liquefaction evidence for strong earthquakes of holocene and latest pleistocene ages in the states of indiana and illinois usa abstract sand and gravel filled clastic dikes of seismic liquefaction origin occur throughout much of southern indiana and illinois nearly all of these dikes originated from prehistoric earthquakes centered in the study area in this area at least seven and probably eight strong prehistoric earthquakes have been documented as occurring during the holocene and at least one during the latest pleistocene the recognition of different earthquakes has been based mainly on timing of liquefaction in combination with the regional pattern of liquefaction effects but some have been recognized only by geotechnical testing at sites of liquefaction most paleo earthquakes presently recognized lie in indiana but equally as many may have occurred in illinois studies in illinois have not yet narrowly bracketed the age of clastic dikes at many sites which sometimes causes uncertainty in defining the causative earthquake but even in illinois the largest paleo earthquakes probably have been identified prehistoric magnitudes were probably as high as about moment magnitude m 7 5 this greatly exceeds the largest historic earthquake of m 5 5 centered in indiana or illinois the strongest paleo earthquakes struck in the vicinity of the concentration of strongest historic seismicity elsewhere paleo earthquakes on the order of m 6 7 have occurred even where there has been little or no historic seismicity both geologic and geotechnical methods of analysis have been essential for verification of seismic origin for the dikes and for back calculating prehistoric magnitudes methods developed largely as part of this study should be of great value in unraveling the paleoseismic record elsewhere

palaeoseismology review of the state of the art abstract historical seismicity provides only a partial indication of the seismotectonic character i e earthquake potential of a given region even in italy where a relatively long historical record exists available catalogues are generally unsatisfactory for this purpose fortunately strong earthquakes often leave geological evidence herein referred to as seismites that are mainly related to surface faulting folding or other deformation and occasionally to secondary ground failures e g landslides liquefaction features etc these features may be preserved and therefore palaeoseismological studies may detect and date them thereby permitting extension of knowledge beyond the local historical threshold up to 2000 years in the most fortunate cases this paper provides a summary of criteria which may aid in the identification of areas suitable for palaeo earthquake investigation historical seismicity and the presence of well developed tectonic geomorphic features are recognized as the most reliable criteria for identifying active faulting however lack of these characteristics cannot be considered conclusive evidence for lack of activity palaeoseismological techniques aim at identifying not only the obvious effects of surface faulting such as offset of young geologic units but also the more subtle tectonic or non tectonic features including liquefaction structures gravity features and coseismic uplift and or subsidence finally we discuss some questions that pertain to palaeoseismicity evaluation techniques among these are the reliability of the quaternary dating techniques the evaluation of the seismic energy released minimum magnitude and principally the unequivocal identification of a seismic origin for the considered geological structures

seismically generated hydroplastic deformation structures in the late miocene lacustrine deposits of the malatya basin eastern turkey abstract the late miocene succession of continental deposits in the malatya basin eastern anatolia comprises alluvial fan lacustrine and fluvial facies associations this fault bounded basin formed in a tectonically active region notorious for strong earthquakes still today the lacustrine deposits in the northern part of the basin show several isolated horizons of soft sediment deformation including such structures as slump folds load and flame features sand dikes and small scale synsedimentary reverse faults with associated folds there is no direct evidence supporting instabilities due to unequal loading or overloading wave induced cyclical and or impulsive stresses sudden changes in groundwater level or bioturbation capable of producing these deformation structures the soft sediment deformation structures described in the lacustrine deposits are interpreted as having developed as a result of seismic activity taking place along the malatya fault zone based on the tectonic setting of the basin the lateral extent of the soft sediment deformation structures over hundreds of metres their confinement by undeformed layers the presence of complex structures and similarities with structures interpreted as being seismically induced in other areas and those obtained experimentally

neogene sedimentary deformation in the chilean forearc and implications for andean basin development seismicity and uplift neogene sediments in the northern chilean forearc display a wide range of near syndepositional structures analysis of the origin and distribution of these structures in space and time offers new insights into the development of the forearc basins the structures are described in detail and show many features associated with soft sediment deformation pseudo diapirism and slope failure synsedimentary deformation reached a peak in the late miocene to early pliocene while the sediments were saturated in a largely plastic state and many of the structures were probably triggered by seismic shock late stage tilting of the forearc generated shear stresses in the sediments leading to slumping and sliding base level revision and drainage incision led to sediment bypass and cessation of lacustrine sedimentation that was not necessarily linked to climate change compaction and dewatering of the basins caused transition of the sediments from a plastic to a brittle state the age and distribution of structures associated with seismicity appears to correlate with increasing subduction erosion and westward drift of south america but not with basin subsidence shortening rates or plate convergence this suggests that upper crustal deformation is at least partly decoupled from plate movement

modelling seismites with a digital shaking table abstract soft sediment deformation structures induced by seismically triggered liquefaction and or fluidization seismites have been reproduced with a digital shaking table we have used natural sediments with variable granulometric ranges clay silt and sand and an earthquake simulator that is able to reproduce real tridimensional seismograms acceleration and pore pressure recording allowed us to follow liquefaction and or fluidization processes in unconsolidated sediments during earthquakes different types of seismites were produced by variations in the tested sedimentary column

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

soft sediment deformation structures induced by cyclic stress of storm waves in tempestites miocene guadalquivir basin spain the identification of triggering agents for soft sedimentation structures is an enigmatic geological problem mainly seismic induced soft sediment structures have been recognized in ancient sediments rather than those resulting from storm waves we analyse soft sediment deformation structures in upper miocene calcarenitic tempestites of the guadalquivir basin southern spain the most common structures are load casts which vary in height and width from 10 centimetres to several metres the structures are always restricted to a small part of the stratigraphic sections in exclusive association with tempestites the analysed soft deformation structures are interpreted to be the result of liquidization processes chiefly from their inferred depositional environment and subordinately from the deformation style we have devised basic criteria to identify the trigger mechanism in these soft sediment deformation structures the liquefaction was triggered by pore pressure changes induced by cyclic and residual stress of storm waves

