present day kinematics of the mediterranean a comprehensive overview of gps results i combine recently published gps results to derive a geodetic horizontal velocity field consistent at the scale of the mediterranean and the surrounding alpine belts the velocity field is then used to discuss the boundary conditions around each major deforming area in the mediterranean to describe the main patterns of motion and deformation to critically review the existing kinematics models and to finally point out the main unresolved kinematics questions strain rate in europe north of the alpines belt is dominated by the signature of the glacial isostatic adjustment and tectonic strain remains below the current accuracy of gps results in the western mediterranean deformation is restricted to the betics the alboran and the morrocan rif with west to southwestward motion with respect to iberia which is part of stable europe shortening consistent with the relative nubia eurasia plate motion is found throughout the maghrebides but the distribution of deformation in northern africa remains largely unknown the central mediterranean is dominated by the counter clockwise rotation of the adriatic the junction between the southern adriatic domain and nubia has yet to be firmly established the deformation over a wide area east of the maghrebides in tunisia and the gulf of sirte in libya still remains to be quantified in the eastern mediterranean the velocity field is dominated by a general anti clockwise rotation and a general trend towards the hellenic trench with velocity magnitude increasing with decreasing distances from the trench this trend is observed not only in the aegean and anatolia but also in the southern balkans geodetic results emphasize that the convergence of the nubia and arabia plates towards eurasia directly controls the deformation across only very few segments along the plate boundary zone additional processes are therefore required to explain the observed velocity field and deformation pattern

geometry and evolution of salt structures in a marginal rift basin of the gulf of mexico east texas the geometry and distribution of salt structures in the east texas basin shown in an isometric block diagram reveal that a minimum of 1 500 m of mid jurassic louann salt accumulated in a north northeast trending trough floored by thinned continental crust above a threshold thickness of 600 m salt was mobilized by 1 loading beneath a carbonate wedge 2 differential loading by prograding terrigenous clastics and 3 basin edge tilting and erosion salt structures evolved from salt pillows to active diapirs with maximum gross growth rates of 400 to 530 m m y each stage lasted 10 to 30 m y three generations of diapirs were successively activated in different areas by different forces

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

an investigation of the geometric controls on the morphological evolution of small scale salt terrains cardona spain small scale terrains on salt materials were surveyed with a total station and a series of digital elevation models dems constructed two sets of observations were made eight months apart during which the terrains underwent significant erosion the difference in elevation shown by the dems calculated by subtraction is a measure of surface erosion of the salt terrains the erosion rate was analysed with respect to four terrain parameters calculated in the software high erosion rates and their strong control by terrain slope are demonstrated supporting an earlier study using erosion pins slope profile curvature is also indicated as having some influence the combination of scanning total station and dem software is shown to be an effective tool for investigating rapid geomorphic change at this scale of study

double evaporitic decollements influence of pinch out overlapping in experimental thrust wedges abstract this article focuses on how deformation and displacements are transferred between two decollements located at different stratigraphic levels by means of analogue modeling using brittle viscous sand silicone systems we present results from ten analogue models in which we varied key parameters such as the amount of horizontal offset or overlap between the pinch outs of the upper and lower decollements the total amount of shortening and the planform geometry of the upper decollement results indicate that i structures root onto the basal and upper decollement defining an inner and an outer domain and ii the offset overlap of the decollements controls the geometry of the transition zone located between the two decollements the propagation of deformation into the foreland both in space and time and the deformation style and kinematics in the different domains of the model when the pinch out of the upper decollement is at an angle with the backstop oblique structures form and the geometry and propagation mode of the structures change progressively along strike we compare our experimental results with other silicone sand analogue models and with the natural examples of the southern pyrenees where upper triassic and eocene oligocene syn tectonic evaporites acted as basal and upper decollements respectively

post miocene rifting and diapirism in the northern red sea abstract rifts and diapirs are the dominant structures in the bathyal zone of the northern red sea where commonly the diapirs ascend along normal faults associated with the rifts in this manner the diapirs form elongated features sometimes exceeding lengths of 30 km and widths of 4 km they also penetrate a sedimentary sequence about 1000 m thickness or less thicknesses generally considered to be barely adequate for the gravity conversion required to initiate diapiric motion we suggest that development of diapirs under these minimal overburden conditions was made possible by the high thermal gradients in the area resulting from the underlying attenuated continental crust and ascending mantle that prevail in the rift system of the northern red sea diapiric evolution was also dependent on the extensional tectonic regime with its numerous normal faults forming weaknesses along which the diapirs could move upwards

triassic evaporites and plio quaternary diapirism in western greece wide triassic evaporite outcrops run parallel to the strike of hellenide thrust faults in western greece they crop out along the leading edges of thrust sheets emplaced as part of the foreland migrating fold and thrust belt the evaporites acted as the plane of decollement for thrust sheet emplacement over much of the external hellenides plio quaternary diapirs occur locally within the broad outcrops of triassic evaporite they are the result of local mobilization of evaporite after its emplacement their rise may have been initially triggered by hellenide thrust sheet loading and subsequently accentuated by plio quaternary subsidence geophysical records and onland exposures show that diapiric rise controlled local sedimentation patterns above the sites of earlier hellenide thrusts the subsequent intrusion of diapirs into these cover sediments caused localized extensional structures to develop this is best seen in se zakinthos where strain hardened conjugate faults developed in friable pliocene sandstones early in the intrusion history principal strains calculated from these sets demonstrate patterns of extension sub orthogonal to intrusion margins they are comparable with patterns known from other field and experimental examples but contrast with some recent studies on diapir related strains

calibration of the hglp seismograph network and centroid moment tensor analysis of significant earthquakes of 1976 abstract a methodology is developed for determining accurate instrument response functions for seismographs of the high gain long period hglp network recordings of daily transient calibration pulses provide a detailed history of the time varying responses of the hglp stations when the instrument displacement transfer function is available knowledge of the seismometer mass calibration coil constant and calibration current allows for the prediction of the shape and amplitude of the calibration signal by simple integration of the transfer function in theory the inverse of this statement is also true but in practice noise in the recordings contaminates the instrument response function recovered through direct differentiation of the calibration pulse the unknown transfer function of the seismograph system is instead first described by the product of the nominal responses of its mechanical and electromagnetic components specific values of the characteristic parameters for each seismograph component are subsequently determined by iterative least squares minimization of the misfit between observed and model transient calibration pulses by application of this method to daily calibration pulses recorded on the ten stations of the hglp network refined instrument response functions for 1976 and part of 1975 are determined the results agree well with single frequency amplitude calibration data recovered from station maintenance records and produce synthetic waveforms which are consistent with data from other well calibrated stations we use the recalibrated hglp data together with long period data from early international deployment of accelerometers ida and seismic research observatory sro digital stations to determine 108 centroid moment tensor cmt solutions for moderate and large earthquakes of 1976 the new cmt results for several major earthquakes including the tangshan guatemala and friuli events are compared with those of previous studies

structure and seismogenic properties of the mentawai segment of the sumatra subduction zone revealed by local earthquake traveltime tomography 1 on 12 september 2007 an mw8 4 earthquake occurred within the southern section of the mentawai segment of the sumatra subduction zone where the subduction thrust had previously ruptured in 1833 and 1797 traveltime data obtained from a temporary local seismic network deployed between december 2007 and october 2008 to record the aftershocks of the 2007 event was used to determine two dimensional 2 d and three dimensional 3 d velocity models of the mentawai segment the seismicity distribution reveals significant activity along the subduction interface and within two clusters in the overriding plate either side of the forearc basin the downgoing slab is clearly distinguished by a dipping region of highvp 8 0 km s which can be a traced to 50 km depth with an increased vp vs ratio 1 75 to 1 90 beneath the islands and the western side of the forearc basin suggesting hydrated oceanic crust above the slab a shallow continental moho of less than 30 km depth can be inferred suggesting that the intersection of the continental mantle with the subducting slab is much shallower than the downdip limit of the seismogenic zone despite localized serpentinization being present at the toe of the mantle wedge the outer arc islands are characterized by low vp 4 5 5 8 km s and high vp vs greater than 2 0 suggesting that they consist of fluid saturated sediments the very low rigidity of the outer forearc contributed to the slow rupture of the mw 7 7 mentawai tsunami earthquake on 25 october 2010

stratal architecture of a halokinetically controlled patch reef complex and implications for reservoir quality a case study from the aptian james limestone in the fairway field east texas basin abstract widespread carbonate platform growth in the cretaceous tethys is associated with expansive reef margin and interior patch reef development these reefs and their associated facies have the potential to be significant hydrocarbon reservoirs but characterization is challenging because of complex facies distributions inadequate understanding of biotic communities and processes impacting their development and difficulties delineating timelines in systems that build their own topography other factors that may impact underlying topography such as tectonics or halokinesis further complicate the story this study delves into these complexities in a dataset from the fairway field a large oil and gas field 115 km2 410 million barrels original oil in place that produces from the aptian james limestone in the east texas basin texas usa the field contains a patch reef complex here defined as an assemblage of patch reefs that grew near each other without necessarily being physically connected that has significant lateral and vertical facies heterogeneity previous attempts at characterization have failed to fully recognize the importance of its proximity to four salt domes which modified topography and influenced deposition prior to and during reef development here we reassess the stratal architecture of the fairway field from a sequence stratigraphic perspective with the goal of augmenting understanding of timing of reef development and facies distributions and ultimately building a better stratigraphic framework for a halokinetically influenced patch reef complex core descriptions and core calibrated wireline log correlation across the field yield a model that explains the relationship between halokinetic topography energy regime relative water depth and reef and reef associated facies development porosity and permeability measurements taken across the field are analyzed to determine best reservoir facies and their distribution the new stratigraphic model is useful for predicting facies architecture in other analogous reef complexes such as those elsewhere in the gulf of mexico and in the middle east its tie to reservoir facies distributions also improves its utility for exploration purposes furthermore this work demonstrates that halokinesis has a major impact on carbonate development and necessitates a new generalized model for halokinetically altered carbonate platforms

earthquake supercycles inferred from sea level changes recorded in the corals of west sumatra records of relative sea level change extracted from corals of the mentawai islands sumatra imply that this 700 kilometer long section of the sunda megathrust has generated broadly similar sequences of great earthquakes about every two centuries for at least the past 700 years the moment magnitude 8 4 earthquake of september 2007 represents the first in a series of large partial failures of the mentawai section that will probably be completed within the next several decades

speleogenetic history of the hungarian hydrothermal karst the hydrothermal karst of hungary displays at least two principal stages of development in two differing environments caves of an early stage were formed within a deep zone of low thermal gradient these caves vugs are small tens of centimeters and lined with scalenohedral crystals of calcite that are often in association with barite calcite yields fluid inclusion temperatures of 55 95 c and is depleted in18o 11 2 to 17 6 per mil pdb the caves were formed by ascending thermal waters charged with co2 solubility of caco3 in such a system gradually increases with the ascent of the fluid solutional zone but drops sharply at a depth of 250 m to 500 m below the water surface depositional zone caves formed in the solutional zone may be shifted into the depositional zone due to tectonic uplift and calcite lines their walls large caves tens to thousands of cubic meters of a late stage were formed within a shallow zone of high thermal gradient immediately below and above the thermal water table the calcite of the phreatic crusts has a rhombohedral habit displays lower fluid inclusion temperatures 35 55 c and less and a depletion in18o of 9 5 to 14 6 per mil pdb several powerful cave forming processes may operate there including convection mixing cooling corrosion and condensation corrosion due to differences in the rate of tectonic uplift rate of hydrothermal system decay and hydrogeologic pattern these caves were either filled with water for a long period of time phreatic calcite crusts are formed or partly dewatered early in their history waterline and subaerial speleothems are formed the zones of thermal cave formation recognized in hungary may have a universal character very similar features are found in other hydrothermal karst areas of the world kirghizia algeria south dakota

