holocene evolution of seasonal stratification in the celtic sea refined age model mixing depths and foraminiferal stratigraphy published stable isotopic oxygen carbon and preliminary foraminiferal data from a holocene vibrocore from the celtic sea northwest european continental shelf have been interpreted in terms of the progressive replacement of tidally mixed by seasonally stratified water the first study of the long term dynamics of seasonal stratification this study was hampered by poor age control and the foraminiferal data were based on processing with a 125 m sieve which has been shown not to recover critical small taxa we present here a new age model for this vibrocore bgs 51 07 199 based on 12 accelerator mass spectrometry 14c dates on foraminifera and molluscs radionuclide 137cs 40k profiles from the vibrocore and juxtaposed multicores and a complete foraminiferal stratigraphy based on sieving at 63 m together the three datasets enable a mixing model to be proposed which clarifies the resolution of the record which is confirmed as extending from the late glacial to the late holocene correction for autocompaction reveals an increase in sedimentation rate and mixing depth from the early to the late holocene a temporary increase in sedimentation rate at 6650 yr cal bp is attributed to migration of the productive frontal zone across the core site some time after 3000 yr cal bp sedimentation either slowed abruptly or ceased completely giving the modern mixed layer an apparent age of 3000 yr cal bp the mixed layer depth indicates strongly that the apparent transition to stratification during the early holocene is primarily a threshold change attenuated by bioturbation secondary attentuation is related to reworking the mixed layer model adopted suggests that this isotopic transition occured between 8990 and 8440 yr cal bp 8720 2 the foraminiferal analyses in the light of modern foraminiferal distributional data support the inference that the succession can be interpreted as a response to the progressive seasonal stratification of the celtic sea during the holocene the data highlight the value of key taxa as indicators of shelf palaeostratification in the geological record notably of textularia bocki and stainforthia fusiformis as mixed frontal and frontal stratified indicators respectively the critical change to this frontal assemblage occurs at the same depth as the isotopic threshold based on the mixing model these data affirm the earlier interpretation of the isotopic record as registering bottom water temperature and water column productivity changes driven by the evolution of seasonal stratification the clear association between grain size and sedimentation as well as these isotopic and faunal data indicates that the shelf record of highstand sedimentation is preferentially biased towards the preservation of sequences deposited under seasonally stratified rather than mixed water masses

erratum to observation and prediction of dynamic ground strains tilts and torsions caused by the mw 6 0 2004 parkfield california earthquake and aftershocks derived from upsar array observations online material corrected figures and strain rotation and displacement gradient time series

toward understanding subtle instrumentation effects associated with weak seismic events in the near field abstract broadband observations of small earthquakes at short epicentral distances reveal a mixture of near field effects and instrumental artifacts we investigated these phenomena at a station equipped with an sts 2 and cmg 40t sensor situated almost above shallow m 3 0 to 3 8 events peak ground acceleration 2 10 1 m sec 2 the horizontal components were systematically accompanied by tiltlike disturbances and the tilt obtained from the sts 2 records exceeded more than 10 times the values predicted by the source model we also observed a so far uncommonly recognized type of disturbance whose shape is the first derivative of the tiltlike disturbance the most likely explanation seems to be clipping of high frequency signal peaks within the sensor system a computational model of a broadband feedback velocimeter as a linear dynamic system with saturation proved this interpretation on a qualitative level generally any asymmetry in the transfer of high frequencies in the feedback velocimeter would produce a long period disturbance of this type users of near fault broadband velocigrams may numerically simulate the disturbances without any knowledge of their physical nature and subtract them from the records the decontaminated records still may have a strange bow shaped form related to the near field ramp and the static displacement of the order of 1 10 5 m in this article the effects studied in this article seem to have a general character for apparently any feedback controlled broadband velocimeter

