rupture process of the 1990 luzon philippines mw 7 7 earthquake the rupture process of the destructive july 16 1990 luzon philippines earthquake is analyzed using a long period surface wave spectral inversion technique to estimate the average source properties and a broadband body wave and surface wave empirical green function technique to investigate the slip distribution the average source model has a seismic moment of 4 2 0 1 1020 n m mw 7 7 a total duration of 30 to 35 s a left lateral strike slip focal mechanism with strike 153 dip 89 and rake 16 and a north northwestward directivity these results are consistent with previous work on the luzon earthquake however the broadband analysis indicates that for periods longer than about 20 s the teleseismic source time function is characterized by a single relatively smooth pulse of energy release with azimuthal variations in duration of 24 to 60 s this contrasts with previous body wave results that inferred two discrete pulses of energy release the simpler source process is inferred as a result of using empirical green functions rather than standard theoretical green functions for a layered crustal model and by considering only the seismic energy with periods longer than 20 s the luzon earthquake began rupturing bilaterally but evolved into a predominantly northwest directed rupture that extended for 75 to 100 km the largest slip 10 15 m occurred about 25 km northwest of the epicenter beyond which the slip decreased gradually as the rupture propagated into a restraining bend the peak slip at depth appears to exceed the surface rupture by a factor of 2 to 3 there is little evidence for significant energy release later than 50 s after the rupture initiated

practical application of the sequential balancing technique an example from the irish variscides the process of sequential restoration presented by cooper trayner 1986 is applied to a n s cross section through the irish variscides to demonstrate that this approach improves the accuracy of thin skinned structural modelling and allows the progressive deformation of a marginal belt to be examined the principles and methods of sequential restoration are illustrated the cross section is restored in four steps and gives a bulk shortening of 52 in this model the fold belt evolved as the basal decollement migrated northwards and considerable ductile shortening by folding and cleavage formation preceded faulting although faulting gradually became more important towards the north the section is divided into four structural domains based upon different deformation histories each is restored independently by removing the ductile strain before restoring the faulting from this example it is clear that many models derived from single step balancing especially those through ductile deformed areas should be re examined

sedimentology and stratigraphy of thetownsend tuff bed lower old red sandstone in south wales and the welsh borders the townsend tuff bed has a highly distinctive internal stratigraphy which allows it to be recognized at a large number of localities scattered over the welsh borders and south wales it is a group of 3 almost directly superimposed normally graded air fall tuffs that originated in distant but powerful plinian eruptions centre unknown and became spread over extensive but practically featureless coastal mud flats the bed occurs in a barren interval within the early lower old red sandstone between a silurian invertebrate vertebrate fauna below and an already devonian vertebrate assemblage above the base of the devonian system in south wales and the welsh borders is accordingly defined as occurring at a regionally uniform lithological contact within the townsend tuff bed

fault plane orientations of small earthquakes of the 1997 umbria marche italy seismic sequence from p wave polarities and rise times summary a two step technique has been developed with the aim of retrieving the fault plane orientation of a small magnitude earthquake the technique uses a set of non linear equations which relate the rise times of first p waves to source parameters source dimension l dip and strike of the fault and intrinsic qp at the first step of the technique the inversion of p polarities provides two fault plane orientations for each focal mechanism solution at the second step the inversion of rise times is carried out to retrieve l and qp by fixing and to the values of the fault plane orientation inferred at the first step a robust analysis based on the random deviates technique allows us to evaluate if one fault plane exists which systematically better fits data and can be considered the true fault plane a parameter is introduced to quantify the level of resolution of the true fault plane a probabilistic approach based on the assumption that errors on data are gaussian distributed allows us to a posteriori validate or reject the true fault plane the technique has been applied to 47 small earthquakes 1 3 ml 3 9 occurred below the town of sellano during the 1997 umbria marche central italy seismic crisis the strike of the inferred fault planes is generally along the apennine direction fault plane solutions can be mainly subdivided into two groups a first group of sw dipping faults and a second group of ne dipping faults these results agree with the present day knowledge of the fault systems in the area an average qp equal to 354 63 has been estimated in agreement with previous attenuation studies

the macroseismic field generated by the mw 8 0 jalisco mexico earthquake of 9 october 1995 abstract the mw 8 0 earthquake of 9 october 1995 occurred within the jalisco block that represents the northern part of the mexican subduction zone where the rivera plate subducts beneath the north america plate along the middle american trench the source rupture of the 1995 low angle thrust type event was complicated the studies of rupture history had shown that the slip occurred within an area of about 180 90 km 2 along the middle american trench at the depth interval from 9 to 33 km the rupture duration was estimated in interval from 55 to 62 sec at least three main asperities ruptured along the fault plane the earthquake was felt along the 600 km coast of the mexican states of colima jalisco and michoacan and in the continental part of mexico the macroseismic study presented in this article was carried out in march through july 1997 more than one year after the earthquake we had about 300 interviews with people who felt the earthquake in their houses located in 56 cities and towns of the states of colima jalisco and michoacan all our estimates of the earthquake intensity were referred to the intermediate type of masonry situated on the intermediate type of soils for this purpose corrections were introduced for type of soil and masonry the study of macroseismic effects related to the 1995 jalisco earthquake allows description of some properties of the macroseismic field generated by the earthquake 1 three zones of intensity 4 5 and 6 to 7 grades of mm modified mercalli scale were distinguished 2 the zone of maximum intensity of 6 to 7 mm was heterogeneous this heterogeneity was in accordance with the rupture asperities distribution 3 the study of intensity attenuation along the coast had demonstrated the asymmetry in intensity distribution according to the epicenter the maximum intensities were observed for the sites that were situated to the northwest of the epicenter 4 a good correlation was observed between the observed intensities and the values of gps displacements

diverse sauropod theropod and ornithopod track assemblages and a new ichnotaxon siamopodus xui ichnosp nov from the feitianshan formation lower cretaceous of sichuan province southwest china abstract copper mining activities in a huge quarry in the fluvial lacustrine lower cretaceous feitianshan formation near zhaojue sichuan province have temporarily exposed large track bearing surfaces that require rapid documentation before they are subject to erosion or damage from collapse or destruction by mining due to the urgent need to document these sites several preliminary studies of representative material have been completed and more than 1000 tracks have been observed here we present maps of two large surfaces with a combined area of 1000 m2 representing the same stratigraphic level and yielding multiple trackways of measurable quality including at least 8 theropod 7 sauropod and 22 ornithopod trackways additional trackmakers of the two latter groups are also well represented by natural casts derived from an overlying unit disturbed by quarrying the sauropod tracks are assigned to the ubiquitous ichnogenus brontopodus the ornithopod tracks belong to the ichnogenera caririchnium attributed to quadrupeds or facultative bipeds and ornithopodichnus corresponding to smaller bipeds based on size and morphology the theropod trackways appear to represent diverse morphotypes including one attributed to the new ichnospecies siamopodus xui the feitianshan formation ichnofauna which also includes pterosaur tracks from other nearby surfaces is moderately diverse and indicates an abundant presence of archosaurs in the region during the early cretaceous

palaeoecology of an early permian playa lake trace fossil assemblage from castle peak texas usa abstract the early permian choza formation of the clear fork group at castle peak in texas usa contains a diverse and remarkably abundant trace fossil assemblage comprising exquisitely preserved arthropod trackways diplichnites gouldi types a and b diplichnites isp a and b lithographus isp and cf kouphichnium isp striated trails cruziana problematica and isolated resting traces rusophycus carbonarius and r furcosus surface or shallow subsurface grazing trails or burrows gordia indianensis helminthoidichnites tenuis treptichnus isp a nodular trail and unilobate epichnial trails backfilled deposit feeding burrows planolites beverleyensis meniscate backfilled burrows taenidium barretti horizontal branching networks and tetrapod trackways dromopus palmatus erpetopus willistoni varanopus curvidactylus and cf amphisauropus isp trace fossils formed in and around the margins of a shallow ephemeral playa lake within an alluvial plain and provide evidence of temporary communities comprising arthropods most notably notostracan branchiopod crustaceans as well as euthycarcinoids myriapods insects and tetrapods including protorothyridid captorhinid and araeoscelid reptiles and rare amphibians periodic influxes of water into the alluvial plain filled various depressions creating temporary habitats and flourishes of life and activity the trace fossil assemblage is typical of the scoyenia ichnofacies and is similar to other assemblages from a range of different transitional subaqueous to subaerial settings indicating that the distribution of trace fossils is not inextricably linked to the depositional setting itself but rather to the environmental factors that arise such diverse trace fossil assemblages probably reflect relatively long lived ephemeral water bodies whereas more impoverished examples probably represent shorter lived ephemeral water bodies assemblages such as castle peak with abundant delicate arthropod trackways probably reflect low energy conditions conducive to the presence of an abundant vagile epifauna and the preservation of their trackways whereas assemblages with open vertical burrows tend to lack arthropod trackways and probably reflect higher energy conditions trace fossil assemblages dominated by arthropod and tetrapod trackways may represent fleeting preservation windows following sheetfloods on floodplains

alpine faunas from the white mountains california adaptive change in the late prehistoric great basin abstract high elevation archaeological sites in the white mountains of eastern california document the establishment of small villages at elevations above 3100 m at about ad 800 replacing occupations that lacked substantial structures storage facilities and abundant plant processing equipment previllage faunas are far more tightly focused on large artiodactyls than on smaller mammals but do not differ significantly from village faunas in richness or diversity these differences do not provide strong support for the bettinger baumhoff 1982 model of late prehistoric adaptive change in the great basin but adequate testing of more subtle versions of such hypotheses may require a massive research effort

