an integrated model of extrusive sand injectites in cohesionless sediments clastic injection and surface expression of subsurface sediment remobilization is a phenomenon which is becoming increasingly recognized however understanding of the physical mechanisms that control these features remains limited dominated by inference from outcrop and seismic studies here this limitation is addressed through a set of experiments focused on the development and evolution of fluidization features in non cohesive bedded sequences fluidization and the onset of piping are shown to occur progressively through a sequence of discrete phases with initial void formation development of infiltration horizons rupture and finally pipe formation critically the style of piping the stability of piping and the temporal evolution of venting are shown to exhibit considerable variability in particular pipes may either be stable or very mobile migrating laterally over large distances these produce deposits that are typically interpreted in outcrop as being the product of en masse liquefaction rather than localized dynamic fluidization these differing elements are synthesized to produce a model of sand extrudites in addition the implications of this model are explored

energy levels phase and amplitude modulation of the baroclinic tide off hawaii abstract inverted echo sounder data from station aloha north of oahu hawaii are used to determine the absolute energy levels and time varying nature of the first mode baroclinic tide north of hawaii the semidiurnal tide amplitude and phase are modulated with 60 120 day periodicity which indicates interaction between the baroclinic tide and intra annual mesoscale variability seen off hawaii close to the presumed generation site there is less phase modulation and amplitude modulation is uncorrelated with the far field variability these results are consistent with a model of phase locked generation together with phase and amplitude distortion during propagation the sense of the amplitude modulation is opposite to that previously observed at decadal timescales semidiurnal energy flux at station aloha ranges from 2 2 to 8 0 kw m 1 with a mean value of 4 4 kw m 1

experimental studies of the fluidization of layered sediments and the formation of fluid escape structures experiments demonstrate that fluid escape structures can be produced as a result of unstable fluidization behaviour where a lower base layer of granular material is inhibited from fluidizing by the presence of an overlying non fluidizing top layer before the base layer can fluidize the weight of the overlying material must be balanced and this is accomplished by base layer material pressing against the bottom surface of the confining top layer forming a static layer this static layer allows the top layer to lift away from the base layer which is then free to fluidize a water filled crack forms below the static layer and as this grows instability causes the static layer and top layer to bend and conical voids to form below the antiformal sections rupture occurs at the apex of the water void allowing the underlying water and fluidizing material to burst out through the top layer the fluidized base layer material then flows through the rupture until all of this material except that in the static layer is deposited above the previously overlying layer and a stable fluidization system results the top layer material is bent upwards around the rupture and the resulting pillar type escape structure is preserved if flow then ceases the vigour of the burst out is greatest when the base layer material has a grain size 15 of the top layer material if the base layer grain size is less than 8 of the top layer then base layer material will pass through the top layer pore spaces without forming an escape structure if cohesive material is present escape structures form when a layer of fine grained cohesive material overlies a layer of cohesionless material at low flow rates small pipes with scattered angular bends pierce the top layer and base layer material passes through them the base layer material is ejected on to the top layer and builds up around the mouth of each pipe to form constructional structures sand volcanoes this is in contrast to the cohesionless experiments where the weight of material being deposited on the top layer caused an ejecta filled depression to form around the rupture if flow then ceases both the pipes and the sand volcanoes are preserved at high flow rates where the base layer fluidizes the top cohesive layer becomes fragmented small fragments circulate within the fluidizing base layer and are preserved as floating clasts large fragments sink to the bottom of the fluidizing base layer erosion of the bottom surface of these larger fragments causes this surface to become convex downward the experimentally derived structures are similar to pillar type structures observed in the field and the processes described can be used to investigate the development of these structures fluidization experiments also demonstrate the genesis of dish structures and the cohesive behaviour can be applied to the deformation of these structures after initial formation

