paraburdoo spherule layer hamersley basin western australia distal ejecta from a fourth large impact near the archean proterozoic boundary we report the discovery of the paraburdoo spherule layer which consists entirely of replaced impact produced melt spherules it is distal ejecta from a large impact close to the archean proterozoic boundary in the hamersley basin of western australia the spherule layer occurs in the paraburdoo member of the wittenoom formation and was deposited ca 2 57 ga date via u pb age interpolation in a deep shelf environment the layer consists of microkrystites rich in plagioclase and ferromagnesian crystals replaced by k feldspar and a phlogopite like sheet silicate respectively the skeletal textures indicate rapid cooling of a melt with mafic to ultramafic composition and suggest oceanic target rocks the paraburdoo spherule layer is 2 cm thick normally graded and was probably deposited by suspension settling as there is no evidence of reworking it is strikingly similar to the reivilo spherule layer in the griqualand west basin south africa appears to provide a third impact related high resolution stratigraphic correlation between these two basins and points to a high frequency of large impacts around the archean proterozoic boundary

extracting source characteristics and dynamics of the august 2010 mount meager landslide from broadband seismograms 1 seismic methods can substantially improve the characterization of the dynamics of large and rapid landslides such landslides often generate strong long period seismic waves due to the large scale acceleration of the entire landslide mass which according to theory can be approximated as a single force mechanism at long wavelengths i apply this theory and invert the long period seismic waves generated by the 48 5 mm3 august 2010 mount meager rockslide debris flow in british columbia using data from five broadband seismic stations 70 to 276 km from the source i obtain a time series of forces the landslide exerted on the earth with peak forces of 1 0 1011 n the direction and amplitude of the forces can be used to determine the timing and occurrence of events and subevents using this result in combination with other field and geospatial evidence i calculate an average horizontal acceleration of the rockslide of 0 39 m s2 and an average apparent coefficient of basal friction of 0 38 0 02 which suggests elevated basal fluid pressures the direction and timing of the strongest forces are consistent with the centripetal acceleration of the debris flow around corners in its path i use this correlation to estimate speeds which peak at 92 m s this study demonstrates that the time series recording of forces exerted by a large and rapid landslide derived remotely from seismic records can be used to tie post slide evidence to what actually occurred during the event and can serve to validate numerical models and theoretical methods

numerical modeling of the mount meager landslide constrained by its force history derived from seismic data we focus on the 6 august 2010 mount meager landslide that occurred in southwest british columbia canada this 48 5 mm3 rockslide that rapidly changed into a debris flow was recorded by over 25 broadband seismic stations we showed that the waveform inversion of the seismic signal making it possible to calculate the time history of the force applied by the landslide to the ground is very robust and stable even when using only data from a single station by comparing this force with the force calculated through numerical modeling of the landslide we are able to support the interpretation of seismic data made using a simple block model however our study gives different values of the friction coefficients involved and more details about the volumes and orientation of the subevents and the flow trajectory and velocity our sensitivity analysis shows that the characteristics of the released mass and the friction coefficients all contribute to the amplitude and the phase of the force despite this complexity our study makes it possible to discriminate the best values of all these parameters our results suggest that comparing simulated and inverted forces helps to identify appropriate rheological laws for natural flows we also show that except for the initial collapse peaks in the low frequency force related to bends and runup over topography changes are associated with high frequency generation possibly due to an increased agitation of the granular material involved

response of shallow marine carbonate facies to third order and high frequency sea level fluctuations hauptrogenstein formation northern switzerland abstract facies patterns in shallow marine carbonates of the hauptrogenstein formation of northern switzerland middle bajocian to early bathonian reflect small changes in sea level third order sea level fluctuations calculated from large scale facies patterns alternations of marl and carbonate dominated sedimentary units on the level of members and subsidence show two phases of sea level rise and fall in the late bajocian and a relative sea level rise in the early bathonian most of the sedimentary rocks were produced during phases of relative rise and highstand of sea level no periods of emergence during lowstands are preserved sea level changes of a higher order have been analyzed by facies changes at the outcrop scale thin shallowing up parasequences 0 5 6 m thick have been correlated across platform ramp and offshore sedimentary environments in each of these environments carbonates react differently to sea level fluctuations relative rises in sea level are represented by non deposition and biogenic sediments periods of stable or slightly falling sea level are dominated by oolitic sediments 1 in the offshoal environment marl layers at the base of thin shallowing up units are covered by increasingly proximal tempestites 2 in the ramp environment oblique stratified oolitic and bioclastic grainstones are bounded by marine flooding surfaces 3 on the platform marine flooding surfaces are overlain by beds deposited under moderate energy conditions coral beds oncoid beds platform tempestites which are in turn covered by high energy oblique stratified oolitic grainstones such parasequences deposited in response to small scale high frequency sea level changes can be correlated over distances of more than 100 km a model for evolution and response of carbonate facies to sea level changes is presented

deposition and textural evolution of cool water limestones outcrop analog for reservoir potential in cross bedded calcitic reservoirs the eocene miocene te kuiti group is a succession of cool water carbonate and siliciclastic rocks on the north island of new zealand the limestones are subtidal bioclastic and largely composed of bryozoans echinoderms and benthic foraminifers these rocks can be divided into a horizontally bedded facies assemblage and a cross bedded facies assemblage the horizontally bedded facies assemblage represents deposition on a wave storm dominated shelf and is composed of grainstones and packstones containing textures resulting from biologic processes the cross bedded facies assemblage represents deposition on a current dominated shelf and consists of grainstones with textures formed chiefly by physical processes the te kuiti group can be used as an outcrop analog for cross bedded calcite dominated hydrocarbon reservoirs porosity permeability and reservoir potential of the horizontally bedded facies assemblage decreased rapidly during late shallow burial owing to mechanical compaction and to the fine grain size close packing and ineffective early cementation of the rock coarser grain size open framework and earlier cementation within the cross bedded facies assemblage resulted in significant heterogeneity and good reservoir potential before moderate burial tabular lens shaped and sigmoidal reservoir units are proposed primary porosity and early developed traps are essential to reservoirs formed of cool water limestones and those carbonates from calcite seas the influence of depositional setting extends into the eventual bedding style texture physical properties and reservoir potential of the rock

the relationship between bulk mass momentum and short period seismic radiation in catastrophic landslides the relationship between bulk mass dynamic properties of catastrophic landslides and the generation of short period seismic waves is investigated with a particular focus on the momentum of the landslide mass and the envelope of high frequency seismograms twelve very large landslides that occurred in different geological settings worldwide between 1999 and 2014 are selected for study based on the existence of detailed descriptions of their force histories determined from long period seismic waves frequency lower than 0 1 hz as well as the availability of nearby high quality short period seismic recordings a high average correlation 0 94 is found between the modulus of the landslide momentum and the envelope of the high frequency seismograms band passed filtered between 3 and 10 hz recorded on nearby stations the best correlation is seen during the acceleration phase of each landslide comparatively poor average correlation 0 57 is found between the modulus of the landslide force and the seismogram envelopes a possible scaling between the momentum and the amplitude of short period radiation is investigated the maximum amplitudes of short period seismograms for the nine best recorded landslides are corrected for local attenuation and correlated with the maximum momentum of the landslides the nine data points scatter around a best fitting line that defines a nearly linear relationship between momentum and peak short period radiation it is hypothesized that bulk mass momentum linearly modulates landslide processes that generate short period seismic waves but that the efficiency of short period radiation is highly variable between landslides

