microseismicity in the region of tehran we record and analyze small earthquakes around tehran iran using the permanent seismological network of the institute of geophysics of the university of tehran and two temporary dense seismological networks installed for several weeks during 1999 and 2000 regional seismicity is distributed throughout central alborz extending from the caspian sea to the iran plain with the highest level of activity east of tehran related to the mosha and to the garmsar faults which both dip northward and have had strong historical earthquakes our focal mechanisms the first for these faults confirm a left lateral strike slip motion

detrital zircon u pb dating of low grade metamorphic rocks in the sulu uhp belt evidence for overthrusting of the north china craton onto the south china craton during continental subduction the shiqiao pingshang low grade metasedimentary rocks sporadically crop out in the sulu ultrahigh pressure uhp belt in east central china major and trace element data indicate that they were deposited in a passive margin basin probably located at the southern margin of the north china craton sensitive high resolution ion microprobe shrimp u pb dating of detrital zircons from a quartzite sd53 from pingshang and a quartz schist sd54 from shiqiao records ages ranging from 2800 to 1900 ma three age populations are defined at 2660 2500 2350 2150 and 2100 1900 ma with peak ages at 2522 2212 and 2020 ma respectively muscovite ar ar dating of the quartz schist sd54 yields a plateau age of 265 9 1 2 ma these data support the view that the shiqiao pingshang low grade metasedimentary rocks originated from the north china craton and underwent deformation in the permian during subduction of the south china craton yangtze block beneath the north china craton this requires that the low grade metasedimentary rocks were overthrust for several tens of kilometres onto the south china craton explaining why source materials from the north china craton are common in triassic to jurassic sedimentary basins adjacent to the dabie sulu orogenic belt

spinel granulite in odesan area south korea tectonic implications for the collision between the north and south china blocks abstract spinel granulite formed in the fe al rich layers in migmatitic gneiss adjacent to a late paleozoic collision related mangerite intrusion in the odesan area eastern gyeonggi massif south korea contains the high temperature ht assemblage crd spl crn spinel and cordierite compositions indicate peak metamorphic conditions of 914 1157 c retrograde metamorphism reached amphibolite facies where garnet and cordierite broke down to biotite sillimanite and quartz these conditions and the reactions inferred from mineral textures are consistent with a clockwise p t path metamorphic zircon overgrowths in the spinel granulite and enclosing migmatitic gneiss dated by shrimp u pb yield permo triassic ages of 245 10 and 248 18 ma respectively consistent with the metamorphism being a product of the late paleozoic collision between the north and south china blocks within south korea the zircon core ages and textures suggest that the ultimate source of the spinel granulite was a paleoproterozoic 1852 14 ma igneous rock the protolith of the host migmatitic gneiss was a sediment derived principally from 2 49 2 16 and 1 86 ga sources the age and conditions of spinel granulite metamorphism are similar to those of spinel bearing granulite in the higo terrane in west central kyushu 250 ma 950 c at 8 9 kbar consistent with a continuation of the dabie sulu collision zone into japan through the odesan area

the effect of bottom friction on shallow water flow past an isolated obstacle abstract the effect of bottom friction on fluid flow past an isolated obstacle is investigated in the shallow water framework the controlling parameter for this effect is the nondimensional bottom friction number defined as a ratio of friction to inertia with the bottom stress related to the horizontal wind via standard bulk aerodynamic formula the friction number is proportional to the surface roughness the horizontal scale of the obstacle and the inverse of the upstream fluid depth thus under otherwise identical conditions the flow past larger obstacles will be more viscous bottom friction modifies the vorticity generation in several ways but under normal conditions the wake formation remains dominated by a pseudoinviscid process related to the presence of hydraulic jumps however friction strongly controls the velocity deficit region of the wake and thus influences the stability of the steady state wakes predictions of the linear stability analysis are compared with numerical simulation

a linear theory of three dimensional land sea breezes abstractland sea breezes lsbs induced by diurnal differential heating are examined using a three dimensional linear model employing fast fourier transform with emphasis on the complex coastline shape and geometry the earth s rotation and background wind effects it has been demonstrated that the low level vertical motion associated with lsb can be significantly enhanced over a bay peninsula because of convergence of perturbations induced by differential heating along a seaward concave convex coastline the dependence of surface winds and vertical motion patterns and their evolutions on the coastline geometries such as the width and the aspect ratio of the bay the earth s rotation and the background winds are investigated the lsb induced by an isolated tropical island is characterized by onshore flow and ascent over the island in the afternoon to early evening with a reversal of direction from midnight to early morning the diurnal heating induced vertical motion is greatly enhanced over the isl

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

catalina eddies and coastally trapped disturbances abstract observations show that coastally trapped disturbances ctds often accompany catalina eddies that appear in the southern california bight in a previous modeling study of ctds using simple environments and forcings simulations of ctds also evolved a mesoscale eddy that played a critical role in ctd formation and evolution in this study the simple environments and forcings are extended to model the southern california bight and simulations produce both catalina eddies and ctds the simulated catalina eddies and the mesoscale eddies in the previous ctd studies are dynamically equivalent the primary mechanism for eddy formation in the simulations is lee troughing and eddies and ctds are produced provided that 1 there is sufficient stratification in the environment 2 the offshore flow is of sufficient strength breadth and duration and 3 there is sufficient terrain to produce significant lee troughing the simulations show that ctds can propagate out of the bight region when synoptic winds

aspects of the tectonic evolution of china the subject of this special publication is one of the most interesting in global geoscience the tectonic evolution of china the assemblage of terranes that underlie this part of the world provides outstanding opportunities to elucidate global processes and many of the factors that shape the earth s lithosphere are best exemplified by the geology of china and its immediately adjacent areas in addition there are geological features that are particular and unique to the region some have been the focus of recent attention and have attracted international interest because of their global importance this volume provides accounts of up to date research by chinese and international geological teams on key aspects of the tectonic evolution of china and its surrounding areas the papers describe the formation of the geological terranes that make up this part of east asia place constraints on plate tectonic models for their assembly and provide accounts of unique geological feature of the subcontinent

u pb zircon dating of granulite metamorphism in the sludyanskiy complex eastern siberia abstract conventional multigrain and single grain zircon u pb ages were obtained for syn and post metamorphic granitoids from the sludyanskiy complex in the south western baikal region regarded as a classical precambrian terrain in the eastern siberia single grains of magmatic zircon from the syn metamorphic hypersthene bearing biotite trondhjemite and two pyroxene trondhjemite have yielded concordant u pb ages of 488 5 0 6 ma and 488 0 5 ma concordant u pb data for zircons of metamorphic origin in the syn metamorphic two pyroxene trondhjemite yield an age for the peak of the granulite facies metamorphism in the sludyanskiy complex as 477 6 2 ma the pattern of multigrain magmatic zircon samples from syn metamorphic granitoids reflects significant pb loss during the metamorphic episode this came to an end before 471 1 2 ma as demonstrated by concordant zircon data for the intrusion of post metamorphic amphibole two pyroxene quartz syenite our zircon data establish that the granulite facies reworking of the sludyanskiy complex took place during the palaeozoic and not during the paleoproterozoic as was previously suggested the age span between the intrusions of syn metamorphic and post metamorphic granitoids constrains the duration of the metamorphic episode to about 20 ma

diurnal variation of lee vortices in taiwan and the surrounding area abstract lee vortices have been frequently observed in the wake of mesoscale mountains under a low froude number flow regime during the taiwan area mesoscale experiment tamex a cyclonic vortex was observed to the ice of taiwan by a p 3 aircraft in this paper a numerical simulation is carried out to study this event it is shown that the numerical results are capable of recapturing the detailed features as observed by airplane and surface analysis the simulated surface pressure wind field and ice vortex are in good agreement with observations the diurnal oscillation of cloudiness and precipitation in taiwan is also consistent with the observations under undisturbed conditions during the tamex period under a prevailing southwesterly to westerly summer monsson flow numerical results demonstrate that the observed cyclonic vortex initially develops to the southeast of taiwan after sunset then drifts northeastward the diurnal forcing not only generates land sea breezes but also controls the vortex

