impact experiments on ice the results of cratering and fragmentation experiments on pure ice are reported the projectiles used are cylindrical aluminum poly carbonate teflon and pyrophyllite fired at velocities between 110 m sec and 680 m sec with kinetic energies at impact between 2 and 500 joules crater diameters pit diameters in the ice were about two times larger than craters in the same energy range in basalts the ratios of pit diameter spall diameter are about three and the ratios of depth of crater spall diameter are between 0 1 and 0 3 which are close to the depth diameter ratios observed in basalts the crater diameter in ice is also well expressed as a single function of the late stage effective energy defined recently by mizutani et al 1983 the specific energy for complete destruction of ice target is about 50 j kg which is two orders of magnitude smaller than that of basalt the present experimental data on cratering and fragmentation of ice show that the impacts associated with the largest craters on callisto and mimas must have severely fractured the whole satellites and that those giant impacts with the kinetic energy of 1023 to 1027 joules probably affected significantly the evolution of the satellites

high resolution reservoir characterization by an acoustic impedance inversion of a tertiary deltaic clinoform system in the north sea fluvio deltaic sedimentary systems are of great interest for explorationists because they can form prolific hydrocarbon plays however they are also among the most complex and heterogeneous ones encountered in the subsurface and potential reservoir units are often close to or below seismic resolution for seismic inversion it is therefore important to integrate the seismic data with higher resolution constraints obtained from well logs whereby not only the acoustic properties are used but also the detailed layering characteristics we have applied two inversion approaches for poststack time migrated seismic data to a clinoform sequence in the north sea both methods are recursive trace based techniques that use well data as a priori constraints but differ in the way they incorporate structural information one method uses a discrete layer model from the well that is propagated laterally along the clinoform layers which are modeled as sigmoids the second method uses a constant sampling rate from the well data and uses horizontal and vertical regularization parameters for lateral propagation the first method has a low level of parameterization embedded in a geologic framework and is computationally fast the second method has a much higher degree of parameterization but is flexible enough to detect deviations in the geologic settings of the reservoir however there is no explicit geologic significance and the method is computationally much less efficient forward seismic modeling of the two inversion results indicates a good match of both methods with the actual seismic data

cooperative inversion of geophysical data geophysical inversion by iterative modeling involves fitting observations by adjusting model parameters both seismic and potential field model responses can be influenced by the adjustment of the parameters of the rock properties the objective of this cooperative in version is to obtain a model which is consistent with all available surface and borehole geophysical data al though inversion of geophysical data is generally non unique and ambiguous we can lessen the ambiguities by inverting all available surface and borehole data this paper illustrates this concept with a case history in which surface seismic data sonic logs surface gravity data and borehole gravity meter bhgm data are ad equately modeled by using least squares inversion and a series offorward modeling steps the traditional analysis of various geophysical data sets has been termed integrated interpretation such analysis has traditionally involved much processing modeling and subjec tive interpretation in order to develop a geologic model which is consistent with various surface and borehole geophysical data a method which automates some of the above pro cedures is least squares inversion this procedure perturbs an initial set of model parameters in order to fit the observed data least squares inversion is described in many papers in cluding those of jackson 1972 wiggins 1972 jupp and vozoff 1975 and lines and treitel 1984 this inversion technique could also be termed automated iterative mod eling in terms of modeling different geophysical data sets there are many possible approaches which allow inversion of a given data set and it is doubtful whether one single recipe will prove suitable for all problems nevertheless by jointly invert ing various types of geophysical observations we may lessen the extent of some of the ambiguities inherent in individual data sets lafehr 1984 gives a germane discussion of several reasons for this type of coordinated geophysical effort in the present study we define cooperative inversion as the esti mation of a subsurface model which is consistent with various independent geophysical data sets in the case discussed in this paper these data sets include surface and borehole observa tions of the seismic and gravity responses in our definition cooperative inversion may include either joint inversion or sequential inversion

glacial flow of floating marine ice in snowball earth 1 simulations of frigid neoproterozoic climates have not considered the tendency of thick layers of floating marine ice to deform and spread laterally we have constructed a simple model of the production and flow of marine ice on a planetary scale and determined ice thickness and flow in two situations when the ocean is globally ice covered hard snowball and when the tropical waters remain open soft snowball in both cases ice flow strongly affects the distribution of marine ice flowing ice probably carries enough latent heat and freshwater to significantly affect the transition into a snowball earth climate we speculate that flowing marine ice rather than continental ice sheets may be the erosive agent that created some neoproterozoic glacial deposits

