climatology and interannual variability of north atlantic hurricane tracks the spatial and temporal variability of north atlantic hurricane tracks and its possible association with the annual hurricane landfall frequency along the u s east coast are studied using principal component analysis pca of hurricane track density function htdf the results show that in addition to the well documented effects of the el nino southern oscillation enso and vertical wind shear vws north atlantic htdf is strongly modulated by the dipole mode dm of atlantic sea surface temperature sst as well as the north atlantic oscillation nao and arctic oscillation ao specifically it was found that atlantic sst dm is the only index that is associated with all top three empirical orthogonal function eof modes of the atlantic htdf enso and tropical atlantic vws are significantly correlated with the first and the third eof of the htdf over the north atlantic ocean the second eof of north atlantic htdf which represents the zonal gradient of north atlantic hurricane track density showed no significant correlation with enso or with tropical atlantic vws instead it is associated with the atlantic sst dm and extratropical processes including nao and ao since for a given hurricane season the preferred hurricane track pattern together with the overall basinwide hurricane activity collectively determines the hurricane landfall frequency the results provide a foundation for the construction of a statistical model that projects the annual number of hurricanes striking the eastern seaboard of the united states

causes of enhanced sst variability over the equatorial atlantic and its relationship to the atlantic zonal mode in cmip5 abstracta spurious band of enhanced sea surface temperature sst variance sbev is identified over the northern equatorial atlantic in the geophysical fluid dynamics laboratory gfdl climate model version 2 1 the sbev is especially pronounced in boreal spring owing to the combined effect of both anomalous atmospheric thermal forcing and oceanic vertical upwelling the sbev is a common bias in phase 5 of the coupled model intercomparison project cmip5 found in 14 out of 23 models the sbev in cmip5 is associated with the atmospheric thermal forcing and the oceanic vertical upwelling similar to gfdl cm2 1 while the tropical north atlantic variability is only weakly correlated with the atlantic zonal mode azm in observations the sbev in cmip5 produces conditions that drive and intensify the azm variability via triggering the bjerknes feedback this partially explains why azm is strong in some cmip5 models even though the equatorial cold tongue and easterly trades are biased low

geology and petrogenesis of the edgecumbe volcanic field se alaska the interaction of basalt and sialic crust the edgecumbe volcanic field is a holocene volcanic province located on kruzof island se alaska exposed within the 260 km2 field are basalt andesitic basalt andesite dacite and rhyodacite the rhyodacites were erupted after the basalts and before the andesites the volcanics which are al rich 14 18 wt and lack an iron enrichment trend range from tholeiites 47 wt sio2 through rhyodacites 72 but a compositional gap of approximately 9 wt separates the dacites and rhyodacites initial 87sr 86sr ranges from 0 70297 in the basalts to 0 70440 in a pyroxene andesite 18o increases across the suite 5 8 to 7 9 plagioclase an32 86 is the dominant phenocryst in all but one lava olivine fo58 86 occurs in the basic lavas 53 wt sio2 but is replaced by orthopyroxene en43 73 and clinopyroxene en31wo41 en48wo40 in the more siliceous volcanics in the basalts and rhyodacites plagioclase is weakly zoned but extreme zoning 30 mole an is characteristic of phenocrysts in the intermediate lavas fractionation of the observed phenocryst assemblages could not have produced the more silicous volcanics instead they were generated by partial melting of intrusive basement 87sr 86sr 0 70487 18o 8 7 9 3 by basaltic magma and subsequent assimilation mass balance calculations show the rhyodacites are almost pure partial melt 5 basaltic component whereas the intermediate lavas contain between 30 and 60 partial melt

simple climatic indices for the tropical atlantic ocean and some applications two indices related to the sea surface temperature sst variability in the tropical atlantic are proposed one index describes the sst averaged over the whole basin 30 n to 20 s 60 w to 15 e and the other illustrates a meridional dipole between the northern and southern hemispheres the computational method for obtaining these indices is intentionally kept simple the objective being to reproduce the signature of the main results previously provided from more complicated statistical analyses monthly time series for both indices are produced from 1964 up to the present time the whole basin index exhibits principally a sustained warming which has intensified since about 1975 and it has a significant periodicity close to that of the quasi biennial oscillation the dipole index exhibits a decadal scale variation and its building up seems to be related to other worldwide climatic changes as for instance el nino southern oscillation extreme episodes rainfall variabilities over the brazilian nordeste and african sahel

