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

age and significance of earthquake induced liquefaction near vancouver british columbia canada in late 1994 sand dykes large sand blows and deformed strata were exposed in the walls of an excavation at annacis island on the fraser river delta near vancouver british columbia the features record liquefaction during a large earthquake about 1700 years ago this was perhaps the largest earthquake to affect the vancouver area in the last 3500 years similar less well dated features have been reported from several other sites on the fraser delta and may be products of the same earthquake three radiocarbon ages that closely delimit the time of liquefaction on annacis island are similar to the most precise radiocarbon ages on coseismically subsided marsh soils at estuaries in southern washington and oregon both the liquefaction and the subsidence may have been produced by a single great plate boundary earthquake at the cascadia subduction zone alternatively liquefaction at annacis island may have been caused by a large crustal or subcrustal earthquake of about the same age as a plate boundary earthquake farther west the data from annacis island and other sites on the fraser delta suggest that earthquakes capable of producing extensive liquefaction in this area are rare events further liquefaction analysis using historical seismicity suggests that current assessment procedures may overestimate liquefaction risk

volcanology and petrology of volcanic products from the island of milos and neighbouring islets abstract new geochronological and volcanological data from volcanics of the island group of milos south aegean active volcanic arc allow four main cycles of volcanic activity to be distinguished ranging in age between 3 5 and 0 1 m y b p the oldest volcanic activity consists almost totally of pyroclastics and submarine products followed by subaerial ones the eruptive centers migrated in time and concentrated during the most recent volcanic phase in the central part of milos and on the island of antimilos the oldest products are dominated by andesites and dacites while the most recent ones mainly consist of rhyolites the volcanic evolution and the geochemical characters of the erupted products suggest that the feeding system of the oldest volcanism was located in the deep continental crust where contamination and fractional crystallization jointly occurred the younger cycle of volcanic activity was fed from small and relatively shallow magma chambers where contamination processes played a minor role these magma bodies are considered to responsible for the shallow thermal anomaly giving rise to the high enthalpy field on milos

late quaternary earthquake related soft sediment deformation along the belgian portion of the feldbiss fault lower rhine graben system abstract trench investigations along the bree fault scarp in belgium in the framework of a first paleoseismological experience in the area of the lower rhine graben system have not only demonstrated the existence of seismogenic faults almost extending to the present ground surface but also exposed several types of soft sediment deformation affecting sandy sediments and soils of inferred late weichselian to holocene age the observed features include asymmetric folding small scale normal faulting possible sand intrusions and small water escape or load structures establishing a seismic origin for the individual features is not always possible based on their sedimentary characteristics only particularly due to the potential confusion with periglacial phenomena but their abundance the close association of different deformational styles and their vicinity to a known active fault all seem to be compatible with an earthquake induced scenario the features are to some extent comparable to those generated during the recent ms 5 3 roermond earthquake at the opposite side of the roer valley graben stratigraphical and mutual geometrical relationships suggest the occurrence of at least three distinct deformational events since probably 30 000 years and one event before that time since nothing is yet known about their regional distribution however estimating the associated paleomagnitudes from these soft sediment deformations is premature

paleoliquefaction study of the clarendon linden fault system western new york state abstract the lack of earthquake induced liquefaction features in late wisconsin and holocene sediments in genesee wyoming and allegany counties suggests that the clarendon linden fault system clf did not generate large moment magnitude m 6 earthquakes during the past 12 000 years given that it was the likely source of the 1929 m 4 9 attica earthquake however the clarenden linden fault system probably is capable of producing future m 5 events during this study we reviewed newspaper accounts of the 1929 attica earthquake searched for earthquake induced liquefaction features in sand and gravel pits and along tens of kilometers of river cutbanks evaluated numerous soft sediment deformation structures compiled geotechnical data and performed liquefaction potential analysis of saturated sandy sediments we found that the 1929 m 4 9 attica earthquake probably did not induce liquefaction in its epicentral area and may have been generated by the western branch of the clarendon linden fault system most soft sediment deformation structures found during reconnaissance did not resemble earthquake induced liquefaction features and even the few that did could be attributed to non seismic processes our analysis suggests that the magnitude threshold for liquefaction is between m 5 2 and 6 that a large m 6 earthquake would liquefy sediments at many sites in the area and that a moderate earthquake m 5 5 9 would liquefy sediments at some sites but perhaps not at enough sites to have been found during reconnaissance we conclude that the clarendon linden fault system could have produced small and moderate earthquakes but probably not large events during the late wisconsin and holocene

liquefaction and ground failure induced by the 1988 saguenay quebec earthquake ongoing geological and geotechnical investigations are under way for two sites in ferland quebec where sand boil deposits ground fissures and liquefaction related damage to homes were documented immediately following the m 5 9 saguenay earthquake of november 25 1988 both sites are about 26 km from the epicentre to date the geological investigation of the sites suggests that i liquefaction and ground failure have occurred in this area in the past ii lateral spreading was the principal mode of ground failure in 1988 and in the past iii 1988 and earlier displacements due to lateral spreading were on the order of centimetres and iv topography played an important role in the localization and characterization of ground failure the geotechnical investigation suggests that i liquefaction at these sites is predictable using seed s method and ii the material that liquefied during the saguenay earthquake is a gray siltysand or sandy silt that is about 0 3 m thick and occurs at a depth ran