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

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

hummocky cross stratification tropical hurricanes and intense winter storms most previous workers have inferred a storm origin for hummocky cross stratification which typically occurs in shallow marine deposits on the modern earth the only storms capable of profoundly affecting shallow marine depositional environments are severe tropical cyclones hurricanes and mid latitude winter wave cyclones intense winter storms this paper examines the palaeogeographic distribution including palaeolatitude and palaeogeographic setting of 107 occurrences of hummocky cross stratification ranging in age from the proterozoic to recent in each of these stratigraphic units both palaeolatitude and palaeogeography are consistent with a direct storm influence associated with the passage of hurricanes or winter storms directly over the site of deposition this palaeogeographic evidence lends support to the inferred storm origin for hummocky cross stratification further the distribution of the structure suggests that most occurrences 73 were generated by tropical hurricanes the remaining 27 being generated by intense mid latitude winter storms the preferential generation of hummocky cross stratification by hurricanes is consistent with 1 the known differences in the nature of the bottom flows generated by the two major storm types and 2 the inferred nature of the flows which form hummocky cross stratification hurricanes couple less effectively with the water column than do intense winter storms due to this ineffective coupling hurricane generated bottom flows tend to be oscillatory or multidirectional dominant with only minor unidirectional components of motion in contrast intense winter storms generally do couple effectively with the water column generating bottom flows which possess a dominant or significant unidirectional component most previous workers have suggested that hummocky cross stratification forms under oscillatory or multidirectional dominant flow thus it is conceptually reasonable that the vast majority of ancient occurrences of hummocky cross stratification were probably hurricane generated as suggested by the aforementioned palaeogeographic distribution the proterozoic palaeozoic neogene and quaternary were times when global climate was similar to that of today the distribution of hummocky cross stratification deposited during these times suggests that both hurricanes and intense winter storms occupied latitudinal belts during these times which were essentially identical to those occupied by their modern counterparts the mesozoic and palaeogene were non glacial times when global climate was much warmer than that of today the distribution of hummocky cross stratification deposited during this interval suggests that hurricanes occurred more frequently at higher latitudes during non glacial times than they do at present the possibility of a broadened hurricane belt during the mesozoic and palaeogene is consistent with climatic considerations a limited number of mesozoic and palaeogene rock units containing hummocky cross stratification were deposited in palaeogeographic settings that preclude a direct hurricane influence these examples were deposited in the middle latitudes suggesting that intense winter storms continued to form hummocky cross stratification in the middle latitudes during these much warmer times some previous workers have suggested that tsunamis may be capable of generating hummocky cross stratification the palaeogeographic distribution of the structure does not support an origin due to tsunamis lacustrine examples of hummocky cross stratification reported herein are the first known non marine occurrences they suggest that storm effects strongly influence the sedimentary record of some lakes

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

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

extensive soft sediment deformation structures in the early darriwilian middle ordovician shallow marine siliciclastic sediments formed on the baltoscandian carbonate ramp northwestern estonia abstract the nearshore middle ordovician early darriwilian deposits of the baltoscandian basin formed on the flank of tectonically stable fennoscandian shield comprise numerous soft sediment deformation structures the areal extent of the deformed interval extends up to 9000 km 2 from nw estonia to se sweden the deformation structures occur within a meter scale sandstone horizon that includes load casts flame structures ball and pillow morphologies up to 2 m wide sedimentary dykes autoclastic breccias sand volcanoes and other related soft sediment deformation structures evidently these deformation structures formed during a single seismic event that caused liquefaction and fluidization of the water saturated unconsolidated shallow marine sediments within almost the entire sandstone unit pakri formation probably a unique catastrophic earthquake of magnitude 7 or higher occurred in this region penecontemporaneously with the deposition of these sediments the ultimate cause of seismic event of such magnitude in the tectonically stable baltoscandian basin is unclear however deposition and deformation of the pakri formation fall within the middle ordovician meteoritic bombardment period which resulted from the disruption of a large parent body in the asteroid belt approximately 470 ma ago this in turn suggests a potential impact origin for the single catastrophic earthquake in the tectonically stable study region although impact crater of suitable age is currently not known from the region then previous studies have documented some impact metamorphic shock lamellae i e pdfs and abundant extraterrestrial chromite grains from the deformed sediments

seismically induced deformation structures in oligocene shallow marine and aeolian coastal sands paris basin abstract soft sediment deformation structures have been identified in the oligocene coastal sand body in the southern part of the paris basin stampian sables de fontainebleau formation these coastal barrier sediments are characterized by pure fine grained sands the deformed beds are observed over some 60 110 km2 and are present either in foreshore sands or aeolian sand dunes convoluted laminations of an average amplitude around 0 70 m were identified in the foreshore or interdune sediments these are interpreted as the result of liquefaction conversely deformed sets of aeolian dune sand often involve large amounts of sediment these large scale contorted laminae several metres thick with minor internal faulting suggest deformation by slope failure under wet conditions such large scale soft sediment deformations may have been generated by storm surges and earthquakes which have similar liquefaction potentials we propose that the deformation structures were created by a single triggering event because of the absence of superposition of deformed layers over the study area the earthquake triggering hypothesis is supported by the large amount of sand involved in the slope failure features and the persistence of the contorted laminations over a wide area

