reflection seismic investigations in the western part of the paleoproterozoic vhms bearing skellefte district northern sweden the skellefte district forms part of the svecofennian ca 1 90 to 1 80 ga supracrustal sequence and associated intrusive rocks in the northern part of sweden the western part of the skellefte district which is the most important metallogenic province in northern sweden today hosts major volcanic hosted massive sulfide vhms deposits e g the 23 million metric tons mt kristineberg cu zn pb ag au deposit in order to obtain a better understanding of the vhms ore potential at depth new seismic reflection data were acquired along two parallel and 25 km long profiles in the kristineberg area in 2003 the data were collected with the purpose of obtaining high resolution images of the top 10 km of the crust and are presented here for the first time although the structural setting is very complex the stacked sections reveal numerous reflections that can be correlated with surface geology visible on both profiles is a pronounced north dipping band of reflections marking a boundary between relatively transparent crust above and significantly more reflective crust beneath it we interpret this reflective crust to represent a structural basement to the ore bearing skellefte group possibly constituting bothnian basin metasedimentary rocks bordering the skellefte district to the south this new interpretation is important for the understanding of the tectonic evolution of the skellefte district and for defining exploration strategies in the area the seismic results suggest that the kristineberg and ravliden deposits occur on the northern limb of a kilometer scale local second order syncline within the hinge zone of a major antiform results from a profile located approximately 8 km to the west of the kristineberg mine indicate that the revsund granitoid has a thickness of about 3 to 3 5 km ultramafic rocks are also imaged clearly diffraction patterns and bright spot reflectivity is interpreted as originating from either mafic to ultramafic intrusions or a mineralization zone at 3 to 5 km depth these results help to identify new prospective areas and mineral potential both downplunge from known ores and on the same stratigraphic horizon on the southern limb of the ore bearing syncline the seismic reflection profiling has been effective in imaging the major structures around the kristineberg orebody demonstrating that this technique can be used for delineating complex structures significant for mineral exploration

imaging and interpreting the shallow crystalline crust abstract in the past many tests of high resolution seismic imaging methods utilizing off the shelf technology from hydrocarbon exploration have had only limited success some problems associated with the application of seismic profiling in the shallow crystalline crust differ from those encountered in sedimentary basins perhaps the most fundamental distinction stems from differences in statistical properties of the reflection coefficient time series analysis of power spectra derived from borehole data indicates that the reflection coefficients in the crystalline crust are depleted in the seismic bandwidth relative to sedimentary basins this fundamental difference must be considered in the design of shallow crustal seismic surveys in order to achieve success to a first approximation acoustic impedance variations in sedimentary basins are controlled by velocity changes whereas velocity and density can vary independently in the crystalline crust and changes in density may be relatively more important in controlling reflectivity in certain instances density fluctuations outweigh velocity fluctuations for example physical rock property data from mining districts in the canadian shield suggest that massive fe oxide or sulphide bodies will generate strong seismic reflections

empirical ground motion relations for subduction zone earthquakes and their application to cascadia and other regions ground motion relations for earthquakes that occur in subduction zones are an important input to seismic hazard analyses in many parts of the world in the cascadia region washington oregon northern california and british columbia for example there is a significant hazard from megathrust earthquakes along the subduction interface and from large events within the subducting slab these hazards are in addition to the hazard from shallow earthquakes in the overlying crust we have compiled a response spectra database from thousands of strong motion record ings from events of moment magnitude m 5 8 3 occurring in subduction zones around the world including both interface and in slab events the 2001 m 6 8 nis qually and 1999 m 5 9 satsop earthquakes are included in the database as are many records from subduction zones in japan kyoshin net data mexico guerrero data and central america the size of the database is four times larger than that available for previous empirical regressions to determine ground motion relations for subduc tion zone earthquakes the large dataset enables improved determination of attenu ation parameters and magnitude scaling for both interface and in slab events soil response parameters are also better determined by the data we use the database to develop global ground motion relations for interface and in slab earthquakes using a maximum likelihood regression method we analyze regional variability of ground motion amplitudes across the global database and find that there are significant regional differences in particular amplitudes in cascadia differ by more than a factor of 2 from those in japan for the same magnitude distance event type and national earthquake hazards reduction program nehrp soil class this is believed to be due to regional differences in the depth of the soil profile which are not captured by the nehrp site classification scheme regional correction factors to account for these differences are proposed for cascadia and japan the results of this study differ significantly from previous analyses based on more limited data and have important implications for seismic hazard analysis the ground motion relations predict that a great megathrust earthquake m 8 at a fault distance of about 100 km would produce pseudoacceleration psa 5 damped horizontal component on soil sites of about 110 cm sec 2 at 0 5 hz 660 cm sec 2 at 2 5 hz and 410 cm sec 2 at 5 hz with a peak ground acceleration of about 180 cm sec 2 these damaging levels of motion would be experienced over a very large area corresponding to a rectangular area about 300 km wide by 500 km long large in slab events m 7 5 would produce even higher psa values within 100 km of the fault but the in slab motions attenuate much more rapidly with distance thus the hazard posed by moderate to large in slab events such as the 2001 nisqually earth quake is modest compared to that of a cascadia megathrust earthquake of m 8 in terms of the area that would experience damaging levels of ground motion

