structure of the vakhsh fold and thrust belt tadjik ssr geologic mapping on a landsat image base an enhanced landsat image of the northeastern tadjik depression in the soviet union was combined with field data to produce a 1 250 000 geologic map of the vakhsh fold and thrust belt and adjacent autochthon mapping of the relatively continuous geologic structure in this region first required recognizing marker beds and contacts at or near the resolution of the landsat sensor and then defining mappable units satellite image mapping was complemented by field study which was necessary in this recently deformed area both to verify the image mapping and to obtain more accurate structural dips deformation of the cretaceous and tertiary strata of the fold and thrust belt is in the western half of the mapped area conspicuously absent north of a buried basement fault that marks the hinge zone of the late mesozoic passive margin in the eastern half of the mapped area however the major thrusts displacing rocks northward have moved coherent sheets over the block fault these sheets now lie flat atop the autochthon to the north tectonically these observations indicate that 1 the crustal structure inherited from the mesozoic extensional phase has strongly influenced the late cenozoic pattern of deformation 2 the thrust sheets that are displaced over the paleo hinge zone actively load the basement rocks to the north and 3 the development of the fold and thrust belt which is markedly asymmetric has included the progressive overlapping of thrusts the later thrusts apparently formed internal to the older thrusts and subsequently overrode them

modelling shoreface profile evolution current knowledge of hydro sediment and morpho dynamics in the shoreface environment is insufficient to undertake shoreface profile evolution modelling on the basis of first physical principles we propose a simple panel type model to map observed behaviour the internal dynamics are determined by slope dependent wave induced cross shoreface transports while the external driving factors are lateral sediment supply and sea level rise this model concept is tested with reasonable success against the observed behaviour of the central holland coast considering two hindcast periods one covering the evolution over the last century the other the subboreal subatlantic evolution a limitation of this model is that the cross shoreface dynamics are solely steered by the variations of shoaling short waves since a variety of other wave and current dynamics may be expected to be present in the coastal boundary layer it may well be that the effects of the mechanisms and conditions which are not represented are hidden in the coefficients of the sediment transport formula this limits the accuracy of the coefficients as used and our findings should be considered as an order of magnitude estimate only indeed behaviour oriented modelling implies that generalization of results to arbitrary situations and conditions is not straightforward yet we expect that some of the conclusions are more generally applicable this concerns the substantiation of the assumption that the upper shoreface responds on a much smaller time scale than the lower shoreface and the idea that the shoreface profile is not always and everywhere in equilibrium with its forcing a worthwhile observation from the holland coast application is that the bottom slope effect on the transport is only important at geological time scales the profile evolution at the engineering time scales say 10 to 100 years is effectively quasi static in that there is no feedback between the long term averaged transport and the state of the profile this implies that at these smaller scales the profile changes can be predicted on the basis of a static sediment balance this does not mean that the gravitational downslope transport is unimportant as a physical phenomenon in coastal profile evolution it is only unimportant if a highly aggregated model like this is applied at relatively short time scales

architecture and growth of normal fault zones in multilayer systems a 3d field analysis in the south eastern basin france abstract 3d field data on mesoscale normal faults were collected to examine the geometries and growth of faults in multilayer systems observation and analysis of the fractures include the collection of geometric attributes such as fault dips and fault zone thicknesses detailed mapping in cross sections and plan views and the construction of individual and cumulative displacement profiles fault zone growth is consistent with a coherent model and is strongly influenced by the multilayer system in the limestone layers faults grew in several steps including opening and frictional sliding on 80 dipping segments faulting in clay layers was in the form of 40 dipping faults and sub horizontal faults the latter being mostly early features developed under the same extensional regime as normal faults and disturbing the fault architecture the fault zone thickness increases with the limestone thickness and the presence of sub horizontal faults in clay beds numerous connections occur in clay units the moderate 0 08 and low

the gutenberg richter or characteristic earthquake distribution which is it abstract paleoearthquake and fault slip rate data are combined with the cit usgs catalog for the period 1944 to 1992 to examine the shape of the magnitude frequency distribution along the major strike slip faults of southern california the resulting distributions for the newport inglewood elsinore garlock and san andreas faults are in accord with the characteristic earthquake model of fault behavior the distribution observed along the san jacinto fault satisfies the gutenberg richter relationship if attention is limited to segments of the san jacinto that are marked by the rupture zones of large historical earthquakes or distinct steps in fault trace the observed distribution along each segment is consistent with the characteristic earthquake model the gutenberg richter distribution observed for the entirety of the san jacinto may reflect the sum of seismicity along a number of distinct fault segments each of which displays a characteristic earthquake distribution the limited period of instrumental recording is insufficient to disprove the hypothesis that all faults will display a gutenberg richter distribution when averaged over the course of a complete earthquake cycle but given that 1 the last 5 decades of seismicity are the best indicators of the expected level of small to moderate size earthquakes in the next 50 years and 2 it is generally about this period of time that is of interest in seismic hazard and engineering analysis the answer to the question posed in the title of the article at least when concerned with practical implementation of seismic hazard analysis at sites along these major faults appears to be the characteristic earthquake distribution

normal fault development during two phases of non coaxial extension an experimental study we use scaled experimental analog models to study the effect of a pre existing fault fabric on fault development during extension in our models a homogeneous layer of wet clay undergoes two noncoaxial phases of extension whose directions differ by up to 45 the normal faults that develop during the first phase create a pronounced fault fabric that influences normal fault development during the second phase in all models the pre existing faults are reactivated during the second phase of extension their sense of slip depends on the angle between the first and second phase extension directions specifically the component of dip slip relative to strike slip decreases as the angle between the first and second phase extension directions increases new normal faults also form during the second phase of extension in all models the number of new fault segments increases as the angle between the first and second phase extension directions increases the orientations of the new normal fault segments are both orthogonal and oblique to the second phase extension direction indicating that both the secondphase extension direction and the pre existing fault fabric control the orientation of new fault segments some of the new normal faults cut and offset the pre existing faults whereas others terminate against them producing complex fault patterns and interactions the modeling results explain fault interactions observed in the jeanne d arc rift basin of offshore newfoundland canada and the reactivation of abyssal hill normal faults at outer highs near subduction zones

the stress field in the frontal part of the eastern alps austria from borehole image log data abstract stress orientations in the frontal part of the eastern alps are inferred from borehole breakouts and drilling induced tensile fractures depicted in image logs from 62 vertical or slightly deviated wellbores with up to 5 km depth borehole breakouts 2463 individual features with 1673 9 m cumulative length are observed in all the wells except one whereas drilling induced fractures only occur in four wells microresistivity image log data from the alpine foreland the external thrust sheets allochthonous molasse helvetic and flysch nappes and the autochthonous units in the footwall of the alpine units reveal consistent in situ stress orientations with approximately n s directed maximum horizontal stresses shmax indications for stress partitioning across thrusts including the alpine floor thrust are not observed in the western sector of the study area the mean shmax is oriented 002 with a standard deviation sd of 11 1 in the central and eastern sector the mean shmax is oriented 177 sd 14 and 173 sd 14 3 respectively indicating a counterclockwise rotation of shmax of about 10 from west to east the observed stress indicators and the analysis of deviated wells suggest a strike slip regime for the western and central sector whereas a thrust regime is probable in the east of the study area the thrust regime there coincides with the occurrence of middle pleistocene conglomerates which were previously described to be displaced by alpine thrust faults the orientations of shmax fit into the general observation that shmax directions at the alpine front are oriented about perpendicular to the strike of the mountain belt and rotate along the alpine arc our stress orientations including those derived from the autochthonous basement are however markedly different from the nw se directed maximum horizontal stresses reported from the variscan units in the european foreland north of the study area

evaluation of depth of closure using data from duck nc usa using 12 years of frequent high precision profiles collected on a wave dominated sandy oceanic beach to 8 m depth the characteristics and interpretation of depth of closure or the seaward limit of significant profile change is critically examined this includes evaluation of the predictive capability of d1 the seaward boundary of the littoral zone as originally defined by hallermeier 1981 hallermeier r j 1981 a profile zonation for seasonal sand beaches from wave climate coastal eng 4 253 277 depth of closure during major erosional events is usually produced by the seaward limit of offshore bar movement following the original recommendation of hallermeier 1981 d1 based on 12 h exceeded wave height and a reference depth of mean low water provides a robust limit to the observations using a 6 cm change criterion empirically the observed depth of closure is 69 of d1 although the scatter is large this scatter is partly controlled by pre event profile shape most particularly bar configuration depth of closure under accretional conditions can also be measured but it is time scale dependent as accretion is a slow steady process d1 underpredicts closure for accretional situations time interval e g annual depth of closure represents the integral effect of erosional and accretional events an important observation of the data is that depth of closure increases with time scale however the full population of time interval observations is not resolved at duck due to the measurement limit 8 m depth as time interval increases from 1 year to 8 years less cases close most non closing time interval cases coincide with the periods influenced by the most energetic wave events however time interval closures are generally deeper than the biggest event closure in the period showing that it represents more than the largest event the frequency distribution of the data suggests that most if not all of these missing data simply represent closures deeper than 8 m depth up to a 4 year time interval d1 t appears to provide a reasonable limit to the quantified observations it is an interesting result that d1 an event based approach might provide a limit to closure over periods up to 4 years as these time interval closures are generally larger than those produced by single storms therefore the general applicability of this result for more complete data sets or on rapidly evolving i e eroding or accreting coasts is uncertain the present data also suggest that on swell dominated coastlines where accretional processes are dominant d1 may underpredict closure suggesting an important limitation to this approach but as sediment would be moving onshore this may not be a practical problem therefore within the limits of the data set hallermeier s 1981 approach is found to define robust estimates of depth of closure particularly for individual erosional events this useful result is expected to find widespread application in coastal geology and engineering

inversion of field data in fault tectonics to obtain the regional stress iii a new rapid direct inversion method by analytical means summary a new method for determining the reduced stress tensor with four degrees of freedom the orientations of the three principal stress axes as well as the ratio of principal stress differences using fault slip data or focal mechanisms of earthquakes is presented from a computational point of view the inversion of fault slip data is made in a direct way by purely analytical means as a result the determination process is extremely fast and adaptable on small microcomputers from a physical point of view the method aims at simultaneously i minimizing the angles between theoretical shear stress and actual slip vector and ii having relative magnitudes of shear stress large enough to induce slip despite rock cohesion and friction examples of application to actual fault slip data sets with good or poor variety of fault slip orientations are shown the double significance of the basic criterion adopted results in a more realistic solution of the inverse problem than the single minimization of the shear stria angle

