development of magnitude bound relations for paleoliquefaction analyses new zealand case study abstract magnitude bound relations are often used to estimate paleoearthquake magnitudes from paleoliquefaction data this study proposes new zealand based magnitude bound curves that are developed using a liquefaction field observations and b a newly proposed back calculation approach that combines the simplified liquefaction evaluation procedure with a regionally appropriate ground motion prediction equation for b both deterministic and probabilistic frameworks are proposed the magnitude bound curves back calculated using either the deterministic or probabilistic frameworks are advantageous in that they can be used to predict the spatial distribution of liquefaction in regions where historical liquefaction field observations are limited or poorly documented and because soil and site specific conditions can be incorporated into magnitude bound analyses moreover curves developed using the probabilistic framework allow for the range of possible causative earthquake magnitudes to be better understood and quantified to demonstrate the use of the proposed relations paleoliquefaction features discovered in eastern christchurch nz are analyzed the 1869 mw4 8 christchurch earthquake and or 1717 mw8 1 alpine fault earthquake are found to be the most likely candidates amongst known historical and paleoearthquakes for triggering liquefaction over the permissible time range ca 1660 to 1905 a d this study demonstrates the potential of the proposed magnitude bound curves to provide insight in to past present and future hazards proving their utility even in cases of limited evidence the approach of developing and applying magnitude bound curves proposed herein is not limited to parts of new zealand but rather can be applied worldwide

surface rupture during the 2010 mw 7 1 darfield canterbury earthquake implications for fault rupture dynamics and seismic hazard analysis the september 2010 m w 7 1 darfield canterbury earthquake in new zealand is one of the best recorded earthquakes of this magnitude the earthquake occurred on a previously unidentified fault system and generated a 29 5 0 5 km long surface rupture across a low relief agricultural landscape high accuracy measurements of coseismic displacements were obtained at over 100 localities along the greendale fault maximum net displacement d max 5 3 0 5 m and average net displacement d avg 2 5 0 1 m are anomalously large for an earthquake of this m w d max surface rupture length srl and d avg srl ratios are among the largest ever recorded for a continental strike slip earthquake geologically derived estimates of moment magnitude m w g are less than the seismologically derived m w derived using widely employed srl m w scaling regressions m w g is greater than m w using d max and d avg m w regressions the geologically derived static stress drop of 13 9 3 7 mpa provides a context with which to compare this earthquake rupture to interplate and intraplate ruptures of similar m w this data set provides fundamental information on fault rupture processes relevant to seismic hazard modeling in this region and analogous settings globally

the 2002 denali fault earthquake alaska a large magnitude slip partitioned event the mw moment magnitude 7 9 denali fault earthquake on 3 november 2002 was associated with 340 kilometers of surface rupture and was the largest strike slip earthquake in north america in almost 150 years it illuminates earthquake mechanics and hazards of large strike slip faults it began with thrusting on the previously unrecognized susitna glacier fault continued with right slip on the denali fault then took a right step and continued with right slip on the totschunda fault there is good correlation between geologically observed and geophysically inferred moment release the earthquake produced unusually strong distal effects in the rupture propagation direction including triggered seismicity

a reinterpretation of glacial and marine limits around the northwestern laurentide ice sheet seven new radiocarbon dates pertaining to deglaciation of northern prince of wales island place the margin of the laurentide ice sheet on the island by 11 000 bp this requires a revision of the proposed age for the viscount melville sound ice shelf of 10 300 9880 bp a revised age of 11 300 11 000 bp is suggested the new dates also require revisions of the proposed wisconsinan and holocene history of banks island shells thought to have been thrust onshore to an elevation of 88 m by the ice shelf on northern banks island after 10 600 bp are reinterpreted as undisturbed postglacial marine shells recording a relative sea level of 88 m or more this in turn suggests that the east coast sea and jesse till are of late wisconsinan rather than early wisconsinan age and that the late wisconsinan glacial limit on banks island as figured on the 1968 glacial map of canada rather than on recent revisions is essentially correct

sabkhas slumping and compaction at mufulira zambia algal structures such as stromatolites have long been recognized as closely associated with the cupriferous dolomitic shales of the katanga supergroup of zaire and zambia discovery of bioherms and biostromes in the predominantly arenaceous deposits of the mufulira copper mine indicates a similar origin with the more common copper deposits in dolomitic shale and their barren gaps due to bioherms renfro 1974 recognized the worldwide association of sabkhas algal mats and stratiform copper deposits his interpretation of sabkha environments in cyclic depositional sequences at mufulira is corroborated by detailed features in the mine recognition of abundant carbonized debris of algal mat from 0 5 m down to microscopic size in the marine sediments of mufulira indicates an accumulation of decomposing vegetable debris that is more than sufficient to promote anoxic conditions in the bottom waters of the lagoons with resulting precipitation of copper and iron sulfides contemporaneously with sedimentation compaction of algal material explains the 80 percent contraction of sun cracked mud flakes also compaction by roughly two thirds of the algal rich graywacke and the c orebody accounts for the rapid sagging of overlying sabkha and terrestrial sediments which was followed by a second marine invasion allowing deposition of the b orebody and central graywacke similar rapid compaction of the latter under its cover of sabkha and red bed sediment caused further sagging marine invasion and deposition of the a orebody and graywacke vertically above the c and b graywackes although renfro s hypothesis of mineralization by ascending groundwaters may account for some initial precipitation of sulfides beneath algal mats the bulk of the preserved mineralization at mufulira exhibits features more compatible with syngenetic deposition of sulfides associated with decaying transported algal material in marine lagoons

continental extension of the pacific plate at the southern termination of the hikurangi subduction zone the north mernoo fault zone offshore new zealand a complex transition from subduction at the hikurangi margin to transpressive continental collision across the southern alps occurs in the ne south island region of new zealand offshore the southern limit of oceanic subduction is constrained by the chatham rise a submerged continental plateau on the pacific plate which is presumably too buoyant for normal subduction in the nw corner of the rise is the north mernoo fault zone nmfz a 100 by 300 km region of basement involved active normal faulting of late miocene circa 8 6 ma to recent age the nmfz evolved contemporaneously with the rotation and development of the adjacent plate boundary zone growth faulting is characteristic within the sedimentary cover which is generally less than 2 km thick but the distribution of faulting has varied temporally the amount of mid pliocene recent extension is estimated to be not more than a few percent the nmfz consists of an array of overlapping south dipping normal faults which are typically 2 5 km apart and which trend roughly e w at a high angle to the plate boundary zone late quaternary surface traces are widely distributed on the mid to upper continental slope but many surface scarps are poorly preserved due to extensive erosion of the seafloor the western end of the fault zone crosses submarine canyons at the southern end of the hikurangi trough and almost abuts two fold and thrust fault systems on the ne south island continental margin although few data constrain the kinematics of extension a single mw 6 1 earth quake at the western end of the nmfz suggests planar rotating faults with a component of left lateral oblique slip two possible models of regional extension are considered 1 lateral buckling of the upper crust in which faulted slivers of crust are peeled off as the chatham rise slides past the transpressive marlborough fault system toward the southern alps and 2 flexure of the edge of continental pacific plate as the chatham rise is bent downward into the southern end of the hikurangi subduction zone improved seismological data and deep crustal seismic reflection profiles may help to constrain the kinematics of deformation

quaternary ice transport in the canadian arctic and extent of late wisconsinan glaciation in the queen elizabeth islands most of the ice rafted debris in channels off the queen elizabeth islands nunavut is of local origin particularly in the inner part of the archipelago but samples from the arctic shelf contain as much as 40 grains from sources as far away as 2000 km including the siberian shelves particle transport by drifting sea ice from distant shelves is an important process on the arctic continental shelf of the queen elizabeth islands in the interior of the queen elizabeth islands and in the viscount melville and lancaster sounds particle transport is limited to distances of approximately 200 km mixing is more common among grains of coarse silt to fine sand than in the 250 m fraction but even the latter contains debris from sources far apart during the late wisconsinan the northern southern and eastern queen elizabeth islands were covered by glaciers flowing radially from ice centers on the islands into the inter island channels queens channel was completely filled by ice and a glacier lobe moved