research aircraft observations and numerical simulations of a warm front approaching vancouver island abstract the mesoscale structure of the low level flow and the character of the turbulence are investigated for a warm front as it approached the prominent terrain of the pacific northwest in the vicinity of vancouver island flight level and airborne doppler radar measurements collected from a national oceanic and atmospheric administration p 3 research aircraft on 9 december 1995 during the coastal observation and simulation with topography experiment and high resolution numerical simulations performed with the naval research laboratory s nonhydrostatic coupled ocean atmosphere mesoscale prediction system coamps model have been used to document the warm front as it approached the coast and the structure of cool air trapped along vancouver island this air mass was capped by a flat thin transition zone of enhanced static stability and vertical wind shear the flow within the trapped air mass was oriented parallel to the terrain of vancouver island but appears to have been more an outflow from the s

observation and prediction of dynamic ground strains tilts and torsions caused by the mw 6 0 2004 parkfield california earthquake and aftershocks derived from upsar array observationsdynamic ground strains tilts and torsions caused by the 2004 parkfield california earthquake

single couple component of far field radiation from dynamical fractures abstract we reexamine two canons of the seismological literature that elastic displacements in the far field are proportional to slip velocities on the dynamical fault surface and that dynamical in plane slip on an earthquake fault has a double couple body force equivalent we show that if faulting takes place on a fault of finite thickness and there is a strength weakening zone near the advancing crack tip there is an additional single couple term in the body force equivalence and additional terms in the far field displacement which are proportional to the time rate of increase of stress drop in the advancing weakening zone we also show that the single couple equivalent does not violate principles of newtonian mechanics because the torque imbalance in the single couple is counterbalanced by rotations within the fault zone the crack therefore radiates torque waves and a rotational deformation field

late quaternary sea level changes crustal movements and coastal evolution in northumberland uk northumberland lies in the transition between holocene emergence and submerg ence and is thus a critical zone for testing models of isostatic rebound we have collected data from this area to reconstruct relative sea level changes and lateral coastline movements for the last 14000 y these are deposits from tidal marsh back barrier wetland and terrestrial environ ments producing 47 sea level index points from 12 sites there is no unequivocal evidence for late devensian sea levels above present and the reliable sea level index points are restricted between 26 m and 12 5 m relative to present and 9 0 2 5 kyr cal bp analysis of these quantifies differential responses to glacio and hydroisostatic rebound with the northern sites recording a mid holocene sea level maximum ca 2 5 m above present whereas the southern sites show a maximum ca 0 5 m above present these observations show a reasonable fit with the predictions from quantitative models of glacio and hydroisostatic rebound but there is currently no unique solution of earth and ice model parameters that will explain all the sea level observations copyright 2000 john wiley sons ltd

tilts in strong ground motion most instruments used in seismological practice to record ground mo tion are pendulum seismographs velocigraphs or accelerographs in most cases it is assumed that seismic instruments are only sensitive to the translational motion of the instrument s base in this study the full equation of pendulum motion including the inputs of rotations and tilts is considered it is shown that tilting the accelerograph s base can severely impact its response to the ground motion the method of tilt evaluation using uncorrected strong motion accelerograms was first suggested by graizer 1989 and later tested in several laboratory experiments with different strong motion instruments the method is based on the difference in the tilt sensi tivity of the horizontal and vertical pendulums the method was applied to many of the strongest records of the mw 6 7 northridge earthquake of 1994 examples are shown when relatively large tilts of up to a few degrees occurred during strong earthquake ground motion residual tilt extracted from the strong motion record at the pacoima dam upper left abutment reached 3 1 in n45e direction and was a result of local earthquake induced tilting due to high amplitude shaking this value is in agreement with the residual tilt measured by using electronic level a few days after the earthquake the method was applied to the building records from the north ridge earthquake according to the estimates residual tilt reached 2 6 on the ground floor of the 12 story hotel in ventura processing of most of the strongest records of the northridge earthquake shows that tilts if happened were within the error of the method or less than about 0 5

