Determination of earthquake magnitudes using duration of
high-frequency energy radiation and maximum displacement amplitudes: application
to the November 14, 2007
Tatsuhiko Hara
International
Recently, we developed a new method to determine earthquake
magnitudes using the following formula (Hara, 2007a, b):
where M is an earthquake magnitude, 
is the maximum
displacement during high-frequency energy radiation from the arrival time of a
P-wave, 
is the epicentral distance, 
is duration of
high-frequency energy radiation. The duration of high-frequency energy
radiation can be estimated by band-pass filtering of first arriving P-waves (e.g.,
Hara, 2007a). 
are 0.79, 0.83, 0.69, and 6.47, respectively (the units of 
were m, km, and s,
respectively).
We applied this method to the November 14, 2007
Fig. 1. An example of measurements of high frequency
energy radiation. The upper, middle and lower traces are an observed
seismogram, the squares of the band-pass (2-4 Hz) filtered seismogram, and its
smoothed time series (normalized by the maximum value), respectively. “A” and “F” in the lower trace denote the arrival of P-wave and
estimated end of high frequency energy radiation, respectively.
References
Hara, T., Measurement of duration of
high-frequency energy radiation and its application to determination of
magnitudes of large shallow earthquakes, Earth
Planets Space, 59, 227–231, 2007a.
Hara, T., Magnitude determination
using duration of high frequency energy radiation and displacement amplitude:
application to tsunami earthquakes, Earth
Planets Space, 59, 561–565, 2007b.
Last Updated: 2007/11/19