a numerical simulation of quasi stationary tropical convective bands a method of imposing large scale ascent on a three dimensional numerical model is introduced and this is shown to be crucial in maintaining the quasi stationary convective bands observed in gate the effects of ascent on the overall convective development are to enhance updraughts and particularly to maintain the development of new convection cells the magnitutude of the forcing is varied to show the sensitivity of growth on convergence a quasi stationary convective band aligned approximately parallel to the low level wind shear is simulated in an initial environment defined from soundings obtained from the gate ships researcher and oceanographer on 3 september 1974 the organization is therefore quite distinct from that of fast moving squall lines aligned at right angles to the shear the simulated convective system has marked dynamical similarity to the observed bands these consisted of a number of cumulonimbus cells with new cells developing on the eastern end of the hand with deeper cells to the west the cells generally travel along the line the large shear due to the strong low level jet is crucial in influencing the band development and orientation the dynamical structure of the convective band is investigated by a trajectory analysis which indicates an organized three dimensional structure the transports of heat moisture and momentum are calculated and a quasi balance between large scale ascent and cloud induced descent on a time scale of a few hours is shown to exist apparent heat sources and moisture sinks are calculated and these have a bi modal vertical structure in general agreement with those in observed tropical cloud clusters

numerical simulation of the 2008 west bohemian earthquake swarm abstract co 2 has long been suspected of driving the bohemian earthquake swarms because of the migrating nature of the swarms and expressions of co 2 degassing at the surface modeling to date primarily employed linear diffusion models but more sophisticated modeling that includes a coupled fluid and rock mechanical model has been lacking in this work we apply a model that couples mechanics to heat and flow of a super critical co 2 through a fracture network we present a continuum mechanical approach to derive the seismic moment magnitude using the deviatoric strain as an indicator of rupturing processes during individual events we use a peak detection algorithm to identify rapid changes in deviatoric strain indicative of slip events this method has been shown to work very well in dry and fluid induced fracturing experiments at the laboratory scale and in this work we extend the method to the scale of the west bohemia vogtland earthquake swarms we show very good agreement between model results and observations of the 2008 swarm further supporting the hypothesis that the bohemian earthquake swarms are predominately fluid driven

crustal structure due to collisional and escape tectonics in the eastern alps region based on profiles alp01 and alp02 from the alp 2002 seismic experiment 1 alp01 and alp02 are the longest profiles recorded during alp 2002 a large international seismic refraction and wide angle reflection experiment undertaken in the eastern alps in 2002 alp01 crosses the alpine orogen from north to south thus providing a cross section mainly affected by the collision between europe and the adriatic microplate alp02 extends from the eastern alps to the pannonian basin supplying evidence on the relation between alpine crustal structure and tectonic escape to the pannonian basin during this experiment 363 single channel recorders were deployed along these profiles with an average spacing of 3 2 km recordings from 20 inline shots were used in this study two dimensional forward modeling using interactive ray tracing techniques produced detailed p wave velocity models that contain many features of tectonic significance along alp01 the european moho dips generally to the south and reaches a maximum depth of 47 km below the transition from the eastern to the southern alps the adriatic moho continues further south at a significantly shallower depth moho topography and a prominent south dipping mantle reflector in the alpine area support the idea of southward subduction of the european lithosphere below the adriatic microplate the most prominent tectonic feature on the alp02 profile is a vertical step of the moho at the transition between the alpine and pannonian domains suggesting the existence of a separate pannonian plate fragment the development of the pannonian fragment is interpreted to be a consequence of crustal thinning due to tectonic escape from the alpine collision area to the pannonian basin

the evolution of a thrust fault system processes of rupture initiation propagation and termination in the 1980 el asnam algeria earthquake summary we discuss work completed to date on the 1980 algerian earthquake and introduce a description of the earthquake in terms of rupture propagation using the nomenclature of fracture mechanics field and teleseismic studies have shown the earthquake fault to be divided into three major thrust segments rupture began at the sw end of the system and propagated along successive segments geological sections reveal that different fault segments have suffered different amounts of displacement in the past the amount of geological displacement increases systematically from almost zero at the sw end of the fault to several hundred metres further ne faulting at the sw end is very young and appears to be extending the thrust system along strike the aftershock data of ouyed et al reveal that strike slip aftershocks occur beyond the sw end of the thrust fault these are accommodating compression by conjugate strike slip faulting on north and west trending planes this network of conjugate faults plays a crucial role in the initiation of major eathquakes on the thrust system and may be regarded as a plastic zone beyond the end of the thrust fault increasing horizontal stress causes the strike slip system to evolve into a zig zag network of thrusts which is partly controlled by the pre existing strike slip faults finally a through going thrust can develop and leads to catastrophic rupture along the main fault plane to describe the propagation of the main shock we extend aki s concept of geometric barriers and divide these into two types in conservative barriers the slip vector is common to both fault planes whereas in non conservative barriers the slip vectors are different on the two fault planes that meet at the barrier although both types of barrier arrest dynamic rupture only nonconservative barriers need produce aftershocks as off fault deformation is required to accommodate the difference in slip vectors by considering the aftershock zones as areas of distributed deformation we show that fracture toughness in the earth is not a material constant but is related to fault geometry and therefore changes as fault systems evolve the current south westwards growth of the el asnam thrust system can be seen as the latest phase in an evolution consisting of periods of along strike extension alternating with periods of increasing net displacement during which no fault growth occurs these two types of behaviour allow a segmented fault system to be produced

