rank ordering statistics of extreme events application to the distribution of large earthquakes rank ordering statistics provide a perspective on the rare largest elements of a population whereas the statistics of cumulative distributions are dominated by the more numerous small events the exponent of a power law distribution can be determined with good accuracy by rank ordering statistics from the observation of only a few tens of the largest events using analytical results and synthetic tests we quantify the systematic and the random errors we also study the case of a distribution defined by two branches each having a power law distribution one defined for the largest events and the other for smaller events with application to the worldwide harvard and southern california earthquake catalogs in the case of the harvard moment catalog we make more precise earlier claims of the existence of a transition of the earthquake magnitude distribution between small and large earthquakes the b values are b2 2 3 0 3 for large shallow earthquakes and b1 1 00 0 02 for smaller shallow earthquakes however the crossover magnitude between the two distributions is ill defined the data available at present do not provide a strong constraint on the crossover which has a 50 probability of being between magnitudes 7 1 and 7 6 for shallow earthquakes this interval may be too conservatively estimated thus any influence of a universal geometry of rupture on the distribution of earthquakes worldwide is ill defined at best we caution that there is no direct evidence to confirm the hypothesis that the large moment branch is indeed a power law in fact a gamma distribution fits the entire suite of earthquake moments from the smallest to the largest satisfactorily there is no evidence that the earthquakes of the southern california catalog have a distribution with two branches or that a rolloff in the distribution is needed for this catalog b 1 00 0 02 up to the largest magnitude observed mw 7 5 hence we conclude that the thickness of the seismogenic layer has no observable influence whatsoever on the frequency distribution in this region

large internal waves advection in very weakly stratified deep mediterranean waters the eastern mediterranean sea contains relatively small trenches o 1 10 km horizontal width that go deeper than 4000 m at a first glance these deep waters are homogeneous with weak currents 0 1 m s 1 this viewpoint is modified after evaluation of new detailed yearlong temperature observations using 103 high precision sensors that reveal intense variability of internal waves even though temperature variations are within the range of a few mk only requiring precise correction for the adiabatic lapse rate during post processing the images are permanently dynamic the weak density stratification of buoyancy close to the inertial frequency supports large turbulent overturns indirectly governed or advected by large internal waves in strongly stratified near surface waters low frequency inertial internal motions are horizontal but here they attain a vertical current amplitude sometimes comparable to horizontal currents this results in occasionally very large internal wave amplitudes 250 m peak trough which are generated via geostrophic adjustment presumably from local collapse of fronts citation van haren h and l gostiaux 2011 large internal waves advection in very weakly stratified deep mediterranean waters geophys res lett 38 l22603 doi 10 1029 2011gl049707

large scale spreading of deep waters in the western mediterranean sea by submesoscale coherent eddies abstract two large scale free drifting isobaric floats experiments sofargos marine science and technology programme phase 2 mast2 and mass transfer and ecosystem response mater mast3 undertaken in 1994 95 in the northwestern mediterranean sea and in 1997 98 in the algerian basin respectively have revealed for the first time that western mediterranean deep water newly formed by deep convection in the gulf of lion the so called medoc site can be advected several hundreds of kilometers away from the formation area by anticyclonic submesoscale coherent vortices scvs this behavior implies that scvs participate actively in the large scale thermohaline circulation and deep ventilation of the western mediterranean sea these scvs are characterized by small radius 5 km very low potential vorticity high aspect ratio 0 1 and extended lifetime 0 5 yr

calcite twin widths and intensities as metamorphic indicators in natural low temperature deformation of limestone abstract twins in naturally deformed coarse grained limestones of the northern subalpine chain france show a direct relationship of twin width and intensity number of twins per mm to the peak metamorphism under diagenetic and anchimetamorphic conditions the transition from dominant thin twinning to dominant thick twinning occurs between a mean vitrinite reflectance ro of 1 60 and 2 60 or temperatures of between 150 and 200 c below the transition temperature increasing strain is apparently accommodated by adding new twins and above the transition temperature increasing strain is accommodated by twin widening similar transitions from thin to thick twinning with increasing metamorphism are also present in the helvetic alps the prealps and the central appalachian valley and ridge province these data for naturally deformed limestones support the interpretation from experimental studies of a temperature effect on twin width and intensity and indicate that the twinning in the northern subalpine chain occurred at or near peak metamorphism

distribution and mechanisms of strain within rocks on the northwest ramp of pine mountain block southern appalachian foreland a field test of theory fractures faults stylolites and strain determined from an analysis of twinning in calcite in the mississippian newman limestone at the base of the pine mountain block show that deformation was accomplished primarily by a combination of bedding plane slip and layer parallel shortening poles to joints are either parallel to strike of the thrust sheet or are in the transport plane small slip surfaces with syntaxial calcite fibers lie either parallel to bedding or parallel to the strike of the pine mountain block and dip steeply movement along the former is in the direction of transport of the block whereas movement on the latter is approximately along strike tectonic stylolites are rare but appear to be controlled by subtle changes in lithology wackestones contain more stylolites than do packstones strains in calcite from closely spaced samples show the converse relationship they are highest in units without stylolites maximum shortening strain e 1 10 4 and lowest in units with stylolites or small faults e 1 2 0 the maximum principal shortening strain directions however are identical within the error and are parallel to both bedding and the transport direction a sequence of events in this portion of the pine mountain block is 1 layer parallel shortening producing tectonic stylolites and a strong preferred orientation of compression axes 2 development of fractures parallel to the strike of the block on the lower hinge of the ramp to accommodate stretching parallel to the transport direction these strike parallel fractures can also be interpreted as having occurred quite late 3 during 2 above and continuing the start of bedding plane slip marked by syntaxial calcite fibers which trend in the direction of transport and 4 complications such as shear parallel to the strike of the pine mountain fault as a result of motion of the entire block between bounding tear faults events 2 through 4 most likely overlapped in time these data suggest that the acquisition of dip of the rocks on the ramp was primarily accomplished by bedding plane slip on the slip surfaces which experienced a shear stress of

kinematic model of a continuous heart mountain allochthon two fundamentally different models describing the geometry kinematics and mechanism of emplacement of the allochthon of the heart mountain detachment have been advocated the traditional tectonic denudation model comprises catastrophic gravity sliding of numerous detached blocks with widespread subaerial exposure of the detachment by tectonic denudation in this view catastrophic volcanism covered the allochthonous blocks and the denuded detachment immediately after emplacement of the slide blocks the alternative continuous allochthon model comprises noncatastrophic gravity spreading of a continuous allochthon without tectonic denudation of the detachment in this view volcanism was noncatastrophic and predominantly coeval with rather than subsequent to faulting and volcanic rocks constitute a large volume of the allochthon recent field studies indicate that the continuous allochthon model is geometrically and kinematically in accord with field relationships analog models geometric models and relationships characterizing other detachment complexes whereas the tectonic denudation model is not similarly substantiated in particular the tectonic denudation model is disproven by field relationships which demonstrate that volcanic rocks once thought to postdate faulting were instead tectonically emplaced in addition theoretical studies indicate that emplacement of the allochthon envisioned in the continuous allochthon model is mechanically plausible whereas the catastrophic emplacement of detached blocks envisioned in the tectonic denudation model is mechanically implausible

