Two Energies for One Earthquake: The Moment–Radiation Split and What Apparent Stress Says About Faults

Seismic moment and radiated energy are computed from the standard relations log10 M0 = 1.5M + 9.1 and log10 Es = 1.5M + 4.8 over M 5.0-9.5. Their ratio Es/M0 = 5.0119e-05 and apparent stress tau_a = 1.5036 MPa (mu = 30 GPa) are exactly magnitude-independent under the two relations. Measured catalogues show more than an order of magnitude of scatter in apparent stress, and most of the energy of slip is dissipated as frictional heat and fracture energy rather than radiated.