Abstract: A method for modeling geological structures includes obtaining seismic data and using these data to derive an initial density model. Potential fields data is used to update the initial geophysical model by an inversion process using vector or tensor components of gravity and/or magnetic data. In regions having an anomalous density zone, the initial model includes a topographic or bathymetric surface and a 2D or 3D density model including the top of any zones of anomalous density. Potential fields data is then used to derive the lower boundary of the anomalous density zones by using an inversion process. The final density model from the inversion may be further refined using the seismic data in conjunction with the model obtained by inversion of the potential fields data. The model data are integrated two or three dimensions to determine an overburden stress for the subsurface that includes a proper treatment of the anomalous density zone.

Abstract: A method for modeling geological structures beneath anomalous density zones includes receiving seismic data and using this data to derive the top of a geologic model. Non-seismic data, such as gravity or magnetic data are used to derive the lower boundary of the geologic model in an inversion process. In one embodiment, the predicted parameters are combined with seismic data to obtain a depth image and to derive a velocity model in delineating formations of interest. In another embodiment, the processed seismic data is used to further constrain the inversion of the non-seismic data. Another novel aspect of the invention is the filtering of the non-seismic data during the inversion process in a manner that is consistent with Laplace's equation.

Abstract: The present invention relates to an improved downhole seismic source with an epicyclic eccentric weight system for the simultaneous generation of elliptically polarized shear wave seismic energy and compression wave seismic energy coupled into a borehole. The apparatus includes a cylindrical housing and a drive means or electric motor disposed in the housing which provides rotational output to an epicyclic eccentric weight system also disposed in the housing. Expandable tapered wedging collars are used to firmly secure the motor and the epicyclic eccentric weight systems within the housing. A flexible shaft interconnects the centerline of the epicyclic cylindrical roller and the motor whereby the roller receives the rotational output from the motor. The shaft rotates in one direction and the roller rotates in the opposite direction thereby producing an epicyclic motion.

Abstract: A method for obtaining two way travel times for source and receiver pairs includes the steps of determining a set of one way travel times for each source to a plurality of image points and a set of one way travel times for each receiver to the plurality of image points. Ray sets are generated for both the sources and receivers. Travel times from a surface position to image points are computed by two point interpolation using the ray sets. Two way travel time is computed by summing two sets, one set each for the source and receiver positions. A two way travel time set is obtained for a particular source and receiver combination for all imaging points.