crooked line 2d seismic reflection imaging in crystalline terrains part 2 migration seismic reflection surveys are frequently conducted over very complicated geological structure but surveying often must be confined to existing crooked roads or tracks typically data from such 2d crooked line surveys are processed using standard common midpoint cmp stacking techniques to obtain a 2d time section which is then 2d migrated in part i we show that a reflector dip component across the processing line can cause serious problems for standard cmp stacking we also propose a supplementary processing step in which cross dip is determined locally and cross dip moveout cdmo is removed from data to form an optimum cross dip stack however a crooked line survey is really a swath 3d survey and ideally we would like to obtain a 3d image of reflectivity surrounding the profile here we investigate the potential of 3d prestack kirchhoff migration to directly image all observed reflections i e we attempt to construct a 3d image volume of all reflectors viewed by the survey because reflectors t

turbulence structure above a vegetation canopy we compare the turbulence statistics of the canopy roughness sublayer rsl and the inertial sublayer isl above in the rsl the turbulence is more coherent and more efficient at transporting momentum and scalars and in most ways resembles a turbulent mixing layer rather than a boundary layer to understand these differences we analyse a large eddy simulation of the flow above and within a vegetation canopy the three dimensional velocity and scalar structure of a characteristic eddy is educed by compositing using local maxima of static pressure at the canopy top as a trigger the characteristic eddy consists of an upstream head down sweep generating hairpin vortex superimposed on a downstream head up ejection generating hairpin the conjunction of the sweep and ejection produces the pressure maximum between the hairpins and this is also the location of a coherent scalar microfront this eddy structure matches that observed in simulations of homogeneous shear flows and channel flows by several workers and also fits with earlier field and wind tunnel measurements in canopy flows it is significantly different from the eddy structure educed over smooth walls by conditional sampling based only on ejections as a trigger the characteristic eddy was also reconstructed by empirical orthogonal function eof analysis when only the dominant sweep generating head down hairpin was recovered prompting a re evaluation of earlier results based on eof analysis of wind tunnel data a phenomenological model is proposed to explain both the structure of the characteristic eddy and the key differences between turbulence in the canopy rsl and the isl above this model suggests a new scaling length that can be used to collapse turbulence moments over vegetation canopies

a review of seismic hazard assessment of gujarat a highly active intra plate region abstract large intraplate earthquakes that occur in the interior of continental plates are rare and often very destructive the gujarat region of western india that witnessed the deadly mw 7 6 earthquake on january 26 2001 and the mw7 8 quake on june 16 1819 is one of the most active intraplate regions of the world the tragedy caused by the 2001 earthquake marked a turning point in the disaster awareness and preparedness in the region in the aftermath of this earthquake several workers investigated the important issue of mitigating seismic hazard through new knowledge based techniques of probabilistic and deterministic ground motion prediction micro and macro zoning of vulnerable areas this paper reviews the results of seismic hazard estimation in the gujarat region from different methodologies we note that the probabilistic seismic hazard estimates by different workers are not consistent even within the same region because of uncertainties in constraining the hazard parameters akin to the global observations using a logical approach we evaluate all the ground motion predictions from different methodologies and constrain the level of expected peak ground acceleration pga by adjusting all the values onto a common platform our assessment reveals that the pga values in gujarat vary from 0 04 to 0 35 g and 0 07 to 0 77 g for 10 and 2 probability of exceedance in 50 years at the engineering bedrock vs 760 m s level the hazard values thus estimated in this study can be directly used to estimate the pgas at the surface by incorporating local site effects which in turn can be utilized in planning and mitigating earthquake hazards further the estimates of pga from deterministic approaches range from 0 05 to 0 90 g we see that within gujarat the ground motion values obtained by deterministic and probabilistic methodologies do not show much variation we affirm that we need to undertake such a logical approach to arrive at realistic probabilistic hazard values that are in conformity with the estimates from deterministic assessment we also advocate the need to upgrade the classical methods of probabilistic and deterministic hazard assessment and incorporate the source and site complexities while estimating the hazard further a comparison of the hazard values of gujarat with those from other intraplate regions of the world reveals that the hazard level in gujarat is higher than in australia brazil and western europe and comparable to north china eastern canada and the new madrid seismic zone

revisiting the 1956 anjar earthquake in western india empirical green s function approach we estimated ground motions at 12 selected sites in the kachchh rift basin of gujarat in the western peninsular shield area of india where the damaging 1956 anjar earthquake m w 6 0 was experienced the ground motions are estimated by applying the empirical green s function approach using an earthquake of m w 4 5 which occurred on the inferred rupture plane of the anjar earthquake with a nearly similar fault mechanism the estimated peak ground acceleration pga varies between 114 and 22 cm s2 at these sites located at distances of 21 127 km from the epicenter respectively the maximum accelerations are correlated with the modified mercalli intensity reported for the anjar earthquake using the empirical relationship between the pga and intensity at most of the sites the level of acceleration could explain the reported damage at a few sites the instrumental intensity estimated using the acceleration values obtained from the synthesis is larger than the felt intensity the ground motion prediction equation gmpe developed for the region estimates the maximum pga near the epicenter area in the 250 300 cm s2 range and the acceleration obtained by our analysis is found to be closer to the predicted acceleration obtained by gmpe our analysis assesses the level of ground motion that was experienced during the 1956 anjar earthquake fairly well and corroborates that reasonable prediction of the ground motion of a historical earthquake is achievable if strong motion recordings are available from the rupture plane of the historical earthquake

