masw for geotechnical site investigation multichannel anaylsis of surface waves masw is a seismic surface wave technique developed specifically for near surface applications at depths usually shallower than a few tens of meters park et al 1999 since its introduction in the late 1990s use of the technique has rapidly increased for two reasons 1 it provides the shear wave velocity vs of ground materials which is one of the most important geotechnical parameters in civil engineering and 2 it is easier to use than other common seismic approaches e g refraction reflection and surface wave surveys

data resolution matrix and model resolution matrix for rayleigh wave inversion using a damped least squares method inversion of multimode surface wave data is of increasing interest in the near surface geophysics community for a given near surface geophysical problem it is essential to understand how well the data calculated according to a layered earth model might match the observed data a data resolution matrix is a function of the data kernel determined by a geophysical model and a priori information applied to the problem not the data a data resolution matrix of high frequency 2 hz rayleigh wave phase velocities therefore offers a quantitative tool for designing field surveys and predicting the match between calculated and observed data we employed a data resolution matrix to select data that would be well predicted and we find that there are advantages of incorporating higher modes in inversion the resulting discussion using the data resolution matrix provides insight into the process of inverting rayleigh wave phase velocities with higher mode data to estimate s wave velocity structure discussion also suggested that each near surface geophysical target can only be resolved using rayleigh wave phase velocities within specific frequency ranges and higher mode data are normally more accurately predicted than fundamental mode data because of restrictions on the data kernel for the inversion system we used synthetic and real world examples to demonstrate that selected data with the data resolution matrix can provide better inversion results and to explain with the data resolution matrix why incorporating higher mode data in inversion can provide better results we also calculated model resolution matrices in these examples to show the potential of increasing model resolution with selected surface wave data

directions and intensities of the earth s magnetic field during a reversal results from the permo triassic siberian trap basalts russia abstract an extensive palaeomagnetic study was carried out on an approximately 250 ma old reversed to normal transition of the earth s magnetic field emf recorded in 86 volcanic lava flows of the siberian trap basalts north siberia russia in addition to the investigation of the directional behaviour of the field 700 specimens a total of 298 specimens was subjected to thellier type palaeointensity determinations adding several modifications to the original thellier experiment such as tests for md tails and the additivity of partial thermoremanent magnetisation yields highly reliable palaeointensity estimates of the late permian early triassic emf transitional directions of the emf were obtained from 20 flows during the reversal a clustering of the virtual geomagnetic poles vgps is observed 15 flows palaeointensity estimates suggest that this feature is not an artifact due to rapid flow emplacement since the directional cluster is associated with a well defined increase in palaeointensity from 6 to 13 t subsequently the next vgps move towards the pole position of normal polarity departing in a sudden movement from normal polarity the vgps form a second directional cluster comprising the results of 14 flows this feature is interpreted as a post transitional excursion but lacks the characteristic intensity variation recorded during the first transitional cluster the rest of the section 41 flows is of normal polarity the characteristic features of this reversal low intensities and directional clustering during the reversal and an excursion shortly after the reversal were also observed in records of polarity transitions of younger age this suggests that the underlying reversal processes were similar the mean virtual dipole moment calculated for the stable normal part of the studied section yields a rather low value of 2 2 0 9 1022 am2 these findings confirm that the mesozoic dipole low extends at least down to the late permian early triassic the geomagnetic vgp dispersion was calculated for the stable normal part of the section and yields values similar to those for the last 5 ma considering that the intensity of the emf was considerably higher in this time interval than in the early triassic a direct relationship between intensity and secular variation seems unlikely

combining seismic and electric methods for predicting bedrock depth along a mediterranean soil toposequence abstract bedrock depth provides important information for many environmental and agricultural applications such as shallow groundwater monitoring the determination of soil water availability and the estimation of crop production potential direct estimates of bedrock depth from destructive soil observations are discontinuous and too expensive to be used in large areas geophysical methods are often cited as possible alternatives however their ability to provide reliable estimations of bedrock depth is known to depend greatly on local site characteristics therefore combining geophysical methods based on different physical parameters may help to provide better predictions this study examines the ability of the spectral analysis of surface waves sasw method combined with the classical high resolution electrical resistivity tomography ert method to predict soil depths in a 500 m ranged mediterranean hillslope southern france with increasing soil depths along the slope sasw was performed using the data measured in the field with classical seismic equipment impulse source and geophones distributed along a line in the same place eight transects of ert wenner schlumberger array 1 m electrode spaced were measured under wet and dry conditions to calibrate the geophysical measurements 81 boreholes from two to 5 m deep were interpreted to determine the bedrock depth which was defined as the occurrence in the depth of heterogeneous marine miocene loose sandstone with centimetric laminations ert and sasw were found to have highly variable performances for predicting separately the bedrock depth along the hillslope sasw correctly predicted the bedrock depth in the lower part of the hillslope whereas the data from ert were disrupted by shallow permanent groundwater conversely ert correctly predicted bedrock depth within the upper part of the hillslope whereas a high variability of sasw data near the topsoil caused difficulties for bedrock depth prediction from these results it was possible to define an estimator of bedrock depth according to the presence of shallow groundwater which varies along the slope such that more importance is given to ert estimates in the upper part of the hillslope and more importance is given to sasw in the lower part this study shows the usefulness of such a sensor combination to estimate soil properties when the uncertainties of making predictions vary according to the geophysical methods

quantitative assessment of in situ salt karstification using shear wave velocity dead sea abstract the dead sea ds coastal areas have been dramatically affected by sinkhole formation since around 1990 such sinkholes along both israeli and jordanian shores are linked to karst cavities that form through slow salt dissolution a quantitative estimate of such in situ salt karstification would be an important indicator of sinkhole hazard one of the indications of salt karstification is its increased hydraulic conductivity caused by the development of dissolution cavities forming conducting channels within the salt layer we measured the hydraulic conductivity k versus shear wave velocity vs of ds salt in situ for estimating the actual salt karstification in areas of sinkhole development these parameters were measured with the magnetic resonance sounding mrs and multichannel analysis of surface waves masw methods respectively understanding of the field relationships was augmented by similar inter relations obtained in the laboratory on samples of ds salt in situ salt velocities vs vary from 750 m s to over 1650 m s while hydraulic conductivity k in the same zones varies between about 10 4 m s to slightly over 10 8 m s both field and laboratory k and vs values fit the exponential function ln k 0 0045 vs 5 416 with a determination coefficient r2 of 0 88 a classification based on vs and k was generated for salt conditions and the corresponding degrees of sinkhole hazard which was verified in the mineral beach sinkhole development area the mapping of sinkhole sites shows that they form within highly conductive zones with k 5 5 10 5 it is suggested that this methodology with some modification can be used for evaluating the conductive properties of karstified rock and associated sinkhole hazards

latest pleistocene and holocene geomagnetic paleointensity on hawaii geomagnetic paleointensity determinations from radiocarbon dated lava flows on the island of hawaii provide an estimate of broad trends in paleointensity for holocene time and offer a glimpse of intensity variations near the end of the last glacial period when the data from hawaii are compared with others worldwide the intensity of the geomagnetic field seems to have been reduced from the holocene average by about 35 percent between 45 000 and 10 000 years ago a long term reduction of this magnitude is compatible with reported increases in the production rate of cosmogenic nuclides during the same interval

palaeomagnetic investigation of tertiary lava from barrington tops nsw australia using thermal and microwave techniques abstract tertiary lava 53 ma from barrington tops new south wales australia has been studied using conventional thermal and microwave techniques twenty seven flows in two sections were sampled and their rock magnetic characteristics determined on heating the majority of samples exhibited a single curie temperature at around 200 c indicating a titanium rich titanomagnetite some samples exhibited two magnetic phases and a few a single low titanium titanomagnetite phase thermal demagnetisation yielded a mean direction of d 189 5 i 63 6 95 4 3 which corroborates the previous findings of wellman et al geophys j r astron soc 18 1969 371 395 a pilot conventional thellier palaeointensity analysis was unsuccessful mainly due to the samples being highly susceptible to thermo chemical alteration far greater success was achieved 58 using the microwave palaeointensity technique where heating of the bulk sample and hence alteration is vastly reduced palaeointensity estimates range from 3 to 28 t mean 11 5 t which assuming that the remanence is a primary thermal remanent magnetisation indicates a low field intensity a fifth of the present day value in the early tertiary this study demonstrates the applicability of the microwave palaeointensity technique to ancient lava