a geodetic study of the 2003 january 22 tecoman colima mexico earthquake we use coseismic displacements and aftershock information from global positioning system gps measurements at 27 sites in western mexico and a 12 station local seismic network to determine the characteristics of the 2003 january 22 m w 7 2 subduction thrust earthquake near tecoman colima mexico estimates of the earthquake moment slip direction and best fitting slip distribution are derived by optimizing the fit to the gps displacements for a 3 d finite element mesh that simulates the study area the calculated moment release is 9 1 10 19 n m m w 7 2 with maximum slip of 2 m at a depth of 24 km and a maximum rupture depth of 35 40 km the inversion indicates that coseismic rupture extended downdip from depths of 9 to 40 km along a 80 km along strike region that is bounded by the edges of the manzanillo trough the optimal solution is robust with respect to plausible changes in the subduction interface geometry and differing subsets of the data a comparison of the cumulative post seismic slip that can be inferred separately from earthquake aftershocks and gps measurements within a year of the earthquake indicates that 95 per cent or more of the post seismic deformation was aseismic near term post seismic measurements indicate that slip propagated downdip to areas of the subduction interface beneath the coastline within days following the earthquake as also occurred after the nearby m w 8 0 colima jalisco subduction earthquake in 1995 the similar behaviours and locations of the 1995 2003 earthquake sequence to two earthquakes in june of 1932 suggests that thrust earthquakes along the subduction interface northwest of the manzanillo trough may trigger earthquakes in the vicinity of the manzanillo trough however our modelling of coulomb stress changes caused by the 1995 earthquake indicate that it induced only modest unclamping of the subduction interface in the vicinity of the tecoman rupture in addition gps measurements indicate that elastic shortening characterized areas onshore from the tecoman rupture from mid 1997 up until the time of the rupture consistent with progressively stronger clamping of the subduction interface during this period this precludes any obvious triggering relationship with the 1995 earthquake the apparent coincidence of the edge of both the 1932 and 1995 2003 rupture sequences with the edge of the manzanillo trough may indicate that the trough is a mechanical barrier to along strike rupture propagation this implies a limit to the area of potential slip and hence rupture magnitude during future large earthquakes in this region

observational constraints on the fracture energy of subduction zone earthquakes we relate seismologically observable parameters such as radiated energy seismic moment rupture area and rupture speed to the dynamics of faulting to achieve this objective we computed the radiated energy for 23 subduction zone earthquakes recorded between 1992 and 2001 most of these earthquakes have a magnitude m w 7 5 but we also included some smaller m w 6 7 well studied subduction zone earthquakes and six crustal earthquakes we compiled static stress drop estimates for these 29 earthquakes from literature and used a slip weakening model to determine the radiation efficiency of these earthquakes we also determined the rupture speed of these earthquakes from literature from fracture mechanics fracture energy and hence radiation efficiency can be related to the rupture speed the radiation efficiencies estimated from the partitioning of energy as given by the slip weakening model are consistent with the rupture speed estimated for these earthquakes most earthquakes have radiation efficiencies between 0 25 and 1 and are hence efficient in generating seismic waves but tsunami earthquakes and two deep earthquakes the 1994 bolivia and the 1999 russia china border earthquakes have very small radiation efficiencies 0 25 and hence dissipate a large amount of energy during faulting we suggest that differences in the radiation efficiencies of different types of earthquakes could be due to fundamental differences in their rupture mechanics in deep events the energy is probably dissipated in thermal processes in the fault zone while it is possible that the morphology of the trench causes large energy dissipation during the rupture process of tsunami earthquakes

high density bioturbated sandstones in the mississippian mauch chunk formation eastern pennsylvania usa implications for continental ecospace exploitation abstract continental communities represented by complex rapidly evolving invertebrate ecosystems first appeared during the early palaeozoic era and are recorded in surface and subsurface bioturbation the mississippian age mauch chunk formation contains several high density bioturbated fine grained sandstones that are preserved as erosively based fluvial channel fills several of these channel sandstone bodies are almost completely homogenized by subsequent bioturbation throughout their entire thickness up to a maximum depth of 1 6 m the mauch chunk ichnofossil record demonstrates that high density bioturbation occurred at least 30 my prior to the permian and well before its widespread distribution in the triassic hence the late mississippian high density bioturbated sandstones demonstrate a much earlier high density exploitation of the continental subsurface ecospace than previously known

ichnology paleosols and palimpsests surfaces in the tinat member of the nuayyim formation unayzah group subsurface saudi arabia trace fossils and genetic stratigraphy in continental settings abstract the nuayyim formation of the unayzah group is widespread in subsurface central saudi arabia and constitutes a laterally variable stratigraphic unit with a complex mosaic of facies sedimentation for the tinat member took place majorly in a continental setting dominated by aeolian processes that resulted in dunes interdunes ephemeral stream deposits terminating with regional development of paleosols facies ichnofacies and palynological analysis suggest an arid to semi arid setting with biogenic activity in the form of continental fauna and plants in deposits associated with pedogenetical alteration in paleosol horizons therein burrowing exhibits elements of the scoyenia ichnofacies in beds with sparse to abundant bioturbation tectonic uplift and subaerial exposure resulted in the exhumation of previously buried substrates leading to the formation of burrowed palimpsests surfaces associated with paleosols at the end of unayzah deposition prior to the onset of the khuff formation progressive thermal updoming is interpreted to have occurred during the latest portion of the unayzah group sedimentation cycle in the arabian plate culminating in the regional pre khuff unconformity at the top of this megacycle recognized in this study by biogenically demarcated diastems ichnological and sedimentological observations outlined in this study are significant because they i refine existing interpretations of the paleoenvironmental history in the study area ii document diastems marking breaks in sedimentation and iii outline several soil forming cycles that allowed the establishment of a trace fossil suite with continental affinities thus demarcating the end of an entire sedimentation cycle the recognition and delineation of burrowed horizons associated with paleosols provides a tool to understand the tectono stratigraphic evolution of similar successions in the rock record

the irish variscides a fold belt developed within a major surge zone an arcuate fold belt characterizes the irish variscides south of the dingle dungarvan line the folds are cross cut by numerous faults which tend to be sinistral in the west and dextral in the east clockwise transection of major fold axes by minor folds and by cleavage has been recorded in the east while anticlockwise transections are common in the west these and other features suggest that north south dextral and sinistral shearing occurred in the east and west respectively this is considered to be a consequence of the morphology of the munster basin which allowed the development of a surge zone in the centre of the fold belt the variscan sole thrust is believed to lie at the base of or within the old red sandstone however to the east thinning of the upper palaeozoic cover sequence forces the sole thrust to cut down laterally stratigraphic section into lower palaeozoic basement in the depocentre the sole thrust surged ahead by propagating along bedding surfaces or possibly a devonian carboniferous extensional detachment beneath the basin while to the east and offshore to the west its propagation was inhibited by the absence of easy decollement horizons within the basement consequently the tip line became strongly arcuate and the thrust developed into a surge zone the sole thrust propagated northwards by stick slip processes much of the deformation within the cover sequence occurred during sticking events particularly fold tightening and accommodation faulting

non marine bivalves and associated burrows in the catskill magnafacies upper devonian of new york state abstract large near vertical endichnial burrows with distinctive meniscate fillings are associated with in situ moulds of the bivalve archanodon within river channel and overbank deposits of the frasnian oneonta and walton formations new york state the burrows are interpreted as due to upward escape of bivalves following workers such as eagar berg thoms hardy and broadhurst who described similar occurrences from late paleozoic fluvial and deltaic deposits trails passing laterally into the in situ archanodon moulds indicate that the bivalves moved around on the channel bar surfaces vertically oriented large beaconites burrows are similar to those described here and may have similarly originated by bivalve escape

far field simulation of tsunami propagation in the pacific ocean impact on the marquesas islands french polynesia the islands in the marquesas archipelago are most exposed to far field tsunamis in french polynesia four recent earthquakes located at the pacific rim kurile 1994 chile 1995 mexico 1995 and peru 1996 earthquakes generated trans pacific tsunamis and caused contrasting inundations in several inhabited marquesian bays the aim of this study is to better understand the amplification phenomena observed in the marquesas islands and to improve the risk assessment we present here numerical simulations of these four tsunamis by means of a finite difference model solving the equations of tsunami propagation at different scales the water heights computed in the bays are in excellent agreement with the available observations and thus validate our numerical method these numerical results allow us to determine 1 which propagation azimuths are dangerous for the whole marquesas archipelago and 2 the behavior of each studied bay amplitude frequency in response to tsunami waves we observe that the seismogenic subduction zone along south america is likely to define one of the most dangerous tsunami generation areas for the marquesas archipelago owing to the source geometries and to the trapping of the tsunami energy by bathymetric features in the southern pacific ocean fracture zones seamount chains

late cretaceous ornithopod dominated theropod and pterosaur track assemblages from the nanxiong basin china new discoveries ichnotaxonomy and paleoecology re examination of the late cretaceous yangmeikeng tracksite in the zhutian formation nanxiong group near nanxiong guangdong province china has led to the documentation of over 30 vertebrate tracks the track assemblage is dominated by large and small ornithopod tracks the larger ornithopod tracks have been assigned to hadrosauropodus nanxiongensis and hadrosauropodus isp indet the smaller ornithopod tracks are consistently incomplete showing only three pes digit traces without heel or manus impressions for this reason the smaller tracks probably represent pes tracks penetrating from a higher layer and therefore have not been assigned to any particular ichnotaxon previous photography at yangmeikeng site confirms the presence of at least one small wupus like theropod track and a pteraichnus like pterosaur pes track large enigmatic didactyl tracks could be of deinonychosaurian affinity but are more likely the poorly preserved prints of a tridactyl theropod trackmaker the nanxiong dinosaur tracks and skeleton records represent the most important and diverse ichnofauna from upper cretaceous strata of south china and can be compared with the shandong and heilongjiang late cretaceous faunas the composition of the ichnofauna is significant because it reflects a diverse tetrapod community with hadrosaurs avian theropods non avian theropods and pterosaurs a co occurrence not evident from the skeletal record of this region from a global perspective this assemblage permits a unique insight into archosaur communities and interaction of animals in a typical late cretaceous lakeshore environment non avian theropods may have been attracted by the other groups that were considered as a potential prey

subsidence and strike slip tectonism of the upper continental slope off manzanillo mexico the direction of convergence between the rivera and north american plates becomes progressively more oblique in a counter clockwise sense as measured relative to the trench normal direction northwestward along the jalisco subduction zone by analogy to other subduction zones the forces resulting from this distribution of convergence directions are expected to produce a nw moving fore arc sliver and a nw se stretching of the fore arc area also a series of roughly arc parallel strike slip faults may form in the fore arc area both onshore and offshore as is observed in the aleutian arc in the jalisco subduction zone the jalisco block has been proposed to represent such a fore arc sliver however this proposal has encountered one major problem namely right lateral strike slip faulting within the fore arc sliver and between the fore arc sliver and the north american plate should be observed however evidence for the expected right lateral strike slip faulting is sparse some evidence for right lateral strike slip faulting along the jalisco block north american plate boundary the tepic zacoalco rift system has been reported although some disagreement exists right lateral strike slip faulting has also been reported within the interior of the jalisco block and in the southern colima rift which forms the se boundary of the jalisco block threefold multi channel seismic reflection data were collected in the offshore area of the jalisco subduction zone off manzanillo in april 2002 during the famex campaign of the n o l atalante these data provide additional evidence for recent strike slip motion within the fore arc region of the jalisco subduction zone this faulting offsets right laterally a prominent horst block within the southern colima rift from which we conclude that the sense of motion along the faulting is dextral these data also provide additional evidence for recent subsidence within the area offshore of manzanillo as has been proposed