a diagnostic study of pacific basin circulation regimes as determined from extratropical cyclone tracks abstract the interannual and intraseasonal track variability of cold season extratropical cyclones in the pacific basin is examined using an 8 year cyclone track dataset an eof technique incorporating varimax rotation in time is used to objectively describe the regime nature of the variations based upon this analysis we conclude that the cyclone behavior can be classified into six major regime types corresponding to the positive and negative amplitude excursions of each of the first three rotated eofs each of these rotated eofs explains approximately equal fractions of the total variance a study of the cyclone tracks for individual extreme periods confirms the existence of times where each of these patterns dominate the average 500 mb height fields for these extreme periods have been examined and are generally consistent with the cyclone track anomalies the resultant regime description shows strong interannual variability however there appears to be little obvious correlation with the enso signal

inversion of field data in fault tectonics to obtain the regional stress iii a new rapid direct inversion method by analytical means summary a new method for determining the reduced stress tensor with four degrees of freedom the orientations of the three principal stress axes as well as the ratio of principal stress differences using fault slip data or focal mechanisms of earthquakes is presented from a computational point of view the inversion of fault slip data is made in a direct way by purely analytical means as a result the determination process is extremely fast and adaptable on small microcomputers from a physical point of view the method aims at simultaneously i minimizing the angles between theoretical shear stress and actual slip vector and ii having relative magnitudes of shear stress large enough to induce slip despite rock cohesion and friction examples of application to actual fault slip data sets with good or poor variety of fault slip orientations are shown the double significance of the basic criterion adopted results in a more realistic solution of the inverse problem than the single minimization of the shear stria angle

the thrace basin in the rhodope province of ne greece a tertiary supradetachment basin and its geodynamic implications abstract detailed tectonic analysis and geological mapping on the tertiary molassic and volcanosedimentary rocks of the thrace basin in northeastern greece allowed us to reconstruct the structural evolution of the basin and its geotectonic setting as well as the orientation of the regional paleostress field sedimentation was linked with a calc alkaline and locally shoshonitic magmatism associated with the tertiary syn to late orogenic extension in the rhodope province we interpret the molassic tertiary greek part of the thrace basin as a supradetachment basin associated with sedimentary and volcanic infilling five 5 deformational events t1 to t5 have been distinguished during basin evolution from eocene to quaternary time t1 is related to a low angle normal detachment fault zone with a top to the sw to ssw sense of movement and initial basin subsidence during middle late eocene to oligocene time simultaneously with uplift and exhumation of the footwall rhodope metamorphic rocks stacking and crustal thickening in the more external parts of the hellenic orogenic belt have taken place during the same time t2 evolved during oligocene miocene time it was characterized by transpressional tectonics and formation of large strike slip faults and extensional fractures as well as conjugate thrust faults and folds with n nw or s se sense of movement during miocene pliocene time the third t3 event took place it was responsible for the high angle normal faults dismembering the eocene oligocene molassic basin into neogene grabens the t4 event affected the neogene sediments of the basin with minor reverse strike slip faults as well as normal faults the following t5 event is related to large normal active faults they coincided with the active tectonics of the study area defined by the earthquake focal mechanisms

determination of stress from slip data faults and folds a new technique is derived to invert slickenside data for the stress field that caused the faulting episode this inversion is simplified by the assumption that the magnitude of the tangential traction on the various fault planes at the time of rupture is similar study of three normal faulting regimes shows that the inversion derived with this assumption yields results that closely match older inversions that did not include the assumption hence the assumption may be valid and is shown to be justified by analyzing a simple fracture criterion application of slip data inversions is extended from faulting regimes to the slip on bedding plane faults in folding regimes comparison of the inversion results with the geometry of the folds shows this application to be successful greatly increasing the number of data sets that can be used to find the paleostress field