broad trends in geomagnetic paleointensity on hawaii during holocene time paleointensity determinations have been obtained from 22 basaltic lava flows on the island of hawaii using the thelliers method radiocarbon dating indicates that these flows erupted at intervals ranging from about 200 to 1000 years and results of the experiments provide an estimate of broad trends in geomagnetic paleointensity during holocene time in the vicinity of hawaii most of the samples were obtained from quickly cooled flow margins and as a consequence typically contain two titanomagnetite populations only two of the 79 samples analyzed failed to yield an estimate of the paleofield demonstrating that paleointensities can be obtained from such samples if carefully selected virtual dipole moments calculated for the flows are compared with a published curve of dipole field intensity that was constructed using worldwide archeomagnetic data the large nondipole fields that were previously postulated for the vicinity of hawaii are confirmed and the present data indicate that they were present from about 5000 years b p to perhaps as recently as the past 200 years the data indicate however that these nondipole sources must have been virtually absent between about 12 000 and 5000 years b p as they are at the present time

dipping interface mapping using mode separated rayleigh waves multichannel analysis of surface waves masw method is a non invasive geophysical technique that uses the dispersive characteristic of rayleigh waves to estimate a vertical shear s wave velocity profile a pseudo 2d s wave velocity section is constructed by aligning 1d s wave velocity profiles at the midpoint of each receiver spread that are contoured using a spatial interpolation scheme the horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval based on the assumption that a dipping layer model can be regarded as stepped flat layers high resolution linear radon transform lrt has been proposed to image rayleigh wave dispersive energy and separate modes of rayleigh waves from a multichannel record with the mode separation technique therefore a dispersion curve that possesses satisfactory accuracy can be calculated using a pair of consecutive traces within a mode separated shot gather in this study using synthetic models containing a dipping layer with a slope of 5 10 15 20 or 30 degrees and a real world example we assess the ability of using high resolution lrt to image and separate fundamental mode rayleigh waves from raw surface wave data and accuracy of dispersion curves generated by a pair of consecutive traces within a mode separated shot gather results of synthetic and real world examples demonstrate that a dipping interface with a slope smaller than 15 degrees can be successfully mapped by separated fundamental waves using high resolution lrt

a neogene geomagnetic polarity transition record from lavas of the canary islands spain episodic volcanism and or metastable transitional fields summary we present results from a study of a partial magnetic polarity transition record from a 9 7 ma 40ar 39ar dated volcanic section on the island of gomera canary islands spain the record provides results that bear on the debate over whether long term persistent features of field behaviour exist during transitions the sampled section containing more than 20 flows begins after the onset of the transition the nine lowermost flows in the section which are all transitional yield virtually identical directions and similar low paleointensities following the recovery of virtual geomagnetic pole positions vgps to near the spin axis paleointensities progress to very high values transitional directions lay due west reflecting the presence of a non zonal intermediate field vgps for these flows cluster in the west atlantic which according to hoffman would correspond to a zone of fastest p wave propagation in the lower mantle and to a radial flux centre of the present day non dipole field hoffman had noted a similar occurrence at two other locations he found that in a select set of volcanic records vgps tended to group over two areas australia and south america which also corresponded to fast p wave and non dipole field anomalies given the discontinuous and irregular character typical of volcanic sequences it is natural to question whether these clusters are merely artefacts of episodic volcanism or actually reflect standstills of the reversing field we address this question for our record by comparing chemical and magnetomineralogic characteristics of the flows we find that all of the transitional flows have very similar chemical and rock magnetic properties furthermore these flows differ significantly from the overlying reverse flows which give distinctly different values and much greater flow to flow variation from this we conclude that the packet of transitional flows was derived from the same source and had erupted over a relatively short period of time as reflected by a magma source that presumably did not have time to evolve significantly while the vgp cluster in the gomera record is consistent with long term mantle control on transitional fields we cannot conclude that the cluster represents a standstill of the field these results highlight the difficulties of interpreting temporal changes in field behaviour from volcanic sequences in addition they provide a clear incentive for investigating physical characteristics of lavas to assess relative eruptive rates

further evidence for low intensity of the geomagnetic field during the early cretaceous time using the modified shaw method and microwave technique summary we report new absolute palaeointensity estimates using basalts from northeastern china k ar age 125 120 ma using the modified shaw method in conjunction with the microwave technique samples for the palaeointensity experiments were selected mainly based on their good reversibility of thermomagnetic curves and single primary magnetization characteristics using the modified shaw method 28 out of 45 measured samples from 10 cooling units give a virtual dipole moment of 3 1 1 0 10 22 am 2 and the microwave technique using 14 acceptable determinations out of 20 measured give an average value of 2 9 0 9 10 22 am 2 results using both the modified shaw method and the microwave technique demonstrate that the geomagnetic field strength recorded by these lavas was low this is in agreement with previous results of the same time interval obtained by the thellier method with partial thermal remanence p trm checks the fact that different techniques give qualitatively compatible low palaeointensity results provides greater confidence that the weak field features seen just prior to the cretaceous normal superchron cns are the result of the actual field recorded by the basalts as opposed to artefacts of the method analysis this study also demonstrates that the microwave technique can be used for very old basalts

three component seismic land streamer study of an esker architecture through s and surface wave imaging we deployed a newly developed 3c microelectromechanical system based seismic land streamer over porous glacial sediments to delineate water table and bedrock in southwestern finland the seismic so

identification of lateral discontinuities via multi offset phase analysis of surface wave data surface wave methods are based on the inversion of observed rayleigh wave phase velocity dispersion curves the goal is to estimate mainly the shear wave velocity profile of the investigated site the model used for the interpretation is 1d hence results obtained wherever lateral variations are present cannot be considered reliable in this paper we study four synthetic models all with a lateral heterogeneity when we process the entire corresponding seismograms with traditional f k approach the resulting 1d profiles are representative of the subsurface properties averaged over the whole length of the receivers lines these results show that classical analysis disregards evidences of sharp lateral velocity changes even when they show up in the raw seismograms in our research we implement and test over the same synthetic models a novel robust automated method to check the appropriateness of 1d model assumption and locate the discontinuities this new approach is a development of the recent multi offset phase analysis with the following further advantages it does not need previous noise evaluation and more than one shot only once the discontinuities are clearly identified we confidently perform classical f k dispersion curve extraction and inversion separately on both sides of the discontinuity thus the final results obtained by putting side by side the 1d profiles are correct 2d reconstructions of the discontinuous s wave distributions obtained without any additional ad hoc hypotheses

paleointensity experiments using alternating field demagnetization abstract experiments for absolute paleointensity involve a large number of heatings and thus increase the probability of mineralogical changes which considerably reduce the success rate magnetic granulometry also plays an important role in the presence of multidomain grains thermal demagnetization of natural remanent magnetization nrm is not linearly related to acquisition of thermal remanence trm in the laboratory so that the nrm trm diagrams are characterized by two slopes neither of them providing a correct field determination after briefly reviewing most current techniques for paleointensity and various attempts to improve the results the present paper investigates approaches relying on alternating field a f demagnetization measurements have been performed on at least eight samples from seven contemporary flows from hawaii classical thermal experiments were also conducted with poor success in contrast 30 of the nrm trm curves obtained after a f demagnetization were perfectly linear over the entire spectrum of coercivities and thus appropriate to determine a paleointensity this difference was caused by the possibility of measuring a much larger number of samples the mean field is less than 10 higher than the present field and in better agreement for a subset of samples with nrm and trm heated at 300 c prior to a f demagnetization these values are acceptable within the uncertainties inherent in any study of absolute paleointensity thus a f techniques can be used with confidence provided that the whole spectrum of coercivities is involved in the field determination and exempt from any correction this condition is necessary and sufficient to demonstrate the absence of alteration after heating because of the rapidity of such experiments an approach combining a f and thermal experiments is certainly the best way to increase considerably the number of field determinations per lava flow and hence the overall quality of paleointensity studies