using the effects of depth phases on p wave spectra to determine earthquake depths for shallow earthquakes the surface reflected depth phases pp and sp arrive shortly after the primary arrival and the time separation among the three phases can be used to determine the origin depth of the earthquake to model the relative arrival times and amplitudes of these phases and the core reflections and water column reverberations for a given earthquake we construct stick seismograms using the iaspei91 velocity model and the harvard cmt focal mechanisms at the distances and azimuths of the recording seismometers while the differing arrival times and amplitudes are features observable in the time series they also affect the spectrum and we compute the spectrum for a time window that includes the p wave and subsequent arrivals we quantify the effects of variations in these properties over the focal sphere in terms of differences in the slope of the log spectrum at different stations to determine the depth of an earthquake we compare our observed spectral variations with the predicted spectral variations for earthquakes originating at depths within 30 km of the pde depth and identify the depth with the smallest l1 misfit as the true earthquake depth we demonstrate the effectiveness of this method by applying it to a group of 35 thrust earthquakes in the aleutian arc near the andreanof islands but we also describe some complications introduced by strongly directive ruptures as illustrated for the 1995 jalisco mexico event online material observed and predicted variations in pulse width for aleutian island earthquakes

the role of pressure solution and intermicrolithon slip in the development of disjunctive cleavage domains a study from helvick head in the irish variscides the offset of sedimentary laminae bedding surfaces veins and other passive markers across disjunctive cleavage domains has commonly been attributed solely to pressure solution a detailed study of disjunctive cleavage within siltstones and sandstones from helvick head co waterford on the eastern margin of the irish variscides indicates that the cleavage domains were initially formed by pressure solution processes however the study also revealed features which cannot be explained by pressure solution alone the cleavage domains represent planes of weakness within otherwise relatively homogeneous rock during fold tightening they were rotated out of parallelism with the principal xy plane of the finite strain ellipsoid thus enabling shear movement between the microlithons it is considered that this intermicrolithon slip caused a rotation of the elongate quartz grains within the cleavage domains resulting in an asymmetry of their long axes with respect to the cleavage domain margin grain microfracturing and occasionally slickensides on cleavage surfaces intermicrolithon slip is unlikely to be a localized phenomenon but is probably widespread throughout the irish variscides and other orogenic belts

thirty thousand years of vegetation changes in the alabama hills owens valley california abstract twenty packrat neotoma middens recovered from three sites 1265 1535 m in the alabama hills inyo county california provide a ca 31 450 yr record of vegetation change located ca 7 km east of the sierra nevada the middens document that utah juniper juniperus osteosperma joshua tree yucca brevifolia and bitterbush purshia tridentata occupied the site between 31 450 and 19 070 yr b p joshua tree and bitterbush departed by ca 17 760 yr b p with cliffrose purshia mexicana and joint fir ephedra viridis appearing by 13 350 yr b p blackbush coleogyne ramosissima and cholla opuntia echinocarpa entered the record between 9540 and 7990 yr b p utah juniper and other species now extralocal to the sites departed and modern components such as wolfberry lycium andersonii and rubber rabbitbrush chrysothamnus teretifolius appeared the middle holocene records little variation in plant macrofossil composition however pollen analysis reflects an increase in aquatic pollen types which might suggest more open conditions the transition to the modern vegetation associations at the sites occurred after ca 2800 yr b p the record from the alabama hills correlates well with that of other regional vegetation data but documents conditions of increasing aridity earlier than many other packrat midden sites a shift in understory vegetation between 19 070 and 17 760 yr b p may reflect a transition from glacial maximum to post maximum conditions in the eastern sierra nevada

the october 9 1995 colima jalisco mexico earthquake mw8 an aftershock study and a comparison of this earthquake with those of 1932 data from portable seismographs and a permanent local network called resco are used to locate the aftershocks of the october 9 1995 colima jalisco earthquake mw 8 0 the maximum dimension of the aftershock area which is rectangular in shape is 170 km 70 km our study shows that the mainshock nucleated 24 km south of manzanillo near the foreshock of october 6 1995 mw 5 8 and propagated 130 km to the nw and 40 km to se the aftershock area lies offshore and is oriented parallel to the coast the observed subsidence of the coast is a consequence of this offshore rupture area the aftershocks reach unusually close to the trench within 20 km this may be due to lack of sediments with high pore pressure at shallow depth there are some similarities between this earthquake and the two great earthquakes of 1932 3 june ms 8 1 18 june ms 7 8 which occurred in this region in both cases the aftershocks were located offshore and the coastline subsided the sum of seismic moments and the rupture lengths of the 1932 events 1 8 1021 n m and 280 km respectively however were greater than the 1995 earthquake also a comparison of seismograms of 1932 and 1995 earthquakes show great differences it seems that the 1995 event is not a repeat of either june 3 or june 18 1932 earthquakes

seismotectonic constraints on the convergence rate between the rivera and north american plates there are two significantly different types of models for the convergence rate between the rivera and north american plates the first type the high rate model bandy 1992 predicts convergence rates of approximately 5 0 cm yr near the southern end of the rivera north america subduction zone and between 2 0 and 3 0 cm yr at its northern end in contrast the second type the low rate model e g demets and stein 1990 predicts convergence rates of between 2 0 and 3 3 cm yr near the southern end of the rivera north america subduction zone and between 0 6 and 1 7 cm yr at its northern end seismotectonic relationships which relate seismic characteristics of subduction zones maximum magnitudes maximum seismic depths etc to plate tectonic parameters convergence rates age of the oceanic lithosphere etc provide a means of distinguishing between the two different models three such relationships suggest that the rivera north american and cocos north american convergence rates should be roughly equal across the rivera cocos plate boundary favoring the high rate model employing the high rate model one can evaluate the magnitude and distribution of the strike slip component of forearc motion vss produced by oblique convergence between the rivera and north american plates the analysis indicates both a progressive increase and clockwise reorientation of vss northwestward along the plate contact zone of the rivera north america subduction zone such a distribution in vss should produce a northwestward movement of and nw se oriented extension within the interior of the jalisco block consistent with previous proposals of jalisco block motions also such a distribution in vss should produce a slight clockwise rotation of the jalisco block in the vicinity of bahia de banderas consistent with paleomagnetic data

fault slip distribution of the 1995 colima jalisco mexico earthquake abstract broadband teleseismic p waves have been analyzed to recover the rupture history of the large m s 7 4 colima jalisco mexico shallow interplate thrust earthquake of 9 october 1995 ground displacement records in the period range of 1 60 sec are inverted using a linear finite fault waveform inversion procedure that allows a variable dislocation duration on a prescribed fault the method is applied using both a narrow fault that simulates a line source with a dislocation window of 50 sec and a wide fault with a possible rise time of up to 20 sec that additionally allows slip updip and downdip from the hypocenter the line source analysis provides a spatio temporal image of the slip distribution consisting of several large sources located northwest of the hypocenter and spanning a range of rupture velocities the two dimensional finite fault inversion allows slip over this rupture velocity range and indicates that the greatest coseismic displacement 3 4 m is located between 70 and 130 km from the hypocenter at depths shallower than about 15 km slip in this shallow region consists of two major sources one of which is delayed by about 10 sec relative to a coherent propagation of rupture along the plate interface these two slip sources account for about one third of the total p wave seismic moment of 8 3 10 27 dyne cm m w 7 9 and may have been responsible for the local tsunami observed along the coast following the earthquake

the 14 september 1995 m 7 3 copala mexico earthquake a source study using teleseismic regional and local data we analyze source characteristics of the 14 september 1995 copala mexico earthquake m 7 3 using teleseismic regional and local seismograms in the analysis of the teleseismic and the regional seismic waves we apply the empirical green s function egf technique the recording of an appropriate aftershock is taken as the egf and is used to deconvolve the mainshock seismogram thus obtaining an apparent far field source time function at each station the deconvolution has been done using surface waves for teleseismic data we apply a spectral deconvolution method that enables us to obtain 37 apparent source time functions astfs at 29 stations in the analysis of the regional broadband seismograms we use two different aftershocks as egf and the deconvolution is performed in the time domain with a nonlinear method imposing a positivity constraint and the best azimuth for the directivity vector is obtained through a grid search approach we also analyze two near source accelerograms the traces are inverted for the slip distribution over the fault plane by applying a linear inversion technique with the aid of a time window analysis we obtain an independent estimation of the source time function and a more detailed description of the source process the analysis of the three datasets permits us to deduce the main characteristics of the source process the rupture initiated at a depth of 16 km and propagated in two directions updip along the plate interface toward 165 n and toward 70 n the source duration was between 12 and 14 sec with the maximum of energy release occurring 8 sec after the initiation of the rupture the estimated rupture dimension of 35 45 km is about one fourth of the aftershock area the average dislocation over the fault was 1 4 m with a maximum dislocation of 4 1 m located 10 km south of the hypocenter which gives roughly 1 mpa as the average static stress drop

the great jalisco mexico earthquakes of 1932 subduction of the rivera plate we have analyzed seismograms of the 3 june 1932 ms 8 2 and the 18 june 1932 ms 7 8 jalisco earthquakes and their aftershocks at manzanillo mnz guadalajara gum and tacubaya tac the aftershocks locations the first motions at mnz and the isoseismic maps of the two main shocks strongly suggest that a the 3 june 1932 earthquake initiated nw of but close to mnz and propagated nw for an estimated length of rupture of 220 km b the 18 june 1932 earthquake nucleated sw of mnz offshore and perhaps ruptured a length of about 60 km and c the width of rupture was approximately 80 km there is no evidence of events occurring se of mnz even up to 1 1 2 yr after the first main shock a gap of about 60 km remains between the aftershock areas of the 1932 jalisco and the 1973 colima earthquakes whose seismic potential is unknown although the boundary between the rivera and cocos plates is uncertain there is little doubt that the 1932 earthquakes broke the shallow part of the rivera subduction zone our results may help in quantifying seismic potential of tectonically similar areas such as the juan de fuca subduction zone in the nw united states