co 2 degassing in the hartousov mofette area western eger rift imaged by co 2 mapping and geoelectrical and gravity surveys strong subcontinental mantle dominated co2 degassing occurs in the hartousov and bublak mofette fields in the western eger rift the combination of co2 gas flux and soil gas measurements as well as gravity and geoelectric surveys provides insight into the surface and subsurface of this unique mofette area co2 soil gas and gas flux measurements reveal that large amounts of carbon dioxide are released via channels with diameters below 1 m carbon dioxide emissions of several tens and up to more than 100 kg day 1 are ejected via these small seeps measurements with small spacings are necessary to account for the point like focused gas discharge in the lesser degassing surrounding we estimate that between 23 and 97 tons of co2 are released over an area of about 350 000 m2 each day in the hartousov mofette field the application of widely used geostatistical tools leads to estimations of the co2 discharge with very high standard deviations due to the strong positive skewness of the data distribution geophysical investigations via electrical resistivity tomography and gravity measurements were carried out over areas of strong seepage and reveal distinct anomalies in the subsurface below mofettes indicating rock and sediment alterations and or sediment transport by pressurised ascending co2 and water mobilised by it this study reveals that the gas emanations only occur west of a morphological step which is related to a n s oriented fault zone the pocatky plesna fault zone the results of co2 mapping and the geophysical studies can track the course of this fault zone in this area our results fit into a tectonic model in which the mofette fields are in the centres of two independent pull apart basin like structures we hypothesise that the sinistral strike slip movement of the pocatky plesna fault zone leads to a pull apart basin like opening at which the strong mantle derived co2 degassing occurs nowadays since the hartousov and bublak mofette fields only illustrate examples along the n s striking pocatky plesna fault zone its role and other n s striking faults roles of the regensburg leipzig rostock zone for upper mantle degassing might have been underestimated previously

analysis of a heavy rainfall event during tamex abstract a heavy rainfall event during the taiwan area mesoscale experiment intensive observing period 13 has been studied using upper air surface mesonet and dual doppler radar data the heavy rainfall 231 mm day 1 occurred over northwestern taiwan with the maximum rainfall along the northwestern coast and was caused by a long lived convective rainband in the prefrontal atmosphere it occurred in an upper level divergence region and along the axis of the maximum equivalent potential temperature at the 850 hpa level as a mei yu front advanced southeastward the postfrontal cold air in the lowest levels was retarded by the hilly terrain along the southeastern china coast as a result a low level wind shift line associated with a pressure trough at the 850 hpa level moved over the taiwan strait before the arrival of the surface front the westerly flow behind the trough interacted with a barrier jet along the northwestern coast of taiwan the barrier jet is caused by the interaction between the pref

compositional and metamorphic controls on velocity and reflectivity in the continental crust an example from the grenville province of eastern quebec we present velocity and density data for a suite of gabbros and metagabbros over a range of metamorphic grades from subgreenschist to the eclogite facies most of these rocks have a mesocratic protolith with overlapping bulk chemistry ranges providing an opportunity to investigate the systematics of mineralogy and physical properties across a wide range of metamorphic grades with minimal compositional variation in addition more mafic gabbros in the eclogite facies were also investigated in order to take into account variations in the extent of transformation of gabbro to eclogite controlled by bulk chemistry the physical properties data are used as the basis for a first order crustal model composed of granitic anorthositic and gabbroic components the objective of constructing the crustal model is to evaluate the relative contribution of compositional variation and metamorphism to the velocity density and reflectivity structure of the continental crust the model suggests that in the upper crust if fracture porosity is neglected composition dominates the velocity and density structure while in the middle and lower crust composition and metamorphism play equally important roles simulations designed to predict potential reflection coefficient size distributions for the various bulk chemistries and mineralogies in the crustal model indicate step increases in the potential for large reflection coefficients that are dominantly controlled by metamorphic grade step increases in reflectivity are predicted between the lower and upper amphibolite facies and between incompletely and completely eclogitized metagabbros in the eclogite facies we also consider several alternative mixing models which account for the effects of one of the three lithologic components occurring as isolated bodies rather than perfectly mixed with the other two components these models indicate a reduction of the potential for large reflection coefficients by as much as 50 emphasizing the importance of the degree of mixing for crustal reflectivity

mechanics and mechanisms of magmatic underplating inferences from mafic veins in deep crustal mylonite dioritic to gabbro dioritic veins with extreme length to width ratios 1000 1 are localized along an amphibolite facies shear zone the cmb line between exposed segments of originally middle and lower continental crust strona ceneri and ivrea verbano zones northern italy the geometry of these veins and their mutual cross cutting relationships with the mylonitic foliation indicate that veining was coeval with noncoaxial flattening of the lower crust in early permian time the veins formed as closely spaced extensional shear fractures and propagated parallel to the originally gently to moderately dipping 30o mylonitic foliation vein opening at high angles 60 90o to the inferred1 direction and subparallel to the pre existing planar fabric requires that melt pressure slightly exceeded the lithostatic pressure and that differential stress was low 10 20 mpa in the vicinity of the veins the interaction of regions of tensile stress concentration at vein tips caused the concordant veins to curve and link up across the mylonitic foliation once interconnected the veins served as conduits for the rapid movement of mafic melt along the shear zone thermal modelling constrains the mafic melt in the narrowest 1 mm wide veins to have crystallized almost instantaneously such veins extend no more than a meter from host veins into the country rock indicating that the minimum rate of vein tip propagation and melt flow was at least several m s maximum crystallization times of only hundreds to thousands of years for even the thickest mafic veins 10 100 m in the ivz are short compared to the 15 20 ma duration of early permian crustal attenuation and magmatism in the southern alps this suggests that veining in the lower crust occurred episodically during extended periods of mylonitic creep concordant vein networks within deep crustal shear zones that are inclined as the cmb line may have been can also channel overpressurized mafic melt from deeper sources e g lower crustal magma chambers into cooler intermediate crustal rock this locally widens the depth interval of combined viscous and brittle deformation within the crust and can trigger partial melting of the country rock 1999 elsevier science b v all rights reserved

momentum flux by lines of cumulonimbus over the tropical oceans abstract examination of aircraft and rawinsonde data gathered in nine tropical mesoscale convective line cases indicates that all but two lines systematically increased front to rear momentum at heights greater than about 4 km and rear to front momentum at lower levels where front is defined as the direction toward which the line is moving the convective lines were characterized by a leading 10 20 km wide band of convective clouds and a trailing region of stratiform cloudiness most wore propagating lines moving into the wind at all levels consistent with mixing length theory the vertical transport of the horizontal wind component parallel to the lines was down the vertical gradient of the component resulting in a decrease of its vertical shear smaller more random cloud groups and the upper portions of a convective line with isolated towers transported both components of horizontal momentum downgradient normalization of the vertical flux of horizontal momentum normal to the line u w su

