teleseismic source parameters of the rigan county earthquakes and evidence for a new earthquake fault two medium sized earthquakes occurred on 20 december 2010 and 27 january 2011 in rigan county kerman province southeastern iran according to the dislocation grid search method results the first event was nearly strike slip including reverse component strike 115 dip 50 and rake 5 whereas the second event had some amount of reverse component strike 125 dip 75 and rake 5 based on synthetic green s function deconvolution and aftershock distribution the down dip propagated rupture migrated toward southeast districts with low population distribution confirming the reason for low casualties meanwhile the aftershock distribution indicates the existence of a new earthquake fault for which we suggest the name rigan earthquake fault however the same aftershock distribution indicates that the second mainshock was inevitably triggered by the first one most probably along the continuation of the bam earthquake fault

geodynamics magmatism and degassing of the earth abstract in this study terrestrial degassing processes are identified formalized both on local and global scales and combined in a single model of evolution of the upper mantle which constitutes 1 3 of the silicate earth the crust and the atmosphere unknown parameters of these processes are estimated by means of numerical modelling the model envisages early intensive convection and fractionation in the upper mantle resulting in sharp degassing of its matter later relatively slow convection in this reservoir accompanied by partial melting of silicate matter in rift and subduction zones uplift of melts into the oceanic and continental crust and their degassing early formation and subsequent recycling of the continental crust and its degassing due to intracrustal magmatism and metamorphism and accumulation of gases excepting he in the atmosphere magmatic processes are considered the most important for terrestrial degassing two stages of these processes i e partitioning of the gases between melted and solid portions and partial degassing of melt yield a pronounced u shaped fractionation of noble gases helium and neon due to high solubility and accordingly conservation in partially degassed melts as well as xenon due to a high partition coefficient and accordingly conservation in residual portions are released from partially melted matter much more slowly than argon to reconcile calculated and observed noble gas data a high rate of recycling of mantle matter must be provided in the past 74 10 17 g y during the first 0 1 ae about 90 of 36 ar had been released into the atmosphere at that time later this rate decreased sharply down to its contemporary value of about 0 6 10 17 g y less than 0 3 of 36 ar is still conserved in the upper mantle the degassing process resulted in a pronounced u shaped fractionation of noble gases in this reservoir 20 ne 36 ar m 20 ne 36 ar air 3 and 130 xe 36 ar m 130 xe 36 ar air 7 4 he 3 he and 40 ar 36 ar in the upper mantle both depend on the radioactive decay of parent elements and the rate of mantle degassing note that the noble gas radiogenic degassing clock was the only one functional during early stages of the evolution of the earth the complementary reservoir continental crust was formed very early its mass attaining the contemporary value at about 4 ga self consistent concentrations of radioactive elements in the silicate earth upper mantle crust are considerably higher than recent estimates a concentration of k equal to 0 048 is determined by 40 ar amounts in the mantle the crust and mainly in the atmosphere correspondingly u becomes 0 038 ppm and th 0 152 ppm contemporary ratios of k u 13 000 and solth u 4 being assumed for all silicate reservoirs the total contemporary fluxes atoms cm 2 sec of 3 he 4he and 40 ar rad are equal to 4 3 2 0 10 6 and 0 66 10 6 respectively practically the whole 3 he flux and 1 4 of the 4 he flux are produced by upper mantle degassing the residence times for k and 40 ar rad in the upper mantle are 1 1 and 4 1 ga respectively resulting in an enormously high value for its k ar age 4 4 ga the continental crust residence times for both species k and ar are high and the crustal mean k ar age is 1 6 ga

lateral structural variations and drainage response along the misikantage anticline in the western kuqa fold and thrust belt southern tianshan nw china abstract the cenozoic kuqa fold and thrust belt kftb along the southern piedmont of the tianshan mountains nw china provides excellent chances for investigating active deformation and its controls on landscape topography in contrast to the well imaged eastern kftb the structural deformation in the western part complicated by the development of early stage salt structures still has not been well investigated on the basis of seismic reflection profiles well data and surface geology combined with previously determined paleomagnetic ages this study focuses on the deformation style onset and average shortening rate of the misikantage anticline in the western kftb together with the morphometric analysis of satellite images and digital elevation models dems we have demonstrated that 1 the misikantage anticline is an asymmetric detachment fold where the fold geometry amounts of shortening outcropping strata and channel network patterns vary along strike 2 syntectonic growth strata recognized from seismic profiles combined with paleomagnetic ages indicate that the folding started at 2 4 ma and resulted in 0 3 0 9 km of shortening yielding an average shortening rate of 0 12 0 38 mm yr 3 the landscape topography and drainage networks markedly change in response to lateral structural variations these findings would provide a basis for further comparisons of compressional structures between the eastern and western kftb which are also helpful in better understanding active folding in fold and thrust belts particularly where thick salt is involved in deformation

empirical observations regarding reverse earthquakes blind thrust faults and quaternary deformation are blind thrust faults truly blind active thrust faults pose a significant seismic hazard worldwide many of these faults include blind thrusts where the propagating fault tip does not reach the earth s surface and buried faults where the geomorphic expression of the fault is obscured by subsequent sedimentation and or erosion this raises the issue of whether conventional geologic geomorphic and paleoseismic methods can be used to identify and characterize thrust faults for the assessment of seismic hazards or whether these faults sometimes are truly blind we compiled a data base of 148 worldwide moderate to large magnitude thrust reverse earthquakes to evaluate whether or not the event occurred on a fault that could have been identified prior to the earthquake on the basis of recognizable quaternary surface deformation i e a pre existing fault or fold analysis of the data shows that interplate reverse earthquakes almost always are associated with pre existing quaternary deformation that was or could have been recognized prior to the earthquake in particular most interplate reverse earthquakes are associated with an active reverse fault at the surface and or an active anticline in contrast intraplate reverse earthquakes seldom occur on faults associated with pre existing recognizable surface deformation we conclude that thrust faults can be detected in interplate regions with careful quaternary geologic and geomorphic mapping furthermore the absence of quaternary surface deformation can be used to infer the absence of an underlying active blind thrust fault in interplate tectonic settings however the data show that quaternary geologic mapping techniques alone likely are insufficient to characterize blind thrusts in intraplate regions in these areas inclusion of a floating or random earthquake may be necessary to assess earthquake hazards

the 1994 sefidabeh earthquakes in eastern iran blind thrusting and bedding plane slip on a growing anticline and active tectonics of the sistan suture zone summary in 1994 a sequence of five earthquakes with mw 5 5 6 2 occurred in the sistan belt of eastern iran all of them involving motion on blind thrusts with centroid depths of 5 10 km coseismic ruptures at the surface involved bedding plane slip on a growing hanging wall anticline displaying geomorphological evidence of uplift and lateral propagation the 1994 earthquakes were associated with a nw trending thrust system that splays off the northern termination of a major n s right lateral strike slip fault elevation changes along the anticline ridge suggest that displacement on the underlying thrust dies out to the nw away from its intersection with the strike slip fault this is a common fault configuration in eastern iran and accommodates oblique ne sw shortening across the n s deforming zone probably by anticlockwise rotations about a vertical axis this style of fault kinematics may be transitional to a more evolved state that involves partitioning of the strike slip and convergent motion onto separate subparallel faults

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

estimates of heat flow derived from gas hydrates a gas hydrate phase boundary in marine sediments is often observed as an anomalous reflector in seismic profiling data from the depth of the reflectors heat flow values can be estimated using the phase relation of the gas hydrate system and inferred density and thermal conductivity of sediments this method is applied to the data in the nankai trough around central america and along the blake outer ridge the estimated values consistent with those measured by conventional means suggest that derivation of heat flow by this method is feasible on the landward slope of the nankai trough we find that heat flow increases downslope toward the floor of the trough

active faulting within a megacity the geometry and slip rate of the pardisan thrust in central tehran iran geological survey of iran christ church college oxford natural environment research council economic and social research council

uniform postglacial slip rate along the central 600 km of the kunlun fault tibet from 26al 10be and 14c dating of riser offsets and climatic origin of the regional morphology late pleistocene holocene sinistral slip rates on several segments of the kunlun fault in northeastern tibet have been determined these determinations are based on the measured displacement of alluvial surfaces whose surface ages were determined by cosmogenic 2 6 al and 1 0 be dating of quartz pebbles and by 1 4 c dating of charcoal in the west at three sites along the xidatan dongdatan segment of the fault near 94 e terrace riser offsets ranging from 24 to 110 m with cosmogenic ages ranging from 1800 to 8200 yr yield a mean left lateral slip rate of 11 7 1 5 mm yr 1 field observations indicate minimum offsets of 9 12 m this offset when combined with the long term slip rate indicates that great earthquakes m 8 rupture this segment of the fault with a recurrence interval of 800 1000 yr at two sites along the dongxi anyemaqin segment of the fault near 99 e terrace riser offsets ranging from 57 to 400 m with 1 4 c ages ranging from 5400 to 37 000 yr bp yield a minimum slip rate of 10 mm yr 1 at one site the 1937 january 7 m 7 5 and the penultimate earthquakes produced 4 m of left slip and 0 4 m of reverse slip the maximum recurrence interval of earthquakes with such characteristic slip is thus 400 yr farther east near 100 5 e along the maqen segment of the fault the 180 m offset of a lateral moraine emplaced between the last glacial maximum 20 ka and 11 100 yr bp yields a mean slip rate of 12 5 2 5 mm yr 1 the slip rates are constant within uncertainty throughout the 600 km of the kunlun fault that we studied the average slip rate is 11 5 2 0 mm yr 1 extrapolating this rate to the reminder of the fault we conclude that most 80 per cent of the 300 morphological offsets measured in the field or on spot satellite images post date the last glacial maximum most of the terraces we studied were deposited during the humid period of the early holocene optimum 9 5 ka the formation of younger terraces reflects late holocene climate change

borehole heat flow along the eastern flank of the juan de fuca ridge including effects of anisotropy and temperature dependence of sediment thermal conductivity the thermal conductivities of 15 whole round sediment samples collected during ocean drilling program odp leg 168 between 17 and 440 m below the seafloor on the eastern flank of the juan de fuca ridge were tested to document their anisotropy and temperature dependence using the divided bar technique tests over a temperature range of 5 c to 60 c reveal variations in conductivity of up to 15 the sign and amplitude of these variations depend on the thermal conductivity at laboratory room temperature rt if rt 0 8 w m 1 k 1 high porosity conductivity increases with temperature if rt 1 2 w m 1 k 1 moderate porosity conductivity does not change with temperature if rt 1 6 wm 1k 1 low porosity conductivity decreases with temperature this behavior results from a positive temperature coefficient for seawater t and a negative coefficient for rock matrix 1 t a special sampling technique for unconsolidated sediments made it possible to measure horizontal hor and vertical ver components of thermal conductivity independently and to determine a mean anisotropy value hor ver of 1 2 corrections which are 10 for anisotropy and 1 for temperature were applied using in situ temperatures shipboard line source thermal conductivities porosities and the geometric mean mixing model that accounts for matrix and porewater constituent conductivities on the basis of these corrected conductivities and a harmonic averaging of values weighted according to the lithologic division of the sediment sections into clay rich and sand rich units values of heat flow estimated from borehole temperature measurements are lower than those previously estimated by 10 except for one site where the section is dominated by sand shallow seafloor heat flow measured with gravity driven probes may also need to be corrected for anisotropy although the degree of anisotropy in the unconsolidated high porosity sediments within a few meters of the seafloor is poorly constrained

