Seismology is arguably
the most powerful tool for monitoring restless volcanoes. Traditional seismology is the
study of elastic waves propagating in the earth. Traditional seismology coupled
with the study of acoustic waves (i.e., sound waves) in the atmosphere
is an even more powerful tool for monitoring restless volcanoes.
Seismometers are
sensors that are buried in the ground and are sensitive to very slight ground
motions. Seismograms are
time-series records of ground motion displayed in graphical
format.
Microphones are sensors, which
typically measure pressure fluctuations in the atmosphere. Usually they are used to record sound waves
in the audible bandwidth. Infrasonic
microphones (or pressure sensors or transducers) are devices that are sensitive
to low-frequency pressure oscillations in the atmosphere. There is no broadly used
word for an infrasonic pressure record, but I will use the term acoustogram
throughout this powerpoint.