interactions between the ebb tidal delta and landward shoreline price inlet south carolina abstract patterns of erosion and deposition along the shoreline of price inlet south carolina are strongly influenced by ebb tidal delta processes the ebb delta goes through cycles of growth and decay 15 20 change in volume which last from 4 to 7 years in the growth phase large intertidal bar complexes are formed on both sides of the main ebb channel by the coalescence of landward migrating swash bars during this stage waves refracting around the southern bar complex produce a reversal in the longshore transport direction on the downdrift shoreline this results in little sediment escaping the inlet and delta system the sand trapping mechanism ceases and the delta reduces in volume when the bar complexes migrate onshore and attach to the beach the inlet shoreline also goes through cycles of 7 to 42 years duration in which its offset configuration changes the shift in shoreline alignment is controlled by the orientation of the main ebb channel and the resulting ebb tidal delta morphology when the inlet has a downdrift offset configuration the ebb tidal delta is skewed along the updrift shoreline in this position bar complexes preferentially accrete along the updrift beach causing a progradation of the shoreline at the same time the downdrift shoreline erodes due to little sediment bypassing the inlet this pattern of sedimentation eventually produces an updrift offset inlet the erosional depositional processes are reversed when the ebb flow in the channel thalweg is deflected off the prograding updrift inlet shore ine this causes a clockwise rotation of the main ebb channel and a shift in the ebb delta to a position along the downdrift shoreline in this configuration the updrift shoreline erodes and the downdrift shoreline accretes this study documents the close relationship that exists at price inlet south carolina between the ebb tidal delta and landward shoreline evidence is presented to show that this relationship may hold for other mixed energy tidal inlets as well

meso scale transfer of sand during and after storms implications for prediction of shoreline movement abstract monitoring beach volume changes of the texas coast following a major hurricane reveals the impact of storms on sand dispersal and shoreline movement at spatial and temporal scales encompassing tens of kilometers and decades beach volume histories at profile sites show the interdependence of sand exchange among adjacent sites and the spatial autocorrelation of sand movement beach volume histories also indicate periods when either longshore or cross shore transport predominate and illustrate the long term effects of coastal structures on beach mobility this study confirms that net losses of sand from updrift barriers may not be directly linked with net gains of sand on adjacent downdrift barriers instead sand dispersal within a coastal compartment may depend partly on the dynamics of shoals and temporary sand storage at the intervening tidal inlet in our study sand eroded from the updrift barrier galveston island is deposited in a terminal sand flat of the barrier whereas sand accreted to the downdrift barrier follets island is derived from the intermediate ebb tidal delta san luis pass unlike continuous sand bypassing on some microtidal wave dominated coasts sand bypassing at san luis pass is episodic event driven and inefficient and sand is not transferred directly from one barrier to the next p because storms rapidly redistribute beach sediment they can be the most important factor controlling short term

observations and fine grid simulations of a convective outbreak in northeastern spain importance of diurnal forcing and convective cold pools the life cycle and interactions of a series of convective systems that developed in northeastern spain during the afternoon of 7 august 1996 are examined based on remote sensing products surface observations and numerical simulations most of the convection was organized in two mesoscale convective systems mcss and a line of storms attached to the pyrenees mountains one of these storms produced rainfalls in excess of 200 mm in 3 h and severe flash floods in the biescas area the end of the convection in the biescas area occurred after merger of the storm with one of the mcss that approached from the southwest a high resolution 4 km grid length simulation of the event reproduces the observed timing and interactions of the convective systems as well as the general rainfall pattern the highly localized rainfall core at biescas is well located although the peak rainfall amount is underestimated the success of the model at triggering the convection at the proper locations and time results from a reasonably accurate prediction of mesoscale features of the low level flow pattern such as a thermal mesolow in the ebro valley deformation zone upslope wind systems and the pushing of a cold front in the upper portion of the valley after the onset of the initial convection the role of the convectively induced cold pools and outflows for the propagation of the convective systems is shown to be very important in particular the mcs interacting with the biescas convection was driven by strong mesoscale ascent established between the convectively induced outflows the upvalley southeasterly winds sustained by the mesolow and the downvalley northwesterly winds associated with the cold front after the interaction the convection in biescas ceased because of the interruption of the southerly upslope flow caused by the convective cold pools finally the explosive character of convection after noon and its initial focusing in uplands and slopes suggest that diurnal forcing could have played a decisive role this idea is validated by means of simulations

