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

detailed crustal thickness variations beneath the illinois basin area implications for crustal evolution of the midcontinent we present high resolution imaging results of crustal and upper mantle velocity discontinuities across the illinois basin area using both common conversion point stacking and plane wave migration methods applied to p wave receiver functions from the earthscope oiink ozark illinois indiana and kentucky experiment the images reveal unusually thick crust up to 62 km throughout the central and southeastern illinois basin area a significant moho gradient underlies the nw trending ste genevieve fault zone which delineates the boundary between the illinois basin and ozark dome relatively thinner crust 45 km underlies most of the precambrian highlands surrounding the illinois basin and beneath the rift related structures of the reelfoot rift and the rough creek graben we consider four hypotheses to explain the presence of thick crust under the central and southeastern illinois basin crustal thickening may have been produced 1 prior to its accretion to north america around 1 55 ga and is an inherited characteristic of this crustal province 2 by underthrusting or shortening during proterozoic convergent margin tectonics around 1 55 1 35 ga 3 by late precambrian magmatic underplating at the base of older crust associated with the creation of the eastern granite rhyolite province around 1 3 ga and 4 through crustal relamination during an episode of proterozoic flat slab subduction beneath the illinois basin possibly associated with the grenville orogeny

constraining lithologic variability along the alleghanian detachment in the southern appalachians using passive source seismology polarities and amplitudes of intracrustal p sv conversions p waves converted to vertically polarized shear waves in receiver functions from the southeastern suture of the appalachian margin experiment array and usarray transportable array provide new constraints on the origin of seismic reflectivity delineating the alleghanian detachment in the southern appalachians eastern united states forward modeling of receiver functions is consistent with a 3 5 km thick high shear wave velocity vs 3 9 km s section of deformed paleozoic platform metasedimentary rocks beneath the blue ridge at 3 6 5 km depth in the inner piedmont conversions from the top and base of a low vs zone 3 1 km s at depths of 5 9 km are interpreted as a package of metasedimentary rocks or a shear zone characterized by radial anisotropy the detachment continues to the southeast beneath the carolina terrane where high amplitude negative conversions at 10 13 km depth are consistent with arc rocks vs 4 0 km s overlying sheared rocks with lower vs 3 2 km s southeast dipping conversions at 5 10 km depth mark the boundary between the inner piedmont and carolina terrane this study demonstrates that relatively high frequency receiver functions up to 3 hz though still lower in frequency than p wave energy analyzed for reflection profiling 20 hz can provide important links between surface geology and active source experiments to better constrain models of crustal structure

clastic dykes in east belgium evidence for upper pleistocene strong earthquakes west of the lower rhine rift segment fissures of seismic origin are described from terrace deposits of the meuse river in the liege maastricht area west of the lower rhine roer rift segment though associated with hydroplastic deformation of the sediments they are not injection structures they are interpreted as tension cracks resulting from local deformation of susceptible layers inferred to be due to cyclic loading by seismic waves the fissures have been tilled afterwards from above by vertically laminated sands and silts the distribution of the fissured areas and the special features of some ground cracks suggest that they could be linked to more than one earthquake between 650 and l00 ka bp by comparison with liquefaction phenomena described in relation to actual earthquakes the failure of the meuse terrace deposits could have been produced by seismic events of m l 6 5

the effect of crustal anisotropy on reflector depth and velocity determination from wide angle seismic data a synthetic example based on south island new zealand when deriving velocity models by forward modelling or inverting travel time arrivals from seismic refraction data a heterogeneous but isotropic earth is usually assumed in regions where the earth is not isotropic at the scale at which it is being sampled the assumption of isotropy can lead to significant errors in the velocities determined for the crust and the depths calculated to reflecting boundaries laboratory velocity measurements on rocks collected from the haast schist terrane of south island new zealand show significant up to 20 compressional p wave velocity anisotropy field data collected parallel and perpendicular to the foliation of the haast schist exhibit as much as 11 p wave velocity anisotropy we demonstrate using finite difference full wavefield modelling the types of errors and problems that might be encountered if isotropic methods are used to create velocity models from data collected in anisotropic regions these reflector depth errors could be as much as 10 15 for a 10 km thick layer with significant 20 p wave velocity anisotropy the implications for south island new zealand where the problem is compounded by extreme orientations of highly anisotropic rocks foliation which varies from horizontal to near vertical are considered finally we discuss how the presence of a significant subsurface anisotropic body might manifest itself in wide angle reflection refraction and passive seismic datasets and suggest ways in which such datasets may be used to determine the presence and extent of such anisotropic bodies d 2002 elsevier science b v all rights reserved

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

reprocessing and reinterpretation of cocorp southern appalachian profiles abstract reprocessing of cocorp southern appalachian data was focused on basic seismic evidence for continuation of sediments beneath a master decollement the most important evidence is a nearly continuous series of subhorizontal reflections extending from the valley and ridge province into the piedmont province continuity of subhorizontal reflections becomes tenuous in the inner piedmont careful reprocessing has yielded evidence for termination of strong reflections beneath the allochthon and the beginning of a relatively weak and complex series of events termination of sedimentary rocks beneath the piedmont is interpreted from true amplitude seismic data a zone of detachment continues southeast of the sediment termination as far as the master decollement root zone research on stacking velocities has indicated that complex velocity structures could create apparent low stacking velocities this phenomenon may occur in the charlotte belt of georgia bouguer gravity can be modeled as a former craton of normal density with an accreted margin of very slightly higher density variation in crustal thickness also contributes to the bouguer gravity gradient no continuous large scale overthrust is needed southeast of the interpreted master decollement root zone located beneath the kings mountain belt and charlotte belt

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

a coupled fluid fracture approach to propagation of clastic dikes during earthquakes abstract the propagation of clastic dikes was studied in ami az plain where hundreds of clastic dikes cross cut the soft rock of the late pleistocene lacustrine lisan formation within the seismically active dead sea basin two analytic models were established to estimate the dike propagation velocities the dike emplacement duration and the driving pressures that were associated with dike propagation either under laminar or turbulent flow conditions these models depend on the host rock and fluid properties dike width and length based on these properties and field limitations the results indicate that the dikes were propagated under turbulent flow conditions and propagation velocities of 4 65 m s the emplacement duration of the clastic dikes is between 0 8 and 2 s which is similar to the order of the acoustic wave duration that passes through the soft rock during an earthquake event this implies that the propagation of dikes could form during the passing acoustic waves and may thus be considered as an earthquake induced impact structures the calculated driving pressures that were generated during the earthquake events near the surface are 1 2 mpa one order of magnitude larger than the pressure due to the overburden on the source layer

the origin of reflections beneath the blue ridge piedmont allochthon a view through the grandfather mountain window a perplexing variety of crustal models have been proposed for the region beneath the southern appalachian overthrust determining the true nature of crustal composition and structure in this region carries important scientific and economic implications to evaluate the numerous models compressional wave velocities and densities were measured on 30 rock samples collected within the grandfather mountain window in the blue ridge of north carolina the window breaches high grade crystalline rocks exposing grenville gneisses late proterozoic metasedimentary and metavolcanic rock and cambrian quartzite phyllite and dolostone that are likely to underlie the regional blue ridge piedmont thrust measured velocities range widely from 4 21 km s 1 for cambrian phyllite to 7 47 km s 1 for tectonized cambrian shady dolomite at 200 mpa velocity anisotropy is as great as 47 in the phyllite the samples exhibit a broad range in densities as well from 2500 kg m 3 in fractured quartzite to 3000 kg m 3 in metabasalts synthetic reflection seismograms were generated using these physical properties to consider the origin of subthrust reflection events in addition to the much publicized interpretation of paleozoic sedimentary rocks residing beneath the crystalline sheet modeling reveals that the reflections could also be explained by metamorphosed paleozoic strata by the regional late proterozoic metavolcanic and metaclastic rift sequence and by pervasive shear zones i e mylonites within compositionally homogeneous gneisses we interpret field data to strongly favor mylonitic gneisses as the subthrust reflectors still surface data remain sufficiently ambiguous that the question will not be definitively settled without continental drilling

gps measurements of crustal deformation in the baikal mongolia area 1994 2002 implications for current kinematics of asia 1 we present new geodetic results of crustal velocities over a large part of northern asia based on gps measurements in the baikal rift zone and mongolia spanning the 1994 2002 period we combine our results with the gps velocity field for china of wang et al 2001 and derive a consistent velocity field for most of asia we find contrasted kinematic and strain regimes in mongolia with northward velocities and n s shortening in westernmost mongolia but eastward to southeastward motion and left lateral shear for central and eastern mongolia this eastward to southeastward motion of central and eastern mongolia is accommodated by left lateral slip on the e w trending tunka bolnay and gobi altay faults 2 1 2 mm yr 1 2 6 1 0 mm yr 1 and 1 2 mm yr 1 respectively and by about 4 mm yr 1 of extension across the baikal rift zone consequently 15 of the india eurasia convergence is accommodated north of the tien shan by n s shortening combined with dextral shear in the mongolian altay and by eastward displacements along major left lateral strike slip faults in central and eastern mongolia we find a counterclockwise rotation of north and south china as a quasi rigid block around a pole north of the stanovoy belt which rules out the existence of an amurian plate as previously defined and implies 2 mm yr 1 of left lateral slip on the qinling shan fault zone