structural analysis of the gachsar sub zone in central alborz range constrain for inversion tectonics followed by the range transverse faulting analysis of the gachsar structural sub zone has been carried out to constrain structural evolution of the central alborz range situated in the central alpine himalayan orogenic system the sub zone bounded by the northward dipping kandovan fault to the north and the southward dipping taleghan fault to the south is transversely cut by several sinistral faults the kandovan fault that controls development of the eocene rocks in its footwall from the paleozoic mesozoic units in the fault hanging wall is interpreted as an inverted basin bounding fault structural evidences include the presence of a thin skinned imbricate thrust system propagated from a detachment zone that acts as a footwall shortcut thrust development of large synclines in the fault footwall as well as back thrusts and pop up structures on the fault hanging wall kinematics of the inverted kandovan fault and its accompanying structures constrain the n s shortening direction proposed for the alborz range until late miocene the transverse sinistral faults that are in acute angle of 15 to a major magnetic lineament which represents a basement fault are interpreted to develop as synthetic riedel shears on the cover sequences during reactivation of the basement fault this overprinting of the transverse faults on the earlier inverted extensional fault occurs since the late miocene when the south caspian basin block attained a ssw movement relative to the central iran therefore recent deformation in the range is a result of the basement transverse fault reactivation

book reviewthe techniques of modern structural geology vol 1 strain analysis j g ramsay and m i huber academic press london 1983 xiii 307 pp us 55 00 28 00 hardcover

north and south china collision along the eastern and southern north china margins abstract lithofacies distribution and petrography and intracontinental deformation in the north china block ncb and the south china block scb show an active continental margin flanked by the eastern ncb and a passive continental margin was present along the west side of the scb both margins initially trending n ne the tanlu fault possibly initiated as part of the subduction zone during paleozoic time along the eastern margin on the ncb the ncb and the scb were divided along the eastern southern north china margin by the qinling dabie tanlu sulu imjingang yanji zone from southwest to northeast these two continental blocks made contact first in the northeast during late early permian time finally in the southeast at late triassic time and the clockwise collision probably lasted to middle jurassic time the eastern suture the yanji imjingang sulu tanlu zone was dominated by contractional deformation the southern suture the qinling dabie zone was a transpression belt dominated by right lateral strike slip

the dynamics of wave clouds upwind of coastal orography abstract the naval research laboratory s coupled ocean atmosphere mesoscale prediction system coamps is used in conjunction with satellite observations and data from the coastal waves 1996 experiment to investigate the dynamics of unusual wave clouds that occur upwind and offshore of orographic features along the california coast results indicate that supercritical flow within the marine boundary layer interacting with blocking coastal orography is forced to decelerate and an atmospheric bow shock forms the location and orientation of the coamps forecast shock matches well with the leading edge of the wave clouds in satellite imagery and the modeled jump in boundary layer depth across the shock is in good agreement with the aircraft observations in the parameter space of froude number and jump strength that develops within the flow observed and modeled the shock manifests itself as an undular bore on the innermost grid x km long lineal variations in the wind temperature and moisture

the marine permian of east and northeast asia an overview of biostratigraphy palaeobiogeography and palaeogeographical implications abstract the permian marine biostratigraphy faunal successions and mutual correlations where possible throughout east and northeast asia are synthesized region by region based on both published literature and the author s field observations in certain parts of the region the correlation of the permian marine successions of ne asia with the permian international timescale and in particular with gondwanan permian marine sequences remains a major challenge due to profound marine provincialism during the permian however by employing biogeographically mixed faunas from east asia se mongolia ne china south primorye of far east russia and the south kitakami terrane of japan as biostratigraphic gateways coupled with some bipolarly and bi temperately shared permian marine taxa and faunas it has been possible to correlate with reasonable confidence some of the high palaeolatitude permian marine rock units and faunas of ne asia with those of the tethyan region and gondwana palaeobiogeographically the permian marine faunas of east and ne asia are assigned to four major provinces verkolyman sino mongolian japanese cathaysian and panthalassan provinces on the basis of their palaeogeographical distribution patterns and characteristics of faunal assemblages of these the sino mongolian japanese province has considerable significance for regional palaeogeographical plate tectonic and palaeoceanographical reconstructions during the middle permian because of its conspicuously mixed cool and warm water marine biota the origin of this biogeographically mixed marine biota is interpreted to have resulted from a combination of some key factors including the increased tectonic convergence between the bureya jiamusi terrane and the sino korean platform during the permian and the intermingling of both warm and cold water ocean currents off the eastern coastal areas of the bureya jiamusi terrane and the sino korean platform during the middle permian

kinematic links between the eastern mosha fault and the north tehran fault alborz range northern iran kinematic interaction of faults is an important issue for detailed seismic hazard assessments in seismically active regions the eastern mosha fault emf and the north tehran fault ntf are two major active faults of the southern central alborz mountains located in proximity of tehran population similar to 9 million we used field geomorphological and paleoseismological data to explore the kinematic transition between the faults and compare their short term and long term history of activity we introduce the niknamdeh segment of the ntf along which the strike slip kinematics of emf is transferred onto the ntf and which is also responsible for the development of a pull apart basin between the eastern segments of the ntf the ira trench site at the linkage zone between the two faults reveals the history of interaction between rock avalanches active faulting and sag pond development the kinematic continuity between the emf and ntf requires updating of seismic hazard models for the ntf the most active fault adjacent to the tehran metropolis study of offsets of large scale morphological features along the emf and comparison with estimated slip rates along the fault indicates that the emf has started its left lateral kinematics between 3 2 and 4 7 ma according to our paleoseismological data and the morphology of the nearby emf and ntf we suggest minimum and maximum values of about 1 8 and 3 0 mm year for the left lateral kinematics on the two faults in their linkage zone averaged over holocene time scales our study provides a partial interpretation based on available data for the fault activity in northeastern tehran region which may be completed with studies of other active faults of the region to evaluate a more realistic seismic hazard analysis for this heavily populated major city c 2014 elsevier b v all rights reserved

late paleozoic high pressure metamorphic belts in japan and sikhote alin possible oceanic extension of the chinese dabie su lu suture detouring korea

geometry and kinematics of the mosha fault south central alborz range iran an example of basement involved thrusting abstract field investigation of the western part of the mosha fault in several structural sections in the south central alborz range showed that the fault has a high angle of dip to the north and emplaces precambrian to cenozoic rocks over the eocene karaj formation study of the kinematics of the mosha fault in this area based on s c fabric and microstructures demonstrates that it is a deep seated semi ductile thrust strain analysis on rock samples from different sections across the mosha fault shows a flattening pattern of deformation in which the long axis of the strain ellipsoid is aligned in the fault shear sense the mosha fault is associated with a large hanging wall anticline cored by precambrian rocks and series of footwall synclines formed of late tertiary rocks this geometry together with several low angle short cut thrusts in the fault footwall implies that the mosha fault is an inverted normal fault which has been reactivated since the late tertiary in the study area the reverse fault mechanism was associated with the rapid uplift and igneous activity in the central alborz range during the late tertiary unlike in the eastern portion of the fault where the fault kinematics was replaced by a strike slip mechanism in the late miocene