improvements in procedure and paleointensity selection criteria picrit 03 for thellier and thellier determinations application to hawaiian basaltic long cores abstract in this paper we first describe the paleointensity furnaces and the procedures specifically designed to minimize oxidation of the samples during thellier and thellier paleointensity experiments routinely used at gif we also propose some improvements to the set of criteria commonly used to select the results of the thellier experiments in order to further increase the reliability of paleointensity determination finally to be included in databases the new set of paleointensity criteria picrit 03 paleointensity criteria in 2003 is discussed and the results obtained from two long hawaiian basaltic cores the scientific observation hole 4 soh 4 and the hawaiian scientific drilling project 1 hsdp1 are used to illustrate its effectiveness some of the results are re evaluated and a new composite record of absolute paleointensity and inclination spanning 420 kyr is presented the inclination values obtained from the two cores combined support the hypothesis of persistent shallow inclinations at hawaii in intensity the upper 100 kyr are covered by the data from soh 4 with 309 reliable determinations out of 766 examined obtained from 143 units which belong to the kilauea volcano at the top of this core the 341 reliable data covering the 100 420 kyr interval are from 149 units of core hsdp1 belonging to the mauna kea volcano the interval 320 to 420 kyr is particularly detailed because of high extrusion rate of the volcano the use of more stringent criteria decreases the number of determinations considered as reliable in previous publications but it improves their accuracy and robustness

a method and example of seismically imaging near surface fault zones in geologically complex areas using vp vs and their ratios abstract the determination of near surface vadose zone and slightly below fault locations and geometries is important because assessment of ground rupture strong shaking geologic slip rates and rupture histories occurs at shallow depths however seismic imaging of fault zones at shallow depths can be difficult due to near surface complexities such as weathering groundwater saturation massive nonlayered rocks and vertically layered strata combined p and s wave seismic refraction tomography data can overcome many of the near surface fault zone seismic imaging problems because of differences in the responses of elastic bulk and shear moduli of p and s waves to shallow depth fault zone properties we show that high resolution refraction tomography images of p to s wave velocity ratios v p v s can reliably identify near surface faults we demonstrate this method using tomography images of the san andreas fault saf surface rupture zone associated with the 18 april 1906 m 7 9 san francisco earthquake on the san francisco peninsula in california there the saf cuts through franciscan melange which consists of an incoherent assemblage of greywacke chert greenstone and serpentinite a near vertical zone 75 northeast dip of high p wave velocities up to 3000 m s low s wave velocities 150 600 m s high v p v s ratios 4 8 8 and high poisson s ratios 0 44 0 49 characterizes the main surface rupture zone to a depth of about 20 m and is consistent with nearby trench observations we suggest that the combined v p v s imaging approach can reliably identify most near surface fault zones in locations where many other seismic methods cannot be applied

long term variations in palaeointensity we compile a dataset of reliable palaeointensity estimates based both on published work and on new data from basaltic glass the basaltic glass data more than double the number of reliable thellie

global changes in intensity of the earth s magnetic field during the past 800kyr recent advances in palaeomagnetic and dating techniques have led to increasingly precise records of the relative intensity of the earth s past magnetic field at numerous field sites the compilation and analysis of these records can provide important constraints on changes in global magnetic field intensity and therefore on the earth s geodynamo itself a previous compilation for the past 200 kyr integrated 17 marine records into a composite curve1 with the geomagnetic origin of the signal supported by an independent analysis of 10be production made on different cores2 the persistence of long term features in the earth s magnetic intensity or the existence of long term periodic changes cannot however be resolved in this relatively short time span here we present the integration of 33 records of relative palaeointensity3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 into a composite curve spanning the past 800 kyr we find that the intensity of the earth s dipole field has experienced large amplitude variations over this time period with pronounced intensity minima coinciding with known excursions in field direction reflecting the emergence of non dipole components no stable periodicity was found in our composite record and therefore our data set does not support the hypothesis that the earth s orbital parameters have a direct and strong influence on the geodynamo

paleointensity high at 9000 years ago from volcanic rocks in japan six paleointensities were determined from young lava flows of fuji and oshima volcanoes whose ages are around 8000 to 15000 years b p two lava flows which have well defined ages at 8970 390 years b p and 9260 430 years b p give large paleointensities of 67 12 and 65 6 t respectively another lava flow of less accurate age also gives large paleointensity of 63 6 t the new paleointensity data are consistent with the trend of averaged paleointensity variation in japan for the last 9000 years they form a peak of paleointensity high at around 9000 years b p comparable to the well documented one at 2000 years b p this suggests that there exists a dominant component with a characteristic period of about 7000 years in paleointensity variation large paleointensity at about 8000 10000 years ago is also reported in france and iceland paleointensity variation averaged every 1000 years for the last 14000 years is quite similar in europe and japan the sine curve like variation of paleointensity observed in both europe and japan probably reflects the nature of the dipole moment if we consider much difference of longitude between the two regions

paleointensities for 10 22 ka from volcanic rocks in japan and new zealand abstract eight volcanic rocks from japan and new zealand in the age range 10 50 ka b p were studied using the thellier method paleointensity experiment and yielded five successful results for 10 22 ka samples from the shikotsu kuttara and daisen volcanoes in japan were taken from pyroclastic flows both welded and non welded and a pumice fall deposit one of the two new zealand rocks is a rhyolite lava from the taupo volcanic zone four sites out of seven located on rocks that are not usually subjected to thellier s experiment yielded successful results which indicates that volcanic products such as pyroclastic flows and rhyolite lavas are as good a material as basalt and andesite lavas for application of the paleointensity experiment one paleointensity from new zealand at 9 9 ka is very large at about 100 t and provides support for the paleointensity high found in europe and japan 1 2 the other four paleointensities for 14 22 ka are smaller than the present day value and this agrees with the idea of a broad paleointensity minimum for the period 10 50 ka that was suggested by mcelhinny and senanayake 3 it is also noted that the variation curve of absolute paleointensity from the volcanic rocks is reasonably similar to the relative paleointensity curves from marine and lake sediments which were summarized by tauxe 4

an absolute palaeointensity record from soh1 lava core hawaii using the microwave technique absolute palaeointensity results were obtained from 392 samples 166 of 241 flows from the upper 779 m of the scientific observation hole 1 soh1 basalt core kilauea volcano hawaii using the microwave palaeointensity technique based on k ar dates and a previously published age model this covers the last 45 ka thus giving a high resolution record of geomagnetic intensity in hawaii comparisons with other hawaiian absolute palaeointensity data show similar trend of higher intensity than present day for the last 3 ka and then a general decrease in intensity over the last 45 ka though this study reports consistently lower palaeointensity values direct comparison with previous thellier data from the soh1 core shows some discrepancies between the two methods with the thellier data yielding generally higher palaeointensity estimates than the microwave data in view of these discrepancies between the two methods the introduction of raw palaeointensity data into the public domain is suggested

field investigation of love waves in near surface seismology we examine subsurface conditions and survey parameters suitable for successful exploitation of love waves in nearsurface investigations love wave generation requires the existence of a low shear velocity surface layer we examined the minimum thickness of the near surface layer necessary to generate and record usable love wave data sets in the frequency range of 5 50 hz we acquired field data on a hillside with flat lying limestone and shale layers that allowed for the direct testing of varying overburden thicknesses as well as varying acquisition geometry the resulting seismic records and dispersion images were analyzed and the love wave dispersion relation for two layers was examined analytically we concluded through theoretical and field data analysis that a minimum thickness of 1 m of low velocity material is needed to record usable data in the frequency range of interest in near surface love wave surveys the results of this study indicate that existing guidelines for rayleigh wave data acquisition such as receiver interval and line length are also applicable to love wave data acquisition