earthquakes gravity and the origin of the bali basin an example of a nascent continental fold and thrust belt we infer from the bathymetry and gravity field and from the source mechanisms and depths of the eight largest earthquakes in the bali region that the bali basin is a downwarp in the crust of the sunda shelf produced and maintained by thrusting along the flores back arc thrust zone earthquake source mechanisms and focal depths are inferred from the inversion of long period p and sh waves for all events and short period p waves for two of the events centroidal depths that give the best fit to the seismograms range from 10 to 18 km but uncertainties in depth allow a range from 7 to 24 km the p wave nodal planes that dip south at 13 to 35 7 strike roughly parallel to the volcanic arc and are consistent with thrusting of crust of the bali basin beneath it the positions of the earthquakes with respect to crustal features inferred from seismic and gravity data suggest that the earthquakes occur in the basement along the western end of the flores thrust zone the slip direction for the back arc thrust zone inferred from the orientation of the earthquake slip vectors indicates that the thrusting in the bali basin is probably part of the overall plate convergence as it roughly coincides with the convergence direction between the sunda arc and the indian ocean plate summation of seismic moments of earthquakes between 1960 and 1985 suggests a minimum rate of convergence across the thrust zone of 4 2 mm a the presence of back arc thrusting suggests that some coupling between the indian ocean plate and the sunda arc occurs but mechanisms such as continental collision or a shallow subduction of the indian ocean plate probably can be ruled out the present tectonic setting and structure of the bali basin is comparable to the early forelands of the andes or western north america in that a fold and thrust belt is forming on the continental side of an arc trench system at which oceanic lithosphere is being subducted the bali basin is flanked by the tertiary java basin to the west and the oceanic flores basin to the east and thus provides an actualistic setting for the development of a fold and thrust belt in which structure and timing of deformation can change significantly along strike on the scale a few hundred kilometers

source parameters for 11 earthquakes in the tien shan central asia determined by p and sh waveform inversion the tien shan mountain belt of central asia was formed in late paleozoic time and reactivated in tertiary time following the collision of india with eurasia more than 1500 km to the south to study the style and distribution of faulting occurring today in the tien shan we digitized long period world wide standard seismograph network p and sh waveforms of 11 of the largest tien shan earthquakes between 1965 and 1982 and then used a least squares inversion routine to constrain their fault plane solutions and depths four of the earthquakes occurred near the southern edge of the tien shan and two occurred in the intermontane fergana basin these earthquakes occurred at depths of 10 20 km and are associated with thrust faulting on east west to southwest northeast striking fault planes that dip moderately 35 55 the other five earthquakes in the northern tien shan were mostly deeper 15 44 km and the fault plane solutions of four of them are similar to the events farther south the exception an event on june 2 1973 probably occurred on a gently northward dipping east west striking fault plane all events occur within the basement at depths of 10 km or greater waveforms for earthquakes near the edges of the dzungarian fergana and kucha basins are fit best using velocity structures with thick sediment layers implying that sediments from these basins have been and are being underthrust beneath the neighboring mountains we examined only the relatively small mb 5 5 6 2 events after 1965 and did not study any of the largest events ms 8 that occurred in the tien shan earlier in this century still we can conclude that north south shortening is presently occurring in the tien shan with the formation of basement uplifts flanked by moderately dipping thrust faults the present day tectonics of the tien shan seem to be analogous to those of the rocky mountains in colorado wyoming and utah during the laramide orogeny in late cretaceous and early tertiary time

collision and stress trajectories in taiwan a finite element model abstract field analyses of plio quaternary compressional deformations in taiwan have enabled us to reconstruct the paleostress trajectories resulting from the collision of the luzon arc philippine sea plate with the chinese continental margin eurasian plate the direction of the maximum compressional stress 1 shows a fan shaped pattern that we interpret as resulting from the collision of a rigid body the luzon arc indenting a more deformable material the thick sediments of the chinese continental margin simple analytical models qualitatively explain the fan shaped pattern but the influence of various parameters such as boundary conditions and rheology cannot be quantitatively accounted for by this approach consequently we have used a finite element technique to compute the stresses and strains induced by the push of a rigid body against a two dimensional viscous material the boundary conditions are the velocities based on plate kinematics a motion in the n300 e direction best explains the stress trajectories observed in central taiwan viscosity contrasts as well as small changes in the shape of the northern edge of the indenter have little influence on the computed stress pattern the most important parameter is the direction of convergence our model quantitatively explains the general pattern of the stress trajectories observed in the collision zone of taiwan between the philippine sea plate and eurasia

focal depths and fault plane solutions of earthquakes and active tectonics of the himalaya synthetic seismograms were compared with long period body waves for nine earthquakes with epicenters in the himalayan arc to determine depths of foci and to improve fault plane solutions focal depths are shallow 10 20 km inferred slip vectors are locally perpendicular to the mountain range they plunge very gently about 10 deg in the eastern sections of the range and more steeply about 25 deg in western sections assuming india to be a rigid plate the radially oriented slip vectors imply that southern tibet extends at about half the rate of underthrusting in the himalaya and therefore probably at about 5 10 mm yr the shallow depths and gentle dips of the fault planes at least for the events in the eastern half of the range are consistent with coherent underthrusting of the indian plate beneath at least the lesser himalaya the steeper dips of fault planes in the western part of the arc might reflect deformation of the overriding thrust plate or simply a steepening of the main underthrusting zone beneath the greater himalaya

validity of the equilibrium beach profiles nile delta coastal zone egypt abstract beach profile equilibrium is the principal concept assumed by most numerical modelling the response of beach profile configuration to natural and anthropogenic changes could be predicted to help in selecting the most appropriate engineering design required to mitigate coastal erosion and accretion alongshore thus in order to apply coastal engineering projects the predicted profile of equilibrium should be close enough to the measured profile therefore before application of numerical modelling techniques equilibrium expressions have to be validated at the study site this research aims to assess the validity of the equilibrium profile concept on the nile delta coast based on beach profiles surveyed in 1990 from the main promontories abu quir bay the rosetta promontory and the el burullus promontory the results indicate that the equilibrium beach profile is consistent with the measured profiles at the study sites beyond 200 m distance offshore at 4 m depth in contrast the equilibrium status is not valid along the beach face at 1 m depth accreted beaches at abu quir bay and burullus promontory are characterized by wide berms and gentle beach face whereas eroded stretches at rosetta promontory have a narrow berm and steep beach faces the measured profiles are also compared with the exponential beach profile concept an exponential hypothesis is not valid along the nile delta coast profiles measured at abu quir rosetta and el burullus depart significantly from the exponential equation despite the fact that equilibrium expression can describe beach profiles along the nile delta one equilibrium profile equation is not sufficient to assess all beach profiles this can be explained as the morphology of beach profiles is subjected to some factors including sediment characteristics wave parameters and closure depth which vary alongshore analysis of the validity of the equilibrium beach profile is recommended to get accurate results in modelling simulations and design the most appropriate engineering projects required for shore protection

rock assemblages in central asia and the evolution of the southern asian margin by looking in detail at the rock record in central asia it is possible to map rock assemblages that are diagnostic of particular plate settings simplest of the assemblages include the rocks of the tadjik depression where mesozoic and paleogene sediments record the development of a south facing passive continental margin analysis of igneous activity in central asia and of the timing of deformation of these miogeoclinal rocks indicates that the paleotethyan ocean to the south was in the mesozoic subducting to the south beneath a migratory arc consisting of parts of iran afghanistan and the pamir only in the late tertiary does the tadjik depression develop a peripheral foreland assemblage which indicates any deformation of the miogeocline this presumably occurred as a result of the closing of the paleotethyan ocean and accretion of this portion of the arc to the southern margin of asia it appears unlikely that the depression passive margin sequence developed in a normal rift margin setting analysis of assemblages in the hercynian orogen tien shan to the north indicates that unlike the uralian section of the orogen the deformation here occurred due to the closure of a marginal basin and overthrusting of its basement rocks over a south facing arc thus considering depression basement composition it appears that the passive margin assemblage is superimposed over either a late paleozoic forearc or paleozoic ocean floor paleozoic rocks exposed north of the herat suture in afghanistan may require the forearc basement interpretation noting that the geometry of subduction and the timing of paleotethyan suturing seem to have varied along strike in the orogen a more complicated model of tectonic accretion is required

the modified bruun rule extended for landward transport article i nfo the bruun rule bruun 1954 1962 provides a relationship between sea level rise and shoreline retreat and has been widely applied by the engineering and scientific communities to interpret shoreline changes and to plan for possible future increases in sea level rise rates the bruun rule assumes that all sand removed from the upper profile is deposited offshore as sea level rises although overwash during storms and landward aeolian transport clearly indicate otherwise herein we examine processes associated with sandy beach evolution in response to relative sea level rise and propose a modified form of the bruun rule that considers the full range of parsing cross shore transport from completely seaward to completely landward depending on the prevailing storm and surge conditions and whether there is a surplus or deficit of sand in the profile with respect to the equilibrium beach profile a methodology is proposed that more appropriately represents the long term processes and beach response however an improved quantitative understanding of landward transport is required for optimal application of the proposed method published by elsevier b v

seismological evidence for shallow thrusting north of the timor trough summary the eastern sunda arc in indonesia is the site of subduction of the continental crust of australia and its shallow seismicity is manifested by infrequent large ms 7 earthquakes that occur near the volcanic arc within the upper plate rather than as interplate events beneath the forearc in the same region volcanic activity has ceased and small shallow earthquakes are rare we examine two of the larger earthquakes the events of 1962 may 15 ms 7 2 and 1977 august 27 ms 7 0 the 1977 event occurred north of central timor and the inversion of long period p and sh waves indicates a nearly pure thrust mechanism at a depth of 10 km below sea level and a seismic moment of 4 1 1026 dyne cm the p wave nodal planes for this solution strike roughly parallel to the mapped trace of a thrust zone the wetar thrust zone at the southern margin of the backarc basin and the south nodal dipping plane is consistent with the sense of thrusting on this thrust zone a broad zone of compressional deformation is evident in seismic reflection profiles over the epicentral region of the 1977 event and gravity data suggest that a small amount of either isostatically uncompensated crustal thickening or flexure of the underthrusting plate has occurred the 1962 earthquake occurred approximately 300 km north east of the 1977 earthquake and near the eastern end of the volcanically quiet section of the banda arc the similarity of the few available waveforms to those at the same stations for the 1977 event suggests a similar source mechanism modelling of pdif waveforms for the 1962 event indicates a depth of less than 40 km and a preferred centroidal depth of 20 km for which a seismic moment of 5 1026 dyne cm is estimated these fault plane solutions indicate that most of the seismic energy released by the collision between australia and the sunda arc is generated by faulting within the overriding plate and we infer that a major change in the plate geometry is imminent we suggest that most of the relative convergence between the plates is accommodated by thrusting of the marginal basin the banda sea southward beneath the arc and that the present geometry represents the initial stage of the reversal of the arc s polarity