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

reinterpretation of adcoh and cocorp seismic reflection data with constraints from detailed forward modeling of potential field data implications for laurentia peri gondwana suture abstract to better constrain the structure of the laurentian peri gondwana suture zone maps and a 2 dimensional regional cross section model constrained by seismic data and surface geology have been developed by forward and inverse modeling the aeromagnetic and gravity fields the central piedmont suture cps the boundary between the laurentian inner piedmont and the peri gondwanan carolina terrane is a low angle thrust fault 30 ramping up from an alleghanian mid crustal detachment at depths of about 12 km adcoh and cocorp seismic data image anticlinal structures in the footwalls of the hayesville thrust and the cps above the alleghanian decollement the footwall rocks have previously been interpreted as paleozoic shelf strata on the basis of sub horizontal seismic reflectors however the high densities required to fit the observed gravity anomaly suggest that the folded footwall reflectors may need to be reinterpreted as horse blocks or duplex structures of grenvillian basement the appalachian paired gravity anomaly can be explained by an increase in crustal thickness and a decrease in upper crustal density moving northwestward from the carolina terrane toward the appalachian core a change in lower crustal density is not required so that grenville basement rocks may extend farther to the southeast than previously thought the 5 to 10 km of alleghanian uplift and exhumation predicted by p t crystallization data compiled in this paper can be easily accommodated by thrusting on four major low angle thrust systems great smoky mountain thrust gsmt hayesville brevard and cps unroofing of metamorphic core complexes by normal faulting may therefore not be required to explain the observed exhumation alleghanian collision along the southeastern appalachian margin was predominately orthogonal to strike consistent with the previous reconstructions that call for the counter clockwise rotation of gondwanan west africa creating head on collision in the southern appalachians and at least 370 km of shortening

estimation and propagation of error in measurements of river channel movement from aerial imagery rates of river channel migration or widening are only valid if it can be demonstrated that the amount of change in the measured parameters exceeds the measurement errors however it is still uncommon to see estimates of errors presented alongside rates of river channel change measured from aerial photography here detailed methods are presented for the estimation of errors in quantifying channel migration rates that can be easily applied to gis based analysis of planform change in addition the impact of relaxing assumptions regarding error independence between image dates and systematic registration errors is presented and discussed copyright 2005 john wiley sons ltd

a comprehensive classification of earthquake archaeological effects eae in archaeoseismology application to ancient remains of roman and mesoamerican cultures one of the key tasks in archaeoseismolo gy is to test whether the recorded building damage in ancient cities can be related to ancient earthquakes archaeologists often claim abandonment ruin or war instead of natural causes to explain the recorded damage in archaeological findings this work proposes a comprehensive classification of earthquake archaeological effects eae based on the seismic deformation of buildings and monuments within urban areas of ancient cities accordingly the proposed eae classification differentiates the seismic deformation on the structure of buildings in two groups from transient shaking and from permanent ground deformation the first type of eae corresponds to fractured walls and fallen key stones in arches for example the second type of eae are tilted walls and shock breakouts of flagstones due to basement failure to illustrate the proposed eae classification examples of earthquake damage on ancient buildings are described baelo claudia and tolmo de minateda cities roman and visigothic periods 1st 6th century ad respectively south of spain and teotihuacan and tarascan sites early classic ca ivth century ad and upper post classic period xiiith century ad central mexico

crustal evolution across the southern appalachians initial results from the sesame broadband array 1 receiver functions from the earthscope southeastern suture of the appalachian margin experiment broadband deployment and u s transportable array were analyzed to constrain average crustal thickness and composition across the southern appalachians low vp vs ratios 1 69 1 72 across the carolina terrane and parts of the inner piedmont indicate that the crust has a felsic average composition the results are consistent with models of thin skinned thrusting of carolina arc fragments over laurentian basement whereas arc collision models require significant crustal modification to explain the low vp vs new crustal thickness estimates provide constraints on the extent of the blue ridge crustal root the present root may be a remnant of a broader structure formed by alleghanian thrust loading root preservation is attributed to mesozoic heating and thinning of the lower crust beneath outboard terranes leaving colder blue ridge crust largely intact however thickened crust 50 55 km across the region may also be inherited from continental collision during the proterozoic grenville orogeny

investigating the accuracy of photointerpreted unvegetated channel widths in a braided river system a platte river case study abstract the central platte river in nebraska usa has undergone substantial channel narrowing since basin settlement in the mid nineteenth century many researchers have studied the causes of channel narrowing and its implications for endangered species that use wide shallow channel segments with barren sandbars as a result changes in metrics such as unvegetated channel width have been studied with few exceptions these measures are estimated from aerial imagery without mention of error in relation to actual channel conditions and or investigator bias this issue is not unique to central platte river studies as a general lack of commentary is apparent regarding the direct comparison of channel planform characteristics interpreted from aerial imagery relative to those measured in the field here we present a case study where data collected by the platte river recovery implementation program was used to make multiple comparisons using three years of field measured unvegetated channel widths and those photointerpreted from aerial imagery widths were interpreted by three investigators who identified similar widths in almost all cases photointerpretation from imagery collected during the fall resulted in unvegetated width estimates that were more consistent with field measurments than estimates derived using imagery collected in june differences were attributed to three main factors 1 influences of discharge on photointerpretation of unvegetated channel width 2 increases in vegetative cover throughout the growing season and 3 resolution of imagery most importantly we concluded that photointerpretation of unvegetated widths from imagery collected during high flows can result in significant over estimation of unvegetated channel width

soft sediment deformation structures in the earth s oldest seismites abstract the chaibasa formation in eastern india which was deposited between 2100 and 1600 million years ago shows deformations that must have formed when the sediments were not yet consolidated some of these deformation structures have never been described before here they are described depicted and their origin is analysed we show that they must be the result of shocks which can only be explained satisfactorily as triggered by earthquakes the layers containing these deformation structures are termed seismites they are among the earliest records of earthquakes known in the earth s history

paleoseismic features as indicators of earthquake hazards in north coastal san diego county california usa abstract new road cut and mass grading excavations in the north coastal area of san diego county california expose heretofore generally unrecognized probable late holocene tsunami deposits and paleoseismically deformed sediments remnant tsunami deposits occur up to 100 m in elevation around the margins of modern coastal lagoons and estuaries and combined with local mima mounds of possible sand blow origin provide indirect but compelling evidence for the late quaternary activity of onshore and offshore faults in the immediate study area probable paleoliquefaction features are regionally widespread and range from fissures filled with sediments derived from overlying marine terrace sand and soil to the more traditional sand filled injection dikes and sills lateral spreads and filled craterlets the source of most liquefied sediment is underlying tertiary bedrock sand and local quaternary marine terrace deposits a paleoseismic liquefaction origin rather than soft sediment loading is deduced for these features based on morphology internal stratigraphy field setting and near proximity to known seismogenic sources some paleoseismic events impacted late holocene indian middens and burial sites the last seismic event probably occurred within the past 1 to 3 ka and possibly even records the historic earthquakes of either november 22 1800 or may 27 1862 the liquefaction features also affect marine terrace sediments tens of meters above modern regional water levels inferentially recording paleoseismic events in this mediterranean type climatic region during winter rains when high level perched water saturates the several meter thick source sediments based on their regional extent the paleoseismic features were likely caused by m 7 tectonic events inferentially generated by the nearby offshore newport inglewood rose canyon fault system or possibly by smaller recently exposed related and localized faults accordingly the seismic hazard of the north coastal area of san diego county may be substantially higher than previously assumed and hence of concern owing to the rapid ongoing and projected population increase

estimation of error in bankfull width comparisons from temporally sequenced raw and corrected aerial photographs this study investigates the propagation of error through image to image comparison of 285 river bankfull width measurements of the afon trannon mid wales bankfull width is quantified from both aerial photographs analysed as rectified images in erdas imagine orthomax and raw images in paintshop pro a method for the robust estimation of bankfull width measurement error through temporal sequences of scanned aerial photographs is presented and the improvement in accuracy achieved using rectified imagery is quantified results from this study are placed in the context of previously published rates of bankfull width change from a wide range of river scales and the bankfull change rates for robust medium term analysis using approximately 1 10 000 historical aerial photography are identified

kinematics topography shortening and extrusion in the india eurasia collision we examine the problem of partitioning between shortening and extrusion in the india asia collision since 45 ma we compute the amount of shortening expected from the kinematics of india s motion with respect to eurasia using the reconstruction at collision time to put bounds on the possible amounts of surface loss within greater india and within eurasia we then compute the amounts of surface loss corresponding to the thickened crust of tibet and of the himalayas assuming conservation of continental crust the spatial distribution of the topography reveals a large systematic deficit of crustal thickening distributed rather uniformly west of the eastern syntaxis but an excess of shortening east of it this distribution indicates an important eastward crustal mass transfer however the excess mass east of the eastern syntaxis does not account for more than one third to one half of the deficit west of the eastern syntaxis the deficit may be accounted either by loss of lower crust into the mantle for example through massive eclogitization or by lateral extrusion of nonthickened crust a mass budget of the crust of the himalayas indicates that lower crust has not been conserved there but the deficit is so large that local loss in the mantle is unlikely to be the unique cause of the deficit alternatively following zhao and morgan 1985 lower crust may have been transferred below the tibetan crust we conclude that a combination of possible transfer of lower crust to the mantle by eclogitization and lateral extrusion has to account for a minimum of one third and a maximum of one half of the total amount of shortening between india and asia since 45 ma this conclusion leaves open the possibility that the partitioning between extrusion and loss of lower crust into the mantle on the one hand and shortening on the other hand has significantly changed during the 45 m y history of the collision

channel patterns braided anabranching and single thread a new channel pattern classification is presented based on theoretically derived channel pattern discriminant functions the thresholds are formulated as power laws that relate the critical slope associated with a change in channel pattern to dimensionless discharge and relative bank strength one threshold demarcates the boundary between stable single thread channels both straight and meandering and stable multiple thread channels anabranching another threshold separates anabranching from braided channels where braided channels are considered to be fundamentally unstable the exponents of the thresholds are nearly identical to that in the threshold equation originally proposed by leopold and wolman 1957 and the coefficients are quite similar as well an analysis of their data set using our dimensionless approach reveals that no fundamental difference exists between meandering and straight patterns and thus data from both types are grouped together under the more general heading of single thread channels furthermore we demonstrate that over a limited range of conditions an unstable single thread channel can form stable multiple threads but that for systems far from the threshold bounding the single thread channels the number of divisions required to produce stable anabranches grows geometrically this motivates a separation of multiple thread channels into anabranching and braided types our theoretical thresholds are then compared against several large data sets of field data and the results broadly confirm our proposed thresholds