evaluating hazards at salt cavern sites using multichannel analysis of surface waves subsidence resulting in sinkholes within dissolution mine fields in and around the city of hutchinson kansas usa figure 1 has been reported for more than 90 years salt dissolution and the resulting unpredictable upward migration of the dissolution voids can be observed both in proximity to well bores dissolution mining brine disposal and oil wells seismic shot holes etc and in areas known to experience natural dissolution with no apparent anthropogenic influences one potential outcome of the upward migration of these long inactive dissolution voids in the city of hutchinson is significant structural damage to facilities infrastructure or traffic areas monitoring the condition of a void s roof is key to determining and managing this risk drilling is expensive for this investigative application in part because of the number of potential targets at a depth of approximately 120 m most surface geophysical methods have neither the sensitivity nor resolution necessary to detect these voids mu

characteristics of the horizontal component of rayleigh waves in multimode analysis of surface waves in surface wave analysis s wave velocity estimations can be improved by the use of higher modes of the surface waves the vertical component of p sv waves is commonly used to estimate multimode rayleigh waves although rayleigh waves are also included in horizontal components of p sv waves to demonstrate the advantages of using the horizontal components of multimode rayleigh waves we investigated the characteristics of the horizontal and vertical components of rayleigh waves we conducted numerical modeling and field data analyses rather than a theoretical study for both components of rayleigh waves as a result of a simulation study we found that the estimated higher modes have larger relative amplitudes in the vertical and horizontal components as the source depth increases in particular higher order modes were observed in the horizontal component data for an explosive source located at a greater depth similar phenomena were observed in the field data acquired by using a dynamite source at 15 m depth sensitivity analyses of dispersion curves to s wave velocity changes revealed that dispersion curves additionally estimated from the horizontal components can potentially improve s wave velocity estimations these results revealed that when the explosive source was buried at a greater depth the horizontal components can complement rayleigh waves estimated from the vertical components therefore the combined use of the horizontal component data with the vertical component data would contribute to improving s wave velocity estimations especially in the case of buried explosive source signal

the proterozoic hustad igneous complex a low strain enclave with a key to the history of the western gneiss region of norway the hustad igneous complex hic is a concentrically zoned high k calc alkaline intrusive complex with a core of quartz monzonite and granite surrounded successively by monzodiorite and pyroxenite preserved in a 10 km2 lens within the strongly caledonised western gneiss region wgr of norway upper intercept u pb zircon ages of 1654 1 and 1653 2 ma obtained from the granite and the monzodiorite respectively overlap with a rb sr whole rock age of 1656 49 ma i r 0 70193 0 0009 mswd 6 6 obtained from the felsic members of the complex and a sm nd whole rock age of 1555 180 ma i r 0 51067 13 mswd 3 3 the u pb age of 1654 1 ma is interpreted to date the time of intrusion a 50 m thick dolerite dyke that can be followed for almost 4 km across the hic yields a u pb zircon and baddeleyite age of 1251 3 ma the dyke also contains a secondary polycrystalline zircon generation which together with baddeleyite defines a lower intercept age of 384 9 ma the caledonian events were also marked by the emplacement of a swarm of pegmatites which crosscut all the other units and provide a u pb zircon age of 401 1 ma a rb sr whole rock age for the pegmatites is older at 452 26 ma i r 0 7105 mswd 4 3 indicating some initial isotopic heterogenity and formation of the pegmatites from material with a long crustal residence time a concordant u pb monazite age of 390 2 ma from the pegmatite and the above 384 9 ma lower intercept age date metamorphism caused by percolating fluids post pegmatite deformation transformed the complex along shear zones into gneisses indiscernible from the surrounding gneisses the hic is characterised by high mg numbers 0 39 0 80 high ni and cr values and depletion of nb and ta relative to lil elements phenocrysts of ortho and clinopyroxene have high concentrations of cr supporting the cr rich nature of the complex the suite is lree enriched has a fractionated and u shaped ree pattern cen 90 143 ybn 12 40 end values ranging from 0 0 to 2 7 and the felsic members display weak positive eu anomalies while the pyroxenite has a negative eu anomaly the complex bears a geochemical resemblance to the late tectonic high ba sr granite complexes of west scotland and particularly to their volcanic counterparts the mg rich old red sandstone andesites overall the data suggest generation of the suite in a subduction environment from material derived by melting of a recently enriched but previously long term lree depleted mantle the hic is one of the few well preserved remnants of the igneous protoliths of the 1686 1640 ma gneisses that make up the wgr in fact the pyroxenite is compositionally identical to orthopyroxene eclogite found as lenses in the surrounding gneisses and forms a likely protolith to this enigmatic rock the metamorphism had little influence on the rb sr and sm nd systems of the felsic rocks but it appears to have affected more strongly those in the mafic rocks probably as a result of the more intense mineralogical transformations and metasomatic loss of rb and lree during high grade metamorphism

impact fragmentation of lonar crater india implications for impact cratering processes in basalt impact fragmentation is an energetic process that has affected all planetary bodies to understand its effects in basalt we studied lonar crater which is a rare terrestrial simple impact crater in basalt and analogues to kilometer scale simple craters on mars the lonar ejecta consists of basaltic fragments with sizes ranging from silt to boulder the cumulative size and mass frequency distributions of these fragments show variation of power index for different size ranges suggesting simple and complex fragmentation the general shape of the fragments is compact platy bladed and elongated with an average edge angle of 100 the size distribution of cobble to boulder sized fragments is similar to the fracture spacing distribution in the upper crater wall indicating the provenance of those large fragments its consistency with a theoretical spallation model suggests that the large fragments were ejected from near surface of the target whereas the small fragments from deeper level the petrophysical properties of the ejecta fragments reflect the geophysical heterogeneity in the target basalt that significantly reduced the original size of spall fragments the presence of fe mg phyllosilicates smectites both in the ejecta and wall indicates the role of impact in excavating the phyllosilicates from the interior of basaltic target affected by aqueous alteration the seismic images reveal a thickness variation in the ejecta blanket segregation of boulders fractures and faults in the bedrock beneath the crater rim the fracturing fragmentation and fluvial degradation of lonar crater have important implications for mars

delineation of a collapse feature in a noisy environment using a multichannel surface wave technique a collapse developed at calvert cliffs nuclear power plant maryland in early 2001 the location of the collapse was over a groundwater drainage system pipe buried at an elevation of 0 9 m reference is to chesapeake bay level the cause of the collapse was a subsurface drain pipe that collapsed because of saltwater corrosion of the corrugated metal pipe the inflow outflow of sea water and groundwater flow caused soil to be removed from the area where the pipe collapsed to prevent damage to nearby structures the collapse was quickly filled with uncompacted sand and gravel 36 000 kg however the plant had an immediate need to determine whether more underground voids existed a high frequency multichannel surface wave survey technique was conducted to define the zone affected by the collapse although the surface wave survey at calvert cliffs nuclear power plant was conducted at a noise level 50 100 times higher than the normal environment for a shallow seismic survey the shear s wave velocity

iaga paleointensity database distribution and quality of the data set abstract the aim of this paper is to provide details about the design of the paleointensity database and focus on the distribution of the available data set version 2003 of the paleointensity database comprises 3128 data from 215 references only absolute paleointensity determinations from igneous rocks and baked contacts are considered regardless which method of paleointensity determination was used the entries in the database correspond to cooling units all polarities as well as all units are considered normal reverse or transitional the earth s magnetic field is the only surface trace of the working of the geodynamo and is therefore a very important tool for our understanding of the earth s deep interior especially its variation with geologic time however to study the long term variation of the paleomagnetic field non dipole effects have to be removed in recent years the production rate of paleointensity data has strongly increased and the most reliable methods were more frequently used however the present data set still has an important temporal bias with 35 of the rocks having ages less than 1 ma as well as a strong geographic bias towards the northern hemisphere especially north america and europe for most time intervals secular variation cannot be averaged out neither temporally nor spatially therefore interpretation of the averaged field is very limited and is avoided here for the future a harmonization or a combination of all iaga databases would be desirable furthermore the input of raw data at the specimen level would be useful in order to allow reinterpretation of data with more developed and sophisticated methods based on our increasing understanding of rock magnetism finally new reliable data are very much needed