development of microporosity in a micritic limestone reservoir lower cretaceous middle east abstract abundant intercrystalline microporosity is developed within the matrix of micritic limestones over several hundreds of meters of section in the thamama group lower cretaceous at sajaa field eastern u a e sediments in the upper shuaiba formation uppermost tamama group include muddy rudist algal coralgal and orbitolina dominated lithofacies matrix is composed of euhedral to subhedral micro rhombic low mg calcite crystals with average diameters of about 5 m microporosity development was not related to leaching chalkification of lithified micrite during post depositional emergence of the shuaiba formation features diagnostic of emergence are lacking in core below the upper contact of the unit matrix microporosity is believed to have been an early developed property of micritic limestones trace element compositions of matrix reflect a diagenetic process that involved conversion of a calcitic lime mud into micro rhombic micrite and microspar using a closed system geochemical model the observed matrix oxygen isotope compositions 18 o of 4 to 5 pdb are compatible with dissolution of aptian lime mud 18 o of 2 pdb and reprecipitation of calcite in fluids of marine composition under conditions corresponding to burial depths of 550 800 m porosity of 30 50 at 40 50 c closed system conditions are consistent with textural constraints for limited or arrested cementation in the matrix chemical compaction was responsible for partial occlusion of matrix microporosity as microporosity is decreased in zones of intense stylolitization slight corrosion of matrix crystals and leaching of peloids and orbitolina postdated cementation and chemical compaction during deep burial

dynamics of the bingham canyon mine landslides from seismic signal analysis joint interpretation of long and short period seismic signals generated by landslides sheds light on the dynamics of slope failure providing constraints on landslide initiation and termination and on the main phases of acceleration and deceleration we carry out a combined analysis of the seismic signals generated by two massive landslides that struck the bingham canyon mine pit on 10 april 2013 inversion of the long period waveforms yields time series for the bulk landslide forces and momenta from which we deduce runout trajectories consistent with the deposit morphology comparing these time series with the short period seismic data we are able to infer when and where major changes take place in landslide momentum along the runout path this combined analysis points to a progressive fracturing of the masses during acceleration indicates that deceleration starts the moment they reach the pit floor and suggests that the bulk movement is stopped by a topographic barrier

complex force history of a calving generated glacial earthquake derived from broadband seismic inversion the force applied to the earth by the calving of two icebergs at jakobshavn isbrae greenland has been quantified the source force history was recovered by inversion of regional broadband seismograms without any a priori constraint on the source time function in contrast with previous studies for periods 10 100 s the three component force can be obtained from distant stations alone and is proportional to the closest station seismograms this inversion makes it possible to quantify changes of the source force direction and amplitude as a function of time and frequency a detailed comparison with a video of the event was used to identify four forces associated with collision then bottom out and top out rotation of the first and second icebergs and ice melange motion only the two iceberg rotations were identified in previous studies all four processes are found here to contribute to the force amplitude and variability such a complete time frequency force history provides unique dynamical constraints for mechanical calving models

controls on sonic velocity in carbonates compressional and shear wave velocities v p and v s of 210 minicores of carbonates from different areas and ages were measured under variable confining and pore fluid pressures the lithologies of the samples range from unconsolidated carbonate mud to completely lithified limestones the velocity measurements enable us to relate velocity variations in carbonates to factors such as mineralogy porosity pore types and density and to quantify the velocity effects of compaction and other diagenetic alterations

seismic modeling of an early jurassic drowned carbonate platform djebel bou dahar high atlas morocco 1 along the southern margin of the high atlas of morocco early jurassic carbonate platforms developed in a transtensional rifted basin one of these platforms was the djebel bou dahar platform which grew to a vertical relief of 500 m drowned and was onlapped by deep marine sediments exceptional outcrops allowed detailed lithologic models of the platform to be made with a resolution of a few meters we constructed a geometric model from building blocks comprising particular rock types we estimated p wave velocities and bulk densities of these lithologies from hand specimens and we assumed these properties to be homogeneous and invariant throughout the building blocks we constructed time sections of reflectivity from vertical incidence and image ray migration techniques these time sections were convolved with 25 to 200 hz ricker wavelets to produce synthetic seismic sections large scale features such as the platform and the drowning unconformity were resolved regardless of the frequencies and modeling techniques used broad low frequency wavelets resulted in profiles with apparent truncation of bedding and basinward shifts in the point of onlap smaller scale features such as reef knolls and sand bodies at the platform margin were poorly resolved at frequencies up to 50 hz however we inferred the existence and location of these smaller features from the disturbance and distortion of other reflections this distortion is most obvious in image ray migration modeling because of the refraction of rays through the small scale features geometric effects caused lateral amplitude variations due to wavelet interference along the unconformity reflection where no petrophysical changes were modeled the seismic models of the djebel bou dahar in its present stage may be good analogs for seismic lines of deeply buried carbonate platforms to make a comparison with real seismic lines of less deeply buried platforms possible we reconstructed both the geometry and petrophysical properties and the subsequent seismic modeling of the djebel bou dahar carbonate platform as it was prior to the onset of deep burial at this stage impedance contrasts were at their maximum this study clearly demonstrates the significance of modeling the seismic response of a detailed outcrop based stratigraphic model and shows that seismic modeling of specific sequence stratigraphy can reveal what features are likely to be resolved under ideal conditions and what pitfalls may await the interpreter

quantitative characterization of carbonate pore systems by digital image analysis a new method of digital image analysis can quantify pore parameters over more than three orders of magnitude from a submicron to a millimeter scale this porosity characterization does not require knowledge of lithology age burial depth or diagenesis of the sample the method is based on digital analyses of images from thin sections at variable magnifications taken under an optical microscope om and under an environmental scanning electron microscope esem the results help explain variations in permeability for carbonate samples with a variety of complex pore structures the analyses however can be done on any thin sections of other rock types the om images provide macroporosity information whereas the esem images yield information on microporosity the boundary between macroporosity and microporosity is defined at a pore area of 500 m2 which translates to a pore length of approximately 20 m which is roughly the thickness of a thin section and thus the resolution of the om the digitized thin section images are binarized into a macropore and a matrix phase om or a micropore and a solid phase esem a standard digital image analysis program is used to detect all individual pores and to measure pore area and pore perimeter based on these analyses one can calculate for each sample the amount of macroporosity the amount of microporosity within the matrix intrinsic microporosity the shapes of the macropores perimeter over area and the pore size distribution comparison of total porosity determined from plugs indicates that macroporosity and microporosity values based on this methodology match the plug data confirming the validity of the method the combination of macroporosity and microporosity data yields pore size distribution and pore shape information that can explain the distribution of physical properties in particular permeability in parameter sensitivity analyses using neural networks permeability appears to be mainly controlled by the macropore shape in high permeability samples and by the amount of intrinsic microporosity in the low permeability samples