the influence of alongshore and cross shore wave energy flux on large and small scale coastal erosion patterns a strong low pressure system traveled along the japanese main island honshu in october 2006 high waves and storm surge attacked the kashima coast resulting in huge erosion over the area airborne laser data measured in october 2005 and november 2006 were analyzed to estimate cross sectional changes within the subaerial zone the results of the alongshore distribution of the changes of cross sectional area indicate that the amount of erosion of the 38 km long northern and 15 km long southern parts decreased toward the south in each part and that the amount of erosion was smaller in protected areas with artificial headlands than in unprotected areas the local alongshore variation of the erosion and accretion patterns showed wavy fluctuations of several hundreds of meters the total amounts of the estimated eroded volume of the subaerial zone over the northern and southern parts were 620 000 m3 and 600 000 m3 respectively the simulating waves nearshore swan wave model was applied to estimate wave conditions along the coast during the storm the computational results were verified and then the alongshore distribution of wave energies expressed as the alongshore and cross shore components of the wave energy flux was compared with the alongshore distribution of cross sectional change the results show that the distribution of energy flux explains the distribution of erosion well the alongshore variability in the cross shore energy flux is responsible for the large scale variability in erosion and shorter scale variability is due to gradients in the alongshore energy fluxes especially for the areas without coastal works copyright 2011 john wiley sons ltd

seabed texture and composition changes offshore of port royal sound south carolina before and after the dredging for beach nourishment abstract beach nourishment has been a strategy widely used to slow down coastal erosion in many beaches around the world the dredging of sand at the borrow site however can have complicated physical geological and ecological impacts our current knowledge is insufficient to make accurate predictions of sediment infilling in many dredging pits due to lack of detailed sediment data two sites in the sandy shoal southeast of port royal sound prs of south carolina usa were sampled 8 times from april 2010 to march 2013 one site defined as borrow site was 2 km offshore and used as the dredging site for beach nourishment of nearby hilton head island in beaufort county south carolina and the other site defined as reference site was 10 km offshore and not directly impacted by the dredging a total of 184 surficial sediment samples were collected randomly at two sites during 8 sampling periods most sediments were fine sand with an average grain size of 2 3 phi and an organic matter content less than 2 after the dredging in december 2011 january 2012 sediments at the borrow site became finer changing from 1 0 phi to 2 3 phi and carbonate content decreased from 10 to 4 changes in mud content and organic matter were small compared with the reference site the borrow site experienced larger variations in mud and carbonate content an additional 228 sub samples were gathered from small cores collected at 5 fixed stations in the borrow site and 1 fixed station at the reference site 0 3 6 9 and 12 months after the dredging these down core sub samples were divided into 1 cm slices and analyzed using a laser diffraction particle size analyzer most cores were uniform vertically and consisted of fine sand with well to moderately well sorting and nearly symmetrical averaged skewness based on the analysis of grain size populations 2 phi and 3 phi sized sediments were the most dynamic sand fractions in prs mud deposition on shoals offshore of prs presumably happens when offshore mud transport is prevalent and there is a following rapid sand accumulation to bury the mud however in this borrow site there was very little accumulation of mud this will allow the site to be used in future nourishment projects presuming no accumulation of mud occurs in the future

hurricane associated ebb tidal delta sediment dynamics bathymetric surveys conducted before and after the 2005 hurricane season at little pass timbalier in the mississippi river delta plain united states demonstrate that 9 1 2 4 10 6 m 3 of sediment was eroded from a 47 9 km 2 area between the two surveys hurricanes cindy katrina and rita passed within 300 km of the tidal inlet comparison of before and after bathymetric data sets shows that the distal portion of the ebb tidal delta etd was the site of 63 of the total erosion locally resulting in 400 m of shoreface retreat shoaling 0 75 1 0 m in the seawardmost portion of the ebb channel and erosion in the landward portion 1 5 m resulted in a 160 m landward shift of the inlet throat collectively these processes forced the landward migration of the entire tidal inlet and etd system there has been considerable discussion about large volumes of mineral sediment deposited on the mississippi river delta plain interior marsh surface as a result of hurricanes however the origin of this sediment is unknown we identify the distal portion of an etd as one possible sediment source and hypothesize that etd and shoreface sediment is mobilized by hurricane waves and transported landward by surge induced currents our results emphasize the role of frequent and intense hurricanes in long term coastal evolution and as a mechanism for regional sediment retention within the transgressive system beyond typical barrier overwash processes