rapid estimation of rupture directivity application to the 1992 landers ms 7 4 and cape mendocino ms 7 2 california earthquakes using empirical green functions with regional and teleseismic surface waves it is possible to resolve fault finiteness effects in many cases uniquely defining the fault plane for relatively large earthquakes the technique requires very little data processing and can be applied in near real time with the current distribution of seismic stations the landers strike slip earthquake was dominated by two sub events with predominantly north northwestward rupture the second sub event was 1 5 times larger and rotated in strike by 12 counterclockwise relative to the first the cape mendocino thrust event had a relatively smooth rupture that propagated to the southwest on a shallow dipping fault

late silurian and early devonian terrestrialisation ichnological insights from the lower old red sandstone of the anglo welsh basin u k abstract late silurian to early devonian deposits from the lower old red sandstone anglo welsh basin preserve a diverse assemblage of trace fossils that collectively comprise an important record of early terrestrialisation five main palaeoenvironmental categories are represented 1 perennial rivers 2 ephemeral rivers 3 floodplain lakes 4 alluvial fan and 5 marginal marine ichnocoenoses mainly reflect the activity of aquatic and or semi aquatic animals fluvial deposits preserve evidence for colonisation by eurypterids fish and myriapods ephemeral river channel margins splays preserve the most diverse ichnofauna composed of deposit feeders burrows and trackways produced by arthropods feeding and foraging in channel margin soft grounds that were colonised after fluvial flood events high densities of deposit feeding structures may indicate of explosive population growth in response to periodic acyclical replenishment of nutrients in these aquatic settings ichnotaxa common to both perennial and ephemeral fluvial environments suggest that there might have been only one aquatic ecosystem the degree to which the channel margin ichnofaunas record a truly subaerial terrestrial arthropod signature is difficult to ascertain and most trace makers were probably semi aquatic some terrestrial animals invaded channel margin areas to feed and were also capable of inhabiting high energy alluvial fan environments however the fans contain low diversity ichnological assemblages and were likely to have been inhabited by an opportunistic fauna possibly the only truly subaerial terrestrial ichnocoenosis is that of pedogenically modified mudrock with scoyenia which represents an early soil ichnofauna the majority of ichnocoenoses described from continental palaeoenvironments could be classified under the scoyenia ichnofacies marginal marine deposits contain an impoverished skolithos cruziana ichnofacies typical of silurian devonian brackish water assemblages

non tetrapod trace fossils from the middle devonian tetrapod tracksite at zachelmie quarry holy cross mountains poland abstract the middle devonian eifelian dolomites exposed in the zachelmie quarry holy cross mountains southern poland contain the earliest fossil record of tetrapods low diversity but unique assemblages of trace fossils characterize the track bearing interval within the lower complex of the wojciechowice formation the reconstructed environment of the trace fossil rich beds includes ephemeral lakes and or shallow water lagoons separated from an open marine area by sparsely vegetated islands and spits the most abundant non tetrapod trace fossils from these beds are large horizontal to vertical burrows and dish circular to oval shaped shallow depressions the burrows are abundant on the upper surfaces of thick dolomicritic beds especially in some palaeosol levels but they are also associated with tetrapod trackways large semi aquatic or terrestrial animals e g arthropods or vertebrates most likely produced these burrows the circular to oval shaped depressions observed on a large surface and other smaller isolated blocks from the same stratigraphical level are interpreted as fish feeding nesting resting traces piscichnus sanctacrucensis isp nov is proposed as a new ichnospecies of the oval shaped fish trace fossil from the middle devonian of poland a single medium sized undichnia specimen a fish swimming trace is associated with the piscichnus traces the described trace fossils provide new insight into the palaeoecology and taphonomy of the middle devonian tetrapod tracksite from poland and clarify remaining controversies regarding the interpretation of some poorly preserved trace fossils from the zachelmie quarry

packrat midden evidence of late quaternary vegetation change in the white mountains california nevada packrat neotoma spp middens from the white mountains indicate climatic and plant community conditions for the last 19 000 yr during full glacial times ca 19 000 yr b p and at the pleistocene holocene boundary juniper woodlands were 600 m lower in elevation than at present midden assemblages and stable isotope data suggest lower temperatures and increased precipitation relative to the present into the early holocene two early holocene middens ca 8000 yr b p from lower elevations of the white mountains contain fragments of pinyon pine and indicate that both pinyon and juniper grew at a site that today supports only a pinyon woodland two middle holocene middens ca 5000 yr b p indicate that there was an upward migration of pinyon juniper woodlands along a high elevation ecotone but little change in the middle of the pinyon juniper woodland middens from the late holocene indicate that present day plant communities were in place by ca 2000 yr b p or before

the discovery of a new devonian tetrapod trackway in sw ireland a tetrapod trackway has been discovered in devonian sedimentary rocks of sw ireland it is the first discovery of its kind in europe details of the footprints are not preserved probably because of strong variscan pressure solution cleavage however after removing the effect of variscan deformation the large number of footprints more than 150 makes it possible to calculate the original dimensions of the footprint pattern stride approximately 34 cm and pace approximately 35 cm these values are higher than those for other traces of comparable age the total length of the tetrapod is estimated to be 1 m lithostratigraphical and biostratigraphical arguments indicate an age of mid to late devonian

tectono sedimentary ripples in devonian shallow marine siliciclastic sediments southern ireland abstract tectonically altered sedimentary ripples occur commonly in the marine devonian old head sandstone formation of southern ireland these tectono sedimentary ripples are dominantly wave produced and have sharp v shaped troughs where spaced pressure solution cleavage surfaces are located at a high angle to bedding the ripples control the spacing of cleavage and influence cleavage orientation the profile shape of the ripple is a function of stress refraction and concentration within the stiff sandstone layers of a multilayer sequence ripple symmetry is affected by tectonic deformation which plays an important role in the development of tectono sedimentary ripples tectonically flattened wave produced ripples occur where cleavage is oriented parallel to bedding due to an anomalous deformation in the old head sandstone formation at galley head selected ripple profiles have been undeformed by computer simulation to reconstruct ancient wave conditions this use of tectono sedimentary ripples for this purpose has its limitations and a number of guidelines are given for application of this technique elsewhere

rapid postseismic transients in subduction zones from continuous gps 1 continuous gps time series from three of four recently measured large subduction earthquakes document triggered rapid postseismic fault creep representing an additional moment release upward of 25 over the weeks following their main shocks data from two mw 8 0 and mw 8 4 events constrain the postseismic centroids to lie down dip from the lower limit of coseismic faulting and show that afterslip along the primary coseismic asperities is significantly less important than triggered deep creep time series for another mw 7 7 event show 30 postseismic energy release but here we cannot differentiate between afterslip and triggered deeper creep a fourth mw 8 1 event which occurred in the broad chilean seismogenic zone shows no postseismic deformation despite coseismic offsets in excess of 1 m for the three events which are followed by postseismic deformation stress transferred to the inferred centroids at 34 60 and 36 km depths by their respective main shock asperities increased reverse shear stress by 0 5 0 8 and 0 2 bar with a comparatively small decrease in normal stress 0 01 bar constraining the coulomb stress increase required to force slip along the metastable plate interface deep triggered slip of this nature is invisible without continuous geodesy but on the basis of these earthquakes would appear to constitute an important mode of strain release from beneath the seismogenic zones of convergent margins these events captured by some of the first permanent gps networks show that deep moment release is often modulated by seismogenic rupture updip and underscore the need for continuous geodesy to fully quantify the spectrum of moment release in great earthquakes index terms 7209 seismology earthquake dynamics and mechanics 3040 marine geology and geophysics plate tectonics 8150 8155 8157 8158 8150 tectonophysics plate boundary general 3040 7230 seismology seismicity and seismotectonics keywords subduction zone earthquake postseismic moment release

rupture length of the october 9 1995 colima jalisco earthquake mw8 estimated from tsunami data we analyze tsunami data of the great 1995 colima jalisco mexico earthquake recorded in cabo san lucas baja california sur to estimate its rupture length l to model the tsunami arrival time we assume a rectangular source area oriented parallel to the trench whose se limit is fixed at the point of rupture initiation the nw limit of the source area i e l is varied between 120 and 200 km the comparison between synthetic and observed data strongly suggests that l of the earthquake was 160 20 km this length agrees with those reported in various other studies of the earthquake it however disagrees with a previous study based on the same tsunami data which suggested that the rupture may have extended 250 km nw from the epicenter tanioka and ruff 1996 the cause of this discrepancy is most likely an error in the timing of the records used by tanioka and ruff 1996 we conclude that the earthquake only partially ruptured the rivera north america plate interface a 120 km long segment in the nw extreme of this interface which apparently ruptured in 1932 remains presently unbroken

structural evolution of the irish variscides the effects of the variscan orogeny on the upper palaeozoic succession are recognizable throughout central and southern ireland the deformation can be zoned using structural styles and trends which illustrate a northward decrease in deformation intensity coupled with increasing control by pre variscan structures in the basement the most intense deformation occurs to the south of the dingle dungarvan line where shortening approaches 50 as a result of layer parallel shortening followed by buckling and finally thrusting the deformation is considered to have developed above a shallow dipping sole thrust which has been located offshore by the swat seismic reflection profiles cross faults which are common throughout the orogen resulted from n s shear couples this is consistent with their origin as accommodation structures due to differential shortening along strike the original shape of the munster basin has exerted a control on the distribution and overall facing of the major structures the sole thrust extends to the north of the dingle dungarvan line and the structural zonation of the orogen is due to variations in the stratigraphic level of this thrust the leinster massif is considered to be essentially autochthonous slip on the sole thrust decays towards the massif which acted as a rigid passive block and was partially responsible for the arcuate trend of the orogen

sandy high energy flood sedimentation some criteria for recognition with an example from the devonian of s w england abstract many modern sand deposits resulting from episodic floods in semi arid zones are dominated by parallel laminations but parallel laminated sands are not a major feature in perennial streams single flood events may deposit over 1 5 m of parallel laminated sand hence ancient parallel laminated sand dominated alluvial deposits may be the product of ephemeral flows the trentishoe formation hangman sandstone group middle devonian of north devon consists in part of laterally extensive beds of parallel laminated fine grained red sandstones that build multistorey sand bodies individual beds are little more than 1 m thick but may extend laterally for hundreds of metres a vertical sequence of erosion surface sparse silt clasts parallel laminations silt drape is often found suggesting high flow stage deposition of plane bedded sand followed by a very rapid waning of flow with silt fallout in the final stages of the flood this sequence bears marked similarity to certain modern ephemeral flow sands