linear zones seismicity and the possibility of a major earthquake in the intraplate western lake ontario area of eastern north america seismic hazard assessments conducted in eastern canada rely on seismological data which are essential but alone inadequate that is because the earthquake record is too short to provide a representative picture of where large earthquakes have occurred in the past consequently seismic hazard may be underestimated in areas such as that encompassing western lake ontario that are devoid of documented large earthquakes to attempt to ascertain the likelihood of a major earthquake occurring in that highly populated and industrialized area three regionally extensive geophysically expressed lineaments were investigated and the results were combined with available seismological information the most conspicuous is the niagara pickering linear zone within which there have been at least two if not three periods of brittle faulting including displacements compatible with the current stress field it also appears to represent the same major structure as the akron magnetic boundary in eastern ohio the site of the mb 4 9 leroy earthquake the second is the georgian bay linear zone which extends from georgian bay to new york state it displays evidence of recent outcrop scale faulting an alignment of earthquakes along its southwestern boundary and a possible spatial relationship to other earthquakes including two of m 5 lastly there is the hamilton lake erie lineament which is parallel and proximal to a possible fault and coincides with a linear array of small to moderate earthquakes all three converge on the western lake ontario area which has a higher frequency of seismicity than the adjacent areas thus the western lake ontario area might have a greater potential to experience a major earthquake than heretofore believed resume les evaluations des risques sismiques dans l est du canada sont fondees sur les donnees sismologiques dont

liquefaction and foundation failure of chevron oil and gasoline tanks at moss landing california liquefaction of gray coarse to medium grained esturine sand during the october 17 1989 loma prieta ms 7 1 earthquake led to foundation failures of oil and gasoline tanks at the chevron marine station at moss landing located about 25 km south southeast of the epicenter differential settlement of the foundations resulted in 1 degree to 6 degree tilting of the tanks towards one another and an associated 2 degree to 7 degree inclination of tank piping in addition sand was vented around the bases of the tanks that contained the most oil and from adjacent cracks liquefaction and related ground failure was not restricted to the vicinity of the chevron tanks but was a widespread phenomenon at moss landing analysis of geological and geotechnical data at sites such as the chevron marine station will serve to check and to advance current methods of assessing liquefaction potential at a site and of mapping liquefaction hazard on a regional scale

a mid european decadal isotope climate record from 15 500 to 5000 years b p oxygen isotope ratios of precipitation delta18op inferred from deep lake ostracods from the ammersee southern germany provide a climate record with decadal resolution the record in detail shows many of the rapid climate shifts seen in central greenland ice cores between 15 000 and 5000 years before the present b p negative excursions in the estimated delta18op from both of these records likely reflect short weakenings of the thermohaline circulation caused by episodic discharges of continental freshwater into the north atlantic deviating millennial scale trends however indicate that climate gradients between europe and greenland changed systematically reflecting a gradual rearrangement of north atlantic circulation during deglaciation

evidence for late glacial and holocene environmental changes from subfossil assemblages in sediments of lake neuchâtel switzerland abstract ostracod and diatom assemblages mollusc remains plus pollen and sediment stratigraphy from three cores taken at sites 40 80 and 135 m deep in lake neuch tel switzerland show distinct changes since deglaciation shifts are interpreted in terms both of climatic change and major changes in the catchment input caused by the aar river entering or bypassing lake neuch tel three palaeoenvironmental phases are recognized 1 the late glacial with the inflow of the river before 10 000 yr b p 2 the early to mid holocene with temporary bypassing of the river between 10 000 and 4850 yr b p and 3 the mid to late holocene without river input after approx 4850 yr b p during periods with river input rhythmites were deposited ostracods indicate a well oxygenated hypolimnion suggesting deep ventilation enhanced by the river inflow the diatom assemblage indicates eutrophic to mesotrophic conditions and is dominated by generally well preserved periphytic species the high number of unidentifiable pollen suggests oxidation during transport in the river during periods without river input a massive calcareous silt with abundant authigenic calcite was deposited diatoms indicate a change to mesotrophic and oligotrophic conditions and decreased sedimentation rates and higher alkalinity enhanced the dissolution of diatoms terrestrial and littoral molluscs as well as periphytic diatoms indicate erosion of the shore when the lake level rose or fell with onset or offset of the river inflow before 12 600 yr b p the patchy vegetation cover led to intensive soil erosion and high sedimentation rates the lake was still frozen during the winter months after approx 12 600 yr b p the sediment changed from clastic rhythmites to thinly bedded non glacial rhythmites the vegetation cover became denser the abundance of ostracods increased and molluscs started to colonize the profundal zone of the lake the younger dryas approx 10 700 10 000 yr b p displays maximum abundance of ostracods indicating deep ventilation the transition to the holocene is characterized by a change in the ostracod assemblage and the river bypassed the lake between approximately 10 000 and 8900 yr b p when the river reentered the lake after approximately 8900 yr b p a new ostracod species appeared after two short periods of river bypassing between approximately 7200 and 6950 yr b p diatoms indicate a higher trophic level about 6000 5000 yr b p associated with higher erosion rates and increased nutrient input due to neolithic agricultural activities after approximately 4850 yr b p the river bypassed the lake again and the trophic level decreased in contrast to the early to mid holocene periods of decreased oxygen supply the mid to late holocene is characterized by deep ventilation this is attributed to the northward retreat of the polarfront and enhanced westerlies consequent to decreased insolation after 6000 yr b p the change of the river flow pattern correlates with glacier oscillations and may suggest a climatic control the final cessation of the inflow is attributed to diversion of the river consequent to isostatic uplift and late neolithic clearance activity

3000 year paleoseismological record from the region of the 1988 saguenay quebec earthquake abstract the 1988 magnitude m b 5 9 m blg 6 5 saguenay quebec earthquake occurred in a region considered to be aseismic but the epicenter was less than 100 km northwest of the seismically active region of charlevoix lake sediment cores representing some 3000 yr of sediment accumulation contain abnormal silt layers attributed to seismic shaking events prior to the 1988 earthquake the layers are formed by the relatively rapid settling of the silt portion of the seismically resuspended organic rich sediment cores were obtained over a distance of 120 km perpendicular to the saguenay graben structure several silt layers are much thicker and more widely distributed than the effect of the 1988 earthquake and are comparable to those observed at charlevoix that were produced by magnitude 6 to 7 events the silting events do not correlate between the sampled lakes nor does the pattern match that at charlevoix so that the shaking events are interpreted to be of local origin the recurrence interval for magnitude 6 earthquakes ranges from 350 to 1000 yr in contrast to the roughly 75 yr historical recurrence of earthquakes of magnitude greater than 6 at charlevoix

