A MAN/COMPUTER INTERPRETATION SYSTEM FOR RESISTIVITY SOUNDINGS OVER A HORIZONTALLY STRAFIFIED EARTH*

The proposed system works as follows:

• 1 By a trial-and-error procedure using a graphic display terminal a geologically relevant layer sequence with parameters (ρ_j, d_j) is adjusted to yield roughly the measured curve.
• 2 The resulting layer sequence is used as starting model for an iterative least squares procedure with singular value decomposition. Minimization of the sum of the squares of the logarithmic differences between measured and calculated values with respect to the logarithms of the resistivities and thicknesses as parameters linearizes the problem to a great extent, with two important implications:

• a) a considerable increase in speed (the number of iterations goes down), thus making it cheap to achieve the optimum solution;
• b) the confidence surfaces in parameter space are well approximated by the hyper-ellipsoids defined by the eigenvalues and eigenvectors of the normal equations.

Since these are known from the singular value decomposition we do in fact know all possible solutions compatible with the measured curve and the geological concept.

• 3 It is possible to “freeze” any combination of parameters at predetermined values. Thus extra knowledge and/or hypotheses are easily incorporated and can be tested by rerunning step (2). The overall computing time for a practical case is of the order of 10 sec on a CDC 6400.

     

GEOPHYSICAL ANOMALY INTERPRETATION OF POTENTIAL FIELDS BY MEANS OF SINGULAR POINTS METHOD AND FILTERING*

The calculation of potential field anomalies on different levels below the measuring level permits to localize the singular points related to the sources of anomalies. It is possible to achieve considerable improvement of the resolution of this method

• 1) filtering of analytical downward continuation,
• 2) the use of the magnitude of the gravitational vector,
• 3) calculation of physe changes.

The numerical examples confirm these assumptions.     

Antiplane dynamic soil-bridge interaction for incident plane SH-waves

The analysis of dynamic soil-bridge interaction has been performed in three steps. These are:

• 1. The analysis of input motions.
• 2. The force-displacement relationships for the foundations.
• 3. The dynamic analysis of the structure itself, i.e. the bridge.

Based on the exact solution of the first two steps, the dynamic interaction of a simple two-dimensional bridge model erected on an elastic half-space has been investigated for a single span case. The two-dimensional model under study consists of an elastic shear girder bridge supported by two rigid abutments and rigid foundations which have a circular cross-section and are welded to the half-space. It has been shown that the dynamic interaction depends on:

• 1. The incidence angle of plane SH-waves.
• 2. The ratio of the rigidity of the girder and the soil.
• 3. The ratio of the girder mass to the mass of the rigid abutment-foundation system.
• 4. The span of the bridge.

The dynamic response of the girder and the effect of the radiative damping in the half-space on the interaction of the girder have been studied.     

Studies on the Toxicity of a few Pesticides on Colisa fasciatus and Notopterus notopterus with Reference to Histopathology and Histochemistry. Part 1: Bioassay Studies

An attempt has been made to study the toxicity of two commonly used pesticides aldrin (organochlorine) and ethyl-parathion (organophosphorus) to the fish Colisa fasciatus (Anabantidae) and Notopterus notopterus (Notopteridae). During bioassay studies, the behaviour of the fishes was recorded. The aldrin concentration used lies between 0.021 mg/1 and 0.042 mg/1 for C. fasciatus and 0.00056 mg/1 and 0.00135 mg/1 for N. notopterus. The ethyl-parathion concentration used lies between 1.8 mg/1 and 3.7 mg/1 for C. fasciatus and 0.49 mg/1 and 1.00 mg/1 for N. notopterus.

• – The effect of lethal aqueous concentrations of pesticides on the Fishes prior to death are usually manifested by excitation, erratic swimming ability, difficulty in respiration, increasing in ventilation rate, jerky movements of body and fin fast, up- and downward movements, convulsions, loss of equilibrium, loss of the original colour of the body skin and the excess secretion of mucus by the gills and the body wall.
• – the TL_m values for 24, 48 and 96 hours of exposition are determined for both species of fish and both pesticides at the following variables:

• ? three levels of temperature,
• ? three levels of dissolved oxygen,
• ? three levels of pH,
• ? three fish sizes.

