active flexural slip faulting a study from the pamir tian shan convergent zone nw china the flexural slip fault fsf a type of secondary fault generated by bed parallel slip occurs commonly and plays an important role in accommodating fold growth although the kinematics and mechanics of fsfs are well studied relatively few field observations or geometric models explore its geomorphic expression in the pamir tian shan convergent zone nw china suites of well preserved fsf scarps displace fluvial terraces in the mingyaole and wulagen folds integrating interpretations of google earth images detailed geologic and geomorphic mapping and differential gps measurements of terrace surfaces we summarize geomorphic features that typify these faults and create kinematic models of active flexural slip faulting our study indicates the following i fsf scarps commonly occur near synclinal hinges irrespective of whether a the dip direction of beds on either side of the hinge is unidirectional or in opposite directions b the hinge is migrating or fixed or c the hinge shape is narrow and angular or wide and curved ii active fsfs are likely to produce higher scarps on steeper beds whereas lower or no topographic scarps typify gentler beds iii tilt angles of the terrace surface displaced above fsfs progressively decrease farther away from the hinge with abrupt changes in slope coinciding with fsf scarps the changes in tilt angle and scarp height have a predictable geometric relationship iv active fsfs can accommodate a significant fraction of total slip and play a significant role in folding deformation v active fsfs may be used to assess seismic hazards associated with active folds and associated blind thrusts

geomorphic constraints on listric thrust faulting implications for active deformation in the mackenzie basin south island new zealand 1 deformed fluvial terraces preserved over active thrust related folds record the kinematics of folding as fault slip accumulates on the underlying thrust in the mackenzie basin of southern new zealand the kinematics revealed by folded fluvial terraces along the active ostler and irishman creek fault zones are inconsistent with traditional models for thrust related folding in which spatially uniform rock uplift typically occurs over planar fault ramps instead warped and tilted terraces in the mackenzie are characterized by broad continuous backlimbs and abrupt forelimbs and suggest folding through progressive limb rotation by relating this pattern of surface deformation to the underlying thrust with a newly developed simple geometric and kinematic model we interpret both faults as listric thrusts rooted at depth into gently dipping planar fault ramps constraints on the model from detailed topographic surveying of deformed terraces ground penetrating radar over active fault scarps and luminescence dating of terrace surfaces suggest slip rates for the ostler and irishman creek faults of 1 1 1 7 mm yr and 0 5 0 7 mm yr respectively the predicted depth of listric faulting for the ostler fault 0 7 0 2 0 1 km and the irishman creek fault 1 3 0 5 0 1 km generally agrees with geophysical estimates of basin depth in the mackenzie and suggests control of preexisting basin architecture on the geometry of active thrusting despite the potential effects of changes in fault curvature and hanging wall internal deformation the methodology presented here provides a simple tool for approximating the kinematics of surface deformation associated with slip along listric or curviplanar thrust faults

sequence stratigraphy depositional history and middle to late quaternary sea levels of the ventura shelf california abstract high resolution shallow seismic profiles from the ventura shelf reveal two contrasting structurally controlled styles of deposition on the northern shelf folded plio pleistocene strata comprising the south limb of the ventura avenue anticline are unconformably overlain by undeformed late quaternary strata in contrast a thicker section of undeformed prograding deltaic sequences preserved on the subsiding southern shelf contains a detailed record of at least five middle and late quaternary glacioeustatic sea level oscillations a transgressive surface at 140 m in upper pleistocene saugus deposits is overlain by transgressive and highstand systems tracts a shelf margin systems tract subsequently developed as the sea level lowered marking the end of saugus deposition thereafter over 50 m of post saugus upper pleistocene sediment accumulated during a period of smaller scale sea level oscillations followed by the development of a pair of marine terraces presently at 50 and 33 m and a large fluvial channel now buried at 113 m correlations of saugus and terrace marker horizons with the middle to late quaternary paleosea level curve suggest development of the saugus marker horizons during oxygen isotopic stages 7 5e and formation of the terraces during wisconsinan high sea levels maximum rates of vertical separation on the oak ridge and pitas point faults are estimated to be 0 13 and 0 30 m 1000 yr respectively

fold uplift and synkinematic stratal architectures in a region of active transtensional tectonics and volcanism eastern tyrrhenian sea the detailed stratigraphic analysis of synkinematic stratal architectures permits the calculation of fold uplift rates and the reconstruction of fold kinematics this approach was applied to active folds in the bay of pozzuoli eastern tyrrhenian sea this area features late quaternary volcanism shallow magmatic intrusions and transtensional tectonics seismostratigraphic analysis of synkinematic strata is constrained by a physical correlation to an already established stratigraphic succession in the neighboring campi flegrei and by tephra layers in a gravity core located in pozzuoli bay a stratigraphic resolution in thousands of years was established structural and stratigraphic analyses yield quantitative data on the timing of fold inception kinematics and the amount and rates of uplift the folds extend over 2 km and display a curved axial pattern and wedge shaped packages of synkinematic strata the rate of fold uplift ranges from 1 to 20 mm yr the structures feature limb rotation kinematics and decreasing uplift rates the uplift rates and geometry of the pozzuoli bay folds suggest that they are of tectonic origin and are a product of detachment folding their limited longitudinal extent and arcuate axial trends are compatible with an east trending left transtensional shear zone that was active along the eastern tyrrhenian sea during the late quaternary a relative sea level curve was calculated for an anticline culminating in the city of pozzuoli this relative sea level curve highlights the relationship between the deformation timing and the genesis of related abrupt changes in sedimentary facies and erosional surfaces

stream profile adjustment to crustal warping nonlinear results from a simple model three numerical experiments have been performed modeling response of a greatly simplified stream system to initiation of crustal tilting and domal uplift model results show signs of nonlinear behavior in varying degrees these signs include river profile adjustments that have forms quite different from the geometries of crustal movements cases of channel erosion following deposition at the same location and spatial transition points between opposing adjustments i e erosion and deposition that fail to coincide with boundaries or axes of crustal movement particular nonlinear effects wax or wane as the system adjusts to a new dynamic equilibrium with the continuing crustal movement the modeled features of stream adjustment are not in so extreme a class as the commonly discussed complex response of fluvial systems but they do serve to suggest some caution in studies that employ stream profile information as an indicator of crustal movement

late quaternary slip rates across the central tien shan kyrgyzstan central asia 1 slip rates across active faults and folds show that late quaternary faulting is distributed across the central tien shan not concentrated at its margins nearly every intermontane basin contains neogene and quaternary syntectonic strata deformed by holocene north south shortening on thrust or reverse faults in a region that spans two thirds of the north south width of the central tien shan slip rates on eight faults in five basins range from 0 1 to 3 mm yr fault slip rates are derived from faulted and folded river terraces and from trenches radiocarbon optically stimulated luminescence and thermoluminescence ages limit ages of terraces and aid in their regional correlation monte carlo simulations that sample from normally distributed and discrete probability distributions for each variable in the slip rate calculations generate most likely slip rate values and 95 confidence limits faults in basins appear to merge at relatively shallow depths with crustal scale ramps that underlie mountain ranges composed of pre cenozoic rocks the sum and overall pattern of late quaternary rates of shortening are similar to current rates of north south shortening measured using global positioning system geodesy this similarity suggests that deformation is concentrated along major fault zones near range basin margins such faults separated by rigid blocks accommodate most of the shortening in the upper crust index terms 8107 tectonophysics continental neotectonics 9320 information related to geographic region asia 8010 structural geology fractures and faults

