new insights into the tectonic evolution of the andaman basin northeast indian ocean multibeam swath bathymetry data acquired over an area of about 30 000 km2 together with magnetic and single channel seismic data have been analyzed to understand the tectonic evolution of the andaman basin northeast indian ocean swath bathymetry data revealed several morphotectonic features that divide the basin into a complex western part comprising arc parallel seamount chains and n s trending fault systems and a relatively smooth eastern part a sw ne trending spreading ridge bisects the basin an offset of about 11 8 km at 94 21 e longitude divides the spreading ridge into sw and ne segments high resolution bathymetry and magnetic data enabled us to identify two finer scale segments over the sw part of the ridge that display distinct topographic fabric compared to the ne segment thin sediment cover and presence of axial seamounts characterize sw segments of the ridge whereas the ne segment has thick sediment cover and well maintained rift valley kinematics of basin evolution derived from the identification of the seafloor spreading magnetic anomalies suggest very slow initial opening rates of about 1 6 cm yr and an increase in the spreading rate to about 3 8 cm yr from anomaly 2 to present although this interpretation relies only on magnetic anomalies in the two westernmost segments it is suggested that the true seafloor spreading started about 4 ma in the andaman backarc basin rather than the 11 ma postulated previously we infer based on the integrated analysis of swath bathymetry magnetic and seismological data that the basin has evolved as a consequence of extrusive tectonics that prompted extension and rifting along the plane joining the sagaing and semengko fault systems extension by seafloor spreading during the past 4 myr resulted in the formation of the deep andaman backarc basin this phase has also experienced westward propagation of the spreading center

observations of preferential flow during a liquid release experiment in fractured welded tuffs author s salve rohit abstract to better understand preferential flow in fractured rock we carried out an in situ field experiment in the exploratory studies facility at yucca mountain nevada this experiment involved the release of 22 m3 of ponded water at a pressure head of 0 04 m over a period of 7 months directly onto a 12 m2 infiltration plot located on a fractured welded tuff surface as water was released changes in moisture content were monitored along horizontal boreholes located in the formation 19 22 m below distinct flow zones varying in flow velocity wetted cross sectional area and extent of lateral movement intercepted the monitoring boreholes there was also evidence of water being diverted above the ceiling of a cavity in the immediate vicinity of the monitoring boreholes observations from this field experiment suggest that isolated conduits each encompassing a large number of fractures develop within the fractured rock formation to form preferential flow paths that persist if there is a continuous supply of water in addition in fractured welded tuffs the propensity for fracture matrix interactions is significantly greater than that suggested by existing conceptual models in which flow occurs along a section of fracture surfaces an overriding conclusion is that field investigations at spatial scales of tens of meters provide data critical to the fundamental understanding of flow in fractured rock

tectonics of the western margin of the shan plateau central myanmar implication for the india indochina oblique convergence since the oligocene abstract we present new data and interpretations on the neogene tectonics of the shan scarp area central myanmar and its relationship with the india indochina oblique convergence we describe ductile and brittle fabrics associated with the major features in this area the mogok metamorphic belt mmb the shan scarp and the sagaing fault from these data we identify a succession of two tectonic regimes first a dominant nnw sse trending extension marked by ductile stretching that characterizes the mmb and associated n70e brittle normal faults later from middle or upper miocene to the present these structures were cross cut by brittle right lateral faults among which the most important are the n20w transpressive shan scarp fault zone and the n s sagaing fault to explain this transition from a dominant transtensive to a transpressive stress regime that occurred during miocene we place our data within a larger geodynamic context we suggest that like the intraplate deformation in the indian ocean the end of spreading in the south china sea the opening of the andaman basin or the end of subduction within the indo burma range the change in the tectonic regime in central myanmar could be in response to a major miocene regional plate kinematic reorganization

