recognizing and dating prehistoric liquefaction features lessons learned in the new madrid seismic zone central united states the new madrid seismic zone nmsz which experienced severe liquefaction during the great new madrid missouri earthquakes of 1811 and 1812 as well as during several prehistoric earthquakes is a superb laboratory for the study of world class earthquake induced liquefaction features and their use in paleoseismology in seismically active regions like the nmsz frequent large earthquakes can produce a complex record of liquefaction events that is difficult to interpret lessons learned studying liquefaction features in the nmsz may help to unravel the paleoseismic record in other seismically active regions soil characteristics of liquefaction features as well as their structural and stratigraphic relations to native american occupation horizons and other cultural features can help to distinguish prehistoric liquefaction features from historic features in addition analyses of artifact assemblages and botanical content of cultural horizons can help to narrow the age ranges of liquefaction features future research should focus on methods for defining source areas and estimating magnitudes of prehistoric earthquakes from liquefaction features also new methods for dating liquefaction features are needed

sand boils induced by the 1993 mississippi river flood could they one day be misinterpreted as earthquake induced liquefaction in areas that are seismically active but lacking clear surficial faulting many paleoearthquake studies depend on the interpretation of ancient liquefaction features sand blows as indicators of prehistoric seismicity sand blows however can be mimicked by nonseismic sand boils formed by water seeping beneath levees during floods we examined sand boils induced by the mississippi river flood of 1993 in order to compare their characteristics with sand blows of the new madrid earthquakes of 1811 1812 we found a number of criteria that allow a distinction between the two types of deposits 1 earthquake induced liquefaction deposits are broadly distributed about an epicentral area whereas flood induced sand boils are limited to a narrow band along a river s levee 2 the conduits of most earthquake induced sand blows are planar dikes whereas the conduits of flood induced sand boils are most commonly tubular 3 depression of the preearthquake ground surface is usual for sand blows not for sand boils 4 flood induced sand boils tend to be better sorted and much finer than sand blow deposits 5 source beds for earthquake induced deposits occur at a wide range of depths whereas the source bed for sand boils is always near surface 6 materials removed from the walls surrounding the vent of a sand blow are seen inside sand blows but are rarely seen inside sand boils in general flood induced sand boils examined are interpreted to represent a less energetic genesis than earthquake induced liquefaction

luminescence dating of pleistocene outwash sediments of the senne area eastern munsterland germany abstract results of combined gsl and irsl dating of glaciofluvial sediments of the senne the southern slope of the teutoburger wald eastern westfalia germany differ significantly from hitherto known ages seraphim 1979 berichte der naturwissenschaftliche vereinigung bielefeld 24 319 344 and skupin 1985 geologia kt nordrh westfaelische 1 100 000 erl c 4318 2 aufl 55 s krefeld suggest a saalian age for the sand body of the schlegel sand pit near augustdorf examined in this study according to seraphim 1979 the outwash sediments were deposited as a kame terrace between the north eastern slope of the teutoburger wald and drenthe stadial dead ice in the westfalian bucht skupin 1985 explains the sediments as drenthe stadial outwash sands from the emsland and the munsterland glacier using different luminescence methods nine samples of these sediments exhibit ages of 15 000 40 000 years accepted saalian aged sediments were sampled ca 5 km north of senne area here sediments beneath a saalian moraine show ages of 100 000 250 000 years in the light of these new data we suggest a model in which saalian aged sediments were totally reworked and finally deposited by aeolian and solifluction processes during weichselian time

high thermal maturity in the lower saxony basin intrusion or deep burial abstract the lower saxony basin lsb is situated at the southern rim of the northern permian basin the most important hydrocarbon bearing province in europe in its southern part areas of high thermal maturation up to 6 rr occur which were previously explained as being caused by magmatic intrusions of turonian to santonian age that affected carboniferous to lower cretaceous rocks in this area 2d numerical basin modelling was carried out in order to reconstruct the temperature histories along two parallel n s trending seismic sections along these sections new data about maturity distribution and temperature history were obtained by vitrinite reflectance measurements and apatite fission track analysis for the areas with highest maturity values low coalification gradients were established which agree well with earlier published data on wells further towards the west this new information does not support previous hypotheses on high heat flows from magmatic intrusions even if lateral heat transport is taken into account instead comparisons with a recently published map of the subsurface structure of the lsb indicate that maturity distribution may be closely related to major tectonic structures deep burial of individual structures of the lsb which are bordered by deep e w to ese wnw trending faults is further suggested by a rapidly increasing thicknesses of preserved cretaceous strata towards the south and b structural restoration of one of the seismic sections to achieve a fit between measured and calculated palaeo temperature and vitrinite reflectance data deep burial of carboniferous source rocks during cretaceous time has to be assumed due to an inversion phase in the early and middle upper cretaceous major amounts of sediment were removed and further uplift occurred in tertiary times in contrast the northern part of the lsb experienced maximum burial and temperatures during tertiary times

holocene soft sediment deformation of the santa fe sopetran basin northern colombian andes evidence for pre hispanic seismic activity abstract the detailed study of four deformed intervals from the holocene fluvio lacustrine deposits of the santa fe sopetran basin in northern colombia shows 17 types of soft sediment deformation ssd structures evidence indicates that seismic activity was responsible for the ssd structures a conclusion reached after considering the environmental conditions at the time of sediment deposition and shortly after and the detailed analysis of the driving force systems other triggers i e overloading and rapid sedimentation however are not discarded intervals showing ssd structures occurred at centennial frequencies and apparently resulted from mw 6 7 earthquakes the holocene age of these major shaking events should be seriously considered when evaluating the seismic hazard and risk for the middle cauca valley and the nearby city of medellin with 3 million inhabitants

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

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

earthquake magnitude frequency epicentral distance and soft sediment deformation in sedimentary basins abstract empirical equations available for earthquake magnitude frequency and the maximum epicentral distance of liquefied sites versus magnitude are combined with the characteristic instantaneous sediment deposition rate at a station in a sedimentary basin to form a model for the local stratigraphic frequency of earthquake induced soft sediment deformation structures both the style of sedimentation and the characteristics of the earthquake source combine to determine the pattern of incidence of the structures in a basin the model is probably most directly applicable to the geodynamic interpretation of fluvial basins in which substantial volumes of readily liquefied sands accumulate at high local short term rates

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

abraded sand volcanoes as a tool for recognizing paleo earthquakes with examples from the cisuralian talchir formation near angul orissa eastern india abstract one of the bedding planes of a sandstone unit belonging to the cisuralian talchir formation is well exposed along the nandir jhor river in eastern india it shows a few dozens of circular structures commonly with diameters of a few decimetres a concentration is found in an area of some 50 m 2 where 12 well developed specimens occur the structures are interpreted as abraded sand volcanoes which interpretation is supported by the occurrence on the same bedding plane of a sand volcano with a diameter of over a meter the concentrated structures thus represent a sand volcano field a phenomenon that has not been recognized earlier in the pre holocene geological record but that in recent times seems always to be related to an earthquake the structures described here might therefore help to recognize earthquakes that occurred in the geological past

the geometry and emplacement of conical sandstone intrusions conical sandstone intrusions with a geometry comparable with that of many igneous sills have been identified using 3d seismic data from large areas of the north sea and faeroe shetland basins these intrusions are of reservoir scale ranging from 100 to 2000 m or so in diameter 50 300 m in height and 1 80 m in thickness aperture they are concentrated in specific stratigraphic intervals in the cenozoic fills of both basins two geometrical end members are recognised and defined here apical cones and flat based bowls the former consist of inward dipping conical inclined sheets meeting at a prominent apex and the latter of similarly dipping discordant margins climbing from the edges of a concordant sheet both end members are associated with domal folds that are interpreted as resulting from the hydraulic elevation of the overburden during intrusion and which are analogous to similar structures associated with bowl shaped igneous sills measurements of aperture versus distance exhibit systematic relationships with the structural relief of these folds offering a potentially predictive method for estimation of sandstone intrusion aperture and reservoir volume prior to drilling a growth model for these end member geometries is presented drawing on existing theory for igneous sill emplacement aperture versus distance plots x are used to illustrate two contrasting models for aperture inflation during propagation but these require much further data before any specific growth model can be adopted

physical modelling of sand injectites abstract sand injectites are structures that result from intrusion of fluidized sand into fractures we have studied them in the tampen spur area of the north sea and have reproduced them experimentally by driving compressed air through layers of sand glass microspheres and silica powder the silica powder was cohesive and capable of hydraulic fracturing whereas the sand and glass microspheres were almost non cohesive and therefore able to fluidize the models were dynamically similar to their natural counterparts for as long as equilibrium was static when the processes became dynamic so that inertial forces were significant the scaling was approximate and the corresponding reynolds numbers differed the experimental apparatus was a square box 1 m 1 m wide resting on a grid of fluid diffusers during the experiments the fluid pressure increased until it attained and surpassed the weight of overburden flat lying hydraulic fractures containing air formed within cohesive and least permeable layers heterogeneities in material properties and layer thicknesses were responsible for localizing fracture networks when any one network broke through to the surface rapid flow of air through the fractures fluidized the underlying mobile materials and even depleted some of the layers some of the fluidized material extruded at the surface through vents forming volcanoes and sheets the remainder lodged at depth forming sand injectites or laccoliths conical sand injectites formed preferentially where layers had high resistance to bending laccoliths formed nearer the surface where overlying layers had low resistance to bending the experimental sand injectites were broadly similar to those in the tampen spur area of the north sea as well as other areas

activity along the osning thrust in central europe during the lateglacial ice sheet and lithosphere interactions abstract the osning thrust is one of the major fault systems in central europe with a length of approximately 115 km it underwent a polyphase tectonic evolution in the mesozoic that ranged from extensional movements in the jurassic to reverse faulting and thrusting during inversion in the late cretaceous a series of complex metre scale faults and related fold structures are developed within the upper pleistocene alluvial aeolian complex of the upper senne 1 km away from the thrust the faults dip towards the north and show offsets in a range of several decimetres growth strata indicate a two fold evolution of the structures the faults began as normal faults and were later transformed into reverse faults which resulted in the formation of small scale inversion structures with a typical harpoon shape glaciotectonics can be ruled out as the driving mechanism for these structures because new optically stimulated luminescence osl ages imply that the sedimentary succession was deposited during the late pleistocene between 29 3 2 9 ka and 13 1 1 5 ka at which time the ice margin was much further to the northeast we believe the inversion structures were caused by movement on the osning thrust due to generation of a forebulge of the late pleistocene weichselian ice sheet this led to normal faulting as a consequence of extension in the forebulge area during glaciation the osl ages for the normal fault related growth strata are in a range of 16 13 ka later reverse movements occurred during deglaciation due to the n s directed compressional stress field in northern germany numerical simulations of the deglaciation seismicity point to seismic events with a thrust mechanism in the study area between 15 5 and 12 3 ka bp although normal faulting is also possible in this time period numerous soft sediment deformation structures imply that movement on the osning thrust caused earthquakes with a significant magnitude in the autumn of 1612 an earthquake took place in this area it is very likely that this event is related to background seismicity on this fault although movement due to the influence of the ongoing glacial rebound in fennoscandia is also possible