seismotectonic implications of sand blows in the southern mississippi embayment we explore seismically induced sand blows from the southern mississippi embayment and their implications in resolving the question of near or distal epicentral source region this was accomplished using aerial photography field excavations and cone penetration tests our analysis shows that three sand blow fields exhibit a distinct chronology of strong ground motion for the southern embayment 1 the ashley county arkansas sand blow field near the arkansas louisiana state border experienced four holocene sand venting episodes 2 to the north the desha county field experienced at least three episodes of liquefaction and 3 the lincoln jefferson counties field experienced at least one episode cone penetration tests cpt conducted in and between the sand blow fields suggest that the fields may not be distal liquefaction associated with new madrid seismic zone earthquakes but rather are likely associated with strong earthquakes on local faults this conclusion is consistent with the differences in timing of the southern embayment sand venting episodes and those in the new madrid seismic zone these results suggest that active tectonism and strong seismicity in intraplate north america may not be localized at isolated weak spots but rather widespread on fault systems that are favorably oriented for slip in the contemporary stress field

intra annual oscillations at station aloha north of oahu hawaii inverted echo sounders have been used to make continuous measurements of dynamic height at a site chosen to be representative of the central pacific subtropical gyre these show that the dominant features in dynamic height are fluctuations having peak to peak amplitudes of up to 27 dyn cm and timescales of about 100 days empirical orthogonal function analyses of temperature and salinity profiles suggest that if the oscillations are due to vertical motion within the water column the motion is not that of first baroclinic mode but has much higher vertical wavenumber structure zonal wavenumbers associated with the oscillations indicate westward phase propagation and meridional wavenumbers are close to zero the dominant periods are too short for freely propagating rossby waves two explanations of these observations are that the waves could be doppler shifted by the mean flow or that the region could be an area of active forcing

clastic pipes and soft sediment deformation of the jurassic carmel formation southern utah u s a implications for pipe formation mechanisms and host rock controls abstract vertically oriented columns of sandstone termed clastic pipes are common in jurassic deposits of the colorado plateau exposures in the sabkha to fluvial strata of the carmel formation in southern utah provide an excellent opportunity to understand pipe formation mechanisms and controls on their expressions these clastic pipes demonstrate significant variability and fall into two major categories 1 primary textural pipes and 2 non textural pipes primary textural pipes show significant textural differences relative to the host rock including an internal outward grain coarsening indicative of traction structures the pipes contain entrained brecciated host material and the surrounding host rock has associated soft sediment deformation primary textural pipes formed through multiple liquefaction and fluidization events as evident from crosscutting pipes multiple eruption horizons traction structures and other evidence of fluid suspended sediment transport non textural pipes do not have significant textural differences from the surrounding host rock but have clear diagenetic differences e g mineral coloration and cement differences relative to the host rock these non textural pipes formed through the upward expulsion of fluids similar to primary textural pipes but the fluid forces were likely insufficient to fully fluidize the sand overall the porous sandstone host rock plays a key role in explaining pipe characteristics including their cylindrical geometry versus tabular geometries in mudstones and diagenetic expression pipe variability typically corresponds to lithologic and stratigraphic changes in the surrounding host rock these pipe examples are key paleoenvironmental indicators which give valuable information about subsurface fluids and the presence of a near surface groundwater system

geometry and origin of large scale deformation structures in some ancient wind blown sand deposits large scale deformational features that disrupt the cross bedded strata of some ancient wind blown dune sand deposits jurassic aztec and navajo sandstones u s a can betraced laterally for at least tens of metres information from four exposures leads to an idealized deformation style characterized by 1 a head portion marked by collapse features 2 a middle portion marked by a thrust ramp or a large recumbent fold and 3 a toe portion marked by a planar shear zone with small recumbent folds drag folds and possibly small horizontal shear faults an hypothesis involving earthquake induced liquefaction and collapse of the dunes is proposed sands liquefied during earthquakes cannot support an unequal surface load resulting in the collapse of surface dunes above the liquefied substrate compensatory lateral squeezing of liquefied sand and buried strata produces the shear zone in the toe portion engineering studies suggest that buried strata underlying interdunal lows where over burden stress is least will be most susceptible to liquefaction other considerations suggest that it will be the steeper lee sides of advancing surface dunes that collapse squeezing liquefied sand forward or downwind i e away from the lee slope of surface dunes if the liquefied condition persists load structures can be formed when unliquefied layers founder into the liquefied substrate