a systematic technique for the sequential restoration of salt structures abstract a method is described for the sequential restoration of cross sections in areas of salt tectonics where deformation is confined to the salt and higher layers the subsurface geometry evolves with time through the interaction of various processes sedimentation compaction isostatic adjustment thermal subsidence if present faulting and salt withdrawal diapirism the technique systematically calculates and removes the effects of each of these processes during specified time intervals defined by the interpreted horizons it makes no assumptions about salt kinematics and generally results in the area of the salt layer changing through time the method is described for restoration of extensional terranes but it is also suitable for areas of contractional salt tectonics with only minor modifications after converting an interpreted seismic profile to depth the top layer is stripped off and the underlying section is decompacted according to standard porosity depth functions a deep baseline unaffected by compaction or deformation is used to restore any isostatic compensation or thermal subsidence isostasy is calculated according to the airy model and differential sedimentary loading across a section is shown to be approximately balanced by changes in salt thickness so that the load is evenly distributed after these processes have been reversed the resulting geometry and the seismic data are used to create the sea floor template for structural restoration fault offsets are removed and the layers down to the top salt are restored to this template while the base salt remains fixed the resulting space between the restored top salt and the fixed base salt defines the restored salt geometry in addition the difference between the sea floor template and a fixed sea level provides a measure of the change in water depth ignoring eustatic changes in sea level the technique is applied to an interpreted seismic profile from the eastern green canyon ewing bank area of offshore louisiana the section is characterized by a variety of salt structures including salt rollers a diapiric massif a remnant salt sheet and a salt weld which are shown to have derived from an originally continuous salt sheet which has been modified by sedimentary loading early loading created vertical basin growth that was accommodated primarily by salt withdrawal and associated diapiric rise through the process of downbuilding once the salt weld formed continued sedimentation was accommodated by a lateral increase in basin size caused by down dip extension on listric growth faults

source complexity of the 1988 armenian earthquake evidence for a slow after slip event we analyzed teleseismic p and s waves using a multiple event deconvolution method to investigate the source process of the spitak armenia earthquake of december 7 1988 teleseismic long period body waves exhibit complex waveforms significantly more complex than those normally seen for an event of this size we identified two groups of subevents one is a group of strike slip events during the first 20 s the other is a dip slip event initiating at about 30 s after the initial rupture the tensor sum of all the subevents is essentially strike slip strike 302 dip 59 rake 143 with a scalar moment of 1 47 10 19 n m the seismic moment of the dip slip event strike 89 dip 60 rake 88 is 5 6 10 18 n m nearly 40 of the total and the moment release rate is slower than the other subevents with a strike slip mechanism we call this event a slow after slip event the mechanism of the after sup event is consistent with the present day deformation pattern in the caucasus where north south compression is predominant due to the continental collision between the arabian plate and the russian platform this result suggests that in a region where both strike slip motion and crustal shortening are taking place like southern california a large strike slip event may accompany large thrust events and vice versa in order to determine the total coseismic deformation pattern it is essential to resolve these multiple events in time space and mechanism

strain partitioning during oblique plate convergence in northern sumatra geodetic and seismologic constraints and numerical modeling global positioning system gps measurements along the subduction zone of northern sumatra 2 s to 3 n reveal that the strain associated with the oblique convergence of the australian plate with eurasia is almost fully partitioned between trench normal contraction within the forearc and trench parallel shear strain within a few tens of kilometers of the sumatran fault kinematic analyses of interplate earthquake slip vectors provide slip rates on the sumatran fault within a few millimeters per year of gps and geologic rates giving us more confidence in the use of slip vectors for inferring slip partitioning elsewhere the inferred slip rate on the sumatran fault is 1 3 less than the full margin parallel component of plate motion an across forearc rotation in the slip vectors suggests that the missing arc parallel shear occurs seaward of the geodetic network between the forearc islands and the trench simple finite element models are used to explore the conditions under which the change in the principal strain rate directions between the forearc and the arc region can occur modeling suggests that neither a preexisting strike slip fault nor a zone of thermally induced lithospheric weakness in the overriding plate is needed for strain partitioning to occur in general forearc slivers form over the region of interplate coupling and are driven along strike by the basal shear a volcanic arc can help the partitioning process by localizing the margin parallel shear strain in the upper plate if its crust and mantle are weaker than its surroundings interplate slip vectors and geodetic results from sumatra together suggest that the highest coupling on the plate boundary occurs beneath and seaward of the forearc islands consistent with inferences about the rupture zones of great nineteenth century earthquakes there the sumatra example suggests that geodetic measurements of interseismic margin parallel shear strain at oblique convergent margins can be used to map the landward extent of the relatively high basal stress beneath the overriding plate if one can correct for strain localization caused by weak upper plate strike slip faults

uranium series dating of the draining of an aquifer the example of wind cave black hills south dakota wind cave south dakota is a three dimensional rectilinear maze cave developed in 90 m of mississippian limestone and dolomite that is overlain by thick clastic cover strata beneath an area of 1 8 km 2 87 km of small drained phreatic passages are known exploration terminates at a water table 160 m below the highest parts of the cave as the cave was draining calcite precipitated from its waters uranium series measurements 85 were taken on fragments of broken calcite crusts collected in the lower 93 m of the cave the measurements reveal that it has been draining as a backwater for at least the past 300 000 yr 234 u 238 u ratios in the water were remarkably constant allowing estimation of ages beyond 400 ky b p after deducting glacial interglacial cyclic oscillations of 10 to 20 m amplitude the water table appears to have been lowered at a steady rate of 0 4 m per 10 3 yr since 400 ky b p most of this fall is attributed to the increase of hydraulic conductivity in the 260 m of cover strata that separates the carbonate aquifer from its spring discharge points a subaqueous calcite deposition zone extended to 70 m below the contemporary water table at all times where mean rates of deposition were 0 12 mm per 10 3 yr or less modeling of the precipitation kinetics suggests a well mixed water body with a ca 2 concentration close to the thermodynamic equilibrium value and variations of depositional rate being controlled by hydrostatic pressure

tectonic history and setting of a seismogenic intraplate fault system that lacks microseismicity the saline river fault system southern united states abstract although the northwest striking saline river fault system of southeastern arkansas is not defined by microseismicity it is associated with sand blows and shows evidence of pleistocene and holocene surface ruptures suggesting a significant seismogenic potential this fault system is within the northern gulf of mexico interior coastal plain a region only recently recognized as containing seismogenic faults to better characterize this active fault system we reconstructed its post paleozoic history using petroleum and coal industry wire line well log and seismic reflection subsurface data the saline river fault system initiated as a series of northwest striking grabens during triassic jurassic uplift and incipient gulf of mexico rifting along the basement alabama oklahoma transform margin of the north american proterozoic craton during post rift subsidence these grabens were buried by gulf sediments until mid cretaceous uplift and igneous activity resulted in minor extensional reactivation of graben faults faulting style changed from extension to transpression during the late cretaceous due to compression of eastern north america as the north atlantic rapidly widened and due to thermal weakening of the alabama oklahoma transform lithospheric discontinuity as it obliquely crossed a mantle hot spot in the late cretaceous graben faults experienced contractional reactivation and steep deeply rooted transpressional faults developed within and parallel to the graben system these transpressional faults locally displace eocene pleistocene and holocene sediments fault activity continues on the saline river fault system due to thin crust along the alabama oklahoma transform and to high heat flow which act together to weaken the crust and promote seismogenic tectonism the fault system may lack appreciable microseismicity because the aftershock sequence of the last large earthquake has had time to dissipate

response of the san andreas fault to the 1983 coalinga nunez earthquakes an application of interaction based probabilities for parkfield 1 the parkfield cholame section of the san andreas fault site of an unfulfilled earthquake forecast in 1985 is the best monitored section of the world s most closely watched fault in 1983 the m 6 5 coalinga and m 6 0 nunez events struck 25 km northeast of parkfield seismicity rates climbed for 18 months along the creeping section of the san andreas north of parkfield and dropped for 6 years along the locked section to the south right lateral creep also slowed or reversed from parkfield south here we calculate that the coalinga sequence increased the shear and coulomb stress on the creeping section causing the rate of small shocks to rise until the added stress was shed by additional slip however the 1983 events decreased the shear and coulomb stress on the parkfield segment causing surface creep and seismicity rates to drop we use these observations to cast the likelihood of a parkfield earthquake into an interaction based probability which includes both the renewal of stress following the 1966 parkfield earthquake and the stress transfer from the 1983 coalinga events we calculate that the 1983 shocks dropped the 10 year probability of a m 6 parkfield earthquake by 22 from 54 22 to 42 23 and that the probability did not recover until about 1991 when seismicity and creep resumed our analysis may thus explain why the parkfield earthquake did not strike in the 1980s but not why it was absent in the 1990s we calculate a 58 17 probability of a m 6 parkfield earthquake during 2001 2011 index terms 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics 7260 seismology theory and modeling keywords coalinga earthquake parkfield stress change earthquake probability seismicity rate

late holocene episodic displacement on fault scarps related to interstratal dissolution of evaporites teruel neogene graben ne spain abstract the mio pliocene formations of the turolian type section teruel graben spain have sagged due to dissolution of the underlying triassic evaporites generating a 1 7 km long monocline and accompanying synform with 130 m of structural relief the crest of the monocline is affected by a graben that counterbalances the shortening caused by passive bending in the adjacent syncline this graben is controlled by a master synthetic fault and a swarm of antithetic and synthetic faults with a conspicuous geomorphic expression after acquiring ground penetrating radar gpr profiles three trenches were excavated in depressions associated with uphill facing fault scarps to our knowledge these are the first trenches excavated across faults caused by deep seated dissolution of evaporites the geometrical relationships observed in two trenches indicate late holocene episodic displacement as many as 3 events some of the parameters estimated for the investigated faults are clearly different from those expectable for tectonic faults in this intraplate area they include high apparent vertical slip rates 0 6 1 mm yr low average recurrence of faulting events 1 2 2 ka and very high displacement per event values 65 cm for surface ruptures less then 200 m long our findings suggest that considering evaporite collapse faults as creeping structures is not a reliable criterion to differentiate between tectonic faults seismogenic and dissolution induced gravitational faults nonseismogenic

haynesville and bossier mudrocks a facies and sequence stratigraphic investigation east texas and louisiana usa abstract upper jurassic haynesville and bossier shale gas plays of the northwestern gulf of mexico gom basin produce from organic rich marine transgressive to highstand mudrocks within mixed carbonate clastic depositional systems modern wireline log suites from 200 deep wells were used for detailed correlations and 10 cores throughout the upper kimmeridgian to lower tithonian basin were incorporated into detailed facies stratigraphic and lithologic analyses the haynesville shale lies within a 2nd order transgressive systems tract tst that encompasses back stepping ramp carbonates proximal and marine shales distal below a maximum flooding surface mfs this shale onlaps retrogradational carbonates and basement highs and is capped by the 2nd order mfs bossier shales and local sandstones prograde basinward above the haynesville shale and downlap the 2nd order mfs they grade upward and updip into the thick highstand systems tract hst fluvio deltaic sandstones of the cotton valley group distally organic rich facies developed in restricted bossier environments creating another productive gas shale opportunity several preexisting basement highs in the south and carbonate platforms in the northwest and west restrict and partition the basin thus influencing deposition of highly organic versus nonorganic and siliciclastic dominated versus carbonate dominated lithologies haynesville and bossier shales each compose three upward coarsening cycles that probably represent 3rd order sequences within the larger 2nd order tst and early hst respectively most of the three bossier 3rd order cycles are dominated by varying amounts of siliciclastics deposition of the haynesville mudrocks occurred below storm wave base under mostly dysoxic conditionsm allowing settlement of benthic bivalve communities and bioturbating organisms and oscillating periodically to more anoxic conditions on the seafloor however most of the sparse faunae found in these mudrocks are of planktonic origin bossier mudrocks exhibited more oxygenated and clastic rich lithologies related to progradation of the clastic shoreline and sea level highstand knowledge of lithologic stratigraphic geochemical and faunal variations across mudrock basins needs to be detailed so that shale gas basins might be successfully explored