evidence from seismites for glacio isostatically induced crustal faulting in front of an advancing land ice mass rugen island sw baltic sea abstract it is hitherto commonly thought that earthquakes triggered by geologically rapid changes in the pressure caused by the fluctuating extent of thick land ice masses occur exclusively during ice retreat our study of deformed sediment layers within an undeformed glaciolacustrine and glaciofluvial succession exposed in a coastal cliff on rugen island south western baltic sea challenges this widespread idea based on their structural and deformational features the layers under investigation are interpreted as seismites which formed as a result of seismically induced liquefaction the stratigraphic context aided by optically stimulated luminescence osl dating indicate that the documented seismites must have formed shortly before the front of the pleistocene scandinavian ice sheet reached the study area during the last glacial maximum thus during a stage of ice advance this implies that the flexural isostatic response of the earth s crust as a consequence of the ice load during ice advance was accompanied by earthquakes probably due to local re activation of pre existing faults the crustal response to an increasing ice load was consequently less gradual than previous studies about glaciation related tectonics suggest

seismically induced soft sediment deformation structures in an active seismogenic setting the plio pleistocene karewa deposits kashmir basin nw himalaya abstract recent uplift in the nw himalaya has exposed more than 1000 m of the plio pleistocene so called karewa deposits in kashmir these deposits mostly consist of horizontal stratified sand silt clay conglomerates and lignite beds the sedimentary succession belongs to the kashmir basin that is located in a seismically active zone the area was previously affected by large earthquakes the observed soft sediment deformation structures ssds are predominantly developed in the sand silt and clay beds and include load and water escape structures intrusive sedimentary bodies convolute bedding disturbed laminites and slump structures deformation mechanism and driving forces of the ssds were seismic shock waves sediment loading and storm events as driver for the ssds are less likely and the proximity of the ssds to faults underlines the seismic origin of these structures syn and post depositional faults and deformation bands developed in the karewa deposits support the interpretation of neotectonic activity and point to an earthquake of magnitude 5 5 that struck the kashmir basin in the plio pleistocene

genesis and diagnostic value of soft sediment deformation structures a review abstract soft sediment deformation structures are recognized as important diagnostic features in the rock record for determination of depositional environments and slope processes the diagnostic value of these structures is reevaluated by analysis of the parameters controlling sediment deformation soft sediment deformation is contemporaneous with deposition and occurs dominantly in course silt to fine sand the high depositional rate low permeability and low shear strength of grains within this sediment range maximize the occurrence of deformation the dominant mechanisms responsible for sediment deformation include 1 liquefaction or fluidization 2 reverse density gradation 3 slumping or slope failure and 4 shear stress in most cases a combination of these mechanisms occurs the processes function in a continuum producing features that are microscopic to megascopic in scale it is shown that the processes and thus the structures are not environment specific the true diagnostic value of the structures may be in defining hydrodynamic conditions and in interpreting paleocurrents and paleoclimatic and paleoseismic events ultimately for the best diagnostic results soft sediment deformation structures should be studied in association with all other available lithologic structural and paleontological information

crustal memory and basin evolution in the central european basin system new insights from a 3d structural model abstract the central european basin system cebs is composed of a series of subbasins the largest of which are 1 the norwegian danish basin 2 the north german basin extending westward into the southern north sea and 3 the polish basin a 3d structural model of the cebs is presented which integrates the thickness of the crust below the permian and five layers representing the permian cenozoic sediments structural interpretations derived from the 3d model and from backstripping are discussed with respect to published seismic data the analysis of structural relationships across the cebs suggests that basin evolution was controlled to a large degree by the presence of major zones of crustal weakness the nw se striking tornquist zone the ringkobing fyn high rfh and the elbe fault system efs provided the borders for the large permo mesozoic basins which developed along axes parallel to these fault systems the tornquist zone as the most prominent of these zones limited the area affected by permian cenozoic subsidence to the north movements along the tornquist zone the margins of the ringkobing fyn high and the elbe fault system could have influenced basin initiation thermal destabilization of the crust between the major nw se striking fault systems however was a second factor controlling the initiation and subsidence in the permo mesozoic basins in the triassic a change of the regional stress field caused the formation of large grabens central graben horn graben gluckstadt graben perpendicular to the tornquist zone the ringkobing fyn high and the elbe fault system the resulting subsidence pattern can be explained by a superposition of declining thermal subsidence and regional extension this led to a dissection of the ringkobing fyn high resulting in offsets of the older nw se elements by the younger n s elements in the late cretaceous the nw se elements were reactivated during compression the direction of which was such that it did not favour inversion of n s elements a distinct change in subsidence controlling factors led to a shift of the main depocentre to the central north sea in the cenozoic in this last phase n s striking structures in the north sea and nw se striking structures in the netherlands are reactivated as subsidence areas which are in line with the direction of present maximum compression the moho topography below the cebs varies over a wide range below the n s trending cenozoic depocentre in the north sea the crust is only 20 km thick compared to about 30 km below the largest part of the cebs the crust is up to 40 km thick below the ringkobing fyn high and up to 45 km along the teisseyre tornquist zone crustal thickness gradients are present across the tornquist zone and across the borders of the ringkobing fyn high but not across the elbe fault system the n s striking structural elements are generally underlain by a thinner crust than the other parts of the cebs the main fault systems in the permian to cenozoic sediment fill of the cebs are located above zones in the deeper crust across which a change in geophysical properties as p wave velocities or gravimetric response is observed this indicates that these structures served as templates in the crustal memory and that the prerift configuration of the continental crust is a major controlling factor for the subsequent basin evolution

sedimentary and structural evolution of a pleistocene small scale push moraine in eastern poland new insight into paleoenvironmental conditions at the margin of an advancing ice lobe abstract recent studies of push moraines have focused on the interplay between the dynamics of ice margins and the environmental variables of the foreland into which they advance these studies showed that the spatial distribution geometry and style of the glaciotectonic deformation of push moraines are controlled by ice induced stresses the strain rate the rheology of the deposits and hydraulic conductivity in this work we provide new insight into this interplay at a small spatio temporal scale specifically the ancient glacial system of the liwiec ice lobe within the younger saalian ice sheet in eastern poland the paleoenvironmental variables that are analysed here refer to the dynamics of the hydrological processes that affected the patterns and sediment deposition rate on the terminoglacial fan and the resulting mechanical stratigraphy and hydraulic conductivity of the foreland we document the progradational sequence of the fan deposits that developed as a result of the ice lobe thickening and the steepening of its stationary front the sedimentary features of the fan the lithology of its basement and the hydraulic conductivity of the foreland strongly influenced the geometry and kinematics of fold growth during the advance of the ice lobe the predominance of flexural slip and the development of fractures including fold accommodation faults were interpreted to be an effect of buckle folding due to horizontal shortening induced by ice advance the partial overriding of the push moraine by the ice lobe and thus the submarginal conditions for deformation were inferred from the significant hinge migration and internal deformation of the strata under undrained conditions in one of the folds the synfolding deposition pattern of the fan growth strata allowed us to suggest that the push moraine was probably formed by a sustained advance rather than surge

experimental studies of gas escape and water escape structures mechanisms and morphologies abstract water escape and gas escape structures were generated in the laboratory to assess variations in deformational structures generated during these events particulate fluidization was observed to be the method by which grains were redistributed during water escape resulting structures of particulate fluidization comprised disrupted and downward deflected primary laminations and a massive appearing column of sand above the point source gas experiments with a low flow rate 6 167 10 6 m3 s allowed gas to disperse through fractures and only subtle deformation was achieved aggregative fluidization i e fluid movement through sediment as bubbles was the mechanism for grain displacement during gas escape with increased flow rate 7 67 10 5 m3 s aggregative fluidization occurred and particles were carried upward in the wake of the passing gas bubble aggregative fluidization resulted in broken upwards warping laminations and convoluted bedding experiments illustrate a significant morphological difference between water escape and gas escape water escape structures were bounded by downwards warping laminations consistent with water escape structures encountered in the rock record gas escape structures displayed upwards warping laminations and could represent a formation mechanism for convolute bedding

palaeoseismic liquefaction event in late quaternary lake sediment at glen roy scotland late quaternary lake sediment deposits from a former ice dammed lake at glen roy scotland contain deformation structures indicative of liquefaction the distribution of deformation styles reflects a concentric pattern of the degree of liquefaction a possible fault rupture and several landslides are also observed in the central area the liquefaction structures the zonation of the sediment deformation and the association of deformation with landsliding can most simply be interpreted in terms of ground shaking during a major earthquake occurring at the end of the last glacial episode in scotland c 10 000 bp

evolution of the lower saxony basin abstract the lower saxony basin is a 300 km long and 65 km wide late jurassic and early cretaceous trough which parallels the northern margin of the rhenish massif this basin became inverted during the senonian and paleocene the lower saxony basin is the most important oil province of germany past production amounts to 200 10 6 t of oil 1 5 10 9 bbl the lower saxony basin is superimposed on the late carboniferous variscan foredeep basin and the frontal structures of the variscan fold belt during the permian to middle jurassic the area formed part of the northwest european basin differential subsidence of the lower saxony basin was initiated during the late jurassic and persisted till albian time this involved reactivation of permo carboniferous fracture systems by divergent wrenching a major aptian deep seated laccolith is evident in the western part of the lower saxony basin during the senonian and paleocene sinistral convergent wrenching induced uplift of the basin floor and folding of its sedimentary fill the margins of the inverted lower saxony basin are thrust over the adjacent stable platform areas the differential subsidence of the lower saxony basin can be related to a period of major crustal extension in the north sea rift basin inversion coincides with important orogenic events in the alpine system and is thought to have been induced by intra plate compressional stresses

lake sediment evidence of paleoseismicity timing and spatial occurrence of late and postglacial earthquakes in finland abstract sediment profiles in six lake basins located near the late and postglacial fault surface ruptures in northern finland were investigated for turbidites and soft sediment deformation structures that could reveal information on the timing and spatial occurrence of paleoearthquakes in the area we used geophysical sub bottom profiling and lithological logging of sediment cores combined with radiocarbon and paleomagnetic dating in three lakes immeljarvi aakenus and laukkujarvi sediment records provided evidence of postglacial earthquakes or landslides whereas in three others lakes pyhajarvi kallojarvi and syvajarvi no disturbance structures were observed in their sequences that cover roughly the holocene period combined with previous data on paleoseismicity in finland the results enhance the non stationary hypothesis of seismicity throughout the late weichselian and the holocene with three general maxima that cluster around the deglaciation 12 0 10 0 kyr bp the mid holocene 5 0 7 0 kyr bp and the late holocene 1 5 3 0 kyr bp a strong asymmetry of the offset profiles of the finnish postglacial fault complexes indicate that the general rupture propagation was from sw to ne the present data also indicates that the oldest and highest magnitude events mw 7 or higher generally took place in the sw sector of the finnish pgf complexes during or soon after the retreat of the continental ice sheet the ruptures then propagated towards the ne sector of pgf complexes in a cascading fashion and were generally characterized by lower magnitude events mw 6 during the holocene

