precambrian stromatolites image analysis of lamina shape a morphometric study of 808 lamina profiles of 18 previously published stromatolite taxa was performed using an image analyser the data were plotted using different shape factors as coordinates and were subjected to multivariate statistical analysis visual inspection of the scatter diagrams allows similarities and differences to be readily perceived cluster analysis yielded similarity coefficients and dendrograms based thereon providing quantitative statements of resemblance of lamina profiles three major groupings of lamina shape are recognized 1 those with comparatively uniform flattened convex profiles associated with unbranching stromatolites or those with essentially parallel branches 2 those with variable convex profiles associated with divergent branches and 3 those with conical laminae subsidiary groupings of more closely related taxa occur in each of the three groupings the combination of image analysis and multivariate statistical analysis offers a practical and objective adju

evidence of earthquake triggering by the solid earth tides article i nfo clearevidence forearthquake triggeringbythe earth tides hasremained elusive for morethan a century using the largest global earthquake catalog available the neic catalog with 442412 events we observe a clear correlation with 99 confidence between the phase of the solid earth tide and the timing of seismic events earthquakes occur slightly more often at the time of ground uplift by the earth tide i e when normal stresses are reduced within the lithosphere we observe that this phase distribution anomaly is larger for smaller and shallowerearthquakes although earthquakes inregionswithdominantlynormalandstrike slip faulting seem to exhibit more tidal triggering than regions dominated by thrust faulting there is no statistically significant evidence for a focal mechanism dependence on earthquake triggering finally we show here that it is highly probablethat the observedtriggeringiscaused bythe solid earth tide ratherthan byloading fromthe oceanor atmospheric tides although an additional impact due to loading from ocean tides is possible and probable we cannot detect it here because the earthquake database is not sufficiently complete and homogeneous more smallmagnitudeearthquakesinoceanicareasareneeded ourresultsareconsistentwiththeideaofadamped

crustal shortening at the sierra pie de palo sierras pampeanas argentina near surface basement folding and thrusting the sierras pampeanas consist of basement uplifts that are mainly controlled by w verging crustal thrusts one of these the sierra pie de palo is controlled by a blind thrust whose kinematics is debated we analysed the reverse faults located along the eastern side of the range and show that these are characterized by small displacements few hundreds of metres of the neogene and quaternary deposits controlled by the inherited basement metamorphic foliation and shear zones at the sierra scale the inherited foliation pattern appears already folded before the cenozoic shortening forming a series of antiforms and synforms with various wavelengths we propose that this structure is amplified during the plio quaternary shortening resulting in a large asymmetrical basement cored anticline where foliation parallel slip can act as folding mechanism the overall kinematics is consistent with an e verging fault propagation fold this proposed kinematics is an alternative to the frequently suggested w verging fault bend fold model finally we propose a new alternative and speculative crustal and lithospheric structure for this region consisting of two e verging basement thrusts coeval to w verging pampean thrusts both rooting below the precordillera above an eclogitized lower crust

structural styles of mountain building controls of lithospheric rheologic stratification and extensional inheritance 1 the strength of the crust and the mantle lithosphere are strongly influenced by the temperature the thickness and the composition of the crust and mantle lithosphere and by inherited weaknesses it consequently strongly depends on the geodynamic setting and is then expected to be different from one orogen to another which might explain the diversity of deformation styles here we use 2d thermomechanical models at lithospheric scale to study the effect of the strength of the upper and middle crust on the geometry of contractional systems the role of extensional inheritance is included by forward modeling the formation of rift basin or passive margin and using the resulting extensional structure as initial condition for lithospheric scale inversion our results demonstrate that 1 crustal strength strongly controls the width and the elevation of orogenic wedge 2 relative weak crust facilitates efficient propagating of thick skinned crustal scale thrusts 3 contraction of a strong crust leads to the formation of long thrust sheets and an anti formal stack in the core of the orogen or the accretion of upper crust depending on the depth of the decoupling zone in the mid crust 4 erosion processes favor the localization of shortening in a narrow crustal orogen 5 rifting inheritance can explain the presence at shallower depth of lower crustal or mantle material previously upwelled and facilitates the propagation of the deformation in the external part of the chain the range of predicted behaviors is compared to first order with the zagros the alps and the pyrenees three natural examples for which the crustal structure is well constrained by geophysical data

weak faults rotten cores earthquakes are triggered when crustal deformation produces displacements along fault zones the rock in these zones is found to be weaker than adjacent material but what are the mechanisms of this loss of strength in his perspective holdsworth 1 discusses how recent studies of exposed ancient fault zones combined with laboratory analyses are revealing that rock properties at the grain scale can determine the large scale behavior of crustal deformation 1 http www sciencemag org cgi content full 303 5655 181

the role of basement involved normal faults in the recent tectonics of western taiwan in the foreland area of western taiwan some of the pre orogenic basement involved normal faults were reactivated during the subsequent compressional tectonics the main purpose of this paper is to investigate the role played by the pre existing normal faults in the recent tectonics of western taiwan in nw taiwan reactivated normal faults with a strike slip component have developed by linkage of reactivated single pre existing normal faults in the foreland basin and acted as transverse structures for low angle thrusts in the outer fold and thrust belt in the later stage of their development the transverse structures were thrusted and appear underneath the low angle thrusts or became tear faults in the inner fold and thrust belt in sw taiwan where the foreland basin is lacking normal fault reactivation the pre existing normal faults passively acted as ramp for the low angle thrusts in the inner fold and thrust belt some of the active faults in western taiwan may also be related to reactivated normal faults with right lateral slip component some main earthquake shocks related to either strike slip or thrust fault plane solution occurred on reactivated normal faults implying a relationship between the pre existing normal fault and the triggering of the recent major earthquakes along strike contrast in structural style of normal fault reactivation gives rise to different characteristics of the deformation front for different parts of the foreland area in western taiwan variations in the degree of normal fault reactivation also provide some insights into the way the crust embedding the pre existing normal faults deformed in response to orogenic contraction

extensional inheritance and surface processes as controlling factors of mountain belt structure surface processes and inherited structures are widely regarded as factors that strongly influence the evolution of mountain belts the first order effects of these parameters have been studied extensively throughout the last decades but their relative importance remains notoriously difficult to assess and document we use lithospheric scale plane strain thermomechanical model experiments to study the effects of surface processes and extensional inheritance on the internal structure of contractional orogens and their foreland basins extensional inheritance is modeled explicitly by forward modeling the formation of a rift basin before reversing the velocity boundary conditions to model its inversion surface processes are modeled through the combination of a simple sedimentation algorithm where all negative topography is filled up to a prescribed reference level and an elevation dependent erosion model our results show that 1 extensional inheritance facilitates the propagation of basement deformation in the retro wedge and 2 increases the width of the orogen 3 sedimentation increases the length scale of both thin skinned and thick skinned thrust sheets and 4 results in a wider orogen 5 erosion helps to localize deformation resulting in a narrower orogen and a less well developed retro wedge a comparison of the modeled behaviors to the high atlas the pyrenees and the central alps three extensively studied natural examples characterized by different degrees of inversion is presented and confirms the predicted controls of surface processes and extensional inheritance on orogenic structure