• – statistical analysis of variance shows, that all variables have a significant effect on the TL_m values of both pesticides for both fish species;
• – Aldrin (chlorinated hydrocarbon) is more toxic than ethylparathion (organophosphate) at all variables;
• – Colisa fasciatus is the more resistant species than Notopterus notopterus.
• – the relationship between the total number of the fishes N₀, survival numbers N and time t can be expressed by a mathematical formula as:
• – the harmless concentration to C. fasciatus ranged from 0.0049 mg/1 to 0.0161 for aldrin, 0.54 mg/1 to 0.99 mg/1 for ethyl-parathion and to N. notopterus from 0.00012 mg/1 to 0.00045 mg/1 for aldrin, 0.10 mg/1 to 0.21 mg/1 for ethyl-parathion;
• – the aldrin should be diluted at least 4000 times and ethyl-parathion 320 times of its actual concentration.

     

FIRST EXPERIENCE AND RESULTS WITH A NEW SEISMIC INTERPRETATION METHOD*

At the EAEG meeting in Venice (May 1969) Linsser presented a new method for the interpretation of seismic measurements (“Transformation of Seismic Data into Geological Models by Digital Template Analysis”). First results were presented during the S.E.G. convention in Calgary (September 1969). Meanwhile some experience concerning the possibility of the application of this method is available. Starting from the fact that the computer is able to store several physical parameters (amplitude, wave-length, direction of the seismic event, coincidence with a template and the beginning and the end of each reflection), the importance of these data for the investigation of special geophysical questions will be discussed. This method has been tested with several examples on the following problems:

• 1 Proving and exact localisation of faults.
• 2 Investigation of velocities of interesting layers.
• 3 Additional information for the geological interpretation of seismic sections.
• 4 Picking of weak reflections in the “Pre-Zechsteinian” in Northern Germany.

Finally the possibilities of further applications and developments are discussed.     

ESTIMATION OF REFLECTOR PARAMETERS BY THE VIRTUAL IMAGE TECHNIQUE*

The seismic interpretation process generally exploits three of the following independent basic assumptions:

• 1 Input quantities are obtained by simplification of measured data (travel time curves).
• 2 2. The geological model contains only a few parameters (for example, plane interfaces and constant interval velocities).
• 3 3. Approximate transformations may be applied.

The first two are related to the simplification of the phenomena and enhance their essential features. The transformation which establishes relations between simplified data and model is required to be unique, stable, and sufficiently accurate. Practically, the travel time curves are almost exclusively regarded as hyperbolas. We also accept this approximation. The paper presents a simple recursive algorithm for the evaluation of the depth and dip of plane reflectors and the interval velocities. It is a simple fact, that there exists a unique relationship between three hyperbolic parameters and a homogeneous dipping layer. Accordingly, two layers can be replaced by a single layer and the parameters of the lower boundary can be estimated when the upper one is known, initiating virtual shotpoints and geophone points (virtual surface). So, the case of multilayered media can be reduced in sequential steps to the case of a single homogeneous layer using a stripping type procedure. Some synthetic model examples are provided to demonstrate the abilities of the algorithm.     

IMPEDANCE OF A PLANE ELECTROMAGNETIC WAVE AT THE SURFACE OF A LAYERED CONDUCTING EARTH WITH DIPPING ANISOTROPY*

The problem of a plane wave incident on a non-isotropic dipping layer lying over an isotropic conducting substratum has been studied and some numerical results are presented to show the effects of

• 1) degree of anisotropy m,
• 2) conductivity contrast between the substratum to the upper layer b,
• 3) angle of inclination of the axis of anisotropy α,

on the variation of amplitude and phase difference of the wave impedance with the normalized skin-depth (d/δ₁).     