the configuration of equilibrium beach profile in south china abstract to understand the evolution and stability of beaches prediction of the equilibrium beach profile ebp is theoretically and practically important in the present paper a new equation h ae bx c is developed to predict the change in beach profile for sections above the water level and the adjacent nearshore portions moreover fractal analysis is applied to predict types of ebp for the first time using the field data collected from liao zuikou and nanwan beaches south china three types of ebp termed upward concave ebp u ebp downward concave ebp d ebp and medium characteristic ebp m ebp are given for the studied region of south china

numerical model of the shoreline change at oarai beach abstract kraus n c and harikai s 1983 numerical model of the shoreline change at oarai beach coastal eng 7 1 28 a numerical simulation was made of the long term shoreline evolution of the sandy beach adjacent to oarai harbor japan the sand transport and shoreline change at oarai are dominated by wave diffraction at a long breakwater and interruption of the current and sand transport at a large groin the model was first calibrated using detailed wave data for a recent 7 1 2 month period the shoreline change which occurred over three years was then simulated to verify the model s predictive capability the calculation procedure for the breaking wave height and angle along the beach under combined diffraction and refraction was also verified with field measurements the availability of detailed wave and survey data stimulated a number of improvements in the calculation procedures for the breaking waves and shoreline change a comprehensive description of the site is given and relevant shoreline survey and wave data are listed in an appendix to enable interested parties to test and refine their own models

extreme erosion on high energy embayed beaches influence of megarips and storm grouping abstract megarips have long been recognised as an important yet poorly documented mechanism of beach erosion on high energy embayed beaches the persistence and cumulative effect of megarips during storm groups are described from three embayed beaches arrifana mt clerigo and amoreira exposed to high energy wave conditions in the mesotidal bedrock dominated southwestern coast of portugal morphological changes determined by topographic monitoring and supplemented by interpretation of digital imagery over two years revealed the development of storm induced megarips which exerted a major influence on beach erosion differences in megarip influence within and between beaches are related to embayment geometry and orientation which significantly influence the nearshore wave field rip location is topographically controlled being determined by alongshore variations in breaking wave height and obliquity along with interaction of wave driven circulation patterns and embayment nearshore topography moderate beach sand loss during individual storms was linked to the development of megarips with associated rip neck and feeder channels extreme erosion however occurred when megarips and feeder channels persisted during successive storms promoting continued erosion and seaward sediment export observations show that once initiated megarip channels persist for several months and continue to act as conduits for offshore sediment transport under non storm conditions the maintenance of such rip circulation systems driven by morphodynamic feedback reduces beach recovery ability until the rip neck and feeder channels are infilled

stress field evolution of the southernmost andean cordillera from paleostress analysis argentine tierra del fuego this work has been funded by projects ctm2011 30241 c02 02 ctm201460451 c2 2 p and ctm2017 89711 c22 p of the spanish r d national plan and by pict funding from anpcytfoncyt argentina

evidence for a high velocity slab associated with the hindu kush seismic zone we used teleseismic travel time residuals to determine lateral velocity variations of the crust and upper mantle in the pamir hindu kush region in tadjikistan and afghanistan data from 29 analog seismic stations in tadjikistan and northern afghanistan were used to determine travel time residuals for 210 teleseismic events ranging in distance from 28 to 87 and covering a broad range of azimuths we inverted for velocity perturbations over a rectangular grid with a block size of 99 99 km the model extended to a depth of 350 km with a 50 km thick first layer and two 150 km thick deeper layers the results show a strong and well resolved zone of high velocities in the upper mantle at depths greater than 200 km coincident with the location of the hindu kush seismic zone no clear velocity perturbations are associated with the pamir seismic zone above 200 km little correlation is observed with the seismic zone but indications of thicker crust under the pamir and thinner crust under the tadjik depression are seen the high velocities are most likely caused by the presence of oceanic lithosphere at depth

simulating the evolution of coastal morphology and stratigraphy with a new morphological behaviour model geombest abstract a new morphological behaviour model is used to simulate evolution of coastal morphology associated with cross shore translations of the shoreface barrier and estuary the model encapsulates qualitative principles drawn from established geological concepts that are parameterized to provide quantitative predictions of morphological change on geological time scales order 10 3 years as well as shorter time scales applicable for long term coastal management order 10 1 to 10 2 years changes in sea level and sediment volume within the shoreface barrier and estuary drive the model behaviour further parameters defining substrate erodibility sediment composition and time dependent shoreface response constrain the evolution of the shoreface towards an equilibrium profile results from numerical experiments are presented for the low gradient autochthonous setting of north carolina and the steep allochthonous setting of the washington shelf simulations in the currituck region of north carolina examined the influence of sediment supply substrate composition and substrate erodibility on barrier transgression results demonstrate that the presence of a lithified substrate reduces the rate of barrier transgression compared to scenarios where an erodible sand rich substrate exists simulations of the washington coast 20 km north of the columbia river confirmed that the model can reproduce complex stratigraphy involving regressive and transgressive phases of coastal evolution results suggest that the first major addition of sediment to the shelf occurred around 12 900 years ago and resulted from the rapid addition of sediment volume from the columbia river attributed to the missoula floods this was followed by a period where little or no sediment was added 12 400 9100 bp and a third period when most sediment was added to the shelf 9100 bp to present from the columbia river comparing results from each setting demonstrates an indirect control that substrate slope has on shoreface transgression rates shoreface transgression is shown to be sensitive to the rate of estuarine sedimentation with the sensitivity increasing as substrate slope decreases

thrusting of the hindu kush over the southeastern tadjik basin afghanistan evidence from two large earthquakes we infer from the mechanisms and depths of two large earthquakes that the hindu kush is actively thrusting northwest over the tadjik basin and that the basin is closing rather than being displaced to the west teleseismic body waves were used to determine focal mechanisms and depths for the two largest shallow earthquakes on the southern edge of the basin the two earthquakes on june 24 1972 mb 6 0 and december 16 1982 mb 6 2 have seismic moments of 2 1018 n m and 6 1018 n m respectively focal mechanisms of both events indicate almost pure thrust faulting with nodal planes striking northeast southwest the inferred fault planes dip southeast at 20 for the first event and 50 for the second the p axes for both events are oblique to the direction of relative motion between india and asia suggesting that the pamir is overthrusting the basin to the west depths for both earthquakes are between 20 and 25 km and place them well below the tadjik basin sediments the depths and steep fault planes suggest that these earthquakes represent a downdip extension within the basement of shallow folding and thrusting seen in the sediments northwest of the events thus convergence in afghanistan between india and eurasia is taken up along southeast dipping thrust faults north of the hindu kush as well as by northward subduction under the southern part of the range

maximum horizontal stress orientations in the cooper basin australia implications for plate scale tectonics and local stress sources summary borehole breakouts and drilling induced tensile fractures ditfs were interpreted in 61 wells in the cooper basin indicating an average maximum horizontal stress orientation of 101 n a total of 890 borehole breakouts and 608 ditfs were interpreted in the cooper basin the approximately east west maximum horizontal stress orientation is consistent over much of the basin except in the patchawarra trough where maximum horizontal stress rotates to a northwest southeast orientation this rotation in maximum horizontal stress orientation is consistent with in situ stress data to the northwest of the cooper basin the stress field in the cooper basin appears to mark the apex of a major horseshoe shaped rotation in maximum horizontal stress direction across central eastern australia finite element modelling of the in situ stress field of the indo australian plate iap using a range of plate scale tectonic forces is able to match the regional maximum horizontal stress orientation over most of australia reasonably well including the mean east west maximum horizontal stress orientation in the cooper basin however plate boundary scale modelling does not adequately match the horseshoe shaped stress rotation across central eastern australia the average east west maximum horizontal stress orientation in the cooper basin indicates that stresses from tensional forces acting along the tonga kermadec subduction zone are not transmitted into the interior of the australian plate the majority of the tensional forces associated with the tonga kermadec subduction zone are most likely accommodated along the numerous spreading centres within the lau havre backarc basin a number of more localized stress anomalies have also been identified these cannot be explained by plate scale tectonic forces and are possibly a result of geological structure and or density contrasts locally perturbing the stress field

seismicity fault plane solutions depth of faulting and active tectonics of the andes of peru ecuador and southern colombia the intracontinental seismicity of the andes of peru ecuador and southern colombia is concentrated along the easternmost flank of the cordillera beneath the western margin of the sub andes the focal depths and fault plane solutions of the largest events were constrained by comparing the observed long period p waves with synthetic waveforms in general the fault plane solutions show reverse faulting on steeply dipping nodal planes striking northwest southeast and reflect crustal shortening perpendicular to the range probably in response to the subduction of the nazca plate to the west earthquakes in the sub andes occur at depths of between 8 and 38 km indicating that much of the crust deforms in a brittle manner the seismicity seems to reflect antithetic underthrusting of the brazilian shield beneath the eastern margin of the andes however the earthquakes are too deep and their nodal planes are too steep to be associated with the thin skinned decollement of the sedimentary cover instead they appear to reflect the tectonic deformation of the underthrust basement west of the zone of active deformation at the surface in the sub andes hence the earthquakes on the east side of the andes may reflect the style of deformation in the hinterland of fold and thrust belts such as in the canadian rockies while much of the decollement farther east occurs aseismically in contrast normal faulting occurs in the high andes on planes parallel to the strike of the mountain belt thus there is a delicate balance between the compressive stress applied to the andes in the direction of subduction which causes thrust faulting in the sub andes and the gravitational body forces acting on the topographically higher parts and the crustal root of the andes which may cause normal faulting at high elevation

development of a medium long term beach evolution model abstract a new medium long term beach evolution model is proposed this model is based on an analytically integrated sediment conservation equation and on a beach profile evolution model the sediment conservation equation provides the sediment supplies or losses the beach profile evolution model redistributes the sediment supplies or losses along the beach profile in the beach profile evolution model the definition of the complete profile is incorporated breaking zone transition zone exterior zone and geological zone the proposed model has been applied to several theoretical cases and to field data showing the advantages of this model compared to classical one line models

miocene rifting of fuerteventura canary islands 1 the older geological units of the volcanic island of fuerteventura canary islands i e the so called basal complex and the lower part of the subaerial volcanic rocks show abundant structures indicative of a long lived period of miocene tectonic activity these structures include faults dike swarms kilometer scale folds tilted sequences and fissural and central volcanic edifices a detailed structural study based on geological mapping and the use of fault slip inversion techniques and statistical analysis of dike orientation has allowed the identification of three separated miocene deformation phases m d1 m d2 and m d3 the average extension directions determined for these phases are nw se nne ssw and ene wsw respectively a model of oceanic lithosphere rifting is proposed to account for this deformation history a buoyant anomalous sublithosphere mantle triggered the extension in the lithosphere beneath fuerteventura isolating it during the early and middle miocene from the plate scale collision regime predominant in the nw corner of the african plate