a theory for strong long lived squall lines abstract we study herein the mechanics of long lived line oriented precipitating cumulus convection squall lines using two and three dimensional numerical models of moist convection these models used in juxtaposition enable us to address the important theoretical issue of whether a squall line is a system of special long lived cells or whether it is a long lived system of ordinary short lived cells our review of the observational literature indicates that the latter is the most consistent paradigm for the vast majority of cases but on occasion a squall line may be composed of essentially steady supercell thunderstorms the numerical experiments presented herein show that either type of squall line may develop from an initial line like disturbance depending on the magnitude and orientation of the environmental shear with respect to the line with shallow shear oriented perpendicular to the line a long lived line evolves containing individually short lived cells our analysis of this type o

upstream effects of mesoscale mountains abstract the alpine experiment alpex has revealed that low level air is typically diverted around the alps without reaching the mountaintop in pursuit of an understanding of the physical basis of this phenomenon and of its generality we have explored the characteristics of orographic blocking of a rotating continuously stratified quid as revealed in a simple model problem retaining full nonlinear and transient effects hydrostatic dynamics is assumed and the obstacle is taken to be an infinitely long ridge with height h x the key questions treated are the strength of the upstream deceleration of cross mountain flow and the length scale over which the decelerated region extends by means of scale analysis the controlling parameters are found to be the rossby number ro u fl and the froude number fr nhm u where u is the speed of the oncoming flow f is the coriolis parameter l the mountain half width n the brunt vaisala frequency and hm is the maximum mountain height the scale analysis also

crustal and uppermost mantle structure of the bohemian massif based on celebration 2000 data 1 the deep structure of the bohemian massif bm the largest stable outcrop of variscan rocks in central europe was studied using the data of the international seismic refraction experiment central european lithospheric experiment based on refraction celebration 2000 the data were interpreted by seismic tomographic inversion and by two dimensional 2 d trial and error forward modeling of p and s waves additional constraint on crustal structure was given by amplitude modeling using the reflectivity method and gravity modeling though consolidated the bm can be subdivided into several tectonic units separated by faults shear zones or thrusts reflecting varying influence of the cadomian and variscan orogeneses the saxothuringian barrandian moldanubian and moravian velocity models determine three types of crust mantle transition in the bm reflecting variable crustal thickness and delimiting contacts of tectonic units in depth the nw area the saxothuringian has a highly reflective lower crustal layer above moho with a strong velocity contrast at the top of this layer this reflective laminated lower crust reaches depths of 26 35 km and is characteristic for the saxothuringian unit which was subject to eastward subduction the moldanubian in the central part is characterized by the deepest 39 km and the most pronounced moho within the whole bm with a strong velocity contrast 6 9 8 1 km s 1 a thick crust mantle transition zone in the se with velocity increase from 6 8 to 7 8 km s 1 over the depth range of 23 40 km seems to be the characteristic feature of the moravian overthrusted by the moldanubian during variscan collision

lithospheric structure of the bohemian massif and adjacent variscan belt in central europe based on profile s01 from the sudetes 2003 experiment 1 the sudetes 2003 seismic experiment investigated the lithospheric structure of the eastern part of the variscan belt of central europe the key profile of this experiment s01 was 630 km long and extended southwestward from the margin of the east european craton across the trans european suture zone tesz and sudetes and across the bohemian massif that contains the active eger ohre rift which is an element of the european cenozoic rift system good quality first arrivals and later phases of refracted reflected p and s waves were interpreted using 2 d ray tracing techniques the derived seismic model shows large variations in the internal structure of the crust while the depth to the moho varies in the relatively narrow depth interval of 28 35 km except for the polish basin on the northeast end of the profile the sedimentary cover is thin the crystalline upper and middle crust with velocities of 5 9 6 4 km s 1 is about 20 km thick and the 7 10 km thick lower crust can be divided into three regions based on p wave velocities a low velocity region 6 5 6 6 km s 1 beneath eger rift and sudetes that is bounded on the southwest and northeast by regions of significantly higher velocity 6 8 7 1 km s 1 beneath the saxothuringian and moldanubian in the southwest and fore sudetic monocline and polish basin in the northeast high velocity bodies vp 6 5 km s 1 were delineated in the upper crust of the eger rift region the seismic structure along the s01 profile images a variscan orogenic wedge resting on the down warped margin of the plate margin containing the tesz this situation implies the northerly directed subduction of the rheic ocean that existed between the southern margin of the old red continent and the armorican terranes presently accreted into the variscan belt closure of this ocean produced the rheic suture between low velocity crust of the variscan orogenic wedge and higher velocity crust of the tesz

monitoring of helium and carbon isotopes in the western eger rift area czech republic relationships with the 2014 seismic activity and indications for recent 2000 2016 magmatic unrest abstract we report new data of the regional distribution pattern of total gas compositions as well as he and co2 isotopic compositions from 25 gas exhalations in the western eger rift and its surroundings additionally the first time series data from gas exhalations in a clay pit within the cheb basin cb are given at 21 degassing locations the first data were obtained 20 years ago from 7 locations within the degassing center cb and from 3 degassing sites belonging to the marianske lazn ml degassing center neon and argon isotope compositions were determined also co2 is the major component at all degassing sites the 13c values display a small range 1 7 to 5 1 and the 3he 4he ratios vary from 1 9 to 5 9 ra the highest 3he 4he ratios are found at locations along the pocatky plesna fault zone followed by the degassing site in the clay pit on the nova ves fault and the locations on the ml fault at the edge of the cb although gas flow and co2 concentrations in all degassing centers are very high the fractions of mantle derived helium are different with presently up to 94 in relation to the sclm 3he 4he of 6 32 ra in the cb up to 73 in the ml and up to 35 in the karlovy vary degassing center at the locations in the eastern part of the cb a clear progressive increase of the 3he 4he ratio has been observed since the first sampling campaigns there in 1993 and 1994 whereas at the other degassing sites the helium isotope ratio remained essentially the same the progressive increase of the 3he 4he ratio in the eastern part of the cb together with further short time increases up to 6 3 ra at one location bublak before both the 2000 and 2008 earthquake swarms indicate an ongoing magmatic process beneath this area which seems to be associated with the occurrence of seismicity the cb is located close to the nov kostel focal zone where since the beginning of our investigations four strong periods of seismicity with magnitudes 3 occurred the latest gas data confirm our earlier findings time series studies showed that in relation with seismic events decreased 3he 4he ratios were repeatedly observed due to admixed seismically released crustal helium presently the eastern part of the cb is the most active non volcanic region in the european cenozoic rift system with gas signatures similar to those found in free mantle derived gases from the east african rift system