Phylogenetic systematics of chelonioid sea turtles

Abstract Chelonioid sea turtles (Order Testudinata; Superfamily Chelonioidea) first appear in the early Cretaceous (Aptian-Albian). Their long fossil record is excellent compared to most marine tetrapods. Nonetheless, there has been no inclusive attempt to provide an analysis of cladistic relationships among this group. In this paper, the following chelonioid classification is proposed, based on 76 characters among 20 fossil and six living well- represented genera:

• 1 Family Cheloniidae (Coniacian to Recent); Toxochelys, Ctenochelys, Osteopygis, Erquelinnesia, Allopleuron, Argillochelys, Puppigerus, Eochelone, Syllomus, Natator, Eretmochelys, Chelonia, Caretta, Lepidochelys
• 2 Family Protostegidae (Aptian to Maastrichtian?); ‘Santana new protostegid’,Rhinochelys, Notochelone, Desmatochelys, Chelosphargis, Protostega, Archelon
• 3 Family Dermochelyidae (Santonian? to Recent); Corsochelys, ‘HMG new dermo-chelyid’, Eosphargis, Psephophorus, Dermochelys.

     

RELATIVE CONTRIBUTION TO SIGNAL BY GROUND ELEMENTS IN TWO-COIL INDUCTION LOGGING SYSTEM*

A two-coil induction logging system in an infinite homogeneous medium has been theoretically analysed for the relative contributions of various ground elements to the total signal at the receiver. Unlike an earlier approximate treatment by Doll (1949), the present analysis takes skin effect into account (while neglecting displacement currents). Contour diagrams depicting relative contributions from every ground point and diagrams for vertical and radial/lateral investigation characteristics are presented. The results differ significantly from Doll's in the following points:

• 1 The relative contribution is frequency and conductivity dependent;
• 2 It does not show symmetry with respect to the center of coil system;
• 3 It alternates between positive and negative values with distance;
• 4 Real and imaginary contributions for a given conductivity and frequency are different from each other.

The possibilities of a horizontal-horizontal sonde is briefly examined and found to be inferior to the usual sonde because of its higher sensitivity to the mud column and the invaded zone.     

RADON DEPTH MIGRATION1

A depth migration method is presented that uses Radon-transformed common-source seismograms as input. It is shown that the Radon depth migration method can be extended to spatially varying velocity depth models by using asymptotic ray theory (ART) to construct wavefield continuation operators. These operators downward continue an incident receiver-array plane wave and an assumed point-source wavefield into the subsurface. The migration velocity model is constrained to have longer characteristic wavelengths than the dominant source wavelength such that the ART approximations for the continuation operators are valid. This method is used successfully to migrate two synthetic data examples:

• 1 a point diffractor, and
• 2 a dipping layer and syncline interface model.

It is shown that the Radon migration method has a computational advantage over the standard Kirchhoff migration method in that fewer rays are computed in a main memory implementation.     

DEVELOPMENT OF MORE EFFICIENT AIRGUN ARRAYS: THEORY AND EXPERIMENT*

Source strength of an airgun array may be increased by:

• — utilizing higher pressure,
• — increasing total array volume,
• — employing more guns,
• — improving gun efficiency.

One measure of gun efficiency is “specific source strength”, P_a*, defined as source strength per unit quantity of air used. Typical units are MPa m/l. Most developments are directed toward increasing gun pressure and/or gun volume to increase source strength of the array. These efforts require that more air compressors be installed onboard the ship. Consequently, a larger ship may be needed for the additional compressors, guns, and auxiliary equipment. A development program was initiated in 1976 to increase source strength of the array without using a larger ship. New guns were designed and built—one for 41.4 MPa and 7.37 liter (6000 p.s.i./450 in³) operation and another with 13.8 MPa and 4.92 liter (2000 p.s.i./300 in³) capability. Experiments were conducted with these new guns (and existing guns) over a range of pressures from 13.8 to 41.4 MPa (2000 to 6000 p.s.i.). Design of the new guns was aided by a mathematical model. The model relates physical dimensions of the airgun to acoustic pressure in the water. It consists of four nonlinear differential equations relating

• — shuttle motion,
• — bubble pressure,
• — chamber pressure,
• — bubble radius.

The last equation is the “free-bubble-oscillation equation” and represents the ideal case of a pressurized bubble released instantaneously in water. The three other equations modify this ideal case; the four equations together model an airgun of the type manufactured by Bolt Associates, Inc.     