evidence for late messinian seismites nijar basin south east spain the feos formation of the nijar basin comprises sediments deposited during the final stage of the messinian salinity crisis when the mediterranean was almost totally isolated levels of soft sediment deformation structures occur in both conglomeratic alluvial sediments deposited close to faults and the hyposaline lago mare facies a laminated and thin bedded succession of whitish chalky marls and intercalated sands alternating with non marine coastal plain deposits deformation structures in the coarse clastics include funnel shaped depressions filled with conglomerate liquefaction dykes terminating downwards in gravel pockets soft sediment mixing bodies chaotic intervals and flame structures evidence for soft sediment deformation in the fine grained lago mare facies comprises syndepositional faulting and fault grading sandstone dykes mixed layers slumping and sliding of sandstone beds convolute bedding and pillar and flame structures the soft sediment deformed intervals resemble those ascribed elsewhere to seismic shaking moreover the study area provides the appropriate conditions for the preservation of deformation structures induced by seismicity such as location in a tectonically active area variable sediment input to produce heterolithic deposits and an absence of bioturbation the vertical distribution of soft sediment deformation implies frequent seismic shocks underlining the importance of seismicity in the betic region during the late messinian when the nijar basin became separated from the sorbas basin to the north the presence of liquefied gravel injections in the marginal facies indicates strong earthquakes m 7 the identification of at least four separate fissured levels within a single lago mare interval suggests a recurrence interval for large magnitude earthquakes of the order of millennia assuming that the cyclicity of the alternating lago mare and continental intervals was precession controlled this suggestion is consistent with the present day seismic activity in se spain

earthquake induced structures in young sediments abstract soft sediment deformational structures have been identified in several plio quaternary horizons near burdur in southwest turkey these horizons satisfy criteria for correlating such structures with seismic events and it is proposed that the structures were formed by earthquake induced liquefaction the deformational structures are thus interpreted to represent seismic events which occurred up to 2 3 ma ago

late pleistocene seismites from lake issyk kul the tien shan range kyrghyzstan abstract the aim of the study is to record the occurrence of sediment deformation structures in one of the tectonically most active areas on the globe the tien shan range in central asia and to examine the significance of the deformations as indicators of palaeoseismicity soft sediment deformation structures in form of balls and pseudo nodules are exposed in the issyk kul basin within interfingering beds of shallow lacustrine beach and fluviatile origin additional deformation structures that were encountered are a complex and chaotic folded structure giant balls and a pillar structure which has not been previously reported where marl intrudes down into coarse pebbley sand and forms pillar morphology liquefaction features and bedforms related to storm and breaking waves were not encountered neither was there evidence of turbidites seven field criteria for relating soft sediment deformation to palaeoseismic triggering provide strong evidence for a seismic origin of the deformation structures empirical relationships between magnitude and the maximum distance from an epicenter to liquefaction sites make the active epicentral zone north of lake issyk kul with its frequent high magnitude events the most favorable source for the deformation structures luminescence dating of the sediments gives a time window of 26 2 1 to 10 5 0 7 ka bp indicating latest pleistocene seismic activity

a possible tsunami deposit around the jurassic cretaceous boundary in the boulonnais area northern france abstract an unusual succession of facies locally deposited around the jurassic cretaceous boundary in the boulonnais northern france is attributed to a tsunami event by comparison with recent tsunami deposits this sedimentary succession includes basal erosion with reworked lithified blocks soft sediment deformations an erosional conglomerate overlain by wood fragments and clays containing continental and marine fossils in one setting and conglomerate with mixed fauna in an other setting the tsunami probably affected the coast of the boulonnais area of the london brabant massif the origin of the event is unknown it was most probably triggered by an earthquake but other origins such as volcanic eruptions a giant landslide or even the impact of an extraterrestrial bolide into the ocean may also be considered

paleo earthquakes in passive margin settings an example from the paleocene of the golfo san jorge basin argentina abstract paleocene sedimentary rocks in the golfo san jorge basin include the marine salamanca formation and the continental rio chico formation both units contain soft sediment deformation features and evidence of contemporary tectonics which include 1 sediment filled fissures hosted in muddy marine sediments of the salamanca formation fragmentosa section where the sandy infill of the fissures took place from above 2 synsedimentary normal faults in the uppermost levels of the salamanca formation with vertical throws rarely exceeding 1 m 3 fault graded beds in the banco negro inferior marine continental transition which show a deformed sequence with small scale normal faults at the bottom and intraformational breccias on top and 4 liquefaction and or fluidization pillars v or funnel shaped with vertical extension of up to 5 m and preserved into fluvial channels of the rio chico formation deformed strata are bounded by undisturbed horizons and some of these features can be correlated along 60 km of exposures the suite of soft sediment deformation structures is considered a secondary evidence of synsedimentary paleo earthquakes seismites in this portion of the south american passive margin this work shows new evidence of syndepositional tectonic activity in the lowermost paleogene of the golfo san jorge basin

soft sediment deformation structures from an ice marginal storm tide interactive system permo carboniferous talchir formation talchir coalbasin india abstract permo carboniferous talchir formation talchir coalbasin india records sedimentation during a phase of climatic amelioration in an ice marginal storm affected shelf evidences of subtidal processes are preserved only under thick mud drapes deposited during waning storm phases various soft sediment deformation structures in some sandstone siltstone mudstone interbeds like syn sedimentary faults deformed laminations sand silt flows convolute laminations and various flame structures suggest liquefaction and fluidization of the beds due to passage of syn depositional seismic shocks in the late paleozoic ice marginal shelf such earthquake tremors could be generated by crustal movements in response to glacioisostatic adjustments of the basin floor