seismic hazard assessment and mitigation in india an overview the indian subcontinent is characterized by various tectonic units viz himalayan collision zone in north indo burmese arc in north east failed rift zones in its interior in peninsular indian shield and andaman sumatra trench in south east indian territory during the last about 100 years the country has witnessed four great and several major earthquakes soon after the occurrence of the first great earthquake the shillong earthquake m w 8 1 in 1897 efforts were started to assess the seismic hazard in the country the first such attempt was made by geological survey of india in 1898 and since then considerable progress has been made the current seismic zonation map prepared and published by bureau of indian standards broadly places seismic risk in different parts of the country in four major zones however this map is not sufficient for the assessment of area specific seismic risks necessitating detailed seismic zoning that is microzonation for earthquake disaster mitigation and management recently seismic microzonation studies are being introduced in india and the first level seismic microzonation has already been completed for selected urban centres including jabalpur guwahati delhi bangalore ahmadabad dehradun etc the maps prepared for these cities are being further refined on larger scales as per the requirements and a plan has also been firmed up for taking up microzonation of 30 selected cities which lie in seismic zones v and iv and have a population density of half a million the paper highlights the efforts made in india so far towards seismic hazard assessment as well as the future road map for such studies

near source attenuation of peak horizontal acceleration strong motion data recorded within 50 km of the rupture zone were used to study near source attenuation characteristics of horizontal peak ground acceleration for worldwide earthquakes of magnitudes 5 0 to 7 7 the data base consisted of 229 horizontal components of peak acceleration recorded from 27 earthquakes including the 15 october 1979 imperial valley earthquake these data were found to be adequately represented by the functional relationship pga a exp b m r c m d where pga represents the mean of the peak values scaled from the two horizontal components of each recording m is richter magnitude and r is distance from the fault rupture zone peak acceleration was found to be lognormally distributed with a standard error representing a 45 per cent increase in the median estimate the regression analysis statistically confirmed the results of earthquake simulation studies that have predicted peak acceleration to become independent of magnitude and distance in the near field an extensive sensitivity study showed that predictions based on our attenuation relationships are stable with respect to reasonable model and parameter variations an analysis of residuals was used to investigate the behavior of peak acceleration with respect to various earthquake site and recording parameters the more significant findings being 1 a similarity in the level of acceleration recorded on soil or rock 2 larger than average accelerations recorded at sites located on shallow soils or in areas of steep topography 3 larger than average accelerations associated with earthquakes having reverse fault mechanisms and 4 lower than average accelerations recorded in large embedded structures

experimental estimation of velocities and anisotropy of a series of swedish crystalline rocks and ores to provide a guide for future deep 1 5 km seismic mineral exploration and to better understand the nature of reflections imaged by surface reflection seismic data in two mining camps and a carbonatite complex of sweden more than 50 rock and ore samples were collected and measured for their seismic velocities the samples are geographically from the northern and central parts of sweden ranging from metallic ore deposits meta volcanic and meta intrusive rocks to deformed and metamorphosed rocks first ultrasonic measurements of p and s wave velocities at both atmospheric and elevated pressures using 0 5 mhz p and s wave transducers were conducted the ultrasonic measurements suggest that most of the measured velocities show positive correlation with the density of the samples with an exception of a massive sulphide ore sample that shows significant low p and s wave velocities the low p and s wave velocities are attributed to the mineral texture of the sample and partly lower pyrite content in comparison with a similar type sample obtained from norway which shows significantly higher p and s wave velocities later an iron ore sample from the central part of sweden was measured using a low frequency 0 1 50 hz apparatus to provide comparison with the ultrasonic velocity measurements the low frequency measurements indicate that the iron ore sample has minimal dispersion and attenuation the iron ore sample shows the highest acoustic impedance among our samples suggesting that these deposits are favourable targets for seismic methods this is further demonstrated by a real seismic section acquired over an iron ore mine in the central part of sweden finally a laser interferometer device was used to analyse elastic anisotropy of five rock samples taken from a major deformation zone in order to provide insights into the nature of reflections observed from the deformation zone up to 10 velocity anisotropy is estimated and demonstrated to be present for the samples taken from the deformation zone using the laser interferometery measurements however the origin of the reflections from the major deformation zone is attributed to a combination of anisotropy and amphibolite lenses within the deformation zone

seismic reflection and borehole geophysical investigations in the matagami mining camp a high frequency vibroseis seismic survey was conducted by lithoprobe across a well known section of the matagami mining camp to assess the usefulness of seismic methods in lithological mapping the data have been reprocessed to enhance shallow reflections critical processing steps for the preservation of the shallow features include refraction static corrections cross dip corrections and first break mutes the seismic data were calibrated using geophysical logs from two boreholes adjacent to the profile physical rock property measurements suggest that strong reflectivity within the volcanic sequence occurs at rhyolite gabbro contacts the lower wabassee group a sequence of gabbros and basalts with interlayered rhyolite horizons has been identified as a seismic marker this reflective package overlays the horizon where most sulphide deposits are known to be located in the matagami mining camp seismic reflection methods can be used to map the deep volcanic stratigraphy and structures