quantification of three dimensional folding using fluvial terraces a case study from the mushi anticline northern margin of the chinese pamir fold deformation in three dimensions involves shortening uplift and lateral growth fluvial terraces represent strain markers that have been widely applied to constrain a fold s shortening and uplift for the lateral growth however the utility of fluvial terraces has been commonly ignored situated along northern margin of chinese pamir the mushi anticline preserves along its northern flank flights of passively deformed fluvial terraces that can be used to constrain three dimensional folding history especially lateral growth the mushi anticline is a geometrically simple fault tip fold with a total shortening of 740 110 m and rock uplift of 1300 m geologic and geomorphic mapping and dgps surveys reveal that terrace surfaces perpendicular to the fold s strike display increased rotation with age implying the fold grows by progressive limb rotation we use a pure shear fault tip fold model to estimate a uniform shortening rate of 1 5 1 3 0 5 mm a and a rock uplift rate of 2 3 2 1 0 8 mm a parallel to the fold s strike longitudinal profiles of terrace surfaces also display age dependent increases in slopes we present a new model to distinguish lateral growth mechanisms lateral lengthening and or rotation above a fixed tip this model indicates that eastward lengthening of the mushi anticline ceased by at least 134 ka and its lateral growth has been dominated by rotation our study confirms that terrace deformation along a fold s strike not only can constrain the lateral lengthening rate but can serve to quantify the magnitude and rate of lateral rotation attributes that are commonly difficult to define when relying on other geomorphic criteria

emplacement of the santa rita flat pluton as a pluton scale saddle reef regional mapping indicates that the middle jurassic santa rita flat pluton exposed in the inyo range of eastern california is situated within the core of a south plunging synform defined by bedding in the surrounding metasedimentary wall rocks which dip beneath the pluton however bedding in rocks preserved above the pluton defines a south plunging antiform anisotropy of magnetic susceptibility analysis revealed that magnetic foliation within the pluton also defines a south plunging antiform and the accompanying magnetic lineation plunges subparallel to the axis of this antiform our data indicate that the pluton was initially intruded as a sill in the hinge zone of the enveloping synform subsequent vertical inflation of the sill resulted in upward doming of the overlying roof and formation of the antiform now observed at the current erosion level in the pluton and preserved roof rocks emplacement of the pluton at 164 1 5 ma u pb zircon age overlaps in time with regional thrust faulting and folding ca 185 148 ma recognized in the southern inyo range we speculate that space for initial emplacement of the pluton was produced during folding by layer parallel slip and hinge zone dilation producing a saddle reef like structure

dynamic pedogenesis new views on some key soil concepts and a model for interpreting quaternary soils abstract inasmuch as soils are open systems and rarely if ever achieve equilibrium with their environments it is philosophically sound to view all soils as expressing varying levels of polygenesis as that term has been redefined soil genesis and resultant morphology may then be viewed in a comprehensive framework of soil evolution that consists of two linked pathways one developmental and the other regressive that reflect interactions of both exogenous and endogenous vectors vectors are factors processes and conditions of pedogenesis following this philosophy a model of pedogenesis is framed in an evolutional paradigm that emphasizes the integrated effects of dynamic and passive pedogenic vectors in directing pathways and in controlling rates of soil genesis through time the dynamic vectors include energy and mass fluxes frequencies of soil wetting and drying water table dynamics organisms feedback processes and pedoturbation the passive vectors include parent materials soil chemical environment stability of geomorphic surfaces and various evolved soil properties and conditions accessions both sets of vectors vary spatially and the dynamic vectors more so than passive vectors fluctuate through time the model is expressed as s f d p dd dt dd dt where s is the state of the soil or degree of profile evolution d is the set of dynamic vectors p is the set of passive vectors and dd dt and dp dt denote change through time t the model helps explain the apparent minimal development and regressed character of some old soils and the rapid and strong development of some young ones

fluid pressure induced seismicity at regional scales the role of high fluid pressure as a seismogenic agent has been the subject of intense study hubert and rubey 1959 hanshaw and bredehoeft 1968 healy and rubey 1968 simpson 1976 walder and nur 1984 sibson 1990 of particular interest is the so called fault valve mechanism sibson 1976 sibson 1990 a hypothesis whereby fluid pressure rises as a result of tectonic compression and pore volume reduction until crustal failure occurs triggering seismic activity and upward fluid discharge sealing and healing of the rock matrix richter and simmons 1977 sprunt and nur 1979 angevine et al 1982 following coseismic stress drop facilitates reaccumulation of fluid pressure initiating another loading cycle the fault valve mechanism is entertained as a plausible explanation for present day seismic activity in the western transverse ranges of california we provide a quantitative test of the fault valve hypothesis that uses geologic data and rates of active tectonics for a cross section through an active fold and thrust belt on the flank of a developing mountain range rates of fluid pressure buildup and average recurrence times of large earthquakes in the fold and thrust belt are estimated to be on the order of 104pa yrand hundreds of years respectively

late pleistocene slip rate on a blind thrust in the western qilian shan nw china abstract in the western front of the qilian shan ne tibetan plateau a series of 5 fluvial t1 t5 terraces developed along the baiyang river are deformed across the shiyougou anticline which is related to the yumen beidahe yb blind thrust in this study we measure the deformed terraces across the anticline using differential gps which provides data for us to reconstruct the thrust fault geometry the ages of terrace abandonment are constrained by 10be exposure dating for t2 t4 and t5 to be 8 6 1 7 ka 21 6 1 4 ka and 48 4 2 1 ka respectively a four segment fault model is inferred with changing dips at depths of 0 3 0 1 km 2 2 0 1 km and 5 9 0 9 km combining terrace ages with the fault geometry model we derive a vertical slip rate of 0 9 0 1 mm yr and a shortening rate of 1 9 0 5 mm yr for the yb blind thrust this result suggests that the northern frontal thrust system accommodates only 30 of the total shortening rates across the western qilian shan the river incision rate has increased from 1 5 mm yr to 5 2 mm yr from the late pleistocene to the holocene the mismatch between river incision and rock uplift is likely related to climate change since the last glacial maximum

drainage development and sediment supply within rifts examples from the sperchios basin central greece drainage systems juxtaposed with modern depositional environments within the sperchios rift allow detailed analysis of the relationships between drainage catchments sediment supply and alluvial fan fan delta geometries prominent footwall escarpments within the rift are created by e w trending normal faults and variations in the topography of these escarpments are related to fault segmentation and bedrock lithology drainage catchments within the rift are classified on the basis of morphology area bedrock lithology and relationship to fault geometries five drainage domains can be identified within the sperchios rift i footwall ii hanging wall iii transfer zone iv axial and v karst domains bedrock lithology has a major control on the size of catchments in all drainage domains in addition topographic lows associated with transfer zones along the border fault are sites of major drainage catchments and act as conduits for sediment supply to the rift variations in drainage catchments the resultant sediment supply and accommodation development along the rift produce a range of stratigraphic architectures along fault segments low sediment supply and high subsidence rates lead to aggradational sequence sets whereas progradational sequence sets develop at transfer zones where rates of sedimentation are high and the rate of subsidence is low

active faulting and block rotations in the western transverse ranges california the geometry of faulting slip vectors of major earthquakes and results of very long baseline interferometry vbli are consistent with active clockwise rotation of crustal blocks in the western transverse ranges about vertical axes oblique left lateral thrust faults trending roughly east west across the western transverse ranges apparently separate long east west blocks of upper crust and the large components of lea lateral shear on east striking planes suggest that the blocks rotate with respect to the san andreas fault in the mojave region between the western transverse ranges and the mojave desert paleomagnetic declinations indicate some 35 and possibly 60 of clockwise rotation since about 10 ma and more importantly the relative velocity between the only two frequently measured vbli sites in the western transverse ranges is consistent with a rotation rate of 6 ma 3 ma during a 5 year period in the 1980s azimuths of slip vectors of major earthquakes are essentially orthogonal to the segment of the san andreas fault across the western mojave desert indicating that crustal shortening across the region is absorbed by crustal thickening and not by lateral translation extension of material parallel to that segment of the fault plate motions late quaternary offsets on the san andreas and san jacinto faults and geodetic measurements in the mojave region yield a calculated direction of relative motion between the san gabriel mountains and the pacific plate across the western transverse ranges that also is perpendicular to the san andreas fault in the mojave region rotation rates associated with simple mechanisms for applying essentially normal tractions to the lateral margins of blocks are not consistent with the observed geometry of faulting and with average rotation rates the rotation rate of 2 8 5 3 ma calculated assuming that the long east west blocks rotate in response to a uniform compression of a viscous substratum to the western transverse ranges however overlaps the range of observed average rotation rates thus the hypothesis that blocks of continental crust move as if carried passively by a substratum undergoing continuous deformation passes one test that can be made of it