superposed deformed beds produced by single earthquakes tecopa basin california insights into paleoseismology abstract well exposed soft sediment deformation ssd structures occur in tecopa paleolake beds largely composed of ash from the bishop 760 kyr and the lava creek 640 kyr ultra plinian eruptions in both cases the ssd structures affected volcaniclastic deposits concentrated by overland flow from the surrounding topography into the lower slope and lake environments re sedimentation of ash produced alternations of volcaniclastic layers with different grain sizes and ash content that allowed for reverse density gradients which favoured liquefaction and deformation in the tecopa basin extensive outcrops show these deformed strata continuing laterally for hundreds of metres along with three dimensional exposures this study illustrates the 3 d complexity of soft sediment deformation including some novel morphologic features of particular interest were examples of superposed deformed beds that laterally change into one single deformed horizon heterogeneities in ash concentration grain size and water content produced contrasting permeabilities that were barriers to liquefaction and soft sediment deformation the probable causes for liquefaction were middle pleistocene paleo earthquakes there are several active faults in the region with enough seismic potential to produce moderate to large earthquakes the fact that a single deformed deposit laterally merges into multiple superposed deformed beds indicates that multilayer liquefaction could be produced by a single shaking event in these cases ssd layers are insufficient and unreliable indicators of paleo seismic recurrence intervals

discussion on palaeoseismic structures in quaternary sediments related to an assumed fault zone north of the permian peissen gnutz salt structure nw germany neotectonic activity and earthquakes from the saalian to the holocene grube 2019 abstract we discuss the significance of deformation structures in quaternary sediments observed by grube 2019 in the peissen quarries nw germany in light of the geological context evidence for polygonal patterns visible in aerial images in the study area shows that the wedge structures interpreted by grube 2019 as earthquake induced sand blows may rather correspond to thermal contraction cracks filled with aeolian sand in a permafrost environment in the study sites brittle deformations caused by i the rise of a salt diapir ii salt dissolution iii the development of pleistocene permafrost and iv possibly water circulation under pressure in the scandinavian ice sheet margin may have coexisted we support the idea that while the morphology of deformation generally makes it possible to determine the stress state to which the sediments have been subjected and the quantity of water available in the system at the time of deformation the nature of the factors causing the stresses remains difficult to identify in the end we highlight other useful criteria that should be privileged for palaeoseismic research in such complex geological settings

morphology and paleoenvironmental significance of quaternary sand veins sand wedges and composite wedges tuktoyaktuk coastlands western arctic canada sand and sand ice fillings of quaternary thermal contraction cracks on summer and hadwen islands western arctic canada comprise sand veins sand wedges and composite wedges sand wedges in diamicton poor ice diamicton rich ice and ice rich sand generally have simple v shapes whereas those in ice poor sand vary from v shaped to irregular forms and may contain inclusions of host sand these morphological differences are explained in terms of the relative tensile strength of the wedge and host materials bundles of sand veins within sand wedges indicate discrete stages of wedge growth criteria previously proposed for identifying relict sand wedges are reevaluated 1 not all wedges are v shaped some are irregular forms with offshoot sand veins 2 a vertical or steeply dipping lamination is not apparent within all wedges some appear to have a massive fill suggesting that the sand source can be texturally and mineralogically very uniform 3 individual sand veins and groups of veins can be just as common within sandy host materials as the better known sand wedges composite sand ice wedges at crumbling point summer island commenced growth as composite wedges continued as sand wedges were modified by thermokarst and in some cases recommenced at a stratigraphically higher level as ice wedges the sand wedge and ice wedge stages reflect environmental change from cold arid and windy proglacial conditions during oxygen isotope stage 2 to warmer and wetter interglacial conditions during oi stage 1

liquefaction at oceano california during the 2003 san simeon earthquake the 2003 m 6 5 san simeon california earthquake caused liquefaction induced lateral spreading at oceano at an unexpectedly large distance from the seismogenic rupture we conclude that the liquefaction was caused by ground motion that was enhanced by both rupture directivity in the mainshock and local site amplification by unconsolidated fine grained deposits liquefaction occurred in sandy artificial fill and undisturbed eolian sand and fluvial deposits the largest and most damaging lateral spread was caused by liquefaction of artificial fill the head of this lateral spread coincided with the boundary between the artificial fill and undisturbed eolian sand deposits values of the liquefaction potential index in general were greater than 5 at liquefaction sites the threshold value that has been proposed for liquefaction hazard mapping although the mainshock ground motion at oceano was not recorded peak ground acceleration was estimated to range from 0 25 and 0 28 g on the basis of the liquefaction potential index and aftershock recordings the estimates fall within the range of peak ground acceleration values associated with the modified mercalli intensity vii reported at the u s geological survey usgs did you feel it web site

seismological hazard assessment for a site in northern germany an area of low seismicity abstract potential sites of nuclear waste deposits in the federal republic of germany are situated in areas of low seismicity nevertheless seismic hazard assessment has to be performed for a very long time period in order to prove the facilities of the repositories able to withstand seismic induced loads even though there is a considerable debate whether or not it is possible to quantify the seismic risk in such an area a combination of deterministic and probabilistic methods is used to assess the seismic hazard for a site in northern germany fulfilling the standards of the german building code for nuclear power plants as an example the site of the former iron ore mine konrad is investigated the deterministic method is based on the assumption that the strongest earthquakes inside a tectonic region can happen everywhere there also near the selected site for the probabilistic method several models describing the seismicity in an area of 200 km around the site are used to show the influence of the variability in input parameters like the maximum intensity of each source region on the exceeding probability of the site intensity it can be shown that the seismic hazard of a site in an area of low seismicity is mainly caused by the effects of distant but strong source regions and the background seismicity for very low probabilities probabilistic evaluation has the advantage of quantifying the seismic risk but deterministic and probabilistic methods together seem a practical tool for mutual control of the results and to overcome the weakness of each approach alone the historical german earthquake catalog with an observation period of about 1200 years is the basis for the input data for a probabilistic model from a deep knowledge of geological development and structural geology the time history of the surrounding faults is developed indications were found that the nearest and most important fault was active at least 5 ma ago the combination of both seismicity and tectonics provides the basis for a long term prognostic with probabilities of exceedance in the order of 10 5 per year for the investigated site the following parameters were derived site intensity as a function of exceeding probability site acceleration strong motion duration site dependent response spectra for the surface and the underground inside the mine

on the origin of the southern permian basin central europe abstract a detailed study of the structural and stratigraphic evolution of the southern permian basin during latest carboniferous to early jurassic times supported by quantitative subsidence analyses and forward basin modelling for 25 wells leads us to modify the conventional model for the rotliegend zechstein development of this basin the late permian early jurassic tectonic subsidence curves are typical for a permian to early triassic extensional stage that is followed by thermal subsidence however a purely extensional model is extremely problematic because active faulting during this time is minor and generally hard to document using inverse techniques to model the subsidence curves we quantitatively show that a significant component of late permian and triassic tectonic subsidence can be explained by thermal relaxation of early permian lithospheric thinning and by delayed infilling of paleo topographic depressions that developed during the early permian in this interpretation stephanian autunian wrenching resulted in thermal destabilisation of the lithosphere deep fracturing of the crust disruption and erosion of its sedimentary cover and regional uplift of the area of the future southern permian basin upon termination of wrench tectonics and associated volcanism towards the end of the autunian the southern permian basin began to subside in response to thermal contraction of the lithosphere the evolving basin was isolated from the world oceans and had subsided possibly up to some 700 m below their level at the beginning of upper rotliegend sedimentation after catastrophic flooding of this paleo topographic depression at the beginning of the zechstein changing sea level sedimentation and subsidence rates remained essentially in balance although the effects of triassic rifting overprinted parts of the southern permian basin its overall subsidence pattern persisted well into the jurassic in contrast to the remainder of the southern permian basin permian and triassic crustal extension contributed significantly to the subsidence of the polish trough

new information on the thermal history of the southwestern lower saxony basin northern germany based on fission track analysis the southwestern part of the lower saxony basin lsb is characterized by gravity and magnetic anomalies and by an extremely high thermal maturity of organic matter this was for many years attributed to a late cretaceous intrusion but actually deep burial is being debated the complex thermal history of the area has been studied by fission track analysis zircon data provide evidence for widespread hydro thermal activity during the permian and upper jurassic lower cretaceous apatite ages indicate a major cooling event in the mid cretaceous 89 72 ma reflecting the time of inversion of the lsb during the cretaceous the cooling of the basin centre was rapid compared to the basin margins apatite fission track ages from borehole samples which are recently within the upper part of the apaz indicate a young heating of the sedimentary sequences until present

syndepositional tectonics recorded by soft sediment deformation and liquefaction structures continental lower permian sediments southern alps northern italy stratigraphic significance abstract the lower permian succession of the central southern alps lombardy northern italy was deposited in fault controlled continental basins probably related to transtensional tectonics we focussed our study on the stratigraphic record of the lower permian orobic basin which consists of a 1000 m thick succession of prevailing continental clastics with intercalations of ignimbritic flows and tuffs pizzo del diavolo formation pdv resting on the underlying prevailing pyroclastic flows of the cabianca volcanite the pdv consists of a lower part composed of conglomerates passing laterally to sandstones and distally to silt and shales a middle part pelitic with carbonates and an upper part alternating sandstone silt and volcanic flows syndepositional tectonics during the deposition of the pdv is recorded by facies distribution thickness changes and by the presence of deformation and liquefaction structures interpreted as seismites deformation is recorded by both ductile structures ball and pillow plastic intrusion disturbed lamination convolute stratification and slumps and brittle structures sand dykes and autoclastic breccias both the sedimentological features and the geodynamic setting of the depositional basin confidently support the interpretation of the described deformation features as related to seismic shocks the most significant seismically induced deformation is represented by a slumped horizon about 4 m thick on average which can be followed laterally for more than 5 km the slumped bed consists of playa lake deposits alternating pelites and microbial carbonates associated with mud cracks and vertebrate tracks the lateral continuity and the evidence of deposition on a very low angle surface along with the deformation liquefaction of the sediments suggest that the slump was triggered by a high magnitude earthquake the stratigraphic distribution of the seismites allows us to identify time intervals of intense seismic activity which correspond to rapid and basin wide changes in the stratigraphical architecture of the depositional basin and or to the reprise of the volcanic activity the nature of the structures and their distribution suggest that the magnitude of the earthquakes responsible for the observed structures was likely higher than 5 in order to produce sediment liquefaction and probably reached intensity as high as 7 or more the basin architecture suggests that the foci of these earthquakes were located close to the fault controlled borders of the basin or within the basin itself