rapid estimation of rupture directivity application to the 1992 landers ms 7 4 and cape mendocino ms 7 2 california earthquakes using empirical green functions with regional and teleseismic surface waves it is possible to resolve fault finiteness effects in many cases uniquely defining the fault plane for relatively large earthquakes the technique requires very little data processing and can be applied in near real time with the current distribution of seismic stations the landers strike slip earthquake was dominated by two sub events with predominantly north northwestward rupture the second sub event was 1 5 times larger and rotated in strike by 12 counterclockwise relative to the first the cape mendocino thrust event had a relatively smooth rupture that propagated to the southwest on a shallow dipping fault

teleseismic double difference relocation of earthquakes along the sumatra andaman subduction zone using a 3 d model 1 we have extended the double difference seismic tomography method to teleseismic distances with 3 d ray tracing conducted through nested regional global velocity models and applied the method to relocate seismicity from the sumatra andaman region before and after the great earthquakes of 2004 and 2005 we tested the algorithm s accuracy using both independent local data and an alternate relocation method and found good agreement between the results the use of depth phases differential times and a realistic 3 d velocity model improves the accuracy and precision of epicenters and focal depths systematically shifting them perpendicular to the trench and shallower respectively the relocations refine the location of the megathrust and other faults the patterns of aftershocks and their relation to slip during the two great earthquakes in addition the relocations reveal several discrete features not readily discernible in the scatter of teleseismic catalogs including an arcuate narrow band of earthquakes presumed to define the updip rupture limit in the 2005 event and a lineation at depth tracing the subduction of the investigator fracture zone when viewed in conjunction with tomography results the geometry and structural features of the subduction zone are revealed in unprecedented detail

3d gravity modeling of the triassic salt diapirs of the cubeta alavesa northern spain abstract up to now subsurface information permitted the delineation of the top of the triassic salt all throughout the cantabro navarro domain although little was known on the location and geometry of its base and thus on the estimation of the total salt thickness a 3d gravity inversion scheme combined with a 3d analytic method has been conducted to map out the geometry of the main salt structures of the basin the gravity modeling results have been constrained by well log information and available geological and reflection seismic data the combined 3d scheme integrated with available geological and geophysical data has allowed us to obtain the geometry of the main diapirs that characterize the central and marginal regions of the basin from our interpretation the salinas de anana diapir has almost vertical flanks and can be divided into two different parts one of them forming a lateral overhang of the main body the salinas de oro diapir has near vertical flanks and a main axis in the n s direction also the anomaly is rather more extensive than the outcrop of the diapir which implies an important expansion of non outcropping salt in this area like the hoz sobron diapir the salinas de ollo diapir is long and narrow stretching in the nw se direction which includes three important highs plus an intense zone of salt migration the estella and alloz diapirs crop out individually in spite of being connected at depth also two non outcropping salt domes have been detected to the south of atauri that like the estella diapir are related to the thrust front we point out the gravity signature of the murguia diapir which shows an intense gravity high probably due to the presence of high density rocks in the cap rock or more probably due to the existence of triassic volcanites of ophitic texture pinched off into the diapir

tectonic speleogenesis of devils hole nevada and implications for hydrogeology and the development of long continuous paleoenvironmental records devils hole in southern nevada is a surface collapse into a deep planar steeply dipping fault controlled fissure in cambrian limestone and dolostone the collapse intersects the water table about 15 m below land surface and the fissure extends at least 130 m deeper below water most of the fissure is lined with a 30 cm thick layer of dense maxillary calcite that precipitated continuously from groundwater for 500 000 yr the thick mammillary calcite coat implies a long history of calcite supersaturated groundwaters which combined with the absence of dissolutional morphologies suggests that devils hole was not formed by karst processes devils hole is located in a region of active extension its tectonic origin is shown by evidence of spreading of its planar opening along a fault and by the orientation of its opening and others nearby perpendicular to the northwest southeast minimum principal stress direction of the region most quaternary tectonic activity in the area including seismicity and quaternary faults and fractures occurs on or parallel to northeast striking structures the hydrogeologic implications of this primarily structural origin are that fracture networks and caves opened by extensional tectonism can act as groundwater flowpaths functionally similar to those developed by karst processes and that during active extension transmissivity can be maintained despite infilling by mineral precipitation such extensional environments can provide conditions favorable for accumulation of deposits preserving long continuous paleoenvironmental records the precipitates in devils hole store chronologies of flow system water level fluctuations hydrochemistry a half million yr proxy paleoclimate record evidence of devils hole s tectonic origin and probably atmospheric circulation

age distribution estimation for karst groundwater issues of parameterization and complexity in inverse modeling by convolution summary convolution modeling is useful for investigating the temporal distribution of groundwater age based on environmental tracers the framework of a quasi transient convolution model that is applicable to twodomain flow in karst aquifers is presented the model was designed to provide an acceptable level of statistical confidence in parameter estimates when only chlorofluorocarbon cfc and tritium 3 h data are available we show how inverse modeling and uncertainty assessment can be used to constrain model parameterization to a level warranted by available data while allowing major aspects of the flow system to be examined as an example the model was applied to water from a pumped well open to the madison aquifer in central usa with input functions of cfc 11 cfc 12 cfc 113 and 3 h and was calibrated to several samples collected during a 16 year period a bimodal age distribution was modeled to represent quick and slow flow less than 50 years old the effects of pumping and hydraulic head on the relative volumetric fractions of these domains were found to be influential factors for transient flow quick flow and slow flow were estimated to be distributed mainly within the age ranges of 0 2 and 26 41 years respectively the fraction of long term flow 50 years was estimated but was not dateable the different tracers had different degrees of influence on parameter estimation and uncertainty assessments where

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

constraining the boundary between the sunda and andaman subduction systems evidence from the 2002 mw 7 3 northern sumatra earthquake and aftershock relocations of the 2004 and 2005 great earthquakes the 2004 m w 9 0 sumatra andaman earthquake initiated along the andaman subduction zone north of the last great sumatra earthquake along the sunda trench in 1861 during the 2005 m w 8 7 banyak islands earthquake a portion of the 1861 rupture subsequently failed the boundary between the 2004 and 2005 ruptures broadly coincides with local trench rotation and the southern edge of the andaman microplate which suggests structural control on fault segmentation aftershock relocations of the 2004 and 2005 earthquakes show little overlap and the sharp boundary between the series locates near the 2002 m w 7 3 northern sumatra earthquake we posit that these features represent the southern extent of the stable andaman microplate 50 100 km northwest of what was previously reported broadband analyses of the 2002 earthquake yield a bilateral rupture pattern that is used to model coulomb stress changes near the 2004 hypocenter to assess stress interactions along adjacent fault segments

basin edge diapirism and updip salt flow in zechstein of southern north sea some unusual and interesting structural geometries have been recognized on seismic lines recorded in the united kingdom sector of the southern permian basin of the north sea they seem to be the result of diapirism at the northern edge of the upper permian zechstein salt basin and involve the preservation of a 75 km 47 mi long prism of a younger mesozoic sequence replaced elsewhere by the widespread jurassic cretaceous late kimmerian unconformity it is suggested that the diapiric features described are due to the movement of salt toward the basin edge having been dammed by a change in facies from basinal halite to shelf lithologies over a short distance

origin of the salt valleys in the canyonlands section of the colorado plateau evaporite dissolution collapse versus tectonic subsidence abstract the salt valleys over the axis of the salt cored anticlines in the paradox fold and fault belt canyonlands utah and colorado are created by subsidence of the anticline crests traditionally the collapse of the anticlinal crests was attributed to dissolution of the salt walls diapirs forming the anticline cores recent studies based on scaled physical models and field observations propose that the salt valleys are a result of regional extension and that salt dissolution had only a minor influence in the development of the axial depressions this paper presents several arguments and lines of evidence that refute the tectonic model and support the salt dissolution subsidence interpretation the development of contractional structures in salt dissolution experiments led the advocates of the tectonic interpretation to reject the dissolution induced subsidence explanation however these salt dissolution models do not reproduce the karstification of salt walls in a realistic way since their analog involves removal of salt from the base of the diapirs during the experiments additionally numerous field examples and laboratory models conducted by other authors indicate that brittle subsidence in karst settings is commonly controlled by subvertical gravity faults field evidence against the regional extension model includes 1 a thick cap rock at the top of the salt walls 2 the concentration of subsidence deformation structures along the crest of the anticlines salt walls 3 deformational structures not consistent with the proposed nne extension like crestal synforms and ne sw grabens 4 dissolution induced subsidence structures controlled by ring faulting revealing deep seated dissolution 5 large blocks foundered several hundred meters into the salt wall 6 evidence of recent and active dissolution subsidence and 7 the aseismic nature of the recently active collapse faults although underground salt dissolution seems to be the main cause for the generation of the salt valleys this phenomenon may have been favored by regional extension tectonics that enhance the circulation of groundwater and salt dissolution

salt tectonics in the norwegian danish basin a study is presented of salt tectonics in a 28 000 km2 area in the norwegian danish basin of the north sea the basin is mainly of permian to early jurassic age and contains sediments which locally reach 8 km in thickness zechstein upper permian salt occurs widely in the basin and has given rise to widespread and intense salt tectonics using seismic reflection sections with a total length of 14 000 km as well as borehole data 86 salt structures have been mapped within the study area the floor of the basin that is the base of the zechstein salt and the faults affecting this floor have also been mapped it is therefore possible to investigate the association of faults and salt structures and hence to ascertain to what extent faulting of the basin floor may have initiated salt movement various lines of investigation and reasoning have been developed to arrive at an estimate of the number of structures for which salt movement is likely to have been initiated by faulting of the basin floor it is found that only for a limited number of salt structures probably about five out of a total of 86 structures the salt movement is likely to have been initiated by faulting the very large majority of the salt structures originated independent of faulting the mechanism responsible for the initiation of salt movement in this majority has also been studied it is found that these salt structures can be divided into two groups one group comprises about 37 salt structures which are randomly distributed nearly all of them are situated where the present basin floor is relatively flat and at its deepest they are thought to be the result of classical halokinesis that is the autonomous upward movement under the influence of gravity of mobile salt at locations where the sedimentary overburden at the time of initial movement was locally less heavy a second group comprises about 43 individual structures which are aligned along nine so called trend lines it is first shown that these trend lines are independent of faults and fault trends in the basin floor the origin of these trends is then discussed by considering two alternative hypotheses for the mechanism responsible for the initiation of salt movement along these trend lines the first hypothesis assumes that salt ridges in the subsurface are initially pushed up by a prograding sedimentary overburden the second hypothesis assumes that initial ridges of mobilized salt are formed along a palaeo depth contour which migrates up the flank of the subsiding basin both hypotheses assume that the salt ridges thus formed can subsequently develop into individual salt structures which produce the observed pattern of trend lines a critical analysis of these two alternative hypotheses leads to the conclusion that the second one involving the concept of a palaeo depth contour which migrates up flank is the more acceptable the mechanism involved may be characterized as a special type of halokinesis namely as halokinesis constrained to operate along a line