reactivated interstratal karst example from the late silurian rocks of western lake erie u s a abstract interstratal karst developed in the late silurian rocks of western lake erie that after a long interruption was exhumed and reactivated the dissolution front of the g evaporite of the salina group receded in the downdip direction during these two well documented periods of subaerial exposure the karst features that developed in the overlying bass islands dolomite pridolian consist of a large tabular body of collapse breccia and a number of smaller features including breccia pipes partially filled pipes blister caves and collapse dolines the tabular breccia body and the breccia pipes which originated penecontemporaneously during post silurian and pre middle devonian subaerial exposure occur along the updip edge of the present outcrop belt of the dolostone they are monolithologic fragment supported rubble breccias with the pipes exhibiting a greater fragment displacement rotation and rounding and a smaller fragment size the matrix sediment of the tabular body is a quartz sand an equivalent of the basal sandstone that filtered down from the erosion surface the presence in the matrix sediment of nodular celestite a later replacement of evaporites that formed when the sediment was still soft indicates that a sabkha environment existed at the time the breccia was infilled the partially filled pipes which form cylindrical caves that are lined with late diagenetic celestite are believed to be cogenetic with the collapse breccias the blister caves and dolines occur downdip from the breccias postdating pleistocene glaciation and predating isostatic rebound these caves are isolated crescent or oval shaped openings with domed roofs averaging about 60 m in width and 4 m in height the hydration and resulting expansion of lenticular bodies of anhydrite along the receding solution front of the g unit is believed to be the cause of doming the numerous crescentic caves originating from the dissolution of this gypsum and the subsequent collapse of the domed roofs are expressed at the surface as shallow dolines

implications of the 26 december 2004 sumatra andaman earthquake on tsunami forecast and assessment models for great subduction zone earthquakes results from different tsunami forecasting and hazard assessment mod els are compared with observed tsunami wave heights from the 26 december 2004 indian ocean tsunami forecast models are based on initial earthquake information and are used to estimate tsunami wave heights during propagation an empirical forecast relationship based only on seismic moment provides a close estimate to the observed mean regional and maximum local tsunami runup heights for the 2004 indian ocean tsunami but underestimates mean regional tsunami heights at azimuths in line with the tsunami beaming pattern e g sri lanka thailand standard forecast models developed from subfault discretization of earthquake rupture in which deep ocean sea level observations are used to constrain slip are also tested forecast models of this type use tsunami time series measurements at points in the deep ocean as a proxy for the 2004 indian ocean tsunami a transect of deep ocean tsunami amplitudes recorded by satellite altimetry is used to constrain slip along four subfaults of the m 9 sumatra andaman earthquake this proxy model performs well in comparison to observed tsunami wave heights travel times and inundation patterns at banda aceh hypothetical tsunami hazard assessments models based on end member estimates for average slip and rupture length m w 9 0 9 3 are compared with tsunami observations using average slip low end member and rupture length high end member m w 9 14 consistent with many seismic geodetic and tsunami inversions adequately estimates tsunami runup in most regions except the extreme runup in the western aceh province the high slip that occurred in the southern part of the rupture zone linked to runup in this location is a larger fluctuation than expected from standard stochastic slip models in addition excess moment release 9 deduced from geodetic studies in comparison to seismic moment estimates may gen erate additional tsunami energy if the exponential time constant of slip is less than approximately 1 hr overall there is significant variation in assessed runup heights caused by quantifiable uncertainty in both first order source parameters e g rupture length slip length scaling and spatiotemporal complexity of earthquake rupture

a note on unsaturated flow in two dimensional fracture networks 1 although considerable progress has been made in understanding unsaturated flow processes in a single fracture our knowledge of unsaturated flow in fracture networks remains incomplete in this study we present a numerical investigation of steady flow behavior in two dimensional fracture networks containing thousands of fractures within a 10 m 10 m domain simulation results indicate that flow paths are generally vertical as a result of gravity dominated flow behavior with subhorizontal fractures providing pathways for communications between vertical flow paths inducing horizontal spreading of these paths although many fractures with small trace lengths do not contribute to the global flow through a fracture network some of them are still connected to the major flow paths and thus contribute to the overall connectivity of the network they may also considerably affect the interaction between fractures and the matrix on the basis of our simulation results we hypothesize that average spacing between flow paths in a layered system tends to increase with depth as long as flow is gravity driven we also discuss the concept of an influence zone of a capillary barrier to describe seepage from fracture networks to underground openings drifts our simulation results imply that three dimensional fracture network models are needed for providing a more realistic evaluation of capillary barrier effects

