the vallo di diano fault system new evidence for an active range bounding fault in southern italy using shallow high resolution seismic profiling range bounding normal faults can presentsignificant challenges for seis mic exploration this is the case of the fault system bounding the vallo di diano the largest intermountain basin in the southern apennines seismic belt industry reflection profiles define the large scale structure of the basin but barely image the shallow fault system due to unfavorable topographic and near surface conditions along the foothills of the eastern range we present two high resolution hr wide aperture profiles recorded attheeastern marginof thebasin acrossunreported scarpsthat affect middle late pleistocene alluvial fans and slope debris the survey is aimed at identifying possible recent faulting across these challenging terrains and at understanding the re lationship between shallow structures and the master range bounding fault at depth common depth point processing of wide aperture reflection data and first arrival tra vel time tomography provide detailed images of the upper 200 300 m and sounding evidence of recent activity along previously unknown splays of the fault system these splays dissect the mesozoic limestone bedrock and alluvial fan sequences affecting theirdepositionalpattern veryhighresolutionvpandreflectivityimagesalsogivehints ofpossiblecoseismicsurfacefaultinginholocenecolluvia theseresultshaverelevant implicationsfortheevaluationoftheseismogenicpotentialoftherange boundingfault systemandforseismichazardassessmentofthedenselyurbanizedvallodidianobasin online material table of acquisition and data processing parameters and figures showing schematic stratigraphy of the vallo di diano basin restoration of fault dis placement along the hr profile and resolution of the p velocity tomographic images for the vhr profile

glacial outburst floods and loess sedimentation documented during oxygen isotope stage 4 on the columbia plateau washington state abstract stratigraphy and age control of late pleistocene loess associated glacial outburst flood deposits and flood cut unconformities in the channeled scabland washington state united states indicate a significant cordilleran ice sheet advance during marine oxygen isotope stage 4 glacial outburst flood deposits from stage 2 classic bretz flood deposits ca 21 to 13 ka and related features in the channeled scabland overlie a widespread layer of loess that contains buried soils and the mount st helens set c tephra ca 46 ka this loess in turn overlies deposits of the penultimate episode of giant outburst floods and an unconformity cut by those floods regional trends in the thickness texture and overall composition of the older loess are strikingly similar to those from the youngest loess known to be derived from stage 2 flood deposits we conclude that the older loess also is derived from fine grained flood deposits luminescence ages tephrochronology and soil development rates indicate that the bulk of deposition of the older loess occurred during stage 3 following glacial outburst flooding marked by a regional flood cut unconformity the apparent cyclical pattern of cold climate buried soils flood deposits and thick loess accumulations demonstrate that sediment supply renewed by flood episodes is a major control on accumulation of loess on glacial timescales

dual simulations of fluid flow and seismic wave propagation in a fractured network effects of pore pressure on seismic signature summary fluid flow in the earth s crust plays an important role in a number of geological processes in relatively tight rock formations such flow is usually controlled by open macrofractures with significant implications for ground water flow and hydrocarbon reservoir management the movement of fluids in the fractured media will result in changes in the pore pressure and consequently will cause changes to the effective stress traction and elastic properties the main purpose of this study is to numerically examine the effect of pore pressure changes on seismic wave propagation i e the effects of pore pressures on amplitude arrival time frequency content this is achieved by using dual simulations of fluid flow and seismic propagation in a common 2 d fracture network note that the dual simulations are performed separately as the coupled simulations of fluid flow and seismic wave propagations in such fracture network is not possible because the timescales of fluid flow and wave propagation are considerably different typically fluid flows in hours whereas wave propagation in seconds the flow simulation updates the pore pressure at consecutive time steps and thus the elastic properties of the rock for the seismic modelling in other words during each time step of the flow simulations we compute the elastic response corresponding to the pore pressure distribution the relationship between pore pressure and fractures is linked via an empirical relationship given by schoenberg and the elastic response of fractures is computed using the equivalent medium theory described by hudson and liu therefore we can evaluate the possibility of inferring the changes of fluid properties directly from seismic data our results indicate that p waves are not as sensitive to pore pressure changes as s and coda or scattered waves the increase in pore pressure causes a shift of the energy towards lower frequencies as shown from the spectrum as a result of scattering attenuation another important observation is that the fluid effects on the wavefield vary significantly with the source receiver direction that is the azimuth relative to the fracture orientation these results have significant implications for the characterization of naturally fractured reservoirs using seismic methods and may impact on experimental design to infer such attributes in a real reservoir situation particularly in acquiring time lapse seismic data

holocene paleoseismicity temporal clustering and probabilities of future large m 7 earthquakes on the wasatch fault zone utah the chronology of m 7 paleoearthquakes on the central five segments of the wasatch fault zone wfz is one of the best dated in the world and contains 16 earthquakes in the past 5600 years with an average repeat time of 350 years repeat times for individual segments vary by a factor of 2 and range from about 1200 to 2600 years four of the central five segments ruptured between 620 30 and 1230 60 calendar years b p the remaining segment brigham city segment has not ruptured in the past 2120 100 years comparison of the wfz space time diagram of paleoearthquakes with synthetic paleoseismic histories indicates that the observed temporal clusters and gaps have about an equal probability depending on model assumptions of reflecting random coincidence as opposed to intersegment contagion regional seismicity suggests that for exposure times of 50 and 100 years the probability for an earthquake of m 7 anywhere within the wasatch front region based on a poisson model is 0 16 and 0 30 respectively a fault specific wfz model predicts 50 and 100 year probabilities for an m 7 earthquake on the wfz itself based on a poisson model as 0 13 and 0 25 respectively in contrast segment specific earthquake probabilities that assume quasi periodic recurrence behavior on the weber provo and nephi segments are less 0 01 0 07 in 100 years than the regional or fault specific estimates 0 25 0 30 in 100 years due to the short elapsed times compared to average recurrence intervals on those segments the brigham city and salt lake city segments however have time dependent probabilities that approach or exceed the regional and fault specific probabilities for the salt lake city segment these elevated probabilities are due to the elapsed time being approximately equal to the average late holocene recurrence time for the brigham city segment the elapsed time is significantly longer than the segment specific late holocene recurrence time

chemistry of modern soils as a guide to interpreting precambrian paleosols precambrian paleosols are potentially one of our best sources of information about the composition of the atmosphere early in earth s history to be used this way however an alteration profile must be shown to be an in situ product of vadose processes data from modern soils show that the ratios of less mobile elements such as zr ti and al can be used as a preliminary screen to test for the in situ nature of a profile if the ti zr ratio departs from that of the host rock by more than 40 or the ti al ratio departs by more than 50 for moderate degrees of weathering then a significant allochthonous contribution to the profile is indicated this technique correctly separates in place from allochthonous horizons when applied to independent data from two modern profiles a review of published precambrian profiles identifies two often cited examples denison and pronto as suspect based on these criteria in the interpretation of paleoatmospheres it is also necessary to show that fe is controlled not b

an evaluation of geochemical weathering indices in loess paleosol studies abstract applying geochemical proxies as measure for the weathering intensity of paleosols and sediments such as loess the quaternary scientist is confronted with various element ratios that have been proposed in literature this paper gives an overview on the principle of geochemical weathering indices different types of indices are evaluated with respect to the suitability for loess paleosol sequences regarding the special characteristics of this type of sediments and paleosols case examples in this study are key sections in southeastern and eastern europe the loess paleosol sequences batajnica stari slankamen serbia mircea voda romania and stary kaydaky ukraine which represent archives of the late and mid pleistocene climate change of the region considering element behavior during weathering or diagenesis the chemical proxy of alteration cpa i e the molar ratio al2o3 al2o3 na2o 100 is proposed as the most appropriate index for silicate weathering the cpa was evaluated against commonly used weathering indices including the chemical index of alteration cia the chemical index of weathering ciw the plagioclase index of alteration pia the index b of kronberg and nesbitt and the ba sr and rb sr ratio depth profiles of sr type indices e g ba sr rb sr are likely to be influenced by the dynamics of secondary carbonate on the other hand common na type indices e g cia pia ciw may suffer from uncertainties in separating carbonate ca from silicate ca or from biases due to k fixation illitization the cpa is insensitive against such effects additionally using the cpa as with other na type indices provides the possibility to evaluate the homogeneity of the parent material regarding the relevant host minerals via the a cn k diagram