petrophysical properties of bioclastic platform carbonates implications for porosity controls during burial abstract this study is based on rock mechanical tests of samples from platform carbonate strata to document their petrophysical properties and determine their potential for porosity loss by mechanical compaction sixteen core plug samples including eleven limestones and five dolostones from miocene carbonate platforms on the marion plateau offshore northeast australia were tested at vertical effective stress 1 of 0 70 mpa as lateral strain was kept equal to zero the samples were deposited as bioclastic facies in platform top settings having paleo water depths of 1 50 mpa whereas six samples tested saturated with brine under drained conditions had up to 0 33 strain the yield strength was reached in five of the plugs the measured strains show an overall positive correlation with porosity vp ranges from 3640 to 5660 m s and vs from 1840 to 3530 m s poisson coefficient is 0 20 0 33 and young s modulus at 30 mpa ranged between 5 and 40 gpa water saturated samples had lower shear moduli and slightly higher p to s wave velocity ratios creep at constant stress was observed only in samples affected by pore collapse indicating propagation of microcracks although deposited as loose carbonate sand and mud the studied carbonates acquired reef like petrophysical properties by early calcite and dolomite cementation the small strains observed experimentally at 50 mpa indicate that little mechanical compaction would occur at deeper burial however as these rocks are unlikely to preserve their present high porosities to 4 5 km depth further porosity loss would proceed mainly by chemical compaction and cementation

geochemical indicators of depositional and early diagenetic facies in holocene carbonate muds and their preservation potential during stabilisation holocene carbonate muds 63 m fraction and macro organic matter were collected from marine subtidal mudbanks and supralittoral mud islands of florida bay and freshwater marshes of the florida everglades u s a geochemistry sedimentology and mineralogy were used to determine whether carbonate mud formation in specific marine and freshwater environments was geochemically distinct and to assess the importance of early diagenetic reactions on mud chemistry and mineralogy significant variations were found in the relative amounts of carbonate minerals not just between the marine and freshwater environments but also within florida bay in particular mg calcite is enriched in crane key muds by 10 relative to nearby cross bank the mg calcite appears to precipitate in the surface living cyanobacterial mats of the key and seems to be linked to mg chelation by the cyanobacterial organic matter this mg calcite has a distinct 13c around 4 6 lighter than mg calcite derived from thalassia epibionts in the cross bank muds dolomite was found just below the cyanobacterial mats forming in the only part of the core where reactive organic carbon has been completely removed by sulphate reducing bacteria the 13c values of this dolomite at least 4 are consistent with previously published 13c values of dissolved inorganic carbon in pore waters at this horizon which support dolomite formation in situ mg supply for dolomite formation may be from dissolution of the overlying cyanobacterial mat mg calcite the various types of organic matter have distinctive 13c values ranging from 25 mangrove and sawgrass to 10 cyanobacterial mats and 8 thalassia seagrass values intermediate between these end members record mixing of the organic matter types which shows particularly the time when the bank muds became dominated by thalassia organic matter i e were relatively removed from mangrove vegetation five holocene mud suites bank key cyanobacterial mats mangrove swamp and freshwater everglades swamp show distinct chemical signatures in their mean 13c 18o mgco3 and sr values na distinguishes between seawater and non seawater influenced environments but fe mn and p are mainly controlled by non carbonate materials comparison with published stable isotope and elemental data for pleistocene limestones in the south florida area suggests that only the facies diagnostic signatures of 13c and mg will be resolvable once the muds have been stabilised to micrite alteration of the 18o and sr values during stabilisation will probably be more severe to the extent that original facies variations are destroyed

centroid single force inversion of seismic waves generated by landslides the centroid moment tensor cmt waveform inversion method of dziewonski et al 1981 is modified to analyze long period seismic waves generated by single force events such as the gigantic landslides associated with the 1980 eruption of mount st helens we refer to the method as centroid single force csf inversion as the result of the inversion we obtain the spatio temporal centroid and three components of a vector we call the csf vector which is the seismic point source representation of a landslide and whose direction is the opposite of the direction of sliding the sealer magnitude of the csf vector measures the overall size of the landslide and is given by mcsf md where m is the mass of the sliding object and d is the sliding distance we apply csf inversion to the long period surface waves generated by the 1980 mount st helens event the 1975 kalapana earthquake and the 1974 mantaro landslide using seismograms from the gdsn ida and hglp networks the csf solution for the st helens event is remarkably consistent with the actual geological observations and proves the efficacy of csf inversion the csf solution for the kalapana event does not fit the overall waveforms better than the cmt solution does however because the cmt solution does not explain the observed love wave radiation pattern it may be necessary to invoke a combination of both types of mechanism for this event although the geometry of the csf solution the direction of the force for the mantaro event is consistent with the actual landslide mcsf is about 5 times smaller than that expected from the mass and travel distance of the landslide estimated by geological observations this discrepancy may suggest either the relatively aseismic nature of this landslide or that the total volume of the slide was overestimated by analogy to single station cmt inversion single station csf inversion also appears to be stable and useful

analysis of long period seismic waves excited by the may 18 1980 eruption of mount st helens a terrestrial monopole long period 100 to 260 s love and rayleigh waves excited by the eruption of mount st helens on may 18 1980 and recorded by ida sro and asro stations were analyzed to determine the mechanism of the eruption the amplitude radiation patterns of both rayleigh and love waves are two lobed with a nodal direction in e5 s for rayleigh waves and in n5 e for love waves these radiation patterns preclude any double couple mechanism the radiation pattern the initial phase the relatively large amplitude ratio of love to rayleigh waves and the existence of clear nodes in the radiation patterns of fundamental mode and higher mode rayleigh waves suggest that the source is represented by an almost horizontal less than 15 from the horizontal single force pointed toward s5 w the surface wave spectra fall off very rapidly at periods shorter than 75 s suggesting a very slow source process although the details of the source time history could not be determined a smooth bell shaped time function f o s t 1 2 f o l cos t for 0 t 2 and f o s t 0 for t 2 with 75 s is considered appropriate on the basis of comparison between synthetic and observed seismograms and of the shape of the source spectrum the peak value of the force f 0 is about 10 18 dynes the tailing end of the source time function could not be resolved and some overshoot may be added the magnitude and the time history of the force can be explained by a northward landslide followed by a lateral blast observed at the time of the eruption two distinct events about 110 s apart can be identified on body wave and short period surface wave records the first event may correspond to the earthquake which triggered the landslide and the lateral blast the second event appears to correspond to a second large earthquake and explosion which took place about 2 minutes after the first earthquake

