par TANG MUOI
Comité géologique du Vietnam, Hanoi
A fixed d.c. emitter introduces a current into an isotropic heterogeneous
soil with a plane surface, in which the conductivity 
varies
according to the relation 
(k
is a positive constant). We determine the vertical magnetic component at the
surface of the soil (z = 0) for the case in which 
assumes
the form:
(Ci,
Cii, positive constants)
where Ri and are the distances between the measuring point and the "conductivity
center" Si. Using a classical procedure and by calculating a double integral
we also obtain the horizontal magnetic components.
Several practical numberical examples are presented in the form of maps of
isodynamic lines in the plane z = 0 for the distribution of the anomalous components
Za, Xa and Ya as well as for the distribution of the total horizontal component
Ha and of the total field |Ha| .