geochemical effects of co2 sequestration in sandstones under simulated in situ conditions of deep saline aquifers abstract the geochemical effects of brine and supercritical co 2 scco 2 on reservoir rocks from deep 1500 2000 m saline aquifers were examined via experimental simulation at in situ conditions dry sandstone samples were mounted in a triaxial cell and autoclave system evacuated and saturated with 1 m nacl solution the brine rock system was allowed to react at 30 mpa confining pressure 15 mpa pore fluid pressure and 60 c while scco 2 was injected at a pressure gradient of 1 2 mpa the experiment was conducted for a period of 1496 h during which fluids were periodically sampled and analyzed the ph measured in partially degassed fluid samples at 25 c decreased from a starting value of 7 0 4 3 9 days and finally 5 1 after saturation with scco 2 fluid analyses indicate that most of the major e g ca mg fe mn and trace elements e g sr ba pb of the sandstone increase in concentration during the reaction with brine and scco 2 these results are supported by scanning electron microscopy which indicates dissolution of dolomite cement k feldspar and albite in addition to dissolution reactions the formation of montmorillonite was observed by adjusting surface area and reaction rates of dissolution and precipitation geochemical modeling of the experiments could reproduce long term trends in solution chemistry and indicated limited rates of dissolution as the system remained strongly undersaturated with most minerals including carbonates the geochemical models could not account for decreases in concentration of some elements changes in solution composition resulting from changes in imposed pressure gradient and the observed ca mg and si al ratios in solution

mechano chemical interactions in sedimentary rocks in the context of co2 storage weak acid weak effects abstract due to the corrosive nature of dissolved co2 the potential short or long term alteration of rock properties represents a major issue in several sites where natural co2 circulation is observed as well as in reservoirs targeted for storage of anthropogenic co2 to date this has been primarily studied from a transport chemical perspective with laboratory evidence of microstructural modifications together with the consequences for flow properties compared to the transport chemical aspects the mechanical chemical aspects have been less investigated though it is to be expected that mechanical properties e g elastic properties failure parameters and time dependent mechanical behaviour could potentially be affected in a similar manner to hydraulic parameters yet since co2 is a weak acid the ph drop is expected to be moderate with a likely lower limit close to 4 0 the buffering of ph by calcite minerals present in most reservoirs targeted for storage may further limit the ph drop as well as confining it to a localized rock volume around the injection well this leads to the question of the magnitude and time spatial scales of chemically mediated mechanical processes during co2 sequestration the authors propose to address this issue by reviewing recent laboratory based studies restricted to sedimentary rocks namely reservoir rocks carbonate or sandstone intact or fractured caprocks and fault rocks key findings include the following 1 the short term impact on the elastic and inelastic behaviour of intact caprocks remains limited 2 shear strength weakening is likely to be respectively low and low to moderate for shale clay rich and anhydrite rich faults but without modifying slip stability in either case 3 the largest impact is located within carbonate reservoirs but with a broad range of reported responses depending on hydrodynamic conditions closed or open and on dissolution regime uniform or channelling and 4 creep experiments confirm that co2 induced dissolution may enhance long term compaction of carbonate reservoirs but the magnitude of acceleration varying from non significant to 50 times depends to a large extent on site specific conditions grain size ph temperature effective stress state etc which renders any direct extrapolation from laboratory to reservoir scale difficult finally some directions for future research studies are discussed

abrupt tectonics and rapid slab detachment with grain damage a simple model for necking and detachment of subducting slabs is developed to include the coupling between grain sensitive rheology and grain size evolution with damage necking is triggered by thickened buoyant crust entrained into a subduction zone in which case grain damage accelerates necking and allows for relatively rapid slab detachment i e within 1 my depending on the size of the crustal plug thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking oceanic lithosphere with normal or slightly thickened crust subducts without necking the model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and or induce abrupt continental rebound