degradation of 100 m scale rocky ejecta craters at the insight landing site on mars and implications for surface processes and erosion rates in the hesperian and amazonian rocky ejecta craters recs at the interior exploration using seismic investigations geodesy and heat transport insight landing site on elysium planitia mars provide constraints on crater modification and rates for the hesperian and amazonian the recs are between 10 m and 1 2 km in diameter and exhibit five classes of preservation class 1 represents pristine craters with sharp rims and abundant ejected rocks from classes 2 to 5 rims become more subdued craters are infilled and the ejecta become discontinuously distributed high resolution imaging science experiment digital elevation models indicate a maximum depth to diameter ratio of 0 15 which is lower than pristine models for craters of similar size the low ratio is related to the presence of a loosely consolidated regolith and early stage eolian infill rim heights have an average height to diameter ratio of 0 03 for the most pristine class the size frequency distribution of recs plotted using cumulative and differential methods indicates that crater classes within the diameter range of 200 m to 1 2 km are separated by 100 to 200 myr smaller craters degrade faster with classes separated by 100 myr rim erosion can be entirely modeled by nonlinear diffusional processes using the calculated timescales and a constant diffusivity of 8 10 7 m 2 year for craters 200 to 500 m in diameter diffusion models only partly capture depth related degradation which requires eolian infill depth degradation and rim erosion rates are 10 2 to 10 3 m myr respectively the rates are consistent with relatively slow modification that is typical of the last two epochs of martian history

mach number scaling of impact craters in unconsolidated granular materials abstract the formation of impact craters in unconsolidated granular materials is a topic of enduring interest in solid earth geophysics planetary science and several branches of engineering science in particular a general relationship between crater size impact parameters and target material properties is often sought this paper presents a new empirical relationship based on dimensional analysis and inspired by gas dynamic shock physics for the diameters of low and high speed impact craters in dry granular materials based on the hypothesis that surface gravity and shock wave phenomena primarily set crater size the final relationship involves the impacting object s kinetic energy and speed the target material s density angle of repose and sound speed and the gravitational acceleration at the impact location it is formulated in terms of a dimensionless crater diameter an algebraic combination of froude number mach number and the tangent of the target material s angle of repose using an analogy to gas dynamics and an empirical power law for the dependence of granular material sound speed on gravitational acceleration the coefficient of determination for the final fit is 0 969 based on experimental impact data from 325 individual impacts spanning parametric ranges of 400 in crater diameter 1010 in impact energy 500 in gravitational acceleration and 40 in target material density for two different angles of repose the final formula provides insight into how impact energy conversion depends on mach number and may be useful for predictive and forensic analysis of planetary impact craters and for granular flow code validation

impact experiments in low temperature ice new results of low velocity impact experiments in cubic and cylindrical 20 cm water ice targets initially at 257 and 81 k are reported impact velocities and impact energies vary between 0 1 and 0 64 km sec and 10 9 and 10 10 ergs respectively observed crater diameters range from 7 to 15 cm and are two to three times larger than values found for equal energy impacts in basaltic targets crater dimensions in ice targets increase slightly with increasing target temperatures crater volumes of strength controlled ice craters are about 10 to 100 times larger than those observed for craters in crystalline rocks based on similarity analysis general scaling laws for strength controlled crater formation are derived and are applied to crater formation on the icy galilean and saturnian satellites this analysis indicates that surface ages based on impact crater statistics on an icy crust will appear greater than those for a silicate crust which experienced the same impact history the greater ejecta volume for cratering in ice versus cratering in silicate targets leads to accelerated regolith production on an icy planet

ice shelf response to ice stream discharge fluctuations i unconfined ice tongues abstract unsteady thickness and flow observed on the ross ice shelf are thought to result primarily from fluctuations of ice streams and outlet glaciers that feed the ice shelf at its inland boundaries ice stream discharge fluctuations constitute an independent means of forcing unsteady ice shelf behavior and their effect must be distinguished from those of oceanic and atmospheric climate to understand ice shelf change ice stream generated fluctuations of a one dimensional ice shelf are found to propagate through the ice shelf environment along the two characteristics of the hyperbolic governing equations one characteristic permits instantaneous transmission of grounding line velocity changes to all points downstream the other characteristic represents slow transmission of grounding line thickness changes along lagrangian particle paths

