earthquakes in northern europe in 1375 1989 abstract an updated version of the catalogue of earthquakes in northern europe is presented it comprises events inside a region window of about 55 80 n and 10 w 45 e covering a 615 year period from 1375 to 1989 the data have been compiled using all the available historical publications catalogues studies and reports of the region and for events from 1984 to 1989 a regional seismic parameter database maintained by the institute of seismology of the university of helsinki the number of events exceeds 5200 of which more than 40 have been registered since 1980 the huge increase of event reports is the result of the installation of new high frequency networks for microearthquake studies and the upgrade of the seismic instrumentation because of the different degree of accuracy and homogeneity of the parameter data the events were divided into historical 1375 1964 and instrumental 1965 1989 datasets the source parameters are mainly macroseismic for historical events and obtained by iterative location procedure for instrumental data by assuming internal homogeneity between the different regional magnitude scales we estimated the catalogue to be complete for events with magnitude 4 5 since the 1880 s magnitude 4 0 4 4 since the 1940 s and magnitude 3 5 3 9 since the 1970 s although the distribution of seismicity exhibits similar patterns in both datasets the clustering of epicenters and offshore seismicity is more distinct in the instrumental period the occurrence of the greatest events can be seen more clearly in the historical data the earthquake epicenters are concentrated in the geologically younger tectonic provinces in the western part of the region and follow with some exceptions the tectonic fracture and fault zones in the fennoscandian area 80 of the earthquakes occurred in the upper 20 km of the earth s crust the deepest epicenters are in the southwestern corner of the region where the crust is thinnest

tropopause inversion layer seasonal and latitudinal variations and representation in standard radiosonde data and global models 1 previous publications have given information on the seasonal and latitudinal variations of the tropopause inversion layer til as seen in high resolution radiosonde data sets when soundings are averaged using the tropopause as a reference level this paper presents a more quantitative analysis of the latitudinal and seasonal structure of the til than has been given previously to do this we define the region over which the static stability relaxes from its overshoot value at the tropopause to its local minimum in the stratosphere this region is seen to increase monotonically in thickness from about 1 km at low latitudes to about 4 to 5 km at high latitudes when the seasons are defined as winter djf spring mam summer jja and fall son the transition from tropical behavior occurs a little poleward of 20 n in both djf and mam and moves to a little poleward of 30 n in jja and son somewhat surprisingly it is also shown that almost identical information about the til can be derived from standard radiosonde data for our period of analysis because of their reporting of the tropopause and other significant levels but caution needs to be used in doing this since the number of reported significant levels has varied significantly over the long term and with some distinct discontinuities finally we discuss what sort of information on the til can be obtained from global models given their relatively coarse vertical resolution

observations and numerical modelling of mountain waves over the southern alps of new zealand a detailed case study of mountain waves observed over the south island of new zealand during the southern alps experiment is presented the purpose of the study is to document the waves generated over this region to explore the extent to which high resolution radiosonde data can be used to determine gravity wave parameters and to estimate the vertical flux of horizontal momentum produced by flow over the southern alps organized wave clouds were observed in a visible satellite image on 20 october 1996 and are thought to have been produced by partially trapped lee waves using background flow fields derived from a radiosonde sounding the theoretical horizontal wavelength of the partially trapped mode is calculated and agrees well with that measured from the satellite image a technique called the horizontal projection method is developed to analyse radiosonde soundings for mountain waves specifically the technique determines the dominant horizontal wavelength over the entire depth of a radiosonde sounding this method uses a coordinate transformation to take account of vertical changes in the background flow and hence vertical variations in the vertical wave number as well as changes in the path of the radiosonde this method is applied to a radiosonde sounding to identify the dominant wave mode and emphasizes that radiosonde soundings should not in general be treated as instantaneous vertical profiles when analysing mountain waves the mountain waves observed are simulated using a high resolution numerical model and the results are used to check the consistency of the analysis the numerical model produces a horizontally averaged value of momentum flux in the lower stratosphere of 0 02 n m 2 although this value is probably underestimated by at least a factor of four