defining fault avoidance zones and associated geotechnical properties using masw a case study on the springfield fault new zealand abstract the springfield thrust fault at dalethorpe west canterbury new zealand provides a test case to explore the correlation between shear wave velocities at a range of scales and direct field observations of distributed deformation and outcrop properties the springfield fault ruptures to the surface through hard torlesse greywacke overlain on a flight of late quaternary glacio fluvial terraces by 5 m of gravel fault slip has displaced all but the lowest terraces revealing the geometry and location of faulting we used multi channel analysis of surface waves and meter scale cross hole measurements to map shear wave velocities below the lowest apparently undisplaced terrace we correlated these surveys with geotechnical parameters measured at outcrops and investigated relationships in the laboratory both field and laboratory results indicate that the shear wave velocity of torlesse greywacke declines sharply with increasing fracture density field surveys further indicate that relatively unweathered high velocity greywacke is being exhumed in a bivergent wedge between two opposite facing thrusts the fracturing and low shear wave velocities are focused in a wide low velocity damage zone that has developed in the hanging wall of the main thrust and a smaller but similar feature in the hanging wall of the backthrust this is consistent with the geomorphology of the site our correlations of geomorphic indicators of deformation with fault zone velocity structure provide a useful method with which to characterize the distribution of cumulative strain this type of analysis has utility for land use planning on or close to active faults especially where they are obscured by fluvial deposits

site specific relationships between bedrock depth and hvsr fundamental resonance frequency using kik net data from japan it is commonly accepted that the horizontal to vertical spectral ratio hvsr technique enables the detection of the fundamental resonance frequency f text hvsr of a given site the utility of this f text hvsr is analyzed using the nonlinear regression relationships between f text hvsr and bedrock depth h the derived relationships are mostly site specific so that the present paper consists of two main parts the first is a literature review for the available empirical relationships between f text hvsr and h the aim of this part is to highlight the practical limitations of these established relationships and to make fair comparisons the second is to generate new relationships taking advantage of the very wide range of available lithological geophysical and geotechnical borehole drilling data of the 697 kik net seismic stations in japan for this purpose hvsr are calculated using 10 000 weak earthquakes or linear events recorded at kik net stations to determine the f text hvsr and correlate it with the corresponding h the overlying layers bedrock interface falling within sedimentary igneous or metamorphic layers significantly affect the derived frequency depth relationships in addition these relationships are strongly reproduced by the v text p v text s ratio of the bedrock in the range of 1 6 2 2 interestingly it is found that f text hvsr less than 1 hz corresponding to h more than 100 m leads the trend of the overall frequency depth relationship

absolute paleointensity from hawaiian lavas younger than 35 ka abstract paleointensity studies have been conducted in air and in argon atmosphere on nine lava flows with radiocarbon ages distributed between 3 3 and 28 2 ka from the mauna loa volcano in the big island of hawaii determinations of paleointensity obtained at eight sites depict the same overall pattern as the previous results for the same period in hawaii although the overall average field intensity appears to be lower since the present results were determined at higher temperatures than in the previous studies this discrepancy raises questions regarding the selection of low versus high temperature segments that are usually made for absolute paleointensity the virtual dipole moments are similar to those displayed by the worldwide data set obtained from dated lava flows when averaged within finite time intervals the worldwide values match nicely the variations of the sint 200 synthetic record of relative paleointensity and confirm the overall decrease of the dipole field intensity during most of this period the convergence between the existing records at hawaii and the rest of the world does not favour the presence of persistent strong non dipole components beneath hawaii for this period

frequency dependent multi offset phase analysis of surface waves an example of high resolution characterization of a riparian aquifer multi offset phase analysis of seismic surface waves is an established technique for the extraction of dispersion curves with high spatial resolution and consequently for the investigation of the subsurface in terms of shear wave velocity distribution however field applications are rarely documented in the published literature in this paper we discuss an implementation of the multi offset phase analysis consisting of the estimation of the rayleigh wave velocity by means of a moving window with a frequency dependent length this allows maximizing the lateral resolution at high frequencies while warranting stability at the lower frequencies in this way we can retrieve the shallow lateral variability with high accuracy and at the same time obtain a robust surface wave velocity measurement at depth in this paper we apply this methodology to a dataset collected for hydrogeophysical purposes and compare the inversion results with those obtained by using refraction seismics and electrical resistivity tomography the surface wave results are in good agreement with those provided by the other methods and demonstrate a superior capability in retrieving both lateral and vertical velocity variations including inversions our results are further corroborated by the lithological information from a borehole drilled on the acquisition line the availability of multi offset phase analysis data also allows disentangling a fairly complex interpretation of the other geophysical results

spatial variability of the depth of weathered and engineering bedrock using multichannel analysis of surface wave method in this paper an attempt has been made to evaluate the spatial variability of the depth of weathered and engineering bedrock in bangalore south india using multichannel analysis of surface wave masw survey one dimensional masw survey has been carried out at 58 locations and shear wave velocities are measured using velocity profiles the depth of weathered rock and engineering rock surface levels has been determined based on the literature shear wave velocity of 330 30 m s for weathered rock or soft rock and 760 60 m s for engineering rock or hard rock has been considered depths corresponding to these velocity ranges are evaluated with respect to ground contour levels and top surface levels have been mapped with an interpolation technique using natural neighborhood the depth of weathered rock varies from 1 m to about 21 m in 58 testing locations only 42 locations reached the depths which have a shear wave velocity of more than 760 60 m s the depth of engineering rock is evaluated from these data and it varies from 1 m to about 50 m further these rock depths have been compared with a subsurface profile obtained from a two dimensional 2 d masw survey at 20 locations and a few selected available bore logs from the deep geotechnical boreholes

geomagnetic intensity and inclination variations at hawaii for the past 98 kyr from core soh 4 big island a new study and a comparison with existing contemporary data abstract reliable thellier thellier paleointensity determinations were obtained from 321 out of 766 examined samples from the upper 200 units 675 m of core soh 4 drilled in the kilauea volcano the main trend of the soh 4 record is a marked decrease from values higher than present in the last 4 kyr to values about 40 smaller from about 20 kyr to the bottom of the sampled interval three main lows coinciding with shallow or negative inclinations observed in the record were identified with an excursion previously documented in hawaii and the mono lake and laschamps events for the last 15 kyr the soh 4 intensities are largely in agreement with the worldwide distribution of volcanic data in the 15 75 kyr interval the general lack of volcanic data makes comparison with the soh 4 data difficult the soh 4 record is similar to a composite record of paleointensity largely based on a recent north atlantic sedimentary paleointensity stack napis 75 the soh 4 record is also generally consistent with a record of geomagnetic field intensity obtained from a study of 36 cl in the grip ice core calculated with the assumption that the production rate of 36 cl is controlled only by the geomagnetic field one pronounced discrepancy between the different records is observed around 50 kyr bp when the sedimentary and cosmogenic based records document high intensities which are not observed in soh 4 these high intensities are also absent in a recent record based on the analyses of sea floor magnetic anomalies the histogram of vadms obtained from soh 4 is different from that obtained from the sedimentary or 36 cl based records and is more skewed than the distribution given by kono and tanaka for the last 2 5 million years