geological setting and controls on the development of graphite sillimanite and phosphate mineralization within the jiamusi massif an exotic fragment of gondwanaland located in north eastern china abstract china is the world s biggest producer and exporter of graphite and also possesses the world s largest reserves of crystalline graphite one of the main production areas is in northeastern china around jixi in heilongjiang province where graphite sillimanite and phosphate form in original sedimentary horizons within the mashan group the mashan group is composed of khondalitic metasediments and tectonically interleaved orthogneisses all metamorphosed to granulite facies the peak conditions have been calculated at 800 850 c at 5 3 6 2 kb and the p t t path defines a tight clockwise loop involving simultaneous decrease in temperature and pressure falling to 410 490 c at less than 3 kb this metamorphic event is interpreted as resulting from continent continent collision with emplacement of mantle derived mafic magma and possible delamination at the base of the crust metamorphism has been precisely dated at 500 ma using u pb zircon shrimp techniques it appears likely that this terrane formed part of an originally more extensive orogenic belt of late pan african age rocks of similar age are recorded from east antarctica western australia india and sri lanka suggesting that the mashan group was most likely juxtaposed with these areas within gondwanaland the mechanism by which the mashan group arrived at its present position between the siberian and north china cratons is poorly constrained but it appears likely that along with the north china south china and tarim blocks it underwent a northward drift from an initial location off northern australia to finally dock with the siberian craton in the late permian to late jurassic

sedimentary record of late paleozoic to recent tectonism in central asia analysis of subsurface data from the turan and south kazak domains abstract the turan and south kazak domains tsk are in central asia between the caspian sea and the tien shan the area is covered by sediments deposited since the late permian during a series of tectonic events closely related to the history of two oceanic domains paleotethys and neotethys sedimentary basins on the tsk therefore provide constraints on the tectonic development of the southern margin of eurasia since the late permian our study is based on structure contour maps and isopach maps of five key stratigraphic markers of late permian to tertiary age isopach maps help locate major faults and delimit sedimentary basins providing information on vertical motions and in some instances horizontal motions subsidence associated with extension appears to have dominated the tsk from the late permian to the eocene the extension may have been of back arc type in southern eurasia next to the active margin where the paleotethys and neotethys successively subducted toward the north here sedimentary basins are both wide and deep up to 15 km during the mesozoic two compressional events of regional significance occurred in association with accretion of continental blocks at the southern margin of eurasia the first one at the end of the triassic led to strong selective inversion of basins over the turan domain the second one during the late jurassic early cretaceous had weaker effects since the oligocene following collision of both india and arabia with eurasia inversion has become more generalized and compressional basins have formed on the tsk throughout the entire history of development of the tsk from the late permian to the tertiary structures of paleozoic and early mesozoic age have exerted a strong control on sedimentation and especially on the location of depocenters the south kazak domain has registered little subsidence in comparison with the turan domain where some basins have become very deep

foreland basement involved structures basement involved structures commonly occur as long irregular chains of uplifts in foreland basins these structures commonly contain significant hydrocarbon accumulations with most major fields located on the broad crests of these structures the search for complex traps in deeper targets and in subthrust structures requires an improved understanding of the geometry and evolution of these structures characteristic features of basement structures include deformation zones within the sedimentary cover that dissipate significant fault slip and gently dipping frontlimbs and backlimbs fault slip in the basement is usually accommodated in the cover by a triangular widening upward deformation zone on the forelimb with the nature of deformation controlled primarily by the mechanical stratigraphy if the cover contains interlayered competent and incompetent units the incompetent units are characterized by significant penetrative deformation whereas the competent units are faulted after a relatively small amount of penetrative deformation depending on the competency contrast between the basement and cover the nature of basement and the physical conditions of deformation the deformation zone may also propagate downward into the basement gently dipping backlimb and frontlimb panels are related to movement of the hanging wall over synclinal and anticlinal bends in the major fault respectively many basement faults are characterized by a number of synclinal fault bends within the basement which result in long and gently dipping backlimbs forelimb panels are related to anticlinal bends that typically occur at the basement cover interface as well as at one or more locations in the sedimentary cover case studies of well constrained examples of structures from the bighorn and uinta basins and the central basin platform demonstrate the development of these characteristic features and their strong dependence on the mechanical stratigraphy these models and case studies will be useful in interpreting foreland basement structures in areas with poor or limited data

mesoscale simulation of supercritical subcritical and transcritical flow along coastal topography abstract a mesoscale atmospheric model is used to address the characteristics of stratified flow bounded by a side wall along a varying coastline initial froude number values are varied through alteration of marine inversion strength permitting examination of supercritical subcritical and transcritical flow regimes encountering several coastal configurations consistent with shallow water models sharp drops in boundary layer depth and flow acceleration occur in flow rounding convex bends however significant flow response occurs in the stratified layer aloft which is unexplained by conventional shallow water theory the strongest flow acceleration occurs in the transcritical case while regardless of inversion strength the deformation of the isentropes aloft shows general structural similarity advection of horizontal momentum is an important component of the horizontal force balance a simulation having several coastline bends exhibits a detached oblique hydraulic jump upwind of a concave bend t

the structure of strongly stratified flow over hills dividing streamline concept in stably stratified flow over a three dimensional hill we can define a dividing streamline that separates those streamlines that pass around the hill from those that pass over the hill the height hs of this dividing streamline can be estimated by sheppard s simple energy argument fluid parcels originating far upstream of a hill at an elevation above hs have sufficient kinetic energy to rise over the top whereas those below hs must pass around the sides this prediction provides the basis for analysing an extensive range of laboratory observations and measurements of stably stratified flow over a variety of shapes and orientations of hills and with different upwind density and velocity profiles for symmetric hills and small upwind shear sheppard s expression provides a good estimate for hs for highly asymmetric flow and or in the presence of strong upwind shear the expression provides a lower limit for hs as the hills become more nearly two dimensional these experiments become less well defined because steady state conditions take progressively longer to be established the results of new studies are presented here of the development of the unsteady flow upwind of two dimensional hills in a finite length towing tank these measurements suggest that a very long tank would be required for steady state conditions to be established upstream of long ridges with or without small gaps and cast doubt upon the validity of previous laboratory studies

low froude number flow past three dimensional obstacles part i baroclinically generated lee vortices abstract we study the flow of a density stratified fluid past a three dimensional obstacle using a numerical model our special concern is the response of the fluid when the froude number is near or less than unity linear theory is inapplicable in this range of froude number and the present numerical solutions show the rich variety of phenomena that emerge in this essentially nonlinear flow regime two such phenomena which occupy parts i and ii of this study are the formation of a pair of vertically oriented vortices on the lee side and a zone of flow reversal on the windward side of the obstacle the ice vortices have been explained as a consequence of the separation of the viscous boundary layer from the obstacle however this boundary layer is absent by design in the present experiments and lee vortices still occur we argue that a vertical component of vorticity develops on the lee side owing to the tilting of horizontally oriented vorticity produced baroclinically as the isentropes deform in r