seismicity and tectonics of the rivera plate and implications for the 1932 jalisco mexico earthquake seismicity on and near the boundaries of the rivera plate is examined in order to determine the subduction regime of the rivera plate and its influence on the earthquake behavior of the northernmost section of the mid america trench in particular we address the question of a rivera cocos boundary there have been several large historic earthquakes in the coastal areas of the mexican states colima and jalisco but the last large event was in june 1932 the 1932 jalisco earthquake ms 8 1 the present quiescence has lasted longer than the average recurrence interval for the mexican subduction zone and the jalisco area is now categorized as a seismic gap however if subduction in this area is dominated by the motion of the rivera plate which is subducting at half the rate of the cocos plate the deficiency of earthquake activity may not be unusual in an attempt to better delineate the rivera cocos boundary intermediate sized earthquakes along and near the rivera fracture zone and the mid america trench were relocated with the joint epicenter determination method we found that in general the catalog locations are fairly accurate with the average change in epicenter upon relocation being 12 km seismicity along the rivera fracture zone follows the physiographic trend of the fracture zone but east of its intersection with the east pacific rise seismicity is more diffuse two intermediate sized earthquakes in this diffuse area have focal mechanisms suggesting that they represent rivera cocos boundary motion reexamination of arrival time data for the 1932 jalisco earthquake yields an epicenter at 19 57 n 104 42 w close to the boundary zone inferred from these two earthquakes we conclude that the possibility that the 1932 jalisco earthquake broke the northernmost section of the cocos north american plate interface as opposed to the rivera north american plate interface cannot be ruled out

teleseismic estimates of radiated seismic energy the e m 0 discriminant for tsunami earthquakes we adapt the formalism of boatwright and choy for the computation of radiated seismic energy from broadband records at teleseismic distances to the real time situation when neither the depth nor the focal geometry of the source is known accurately the analysis of a large data set of more than 500 records from 52 large recent earthquakes shows that this procedure yields values of the estimated energy ee in good agreement with values computed from available source parameters for example as published by the national earthquake information center neic the average logarithmic residual being only 0 26 units we analyze the energy to moment ratio by defining log10 ee m0 for regular earthquakes this parameter agrees well with values expected from theoretical models and from the worldwide neic catalogue there is a one to one correspondence between values of that are deficient by one full unit or more and the so called tsunami earthquakes previously identified in the literature as having exceedingly slow sources and believed due to the presence of sedimentary structures in the fault zone our formalism can be applied to single station measurements and its coupling to automated real time measurements of the seismic moment using the mantle magnitude mm should significantly improve real time tsunami warning

the 1995 colima jalisco mexico earthquake mw 8 a study of the rupture process in this study we map rupture characteristics of the great shallow thrust earthquake of october 9 1995 which caused extensive damage to the coastal towns of colima and jalisco to isolate the earthquake rupture details we deconvolve surface waves with two empirical green s functions the aftershock of october 12 1995 mw 5 9 and the foreshock of october 6 1995 mw 5 8 from the corresponding mainshock records specifically we use a spectral water level deconvolution to obtain 80 apparent source time functions astf at 62 stations rayleigh and love waves durations of the astf as a function of azimuth indicate that the rupture propagated toward n70 w the duration of the source time function stf is around 62 s with a large pulse at 45 s to map the main characteristics of the rupture we use an inverse radon transform of the astfs assuming a ribbon fault model aligned in the direction of the rupture propagation our analysis indicates that the rupture initiated about 20 km offshore of manzanillo and propagated almost unilaterally for 150 km towards n70 w with an average rupture velocity of approximately 2 8 km s the earthquake was a composite of three significant subevents the largest occurred 45 s after the initiation of the rupture and was located about 100 km away this result is in good agreement with the inversion of deformation data measured with gps melbourne et al 1997

strains and folds within thrust sheets an analysis of the heilam sheet northwest scotland abstract the changes of shape and orientation of fossil worm burrows have been used to carry out a detailed strain analysis of the heilam thrust sheet in the moine thrust zone northwest scotland the strains have been factorised into components of layer parallel shear 1 layer normal shear 2 and layer parallel shortening or elongation variations in the 1 shear are largely lithologically controlled some strain is due to flexural processes as the thrusts and overlying beds change dip over thrust ramps or are tightened by later deformation while there may also be a component of drag which increases towards the overlying thrust this predating the shear due to flexure a contoured map of the values suggests that major folds within the thrust sheet developed as a result of stick or drag on the floor thrust prior to ramp climb this led to differential movement in the transport direction causing layer parallel shortening accompanied or followed by buckling of the layers a map showing layer normal shear strains 2 suggests that the heilam sheet forms a major surge zone the central part having moved further wnw than the northern and southern parts this has led to components of lateral shear along parts of the sheet especially in the north producing curvature of the imbricate faults

complex strain patterns developed at the frontal and lateral tips to shear zones and thrust zones abstract many of the complex strain patterns seen in shear zones and thrust zones such as variable fabric orientations refolded folds and fabrics together with folds with hinges almost parallel to the main transport direction can be explained in terms of differential movement within the shear zones these strains are developed at the frontal and lateral tips of the zones as they propagate examples are taken from the moine thrust zone of scotland which show variations in strains particularly at the lateral tips the form of differential movement described here may lead to complex strain paths and non plane strain ellipsoids and the spatial variations in finite strain may be used to delineate zones of extensional and compressional flow and differential movement in the shear zones or thrusts

site effects and peak ground accelerations observed in guadalajara mexico for the 9 october 1995 mw 8 colima jalisco earthquake on 3 june 1932 an m s 8 2 shallow thrust subduction earthquake struck the colima jalisco cj region of mexico at an epicentral distance of 250 km from guadalajara the second largest town in mexico the return period of these cj earthquakes has been estimated from 77 to 126 years which suggests the next is likely to occur between 2009 and 2058 as a step toward estimating the seismic hazard posed by potential m s 8 2 events on guadalajara we present a study consisting of the following 1 the analysis of the strong ground motions recorded at guadalajara on 11 free field accelerographs for the cj 9 october 1995 m w 8 earthquake 2 the analysis of the site effects in guadalajara observed for this earthquake and 3 the estimation of the spatial distribution of peak ground acceleration pga in guadalajara for this event we propose validate and apply a recurrent neural network rnn technique to the recorded pga important site effects were identified using the horizontal to vertical and h hrocksite techniques on guadalajara s sandy soil layers with thicknesses h 20 m to the basaltic rock basement the estimated pgas in guadalajara for the cj 1995 earthquake varied from 2 to 27 cm s2 for soil layers with h 5 m and h 50 m respectively we expect the hybrid technique to obtain broadband synthetics chavez et al 2011 and the proposed rnn methodology can be used to estimate guadalajara s seismic hazard for m w 8 cj scenario earthquakes online material figures of fourier amplitude spectra h v and h h spectral ratios and signal to noise spectral ratios

the 13 january 2001 el salvador earthquake a multidata analysis 1 on 13 january 2001 a large normal faulting intermediate depth event mw 7 7 occurred 40 km off the el salvadorian coast central america we analyze this earthquake using teleseismic regional and local data we first build a kinematic source model by simultaneously inverting p and sh displacement waveforms and source time functions derived from surface waves using an empirical green s function analysis in an attempt to discriminate between the two nodal planes 30 trenchward dipping and 60 landward dipping we perform identical inversions using both possible fault planes after relocating the hypocentral depth at 54 km we retrieve the kinematic features of the rupture using a combination of the neighborhood algorithm of sambridge 1999 and the simplex method allowing for variable rupture velocity and slip we find updip rupture propagation yielding a centroid depth around 47 km for both assumed fault planes with a larger variance reduction obtained using the 60 landward dipping nodal plane we test the two possible fault models using regional broadband data and near field accelerograms provided by universidad centro americana 2001 near field data confirm that the steeper landward dipping nodal plane is preferred rupture propagated mostly updip and to the northwest resulting in a main moment release zone of approximately 25 km 50 km with an average slip of 3 5 m the large slip occurs near the interplate interface at a location where the slab steepens dip significantly the occurrence of this event is well explained by bending of the subducting plate

early middle triassic trace fossils from the luoping biota southwestern china evidence of recovery from mass extinction trace fossils have proven useful for studying the timing and process of biotic recovery after the permian triassic mass extinction ptme recovery stages are defined by comparing successive ichnoassemblages from the latest permian to the early middle triassic lower triassic trace fossils have been explored in some detail but those of the lower middle triassic are less well known here well preserved fossil materials from the luoping biota from yunnan province south china suggest that a fully recovered shallow marine ecosystem was re established by the early middle triassic trace fossil assemblages of the luoping biota are characterized by high ichnodiversity with 14 ichnogenera in the shallow marine environment of an intra carbonate platform basin and nine ichnogenera in the subtidal environment such moderate to high ichnodiversity together with a marked increase in burrow sizes and the common occurrence of key ichnotaxa e g rhizocorallium and thalassinoides suggests that the ichnofauna had reached recovery stage four in contrast non turbiditic strata of the offshore setting record only three ichnogenera with bioturbation indices never exceeding one periodic anoxia in bottom waters was presumably the main control for such a protracted trace fossil recovery in an offshore setting which otherwise aided the fine preservation of body fossils of the luoping biota furthermore event sedimentation turbidite deposits in the offshore setting incorporated moderate ichnodiversity and moderate to high bioturbation indices both interpreted as a result of short term colonization by transported infaunal animals from proximal settings the occurrence of variable crustacean traces e g sinusichnus spongeliomorpha and thalassinoides at luoping and the locomotion traces of marine reptiles together with abundant fishes and fossil decapods highlights the value of trace fossils in ecosystem reconstruction after the ptme

the palaeoenvironment and deformation of beaconites like burrows in the old red sandstone at gortnabinna sw ireland the gortnabinna area contains a number of well preserved deformed burrows within the fluviatile old red sandstone of s ireland detailed logging of the local succession enables subdivision into four facies facies 1 represents sheet flood deposits facies 2 ephemeral stream channels facies 3 marginal sheet flood deposits and facies 4 low energy settling of fines the burrows occur in facies 1 and 4 the sediments are now folded into a large upright westward plunging anticline the fold has a well developed axial planar cleavage and is extended along strike by listric normal faults the burrows in facies 1 were originally circular and orthogonal to bedding and reveal a n s layer parallel shortening strain of 2 1 followed by a shear strain of 1 48 during folding these burrows have a bimodal distribution of diameters with peaks in the ranges 50 80 and 110 170 mm the burrows of facies 4 are sub parallel to the bedding plane and are generally curved with a maximum width of 180 mm and lengths of up to 2 3 m these burrows display passive infill following abandonment the burrows are morphologically similar though distinct from beaconites barratti which has been described from elsewhere in the old red sandstone and are tentatively interpreted as lungfish burrows