earthquake hazard assessment in the north sea abstract the assessment of seismic hazard in regions such as the north sea where the activity rate is comparatively low requires the adoption of a methodology designed to maximize the use of available sources of information including historical and instrumental seismicity geology tectonics and local soil properties in a series of site specific studies of seismic hazard in the norwegian sector of the north sea a procedure has been developed which reduces uncertainties through emphasis on primary data thus the sizes and locations of felt extents have been reassessed from original historical documents the epicentres of early twentieth century events have been relocated using instrumental data and a correlation between felt areas and ms has been developed which allows magnitudes to be assigned to historical earthquakes recently recorded instrumental data have been used in delineating the finer details of the current seismicity patterns an essential part of the adopted methodology is a thorough geological study based on seismic reflection and other geophysical data with the main purpose to delineate possible active faults the computation of seismic hazard includes the modelling of tectonic regions as derived from a seismotectonic synthesis of both seismological and geological data as well as the modelling of individual active faults where also non planar geometries such as listricities are accounted for a reliable hazard assessment also requires much emphasis on strong motion attenuation models where new relationships now have been derived specifically applicable to north sea conditions a seismic hazard assessment finally requires a comprehensive analysis of uncertainties both because a total uncertainty estimate for the computed loads is needed and because it is essential to know the relative importance of the different sources of uncertainty for this purpose a method has been adopted based essentially on a bayesian analysis in combination with a monte carlo technique

sharpness of the extratropical tropopause in baroclinic life cycle experiments 1 the sharpness of the extratropical tropopause is investigated using baroclinic life cycle experiments in these simulations slow synoptic scale dynamics leads to a net tropopause sharpening the mechanism involves vertical convergence of the ageostrophic wind the results support earlier suggestions from idealized theoretical studies

transport and mixing in the extratropical tropopause region in a high vertical resolution gcm part ii relative importance of large scale and small scale dynamics abstract the relative roles of atmospheric motions on various scales from mesoscale to planetary scale in transport and mixing in the extratropical tropopause region are investigated using a high vertical resolution general circulation model gcm the gcm with a vertical resolution of about 300 m explicitly represents the propagation and breaking of gravity waves and the induced transport and mixing a downward control calculation shows that the eliassen palm e p flux of the gravity waves diverges and induces a mean equatorward flow in the extratropical tropopause region which differs from the mean poleward flow induced by the convergence of large scale e p fluxes the diffusion coefficients estimated from the eddy potential vorticity flux in tropopause based coordinates reveal that isentropic motions diffuse air between 20 k below and 10 k above the tropopause from late autumn to early spring while vertical mixing is strongly suppressed at around 10 15 k above the tropopause throughout the year t

gravity waves generated by convection during twp ice i inertia gravity waves gravity waves are analyzed in radiosonde soundings taken during the tropical warm pool international cloud experiment twp ice campaign the properties of the inertia gravity waves are analyzed in part i whereas part ii focuses on high frequency gravity waves two groups of inertia gravity waves are detected group l long vertical wavelength in the middle stratosphere during the suppressed monsoon period and group s short vertical wavelength in the lower stratosphere during the monsoon break period waves belonging to group l propagate to the southeast with a mean intrinsic period of 35 h and have vertical and horizontal wavelengths of about 5 6 km and 3000 6000 km respectively ray tracing calculations indicate that these waves originate from a deep convective region near indonesia waves belonging to group s propagate to the south southeast with an intrinsic period vertical wavelength and horizontal wavelength of about 45 h 2 km and 2000 4000 km respectively these waves appear to originate from convection in the vicinity of new guinea

earthquake frequency distribution and the mechanics of faulting the level of intraplate seismicity in japan generally shows a positive correlation with the density of quaternary faulting in southwest japan where intraplate seismicity is concentrated on land rates of seismic moment release m 0 are similar when calculated from either the 400 year historical record of seismicity or geologically determined slip rates of quaternary faults a data set of 18 earthquakes with seismic moments m0 ranging from 0 01 to 3 1027 dyn cm shows a relationship between rupture lengthl and m0 log m0 23 5 1 94 log l when seismic moment on each quaternary fault is assumed to occur in discrete events every t m0 m 0g years where m0 is estimated for a rupture extended over the entire fault length and m 0g is proportional to the slip rate of each quaternary fault the moment frequency distribution of earthquakes log n a b log m0 predicted from the geologic record is virtually identical to that seen with the 400 year record of seismicity in contrast if it is assumed that earthquakes on each fault occur according to the gutenberg richter relation we obtain poor agreement with the observed seismicity thus while regional seismicity satisfies the relation log n a b log m0 or equivalently log n a b log m where m is magnitude it appears that seismicity on individual faults does not this further implies that the primary factor that leads to the magnitude frequency distribution in regional seismicity studies is the relative distribution of the slip rates and lengths of preexisting faults

