and mineralogic data can be used to identify rock water interaction in granites however if rock samples have favorable radiogenic to common pb ratios both the amount and approximate timing of u or pb mobility can be obtained through the use of isotopic studies such information can be extremely important in the search for favorable hosts for containment of radioactive waste rocks such as the gotemar granite have undergone considerable rock water interaction most of which occurred 400 myr ago and little in recent times thus a search for zones that have experienced only a little interaction with water may provide a misleading prediction as to the ability of such zones to shield radioactive wastes from the modern biosphere from an isotopic point of view an ideal candidate for evaluation as a host rock for radioactive wastes would have the following characteristics 1 a high ratio 2 of radiogenic to common pb in order to optimize precision of the results 2 a simple two stage geologic history so that results could be interpreted without multiple working hypotheses and 3 an originally high percentage 50 of labile u so that the results would be highly sensitive to even small amount of rock water interaction these characteristics should produce rocks with marked radioactive disequilibrium in surface samples the disequilibrium should grade to radioactive equilibrium with increasing depth until zones in which water has not circulated are found extensive regions of such zones must exist because u th pb systematics of most analyzed granitoids demonstrate closed system behavior for almost all of their history except for their recent history in the near surface environment

review of the modelling of radionuclide transport from u series disequilibria and of its use in assessing the safe disposal of nuclear waste in crystalline rock abstract u series disequilibia from crystalline rocks and u deposits have been used to estimate the timing of hydrogeological events for u and ra mobility and to model the transport rates of u and ra both with some sucess unfortunately activity ratio data alone are not unique to a given process or model and it is shown how inappropriate choice of the model can have quite diverse consequences for interpretation of the data information from other sources is needed to help minimise these non uniqueness problems but as yet the state of methodology is unadequate to assess completely the validity of the models in particular the rate of deposition of u in fractures seems highly dependent upon the availability of trivalent fe and other low temperature minerals whose rates of formation are largely unknown this review reinforces the need to assess closely the suggestion that chemisorption is an effective retardant of fracture borne borne repository source radionuclides

geometry and mechanism of faulting of the 1980 el asnam algeria earthquake from inversion of teleseismic body waves and comparison with field observations the el asnam earthquake of october 10 1980 ms 7 3 provided a wealth of geological and seismological data and is an ideal event for comparing geologically and seismologically derived models the event produced extensive surface faulting in addition to the main tectonic deformation which is clearly a thrust widespread secondary normal faulting was observed at the surface in the southwest region the surface break of a thrust fault could be traced for 24 km in the northeast part of the fault zone normal faults with throws of several meters were observed although no clear thrust type surface breaks were observed in this region geodetic measurements and aftershocks indicate that thrusting was nonetheless the main tectonic mode of deformation in this paper the rupture process of the el asnam earthquake is investigated by inversion of teleseismic p and sh waves the effort is concentrated on the late part of the waveforms which carries information about the faulting in the least understood north eastern segment of the fault zone during the earthquake rupture initiated at the southern terminus of the southwestern fault segment and propagated northward as indicated by the epicentral location and the observable azimuthal directivity of the body wave shapes and amplitudes the seismogenic faulting in the southwestern segment has a thrust mechanism with the following average parameters seismic moment 3 9 1019 n m depth 6 km strike 220 dip 46 and rake 72 the duration of rupture on this fault segment was approximately 10 s which together with the observed fault length of 24 km indicates a rupture velocity of 2 4 km s unconstrained inversions suggest normal faulting in the northeast part of the source region that began immediately following the arrival of the rupture to the northeast region the normal faulting mechanism is in agreement with that observed for the large surface fault scarps in this region guided by the evidence from aftershocks and geodetic measurements a solution with a thrust type mechanism was also sought using a priori constraints based on the field observations the observed strike and slip angle we obtain the following thrust source mechanism for the northeast segment seismic moment 3 6 1019 n m depth 6 km strike 230 dip 20 and rake 91 this solution requires that the thrusting in the northeast be initiated 10 s after the arrival of the rupture from the southwest suggesting that some time is required to overcome the geometric barrier marked by the abrupt change in the dip and azimuth inversions are nonunique with respect to the seismic moment associated with normal faulting the ambiguity being caused by the limited bandwidth of the observed body waves the moment estimated from the surface waves at periods about 300 s however favors thrust faulting to be dominant in the northeast region

reconnaissance microearthquake survey of sulawesi indonesia several hundred earthquakes were recorded during the operation of a two week five station portable seismograph network on sulawesi indonesia forty one of these events were locatable and half of these occurred beneath the eastern gorontalo basin in a north dipping zone which extends from the batui thrust on the east arm of sulawesi to about 100 km depth beneath the gorontalo basin the batui thrust is the site of thrusting of the banggai islands continental fragment beneath the east arm ophiolite and oceanic crust of the gorontalo basin the observation of a zone of earthquakes dipping to the north from this thrust zone suggests that the leading edge of the banggai island block was subducted to at least 100 km depth the eastern gorontalo basin earthquake zone may connect with a deep seismic zone beneath the celebes basin beneath the western gorontalo basin a very narrow zone of earthquakes dips to the south probably within lithosphere of the celebes basin subducted at the north sulawesi trench three shallow earthquakes occurred near lake matano in central sulawesi possibly on the matano fault and their composite focal plane solution suggests east west extension the occurrence of only one earthquake on the palu fault and the lack of short s p times at a station operated on the fault indicate that this feature was very quiet during the survey period