liquefaction during the 1977 san juan province argentina earthquake ms 7 4 liquefaction effects generated by the 1977 san juan province argentina earthquake ms 7 4 are described the larger and more abundant effects were concentrated in the 60 km long band of the lowlands in the valle del bermejo and in an equally long band along the rio san juan in the valle de tulum fissures in the valle del bermejo were up to several hundred meters long and up to several meters wide sand deposits from boils that erupted through the fissures covered areas up to tens of square meters fissures generally parallelled nearby stream channels because the valle del bermejo is undeveloped these large features caused no damage liquefaction in the valle del tulum caused important or unusual damage at several localities including the following five sites 1 at the barrio justo p castro a subdivision of caucete liquefaction of subsurface sediments decoupled overlying unliquefied stiff sediments producing a form of ground failure called ground oscillation the associated differential ground movements pulled apart houses and pavements in extension while shearing curbs and buckling canal linings in compression at the same locality 2 at the escuela normal in caucete the roof of a 30 m long single story classroom building shifted westward relative to the foundation that displacement fractured and tilted columns supporting the roof the foundation was fractured at several places leaving open cracks as wide as 15 mm the cumulative width of the open cracks was 48 mm an amount roughly equivalent to the 63 mm of offset between the roof and foundation at the east end of the building the ground and foundation beneath the building extended or spread laterally opening cracks and lengthening the foundation while the roof remained in place 3 the most spectacular damage to structures at the community of san martin was the tilting of a 6 m high water tower and the toppling of a nearby pump house into a 1 m deep crater similarly a small crater developed beneath a hand pump in an open area and a large 6 m diameter crater formed nearby the following sequence of events created the craters and toppled the pump structures during the earthquake ground shaking generated excess pore pressures which were dissipated by upward flow of groundwater free drainage was restricted by an impermeable plastic silt layer water apparently accumulated below the plastic silt layer and then burst to the surface through several holes and cracks including holes around well casings 4 at the san isidro winery nine storage tanks tilted 2 to 5 five reinforced concrete tanks were dismantled but four steel tanks were repaired by placing new footings and jacking the structures into an upright position 5 at escuela j j pasos differential settlement beneath building fractured several columns and walls the largest settlements were about 60 mm and the maximum settlement of footings supporting columns was about 40 mm in spite of the damage the buildings were in no danger of collapse

isostatic compensation for a portion of the southern appalachians evidence from a reconnaissance study using wide angle three component seismic soundings wide angle reflections generated by five controlled blasts and over 110 timed quarry blasts in the southern appalachians were used to test models for isostatic compensation of topography the profiles cross the appalachian gravity gradient and gravity low and sample the highest elevations within the orogen migration of p sv and sh reflections suggests that crustal thickness varies from 35 to 39 km within the coastal plain and 37 39 km within the carolina terrane it increases northwestward from 40 to 45 km across the inner piedmont and then thickens to 50 52 km along the southeastern flank of the blue ridge mountains crustal thickness within the blue ridge mountains ranges from 47 to 56 km receiver functions for broadband stations goga and mync show a similar pattern in crustal thickness assuming airy compensation the correlation between elevation and moho depth suggests a range of 50 150 kg m 3 for the density contrast between the crustal root and mantle the greatest moho depths are associated not with the tallest peaks but rather with the broadest portions of the mountain chain this observation is consistent with regional bending of the lithosphere however the planar basement surface suggests that the root either predates alleghanian thrusting and therefore is unrelated to the present topography or formed in response to some other mechanism bounds on curvature of the basement surface suggest a lower bound of 30 40 km for the effective elastic thickness of the lithosphere this is consistent with previous estimates for the southern appalachians based on analysis of gravity data

freshwater megaflood sedimentation what can we learn about generic processes abstract there is growing recognition that sedimentary deposits related to high energy large scale freshwater floods are widespread across the continents and in the main can be related to quaternary outbreak flows from ice dammed lakes such deposits may also occur in the neogene and earlier recognition of these megaflood deposits is hindered by the lack of well conditioned stratigraphic models of depositional successions however descriptions of successions from many locations often exhibit commonalities when compared carefully thus the primary purpose of this paper is to examine and condense the published stratigraphic and sedimentological evidence so as to identify the key signatures of megaflood successions the deposits often are the only record of a flood and so the secondary purpose is to interpret the sedimentary sequences in order to recreate the behaviour of floods through single and multiple events finally some pointers are provided as to those areas of sedimentological research that might be profitably explored in more depth to improve understanding of megaflood dynamics a key characteristic of megaflood deposits is the apparent massive appearance of single units which on closer inspection usually are amalgamated layers of similar grain size distribution individual beds and sets of beds are commonly near horizontal planar and laterally extensive successions evidently are not channelized and extensivity is indicative of simultaneous and coherent deposition over large areas localised large scale clinoforms or smaller scale cross beds are common associated with bar front or dune progradation respectively but otherwise extensivity implies that cross cutting erosional contacts notably steeply inclined examples and small scale scours are not common except immediately around large isolated clasts such as dropstones and ice blocks a common vertical stack of sequences in any one succession consists of 1 basal thick coarse parallel bedded units 2 large scale clinoforms 3 horizontally bedded thin laminated units 4 ripple and dune cross beds 5 silt beds and 6 succession capping debris flow deposits in some cases such a succession usually is indicative of a single cycle of waxing and waning flood flow generally dominated by high concentration suspension deposition onto plane beds the high power allows the transport of fine gravel and coarse sand in suspension leading upon deposition to relatively coarse beds from suspension fall out clay and silt is generally sparse or absent being transported further down the system at the scale of the hydrograph the successions indicate that flows initially accelerate and then decelerate with significant shorter period flow pulses also evident in the sedimentary signatures in parallel bedded sequences primarily during waxing flows bedload transport often was ineffective in sorting sediment due to the high rates of deposition from the highly sediment charged waters resulting in diffuse accretion surfaces at each location similar sequence stacks are common leading to the impression of rhythmic deposition from pulsing flow including from repetitive series of floods although often composed of coarse grains many sequence stacks excluding any debris flows are not dissimilar to turbidity flow sequences the bouma sequence in particular although there is limited experimental evidence for turbidity currents associated with high energy freshwater flows theory does not preclude the deposition of similar sedimentary motifs from high concentration flows such that an analogy between some megaflood sedimentary beds and turbidites is not unreasonable despite considerable variation in megaflood sedimentary successions commonalities occur which are indicative of similar processes of deposition from high energy floods at geographically different locations the changes in style of deposition throughout a succession provide clues as to the nature of the flood flows and this information could be used to improve estimates of flood hydrograph behaviour however hypotheses linking deposit characteristics to flow dynamics are currently ill conditioned and often poorly tested the majority of published studies describe the coarser scale stratigraphy with only passing reference to the fine scale structure of individual beds closer attention to lamination styles particle orientation and syn depositional deformation structures for example should provide information on the flow mechanics at the time of bed deposition thus better consideration of the sedimentology of megaflood deposit beds will lead to better understanding of the controlling hydraulics and should result in better models of flood deposition

refining measurements of lateral channel movement from image time series by quantifying spatial variations in registration error abstract remotely sensed data provides information on river morphology useful for examining channel change at yearly to decadal time scales although previous studies have emphasized the need to distinguish true geomorphic change from errors associated with image registration standard metrics for assessing and summarizing these errors such as the root mean square error rmse and 90th percentile of the distribution of ground control point gcp error fail to incorporate the spatial structure of this uncertainty in this study we introduce a framework for evaluating whether observations of lateral channel migration along a meandering channel are statistically significant given the spatial distribution of registration error an iterative leave one out cross validation approach was used to produce local error metrics for an image time series from savery creek wyoming usa and to evaluate various transformation equations interpolation methods and gcp placement strategies interpolated error surfaces then were used to create error ellipses representing spatially variable buffers of detectable change our results show that for all five sequential image pairs we examined spatially distributed estimates of registration error enabled detection of a greater number of statistically significant lateral migration vectors than the spatially uniform rmse or 90th percentile of gcp error conversely spatially distributed error metrics prevented changes from being mistaken as real in areas of greater registration error our results also support the findings of previous studies second order polynomial functions on average yield the lowest rmse and errors are reduced by placing gcps on the floodplain rather than on hillslopes this study highlights the importance of characterizing the spatial distribution of image registration errors in the analysis of channel change

geometry of the fault zone of the 2003 ms 7 5 chuya earthquake and associated stress fields gorny altai abstract the co seismic deformations produced during the september 27 2003 chuya earthquake ms 7 5 that affected the gorny altai russia are described and discussed along a 30 km long segment the co seismic deformations have manifested themselves both in unconsolidated sediments as r and r shears extension fractures and contraction structures and in bedrock as the reactivation of preexisting schistosity zones and individual fractures as well as development of new ruptures and coarse crushing zones it has been established that the pattern of earthquake ruptures represents a typical fault zone trending nw se with a width reaching 4 5 km and a dextral strike slip kinematics the initial stress field that produced the whole structural pattern of co seismic deformations during the chuya earthquake is associated with a transcurrent regime with a nnw sse almost n s trending of compressional stress axis 1 and a ene wsw almost e w trending of tensional stress axis 3 the state of stress in the newly formed fault zone is relatively uniform the local stress variations are expressed in insignificant deviation of 1 from n s to nw se or ne sw in short term fluctuations of relative stress values in keeping their spatial orientations or in a local increase of the plunge angle of the 1 the geometry of the fault zone associated with the chuya earthquake has been compared with the mechanical model of fracturing in large continental fault zones with dextral strike slip kinematics it is apparent that the observed fracture pattern corresponds to the late disjunctive stage of faulting when the master fault is not fully developed but its segments are already clearly defined it has been shown that fracturing in widely different rocks follows the common laws of the deformation of solid bodies even close to the earth surface and with high rates of movements