holocene shelf sea evolution offshore northeast england abstract spatial and temporal changes of tidally mixed and stratified water conditions during the holocene are poorly understood and constrained within the north sea region this study investigates the changing tidal conditions at a core site from offshore northeast england through the holocene a continuous holocene sedimentary record in british geological survey vibrocore 54 02 97 54 53 05 n 1 3 88 w water depth 55 m collected from a natural trough in the north sea has been investigated a multiproxy approach including the interpretation of magnetic susceptibility values bulk sedimentological characteristics benthic foraminifera faunal and isotopic data is adopted the chronology of this record is constrained by a total of ten accelerator mass spectrometry 14 c dates obtained from molluscs and mixed benthic foraminiferal samples the age derived from benthic foraminifera and molluscs obtained at the same core depth are statistically the same these results suggest that benthic foraminifera tests do not undergo significant post mortem reworking at this shallow site and that the foraminifera based proxy records are reliable sedimentary characteristics indicate that tidally mixed waters between 11 150 and 5869 calendar cal yr bp affected the core site the core site was bathed by tidally mixed water conditions indicated by the presence of ammonia batavus hofker with stratified conditions and associated frontal systems developing at or close to the core site between 5869 and 2032 cal yr bp based on the presence of stainforthia fusiformis williamson finally species that are indicative of fully stratified water such as bulimina marginata d orbigny hyalinea balthica schroter and s fusiformis record the transition from mixed frontal to stratified conditions at 1158 cal yr bp this site records a faunal change in the last 500 years that may be a consequence of fully stratified conditions and enhanced phytodetritus delivery to the sea floor alternatively supported to some extent by heavy metal concentrations the fauna may be responding to eutrophication of coastal waters through anthropogenic influences

ground rotational motions of the 1999 chi chi taiwan earthquake as inferred from dense array observations 1 large rotational motions excited by the 1999 chi chi taiwan earthquake are inferred from a dense acceleration array near the northern end of the rupture fault where large surface slips along the fault are observed the estimated major frequency content is from 0 1 to 1 0 hz with a peak near 0 2 hz it is found that in the footwall region the observed strong rotational ground motions were most probably excited by the slip of the northern rupture ending segment of the chi chi earthquake fault and that its thrust slips induced a major rock motion in the radial component the analysis here indicates that during the chi chi earthquake significant rotation seismic energy was radiated from the bent northern end of the earthquake fault further analysis of rotational ground motions may provide useful constraints for its rupture mechanisms

rupture velocity inferred from near field shear strain analysis s u m m a r y we propose a new technique to determine the rupture velocity of large strike slip earthquakes by means of simple numerical ground motion simulations we show that when the rupture penetrates a shallow layer of sediment or fractured rock shock waves propagate along the surface fault trace in the forward rupture direction such shock waves which are insensitive to the complexity of slip over the fault plane propagate at a phase velocity equal to the rupture speed we show that those shock waves can be easily isolated in the frequency domain and that phase velocity can then be simply obtained from shear strain

a reassessment of sand transport paths in the bristol channel and their regional significance abstract data on bedform morphology sediment parameters heavy mineral abundance current measurements sand transport rates numerical models of shear stress sea bed drifters and wave activity are all considered it is concluded that the dominant transport of sand and gravel is westwards from the transverse bristol channel bed load parting the notion of easterly transport of sand apart from wave induced transport on the beach and in the nearshore zone by the flood tidal current in continuous zones along the northern and southern margins of the bristol channel is largely discounted however there are some small disconnected areas where easterly transport of sand is locally induced by coastal irregularities by sand bank relief and by a local deep the ground for up to 2 km north of scarweather sands provides a rare example of the net sand transport direction being determined by the weaker but substantially longer flowing flood tidal current a facies model of the deposits is outlined

an observational and modeling study of the interaction of low level southwesterly flow with the olympic mountains during coast iop 4 abstract this paper presents an observational and modeling study of the three dimensional flow and precipitation around the olympic mountains of northwest washington state for a case of relatively steady south southwesterly flow this study utilized data from coast iop 4 the fourth intensive observing period during the coastal observation and simulation with topography field experiment that took place during 9 10 december 1993 one of the most important data sources was the noaa p 3 aircraft which provided flight level data reflectivity and doppler winds as it flew around the olympics features that were mapped successfully with the noaa p 3 included flow splitting around the windward pressure ridge strong southeasterlies to approximately 25 m s 1 northeast of the olympics caused by downgradient acceleration into the lee trough the rapid transition from strong southeasterlies to lighter easterlies 5 10 m s 1 in the strait of juan de fuca strong downslope flow and a hydraulic jump like transiti