natural and human induced dissolution and subsidence processes in the salt outcrop of the cardona diapir ne spain the cardona diapir in ne spain with a salt outcrop about 0 9 km2 in area has a well developed endokarstic system that used to discharge into the cardener river underground mining for potassium salt carried out from 1930 to 1990 caused significant changes in the topography and hydrology of the diapir the accumulation of two halite slag heaps totalling around 10 million tons locally dammed the surface drainage creating closed depressions and preferential zones of water recharge the waters that infiltrated in one of these depressions largely derived from uncontrolled sewage disposal led to the generation of a 335 m long human induced cave excavated in one of the slag heaps moreover the inflow of freshwater from the surrounding sandstone aquifer caused by the excavation of a ventilation gallery resulted in the generation of a 280 m long cave in march 1998 the interception of a phreatic conduit by a halite mine gallery 50 m deep caused dramatic changes in the hydrology and geomorphology of the diapir including a a sudden decline in the piezometric level of the karstic aquifer b the inflow of freshwater and debris from the cardener river into the endokarstic system and the mine galleries a tunnel had to be constructed to divert the river flow from the salt outcrop c massive dissolution of salt creating new cavities and enlarging the pre existing ones including both mine galleries or cave passages the 4 300 m long salt meanders cave was largely generated by the inrush of water from the cardener river into the mine galleries and d the generation of a large number of sinkholes in the vicinity of the cardener river an inventory of 178 sinkholes has allowed us to estimate minimum probability values of 4 7 and 8 sinkholes km2 year for time intervals previous and subsequent to the 1998 mine flood event respectively

late quaternary paleoclimate in semiarid northeastern brazil from u series dating of travertine and water table speleothems abstract fossil travertine and subaqueous speleothems in presently dry caves suggest periods of enhanced ground water recharge during the quaternary period in semiarid northeastern brazil travertine deposits and water table speleothems were dated by the 230 th 234 u technique yielding new evidence for the timing of past periods of increased rainfall the travertine was deposited in two distinct phases extensive in situ deposits during marine isotope stage 2 and fragmentary indurated deposits dating to ca 400 000 yr b p possibly marine isotope stage 10 or 12 dating of water table speleothems showed that the regional water table was 13 1 m above the present level at the last glacial maximum a second site yielded ages suggesting a still higher water table during marine isotope stage 6 these new data demonstrate that northeastern brazil did not follow the general pattern of a dry last glacial maximum as suggested by other continental records in amazonia and southeastern brazil and as depicted in recent general circulation model gcm simulations our results thus indicate that significant variability in regional rainfall patterns occurred in the area during glaciations and caution against overgeneralization of paleoclimate patterns

stress triggering in thrust and subduction earthquakes and stress interaction between the southern san andreas and nearby thrust and strike slip faults 1 we argue that key features of thrust earthquake triggering inhibition and clustering can be explained by coulomb stress changes which we illustrate by a suite of representative models and by detailed examples whereas slip on surface cutting thrust faults drops the stress in most of the adjacent crust slip on blind thrust faults increases the stress on some nearby zones particularly above the source fault blind thrusts can thus trigger slip on secondary faults at shallow depth and typically produce broadly distributed aftershocks short thrust ruptures are particularly efficient at triggering earthquakes of similar size on adjacent thrust faults we calculate that during a progressive thrust sequence in central california the 1983 mw 6 7 coalinga earthquake brought the subsequent 1983 mw 6 0 nunez and 1985 mw 6 0 kettleman hills ruptures 10 bars and 1 bar closer to coulomb failure the idealized stress change calculations also reconcile the distribution of seismicity accompanying large subduction events in agreement with findings of prior investigations subduction zone ruptures are calculated to promote normal faulting events in the outer rise and to promote thrust faulting events on the periphery of the seismic rupture and its downdip extension these features are evident in aftershocks of the 1957 mw 9 1 aleutian and other large subduction earthquakes we further examine stress changes on the rupture surface imparted by the 1960 mw 9 5 and 1995 mw 8 1 chile earthquakes for which detailed slip models are available calculated coulomb stress increases of 2 20 bars correspond closely to sites of aftershocks and postseismic slip whereas aftershocks are absent where the stress drops by more than 10 bars we also argue that slip on major strike slip systems modulates the stress acting on nearby thrust and strike slip faults we calculate that the 1857 mw 7 9 fort tejon earthquake on the san andreas fault and subsequent interseismic slip brought the coalinga fault 1 bar closer to failure but inhibited failure elsewhere on the coast ranges thrust faults the 1857 earthquake also promoted failure on the white wolf reverse fault by 8 bars which ruptured in the 1952 mw 7 3 kern county shock but inhibited slip on the left lateral garlock fault which has not ruptured since 1857 we thus contend that stress transfer exerts a control on the seismicity of thrust faults across a broad spectrum of spatial and temporal scales

lateral variations of the midcrustal seismicity in western nepal seismotectonic implications abstract the midcrustal seismicity along the himalayas depicts some lateral variations this seismicity is often related to stress build up at depth along the downdip extent of the fault segments producing large and great earthquakes to better characterize these variations we deployed the first temporary seismological network in west nepal hiknet as a complement to the nepalese national network we used automatic picks manually validated to perform absolute and relative location of the earthquakes the resulting catalog contains 2190 local events shallow to midcrustal 8 16 km the comparison between the seismicity and the geologic balanced cross sections shows that most earthquakes occur within the hanging wall of the main himalayan thrust fault nearby ramps or suspected contacts between lesser himalayan slivers some of the events associated with these geological structures are clustered within weeks long earthquake swarms with seismic envelopes migrating at 35 50 m day these transients are possibly related to fluid migrations or geodetically unresolved slow slip events the lateral variations of some of the structures associated to this seismicity are likely partially controlling the extent of the coseismic ruptures during intermediate earthquakes that break partly the locked fault zone in a similar way to what was reported after the mw7 8 2015 gorkha nepal earthquake a better characterization of the faults segmentation including a better location and extent of the seismogenic segments at depth is an important input for seismic hazard studies

holocene marine terraces on two salt diapirs in the persian gulf iran age depositional history and uplift rates slightly inclined holocene marine terraces cover parts of two circular salt diapirs hormoz and namakdan in the persian gulf their relative altitude above present sea level results from a combination of general marine transgression regression affecting the whole area and of local uplift related to salt diapirism differential uplift rate of the studied diapirs in centre to rim profiles was calculated from results based on i radiocarbon ages of skeletal remains of benthic faunas 19 samples which originally grew close to sea level ii original altitude of samples estimated from general sea level oscillation curves for the last 10 kyr and iii present sample altitude measured in the field calculated uplift rates increase from rim to centre on both diapirs in the range from 2 mm yr 1 at the rim to 5 6 mm yr 1 at the interior of hormoz and 1 3 mm yr 1 at the rim to 3 5 mm yr 1 at the interior of namakdan such uplift rate distributions fit into the parabolic profile of newtonian fluid rather than to profiles typical for pseudoplastic fluids the increase in uplift rate with distance from rim to centre of diapirs is gradual as demonstrated also by generally smooth surface of marine terraces no tectonic dissections were found the depositional history on both salt diapirs is similar although they are situated more than 100 km apart marine sedimentation started at about 9 6k cal yr bp on hormoz and at 8 6k cal yr bp on namakdan owing to rapid transgression the sea partially truncated both salt diapirs and rapidly deepened and carbonate mud was deposited on the peripheries of both salt diapirs between 7 and 5k cal yr bp beach deposition replaced carbonate mud soon after 5k cal yr bp the sea retreated from most of the marine terraces on both salt diapirs copyright 2006 john wiley sons ltd

neotectonics of the sumatran fault indonesia the 1900 km long trench parallel sumatran fault accommodates a significant amount of the right lateral component of oblique convergence between the eurasian and indian australian plates from 10 n to 7 s our detailed map of the fault compiled from topographic maps and stereographic aerial photographs shows that unlike many other great strike slip faults the sumatran fault is highly segmented cross strike width of step overs between the 19 major subaerial segments is commonly many kilometers the influence of these step overs on historical seismic source dimensions suggests that the dimensions of future events will also be influenced by fault geometry geomorphic offsets along the fault range as high as 20 km and may represent the total offset across the fault if this is so other structures must have accommodated much of the dextral component of oblique convergence during the past few million years our analysis of stretching of the forearc region near the southern tip of sumatra constrains the combined dextral slip on the sumatran and mentawai faults to be no more than 100 km in the past few million years the shape and location of the sumatran fault and the active volcanic arc are highly correlated with the shape and character of the underlying subducting oceanic lithosphere nonetheless active volcanic centers of the sumatran volcanic arc have not influenced noticeably the geometry of the active sumatran fault on the basis of its geologic history and pattern of deformation we divide the sumatran plate margin into northern central and southern domains we support previous proposals that the geometry and character of the subducting investigator fracture zone are affecting the shape and evolution of the sumatran fault system within the central domain the southern domain is the most regular the sumatran fault there comprises six right stepping segments this pattern indicates that the overall trend of the fault deviates 4 clockwise from the slip vector between the two blocks it separates the regularity of this section and its association with the portion of the subduction zone that generated the giant m w 9 earthquake of 1833 suggest that a geometrically simple subducting slab results in both simple strike slip faulting and unusually large subduction earthquakes

the updip seismic aseismic transition of the sumatra megathrust illuminated by aftershocks of the 2004 aceh andaman and 2005 nias events great subduction earthquakes exhibit segmentation both within the rupture of individual events and in the long term history of the margin the 2004 december 26 aceh andaman and 2005 march 28 nias event in northern sumatra are two of the largest earthquakes in recent years with both co and post seismic displacements constrained in unprecedented detail using aftershock locations from a temporary seismic array in the boundary region between both events and waveform modelling of large aftershocks we demonstrate that the vast majority of aftershocks in the study region occur on the plate interface within a narrow band 20 km seaward of the outer arc high comparing the seismicity distribution to the co and post seismic displacements we infer that the seismic band marks the transition between the seismogenic zone and stable sliding the location of the band and therefore the transition appears to be correlated with the 500 m bathymetry contour this close correspondence is disrupted at the boundary between the two great earthquakes where the transition to seismogenic behaviour occurs further landward by 25 km to the west of simeulue where seafloor bathymetry throughout the forearc is deeper than 500 m the seismic band terminates abruptly and the focus of aftershock activity is found near the trench the seismic efficiency of afterslip varies dramatically along strike the segment below the banyak islands in the gap between the two main asperities of the nias earthquake accommodates a much larger proportion of afterslip seismically