the ainsa fold and thrust oblique zone of the central pyrenees kinematics of a curved contractional system from paleomagnetic and structural data this work was funded by the project intectosal cgl2010 21968 c02 01 and by the grup de recerca de geodinamica i analisi de conques 2009sgr1198 secretaria d universitat i recerca del departament d economia i coneixement de la generalitat de catalunya josep poblet acknowledges financial support by research projects geociencias en iberia estudios integrados de topografia y evolucion 4d topo iberia csd2006 041 and desarrollo de fracturas y venas asociadas al plegamiento fraveple cgl2011 23628 funded by spanish ministries

absence of earthquake correlation with earth tides an indication of high preseismic fault stress rate because the rate of stress change from the earth tides exceeds that from tectonic stress accumulation tidal triggering of earthquakes would be expected if the final hours of loading of the fault were at the tectonic rate and if rupture began soon after the achievement of a critical stress level we analyze the tidal stresses and stress rates on the fault planes and at the times of 13 042 earthquakes which are so close to the san andreas and calaveras faults in california that we may take the fault plane to be known we find that the stresses and stress rates from earth tides at the times of earthquakes are distributed in the same way as tidal stresses and stress rates at random times while the rate of earthquakes when the tidal stress promotes failure is 2 higher than when the stress does not this difference in rate is not statistically significant this lack of tidal triggering implies that preseismic stress rates in the nucleation zones of earthquakes are at least 0 15 bar h just preceding seismic failure much above the long term tectonic stress rate of 10 4 bar h

modelling role of basement block rotation and strike slip faulting on structural pattern in cover units of fold and thrust belts a series of scaled analogue models are used to study de coupling between basement and cover deformation rigid basal blocks were rotated about a vertical axis in a bookshelf fashion which caused strike slip faulting along the blocks and in the overlying cover units of loose sand three different combinations of cover basement deformations are modelled i cover shortening before basement fault movement ii basement fault movement before cover shortening and iii simultaneous cover shortening with basement fault movement results show that the effect of the basement faults depends on the timing of their reactivation pre and syn orogenic basement fault movements have a significant impact on the structural pattern of the cover units whereas post orogenic basement fault movement has less influence on the thickened hinterland of the overlying belt the interaction of basement faulting and cover shortening results in the formation of rhombic structures in models with pre and syn orogenic basement strike slip faults rhombic blocks develop as a result of shortening of the overlying cover during basement faulting these rhombic blocks are similar in appearance to flower structures but are different in kinematics genesis and structural extent we compare these model results to both the zagros fold and thrust belt in southwestern iran and the alborz mountains in northern iran based on the model results we conclude that the traces of basement faults in cover units rotate and migrate towards the foreland during regional shortening as such these traces do not necessarily indicate the actual location or orientation of the basement faults which created them

eemian and post eemian fluvial dynamics in the lesser caucasus abstract mountain regions such as the lesser caucasus are a focus of ongoing environmental changes to understand their future evolution information about their former geomorphic and environmental dynamics is required the former fluvial dynamics derived from fluvial sediment archives can offer such insights however the fluvial dynamics of the lesser caucasus since the eemian interglacial have not been systematically investigated so far thus we have studied late pleistocene and holocene sediments of several rivers originating from the central lesser caucasus the studied rivers show a mostly coherent record of fluvial dynamics minor aggradation occurred during early marine isotope stage mis 5 incision during late mis 5 or early mis 4 intensive silty aggradation at least during late mis 3 incision during early mis 2 coarse grained aggradation probably during some millenia until ca 19 ka and aggradation ca 14 13 ka following incision around the pleistocene holocene transition aggradation resumed around 6 0 3 4 2 0 and 0 5 0 15 cal ka bp generally periods of aggradation incision and stability could be linked with regional climatic or anthropogenic influences on regional landscape stability and water availability the fluvial dynamics of the central lesser caucasus mostly differed even between neighbouring regions and only in cases of significant hemispheric climatic fluctuations as around 20 ka during the pleistocene holocene transition or the little ice age were similar over regional fluvial patterns observed this demonstrates the individual character of river systems especially in mountain regions such as the southern caucasus with strong geoecological gradients thus to understand the former landscape dynamics of mountain landscapes investigations of fluvial sediment archives on a regional to sub regional scale are necessary

propagation of a fold and thrust belt over a basement graben abstract we demonstrate the mechanical feasibility of the propagation of a thin skin deformation front on a decollement previously cut and lowered by a normal fault using a numerical implementation of the limit analysis theory we confirm the common understanding that any discontinuity of the decollement layer will trigger the formation of a ramp conducting the slip to the surface upon further remotely applied shortening we show with both numerical and analogue models that the growing relief created by the ramp will reach a height and a horizontal extent such that the lower portion of the decollement will eventually be activated and the belt will resume its growth further along its initial decollement layer even though it is deeper the required extra relief depends mainly on the friction angles of the bulk material and of the existing faults the analogue experiments show that the step in the decollement acts as a temporary catching point in the propagation of the deformation front resulting in a characteristic tectonic style composed of a stack of faults above the step separated from the following structures by a long and flat partially buried syncline the thin skin jura fold and thrust belt developed during mio pliocene times on a triassic decollement locally lowered by reactivation of earlier grabens with a dedicated mechanical prototype we show that realistic friction values are compatible with the propagation of deformation across these grabens along the depressed zones of the triassic decollement without having recourse to thick skinned tectonics

thermal mechanical modeling of salt based mountain belts with pre existing basement faults application to the zagros fold and thrust belt southwest iran 1 two dimensional thermal mechanical models of thick skinned salt based fold and thrust belts such as the zagros sw iran are used to address 1 the degree of deformation and decoupling between cover and basement rocks due to the presence of a weak salt detachment 2 the reactivation potential of pre existing basement normal faults due to brittle or ductile behavior of the lower crust as related to cold or hot geothermal gradients and 3 variations in deformation style and strain distribution the geometry and kinematics of the orogenic wedge and the activity of pre existing basement faults are strongly influenced by the geothermal gradient defined by the moho temperature mt and basement rheology we infer that the mt plays a major role in how the lower and upper crust transfer deformation toward the foreland in relatively hot geotherm models mt 600 c at 36 km depth the lowermost basement deforms in a ductile fashion while the uppermost basement underlying the sedimentary cover deforms by folding thrusting and displacements along pre existing basement faults in these models cover units above the salt detachment occur within a less deformed wide plateau in the hinterland in relatively cold geotherm models mt 400 c at 36 km depth deformation is mainly restricted to basement imbricate thrusts that form within the orogenic hinterland detachment folding thrusting and gravity gliding occur within cover sediments above uplifted basement blocks gravity gliding contributes to a larger amount of shortening in the cover compared to the basement