geomorphic constraints on active mountain growth by the lateral propagation of fault related folding a case study on yumu shan ne tibet the mountain range of the yumu shan in ne tibet is the topographic expression of actively growing fault related folds developed in the hanging walls of a system of mostly northeast vergent blind thrusts here we present a tibetan example on the geomorphic response to lateral fold propagation using both qualitative analysis of the geomorphic characteristics of this region e g wind and water gaps drainage density and along strike topography of the range crest and quantitative analysis based on cosmogenic be 10 surface exposure dating and optically stimulated luminescence dating on the rates of uplift and lateral propagation of the anticline the elevations of the past positions of successively deflected paleo rivers show a systematic decrease toward the eastern tip of the anticline in tandem with an eastward decrease in drainage density combining the age data obtained by cosmogenic be 10 and osl dating methods with the heights of abandoned terraces we calculated average uplift and lateral propagation rates of similar to 378 mm ka over the past similar to 185 ka and similar to 40 mm yr over the past similar to 150 ka respectively our single site evaluation of the relation between tear faulting and channel deflection suggests that the tear faulting occurs along weakened bedrock already dissected by the former stream this finding is inconsistent with the conventional hypothesis that the route of the deflecting stream is controlled by the orientation of the tear faulting zone topographic vertical and lateral fold growth of the yumu shan were probably driven by the eastward propagation of a blind thrust since the late neogene following the initial deposition of sediments in the hexi corridor which were transported from the qilian shan c 2011 elsevier ltd all rights reserved the mountain range of the yumu shan in ne tibet is the topographic expression of actively growing fault related folds developed in the hanging walls of a system of mostly northeast vergent blind thrusts here we present a tibetan example on the geomorphic response to lateral fold propagation using both qualitative analysis of the geomorphic characteristics of this region e g wind and water gaps drainage density and along strike topography of the range crest and quantitative analysis based on cosmogenic be 10 surface exposure dating and optically stimulated luminescence dating on the rates of uplift and lateral propagation of the anticline the elevations of the past positions of successively deflected paleo rivers show a systematic decrease toward the eastern tip of the anticline in tandem with an eastward decrease in drainage density combining the age data obtained by cosmogenic be 10 and osl dating methods with the heights of abandoned terraces we calculated average uplift and lateral propagation rates of similar to 378 mm ka over the past similar to 185 ka and similar to 40 mm yr over the past similar to 150 ka respectively our single site evaluation of the relation between tear faulting and channel deflection suggests that the tear faulting occurs along weakened bedrock already dissected by the former stream this finding is inconsistent with the conventional hypothesis that the route of the deflecting stream is controlled by the orientation of the tear faulting zone topographic vertical and lateral fold growth of the yumu shan were probably driven by the eastward propagation of a blind thrust since the late neogene following the initial deposition of sediments in the hexi corridor which were transported from the qilian shan c 2011 elsevier ltd all rights reserved

episodic folding inferred from syntectonic carbonate sedimentation the santaren anticline bahamas foreland abstract sedimentation coeval with growth of the santaren anticline provides an excellent opportunity to study the relationships between sedimentation and anticline uplift through time the santaren anticline is a kilometre scale nw se trending fold offshore of cuba in the bahamas foreland of the cuban fold and thrust belt the growth strata associated with this anticline consist of a thick package of carbonate sediments that were deposited without major interruptions from neogene and perhaps before to present day the excellent seismic resolution and age control of a number of seismic horizons within the growth strata allowed us to define 25 growth beds each of them representing between 0 1 and 3 2 ma an analysis of the thickness of these beds allowed us to determine accurate quantitative values of cumulative decompacted thickness and crestal structural relief at the time of their deposition in addition for the same periods sedimentation and fold uplift rates were calculated moreover some information on relationships between sedimentation and fold uplift rates was inferred from the growth stratal geometry growth beds that overlap the fold crest and thin over it indicate that sedimentation rates outpaced fold growth rates during their deposition some overlapping beds have constant thickness indicating that no fold uplift occurred during their sedimentation the rest of the growth beds exhibit onlap offlap geometries that do not indicate a unique sedimentation fold uplift rate relationship only in those cases in which the geometry of the underlying bed at the end of its deposition is known is it possible to infer a specific sedimentation fold uplift rate relationship as a result of this analysis we have been able to 1 illustrate that the geometry of the growth strata associated with the santaren anticline results from competition between sedimentation and tectonic fold uplift 2 document the episodic and non steady nature of fold growth and 3 show that short term rates at the scale of hundreds of thousands years provide much insight into the interplay between sedimentation and tectonic fold uplift that control the growth stratal patterns

isostatic compensation of tectonic features of the mid atlantic ridge 25 27 30 s we investigate the isostatic compensation of tectonic features along the mid atlantic ridge 25 27 30 s through a detailed examination of the relationship between bathymetry and gravity anomalies the study area includes three ridge segments spreading at an average full rate of 35 mm yr their flanks out to about 6 m y old crust and the intervening rio grande and moore fracture zones in a three dimensional analysis of gravity and sea beam bathymetry data we focus on crustal thickness variations and mantle density anomalies by removing from the observed fields the predicted contribution of simple crustal and mantle models positive residual gravity anomalies over the northern wall of the rio grande fracture zone indicate that in spots the crust is 2 3 km thinner than average there in contrast to the moore fracture zone where little thinning is observed the greater than average depths of the fracture zones as a whole are not locally compensated by thin crust but the deepest basins within the active transform parts of the fracture zones are partially compensated by thin crust or cooler mantle a narrow linear ridge that crosses one of the inactive branches of the moore fracture zone had been suggested to be the product of an episode of excess volcanism but is found to be underlain by thinner not thicker crust there is no indication of thicker crust beneath topographic highs at the inside corners of ridge transform intersections presumably these highs are dynamically maintained as must be the median valleys characteristic of most the length of the ridge segments judging from the absence of axial residual gravity anomalies there is a residual gravity low associated with an unusually shallow 15 to 20 km section of the ridge segment between the rio grande and moore offsets where the median valley virtually disappears our analysis suggests that while part of the anomalous elevation of this section of the ridge axis is attributable to excess volcanism and a thicker crust much of the elevation contrast is simply caused by the diminution of the dynamic mechanism responsible for median valley formation two dimensional fourier transforms of the gravity and bathymetry fields show that seafloor topography is strongly aligned parallel to either ridges or transforms while density anomalies are more randomly oriented this implies that the tectonic processes that control the gross ridge transform topography are not the dominant control on the magmatic processes that determine the upper mantle and crustal density structure statistical analysis of the coherence between the gravity and bathymetry fields indicates that the average effective elastic plate thickness in the study area is about 6 km

a geometric model to estimate slip rates from terrace rotation above an offshore listric thrust fault kaikōura new zealand abstract the kaik ura peninsula lies at the transition from subduction to continental collision at the southern end of the hikurangi subduction system this study uses a 2012 lidar survey over the kaik ura peninsula to re map a flight of four uplifted late pleistocene marine terraces at high resolution the lidar shows that the terraces are being progressively tilted landwards in a manner consistent with listric thrust faulting offshore the fault known as the kaik ura peninsula fault dips shallowly at c 30 to the northwest at depth and probably truncates the seaward segment of the hope fault in the footwall of the jordan thrust geometric analysis of the tilt using ages based on previous dating and a regional sea level curve suggests that slip rates on the kaik ura peninsula fault have ranged between 2 3 1 5 mm yr and 4 1 1 3 mm yr over the late pleistocene the elevations of late holocene fringing beaches track regional sea level changes apart from a departure indicating a single uplift event penultimate earthquake in the late 18th to earliest 19th century 1702 1838 ce followed by uplift in the 2016 kaik ura earthquake the slip rate calculated from beach uplift including the kaik ura earthquake is consistent with longer term rates the accumulation of the slip over only c 220 years following 2000 years of quiescence suggests that the offshore thrust and associated faults exhibit clustered behavior possibly as a result of keystone 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

