Earthquake magnitude estimation from early radiated energy

From inspection of a large set of Japanese events, we
investigate the scaling of the early radiated energy, inferred
from the squared velocity integral (IV2) with the final
magnitude of the event. We found that the energy can only
discriminate whether the event has a magnitude larger or
smaller than 5.8, and in the latter case it can allow for realtime
magnitude estimation. However, by normalizing IV2
for the rupture area, the initial slip scales with the magnitude
between 4 < M < 7 following the expected scaling laws. We
show that the ratio between the squared peak displacement
and IV2 is a proxy for the slip following the same scaling
but it can be directly derived from the data, without any
assumption on the rupture area. The scaling relationship
between initial slip and magnitude can be used for early
warning applications, when integrated in a probabilistic,
evolutionary approach. Citation: Festa, G., A. Zollo, and M.
Lancieri (2008), Earthquake magnitude estimation from early
radiated energy, Geophys. Res. Lett., 35, L22307, doi:10.1029/
2008GL035576.

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