geomagnetic field strength during late miocene first paleointensity results from baja california 1 thellier paleointensity experiments were carried out on 73 selected samples from the late miocene baja california volcanic flows for the first time the selected samples showed a stable remanent magnetization observed upon thermal treatment and reasonably reversible continuous susceptibility curves compatible with ti poor titanomagnetites judging from the ratios of hysteresis parameters it seems that the samples fall in the small pseudosingle domain grain size region thirty three samples from 10 individual flows yielded acceptable paleointensity estimates the natural remanent magnetization nrm fractions used for paleointensity determination range from 37 to 81 and the quality factor varies between 4 5 and 24 5 being normally 5 the mean paleointensity values per flow obtained in this study range from 18 1 3 1 to 45 6 4 3 t and the corresponding virtual dipole moments vdms range from 3 8 0 6 to 8 8 0 8 1022 a m2 these values correspond to mean value of 6 6 1 7 1022 a m2 which is 85 of the present geomagnetic axial dipole the average vdm value for late miocene according to all available selected data is 6 1 1 5 1022 a m2 which is higher than average paleofield for the period 5 160 ma 4 2 2 3 1022 a m2 after juarez and tauxe 2000 given the large dispersion and the very poor distribution of reliable absolute intensity data it is hard to draw any firm conclusions regarding the time evolution of the geomagnetic field more high quality determinations are strongly needed

magmatic history of the east rift zone of kilauea volcano hawaii based on drill core from soh 1 abstract deep drilling has allowed for the first time an examination of most of the shield stage of a hawaiian volcano when it is centered over the hotspot and most of its volume is produced we determined the lithologies ages geochemical characteristics and accumulation rates of rocks from the continuously cored 1 7 km deep scientific observation hole soh 1 which was drilled into kilauea s east rift zone the uppermost 750 m of this hole contain relatively unaltered subaerially quenched lavas the lower portion is a mixture of weakly to moderately altered hyaloclastites and massive basalts intruded by dikes unspiked k ar dating was attempted on 14 lavas but only four yielded geologically reasonable ages the oldest age is 351 12 ka for a sample from 1541 m eighty xrf major and trace element analyses of lavas from throughout the section demonstrate that these lavas have the same compositional range as historical kilauea lavas and that there was no systematic geochemical variation for the volcano over the last 350 ka kilauea s average yearly magma supply during this period was probably 0 05 01 km 3 which is identical to its average historical magma supply rate thus kilauea s overall source and melting conditions have remained remarkably constant for the last 350 ka despite its having drifted 42 km over the hawaiian plume these results require that the portion of the plume being melted to produce kilauea magmas be relatively large and well mixed which is inconsistent with models that place this source on the margin of a radially zoned plume

integrated geophysical approach in assessing karst presence and sinkhole susceptibility along flood protection dykes of the loire river orleans france abstract non invasive geophysical methods are often used for detecting near surface defects and monitoring seepage in river dykes or dams between 2008 and 2009 a series of geophysical experiments was conducted to detect karst features below the dykes of the loire river orleans france multi channel analysis of seismic surface waves masw was used to obtain the shear wave velocity vs profile of the subsurface below the dykes as an effective approach to investigating the structure of the dykes multi channel resistivity surveys were also used to evaluate the electrical properties of material inside and under the dykes this study discusses the exploration strategy and results for several sections of the dyke system based on the experimental data vs contours are used to geometrically and qualitatively describe the subsurface under the dykes and identify areas of mechanical weakness corresponding to karst features while resistivity contours allow distinguishing interactions between the karst and the dykes through the identification of areas of downward material movement known and unknown anomalies are identified a practical approach that combines seismic and electric resistivity results is proposed to assess karst presence and sinkhole hazards along the investigated dykes using a susceptibility index referring to the likelihood level of the events as a validation method areas of strong karst susceptibility index along the dykes are compared to known collapse event sinkholes dyke breaches etc locations available in databases

delineating a shallow fault zone and dipping bedrock strata using multichannal analysis of surface waves with a land streamer the multichannel analysis of surface waves masw seismic method was used to delineate a fault zone and gently dipping sedimentary bedrock at a site overlain by several meters of regolith seismic data were collected rapidly and inexpensively using a towed 30 channel land streamer and a rubberband accelerated weight drop seismic source data processed using the masw method imaged the subsurface to a depth of about 20 m and allowed detection of the overburden gross bedding features and fault zone the fault zone was characterized by a lower shear wave velocity vs than the competent bedrock consistent with a large scale fault secondary fractures and in situ weathering the masw 2d vs section was further interpreted to identify dipping beds consistent with local geologic mapping mapping of shallow fault zones and dipping sedimentary rock substantially extends the applications of the masw method

interferometric multichannel analysis of surface waves imasw abstract refraction microtremor remi and multichannel analysis of surface waves masw are effective approaches to estimate shallow shear wave velocity v s structure often needed to estimate ground motions using recent ground motion prediction relations interferometric masw imasw uses slowness frequency slant stack analyses combined with interferometric time domain dispersion analyses to improve resolution of lower frequency rayleigh wave dispersion to better constrain v s cross correlation interferometry is used to obtain deterministic correlation green s function cgf imasw seismograms from ambient noise and or active source wave fields contained in remi and or masw data the cgfs are processed using the multiple filter technique to estimate phase and group dispersion in the imasw approach active seismic sources ensure that the stationary phase contributions to cross correlations dominate cgf responses in a single imasw profile each geophone represents a virtual source and the imasw approach stacks cgf common offset data from all virtual sources to obtain a single averaged forward and reverse record section cgf time domain and slowness frequency phase slowness estimates are combined with cgf time domain group slowness estimates for a consistency check on dispersion picks a multistate monte carlo approach is used to estimate mean slowness depth and slowness uncertainties imasw is evaluated with passive remi data from two sites and active source imasw at six sites with independent downhole velocity depth logs comparison of six p s suspension log imasw profile pairs across the van norman complex in northern san fernando valley shows that on average 30 m depth shear wave velocity estimates between the two methods differed by p s suspension log measurements of v s were made at the imasw profile midpoint the imasw v s depth inversions resolve 3 m thickness v s variations accurately to the bottom of one borehole at 40 m depth and to 100 m depth at a 200 m deep borehole site

geomagnetic field intensity at hawaii for the last 420 kyr from the hawaii scientific drilling project core big island hawaii four hundred twenty five new paleointensity thellier thellier determinations out of 545 analyzed samples have been obtained from core hsdp which penetrates about 1000 meters 208 flows of the mauna loa and mauna kea volcanic series encompassing the last 420 kyr rock magnetic investigations identify pseudo single domain magnetite as the main magnetic mineral inclinations are shallower than expected from a geocentric dipole field but are consistent with data from other geographical regions at the same latitude the inclination record reveals three episodes of negative inclination whose interpolated age correlates well with that of known geomagnetic events the paleointensity record from the mauna loa sequence is not very detailed and does not allow precise comparison with other data in the 0 50 kyr interval the record from the mauna kea sequence on the contrary is very detailed and documents relatively short lived episodes of low and high field strength from 15 to 60 t the average virtual dipole moment 8 7 3 0 10 22 a m 2 is not significantly different from the value reported by kono and tanaka 1995 for the last 2 5 myr a comparison with other data from hawaii and other geographical regions is described in detail there are no drastic changes in paleointensity with the inclination anomaly in agreement with previous results from hawaii but in contrast with most published results which however consider data from polarity transition spectral analysis of a particularly detailed portion of the record between 420 and 326 kyr documents significant periodicities at 36 8 5 and 4 ka in the inclination record but not in the intensity record suggesting that changes in time of the inclination are to a certain extent independent from those of the intensity