mid to late holocene flood frequency changes in the northeastern alps as recorded in varved sediments of lake mondsee upper austria abstract annually laminated varved lake sediments with intercalated detrital layers resulting from sedimentary input by runoff events are ideal archives to establish precisely dated records of past extreme runoff events in this study the mid to late holocene varved sediments of lake mondsee upper austria were analysed by combining sedimentological geophysical and geochemical methods this approach allows to distinguish two types of detrital layers related to different types of extreme runoff events floods and debris flows and to detect changes in flood activity during the last 7100 years in total 271 flood and 47 debris flow layers deposited during spring and summer were identified which cluster in 18 main flood episodes fe 1 18 with durations of 30 50 years each these main flood periods occurred during the neolithic 7100 7050 vyr bp and 6470 4450 vyr bp the late bronze age and the early iron age 3300 3250 and 2800 2750 vyr bp the late iron age 2050 2000 vyr bp throughout the dark ages cold period 1500 1200 vyr bp and at the end of the medieval warm period and the little ice age 810 430 vyr bp summer flood episodes in lake mondsee are generally more abundant during the last 1500 years often coinciding with major advances of alpine glaciers prior to 1500 vyr bp spring summer floods and debris flows are generally less frequent indicating a lower number of intense rainfall events that triggered erosion in comparison with the increase of late holocene flood activity in western and northwestern nw europe commencing already as early as 2800 yr bp the hydro meteorological shift in the lake mondsee region occurred much later these time lags in the onset of increased hydrological activity might be either due to regional differences in atmospheric circulation pattern or to the sensitivity of the individual flood archives the lake mondsee sediments represent the first precisely dated and several millennia long summer flood record for the northeastern ne alps a key region at the climatic boundary of atlantic mediterranean and east european air masses aiding a better understanding of regional and seasonal peculiarities of flood occurrence under changing climate conditions

a review of evidence of glacially induced faulting and seismic shaking in eastern canada abstract evidence of early postglacial glacially induced seismic activity should be abundant in eastern canada which was formerly covered by the laurentide ice sheet during the late wisconsinan glaciation this review identified only two probable and at most nine possible examples of glacially induced faulting over an area of 4 million km2 a far lower number than that expected from a long term rate of background seismicity the probable sites are the holy grail scarp manitoba and the series of faults buried in the sub bottom of round lake ontario the possible nine glacially induced faults include the aspy fault nova scotia and timiskaming east shore fault ontario but there is little published information on the other seven features despite this low number the common occurrence of subaqueous mass transport deposits interbedded within or immediately overlying glaciolacustrine glaciomarine deposits in many modern lake basins strongly hints at an elevated period of glacially induced seismicity over widespread areas of eastern canada in southern quebec the age of these mass transport deposits suggests that glacially induced earthquake activity began as early as about 13 5 ka cal bp which corresponds to the time of local ice melt back this indicates that glacially induced seismicity began at the time of local deglaciation in southern quebec rather then being delayed as existing fault instability models imply it is anticipated that new candidate glacially induced or younger faults will be identified in eastern canada over the next decade or so because of the increasing availability of new high resolution data imagery sources

did two massive earthquakes in the holocene induce widespread landsliding and near surface deformation in part of the ottawa valley canada recent evidence based on ages of large landslides and the existence of severely disturbed terrain in champlain sea sediments to the east of ottawa suggests that this area may have been the site of two of the most geologically destructive earthquakes in eastern canada the walls of several paleochannels downcut into sensitive marine clayey silts are scarred by numerous large earthflows of sizes unequaled in historical time while radiocarbon ages of 15 landslides as much as 35 km apart range from ca 1870 to 5130 yr b p the majority of events cluster at ca 4550 yr b p the coincidence of numerous large failures in different paleovalleys occurring concurrently long after channel abandonment and at a time of drier climate suggests that the widespread landsliding was triggered by a strong earthquake close to the landslide area areas of very disturbed terrain in a flat erosional plain show severely deformed bedding and irregular ground subsidence and are attributed to a large earthquake ca 7060 yr b p that strongly shook a thick sequence of sensitive material filling deep steep sided bedrock basins

paleoseismology in venezuela objectives methods applications limitations and perspectives abstract the privileged location of venezuela along an active interplate deformation belt despite of being a so called developing country has led to a long paleoseismic tradition as attested by 45 trench assessments since 1968 since then a first 2 trench study was carried out by the american woodward clyde company across the oca fault at sinamaica since 1980 all further paleoseismic studies have been performed by funvisis and the uribante caparo hydroelectric project southern merida andes became their first assessment where 22 huge trenches were bulldozer dug except for these compania anonima de administracion y fomento electrico cadafe financed trenches and two others all other assessments were for petroleos de venezuela s a pdvsa in this paper geographic and geologic factors as well as logistic limitations conditioning success in paleoseismic studies by trenching shall be discussed based on the venezuelan experience developed over the years the scientific contribution of this approach refer to confirmation of holocene fault activity slip per event and average slip rate of a given fault or segment seismic potential repeat of maximum credible earthquakes of known faults fault segmentation fault interaction as consequence of stress loading by stick slip on contiguous faults time space distribution of seismic activity along a given tectonic feature seismotectonic association of historical earthquakes and landscape evolution on the short term and its implications on the long term evolution poorly discussed since this is really part of the field of neotectonics in recent years since 1999 a new approach has been introduced in venezuela consisting in complementing the seismic history derived from trenching studies with the evaluation of seismically induced perturbations in the continuous quaternary sedimentary record of either active or fossil lakes the future of this discipline in venezuela heads to more trenching and lake coring in order to gather more data on the previously mentioned aspects other paleoseismic approaches have been developed very little in venezuela since either climate or the geodynamic setting do not favor their application

