New Instrumental and Experimental Approaches and Results Chairpersons: L. Szarka and P.T.L. Menezes 9.1 A MODEL TO DESCRIBE LOW-FREQUENCY ELECTRICAL POLARIZATION OF ROCKS Carlos A. Dias Petroleum Engineering and Exploration Laboratory, North Fluminense State Univesity, Macae, Brazil dias@lenep.uenf.br A five parameters conductivity complex function is presented, describing the electrical polarization of rocks in the frequency range of 1 MHz to 10-4 Hz , good inclusive for some non-linear data. The new parameters have from the beginning clear petrophysical and electrochemical meanings and well-defined ranges of variation, with some classical models derived as particular cases. The author analyses the main existing models describing induced polarization (IP) and group most of them together under a common circuit analog representation and a respective generating funciton; to each model is assigned a circuit analog. Particularly, the multi- Cole-Cole model circuit analog reveals intrinsic constraints involving the values of its circuit elements. Because of these constraint relations and the relaxation times ratio (t1/t2) - this model has no physical validation to represent single-phase material systems (in the sense of the polarization). The performance and analysis of the various models to describe a few well-selected experimental data show that only two models, the multi - Cole- Cole and the author's models, can provide a function structure capable of fitting these data. This performance, the associated petrophysical interpretation consistency and the basic characteristics of these two models, such as the way they were derived (empirically the former; phenomenologically, the latter) and the number of coefficients in the function (directly related to the degree of ambiguity of their determination), make the author's model attractive and promising. 9.2 NEW TRENDS IN MULTIFUNCTIONAL EM EQUIPMENT DEVELOPMENT J. Dodds and O.I. Ingerov Phoenix Geophysics Ltd., Toronto, Canada alingers@arvotek.net The performance envelope of multifunctional EM equipment is a critical factor. The very demanding requirements of AMT/MT acquisition mean that the relevant performance envelope exceeds that required for other EM techniques. Hence AMT/MT equipment can readily be adapted to include other EM techniques, while the opposite is not necessarily true. AMT/MT equipment must have wide frequency range (up to 7.5 decades) , wide dynamic range (132 dB or more in 24 bit systems), very low noise engineering to accommodate weak signal in some parts of the frequency range, minimum 5 input channels, and precise synchronization. It must also be light in weight, and be battery-powered, with low power consumption. The "fourth generation" (ca. 1986) of multifunctional equipment typically had a central unit with up to 16 input channels, and used auxiliary 2E or 5EH preamplifiers and signal processors, connected by cable to the central box. The central box had a microprocessor capable of real time data reprocessing; and keyboard/display for the operator interface (V5, MT-1, MMS-05, GDP-16, CES-4, CES-MGD). The fourth generation made big progress in MT, AMT, TEM and CSAMT in terms of increased productivity, survey cost reduction, and higher data quality due (MT, AMT) to remote reference reprocessing). But today, fourth generation equipment is non-competitive, due to its cables, weight, power consumption, high level of operator qualification requirement, etc. The fifth generation of MT equipment (illustrated by System 2000) comprises an unlimited number of independent, light (5kg) 2E or 5EH, 24-bit, GPS-synchronized boxes. In the System 2000, boxes for AMT (10,000-1Hz), MT (400 - 1/2000Hz) and Long Period MT (1 - 1/30,000 Hz) all have the same basic structure and software. The differences relate (for example) to high-speed data processing and storage (AMT) or minimized power (LPMT). No data reprocessing takes place inside the box, and the user interface (and data processing) is offloaded to an external computer. This makes the box construction simple and reliable. The internal processor provides basic filtering and mass storage in flash memory up to 100Mb or more. The simple operation doesn't require highly qualified operators. Permanent, precise synchronization is realized via GPS, allowing reprocessing of data recorded even on different continents. The 5th generation has already been adapted (1999) to 4-D EM monitoring and foresees additional functions such as TEM, CSAMT, IP etc. 9.3 REDUCTION OF OVERBURDEN DISTORTIONS IN EM PROFILES BY FREQUENCY DIFFERENCE TECHNIQUE Marcia E.S. Silva and Om P. Verma Departamento de Geofisica, Universidade Federal do Para, Belem, Brazil verma@ufpa.br Electromagnetic anomalies of a conducting ore body is severly modified by the presence of a partially conducting overburden. More so when they are in galvanic contact. Heterogeneities in overburden deform further these anomalies and may even mask them completely. To remove these overburden effects, the application of the frequency difference technique is studied to obtain cleaner anomalies. Scale model experiments are carried out with horizontal coplanar coil system over inclined half-planes of varying conductances, dips and depths, and varying overburden conductances. Half-plane models are simulated by graphite and antracite sheets and the overburden by amonium chloride solutions. Frequencies used are 12.5, 25, 50 and 100 kHz. The frequency difference technique is based on the fact that overburden and the heterogeneities therein, usually posses low induction numbers, and in this range quadrature response is proportional to the frequency and the inphase to the square of the frequency. On the other hand, for ore bodies of higher induction numbers these relations are not valid. Therefore, the response difference after normalizing for reasonaly spaced frequencies will result in null responses for overburdens but not for ore bodies. The model results show that this technique is highly efficient in removing the distortions due to the overburden resulting in cleaner anomalies and approximating their original shapes even in the case of current gathering, particularly at low frequency pairs. However, the frequency difference operation reduces also the ore body anomaly amplitudes. 9.4 THE BAD KOENIGSHOFEN EM EXPERIMENT: AN INTEGRATED METHODOLOGICAL APPROACH Klaus Spitzer(1), Bernhard Fluche(2), and Wolfgang Storz(3) (1) Institute of Geophysics, Freiberg University of Mining and Technology, Gustav-Zeuner-Str. 12, 09596 Freiberg, Germany (2) Comsol AB, Merkelstr. 31, 37085 Goettingen, Germany (3) Hydrogeologie GmbH, Sueptitzer Weg, 04860 Torgau, Germany klaus.spitzer@geophysik.tu-freiberg.de We employed four different electromagnetic methods in the integrated EM experiment in Bad Koenigshofen to investigate the subsurface conductivity structure (Vertical Gradient Method [VG], Magnetotellurics [MT], DC soundings and borehole geoelectrics [BG]). The objective is to understand the individual differences in the physical responses between the four methods. We focus on results from the Vertical Gradient Method. The data show a skin effect of approximately 30 per cent in amplitude and -10 degrees in phase. They are obtained from synchronous magnetometer registrations at the surface and within a borehole at a depth of 832 m. It is the first time that the significance of the skin effect transfer function is experimentally verified in direct comparison with MT results. The signatures of MT and VG responses agree extremely well. However, the encountered skin effect is stronger than the one derived from borehole measurements and DC soundings. Therefore, the integrated conductance between the surface and the operational depth of the borehole magnetometer is investigated in greater detail. Three-dimensional modeling for DC and BG suggests both methods to be corrected for the local conductivity environment dominated by near-surface conductive fracture zones and an extremely saline borehole fluid, respectively. Taking this into account, all methods converge towards a uniform conductance. 