india and sunda plates motion and deformation along their boundary in myanmar determined by gps using a regional gps data set including 190 stations in asia from nepal to eastern indonesia and spanning 11 years we update the present day relative motion between the indian and sundaland plates and discuss the deformation taking place between them in myanmar revisiting measurements acquired on the main boundary thrust in nepal it appears that points in southern nepal exhibit negligible deformation with respect to mainland india including these points using a longer time span than previous studies and making an accurate geodetic mapping in the newest reference frame allows us to refine the present day indian motion our results confirm that the current motion of india is slower than predicted by the nuvel 1a model and in addition our india eurasia motion is significantly 5 mm yr slower than previous geodetic determinations this new indian motion combined with a refined determination of the sundaland motion gives way to a relative india sunda angular velocity of 20 2 n 26 1 e 0 370 myr in itrf2000 predicting a relative motion of 35 mm yr oriented n10 at the latitude of myanmar there the sagaing fault accommodates only 18 mm yr of right lateral strike slip only half of the shear component of motion we present two models addressing how and where the remaining deformation may occur a first model of distributed deformation implies convergence on the arakan subduction the northern continuation of the now famous sumatra andaman trench and wrench faulting in the arakan wedge the second model uses localized deformation where deformation observed west of the sagaing fault is entirely due to elastic loading on a faster and oblique arakan subduction 23 mm yr this latter model predicts that a major earthquake of mw 8 5 may occur every century on this segment of the subduction

the 1996 earthquakes in sulawesi indonesia we study the rupture process of the 1 january mw 7 9 16 july mw 6 6 and 22 mw 7 july 1996 earthquakes in sulawesi indonesia a teleseismic body waveform inversion of very broadband records shows that these events occurred beneath the accretionary prism the main shock was due to a well determined fault with a strike of 53 n and a very shallow dip of 7 from its source time function duration 30 sec and the aftershock distribution we estimate a rupture area of 90 60 km2 and an average slip of 1 80 m the surface displacement computed with our best model fits well the displacement vector at the only available gps station at tomini the tsunami generated by the mainshock had an approximate source radius of 45 km which roughly agrees with the rupture size estimated above the earthquakes took place in a relay zone between the trench and the palu koro transcurrent fault they ruptured a shallow dipping thrust fault which corresponds to the subduction interface under the north sulawesi arm the slip vectors of all the events have a nnw orientation parallel to the direction of convergence between the north sulawesi arm and the celebes sea among the peculiarities of the rupture process we found that the july 22 aftershock was the only event to have a well defined precursor 1 8 sec before the main p wave onset

esr dating in quaternary geology abstract electron spin resonance esr a relatively new dating technique was first suggested by zeller et al 1967 zeller 1968 and levy 1968 it has made substantial progress in frequent applications in the last few years esr dating is based on the direct measurement of the amount of radiation induced paramagnetic electrons trapped in crystal defects these free electrons were generated by alpha beta and gamma radiation of natural radioelements e g u th k and have accumulated in the minerals over geologic time the esr age is obtained by dividing the total amount of accumulated radiation dose archaeological dose ad by the dose per year annual dose this review comprises four major parts the principles of the method the determination of the archaeological dose ad the determination of the annual dose and a compilation of datable materials several questions remain the evaluation of the ad the determination of the annual dose and particularly with respect to the nature and stability of the electron traps used for dating

application of ground penetrating radar imaging to deepwater turbidite outcrops ground penetrating radar gpr provides a high resolution image of bed scale features within the interior of an outcrop this geophysical technique has been used successfully in fluvial deltaic sequences but its successful use in deepwater deposits is less documented the present paper demonstrates the ability of gpr to define the nature of channel margins and to distinguish internal channel facies at turbidite outcrops in wyoming cretaceous lewis shale usa profiles obtained behind the lewis shale outcrops show channel fills having complex slumped margins between channel sandstones and adjacent levee thin beds as well as onlap of sandstone beds onto the channel margins within the channel fill facies distinguished by gpr vary from interbedded debris flows and turbidites on one side of a channel to cross bedded sandstones on the other side lateral accretion surfaces and onlap features which cannot be observed at the outcrop scale are present on gpr profiles they may represent cross channel sediment transport and deposition within a sinuous channel these examples suggest that when used together with geologic mapping photomosaics and available behind outcrop drilling and logging gpr surveys spanning large outcrops may provide valuable sub seismic scale architectural information for building more robust 3 d models of deepwater reservoirs q 2003 elsevier ltd all rights reserved