airborne observations of turbulence mixing and gravity waves in the tropopause region 1 in situ observations of small scale dynamics and compositional structure in the tropopause region are presented the measurements were made aboard the grob egrett high altitude research aircraft above aberystwyth wales in the summer of 2000 the observations presented here show evidence of mixing of ozone and water vapor in a patch of intense turbulence just above the tropopause this turbulence is shown to be the result of wind shear above a tropospheric jet stream the value of the vertical eddy diffusion coefficient in this turbulence is estimated to be 0 9 m2 s 1 it is also shown that wavelike perturbations superimposed on the overall tracer structure can be accounted for by a gravity wave

airborne measurements of gravity wave breaking at the tropopause 1 a breaking atmospheric gravity wave was investigated with a combination of airborne in situ dynamical measurements and ground based vhf radar observations the wave was generated by flow over mountains and it was observed to break near the tropopause the measurements reveal that the wave was overturning at the tropopause and that the initial breakdown into turbulence involved the generation of smaller oscillations with a horizontal wavelength of around 500 m there was also evidence that the turbulence associated with the wave breaking can cause substantial mixing in the tropopause region

static stability in the extratropical tropopause region abstract idealized axisymmetric anomalies of potential vorticity pv on a midlatitude f plane and their related response in terms of balanced wind and temperature are investigated with special focus on the static stability in the tropopause region the pv anomalies are specified such that they can be interpreted as the result of conservative advection in the tropopause region across the gradients of a prescribed background atmosphere with piecewise constant buoyancy frequency squared n2 related cyclones and anticyclones are treated identically except for the sign of the tropopause potential temperature anomaly composite profiles of n2 are computed for which the thermal tropopause is used as a common reference level and where the number of cyclones in the composite equals the number of anticyclones one obtains a pronounced peak of n2 just above the tropopause and slightly enhanced values below the tropopause in comparison with the background profile within the framework of pv inversion various mechan

the meloy earthquake sequence northern norway source parameters and their scaling relations the intraplate meloy earthquake sequence in northern norway began in november 1978 and lasted a few months during which time more than 10 000 tremors were recorded with magnitudes ml up to 3 2 three component field systems with flat velocity response in the range 5 to 80 hz were used for closein 10 km recordings of events in the magnitude range 0 4 to 2 2 through spectral analysis of s wave data we find that corner frequencies range from 30 to 16 hz with seismic moments m o between 1017 and 3 1019 dyne cm and a moment magnitude relationship of log m o 0 9 ml 17 5 source parameters have been computed for a simple circular source model giving stress drop values between 0 6 and 22 bars source radius between 84 and 45 m and average displacement between 0 1 and 4 1mm corner frequencies increase only very slowly with decreasing seismic moment and with the source model used this causes stress drop to decrease rapidly with decreasing moment while the source dimension decreases very slowly this is commonly observed for small inter and intraplate earthquakes it is hypothesized that for weak events the relationships between corner frequency and other source parameters as predicted by theory may not hold

radiosonde observations of partially trapped lee waves over tasmania australia a well defined family of lee waves over southern tasmania australia is analyzed using a routine radiosonde sounding released from hobart at 1100 utc june 18 1991 pronounced fluctuations in the ascent rate of the radiosonde are analyzed using a new technique called the horizontal projection method the dominant horizontal wavelength is found to be 8249 m an advanced very high resolution radiometer avhrr infrared satellite image at 1554 utc is used to check this calculation and gives a horizontal wavelength of 8 9 1 4 km the horizontal projection method takes account of the vertical variation of background flow and the trajectory of the radiosonde when the scorer parameter is a strong function of height as is the case with the 1100 utc sounding it is inappropriate to assume that the vertical wavenumber is constant with height in particular the vertical wavelength at low levels is about 4 5 km the waves become evanescent between the heights of 2 5 km and 9 km and above that the vertical wavelength is typically 10 15 km as a consistency check linear wave theory is used to calculate the resonant wave modes supported by the background profiles of wind and potential temperature these are the wave modes that are most likely responsible for the lee wave clouds seen in the avhrr satellite image the horizontal wavelength for the resonant wave mode is 8188 m in agreement with the estimates based on the avhrr satellite image and from the horizontal projection method the paper highlights the dangers of interpreting radiosonde soundings as vertical snapshots of the atmosphere and assuming that the vertical wavenumber can be characterized by a single value it is shown that treating the radiosonde sounding as a vertical profile and analysing wave like structures in the ascent rate using standard spectral methods gives an incorrect vertical wavelength of 1906 238 m the paper concludes that operational radiosonde soundings can be used to make accurate quantitative measurements of orographically generated waves provided that the vertical variation in the background flow and the motion of the radiosonde through the wave field are taken into account