bayesian estimation in seismic inversion part i principles1 this paper gives a review of bayesian parameter estimation the bayesian approach is fundamental and applicable to all kinds of inverse problems its basic formulation is probabilistic information from data is combined with a priori information on model parameters the result is called the a posteriori probability density function and it is the solution to the inverse problem in practice an estimate of the parameters is obtained by taking its maximum well known estimation procedures like least squares inversion or l 1 norm inversion result depending on the type of noise and a priori information given due to the a priori information the maximum will be unique and the estimation procedures will be stable except in theory for the most pathological problems which are very unlikely to occur in practice the approach of tarantola and valette can be derived within classical probability theory the bayesian approach allows a full resolution and uncertainty analysis which is discussed in part ii of the paper

a review of least squares inversion and its application to geophysical problems geophysical inversion involves the estimation of the parameters of a postulated earth model from a set of observations since the associated model responses can be nonlinear functions of the model parameters nonlinear least squares techniques prove to be useful for performing the inversion a common type of inversion applies iterative damped linear least squares through use of the marquardt levenberg method traditionally this method has been implemented by solving the associated normal equations in conventional ways however singular value decomposition svd produces significant improvements in computational precision when applied to the same system of normal equations iterative least squares modeling finds application in a wide variety of geophysical problems two examples illustrate the approach 1 seismic wavelet deconvolution and 2 the location of a buried wedge from surface gravity data more generally nonlinear least squares inversion can be used to estimate earth models for any set of geophysical observations for which an appropriate mathematical description is available

anisotropic resistivity tomography geophysical tomographic techniques have the potential to remotely detect and characterize geological features such as fractures and spatially varying lithologies by their response to signals passed through these features anisotropic behaviour in many geological materials necessitates the generalization of tomographic methods to include anisotropic material properties in order to attain high quality images of the subsurface in this paper we present a finite element fe based direct current electrical inversion method to reconstruct the conductivity tensor at each node point of a fe mesh from electrical resistance measurements the inverse problem is formulated as a functional optimization and the non uniqueness of the electrical inverse problem is overcome by adding penalty terms for structure and anisotropy we use a modified levenberg marquardt method for the functional optimization and the resulting set of linear equation is solved using pre conditioned conjugate gradients the method is tested using both synthetic and field experiments in cross well geometry the acquisition geometry for both experiments uses a cross well experiment at a hard rock test site in cornwall southwest england two wells spaced at 25 7 m were equipped with electrodes at a 1 m spacing at depths from 21 108 m and data were gathered in pole pole geometry the test synthetic model consists of a strongly anisotropic and conductive body underlain by an isotropic resistive formation beneath the resistive formation the model comprises a moderately anisotropic and moderately conductive half space intersected by an isotropic conductive layer this model geometry was derived from the interpretation of a seismic tomogram and available geological logs and the conductivity values are based on observed conductivities we use the test model to confirm the ability of the inversion scheme to recover the known true model we find that all key features of the model are recovered however the inversion model is smoother than the true model and the difference in absolute value of anisotropy and conductivity between features is slightly underestimated using an anisotropic conductivity distribution aggravates the problem of non uniqueness of the solution of the inverse electrical problem this problem can be overcome by applying appropriate structural and anisotropy constraints we find that running a suite of inversions with varying constraint levels and subsequent examination of the results including the inspection of residual maps offers a viable method for choosing appropriate numerical values for the imposed constraints inversion of field data reveals a strongly anisotropic subsurface with marked spatial variations of both magnitude of anisotropy and conductivity average conductivities range from 0 001 s m 1 1000 m to 0 003 s m 1 333 m and anisotropy values range from 0 per cent to more than 300 per cent as an independent test of the reliability of the structures revealed by anisotropic electric tomography anisotropic seismic traveltime tomograms were calculated we find a convincing structural agreement between the two independently derived images areas of high electric anisotropy coincide with seismically anisotropic areas and we observe an anticorrelation between electric conductivity and seismic velocity both observations are consistent with anisotropy anomalies caused by fracturing or layering

interpretive advantages of 90 phase wavelets part 2 seismic applications we examine field seismic data to test the benefits of 90 phase wavelets in thin bed interpretation that are predicted by seismic modeling in part 1 of this paper in an interbedded sandstone shale miocene succession in the gulf of mexico basin a 90 phase shift of nearly zero phase seismic data significantly improves lithologic and stratigraphic interpretation a match between seismic and acoustic impedance ai profiles results in a better tie between seismic amplitude traces and lithology indicative logs better geometric imaging of ai units that does not use dual polarity seismic events results in easier and more accurate reservoir delineation less amplitude distortion and the stratigraphy independent nature of thin bed interference significantly improves stratigraphic resolution and seismic stratigraphic profiling for a ricker like wavelet having small side lobes stratigraphic resolution of 90 phase data is considerably higher than that of zero phase data in this specific case stratigraphic re

