Earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records

We show that the low-pass filtered, peak amplitudes of
initial P- and S-wave seismic signals recorded in the
vicinity of an occurring earthquake source correlates with
the earthquake magnitude and may be used for real-time
estimation of the event size in seismic early warning
applications. The earthquake size can be therefore estimated
using only a couple of seconds of signal from the P- or
S-wave onsets, i.e. while the rupture itself is still
propagating and rupture dimension is far from complete.
We argue that dynamic stress release and/or slip duration on
the fault in the very early stage of seismic fracture, scales
both with the observed peak amplitude and with the elastic
energy available for fracture propagation. The probability
that a fracture grows to a larger size should scale with the
energy initially available.