high resolution seismic images of potentially seismogenic structures beneath the northwest canterbury plains new zealand 1 the transpressional boundary between the australian and pacific plates in the central south island of new zealand comprises the alpine fault and a broad region of distributed strain concentrated in the southern alps but encompassing regions further to the east including the northwest canterbury plains low to moderate levels of seismicity e g 2 m 5 events since 1974 and 2 m 4 0 in 2009 and holocene sediments offset or disrupted along rare exposed active fault segments are evidence for ongoing tectonism in the northwest plains the surface topography of which is remarkably flat and even because the geology underlying the late quaternary alluvial fan deposits that carpet most of the plains is not established the detailed tectonic evolution of this region and the potential for larger earthquakes is only poorly understood to address these issues we have processed and interpreted high resolution 2 5 m subsurface sampling interval seismic data acquired along lines strategically located relative to extensive rock exposures to the north west and southwest and rare exposures to the east geological information provided by these rock exposures offer important constraints on the interpretation of the seismic data the processed seismic reflection sections image a variably thick layer of generally undisturbed younger i e 59 ka quaternary sedimentary sequence that shows evidence of moderate faulting and folding during and subsequent to deposition these quaternary units are in unconformable contact with late cretaceous tertiary interbedded sedimentary and volcanic rocks that are highly faulted folded and tilted the lowest imaged unit is largely reflection free permian triassic basement rocks quaternary age deformation has affected all the rocks underlying the younger alluvial sediments and there is evidence for ongoing deformation eight primary and numerous secondary faults as well as a major anticlinal fold are revealed on the seismic sections folded sedimentary and volcanic units are observed in the hanging walls and footwalls of most faults five of the primary faults represent plausible extensions of mapped faults three of which are active the major anticlinal fold is the probable continuation of known active structure a magnitude 7 1 earthquake occurred on 4 september 2010 near the southeastern edge of our study area this predominantly right lateral strike slip event and numerous aftershocks ten with magnitudes 5 within one week of the main event highlight the primary message of our paper that the generally flat and topographically featureless canterbury plains is underlain by a network of active faults that have the potential to generate significant earthquakes

settling analysis of fine sediment in salt water at concentrations low enough to preclude flocculation abstract a new method for measuring settling velocities of fine sediment in salt water at small 1 10 mg 1 1 concentrations is outlined the method combines conventional settling tube procedures with aliquot volume measurements using a coulter counter sensitivity of the coulter counter in volume measurements allow settling tube experiments to be conducted at particle concentrations that preclude flocculation from occurring during the measurement period the procedures have been applied to samples of north pacific clays with initial concentrations of 1 6 600 ppm these results show by differences in settling distributions that flocculation effects occur at concentrations as low as 50 ppm absence of flocculation at lower concentrations is confirmed by an experiment conducted in fresh water

high resolution relocation of aftershocks of the mw 7 1 darfield new zealand earthquake and implications for fault activity 1 low slip rate regions often represent under recognized hazards and understanding the progression of seismicity when faults in such areas rupture will help us to better understand earthquake rupture patterns the 3 september 2010 utc mw 7 1 darfield earthquake revealed a formerly unrecognized set of faults in the canterbury region of new zealand an area that had previously been mapped as one of the lower hazard areas in the country in this study we analyze the first four months of its aftershock sequence to identify active faults and temporal changes in seismicity along them we jointly invert for three dimensional p wave and s wave velocities and hypocentral locations using data for 2840 aftershocks recorded at 36 temporary and permanent seismic stations within 70 km of the main shock epicenter these relocations delineate eight individual faults active prior to the 22 february 2011 mw 6 3 christchurch earthquake the largest aftershock of the darfield earthquake two of these faults are in the christchurch region one of which corresponds to geodetically determined rupture planes of the christchurch earthquake using focal mechanisms calculated from first motion polarities we find mainly strike slip faulting events with some reverse and normal faulting events as well we compare the orientations of these faults to the prevailing regional stress directions to identify which faults may have been active prior to the darfield earthquake and which may be newly developed

two circulation regimes of the wind driven arctic ocean the major goal of this paper is to demonstrate the existence in the arctic ocean of two regimes of wind forced circulation we simulated the vertically averaged currents sea level heights and ice drift in the arctic ocean from 1946 to 1993 using a two dimensional wind forced barotropic model that includes frictional coupling between the ocean and ice the model has a spatial resolution of 55 5 km and is driven by winds river runoff and an imposed but realistic sea level slope between the pacific and the atlantic oceans there is a good agreement between velocities from observed buoy motions and velocities of modeled ice drift even though the model lacks ocean baroclinicity and ice thermodynamics the results indicate that wind driven motion in the central arctic alternates between anticyclonic and cyclonic circulation with each regime persisting for 5 7 years based upon our analysis of the modeled sea level and ice motion anticyclonic wind driven motion in the central arctic appeared during 1946 1952 1958 1963 1972 1979 and 1984 1988 and cyclonic motion appeared during 1953 1957 1964 1971 1980 1983 and 1989 1993 shifts from one regime to another are forced by changes in the location and intensity of the icelandic low and the siberian high the two regimes may help explain the significant basin scale changes in the arctic s temperature and salinity structure observed recently the great salinity anomaly and the variability of ice conditions in the arctic ocean

fault damage zones of the m7 1 darfield and m6 3 christchurch earthquakes characterized by fault zone trapped waves abstract to characterize the subsurface structure of the damage zones caused by the 2010 2011 canterbury earthquake sequence in new zealand s south island we installed two short linear seismic arrays array 1 across the greendale fault gf surface rupture and array 2 over the surface projection of the blind port hills fault phf that ruptured in the 2010 m7 1 darfield and 2011 m6 3 christchurch earthquakes respectively we recorded 853 aftershocks for 4 months after the christchurch earthquake fault zone trapped waves fztws identified at array 1 for aftershocks occurring on both the gf and the phf show that the post s durations of these fztws increase as focal depths and epicentral distances from the array increase suggesting an effective low velocity waveguide formed by severely damaged rocks existing along the gf and phf at seismogenic depths locations of aftershocks generating prominent fztws delineates the subsurface gf rupture extending eastward as bifurcating blind fault segments an additional 5 8 km beyond the mapped 30 km surface rupture into a zone with comparably lower seismic moment release west of the phf rupture which extends westward to within 5 3 1 km of the subsurface gf the propagation of fztw through the intervening gap indicates moderate gf phf structural connectivity we interpret this zone as a fracture mesh reflecting the interplay between basement faults and stress aligned microcracks that enable the propagation of phf sourced fztws into the gf damage zone simulations of observed fztws suggest that the gf rupture zone is 200 250 m wide consistent with the surface deformation width velocities within the zone are reduced by 35 55 with the maximum reduction in the 100 m wide damage core zone corresponding with surface and shallow subsurface evidence for discrete fracturing the damage zone extends down to depths of 8 km or deeper consistent with hypocentral locations and geodetically derived fault models

decadal climate oscillations in the arctic a new feedback loop for atmosphere ice ocean interactions a combined complex empirical orthogonal function analysis of 40 years of annual sea ice concentration sic and winter sea level pressure slp data reveals the existence of an approximately 10 year climate cycle in the arctic and subarctic the cycle is characterized by a clockwise propagating signal in the sic anomalies and a standing oscillation in the slp anomalies the latter being linked to a fluctuation between the two phases of the north atlantic oscillation to describe the formation and evolution of the sic and slp anomalies associated with the cycle a simple feedback loop is proposed