9.5 ADVANCED TECHNOLOGY FOR INTERPRETING RESISTIVITY LOGGING DATA Zhiyi Zhang Baker Atlas, Houston, Texas, USA Ian.Zhang@waii.com Modern resistivity logging tools are replacing traditional tools to provide high resolution data for more accurate reservoir detection and description. A typical data set consists of several dozen measurements at each logging depth, acquired at a sampling rate as high as 24 samples/m, and spans several hundred meters. Interpretation of such large data sets is complicated by systematic noise unique to the borehole environment, such as the yo-yo effect, stick-and-pull, and eccentericity. In this paper, we attempt to provide an overview on recent advances in interpreting resistivity logging data. These advances mainly focus on a) speeding up forward modeling and calculating sensitivities, b) breaking large and complicated problems into smaller pieces using dimensional reduction, c) generating petrophysically consistent and robust results, and d) resolving complicated formation in 3D, anisotropic, and horizontal well environments. Approximate forward modeling based upon numerical linearization (eg., Doll's/Born's approximations) or physical linearization (skin effect correction), has been used to accelerate the inversion process. Recent progress on neural network simulation provides the essential tool to construct real time inversion algorithms. Approximate sensitivities (e.g., obtained from Broyden's method) have been used to cut the inversion turnaround time. The Approximate Inverse Mapping (AIM) technique, which avoids the use of sensitivities in the inversion, has been adjusted to logging data to provide fast estimation for inversion solutions. Dimensional reduction is another way to accelerate inversions and is achieved by a) picking and fixing the bed boundaries before performing inversion, b) using borehole effect corrected data, or c) breaking a 2D problem into a series of radial and vertical 1D inverse problems. To generate inversion results consistent with other available petrophysical information, we have developed petrophysically constrained inversion algorithms to utilize gamma ray, neutron, porosity, and resistivity logging data. Joint inversion of these logging data allows us to achieve a consistent interpretation across suits of logs. Synthetic and field data examples demonstrate effectiveness of these new developments. 9.6 ESTIMATION OF THE PERMEABILITY OF LAYERS BY ELECTROKINETIC SOUNDING V. Hallbauer-Zadorozhnaya(1) and V. Lepyoshkin(2) (1) Terra Sounding and Analytical Ltd., P.O. Box 2142, Somerset West, South Africa (2) Nizhnevolzhsky Geology and Geophysics Research Institute, Saratov, Russia dkh@mweb.co.za We describe the estimation of permeability for shallow layers using seismo-electrokinetic sounding, EK. Using field data of an actual seismo-electric survey as input to our mathematical model, we show that an estimation of permeability can be obtained and layers be identified as suitable, potential aquifers. Using the original formula from Chandler, 1981, we have extended its application from a step function as input to delta functions and more complex wave forms. Our model is a three-layer design having layers of, 1. high permeability without water, 2. medium-high permeability and water saturation and, minimal permeability. For this model we investigated three mechanisms of EK interaction: surface wave, reflected wave and head wave. EK signals in permeability layers are the sources of the second EM field of the diffusion type. We also estimated the values of transient EM fields on the surface. The calculations using actual field data showed that the permeability of the first layer is about 2-7x10-3 mD, which corresponds to a small to medium grained, sandy argillite. The EK effect of head waves was calculated as the sum of signals generated within the elements of the second layer. The estimation of the permeability of the second layer showed higher values, between 3 and 12x10-3 mD. 9.7p STATE AND POSSIBILITY OF PHYSICAL MODELING Borys T. Ladanivskyy Carpathian Branch of Subbotin Institute of Geophysics, National Academy of Sciences of the Ukraine, 3B Naukova st., 79053 Lviv, Ukraine borys_lad@mail.com The abstract aims at presenting current state of physical modeling of electromagnetic fields in inhomogeneous media which are characteristic of real geoelectric situations. Physical modeling may be used when immediate observation, and mathematical modeling is impossible or very expensive. Special laboratory installations for physical modeling must satisfy a number of complicated technical requirements that restrict its usage. Our laboratory installations are based on electrolitic tank with dimensions 5m-5m-0.7m where scale models of muli-layer inhomogeneous geoelectric sections are created. Variations both of natural electromagnetic fied or man- made sources are simulated by harmonic plane-homogeneous or dipole field. Recently hardware and software for automated measuring and for data processing is developed. Automated measuring and recording of electromagnetic field enables effective application of processing and interpreting routines, reduce the duration of experiment, and increase the accuracy of modeling data. The results of modeling may be represented as a traditional geoelectric parameters. The frequency dependences of main and additional impedance tensor components, argument of impedance, apparent resistivities, tippers, polar diagrams of impedance and spatial structure of EM field components of 3D inhomogeniety demonstrate the potentials of this method for MT case. 9.8p PHYSICAL AND NUMERICAL MODELING RESULTS: COMPARISON OF EM FIELD 3D INHOMOGENEITY Borys T. Ladanivskyy(1), Valentyna M. Kobzova(1), Branislav Kartik(2), and Jan Vozar(2) (1) Carpathian Branch of Subbotin Institute of Geophysics, National Academy of Sciences of the Ukraine, 3B Naukova st., 79053 Lviv, Ukraine (2) Institute of Geophysics, Slovak Academy of Sciences borys_lad@mail.com The basic model on the laboratory installation is a three-layer section of K type. The simple 3D rectangular structure, was insert in the upper well-conducting sedimentary layer. The results of modelling in alternating fields are similar to those in natural field provided electrodynamic similarity law is observed. In the present investigation EM field of the scale model is identical to the geoelectric section where in a sedimentary layer with thickness of 7.75 km and resistivity of the order of 10 Ohm-m there is a 3D uplift measuring 50-30-7.5 km with 300 Ohm-m. The basement of 2000 Ohm-m is characterized by well conducting crust layer at a depth of order of 30 km. Spatial structure of five EM field components obtained using both a integral equation method and a scale analogue model method was compared. The results indicate a good compatibility between the two methods. However, in some points maximal difference is 20-30% for Ex and Hz components. The difference between the results can be attributed to the accuracy of each method. A finite size detector smoothes out the behaviour of the electromagnetic fields in the neighbourhood of a conductivity discontinuity. Also, the accuracy of a numerical method depends on the size of grid intervals as well as on the uniformity of grid spacings. Each of methods have a possibility to increase his accuracy. 