fault related folding near the wind river thrust wyoming usa reflection profiles across the wind river uplift in wyoming usa show that folding of basement rocks occurs in the footwall of the main fault at depths between 6 and 10km it is shown using elastic modelling that these features are a consequence of uneven fault slippage slip on the fault must be greater at depths between 3 and 18 km but reduced outside this range this is the depth range of catastrophic rupture associated with earthquakes in the continental crust

structural analysis and interpretation of the surface deformations of the el asnam earthquake of october 10 1980 the el asnam earthquake of october 10 1980 represents the major seismotectonic event of these last decades in the west mediterranean area it has induced a large amount of surface breaks this earthquake reveals the importance of compressional phenomena that characterize nowadays the tectonics of north africa the tectonic analysis of surface rupture shows the complexity of the deformation mechanism the principal mechanism consists of the activation of a nw se trending thrust fault accompanied with a left lateral motion and with an intense deformation of the northwestern overthrusting block an accurate description of these deformations shows that for a large part the breaks geometry depends closely on the substratum structure finally the analysis of the dislocations on irrigation ducts just above the fault traces allowed a quantitative study of the deformation

quaternary blind thrusting in the southwestern sacramento valley california patterns of microearthquakes and quaternary surface deformation suggest that the tectonic setting of the sw sacramento valley is similar to areas of the western san joaquin valley known to be underlain by seismogenic blind thrust faults on the basis of previous work and analysis of geologic and seismic reflection data the following late cenozoic tectonic features and processes are identified 1 uplift of the northern coast ranges beginning approximately 3 4 ma and eastward propagation of uplift into the southwestern sacramento valley by 1 0 ma 2 uplift and homoclinal flexure of plio pleistocene strata at the eastern coast ranges mountain front 3 uplift and folding above blind thrusts approximately 15 km east of the mountain front in the southwestern sacramento valley similar associations of structures and processes have been observed in thrust belts in pakistan the peruvian andes and the canadian cordillera and are commonly attributed to thrusting within an intercutaneous wedge or triangle zone by using other thrust belts as analogs the propagation of an eastward tapering triangle zone is interpreted to be the principal mechanism for uplift and homoclinal flexure at the eastern coast ranges mountain front seismic reflection profiles reveal that 1 the triangle zone consists primarily of east vergent blind thrusts and 2 west vergent backthrusts exposed in the the eastern coast ranges and southwestern sacramento valley are rooted in the east vergent thrusts transfer of slip from the east vergent blind thrusts to the west vergent backthrusts occurs locally beneath the southwestern sacramento valley fault bend folding in the hanging walls of the backthrusts has created a north northwest striking chain of low hills approximately 15 km east of the mountain front the folds deform 3 4 1 0 ma fluvial sediments and thus are middle pleistocene in age or younger local variations in strike suggest that the fold chain is segmented like the new idria coalinga kettleman hills segmented fold chain in the southwestern san joaquin valley stein and ekstrom 1989 these data have implications for seismic hazard assessment anecdotal accounts indicate that two m 6 0 events of the 1892 winters vacaville earthquake sequence probably occurred beneath the eastern coast ranges dale 1977 toppozada et al 1981 ground cracking was observed following the main shocks along the mountain front in the southwestern sacramento valley we propose that the earthquakes were generated by slip on a blind thrust beneath the coast ranges and that the ground cracking in the valley represents propagation of the eastward tapering triangle zone the 1892 earthquake sequence suggests that blind thrusts beneath the southwestern sacramento valley are active and capable of generating moderate to large magnitude earthquakes

earthquakes and folding coalinga california the magnitude 6 6 coalinga earthquake of may 2 1983 and most of the other earthquakes of magnitude 4 and greater near that town are tentatively attributed here to flexural slip on the flanks of growing folds this explanation apparently conflicts with the 100 yr old theory that all tectonic earthquakes are caused by slip on faults perhaps the coalinga events in an area where no active faults had been mapped will serve to suggest another possible mechanism for the generation of some earthquakes here the strongly folded and long coalinga anticline and syncline in a thick stratigraphic section seem to require a mechanism of bedding plane slip the magnitude 2 5 lompoc earthquake of april 7 1981 can also be attributed to flexural slip on the limb of a fold flexural slip bedding plane slip usually unseen and unmappable is clearly revealed in several areas in southern california many small earthquakes may be produced in these and other areas where direct evidence of active flexural slip by folding is unavailable if the may 2 coalinga earthquake was caused by folding unusual geologic conditions may be responsible for its high intensity

seismic potential revealed by surface folding 1983 coalinga california earthquake the 2 may 1983 coalinga california earthquake magnitude 6 5 failed to rupture through surface deposits and instead elastically folded the top few kilometers of the crust the subsurface rate of fault slip and the earthquake repeat time are estimated from seismic geodetic and geologic data three larger earthquakes up to magnitude 7 5 during the past 20 years are also shown to have struck on reverse faults concealed beneath active folds

use of sinkhole and specific capacity distributions to assess vertical gradients in a karst aquifer the carbonate rock aquifer in the great valley west virginia usa was evaluated using a database of 687 sinkholes and 350 specific capacity tests to assess structural lithologic and topographic influences on the groundwater flow system the enhanced permeability of the aquifer is characterized in part by the many sinkholes springs and solutionally enlarged fractures throughout the valley yet vertical components of subsurface flow in this highly heterogeneous aquifer are currently not well understood to address this problem this study examines the apparent relation between geologic features of the aquifer and two spatial indices of enhanced permeability attributed to aquifer karstification 1 the distribution of sinkholes and 2 the occurrence of wells with relatively high specific capacity statistical results indicate that sinkholes funnel and collapse occur primarily along cleavage and bedding planes parallel to subparallel to strike where lateral or downward vertical gradients are highest conversely high specific capacity values are common along prominent joints perpendicular or oblique to strike the similarity of the latter distribution to that of springs suggests these fractures are areas of upward convergent flow these differences between sinkhole and high specific capacity distributions suggest vertical flow components are primarily controlled by the orientation of geologic structure and associated subsurface fracturing

prospects for larger or more frequent earthquakes in the los angeles metropolitan region far too few moderate earthquakes have occurred within the los angeles california metropolitan region during the 200 year long historic period to account for observed strain accumulation indicating that the historic era represents either a lull between clusters of moderate earthquakes or part of a centuries long interseismic period between much larger moment magnitude m w 7 2 to 7 6 events geologic slip rates and relations between moment magnitude average coseismic slip and rupture area show that either of these hypotheses is possible but that the latter is the more plausible of the two the average time between m w 7 2 to 7 6 earthquakes from a combination of six fault systems within the metropolitan area was estimated to be about 140 years

the evolution of a thrust fault system processes of rupture initiation propagation and termination in the 1980 el asnam algeria earthquake summary we discuss work completed to date on the 1980 algerian earthquake and introduce a description of the earthquake in terms of rupture propagation using the nomenclature of fracture mechanics field and teleseismic studies have shown the earthquake fault to be divided into three major thrust segments rupture began at the sw end of the system and propagated along successive segments geological sections reveal that different fault segments have suffered different amounts of displacement in the past the amount of geological displacement increases systematically from almost zero at the sw end of the fault to several hundred metres further ne faulting at the sw end is very young and appears to be extending the thrust system along strike the aftershock data of ouyed et al reveal that strike slip aftershocks occur beyond the sw end of the thrust fault these are accommodating compression by conjugate strike slip faulting on north and west trending planes this network of conjugate faults plays a crucial role in the initiation of major eathquakes on the thrust system and may be regarded as a plastic zone beyond the end of the thrust fault increasing horizontal stress causes the strike slip system to evolve into a zig zag network of thrusts which is partly controlled by the pre existing strike slip faults finally a through going thrust can develop and leads to catastrophic rupture along the main fault plane to describe the propagation of the main shock we extend aki s concept of geometric barriers and divide these into two types in conservative barriers the slip vector is common to both fault planes whereas in non conservative barriers the slip vectors are different on the two fault planes that meet at the barrier although both types of barrier arrest dynamic rupture only nonconservative barriers need produce aftershocks as off fault deformation is required to accommodate the difference in slip vectors by considering the aftershock zones as areas of distributed deformation we show that fracture toughness in the earth is not a material constant but is related to fault geometry and therefore changes as fault systems evolve the current south westwards growth of the el asnam thrust system can be seen as the latest phase in an evolution consisting of periods of along strike extension alternating with periods of increasing net displacement during which no fault growth occurs these two types of behaviour allow a segmented fault system to be produced

formation of interior basins associated with curved faults in alaska the positions of certain nonmarine sedimentary basins in central and southern alaska are spatially related to the geometry of adjacent curved faults these interior basins occur along the northern convex side of these fault systems which change trend from northwest in canada and eastern alaska to east west in central alaska and to northeast in western alaska the basins probably initiated in early to middle tertiary time and deposition within all basins continued through the quaternary broadly synchronous with tertiary strike slip displacements along the tintina denali and border ranges fault systems we examine the spatial and temporal relationship between basins and faults by using a mechanical model of curved strike slip faults based on boundary elements we relate slip along the curved faults to tertiary pacific north american plate motions by using principal stress directions inferred from the plate motion directions locations of the predicted mean stress reductions around the fault bends caused by fault slip correlate well with positions of the interior basins our results suggest that basin subsidence and location were controlled primarily by the geometry of adjacent curved fault systems and the state of stress in alaska during the tertiary mechanical interaction between curved alaskan fault systems increases the tendency for basin subsidence stresses inferred from early tertiary plate motion vectors are not oriented correctly to drive right lateral slip along kaltag farewell and parallel faults in western alaska furthermore these stress states would have produced left lateral displacements for which there is no evidence along these western faults in their present orientations we find that a combination of slightly rotated fault geometry and low friction along the faults appears to facilitate right lateral slip along the faults in western alaska our results show that deformation well inside the continent can be explained in terms of the pacific north american plate motions thus tertiary plate motions have resulted in a broad zone of fault slip uplift and subsidence in the nonrigid north american plate producing several large basins

the geometry of echelon fractures in rock implications from laboratory and numerical experiments abstract the traces of echelon joints veins and dikes in rock range from curving to straight theoretical analyses using boundary element numerical methods have concluded that straight open fractures imply a significant remote differential stress whereas curving traces imply a more nearly isotropic stress we present a series of laboratory experiments which investigate the two dimensional propagation paths of echelon fractures in pmma plates as a function of the applied biaxial loading and the initial geometry of a simple fracture array the experimental results support the theoretical conclusions and verify the accuracy of the numerical method at the grain scale rock does not rigorously conform to the assumptions of isotropy homogeneity and linear elasticity demanded by the numerical method nevertheless results from crack path stability theory suggest that small scale deviations of a fracture from the ideal path generally do not affect its large scale behavior fracture paths which become kinked or curved by local heterogeneities are found to self correct to a path governed by competition between the fracture tip and remote stress fields provided the remote differential stress is non zero this enhances our confidence that the numerical method can be used to produce and explain realistic fracture geometries in rock an unexpected experimental result is the non perpendicular intersection of fractures grown in the laboratory free surface boundary conditions require that the walls of an open fracture be free of shear stress the principal stresses are therefore aligned with the crack wall and we might consequently expect an approaching opening mode fracture either to intersect the free surface at a right angle or to turn away and follow an asymptotic nonintersecting path experimental and numerical modeling however shows how the near tip stresses generated by an approaching fracture dominate the local stress field and allow it to propagate along an oblique path very close to intersection with the adjacent free surface