annual monsoon rains recorded by jurassic dunes pangaea the largest landmass in the earth s history was nearly bisected by the equator during the late palaeozoic and early mesozoic eras modelling experiments and stratigraphic studies have suggested that the supercontinent generated a monsoonal atmospheric circulation that led to extreme seasonality1 2 3 but direct evidence for annual rainfall periodicity has been lacking4 in the mesozoic era about 190 million years ago thick deposits of wind blown sand accumulated in dunes of a vast low latitude desert at pangaea s western margin5 6 7 these deposits are now situated in the southwestern usa here we analyse slump masses in the annual depositional cycles within these deposits which have been described for some outcrops of the navajo sandstone8 twenty four slumps which were generated by heavy rainfall appear within one interval representing 36 years of dune migration we interpret the positions of 20 of these masses to indicate slumping during summer monsoon rains with the other four having been the result of winter storms the slumped lee faces of these jurassic dunes therefore represent a prehistoric record of yearly rain events

jurassic earthquake sequence recorded by multiple generations of sand blows zion national park utah earthquakes along convergent plate boundaries commonly occur in sequences that are complete within 1 yr and may include 8 10 events strong enough to generate sand blows dune crossbeds within the jurassic navajo sandstone of utah western united states enclose intact and truncated sand blows and the intrusive structures that fed them we mapped the distribution of more than 800 soft sediment dikes and pipes at two small sites all water escape structures intersect a single paleo surface and are limited to the upper portion of the underlying set of cross strata and the lower portion of the overlying set a small portion of one set of crossbeds that represents 1 yr of dune migration encloses eight generations of eruptive events we interpret these superimposed depositional and deformational structures as the record of a single shock aftershock earthquake sequence the completeness and temporal detail of this paleoseismic record are unique and were made possible when sand blows repeatedly erupted onto lee slopes of migrating dunes similar records should be sought in modern dunefields with shallow water tables

biostratigraphic constraints and depositional environment of thelower cretaceous albian boulder creek formation monkman area northeastern british columbia a full core through the boulder creek formation in the monkman area of northeastern british columbia yielded foraminifera from the overlying hasler formation and underlying hulcross formation ther

geosat and advanced very high resolution radiometer observations of oceanic planetary waves adjacent to the hawaiian islands geosat observations of the central north pacific ocean show westward propagating mesoscale features with length scales 500 km time scales 105 155 days and observed zonal phase speeds commensurate with those of nearly nondispersive baroclinic rossby waves advanced very high resolution radiometer derived sea surface temperatures observed during april 1988 showed a cusp shaped pattern north of the hawaiian islands congruent with concurrent geosat derived sea level height anomalies it is believed that the cusp shaped pattern is the surface manifestation of a baroclinic rossby wave the observed wavelength of the cusp shaped pattern was 560 km it had an observed meridional extent horizontal amplitude of 200 300 km and an inferred zonal propagation speed of 0 052 m s 1 the westward propagating sea level height structure was observed to amplify as it approached 150 w reaching amplitudes of 0 06 0 08 m in the vicinity of the cusp shaped feature these waves are believed to be locally forced by the topography either as the result of eastward flow over the submerged island ridge or as a result of baroclinic instability during periods of westward flow

sand boils without earthquakes sedimentary deformation caused by liquefaction has become a popular means for inferring prehistoric strong earthquakes in this report we describe a new mechanism for generating such features in the absence of earthquakes sand boils and a 180 m long sand dike formed in fremont valley california when sediment laden surface runoff was intercepted along the upslope part of a 500 m long preexisting ground crack flowed subhorizonally in the crack and then flowed upward in the downslope part of the crack where it discharged as sand boils on the land surface if the sand boils and their feeder dike were stratigraphically preserved they could be misinterpreted as evidence for earthquake induced liquefaction