pedogenic calcite as evidence for an early holocene dry period in the san francisco bay area california rainfall at the site of union city california during early holocene time appears to have been about half that of today 470 mm yr we base this conclusion on detailed descriptions and particle size analyses of 12 soil profiles and 1 20 scale logs of the fluvial stratigraphy in two 100 m long 5 m deep excavations dug perpendicular to the axis of an alluvial fan along the hayward fault subsidence and right lateral movement along the fault allowed an offset stream to produce a nearly continuous alluvial record documented by 35 14 c ages on detrital charcoal bk calcitic horizons in paleosols developed in the fan suggest that a relatively dry climatic period occurred from 10 to 7 ka calendar corrected ages the pedogenic calcite exists primarily as vertically oriented filaments and fine cavernous nodules formed at ped intersections soils and paleosols formed before 10 ka or since 7 ka did not have bk horizons bk horizons that were buried suddenly at 7 ka were overlain by leached zones averaging 41 3 cm thick about half the current depth of leaching

genesis of typhoon chanchu 2006 from a westerly wind burst associated with the mjo part ii roles of deep convection in tropical transition abstractin this study the life cycles of a series of four major mesoscale convective systems mcss during genesis and their roles in transforming a vertically tilted vortex associated with a westerly wind burst hereafter the wwb vortex into typhoon chanchu 2006 are examined using 11 day cloud resolving simulations presented in part i it is found that the tilted wwb vortex at early stages is characterized by an elevated cold core layer about 200 hpa thick below and a weak warm column above with large vertical wind shear across the layer which extends over a horizontal distance of about 450 km between the vortex s 400 and 900 hpa centers during the final two days of the genesis process the upper level warm column increases in depth and intensity as a result of the absorption of convectively generated vortices cgvs including a mesoscale convective vortex mcv causing more rapid amplification of cyclonic vorticity in the middle than the lower troposphere the commencement of sustained intens

multiscale convective overturning in mesoscale convective systems reconciling observations simulations and theory abstract an analysis of how parameterized convection interacts with hydrostatic explicitly resolved precipitation processes to represent multiscale convective overturning in a mesoscale resolution numerical simulation is presented critically important ingredients of the successful simulation are identified and the degree to which simulations are consistent with observations and theoretical considerations is examined of particular concern is how convective parameterization routines reconcile the deep moist absolutely unstable structures that form in mesoscale convective systems it is found that these structures arise primarily from resolvable scale vertical motion and that the model responds to these structures not only by maintaining parameterized convection but also by developing a hydrostatic manifestation of convective overturning on its smallest resolvable horizontal scales the strongest and most distinctive mesoscale perturbations develop in regions where the mesoscale contribution to convectiv

initiation and organizational modes of an extreme rain producing mesoscale convective system along a mei yu front in east china abstractthe initiation and organization of a quasi linear extreme rain producing mesoscale convective system mcs along a mei yu front in east china during the midnight to morning hours of 8 july 2007 are studied using high resolution surface observations and radar reflectivity and a 24 h convection permitting simulation with the nested grid spacing of 1 11 km both the observations and the simulation reveal that the quasi linear mcs forms through continuous convective initiation and organization into west east oriented rainbands with life spans of about 4 10 h and their subsequent southeastward propagation results show that the early convective initiation at the western end of the mcs results from moist southwesterly monsoonal flows ascending cold domes left behind by convective activity that develops during the previous afternoon to evening hours suggesting a possible linkage between the early morning and late afternoon peaks of the mei yu rainfall two scales of convective organization are found d