strain tilt and rotation associated with strong ground motion in the vicinity of earthquake faults abstract in the absence of near field records of differential ground motion induced by earthquakes we simulate the time histories of strain tilt and rotation in the vicinity of earthquake faults embedded in layered media we consider the case of both strike slip and dip slip fault models and study the effect of different crustal structures the maximum rotational motion produced by a buried 30 km long strike slip fault with slip of 1 m is of the order of 3 10 4 rad while the corresponding rotational velocity is about 1 5 10 3 rad sec a simulation of the san fernando earthquake yields maximum longitudinal strain and tilt a few kilometers from the fault of the order of 8 10 4 and 7 10 4 rad these values being small compared to the amplitude of ground displacement the results suggest that most of the damage occurring in earthquakes is caused by translation motions we also show that strain and tilt are closely related to ground velocity and that the phase velocities associated with strong ground motions are controlled by the rupture velocity and the basement rock shearwave velocity

a theoretical study of the radiation from small strikeslip earthquakes at close distances abstract we present a study of the seismic radiation of a physically realistic source model the circular crack model of madariaga at close distance range and for vertically heterogeneous crustal structures we use this model to represent the source of small strike slip earthquakes we show that the characteristics of the radiated seismic spectra like the corner frequency are strongly affected by the presence of the free surface and by crustal layering and that they can be considerably different from the ones of the homogeneous medium far field solution the vertical and radial displacement spectra are the most strongly affected we use this source model to calculate the decay of peak ground velocity with epicentral distance and source depth for small strike slip earthquakes in california for distances between 10 and 80 km the peak horizontal velocity decay is of the form r 1 25 for a 4 km hypocentral depth and r 1 65 for deeper sources the predominance of supercritically reflected arrivals beyond epicentral distances of 70 to 80 km produces a sharp change in the rate of decay of the ground motion for most of the cases considered the peak ground velocity increases between 80 and 100 km we also show that the s wave velocity in the source layer is the lower limit of phase velocities associated with significant ground motion

high resolution observations of the trowal warm frontal region of two continental winter cyclones abstract this paper compares the structure of the trough of warm air aloft trowal warm frontal region of two continental wintertime cyclones the cyclones were observed over the central great lakes region during the lake induced convection experiment snowband dynamics project field campaign the cyclones had different origins with the first forming east of the colorado rockies and the second forming over the gulf of mexico they were associated with different upper level flow regimes one located just north of a nearly zonal jet and the other located just west of a nearly meridional jet both storms produced heavy swaths of snow across the states of illinois wisconsin and michigan high resolution observations of frontal structure were made during flights of the national center for atmospheric research electra aircraft using dropsondes and the electra doppler radar tail radar system the high resolution observations suggest a different arrangement of air masses in the trowal region compared with the

source and basin effects on rotational ground motions comparison with translations the recent availability of accurate observations of rotational ground mo tions has reopened interest in understanding near fault characteristics of such motions in the context of strong ground motion and earthquake engineering in order to in vestigate source and structure dependent variations of rotational motions we simulate several m 7 earthquakes with varying source scenarios on the newport inglewood ni fault embedded in the 3d los angeles basin using a finite difference method in the frequency range up to 0 5 hz we use a precalculated database with several hundred numerical green s functions for a discretized model of the ni fault that al lows arbitrary finite fault scenarios to be synthesized by superposition we investigate source and basin effects on the rotational part of ground motion namely maximum peak ground rotation rates and their variations and compare them with the corre sponding values of translational motion our main conclusions are 1 the pure strike slip source mechanism leads to larger rotation rates around the vertical axis than around the horizontal ones 2 variation of hypocenter introduces more scatter on ground rotation rate than variations of slip history 3 the coprocessing of translation and rotation recordings might reveal information on local velocity structure as indi cated by plane wave theory and 4 the attenuation of accelerations horizontal com ponents and rotation rate vertical component with distance from the fault are very similar suggesting that similar expressions as a function of distance as for the peak accelerations can be adopted for the peak rotation rates when determining their at tenuation relations