source parameters of the great sumatran megathrust earthquakes of 1797 and 1833 inferred from coral microatolls large uplifts and tilts occurred on the sumatran outer arc islands between 0 5 and 3 3 s during great historical earthquakes in 1797 and 1833 as judged from relative sea level changes recorded by annually banded coral heads coral data for these two earthquakes are most complete along a 160 km length of the mentawai islands between 3 2 and 2 s uplift there was as great as 0 8 m in 1797 and 2 8 m in 1833 uplift in 1797 extended 370 km between 3 2 and 0 5 s the pattern and magnitude of uplift imply megathrust ruptures corresponding to moment magnitudes m w in the range 8 5 to 8 7 the region of uplift in 1833 ranges from 2 to at least 3 2 s and judging from historical reports of shaking and tsunamis perhaps as far as 5 s the patterns and magnitude of uplift and tilt in 1833 are similar to those experienced farther north between 0 5 and 3 n during the giant nias simeulue megathrust earthquake of 2005 the outer arc islands rose as much as 3 m and tilted toward the mainland elastic dislocation forward modeling of the coral data yields megathrust ruptures with moment magnitudes ranging from 8 6 to 8 9 sparse accounts at padang along the mainland west coast at latitude 1 s imply tsunami runups of at least 5 m in 1797 and 3 4 m in 1833 tsunamis simulated from the pattern of coral uplift are roughly consistent with these reports the tsunami modeling further indicates that the indian ocean tsunamis of both 1797 and 1833 unlike that of 2004 were directed mainly south of the indian subcontinent between about 0 7 and 2 1 s the lack of vintage 1797 and 1833 coral heads in the intertidal zone demonstrates that interseismic submergence has now nearly equals coseismic emergence that accompanied those earthquakes the interseismic strains accumulated along this reach of the megathrust have thus approached or exceeded the levels relieved in 1797 and 1833

thermal evolution of the north central gulf coast the subsidence history of the north louisiana salt basin determined from well data indicates that the region underwent extension during rifting and has since passively subsided due to conductive cooling of the lithosphere timing of the rifting event is consistent with opening of the gulf of mexico during late triassic to early jurassic time crustal extension by a factor of 1 5 to 2 was computed from tectonic subsidence curves however data from the early subsidence history are insufficient to distinguish between uniform and nonuniform extension of the lithosphere the magnitude of extension is in good agreement with total sediment and crustal thicknesses from seismic refraction data in the adjacent central mississippi salt basin the temperature distribution within the sediments is calculated using a simple heat conduction model temperature and subsidence effects of thermal insulation by overlying sediments are included the computed temperature distribution is in good agreement with bottom hole temperatures measured in deep wells temperature histories predicted for selected stratigraphic horizons within the north louisiana salt basin suggest that thermal conditions have been favorable for hydrocarbon generation in the older stata results from a two dimensional heat conduction model suggest that a probable cause for the early formation of the adjacent uplifts is lateral heat conduction from the basin rapid extension of the lithosphere underneath areas with horizontal dimensions of 50 100 km produces extremely rapid early subsidence due to lateral heat conduction the moderate subsidence rate observed in the north louisiana salt basin during the jurassic and early cretaceous suggests slow extension over a long period of time

the great sumatra andaman earthquakes imaging the boundary between the ruptures of the great 2004 and 2005 earthquakes segmentation along convergent margins controls earthquake magnitude and location but the physical causes of segment boundaries and their impact on earthquake rupture dynamics are still poorly understood one aspect of the 2004 and 2005 great sumatra andaman earthquakes is their abrupt termination along a common boundary this has led to speculation on the nature of the boundary its origin and why it was not breached for the first time the boundary has been imaged and with newly acquired marine geophysical data we demonstrate that a ridge on the subducting indo australian oceanic crust may exert a control on margin segmentation this suggests a lower plate influence on margin structure particularly its segmentation the ridge is masked by the sedimentary cover in the trench its most likely trend is nne ssw it is interpreted as a fracture zone on the subducting oceanic plate a ramp or tear along the eastern flank of the subducting fracture zone beneath simeulue island may be considered as an intensification factor in terms of rupture propagation barrier

subduction system variability across the segment boundary of the 2004 2005 sumatra megathrust earthquakes subduction zone earthquakes are known to create segmented patches of co seismic rupture along strike of a margin offshore sumatra repeated rupture occurred within segments bounded by permanent barriers whose origin however is still not fully understood in this study we image the structural variations across the rupture segment boundary between the mw 9 1 december 26 2004 and the mw 8 6 march 28 2005 sumatra earthquakes a set of collocated reflection and wide angle seismic profiles are available on both sides of the segment boundary located offshore simeulue island we present the results of the seismic tomography modeling of wide angle ocean bottom data enhanced with mcs data and gravity modeling for the southern 2005 segment of the margin and compare it to the published model for the 2004 northern segment our study reveals principal differences in the structure of the subduction system north and south of the segment boundary attributed to the subduction of 96 e fracture zone the key differences include a change in the crustal thickness of the oceanic plate a decrease in the amount of sediment in the trench as well as variations in the morphology and volume of the accretionary prism these differences suggest that the 96 e fracture zone acts as an efficient barrier in the trench parallel sediment transport as well as a divider between oceanic crustal blocks of different structure the variability of seismic behavior is caused by the distinct changes in the morphology of the subduction complex across the boundary related to the difference in the sediment supply

floating rafts of calcite crystals in cave pools central texas u s a crystal habit vs saturation state abstract calcite precipitation at the air water interface in cave pools in central texas u s a produces floating rafts of interconnected low mg calcite crystals with individual crystal habits that range from equant length to width 1 1 to prismatic 4 1 saturation state for the waters ranges from 0 19 to 1 35 sic log iap k equant crystals precipitate from waters with a lower saturation index sic and form rafts with a fused fabric whereas prismatic crystals precipitate from higher sic waters and form rafts with an interlaced fabric the pools contain low magnesium molal mg ca 0 6 calcium bicarbonate and calcium bicarbonate nitrate type waters with temperatures that range from 13 8 c to 20 7 c and ph readings from 6 7 to 8 4 equant euhedral crystals precipitate from water with saturation states close to equilibrium visible defects in the equant crystals include incomplete edges between faces and nearly circular mean diameter 9 m to angular holes in faces the holes apparently result from crystallite growth around foreign objects on the crystal surface such as gas bubbles prismatic crystals precipitate from supersaturated water faces of these subhedral crystals are smaller in area than the faces of the equant crystals no intrafacial circular holes are seen but trigonal intercrystallite pores are common in the prismatic crystals the variety in crystal habits from equant to prismatic is due to preferential growth along one crystallographic axis thus in these cave pools crystal habit is related to the saturation state of the water

relaxation of continental lithosphere an explanation for late cretaceous reactivation of the sabine uplift of louisiana texas with few unconstrained assumptions a simple quantitative model for flexural isostasy between two crustal blocks of different thickness that subsequently undergoes partial relaxation of accumulated stress can explain reactivation of the sabine uplift in the mid cretaceous thin salt over the sabine uplift indicates that it was a positive area in the middle jurassic but began to subside during the late jurassic during the late jurassic and early cretaceous the sabine uplift had no topographic expression and was the center of a large flat bottomed basin covering most of east texas and north louisiana reactivation of the sabine uplift in the mid cretaceous caused a minimum of 150 m of uplift and extensive erosion of lower cretaceous rocks during the late cretaceous and tertiary the sabine uplift resumed subsiding but at a slower rate than the adjacent basins since the mid cretaceous the sabine uplift has risen more than 1 km relative to the east texas basin we suggest that this structural history is consistent with the following simple quantitative model for flexural isostasy during formation of the gulf of mexico in the late triassic early jurassic by rifting and extension of the lithosphere brittle deformation of the crust created small scale wavelength of tens of kilometers lateral variations in crustal thickness initially the newly formed margin was in point wise airy isostatic equilibrium thus synrift and or early postrift subsidence was characterized by a series of rift valleys or half grabens separated by uplifts however as the margin cooled and contracted the lithosphere became stronger and subsequent loading was regionally compensated thus postrift subsidence was characterized by a broad regional downwarp if at some later point in time the rigid portion of the lithosphere was weakened or relaxed then lateral density variations would have been recompensated at shorter wavelengths thus areas of little or no crustal extension would have been uplifted and areas of high extension would have experienced additional subsidence gravity and total tectonic subsidence interpretations agree that the sabine uplift region is underlain by thicker crust than the adjacent east texas and north louisiana basins possible mechanisms for relaxation of continental lithosphere are thermal rejuvenation horizontal in plane stress viscous relaxation and extensional faulting

the episodic rise net growing rate and kinematics of radial faults of the salinas de oro diapir using paleoseismological techniques ne spain salt upwelling versus karstic subsidence abstract this paper explores the use of trenching and paleoseismological techniques to determine salt flow rates into a salt diapir for the first time in the literature the salinas de oro diapir located in the northern spanish pyrenees is an oval shaped triassic salt stock that extends vertically for 7 km down to the paleozoic basement salt dissolution subsidence and diapir growth are coeval active processes karstification is responsible for the development of large sinkholes a thick caprock and the monocline folding and ring faulting of the cretaceous and early tertiary limestone rim the evaporite karstic aquifer discharges high concentration water of up to 137 g l of total dissolved solids and a conductivity over 200 ms cm into the salado creek which drains the diapir top the salinity monitoring of this drainage provides a maximum karstic surface lowering rate of around 2 8 mm yr salt upwelling has caused the 150 m uplift of the annular limestone escarpment and the development of 3000 m long radial grabens with up to 90 m of vertical offset that disrupt drainages displace quaternary deposits and overprint concentric faults the 260 cm drag folding of lacustrine facies exposed in a 42 m long and 6 5 m deep trench due to the creep motion of the western radial fault of azanza graben yielded a minimum short term uplift slip rate of 1 75 mm yr for the last 1485 years and provides a minimum salt supply rate of over 5 mm yr considering karstification lowering this value that is several hundred times higher than average evidence the discontinuous growth of salinas de oro diapir

sibling earthquakes generated within a persistent rupture barrier on the sunda megathrust under simeulue island a section of the sunda megathrust underneath simeulue is known to persistently halt rupture propagation of great earthquakes including those in 2004 mw 9 2 and 2005 mw 8 6 yet the same section generated large earthquakes in 2002 mw 7 3 and 2008 mw 7 4 to date few studies have investigated the 2002 and 2008 events and none have satisfactorily located or explained them using near field insar gps and coral geodetic data we find that the slip distributions of the two events are not identical but do show a close resemblance and largely overlap we thus consider these earthquakes siblings that were generated by an anomalous parent feature of the megathrust we suggest that this parent feature is a locked asperity surrounded by the otherwise partially creeping simeulue section perhaps structurally controlled by a broad morphological high on the megathrust

syn to post rift diapirism and minibasins of the central high atlas morocco the changing face of a mountain belt the atlas mountains are classically regarded as a failed mesozoic rift arm subject to alpine inversion folding and thrusting here we present new integrated structural and sedimentological studies that have revealed numerous early middle jurassic diapiric ridges and minibasins characterized by distinctive halokinetic structures diachroneity in halokinesis is observed across the central high atlas waning first in the sw during the early middle jurassic jbel azourki and tazoult ridges and continuing to late middle jurassic towards the ne imilchil region the halokinetic structures are readily differentiated from the effects of later alpine deformation allowing a new picture of the central high atlas to emerge the most pervasive deformation in the central high atlas is associated with early middle jurassic diapirism whereas the impact of alpine inversion is mostly focused at the basin margins this new understanding helps explain previously problematic aspects of the atlas mountains which we now recognize as an exceptionally well exposed natural laboratory for understanding the interactions between halokinesis tectonics and sedimentation