friction weakening in granular flows deduced from seismic records at the soufriere hills volcano montserrat accurate modeling of rockfalls and pyroclastic flows is still an open issue partly due to a lack of measurements related to their dynamics using seismic data from the soufriere hills volcano montserrat and granular flow modeling we show that the power laws relating the seismic energy e s to the seismic duration t s and relating the loss of potential energy e p to the flow duration t f are very similar like the power laws observed at piton de la fournaise reunion island observations showing that t f t s suggest a constant ratio e s e p 10 5 this similarity in these two power laws can be obtained only when the granular flow model uses a friction coefficient that decreases with the volume transported furthermore with this volume dependent friction coefficient the simulated force applied by the flow to the ground correlates well with the seismic energy highlighting the signature of this friction weakening effect in seismic data

porosity loss fluid flow and mass transfer in limestone reservoirs application to the upper jurassic smackover formation mississippi ooid grainstones of the upper jurassic smack over formation are buried to a depth of over 6 km and exposed to temperatures in excess of 200 c at black creek field mississippi combined effects of mechanical compaction intergranular pressure solution and cementation have reduced intergranular porosity of these ooid grainstones to 0 indicating that porosity reduction has gone to completion modal analysis of 24 samples lacking preburial cements indicates that from the original 40 porosity 13 porosity units range 4 to 21 were lost by mechanical compaction 15 porosity units range 8 to 23 were reduced by intergranular pressure solution and 12 porosity units range 1 to 26 were destroyed by cementation intergranular pressure solution caused an average of 28 range 15 to 51 vertical shortening in smackover ooid grainstones under ideal conditions the 28 vertical shortening will generate enough calcium carbonate to precipitate 10 calcite cement this is close to the measured volume of cements in smackover grainstones 12 suggesting that intergranular pressure solution provided most of the calcite cement present no external sources of calcium carbonate are required fine grained samples that experienced high degrees of intergranular pressure solution and contain only small amounts of cement occur at the top of the reservoir whereas coarse grained samples with abundant cement and low degrees of pressure solution occur in the middle and basal parts of the reservoir suggesting that the fine grained intervals acted as sources and the coarse grained intervals as sinks for calcium carbonate mass transfer of pressure solution generated calcium carbonate from the top of the unit to precipitation sites in the middle and basal parts of the reservoir could have occurred by a non rayleigh type convection cell due to calcite s reverse solubility with respect to temperature the cooling upward moving limb of the convection cell would become progressively more undersaturated and hence able to transport more dissolved calcium carbonate released by intergranular pressure solution in the upper portion of the reservoir pore fluids descending in the downward moving limb of the cell would become progressively more supersaturated and calcium carbonate would tend to precipitate as cement in the middle and basal parts of the reservoir as fluids become progressively hotter

seismic signals associated with landslides and with a tsunami at stromboli volcano italy in this article we analyze the seismic signals produced by two landslides that occurred at the stromboli volcano on 30 december 2002 recorded by both broadband and short period seismic stations located in the 2 5 22 km distance range from the source for both landslides the characteristics of the low frequency seismograms indicate a complex time history in the release of seismic energy the first landslide occurred over the submerged part of the northwest sector of the volcano and had associated a large amplitude low frequency pulse representative of the abrupt detachment of a large mass lower amplitude phases in the following 3 minutes possibly indicate minor detachment events the highest amplitude low frequency signals are well described by a single force source model the second mass failure episode is also characterized by a complex source and can be interpreted as a multiple event with a less abrupt onset and at least four detachments occurring during 4 5 minutes and producing low frequency signals synthetic seismograms generated by a shallow single force located in the submerged area of sciara del fuoco and directed upslope fit well the first low frequency seismic pulse recorded at stromboli and panarea by three component stations from this simulation we estimated the force exerted by the first mass failure the estimate of the volume through two different procedures gives values in the range of 1 0 1 5 million m3 and about 14 million m3 respectively the landslides which involved both the submarine and the subaerial northwest flank of the volcano produced a tsunami that struck the coast of stromboli island and in a few minutes reached the other islands of the aeolian archipelago three broadband seismic stations installed on land about 100 m from the coastline at panarea island located 20 km southwest of stromboli recorded very long period seismic signals produced by the tsunami waves analysis of these signals gives invaluable information on the spectral content and propagation properties of tsunami waves and on their interaction with the ground at a short distance from the coast synthetic tsunami waves obtained by a landslide source model and taking into account the bathymetry of the sea surrounding stromboli and panarea islands fit the observed phenomena and the experimental data very well manuscript received 19 november 2003

numerical modeling of the mount steller landslide flow history and of the generated long period seismic waves the rock ice avalanche that occurred in 2005 on mount steller alaska and the resulting long period seismic waves have been simulated for different avalanche scenarios i e flow histories with and without erosion processes taken into account this 40 60 mm3 avalanche traveled about 10 km down the slope mainly on top of a glacier eroding a significant amount of ice it was recorded by 7 broadband seismic stations the simulations were compared with the recorded long period seismic signal and with the inverted flow history the results show that when erosion processes are taken into account the simulations reproduce the observed signal at all the stations over a wide range of azimuths and source station distances 37 623 km this comparison makes it possible to constrain the rheological parameters involved which should help constrain the volume of eroded material because landslides are continuously recorded by seismic networks this method could significantly broaden quantitative insights into natural flow dynamics

contrasting diagenetic evolution patterns of platform margin limestones and dolostones in the lower triassic feixianguan formation sichuan basin china abstract deeply buried carbonate reservoirs from the lower triassic feixianguan formation in the sichuan basin of china host extensive natural gas resources these reservoirs are predominantly found in oolitic shoals with the reservoir quality of dolomitized zones being higher than that of undolomitized limestone counterparts here we present a combination of petrographic isotopic fluid inclusion and quantitative porosity data in order to understand and predict the diagenetic processes that have impacted the reservoir quality of dolostones and limestones the porosity of limestones has been reduced to 7 5 due to calcite cementation whereas the porosity in oolitic dolostones is not cemented with calcite and typically has 23 5 porosity dolomitization and concurrent early diagenetic gypsum growth played crucial roles on the development and preservation of high porosity in the oolitic dolostone first by stabilizing the rock fabric to inhibit loss of porosity during burial and secondly through the generation of new porosity by dissolution of carbonate and anhydrite a negative shift of 18 o and salinity values 13 c values 20 vpdb and 18 o 10 vpdb together with elevated calcite precipitation temperatures 110 c it is likely that tsr was responsible for the formation of enlarged dissolution vugs that increased porosity by 2 in dolostones due to i anhydrite dissolution ii production of significant amounts of water resulting in formation water undersaturated with respect to calcite and dolomite iii generation of h 2 s and co 2 and the consequent reaction of h 2 s with the siderite feco 3 component in calcite and dolomite this study demonstrates the importance of diagenesis in the formation of deeply buried high quality reservoirs in ooid dominated grainstones influenced by the presence of evaporites our results should be useful for guiding future exploration and reservoir developments in similar paleogeographic and diagenetic settings