noble gas elemental and isotopic abundances in deep sea trenches in the western pacific abstract noble gas elemental and isotopic abundances were measured in seven deep sea water samples from five different sampling sites in the nankai trough the japan trench and the kuril trench the samples were obtained by the manned submersible nautile most of the sampling sites are associated with clam colonies and or fluid venting excesses both in 3 he 4 he ratio and he concentration are observed in a seawater sample collected a few kilometers off the clam colonies which were found at a depth of 3830 m at the mouth of the tenryu canyon concentrations of noble gases ne ar kr and xe in this sample show progressive depletion from ne to xe relative to those in 1 c air saturated seawater which can be attributed to mixing of hot water 15 c with cold ambient water 1 c isotopic compositions of ne ar kr and xe in this sample are atmospheric these observations may reflect venting of hot pore water around the tenryu canyon all the other samples show a significant excess in concentration of all noble gases relative to 1 c air saturated seawater and the isotopic compositions are atmospheric this excess of noble gas concentrations may appear to be air contamination in the samples however results of hydrocarbon analyses of the kaiko samples imply that such large amount of air contamination is improbable decomposition of gas hydrate in deep sea sediments is a more likely explanation for the observed excess of noble gas concentration

noble gas evidence for two fluids in the baca valles caldera geothermal reservoir noble gas elemental and isotopic abundances were measured in steam from four wells in the baca geothermal reservoir located in the valles caldera new mexico the 40ar36ar ratio and noble gas elemental abundances relative to 36ar are all strongly correlated with 1 36ar the inverse of the argon content ratios of n produced 21ne and radiogenic 40ar to total 4he dominantly radiogenic are nearly constant at 2 1 10 8 and 0 20 respectively the 3he4he ratio covers a restricted range of 3 9 to 4 8 times atmospheric the high 3he content of the gas indicates the presence of a helium component ultimately derived from the mantle kr and xe isotopic compositions are close to atmospheric excess 129xe is 0 25 of the total 129xe the high degree of linear correlation among the various noble gas results strongly suggests that the baca reservoir contains two distinct fluids that are produced in varying proportions from individual wells the noble gases in fluid a 2900 mg 1 c1 are air like but with lighter gases and isotopes preferentially enriched the fluid a 36ar content is low only 13 that of 10 c air saturated water asw the second fluid b 1700 mg 1 c1 is the dominant carrier of the radiogenic and mantle derived gases the heavier non radiogenic gases are preferentially enriched in fluid b and its 36ar content is very low only 5 7 asw the source of the noble gases in fluid a is tentatively ascribed to leaching of the relatively young 1 4 m y volcanic bandelier tuff the radiogenic gases and mantle derived helium in fluid b suggest a deeper source possibly including gases escaping from a magma

search for the mantle nitrogen in the ultramafic xenoliths from san carlos arizona abstract mineral separates olivine ol clinopyroxene cp and orthopyroxene op of ultramafic xenoliths from san carlos have been analyzed for nitrogen and noble gases in an effort to evaluate the isotopic signatures for the sub continental mantle the concentrations of noble gases are generally small but in one clinopyroxene separate cp1 they are about an order of magnitude higher the gases seem mostly to be sited in fluid inclusions elevated isotopic ratios of 20 ne 22 ne 40 ar 36 ar 129 134 136 xe 132 xe with respect to air clearly show the presence of mantle noble gas components in san carlos xenoliths isotopic ratios of xe and ar show that the noble gas systematics in san carlos xenoliths can be explained as a mixture of morb and air like components nitrogen contents in these separates range from 0 1 to 1 5 ppm the 15 n varying from 2 to 5 in totals and from 9 to 10 in the temperature fractions the nitrogen data can be explained by the presence of at least three components a a light nitrogen component 15 n 9 of mantle origin b a heavy nitrogen component 15 n 15 from recycled materials and c an air like nitrogen component 15 n 0 which is incorporated during the emplacement of the host magma while the noble gas isotopic ratios cannot clearly distinguish between an atmospheric and a recycled component 15 n clearly resolves these two using the noble gas and nitrogen isotopic systematics and the end member values from the literature a contribution of 30 to 60 recycled nitrogen component has been estimated in the mantle source region of san carlos xenoliths

drainage diversions as evidence of propagating active faults example of the el asnam and thenia faults algeria digital elevation models and aerial photographs provide evidence of past drainage diversions associated with known and inferred active faults in northern algeria the el asnam anticline is a fault bend fold that is growing in response to displacement on the historically active el asnam fault the diversion of the fodda river and a sequence of uplifted palaeovalleys across the anticline formed in response to the active southwestward propagation of the sidi ada el ardja segment of the el asnam anticline deformation associated with the 1980 el asnam earthquake ms 7 3 and its effect on drainage demonstrate the occurrence of coseismic uplift of the el asnam anticline associated with slip on the underlying thrust fault similar geomorphic relations are observed between the isser river and the thenia fault diversions of the isser river and evidence for quaternary uplift indicate that the thenia fault which is close to algiers is tectonically active and should be considered to be a source of potentially damaging earthquakes

the structural evolution of active fault and fold systems in central otago new zealand evidence revealed by drainage patterns abstract central otago in new zealand is an area of active continental shortening in which a peneplain surface cut into schist has been deformed by folds which are developed above buried reverse faults we use the drainage patterns in this region to demonstrate various processes in fold and fault growth and interaction that would be difficult to identify by other means in particular we show 1 how simple asymmetric folds can develop into box folds 2 how apparently continuous ridges were formed by the coalescing of quite separate propagating fold and fault segments 3 evidence for the relative ages or relative uplift rates of adjacent structures and 4 evidence for the propagation direction of folds or faults as they grow the few quantitative estimates we obtain for fault propagation rates suggest an increase in length of 10 50 m per earthquake on faults about 20 km long these estimates are very uncertain but are similar in magnitude to an estimate made in nevada for a normal fault of similar size and are also similar to predicted estimates from theoretical growth models they raise the question of whether fault growth earthquake recurrence rates and climate change can interact to produce semi regular discrete features in an active landscape

gas hydrate stability and the assessment of heat flow through continental margins summary a prominent feature across some continental margins is a bottom simulating reflector bsr this seismic reflection generally coincides with the depth predicted for the base of the gas hydrate stability field because the occurrence of gas hydrates is controlled by temperature and pressure conditions it has been suggested that bsrs mark an isotherm and they have therefore been used to estimate the heat flow through continental margins crucial parameters are the temperature at bsr depth and at the seafloor and the thermal conductivity structure between the bsr and the seabed however very often the required parameters are not available and therefore they have been derived from models for gas hydrate stability and empirical relationships to obtain thermal conductivities from seismic velocities here we use downhole temperature thermal conductivity porosity and logging data from 10 ocean drilling program odp sites drilled into and through the gas hydrate field to investigate the quality of estimates our analyses and application of constraints to the makran margin off pakistan indicate the following i the temperature at bsr depth could be approximated by a seawater methane system although capillary forces chemical impurities or non equilibrium conditions can lower or increase the temperature if calibration by heat probe measurements is possible errors of geothermal gradients are less than 10 per cent otherwise uncertainties of 20 per cent or even higher may arise in addition seasonal variations of bottom water temperature have to be considered because they may affect thermal gradients by up to y10 per cent ii the impact of typical quantities of low thermal conductivity gas hydrate on the bulk thermal conductivity is insignificant iii the thermal conductivity profile between the bsr and the seabed can generally be approximated by a mean value thus iv seabed measurements should be used instead of empirical relationships which may produce errors of 5 30 per cent consequently in addition to high quality seismic data a prerequisite should be a large data set of thermal conductivities and oceanographic data heat probe measurements are recommended to constrain geothermal gradients in this case the uncertainty of heat flow is 5 10 per cent of the estimated heat flow if these data are not available errors uncertainties can reach 50 60 per cent of the calculated value

control of detachment dip on drainage development in regions of active fault propagation folding we have studied drainage development on active folds by using a numerical model that couples the kinematics of fault propagation folding to a physical description of surface processes modeling results suggest that the dip of the underlying detachment exerts a major control on drainage development for a nonzero detachment dip the lateral displacement gradient sets up an axial slope behind the growing fold that diverts drainage so that the fold is shielded from rivers with large incision capacity in this case the characteristic fault segment length rather than the relative rates of fold uplift and incision may control the spacing of transverse streams we apply our model to the foothills of the nepal himalayas and suggest that striking differences in drainage patterns between central and western nepal are controlled to a first order by variations in the dip of the underthrusting indian plate

strike slip faulting rotation and along strike elongation in the kopeh dagh mountains ne iran summary the kopeh dagh is a linear mountain range separating the shortening in iran from the stable flat turkmenistan platform in its central part is an array of active right lateral strike slip faults that obliquely cut the range and produce offsets of several kilometres in the geomorphology and geological structure they are responsible for major destructive earthquakes in the 19th and 20th centuries and represent an important seismic hazard for this now populous region of ne iran these strike slip faults all end in thrusts revealed by the uplift and incision of late quaternary river terraces and do not continue beyond the atrak river valley which forms the southern margin of the kopeh dagh the cumulative offset on these strike slip faults and their associated rotation about vertical axes can account for 60 km of n s shortening this value is similar to estimates of the late quaternary n s right lateral shear between central iran and afghanistan which must be accommodated in ne iran the strike slip faults also require 30 km of along strike extension of the kopeh dagh which is taken up by the westward component of motion between the south caspian basin and both eurasia and central iran it is probable that these motions occurred over the last 10 ma

application of aster data for exploration of porphyry copper deposits a case study of daraloo sarmeshk area southern part of the kerman copper belt iran abstract the cenozoic urumieh dokhtar magmatic belt udmb of iran is a major host to porphyry cu mo au deposits pcds most known pcds in the udmb occur in the southern section of the belt also known as the kerman copper belt kcb three major clusters of pcds are distinguished in the kcb and include the miduk sarcheshmeh and daraloo clusters the daraloo and sarmeshk deposits occur in a northwest southeast trending fault zone that is characterized by the presence of a narrow zone of alteration mineralization that contains a series of oligocene granitoids and miocene porphyritic tonalite granodiorite plutons that cut eocene andesitic lava flows and pyroclastic rocks here we use various techniques including different ratio images minimum noise fraction pixel purity index and matched filter processing to process aster data 14 bands and generate maps that portray the distribution of hydrothermal minerals e g sericite kaolinite chlorite epidote and carbonate related to pcd alteration zones in order to validate the aster data follow up ground proofing and related mineralogical work was done which in all cases proved to be positive the results of this work have identified the regional distribution of hypogene alteration zones i e phyllic argillic propylitic and silicic in addition to areas of secondary fe oxide formation which are coincident with known sites of pcds the regional distribution and extent of the alteration zones identified also highlighted the role of regional structures in focusing the mineralizing altering fluids these results demonstrate very convincingly that aster imagery that uses the appropriate techniques is reliable and robust in mapping out the extent of hydrothermal alteration and lithological units and can be used for targeting hydrothermal ore deposits particularly porphyry copper deposits where the alteration footprint is sizeable