3 d velocity structure of damavand volcano iran from local earthquake tomography damavand volcano is a large intraplate quaternary composite cone overlying the active fold and thrust belt of the central alborz mountains in northern iran in this study we present the first 3 d

influence of a transverse basement fault on along strike variations in the geometry of an inverted normal fault case study of the mosha fault central alborz range iran abstract inverted normal faults show variations in structural geometry from footwall shortcut thrusts to hanging wall break back thrusts in the present study we evaluated along strike variations in the geometry of the mosha fault central alborz range iran detailed structural mapping within the taleqan mountains revealed that the mosha fault in the eastern part of the study area is associated with a large basement cored hanging wall anticline thrust over tertiary rocks that occur as a syncline or cut by footwall shortcut thrusts in the western part of the study area however the hanging wall consists of break back thrust sheets of paleozoic mesozoic rocks these thrust sheets occur as a duplex system and have allochthonous masses gravitationally emplaced in the foothills of the taleqan mountains curved fold axial traces and scattered intrusive bodies are observed in the valian valley area where the mosha fault is displaced across a transverse basement fault this basement fault controlled along strike variations in the geometry of the mosha fault during its evolution from a basin bounding fault to an inverted normal fault inversion of the fault in the eastern part of the study area where the fault is relatively steep involved basement rocks in the western part of the study area where the fault is relatively shallowly dipping deformation in the hanging wall is accommodated by thin skinned break back thrust sheets

neoarchean to paleoproterozoic continental evolution and tectonic history of the north china craton a review rocks of archean age are widely distributed in the north china craton ncc and can be divided into high grade regions and granite greenstone belts even though most underwent amphibolite to granulite facies metamorphism quartzo feldspathic gneisses occupy 70 to 85 of the total exposure of archean rocks in the craton supracrustal rocks commonly consist of intercalated volcano sedimentary rocks including metabasites meta intermediate to acid rocks banded iron formations metapelites and minor marbles the oldest rocks outcrop over a small area of 4 km2 and are a quartzite amphibolite sequence that yield 3 8 3 5 ga isotopic ages chemical and geochronological data constrain the earliest main crust forming episode at ca 2 9 2 7 ga when most rocks were metamorphosed to upper amphibolite or granulite facies at moderate pressures mafic granulites can be classified into two textural types referred to as near isobaric cooling ibc and near isothermal decompression itd types high pressure granulites and retrograded eclogites occur mainly near the junction of the provinces of hebei shanxi and inner mongolia in the central ncc and in eastern shandong province of the eastern ncc as well as locally in henan province in the southern ncc these high pressure rocks show clockwise p t paths indicating decompression from 14 kb to 5 6 kb an exposed section interpreted as representing precambrian continental lower crust has also been identified in the northern part of the craton although some mafic ultramafic metamorphic rocks have been interpreted as remnants of ancient oceanic crust and mantle by a number of geologists geochemical and petrological evidence demonstrates that many supracrustal orthogneiss associations have island arc affinities therefore several tectonic models have been proposed including continent continent collision and island arc terrain accretion achieved by arc arc or arc microcontinent collision the ncc underwent multiple high grade metamorphic events of which the two most important took place during the intervals 2600 2450 ma and 1950 1750 ma which are considered to be related to early precambrian supercontinental cycles

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

pan african metamorphic and magmatic rocks of the khanka massif ne china further evidence regarding their affinity the khanka massif is a crustal block located along the eastern margin of the central asian orogenic belt caob and bordered to the east by late jurassic early cretaceous circum pacific accretionary complexes of the eastern asian continental margin it consists of graphite sillimanite and cordierite bearing gneisses carbonates and felsic paragneisses in association with various orthogneisses metamorphic zircons from a sillimanite gneiss from the hutou complex yield a weighted mean 206 pb 238 u age of 490 4 ma whereas detrital zircons from the same sample give ages from 934 610 ma magmatic zircon cores in two garnet bearing granite gneiss samples also collected from the hutou complex yield weighted mean 206 pb 238 u ages of 522 5 ma and 515 8 ma whereas their metamorphic rims record 206 pb 238 u ages of 510 500 ma these data indicate that the hutou complex in the khanka massif records early palaeozoic magmatic and metamorphic events identical in age to those in the mashan complex of the jiamusi massif to the west the older zircon populations in the sillimanite gneiss indicate derivation from neoproterozoic sources as do similar rocks in the jiamusi massif these data confirm that the khanka massif has a close affinity with other major components of the caob to the west of the dun mi fault based on these results and previously published data the khanka massif is therefore confirmed as having formed a single crustal entity with the jiamusi and possibly the bureya massif since neoproterozoic time

fault kinematic and geomorphic observations along the north tehran thrust and mosha fasham fault alborz mountains iran implications for fault system evolution and interaction in a changing tectonic regime summary neighbouring faults can interact potentially link up and grow and consequently increase the seismic and related natural hazards in their vicinity despite evidence of quaternary faulting the kinematic relationships between the neighbouring mosha fasham fault mff and the north tehran thrust ntt and their temporal evolution in the alborz mountains are not well understood the ene striking ntt is a frontal thrust that delimits the alborz mountains to the south with a 2000 m topographic front with respect to the proximal tehran plain however no large instrumentally recorded earthquakes have been attributed to that fault in contrast the sigmoidally shaped mff is a major strike slip fault located within the alborz mountains sinistral motion along the eastern part of the mff is corroborated by microseismicity and fault kinematic analysis which documents recent transtensional deformation associated with nne ssw oriented shortening to better understand the activity of these faults on different timescales we combined fault kinematic analysis and geomorphic observations to infer the kinematic history of these structures our fault kinematic study reveals an early dextral shear for the ntt and the central mff responsible for dextral strike slip and oblique reverse faulting during nw oriented shortening this deformation regime was superseded by ne oriented shortening associated with sinistral oblique thrusting along the ntt and the central western mff sinistral strike slip motion along subsidiary faults in the central mff segment and folding and tilting of eocene to miocene units in the mff footwall continued thrusting along the ntt took place during the quaternary however folding in the hanging wall and sinistral stream offsets indicate a left oblique component and quaternary strike slip reactivation of the eastern ntt segment close to its termination this complex history of faulting under different stress directions has resulted in a composite landscape with inherited topographic signatures our study shows that the topography of the hanging wall of the ntt reflects a segmentation into sectors with semi independent uplift histories areas of high topographic residuals and apparent high uplift underscore the fault kinematics combined our data suggest an early mechanical linkage of the ntt and mff fault systems during a former dextral transpressional stage caused by nw compression during ne oriented shortening the ntt and mff were reactivated and incorporated into a nascent transpressional duplex the youngest manifestation of motion in this system is sinistral transtension however this deformation is not observed everywhere and has not yet resulted in topographic inversion

remote sensing of damavand volcano iran using landsat imagery implications for the volcano dynamics abstract remote sensing techniques are applied to retrieve land surface temperature lst radiative heat flux rhf geothermal heat flux ghf and to map hydrothermal alteration zones around the damavand stratovolcano iran landsat enhanced thematic mapper plus etm day and nighttime images are used and merged to available geological data to identify thermal anomaly areas rhf is determined using the stefan boltzmann equation after preprocessing geometric radiometric and atmospheric correction and processing emissivity calculation and lst retrieval of thermal infrared bands in order to estimate ghf from daytime image solar radiation and albedo maps are generated to minimize these effects the ghf values are derived from nighttime image using the background subtraction technique using boolean operation only those pixels with the ghf values greater than 30 w m 2 obtained from daytime image and the ghf values greater than 10 w m 2 estimated from nighttime image are identified as thermal anomalies the geothermal areas are identified by combining the thermal anomaly map and other geological information thermal anomalies have close spatial correlation to faults thermal springs and high heat flow measurements from subsurface data and lithology some of the thermal anomalies and hydrothermal alteration areas also overlap active deformation areas this suggests role of heat and hydrothermal alteration on flank instability processes the thermal anomaly areas show an arc shaped pattern this pattern and the concentration of higher ghf areas in the eastern sector of the volcano are consistent with a release of fluids in a transition zone between a transpressional and a transtensional tectonic regime the combination of thermal infrared data with other geological information layers can be used to detect geothermal areas as well as to analyze the complex relationships among geothermal activity active tectonics and gravity instability processes on volcanoes

shrimp u pb zircon dating of the neoproterozoic penglai group and archean gneisses from the jiaobei terrane north china and their tectonic implications abstract archean basement gneisses and supracrustal rocks together with neoproterozoic sinian metasedimentary rocks the penglai group occur in the jiaobei terrane at the southeastern margin of the north china craton shrimp u pb zircon dating of an archean ttg gneiss gave an age of 2541 5 ma whereas metasedimentary rocks from the neoproterozoic penglai group yielded a range in zircon ages from 2 9 to 1 8 ga the zircons can be broadly divided into three age populations at 2 0 1 8 ga 2 45 2 1 ga and 2 5 ga detrital zircon grains with ages 2 6 ga are few in number and there are none with ages