geomorphic and stratigraphic evidence of quaternary diapiric activity enhanced by fluvial incision navarres salt wall and graben system se spain abstract the structural and stratigraphic geological features associated with salt structures have received extensive attention from geologists however there is limited work on the geomorphic and quaternary record of diapiric activity despite its practical implications e g salt and hydrocarbon extraction geostorage activities this work analyses the quaternary geomorphic and stratigraphic evidence of diapiric activity in the navarres salt wall se spain developed along the axis of a neogene graben this salt system is located in a region characterized by a peculiar network of orthogonal grabens that control the configuration and evolution of the drainage network the protruding salt walls are spatially associated with the erosionally unloaded and deeply entrenched graben sections situated close to the regional base level evidence of recent current activity in the navarres salt wall include 1 internally drained areas in a marginal withdrawal basin with long sustained aggradation 2 distorted drainage network defeated and deflected streams wind gaps knickpoints changes in fluvial style which changed from an initial axial longitudinal pattern to a longitudinal marginal distribution at the flanks of the salt wall 3 development of diapiric fault scarps at the edge of the salt wall 4 tilted fluvial terraces dipping away from the salt wall and with localized sediment thickening the available data indicate along strike variability in deformation style and long term vertical deformation rates these range from 0 09 mm yr to significantly higher values 0 2 0 4 mm yr in the section where the salt wall displays a more prominent relief and is affected by deep fluvial entrenchment the regional analysis and the characterization of the navarres salt wall suggest that quaternary diapirism in the region is enhanced by erosional unloading related to fluvial entrenchment which expands from the regional base level through the upstream propagation of an incision wave

evolution of the destin dome offshore florida north eastern gulf of mexico abstract structural and stratigraphic relationships indicated by seismic reflection data suggest that uplift of the destin dome anticline resulted mainly from salt movement during late cretaceous to early cenozoic time a thick succession of lower cretaceous sediment was deposited in the central part of the basin seaward of the present day destin dome sediment loading squeezed the salt both updip onto the shelf and downdip into the basin a step in the pre salt basement limited movement of salt and controlled the location of the dome vertical movement of salt was accommodated by extensional faulting during the early cenozoic sediment touchdown onto the pre salt basement formed a salt weld between the anticline and the de soto canyon diapir field cut off the supply of salt and stopped growth of the structure the minimum accumulation thickness of the mother salt is estimated to be 760 m and the original volume of salt deposited at the present day location of the destin dome anticline on the florida shelf is estimated to be 1000 km3 the volume of salt in place today is in excess of 2300 km3

a unified gps based earthquake catalog for the sumatran plate boundary between 2002 and 2013 we have compiled the first self consistent gps based earthquake catalog for the sumatran plate boundary using continuous daily position time series from the sumatran gps array sugar we document 30 earthquakes which occurred within or outside the sugar network from august 2002 through the end of 2013 and we provide estimates of both vertical and horizontal coseismic offsets associated with 1 m9 2 3 m8 6 m7 19 m6 and 1 m5 9 earthquakes as well as postseismic decay amplitudes and times associated with 9 m 7 earthquakes and 1 m6 7 earthquake for most of the previously studied earthquakes our geodetic catalog provides more complete coseismic displacements than those published showing consistent patterns of motion across a large range of distances for many of the moderate to large earthquakes we publish their coseismic displacements for the first time providing new constraints on their locations and slip distributions for the postseismic time series we have tackled the challenge of separating the signals for individual events from the overlapping effects of many other earthquakes as a result we have obtained either new or much longer time series than previously published based on our long time series we find logarithmic decay times ranging from several days to more than 20 years and sometimes a second decay time is needed suggesting that when studying large to great sumatran earthquakes we need to consider multiple postseismic mechanisms our geodetic catalog provides rich spatial and temporal sumatran earthquake cycle information for future studies of the physics and dynamics of the sumatran plate boundary

basin architecture salt tectonics and upper jurassic structural styles desoto canyon salt basin northeastern gulf of mexico despite awareness of the importance of continental extension during rifting there are few quantitative studies that show the influence of crustal extension on basin architecture the distribution of salt and late jurassic sedimentation in the desoto canyon salt basin northeastern gulf of mexico application of simplified isostatic principles using a lithospheric buoyancy model allow quantification of total tectonic subsidence crust thickness crustal extension and crust type interpretation of over 4800 km of migrated multifold seismic reflection profiles and well data integrated with computed isostatic relations provide the basis to characterize middle jurassic callovian age salt halokinetic processes and to describe the structural development of overlying upper jurassic strata an average crustal thickness of 25 km and crustal extension s values between 1 4 and 1 8 suggest the sedimentary succession is underlain by moderately stretched and attenuated continental crust the widespread distribution and geometry of dipping subsalt reflectors particularly in the shelfal areas provide evidence for a late triassic early jurassic phase of rifting prior to deposition of middle jurassic salt the distribution of autochthonous salt and the overlying upper jurassic sediments reflect the presalt structural imprint and suggest that the basic architecture of the basin was established by the middle jurassic following significant attenuation of the crust although deposition occurred in a slowly subsiding stable marginal setting salt movement and associated growth faulting are the most significant tectonic elements affecting the stratigraphic and structural development of the overlying strata faults related to growth of salt structures root at the base of salt in what appears to be a common detachment or decollement for salt movement the original distribution of salt is widespread and sheetlike with an estimated minimum thickness of 760 m progressive basinward subsidence of the margin and differential sediment loading by the overburden are the primary mechanisms initiating mobilization of salt and subsequent deformation of sediments during the late jurassic and from the late cretaceous through the early cenozoic

a comparative study of the sumatran subduction zone earthquakes of 1935 and 1984 a m s 7 7 earthquake struck the western equatorial coast of sumatra in december 1935 it was the largest event in the region since the two devastating giant earthquakes of 1833 and 1861 historical seismograms of this event from several observatories around the world provide precious information that constrains the source parameters of the earthquake to more precisely quantify the location geometry and mechanism of the 1935 event and to estimate the coseismic deformation we analyze the best of the available teleseismic historical seismograms by comparing systematically the records of the 1935 earthquake with those of a smaller event that occurred in the same region in 1984 first we constrain the source parameters of the 1984 event using teleseismic records then we compare the records of the 1935 event with those of 1984 from the same sites and instruments to do this we choose several time windows in the corresponding seismograms that contain clearly identifiable phases and deconvolve the modern event from the older one the deconvolutions result in very narrow pulses with similar sizes thus confirming similar locations and mechanisms for the events the initiation of the 1984 event was on the subduction interface at a depth of 27 2 km its m 0 is 6 5 x 10 19 n m m w is 7 2 the sense of slip was nearly pure thrust on a plane dipping 12 the 1935 event also involved rupture of the shallow subduction interface but was about five times larger m 0 3 3 x 10 20 n m m w 7 7 and initiated a few kilometers to the southeast along strike the 1935 rupture propagated unilaterally toward the southeast the along strike rupture length was about 65 km from these source parameters we calculate the surface deformations assuming an elastic multilayered medium these deformations compare favorably with those actually recovered from paleoseismic data in the form of coral microatolls

anhydrite and the sr isotope evolution of groundwater in a carbonate aquifer major element concentrations and 87 sr 86 sr ratios were measured in groundwaters and bedrock from the madison aquifer in western south dakota in this region the madison aquifer is primarily comprised of dolomite belonging to the madison limestone group the purpose of the study was to investigate controls on the downgradient evolution of dissolved sr 2 in a carbonate groundwater system that is recharged by waters with high 87 sr 86 sr ratios draining precambrian basement rocks and to establish the sources of sr 2 added to the waters by reaction with the aquifer lithology a mass balance model following previous workers was used to calculate amounts and effective rates of mineral dissolution and precipitation during groundwater transport along a 240 km flow path both the calculated reaction rates and data for the sr isotope geochemistry of the reacting phases were then used to develop a self consistent and quantitative description of the concentration and isotopic composition of dissolved sr 2 in the aquifer waters the major ion chemistry of madison aquifer groundwater is known to evolve according to dolomite dissolution anhydrite dissolution calcite precipitation and ion exchange with clay minerals dissolved 87 sr 86 sr ratios in the madison aquifer decrease downgradient input waters draining the igneous black hills have 87 sr 86 sr ratios of 0 723 while highly evolved waters in the aquifer have 87 sr 86 sr ratios of 0 708 dissolved sr 2 concentrations undergo a concurrent increase from 1200 to 66 000 nmol l model results indicate that dolomite dissolution exerts a critical control on the major ion chemistry but is not the primary source of nonradiogenic sr 2 as both the dissolution rate and sr concentration of dolomite are very low anhydrite is readily soluble in water has a low 87 sr 86 sr ratio 0 708 and a very high sr concentration 50 000 nmol g anhydrite is also greatly undersaturated in the groundwaters and the downgradient evolution of sr 2 accompanies an 80 fold increase in dissolved so 4 2 while anhydrite has a very low abundance in the aquifer rocks the flow model indicates that anhydrite dissolution provides 300 times more sr 2 per liter of water relative to dolomite dissolution these findings suggest that anhydrite dissolution governs the sr 2 geochemistry of madison aquifer groundwaters whereas dolomite dissolution and calcite precipitation control the bulk chemistry lastly it is shown that the calculation of net mineral masses transferred to solution requires very high relative proportions of anhydrite and clay to dolomite mineral masses obtained by this approach actually represent bulk contributions without consideration of the intrinsic reaction rates of the phases or their modal abundances in the aquifer rocks however consideration of these parameters in a transport equation for flow through porous media shows that the high apparent abundances are not a real requirement this latter approach is consistent with laboratory experiments and indicates that as little as 0 04 wt of very soluble anhydrite and 0 3 wt of exchangeable clay in the aquifer rock are sufficient to produce the observed groundwater chemistry in most of the flow path

evolution of salt structures east texas diapir province part 1 sedimentary record of halokinesis post aptian post 112 ma strata in the east texas basin were strongly influenced by halokinesis and therefore record the evolution of associated salt structures dome induced changes in patterns of sandstone distribution depositional facies and reef growth indicate that thickness variations in strata surrounding domes were caused by syndepositional processes rather than by tectonic distortion salt domes in the east texas basin exhibit three stages of growth pillow diapir and post diapir each of which affected surrounding strata differently pillow growth caused broad uplift of strata over the crest of the pillows the resulting topographic swell influenced depositional trends and was susceptible to erosion fluvial channel systems bypassed pillow crests and stacked vertically in primary peripheral sinks on the updip flanks of the pillows diapir growth was characterized by expanded sections of shelf and deltaic strata in secondary peripheral sinks around the diapirs lower cretaceous reefs on topographic saddles between secondary peripheral sinks now host major oil production at fairway field post diapir crestal uplifts and peripheral subsidence affected smaller areas than did equivalent processes during pillow or diapir stages documented facies variations over and around domes at different stages of growth enable prediction of subtle facies controlled hydrocarbon traps facies controlled traps are likely to be the only undiscovered ones remaining in mature petroliferous basins such as the east texas basin

deformation and slip along the sunda megathrust in the great 2005 nias simeulue earthquake seismic rupture produced spectacular tectonic deformation above a 400 kilometer strip of the sunda megathrust offshore northern sumatra in march 2005 measurements from coral microatolls and global positioning system stations reveal trench parallel belts of uplift up to 3 meters high on the outer arc islands above the rupture and a 1 meter deep subsidence trough farther from the trench surface deformation reflects more than 11 meters of fault slip under the islands and a pronounced lessening of slip trenchward a saddle in megathrust slip separates the northwestern edge of the 2005 rupture from the great 2004 sumatra andaman rupture the southeastern edge abuts a predominantly aseismic section of the megathrust near the equator