seismic attenuation in faroe islands basalts we analysed vertical seismic profiling vsp data from two boreholes at glyvursnes and vestmanna on the island of streymoy faroe islands to determine the magnitude and causes of seismic attenuation in sequences of basalt flows the work is part of seifaba a major project integrating data from vertical and offset vsp surface seismic surveys core samples and wireline log data from the two boreholes values of effective seismic quality factor q obtained at glyvursnes and vestmanna are sufficiently low to significantly degrade the quality of a surface reflection seismic image this observation is consistent with results from other vsp experiments in the north atlantic region we demonstrate that the most likely cause of the low values of effective q at glyvursnes and vestmanna is a combination of 1d scattering and intrinsic attenuation due to seismic wave induced fluid flow within pores and microcracks tests involving 3d elastic wave numerical modelling with a hypothetical basalt model based on field observations indicate that little scattering attenuation is caused by lateral variations in basalt structure

fracture properties from seismic scattering the seismic trace is a complex aggregate of reflected and scattered signals from subsurface formation interfaces and heterogeneities although many varieties of random noise may also be present in the trace we know from reacquiring the same seismic survey that seismic data are highly repeatable indicating that significant information about the subsurface is contained in the trace but not yet used by our standard analysis methods seismic scattering is a type of signal contained in the data that is generally not utilized

investigating the architecture of the paganica fault 2009 mw 6 1 earthquake central italy by integrating high resolution multiscale refraction tomography and detailed geological mapping this article has been accepted for publication in geophysical journal internationa 2017 published by oxford university press on behalf of the royal astronomical society all rights reserved

evidence for active folding and faulting at the northern apennines mountain front near bologna italy from high resolution seismic reflection profiling 1 we have acquired and processed an 2 km long high resolution seismic reflection profile across a segment of the northern apennine mountain front italy west of the city of bologna the profile constrained by several wells targets a long postulated shallow blind or emergent thrust called the pede apenninic thrust fault despite decades of reflection seismology in this part of the apennines a shallow or emergent structure consistent with the surface geology has yet to be definitively identified a problem likely caused by the topography of the apennine front and the traditional focus on deep hydrocarbon targets where the first 0 5 km of strata is poorly imaged our seismic data show an 300 m deep high resolution picture of the po foreland as it meets the apennine mountain front all imaged reflectors are continuous at the mountain front and are foreland dipping showing clear growth relationships higher angle reflectors are interpreted as faults our interpretation includes a possible hinterland dipping blind thrust and surface normal faults which offset late pleistocene holocene deposits as much as 60 m long term slip rates of 0 1 0 25 mm yr that disrupt but do not conceal the growth strata relationships vp tomographic imaging also suggests coseismic surface faulting in holocene colluvium these results have implications relevant for the effective data collection and processing techniques for these kinds of shallow active structures as well as a re evaluation of the seismogenic potential of densely populated cities like bologna along the apennine mountain front

imaging the structural style of an active normal fault through multidisciplinary geophysical investigation a case study from the mw 6 1 2009 l aquila earthquake region central italy firb abruzzo high resolution analyses for assessing the seismic hazard and risk of the areas affected by the 2009 april 6 earthquake no rbap10zc8k 005

tomographic imaging of late quaternary faulting oquirrh mountains utah 1 seismic tomography can be used to image colluvial material in the subsurface by inverting first arrival travel times for velocity colluvial material deposited at the base of a fault scarp free face often appears as a low velocity zone lvz on a tomogram because it is generally less compacted and cemented than the surrounding alluvium a tomogram generated from a forward model of a synthetic velocity structure successfully images two lvzs stacked in the hanging wall of a normal fault the mercur fan oquirrh mountains utah provides an opportunity to look for stacked lvzs in a distributed fault zone three tomographic images across fault scarps on an intermediate age alluvial fan can be used to identify two stacked low velocity zones interpretation of a fourth tomogram is less conclusive these two low velocity zones are interpreted as colluvial packages separated by higher velocity alluvial material and suggest that tectonic activity is interspersed with pulses of fan building

seismic attenuation of atlantic margin basalts observations and modeling paleogene basalts are present over much of the northeastern atlantic european margin in regions containing significant thicknesses of layered basalt flows conducting seismic imaging within and beneath the volcanic section has proven difficult largely because the basalts severely attenuate and scatter seismic energy we use data from a vertical seismic profile vsp from well 164 07 1 that penetrated 1 2 km of basalt in the northern rockall trough west of britain to measure the seismic attenuation caused by the in situ basalts the effective quality factor qeff of the basalt layer is found from the vsp to be 15 35 which is considerably lower more attenuative than the intrinsic attenuation measured on basalt samples in the laboratory we then run synthetic seismogram models to investigate the likely cause of the attenuation full waveform 1d modeling of stacked sequences of lava flows based on rock properties from the same well indicates that much of the seismic attenuation observed from the vsp can b

evolution of eureka flat a dust producing engine of the palouse loess usa sedimentologic stratigraphic and pedologic evidence demonstrates that eureka flat ef a narrow 80 km long deflation plain in south central washington usa is the source for the thick and widespread loess of the palouse region located in the southern columbia plateau ef has been a depocenter for abundant clay to sand sized sediment derived from repeated glacial outburst floods that swept through the area during the pleistocene prevailing sw winds that were funneled across ef remobilized flood sediment into sand dunes sand sheets and loess an eolian sand sheet buried beneath 1 8 m of loess at the downwind end of ef attests to bioclimatically driven changes in the style of eolian deposition the depositional transition from sand sheet to loess is characterized by a change from wind rippled strata to structureless bimodal sand and silt with insect burrows and rhizoliths to unimodal sandy loess soil moisture and density of dust trapping vegetation control where sand dunes and loess accumulate up to 4 5 m of post lgm loess mantles the landscape adjacent to and downwind from ef some of the thickest loess deposits owe their origins to the sequestering of eolian sand particles by topographic traps such as the touchet river and its tributary valleys the removal of saltating sand from the eolian system promotes thick accumulation of loess downwind of topographic traps patterns of loess accumulation across the columbia plateau are identified on isopach maps of major pre and post lgm loess units and show that ef has been the major engine for the production of atmospheric dust and loess during both times

magnetostratigraphic evidence from the cold creek bar for onset of ice age cataclysmic floods in eastern washington during the early pleistocene this study provides a detailed magnetostratigraphy of sediments composing the cold creek cataclysmic flood bar in the pasco basin washington our interpretation suggests onset of missoula floods or similar events prior to 1 1 myr later than previously suggested by bjornstad et al bjornstad b n fecht k r pluhar c j 2001 long history of pre wisconsin ice age cataclysmic floods evidence from southeastern washington state journal of geology 109 6 695 713 nonetheless these data suggest that channeled scabland features formed over a much longer timespan than commonly cited that continental ice sheets of the early pleistocene reached as far south as those of the late pleistocene and that similar physiography existed in eastern washington and perhaps montana to both generate and route missoula flood like events this study adds paleomagnetic polarity results from 213 new samples of silts and sands derived from nine new drill cores penetrating the cold creek cataclysmic flood bar to our previous database of 53 samples from four boreholes resulting in a much more robust and detailed magnetostratigraphy rock magnetic studies on these sediments show pure magnetite to be the predominant remanence carrying magnetic mineral ruling out widespread remagnetization by secondary mineralization the magnetostratigraphy at eastern cold creek bar is characterized by a normal polarity interval bracketed by reversed polarities equating the normal zone with the jaramillo subchron 0 99 1 07 myr affords the simplest correlation to the magnetic polarity timescale western cold creek bar was likely deposited during the brunhes chron 0 0 78 myr since it exhibits mainly normal polarities with only two thin reversed polarity horizons that we interpret as magnetic excursions during the brunhes

reconstruction of the late pleistocene grassland of the columbia basin washington usa based on phytolith records in loess abstract silica phytoliths preserved in three loess sections in southeastern washington state revealed a 100 000 year history of the columbia basin grassland changes in the proportion of different morphotypes indicate large shifts in vegetation composition during the last 100 ka a low elevation section 677 m asl near the center of the basin provided a record of alternating xeric festuca poa and mesic festuca koeleria grassland the middle slope section 1095 m asl supported picea abies or pinus ponderosa forest or non analog parkland at different times some trees were present at or near the site even during the last glacial maximum the highest site 1220 m asl supported stipa festuca and poa dominated grassland with some artemisia shrub during most of the late pleistocene but supports a coniferous forest today variations in vegetation can be explained as a response to changes in large scale climatic controls grasslands and shrub steppe were apparently more widespread and forests more restricted than today during the marine isotope stages 2 and 4 probably as a result of cooler and drier conditions the three new records are well correlated with previously published paleo reconstructions based on phytolith cicada burrow and stable isotope data from a nearby kp 1 loess section carp lake pollen record and global ice volume variations

