Does apparent stress vary with earthquake size?



Seismic energy is distributed across a wide frequency band so that limited bandwidth recording can lead to substantial underestimates of the radiated seismic energy or introduce an artificial upper bound of radiated energy. We estimate an adjustment factor to account for the probable missing energy and apply it to three previously studied data sets with limited recording bandwidth. We find that this adjustment, together with accounting for possibly missing events, eliminates much of the moment dependence of radiated energy found previously. We obtain a nearly constant ratio of radiated energy to seismic moment, 3 × 10−5, or 1 MPa of apparent stress drop, over 17 orders of seismic moment. This suggests that deviation from similarity of the energy radiation for seismic events essentially the entire observable range of earthquake size may not yet be resolved.