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

characteristics of coarse grained sequences deposited in nearshore wave dominated environments examples from the miocene of south west oregon the conglomeratic sandstone of the sandstone of floras lake miocene is a superbly exposed example of a coarse grained sequence deposited in a high energy storm wave dominated shallow marine environment the features of the unit suggest deposition on a shoreface in proximity to a fluvial source distinguishing characteristics include amalgamated hummocky stratified sandstone low angle cross stratified conglomerate beds lenticular conglomerate beds tabular conglomerate beds high angle scours trough cross bedded sandstone organic rich beds and burrows of several sizes these features are interpreted in terms of their depths of deposition generation by fair weather storm and or flood processes and as indicators of relative rates of sedimentation the unit records complex interaction of tectonic wave fluvial and tidal processes relative depth changes indicated in the sequence probably reflect changes in the balances between sediment supply basin subsidence and eustatic sea level changes wave processes are manifest in the presence of structures deposited both above and below fair weather wave base deposition and reworking by chaotic seas associated with local storms and by long period swell associated with distant storms may be indicated by the interbedding of amalgamated hummocky stratified sandstone and conglomerate beds the effects of the lateral migration of a fluvial source with time are reflected by the changing nature and apparent rates of supply of sediments deposited in the nearshore zone tidal processes are manifest largely as superimposed features on wave and current generated structures biogenic structures are an important clue to the rates and frequencies of all these processes the conglomeratic sandstone was deposited on a high energy tectonically active continental margin similar to the present setting of the southern oregon coast it was deposited at varying depths in a subsiding basin during a time of world wide sea level rise the sequence provides an opportunity for the study of coarse grained nearshore marine sediments and the delineation of the interaction of various processes during deposition detailed sedimentologic and palaeoecologic analysis provides insight into the nature of storm and flood processes that are difficult to observe in the modern environment

recumbent flame structures in the lower gondwana rocks of the jharia basin india a plausible origin abstract a set of recumbent flame structures was found within a stacked channel complex belonging to the raniganj formation upper permian of the lower gondwana sediments of the jharia basin india the characteristics particularly the relation with the erosional base of the overlying channel the nature of the host layer and the geometry of the flame structures suggest that the horizontal gradient in pore fluid pressure developed within the concealed layer in response to the differential loading due to partial removal of the overburden during erosional incision was responsible for triggering the static liquefaction of the sediments and the density driven deformation of the sand mud interface took place rounded excrescence of sand bulged downward into the underlying mud which in turn was projected upward in the form of sharp flames following the trajectory of the pore fluid gradual bending of the flow trajectory towards the horizontal direction due to the presence of the overlying impermeable mud layer led to the development of the recumbent geometry of the flame structures

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

some aspects of the recent tectonics in the strait of messina italy abstract during pliocene and pleistocene times the strait of messina was subjected to extensional tectonism which was contemporaneous with marine sedimentary processes various tectonic sedimentary features created by this combination of processes are reviewed depocentres synsedimentary truncations and the association of sedimentary dykes related to extensional fissuring and hydraulic fracturing these features are regarded as characteristic accompaniments to extensional block faulting the recent structural evolution of the strait of messina margins provides an illustration of high magnitude vertical movements occurring within a short time interval the subsidence phase is related to fault movements which generate important fault scarps and sedimentary dykes phases of upheaval in contrast correspond to a general uplift of the margins unrelated to the local fault movements

engineering geologic and geotechnical analysis of paleoseismic shaking using liquefaction effects field examples abstract the greatest impediments to the widespread acceptance of back calculated ground motion characteristics from paleoliquefaction studies typically stem from three uncertainties 1 the significance of changes in the geotechnical properties of post liquefied sediments e g aging and density changes 2 the selection of appropriate geotechnical soil indices from individual paleoliquefaction sites and 3 the methodology for integration of back calculated results of strength of shaking from individual paleoliquefaction sites into a regional assessment of paleoseismic strength of shaking presented herein are two case studies that illustrate the methods outlined by olson et al engineering geology this issue for addressing these uncertainties the first case study is for a site near memphis tennessee wherein cone penetration test data from side by side locations one of liquefaction and the other of no liquefaction are used to readily discern that the influence of post liquefaction aging and density changes on the measured in situ soil indices is minimal in the second case study 12 sites that are at scattered locations in the wabash valley and that exhibit paleoliquefaction features are analyzed the features are first provisionally attributed to the vincennes earthquake which occurred around 6100 years bp and are used to illustrate our proposed approach for selecting representative soil indices of the liquefied sediments these indices are used in back calculating the strength of shaking at the individual sites the results from which are then incorporated into a regional assessment of the moment magnitude m of the vincennes earthquake the regional assessment validated the provisional assumption that the paleoliquefaction features at the scattered sites were induced by the vincennes earthquake in the main which was determined to have m 7 5 the uncertainties and assumptions used in the assessment are discussed in detail

seismically induced clastic dikes as a potential approach for the estimation of the lower bound magnitude intensity of paleoearthquakes abstract we compiled a database that includes 36 sites wherein the injection and neptunian dikes associated with 16 instrumental seismic events were studied some information in the database was obtained from our field work in the epicentral area of the 2003 ms 7 5 chuya and the 1950 ms 7 mondy earthquakes the bounding relationships between the surface wave magnitude ms and maximum width w cd visible maximum height h cd and intensity index of clastic dikes i cd and local macroseismic intensity i l and the same three parameters were established as was hypothesized larger metrics of clastic dikes can be expected from earthquakes with higher magnitudes and macroseismic intensities the analysis of the obtained relationships showed that when estimating the lowest potential magnitude or local macroseismic intensity it is better to use all three parameters of clastic dikes and take the maximum level for seismic hazard evaluation this reduces the underestimation of the earthquake potential thus clastic dikes can be applied as a potential approach for a lower bound magnitude intensity estimation of paleoearthquakes which is particularly important in the construction of critical facilities this work should stimulate geologists to record the metrics of seismically induced clastic dikes to improve the equations proposed in the present paper

nanga parbat crustal anisotropy implications for interpretation of crustal velocity structure and shear wave splitting the nanga parbat haramosh massif repre sents a unique exposure of mid lower continental crust from beneath the himalayan orogen seismic velocity measure ments on a suite of quartzofeldspathic gneisses show up to 12 5 velocity anisotropy for compressional waves and up to 21 for shear waves the degree of anisotropy is a func tion of mica content and rock fabric strength over 30 of the samples have maximum compressional wave velocities of 6 4 6 5 km s velocities typically associated with more mafic lithologies these results have implications for the inter pretation of crustal velocity structure obtained from wide angle seismic surveys where in situ velocity measurements are made from refracted or turning rays that potentially spend a substantial portion of their travel path propagat ing in the foliation plane velocities determined from these surveys may overestimate mean velocities of crustal rocks with well developed horizontal fabric in addition crustal anisotropy due to the development of pervasive rock fabric has the potential to be a significant contributing factor to shear wave splitting observations

liquefaction induced structures in quaternary alluvial gravels and gravelly sediments ne brazil abstract we have identified numerous well preserved elutriation and fluidization structures probably induced by liquefaction in quaternary gravels and gravelly sediments of braided fluvial channel deposits in the rio grande do norte and ceara states northeastern brazil they show evidence of upward directed water escape after sediment deposition and before sediment compaction among the several types of structures observed the most frequent are pillars pockets and dikes these structures range in width from a few centimeters to as much as 4 m and in height from 60 cm to 4 m dikes pillars and pockets are systematically associated clastic dikes vented large quantities of sand to the upper layers or the surface pebbles and cobbles from the host rock sank into the dikes and formed pillars and pockets pockets form the root part pillars form the intermediate part and dike the upper part of the composite structure the morphology of the structures in sectional and plan views indicates a 3d geometry composed of a tabular dike and pillar that present a downward continuous transition to a bowl shaped pocket this stratigraphy of liquefaction features is different from that usually presented in the current literature field data suggest that both the location and the geometry of the features were controlled by sedimentary properties rather than joints and small faults the size and abundance of these features suggest that they were formed by great events rather than localized mechanisms field evidence also indicates that these features are the product of fluidization and elutriation and may have been induced by liquefaction processes associated with seismic shaking a nonseismic origin related to elutriation processes however cannot be ruled out for some of the features

magnitude versus faults surface parameters quantitative relationships from the aegean region historical and seismotectonic data from the broader aegean region have been collected and all possible information relative to ground deformation associated to earthquakes that hit the area have been re evaluated all events associated to co seismic surface faulting have been selected and further investigated while geomorphologic and geological criteria have been used to recognise and characterise the seismogenic faults associated to these morphogenic earthquakes sensu bull inqua 16 1993 24 in particular in order to perform seismic hazard analyses we compiled a list of all earthquakes where the surface rupture length srl the maximum vertical displacement mvd or the average displacement ad is available we thus obtained reliable values of these source parameters for 36 earthquakes of which 26 occurred during the 20th century 6 in the 19th century and the 3 remaining earlier magnitude versus srl and mvd has been compiled for estimating empirical relationships the calculated regression equations are ms 0 90 log srl 5 48 and ms 0 5 9log mvd 6 75 showing good correlation coefficients equal to 0 84 and 0 82 respectively co seismic fault rupture lengths and especially maximum displacements in the aegean region have systematically lower values than the same parameters worldwide but are similar to those of the eastern mediterranean middle east region the envelopes of our diagrams are also calculated and discussed for estimating the worst case scenario furthermore for all investigated seismogenic structures based on several geological criteria we measured the geological fault length gfl which is the total length of the neotectonic faults showing cumulative recent activity we then compared srl with gfl and their ratio shows a clear bimodal distribution with a major peak at 0 8 1 0 indicating that about 50 of the investigated earthquakes ruptured almost the entire fault length while a second peak around the value of 0 5 is clearly related to a segmentation process of longer neotectonic structures further implications of this distribution are also discussed eventually from the distribution of gfl versus magnitude we also infer an important geological threshold for the occurrence of morphogenic earthquakes at about 5 5 degrees