Comparative analysis of the seismic risk in sites of different seismicity

Four sites (a, b, c, d) are considered of differing seismicity. The calculations, for two different buildings on each site, consisted of:

• 1. The total monetary cost as a function of the design seismic coefficient c.
• 2. The marginal cost of a saved life, ΔD/ΔL, also depending on c.
• 3. The ratios between the design seismic coefficients in the various sites, c_d/c_a, c_d/c_b, c_d/c_c, that lead to the same marginal cost ΔD/ΔL in all sites.

The marginal cost ΔD/ΔL turns out to be highly sensitive to uncertainties, but the other ratios are scarcely influenced by the uncertainties met in analysing the problem. This would suggest the adoption of a rationalized principle for comparing the levels of severity in the Codes for sites with differing degrees of seismicity. If a criterion for evaluating indirect cost due to damage or collapse is fixed for each building and each site the values of c corresponding to minimum monetary cost are not strongly influenced by the said uncertainties. This would make it possible to look into the problem of the minimum levels of severity in the Codes. Of course, this assumes that the levels of severity should always be higher than those corresponding to the minimum monetary cost.     

Analysis of riverbank instability due to toe scour and lateral erosion

This paper provides instruction in the use of the computer spreadsheet to undertake the calculations necessary to apply the Osman–Thorne bank stability analysis for steep, eroding riverbanks. The guide explains how to input the necessary parameters into the LOTUS 123 spreadsheet in order to:

• 1 find the initial factor of safety of the bank with respect to slab-type failure;
• 2 test the sensitivity of bank stability to changes in the engineering properties of the bank material;
• 3 analyse the response of bank stability to toe scour and/or lateral erosion and find the critical condition;
• 4 find the geometry of the failure surface and failure block;
• 5 analyse the response of bank stability to further toe scour and/or lateral erosion;
• 6 find the geometry of the failure surface and failure block in subsequent failures.

     

Partitioning of rainfall in a eucalypt forest and pine plantation in southeastern australia: IV the relationship of interception and canopy storage capacity,the interception of these forests,and the effect on interception of thinning the pine plantation

A study of partitioning of rainfall into throughfall, stemflow, and interception was conducted in a dry sclerophyll eucalypt forest and an adjacent pine plantation over a period of seven years, on a rainfall event basis. The following three issues are discussed: (1) the relationship between canopy storage capacity and interception of continuous events, (2) interception, throughfall, and stemflow, and (3) the effect on interception of thinning the pine plantation.

• 1 The canopy storage capacity/interception interaction for the eucalypt forest was assessed by comparing a gravimetric estimate of canopy storage capacity with interception. The maximum possible value for canopy storage capacity was found to be a small proportion of interception for events of all sizes. This suggests that evaporation of intercepted water during the continuous events was responsible for most of the interception. This ‘within event’ evaporation appears to be responsible also for the net rainfall/gross rainfall estimate of canopy storage capacity being four times the gravimetric value. For the pines the regression estimate was more closely related to interception.
• 2 Interception, throughfall, and stemflow of these forests were measured for four years. Data are presented for each year with overall average interception being 11-4 per cent of precipitation for the eucalypt forest and 18-3 per cent for the pine plantation. Topography and rainfall event type are considered in the comparison.

Species composition and tree type are considered when comparing these results with published studies from similar forest types in southeastern Australia. The periodic (annual) variations of interception in this and the other studies makes comparison difficult.

• 3 The effect of thinning on the throughfall, stemflow, and interception in a Pinus radiata plantation is examined. Throughfall increased, interception decreased but not in proportion to the removed biomass; stemflow decreased on an area basis, but increased on a per tree basis. A positive relationshiip is established between interception and stemflow on the thinned plantation but not in the unthinned. Reasons for this are suggested. The results are compared to those reported from similar experiments in other forests.
• 4 The periodic variations in interception and errors inherent in its estimation suggest that caution should be exercised when using average interception figures in water balance studies.