experimental soft sediment deformation structures formed by the liquefaction of unconsolidated sands and some ancient examples the effects of liquefaction in saturated sand bodies under a variety of driving forces are described from shaking table experiments and structures from the geological record are presented which are analogous to the experimental structures the collapse of sloping heaps of cross bedded sand under a gravitational body force generates low angle essentially uncontorted stratification a basal zone of shearing may be present with steepened and folded foresets stretching of foresets may be accommodated on normal faults and bottomsets may be contorted into inclined folds in natural systems the substrate may also liquefy causing deformation driven by an unevenly distributed confining load stratification in the surface bedform is flattened and stratification in the substratum contorted experiments failed to produce relative displacement at the interface between stacked sand bodies liquefaction of gravitationally unstable systems in sands generates load structures comparable to those from sand mud systems recumbent folded deformed cross bedding is formed by current shear over a liquefied bed as has been inferred from field and theoretical analyses shear of nonliquefied sand forms angular folds other deformation mechanisms such as fluidization or seepage may generate structures similar to all of these local water escape structures driven by fluidization occur in the upper parts of some liquefied sand bodies they include cusps sand volcanoes and clastic dykes transient cavities formed in some experiments and seemed to be preserved as breached cusps although the experiments tried to isolate individual driving forces driving forces may operate together and there may be a continuum between deformation driven by water escape and deformation driven by loading different structures from those described here may form where liquefaction develops in a buried layer as opposed to at the sediment surface

giant stromatolites and a supersurface in the navajo sandstone capitol reef national park utah at capitol reef national park utah 5 m high stromatolites are present locally on interdune carbonate lenses in the early jurassic navajo sandstone the stromatolites display both finely laminated and fenestral internal fabrics and grew along south facing interdune margins these stromatolites formed during a high water table episode engendered by a dune dammed paleodrainage in a stabilized navajo erg these stromatolites and the thick interdune section associated with them suggest a hiatus in erg accumulation and the presence of a super bounding surface

recurrent deformations of aeolian desert dunes in the cretaceous of the south china block trigger mechanisms variability and implications for aeolian reservoirs abstract deposits of aeolian dunes accumulated in cretaceous intramontane deserts in the south china block underwent recurrent deformation processes affecting their toesets and foreset sediments the mid cretaceous matoushan formation preserves examples of soft sediment deformation deformations associated with theropod tracks in aeolian dune apron sandstones the late cretaceous tangbian formation in the xinjiang basin shows i seismites associated with dry interdune laminated deposits and sand injection into the interdune laminated facies generating intraclast breccias ii mass flow deposits associated with heavy rains generating interbedding of non deformed and deformed intervals in aeolian dune foresets deformed intervals display a variety of deformation styles including thrust duplexes upturned and deformed stratification recumbent folds and microfolds and liquefied intervals covered by overlying draa mega cross bedded sets animal tracks seismites monsoon rains and earthquakes are proposed as the main trigger mechanisms of the failures that led to deformation hydroseismicity associated with monsoon rains is a probable but difficult to prove trigger mechanism this process could be an important deformation agent in the case of large scale deformation recorded in ancient erg sequences mass wasting deposits in ancient erg extensive sandy deserts characterized by aeolian dunes sequences constitute significant heterogeneities for hydrocarbon migration and its architectural variability could determine the development of effective sedimentary traps in aeolian reservoirs

on using satellite altimetric heights to provide a spatial context for the hawaii ocean time series measurements abstract it is assumed that the hawaiian ocean time series hot measurements would be usefully complemented by datasets capable of providing a spatial context for the variability observed at the hot site the potential usefulness of high quality sea surface heights from satellite altimeters is evaluated by analyzing data from the topex poseidon t p mission three signals are examined an intra annual oscillation the annual variability and an interannual sea level drop observed at the hot site during 1993 the intra annual signal observed at the hot site is shown to be part of a propagating disturbance that moves energy to the northwest but propagates phase to the southwest farther to the northwest however the energy and phase propagate nearly due west at the annual period the small amplitude observed at the hot site is confirmed but this is not true of the larger scale where annual amplitudes reach 5 10 cm the annual phase is largely consistent with the sea surface response to annual heating although the interannual event is barely resolved by the t p series the drop of dynamic height observed at the hot site is shown to be part of a larger scale event this event is stationary in space and is initially characterized by positive height anomlies near the ridge and negative anomalies further offshore the signs of these two anomalies reverse in just over 1 year the observed pattern gives rise to significant meridional sea surface height gradients and the associated mass transport anomalies are estimated to be 8 sv in all three cases the t p time series although less than 2 years in duration provide information about the spatial structure of the signals that extends the descriptions that would be possible using the hot data alone