paleoliquefaction features on tenerife canary islands in holocene sand deposits on tenerife one of the canary islands a series of clastic dikes and tubular vents is attributed to liquefaction of sediments during a high intensity paleoearthquake geotechnical geological tectonic and mineralogical investigations have been carried out to identify the soil composition and structure as well as the geological processes operating in the area geochronological analysis has indicated an age ranging from 10 081f933 to 3490f473 years bp for the liquefaction features the area in which these liquefaction features are found has undergone tectonic uplift and is affected by two faults one of these faults was responsible for displacing the holocene materials the paleoearthquake responsible for this liquefaction has been analysed in terms of its peak ground acceleration pga and magnitude by back calculation analysis based on the cyclic stress and ishihara methods a range of 0 22 0 35g was obtained for the pga with the value of 0 30g being selected as most representative from this an earthquake modified mercalli intensity of imm ix was estimated for the liquefaction site the magnitude bound method and energy based approaches were used to determine the magnitude of the paleoearthquake providing a moment magnitude m in the range of 6 4 7 2 m 6 8 is taken as the representative figure d 2004 elsevier b v all rights reserved

basin evolution in a folding lithosphere altai sayan and tien shan belts in central asia abstract central asia is a classical example for continental lithospheric folding in particular the altay sayan belt in south siberia and the kyrgyz tien shan display a special mode of lithospheric deformation involving decoupled lithospheric mantle folding and upper crustal folding and faulting both areas have a heterogenous crust with a long history of accretion collision subsequently reactivated as a far field effect of the indian eurasian collision thanks to the youthfulness of the tectonic deformation in this region peak deformation in late pliocene early pleistocene the surface expression of lithospheric deformation is well documented by the surface topography and superficial tectonic structures a review of the paleostress data and tectono stratigraphic evolution of the kurai chuya basin in siberian altai zaisan basin in kazakh south altai and issyk kul basin in kyrgyz tien shan suggests that they were initiated in an extensional context and inverted by a combination of fault controlled deformation and flexural folding in these basins fault controlled deformation alone appears largely insufficient to explain their architecture lithospheric buckling inducing surface tilting uplift and subsidence also played an important role they form typical basins in a folding lithosphere flb their characteristic basin fill and symmetry inner structure folding wavelength and amplitude thermal regime time frame are examined in relation to basement structure stress field strain rate timing of deformation and compared to existing modelling results

the brevard zone in south carolina and adjacent areas an alleghanian orogen scale dextral shear zone reactivated as a thrust fault the displacement history of the brevard zone a linear orogen scale structure in the metamorphic core of the southern appalachians has been controversial geological and seismic data indicate that the brevard zone and the taconic acadian metamorphic rocks in which it resides are contained in a huge crystalline thrust sheet that overlies relatively unmetamorphosed platform sedimentary rocks along a major alleghanian thrust fault along a 100 km segment in south carolina and adjacent states the brevard zone contains three separate structural features all of which dip moderately se 1 the narrow rosman fault which contain tectonic breccia and slices of the buried platform sedimentary rocks 2 the brevard mylonite zone which contains mylonitic rocks that extend about 3 km on either side of the rosman fault and exhibits shear sense criteria which consistently indicate dextral strike slip 3 the brevard fault zone se of the rosman fault which contains stratified metamorphic rocks that are repeated

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

liquefaction features interpreted as seismites in the pleistocene fluvio lacustrine deposits of the neuquen basin northern patagonia abstract superbly exposed soft sediment deformation structures in pleistocene fluvio lacustrine deposits along the southern border of the depression area called bajo de anelo departamento de anelo neuquen basin have been analysed in the study area five stratigraphic sections were measured in detail facies distributions and stacking patterns show that these sediments result from the interaction between fluvial and lacustrine systems represented by cross bedded and rippled strata and varved deposits the lateral extent of the deformation is some hundred metres and the deformed bed involves the lower mid part of the 30 metre thick succession deformation affects about 1 5 m of coarse grained sand fine grained sand and rare gravel alternations the base and top of the deformed layer are defined by planar surfaces undeformed beds of similar thickness lithology and facies to the deformed layer occur above and below deformation is represented by a complex vertical succession of disturbed layers each layer shows a general load structure morphology it can be described as a multilayered unstable density gradient system in each bed a partial gravitational re adjustment occurred after liquefaction unequal loading related to lateral variation of both bed thickness and grain packing and porosity is a probable additional driving force that can be described in the undeformed beds trigger mechanism recognition for the observed liquefaction features can be based on the study of the geometry of deformed beds and on facies analysis results two key factors drive our interpretation 1 the occurrence of undeformed beds below and above the deformed bed 2 deformed and undeformed beds showing the same sedimentological features these field data allow us to exclude the action of internal erosive and or sedimentary processes such as overloading wave action etc as possible trigger agents for liquefaction since deformation is totally absent in beds with similar sedimentary features furthermore each internal erosive and or sedimentary process can be discussed and easily excluded by analysing its specific signature in the geological record having excluded every possible internal trigger autokinetic processes the observed liquefaction effects can reasonably be interpreted as seismically induced allokinetic trigger from this point of view this deformed bed is an important record of seismic activity in this sector of the neuquen basin during the pleistocene

seismogenically induced fluidization of jurassic erg sands south central utah large bodies of fluidized sandstone occur in the jurassic entrada carmel page and navajo formations at several locations in south central utah they are most abundant in the entrada sandstone where they commonly occur in clusters have a cylindrical form and have a sharp contact with their cross bedded host rock these clastic pipes are as wide as 75 m and have exposed heights of as much as 100 m some of the entrada pipes extend well into the underlying carmel redbeds other clastic pipes in the entrada sandstone are less deformed and display various degrees of brittle to hydroplastic deformation and liquefaction clastic pipes in the page and navajo sandstones are less common but are similar in size and form to those in the entrada and carmel and probably have a similar origin some massive sandstone bodies are irregular in form and have tongue like projections into the host rock implying forcible injection of fluidized sand several pipe host contacts in the entrada sandstone display small scale ring faults where relative displacement can be clearly demonstrated pipe sandstones are invariably down faulted locally as much as 5 m at two sites carmel host rock is upwarped around the entrada pipes stratified and cross bedded breccia blocks occur in many entrada pipes and preliminary petrographic analysis indicates that at least some of these breccia blocks are derived from the host rock homogeneous pipe sandstones are also petrographically similar to their entrada host rock suggesting that some pipes originate through fluidization of the fine grained entrada fluidization of the entrada must have occurred in a water saturated environment during early diagenesis but before complete lithification most probably under considerable porewater pressure although there are no known modern analogues to these huge masses of structureless sandstone they may have a small scale modern counterpart in earthquake induced sandblows these features were most probably caused by large magnitude seismic events during the middle jurassic although other possibilities cannot be ruled out at this point

imaging the shallow crust with teleseismic receiver functions summary teleseismic receiver functions rfs represent an estimate of the site response to incoming seismic energy this technique has long been a staple of the global earthquake community as rfs are sensitive to impedance contrasts associated with major discontinuities in the crust and upper mantle however there is substantial debate in the community concerning the lateral and vertical resolution limits possible using these methods due to limitations resulting from ambient noise and non uniform spatial sampling of finite frequency wave kernels here we take advantage of data from the labarge passive seismic experiment to examine these questions in more detail we find 1 that rfs can provide a robust image of the near surface 5 km structure 2 that vertical resolution may exceed 500 m and 3 that our results compare favourably to nearby wells these results indicate that rf analysis can provide high resolution images of the shallow crust which has potential value for hydrocarbon exploration

relationship between observed upper mantle structures and recent tectonic activity across the southeastern united states the lithospheric structure of the southeastern united states is a product of earlier episodes of continental collision and breakup the region is located in the interior of the north american plate away from active plate margins however there is ongoing tectonism in the region with multiple zones of seismicity uplifting arches and cenozoic intraplate volcanism the mechanisms controlling this activity and the state of stress remain enigmatic two important factors are plate strength and preexisting inherited structures here we present new tomographic images of the upper mantle beneath the southeastern united states revealing large scale structural variations in the upper mantle examples include the relatively thick lithospheric mantle of stable north america that abruptly thins beneath the paleozoic appalachian orogeny and the slow upper mantle of the proterozoic reelfoot rift our results also indicate fast seismic velocity patterns that can be interpreted as ongoing lithospheric foundering this provides a viable explanation for seismicity uplifting and young intraplate volcanism we postulate that not only tectonic inheritance but also continuing lithospheric foundering may control the ongoing activity of the region long after it became a passive margin based on distinct variations in the geometry and thickness of the lithospheric mantle and foundered lithosphere we propose that piecemeal delamination has occurred beneath the region throughout the cenozoic removing a significant amount of reworked deformed mantle lithosphere ongoing lithospheric foundering beneath the eastern margin of stable north america explains significant variations in thickness of lithospheric mantle across the former grenville deformation front

assessment of liquefaction potential for two liquefaction prone areas considering the may 20 2012 emilia italy earthquake abstract on the 20th and 29th of may 2012 two earthquakes occurred in emilia romagna region northern italy triggering extensive liquefaction of the subsoil units the consequences of liquefaction have been observed and reported by several agencies in a widespread area the most impressive liquefaction manifestations were documented in a zone 3 4 km long and 1 km wide where the villages of sant agostino san carlo and mirabello are located the existing post earthquake reports and the availability of geotechnical data provided by in situ tests consist the basic ingredients for a computation of the liquefaction potential parameters within this zone in particular the liquefaction potential index lpi and liquefaction severity number lsn indexes were evaluated and then correlated by considering liquefaction phenomena either observed on site or not thus the existing classifications of the lpi and lsn were evaluated and compared with the observed liquefaction induced deformations the latter was applied and validated for the first time within a liquefiable area using post earthquake data after the development by tonkin and taylor 2013 the outcome of this study shows that a threshold value of lpi around 13 or 14 is better to be taken into account instead of 5 for discriminating sites where liquefaction surface evidences should be expected from the non liquefied ones moreover from the correlation of the lsn values with the cases of liquefaction induced ground disruption it is concluded that the proposed threshold value of 10 fits statistically well with our dataset in addition a preliminary correlation of lpi and lsn indicates a trend that could be useful in future studies for delineating sites likely to liquefaction