numerical investigation of deformation mechanics in fold and thrust belts influence of rheology of single and multiple decollements 1 thin skinned fold and thrust belts related to convergence tectonics develop by scraping off a rock sequence along a weaker basal decollement often formed by water saturated shale layers or low viscosity salt horizons a two dimensional finite element model with a viscoelastoplastic rheology is used to investigate the structural evolution of fold and thrust belts overlying different types of decollements in addition the influence of multiple weak layers in the stratigraphic column is studied model shale decollements are frictional with lower friction angles as the cover sequence model salt layers behave linear viscous due to a lower viscosity as the cover sequence or with a power law rheology single viscous decollement simulations have been compared to an analytical solution concerning faulting versus folding results show that fold and thrust belts with a single frictional basal decollement generate thrust systems ramping from the decollement to the surface spacing between thrust ramps depends on the thickness of the cover sequence the structural evolution of simulations with an additional low frictional layer depends on the strength relationship between the basal and the intersequential decollement tectonic underplating and antiformal stacking occur if the within sequence decollement is weaker in the frontal part of models deformation is restricted to the upper part and imbrication occurs with a wavelength depending on the depth of the intermediate weak layer salt decollement with a viscosity of 10 18 pa s leads to isolated box folds detachment folds multiple salt layers 10 18 pa s result in long wavelength folding our results for both frictional and viscous decollements are in bulk agreement with the mohr coulomb type critical wedge theory citation ruh j b b j p kaus and j p burg 2012 numerical investigation of deformation mechanics in fold and thrust belts influence of rheology of single and multiple decollements tectonics 31 tc3005 doi 10 1029 2011tc003047

major earthquakes occur regularly on an isolated plate boundary fault the scarcity of long geological records of major earthquakes on different types of faults makes testing hypotheses of regular versus random or clustered earthquake recurrence behavior difficult we provide a fault proximal major earthquake record spanning 8000 years on the strike slip alpine fault in new zealand cyclic stratigraphy at hokuri creek suggests that the fault ruptured to the surface 24 times and event ages yield a 0 33 coefficient of variation in recurrence interval we associate this near regular earthquake recurrence with a geometrically simple strike slip fault with high slip rate accommodating a high proportion of plate boundary motion that works in isolation from other faults we propose that it is valid to apply time dependent earthquake recurrence models for seismic hazard estimation to similar faults worldwide

are earthquakes predictable summary the answer to the above question depends on the definition of earthquake prediction we discuss several definitions and possible classifications of earthquake prediction methods we also consider various measures of prediction efficiency review several recent examples of earthquake prediction and describe the methods that can be used to verify prediction schemes we conclude that an empirical search for earthquake precursors that forecast the size of an impending earthquake has been fruitless despite considerable effort in several countries no statistically rigorous validation of proposed precursory phenomena is available therefore reported cases of precursors can be explained by random noise or by chance coincidence we present evidence that earthquakes are non linear chaotic scale invariant phenomena the most probable consequence of earthquake self similarity is a lack of earthquake predictability as popularly defined that is a forecast of a specific individual earthquake many small earthquakes occur throughout any seismic zone demonstrating that the critical conditions for earthquake nucleation are satisfied almost everywhere apparently any small shock can grow into a large event thus it is likely that an earthquake has no preparatory stage this sceptical view of current earthquake prediction efforts should not be interpreted as a statement that any further attempts to mitigate the destructive effects of earthquakes are futile the seismic moment conservation principle when combined with geodetic deformation data offers a new way to evaluate the seismic hazard not only for tectonic plate boundaries but also for areas of low seismicity that is the interiors of continents earthquake clustering with a power law temporal decay omori s law can be used to estimate the rate of future earthquake ocurrence realtime seismology can facilitate relief efforts after large earthquakes and eventually provide an immediate warning of severe shaking a few seconds or tens of seconds before the shaking starts

influence of periodic variations in water level on regional seismic activity around a large reservoir field data and laboratory model abstract the reservoir induced changes of the regional seismic activity around the enguri high dam reservoir in western georgia are found to be influenced by the water level of the reservoir the water level variations of the enguri high dam reservoir and the seismic data sets recorded by the local network have been analyzed by means of statistical linear nonlinear and phase synchronization analysis methods it is shown that seismic activity increases during the flooding period according to the well known concepts of reservoir induced seismicity ris as a new result we see that the released energy value essentially decreases when the variation of the water level in the reservoir becomes periodic furthermore acoustic emission data obtained during laboratory stick slip experiments with superimposed weak periodic perturbations have been investigated as a model of natural seismicity we conclude that the decrease in seismic activity around enguri high dam is induced by periodic changes of water level in the reservoir based on the field and laboratory data analysis we have generalised our conclusion and suppose that probability of decrease of strong earthquakes occurrence around large reservoirs may be explained by the phase synchronization effect between the complex seismic process and small periodic influences related to changes in water level

forced folds and fractures this volume is concerned with defining the major similarities and difference between forced folds and buckle folds in order that these differences can be used to recognize the type of folding and therefore the expected fracture pattern present in regions of poor exposure or where the geologist has to rely on seismic images an understanding of the differences between the two fold types their 3d geometry spatial organization fracture patterns etc provides an invaluable tool for earth scientists concerned with assessing the possible role of folds and their associated fracture patterns in controlling fluid migration and concentration within the crust the papers presented here are grouped into 4 sections contributions in the first section describe the use of numerical analyses to investigate the formation of fractures in forced folds including compaction folds and the section contains a description of large scale compaction folding in which the associated fracturing has given rise to the development of large sandstone dykes the papers in the second section deal with the formation of forced folds as a result of normal faulting in various geological environments including along a classical graben margin and around a resurgent caldera the third section contains papers relating to forced folding in compressional and strike slip regimes the final section considers the temporal and spatial relationships between forced folds and buckle folds the formation of crustal scale folds and a method of determining the distribution of strain on any folded surface a key parameter controlling the distribution of fractures

basement composition and basin geometry controls on upper crustal deformation in the southern central andes 30 36 s deformation and uplift in the andes are a result of the subduction of the nazca plate below south america the deformation shows variations in structural style and shortening along and across the strike of the orogen as a result of the dynamics of the subduction system and the features of the upper plate in this work we analyse the development of thin skinned and thick skinned fold and thrust belts in the southern central andes 30 36 s the pre andean history of the area determined the formation of different basement domains with distinct lithological compositions as a result of terrane accretions during palaeozoic time the development of a widespread permo triassic magmatic province and long lasting arc activity basin development during palaeozoic and mesozoic times produced thick sedimentary successions in different parts of the study area based on estimations of strength for the different basement and sedimentary rocks calculated using geophysical estimates of rock physical properties we propose that the contrast in strength between basement and cover is the main control on structural style thin v thick skinned and across strike localization of shortening in the study area