elliptical calderas in active tectonic settings an experimental approach abstract caldera volcanoes form due to collapse of a magma chamber roof into the underlying magma chamber many field theoretical and experimental studies have postulated that calderas are delimited by reverse ring faults and are surrounded by peripheral concentric normal faults in the simplest theoretical scenario circular magma chambers produce circular calderas many calderas however are elliptical in shape particularly those in extensional and compressive tectonic settings several factors may explain elliptical calderas the first is the presence of an elliptical magma chamber established by for instance preferential intrusion along pre existing basement structures or differential spalling of the magma chamber walls the second is the overlap nesting of several discrete calderas to form a single larger elliptical structure the third is asymmetric subsidence the fourth is variable pre collapse topography a fifth possible factor is distortion of the caldera faults by the regional stress field during caldera formation a sixth factor is the post collapse distortion of the caldera structure due to continued regional deformation to better understand relationships between caldera surface expression reservoir geometry and regional tectonic stresses we conducted scaled analogue experiments these experiments examined the impact of regional stress and associated structures on calderas formed during evacuation of reservoirs circular rubber balloons of known dimensions and depths the results show that in principle calderas produced in compression extension experiments are elongated parallel to the direction of minimum horizontal compressive stress despite the chamber beneath being circular in plan view as a consequence model ring fault orientation varied from steeply dipping where striking perpendicular to the minimum horizontal regional compressive stress to shallower dips where striking parallel to the minimum horizontal regional compressive stress this leads us to suggest that the influence of a regional stress field on caldera fault orientation during and or after caldera formation may be significant in the development of elliptical calderas in addition such variation of caldera ring fault dip from steep to relatively shallow could influence location and behaviour of ring fissure eruptions

mapping ground deformation over houston galveston texas using multi temporal insar abstract houston galveston hg region in texas has been subsiding due to the combined effects of groundwater withdrawal hydrocarbon extraction salt dome movement and faulting this human and partially nature induced ground deformation has gradually threatened the stability of urban infrastructure and caused the loss of wetland habitat along the gulf of mexico interferometric synthetic aperture radar insar techniques can measure ground motions in high spatial resolution over large coverage the purpose of this study is to map the spatial and temporal variations in surface deformation around the hg region using a multi temporal insar mti technique and to assess the role of fluid withdrawal groundwater withdrawal and hydrocarbon extraction salt tectonics and fault activity in land surface deformation mti derived land surface deformation measurements are then compared to gps and extensometer observations geologic and hydrologic data and information about hydrocarbon extraction to address the causes of the observed deformation the mti measurements based on ers 1 2 datasets have mapped regional subsidence up to 53 mm yr in the northwestern hg as well as a slight uplift at 20 mm yr in the southeastern hg from 1993 to 2000 insar measurements obtained from envisat and alos data reveal subsidence rate of up to 30 mm yr over the northwestern hg between 2004 and 2011 our results indicate that the pattern of ground deformation was nearly concentric around locations of intense groundwater withdrawal and the spatial extent of the subsiding area has been shrinking and migrating toward the northeast after 2000 we have resolved localized ground subsidence cones over hydrocarbon exploration fields which were likely caused by reservoir compaction we have differentiated ground surface deformation over salt domes which was due to ongoing differential movement of individual salt spines we have identified 5 40 mm yr differential subsidence across a number of faults in the region these faults functioned as water barriers disrupting the integrity of ground water flow and aggravating localized surface displacements

evolution of salt diapir and karst morphology during the last glacial cycle effects of sea level oscillation diapir and regional uplift and erosion persian gulf iran abstract marine fluvial and cave sediments and karst phenomena were studied and dated by 14 c u series and osl methods to determine the evolution of the namakdan diapir and the world s longest salt cave 3n cave during the holocene and the last glacial sea level oscillations the uplift rate of the diapir and its surroundings and erosion are the main factors influencing the diapir morphology although the diapir uplift rate has been constant for the last 50 kyr 4 mm yr at a distance 600 m from the diapir edge the uplift rate decreases with the distance from the diapir center drag induced host rock deformation extends for 300 m from the outside edge of the diapir and host rocks in this zone have an uplift rate of 0 4 0 6 mm yr which is 2 3 times greater than the regional uplift rate based on known sea level oscillations radiometric dating and geological evidence the namakdan diapir was repeatedly flooded by sea water between 130 and 80 kyr bp submarine residuum composed mainly of gypsum and dolomite formed cap rock on the diapir after 80 kyr bp surficial drainage network and karst development started blind valleys and their corresponding cave systems evolved continuously for 20 30 kyr between 9 and 6 cal kyr bp the rate of sea level rise exceeded the namakdan diapir uplift rate by the factor of 3 as a consequence upward incision of cave streams paragenetic trend occurred and blind valleys near the seashore were filled with gravels cave passages now accessible on the namakdan and hormoz diapirs started to form 3 6 cal kyr bp when sea level stabilized and downward stream incision began older cave levels are still preserved but are filled with sediments and salt precipitates a comparison of the namakdan diapir evolution with data from the hormoz and larak diapirs shows that the evolution of diapir morphology is strongly affected by the differences in uplift rates and geological settings the general scheme of the evolution of the namakdan diapir is believed to be partly applicable to many other diapirs in coastal settings

seismicity associated with the sumatra andaman islands earthquake of 26 december 2004 the u s geological survey national earthquake information center usgs neic had computed origins for 5000 earthquakes in the sumatra andaman islands region in the first 36 weeks after the sumatra andaman islands mainshock of 26 december 2004 the cataloging of earthquakes of m b usgs 5 1 and larger is essentially complete for the time period except for the first half day following the 26 december mainshock a period of about two hours following the nias earthquake of 28 march 2005 and occasionally during the andaman sea swarm of 26 30 january 2005 moderate and larger m b 5 5 aftershocks are absent from most of the deep interplate thrust faults of the segments of the sumatra andaman islands subduction zone on which the 26 december mainshock occurred which probably reflects nearly complete release of elastic strain on the seismogenic interplate thrust during the mainshock an exceptional thrust fault source offshore of banda aceh may represent a segment of the interplate thrust that was bypassed during the mainshock the 26 december mainshock triggered a high level of aftershock activity near the axis of the sunda trench and the leading edge of the overthrust burma plate much near trench activity is intraplate activity within the subducting plate but some shallow focus near trench reverse fault earthquakes may represent an unusual seismogenic release of interplate compressional stress near the tip of the overriding plate the interplate thrust nias earthquake of 28 march 2005 in contrast to the 26 december aftershock sequence was followed by many interplate thrust aftershocks along the length of its inferred rupture zone

hydrocarbon generation and migration routes in the east texas basin the east texas basin is a prolific mature hydrocarbon province producing oil and gas from several reservoirs and a variety of trap types many of the liquid hydrocarbons discovered in the basin are trapped in structures related to movement of the underlying louann salt by determining the structural evolution of the basin we constructed a framework to model the generation of hydrocarbons in the basin geochemical data indicate three major oil types jurassic oil lower cretaceous oil and upper cretaceous oil the jurassic source is mature throughout the basin and began to expel oil at approximately 88 ma the distribution of jurassic oil in cretaceous reservoirs shows that vertical migration routes predominated prospective lower cretaceous source rocks are only matur in the deep central portion of the basin where expulsion began about 47 ma distribution of this oil type suggests that lower cretaceous source rocks occur only in localized areas of the east texas basin organic rich upper cretaceous shales are immature in the main part of the basin but are mature south of the angelina caldwell flexure where they reached peak generation at approximately 20 ma long distance lateral migration routes are necessary to explain the distribution of this oil type migration routes to the giant east texas field may be 100 km or more modeling of this basin suggests an exploration approach in mature basins of defining migration pathways and seeking traps astride them traps in this position have a better probability of being filled and all else being equal are likely to be better fields than traps located away from the major migration routes

uplift and subsidence associated with the great aceh andaman earthquake of 2004 rupture of the sunda megathrust on 26 december 2004 produced broad regions of uplift and subsidence we define the pivot line separating these regions as a first step in defining the lateral extent and the downdip limit of rupture during that great m w 9 2 earthquake in the region of the andaman and nicobar islands we rely exclusively on the interpretation of satellite imagery and a tidal model at the southern limit of the great rupture we rely principally on field measurements of emerged coral microatolls uplift extends from the middle of simeulue island sumatra at 2 5 n to preparis island myanmar burma at 14 9 n thus the rupture is 1600 km long the distance from the pivot line to the trench varies appreciably the northern and western andaman islands rose whereas the southern and eastern portion of the islands subsided the nicobar islands and the west coast of aceh province sumatra subsided tilt at the southern end of the rupture is steep the distance from 1 5 m of uplift to the pivot line is just 60 km our method of using satellite imagery to recognize changes in elevation relative to sea surface height and of using a tidal model to place quantitative bounds on coseismic uplift or subsidence is a novel approach that can be adapted to other forms of remote sensing and can be applied to other subduction zones in tropical regions

geodetic observations of an earthquake cycle at the sumatra subduction zone role of interseismic strain segmentation 1 we use survey mode and continuous gps data from 1991 to 2007 to examine fault segmentation in the earthquake cycle at the sumatra megathrust site of the 26 december 2004 mw 9 1 sumatra andaman the 28 march 2005 mw 8 7 nias simeulue and the 12 september 2007 mw 8 4 mentawai earthquakes these data including new observations from 2006 and 2007 allow us to observe the final few years of one earthquake cycle and the beginning of the next our analysis reveals that the megathrust is segmented a characteristic that may persist through multiple earthquake cycles the nias simeulue earthquake ruptured approximately the same region that broke in 1861 a 300 km long segment abutting the sumatra andaman rupture zone farther southeast the mentawai segment of the megathrust 0 5 s 5 s which produced m 8 earthquakes in 1797 and 1833 is fully locked in the interseismic period but is flanked by two freely slipping regions the batu islands in the nw and enggano in the se the 12 september 2007 mentawai earthquake sequence ruptured only the southern one third of the 1833 rupture zone we model postseismic deformation from the sumatra andaman and nias simeulue earthquakes and find that afterslip was concentrated updip and downdip respectively from the main shocks comparing the velocity fields before and after 2001 we find the subduction zone underneath the batu islands and enggano which prior to the earthquakes was partially to fully coupled appears now to be slipping freely thus while the segmentation of the subduction zone is preserved interseismic coupling on the subduction fault may vary with time

seismic history and seismotectonics of the sunda arc historic records of the last 300 years reveal two great interplate earthquakes 1833 mw 8 1861 mw 8 8 which ruptured major segments of the sumatra fore arc in western indonesia a significant percentage of interplate slip along this portion of the plate boundary appears to occur seismically the ends of these rupture zones are coincident with clusters of large ms 7 and moderate 6 ms 7 shocks and with heterogeneities in the plate interface as inferred from geologic and geophysical data the northern extent of the 1833 rupture zone is coincident with a group of moderate and large earthquakes a structural arch in the fore arc and a fracture zone on the subducted plate the southern portion is coincident with a very prominent cluster and the along strike extension of a sediment filled trough on the subducted plate prior to this study sumatra was characterized as relatively aseismic as inferred from the lack of great earthquakes in the instrumental record of this century java and the lesser sunda islands had major ms 6 earthquakes in the historic record but none are of the same magnitude as the great events near sumatra there is no clear evidence that shocks in the java fore arc were interplate events yet geophysical data indicate recent uplift of the trench slope break and a change in strike of the trench axis where the northernmost flank of the roo rise a prominent bathymetrie high appears to be interacting with the fore arc this feature was formed at a ridge crest and is more buoyant and thus more difficult to subduct than the surrounding seafloor there is no increase in seismicity associated with this tectonism however that may indicate a lack of contact between the crystalline portions of the plates at this time we infer that a majority of slip on the plate interface near java occurs aseismically the variation in occurrence of great interplate earthquakes along the sunda arc may be interpreted in terms of a model that attributes variation in interplate coupling to the age of the subducted lithosphere great interplate earthquakes occur near sumatra where the age of the youngest crust is 46 ma the characteristics of the sunda arc and analogies with pacific arcs imply that the entire length of sumatra has the potential to produce great thrust earthquakes its seismic potential should be considered high as there has been no recurrence of the great events of 1833 and 1861 in contrast no such events have been reported off java and the lesser sunda islands where the oldest crust is 152 ma the plate interface near java and the lesser sunda islands should be considered to have low seismic potential

