Publication Date:
2017-04-04
Description:
Repeating volcano-tectonic (VT) earthquakes, taking place at Mt. Etna during 1999–2009,were detected and analyzed
to investigate their behavior. We found 735 families amounting to 2479 VT earthquakes, representing
~38% of all the analyzed VT earthquakes. The number of VT earthquakes making up the families ranges from 2
to 23. Over 70% of the families comprise 2 or 3 VT earthquakes and only 20 families by more than 10 events.
The occurrence lifetime is also highly variable ranging from some minutes to ten years. In particular, more
than half of the families have a lifetime shorter than 0.5 day and only ~10% longer than 1 year. On the basis of
these results, most of the detected families were considered “burst-type”, i.e., show swarm-like occurrence,
and hence their origin cannot be explained by a temporally constant tectonic loading. Indeed, since the analyzed
earthquakes take place in a volcanic area, the rocks are affected not only by tectonic stresses related to the fairly
steady regional stress field but also by local stresses, caused by the volcano, such as magma batch intrusions/
movements and gravitational loading.We focused on the five groups of families characterized by the longest repeatability
over time, namely high number of events and long lifetime, located in the north-eastern, eastern and
southern flanks of the volcano. Unlike the first four groups, which similarly to most of the detected families show
swarm-like VT occurrences, group “v”, located in the north-eastern sector, exhibits a more “tectonic” behavior
with the events making up such a group spread over almost the entire analyzed period. It is clear how both
occurrence and slip rates do not remain constant but vary over time, and such changes are time-related to the
occurrence of the 2002–2003 eruption. Finally, by FPFIT algorithm a good agreement between directions identified
by nodal planes and the earthquake epicentral distribution was generally found.
Description:
Published
Description:
1223 – 1236
Description:
1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
Description:
JCR Journal
Description:
restricted
Keywords:
repeating earthquakes
;
Etna
;
04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Permalink