structure and tectonic evolution of hybrid thick and thin skinned systems in the malargue fold thrust belt neuquen basin argentina andean cenozoic shortening within the malargue fold thrust belt of west central argentina has been dominated by basement faults largely influenced by pre existing mesozoic rift structures of the neuquen basin system the basement contractional structures however diverge from many classic inversion geometries in that they formed large hanging wall anticlines with steeply dipping frontal forelimbs and structural relief in the order of several kilometres during cenozoic e w shortening the reactivated basement faults propagated into cover strata feeding slip to shallow thrust systems that were later carried in piggyback fashion above newly formed basement structures yielding complex thick and thin skinned structural relationships in the adjacent foreland cenozoic clastic strata recorded the broad kinematic evolution of the fold thrust belt we present a set of structural cross sections supported by regional surface maps and industry seismic and well data along with new stratigraphic information for associated neogene synorogenic foreland basin fill collectively these results provide important constraints on the temporal and geometric linkages between the deeper basement faults including both reactivated and newly formed structures and shallow thin skinned thrust systems which in turn offer insights for the understanding of hydrocarbon systems in the actively explored neuquen region of the andean orogenic belt

image analysis of stromatolite fabric using a spatial frequency power spectrum analysis system spatial frequency power spectrum analysis is combined with statistical data processing in a morphological study of stromatolite fabric fourteen photographs of stromatolite fabrics from the holotypes of published taxa and 10 line drawings simulating stromatolite fabric were used for the input images the output data were plotted to make curves of power spectra for each input image and the data from the 14 stromatolite samples were subjected to q mode hierarchical cluster analysis the diagrams of the power spectrum curves allow similarity dissimilarity among the analyzed images to be readily perceived by visual inspection cluster analysis using different data matrices yielded dendrograms that provided quantitative evaluation of similarity dissimilarity in fabric features between the 14 stromatolite taxa the results clearly show the efficiency and utility of this approach in recognition and classification of complex stromatolite fabric patterns and this method may have a wider application for comparati

reactivation inversion and basement faulting and thrusting in the sierras pampeanas of cordoba argentina during andean flat slab deformation the sierras pampeanas of cordoba are the easternmost uplifted blocks caused by andean foreland deformation over 700 km from the chile trench this deformation started at c 340 ma through basement faults thrusts and reactivation of normal faults of the cretaceous rift during the opening of the atlantic ocean other older faults major oblique lineaments were also reactivated thermochronological and geothermobarometric data indicate that some topographic relief could have been palaeozoic mesozoic relicts and not only produced by the andean orogeny faults are partially controlled by the early cambrian s 2 metamorphic foliation coincident with the curved fault traces at map scale during pliocene time two deformation phases post dating miocene pliocene magmatism are recognized shallow seismicity data c 25 km depth indicate that the sierras de cordoba accommodate quaternary displacement magnetotelluric studies detect the interface between the pampia terrane and the rio de la plata craton the role of the oblique lineaments in the nucleation and development of the tertiary faulting has been little considered they could be correlated with an old pan gondwanan trend during the cretaceous period these lineaments worked in a transtensive way producing the uplift of high grade rocks and segmentation of the mountain chain favouring the diachronous uplift along the ranges recently both the brittle ductile transition at c 23 km depth and the crustal thickness have been determined by seismicity analysis the oblique lineaments displace normally the mohorovicic discontinuity main basement thrusts were probably rooted in the suture between the pampia terrane and the rio de la plata craton

fracture porosity creation and persistence in a basement involved laramide fold upper cretaceous frontier formation green river basin usa fracture hosted porosity and quartz distribution along with crack seal texture and fluid inclusion assemblage sequences in isolated bridging quartz deposits show that open fractures can persist through protracted burial and uplift in foreland basins fractures oriented at a high angle to current maximum compressive stress remain open and were weak mechanical discontinuities for millions of years even at great depth upper cretaceous frontier formation sandstones in the basement involved laramide table rock anticline eastern greater green river basin wyoming sampled by two horizontal wells cut parallel or nearly parallel to bedding and at a high angle to steeply dipping fractures have 41 5 m of rock in four cores at depths of 4538 4547 m cores intersect older e striking set 1 fractures are abutted by or locally cross cut by n striking set 2 fractures both sets contain quartz and porosity sequenced using quartz crack seal cement texture maps set 1 fluid inclusion assemblage fia trapping temperatures increase progressively from 140 to 165 c then decrease to c 150 c compatible with fracture opening over c 15 ma during rapid burial followed by uplift in eocene oligocene time set 2 opened at c 160 c probably near maximum burial after a period of quiescence set 2 reopened at c 5 ma at c 140 c on a cooling trajectory intermittent set 2 movement could reflect local basement involved fault movement followed after a pause by further set 2 reactivation in the modern stress field during uplift interpretations are sensitive to available burial thermal histories which have considerable uncertainty

intermittent type temporal fluctuations in seismicity of the irpinia southern italy region we present a new approach to investigate the temporal fluctuations of seismicity in terms of intermittency as the underlying dynamical mechanism for the variability of seismic activity analyzing the 1983 1997 irpinia southern italy seismicity we base our analysis on the multifractal formalism combined with the estimate of the correlation codimension our findings show that the seismic activity of the area investigated is strongly intermittent and the degree of intermittency lowers if aftershock clusters associated to the larger events are removed

the influence of the great falls tectonic zone on the thrust sheet geometry of the southern sawtooth range montana usa the reactivation potential of pre existing deep seated structures influences deformation structures produced in subsequent compression this contribution investigates thrust geometries produced in surface thrust sheets of the sawtooth range montana usa deforming over a previously faulted sedimentary section surface thrust fault patterns were picked using existing maps and remote sensing thrust location and regional transport direction was also verified in the field these observations were used to design a series of analogue models involving deformation of a brittle cover sequence over a lower section with varying numbers of vertical faults a final model tested the effect of decoupling the upper cover and lower section with a ductile detachment in a scenario closer to that of the sawtooth range results demonstrate that complexity in surface thrust sheets can be related to heterogeneity within the lower sedimentary section even when there is a detachment between this section and the rest of the cover this complexity is best observed in the map view as the models do not show the deep seated faults propagating into the cover these results were then used to predict specific locations of discrete basement fault strands in the study area associated with what is generally mapped as the scapegoat bannatyne trend the deep seated faults are more likely to be reactivated as strike slip features in nature given the small obliquity between the ene directed compression direction and the ne oriented basement faults more generally these results can be used to govern evaluation of thrust belts deforming over faulted basement and to predict the locations of specific fault strands in a region where this information is unknown