flexural shear in a periclinal fold from the irish variscides abstract periclinal folds occur in a structural culmination in the centre of the irish variscan fold belt the culmination marks a zone of enhanced shortening which is associated with a locally attenuated stratigraphy and an anomalous deformation sequence with respect to the remainder of the orogen originally vertical burrows have been used along with cleavage fold relations to study both the three dimensional evolution of the periclinal folding and the temporal relationship between folding and cleavage as well as cleavage forming flattening strains the burrows record along strike shear related to the propagation of the periclinal folds a comparison with strain measurements made outside the culmination zone shows that the galley head area suffered higher strains integration of field data with published analyses of plasticine modelling of periclinal folds yields models for the propagation of a pericline and for the geometry of its lateral terminations

a 180 000 year pollen record from owens lake ca terrestrial vegetation change on orbital scales abstract pollen from the upper 90 m of core ol 92 from owens lake is a climatically sensitive record of vegetation change that indicates shifts in the plant associations representing warm and cold desertscrub pinyon juniper woodland and pine fir forest during the past 180 000 years these changes are synchronized with glacial interglacial cycles during glacial and stadial climates juniper woodland expanded downslope and replaced warm desert shrubs while upper montane and subalpine forests in the arid inyo mountains also expanded and those in the sierra nevada were displaced by the ice cap and periglacial conditions conversely during interglacial and interstadial climates warm desert plants expanded their range in the lowlands juniper and sagebrush retreated upslope and montane and subalpine forests expanded in the sierra nevada the reconstructed vegetation history demonstrates a regional climatic response and the congruence of the pollen sequence with marine and ice cap oxygen isotope stratigraphies suggests a link between regional vegetation and global climate change at orbital scales

continuous lake sediment records of glaciation in the sierra nevada between 52 600 and 12 50014c yr b p the chemistry of the carbonate free clay size fraction of owens lake sediments supports the use of total organic carbon and magnetic susceptibility as indicators of stadial interstadial oscillations owens lake records of total organic carbon magnetic susceptibility and chemical composition of the carbonate free clay size fraction indicate that tioga glaciation began 24 500 and ended by 13 60014c yr b p many of the components of glacial rock flour e g tio2 mno bao found in owens lake sediments achieved maximum values during the tioga glaciation when valley glaciers reached their greatest extent total organic carbon and sio2 amorphous concentrations reached minimum values during tioga glaciation resulting from decreases in productivity that accompanied the introduction of rock flour into the surface waters of owens lake at least 20 stadial interstadial oscillations occurred in the sierra nevada between 52 600 and 14 00014c yr b p total organic carbon data from a pyramid lake sediment core also indicate oscillations in glacier activity between 39 500 and 13 60014c yr b p alpine glacier oscillations occurred on a frequency of 1900 yr in both basins suggesting that millennial scale oscillations occurred in california and nevada during most of the past 52 600 yr

the geodetic signature of the m8 0 oct 9 1995 jalisco subduction earthquake the october 1995 mw 8 0 jalisco subduction earthquake has provided a thorough geodetic observation of the coseismic subduction process an 11 station regional gps network located directly onshore of the rupture demonstrates consistent vertical subsidence verified by tide gauge data and southwest directed extension with measured displacements reaching 1 meter unusually shallow and non uniform faulting is required to explain the displacements we determine that up to 5 meters of slip occurred within the upper 15 km of the thrust fault zone and 2 meters possibly as shallow as 8 km and that slip was likely distributed in two main patches the paucity of continental sediments in this subduction zone could be responsible for the anomalously shallow faulting

occurence of the trace fossil beaconites antarcticus in the lower carboniferous fluviatile rocks of county mayo ireland abstract large straight curved or sinuous endichnial burrows with a meniscus pattern of infilling are described from lower carboniferous red beds of county mayo ireland the burrows have been identified as beaconites antarcticus the burrows show a strong facies association being concentrated in the upper parts of sandstones deposited during floods in shallow possibly ephemeral stream channels they appear to be absent from the overlying non red fluvial sandstones which show evidence for deeper more sinuous and more permanent channels it is suggested that burrowing was related to varying moisture content of the sediment the burrows were probably formed by locomotory back packing of arthropods or vertebrates but the precise nature of the producer remains unknown

invertebrate trace fossils in semi arid to arid braided ephemeral river deposits of the mississippian middle member of the mauch chunk formation eastern pennsylvania usa abstract the rapid diversification of terrestrial ecosystems was initiated in the silurian and subsequently continued through the mississippian detailed collecting of the middle member of the mississippian mauch chunk formation in eastern pennsylvania has yielded a number of important vertebrate and invertebrate trace fossils indicating the presence of a significant terrestrial biotic diversity during the early carboniferous this report illustrates the diverse invertebrate trace fossil assemblage associated with the ephemeral river systems of the mauch chunk the mauch chunk invertebrate ichnoassemblage consists of backfilled burrows of deposit feeders both meniscate taenidium and non meniscate planolites that typically cross cut bedding arthropod trackways diplichnites diplopodichnus stiaria kouphichnium and stialla striated trails cruziana and resting traces rusophycus and surface or shallow subsurface grazing trails or burrows gordia tetrapod footprints mostly made by temnospondyl amphibians are also part of this ichnoassemblage the mauch chunk invertebrate ichnoassemblage corresponds well to the scoyenia ichnofacies in consisting of simple burrows trackways striate and bilobate trails and pits and simple meniscate burrows typically trace fossils of the scoyenia ichnofacies indicate opportunistic behaviors in subaerial environments that are temporarily or periodically inundated indeed the palaeoenvironmental setting of these traces is a semi arid to possibly arid braided ephemeral river system with extensive overbank deposits the invertebrate traces were developed both as infaunal burrows in the tops and within channel sandstones and as surface and grazing traces on in channel mudstone draped bedforms and in proximal overbank deposits the in channel mudstone draped bedforms display both vertebrate and invertebrate trace fossils the mauch chunk invertebrate ichnofossil assemblage resembles other devonian through triassic ichnoassemblages from ephemeral fluvial red beds confirming that the terrestrial invertebrate fauna had already fully colonized fluvial environments by mississippian time furthermore the development of the scoyenia ichnoguild in the mauch chunk formation in the form of abundant traces of deposit feeders of a shallow to intermediate depth infauna esp taenidium is unusually early when compared to the previously known palaeozoic record

teleseismic body wave analysis of the 9 october 1995 mw 8 0 colima jalisco mexico earthquake and its largest foreshock and aftershock the source process of the october 9 1995 colima jalisco mexico earthquake mw 8 0 and its largest foreshock and aftershock were determined from teleseismic body waves using a least squares inversion scheme the three events are shallow dipping thrust fault earthquakes in agreement with the relative plate motions for rivera north america and cocos north america plate boundaries neither the foreshock nor the largest aftershock show significant differences in focal mechanism nor centroidal depth with respect to the average mechanism of the mainshock the rupture of the mainshock began near the foreshock hypocenter and propagated with a variable rupture velocity towards the nw the source time function for this event shows four distinct episodes of energy release about 50 of the moment was released at the northern end of the rupture between 90 and 110 km from the epicenter this rupture geometry is in agreement with crustal deformation observed inland using gps measurements however the scalar seismic moment of the main shock obtained in this study mo 1 84 1020 is smaller with respect to the lower frequency cmt results reported by harvard mo 1 15 1021

imaging the seismic crustal structure of the western mexican margin between 19 n and 21 n three thousand kilometres of multichannel mcs and wide angle seismic profiles gravity and magnetic multibeam bathymetry and backscatter data were recorded in the offshore area of the west coast of mexico and the gulf of california during the spring 1996 cortes survey the seismic images obtained off puerto vallarta mexico in the jalisco subduction zone extend from the oceanic domain up to the continental shelf and significantly improve the knowledge of the internal crustal structure of the subduction zone between the rivera and north american na plates analyzing the crustal images we differentiate 1 an oceanic domain with an important variation in sediment thickness ranging from 2 5 to 1 km southwards 2 an accretionary prism comprised of highly deformed sediments extending for a maximum width of 15 km 3 a deformed forearc basin domain which is 25 km wide in the northern section and is not seen towards the south where the continental slope connects directly with the accretionary prism and trench thus suggesting a different deformational process and 4 a continental domain consisting of a continental slope and a mid slope terrace with a bottom simulating reflector bsr identified in the first second of the mcs profiles the existence of a developed accretionary prism suggests a subduction accretion type tectonic regime detailed analysis of the seismic reflection data in the oceanic domain reveals high amplitude reflections at around 6 s two way travel time twtt that clearly define the subduction plane at 2 s twtt depth we identify a strong reflection which we interpret as the moho discontinuity we have measured a mean dip angle of 7 1 at the subduction zone where the rivera plate begins to subduct with the dip angle gently increasing towards the south the oceanic crust has a mean crustal thickness of 6 0 6 5 km we also find evidence indicating that the rivera plate possibly subducts at very low angles beneath the tres marias islands

vertebrate burrows in late pleistocene paleosols at korean palaeolithic sites and their significance as a stratigraphic marker abstract a vertebrate burrow bearing layer of late pleistocene age is commonly found at many paleolithic archaeological sites in korea the burrows are straight to slightly curved in horizontal plan view and gently inclined in lateral sectional view they are interpreted as having been produced by rodent like mammals based on their size and architecture the significance of such burrow bearing layers as a characteristic stratigraphic marker unit is demonstrated by high burrow abundance consistent stratigraphic position lack of stratigraphic recurrence at these sites and widespread geographic extent three dating methods tephrochronology radiocarbon and osl dating were used to infer the age of these burrow bearing layers the dating results indicate that they were formed between ca 40 000 and 25 000 yr mis 3 2 and this suggests that this layer can be used as a stratigraphic time marker in late pleistocene paleosol sequences for this region

large vertebrate burrow from the upper mississippian mauch chunk formation eastern pennsylvania usa abstract a burrow of probable amphibian origin was discovered in the upper member of the mississippian mauch chunk formation in eastern pennsylvania facies analysis of the upper member indicates that deposition occurred in an ephemeral braided stream setting the burrow is housed in a mudstone and is filled by two graded beds of conglomerate to sandstone it is characterized by a flared opening leading into a narrower slightly helical tunnel that ends in an inflated ovate chamber approximately 51 to 60 cm in diameter with a maximum height of 20 cm the flared opening is stratigraphically higher than the elevation at the base of the chamber the tunnel has a semicircular base the geometries abrupt angle changes inflated termination width to height ratios of the terminal chamber and graded fill indicate that the structure was an open void prior to sedimentation the geometry and size of this structure are incompatible with known invertebrate burrows and erosional features palaeosauropus primaevus an amphibian footprint ichnotaxon recovered from the mauch chunk formation was made by an amphibian of sufficient size to create such a large burrow this type of burrowing was most likely a response to seasonal droughts as local water sources evaporated