late holocene slip rate and recurrence of great earthquakes on the san andreas fault in northern california the slip rate of the san andreas fault 45 km north of san francisco at olema california is determined by matching offset segments of a buried late holocene stream channel stream deposits from 1 800 plus minus 78 yr b p are offset 42 5 plus minus 3 5 m across the active 1906 fault trace for a minimum late holocene slip rate of 24 plus minus 3 mm yr when local maximum coseismic displacements of 4 9 to 5 5 m from the 1906 earthquake are considered with this slip rate the recurrence of 1906 type earthquakes on the north coast segment of the san andreas fault falls within the interval of 221 plus minus 40 yr both comparable coseismic slip in 1906 and similar late holocene geologic slip rates at the olema site and a site 145 km northwest at point arena prentice 1989 suggest that the north coast segment behaves as a coherent rupture unit

present tectonic motion across the coast ranges and san andreas fault system in central california geodetic results from very long baseline interferometry vlbi satellite laser ranging slr and the global positioning system gps are used to estimate angular velocities between the sierran microplate pacific plate and north american plate the sierra pacific pole of rotation lies nearer to the san andreas fault than does the pacific north america pole of rotation and leads to different tectonic implications than if the latter is used the angular velocities show that the san andreas fault system and central california coast ranges accommodate motion of 39 2 mm yr mainly by strike slip faulting all confidence limits following signs in this paper are 95 confidence limits fault normal motion is small is mainly convergent at rates up to 3 3 1 0 mm yr and varies along the coast but is divergent at 2 6 1 2 mm yr across san pablo bay and associated topographic lows across which the sierran and central valley watershed drains to the pacific ocean the mountain ranges tend to be larger where the fault normal convergence rates are larger the low convergence rate 0 5 1 8 mm yr normal to the san andreas fault in the carrizo plain differs sharply from that previously inferred 8 2 1 2 mm yr and 4 9 1 6 mm yr by feigl et al 1993 the difference is due to differences between their and our elastic strain accumulation models and between how their and our pacific plate reference frames are defined the ranges in most places require a minimum of 4 2 1 m y of fault normal convergence at the present rate to attain their present cross sectional area if erosion is neglected more if it is not the amount of convergence previously estimated from a balanced cross section across the diablo range in central california requires 10 8 3 m y of convergence at the present rate the former is consistent with widely held views about the onset of the coast range orogeny but the latter is not both are consistent however with the recent plate reconstructions by s cande j stock and colleagues which indicate that pacific plate motion relative to north america changed to a more convergent direction 20 25 clockwise of its prior direction at ca 8 to 6 ma and not at 3 5 ma as had been previously inferred the inferred change in direction of plate motion is large compared with the present angle of convergence across the straight and narrow segment of the san andreas fault of 0 7 4 7 from which we infer that the sierran microplate changed motion relative to north america at the same time ca 8 to 6 ma as did the pacific plate we further infer that the motion accommodated across the great basin must also have changed at the same time we also examine the hypothesis that stable sliding occurs along the san andreas fault and other northwest striking strike slip faults in central california where the fault normal convergence rate is low or negative and that these faults are unstable where the fault normal convergence rate is high such a relationship appears to hold in general but fails in detail in particular there are substantial sections of fault with small inferred rates of fault normal convergence across which the san andreas fault is locked moreover the creeping section of the san andreas fault i e the section between parkfield and the calaveras junction is the locus of greater fault normal convergence 3 2 1 4 mm yr than is the locked part of the fault 0 5 1 8 mm yr south of parkfield thus this hypothesis is at best a partial explanation for the observed distribution of locked and nonlocked sections of the fault

resolution of fault slip along the 470 km long rupture of the great 1906 san francisco earthquake and its implications data from all available triangulation networks affected by the 1906 earthquake have been combined to assess the trade off between slip resolution and its uncertainty and to construct a conservative image of coseismic slip along the rupture because of varying network aperture and station density slip resolution is very uneven although slip is determined within uncertainties of 1 0 m along 60 of the fault constraints are poor on the remaining mostly offshore portions of the rupture slip decreases from maxima of 8 6 and 7 5 m at shelter cove and tomales bay to 4 5 m near mount tamalpais and 2 7 m at loma prieta the geodetically derived slip distribution is in poor agreement with estimates based on analysis of s wave seismograms probably because these waves register only 20 30 of the total seismic moment obtained from longer period surface waves consideration of a range of fault geometries for 1906 slip near loma prieta indicates right lateral motions lie between 2 3 and 3 1 m these values are considerably greater than the 1 5 m of measured surface slip on which several assessments of high earthquake hazard for this fault segment were based this factor along with the absence of 1989 slippage where 1906 surface slip was used to make the forecasts casts doubt on some claims of success in predicting the 1989 m 6 9 loma prieta earthquake