atlantic seasonal hurricane frequency part i el nino and 30 mb quasi biennial oscillation influences abstract this is the first of two papers on atlantic seasonal hurricane frequency in this paper seasonal hurricane frequency as related to e1 nino events during 1900 82 and to the equatorial quasi biennial oscillation qbo of stratospheric zonal wind from 1950 to 1982 is discussed it is shown that a substantial negative correlation is typically present between the seasonal number of hurricanes hurricane days and tropical storms and moderate or strong 15 cases el nin off the south american west coast a similar negative anomaly in hurricane activity occurs when equatorial winds at 30 mb are from an easterly direction and or are becoming more easterly with time during the hurricane season this association of atlantic hurricane activity with el nino can also be made with the southern oscillation index by contrast seasonal hurricane frequency is slightly above normal in non el nino years and substantially above normal when equatorial stratospheric winds blow from a westerly direction and or are bec

temporal variation of meandering intensity and domain wide lateral oscillations of the gulf stream the path of the gulf stream exhibits two modes of variability wavelike spatial meanders associated with instability processes and large scale lateral shifts of the path presumably due to atmospheric forcing the objectives of this study are to examine the temporal variation of the intensity of spatial meandering in the stream to characterize large scale lateral oscillations in the stream s path and to study the correlation between these two dynamically distinct modes of variability the data used for this analysis are path displacements of the gulf stream between 75 and 60 w obtained from avhrr derived advanced very high resolution radiometer infrared images for the period april 1982 through december 1989 meandering intensity measured by the spatial root mean square displacement of the stream path displays a 9 month dominant periodicity which is persistent through the study period the 9 month fluctuation in meandering intensity may be related to the interaction of rossby waves with the stream interannual variation of meandering intensity is also found to be significant with meandering being much more intense during 1985 than it was in 1987 annual variation however is weak and not well defined the spatially averaged position of the stream which reflects nonmeandering large scale lateral oscillations of the stream path is dominated by an annual cycle on average the mean position is farthest north in november and farthest south in april the first empirical orthogonal function mode of the space time path displacements represents lateral oscillations that are in phase over the entire study domain interannual oscillations are also observed and are found to be weaker than the annual oscillation the eigenvalue of the first mode indicates that about 21 5 of the total space time variability of the stream path can be attributed to domain wide lateral oscillations the correlation between meandering intensity and domain wide lateral oscillations is very weak

a document based 318 year record of tropical cyclones in the lesser antilles 1690 2007 the most comprehensive and longest document based time series of tropical cyclone activity for any area of the world is presented for the atlantic and caribbean region of the lesser antilles for the years 1690 2007 newspaper accounts ships logbooks meteorological journals and other document sources were used to create this new data set and a new methodology was applied for classifying historical tropical cyclone intensity this compilation estimates the position and intensity of each tropical cyclone that passes through the 61 5 w meridian from the coast of south america northward through 25 0 n the additional resources used here fills in gaps in the hurdat record which undercounts tropical storms and hurricanes by 28 7 in the years 1851 1898 1899 1930 over populated islands from 12 to 18 n the numbers of tropical cyclones show no trends that were significant at the 5 level the time span 1968 1977 was probably the most inactive period since the islands were settled in the 1620s and 1630s

inversion of field data in fault tectonics to obtain the regional stress i single phase fault populations a new method of computing the stress tensor summary we attempt a general definition of the inverse problem of computing the components of the regional stress tensor from a set of field data including the measurements of the strike and dip of several faults and the directions and senses of relative motion along these faults as indicated by slickenslides in previous treatments of this problem no experimental errors could be taken into account except those in measuring the pitch of slickenslides thus errors in the orientation of the fault strike and dip which have considerable practical importance were neglected in our work all experimental errors in the field measurements are taken into account so that the agreement between the computed stress tensor and the set of field measurements can be rigorously checked