low coda qc in the epicentral region of the 2001 bhuj earthquake of mw 7 7 on 26 january 2001 03 46 55 ut a devastating intraplate earthquake of m w 7 7 occurred in a region about 5 km nw of bhachau gujarat 23 42 n 70 23 e the epicentral distribution of aftershocks defines a marked concentration along an e w trending and southerly dipping 45 zone covering an area of 60 40 km2 the presence of high seismicity including two earthquakes of magnitudes exceeding 7 7 in the 200 years is presumed to have caused a higher level of shallow crustal heterogeneity in the kutch area a site lying in the seismic zone v zone of the highest seismicity for potentially m8 earthquakes on the seismic zoning map of india attenuation property of the medium around the epicentral area of the bhuj earthquake covering a circular area of 61 500 km2 with a radius of 140 km is studied by estimating the coda q c from 200 local earthquakes of magnitudes varying from 3 0 4 6 the estimated q 0 values at locations in the aftershock zone high seismicity are found to be low in comparison to areas at a distance from it this can be attributed to the fact that seismic waves are highly scattered for paths through the seismically active and fractured zone but they are well behaved outside the aftershock zone distribution of q 0 values suggests that the local variation in q 0 values is probably controlled by local geology the estimated q 0 values at different stations suggest a low value of q 102 0 80 f 0 98 0 02 indicating an attenuative crust beneath the entire region the frequency dependent relation indicates a relatively low q c at lower frequencies 1 3 hz that can be attributed to the loss of energy due to scattering attenuation associated with heterogeneities and or intrinsic attenuation due to fluid movement in the fault zone and fluid filled cracks the large q c at higher frequencies may be related to the propagation of backscattered body waves through deeper parts of the lithosphere where less heterogeneity is expected based on the attenuation curve estimated for q 0 102 the ground acceleration at 240 km distance is 13 of 1 g i e 0 13 g agreeing well with the ground acceleration recorded by an accelerograph at ahmedabad 0 11 g hence it is inferred that the q 0 value obtained from this study seems to be apt for prediction of ground motion for the region

results from local earthquake velocity tomography implications toward the source process involved in generating the 2001 bhuj earthquake in the lower crust beneath kachchh india to comprehend the source processes of the 26 january 2001 bhuj earthquake sequence of m w 7 7 and its influence on the seismic hazard of the kachchh we estimate various seismological parameters using reliable and accurate aftershock data the estimated parameters led to several important findings including the delineation of an east west trending south dipping 45 fault north wagad fault nwf which touches the surface about 25 km north of kachchh mainland fault kmf the aftershock zone is confined to a 60 km long and 40 km wide region lying between the kmf to the south and nwf to the north extending from 10 to 45 km depth focal mechanism solutions of the mainshock and 25 significant aftershocks of m w 3 0 obtained from waveform inversion of broadband data and local earthquake moment tensor inversion suggest that the region between the kmf and nwf is mainly characterized by reverse faults with east west trend and southerly dip matching with the geological faults in the region the tomographic inversion technique is used to invert 5516 p wave travel times and 4061 s p travel time differences from 600 aftershocks recorded at 8 18 stations tomographic results suggest a regional high velocity body characterized by high v p 7 0 8 5 km sec high v s 4 0 4 8 km sec and low 0 24 0 26 with a head extending 60 km in north south and 40 km in east west at 10 40 km depths this high velocity anomaly is inferred to be a mafic pluton rift pillow which might have intruded during the rifting time 135 ma this crustal mafic pluton must be contributing significantly in accumulating large crustal stresses resulting in the generation of large earthquakes in this intraplate area another important result of our study is the detection of a low velocity zone low v p 6 5 7 0 km sec low v s 3 6 4 0 km sec large 0 26 0 265 within the mafic body at the hypocentral depth of the mainshock 18 25 km which is inferred to be a fluid filled trapped aqueous fluid resulting from metamorphism fractured rock mass the analysis of depth distribution of b values suggests a high b value zone between 15 and 25 km depths which further supports this contention hence the presence of fluids at the hypocenter might have facilitated the occurrence of the 2001 bhuj earthquake within the inferred mafic body in the lower crust

3d seismic imaging of volcanogenic massive sulfide deposits in the flin flon mining camp canada part 2 forward modeling abstractwe applied seismic modeling for a detailed 3d geologic model of the flin flon mining camp canada to address some imaging and interpretation issues related to a 17 km2 3d survey acquired in the camp and described in a complementary paper part 1 a 3d geologic volumetric model of the camp was created based on a compilation of geologic data constraints from drillholes surface geologic mapping interpretation of 2d seismic profiles and 3d surface and grid geostatistical modeling techniques the 3d modeling methodology was based on a hierarchical approach to account for the heterogeneous spatial distribution of geologic constraints elastic parameters were assigned within the model based on core sample measurements and correlation with the different lithologies the phase screen algorithm used for seismic modeling was validated against analytic and finite difference solutions to ensure that it provided accurate amplitude variation with offset behavior for dipping strata synthetic data were gener

