This dissertation contains investigations of radiated seismic energy measurements from large earthquakes and duration determinations as significant properties of the dynamic earthquake rupture and its applications in the identification of very large and slow source rupturing earthquakes. This includes a description of earthquake released seismic energy from 1997 to 2010 and identification of slow source tsunami earthquakes in that time period. The implementation of these measurements in real-time since the beginning of 2009, with a case study of the Mentawai 2010 tsunami earthquake are also discussed. Further studies of rupture duration assessments and its technical improvements for more rapid and robust solutions are investigated as well, with application to the Tohoku-Oki 2011 earthquake an a case of directivity in the 2007 Mw 8.1 Solomon islands earthquake. Finally, the set of routines and programs developed for implementation at Georgia Tech and IRIS to produce the real-time results since 2009 presented in this study are described.