depositional environment diagenetic evolution and their impact on the reservoir quality of the carboniferous kt ii carbonate in the zhanazhol reservoir pre caspian basin kazakhstan abstract the carboniferous kt carbonate unit late serpukhovain to early moscovian of the zhanazhol reservoir in the pre caspian basin is a giant condensate reservoir with great heterogeneity although the depositional characteristics and their impact on reservoir quality have been well documented by previous studies few studies have focused on diagenesis the interplay between depositional environment and their controls on reservoir heterogeneity in this study combining sedimentological petrographic and geochemical analyses we reconstructed the depositional settings and diagenetic history of the kt carbonate and assess their impacts on reservoir quality according to the vertical and lateral distribution of 12 observed microfacies types we proposed a depositional model of a northward deepening ramp consisting of tidal flat inner ramp and middle ramp which has played a critical role in controlling the reservoir quality mainly through grain types and matrix content fusulinidal grainstones packstones have the best reservoir quality because of its porous fusulinidal fragments and low micritic matrix content the major diagenetic events including cementation eight cement types dissolution fabric and non fabric selective dissolution compaction pressure dissolution and microfracturing early and late were grouped into six diagenetic environments marine meteoric shallow burial epigenic karstification intermediate burial and deep burial marine cementation and compaction are the main reason for porosity decreasing in upper inner ramp and middle ramp respectively the minor moldic pores created by fabric selective dissolution during meteoric stage were enlarged by freshwater leaching during epigenic karstification and its associated cementation occluded pores in the underlying bioclastic grainstones packstones late non fabric selective dissolution and cementation likely resulted in local porosity rearrangements without net porosity gain or loss but certainly reduced reservoir heterogeneity the interaction between depositional environment and diagenetic evolution played a vital role in the formation of two types of vertical distribution patterns of porosity types and understanding this interaction and its impacts on reservoir quality within a sequence stratigraphic framework can more reliably predict the distribution of reservoir properties and provides insights for adjacent fields with similar settings

detection of landslides and submarine slumps using broadband seismic networks 1 we detected 52 seismic events associated with landslides and submarine slumps on 8 august 2009 when typhoon morakot hit taiwan these events were neither felt nor reported because their seismic energy was primarily in the long period band 20 50 s most of these events were located in mountain areas where the accumulated rainfall was extremely high though some were found offshore southern taiwan among all events the fatal landslide earthquake was located at hsiaolin village where 474 people were buried inversion modelling of the seismic waveforms generated by the hsiaolin landslide shows that the seismic source was represented by single force consistent with downhill sliding some offshore seismic events indicate that submarine slumps probably occurred along submarine canyons and steep slopes our study shows that broadband seismic monitoring can be used to issue early warnings for mitigating disasters generated by inland and offshore landslides

distribution of porosity and permeability in platform dolomites insight from the permian of west texas saller and henderson 1998 presented an article concerning porosity and permeability variations in two west texas oil fields north riley and south cowden fields these fields occur within dolomitized permian platform carbonates near the basinward shelf edge of the central basin platform a paleogeographic element that influenced permian deposition in west texas their carefully documented study outlines several anomalous aspects concerning porosity distribution they noted in particular that porosity distribution is not strictly facies dependent but that porosity tends to increase in a basinward direction they suggested that porosity developed largely during dolomitization by the action of hypersaline evaporative fluids that flowed downdip in a basinward direction during the permian these brines were generated in restricted shelf interior lagoons and moved downdip parallel with bedding in a shallow reflux type of hydrologic system driven by subsurface fluid density differences in the permian clear fork and grayburg formations as shown here in figure 1 see figure 18 in saller and henderson 1998 figure 1 part a shows the scenario proposed by saller and henderson 1998 for porosity creation dolomitization and dolomite cementation of the permian clear fork and grayburg formations of west texas they suggested that macrodissolution of calcium carbonate occurred contemporaneously with dolomitization and dolomite cementation this process of brine backreaction however would cause a net increase of porosity in the shelf interior the opposite of what is observed part b shows a two stage scenario proposed here to circumvent the problem of limestone macrodissolution by shelf interior brines that must have been initially in approximate bulk equilibrium with calcium carbonate the first stage records dolomitization by replacement of limestone with little macrodissolution in stage two evaporative shelf interior brines may have evolved in equilibrium with dolomite only and became undersaturated with calcite and aragonite reflux migration of these brines downdip may

pore networks in holocene carbonate sediments abstract permeabilities of holocene carbonate sediments from florida and the bahamas determined for 74 samples by water flow rates in a variable head permeameter range from 0 6 to 57 000 millidarcies porosities range from 40 to 78 percent these parameters are related to depositional texture as follows table the muddiest sediments i e the finest grained have the highest porosities but lowest permeabilities this negative correlation between porosity and permeability is the reverse of the situation found in carbonate rocks even as young as pleistocene high porosity and low permeability in sediments show a strong correlation with percentage of fines 62 m from capillary pressure curves it is inferred that many of the pore throats of muddy carbonate sediments are less than 1 m in diameter at least after drying measured permeabilities are used to calculate cementation rates for simple models of upper phreatic zone cementation the calculated rates would require excessive time to produce the degree of cementation seen in late pleistocene rocks of florida and the bahamas the amounts of rainfall and evaporation are the most important factors in the degree of cementation

dynamic landslide processes revealed by broadband seismic records 1 we use broadband seismic recordings to trace the dynamic process of the deep seated akatani landslide that occurred on the kii peninsula japan which is one of the best recorded large slope failures combining analyses of the seismic records with precise topographic surveys done before and after the event we can resolve a detailed time history of the mass movement during 50 s of the large landslide we observe a smooth initiation acceleration with changes in basal friction and reversal of the momentum when the mass collides with the opposite valley wall of particular importance is the determination of the dynamic friction during the landslide the coefficient of friction is estimated to be 0 56 at the beginning of the event and drops to 0 38 for most of the sliding the change in the frictional level on the sliding surface may be due to liquefaction or breaking of rough patches and contributes to the extended propagation of the large landslide

recent sedimentary facies of isolated carbonate platforms belize yucatan system central america abstract distribution of recent sedimentary facies is significantly different in four closely spaced isolated carbonate platforms off the coasts of belize and yucatan se mexico these differences are largely controlled by variations in submarine topography which are likely the result of differential subsidence and karstification from platform to platform a variety of depositional styles and patterns is found in platform interiors that developed during the same holocene sea level rise composition and texture of surface sediment samples were used to define four major sediment types and to distinguish nine depositional environments within the platforms facies maps are based on analysis of 454 sediment samples and high resolution satellite imagery glovers reef is characterized by a circular facies distribution the nearly continuous reef margin is composed of a coral red coralline algae halimeda grainstone mixed nonskeletal peloidal skeletal wackestones and packstones are present in shallow lagoon parts 5 m water depth behind the margin the deep interior from 5 to 18 m water depth is characterized by mollusk foram halimeda wackestones with over 860 patch reefs of coral red algae halimeda mollusk packstones lighthouse reef also has a coral grainstone and coral red algae halimeda grainstone rim but the facies distribution in the interior is strongly asymmetrical the 8 m deep eastern lagoon is floored by mollusk foram halimeda wackestones and packstones the 3 m deep western lagoon has the mixed peloidal skeletal wackestone to grainstone facies a linear trend of coalescing patch reefs and skeletal grainstone facies separates the two lagoons banco chinchorro is similar to lighthouse reef inasmuch as facies distribution patterns of the interior are strongly asymmetrical mollusk foram halimeda wackestones grainstones are present in eastern lagoon areas whereas shallow 5 m western parts of the lagoon are composed of mixed peloidal skeletal grainstones packstones and wackestones most of turneffe islands is protected on the east by lighthouse reef accordingly turneffe has a narrower reef and skeletal grainstone rim than the other two platforms restricted interior lagoons are up to 8 m deep and are enclosed by wide mangrove rims and surface sediments dominated by halimeda rich wackestone rich in organic matter coral patch reefs are absent in contrast the unprotected northernmost part of turneffe has a wide reef and grainstone rim and the open lagoon area consists of mollusk foram halimeda wackestones packstones with abundant patch reefs