quaternary rate of folding of the ventura avenue anticline western transverse ranges southern california upper quaternary terraces of the ventura river california are uplifted tilted and folded over the ventura avenue anticline rates of uplift and tilting have decreased since inception of the structure over the past 200 ka assuming that the chronology based on amino acid racemization 14c dates and soils correlation is approximately correct then the minimum possible average rate of uplift in the axial region of the fold has decreased from 14 mm yr to 2 mm yr during the past 200 ka interval rates of uplift for the periods 200 ka to 80 or 105 ka 80 or 105 ka to 30 ka and 30 ka to present are respectively about 20 mm yr 9 mm yr and 5 mm yr the rate of tilting shows a similar trend decreasing from 5 8 urad yr 2 5 urad yr and 1 2 urad yr for the same time intervals respectively based on the mechanics of flexural slip folds in stratified sedimentary rocks these data suggest that the rootless ventura avenue anticline is a fold that has been shortening at a relatively constant rate of about 9 mm yr since its inception

late pleistocene differential uplift inferred from the analysis of fluvial terraces southern apennines italy abstract the stratigraphic architecture and morphological assemblage of the pleistocene fluvial terraces contained in two contiguous fluvial valleys are used to understand the spatial distribution and the timing of the differential uplift that affected two different geological and geomorphological settings of an active orogen the study areas both placed in the eastern sector of the southern apennines of italy are the sant arcangelo sedimentary basin and the valsinni ridge anticline pleistocene uplift rate of 0 7 0 9 mm y 1 and historical earthquakes affecting those areas suggest active tectonics based on the synthem units used to classify the fluvial deposits in the field several strath fill and fill cut terraces have been mapped in the middle valleys of the agri and sinni rivers four middle pleistocene high terraces qes are found in the sant arcangelo basin and cut its infill and three late pleistocene low terraces qt are found at both the agri and sinni valley flanks the agri and sinni rivers cross cut the nw se oriented fold and thrust belt of the southern apennines from w to e producing a transverse drainage as a result ten to hundred metre deep gorges and wide floodplains were created in the middle reach of the river valleys computation of the bedrock incision rates from the qes1 qes4 and sqt1 terraces corresponding to 1 2 0 2 mm y 1 at 400 240 ka and 0 8 0 2 mm y 1 in the last 240 ka together with the terrace profile arrangements in the agri and sinni valleys allow for the documentation of i the differential uplift of the study area and ii the age of terrace abandonment corresponding to the beginning age of the vertical incision in the valley floor sediments to form the qt terraces the differential uplift is subsequently discussed in a space and time sequence evolution of the late pleistocene to assess the complex morphotectonic development that occurred in the eastern threshold of the basin the differential uplift of both the sant arcangelo basin and valsinni ridge would appear to indicate that buried fold and thrust structures that affect the mesozoic cenozoic sedimentary nappes are still active and they also controlled the slab retreat processes in the mediterranean region during the late pleistocene

a comparison of mineralogical techniques and potassium adsorption isotherm analysis for relative dating and correlation of late quaternary soil chronosequences abstract the utility of potassium adsorption isotherm analysis kia for relative dating and correlation of soil chronosequences was assessed by a comparison with some widely used mineralogical techniques the soils studied near detroit michigan are brown 10yr calcareous entisols developed in holocene 4 ka floodplain sediments and inceptisols and alfisols with redder 7 5yr 5yr cambic and argillic b horizons formed on late pleistocene 14 5 12 4 ka fluvial terraces fluvial paleochannels and paleoshorelines beach ridges of proglacial lakes the soils show a positive linear correlation between soil age and clay content depth of carbonate leaching and fe oxide accumulation in contrast the duration of soil formation is too short for variations in heavy mineral frequencies to discriminate soil age reliably scanning electron microscopy shows that chemical weathering stage is indicated by progressive etching and pitting of calcite apatite and amphibole with increasing soil age k isotherms are linear or slightly curvilinear indicating that ion exchange is dominant over specific adsorption a statistically significant linear correlation between k distribution constant and soil age attributed to progressive weathering of mica suggests that kia is useful for relative dating of genetically related soils once a well dated chronosequence is established kia produces results comparable to or better than mineralogical techniques however soil morphology and a clay redness index are more effective than mineralogical and chemical techniques for interchronosequence correlation

denudation vertical crustal movements and sedimentary basin infill denudation and vertical crustal movements are linked through the isostatic equation for conservation of lithospheric mass recent empirical results from a wide range of sources are presented on the rates of these processes denudation alone can cause non tectonic isostatic surface uplift of the right magnitude predicted by theory a case is made following ahnert for a single linear relationship although with much scatter between denudation rate and mean drainage basin relief for large basins some recent determinations of denudational time constants have neglected to include tectonic and isostatic terms which oppose the reduction of relief by denudation application of diffusional transport models to determine the rate of sediment deposition are severely limited by inherent one dimensionality and neglect of suspended and washload contributions basin infill sequences may be used to determine past sediment transfer coefficients from a hinterland but problems arise in the apportionment of the various hinterland fluxes that occur in real world three dimensional basins sediment yields in smaller half graben and growth fold basins must reflect the magnitude of drainage basins and the complex local controls upon sediment yields examples are given from extensional basins in the western usa and greece the length of tectonic relief produced in tilt blocks and growth folds will control the area of drainage basin developed through the fractal form of hack s law and hence the magnitude of deposition in sedimentary basins adjoining tectonic uplands

geomorphological analysis of the drainage system on the growing makran accretionary wedge abstract the morphology of six adjacent major catchments draining the onshore makran accretionary wedge in southeast iran and southwest pakistan was studied to examine how the channel pattern and the length profiles may reflect the recent and active growth of the wedge qualitative field surveys were combined with the quantitative analysis of channel steepness and concavity measured from digital elevation models these profiles were compared with modelled profiles using a stream power approach assuming homogeneously uplifting uniform rock substratum results show a distinct difference between the studied western and eastern catchments the three western rivers are in morphological equilibrium whereas the two eastern rivers exhibit profiles with prominent convexities and knickpoints thus notably diverging from equilibrium concave up shapes all the studied catchments share the same base level flow on similar lithologies and developed under uniform climate conditions therefore we interpret the morphometric differences in terms of differential rock uplift rate as a response to local tectonic activity this interpretation is consistent with both uplift rates of marine terraces along the coast of makran and the recorded seismicity the geomorphological analysis presented here extends coastal information to wide inland areas and documents longer term tectonic behaviour than the seismotectonic record hence the steeper surface slope and faster surface uplift rates recorded by the eastern catchments compared to equilibrium of the western catchments are regional long term signals relevant for a wide part of the makran accretionary wedge we attribute the regional geomorphic difference to quaternary variations in tectonic regimes that forced differential uplift rates of the wedge surface we hypothesize that the different tectonic regimes are related to different subduction rates

kinematics and deformation of central and southwestern greece from historical triangulation data and implications for the active tectonics of the aegean abstract changes in the coordinates of 38 stations 32 of which were common to three historical triangulation surveys 1889 1905 1927 1930 and 1950 1970 in central greece were computed based on conventional adjustment techniques and the assumption of a nearly fixed baseline length some of the calculated coordinate changes are significant against the a posteriori network adjustment errors and are likely to indicate tectonic motions consistent with those deduced from geological and geophysical data and other geodetic studies comparison of the first survey network with gps data more explicitly the historical geodetic data confirm the rotational character of the deformation in the area but they show that the strain pattern is likely to have changed after 1930 between 1890 and 1930 strain was changing smoothly as if no strain discontinuities existed while the peloponnesus was under contraction from the northeast probably reflecting accommodation of strain from the arc significant left lateral shear in the gulf of corinth and n s extension in the whole of the study area were observed only after 1930 estimates of strain are consistent with those deduced from comparison of historical triangulation and gps data corrected for the scale error that exists in the terrestrial geodetic data in greece and estimates of strain from seismological data the change in the kinematic pattern after 1930 seems to be confirmed by changes in the shear strain computed directly from changes in observed angles between stations and from changes in the seismicity rates such changes although not unusual in the geological record are not easy to explain but may reflect elastic rebound effects in area with an extremely complicated tectonic fabric or hysteresis in the accommodation of e w compression from the arc by n s stretching