local site characterization and seismic zonation study by utilizing active and passive surface wave methods a case study for the northern side of ankara turkey abstract this study encompasses dynamic soil characterization and site classification zonation mapping of the plio quaternary and especially quaternary alluvial sediments based on the current seismic codes the study area is located in the cubuk district and its surrounding area that is situated towards the north of ankara the capital of turkey the project site is located in a region which has the potential of being seriously affected by probable seismic events occurring along the cubuk fault zone the cubuk fault zone is thought to be a continuation of the dodurga fault zone and a sub fault belt of the north anatolian fault system that is one of the most prominent fault systems in turkey with a significant earthquake potential sediment characteristics were determined and soil profiles were characterized by surface wave methods at different locations non invasive seismic methods were used to obtain a shear wave velocity profile at 41 sites and two measurements were taken at each site for passive and active surface wave methods the multichannel analysis of surface wave method masw and the microtremor array method mam which gave comparable results were used as active and passive surface wave methods respectively by combining these two techniques the shear wave velocity profile of the site was obtained additionally the mam survey alone was implemented at 10 of the sites especially to get information on the deeper parts of the soil profiles the geological characteristics of these sedimentary units were compared with the geological and geotechnical boring and seismic site characterization studies to classify the soil deposits therefore the average shear wave velocity results and the variable characteristics of the seismic data along the soil profiles were correlated with these boring studies this was performed to develop site categories which took site conditions into account according to the design codes of ibc international building code 2006 and tsc turkish seismic code 1998 consequently the regional site classification map of the north of the cubuk basin considering site classes was assessed based on the average shear wave velocity vs30 results in ibc 2006 and the shear wave velocity data and thickness of the surface layer based on the vs values in the tsc

characterizing landslides through geophysical data fusion example of the la valette landslide france many studies show that certain geophysical methods such as seismic and electrical resistivity imaging appear to be well adapted for investigating the internal structures of landslides and understanding the related hydro mechanical mechanisms these are methods that allow the direct and non intrusive measurement of acoustic p and shear s wave velocities and electrical resistivity which are three physical parameters considered as essential for estimating the mechanical properties of moving reworked material we applied these techniques to the la valette landslide southern french alps a typical example of an intra material landslide carrying out measurements simultaneously along two profiles 400 m and 300 m long and respectively perpendicular to and along the slide direction we then used suitable inversion algorithms to estimate both the p and s wave velocity fields and the electrical resistivity field from the recorded data the results aided by field surface observations show that a correlation exists between the state of the material and the seismic velocity and or electrical resistivity data thus confirming that the simultaneous use of the two methods provides complementary information on the geomechanical behavior of the landslide more particularly the seismic data provide information on fissure density variations and the presence of shear bent material whereas the electrical resistivity data provide information on the groundwater content to enable a more integrated petrophysical interpretation we applied a data fusion strategy based on fuzzy subsets to the geophysical datasets through combining the tomograms we identified a surface layer of soft material along the two profiles the bottom of this layer was also recognized in a borehole from a methodological point of view the results show the applicability of adopting geomechanical hypotheses as inputs of geophysical data fusion for identifying areas where sediment mobilization could occur

refraction and amplitude attenuation tomography for bedrock characterization trabzon case turkey abstract the purpose of this study was to characterize the geomaterials and rock quality of eocene neogene aged volcanic sedimentary rocks in northeastern pontides trabzon turkey geomaterials characterization is a basic step for constructions structural design excavation and seismic microzonation studies volcanic sedimentary rocks have a wide distribution in the trabzon and are foundation rock for many buildings and roads they are also frequently used for surface work such as road pavement refraction tomography and amplitude attenuation tomography were applied to map p wave velocities vp and attenuation coefficients to determine rock quality and construction plans a 3 d vp and map was created from parallel lines of 2 d seismic data multichannel analysis of surface wave masw was also used to determine shear wave velocities vs four boreholes close to our seismic lines were used to determine the underground structure of the layers rock quality designation rqd and weathering degree laboratory tests were conducted on cylindrical specimens obtained from the boreholes to measure ultrasonic pulse velocities upv for saturated and dry conditions of basalts we also calculated the uniaxial compressive strength ucs water saturation water absorption in weight and effective porosity of samples the results indicated the studied area consists of three layers the surface layer was classified as topsoil with vp from 0 5 to 0 8 km s and thickness from 0 8 to 4 m the second layer was weathered basalt having vp from 1 6 to 2 3 km s and a thickness 2 6 m the bottom layer was identified as slightly weathered and massive basalt vp of this bedrock ranges from 2 4 to 3 8 km s with beginning at depth of about 4 m the average vs from masw was 0 95 km s 1 values were 8 and 23 for weathered and slightly weathered or massive basalt respectively regression analysis assessing the relation among upv ucs and porosity indicated a high correlation among them the seismic velocities 1 values boreholes logs and laboratory tests show that the bedrock is shallower and rock quality is better at the northern part of the study area therefore the northern part seems more suitable for constructions the combination of masw and seismic refraction plus traveltime and amplitude attenuation tomography revealed fractured and weathered zones more reliably and with greater detail than any one method could have done

changes in trm and arm in a basalt due to laboratory heating abstract laboratory heating in air often results in irreversible changes of remanence properties in natural rocks such an effect was traced for a recent basalt sample containing titanomagnetite x 0 4 as the main remanence carrier for heating times between 3 and 300 min it is shown that the change can be explained by the scheme of high temperature oxidation titanomagnetite psd md iron rich phase sd ilmenite remanent magnetizations in both the original and heated samples are the mixtures of two components high blocking temperature high coercivity fraction and low blocking temperature low coercivity fraction the trm and arm show distinctly different behaviors in this change showing the limitation of using the arm as an analog of the trm

horizontal resolution of multichannel analysis of surface waves abstractthe multichannel analysis of surface wave masw method has been effectively and widely used to determine near surface shear wave velocity horizontal resolution of the masw method represents the minimum horizontal length of recognizable geologic anomalous bodies on a pseudo 2d s wave velocity vs section accurately assessing the achievable lateral resolution is one of the main issues in lateral variation reconstruction using the masw method it is difficult to quantitatively estimate the horizontal resolution of the masw method because of the many influencing factors such as parameters of the observation system the depth of an anomalous body and the velocity contrast between the anomalous body and the surrounding rocks we first analyzed the horizontal resolution of the masw method based on numerical simulation experiments according to different influencing factors of the horizontal resolution we established different laterally heterogeneous models and observation systems and then simulated

multichannel analysis of surface waves to map bedrock in many geologic settings topographic variations and discontinuities in the surface of bedrock can influence the transport and eventual fate of contaminants introduced at or near the ground surface determining the nature and location of anomalous bedrock can be an essential component of hydrologic characterization preliminary analysis of the hydrologic characteristics of a site in olathe kansas u s based primarily on borehole data alone suggested that a cluster of fractures and or an unmapped buried stream channel may influence fluid movement along the drill defined bedrock surface

surface wave observations after integrating active and passive source data empirical green s function egf retrieval and turning ambient noise into useful signal by crosscorrelation or seismic interferometry curtis et al 2006 has been a popular topic in recent years in the seismological community many have discussed how the interstation distance or its equivalent affects the accuracy of the green s function that can be retrieved by crosscorrelation of long range noise between two stations e g snieder 2004 bensen et al 2007 halliday and curtis 2008 tsai 2009 kimman and trampert 2010 it is generally accepted that the necessary or optimum interstation distance strongly depends on source distribution length of records and hence is naturally related to source distribution and the duration of the green s function to be retrieved noise generated by a surface source can be efficiently used to reconstruct the green s function of surface waves if we focus on the accuracy of the phase and not be too concerned with the amplitude accuracy of the retrieved green s