a high resolution seismic reflection and gravity survey of quaternary deformation across the wasatch fault utah high resolution reflection seismic and detailed gravity data were acquired across an exposure of the wasatch fault utah near a trench excavated for dating of quaternary fault displacement the seismic data across the quaternary wasatch fault are interpreted to show three subparallel surfaces dipping from 70 w at the surface to an estimated 45 w at 40 m displaced unconsolidated sediments and colluvial material abutting the main fault detailed gravity data were of assistance in mapping the sediment bedrock interface from the rangefront across the wasatch fault zone a combined high resolution seismic and gravity interpretation reveals that bedrock is 80 m deeper in the hanging wall than in the footwall suggesting that displacement has occurred on several en echelon blocks in the near surface of the wasatch fault movement on the most recent wasatch fault trace began prior to deposition of pleistocene lacustrine sediments the twelvefold high resolution reflection seismic data were recorded and processed to achieve vertical resolution of approximately 1 m and horizontal resolution fresnel zone radii of as good as 5 m on the deepest reflecting interfaces at 40 m reasonably high frequencies and good bandwidth about 80 300 hz in the stacked seismic data permitted a direct comparison to the trenched cross section good correlation between the trench stratigraphy and structure and the seismic data suggests high resolution seismic data can be a valuable tool for analyzing near surface faulting in unconsolidated sediment and for locating potential trench sites

transient electromagnetic investigations in a tectonic domain of the kachchh intraplate region western india a morphotectonic study of the kachchh mainland fault

new stratigraphic markers in the late pleistocene palouse loess novel fossil gastropods absolute age constraints and non aeolian facies four stratigraphic sections in the southern part of the columbia basin preserve a sequence of aeolian and non aeolian sediments ranging in age from 9ae43 to 47ae0 14 c ka based on accelerator mass spectrometry radiocarbon dating of fossil molluscs geochemistry of cascade mountain sourced tephra and association with formally recognized pedostratigraphic units the washtucna and old maid coulee soils study sections are interpreted as representing concurrent deposition of loess and distal missoula flood rhythmites in valleys tributary to main drainages backflooded during the missoula floods and formation of carbonate and iron rich soils sediments belong to the formally recognized l 1 and l 2 loess units established for the palouse loess which were deposited in the columbia basin subsequent to events of glacial outburst flooding sediments associated with the mount saint helens set s and set c tephras in the study sections preserve a fauna of five species of gastropod mollusc which have not been reported previously from sediments of late pleistocene age in the palouse region the fossils comprise two distinct faunules stratigraphically separated by the mount saint helens so tephra accelerator mass spectrometry radiocarbon dating of the fossils collected above the tephra in two of the sections yielded ages of 12ae48 0ae06 and 9ae43 0ae05 14 c kyr these ages suggest that independent determinations of the 13ae35 14 c kyr age of the so tephra in other areas where missoula flood sediments are preserved are probably accurate and help to refine the age of the latest events in the most recent sequence of catastrophic glacial outburst flooding

record of pre late wisconsin giant floods in the channeled scabland interpreted from loess deposits loess deposits adjacent to flood coulees on the columbia plateau in eastern washington state record multiple episodes of pre late wisconsin cataclysmic floods evidence in the loess consists of flood cut unconformities upward fining in individual loess strata and flood deposits that consist of basaltic gravel fragments of calcified paleosols and slackwater sediment at least six episodes of floods during the pleistocene are indicated by paleomagnetic measurements tephra correlations and the stratigraphic position of flood indicators one episode of the six occurred prior to 790 ka the most recent episode before the last glacial floods occurred at 36 ka at the latest

reservoir fracture characterization from seismic scattered waves the measurements of fracture parameters such as fracture orientation fracture density and fracture compliance in a reservoir is very important for field development and exploration traditional seismic methods for fracture characterization include shear wave birefringence gaiser and dok 2001 dok et al 2001 angerer et al 2002 vetri et al 2003 and amplitude variations with offset and azimuth avoa ruger 1998 shen et al 2002 hall et al 2003 liu et al 2010 lynn et al 2010 these methods are based on the equivalent medium theory with the assumption that fracture dimension and spacing are small relative to the seismic wave length so a fracture zone behaves like an equivalent anisotropic medium but fractures on the order of seismic wave length are also very important for enhanced oil recovery and they are one of the important subsurface scattering sources that generate scattered seismic waves willis et al 2006 developed the scattering index method to extract the fracture scattering characteristics by calculating the transfer funtion of a fracture zone fang et al 2011 proposed a modification of the si method the fracture transfer function ftf method that leads to a more robust fracture characterization in this paper we use both laboratory data and field data to explore the capability of the ftf method

detecting young slow slipping active faults by geologic and multidisciplinary high resolution geophysical investigations a case study from the apennine seismic belt italy 1 the southern apennines range of italy presents significant challenges for active fault detection due to the complex structural setting inherited from previous contractional tectonics coupled to very recent middle pleistocene onset and slow slip rates of active normal faults as shown by the irpinia fault source of a m6 9 earthquake in 1980 major faults might have small cumulative deformation and subtle geomorphic expression a multidisciplinary study including morphological tectonic paleoseismological and geophysical investigations has been carried out across the extensional monte aquila fault a poorly known structure that similarly to the irpinia fault runs across a ridge and is weakly expressed at the surface by small scarps warps the joint application of shallow reflection profiling seismic and electrical resistivity tomography and physical logging of cored sediments has proved crucial for proper fault detection because performance of each technique was markedly different and very dependent on local geologic conditions geophysical data clearly 1 image a fault zone beneath suspected warps 2 constrain the cumulative vertical slip to only 25 30 m 3 delineate colluvial packages suggesting coseismic surface faulting episodes paleoseismological investigations document at least three deformation events during the very late pleistocene 20 ka and holocene the clue to surface rupturing episodes together with the fault dimension inferred by geological mapping and microseismicity distribution suggest a seismogenic potential of m6 3 our study provides the second documentation of a major active fault in southern italy that as the irpinia fault does not bound a large intermontane basin but it is nested within the mountain range weakly modifying the landscape this demonstrates that standard geomorphological approaches are insufficient to define a proper framework of active faults in this region more in general our applications have wide methodological implications for shallow imaging in complex terrains because they clearly illustrate the benefits of combining electrical resistivity and seismic techniques the proposed multidisciplinary methodology can be effective in regions characterized by young and or slow slipping active faults

changes in attenuation with depth in an ocean carbonate section ocean drilling program sites 806 and 807 ontong java plateau changes of in situ seismic attenuation with depth are estimated from full waveform acoustic logs in a soft formation rock with shear velocity less than borehole fluid velocity the relative attenuation qp 1 is computed from the variation with depth of the p wave amplitude spectrum of a single source receiver pair the method is applicable when unknown source and receiver responses of the sonic tool make other methods difficult to apply tests with synthetic data generated by a full waveform method verify that in a soft formation the decay of the p wave amplitude spectrum depends mainly on attenuation the method is applied to ocean drilling program data from holes 806b and 807a on the ontong java plateau in the western pacific ocean four attenuation logs were computed independently using data from four source receiver pairs agreement of the four logs at each site and agreement of results from the two sites suggest that the method is robust and practical the attenuation logs show a maximum attenuation between 300 and 500 m below the seafloor they agree well with compilations of high frequency attenuation versus porosity and frequency in marine sediments but are somewhat greater than results from seismic experiments possibly owing to the presence of sedimentary microbeds and the three decade difference between the seismic and sonic frequency bands