vertical structure of the baroclinic tides in the central north pacific subtropical gyre abstract cruises are made monthly to the world ocean circulation experiment deep water station about 100 km north of oahu hawaii during these cruises the principal causes of variability in dynamic height are the internal tides having a range about 30 of the annual range in dynamic height the internal tides have peak to peak vertical displacements of up to 30 dbar but show little vertical coherence at the diurnal frequencies modal fits typically require 6 8 baroclinic modes to account for 90 of the variance suggesting that the diurnal tide should not be described in terms of dynamic modes the semidiurnal tide has about two to three times the amplitude of the diurnal tide and shows more vertical phase coherence but still requires three or four modes to describe it generally the dominant mode is the second or third mode

on the potential energy of baroclinic rossby waves in the north pacific abstract estimates of baroclinic rossby wave potential energy spectra for various parts of the north pacific were calculated from published material containing information about this energy in many different formats definitions and units the standardized results lead to frequency spectra of potential energy ranging from 0 1 to 0 45 cpy cycles per year in 34 5 squares between 20 and 30 n to energy spectra ranging from 0 28 to 2 11 cpy in eight subsections of the great circle route from honolulu to san francisco and to a map of annual rossby wave energy between 30 and 40 n the most remarkable finding is a consistent sequence of interannual rossby wave spectra with a peak at 0 15 cpy i e at a wave period of 6 7 years covering the area 20 25 n and 175 130 w the most complete information is available for a 5 square east of the hawaiian islands there the spectrum shows besides the 0 15 cpy peak another broad peak ranging from about 0 4 to 1 4 cycles per year

clastic pipes and mud volcanism across mars terrestrial analog evidence of past martian groundwater and subsurface fluid mobilization abstract clastic pipes are cylindrical injection features that vertically crosscut bedding with sharp contacts terrestrial pipes have cylindrical morphologies massive or radially graded interiors and raised outer rims increased grain size and subsequent cementation along the more porous edges makes the rims more resistant to weathering pipes have crosscutting relationships with other pipes due to multiple formation events or migrating eruption centers and are associated with other soft sediment deformation features terrestrial clastic pipes form via liquefaction and fluidization which require a near surface groundwater system to initiate i e sand sized sediments must be saturated for pipes to form clastic pipes cm to 1000 m diameters occur on mars across multiple time periods and terrains and are recognized in both rover and orbital imagery a conical or cylindrical geometry and massive interior core characterize these features the pipes on mars show various geomorphic expressions and are classified into five types by the presence or absence of a raised outer rim or a central pit these types are interpreted to represent the erosional evolution of pipes at different stages from their initial surface eruptive structures to their weathered remnants eroded conical hills martian pipes formed via fluidization as evidenced by 1 raised outer rims possibly indicating textural differences along the pipe edges from traction interactions of fluid suspended sediment 2 crosscutting relationships with other pipes suggesting reactivated fluidization pathways or migrating eruptive vents and 3 close spatial association between pipes and other features thought to form by soft sediment deformation e g contorted bedding integration of terrestrial analog data with the mars observations provides evidence for past martian groundwater and subsurface fluid mobilization

burrow architecture and burrowing dynamics of ctenomys in foredunes and paleoenvironmental implications abstract ctenomys sp also known as tuco tuco is a solitary subterranean small rodent that inhabits sandy soils in south america we studied burrow system architecture of ctenomys flamarioni communities from the foredunes of the southern brazil coastal plain by inserting plaster of paris and excavating the tunnels the structure of the burrow system is complex with interlinked tunnels one occasionally open entrance multiple chambers and turnarounds blind laterals varying slopes t junctions bifurcations and two different levels a specific isolated chamber is used as a latrine while another is used as a nest the burrow entrance is open only when the rodent is taking out sand or feeding the tunnels have an average depth of 35 cm deepest at 55 cm and the most superficial at 15 cm near the entrance the average burrow length ranges from 190 to 500 cm the tunnels have different heights and widths varying from 5 5 9 3 cm wide to 6 11 cm high the entrance is inclined 28 the central part of the burrow system has a steeper slope with an inclination of 38 the plaster molds preserve claw marks of four digits of up to 4 mm in depth collapsed burrows are rapidly sealed to avoid the entrance of predators ctenomys sp burrows provide a suitable microhabitat which is used by the animals as protection from adverse environmental conditions particularly during the winter when wind impacts the coastal area the extensive interlinking tunnels provide underground routes to escape from predators ctenomys burrows in coastal dune environments are appreciably more complex than those excavated in arid environments which are shallower with no chambers and a slope of up to 20 such difference in the architecture of the burrows can be used as a criterion to reconstruct the paleoenvironment of burrow systems in the rock record