active deformation in the new guinea fold and thrust belt seismological evidence for strike slip faulting and basement involved thrusting the new guinea fold and thrust belt forms a 1000 km long mountain chain running the length of new guinea but its trend is oblique to the predicted convergence direction a large component of left lateral shear across the mountain belt is expected but geological evidence for such motion is ambiguous surface structures in the fold and thrust belt show mountain building by folding and thrusting supposedly thin skinned of pre pliocene continental shelf sediments although some evidence indicates that active faulting penetrates the basement we examine the active deformation of this mountain belt by using teleseismic long period p and sh waveforms short period p waveforms and p wave first motions to determine reliable focal mechanisms and source depths for the 18 largest earthquakes in the new guinea fold and thrust belt since 1964 eight thrust events with seismic moments m0 between 1017 and 2 1018 n m are distributed throughout the thrust belt at depths ranging from 0 5 to 45 km and have steeply dipping fault planes that strike parallel to surface structural trends six of the eight events are between 11 and 25 km deep the steep dips of nodal planes the depths of these earthquakes and the known thicknesses of the sedimentary section show that thrust faulting is not exclusively thin skinned i e confined above a shallow detachment surface but penetrates the crystalline basement at high angles most earthquakes in the western half of the thrust belt including the three largest earthquakes examined m0 5 1018 n m show strike slip faulting with the probable fault plane oriented east west so that displacement is left lateral the nine strike slip earthquakes account for almost 90 of the observed seismic moment in the period 1964 1985 and indicate a seismic slip rate of 5 25 mm a all but one of these strike slip earthquakes are shallower than the thrust earthquakes suggesting that east northeast convergence across the fold and thrust belt is accommodated by a decoupled system of strike slip and dip slip faults while the great height of the mountain belt is an obvious indication that crustal thickening is an important consequence of plate motion in new guinea seismological evidence suggests that translation by strike slip faulting may play a much greater role than previously recognized by analogy in older collisional orogens whose motions can be inferred only from remnant structures and not from seismicity strike slip faulting may have been equally important in accommodating convergence we estimate from seismic moments of earthquakes and from the volume of the mountains that deformation of the new guinea highlands may account for 5 20 of the total convergence between the pacific plate and australia in new guinea

the geology and petroleum potential of the north afghan platform and adjacent areas northern afghanistan with parts of southern turkmenistan uzbekistan and tajikistan the north afghan platform has a pre jurassic basement unconformably overlain by a jurassic to paleogene oil and gas bearing sedimentary rock platform cover unconformably overlain by neogene syn and post orogenic continental clastics the pre jurassic basement has four units 1 an ordovician to lower devonian passive margin succession developed on oceanic crust 2 an upper devonian to lower carboniferous tournaisian magmatic arc succession developed on the passive margin 3 a lower carboniferous visean to permian rift passive margin succession 4 a triassic continental magmatic arc succession the mesozoic palaeogene cover has three units 1 a late triassic to middle jurassic rift succession is dominated by variable continental clastics thick coarse lenticular coal bearing clastics were deposited by braided and meandering streams in linear grabens while bauxites formed on the adjacent horsts 2 a middle to upper jurassic transgressive regressive succession consists of mixed continental and marine bathonian to lower kimmeridgian clastics and carbonates overlain by regressive upper kimmeridgian tithonian evaporite bearing clastics 3 a cretaceous succession consists of lower cretaceous red beds with evaporites resting unconformably on jurassic and older deposits overlain usually unconformably by cenomanian to maastrichtian shallow marine limestones which form a fairly uniform transgressive succession across most of afghanistan 4 a palaeogene succession rests on the upper cretaceous limestones with a minor break marked by bauxite in places thin palaeocene to upper eocene limestones with gypsum are overlain by thin conglomerates which pass up into shales with a restricted brackish water upper oligocene lower miocene marine fauna the neogene succession consists of a variable thickness of coarse continental sediments derived from the rising pamir mountains and adjacent ranges almost all the deformation of the north afghan platform began in the miocene oil and gas traps are mainly in upper jurassic carbonates and lower cretaceous sandstones across the entire north afghan block upper jurassic carbonate traps sealed by evaporites occur mainly north of the southern limit of the upper jurassic salt lower cretaceous traps consist of fine grained continental sandstones sealed by aptian albian shales and siltstones upper cretaceous palaeocene carbonates sealed by palaeogene shales are the main traps along the northern edge of the platform and in the tajik basin almost all the traps are broad anticlines related to neogene wrench faulting in this respect like similar traps along the san andreas fault hydrocarbon sources are in the mesozoic section the lower middle jurassic continental coal bearing beds provide about 75 of the hydrocarbons the callovian oxfordian provides about 10 the neocomian a meagre 1 and the aptian albian about 14 the coal bearing source rocks decrease very markedly in thickness southwards cross the north afghan platform much of the hydrocarbon generation probably occurred during the late cretaceous paleogene and migrated to structural traps during neogene deformation since no regional structural dip aids southward hydrocarbon migration and since the traps are all structural and somewhat small then there is little chance of very large petroleum fields on the platform nevertheless further studies of the north afghan platform should be rewarding because a the traps of strike slip belts are difficult to find without detailed exploration b the troubles of the last 20 years mean that almost no exploration has been done and c conditions may soon become more favorable there should be ample potential for oil and particularly gas discoveries especially in the northern and western parts of the north afghan platform

role of lithospheric strength heterogeneities in the tectonics of tibet and neighbouring regions unlike rigid oceanic plates continents show diffuse deformation for example the tibetan plateau that has accommodated much of the convergence of india with asia we interpret the tertiary deformation of asia as the three dimensional strain of a non linear viscous continental lithosphere lateral strength contrasts modify this deformation stress concentration around the relatively strong tarim basin gives rise to local crustal thickening in the tien shan to the north and to strike slip in the altyn tagh along its southern margin

using stress deflections to identify slip events in fault systems abstract a new approach for identifying past slip events in strike slip fault systems without geological markers is presented a 2 d distinct element modeling code is used to simulate the stress distribution around a strike slip fault zone after a major slip event mature and immature fault zones are investigated slip on the fault is responsible for stress rotations near the active fault strand series of experiments reveal that the stress deflections are qualitatively the same whatever the fault strike fault friction and far field differential stresses for a left lateral fault stresses are rotated clockwise in the two compressive quadrants near the fault tips and counterclockwise in the two extensive quadrants the stress field signature of a slip event thus highlights the extent of the active fault strand conversely the reconstruction of paleostress fields through inversion of minor striated faults that commonly follow slip on the master fault and the analysis of their deflections allow recognition of the fault strands that slipped in a close or remote past application to the left lateral pontarlier fault zone in the jura fold and thrust belt france late cenozoic in age shows that the fault activity has migrated northward in agreement with the in sequence development of the mountain belt

active tectonics of the pamirs and karakorum the source parameters of moderate to large sized earthquakes and the spatial distribution of earthquake hypocenters are used to investigate the active tectonics and three dimensional configuration of the subducted lithosphere in the pamir karakorum intracontinental convergence zone the continental collision has resulted in intense deformation in the upper crust the deformation is distributed over a broad area and is absorbed by thrust and strike slip faulting along the northern margin of the pamirs where the deformation due to continental collision is most intense the northern pamir thrust and several major fault zones mark the present boundary most of the earthquakes that occurred in these fault zones are shallow crustal events with focal mechanism solutions correlated with the tectonic features of the region along the pamir front thrust faulting dominates while on the western and eastern edges of the pamirs the style of deformation is characterized by oblique thrusting with a component of strike slip motion thrust type events beneath the tadjik depression indicate that both the sedimentary rocks and the basement are involved in shortening right lateral strike slip motion is observed on the eastern edge of the pamirs where they border the tarim basin and in the talas fergana kun lun fault zone a southward dipping seismic zone beneath the pamirs and karakorum indicates that the asian lithosphere has been subducted along the pamir front to a depth of at least 200 km this interpretation is consistent with published geological and geophysical data focal mechanism solutions of some intermediate depth events beneath the pamirs show strike slip faulting with approximately n s horizontally oriented p axes indicating that nearly horizontal compression at the intermediate depth is the predominant mode of deformation a 90 km deep event beneath the karakorum is interpreted as occurring in the subducted asian lithosphere the fact that the p axis of this event is oriented parallel to the descending plate suggests downdip compression within the asian lithosphere the overall tectonics of the region is interpreted as a consequence of the underthrusting asian lithosphere being impinged upon by the shallow northward underthrusting indian lithosphere

tr method a practical tool to analyze focal mechanisms and identify the real seismogenic fault of an extensional or compressional shallow earthquake sequence abstract the recently proposed tr method that separates heterogeneous fault slip data in extensional and compressional stress regimes is applied on focal mechanisms of a number of earthquake sequences aiming to identify the main seismogenic fault plane the method only requires the earthquake sequence to be classified as related to an extensional or compressional stress regime in particular the nodal planes of the compressional or extensional focal mechanisms have been subdivided into two opposite dipping groups taking into account the average trend of their horizontal p or t axis in the tr diagrams where we plot the slip deviation from the dip slip activation of the nodal plane versus the angle between the dip direction of the nodal plane and the average trend of the p or t axis the comparison of the geometric kinematic dynamic and mechanical compatibility of the two opposite nodal plane groups is possible moreover a quality number trn is devised in order to assess the two opposite facing groups quantitatively five earthquake sequences related with an extensional stress regime and two related with a compressional stress regime are processed in order to demonstrate and validate the potential and efficiency of the method these cases indicate that the tr method can be fairly used as a practical tool to assess which nodal planes are more likely to identify the main seismogenic fault plane the main advantages of the method are a the assessment of the nodal plane groups without the necessity to determine all the parameters of the driving stress tensor i e stress axes and stress ratio b the consideration of the slip tendency

the seismicity of kohistan pakistan source studies of the hamran 1972 9 3 darel 1981 9 12 and patan 1974 12 28 earthquakes abstract long period body waves are examined to show that the hamran 1972 9 3 darel 1981 9 12 and patan 1974 12 28 earthquakes in kohistan had focal depths of about 8 10 km all involved high angle reverse faulting thrusting and had seismic moments of about 2 2 to 2 7 1025 dyne cm these shallow depths contrast with the deeper hypocentres found in the hindu kush and northeast karakoram to the north and in hazara to the south the hamran and patan shocks were assigned depths of 45 km by the isc indicating that even well recorded events in this region may have focal depths in error by 30 km

grouping and migration of surface faulting and variations in slip rates on faults in the great basin province abstract nonuniformity of the occurrence of large slip events producing surface ruptures on seismogenic faults and variations in slip rate probably characterize seismogenic faulting in the great basin province western united states examples include the grouping of faulting events along the lost river fault idaho changes in tilt rates of the east range and cortez mountains nevada extension of slip along a fault on the northwest flank of the humboldt range nevada and migration or shifting of slip back and forth from one fault to another along subparallel range front faults in dixie valley nevada