an aem tem study of weathering and diagenesis abert lake oregon i weathering reactions in the volcanics abstract abert lake in south central oregon provides a site suitable for the study of sequential weathering and diagenetic events in this first of two papers transmission electron microscopy was used to characterize the igneous mineralogy subsolidus alteration assemblage and the structural and chemical aspects of silicate weathering reactions that occur in the volcanic rocks basalts basaltic andesites and dacitic rhyolitic extrusive and pyroclastics that outcrop around the lake olivine and pyroxene replacement occurred topotactically whereas feldspar and glass alteration produced randomly oriented smectite in channels and cavities the tetrahedral octahedral and interlayer compositions of the weathering products largely dioctahedral smectites varied with primary mineral composition rock type and as the result of addition of elements released from adjacent reaction sites weathering of the highly evolved fe rich jug mountain complex at the north end of the lake produced a homogeneous smectite assemblage that contrasts with the heterogeneous smectite assemblage replacing the volcanics along the eastern margin of the lake the variability within and between the smectite assemblages highlights the microenvironmental diversity fluctuating redox conditions and variable solution chemistry associated with mineral weathering reactions in the surficial environment late stage exhalative and aqueous alteration of the volcanics redistributed many components and formed a variety of alkali and alkali earth carbonate chloride sulfate and fluoride minerals in vugs and cracks overall substantial mg si na ca and k are released by weathering reactions that include the almost complete destruction of the mg smectite that initially replaced olivine the leaching of these elements from the volcanics provides an important source of these constituents in the lake water the nature of subsequent diagenetic reactions resulting from the interaction between the materials transported to the lake and the solution will be described in part ii banfield et al 1991

liquefaction at moss landing during loma prieta earthquake a study of liquefaction at five sites in the moss landing area during the 1989 loma prieta earthquake is presented results of this case history study include 1 a large set of cone penetration test cpt data for sites where evidence of liquefaction was and was not observed 2 information regarding the influence of thin soil strata on overall site behavior 3 inclinometer data on deformations at depth due to lateral spreading of a shoreline 4 a description of the apparent liquefaction of a marshland clayey silt deposit 5 seismic shear wave velocity data at sites where evidence of liquefaction was and was not observed and 6 an evaluation of how interpretation methods affect the development and use of cpt based liquefaction correlations

evidence for an earthquake triggered basin collapse in saguenay fjord canada abstract on february 5 1663 perhaps the largest earthquake ever witnessed in eastern north america struck the saguenay fjord basin with such force that landslides and submarine slides were triggered over a wide region over 3 km 3 of clayey holocene sediments collapsed from the margins of the fjord resulting in amalgamated debris flow and slide deposits that covered much of the basin floor these deposits reached thicknesses of up to 100 m and extended over an area of 100 km 2 the ambient seafloor was compressed under the impact and load of these debris masses and or liquefied under the cyclic stress of the seismic wave a 0 2 km 3 landslide also occurred at this time blocking the saguenay river and possibly facilitating an extra large spring freshet discharge biotracers planktonic and benthic foraminifera arcellaceans pollen and wood in conjuction with mass physical properties of sediment cores and high resolution seismic and sidescan profiler data have been used to identify local and distal sediment sources including their original water depth of deposition and their subsequent mode of mass gravitational transport the landslide material was eroded by the river and super elevated sediment concentrations are considered responsible for a long lasting 28 days turbidity current that entered the saguenay fjord depositing a single 0 3 km 3 turbidite the 2 to 10 m thick turbidite is considered to have been self igniting having eroded into the surface of the collapsed basin debris paleo hydraulic calculations suggest that this turbid flow averaged 0 45 m s and reached a flow thickness of 30 m

the july 1996 flood deposit in the saguenay fjord quebec canada implications for sources of spatial and temporal backscatter variations in july 1996 a major rainstorm and flood took place in the saguenay fjord backscatter strength measurements made with a simrad em1000 multibeam echosounder in 1993 1997 and 1999 have shown spatial and temporal variations which are interpreted in relation to the occurrence of the flood after empirical calibration of the different maps the data show an overall diminution of 5 db in backscatter strength in 1997 1 yr after the flood took place while the data sets obtained in 1993 and 1999 show comparable levels of backscatter strength the different data sets show a similar pattern of low and high backscatter patches which represent variations of the backscatter strength of a few decibels several grain size and water content measurements were also carried out on sediment box core and grab samples from the fjord bottom in 1997 and 1999 these have shown that the areas with higher acoustic backscatter correspond to the finer sediments while the low backscatter patches correspond to the coarser material the data show little relation between water content and backscatter strength thus indicating a poor dependence between the impedance terms bulk density and sound speed and the backscatter having taken this into account the major contribution to backscatter strength is assumed to result from differences in surface and volume roughness of the sediment since finer grain sizes offer higher backscatter the grain size of the sediment is not considered as being a major contributor to roughness and hence backscatter strength the major factor that seems to control roughness generation in the saguenay fjord is considered to be bioturbation the areas where geological processes most physically disturb the bottom which coincide with the areas where also most accumulation takes place and the coarser grain sizes are deposited are more sparsely colonized by organisms this results in a lower degree of bioturbation lower roughness and thus backscatter strength this hypothesis helps explain the variation in backscatter strength observed between the different measurement years the several million tons of sediment deposited in the fjord bottom after the 1996 flood buried the benthic fauna which was still recovering 1 yr later the less bioturbated sediment at this time would present lower roughness with respect to the 1993 and 1999 data resulting in a lower backscatter strength