interaction of an upper tropospheric jet with a squall line originating along a cold frontal boundary abstracton 8 june 2003 an expansive squall line along a surface cold frontal boundary was sampled during the bow echo and mesoscale convective vortex experiment the naval research laboratory p 3 aircraft and the national oceanic and atmospheric administration p 3 aircraft simultaneously sampled the leading and trailing edge of this squall line respectively with x band doppler radars data from these two airborne radar systems have been synthesized to produce a pseudo quad doppler analysis of the squall line yielding a detailed three dimensional kinematic analysis of its structure a simulation of the squall line was carried out using the weather research and forecasting model to complement the pseudo quad doppler analysis the simulation employed a 3 km convection allowing nested domain centered over the pseudo quad doppler domain along with a 9 km parent domain to capture the larger synoptic scale cyclone the pseudo quad doppler analysis reveals that the convective line was embedded within the up

subkilometer simulation of a torrential rain producing mesoscale convective system in east china part i model verification and convective organization abstracta nocturnal torrential rain producing mesoscale convective system mcs occurring during the mei yu season of july 2003 in east china is studied using conventional observations surface mesoanalysis satellite and radar data and a 24 h multinested model simulation with the finest grid spacing of 444 m observational analyses reveal the presence of several larger scale conditions that were favorable for the development of the mcs including mei yu frontal lifting moderate cold advection aloft and a moist monsoonal flow below and an elongated old cold dome left behind by a previously dissipated mcs results show that the model could reproduce the evolution of the dissipating mcs and its associated cold outflows the triggering of three separate convective storms over the remnant cold dome and the subsequent organization into a large mcs and the convective generation of an intense surface meso high and meso scale radar reflectivity morphologies in particular the model reproduces the passage of

the vertical vorticity structure within a squall line observed during bamex banded vorticity features and the evolution of a bowing segment abstracta quasi linear convective line with a trailing stratiform region developed during the bow echo and mesoscale convective vortex experiment bamex while being sampled by two airborne doppler radars the finescale reflectivity and doppler velocities recorded by the radars documented the evolution of the convective line bands of positive and negative vertical vorticity oriented parallel to the convective line were resolved in the analysis this type of structure has rarely been reported in the literature and appears to be a result of the tilting and subsequent stretching of ambient horizontal vorticity produced by the low level wind shear vector with a significant along line component the radar analysis also documented the evolution of an embedded bow echo within the convective line embedded bow echoes have been documented for a number of years however a detailed analysis of their kinematic structure has not been previously reported in the literature the counterrotating circulation patterns tha

sea level rise and coastal marsh sustainability geological and ecological factors in the mississippi delta plain chronostratigraphic approaches to coastal geomorphology frequently include consideration of salt marsh deposits as indicators of past sea level positions continuous horizons of such deposits can be used to infer that salt marshes were keeping pace with local rates of relative sea level rise rslr rates of past accumulation estimated using dating techniques are then used to hindcast the rate of sea level rise in that area estimates of contemporary sea level rise rates are often derived from tide gauge records this approach allows identification of subdecadal variations in mean water level accumulation rates of both organic and inorganic sediments can also be derived at these time scales and studies from many coastal marshes demonstrate the episodic nature of inorganic sediment deposition the frequency and spacing of these events does not necessarily coincide with periods of increased local sea level in addition short term increases in sea level could result in marsh deterioration as soils become excessively waterlogged a conceptual model of changes in geomorphic and ecological processes contributing to marsh sustainability during the holocene has been developed for the mississippi delta plain mdp the survival of some marshes in this area despite high rates of subsidence indicates that the combined effect of organic and inorganic accumulation processes can be adequate to sustain coastal marshes in the face of sea level rise