paleostress states at the south western margin of the central european basin system application of fault slip analysis to unravel a polyphase deformation pattern abstract we analyse the deformation pattern along the south western margin of the central european basin system cebs where upper carboniferous mesozoic rocks are uplifted due to the late cretaceous basin inversion the geometry of mesoscale faults and associated striae are used to calculate the stress state s responsible for the observed deformation each reduced stress tensor obtained comprises i the directions of the principal stress axes 1 2 and 3 1 2 3 and ii the ratio of principal stress differences r 2 3 1 3 we present a stress inversion technique that allows each stress state inherent in a heterogeneous fault population to be identified by integrating the results of the pbt method turner f j 1953 nature and dynamic interpretation of deformation lamellae in calcite of three marbles american journal of sciences 251 4 276 298 sperner b ratschbacher l and ott r 1993 fault striae analysis a turbo pascal program package for graphical presentation and reduced stress tensor calculation computers geosciences 19 1361 1388 and the multiple inverse method yamaji a 2000 the multiple inverse method a new technique to separate stresses from heterogeneous fault slip data journal of structural geology 22 4 441 452 this comprehensive approach not only facilitates the separation of complex data sets into homogeneous subsets but also guarantees that each stress state derived fulfils both the criteria of low misfit angles wallace bott hypothesis and high shear to normal stress ratios mohr coulomb criterion the reliability of our technique is confirmed by the fact that irrespective of i the number of fault slip data from an outcrop ii the number of subsets they represent and iii the proportion of newly formed and reactivated faults we obtain consistent results from outcrops of variously aged rocks this consistency concerns both calculated stress states as well as locally observed deformation sequences such local chronologies are derived from cross cutting relationships and superimposition of different fault slip data which individually are assigned to a consistent stress state a synthesis of results from different locations of the study area argues for the superposition of two main deformation events most prominently the area was affected by a stress state with a horizontal n s to ne sw directed maximum compression 1 and a low stress ratio which induced reverse and strike slip faulting a pure strike slip regime of e w to nw se directed compression with moderate stress ratios is less prevalent and probably younger the age of the youngest rocks documenting these two phases proves the stress fields to correspond to the polyphase late cretaceous tertiary basin inversion of the cebs during post cenomanian times the youngest tectonic imprints detected in the study area correspond to locally appearing extensional stress states with varying directions of 3 at many sites the youngest derived paleostress state coincides with the present day stress field in terms of the direction of the maximum horizontal stress axis s hmax the only stress state detected which pre dates the basin inversion corresponds to an extensional regime with an wnw ese to nw se directed 3 axis observed only locally in the n s striking leine graben and its prolongation to the north the fact that the majority of variously aged rocks exhibit only the traces of the latest deformation phases indicates a high degree of fault plane reactivation in the study area

the action of wind and water in a mid cretaceous subtropical erg margin system close to the variscan iberian massif spain aeolian processes and ephemeral water influx from the variscan iberian massif to the mid cretaceous outer back erg margin system in eastern iberia led to deposition and erosion of aeolian dunes and the formation of desert pavements remains of aeolian dunes encased in ephemeral fluvial deposits aeolian pods demonstrate intense erosion of windblown deposits by sudden water fluxes the alternating activity of wind and water led to a variety of facies associations such as deflation lags desert pavements aeolian dunes pebbles scattered throughout dune strata aeolian sandsheets aeolian deposits with bimodal grain size distributions mud playa ephemeral floodplain pebble sand and cobble sand bedload stream pebble cobble sand sheet flood sand bedload stream debris flow and hyperconcentrated flow deposits sediment in this desert system underwent transport by wind and water and reworking in a variety of sub environments the nearby variscan iberian massif supplied quartzite pebbles as part of mass flows pebbles and cobbles were concentrated in deflation lags eroded and polished by wind driven sands facets and ventifacts and incorporated by rolling into the toesets of aeolian dunes the back erg depositional system comprises an outer back erg close to the variscan highlands and an inner back erg close to the central erg area the inner back erg developed on a structural high and is characterized by mud playa deposits interbedded with aeolian and ephemeral channel deposits in the inner back erg area ephemeral wadis desiccated after occasional floods were mud cracked and overrun episodically by aeolian dunes subsequent floods eroded the aeolian dunes and mud cracked surfaces resulting in largely structureless sandstones with boulder size mudstone intraclasts floods spread over the margins of ephemeral channels and eroded surrounding aeolian dunes the remaining dunes were colonized occasionally by plants and their roots penetrated into the flooded aeolian sands upon desiccation deflation resulted in lags of coarser grained sediments a renewed windblown supply led to aeolian sandsheet accumulation in topographic wadi depressions synsedimentary tectonics caused the outer back erg system to experience enhanced generation of accommodation space allowing the accumulation of aeolian dune sands ephemeral water flow to the outer back erg area supplied pebbles eroded aeolian dunes and produced hyperconcentrated flow deposits fluidization and liquefaction generated gravel pockets and recumbent folds dune damming after sporadic rains the case of the namib desert monsoonal water discharge thar desert and meltwater fluxes from glaciated mountains taklamakan desert are three potential non exclusive analogues for the ephemeral water influx and the generation of hyperconcentrated flows in the cretaceous desert margin system an increase in relief driven by the aptian anti clockwise rotation of iberia led to an altitude sufficient for the development of orographic rains and snowfall which fed melt water fluxes to the desert margin system quartzite conglomerates and sands dominantly consisting of quartz and well preserved feldspar grains which are also observed in older cretaceous strata indicate an arid climate and the mechanical weathering of precambrian and palaeozoic metamorphic sediments and felsic igneous rocks unroofing of much of the cover of sedimentary rocks in the variscan iberian massif must therefore have taken place in pre cretaceous times

periglacial microjointing and faulting in weichselian fluvio aeolian deposits a weichselian late pleniglacial fluvio aeolian deposit has been investigated in the southern netherlands three main structural lineaments have been distinguished 1 very small vertical platy structures microjoints in a parallel and a columnar configuration 2 large joints and normal faults with minor displacement grubbenvorst type arranged in a conjugate fault system 3 large joints and normal faults wedge type located adjacent to ice wedge casts since clay is absent the occurrence of the vertical platy structures cannot be attributed to desiccation cracking the vertical platy structures are interpreted as the result of thermal contraction cracking of a relatively thin layer due to a sudden temperature drop the large joints and normal faults of the grubbenvorst type are the result of failure of the sediment due to the melting of the permafrost in the late pleniglacial just before the formation of the beuningen gravel bed in other areas large periglacial convolutions have been formed during the same period the normal faults and joints of the wedge type are more generally known they are the result of failure of the sediment adjacent to a melting ice wedge

different modes of the late cretaceous early tertiary inversion in the north german and polish basins several selected seismic lines are used to show and compare the modes of late cretaceous early tertiary inversion within the north german and polish basins these seismic data illustrate an important difference in the allocation of major zones of basement thick skinned deformation and maximum uplift within both basins the most important inversion related uplift of the polish basin was localised in its axial part the mid polish trough whereas the basement in the axial part of the north german basin remained virtually flat the latter was uplifted along the sw and to a smaller degree the ne margins of the north german basin presently defined by the elbe fault system and the grimmen high respectively the different location of the basement inversion and uplift within the north german and polish basins is interpreted to reflect the position of major zones of crustal weakness represented by the wnw ese trending elbe fault system and by the nw se striking teisseyre tornquist zone the latter underlying the mid polish trough therefore the inversion of the polish and north german basins demonstrates the significance of an inherited basement structure regardless of its relationship to the position of the basin axis the inversion of the mid polish trough was connected with the reactivation of normal basement fault zones responsible for its permo mesozoic subsidence these faults zones inverted as reverse faults facilitated the uplift of the mid polish trough in the order of 1 3 km in contrast inversion of the north german basin rarely re used structures active during its subsidence basement inversion and uplift in the range of 3 4 km was focused at the elbe fault system which has remained quiescent in the triassic and jurassic but reproduced the direction of an earlier variscan structural grain in contrast n s oriented mesozoic grabens and troughs in the central part of the north german basin avoided significant inversion as they were oriented parallel to the direction of the inferred late cretaceous early tertiary compression the comparison of the north german and polish basins shows that inversion structures can follow an earlier subsidence pattern only under a favourable orientation of the stress field a thick zechstein salt layer in the central parts of the north german basin and the mid polish trough caused mechanical decoupling between the sub salt basement and the supra salt sedimentary cover resultant thin skinned inversion was manifested by the formation of various structures developed entirely in the supra salt mesozoic cenozoic succession the zechstein salt provided a mechanical buffer accommodating compressional stress and responding to the inversion through salt mobilisation and redistribution only in parts of the ngb and mpt characterised by either thin or missing zechstein evaporites thick skinned inversion directly controlled inversion related deformations of the sedimentary cover inversion of the permo mesozoic fill within the mid polish trough was achieved by a regional elevation above uplifted basement blocks conversely in the north german basin horizontal stress must have been transferred into the salt cover across the basin from its sw margin towards the basins centre this must be the case since compressional deformations are concentrated mostly above the salt and no significant inversion related basement faults are seismically detected apart from the basin margins this strain decoupling in the interior of the north german basin was enhanced by the presence of the elbe fault system which allowed strain localization in the basin floor due to its orientation perpendicular to the inferred late cretaceous early tertiary far field compression

layered structure associated with low potential vorticity near the tropopause seen in high resolution radiosondes over japan horizontal wind and temperature data obtained from operational radiosondes over japan have recently been available with high vertical resolution analyzing these data over 4 yr has indicated horizontal velocity layers with vertical scales of about 5 km lasting for a week or more the layers appear frequently in winter at several stations simultaneously and are dominant in the height range of 8 16 km an empirical orthogonal function eof analysis for the time series of layered disturbance amplitude in winter indicates that there are two dominant principal components the first component eof1 describes layered disturbances in the middle of japan 308 378n and the second one eof2 describes disturbances in the south of japan 238 308n using global analysis data the background field of the layered disturbances was examined an interesting result is that the background potential vorticity pv is approximately zero or negative for eof2 disturbances even though located in a relatively high latitude region this fact suggests that the eof2 disturbances are due to inertial instability it is also shown that negative pv occurs more than 30 of the time in winter in a zonally elongated region of 238 298n in the western pacific on an isentropic surface of 345 k 10 km altitude such a high frequency of negative pv is not observed at other longitudes in this latitude band to determine the origin of the anomalous pv backward trajectories were analyzed for eof2 disturbances air parcels having mostly negative pv are traced back to the equatorial region in the longitude band 208w 1408e within a few days this is due to a strong northward branch of the hadley circulation associated with deep convection over the maritime continent and a strong northeastward subtropical jet stream on the other hand the background pv is low but scarcely negative for eof1 disturbances air parcels at eof1 stations are traced back to the far west because they are advected mostly by a strong eastward jet stream thus it is inferred that the eof1 disturbances may be due to inertia gravity waves trapped in a duct of the westerly jet core