strong motion seismology although this is the first review on this topic to appear in a quadrennial report the roots of strong motion seismology extend back to at least 1932 when far sighted engineers in the seismological field survey of the u s coast and geodetic survey installed rugged fieldworthy instruments designed to make on scale recordings of large earthquakes carder 1964 these instruments are called accelerographs for their output closely mimics ground acceleration hudson 1979 the original instruments and their offspring have provided a wealth of information about ground motions of direct use to engineers due in large part to the continued devotion of the seismological field survey now part of the branch of engineering seismology and geology at the u s geological survey the number of recordings has increased substantially particularly in the last two decades and multiple recordings of a few california earthquakes have provided the data necessary to begin to unravel the complexities of the ground motions and to predict these motions on an empirical basis although seismologists used accelerograph records in studies of earthquake energy and ground motion attenuation as long ago as 1942 gutenberg and richter 1942 1956 widespread seismological use of the records began with aki s 1968 analysis of the 1966 parkfield earthquake

appalachian cold air damming abstract appalachian cold air damming is investigated by means of 1 a 50 yr monthly climatology 2 a synoptic case study of the event of 21 23 march 1985 and 3 an investigation of the flow structure and force balance within the cold dome the climatology reveals cold air damming is a year round phenomenon in the southern appalachians with the most frequent prolonged and intense events occurring in winter particularly december and march when three five events per month can be expected cold air damming is least frequent and intense in july the synoptic case study reveals that cold air damming is critically dependent upon the configuration of the synoptic scale flow the cold dome can be identified by a u shaped ridge trough in the sea level isobar thermal patterns and the 930 mb height temperature fields representative of conditions at the base of the inversion overlying the cold dome differential horizontal and vertical thermal advection as well as adiabatic and evaporative cooling are r

the 1998 ice storm analysis of a planetary scale event abstract the ice storm of 5 9 january 1998 affecting the northeastern united states and the eastern canadian provinces was characterized by freezing rain amounts greater than 100 mm in some areas the event was associated with a 1000 500 hpa positive warm thickness anomaly whose 5 day mean exceeded 30 dam 15 c over much of new york and pennsylvania the region of maximum precipitation occurred in a deformation zone between an anomalously cold surface anticyclone to the north and a surface trough axis extending from the gulf of mexico into the great lakes the thermodynamic impact of this unprecedented event was studied with the use of a four dimensional data assimilation spanning an 18 day period ending at 0000 utc 9 january 1998 a moisture budget for the precipitation region reveals the bulk of the precipitation to be associated with the convergence of water vapor transport throughout the precipitation period the ice storm consisted of two primary synoptic scale cyclonic events the first even

the effects of seismic rotations on inertial sensors summary with the important increase in the number of instruments especially in the near field of quite significant earthquakes unsaturated traces have led seismologists to question what they are really measuring we have performed a review of previous studies related to the effects of rotations on both horizontal and vertical components of various sensors illustrations of near field records show that the recovering static displacement requires an accurate rotation estimation that present day seismometers cannot achieve estimations of coseismic tilts rotation around an horizontal axis using seismometers cannot be achieved independently of translational motion therefore for specific configurations such as near field or long period far field reconstruction of the ground motion requires specific rotation measurements effects of the chi chi earthquake 1999 on accelerograms make the static displacement estimation unreliable for long period background noise far field horizontal seismic signals present unexpected n45 polarization which is explained by the similar influence of the rotation around the vertical axis on the two horizontal components for the geoscope network this feature has been seen for stations with a streckeisen sts 1 sensor while those with a streckeisen sts 2 sensor do not show this polarization feature this study suggests that sensor installation should follow a protocol that will better guarantee the verticality of the sensors moreover rotational recordings with ad hoc sensors are necessary and by adequately correcting the traces they will enable us to reconstruct the translational motion from recorded seismic signals