9.9p EXPERIENCE OF PHYSICAL MODELING APPLICATION FOR CONDUCTANCE ANISOTROPIC INVESTIGATION Valentyna M. Kobzova(1), Borys T. Ladanivskyy (1), Tomasz Ernst(2), and Michal Stefaniuk(3) (1) Carpathian Branch of Subbotin Institute of Geophysics, National Academy of Sciences of the Ukraine, 3B Naukova st., 79053 Lviv, Ukraine (2) Institute of Geophysics, Polish Academy of Sciences, 64 Ksiecia Janusza st., 01-452 Warsaw, Poland (3) University of Mining and Metallurgy, al.Mickiewicza 30, 30-059 Cracow, Poland vkobzova@mail.com borys_lad@mail.com The interpretation of EM data of geophysical methods is based on isotropic geoelectrical models. However recent investigations demonstrate that the upper layers of the crust and mantle may be highly heterogenous. Conductivity anisotropy means that the formation conductivity varies in different directions. Method of analogue physical modeling has been used by us for investigation of lateral and vertical anisotropy of conductance sedimentary formations. We used installation "Model" worked out in Carpathian Branch of Institute of Geophysics. The scale 3D models of geoelectric sections are created in the electrolytic tank with dimensions of 5.0-5.0-0.7m. Geoelectromagnetic variations are simulated by harmonic plane-homogeneous field. The process of making anisotropic models has been developed. There may be surface or deep, local or regional anisotropic zones of any size and form. The results of investigating both lateral anisotropy of the 3D uplift 50-50-7.5km and vertical anisotropy of regional sedimentary deposits that cover the crossing faults are represented here. The anisotropy coefficient is about ten both lateral and vertical anisotropy models. MT-sounding curves and spatial structure of electromagnetic field components of anisotropic and identifical isotropic scale models have been compared to estimate influence of anisotropy. The basic conclusion is follows: the EM pattern of anisotropic inhomogeneity field is defined only by conductance along the corrent direction despite conductance along other directions. 9.10p MAGNETOTELLURIC SOUNDING IN UKRAINE: DATA COLLECTION, PROCESSING, INTERPRETATION AND PHYSICAL MODELLING V. Korepanov(1), V. Kobzova(2), and V. Tregubenko(3) (1) Lviv Centre of Institute of Space Research, 5-A Naukova St., 79000, Lviv, Ukraine (2) Carpathians Branch of Geophysical Institute, Lviv, Ukraine (3) Ukrainian State Geological R & D Institute, Kyiv, Ukraine vakor@isr.lviv.ua The successful application of seismic methods for the prospecting of structures perspective for hydrocarbonic deposits in recent 20 years lowered the interest to the geophysical methods using natural sources of electromagnetic radiation. But both the growing experience in geophysical prospecting methods application and the advances in electronics and sensors development showed that in many cases electromagnetic methods give very good results, especially in complicated geological situation (e.g., near-mountain regions). Between them the magnetotelluric sounding (MTS) is one of the fast developing methods able to solve enough reliably even three-dimensional (3-D) inverse problem and to compose 3-D deposit model, the response function of which suits well the observed electromagnetic signals. In cooperation with seismic methods MTS allows to make the mapping of structure tectonic situation much more in details as well as to detect directly the hydrocarbon deposits. Other advantages of MTS is much lower price of field works, higher productiveness and ecological cleanliness. The MTS methodology, field data collection instrumentation and interpretation software packet are developed and successfully tested in field conditions. As a result of more than 25 years of investigations practically all territory of Ukraine is covered by MTS survey with the scale 1:500000. Western part of Ukraine with Carpathians seismo-active region of Alps age and south-west edge of precambrian East-European plate is covered by 25x25 km network. Data processing was made by narrow-band filtration of magnetograms with following least-squares method application. It allowed to construct frequency dependencies of the impedance tensor components and Vise-Parkinson matrixes for the periods from 0,1 until 1000 s. Also amplitude and phase MTS curves were obtained and corresponding maps and geoelectric cross-sections of MTS parameters with scale 1:25,000,000 were made. In the limits of this region Lutsk electric conductivity anomaly of isometric shape with diameter about 200 km is located. The transversal zonality of Ukrainian Carpathians by electric resistivity was discovered. A set of field experiments during the summer 1998 was carried out in frames of an international experiment "Baltic Electromagnetic Array Research (BEAR)". New developed MT-stations LEMI-404 were used in this experiment and wide-band high quality data were obtained what allowed to construct the conductivity curves in the period range from 0.01 to 100,000 s. The parameters of the LEMI-404 MT-station and peculiarities of its operation are discussed. In order to compare the efficiency of numerical modelling for interpretation quality estimation the physical modelling using analogue scale 3D presentation of conductivity inhomogeneity was made. Special laboratory facilities were used for the physical modelling. It is intended to study anomalous electromagnetic field generated by arbitrary conductive inhomogeneities of the geological medium. Scale 3D models of geoelectric sections are created in the electrolytic tank 5 x 5 x 7 m. Geoelectromagnetic variations are simulated under laboratory conditions by harmonic plane homogeneous field generated by two perpendicular antenna systems. The working frequency range is 0.1 10 MHz depending on scale coefficients both short-period and long-period geoelectromagnetic variations may be simulated. Spatial structure of EM field components and difference between it has been demonstrated. The results of this work and the investigation directions aimed at further progress of MT analysis are reported. 9.11p ESTIMATION OF THE EARTH'S CRUST STRENGTH IN THE BAIKAL REGION ON MATHEMATICAL MODELLING DATA AND GPS-GEODESY Anatoly M. Popov, Vladimir A. San'kov, and Andry V. Lukhnev Institute of Earth Crust of Siberian Branch RAS, 664033, Irkutsk, Russia popov@earth.crust.irk.ru It is known that the limit (destructive) Earth's crust deformations, attendant the earthquakes are estimated to be the (1-2)? 