Abstract: Method for processing converted mode seismic data. Compressional and converted compressional to shear wave data is acquired by generating compressional energy into a subsurface formation and recording the amplitude of reflections as a function of time at spaced locations along a line of exploration. A series of compressional to shear wave velocity (Vp/Vs) ratios are selected based on an analysis of the acquired seismic data and the shear wave velocity for each Vp/Vs ratio is determined according to the following relationship: ##EQU1## where k=Vp/Vs. Data corresponding to each Vp/Vs ratio is stacked together, the series of stacks are correlated to the originally acquired seismic data to determine the actual Vp/Vs ratio for the formation and the shear wave velocity is derived. The originally collected data is then corrected for normal moveout and stacked.

Abstract: A method of magnetotelluric exploration is disclosed which features multiple measurements of the earth's electric field at a plurality of locations and one or more magnetic field measurements being made simultaneously. A specific form of cable for connecting measurement apparatus with recording apparatus is also disclosed.

Abstract: In seismic exploration, linear, multiple fold, common depth point sets of seismograms with three dimensional reflection geometry are used to determine the dip and strike of the subsurface reflecting interfaces and the average velocity of the path of the seismic energy to the reflecting interface. The reflections in each set appear with time differences on a hyperbola with trace spacings determined by the source receiver coordinate distance along the lines of exploration. The offset of the apex of this hyperbola is determined from a normal move-out velocity search of the type performed on two dimensional CDP sets. This search identifies the correct stacking velocity and hyperbola offset which are used to determine dip, strike and average velocity.