eocene oligocene tectonics and kinematics of the rhine saone continental transform zone eastern france a tectonic analysis of brittle deformaton was performed in the rhine saone transform in order to decipher and understand the deformation processes in a typical continental hansfer zone cenozoic major and minor fault patterns are described and brittle structures are interpreted in terms of paleostress orientations the eocene n s compression related to africa eurasia convergence is marked mainly by strike slip faults it was followed by a major phase of crustal extension mainly oligocene in age related to the west european rifting this extensional phase is expressed by normal faults tension gashes and extensional strike slip faults which are especially abundant in the transform zone these two events are found to be quite different in terms of distribution of horizontal shess trajectories the trend of ol axes is very homogeneous for the n s compression whereas o3 orientations associated with the major extension vary from e w in most of the rift system to i v se within the transform zone finally the mio pliocene tectonic emplacement of the jura fold and thrust belt is marked in the field by strike slip faults associated with a well defined trend of ol oriented w iiw e se to nw se the preexisting basement fracture pattern between the grabens was also considered in order to estimate which faults were likely to have been reactivated during the oligocene transform kinematics and the theoretical shear motion on these inherited fault surfaces when submitted to e w extension was calculated left laterauextensional reactivation of a preexisting 60 n trending fault system in the brittle upper crust is likely to have accommodated the shear strain arising between the rift segments in response to crustal stretching two independent numerical modelings based on distinct element and finite element analyses respectively enabled us to verify and to refine the hypothesis of transform kinematics related to e w extension and inducing regional perturbations of extensional stress trajectories the overall mechanism and the transtensional kinematics of the rhine saone transform zone are thus tightly conshained the inherited crustal anisotropy the large scale perturbations of extensional stress trajectories and the development of distributed brittle deformation within the sedimentary cover are found to play a major role in the tectonic evolution of continental rift transform systems

stress changes induced at neighbouring faults by the june 2000 earthquakes south iceland seismic zone the south iceland seismic zone sisz is an e w trending active transform zone with high seismicity n s trending right lateral strike slip faults accommodate the left lateral transform motion using seismological data recorded from 1991 to 2007 we carried out stress inversion of focal mechanisms of 1340 earthquakes that affected the skard and leirubakki faults eastern sisz not only did the inversion show typical deviations of stress across the faults it also revealed anticlockwise and clockwise rotations of stress axes with time numerical models of the leirubakki fault show that these rotations are consistent with the mechanical effect of a lowered friction coefficient during the post seismic period relative to the pre seismic period the skard fault reveals a more complex behaviour associated with a higher post seismic friction resulting from a higher density of pre existing fracturing and probable stress interaction between faults our results suggest that faults where micro earthquakes occur during neighbouring major seismic events may undergo significant stress changes at the scale of several kilometres and on time scales of several years

an energetics total load sediment transport model for a plane sloping beach bagnold s energetics based total load sediment transport model for streams is used as a basis for the development of a total load model of time varying sediment transport over a plane sloping bed in both the bedload and suspended load the transport rate vectors are found to be composed of a velocity induced component directed parallel to the instantaneous velocity vector and a gravity induced component directed down slope the model is applied to idealized surfzone conditions leading to estimates of the local longshore and onshore offshore sediment transport rates as well as the equilibrium beach slope as a function of the local wave and current conditions the model is combined with a nonlinear longshore current model and spatially integrated to obtain predictions of the total longshore transport rate as a function of the incident wave conditions the results support the general form of the wave power equation except that the wave power coefficient is no longer constant but is instead a complex function of the incident wave and beach characteristics

holocene sand beaches of southern california enso forcing and coastal processes on millennial scales abstract a proxy record of sand beach accretion for the past 10 000 years has been assembled from radiocarbon dates on the pismo clam tivela stultorum in archaeological sites along the southern california coast when this record is compared with numerous climate proxies it appears that el nino southern oscillation enso controls on wave climate and sediment flux have acted upon regional geomorphology at different sea levels to either accrete or erode the holocene beaches of southern california tivela dates from the santa maria coast indicate that perennial sand beaches built by 9000 years ago in response to abundant riverine sediment contained by the natural groin at point sal wave sheltering by the massive headland of point buchon and early holocene el nino events on the western santa barbara coast sand beaches were forming by 7000 years ago in response to high sand fluxes from the santa ynez mountains to the many small littoral catchments possibly aided by high local rates of uplift decline of these sand beach habitats 5000 4000 years ago coincides with increased el nino driven wave energy in accord with slowing in sea level rise ca 6000 years ago sand beaches were most widespread in the period 6000 5000 years ago on estero bay the western santa barbara coast and west of point dume however tivela dates first appear 5000 years ago in the oceanside and silver strand littoral cells of the san diego region this lag coincides with the middle holocene shift to a more variable climate and modern periodicity in el nino events that increased sediment supply to the southern coast the ontogeny of the littoral cells provides timelines for modeling coastal evolution with implications for sand beach ecology prehistoric human coastal adaptations and coastal planning for future climate change

the repetition of large earthquake ruptures abstract this survey of well documented repeated fault rupture confirms that some faults have exhibited a characteristic behavior during repeated large earthquakes that is the magnitude distribution and style of slip on the fault has repeated during two or more consecutive events in two cases faults exhibit slip functions that vary little from earthquake to earthquake in one other well documented case however fault lengths contrast markedly for two consecutive ruptures but the amount of offset at individual sites was similar adjacent individual patches 10 km or more in length failed singly during one event and in tandem during the other more complex cases of repetition may also represent the failure of several distinct patches the faults of the 1992 landers earthquake provide an instructive example of such complexity together these examples suggest that large earthquakes commonly result from the failure of one or more patches each characterized by a slip function that is roughly invariant through consecutive earthquake cycles the persistence of these slip patches through two or more large earthquakes indicates that some quasi invariant physical property controls the pattern and magnitude of slip these data seem incompatible with theoretical models that produce slip distributions that are highly variable in consecutive large events

evolution of stress fields and faulting in seismic zones measurements indicate that stress magnitudes in the crust are normally limited by the frictional equilibrium on pre existing optimally oriented faults fault zones where these limitations are frequently reached are referred to as seismic zones fault zones in the crust concentrate stresses because their material properties are different from those of the host rock most fault zones are spatially relatively stable structures however the associated seismicity in these zones is quite variable in space and time here we propose that this variability is attributable to stress concentration zones that migrate and expand through the fault zone we suggest that following a large earthquake and the associated stress relaxation shear stresses of a magnitude sufficient to produce earthquakes occur only in those small parts of the seismic zone that because of material properties and boundary conditions encourage concentration of shear stress during the earthquake cycle the conditions for seismogenic fault slip migrate from these stress concentration regions throughout the entire seismic zone thus while the stress concentration regions continue to produce small slips and small earthquakes throughout the seismic cycle the conditions for slip and earthquakes are gradually reached in larger parts of and eventually the whole seismogenic layer of the seismic zone prior to the propagation of an earthquake fracture that gives rise to a large earthquake the stress conditions in the zone along the whole potential rupture plane must be essentially similar this follows because if they were not then on entering crustal parts where the state of stress was unfavourable to this type of faulting the fault propagation would be arrested the proposed necessary homogenisation of the stress field in a seismic zone as a precursor to large earthquakes implies that by monitoring the state of stress in a seismic zone its large earthquakes may possibly be forecasted we test the model on data from iceland and demonstrate that it broadly explains the historical as well as the current patterns of seismogenic faulting in the south iceland seismic zone

new constraints for indentation mechanisms in arcuate belts from the jura mountains france the mechanism of indentation in arcuate belts is discussed using the jura mountains as an example using fault inversion analysis from numerous sites the miocene pliocene stress pattern is reconstructed two superimposed compressional stress fields have been recognized considering the theoretical distribution of compression in front of a rigid indenter we interpret the complex stress pattern in the jura mountains as a result of a major change in the mechanism of indentation of the jura by its hinterland initially the indenter was narrower and limited in the southwest by the vuache transfer fault with time it expanded to the southwest and included the entire molasse basin this evolution highlights the importance of decoupling along faults which here controlled the indenter shape

an energetics bedload model for a plane sloping beach local transport bagnold s energetics based sediment transport model for streams is used as a basis for the development of a model for the time varying transport of bedload over a plane sloping bed the sediment transport vector is found to consist of two components the velocity induced transport directed parallel to the instantaneous velocity vector and the gravity induced transport vector directed downslope the model is applied to the case of sediment transport within the surf zone for the separate cases of weak and strong longshore currents relative to the wave bore oscillatory water velocity the results suggest the bagnold s oscillatory sediment transport model which forms the basis for a number of longshore sediment transport models is only correct for the special case of weak longshore currents and near normal incident waves for an artibrary strength longshore current v and a local incident wave angle a the longshore transport rate is found to be proportional to sina v 1 sin sup 2 a v sup 3 where u is the wave induced oscillatory water velocity the model also predicts the onshore offshore sediment rate for weak longshore currents and near normal incident waves the predicted equilibrium beach slope is equal to tanf strong longshore currents and or significant local wave angle conditions however cause amore change in this equilibrium beach slope less authors bailard j a inman d l publication date 1981 03 20 osti identifier 6767919 resource type journal article resource relation journal name j geophys res united states journal volume 86 c3 research org scripps institution of oceanography university of california la jolla california 92093 country of publication united states language english subject 58 geosciences shores sedimentation coastal waters gravitation sediments silt velocity water currents currents surface waters 580500 oceanography 1980 1989

performance of submerged nearshore sand filled geosystems for coastal protection abstract nearshore submerged structures made of sand filled geosystems are an interesting use for this type of coastal protection technology these systems have an advantage over more traditional materials such as concrete units or rock which is the limited and non permanent impact on natural coastal processes on top of that are also some important research achievements and improvements at the level of the materials however at more exposed hydraulic conditions under high wave energy its application is still hampered by the lack of knowledge about their performance this paper describes research results based on a series of laboratory measurements of the hydrodynamic and morphodynamic change produced in the vicinity of submerged nearshore structures an analysis of the different model outputs produced with respect to sediment transport wave reflection and wave induced pressures has been made and is discussed throughout the paper such a comparative analysis provides insights into the efficiency of each defence scheme in maintaining a beach and in protecting the shoreline the sand filled geosystems as nearshore submerged structures proved to be efficient in retarding the offshore movement of sediments and in maintaining the shoreline even if instabilities due to elements displacement and local scour have been observed