noble gas isotopic systematics of fe ti v oxide ore related mafic ultramafic layered intrusions in the panxi area china the role of recycled oceanic crust in their petrogenesis olivine and clinopyroxene grains have been separated from four large fe ti v oxide ore bearing intrusions panzhihua hongge baima and taihe in the panxi area emeishan large igneous province southwest china for he and ar isotope studies the samples examined revealed extremely low 3 he 4 he ratios 0 078 4 34 ra with the mean value 0 78 ra for gases extracted by stepwise heating this feature combined with low 40 ar 36 ar ratios can be interpreted as due to addition of subduction related fluids and melts that had been stored in the lithospheric mantle for long periods considering the regional geologic history such addition can be attributed to the paleo subduction that occurred along the western margin of the yangtze block during the neoproterozoic the subducted oceanic crust beneath the panxi area underwent eclogite facies metamorphism and subsequent exhumation the infiltration of subduction related melts and fluids into the lithospheric mantle led to enriched isotopic signatures from that of the slightly depleted asthenopheric mantle which has been suggested by the sr nd and pb isotopic data of the emeishan basalts and picrites in addition considerable amounts of eclogitic melts produced by partial melting of eclogite facies oceanic crust extensively contaminated the lithospheric mantle during the late permian partial melting of an upwelling mantle plume that contained an eclogite or pyroxenite component generated the parental fe rich magma that supplied the ore bearing intrusions the combination of these factors may have been the crucial reason that many world class fe ti v oxides deposits are clustered in the panxi area

estimation of slip rates in the southern tien shan using cosmic ray exposure dates of abandoned alluvial fans cosmic ray exposure dates based on in situ produced 10 be in combination with measured heights of fault scarps that cut three abandoned fans imply a slip rate of less than 2 mm yr on the bounding thrust fault along a segment of the southern flank of the tien shan of central asia this rate somewhat lower than those for the segment farther west and for the northern margin of the belt implies that the distribution of shortening across the tien shan must change markedly along the belt the date of abandonment of the smallest of the three fans is consistent with fan formation since the last glacial maximum but the other two fans appear to have been formed and abandoned prior to that time these and other results suggest that advances and retreats of alpine glaciers may not be synchronized with continental ice sheets and that not all prominent geomorphological features in arid asian regions have formed since the last glacial maximum in this study we have assessed the relationship between cosmogenic nuclide content of individual clasts and the time since their deposition on a surface cosmogenic nuclide accumulation represents the integrated total surface exposure of rocks in source regions during transport and since deposition postdepositional processes erosion burial bioturbation and cryoturbation all of which decrease the quantity of cosmogenic nuclides produced in a rock in a given time and hence the apparent exposure age also cause significant scatter among apparent ages of samples from the surfaces very low 10 be concentrations in material from active streambeds and at depth below one of the fan surfaces indicate that exposure prior to deposition onto fan surfaces was minimal

reply to comment on near surface location geometry and velocities of the santa monica fault zone los angeles california by r d catchings g gandhok m r goldman d okaya m j rymer and g w bawden by t l pratt and j f dolan in a comment on our 2008 paper catchings gandhok et al 2008 on the santa monica fault in los angeles california pratt and dolan 2010 herein referred to as p d cite numerous objections to our work inferring that our study is flawed however as shown in our reply their objections contradict their own published works published works of others and proven seismic methodologies rather than responding to each repeated invalid objection we address their objections by topic in the subsequent sections in catchings gandhok et al 2008 we presented high resolution seismic reflection images that showed two near surface faults in the upper 50 m beneath the grounds of the wadsworth veterans administration hospital wvah although p d suggest we effectively duplicated their seismic acquisition our survey was not a duplication of their efforts rather we conducted a seismic imaging survey over a similar profile as pratt et al 1998 but used a different data acquisition system and different data processing methods to evaluate methods of seismically imaging blind faults in the wake of the 17 january 1994 m 6 7 northridge earthquake we used an acquisition method that provides both tomographic seismic velocities and reflection images our combined data approach allowed for shallower imaging 2 5 m minimum than the 20 m minimum of pratt et al 1998 clearer images of the fault zone and more accurate depth determinations rather than time images in processing the reflection images we used prestack depth migration which is generally accepted as the only proper imaging method for imaging subsurface structures with strong lateral velocity variations versteeg 1993 a condition shown to exist at the wvah site we correlated our reflection images with refraction tomography images borehole lithology and velocity data interferometric synthetic aperture radar images and changes in groundwater depths except for some minor differences our seismic reflection images coincide with previously published seismic reflection

active faulting earthquakes and restraining bend development near kerman city in southeastern iran abstract we provide descriptions of strike slip and reverse faulting active within the late quaternary in the vicinity of kerman city in southeastern iran the faults accommodate north south right lateral shear between central iran and the dasht e lut depression the regions that we describe have been subject to numerous earthquakes in the historical and instrumental periods and many of the faults that are documented in this paper constitute hazards for local populations including the city of kerman itself population 200 000 faults to the north and east of kerman are associated with the transfer of slip from the gowk to the kuh banan right lateral faults across a 40 km wide restraining bend faults south and west of the city are associated with oblique slip on the mahan and jorjafk systems the patterns of faulting observed along the mahan jorjafk system the gowk kuh banan system and also the rafsanjan rayen system further to the south appear to preserve different stages in the development of these oblique slip fault systems we suggest that the faulting evolves through time topography is initially generated on oblique slip faults as is seen on the jorjafk fault the shortening component then migrates to reverse faults situated away from the high topography whereas strike slip continues to be accommodated in the high mountainous regions as is seen for example on the rafsanjan fault the reverse faults may then link together and eventually evolve into new through going strike slip faults in a process that appears to be occurring at present in the bend between the gowk and kuh banan faults

deep sea drilling project geothermal measurements a review in this article the geothermal measurements made from the scientific drilling ship glomar challenger are evaluated edited and reviewed for a number of sites the heat flow values given in the initial reports of the deep sea drilling project have been revised less than half of the boreholes in which thermal measurements were attempted gave reliable data by the end of the deep sea drilling project dsdp in 1983 reliable borehole heat flow measurements had been obtained at some 80 sites in all of the world oceans except the arctic the reliable values are considered to represent the deeper heat flux to within 20 for a few the accuracy is within 5 most temperature measurements have been obtained using probes penetrating the undisturbed sediments at the bottom of the hole at subbottom depths of between 75 m and 250 m although some data have been obtained at depths less than 30 and over 1000 m temperatures have been obtained a significant distance into the crust in eight holes the main general conclusions are as follows 1 there are no large or systematic differences between borehole heat flow values and oceanographic probe values obtained nearby such a test of shallow penetration oceanographic probe measurements was one of the first objectives of the dsdp heat flow program 2 there are very few clear smooth changes of borehole heat flow with depth in areas with thick sedimentary sections that are indicative of either long term bottom water temperature changes tens to thousands of years or large heat production in the sediments vertical migration of sediment interstitial pore water is suggested by nonlinear temperature depth profiles at a few sites particularly where the sediment is relatively thin and the temperature gradient is high 3 temperatures in the crustal parts of deep sea drill holes exhibit a wide range of behavior generally indicating hydrothermal circulation in the upper crust at five sites seawater is inferred to be moving down the holes into the crust indicating low formation pressures and very high permeability in the upper crust in two deep holes however such flow is limited to above several hundred meters into the crust and heat fluxes close to theoretical cooling lithosphere values for the age of the crust 6 and 7 ma are found at greater depth these sites suggest that hydrothermal circulation may be concentrated at shallow depths in the crust summary tables are presented of the heat flow data considered to be reliable after review and revision and an appendix provides detailed comments on all the measurements for which data are available geothermal measurements are continuing on the new ocean drilling program ship joides resolution

late cretaceous to recent deformation related to inherited structures and subsequent compression within the persian gulf a 2d seismic case study abstract the persian gulf is part of an asymmetric foreland basin related to the zagros orogen few published studies of this basin and associated onshore areas include seismic reflection data we present a seismic stratigraphic interpretation based on marine 2d seismic data which reveals the presence of two types of compressional structures within the basin 1 faulted domes related to salt movement and the offshore trace of a nne ssw trending dextral basement fault the kazerun fault 2 long wavelength 16 km low amplitude 60 ms two way travel time folds relating to the advancing deformation front associated with the orogen thinning of age constrained stratal units across structures related to the offshore trace of the kazerun fault implies a distinct pulse of uplift on this fault during the maastrichtian the geometry of growth strata across other intra basin structures suggests a second later stage of deformation which began in the middle miocene thickening and folding of post middle miocene stratal units towards the ne i e towards the zagros orogen is interpreted to reflect rapid loading subsidence and compression related to southwestwards advance of the orogen the results of this study have implications for the interaction between pre existing structures and later compressional events both within the persian gulf and elsewhere

geomorphic criteria to determine direction of lateral propagation of reverse faulting and folding fault related folds develop above active faults and as these faults propagate laterally so do the folds they produce geomorphic criteria useful in evaluating rates and direction of lateral propagation of active folds in the direction of propagation are 1 decrease in drainage density and degree of dissection 2 decrease in elevation of wind gaps 3 decrease in relief of the topographic profile along the crest 4 development of characteristic drainage patterns 5 deformation of progressively younger deposits or landforms and 6 decrease in rotation and inclination of forelimb all these criteria are consistent with lateral propagation but do not prove it the presence of more than one wind or water gap formed by the same stream however is strong evidence of lateral propagation rates of lateral propagation of folding may be several times the rate of uplift and fault slip lateral propagation of anticlinal folds allows for a new explanation of how drainage may develop across active fold belts development of drainage across an active fold belt is probably a function of relatively long structurally controlled drainage diversion parallel to fold axes and development of relatively short antecedent stream reaches around the nose plunge panel of a fold water and or wind gaps form as uplift drainage diversion and stream capture associated with fold growth continue

geographical distribution of 3he 4he ratios in japan implications for arc tectonics and incipient magmatism the 3he 4he and 4he 20ne ratios of 115 natural gas samples including various types of gases from volcanoes hot springs mineral springs water wells petroleum fields and natural gas fields were measured using a mass spectrometer the observed 3he 4he and 4he 20ne ratios range from 7 47 10 8 to 9 65 10 6 and from 0 26 to 1100 respectively the 3he 4he ratios reflect well the geotectonic structure of the japanese islands in northeastern ne japan there is a clear geographical difference in the 3he 4he ratios between the frontal arc forearc and volcanic arc back arc regions lower ratios were found in the trench side region and higher ratios in the back arc side this result suggests that the mantle derived helium in the volcanic arc region is associated with the diapiric uprise of a magma lower 3he 4he ratios in the frontal arc region may be due to radiogenic he produced by radioactive decay of u and th in the crustal and sedimentary rocks in southwestern sw japan there is no clear geographical contrast in the 3he 4he ratios some samples in the frontal arc region show quite high 3he 4he ratios the tendency of the 3he 4he ratios agrees with the distribution of terrestrial heat flow data and reflects geotectonic structures different from ne japan the high 3he 4he ratios observed in the frontal arc region in sw japan may be indicative of renewed or incipient magmatism due to a descending young and warm slab