fission track and fault kinematics analyses for new insight into the late cenozoic tectonic regime changes in west central sulawesi indonesia abstract the left lateral strike slip central sulawesi fault system csfs composed of the nnw palu koro pkf and the ese matano faults is located within the eastern indonesian triple junction between the pacific indo australian and eurasian plates fault kinematic and fission track analyses show that the late cenozoic central sulawesi deformation results from three successive tectonic regimes 1 a late miocene early pliocene 5 ma wnw trending shortening characterized by transpressional deformation along the pkf and compressional in the poso area this tectonics resulted from the collision between the banggai sula block with sulawesi it produced locally a transpressional regime as a consequence of the northward extrusion of the central sulawesi block limited by the pkf 2 a pliocene collapse tectonic regime associated with w trending extension coeval with these events regional cooling and exhumation took place 3 a quaternary transtensional regime resulting from the combined effects of the central sulawesi block northward motion and extension related to back arc spreading behind the north sulawesi subduction tomini gulf

the use and application of gpr in sandy fluvial environments methodological considerations ground penetrating radar gpr is a popular technique for imaging and interpreting sedimentary architecture however current literature shows a wide range in the quality of information provided on the gpr methodology and processing technique it is therefore difficult to judge the validity of the gpr interpretations and this produces inherent difficulties for comparison between surveys this paper describes the key steps required to collect process and interpret gpr surveys in sandy fluvial sediments gpr data from the south saskatchewan river canada are used to illustrate each stage of data collection and processing particular attention is given to the appropriate set up conditions for the gpr software and hardware the selection of data processing techniques and velocity analysis methods for the interpretation of gpr reflectors are also investigated using ground truth control provided by a cut face exposure this paper presents recommendations for a systematic and rigorous methodology for the collection processing and interpretation of gpr data in sandy fluvial environments the paper suggests that all data collection parameters and processing steps should be recorded or tabulated in any gpr publication to facilitate comparisons between surveys

mantle flow beneath a continental strike slip fault postseismic deformation after the 1999 hector mine earthquake two recent large earthquakes in the mojave desert california the magnitude 7 3 1992 landers and magnitude 7 1 1999 hector mine earthquakes have each been followed by elevated crustal strain rates over periods of months and years geodetic data collected after the hector mine earthquake exhibit a temporally decaying horizontal velocity field and a quadrant uplift pattern opposite to that expected for localized shear beneath the earthquake rupture we interpret the origin of this accelerated crustal deformation to be vigorous flow in the upper mantle in response to the stress changes generated by the earthquake our results suggest that transient flow in the upper mantle is a fundamental component of the earthquake cycle and that the lower crust is a coherent stress guide coupling the upper crust with the upper mantle

centroid moment tensor solutions for july september 1995 abstract centroid moment tensor solutions are presented for 230 earthquakes that occurred during the third quarter of 1995 the solutions are obtained using corrections for aspherical earth structure represented by a whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward 1992 acoustical imaging plenum press pp 785 797 a new model of anelastic attenuation of durek and ekstrom 1994 eos trans am geophys union spring meet suppl 75 83 is used to predict the decay of the waveforms

recognizing surface scattering in ground penetrating radar data ground penetrating radar gpr data may show strong noise events as a result of scattering by surface objects on the ground or above the survey line the relative strength of these events can be large in comparison to reflections from geologic features because radar signals in the ground attenuate exponentially whereas signals that travel in the air attenuate geometrically migration of gpr field data from clastic and carbonate sequences in central oklahoma distinguishes between scattered events and geologic events because the former are focused at the air wave velocity while the latter are focused at the ground wave velocity forward modeling using locations of scatterers derived from migration confirms the presence of scattered events and common midpoint cmp gathers are helpful in identifying surface scattering scattered events displayed at a horizontal vertical scale of 1 1 are easily mistaken for subhorizontal geologic reflections methods of recognizing scattered events and removing them if possible are therefore crucial to correct geological interpretation of gpr data

migration of seismicity and earthquake interactions monitored by gps in se asia triple junction sulawesi indonesia 1 global positioning system gps measurements made in sulawesi indonesia from 1992 to 1999 detected coseismic and transient postseismic deformation related to the 1 january 1996 mw 7 9 earthquake on the north sulawesi minahassa trench these motions are superimposed on the long term secular motion 40 mm yr of the left lateral palu fault in central sulawesi and continued for about 1 5 2 years following the earthquake a string of earthquakes of magnitude 6 migrated along the minahassa trench from west to east subsequently two earthquakes of magnitude 6 occurred on or near the palu fault migrating toward the south modeling the increase in coulomb stress generated by the successive earthquakes agrees with the hypothesis of interacting events an unclamping effect possibly due to fluid migration in the palu area is also suggested by the stress computations and the detected gps displacements

observing plate motions in s e asia geodetic results of the geodyssea project this paper presents the final geodetic results of the geodyssea project the gps data from a 42 station network observed during two field campaigns 1994 1996 were analyzed by four groups using different software packages and analysis strategies the precision of both campaign coordinate solutions was found to be 4 7 mm for the horizontal and 1 cm for the vertical component the campaign solutions were merged into one unique solution which was accurately mapped into the itrf 96 reference frame the global accuracy of this solution with respect to itrf 96 is 1 cm while the resolution of the relative horizontal velocities is estimated to be at the level of 2 3 mm yr this solution was used as the basis for all scientific interpretations which are published in separate papers the velocity estimates of a part of the network provided the first direct measurement of a relative motion of the sundaland block with respect to eurasian plate