delineating ophiolite derived host rocks of massive sulfide cu co zn deposits with 2d high resolution seismic reflection data in outokumpu finland abstractseismic reflection data was applied to a study of the upper crustal structures in the outokumpu mining and exploration area in eastern finland the cu co zn sulfide ore deposits of the outokumpu area are hosted by palaeoproterozoic ophiolite derived altered ultrabasic rocks serpentinite skarn rock and quartz rock and black schist within turbiditic mica schist mining in the outokumpu area has produced a total of 36 mt of ore from three historical and one active mine seismic data comprises 2d vibroseis data surveyed along a network of local roads the seismic sections provide a comprehensive 3d view of the reflective structures acoustic rock properties from downhole logging and synthetic seismograms indicate that the strongly reflective packages shown in the seismic data can be identified as the host rock environments of the deposits reflectors show excellent continuity along the structural grain of the ore belt which allows correlating reflectors with surface geology magnetic map and dri

applications of algebraic reconstruction techniques to crosshole seismic data tomographic imaging techniques were applied to two crosshole data sets to determine the velocity structures and the reliability and resolution of the algorithms on real data the experiments were carried out at the retsoff salt mine in new york and at the underground radioactive waste study site at the stripa mine facility in sweden the traveltimes at restoff were high quality and were obtained over raypaths of up to 500 m in length the structure was quite complicated with velocity contrasts up to 50 percent the stripa site was in granitic rock with velocity contrasts of only a few percent the dimensions of the experiment were small with maximum ray lengths of just over 10 m the data at this site were collected with very high accuracy source and receiver locations were measured to better than 1 0 mm and traveltimes were read to 0 001 ms a number of algorithms similar to the algebraic reconstruction techniques art used in medical imaging have been applied to the data some modifications of the algorithms such as the application of weighting schemes damping parameters and curved raypaths were performed the resulting velocity fields were compared to the known fields and with each other to determine an optimal method the algorithms were found to be a rapid reliable means of reconstructing the slowness field of real data low velocity zones were recovered with accuracy in location and value it was also found that great care was necessary in application of the techniques to ensure that proper damping parameters are used and the proper number of iterations taken otherwise poor reconstructions will result

2001 bhuj india earthquake engineering seismoscope recordings and eastern north america ground motion attenuation relations engineering seismoscope data collected at distances less than 300 km for the m 7 7 bhuj india mainshock are compatible with ground motion attenuation in eastern north america ena the mainshock ground motion data have been corrected to a common geological site condition using the factors of joyner and boore 2000 and a classification scheme of quaternary or tertiary sediments or rock we then compare these data to ena ground motion attenuation relations despite uncertainties in recording method geological site corrections common tectonic setting and the amount of regional seismic attenuation the corrected bhuj dataset agrees with the collective predictions by ena ground motion attenuation relations within a factor of 2 this level of agreement is within the dataset uncertainties and the normal variance for recorded earthquake ground motions

attenuation of peak horizontal acceleration and velocity from italian strong motion records italian strong motion data were used to study attenuation characteristics of horizontal peak ground acceleration and velocity the data base consisted of 190 horizontal components of accelerograms recorded in italy since 1976 from 17 earthquakes of magnitudes 4 6 to 6 8 the resulting equations are log a 1 562 0 306 m log r 2 5 8 2 1 2 0 169 s log v 0 710 0 455 m log r 2 3 6 2 1 2 0 133 s where a is peak horizontal acceleration in g v is peak horizontal velocity in centimeters second m is magnitude r is the closest distance to the surface projection of the fault rupture in kilometers and s is a variable taking the values of 0 and 1 according to the local site geology peak acceleration and velocity were found to be lognormally distributed with a standard error representing respectively a 49 and 64 per cent increase in the median estimate we considered a magnitude dependent shape of the attenuation curves but we found no basis for it in the data attenuation relationships developed using epicentral distance in place of fault distance gave similar results with higher standard errors and higher predicted values for short distances and high magnitudes sensitivity studies performed with the analysis of the residuals showed that predictions based on our relatiaons are stable with respect to reasonable variations of the model and the seismic areas providing the data comparisons with attenuation relationships proposed for western north america showed differences of the same order of magnitude as the statistical prediction uncertainty

waving plants and turbulent eddies new large eddy simulations of flow over a flexible plant canopy by dupont et al j fluid mech 2010 this issue vol 652 pp 5 44 have produced apparently paradoxical results work over the last three decades had suggested that turbulent eddies could lock onto to the waving frequency of uniform cereal canopies their new simulations contradict this view although a resolution may lie in the essentially three dimensional nature of the instability process that generates the dominant eddies above plant canopies

coulomb static stress variations in the kachchh gujarat india implications for the occurrences of two recent earthquakes mw 5 6 in the 2001 bhuj earthquake region summary double difference algorithm was used to relocate aftershock sequences of two mw 5 6 kachchh earthquakes india which have occurred on 2006 march 7 and april 6 along almost vertical strike slip gedi fault gf and south dipping reverse north wagad fault nwf respectively the relocated focal depths delineate a marked variation of 4 and 7 km in the brittle ductile transition depths beneath gf and nwf respectively we modelled the coulomb failure stress change cfs produced by the 2001 mainshock and 2006 gedi events on an optimally oriented plane a strong correlation with occurrences of aftershocks and regions of increased cfs is obtained on both the faults the predicted cfs on the gf increased by 0 14 mpa at 3 km depth where the 2006 march 7 mw 5 6 event occurred the variation in brittle ductile transition depths may be related to the perturbation in geothermal gradient resulted from the presence of intrusives or varying saturation state of fluid filled fractured rock matrix beneath both the fault zones