review progress in rotational ground motion observations from explosions and local earthquakes in taiwan rotational motions generated by large earthquakes in the far field have been successfully measured and observations agree well with the classical elasticity theory however recent rotational measurements in the near field of earthquakes in japan and in taiwan indicate that rotational ground motions are 10 to 100 times larger than expected from the classical elasticity theory the near field strong motion records of the 1999 mw 7 6 chi chi taiwan earthquake suggest that the ground motions along the 100 km rupture are complex some rather arbitrary baseline corrections are necessary in order to obtain reasonable displacement values from double integra tion of the acceleration data because rotational motions can contaminate acceleration observations due to the induced perturbation of the earth s gravitational field we started a modest program to observe rotational ground motions in taiwan three papers have reported the rotational observations in taiwan 1 at the hgsd station liu et al 2009 2 at the n3 site from two taiwan integrated geodynamics research taiger explosions lin et al 2009 and 3 at the taiwan campus of the national chung cheng university nccu wuet al 2009 in addition langston et al 2009 reported the results of analyzing the taiger explosion data as noted by several authors before we found a linear relationship between peak rotational rate prr in mrad sec and peak ground acceleration pga in m sec 2 from local earthquakes in taiwan prr 0 002 1 301 pga with a correlation coefficient of 0 988

evolution of seasonal stratification in the celtic sea during the holocene seasonal thermocline development in the shelf seas of nw europe results in the formation of pronounced frontal regions which separate stratified from well mixed water numerical m 2 palaeotidal modelling of the nw european continental shelf during successive stages of the holocene transgression indicates that seasonal stratification started to develop in the central celtic sea once a critical threshold water depth had been exceeded at around 9000 years bp this hypothesis has been tested through faunal isotopic and geochemical analysis of an ams 14 c dated british geological survey vibrocore from the celtic deep bathymetric basin a record which spans the last 12 000 years marked positive trends in the stable oxygen isotopic data from the benthic foraminifera ammonia batavus and quinqueloculina seminulum between 9000 and about 5000 years bp represent a 4 5 c cooling in summer bottom water temperature caused by the progressive replacement of tidally well mixed by stratified water stable carbon isotopic data from the same species measured through the same core intervals show a negative trend consistent with net oxygen utilization and decomposition of organic matter beneath the productive frontal zone these geological data indicate the progressive evolution of seasonally stratified water in the celtic sea during the earlier part of the holocene modern shelf sea frontal and thermocline development are known to influence biological productivity sedimentation rates the organic content of shelf sediments and the climate of surrounding landmasses hence these palaeodata have significance in defining the role of shelf sea environments in the climate system

late devensian and holocene shorelines of the british isles and north sea from models of glacio hydro isostatic rebound sea level change around the british isles since the time of the last glacial maximum is largely due to of the crustal rebound from the glacial unloading of northern britain and the concomitant melt water loading of the adjacent seas and atlantic ocean minor but not insignificant contributions also result from the rebound caused by the unloading of the distant ice sheets including fennoscandia and north america observations of sea level change for this period constrain the glacio hydro isostatic rebound model parameters describing the effective lithospheric thickness or rigidity and the effective mantle viscosity as well as certain ice sheet characteristics such as the ice thickness at the time of the last glacial maximum the models permit palaeobathymetry and palaeoshorelines to be predicted for the british isles region including the north sea the resulting evolution of the coastlines exhibits a complex behaviour through time one that is quite different from the usual models in which sea level change is assumed to be a function of time only in part this is because of the delayed response of the mantle to the spatially variable and time dependent ice and water loads and in part because the unloading history of the british ice sheet is different from those of the major global ice sheets thus maximum emergence of the north sea occurred after deglaciation had started and lasted for an extended period from about 15 000 to 12 000 radiocarbon years bp during this relative sea level still stand shoreline features could have formed for example along the western edge of the norwegian trough when access to the firths of eastern scotland would have been via a long and shallow marine inlet shoreline retreat across the north sea became relatively rapid after about 10000 years the model predictions for the irish and celtic seas also suggest a complex behaviour with the formation of a wide land bridge between about 20000 and 13 000 years ago the model also suggests that as long as the scottish ice extended across the northern irish sea until about 14 000 years ago there would have been a large freshwater periglacial lake located further south both the predicted sea level height age relations and the shoreline positions are consistent with a large body of observational evidence but some discrepancies occur particularly in northern scotland and ireland where the ice heights may have been somewhat greater than assumed in the model