determining the sula block kinematics in the triple junction area in indonesia by gps summary the point of convergence of the eurasian philippine and australian plates is situated adjacent to the island of sulawesi indonesia the relative plate velocities are estimated by nuvel1 to be 7 to 9 cm yr 1 the complex tectonic mechanism of the triple junction has been studied over a two year period in the course of the geodyssea southeast asian project the gps investigations concentrate on measurements of both the sulawesi eastern indonesia part of the inter regional geodyssea network and a local subnetwork on sulawesi motions derived using data from the subnetwork con rm what the results of the inter regional geodyssea network have suggested that is that current deformation is high and there are distinct deformation domains in the study area on sulawesi the tectonic mechanism of the triple junction has been analysed using a rigid microblock model the triple junction area can best be interpreted as a headland of the australian plate de ected by its collision with the philippine plate thereby identifying the driving forces of the current deformation the northern part is dominated by the sula domain which shows clockwise rotation to the south it is connected to the australian plate by an ensemble of microblocks undergoing counterclockwise rotation in addition to the above our tectonic model permits the determination of the local in uence of two large earthquakes m 7 8 1996 january 1 and m 7 0 1996 july 22 on the motion of the station tomini north sulawesi more observations and a denser gps network are planned in order to study the behaviour of the palu koro fault the main fault on the western limit of the sula block

source parameters and slip distribution of the 2018 mw 7 5 palu indonesia earthquake estimated from space based geodesy abstract the 2018 mw 7 5 palu earthquake is one of the most geometrically complex events ever recorded on central sulawesi island it caused devastating tsunamis and landslides after the mainshock resulting in great casualties and damages to the infrastructures in palu city and surrounding areas in this study we combined far field insar near field sar and optical sub pixel correlation data to determine the fault geometry source parameters and fault slip distribution of this event along the palu koro fault zone our best fitting fault model contains three fault segments with variable strike angles showing that the coseismic rupture is dominated by a left lateral strike slip motion accompanied by minor normal slip and reverse slip components on the onshore segments the maximum slip is up to 8 4 m with a left lateral strike slip component of 6 8 m at a depth of 4 km on the central segment near palu city a normal slip component of 4 3 m in the left releasing step over and a reverse slip component of 3 2 m in the offshore area near the palu bay on the offshore segment the maximum slip is up to 4 2 m with a normal slip component of 1 8 m we argue that the offshore reverse slip motion might have played a key role in the generation of the palu tsunami we also suggest that the linking normal segment contributed to the rupture propagation across the left releasing step over from the central segment to the southern segment while the linking reverse segment arrested the rupture propagation across the right restraining step over to north the coulomb stress change reveals that there is possibility of future great earthquakes occurring on several major faults in the northeast of palu city our results have great significance to qualitatively assess the risk of future seismic hazards in such a geometrically complex fault system

tsunami simulations of the sulawesi m w 7 5 event comparison of seismic sources issued from a tsunami warning context versus post event finite source the 28 september 2018 sulawesi earthquake generated a much larger tsunami than expected from its mw 7 5 magnitude and from its dominant strike slip mechanism within a few minutes after the earthquake the tsunami devastated the seafront of palu bay destroying houses and infrastructures over a few hundred meters coastal subsidence and slumping at various locations around the bay were also observed there is debate in the scientific community as to whether submarine landslides and shore collapses contributed to the generation of strong and destructive waves locally the objective of this study is threefold first to determine whether standard seismic inversions could predict the source in the context of tsunami early warning second to define a new seismic source built from optical image correlation and based on the geological and tectonic context third to assess whether the earthquake alone is able to generate up to 9 m wave heights at the coast numerical simulations of the tsunami propagation are performed for different seismic dislocation sources nonlinear shallow water equations are solved by a finite difference method in grids with 200 m and 10 m resolutions the early cmt focal solutions calculated by seismological institutes show dominant strike slip mechanisms with a homogenous slip distribution these sources produce maximum tsunami heights of 40 cm on the coast of palu city two heterogeneous sources are tested and compared the usgs finite fault model calculated from seismic inversion and a new hybrid source inferred from different techniques the latter is based on a segmented fault in agreement with the geological context and built from both from seismic parameters of a cmt solution and the observed horizontal ground displacements this source produces water wave heights of 4 to 5 m in the palu bay the observed inundation heights and distances are reproduced satisfactorily by the model at pantoloan and at the southwestern tip of palu bay however the hybrid source is unable to reproduce the largest 8 to 12 m water heights as reported from field surveys thus even though this hybrid source produces most of the reported tsunami energy we cannot exclude that the numerous coastal collapses observed in palu bay contributed to increase the local tsunami run up