seismic imaging and potential field modelling to delineate structures hosting vhms deposits in the skellefte ore district northern sweden the skellefte district in northern sweden is a roughly 150 by 50 km2 large early proterozoic massive sulphide belt based on high resolution reflection seismic data along two parallel seismic profi

modelling waving crops using large eddy simulation comparison with experiments and a linear stability analysis in order to investigate the possibility of modelling plant motion at the landscape scale an equation for crop plant motion forced by an instantaneous velocity field is introduced in a large eddy simulation les airflow model previously validated over homogeneous and heterogeneous canopies the canopy is simply represented as a poroelastic continuous medium which is similar in its discrete form to an infinite row of identical oscillating stems only one linear mode of plant vibration is considered two way coupling between plant motion and the wind flow is insured through the drag force term the coupled model is validated on the basis of a comparison with measured movements of an alfalfa crop canopy it is also compared with the outputs of a linear stability analysis the model is shown to reproduce the well known phenomenon of honami which is typical of wave like crop motions on windy days the wavelength of the main coherent waving patches extracted using a bi orthogonal decomposition bod of the crop velocity fields is in agreement with that deduced from video recordings the main spatial and temporal characteristics of these waving patches exhibit the same variation with mean wind velocity as that observed with the measurements however they differ from the coherent eddy structures of the wind flow at canopy top so that coherent waving patches cannot be seen as direct signatures of coherent eddy structures finally it is shown that the impact of crop motion on the wind dynamics is negligible for current wind speed values no lock in mechanism of coherent eddy structures on plant motion is observed in contradiction with the linear stability analysis this discrepancy may be attributed to the presence of a nonlinear saturation mechanism in les 2010 cambridge university press

sediment thicknesses and qs vs qp relations in the kachchh rift basin gujarat india using sp converted phases delineation of the top sedimentary structure and its qs vs qp relationship using the travel time difference of direct s and converted sp phase is key to understanding the seismic hazard of any sedimentary basin area we constructed filtered displacement waveforms from local etna episensor acceleration recordings as well as local velocity recordings of aftershocks of the 2001 bhuj earthquake recorded by the kachchh seismological network of the national geophysical research institute ngri hyderabad india during 2001 2004 stations are within 15 70km of epicenters and the resulting displacement waveforms are generally simple displaying prominent p sp and s wave pulses particle motion of p and s waves suggest near vertical raypaths consistent with preliminary depth estimates the direct s wave on the horizontal component is characterized by lower frequency content than the converted sp phase on the vertical component this difference in frequency content between s and sp phases can be explained in terms of different attenuation effects for p and s waves in the unconsolidated sediments the sp phase is generated by s to p phase conversion at the base of mesozoic sediments of the kachchh basin travel time inversion velest of 2565 p and 2380 s arrivals from 658 well located aftershocks recorded at 8 14 three component local seismic stations led to 1 d velocity models indicated very slow sediments in the upper 0 2 km depth range vp 2 92 km s and vs 0 90 km s and an increasing trend of velocities with depth at 2 40 km depth the estimated sediment thicknesses beneath 12 accelerograph and 6 seismograph sites from the estimated velocity model and the travel time difference between s and converted sp phases reaches a maximum of 1 534 0 117 km beneath bandri near the location of 2001 bhuj mainshock and attains a minimum sediment thickness of 0 858 0 104 km beneath ramvav and burudia the spectral ratios between sp and s from 159 three component accelerograms have been used to study seismic wave attenuation in the kachchh rift basin the estimated qs vs qp relations for 12 accelerograph sites vary from qs 0 184 qp at chobari to qs 0 505 qp at dudhai for stations chobari chopdwa jahawarnagar vondh and tapar the spectral ratio slopes and hence the calculated qs vs qp relations are effectively the same and the correlation coefficients are quite high 0 91 0 93 stations adhoi manfara new dudhai dudhai and sikara have similar qs vs qp relationships to each other and also have high correlation coefficients 0 78 0 87 the spectral ratios for stations anjar and ramvav are small and poorly constrained resulting in less reliable qs vs qp relations this could be due to noisy data fewer available waveforms or scattering due to velocity heterogeneities and or interface irregularities

ground motion modelling in the gujarat region of western india using empirical green s function approach abstract in this study ground motions are estimated for scenario earthquakes of mw 6 0 6 5 and 7 0 at 17 sites in gujarat region using empirical green s function technique the dholavira earthquake of june 19 2012 mw 5 1 which occurred in the kachchh region of gujarat is considered as an element earthquake we estimated the focal mechanism and source parameters of the element earthquake using standard methodologies the moment tensor inversion technique is used to determine the fault plane solution strike 8 dip 51 and rake 7 the seismic moment and the stress drop are 5 6 10 16 nm and 120 bars respectively the validity of the approach was tested for a smaller earthquake a few possible directivity scenarios were also tested to find out the effect of directivity on the level of ground motions our study reveals that source complexities and site effects play a very important role in deciding the level of ground motions at a site which are difficult to model by gmpes our results shed new light on the expected accelerations in the region and suggest that the kachchh region can expect maximum acceleration of around 500 cm s 2 at few sites near source and around 200 cm s 2 at most of the sites located within 50 km from the epicentre for a mw 7 0 earthquake the estimated ground accelerations can be used by the administrators and planners for providing a guiding framework to undertake mitigation investments and activities in the region