shrimp u pb zircon geochronology of palaeoproterozoic metasedimentary rocks in the north china craton evidence for a major late palaeoproterozoic tectonothermal event abstract although metasedimentary successions are widely distributed across the north china craton those of palaeoproterozoic age are restricted to three orogenic belts namely the trans north china orogen the khondalite belt and the jiao liao ji belt prior to this work some of those successions were considered to be archaean in age the palaeoproterozoic metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3 0 to 2 1 ga with the majority recording an age between 2 3 and 2 0 ga this latter group define a series of magmatic events that occurred between formation of the archaean basement and deposition of the metasedimentary rock protoliths the metasedimentary rocks occur as two associations older volcano sedimentary units that formed between 2 37 and 2 0 ma and younger sedimentary units that formed mainly between 2 0 and 1 88 ga all these rock associations were then subjected to metamorphism during the late palaeoproterozoic 1 88 and 1 85 ga tectonothermal event named the luliang movement in early chinese literature which was a continent continent collision that led to the amalgamation of the north china craton

thrust tectonics of the binalood region ne iran the binalood region in ne iran which is an eastern segment of the alborz mountains is affected by thin skinned tectonics lower paleozoic jurassic cretaceous and cenozoic rock sequences as well as remnants of the paleo tethys oceanic realm are transported in a southwestward direction by several thrust faults which are of two generations 1 cimmerian and 2 alpine structural units in this region form either single thrust sheets or duplexes they have been displaced sequentially in a piggyback style from the hinterland ne to foreland sw under ductile brittle ductile and brittle conditions geometrically they constitute an antiformal stack breached on its southwestern side by major and minor out of sequence thrusts

lee vortex formation in free slip stratified flow over ridges part ii mechanisms of vorticity and pv production in nonlinear viscous wakes abstract the formation of orographic wakes and vortices is studied within the context of numerically simulated viscous flow with uniform basic state wind and stability past elongated free slip ridges the viscosity and thermal diffusivity are sufficiently large that the onset of small scale turbulence is suppressed it is found in part i of this study that wake formation in the viscous flow is closely tied to the dynamics of a low level hydraulic jump like feature in the lee of the obstacle here the role of the hydraulic jump in producing the vorticity and potential vorticity pv of the viscous wake is considered a method for diagnosing vorticity production is developed based on a propagator analysis of the lagrangian vorticity equation that generalizes cauchy s formula for the evolution of vorticity in a lagrangian framework application of the method reveals that the vertical vorticity of the wake originates through baroclinic generation and tilting in the mountain wave upstream of the jump however

cenozoic exhumation history of the alborz mountains iran new constraints from low temperature chronometry the alborz mountains in the north of the turkish iranian plateau mainly developed in the cenozoic as a consequence of the closure of neo tethys and continental collision between arabia and eurasia cenozoic growth of the fold and thrust belt exploited an older palaezoic mesozoic crustal fabric but the extent to which this governed the overall form of the mountain belt is unclear to determine when and how the alborz mountain belt has grown apatite fission track aft and u th he ahe thermochronometry were performed on 46 bedrock samples collected along 8 transects across the range aft central ages range from 157 24 ma to 10 1 ma with most ages falling between 40 ma and 10 ma ahe ages range from 17 2 ma to 6 1 ma the data revealed enhanced exhumation ca 35 5 ma minor exhumation between ca 30 20 ma and an increase in exhumation thereafter this pattern matches the tripartite mid cenozoic stratigraphy of central iran where upper oligocene lower miocene carbonates are sandwiched between terrestrial clastic formations the most intriguing thermochronometric signal found is a major acceleration of exhumation that initiated in the late miocene to early pliocene recorded by the ahe data there does not appear to be a direct tectonic cause for pliocene intensified erosion as convergence rates between arabia and eurasia have remained relatively constant enhanced exhumation at this time may reflect a climatically induced intensification of erosion during caspian isolation and base level fall or a regional tectonic re organization of the arabia eurasia collision or both

plio quaternary tectonic regime changes in the transition zone between alborz and kopeh dagh mountain ranges ne iran abstract this paper is concerned with the changes in the plio quaternary stress states in ne iran and provides evidence for regional active deformation across a wide transition zone between the alborz and kopeh dagh mountains the arabia eurasia convergence is involved in the strike slip faulting along ne trending left lateral faults in the eastern alborz as well as nw trending right lateral faults in the western kopeh dagh the inversion result of fault kinematic data slip vector measurement of fault plane and focal mechanisms strongly indicates an active transpressional tectonic regime in the study area we provide evidence for drastic temporal changes in the stress state during the plio quaternary based on the inversions of fault kinematic data a regional transpressional tectonic regime with a mean n036 20 e trending horizontal 1 is representative for the modern stress state the older state reveals compressional to transpressional tectonic regimes comprising a n135 20 e trending horizontal 1 the modern transpressional tectonic regime characterized by a regional ne trending 1 is consistent with the inversion of earthquake focal mechanisms that yield a n47 e trending 1 for the present day stress state the kinematic results are significantly homogeneous and mechanically compatible with the active geological structures in the way that reverse and strike slip faulting are coherent with a single 1 direction

supercritical flow interaction within the cape blanco cape mendocino orographic complex abstract supercritical flow interaction occurring in the marine boundary layer between closely spaced coastal capes is investigated with a mesoscale numerical prediction model as an extension of previous work the u s navy s coupled ocean atmosphere mesoscale prediction system coamps is used to perform idealized model simulations with marine layers of varying upstream froude number to elucidate the different flow responses for a single convex bend the impact upon the supercritical flow of introducing a series of closely spaced coastal bends is then investigated the expansion fan is significantly reduced in magnitude and size by the formation of a compression wave at a blocking concave bend approximately 150 km downstream building upon the idealized marine layer response real data forecasts are then examined for several time periods of supercritical flow interaction between cape blanco oregon and cape mendocino california observations from the coastal waves 1996 cw96 field program were colle

on the dynamics of hawaiian cloud bands island forcing abstract this study focuses on basic island scale forcing mechanisms for the formation and evolution of a band cloud typically present upwind of the island of hawaii by means of numerical experiments and verification of our results against observations and laboratory experiments reported in the literature we show that the band cloud is a complex three dimensional phenomenon which is inseparable from the airflow around the island in particular we demonstrate that the event needs to be analyzed in terms of the basic fluid dynamics of strongly stratified flow past a three dimensional obstacle the band cloud is found to arise primarily from the dynamic interaction of the trade winds with the island the upwind surface flow forms a separation line with an associated stagnation point a low level convergence zone forms along this line resulting in an updraft line if the updrafts are strong enough a band cloud forms formation and characteristics of such a system are mostly controlled by the environmenta

the dynamics of orographic wake formation in flows with upstream blocking the development of orographic wakes and vortices is revisited from the dynamical perspective of a three dimensional 3d vorticity vector potential formulation particular emphasis is given to the role of upstream blocking in the formation of the wake scaling arguments are first presented to explore the limiting form of the 3d vorticity inversion for the case of flow at small dynamical aspect ratio it is shown that in the limit of small the inversion is determined completely by the two horizontal vorticity components that is the part of the velocity induced by the vertical component of vorticity vanishes in the small limit this result leads to an approximate formulation of small fluid mechanics in which the three governing prognostic variables are the two horizontal vorticity components and the potential temperature the remainder of the study then revisits the problem of orographic wake formation from the perspective of this small vorticity dynamics framework previous studies have suggested that one of the potential routes to stratified wake formation is through the blocking of flow on the upstream side of the barrier this apparent link between blocking and wake formation is shown to be relatively straightforward in the small vorticity context in particular it is shown that blocking of the flow inevitably leads to a horizontal vorticity distribution that favors deceleration of the leeside flow at the ground this process of leeside flow deceleration as well as the subsequent time evolution of the wake is illustrated through a series of numerical initial value problems involving flows past 2d and 3d barriers it is proposed that the initiation of the wake flow in these stratified problems resembles the flow produced by a retracting piston in shallow water theory