conceptual model of the geometry and physics of water flow in a fractured basalt vadose zone a conceptual model of the geometry and physics of water flow in a fractured basalt vadose zone was developed based on the results of lithological studies and a series of ponded infiltration tests conducted at the box canyon site near the idaho national engineering and environmental laboratory the infiltration tests included one 2 week test in 1996 three 2 day tests in 1997 and one 4 day test in 1997 for the various tests initial infiltration rates ranged from 4 1 cm d 4 75 10 7 m s to 17 7 cm d 2 05 10 7 m s and then decreased with time presumably because of mechanical or microbiological clogging of fractures and esicular basalt in the near surface zone as well as the effect of entrapped air the subsurface moisture redistribution was monitored with tensiometers neutron logging time domain reflectrometry and ground penetrating radar a conservative tracer potassium bromide was added to the pond water at a concentration of 3 g l to monitor water flow with electrical resistivity probes and water sampling analysis of the data shows evidence of preferential flow rather than the propagation of a uniform wetting front we propose a conceptual model describing the saturation desaturation behavior of the basalt in which rapid preferential flow occurs through the largest vertical fractures followed by a gradual wetting of other fractures and the basalt matrix fractures that are saturated early in the tests may become desaturated thereafter which we attribute to the redistribution of water between fractures and matrix lateral movement of water takes place within horizontal fracture and rubble zones enabling development of perched water bodies

geophysical characteristics of the ninetyeast ridge andaman island arc trench convergent zone abstract the convergence tectonics of the ninetyeast ridge ner upon the andaman island arc trench system is examined through an analysis of etopo2 bathymetry satellite derived free air gravity and seismic data oblique subduction and the buoyancy forces arising from subduction of the ner render the subduction processes near the andaman arc highly complex the bathymetric expression of the ner is visible up to lat 10 n but seismic reflection data indicate that it extends up to about lat 17 n the gravity anomalies are strongly positive over the exposed segment of the ridge but are subdued over the buried portion there is a prominent break in the continuity of the trench gravity low where the ner seems to impinge upon the island arc further a strong curvilinear belt of negative anomalies just behind and running parallel to the island arc associated with the forearc basin is a dominant feature of the gravity map an offset in the continuity of this strong negative anomaly occurs at about the same latitude where the ner seems to be converging upon the island arc seismic reflection data indicate that the ner is very close to the trench flexural modeling of the gravity anomalies for the subducting indian ocean lithosphere loaded by sediments and the ner indicates that the ner is at the starting phase of its collision with the island arc and may not have started affecting the subduction process itself we infer that the en echelon block structure of the ner in the proximity of the convergent zone is a consequence of complex strike slip and subduction related tectonic forces

long term infiltration and tracer transport in fractured rocks field observations and model analyses summary this paper presents modeling analyses of long term infiltration and tracer tests in fractured tuffs at yucca mountain nv usa the experiments were conducted on a 20 m thick tuff section in a flyover formed by two exploratory tunnels the infiltration test last for 870 days both measured infiltration and seepage show significant temporal and spatial variations the tracer test used inorganic tracers i br f and organic tracers fluorobenzoic acids released 559 days after the infiltration test started leaching from dry salts from fracture walls was found to have affected tracer breakthroughs the unsaturated flow was evaluated by optimizing 45 parameter values in a three dimensional model which accounts for fracture matrix interaction and heterogeneous hydraulic properties in a column based scheme the field data are valuable asset to evaluate the modeling approaches for fractured rocks and the relative importance of the matrix diffusion process results show that matrix diffusion is an important process for transport and that effective matrix diffusion coefficients at the field scale are larger than those at the laboratory scale for the solutes

an active fracture model for unsaturated flow and transport in fractured rocks the unsaturated zone at yucca mountain a potential repository site of high level nuclear waste is a complex hydrologic system in which a variety of important flow and transport processes is involved to quantify these processes as accurately as possible is a theoretically challenging and practically important issue in this study we propose a new formulation for modeling flow and transport in unsaturated fractured rocks the formulation is mainly based on a hypothesis that only a portion of connected fractures are active in conducting water analysis of the relevant data with the new formulation suggests that about 18 27 of the connected fractures in the topopah spring welded tsw unit the potential repository unit of yucca mountain are active under ambient conditions the relatively high percentage of active fractures is consistent with field observations from a variety of sources sensitivity analyses are performed to investigate effects of the activity of connected fractures on flow and transport behavior in unsaturated rocks