from orientation to magnitudes in paleostress determinations using fault slip data abstract determinations of reduced stress tensors using fault slip data yield the orientation of principal stress axes and the ratio of the differences between principal stress magnitudes the use of rupture and friction laws allows determination of the two remaining unknowns that is the reconstruction of the complete stress tensor taking into account the depth of overburden brings an additional constraint the method is applied and discussed in the case of the hoover dam site western u s a where large data sets and rock mechanics information are available differences between intact sample and rock mass properties account for apparent disagreements between paleostress levels determined in similar tectonic environments pore pressure plays an important role where information about pore pressure is absent zero and hydrostatic pore pressure cases should be considered as limits

classification seasonality and persistence of low frequency atmospheric circulation patterns abstract orthogonally rotated principle component analysis rpca of northern hemisphere 1 month mean 700 mb heights is used to identify and describe the seasonality and persistence of the major modes of interannual variability the analysis is detailed and comprehensive in that 1 a high resolution approximately equal area 358 point grid is used for the virtually maximum possible 35 year period of record 2 a positive bias in the nmc data base in the early 1950s in the subtropics is largely eliminated for the first time and 3 homogeneous separate analyses of each month of the year are carried out detailing the mouth to month changes in the dominant circulation patterns winter results are similar to those of other recent rpca and teleconnection studies except that some less obvious patterns are identified and further detail of the better known patterns is provided two north south dipole patterns are found over the pacific ocean west pacific oscillation and east pacific pattern and over the atla

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

an inverse problem in microtectonics for the determination of stress tensors from fault striation analysis abstract a method is proposed to compute some characteristics of a possible stress tensor related to striations measured in a given faulted area if several tectonic phases are responsible for the striations the method separates and determines the successive stress tensors the iterative algorithm consists of alternatively a sorting the data attributed to a tectonic phase and b computing the characteristics of the stress tensor of this phase the method is tested using an application to synthetic and actual data

evolution of gravity driven rock slope failure and associated fracturing geological analysis and numerical modelling abstract an accurate analysis of fracture and cleavage anisotropies along two landslides in the argentera massif french southern alps was performed in order to relate the fracturing mode to the rock slope failure state the mature la clapiere landslide and the incipient isola landslide were investigated in both cases the gneissic rock schistosity was found sub horizontal in the vicinity of the landslides at shallow depths while it was sub vertical elsewhere at the massif s scale in addition to the well known regional tectonic fracture sets we identified in both cases a new family of vertical valley parallel vp fractures the vp fractures were only observed on the lower part of slopes affected by landslides where schistosity was found sub horizontal the vp fractures are clearly related to the decrease in schistosity dip and correspond to fold extrado like joints the proximity of the schistosity folds and the associated vp joints to the landslides suggests that they are gravity driven the presented 2 d finite difference models of the slope destabilisation in the la clapiere site shade light on possible mechanisms of the indicated gravity induced processes a progressive degradation of the material strength was imposed in these models to simulate the weathering effect which led to inelastic deformation damage at the lower part of slope this was followed by the formation of dense sub vertical deformation bands and then by the initiation of a landslide in the area corresponding to the actual position of the la clapiere landslide it is suggested that the gravity induced damage in the lower part of slope increases the permeability and thereby accelerates the weathering that causes a more rapid strength reduction the latter results in the tilting folding of pre existing fabrics and the related vp fracturing the la clapiere landslide is initiated in the upper part of this zone

decadal and interannual sst variability in the tropical atlantic ocean abstract the mechanisms regulating interannual and decadal variations of sea surface temperature sst in the tropical atlantic are examined observed variations of sea surface temperature are typically in the range of 0 3 0 5 c and are linked to fluctuations in rainfall on both the african and south american continents the authors use a numerical model to simulate the observed time series of sea surface temperature for the period 1960 1989 based on the results experiments are conducted to determine the relative importance of heat flux and momentum forcing two dominant timescales for variability of sst are identified a decadal timescale that is controlled by latent heat flux anomalies and is primarily responsible for sst anomalies off the equator and an equatorial mode with a timescale of 2 5 years that is dominated by dynamical processes the interhemispheric gradient of anomalous sst the sst dipole is primarily linked to the former process and thus results from the gradual strengthening and weak