implications for karst hydrology from 3d geological modeling using the aquifer base gradient approach we use the gradient of the aquifer base to investigate the hydrology of mature shallow karst systems we first present a 3d geological model of the gempen plateau nw switzerland that reveals the geometry of aquifers and aquitards and their displacement at faults then transfer the 3d geological model to a hydrological model the transformation is based on a conceptual karst model approximating subsurface flow in mature shallow karst systems to open surface flow on the top of the uppermost aquitard or aquifer base the gradient of this surface is expected to mainly influence regional groundwater flow patterns we use the hydrological model to delineate spring catchment areas the discharge areas and corresponding catchment areas of the model are compared with the occurrence of springs in the study area and with hydraulic links confirmed by tracer tests we also describe the way in which the hydrological model contributes to identifying flow processes the proposed aquifer base gradient approach enhances vulnerability assessment in mature shallow karst regions by 1 localizing catchment areas as a precondition of source protection strategies and 2 indicating dominant flow processes associated with individual springs

interseismic coupling and asperity distribution along the kamchatka subduction zone 1 gps measurements of interseismic horizontal surface velocities reveal the degree of kinematic coupling of the plate boundary thrust along the kamchatka subduction zone from about 51 degrees to 57 degrees n latitude inversions for the distribution of aseismic slip rate along the similar to 15 degrees nw dipping underthrust suggest a nonslipping plate interface in southern kamchatka above similar to 50 km depth along the segment that ruptured in the m w 9 1952 earthquake north of similar to 53 degrees n the subduction interface experiences significant aseismic slip consistent with the lower seismic moment release in m 8 5 earthquakes along this portion of the subduction zone the gps velocities are consistent with a boundary element forward model in which historic earthquake rupture zones are represented as locked asperities surrounded by a zero shear stress subduction interface loaded by plate convergence models in which the complete rupture zones of historic earthquakes are considered locked greatly overpredict the degree of kinematic coupling reducing the area of the locked model asperities to the central 25 area of historic rupture zones fits the data well suggesting that large earthquakes involve small fully locked core asperities surrounded by conditionally stable portions of the plate interface areas of low aseismic slip rate appear to be roughly correlated with areas of low isostatic gravity anomalies over offshore forearc basins while less coupled portions of the kamchatka subduction zone coincide with high gravity anomalies offshore of two peninsulas possibly related to the subduction of the emperor meji seamount chain and the kruzenstern fracture zone

tree ring based mass balance estimates for the past 300 years at peyto glacier alberta canada tree rings were used to reconstruct mass balance for peyto glacier in the canadian rocky mountains from a d 1673 to 1994 summer balance was reconstructed from tree ring estimates of summer temperature and precipitation in the canadian rockies winter balance was derived from tree ring data from sites bordering the gulf of alaska and in western british columbia the models for winter and summer balance each explain over 40 of the variance in the appropriate mass balance series over the period 1966 1994 the correlation between the reconstructed and measured net balances is 0 71 strong positive mass balances are reconstructed for 1695 1720 and 1810 1825 when higher winter precipitation coincided with reduced ablation periods of reconstructed positive mass balance precede construction of terminal moraines throughout the canadian rockies ca 1700 1725 and 1825 1850 positive mass balances in the period 1845 1880 also correspond to intervals of glacier readvance mass balances were generally negative between 1760 and 1805 from 1673 to 1883 the mean annual net balance was 70 mm water equivalent per year w e yr but it averaged 317 mm w e yr from 1884 to 1994 this reconstructed mass balance history provides a continuous record of glacier change that appears regionally representative and consistent with moraine and other proxy climate records

seismicity and geometry of a 110 km long blind thrust fault 1 the 1985 kettleman hills california earthquake the august 4 1985 kettleman hills earthquake was the third in a sequence of moderate shocks to occur beneath the northern half of a 110 km long fold chain bounding the eastern california coast ranges the 1982 mw 5 4 new idria 1983 mw 6 5 coalinga and 1985 mw 6 1 kettleman hills events define a southward progression of seismic activity beneath the fold we use teleseismic waveforms geodetic modeling hypocenters relocated in a three dimensional velocity model and subsurface structural data to investigate the kettleman hills earthquake the main shock results from motion on a shallowly dipping thrust fault buried at 10 km depth aftershocks and coseismic fault slip extend 20 km along the fold axis nearly the full extent of the kettleman hills north dome anticline aftershocks occur primarily several kilometers in front of the fault tip and in the core of the anticline the main shock and several foreshocks occurred at a 2 km right step in the quaternary fold axis which also corresponds to the southern end of the 1983 coalinga and northern end of the 1985 kettleman hills aftershock zones from this we infer that the step in the fold is caused by an offset or tear in the underlying fault the scalar seismic moment is 1 6 1018 n m consistent with the geodetic deformation and the duration of rupture is 16 s 3 4 times greater than for the average earthquake with this scalar moment the slow rate of moment release provides an explanation for the low level of ground shaking and low local magnitude reported for the event the peak of the geodetic uplift is located 5 km perpendicular to the quaternary fold axis we argue that the fault is propagating northeast into the undeformed san joaquin valley sediments and that the overlying fold is growing at about 0 5 mm yr

rupture process of the 1987 superstition hills earthquake from the inversion of strong motion data a pair of significant earthquakes occurred on conjugate faults in the western imperial valley involving the through going superstition hills fault and the elmore ranch cross fault the first event was located on the elmore ranch fault m s 6 2 and the larger event on the superstition hills fault m s 6 6 the latter event is seen as a doublet teleseismically with the amplitudes in the ratio of 1 2 and delayed by about 8 sec this 8 sec delay is also seen in about a dozen strong motion records these strong motion records are used in a constrained least squares inversion scheme to determine the distribution of slip on a 2 d fault upon closer examination the first of the doublets was found to be itself complex requiring two episodes of slip thus the rupture model was allowed to have three separate subevents treated as separate ruptures with independent locations and start times the best fits were obtained when all three events initiated at the northwestern end of the fault near the intersection of the cross fault their respective delays are 2 1 and 8 6 sec relative to the first subevent and their moments are 0 4 0 9 and 3 5 10 25 dyne cm which is about half of that seen teleseismically this slip distribution suggests multi rupturing of a single asperity with stress drops of 60 200 and 15 bars respectively the first two subevents were confined to a small area around the epicenter while the third propagated 18 km southwestward compatible with the teleseismic and afterslip observations

detection of a locked zone at depth on the parkfield california segment of the san andreas fault the parkfield california segment of the san andreas fault is transitional in character between the creeping segment of the fault to the northwest and the locked carrizo plain segment to the southeast the rate of shallow fault slip decreases from 25 30 mm yr northwest of the epicenter of the 1966 parkfield earthquake to zero at the southeastern end of the 1966 rupture zone data from a network of trilateration lines spanning the san andreas fault near parkfield and extending to the pacific coast near san luis obispo shed light on the rate of fault slip at depth since the 1966 earthquake in this study average rates of line length change and shallow fault slip were inverted to determine the slip rate at depth on the parkfield fault segment the fault is taken to be a vertical surface with unknown distribution of strike slip displacement in an elastic half space a striking result of the inversions is that all solutions providing acceptable fits to the data exhibit a locked zone essentially coincident with the rupture surface of the 1966 parkfield earthquake the data require that the locked zone extend nearly as far north as the 1966 epicenter however the vertical extent of the locked zone is not well resolved over much of the parkfield segment the fault is slipping faster at the earth s surface than it is at seismogenic depths in order to fit the trilateration measurements it is necessary to include a component of contraction normal to the trend of the san andreas the inversion results suggest a spatially uniform normal strain of 0 06 strain yr the orientation of the contraction is compatible with geologic and seismic evidence of active folding and reverse faulting in the region the magnitude of the contraction is consistent with convergence rates inferred from global plate motion models

changes in static stress on southern california faults after the 1992 landers earthquake the magnitude 7 5 landers earthquake of 28 june 1992 was the largest earthquake to strike california in 40 years the slip that occurs in such an earthquake would be expected to induce large changes in the static stress on neighbouring faults these changes in stress should in turn affect the likelihood of future earthquakes stress changes that load faults towards failure have been cited as the cause of small1 5 moderate6 and large7 earthquakes conversely those that relax neighbouring faults have been related to a decrease in seismicity5 here we use an elastic half space model8 to estimate the stress changes produced by the landers earthquake on selected southern california faults including the san andreas we find that the estimated stress changes are consistent with the triggering of four out of the five aftershocks with magnitude greater than 4 5 and that the largest changes 1 10 bar occurring on part of the san bernardino segment of the san andreas fault may have decreased the time to the next magnitude 8 earthquake by about 14 years

seismicity and geometry of a 110 km long blind thrust fault 2 synthesis of the 1982 1985 california earthquake sequence during 1982 1985 three 5 4 mw 6 5 earthquakes migrated 65 km along the north half of a string of quaternary folds at the east front of the california coast ranges there is no surface fault associated with these earthquakes but the fold chain oriented parallel to the san andreas fault 30 km to the west takes up contraction normal to the san andreas fault identification of active blind thrust faults is hindered by the absence of a fault trace but may be revealed by the presence of growing folds at the surface and by earthquakes at depth because of excellent seismic geodetic and geologic data this earthquake sequence illuminates the geometry of the blind faults and enables us to probe their mechanics we relocate seismicity and compute focal mechanisms in a three dimensional velocity space and model the vertical deformation associated with the 1983 m 6 5 coalinga earthquake the aftershock zones abut at echelon offsets in the fold axes and the mainshocks display reverse slip perpendicular to the axes suggesting that the folds conceal a contiguous segmented thrust fault background seismicity concentrates at bends and breaks in the fold chain sites that may correspond to tears and ramps in the thrust fault at depth seismic reflection profiles reveal thrust and reverse faults dipping toward the san andreas fault at depths of 5 10 km with several kilometers of cumulative slip and high angle reverse faults in the anticlines with several hundred meters cumulative slip coseismic fold uplift accompanied the coalinga and kettleman hills north dome earthquakes suggesting that fold growth is episodic and coupled closely to repeated earthquakes on the underlying thrusts the north half of the fold chain has been the site of several 6 m 6 5 earthquakes since 1885 thus kettleman hills middle dome the next fold segment to the south has an elevated seismic potential the aftershock zones of the three main shocks are diffuse and occupy a region much larger than the site of seismic slip aftershocks occur 5 7 km from the fault regions where on the basis of a boundary element model the shear strain increase caused by the fault slip exceeds 20 ppm equivalent to about 0 7 mpa we argue that the broad aftershock zone is a product of high sustained off fault stress caused by repeated displacement on faults that do not cut the earth s surface the fault tip stresses lead to the formation of secondary faults which can become sites of aftershocks and postseismic creep