recent changes in arctic ocean sea ice motion associated with the north atlantic oscillation examination of a new ice motion dataset of the arctic ocean over a recent eighteen year period 1978 1996 reveals patterns of variability that can be linked directly to the north atlantic oscillation the intensity of the icelandic low one of its centers of action modulates the sea level pressure distribution over a broad region of the arctic ocean and the greenland iceland norwegian and barents seas over the winters of 1988 through 1995 the oscillation has remained in its positive phase contributing to coherent large scale changes in the intensity and character of ice transport in the arctic ocean the significant changes include the weakening of the beaufort gyre the increase in ice export through the fram strait the increase in ice import from the barents kara seas the enhanced eastward transport of sea ice from the laptev sea the weakening of the transpolar drift stream and the reduction in ice extent in the nordic seas all of these changes affect the regional and total sea ice mass balance of the arctic ocean

sediments in arctic sea ice implications for entrainment transport and release despite the arctic sea ice cover s recognized sensitivity to environmental change the role of sediment inclusions in lowering ice albedo and affecting ice ablation is poorly understood sea ice sediment inclusions were studied in the central arctic ocean during the arctic 91 expedition and in the laptev sea east siberian arctic region expedition 1992 results from these investigations are here combined with previous studies performed in major areas of ice ablation and the southern central arctic ocean this study documents the regional distribution and composition of particle laden ice investigates and evaluates processes by which sediment is incorporated into the ice cover and identifies transport paths and probable depositional centers for the released sediment in april 1992 sea ice in the laptev sea was relatively clean the sediment occasionally observed was distributed diffusely over the entire ice column forming turbid ice observations indicate that frazil and anchor ice formation occurring in a large coastal polynya provide a main mechanism for sediment entrainment in the central arctic ocean sediments are concentrated in layers within or at the surface of ice floes due to melting and refreezing processes the surface sediment accumulation in central arctic multi year sea ice exceeds by far the amounts observed in first year ice from the laptev sea in april 1992 sea ice sediments are generally fine grained although coarse sediments and stones up to 5 cm in diameter are observed component analysis indicates that quartz and clay minerals are the main terrigenous sediment particles the biogenous components namely shells of pelecypods and benthic foraminiferal tests point to a shallow benthic marine source area apparently sediment inclusions were resuspended from shelf areas before and incorporated into the sea ice by suspension freezing clay mineralogy of ice rafted sediments provides information on potential source areas a smectite maximum in sea ice sediment samples repeatedly occurred between 81 n and 83 n along the arctic 91 transect indicating a rather stable and narrow smectite rich ice drift stream of the transpolar drift the smectite concentrations are comparable to those found in both laptev sea shelf sediments and anchor ice sediments pointing to this sea as a potential source area for sea ice sediments in the central arctic ocean sea ice clay mineralogy is significantly different from deep sea clay mineral distribution patterns the contribution of sea ice sediments to the deep sea is apparently diluted by sedimentary material provided by other transport mechanisms

contemporary horizontal velocity and strain rate fields of the pacific australian plate boundary zone through new zealand we have inverted velocity solutions from nine geodetic networks distributed across new zealand to derive present day continuous horizontal velocity and strain rate fields at the earth s surface throughout the country the nine networks contain a total of 362 global positioning system gps stations that have been observed at least twice and at least a year apart between 1991 and 1998 the model velocity field is expanded as bicubic spline interpolation functions defined within a curvilinear grid that covers the country and extends into the assumed rigid australian and pacific plates to west and east the inversion jointly minimizes the magnitudes of fitted strain rates and the misfit to the observed velocity data the spline technique allows high spatial resolution of strain rate variations especially in regions with spatially dense gps data expansion of the model velocity field on the surface of a sphere allows arbitrarily large areas to be studied previously known aspects of new zealand plate boundary deformation are highlighted with improved resolution including back arc extension in the taupo volcanic zone rotation of the hikurangi forearc away from this zone in the north island and a band of high shear strain rate under the southern alps to the southeast of the alpine fault our results reveal several new features including a region of enhanced shear straining apparently associated with strike slip faults in the southern north island and a band of contractional straining subparallel and well east of the alpine fault that is similar to features found in numerical and sandbox models of continental collision

sources and dispersal patterns of clay minerals in surface sediments from the continental shelf areas off alaska the three mineral suites were recognized in the gulf of alaska the glaciomarine sediments of fjords and the eastern shelf consist typically of the primary phyllosilicates micas and chlorites derived locally from argillite graywacke and metavolcanics under conditions of mild chemical weathering more glycol expandable clay minerals gecm in the north gulf substantiate clay supply to that region primarily from the yakataga and poul creek formations and to a lesser extent from the copper river the northern gulf clay mineral suite is transported to central prince william sound and northeast kodiak shelf by the alaska coastal current in the western gulf clay minerals adjacent to the alaska peninsula are derived principally from the susitna river via cook inlet whereas those of the outer shelf presumably have their provenance in kodiak island and the katmai ash submarine deposit in the southeast bering sea a progressive northwestward decrease in gecm from 65 to 11 is caused by a gradually decreased sediment export from the alaska peninsula and the aleutians with a possible minor increase in illite from the kuskokwin river the yukon river is the predominant clay source for the north bering sea as signified by an abrupt increase in that area of gecm 20 to 35 and of kaolinite chlorite ratios clay mineralogy indicates that the central chukchi sea is the major repository of the yukon clays suggesting that clay mineral stratigraphic studies have implications for interpretation of the quaternary paleogeography of beringia in the beaufort sea nearshore influence of different fluvial inputs and their dispersals by currents are sharply defined the lack of a definite pattern to the distribution of clay minerals in the outer continental shelf may be due to haphazard transport of clays by ice rafting and or reworking and redistribution of sediments resulting from ice gouging of the sea substrate movement of sediment to the west in the alaskan portion of the inner shelf of beaufort sea is evident an apparent seaward increase in illite gecm ratio in the colville delta is tentatively ascribed to regeneration of degraded illite micas by k fixation in saline waters an isolated area of sediment rich in expandable clay minerals in the central beaufort shelf presumably is relict

sea ice transport of riverine particles from the laptev sea to fram strait based on clay mineral studies the aim of this study was to identify pathways and processes of modern sediment transport from the siberian hinterland to the laptev sea and further to the arctic ocean clay mineral analyses were performed on riverine suspended particulate material spm surface sediments of the laptev sea shelf and sea ice sediments sis material collected during seven expeditions was included in this study clay mineral assemblages are used to decipher the distribution of riverine sediments on the shallow laptev sea shelf the entrainment of fine particles into newly forming ice and the transport of sis from the laptev sea towards the ablation areas a cluster analysis of our data set shows that the clay mineral assemblages of laptev sea shelf sediments and sis are controlled mainly by the input of riverine spm supplied by the khatanga lena and yana rivers whereas the western shelf clay mineral province is characterized by enhanced smectite concentrations supplied by the khatanga river the eastern laptev sea is dominated by illite discharged through the lena and yana rivers the sis smectite concentration serves as an indicator for sediment source areas on the circum arctic shelves subsequently the transpolar drift can be distinguished into a siberian branch fed from the eastern kara sea and the western laptev sea and a polar branch originating from the eastern laptev sea