geological and geomorphic evidences of neotectonic activity along the himalayan frontal thrust nahan salient nw himalaya india abstract in this paper we report geomorphic signatures of neotectonic activity identified from the area around nahan salient along himalayan frontal thrust hft using remote sensing and field investigations we document two newly discovered exposures of hft fault zone and active fault traces along the mountain front at khetpurali nahan salient nw himalaya india we demonstrate that hft fault zone at khetpurali is not blind instead it is exposed at the surface along with highly deformed folded strata in the hanging wall and its geometry is quite variable with the possibility of along strike segmentation the geometry of fold and various deformational features preserved in the hanging wall indicate a process of fault propagation fold this is in contrast to the previous observation of fault bent folding within the nahan salient two three levels of river terraces are preserved and truncated in the hanging wall along with the active fault scarps which are linked to uplift along hft fault zone the khetpurali anticline ka is a fault propagating fold formed due to displacement and shortening along hft which dips 30 towards north and strike wnw ese the uplift u along the ka is calculated to be 73 m and accommodated 7 3 shortening of the original length before the fault tip truncated the fold various deformational structures have been identified within the hanging wall around tip damage zone of 80 m perpendicular to hft fault zone and in the core of ka northwest of khetpurali a south facing hogback structure 100 m high is formed due to erosion of forelimb of the anticline at khetpurali tectonic control due to folding of strata and uplift of river terraces is evident as the dudhgarh river forms v shaped profile near the thrust compared to the wide floodplain before and after crossing the hft fault zone along strike segmentation of hft and associated anticlines is observed as the surface trace of hft is offset at khetpurali trilokpur and sabilpur due to the strike slip faults the study reveals that hft has been truncated by tear faults and has different subsurface geometries in study area which may have implication on seismic hazard in the nahan salient where three thrusts himalayan frrontal thrust hft nahan thrust nt and main boundary fault mbf are located at relatively shorter distance of 6 km as compared to the surrounding recesses

strike slip fault bridge fluid pumping mechanism insights from field based palaeostress analysis and numerical modelling abstract we present a finite element study of stress perturbation in evolving compressive and extensional strike slip fault bridges the results are compared with a fracture study of a compressive bridge at st donats uk horizontally interbedded calcareous mudstone and bioclastic calcilutite at st donats have a distinct vertical permeability anisotropy this sedimentary sequence behaves as a set of horizontal aquifers the fluid flow in these aquifers is sensitive to mean stress gradients paleostress analysis of field fracture data verified by finite element modelling indicates a rotation of 1 towards parallelism with boundary faults inside the growing compressive bridge boundary faults and bridge faults recorded numerous fluid flow events the modelled mean stress pattern shows a regional maximum within the bridge and local maxima minima pairs at boundary fault tips finite element modelling of an extensional bridge indicates that 3 rotates towards parallelism with boundary faults the mean stress pattern is similar to the pattern in compressive bridge but with maxima and minima locations interchanged the stress patterns are reestablished by each stress build up preceding the rupturation of the boundary faults throughout the development stages of strike slip fault bridges mean stress gradients developed pre failure control the fluid flow in fractures of the strike slip fault system at and after the end of each stress build up and the fluid flow in boundary faults post failure fracture reactivation and new fracture generation within an evolving bridge is a process consisting of multiple successive events that retain the storage capacity of the bridge rupture and sealing of the main bounding faults is a step wise process that opens and closes fluid conduits between areas with different pressures

geodetic measurement of deformation in the ventura basin region southern california we have measured the deformation in the ventura basin region southern california with global positioning system gps measurements carried out over 4 6 years between 1987 and 1992 the deformation within our network is spatically variable on scales of tens of kilometers with strain rates reaching 0 6 1 micro rad yr in the east central basin blocklike rotations are observed south and northwest of the basin where the maximum shear strain rates are an order of magnitude lower 0 06 1 micro rad yr to the south we also observed clockwise rotations of 1 deg 7 deg m y shear strain rates determined by comparing angle changes from historical triangulation spanning several decades and gps measurements give consistent though less precise results the geodetic rates of shortening across the basin and western transverse ranges are lower than those estimated from geological observations but the patterns of deformation from the two methods agree qualitatively

continental break up mechanism lessons from intermediate and fast extension settings continental break up mechanisms vary systematically between slow and fast extension systems slow extension break up has been established from studies of the central atlantic european and adria margins this study focuses on the intermediate and fast cases from gabon and east india and draws from the interpretation of reflection seismic gravimetric and magnetic data interpretation indicates continental break up via continental mantle unroofing in all systems with modifications produced by magmatism in faster extension systems break up of the intermediate extension gabon system involves partial upper continental crustal decoupling from continental mantle whereas in the fast east coast india system decoupled and lower crustal regimes underwent upwarping in soggy zones in the footwalls of major normal faults usually upper crustal break up is affected by pre existing anisotropies which form systems of constraining rails for extending continental crust this modifies the local stress regimes they regain a regional character as the function of constraining rails vanishes during progressive unroofing of the upper mantle different regions attain different amounts of upper crustal stretching prior to the break up the break up location is then controlled by the upper crustal energy balance principle of wound linkage by which the minimum physical work is performed for linking upper crustal wounds leading to successful upper crustal break up

coseismic fault related fold model growth structure and the historic multisegment blind thrust earthquake on the basement involved yoro thrust central japan 1 we use high resolution seismic reflection profiles boring transects and mapping of fold scarps that deform late quaternary and holocene sediments to define the kinematic evolution subsurface geometry coseismic behavior and fault slip rates for an active basement involved blind thrust system in central japan coseismic fold scarps on the yoro basement involved fold are defined by narrow fold limbs and angular hinges on seismic profiles suggesting that at least 3 9 km of fault slip is consumed by wedge thrust folding in the upper 10 km of the crust the close coincidence and kinematic link between folded horizons and the underlying thrust geometry indicate that the yoro basement involved fold has accommodated slip at an average rate of 3 2 0 1 mm yr on a shallowly west dipping thrust fault since early pleistocene time past large magnitude earthquakes including an historic m 7 7 event in a d 1586 that occurred on the yoro blind thrust are shown to have produced discrete folding by curved hinge kink band migration above the eastward propagating tip of the wedge thrust coseismic fold scarps formed during the a d 1586 earthquake can be traced along the en echelon active folds that extend for at least 60 km in spite of different styles of folding along the apparently hard linked nobi ise blind thrust system we thus emphasize the importance of this multisegment earthquake rupture across these structures and the potential risk for similar future events in en echelon active fold and thrust belts

large transverse range earthquakes cause coastal upheaval near ventura southern california abstract slip on the pitas point thrust produces uplift and folding of the ventura avenue anticlinal vaa trend in the western transverse ranges of southern california rapid convergence has resulted in 2 7 km of uplift on the vaa over the past 200 300 ka with as much as 320 m in the past 45 50 ka indicating a long term uplift rate of 6 7 mm yr four holocene emergent marine terraces are present between carpinteria and ventura with the fourth terrace uplifted a minimum of 38 m the most recent emergence event uplifted a chumash indian village at pitas point by 5 6 m about 950 yrs ago the first terrace which formed when the sea level was 0 5 1 m lower than at present is nearly continuously preserved from east of pitas point toward the fold crest of the vaa where its elevation increases reaching an altitude of 7 8 m this implies a large amount of slip on the causative fault at depth radiocarbon dates on marine shells and culturally derived charcoal indicate terrace emergence events occurred at about 0 95 2 09 4 4 and 6 7 ka