source and progression of a submarine landslide and tsunami the 1964 great alaska earthquake at valdez like many subduction zone earthquakes the deadliest aspects of the 1964 m 9 2 alaska earthquake were the tsunamis it caused the worst of these were generated by local submarine landslides induced by the earthquake these caused high runups engulfing several coastal towns in prince william sound in this paper we study one of these cases in detail the port valdez submarine landslide and tsunami we combine eyewitness reports preserved film and careful posttsunami surveys with new geophysical data to inform numerical models for landslide tsunami generation we review the series of events as recorded at valdez old town and then determine the corresponding subsurface events that led to the tsunami we build digital elevation models of part of the pretsunami and posttsunami fjord head delta comparing them reveals a 1500 m long region that receded 150 m to the east which we interpret as the primary delta landslide source multibeam imagery and high resolution seismic reflection data identify a 400 m wide chute with hummocky deposits at its terminus which may define the primary slide path using these elements we run hydrodynamic models of the landslide driven tsunamis that match observations of current direction maximum inundation and wave height at valdez old town we speculate that failure conditions at the delta front may have been influenced by manmade changes in drainage patterns as well as the fast retreat of valdez and other glaciers during the past century

implications of halide leaching on 36cl studies at yucca mountain nevada 1 chlorine 36 was generated from nuclear tests in the 1950s and 1960s and has been used to identify fast flow paths at yucca mountain the proposed repository for high level nuclear waste fabryka martin et al 1997 1998 bomb pulse 36cl brought into the subsurface by infiltrating rainwater presumably resides along fracture surfaces because of the extremely low rock matrix permeability however leaching a rock sample to extract this salt inevitably extracts pore water chloride cl and rock matrix chloride thereby making it difficult to obtain reproducible measurements or detect the specific bomb pulse signatures complexities introduced by these sources of older chloride include dilution of bomb pulse 36cl cl ratios for samples from strata with a high cl concentration variations in measured ratios as a function of leaching time rock chip size and the differing effects of active leaching from those of passive leaching this work provides both a conceptual model and a mathematical solution for the leaching processes and examines the role of sample leaching in the 36cl studies of yucca mountain rocks an analytical solution is derived for the diffusion of cl and 36cl in composite media rock matrix and water to accommodate variable diffusivity this solution is subsequently used to develop a leaching model that takes into account bomb pulse signal matrix pore water and relatively hard to leach components isolated fluid inclusion and mineral boundary salts the model is then applied to samples from stratigraphic units at yucca mountain to obtain leachate concentrations from different setup methods protocols including duration chip size and gravitational settling of the water rock mixture the model results show that the probability of detecting a 36cl cl bomb pulse signal is severely diminished under longer leaching times and smaller rock fragment sizes and that leaching times of 1 to 10 hours are most likely to be successful in detecting a bomb pulse signal bomb pulse 36cl cl ratios are more likely to be observed if pore water cl concentrations were initially low prior to the introduction of bomb pulse carrying water

the great sumatra andaman earthquake of 26 december 2004 the two largest earthquakes of the past 40 years ruptured a 1600 kilometer long portion of the fault boundary between the indo australian and southeastern eurasian plates on 26 december 2004 seismic moment magnitude mw 9 1 to 9 3 and 28 march 2005 mw 8 6 the first event generated a tsunami that caused more than 283 000 deaths fault slip of up to 15 meters occurred near banda aceh sumatra but to the north along the nicobar and andaman islands rapid slip was much smaller tsunami and geodetic observations indicate that additional slow slip occurred in the north over a time scale of 50 minutes or longer

indian ocean high productivity event 10 8 ma linked to global cooling or to the initiation of the indian monsoons uplift of the himalayas and tibetan plateau ca 10 8 ma has been said to be the main cause of the origin or intensification of the indian monsoon system because mountains modulate the land sea thermal contrast the intensification of the monsoons in turn is seen as the cause of major changes in fauna and flora on land as a result of changing precipitation patterns as well as in the indian ocean where the monsoons drive increased upwelling and thus increased productivity we argue that the interactions between the elevation of the himalayas and tibetan plateau the onset of the monsoons and their effects on the indian ocean biota remain uncertain the timing of these events uplift monsoons and biotic change is not well constrained neogene deep sea benthic foraminiferal faunal and isotope records of the ninetyeast ridge combined with published data show that a major increase in bio genic productivity occurred at 10 8 ma throughout the indian ocean the equatorial pacific and southern atlantic we suggest that this indian ocean high productivity event was not simply the result of monsoon induced upwelling or nutrient delivery from the weathering of newly uplifted mountains but may have been caused by strengthened wind regimes resulting from global cooling and the increase in volume of the antarctic ice sheets

high resolution bathymetry of the eastern slope of the porcupine seabight the topography of the eastern margin of the porcupine seabight was surveyed in june 2000 utilizing swath bathymetry the survey was carried out during rv polarstern cruise ant xvii 4 as part of the geomound project the main objective was to map and investigate the seafloor topography of this region the investigated area contains a variability of morphological features such as deep sea channels and giant mounds the survey was planned and realized on the basis of existing data so as to guarantee the complete coverage of the margin in order to achieve a resolution of the final digital terrain model dtm that meets the project demands data processing was adjusted accordingly the grid spacing of the dtm was set to 50 m and an accuracy better than 1 of the water depth was achieved for 96 of the soundings