fault kinematics and surface deformation across a releasing bend during the 2010 mw 7 1 darfield new zealand earthquake revealed by differential lidar and cadastral surveying dextral slip at the western end of the east west striking greendale fault during the 2010 m w 7 1 darfield earthquake transferred onto a northwest trending segment across an apparent transtensional zone here named the waterford releasing bend we used detailed surface mapping differential analysis of pre and postearthquake light detection and ranging lidar and property boundary cadastral resurveying to produce high resolution centimeter scale estimates of coseismic ground surface displacements across the waterford releasing bend our results indicate that the change in orientation on the greendale fault incorporates elements of a large scale releasing bend from the viewpoint of westward motion on the south side of the fault as well as a smaller scale restraining stepover from the viewpoint of southeastward motion on the north side of the fault these factors result in the waterford releasing bend exhibiting a decrease in displacement to near zero at the change in strike and the presence within the overall releasing bend of a nested localized restraining stepover with contractional bulging the exceptional detail of surface deformation and kinematics obtained from this contemporary surface rupture event illustrates the value of multimethod investigations our data provide insights into strike slip fault bend kinematics and into the potentially subtle but important structures that may be present at bends on historic and prehistoric rupture traces

origin of the nchanga copper cobalt deposits of the zambian copperbelt the zambian copperbelt forms the southeastern part of the 900 km long neoproterozoic lufilian arc and contains one of the world s largest accumulations of sediment hosted stratiform copper mineralization the nchanga deposit is one of the most significant ore systems in the zambian copperbelt and contains two major economic concentrations of copper and cobalt hosted within the lower roan group of the katangan supergroup a lower orebody copper only and upper orebody copper and cobalt occur towards the top of arkosic units and within the base of overlying shales the sulfide mineralogy includes pyrite bornite chalcopyrite and chalcocite although in the lower orebody sulfide phases are partially or completely replaced by malachite and copper oxides carrollite is the major cobalt bearing phase and is restricted to fault propagation fold zones within a feldspathic arenite hydrothermal alteration minerals include dolomite phlogophite sericite rutile quartz tourmaline and chlorite quartz veins from the mine sequence show halite saturated fluid inclusions ranging from 31 to 38 wt equivalent nacl with homogenisation temperatures thtot ranging between 140 and 180 c diagenetic pyrites in the lower orebody show distinct relatively low 34s ranging from 1 to 17 whereas arenite and shale hosted copper and cobalt sulfides reveal distinctly different 34s from 1 to 12 for the lower orebody and 5 to 18 for the upper orebody there is also a clear distinction between the 34s mean of 12 1 3 3 n 65 for the upper orebody compared with 5 2 3 6 n 23 for the lower orebody the 13c of dolomites from units above the upper orebody give 13c values of 1 4 to 2 5 consistent with marine carbon however dolomite from the shear zones and the alteration assemblages within the upper orebody show more negative 13c values 2 9 to 4 0 and 5 6 to 8 3 respectively similarly shear zone and upper orebody dolomites give a 18o of 11 7 to 16 9 compared to lower roan dolomites which show 18o of 22 4 to 23 0 two distinct structural regimes are recognized in the nchanga area a weakly deformed zone consisting of basement and overlying footwall siliciclastics and a moderate to tightly folded zone of meta sediments of the katangan succession the fold geometry of the lower roan package is controlled by internal thrust fault propagation folds which detach at the top of the lowermost arkose or within the base of the overlying stratigraphy and show vergence towards the ne faulting and folding are considered to be synchronous as folding predominantly occurred at the tips of propagating thrust faults with local thrust breakthrough the data from nchanga suggests a strong link between ore formation and the development of structures during basin inversion as part of the lufilian orogeny sulfides tend to be concentrated within arenites or coarser grained layers within shale units suggesting that host rock porosity and possibly permeability played a role in ore formation however sulfides are also commonly orientated along but not deformed by a tectonic fabric or hosted within small fractures that suggest a significant role for deformation in the development of the mineralization the ore mineralogy hydrothermal alteration and stable isotope data lend support to models consistent with the thermochemical reduction of a sulfate and metal enriched hydrothermal fluid at the site of mineralization there is no evidence at nchanga for a contribution of bacteriogenic sulfide produced during sedimentation or early diagenesis to the ores

double difference tomography the method and its application to the hayward fault california we have developed a double difference dd seismic tomography method that makes use of both absolute and relative arrival times by reducing systematic errors using the more accurate relative arrival times the method produces an improved velocity model simultaneously it yields event locations of a quality equivalent to those of the dd location method while avoiding simplifying assumptions of that method we test this method on a synthetic dataset and find that it produces a more accurate velocity model and event locations than standard tomography we also test this method on a hayward fault california earthquake dataset spanning 1984 1998 the earthquakes relocated by this method collapse to a thin line along the fault trace consistent with previous results the dd velocity model has sharper velocity contrasts near the source region than the standard tomography model

support for the innuitian ice sheet in the canadian high arctic during the last glacial maximum the extent of glacier ice in the canadian high arctic during the last glacial maximum lgm has been debated for decades one school proposed a regional innuitian ice sheet whereas another proposed a smaller non contiguous franklin ice complex research throughout western nares strait supports coalescent innuitian and greenland ice during the lgm based on widespread glacial and marine deposits dated by 14c and amino acid analyses this coalescence likely promoted a vigorous regional ice flow westward across ellesmere island to eureka sound post glacial emergence in eureka sound suggests a former ice thickness at least as great as that in nares strait 1 km recently independent field studies elsewhere in the high arctic also support an innuitian ice sheet during the lgm collectively these studies resolve a long standing debate and initiate new opportunities concerning the reconstruction of high latitude palaeoenvironmental and palaeoclimatic change 1998 john wiley sons ltd

evidence from driftwood records for century to millennial scale variations of the high latitude atmospheric circulation during the holocene different holocene sea ice drift patterns in the arctic ocean have been hypothesized by dyke et al from radiometric analyses of driftwood collected in the canadian arctic archipelago a dynamic thermodynamic sea ice model is used to simulate the modes of arctic ocean ice circulation for different atmospheric forcings and hence determine the atmospheric circulations which may have accounted for the inferred ice drift patterns the model is forced with the monthly mean wind stresses from 1968 a year with very large ice export and 1984 very low ice export two years with drastically different winter sea level pressure patterns and with different phases of the nao index the simulations show that for the 1968 wind stresses a weak beaufort gyre with a broad transpolar drift stream tds shifted to the east are produced leading to a large ice export from the arctic similarly the 1984 wind stresses lead to an expanded beaufort gyre with a weak tds shifted to the west and a low ice export these results correspond to the patterns inferred by dyke et al based on the simulations the driftwood record suggests that for centuries to millennia during the holocene the high latitude average atmospheric circulation may have resembled that of 1968 1984 and today s climatology with abrupt changes from one state to the other

atlantic water flow pathways revealed by lead contamination in arctic basin sediments contaminant lead in sediments underlying boundary currents in the arctic ocean provides an image of current organization and stability during the past 50 years the sediment distributions of lead stable lead isotope ratios and lead 210 in the major arctic ocean basins reveal close coupling of the eurasian basin with the north atlantic during the 20th century they indicate that the atlantic water boundary current in the eurasian basin has been a prominent pathway that contaminant lead from the laptev sea supplies surface water in the transpolar drift and that the canadian and eurasian basins have been historically decoupled

revisiting the canterbury earthquake sequence after the 14 february 2016 mw 5 7 event on 14 february 2016 an mw 5 7 gns science moment magnitude earthquake ruptured offshore east of christchurch new zealand this earthquake occurred in an area that had previously experienced significant seismicity from 2010 to 2012 during the canterbury earthquake sequence starting with the 2010 mw 7 0 darfield earthquake and including four mw 6 0 earthquakes near christchurch we determine source parameters for the february 2016 event and its aftershocks relocate the recent events along with the canterbury earthquakes and compute coulomb stress changes resolved onto the recent events and throughout the greater christchurch region because the february 2016 earthquake occurred close to previous seismicity the coulomb stress changes resolved onto its nodal planes are uncertain however in the greater christchurch region there are areas that remain positively loaded including beneath the city of christchurch the recent earthquake and regional stress changes suggest that faults in these regions may pose a continuing seismic hazard