reconciling rapid strain accumulation with deep seismogenic fault planes in the ventura basin california global positioning system measurements across the east central ventura basin transverse ranges southern california before the nearby 1994 northridge earthquake show high strain rates interpreting this rapid strain accumulation using the usual model of deep slip on a dislocation in a uniform elastic half space requires slip to extend to within 5 km of the surface such shallow slip is difficult to reconcile with the substantial coseismic displacement at depths from 7 to 19 km during the northridge earthquake here we model the displacement and velocity fields throughout the earthquake cycle using a two dimensional finite element model with a viscoelastic rheology displacements are driven by far field and basal velocity boundary conditions and by imposed periodic earthquakes on the thrust faults bounding the basin the thrust faults rupture through an elastic upper crust to a depth of 15 km after a transient stage during which stresses and strains build up to quasi equilibrium values the behavior of the model becomes periodic the sum of the coseismic displacement divided by the repeat interval plus the average interseismic velocity is equal to the geologic velocity the temporal variation in surface velocity depends mainly on the elsasser relaxation time proportional to the product of the maxwell time of the lower crust and the ratio of the thicknesses of the entire crust and viscoelastic lower crust we are able to match the observed high strain rate only if we include the observed variations in elastic modulus associated with the deep basin sediments the model reconciles geologic geodetic and seismological observations of deformation there are trade offs among the far field convergence rate the elsasser time the earthquake repeat time and the time into the earthquake cycle acceptable convergence rates range from 8 mm yr for a relaxation time of the lower crust of 300 years to 12 mm yr for a 30 year relaxation time

relief inversion in the avrona playa as evidence of large magnitude historical earthquakes southern arava valley dead sea rift the arava valley section of the dead sea transform dst in southern israel is characterized by the absence of seismic activity in recent times however paleoseismic analysis of sediments in the avrona playa a pull apart basin along the dst reveals that at least six m 6 tectonic events have affected the avrona playa in the last 14 000 yr the recurrence interval of the events is approximately 2000 yr trenched normal faults and push up ridges in the playa show that the upper 2 m of the deformed sedimentary sequence consists of playa deposits with uniform soil development the deformed sediments and the soil are typical of basins with an endoreic fluvial system based on the limiting age of the sequence and the extent of soil development faulting in the playa followed by compression and uplift occurred in the last 1000 yr this most recent tectonic event displaced the surface by at least 1 m consistent with a m 6 5 earthquake this earthquake changed the morphology of the avrona playa from a closed system with internal drainage to an open basin resulting in relief inversion the seismic quiescence in the arava may indicate a seismic gap in this segment of the dst

earthquake induced flooding and paleoseismicity of the el asnam algeria fault related fold late quaternary activity of the el asnam thrust fault responsible for the october 10 1980 ms 7 3 earthquake and 36 km coseismic faulting is explored through diverse paleoseismological field methods we trenched through the main and secondary 1980 coseismic scarps made an analysis of earthquake induced flood deposits conducted a geomorphic study of leveling profiles and offset geological units across thrust and normal scarps and considered the geomorphology of the active fold twenty five radiocarbon ages from colluvial and alluvial deposits along with conventional fossils and artefacts dating of geological units show the timing of successive net vertical displacements on the thrust related fold and bending moment faults previous work showed that eight pre 1980 earthquakes occurred in clusters during the late holocene cumulative net vertical slip that amounts to 3 times the 1980 displacement is observed on multiple thrust fault scarps and offsets of geological units on bending moment faults maximum cumulative vertical displacements which are visible in different zones along the fault segments can reach 10 to 25 times the 1980 coseismic displacements the late quaternary uplift rate on the el asnam fault is 0 6 mm yr and taking into account slip variation along the fault this rate may range between 0 25 1 6 mm yr from which we obtain a shortening rate of 0 17 1 2 mm yr because the tell atlas mountains exhibit comparable seismogenic fault related folds with parallel and sequential structures of active faults a total average shortening rate of 2 05 mm yr during the late quaternary represents part of the convergence accommodated along the africa eurasia plate boundary

modeling the shortening history of a fault tip fold using structural and geomorphic records of deformation 1 we present a methodology to derive the growth history of a fault tip fold above a basal detachment our approach is based on modeling the stratigraphic and geomorphic records of deformation as well as the finite structure of the fold constrained from seismic profiles we parameterize the spatial deformation pattern using a simple formulation of the displacement field derived from sandbox experiments assuming a stationary spatial pattern of deformation we simulate the gradual warping and uplift of stratigraphic and geomorphic markers which provides an estimate of the cumulative amounts of shortening they have recorded this approach allows modeling of isolated terraces or growth strata we apply this method to the study of two fault tip folds in the tien shan the yakeng and anjihai anticlines documenting their deformation history over the past 6 7 myr we show that the modern shortening rates can be estimated from the width of the fold topography provided that the sedimentation rate is known yielding respective rates of 2 15 and 1 12 mm yr across yakeng and anjihai consistent with the deformation recorded by fluvial and alluvial terraces this study demonstrates that the shortening rates across both folds accelerated significantly since the onset of folding it also illustrates the usefulness of a simple geometric folding model and highlights the importance of considering local interactions between tectonic deformation sedimentation and erosion

late pleistocene shortening rate on the northern margin of the yanqi basin southeastern tian shan nw china abstract how strain is distributed and partitioned on individual faults and folds on the margins of intermontane basins remains poorly understood the haermodun ha anticline located along the northern margin of the intermontane yanqi basin on the southeastern flank of the tian shan preserves flights of passively deformed alluvial terraces these terraces cross the active anticline and can be used to constrain local crustal shortening and uplift rates geologic and geomorphic mapping in conjunction with high resolution dgps topographic surveys reveal that the terrace surfaces are perpendicular to the fold s strike and display increased rotation with age implying that the anticline has grown by progressive limb rotation combined with the open sinusoidal curve model and excess area method we calculated uplift and shortening values for each terrace since abandonment using the published exposure ages of each terrace we found the vertical uplift rate gradually decreased from 0 43 to 0 11 mm a whereas the shortening rate remained constant at 0 3 mm a since the anticline began to grow a fresh fault scarp 0 4 0 1 m high is visible along the southern portion of the ha anticline and is interpreted to be the most recent evidence of seismic activity using an estimated rupture area and the length of the fresh offset created by this earthquake we estimate that the main thrust underlying the ha anticline has generated moderate m

rates and kinematics of active shortening along the eastern qilian shan china inferred from deformed fluvial terraces in the eastern qilian shan a flight of fluvial terraces developed along the jinta river valley are deformed across the nanying anticline four individual fluvial terraces are preserved at different elevations above the river and higher terrace treads are draped by systematically thicker aeolian loess optically stimulated luminescence dating of deposits at the base of the loess provides constraints on the timing of surface abandonment terraces were abandoned at 69 4 ka b p t4 57 4 ka b p t3 and between 34 3 ka b p t2 respectively differential gps measurement of the terrace profile across the anticline allows reconstruction of subsurface fault geometry we model terrace deformation above a listric thrust fault with a tip line at 2 2 0 1 km depth and whose dip shallows systematically to 23 3 degrees at depth of 5 8 1 1 km combining terrace ages with this model of fault geometry we estimate a shortening rate of 0 8 0 2 mm a across the nanying fold and a shortening rate of similar to 0 1 mm a across the mountain front fault since similar to 70 ka b p this rate suggests that the frontal fault system along the eastern qilian shan accomplishes crustal shortening at rates of approximately 0 9 0 3 mm a during late pleistocene time