2004 indian ocean tsunami inflow and outflow at phuket thailand at bangtao beach phuket the 2004 indian ocean tsunami produced a repeated sequence in which rapid inflow of turbulent water was followed by ponding and then by gradual outflow photographs and eyewitness accounts show an initial withdrawal followed by series of inflows the tsunami left behind a sand sheet as much as 25 cm thick that contains parallel inclined landward and seaward lamina in addition to the normal grading commonly reported from tsunami deposits the sheet contains evidence for two times of vigorous inflow each of these is marked by mud rip ups medium to coarse sand that grades upward to fine landward inclined laminae and a sharp basal contact the top of the sand sheet when observed in the first days after the tsunami abounded in current dune and ripple bedforms of mostly landward orientation the tsunami s first positive wave left noonshore sedimentary record in this pitting area the second wave deposited sand that is much less extensive and slightly finer than that of the third wave the deposit of both these waves contains multiple fining upward sequences possibly due to multiple surges in one wave train the depth averaged flow velocity estimated from thickness and grain size are in the range 7 21 m s whereas a near bottom threshold velocity calculated from bedforms reveals the order of magnitude difference from 1 74 to 1 03 m s 2007 elsevier b v all rights reserved

shear wave velocity structure over the eastern indian subcontinent abstract fundamental mode surface wave generated by twelve earthquakes which occurred in northeastern india and nearby regions and were recorded at the shillong shl and chiengmai chg seismic stations are used to determine the shear wave velocity structure beneath these regions the frequency time analysis method is used to determine the group velocities for periods ranging from 4 to 50 s for fundamental mode rayleigh and love waves a high shear wave velocity 4 2 4 7 km s 1 is estimated in the lower 30 34 km of the crust crustal thickness is found to vary from 36 to 56 km with an overlying 2 4 km sedimentary thickness of shear wave velocity of 2 55 2 75 km s 1 the shear wave velocity in the upper 10 km of crust is 3 5 3 7 km s 1 below the sedimentary layer the inferred high shear velocity for the lower crust beneath these regions suggests an oceanic affinity and they are different from the indian shield structure the lower crust must have an oceanic origin as derived from the reminiscent of a certain oceanic lithosphere the available data do not permit us to estimate the upper mantle structure precisely however it shows a higher upper mantle shear velocity of 5 1 5 3 km s 1 this may be indicative of active tectonism beneath these regions in the uppermost mantle the moho boundary is not sharply defined here the increase in crustal thickness may be due to the collision of the indian and eurasian plates in the north and subduction of the indian plate beneath the burmese arc in the east

effective matrix diffusion in kilometer scale transport in fractured crystalline rock concentrations of tritium 3h and dichlorodifluoromethane cfc 12 in water samples taken from glacial drift and fractured crystalline rock over 4 km2 in central new hampshire are interpreted to identify a conceptual model of matrix diffusion and the magnitude of the diffusion coefficient dispersion and mass transfer to and from fractures has affected the 3h concentration to the extent that the peak 3h concentration of the 1960s is no longer distinguishable because of heterogeneity in the bedrock the sparsely distributed chemical data do not warrant a three dimensional transport model instead a one dimensional model of cfc 12 and 3h migration along flow lines in the glacial drift and bedrock is used to place bounds on the processes affecting kilometer scale transport arid model parameters are varied to reproduce the measured relation between 3h and cfc 12 rather than their spatial distributions a model of mass exchange to and from fractures that is dependent on the time varying concentration gradient at fracture surfaces qualitatively reproduces the measured relation between 3h and cfc 12 with an upper bound for the fracture dispersivity approximately equal to 250 m and a lower bound for the effective matrix diffusion coefficient equal to 1 m2 yr 1 the diffusion coefficient at the kilometer scale is at least 3 orders of magnitude greater than laboratory estimates of diffusion in crystalline rock the large diffusion coefficient indicates that diffusion into an immobile fluid phase rock matrix is masked at the kilometer scale by advective mass exchange between fractures with large contrasts in trarismissivity the measured transmissivity of fractures in the study area varies over more than 6 orders of magnitude advective mass exchange from high permeability fractures to low permeability fractures results in short migration distances of a chemical constituent in low permeability fractures over an extended period of time before reentering high permeability fractures viewed at the kilometer scale this process is analogous to the chemical constituent diffusing into and out of an immobile fluid phase