carbon dioxide reaction processes in a model brine aquifer at 200 c and 200 bars implications for geologic sequestration of carbon the reactive behavior of supercritical co2 under conditions relevant to geologic storage and sequestration of c is largely unknown experiments were conducted in a flexible cell hydrothermal apparatus to determine the extent of fluid rock reactions in addition to carbonate mineral precipitation that may occur in a brine aquifer aquitard system that simulates a saline aquifer storage scenario the system was held at 200 c and 200 bars for 59 days 1413 h to approach steady state then injected with co2 and allowed to react for another 80 days 1924 h in addition to magnesite precipitation silicate minerals quartz plagioclase microcline and biotite in the aquifer and the aquitard display textures etch pits mineralization indicating significant reaction changes in elemental abundances in the brine following addition of co2 include ph decrease and enrichment in cl partly due to supercritical co2 desiccation of the brine geologic sequestration systems have potential for geochemical reactions that extend beyond simple aqueous dissolution of co2 and precipitation of carbonate these reactions may produce geochemical and geotechnical consequences for sequestration and provide important characteristics for monitoring and evaluation of stored co2 a n understanding of multi phase equilibrium relationships between supercritical co2 and aquifer brine systems also raises new questions for a variety of geologic systems multi phase fluid equilibria may for example account for the large amounts and heterogeneous distributions of calcite cement in a wide variety of geologic systems particularly in sedimentary basin sandstones published by elsevier science ltd

products and timing of diagenetic processes in upper rotliegend sandstones from bebertal north german basin parchim formation flechtingen high germany aeolian fluvial upper rotliegend sandstones from bebertal outcrops flechtingen high north germany are an analogue for deeply buried permian gas reservoir sandstones of the north german basin ngb we present a paragenetic sequence as well as thermochronological constraints to reconstruct the diagenetic evolution and to identify periods of enhanced mesodiagenetic fluid rock reactions in sandstones from the southern flank of the ngb bebertal sandstones show comparatively high concentrations of mesodiagenetically formed k feldspar but low concentrations of illite cements illite rich grain rims were found to occur preferentially directly below sedimentary bounding surfaces i e aeolian superimposition surfaces and indicate the lowest intergranular volume illite grain rims also indicate sandstone sections with low quartz and feldspar cement concentrations but high loss of intergranular volume due to compaction 40ar 39ar age determination of pronounced k feldspar grain overgrowths and replacements of detrital grains indicates two generations an early triassic and a late jurassic generation the latter age range is similar to published diagenetic illite ages from buried rotliegend reservoir sandstones the first generation suggests an early intense mesodiagenetic fluid flow with remarkably high k activity synchronous with fast burial of proximal initial graben sediments on the southern flank of the ngb accordingly zircon fission track data indicate that the strata already reached the zircon partial annealing zone of approximately 200 c during early mesodiagenesis zircon u th he ages 92 12 ma as well as apatite fission track ages 71 75 ma indicate the termination of mesodiagenetic processes caused by rapid exhumation of the flechtingen high during late cretaceous basin inversion

case history using time lapse vertical seismic profiling data to constrain velocity saturation relations the frio brine pilot co2 injection author s al hosni m caspari e pevzner r daley tm gurevich b abstract 2016 european association of geoscientists a engineers co2 sequestration projects benefit from quantitative assessment of saturation distribution and plume extent for field development and leakage prevention in this work we carry out quantitative analysis of time lapse seismic by using rock physics and seismic modelling tools we investigate the suitability of gassmann s equation for a co2 sequestration project with 1600 tons of co2 injected into high porosity brine saturated sandstone we analyze the observed time delays and amplitude changes in a time lapse vertical seismic profile dataset both reflected and transmitted waves are analyzed qualitatively and quantitatively to interpret the changes obtained from the vertical seismic profile we perform a 2 5d elastic finite difference modelling study the results show a p wave velocity reduction of 750 m s in the proximity of the injection well evident by the first arrivals travel time delays and amplitude change and reflected wave amplitude changes these results do not match with our rock physics model using gassmann s equation predictions even when taking uncertainty in co2 saturation and grain properties into account we find that time lapse vertical seismic profile data integrated with other information e g core and well log can be used to constrain the velocity saturation relation and verify the applicability of theoretical models such as gassmann s equation with considerable certainty the study shows that possible nonelastic factors are in play after co2 injection e g co2 brine rock interaction and pressure effect as gassmann s equation underestimated the velocity reduction in comparison with field data for all three sets of time lapse vertical seismic profile attributes our work shows the importance of data integration to validate the applicability of theoretical models such as gassmann s equation for quantitative analysis of time lapse seismic data