strike slip kinematics in central and eastern iran estimating fault slip rates averaged over the holocene 1 according to gps measurements the right lateral shear between central iran and afghan blocks amounts to 16 mm yr a model based on very long term estimates of fault rates suggests the current shear originated about 5 ma ago and has been accommodated by strike slip faulting limited to the western 2 mm yr gowk nayband fault and eastern 14 mm yr sistan system fault edges of the lut block we have used high resolution spot5 pixel size 2 5 m images to measure recent cumulative offsets and estimate slip rates over shorter time periods that average several seismic cycles only recent offsets a few tens of meters have been found along the anar fault inside the central iran plateau and along the sistan faults east of the lut the offset morphologies postdate the last incision of the network and are most probably of holocene age 12 2 ka the corresponding slip rates range between 0 5 0 75 mm yr 1 75 2 5 mm yr 1 5 mm yr 1 2 5 mm yr for the anar east neh west neh and asagie fault respectively these estimates suggest the gps shear rate across the lut may not extrapolate over the holocene they also indicate strike slip faulting is not confined to the lut edges but also occurs in central iran suggesting the ongoing strike slip tectonics might have originated between 8 and 22 ma ago earlier than considered previously and consistent with observations in ne iran

interseismic and postseismic shallow creep of the north qaidam thrust faults detected with a multitemporal insar analysis understanding the mechanisms by which earthquake cycles produce folding and accommodate shortening is essential to quantify the seismic potential of active faults and integrate aseismic slip within our understanding of the physical mechanisms of the long term deformation however measuring such small deformation signals in mountainous areas is challenging with current space geodesy techniques due to the low rates of motion relative to the amplitude of the noise here we successfully carry out a multitemporal interferometric synthetic aperture radar analysis over the north qaidam fold thrust system in ne tibet where eight mw 5 2 earthquakes occurred between 2003 and 2009 we report various cases of aseismic slip uplifting the thickened crust at short wavelengths we provide a rare example of a steep shallow 13 km long and 6 km wide afterslip signal that coincides spatially with an anticline and that continues into 2011 in response to a mw 6 3 event in 2003 we suggest that a buried seismic slip during the 2003 earthquake has triggered both plastic an elastic folding and aseismic slip on the shallow thrusts we produce a first order two dimensional model of the postseismic surface displacements due to the 2003 earthquake and highlight a segmented slip on three fault patches that steepen approaching the surface this study emphasizes the fundamental role of shallow aseismic slip in the long term and permanent deformation of thrusts and folds and the potential of interferometric synthetic aperture radar for detecting and characterizing the spatiotemporal behavior of aseismic slip over large mountainous regions

cenozoic kinematic evolution of southwestern central iran strain partitioning and accommodation of arabia eurasia convergence abstract the yazd block of southwestern central iran is located in the back of the zagros fold thrust belt and monitors accommodation of cenozoic shortening within the arabia eurasia collision zone the saghand area within the yazd block exposes a basin and range type morphology which results from ne respectively e w direction of shortening and a major tectonic change in structural trends within the southwestern central iranian block the nne structural trend of various lithotectonic units including the eocene chapedony metamorphic core complex in the north is parallel to prominent cenozoic nne trending chapedony and posht e badam strike slip faults in the south the nnw trending anar kharanagh zarrin behabad and kuhbanan faults are parallel to the zagros fold thrust belt and represent dextral strike slip respectively ne directed thrust faults the thrust component representing a back thrust component to the zagros fold thrust belt results of interpretation of satellite images and structural and geomorphic field observations show a distributed deformation pattern covering a wide domain within southwestern central iran morphotectonic features like linear mountain ranges and intervening basins kavirs are interpreted to result from neogene to recent crustal scale folding with uplifting mountain ranges and subsiding basins active thrust faults and evidence for block tilting are common on the eastern side of mountain blocks five distinct regional deformation phases respectively paleostress tensor groups have been recognized in the central iran from the major structures and through using paleostress inversion techniques for fault slip data the first phase occurred in the late paleocene to oligocene and is characterized by a subvertical 1 and ca n s oriented 3 which indicate n s extension associated with late stages of normal faulting possibly due to post orogenic collapse during exhumation of the chapedony metamorphic complex the second phase occurred from late oligocene time onwards with an nne ssw to ne sw trending subhorizontal 1 and wnw ese to nw se trending 3 patterns due to transpressional deformation associated with a combination of thrusting and strike slip faulting the ne sw to ene wsw compressional deformation phase is spectacular evidence of thrust faulting and block tilting affecting the region up to holocene this deformation phase is consistent with geodetic gps based kinematic data indicating ca n10 e motion which implies strain partitioning with ne sw shortening and dextral displacement along n and nw trending strike slip faults

zagros orogeny a subduction dominated process this paper presents a synthetic view of the geodynamic evolution of the zagros orogen within the frame of the arabia eurasia collision the zagros orogen and the iranian plateau preserve a record of the long standing convergence history between eurasia and arabia across the neo tethys from subduction obduction processes to present day collision from 150 to 0 ma we herein combine the results obtained on several geodynamic issues namely the location of the oceanic suture zone the age of oceanic closure and collision the magmatic and geochemical evolution of the eurasian upper plate during convergence as testified by the successive sanandaj sirjan kermanshah and urumieh dokhtar magmatic arcs the p t t history of the few zagros blueschists the convergence characteristics across the neo tethys kinematic velocities tomographic constraints subduction zones and obduction processes together with a survey of recent results gathered by others we provide lithospheric scale reconstructions of the zagros orogen from 150 to 0 ma across two sw ne transects the evolution of the zagros orogen is also compared to those of the nearby turkish and himalayan orogens in our geotectonic scenario for the zagros convergence we outline three main periods regimes 1 the mid to late cretaceous 115 85 ma corresponds to a distinctive period of perturbation of subduction processes and interplate mechanical coupling marked by blueschist exhumation and upper plate fragmentation 2 the paleocene eocene 60 40 ma witnesses slab break off major shifts in arc magmatism and distributed extension within the upper plate and 3 from the oligocene onwards 30 0 ma collision develops with a progressive sw migration of deformation and topographic build up sanandaj sirjan zone 20 15 ma high zagros 12 8 ma simply folded belt 5 0 ma and with partial slab tear at depths 10 ma to present our reconstructions underline the key role played by subduction throughout the whole convergence history we finally stress that such a long lasting subduction system with changing boundary conditions also makes the zagros orogen an ideal natural laboratory for subduction processes

nankai trough and zenisu ridge a deep sea submersible survey abstract eight submersible dives between 3000 and 4200 m water depth were made off southern japan in the eastern nankai subduction zone benthic communities associated with chemosynthetic processes were discovered along the 800 m wide active tectonic zone at the toe of the accretionary prism a benthic community was also discovered along a zone of active compression at the foot of zenisu ridge 30 km south of nankai trough temperature measurements within the sediments below the benthic communities confirm that upward motion of interstitial water occurs there studies of water samples indicate advection of methane and light hydrocarbons specimens of the benthic community have been shown to have included in their shells carbonate resulting from methane consumption thus the benthic communities are related to overpressure driven fluid advection along tectonic zones with active surface deformation a 300 m high active scarp at the toe of the accretionary prism is related to relative motion in a 280 direction which is close to the 305 average direction of subduction in this area the dives establish further that compressive deformation is presently occurring at the foot of zenisu ridge the previous interpretation of the zenisu ridge as a zone of recent north south intraplate shortening 40 km south of the nankai trench is confirmed we conclude that tectonic evolution might well lead to future detachment of the zenisu ridge and overthrusting of this large piece of oceanic crust over the continental margin such a process might be an efficient one to emplace ophiolites over continents

origin of bottom simulating reflectors geophysical evidence from the cascadia accretionary prism vertical seismic profile vsp data from two drill sites on the cascadia margin show low velocity zones indicative of free gas be neath a bottom simulating reflector bsr offshore oregon at ocean drilling program odp site 892 velocities drop from an average of 1750 m s above the bsr to less than 1250 m s below it sonic logs confirm that seismic velocity in the sediments adjacent to the borehole is less than that of water for at least 50 m beneath the depth of the bsr at this site similarly at odp site 889 offshore vancouver velocities range from 1700 to 1900 m s in the 100 m above the bsr and drop abruptly to 1520 m s in the 15 m just beneath it the low velocities observed beneath the bsr are strong evidence for the presence of 1 5 free gas by volume the bsr at these two sites results from the contact between gas free sediments containing a small quantity of hydrate above the bsr and a low velocity free gas zone beneath it although the bsr is associated with the base of the hydrate stability field hydrate appears to account for relatively little of the velocity contrast that produces the bsr velocity above the bsr at site 889 is only about 100 m s greater than that expected for sediments of similar porosity sediments above the bsr at site 892 appear to have normal velocity for their porosity and may contain little hydrate

a 900 k y record of strath terrace formation during glacial interglacial transitions in northwest china the timing of the development of strath terraces with respect to climatic variability remains equivocal previous studies attribute strath terrace formation to glacial or interglacial climates or to variations in sediment and water fluxes that cause lateral erosion followed by vertical incision a chronology of strath terrace formation spanning similar to900 k y has been generated on the basis of loess paleosol couplets and paleomagnetic thermoluminescence and radiocarbon dating of strath terraces in the qilian shan of northeastern tibet repetitive stratigraphic and geomorphic patterns on each terrace indicate that they formed during glacial interglacial transitions long term bedrock incision rates and inferred rock uplift rates appear steady and unrelated to strath formation over the past 900 k y

nankai trough japan trench and kuril trench geochemistry of fluids sampled by submersible nautile abstract deep water samples collected during the kaiko project are often associated with biological communities located on geological structures favorable to fluid venting the evidence of fluid venting are the temperature anomalies the decrease in sulfate concentrations the content in methane and the lowc 1 c 2 c 3 ratio of light hydrocarbons because of large dilution by ambiant seawater during sampling it is difficult to compute the composition of the advected end member pore fluid part of this fluid should originate in the petroleum window i e at temperature about 60 c modeling the upward flow of water taking into account the anomalies of temperature measured on the seafloor and the geochemical anomalies leads to non steady state advection of the pore fluid the occurrence of a deep component in the fluid has implications for the geological and tectonic models of the subduction zones off japan

holocene slip rate on the sabzevar thrust fault ne iran determined using optically stimulated luminescence osl abstract fault slip rates and the recurrence interval between earthquakes can be determined from reliable dating of deformed sediments we report optically stimulated luminescence osl ages of alluvial gravels fine grained sediments and colluvial deposits associated with the sabzevar thrust fault in northeastern iran six samples of the late quaternary deposits were dated by osl using the single aliquot regenerative dose sar protocol the osl ages indicate deposition of alluvial gravels in the study region between 30 and 9 13 ka followed by a period of fluvial incision which is ongoing at the present day the alluvial deposits have been uplifted by 9 5 m relative to the river level indicating a holocene slip rate of 1 mm yr and a rate of convergence across the fault of 0 4 0 6 mm yr assuming a maximum fault dip of 60 the average interval between large earthquakes on the sabzevar fault will be 3000 years if the fault dips 60 and less if the fault dip is less the last earthquake to destroy sabzevar was in 1052 a d