age of palaeozoic granites and metamorphism in the tuvino mongolian massif of the central asian mobile belt loss of a precambrian microcontinent abstract the tuvino mongolian massif tmm was previously interpreted as a precambrian block within the central asian mobile belt according to this idea it consists of tectonic slices composed of metamorphic rocks of pre mesoproterozoic basement that experienced two episodes of regional metamorphism and mesoproterozoic cover rocks that were reworked together with the basement during high grade metamorphism zircon u pb dating of granitoids from all metamorphic complexes demonstrates that the earliest metamorphic event occurred at 536 6 ma significantly later than the deposition of the cover rocks regional upper amphibolite facies metamorphism which affected all metasedimentary units of the tmm occurred in the short time interval of 497 4 to 489 3 ma we propose that there is no simple basement cover relationship in the tuvino mongolian massif instead the massif consists of tectonic domains composed of heterogeneous metasedimentary successions with distinct pre metamorphic and pre tectonic histories that were juxtaposed by thrusting prior to 497 ma and then metamorphosed under upper amphibolite facies conditions we suggest that this thrusting event was associated with early palaeozoic collisional processes related to amalgamation of the central asian mobile belt our new model for the evolution of the tmm implies derivation of neoproterozoic terrigeneous metasediments from 800 900 ma granitoids formed in an andean type active continental margin setting

fault zone migration by footwall shortcut and recumbent folding along an inverted fault example from the mosha fault central alborz northern iran the mosha fault is a multiply inverted fault in the central alborz field observations and structural data from this fault show that a footwall shortcut is the major mode of response of this fault to contractional deformation although the mosha fault is a basement involved fault there is no evidence of involvement of basement along its footwall shortcuts at least in the study area footwall shortcuts along this fault vary in size from several hundreds of metres to tens of kilometres suggesting that a footwall shortcut can be scale independent it is proposed that footwall shortcuts can also occur as blind thrusts under fault related folds in the terrains near the major inverted faults similar cases also exist in other regions such as japan some large footwall shortcuts may be the causative fault of devastating earthquakes in the active inverted terrains such as the south central alborz incompetent layers acting as detachments may play an important role in the development of footwall shortcuts recu

numerical simulation of the 1981 sichuan flood part i evolution of a mesoscale southwest vortex abstract during the period 11 15 july 1981 heavy rainfall occurred over the sichuan basin in china resulting in severe floods that took a large toll in human life and property damage mesoscale analyses by kuo cheng and anthes have shown that the flood was directly related to the development of a long lived mesoscale southwest sw vortex over the basin in this paper we present the results of numerical experiments aimed at 1 testing the capability of a limited area mesoscale model to predict the evolution of the sw vortex and the accompanying heavy precipitation 2 examining the structure of the simulated vortex using the model data and 3 elucidating the role of various physical processes in the evolution of the sw vortex principal findings are 1 the control experiment which utilized an 80 km grid spacing and simple physical parameterizations was able to simulate the evolution of the mesoscale sw vortex and the accompanying heavy precipitation the simulation captured many observed features a

mesozoic terrane accretion in northeast china sikhote alin and japan regions abstract the nadanhada range in northeast china is composed of upper paleozoic limestone greenstone middle to late triassic bedded chert and middle jurassic siliceous shale these rocks are enclosed in post middle jurassic clastic rocks the lithologic association ages radiolarian assemblages and geologic structure of the nadanhada range are very similar to those of the tamba mino ashio terrane in southwest japan this indicates that the nadanhada range is the northern extension of the tamba mino ashio terrane mesozoic tectonostratigraphic terranes identified in northeast china sikhote alin and southwest japan are the khanka terrane a micro continent composed of precambrian metamorhic rocks and paleozoic to mesozoic sedimentary and volcanic covers the nadanhada western sikhote alin terrane a disrupted terrane composed of upper paleozoic to jurassic sedimentary rocks the eastern sikhote alin terrane a terrane composed mainly of early cretaceous clastics the tetyukhe terrane a disrupted terrane composed of upper paleozoic to early cretaceous sedimentary rocks the hida terrane a continent type stratigraphic terrane composed of precambrian and upper paleozoic basement covered with jurassic to cretaceous coarse clastics and the tamba mino ashio terrane a disrupted terrane composed of upper paleozoic to earliest cretaceous sedimentary rocks accretionary history of these terranes is discussed on the basis of paleomagnetic and paleobiogeographic data

exhumation of the west central alborz mountains iran caspian subsidence and collision related tectonics crystallization and thermal histories of two plutons in the west central alborz also elburz elburs mountains northern iran are combined with crosscutting relations and kinematic data from nearby faults to determine the cenozoic tectonic evolution of this segment of the youthful euro arabian collision zone u pb 40 ar 39 ar and u th he data were obtained from zircon biotite k feldspar and apatite the akapol pluton intruded at 56 2 ma cooled to 150 c by ca 40 ma and stayed near that temperature until at least 25 ma the nearby alam kuh granite intruded at 6 8 0 1 ma and cooled rapidly to 70 c by ca 6 ma these results imply tectonic stability of the west central alborz from late eocene to late miocene time consistent with miocene sedimentation patterns in central iran elevation correlated u th he ages from the akapol suite indicate 0 7 km m y exhumation between 6 and 4 ma and imply 10 km of alborz uplift that was nearly synchronous with rapid south caspian subsidence suggesting a causal relation uplift south caspian subsidence and subsequent folding reversal of alborz strike slip from dextral to sinistral and eastward extrusion of central iran coarse zagros molasse deposition dead sea transform reorganization red sea oceanic spreading and north and east anatolian fault slip all apparently began ca 5 2 ma suggesting a widespread tectonic event that we infer was a response to buoyant arabian lithosphere choking the neo tethyan subduction zone

the santa cruz eddy part i observations and statistics a shallow cyclonic circulation that occurs in the summertime over the monterey bay california is investigated since it is often centered offshore from the city of santa cruz and has never been studied in detail before it is named the santa cruz eddy sce in this study its horizontal size is 10 40 km and its vertical extent is 100 500 m the sce is important for local weather because it causes surface winds along the santa cruz coast to blow from the east instead of from the northwest the latter being the climatological summer pattern for this area as a consequence of the eddy cool and moist air is advected from the south and southeast into the santa cruz area bringing both relief from the heat and fog to the city the sce is unique in its high frequency of occurrence most vortices along the western american coast form only during unusual weather events whereas the sce forms 78 79 of the days during the summer the sce frequency was determined after analyzing two years of data with empirical orthogonal functions eofs from a limited observational network and satellite imagery an explanation of the formation mechanism of the sce will be provided in part ii of this study

collision belt between the khanka block and the north china block in the yanbian region northeast china the pre jurassic geotectonics in northeast china and its adjacent regions are characterized by collision of microcontinental blocks the yanbian region lies between the north china block ncb and the khanka block kb along the dashanzui antu kaishantun collision belt the yanbian pre jurassic fold belt can be divided into two parts one part represents the western margin of the kb which consists of late proterozoic metamorphic basement and a permian active continental margin the other one is located at the eastern margin of the ncb and is composed of proterozoic passive margin deposits where the seluohe and qinglongcun groups are developed and rocks of the permian passive margin collision of these two parts took place along the dashanzui antu kaishantun collision zone during the late permian to early triassic as evidenced by the emplacement of syncollision granites and a type granites in northeast china and adjacent regions a series of microcontinental blocks collided with one other from the end of early paleozoic to the early triassic the collision event that took place in the yanbian region may represent the latest collision event in the paleo asian oceanic domain c 2003 elsevier ltd all rights reserved