facies and flow regimes of sandstone hosted columnar intrusions insights from the pipes of kodachrome basin state park sandstone hosted intrusions are found in a wide variety of environments but remain poorly understood compared with their mudstone hosted counterparts in particular they remain largely unrecognized in the subsurface in part because they are problematic to image in seismic data this study reports on the facies and fluid flow associated with a 20 000 km3 sandstone intrusion province in utah usa forming a small portion of this intrusion province the intrusions cropping out in kodachrome basin state park display a very wide array of facies and morphologies factors which would make their identification in core a significant challenge remobilized sediment is shown to have been injected at least 200 m vertically from its source with flow prolonged enough to concentrate heavy minerals in placer style deposits at the pipe margins evidence for lateral pipe migration and for associated broader fluidization regions is also presented a new approach to estimating flow parameters in injectites is implemented herein and indicates that previous work has overestimated velocities and flow reynolds numbers by up to two orders of magnitude flow modelling suggests turbulent flow in the pipes that is consistent with field observations of erosive margins and chaotic internal structures post emplacement these pipes remained as long term fluid conduits as revealed by their diagenetic history focussing and facilitating flow of extraformational fluids despite the relatively high porosity and permeability of the aeolian host strata

evidence for episodic sand blow activity during the 1811 1812 new madrid missouri earthquake series four major earthquakes of the 1811 1812 new madrid series caused widespread ground disturbance mostly in the form of sand blows in the alluvial valley of the mississippi river although a recurrence interval of 600 700 yr has been estimated for major shocks recent excavations at an archeological site in northeastern arkansas revealed no evidence of ground disturbance for at least 1 3 ka prior to 1811 sand blows attributed to the new madrid series show that such features can have multiple episodes of sand extrusion through a single dike and vent

long aftershock sequences within continents and implications for earthquake hazard assessment one of the most powerful features of plate tectonics is that the known plate motions give insight into both the locations and average recurrence interval of future large earthquakes on plate boundaries plate tectonics gives no insight however into where and when earthquakes will occur within plates because the interiors of ideal plates should not deform as a result within plate interiors assessments of earthquake hazards rely heavily on the assumption that the locations of small earthquakes shown by the short historical record reflect continuing deformation that will cause future large earthquakes here however we show that many of these recent earthquakes are probably aftershocks of large earthquakes that occurred hundreds of years ago we present a simple model predicting that the length of aftershock sequences varies inversely with the rate at which faults are loaded aftershock sequences within the slowly deforming continents are predicted to be significantly longer than the decade typically observed at rapidly loaded plate boundaries these predictions are in accord with observations so the common practice of treating continental earthquakes as steady state seismicity overestimates the hazard in presently active areas and underestimates it elsewhere

recurrent liquefaction in christchurch new zealand during the canterbury earthquake sequence continuous observational monitoring of a study site in eastern christchurch new zealand following the 2010 m w 7 1 darfi eld earthquake has recorded ten distinct liquefaction episodes in the mainshock aftershock sequence three nearby accelerometers allow calibration between the geological expressions of liquefaction and the intensity of earthquake induced surface ground motion at the site sand blow formation was generated by m w 5 2 7 1 earthquakes with m w 7 5 normalized peak ground accelerations pga 7 5 of 0 057 g acceleration due to gravity silt drapes between successive sand blow deposits provide markers for delineating distinct liquefaction inducing earthquakes in the geologic record however erosion quickly modifi es the surface of sand blows into alluvial and aeolian forms that complicate geologic diagnosis the two feeder dike generations identifi ed in subsurface investigations signifi cantly underrepresent the number of liquefaction inducing earthquakes due to extensive dike reactivation new constitutive equations enable pga 7 5 variations to be estimated from the thickness and areal extent of sand blows