variability of fram strait ice flux and north atlantic oscillation we estimate the winter sea ice export through the fram strait using ice motion from satellite passive microwave data sea ice motion october may is obtained by tracking the displacement of common features in sequential 85 and 37 ghz brightness temperature fields the average winter area flux over the 18 year record 1978 1996 is 670 000 km2 7 of the area of the arctic ocean the winter area flux ranges from a minimum of 450 000 km2 in 1984 to a maximum of 906 000 km2 in 1995 the daily monthly and interannual variabilities of the ice area flux are high there is an upward trend in the ice area flux over the 18 year record the average winter volume flux over the winters of october 1990 through may 1995 is 1745 km3 ranging from a low of 1375 km3 in the 1990 flux to a high of 2791 km3 in 1994 the sea level pressure gradient across the fram strait explains more than 80 of the variance in the ice flux over the 18 year record we use the coefficients from the regression of the time series of area flux versus pressure gradient across the fram strait and ice thickness data to estimate the summer area and volume flux the average 12 month area flux and volume flux are 919 000 km2 and 2366 km3 we find a significant correlation r 0 86 between the area flux and positive phases of the north atlantic oscillation nao index over the months of december march correlation between our 5 years of volume flux estimates and the nao index gives r 0 56 during the high nao years a more intense icelandic low increases the gradient in the sea level pressure by almost 1 mbar across the fram strait thus increasing the atmospheric forcing on ice transport correlation is reduced during the negative nao years because of decreased dominance of this large scale atmospheric pattern on the sea level pressure gradient across the fram strait

evidence for a recent change in the link between the north atlantic oscillation and arctic sea ice export evidence for a recent change in the link between the north atlantic oscillation nao and arctic sea ice export through fram strait during wintertime djfm is presented from the analysis of simulated arctic sea ice and observations for the period 1958 1997 whereas no correlation between the two time series is found from 1958 to 1977 r 0 1 the correlation increased significantly thereafter r 0 7 1978 1997 the increased coherency between the nao and arctic sea ice export through fram strait during the last two decades resulted from anomalous meridional wind components near fram strait which were associated with the more easterly position of the nao s centers of interannual variability compared to 1958 1977

radiocarbon content of pre bomb marine mollusks and variations in the 14c reservoir age for coastal areas of the barents and kara seas russia fourteen mollusks collected alive between 1900 and 1945 from the russian barents and kara seas were analyzed by ams 14c dating to evaluate variations in the 14c marine reservoir for arctic coastal sites which is important for correcting ages in paleoenvironmental time series and advancing understanding of the exchange of carbon the 14c ages on the mollusks reveal a range of marine reservoir values r t from 159 14c yr to 764 14c yr the oldest r t values of 764 to 620 14c yr are for the bivalve portlandia arctica which often inhabit cold and low salinity waters and muddy substrates the depleted 14c content for this bivalve reflects possibly the incorporation of old carbon from freshwater inputs and or the consumption of old organic matter from the underlying sediments and pore waters other mollusks with sessile habitats and pelagic food sources gave significantly lower r t values between 159 and 344 14c yr the youngest r t values indicate enrichment in 14c and may partially reflect enhanced transfer of 14c enriched co2 from the atmosphere to the ocean surface with wind generated wave agitation this study underscores that a variety of processes can lead to variable 14c depletion and enrichment of surface waters yielding a ca 600 year age span for contemporaneous arctic mollusks there may be added uncertainty in the 14c reservoir correction for deposit feeder species such as portlandia sp and perhaps for certain benthic foraminifera e g nonion labradoricum because these taxa often incorporate old organic matter from the substrate a reservoir correction of 700 years may be more appropriate for infaunal deposit eater species particularly in glacier dominated environments mollusks and foraminifera with sessile habits and pelagic food sources should be selected preferentially for 14c dating because their shells may more closely reflect the 14c content of the global ocean mixed layer

slip in the 2010 2011 canterbury earthquakes new zealand the 3rd september 2010 mw 7 1 darfield and 21st february 2011 mw 6 3 christchurch new zealand earthquakes occurred on previously unknown faults we use insar ground displacements sar amplitude offsets field mapping aerial photographs satellite optical imagery a lidar dem and teleseismic body wave modeling to constrain the pattern of faulting in these earthquakes the insar measurements reveal slip on multiple strike slip segments and secondary reverse faults associated with the darfield main shock fault orientations are consistent with those expected from the gps derived strain field the insar line of sight displacement field indicates the main fault rupture is about 45 km long and is confined largely to the upper 10 km of the crust slip on the individual fault segments of up to 8 m at 4 km depth indicate stress drops of 6 10 mpa in each event rupture initiated on a reverse fault segment before continuing onto a strike slip segment the non double couple seismological moment tensors for each event are matched well by the sum of double couple equivalent moment tensors for fault slip determined by insar the slip distributions derived from insar observations of both the darfield and christchurch events show a 15 km long gap in fault slip south west of christchurch which may present a continuing seismic hazard if a further unknown fault structure of significant size should exist there

paleoseismology of the 2010 mw 7 1 darfield canterbury earthquake source greendale fault new zealand abstract the previously unknown greendale fault ruptured in the september 2010 moment magnitude mw 7 1 darfield earthquake surface rupture fracture patterns and displacements along the fault were measured with high precision using real time kinematic rtk gps tape and compass airborne light detection and ranging lidar and aerial photos no geomorphic evidence of a penultimate surface rupture was revealed from pre 2010 imagery the fault zone is up to 300 m wide and comprises both distributed folding and discrete faulting deformation dominated by right lateral displacement surface fracturing accommodates 30 of the total right lateral displacement in the central fault zone the remainder is accommodated by distributed deformation ground penetrating radar and trenching investigations conducted across the central greendale fault reveal that most surface fractures are undetectable at depths exceeding 1 m however large discrete riedel shears continue to depths exceeding 3 m and displace interbedded gravels and sand filled paleochannels at one trench site a riedel shear displaces surface agricultural markers e g fences and plow lines and a subsurface 0 6 m deep paleo channel by 60 cm right laterally and 10 cm vertically indicating the paleochannel has been displaced only in the darfield earthquake optically stimulated luminescence osl dating of the displaced paleochannel yields an age of 21 6 1 5 ka two additional paleochannels at 2 5 m depth with osl ages of 28 4 2 4 ka and 33 2 ka have been displaced 120 cm right laterally and 20 cm vertically the doubling of displacement at depth is interpreted to indicate that in the central section of the greendale fault the penultimate surface rupturing event occurred between ca 20 and 30 ka the greendale fault remained undetected prior to the darfield earthquake because the penultimate fault scarp was eroded and buried during late pleistocene alluvial activity similar active faults with low slip rates i e lower than sedimentation erosion rates are likely to be concealed in alluvial settings globally

variability of fluvial sediment supply to the laptev sea continental margin during late weichselian to holocene times implications from clay mineral records three sediment cores from the laptev sea continental margin were investigated for their clay mineralogy by x ray diffraction to study the fluvial sediment supply since the late weichselian in the study area the clay mineral composition of surface sediments is characterized by distinct regional variations the source area for smectite in the eastern eurasian basin is the putoran plateau drained by the khatanga and yenisei rivers currents caused by river discharge and the inflow of atlantic water masses along the eurasian continental margin are responsible for sediment distribution in the sediment cores smectite and illite contents show an opposite trend which mainly results from variable smectite supply during mis 2 the amount of smectite on the laptev sea continental margin never exceeds 10 rel probably reduced river discharge and the lowered sea level during mis 2 caused a decreased sediment supply to the laptev sea additionally the putoran plateau was covered by an ice sheet during the late weichselian preventing the erosion of smectite rich soils in contrast maximum smectite contents up to 30 rel in holocene sediments result from increased sediment input by the khatanga river and from the kara sea through the vilkitsky strait and via st anna trough into the western laptev sea