10-4 values. These values are extremely low compared to laboratory data that determine the limit deformations of rocks destruction as 10-3 and more. This contradiction is explained by the presence of numerous cracks in the Earth's crust that decreases the strength properties of the latter. It can be supposed that these cracks' presence is caused by the external loads' frequent influence on the Earth's crust. If these loads are numerous, the endurance effect of fragile rock's destruction arises under the tensions being considerably less than the rock's strength properties. The excellent opportunity to test these hypothesis exists in Baikal region. The huge water-body - the lake Baikal, the level of which changes within 1-1.2 ? during the year is situated here. The water-level influences on the displacement level of the lake-sides can be determined theoretically basing on the joint solution of equation of equilibrium and general Hook's law. Otherwise, such season lake- sides' displacements are possible to be determined on the base of repeated measurements by the GPS-geodesy method in the strictly fixed bench-mark. We carried out these measurements according to the above mentioned principles during 1997-1999 years in the point Turka, which is situated on the east lake-side. The maximum displacement of the point corresponding to the lake-side is determined to be 2,5-3 mm. At that, the elastic parameters have been taken according to the seismic investigations' data - E (Yung's modul) = 700000 bar, µ - (Poisson coefficient ) = 0.25. The displacements in lateral component of the lake-sides according to the GPS-geodesy data turned to be 30-35 mm that an exponent more than the first values. The values given are in line with the differences of the limit deformations of the rocks destruction according to the laboratory data and natural ones obtained basing on the rocks destruction basing on the earthquakes' investigations. It would be rather logically to suppose that given differences in the rocks displacements are caused by the fact that the Earth's crust is penetrated by the net of microcracks as a result of the endurance effect of fragile rocks destruction that roughly decreases the strength of the Earth's crust. Using the modelling results, the elastic Earth's crust parameters can be selected as well as its strength properties using the Baikal lake-sides displacements "in situ" according to GPS-geodesy data. The above mentioned parameters turned to be equal to: E =50,000 bar, µ=0.2. As the true strength of the rocks is estimated to be an exponent less than that of Young's values, the roughly taken limit Earth's crust strength in the region is 5,000 bar. The tidal deformations, large-scaled movements of the air-bodies such as cyclones-anticyclones, tornado, season atmospheric tension drops can also act as variable external loads decreasing the Earth's crust strength. 9.12p EARTHQUAKES TRIGGERS AND ELECTROMAGNETIC FIELD MONITORING IN BAIKAL RIFT ZONE A.M. Popov(1), V.M. Akulov(2), Yu.B. Bashkuev(3), N.N. Klimov(4), M. Dembelov M., A.N. Maksimovich, and A.V. Mashanov (1) Institute of the Earth's Crust, Siberian Branch of the Academy of Sciences (2) East-Siberian Scientific Institute of Physics and Technical Radio Measurements (3) Bouriat Institute of Natural Sciences (4) Irkutsk State Technical University popov@earth.crust.irk.ru The increasing of the conductivity in the precursory strains and stresses zones (zones of earthquakes preparing) and in the earth's atmosphere is supposedly caused by greater concentration of the gas-fluid component in the above mentioned zones. The assumption of considerable role of the fluid in seismo-tectonic processes and consequently in processes of creating different precursor features proceeds from the crust conductive layer's activity in the region (e.g. its rise with approaching to seismically active regions) the nature of which is obviously caused by fluid component existence. The authors determine such correlation to be a result of the consecutive solar activity influence on the changes of the troposphere physic state and air bodies circulation in the atmosphere, climate in the near-land layers, water-level in the Lake Baikal, fluid regime in the earth's crust and seismicity in the region. The fluid regime is changed at the expense of the surface-water penetration at the great depths as a result of arising of zones of a greater permeability under affect of variable internal load on the earth's crust. Cyclones-anticyclones may act as triggers being the factors affecting the renewing the micropores and forming the new ones that affects the permeability of the crust, crustal fluid regime and consequently seismic regime of the region. We have carried out the mathematical modelling of the cyclone- anticyclone situation of the average sizes with the pressure overfall ± 0,03 bar. Mathematical modelling have been based on the joint solution of the equation of equilibrium and general Hook's law in 3D. The calculation results are the following: horizontal displacements formed just some millimeters and vertical ones - achieved several centimetres. To study the effect of the precursory strains and stresses zone (zones of earthquakes preparing) on the parameters of the electromagnetic signals, we have elaborated the equipment complex for observing the variations of the moon phases and amplitude of high-stable signals. As a source of the signals, the specialized radiostation (RTZ) located near Irkutsk has been used. The indicated station radiates the standard signals with frequency of 50 Hz and power of 10 kW at that the average-day value of the standard signals is coordinated with the frequency value being reproduced by the State Standard of the Frequency and Time (SSFT) with the relative error no more than 5x10--12. The standard-copy being the base of the service of time has the relative error of keeping and reproducing the units of time and frequency in the system of SSFT no more than 2 x 10 -14. At that, the measurement of time and frequency phase of the main frequency signal of the RTZ station with the error no more than 0.03 ms. (0,5o) has been provided. The line Irkutsk-Ulan-Ude with the length of 280 km crossing the seismically active Baikal Rift Zone has been chosen for the observations. Basing on the values taken while the period of 4 hours (the wave is in line with the surface one) the annual amplitude motion of 30 db and that of the phase of 1,5 ms. of signals have been obtained. According to the calculations, the obtained season (winter-summer) phase and amplitude variations are not sufficient for creating the anomaly value which is being observed. One strong anomaly which occured 4 hours later the moment of the earthquake (M=3.4) dated by 13 of August 1996 (post-factum) at the distance of 100 km to the south-west direction from Ulan-Ude has been revealed under the motion of the amplitude-phase signals characteristics fixed for the time of 4 hours (UT). The indicated anomaly is revealed either in phase and amplitude curves. Some of the earthquakes with the epicenters located near the road and Lake Baikal water-body have not been revealed in the above mentioned characteristics. Obviously, the effects from the earthquakes are displayed in the conductive mediums. 