progressive abandonment and planform changes of the central platte river in nebraska central usa over historical timeframes this paper presents data compiled from aerial photography general land office maps glos and discharge data from the central platte river in nebraska that quantify and provide a new understanding of channel evolution and abandonment in a braided stream analyses of aerial photographs and glos in arcmap show that channel area decreased by an average of 46 from 1938 to 2006 and that channel widths in 1858 were an average of 539 greater than in 2006 annual discharge during 1942 2006 does not show a clear long term relationship with the decrease in channel width and area rather stabilization through vegetation of bars and channel banks is cited as the major contributing factor to channel shrinkage and the development of an anabranching system within the boundaries of the 1858 channel the stabilization of anabranches and the encroachment of vegetation onto banks abandoned channels and islands have significantly impacted the riparian ecosys tem as mobile sandy bars gradually disappeared annual aerial photographs of the platte river from 1984 to 2001 show that the river responds to year to year changes in mean discharge through the formation and disappearance of in channel features such as medium size transverse bars large transverse bars open channels exposed channel surfaces laterally accreted surfaces and vegetated channel islands vegetated channel islands and stable anabranches also increased during 1984 2009 significant change has also occurred since the beginning of the twentieth century on the wood river a local tributary to the platte river the wood river experienced a long term increase in sinuosity after it occupied the abandoned north channel of the platte river which last experienced major sediment transport 350 50 years ago according to an optically stimulated luminescence date the modern wood river is also superimposed on a prehistoric meandering pattern with significantly greater meander amplitude we present the first channel abandonment model to account for the gradual abandonment of the platte river braided stream system and its evolution from a braided to an anabranching system in stage 1 the channel prominently features macroform bars comprising downstream migrating foresets in stage 2 downstream migrating dunes are deposited over channel bed features and in stage 3 there is a shift from a braided stream to a stream dominated by anabranches and only channel bed features e g three dimensional dunes are present our new model characterizes the features expected to be found in abandoned braided channels as well as more temporary features that form and are destroyed through successive stages of abandonment

relationships between earthquake magnitude source geometry and slip mechanism abstract the empirical relationships between source area source length source width and magnitude m s are investigated for globally distributed earthquakes of different slip mechanism types a total of nearly 400 events having magnitudes approximately between 4 5 and 8 5 were considered the analyses of specially selected events outlined that the regional setting has no influence on the relationships between m s and source dimensions as well as between rupture length and width instead they depend on the slip mechanism type strike slip reverse and normal oblique slip as mechanisms change from strike slip to oblique slip and further from oblique slip to reverse and normal slip sources of similar length size exhibit increasing magnitudes in steps of 0 8 1 6 in the overall mentioned spectrum of the mechanism types whereas sources of similar areas correspond to the different slip type events with magnitudes increasing in steps of 0 5 0 8 source widths increase by about three times for earthquakes of equal rupture length when the mechanism changes from strike slip to reverse and normal slip therefore it can be concluded that sources of equal length have different areas and length width ratios for various types of mechanism accordingly stress drop may be larger for strike slip sources than for sources with prevailing vertical displacement the regressions of rupture dimensions on surface wave magnitude for different single slip mechanism types restricted in most cases to the magnitude range between 5 5 and 8 0 are strongly correlated having standard deviations of 0 15 0 25 magnitude units corresponding regression coefficients are different at 95 level of significance for different slip mechanism types of each pair of correlated parameters the single slip type regressions have smaller standard deviations and higher correlation coefficients than the all slip type regressions this observation validates the conclusion about strong dependencies of source dimensions and surface wave magnitudes on slip mechanism type the results can be used to evaluate the event magnitude source area length width and mechanism type when any two of these parameters are known

cenozoic tectonic evolution of asia a preliminary synthesis abstract asia has been a major testing ground for various competing models of continental deformation due to its relatively well understood plate boundary conditions in the cenozoic exceptional exposure of active structures and strain distribution and widespread syn collisional igneous activity as a proxy for the thermal state of the mantle and crust two cenozoic orogens dominate the continent the himalayan tibetan orogen in the east induced by the india asia collision and the turkish iranian caucasus orogen in the west induced by the arabia asia collision the development of the two orogens was accomplished by shortening in the early stage followed by strike slip faulting and extension in the late stage in the himalayan tibetan orogen shortening across two discrete thrust belts at 55 30 ma in southern and northern tibet created a large intracontinental basin the paleo qaidam basin in between subsequent crustal thickening and a possible thermal event in the mantle e g convective removal of central tibetan mantle lithosphere may have raised the elevation of this early intra plateau basin up to 2 3 km to its current height collision between india and asia also caused lateral extrusion of southeast asia between 32 ma and 17 ma the latest stage of the india asia collision was expressed by north trending rifting and the development of trench facing v shaped conjugate strike slip faults in central mongolia central tibet eastern afghanistan and southeast asia in the turkish iranian caucasus orogen early crustal thickening in the orogenic interior began at or prior to 30 20 ma this style of deformation was replaced by strike slip faulting at 15 5 ma associated with further northward penetration of arabia into asia westward extrusion of the anatolia turkey block and rapid extension across the sea of crete and sea of aegean the late stage extension in both orogens was locally related to extensional core complex development the continental margin extension of east asia was developed in two stages initially in a widely distributed zone that has an east west width of 500 800 km during 65 35 ma which was followed by localized extension and opening of back arc basins associated with the development of spreading centers at 32 17 ma e g japan sea or east korea sea bohai bay and south china sea opening of the back arc basins could be induced by 1 rapid eastward migration of the western pacific trench system or 2 oblique subduction of pacific plate beneath asia that had produced a series of en echelon right slip primary shear zones linking with back arc spreading centers oriented obliquely to the strike of the nearby trench since 15 ma the eastern margin of asia became contractional in the east west direction as indicated by the collapse of back arc basins in the western pacific and the development of fold thrust belts along the eastern continental margin coeval with the contraction is widespread east west extension in siberia north china and the tibetan plateau the above observations can be explained by a change in boundary condition along the eastern margin of asia that allowed the thickened asian continent to spread eastward causing east west extension in its trailing edge and east west compression in its leading edge in west asia continental margin extension started at about 25 20 ma in the aegean and cretan regions which was associated with a rapid southward retreat of the hellenic arc the complex evolution of cenozoic deformation in asia may be explained by a combined effect of temporal changes in plate boundary conditions thermal evolution of the upper mantle perturbed by collisional tectonics and the built up of gravitational energy through crustal thickening and thermal heating although the past research in asia has treated the india asia and arabia asia convergence as separate collisional processes their interaction may have controlled the far field cenozoic deformation in asia the most pronounced result of this interaction is the creation of a northeast trending 300 400 km wide and 1500 km long zone of northwest striking right slip faults which extends from the zagros thrust belt in the south to western mongolia in the north and links with the active tian shan and altai shan intracontinental orogens cenozoic deformation and coeval igneous activity spatially overlap with one another in the himalayan tibetan and turkish iranian caucasus orogens a large cenozoic magmatic gap exists between tibet in the south and mongolia in the north where cenozoic deformation has not been associated with any coeval igneous activity finally cenozoic igneous activity is always associated with jurassic cretaceous magmatic arcs suggesting a causal relationship between the early arc magmatism and later syn collisional magmatism

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

altai megafloods the temporal context abstract pleistocene floods from ice dammed lakes in the russian altai mountains are among the largest freshwater megafloods in earth history improved dating techniques have led to new dates constraining the timing of flood erosional and depositional events in addition to a variety of interpretations and explanations of event histories a proliferation of dates may increase confusion with respect to the characteristics and chronology of the flood events in a succinct review the main ice dammed lakes features the outburst floods and their repeated formation are presented among other indicators interbedded units of lacustrine deposits and outburst flood sediments in inya river valley demonstrate conclusively that there was a series of outburst floods with significant evidence for at least three high magnitude flood events prior study focussed on the interpretation of lake sediments shorelines giant bars gravel dunes dated by radiocarbon luminescence and cosmogenic nuclide assay the literature presents sometimes contradictory findings with respect to flood chronology these different interpretations evidence and arguments are reviewed for plausibility and consistency this consideration includes methodical and technical dating problems limited bleaching for luminescence techniques low purity for cosmogenic nuclide dating contamination of samples dated by radiocarbon assay at the current stage of knowledge the main period of repeated high magnitude outburst floods occurred between 28 ka and 15 ka bp indicators of earlier events are less distinct possible younger smaller floods can be identified after 15 ka bp but it is difficult to relate these to catastrophic lake draining rather they may relate to non catastrophic draining of residual small lakes within the larger basins the termination of the lake period took place before 9 9 0 3 ka cal bp in the kuray basin and in the chuya basin before 8 2 0 2 ka cal bp indicators are lacking for any drainage events after 7 7 0 6 ka as indicated by osl ages of aeolian deposits at low elevations in the katun valley relating the outburst floods to the temporal and spatial dynamics of the impounding glacier is challenging as with regard to pleistocene glaciation several conceptual models have been established supported by field evidence that in part can be contradictory during the period of the high magnitude outburst floods the extension thickness of the impounding valley glaciers were sufficient to form deep glacial lakes around the time of the last glacial maximum lgm yet the timing of the lgm remains controversial transferring glacial chronologies from mountain areas adjacent to the russian altai mountains to the environment of the megafloods does not provide a clearer picture as there is evidence for maximum stages at mis 4 and mis 3 in addition to recent postulations of a lgm in mis 2 for the russian altai mountains the russian altai mountains are located in a climatic transitional zone across which different lgm stages could be developed due to different moisture availability and temperature chronologies the effects of spatially variable rain shadows influencing the supply of moisture from the regional prevailing winds and local moisture sources from expanded ice dammed lakes complicates the picture and require further investigations