the relative importance of gravity induced versus current controlled sedimentation during the quaternary along the mideast u s outer continental margin revealed by 3 5 khz echo character abstract a detailed echo character map based on more than 50 000 km of 3 5 khz echograms reveals the relative importance of contour currents turbidity currents and mass wasting processes for the upper 50 100 m of sea floor sediments along the u s continental margin between southern georges bank and cape hatteras nineteen individual echo types are mapped and interpreted as deposits produced either by current controlled or gravity induced processes based on echo type distribution analysis of selected sediment core samples and the published results of other workers turbidity currents and mass wasting have apparently been the primary depositional agents throughout 60 of the region in contrast contour currents alone appear to have influenced only 10 of the region however combined processes i e non separable interaction between downslope and parallel to contour processes have influenced an estimated 25 of the margin the remaining 5 of the study area constitutes the outermost continental shelf echo types here reflect the influence of fluvial deltaic and shallow marine sedimentary processes changes in the relative distributions of various echo types with sea floor depth indicate that the dominant sedimentary processes change downslope and are significantly different within each physiographic province deposits formed by mass wasting dominate the continental slope where 50 of the sea floor is eroded and gullied by slides slumps and the heads of debris flows deposits developed under the influence of combined processes are most wide spread on the upper continental rise and cover 40 of the sea floor primarily in the form of deep sea channel levees modified by contour currents on the lower continental rise turbidites form more than 50 of the sea floor deposits the downslope deposits turbidity currents slumps debris flows etc were emplaced primarily during the pleistocene glacioeustatic sea level lowering moved beaches and rivers across the exposed continental shelf to the shelf edge where massive fluxes of terrigenous sediment could be delivered to the continental slope and rise by turbidity currents significant amounts of this sediment were transported through submarine canyons and leveed deep sea channels to the lower continental rise and formed the lower continental rise terrace a flat turbidite basin ponded behind the hatteras outer ridge southwest of the wilmington channel this glacially derived influx was diminished however depositional patterns indicate that downslope processes continued to be dominant at least as far south as cape hatteras where rapid deposition on the continental slope and uppermost continental rise created instabilities slope failure produced slumps slides and debris flows and provided an additional volumetrically important redistribution of sediment downslope the influence of contour currents is clearly observed only in those areas topographically shielded from the masking effects of downslope processes in particular along the seaward side of the buried chesapeake drift and the hatteras outer ridge

the holocene storegga slide tsunami in the united kingdom all currently known sites in the united kingdom with evidence for the holocene storegga slide tsunami are described information on the altitude distribution stratigraphical context age particle size profile and microfossil characteristics of the deposits is presented the tsunami involved a greater area than previously described reaching a coastline over 600 km long the ubiquitous sand layer which forms the main deposit associated with the event is shown to exhibit a consistent morphology and a particle size profile marked by fining upwards sequences an analysis of new and previously published radiocarbon dates indicates that from evidence in the united kingdom the event took place sometime around 7100 radiocarbon years bp 7900 calibrated years bp a new isobase model for mainland scotland and adjacent areas providing a preliminary estimate of land uplift since the tsunami is presented the model estimates contemporary sea surface level offshore at 14 m below the present day mean high water spring tides tsunami sediment run up is greatest in inlets where it reaches at least 25 m on shetland and at least 5 m along the mainland coastline to the south and run up of the tsunami would have exceeded these values the tsunami sediments identified here are considered particularly valuable as a synchronous marker horizon

deep burial diagenesis its implications for vertical movements of the crust uplift of the lithosphere and isostatic unroofing a review abstract various techniques of study of strata exposed at the surface in undeformed areas of the appalachian basin and ozark done imply that these strata have been heated to temperatures that suggest a former great depth of burial the data reveal that the strata have been much more deeply buried than previously thought if such former deep burial has taken place then subsequent uplift and erosion must also have taken place to bring these formerly deeply buried strata to the present land surface unexpectedly large amounts of uplift and erosion ranging from 4 3 to 7 km have re exposed these formerly deeply buried rocks this leads to the surprising conclusion that isostatic unroofing has stripped off thick sections of strata whose presence was previously unsuspected therefore the lithosphere in its isostatic unroofing of thick sequences of sedimentary strata has undergone much larger vertical motions than many geologists had previously estimated case histories in this review include strata of the silurian of the northern appalachian basin and of the ordovician of the ozark dome which reached interpreted maximum burial depths of 5 and 4 3 km respectively devonian strata in the catskill mountains of new york imply a former depth of burial of 6 5 km lower ordovician carbonate sequences of the northern appalachian basin imply a depth of burial in excess of 7 km middle ordovician strata from the same basin signify a depth of burial of approximately 5 km and devonian strata a paleodepth of 4 5 5 km such former great depths of burial of undeformed strata which are now exposed at the surface reflect large scale vertical movements of the crust and uplift of the lithosphere these drastic changes represent isostatic unroofing with widespread implications for paleogeography of a kind unrecognized at present

