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Table 1 Earth conductivity profiles Figure File Name Apx. Depth Remarks References 1. Global Models 1939-69 LAPR39 0--1250 global Sq, Dst LAHIRI and PRICE, 1939; PRICE, 1973 RIKI50 0--1400 misc. data sources RIKITAKE. 1950; 1966 MCD057 0--2900 LAPR39 + secular change McDoNALD, 1957 CANT60 100--600 see ECKHARDT et a!. , 1963 CANTWELL, 1960 YUKU65 380--1900 ring current YUKUTAKE, 1965 BANK69 0--1700 ring current BANKS, 1969; 1972 2. Global Models 1970--74 BFRS70 100--700 Sq, Dst 27-d variations BERDICHEVSKY et a!. , 1970; 1973 PRKR70 0--3200 rework BANKS, 1969, data PARKER, 1970 SCJA72 0--1000 pulsations, bays, Sq, Dst SCHMUCKER and JANKOWSKI, 1972 BANK72 230--1250 model summary BANKS, 1972 JADY74 0--2951 Sq, 27-d, annual variations JADY, 1974 FAR074 300--1500 with BFRS70 FAINBERG and ROTANOVA, 1974 SCHM74 0--1000 see HAAK, 1980 SCHMUCKER, 1974 DMRB77 0--1450 all available data DMITRIEV et al. , 1977 Global Models 1974-1983 3. PRKN74 60-430 Sq PARKINSON, 1974 DUCM80 0--2900 annual means DUCRUIX et a!. , 1980 ISIK80 320--2020 Sq, Dst, annual, solar cycle ISIKARA, 1980 ACMC81 0--2875 secular impulse ACACHE et a!. , 1980 ROKI82 350--1200 various methods ROKITYANSKY. 1982 JAPA83 0--1200 Dst JADY and PATERSON, 1983 4. Pacific Models LAUN74 0--500 near Calif. ; see DRURY, 1978 LAUNAY, 1975 LARSEN, 1975 LAHA75 0--800 Hawaii 7-1350 FILL80 NE Pacific FILLOUX, 1980 LAW and GREENHOUSE, LWGR81 0--200 Juan de Fuca 1981 0--250 Juan de Fuca OLDENBURG et a!. , 1984 OLJA84 OLCA84 0-250 near Calif. OLDENBURG et al. , 1984 OLNC84 0--250 N. cent. Pacific OLDENBURG et ai.
The electrical conductivity of the earth appears to pass through a minimum value at moderate depths, probably between 10 and 20 kilometers. At lesser depths, rocks contain sufficient water-filled void space to be moderately conductive, and at greater depths, increased temperatures again render rocks conductive. The problem of determining the conductivity in this minimum zone is a difficult one. A possible solution lies in the use of electromagnetic coupling measurements for studying this zone in the crust.
Electrical conductivity is a parameter which characterizes composition and physical state of the Earth's interior. Studies of the state equations of solids at high temperature and pressure indicate that there is a close relation be tween the electrical conductivity of rocks and temperature. Therefore, measurements of deep conductivity can provide knowledge of the present state and temperature of the Earth's crust and upper mantle matter. Infor mation about the temperature of the Earth's interior in the remote past is derived from heat flow data. Experimental investigation of water-containing rocks has revealed a pronounced increase of electrical conductivity in the temperature range D from 500 to 700 DC which may be attributed to the beginning of fractional melting. Hence, anomalies of electrical conductivity may be helpful in identitying zones of melting and dehydration. The studies of these zones are perspective in the scientific research of the mobile areas of the Earth's crust and upper mantle where tectonic movements, processes ofthe region al metamorphism and of forming mineral deposits are most intensive. Thus, in the whole set of research on physics of the Earth the studies of electrical conductivity of deep-seated rocks appear, beyond doubt, very important.
Table 1 Earth conductivity profiles Figure File Name Apx. Depth Remarks References 1. Global Models 1939-69 LAPR39 0--1250 global Sq, Dst LAHIRI and PRICE, 1939; PRICE, 1973 RIKI50 0--1400 misc. data sources RIKITAKE. 1950; 1966 MCD057 0--2900 LAPR39 + secular change McDoNALD, 1957 CANT60 100--600 see ECKHARDT et a!. , 1963 CANTWELL, 1960 YUKU65 380--1900 ring current YUKUTAKE, 1965 BANK69 0--1700 ring current BANKS, 1969; 1972 2. Global Models 1970--74 BFRS70 100--700 Sq, Dst 27-d variations BERDICHEVSKY et a!. , 1970; 1973 PRKR70 0--3200 rework BANKS, 1969, data PARKER, 1970 SCJA72 0--1000 pulsations, bays, Sq, Dst SCHMUCKER and JANKOWSKI, 1972 BANK72 230--1250 model summary BANKS, 1972 JADY74 0--2951 Sq, 27-d, annual variations JADY, 1974 FAR074 300--1500 with BFRS70 FAINBERG and ROTANOVA, 1974 SCHM74 0--1000 see HAAK, 1980 SCHMUCKER, 1974 DMRB77 0--1450 all available data DMITRIEV et al. , 1977 Global Models 1974-1983 3. PRKN74 60-430 Sq PARKINSON, 1974 DUCM80 0--2900 annual means DUCRUIX et a!. , 1980 ISIK80 320--2020 Sq, Dst, annual, solar cycle ISIKARA, 1980 ACMC81 0--2875 secular impulse ACACHE et a!. , 1980 ROKI82 350--1200 various methods ROKITYANSKY. 1982 JAPA83 0--1200 Dst JADY and PATERSON, 1983 4. Pacific Models LAUN74 0--500 near Calif. ; see DRURY, 1978 LAUNAY, 1975 LARSEN, 1975 LAHA75 0--800 Hawaii 7-1350 FILL80 NE Pacific FILLOUX, 1980 LAW and GREENHOUSE, LWGR81 0--200 Juan de Fuca 1981 0--250 Juan de Fuca OLDENBURG et a!. , 1984 OLJA84 OLCA84 0-250 near Calif. OLDENBURG et al. , 1984 OLNC84 0--250 N. cent. Pacific OLDENBURG et ai.
The electrical properties of the crust can be measured directly in the field or estimated for in situ conditions from suitable measurements made in the laboratory. Unfortunately, removal of rocks from their in situ location often changes significantly the characteristics of the rock that control the electrical conductivity; modelling those characteristics has been uncertain in the past. Thus, the problems that are inherent in the use of data measured in the laboratory to infer electrical properties of rocks in situ in the earth's crust are (1) preventing sample bias, (2) duplicating the condition of rock in situ and at depth (including pressure, temperature, and several other variables), and (3) modelling the properties of the pore fluids. In this paper, we report new data obtained in the laboratory for several representative samples from the eastern United States. We believe that we have modelled properly all characteristics of the samples that affect significantly the electrical properties. We use the data to estimate a standard electrical model for the upper crust of the eastern United States.