a simulation based approach to forecasting the next great san francisco earthquake in 1906 the great san francisco earthquake and fire destroyed much of the city as we approach the 100 year anniversary of that event a critical concern is the hazard posed by another such earthquake in this article we examine the assumptions presently used to compute the probability of occurrence of these earthquakes we also present the results of a numerical simulation of interacting faults on the san andreas system called virtual california this simulation can be used to compute the times locations and magnitudes of simulated earthquakes on the san andreas fault in the vicinity of san francisco of particular importance are results for the statistical distribution of recurrence times between great earthquakes results that are difficult or impossible to obtain from a purely field based approach

deformation by overburden of a coarse quartzite conglomerate the conglomerate of the pass peak formation a coarse eocene basin edge deposit in western wyoming is crushed though not by tectonic forces each cobble is in point to point contact with up to 10 other cobbles within a poorly consolidated micaceous sand matrix crushing appears to be due to stress concentration at contact points three degrees of deformation have been defined 1 faint contact marks on the cobble surfaces where the surface polish has been destroyed and a rim of better lithified matrix formed randomly oriented and distributed fractures cutting a few grains within the cobble 2 throughgoing fractures often parallel to one another with intervening complex networks of minor fractures not necessarily starting or ending at a contact mark 3 reduction of grain size by crushing up to 60 around contact marks contact marks are enlarged and bundles of fractures form a complex network connecting these contact marks simple calculations show that the 700 m of overburden over the outcrops st

record breaking intervals detecting trends in the incidence of self similar earthquake sequences we introduce a method of resolving temporal incidence trends in earthquake sequences we have developed a catalog partitioning method based on canonical earthquake scaling relationships and have further developed a metric based on record breaking interval rbi statistics to resolve increasing and decreasing seismicity in time series of earthquakes we calculated the rbi metric over fixed length sequences of earthquake intervals and showed that the length of those sequences is related to the magnitude of the earthquake to which the method is sensitive longer sequences resolve large earthquakes shorter sequences resolve small magnitude events this sequence length effectively constitutes a local temporal catalog constraint and we show that spatial constraints can be defined from rupture length scaling we have applied the method to several high profile earthquakes and have shown that it consistently resolves aftershock sequences after a period of accelerating seismicity before the targeted mainshock the method also suggests a minimum detectable forecastable mainshock magnitude on the basis of the catalog s minimum completeness magnitude m rm c

strength characteristics of the r f and c slip systems in calcite abstract numerical modelling of crystallographic preferred orientation or texture development in plastically deformed materials requires specification of all potential slip and twinning systems and their relative strengths or critical resolved shear stresses crrs it is widely believed that the most important intracrystalline deformation systems in calcite are twinning on e 1 018 40 4 1 slip on r 10 1 4 2 021 and slip on f 1 012 2 2 01 the superscripted signs indicating slip sense it is these systems which have been used in modelling texture development in calcite polycrystals to date however modelling has been limited by insufficient and partly conflicting data on the relative strengths of the various slip and twinning systems in calcite deformation experiments on calcite single crystals performed by us in recent years taken together provide new data for a more complete and consistent quantification of the strength properties of the calcite glide systems in our experiments single crystals of calcite were compressed in both the 4041 and 2243 orientations at temperatures and constant strain rates in the range 300 800 c and 3 10 4 3 10 8 s 1 respectively the stress strain curves obtained mostly show two yield points slip line analysis shows that these yield points are related to the onset of macroscopically observable slip first on an r 2 021 system and then on an f 10 1 1 or c a system the latter two systems dominate at higher temperature 600 c at strain rate 3 10 5 s 1 and have not been taken into account in any texture modelling so far with increasing absolute temperature tabs calculated crss values c for the r f and c systems decrease in a manner which can be described by empirical power law functions of the type c a tabs b where b r 2 021 and f 10 1 1 systems the yield stresses for r 2 021 and f 10 1 1 slip were found to be rather insensitive to strain rate with conventional power law stress exponents 12 comparing the present results with previous data we conclude that two regimes of slip system activity exist namely a low temperature regime involving e twinning slip on r 2 021 and on f 2 2 01 positive direction not reported and a high temperature regime with r 2 021 f 10 1 1 and c a slip this slip system transition occurs at t 400 c at strain rate 10 4 10 5 s 1 and is expected to be associated with one or more texture transitions the results point to a clear need for renewed texture modelling of calcite polycrystals

regional shortening fabrics in eastern north america far field stress transmission from the appalachian ouachita orogenic belt paleozoic carbonates of cratonic eastern north america comprise the footwall of the appalachian ouachita fold and thrust belt and contain a layer parallel shortening lps fabric that is preserved by mechanically twinned calcite shortening directions are generally parallel to the appalachian ouachita thrust transport direction in carbonates of the thrust belt proper restored width 400 km and within carbonates up to 1700 km into the foreland giving a pre thrusting sedimentary prism 2100 km wide through which compressive orogenic stresses were transmitted the shortening strain magnitudes 6 and the inferred calcite twinning differential stress magnitudes 90 mpa decrease exponentially away from the orogenic front calcite twinning strain patterns in other adjacent tectonic provinces such as the grenville laramide keweenawan rift and newark basin are distinct from the twinning strains preserved in the cratonic paleozoic carbonates appalachian orogen far field stresses calcite microstructures

a synthetic seismicity model for southern california cycles probabilities and hazard the absence of a long historical catalog of observed seismicity with which to constrain earthquake recurrence behaviors is a fundamental stumbling block to earthquake prediction in california conceding that this limitation is not likely to relax in the foreseeable future alternative approaches must be sought to extend the catalog artificially in this article i evaluate the long term behaviors of earthquakes on a map like set of southern california faults through computer simulations that incorporate the physics of earthquake stress transfer and are constrained by excellent but restricted bodies of geological and seismological data i find that model seismicity fluctuates on both short decades and long centuries timescales but that it possesses a well defined mean and standard deviation seismicity fluctuations correlate across different magnitudes and the long term cycles of smaller events seem to lead cycles of larger events short period seismicity fluctuations do not exhibit this tendency and short term changes in low magnitude m5 seismicity are not likely to be an effective predictor of future large events at least for the region as a whole as do real faults the model faults produce characteristic and power law quakes in variable ratios with diverse periodic and nonperiodic behaviors generally larger events tend to occur quasi periodically and smaller ones tend to cluster however only for a few earthquake classes and certain locations is recurrence notably non poissonian an important use of synthetic seismicity is in the construction of earthquake hazard maps because it firmly grounds previously ad hoc assumptions regarding frequency magnitude distributions multiple segment failure statistics and rupture extents while satisfying a spectrum of geological constraints such as fault slip rate segment recurrence interval and slip per event with its depth of temporal and spatial coverage synthetic seismicity also provides a means to investigate the time dependence of seismic hazard because hazard likelihood is a concatenation of the recurrence statistics from many seismic sources in only about 40 50 of the regions near the major faults do sequences of 0 1 g or 0 2 g exceedances differ from poissonian