9.13p BAIKAL: MONITORING OF THE EARTH'S CRUST ELECTRICAL CONDUCTIVITY AND SEARCH FOR THE EARTHQUAKE PRECURSORS Yu.F. Moroz, M.M. Mandel'baum, and I.P. Shpak Institute of Volcanic Geology and Geochemistry, 9, Piip blvd., Petropavlovsk-Kamchatsky, Russia, 683006 ivgg@svyaz.kamchatka.su moroz@irk.ru We present here the data on the monitoring of the electromagnetic field with an artificial source performed during 18 years at the eastern Baikal lakeside. The number of observation sites is 12. The distance between them is from 1 to 40 km. One site is located at the opposite side of the lake. Measurements are made once a day. The depth of the studied parts of the Earth's crust does not exceed 2-3 km. The long-term time series of apparent resistivities, meteoparameters and water level in the Baikal lake have been studied using computer programs of multivariate analysis. It has been shown that the electrical conductivity of the upper crust does not virtually depend upon the water level, atmospheric pressure and air temperature. The increase of the canonical coherence of the apparent resistivities multivariate series prior to intensive seismical activity has been established within the Baikal rift zone. The enhanced coherence anticipates earthquakes of 15 and higher energy class within a radius of up to 650 km. The anomalous effects have been also determined in the aggregated signal of the apparent resistivities multivariate series, associated with the 12 and 3 energy class earthquakes with the epicentral distance of up to 40 km. The aggregated signal resolution increases at increasing of the number of channels, and the effects of more distant earthquakes are manifested in the signal. The canonical coherence and aggregated signal anomalies can be precursors for strong earthquakes within the Baikal rift zone. 9.14p SEISMOGALVANIC EFFECT IN THE MAGNETOTELLURIC FIELD Yu.F. Moroz Institute of Volcanic Geology and Geochemistry, 9, Piip blvd., Petropavlovsk-Kamchatsky, Russia, 683006 ivgg@svyaz.kamchatka.su moroz@irk.ru Here we discuss the data on the magnetotelluric field monitoring performed during 1993 in the seismofocal zone of the eastern coast of Kamchatka. On June 8, 1993, a large earthquake of M=7.7 took place here. For the time periods of 1024 minutes the impedances have been determined within the period range of 200 to 2500 s. For the periods exceeding 400s the environment is nearly two-dimensionally heterogeneous. The major impedance axes are oriented along and across the strike of the seismofocal zone. The strong shore effect is manifested in the transverse impedance. Impedance modules are affected by the galvanic effect in all directions. Within the period range of 900 to 2500s the transverse (maximal) impedance is defined more effectively. Transverse impedance time series is studied within the period of 2500s. In most cases impedance varies within the limits of the mean square deviation, which equals 12%. However, during the period of the earthquake occurrence the impedance module increased by a factor of 1.5 times at some time intervals. 10 days after the earthquake the impedance returned to its initial value. The factors that caused variations of impedance module did not cause changes in its phase, which indicates the presence of the galvanic effect. The anomaly is caused by precipitation and other meteofactors. It is more likely associated with the earthquake. The revealed effect can be considered seismogalvanic. It is evidently conditioned by the variation of the subsurface geoelectric heterogeneities caused by the earthquake. The effect discovered requires more profound study. 9.15p MAGNETOTELLURIC AND MAGNETOVARIATIONAL STUDY OF A REGION SENSITIVE TO SEISMIC ELECTRIC SIGNALS (SES) K. Eftaxias, I. Rokityansky, N. Bogris, G. Balasis, and P. Varotsos Solid Earth Physics Institute, University of Athens, Greece pvaro@otenet.gr In principle, it was expected that the amplitude of precursory Seismic Electric Signals (SES) would be larger if the measuring station lies at a smaller epicentral distance from the impending earthquake (EQ). However, this expectation turned out to be strongly violated: SES are observable at particular sites (sensitive sites) at the earth's surface but not at others, which may lie at shorter epicentral distances. This SES property was called sensitivity. The effect has been explained by a simple model which assumes that a highly conductive path lies close to the emitting source and terminates (below the earth's surface and) close to the observation site. It is the scope of this work to present a conductivity structure study in Ioannina area (NW Greece), where one of the most sensitive stations is located. Five components MT measurements have been carried out, in the band 0.01-1000 s, at 42 sites and the data were analyzed by various procedures suggested to date. Maps of the real and imaginary induction vectors, for various periods, were constructed as well. 9.16p PROCESSING AND MODELLING OF AMT DATA FOR MINERAL APPLICATIONS Xavier Garcia and Alan G. Jones Geological Survey of Canada, 615 Booth St., Ottawa, Ontario, K1A 0E9, Canada garcia@cg.NRCan.gc.ca The high-frequency magnetotelluric method, AMT, is currently being widely used for mining exploration, especially in Canada. However, there are still some aspects regarding its implementation that need to be improved. These range from signal detection and time series processing to response function analysis to appreciation of three-dimensional effects. The main natural electromagnetic source at the range of frequencies covered by mining-scale MT, audio-frequencies of 10 Hz - 20 kHz, is the global system of lightning. Due to the physical characteristics of the Earth's ionosphere and atmosphere, there is a minimum in the electromagnetic spectrum around 1,000-3,000 Hz, especially during the daytime. This AMT "dead-band" is exactly the frequency range that is first sensitive to the presence of a typical economic target body. Another approach is the use of a remote site that can help to obtain a prediction of the magnetic field from the telluric fields. Some ore deposit exploration are being carried out in areas where there is existing mining activity, thus the data can be seriously affected by noise. The classical processing schemes are based on either the Fourier or the windowed Fourier transforms, and these methods do not readily separate noise from signal in the actual conditions. The application of the wavelet transform offers an analysis of the time series at the frequency and time domains simultaneously. This analysis can be use to locate events in the time series that can be use in a posterior processing to obtain reliable estimates in that dead band. In this paper we describe our efforts in these two aspects of processing MT data for mining exploration. 9.17p CRUSTAL POROSITY AND PERMEABILITY DERIVED FROM CONDUCTIVITY DATA L.L. Vanyan Shirshov Institute of Oceanology, Moscow, Russia vanyan@geo.sio.rssi.ru Conductivity/porosity relationship is a well-known Archie Law used for estimation of crustal porosity. Resistive upper crust corresponds to the low-porosity layer with porosity about o.oo1-o.oo3. Conductive deep crust has a porosity approximately one order of magnitude higher than that of the upper crust. However seldom used conductivity/permeability relationship seems to be even more natural because both conductivity and permeability are the transport parameters of the rock with fluid in microcracks. This relationship was studied by Brace,1968,for sea-water saturated granite. We used the results of Brace reduced to higher conductivity of the pore fluid according to Nesbitt, who considered brines as the most probable crustal fluid. After the reduction a very low permeability around 1 nanoDarcy was estimated for the resistive uper crust. Permeability of the more conductive middle crust is about 1000 times higher, it reaches 1microDarcy. Recently Manning and Ingebritsen, 1999, estimated permeablity of the tectonically active crust by means of geological analyses of metamorphism. They found a value about 1 microDarcy in depth interval 15-30km that corresponds well with the estimations based on conductivity. 