destruction of rocks by low velocity impact and its implications for accretion and fragmentation processes of planetesimals recent experimental results on impact destruction of rocks basalt and tuff are summarized the mode of destruction and some empirical relations between the mass of the largest fragment ml the released kinetic energy divided by target mass ei and the work done during impact w are presented the mass ml can be related to both ei and w log ml mt a log ei and log ml mt b log w an effect due to the difference in impact velocity on the ml versus ei relation can be observed but there seems to be no effect due to impact velocity on the ml versus w relation thus it may be suggested that w is a useful means of describing phenomena associated with the impact destruction of rocks target shape also affects the ml versusei relation but no large differences have been observed between various rocks the size distribution of fragments can be adequately expressed in terms of an inverse power law relation in which slope of the size distribution i e exponent increases with increasing ei 0 90 0 36 log ei for basalt and 1 94 0 24 log ei for tuff based on the empirical ei relations a fragmentation model of the parent bodies of eos and koronis families is presented it is suggested that the parent bodies of eos and koronis families had been differentiated prior to fragmentation and were completely fragmented at ei 2 104 joule kg and 2 103 joule kg

automatic 1 d waveform inversion of marine seismic refraction data summary full waveform synthetic seismograms are now used as standard in the interpretation of marine refraction data but only with a laborious trial and error fitting procedure we show how the matching of observed waveforms with wkbj synthetic seismograms can be efficiently and automatically performed for 1 d earth models automation of the inversion is difficult because of the multi modal irregular form of the misfit of data and synthetics a sequence of three steps is required for a complete inversion location of the deepest valley of the misfit function descent to the global minimum and description of the neighbourhood of the minimum for error analysis the first step is accomplished with a monte carlo search through a very large model space defined by poor prior knowledge of velocities and gradients of the solution weak traveltime constraints are used to eliminate poorly fitting models from waveform calculations a comparison of the traveltime and waveform misfits of the monte carlo models clearly illustrates that waveforms are providing more information than traveltimes alone bayesian statistics are used to construct marginal probability distributions and the covariance matrix which give a rough preliminary error analysis in the second step damped least squares linearized inversion makes small adjustments to the best fitting monte carlo model as it descends to the global minimum finally the immediate neighbourhood of the global minimum is explored with constrained least squares inversion realistic error bounds on each parameter are defined from the resulting slices through the misfit function these bounds are much narrower than traveltime inversion provides correlations between parameters are obtained from the covariance matrix constructed from models examined during this error analysis the inversion methods are illustrated on the ff2 refraction data set of the scripps institution of oceanography the monte carlo search successfully locates the valley of the global minimum as well as a nearby secondary minimum the error analysis puts realistic error bounds on the detailed inversion of this data set by spudich orcutt

cratering efficiency on coarse grain targets implications for the dynamical evolution of asteroid 25143 itokawa abstract remote sensing observations made by the spacecraft hayabusa provided the first direct evidence of a rubble pile asteroid 25143 itokawa itokawa was found to have a surface structure very different from other explored asteroids covered with coarse pebbles and boulders ranging at least from cm to meter size the cumulative size distribution of small circular depressions on itokawa most of which may be of impact origin has a significantly shallower slope than that on the moon small craters are highly depleted on itokawa compared to the moon this deficiency of small circular depressions and other features such as clustered fragments and pits on boulders suggest that the boulders on itokawa might behave like armor preventing crater formation the armoring effect this might contribute to the low number density of small crater candidates in this study the cratering efficiency reduction due to coarse grained targets was investigated based on impact experiments at velocities ranging from 70 m s to 6 km s using two vertical gas gun ranges we propose a scaling law extended for cratering on coarse grained targets i e target grain size projectile size we have found that the crater efficiency reduction is caused by energy dissipation at the collision site where momentum is transferred from the impactor to the first contact target grain and that the armoring effect can be classified into three regimes 1 gravity scaled regime 2 reduced size crater regime or 3 no apparent crater regime depending on the ratio of the impactor size to the target grain size and the ratio of the impactor kinetic energy to the disruption energy of a target grain we found that the shallow slope of the circular depressions on itokawa cannot be accounted for by this new scaling law suggesting that obliteration processes such as regolith convection and migration play a greater role in the depletion of circular depressions on itokawa based on the new extended scaling law we found that the crater retention age on itokawa is 3 33 myr in the main belt which is in good agreement with the cosmic ray exposure ages for returned samples from itokawa which may reflect the age of material a few meters beneath the surface these ages strongly suggest that the global resurfacing that reset the 1 10 m deep surface layer may have occurred in the main belt long after the possible catastrophic disruption of a rigid parent body of itokawa suggested by ar degassing age 1 3 gyr