reconstructing the origin and trajectory of drifting arctic sea ice recent studies have indicated that drifting arctic sea ice plays an important role in the redistribution of sediments and contaminants here we present a method to reconstruct the back ward trajectory of sea ice from its sampling location in the eurasian arctic to its possible site of ori gin on the shelf based on historical drift data from the international arctic buoy program this method is verified by showing that origins derived from the backward trajectories are generally con sistent with other indicators such as comparison of the predicted backward trajectories with known buoy drifts and matching the clay mineralogy of sediments sampled from the sea ice with that of the seafloor in the predicted shelf source regions the trajectories are then used to identify regions where sediment laden ice is exported to the transpolar drift stream from the new siberian islands and the central kara plateau calculation of forward trajectories shows that the kara sea is a major contributor of ice to the barents sea and the southern limb of the transpolar drift stream

growth and seismic hazard of the montserrat anticline in the north canterbury fold and thrust belt south island new zealand abstract fault related fold growth is a seismic hazard in north canterbury new zealand the north canterbury fold and thrust belt ncftb is located at the southern end of the hikurangi subduction zone south island new zealand where the pacific plate transitions from subduction to transpression along the alpine fault transpression causes shortening beneath the south island resulting in basement thrusts generating folds such as the montserrat anticline we focus on fault geometry and seismic hazard associated with this structure exposed along the coast where pleistocene marine terraces on the backlimb record tectonic uplift to constrain parameters associated with evolution of this fault related fold we model the fold using several trishear kinematic models a listric fault is most compatible with field and regional geophysical studies ages of marine terraces and inner edge elevations constrain uplift rate due to slip on the glendhu fault to 1 1 0 1 m ka 1 an 800 year recurrence interval is calculated for the glendhu fault listric fault geometry lengthens the recurrence interval relative to other fault geometry models an accurate understanding of subsurface fault geometry and kinematics is important for estimating seismic hazard in regions of fault related folding such as the ncftb because it affects recurrence interval estimations

anhydrite pseudomorphs and the origin of stratiform cu co ores in the katangan copperbelt democratic republic of congo the stratiform cu co ore mineralisation in the katangan copperbelt consists of dispersed sulphides and sulphides in nodules and lenses which are often pseudomorphs after evaporites two types of pseudomorphs can be distinguished in the nodules and lenses in type 1 examples dolomite precipitated first and was subsequently replaced by cu co sulphides and authigenic quartz whereas in type 2 examples authigenic quartz and cu co sulphides precipitated prior to dolomite and are coarse grained the sulphur isotopic composition of the copper cobalt sulphides in the type 1 pseudomorphs is between 10 3 and 3 1 relative to the vienna canyon diablo troilite indicating that the sulphide component was derived from bacterial sulphate reduction bsr the generation of text hco 3 during this process caused the precipitation and replacement of anhydrite by dolomite a second product of bsr is the generation of h2s resulting in the precipitation of cu co sulphides from the mineralising fluids initial sulphide precipitation occurred along the rim of the pseudomorphs and continued towards the core precipitation of authigenic quartz was most likely induced by a ph decrease during sulphide precipitation fluid inclusion data from quartz indicate the presence of a high salinity 8 18 eq wt nacl fluid possibly derived from evaporated seawater which migrated through the deep subsurface 87sr 86sr ratios of dolomite in type 1 nodules range between 0 71012 and 0 73576 significantly more radiogenic than the strontium isotopic composition of neoproterozoic marine carbonates 87sr 86sr 0 7056 0 7087 this suggests intense interaction with siliciclastic sedimentary rocks and or the granitic basement the low carbon isotopic composition of the dolomite in the pseudomorphs 7 02 and 9 93 relative to the vienna pee dee belemnite v pdb compared to the host rock dolomite 4 90 and 1 31 v pdb resulted from the oxidation of organic matter during bsr

shear wave automatic picking and splitting measurements at ruapehu volcano new zealand automatic shear wave picking and shear wave splitting measurement tools multiple filter automatic splitting technique mfast are combined to build a near real time application for monitoring local stress around volcanoes we use an adapted version of diehl et al 2009 on seismograms provided by the new zealand geonet network and having an origin time and location based only on p picks the best automatic picks are processed by mfast which computes the corresponding shear wave fast direction and splitting delay time t interpreted respectively as the principal direction of stress underneath the station and the amount of anisotropy integrated along the wave raypath we applied our system to 9 years of local earthquakes recorded at seven stations around ruapehu volcano new zealand results are compared against mfast measurements from manual s picks when available and show less than 10 difference for 90 of measurements and less than 0 05 s difference for 95 of t measurements shear wave splitting from automatic s arrival times are slightly more consistent than those from manual arrival times at some stations two populations of delay times occur which depend upon computed initial polarization this may be caused in part by cycle skipping an artifact usually associated with monochromatic signals however spatial consistency in the behavior suggests a physical cause as well such as focal mechanisms varying with earthquake source location or a spatially varying near source anisotropic region the numbers of events in each population group vary over time possibly related to activity at ruapehu volcano

the great salinity anomaly in the northern north atlantic 1968 1982 the widespread freshening of the upper 500 800m layer of the northern north atlantic which this paper describes represents one of the most persistent and extreme variations in global ocean climate yet observed in this century though a range of explanations have been advanced to explain this event including in situ changes in the surface moisture flux this paper describes the great salinity anomaly as largely though not entirely an advective event traceable around the atlantic subpolar gyre for over 14 years from its origins north of iceland in the mid to late 1960s until its return to the greenland sea in 1981 1982 the overall propagation speed around this subpolar gyre is estimated at about 3cm s 1 of the total salt deficit associated with the anomaly as it passed south along the labrador coast in 1971 1973 about 72 109 tonnes a deficit equivalent to about two thirds of this figure 47 109 tonnes ultimately passed through the faroe shetland channel to the barents sea arctic ocean and greenland sea during the mid 1970s possible effects on deep water formation and on the representativeness of historical section data are discussed

stratiform copper deposits and interactions with co existing atmospheres hydrospheres biospheres and lithospheres abstract fundamental evidence from world class stratiform copper deposits repeatedly indicates that they originated by a two stage mineralization process a syn diagenetic enrichment of the host sediment in iron sulfide followed by a sub surface addition of copper during early diagenesis of the sediment in contrast to the previously favored syngenetic hypothesis which suggested an open equilibration between atmosphere hydrosphere biosphere and upper lithosphere during mineralization the two stage model implies that only the initial deposition of iron sulfides should take place with open exchanges between the upper spheres the sub surface emplacement of copper should occur in relative isolation from surface environments and therefore the occurrence and distribution of stratiform copper deposits through time and space should not be used to make direct interpretations of contemporaneous conditions in the upper spheres

late pleistocene and holocene meltwater events in the western arctic ocean accelerator mass spectrometer 14 c dated stable isotope data from neogloboquadrina pachyerma in cores raised from the mendeleyev ridge and slope provide evidence for significant influx of meltwater to the western arctic ocean during the early part of marine oxygen isotope stage 1 ois 1 and during several intervals within ois 3 the strongest ois 3 meltwater event occurred before ca 45 ka conventional radiocarbon age and was probably related to the deglaciation at the beginning of ois 3 major meltwater input to the western arctic ocean during the last deglaciation coincides closely with the maximum rate of global sea level rise as determined from the barbados sea level record demonstrating a strong link between the global record and changes in the central arctic ocean ois 2 which includes the last glacial maximum is very condensed or absent in the cores abundance and 13 c values for n pachyderma in the middle part of ois 3 are similar to modern values indicating high productivity and seasonal ice free areas along the arctic margin at that time these records indicate that the arctic ocean was a source of heat and moisture to the northern polar atmosphere during parts of ois 3