influence of localised igneous activity on cleat dawsonite formation in late permian coal measures upper hunter valley australia abstract stable 13 c and 18 o and radiogenic 87 sr 86 sr isotopic data have been used to investigate the origin of cleat dawsonite naalco 3 oh 2 in the late permian wittingham coal measures of the upper hunter region in the sydney basin new south wales the 13 c pdb values have a narrow range 1 7 to 2 4 with an average of 0 3 suggesting a magmatic source for the carbon in contrast 18 o smow values have a wide range 13 6 to 19 8 and decrease systematically with decreasing distance from a major intrusion this systematic variation reflects establishment of localised hydrothermal cells water rock interaction between fluids associated with these hydrothermal cells and rb poor volcaniclastic detritus in the coal measures produced mantle like 87 sr 86 sr 0 705032 to 0 706464 in the dawsonite

geochemical and geomechanical effects of scco2 and associated impurities on physical and petrophysical properties of permotriassic sandstones germany an experimental approach effects of impurities sox nox and o2 from the extraction processes of the power plants in the scco2 fluids are studied with an experimental approach combining geochemical alteration in high p medium t autoclaves compressional tests in a heated triaxial testing device as well as geochemical and mineralogical analyses before and after the influences of distinct scco2 fluids on 140 70 mm sized samples of reservoir sandstones from the north german basin with carbonate cementation silicate cementation and a combined silicate carbonate cementation on the background of variable lithological compositions the attempt was made to normalize the scattering geomechanical data by the pure co2 behavior measurement data to achieve a direct impression of any differences due to the impurities changes in the chemical composition of the saline fluids were systematically measured during the scco2 alteration experiments in the autoclave systems at distinct pt conditions the development of the silica concentrations and of the ph value in the fluid solution during alteration showed a clear dependency on the fluid composition through systematical analysis of changes on the mineral surfaces using sem microscopy images before and after scco2 impurities alteration experiments or triaxial compression tests corrosion effects were detected but no differences which could be directly related to differences in the fluid composition could be identified in all the types of sandstones visible or measurable changes on mineral surfaces and pore fluid composition respectively take place as an interaction of rock with fluids of scco2 with and without impurities changing deformability and compressive strength of the rocks are the most apparent consequences due to these compositional changes it is supposed that the chemical fluid differences are responsible for these changes also a specific distribution of the different fluids in the ambient pore space is indicated with even undetected consequences for the fluid influence on stress transmission and distribution within the grain structure all work was performed within the project co2 purity for capture and storage cooral supported by the german federal ministry for economic affairs and energy

effect of sub core scale heterogeneities on acoustic and electrical properties of a reservoir rock a co2 flooding experiment of brine saturated sandstone in a computed tomography scanner the effect of sub core scale heterogeneity on fluid distribution pattern and the electrical and acoustic properties of a typical reservoir rock was studied by performing drainage and imbibition flooding tests with co2 and brine in a laboratory moderately layered rothbach sandstone was used as a test specimen two core samples were drilled one perpendicular and the other parallel to the layering to allow injection of fluids along and normal to the bedding plane during the test 3d images of fluid distribution and saturation levels were mapped by an industrial x ray ct scanner together with simultaneous measurement of electrical resistivity ultrasonic velocities as well as amplitudes the results showed how the layering and the flooding direction influenced the fluid distribution pattern and the saturation level of the fluids for a given fluid saturation level the measured changes in the acoustic and electrical parameters were affected by both the fluid distribution pattern and the layering orientation relative to the measurement direction the p wave amplitude and the electrical resistivity were more sensitive to small changes in the fluid distribution patterns than the pwave velocity the change in amplitude was the most affected by the orientation of the layering and the resulting fluid distribution patterns in some instances the change due to the fluid distribution pattern was higher than the variation caused by the change in co2 saturation as a result the gassmann relation based on uniform or patchy saturation pattern was not suitable to predict the p wave velocity variation overall the results demonstrate the importance of core imaging to improve our understanding of fluid distribution patterns and the associated effects on measured rock physics properties