observation of gravity wave generation and breaking in the lowermost stratosphere measurements with the aberystwyth vhf radar have revealed a striking illustration of gravity wave generation and breaking in the lowermost stratosphere horizontal wind measurements show an inertia gravity wave that was essentially monochromatic and persisted for longer than 5 days with a maximum perturbation amplitude of approximately 10 ms 1 radiosonde measurements show that this wave induced shear instability that led to intense turbulence close to the tropopause the event was associated with a highly curved jet stream over europe suggesting that geostrophic adjustment was a likely source mechanism

seismicity and seismotectonics of norway and nearby continental shelf areas the earthquake activity of norway and nearby offshore areas is low to intermediate with few events above magnitude 5 recent significant improvements in instrumental coverage in parallel with a better utilization of older including historical data have shown that the seismicity in the south is predominantly confined to the coastal areas and to the viking graben while from the northern north sea to svalbard the earthquakes in a broad sense follow the continental margin fifty one focal mechanism solutions from these areas about half of them new reveal stress directions that clearly indicate a connection to the plate tectonic ridge push force at least for the areas at a minimum distance from the continental margin along the margin stress directions also indicate a possible connection to postglacial uplift as well as to lithospheric loading effects a dominance of normal faulting on the landward side and reverse faulting on the oceanic side agrees with this interpretation on a regional level the seismicity in these areas correlate quite well with geologic features such as grabens fault zones fault complexes fracture zones and the margin itself indicating that these structures act in a general sense as weakness zones in the presence of a regionally more stable stress field in the northern north sea however an area with quite anomalous stress orientations with strike slip faulting is found in a region transitional between normal and reverse faulting most of the earthquake foci are confined to the presumably brittle parts of the crust but many events are also located quite close to and on both sides of the moho discontinuity

fennoscandian dynamics present day earthquake activity abstract the fennoscandian earthquake catalogue is constantly updated and revised and we present the best available map of earthquake activity it exhibits significant differences between areas of high and low seismicity the focal mechanisms have been determined for many of the earthquakes the total set of these focal mechanisms shows that the stress pattern is very consistent the horizontal deviatoric stresses are characterized by a grouping in the nw se directions for the maximum compression this stress field is not distorted even by the significant crustal inhomogeneity in the fennoscandian border zone this orientation of the maximum horizontal compression is precisely that expected from ridge push forces from the north atlantic ridge it is not consistent with the stress field expected from postglacial uplift after the last ice age however recently large neotectonic faults have been identified and studied in northern scandinavia and these are taken as indicators of large scale displacements shortly after the end of the last ice age seen in parallel with similar studies in scotland this shows that the stress field has changed drastically with time the present day uniform stress field and the relatively scattered distribution of observed earthquakes lead to the conclusion that the earthquakes concentrate in specific zones of brittle weak crust we claim that arguments based on tectonics must be dependent on the specific tectonic characteristics of each area separately and this remains the outstanding problem of fennoscandian earthquake activity as observed presently

strengthening of the tropopause inversion layer during the 2009 sudden stratospheric warming a merra 2 study abstractthe behavior of the tropopause inversion layer til during the 2009 sudden stratospheric warming ssw is analyzed using nasa s modern era retrospective analysis for research and applications version 2 merra 2 and short term simulations with the merra 2 general circulation model consistent with previous studies it is found that static stability in a shallow layer above the polar tropopause sharply increases following the ssw leading to a strengthening of the high latitude til simultaneously the height of the thermal tropopause decreases by around 1 km similar behavior is also detected during other major ssw events between the years 2004 and 2013 using an ensemble of general circulation model forecasts initialized from merra 2 it is demonstrated that the primary cause of the strengthening of the til is an increased convergence of the vertical component of the stratospheric residual circulation in response to an ssw induced acceleration of the mean downward motion between 75 and 90 n