simple scaling of catastrophic landslide dynamics catastrophic landslides involve the acceleration and deceleration of millions of tons of rock and debris in response to the forces of gravity and dissipation their unpredictability and frequent location in remote areas have made observations of their dynamics rare through real time detection and inverse modeling of teleseismic data we show that landslide dynamics are primarily determined by the length scale of the source mass when combined with geometric constraints from satellite imagery the seismically determined landslide force histories yield estimates of landslide duration momenta potential energy loss mass and runout trajectory measurements of these dynamical properties for 29 teleseismogenic landslides are consistent with a simple acceleration model in which height drop and rupture depth scale with the length of the failing slope

refinements to the method of epicentral location based on surface waves from ambient seismic noise introducing love waves summary the purpose of this study is to develop and test a modification to a previous method of regional seismic event location based on empirical green s functions egfs produced from ambient seismic noise elastic egfs between pairs of seismic stations are determined by cross correlating long ambient noise time series recorded at the two stations the egfs principally contain rayleigh and love wave energy on the vertical and transverse components respectively and we utilize these signals between about 5 and 12 s period the previous method based exclusively on rayleigh waves may yield biased epicentral locations for certain event types with hypocentral depths between 2 and 5 km here we present theoretical arguments that show how love waves can be introduced to reduce or potentially eliminate the bias we also present applications of rayleigh and love wave egfs to locate 10 reference events in the western united states the separate rayleigh and love epicentral locations and the joint locations using a combination of the two waves agree to within 1 km distance on average but confidence ellipses are smallest when both types of waves are used

evolution and distribution of porosity associated with subaerial exposure in upper paleozoic platform limestones west texas middle pennsylvanian lower permian limestones in the subsurface of west texas were studied to determine how subaerial exposure and freshwater diagenesis karstification affected porosity distribution in meter scale cycles approximately 87 depositional cycles are present in the gross reservoir interval depths of 2600 3000 m and each cycle is interpreted to represent a glacio eustatic sea level fluctuation using recent radiometric age dating average cycle duration is estimated at 160 000 yr per cycle reservoir grade porosity 4 occurs in 5 25 of the gross reservoir section porosity is stratified occurring in 1 6 m thick intervals in the upper part of cycles that were subaerially exposed however many cycles that were subaerially exposed now lack porosity diagenesis and porosity development have distinct patterns related to duration of subaerial exposure four stages of porosity development are identified 1 very brief or no subaerial exposure estimated at less than 5000 yr caused little or no diagenetic change 2 brief to moderate subaerial exposure estimated at 5000 50 000 yr resulted in most primary pores being filled with calcite cement and dissolution creating fine matrix pores molds and intercrystalline pores 3 moderately long subaerial exposure estimated at 50 000 130 000 yr resulted in cements filling primary pores and some fine secondary pores and dissolution creating small conduit pores vugs fractures fissures 4 prolonged subaerial exposure estimated at greater than 130 000 yr resulted in most primary and secondary matrix pores being filled with calcite cement but dissolution enlarged conduit pores vugs fractures fissures present subsurface porosity in this field preferentially occurs in thick grainstones phylloid algal boundstones and a few wackestone packstones in cycles subjected to brief subaerial exposure stages 2 and 3 matrix porosity molds intercrystalline pores is dominant because most conduit pores formed during prolonged subaerial exposure were filled with either shale during subsequent transgressions or burial cements derived from pressure solution associated with the shales the distribution of porosity in the southwest andrews area indicates that duration of subaerial exposure and supply of clastics are major factors determining ultimate porosity in limestones subjected to subaerial exposure and karstification

porosity permeability relationships in miocene carbonate platforms and slopes seaward of the great barrier reef australia odp leg 194 marion plateau this paper reports a series of 700 porosity permeability analyses and supporting petrographic and sedimentologic descriptions from early to late miocene carbonate strata cored on the marion plateau offshore from north eastern australia during ocean drilling program odp leg 194 the samples analysed are not only mainly coarse bioclastic limestones and dolomitized equivalents from platform top facies but also include 79 plugs from deeper water slope to hemipelagic drift facies outstanding characteristics of this data set are the wide ranges of porosity and permeability in both limestones and dolostones the large degree of short range heterogeneity typical of these strata and the better porosity permeability correlation of dolostones than limestones the platforms have experienced widely varying calcite cementation dolomitization and dissolution but show little clear evidence of meteoric diagenesis suggesting that subaerial exposure may have played little role in porosity permeability evolution permeability for given porosity is controlled by grain size and calcite cement content in grainstones and by occurrence of larger shelter pores and vugs in mud rich samples dolomitization tends to reduce the variation of permeability for given porosity by recrystallizing mud matrix to form intercrystalline macroporosity that connects vugs and moulds to become integrated with the effective pore system as a result there are no differences in permeability porosity trends for different dolostone textures whether dominated by intercrystalline vuggy or preserved intergranular pore types two platform top sites separated by only 5 km display a major lateral variation in dolostone porosity permeability characteristics within the youngest dolostone units this difference is interpreted as reflecting a relatively windward current facing setting of the site with the overall higher permeability for given porosity site 1199 that led to less muddy depositional facies greater cementation and lesser grain dissolution pore geometry parameters measured by petrographic image analysis confirm that the windward dolostones have pores that are both larger and less intricate than dolostones comprising the more current protected location