shorerise and bar berm profiles on ocean beaches a beach equilibrium model is developed that treats the outer shorerise portion of the profile independently from that of the inner bar berm portion the two portions are matched at the breakpoint bar the partitioning of the profile in this way is consistent with the different forcing modes on either side of the breakpoint this formulation utilizes beach profile data not previously available it is shown that both portions of the profile are well fitted by curves of the form h axm where h is positive downward and x is the positive offshore coordinate surprisingly the value of m 0 4 is nearly the same for shorerise and bar berm and does not change significantly with seasonal beach changes summer winter the principal difference between seasonal profiles is that in winter higher waves the breakpoint bar is deeper and farther offshore while the berm crest is displaced landward thus the changes in seasonal equilibria are manifested by simple self similar displacements of the bar berm and shorerise curves as a consequence of changes in surf zone width and o 1 variations in the factor a

development and testing of a 3d velocity model for improved event location a case study for the india pakistan region 3d velocity models will play an important role in improving location accuracies of small events within the context of a comprehensive nuclear test monitoring treaty commonly such models are developed using tomographic methods that require the initial velocity model to be a reasonable approximation of the true earth structure in this article we present a method for the development of an a priori model for the crust and upper mantle in the india pakistan region and techniques for evaluating its suitability for use as an initial model in tomographic studies we developed the weston india pakistan 3d velocity model winpak3d by integrating the results of more than 60 previous studies related to crustal velocity structure in the region a well located event that occurred near nilore pakistan on 14 february 1977 provided a basis for testing the model via several different approaches evaluation of the 3d model included 1 cross validation analysis 2 comparison of model determined hypocenters with a known event location and 3 comparison of model based and empirically derived travel time correction surfaces generated for an event within 5 km of the seismic station at nilore the 3d model is demonstrated to improve the regional location of the 1977 event as compared to 1d models the epicenter mislocation using the first arrival phase at 23 regional stations determined by the 3d model was only 6 2 km compared to 13 1 km and 15 4 km for a regional 1d model and the iasp91 model respectively results of extensive testing demonstrate that winpak3d will be a particularly good initial model for tomographic studies as it improves regional location accuracy specifically for sparse networks these results demonstrate that 3d velocity models are essential for improving location accuracy in regions that have complicated crustal geology and structures such 3d models may be a prerequisite for achieving location accuracies as called for by the comprehensive nuclear test ban treaty particularly for small events that are not recorded teleseismically

characterization of stress perturbations near major fault zones insights from 2 d distinct element numerical modelling and field studies jura mountains abstract we consider and discuss the presence of discontinuities in the crust as a major source of stress perturbations based on 2 d distinct element modelling we reconstruct the local stress field around a vertical discontinuity in various geological contexts the resulting stress distribution reveals that major directional stress changes occur near the tips of the discontinuity so that stress deviations can reach values as large as 50 we establish simple relationships controlling stress changes around a pre existing fault zone as a function of 1 the remote differential stress magnitude 1 3 2 the friction coefficient on the discontinuity and 3 the strike of the discontinuity relative to the far field stress as a geological example we present the morez fault zone in the internal jura paleostress reconstruction in forty two sites indicates that the trends of the mio pliocene compression are n110 on average near the fault whereas they are n130 in the surrounding areas a comparison between the results of the tectonic study and those of theoretical modelling suggests that the 20 counterclockwise deviation is directly related to the reactivation of this large weak zone we thus evaluate the role of mechanical decoupling along pre existing zones of weakness especially with consideration to the accommodation of the alpine deformation in the jura belt

parameterization of erosion vulnerability at coasts with multiple bars a case study of baltic sea coastal segment in poland abstract the paper proposes a method of detection of erosion prone multiple bar beaches only based on recorded bathymetric profiles without any frequently missing hydrodynamic information for this purpose a 45 km long pristine coastal segment of the polish coast was analyzed the bathymetric profiles there spaced every 500 m were measured in 2005 and 2011 from a dune cliff crest up to a seabed depth of about 15 m one or two monotonic components were identified in seabed topography with signal processing tools their shapes closely resemble theoretical upward concave beach equilibrium profiles reflecting intensive wave breaking in those regions although saturated wave energy dissipation often occurs only along a portion of those regions the assumption of such regime allows for straightforward evaluation of the uppermost limit of wave energy dissipation capacity for each studied bathymetric profile this problem was thoroughly examined and validated in the study knowing the intensity of energy dissipation in saturated regime and the length of segments where it occurs we can calculate wave energy dissipation potential profile by profile hence erosion prone sub segments can be identified where wave energy dissipation is remarkably lower than that established at neighbouring profiles the presented methodology can be particularly recommended for dissipative beaches with multiple bars where beach fills are often considered to mitigate coastal erosion

incorporating fault mechanics into inversions of aftershock data for the regional remote stress with application to the 1992 landers california earthquake abstract we present a new stress inversion algorithm that accounts for the physics relating the remote stress slip along complex faults and aftershock focal mechanisms in a linear elastic heterogeneous isotropic whole or half space for each new remote stress the solution of the simulation is obtained by the superposition of three pre calculated solutions leading to a constant time evaluation consequently the full three dimensional boundary element method model need not be recomputed and is independent of the structural complexity of the underlying model using a synthetic model we evaluate several different measures of fit or cost functions between aftershocks and model results cost functions that account for aftershock slip direction provide good constraint on the remote stress while functions that evaluate only nodal plane orientations do not inversion results are stable for values of friction 0 5 on mainshock faults we demonstrate the technique by recovering the remote stress regime at the time of the 1992 m 7 3 landers california earthquake from its aftershocks and find that the algorithm performs well relative to methods that invert earthquakes occurring prior to the landers mainshock in the mechanical inversion incorporating fault structures is necessary but small differences in fault geometries do not impact these inversion results each inversion provides a complete solution for an earthquake as output including fault slip and the stress and deformation fields around the fault s this allows for many additional datasets to be used as input including fault surface slip gps data insar data and or secondary fracture orientations

bar generating cross shore flow mechanisms on a beach random waves normally incident on a dissipative beach induce a variety of cross shore flows such as asymmetric oscillatory flow wave grouping induced long wave flow breaking induced turbulent flow and momentum decay induced undertow these flows are identified analyzed and hindcasted in a set of laboratory experiments with the aim of revealing the role of each of the flow mechanisms in the two dimensional case of bar generation on a beach

mesozoic ophiolites sutures and arge scale tectonic movements in afghanistan abstract the tectonic history of afghanistan appears to be the result of successive accretion of fragments of gondwana to the active margin of laurasia since the end of the paleozoic the margin in afghanistan lies along the present herat and panjshir faults south of hindu kush swings around the central pamirs and can presumably be traced along the present western altyn tagh and kunlun faults in tibet north of this boundary paleozoic rocks have been deformed in the upper paleozoic whereas south of it there is no trace of the hercynian orogeny the first collision of gondwanian fragments with laurasia probably occurred in the early mesozoic along the hindu kush and kunlun to the south ophiolites along the panjao and pangong nu chiang sutures respectively in central afghanistan and central tibet testify for another suturing event in the upper jurassic or lower cretaceous the indus tsangpo suture between india and tibet corresponds in eastern afghanistan to two ophiolite subbelts near kabul and khost both ophiolite complexes have been emplaced between maestrichtian and lower eocene by choking of two northward dipping subduction zones after complete contact between the indian and asian continents was achieved presumably in the end of eocene the penetration of india into asia caused large scale intra continental shortening a large part of the shortening was accommodated by strike slip faulting along mesozoic and more ancient sutures central afghanistan in particular was extruded to the west along the herat suture by the protrusion of the pamir wedge it subsequently collided with the lut block

palaeostress perturbations near the el castillo de las guardas fault sw iberian massif use of stress inversion methods on faults measured at 33 sites located at the northwestern part of the south portuguese zone variscan iberian massif and analysis of the basic dyke attitude at this same region has revealed a prominent perturbation of the stress trajectories around some large crustal scale faults like the el castillo de las guardas fault the results are compared with the predictions of theoretical models of palaeostress deviations near master faults according to this comparison the el castillo de las guardas fault an old structure that probably reversed several times its slip sense can be considered as a sinistral strike slip fault during the moscovian these results also point out the main shortcomings that still hinder a rigorous quantitative use of the theoretical models of stress perturbations around major faults the spatial variation in the parameters governing the brittle behaviour of the continental crust and the possibility of oblique slip along outcrop scale faults in regions subjected to general non plane strain

final stages of the variscan orogeny at the southern iberian massif lateral extrusion and rotation of continental blocks 1 the southern part of the iberian massif contains one of the sutures of the european variscan belt several systems of faults and dikes appear as a result of a period of brittle deformation during the late stages of the variscan tectonic evolution of this zone a detailed analysis of these structures has been carried out in this work four successive deformation phases have been identified a first strike slip normal faulting stage a transcurrent stage a second strike slip normal faulting stage and finally a thrusting stage the age of these phases vary between around 310 ma and less than 270 ma the computed trajectories of the deformation axes show a progressive anticlockwise rotation of around 90 these data together with the results of previous geological and geophysical studies of this zone and of the variscan belt as a whole lead us to propose a model of tectonic evolution for the last stages of the variscan collision comparison with modern examples of collisional belts and with the results of analog experiments suggests that a promontory of the continental lithosphere of the downgoing plate indented against the active continental margin of the upper plate the indenter suffered an intense deformation in accordance with the predictions of some recent analog models simulating the indentation of a four layer continental lithosphere the variscan and late variscan brittle deformation episodes represent the waning stages of the variscan collision and not an independent tectonic event

reduction of sand demand for shore protection beach nourishment is an environmentally preferred method of shore protection but the annual sand requirement may lead to substantial maintenance costs the shoreline processes involving the surf zone beach and dune are reviewed with the aim of reducing the annual sand requirement of eroding shorelines it is shown that surf zones with equilibrium profiles on which the wave energy conversion is evenly distributed across the surf zone from experience for given conditions indicate least loss of sand on steep eroding shorelines it may be difficult to establish an equilibrium profile for such cases the use of perched surf zones is recommended which are supported at the seaward limit by an underwater sill for reduction of littoral transport the use of pervious pile groynes is recommended these are arguably more efficient than impervious groynes the sand loss from a usually dry beach by raised water levels is shown to be a function of the beach slope and is least when the storm waves at raised water levels do not cut an erosion escarpment the loss of sand from a dune by infrequent severe storm tides can be prevented with the aid of a built in membrane these sand losses are usually large and constitute an uneconomic use of this sand resource the proposed concepts and measures are linked to existing knowledge augmented by data from the large wave flume lwf in germany and field data from the north and baltic sea coasts

crustal stress field in southern california and its implications for fault mechanics we present a new high spatial resolution image of stress orientation in southern california based on the inversion of earthquake focal mechanisms we use this image to study the mechanics of faulting in the plate boundary region the stress field contains significant spatial heterogeneity which in some cases appears to be a result of the complexity of faulting and in other cases appears to be a cause temporal changes in the stress field are also observed primarily related to major earthquakes the observed 15 10 rotation of the stress axes due to the 1992 m7 3 landers mainshock implies that the deviatoric stress magnitude in the crust is low of the order of 10 mpa this suggests that active faults in southern california are weak the maximum principal stress axis near the san andreas fault is often at 50 to the fault strike indicating that the shear stress on the fault is comparable to the deviatoric stress the san andreas in southern california may therefore be a weak fault in a low strength crust