tectonic characteristics of the lishan piedmont fault in the se weihe graben central china as revealed by the geomorphological and structural analyses abstract the fault kinematics slip rate and paleoseismicity along the approximate ew trending lishan piedmont fault lpf in the se weihe graben central china have been determined the results of geomorphological analysis field investigations and radiocarbon 14 c age dating indicate that i slope angles of the observed triangular facets cluster around 20 ii empirical correlations yield a vertical slip rate throw rate of 0 11 0 25 mm yr 1 which is lower than the neighboring active faults iii the lpf is characterized by almost purely normal slip and was active within the past 18 000 yr these findings can provide a basis for the assessment of seismic risk in and around the densely populated city of xi an an old capital of china however we suggest more precise constraints on the fault slip rate and detailed paleoseismological studies on the timing of the most recent earthquake and the repeat time of paleo earthquakes are needed in order to better understand the seismogenic behaviors of the active lpf

southern california earthquake center geologic vertical motion database the southern california earthquake center geologic vertical motion database vmdb integrates disparate sources of geologic uplift and subsidence data at 104 to 106 year time scales into a single resource for investigations of crustal deformation in southern california over 1800 vertical deformation rate data points in southern california and northern baja california populate the database four mature data sets are now represented marine terraces incised river terraces thermochronologic ages and stratigraphic surfaces an innovative architecture and interface of the vmdb exposes distinct data sets and reference frames permitting user exploration of this complex data set and allowing user control over the assumptions applied to convert geologic and geochronologic information into absolute uplift rates online exploration and download tools are available through all common web browsers allowing the distribution of vertical motion results as html tables tab delimited gis compatible text files or via a map interface through the google maps web service the vmdb represents a mature product for research of fault activity and elastic deformation of southern california

inferring a thrust related earthquake history from secondary faulting a long rupture record of la laja fault san juan argentina abstract trenches excavated across the surface rupture of the 15 january 1944 m w 7 san juan argentina earthquake show evidence for repeated rupture of la laja fault in the late pleistocene and holocene the 1944 rupture extended for about 7 km striking n35 e and dipping 42 e parallel to neogene bedding with a maximum east side up vertical displacement of 30 cm we interpret nine discrete colluvial wedges each capped by a soil as evidence for nine surface ruptures in the past 32 35 ka our topographic profile of the t3 terrace surface projected across the fault suggests these nine events collectively produced 10 3 m of dip displacement we used radiocarbon and optically stimulated luminescence dating to define the timing of past events yielding an average recurrence interval of 3 9 0 3 ka the average estimate for displacement per event is about 1 1 m compared with the 0 5 m of dip slip that occurred in 1944 using a fault related fold model that infers 28 m of shortening based on the axial surface migration for the t 3 terrace along with the 35 ka age of the terrace yields a shortening rate of 0 8 mm yr by the 1944 source thrust fault which is about 20 of the global positioning system constrained total shortening rate across the precordillera using this shortening rate and an assumed fault dip of 30 implies a fault slip rate of about 1 1 mm yr which combined with the average recurrence interval implies 4 m of average slip per event on the causative fault at depth online material unit descriptions from the trenches stepwise reconstruction from trench 1 and annotated photographs of the la laja region

unfolding an inverse approach to fold kinematics preservedfoldshapesusuallyreveallittleabouttheirkinematicevolution syntectonic strata preserved in growth synclines in contact with a fold however can permit unfolding a sequential reconstruction of fold growth backward through time from a geometry observed at present to an initial undeformed state such reconstructions can define the kinematics of fold growth growth strata associated with anticlinal forelimbs in the ebro basin exhibit depositional tapering of beds on fold flanks and progressive limb rotation unfoldingawell dateddetachmentfolddefinesitskinematicevolutionandcoevallyvarying rates of shortening forelimb uplift and forelimb rotation interplay of these rates with sedimentation rates controls onlap and offlap relations

deformation across the western united states a local estimate of pacific north america transform deformation we obtain a locally based estimate of pacific north america relative motion and an uncertainty in this estimate by integrating deformation rate along three different paths leading west across southwestern north america from east of the rio grande rift to near the continental escarpment data are primarily quaternary geologic slip rate estimates and resulting deformation determinations therefore are instantaneous in a geologic sense but long term with respect to earthquake cycles we deduce a rate of motion of the pacific plate relative to north america that is 48 2 mm yr a rate indistinguishable from that predicted by the global kinematic models rm2 and nuvel 1 however we obtain an orientation that is 5 9 counterclockwise of these models a more westerly motion of the pacific plate with respect to north america is calculated from all three paths the relatively westerly motion of the pacific plate is accommodated by deformation in the north american continent that includes slip on relatively counterclockwise oriented strike slip faults including the san andreas fault which is especially relevant in and south of the transverse ranges and a margin normal component of net extension across the continent which is especially relevant north of the transverse ranges deformation of the sw united states occurs in regionally coherent domains within which the style of deformation is approximately uniform in the vicinity of the transverse ranges two important shear systems splay from the san andreas fault the eastern california shear zone trending nnw from the eastern transverse ranges and the trans peninsular faults trending sse from the western and central transverse ranges within the transverse ranges the right lateral san andreas fault steps left seemingly requiring large amounts of convergence there however most of this convergence is avoided through a funneling flow of the crust toward the western transverse ranges and into the relatively narrow central california coast ranges and the northern motion of the mojave the former process involves an alternation of rotation direction from counterclockwise in and south of the central transverse ranges to clockwise in the western transverse ranges

blind thrusting surface folding and the development of geological structure in the mw 6 3 2015 pishan china earthquake the relationship between individual earthquakes and the longer term growth of topography and of geological structures is not fully understood but is key to our ability to make use of topographic and geological datasets in the contexts of seismic hazard and wider scale tectonics here we investigate those relationships at an active fold and thrust belt in the southwest tarim basin central asia we use seismic waveforms and interferometric synthetic aperture radar insar to determine the fault parameters and slip distribution of the 2015 mw 6 3 pishan earthquake a blind reverse faulting event dipping towards the tibetan plateau our earthquake mechanism and location correspond closely to a fault mapped independently by seismic reflection indicating that the earthquake was on a pre existing ramp fault over a depth range of 9 13 km however the geometry of folding in the overlying fluvial terraces cannot be fully explained by repeated coseismic slip in events such as the 2015 earthquake nor by the early postseismic motion shown in our interferograms a key role in growth of the topography must be played by other mechanisms the earthquake occurred at the tarim tibet boundary with the unusually low dip of 21 we use our source models from pishan and a 2012 event to argue that the tarim basin crust deforms only by brittle failure on faults whose effective coefficient of friction is 0 05 0 025 in contrast most of the tibetan crust undergoes ductile deformation with a viscosity of order 1020 1022 pa s this contrast in rheologies provides an explanation for the low dip of the earthquake fault plane

re examining pluton emplacement processes abstract previous pluton emplacement studies have attempted to explain how space is made during pluton emplacement in fact the only means of making space during emplacement of mantle derived magmas in the crust are 1 lowering the moho or 2 outward displacement of the earth s surface other pluton emplacement mechanisms are material transfer processes mtps that do not increase the volume of the crust one frequently cited mtp for emplacement of concentrically zoned and ballooning plutons is ductile flow of wall rocks around the plutons the expected structures and total strains near such plutons are dependent on the three dimensional pluton shape the width of the deforming aureole whether the pluton is a piercing or non piercing diapir and in the latter case the number of body radii the pluton travels we have re examined a few such plutons and calculated the amount of material transfer caused by ductile flow in no case is more than 40 and in most cases only 15 35 of the required material transfer accommodated by wall rock flow the contact aureoles around these plutons are too narrow and or strains too low indicating that the plutons are predominantly discordant bodies with narrow 0 1 0 4 pluton radii concordant aureoles a comparison of strains in natural contact aureoles and those made in mechanical models of diapirs indicates that natural strains are at least an order of magnitude less than model strains we suggest that the similarities between models of diapiric ascent of spherical bodies and concentrically zoned plutons are superficial because the models are too simplistic instead we argue that the ascent and emplacement of magmas require multiple near field and far field mtps these mtps will show gradients with depth distance from the magma and with time rates of near field mtps must be rapid whereas far field rates are probably nearer to long term average rates of orogenic processes