late cretaceous cenozoic evolution of the north german basin results from 3 d geodynamic modelling abstract the late cretaceous cenozoic evolution of the north german basin has been investigated by 3 d thermomechanical finite element modelling the model solves the equations of motion of an elasto visco plastic continuum representing the continental lithosphere it includes the variations of stress in time and space the thermal evolution surface processes and variations in global sea level the north german basin became inverted in the late cretaceous early cenozoic the inversion was most intense in the southern part of the basin i e in the lower saxony basin the flechtingen high and the harz the lower crustal properties vary across the north german basin north of the elbe line the lower crust is dense and has high seismic velocity compared to the lower crust south of the elbe line the lower crust with high density and high velocity is assumed to be strong lateral variations in lithospheric strength also arise from lateral variations in moho depth in areas where the moho is deep the upper mantle is warm and the lithosphere is thereby relatively weak compression of the lithosphere causes shortening thickening and surface uplift of relatively weak areas tectonic inversion occurs as zones of preexisting weakness are shortened and thickened in compression contemporaneously the margins of the weak zone subside cenozoic subsidence of the northern part of the north german basin is explained as a combination of thermal subsidence and a small amount of deformation and surface uplift during compression of the stronger crust in the north the modelled deformation patterns and resulting sediment isopachs correlate with observations from the area this verifies the usefulness and importance of thermomechanical models in the investigation of intraplate sedimentary basin formation

experimental evaluation of the impact of the interactions of co2 so2 brine and reservoir rock on petrophysical properties a case study from the ketzin test site germany the objective of this study is to evaluate the impact of impure co2 on a possible co2 repository here we present experimental data on the simulation of the injection of pure co2 and co2 and cocontaminant so2 into a saline aquifer long term exposure experiments with pure co2 reveal no significant changes in the petrophysical properties electrical resistivity elastic wave velocity and permeability in contrast for the injection of co2 and cocontaminant so2 1 vol we have observed significant and irreversible changes of all monitored physical parameters on the one hand the decrease of p wave velocity and the increase of electrical resistivity indicate a dissolution of some framework material on the other hand the decrease of permeability points to the mobilization and redistribution of fines these data might be relevant for subsequent modeling and estimations about tolerable concentration limits regarding the contaminants of co2 to be stored

numerical studies on co2 injection brine extraction process in a low medium temperature reservoir system co2 sequestration in deep saline formations has been proved to be an effective method for reducing greenhouse emissions into the atmosphere however pure sequestration of co2 will add to the costs incurred by both industries and governments a win win method of co2 injection and hot brine water extraction can become attractive to the investors as it will not only increase the storage capacity of the injected co2 but also offset the costs by selling and using the produced hot water for industrial agricultural or household purposes for instance water from very hot geothermal reservoirs t 150 c can be used for electricity generation in power plants and water from low medium temperature reservoirs the most predominant in natural systems are more popular for direct use e g in heating systems household hot water baths aquaculture etc in this paper low medium geothermal reservoirs widely distributed in china especially those in the ordos basin were selected for the numerical case studies using tough2mp with the eco2n module for the simulations generally simulation parameters were taken from the ordos basin where the first full integration co2 sequestration project had been operated since 2010 the simulations in the base case study lasted 35 years based on the lifespan of a normal geothermal project shallow re injection systems were also considered to investigate the influence of thermal breakthrough pressure perturbation etc results show that injection of cold co2 causes sharp decrease in temperature in the reservoir region near the injection well which is enlarged with continuous injection the region near the production well is dominated by different fluid phases during the co2 driven process including a single water phase a two phase fluid water and co2 and a phase of almost pure co2 results also show that the co2 breakthrough lags far behind the pressure response in the geothermal production system before breakthrough the injected co2 pressurizes the reservoir improving the overall performance of the geothermal reservoir furthermore the heat extraction efficiency of co2 based system is obviously higher than h2o based system

