31 Earthquakes
At The Irazú
Volcano Thursday
The Volcán Irazú
shook and shook
and shook - a
total of 31
times - between
5am and 11am on
Thursday, though
only one of the
tremors was
perceived by the
population,
registering 3.1
on the Richter
scale.
Rodolfo Van Der
Laat, geologist
of the
Observatorio
Vulcanológico y
Sismológico de
Costa Rica (OVSICORI)
explained that
the Irazú is a
very active zone
but currently
there is no
report of
changes in the
structure of the
volcano.
The origin of
the earthquakes
are due to the
activation of a
local fault and
not the
collision or
convergence of
tectonic plates.
The activity at
the Irazú
Thursday is
called a seismic
or earthquake
swarm, events
where a local
area experiences
sequences of
many earthquakes
striking in a
relatively short
period of time.
The length of
time used to
define the swarm
itself varies,
but the United
States
Geological
Survey points
out that an
event may be on
the order of
days, weeks, or
months. They are
differentiated
from earthquakes
succeeded by a
series of
aftershocks by
the observation
that no single
earthquake in
the sequence is
obviously the
main shock.
Earthquake
swarms are one
of the events
typically
preceding
eruptions of
volcanoes.
Unrelated, a 4.1
earthquake
registered west
of Puerto
Armuelles, in
the southern
zone, at
12:29pm. |
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