fracture related wavefield polarization and seismic anisotropy across the greendale fault we investigate seismic signatures of fracturing in a newly ruptured strike slip fault by determining the wavefield polarization in the new zealand canterbury plains area and across the greendale fault which was responsible for the 3 september 2010 darfield mw 7 1 earthquake previous studies suggested that fractured rocks in fault damage zones cause directional amplification and ground motion polarization in the fracture perpendicular direction as an effect of stiffness anisotropy and cause velocity anisotropy with shear wave velocity larger in the fracture parallel component an array of 14 stations was installed following the darfield earthquake we assess polarization both in the frequency and time domains through the individual station horizontal to vertical spectral ratio and covariance matrix analysis respectively and compare the results to previously reported anisotropy measurements from shear wave splitting stations installed in the canterbury plains have an amplification peak between 0 1 and 0 3 hz for both earthquakes and ambient noise we relate the amplification to the resonance of a considerable thickness c 1 km of soft sediments lying over the metamorphic bedrock analysis of seismic events revealed the existence of another peak in amplification between 2 and 5 hz at two on fault stations which was not visible in the noise analysis in contrast to the lower frequency peak the ones between 2 and 5 hz are more strongly anisotropic attaining amplitudes up to a factor of 4 in the n52 direction to interpret this effect we model the fracture pattern in the fault damage zone produced by the fault kinematics we conclude that the horizontal polarization is orthogonal to extensional fractures which predominate in the shallow layers 2 km expected in n101 direction on the basis of the model thus different fracture distribution at different depths may explain different results for amplification compared to anisotropy we propose polarization amplification analysis as a complementary method to s wave splitting analysis polarization analysis is rapidly computed and robust and it can be applied to either earthquakes or ambient noise recordings giving useful information about the predominant fracture patterns at various depths

the siberian coastal current a wind and buoyancy forced arctic coastal current we describe circulation and mixing in the siberian coastal current scc using fall shipboard measurements collected between 1992 and 1995 in the western chukchi sea the scc forced by winds siberian river outflows and ice melt flows eastward from the east siberian sea it is bounded offshore by a broad 60 km front separating cold dilute siberian coastal water from warmer saltier bering sea water the alongshore flow is incoherent because the current contains energetic eddies and squirts probably generated by frontal baroclinic instabilities these enhance horizontal mixing and weaken the cross shore density gradient along the scc path eventually the scc converges with the northward flow from bering strait whereupon it deflects offshore and mixes with that inflow deflection occurs where the alongshore pressure gradient vanishes that location varies on synoptic and seasonal timescales because this gradient depends on the winds buoyancy fluxes and the sea level difference between the pacific and arctic oceans deflection usually occurs on the chukchi shelf but the scc occasionally flows southward through bering strait such events are short lived 1 10 days and occur mainly in fall and winter under northerly winds scc transport is likely small 0 1 sv but its dilute waters could substantially freshen the bering strait inflow and affect the disposition of pacific waters in the arctic ocean arctic river outflows should preferentially form surface advected fronts rather than bottom advected fronts because vertical mixing energy is low on arctic shelves surface advected fronts are more susceptible to upwelling winds and for the scc the pressure gradient between the pacific and arctic oceans than bottom advected fronts the scc never developed in fall 1995 because of anomalously steady upwelling winds the western chukchi shelf could have formed upper halocline source water in the winter of 1995 1996

a record of past ocean atmosphere radiocarbon differences from the northeast pacific a record of the 14c age differences between atmosphere and the mixed layer of the northeast pacific ocean was obtained from 58 radiocarbon measurements on shells and associated wood from coastal sediments in british columbia this series of mixed layer reservoir ages spans the holocene and extends into the period of the younger dryas cold event in the north atlantic and surrounding regions the data reflect the extent of upwelling in the northeast pacific and thus constrain models of carbon cycling and ocean circulation most of the reservoir ages are only slightly less than than the present preindustrial value of about 800 years and may be identical when probable sampling errors are taken into account either the north pacific reached a state close to its present mode of circulation at or before the end of the younger dryas or a different circulation fortuitously produced a similar reservoir age our results support the hypothesis that slow changes in atmospheric radiocarbon concentrations over the holocene arose from 14c production rate changes data corresponding to a radiocarbon age of around 6400 years b p give a reservoir age of 1200 years if this result is confirmed it indicates a much greater variability for the holocene ocean circulation than was previously believed possible

composition and flux of holocene sediments on the eastern laptev sea shelf arctic siberia a 467 cm long core from the inner shelf of the eastern laptev sea provides a depositional history since 9400 cal yr b p the history involves temporal changes in the fluvial runoff as well as postglacial sea level rise and southward retreat of the coastline although the core contains marine fossils back to 8900 cal yr b p abundant pf ant debris in a sandy facies low in the core shows that a river influenced the study site until similar to 8100 cal yr b p as sea level rose and the distance to the coast increased this riverine influence diminished gradually and the sediment type changed by 7400 cal yr b p from sandy silt to clayey silt although total sediment input decreased in a step like fashion from 7600 to 4000 cal yr b p this interval had the highest average sedimentation rates and the greatest fluxes in most sedimentary components while this maximum probably resulted from middle holocene climate warming the low input of sand to the site after 7400 cal yr b p probably resulted from further southward retreat of the coastline and river mouth since about 4000 cat yr b p total sediment flux has remained rather constant in this part of the laptev sea shelf due to a gradual stabilization of the depositional regime after completion of the holocene sea level rise

climatic effects of reduced arctic sea ice limits in the giss ii general circulation model in this paper we present results of an atmospheric general circulation model gcm experiment in which arctic sea ice limits were substantially reduced in all months march sea ice limits were set equivalent to modern september limits and all sea ice was removed in september sea ice coverage for other months varied between these two extremes this climate sensitivity experiment makes predictions about mean northern hemisphere atmospheric conditions including temperature pressure wind patterns and precipitation consistent with these boundary constraints the major effects of reduced sea ice limits are observed in winter they include large regional warming of the circum arctic region northward migration of the icelandic low pressure system and strengthening of the azores high changes in net heating over the north atlantic ocean suggest that increases in sea surface temperatures and salinities in this region would also accompany reductions in arctic sea ice limits in the wind field a weakening of the polar easterlies and an intensification of cyclonic circulation over the norwegian greenland sea suggest that surface water exchange between the atlantic and arctic would increase when sea ice limits are reduced however zonally averaged changes in strength of the westerlies or upper level jet stream are minimal the late pliocene cooling of the north atlantic ocean and north american arctic margin may have been linked in part to the development of perennial sea ice cover