near field etas constraints and applications to seismic hazard assessment the epidemic type aftershock sequence etas statistical model of aftershock seismicity combines various earthquake scaling relations to produce synthetic earthquake catalogs or estimates of aftershock seismicity rates based on recent earthquake activity one challenge to etas based hazard assessment is the large number of free parameters involved in this paper we introduce an approach to constrain this parameter space from canonical scaling relations empirical observations and fundamental physics we show that etas parameters can be estimated as a function of an earthquake s magnitude m based on the finite temporal and spatial extents of the rupture area this approach facilitates fast etas based estimates of seismicity from large seed catalogs and it is particularly well suited to web based deployment and otherwise automated implementations it constitutes a significant improvement over contemporary etas by mitigating variability related to instrumentation and subjective catalog selection

variability of internal frontal bore breaking above opouawe bank methane seep area new zealand large internal wave breaking is observed exceeding a vertical array of 61 high resolution temperature sensors at 1 m intervals between 7 and 67 m above the bottom the array was moored for 5 days at 969 m of opouawe bank new zealand a known methane seep area as breaking internal waves dominate sediment resuspension above sloping topography in other ocean areas they are expected to also influence methane transport despite being visible in single beam echosounder data indications for turbulence due to rising gas bubbles are not found in the present 1 hz sampled temperature records likely the mooring was too far away from the very localized bubble release spot instead the temperature sensors show detailed internal wave turbulence transitions every tidal cycle a solibore a frontal turbulent bore with a train of trailing solitary waves changes shape and intensity these solibores are highly turbulent and they restratify the bottom boundary layer thereby maintaining efficient mixing details of different turbulent bore developments are discussed averaged over a few tidal cycles and over the sensors range mean vertical eddy diffusivity amounts to 3 1 10 3 m2 s 1 and mean turbulent kinetic energy dissipation to 1 6 0 7 10 7 w kg 1 with variations over 4 orders of magnitude such turbulence will affect the distribution of dissolved methane and other geochemical species in the lower 100 150 m above the bottom and their release from the bottom the above mean values are remarkably similar to those found at various other sites in the ne atlantic ocean

analysis of variscan dynamics early bending of the cantabria asturias arc northern spain calcite twinning analysis in the cantabria asturias arc caa of northern spain provides a basis for evaluating conditions of variscan stress and constrains the arc s structural evolution twinning typically occurs during earliest layer parallel shortening offering the ability to define early conditions of regional stress results from the somiedo correcilla region are of two kinds early maximum compressive stress oriented layer parallel and at high angles to bedding strike d1c1 and later twin producing compression oriented sub parallel to strike d2c1 when all d1 compressions are rotated into a uniform east west reference orientation a quite linear north south trending fold thrust belt results showing a slight deflection of the southern zone to the south southeast north south directed d2c1 compression was recorded prior to bending of the belt calcite twinning data elucidate earliest structural conditions that could not be obtained by other means whereas the kinematics of arc tightening during d2 is constrained by paleomagnetism a large and perhaps protracted d2c1 is suggested by our results as manifested by approximately 50 arc tightening prior to acquisition of paleomagnetic remagnetizations throughout the caa early east west compression d1c1 likely resulted from the ebro aquitaine massif docking to laurussia whereas the north directed collision of africa d2c1 produced clockwise bending in the northern zone radial folding in the hinge and rotation of thrusts in the southern zone fl 2000 elsevier science b v all rights reserved

deformation mechanisms in the southeastern ramp region of the pine mountain block tennessee a field and petrofabric study of the southwestern part of the pine mountain thrust sheet shows that most deformation features may be attributed to one of two processes the first layer parallel compression is responsible for a a layer parallel maximum shortening direction in the mechanically twinned fabric of the limestone and dolomite country rock b transport parallel extension fractures and joints c transport normal stylolite surfaces and d some small thrusts the second bending at thrust ramp hinges is responsible for a non bedding parallel maximum shortening directions in mechanically twinned calcite from fracture fillings b transport normal extension fractures and joints and c small normal faults possible explanations for the failure of calcite in the country rock to twin in response to bending at the ramp include both 1 an early imposed pre thrusting calcite twin strain hardening and 2 deformation of the country rock by competing mechanisms such as pressure solution small normal faults are parallel to the strike of the thrust sheet and seem to have evolved from strike parallel extension fractures in response to continued extension both small thrusts and stylolite surfaces are rare in outcrop there seems to be no major change in deformation of rocks which have traveled through different fractions of the total ramp length so long as the rocks have passed onto the ramp

observations with moored acoustic doppler current profilers in the convection regime in the golfe du lion abstract in the golfe du lion south of france favorable conditions for deep winter convection exist and were documented by the medoc experiments during 1969 75 a renewed investigation of that regime with upward looking moored acoustic doppler current profilers adcps was carried out during 24 january 5 march 1987 to record the three dimensional currents associated with the deep mixing while in the earlier studies initial deep convection did not begin until fairly late in the winter season a very strong mistral around 10 january 1987 had already generated a 1arge deep mixed patch homogeneous down to around 2000 m at deployment time three adcps two working at 150 khz and one at 75 khz were moored in a triangle of 15 km sidelength at 550 780 m depth full records at 1 hour ensemble time intervals 400 pings per ensemble 8 m bin lengths were obtained by the 75 khz and one of the 150 khz adcps in mid february a second mistral hit the region with the onset of strong winds and surface cooling the

paleostress in cratonic north america implications for deformation of continental interiors compressive paleostresses as recorded by twinned calcite in carbonate rocks that cover cratonic northwestern north america are perpendicular to the orogenic front of the late cretaceous to early cenozoic sevier fold thrust belt inferred differential stresses decrease from 100 megapascals mpa at the orogenic front to 20 mpa up to 2000 kilometers inland new analyses near the late paleozoic appalachian front refine earlier results from the eastern midcontinent the appalachian and sevier stress data in north america9s continental interior are remarkably similar in spite of distinctly different tectonic properties this suggests that continental interior stresses are largely insensitive to tectonic characteristics of compressive plate margins and that far field stress transmission is filtered by deformation styles in mountain belts

catastrophic emplacement of the heart mountain block slide wyoming and montana usa the mechanism that allowed many tens of km of movement of the enormous block slide floored by the rootless heart mountain detachment fault in nw wyoming has long been a puzzle carbonat rich microbreccia that is widespread along the fault and in dikes in the upper plate contains accreted grains indistinguishable from those observed as fallout from volcanic eruption clouds accretionary lapilli and impact ejecta clouds and in intrusive diatremes in these settings and also in industrial processing accreted grains form when particles in a turbulent gaseous suspension containing limited water adhere to a nucleating grain or to each other elongate grains in thick microbreccia have strong but diverse shap preferred orientations unlike those reported from other fault rocks but instead suggestive of turbulent flow and the microbreccia contains layering and other features of sedimentary character that appear to record deposition from suspension rather than frictional processes along a fault we suggest that frictional heating led to dissociation of carbonate rock along the fault producing supercritical co 2 as the suspending medium high co 2 pressure drastically reduced friction along the fault and allowed continuation of catastrophic movement probably initiated by a volcanic or phreatomagmatic explosion resulting in very large displacement on a low dipping surface earlier slower sliding may have occurred but final emplacement was rapid minutes and spectacular