basement involved reactivation in foreland fold and thrust belts the alpine carpathian junction austria the late eocene early miocene alpine carpathian fold and thrust belt ftb lies in the transition between the eastern alps and the western carpathians se of the bohemian crystalline massif our study shows the involvement of crystalline basement from the former european jurassic continental margin in two distinct events a first extensional event coeval with eggerian karpatian c 28 16 ma thin skinned thrusting reactivated the rift basement fault array and resulted from the large degree of lower plate bending promoted by high lateral gradients of lithospheric strength and slab pull forces slab break off during the final stages of collision around karpatian times c 17 16 ma promoted large wavelength uplift and an excessive topographic load this load was reduced by broadening the orogenic wedge through the reactivation of the lower plate deep detachment beneath and ahead of the thin skinned thrust front with the accompanying positive inversion of the basement fault array and ultimately by the collapse of the hinterland summits enhanced by transtensional faulting although this work specifically deals with the involvement of the basement in the alpine carpathian junction the main conclusions are of general interest to the understanding of orogenic systems

late miocene deformation kinematics along the nw zagros fold thrust belt kurdistan region of iraq constraints from apatite u th he thermochronometry and balanced cross sections

earthquake prediction a critical review summary earthquake prediction research has been conducted for over 100 years with no obvious successes claims of breakthroughs have failed to withstand scrutiny extensive searches have failed to find reliable precursors theoretical work suggests that faulting is a non linear process which is highly sensitive to unmeasurably fine details of the state of the earth in a large volume not just in the immediate vicinity of the hypocentre any small earthquake thus has some probability of cascading into a large event reliable issuing of alarms of imminent large earthquakes appears to be effectively impossible key word earthquake prediction

growth morphologies of modern marine stromatolites a case study from highborne cay bahamas abstract stromatolites are a uniquely coupled geo biosphere system which potentially records important paleoenvironmental and biological information characterizing and distinguishing between the biological and physical factors that control stromatolite morphogenesis therefore has important implications for the understanding of modern stromatolites and the interpretation of ancient systems this paper documents the occurrence and distribution of stromatolites with distinct growth morphologies in the highborne cay reef system and other locations in exuma cays bahamas and explores the relative contributions of physical and biological environmental factors controlling stromatolite shape our observations suggest that macro scale growth morphologies of exuma stromatolites are primarily controlled by accommodation space hydrodynamics and sedimentation patterns the latter are critical for the stromatolite ecosystem in that the suspended sediment provides grains for trapping and binding and thus stromatolite accretion furthermore sediment burial removes macroalgae allowing the prokaryotic community to dominate changes in sedimentation patterns and frequency allow for the colonization of stromatolites by macroalgae and boring macrofauna which in time destroy and degrade the stromatolite structure

earthquake cycle fault zones and seismicity patterns in a rheologically layered lithosphere we study the coupled evolution of earthquakes and faults in a model consisting of a seismogenic upper crust governed by damage rheology over a viscoelastic substrate the damage rheology has two types of functional coefficients 1 a generalized internal friction separating states associated with material degradation and healing and 2 damage rate coefficients for positive degradation and negative healing changes the evolving damage modifies the effective elastic properties of material in the upper crust as a function of the ongoing deformation this simulates the creation and healing of fault systems in the upper seismogenic zone in addition to the vertically averaged thin sheet approximation we introduce a green function for three dimensional elastic half space for the instantaneous component of deformation the formulation accounts in an internally consistent manner for evolving deformation fields evolving fault structures aseismic energy release and spatiotemporal seismicity patterns these developments allow us to simulate long histories of crustal deformation and to study the simultaneous evolution of regional earthquakes and faults for various model realizations to focus on basic features of a large strike slip fault system we first consider a simplified geometry of the seismogenic crust by prescribing initial conditions consisting of a narrow damage zone in an otherwise damage free plate for this configuration the model generates an earthquake cycle with distinct interseismic preseismic coseismic and postseismic periods model evolution during each period is controlled by a subset of physical properties which may be constrained by geophysical geodetic rock mechanics and seismological data in the more generic case with a random initial damage distribution the model generates large crustal faults and subsidiary branches with complex geometries the simulated statistics depend on the space time window of the observational domain the results indicate that long healing timescale h describing systems with relatively long memory leads to the development of geometrically regular fault systems and the characteristic frequency size earthquake distribution conversely short h relatively short memory leads to the development of a network of disordered fault systems and the gutenberg richter earthquake statistics for intermediate values of h the results exhibit alternating overall switching of response from periods of intense seismic activity and the characteristic earthquake distribution to periods of low seismic activity and gutenberg richter statistics

role of tectonic burial and temperature on the inversion of inherited extensional basins during collision the style of inversion of inherited extensional basins in the western alps is investigated through thermo mechanical modelling two dimensional models consist of a half graben embedded in a relatively strong crust basement and filled with weak syn rift sediments cover we investigate the relative influence of the internal friction of the basin bounding normal fault tectonic burial h under an overlying nappe and the geothermal gradient we use a viscoplastic model with symmetrical shortening the inherited normal fault is implemented as a curved thin body with a variable friction coefficient ranging from 0 1 to 0 6 the style of basin inversion is controlled at shallow depth by the internal friction coefficient whose influence decreases with the increase of both burial depth and geothermal gradient with increasing burial and or geothermal gradient fault reactivation is inhibited and distributed deformation in the basement induces the vertical extrusion of the cover the basin inversion is accompanied by distributed deformation in the cover and by the shearing of the basin and basement interface the results are consistent with the style of inversion of inherited half grabens in the external western alps where no significant fault reactivation occurred owing to tectonic burial underneath the alpine internal units during the early alpine collision

blue green algal mats of the salinas in san ya hai nan island china structure taxonomic composition and implications for the interpretation of precambrian stromatolites abstract the study of the algal mats in salinas used for salt production on hai nan island china revealed the presence of five morphological types which are dominated by different blue green algae 1 orange high pinnacle mats dominated by phormidium hypersalinum and p hypolimneticum 2 pale green low pinnacle mats dominated by p hypolimneticum p hypersalinum and aphanothece sp 3 pale green spongy mats dominated by the unicellular blue green algae aphanothece sp chroococcus minutus aphanocapsa concharum 4 yellow green gelatinous mats dominated by p hypolimneticum and microcoleus tenerrimus 5 blue green flat mats with finger like projections dominated by m tenerrimus and m chthonoplastes the distribution of these different mats is correlated to the main ecological parameters monitored salinity temperature and water depth the role of the constituent blue green algae and of the ecological parameters in the control of the composition and morphology of algal mats as well as the implications of these findings for the interpretation of precambrian stromatolites are discussed