colluvial wedge imaging using traveltime and waveform tomography along the wasatch fault near mapleton utah summary four high resolution seismic surveys were conducted across the wasatch fault zone near mapleton utah the objective was twofold 1 to use velocity tomograms and reflection images to delineate fault structures and colluvial wedges to more than twice the depth of the mapleton megatrench excavated by urs personnel 2 to assess the strengths and limitations of traveltime and waveform tomography by synthetic studies and comparison of the tomogram to the ground truth seen in the megatrench log four out of the five faults within the trench area are accurately identified in the migrated image and in the tomograms and the main fault s dip angle is estimated to be between 71 and 80 two additional faults are interpreted outside the trench the faults can be delineated down to 30 m below the surface which is 20 m deeper than the excavated trench five out of six colluvial wedges found in the trench log were seen as low velocity zones lvzs in the tomogram however the biggest colluvial wedge could not be identified by either tomography method waveform tomography prevailed over ray based traveltime tomography by more clearly recovering the faults and lvzs a newly discovered lvz at a depth of 18 21 m below the surface possibly represents a colluvial wedge and is estimated to be less than 21 000 years old if this lvz is a colluvial wedge the earthquake history obtained by trenching can be extended from 13 500 to 21 000 yr with seismic tomography our results further demonstrate the capability of tomography in identifying faults and show that waveform tomography more accurately resolves colluvial wedges compared to traveltime tomography however despite the successful recovery of most faults and some but not all colluvial wedges both tomography methods show many more lvzs besides the wedges so that an unambiguous interpretation cannot be made a major part of the ambiguity in the tomograms is due to the many major faults which result in an uneven raypath coverage as our synthetic studies show hence seismic trenching will be more successful at simple fault geometries however even under optimal conditions there will be some ambiguity in the interpretation so that detected lvzs should be drilled cored and dated to determine the history of the ancient earthquakes

cosmogenic 14c in carbonate rocks abstract the rate of in situ production of cosmogenic 14 co in limestone is 18 3 atom g caco3 year corrected to high latitude and sea level based on measurements of 14 co in limestone associated with the bonneville provo shoreline complex in utah in situ cosmogenic 14 co was separated cryogenically from co2 using 14 c dead co as a carrier for in situ cosmogenic 14 co this rate of production was used to estimate an age of 4360 1220 cal year b p for the last movement on the south oquirrh mountain fault zone in northern utah and an age of at least 10 600 900 years for the penultimate event of the pleasant valley fault in northern nevada

introduction seismic wave scattering in three dimensionally heterogeneous earth the classical earth model of spherical symmetry or layered structure is undergoing a revolution the earth has been revealed to be laterally heterogeneous everywhere from the crust mantle to the core with scale from the grain size of rocks to the lowest orders of global spherical harmonics figure 1 shows the strength and scale length of heterogeneities in the crust and mantle of the earth in terms of v the perturbation index of seismic p or s wave speed defined as the r m s fractional variations of wave speed over the measured region the scale length of heterogeneities revealed by seismic waves not including the laboratory measurements of rock samples spans 8 orders of magnitude these heterogeneities with different scales have different effects to seismic waves the velocity and density heterogeneities can cause the change in waveform phase or travel time and amplitude fluctuation as well as apparent attenuation of the direct arrivals they can also generate coda waves such as the p coda s coda and lg coda caused by the lithospheric heterogeneities and precursory waves such as the scattered pkp waves as the precursors to pkikp caused by the heterogeneities near the core mantle boundary the near source or near receiver structures can modify the seismic waveforms by resonance and other effect rough topography or rough interface can cause the coupling between body wave and surface wave aligned cracks in the crust can produce the effective anisotrophy a great complexity arises when heterogeneities have interaction with anisotrophy and nonlinearity

resolution limits for crosswell migration and traveltime tomography summary equations are derived for the point scatterer response of the crosswell migration and traveltime tomography operators these formulas are used to estimate the limits of spatial resolution in reflection migration images and traveltime tomograms in particular for a crosswell geometry with borehole length l well offset 2x0 source wavelength and a centred point scatterer i show the following 1 the vertical resolution zmig of the reflection migration image is equal to 2 x0 l under the far field approximation under the fresnel approximation zmig 2 x0 l 2 2 l which says that images become better resolved with an increase in aperture and a decrease in wavelength and well offset 2 the horizontal resolution zmig of the migration image is equal to 16 x02 l2 the lateral resolution of the migrated image is worse than the vertical resolution by a factor of 8x0 l where x0 l 1 under the far field approximation 3 the vertical resolution ztomo of the traveltime velocity tomogram is proportional to x0 this estimate agrees with that of a previous study however the tomographic image of the slowness perturbation behaves as a non local cosine function along the depth axis whereas the migration image behaves as a localized squared sine function in the depth coordinate this is consistent with the empirical observation that interface boundaries are more sharply resolved by migration than by traveltime tomography 4 the horizontal resolution of the slowness image in a traveltime tomogram is equal to 4x0 l 3x0 4 a factor more than 4x0 l worse than the vertical resolution 5 for ns sources and ng geophones the dynamic range of the migrated image is proportional to nsng the dynamic range of the slowness tomogram is proportional to ngns many of the estimates for the resolution limits have simple geometrical interpretations for example the minimum vertical horizontal resolution in a migrated reflectivity section corresponds to the minimum vertical horizontal stretch that a migrated wavelet undergoes in going from the time domain to the depth domain in addition the minimum vertical horizontal resolution in a traveltime tomogram corresponds to the minimum vertical horizontal width of the wavepath at the scatterer location

loess paleosol carbonate clumped isotope record of late pleistocene holocene climate change in the palouse region washington state usa the channeled scabland palouse region of the pacific northwest pnw of the united states preserves geomorphic and pedosedimentary records that inform understanding of late pleistocene holocene paleoclimate change in a region proximal to the last glacial period cordilleran ice sheet we present a clumped 47 and conventional 18 o 13 c isotopic study of palouse loess paleosol carbonates in combination with carbonate radiocarbon 14 c dating to provide new measures of regional late last glacial 31 20 cal ka bp and holocene soil conditions average clumped isotope temperatures t 47 for last glacial palouse loess paleosol carbonates 9 4 c are significantly lower than those for holocene aged carbonates t 47 18 2 c in study sections calculated soil water 18 o vsmow values 16 2 for last glacial carbonates are also offset relative to those for holocene aged samples 11 1 whereas calculated soil co 2 13 c vpdb values are similar for the holocene 16 9 0 2 and late last glacial 16 7 1 1 periods together these paleoclimate metrics indicate late last glacial conditions of pedogenic carbonate formation in the c 3 grassland soils of the palouse were measurably colder 9 5 c than during the holocene and potentially reflect a more arid last glacial paleoclimate across the palouse findings in agreement with previous proxy studies and climate model simulations for the region

quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols abstract paleosols fossil soils are preserved throughout the geologic record in depositional settings ranging from alluvial systems to between basalt flows until recently paleosols were studied using primarily qualitative methods in recent years paleopedology has shifted from a largely qualitative field based on comparisons with modern analogues to an increasingly quantitative endeavor some of this change has been a result of applying existing techniques to new materials but many of the innovations have been the result of applying new techniques to new materials including thermodynamic modeling of soil formation isotope geochemistry and applications of empirical relationships derived from modern soils a variety of semi quantitative and quantitative tools has been developed to examine past weathering and pedogenesis and to reconstruct both paleoenvironmental and paleoclimatic conditions at the time that the paleosols formed though it is often not possible to achieve the same temporal resolution as with marine records for paleoclimatic reconstructions proxies based on paleosols are potentially a much more direct means of making paleoclimatic reconstructions because soils form at the earth s surface in direct contact with the atmospheric and climatic conditions at the time of their formation paleoclimatic and environmental properties that may be reconstructed using the new proxies include provenance weathering intensity mean annual precipitation and temperature during pedogenesis nutrient fluxes into and out of the paleosols the atmospheric composition of important gases including co2 and o2 the moisture balance during pedogenesis the soil gas composition reconstructed vegetative covering and paleo altitude