reconstruction of monthly sst in the tropical pacific ocean during 1868 1993using adaptive climate basis functions abstract an eof based reconstruction of monthly sst anomaly fields is calculated for the years 1868 1993 in the tropical pacific ocean the eofs are computed from optimally interpolated sst anomaly fields from november 1981 to october 1995 from the same region these are used as a functional basis set for projecting sst anomalies from the comprehensive ocean atmosphere data set coads to produce a smooth spatially complete reconstruction the optimal number of eof modes for each month s reconstruction is chosen using large scale error analysis a modern subset of the coads sst is subsampled according to the distribution of observations in the historical month being reconstructed forming a testbed on which to evaluate the reconstruction based on a variable number of modes the test bed is least squares fit to the basis eofs the difference fields between the reconstruction and a smoothed version of the test bed is found the total variance of difference fields residual is minimized with respect to the

enso s impact on regional u s hurricane activity abstract regional variations in north atlantic hurricane landfall frequency along the u s coastline are examined in relation to the phase of el nino southern oscillation enso enso warm cold phases are known to reduce increase hurricane activity in the north atlantic basin as a whole using best track data from the u s national hurricane center regional analysis reveals that enso cold phase landfall frequencies are only slightly larger than neutral phase landfall frequencies along the florida and gulf coasts however for the east coast from georgia to maine a significant decrease in landfall frequency occurs during the neutral enso phase as compared to the cold phase along the east coast two or more major category 3 or above hurricanes never made landfall in the observational record 1900 2004 during a single hurricane season classified as an enso neutral or warm phase

climate modulation of north atlantic hurricane tracks the variability of north atlantic tropical storm and hurricane tracks and its relationship to climate variability is explored tracks from the north atlantic hurricane database for the period 1950 2007 are objectively separated into four groups using a cluster technique that has been previously applied to tropical cyclones in other ocean basins the four clusters form zonal and meridional separations of the tracks the meridional separation largely captures the separation between tropical and more baroclinic systems while the zonal separation segregates gulf of mexico and cape verde storms general climatologies of the seasonality intensity landfall probability and historical destructiveness of each cluster are documented and relationships between cluster membership and climate variability across a broad spectrum of time scales are identified composites with respect to cluster membership of sea surface temperature and other environmental fields show that regional and remote modes of climate variability modulate the cluster members in substantially

possible influence of western north pacific monsoon on tc activity in mid latitudes of east asia this study analyzed the correlation between tropical cyclone tc frequency and the western north pacific monsoon index wnpmi which have both been influential in east asia s mid latitude regions during the summer season over the past 37 years 1977 2013 a high positive correlation existed between these two variables which was not reduced even if el nino southern oscillation enso years were excluded to determine the cause of this positive correlation the highest positive wnpmi phase and lowest wnpmis negative wnpmi phase during a nine year period were selected to analyze the mean difference between them excluding enso years in the positive wnpmi phase tcs were mainly generated in the eastern seas of the tropical and subtropical western north pacific passing through the east china sea and moving northward toward korea and japan in the negative phase tcs were mainly generated in the western seas of the tropical and subtropical western north pacific passing through the south china sea and moving westward toward china s southern regions therefore tc intensity in the positive phase was stronger due to the acquisition of sufficient energy from the sea while moving a long distance up to east asia s mid latitude additionally tcs occurred more in the positive phase regarding the difference of the two phases between the 850 and 500 hpa streamlines anomalous cyclones were strengthened in the tropical and subtropical western north pacific whereas anomalous anticyclones were strengthened in east asia s mid latitude regions due to these two anomalous pressure systems anomalous southeasterlies developed in east asia s mid latitude regions which played a role in the anomalous steering flows that moved tcs into these regions furthermore due to the anomalous cyclones that developed in the tropical and subtropical western north pacific more tcs could be generated in the positive phase both the lower and upper tropospheric layers had warm anomalies in most regions of the western north pacific while relative humidity in the middle tropospheric layer showed a positive anomaly in the tropical and subtropical western north pacific which provided a better environment to strengthen tc intensity in the positive wnpmi phase furthermore a negative anomaly was manifested not only in the tropical and subtropical western north pacific but also in east asia s mid latitude regions with 200 850 hpa vertical wind shear while a warm sea surface temperature anomaly was shown in east asia s mid latitude seas which further strengthened tc intensity in the positive phase the analysis on the global scale atmospheric circulations showed that converged air in the lower layer of the subtropical western pacific during the positive phase diverged in the upper layer which moved westward and converged in the upper layer of the equatorial indian ocean and then diverged in its lower layer