paleozoic and grenvillian structures in the southern appalachians extended interpretation of seismic reflection data interpretive reprocessing of seismic reflection data has elucidated paleozoic and grenvillian structures in the southern appalachians the seismic data include a 7500 km grid of adcoh seisdata and cocorp reflection profiles that traverse the blue ridge and inner picdmont geologic provinces of north carolina south carolina and georgia surface geology and potential field data were used to constrain the interpretation the reprocessed seismic reflection data have delineated the internal and external geometry of the crystalline blue ridge inner piedmont allochthon including the locations of the blue ridge master decollement haycsville fault and brevard fault zone on the basis of the reprocessed data all of the major faults within the allochthonous upper crust sole in the blue ridge master decollement reflections extending to the southeast from beneath the surface location of the hayesville fault to the blue ridge thrust might be the seismic signature of a high strain zone this implies that internal deformation of the blue ridge allochthon associated with the alleghanian orogeny might have occurred farther to the west than has been previously documented from field studies relative amplitude seismic data enabled the discrimination between blue ridge inner piedmont crystalline rocks and underlying lower paleozoic shelf strata thereby delineating the blue ridge thrust the interpreted geometry constrains the top of the shelf sequence beneath the blue ridge to depths of less than 3 km this relatively shallow depth of the shelf strata together with the presence of duplex structures and bright spots that are imaged within the sequence might imply favorable conditions for hydrocarbon exploration beneath the blue ridge midcrustal reflections from within the upper to iower crust are interpreted to originate from preserved grenvillian structures that were reactivated at the basement surface during late proterozoic early cambrian extension reflection continuity is occasionally disrupted by interpreted post grenvillian pre early cambrian low density intrusions topography at the basement surface possibly caused by the intrusions is interpreted to have controlled the formation of some of the structures within the overlying allochthon including blue ridge and brevard fault zone ramps correlation of seismic time structure contour maps with available gravity data and two dimensional gravity modeling suggest that anomalies in the gravity field can be attributed to low density sources within the autochthonous crust discontinuous reflection packages from depths of 36 42 km are interpreted to originate from the mohorovi i discontinuity the reflectors trend about n15 e with a true dip of approximately 15 nw

seismically induced soft sediment deformation structures seismites around sumdo in the lower spiti valley tethys himalaya abstract soft sediment deformation structures were observed in 120 m thick fluvio lacustrine sediments exposed in the sumdo area in the lower spiti valley tethys himalaya himachal pradesh india these structures vary in their morphology and pattern and occur at eight stratigraphic levels s1 s8 spaced at irregular intervals the deformation structures include over steepened stratification diapiric flame like intrusions of clayey material or complex type recumbent folding of flame like nature pseudonodules large scale soft sediment folding faulting small scale associated with folding and sand dykes these structures are restricted to single stratigraphic layers separated by undeformed beds and can be correlated over a large distance the deformation of the soft sediments is attributed to the combined effects of fluidization liquefaction and shear stress and can be related to past seismic activity in the area recently on 19 january 1975 a major earthquake kinnaur earthquake of magnitude 6 8 caused extensive damage including ground rupturing in the sumdo kaurik area this earthquake has been related to the activation of the kaurik chango fault the deformed layers seismites reported here lie adjacent to this fault zone and can be related with episodic seismicity along this fault it is evident from this study that the kaurik chango fault has been re activated a number of times and that the area suffered at least nine major earthquakes with a magnitude of more than 6 during late pleistocene holocene time including the 1975 kinnaur earthquake

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

accuracy assessment of georectified aerial photographs implications for measuring lateral channel movement in a gis aerial photographs are commonly used to measure planform river channel change we investigated the sources and implications of georectification error in the measurement of lateral channel movement by testing how the number 6 30 and type human versus natural landscape features of ground control points gcps and the order of the transformation polynomial first second and third order affected the spatial accuracy of a typical georectified aerial photograph error was assessed using the root mean square error rmse of the gcps as well as error in 31 independent test points the rmse and the mean and median values of test point errors were relatively insensitive to the number of gcps above eight but the upper range of test point errors showed marked improvement i e the number of extreme errors was reduced as more gcps were used for georectification using more gcps thus improved overall georectification accuracy but this improvement was not indicated by the rmse suggesting that independent test points located in key areas of interest should be used in addition to rsme to evaluate georectification error the order of the transformation polynomial also influenced test point accuracy the second order polynomial function yielded the best result for the terrain of the study area gcp type exerted a less consistent influence on test point accuracy suggesting that although hard edged points e g roof corners are favored as gcps some soft edged points e g trees may be used without adding significant error based upon these results we believe that aerial photos of a floodplain landscape similar to that of our study can be consistently georectified to an accuracy of approximately f5 m with 10 chance of greater error the implications of georectification error for measuring lateral channel movement are demonstrated with a multiple buffer analysis which documents the inverse relationship between the size of the buffers applied to two channel centerlines and the magnitude of change detected between them this study demonstrates the importance of using an independent test point analysis in addition to the rsme to evaluate and treat locational error in channel change studies d 2005 published by elsevier b v

soft sediment deformation in contemporary reservoir sediment a repository of recent major earthquake events in garhwal himalaya abstracttwo discrete 10 20 cm thick zones of soft sediment deformation ssd structures in horizontal beds occur in a 2 35 m thick sandbar in the asan reservoir in the northwestern sub himalaya the sediment column shows uninterrupted fluviolacustrine deposition since 1975 the depositional and deformational features boundary conditions and sedimentation rate suggest that the discrete ssd features formed in an apparent reverse density gradient and were triggered by the 1991 uttarkashi and 1999 chamoli earthquakes these triggering events occurred within 100 150 km of the reservoir which lay in intensity zones v vi the observations correspond well to the empirical relationship between distances to a liquefaction zone from an epicenter the highly liquefiable sediments in the asan reservoir provide a unique depositional and tectonic setting to record ssd triggering of ssd by contemporary seismic events demonstrates the validity of interpretations of similar causes of ssd in older sediments this is pr

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

a fluctuating ice front over an esker near ryssjon s sweden as a cause of a giant load cast abstract a well exposed section in an esker near ryssjon s sweden strongly affected by several phases of glacitectonism showed two phenomena that are uncommon and that seem to have a causal relationship the first phenomenon is the occurrence of a load cast consisting predominantly of gravel in deposits formed just inside or outside a tunnel mouth the load cast is over 3 m high and 8 m wide a size that has previously not been described from unconsolidated sediments two nearby somewhat smaller load casts consisting mainly of sand also have dimensions of over 2 m indicating that the formation of huge load casts was apparently a feature related to the special conditions under which loading could develop at this site the second remarkable feature is that not only is a till present in the succession above the load cast thus indicating re advance of the ice but deposits overlying this till are also deformed by glacitectonism proving that at least a second phase of ice re advance must have occurred this situation has not previously been documented it is concluded that the varying differential overburden of sediment and particularly the retreating and re advancing ice in this area were responsible for the formation of the extremely large load casts possibly triggered by seismic shocks related to isostatic adjustment caused by oscillations of the ice front

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

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

integrating seismic reflection and geological data and interpretations across an internal basement massif the southern appalachian pine mountain window usa the southern appalachian pine mountain window exposes 1 1 ga grenvillian basement and its metasedimentary paleozoic cover through the allochthonous inner piedmont the issue of whether the crustal block inside the window was either transported above the master appalachian late alleghanian decollement or is an autochthonous block that was overridden by the decollement has been debated for some time new detrital zircon geochronologic data from the cover rocks inside the window suggest this crustal block was derived from gondwana but docked with laurentia before the alleghanian event reprocessed deep seismic reflection data from west central georgia pr and poststack noise reduction amplitude variation analysis and prestack depth migration indicate that a significant band of subhorizontal reflections occurs almost continuously beneath the window collinear with the originally recognized decollement reflections north of the window a marked variation in the decollement image from strong and coherent north of the window to more diffuse directly beneath the window is likely a partial consequence of the different geology between the inner piedmont and the window the more diffuse image beneath the window may also result from imaging problems related to changes in topography and fold of cover i e signal to noise ratio two alternative tectonic models for the pine mountain window can partially account for the observed variation in the decollement reflectivity 1 the pine mountain block could be truncated below by a relatively smooth continuation of the decollement the window would thus expose an allochthonous basement duplex or hors block thrust upward from the south along the late proterozoic rifted continental margin 2 the window represents localized exhumation of autochthonous basement and cover along a zone of distributed intrabasement shearing directly beneath the window either model is viable if only reflector geometry is considered model 1 is favored if both geometry and kinematics of blue ridge piedmont thrust sheet emplacement are incorporated in either model the southern margin of the window merges to the west with the iapetan early alleghanian central piedmont suture which juxtaposes north american affinity piedmont rocks to the north and exotic panafrican rocks of the carolina avalon terrane to the south immediately south of the window this suture dips southward and merges in the lower crust with the late alleghanian suture joining the appalachians with gondwana