cenozoic tectonic model of the bohai bay basin in china modelling results and seismic interpretation illustrate that the cenozoic evolution of the bohai bay basin bbb can be divided into different stages a transtensional phase during paleocene early oligocene time created ne trending strike slip faults and e w trending normal faults which were driven roughly by n s extension making an angle of 25 with the strike slip faults seismic data interpretation yields evidence that inversion phases occurred within the ne xialiaohe depression of the greater bohai bay basin this inversion phase is attributed to rotation and partial inversion that occurred during late oligocene time leading to formation of inversion structures along the ne part of tanlu fault this episode is attributed to an anticlockwise rotation of the eastern part of the bbb driven by the convergence between the pacific and eurasian plates the tectonic scenario described was simulated in scaled analogue models which were extended by pulling two basement plates away from each other partial inversion was simulated by rotation of one of the plates relative to the other model results show many of the features observed in the bbb our model results are used to argue that unlike the two episode extension and whole basin inversion models previously proposed for the bbb a single n s aligned extension followed by anticlockwise rotation accounts for the cenozoic evolution of the bbb and produces some of the structural complexities observed in the basin

accelerated seismic release and related aspects of seismicity patterns on earthquake faults observational studies indicate that large earthquakes are sometimes preceded by phases of accelerated seismic release asr characterized by cumulative benioff strain following a power law timeto failure relation with a term tf t m where tr is the failure time of the large event and observed values of m are close to 0 3 we discuss properties of asr and related aspects of seismicity patterns associated with several theoretical frameworks the subcritical crack growth approach developed to describe deformation on a crack prior to the occurrence of dynamic rupture predicts great variability and low asymptotic values of the exponent m that are not compatible with observed asr phases statistical physics studies assuming that system size failures in a deforming region correspond to critical phase transitions predict establishment of long range correlations of dynamic variables and power law statistics before large events using stress and earthquake histories simulated by the model of ben zion 1996 for a discrete fault with quenched heterogeneities in a 3 d elastic half space we show that large model earthquakes are associated with nonrepeating cyclical establishment and destruction of long range stress correlations accompanied by nonstationary cumulative benioff strain release we then analyze results associated with a regional lithospheric model consisting of a seismogenic upper crust governed by the damage rheology of lyakhovsky et al 39 over a viscoelastic substrate we demonstrate analytically for a simplified 1 d case that the employed damage rheology leads to a singular power law equation for strain proportional to t f t 1 3 and a nonsingular power law relation for cumulative benioff strain proportional to t f t 1 3 a simple approximate generalization of the latter for regional cumulative benioff strain is obtained by adding to the result a linear function of time representing a stationary background release to go beyond the analytical expectations we examine results generated by various realizations of the regional lithospheric model producing seismicity following the characteristic frequency size statistics gutenberg richter power law distribution and mode switching activity we find that phases of asr exist only when the seismicity preceding a given large event has broad frequency size statistics in such cases the simulated asr phases can be fitted well by the singular analytical relation with m 1 3 the nonsingular equation with m 0 2 and the generalized version of the latter including a linear term with m 1 3 the obtained good fits with all three relations highlight the difficulty of deriving reliable information on functional forms and parameter values from such data sets the activation process in the simulated asr phases is found to be accommodated both by increasing rates of moderate events and increasing average event size with the former starting a few years earlier than the latter the lack of asr in portions of the seismicity not having broad frequency size statistics may explain why some large earthquakes are preceded by asr and other are not the results suggest that observations of moderate and large events contain two complementary end member predictive signals on the time of future large earthquakes in portions of seismicity following the characteristic earthquake distribution such information exists directly in the associated quasi periodic temporal distribution of large events in portions of seismicity having broad frequency size statistics withrandom or clustered temporal distribution of large events the asr phases have predictive information the extent to which natural seismicity may be understood in terms of these end member cases remains to be clarified continuing studies of evolving stress and other dynamic variables in model calculations combined with advanced analyses of simulated and observed seismicity patterns may lead to improvements in existing forecasting strategies

evidence of active shortening along the eastern border of the san rafael basement block characterization of the seismic source of the villa atuel earthquake 1929 mendoza province argentina on the 30 may 1929 a massive earthquake occurred in the san rafael area southern mendoza province leading to the destruction of the villa atuel and las malvinas towns the region affected by the ground shaking covers a large part of southern south america although no surface breaks have been detected on the surface several authors have pointed out active faults that could be related to the event of 1929 using satellite imagery and field observations we investigated two active faults situated on the eastern border of the san rafael block srb close to or within the epicentral area the most prominent faults are the c 40 km long las malvinas and c 30 km long cerro negro reverse faults which are located near the epicentral area geological and morphological observations allow us to describe late pleistocene activity and estimate the long term slip rates of these faults possible ruptures that match our observations and which are compatible with the cartographic length of these faults would account for a seismic moment magnitude of m 0 2 8 10 19 n m and a moment magnitude of m w 6 9 the morphological signatures of these fault segments and the occurrence of the san rafael earthquake suggests that the southern mendoza province is still currently submitted to shortening

andean shortening inversion and exhumation associated with thin and thick skinned deformation in southern peru a balanced cross section spanning the eastern cordillera and subandean zone of southern peru 13 15 s constrains 130 km 38 of cenozoic orogen normal sw ne andean deformation accommodated by thick and thin skinned retro arc fold thrust belt shortening that overprinted pre andean triassic normal faults zircon and apatite u th he ages demonstrate continuous oligocene to miocene cooling of the permo triassic coasa pluton in the eastern cordillera zircon u th he ages 34 18 ma are reset and define a steep age versus elevation relationship apatite u th he results reveal reset ages that define two spatially separated groups with ages of 30 26 ma and 17 11 ma detrital zircon u pb geochronologic results from cretaceous cenozoic siliciclastic rocks from the altiplano eastern cordillera record andean fold thrust belt and magmatic arc sediment sources correlative subandean zone rocks preserve a cratonic sediment contribution with minor andean sediment appearing in some cenozoic rocks we propose that earliest andean deformation and structural compartmentalization of the eastern cordillera was linked to selective inversion of inherited permo triassic basement involved normal faults that guided subsequent thick and thin skinned deformation provenance variations between the hinterland and foreland depocentres reveal competing eastern and western sediment sources reflecting an axial zone in the eastern cordillera that coincided with the inherited triassic graben and impeded sediment source mixing our zircon and apatite u th he ages are consistent with published constraints along strike and support pulses of eocene to late miocene exhumation that were likely driven by normal fault reactivation and protracted eastern cordillera deformation