glacio seismotectonics ice sheets crustal deformation and seismicity abstract the last decade has witnessed a significant growth in our understanding of the past and continuing effects of ice sheets and glaciers on contemporary crustal deformation and seismicity this growth has been driven largely by the emergence of postglacial rebound models pgm constrained by new field observations that incorporate increasingly realistic rheological mechanical and glacial parameters in this paper we highlight some of these recent field based investigations and new pgms and examine their implications for understanding crustal deformation and seismicity during glaciation and following deglaciation the emerging glacial rebound models outlined in the paper support the view that both tectonic stresses and glacial rebound stresses are needed to explain the distribution and style of contemporary earthquake activity in former glaciated shields of eastern canada and fennoscandia however many of these models neglect important parameters such as topography lateral variations in lithospheric strength and tectonic strain built up during glaciation in glaciated mountainous terrains glacial erosion may directly modulate tectonic deformation by resetting the orogenic topography and thereby providing an additional compensatory uplift mechanism such effects are likely to be important both in tectonically active orogens and in the mountainous regions of glaciated shields in general the short term response to ice fluctuations is similar to the earth s response to fluctuations in water reservoirs with the subsequent increase or decrease in seismicity which depends on the pre existing stress state when the ice fluctuations occur on the spatial scale and magnitude of the late pleistocene glaciation and deglaciation however the viscoelastic response of the earth especially the mantle causes significant changes in crustal deformation and earthquake activity that is spatially extensive and temporally complex the regions of greatest ice thickness and the regions marginal to the late pleistocene ice sheets indicate the most dramatic evidence of earthquake faulting the mantle response to these large ice mass fluctuations and the change in mass between the oceans and land caused and continues to cause measureable crustal deformation at hundreds of kilometres from the ice margins for both tectonically active and cratonic regions palaeoseismic investigations of late pleistocene and holocene faults are an important tool in evaluating earthquake hazard the predicted response of the earth over this time however is very dependent on the model assumed for most regions far more carefully designed field observations are needed to constrain the existing rheological and ice models

vented sediments and tsunami deposits in the puget lowland washington differentiating sedimentary processes the sandy deposits produced by tsunamis and liquefaction share many sedimentary features and distinctions between the two are important in seismically active coastal zones both types of deposits are present in the wetlands bordering puget sound where one or more earthquakes about 1100 years ago caused both tsunami flooding and sediment venting this co occurrence allows an examination of the resulting deposits and a comparison with tsunami and liquefaction features of modern events vented sediments occur at four of five wetland field localities and tsunami deposits at two in comparison with tsunami deposits vented sediments in this study and from other studies tend to be thicker although they can be thin vented sediments also have more variable thickness at both outcrop and map scale are associated with injected dykes and contain clasts derived from underlying deposits further vented sediments tend to contain a greater variety of sedimentary structures and these structures vary laterally over metres tsunami deposits compared with vented sediments are commonly thinner fine and thin landward more consistently have more uniform thickness on outcrop and map scales and have the potential of containing coarser clasts up to boulders for both tsunami deposits and vented sediments the availability and grain size of source material condition the characteristics of the deposit in the cases presented in this paper both foraminifera and diatom assemblages within tsunami deposits and vented sediments consisted of brackish and marine species and no distinction between processes could be made based on microfossils in summary this study indicates a need for more careful analysis and mapping of coastal sediments associated with earthquakes to avoid misidentification of processes and misevaluation of hazards

palaeoecology of late glacial and holocene profundal ostracoda of pre alpine lake mondsee austria a base for further palaeo biological research succession of profundal ostracod palaeoassemblages in response to environmental changes during the late glacial and holocene was studied in a similar to 15 m long sediment sequence from pre alpine lake mondsee austria first local ostracod assemblage zone loaz 1 prior to 15 700 a bp with low abundances of leucocythere mirabilis and limnocytherina sanctipatricii followed by cytherissa lacustris corresponds to the pleniglacial phase of clastic detrital sedimentation at relatively high rates most of the key species of loaz 2 15 590 to 13 940 a bp including the pleniglacial late glacial transition i e limnocytherids fabaeformiscandona cf harmsworthi f tricicatricosa c lacustris and candona candida reveal the significant association with high al contents and low sedimentation rates and are classified as preferring low productivity conditions in contrast candona neglecta dominant in loaz 3 13 820 to 9960 a bp palynologically defined as balling early holocene and in the last loaz 4 9780 a bp to present as well as cypria ophtalmica second key species in loaz 4 show relationship with higher productivity elevated sedimentation rates and decreasing al contents furthermore valve biodegradation and shape disparity at different time periods and in relation to sedimentation rate changes were investigated in a 3 juveniles of candona neglecta the highest percentage of valves biodegraded by actinobacteria was recorded during the allerod younger dryas and early holocene when the lowest sedimentation rates occurred whereas significantly lower frequencies of biodegraded valves were recorded during the mid holocene and late holocene when sediment accumulation was much higher it is also hypothesised that the degree of the valve shape variation was related to the lake productivity during the allerod younger dryas and early holocene a valve shape variation significantly lower than that recorded during late holocene intervals characterised by intensified lake productivity was observed additionally an agenda of potential questions and approaches that should be considered and form the core of further palaeo biological research projects is offered c 2014 elsevier b v all rights reserved

a multidisciplinary assessment of postglacial seismic disturbance miramichi area new brunswick canada abstract examination of deformed alluvial sediments archaeological projectile points and historical seismicity formed the basis for an assessment of paleoseismicity at the oxbow site in the miramichi region of new brunswick canada deformed masses of layered sediment containing discontinuous and folded layering were interpreted to have been caused by seismically induced liquefaction of unfrozen sediment artifacts and radiocarbon dating provided a chronological record extending over 2500 years and enabled relative dating of deformation of the sediments to between the 1700s and early 1900s results supported the inference that the region is subject to repeated ground disturbance from periodic earthquakes of magnitude 5 or greater

postglacial tectonics of the scottish glacio isostatic uplift centre new evidence combined with a detailed re evaluation of postglacial fault movements seismic activity and shoreline sequences suggests that the period of deglaciation and the early holocene was more seismically active than the mid to late holocene it is proposed that the large scale lateral displacements formerly proposed can not be justified rather all postglacial fault movements appear to be limited to metre scale vertical movements along pre existing fault lines in addition it is argued that the younger dryas ice advance may have produced localised crustal redepression but not the more widespread impact formerly proposed both tectonic and postglacial rebound stresses however may be needed to explain the contemporary seismotectonics of the scottish highlands