bristlecone pine paleoclimatic model for archeological patterns in the white mountain of california abstract archeologists recognize that prehistoric human populations were a significant variable in the operation of past california ecosystem processes and that a changing environment created constraints and opportunities for prehistoric cultural adaptation the tie between paleoclimatology and archeology is an evolving interdisciplinary field of study that aims to facilitate a better understanding of prehistoric subsistence settlement patterns relative to climate variability a paleoclimatic model based on temperature inferences and precipitation reconstruction from tree ring widths of bristlecone pine in the white mountains of california is used to explain the distribution of prehistoric alpine villages in the white mountains the paleoclimatic model is visually and statistically compared with calendar ages converted from calibrated 14 c dates from the village sites results elucidate the role of water availability in the frequency and intensity of settlement as 88 of the calendar dates associated with 14 c dates fall within wet periods 0 05 p 0 005 the coincidence of the calendar dates around above average precipitation periods confirms that long term available resources are contingent on the availability of moisture the key to life in the desert environment

imaging coseismic rupture in far field by slip patches summary since the end of the 1970s teleseismic waves are used routinely to infer the first order characteristics of the event location depth duration focal mechanism but finding the second order kinematic parameters spatial distribution of slip rupture velocity and more basically the discrimination between the fault plane and the other nodal plane of distant events remains a difficult task classically these events are studied by two different methods either they are seen as a succession of subevents each of which is considered as a point source or like in near field as extended sources where the kinematic parameters are retrieved on a grid the first approach is not physically satisfactory and can lead to erroneous interpretations of the

two stage composite megathrust rupture of the 2015 mw8 4 illapel chile earthquake identified by spectral element inversion of teleseismic waves the mw8 4 illapel earthquake occurred on 16 september was the largest global event in 2015 this earthquake was not unexpected because the hypocenter was located in a seismic gap of the peru chile subduction zone however the source model derived from 3 d spectral element inversion of teleseismic waves reveals a distinct two stage rupture process with completely different slip characteristics as a composite megathrust event the two stages were temporally separated rupture in the first stage with a moment magnitude of mw8 32 built up energetically from the deeper locked zone and propagated in the updip direction toward the trench subsequently the rupture of the second stage with a magnitude of mw8 08 mainly occurred in the shallow subduction zone with atypical repeating slip behavior the unique spatial temporal rupture evolution presented in this source model is key to further in depth studies of earthquake physics and source dynamics in subduction systems

relative motions of the pacific rivera north american and cocos plates since 0 78 ma we use magnetic anomaly and fracture zone crossings from 3 n 24 n along the east pacific rise to define the boundaries and relative velocities of the rigid pacific rivera north american and cocos plates since 0 78 ma and to test several hypotheses regarding the nature of deformation between these plates crossings of the 0 78 ma isochron from the pacific rivera rise north of 22 0 n are significantly better fit by the 0 0 78 ma pacific north america rotation than by a pacific rivera rotation thereby supporting a recently proposed model for accretion of the northern part of the rivera plate to north america a significant misfit of the pacific cocos rotation to crossings of anomaly ln from the east pacific rise north of 16 4 n suggests that seafloor north of 16 n moves relative to the rigid pacific or cocos plates we also find that nine crossings of the eastern rivera fracture zone and eight crossings of anomaly ln flanking the manzanillo spreading segment are fit well by a pacific rivera rotation the rivera cocos angular velocity derived from the best fitting pacific cocos and pacific rivera angular velocities predicts 19 3 mm yr 1 95 confidence limit of n s convergence near the center of the rivera cocos boundary nearby left lateral strike slip earthquakes with north trending fault planes suggest that convergence is accommodated via sinistral shear along a north trending zone the unambiguous kinematic and seismologic evidence for significant rivera cocos motion indicates that the absence of a well defined rivera cocos plate boundary cannot be interpreted as evidence that rivera cocos motion is slow or zero as is postulated in several previous studies the rivera cocos angular velocity predicts oblique rivera cocos convergence at the el gordo graben and beneath the manzanillo trough and southern colima graben any extension across these features since 0 78 ma thus cannot have resulted from divergence between the subducting rivera and cococs plates

rupture properties of the giant sumatra earthquake imaged by empirical green s function analysis empirical green s function egf analysis has remained little used to image the rupture properties of the giant 26 december 2004 sumatra earthquake the 2 november 2002 foreshock m w 7 2 close to the mainshock epicenter gives us the opportunity to use its waveforms to empirically simulate the rayleigh wave propagation of the sumatra earthquake we first show that the exceptional size of the sumatra earthquake does not prevent use of the egf technique four aftershocks m w 5 9 6 1 distributed along the sumatra andaman trench are shown to have consistent rayleigh waves for periods between 100 and 200 sec at a lower frequency we present two large earthquakes of the mexican subduction zone m w 7 2 7 3 close to the selected egf magnitude for which long period green s functions 100 2000 sec remain very similar even if event epicenters are separated by about 650 km this justifies the possibility of using the 2002 foreshock as an egf for the whole rupture process of the sumatra earthquake and shows more generally the very broad range of application of egf technique then a specific analysis reveals that seismic moment magnitude is close to 9 1 seismic moment equal to 5 6 10 22 n m moment release analysis along the sumatra andaman trench shows two main slip episodes one next to the northern extremity of sumatra 20 m slip and the other one along the nicobar islands 10 m slip with a global extent of 1150 1200 km rupture velocity varies between values around 2 5 km sec in the first half of the rupture and values closer to 2 km sec in the second half total duration imaged by rayleigh waves is 580 sec 20 sec and no activity of the fault is found in the time scale between 600 and 2000 sec in the hypothesis of even longer timescale slip this phenomenon would be of the order of 10 20 of the global moment and likely restricted to the andaman islands

crustal architecture at the collision zone between rivera and north american plates at the jalisco block tsujal project processing and analysis of new multichannel seismic records coincident with wide angle seismic profiles acquired in the framework of the tsujal project allow us to investigate in detail the complex structure of the oceanic domain in the collision zone between rivera plate and block jalisco at its northern termination the subducting rivera plate which is overridden by the north american plate jalisco block is clearly identified up to 21 5 n just south of maria magdalena island as a two clear reflections that we interpret as the interplate and moho discontinuities north of the tres marias islands the seismic images display a different tectonic scenario with structures that are consistent with large faulting and rifted margin a two dimensional velocity approach for the crustal geometry is achieved using joint refraction reflection travel time tomography the uncertainty of the results is assessed by means of monte carlo analysis our results show an average oceanic crustal thickness of 6 7 km with a moderate increase towards the jalisco block an anomalous thick layers 3 0 km displaying a relatively low velocity 5 5 km s underneath maria magdalena rise and an estimated moho depth deeper than 15 km in the collision zone between rivera plate and jalisco block we have also determined an anomalous crust on the western flank of the tres marias islands which may be related to the initial phases of continental breakup of the baja california peninsula and mexico mainland high resolution bathymetry provides remarkable images of intensive slope instabilities marked by relatively large slides scars of more than 40 km2 extent and mass wasting deposits probably triggered by the intense seismicity in the area

the sedimentary record of carboniferous rivers continuing influence of land plant evolution on alluvial processes and palaeozoic ecosystems abstract evidence from modern rivers and the deep time geological record attests to the fundamental importance of plant life for the construction of physical habitats within fluvial environments data from an extensive literature review and original fieldwork demonstrates that many landforms and geomorphic features of modern river systems appear in the palaeozoic stratigraphic record once terrestrial vegetation had adopted certain evolutionary advances for example stable point bars are associated with the onset of rooted plants in the siluro devonian and avulsive and anabranching fluvial systems become common at the same time as extensive arborescent vegetation in the carboniferous in this paper we demonstrate a correlation between the diversification of physical fluvial environments and the expansion of terrestrial fauna and flora with an emphasis on the culmination of these trends within carboniferous alluvial systems many extrinsic factors have been considered as possible controls on the evolutionary timelines of terrestrialization for organisms however a fundamental prerequisite for achieving terrestrial biodiversity was the variety of physical habitats especially riparian systems available for newly evolved organisms in association with abundant lowland meandering systems the widespread appearance across carboniferous alluvial plains of fixed channel and anabranching reaches created further physical landforms for colonization and would have promoted increasingly complex hyporheic flow regimes furthermore the associated increase in arborescent vegetation and supply of large woody debris to inland and coastal rivers would have created a wealth of microhabitats for continental organisms we argue that the expanding extent and diversity of physical alluvial niches during the palaeozoic is an underappreciated driver of the terrestrialization of early continental life the study of the deep time fossil and stratigraphic record also illustrates that vegetation is a fundamental prerequisite for the creation of biogeomorphic alluvial landforms and physical habitats and microhabitats

source tomography by simulated annealing using broad band surface waves and geodetic data application to the mw 8 1 chile 1995 event summary we invert surface wave and geodetic data for the spatio temporal complexity of slip during the mw 8 1 chile 1995 event by simulated annealing this quasi global inversion method allows for a wide exploration of model space and retains the non linearity of the source tomography problem complex source spectra are obtained from 5 to 45 mhz from first and second orbit fundamental mode rayleigh waves using an empirical green s function cross correlation technique coseismic displacement vectors were measured at 10 gps sites near antofagasta they are part of a french chilean experiment which monitors the northern chile seismic gap the spectra together with the geodetic data are inverted for the moment distribution on a 2 d dipping fault under the physical constraints of slip positivity and causality marginal a posteriori distributions of the model parameters are obtained from several independently inverted solutions in general features of the slip model are well resolved data are well fitted by a purely unilateral southward rupture with a nearly uniform velocity around 2 5 3 0 km s 1 and a total duration of 65 s several regions of moment release were imaged one near the hypocentre a major one 80 km south of it and a minor one 160 km south of it the major patch of moment release seemed to have propagated to relatively shallow depths near the trench 100 km ssw of the epicentre the region of major slip is located updip of the 1987 mw 7 5 earthquake suggesting a causal relationship most of the slip occurred updip of the hypocentre 36 km but the entire coupled plate interface 20 40 km ruptured during the chile 1995 event