observations and scale analysis of coastal wind jets abstract blocking of onshore flow by coastal mountains was observed south of vancouver island british columbia by the noaa p 3 aircraft on 1 december 1993 winds increased from 10 m s 1 offshore to 15 m s 1 nearshore and became more parallel to shore in the blocked region which had a vertical scale of 500 m and an offshore scale of 40 50 km these length scale and velocity increases are comparable to theory the flow was semigeostrophic with the coast being hydrodynamically steep that is the coast acts like a wall and the alongshore momentum balance is ageostrophic this is shown by the nondimensional slope parameter the burger number b hmn flm being greater than 1 where hm and lm are the height and half width of the mountain n is the stability frequency and f is the coriolis parameter the height scale is given by setting the local froude number equal to 1 that is hl u n 500 m where u is the onshore component of velocity this scale is appropriate when hl is less than the mountain height

from the variscan to the alpine orogeny crustal structure of the bohemian massif and the western carpathians in the light of the sudetes 2003 seismic data summary the variscan orogeny is the major middle to late palaeozoic tectonometamorphic event in central europe and the bohemian massif is the largest exposure of rocks deformed during this orogeny the bohemian massif consists of the saxothuringian barrandian and moldanubian units adjacent to this massif in the southeast the western carpathians form an arc shaped mountain range related to the alpine orogeny during the cretaceous to tertiary the complex crustal scale geological structure of the variscan bohemian massif and the western carpathians and especially their contact were analysed in this study employing the data of the sudetes 2003 international seismic refraction experiment the analysed seismic data were acquired along the 740 km long nw se oriented s04 profile that crossed the bohemian massif and the western carpathians before terminating in the pannonian basin the data were interpreted by 2 d trial and error forward modelling of p waves and additional constraints on crustal structure were provided by gravity modelling the complex velocity structure derived in our analysis included low velocities of 5 85 km s 1 at the contact of the saxothuringian and barrandian units that reflect the presence of low density granites there are distinct lateral variations in deep crustal structure in the transition between the bohemian massif and the western carpathians the abrupt change of the crustal thickness in this transition zone may be associated with the pieniny klippen belt a deep seated boundary between the colliding palaeozoic lithospheric plate to the north and the alcapa microplate to the south in the upper crust of this transition low velocities of 4 km s 1 extend to 6 km and represent the sedimentary fill of the carpathian flysch and foredeep that thins towards the foreland this basin is also expressed as a pronounced gravity low the moho in the carpathians reaches a depth of 32 33 km in contrast in the pannonian basin the moho rises to a depth of 25 km which corresponds to the pannonian gravity high

structure and evolution of numerically simulated squall lines abstract using a three dimensional numerical cloud model we investigate the effects of vertical wind shear on squall line structure and evolution over a wide range of shear magnitudes depths and orientations relative to the line we find that the simulated squall lines are most sensitive to the magnitude of the component of shear perpendicular to the line and that we may reproduce much of the range of observed structures by varying this single parameter for weak shear a line of initially upright to downshear tilted short lived cells quickly tilts upshear producing a wide band of weaker cells extending behind the surface outflow boundary for moderate to strong shear the circulation remains upright to downshear tilted for longer periods of time with vigorous short lived cells confined to a relatively narrow band along the system s leading edge at later times however these systems may also weaken as the circulation tilts upshear for strong deep shears oriented obliquely to the line the squal

seismically triggered anomalies in the isotope signatures of mantle derived gases detected at degassing sites along two neighboring faults in nw bohemia central europe the vogtland and nw bohemia region is known for its earthquake swarms the most intensive swarm since 1985 86 occurred in october 2008 to find further indications for the interaction of ascending mantle derived fluids and the occurrence of earthquake swarms detailed fortnightly studies of gas compositions co2 n2 ar he h2 and ch4 and isotope ratios 13c 15n and 3he 4he were carried out between october 2008 and april 2011 at four locations close to the nov kostel focal zone and at the wettinquelle spring bad brambach from the start of the 2008 earthquake swarm seismically induced isotope geochemical anomalies were recorded at locations along the pocatky plesna fault zone ppz and were for the first time also found at degassing locations on the marianske lazn fault zone mlf variations were observed in both the temporal and spatial distributions of the anomalies as well in anomaly strengths probably due to the positions of these fault zones relative to the focal zone and to differences in fluid migration pathways prior to both the 2000 and 2008 swarms 3he 4he ratios 6 ra were recorded at the bublak mofette these anomalous pre seismic 3he 4he ratios suggest that both the 2000 and 2008 swarms may have been associated with the supply of fresh magma from a less degassed reservoir in the lithospheric mantle the temporal 13cco2 pattern from detailed studies at bublak between 2005 and 2011 indicates progressive magma degassing as well as seismically induced variations in the 13c providing additional support to the interpretation derived from the 3he 4he ratios