seismic reflection imaging over a massive sulfide deposit at the matagami mining camp quebec a 2 d seismic reflection profile was shot across the southern flank of the matagami mining camp almost directly above the recently discovered bell allard massive sulfide deposit now estimated at more than 6 million metric tons all orebodies found in the southern part of the mining camp including bell allard are located at the contact between the primarily basaltic wabassee group and the underlying rhyolitic watson lake group seismic reflections were recorded from the basalt rhyolite contacts of the lower wabassee group as well as from gabbro sills that intrude much of the volcanic stratigraphy a strong reflection from the top of the bell allard orebody was also detected but the reflection does not extend over the full width of the deposit as defined by drilling appearing to correlate with the lower pyrite rich zone faulting which can be interpreted from discontinuities in the observed reflections probably controlled the formation of the bell allard deposit if the interpreted gabbro sills are accepted as isotime markers then faulting of the deeper sill complex defines a series of half grabens within the rhyolitic watson lake group the bell allard deposit is found at the intersection of one of these apparently low angle normal faults with the top of the watson lake group indicating that sulfide mineralization may have been associated with fluid flow along the fault which likely penetrates to the underlying mafic intrusion although the precise geometry of subsurface faulting cannot be estimated from a single 2 d seismic profile these results indicate that a full 3 d seismic survey should allow the mapping of many of the subsurface fault systems and the verification of hypotheses of fault controlled deposit formation

seismic methods in mineral exploration and mine planning a general overview of past and present case histories and a look into the future abstractdue to high metal prices and increased difficulties in finding shallower deposits the exploration for and exploitation of mineral resources is expected to move to greater depths consequently seismic methods will become a more important tool to help unravel structures hosting mineral deposits at great depth for mine planning and exploration these methods also can be used with varying degrees of success to directly target mineral deposits at depth we review important contributions that have been made in developing these techniques for the mining industry with focus on four main regions australia europe canada and south africa a wide range of case studies are covered including some that are published in the special issue accompanying this article from surface to borehole seismic methods as well as petrophysical data and seismic modeling of mineral deposits at present high resolution 2d surveys mostly are performed in mining areas but there is a general increasing trend in the use of 3

crustal scale fluid pathways and source rocks in the victorian gold province australia insights from deep seismic reflection profiles deep seismic reflection data collected across the western lachlan orogen of southeast australia have provided important insights into crustal scale fluid pathways and possible source rocks in one of the richest orogenic gold provinces in the world the profiles span three of the most productive structural zones in victoria the stawell bendigo and melbourne zones zone scale variations in the age and style of gold deposits correspond with differences in crustal structure and composition the bilateral distribution of gold production in the stawell and bendigo zones is related to the v shaped crustal scale geometry of the two zones in cross section major first order faults like the east dipping moyston fault and a set of west dipping listric faults within the bendigo zone were probably major fluid conduits in the lower to middle crust during gold mineralization first order faults in the stawell and bendigo structural zones appear to have accommodated large scale thickening down to the lower crust the faults converge in a region beneath the western bendigo zone where a thick section of mafic volcanic rocks and lesser sedimentary rocks are identified as a likely common source of gold bearing fluid that was largely generated by late ordovician to early silurian metamorphism the areas with the greatest gold endowment lie above lower crustal regions that have preserved the thickest succession of fertile mafic igneous rocks up to about 25 km thick they also correspond to a region of thin or absent precambrian lithosphere mafic rocks in the stawell zone and far western bendigo zone were probably partly consumed by cambrian west dipping subduction similar rocks in the rest of the bendigo zone lay outside the influence of cambrian subduction accretion and were deformed later probably beginning in the late ordovician early silurian benambran orogeny during crustal scale imbrication this imbrication preserved much of the mafic rocks to form the lower to middle crust first order listric faults in the bendigo zone are interpreted as major controls on the locations of goldfields even though they are largely unmineralized near the present surface the shallow dipping segments of first order listric faults were favorably oriented for reactivation at the time of gold mineralization and acted as major fluid conduits in the lower to middle crust in contrast the upper steeply dipping segments of first order listric faults were unfavorably oriented for reactivation and were poor fluid conduits the seismic data show that the transition from predominantly shallow to steeply dipping fault segments occurs in the middle to upper crust near the boundary between thick imbricated metavolcanic rocks that lie immediately below 6 to 15 km of folded metasedimentary rocks this transition may have coincided with fluid escape zones that aided the transfer of permeability away from first order faults and into the overlying fold dominated turbidites this transfer of permeability was enhanced by the growth of subvertical fold related fault and fracture meshes in the upper crustal turbidites the fault and fracture meshes consisted of bedding parallel faults limb thrusts and tension vein arrays that developed along fold hinges in the bendigo zone individual fold hinges and regional fold culminations were important controls on the distribution of fluid flow fluid flow was partly syndeformational but overlapped into the immediate postdeformational period of the benambran orogeny later reactivation of first order faults in the late silurian to early devonian and again in the late devonian led to further although less important mineralizing events as fluids exploited the preexisting fault architecture deeply penetrating north dipping listric faults in the less gold rich melbourne zone cut into inferred proterozoic basement and may have been fluid conduits during a late devonian mineralizing event