bedding plane slip in initial stages of fault related folding abstract frictional slip along bedding planes contributes to fault related folding of layered rocks we use numerical experiments to investigate the deformation of frictional bedding planes near dipping faults under layerparallel contraction and extension within the numerical experiments contraction boundary conditions produce asymmetric anticlines and extension produces asymmetric synclines the fold shape may be used to infer dip of the underlying fault in situations where the fault may not be observable additionally sense of slip along bedding planes may indicate proximity to the fault tip under uniform remote tectonic strain fault slip induces deformation in both the hangingwall and the footwall at depths as shallow as 1 km there is no significant difference between fold amplitudes in the hangingwall and the footwall this result is contrary to many kinematic models currently in use kinematic models of fault related folds commonly include the development of flat ramp and flat ramp flat fault geometries which may be attributed to initial ramp thrusting and later flat development our mechanical models show that fault flats may be produced from fault ramps due to slip along frictional bedding planes near the thrust fault tips our numerical experiments also evaluate joint initiation joints perpendicular to bedding are promoted in extensional environments we compare the results of the mechanical model to kinematic models of fault propagation folds and conclude that mechanical models offer important insights to better understand the folding process

the initiation and growth of en echelon veins abstract numerical models are used to understand the evolution of mode i opening fractures from spatially random distributions in a brittle elastic material en echelon arrays commonly develop because mechanical fracture interaction promotes growth for this geometry this provides a new mechanism for en echelon vein formation in rock which is distinctly different than previously proposed mechanisms it is suggested that some macroscopic en echelon vein arrays may have served as zones of weakness that localized later shear zone development in a manner analogous to that observed by experimentalists examining micro cracking and subsequent shear rupture of rocks loaded under compression sigmoidally shaped veins and vein fillings are explicitly modeled showing that they can form in response to the mechanical interaction of neighboring fractures which redirects the propagation path numerical comparison of sigmoidal veins formed by brittle fracture and by ductile shear zones demonstrates some of the pitfalls of failing to correctly identify the mechanism of formation

influence of static stress changes on earthquake locations in southern california earthquakes induce changes in static stress on neighbouring faults that may delay hasten or even trigger subsequent earthquakes1 10 the length of time over which such effects persist has a bearing on the potential contribution of stress analyses to earthquake hazard assessment but is presently unknown here we use an elastic half space model11 to estimate the static stress changes generated by damaging magnitude m 5 earthquakes in southern california over the past 26 years and to investigate the influence of these changes on subsequent earthquake activity we find that in the 1 5 year period following a m 5 earthquake any subsequent nearby m 5 earthquake almost always ruptures a fault that is loaded towards failure by the first earthquake after this period damaging earthquakes are equally likely to rupture loaded and relaxed faults our results suggest that there is a short period of time following a damaging earthquake in southern california in which simple coulomb failure stress models could be used to identify regions of increased seismic hazard

a high resolution reconstruction of storglaciaren mass balance back to 1780 81 using tree ring data and circulation indices storglaciaren in northernmost sweden has the world s longest ongoing continuous mass balance record starting in 1946 to extend this massbalance record we have reconstructed summer bs and winter bw mass balances separately back to the mass balance year 1780 81 with annual resolution we used tree ring data for bs and a set of circulation indices based on the sea level pressure for bw both proxies have correlation coefficients with respective mass balance components of ca 0 7 the reconstructed net balance bn of storglaciaren was well correlated to the observations during 1946 1980 r 0 8 p 0 05 our reconstruction agrees well with previously obtained results of northern sweden glacier variability where the predominantly positive bn years between 1890 and 1910 correspond to the well documented post little ice age advance of storglaciaren furthermore the results suggest that bs as a function of summer temperatures is more important than bw in determining the bn which is contrary to glaciers in the maritime parts of western scandinavia in general bn has been negative over the last 220 yr suggesting a predomination of continental conditions over northern sweden however the influence of bw increased in the late twentieth century indicating a shift to a more oceanic climate regime

the paradox of the loma prieta earthquake why did rupture terminate at depth the 1989 loma prieta earthquake was an oblique thrusting event that raptured a moderately dipping fault that is subparallel to the san andreas fault rupture initiated at 18 km and propagated both updip and bilaterally seismic and geodetic studies indicate that rupture terminated between 8 and 5 km depth we examine the role of the elastic properties of the crust as a mechanism for reducing stress in the upper crust and terminating rupture we use linear elastic fracture mechanics and the finite element method to model the loma prieta fault rupture as a mode ii and mode iii shear crack in a layered elastic crust our analysis shows that a low stress condition generated in our models by a change in material properties in the upper crust is capable of stopping rapture we also examine the stress condition at the intersection of the san andreas and loma prieta faults to determine the present state of stress and seismic hazard in the region we find that the loma prieta fault in the upper crust is still closer to the point of failure than the san andreas fault over the same depth rupture of the loma prieta fault did not increase the seismic hazard of the san andreas fault within the crustal volume above the loma prieta rupture

improving a tree ring reconstruction from west central scandinavia 900 years of warm season temperatures dendroclimatological sampling of scots pine pinus sylvestris l has been made in the province of jamtland in the west central scandinavian mountains since the 1970s the tree ring width trw chronology spans several thousand years and has been used to reconstruct june august temperatures back to 1632 bc a maximum latewood density mxd dataset covering the period ad 1107 1827 with gap 1292 1315 was presented in the 1980s by fritz schweingruber here we combine these historical mxd data with recently collected mxd data covering ad 1292 2006 into a single reconstruction of april september temperatures for the period ad 1107 2006 regional curve standardization rcs provides more low frequency variability than non rcs and stronger correlation with local seasonal temperatures 51 variance explained the mxd chronology shows a stronger relationship with temperatures than the trw data but the two chronologies show similar multi decadal variations back to ad 1500 according to the mxd chronology the period since ad 1930 and around ad 1150 1200 were the warmest during the last 900 years due to large uncertainties in the early part of the combined mxd chronology it is not possible to conclude which period was the warmest more sampling of trees growing near the tree line is needed to further improve the mxd chronology

weakening climatic signal since mid 20th century in european larch tree ring chronologies at different altitudes from the adamello presanella massif italian alps abstract tree rings from temperature limited environments are highly sensitive climate proxies widely used to reconstruct past climate parameters for periods prior to the availability of instrumental data and to analyse the effect of recent global warming on tree growth an analysis of the climatic signal in five high elevation tree ring width chronologies of european larch larix decidua mill from the tops of five different glacial valleys in the italian central alps revealed that they contain a strong summer temperature signal and that tree ring growth is especially influenced by june temperatures however a moving correlation function analysis revealed a recent loss of the june temperature signal in the tree ring chronologies this signal reduction primarily involves the two lowest altitude chronologies it is probable that the observed increasing importance of late summer temperature for tree ring growth over the past 50 yr is an effect of the lengthening growing season and of the variations in the climate tree ring relationship over time all the chronologies considered especially those at the highest altitudes show an increasing negative influence of june precipitation on tree ring growth the climatic signal recorded in tree ring chronologies from the italian central alps varies over time and is also differentially influenced by climatic parameters according to site elevation

mechanical models of trishear like folds previous workers have formulated velocity descriptions of the trishear kinematic model of fault propagation folds which are inherently non unique we present two complete mechanical models of fault related folding and assess the validity of the assumptions used in the assignment of velocities in the trishear description and to eliminate the untenable situation of an infinite number of possible solutions for velocity fields the mechanical model of forced folding forced fold based on viscous folding theory is used to derive the velocity fields in an anisotropic sedimentary cover overlying faulted and displaced rigid basement blocks the solution of displacements around a stress free fault in an elastic body is used to model fault arrest folds that form around a fault imbedded in a deformed medium the results indicate that the velocity fields assumed in the trishear model more closely resemble the velocities derived in the mechanical forced fold model than the mechanical model of fault arrest folding the forced fold model produces a triangular region of concentrated deformation similar to the trishear region assumed in the kinematic models while the deformation produced by the fault arrest model is not concentrated within a triangular zone

alternative model of thrust fault propagation a widely accepted explanation for the geometry of thrust faults is that initial failures occur on deeply buried planes of weak rock and that thrust faults propagate toward the surface along a staircase trajectory we propose an alternative model that applies gretener s beam failure mechanism to a multilayered sequence invoking compatibility conditions which demand that a thrust propagate both upsection and downsection we suggest that ramps form first at shallow levels and are subsequently connected by flat faults this hypothesis also explains the formation of many minor structures associated with thrusts such as backthrusts wedge structures pop ups and duplexes and provides a unified conceptual framework in which to evaluate field observations

tectonic wedging along the rear of the offshore taiwan accretionary prism abstract the structural geometry kinematics and density structure along the rear of the offshore taiwan accretionary prism were studied using seismic reflection profiling and gravity modeling deformation between the offshore prism and forearc basin at the point of incipient collision and southward into the region of subduction has been interpreted as a tectonic wedge similar to those observed along the front of mountain ranges this tectonic wedge is bounded by an east dipping roof thrust and a blind west dipping floor thrust an east dipping sequence of forearc basin strata in the hanging wall of the roof thrust reaches a thickness in excess of 4 km near the tip of the interpreted tectonic wedge section restoration of the roof sequence yields an estimate of 4 km of shortening which is small compared with that inferred in the collision area to the north based on the variation in distance between the apex of the prism and the island arc previous studies propose that either high angle normal faulting or backfolding has exhumed the metamorphic rocks along the eastern flank of the central range in the collision zone on land to better constrain the initial crustal configuration we tested 350 crustal models to fit the free air gravity anomaly data in the offshore region to study the density structure along the rear of the accretionary prism in the subduction and initial collision zones before the structures become more complex in the collision zone on land the gravity anomaly observed in the region of subduction 20 2 n can be modeled with the arc basement forming a trenchward dipping backstop that is overlain by materials with densities in the range of sedimentary rocks near the point of incipient collision 20 9 n however the free air gravity anomaly over the rear of the prism is approximately 40 mgal higher compared with the region of subduction and requires a significant component of high density crustal rocks within the tectonic wedge these results suggest that the forearc basement may be deformed along the rear of the prism associated with the onset of collision but not in the subduction region further to the south