statistics of characteristic earthquakes statistical methods are used to test the characteristic earthquake hypothesis several distributions of earthquake size seismic moment frequency relations are described based on the results of other researchers as well as my own tests evidence of the characteristic earthquake hypothesis can be explained either by statistical bias or statistical artifact since other distributions of earthquake size provide a simpler explanation for available information the hypothesis cannot be regarded as proven

faulting associated with large earthquakes and the average rate of deformation in central and eastern asia we determine approximate average rates of deformation in portions of eastern and central asia for the last 80 years these rates are based on estimates of source dimensions average displacements seismic moments and orientations of faults of all large earthquakes m 7 5 and as many other major earthquakes m 7 0 as possible in asia since 1900 a major part of this study is the compilation of these data for separate parts of asia we combine seismic moment tensors to estimate the average rotational strain or deformation tensors for these regions for the last 80 years we estimate that shortening across the tien shan has occurred at 11 mm yr between 5 and 19 mm yr left lateral shear on easterly trending planes in mongolia in northwestern tibet gansu and ningxia and on the xianshuihe fault in western sichuan has been very rapid more than 10 mm yr in each region and apparently as rapid as 40 mm yr in northwestern tibet gansu and ningxia slower rates of a few to 10 mm yr appear to characterize east west extension and conjugate north south shortening of tibet the earthquake history of the himalaya is consistent with rates of underthrusting of more than 10 mm yr but is probably less than the convergence rate of india with eurasia of about 50 mm yr the overall strain field is consistent with a large part of india s penetration into eurasia being absorbed by the extrusion of material out of india s way as a result southeast china moved at about 21 mm yr east southeast with respect to eurasia in the last 80 years with an uncertainty of about a factor of 2 in this estimated rate

paleomagnetism and tectonics of the jura arcuate mountain belt in france and switzerland abstract goethite and hematite in ferriferous oolitic beds of callovian age from the jura mountains switzerland france carry either pre and or post tectonic magnetization the frequent pre tectonic origin of goethite magnetization indicates a temperature range during formation of the arcuate jura mountain belt below the goethite neel temperature of about 100 c the scatter of the pre tectonic paleomagnetic directions d 11 5 e i 55 5 95 4 7 which reside both in goethite and hematite provides strong evidence that the arcuate mountain belt was shaped without significant rotation the paleomagnetic results support tectonic thin skinned models for the formation of the jura mountain belt

kinematics and surface fracture pattern of the anaran basement fault zone in nw of the zagros fold thrust belt the preexisting north south trending basement faults and their reactivation played an important role during the evolution of the zagros fold thrust belt the anaran basement fault in the lurestan r

plate collision and paleostress trajectories in a fold thrust belt the foothills of taiwan abstract field analyses of compressional faulting and folding in the foothills of western taiwan enable us to reconstruct paleostress trajectories over a large area and to establish the relative chronology of tectonic events two main compressional events have contributed to the present structure of the fold thrust belt stratigraphic data show that these events are plio pliocene in age older normal faulting indicates nnw sse extension across the chinesse passive continental margin during the neogene the two main compressional events of the taiwan collision correspond to similar fan shaped distributions of maximum compressive stress trajectories with a counterclockwise shift of 30 50 between the two events using the relationship between recent stress trajectories and the direction of recent plate motion as a guide we reconstruct the direction of plate convergence for the older event we suspect that the relative motion philippine sea plate eurasia has rotated counterclockwise of at least 35 45 in taiwan during collision this conclusion is in agreement with independent plate tectonic reconstructions several problems provide objectives to further tectonic and paleomagnetic studies including the duration and diachronism of compressional events as well as possible clockwise rotation of northernmost taiwan

initial spreading of a mega feeder nourishment observations of the sand engine pilot project sand nourishments are a widely applied technique to increase beach width for recreation or coastal safety as the size of these nourishments increases new questions arise on the adaptation of the coastal system after such large unnatural shapes have been implemented this paper presents the initial morphological evolution after implementation of a mega nourishment project at the dutch coast intended to feed the surrounding beaches in total 21 5 million m3 dredged material was used for two shoreface nourishments and a large sandy peninsula the sand engine peninsula a highly concentrated nourishment of 17 million m3 of sand in the shape of a sandy hook and protruding 1 km from shore was measured intensively on a monthly scale in the first 18 months after completion we examine the rapid bathymetric evolution with concurrent offshore wave forcing to investigate the feeding behaviour of the nourishment to the adjacent coast our observations show a large shoreline retreat of o 150 m along the outer perimeter of the peninsula with locally up to 300 m retreat the majority 72 of the volumetric losses in sediment on the peninsula 1 8 million m3 were compensated by accretion on adjacent coastal sections and dunes confirming the feeding property of the mega nourishment further analyses show that the morphological changes were most pronounced in the first 6 months while the planform curvature reduced and the surf zone slope flattened to pre nourishment values in the following 12 months the changes were more moderate overall the feeding property was strongly correlated to incident wave forcing such that months with high incoming waves resulted in more alongshore spreading months with small wave heights resulted in minimal change in sediment distribution alongshore and mostly cross shore movement of sediment

microearthquake seismicity and fault plane solutions related to arc continent collision in the eastern sunda arc indonesia the collision of australia with the eastern sunda and banda arcs of indonesia represents a modern example of the early stages of arc continent collision in order to obtain a more detailed view of the tectonics of the collision zone a microearthquake survey was conducted around the savu sea the region that encompasses the transition from subduction of indian ocean lithosphere on the west to collision or subduction of australian continental litho sphere on the east intermediate depth earth quakes were concentrated near pantar island the easternmost active volcano of the sunda arc and outline a northwest dipping zone that strikes n65oe from 70 to 150 km depth the seismic zone probably marks the western edge of the collision zone and its more northerly strike and the orientations of nodal planes from fault plane solutions indicate a 25 o bend in the subducted slab to a depth of at least 150 km because the convergence rate and the timing of collision from geologic observations on timor suggest that the oart of the slab now at 150 km depth was at the trench when australia first collided with timor we infer that continental crust or at least rifted continental margin crust caused the bend in the convergent margin and has been subducted to 150 km depth fault plane solutions of several events show nearly vertical nodal planes that trend parallel to the strike of the seismic zone along which a northwest side down sense of dis placement is indicated these events are concentrated at the southern top side of the seismic zone and suggest that the subducted lithosphere is presently detaching in the 50 100 km depth range beneath the eastern savu sea fault plane solutions for earthquakes within the upper part of the detaching slab 70 100 km depth have p and t axes whose trends lie parallel to the strike of the seismic zone and horizontal southeast trending b axes these earthquakes are interpreted as due to stresses caused by the bend in the subducting plate

structural inheritance and cenozoic stress fields in the jura fold and thrust belt france abstract based on an analysis of 8000 minor fault slip data in the jura mountains france we discuss the influence of pre existing discontinuities on the development of fold and thrust belts we present palinspastic maps showing the stress fields and active faults during the cenozoic pre orogenic events in the jura belt prior to the main late miocene fold and thrust tectonics during the eocene a n s strike slip regime produced a few nne ssw sub vertical strike slip faults in the central external jura and a few e w reverse faults in the eastern jura near the future frontal thrust during the oligocene an average wnw ese extension with irregular stress trajectories resulted in normal faulting along n s to ne sw trends in the external part of the belt wnw ese trends along the future northern and northeastern frontal thrust and nw se trends in the internal jura the late miocene tectonics began with a strike slip regime with a fan shaped compressional trajectory it was followed by a stress field with similar stress direction but local 2 3 stress permutation resulted in strike slip regime domains contrasting with reverse regime domains stress deflections and permutations occurred near inherited cover and basement discontinuities major deformation zones like the jura frontal thrust onto the foreland the thrust of the internal central jura onto the external jura and the narrow deformation bands within the flat lying plateaus formed close to the inherited faults the structural style of the jura belt thus partly mimics the pre orogenic fault pattern stress deflections point to the pre orogenic faults express the indentation process of the jura by its hinterland and highlight successive slip events along major faults during the fold and thrust tectonics this case study illustrates the relevance of minor fault slip studies for characterizing both the pre orogenic tectonics and the kinematics of the deformation

paleostress reconstruction from calcite twin and fault slip data using the multiple inverse method in the east walanae fault zone implications for the neogene contraction in south sulawesi indonesia abstract a new approach for paleostress analysis using the multiple inverse method with calcite twin data including untwinned e plane was performed in the east walanae fault ewf zone in south sulawesi indonesia application of untwinned e plane data of calcite grain to constrain paleostress determination is the first attempt for this method stress states caused by the collision of the south east margin of sundaland with the australian microcontinents during the pliocene were successfully detected from a combination of calcite twin data and fault slip data this pliocene ne sw to e w directed maximum compression activated the ewf as a reverse fault with a dextral component of slip with pervasive development of secondary structures in the narrow zone between bone mountain and walanae depression

velocity structure of the pamir hindu kush region possible evidence of subducted crust the arrival times of compressional p and shear s waves from approximately 580 microearthquakes recorded by a temporary array in the pamir hindu kush region in central asia are used to deduce one and three dimensional velocity structures of this region the results for one dimensional structures imply that the moho is at 70 5 depth also there is a velocity reversal near 160 km depth which is inferred to be the beginning of the low velocity zone this reversal continues to depths of approximately 230 km below 230 km velocities are somewhat higher than those of normal mantle at similar depths 9 3 km s versus 8 4 km s for p waves the outstanding feature of the results for three dimensional velocity structures is a broad 40 km centrally located region with 8 to 10 lower velocities than those in the surrounding regions this low velocity region envelopes the seismic zone at depths between 70 and 150 km the region may actually extend beyond these depths but the results for shallower and deeper structure lack sufficient resolution to decide several tests using both hypothetical and real data were performed to estimate the reliability of the three dimensional solutions the results of these tests suggest that the inferred velocities are reasonably accurate representations of the average velocities in the blocks although one must be cautious of the effects of averaging in interpreting the solution the low velocity region is inferred to be a manifestation of substantial quantities of subducted continental crust therefore while subduction has occurred in the pamir hindu kush the results of the three dimensional inversions suggest that continental rather than only oceanic lithosphere has been subducted to depths of at least 150 km appendices are available with the entire article on microfiche order from american geophysical union 2000 florida avenue n w washington d c 20009 document j81 013 1 00 payment must accompany order