the case for tectonic denudation by the heart mountain fault a response two basic concepts pertaining to the history of the heart mountain fault of northwestern wyoming have recently been challenged one that there was tectonic denudation and two that volcanic rock of the wapiti formation was deposited on the exposed fault surface tectonic denudation is believed to have occurred as a consequence of the upper plate having broken into numerous blocks that separated as movement progressed along a nearly horizontal fault surface thus leaving the fault surface exposed between blocks volcanic rocks of the wapiti formation were then deposited both on the exposed fault surface and against and over the upper plate blocks two formations of eocene volcanic rocks are involved the older volcanic unit the cathedral cliffs formation and the paleozoic carbonate rocks are part of the upper plate of the heart mountain fault and moved with it whereas the younger wapiti formation was deposited on the fault surface after movement had ceased in an alternate interpretation recently advanced by t a hauge subdivisions of the absaroka volcanic supergroup of which the cathedral cliffs and wapiti formations are units are not recognized the upper plate of the heart mountain detachment is interpreted as having been a single continuous allochthon composed largely of volcanic rocks with small amounts of paleozoic rocks during heart mountain faulting extension of the once continuous slab of paleozoic sedimentary rock is alleged to have been accompanied by the formation of ten or more grabens now filled predominantly by absaroka volcanic rocks this interpretation further proposes that the volcanic rocks were emplaced while the separating blocks of paleozoic strata were still moving and that the basal part of the volcanic rock between these blocks is in fault contact rather than depositional contact with the strata beneath the heart mountain fault many lines of geologic field evidence indicate that the wapiti formation is younger than the heart mountain fault and was deposited on the technically denuded fault surface 1 wapiti rocks bury the break away fault 2 fault breccia at the base of the upper plate carbonate blocks is composed entirely of carbonate fault breccia and has no volcanic component 3 small blocks of upper plate rocks have been displaced by gravity from the upper part of the allochthon to the detachment fault surface 4 eocene stream channel deposits locally cut into the surface of tectonic denudation and also have been displaced on the heart mountain fault 5 the volume of wapiti formation filling the spaces between allochthonous blocks in proportion to the volume of those blocks is much too great for the wapiti to have been allochthonous 6 clastic dikes of carbonate fault breccia penetrate wapiti volcanic rocks 7 some of these clastic dikes of fault breccia contain precambrian xenoliths and wood phenoclasts requiring surface exposures of the fault breccia before injection as dikes 8 wapiti volcanic rocks having chilled borders are in tightly bonded contact with upper plate paleozoic rocks 9 faults present in the upper plate blocks do not penetrate the overlying wapiti formation 10 volcanic fault breccia is absent where volcanic rocks overlie carbonate fault breccia 11 a mound of carbonate fault breccia is not mixed with overlying wapiti formation the continuous allochthon interpretation is based on several erroneous assumptions that cannot be supported by field observations 1 faults to transport and emplace the wapiti formation onto and along the heart mountain fault do not exist 2 the contact between volcanic rocks and the allochthon west of corral creek at the west end of cathedral cliffs cited by hauge as a fault in an extending allochthon is a depositional contact 3 the volcanic rock adjoining allochthonous paleozoic rocks north of pilot creek cannot be part of an extending allochthon because a it is cathedral cliffs formation which is pre heart mountain fault and b its direction of movement is horizontal rather than down dip as required in an extending allochthon 4 most of the igneous dikes were intruded after the heart mountain fault movement ceased and so they could not accommodate significant extension of the upper plate 5 striae reported as indicating fault emplacement of volcanic rock wapiti formation on the heart mountain fault actually lire flow features formed as the wapiti formation was deposited on the exposed fault surface tectonic denudation is the only model that is consistent with evidence observable in the field although the process by which tectonic denudation was accomplished remains enigmatic tectonic denudation remains a constraining fact in any model for the origin of the heart mountain fault

strain variations across the proterozoic penokean orogen usa and canada abstract strata in the huron 2 5 2 0 ga and animikie 2 2 1 85 ga basins were deposited on the southern margin of the archean superior province these rocks were deformed during the penokean orogeny 1850 ma followed by subsequent accretionary orogens to the south at 1750 ma yavapai and 1630 ma mazatzal strain patterns are unique to each orogenic belt with no far field effect archean wawa terrane rocks in the penokean foreland preserve deformation associated with archean accretion with no younger penokean yavapai or mazatzal strain overprint the penokean orogeny deformed huron animikie basin sediments into a north vergent fold and thrust belt with no yavapai or mazatzal strain overprint yavapai orogen strains sw ne margin parallel shortening are unique when compared to the younger mazatzal shortening n20 w shortening with no strain overprint penokean deformation is characterized by shortening from the south including uplifted archean gneisses and a northerly thin skinned fold and thrust belt with north vergent nappes and a gently dipping foreland our study of finite and calcite twinning strains n 60 along 1500 km and across 200 km the penokean belt indicate that this orogeny was collisional as layer parallel shortening axes are parallel across the belt or parallel to the tectonic transport direction n s penokean nappe burial near the margin resulted in vertical shortening strain overprints some of which are layer normal the sudbury impact layer 1850 ma is found across the animikie basin and provides a widespread deformation marker with many local unique strain observations we also report new geochronology u pb zircon and apatite for the gneiss mafic dike rocks at wissota chippewa falls wi and arbutus black river falls wi dams respectively which bears on penokean yavapai deformation in the archean marshfield terrane which was accreted during the penokean orogen pseudotachylite formation was common in the superior province archean basement rocks especially along terrane boundaries reactivated by contemporaneous penokean trans hudson cape smith and new quebec deformation in the hinterland south the younger yavapai orogen 1750 ma n 8 deformation is preserved as margin parallel horizontal shortening sw ne in yavapai crust and up to 200 km to the north in the penokean thrust belt as a strain and barrovian metamorphic overprint mazatzal deformation 1630 ma n 16 is preserved in quartzites on yavapai and penokean crust with layer parallel and layer normal shortening strains oriented n20 w

fluids and the heart mountain fault revisited stable isotopic results from the heart mountain fault in northwestern wyoming show that fluids migrated along the detachment during faulting we report herein calcite 18 o and 13 c values in fault breccias shifted by as much as 15 o relative to smow and 5 o relative to pdb respectively which demonstrate focusing of meteoric waters along the detachment the isotopic depletions systematically increase toward the northwestern margin of the fault terrane where absaroka intrusive centers may have provided a source region for hydrothermal fluids in addition isotopic disequilibrium between vein and wallrock samples and enhanced 18 o and 13 c depletions in lower plate calcite veins suggest that the fluids were externally derived and migrated upward to the detachment we advocate a model in which heart mountain faulting and syntectonic fluid flow occurred beneath a continuous allochthon

a geometric frequency magnitude scaling transition measuring b 1 5 for large earthquakes abstract we identify two distinct scaling regimes in the frequency magnitude distribution of global earthquakes specifically we measure the scaling exponent b 1 0 for small earthquakes with 5 5 m b 1 5 for large earthquakes with 7 6 m m t 7 6 can be explained by geometric constraints on the rupture in conjunction with supporting literature this corroborates theories in favor of fully self similar and magnitude independent earthquake physics we also show that the scaling behavior and abrupt transition between the scaling regimes imply that earthquake ruptures have compact shapes and smooth rupture fronts