tectonics and history of the andaman sea region abstract the andaman sea is an active backarc basin lying above and behind the sunda subduction zone where convergence between the overriding southeast asian plate and the subducting australian plate is highly oblique the effect of the oblique convergence has been formation of a sliver plate between the subduction zone and a complex right lateral fault system the late paleocene collision of greater india and asia with approximately normal convergence started clockwise rotation and bending of the northern and western sunda arc the initial sliver fault which probably started in the eocene extended through the outer arc ridge offshore from sumatra through the present region of the andaman sea into the sagaing fault with more oblique convergence due to the rotation the rate of strike slip motion increased and a series of extensional basins opened obliquely by the combination of backarc extension and the strike slip motion these basins in sequence are the mergui basin starting at 32 ma the conjoined alcock and sewell rises starting at 23 ma east basin separating the rises from the foot of the continental slope starting at 15 ma and finally at 4 ma the present plate edge was formed alcock and sewell rises were separated by formation of the central andaman basin and the faulting moved onshore from the mentawai fault to the sumatra fault system bisecting sumatra

tracer transport in fractured crystalline rock evidence of nondiffusive breakthrough tailing extended tailing of tracer breakthrough is often observed in pulse injection tracer tests conducted in fractured geologic media this behavior has been attributed to diffusive exchange of tracer between mobile fluids traveling through channels in fractures and relatively stagnant fluid between fluid channels along fracture walls or within the bulk matrix we present a field example where tracer breakthrough tailing apparently results from nondiffusive transport tracer tests were conducted in a fractured crystalline rock using both a convergent and weak dipole injection and pumping scheme deuterated water bromide and pentafluorobenzoic acid were selected as tracers for their wide range in molecular diffusivity the late time behavior of the normalized breakthrough curves were consistent for all tracers even when the pumping rate was changed the lack of separation between tracers of varying diffusivity indicates that strong breakthrough tailing in fractured geologic media may be caused by advective transport processes this finding has implications for the interpretation of tracer tests designed to measure matrix diffusion in situ and the prediction of contaminant transport in fractured rock

geodynamics of burma and andaman nicobar region on the basis of tectonic stresses and regional seismicity abstract the nature and distribution in depth and latitude of earthquakes and deformation in different regions of burma and andaman nicobar indicate rather unequal horizontal compression and relative movement of different segments the east west longitudinal distribution of earthquakes delineates well defined zones of seismicity dipping 30 50 degrees from the andaman trench to a depth of about 180 km under the andaman islands fault plane solutions show that the strike slip normal and thrust faults are associated with seismic and aseismic regions the change in nature of volcanism from andesite south to basalt north in burma suggested that the stress field changed from compressional to tensional the mechanical coupling by the deformation of two different segments caused an extensive contortion of the sediments in the southern assam massif

organic geochemistry and oil source correlations paleozoic of ohio routine analytical methods and new kerogen kerogen pyrolyzate techniques used for detailed petroleum geochemical studies permit the correlation of oils to their respective source rocks in ohio in the paleozoic section four good to excellent source units were identified the mississippian sunbury shale the devonian ohio shale and olentangy shale and the shales of the ordovician point pleasant formation these marine shales are dominantly oil prone with maturation levels that span the immature to peak oil generation range no source rocks examined exceeded an ro of 1 0 1 1 or equivalent the reservoired oils in ohio are mostly supermature based on normal alkanes pristane n c17 to phytane n c18 ratios low asphaltene and sulfur contents and high paraffin indices three basic oil groups were identified using oil characterization procedures group 1 consists of cambrian ordovician and some silurian oils group 2 consists of some silurian devonian one mississippian and some pennsylvanian oils and group 3 consists of oil from the mississippian berea sandstone oil source rock correlation techniques permitted the assignment of probable source rocks to each oil group group 1 oil was probably derived from the point pleasant shales group 2 oil was derived from the ohio shale and olentangy shale and group 3 oil came from the sunbury shale because the supermature oils in ohio occur in reservoirs with maturities generally under 0 8 ro the oils would have had to migrate from deep within the appalachian basin migration could have followed fracture zones unconformities or extensive and permeable units such as the silurian clinton sands