examples of reverse time migration of single channel ground penetrating radar profiles a single channel ground penetrating radar gpr profile portrays a distorted unfocused image of subsurface structure due to apparent position shifts associated with dipping reflectors and to diffractions from corners and edges a focused image may be produced from such data by using any of the migration algorithms previously developed for seismic data we use reverse time migration based on the scalar wave equation field work was performed over a simple stratigraphic soil sequence and a complicated fluvial environment in the migrated images reflector continuity is enhanced and the level of detail available for high resolution interpretation is significantly increased

study of two alteration systems as natural analogues for radionuclide release and migration abstract u deposit hosted in hydrothermally altered tuffs in mexico together with weathering profiles from cameroon were studied as natural analogues of radionuclide release and migration using petrological and spectroscopic methods infrared and electron paramagnetic resonance we have distinguished successive secondary mineral parageneses and the behaviour of radionuclides in the u deposit the mineral parageneses show that uranium migration is mainly controlled by the redox potential and silica activity of the altering solutions the high silica content of the solutions is caused by the intense alteration of volcanic rocks two types of secondary clay mineral parageneses are evidenced a kaolinization intense where uranium is accumulated in the welded tuffs and a smectitization mainly developed in the underlying weakly welded tuffs several types of kaolinite have been defined according to their genesis fillings in fissures and feldspar pseudomorphs their location relative to a breccia pipe where uranium has accumulated core and rim of the pipe surrounding rhyolitic tuffs and particle morphology structural order and substitutional fecontent it is shown that the variations of the concentration of paramagnetic defect centres always more than ten times as important than those measured in weathering kaolinites are only correlated to the location of the kaolinites the highest values correspond to the breccia pipe kaolinites e g kaolinites located in the uranium accumulation zones moreover one or two main defects centres are detected depending on the intimate association of kaolinites with uranium bearing minerals besides in weathering kaolinites from u depleted laterites defect centre concentrations are correlated to the total fe203 content in bulk samples this means that the defect centre acts as a memory of the travel of uranium when this element was sorbed onto iron gels in the first stage of weathering it is concluded that paramagnetic defect centres in kaolinites might allow an efficient fingerprint of successive irradiations in the natural analogues under study and could be an useful tool to control radionuclides migration through kaolinite containing clayey materials such as those used for waste repository a better understanding of radiation efficiency as well as accurate dose ratekaolinite containing clayey materials such as those used for waste reposit estimation are needed for a quantitative tracing of the migration ofa better understanding of radiation efficiency as well as accurate dose ratekaolin radionuclide elements with this aim a simulation has been undertaken withestimation are needed for a quantitative tracing of the migration of various radiations sources we have determined for each irradiation the parameters of the paramagnetic centres created in order to understand the way they are forming the knowledge of the parameters governing the formation and the stability of the radiation centres in kaolinites allow to use this mineral as a natural dosimeter

hydrothermal and supergene clays of the oklo natural reactors conditions of radionuclide release migration and retention abstract mineralogical chemical and o isotopic analyses were performed on the clay matrices surrounding two natural fission reactors of the oklo deposit in the deeply preserved reactor 10 450 m clays are composed of hydrothermal mg chlorites and sudoites al chlorites the wide range of their o isotopic compositions from 0 0 to 15 1 smow is consistent with crystallisation during conditions of criticality when the reactors created a thermal gradient of 100 c m the temperature in the core of reactor is calculated to have been approximately 400 c in contrast in the shallow reactor 9 120 m deep vermiculitized al chlorites are the products of the weathering of the hydrothermal chlorites these vermiculitized al chlorites are 18 o enriched 18 o 18 smow and underwent interaction with surface fluids 2 to 5 149 sm 147 sm isotopic ratios of the clays of reactor 9 show a wide dispersion 2 3 m of the fissiogenic sm around the reactor the migration of the fissiogenic sm which is usually retained in the deep reactors is here related to the circulation of meteoric water under oxidising conditions

crustal motion and block behaviour in se asia from gps measurements results acquired using global positioning system gps data taken over a large part of se asia indicate that sundaland i e indochina along with the western and central part of indonesia constitutes a stable tectonic block moving approximately east with respect to eurasia at a velocity of 12 3 mm yr 31 with respect to india and australia this block moves due south significant motion has not been detected along the northern boundary to south china i e along the red river fault whereas nearly 50 mm yr 31 of right lateral motion has to be accommodated between india and sundaland in the andaman burma region fl 2001 elsevier science b v all rights reserved