active magmatic underplating in western eger rift central europe the eger rift is an active element of the european cenozoic rift system associated with intense cenozoic intraplate alkaline volcanism and system of sedimentary basins the intracontinental cheb basin at its western part displays geodynamic activity with fluid emanations persistent seismicity cenozoic volcanism and neotectonic crustal movements at the intersections of major intraplate faults in this paper we study detailed geometry of the crust mantle boundary and its possible origin in the western eger rift we review existing seismic and seismological studies provide new interpretation of the reflection profile 9hr and supplement it by new results from local seismicity we identify significant lateral variations of the high velocity lower crust and relate them to the distribution and chemical status of mantle derived fluids and to xenolith studies from corresponding depths new interpretation based on combined seismic and isotope study points to a local scale magmatic emplacement at the base of the continental crust within a new rift environment this concept of magmatic underplating is supported by detecting two types of the lower crust a high velocity lower crust with pronounced reflectivity and a high velocity reflection free lower crust the character of the underplated material enables to differentiate timing and tectonic setting of two episodes with different times of origin of underplating events the lower crust with high reflectivity evidences magmatic underplating west of the eger rift of the late variscan age the reflection free lower crust together with a strong reflector at its top at depths of 28 30 km forms a magma body indicating magmatic underplating of the late cenozoic middle and upper miocene to recent spatial and temporal relations to recent geodynamic processes suggest active magmatic underplating in the intracontinental setting

mesoscale motion fields associated with a slowly moving gate convective band abstract the structure of the convective band of 14 september in the dense gate observing array is determined using wind and thermodynamic data primarily from multiple aircraft penetrations which are well distributed in the vertical and in time the well defined mesoscale features in the line which are 10 40 km in scale quasi two dimensional and persist for several hours determine the distribution of the convective scale features which are 5 km or less in size three dimensional not generally detectable for more than one flight leg at the leading edge a 30 km zone of strong ascent is computed from two dimensional continuity here lifting of the ambient air creates a favorable environment not found elsewhere for deep cumulonimbus clouds to develop their updrafts are weak 2 4 m s 1 on the average behind the updraft zone below 3 4 km is a broad descent zone it corresponds to the stratiform rain area and has little convection and some drying at lower levels on the average the mass flux by

principal earthquakes theory and observations from the 2008 west bohemia swarm abstract earthquakes that occur on optimally oriented fault planes with respect to the tectonic stress regime display two distinct focal mechanisms and are fundamental characteristics of each seismically active region these earthquakes which we term principal need not coincide with the strongest earthquakes or need not occur along the major active faults in the region stability analysis of diversely oriented fault planes under a given stress reveals that the focal mechanisms connected with unstable fault planes should not be very distinct from those of the principal earthquakes the p t axes form clusters with a typical two wing or butterfly pattern this pattern is particularly visible when constructing the failure curves defined as a projection of the mohr coulomb failure criterion in the mohr s diagram onto the focal sphere the position shape and size of the failure curves depend on the stress orientation shape ratio friction and on the size of the instability area in the mohr s diagram the theoretical analysis is tested using accurately determined focal mechanisms of 99 micro earthquakes that occurred during the 2008 earthquake swarm in the west bohemia vogtland region the distribution of p t axes reveals the butterfly wing pattern predicted in numerical modelling the activated fault planes concentrate in the area of validity of the mohr coulomb failure criterion the average friction of faults is 0 5 and corresponds to a deviation of 32 of the principal faults from the 1 axis the left lateral strike slip principal fault was the most active fault during the swarm it shows little geological expression at the surface but it is clearly defined by a linear cluster of hypocentres at depth the right lateral strike slip principal fault was less active but it is geologically well manifested on the earth s surface

seismic imaging of the geodynamic activity at the western eger rift in central europe the western eger rift at the czech german border in central europe is an important geodynamically active area within the european cenzoic rift system ecrs in the forelands of the alps along with two other active areas of the ecrs the french massif central and the east and west eifel volcanic fields it is characterized by numerous co2 rich fluid emission points and frequent micro seismicity existence of a plume s is indicated in the upper mantle which may be responsible for these observations here we reprocess a pre existing deep seismic reflection profile 9hr and interpret the subsurface structures as mapped by seismic reflectivity with previous findings mainly from seismological and geochemical studies to investigate the geodynamic activity in the subsurface we find prominent hints of pathways which may allow magmatic fluids originating in the upper mantle to rise through the crust and cause the observed fluid emanations and earthquake activity

seismic evidence for asthenospheric updoming beneath the western bohemian massif central europe 1 detailed images of the lithosphere beneath the western bohemian massif were obtained by analysis of more than 8500 p receiver functions at the intersection of regensburg leipzig rostock zone and eger rift crustal thickness decreases to 26 km from approx 31 km in the surroundings the receiver functions display a positive phase at about 6 s delay time and a strong negative phase at 7 to 8 s which coincides with an area of moho updoming co2 mantle derived degassing and earthquake swarm activity these phases can be modeled by a velocity increase at 50 km and a velocity decrease at 65 km depth the velocity decrease observed over an area of 5300 km2 gives evidence for local asthenospheric updoming and or a confined body of partial melt which might be the cause for high co2 mantle fluid flow and earthquake swarm activity in this recently nonvolcanic intracontinental rift area

detection of high frequency tensile vibrations of a fault during shear rupturing observations from the 2008 west bohemia swarm summary the analysis of 12 earthquakes of magnitudes between 1 7 and 3 7 that occurred in 2008 in west bohemia czech republic reveals that shear rupturing along a fault is accompanied by weak tensile vibrations of the fault the vibrations are of a narrow frequency band with frequencies distinctly higher than those of shear rupturing the tensile vibrations decay slowly in time and often resemble resonant waves they complicate the radiated p waveforms and the p wave radiation pattern the tensile vibrations can be observed in waveforms in directions near the nodal lines where the dominance of shear faulting radiation is lost the tensile vibrations are probably generated by opening of the fault during shear rupturing or by creating a wing tensile crack at the tip of the fault when shear fracturing stops