magnitude frequency relation for small earthquakes a clue to the origin of ƒmax of large earthquakes in order to test the hyothesis that the max of large earthquakes is due to the source effect and is causally related to the corner frequency of small earthquakes when it becomes constant below magnitude about 3 we constructed the frequency magnitude relation for earthquakes with magnitude range from 1 3 to 4 recorded at a borehole seismograph station operated by the university of southern california at baldwin hills in the middle of the newport inglewood fault a procedure was developed for an accurate estimation of moment magnitude from the measurement of coda amplitude as a function of lapse time the cumulative number of earthquakes per unit time period and area was estimated by finding the detection limit for ts p for each magnitude we found a clear depature of the observed log frequency magnitude relation for m 3 the observed frequency of earthquakes with m 0 5 is almost 10 times less than that expected from the extrapolation of empirical relation for earthquakes with magnitudes larger than 3 we conclude that the observed frequency magnitude relation departs from self similarity for earthquakes with magnitude smaller than about 3 this departure coincides with the widely observed departure of the moment corner frequency relation from self similarity these observations are consistent with the interpretation of max of large earthquakes in terms of the slip weakening instability model in which the critical slip may be a few tenths of a meter to a few meters and the cohesive zone size may be a few hundred meters to a few kilometers

idealized models of slantwise convection in a baroclinic flow intermediate or deep convection in a baroclinic flow occurs along slanted paths parallel to the alongflow absolute momentum surfaces these surfaces are principally tilted due to the vertical shear in velocity but can be further modified by a nonvertical axis of rotation an inviscid lagrangian parcel model using realistic parameters is utilized to illustrate qualitatively the different scenarios resulting from the combined action of inertial and gravitational forces acting on sinking parcels of dense fluid more quantitative results are derived from a series of numerical experiments using a zonally invariant high resolution nonhydrostatic model convection occuring in a flow with tilted absolute momentum surfaces will mix properties along these slanted surfaces this implies that the fluid can retain a weak vertical stratification while overturning and also more importantly that the evolution of the convective layer cannot be described in terms of one dimensional vertical mixing the authors show for conditions typical of the labrador sea that the convective layer depth difference between that estimated by mixing vertically and one obtained allowing for slantwise mixing can be greater than 100 m slantwise convection reaches deeper because of the reduced stratification along the slanted paths an alternative slantwise mixing scheme based on the assumption of zero potential vorticity of the convected fluid is proposed

quantifying the seismicity on taiwan summary we quantify the seismicity on the island of taiwan using the frequency magnitude statistics of earthquakes since 1900 a break in gutenberg richter scaling for large earthquakes in global seismicity has been observed this break is also observed in our taiwan study the seismic data from the central weather bureau seismic network are in good agreement with the gutenberg richter relation taking b 1 when m 8 earthquake in the study region about every 25 yr however our analysis shows a lower frequency of occurrence of large earthquakes so that the expected frequency of m 8 earthquakes is about 200 yr the level of seismicity for smaller earthquakes on taiwan is about 12 times greater than in southern california and the possibility of a m 9 earthquake north or south of taiwan cannot be ruled out in light of the fukushima japan nuclear disaster we also discuss the implications of our study for the three operating nuclear power plants on the coast of taiwan

calcite e twins as markers of recent tectonics insights from quaternary karstic deposits from se spain abstract superficial pleistocene karstic coatings found in the boundary region between the iberian and betic chains spain are often offset by normal faults these travertines were sampled to investigate whether mechanical twins in calcite can develop at low paleodepths surprisingly twinned grains are very abundant in sparry grains which are found in the proximity of the fault planes mean twin densities 28 twins mm paleostress determinations based on the analysis of calcite e twinning yielded the same principal stress orientations as the fault population analysis i e a nw se extension tectonic regime therefore calcite e twin analysis is a useful method with which to establish the orientation of recent stress tensors calcite e twins develop under conditions of minimum overburden 300 m during fault slip the low differential stresses during the fault slip event suggest that the critical resolved shear stress on the twin plane must be lower than the expected mean value of 10 mpa or that local stresses experienced by rock in and near the fault zone exceed ambient stress conditions during fault slip

gravity spreading origin of the heart mountain allochthon northwestern wyoming field studies of the heart mountain detachment and overlying volcanic rocks reveal that autochthonous eocene volcanic rocks previously reported as postdating faulting are tectonically emplaced and in many places far traveled evidence of tectonic deformation of these volcanic rocks is documented in areas where volcanic rocks directly overlie the detachment as well as at structurally higher levels within the allochthon such evidence includes shearing brecciation and faulting of volcanic rocks and tilting and truncation of volcanic strata this widespread deformation casts doubt concerning earlier suggestions that volcanic rocks were deposited upon the detachment and upon numerous detached slide blocks after detachment faulting in light of these new data the upper plate of the heart mountain detachment is interpreted as having been a single continuous allochthon composed largely of volcanic rocks rather than as having consisted of numerous separate slide blocks as was previously envisioned crosscutting relationships between dikes and faults within the allochthon suggest that allochthon emplacement occurred coeval with volcanism and contrary to earlier suggestions need not have been catastrophic the mechanism of emplacement of the allochthon which once may have covered 3 400 km 2 is viewed in terms of gravity induced spreading on the flanks of an active volcanic field kinematic data indicate that transport of the allochthon was locally directed to the north northeast east and southeast generally away from active volcanoes as well as downslope toward the bighorn basin transport was accompanied by variably directed extension of the allochthon accommodated by normal oblique normal and strike slip faults tilting of fault bounded blocks within the allochthon and dike intrusion

timing of deformation in overthrust belt and foreland of idaho wyoming and utah a review of the timing and displacement evidence of the major structures of the western wyoming overthrust belt and foreland shows there is a progression in thrust displacement apparent duration of motion and palinspastic position of thrust traces from west to east those toward the west moved farther for an apparently longer period of time and are more widely spaced in their restored positions than those toward the east however average thrust velocities are all on the order of 0 5 0 5 cm yr 0 2 in yr foreland events are in part synchronous with thrust belt events and had an effect on them although dating precision varies widely on major normal faults present evidence does not contradict the generally held view that all normal faults postdate the youngest thrusting

determination of deviatoric stress tensors based on inversion of calcite twin data from experimentally deformed monophase samples preliminary results abstract following previous successful paleo stress determinations from numerically generated aggregates and naturally deformed samples preliminary results about stress reconstructions based on inversion of calcite twin data from experimentally deformed monophase samples are reported this new study carried out on samples of carrara marble and crinoidic limestone from eastern france provides a test of the validity of stress reconstructions using inverse methods which had not been properly calibrated before the percentages of correlated twins are discussed for each stress tesnor and the range of uncertainties on the determination of stress orientations and differential stress magnitudes is evaluated