sedimentology of the neoproterozoic c 580 ma squantum tillite boston basin usa mass flow deposition in a deep water arc basin lacking direct glacial influence abstract the squantum tillite c 593 570 ma consists of thick up to 215 m massive and crudely stratified diamictites conformably interbedded with subaqueously deposited conglomerates and sandstones within a thick 7 km boston basin fill which is dominated by argillite turbidites the squantum tillite was first interpreted as being glacigenic in origin in 1914 because of the presence of diamictites argillites were interpreted as glaciolacustrine varves with rare ice rafted debris and conglomerates as glaciofluvial outwash more recently these have been shown to be the product of deep marine mass flow processes with no glacial influence yet because of its age equivalence with the deep marine glacially influenced gaskiers formation the squantum tillite is still seen by some as supporting evidence for a widespread snowball earth event at c 580 ma new sedimentological work confirms that conglomerate and sandstone facies are deep marine sediment gravity flows genetically related to massive homogeneous and crudely stratified heterogeneous diamictites produced subaqueously by downslope mixing of gravel and cobbles with muddy facies rare horizons of ice rafted debris in thin bedded and laminated turbidite facies interbedded with thick debrites show a weak but positive correlation of lamina thickness with grain size suggesting these facies are non glacial co genetic debrite turbidite couplets a significant volcanic influence on sedimentation is identified from reworked lapilli tuff beds and reworked ash in turbidites the depositional setting of the squantum tillite appears to be that of a submarine slope fan setting in an open marine volcanic arc basin receiving large volumes of poorly sorted sediment on the mid latitude active margin of gondwana no direct glacial influence is apparent

3 d geometry and luminescence chronology of quaternary soft sediment deformation structures in gravels northeastern brazil abstract this paper reports and describes soft sediment deformation in gravels and gravelly sediments in quaternary alluvial deposits of the potiguar basin northeastern brazil deformation structures were measured in terms of geometry size and relationship with sedimentary bedding using geological mapping and ground penetrating radar tl and osl irsl methods following mar and sar protocols were used to date sediments and soft sediment deformation events our results indicate that soft sediment deformation structures are widely distributed in several stratigraphic intervals of alluvial channel deposits in a low lying topographic valley depending on their geometry and composition two types of soft sediment deformation structures occur pockets and dome like load structures these structures resulted from the shaking of sediments with a reverse density gradient system which caused collapse and realignment of pebbles these features are similar in morphology and size to modern examples of seismically induced soft sediment deformation in coarse sediments tl and osl ages indicate that sediment deposition and associated soft sediment deformation occurred at least six times from 352 ka to 9 ka

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

soft sediment deformation structures in the lixian lacustrine sediments eastern tibetan plateau and implications for postglacial seismic activity abstract the eastern margin of the tibetan plateau is characterized by frequent earthquakes which are closely associated with tectonic activity to assess tectonic activity during the late pleistocene we studied a well exposed 23 m thick lacustrine sequence on the eastern margin of the plateau and found a variety of soft sediment deformation ssd structures distributed in 24 stratigraphic levels they comprise clastic dykes ball and pillow structures flame structures clastic gravels micro faults and slump folds most of the ssd structures indicate deformation mechanisms related to liquefaction and or fluidization processes most probably triggered by paleoseismic events given at least 4 historical earthquakes of m 7 in the study area most ssd structures in the lixian lacustrine sequence indicate seismic events with m 6 while simple flame structures point to some lower magnitude earthquakes osl dating indicates that the sequence accumulated between 15 8 and 6 0 ka giving a mean recurrence interval of 480 years for the 24 events and demonstrating that lacustrine sediments in eastern tibet have the potential to record a continuous seismic history on the centennial scale

soft sediment deformation structures from the diexi paleo dammed lakes in the upper reaches of the minjiang river east tibet abstract the north south trending upper reaches of the minjiang river run along the longmen shan min shan fault zone a zone of abrupt topographic change along the eastern margin of the tibetan plateau multiple levels of well preserved soft sediment deformation structures seismites occur in sediments deposited in paleo dammed lakes in the upper part of the minjiang river valley these deformation structures include liquefied convolute deformation water escape structures flame structures pseudonodules ball and pillow structures sedimentary dykes mud lenses and large scale folds several kilometers from the barrier bar of the diexi paleo dammed lakes seven deformed structural layers were identified at different heights in late quaternary stratigraphic sequences near shawan village maoxian county analyses of the deformation structures landforms and the structural environment indicate that these deformation structures were caused by earthquakes slumps and landslides osl optical stimulated luminescence and 14c dating of soft sediment layers from the shawan site indicate that intense earthquakes occurred during the period 25 20 ka b p therefore accurate geological dating of deformed features in dammed lake deposits in high mountains and canyons enables the record of moderate to large magnitude earthquakes to be extended to the late pleistocene holocene upon the eastern tibetan plateau