empirical green function deconvolution of broadband surface waves rupture directivity of the 1992 landers california mw 7 3 earthquake we present a simple method to determine gross temporal and spatial characteristics of faulting that can uniquely define the fault plane for a relatively large earthquake the technique involves deconvolution of teleseismic and regional broadband surface waves and or body waves of a small event an empirical green function from the corresponding signals at the same stations for a large mainshock this deconvolution corrects each mainshock seismic record for propagation and instrument response and if the focal mechanisms and centroid depths are identical deconvolution provides relative source time functions for the mainshock azimuthal variations of source time function width or subevent interference reveal the mainshock rupture directivity changes in the source mechanism during rupture can be evaluated for some classes of events our empirical green function procedure is novel in its application to surface waves and its use for large m 7 earthquakes we perform synthetic tests to establish intrinsic limitations of the method the procedure requires very little data processing and can be applied in near real time with the current distribution of seismic stations that have dial up data retrieval capability it also provides a straightforward procedure for reducing bias in source duration estimates resulting from aspherical heterogeneity and for detecting anomalous long period radiation we apply the procedure to the 28 june 1992 landers california mw 7 3 earthquake the landers earthquake source duration lasted about 25 sec and was dominated by two subevents with predominantly north northwestward rupture extending 60 to 70 km the subevents show counter clockwise rotations of at least 12 in strike that correlate well with mapped surface rupture

optimum sea surface displacement and fault slip distribution of the 2017 tehuantepec earthquake m w 8 2 in mexico estimated from tsunami waveforms

ichnology and sedimentology of the trace fossil bearing fluvial red beds from the lowermost member of the paleocene funing formation in the jinhu depression subei basin east china abstract the lowermost member of the paleocene funing formation which is composed of bioturbated fluvial red beds is extensively distributed throughout the jinhu depression subei basin east china despite its economic value as one of the most important oil bearing reservoirs in the subei basin the sedimentology ichnology and paleoenvironment of this formation in the jinhu depression remain poorly understood in this work we investigated the ichnofossils and sedimentary facies analyzed the ichnofacies and potential tracemakers and reconstructed the paleoenvironment of the jinhu depression based on cores from the lowermost member of the paleocene funing formation this formation contains a moderately diverse ichnofauna 9 ichnotaxa of the scoyenia ichnofacies that includes meniscate burrows taenidium barretti taenidium satanassi and beaconites coronus simple horizontal cylindrical burrows palaeophycus tubularis palaeophycus heberti and planolites isp simple vertical or subvertical burrows skolithos linearis and skolithos isp and plant root traces the other complex branched and chambered burrows are left in open nomenclature these ichnofossils are widespread throughout the three facies associations identified in this study 1 ephemeral fluvial channel 2 crevasse splay and 3 distal floodplain facies associations multiple lines of sedimentological and ichnological evidence namely the predominance of massive and upper flow regime structures the occurrence of invertebrate burrows e g skolithos and taenidium in the lower and middle parts of the channel deposits and the dramatic changes in the color and mottling in channel and overbank sediments indicate that the river discharge was short lived and that the water table was highly variable the variations in the discharge and water level are attributed to the influence of seasonal rainfall the cyclic nature of intense rainfall events and dry periods suggests that the subei basin was likely located in a semiarid region with a seasonal rainfall pattern during the early paleocene this study also reveals that the ephemeral fluvial channel is the facies association with the highest potential to yield oil bearing reservoirs in the paleocene red beds of the jinhu depression additionally the influence of bioturbation on the reservoir quality in this region should be considered in future research

fluvial sedimentation in the lower carboniferous of clew bay county mayo ireland abstract a succession of about 300 m of fluvial sediments from the lower carboniferous of northwest ireland is described and interpreted a lower mainly red formation contains fluvial channel deposits dominated by flat laminated sandstone these are separated by interbedded sandstones and mudrocks with local caliche horizons and abundant mudcracks interpreted as levee and flood basin deposits an upper mainly non red formation contains fluvial channel deposits with common trough cross stratification and epsilon cross stratification also separated by interbedded sandstones and mudrocks evidence of desiccation is less common in the uppermost beds which pass transitionally upwards into marine sediments the change in fluvial channel style is interpreted as due to increasing sinuosity and permanence of flow which may have been partly temporally and partly spatially controlled the predominance of coarse sediments is thought to be largely controlled by limited subsidence the lower carboniferous transgression was the major overall control of alluviation

influences of recurrence times and fault zone temperatures on the age rate dependence of subduction zone seismicity correlations among subduction zone seismicity convergence rate and subducting plate age are reassessed considering the possible roles of both recurrence times and fault zone temperatures distributions of earthquakes with respect to subducting lithosphere age and convergence rate are grossly explained by a recurrence relation when ages and rates at the world s trenches are taken into account correlations between maximum earthquake size m w max and convergence rate occur because faster subduction lowers the average recurrence time so that at random within a limited sampling time faster subduction zones have larger earthquakes published empirical slopes of an assumed linear relationship between m w max and convergence rate are predicted to within 1 standard deviation by such a recurrence model recurrence predicts that m w max should be related to the logarithm of convergence rate and revised age rate m w max data agree with such a relationship no resolvable global correlation between age and m w max is found hence mechanical explanations of subduction zone seismicity based on such correlations are not required predicted average steady state temperatures based on age and dip of the subducting lithosphere and convergence rate at most subduction zone thrust faults are within a small range of values 50 c the few warm outliers that is cascadia mexico and southernmost chile south of chile rise that subduct very young lithosphere also have low seismic coupling coefficients suggesting that high temperature may inhibit seismicity fault zone temperatures can explain global variations in seismic coupling coefficients as well as the slab anchor model of scholz and campos 1995 applying this to the cascadia subduction zone in contrast to conclusions drawn from mechanical models of subduction and consistent with many other observations due to its extremely high temperature cascadia may be a region where aseismic subduction predominates

self consistent retrieval of source parameters using mantle waves the large number of high quality stations from global networks e g iris geoscope allows for rapid and robust recovery of source parameters of large earthquakes we present a self consistent analysis of surface waves in terms of directivity parameters the boxcar is often used to recover source parameters but is rarely a faithful representation of an event s time function we demonstrate that more reliable estimates of directivity parameters can be obtained when we take into account the source time function stf of the event a low frequency stf is obtained from first r1 and second r2 orbit rayleigh waves in the range 2 to 15 mhz with a spectral synthesis and inversion method we measure the differential amplitudes between data and 3d synthetics we use the r1 r2 ratio of differential amplitudes to invert in a single narrow frequency band for the event s apparent rupture azimuth and velocity for the mw 8 1 chile 1995 event data are consistent with unilateral southward propagation with a velocity of about 2 4 km sec for the mw 7 9 mexico 1995 earthquake the rupture propagated toward the nw at about 2 0 km sec our low frequency estimates agree with broadband studies of both events and can be retrieved rapidly on a routine basis after a large earthquake

a 1000 year record of temperature and precipitation in the sierra nevada abstract tree ring data from subalpine conifers in the southern sierra nevada were used to reconstruct temperature and precipitation back to a d 800 tree growth of foxtail pine pinus balfouriana and western juniper juniperus occidentalis ssp australis is influenced by nonlinear interactions between summer temperature and winter precipitation reconstruction of the separate histories of temperature and precipitation is feasible by explicitly modeling species and site differences in climatic response using response surfaces the summer temperature reconstruction shows fluctuations on centennial and longer time scales including a period with temperatures exceeding late 20th century values from ca 1100 to 1375 a d corresponding to the medieval warm period identified in other proxy data sources and a period of cold temperatures from ca 1450 to 1850 corresponding to the little ice age precipitation variation is dominated by shorter period decadal scale oscillations the long term record presented here indicates that the 20th century is anomalous with respect to precipitation variation a tabulation of 20 and 50 yr means indicates that precipitation equaling or exceeding 20th century levels occurred infrequently in the 1000 yr record

cleavage geometry and the development of the church bay anticline co cork ireland abstract the church bay anticline is one of a series of e w trending hercyman folds in southern ireland the fold has a crudely axial planar cleavage which was initiated early in the buckling history the cleavage was deformed subsequently by a number of discrete bedding parallel shear zones as the fold continued to amplify this has resulted in a characteristically sigmoidal cleavage geometry in the fold profile plane the cleavage also displays kink bands and sharp angular changes across bedding planes in the fold hinge as a result of shearing within these sheared zones the cleavage is intensified indicating that conditions for cleavage formation were maintained throughout the development of the fold no new cleavage has formed despite the rotation of the cleavage during the deformation history

slip kinematics and dynamics during and after the 1995 october 9 mw 8 0 colima jalisco earthquake mexico from gps geodetic constraints we use horizontal and vertical crustal displacements derived from gps measurements at 26 sites in western mexico to study the coseismic and post seismic kinematics and dynamics of the 1995 october 9 m w 8 0 colima jalisco earthquake along the middle america trench the measurements bracket the entire landward edge of the approximately 150 km long rupture zone and span a 4 yr period for most sites we solve for the temporal evolution of slip along the subduction interface by inverting gps displacements for the coseismic and four post seismic intervals march 1995 march 1999 subject to the assumption that the crust responds elastically to slip along a shallow dipping curved subduction interface coseismic rupture of up to 5 m was largely focused above depths of 20 km and was limited to a 120 140 km long segment of the subduction zone within one week of the earthquake post seismic slip migrated downdip to depths of 16 35 km where it has since decayed logarithmically we also find evidence for shallow aseismic slip during 1996 or early 1997 northwest of the coseismic rupture zone and increasingly widespread relocking of shallow regions of the subduction interface after early 1997 the relative lack of afterslip in shallow regions of the subduction interface suggests that the interface lies in the unstable frictional regime and hence is strongly coupled between earthquakes by 1999 the cumulative slip moment associated with post seismic slip equaled 70 per cent of the coseismic moment with nearly all of this slip occurring downdip from the coseismic rupture zone the migration of slip after the earthquake to a deeper and presumably velocity strengthening area of the subduction interface and the logarithmic decay of afterslip conform to the qualitative and quantitative predictions of a model in which the fault kinematics are prescribed by rate and state variable frictional laws however misfits to the geodetic displacements exceed the average displacement uncertainties for all epochs implying one or more of the following 1 the elastic response is heterogeneous due to slip along unmodelled upper crustal faults or variations in the elastic properties of the crust 2 other post seismic mechanisms such as viscoelastic or poroelastic effects contribute to or possibly dominate the post seismic response 3 we have underestimated the uncertainties in the gps displacements