Publication Date:
2017-04-04
Description:
The seismotectonics of the Upper Tiber Valley are dominated by the Altotiberina
Fault (ATF), an NE-dipping low-angle normal fault system, and its antithetic
W-dipping high-angle normal faults. A
lthough the southern part of the ATF
was demonstrated to creep, its capability to generate strong or moderate
earthquakes is still under debate. On April 26, 1917 at 9:35:59 (GMT) a strong
earthquake struck the northernmost portion of the Upper Tiber Valley (Tuscany)
producing severe damages and about 20 fatalities. The Catalogue of Strong Italian
Earthquakes reports this event as the so-c
alled Monterchi earthquake, relating
to 134 macroseismic observations, mainly distributed on the western side of the
Tiber Valley. The maximum and epicentral intensity was determined as Io=IX-
X (MCS), corresponding to an equivalent magnitude of Me=6, that defines this
event as the most important of the area. A total of 49 historical seismograms
from 19 different Euro-Mediterranean observatories are available in the database
of the SISMOS Project - INGV. The BAAS bulletin of 1917 reports a list of 21
seismological observatories that record
ed the P and S-phases for this earthquake.
We included additional arrival-times deriving from further seismic bulletins - and
from digitalizing original historical seismograms. We obtain a new, robust and
consistent hypocentral solution, coherent with the macroseismic data, in particular
by using S-P travel time differences for recordings where the absolute timing is
uncertain. An accurate research on the technical characteristics of the recording
historical seismometers (period, dampin
g, gain etc.), allowed to deconvolve the
original digitalized seismic traces (i) to determine the main seismic parameters (Mo,
Mw, Circular Fault Radius), (ii) to constrain the possible source mechanism, by
a combination of first motion analysis and modelling of synthetic seismograms,
and (iii) to implement the solution in the framework of the regional tectonic
setting.
Description:
Published
Description:
Pasadena, California, USA
Description:
2T. Tettonica attiva
Description:
open
Keywords:
Historical earthquake
;
Seismic analysis
;
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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