palaeoseismicity and de geer moraines abstract de geer moraines are small moraine ridges formed partly in crevasses at the base of glacier ice there may be several different origins of the crevasses one possibility proposed by gerard de geer who first studied these ridges was seismic activity in connection with the isostatic rebound during the deglaciation the present study shows a close connection between occurrences of de geer moraines in fennoscandia and seismic activity or fresh looking fault lines and other features indicating neotectonic movements this supports de geer s theory but does not exclude formation in crevasses formed in other ways there is no real proof that the tectonic movements took place in the quaternary but the close connection between the moraines and tectonic features is evidence pointing in this direction if this is correct it has important implications for the stability within cratons of precambrian crystalline bedrock

the interaction between the tropopause inversion layer and the inertial gravity wave activities revealed by radiosonde observations at a midlatitude station the interaction between the tropopause inversion layer til and the inertial gravity wave igw activities is first presented by using a high vertical resolution radiosonde data set at a midlatitude station boise idaho 43 57 n 116 22 w for the period 1998 2008 the tropopause based vertical coordinate is used for the til detection and for meticulously studying the igw variation around the til the broad spectral method is used for the igw extraction generally the til at the midlatitude station is stronger and thicker in winter and spring which is consistent with previous studies our study confirmed the intense interaction between the til and igw it is found that the til not only could inhibit the upward propagation of igws from below but also imply the possible excitation links between the til and igw the results also indicate that the enhanced wind shear layer just 1 km above the tropopause may result in instability and finally leads to the igw breaking and intensive turbulence subsequently the igw induced intensive turbulence leads to strong wave energy dissipation and a downward heat flux this downward heat transportation could significantly cool the tropopause while it has only negligible thermal effect on the atmosphere above the tropopause then the igw induced cooling at the tropopause makes the tropopause colder and sharper and finally forms the til these suggest besides previously proposed mechanisms that igws also contribute greatly to the formation of til which is consistent with a recent related simulation study

fine scale structure of the extratropical tropopause region 1 a vertically high resolved climatology of the thermal and wind structure of the extratropical tropopause region is presented the climatology is based on data from 80 u s radiosonde stations covering the period 1998 2002 time averages for each radiosonde station are computed using the tropopause as a common reference level for all vertical profiles within the mean a strong inversion at the tropopause in the mean vertical temperature gradient is uncovered that is temperature strongly increases with altitude within the lowermost stratosphere this tropopause inversion layer exists on average throughout the investigated extratropics about 30 n to 70 n accordingly the static stability parameter shows considerably enhanced values within the lowermost extratropical stratosphere compared to typical extratropical stratospheric values further aloft conventional averages are not able to capture the tropopause inversion layer mean profiles of the horizontal wind show behavior qualitatively corresponding to thermal wind balance winter and summer exhibit distinctly different climate states in the extratropical tropopause region an approximated potential vorticity is considered and found to be close to well mixed within the troposphere as well as within the tropopause inversion layer this suggests the view of the tropopause inversion layer as representing a dynamically active atmospheric layer some potential implications are discussed

late pleistocene glacial equilibrium line altitudes in the colorado front range a comparison of methods abstract six methods for approximating late pleistocene pinedale equilibrium line altitudes elas are compared for rapidity of data collection and error rmse from first order trend surfaces using the colorado front range trend surfaces computed from rapidly applied techniques such as glaciation threshold median altitude of small reconstructed glaciers and altitude of lowest cirque floors have relatively high rmses 97 186 m because they are subjectively derived and are based on small glaciers sensitive to microclimatic variability surfaces computed for accumulation area ratios aars and toe to headwall altitude ratios thars of large reconstructed glaciers show that an aar of 0 65 and a thar of 0 40 have the lowest rmses about 80 m and provide the same mean ela estimate about 3160 m as that of the more subjectively derived maximum altitudes of pinedale lateral moraines rmse 149 m second order trend surfaces demonstrate low elas in the latitudinal center of the front range perhaps due to higher winter accumulation there the mountains do not presently reach the ela for large glaciers and small front range cirque glaciers are not comparable to small glaciers existing during pinedale time therefore pleistocene ela depression and consequent temperature depression cannot reliably be ascertained from the calculated ela surfaces

