The seismic wave energy is evaluated for 35 large earthquakes by inverting far-field long-period P waves into the multiple-shock sequence. The results show that the seismic wave energy thus obtained is systematically less than that inferred from the Gutenberg-Richter's formula with the seismic magnitude. The difference amounts to one order of magnitude. The results also show that the energy-moment ratio is well confined to a narrow range: 10−6 < ES/Mo < 10−5 with the average of ∼5 × 10−6. This average value is exactly one order of magnitude as small as the energy-moment ratio inferred from the Gutenberg-Richter's formula using the moment magnitude. Comparing the energy-moment ratio with Δσo/2μ, where Δσo and μ are the stress drop and the rigidity, we obtain an empirical relation: ES/Mo ∼ 0.1 × Δσ0/2μ. Such a relation can be interpreted in terms of a subsonic rupture where the energy loss due to cohesion is not negligible to the seismic wave energy.