observations and mixed layer modeling of a terrain induced mesoscale gyre the denver cyclone abstract in northeastern colorado a frequently observed feature of the surface wind field is a stationary terrain induced mesoscale gyre which is often associated with the formation of severe weather because of the gyre s proximity to the denver metropolitan area local weather forecasters frequently refer to it as the denver cyclone the development of one such cyclone which occurred on 1 august 1985 is documented with mesonet radiosonde wind profiler radiometer and tower data mixed layer model simulations of this event closely agree with the observed gyre structure and indicate that the gyre is associated with a plume of warmer potential temperature air which originates from a ridge of higher terrain to the south of denver and advects northward into the area of gyre formation a mixed layer vorticity budget demonstrates that the formation of the gyre results from the baroclinic and slope effects on the turbulent stress divergence profile

accommodation of late cenozoic oblique shortening in the alborz range northern iran abstract the alborz range northern iran deforms by strain partitioning of oblique shortening onto range parallel left lateral strike slip and thrust faults deformation is due to the north south arabia eurasia convergence and westward motion of the adjacent south caspian relative to iran roughly north south shortening occurs on thrusts that dip inwards from the range margins precambrian basement is not exposed because of detachment along upper proterozoic evaporites and the thickness of overlying strata 10 km other detachments occur within phanerozoic sediments active left lateral strike slip faults trend ene in the east of the range wnw in the west the eastern mosha fault has a left lateral offset of 30 35 km shortening across the range is 30 km 25 30 at the longitude of tehran this is hard to reconcile with the crustal thickness of 35 km which is similar to adjacent basins percentage shortening across the alborz is similar to the adjacent kopet dagh but because the latter is twice as wide finite shortening is roughly half the difference may be accommodated by subduction of the adjacent south caspian basin northwards under the middle caspian south caspian sediments began folding in the pliocene the present kinematics of the alborz may have begun at this time including a reversal from range parallel right lateral to left lateral strike slip faulting but the regional stratigraphy indicates uplift as early as the mid tertiary

epma u th pb monazite and shrimp u pb zircon geochronology of high pressure pelitic granulites in the jiaobei massif of the north china craton the jiaobei massif constitutes the southern segment of the paleoproterozoic jiao liao ji belt in the eastern block of the north china craton and contains high pressure hp mafic and pelitic granulites the hp pelitic granulites contain four distinct mineral assemblages garnet kyanite biotite muscovite rutile m1 garnet kyanite ternary feldspar biotite muscovite rutile m2 garnet sillimanite biotite perthite anti perthite m3 and biotite muscovite sillimanite plagioclase m4 of which m2 is a typical hp pelitic assemblage the origin of these hp granulites is important for understanding the tectonic evolution of the jiao liao ji belt but the timing of the hp event still remains unknown this study applied the epma u th pb monazite and shrimp u pb zircon dating techniques to determine the metamorphic ages of the hp pelitic granulites in the jiaobei massif cl images and th u ratios show that all monazite and zircon grains in the analyzed samples are of metamorphic origin eighty two epma analyses on 16 monazite grains from two samples yielded three age groups at 1895 to 1882 ma 1814 to 1813 ma and 1706 to 1692 ma and the ages of 16 shrimp analyses on 14 zircon grains from one sample range from 1864 to 1803 ma the oldest ages of 1895 to 1882 ma were yielded from high y monazite grains enclosed in garnet and sillimanite pseudomorph after kyanite and thus interpreted as the time of the hp m2 granulite facies metamorphism the epma monazite ages of 1814 to 1813 ma and shrimp zircon ages of 1864 to 1803 ma are interpreted as the approximate ages of the post hp granulite facies metamorphism m3 most probably resulting from the exhumation of the hp granulites to the medium pressure granulite facies levels the youngest age group of 1706 to 1692 ma obtained from low y monazite grains in the matrix can be interpreted as the age of late cooling and retrograde metamorphism m4 that occurred when the hp pelitic granulites were exhumed to the upper crust the presence of paleoproterozoic hp mafic and pelitic granulites in the southern segment of the jiao liao ji belt suggests that the evolution of the jiao liao ji belt in the eastern block of the north china craton must have been involved in subduction or collision related tectonic processes

extreme crustal metamorphism during columbia supercontinent assembly evidence from north china craton abstract a vast supracrustal belt of khondalites granulite facies metapelites occur along the northern margin of the north china craton we report here for the first time spinel quartz equilibrium assemblage from these rocks in two textural settings 1 high zno up to 14 47 wt spinel with quartz as inclusions within garnet porphyroblasts defining pressure above 12 kbar and temperature of 900 c and 2 low zno down to 1 2 wt spinel in association with quartz in the matrix assemblage formed during peak ultrahigh temperature conditions ca 975 c and 9 kbar we present a unique case of decompression where the metamorphic conditions of the rocks traversed mostly through the spinel quartz extended stability field monazite grains in textural association with both types of spinel quartz textures were analysed for age determination and the data define two age peaks at 1927 11 ma and 1819 11 ma since the peak thermal regime of the khondalites was close to or exceeded the theoretical closure temperature of pb in monazite we infer the 1819 11 ma age as the timing of ultrahigh temperature event in this craton our data lend support to the idea of ca 1 9 1 8 ga e w collisional orogen at the northern margin of the north china craton we correlate the extreme crustal metamorphism with tectonics associated with the assembly of the north china craton within the columbia supercontinent

numerical experiments of vortices in the wakes of large idealized mountains abstract the purdue mesoscale model pmm is applied to study the flow past large idealized mountains under a low froude number results show that for reynolds numbers in the range of 4 100 results also show that small perturbations in the oncoming wind the inclination of the oncoming wind and major axis of the mountain the mountain shape and the coriolis force all can contribute to atmospheric vortex shedding the reynolds number is not a good indicator of whether a vortex will stay or break away from the mountain in the atmosphere when the earth s rotation is included the simulated pressure field and wind increase considerably on the left hand side facing downstream of the mountain whic

an unusual aerial photograph of an eddy circulation in marine stratocumulus clouds abstractan aerial photograph of a cyclonic von karman like vortex in the marine stratocumulus clouds off the california coast taken by a commercial pilot near grover beach is presented it is believed that this is the first photograph of such an eddy taken from an airplane to appear in publication the eddy occurred with a strong inversion above a shallow marine boundary layer in the lee of high inversion penetrating terrain tower and surface wind measurements plotted on satellite imagery demonstrate that the grover beach eddy was not just a cloud level feature but extended through the marine atmospheric boundary layer mabl to the surface evolution of the flow during the formation of the eddy appears similar to idealized numerical simulations of blocked mabl flow from the literature the tower measurements sampled the northern part of the eddy circulation during its formation just offshore the 2 3 c temperature increases and then decreases during and after the eddy passage may be indicative o

the denver cyclone part i generation in low froude number flow abstract a numerical model is used to study the denver cyclone a mesoscale vortex that develops in eastern colorado under southerly to southeasterly flow diurnal effects e g surface heating cooling have been excluded from these simulations but are discussed in part ii of this study simulations are first performed with a southerly ambient wind i e parallel to the continental divide if the froude number of the flow based on the height of the palmer divide an east west ridge to the south of denver is small then a vortex forms over the denver region this circulation then propagates northward at just over half the upstream flow velocity leaving essentially stagnant air in the lee of the palmer divide it is shown that coriolis turning has a negligible effect on the flow when the ambient wind is from the south however when the ambient wind is at an angle to the continental divide northerly winds can develop along the foothills due to coriolis turning of the flow as it approaches the divid