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

a 20 000 year record of ocean circulation and climate change from the santa barbara basin much of the evidence for climate driven fluctuations in ocean circulation during the past 20 000 years has come from studies of the north atlantic region1 6 the extent to which such interactions have occurred in other ocean basins and any associated teleconnec tions between basins is poorly understood here we present high resolution palaeoclimate and palaeoceanographic records from a 20 000 year sedimentary sequence from the santa barbara basin on the eastern margin of the north pacific ocean the sequence shows oscillations of the benthic environment between low oxygen conditions laminated sediments during periods of warm climate and higher oxygen conditions non laminated bioturbated sediments during cool intervals age differences between coexisting benthic and planktonic foraminifers indicate climate related changes in the age and source and hence oxygen content of basin bottom waters relatively young bottom waters are associated with the cooler intervals and are considered to reflect high proportions of intermediate waters derived from proximal sources conversely older bottom waters are associated with the warmer intervals and were derived from more distal sources these climate driven variations in ocean circulation appear to be synchronous with the main ocean climate fluctuations in the north atlantic region1 6 suggesting that a tight coupling mechanism operates between the two basins

comparative tomography of reverse slip and strike slip seismotectonic provinces in the northern south island new zealand abstract actively deforming crust and upper mantle around the obliquely convergent pacific australia plate boundary in the northern south island of new zealand have been investigated by seismic tomography using data from a temporary c 50 station network plus geonet the alpine wairau fault principal component of the plate boundary at the surface transects the study area separating the buller nelson bn province of active compressional inversion involving steep reverse faulting to the northwest from the marlborough fault system ma dominated by dextral strike slip faulting to the southeast in the course of this study ma hosted the 2013 seddon earthquake sequence m5 9 6 6 and the 2016 m7 8 kaikoura earthquake active fault structures and present seismicity are associated with a heterogeneous distribution of low velocity and vp vs anomalies elsewhere there is a general association between crustal seismicity and low velocity zones along major fault structures within both the ma and bn seismotectonic provinces along which high vp vs anomalies are locally conspicuous areas of active crustal seismicity are also generally characterized by high vp vs for instance the hypocentre and aftershocks of the 2016 m7 8 kaikoura earthquake overlie a low velocity region with high vp vs the coincidence of anomalously low vp and vs and anomalously high vp vs with zones of high electrical conductivity defined by a previous mt transect is consistent with the notion that upward migration of overpressured hydrothermal fluid from the subducting slab at depth leads to a heterogeneous distribution of overpressured fluid in and around the base of the crustal seismogenic zone weakening the overlying crust and promoting seismic rupture along major fault systems it seems possible that the association of mid crustal low velocity zones with anomalously high vp vs may diagnose rupture preparation zones where frictional strength is being lowered by the build up of fluid overpressure concurrent with accumulating shear stress so that eventual fault failure is dual driven

a holocene record of changing arctic ocean ice drift analogous to the effects of the arctic oscillation 1 the arctic oscillation ao controls the configuration of the transpolar drift tpd if thicker ice from the beaufort gyre were exported the volume of fresh water sea ice in the nordic seas would significantly increase decreasing the formation of north atlantic deep water this would cool large parts of the northern hemisphere and affect global climate therefore in order to understand how the global climate system functions it is imperative to know how the tpd changed over the last millennium or more the provenance of grains in a sediment core located near the confluence of the tpd and the beaufort gyre provides a direct proxy for changes in seaice drift owing to these circulation systems the core has more than 200 cm of holocene sediment with intervals dominated by grains from the russian shelves alternating with intervals of abundant grains from north american sources grains matched to russian shelves indicate that the tpd was shifted toward north america similar to what occurs during a more positive phase of the ao this condition alternated with intervals where few grains matched to russian sources presumably because the tpd was restricted to the russian half of the arctic far from the core site during the last 1300 years increased influx of russian grains occurred approximately every 50 150 years this fluctuation might represent the long term oscillation of the ao which modulates the same tpd shift today

radiocarbon chronology of depositional regimes in the western arctic ocean abstract the foraminiferal abundance and percentage of coarse ice rafted detritus ird define glacial deglacial and interglacial depositional regimes in ams radiocarbon dated box cores from the western arctic ocean sediment deposition rates are generally less than 0 5 cm ka for glacial regimes greater than this for deglacial regimes and greater than 1 2 cm ka for interglacial regimes these differences in deposition rates might account for the much lower average sedimentation rates for the last 780 ka of 1 3 mm ka in cores from the central arctic ocean if glacial regimes dominated this interval foraminiferal abundances are less than 500 g during glacial maxima and mostly higher than 2000 g during deglacial and interglacial regimes slightly higher coarse ird percentages occur in deglacial intervals 5 10 up to 30 compared with interglacial intervals mostly 5 which characterize the last 10 12 ka in the western arctic ocean glacial regimes occurred from about 40 to 11 ka except for a brief interglacial or deglacial interval around 24 28 ka in the central arctic ocean the coarsest deglacial events occurred prior to 45 ka the late wisconsin deglaciation sediments approximately 9 16 ka are difficult to detect in the central arctic ocean sediments because they are only slightly coarser than the holocene and in some box cores less coarse than the holocene a previously unrecognized coarse ird event occurred near the core tops 0 3 cm between 1500 and 3500 radiocarbon years ago in the western arctic ocean only sediment older than 40 ka is coarser than this recent ird event which might correspond to a neoglaciation recognized in the north atlantic and elsewhere

the 2010 2011 canterbury earthquake sequence environmental effects seismic triggering thresholds and geologic legacy abstract seismic shaking and tectonic deformation during strong earthquakes can trigger widespread environmental effects the severity and extent of a given effect relates to the characteristics of the causative earthquake and the intrinsic properties of the affected media documentation of earthquake environmental effects in well instrumented historical earthquakes can enable seismologic triggering thresholds to be estimated across a spectrum of geologic topographic and hydrologic site conditions and implemented into seismic hazard assessments geotechnical engineering designs palaeoseismic interpretations and forecasts of the impacts of future earthquakes the 2010 2011 canterbury earthquake sequence ces including the moment magnitude m w 7 1 darfield earthquake and m w 6 2 6 0 5 9 and 5 8 aftershocks occurred on a suite of previously unidentified primarily blind active faults in the eastern south island of new zealand the ces is one of earth s best recorded historical earthquake sequences the location of the ces proximal to and beneath a major urban centre enabled rapid and detailed collection of vast amounts of field geospatial geotechnical hydrologic biologic and seismologic data and allowed incremental and cumulative environmental responses to seismic forcing to be documented throughout a protracted earthquake sequence the ces caused multiple instances of tectonic surface deformation 3 events surface manifestations of liquefaction 11 events lateral spreading 6 events rockfall 6 events cliff collapse 3 events subsidence 4 events and hydrological 10s of events and biological shifts 3 events the terrestrial area affected by strong shaking e g peak ground acceleration pga 0 1 0 3 g and the maximum distances between earthquake rupture and environmental response r rup both generally increased with increased earthquake m w but were also influenced by earthquake location and source characteristics however the severity of a given environmental response at any given site related predominantly to ground shaking characteristics pga peak ground velocities and site conditions water table depth soil type geomorphic and topographic setting rather than earthquake m w in most cases the most severe liquefaction rockfall cliff collapse subsidence flooding tree damage and biologic habitat changes were triggered by proximal moderate magnitude m w 6 2 earthquakes on blind faults ces environmental effects will be incompletely preserved in the geologic record and variably diagnostic of spatial and temporal earthquake clustering liquefaction feeder dikes in areas of severe and recurrent liquefaction will provide the best preserved and potentially most diagnostic ces features rockfall talus deposits and boulders will be well preserved and potentially diagnostic of the strong intensity of ces shaking but challenging to decipher in terms of single versus multiple events most other phenomena will be transient e g distal groundwater responses not uniquely diagnostic of earthquakes e g flooding or more ambiguous e g biologic changes preliminary palaeoseismic investigations in the ces region indicate recurrence of liquefaction in susceptible sediments of 100 to 300 yr recurrence of severe rockfall event s of ca 6000 to 8000 yr and recurrence of surface rupturing on the largest ces source fault of ca 20 000 to 30 000 yr these data highlight the importance of utilising multiple proxy datasets in palaeoearthquake studies the severity of environmental effects triggered during the strongest ces earthquakes was as great as or equivalent to any historic or prehistoric effects recorded in the geologic record we suggest that the shaking caused by rupture of local blind faults in the ces comprised a worst case seismic shaking scenario for parts of the christchurch urban area moderate m w blind fault earthquakes may contribute the highest proportion of seismic hazard be the most important drivers of landscape evolution and dominate the palaeoseismic record in some locations on earth including locations distal from any identified active faults a high scientific priority should be placed on improving the spatial extent and quality of off fault shaking records of strong earthquakes particularly near major urban centres