review of flanking structures in meso and micro scales a variety of host fabric elements he cut by cross cutting elements ce in rocks defines flanking structures fs on mesoscopic and microscopic scales there has been renewed interest in studying and classifying the fs for their morphologies useful as shear sense indicators and geneses existing non genetic morphologic parameters for the fs are reviewed and two new classification schemes are presented one of these is based on the nature of the ce and whether he penetrates it the other scheme takes account of all the potential combinations of drag no drag and slip no slip of the he deciphering the shear sense of the rock body from fs is complicated because the angular relationship between the ce and the primary shear planes might be opposite to what is found between s and c ductile shear fabrics further single ces can curve and several similar fs occur in reverse forms as with mineral fish the shape asymmetries of microscopic ces indicate the shear sense conjugate fs with non parallel ces with interfering perturbation fields around the ces are more reliable shear sense indicators than fs with single ce during low but increasing bulk strains fs may evolve from one type to another e g from a to s type at high strain fs can resemble intrafolial or sheath fold whether the drag is normal or reverse depends fundamentally on the initial angle between the he and the ce and the relative magnitudes of throw and vertical separation

middle pleistocene saalian lake outburst floods in the munsterland embayment nw germany impacts and magnitudes abstract during the late saalian drenthe glaciation ice damming of the upper weser valley led to the formation of glacial lake weser the lake drained catastrophically into the munsterland embayment as the western ice dam failed releasing up to 110 km3 of water with a calculated peak discharge of 2 5 105 m3 s to 1 3 106 m3 s geographic information systems gis and high resolution digital elevation models dem were used to map streamlined landforms and channel systems in front of lake overspills geological maps 2450 boreholes and the dem were integrated into the 3d modeling program gocad to reconstruct the distribution of flood related deposits palaeotopographic surfaces and the internal facies architecture of streamlined hills the drainage pathways are characterized by the occurrence of deep plunge pools channels streamlined hills and 4 km long and 12 m deep v shaped megaflutes plunge pools are deeply incised into mesozoic basement rocks and occur in front of three major overspill channels the plunge pools are up to 780 m long 400 m wide and 35 m deep approximately 1 10 5 km downslope of the overspill channels fan shaped arrays of streamlined hills are developed each covering an area of 60 130 km2 indicating rapid flow expansion the hills commonly have quadrilateral to elongated shapes and formed under submerged to partly submerged flow conditions when the outburst flood entered a shallow lake in the munsterland embayment hills are up to 4300 m long 1200 m wide 11 m high and have characteristic average aspect ratios of 1 3 3 they are separated by shallow anabranching channels in the outer zones and up to 30 m deep channels in the central zones hills partly display v shaped chevron like bedforms that have apices facing upslope are 1 6 2 5 km long 3 10 m high 0 8 1 2 m from limb to limb with limb separation angels of 20 35 these bedforms are interpreted as mixed erosional depositional features it is hypothesized that the post saalian landscape evolution of the munsterland embayment has considerably been influenced by catastrophic floods of glacial lake weser creating large and deep valleys which subsequently became the new site of river systems the outburst floods probably followed the east west trending saalian rhine meuse river system eventually flowing into the north sea the strait of dover and the bay of biscay it is speculated that the hondsrug ice stream may have been enhanced or even triggered by the formation and outburst of glacial lakes in the study area

debris flow and glacioisostatic induced soft sediment deformation structures in a pleistocene glaciolacustrine fan the southern baltic sea coast poland abstract middle pleistocene glaciolacustrine fan sediments are exposed along a cliff at the baltic sea coast where plastic and brittle soft sediment deformation structures ssds commonly occur 1 fold structures various types of folds and flexures 2 load structures load casts pseudonodules and flame structures 3 water escape structures wes and 4 brittle deformation structures such as faults medium and small scale reverse and normal and fragments of broken up laminae the origins of the ssds can be linked to gravitational processes promoted by shear stresses in subaqueous debris flows on the glaciolacustrine fan and by the weight of overlying sediments and or to the glacial rebound of earth s crust during deglaciation because in the pleistocene the baltic sea and surrounding areas were covered by ice sheets many times the question investigated here concerns recognition of the trigger mechanisms responsible for the development of ssds and the criteria needed to recognize those mechanisms based on the lithological and deformational features of the sediments involved some types of ssds can look similar regardless of trigger mechanisms but some occur more often as a result of a specific mechanism is it possible to distinguish ssds of seismic origin in a glaciolacustrine fan succession affected by multiple debris flows and of ssds that evolved as a consequence of slope processes we suggest criteria to recognize ssds triggered by the glacioisostatic rebound as well as those which can develop as a result of the rebound and slope processes

earthquakes and deformational structures seismites in holocene sediments from the himalayan andaman arc india soft sediment deformational structures from the himalayan arc caused by episodic earthquake recurrences during the holocene recent are produced by the ongoing tectonic processes these small scale subtle structures occur along some major thrusts in the garhwal himalaya and vary from normal faults in the lower zone to compressional structures in the middle zone along the main central thrust in the tons valley the latter includes isoclinal angular kink and disharmonic folds with discrete displacements along their axial surfaces thrusts with decollement listric and overstep thrusts in duplex style and load slumping the upper zone is marked by very low angle thrusts with left lateral displacement and associated displacement shears d riedel shears r and thrust shears p as well as small scale sporadic kinks three zones reveal changing tectonic character from gravity tectonics in the lower zone to compression in both the middle and upper zones with the maximum principal stress 1 oriented n60 to n110 respectively along the tons thrust post depositional structures include drag along normal fault zone characterized by d r and p shears and conjugate fractures that provide localized orientation of stresses 1 at 75 n60 2 at 12 n280 and 3 at 12 n290 earthquake induced liquefaction and subtle variations in physiomechanical properties of soft sediments have primarily controlled the deformational pattern due to localized tectonic stresses ground and sediment deformations during two earthquakes in the himalayan andaman arc provide additional support for the seismogenic origin of such structures preserved in loose or consolidated sediments

towards establishing criteria for identifying trigger mechanisms for soft sediment deformation a case study of late pleistocene lacustrine sands and clays onikobe and nakayamadaira basins northeastern japan five main deformation units discrete sheets of deformed sediments that lie between a significant thickness of undeformed sediment were selected for study within late pleistocene lacustrine sands and clays in the onikobe and nakayamadaira basins northeastern japan the deformed units show evidence of deformation by a variety of mechanisms including fluidization liquefaction brittle failure and cohesive flow driving forces are thought to be primarily reverse density gradient systems but also include gravitational body force shear stress and unequal loading the main trigger mechanisms are firstly earthquakes secondly overloading from volcanic sands and thirdly to a lesser extent subaqueous currents consideration is given to criteria that allow the trigger mechanism to be identified this study shows that the following criteria can be used to identify a seismic triggering agent i setting ii the extent of the deformation units iii absence of evidence relating to other potential trigger mechanisms and iv evidence relating to other potential trigger mechanisms is present but can be seen elsewhere in the stratigraphic section associated with undeformed sediment conversely the following criteria while they are important in interpreting the driving force and deformation mechanism have no relevance to the trigger mechanism i sediment composition ii deformation structures being restricted to a single stratigraphic interval 1 m thick not necessarily correlatable over large areas and iii similarity to structures in the literature

the significance of cryoturbation phenomena in environmental reconstruction cryoturbation results mainly from differential heave related to 1 drainage and thermal conditions and 2 frost susceptibility loadcasting and cryostatic pressures are restricted to wet soils such as pure silt or silty sand the translocation of fine particles resulting from repeated freezing and thawing can promote frost susceptibility in a previously non susceptible material as well as a loss in stability of the surface horizons liquefaction small and metric scale cryoturbations can be explained by this process large scale deformations and injections may be related to abnormal liquefaction not necessarily associated with frost regular patterns are associated with fissure nets upturned injections in a downslope direction attest to cryoturbation and frost creep a lowering of the water table promotes the formation of drop like cryoturbations most of which can be related to seasonal frost in imperfectly to poorly drained soils they are not indicative of permafrost except in well drained situations or in the case of flat bottomed involutions

funnel shaped breccia filled clastic dykes in the late cambrian chaomidian formation shandong province china abstract some examples of a funnel shaped structure filled with both angular and rounded clasts occur in a peloidal grainstone bed of the chaomidian formation late cambrian in the jiulongshan area shandong province china the clasts consist of peloidal grainstone which is the same as that of the walls of the funnels the structures are interpreted as dykes formed by upward escape of pore water and or fluidized sediment through a narrow conduit which was gradually widened by the force of the intruding fluid sediment the erosional capacity of the pressurized fluid sediment mixture consequently diminished upwards which explains the gradual decrease in intensity of fragmentation from the adjoining walls in this direction

intraplate seismicity in northern central europe is induced by the last glaciation there is growing evidence that climate induced melting of large ice sheets has been able to trigger fault reactivation and earthquakes around the migrating ice limit even today the stress due to glacial isostatic adjustment can continue to induce seismicity within the once glaciated region northern central europe lies outside the former ice margin and is regarded as a low seismicity area however several historic earthquakes with intensities of up to vii occurred in this region during the past 1200 years here we show with numerical simulations that the seismicity can potentially be explained by the decay of the scandinavian ice sheet after the weichselian glaciation combination of historic earthquake epicenters with fault maps relates historic seismicity to major reverse faults of late cretaceous age mesozoic normal faults remained inactive in historic times we suggest that many faults in northern central europe are active during postglacial times this is a novelty that sheds new light on the distribution of postglacial faulting and seismicity in addition we present the first consistent model that can explain both the occurrence of deglaciation seismicity and the historic earthquakes in northern central europe

late cretaceous intraplate thrusting in central europe effect of africa iberia europe convergence not alpine collision a well established event of intraplate basin inversion and basement thrusting affected central europe in late cretaceous time it is widely accepted to have resulted from the collision of the alpine orogen with europe s margin at that time an early alpine orogen located on the leading edge of the adria microplate still lay far southeast of its present day position and had entered a phase of extension after a first orogenic event characterized by w to nw directed thrusting this configuration is not likely to have induced ssw nne directed thrusting and folding in the future european foreland that was still separated from the alpine wedge by a strip of oceanic lithosphere by contrast the onset of intraplate contraction coincides with an important change in relative motion between the european and african plates at ca 90 ma africa s sse directed sinistral transform motion relative to europe changed to ne directed convergence this agrees well with the timing and kinematics of intraplate thrusting in central europe structures of similar age and kinematics occurring in southern france spain and north africa suggest that the late cretaceous pulse of contraction was caused by pinching west central europe s thin lithosphere between baltica and africa only since the onset of n directed thrusting in the alps in paleocene or eocene time are the kinematics of the alps and their european foreland compatible indicating that mechanical coupling between africa europe and the adria microplate had been achieved