morphometric analysis of proterozoic stromatolites from india preliminary report on testing of a new technique abstract a recent technique of image analysis of stromatolite laminae has been tested on proterozoic stromatolitic assemblages in the aravalli dolomite of udaipur and jhabua the bhagwanpura limestones of chittorgarh the bilara carbonates of jodhpur and the raipur limestones of the chattisgarh region the technique involves tracing of the upper lamina boundary of each stromatolite column which permits measurements of different profile shape attributes such as area length width vertical and horizontal intercepts and profile inclination the numerical data so generated were subjected to statistical analysis cluster analysis by the pair group method shows mutually correlatable cluster centres dendrograms based thereon have been drawn to depict the nature of correlation four major groupings of lamina shape have been recognized 1 highly convex 2 flattened convex and irregular shape 3 erect highly convex to conical and 4 horizontal development of flattened laminae successful correlation between stromatolites of the bhagwanpura limestone chittorgarh the bilara formation jodhpur and raipur chattisgarh and negative correlation between the aravalli stromatolites of udaipur rajasthan and jhabua madhya pradesh clearly indicate the biostratigraphic utility of morphometric analysis

introduction tectonic evolution and mechanics of basement involved fold and thrust belts defining the structural style of fold and thrust belts is an important step for understanding the factors that control their long and short term dynamics for comprehending seismic hazard associated with them and for assessing their economic potential while the thin skinned model no basement involvement has long been the driving methodology for cross section construction and restoration of foreland fold and thrust belts a wealth of new geological and geophysical studies have shown that they are often thick skinned that is basement involved

evidence for tidal triggering of earthquakes as revealed from statistical analysis of global data 1 we observe tidal triggering of earthquakes by measuring the correlation between the earth tide and earthquake occurrence we used the times locations and focal mechanisms of the 9350 globally distributed earthquakes with magnitude 5 5 or larger from the harvard centroid moment tensor catalog the tidal stress was theoretically computed by using the preliminary reference earth model and a recent ocean tide model nao 99b we considered the shear stress on the fault plane and the trace of stress tensor j1 defining the tidal phase angle at the occurrence time for each earthquake we statistically tested the phase selectivity using the schuster s method for all the earthquakes no significant correlation is found between the earth tide and earthquake occurrence both for the shear stress and for j1 by classifying the data set according to fault types however we find a high correlation with the shear stress for reverse fault type the correlation is particularly clear for shallow and smaller earthquakes of this type significant correlation with j1 also appears for larger earthquakes of reverse fault type and for shallow and larger ones of normal fault type we find no correlation for strike slip type for all the cases of high correlation earthquakes tend to occur when the tidal stress accelerates the fault slip indicating that high correlation is not coincidental but is physically justified this result strongly suggests that a small stress change due to the earth tide encourages earthquake occurrence when the stress in the future focal area is near a critical condition

stromatolites in precambrian carbonates evolutionary mileposts or environmental dipsticks stromatolites are attached lithified sedimentary growth structures accretionary away from a point or limited surface of initiation though the accretion process is commonly regarded to result from the sediment trapping or precipitation inducing activities of microbial mats little evidence of this process is preserved in most precambrian stromatolites the successful study and interpretation of stromatolites requires a process based approach oriented toward deconvolving the replacement textures of ancient stromatolites the effects of diagenetic recrystallization first must be accounted for followed by analysis of lamination textures and deduction of possible accretion mechanisms accretion hypotheses can be tested using numerical simulations based on modern stromatolite growth processes application of this approach has shown that stromatolites were originally formed largely through in situ precipitation of laminae during archean and older proterozoic times but that younger proterozoic stromatolites grew largely through the accretion of carbonate sediments most likely through the physical process of microbial trapping and binding this trend most likely reflects long term evolution of the earth s environment rather than microbial communities

thick skinned tectonics and basement involved fold thrust belts insights from selected cenozoic orogens defining the structural style of fold thrust belts and understanding the controlling factors are necessary steps towards prediction of their long term and short term dynamics including seismic hazard and to assess their potential in terms of hydrocarbon exploration while the thin skinned structural style has long been a fashionable view for outer parts of orogens worldwide a wealth of new geological and geophysical studies has pointed out that a description in terms of thick skinned deformation is in many cases more appropriate this paper aims at providing a review of what we know about basement involved shortening in foreland fold thrust belts on the basis of the examination of selected cenozoic orogens after describing how structural interpretations of fold thrust belts have evolved through time this paper addresses how and the extent to which basement tectonics influence their geometry and their kinematics and emphasizes the key control exerted by lithosphere rheology including structural and thermal inheritance and local regional boundary conditions on the occurrence of thick skinned tectonics in the outer parts of orogens

second order moment of central california seismicity 1969 1982 the second order moment cross correlation function of earthquakes in the u s geological survey central california catalog between 1969 and 1982 was calculated with respect to a magnitude threshold m 4 0 over interevent distances up to 80 km and interevent times up to 320 days the statistical procedure results in a representation of the spatial temporal structure of the catalog associated with m 4 0 earthquakes and is capable of revealing patterns too weak to be detected in the space time distribution of seismicity for individual earthquake sequences a method is introduced for identifying aftershocks based on a physical two parameter model of the earthquake interaction process the results show that the aftershock process dominates the second order moment and may even obscure the statistical expression of a precursory process a concentration of foreshocks within 15 km and 3 days of m 4 0 main shocks exhibits an apparent migration toward the main shock loci with velocity 2 6 5 3 km d this concentration may be related to an observed tendency for m 4 0 events to cluster auto correlate over this interevent range with the identified aftershocks removed the residual catalog is poissonion in space and time when two m 4 0 earthquakes occur within 80 km and 40 days of each other aftershock productivity appears to be relatively enhanced in the earlier sequence this suggests that aftershock populations are not solely dependent on their main shocks and that unusually productive aftershock sequences may be predictors of future moderate earthquakes

fluvial sediments of the algeti river in southeastern georgia an archive of late quaternary landscape activity and stability in the transcaucasian region abstract in order to obtain information about landscape activity and stability during the late quaternary in the transcaucasian region fluvial sediments of the lower algeti river in se georgia were studied by means of geomorphologic sedimentologic and geochronologic methods these investigations show that sediments aggraded by the late pleistocene braided algeti river were strongly incised around the pleistocene holocene transition and subsequently a small scale pattern of diachronous fluvial terraces deposited by the now meandering river developed in the new valley during the holocene prior to ca 3 cal ka bp active phases of river channel aggradation and overbank sedimentation about 6 cal ka bp and 3 4 3 2 cal ka bp can be linked with climate driven vegetation changes i e stronger fluvial dynamics with sedimentation occurred during more arid and colder periods whereas the caucasian holocene climate optimum between 6 and 3 4 cal ka bp was characterized by stable geomorphologic conditions after 3 cal ka bp strongly increased human impact documented by former pollen studies is reflected by the fluvial dynamics as well i e an activity phase of strong overbank sedimentation 2 7 2 1 cal ka bp occurred during a period when forests in the lesser caucasus were burnt down two subsequent activity phases with fluvial sedimentation can be linked with historic events that probably both influenced vegetation distribution of the region i e a period of flourishing of georgia during the middle age and a time of large scale destruction of the country due to a persian invasion at the end of the 18th century ad respectively thus whereas no influence of tectonic events or fluctuations of the caspian sea level on the fluvial dynamics could be detected se georgia shows its fragile character with respect to climate and human driven vegetation changes similar to other semi arid landscapes of the mediterranean region