crustal structure at the easternmost termination of the variscan belt based on celebration 2000 and alp 2002 data abstract the eastern margin of the variscan belt in europe comprises plate boundaries between continental blocks and terranes formed during different tectonic events the crustal structure of that complicated area was studied using the data of the international refraction experiments celebration 2000 and alp 2002 the seismic data were acquired along sw ne oriented refraction and wide angle reflection profiles cel10 and alp04 starting in the eastern alps passing through the moravo silesian zone of the bohemian massif and the fore sudetic monocline and terminating in the tesz in poland the data were interpreted by seismic tomographic inversion and by 2 d trial and error forward modelling of the p waves velocity models determine different types of the crust mantle transition reflecting variable crustal thickness and delimiting contacts of tectonic units in depth in the alpine area few km thick lvz with the vp of 5 1 km s 1 dipping to the sw and outcropping at the surface represents the molasse and helvetic flysch sediments overthrust by the northern calcareous alps with higher velocities in the bohemian massif lower velocities in the range of 5 0 5 6 km s 1 down to a depth of 5 km might represent the se termination of the elbe fault zone the fore sudetic monocline and the tesz are covered by sediments with the velocities in the range of 3 6 5 5 km s 1 to the maximum depth of 15 km beneath the mid polish trough the moho in the eastern alps is dipping to the sw reaching the depth of 43 45 km the lower crust at the eastern margin of the bohemian massif is characterized by elevated velocities and high vp gradient which seems to be a characteristic feature of the moravo silesian slightly different properties in the moravian and silesian units might be attributed to varying distances of the profile from the moldanubian thrust front as well as a different type of contact of the brunia with the moldanubian and its northern root sector the moho beneath the fore sudetic monocline is the most pronounced and is interpreted as the first order discontinuity at a depth of 30 km

pressure and temperature perturbations within a squall line thunderstorm derived from sesame dual doppler data abstract some dynamic and thermodynamic properties of a convective cell within a squall line that occurred on 6 june 1979 were studied based on dual doppler observations the domain under investigation had a horizontal dimension of 27 km 27 km with 12 levels in the vertical the grid spacing used was 1 km vertical velocities were computed from the anelastic continuity equation by integrating downward with variational adjustment fields of deviation perturbation pressure density and virtual temperature were recovered from a three dimensional wind field using the thermodynamic retrieval method these retrieved fields were then subjected to internal consistency checks to determine the level of confidence our findings demonstrate that thermodynamic retrieval is feasible when random errors inherent in the radial wind components are minimized by proper smoothing errors in the computation of vertical velocity can be substantially reduced when a variational approach is used with the anelastic continuity equ

moho depth determination from waveforms of microearthquakes in the west bohemia vogtland swarm area 1 the west bohemia vogtland area is known for its increased geodynamic activity with reoccurrence of intraplate earthquake swarms previous geophysical studies namely active and passive seismic investigations revealed a high velocity lower crust in this area with increased reflectivity to refine this result and retrieve a more detailed structure of the deep crust and the moho discontinuity we analyzed waveforms of local microearthquakes that occurred in this area during the 2008 swarm the waveforms of earthquakes were grouped into clusters with similar focal mechanisms and the clusters were processed separately we developed a new multiazimuthal approach in data processing to increase resolution of moho phases in the waveforms we applied the waveform cross correlation of the p and s waves and rotated aligned and stacked the seismograms to extract the moho sms pmp and pms reflected converted phases these phases were inverted for laterally varying moho depth by ray tracing and a grid search inversion algorithm the model retrieved was verified using modeling of full waveforms computed by the discrete wave number method the multiazimuthal approach reveals details in the velocity structure of the crust mantle transition at each station instead of a single interface with a sharp velocity contrast the inversion indicates a reflective zone at moho depths with one or two strongly reflective interfaces which is in agreement with the zone interpreted by previous investigations the thickness of the zone varies from 2 to 4 km within the depth range of 27 31 5 km and is delimited by reflections from its top and bottom boundaries sometimes with strong reflectors within the zone the average vp vs ratio determined from the moho reflections and conversions is 1 73

structure and evolution of the 22 february 1993 toga coare squall line aircraft observations of precipitation circulation and surface energy fluxes abstract this study documents the precipitation and kinematic structure of a mature eastward propagating oceanic squall line system observed by instrumented aircraft during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare doppler radar and low level in situ observations are used to show the evolution of the convection from an initially linear nnw sse oriented convective line to a highly bow shaped structure with an embedded low to midlevel counterclockwise rotating vortex on its northern flank in addition to previously documented features of squall lines such as highly upshear tilted convection on its leading edge a channel of strong front to rear flow that ascended with height over a rear inflow that descended toward the convective line and a pronounced low level cold pool apparently fed from convective and mesoscale downdrafts from the convective line rearward the observations of this system showed distinct multiple maxima in updraft strength with

basalts water or shear zones in the lower continental crust abstract bright sub horizontal laterally extensive multi cyclic layered reflections have now been recorded in the lower continental crust from many areas in contrast this reflection signature is rare in the continental upper crystalline crust and upper mantle and in the oceanic lithosphere with the present state of knowledge it is sensible to seek a single quantitative explanation for all such layering qualitative explanations for lower crustal layering abound and include igneous metamorphic structural and fluid related models measurements of reflection coefficients from the lower crust place strong quantitative constraints on possible models structurally induced anisotropy metamorphic layering or free fluids cannot realistically produce sufficiently bright reflections igneous layering or the juxtaposition of pre existing heterogeneities by shear zones can produce strong reflections results from crustal xenoliths helium isotope ratios palaeo geothermal gradients and chemistry of flood basalts together with numerical modelling of lithospheric extension and asthenospheric melting suggest that underplating and intrusion of the lower crust with mantle derived mafic igneous rocks is common the apparent spatial relationship between lower crustal layering and continental extension and the strength and continuity of the reflections suggest that underplating related to extension and or elevated mantle temperatures is a good explanation for lower crustal layering

