New types of transient processes observed in electromagnetic sounding

Practical work by several variants of the electromagnetic sounding method has revealed the presence of anomalous transient processes which have been assigned the designation type-a anomalies. Using a modern measurement system there is a change in the sign on xi(t) and after a minimum a monotonic approach to zero. According to classical theory such xi(t) curves are impossible. They can be explained only with additional allowance for polarizability of medium. The increase in measurement accuracy, with registry of processes in the microsecond range, has led to the discovery of still other anomalous processes: type b, with a change in sign, but after a minimum the signal again becomes positive; type c, without a change in the sign on the signal, but in some interval there is a positive sign on the first derivative and in a positive transient process there is a distinct minimum, then a maximum and a subsequent dropoff of the signal; type d, with simple qualitative differences from a normal process absent, but the process not corresponding to the theoretical process, calculated only with allowance for active conductivity of the medium. Processes of these types are registered over sedimentary rocks with resistivity of the layers from tens to several thousand ohm.m.