do storms cause long term beach erosion along the u s east barrier coast abstract in a few hours or days scores of meters of beach width can be lost due to a severe storm however newly available shoreline data from the u s east coast show that beaches recover after storms to positions consistent with their long term 100 yr trend even the largest storms such as the ash wednesday storm of 1962 considered to be the most damaging in the twentieth century appear to have had little effect on the long term trend the gradual recession of beaches along the u s east coast is mainly controlled by other factors such as sea level rise and variations of sediment supply therefore it follows that barrier beaches in a coastal plain setting would not experience long term erosion in response to storm impact if the sea were to stop rising and sediment supply did not change

kinematics of the pacific north america plate boundary zone northern california we measured motions of 54 sites in an east west transect across northern california at 38 40 north by global positioning system gps observations over a 4 year we estimate the total slip rate on the san andreas fault system to be 39 6 0 6 1 5 mm yr 68 6 upper and lower confidence intervals from a nonlinear inversion are indicated by superscripts and subscripts slip rates on the individual faults are determined less precisely due to the high correlations between the estimated parameters our best fitting model fits the fault parallel velocities with a mean square error of 1 04 and the following estimated fault slip rates all in mm yr san andreas 17 4 3 1 2 5 ma acama 13 9 2 8 4 1 and bartlett springs 8 2 1 9 2 1 the data are fit best by models in which the san andreas fault is locked to 14 9 7 1 12 5 km the ma acama fault locked to 13 4 4 8 7 4 km except for shallow creep in the upper 5 km and the bartlett springs fault creeping at all depths the ma acama fault most likely poses a significant seismic hazard as it has a high slip rate and has accumulated a slip deficit large enough to generate a magnitude 7 earthquake we find little evidence for contraction across coast ranges except at western edge of great valley where 1 3 mm yr of shortening is permitted by the data no strain is observed within the great valley or sierra nevada except that associated with right lateral strike slip on the san andreas fault system this is consistent with models of the pacific north america plate boundary zone in which the relative plate motion is partitioned into two domains one strike slip and one dominantly extensional separated by the elastically deforming sierra nevada great valley block

the generation and preservation of multiple hurricane beds in the northern gulf of mexico abstract cores collected from mississippi sound and the inner shelf of the northeast gulf of mexico have been examined using 210 pb and 137 cs geochronology x radiography granulometry and a multi sensor core logger the results indicate that widespread event layers were probably produced by an unnamed hurricane in 1947 and by hurricane camille in 1969 physical and biological post depositional processes have reworked the event layers producing regional discontinuities and localized truncation and resulting in an imperfect and biased record of sedimentary processes during the storms the oceanographic and sedimentological processes that produced these event beds have been simulated using a suite of numerical models 1 a parametric cyclone wind model 2 the swan third generation wave model 3 the adcirc 2d finite element hydrodynamic model 4 the princeton ocean model 5 a coupled wave current bottom boundary layer sedimentation model and 6 a model for bed preservation potential as a function of burial rate and bioturbation rate simulated cores from the mississippi sound region are consistent with the observed stratigraphy and geochronology on both the landward and seaward sides of the barrier islands