patterns of historical earthquake rupture in the iranian plateau the iranian plateau accommodates the 35 mrn yr convergence rate be tween the eurasian and arabian plates by strike slip and reverse faults with relatively low slip rates in a zone 1000 km across although these faults have only locally been the subject of paleoseismological studies a rich historical and archeological record spans several thousand years long enough to establish recurrence intervals of 1000 to 5000 yr on individual fault segments several clusters of earthquakes provide evidence of interaction among reverse and strike slip faults probably due to adjacent faults being loaded by individual earthquakes the dasht e bayaz sequence of 1936 to 1997 includes earthquakes on left lateral right lateral and reverse faults the neyshabur sequence of four earthquakes between 1209 and 1405 respected the seg ment boundary between the neyshabur and binalud reverse fault systems the two pairs of earthquakes may have ruptured different faults in each segment similar to the 1971 and 1994 san fernando california earthquakes the 1978 tabas reverse fault earthquake was preceded by the 1968 ferdows earthquake part of the dasht e bayaz sequence the north tabriz fault system ruptured from southeast to north west in three earthquakes from 1721 to 1786 a previous cluster may have struck this region in 855 to 958 the mosha fault north of tehran ruptured in three earthquakes in 958 1665 and 1830 five large earthquakes struck the tehran region from 743 to 1177 but only two that large have struck the area since 1177 other earthquakes occurred in pairs in the talesh mountains near the caspian sea 1863 1896 the iran turkey border 1840 1843 and the nayband gowk fault system both 1981 other historical events did not occur as parts of sequences the historic seismic moment release in iran accounts for only a small part of the plate convergence rate which may be due to aseismic slip or to the iranian historical record long as it is being too short to sample long term deformation across the plateau no historic earthquakes of m 8 have struck iran however several long straight strike slip faults doruneh west neh east neh and nayband have not sustained large historical earthquakes raising the possibility that these long faults could produce earthquakes of m 8 thereby removing at least part of the apparent slip deficit an increased understanding of iran s seismic hazard could be obtained by an extensive paleoseismology program and space geodetic arrays supplementing the abundant historical and archaeological record

cumulative right lateral fault slip rate across the zagros makran transfer zone role of the minab zendan fault system in accommodating arabia eurasia convergence in southeast iran the zendan minab zone is the transition zone between the zagros collision to the west and makran subduction to the east it is also linked to the north with the nayband gowk fault system that bounds the lut block to the east the total convergence rate between arabia and eurasia is estimated to range between 23 and 35 mm yr 1 in a nne trending direction the deformation through the minab zendan system is accommodated within two fault systems the western n160 e trending minab zendan fault system and the eastern north south sabzevaran jiroft fault system the study area is characterized by a well defined succession of quaternary deposit levels the age of these deposits was estimated by archaeological data regional palaeoclimate correlations and constrained by additional in situ10be dating in another paper in this study these deposits exhibit offsets both lateral and vertical that are evaluated by satellite image analysis and gps profiles thanks to offsets and ages the strike slip rates associated with the minab zendan and the sabzevaran jiroft fault systems are calculated to be 5 1 1 3 or 6 6 1 5 and 6 2 0 7 mm yr 1 respectively these results allow an evaluation of the velocity vector of the musandam peninsula oman with respect to the lut block of 11 4 2 0 or 12 9 2 2 mm yr 1 in a n10 15 e direction close to the gps estimates this study also constrains the in plane slip rates for each fault previous works indicate that the zagros accommodates only 10 mm yr 1 of shortening while 10 mm yr 1 should be accommodated by the alborz mountains in northern iran this last 10 mm yr 1 may be accommodated through the nayband gowk system and the east iranian ranges implying that the two fault systems constituting the zagros makran transfer zone have different geodynamic roles the western minab zendan fault system links the makran and zagros deforming zones whereas the northwestern jiroft sabzevaran fault system is transmitting the deformation to the nayband gowk system and then to the alborz ranges the presence of another such strike slip zone within the makran seems to indicate that the accommodation zone between the zagros and makran is wide of the order of 400 km we interpret this deformation pattern that accompanies the genesis of the immature transform zone by a flexure of the slab under the zagros makran transfer zone instead of a tear in the slab that may be expected to induce a sharper transition zone

present day kinematics and fault slip rates in eastern iran derived from 11 years of gps data we analyze new gps data spanning 11 years at 92 stations in eastern iran we use these data to analyze the present day kinematics and the slip rates on most seismogenic faults in eastern iran the east lut west lut kuhbanan anar dehshir and doruneh faults are confirmed as the major faults and are found to currently slip laterally at 5 6 0 6 4 4 0 4 3 6 1 3 2 0 0 7 1 4 0 9 and 1 3 0 8 mm yr respectively slip is right lateral on the ns striking east lut west lut kuhbanan anar and dehshir faults and left lateral on the ew doruneh fault the ns faults slice the eastern iranian crust into five blocks that are moving northward at 6 13 mm yr with respect to the stable afghan crust at the eastern edge of the collision zone the collective behavior of the ns faults might thus allow the arabian promontory to impinge northward into the eurasian crust the ns faults achieve additional ns shortening by rotating counterclockwise in the horizontal plane at current rates up to 0 8 ma modeling the gps and available geological data with a block rotation model suggests that the rotations have been going on at a similar rate 1 0 4 ma over the last 12 ma we identify large strains at the tips of the rotating east lut west lut and kuhbanan faults which we suspect to be responsible for the important historical and instrumental seismicity in those zones

neogene to present paleostress field in eastern iran sistan belt and implications for regional geodynamics we conducted a stress eld analysis of the northern part of the 700 km long north south trending seismically active sistan orogenic belt of eastern iran formed as a result of the closure of a branch of the neo tethys during the early cenozoic fault kinematic data reveal drastic changes in the stress regime of eastern iran during the late cenozoic with three successive directions of compression 1 from 90 n during the middle late miocene to 60 n during the late pliocene and 25 n during the plio quaternary thereby evidencing a counterclockwise rotation of about 65 of 1 in less than 10 myr as shown by compilation of paleostress data plio quaternary direction of compression in sistan coincides with the one recorded across the whole of iran and with present day arabia eurasia convergence direction this result suggests effective stress transfer from the zagros collision and that sistan is at present mechanically coupled and shortened along with the rest of the iranian crust lithosphere by contrast miocene compression is markedly different in the iranian hinterland e g sistan central iran and kopet dagh and in the zagros orogen this could tentatively be related to the end of sistan collision and or to the imprint of active deformation occurring further to the east the intermediate late pliocene compression i e 60 n could correspond to the progressive reorientation of the stress regime as sistan gets mechanically coupled to the zagros collision

first evidence for large earthquakes on the deshir fault central iran plateau although sliced by several strike slip faults a large part of central iran remained aseismic during the period of time covered by the instrumental and historical seismic records stating the existence of earthquakes in the holocene is therefore important for the assessment of the regional seismic hazard a palaeoseismic study of the deshir fault demonstrates that central iran hosted large earthquakes during latest pleistocene and holocene the last event corresponds to 1 m deep fissures which sandy infilling yielded an optically stimulated luminescence osl age of 2 8 1 4 ka at least two previous events outlined by older fissures and or colluvial wedges have been recorded over the last 10 30 ka the magnitudes are difficult to assess because the actual slips per event are unknown the size of the fissures and the significant vertical displacement associated with a colluvial wedge are nevertheless compatible with m 7 events along a primary strike slip surface break

isotopic composition of noble gases in geothermal fluids of the krusne hory mts czechoslovakia and the nature of the local geothermal anomaly abstract the contents and isotopic composition of all noble gases in the fluids from two localities karlovy vary and frantiskovy lazn in western czechoslovakia are given the data show 1 atmospheric ne ar kr and xe which indicates meteoric recharge 2 excess he attributed to radiogenic contributions 3 a small excess of ne but the data shed no light on its origin even though there is no evidence of any juvenile component in these mineral waters part of the dissolved he is believed to be of deep mantle origin correlation between the ratio 3 he 4 he and heat flow has been reported in the literature our data enabled a direct test of this relationship and proved its fairly good validity the combined interpretation of the heat flow and isotopic composition shows that the local heat flow anomaly in the krusne hory graben is of deep origin and was produced by the mass outflow which occurred during the alpine activation of the bohemian massif

lead isotope signatures of the igneous rocks and porphyry copper deposits from the kerman cenozoic magmatic arc se iran and their magmatic metallogenetic implications abstract copper deposits in the kerman cenozoic magmatic arc kcma of iran are genetically related to miocene porphyries the porphyries and their associated cu deposits were intruded and emplaced into eocene volcanic sedimentary successions lead isotope compositions of the eocene volcanic rocks exhibit homogeneous non radiogenic values 206 pb 204 pb 18 40 to 18 49 207 pb 204 pb 15 41 to 15 48 and 208 pb 204 pb 38 15 to 38 36 in contrast the miocene ore hosting porphyries and associated sulfide minerals also show a relatively radiogenic and homogenous pb isotopic values with orogen character 206 pb 204 pb 18 52 to18 60 207 pb 204 pb 15 58 to 15 64 and 208 pb 204 pb 38 57 to 38 80 the shift in the pb isotopic composition of igneous rocks with time towards higher pb isotopic values precludes derivation of the ore hosting porphyries from a reservoir of similar composition to those in the eocene volcanic rocks the non radiogenic pb isotope signature of the eocene volcanic rocks indicates an origin from subduction related mantle derived magmas whereas the higher pb isotopic values of the miocene ore hosting porphyries suggest an increasing involvement of crustal materials with lower u pb ratios than the upper crust in the source region of these rocks combining the pb isotope data with petrogenetic considerations suggests derivation of the middle miocene ore hosting porphyries from a mixed reservoir with slightly radiogenic pb values such as a hybridized lower continental crustal source this source probably formed because of the involvement of cretaceous oligocene subduction related mantle derived mafic magmas at the base of arc crust the contribution of the miocene collision related mantle derived mafic magma in melting of the hybridized lower continental crust caused generation of the middle miocene porphyries hosting large copper deposits with the least 206 pb 204 pb ratios among other porphyries the higher 206 pb 204 pb ratios of the late miocene pliocene porphyries hosting small copper deposits as well as barren porphyries may reflect a decreasing involvement of collision related mantle derived mafic magma in the source of the late miocene pliocene porphyries the overall similarity in pb isotope values between sulfide minerals and ore hosting porphyries suggests a magmatic source for most of the pb and possibly other metals the more radiogenic isotopic ratios of some late sulfide minerals suggest an insignificant metal contribution from an external source such as local country rocks during hydrothermal circulation