soft sediment deformation in a tectonically active area the plio pleistocene zarzal formation in the cauca valley western colombia abstract the plio pleistocene zarzal formation corresponds to fluvio lacustrine sediments deposited in an intramontane depression within the colombian andes associated with the cauca romeral fault system it crops out mainly in the cauca valley where numerous field sections have permitted the mapping of the vertical and lateral lithological variations lacustrine deposits of sands silts clays and diatomites are interbedded with fluvial sand and gravel beds and fluvio volcanic mass flows derived from the volcanic central cordillera numerous soft sediment deformation structures are encountered in this formation particularly in fine to medium grained sands silts and clays load structures load casts flame structures pseudonodules water escape structures water escape cusps dish and pillar and pocket and pillar structures soft sediment intrusions clastic sills and dykes disturbed laminites convolute laminations slumps and synsedimentary faulting deformation mechanisms and driving forces are related essentially to gravitational instabilities dewatering liquidization and brittle deformations field and regional geological data show that most of these deformations are related to seismicity and can be interpreted as seismites this area has a geological and recent seismic history and outcrops show both syn and post depositional faulting related to the transpressional regime of this part of the colombian andes which generates strike slip faults and associated local normal faults the drainage pattern within the zarzal formation shows the signature of neotectonics moreover the fine to coarse grained sands of the zarzal formation are lithologies prone to liquefaction when affected by seismic waves the intercalation of the deformed intervals within undisturbed strata confirms the catastrophic nature of the events finally the large areal extent of the deformations and the type of structures are compatible with seismites consequently the existence of seismites in the zarzal formation represents corroboration of tectonic activity in this area during the pleistocene earthquakes with a magnitude higher than 5 can be postulated based upon the proximity of active faults and the types of deformations

the holocene paleolimnology of lake issyk kul kyrgyzstan trace element and stable isotope composition of ostracodes the stable isotope and trace element geochemistry of ostracode shells from lake issyk kul kyrgyzstan provide an important new paleoclimate record for central asia the n 18 o n 13 c sr ca mg ca and u ca composition of shells from the species candona neglecta found in two piston cores constrains the paleohydrology of the lake from 8700 to 1000 calendar yr before present these data combined with robust chronologies based on 16 ams 14 c dates suggest that the region went from a relatively moist climate in the early holocene to a more arid climate in the late holocene intense freshwater input presumably glacial runoff flowed into the lake from 8700 to 8300 cal yr bp as evident from the n 18 o and n 13 c values from 8300 to 6900 cal yr bp n 18 o and sr ca values indicate that the lake was relatively fresh and an open basin and u ca values suggest that the lake was well mixed with well oxygenated bottom waters there is a transition zone between 6900 and 4900 cal yr bp when n 18 o and sr ca values rapidly increase and mg ca and u ca values rapidly decrease during this period the lake evolved from an open freshwater well mixed lake to a closed more saline less well mixed lake for the remainder of the record n 18 o sr ca mg ca and u ca are relatively constant implying conditions similar to modern conditions although the slight increasing trend in sr ca may suggest an increase in salinity over this period the n 13 c values were approximately in equilibrium with atmospheric co2 in the early part of the record but became relatively negative in the later part of the record this indicates that the dominant mechanism controlling the isotopic composition of dissolved inorganic carbon shifted from exchange with the atmosphere to variations in biological productivity fl 2001 elsevier science b v all rights reserved

synsedimentary deformation of pleistocene glaciolacustrine deposits in the albese con cassano area southern alps northern italy and possible implications for paleoseismicity abstract we describe and interpret the well exposed soft sediment deformations preserved in a mid pleistocene proglacial sequence outcropping at albese con cassano near como southern alps n italy the observed deformations affect six distinct stratigraphic intervals within the same depositional sequence the stratigraphy of this sequence the geomorphic setting and the careful geological mapping of the area clearly show that these deformations are not the result of glaciotectonics or cryoturbation but are due to six separate events of synsedimentary liquefaction in particular the 3 basal deformed units include sand and gravel volcanoes that formed at the bottom of a proglacial lake we examined several hypothesis of possible causative mechanism for the formation of these features taking into account all the information available on the local geology and sedimentary environment it is possible to assess that the liquefaction features at albese con cassano had a coseismic origin to our knowledge this would be the first report of similar evidence of paleoseismicity in the lombardia southern alps also there is no record of historical liquefaction triggered by seismic events in an area of ca 70 km of radius near albese con cassano including the town of como the large metropolitan area of milano and most of w lombardia that is one of the largest industrial districts in europe therefore the interpretation of the observed deformations can have critical impact for understanding the current seismicity level in the region and mitigating the associated risk in this paper we show that this interpretation is not a simple process liquefaction features must be treated with caution in order to derive suitable information for seismic hazard characterization even if their coseismic origin has been definitely proved it is necessary to understand the amount of seismic shaking for instance in terms of local macroseismic intensity that can have produced that specific feature at that specific site the location of the causative seismic event epicenter and focal depth and eventually its size in terms of epicentral intensity and or earthquake magnitude in the case of albese con cassano the implications in terms of seismic hazard of the observed possible earthquake paleoliquefactions can only be assessed through the definition of several scenarios taking into account a different thresholds of shaking for triggering the described synsedimentary structures and b different seismotectonic frameworks related to the mid pleistocene to holocene evolution of the s alps including seismicity induced by isostatic glacial rebound we conclude that it is worth checking these scenarios in the field with further paleoseismological research on other possible evidence of past earthquakes there are no unequivocal sedimentological indicators of paleoseismicity however when carefully interpreted within the proper local seismotectonic context and compared with other earthquake induced features soft sediment deformations can offer information of critical value for seismic hazard assessment