the 2004 mw 4 4 rotenburg northern germany earthquake and its possible relationship with gas recovery we study the 20 october 2004 m w 4 4 rotenburg wumme neuenkirchen earthquake located in a previously aseismic region in the northern german sedimentary basin we constrain the source parameter by using different techniques a possible relationship between this event the regional tectonic setting and local gas recovery is investigated different waveform inversion and modeling approaches constrain the depth of the mainshock between 5 and 7 km the source mechanism was oblique normal faulting on planes striking roughly north south an inversion for kinematic rupture parameters indicates a unilateral rupture propagation toward the north consistent with the higher macroseismic intensities found toward the north in the region of hamburg compared with those at a similar distance toward the south in the region of hannover relocations of the mainshock and three of the largest aftershocks indicate that these events occurred within a few kilometers of three major gas fields and at depth close to gas production intervals comparison with seismicity triggered in the northern netherlands by depletion of similar gas reservoirs in a similar tectonic environment suggests that the m w 4 4 rotenburg event may be related to gas recovery online material focal mechanism and waveform fit

geologic evidence for recurrent moderate to large earthquakes near charleston south carolina multiple generations of earthquake induced sand blows in quaternary sediments and soils near charleston south carolina are evidence of recurrent moderate to large earthquakes in that area the large 1886 earthquake the only historic earthquake known to have produced sand blows at charleston probably caused the youngest observed blows older late quaternary sand blows in the charleston area indicate at least two prehistoric earthquakes with shaking severities comparable to the 1886 event

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

some seismological and geometric features of intraplate earthquakes to understand the nature and cause of intraplate earthquakes we carried out a systematic search for common features associated with them various geological geophysical and seismic data were analyzed and geometric and seismic parameters were compared for 29 intraplate events m 4 5 occurring worldwide the results suggest that intraplate earthquakes occur by the reactivation of pre existing zones of weakness in a compressional stress regime which is generally oriented parallel to the absolute direction of plate motion two styles of faulting were observed for type a earthquakes observed in the eastern united states eastern china western europe and west africa deformation occurs by strike slip motion on steeply dipping faults type b events are usually associated with thrust or normal faulting and were observed in eastern canada fennoscandia australia and peninsular india focal depths did not explain the differences between type a and type b earthquakes rather the differences are due to the perturbation of a regional stress field by a local stress field the regional stress field for type a events is primarily due to ridge push forces the method of stress perturbation varied from region to region the earthquakes in the type b category were further divided into three subcategories type b1 occurring in eastern canada and fennoscandia type b2 occurring in australia peninsular india and central brazil and type b3 occurring in the gulf coast of the u s the inferred causes of the perturbing stresses are deglaciation intracontinental resistive forces resulting from the collision of plates and the deposition of a large thickness of sediments respectively type a events were found to be associated with intersecting faults and generally supported the intersection model of talwani 1988 and had analogs in plate boundary events

the final phase of dead ice moraine development processes and sediment architecture kotlujokull iceland consecutive phases of de icing of ice cored moraines and the formation of dead ice moraine were monitored over a 4 year period at the terminus of the kotlujokull glacier iceland particularly the transition from partially ice cored moraine with isolated dead ice blocks to the ice free landscape receives attention in this paper in order to link the final melting processes to the architecture of the sedimentary end product in the current humid sub polar climate of south iceland de icing of partially ice cored moraines results chiefly from melting along the bottom surface of ice cores with an annual average rate of 25 cm the final de icing is associated with an interrelated group of re sedimentation processes and surface features series of sinkholes evolve at the toe of dead ice blocks which initiate retrogressive rotational sliding or backslumping of the ice cored slopes and the formation of distinct edges and fractures in the adjacent basins although backslumping is the dominant process in this phase of re sedimentation structures resulting from this process are rarely recognized in the ice free landscape as ice cores gradually diminish the effect of the latest re sedimentation events will overprint or destroy most existing sedimentary characteristics thus in the ice free landscape structures mainly related to the formation of sinkholes and fractures remain imprinted on the sediment succession generally no inversion of the topography occurs during the final phase of de icing the overall topography recognized in the late phase of the fully ice cored terrain is merely lowered and the amplitude of the relief reduced as de icing progresses the sediment architecture of the ice free landscape is characterized by heterogeneous and often slumped diamict sediments with variable thickness and lateral distribution clast orientation is related to the direction of slopes and boulders are found in isolated groups or in linear arrangements

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

an experimental setup for fluid venting in unconsolidated sediments new insights to fluid mechanics and structures abstract focused outflow of water at the seafloor termed seepage or fluid venting is a widely recognized global phenomenon in an effort to better understand the mechanisms by which fluid flow related structures form we performed laboratory seepage experiments using samples representing a broad range of grain sizes and hydraulic conductivities 10e 3 to 10e 7 m s detailed observations led to the recognition of a typical often repeated progression of fluid flow structures that form during processes of increasing and decreasing hydraulic gradients the development of fluid flow structures like macro pores conduits and pipes is strongly dependant upon cohesion but is unrelated to grain size variations from sample to sample partial liquefaction leads to permanent changes in the grain fabric and to an increase in hydraulic conductivity our observations explain the longevity of seep sites and systematic relationships between hydraulic gradients grain fabric appearance and hydraulic conductivity that could be used to estimate flow rates based on structural findings

response of salt structures to ice sheet loading implications for ice marginal and subglacial processes abstract during the past decades the effect of glacioisostatic adjustment has received much attention however the response of salt structures to ice sheet loading and unloading is poorly understood our study aims to test conceptual models of the interaction between ice sheet loading and salt structures by finite element modelling the results are discussed with regard to their implications for ice marginal and subglacial processes our models consist of 2d plane strain cross sections which represent simplified geological cross sections from the central european basin system the model layers represent i sedimentary rocks of elastoplastic rheology ii a viscoelastic diapir and layer of salt and iii an elastoplastic basement on top of the model a temporarily variable pressure simulates the advance and retreat of an ice sheet the durations of the individual loading phases were defined to resemble the durations of the pleistocene ice advances in northern central europe the geometry and rheology of the model layers and the magnitude spatial distribution and timing of ice sheet loading were systematically varied to detect the controlling factors all simulations indicate that salt structures respond to ice sheet loading an ice advance towards the diapir causes salt flow from the source layer below the ice sheet towards the diapir resulting in an uplift of up to 4 m the diapir continues to rise as long as the load is applied to the source layer but not to the crest of the diapir when the diapir is transgressed by the ice sheet the diapir is pushed down up to 36 m as long as load is applied to the crest of the diapir during and after ice unloading large parts of the displacement are compensated by a reversal of the salt flow plastic deformation of the overburden is restricted to the area immediately above the salt diapir the displacements after unloading range between 3 1 and 2 7 m larger displacements are observed in models with deep rooted diapirs thicker ice sheets longer duration of the loading phase thicker salt source layers and lower viscosity of the salt the rise or fall of diapirs triggered or amplified by ice sheet loading are likely to affect glacigenic deformation erosion and deposition above the diapir and within the rim synclines ice load induced uplift in front of an ice sheet will provide favourable conditions for the formation of push moraines for example by creating a topographic obstacle and inclining potential detachments subglacial subsidence of salt structures will enhance erosion by providing a preferential drainage pathway and fracturing of the overburden of the salt structure and thereby contribute to the incision of tunnel valleys however the resulting displacements are probably too low to have a marked effect on the advance or retreat pattern of the ice sheets

liquefaction features on the fraser delta evidence for prehistoric earthquakes sand dykes and sills and vented sand boils on the fraser river delta and adjacent serpentine river floodplain in southwestern british columbia record one or more major liquefaction events the source of the dykes is a shallow subsurface saturated sand unit that was deposited in foreslope and distributary channel environments during holocene progradation of the fraser delta the dykes cut steeply through a crust of delta topset muds and locally flatten out as sills in overlying peaty sediments at two sites evidence was found for venting of sand onto a subaerial or intertidal surface liquefaction and upward movement of sand and water locally deformed the intruded sediments causing some subsidence and uplift of the delta surface all observed liquefaction features are younger than ca 3500 bp and at least some are younger than 2400 bp it is not clear however whether they formed during one or several separate events a review of possible causes suggests that the liquefaction features probably are seis

ice wedges growth thaw transformation and palaeoenvironmental significance frost cracking and ice wedge growth are fundamental processes within the permafrost environment extensive areas of contemporary permafrost terrain are characterised by frost fissure polygons formed by repeated thermal contraction cracking of the ground the incremental growth of ice veins and wedges along the axes of contraction cracks contributes significantly to the volume of ground ice in near surface permafrost in areas beyond the present limit of permafrost the recognition of ice wedge pseudomorphs provides one of the few unambiguous indications of the former existence of permafrost conditions an understanding of the processes of ice wedge growth and thaw transformation is essential if contemporary ice wedges are to be used as analogues for pleistocene frost fissure structures in palaeoenvironmental reconstructions

aseismic controls on in situ soft sediment deformation processes and products in submarine slope deposits of the karoo basin south africa intervals of soft sediment deformation features including vertical fluid escape and load structures are common and well exposed in permian lower slope deposits of the tanqua depocentre karoo basin the structures mainly comprise elongated flames and load structures associated with ruptured sandstones and structureless siltstones observed over a range of scales the presence of an upper structureless siltstone layer linked to the flames interpreted as a product of the debouching of fine grained material transported through the flame onto the palaeo seabed together with the drag and upward folding of lower sandstone layers is evidence that the flames were formed in situ by upward movement of sediment rich fluids flames are oriented parallel to the deep water palaeoslope in lateral splay deposits between two major slope channel complexes statistical correlation and regression analyses of 180 flame structures from seven stratigraphic intervals suggest a common mechanism for the deformation and indicate the importance of fluidization as a deformation mechanism importantly deformation occurred in an instantaneous and synchronous manner liquefaction and fluidization were triggered by incremental movement of sediment over steeper local gradients that were generated by deposition of a lateral splay on an inherited local north west facing slope seismic activity is not invoked as a trigger mechanism because of the restricted spatial occurrence of these features and the lack of indications of earthquakes during the time of deposition of the deep water succession the driving mechanisms that resulted in the final configuration of the soft sediment deformation structures involved a combination of vertical shear stress caused by fluidization development of an inverse density gradient and a downslope component of force associated with the local slope ground penetrating radar profiles confirm the overall north east orientation of the flame structures and provide a basis for recognition of potential larger scale examples of flames in seismic reflection data sets

