Slow earthquakes and low frequency tremor along the Apennines, Italy

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R. Scarpa
A. Amoruso
L. Crescentini
C. Fischione
L. A. Formisano
M. La Rocca
F. Tronca


This paper reviews the main observations on slow earthquakes and low frequency tremor made along the Apennines,
the main seismic active zone of Italy. These observations have been made using a geodetic interferometer
system operating since 1994 in the underground tunnel of Gran Sasso, central Italy, and an underground seismic
array (UNDERSEIS) operating since 2002 in the same environment.
The observations made in recent years indicate that both phenomena are quite rare and apparently uncorrelated.
Slow earthquakes, mainly recorded in 1997 and occasionally later, have probably been caused by the activity of
a shallow fault system located near the interferometers. Until now only one tremor episode characterized by low
frequency content and duration of several hours has been detected in January 2004, without any correlations with
the occurrence of slow or regular earthquakes. The signal to noise ratio of this event is very low, but the results
of our detailed analysis show that its frequency contents and wave field characteristics are compatible with a low
frequency non volcanic tremor.

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How to Cite
Scarpa, R., Amoruso, A., Crescentini, L., Fischione, C., Formisano, L. A., La Rocca, M. and Tronca, F. (2008) “Slow earthquakes and low frequency tremor along the Apennines, Italy”, Annals of Geophysics, 51(2-3). doi: 10.4401/ag-3028.

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