geometry and kinematics of active normal faults south oquirrh mountains utah implication for fault growth the nnw striking south oquirrh mountains normal fault zone consists of four individual faults the individual faults are arranged in a right stepping pattern in the north and a left stepping pattern in the south forming a convex shaped fault zone in map view with the apex towards the hanging wall late quaternary fault activity is characterized by 2 0 4 5 m high discontinuous fault scarps developed in both late quaternary alluvium and bedrock the fault scarps in bedrock contain evidence of two large rupture events the last large earthquake occurred prior to the highstand of the bonneville lake cycle 15 ka based on cross cutting relationship between the bonneville shoreline and the fault scarp and on comparisons of fault scarp morphology cumulative displacement patterns inferred from range crest elevations bouguer gravity data in the adjacent basin and rotation of the subsidiary faults adjacent to the west mercur fault are similar to the pattern of displacements measured across late quaternary fault scarps that is the maximum displacement is near the apex of the convex shaped fault zone where the west mercur fault is located and then tapers off towards both ends of the fault zone fault traces that range from a few meters to tens of kilometers long are characterized by two dominant orientations strike n11 w and n43 w the two orientations are separated from each other by a statistically constant angle of 33 3 slip directions concentrate on a trend of s70 w for both groups of faults perpendicular to the average strike of the fault zone these data indicate that the geometry of the fault surfaces is non cylindrical and may be composed of self similar structural ridges and troughs of variable wavelength and amplitude that are elongated parallel to slip direction the relationships between fault geometry displacement and geomorphology in the south oquirrh mountains fault zone suggests a growth model of normal faults in which apex points on the convex shaped fault sections mark the nucleation points of primary faults secondary faults developed at the ends of the primary fault step into the footwall block as the fault zone grows laterally intersecting regions between two laterally growing fault zones are concave shaped in map view

luminescence dating of loess from the northwest united states thermoluminescence tl and infra red stimulated luminescence irsl ages have been determined for loess from the columbia plateau region of southeast washington and northeast oregon u s a the irsl ed values and ages appear to be tending towards a maximum level lower than that of the tl ed values and ages in general the tl ages are in stratigraphic order and agree well with the age control in the form of 14c and tl dated tephra units derived from various eruptions of mount st helens

seismic attribute inversion for velocity and attenuation structure using data from the glimpce lake superior experiment a simultaneous inversion for velocity and attenuation structure using multiple seismic attributes has been applied to refraction data from the 1986 glimpce lake superior experiment the seismic attributes considered include envelope amplitude instantaneous frequency and travel time of first arrival data instantaneous frequency is converted to t using a matching procedure which approximately removes the effects of the source spectra the derived seismic attributes are then used in an iterative inversion procedure referred to as aft inversion for amplitude instantaneous frequency and time uncertainties and resolution of the velocity and attenuation models are estimated using covariance calculations and checkerboard resolution maps a simultaneous inversion of seismic attributes from the glimpce data results in a velocity model similar to that of previous studies across lake superior a central rift basin and a northern basin are the most prominent features with an increase in velocity near the isle royale fault although there is an indication of the central and northern basins in the attenuation model for depths greater than 4 km the separation is not evident for shallower depths this may result from microfractures masking compositional variations in the attenuation model for shallower depths attenuation q values range from approximately 60 near the surface to near 500 at 10 km depth a relationship between inverse q and velocity of q 0 0210 0 0028 v was found with a correlation coefficient of 0 96 this suggests a nearly linear inverse relationship between q l and velocity beneath lake superior which supports previous laboratory results the inverted velocity and attenuation models provide important constraints on the lithology and physical properties of the midcontinent rift beneath lake superior

seismic wave attenuation in methane hydrate bearing sediments vertical seismic profiling data from the nankai trough exploratory well offshore tokai central japan 1 data from two vertical seismic profiles vsps from the nankai trough exploratory well offshore tokai central japan are used to estimate compressional attenuation in methane hydrate mh bearing sediments at seismic frequencies of 30 110 hz we compare spectral ratio and centroid frequency shift methods for measuring attenuation to isolate intrinsic attenuation from total attenuation attenuation is computed from multiples using one dimensional synthetic vsp data from sonic and density logs the use of two different measurement methods and two vsps recorded at just 100 m separation provides an opportunity to validate the attenuation measurements no significant compressional attenuation was observed in mh bearing sediments at seismic frequencies macroscopically the peaks of highest attenuation in the seismic frequency range correspond to low saturation gas zones in contrast high compressional attenuation zones in the sonic frequency range 10 20 khz are affected by the presence of methane hydrates in the same well locations thus this study demonstrated the frequency dependence of attenuation in mh bearing sediments mh bearing sediments cause attenuation in the sonic frequency range rather than the seismic frequency range

2 d seismic trenching of colluvial wedges and faults abstract images of the depth and shape of colluvial wedges by 3 d travel time tomography can be valuable in estimating the past history of ancient earthquakes and assessing the earthquake hazard of a fault unfortunately 3 d seismic surveys can be both costly and time consuming in this paper we report our first successful results of detecting the shapes and depths of colluvial wedges with 2 d travel time tomography the locations of the colluvial wedges are along the oquirrh fault and the salt lake city segment of the wasatch fault we also report that the tomogram from one of our 2 d surveys suggests the possibility of detecting multiple colluvial wedges at depth using both reflection and tomographic images at another site clearly reveals the presence of a known shallow fault and the contact between native soil and recent fill our results suggest the synergistic use of both seismic tomography and reflection imaging we denote as seismic trenching as a means of detecting shallow colluvial wedges and faults seismic trenching has the potential to significantly expand the lateral extent and depth of investigation of paleoseismology

last glacial loess in the conterminous usa the conterminous united states contains an extensive and generally well studied record of last glacial loess the loess occurs in diverse physiographic provinces and under a wide range of climatic and ecological conditions both glacial and non glacial loess sources are present and many properties of the loess vary systematically with distance from loess sources united states midcontinent last glacial loess is probably the thickest in the world and our calculated mass accumulation rates mars are as high as 17 500 g m 2 yr at the bignell hill locality in nebraska and many near source localities have mars greater than 1500 g m 2 yr these mars are high relative to rates calculated in other loess provinces around the world recent models of last glacial dust sources fail to predict the extent and magnitude of dust flux from the mid continent of the united states a better understanding of linkages between climate ice sheet behaviour routing of glacial meltwater land surface processes beyond the ice margin and vegetation is needed to improve the predictive capabilities of models simulating dust flux from this region r 2003 elsevier ltd all rights reserved

seismic imaging of upper crustal structure using travel times from the passcal ouachita experiment a first arrival travel time inversion applied to the 1986 passcal ouachita experiment has been used to image upper crustal structure twenty one shot points every 10 km were recorded along two 100 km long segments with 400 seismographs on each segment a splined velocity model parameterization allowed for the inversion of laterally inhomogeneous models but not velocity discontinuities over 800 travel times were used in the inversion with a variable data covariance weighting the multiple source nature of the experiment design allowed the use of reciprocity relationships among 21 shot points to enhance data correlation a succession of models with velocities specified at 30 90 171 and 221 nodes were inverted for whose horizontal node spacing decreased from 100 to 12 5 km in the final 221 node model vertical node spacings of 3 0 and 1 5 km were used the results of the inversions indicate changes in depth of isovelocity lines which are interpreted as triassic fault structure based on nearby well data the final rms travel time residual is 0 045 s resolution using first arrivals deteriorates rapidly below 9 km depth three distinct velocity gradients can be correlated with geologic units surface exposed cretaceous and jurassic sediments with velocities from 3 0 tomore 3 5 km s extend to 1 5 km depth triassic rift fill sediments which do not outcrop have inverted velocities ranging from 3 5 to 4 75 km s between depths of 1 5 3 0 km paleozoic sediments are imaged by a decreased velocity gradient below a depth of 3 0 km lack of resolution at depths greater than 9 km necessitates detailed modeling of wide angle reflected phases to further constrain deeper crustal structure less

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

seismic q stratigraphy or dissipation the basic problems encountered in extracting estimates of seismic dissipation from data recorded on vertical seismic profiles are analyzed because anomalous dissipation in the subsurface is likely to be associated with conditions or lithologies of limited vertical extent a knowledge of the factors which influence the spatial resolution of an attenuation measurement is of considerable importance by introducing a statistical perspective it is possible to simulate multiple measurements in an inhomogeneous interval and to draw conclusions which apply to an entire class of impedance structures theoretical seismograms are analyzed to demonstrate that for small receiver separations neither a single measurement nor the mean value determined from multiple measurements is likely to give a good estimate of the attenuation for an inhomogeneous depth interval for small receiver separations the attenuation computed from the amplitude ratios method is much more strongly influenced by the local stratigraphy in the