influence of rock failure behaviour on predictions in sand production problems the mechanical strength of rock in terms of shear or compressive failure has been previously adopted as a criterion for sand production and when used solely has been proven to overestimate the process on the other hand ignoring the mechanical strength behaviour of the material increases the tendency for inaccurate estimations of the erosion process in this work an equally proportionated inclusion of the mechanical strength and erosion based criteria in sanding predictions is proposed and assessed by numerical models several rock failure models and their influences on the sanding process have been analysed including models such as the drucker prager dp the drucker prager hardening dp hardening the mohr coulomb mc and the mohr coulomb softening mc softening modelling outcomes show distinct differences in rock response to operating and boundary conditions e g flow rate and drawdown and predictions of sand production it was confirmed by modelling results that despite the low magnitude of stresses and strains developed at the well face and perforation regions post yield hardening behaviour increases the estimation of the amount and intensity of sand production also incorporating a post yield softening behaviour increases the magnitude of stresses and strains however this effect is observed to have a negligible impact on sand production the role of void ratio has been recognised as a dominant factor as its evolution significantly determines the pattern and intensity of sand production a more cautious selection and rigorous coupling of rock strength models in sand production modelling is therefore essential if accuracy of predictions is to be improved

earthquake slip weakening and asperities explained by thermal pressurization for the earth s crust to release accumulated stress in the form of an earthquake a fault must weaken and give way otherwise the movement would quickly grind to a halt due to the surrounding pressure this weakening is not really understood laboratory experiments simply don t match seismologists estimates of the distance a fault must slip before it becomes very weak a new study concludes that the missing ingredient is water geological studies and measurements show the slip zones to be narrow impermeable structures water already in the fault zone can quickly become pressurized by frictional heating as the rocks start to move catalysing large earthquakes from minor movements an earthquake occurs when a fault weakens during the early portion of its slip at a faster rate than the release of tectonic stress driving the fault motion1 2 this slip weakening occurs over a critical distance dc understanding the controls on dc in nature is severely limited however because the physical mechanism of weakening is unconstrained conventional friction experiments typically conducted at slow slip rates and small displacements have obtained dc values that are orders of magnitude lower than values estimated from modelling seismological data for natural earthquakes3 4 5 6 here we present data on fluid transport properties of slip zone rocks and on the slip zone width in the centre of the median tectonic line fault zone japan we show that the discrepancy between laboratory and seismological results can be resolved if thermal pressurization of the pore fluid7 8 9 10 is the slip weakening mechanism our analysis indicates that a planar fault segment with an impermeable and narrow slip zone will become very unstable during slip and is likely to be the site of a seismic asperity

petrology and isotopic geochemistry of dawsonite bearing sandstones in hailaer basin northeastern china abstract the co2 gas reservoir sandstones in the hailaer basin contain abundant dawsonite and provide an ideal laboratory to study whether any genetic relationship exists between dawsonite and the modern gas phase of co2 the origins of dawsonite and co2 in these sandstones were studied by petrographic and isotopic analysis according to the paragenetic sequence of the sandstones dawsonite grew later than co2 charging at 110 85 ma the dawsonite 18o value is 7 4 smow and the calculated 18o values of the water present during dawsonite growth are from 11 4 to 9 2 smow this combined with the nahco3 dominated water linked to dawsonite growth suggests meteoric water being responsible for dawsonite growth the 13c values of gas phase co2 and the ratios of 3he 4he of the associated he suggest a mantle magmatic origin of co2 rich natural gas in hailaer basin dawsonite 13c values are 5 3 to 1 5 average 3 4 and the calculated 13c values of co2 gas in isotopic equilibrium with dawsonite are 11 4 to 7 3 these c isotopic values are ambiguous for the dawsonite c source from the geological context the timing of events together with formation water conditions for dawsonite growth dawsonite possibly grew in meteoric derived water atmospherically derived co2 maybe or at least the dominant c source for dawsonite it seems that there are few relationships between dawsonite and the modern gas phase of co2 in the hailaer basin