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

the genesis of solution pipes evidence from the middle late pleistocene bridgewater formation calcarenite southeastern australia abstract solution pipes are abundant in late pleistocene aeolian calcarenites at cape bridgewater in southwestern victoria and were studied using field work morphometric analysis thin sections mineralogical and chemical analyses and osl dating the solution pipes are vertical tubes formed in aeolian limestone with matrix porosity they are typically 0 1 1 m wide and 1 5 m deep with rounded terminations and cemented rims up to 10 cm thick they are overlain by palaeosols and filled mostly with palaeosol material rhizoliths are commonly present in the solution pipe fills and the surrounding calcarenite the solution pipes have formed by focused dissolution of aeolianite relatively quickly after the sand deposition and concurrently filled with soil as they developed they most likely formed beneath trees as a result of focused infiltration due to stemflow or due to fingered flow unstable wetting front that breaks into fingers as it moves downwards solution pipe formation was strongly dependent on climate periods of solution pipe formation followed the deposition of aeolianites at the end of interglacials mis 7 9 and 11 when the dunes were stabilised by vegetation and there was sufficient rainfall for substantial subsoil dissolution the cemented rims formed in the following drier glacial climates solution pipes are most abundant in the youngest aeolianite probably reflecting the wetter climate at the end of mis 7 that allowed a dense forest to cover the dunes from mis 5 to mis 2 no deposition of calcareous sand occurred on cape bridgewater and combined with a very wet interglacial period mis 5e resulted in additional karstification allowing the pipes in the mis 7 aeolianite to extend deeper and drill down into the underlying member a well developed calcrete layer drapes over these solution pipes and probably formed during the dry windy climate of the last glacial maximum

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

osl and pollen concentrate 14c dating of dammed lake sediments at maoxian east tibet and implications for two historical earthquakes in ad 638 and 952 abstract formation of dammed lakes provides exceptionally important information of continental geological processes responding to tectonic and climatic influences establishing accurate geochronological frameworks within lake strata is challenging because the stratigraphy is often bereft of biostratigraphy and directly dateable material optically stimulated luminescence osl and ams 14 c dating of pollen concentrates are well established tools for dating lake sediments whether they are suitable for lake sediments in high alpine settings remains uncertain in this study osl and ams 14 c dating of pollen concentrate were conducted on the diaolin section in a high alpine setting in the eastern tibetan plateau good match of both dating results suggests that they are fit for dating lake sediments in high alpine settings more than 300 g of sediment is required for preparation of pollen concentrates during the pretreatment 3 naoh solution should be added to the sample and then heated until just boiling 5 min because naoh treatment easily destroys pollen grains applying the heavy liquid flotation with specific gravity of 1 74 1 76 is useful to isolate relatively pure pollen grains sieving with a 20 m and 63 m mesh can concentrate pollen grains substantially the osl and ams 14 c dating yielded the basal age of the diaolin section 650 ad this indicates that the dammed lake formed around 650 ad probably caused by the earthquake occurring in the study area in 638 ad the seismites characterized by soft sediment deformation and phyllite layer happened at 780 980 ad probably corresponding to the earthquake occurring on november 20 952 ad in the study area

a tectonically triggered late holocene seismite in the southern amazonian lowlands brazil abstract definitive criteria for identifying the triggers of soft sediment deformation structures ssdss from sedimentary deposits are still under construction in this work we aimed to contribute to advancing this issue describing the sedimentological characteristics of an interval of ssdss formed in a region of the amazonian lowlands having numerous morphostructural evidences of neotectonic reactivation the deformed interval is 1 5 m thick and consists of load and flame structures interbedded with massive beds sandwiched between well stratified deposits of a fluvial sandy channel succession with a radiocarbon age of 1301 1382 cal yr bp the ssdss are intercepted by numerous small scale normal graded faults the most interesting is that these faults display segmented nw se trending planes that propagate upward after horizontal displacements of a few millimeters processes intrinsic to channel dynamics could not justify this fault morphology which is related to recurrent short lived seismic perturbations with intervening sedimentation following a main tremor a relation to fault reactivation is proposed with basis on the fault trend compatible with the regional structural pattern and the numerous morphostructural anomalies verified in the study area including trellis and sub trellis drainage rectangular and to a less extent annular channels anomalously enlarged channels orthogonal channels and valleys channel captures sudden changes in channel morphology moderate to high basin asymmetry factor af between 10 and 27 moderate to high transverse topography symmetry factor t 0 3 0 5 and anomalous longitudinal river profiles with concavity values 11 to 30 indicative of rivers in process of adjustments the morphology of the fault graded beds described herein might constitute a feature of relevance for identifying seismites in other fluvial deposits

eocene paleoseismic record of the green river formation fossil basin wyoming u s a implications of synsedimentary deformation structures in lacustrine carbonate mudstones abstract laterally extensive intervals containing sedimentary deformation features are identified in outcrops of lacustrine deposits of the eocene 52 51 ma green river formation in fossil basin southwestern wyoming fossil basin is the smallest of the paleo lakes in the green river system and is located in the sevier fold and thrust belt which was tectonically active during deposition deformation structures include convolute lamination load structures hybrid brittle ductile features sedimentary dikes microfaults fluid escape features such as cusps and pipes oil shale breccias and mass transport deposits in most cases these structures are hosted by finely laminated variably organic rich carbonate mudstones that accumulated in a low energy profundal lacustrine environment deformed intervals range from a few centimeters to 5 m in thickness and are bound above and below by undeformed strata of the same facies which demonstrates the early post depositional timing of deformation the distribution of these features indicates a primary control exerted by sediment rheology resulting from variation in grain size clay and organic content and degree of lithification which in turn were governed by the depositional environment and early diagenesis based on their morphological attributes lateral extent and recurrence at different stratigraphic levels along with their sedimentary environment and the tectonic setting of the basin the deformation structures are interpreted to be seismites i e the result of stresses induced by syndepositional earthquakes and other potential trigger agents are rejected moreover stratigraphic relationships indicate that these small scale deformation features as well as the mass transport deposits formed on a virtually flat lake floor ruling out instability caused by the gravitational regime syndepositional deformation in fossil basin points to tectonic activity along the nearby absaroka and or hogsback thrusts and related fault systems seismites point to possible tectonic forcing as a mechanism for changes in bathymetry and sedimentation in the green river formation and consequently demonstrate their potential for elucidating the tectonic history of other lacustrine and marine basins