1d viscoelastic waveform inversion for q structures from the surface seismic and zero offset vsp data wave attenuation is an important physical property of hydrocarbon bearing sediments that is rarely taken into account in site characterization with seismic data we present a 1d viscoelastic waveform inversion scheme for determining the quality factor q from the normal incidence surface seismic and zero offset vertical seismic profile vsp data simultaneously the joint inversion problem is solved by the damped least squares method and the inversion result is successful using synthetic data the effects of initial model thickness q value and the existence of noise were studied through a synthetic example by extracting all of the information contained in the waveforms the waveform inversion of the seismic reflection and transmission data becomes a powerful tool for estimating q for a more comprehensive image of q the tomographic inversion of q is applied to the walkaway vsp and prestack surface seismic data using the waveform inversion result as the initial model results from applying the metho

correlation of distal tephra layers in loess in the channeled scabland and palouse of washington state abstract thirty two distal tephra layers that are interbedded in quaternary loess at 13 sites in the channeled scabland and palouse were sampled as part of a regional study of the stratigraphy and chronology of dominantly windblown sediments on the columbia plateau an electron microprobe was used to determine the elemental composition of volcanic glass in all of the samples and also to determine the composition of ilmenite in 14 of them two of the distal tephra layers correlate with glacier peak eruptions 11 200 yr b p five with mount st helens tephra set s 13 000 yr b p and nine with mount st helens tephra set c ca 36 000 yr b p based on analysis of glass and ilmenite in reference pumices from glacier peak mount st helens mount mazama mount rainier and mount jefferson on the calculation of similarity coefficients for comparisons of both glass and ilmenite reference compositions with those of distal tephras and on considerations of stratigraphic position the composition of glass and ilmenite and the stratigraphic position of one distal tephra layer in the loess suggests that it is from an eruption of mount st helens at least several thousand years older than the set c eruptions glass composition and stratigraphic position of a distal tephra at another site in loess suggested a possible correlation with some layers of the pumice castle eruptive sequence at mount mazama ca 70 000 yr b p but similarity coefficients on ilmenite of only 45 and 48 fail to support the correlation and show why multiple correlation methods should be used similarity coefficients higher than 96 for both glass and ilmenite establish a correlation with mount st helens layer cw for distal layers in two widely separated sites these layers are in sedimentary successions that are closely associated with giant floods in the channeled scabland the 36 000 yr b p radiocarbon age of the mount st helens set c establishes a minimum limiting date for an episode of flooding that predates the widespread late wisconsin floods a correlation of distal tephra layers at two other sites in the scabland and palouse establishes a chronostratigraphic link to a still older episode of flooding within the brunhes normal polarity chron six distal tephra layers in pre late quaternary loess that are not correlated with known or dated eruptions have compositions and distinctive stratigraphic positions relative to magnetic reversal boundaries that make them key markers for future work

shallow high resolution geophysical investigation along the western segment of the victoria lines fault island of malta abstract the victoria lines fault island of malta is a 15 km long and n260 striking segmented normal fault system which is probably inactive since the late pliocene in the westernmost part the fomm ir rih segment displays comparable geologic throw and escarpment height 150 170 m moreover its hangingwall hosts thin patches of middle pleistocene clastic continental deposits red beds which are poorly preserved elsewhere we acquired two seismic transects by collecting ambient vibration recordings processed by using horizontal to vertical spectral ratios complemented by one high resolution 2 d refraction tomography survey crossing this fault where it is locally covered by red beds and recent colluvial deposits we found a resonance peak at 1 0 hz in the hangingwall block whereas clear peaks in the range 5 0 10 0 hz appear when approaching the subsurface fault and we relate them to the fractured bedrock within the fault zone the best fit tomographic model shows a relatively high vp shallow body vp 2200 2400 m s that we relate to the weathered top of the miocene upper coralline limestone fm bounded on both sides by low vp regions 230 m s above the weathered top bedrock our results depict a clear seismic signature of the victoria lines fault characterized by low seismic velocity and high amplification of ground motion we hypothesize that during the middle pleistocene faulting may have affected the basal part of the red beds so that this part of the investigated complex fault system may be considered inactive since 0 6 myr ago

palaeoseismicity of the oquirrh fault utah from shallow seismic tomography the magnitude and frequency of normal fault palaeoearthquakes are usually determined by trenching studies that ascertain the size and number of colluvial wedges along the fault such information can be invaluable in predicting the seismic hazard and potential for a future earthquake in that region digging trenches across normal faults however is environmentally intrusive expensive and limited in the penetration depth to overcome these problems we propose the use of 3 d seismic tomography as a means to identify the shapes and sizes of colluvial wedges along normal faults as an example 2 d and 3 d seismic surveys were conducted across the oquirrh fault utah with the purpose of imaging the normal fault structure to a depth of about 10 m results show that the 3 d tomogram clearly delineates the fault zone and a colluvial wedge both of which correlate extremely well with the geological cross section interpreted from an adjacent trench the thickness of the colluvial wedge image is used in conjunction with a seismic section to compute an estimate of a 6 8 moment magnitude earthquake for the most recent event on this fault which is in close agreement with the 7 0 estimate based on a nearby trenching study these tomographic results demonstrate for the first time that seismic imaging methods can be used in some cases to estimate unambiguously the shapes of colluvial wedges and the sizes of prehistoric earthquakes thus seismic tomography has the possibility of providing cheaper deeper and wider but less resolved images of fault systems than the intrusive excavation of trenches across faults

late quaternary stratigraphy of loess in the channeled scabland and palouse regions of washington state abstract loess deposits of late quaternary age in the channeled scabland and western palouse regions of washington state contain distinctive sequences of calcic buried soils loess layers tephra layers and stratigraphic unconformities caused by cataclysmic flooding four new soil stratigraphic units the sand hills coulee soil washtucna soil old maid coulee soil and the devils canyon soil are recognized across a 100 km transect the pedostratigraphic correlations are strengthened by two tephra layers found at several sites that are correlative with the mount st helens set s radiocarbon ages about 13 000 yr b p mount st helens set c radiocarbon ages about 36 000 yr b p and by a third one that may be from an earlier pre set c mount st helens eruption the set s tephra layer separates the sand hills coulee and washtucna soils the set c tephra layer separates the old maid coulee and devils canyon soils and the pre set c tephra layer underlies the devils canyon soil the well known late wisconsin episode of scabland flooding and two older episodes of flooding are marked by regional stratigraphic unconformities that lie between pedostratigraphic units one unconformity that underlies the washtucna and old maid coulee soils was caused by a major episode of scabland flooding that occurred before 35 000 yr b p probably during the early wisconsin 80 000 to 65 000 yr b p a possible second and older episode of flooding recognized by an unconformity that underlies the devils canyon soil may be illinoian ca 130 000 to 200 000 yr b p in age

summary of pre 1980 tephra fall deposits erupted from mount st helens washington state usa mount st helens has been a prolific source of tephra fall deposits for about 40 000 years these tephra deposits 1 record numerous explosive eruptions 2 form important regional time stratigraphic marker beds and 3 record repeated changes in composition within and between eruptive periods

shallow subsurface imaging of the piano di pezza active normal fault central italy by high resolution refraction and electrical resistivity tomography coupled with time domain electromagnetic data

thermoluminescence dating of late pleistocene loess and tephra from eastern washington and southern oregon and implications for the eruptive history of mount st helens the first numeric dating of late pleistocene loess from the palouse region of eastern washington is reported this loess is interbedded with thin distal tephra layers some identified as mount st helens products both the interbedded tephra layers and thick paleosols that have developed in the loess have previously been correlated across the region a thicker correlative of one of these tephra layers mount st helens set c was collected from summer lake oregon for direct dating by thermoluminescence tl polymineral fine grain tl ages for loess from three chosen sections in washington range from 17 to 83 ka these imply ages for some tephra beds that are significantly older than implied by earlier radiocarbon 14c dating for example tl ages of 17 21 ka for loess bracketing a tephra layer correlated to mount st helens set s suggests a somewhat older age for this ash than the previously accepted 14c age of 15 5 0 5 ka cal yr corrected to calendar years tl ages of 46 6 1 ka and 57 7 ka for loess above and of 53 7 ka and 75 6 ka below a tephra bed correlated to a mount st helens set cw layer along with a tl age of 46 5 ka for fine silt sized glass from a mount st helens set cy bed in oregon revise upward from 38 ka cal yr 14c age is 36 ka b p to 50 ka the age of this regionally important marker ash set several tl ages taken together imply a much longer eruptive history for mount st helens than previously thought a tl age of 83 8 ka just below a previously undated tephra layer from mount st helens emsh ash suggests that the eruptive history of the mountain extends back to at least 80 ka furthermore age depth extrapolation through our sections to an ash wa 5c probably correlated to mount st helens suggests an eruptive history of at least 120 ka