late quaternary deformation and slip rates in the northern san andreas fault zone at olema valley marin county california abstract quaternary sedimentary deposits along the structural depression of the san andreas fault saf zone north of san francisco in marin county provide an excellent record of rates and styles of neotectonic deformation in a location near where the greatest amount of horizontal offset was measured after the great 1906 san francisco earthquake a high resolution gravity survey in the olema valley was used to determine the depth to bedrock and the thickness of sediment fill along and across the saf valley in the gravity profile across the saf zone quaternary deposits are offset across the 1906 fault trace and truncated by the western and eastern boundary faults whose youthful activity was previously unknown the gravity profile parallel to the fault valley shows a basement surface that slopes northward toward an area of present day subsidence near the head of tomales bay surface and subsurface investigations of the late pleistocene olema creek formation qoc indicate that this area of subsidence was located further south during deposition of the qoc and that it has migrated northward since then localized subsidence has been replaced by localized contraction that has produced folding and uplift of the qoc this apparent alternation between transtension and transpression may be the result of a northward diverging fault geometry of fault strands that includes the valley bounding faults as well as the 1906 saf trace the vedanta marsh is a smaller example of localized subsidence in the fault zone between the 1906 saf trace and the western boundary fault analyses of holocene marsh sediments in cores and a paleoseismic trench indicate thickening and probably tilting toward the 1906 trace consistent with coseismic deformation observed at the site following the 1906 earthquake new age data and offset sedimentary and geomorphic features were used to calculate four late quaternary slip rate estimates for the saf at this latitude luminescence dates of 112 186 ka for the middle part of the olema creek formation qoc the oldest quaternary deposit in this part of the valley suggest a late pleistocene slip rate of 17 35 mm year which replaces the unit to a position adjacent to its sediment source area a younger alluvial fan deposit qqf basal age 30 ka is exposed in a quarry along the medial ridge of the fault valley this fan deposit has been truncated on its western side by dextral saf movement and west side down vertical movement that has created the vedanta marsh paleocurrent measurements clast compositions sediment facies distributions and soil characteristics show that the bear valley creek drainage now located northwest of the site supplied sediment to the fan which is now being eroded restoration of the drainage to its previous location provides an estimated slip rate of 25 mm year furthermore the bear valley creek drainage probably created a water gap located north of the qqf deposit during the last glacial maximum 18 ka the amount of offset between the drainage and the water gap yields an average slip rate of 21 30 mm year finally displacement of a 1000 year old debris lobe approximately 20 m from its hillside hollow along the medial ridge indicates a minimum late holocene slip rate of 21 25 mm year similarity of the late pleistocene rates to the holocene slip rate and to previous rates obtained in paleoseismic trenches in the area indicates that the rates may not have changed over the past 30 ka and perhaps the past 200 400 ka stratigraphic and structural observations also indicate that valley bounding faults were active in the late pleistocene and suggest the need for further study to evaluate their continued seismic potential

balanced and unbalanced circulations in a primitive equation simulation of a midlatitude mcc part i the numerical simulation abstract a midlatitude mesoscale convective complex mcc which occurred over the central united states on 23 24 june 1985 was simulated using the regional atmospheric modeling system rams the multiply nested grid simulation agreed reasonably well with surface upper air and satellite observations and ground based radar plots the simulated mcc had a typical structure consisting of a leading line of vigorous convection and a trailing region of less intense stratiform rainfall several other characteristic mcc circulations were also simulated a divergent cold pool in the lower troposphere midlevel convergence coupled with a relatively cool descending rear inflow jet and relatively warm updraft structure and a cold divergent anticyclone in the tropopause region early in the mcc simulation a mesoscale convectively induced vortex mcv formed on the eastern edge of the convective line while frequently associated with mccs and other mesoscale convective systems mcss mcvs are more typically repo

the role of momentum transport in the motion of a quasi idealized mesoscale convective system abstract momentum transport is examined in a simulated midlatitude mesoscale convective system mcs to investigate its contribution to mcs motion momentum budgets are computed using model output to quantify the role of specific processes in determining the low level wind field in the system s surface based cold pool results show that toward the leading convective line of the mcs and near the leading edge of the cold pool the momentum field is most strongly determined by the vertical advection of the storm induced perturbation wind across the middle rear of the system the wind field is largely a product of the pressure gradient acceleration and to a lesser extent the vertical advection of the background environmental i e base state wind the relative magnitudes of the vertical advection terms in an eulerian momentum budget suggest that for gust front driven systems downward momentum transport by the mcs is a significant driver of mcs motion and potentially severe surface winds results furthe

numerical simulation of an intense squall line during 10 11 june 1985 pre storm part i model verification abstract a 24 h nested grid simulation of an intense squall line during the 1985 pre storm experiment is presented using an improved version of the pennsylvania state university national center for atmospheric research three dimensional mesoscale model although the model is initialized at 1200 utc 10 june 1985 with conventional meteorological observations it reproduces remarkably well many observed meso scale features that are analyzed from the high resolution network data these include 1 the generation of two areas of deep convection at the model initial time 2 the timing of the initiation of the squall line along a surface front 9 h into the model integration 3 the development of several convective bands at 2100 utc 4 the rapid intensification and rapid dissipation processes of the squall line as it entered and moved out of the network respectively 5 the generation of a presquall mesolow a squall induced mesohigh and a wake low as well as corresponding multiple surface convergence diverg