the refraction seismic experiment granu95 in the saxothuringian belt southeastern germany summary in this paper we present newly acquired high quality wide angle seismic data of the granu95 project and first models of the crustal structure along two profiles 95 a and 95 b beneath the saxonian granulites a major ellipse shaped exposure of lower crustal material within the mid european variscan belt in southeastern germany saxony the crust is subdivided into four layers the crystalline basement with velocities higher than 6 0 km s 1 is generally reached at shallow depths with three major sedimentary structures as prominent exceptions where velocities considerably lower than 6 0 km s 1 as low as 5 1 km s 1 reach as deep as 4 km the highest upper crustal velocities up to 6 5 km s 1 are not seen below the exposed granulites themselves but at shallow depths 4 km sw of the exposure these shallow high velocities correlate well in depth with highly reflective zones observed on three seismic reflection lines of dekorp 85 4n 95 01 95 02 at their intersection with the seismic refraction line 95 b where they appear as a set of nw se trending dome shaped reflections on profile 95 a this high velocity uppercrustal layer 6 3 km s 1 dips from 5 to 9 km beneath the se margin of the exposed granulites these results suggest that the granulite dome and its western continuation are widely underlain by a ne trending antiformal structure probably a sheet of metabasic rocks where the exposed felsic granulites form just a local cap on top below the upper crustal high velocities a layer with decreased velocity 6 2 6 25 km s 1 extends down to an average depth of 15 km along the variscan strike 95 b and to 11 16 km depth slightly dipping towards the se perpendicular to the terrane boundaries 95 a at mid crustal levels a weak reflection from a layer with a velocity of 6 4 6 6 km s 1 may indicate the classical conrad discontinuity at the depth range 22 24 km the velocity jumps to an average value of 7 0 km s 1 thus defining a prominent high velocity layer in the lower crust which may be viewed as the well known laminated lower crust typical of variscan structures but with higher average velocity than usually detected the crust mantle boundary at about 30 31 km is typical for western europe and confirms the extensional signature of the west european crust below the moho poorly constrained upper mantle velocities of about 7 9 8 0 km s 1 are derived the high velocities observed in the lower crustal layer would not exclude the possibility of mantlederived intrusions but the lack of any sign of an updoming moho favours the interpretation of a more passively driven extension

the influence of the shear induced pressure gradient on thunderstorm motion abstract in the present investigation we propose a simple theory to explain how a veering environmental wind shear vector can cause an initially symmetric updraft to grow preferentially to the right of the shear vector and acquire cyclonic rotation the explanation offered is based on linear theory which predicts that interaction of the mean shear with the updraft produces favorable vertical pressure gradients along its right flank to asses the validity of linear theory for large amplitude updrafts the three dimensional shallow anelastic equations are numerically integrated using a simple parameterization for latent heating within a cloud and the linear and nonlinear forcing terms are separately analyzed these results suggest that although the nonlinear effects strongly promote splitting of the updraft the linear forcing remains the dominant factor in preferentially enhancing updraft growth on the right flank we believe this differential forcing is a major contributor to the observed predominance o

non double couple earthquakes of 1997 january in west bohemia czech republic evidence of tensile faulting summary a mixed family of double couple dc and non double couple non dc earthquakes was observed during the 1997 january earthquake swarm in west bohemia which is a geothermal region typical for the occurrence of earthquakes swarms the dc and non dc earthquakes occurred within a small area of less than 1 km 3 on faults of different orientations the stress in the area is determined from focal mechanisms and attains values plunge azimuth 1 33 156 2 48 20 3 23 262 with a shape ratio of r 0 69 0 15 the error in the stress directions plunge azimuth is up to 5 10 the absolute stress values were estimated to be 1 350 mpa 2 220 mpa and 3 162 mpa the lithostatic stress is 250 mpa the stress analysis shows that the dc earthquakes occurred on optimally oriented faults with high shear traction but the non dc earthquakes occurred on misoriented faults with low shear traction the percentage of the dc in earthquakes clearly correlates with the magnitude of shear traction high low dc is associated with high low shear traction this indicates that the type of faulting is probably controlled by tectonic stress and that the non dc earthquakes are not related to pure shear faulting but may combine shear and tensile faulting the tensile faulting is manifested by positive isotropic and compensated linear vector dipole components the tensile faulting is conditioned by high pore fluid pressure which was estimated to be approximately 244 mpa the fluid pressure is less than the lithostatic stress by 5 mpa the ratio of the fluid pressure to the maximum compressive stress is 0 7

retrieved thermodynamic structure of a subtropical orographically influenced quasi stationary convective line airborne doppler radar and flight level measurements were used to document the three dimensional thermodynamic structure of a convective line that developed off the southeastern coast of taiwan on 16 june 1987 during the taiwan area mesoscale experiment during the period of aircraft observation the convective line appeared to be quasi stationary in a region 90 km away from the coast calculations of perturbation pressure and buoyancy retrieved from the doppler radar derived wind fields show that a high pressure perturbation associated with negative buoyancy existed in the region of heavy precipitation in the lowest level in low levels an elongated zone of low pressure was documented along the line which was closely related to the distributions of buoyancy these retrieved features are basically consistent with those calculated from in situ observations in mid to upper levels the high low pressure perturbation lay around the updraft cores on the upshear downshear of environmental shear the quantitative diagnosis for the perturbation pressure indicates that the positive buoyancy associated with the in cloud latent heat release as well as evaporative cooling occurring near cloud base and subcloud regions is crucial to determine the low level perturbation pressure distributions however dynamic forcing contributing to the pressure perturbation cannot be ignored in middle levels because of updraft shear interaction due to the presence of pronounced cross line wind shear and corresponding updrafts reaching maximum values near midtroposphere in distinct contrast to squall lines which are rapidly moving the near surface temperature gradient across this quasi stationary line was very weak and at low levels no gust front rear inflow or dynamically induced high pressure was evident near the leading edge of the line analyses presented here suggest that the persistent stationary convergence in association with the deceleration of low level southeasterly flow as it approached the nearshore blocked flow played an important role in maintaining and organizing the deep convection in this case

formative stage of a long lived mesoscale vortex observed by airborne doppler radar abstract the formative stage of a long lived mesoscale cyclonic vortex was captured by the noaa p 3 aircraft as it investigated a developing mesoscale convective system mcs near the southeastern coast of taiwan on 16 june 1987 during the taiwan area mesoscale experiment the supporting environment of the mesovortex was characterized by an exceptionally moist atmosphere and moderate ambient vertical shear through a deep layer from the near surface to 6 km with much weaker shear and winds aloft in addition a pronounced low level mesoscale shear convergence zone which resulted from the interaction of southeasterly flow with northeasterly flow confined to the near coast region existed in the vicinity of the observed mesovortex composite three dimensional wind fields derived via pseudo dual doppler synthesis show the vortex had a horizontal diameter expanding from 40 km to 70 km in the lower to midtroposphere respectively and exhibited considerable tilt through this layer contrary to previously d