9.18p EXPERIMENTAL STUDY ON THE MONITORING OF ELECTROMAGNETIC VARIATION IN BEIJING AND THE VICINITY BY USE OF PASSIVE AND ACTIVE ELF SIGNALS Guoze Zhao(1), Ji Tang(1), Jijun Wang(1), Qianhui Deng(1), Junmeng Zhao(1), Alexander Saraev(2), Mikhail Pertel(2), Anton Kocherov(2), and Mikhail Kharlamov(2) (1) Institute of Geology, China Seismological Bureau, Beijing 100029, China (2) St. Petersburg State University, 7/9, Universitetskaya nab., St. Petersburg, 199034, Russia zhaogz@public.bta.net.cn A cooperative observations were carried out in Beijing and the vicinity in 1999 by Institute of Geology, CSB and St. Petersburg State University. The purpose was to measure the ELF signals generated by the Russian ELF transmitter on Kola peninsula and to test the possibility of establishing a network for monitoring of the electromagnetic variation in seismically active area. The daily variations of apparent resistivity obtained by use of natural electromagnetic field for both N-S and E-W direction were observed at site Jixian. The maximum change of apparent resistivity with about 15 percent occurred in N-S direction . Furthermore, coherence of daily variation between N-S apparent resistivity and E-W solid tide deformation and coherence of E-W apparent resistivity and N-S deformation were found. The apparent resistivity variation shown that it was independence from daily temperature variation. The ELF electric and magnetic signal were measured at fix time period of each day among 10 successive days at site Baodi. It was found that the electric and magnetic power density spectrum changed in 1.5 - 2 times within 5 of 10 day's period. The apparent resistivity varied between 24 and 26 Ohmm with a standard deviation of 2.9 percent. 9.19p MEASUREMENTS OF ELECTROMAGNETIC FIELD GENERATED BY THE RUSSIAN ELF TRANSMITTER IN CHINA AT THE DISTANCE OF 7000 KM Alexander Saraev(1), Mikhail Pertel(1), Anton Kocherov(1), Mikhail Kharlamov(1), Guoze Zhao(2), Ji Tang(2), Jijun Wang(2), Qianhui Deng(2), and Junmeng Zhao(2) (1) St. Petersburg State University, 7/9, Universitetskaya nab., St. Petersburg, 199034, Russia (2) Institute of Geology, China Seismological Bureau, Beijing 100029, China elmag@elmag.ecri.pu.ru In 1999 the unique experiment on measurements of electromagnetic field generated by the Russian ELF transmitter "Zevs" in China at the distance of 7000 km from the source was carried out. The objective of the experiment was to study the possibility to use this source for electromagnetic investigation at a long distance. The ELF transmitter is located on Kola Peninsula in the north-western part of Russia. The harmonically varying current in the antenna can reach 300 A. The measurements were carried out using an AKF-2.2 hardware - software complex developed in St. Petersburg State University. As a result of the experiment the signals of electrical and magnetic fields generated by the ELF transmitter at a frequency of 80 Hz were detected confidently. Spectral power density of signals exceeded levels of the natural electromagnetic field 250 times at the used spectral resolution of 0.00032 Hz. The measurements were carried out under unfavorable noise condition in an urban area. The coherence between signals of natural electrical and magnetic fields at the adjacent frequencies was 0.1-0.5, while for ELF transmitters signals the coherence exceeded the value of 0.95. As a result of the experiment the use of the ELF transmitter for electromagnetic soundings and earthquake prediction in China has been shown to be very promising. 9.20p WAVEGUIDE ZONE OF POWERFUL SOURCE OF ELECTROMAGNETIC FIELD Alexander Saraev and Petr Kostkin St. Petersburg State University, Universitetskaya nab., 7/9, St. Petersburg, 199034, Russia elmag@elmag.ecri.pu.ru In realization of activities by CSAMT method with a source as horizontal electrical dipole or cable a near-field, transient and far- field zones are outlined, the measurements and data interpretation in which have a number of distinctions. While using powerful sources of electromagnetic field with a long-range action of a hundred - thousand of kilometers, similar to the Russian extremely low frequency (ELF) transmitter "Zevs", there is the necessity of additional selection of waveguide zone. In this zone the structure of field strongly depends on the influence of ionosphere and displacement currents in air and noticeably differs from the case of far-field zone. The main differences consist of slower fading of amplitudes of electrical and magnetic field components, change of directional diagram of the source, change of configuration of areas, favorable for measurements of Zxy or Zyx impedance, appearance of ellipticity of electrical and magnetic fields polarization. Distance, where arise the waveguide effects for the ELF transmitter "Zevs", is 100 km for direction along and 200 km for direction across antenna. The estimation made for antenna length of 60 km, frequency of 80 Hz, resistivity of earth and ionosphere accordingly equal to 10000 Ohmm and 100 000 Ohmm and altitude of ionosphere of 90 km. 9.21p DISTURBANCES ON MAGNETOTELLURIC DATA DUE TO ELECTRIFIED RAILWAY Marcelo B. Padua, I. Vitorello, and A.L. Padilha INPE, C.P. 515, 12201-970 S.J. Campos, Brazil banik@dge.inpe.br Magnetotelluric soundings were carried out in the period range of 20 to 6000 s along profiles orthogonal to the Campos do Jordao Railway, in the Brazilian southeastern region. The profiles were located over two adjacent regions with contrasting conductivity, the conductive sedimentary region of Taubate Basin and the resistive crystalline region of Serra da Mantiqueira. The railway operates with DC current that produces an intense electromagnetic noise, but only during diurnal periods, being turned off at night. The objective of this study is to characterize the EM noise made by the railway and to verify its effect on the MT parameters. Initially, diurnal and nocturnal data were separately analyzed to estimate the impedance tensor, using the techniques of single station or remote reference, and robust or non-robust algorithms presently available to the scientific community. The comparison between these results was employed to establish the best way to obtain trustworthy MT parameters using contaminated data. As expected, it was observed that the noise produced more irregular plots of apparent resistivity and phase, and larger error bars. Nevertheless, for the combination robust method-remote reference that produced the most reliable results, the values obtained with and without noise are practically the same. As a final testing exercise, all data were used in the analysis. It was observed that the contaminated sections did not distort significantly the MT results, reproducing quite well the nocturnal values, and having the advantage of providing better statistical results with the increase of the analyzed time series. 