evolution of the northern santa cruz mountains by advection of crust past a san andreas fault bend the late quaternary marine terraces near santa cruz california reflect uplift associated with the nearby restraining bend on the san andreas fault excellent correspondence of the coseismic vertical displacement field caused by the 17 october 1989 magnitude 7 1 loma prieta earthquake and the present elevations of these terraces allows calculation of maximum long term uplift rates 1 to 2 kilometers west of the san andreas fault of 0 8 millimeters per year over several million years this uplift in concert with the right lateral translation of the resulting topography and with continual attack by geomorphic processes can account for the general topography of the northern santa cruz mountains

spatial and temporal distribution of deformation at the front of the andean orogenic wedge in southern bolivia new observations from an active orogenic wedge help link the seismotectonic behavior of individual faults to wedge deformation rates and patterns over multiple timescales we provide the first detailed constraints on the distribution and timing of deformation at the front of the andean orogenic wedge in southern bolivia where a recent study suggests that great mw 8 earthquakes could rupture the master fault underlying the wedge we use stratigraphic relationships across fault related folds and elastic dislocation modeling of seismic reflection horizons to obtain probabilistic estimates of wedge front fault ages and slip rates our analyses reveal that at least half of the previously determined gps based wedge loading and quaternary whole wedge shortening rates are absorbed across a 20 40 km wide wedge front zone consisting of 1 4 en echelon and partially to fully overlapping faults and folds associated with blind thrust faults the difference between our slip rates and the geodetic geologic observations combined with evidence for activity across internal wedge structures supports the notion that nonsteady state mass balance conditions coupled with elevated erosional efficiency result in distributed wedge deformation the orogenic wedge in southern bolivia behaves in a similar fashion to the taiwanese and himalayan ranges slip accumulates at downdip locations along the master fault and is released incrementally by earthquakes that rupture the wedge front fault zone the faults and folds comprising this zone pose a major source of seismic hazard accumulating slip is also released in the wedge interior and older internal wedge faults must be considered in any future assessment of regional earthquake risk

geometry and slip distribution in normal fault systems implications for mechanics and fault related hazards normal faults are important sources of large destructive earthquakes in continental rift provinces we investigate the mechanical characteristics of multiple linked master and subsidiary faults using two dimensional boundary element models the master fault system is a coulomb frictional fault that dips 50 from the surface to a depth of 15 km where it is linked to a subjacent shear zone that creeps under low resolved shear stress we consider two basic configurations one in which the shear zone and master fault are coplanar and the other in which the shear zone dips 20 forming a bent or crudely listric fault system antithetic and splay faults are added to the master fault system in each case to model failure of multiple fault systems that are typical of half grabens we focus on the mechanical interactions between the various faults in order to identify points of initial failure spatial variations in the amount of fault slip and the patterns of surface deformation that may precede catastrophic failure of the master fault system in all cases failure on the master frictional fault initiates at the base where it joins the creeping shear zone and at the earth s surface during the same stress increment the listric fault system fails at lower regional differential stress than the planar fault system failure of a large antithetic fault that dips at 70 from the surface to the base of the frictional master fault initiates at lower regional differential stress for the listric than for the planar case several repeated failure episodes may be required to cause surface offset on the antithetic fault if the master fault system is planar but antithetic surface faulting may occur during each master fault failure episode in the listric case modeled splay faults dip from the surface at either greater 70 or lower 50 angles than the frictional master fault to a depth of 5 km where they intersect the master fault in both cases surface slip is greater on the master fault and lesser on the splay fault surface deformation prior to catastrophic failure of the frictional master fault is generated by creep on the deep seated shear zone and during the initial stages of master fault rupture footwall uplift is predicted above a steeply dipping locked coulomb fault and creeping shear zone but the footwall uplift is absent in the listric fault shear zone case a localized zone of increased extensional strain is centered on the surface trace of the master fault as the result of near surface extensional and shear fracturing during the initial stages of fault slip these geodetic anomalies are of interest because they are a near surface phenomenon which may also alter fluid flow and gas flux and be detectable by hydrologic and geochemical instrumentation as well as geodetic measurements

coseismic folding earthquake recurrence and the 1987 source mechanism at whittier narrows los angeles basin california static deformation associated with the october 1 1987 whittier narrows california m 6 0 earthquake was detected by geodetic elevation changes the earthquake uplifted a 1 5 km high quaternary fold the santa monica mountains anticlinorium by 50 mm but caused no fault rupture at the ground surface this suggests that folding and faulting of the los angeles basin sediments are coincident and continuing after correction for surveying errors and nontectonic subsidence we model the 214 geodetic observations with a simple dislocation in an elastic half space a thrust fault with reverse slip of 1 1 0 3 m and dipping 30 4 n with an upper edge at a depth of 12 1 km and a lower edge at 17 1 km fits the geodetic data best and is consistent with the main shock hypocenter fault plane solution and initial aftershock distribution the upper limit on the static stress drop is 17 5 5 0 mpa 175 50 bar the lower limit on the geodetic moment is 1 0 0 2 1025 dyne cm in accord with seismic estimates indicating that most of the slip took place during seismic rupture if earthquakes of m 6 characterize the blind thrust fault on which the earthquake occurred we estimate a 200 year repeat time at whittier narrows and a 5 18 year rate of earthquake occurrence within a 150 km long band in the northern los angeles basin and santa monica bay to the west the 25 year rate of historical occurrence since 1860 is less than this prediction the deficit in moment release implies that either vigorous aseismic slip or infrequent larger earthquakes occur here

a balanced cross section of the 1994 northridge earthquake southern california the northridge earthquake of 17 january 19941 was the latest in a series of very damaging thrust fault generated earthquakes to strike california following the san fernando2 1971 coalinga3 1983 and whittier narrows4 5 1987 events like the last two of these the northridge event occurred along a fault that did not reach the surface and which had not been detected by traditional seismic hazard methods6 7 balanced cross sections8 9 which flatten and remove the crustal deformation can be used to identify and quantify the seismic hazard posed by thrust faults here we present a balanced cross section through the northridge portion of the transverse ranges fold and thrust belt10 which shows that the earthquake occurred on what we call the pico thrust a cross section of this sort constructed before the earthquake would have revealed the fault although it would not have predicted the earthquake cross sectional modelling of the pico thrust yields an average slip rate of 1 4 1 7 mm yr 1 and a recurrence interval of northridge sized mw 6 7 earthquakes every 1 500 1 800 years we show that the pico thrust is the back thrust to the 170 km elysian park thrust3 4 which underlies some of the most densely urbanized portions of the los angeles basin

fracture initiation development and reactivation in folded sedimentary rocks at raplee ridge ut abstract fractures at raplee ridge a 14 km long monoclinal fold of pennsylvanian sedimentary rock in southeast utah are examined to determine their sequential development and to explain the mechanical relationships among the three primary fracture sets and the fold folding is attributed to slip on an unexposed thrust fault of laramide age fracture orientations were measured at 98 sites and fracture patterns were mapped at 8 sites on two sandstone and two limestone units of the rico formation revealing at least four stages of fracture formation stages 1 and 2 occurred pre folding and are defined respectively by e w trending fracture set i and n s trending fracture set ii set i fractures are characterized by a unimodal distribution of attitudes an intermediately developed outcrop pattern and continuous linear traces on bedding surfaces set ii fractures have a greater dispersion of orientations and are poorly to intermediately developed abutting relationships confirm that set i fractures are older than set ii stage 3 occurred during folding when nw se trending set iii fractures initiated both from isolated flaws and as wing cracks due to right lateral shearing along reactivated set i fractures set iii fractures increase in density as the fore limb dip increases from 10 to 30 later stages of deformation are characterized by the formation of fracture subsets iv and v structurally associated with fore limb dips greater than 30 fracture sets i and ii are found throughout the surrounding monument upwarp and are attributed to that structure whereas set iii is attributed to local stresses induced by monoclinal folding and or thrust faulting

geomorphology kinematic history and earthquake behavior of the active kuwana wedge thrust anticline central japan 1 we combine surface mapping of fault and fold scarps that deform late quaternary alluvial strata with interpretation of a high resolution seismic reflection profile to develop a kinematic model and determine fault slip rates for an active blind wedge thrust system that underlies kuwana anticline in central japan surface fold scarps on kuwana anticline are closely correlated with narrow fold limbs and angular hinges on the seismic profile that suggest at least 1 3 km of fault slip completely consumed by folding in the upper 4 km of the crust the close coincidence and kinematic link between folded terraces and the underlying thrust geometry indicate that kuwana anticline has accommodated slip at an average rate of 2 2 0 5 mm yr on a 27 west dipping thrust fault since early middle pleistocene time in contrast to classical fault bend folds the fault slip budget in the stacked wedge thrusts also indicates that 1 the fault tip propagated upward at a low rate relative to the accrual of fault slip and 2 fault slip is partly absorbed by numerous bedding plane flexural slip faults above the tips of wedge thrusts an historic earthquake that occurred on the kuwana blind thrust system possibly in a d 1586 is shown to have produced coseismic surface deformation above the doubly vergent wedge tip structural analyses of kuwana anticline coupled with tectonic geomorphology at 10 3 10 5 years timescales illustrate the significance of active folds as indicators of slip on underlying blind thrust faults and thus their otherwise inaccessible seismic hazards

viscoelastic earthquake cycle models with deep stress driven creep along the san andreas fault system 1 we develop a two dimensional boundary element earthquake cycle model including deep interseismic creep on vertical strike slip faults in an elastic lithosphere coupled to a viscoelastic asthenosphere uniform slip on the upper part of the fault is prescribed periodically to represent great strike slip earthquakes below the coseismic rupture the fault creeps in response to lithospheric shear stresses within a narrow linear viscous fault zone the model is applied to the gps contemporary velocity field across the carrizo plain and northern san francisco bay segments of the san andreas fault as well as triangulation measurements of postseismic strain following the 1906 san francisco earthquake previous analysis of these data using conventional viscoelastic coupling models without stress driven creep segall 2002 shows that it is necessary to invoke different lithosphere asthenosphere rheology in northern and southern california in order to explain the data we show that with deep stress driven interseismic creep on the san andreas fault the data can be explained with the same rheology for northern and southern california we estimate elastic thickness in the range 44 100 km 95 confidence level fault zone viscosity per unit width of 0 5 8 2 1017 pa s m and asthenosphere relaxation time of 24 622 years 0 1 2 9 1020 pa s for northern and southern california we estimate a slip rate of 21 27 mm yr and recurrence time of 188 315 years for the northern san francisco bay san andreas fault and slip rate of 32 42 mm yr with recurrence time of 247 536 years for the carrizo plain