palaeostress estimation using calcite twinning experimental calibration and application to nature abstract by means of high temperature deformation experiments on calcite rocks of different grain sizes we have established the relationships between differential stress and twinning incidence twin density and volume fraction and the way that these relationships depend on grain size both twinning incidence and volume fraction increase with grain size at a constant level of differential stress log twin density is proportional to stress but is independent of grain size at a given grain size volume fraction of twinning increases non linearly with differential stress twinning activity measured by twinning incidence increases linearly with stress the behaviour of each of these parameters is independent of temperature strain and strain rate these relationships can be used as a basis for the estimation of palaeostress values in naturally deformed calcite rocks this is illustrated by a study of twinning activity in limestones close to thrust faults in the cantabrian zone of the variscan orogenic belt in northwestern spain high peak differential stresses were measured ranging from 150 to 250 mpa using the turner dynamic analysis technique however it is clear that shear stresses resolved parallel to the fault planes were very low the attainment of high stress differences when the resistance to faulting was low is attributed either to bending forces induced during the motion of the non planar surfaces relative to each other or to the stress peak being attained prior to the localization of deformation onto the fault surfaces

laboratory experiments with tilted convective plumes on a centrifuge a finite angle between the buoyancy force and the axis of rotation author posting cambridge university press 2004 this article is posted here by permission of cambridge university press for personal use not for redistribution the definitive version was published in journal of fluid mechanics 506 2004 217 244 doi 10 1017 s0022112004008572

hydrography of the labrador sea during active convection the hydrographic structure of the labrador sea during wintertime convection is described the cruise part of the deep convection experiment took place in february march 1997 amidst an extended period of strong forcing in an otherwise moderate winter because the water column was preconditioned by previous strong winters the limited forcing was enough to cause convection to approximately 1500 m the change in heat storage along a transbasin section relative to an occupation done the previous october gives an average heat loss that is consistent with calibrated national centers for environmental prediction surface heat fluxes over that time period 200 wm 22 deep overturning was observed both seaward of the western continental slope which was expected as well as within the western boundary current itself something that had not been directly observed previously these two geographical regions separated by roughly the 3000 m isobath produce separate water mass products the offshore water mass is the familiar cold fresh dense classical labrador sea water lsw the boundary current water mass is a somewhat warmer saltier lighter vintage of classical lsw though in the far field it would be difficult to distinguish these products the offshore product was formed within the cyclonic recirculating gyre measured by lavender et al in a region that is limited to the north most likely by an eddy flux of buoyant water from the eastern boundary current the velocity measurements taken during the cruise provide a transport estimate of the boundary current throughput and offshore recirculation finally the overall trends in stratification of the observed mixed layers are described

experimental test of the calcite strain gage technique at low confining pressure abstract a series of experiments were conducted on indiana limestone to test the applicability of calcite strain gage technique to deformations at low confining pressures experiments were conducted dry at 13 8 mpa 138 bars 2000 psi confining pressure these experiments indicate that both the least squares strain gage technique and the numerical dynamic analysis nda technique locate the principal strain axes to within 5 0 degrees strains calculated by the least squares strain gage technique are accurate at low strains less than 5 and increasingly inaccurate at higher strains at low strains the calculated strain reflects the maximum strain including elastic strain experienced by the core at higher strains the increasing inaccuracy of calculated strain was accompanied by increasing negative expected values in these experiments microcracking played a significant part in deformation and effected twinning in calcite and therefore the recorded strain

intrusive mixing in a mediterranean salt lens intrusion slopes and dynamical mechanisms abstract thermohaline intrusions found in meddy sharon were laterally coherent the slope of these intrusions across density surfaces was in opposite senses in the upper and lower part of the meddy consistent with i the mcintyre instability for prandtl number less than one in which case mass flux assumed equal in heat and salt diffusivity dominates over viscosity or ii double diffusive intrusions in which diffusive fluxes dominate in the upper diffusively unstable portion of the meddy and finger fluxes dominate in the lower fingering unstable part the magnitudes of the intrusion slopes are outside the range of angles for which the mcintyre mechanism can provide energy to the intrusive motions but within the range of angles for which double diffusive mixing can drive the intrusions thus the energy source for the intrusions is not the kinetic or potential energy of the geostrophic shear flow but is the potential energy associated with the lateral salinity and temperature gradients furthe

sevier laramide deformation of the continental interior from calcite twinning analysis west central north america abstract paleozoic mesozoic carbonates that cover cratonic western north america contain a regional layer parallel shortening lps fabric that is preserved by mechanically twinned calcite shortening directions are generally parallel to the sevier thrust transport direction e w in carbonates of the idaho wyoming portion of the thrust belt and within carbonates as far as 2000 km into the plate interior the inferred calcite twinning differential stress magnitudes generally decrease across the thrust belt and decrease exponentially away from the orogenic front into the craton synorogenic calcite cements and veins preserve a distinct twinning deformation history in the thrust belt twinning strains commonly record local out of transport piggyback strain events with high differential stresses

precision and accuracy of the calcite strain gage technique the twinned calcite strain gage technique allows the determination of strain magnitude and direction in mildly deformed sedimentary rocks in that the measurements required for the calculation are rather time consuming it is important to know the minimum number required to obtain a precision that is comparable with the accuracy of the result this paper documents a series of tests on three different limestones having different textures and porosities in order to determine the precision and accuracy of the technique as a function of the number of measurements and the number of perpendicular thin sections the tests show that for most purposes the best measurement strategy will be to make 25 measurements on each of two perpendicular thin sections the best determined principal strain axis is the one having a magnitude that is opposite in sign from the other two over the range of zero to 11 shortening the magnitude of the odd signed strain axis will than have a precision and accuracy of about 11 in magnitude and a precision and accuracy of about 6 to 8 in orientation differences in texture and porosity do not appear to have significant effects upon precision and accuracy

apatite fission track evidence for laramide and post laramide uplift and anomalous thermal regime at the beartooth overthrust montana wyoming the crystalline rocks of the beartooth overthrust in southwest montana and northwest wyoming were uplifted and thrust over the northwest margin of the bighorn basin during the laramide orogeny the timing and geometry of that event is well documented in the synorogenic paleocene and early eocene sedimentary rocks that were deposited ahead of the rising beartooth basement block and partially over ridden as the block advanced the absence of post laramide sedimentary rocks on the block and in the adjacent bighorn basin has however precluded the reconstruction of the post orogenic tectonothermal history of this region we report here the results of fission track analysis of apatite from the three components of the beartooth over thrust with the aim of reconstructing the laramide and post laramide tectono thermal history of the southeast margin of the beartooth mountains apatite fission track ages and corresponding horizontal confined track length distributions hctlds from precambrian basement rocks constituting the upper plate of the beartooth overthrust indicate that from 7 to 12 km of uplift of the red lodge corner of the beartooth block has occurred since early paleocene time this amount of uplift occurred in two stages with an intervening mid tertiary period of tectonic quiescence the latter was a period of either 1 oligocene and or miocene deposition or 2 tectonic quiescence uplift of 4 to 8 km occurred during the first phase of cooling which lasted from early paleocene time 61 ma to early eocene time 52 ma during the second phase which began in late miocene early pliocene time and continues to the present day about 4 km of uplift occurred our fission track data suggest that the thermal regime in rocks above the beartooth overthrust was relatively stable during tertiary time the maximum geothermal gradient permitted by model thermal histories generated from our observed fission track data during post laramide time is 17 c km this value is the same as that of the present day geothermal gradient measured in the amoco beartooth well and suggests that a low geothermal gradient prevailed throughout tertiary time apatite fission track ages and hctlds from jurassic and cretaceous sedimentary rocks beneath the beartooth overthrust indicate that these rocks have remained 10 20 c cooler than overlying rocks in the shear zone and the lowermost part of the upper plate since 61 ma an observation that is not consistent with the stratigraphic position of these rocks we interpret this temperature to be the result of a persistent thermal regime in which ground water circulating through the sedimentary rocks of the lower plate cooled them and insulated them from conductive heat transfer from hotter overlying rocks this ground water circulation may have been responsible for flushing hydrocarbons out of the rock column explored by the beartooth well shear zone rocks experienced a higher temperature during cenozoic time than did rocks of the upper and lower plates this condition was maintained by flow through the shear zone of ground water heated to higher temperatures at deeper levels along the thrust