sandstone dykes in siwalik sandstone sedimentology and basin analysis subansiri district nefa eastern himalaya abstract sandstone dykes including sills of varied thickness and with tapering ends are present either transecting or sills parallel to bedding in the siwalik sandstone of arunachal pradesh nefa eastern himalaya the different sedimentary and microstructural analyses show varied conditions of deposition with changing facies from fluvial channel to alluvial fan to coastal plain fan delta the non marine and shallow marine environments are indicated by the presence of organised and disorganised gradation and the presence of sandstone dykes in the interface regions the orientations of the longer axes of the conglomerate along with the sand bedding indicate palaeoflow

field observation of flow in a fracture intersecting unsaturated chalk flow through a natural fracture crossing unsaturated chalk in an arid region was investigated in a field experiment using a specially designed experimental setup the setup allowed complete control of the flow domain inlet and outlet water flux into and out of the fracture was measured in small segments of the fracture openings and flow trajectories were identified using seven fluorobenzoic acid tracers a 5 day percolation experiment on a 5 3 m long fracture showed significant spatial and temporal variability of the flow regime flow through fracture openings did not reach a steady state either in individual segments or across the entire flow domain although the boundary conditions were kept relatively steady for the entire duration of the experiment flow trajectories within the fracture plane varied over time however most of the flow was confined to small sections of the fracture over 70 of the flux was transmitted through 20 of the studied fracture openings observations from the tracer tests suggest that flow paths can coexist near each other without water mixing probably because the fracture fill generates unconnected flow paths across the main fracture void

morphology of the andaman outer shelf and upper slope of the thai exclusive economic zone following the devastating 2004 tsunami that hit the southwestern coast of thailand the need for detailed bathymetric data of the andaman sea outer shelf became evident in order to better predict tsunami wave propagation and coastal impact bathymetric data and subbottom profiler records covering the outer shelf and upper slope of the thai exclusive economic zone eez were collected onboard thai rv chakratong tongyai in 2006 and 2007 the data cover an area of approximately 3000 km2 between 500 and 1600 m water depth the soundings allowed generating a final bathymetric grid with 50 m grid cell spacing the outer shelf is rather smooth and slightly inclined southward while the upper slope is strongly dissected by gullies several previously unknown features are identified including mud domes pockmarks three large plateaus surrounded by moats gas charged sediment on subbottom profiler records and only few indications for small submarine landslides on the upper slope the largest of these possibly translational submarine landslides involved 2 2 107 m3 of sediment this slide would have generated a tsunami wave of less than 0 12 m wave height considering the entire data there is no evidence that landslides have been the source of tsunami waves in recent geological time highlights

mechanisms of recharge in a fractured porous rock aquifer in a semi arid region abstract eleven porewater profiles in rock core from an upland exposed sandstone vadose zone in southern california with thickness varying between 10 and 62 m were analyzed for chloride cl concentration to examine recharge mechanisms estimate travel times in the vadose zone assess spatial and temporal variability of recharge and determine effects of land use changes on recharge as a function of their location and the local terrain the profiles were classified into four groups reflecting the range of site characteristics century to millennium average recharge varied from 4 to 23 mm y 1 corresponding to 1 moreover the temporal variability of recharge was estimated and along each profile past recharge rates calculated based on the sequence of cl concentrations in the vadose zone recharge rates increased at specific times coincident with historical changes in land use the consistency between the timing of land use modifications and changes in cl concentration and the match between observed and simulated cl concentration values in the vadose zone provide confidence in porewater age estimates travel times recharge estimates and reconstruction of recharge histories this study represents an advancement of the application of the chloride mass balance method to simultaneously determine recharge mechanisms and reconstruct location specific recharge histories in fractured porous rock aquifers the proposed approach can be applied worldwide at sites with similar climatic and geologic characteristics

submarine landslide as the source for the october 11 1918 mona passage tsunami observations and modeling this paper is not subject to u s copyright the definitive version was published in marine geology 254 2008 35 46 doi 10 1016 j margeo 2008 05 001