the growth of geological structures by repeated earthquakes 2 field examples of continental dip slip faults a strong test of our understanding of the earthquake cycle is the ability to reproduce extant fault bounded geological structures such as basins and ranges which are built by repeated cycles of deformation along strike slip faults the coseismic and interseismic deformation can be nearly equal in magnitude and opposite in sign resulting in little permanent deformation except for the fault offset for dip slip faults portions of the crust are lifted and dropped and so buoyancy forces are exerted the seismic and interseismic deformations do not balance and structures grow and become subject to erosion and deposition we consider three examples for which the structure and fault geometry are well known the white wolf reverse fault in california site of the 1952 kern county m 7 3 earthquake the lost river normal fault in idaho site of the 1983 borah peak m 7 0 earthquake and the cricket mountain normal fault in utah site of quaternary slip events basin stratigraphy and seismic reflection records are used to profile the structure and coseismic deformation measured by leveling surveys is used to estimate the fault geometry to reproduce these structures we add the deformation associated with the earthquake cycle the coseismic slip and postseismic relaxation to the flexure caused by the observed sediment load treating the crust as a thin elastic plate overlying a fluid substrate the cumulative deformation is principally dependent on the elastic plate thickness modestly sensitive to the sediment substrate density difference and insensitive to the fluid viscosity for the 4 to 8 ma structures we deduce a longterm flexural rigidity of 2 15 1019 nm this is equivalent to an elastic plate thickness of 2 4 km for a young s modulus of 2 5 1010 nm 2 this value is found where independent estimates of the elastic thickness from the coherence between surface topography and gravity yield values of about 4 km but where coseismic fault slip extends to a depth of 10 15 km thus much of the seismogenic crust must weaken substantially during the life of active faults causing the fault bounded basins to narrow over time

an aftershock study of the el asnam algeria earthquake of 1980 october 10 summary an array of 28 portable seismic stations was operated in the region of el asnam following the magnitude 7 3 ms thrust earthquake of 1980 october 10 locations of 494 events are presented in this paper and provide an indication of the overall form of the aftershock distribution tests to establish location accuracy particularly depth reduce this set to 277 events which it is argued are well constrained p waves alone are used in this study as a consequence of a debate about the reliability of reading s phases from the reduced set of 277 events 81 events provide well constrained focal mechanisms the locations are presented in the form of maps and cross sections and discussed in relation to information already derived from field mapping of surface breaks and teleseismic studies of the waveforms of the main event the zone of surface faulting including secondary normal faulting extended for 35 km but the aftershock distribution extends for twice this distance along the part of the fault which experienced substantial displacement in the main shock the fault plane itself appears to be devoid of aftershocks although many lie in the footwall beneath the fault at junctions between segments of thrust faulting strike slip motion occurs this is apparent in the aftershock focal mechanisms and in the surface ruptures in one place the large number of aftershocks in the north east area appears to be due to the reactivation of a fan like system of smaller reverse faults associated with surface folding activity at the south west end is considerably less than that in the north east and is not obviously associated with recognizable geological or morphological features

the intersection of a pressurized crack with a joint a model is described for considering the partial slip that occurs when a pressurized crack intersects a joint to which it is perpendicular the crack is assumed not to penetrate into the undamaged material rather opening of the crack occurs at the juncture through interfacial slip within the interfacial slip region the resistance to slip is accounted for by prescribing the shear stress there results are obtained as the hydraulic loading in the crack is increased and the subsequent crack growth is investigated it is found that for a prescribed critical value of stress intensity factor the crack length remains fixed until a certain value of pressure is attained above this value the crack length can increase with increased pressure

stress history during propagation of a lateral fold tip and implications for the mechanics of fold thrust belts abstract this paper evaluates the hypothesis of lateral propagation of fold tip lines by comparing paleostress data from the lateral tip of a natural fold with a theoretical stress history at a moving screw dislocation the fold is an asymmetric kink fold exposed in ogden canyon utah where mapping revealed that a cylindrical anticline syncline pair changes along strike into a noncylindrical termination quartz deformation lamellae data from this fold indicate that the stress history in the fold tip was relatively simple with a general pattern of layer parallel compression perpendicular to the fold axis and layer parallel extension subparallel to the fold hinge line in contrast data from the cylindrical part of the fold are complex regardless of the position within the fold the latter is significant because although the symmetry of the cylindrical fold implies a plane strain deformation the paleostress data indicate that the strains were actually three dimensional an observation that is easily explained if the fold propagated laterally along strike during fold growth to test this hypothesis we consider a simple stress model where the non cylindrical fold tip is treated as a moving screw dislocation we conclude that although a broad range of models are allowable this simple model can account for most of the complexities of the data thus we conclude that the fold has propagated laterally during its growth recent studies of two fold related earthquake series the 1980 el asnam earthquake and the 1983 coalinga sequence lend support to models that call on lateral propagation of fault related folds thus these active fold thrust systems as well as our study of an ancient system are consistent with the concept that folding is a three dimensional process rather than a simple plane strain deformation clearly further word is needed to thoroughly test the fold propagation models nonetheless the recognition of lateral propagation of folds is important because it supports elliot s macroscopic creep concept for development of fold thrust belts where propagation of fracture tip lines is a least work process analogous to dislocation creep in crystals

coseismic elastic models of folds above blind thrusts in the betic cordilleras spain and evaluation of seismic hazard abstract although it is generally considered that near surface earthquakes result from movements along faults that cut through the surface several recent large earthquakes have been partly attributed to blind thrusts movements along blind thrusts lead to the formation of surface folds which are highly dependent upon fault geometry at depth and often not considered in seismic hazard evaluation several authors have studied the relationship between surface folding and thrusting for geological situations in which fault geometries are quite simple however active fault geometries can be quite complex e g segmented thrust faults associated with strike slip faults the aim of this contribution is to reconstruct the fault kinematics at depth for a relatively complex geological structure located in the eastern betic cordilleras orihuela guardamar torrevieja region using the patterns of kilometre scale folds observed in the field in order to model surface deformation the assumption is made that surface km scale folds have been created by coseismic deformation associated with movement along blind thrusts by means of a coseismic deformation model movements at depth have been calculated for three possible hypotheses hypothesis 1 assumes that each superficial fold is created by an independent fault hypotheses 2 and 3 assume that a sequence of two superficial folds can be created by movement along a single fault displaying a flat and ramp geometry in hypothesis 2 the flat is a superficial decollement level between the sedimentary cover and the betic basement in hypothesis 3 it is a deeper decollement level within the betic basement knowing the approximate age of surface deformation rough estimates of fault slip rates and recurrence periods for two possible earthquake magnitudes 7 ms and 6 7 ms have been made from calculated dislocations at depth slip rates and recurrence periods for flat and ramp fault geometries are in the range of 0 75 1 mm yr and 1000 2000 yr respectively these values are close to those calculated by direct methods in similar seismotectonic contexts

constitutive relations for fault slip and earthquake instabilities constitutive relations for fault slip are described and adopted as a basis for analyzing slip motion and its instability in the form of earthquakes on crustal faults the constitutive relations discussed include simple rate independent slip weakening models in which shear strength degrades with ongoing slip to a residual frictional strength and also more realistic but as yet less extensively applied slip rate and surface state dependent relations for the latter the state of the surface is characterized by one or more variables that evolve with ongoing slip seeking values consistent with the current slip rate models of crustal faults range from simple single degree of freedom spring slider systems to more complex continuous systems that incorporate nonuniform slip and locked patches on faults of depth dependent constitutive properties within elastic lithospheric plates that may be coupled to a viscoelastic asthenosphere

new long term mass balance series for the swiss alps in this study we present 19 new or re analysed series of glacier wide seasonal mass balance for the swiss alps based on direct measurements the records partly start around 1920 and continue until today previously unpublished and unevaluated observations of point winter and annual balance are compiled from various sources and archives these highly valuable datasets have not yet been consistently evaluated and were thus unavailable to the scientific community using distributed modelling for spatial interpolation and extrapolation and homogenization of the point measurements we infer continuous series of area averaged mass balance the results are validated against independent decadal ice volume changes from photogrammetric surveys six of the new seasonal series cover 60 years and more and add a substantial amount of information on the variations of regional glacier mass change this will strengthen the worldwide collection of glacier monitoring data especially for the data sparse period before the 1980s we compare our results to existing long term series and present an updated assessment of mass balance variability and glacier sensitivity throughout the european alps

karst conduit hydro gradient nonlinear variation feature study case study of zhaidi karst underground river through the analysis of monitoring data with a time interval of 10 min during the rainy season of 2012 for three points of g37 zk8 and zk7 which are located on the main conduit of zhaidi karst underground river system the variation features of water level and hydraulic gradient are studied and the relations are established between gradient and water level or amplitude 1 it is first discovered that there are different function relations such as linear parabola and inverse parabola between the g37 s water level and the hydraulic gradients of different conduit part 2 the peak delay times for water level curves are 50 min and the maximum conducting speed of water press is faster than 13 020 m h 3 the upstream and downstream karst conduits have corresponding enlarging and shrinking amplitude function by the coefficients of 1 899 km and 0 125 km 4 the gradient i variation is still linear to the level difference h made by nine rainstorms the conclusion and the methods of this paper have significance on the study of the regulation and storage capacity and groundwater resources evaluation of karst underground river system

fold geometry at sheep mountain anticline wyoming constructed using airborne laser swath mapping data outcrop scale geologic mapping and numerical interpolation 1 constraints available at the earth s surface on the geometry of geologic folds often are discontinuous consisting of scattered bedding surface outcrops representing the position and orientation of different stratigraphic surfaces for this reason characterization of fold geometry from surface data by methods such as sequential balanced cross sections remains a subjective and interpretive process we present a new method for modeling the geometry of kilometer scale folds using dense precise topographic data available from airborne laser swath mapping alsm outcrop scale geologic mapping and a reproducible numerical interpolation method that is free of subjectivity geologic mapping at sheep mountain anticline wyoming enables the association of hundreds of thousands of alsm data points with 14 weathering resistant bedding surfaces from seven different stratigraphic units ranging in age from mississippian to cretaceous these data supplemented by several hundred strike and dip measurements constraining local orientation of folded strata are projected to the stratigraphic position of a single surface and used as constraint for a smoothed minimum curvature spline interpolation to generate a continuous representation of fold geometry both strengths and weaknesses of the new method are discussed in the context of comparison between the new surface model and an existing model constructed by traditional methods

displacement distance methods in the analysis of fold thrust structures and linked fault systems a new method for analysing the internal strain in thrust sheets is described the displacement distance diagram can be used to quantify the relative shortening or relative stretch between the hangingwall and footwall beds of a thrust and is a useful way of analysing commonly occurring fold thrust structures the stretch is a function of the relative rates of thrust propagation and thrust slip the cumulative displacement distance diagram described here can be used to calculate the absolute shortening or extension when this is accommodated above a single decollement in a linked fault system this method offers a useful way of analysing duplex structures and large scale foreland thrust zones as well as extensional fault systems and can be used as an alternative to or in conjunction with balanced cross sections both methods can be used to quantify the variation in shortening above a single detachment zone this variation may be mechanically significant reflecting lithological control on thrust or normal fault growth