west african squall line thermodynamic structure retrieved from dual doppler radar observations abstract pressure and temperature fields within a west african squall line retrieved from dual doppler radar data collected during the copt 81 convection profonde tropicale experiment are presented the method for derivation of thew results is approximately similar to that proposed by gal chen based on the anelastic equation of motion comparisons between pressure and temperature fields deduced from radar data at the lowest levels and surface network measurements show good agreement the inferred thermodynamic structure displays the influence of a low level frontward flow which is mainly due to a density current of cold air generated in the stratiform region of the squall line and resulting from a mesoscale downdraft this frontward flow contributes to initiate and maintain a frontal updraft through both nonhydrostatic pressure perturbation and temperature difference between entering air and colder frontward flow at higher altitudes mixing with the environment reduces buoyancy in the frontal updr

generation of new continental crust and terrane accretion in southeastern alaska and western british columbia constraints from p and s wave wide angle seismic data accrete abstract the accrete study addresses the question of continental assemblage in southeastern alaska and western british columbia through accretion of exotic terranes and generation of new crust by magmatic addition in a former continental arc we present results of wide angle p and s wave seismic interpretation of a 300 km long marine land seismic line across the contacts between accreted terranes and coast mountains additional constraints on the model are obtained from correlation with geologic mapping our results indicate that the coast shear zone csz is a nearly vertical fault zone probably related to a transpressive regime west of the csz the mid cretaceous 90 ma thrust belt is rooted in the deep crust and is truncated by the csz from the interpretation of the imaged sub vertical reflecting zones we infer the positions of the alexander wrangellia terrane boundary awb and of tertiary extensional grabens within dixon entrance near its intersection with the profile the observed values of vp and vp vs in the lower crust of the alexander terrane are similar to those of oceanic crust and distinctly different from the coast mountains batholith cmb to the northeast the crust under the cmb 32 km is thinner than the average continental crust and the moho is sharp 200 m and highly reflective the low velocity mantle 7 9 km s suggests high temperature consistent with the stability of garnet in mafic rocks in the lower crust the lower crustal velocity of 6 9 km s supports a lower crust composed of interlayered garnet pyroxene granulite and quartzofeldspathic restite related to batholith generation the crustal section under the cmb is seismically identical to the lower two thirds of normal crust heated and inflated by intrusions of tonalite and gabbro interlayered with restites from batholith generation and uplifted during exhumation

crustal anisotropy from local observations of shear wave splitting in west bohemia czech republic abstract the results of a systematic study of shear wave splitting observed in the three component digital seismograms of about 400 local microearthquakes that occurred during the 1985 1986 west bohemian earthquake swarm are presented two shear phases polarized nearly perpendicularly in horizontal projection were observed at all five stations of the local seismic network for most of the events the polarization of the faster shear wave is aligned in the wnw ese direction regardless of the mechanism and hypocenter location of the individual events and coincides with the direction of the maximum horizontal compressive tectonic stress in the region these effects are interpreted in terms of effective anisotropy of the upper crust in the region the maximum delay time between the split shear waves is 0 15 sec and corresponds to 6 anisotropy directional variation of the delay time was observed at the nearest station epicentral distance 5 km this variation was compared with functions predicted by theoretical models of cracked media to resolve which model is the most appropriate for crustal anisotropy surprisingly no agreement could be found for hudson9s model of dry or water filled parallel cracks that is widely used by many authors a successful fit was obtained for schoenberg douma9s model of a medium with parallel fractures the fracture normal pointed n31 e and the optimum fracture parameters were e n 0 4 and e t 0 02 the theoretically calculated fractures are aligned parallel to the tectonic stress direction and do not correspond to any real tectonic lines in the region

upper mantle beneath the eger rift central europe plume or asthenosphere upwelling summary we present the first results of a high resolution teleseismic traveltime tomography and seismic anisotropy study of the lithosphere asthenosphere system beneath the western bohemian massif the initial high resolution tomography down to a depth of 250 km did not image any columnar low velocity anomaly which could be interpreted as a mantle plume anticipated beneath the eger rift similar to recent findings of small plumes beneath the french massif central and the eifel in germany alternatively we interpret the broad low velocity anomaly beneath the eger rift by an upwelling of the lithosphere asthenosphere transition we also map lateral variations of seismic anisotropy of the mantle lithosphere from spatial variations of p wave delay times and the shear wave splitting three major domains characterised by different orientations of seismic anisotropy correspond to the major tectonic units saxothuringian moldanubian and the tepla barrandian and their fabrics fit to those found in our previous studies of mantle anisotropy on large european scales

seismic and geological structure of the crust in the transition from baltica to palaeozoic europe in se poland celebration 2000 experiment profile cel02 abstract the celebration 2000 together with the earlier polonaise 97 deep seismic sounding experiments was aimed at the recognition of crustal structure in the border zone between the precambrian east european craton baltica and palaeozoic europe the cel02 profile of the celebration family is a 400 km long sw ne transect running in poland from the upper silesia block usb across the malopolska block mb and the trans european suture zone tesz to the east european craton eec the structure along cel02 was interpreted using both 2d tomography and forward ray tracing techniques as well as 2d gravity modelling the crustal thickness along cel02 varies from 32 35 km in the usb to 45 47 km beneath the tesz and the eec the usb is a clearly distinctive crustal block with the characteristic high velocity lower crust 7 1 7 2 km s interpreted as a fragment of gondwana the krakow lubliniec fault is a terrane boundary produced by soft docking of the usb with the mb the malopolska crust fundamentally differs from the usb and has a strong connection with baltica it is a transitional 150 to 200 km wide unit composed of the extended baltican lower crust and the overlying low velocity 5 15 5 9 km s neoproterozoic metasediments in the up to 18 km thick upper crust the ysogory unit has its crustal structure identical with that of malopolska thus it is connected with baltica and cannot be interpreted as a gondwana derived terrane higher velocity and density bodies found below the mazovia lublin graben at a depth of 12 km and at the base of the lower crust might be a result of mantle derived mafic intrusions accompanying the extension of baltica by the preliminary 2d gravity modelling we have reconfirmed the need for considering the increased tesz mantle density in comparison to the eec and usb mantle