stromatolites and earth sun moon dynamics inclination of stromatolite columns caused by nonvertical direction of averaged incident solar radiation provides a signal for deducing astronomical and geophysical data at time of stromatolite formation a sample of anabaria juvensis bitter springs formation central australia shows a sinusoidal growth pattern which interpreted as an annual signal obliquity of the ecliptic with daily production of laminae indicates 435 days per year a result consistent with other available estimates a sample of inzeria from the same formation also shows a sinusoidal pattern and a similar estimate for days per year both samples indicate growth rates of centimeters per year several laboratory measurement techniques offer systematic procedures for extracting data

basement involved thin skinned and thick skinned tectonics in the alps the deformation of continental crust during continental collision by folding and thrusting follows three types of structural styles 1 in a true thin skinned style only cover rocks are involved 2 in the case of a thin skinned basement involved style thin slabs of crystalline basement rocks are piled up into a nappe stack 3 in a true thick skinned style the entire upper crust is involved in the deformation in the alps all three styles can be recognized the helvetic nappes and parts of the penninic nappes exhibit true thin skinned style tectonics triassic evaporites jurassic shales and cretaceous marls acted as detachment horizons basement involved thin skinned tectonics is typical for the penninic nappes in the core of the orogen the thickness of the basement thrust sheets is controlled by the effects of mesozoic rifting by deep burial and heating of the subducting crust and by the presence of late palaeozoic structures thick skinned style is observed in the more external parts of the orogen the external massifs and the southalpine nappe system it occurred in the late phase of collision and involved the entire upper crust the basal detachment occurred possibly along phyllonites generated by the breakdown of load bearing feldspar considering the alpine orogen as a whole the lower crust deformed seemingly independently from the upper crust the detachment of the cover units by thin skinned tectonics occurred prior to thrusting related to basement involved thin skinned tectonics thrust faults of both types were overprinted by post nappe folding

first deep seismic reflection images of the eastern alps reveal giant crustal wedges and transcrustal ramps 1 the alps are considered as a classical example for an orogen created by continental plate collision in this study we present new images obtained from deep seismic reflection profiling in the eastern alps between munich and venice which give rise to examine and revise existing concepts the seismic sections exhibit a prominent bi verging reflection pattern at crustal scale a major ramp like structure outcropping at the inn valley fault can be traced southward over 80 km into the mountain root where relics of the subducted penninic ocean are expected new models of the evolution of the eastern alps show an upper lower crustal decoupling along transcrustal thrust faults with opposite thrust directions of both the european and the adriatic african continents

ground based measurements of spatial and temporal variability of snow accumulation in east antarctica the east antarctic ice sheet is the largest highest coldest driest and windiest ice sheet on earth understanding of the surface mass balance smb of antarctica is necessary to determine the present state of the ice sheet to make predictions of its potential contribution to sea level rise and to determine its past history for paleoclimatic reconstructions however smb values are poorly known because of logistic constraints in extreme polar environments and they represent one of the biggest challenges of antarctic science snow accumulation is the most important parameter for the smb of ice sheets smb varies on a number of scales from small scale features sastrugi to ice sheet scale smb patterns determined mainly by temperature elevation distance from the coast and wind driven processes in situ measurements of smb are performed at single points by stakes ultrasonic sounders snow pits and firn and ice cores and laterally by continuous measurements using ground penetrating radar smb for large regions can only be achieved practically by using remote sensing and or numerical climate modeling however these techniques rely on ground truthing to improve the resolution and accuracy the separation of spatial and temporal variations of smb in transient regimes is necessary for accurate interpretation of ice core records in this review we provide an overview of the various measurement techniques related difficulties and limitations of data interpretation describe spatial characteristics of east antarctic smb and issues related to the spatial and temporal representativity of measurements and provide recommendations on how to perform in situ measurements

experimental models of extensional forced folds we have used single layer and multilayer clay models to study the development of forced folds above normal faults our modeling results show that the deformation patterns associated with extensional forced folding depend on the dip of the underlying normal fault and the presence of layer parallel detachments in single layer clay models extensional forced folds are upward widening monoclines anticlinal axial surfaces dip in the same direction as underlying master normal faults and synclinal axial surfaces dip in the opposite direction of master normal faults most secondary faults are upward steepening normal faults if master normal faults are steeply dipping however many secondary normal faults become high angle reverse faults at shallow depths the propagation and linkage of secondary faults into through going normal faults terminates the development of extensional forced folds more folding occurs prior to fault linkage if the master normal fault is steeply dipping rather than gently dipping most dipping beds and secondary faults are preserved in the hanging walls of the through oing normal faults in multilayer clay models with layer parallel detachments extensional forced folds are also upward widening monoclines slip on the lowest detachment laterally transfers extension induced by normal faulting and forced folding from the master normal fault to the detachment edge slip on overlying detachments accommodates minor thickness changes associated with upward widening of the fold secondary faults include low angle normal faults near the anticlinal axial surface minor thrust faults near the synclinal axial surface and high angle normal faults above the detachment edge the model predicted deformation patterns are similar to those of extensional forced folds from the gulf of suez and offshore norway this similarity suggests that our modeling results apply to extensional forced folds and can provide guidelines for interpreting field well and seismic data

mechanisms of basin contraction and reactivation in the basement involved malargue fold and thrust belt central andes 34 36 s we have conducted a structural study of both the basement involved malargue fold and thrust belt mftb and the active san rafael block srb which are located in the central andes at latitude 34 36 s based on several field examples located both in the inner and frontal part of belt and from the distal foreland zone we focus on the relationships between basement and cover deformation with respect to the known palaeogeography and structural inheritance in several zones we point out similarities in the structural and sedimentary responses to andean shortening the recent morphologic response has also been investigated through the analysis of active deformation along the eastern border of the srb we show that these structural and sedimentary processes are continuous in time and space since they can be applied in the various parts of the fold belt and also at different stages of fold and thrust belt building as well finally we propose the illustration of those mechanisms by complete cross section along the rio grande valley and a possible kinematic scenario of deformation propagation

analysis of temporal variation of earthquake occurrences in caucasus from 1960 to 2011 abstract frequency of earthquake occurrences in caucasus is investigated on hourly and daily time scales the observation period is 51 years which is sufficiently long to perform a reliable statistics several methods power spectrum wavelet and hilbert huang transformation are applied to earthquake time series our findings show that earthquakes hourly and daily occurrence is not characterized by the dominant frequencies however many different oscillations with periods from hours to years and longer contribute to the frequency content of the earthquake time distribution although their amplitude is rather low the variation of the power of cyclic components in the temporal features of earthquakes occurrence is not uniform but their amplification corresponds to the decrease of released local seismic energy