poroelastic stressing and induced seismicity near the lacq gas field southwestern france o hundreds of shallow small to moderate earthquakes have occurred near the lacq deep gas field in southwestern france since 1969 these earthquakes are clearly separated from tectonic seismicity occurring in the pyrenees 25 km to the southwest the induced seismicity began when the reservoir pressure had declined by 30 mpa repeated levehng over the field shows localized subsidence reaching a maximum of 60 mm in 1989 segall 1989 suggested that poroelastic stressing associated with volumetric contraction of the reservoir rocks is responsible for induced seismicity associated with fluid extraction to test this model we compare the observed subsidence and hypocentral distributions with the predicted displacement and stress fields we find that the relationship between average reservoir pressure drop and subsidence is remarkably linear lending support to the linear poroelastic model displacements and stresses are computed based on a priori knowledge of the reservoir geometry materim properties and reservoir pressure changes the computed vertical displacements are found to be in excellent agreement with the subsidence observed from leveling stress perturbations accompanying gas extraction computed using the same parameters are found to be 0 2 mpa or less changes in coulomb failure stress are computed assuming that shp occurs on optimally oriented planes the predicted failure zones correlate very well with the spatial distribution of earthquakes if the perturbing stresses are small in comparison to the ambient regional deviatoric stresses and if the minimum regional compresslye stress axis is vertical accurate determination of focal mechanisms of the induced events would allow a more rigorous test of the poroelastic model and could lead to important inferences about the crustal stress state

inverting for slip on three dimensional fault surfaces using angular dislocations the increasing quality of geodetic data synthetic aperture radar interferometry insar dense global positioning system gps arrays now available to geophysicists and geologists are not fully exploited in slip inversion procedures most common methods of inversion use rectangular dislocation segments to model fault ruptures and therefore oversimplify fault geometries these geometric simplifications can lead to inconsistencies when inverting for slip on earthquake faults and they preclude a more complete understanding of the role of fault geometry in the earthquake process we have developed a new three dimensional slip inversion method based on the analytical solution for an angular dislocation in a linear elastic homogeneous isotropic half space the approach uses the boundary element code poly3d that employs a set of planar triangular elements of constant displacement discontinuity to model fault surfaces the use of triangulated surfaces as discontinuities permits one to construct fault models that better approximate curved three dimensional surfaces bounded by curved tiplines shapes that commonly are imaged by three dimensional reflection seismic data and inferred from relocated aftershock data we demonstrate the method s ability to model three dimensional rupture geometries by inverting for slip associated with the 1999 hector mine earthquake the resulting model avoids displacement anomalies associated with the overlapping rectangular dislocations used in previous models improving the fit to the geodetic data by 32 and honors the observed surface ruptures thereby allowing more direct comparisons between geologic and geodetic data on slip distributions online material hector mine input files and file format description

why blind thrust faults do not propagate to the earth s surface numerical modeling of coseismic deformation associated with thrust related anticlines high fault tip stress concentrations are associated with coseismic slip on blind thrust faults and suggest that these structures should readily propagate to the earth s surface seismic profiles of blind thrust related earthquakes reveal diffuse zones of aftershocks surrounding the fault tip which are attributed to inelastic deformation such as flexural slip or extensional fracturing the complex interaction between blind thrust faults and secondary structures may control the evolution of blind thrust systems the influence of bedding plane slip on fault propagation is simulated with numerical models using the boundary element method we use two parameters to estimate the tendency for thrust fault propagation 1 the mode ii stress intensity factor and 2 the maximum coulomb stress near the fault tip calculations from both analyses suggest that shallow thrust faults may exhibit an increased tendency to propagate as a result of interaction with the earth s surface and slip along bedding planes above the fault tip and a decreased tendency to propagate due to slip along bedding planes at or below the fault tip our results demonstrate that the magnitude and style of inelastic deformation in active fault systems control fault propagation

the growth of geological structures by repeated earthquakes 1 conceptual framework in many places earthquakes with similar characteristics have been shown to recur if this is common then relatively small deformations associated with individual earthquake cycles should accumulate over time to create geological structures following this paradigm we show that existing models developed to describe leveling line changes associated with the seismic cycle can be adapted to explain geological features associated with a fault in these models an elastic layer containing the fault overlies a viscous half space with a different density fault motion associated with an earthquake results in immediate deformation followed by a long period of readjustment as stresses relax in the viscous layer and isostatic equilibrium is restored deformation is also caused as a result of the loading and unloading due to sediment deposition and erosion in this paper the parameters that control the growth of dip slip structures are identified we find that the flexural rigidity of the crust or the apparent elastic thickness provides the main control of the width of a structure the loading due to erosion and deposition of sediment determines the ratio of uplift to subsidence between the two sides of the fault the flexure due to sediment load is much more important in this respect than whether the fault is normal or reverse in character we find that in general real structures are associated with apparent elastic thicknesses of 4 km or less and thus with very low flexural rigidities

last millennium northern hemisphere summer temperatures from tree rings part i the long term context abstract large scale millennial length northern hemisphere nh temperature reconstructions have been progressively improved over the last 20 years as new datasets have been developed this paper and its companion part ii anchukaitis et al in prep details the latest tree ring tr based nh land air temperature reconstruction from a temporal and spatial perspective this work is the first product of a consortium called n trend n orthern hemisphere tre e ring n etwork d evelopment which brings together dendroclimatologists to identify a collective strategy for improving large scale summer temperature reconstructions the new reconstruction n trend2015 utilises 54 records a significant expansion compared with previous tr studies and yields an improved reconstruction with stronger statistical calibration metrics n trend2015 is relatively insensitive to the compositing method and spatial weighting used and validation metrics indicate that the new record portrays reasonable coherence with large scale summer temperatures and is robust at all time scales from 918 to 2004 where at least 3 tr records exist from each major continental mass n trend2015 indicates a longer and warmer medieval period 900 1170 than portrayed by previous tr nh reconstructions and by the cmip5 model ensemble but with better overall agreement between records for the last 600 years future dendroclimatic projects should focus on developing new long records from data sparse regions such as north america and eastern eurasia as well as ensuring the measurement of parameters related to latewood density to complement ring width records which can improve local based calibration substantially

flexural slip folding along the eastern elmore ranch fault in the superstition hills earthquake sequence of november 1987 co seismic flexural slip folding of a small anticline along the eastern elmore ranch fault associated with the superstition hills earthquake sequence demonstrates that variations in left lateral slip can be explained locally by folding surface rupture on the eastern branch of the elmore ranch fault was greatest to the northeast of the fold but decreased to zero across the southern limb a kilometer long surface slip gap exists just southwest of the fold being bounded on the northeast with 75 mm of slip and to the southwest with about 60 mm of slip lateral slip continues southwesterly to the faults intersection with the superstition hills fault the gentle to openly folded moderately plunging upright asymmetric anticline experienced left lateral slip on the northern limb and right oblique slip on the southern limb with maximum documented lateral slip along bedding planes of 10 mm slip values were greatest on the limbs and decreased to zero at the fold hinge which is consistent with the flexural slip folding process secondary left lateral faults ruptured both limbs of the anticline and bedding plane slip was not observed hingeward of these faults these data suggest that left lateral strain associated with seismogenic fault rupture was continuous in the subsurface but was accommodated locally by folding at the surface

latest pleistocene and holocene glacier variations in the european alps in the alps climatic conditions reflected in glacier and rock glacier activity in the earliest holocene show a strong affinity to conditions in the latest pleistocene younger dryas glacier advances in the alps related to younger dryas cooling led to the deposition of egesen stadial moraines egesen stadial moraines can be divided into three or in some cases even more phases sub stadials moraines of the earliest and most extended advance the egesen maximum stabilized at 12 2 1 0 ka based on 10be exposure dating at the schonferwall tyrol austria and the julier pass outer moraine switzerland final stabilization of moraines at the end of the egesen stadial was at 11 3 0 9 ka as shown by 10be data from four sites across the alps from west to east the sites are piano del praiet northwestern italy grosser aletschgletscher central switzerland julier pass inner moraine eastern switzerland and val viola northeastern italy there is excellent agreement of the 10be ages from the four sites in the earliest holocene glaciers in the northernmost mountain ranges advanced at around 10 8 1 1 ka as shown by 10be data from the kartell site northern tyrol austria in more sheltered drier regions rock glacier activity dominated as shown for example at julier pass and larstig valley tyrol austria new 10be dates presented here for two rock glaciers in larstig valley indicate final stabilization no later than 10 5 0 8 ka based on this data we conclude the earliest holocene between 11 6 and about 10 5 ka was still strongly affected by the cold climatic conditions of the younger dryas and the preboreal oscillation with the intervening warming phase having had the effect of rapid downwasting of egesen glaciers at or slightly before 10 5 ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate between about 10 5 ka and 3 3 ka conditions in the alps were not conducive to significant glacier expansion except possibly during rare brief intervals past tree line data from kaunertal tyrol austria in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the swiss and austrian alps points to long periods during the holocene when glaciers were smaller than they were during the late 20th century equilibrium line altitudes ela were about 200 m higher than they are today and about 300 m higher in comparison to little ice age lia elas the larstig rock glacier site we dated with 10be is the type area for a postulated mid holocene cold period called the larstig oscillation presumed age about 7 0 ka our data point to final stabilization of those rock glaciers in the earliest holocene and not in the middle holocene the combined data indicate there was no time window in the middle holocene long enough for rock glaciers of the size and at the elevation of the larstig site to have formed during the short infrequent cold oscillations between 10 5 and 3 3 ka small glaciers less than several km2 may have advanced to close to their lia dimensions overall the cold periods were just too short for large glaciers to advance after 3 3 ka climate conditions became generally colder and warm periods were brief and less frequent large glaciers for example grosser aletschgletscher advanced markedly at 3 0 2 6 ka around 600 ad and during the lia glaciers in the alps attained their lia maximum extents in the 14th 17th and 19th centuries with most reaching their greatest lia extent in the final 1850 1860 ad advance