seismites an attempt at critical analysis and classification abstract the main types of seismites are reviewed following the proposed classification and are illustrated by our own case studies the large variety of seismites depends on the sedimentologic hydrodynamic and diagenetic characters of the deposits subject to seismic shocks on a given site generally different types of seismites cane be related to the same seismic event these peculiar but widespread sedimentary structures are not always univocal and may often be related to different causes therefore the structures discussed must necessarily be placed in a detailed geological context

soft sediment deformation structures in nw germany caused by late pleistocene seismicity new data on seismically triggered soft sediment deformation structures in pleniglacial to late glacial alluvial fan and aeolian sand sheet deposits of the upper senne area link this soft sediment deformation directly to earthquakes generated along the osning thrust which is one of the major fault systems in central europe soft sediment deformation structures include a complex fault and fold pattern clastic dikes sand volcanoes sills irregular intrusive sedimentary bodies flame structures and ball and pillow structures the style of soft sediment deformation will be discussed with respect to brittle failure liquefaction and fluidization processes and was controlled by 1 the magnitude of the earthquake and 2 the permeability tensile strength and flexural resistance of the alluvial and aeolian sediments it is the first time in northern germany that fluidization and liquefaction features can be directly related to a fault the occurrence of seismicity in the late pleistocene and in the seventeenth century indicates ongoing crustal movements along the osning thrust and sheds new light on the seismic activity of northern germany the late pleistocene earthquake probably occurred between 15 9 1 6 and 13 1 1 5 ka the association of soft sediment deformation structures implies that it had a magnitude of at least 5 5

recognition of trigger mechanisms for soft sediment deformation in the pleistocene lacustrine deposits of the santʻarcangelo basin southern italy seismic shock vs overloading abstract the lacustrine deposits of the san lorenzo cycle belong to the infill succession of the sant arcangelo basin a pliocene to pleistocene satellite basin developed close to the front of the south apennines thrust belt the lower to middle pleistocene lacustrine succession is made up of siltstone and claystone interbedded with sandstone carbonate and volcaniclastic beds arranged in fining upward sequences the upper to middle part about 50 m thick of the succession about 200 m thick has been investigated in detail in the depocentral sector of the lacustrine basin here soft sediment deformation structures occur in fine grained sandstone and claystone alternations and show a wide morphological variability deformed laminations slumps load structures large vertical water escape structures and neptunian dykes their formation occurred during and after sedimentation with different mechanisms of deformation some structures are related to liquefaction and fluidization processes viscous fluid behaviour while others occurred when sediment had already undergone lithification and its behaviour was plastic and or brittle facies analysis and detailed morphologic study of the soft sediment deformation structures indicate that the main trigger agents for deformation were seismic shocks and overloading induced by sudden deposition of coarser sediments on clays due to the arrival of density currents thus the soft sediment deformation structures provide a continuous record of the tectonic and sedimentary processes that acted in the lacustrine basin from sedimentation until diagenesis

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

triassic to recent tectonic evolution of a crestal collapse graben above a salt cored anticline in the gluckstadt graben north german basin abstract in this study we investigate faulting above a salt wall in the gluckstadt graben north german basin two supra salt faults are mapped from coast to coast over a distance of 6 9 km based on offshore and onshore seismic data these faults form a ca 2 km wide crestal collapse graben and pierce the seafloor salt wall evolution started in the early late triassic to early jurassic due to regional extension and resulting sub salt faulting the salt wall was eroded following exposure to costal and sub aerial erosion by the regional mid late jurassic to early cretaceous uplift late cretaceous to early paleogene compressional tectonics reactivated the vertical salt movement and shortened the salt wall creating a salt cored anticline with the crestal collapse graben above the supra salt faults were reactivated between the late eocene and middle miocene when the principal horizontal stress orientation changed from a ne sw to a nw se the present day orientation stratigraphic data indicate that these faults moved mainly in the cenozoic several observations strongly suggest that the faults continued developing during the pleistocene until today i the pleistocene unconformity is concave upwards and cut by faults ii growth strata within the marine holocene deposits above the graben imply recent tectonic movements iii onshore high resolution p wave vibroseis data of the south eastern eckernforde bay suggest about 10 m of faulted holocene strata and iv marine seismic data show the faults piercing the seafloor we suggest that the recent salt tectonics and upward propagation of supra salt faults resulted from differential ice sheet loading that effect on the salt wall stopped once ice grew over the whole structure at which time the wall subsided because of ice loading the salt wall and faults were reactivated again once the ice front retreated so that the ice loaded only one side of the structure

recognition of cryoturbation for classifying permafrost affected soils cryoturbation is a dominant pedologic process in permafrost affected soils and is used to delineate gelisols in soil taxonomy and cryosols in the canadian and recently proposed world reference base for soil resources and cryozems in russian systems of soil classification in this paper we summarize evidence for cryoturbation that can be used for classifying soils containing permafrost based on a literature review and our own observations cryoturbation in the soil profile is manifested by irregular and broken horizons and textural bands involutions organic matter accumulation on the permafrost table oriented stones silt caps and accumulations and deformed soil material associated with movements due to ice and sand wedge growth

the earthquake potential of the new madrid seismic zone the fault system responsible for new madrid seismicity has generated temporally clustered very large earthquakes in a d 900 100 years and a d 1450 150 years as well as in 1811 1812 given the uncertainties in dating liquefaction features the time between the past three new madrid events may be as short as 200 years and as long as 800 years with an average of 500 years this advance in understanding the late holocene history of the new madrid seismic zone and thus the contemporary tectonic behavior of the associated fault system was made through studies of hundreds of earthquake induced liquefaction features at more than 250 sites across the new madrid region we have found evidence that prehistoric sand blows like those that formed during the 1811 1812 earthquakes are probably com pound structures resulting from multiple earthquakes closely clustered in time or earthquake sequences from the spatial distribution and size of sand blows and their sedimentary units we infer the source zones and estimate the magnitudes of earth quakes within each sequence and thereby characterize the detailed behavior of the fault system it appears that fault rupture was complex and that the central branch of the seismic zone produced very large earthquakes during the a d 900 and a d 1450 events as well as in 1811 1812 on the basis of a minimum recurrence rate of 200 years we are now entering the period during which the next 1811 1812 type event could occur

recurrent liquefaction induced by the 1989 loma prieta earthquake and 1990 and 1991 aftershocks implications for paleoseismicity studies sandblows formed in man made lake deposits near watsonville california resulted from the october 1989 m 7 1 loma prieta earthquake and its april 1990 m 5 5 aftershock and a march 1991 m 4 6 aftershock excavations in the dry bed of soda lake expose the subsurface structure of sandblows induced by the october and april events we also made surface observations three days after the march 1991 event lateral spread fissures developed in the lake sediment during the mainshock and the host deposits were vertically offset 3 to 6 5 cm liquefied sand erupted through the fissures onto the dry lake bed and formed sandblow cone deposits these deposits range from low angle conical structures 30 to 50 cm thick and 2 to 5 m in diameter to elongate deposits up to 35 m long sandblows associated with the april 1990 aftershock commonly reoccupied preexisting fissures but also formed new solitary vents sandblows developed during the march 1991 aftershock erupted only through preexisting vents sandblow vents reactivated in april 1990 contain sediment clasts of sandblow deposits formed in the october 1989 mainshock clasts of host sediment were also present in the sand dikes lamination in the sandblow cones and sand dikes shows that they were not formed in a single episode surface cones and feeder dikes composed of multiple laminated subunits represent the three generations of sandblows the subunits suggest that the cone deposits were formed by pulses of water and sediment expelled from the vent the pulses result from cyclic phases of local excess pore pressure and its release in the liquefied bed at depth the three generations of structures at soda lake formed six months to a year apart have distinct tonal and textural differences that may mimic liquefaction structures formed decades or centuries apart this study provides modern analogs for comparison to and interpretation of prehistoric liquefaction structures that are frequently partly eroded or poorly exposed

field occurrences of liquefaction induced features a primer for engineering geologic analysis of paleoseismic shaking discussed in this paper are the factors that control the typical manifestations of liquefaction that are found in continental field settings the factors are given mainly in terms of the local geologic field situation and the geotechnical properties there a meaningful interpretation of liquefaction based data for quantitative analysis of paleoseismic shaking requires understanding of both geologic and geotechnical roles in the mode of ground failure at a specific site recommendations are made for the size of the field area that must be searched for liquefaction effects in order to develop adequate data for engineering geologic geotechnical analyses of paleoseismicity the areal extent must be based on an appreciation that the tectonic situation can cause seismically induced liquefaction effects to form in some locales but not in others nearby even for a strong earthquake in the region our guidelines for the conduct of the field search and preliminary analysis of the data relate to three issues for which liquefaction features are especially useful in answering has there been strong holocene latest pleistocene shaking in the region where was the tectonic source and what was the strength of shaking understanding of the various factors that control the manifestations of liquefaction effects which we present in this paper is essential for developing credible answers to these questions

soft sediment deformation structures in late miocene pleistocene sediments on the pediment of the matra hills visonta atkar verseg cryoturbation load structures or seismites abstract the studied area built up by silty clayey and partly sandy sediments and paleosols lies on the tectonically active northern margins of the pannonian basin wavy sagging load casts can be observed in the upper part of the late miocene alluvial complex and larger scale sagging load casts flame structures drops and pillows detected in its quaternary cover were studied in detail in order to understand the origins of soft sediment deformation which characterized this young sedimentary suite sedimentological paleopedological and mineralogical observations suggest that 1 one of the reasons for the soft sediment deformation might have been the relatively low cohesive strength of the predominantly smectitic sediment covering a gentle slope similar to the actual landscape 2 on such a surface the down slope gravitational component of the mud blanket might easily have been sufficient to overcome its cohesive strength 3 frost action traceable in the studied formations might also have contributed to the observed deformation particularly along the eroded top of the late miocene sediments combined evidence from field observations and laboratory analyses support the idea that liquefaction fluidization was of prime importance in bringing about the observed structures in conclusion two alternative quaternary holocene scenarios are proposed which might have resulted in the unusual behaviour of the sediments paleosols one is a seismic event the other is the combined effect of freeze thaw cycles and of the sloping foothill position which might have resulted in episodic downslope transport and the associated deformation of the eroded soil material when its water content surpassed a certain threshold we accept that the anomalous abundance of soft sediment deformation in this marginal position may be causally related to paleo earthquakes but the obvious complexity of the phenomenon requires caution in case the proposed scenarios would not have been alternatives but acted simultaneously the analysed phenomena were to be interpreted as the joint results of tectonics and climate change

