To dissipate the energy of a M9 (which happens about once per decade) you'd need about 32,000 quakes of M6 (still big enough to collapse buildings). Energy sca

To dissipate the energy of a M9 (which happens about once per decade) you'd need about 32,000 quakes of M6 (still big enough to collapse buildings). Energy scales as 10^(1.5 × ΔM) ΔM = 9.0 − 6.0 = 3.0 10^(1.5 × 3) = 10^4.5 ≈ 31,600