Inversion -- migration -t- tomography Peter Mora Thinh'ng Machines Corporation ~45 First St. Cambridge, MA, 0~14~ ABSTRACT Seismic inversion, broadly enough defined, is equivalent to doing migration and re- flection tomography shnnltaneonsly. Diffraction tomography and inversion work best when sources and receivers surround the region of interest, as in medical imaging ap- plications. Theoretical studies typically show that the high vertical wavennmher ve- locity perturbations are resolved in seismic reflection experiments where the sources and receivers are restricted to the Earth's surface but low vertical wavenumbers must be obtained using a separate step such as a velocity analysis or reflection tomogra- phy. I propose that an iterative inversion using a varying background velocity obtains all tvavenumbers that are resolvable separately by migration and tomography. (The background velocity must contain abrupt discontinuities.) Reflectors in the background model simnlate sources and receivers within the Earth so the source and receiver cover- age in seismic reflection inverse problems is effectively the same as in medical imaging. Some synthetic examples verify the theoretical predictions and show that reflector lo- cations and interval velocities can be obtained simultaneonsly. INTRODUCTION Typical analyses of the seismic inverse problem with sources and geophones on the Earth's surface indicate that the velocity image will only be partially reconstructed (De- vaney, 1984; Devaney and Beylkln, 1984; Esmersoy et al., 1985; Esmersoy and Levy, 1986; Wu and ToksSz, 1987). Even when source-geophone offsets extend from zero to infinity~ only the high vertical wavenumbers are resolved and inversion results look like migration