shallow burial dolomite cement a major component of many ancient sucrosic dolomites dolomite cement is a significant and widespread component of phanerozoic sucrosic dolomites cements in dolomites that were never deeply buried are limpid have planar faces non saddle forms often distinct zonation in cathodoluminescence and form syntaxial overgrowths on crystals facing pores five samples of sucrosic dolomites interpreted as having had mostly limemudstone or wackestone precursors in four carbonate aquifers provide insights into the abundance of planar cements in sucrosic dolomites such cement comprises 11 to 45 32 mean of peritidal to sub tidal dolomites on an outcrop in the edwards aquifer early cretaceous of central texas 19 to 33 25 mean of ramp dolomites in the hawthorn group oligomiocene and 50 to 70 in shelf dolomites of the avon park formation eocene in the upper floridan aquifer of sub surface peninsular florida 18 to 45 32 mean of sub tidal shelf dolomites in quarry sections of the burlington keokuk formation early mississippian in south eastern iowa and 18 to 76 50 mean in shallow cores and outcrops of outer shelf dolomites from the gambier limestone oligo miocene of south australia backstripping the cement phases revealed by cathodoluminescence colour photomicrographs documents the effects of cements on textural coarsening pore space reduction induration and general maturation of these dolomites most pre holocene dolomites are multiphase crystalline rocks composed of i seed crystals or cores ii crystal cortices that concentrically enlarged the cores and iii free space syntaxial precipitates of limpid cement around the crystals remaining caco3 grains and micrite can be replaced by dolomite but typically they are dissolved between stages ii and iii creating systems of intercrystal and mouldic pores typical of sucrosic dolomites networks of cement overgrowths aided by water filled pore systems under hydrostatic to lithostatic pressure are judged to slow or prevent compaction in sucrosic dolomites it can be argued that cortex growth involves both replacement of caco3 particles and microcementation of their interparticle pores this interpretation and the abundance of cements in so many dolomites would obviate the controversy over the volumetrics of replacement dolomitization limpid planar and syntaxial dolomite cements of early diagenetic origin are interpreted to have precipitated from clear pore waters at low temperatures 30 to 35 c and shallow burial depths 100 m in water saturated networks of dolomite silt and sand cements in many dolomites in island and continental aquifer systems appear to result from event driven processes related to sea level highstands cementation events can follow replacement

model space exploration for determining landslide source history from long period seismic data the seismic signals generated by two large volcanic debris avalanches montserrat lesser antilles 1997 and mount st helens usa 1980 and a large rock ice avalanche mount steller usa 2005 have been analyzed for the two debris avalanches given the times and locations of such landslides their signals were recorded by only a few seismic stations moreover these signals cover only a very narrow frequency band and include considerable noise the mount steller on the contrary was precisely recorded for each event the source mechanism i e point force has been determined by waveform inversion using at most two broadband seismic stations the resulting force is very difficult to interpret in terms of landslide characteristics a monte carlo inversion was therefore performed by imposing a simple force model associated with the landslide based on the schematic view of an accelerating decelerating mass traveling down the slope the best parameter set of the force model was then found by minimizing misfits and maximizing correlations between data and synthetic signals this model appears to contain the minimum degree of complexity required to well reproduce the seismic data we detail here the method for the montserrat debris avalanche and then present it s validation on the well studied mount st helens debris avalanche and the well recorded mount steller rock ice avalanche the horizontal and vertical components of the resulting force have different source time functions the best force model compares well with the force obtained by waveform inversion finally this simple force model was interpreted using analytical and empirical relations derived from the sliding block model granular flow model and landslide studies this made it possible to estimate the order of magnitude of the mass flow duration and direction initial topography slope mean velocity and travel distance of the avalanches for these three avalanches the calculated characteristics are consistent with former studies

origin of atoll lagoons a database of 301 atolls from the pacific indian and atlantic oceans has been analyzed with respect to factors governing maximum atoll lagoon depth statistically significant correlations between maximum atoll lagoon depth and both atoll area and present day rainfall are viewed as the combined effect of paleorainfall precipitation and catchment area in contributing to overall atoll morphology this interpretation is supported by the gross saucer shaped morphology of several of the lau group of the fiji islands and the subsurface cretaceous golden lane atoll of mexico where evidence of reef rim construction is lacking but evidence for significant solution relief is compelling the contribution of reefs to atoll rim construction appears to be limited generally to 10 m leaving more than 20 m of relief to be explained at most atolls at a number of these the last interglacial highstand surface is 15 20 m beneath holocene rim sediments subsidence rates of even 5 cm k y do not suffice to explain the subsea depth of this unconformity suggesting the dominating influence of solution on relief expression calculations of solution rates relative to the residence time of sea level below given depths during the past 700 k y suggest that the observed atoll relief is in part inherited from more than one pleistocene or perhaps earlier glacial stage whatever the precise time of origin the data available strongly suggest that atoll morphology is solution determined rather than growth predicated

single force representation of earthquakes due to landslides or the collapse of caverns summary earthquakes due to landslides and the collapse of caverns are caused by the release of gravitational potential energy rather than elastic strain energy landslide or cavern collapse is assumed to start with dislocation motion along the lubricated interface of the slide block or fallen block that intersects the earth s free surface it can be shown that if each component of the dislocation vector is positionindependent and varies only as a function of time the resultant static displacement is spatially uniform both inside and outside the block and therefore no change occurs in static strain energy in particular if the medium is unbounded the static displacement is zero outside the block the force system equivalent to this dislocation model is a distribution of single forces equal but opposite to the dislocation acceleration multiplied by the density at each point of the volume constituting the slide block the physics behind the equivalence is discussed single force appears to be a common mechanism for indigeneous earthquakes that do not change the static strain field

microfacies diagenesis and oil emplacement of the upper jurassic arab d carbonate reservoir in an oil field in central saudi arabia khurais complex abstract the upper jurassic kimmeridgian arab d reservoir of the arab formation in the arabian peninsula is considered to be the largest hydrocarbon carbonate reservoir in the world despite a relative large number of studies dealing with lithofacies and depositional sequences there are still few studies dealing with diagenesis of this supergiant reservoir in this study petrographic cathodoluminescence and ultra violet light fluorescence microscopy analyses of the arab d reservoir in an oil field of saudi arabia khurais complex have been combined with isotope geochemistry 13c 18o and 87sr 86sr to decipher the sequence of diagenetic events affecting the reservoir before and during oil emplacements and the impact of depositional mineralogies and their modifications during the diagenesis on the reservoir quality and heterogeneity all the analyzed samples correspond to lithofacies that can be ascribed to nine microfacies types mft 1 to mft 9 three stages of carbonate dissolution d1 to d3 four stages of calcite cements c1 to c4 and 5 zones of replacive dolomite and dolomite cement d1 to d5 have been documented from diagenetic environments ranging from marine to late burial abundant oil fluid inclusions have been recognized in calcite c3 and c4 and dolomite d5 from wells located in the flanks of the structure group 2 of cements cements from wells located in the center of the structure are largely oil inclusions free group 1 of cements this distribution suggests that group 2 of cements formed within the oil water transition zone of the reservoir during the oil infilling of the structure allowing to constrain the timing of oil emplacement and suggesting at least two phases of oil charging porosity enhancement by corrosive dissolution d3 occurred during late burial and took place just before precipitation of dolomite d5 and calcite c4 and just before the second stage of hydrocarbon arrival suggesting the presence of aggressive fluids preceding the late phase of hydrocarbon migration cross plot of carbon vs oxygen stable isotopes shows a general trend toward decreasing 18o values with increasing burial depth whereas all 13c values remain positive except for group 2 of c3 and c4 calcites which exhibit negative up to 4 6 13c values the later suggest precipitation from pore waters with increased volumes of 12c as a by product of hydrocarbon maturation except for c4 all the 87sr 86sr values are within the range of the late jurassic seawater suggesting precipitation from jurassic marine or evolved marine pore waters in contrast the more radiogenic calcite c4 suggests a source from fluids that interacted with siliciclastics or clay rich sequences depositional mineralogy of the grainy lithofacies is interpreted to have had an impact on the effectiveness of cementation and dissolution controlling the reservoir heterogeneity due to excess of cementation reservoir quality is worse in grainstone microfacies rich in aragonitic components and better in grainstone and packstone microfacies poorer in aragonitic grains but affected by late dissolution of micrite the integration of all these data resulted in a more precise understanding of the reservoir quality and heterogeneity