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

incipient axial collapse of the main cordillera and strain partitioning gradient between the central and patagonian andes lago laja chile 1 lago laja is a late quaternary volcanic dammed lake located near the drainage divide of the south central andes field observations lake reflection seismic profiles bathymetry and remote sensing data reveal an active fault system that runs parallel to the volcanic arc along the axis of the main cordillera the lago laja fault system llfs normal faults of this extensional system cut late pleistocene volcanics 2 7 mm yr since 7 1 ka the llfs accounts for 0 7 of arc normal extension at an average minimum rate of 1 2 mm yr and strain rate of 10 14 s 1 seismites and surface ruptures evidence m 6 paleoearthquakes the main cordillera at 37 s is a large scale pop up structure uplifted by thrusting along its foothills in this light we interpret extension in the axial and highest part of the andes as incipient synorogenic gravitational collapse in response to uplift and crustal thickening thermal weakening due to elevated heat flow and postglacial lithospheric rebound and unbending have probably contributed to the arc limited collapse and holocene acceleration of deformation rates the lack of significant strike slip offsets along the llfs as well as along both foothills thrust systems at 37 s contrasts with the intra arc dextral fault zone south of 38 s regional structural data indicates that north of 38 s diffusely distributed strain reflects low partitioning of oblique subduction while to the south deformation is localized in a discrete strike slip fault zone along the volcanic arc reflecting a higher degree of partitioning we relate this strain partitioning gradient to favorable fault orientations in the fore arc north of the arauco peninsula a major seismotectonic boundary

pleistocene glaciolacustrine breccias of seismic origin in an active graben central poland varved layers in the partly consolidated glaciolacustrine early saalian deposits exposed in the belchatow mine central poland show specific types of deformations two types dominate half varve deformations constituting the uppermost clayey part of a single varve and multi varve deformations affecting a few varves the latter are found either as clast supported breccia beds with varve fragments in a quasi horizontal position within a clayey matrix or as deformed beds resulting from subsequent plastic deformation and folding the deformed beds are interpreted as seismites derived from earthquakes related to the deep graben structure the magnitudes of the earthquakes have determined the type of deformations the seismites are thought to have originated intraformationally

soft sediment deformation structures in late albian to cenomanian deposits sao luis basin northern brazil evidence for palaeoseismicity soft sediment deformation structures from the alc ntara formation late albian to cenomanian sao luis basin northern brazil consist of 1 contorted structures which include convolute folds ball and pillow structures concave up paths with consolidation lamination recumbently folded cross stratification and irregular convolute stratification that grades into massive beds 2 intruded structures which include pillars dykes cusps and subsidence lobes and 3 brittle structures represented by fractures and faults displaying planes with a delicate ragged morphology and sharp peaks these structures result from a complex combination of processes mostly including reverse density gradients fluidization and liquefaction reverse density gradients promoted by differential liquefaction associated with different degrees of sediment compaction led to the genesis of convolute folds more intense deformation promoted the development of ball and pillow structures subsidence lobes and sand rolls which are attributed to denser and thus more compacted less liquefied portions that sank down into less dense more liquefied sediments irregular convolute stratification that grades into massive beds would have formed at periods of maximum deformation the subsidence of beds was accompanied by lateral current drag and fluid escape from water saturated sands in addition the fractures and faults record brittle deformation penecontemporaneous with sediment deposition all these mechanisms were triggered by a seismic agent as suggested by a combination of criteria including 1 the position of the study area at the edge of a major strike slip fault zone that was reactivated several times from the albian to the holocene 2 a relative increase in the degree of deformation in sites located closer to the fault zone 3 continuity of the deformed beds over large distances several kilometres 4 restriction of soft sediment deformation structures to single stratigraphic intervals bounded by entirely undeformed strata 5 recurrence through time and 6 similarities to many other earthquake induced deformational structures

soft sediment deformation structures related to tectonomagmatic activity a case study from the borate bearing lacustrine deposits of early miocene bigadic basin nw turkey abstract this study documents soft sediment deformation structures in the lacustrine bigadic basin one of the early miocene terrestrial basins in the extensional tectonomagmatic province of northwestern anatolia the focus is on the upper borate unit of the basin fill succession which consists of sedimentary facies including massive conglomerates stratified sandstones siltstones organic rich claystones laminated limestones organic rich limestones marlstones borates and volcaniclastics their deposition including borates occurred in a deep lacustrine environment possible phases of lake shallowing are represented by stratified sandstones facies soft sediment deformation features include small scale folds formed by convolution with occasional basal decollement minor slumps load casts and related flame structures fragmented and mixed beds brecciated by pore water explusion shallow and deep rooted synsedimentary extensional faults with related neptunian dykes and large slump sheets of thick bed packages with recumbent folds these deformation features are interpreted to be of seismo tectonic and seismo volcanic origin related to syndepositional strike slip faulting and volcanic eruptions seismic tremors combined with the basin floor updoming by magma intrusions caused deep rooted normal faults and intra basinal slumps tens of metres thick the study may serve as a guide to similar deformation structures in the underlying part of the bigadic lake fill succession and in the other neogene basins of northwestern anatolia which shared the region s seismo tectonic magmatic palaeogeographic and sedimentation history