controls on the stratigraphic framework and paleoenvironmental change within a holocene estuarine system pamlico sound north carolina usa abstract this study examines the holocene stratigraphic record and paleoenvironmental evolution of a large estuarine system at high temporal and spatial resolution in the context of changing climate sea level and hydrodynamics new data are used to examine two time periods of increased marine influence within pamlico sound in northeastern north carolina interpreted to be the result of extensive barrier island segmentation synchronous with periods of rapid climate change during the late holocene the study reveals the controls on the stratigraphic development and the highly dynamic character of the coastal system in response to climate and sea level change as it interacts with paleotopography these findings can be used to inform projections of future environmental changes estuarine waters occupied paleovalleys in the pamlico sound region as early as ca 7500 cal bp and pleistocene interfluves separated the paleovalleys from the atlantic ocean until ca 5500 cal bp when they were flooded by rising sealevel forming the broad shallow pamlico sound initial barrier islands and shoals likely formed sometime between 5500 and 5000 cal bp providing the geomorphic setting for continued estuarine conditions behind the barriers at ca 4000 cal bp an increase in marine influence and sand content is detected in multiple cores and is correlated to seismic data within the pamlico sound basin this change is interpreted to be the result of increased segmentation of barrier islands thus a greater number of inlets or wider inlets which is consistent with a rapid transgression seen in other areas of the u s east coast the segmentation may have been partially facilitated by a rapid increase in lagoonal area and tidal prism by overtopping of interfluves greater barrier island continuity is evident from 3500 to 1200 cal bp as indicated by muddy deposits with low brackish estuarine foraminiferal assemblages at ca 1200 cal bp seismic sedimentological and micropaleontological data suggest an increase in wave and current energy and marine influence throughout southeastern pamlico sound these changes are interpreted to represent extensive segmentation of the barrier islands during the medieval climate anomaly mca since ca 500 cal bp the pamlico sound system has returned to a more restricted state as inlets have closed currently only three major inlets segment the outer banks the barrier island system fronting pamlico sound but warming climate and increasing rates of sea level rise suggest that another episode of barrier island segmentation began about a half century ago and appears that it may extend into the near future

an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence the orientations of fault planes and slip directions indicated by a population of earthquake focal mechanisms can be used to determine best fit regional principal stress directions and r 2 1 3 1 a measure of relative stress magnitudes under the assumption of uniform stress in the source region this analysis allows for the possibility that failure occurs on preexisting zones of weakness of any orientation in the inversion we perform a grid search of stress models to find the one which requires the smallest total rotation of all the fault planes that is needed to match the observed and predicted slip directions the method allows for errors in orientations of both the fault planes and slip directions we have an objective means for identifying the more likely of the two possible fault planes from each focal mechanism relative to a given stress model thus we do not face the problem of ambiguity of nodal planes which plagues other analyses of this kind by using a grid search of stress models rather than a linearization scheme we are able to perform a realistic error analysis and thus establish confidence limits for the preferred regional stresses the method can be used to investigate possible stress inhomogeneities during earthquake sequences by analyzing subsets of the data population the technique has been applied to 76 events from the san fernando earthquake sequence for which we have found best fit stresses plunge and azimuth 1 7 187 2 27 281 3 62 84 and r 0 65 the average misfit between this stress model and all the data is about 8 and all but eight of the aftershocks have misfits of less than 20 these values are considerably less than the uncertainty of the focal mechanism determinations therefore significant stress inhomogeneities are not required by the data our analysis does not support the suggestion of a change in stresses during the aftershock sequence as proposed by others on the basis of an apparent change in focal mechanisms