sources of interannual baroclinic waves in the eastern subtropical north pacific abstract subsurface temperature and surface salinity observations along the great circle transect between san francisco and honolulu are used to investigate the source of annual baroclinic long waves in the eastern subtropical north pacific ocean long term mean 15 day values 1966 74 of depth of the 9 c isotherm indicative of thermocline depth and of surface salinity are each fit by least squares method with a time varying cosine yielding phase and amplitude of the mean annual cycle at standard locations every 92 6 km 50 mi along the transect local wind stress curl is expected to influence the observed depth of the 9 c isotherm through the mechanism of ekman pumping therefore its annual cycle is computed in a manner like that of the depth of the 9 c isotherm and its effect removed from the latter the residual annual cycle has phase and amplitude profiles along the transect that closely resemble that of model annual baroclinic long waves emanating from a line source of large amplitude wind st

rossby wave analysis of subsurface temperature fluctuations along the honolulu san francisco great circle abstract seven years of xbt observations collected between honolulu and san francisco reveal subsurface temperature fluctuations with strong in phase vertical coherence and fair horizontal coherence over 1000 km distance their annual and semi annual harmonics exhibit randomness of phase suggesting that the fluctuations are modeled better as a stochastic process than as a deterministic signal cross spectral fitting of a stochastic first baroclinic mode rossby wave model to the fluctuations demonstrates the rossby waves could be producing 50 60 of the observed subsurface covariance at periods exceeding nine months phase is seen to propagate northwestward and energy westward and southwestward the corresponding sea surface velocities and sea level fluctuations are of the order 1 cm s 1 and 1 5 cm

paleohydrologic controls on soft sediment deformation in the navajo sandstone abstract many workers have noted the presence of contorted cross strata in the navajo sandstone and other ancient eolianites and have recognized their significance as indicators of sediment saturation during the accumulation history horowitz 1982 proposed a general model for the production of such features in ancient ergs by episodic seismically induced liquefaction of accumulated sand a key feature of that popular model is the prevalence of a flat water table characteristic of a hyper arid climatic regime during deformation under arid climatic conditions the water table is established by regional flow and liquefaction is limited to the saturated regions below the level of interdune troughs however various paleohydrological indicators from navajo sandstone outcrops point toward a broader range of water table configurations during the deformation history of that eolianite some outcrops reveal extensive deformation complexes that do not appear to have extended to the contemporary depositional surface these km scale zones of deformation affecting multiple sets of cross strata and grading upward into undeformed crossbeds may represent deep water table conditions coupled with high intensity triggers which produced exclusively intrastratal deformation such occurrences contrast with smaller scale complexes formed within the zone of interaction between the products of soft sediment deformation and surface processes of deposition and erosion the horowitz model targets the smaller scale deformation morphologies produced in this near surface environment this study examines the implications of a wet climatic regime for the horowitz deformation model it demonstrates how a contoured water table characteristic of humid climates may have facilitated deformation within active bedforms as well as in the accumulation intra dune deformation would enable deflation of deformation features during the normal course of dune migration more parsimoniously accounting for the frequent occurrence of erosionally truncated deformation structures in the navajo sandstone the production of such erosional truncations during bedform climb and aggradation of the accumulation and the dramatic fluctuations in the water table required to deposit dry eolian sand deform those deposits under saturated conditions and then dry the deformed sand to enable deflation

mesoscale eddies northeast of the hawaiian archipelago from satellite altimeter observations 1 enhanced mesoscale eddy activity northeast of the hawaiian archipelago was investigated by using the high pass filtered satellite altimetric sea surface height ssh data of the past 16 years the level of eddy kinetic energy eke shows significant interannual variations which appear well correlated to the large scale atmospheric wind forcing associated with the pacific decadal oscillation index the eke levels in the area along the subtropical front zone in 1997 1998 and 2003 2005 for example were three times as large as those in the low eke years spectral analyses in the 3 latitude by 5 longitude subregions revealed the dominant mesoscale periods ranging from 90 days near 18 n to 180 days near 36 n a 3 layer quasi geostrophic model constrained by world ocean atlas 2005 climatologies was used to explore instability of the regional circulation the analysis shows a geographical match between baroclinic instability strength and the observed rms ssh variability and a temporal match between seasonally varying instability strength and the observed seasonal eke modulation and suggests that baroclinic instability by the vertically sheared regional mean circulation provides the energy source for the enhanced eddy variability northeast of the hawaiian archipelago