integrated geophysical techniques for subsurface imaging of active deformation across the himalayan frontal thrust in singhauli kala amb india abstract non invasive geophysical techniques employed across the himalayan frontal thrust hft at singhauli in the north western frontal himalaya to understand shallow subsurface geological structures and their nature in the context of active tectonics the combination of high resolution ground penetrating radar gpr electrical resistivity tomography ert and multi channel analysis of surface waves masw techniques with the different acquisition parameters found to be beneficial in gaining high resolution images of shallow subsurface geological structures the contact zone of resistivity obtained between 134 m suggests the juxtaposition of dissimilar lithological units explained as two faults dipping to the northwest related to the hft the average separation between fault 0 and fault i is 12m which in general agreement with the trench excavation survey the gpr radargram over a length of 45m show offset reflectors at a horizontal distance of 12 15m close to the active deformation zone the horizontal reflectors abruptly truncate across two northerly dipping planes the 2d vs section masw1 2 exhibited dipping attitude of the litho units with different velocity zones in the northeast direction which are also consistent with the local geological setting prominent liquefaction feature identified in the ert section specifically with the 1 and 1 5m electrode spacing show explicit expression of its existence due to contrasting resistivity ranging between 100 and 450 m a strong correlation has been established between the field based geological observations carried out earlier in this area through a trench excavation survey with the present work using geophysical techniques the integrated approach found to be highly beneficial in those areas where contrasting sub lithological units exist in terms of their physical properties this study argues for judicious use of the ert gpr and masw techniques to delineate shallow subsurface geology across various active faults in the himalayan terrain to comprehend the active deformation related to large magnitude paleoearthquakes and earthquake hazard assessment

genesis and relationship of macromorphology and micromorphology to contemporary hydrological conditions of a welded argixeroll from the palouse in idaho abstract soils formed in distal loess of the palouse region have welded profiles that make assessment of their genesis and pedostratigraphic relationships difficult these soils typically have a mollic cambic horizon sequence that is underlain by a well expressed albic e horizon and a strongly developed argillic horizon in this study we utilized hydrological monitoring combined with micromorphological analysis and new stratigraphic data to help establish the genesis of a representative argixeroll of the region and the relationship of its morphology to ancient and contemporary hydrological conditions monitoring results indicate that the argixeroll is seasonally episaturated for approximately 5 6 months per year ferrimanganiferous nodules segregations hypocoatings and depletion mottles are observed in thin section throughout the pedon but dominate within just above and below the present day e horizon measured soil eh is sufficiently low for fe and mn reduction to occur for 1 3 months during the period of episaturation suggesting that at least some of these redoximorphic features are likely to be contemporary other compound redoximorphic features are clearly relict however as they are coated by illuvial clay which is unaffected by fe mn redistribution processes thick illuvial clay coatings on interpedal fissures of the argillic horizon postdate pockets of holocene tephra within deeply bioturbated aggregates while other channel argillans in the same part of the pedon are clearly older this indicates that at least two distinct phases of clay accumulation have occurred the most recent being contemporaneous with loess aggradation during the holocene our results suggest that these welded profiles consist of a mollic cambic horizon sequence that has formed primarily in holocene loess and an albic argillic sequence that has formed in wisconsinan loess the modern day e horizon was initiated as the clay eluvial surface horizon of the regionally recognized washtucna paleosol that continued forming into the late wisconsinan cold phase and upon burial by holocene loess it has been transformed into an albic horizon and even enlarged as a result of redoximorphic processes associated with seasonal saturation

faunal burrows as indicators of paleo vegetation in eastern washington usa abstract the palouse loess deposits in the pacific northwestern united states contain buried paleosols with distinctive biological fabrics the washtucna soil formed 40 000 15 000 yr ago during the last full glacial contains up to 90 by volume distinctive cylindrical pedotubules that are 1 2 cm in diameter formed by burrowing fauna the overlying post glacial loess and modern surface soils that support perennial grasslands lack these cylindrical burrows we investigated the paleoecological significance of the burrows observations of several types of burrowing fauna under native vegetation indicated that nymphs of cicadas homoptera cicadidae are responsible for cylindrical back filled burrows that match those in the washtucna soil we measured the abundance of active cicada burrows in soils in four native vegetation zones soil sites establishing that cicada burrows comprise 19 of the rooting zone volume in sagebrush steppe but just 1 3 of the rooting zone volume in bunchgrass steppe meadow steppe and coniferous forest this suggests strongly that abundant cicada burrows in paleosols are a proxy for the geographic extent of plant communities that contained sagebrush to assay the activity of cicada nymphs through time we measured burrowed volume by depth from the soil surface down through the washtucna soil i e from the present to ca 40 000 yr bp at five stratigraphic research sites paleosol sites cicada burrowed volume is generally less than 5 in the rooting zone of the surface soils and throughout holocene loess but is up to 94 in the rooting zone of the washtucna soil at paleosol sites that currently support bunchgrass steppe outside the present day sagebrush steppe zone cicada host preferences in vegetation zones today suggest that sagebrush was the dominant shrub as the washtucna soil formed from this reconstruction combined with information from studies of pollen and plant opal we infer that periglacial steppe plant communities dominated by sagebrush spread from 40 000 to 15 000 yr bp into areas of the columbia plateau that support bunchgrass steppe meadow steppe and even some coniferous forest today trace fossils of soil fauna in paleosols are indicators of fluctuations in biological activity in response to climatic changes of the quaternary period in palouse loess deposits

seismic modeling of multidimensional heterogeneity scales of mallik gas hydrate reservoirs northwest territories of canada 1 in hydrate bearing sediments the velocity and attenuation of compressional and shear waves depend primarily on the spatial distribution of hydrates in the pore space of the subsurface lithologies recent characterizations of gas hydrate accumulations based on seismic velocity and attenuation generally assume homogeneous sedimentary layers and neglect effects from large and small scale heterogeneities of hydrate bearing sediments we present an algorithm based on stochastic medium theory to construct heterogeneous multivariable models that mimic heterogeneities of hydrate bearing sediments at the level of detail provided by borehole logging data using this algorithm we model some key petrophysical properties of gas hydrates within heterogeneous sediments near the mallik well site northwest territories canada the modeled density and p and s wave velocities used in combination with a modified biot gassmann theory provide a first order estimate of the in situ volume of gas hydrate near the mallik 5l 38 borehole our results suggest a range of 528 to 768 106 m3 km2 of natural gas trapped within hydrates nearly an order of magnitude lower than earlier estimates which did not include effects of small scale heterogeneities further the petrophysical models are combined with a 3 d finite difference modeling algorithm to study seismic attenuation due to scattering and leaky mode propagation simulations of a near offset vertical seismic profile and cross borehole numerical surveys demonstrate that attenuation of seismic energy may not be directly related to the intrinsic attenuation of hydrate bearing sediments but instead may be largely attributed to scattering from small scale heterogeneities and highly attenuate leaky mode propagation of seismic waves through larger scale heterogeneities in sediments

long history of pre wisconsin ice age cataclysmic floods evidence from southeastern washington state abstract cataclysmic ice age floods in the pacific northwest began as early as 1 5 2 5 ma on the basis of an evaluation of surface exposures and recent borehole studies within southeastern washington field evidence suggests at least two episodes of pre wisconsin i e 130 ka glacial outburst flooding a middle pleistocene flood is identified by normal magnetic polarity calcrete capped deposits that yield maximum th u age dates from 200 to 400 ka the deposits with reversed polarity are correlated to early pleistocene 780 ka floods while exposures of pre wisconsin deposits are limited because of erosion and or burial the record of earlier pleistocene flooding is preserved within giant flood bars these bars show incremental growth representing a composite from cataclysmic floods deposited intermittently through the pleistocene in one giant flood bar up to 100 m thick deposits interpreted as matuyama age indicate that the bar had grown to half its present height by 780 ka furthermore matuy