the relative roles of compaction and early cementation in the destruction of permeability in carbonate grainstones a case study from the paleogene of west central florida u s a abstract how compaction can yield a progressive decrease in the permeability and pore structure of carbonate grainstones is not well documented in this study the destruction of permeability by compaction relative to early cementation is examined in forty five shallow buried 30 440 m grainstones with a range in permeability of 12 to 5180 md compaction and cementation indices calculated from thin section point count data indicate a group of grainstones dominated by cementation and another by compaction log linear cross plots of permeability versus these indices suggest that permeability loss in these two groups occurs by different processes the nature of those processes is elucidated by capillary pressure data and the distribution of cement and compaction fabrics as a function of permeability as cement abundance increases in the cement dominated samples a continuous distribution of cement develops along grain surfaces which is followed by the development of partial and then complete pore filling mosaics permeability is progressively reduced with this succession of cement fabrics and an increasingly greater percentage of pore space is positioned behind progressively smaller throats permeability loss results from porosity reduction progressive constriction of pore throats and increased tortuosity of flow paths once permeability is reduced to tens of millidarcies effective pore radii are all less than 1 m and many are less than 0 1 m but there is no evidence for complete blocking of all pore throats in this suite of samples in absolute terms the pore lining cements reduce permeability by thousands of millidarcies whereas the pore filling cements reduce permeability only by hundreds of millidarcies mechanical compaction is the dominant cause of permeability reduction between 5000 and about 500 md in the compaction dominated samples linear grain contacts and embayed grains become more abundant and close to overly close packing textures become more homogeneously distributed as permeability decreases however there is no concurrent change in the amount of pore space accessed by large or small throats indicating that mechanical compaction does not uniformly constrict or seal pore throats instead the data suggest that mechanical compaction reduces permeability by reducing porosity lengthening pore throats and increasing tortuosity at about 500 md the compaction dominated trend steepens on the log linear plot of permeability versus porosity a change that corresponds to the development of grain to grain pressure solution unlike mechanical compaction grain to grain pressure solution constricts and eliminates pore throats and isolates pore space resulting in a loss of large throats and an increase in the amount of pore volume accessed by small throats in contrast to cement dominated samples the most effective pore radii are still greater than 1 m at tens of millidarcies of permeability such low amounts of permeability can be reached even when pressure solution is not pervasively distributed throughout a sample

numerical modeling of landquakes the thurwieser landslide that occurred in italy in 2004 and the seismic waves it generated have been simulated and compared to the seismic signal recorded a few tens of kilometers from the landslide source i e landquake the main features of the low frequency seismic signal are reproduced by the simulation topography effects on the flowing mass have a major impact on the generated seismic signal whereas they weakly affect low frequency wave propagation simulation of the seismic signal makes it possible to discriminate between possible alternative scenarios for flow dynamics and to provide first estimates of the rheological parameters during the flow as landquakes are continuously recorded by seismic networks our results provide a new way to collect data on the dynamics and rheology of natural flows

sedimentation cycles and their diagenesis on the slope of a miocene carbonate ramp bahamas odp leg 166 numerous small scale depositional cycles are present in the miocene sediments of seismic sequence m along the margin of great bahama bank odp leg 166 these cycles consist of decimetre to metre scale alternations between light grey and dark grey black wackestones packstones the light grey layers are well cemented and nearly uncompacted they contain planktonic and benthic foraminifera and bioclasts bioturbation in these layers is moderate the dark grey wackestones packstones are uncemented strongly compacted and normally strongly bioturbated the main components are planktonic foraminifera and fine grained bioclasts the dark layers are rich in aragonite and organic carbon and contain around 80 carbonate the light layers show low aragonite and organic carbon contents combined with carbonate values of up to 97 5 light 13c and slightly negative 18o values were observed in the dark uncemented layers while the cemented intervals show heavy 13c values and slightly more positive 18o values the carbon isotope signal between the dark and the light layers shows variations of up to 1 45 both 13c and 18o co vary with carbonate content the formation microscanner images reflect the changes in carbonate mineralogy the natural gamma ray tool shows that variations in siliciclastic content of the examined succession displays a different frequency than the cyclic alternations in carbonate mineralogy the internal stacking pattern of the cycles is closely tied to sea level the dark layers are deposited during rising sea level while the light layers reflect sediment production and export during highstand and falling sea level these cycles thus represent a rather continuous sediment shedding pattern that is clearly related to the ramp morphology and differs from the highstand shedding pattern typical for rimmed flat topped platforms most measured parameters suggest that primary sediment composition played an important role in the cementation process the primary differences in composition were enhanced during shallow burial diagenesis the initially high content of metastable carbonate phases in the periplatform sediments triggered rapid cementation of the primary aragonite rich layers leading to the formation of the light beds dissolution of metastable high mg calcite and aragonite was followed by in situ precipitation of more stable dolomite and calcite diagenesis was enhanced by the coarse grain size of the primary aragonite rich layers in contrast the more pelagic dark calcite rich layers were only slightly affected by diagenesis and could preserve their aragonite content the uncemented layers subsequently were subject to strong mechanical compaction whereas the cemented beds stayed nearly uncompacted

landslide mobility and hazards implications of the 2014 oso disaster abstract landslides reflect landscape instability that evolves over meteorological and geological timescales and they also pose threats to people property and the environment the severity of these threats depends largely on landslide speed and travel distance which are collectively described as landslide mobility to investigate causes and effects of mobility we focus on a disastrous landslide that occurred on 22 march 2014 near oso washington usa following a long period of abnormally wet weather the landslide s impacts were severe because its mobility exceeded that of prior historical landslides at the site and also exceeded that of comparable landslides elsewhere the 8 10 6 m 3 landslide originated on a gently sloping

broadband seismic analysis of a massive landslide in southwestern china dynamics and fragmentation implications abstract we analyse broadband seismic records generated by the massive xinmo landslide that occurred in southwestern china at 5 39 on 24 june 2017 beijing time utc 8 characteristics of landslide seismic signals including propagation velocity duration and frequency contents are presented and discussed by comparing them with seismic signals generated by a local earthquake of similar magnitude we perform a long period seismic waveform inversion in the frequency band of 0 01 0 1 hz to acquire the landslide force history using 46 seismic traces from 21 seismic stations with distances from the epicentre extending to 360 km based on the inversion we calculate the dynamic parameters of the landslide and recognize its stages and movement characteristics landslide basal friction coefficients are also acquired using both a constant dip and varying dips along the slope a combined analysis of near field short period seismic records and dynamic inversion results indicates that the high frequency energy of landslide signals is most likely generated by rock fragmentations during collision and scraping