dating the lower paleolithic open air site of holon israel by luminescence and esr techniques abstract the open air acheulian site in holon israel was dated by the luminescence methods and by electron spin resonance esr situated in the coastal plain quaternary kurkar group the holon site was first excavated in the late 1960s when typical lower paleolithic lithics and middle pleistocene fauna were found in order to date the site new test pits were dug adjacent to the earlier excavations and the archaeological bed was exposed in a section comprising a series of paleosols and aeolianites alkali feldspars separated from the sediments were dated using the infrared stimulated luminescence and thermoluminescence signals and quartz was dated using the optically stimulated luminescence signal the age of the archaeological bed is constrained by two samples to 198 000 22 000 201 000 17 000 yr the age of the base of the section is 240 000 29 000 yr and the age of the top is 81 000 8000 yr two teeth from the archaeological bed recovered from the original excavation collection yielded an average esr age of 204 000 16 000 yr calculated using the linear uptake model which is in a very good agreement with the luminescence ages these dates place holon within the range of other late acheulian and acheulo yabrudian sites in this region such as tabun e younger chronology yabrud i archaeological level 18 and berekhat ram

estimation of the paleoepicentral area from the spatial gradient of deformation in lacustrine seismites tierras blancas basin mexico abstract a new methodology is introduced to estimate the most probable epicentral area for a paleoearthquake interpreted from seismites within a quaternary basin seismites were described from various detailed stratigraphic logs within the tierras blancas basin tbb a pleistocene lacustrine area located in the central part of the trans mexican volcanic belt tmvb the lacustrine landscape evolution of tbb has been determined by the recent fault activity of the morelia acambay fault system mafs the tbb is bounded by active normal faults striking e w this fault activity has generated soft sediment deformation structures sand silt and gravel dikes pillows diapirs and decametric slumps disturbing the sedimentary infilling from these seismites and their stratigraphic spatial correlation five strong moderate paleoearthquakes e1 e5 have been established in the basin the spatial distribution of these seismites exhibits a gradient of perturbation defined by the intensity of deformation three different degrees of intensity deformation ddi are associated with the liquefacted grain size sediments i silt liquefaction ii silt and sand liquefaction and iii silt sand and gravel liquefaction this spatial gradient indicates an increase of the energy involved from the seismic activity related with the proximity of the source mapping the boundaries among these zones of deformation and interpolation of each ddi limit for paleoearthquake e4 was used to construct paleoseismic isolines of deformation as a potential indicator of the most probable paleoepicentral zone a 1 5 km 2 elongate zone oriented nnw sse is the potential paleoepicentral area associated with paleoearthquake e4 within the tbb

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

soft sediment deformation structures interpreted as seismites in lacustrine sediments of the prebetic zone se spain and their potential use as indicators of earthquake magnitudes during the late miocene lacustrine formations of late miocene age in the prebetic area se spain show several types of deformational structures that are interpreted as seismites they are present in both marginal and deep lacustrine facies seismites formed in marginal lake environments comprise sand dikes pillows and intruded and fractured gravels in deep lacustrine facies the seismites are represented by pseudonodules mushroom like silts protruding into laminites mixed layers disturbed varved lamination and loop bedding the measured orientations of these structures are consistent with the orientations of the main faults limiting the basins showing that their origin is clearly related to the tectonic stress field that prevailed in the region during the late miocene the magnitudes of the earthquakes that deformed the sediments have been estimated after published data from both ancient and recent lake deposits accumulated in tectonic active regions elsewhere a rank of earthquake magnitudes with two end members i e the lowest magnitudes recorded by loop bedding in laminites and the highest magnitudes represented by intruded and fractured gravels is proposed

two twentieth century mlh 7 5 earthquakes recorded in annually laminated lake sediments from sary chelek western tian shan kyrgyzstan central asia is highly vulnerable to large earthquakes yet existing records of past seismic activity in this area are still insufficient to reliably assess regional earthquake hazard on longer timescales within this study the sediments of sary chelek a mountain lake in the western kyrgyz tian shan were investigated to explore its potential as a natural paleoseismic archive the lacustrine deposits are characterized by a succession of annually laminated varved sediments overlying event deposits that consist of large scale turbidites and distorted lake sediments similar to earthquake related deposits described from other lake sediment records microscopic sediment analysis furthermore revealed distorted varves in the laminated sequence that closely resemble earthquake related soft sediment deformation structures varve counting and radiometric dating determine the formation of the distorted varves and the emplacement of the large scale event deposits to the early 1990s and mid 1940s respectively this is in good temporal agreement with the occurrence of two large earthquakes that struck western kyrgyzstan in ad 1992 and ad 1946 these results and particularly the precise age control of the sary chelek sediment record highlight its potential for establishing a long and precisely dated record of regional earthquake activity

earthquake induced soft sediment deformation structures in late pleistocene lacustrine deposits of issyk kul lake kyrgyzstan abstract this paper discusses the composition and distribution of soft sediment deformation structures induced by liquefaction in late pleistocene lacustrine terrace deposits on the southern shore of issyk kul lake in the northern tien shan mountains of kyrgyzstan the section contains seven deformed beds grouped in two intervals five deformed beds in the upper interval contain load structures load casts and flame structures convolute lamination ball and pillow structures folds and slumps deformation patterns indicate that a seismic trigger generated a multiple slump on a gentle slope the dating of overlying subaerial deposits suggests correlation between the deformation features and strong earthquakes in the late pleistocene

luminescence dating using feldspars a test case from southern north island new zealand abstract luminescence dating using coarse grain potassium rich feldspars is applied to a suite of 12 dune sands collected from southern north island new zealand the expected ages of the samples range from modern to 350 ka luminescence ages were calculated using thermoluminescence and infra red stimulated luminescence measurements to determine total bleach and regeneration equivalent doses for each sample no systematic difference was observed between any of these different methods withstanding the uncertainties in the independent ages of some samples comparison of the luminescence ages with those suggested by the independent age control suggests that reliable luminescence ages can be obtained for samples younger than 130 ka luminescence ages for older samples appear to underestimate the true age and it is suggested that this may be due to long term fading of the luminescence signal as suggested by mejdahl 1989