little ice age proxy glacier mass balance records reconstructed from tree rings in the mt waddington area british columbia coast mountains canada the intention of this research was to explore whether dendroclimatological relationships could be used to reconstruct long term proxy records of little ice age glacier mass balance changes in the southern coast mountains of british columbia tree ring width chronologies from the mt waddington area were used in concert with historical glacier records to construct models spanning the past 450 years the approach was to build models that were based on derived relationships between tree ring growth and glacier mass balance 1 warmer temperatures in the summer positively influence tree growth but are detrimental to glacier health 2 colder temperatures during the winter and deeper snowpack have a negative impact on tree growth whereas they are related to greater accumulation on the glacier during the winter season stepwise regression analyses were applied to tree ring chronologies to predict glacier mass balance at local and regional scales the models of net annual balance for the region regional data set show that periods of positive mass balance occurred in the ad 1750s 1820s to 1830s and 1970s peaks of winter balance correspond closely to these periods showing a sharp drop in winter mass balance towards the end of the nineteenth century wavelet analyses suggest that glacial mass balance regimes in the region respond synchronously to pacific ocean circulation systems such as the el nino southern oscillation and the pacific decadal oscillation

progress in isotope dendroclimatology numerous studies have demonstrated the potential of stableisotopes in tree rings for quantitative terrestrial palaeoclimaticreconstruction ramesh et al 1986 heaton 1999 switsur andwaterhouse 1998 mccarroll and loader 2004 2005 but the earlywidespread application of isotope dendroclimatology has been hin dered by laborious technical procedures that have until recently prevented wider application of this technique and severely con strained progress developments in mass spectrometry preston andowens 1985 barrie et al 1995 filot et al 2006 leuenberger andfilot 2007 and sample preparation techniques leavitt and danzer 1993 loader et al 1997 brendel et al 2000 schulze et al 2004 rinneet al 2005 gaudinskiet al 2005 haverevolutionisedthe eldand enabled development of stable isotope chronologies with aheightened degree of replication gagen et al 2007 and temporalrange treydteetal 2006 thatwaspreviouslynotpracticalandrarelyobserved in any other proxy record outside of dendroclimatology these and associated advances are re ected in the dramatic increasein the number and diversity of isotope tree ring papers presented atrecent international conferences the thirty isotope tree ring paperspresented at the recent 7th international conference on dendrochro nology beijing 11 17june2006 aretrulyinstarkcontrasttothetwodelivered at the 2nd international workshop on global dendroclima tology 1980 long 1982 wigley 1982 in this volume the progressand advances in isotope dendroclimatology are critically reviewed inthe context of the initial work and aspirations of the early pioneers inthis eld and new directions and methodologies are explored dendroclimatology is an established eld of palaeoclimatologyused in its scienti c form since the early 20th century however theapplication of stable isotope techniques to dendroclimatology is morerecent conceptually the seed was planted when urey 1947 statedthat it seems probable that plant carbon compounds synthesised atdifferent temperatures may contain varying amounts of c

elucidating the geometry of the active shanchiao fault in the taipei metropolis northern taiwan and the reactivation relationship with preexisting orogen structures the shanchiao fault is an active normal fault with documented paleoearthquakes in the taipei metropolis taiwan while posing direct seismic threat on the multimillion population its crustal scale fault plane configuration has not been constrained this study presents the first attempt to resolve the fault plane dip changes of the shanchiao fault within the upper crust by forward modeling late quaternary deformation tectonic subsidence over the last 23 ka is estimated from vertical displacements of a rapidly formed alluvial fan horizon deformed into a dramatic rollover monocline a 2 d profile across the shanchiao fault is chosen for elastic half space dislocation modeling and the results suggest that the fault is listric in the shallow crust with an abrupt change from subvertical ramp 85 75 to near horizontal flat 10 15 at 3 4 km depth consistent with an origin from the inversion of an orogen related thrust detachment given the presence of rift related fabrics in the underthrust chinese continental margin basement beneath the taiwanese orogenic wedge listric ramp flat ramp models with a second deeper bend to 60 dip are also tested reasonable fits with the geological observations are produced when the lower ramp is located at greater than 8 km depth which correlates with the hypocentral location of a moderate earthquake in 2004 joint reactivation of preexisting thrust and rift faults by the shanchiao fault is therefore plausible with implications for seismic hazard in the taipei area

variable fault tip propagation rates affected by near surface lithology and implications for fault displacement hazard assessment abstract the fabric of reverse fault zones close to the surface is usually partitioned in between a narrow discrete rupture zone and a more distributed one where folding is predominant this makes quite challenging the adoption of proper setbacks in surface rupture hazard studies for critical facilities or microzoning some of the parameters controlling fault zone fabric are related to mechanics of near surface geology lithology overburden thickness cohesion and water content whose interaction is complex and only partially understood nevertheless these can be seldom measured or derived kinematic models conversely express such an interaction of complex variables as simple synthetic parameters such as the amount of upward propagation of the fault tip for unit of slip usually referred to as the p s ratio propagation on slip here we discuss results on the trishear kinematic inverse modeling of a contractional fault propagation fold at monte netto hill capriano del colle n italy observing a two stage fault and fold growth evolution marked by a significant shift in the p s parameter at this site exceptional sequence of exposures due to ca 10 years of quarry excavations allowed to obtain a series of cross sections across the fault zone we use this detailed high resolution example as a natural analogue for more general large scale surface ruptures involving a thick alluvial cover a very common setting for the siting of critical facilities during the early stage of displacement the fault cut through clast supported fluvial gravels with a high propagation rate p s 7 and a discrete rupture width then during the latest movements of the thrust fault tip propagation slowed down to p s 2 9 as the fault started cutting through several stacked bodies of clays and silty clays pedogenized aeolian silts and overbank deposits causing a pronounced folding of the layers over a wider deformation zone these results strongly suggest that lithological changes in the underlying shallow stratigraphy common in an alluvial plain depositional setting would significantly affect the potential for surface faulting across the same tectonic structure with relevant implications in the fault displacement hazard assessment

evaluation of a hydrodynamic threshold in the zhaidi karst aquifer guangxi province china understanding how the discharge rate and the hydraulic gradient of a karst aquifer varies in response to rainfall events is important for the efficient management of water resources in these aquifers the relationship between discharge and hydraulic gradient is related to aquifer properties such as the physical characteristics of the karstic matrix hydraulic conductivity and the extent to which water is exchanged between conduits and the matrix in this study discharge and hydraulic gradient data were monitored at 4 h intervals for 476 continuous days in the zhaidi karst aquifer located in guilin guangxi province china these data showed that the relationship between flow rate and hydraulic gradient in the aquifer became increasing non linear with increasing flow rates after analyzing the time series data a hydrodynamic threshold between quickflow and baseflow conditions was found to take place at a discharge rate of 0 80 m3 s the linear law and nonlinear equations were obtained between discharge and hydraulic gradient which reflected the flow mechanism of groundwater flow in this karst aquifer

slip patterns and earthquake populations along different classes of faults in elastic solids numerical simulations of slip instabilities on a vertical strike slip fault in an elastic half space are performed for various models belonging to two different categories the first category consists of inherently discrete cellular fault models such are used to represent fault systems made of segments modeled by numerical cells that can fail independently of one another their quasi independence is assumed to provide an approximate representation of strong fault heterogeneity due to geometric or material property disorder that can arrest ruptures at segment boundaries the second category consists of models having a well defined continuum limit these involve a fault governed by rate and state dependent friction and are used to evaluate what types of property heterogeneity could lead to the quasi independent behavior of neighboring fault segments assumed in the first category the cases examined include models of a cellular fault subjected to various complex spatial distributions of static to kinetic strength drops and models incorporating rate and state dependent friction subjected to various spatial distributions of effective stress normal stress minus pore pressure the results indicate that gradual effective stress variations do not provide a sufficient mechanism for the generation of observed seismic response strong and abrupt fault heterogeneity as envisioned in the inherently discrete category is required for the generation of complex slip patterns and a wide spectrum of event sizes strong fault heterogeneity also facilitates the generation of rough rupture fronts capable of radiating high frequency seismic waves the large earthquakes in both categories of models occur on a quasi periodic basis the degree of periodicity increases with event size and decreases with model complexity however in all discrete segmented cases the models generate nonrepeating sequences of earthquakes and the nature of the large quasi periodic events is highly variable the results indicate that expectations for regular sequences of earthquakes and or simple repetitive precursory slip patterns are unrealistic the frequency size fs statistics of the small failure episodes simulated by the cellular fault models are approximately self similar with b 1 2 and ba 1 where b and ba are b values based on magnitude and rupture area respectively for failure episodes larger than a critical size however the simulated statistics are strongly enhanced with respect to self similar distributions defined by the small events this is due to the fact that the stress concentrated at the edge of a rupture expanding in an elastic solid grows with the rupture size when the fault properties e g geometric irregularities are characterized by a narrow range of size scales the scaling of stress concentrations with the size of the failure zone creates a critical rupture area terminating the self similar earthquake statistics in such systems events reaching the critical size become on the average unstoppable and they continue to grow to a size limited by a characteristic model dimension when however the system is characterized by a broad spectrum of size scales the above phenomena are suppressed and the range of apparent self similar fs statistics is broad and characterized by average b and ba values of about 1 the simulations indicate that power law extrapolations of low magnitude seismicity will often underestimate the rate of occurrence of moderate and large earthquakes the models establish connections between features of fs statistics of earthquakes range of self similar regimes local maxima and structural properties of faults dominant size scales of heterogeneities dimensions of coherent brittle zones the results suggest that observed fs statistics can be used to obtain information on crustal thickness and fault zone structure

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

inferring fault characteristics using fold geometry constrained by airborne laser swath mapping at raplee ridge utah 1 we used airborne laser swath mapping alsm data to define the geometry of strata in raplee ridge in southeastern utah that were likely deformed by slip on an underlying fault the fold geometry was used to infer the fault geometry and loading responsible for the folding using the boundary element model poly3d monte carlo markov chain mcmc methods created probability density functions pdfs that reveal the most likely fault geometry and loading conditions and their uncertainties despite the restrictive assumptions of poly3d in which body deformations occur from slip on displacement discontinuities in a homogeneous linear elastic half space the strata deflections are matched remarkably well and the resulting inferences of fault geometry and stress field appear reasonable we propose that similar methods may be used with models that include more complicated rheologies and heterogeneous and anisotropic material properties to estimate fault geometries and loading conditions where only deflection of strata record these parameters

large scale quaternary detachments in ventura basin southern california the ventura basin is an east north east trending trough in the california transverse ranges which records major quaternary detachment faulting at three levels the earliest thrusting occurred along weak siltstone interbeds in a sequence dominated by competent basin plain turbidite sandstone because sedimentation continued during thrusting the age rate and direction of thrusting can be worked out faulting began 1 3 m y ago and ceased 0 65 m y ago with a maximum slip rate of 2 8 mm yr to the southeast the fault set moved up a 45 ramp and ended as a blind thrust the ramp had topographic expression on the seafloor diverting turbidites around the ramp and preserving ash beds along with other hemipelagic sediments on its crest following the end of deposition 0 2 m y ago the competent basin plain turbidites underwent flexural slip folding over an incompetent miocene sequence dominated by shale underlying competent paleogene strata were not folded the south flank of the ventura avenue anticline tilted at 3 4 rad yr the anticlinal crest rose at a rate of 15 16 mm yr decelerating to 4 3 5 2 mm yr and the anticline and an adjacent syncline shortened at a rate of 20 mm yr the high rate of folding in the ventura avenue oil field resulted in overpressured sandstone reservoirs and oil water interfaces which have not had time to reach gravity equilibrium the red mountain san cayetano and santa susana faults mark the surface expression of a seismically active midcrustal detachment which produced convergence across the ventura basin at rates as high as 23 mm yr total convergence across the eastern san cayetano fault near fillmore is 11 600 2000 m in the last million years