anisotropy of magnetic susceptibility ams analysis of basalt dikes at cathedral cliffs wy implications for heart mountain faulting abstract mafic dikes pervade the upper plate of the heart mountain detachment hmd yet the dike concentration in the lower plate is sparse previous workers interpreted that these dikes were emplaced either coeval with or subsequent to the emplacement of the upper plate the magnetic fabrics of 32 mafic dikes at cathedral cliffs were analyzed using low field anisotropy of magnetic susceptibility ams as a proxy for flow these dikes intrude ordovician mississippian carbonate and overlying eocene volcanic rocks and are truncated along the nearly horizontal hmd the dikes trend between n10 w and n20 e are all steeply dipping and range in width between 0 5 and 3 m flow directions for the dikes were determined by the bearing and plunge of the kmax maximum principal susceptibility axes relative to the dike orientation about 66 of the dikes sampled show typical dike ams patterns with kmax and kint in the plane of the dike and kmin normal to the dike plane about 66 of the dikes sampled have kmax inclinations 45 and thus were emplaced upward 16 of the dikes have kmax inclinations of

the chronology of early mesozoic arc magmatism in the yerington district of western nevada and its regional implications the yerington district west central nevada is underlain by arc volcanic sedimentary and plutonic rocks ranging in age from middle triassic to middle jurassic twenty three u pb radiometric dates from eight igneous units have been determined for zircon from both plutonic and volcanic rocks in the district which establish two distinct periods of voluminous intermediate to silicic high k calc alkaline magmatism the earlier period is constrained by zircon dates of 232 and 233 ma on a quartz porphyry and a metadiorite respectively which intrude and are possibly comagmatic with andesitic to rhyolitic volcanic rocks the second period of arc magmatism is constrained by 5 concordant zircon dates that define an approximately 4 m y period 169 165 ma in the middle jurassic during which as much as 4 km of volcanic and volcaniclastic strata accumulated and two major batholiths were emplaced middle jurassic magmatism began with eruption of the volcanics of artesia lake they were intruded by the probably comagmatic 250 km 2 yerington batholith which was differentiated emplaced and crystallized within approximately 1 m y 169 4 168 5 ma granite porphyry dikes 168 5 ma are the latest phase of the yerington batholith and are synchronous with porphyry and skarn copper mineralization disconformably overlying the artesia volcanics is a second volcanic suite consisting of as much as 2 km of latitic volcanics of fulstone spring 166 5 ma the volcanics of fulstone spring were subsequently intruded by quartz monzodiorite porphyry dikes 165 ma and the shamrock batholith 165 8 ma the triassic through lower jurassic stratigraphic column was contact metamorphosed and folded adjacent to and at least in part contemporaneously with emplacement of the yerington and shamrock batholiths 169 4 165 8 ma we interpret the early 232 233 ma period of magmatism to represent a minimum age for the establishment of a west facing triassic volcanic arc within west facing triassic volcanic arc within west central nevada following the permian triassic sonoma orogeny the timing of middle jurassic arc magmatism and deformation in the yerington district and surrounding regions is strikingly similar to the timing of magmatic and tectonic events documented in the klamath mountains region of northwestern california we suggest that the similar record of arc magmatism and deformation in these two regions is not fortuitous but reflects a common tectonic evolution within a single west facing arc constructed along the western edge of north america

changes in frequency size relationship from small to large earthquakes the constant b value observed in frequency magnitude distributions of earthquakes has been taken as an indication of self similarity at all magnitudes hence earthquake properties should scale uniformly in the same way from small to large earthquakes it has often been observed however that the seismic moment released in small earthquakes scales differently with rupture length than it does for large events1 2 where the crossover between small and large events is defined at a rupture dimension equal to the down dip width of the seismogenic zone a possible explanation for this contradiction is that frequency size distributions are biased by small earthquakes small events dominate most global earthquake catalogues because of the short time period covered another source of bias in size distributions is the saturation of earthquake magnitudes for large events here we correct biases in calculations of b values and present evidence for a change in b value in frequency size distributions we find that a break in self similarity from small to large earthquakes occurs at a point where the dimension of the event equals the down dip width of the seismogenic layer

on moment length scaling of large strike slip earthquakes and the strength of faults 1 several large strike slip earthquakes have occurred in various tectonic settings in the past 5 years adding well documented data to the global collection of moment and length estimates for such earthquakes based on this augmented dataset we reexamine the controversial issue of scaling of seismic moment with length of rupture we find that the global dataset of large strike slip earthquakes follows a bi modal distribution most oceanic and or intraplate strike slip earthquakes have stress drops that are 5 times larger than interplate continental ones when distinguishing these two classes the scaling is compatible with that predicted by simple dislocation theory

the upper truncated power law applied to earthquake cumulative frequency magnitude distributions evidence for a time independent scaling parameter earthquake cumulative frequency magnitude cfm distributions are described by the gutenberg richter power law where the exponent is the b value although it has been reported that the b value changes before large earthquakes we find that an upper truncated power law applied to earthquake cfm distributions yields a time independent scaling parameter herein called the value we analyze earthquakes associated with subduction of the nazca plate beneath south america and find a region of isolated seismic activity at depths greater than 500 km between 20 s and 30 s for the entire record 1973 2000 the earthquake cfm distribution in this isolated region is well described by a gutenberg richter power law with b 0 58 the data set includes several large seismic events with m b 6 8 a power law applied to the cfm distributions for short time intervals between the large events yields b values greater than the b value for the entire record cfm distributions for the short time intervals are better described by an upper truncated power law than by a power law the value determined by applying an upper truncated power law to the short time intervals is equal to the b value obtained by applying the gutenberg richter power law to the entire record temporal changes in b value are due to temporal fluctuations in maximum magnitude analysis of four flinn engdahl regions two in subduction zones and two along spreading ridges demonstrates wider applicability of the results the value is an unchanging characteristic of the system that may be determined from a short term record manuscript received 2 july 2001