inverting ground motion from a seismometer array to obtain the vertical component of rotation a test using data from explosions to study factors that affect reliability of the derived vertical rotational ground motions about vertical axis from translational array waveforms we have conducted a field test using explosion the dataset was collected on march 4 2008 from an active source experiment of the taiwan geodynamics research project taiger 2008 in which 750 kg of explosives were set off about 500 m away from a specially designed seismic array in free field consisting of 8 tri axial rotational sensors 13 tri axial accelerometers and 12 six channel 24 bit dataloggers with gps receivers our results show that the waveform fits were greatly improved when the explosion induced crustal strains were less than 2 10 5 for our station configuration as a result our modeling for the large amplitude part of the mainshock was not entirely successful however we have successfully recovered the first order features of the later part of the vertical rotational ground motions using translational velocity waveforms in the 0 5 20 hz bandwidth using the spudich and fletcher s procedure 2009 moreover we used a modified jaeger s 1969 formula and derived similar rotational synthetics we found that the best rotational rate waveform fits were derived using a station configuration of a dense small aperture translational array combined with a few largeoffset stations a small aperture array is needed to fulfill the uniform rotation assumption however inverting data from an array of small spatial dimension requires waveforms of high signal to noise ratio and high sampling rates surprisingly large offset translation stations provided additional constraints in time and space helping to fit the low frequency waveforms using the inverted result we forward predicted the vertical translational waveforms not used in the inversion and got excellent fits this suggests that the inverted results are of good quality for predicting the complete translational ground motions even though only horizontal components were used in the inversion array derived or directly measured rotational ground motions can be used to predict translational ground motions in the near by region lessons learned from this study could be helpful for future studies using translational ground motions to derive dynamic ground strains tilts and torsions

clues for a relation between rotational effects induced by the 2009 mw 6 3 l aquila central italy earthquake and site and source effects abstract the 2009 m w 6 3 l aquila earthquake produced an impressive number of rotational effects on vertically organized objects such as chimneys pillars capitals and gravestones we present a dataset of such effects that consists of 105 observations at 37 different sites and represents a compendium of earthquake induced instances of rotational effects that is unprecedented in recent times we find that the absolute majority of the reported effects were observed in the epicentral zone and that most of the observations are located where the mercalli cancani sieberg intensity is between 7 and 8 9 the evident asymmetry in the distribution of the rotational effects resembles the southeastward directivity of the macroseismic effects and highlights a significant convergence between rotations and damage finally we perform some qualitative analyses to recognize and evaluate which geological and seismological parameters can be significant contributors to local rotations we find that surface geology and amplification of the seismic motion at each reported location strongly influence the occurrence and the nature of the earthquake induced rotational effects conversely the contribution of the pattern of slip distribution on the fault plane plays only a secondary role in enhancing the rotational motion at each site

rotational motions induced by the m8 1 tokachi oki earthquake september 25 2003 1 we report the first consistent observations of rotational motions around a vertical axis induced by distant large earthquakes it is standard in seismology to observe three components up down n s e w of earthquake induced translational ground motions using inertial seismometers however only recently ring laser technology has provided the required sensitivity for observations of the theoretically predicted rotational part of ground motion generated by seismic waves in a wide distance range and frequency band here we show that the rotations observed are consistent in waveform and amplitude with collocated recordings of transverse accelerations recorded by a standard seismometer this suggests that rotations may become a new observable for seismology and related fields with the potential of providing complementary information on earthquake source processes structural properties and ground shaking

introduction to the special issue on rotational seismology and engineering applications rotational seismology is an emerging field for studying all aspects of ro tational ground motions induced by earthquakes explosions and ambient vibrations it is of interest to a wide range of geophysical disciplines including strong motion seismology broadband seismology earthquake engineering earthquake physics seis mic instrumentation seismic hazards seismotectonics and geodesy as well as to physicists using earth based observatories for detecting gravitational waves generated by astronomical sources predicted by einstein in 1916 in this introduction to the bssa special issue on rotational seismology and engineering applications we will include 1 some background information 2 a summary of the recent events that led to this special issue and 3 an overview of its 51 papers 27 articles 11 short notes 4 reviews 6 tutorials and 3 supplementary articles our comments on these 51 papers are very brief and give just a hint of what the papers are about papers in this special issue demonstrate that earthquake monitoring cannot be limited to measuring only the three components of translational motion we also need to simultaneously measure the three components of rotational motion and the many components of strains a golden opportunity to improve our understanding of earth quakes lies in the near field of large earthquakes within about 25 km of the earthquake ruptures where nonlinear rock and soil response influences ground motions in a com plicated way