assessment of vulnerability to erosion digital mapping of a loess cover thickness and stiffness using spectral analysis of seismic surface waves article i nfo non invasive geophysical techniques offer an interesting alternative to traditional soil sampling methods es pecially for estimating spatial variations of soil parameters in the landscape the spectral analysis of seismic surface waves masw can be used to determine the vertical shear wave velocity vs model i e vertical variations in vs with depth in our study masw soundings were determined at each point in a grid spread over a wind eroded field plot of 15 600 m 2 vs was then mapped in terms of the thickness and stiffness of the superficial loamy material horizon which are called thicklm and stifflm respectively to relate the vs values to the soil stiffness cone resistance qd soundings were also performed using a dynamic panda penetrom eter concurrently boreholes were used to sample the same horizon for bulk soil density b measurements based on these measurements large variations in thicklm were observed the distribution of vs values along a 130 m transect allowed for the distinction between two layers corresponding to different mechanical prop erties the vs value of 240 m s was then used as a limit between the loamy material and the underlying clays this limit was validated using drilling observations performed on the same transect therefore it was possi ble to map the thicklm which varied between 0 2 and 6 5 m over the entire field the comparison between the averaged values of vs and qd in the loamy material layer showed a significant correlation r 2 0 4 such that the mapping of stifflm was realised from the vs map and the vs qd relationship density comparison be tween the b measured on drill samples and the b calculated from vs was also performed using previously published relationships however significant correlations were not observed the obtained maps of thicklm and stifflm were consistent with the expected effects of erosion at the catchment scale and provide indica tions of historical erosion events this methodology which provides a structural and mechanical characteri sation of subsurface materials should help to focus conservation measures to the most threatened areas i e the identification of areas that show a reduced thicklm and increased stifflm which are associated with high soil erosion vulnerability and or high compaction state

microwave archaeointensities from peruvian ceramics summary accurate determination of the strength of the ancient geomagnetic field is limited by mineralogical alteration that may occur when samples are heated to produce a thermoremanent magnetization thellier thellier 1959 shaw 1974 by using direct microwave excitation of the magnetic grains we have been able to form a thermoremanent magnetization without significantly heating the bulk sample thus avoiding thermal alteration walton et al 1993 incorporation of this new microwave heating technique with the conventional thellier palaeointensity method has dramatically reduced the scatter of archaeointensity results from peruvian ceramics and clearly defined how the field strength has varied in peru over the past 2000 years the new microwave technique will therefore enhance the feasibility of archaeointensity dating and provide accurate field strength data for geomagnetic modelling

shear wave velocity structure of the shallow sediments in the bohai sea from an ocean bottom seismometer survey abstractto investigate the seismic velocity structure of the shallow sediments in the bohai sea of china we conducted a shear wave velocity inversion of the surface wave dispersion data from a survey of 12 ocean bottom seismometers obss and 377 shots of a 9000 in3 air gun with obs station spacing of approximately 5 km and air gun shot spacing of approximately 190 m high quality scholte wave data were recorded by the obss within 0 4 5 km offset we retrieved the scholte wave phase velocity dispersion for the fundamental mode and first overtone in the frequency band of 0 9 3 0 hz with the phase shift method and inverted for the shear wave velocity structure of the shallow sediments with a damped iterative least squares algorithm pseudo 2d shear wave velocity profiles with a depth of approximately 400 m revealed coherent features of relatively weak lateral velocity variation we also estimated the uncertainty in shear wave velocity structure based on the pseudo 2d profiles from six trial inversions wi

magnetic field intensity study of the 1960 kilauea lava flow hawaii using the microwave palaeointensity technique summary it is extremely valuable to study historic lava flows where the geomagnetic field at their time of extrusion is well known in this study two vertical sections 16 m apart have been sampled from the approximately 1 m thick 1960 kilauea lava flow hawaii variations are seen in the rock magnetic and palaeomagnetic properties between and within the two sections indicating that there are small scale lateral and vertical variations in the lava flow the two sections showed dierent responses to microwave palaeointensity analysis section h6001 generally gave ideal linear behaviour on plots of natural remanent magnetization nrm lost against microwave induced thermoremanent magnetization t m rm gained whilst the majority of samples from h6002 showed anomalous two slope behaviour when all plots were interpreted by taking the best fitting line through all points the flow mean intensity for h6001 was 31 6 3 6 mt and that for h6002 was 37 1 6 4 mt compared with the expected intensity of 36 mt additional historic flows need to be studied in order to ascertain whether this behaviour is typical of all lava and whether it is best to always interpret nrm lost t m rm gained plots by taking the line of best fit regardless of shape

the selection of field acquisition parameters for dispersion images from multichannel surface wave data the accuracy and resolution of surface wave dispersion results depend on the parameters used for acquiring data in the field the optimized field parameters for acquiring multichannel analysis of surface wave masw dispersion images can be determined if preliminary information on the phase velocity range and interface depth is available in a case study on a fill slope in hong kong the optimal acquisition parameters were first determined from a preliminary seismic survey prior to a masw survey field tests using different sets of receiver distances and array lengths showed that the most consistent and useful dispersion images were obtained from the optimal acquisition parameters predicted the inverted s wave velocities from the dispersion curve obtained at the optimal offset distance range also agreed with those obtained by using direct refraction survey

evaluation of the lateral earth pressure coefficients at rest in granular soil deposits using the anisotropic components of s wave velocity abstract determination of the lateral earth pressure coefficients at rest k0 in natural soil deposits is an important issue in geotechnical and geological engineering in this study evaluation of this parameter in a granular soil deposit was examined by using two anisotropic components of the s wave velocity sv and sh wave components to this end thirteen pairs of p and s wave seismic refraction profiles were acquired at two different granular sites in iran the collected shot gathers were processed from which the sv and sh wave velocities were derived the sv wave velocities were obtained by using the multichannel analysis of surface waves masw method while the sh wave velocities were extracted by utilizing the multichannel analysis of love waves malw technique the reference k0 values in the soil deposits were calculated by the mayne and kulhawy s formula based on the friction angles and overconsolidation ratios ocr determined from laboratory tests the curves of the reference k0 values versus the sh sv velocity ratios at both sites strongly confirmed the feasibility of k0 evaluation from the velocity components to develop a global equation for k0 evaluation in granular soil deposits a general regression analysis was conducted on the obtained data from this study combined with those reported in the literature the results showed that reliable values of k0 can be estimated using the sh sv velocity ratios the findings of this study may appropriately serve as references for economic and non invasive in situ k0 identification in granular soil deposits using the surface wave methods

palaeointensity study of the hawaiian 1960 lava implications for possible causes of erroneously high intensities summary it is known that the hawaiian 1960 lava sometimes yields higher palaeointensities than the igrf 36 2 t in order to clarify the causes we have performed a comprehensive investigation of palaeointensity measurements on 19 cores from the lava according to various rock magnetic analyses they are classified into three groups with degrees of the deuteric oxidation in coe s version of the thellier method a significantly larger mean palaeointensity of 49 0 9 6 t n 17 was observed similar to previous studies these palaeointensities showed a dependence on the oxidation indices which can be explained by thermochemical remanent magnetization tcrm acquisition during the natural cooling stage of the lava although it is generally difficult to distinguish the tcrm from thermoremanent magnetization trm a lowtemperature demagnetization ltd treatment on nrm and trm in the thellier experiment seems to allow us to detect the influence of the tcrm on nrm another possible tool for tcrm detection is the double heating technique dht of the shaw method combined with ltd ltd dht shaw method it gave a better average of 39 4 7 9 t n 9 though the success rate was much lower most of the inappropriate results were screened by a combination of the double heating test the arm correction and the ltd treatment if two outliers are further excluded the average is improved to be 35 7 3 3 t n 7 which agrees well with the expected intensity the results of both methods emphasize the importance of taking and measuring samples from the parts of various oxidation degrees in a lava flow

surface wave methods for anomaly detection abstractperimeter defense operations geohazard assessment and engineering characterization require the detection and localization of subsurface anomalies seismic waves incident upon these discontinuities generate a scattered wavefield we have developed various surface wave techniques currently being fielded that have consistently delivered accurate and precise results across a wide range of survey parameters and geographical locations we use the multichannel analysis of surface waves approach to study the multimode rayleigh wave the backscatter analysis of surface waves basw method to detect anomalies 3d visualization for efficient seismic interpretation basw correlation for attribute analysis and instantaneous amplitude integration in the complex basw method discrete linear moveout functions and f k filter designs are optimized for basw considering the fundamental and higher mode dispersion trends of the rayleigh wave synthetic and field data were used to demonstrate multimode basw and mod