probabilistic neural network for evaluating seismic liquefaction potential simplified techniques based on in situ testing methods are commonly used to assess seismic liquefaction potential many of these simplified methods are based on finding the liquefaction boundary separating two categories the occurrence or non occurrence of liquefaction through the analysis of liquefaction case histories as the liquefaction classification problem is highly nonlinear in nature it is difficult to develop a comprehensive model taking into account all the independent variables such as the seismic and soil properties using conventional modeling techniques hence in many of the conventional methods that have been proposed simplified assumptions have been made in this study a probabilistic neural network pnn approach based on the bayesian classifier method is used to evaluate seismic liquefaction potential based on actual field records two separate analyses are performed one based on cone penetration test data and one based on shear wave velocity data the pnn model effectively expl

centrifuge modeling and the influence of fabric anisotropy on seismic response of foundations abstractfailure of foundations induced by earthquakes occurred many times in the past there is a general lack of data recorded during earthquakes in the field about seismic response of such foundations according to the results of some previous laboratory tests and numerical analyses anisotropy of fabric of soil grains has significant influence on dynamic soil response however there is hardly any realistic physical data available to analyze the influence of fabric anisotropy on the response of foundations during earthquakes centrifuge tests are small scaled model tests which have been widely used to study the mechanism of response and to verify and validate design methods and numerical simulations in this study 12 centrifuge tests were carried out to study the effect of fabric anisotropy on seismic response of foundations important parameters in the response are evaluated and implications for design are discussed

evidence for higher than average air temperatures after the 8 2 ka event provided by a central european δ 18 o record the so called 8 2 ka event represents one of the most prominent cold climate anomalies during the holocene warm period accordingly several studies have addressed its trigger mechanisms absolute dating and regional characteristics so far however knowledge about subsequent climate recovery is still limited although this might be essential for the understanding of rapid climatic changes here we present a new sub decadally resolved and precisely dated oxygen isotope o record for the interval between 7 7 and 8 7 ka bp 10 calendar years before ad 1950 derived from the calcareous valves of benthic ostracods preserved in the varved lake sediments of pre alpine mondsee austria besides a clear reflection of the 8 2 ka event showing a good agreement in timing duration and magnitude with other regional stable isotope records the high resolution mondsee lake sediment record provides evidence for a 75 year long interval of higher than average o values directly after the 8 2 ka event possibly reflecting increased air temperatures in central europe this observation is consistent with evidence from other proxy records in the north atlantic realm thus most probably reflecting a hemispheric scale climate signal rather than a local phenomenon as a possible trigger we suggest an enhanced resumption of the atlantic meridional overturning circulation amoc supporting assumptions from climate model simulations

holocene ostracoda crustacea from the shallow lake vrana dalmatia croatia and their paleoenvironmental significance abstract lake vrana in dalmatia is a coastal karstic brackish water environment characterized by a high species richness of ostracods that evolved into their current morphologies during the holocene the results of this study reveal five ostracod zones within an 11 m sediment core taken from the central part of the lake this sedimentary sequence reveals significant changes in both depositional and environmental conditions at local and regional scales the oldest freshwater deposits interpreted as the late pleistocene holocene transition mainly comprise the species candona neglecta juxilyocypris cf schwarzbachi hungarocypris madaraszi darwinula stevensoni and mixtacandona sp although the lake had not formed at this time it is well known that the living environment of most ostracod species is connected to flooded plains marshes rivers springs and interstitial waters in the deepest and oldest sediments within the core from depths between 1101 cm and 945 cm the presence of c neglecta and j cf schwarzbachi are indicative of cold water while the dominant taxa at depths between 945 cm and 874 cm are the brackish species cyprideis torosa and c angulata possibly suggesting the influence of seawater because of the presence of a permeable karstic ridge that separates the lake from the ocean in contrast the dominant ostracod taxa at depths between 874 cm and 813 cm are species typical of freshwater environments subject to colder climatic conditions indicating a marshy low energy wetland we know that the first permanent freshwater body formed at about 8130 cal yr bp a depth of 813 cm while large proportions of pseudocandona marchica heterocypris salina d stevensoni and metacypris cordata are all indicative of warmer shallow waters that are rich in vegetation and have variable water level similarly from 5240 cal yr bp onwards a marine influence within the core is evidenced by the presence of cy torosa while present lake water conditions i e alternating seasonal changes in salinity from freshwater to brackish were established by 2750 cal yr bp the ostracod assemblages in sediments from lake vrana in dalmatia have significant potential for reconstructing the evolution of this lake as well as for understanding environmental changes and rising sea level

the saguenay fjord quebec canada integrating marine geotechnical and geophysical data for spatial seismic slope stability and hazard assessment in 1996 a major flood occurred in the saguenay region quebec canada delivering several km 3 of sediment to the saguenay fjord such sediments covered large areas of the until then largely contaminated fjord bottom thus providing a natural capping layer recent swath bathymetry data have also shown that sediment landslides are widely present in the upper section of the saguenay fjord and therefore should a new event occur it would probably expose the old contaminated sediments landslides in the upper saguenay fjord are most probably due to earthquakes given its proximity to the charlevoix seismic region and to that of the 1988 saguenay earthquake in consequence this study tries to characterize the permanent ground deformations induced by different earthquake scenarios from which shallow sediment landslides could be triggered the study follows a newmark analysis in which firstly the seismic slope performance is assessed secondly the seismic hazard analyzed and finally an evaluation of the seismic landslide hazard is made the study is based on slope gradients obtained from em1000 multibeam bathymetry data as well as water content and undrained shear strength measurements made in box and gravity cores ground motions integrating local site conditions were simulated using synthetic time histories the study assumes the region of the 1988 saguenay earthquake as the most likely source area for earthquakes capable of inducing large ground motions in the upper saguenay region accordingly we have analyzed several shaking intensities to deduce that generalized sediment displacements will begin to occur when moment magnitudes exceed 6 major displacements failure and subsequent landslides could occur only from earthquake moment magnitudes exceeding 6 75 8 2002 elsevier science b v all rights reserved

