This study aims to estimate earthquake magnitude quickly using vertical component data from
Broadband seismographs for improvement of tsunami warnings. We formulate using displacement and
integrated displacement data with a cut-off of more than 100 seconds. Empirical relationships were
obtained for displacement and integrated displacement with moment magnitude. Data selection of
seismic records was done before estimating the relationships of amplitudes by observing the amount of
data to unselect records with gaps and the maximum amplitude to eliminate spike data. We compared
the magnitudes of the formulas for displacement (MD) and integrated displacement (MID). We found that
MID yielded better estimates than MD. MID also produced appropriate estimates for earthquakes with
strike-slip focal mechanisms. On the other hand, for deep earthquakes, MD yielded a better estimate. In
the case of the 2010 Mentawai tsunami earthquake, MID produced an underestimated whereas the
estimate was obtained no more than 3 minutes after the earthquake origin time.
Keywords:
Magnitude estimation, MID, MD, tsunami earthquake.