Publication Date:
2017-04-04
Description:
The Larderello geothermal field is a wide thermal anomaly located in the western part
of Tuscany (Italy). Geophysical investigations in this area suggest a crustal thinning
and intrusion of hot mantle material into the crust. The local seismicity, monitored
since 1978 by a network of 26 short period almost vertical seismic stations, is characterized
by a several hundred of M 1.5 events per year, never exceeding M=3.2 in
the past 25 years. At December 2004 ENEL and INGV started a scientific collaboration,
which includes also exchange of selected datasets. One of the main tasks is to
perform source inversion of low magnitude seismic events recorded in the Larderello
geothermal area. This is of particular interest, because such earthquakes could show
similarities with seismic events recorded on active volcanoes. In order to record also
seismic events below magnitude M = 1 the gain of the ENEL-seismic network is set
rather sensitive. This implicates that seismograms of events with magnitudes M 〉 2.0
are recorded by the entire network, but at low epicentral distances the traces are often
saturated, making a waveform inversion impossible. On the other hand, smaller events
are not strong enough to be recorded also at the more external stations of the network.
In both cases this trade-off results in a limited number of vertical component recordings
available for the inversion. A further difficulty by performing source inversion of
small seismic events is to fit the high frequencies. Therefore we applied the moment
tensor (MT) inversion both in the time domain as well as in the frequency domain and
compared the results. Source inversion was performed both for the full MT as well
as by introducing constraints for doubles couple e/o CLVD. The source inversions of
events occurred in the Travale area show a high double couple percentage and show no
indications for an isotropic source. This seems to indicate a source mechanism which
is typical for tectonic events.
Description:
Published
Description:
Vienna
Description:
1.1. TTC - Monitoraggio sismico del territorio nazionale
Description:
open
Keywords:
Larderello
;
source inversion
;
04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
Poster session
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