paleoseismology in canada a dozen years of progress canadian studies in paleoseismology have led to the publication of over 40 papers in the last 12 years 80 of which have appeared since 1989 considerable progress has been achieved by confirming that the last great earthquake on the cascadia subduction zone happened about 300 years ago and by working toward a chronology of prior earthquakes from their tsunami and turbidite records as yet sparse evidence suggests that the geological effects of large crustal earthquakes are also recorded in southwestern british columbia but there is as yet no chronology in the stable craton of eastern canada studies of silt layers in lakes that are floored by organic sediments have shown considerable potential to provide local earthquake chronologies that can be tested against the more sporadically preserved evidence from liquefaction landslides and other possible indicators of paleoshaking by contrast research using more traditional techniques involving direct examination of faults through geomorphological studies or trenching has been hampered by the difficulty of identifying active faults in the first place on the basis of the past dozen years an accelerating pace of discovery should be expected in the next decade

characteristics and mechanism of the longyao ground fissure on north china plain china abstract among more than 1000 ground fissures developed over the past 30 years having induced severe geohazards in the north china plain the longyao ground fissure in hebei province is famous for its longest length and causing the worst damage and widest influence in this region in order to reveal the origin of its formation the geological background developmental characteristics and genetic mode of the longyao ground fissure were investigated in detail by geological surveys measurements trenching drilling and seismic exploration this fissure has a total length of 39 km and is characterized by normal fault extension left lateral slip and dominant along polyline distribution these characteristics are well consistent with its underlying fault the nei jv fault the fissure causes the damage to buildings structures along a polyline and in the form of a horizontal tensile crack subsidence and shear failure according to the trenching drilling and shallow seismic profiling this fissure possesses the characteristics of synsedimentary faults reflecting the historical stages of fissure activities regarding its genesis this fissure was generated under the coupling action of multiple factors which took shape after the earthquake and was enlarged under the action of groundwater pumping the regional extension first caused a fracture system in the surface strata and then the action of seismic activities started to control the fracture and finally the pumping action of excessive groundwater and other influential factors promoted the formation of the current ground fissure

environmental responses to lateglacial climatic fluctuations recorded in the sediments of pre alpine lake mondsee northeastern alps investigation of the sedimentary record of pre alpine lake mondsee upper austria focused on the environmental reaction to rapid lateglacial climatic changes results of this study reveal complex proxy responses that are variable in time and influenced by the long term evolution of the lake and its catchment a new field sampling approach facilitated continuous and precisely controlled parallel sampling at decadal to sub annual resolution for mu xrf element scanning carbon geochemistry stable isotope measurements on ostracods pollen analyses and large scale thin sections for microfacies analysis the holocene chronology is established through microscopic varve counting and supported by accelerator mass spectrometric 14 c dating of terrestrial plant macrofossils whereas the lateglacial age model is based on delta 18 o wiggle matching with the greenland ngrip record using the gicc05 chronology microfacies analysis enables the detection of subtle salimentological changes proving that depositional processes even in rather large lake systems are highly sensitive to climate forcing comparing periods of major warming at the onset of the lateglacial and holocene and of major cooling at the onset of the younger dryas reveals differences in proxy responses reflecting threshold effects and ecosystem inertia temperature increase vegetation recovery decrease of detrital flux and intensification of biochemical calcite precipitation at the onset of the holocene took place with only decadal leads and lags over a ca 100 a period whereas the spread of woodlands and the reduction of detrital flux lagged the warming at the onset of the lateglacial interstadial by ca 500 750a cooling at the onset of the younger dryas is reflected by the simultaneous reaction of delta 18 o and vegetation but sedimentological changes reduction of endogenic calcite content increase in detrital flux were delayed by about 150 300 a three short term lateglacial cold intervals corresponding to greenland isotope substages gl 1d gl 1c2 and gl 1b also show complex proxy responses that vary in time copyright c 2011 john wiley sons ltd

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

the origin and control of colour of white bentonites from the aegean islands of milos and kimolos greece some of the lower pleistocene bentonites of milos and kimolos islands greece are valued for their white colour and physicochemical properties they contain opal ct and sometimes zeolite along with smectite and have been derived from the alteration of rhyolitic volcanic rocks the miloan white bentonites contain tatatilla type montmorillonite and beidellite the kimolian ones have chambers type montmorillonite the alteration process involved removal of alkalis and uptake of mg probably from sea water si is either redistributed or partially removed the kimolian white bentonites have higher brightnesses l and whiteness index values and lower yellowness index and e ab values compared with the miloan ones the variations in white colour are inversely related to the abundance of fe oxides and anatase the occurrence of fe in the smectite structure and its oxidation state the presence of silica minerals is not an important factor affecting colour but is undesirable since it imparts high abrasiveness in commercial products the formation of white bentonites of high quality requires the removal of alkalis and silica during alteration of acid volcanics in order to avoid crystallization of zeolites and opal ct fe needs to be incorporated into the smectite structure such conditions are rarely attained

active tectonic studies in the united states 1987 1990 the techniques and instrumentation used in active tectonic studies are discussed and recent results are reviewed it is suggested that a critical mass of data on several particular regions has been accumulated making possible critical debates and attempts to assess earthquake hazards particular attention is given to studies of the pacific northwest region basin and range deformation studies and distributed deformation and hidden earthquake sources also included is a comprehensive bibliography for the period