determination of the tectonic stress tensor from slip along faults that obey the coulomb yield condition a new method to calculate the stress tensor associated with slip along a population of faults is derived here the method incorporates two constraints first the stresses in the slip direction satisfy the coulomb yield criterion and second the slip occurs in the direction of maximum shear stress along the fault the computations provide the complete stress tensor normalized by the vertical stress and evaluation of the mean coefficient of friction and the mean cohesion of the faults during the time of faulting the present method is applied to three field cases dixie valley nevada wadi neqarot israel and yuli microearthquakes taiwan it is shown that the coefficieet of friction of the three cases varies between 0 1 to 0 8 further it is demonstrated that previous stress inversion methods implicitly assume zero friction along the faults

late oligocene to pliocene extension in the maltese islands and implications for geodynamics of the pantelleria rift and pelagian platform

impact of the atlantic warm pool on united states landfalling hurricanes 1 the 2010 atlantic hurricane season was extremely active but no hurricanes made landfall in the united states raising a question of what dictated the hurricane track here we use observations from 1970 2010 also extending back to 1950 and numerical model experiments to show that the atlantic warm pool awp a large body of warm water comprised of the gulf of mexico the caribbean sea and the western tropical north atlantic plays an important role in the hurricane track an eastward expansion of the awp shifts the hurricane genesis location eastward decreasing the possibility for a hurricane to make landfall a large awp also induces barotropic stationary wave patterns that weaken the north atlantic subtropical high and produce the eastward steering flow anomalies along the eastern seaboard of the united states due to these two mechanisms hurricanes are steered toward the northeast without making landfall in the united states although the la nina event in the pacific may be associated with the increased number of atlantic hurricanes its relationship with landfalling activity has been offset in 2010 by the effect of the extremely large awp

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

inversion of field data in fault tectonics to obtain the regional stress ii using conjugate fault sets within heterogeneous families for computing palaeostress axes summary in a family of faults that have been neither reactivated nor reoriented each fault whose direction and sense of movement are known can be assigned p and t axes if the rocks are isotropic and the orientation of each fault is controlled only by the orientations of the active principal stress axes and the apparent angle of internal friction that controls the angle 2 between conjugate faults p and t are parallel to the maximum and minimum principal stress axes respectively in most cases however this relationship does not hold accurately defining probability density regions around p and t that take into account variations of fault geometry and using the mathematical process of convolution one can estimate the principal stress axes associated with any family of faults whether the family be homogeneous or heterogeneous the probability regions around p and t are in the form of gaussian functions the orientations of principal stress axes determined using different values for the constant c and reasonable values for and therefore are in good agreement with other numerical methods the only major requirement of the method is the presence of conjugate fault systems within the fault slip data set studied

late cenozoic tectonics and volcanism along the north anatolian fault new structural and geochemical data abstract different types of volcanic activity have developed along the north anatolian fault zone naf in turkey detailed analysis of satellite images and digital elevation models dems and field observations have been made in order to understand the tectonics and the distribution of volcanic vents in the anatolian block some faults are oblique to the naf and delimit extensional escape wedges vents rooted on open tension fractures show that emplacement of the volcanism is related to tensional fracturing of the anatolian continental block which we attribute to the onset of free borders in the south and west along the naf earliest extension 1 is directed s to ssw and the latest 2 towards w to wsw parallel to the sinistral slip along the naf major and trace element geochemical data indicate that the dominant calc alkaline rocks are associated with various alkaline lavas k ar ages of the volcanics range from 22 to 8 5 ma in galatia massif 900 to 100 ka in niksar and 3 to 12 ka in erzincan isotopic and trace element data are interpreted as reflecting a dominantly lithospheric mantle source slightly mixed with asthenospheric liquids most magmas were fractionated and contaminated by continental crust during their ascent 1 and 2 tectono volcanic events have propagated through time and space from west to east the 1 extension is late oligocene in the galatia massif late miocene in niksar and late pliocene in erzincan the 2 extension and strike slip event along the naf began in the late miocene in the galatia massif early pliocene in niksar and quaternary in erzincan signature from an asthenospheric source in the second event in the three regions suggests that an ancient suture zone galatia massif and or the lithospheric naf transform niksar and erzincan have served to channel small quantities of asthenospheric melts existing at the base of the lithosphere