paleoliquefaction in christchurch new zealand liquefaction during the 2010 moment magnitude mw 7 1 darfield earthquake and large aftershocks known as the canterbury earthquake sequence caused severe damage to land and infrastructure in christchurch new zealand liquefaction occurred at mw weighted peak ground accelerations pga7 5 as low as 0 06 g at highly susceptible sites trenching investigations conducted at two sites in eastern christchurch enabled documentation of the geologic expressions of recurrent liquefaction and determination of whether evidence of pre canterbury earthquake sequence liquefaction is present excavation to water table depths 1 2 m below surface across sand blow vents and fissures revealed multiple generations of canterbury earthquake sequence liquefaction feeder dikes that crosscut holocene to recent fluvial and anthropogenic stratigraphy canterbury earthquake sequence dikes crosscut and intrude oxidized and weathered dikes and sills at both sites that are interpreted as evidence of pre canterbury earthquake sequence liquefaction crosscutting relationships combined with 14c dating constrain the timing of the pre canterbury earthquake sequence liquefaction to post a d 1660 to pre ca a d 1905 at one site and post a d 1415 to pre ca a d 1910 at another site the pga7 5 of five well documented historical earthquakes that caused regional damage between 1869 and 1922 are approximated for the study sites using a new zealand specific ground motion prediction equation only the june 1869 mw 4 8 christchurch earthquake produces a median modeled pga7 5 that exceeds the pga7 5 0 06 g threshold for liquefaction prehistoric earthquakes sourced from regional faults including the 1717 alpine fault mw 7 9 0 3 and ca 500 600 yr b p mw 7 1 porters pass fault earthquakes provide additional potential paleoseismic sources for pre canterbury earthquake sequence liquefaction the recognition of pre canterbury earthquake sequence liquefaction in late holocene sediments is consistent with hazard model based predicted return times of pgas exceeding the liquefaction triggering threshold in christchurch residential development in eastern christchurch from ca 1860 to 2005 occurred in areas where geologic evidence for pre canterbury earthquake sequence liquefaction was present highlighting the potential of paleoliquefaction studies to predict locations of future liquefaction and to contribute to seismic hazard assessments and land use planning

long lived pluvial episodes during deposition of the navajo sandstone abstract the navajo sandstone of the american southwest was deposited at approximately 190 ma in a giant subtropical dune field near the western margin of pangea from this unit we report thick intervals of dune cross strata that were churned by insects and trampled by reptiles although dunes continued to migrate freely the distribution of trace fossils shows that plant life in wet interdune areas sustained high levels of animal activity on the dunes for many thousands of years we interpret this suite of structures as the record of a pluvial episode climatologically similar to the period of greening in the sahara 4000 10 000 yr ago a high percentage of the rainfall on the navajo erg recharged the water table and led to the development of highly dilute local groundwater flow systems that discharged into interdune areas

water transfer cylindrical structures in the late proterozoic eolian sandstones in the taoudeni basin west africa abstract vertical cylindrical structures have already been described in literature but none in periglacial eolian dune deposits two types of vertical cylindrical structures have been observed in the late precambrian of western mali type 1 exhibits concentric laminae in subhorizontal transversal section and a cone in cone internal organization in type 2 laminations inherited from the parent sediments are partially preserved the two types are early post depositional cylindrical features both were caused by upward fluid flow responsible for liquefaction fluidization and entire type 1 or partial type 2 remobilization of eolian cross stratification in a proposed hypothetical reconstruction scheme a local overpressure caused by an unknown external impulse creates liquefaction cells which evolve either in an upward explosive way type 2 or in an upward moving liquefaction front type 1