In his doctoral thesis he pioneered the birth of modern seismic-source elastodynamics based on his theory of wave radiation from a finite rupturing fault with subshear or supershear velocity. His theory was confirmed through the observed asymmetric radiation of long-period surface-waves from the great Chilean earthquake of May 22, 1960, where he introduced the fundamental concepts of 'Directivity' and 'Potency' from which the moment tensor is derived. Since then, rupturing fault length, rupture velocity, moment-magnitude and moment energy are routinely calculable from spectra of recorded seismic waves-forms.