mixing layers and coherent structures in vegetated aquatic flows 1 to date flow through submerged aquatic vegetation has largely been viewed as perturbed boundary layer flow with vegetative drag treated as an extension of bed drag however recent studies of terrestrial canopies demonstrate that the flow structure within and just above an unconfined canopy more strongly resembles a mixing layer than a boundary layer this paper presents laboratory measurements obtained from a scaled seagrass model that demonstrate the applicability of the mixing layer analogy to aquatic systems specifically all vertical profiles of mean velocity contained an inflection point which makes the flow susceptible to kelvin helmholtz instability this instability leads to the generation of large coherent vortices within the mixing layer observed in the model at frequencies between 0 01 and 0 11 hz which dominate the vertical transport of momentum through the layer the downstream advection of these vortices is shown to cause the progressive coherent waving of aquatic vegetation known as the monami when the monami is present the turbulent vertical transport of momentum is enhanced with turbulent stresses penetrating an additional 30 of the plant height into the canopy

high resolution seismic reflection profiles reveal fracture zones within a homogeneous granite batholith several countries are investigating the use of plutonic rock bodies for the ultimate disposal of radioactive waste material1 among criteria2 3 that must be met before a rock body is mined for a repository is that it must have a low in situ permeability as the permeability of most unfractured plutonic rocks is very low3 the problem reduces to finding those bodies which do not contain major connected fractures that would allow radioactive material to be transported by water to the biosphere we report here that a high resolution seismic reflection survey across the central region of an archaean granitic pluton which on the basis of other data might be defined as relatively homogeneous identifies major sub horizontal fracture zones at depth such fracture zones which could be a major hazard for the containment of radioactive wastes may therefore be detected before selection of a repository site by a combination of high resolution seismic reflection surveying and suitably located deep drilling

application of modern 2 d and 3 d seismic reflection techniques for uranium exploration in the athabasca basinthis article is one of a series of papers published in this special issue on the theme lithoprobe parameters processes and the evolution of a continent seismic reflection techniques have been applied in several studies over the last 20 years as a uranium exploration tool within the athabasca basin and have been utilized to provide the larger structural context for known uranium deposits within the basin at the crustal scale deposits within the eastern athabasca basin are shown to be associated with deep seated shear zones that originated during trans hudson orogeny and have subsequently been reactivated during and subsequent to deposition of the basin fill sandstones seismic properties of the athabasca sandstones and underlying basement have been determined through in situ borehole measurements reflectivity within the sandstones is generally weak seismically recognizable signatures are primarily associated with variations in fracture density porosity and degree of silicification the basement unconformity and regolith a prime target of exploration is widely imaged as it is characterized by variable but generally distinct reflectivity results fr

ground motion attenuation relation from strong motion records of the 2001 mw 7 7 bhuj earthquake sequence 2001 2006 gujarat india predictive relations are developed for peak ground acceleration pga from the engineering seismoscope srr records of the 2001 mw 7 7 bhuj earthquake and 239 strong motion records of 32 significant aftershocks of 3 1 mw 5 6 at epicentral distances of 1 r 288 km we have taken advantage of the recent increase in strong motion data at close distances to derive new attenuation relation for peak horizontal acceleration in the kachchh seismic zone gujarat this new analysis uses the joyner boore s method for a magnitude independent shape based on geometrical spreading and anelastic attenuation for the attenuation curve the resulting attenuation equation is eqalign ln hbox y 7 9527 1 4043 hbox m rm w ln left hbox r rm jb 2 19 82 2 right 1 2 0 0682 hbox s hfill cr hbox for 3 1 hbox m rm w le 7 7 quad quad hbox std hbox dev left sigma right pm 0 8243 hfill cr where y is peak horizontal acceleration in g mw is moment magnitude rjb is the closest distance to the surface projection of the fault rupture in kilometers and s is a variable taking the values of 0 and 1 according to the local site geology s is 0 for a rock site and s is 1 for a soil site the relation differs from previous work in the improved reliability of input parameters and large numbers of strong motion pga data recorded at short distances 0 50 km from the source the relation is in demonstrable agreement with the recorded strong ground motion data from earthquakes of mw 3 5 4 1 4 5 5 6 and 7 7 there are insufficient data from the kachchh region to adequately judge the relation for the magnitude range 5 7 mw 7 7 but our ground motion prediction model shows a reasonable correlation with the pga data of the 29 march 1999 chamoli main shock mw 6 5 validating our ground motion attenuation model for an mw6 5 event however our ground motion prediction shows no correlation with the pga data of the 10 december 1967 koyna main shock mw 6 3 our ground motion predictions show more scatter in estimated residual for the distance range 0 30 km which could be due to the amplification noise at near stations situated in the kachchh sedimentary basin we also noticed smaller residuals for the distance range 30 300 km which could be due to less amplification noise at sites distant from the kachchh basin however the observed less residuals for the longer distance range 100 300 km are less reliable due to the lack of available pga values in the same distance range