cratering experiments in sands and a trial for general scaling law we report results of vertical impacts of aluminum projectiles into quartz sand the impacts were performed at velocities of 35 to 830 m sec with a single stage powder gun morphology of craters formed in loose sands is generally conical whereas morphology of craters formed in self compacted sands varies from a flat floor type to a double ring type with increasing impact velocity the present data together with previous experimental data and dienes and walsh s late stage equivalence indicate that crater diameter is expressed by a function of the late stage effective energy but not of the impact kinetic energy the diameter of a crater formed in a noncohesive sand was found to be proportional to one fourth the power of the late stage effective energy for a general impact cratering in a target with a finite strength the diameter d versus impact velocity v relation is written as follows vv vv 2 k dd 4 dd 5 2 where v and d are normalizing values of the impact velocity and diameter and k is a constant related to target and projectile properties the relation suggests that there are four regimes in crater diameter versus the kinetic energy relation

acoustic nonlinear full waveform inversion on an outcrop based detailed geological and petrophysical model book cliffs utah analog outcrops are commonly used to develop predictive reservoir models and provide quantitative parameters that describe the architecture and facies distribution of sedimentary deposits at a subseismic scale all of which aids exploration and production strategies the focus of this study is to create a detailed geological model that contains realistic reservoir parameters and to apply nonlinear acoustic full waveform prestack seismic inversion to this model to investigate whether this information can be recovered and to examine which geological features can be resolved by this process outcrop data from the fluviodeltaic sequence of the book cliffs utah are used for the geological and petrophysical two dimensional model eight depositional environments are populated with average petrophysical reservoir properties adopted from a north sea field these units are termed lithotypes here synthetic acoustic prestack seismic data are then generated with the help of an algorithm that includes all internal multiples and transmission effects a nonlinear acoustic full waveform inversion is then applied to the synthetic data and two media parameters compressibility inversely related to the square of the compressional wave velocity vp and bulk density are recovered at a resolution higher than the shortest wavelength in the data this is possible because the inversion exploits the nonlinear nature of the relationship between the recorded data and the medium contrast properties in conventional linear inversion these details remain masked by the noise caused by the nonlinear effects in the data random noise added to the data is rejected by the nonlinear inversion contributing to improved spatial resolution the results show that the eight lithotypes can be successfully recovered at a subseismic scale and with a low degree of processing artifacts this technique can provide a useful basis for more accurate reservoir modeling and field development planning allowing targeting of smaller reservoir units such as distributary channels and lower shoreface sands

mapping sediment dispersal patterns and associated systems tracts in fourth and fifth order sequences using seismic sedimentology example from corpus christi bay texas a seismic sedimentologic study was performed to map fourth and fifth order systems tracts in oligocene frio strata in corpus christi bay south texas guided by third order sequence stratigraphic correlations from seismic and wire line log data we prepared stratal slices from a three dimensional seismic volume to reveal high resolution 10 m 33 ft levels sediment dispersal patterns and associated systems tracts in a relative geologic time domain on average 1200 m 3940 ft of sediments were deposited in the third order lowstand expansion cycle and at least 16 higher order sequences fourth and fifth order sequences were recognized three types of depositional systems were identified in the frio stratigraphic section 1 offshelf lowstand slope fans that are best characterized by submarine channel and levee systems inside and outside incised submarine channels and by fan shaped sand body geometry 2 lowstand prograding deltaic systems that are composed of strike oriented and lobate deltaic sand bodies and 3 highstand systems that are represented by onshelf barrier lagoon and deltaic systems higher order sequence development was controlled by the interaction of relative sea level change sediment supply and gravity tectonics the top of sediment ridges was eroded or decapitated during many of the higher order sequences sand dispersal patterns are primarily controlled by accommodation resulting from rollover topography associated with growth faulting between the boundary fault and the hinge line atop rollover structures strike oriented sandstone bodies dominate within submarine channels and incised valleys and beyond the hinge line to the distal basin dip oriented sandstone bodies prevail sandstone thickness and dispersal patterns can be predicted by integrating wire line log measurements and seismic amplitude patterns