shear wave reflectivity anisotropies poisson s ratios and densities of a southern appalachian paleozoic sedimentary sequence abstract the physical properties of a sequence of paleozoic sedimentary rocks have been examined in detail with an emphasis on laboratory measurements of density shear wave velocity shear wave splitting and vp vs ratios seismic properties of 147 cores from 49 rock samples collected from the thorn hill sedimentary sequence of eastern tennessee are examined in terms of implications for future seismic studies in the southern appalachians the shear wave velocities of these rocks are strongly influenced by the relatively high shear wave velocity of quartz shear wave velocity anisotropy is present in most of the lithologic groups it is highest in the shales while being almost insignificant in the dolostones the related phenomenon of shear wave splitting occurs to some degree in all of the lithologies studied and at high pressures originates from mineral orientation splitting due to preferred mineral orientation is most prominent in the shales but also is significant in some of the carbonates compressional to shear velocity vp vs ratios of approximately 1 82 dolostones and 1 95 limestones effectively characterize the carbonates while other lithologies display wider ranges of vp vs primarily due to the influence of accessory minerals such as quartz densities of the sample suite range from 2 34 g cm3 shale to 2 86 g cm3 dolostone using average data for each lithologic group to calculate normal incidence reflection coefficients significant differences in the shear and compressional reflectivity of hypothetical interfaces are found normal incidence shear and compressional wave synthetic seismograms approximating the subsurface reflectivity of the entire thorn hill section indicate that three zones of high amplitude reflections would be seen on reflection records obtained over this 3327 m thick sequence overall the shear and compressional synthetics are similar in appearance differences are seen at some interfaces in the mississippian devonian interval which are more reflective to shear waves and in the ordovician martinsburg formation which appears more reflective to compressional waves

lake sediment based paleoseismology limitations and perspectives from the swiss alps abstract in regions with moderate seismicity and large intervals between strong earthquakes paleoseismological archives that exceed the historical and instrumental timescale are needed to establish reliable estimates of earthquake recurrence for long return periods in several regions lake sediments have shown to be suitable for paleoseismological studies by causally linking characteristic sedimentological features to historic earthquakes studies on single lakes however do neither allow determining the paleoepicentre nor the paleomagnitude for the potential paleoearthquakes here we compile using shaking induced mass movements and micro deformations summarized as sedimentary event deposits seds the sedimentary paleoseismic record of 11 lakes from switzerland over the last 10 000 years the large dating uncertainty attributed to such deposits up to 250 years does not allow us to conclusively test for one large earthquake hypothesis when comparing the different lake records and therefore represents one of the major limitations of this approach instead using a new approach of exploring the normalized frequency of occurrence averaged over a larger area the compiled dataset reveals striking periods of enhanced occurrence of seds in the studied lakes during several phases of the past 10 000 years centered at 9700 6500 and during the last 4000 cal yr bp moreover we use a calibrated intensity attenuation relation in order to model scenarios of possible epicentral areas and ranges of magnitudes of paleoearthquakes we differentiate two cases i a single earthquake scenario if seds occur simultaneously in various studied lakes or ii a multi earthquake scenario if seds in the studied lakes cluster within a time interval the modelled scenarios allow us to propose maximally possible magnitudes of large paleoearthquakes constituting an important input for seismic hazard assessment in the swiss alps

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

tectonic implications of new appalachian ultradeep core hole adcoh seismic reflection data from the crystalline southern appalachians summary some 180 km of new vibroseis profiles have been acquired in the southern appalachian inner piedmont brevard fault zone and eastern blue ridge as part of the adcoh project site investigation these data are of the highest quality yet obtained in a crystalline terrane in the us perhaps in the world and reveal several conclusions that should have a direct bearing upon the world wide nature of composite crystalline thrust sheets and their modes of interaction with the platform rocks beneath strong reflections previously interpreted as the base of the crystalline sheet are clearly part of the platform sedimentary clastic rocks sequence resting upon the autochthonous basement and early palaeozoic rift basins this reflection package and related transparent zones are clearly repeated beneath the crystalline sheet indicating a complex of thrusts repeating units within the platform succession reflectors granitoid amplibolite contacts in the crystalline sheet in the inner piedmont represent recumbent folds of similar wavelengths and amplitudes to folds mappable on the surface duplexing of platform rocks beneath the crystalline sheet appears to have resulted in doming of the crystalline sheet similarly duplex formation in the platform was probably controlled by both the thickness of the crystalline sheet and the rheological properties of the platform succession

reprocessing and enhanced interpretation of the initial cocorp southern appalachians traverse abstract reprocessing of the 1978 1980 cocorp southern appalachian seismic reflection data has produced improved images of structures related to the emplacement of the blue ridge inner piedmont allochthon the results enhance and extend the interpretation presented previously that the blue ridge and inner piedmont are allochthonous above a shallow and shallow dipping detachment that can be followed from outcrop at the blue ridge valley and ridge transition to at least beneath the carolina terrane the continuity of reflections in the new images supports the interpretation that the southern appalachian detachment is not rooted on the east side of the inner piedmont but rather projects as a low angle detachment or zone of decoupling to beneath the coastal plain an implication of this geometry is that terranes such as the carolina terrane between autochthonous north america and the alleghanian suture beneath the coastal plain are detached thin flakes

large earthquakes in the katun fault zone gorny altai paleoseismological and archaeoseismological evidence abstract paleoseismological and archaeoseismological research in the katun fault zone in gorny altai reveals soft sediment deformation structures ssds in late quaternary sediments that fill the yaloman graben ssds seismites were produced by large paleoearthquakes m 5 5 5 along the katun fault that occurred about 150 and 90 ka in the 38 19 and 19 12 5 ka intervals and after 12 5 ka the event after 12 5 ka within the graben had a magnitude of ms 7 2 7 6 traces of another event shaking intensity i v esi 2007 intensity scale timed in the range from the 3rd century bc to the 1st century ad were discovered during studies of a scythian necropolis at the chultukov log 1 site located within the manzherok graben in the northern end of the katun fault burial mounds near a mountain slope at the site are damaged by colluvium rocks of the same colluvium are scattered over 25 m off the slope and deform burial structures cairns and stone rings and inner stone walls of grave chambers as well as the primary anatomical position of buried bodies including those in burials not damaged by colluvium from outside thus the katun fault was an active structure generating large earthquakes from the middle pleistocene through the holocene

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

imaging crustal structure beneath the southern appalachians with wavefield migration to constrain crustal structures in the southern appalachians and the suture zone with the gondwanan affinity suwannee terrane we applied the 2d grt wavefield migration method to the scattered incident p wavefield recorded by the earthscope southeastern suture of the appalachian margin experiment and adjacent transportable array stations we resolve the root of thickened crust beneath the high topography of the blue ridge mountains and estimate its density contrast with the mantle to be only 104 20 kg m3 a weak velocity contrast across the crustal root moho is observed and may be related to an ongoing crustal delamination event possibly contributing to local tectonic rejuvenation beneath the suwannee terrane we confirm prior observations of a gently south southeastward dipping crustal suture indicating the terminal collision of laurentia and gondwana involved several hundred kilometers of overthrusting

estimating crustal thickness using sspmp in regions covered by low velocity sediments imaging the moho beneath the southeastern suture of the appalachian margin experiment sesame array se atlantic coastal plain

characterizing braided rivers in two nested watersheds in the source region of the yangtze river on the qinghai tibet plateau abstract large and complex braided channels 1 km wide in the source region of the yangtze river sryr on the qinghai tibet plateau china are characterized by a unique alpine environment with very high elevations and glacier sources yet little is known about the morphological complexity and changes of large braided channels owing to the scarcity of hydrological and topographical data in this study we provided the first insight into these issues using compiled long term several decades climatic and suspended sediment data and landsat images of braided channels in two nested headwater watersheds i e tuotuo and tongtian river watersheds in the sryr analysis of annual and monthly mean temperature precipitation and water discharges illustrated the nature of the hydrological regime and their response to glacier melting in the two watersheds examination of annual mean suspended sediment loads and concentrations c led to two sediment rating curves and generally similar c values between the two watersheds among a suite of morphological indices for braided rivers braiding intensity may be quantified using four different ones after comparing the indices we showed that they had similar ability of characterizing braiding patterns and adopted branch count index bit3 for further analysis we found that bit3 was linearly correlated with active valley width wr during both flood and dry seasons for the 17 selected braided reaches distributed within the two nested watersheds in addition braiding density defined as the ratio of bit3 to wr remained approximately unchanged irrespective of elevations and locations of these reaches indicating clearly that morphological structures of braided channels are spatially uniform in the sryr along the main channels of the two nested watersheds over the entire study period bit3 always reached the maximum as rw defined as the ratio of water body to exposed active riverbed area was around 0 43 furthermore rw was always positively correlated with the associated water discharge q variable degrees of braiding adjustment in response to changes of hydrological regime were represented by hysteresis loops between bit3 and q these results revealed relatively homogeneous morphologic properties of braided channels across the two nested watersheds and provided an important benchmark for future morphodynamic research on braided rivers in the sryr

structural control on meso cenozoic tectonic reactivation and denudation in the siberian altai insights from multi method thermochronometry abstract the siberian altai forms part of the central asian orogenic belt and currently is an active intracontinental mountain belt this siberian altai orogen was shaped during multiple phases of intense mountain building and associated denudation throughout the mesozoic and cenozoic we performed a multi method thermochronometric study on the altai basement in siberia in order to distinguish these denudation episodes and to place them in an absolute time frame our data shows that inherited suture zones such as the charysh terekta ulagan sayan suture played a dominant role during this episodic deformation in the altai titanite fission track results reveal late triassic early jurassic cooling which is best expressed in intrusions close to the suture zone apatite fission track aft results reveal a second phase of steady basement cooling during the late jurassic and cretaceous in the suture aft and additional apatite u th sm he ahe data reveal a consistent late cretaceous early palaeogene phase of fast cooling we interpret the mesozoic cooling signals as far field effects of the mongol okhotsk orogeny the intense late cretaceous palaeogene basement cooling signal in the suture zone can be explained as a result of fault reactivation during the collapse of this orogen and the subsequent re organization of crustal blocks during most of the palaeogene and early neogene basement cooling stagnated indicating tectonic quiescence neogene ahe ages for the kurai range directly adjacent to the suture may reflect renewed rapid cooling as a result of denudation of the present day altai mountains we interpret this most recent cooling as an indirect consequence of stress propagation from the india eurasia collision into the caob interior which thus reached as far as southern siberia this study further demonstrates the importance of thermochrological studies on intrusions along major fault zones in order to date and distinguish fault reactivation episodes