the petrophysical behaviour of crustal rocks under the influence of fluids abstract fluid phases of different composition have been found to be present ubiquitously in most crustal rocks down to deep levels in the lower crust they are stored either in isolated fluid inclusions within the mineral grains or in open and frequently interconnected cracks and fissures although the porosity of typical basement rocks usually is very small the presence or absence of fluids is found to be of paramount importance for rock strength and stability experiments of the triaxial deformation cell type were performed with two typical basement rocks a monzogranite and a two mica granite at a confining pressure of 55 mpa and deformation rates 10 7 s 1 at temperatures of 80 250 and 300 c respectively the rock samples were pressurized by fluid phases independent of the confining pressure fluids applied were pure h2o ar co2 compared to drained rock samples i e samples in which internal fluids could leave the rock specimen and the sample chamber during the experiment and no fluid pressure could build up the presence of fluids generally caused a strong reduction in rock strength internal fluid pressures up to 65 mpa independent of the fluid contents were controlled externally the mode of failure also changed sigificantly from a simple shear fracture in the fluid absent case to a subaxial multiple splitting mode when fluids were present the deformation style prior to brittle failure in the wet experiments shows a distinct phase of ductile yielding preceding it intergranular creep i e ductile mineral deformation sensu stricto has not been observed at this stage but change in the mineral fabric has been the interpretation of the brittle to ductile transition of rocks in the earth s crust has to take into account these influences exerted by fluid phases

continental scale magmatic carbon dioxide seepage recorded by dawsonite in the bowen gunnedah sydney basin system eastern australia abstract dawsonite naalco3 oh 2 is widespread as a cement replacement and cavity filling in permo triassic sedimentary rocks of the bowen gunnedah sydney basin system eastern australia the origin of dawsonite in these rocks was studied by petrographic and stable isotope analysis dawsonite d13c pdb values range from 4 0 to 4 1 and are remarkably consistent throughout the bowen gunnedah sydney basin system these values indicate either a marine carbonate or magmatic source for carbon in the dawsonite a magmatic carbon source is considered more likely on the basis that 1 evidence of and the cause for widespread marine carbonate dissolution in the sedimentary successions are not apparen 2 dawsonite is widespread in both marine and nonmarine facies 3 the region has been the site of major igneous activity 4 other dawsonite deposits of similar carbon isotopic composition are linked to igneous activity and 5 magmatic co2 accumulations are known in parts of the bowen gunnedah sydney basin system the timing of igneous activity in the bowen basin constrains the timing of dawsonite formation in the bowen gunnedah sydney basin system to the tertiary consistent with textural relationships which indicate that dawsonite formed late during the burial history of the permo triassic sequences the distribution and interpreted origin of dawsonite implies magmatic co2 seepage in the bowen gunnedah sydney basin system on a continental scale

geomechanical and geochemical effects on sandstones caused by the reaction with supercritical co2 an experimental approach to in situ conditions in deep geological reservoirs the geochemical and geomechanical behaviour of reservoir rocks from deep saline aquifers during the injection and geological storage of co2 is studied in laboratory experiments a combination of geochemical and geomechanical studies was carried out on various sandstones from the north german basin after the mineralogical geochemical and petrophysical characterization a set of sandstone samples was exposed to supercritical sc co2 and brine for 2 4 weeks in an autoclave system one sample was mineralogically and geochemically characterised and then loaded in a triaxial cell under in situ pressure and temperature conditions to study the changes of the geomechanical rock properties after treatment in the autoclaves geochemical alterations mainly in the carbonate but also in the sheet silicate cements as well as in single minerals of the sandstones were observed affecting the rocks granular structure in addition to partial solution effects during the geochemical experiments small grains of secondary carbonate and other mineral precipitations were observed within the pore space of the treated sandstones results of additional geomechanical experiments with untreated samples show that the rock strength is influenced by the saturation degree the confining pressure the pore fluid pressure and temperature the exposure to pure scco2 in the autoclave system induces reduced strength parameters modified elastic deformation behaviour and changes of the effective porosity in comparison to untreated sandstone samples experimental results show that the volume of pore fluid fluxing into the pore space of the sandstones clearly depends on the saturation level of the sample