large wind shears and their implications for diffusion in regions with enhanced static stability the mesopause and the tropopause the ncar whole atmosphere community climate model waccm with a quasi uniform horizontal resolution of 25km and a vertical resolution of 0 1 scale height produces large vertical shear of horizontal wind with peaks around the mesopause and the tropical and midlatitude tropopause in these regions the static stability also reaches peak values and therefore allows large vertical shears before the onset of dynamical instability the wind shear peaks near the mesopause and the tropopause from the simulation compare well with those identified in observations including the magnitude latitudinal dependence and large shear statistics by analyzing the probability density functions of the wind shears and their dependence on the zonal scales it is found that smaller scale processes likely gravity waves contribute significantly to the large shears and may play a dominant role in producing the largest shears climatological tidal waves have secondary contribution to the large winds and shears but spectral analysis suggests that they can modulate wind shear perturbations by gravity waves in the mesosphere and lower thermosphere implications for tracer transport and mixing in these regions are explored by estimating diffusion coefficients based on the root mean square winds shears and corresponding spatial scales from model results

vertical fluctuation energy in united states high vertical resolution radiosonde data as an indicator of convective gravity wave sources 1 convectively generated internal gravity waves at extratropical latitudes are difficult to identify by climatological analysis of the temperature and horizontal wind fields from radiosonde profiles using traditional analysis methods here we show that by analyzing ascent rate profiles we define a new variable vertical fluctuation energy ve we can identify convection sources in climatological analyses analysis of a 9 year time series 1998 2006 of united states high vertical resolution radiosonde data shows that ve maximizes in summer in midlatitudes within the troposphere 2 8 9 km and peaks at local afternoon early evening during the summer over most of the contiguous united states furthermore the apparent dominant vertical wavelength based on fourier analysis of the low pass filtered ascent rate fluctuations also increase and decrease with ve both on diurnal and seasonal timescales ve in the lower stratosphere however does not show this same relationship to convection but analysis of the vertical wavelength does show some of the features seen in tropospheric ve unlike midlatitude stations ve within both the troposphere and the lower stratosphere over tropical western pacific island stations is highly correlated with convective precipitation and inversely correlated with outgoing longwave radiation we interpret this difference by using the 4 d gravity wave regional or global ray tracer ray tracing model with a source spectrum representative of a convection source

late quaternary snowline reconstructions for the southern and central sierra nevada california and a reassessment of the recess peak glaciation abstract in the sierra nevada the recess peak glaciation has been previously defined on the basis of deposits exhibiting relative age characteristics intermediate between those of the little ice age deposits and those of early holocene or older moraines in the absence of reliable chronological control the recess peak deposits were assigned an early neoglacial age although numerous moraines in the central and southern sierra have been attributed to this interval regional snowline gradients reconstructed from these deposits lack internal consistency and appear to represent several distinctly different episodes of glacier advance as a basis for comparison with the recess peak data modern and late pleistocene regional snowlines were reconstructed using accumulation area ratios and cirque floor altitudes these reconstructions display regionally consistent gradients rising gradually southward and more steeply eastward based on these data the full glacial late pleistocene snowline depression is estimated to have been 800 m estimates of recess peak snowline depression vary widely ranging from 140 to 500 m and a reconstructed regional gradient rises northward in opposition to the late pleistocene and modern snowlines limited radiocarbon dating and the irregular pattern derived from the recess peak snowline data suggest that even in the type area these deposits resulted from both pre and post hypsithermal glacier advances

earthquakes and seismic hazard in finland abstract in this paper the seismicity of finland has been re evaluated on the basis of a new regional magnitude scale which gives somewhat lower magnitude values than the previously used macroseismic scale macroseismic magnitudes for finnish earthquakes have been calculated by using the value 4 0 for the coefficient of attenuation and the value 2 0 for the lower limit of intensity at the boundary of the felt area using these parameters we obtained macroseismic magnitudes comparable to those of the instrumental ml scale the distribution of seismicity in finland is presented in an epicentral map and maximum intensity maps 1880 1980 these maps indicate some regional variation of seismic activity the seismicity was also considered as a function of time using strain release curves the b value 0 59 was evaluated from the log n m relationship for the last hundred years the time variation of b values was also studied estimation of magnitude and intensity extremes by gumbel s method yielded the value 5 0 for the upper limit of magnitude and vi vii for the upper limit of intensity the return periods for different magnitudes and intensities were calculated as well as the probabilities that they are exceeded

