Publication Date:
2017-04-04
Description:
The early stages of the 2002–2003 lateral eruption at Mount Etna were accompanied
by slow changes (over some hours) and some rapid step offsets in the local magnetic
field. At five monitoring locations, the total magnetic field intensity has been measured
using continuously operating Overhauser magnetometers at a sampling rate of 10 s. The
very unique aspect of these observations is the close temporal correspondence between
magnetic field offsets and earthquakes that occurred in the upper northern flank of the
volcano on 27 October 2002 prior to a primary eruption. Rapid coseismic changes of the
magnetic field were clearly identified for three of the most energetic earthquakes, which
were concentrated along the Northeast Rift at a depth of about 1 km below sea level.
Coseismic magnetic signals, with amplitudes from 0.5 to 2.5 nT, have been detected for
three of the largest seismic events located roughly midway between the magnetic stations.
We quantitatively examine possible geophysical mechanisms, which could cause the
magnetic anomalies. The comparison between magnetic data, seismicity and surface
phenomena implies that piezomagnetic effects are the primary physical mechanism
responsible for the observed magnetic anomalies although the detailed cause of the rapid
high stress change required is not clear. The modeling of the observed coseismic magnetic
changes in terms of piezomagnetic mechanism provides further evidence of the complex
interaction between volcanic and tectonic processes during dike propagation along the
Northeast Rift.
Description:
Published
Description:
B09103
Description:
3.6. Fisica del vulcanismo
Description:
JCR Journal
Description:
reserved
Keywords:
piezomagnetism
;
earthquakes
;
04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