structural geometry of raplee ridge monocline and thrust fault imaged using inverse boundary element modeling and alsm data abstract we model the raplee ridge monocline in southwest utah where airborne laser swath mapping alsm topographic data define the geometry of exposed marker layers within this fold the spatial extent of five surfaces were mapped using the alsm data elevations were extracted from the topography and points on these surfaces were used to infer the underlying fault geometry and remote strain conditions first we compare elevations extracted from the alsm data to the publicly available national elevation dataset 10 m dem digital elevation model ned 10 and 30 m dem ned 30 while the spatial resolution of the ned datasets was too coarse to locate the surfaces accurately the elevations extracted at points spaced 50 m apart from each mapped surface yield similar values to the alsm data next we used a boundary element model bem to infer the geometry of the underlying fault and the remote strain tensor that is most consistent with the deformation recorded by strata exposed within the fold using a bayesian sampling method we assess the uncertainties within and covariation between the fault geometric parameters and remote strain tensor inferred using the model we apply these methods to the raplee ridge monocline and find that the resolution and precision of the alsm data are unnecessary for inferring the fault geometry and remote strain tensor using our approach however the alsm data were necessary for the mapping of the spatial distribution of surface outcrops our models considered two scenarios one in which fault geometry and remote strains were inferred using a single deformed stratum and another in which all mapped strata were used in the inversion modeled elevations match those observed to within a root mean squared error of 16 18 m and show little bias with position along the fold both single and multilayer inversions image a fault that is broadly constrained to be 4 5 14 km in down dip height 13 30 km in along strike width with a tip line 2 0 9 5 km below the surface at the time of deformation poisson s ratio was not well resolved by the inversion the idealized elastic model is oversimplified when considering the complicated layered nature of this fold however it provides a good fit to the observations thus comparable surface displacements may be produced with a variety of rheological models so independent constraints on factors such as the fault geometry may be required to ascertain the appropriate rheology of the fold

insights into fold growth using fold related joint patterns and mechanical stratigraphy despite how common folds are as structural features along strike fold propagation has proven elusive to document however if a fold grows laterally along its axis early formed fold related joints may differ significantly in orientation from joints that form later in this paper we integrate mechanical stratigraphy with joint pattern analysis to determine relative timing of jointing additionally we demonstrate that joint patterns can be related to stresses on both the top and bottom of the bed during flexure we present joint data from eight sedimentary beds on the fold terminus at sheep mountain anticline wyoming usa the joint patterns around the terminus show two distinct patterns joints in six of the beds show a radial pattern around the terminus whereas joint patterns in the two remaining beds differ from proximal units despite being in the same structural position fracture resistance calculations confirm that the beds with mis oriented fractures are less resistant to fracturing than other units in the study and therefore would have fractured earlier in fold growth history we present a plate bending model that illustrates potential joint patterns around a plunging fold nose from stresses along both the top and bottom of the bed the joint strike predictions for the area in front of the inflection line on the fold nose match the orientations in our less resistant beds which are now positioned behind the inflection line suggesting that the fold grew laterally the combined analysis of fracture pattern and mechanical stratigraphy provides a new way to investigate fold evolution

effect of scaling and regression on reconstructed temperature amplitude for the past millennium 1 examination of large scale millennial long temperature reconstructions reveals a wide range of datasets and methods used for calibration proxy time series are commonly calibrated against overlapping instrumental records representing different seasons northern hemisphere latitudinal bands and including or excluding sea surface temperature data methodological differences include using scaling or regression the calibration time period and smoothing data before calibration we find that these various approaches alone can result in differences in the reconstructed temperature amplitude of about 0 5 c this magnitude is equivalent to the mean annual temperature change for the northern hemisphere reported in the last ipcc report for the 1000 1998 period a more precise assessment of absolute reconstructed temperature amplitudes is necessary to help quantify the relative influences of forcing mechanisms in climate models

bayesian inference of plastosphere viscosities near the kunlun fault northern tibet 1 flow of the mid crust in the tibetan plateau may strongly influence the patterns of deformation and topography within this area this flow requires the lower crust to have low viscosity and so quantifying this viscosity may be used to test the idea of channel flow an application of bayesian methods to geologic and geodetic data from north central tibet yields lower crustal viscosities assumed newtonian of 1 1019 pa s and 2 1021 pa s 95 bounds the lower bound is larger than the value of 1016 1018 pa s required by models of flow of the lower crust of tibet unless the entire lower crust participates in channel flow

summer temperature variations in the european alps a d 755 2004 abstract annually resolved summer temperatures for the european alps are described the reconstruction covers the a d 755 2004 period and is based on 180 recent and historic larch larix decidua mill density series the regional curve standardization method was applied to preserve interannual to multicentennial variations in this high elevation proxy dataset instrumental measurements from high low elevation grid boxes back to 1818 1760 reveal strongest growth response to current year june september mean temperatures the reconstruction correlates at 0 7 with high elevation temperatures back to 1818 with a greater signal in the higher frequency domain r 0 8 low elevation instrumental data back to 1760 agree with the reconstruction s interannual variation although a decoupling between warmer instrumental and cooler proxy data before 1840 is noted this offset is larger than during any period of overlap with more recent high elevation instrumental data even though the proxy time series

a 1052 year tree ring proxy for alpine summer temperatures a june august alpine temperature proxy series is developed back to ad 951 using 1 527 ring width measurements from living trees and relict wood the reconstruction is composed of larch data from four alpine valleys in switzerland and pine data from the western austrian alps these regions are situated in high elevation alpine environments where a spatially homogenous summer temperature signal exists in an attempt to capture the full frequency range of summer temperatures over the past millennium from inter annual to multi centennial scales the regional curve standardization technique is applied to the ring width measurements correlations of 0 65 and 0 86 after decadal smoothing with high elevation meteorological stations since 1864 indicate an optimal response of the rcs chronology to june august mean temperatures the proxy record reveals warm conditions from before ad 1000 into the thirteenth century followed by a prolonged cool period reaching minimum values in the 1820s and a warming trend into the twentieth century this latter trend and the higher frequency variations compare well with the actual high elevation temperature record the new central alpine proxy suggests that summer temperatures during the last decade are unprecedented over the past millennium it also reveals significant similarities at inter decadal to multi centennial frequencies with large scale temperature reconstructions however deviating during certain periods from h h lamb s european north atlantic temperature history

integrated monitoring of mountain glaciers as key indicators of global climate change the european alps the internationally recommended multi level strategy for monitoring mountain glaciers is illustrated using the example of the european alps where especially dense information has been available through historical times this strategy combines in situ measurements mass balance length change with remote sensing inventories and numerical modelling it helps to bridge the gap between detailed local process oriented studies and global coverage since the 1980s mass balances have become increasingly negative with values close to 1 m w e a 1 during the first 5 years of the 21st century the hot dry summer of 2003 alone caused a record mean loss of 2 45 m w e roughly 50 above the previous record loss in 1998 more than three times the average between 1980 and 2000 and an order of magnitude more than characteristic long term averages since the end of the little ice age and other extended periods of glacier shrinkage during the past 2000 years it can be estimated that glaciers in the european alps lost about half their total volume roughly 0 5 a 1 between 1850 and around 1975 another 25 or 1 a 1 of the remaining amount between 1975 and 2000 and an additional 10 15 or 2 3 a 1 in the first 5 years of this century

historically unprecedented global glacier decline in the early 21st century observations show that glaciers around the world are in retreat and losing mass internationally coordinated for over a century glacier monitoring activities provide an unprecedented dataset of glacier observations from ground air and space glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass balance data relating to the impact that glaciers exercise on global sea level fluctuations or on regional runoff in this study we provide an overview and analysis of the main observational datasets compiled by the world glacier monitoring service wgms the dataset on glacier front variations 42000 since 1600 delivers clear evidence that centennial glacier retreat is a global phenomenon intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the little ice age or holocene glaciological and geodetic observations 5200since 1850 show that the rates of early 21st century mass loss are without precedent on a global scale at least for the time period observed and probably also for recorded history as indicated also in reconstructions from written and illustrated documents this strong imbalance implies that glaciers in many regions will very likely suffer further ice loss even if climate remains stable

constraints on the strength of the upper crust from stress inversion of fault slip data the coefficient of friction of small faults in the field are estimated here by stress inversion of fault slip data the small faults that were measured in israel and the grand canyon arizona are considered as representing natural friction experiments the stresses associated with the faulting are determined by a stress inversion method which incorporates the coulomb failure criterion reches 1987 the coefficients of friction determined for 27 fault clusters in limestone sandstone and basalt range from 0 0 to 1 3 with mean value of 0 58 0 37 these values are in general agreement with the friction of 0 6 0 85 determined from laboratory experiments the magnitudes of the calculated principal stresses are compared with in situ stress measurements in similar tectonic environments

fennoscandia revisited a spatially improved tree ring reconstruction of summer temperatures for the last 900 years despite the spatially homogenous summer temperature pattern in fennoscandia there are large spreads among the many existing reconstructions resulting in an uncertainty in the timing and amplitude of past changes also there has been a general bias towards northernmost fennoscandia in an attempt to provide a more spatially coherent view of summer june august jja temperature variability within the last millennium we utilized seven density and three blue intensity scots pine pinus sylvestris l chronologies collected from the altitudinal scandinavian mountains and latitudinal northernmost part treeline to attain a jja temperature signal as strong as possible as well as preserving multicentury scale variability we used a new tree ring parameter where the earlywood information is removed from the maximum density and blue intensity and a modified signal free standardization method two skilful reconstructions for the period 1100 2006 ce were made one regional reconstruction based on an average of the chronologies and one field gridded reconstruction the new reconstructions were shown to have much improved spatial representations compared to those based on data from only northern sites thus making it more valid for the whole region an examination of some of the forcings of jja mean temperatures in the region shows an association with sea surface temperature over the eastern north atlantic but also the subpolar and subtropical gyres moreover using superposed epoch analysis a significant cooling in the year following a volcanic eruption was noted and for the largest explosive eruptions the effect could remain for up to 4 years this new improved reconstruction provides a mean to reinforce our understanding of forcings on summer temperatures in the north european sector