reconstruction of past u migration in a sedimentary deposit coutras france implications for a radwaste repository this study is focused on ancient u mobility in unconsolidated kaolinite bearing sediments from the outcrop area of the coutras u deposit gironde france the analysis of radiation induced defects by electron paramagnetic resonance spectroscopy shows significant variations among the investigated samples and provides the paleodoses due to u at coutras the highest paleodose does not correspond to the highest u concentrations indicative of a past concentration of uranium different from the present one the paleodose gives an estimate of the equivalent u concentrations eu responsible for the defect concentration assuming an age for the kaolinites and considering extreme degrees of disequilibrium among u decay chain as uncertainties of the method the comparison between the equivalent eu and normalized present day u concentrations u norm reveals past migration of u when these two concentrations are different past occurrence of u and daughters is revealed even when this radioelement has been subsequently leached indeed surface sandy beds show a slight barely significant leaching evidence of u eu u norm in contrast several samples show u norm much greater than eu which suggests past accumulation of u younger than the sediment deposition particularly in organic rich clay layers these late enrichments may reach several hundreds ppm u isotopic constraints from the literature imply that accumulation is older than 1 ma in the organic clayey beds although the time of transfer or spatial dispersion of u cannot be specified from the methodology and the limited set of samples the quantitative analysis of radiation induced defects in clays yields intensity of past radioisotope transfers at the geological timescale it is relevant for the analysis of u mobility in sedimentary natural analogues of high level nuclear waste repositories it is also complementary to classical isotopic analysis of u and th series

experimental evidence of uraninite formation from diagenesis of uranium rich organic matter abstract this study focuses on the experimental diagenetic evolution of an uranium rich lignite from the coutras uranium deposit gironde france located in eocene sediments three samples containing 6 to 15 5 wt uranium were analysed and compared to two barren samples located outside the ore deposit in a stratigraphically equivalent unit uranium in the mineralized samples is present as uranyl carboxylic complexes dry thermal maturation was simulated in a cold seal autoclave at 150 200 250 300 and 350 c at 100 mpa for 24 h with increasing temperature uranyl carboxylic complexes decompose while uraninite forms the chemical composition of the experimentally matured barren samples when plotted in a van krevelen diagram h c vs o c parallels the natural trend of land derived type ill organic matter evolution while mineralized samples are characterized by a higher loss of hydrogen above 250 c reduction to form uraninite is directly related to the dehydrogenation of lignite the resulting uraninite has a similar unit cell edge to that of natural uraninites observed in sedimentary environments uraninite not only forms in the pore space but also replaces the lignite constituents the results demonstrate that uraninite may form during thermal evolution of uranium rich organic matter during diagenesis

uranium mobility in the sediment hosted uranium deposit of coutras france abstract recent mobility of u was investigated in the coutras u deposit gironde france located in lutetian sediments near the surface the coutras deposit is a belt of tabular ore bodies separated into two areas by the dronne river the jean vincent area close to the surface and the le fieu area located at a maximum depth of 100 m the immobility of th is supported by whole rock th contents which do not vary significantly with u content the present hydrological regime in the jean vincent area is characterized by oxidizing waters flowing toward the dronne river activity ratios ar of 230th 234u in rocks which range from 0 55 to 12 demonstrate recent u accumulation and leaching the 234u 238u ar range from 0 94 to 1 52 in the rocks and from 0 94 to 1 61 in the waters recent accumulation of u is favored along redox barriers where mo v se and as are also mobilized waters in the le fieu area are nearly stagnant they are reduced and exhibit a different chemical composition than waters in the jean vincent area with higher contents of ca mg na k cl hco3 po4 ra ba mn higher 234u 238u ar 1 33 4 63 and lower u content the le fieu rock samples do not show any isotopic evidence of recent leaching of u but both relative excesses and deficits of 234u are observed preferential mobility of 234u in the reduced le fieu area is interpreted according to the recoil model the results place new constraints on the model of cowart and osmond and should be useful in prospecting for tabular u deposits in reduced environments

the uranium ore from mina fe salamanca spain as a natural analogue of processes in a spent fuel repository abstract in the frame of the enresa natural analogue programme the uranium ore from the mina fe salamanca spain has been studied as a natural analogue of radioactive spent fuel behaviour this uranium mine is hosted in highly fractured schistose rocks a geological setting that has not been envisaged in the spanish options for radioactive waste burial however some analogies with the processes that might be involved in the evolution of these geological repositories suggested this investigation the pitchblende pyrite carbonate paragenesis has been studied in situ as natural analogue of the nuclear spent fuel behaviour under extremely oxidative dissolution conditions similarly secondary fe oxyhydroxides and clay minerals have also been considered as relevant analogue materials for the retention of uranium and other analogous trace metals a multidisciplinary characterisation of the site has been performed in order to study these processes though the intense mining activities in the site hindered precise determination of the original hydrogeological and hydrochemical features of the investigated zone boa fault zone the mineralogy and geochemistry of fracture fillings mineralisation and associated clayey materials have allowed the geochemical evolution of the system to be established three geochemical zones have been clearly differentiated i the oxidised zone from the surface to approximately 20 m depth ii the redox transition zone from 20 to 50 m depth and iii the reduced zone located below the transition zone the oxidised zone is characterised by the presence of the typical mineral association resulting from the strong acid conditions caused by the total oxidation of pyrite and other sulphides the total oxidation dissolution and leaching of u iv as uranyl sulphate aqueous complexes prevailed in this oxidised zone the redox transition zone is characterised by the coexistence of the primary uranium paragenesis oxidised minerals as well as numerous secondary solid phases as a result of the physico chemical changes in the environment the optimal physico chemical conditions for the coffinitisation of pitchblende and the co precipitation of fe iii u vi took place in this zone in the reduced zone where the primary uranium paragenesis is present we currently find the necessary physico chemical conditions to stabilise pitchblende pyrite and carbonates the physico chemical conditions of the oxidised zone are not relevant to disposal conditions in the transition zone two main geochemical processes take place i the coffinitisation of pitchblende which may be an important process for the stability of spent fuel in reducing conditions and ii the co precipitation of the fe iii and u vi as oxyhydroxides another relevant mechanism for the retention of uranium the physico chemical conditions that prevail below 50 m depth should be sufficient to stabilise a spent nuclear fuel repository in the same way as they have been able to preserve the 34 ma old uranium deposit of the mina fe