     

Recursive evaluation of interaction forces of unbounded soil in the time domain

The interaction forces representing the contribution of the linear unbounded soil to the equations of motion of a nonlinear soil-structure-interaction analysis are specified in the form of convolution integrals. They can be evaluated recursively in the time domain. In this procedure, the forces at a specific time are computed from the displacements at the same time and from the most recent forces and most recent past displacements. It is, in principle, only approximate. When the dynamic-stiffness coefficients can be expressed as the ratios of two polynomials in frequency, the appropriately chosen recursive equations are exact. Two possibilities of choosing a recursive equation are discussed.

• (i) The impulse-invariant method, where the unknown recursive coefficients are calculated by solving a system of equations which are established by equating the rigorous and recursive formulations for a discretized unit impulse displacement.
• (ii) In the segment approach, the dynamic-stiffness coefficients in the time domain are interpolated piecewise. Applying the z-transformation analytically then results in an explicit recursive equation without solving a system of equations.

The recursive evaluation of the convolution integrals in the time domain leads to a dramatic reduction in the computational effort up to two and three orders of magnitude and in the storage requirement. This makes the time-domain analysis using the substructure method computationally competitive with the corresponding direct (non-recursive) frequency-domain procedure of determining the complex response which is, however, applicable only to a linear (total) system.     

Detection of underground cavities with monofrequency electromagnetic tomography between boreholes in the frequency range 100 MHz to 1 GHz1

In order to detect underground cavities, we have designed a geophysical method based on the interaction of a monochromatic electromagnetic wave in the frequency band 100 MHz to 1 GHz with the ground situated between two boreholes. Three different approaches are involved in the design of this EM tomographic method.

• 1 The application of an ‘exact’ theory is used to calculate artificial data, based on an integral equation method. These data are inverted using a tomographic algorithm whose basic assumptions are rather coarse. The results show that, however, cavities can very well be detected and their position recovered.
• 2 Data are obtained with a physical reduced-scale model in a water tank, in which all parameters are known in advance. The inversion process confirms the validity of the method.
• 3 Underground cavities are actually detected.

The above approaches are described and discussed and results are shown. The equipment involved and its operation is quite simple: the surface devices are commercially available and only the transmitter and receiver antennae must be specially built. The method is shown to be quite efficient and its cost should be reasonably low.     

THE KALMAN FILTER AS A PREDICTION ERROR FILTER*

In mathematical statistical filtering the deconvolution problem can be solved by two different methods:

• 1 by inverse filtering
• 2 by calculating the prediction error.

Both methods are well known in the theory of Wiener filters. If, however, the generating process of the signal is known and can be described by a set of linear first order differential equations, then the Kalman filter can also be used to solve the deconvolution problem. In the case of the inverse filtering method this was shown by Bayless and Brigham (1970). But, while their method can only be used if the original signal is a colored random process, this paper shows that in the case of a white process the prediction error filtering method is a more appropriate approach. The method is extremely efficient and simple. This can be demonstrated by an example which maybe of special interest for seismic exploration.     

Earthquake response of steel-framed multistorey buildings with set-backs

A study is made of the dynamic behaviour of multistorey steel rigid-frame buildings with set-back towers. The effects of set-backs upon the building frequencies and mode shapes are examined. Then the effects of set-backs on seismic response are investigated by analysing the response of a series of set-back building frame models to the El Centro ground motion. Finally, the computed responses to the El Centro earthquake are compared with some code provisions dealing with the seismic design of set-back buildings. The conclusions derived from the study include the following:

• 1. The higher modes of vibration of a set-back building can make a very substantial contribution to its total seismic response; this contribution increases with the slenderness of the tower.
• 2. Some of the important response parameters for the tower portion of a set-back building are substantially larger than for a related uniform building.
• 3. For very slender towers, the transition region between the tower and the base may be subjected to very large storey shears.