selection of emergency shelter sites for seismic disasters in mountainous regions lessons from the 2008 wenchuan ms 8 0 earthquake china in this paper we use the 12 may 2008 wenchuan earthquake as a background event for analyzing and applying the principles of site selection of emergency shelters for a disastrous earthquake based on field investigations and analyses of remote sensing imagery we identified the distribution of active faults and the locations of co seismic surface rupture zones areas in which buildings are at risk of intensive damage it is important that emergency shelters are located outside of such vulnerable areas one of the lessons learned from the wenchuan earthquake is that high fatality rates occur in areas without life saving shelters the principles that underlie the selection of emergency shelter sites are as follows 1 keep far away from active fault zones with the distance depending on the characteristics of the fault including the nature of hangingwall and footwall structures 2 disaster mitigation strategies should be developed as a multi dimensional system for the management of natural hazards human activities and urban expansion involving keeping away from vulnerable slopes and establishing an early warning system 3 the accessibility of mountainous regions must be considered including establishing small emergency shelters that house large numbers of people and covering regions with an uneven distribution of villages and 4 government and law making agencies in china must establish new earthquake design codes for buildings emphasizing the importance of public facilities including schools collective welfare institutions and medical facilities as emergency shelters during disastrous earthquakes the site selection process requires an interdisciplinary approach involving seismologists engineers environmental and social scientists emergency management personnel and government officials the parameters upon which the above principles are based can be qualitatively determined thereby providing a valuable initial database for further quantitative analysis the preliminary results and knowledge gained in the present paper can be used as a decision making tool to support the government in earthquake recovery and reconstruction programs we also discuss practical examples of site evaluation in regions that suffered heavy damage during the wenchuan earthquake

right lateral shear across iran and kinematic change in the arabia eurasia collision zone summary new offset determinations for right lateral strike slip faults in iran revise the kinematics of the arabia eurasia collision by indicating along strike lengthening of the collision zone before a change to the present kinematic regime at 5 ma a series of right lateral strike slip faults is present across the turkish iranian plateau between 48 e and 57 e fault strikes vary between nw se and nnw sse several of the faults are seismically active and or have geomorphic evidence for holocene slip none of the faults affects the gps derived regional velocity field indicating active slip rates are 2 mm yr 1 we estimate total offsets for these faults from displaced geological and geomorphic markers based on observations from satellite imagery digital topography geology maps and our own fieldwork observations and combine these results with published estimates for fault displacement total right lateral offset of the dehu anar deh shir kashan ab shirin shurab kousht nousrat qom bid hand indes soltanieh and takab faults is 250 km other faults north zanjan saveh jorjafk rafsanjan kuh banan and behabad have unknown or highly uncertain amounts of slip collectively these faults are inferred to have accommodated part of the arabia eurasia convergence three roles are possible which are not mutually exclusive 1 shortening via anticlockwise vertical axis rotations 2 northward movement of iranian crust with respect to stable afghanistan to the east 3 combination with coeval nw se thrusts in the turkish iranian plateau to produce north south plate convergence strain partitioning this strike slip faulting across iran requires along strike lengthening of the collision zone this was possible until the pliocene 5 ma when the afghan crust collided with the western margin of the indian plate thereby sealing off a free face at the eastern side of the arabia eurasia collision zone continuing arabia eurasia plate convergence had to be accommodated in new ways and new areas leading to the present pattern of faulting from eastern iran to western turkey and involving the westward transport escape of anatolia and the concentration of thrusting in the zagros and alborz mountains

aseismic deformation of a fold and thrust belt imaged by synthetic aperture radar interferometry near shahdad southeast iran at depth many fold and thrust belts are composed of a gently dipping basal thrust fault and steeply dipping shallower splay faults that terminate beneath folds at the surface movement on these buried faults is difficult to observe but synthetic aperture radar sar interferometry has imaged slip on at least 600 km 2 of the shahdad basal thrust and splay fault network in southeast iran approximately 70 mm of thrust motion on the 88 dipping shahdad basal thrust occurred 8 30 km to the east of the 14 march 1998 fandoqa earthquake mw 5 6 6 that involved 1 6 m of oblique strike slip and normal slip displacement on a steeply dipping fault that earthquake transferred stress to the shahdad basal thrust and associated splays triggering slip either immediately or in the following six months modeling shows that to produce the observed surface deformation the shahdad faults must have accommodated a nearly complete release of the shear stress increase this could be due to either low friction on the faults or deformation throughout a wedge of material that is everywhere close to failure the anomalously small magnitude of displacement on the shahdad basal thrust and splay faults compared to the area of slip suggests a slip mechanism that is likely aseismic

long term fault slip rates distributed deformation rates and forecast of seismicity in the iranian plateau in this paper the long term crustal flow of the iranian plateau is computed using a kinematic finite element model neokinema software based on the iterated weighted least squares method the models are fitted to the newest data set of iran including updated fault traces geologic fault offset rates geodetic benchmark velocities principal stress directions and velocity boundary conditions we are successful to find the best kinematic model in which geological slip rates geodetic velocities and interpolated stress directions are fitted at levels of 0 35 1 0 and 1 0 datum standard deviation respectively the best fitted model for the first time provides long term fault slip rates velocity and anelastic strain rate field in the iranian plateau from all available kinematic data in order to verify the model the estimates of fault slip rates are compared to slip rates from merely analyzing geodetic benchmark velocities or paleoseismological studies or published geological rates which have not been used in the model our estimated rates are all in the range of geodetic rates and are even more consistent with geological rates than previous gps based estimates using the selected model long term average seismicity maps and long term moment rates are produced on the basis of the shift hypothesis and previous global calibrations our kinematic model also provides a new constraint on ratio of seismic deformation to total deformation for different seismic zones of iran the resulting slip rates and the proposed seismic fraction of deformation provide the necessary input data for future time dependent hazard studies in iran moreover spatial distribution and total number of strong m 6 and major m 7 earthquakes which dominate the seismic hazard are all compatible with the regional seismic catalog

active tectonics and late cenozoic strain distribution in central and eastern iran 1 right lateral shear between central iran and afghanistan is accommodated on n s right lateral strike slip faults surrounding the aseismic dasht e lut north of 34 n the right lateral shear is accommodated on left lateral faults that rotate clockwise about vertical axes little is known of the late tertiary and younger offsets and slip rates on the active fault systems results that are important for understanding the regional tectonics we use observations from satellite imagery to identify displaced geological and geomorphological markers which we use in conjunction with the overall morphology and orientation of the active fault systems to estimate the total cumulative right lateral shear estimates of cumulative fault movements from offset features and inferred vertical axis rotation of fault bounded blocks suggest that the late cenozoic strain is concentrated toward the eastern margin of iran along the sistan shear zone where bedrock offsets of at least 70 km are observed across the active faults the geomorphology of the deh shir anar and great kavir strike slip faults in central iran suggest that although little shortening is accommodated across this region they might still be active and hence capable of producing earthquakes present day activity on these faults in central iran would not be expected from distributions of instrumental and historical earthquakes although speculative the late tertiary strain distribution described in this paper is consistent with what we know of the present day rates of shear in eastern iran and provides a framework to which later more detailed work can be added

controls on cu mineralization in central part of the kerman porphyry copper belt se iran constraints from structural and spatial pattern analysis abstract the sarduiyeh area in the central part of the kerman porphyry copper belt kpcb se iran contains numerous cu deposits and prospects this area is bound by e w trending major faults which show the northern and southern borders of fault duplex minor faults first second or third orders were identified in three trends of nw n s and ne analysis of the fault kinematics data revealed an extensional fault duplex pattern for this area in this fault zone cu deposits are associated with faults that have a special trend this proposed kinematic model for evolution of sarduiyeh extensional fault duplex emphasizes that the main cu deposits in the sarduiyeh area are located within the dilatational zones related to nw se trending normal faults in this study the spatial pattern analysis conducted by fry fractal fracture density and buffer zones methods support the conceptual model of district scale mechanism of structural controls on final emplacement of cu deposits this investigation of sarduiyeh cu mineralization revealed that the nw se trending faults are effective in localization of cu mineralization in the central part of kpcb

seismicity anomalies of the 2003 bam iran earthquake abstract the bam earthquake occurred in an area without any historically recorded major earthquake based on active tectonics and cmt solutions the area is under the influence of shortening and right lateral strike slip faulting seismicity is of a shallow crustal type which is mainly distributed within the koohbanan golbaf lakarkooh shahdad gowk fault systems and the terminal sections of zagros in order to detect temporal seismicity anomalies before this earthquake we compiled a catalog from the isc events and then analyzed it for the magnitude of completeness after declustering this catalog changes in seismicity were assessed by the z value test the temporal variations indicate a relative decrease in z value before the bam earthquake additional to seismic quiescence and decrease in b value before the main shock there are pieces of evidence corresponding to increase in triggered background seismicity after this earthquake

gps constraints on africa nubia and arabia plate motions summary we use continuously recording gps cgps and survey mode gps sgps observations to determine euler vectors for relative motion of the african nubian arabian and eurasian plates we present a well constrained eurasia nubia euler vector derived from 23 igs sites in europe and four cgps and three sgps sites on the nubian plate 0 95 4 8 n 21 8 4 3 e 0 06 0 005 myr 1 we see no significant 1m m yr 1 internal deformation of the nubian plate the gps nubian eurasian euler vector differs significantly from nuvel 1a 21 0 4 2 n 20 6 0 6 e 0 12 0 015 myr 1 implying more westward motion of africa relative to eurasia and slower convergence in the eastern mediterranean the arabia eurasia and arabia nubia gps euler vectors are less well determined based on only one cgps and three sgps sites on the arabian plate the preliminary arabia eurasia and arabia nubia euler vectors are 27 4 1 0 n 18 4 2 5 e 0 40 0 04 myr 1 and 30 5 1 0 n 25 7 2 3 e 0 37 0 04 myr 1 respectively the gps arabia nubia euler vector differs significantly from nuvel 1a 24 1 1 7 n 24 0 3 5 e 0 40 0 05 myr 1 but is statistically consistent at the 95 per cent confidence level with the revised euler vector reported by chu gordon based on a re evaluation of magnetic anomalies in the red sea 31 5 1 2 n 23 0 2 7 e 0 40 0 05 myr 1 the motion implied in the gulf of aqaba and on the dead sea fault dsf by the new gps nubia arabia euler vector i e ignoring possible sinai block motion and possible internal plate deformation grades from pure left lateral strike slip in the gulf and on the southern dsf with increasing compression on the central and northern dsf with relative motion increasing from 5 6 to 7 5 mm yr 1 1m m yr 1 from south to north along the northern dsf i e north of the lebanon restraining bend motion is partitioned between 6 1m m yr 1 left lateral motion parallel to the fault trace and 4 1m m yr 1 faultnormal compression relative motions on other plate boundaries including the anatolian and aegean microplates derived from the gps euler vectors agree qualitatively with the sense of motion indicated by focal mechanisms for large crustal earthquakes m 6 where data are available on fault slip rates on plate bounding faults north anatolian fault east anatolian fault dead sea fault red sea rift they are generally lower than but not significantly different from the full plate motion estimates suggesting that the majority of relative plate motion is accommodated on these structures