insight into the 2004 sumatra andaman earthquake from gps measurements in southeast asia data collected at 60 global positioning system gps sites in southeast asia show the crustal deformation caused by the 26 december 2004 sumatra andaman earthquake at an unprecedented large scale small but significant co seismic jumps are clearly detected more than 3 000 km from the earthquake epicentre the nearest sites still more than 400 km away show displacements of 10 cm or more here we show that the rupture plane for this earthquake must have been at least 1 000 km long and that non homogeneous slip is required to fit the large displacement gradients revealed by the gps measurements our kinematic analysis of the gps recordings indicates that the centroid of released deformation is located at least 200 km north of the seismological epicentre it also provides evidence that the rupture propagated northward sufficiently fast for stations in northern thailand to have reached their final positions less than 10 min after the earthquake hence ruling out the hypothesis of a silent slow aseismic rupture data culled from gps stations in indonesia malaysia singapore thailand india and china have answered more questions relating to the 26 december sumatra andaman megathrust earthquake permanent displacements were seen 3 000 km away final displacements occurred within 10 minutes of the earthquake ruling out slow aseismic slip on the fault

revealing stratigraphy in ground penetrating radar data using domain filtering a common offset ground penetrating radar profile was collected from a mid continent fluvial environment characterized by sand with discontinuous clay layers signal was separated from coherent noise by a domain filter that exploits local differences in dip between signal and noise this filter proved effective in separating reflections from the direct air wave and from system ringing the processed section locates the base of a pleistocene river channel incised into bedrock and shows a change in a recent position of the river on the basis of radar character the water table which lies at a depth of approximately 2 m is characterized by a continuous reflection an earlier reflection is interpreted as a perched lens of water near the ground surface the predominant frequency of both reflections varies greatly with position along the profile shallow cores taken along the profile provide evidence that grain size in the transition zone from saturated to unsaturated sediments may determine the predominant frequency of the associated radar reflection the domain filter is also successful in separating transition zone reflections from saturated layer boundary reflections that are coincident in arrival time it is possible therefore to determine both grain size in the transition zone and the dip of sediments immediately beneath it even if the reflections from the two are superimposed

monitoring of the palu koro fault sulawesi by gps years of gps measurements across the palu koro fault sulawesi indonesia state left lateral strike slip 3 4 cm yr with a small normal component 0 4 cm yr the measurements on intermediate points of the transect show that the fault is locked at a depth estimated around 8 16 km by a very simple model the best measured baseline linking the two most separate sites watatu and toboli shows very interestingly a constant rate of 2 6 cm yr from 1992 to 1995 and an increased rate of 6 3 cm yr since then this increase is due to an earthquake on january 1 1996 in the minahasa trench presumably affecting station toboli s position by 2 cm of co seismic and 2 cm of post seismic displacement which is added to its long term velocity we interpret this phenomenon as additional stress loading on the palu fault driven by the slip during the earthquake 100 km to the north east

a physical basis for time clustering of large earthquakes we develop a theory that links stress interaction between earthquakes and the occurrence of temporal clustering coseismic static stress change in the vicinity 50 km of large earthquakes suggests that perturbations of 0 1 to 1 bars may affect the occurrence of other earthquakes at larger distances interactions also seem to exist four m 8 earthquakes have occurred in mongolia on distant faults 400 km during the last century also paleoseismic observations documenting much longer time periods display a time clustering of major events we demonstrate with simple mechanical concepts that postseismic stress relaxation magnifies the coseismic stress change and has a major effect on fault interaction during the seismic cycle in the simple case where two distant faults are coupled the probabilistic occurrence of triggered earthquakes may increase dramatically due to long range postseismic coupling

evidence of supershear during the 2018 magnitude 7 5 palu earthquake from space geodesy a magnitude 7 5 earthquake hit the city of palu in sulawesi indonesia on 28 september 2018 at 10 02 43 coordinated universal time it was followed a few minutes later by a 4 7 m high tsunami palu is situated in a narrow pull apart basin surrounded by high mountains of up to 2 000 m altitude this morphology has been created by a releasing bend in the palu koro fault a rapidly moving left lateral strike slip fault here we present observations derived from optical and radar satellite imagery that constrain the ground surface displacements associated with the earthquake in great detail mapping of the main rupture and associated secondary structures shows that the slip initiated on a structurally complex and previously unknown fault to the north extended southwards over 180 km and passed through two major releasing bends the 30 km section of the rupture south of palu city is extremely linear and slightly offset from the mapped geological fault at the surface this part of the rupture accommodates a large and smooth surface slip of 4 7 m with no shallow slip deficit almost no aftershock seismicity was recorded from this section of the fault as these characteristics are similar to those from known supershear segments we conclude that the palu earthquake probably ruptured this segment at supershear velocities the devastating 2018 magnitude 7 5 earthquake in palu indonesia ruptured at supershear speeds according to evidence from space geodesy