active deformation in eastern indonesia and the philippines from gps and seismicity data in this study we combine global positioning system gps velocities with information on the style of regional seismicity to obtain a self consistent model velocity and strain rate field for the entire eastern indonesia and philippines region in the process of interpolating 93 previously published gps velocities the style and direction of the seismic strain rate field inferred from earthquakes with m0 1 1020 n m from the harvard centroid moment tensor catalog are used as constraints on the style and direction of model strain rates within the plate boundary zones the style and direction of the seismic strain rate field are found to be self similar for earthquakes up to m0 1 1020 n m equivalent to mw 7 3 our inversion result shows the following the java trench which lacks any significant historic seismicity delineates the australian plate au sunda block sunda plate boundary west of the island of sumba east of sumba convergence is distributed over the back arc and banda sea and there is no subduction at the timor trough suggesting that the northern boundary of the au plate runs north of this part of the banda arc through the banda sea in new guinea most motion is taken up as strike slip deformation in the northern part of the island delineating the pacific plate pa au boundary however some trench normal convergence is occurring at the new guinea trench evidence that the strain is partitioned in order to accommodate oblique pa au motion pa au motion is consistent with nuvel 1a direction but 8 mm yr 1 slower than the nuvel 1a estimate for pa au motion the sulawesi trench and molucca sea delineate zones of high strain rates consistent with high levels of active seismicity the sulawesi trench may take up some of the au sunda motion philippine sea plate motion is in a direction slightly northward of the nuvel ia estimate and is partitioned in some strike slip strain rates along the philippine fault and relatively larger trench normal convergence along the philippine trench and on the philippine mainland in the southern philippines and along the manila trench in the northern philippine islands the high level of strain rate along the manila trench is not released by any significant historic seismic activity for the entire eastern indonesia philippines region seismicity since 1963 has taken up 40 of the total moment rate inferred from our model

inversion related features along the southeastern margin of the north german basin elbe fault system abstract a seismostratigraphic approach constrained by well data is used for the interpretation of the deformation style along the central elbe fault system efs within the sedimentary succession structural analysis allows to qualify to quantify and to date tectonic events the stratigraphic interpretation is complicated by the mobilized upper permian zechstein salt and by erosional events a first order quantification of the inversion related uplift is estimated from vertical fault offsets that reach up to 4 km the main uplift occurred during the maastrichtian paleocene amounts of erosion inferred from comparing the strata thickness on top of the flechtingen high with the surrounding basinal areas range from 3 to 4 km the data indicate a changing deformation style thick skinned deformation with southwest dipping thrusts that vertically offset the pre permian basement is observed along the flechtingen high in the central part of the efs thin skinned deformation occurs in the north german basin where salt detaches the post permian cover from the barely faulted basement it is concluded that during the late cretaceous early tertiary inversion the efs responded to regional compression with uplift and formation of an internal high the flechtingen high a stress sensitive crustal weak zone beneath the efs could be the reason for the repeated strain localization in the area

evolution of shear bands and cracks in multi stage triaxial tests with water saturated sandstone a study of micro tectonics with a fractal perspective abstract a series of multi stage triaxial compression tests revealed quite chaotic reactions of water saturated permotriassic sandstones on changing pore water pressures not before focussing the various test stages with respect to occurring critical phenomena which strike the fabric structures due to their fractal nature during any triaxial testing eventually an approach became tractable pore systems with cracks and shear bands can be widened in a quasi static way but only up to a stability limit thereafter the fabric collapses with a seismogenic contraction of the pore system causing a rise of the pore water pressure changes of structural patterns occur as formation either of fissures up to collapse with acoustic emission or of a rather fractal pattern of crossing shear bands generated without audible noise but with fine grit due to comminution dilation and contraction of the pore system are visible from overall volume changes both modes of pattern formation can be understood as critical phenomena of the mineral solid scale independent features of these changes of fabric patterns can be transferred to the meso and macro scales in the field and in the lithosphere respectively however questions of scale dependent features related to cohesion should be further investigated