9.22p EFFECTIVENESS OF USING THE MT APPARENT RESISTIVITY FOR MONITORING OF GEODYNAMICAL PROCESSES Marina E. Sholpo SPbF IZMIRAN, St Petersburg, 191023, Muchnoi per., 2, box 188, Russia zham@az2608.spb.edu Using numerical modelling it is studied the sensitivity of the MT apparent resistivity to the changes of the resistivity of some element of the 1-D structure (i.e. the derivative of the logarithm of the apparent resistivity by the logarithm of the varying resistivity). It is shown that: (1) The relative changes of the apparent resistivity can several times exceed, under certain conditions, the corresponding relative changes of a layer. On this account the MT apparent resistivity can be recommended as a prediction parameter for monitoring of geodynamical processes; (2) The monitoring is most effective for the study of the resistivity changes of a high-conductive layer. In this case the sensitivity is most high (from 1 to 2) within the wide period range. The period corresponding to the maximal sensitivity exceeds several times the period where sounding curve has a minimum corresponding to this layer. This must be taken into consideration as for choosing the monitoring regime so for determining the depth of geodynamical processes; (3) The behavior of the frequency characteristic of the sensitivity is different for the upper and lower layers. In case of the upper layer the sensitivity within the small period range approach to 1, while in case of lower layer to 0. This fact may be used for clearing up the reason of apparent resistivity changes; (4) The presence of the high-conductive layers makes it difficult to study the changes of the resistivity of the less conductive layer. But the correctly chosen period range allows to find the resistivity changes of that layer even if its conductivity is somewhat less then the conductivity of the surrounding layers. These conclusions can be extended also to more complicated (2-D and 3-D) structures. 9.23p A COPLANAR COIL SYSTEM IN INDUCTION LOGGING Paulo R. Carvalho(1) and Om P. Verma(2) (1) Departamento de Ciencias Exatas e de Engenharia, Faculdade de Ciencias Agrarias do Para, Belem, Brazil (2) Departamento de Geofisica, Centro de Geociencias, Universidade Federal do Para, Belem, Brazil proberto@supridados.com.br verma@ufpa.br None of the known resistivity borehole devices possesses azimuthal focusing properties whereas the unconventional coplanar coil array has, by design, a strong azimuthal focus. In order to understand in detail the influence of this property of the coplanar system, its electromagnetic responses in the varying boreholes conditions are obtained for a two coil array. Although simple, the solutions of a homogeneous conducting medium are exploited in understanding the skin effects phenomena. The coplanar response of a nonhomogeneous medium, obtained through Sommerfeld boundary value problem, is then extended to the various borehole models, particularly the invaded mud filtrate with gradational transition zones, dipping multilayer sequences, thinly laminated zones, and gradational transition zone between two thick beds. Based on the comparative study between the traditional coaxial and the unconventional coplanar coil responses we conclude that: (1) the skin effects are stronger in the coplanar responses than the coaxial but this disadvantage is almost fully compensated by applying the corrections for these effects, (2) the polarization "horns" are obtained in the coplanar profiles in front of bed boundaries consequently, they are their high quality indicators, (3) the coplanar system is an important auxiliary tool to investigate the mud filtrate invasion and the presence of annulus zones which are direct indicators of movable hydrocarbons, and (4) its azimuthal focussing properties can be explored in the borehole investigations of the axially assymetrical geological situations such as vugular or fracture zones and invasion zones in horizontal wells. 9.24p MODIFICATIONS OF ELECTROMAGNETIC ANOMALIES DUE TO INDUCTIVE INTERACTIONS Om Prakash Verma Curso de Pos-Graduacao em Geofisica, Universidade Federal do Para, Belem, Brazil verma@ufpa.br It is well known that a partially conducting host rock or an overburden modifies the electromagnetic anomalies of the conducting targets. The physical causes for these effects are atributed to 1. the propagation effects suffered by the primary and the secondary fields whilst traversing the overburden, and 2. the current channeling when they are in galvanic contact. However, the phenomenon of the inductive interaction among the currents induced in the different componentes of the target's geolectrical model is ignored, considering the effects very small. But, our scale model studies, carried out by me and my students, show that they change the geometry and amplitudes of the anomaly profiles. Obviously, the degree of these changes depends upon the mutual geometric disposition of these conducting bodies and their induction numbers. For example, an extra peak is obtained in the quadrature profile in the dipping side of a low dipping half-plane model below a conductive overburden due to the inductive interaction between them. 9.25p CONTROL SOURCE ELECTROMAGNETIC SOUNDINGS IN FREQUENCY DOMAIN O.I. Ingerov, M. Yamashita, and G. Balint Phoenix Geophysics Ltd., Toronto, Canada alingers@arvotek.net Two independent, parallel developments took place in the western countries and in former Soviet Union (FSU In the west the CSAMT method was developed in the 1970s, to provide a strong artificial signal in the AMT frequency range. Interpretation of scalar, vector and tensor CSAMT relied on MT approaches, limiting the useful frequency range to the "far zone". Multi-channel equipment provided high productivity (V4, GDP-12, etc.). In the FSU, the method called "frequency electromagnetic sounding" (FES) began simultaneously with MT and TEM in the early 1950s. The scalar methodology used a grounded electric dipole as source, and measured amplitude, and phase (relative to source) with a horizontal electric dipole (Ex), and derivative of vertical magnetic field (dBz/dt) using a horizontal loop. In the late 1950s - early 1960s both theory (for horizontal layered Earth) and equipment for low (1000 - 0.1 Hz), middle (20 000 - 2 Hz) frequency range were created. FES was then successfully used for oil & gas exploration and deep crustal study. Simple, rapid field data acquisition provided significant advantages compared to the contemporary MT. A second wave of FES development occurred in the FSU in the early 1980s The INFAS-IP equipment measured amplitude of signal and differential phase parameters (mainly phase shift between first and third harmonic of the square signal). This improved resistivity interpretation and provided information about induced polarization distribution. This technique (named FES-IP) was widely applied in oil and gas exploration and mining exploration. By the mid-1980s, multifunctional equipment (CES-2, CES-3) appeared which was used to perform combined FES-IP and MT for oil and gas prospecting. The EM field components were analyzed separately as well as in impedance mode, in far, intermediate and near zones. Thus CSAMT and FES-IP became quite similar, and Hungarian geophysicists used both Russian FES and western CSAMT equipment. The integrated application of FES-IP/CSAMT with MT in fifth- generation MT-equipment provides a very sensitive, productive and low cost instrument for oil and gas prospecting, as illustrated by the experimental data obtained in 1998 in Hungary. 9.26p EXPLORATION WITH LOTEM UNDER BASALT COVER K.