palaeoseismic structures in quaternary sediments of hamburg nw germany earthquake evidence during the younger weichselian and holocene investigations at a construction site in hamburg nw germany exposed palaeoseismic structures from moderate to strong earthquakes based on the large size of large blowout clastic dykes being up to 2 0 m wide and 2 5 m high as well as the occurrence of infill structures erratics rafts of up to 9 kg in weight seismites s s and decimetre scale folds or seismoslumps the magnitude of the earthquakes could be in the order of up to m 6 this is significantly higher than previously assumed for prehistorical seismic events in nw germany the structures are assigned to earthquakes possibly related to nw se oriented faults that are evident in lidar and sar surface interpretations organic material from blowout related infill bowls assumed to be synchronously formed collapse depressions are analysed for 14c ages the dates reveal ages between 31 500 and 1200 14c cal a bp indicating five prehistoric earthquakes accordingly three of these earthquakes occurred before and after the main weichselian glaciation phase ca 31 350 26 850 and 18 980 14c cal a bp and two occurred during the subatlantic ca 4900 and 1200 14c cal a bp the weichselian events indicate seismic activity in the ice marginal zone during or following interstadials dansgaard oeschger events as well as suggesting that advancing ice sheets foster earthquakes

sedimentological evidence of pleistocene earthquakes in nw poland induced by glacio isostatic rebound abstract soft sediment deformation structures are abundantly present in two levels within warthanian eemian lacustrine sediments at siekierki near the polish german border the two event horizons show intense folding collapse sag and load structures indicative of liquidization and fluidization the structures must have been caused by sudden shocks most probably resulting from earthquakes that were induced by glacio isostatic rebound probably after the warthanian deglaciation such seismites have not been previously recognized in polish quaternary sediments they provide supporting evidence for glacio isostatic movements that were interpreted up till now based on drilling lithostratigraphic geophysical and geodetic data the recognition of seismites in nw poland may help recognize other deformed event horizons in pleistocene sediments as glacio isostatic or neotectonic seismites

use of liquefaction induced features for paleoseismic analysis an overview of how seismic liquefaction features can be distinguished from other features and how their regional distribution and properties of source sediment can be used to infer the location and strength of holocene paleo earthquakes abstract liquefaction features can be used in many field settings to estimate the recurrence interval and magnitude of strong earthquakes through much of the holocene these features include dikes craters vented sand sills and laterally spreading landslides the relatively high seismic shaking level required for their formation makes them particularly valuable as records of strong paleo earthquakes this state of the art summary for using liquefaction induced features for paleoseismic interpretation and analysis takes into account both geological and geotechnical engineering perspectives the driving mechanism for formation of the features is primarily the increased pore water pressure associated with liquefaction of sand rich sediment the role of this mechanism is often supplemented greatly by the direct action of seismic shaking at the ground surface which strains and breaks the clay rich cap that lies immediately above the sediment that liquefied discussed in the text are the processes involved in formation of the features as well as their morphology and characteristics in field settings whether liquefaction occurs is controlled mainly by sediment grain size sediment packing depth to the water table and strength and duration of seismic shaking formation of recognizable features in the field generally requires a low permeability cap above the sediment that liquefied field manifestations are controlled largely by the severity of liquefaction and the thickness and properties of the low permeability cap criteria are presented for determining whether observed sediment deformation in the field originated by seismically induced liquefaction these criteria have been developed mainly by observing historic effects of liquefaction in varied field settings the most important criterion is that a seismic liquefaction origin requires widespread regional development of features around a core area where the effects are most severe in addition the features must have a morphology that is consistent with a very sudden application of a large hydraulic force this article discusses case studies in widely separated and different geological settings coastal south carolina the new madrid seismic zone the wabash valley seismic zone and coastal washington state these studies encompass most of the range of settings and the types of liquefaction induced features likely to be encountered anywhere the case studies describe the observed features and the logic for assigning a seismic liquefaction origin to them also discussed are some types of sediment deformations that can be misinterpreted as having a seismic origin two independent methods for estimating prehistoric magnitude are discussed briefly one method is based on determination of the maximum distance from the epicenter over which liquefaction induced effects have formed the other method is based on use of geotechnical engineering techniques at sites of marginal liquefaction in order to bracket the peak accelerations as a function of epicentral distance these accelerations can then be compared with predictions from seismological models

palaeoseismic structures in quaternary sediments related to an assumed fault zone north of the permian peissen gnutz salt structure nw germany neotectonic activity and earthquakes from the saalian to the holocene abstract this study reports on neotectonic deformation represented as faults graben and horst structures which have been found in the uppermost 10 m of quaternary sediments consisting mainly of saalian glaciofluvial and weichselian periglacial material in northern germany that is generally considered as a low seismicity area an area with up to 35 faults in a 60 m wide zone exhibits mainly extensional structures most of those are se nw oriented and in some cases ne sw soft sediment deformation structures include sand blows blowout related infill structures and growth faults small scaled soft sediment deformation structures are also found based on the large size of the sand blows and the widespread occurrence of small scaled soft sediment deformation structures the magnitude of the earthquakes is estimated in the order of m 5 5 single faults exhibit a displacement of a few metres because some faults are overlain by unfaulted sandur sediments the system has been active over at least 200 ka saalian several faults extend through the weichselian periglacial layer to the present ground surface proving ongoing deformation during the weichselian lateglacial and or the holocene this major activity during the saalian and the weichselian points to the activation of old tectonic structures a possible process can be the glacial loading and unloading associated with the isostatic rebound holocene and late holocene seismic events are shown by the penetration of the weichselian lateglacial periglacial layer by faults and sand blows as well as a possible blowout related bowl with organic material and corresponding young 14c dates of

inversion related features along the southeastern margin of the north german basin elbe fault system abstract a seismostratigraphic approach constrained by well data is used for the interpretation of the deformation style along the central elbe fault system efs within the sedimentary succession structural analysis allows to qualify to quantify and to date tectonic events the stratigraphic interpretation is complicated by the mobilized upper permian zechstein salt and by erosional events a first order quantification of the inversion related uplift is estimated from vertical fault offsets that reach up to 4 km the main uplift occurred during the maastrichtian paleocene amounts of erosion inferred from comparing the strata thickness on top of the flechtingen high with the surrounding basinal areas range from 3 to 4 km the data indicate a changing deformation style thick skinned deformation with southwest dipping thrusts that vertically offset the pre permian basement is observed along the flechtingen high in the central part of the efs thin skinned deformation occurs in the north german basin where salt detaches the post permian cover from the barely faulted basement it is concluded that during the late cretaceous early tertiary inversion the efs responded to regional compression with uplift and formation of an internal high the flechtingen high a stress sensitive crustal weak zone beneath the efs could be the reason for the repeated strain localization in the area

the elbe fault system in north central europe a basement controlled zone of crustal weakness abstract the elbe fault system efs is a wnw striking zone extending from the southeastern north sea to southwestern poland along the present southern margin of the north german basin and the northern margin of the sudetes mountains although details are still under debate geological and geophysical data reveal that upper crustal deformation along the elbe fault system has taken place repeatedly since late carboniferous times with changing kinematic activity in response to variation in the stress regime in late carboniferous to early permian times the elbe fault system was part of a post variscan wrench fault system and acted as the southern boundary fault during the formation of the permian basins along the trans european suture zone sensu geol mag 134 5 1997 585 the teisseyre tornquist zone ttz most probably provided the northern counterpart in a pull apart scenario at that time further strain localisation took place during late mesozoic transtension when local shear within the elbe fault system caused subsidence and basin formation along and parallel to the fault system the most intense deformation took place along the system during late cretaceous early cenozoic time when the elbe fault system responded to regional compression with up to 4 km of uplift and formation of internal flexural highs compressional deformation continued during early cenozoic time and actually may be ongoing the upper crust of the elbe fault system which itself reacted in a more or less ductile fashion is underlain by a lower crust characterised by low p wave velocities low densities and a weak rheology structural seismic and gravimetric data as well as rheology models support the assumption that a weak stress sensitive zone in the lower crust is the reason for the high mobility of the area and repeated strain localisation along the elbe fault system

liquefaction limit during earthquakes and underground explosions implications on ground motion attenuation liquefaction of saturated soils and sediments documented during earthquakes shows an empirical relation log r max 2 05 0 10 0 45 m where r max is the liquefaction limit in meters i e the maximum distance from liquefaction site to the hypocenter and m is the earthquake magnitude combining this with an empirical relation between m and the seismic energy of an earthquake we obtain a relation between the liquefaction limit and the seismic energy e a r max the prefactor corresponds to a threshold energy for liquefaction ranging from 0 004 to 0 1 j m3 the exponent ranging from 3 2 to 3 3 implies that the energy density of ground motion attenuates with distance according to 1 r 3 2 3 3 where r is the distance from the hypocenter the value of the threshold energy suggests a preliquefaction degradation of the shear modulus of soils by more than 3 orders of magnitude liquefaction documented during underground explosions is characterized by a threshold energy several orders of magnitude greater than that for liquefaction during earthquakes but shows a similar functional relation between e and r max as that for liquefaction during earthquakes and implies a similar attenuation relation between ground motion energy density and distance

soft sediment deformation structures in the late miocene şelmo formation around adiyaman area southeastern turkey abstract the elmo formation was deposited in the basins associated with the southeastern anatolian thrust belt and east anatolian fault zone in se turkey these structures developed as a result of compressional stresses created by the movement of the arabian plate to the north and the eurasian plate to the west from early miocene to late pliocene the outcrops of the elmo formation in the ad yaman area se turkey comprise braided river deposits lower alluvial unit at the base lacustrine and deltaic deposits in the middle lacustrine unit and low sinuousity river and alluvial deposits at the top upper alluvial unit soft sediment deformation structures were developed in sandstone siltstone and marl of the deltaic and lacustrine unit of the elmo formation these are slumps recumbent folds load casts ball and pillow structures flame structures neptunian dykes chaotically associated structures and synsedimentary faults the tectonic setting of the basin the lateral extent of the soft sediment deformation structures over tens of kilometers their similarities to deformation structures interpreted as being induced seismically in other regions worldwide or in a laboratory setting and being confined by undeformed layers suggest that the main trigger system was related to seismic activity in the area

soft sediment deformation of late pleistocene sediments along the southwestern coast of the baltic sea ne germany a 1 460 m long profile of a late glacial subglacial glacio fluvial glacio limnic and glacio deltaic sequence exposed at a cliff section on usedom island sw baltic sea coast is described the sequence is up to 31 m thick and shows sedimentary structures typical of a glacial setting soft sediment deformation is encountered and is associated with changes in lithology these deformations include liquefaction slumping and faulting as the most plausible cause earthquake induced shaking is discussed the associated neotectonic activity is seen as a consequence of the postglacial isostatic crustal rebound as the deglaciation earthquake ratio diminishes with time and as the rebound is phasing out no large earthquakes are anticipated for northern germany although in conclusion the lithosphere of the north german basin has to be regarded as weakened by repeated ice loading and deloading