seismic hazard in fennoscandia a regionalized study a seismic hazard evaluation has been conducted for fennoscandia including norway sweden finland denmark areas of russia and adjacent sea areas several subregions were considered data were taken from a fennoscandian earthquake catalog comprising both macroseismic and instrumental observations the analysis was based on a maximum likelihood approach using incomplete historical and complete instrumental data different detection thresholds and assessment of earthquake magnitude uncertainty the output for the selected subregions consists of the probabilities that a given magnitude will not be exceeded in a given interval of time and mean return periods for earthquakes of magnitudes exceeding a given value ml the evaluated parameters are the maximum regional magnitude gutenberg richter b value and annual activity rate all with standard errors the obtained parameters correspond well to the characteristic seismicity features of inspected regions however discrepancies between the data used and the data model behind the applied method were observed both the patterns of earthquake occurrence and the reporting of historical events tend to deviate from the model differences in output can be expected according to the decisions to deal with these discrepancies

the tropopause inversion layer in models and analyses recent high resolution radiosonde climatologies have revealed a tropopause inversion layer til in the extratropics temperature strongly increases just above a sharp local cold point tropopause here it is asked to what extent a til exists in current general circulation models gcms and meteorological analyses only a weak hint of a til exists in ncep ncar reanalysis data in contrast the canadian middle atmosphere model cmam a comprehensive gcm exhibits a til of realistic strength however in data assimilation mode cmam exhibits a much weaker til especially in the southern hemisphere where only coarse satellite data are available the discrepancy between the analyses and the gcm is thus hypothesized to be mainly due to data assimilation acting to smooth the observed strong curvature in temperature around the tropopause this is confirmed in the reanalysis where the stratification around the tropopause exhibits a strong discontinuity at the start of the satellite era

structural diagnostics of the tropopause inversion layer and its evolution the tropopause inversion layer til is marked by a peak in static stability directly above the tropopause the til is quantitatively defined with new diagnostics using global positioning system radio occultation temperature soundings and reanalysis data a climatology of the til is developed from reanalysis data 1980 2011 using diagnostics for the position depth and strength of the til based on the til peak in static stability til diagnostics have defined relationships to the synoptic situation in the upper troposphere and lower stratosphere the til is present nearly all the time the til becomes hard to define in the subtropics where tropical air overlies midlatitude air in a region of complex static stability profiles the mean position of the subtropical til gradient is sharp and is co located with the subtropical tropopause break over the period 1980 2011 the til depth below the tropopause has decreased by 5 per decade and increased above the tropical tropopause by a similar percentage furthermore the latitude of the abrupt change in the til from tropical to extratropical in the lower stratosphere appears to have shifted poleward in each hemisphere by 1 latitude per decade depending on the diagnostic examined reanalysis trends should be treated with caution

the extratropical tropopause inversion layer global observations with gps data and a radiative forcing mechanism global characteristics of the extratropical tropopause inversion layer identified in radiosonde observations by birner are studied using high vertical resolution temperature profiles from gps radio occultation measurements the gps data are organized according to the height of the thermal tropopause in each profile and a temperature inversion layer above the tropopause with an average magnitude of 3 5 k is found to be a ubiquitous climatological feature the gps data show that the inversion layer is present for all seasons in both hemispheres spanning the subtropics to the pole and there is not strong longitudinal structure dependence of the inversion layer on upper troposphere vorticity is studied while anticyclones exhibit a substantially stronger inversion than cyclones as expected from balanced dynamics the inversion is evident for all circulation types radiative transfer calculations indicate that strong gradients in both ozone and water vapor near the tropopause contribute to the inversion significant absorption of both longwave and shortwave radiation by ozone occurs warming the region above the tropopause water vapor near and immediately above the tropopause contributes to cooling effectively enhancing the inversion

mixing layer formation near the tropopause due to gravity wave critical level interactions in a cloud resolving model abstract a plausible mechanism for the formation of mixing layers in the lower stratosphere above regions of tropical convection is demonstrated numerically using high resolution two dimensional 2d anelastic nonlinear cloud resolving simulations one noteworthy point is that the mixing layer simulated in this study is free of anvil clouds and well above the cloud anvil top located in the upper troposphere hence the present mechanism is complementary to the well known process by which overshooting cloud turrets causes mixing within stratospheric anvil clouds the paper is organized as a case study verifying the proposed mechanism using atmospheric soundings obtained during the central equatorial pacific experiment cepex when several such mixing layers devoid of anvil clouds had been observed the basic dynamical ingredient of the present mechanism is quasi stationary gravity wave critical level interactions occurring in association with a reversal of stratospheric westerlies to easterlies b