teleseismic relocation and assessment of seismicity 1918 2005 in the region of the 2004 mw 9 0 sumatra andaman and 2005 mw 8 6 nias island great earthquakes the m w 9 0 2004 sumatra andaman islands and m w 8 6 nias island great earthquake sequences have generated over 5000 catalog reported earthquakes along 1700 km of the sumatra andaman and western sunda regions studies of prior regional seismicity have been limited to global catalog locations that often have poorly constrained epicenters and depths approximately 3650 teleseismically well recorded earthquakes occurring in this region during the period 1918 2005 are relocated with special attention to focal depth reduced uncertainties of epicenters and depths in the region on the order of 15 and 10 km respectively foster interpretation of focal mechanism data and provide additional details about the subducting indian and australian plates the revised earthquake dataset reveals a sharp delineation between aftershocks of the 2004 and 2005 earthquakes near simeulue island and a steepening in slab dip from south to north the downdip width of the aftershock zone of the 2004 m w 9 0 earthquake varies from 200 km at its northern end to 275 km at its southern end and events located between 35 and 70 km focal depth occur more frequently in the southernmost section of this aftershock zone outer rise and near trench normal and strike slip faulting earthquakes also increase in frequency following the 2004 and 2005 earthquakes earthquake swarms triggered along the andaman backarc spreading center both north of sumatra and near siberut island 100 km south of the nias island aftershock sequence illustrate the complex and variable nature of seismicity following these great earthquakes

model for salt deformation on deep margin of central gulf of mexico basin based on available nonexclusive seismic data a preliminary model has been developed for salt deformation on the deep margin of the central gulf of mexico basin in this model the tertiary clastic wedge prograded to the basinward limit of original jurassic salt by the middle miocene as the salt and overburden thinned basinward lateral flow combined with a strong component of downward force exerted by subsiding voluminous middle miocene loading caused the basinward limit of the louann salt to effectively shear off deposition of the upper miocene and pliocene sediments was confined primarily shoreward of an incipient salt swell but pleistocene sediments were eventually able to breach the barrier deformation of the detached salt produced the features present on the slope today preliminary work indicates that most of the detached salt was propelled basinward and upsection toward the present sigsbee escarpment leaving pinch and swell salt structures behind the various types of residual salt structures have been formed as a result of differences in the history of sedimentary loading different stages of development of pinch and swell structures shown on seismic sections illustrate this model

deep confined karst detection analysis and paleo hydrology reconstruction at a basin wide scale using new geophysical interpretation of borehole logs summary deep karst voids can be identified by a new method of geophysical interpretation of commonly used borehole logs in deeply confined carbonate aquifers we show that deep buried karst voids can be characterized by combining this geophysical interpretation together with geological and hydrological data and with known speleological constraints we demonstrate how this characterization can reveal past hydrological regimes and allow mapping of karst distribution on a basin wide scale a combined analysis of geophysical geological hydrological and speleological data in the confined yarkon taninim aquifer israel led us to reconstruct past groundwater levels at different relief and sea levels with the karst voids as a marker for long term flow close to the water table paleo canyons along the mediterranean sea shoreline strongly affected the region s paleo hydrology by serving as major outlets of the aquifer during most of the cenozoic we conclude that intensive karstification was promoted by flow periods of longer duration and or higher flux and flow velocities close to the aquifer s past and present outlets in addition we suggest that karst voids found under shallow confinement were developed by renewed aggressivity due to hypogene water rising in cross formational flow becoming mixed with fresh lateral water flow from the east

gypsum karst features as evidence of diapiric processes in the betic cordillera southern spain in the triassic evaporite deposits of the betic cordillera halokinesis has played a fundamental role in the morphodynamic evolution of gypsum karst as evidenced by the morphology and distribution of dolines and poljes by data obtained from caves and from the types of water associated with evaporite domes distribution patterns of major exokarstic forms display a subcircular array with collapse sinkholes located in the centre of the domes and solution drawdown dolines on the outer limits of the diapiric forms in addition the least mineralized waters are situated in association with the caprock gypsum hypersaline waters which are also hotter drain deeper flow systems that flow out at the edges of the halokinetic structures the morphodynamic and hydrogeological information constitute a valuable tool for the correct interpretation of the tectonic structure of such complex areas

evolution of salt structures east texas diapir province part 2 patterns and rates of halokinesis the effects of salt mobilization on aptian and younger post 112 ma strata in the east texas basin can be used to illustrate patterns of dome growth through time and to estimate rates and amounts of salt movement pre aptian domes grew in three areas around the margin of the diapir province apparently in pre aptian depocenters maximum dome growth along the basin axis coincided with maximum regional sedimentation there during the middle cretaceous aptian albian and cenomanian in the late cretaceous the sites of maximum diapirism migrated to the periphery of the diapir province diapirism began after pillows were erosionally breached leading to salt extrusion and formation of peripheral sinks the duration of pillow and diapir stages of growth was subequal ranging from 10 to 30 ma post diapiric stage of growth continued for more than 112 ma in some cases diapirs grew fastest in the early cretaceous when peak growth rates ranged from 150 to 530 m ma 490 to 1 740 ft ma declining in the early tertiary to 10 to 60 m ma 30 to 200 ft ma assuming steady state conditions over periods of 1 to 17 ma strain rates for the rise of the east texas diapirs averaged 6 7 10 16 sec peak gross rate of growth averaged 2 3 10 15 sec similar to slow orogenic rates the evolution of east texas salt domes essentially ended in the early tertiary with uplift rates less than 30 m ma 100 ft ma

physical modelling of overburden deformation around salt diapirs abstract salt diapirs produce highly complex deformation patterns in the surrounding overburden which are difficult to image seismically or model numerically to further the understanding of deformation around salt structures we have used physical models with brittle granular overburdens and simulated sedimentation accompanying diapiric rise rigid linear indentors produce a crestal horst above the indentor with two flanking graben large amounts of indentation produce predominantly reverse faults along the margins of the diapir and extensional faults over the crest in contrast hemispherical indentors produced inward dipping concentric reverse faults forefully intruded polymer diapirs produce a narrow crestal graben above the diapir crest downbuilt polymer diapirs produce extensional faults on the flanks of the diapirs which offset the diapir walls no clear secondary rim synclines were developed as polymer is withdrawn evenly from the whole of the polymer layer across the model strong and anisotropic layered overburden were simulated using cohesive clay and mica respectively detachments were formed along mica layers which suppressed faults with large throws cohesive layer deformation began with tensile fractures permitting rotation of fractured rafts around the sides of the diapir these progressively slip off the crest and create large gaps in the stratigraphy

hydrograph separation for karst watersheds using a two domain rainfall discharge model highly parameterized physically based models may be no more effective at simulating the relations between rainfall and outflow from karst watersheds than are simpler models here an antecedent rainfall and convolution model was used to separate a karst watershed hydrograph into two outflow components one originating from focused recharge in conduits and one originating from slow flow in a porous annex system in convolution parameters of a complex system are lumped together in the impulse response function irf which describes the response of the system to an impulse of effective precipitation two parametric functions in superposition approximate the two domain irf the outflow hydrograph can be separated into flow components by forward modeling with isolated irf components which provides an objective criterion for separation as an example the model was applied to a karst watershed in the madison aquifer south dakota usa simulation results indicate that this watershed is characterized by a flashy response to storms with a peak response time of 1 day but that 89 of the flow results from the slow flow domain with a peak response time of more than 1 year this long response time may be the result of perched areas that store water above the main water table simulation results indicated that some aspects of the system are stationary but that nonlinearities also exist

persistent termini of 2004 and 2005 like ruptures of the sunda megathrust to gain insight into the longevity of subduction zone segmentation we use coral microatolls to examine an 1100 year record of large earthquakes across the boundary of the great 2004 and 2005 sunda megathrust ruptures simeulue a 100 km long island off the west coast of northern sumatra indonesia straddles this boundary northern simeulue was uplifted in the 2004 earthquake whereas southern simeulue rose in 2005 northern simeulue corals reveal that predecessors of the 2004 earthquake occurred in the 10th century ad in ad 1394 2 and in ad 1450 3 corals from southern simeulue indicate that none of the major uplifts inferred on northern simeulue in the past 1100 years extended to southern simeulue the two largest uplifts recognized at a south central simeulue site around ad 1422 and in 2005 involved little or no uplift of northern simeulue the distribution of uplift and strong shaking during a historical earthquake in 1861 suggests the 1861 rupture area was also restricted to south of central simeulue as in 2005 the strikingly different histories of the two adjacent patches demonstrate that this boundary has persisted as an impediment to rupture through at least seven earthquakes in the past 1100 years this implies that the rupture lengths and hence sizes of at least some future great earthquakes and tsunamis can be forecast these microatolls also provide insight into megathrust behavior between earthquakes revealing sudden and substantial changes in interseismic strain accumulation rates

burma plate motion 1 plate motion in the indo burmese arc andaman sumatra region of burma plate is poorly resolved this is mainly due to lack of relevant data and complex tectonics of the region we analyze 1 azimuths of coseismic displacements due to the 2004 sumatra andaman and 2005 nias earthquakes 2 estimates of interseismic deformation in the indo burmese arc andaman sumatra and sagaing fault regions all based on gps measurements 3 long term plate motion rates across sumatra fault system sagaing fault and andaman sea from geomorphological and other geophysical studies and 4 the earthquake focal mechanisms in the region we suggest that the ssw motion of sunda plate with respect to indian plate may be partitioned into the dextral strike slip motion across the sagaing fault in the north and sumatra fault system in south in the back arc region and the arc normal motion across the sumatra subduction zone which becomes oblique in andaman and southern indo burmese arc region and dextral in the northern indo burmese arc region of the fore arc under the rigid plate approximation we estimate a pole for india burma plate pair at 27 1 n 82 1 1 e with an angular velocity of 0 845 0 12 ma and for burma sunda at 22 3 1 1 n 109 3 2 5 e with an angular velocity of 0 67 0 12 ma thus the plate motion in the northern and southern regions of burma plate namely the indo burmese arc and andaman sumatra arc may be explained by a single pole and does not require a boundary between the two

repeating aftershocks of the great 2004 sumatra and 2005 nias earthquakes abstract we investigate repeating aftershocks associated with the great 2004 sumatra andaman mw 9 2 and 2005 nias simeulue mw 8 6 earthquakes by cross correlating waveforms recorded by the regional seismographic station psi and teleseismic stations we identify 10 and 18 correlated aftershock sequences associated with the great 2004 sumatra and 2005 nias earthquakes respectively the majority of the correlated aftershock sequences are located near the down dip end of a large afterslip patch we determine the precise relative locations of event pairs among these sequences and estimate the source rupture areas the correlated event pairs identified are appropriately referred to as repeating aftershocks in that the source rupture areas are comparable and significantly overlap within a sequence we use the repeating aftershocks to estimate afterslip based on the slip seismic moment scaling relationship and to infer the temporal decay rate of the recurrence interval the estimated afterslip resembles that measured from the near field geodetic data to the first order the decay rate of repeating aftershocks as a function of lapse time t follows a power law decay 1 t p with the exponent p in the range 0 8 1 1 both types of observations indicate that repeating aftershocks are governed by post seismic afterslip