relative depths of simple craters and the nature of the lunar regolith abstract we assessed the morphologies of more than 930 simple impact craters diameters 40 m 10 km on the moon using digital terrain models dtms of a variety of terrains in order to characterize the variability of fresh crater morphology as a function of crater diameter from lunar reconnaissance orbiter camera lroc narrow angle camera nac dtms we determined depth to diameter d d ratios for an extremely fresh set of these craters with diameters less than 400 m and found that their d d ratios range from 0 11 to 0 17 using both nac and kaguya terrain camera dtms we also determined the d d ratios for the set of fresh simple craters larger than 400 m in diameter the d d ratios of these larger craters are typically near 0 21 as expected of gravity dominated crater excavation fresh craters less than 400 m in diameter on the other hand exhibit significantly lower d d ratios various possible factors affect the morphologies and relative depths d d ratios of small strength dominated craters including impactor and target properties e g effective strength strength contrasts porosity pre existing weaknesses impact angle and velocity and degradation state while impact conditions resulting from secondary impacts can also affect crater morphologies we found that d d ratio alone was not a unique discriminator of small secondary craters to investigate the relative influences of degradation and target properties on the d d ratios of small strength dominated craters we examined a subset of fresh craters located on the geologically young rim deposits of tycho crater these craters are deeper and steeper than other craters of similar diameter and degradation state consistent with their relative freshness and formation in the relatively coherent melt rich deposits in this region the d d ratios of globally distributed small craters of similar degradation state and size range on the other hand are relatively shallow with lower average wall slopes consistent with crater excavation in a weak or poorly cohesive layer the widespread predominance of these small shallow craters is consistent with the pervasive poorly cohesive upper regolith

past present and future of geophysical inversion a new millennium analysis geophysicists have been working on solutions to the inverse problem since the dawn of our profession an interpreter infers subsurface properties on the basis of observed data sets such as seismograms or potential field recordings a rough model of the process that produces the recorded data resides within the interpreter s brain the interpreter then uses this rough mental model to reconstruct subsurface properties from the observed data in modern parlance the inference of subsurface properties from observed data is identified with the solution of a so called inverse problem in contrast the forward problem consists of the determination of the data that would be recorded for a given subsurface configuration and under the assumption that given laws of physics hold until the early 1960s geophysical inversion was carried out almost exclusively within the geophysicist s brain since then we have learned to make the geophysical inversion process much more quantitative and versatile by recourse to a

localizing co2 at sleipner seismic images versus p wave velocities from waveform inversion abstractthe presence of injected co2 in the utsira sand at the sleipner site norway is associated with a high negative p wave velocity anomaly that is a low postinjection velocity and a strong seismic response time lapse seismic imaging of co2 injection at sleipner is thus a viable monitoring tool of the injected co2 the work flow usually involves conventional seismic processing including stacking and results in seismic images multiple reflections interference effects such as tuning and the velocity pushdown effect due to co2 injection render these seismic images ambiguous in terms of the localization and the quantification of the co2 in the utsira sand nonetheless seismic images often form the basis for analyses that aim to quantify the injected co2 we employed elastic 2d full waveform inversion to invert prestack seismic sleipner data from preinjection 1994 and postinjection 1999 and compared the resulting postinjection p wave velocity model with the corresponding seismic image we fou

time domain computation of non normal incidence wavefields in plane layered media1 a new time domain method is introduced for the calculation of theoretical seismograms which include frequency dependent effects like absorption to incorporate these effects the reflection and transmission coefficients become convolutionary operators the method is based on the communication theory approach and is applicable to non normal incidence plane waves in flat layered elastic media wave propagation is simulated by tracking the wave amplitudes through a storage vector inside the computer memory representing a goupillaud earth model discretized by equal vertical transit times arbitrary numbers of sources and receivers can be placed at arbitrary depth positions while the computational effort is independent of that number therefore the computation of a whole plane wave vertical seismic profile is possible with no extra effort compared to the computation of the surface seismogram the new method can be used as an aid to the interpretation of plane wave decomposed reflection data where the whole synthetic vertical seismic profile readily gives the interpreter the correct depth position of reflection events