late weichselian to early holocene subaqueous dune formation and burial off the north sea northumberland coast abstract high resolution seismic profiles from the north sea 20 km off northumberland have shown the presence of a 25 km2 subaqueous dune field buried beneath holocene marine mud the dunes are composed of fine to medium sand with occasional pebbles and have heights ranging from 0 5 m to 5 5 m and spacings from 100 m to 600 m most larger dunes 2 m high have their steeper slopes facing to the south and internal reflectors representing foreset bedding that dips to the south suggesting dominant southward sand transport the dunes are inferred to have been produced by tidal currents of between 1 00 and 1 50 m s in a shallow water tidal embayment or large estuary during the initial stages of the post glacial marine transgression in the area sometime between about 10 700 and 9700 yr b p burial of the dunes occurred when the dimensions of the tidal embayment were increased tidal current velocities reduced beneath the threshold for dune formation and finer grained sediment was deposited the tops of the dunes were eroded and a deflation surface formed before burial

orographic influences on the mesoscale structure of the 1998 ice storm abstract the ice storm of 5 9 january 1998 affecting parts of the northeastern united states and the eastern canadian provinces was characterized by freezing rain amounts greater than 100 mm in some areas the region of maximum precipitation occurred in a deformation zone between an anomalously cold surface anticyclone to the north and a surface trough axis extending from the gulf of mexico into the great lakes mesoscale processes were examined to understand their role in regulating the persistence phase and intensity of the event the persistently cold near surface air in the precipitating region was linked to orographic channeling of winds from the cold anticyclone to the north the position of the surface based freezing line was strongly tied to pressure driven channeling of surface winds by orography during the first freezing rain episode 4 7 january while this channeling contributed to the depth of the cold air north of the u s border and governed details of the position of the freezing line

what can be learned from rotational motions excited by earthquakes summary one answer to the question posed in the title is that we will have more accurate data for arrival times of sh waves because the rotational component around the vertical axis is sensitive to sh waves although not to p sv waves importantly there is another answer related to seismic sources which will be discussed in this paper generally not only dislocations commonly used in earthquake models but also other kind of defects could contribute to producing seismic waves in particular rotational strains at earthquake sources directly generate rotational components in seismic waves employing the geometrical theory of defects we obtain a general expression for the rotational motion of seismic waves as a function of the parameters of source defects using this expression together with one for translational motion we can estimate the rotational strain tensor and the spatial variation of slip velocity in the source area of earthquakes these quantities will be large at the edges of a fault plane due to spatially rapid changes of slip on the fault and or a formation of tensile fractures

numerical study of convection observed during the winter monsoon experiment using a mesoscale two dimensional model abstract a two dimensional version of the pennsylvania state university mesoscale model has been applied to winter monsoon experiment data in order to simulate the diurnally occurring convection observed over the south china sea the domain includes a representation of part of borneo as well as the sea so that the model can simulate the initiation of convection also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle this allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck which typically occupies several hundred kilometers of the domain frank and cohen s cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area the major conclusions are ice phase processes are important in determining the level of maximum large scale heating and vertical motion because there is a strong anvil componen

ground rotational motions recorded in near source region of earthquakes large rotational motions excited by earthquakes are recorded during an earthquake swarm of march 1997 offshore ito in izu peninsula japan the largest rotational velocity recorded at kaw is 2 6 10 2 rad s around the north south axis during an earthquake of magnitude 5 2 at 14 09 gmt on march 3 the rotational motions around the vertical axis excited by the largest event is 3 3 10 3 rad s considering a spatial variation of slip velocity which directly relates to excitation of a rotational motion we apply a simple point source model to the largest event and succeed in explaining the observed rotational motion around the vertical axis