The drum records above were recorded on August 19, 2018. The reports contain three events:
Loc.
Time Magn. Depth
Dist.
Fiji
00:30 8.2
350 7652
Fiji
04:42 6.8
263 7631
Indonesia 15:13
6.9
16
9914
Taken together, these three events provide for some interesting
comparisons. First, the two events from Fiji occurred at almost
the same spot, although the second event was not quite so deep.
The magnitude difference (1.4) doesn't seem that great, but the
magnitude scale is logarithmic. 8.2 is a LOT stronger than
6.8. The second event could almost be overlooked in the drum
report.
The second observation is that the depth of the epicenter makes a big
difference in the strength of the signal. The event from
Indonesia and the second Fiji event are comparable in magnitude, but
the Indonesian event was relatively shallow, and both of the events
from Fiji were very deep. Despite the fact that the Indonesian
event was over 2000 miles farther away, it shows up much
stronger. If the 8.2 quake had occurred at a more typical depth
of 25 miles or so, it would have showed up here as a true monster, and
would have driven my sensor beyond the limits of what it is able to
record.