fast deep sinking in mediterranean eddies i large up to 0 03 m s 1 downward vertical water velocities w are observed using yearlong moored adcp at 2400 m in the deep mediterranean sea s algerian basin once every 2 3 months w rapidly increases to o 0 01 0 002 m s 1 before slowly decreasing during a few weeks in association with the passage of mesoscale eddies formed nearby these amplitudes of negative w are o 100 times larger than those commonly linked to mesoscale eddies near the surface subduction and o 10 times larger than settling velocities for marine snow our observations suggest that mesoscale eddies which are important for biological productivity near the surface can also convect nearly fresh material down to the bottom 3000 m there within a few days

slantwise convection a candidate for homogenization of deep newly formed dense waters 1 observations between 1000 and 2750 m from a site in the 2800 m deep part of the western basin of the mediterranean sea located in between the provencal and algerian subbasins indicate large variations in water mass properties and stability that are associated with but not directly caused by dense water formation to the north of the site these variations are apparently dominated by local convection induced by small scale eddies and propagation of inertial waves in stratified and homogeneous layers hereby is the horizontal component of coriolis parameter important governing slantwise tilted convective mixing this mixing creates marginally stable deep waters that are as spicy as near surface waters it is found across some 200 400 m thick layers which thickness is beyond the typical vertical buoyancy scale relevant for double diffusion the observed convection is hypothesized to be important for dense water formation away from near surface sources modifying the ocean s lower half

critical re evaluation of differential stress estimates from calcite twins in coarse grained limestone abstract comparison of two techniques to estimate differential stress magnitude based on calcite twinning reveals significantly different calculated values of differential stress for limestone experimentally and naturally deformed at low temperature this inequality may be due to fundamental differences between the rock type marble versus limestone and deformation temperatures above and below 200 c for samples used in technique calibration versus samples used in testing and application a technique that was empirically derived from marble experimentally deformed at 200 800 c yields values of differential stress that are factors of 2 to 9 times larger than maximum differential stress measured during experimental deformation of limestone at low temperature

structure timing and kinematics of the early eocene south fork slide northwest wyoming usa abstractthe south fork slide sfs is exposed over an area of 800 km2 in northwest wyoming and its evolution is connected in space and time to the adjacent and overlying 48 87 ma heart mountain slide hms the youngest rocks deformed as part of the sfs are the eocene willwood formation sands and mudstones which have a u pb detrital zircon youngest depositional age tuffzirc calculation of 51 80 1 04 1 08 ma as well as a spectrum of older zircons that were eroded from the sevier highlands to the west and the archean beartooth uplift to the north n 379 u pb zircon ages the sfs is overlain by allochthonous paleozoic carbonate and eocene volcanic rocks of the hms the sfs deformation involves shallowly plunging thin skinned folds that trend northeast southwest where the slip surface could have been the top of the jurassic gypsum springs formation detailed mapping reveals the absence of any cleavage or joints and a plethora of minor structures unreported in any thin skinned belt as well as the fac

frequency magnitude characteristics down to magnitude 4 4 for induced seismicity recorded at mponeng gold mine south africa this article aims to investigate the frequency magnitude characteristics and lower magnitude limits of the microseismic catalog recorded with a seismic network sensitive to high frequencies at mponeng mine south africa the network composed of one three component accelerometer and eight acoustic emission sensors is located at a depth of 3 5 km below the surface and covers the limited volume of approximately 300 300 300 m the three component accelerometer was used to estimate the moment magnitude for the limited number of 135 events m w ranged from 4 1 to 0 3 well recorded by the network we use the relation between the moment magnitude estimated from accelerometer data and radiated energy moment magnitude estimated from acoustic emission sensors to extend the catalog to lower magnitudes the magnitude of completeness of selected spatiotemporal subsets of the catalog was estimated for 1 an aftershock sequence of an m w 1 9 event that occurred approximately 30 m from the network and 2 postblasting activity during working days located more than 80 m from the network the data follow the gutenberg richter gr frequency magnitude relationship with no visible deviation from self similar behavior of seismicity between m w 4 4 and 1 9 for the aftershock sequence and between 3 5 and 1 5 for the postblasting dataset we estimated the magnitude of completeness of selected subset as low as 4 3 b 1 26 for the aftershock sequence and 3 4 b 1 17 for the postblasting activity differences in magnitude of completeness are attributed to location of recorded activity and site effects

calcite twins their geometry appearance and significance as stress strain markers and indicators of tectonic regime a review twin lamellae are a widespread feature in calcites of any type and origin twinning in calcite is an important intracrystalline deformation mechanism with low critical resolved shear stress and virtually no temperature dependence in contrast to most slip systems in rock forming minerals twinning therefore permits intracrystalline deformation at very low temperature and very little confining pressure twinning alone however cannot lead to large strains because only one independent slip system is effectively available twins lead to discontinuous shearing on the grain scale which gives rise to considerable strain incompatibilities at grain boundaries twinning consequently leads to strain hardening detailed observations of the geometry of twin lamellae show that incompatibilities at grain boundaries are eliminated by pressure solution on the grain scale at low temperature and dynamic recovery processes at higher temperatures twins are found in various tectonic environments and record very small strains in rocks deformed under very little cover different twinning strain and twinning stress methods and palaeopiezometers are critically reviewed all methods are limited to strains of less than 15 shortening or extension by twinning twinning nevertheless is an important although not directly measurable contribution to the total strain in highly strained calcite rocks at least up to middle greenschist facies under which conditions it is the most effective contributor to the formation of strong lattice preferred orientations in calcite tectonites the appearance of calcite twin lamellae changes systematically as a function of deformation temperature micro twins and straight narrow 1 5 m but fewer twins are developed above approximately 200 c curved twins twinned twins and completely twinned grains indicate the progressive importance of other slip systems and larger intracrystalline strains are possible at ca 250 c and above ancient straight twin lamellae are modified into irregular geometries by recrystallization and grain boundary migration the appearance of calcite twins is proposed as an approximate but rapid and easy to use geothermometer in low temperature environments

calcite twinning strain constraints on the emplacement rate and kinematic pattern of the upper plate of the heart mountain detachment two models that address the emplacement rate of the upper plate of the heart mountain detachment hmd have been advanced these are the catastrophic tectonic denudation model and the slow incremental continuous allochthon model we compared the two models by analyzing upper and lower plate rocks for a detachment related overprint of the older layer parallel laramide sevier calcite twinning strain fabric lower plate pilgrim limestone samples even those collected a few meters below the detachment show no evidence of a detachment related twinning strain overprint negative expected values nevs avg 8 3 of the laramide sevier layer parallel fabric the allochthonous upper plate carbonate rocks preserve the layer parallel laramide sevier shortening strain but the shortening axis e1 for each block occurs in different non ew and both subhorizontal and non subhorizontal orientations for the six upper plate blocks that preserve chaotic shortening axis orientations no evidence of any detachment related twinning strain overprint nevs avg 7 5 was found in the absence of any hmd related twinning overprint the upper plate allochthon motion must have been rapid enough to be accommodated by fracturing of upper plate rocks without additionally twinning any calcite we conclude that the emplacement of the upper plate of the hmd was not accompanied by an overprint of the laramide sevier twinning fabric and that models that require catastrophic rather than slow incremental emplacement rates are best supported by these data