offset and evolution of the gowk fault s e iran a major intra continental strike slip system abstract we use drainage reconstructions to estimate long term offsets on the gowk fault an oblique right lateral strike slip fault in eastern iran on which there have been a number of recent large earthquakes a 3 km horizontal offset is inferred from well preserved geomorphology we further identify a total cumulative offset of 12 km which produces a simple reconstruction of geomorphology across the fault filling in pull apart basins restoring rivers to linear courses across the fault trace and aligning structural and bed rock features the probable age of the gowk fault and k ar dating of offset basalts north of the study region suggest an overall slip rate of 1 5 2 4 mm year this is small compared with the overall 10 20 mm year of shear expected between central iran and afghanistan and the deficit is likely to have been accommodated on other faults east of the gowk fault drainage displaced by dextral movement leads to the development of a series of basins along the fault and a longitudinal topographic profile that resembles an asymmetric saw tooth the geomorphic evolution of the fault zone at the surface includes both normal and reverse faulting components reflecting a probable ramp and flat structure in cross section this interpretation is consistent with evidence from the analysis of seismological radar and surface rupture data in recent earthquakes

active faulting in the birjand region of ne iran 1 we use satellite imagery and field observations to investigate the distribution of active faults around birjand in eastern iran to determine how the transition between conjugate zones of faulting can be accommodated by diffuse active faulting in the south of the study area right lateral strike slip faults of the sistan suture zone end in thrusts which die away westward from the strike slip faults these thrust terminations appear to allow a northward change to e w thrusting in central parts of the study area the introduction of e w thrusting is in turn likely to facilitate a change to e w left lateral faulting north of the study region the relatively diffuse pattern of active faulting at birjand relates to the regional transition between n s and e w strike slip faulting in northeast iran which involves a change from nonrotational to rotational deformation the change from n s to e w faulting is likely to result from the orientation of preexisting structures in iran and western afghanistan which are roughly parallel to the active fault zones the features described at birjand also show the influence of preexisting structure on the location and style of active faulting at a local scale with the position of individual faults apparently controlled by inherited geological weaknesses very few modern earthquakes have occurred in the region of birjand and yet destructive events are known from the historical record the large number of active faults mapped in this study pose a substantial seismic hazard to birjand and surrounding regions

active faulting and seismicity of the dasht e bayaz region eastern iran summary the dasht e bayaz left lateral strike slip fault system in ne iran ruptured over a length of ca 120 km during two earthquakes in 1968 and 1979 we constrain source parameters of the 1968 august 31 dasht e bayaz and 1979 november 27 khuli buniabad earthquakes by analysing long period body wave seismograms both earthquakes involved complex rupture processes with at least two subevents in each case coseismic surface ruptures and cumulative scarps in alluvium indicate fault segmentation on numerous short ca 20 km long strands with small pull aparts between them the earthquake subevents seen in the seismograms probably relate to this segmentation the total cumulative offset on the fault system is estimated at ca 4 5 km this is small compared to the total amount of late tertiary deformation expected in this part of iran and indicates that the dasht e bayaz fault may be relatively young distributed strike slip faulting is widespread in the region and there are indications that the dasht e bayaz fault is evolving from several short faults that are coalescing these results are important not only for understanding of the regional tectonics but for the development and evolution of strike slip faults in general

effects of active folding and reverse faulting on stream channel evolution santa barbara fold belt california abstract the santa barbara fold belt sbfb is an area of active crustal shortening comprising younger east west and older southeast northwest oriented reverse faults and folds changes in channel position and stream incision are the result of active fold growth and uplift rates of incision range from 0 4 0 1 m ka to 1 2 0 04 m ka lateral stream diversion from fold and fault growth varies from 6 7 to 0 4 km minimum uplift of western mission ridge anticline is 0 8 0 1 m ka and minimum uplift on the mesa fault is 0 3 0 4 m ka the hypothesis that east to west folds are younger is suggested by a cross cutting relationship and is tested using geomorphic indices of active tectonics including valley width to height ratios vf mountain front sinuosity smf and drainage densities dd east to west trending structures have mean values of vf smf and dd of 2 7 1 2 and 2 2 km km2 respectively while southeast to northwest trending structures have mean values of 5 0 1 5 and 3 7 km km2 respectively we present a new geomorphic tool the stream diversion index which uses diversion timing and distance to assess relative tectonic activity these values range from 6 to 260 m ka all of these values support the hypothesis that the east to west folds are younger and more active clockwise rotation of the western transverse ranges is probably the process that produced the two sets of structures with rotation the older set that started out east to west eventually became northwest to southeast and more difficult to maintain with the north to south contractional shortening associated with the big bend of the san andreas fault 80 km to the north the second set of younger structures formed with a more favorable east to west orientation to the shortening

seismotectonic rupture process and earthquake hazard aspects of the 2003 december 26 bam iran earthquake summary the catastrophic 2003 m w 6 6 bam earthquake in southern iran attracted much attention and has been studied with an abundance of observations from synthetic aperture radar teleseismic seismology aftershock studies strong ground motion geomorphology remote sensing and surface field work many reports have focused on the details of one or other data type producing interpretations that either conflict with other data or leave questions unanswered this paper is an attempt to look at all the available data types together to produce a coherent picture of the coseismic faulting in 2003 and to examine its consequences for active tectonics and continuing seismic hazard in the region we conclude that more than 80 per cent of the moment release in the main shock occurred on a near vertical right lateral strike slip fault extending from the city of bam southwards for about 15 km with slip of up t o2mb utmostly restricted to the depth range 2 7 km analysis of the strong ground motion record at bam is consistent with this view and indicates that the extreme damage in the city can be attributed at least in part to the enhancement of ground motion in bam because of its position at the end of the northward propagating rupture little of the slip in the main shock reached the earth s surface and more importantly aftershocks reveal that 12 km vertical extent of a deeper part of the fault system remained unruptured beneath the coseismic rupture plane at depths of 8 20 km this may represent a substantial remaining seismic hazard to the reconstructed city of bam we believe that some oblique reverse slip up to 2 m and less than 20 per cent of the released seismic moment occurred at a restricted depth of 5 7 km on a blind west dipping fault that projects to the surface at the bam baravat escarpment an asymmetric anticline ridge that is the most prominent geomorphological feature in the area this fault did not rupture significantly at shallow levels in 2003 and it may also represent a continuing seismic hazard widespread distributed surface ruptures north of the city are apparently unrelated to substantial slip at depth and may be the result of enhanced ground motion related to northward propagation of the rupture the faulting at bam may be in the early stages of a spatial separation partitioning between the reverse and strike slip components of an oblique convergence across the zone such a separation is common on the continents though in this case the slip vectors between the two faults differ only by 20 as a substantial strike slip component remains on the obliquereverse fault the bam earthquake is one in a series of large earthquakes involving faulting along the western edge of the lut desert in addition to the unruptured parts of the faults near bam itself continuing and substantial hazard is represented by unruptured neighbouring faults particularly blind thrusts along the jebel barez mountains to the south and strike slip faulting at sarvestan to the west

growth and lateral propagation of fault related folds in the siwaliks of western nepal rates mechanisms and geomorphic signature 1 we study the controls on drainage development in tectonically active regions using a numerical tectonic surface processes model combining tectonic uplift caused by fault related folding with erosion by fluvial incision hillslope diffusion and landsliding our model shows the fundamental control exerted by the dip of the detachment underlying the folds on drainage evolution when the detachment is horizontal the relative rates of tectonic uplift and fluvial incision control the evolution for a nonzero dip in contrast the lateral displacement gradient associated with fold propagation sets up a lateral slope behind the active structure which deflects the stream network we also demonstrate the importance of landsliding for the attainment of realistic and steady state topography in contrast discontinuous tectonic movements do not appear to influence the system we apply our model to the dundwa fault related fold ridge siwalik nepal we estimate a remarkably low mean propagation rate for different segments of the structure this finding together with the structure and morphology of the ridge leads us to propose that the ridge developed by linkage of several component segments the drainage evolution predicted when modeling this scenario compares favorably with field observations our models provide insights into the dynamics of fault related fold propagation in particular as a result of fault segment linkage estimates of propagation rate of these structures may be strongly scale dependent and the observed morphology and drainage patterns on fault related fold ridges may be controlled by fault geometry rather than by the relative rates of tectonics and surface processes

active tectonics at wheeler ridge southern san joaquin valley california wheeler ridge is an east west trending anticline that is actively deforming on the upper plate of the pleito wheeler ridge thrust fault system holocene and late pleistocene deformation is demonstrated at the eastern end of the anticline where salt creek crosses the anticlinal axis uplift tilting and faulting associated with the eastward growth of the anticline are documented by geomorphic surfaces that are higher and older to the west faulting and associated folding is propagating eastward as indicated by increases in both the degree of surface dissection and the degree of soil development from east to west distinct topographic areas having distinct degrees of surface dissection bounded by tear faults suggest that faulting and folding have propagated eastward in discrete segments numerical dates indicate 1 the anticline is propagating eastward at a rate of about 30 mm yr about 10 times the rate of uplift 2 folding was initiated about 400 ka 3 a prominent wind gap was formed during q3 time about 60 ka when an antecedent stream was defeated forcing the stream east around the nose of the fold today drainage through the ridge is by way of two antecedent streams water gaps east of the wind gap and 4 the rate of uplift at the easternmost and youngest past 1 k y part of the fold is at least 3 mm yr investigations of the tectonic geomorphology of wheeler ridge support the hypothesis that climatic perturbations are primarily responsible for producing geomorphic surfaces such as alluvial fan segments and river terraces tectonic perturbations deform the surfaces

the 1998 march 14 fandoqa earthquake mw 6 6 in kerman province southeast iran re rupture of the 1981 sirch earthquake fault triggering of slip on adjacent thrusts and the active tectonics of the gowk fault zone summary the 1998 march 14 fandoqa earthquake ms 6 6 was the penultimate in a series of five substantial earthquakes on the gowk fault system of southeast iran since 1981 all of which were associated with co seismic surface ruptures we use observations of surface faulting analysis of p and sh body waves sar interferometry and geomorphology to investigate the ruptures in these earthquakes and how they are related both to each other and to the regional active tectonics the 1998 fandoqa earthquake produced 23 km of surface faulting with up to 3 m right lateral strike slip and 1 m vertical offsets sar interferometry and seismic waveforms show that the main rupture plane dipped west at 50 and had a normal component although the surface ruptures were more complicated being downthrown to both the east and the west on steep faults in near surface sediments in addition sar interferometry shows that a nearby thrust with a similar strike but dipping at 6 w moved about 8 cm in a time interval and in a position that makes it likely that its slip was triggered by the fandoqa earthquake the 1998 surface ruptures in the gowk valley followed part of a much longer 80 km set of co seismic ruptures with smaller offsets that were observed after larger earthquakes in 1981 mw 6 6 and 7 1 the main ruptures in these 1981 earthquakes probably occurred on different deeper parts of the same fault system producing only minor reactivation of the shallower faults at the surface although the 1981 1998 earthquake sequence apparently ruptured parts of the same fault system repeatedly these earthquakes had very different rupture characteristics an important lesson for the interpretation of both palaeoseismological trenching investigations and historical accounts of earthquakes the regional kinematics which involve oblique right lateral and convergent motion are evidently achieved by a complex configuration of faults with normal reverse and strike slip components some of the complexity at the surface may be related to a ramp and flat fault geometry at depth but could also be related to the large topographic contrast of 2000 m across the fault system which separates the high kerman plateau from the low dasht e lut desert details of the fault geometry at depth remain speculative but it must be unstable and evolve with time it may be this requirement that causes the principal features of geological flower structures to develop such as series of subparallel faults which accommodate dip slip components of motion