abrupt climate change and collapse of deep sea ecosystems we investigated the deep sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20 000 years in a core from intermediate depth in the northwestern atlantic results show that deep sea benthic community collapses occur with faunal turnover of up to 50 during major climatically driven oceanographic changes species diversity as measured by the shannon wiener index falls from 3 to as low as 1 6 during these events major disruptions in the benthic communities commenced with heinrich event 1 the inter allerod cold period iacp 13 1 ka the younger dryas yd 12 9 11 5 ka and several holocene bond events when changes in deep water circulation occurred the largest collapse is associated with the yd iacp and is characterized by an abrupt two step decrease in both the upper north atlantic deep water assemblage and species diversity at 13 1 ka and at 12 2 ka the ostracode fauna at this site did not fully recover until 8 ka with the establishment of labrador sea water ventilation ecologically opportunistic slope species prospered during this community collapse other abrupt community collapses during the past 20 ka generally correspond to millennial climate events these results indicate that deep sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less

anthropogenic and climate controls on vegetation changes between 1500 bce and 500 ce reconstructed from a high resolution pollen record from varved sediments of lake mondsee austria abstract this study reports a precisely dated pollen record with a 20 year resolution from the varved sediments of lake mondsee in the north eastern european alps 47 49 n 13 24 e 481 m above sea level the analysed part of core spans the interval between 1500 bce and 500 ce and allows changes in vegetation composition in relation to climatic changes and human activities in the catchment to be inferred intervals of distinct but modest human impact are identified at ca 1450 1220 740 490 and 340 190 bce and from 80 bce to 180 ce while the first two intervals are synchronous with prominent salt mining phases during the bronze age and early iron age at the nearby unesco world heritage site of hallstatt the last two intervals fall within the late iron age and roman imperial era respectively comparison with published records of extreme runoff events obtained from the same sediment core shows that human activities including agriculture and logging around lake mondsee were low during intervals of high flood frequency as indicated by a higher number of intercalated detrital event layers but intensified during hydrologically stable intervals comparison of the pollen percentages of arboreal taxa with the stable oxygen isotope and potassium ion records of the ngrip and gisp2 ice cores from greenland reveals significant positive correlations for fagus and negative correlations for betula and alnus this underlines the sensitivity of vegetation around lake mondsee to temperature fluctuations in the north atlantic as well as to moisture fluctuations controlled by changes in the intensity of the siberian high and the north atlantic oscillation nao regime

re evaluation of several large historic earthquakes in the vicinity of the loma prieta and peninsular segments of the san andreas fault california abstract the size and location of several of the largest 19th century earthquakes in the san francisco bay area including the june 1838 8 october 1865 21 october 1868 and 24 april 1890 events are re evaluated by comparing these historic events to several modern events in particular the 1989 loma prieta earthquake similar high intensities in the monterey bay area during both the 1989 and 1838 events indicate that the 1838 shock probably ruptured the loma prieta segment in addition to the peninsular segment of the san andreas fault if so the resulting earthquake would have been of moment magnitude m w 7 2 thus like segments of many other plate boundaries the loma prieta segment exhibits heterogeneous rupture in that sometimes it ruptures with the peninsular segment as in 1906 and probably in 1838 and at other times it ruptures alone as in 1989 in contrast the area of high intensities generated by the 1865 earthquake was centered in the santa clara valley and the eastern foothills of the santa cruz mountains indicating that the 1865 shock probably was located northeast of the loma prieta rupture and not on the san andreas fault in addition the felt areas taken to be one of the best measures of relative source size of modified mercalli intensities mmi v and vi for the 1865 shock are considerably smaller than that of the 1989 event relationships between felt areas of intensities v and vi and moment magnitude are developed for the san francisco bay area based on these relationships the average computed moment magnitudes for the 1865 1868 and 1890 earthquakes are 6 51 0 18 6 84 0 20 and 6 32 0 16 respectively if these results are correct then the loma prieta segment taken to include all faults within the san andreas fault zone i e within a zone up to a few kilometers wide appears to rupture with or without the peninsular segment every 76 11 years these data on repeat times may be the most accurate information now available for ascertaining the date of future rupture of that segment and for testing recurrence models the smaller size of the 1865 earthquake would be consistent with it being part of the long term seismic build up to the 1868 event rather than being paired with it as events of similar size if the 1865 earthquake did occur northeast of the loma prieta segment then a future source of that type located closer to san jose and the santa clara valley could pose a considerable hazard to the southern san francisco bay area on going searches of letters and diaries of missionaries and early settlers could yield new information that should help to further constrain the locations and magnitudes of these and other historic earthquakes

a sedimentary record of holocene surface runoff events and earthquake activity from lake iseo southern alps italy this study presents a record of holocene surface runoff events and several large earthquakes preserved in the sediments of pre alpine lake iseo northern italy a combination of high resolution seismic surveying detailed sediment microfacies analysis non destructive core scanning techniques and ams 14c dating of terrestrial macrofossils was used to detect and date these events based on this approach our data shed light on past seismic activity in the vicinity of lake iseo and the influence of climate variability and human impact on allochthonous detrital matter flux into the lake the 19 m long investigated sediment sequence of faintly layered lake marl contains frequent centimetre to decimetre scale sandy silty detrital layers during the early to mid holocene these small scale detrital layers reflecting sediment supply by extreme surface runoff events reveal a distinct centennial scale recurrence pattern this is in accordance with regional lake level highstands and minima in solar activity and thus apparently mainly climate controlled after c 4200 cal yr bp intervals of high detrital flux occasionally also correlate with periods of enhanced human settlement activity in consequence deposition of small scale detrital layers during the late holocene apparently reflects a rather complex interplay between climatic and anthropogenic influences on catchment erosion processes besides the small scale detrital layers five up to 2 40 m thick large scale detrital event layers composed of basal mass wasting deposits overlain by large scale turbidites were identified which are supposed to be triggered by strong earthquakes the uppermost large scale event layer can be correlated to a documented mw 6 0 earthquake in ad 1222 in brescia the four other large scale event layers are supposed to correspond to previously undocumented local earthquakes these occurred around 350 bc 570 bc 2540 bc and 6210 bc and most probably also reached magnitudes in the order of mw 5 0 6 5