glacial anticyclone recorded in palouse loess of northwestern united states climate simulations for the last glacial maximum using general circulation models typically show a glacial anticyclone that produced an easterly wind anomaly south of the north american ice sheets evidence of this phenomenon has not been found in eolian sedimentary deposits that record surface wind patterns luminescence ages of loess and accompanying paleoecologic records from opal phytoliths and paleosol units across the columbia plateau washington state united states document a decrease up to fivefold in regional dust production and accumulation from 35 ka to 15 ka this interval corresponds to simulations indicating that a glacial anticyclone weakened prevailing south southwesterly winds that have shaped the eolian landscape of the columbia plateau since at least 75 ka at the same time that the glacial anticyclone suppressed dust production and accumulation enhanced cold and dry conditions resulted in soil formation dominated by intense bioturbation in periglacial steppe accompanied by shallow calcium carbonate precipitation this is the first evidence from eolian deposits in north america verifying that the glacial anticyclone altered surface wind patterns and affected eolian systems during the last glacial maximum

spatial orientation and distribution of reservoir fractures from scattered seismic energy wepresentthedetailsofanewmethodfordeterminingthereflection and scattering characteristics of seismic energy from subsurface fractured formations the method is based upon observations we have made from 3d finite difference modeling of the reflected and scattered seismic energy over discrete systems of vertical fractures regularly spaced discrete vertical fracture corridors impart a coda signature which is a ringing tail of scatteredenergy toanyseismicwaveswhicharetransmittedthrough or reflected off of them this signature varies in amplitude and coherence as a function of several parameters including 1 the difference in angle between the orientation of the fractures and the acquisition direction 2 the fracture spacing 3 the wavelength of the illuminating seismic energy and 4 the compliance or stiffness of the fractures this coda energy is most coherent when the acquisition direction is parallel to the strike of thefractures ithasthelargestamplitudewhentheseismicwavelengths are tuned to the fracture spacing and when the fractures have low stiffness our method uses surface seismic reflection tracestoderiveatransferfunctionthatquantifiesthechangeinan apparent source wavelet before and after propagating through a fracturedinterval thetransferfunctionforanintervalwithnoor low amounts of scattering will be more spikelike and temporally compact the transfer function for an interval with high scattering will ring and be less temporally compact when a 3d survey is acquired with a full range of azimuths the variation in the derived transfer functions allows us to identify subsurface areas with high fracturing and to determine the strike of those fractures wecalibratedthemethodwithmodeldataandthenapplied ittotheemiliofieldwithafracturedreservoir themethodyielded results which agree with known field measurements and previously published fracture orientations derived from ps anisotropy

quantifying uncertainties in attenuation estimation at methane hydrate bearing zones using sonic waveform logs abstractapplication of seismic attenuation estimation using sonic waveform data is limited because the estimation methods have not yet been fully developed although the median frequency shift method is considered to be effective and robust compared to the conventional spectral ratio method we demonstrated that the median frequency shift methods strongly depend on reference data under lower signal to noise ratios we modified an existing median frequency shift method not to depend on arbitrarily choosing a reference value and to quantify the uncertainties in attenuation estimation furthermore we implied the optimum selection of receiver pairs used for more stable attenuation analysis our numerical experiments supported the advantage of the proposed method although our main findings by applying the proposed methods in methane hydrate bearing sediments are almost consistent with past field sonic logging measurements we find some differences in the magnitude of attenuation values compared to existing s

rapid precise and high sensitivity acquisition of paleomagnetic and rock magnetic data development of a low noise automatic sample changing system for superconducting rock magnetometers among earth sciences paleomagnetism is particularly linked to the statistics of large sample sets as a matter of historical development and logistical necessity because the geomagnetic field varies over timescales relevant to sedimentary deposition and igneous intrusion while the fidelity of recorded magnetization is modulated by original properties of rock units and by alteration histories ideal paleomagnetic results measure remanent magnetizations of hundreds of samples at dozens of progressive demagnetization levels accompanied by tests of magnetic composition on representative sister specimens we present an inexpensive open source system for automating paleomagnetic and rock magnetic measurements using vacuum pick and place technology and a quartz glass sample holder the system can in one hour measure remanent magnetizations as weak as a few pam2 of 30 specimens in two vertical orientations with measurement errors comparable to those of the best manual systems the system reduces the number of manual manipulations required per specimen 8 fold

long quaternary record in eastern washington u s a interpreted from multiple buried paleosols in loess loess that is from a few meters to 75 m thick covers an area of more than 20 000 km2 on the columbia plateau in washington idaho and oregon the region of deepest loess is in eastern washington and is called the palouse the palouse is downwind of the channeled scabland through which massive outburst floods from glacial lake missoula flowed repeatedly during glacial stages of the pleistocene the deepest stratigraphic section yet studied is in a remnant of the once continuous loess cover that is surrounded by scabland channels a normal over reverse magnetic polarity zonation in this section supports an age of more than 790 000 yr but 15 35 m of loess may be present beneath this section so a total of 1 5 2 million yr is possible upward fining of texture in some layers in the loess at this site and stratigraphic evidence at nearby sites suggest that at least some pulses of loess deposition were triggered by episodes of cataclysmic floods nineteen or more individual paleosols can be recognized in 26 m of section based on field morphology physical and chemical properties and micromorphology the paleosols consist of calcic petrocalcic and duripan horizons many of which are associated with cambic horizons less strongly developed soils in this and other sections have been obscured by partial overlap of soil development in an episodically rising loess landscape paleosols in the loess at other sites reflect a dry to moist climatic gradient from west to east across the region during the pleistocene that was grossly similar to today s accumulation of pedogenic carbonates and silica dominates in a western zone where the present day mean annual precipitation is less than about 450 mm translocation of silicate clays and leaching of carbonates dominate in a central steppe zone where precipitation is between 450 and about 700 mm fragipans are common in an eastern zone along the steppe forest transition at present day precipitation of over 700 mm reconnaissance study suggests that these climatic pedogenic zones have been somewhat stable during many of the episodes of soil development preserved in the loess although some paleosols have different features from the majority of the paleosols in that zone e g paleosols with fragipans in a sequence of paleosols with argillic horizons which suggests that some episodes of soil development took place under different climatic conditions

a loess record of pre late wisconsin glacial outburst flooding pleistocene paleoenvironment and irvingtonian fauna from the rulo site southeastern washington usa abstract worldwide loess paleosol sequences are archives of terrestrial quaternary paleoenvironment data the rulo site is a newly described site in the palouse loess of southeastern washington state usa the site reveals a 19 m thick deposit of loess and flood sediment preserving a total of 30 m of reconstructed stratigraphic section five unconformity bound sequences of sediment are exposed at the site the lowest two of which have yielded fossil remains including the first reported occurrence of flat headed peccary platygonus compressus in northwestern north america the unconformities two diamicts bearing extrabasinal clasts and a number of clastic dikes provide evidence for pre wisconsin glacial outburst floods in southeastern washington more than a dozen paleosols are preserved at the site these soils are relatively unweathered and therefore primarily record periods of slow sedimentation accumulation in the palouse rather than changes in weathering rates a paleosol near the base of the sequence is unusually weathered for palouse paleosols and records a period of increased weathering during the middle pleistocene all units above the sand are normal paleomagnetic polarity additional age control is provided by a tephra in the upper third of the sequence that matches a ca 220 ka tephra from newberry volcano and by stratigraphic correlation of later units to other sites in the palouse the rulo site adds to the record of irvingtonian fauna in north america and supports accumulating evidence for pre late wisconsin glacial outburst floods in the pacific northwest

early arrival waveform tomography on near surface refraction data we develop a waveform tomography method for estimating the velocity distribution that minimizes the waveform misfit between the predicted and observed early arrivals in space time seismograms by fitting the waveforms of early arrivals early arrival waveform tomographyewt naturally takes into account more general wave propagation effects compared to the high frequency method of traveltime tomography meaning that ewt can estimate a wider range of slowness wavenumbers another benefit of ewt is more reliable convergence compared to full waveform tomography because an early arrival misfit function contains fewer local minima synthetic test results verify that the waveform tomogram is much more accurate than the traveltime tomogram and that this algorithm has good convergence properties for marine data from the gulf of mexico the statics problem caused by shallow gassy muds was attacked by using ewt to obtain a more accurate velocity model using the waveform tomogram to correct for statics the stacked section was significantly improved compared to using the normal moveout nmo velocity and moderately improved compared to using the traveltime tomogram inverting high resolution land data from mapleton utah showed an ewt velocity tomogram that was more consistent with the ground truth trench log than the traveltime tomogram our results suggest that ewt can provide supplemental shorter wavelength information compared to the traveltime tomogram for both shallow and moderately deep seismic data