present day crustal deformation and plate kinematics in the middle east constrained by gps measurements in iran and northern oman summary a network of 27 gps sites was implemented in iran and northern oman to measure displacements in this part of the alpine himalayan mountain belt we present and interpret the results of two surveys performed in 1999 september and 2001 october gps sites in oman show northward motion of the arabian plate relative to eurasia slower than the nuvel 1a estimates e g 22 2m m yr 1 at n8 5 e instead of 30 5 mm yr 1 at n6 e at bahrain longitude we define a gps arabia eurasia euler vector of 27 9 0 5 n 19 5 1 4 e 0 41 0 1 myr 1 the arabia eurasia convergence is accommodated differently in eastern and western iran east of 58 e most of the shortening is accommodated by the makran subduction zone 19 5 2m m yr 1 and less by the kopet dag 6 5 2m m yr 1 west of 58 e the deformation is distributed in separate fold and thrust belts at the longitude of tehran the zagros and the alborz mountain ranges accommodate 6 5 2m m yr 1 and 8 2m m yr 1 respectively the right lateral displacement along the main recent fault in the northern zagros is about 3 2m m yr 1 smaller than what was generally expected by contrast large rightlateral displacement takes place in northwestern iran up to 8 mm yr 1 the central iranian block is characterized by coherent plate motion internal deformation 2m m yr 1 sites east of 61 e show very low displacements relative to eurasia the kinematic contrast between eastern and western iran is accommodated by strike slip motions along the lut block to the south the transition zone between zagros and makran is under transpression with right lateral displacements of 11 2m m yr 1

a remote sensing study of active folding and faulting in southern kerman province s e iran geomorphological observations reveal a major oblique fold and thrust belt in kerman province s e iran the active faults appear to link the sabzevaran right lateral strike slip fault in southeast iran to other strike slip faults within the interior of the country and may provide the means of distributing right lateral shear between the zagros and makran mountains over a wider region of central iran the rafsanjan fault is manifest at the earth s surface as right lateral strike slip fault scarps and folding in alluvial sediments height changes across the anticlines and widespread incision of rivers are likely to result from hanging wall uplift above thrust faults at depth scarps in recent alluvium along the northern margins of the folds suggest that the thrusts reach the surface and are active at the present day the observations from rafsanjan are used to identify similar late quaternary faulting elsewhere in kerman province near the towns of mahan and rayen no instrumentally recorded destructive earthquakes have occurred in the study region and only one historical earthquake lalehzar 1923 is recorded in addition gps studies show that present day rates of deformation are low however fault structures in southern kerman province do appear to be active in the late quaternary and may be capable of producing destructive earthquakes in the future this study shows how widely available remote sensing data can be used to provide information on the distribution of active faulting across large areas of deformation

noble gas composition of deep brines from the palo duro basin texas deep groundwaters in sedimentary basins can be sufficiently old 10 m y to have accumulated both radiogenic 4he and 40ar differences in the ratio of u th k for aquifer lithologies lead to variations for 4he40ar in the groundwater these variations can be used to resolve chronologically significant noble gas components application of a binary model to brine samples from the palo duro basin texas yields u th 4he residence times of 100 to 300 m y concentrations of two non radiogenic noble gases 20ne and 36ar provide information on the salinities of the water that recharged these aquifers

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

topographic divides formed by active flexural folding in the ne marginal zone of the tibetan plateau abstract topographic divides along the northeastern marginal zone of the tibetan plateau separate tributary drainage systems that flow into the yellow river field investigations and topographic analysis indicate that i late quaternary holocene sedimentary sequences are deformed into a series of left stepping wnw ese trending en echelon flexural folds ii the folds form topographic divides that separate drainage systems that flow into the yellow river and iii the regional axis of maximum compressive stress as inferred from flexural folds and active fault related structures trends ene wsw consistent with geophysical and seismic data these results demonstrate that the topographic divides formed through active flexural folding and faulting in the northeastern marginal zone of the tibetan plateau corresponding to the ongoing northeastward shortening of the plateau accommodating the eurasia india continental collision

the 2003 bam iran earthquake rupture of a blind strike slip fault a magnitude 6 5 earthquake devastated the town of bam in southeast iran on 26 december 2003 surface displacements and decorrelation effects mapped using envisat radar data reveal that over 2 m of slip occurred at depth on a fault that had not previously been identified it is common for earthquakes to occur on blind faults which despite their name usually produce long term surface effects by which their existence may be recognised however in this case there is a complete absence of morphological features associated with the seismogenic fault that destroyed bam

a study of fold characteristics and deformation style using the evolution of the land surface zagros simply folded belt iran abstract deformation styles within a fold thrust belt can be understood in terms of the spatial organization and geometry of the fold structures in young fold thrust belts such as the zagros this geometry is reflected topographically by concordant landform morphology thus the distribution of deformation structures can be characterized using satellite image analysis digital ele vation models the drainage network and geomorphological indicators the two distinct fold types considered in this study fault bend folds and detachment folds both trending nw se interact with streams flowing ne sw from the high zagros mountains into the persian gulf multiple abandoned stream channels cross fault bend folds related to deep seated thrust faults in contrast detachment folds which propagate laterally relatively rapidly are characterized by diverted major stream channels and dendritic minor channels at the fold tips thus these two fold types can be differentiated on the basis of their ge ometry fault bend folds being long linear and asymmetrical can be distinguished from detachment folds which tend to be shorter and symmetrical and on their associated geomorphological structures the spatial organization of these structures in the zagros simply folded belt indicates that deformation is the result of the interaction of footwall collapse and the associ ated formation of long linear fault bend folds and serial folding characterized by relatively short periclinal folds footwall collapse occurs first followed by serial folding to the ne i e in the hanging wall of the fault bend folds often on higher de tachments within the sediment pile 139

the 2002 june 22 changureh avaj earthquake in qazvin province northwest iran epicentral relocation source parameters surface deformation and geomorphology summary the m w 6 4 changureh avaj earthquake occurred on 2002 june 22 in qazvin province northwest iran we use observations from seismology field investigation and analysis of satellite imagery and digital topography to suggest that slip on a previously unrecognized thrust fault herein named the abdarreh fault was responsible for the earthquake inversion of longperiod p and sh body wave seismograms shows rupture on a thrust fault dipping 49 to the southwest and with a centroid depth of 10 km multiple event relocation of the main shock and aftershock epicentres and discontinuous surface ruptures observed after the earthquake are compatible with a northwest propagating rupture on a southwest dipping thrust but maximum recorded displacements are much less than expected from seismology suggesting that much of the slip failed to reach the surface and was accommodated as folding at the surface instead long term folding is difficult to see in the topography of the epicentral region as the abdarreh fold is growing through a relict neogene topography anticlinal uplift can however be inferred from drainage disruption and stream incision the 2002 june 22 changureh earthquake shows the importance of being able to interpret diagnostic features of active faulting in the landscape

variations in temperature gradients identify active faults in the oregon accretionary prism abstract a multi channel seismic survey mcs yields high resolution images of geologic structures within the oregon accretionary prism in addition to revealing the internal geometry of the prism a prominent bottom simulating reflector bsr provides indirect estimates of temperature gradients the bsr marks the phase transition within the pore space of the sediments of small amounts of solid gas hydrate above the reflector to free gas below although the absolute value of temperature gradients depends on assumptions of gas hydrate stability conditions velocity functions and seafloor temperature relative differences reflecting regional trends and local anomalies are unaffected by the assumptions involved in calculation of temperature gradient from the position of the bsr broad scale landward decreases in temperature gradient reflect the increasing depth to the oceanic crust across the accretionary prism correlation of anomalously high temperature gradients with two out of sequence thrusts indicates that these structures are currently acting as conduits for warm fluids

deciphering oblique shortening of central alborz in iran using geodetic data the alborz is a narrow 100 km and elevated 3000 m mountain belt which accommodates the differential motion between the sanandaj sirjan zone in central iran and the south caspian basin gps measurements of 12 geodetic sites in central alborz between 2000 and 2002 allow to constrain the motion of the belt with respect to western eurasia one site velocity on the caspian shoreline suggests that the south caspian basin moves northwest at a rate of 6 2 mm year with respect to western eurasia north south shortening across the alborz occurs at 5 2 mm year to the south deformation seems to extend beyond the piedmont area probably due to active thrusting on the pishva fault we also observe a left lateral shear of the overall belt at a rate of 4 2 mm year consistent with the geological motion observed along e w active strike slip faults inside the belt e g the mosha fault

growth of faults by accumulation of seismic slip the accommodation of large strains in the upper crust is largely achieved by the accumulation of displacement on faults observation shows that as a fault accumulates displacement it grows in size i e its surface area and its length increase here we address the question for an increase in the amount of displacement on a fault by how much would the length of the fault change it is argued by cowie and scholz 1992a that the displacement on a fault is linearly related to the length of the fault this simple result is expanded upon in this paper by assuming that a fault accumulates displacement by repeated earthquakes two different approaches are presented the first approach considers the balance that must be achieved between the energy available for deformation and the work involved in creating new fault surface area as the fault grows the available energy is provided by changes in strain energy when the fault slips the second approach is to construct a geometrical model for fault growth using the scaling relationship between the slip during a single earthquake and the length of the rupture the total displacement on a fault is the sum of the slips contributed by many earthquakes the usefulness of these two approaches is that the growth of a fault over geologic time can be described by parameters that can be obtained from earthquake and fault data the models presented here predict that 1 the maximum amount a fault can grow in a single earthquake that ruptures the entire fault is of the order of 1 of its previous length and 2 the work of faulting may account for 10 of the total energy available during an earthquake the energy lost from the system is accounted for by work done against friction and seismic radiation consequences of fault growth for the segmentation and thus seismogenic potential of a fault over geologic time are discussed using predictions of the theory

surface expression of thrust faulting in eastern iran source parameters and surface deformation of the 1978 tabas and 1968 ferdows earthquake sequences summary previously unrecognised thrust faults in eastern iran were responsible for a destructive earthquake at tabas 1978 september 16 which produced over 80 km of distributed and discontinuous surface ruptures above a series of low anticlinal hills to the west of a major range front analysis of long period body wave seismograms shows a simple rupture on a gently dipping 16 thrust with a slight right lateral component this is compatible with the locally recorded aftershock distribution body wave analysis of two later smaller events show similar source orientations several indicators of long term active folding at tabas can be recognised in the geomorphology and surface ruptures from 1978 are consistent with co seismic fold growth drainage incision also indicates uplift at depth on thrust faults dipping eastwards beneath the folds body wave seismograms for two earthquakes near ferdows 150 km east of tabas in september 1968 also show thrust faulting at depths of 10 km again the surface geomorphology indicates a region of folding above an eastward dipping thrust fault which is 10 km west of a fault bounded range front in both tabas and ferdows the active faulting appears to show quaternary migration away from the range front possibly in response to stresses produced by the elevated topography the identification of zones of active fault related folding is important for earthquake hazard assessment and also for an understanding of the local tectonics we conclude that the structures which gave rise to the 1968 and 1978 earthquakes could have been recognised beforehand from the clear signals in the geomorphology had we known what to look for at that time