-M. Strack(1), P.B. Pandey(2), and G. Guarino(3) (1) KMS Technologies, USA (2) ONGC, India (3) Electromagnetic Instruments Inc., USA Kurt_strack@KMSTechnologies.com Among the electromagnetic methods Long Offset Transient Electromagnetics has become very promising because in acquisition and processing it is similar to seismic methods and it has high production rates. Here, we will show some new example from a large survey in India and also described the more recent advances in acquisition systems. LOTEM consists out of a grounded wire transmitter and an induction loop and electric field receivers. The data acquisition and processing is almost analogous to that of a seismic system. After pre-stack processing the data is stacked and finally converted into apparent resistivities after further post-stack processing. The apparent resistivities are then either inverted or directly imaged. In basalt covered areas it is often impossible to obtain seismic data. In an example from Germany we show how LOTEM and MT can give complementary results when integrated using joint inversion. The latest generation of EM instruments is actually designed for LOTEM and MT in one instrument. An example from India and uses data acquired during the late 1980s. The field survey that covered several hundred sites in Gujarat was carried out over a total period of 3 months after careful pre-survey design. The data was of very good quality and was interpreted to a stable results. While most data sets were easily interpreted with layered earth inversions, several dyke like feature required 3D modeling to interpret the data. Both indicate a dyke like structure at depth. Since transmitter and receiver have several kilometers offset one also needs to use 3D modeling to verify the lateral extent to ensure whether the anomaly is located below the receiver, between transmitter and receiver or on the other side of the receiver. The case histories have shown that LOTEM is not only a viable method to obtain geophysical information from below basalt covers but also that it can be used commercially. 9.27p FEATURES OF APPARENT RESISTIVITY TIDE VARIATIONS Alexander Saraev(1), Mikhail Pertel(1), Boris Pugachev(1), and Zinoviy Malkin(2) (1) St. Petersburg State University, 7/9, Universitetskaya nab., St. Petersburg, 199034, Russia (2) Institute of Applied Astronomy RAS, 12, Kutuzova nab., St. Petersburg, Russia elmag@elmag.ecri.pu.ru Measurements, carried out in various regions of Russia by methods of audiomagnetotelluric sounding (AMTS) using of natural electromagnetic fields and of extremely low frequency sounding (ELFS) using of fields of the ELF transmitter "Zevs" in frequency range units - hundreds of a hertz have allowed to find a good correlation of apparent resistivity Ra changes and vertical tide deformation of the earth crust dH. Thus rather complicate character of tide variations Ra was observed. Both direct (rise of the earth surface and increase, lowering of the earth surface and decrease of Ra), and inverse relation were obtained. More changes were marked for E-polarization of the electromagnetic field. Various character of relations can be explained by a various degree of rocks water saturation. When small water content the fluid distribution in the rock has islands, not connected character. When increase of pressure the degree of fluid connections increases, the network of interconnected channels grows and rocks resistivity decreases. On the contrary, when biggest water content the fluid completely fills the rock pore space. When increase of pressure in this case happens compression of channels and resistivity of rocks grows. The relation of Ra variations both with depth of research of a geoelectrical cross section (used frequency) and type of rocks was marked. The biggest variations are characteristic for intrusive and metamorphic rocks, and the smallest - for permeable overlaying soil. At significant thickness of permeable soil (hundreds of meters) a noticeable tide variations of Ra were not observed. It is necessary to take into account the tide variations of Ra while working by methods of electromagnetic soundings. In connection with development of these methods the accuracy of measurements was increased, and there is the necessity to take into account factors, which were not considered earlier with smaller accuracy of measurements as possible sources of errors. As earth tides cause changes of stress-strain state of rocks, the observation of Ra tide variations can also be used for modeling of processes of earthquakes preparation because it is rather difficult to obtain the reproduced full-scale data on observations before earthquakes. The work was performed with the support of "Integration" program, project 326.66 9.28p CSEM FREQUENCY SOUNDING OF THE SEAFLOOR WITH THE INHOMOGENEITY L.L. Vanyan and Zalina Djatieva Shirshov Institute of Oceanology, Moscow, Russia vanyan@geo.sio.rssi.ru djatieva@geo.sio.rssi.ru The theoretical basement of the interpretation of the seafloor frequency CSEM sounding developed in Shirshov Institute of Oceanology is the horizontal skin-effect and the fact that the penetration depth is controlled by the transmitter-receiver distance. To investigate the features of the seafloor CSEM sounding in the presence of 3D inhomogenety the scale modeling was carried out in an electolythic tank. The model consists of three layers with an underwater graben. Amplitude and phase of electrical field of horizontal electric dipole in the presence of 3D inhomogenety was investigated. At the lowest frequencies the electric field, both outside and inside the graben, are very close. That confirms a low resolving power of the DC methods under condition of the deep sea. The decrease of the electrical component is more stronger inside the graben than the one outside. This difference reflects stronger attenuation within the conductive graben. To estimate an influence of the graben borders an attenuation of the electrical field was studied on the graben axis. A comparison of 3D curves with 1D resulted in the fact they are almost equal. This coincidence of attenuation curves means that the underwater graben borders have a very weak influence on the low frequency electrical field. This feature is likely to be a result of the horizontal skin-effect, when the EM wave dissipates, propagating from transmitter to receiver along the graben axis. This work was supported by Russian Foundation for Basic Research - project 98-05-64025. 9.29p RADAR DETECTION OF LUNAR ICE George R. Jiracek(1), R. Michael Quesada(1), and A. Peter Annan(2) (1) Department of Geological Sciences, San Diego State University, San Diego, CA 92182, USA (2) Sensors and Software, Inc., Mississauga, ON L4W 3R7, Canada jiracek@moho.sdsu.edu mquesada@geology.sdsu.edu Recent radar and neutron spectrometer evidence for water ice deposits in the lunar polar regions has been received with great enthusiasm. However, the results remain controversial because new earth-based radar findings suggest that the unusual radar echoes were due to rough surface scattering, not ice. We propose a lunar electromagnetic, EM, experiment to detail the stratigraphy of the upper 10s of m of the moon from both orbital and surface modes. The surface radar system would be similar to the Noggin 500 developed by Sensors and Software, Inc. It weighs only 3 kg, has a system performance factor of 160 dB, and radiates 8 W at 500 MHz. The Noggin 500 has been used in controlled field tests where soil-covered blocks of ice were detected within the upper meter of the surface. This expected result simply confirmed that a significant dielectric constant contrast existed between the soil and the ice. It did not unambiguously identify the presence of ice. Ice has a unique EM absorption spectrum, far below the radar frequency range, that we hope to exploit to actually identify water ice if it occurs in the lunar near-surface. Affects of mixtures such as dirty, rock-laden ice at different temperatures, and changes on radar echo polarizations, are also being studied.