inferring stress from faulting from early concepts to inverse methods abstract we review the evolution of concepts on and methods of estimating the state of stress from fault movements theories of failure in isotropic materials suggested a simple geometrical construction of optimal principal stress directions from a fault plane and its associated slip these optimal directions align shear stress and slip directions and maximize the difference between shear stress and frictional resistance on the fault plane optimal stress directions for calcite twinning are obtained by a similar construction with the difference that they maximize shear stress force representation of seismic sources independently introduced pressure p and tension t axes at positions that also maximize shear stress on both nodal planes frictional slip theory and the constraint that slip and shear stress directions be parallel allowed to address reactivation of pre existing faults this suggested that stress could also be inverted from reactivated fault and slip data or earthquake focal mechanisms early methods relied on geometrical constructions as a substitute for calculations whereas later methods relied on software as these calculations became tractable with the help of computers similar methods were developed for the inversion of stress from crystal twin gliding with non optimal geometry with a different criterion that relies on a threshold of the component of shear stress along the gliding line even though these methods seek a common stress tensor compatible with fault and slip data their main use is to separate polyphase data into homogeneous subsets and help deciphering complex tectonic histories fault and slip data can also be analyzed to constrain the strain rather than the stress tensor in most cases this involves a summation and yields an average strain for the considered rock volume stress inversion thus appears better suited for differentiating heterogeneous data whereas strain analysis appears better suited for homogenizing them

stress transferred by the 1995 mw 6 9 kobe japan shock effect on aftershocks and future earthquake probabilities the kobe earthquake struck at the edge of the densely populated osaka kyoto corridor in southwest japan we investigate how the earthquake transferred stress to nearby faults altering their proximity to failure and thus changing earthquake probabilities we find that relative to the pre kobe seismicity kobe aftershocks were concentrated in regions of calculated coulomb stress increase and less common in regions of stress decrease we quantify this relationship by forming the spatial correlation between the seismicity rate change and the coulomb stress change the correlation is significant for stress changes greater than 0 2 1 0 bars 0 02 0 1 mpa and the nonlinear dependence of seismicity rate change on stress change is compatible with a state and rate dependent formulation for earthquake occurrence we extend this analysis to future mainshocks by resolving the stress changes on major faults within 100 km of kobe and calculating the change in probability caused by these stress changes transient effects of the stress changes are incorporated by the state dependent constitutive relation which amplifies the permanent stress changes during the aftershock period earthquake probability framed in this manner is highly time dependent much more so than is assumed in current practice because the probabilities depend on several poorly known parameters of the major faults we estimate uncertainties of the probabilities by monte carlo simulation this enables us to include uncertainties on the elapsed time since the last earthquake the repeat time and its variability and the period of aftershock decay we estimate that a calculated 3 bar 0 3 mpa stress increase on the eastern section of the arima takatsuki tectonic line attl near kyoto causes fivefold increase in the 30 year probability of a subsequent large earthquake near kyoto a 2 bar 0 2 mpa stress decrease on the western section of the attl results in a reduction in probability by a factor of 140 to 2000 the probability of a mw 6 9 earthquake within 50 km of osaka during 1997 2007 is estimated to have risen from 5 6 before the kobe earthquake to 7 11 afterward during 1997 2027 it is estimated to have risen from 14 16 before kobe to 16 22

paleostress regimes from brittle structures of the karakoram kohistan suture zone and surrounding areas of nw pakistan paleostress orientations were calculated from fault populations at 24 sites along the sw ne segment and five sites along the e w yasin segment of the karakoram kohistan suture zone in nw pakistan they demonstrate the importance of combined thrusting and strike slip faulting however several paleostress tensor directions are distinguished a dominant nw se compression and a minor e w compression are compatible with the recent evolution of this part of the hindu kush from the lack of both systematic overprinting relationships and spatial trend the two tensors were obtained at different locations we conclude that in each location any of these two shortening directions can dominate heterogeneously distributed extension is found in some places and is likely due to local conditions these paleostress tensors substantiate a transpressional regime due to far field himalayan compression and document the long term background of the seismogenic deformation in this region

back arc thrusting in the eastern sunda arc indonesia a consequence of arc continent collision the structure of the eastern sunda back arc region is dominated by two large north directed thrusts the wetar and flores thrusts and one or more minor thrusts which may represent early stages of subduction polarity reversal of the arc the relationships between thrusting and magmatic activity surface slopes cross arc faulting uplift forearc structure and collision by the australian continental margin provide constraints on the likely driving mechanisms of thrust formation driving mechanisms are considered in two broad categories one set of possible mechanisms originates within the upper plate and includes gravity sliding gravity spreading and magmatic intrusion the other set focuses on stress propagation between the upper and lower plates and for this arc system the major mechanism is that of continental collision while no one mechanism explains the range of observations we see in the back arc region all of these aspects play some role in the development of the thrusts we can eliminate upper plate mechanisms as primary driving forces because slope effects are similar in areas of both thrusting and nonthrusting in addition the wetar thrust shows a negative relation between thrusting and volcanism and side looking airborn radar images show no evidence of postvolcanic rifting that could accompany intrusion without volcanism collision between the arc and the australian continent provides the clearest driving mechanism but it does not explain the discontinuous nature or the particular location of the thrusts we suggest a sequence that appears to account for the data and to provide insight into the controversies often associated with other such thrust belts thrusting was initiated in those areas where the crust of the forearc region was thick a factor that facilitated stress propagation across the arc and where the crust of the back arc was thin which facilitated back arc thrusting thrusting concentrated at the base of the slope where the slope stress is maximum the early thrusting may have been helped also by thermal weakening of the crust due to volcanism as convergence proceeded volcanism waned then ceased in the eastern part of the arc the crust then strengthened and thrusting required higher stress to maintain and propagate this later stage should show higher seismic energy release which appears to be the case for the wetar thrust region displacement on the flores thrust appears to be matched by deflection of the volcanic arc we have estimated shortening in the back arc from interpretation of reflection profiles and for the flores thrust the value of approximately 30 km is consistent with that estimated for deflection of the arc compressional deformation continues west of the collision zone across the bali basin and into java it is reported in ne sumatra as well this deformation involves much less convergence than the eastern sunda thrusts and it may be related to magmatic processes to subduction of oceanic plateaus such as the roo rise or in the case of the bali basin to efficient lateral propagation of the flores thrust

kinematic development and paleostress analysis of the denizli basin western turkey implications of spatial variation of relative paleostress magnitudes and orientations paleostress orientations and relative paleostress magnitudes stress ratios determined by using the reduced stress concept are used to improve the understanding of the kinematic characteristics of the denizli basin two different dominant extension directions were determined using fault slip data and travertine fissure orientations in addition to their stratigraphically coeval occurrence the almost exact fit of the s2 and s3 orientations for the ne sw and nw se extension directions in the late miocene to recent units indicate that these two extension directions are a manifestation of stress permutations in the region and are contemporaneous this relationship is also demonstrated by the presence of actively developing ne sw and nw se elongated grabens developed as the result of ne sw and nw se directed extension in the region moreover stress ratios plots indicate the presence of a zone of major stress ratio changes that are attributed to the interference of graben systems in the region it is concluded that the plotting of stress orientations and distribution of stress ratios is a useful tool for detecting major differences in stress magnitudes over an area the boundaries of which may indicate important subsurface structures that cannot be observed on the surface q 2005 elsevier ltd all rights reserved

active thrust front of the greater caucasus the april 29 1991 racha earthquake sequence and its tectonic implications although fault bounded thrust sheest are common in the geological record seismic evidence for their motion is sparse the april 29 1991 racha earthquake m s 7 0 the largest instrumentally recorded earthquake in the greater caucasus is one of the largest recent earthquakes in continental thrust belts and provides evidence on mechanisms of thrust sheet motion using data from a deployment of program for array seismic studies of the continental lithosphere passcal digital seismographs and various other instrumental we locate 1952 aftershocks occurring between may 7 and june 30 1991 the aftershocks form a zone 70 km long and 10 25 km wide striking e w following the racha ridge at the southern boundary of the greater caucasus thrust system teleseismic body waves are inverted for source parameters of the mainshock and the two largest aftershocks the solutions show thrust faulting with centroid depths of 3 10 km comparable to depths of locally recorded aftershocks 2 12 km the shallow dipping nodal plane the aftershock distribution and surface geology demonstrate that the main event was caused by faulting on a thrust system dipping nne at 20 o 31 o bounding the southern slope of the greater caucasus this fault system thrusts the greater caucasus structures south over the dzhirula basement massif the inferred fault geometry suggests that the active fault is either a detachment between sediments and dzhirula basement or cuts through the basement at shallow depths the 1500 m high racha ridge overlies the aftershock zone and is a likely consequence of repeated similar earthquakes hence the 1991 earthquake sequence shows that the western greater caucasus is accommodating plate convergence at a rate possibly comparable to the eastern greater caucasus a few millimeters per year along strike geological discontinuities above and below the thrust surface correspond to the eastern end of the mainshock rupture area no strong evidence for transfer structures could be found along strike suggesting that differences in collisional style between the western and eastern greater caucasus may reflect differences in mechanical properties rather than differences in convergence rate a june 15 1991 event and its aftershocks southeast of the primary aftershock zone along strike show fault planes and slip vectors rotated 41 o clockwise from the mainshock this rotation is consistent with an along strike change in direction of the thrust front near 44 o e longitude and demonstrates strong local structural or topographic control on slip direction the rotation requires along strike shortening within the greater caucasus thrust system at a rate comparable to the rate of thrusting

eocene seawater retreat from the southwest tarim basin and implications for early cenozoic tectonic evolution in the pamir plateau article i nfo the pamir plateau lies in the western end of the india eurasia collision zone being an unusual example for studying crustal shortening and evolution of the neotethys ocean here we present new results from the southwestern margin of the tarim basin for discussing tectonic history in the northern pamir plateau as well as for providing precise dates of the final seawater retreat from the studied region our results indicate that early uplift of the northern edge of the pamir plateau occurred at about 55 ma but this uplift preceded the closure of the link between the neotethys and the tarim basin five marine transgression and regression cycles occurred during the early eocene mostly in response to global eustatic sea level fluctuations and the final seawater retreat from the southwest tarim basin occurred at about 47 ma another uplift episode started 34 ma supported by the accumulation of coarse molasse deposits as well as our palynological evi dence suggesting that the convergence between the pamir plateau and the tian shan ranges accelerated since the beginning of the early oligocene

determination of principal stress magnitudes using calcite twins and rock mechanics data abstract this paper proposes a new method for determining principal stress magnitudes based on the use of the deviatoric stress tensor determined from computer inversion of calcite twin data additional evaluation of the vertical stress weight of overburden or of the mean stress is enough to calculate the complete stress tensor we emphasize that the best reasoning consists of combining calcite twin analysis with rock mechanics data failure friction criteria because the determination of the six parameters of the absolute stress tensor is overconstrained