     

Conference listing

• Geographic Information Systems (GIS) and Water Resources III
• Nashville, TN
• 17–19 May 2004
• Website: http://www.awra.org/meetings/Nashville2004/index.html

• CGU/AGU/SEG
• Montreal, Quebec
• 17–21 May 2004
• Website: http://www.agu.org/meetings/sm04/

• North American Genthological Society Meeting
• Vancouver, BC
• 6–10 June 2004
• Website: http://benthos.org/index.cfm

• 61 Eastern Snow Conference
• Portland, Maine, USA
• 9–11 June 2004
• Website: http://www.easternsnow.org/

• International Conference on Groundwater Vulnerability Assessment and Mapping
• Sosnowiec, Poland
• 16–19 June 2004
• Contact: Dr Andrzej J. Witkowski, Secretariat of the Conference, University of Silesia, B?dzińska Str., 60, 41‐200 Sosnowiec, Poland
• Tel: +48 32 291 68 88
• Fax: +48 32 291 58 65
• E‐mail: switkows@us.edu.pl
• Website: http://khgi.wnoz.us.edu.pl/vulnerability.htm

• Riverflow 2004–Second International Conference on Fluvial Hydraulics
• Naples, Italy
• 23–25 June 2004
• Website: http://www.riverflow2004.unina.it

• Riparian Ecosystems and Buffers: Multi‐Scale Structure, Function and Management
• Olympic Valley, CA
• 28–30 June 2004
• Website: http://www.awra.org/Olympic2004/index.html

• BHS International Conference on ‘Hydrology: Science and Practise for the 21^st Century’
• Imperial College, London
• 12–16 July 2004
• Contact: Dr Adrian Butler
• Tel: 020 7954 6122 Fax: 020 7594 6124
• E‐mail: a.butler@ic.ac.uk
• Website: http://www.hydrology.org.uk/index.html

• Italia 2004 32^nd International Geological Congress “From the Mediterranean Area Toward a Global Geological Renaissance” Geology, Natural Hazards and Cultural Heritage
• Florence
• 20–28 August 2004
• Contact: Chiara Manetti, Dipartimento di Scienze della Terra, Via La Pira, 4‐50121 Firenze, Italy
• Tel/Fax: +39 055 2382146
• Email: casaitalia@geo.unifi.it

• Good Water Governance for People & Nature: What Roles for Law, Institutions, Science & Finance
• Dundee, Scotland
• 29 August–1 September 2004
• Website: http://www.awra.org/meetings/Dundee2004/index.html

• XXXIII Congress of IAH—Conference on Groundwater Flow Understanding: From Local to Regional Scale. Joint Conference IAH/ALHSUD
• Mexico
• 11–15 October 2004
• E‐mail: aih@igris.igeograf.unam.mx
• Website: www.igeograf.unam.mx/aih

• Acid Rain 2005 7th International Conference on Acid Deposition
• Prague, Czech Republic
• 12–17 June 2005
• Contact: Jaroslav Santroch Czech Hydrometeorological Institute, Na Sabatce 17, 14306 Prague 4, Czech Republic
• Tel: +420 24 1765803
• Fax: +420 24 1760689
• E‐mail: info@acidrain2005.cz
• Website: http://www.acidrain2005.cz

If you would like your conference included please E‐mail details to Anne Flynn. E‐mail: aflynn@wiley.co.uk Copyright © 2004 John Wiley & Sons, Ltd.     

Recursive evaluation of interaction forces of unbounded soil in the time domain from dynamic-stiffness coefficients in the frequency domain

The interaction forces of the linear unbounded soil in a non-linear soil-structure-interaction analysis can be calculated recursively, starting directly from the dynamic-stiffness coefficients in the frequency domain. Two possibilities of choosing a recursive equation are discussed.

• (i) The recursive equation in the frequency domain. For each frequency, the interaction force at a specific time station is expressed as a function of the corresponding interaction force at the previous time station and of the displacements at the current time station and at the two most recent past time stations. This recursive evaluation of the convolution integral. which can be derived using the z-transformation, is rigorous. By using interpolation in the frequency domain, an approximate procedure results, which leads to a significant reduction in computational effort.
• (ii) The recursive equation in the time domain. By approximating the dynamic-stiffness coefficients as the ratios of two polynomials in frequency using a curve-fitting technique based on the least-squares method and by applying the partial-fraction expansion and using the z-transformation, the recursive coefficients can be determined explicitly. Alternatively, the ratio of two polynomials can also be transformed to an ordinary differential equation together with the initial conditions.

The recursive equations using interpolation in the frequency domain and based on a ratio of two polynomials lead to a reduction in the computational effort of one and up to three orders of magnitude, respectively.