miocene to recent extension in nw sulawesi indonesia the malino metamorphic complex mmc in the western part of the north arm of sulawesi indonesia has previously been suggested to be a metamorphic complex exhumed in the early middle miocene this idea was based on limited k ar and 40ar 39ar age data but no structural data were presented to provide evidence for the mechanism of exhumation here we present new field observations micro structural analyses and a revised stratigraphy of nw sulawesi based on new age data to provide better constraints on the timing and mechanism of exhumation the data presented here suggest that the mmc is a metamorphic core complex which underwent lithospheric extension during the early middle miocene although the mmc experienced significant extension there is no evidence that it was exhumed during this time there is no contact between the mmc and the pliocene ongka volcanics contradicting a previously inferred unconformable contact pliocene undeformed granitoids intruding the mmc indicate the complex was still at depth during their emplacement furthermore pliocene and pleistocene cover sequences do not contain metamorphic detritus a second phase of extensional uplift was accommodated by brittle faulting from the late miocene pliocene onwards during which the mmc was exhumed this extension is widespread as indicated by synchronous exhumation of the adjacent palu metamorphic complex in west sulawesi and rapid subsidence offshore in gorontalo bay it is linked to northward slab rollback of the southward subducting celebes sea since the pliocene gps data show rapid northward motion of the north arm of sulawesi with respect to the celebes sea indicating that this process is ongoing at present day

rapid rotations about a vertical axis in a collisional setting revealed by the palu fault sulawesi indonesia global positioning system gps measurements from 1992 to 1995 indicate that the left lateral palu fault in central sulawesi slips at a rate of 38 8 mm a with a locking depth between 2 and 8 km from the measured slip rate and the historic seismicity of the fault we estimate that the palu fault currently has stored enough strain to produce a mw 7 earthquake the palu and other nearby faults accommodate rapid clockwise rotation of nearly 4 ma of e sulawesi relative to eastern sunda the rotation of east sulawesi transfers e w shortening between the pacific and eurasian plates to n s subduction of the celebes basin beneath sulawesi

historical tsunamis and present tsunami hazard in eastern indonesia and the southern philippines 1 eastern indonesia and the southern philippines comprise a huge and seismically highly active region that has received less than the deserved attention in tsunami research compared with the surrounding areas exposed to the major subduction zones in an effort to redress the balance the tsunami hazard in this region is studied by establishing a tsunami event database which in combination with seismological and tectonic information from the region has allowed us to define and justify a number of credible worst case tsunami scenarios these scenarios have been used in numerical simulations of tsunami generation and propagation to study maximum water level along potentially affected shorelines the scenarios have in turn been combined to provide regional tsunami hazard maps in many cases the simulations indicate that the maximum water level may exceed 10 m locally and even reach above 20 m in the vicinity of the source which is of the same order as what is forecasted along the sumatra and java trenches for comparable return periods for sections of coastlines close to a source a tsunami may strike only a few minutes after it is generated providing little time for warning moreover several of the affected areas are highly populated and are therefore also high risk areas the combination of high maximum water levels short warning times dense populations and relatively short return periods suggests strongly that the tsunami hazard and risk in these regions are alarmingly high

microblock rotations and fault coupling in se asia triple junction sulawesi indonesia from gps and earthquake slip vector data the island of sulawesi eastern indonesia is located within the triple junction of the australian philippine and sunda plates and accommodates the convergence of continental fragments with the sunda margin we quantify the kinematics of sulawesi by modeling gps velocities and earthquake slip vectors as a combination of rigid block rotations and elastic deformation around faults we find that the deformation can be reasonably described by a small number of rapidly rotating crustal blocks relative to the sunda plate the southwestern part of sulawesi makassar block rotates anticlockwise at 1 4 myr the northeastern part of sulawesi the bangai sula domain comprises three blocks the central north sula block moves toward the nnw and rotates clockwise at 2 5 myr the northeastern manado block rotates clockwise at 3 myr about a nearby axis and east sulawesi is pinched between the north sula and makassar blocks along the boundary between the makassar block and the sunda plate gps measurements suggest that the trench accommodates 15 mm yr of slip within the makassar strait with current elastic strain accumulation the tectonic boundary between north sula and manado blocks is the gorontalo fault moving right laterally at about 11 mm yr and accumulating elastic strain the 42 mm yr relative motion between north sula and makassar blocks is accommodated on the palu koro left lateral strike slip fault zone the data also indicate a pull apart structure in palu area where the fault shows a transtensive motion and may have a complex geometry involving several active strands sulawesi provides a primary example of how collision can be accommodated by crustal block rotation instead of mountain building