permian geodynamic setting of northeast china and adjacent regions closure of the paleo asian ocean and subduction of the paleo pacific plate abstract northeast china and adjacent regions are located in the central east asian continent and consist tectonically of both the paleo asian and paleo pacific orogens between the siberian platform and sino korean north china block this paper discusses some hotly debated issues concerning the permian geodynamic setting of these regions based on a comprehensive analysis of available geological geochemical paleobiogeographical and paleomagnetic data spatial and temporal distribution of ophiolites and associated continental marginal sequences permian sedimentary sequences spatial distribution and geochemistry of permian magmatic rocks and the evolution of paleobiogeographical realms imply 1 that the permian marine basins in northeast china and adjacent regions include remnants of the paleo asian ocean in southeastern inner mongolia and central jilin province and active continental margins of the paleo pacific ocean 2 that the suture between the siberian and sino korean paleoplates was finally emplaced in the permian and is located in areas from suolunshan solonker eastwards through regions north to the xar moron river in southeastern inner mongolia and then central jilin province to the yanji area and 3 that the permian crustal evolution of northeast china and adjacent regions as well as parts of the siberian paleoplate was influenced by subduction of the paleo pacific oceanic plate finally the permian tectonic framework and paleogeography of northeast china and adjacent regions in central east asia are discussed briefly and early and late permian palinspastic reconstruction maps are provided

left lateral active deformation along the mosha north tehran fault system iran morphotectonics and paleoseismological investigations abstract the mosha and north tehran faults correspond to the nearest seismic sources for the northern part of the tehran megacity the present day structural relationships and the kinematics of these two faults especially at their junction in lavasanat region is still a matter of debate in this paper we present the results of a morphotectonic analysis aerial photos and field investigations within the central part of the mosha and eastern part of the north tehran faults between the mosha valley and tehran city our investigations show that generally the traces of activity do not follow the older traces corresponding to previous long term dip slip thrusting movements the recent faulting mainly occurs on new traces trending e w to ene wsw affecting quaternary features streams ridges risers and young glacial markers and cutting straight through the topography often defining en echelon patterns right and left stepping these new traces correspond to steep faults with either north or south dipping directions along which clear evidences for left lateral strike slip motion are found at their junction zone the two sinistral faults display a left stepping en echelon pattern defining a positive flower structure system clearly visible near ira village further west the left lateral strike slip motion is transferred along the ene wsw trending niavaran fault and other faults the cumulative offsets associated with this left lateral deformation is small compared with the topography associated with the previous late tertiary thrusting motion showing that it corresponds to a recent change of kinematics

a new concept on tectonic correlation between korea china and japan histories from the late proterozoic to cretaceous abstract the dabie sulu collision belt in china extends to the hongseong odesan belt in korea while the okcheon metamorphic belt in korea is considered as an extension of the nanhua rift within the south china block the hongseong odesan belt divides korea s gyeonggi massif into northern and southern portions the southern gyeonggi massif and the yeongnam massif are correlated with china s yangtze and cathaysia blocks respectively while the northern gyeonggi massif is part of the southern margin of the north china block the southern and northern gyeonggi massifs rifted from the rodinia supercontinent during the neoproterozoic to form the borders of the south china and north china blocks respectively subduction commenced along the southern and eastern borders of the north china block in the ordovician and continued until a triassic collision between the north china and south china blocks while subduction was occurring on the margin of the north china block high p t metamorphic belts and accretionary complexes developed along the inner zone of southwest japan from the ordovician to the permian during the subduction the hida belt in japan grew as a continental margin or continental arc collision between the north and south china blocks began in korea during the permian 290 260 ma and propagated westwards until the late triassic 230 210 ma creating the sinistral tanlu fault in china and the dextral fault in the hida and hida marginal belt in japan phanerozoic subduction and collision along the southern and western borders of the north china block led to formation of the qinling dabie sulu hongseong hida yanji belt

shrimp u pb zircon dating of the wulian complex defining the boundary between the north and south china cratons in the sulu orogenic belt china abstract neoproterozoic metasedimentary and metavolcanic rocks of the wulian group are associated with gneissic granitoids at the northern margin of the sulu uhp belt adjacent to the wulian yantai fault and are collectively referred to as the wulian complex shrimp u pb dating of detrital zircon from the metasedimentary rocks of the wulian group indicates a range in age from 3478 to 625 ma based on zircons 3000 ma with the oldest age being 3339 ma 2700 2400 ma with a peak at 2436 ma 2200 1800 ma with a peak at 2156 ma and at 770 ma these results indicate that deposition of the wulian group was after 770 ma and that some detrital material most likely came from neoproterozoic sources in the south china craton scc shrimp u pb zircon dating of a metavolcanic rock defines a weighted mean 206 pb 238 u age of 761 8 ma which is consistent with other rocks of south china affinity and can be correlated with syn rift magmatism during the breakup of the supercontinent rodinia the wulian group together with neoproterozoic granites of the wulian complex constrains the location of the triassic suture zone between the north china and south china cratons based on our new data the suture must lie north of the wulian complex and is marked by the baichihe yantai fault

the santa cruz eddy part ii mechanisms of formation the formation mechanism of the santa cruz eddy sce is investigated using the fifth generation pennsylvania state university national center for atmospheric research mesoscale model mm5 simulations of 25 26 august 2000 showed that two eddy instances formed on that night a finding supported by observations the two eddies had similar behavior they both formed in the sheltered santa cruz california area and then moved southeastward to finally dissipate after 7 11 h however the first eddy had greater vorticity wind speed horizontal and vertical extents and lifetime than the second eddy numerical simulations showed that the sces are formed by the interaction of the main northwesterly flow with the topographic barrier represented by the santa cruz mountains to the north of monterey bay additional numerical experiments were undertaken with no diurnal heating cycle no molecular or eddy viscosity and no horizontal thermal gradients at ground level in all cases vertical vorticity was still created by the tilting of horizontal vorticity generated by the solenoidal term in the vorticity equation this baroclinic process appeared to be the fundamental formation mechanism for both sces but more favorable conditions in the late afternoon including a south to north pressure gradient flow turning due to the sea breeze and an expansion fan coincided to intensify the first eddy

dynamics of a catalina eddy revealed by numerical simulation abstract through numerical simulations with the pennsylvania state university ncar mesoscale model the dynamics of a catalina eddy event that formed during the period 26 30 june 1988 off the coast of southern california is examined a strengthening and veering of the low level synoptic scale winds from climatological northwesterlies to northerlies results in a more pronounced effect of the coastal orography around the california bight region in particular relative vorticity formed by flow over the coastal terrain remains offshore prior to the formation of a quasi steady eddy within the bight the northerlies are strong enough to advect anomalously high vorticity out of the region the formation of a mature catalina eddy relies on a rapid deceleration of the synoptic scale northerlies on 30 june such that vorticity once formed remains in the bight the eddy is also strongly modulated by the diurnal cycle northwesterly flow around 500 m above mean sea level impinging on the mountains north of the b

a technique for generating idealized initial and boundary conditions for the psu ncar model mm5 abstract a new idealized initialization technique has been developed for the mesoscale model version 5 modeling system the technique allows the specification of baroclinic disturbances that feature vertical variations of the height temperature and wind fields in terms of phase lag wavelength and phase speed the technique involves specifying a sounding profile at some reference point generating the desired height fields using an analytic formulation constructing the wind fields to be in geostrophic balance and generating temperature fields using the hydrostatic relationship a distinct advantage of this technique over existing ones is that the boundary conditions are not restricted to being specified as periodic the flexibility means that 1 users do not have to specify a domain whose size is equal to an integer number of wavelengths of the specified flow 2 users can specify a flow that consists of different wavelengths at different heights as is typically observed and 3 any responses that a