active tectonic studies in the united states 1987 1990 the techniques and instrumentation used in active tectonic studies are discussed and recent results are reviewed it is suggested that a critical mass of data on several particular regions has been accumulated making possible critical debates and attempts to assess earthquake hazards particular attention is given to studies of the pacific northwest region basin and range deformation studies and distributed deformation and hidden earthquake sources also included is a comprehensive bibliography for the period

rates of processes in magmatic arcs implications for the timing and nature of pluton emplacement and wall rock deformation abstract the construction of arcs and in many cases the emplacement of plutons occur in tectonically active regions it is critical therefore to evaluate the rates of structural and magmatic processes when trying to understand the evolution of arcs and the associated pluton wall rock systems our best estimates of average rates or durations of processes in shallow to moderate level arc environments are the following 1 crystal growth rates in magma of 10 4 cm year 1 2 growth rates of metamorphic porphyroblasts between 10 5 and 10 2 cm year 1 3 long term magma supply rates of 10 1 km 3 year 1 and short term rates of up to 350 km 3 year 1 4 diapiric ascent rates for mafic plutons of 1 3 m year 1 5 cooling of plutons to ambient wall rock temperatures in 10 5 10 6 years 6 final crystallization of plutons in a small fraction of the time needed for complete cooling 7 fault displacements of 3 cm year 1 8 development of cleavages in fault zones in less than 10 6 years at strain rates of 10 13 s 1 or higher and 9 the development of regional cleavages in 10 6 years at strain rates of 10 14 s 1 these rates indicate that processes operating in magmatic arcs are relatively rapid pluton emplacement cleavage development etc occur over time spans of tens of thousands to no more than a few million years however the rate of ascent and crystallization of plutons at shallow levels is generally shorter than that needed to get large displacements on faults or widespread cleavages developed at deeper levels or in zones undergoing faster strain rates the time spans of the various processes approach one another thus plutons with otherwise similar characteristics emplaced in regions undergoing fast strain rates or at deeper crustal levels may appear quite different structurally from those emplaced at shallow levels or in regions undergoing slower strain rates comparison of these data also suggests that the rate at which wall rock deforms is the limiting factor controlling the rates of other structural processes during emplacement of plutons unless fast strain rates or multiple deformation mechanisms are considered thus emplacement mechanisms that rely on the transport of magma over 10 5 to 10 6 years are favored and need further consideration finally we argue that the structural and other characteristics of pluton wall rock systems will depend on rates of various processes involved and that these rates at the very least influence and sometimes invalidate the timing criteria previously published by us and others

uplift of the western transverse ranges and ventura area of southern california a four technique geodetic study combining gps insar leveling and tide gauges

rapid active thrusting along the northwestern range front of the tanghe nan shan western gansu china the western part of the tanghe nan shan range southwest of subei western gansu china is presently growing on thrust ramps splaying from the left lateral altyn tagh fault late cenozoic thrusting has folded and sliced oligocene miocence red beds into an imbricate wedge capped by warped and uplifted quaternary terraces that form a 2 to 5 km wide ledge north of the steeply faceted range front seismic scarps 1 5 to 4 5 m high cut young fans along the outer thrusts carbon 14 dating of organic remains collected on strath terraces constrains the chronology of deposition and incision by the streams most of the fans and terraces in the southern part of the subei basin appear to have been emplaced after the last glacial maximum particularly during the early holocene optimum 9 5 ka measurements of the shapes of the warped terraces constrain minimum and maximum throws on the outer thrusts the minimum vertical throw of 34 2 m of a surface dated at 8411 530 years b p at one site provides a minimum vertical uplift rate of 4 1 0 5 mm yr the maximum possible uplift 115 15 m of the oldest terrace surface whose probable age is 15 to 18 ka places an upper bound on the uplift rate of 7 2 mm yr the thrust geometry at depth and the cumulative shortening 10 20 km deduced from balancing sections logged across the imbricate thrust wedge are consistent with a shortening rate of about 5 mm yr and an onset of thrusting at about 4 2 ma such a shortening rate implies a significant northward decrease in slip rate along the altyn tagh fault the recent growth of the western qilian mountain ranges thus appears to be intimately coupled with sinistral motion on the altyn tagh fault and the extrusion of tibet

a comparison of experimental and natural drainage basin morphology across a range of scales 1 numerous quantitative models have been developed to simulate the long term evolution of river basin topography most of these models reach an equilibrium state when the base level is lowered at a constant rate and the substrate and climate are constant in time at equilibrium the erosion balances the base level lowering so the topography remains frozen in time however some recent laboratory experiments contradict this behavior in these experiments the space time mean erosion rate balances the base level lowering rate but the actual erosion rates are highly variable in space and time consequently the channel networks are substantially mobile the experimental flow conditions are approximately similar but not dynamically equivalent to those in nature so it is unclear whether the observed dynamics are representative this paper examines whether the processes occurring in the experiments produce basins that are geometrically similar to typical natural basins to make this comparison the conceptual framework of scaling invariance is used many similarities are observed but we find that the experimental basins are slightly more elongated across a range of scales than the natural basins we consider and the relationship between channel slope and drainage area exhibits a break that is not found in the natural basins we analyze in the experiments the slopes of small channels also depend on the proximity of large channels this dependency is more pronounced for experiments with more mobile channel networks and it is not observed in most of the natural basins we analyze

late quaternary stream incision and uplift in the forearc of the cascadia subduction zone western oregon documentation of a latest pleistocene earliest holocene episode of strath formation and fluvial aggradation in the oregon coast range provides a datum from which long term bedrock stream incision rates are determined variations in long term incision rates probably reflect cumulative differential uplift in the forearc of the cascadia subduction zone although factors such as bedrock and climatic controls and isostatic adjustments to erosion obscure the precise relationship between surface uplift and stream incision patterns of differential incision are most striking near the latitude of newport where a steep gradient divides a region of higher rates 0 6 0 9 mm yr in the northern coast range from a region of lower rates 0 1 0 3 mm yr in the central coast range the steep incision gradient is nearly coincident with abrupt changes in marine terrace 80 125 kyr uplift rates the locations of quaternary faults and the southern flank of a saddle of low historic 40 70 years uplift the exact causes of these variable patterns of incision uplift are unknown analogies with uplift patterns in other subduction zones and comparisons with other neotectonic data in the region indicate that patterns of differential incision probably are caused by variations in permanent strain accumulation along the cascadia subduction zone such variations may be related to differences in seismic moment release during individual earthquakes to changes in plate geometry or rates of wedge accretion to segmentation of earthquake ruptures and or to deformation on active structures in the north american plate and accretionary wedge

geodetic measurement of tectonic deformation in the santa maria fold and thrust belt california we have analyzed geodetic observations to resolve tectonic deformation across the santa maria fold and thrust belt northwest of santa barbara california the geodetic network forms a braced quadrilateral with 40 km sides whose southwest corner is the vandenberg very long baseline interferometry station the data include 1 historical triangulation from the 1880s 1920s and 1950s 2 electronic distance measurement trilateration from 1971 and 1985 and 3 global positioning system observations from 1986 and 1987 we combine the three different types of data to estimate two dimensional station positions and strain rate parameters simultaneously using a model which constrains the relative velocity field to be linear in space and constant in time we find significant strain rates the maximum compressive strain is oriented n17 e 5 e and the compressive strain rate in this direction is 0 13 0 03 strain yr under the assumption that the unresolved rotational component of the velocity field is zero we estimate that the integrated rate of deformation across the basin is 7 1 mm yr oriented at n03 e 13 this vector can be decomposed into 6 2 mm yr of crustal shortening on the general structural trend of n30 e and 3 1 mm yr of right lateral shear across this axis on the basis of these values and earthquake focal mechanisms in the area we infer that the deformation occurs on northwest trending folds and thrusts within the belt these results are consistent with the rate and direction of deformation across the central california coast ranges inferred by balancing pacific north america plate motion against san andreas slip and basin and range extension they imply that the santa maria fold and thrust belt is the primary active element in transforming motion from the coast ranges to the western transverse ranges and the santa barbara channel