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Spatial and temporal seismicity clustering in Central-Northern Apennines: fluids and seismicity
Author(s)
Type
Conference paper
Language
English
Obiettivo Specifico
1.1. TTC - Monitoraggio sismico del territorio nazionale
Status
Published
Conference Name
Issued date
November 13, 2007
Conference Location
Roma
Keywords
Abstract
The Northern Apennines (NAs) are composed by a NE verging thrust-fold belt formed as result of the
collision (Oligo-Miocene) between the European plate (Sardinia-Corsica block) and the Adriatic microplate,
once the westward subduction of the Tethyan oceanic lithosphere was completed (Alvarez, 1972; Reutter et
al., 1980; Argnani, 2002). This mountain chain is dominated by concomitant extension and compression in
two adjacent areas: inner zone of the belt and outer zone (Frepoli and Amato, 1997; Collettini and Barchi,
2002). Our study area is located in the inner zone characterised by Pliocene-Quaternary sedimentation
developed in grabens and half-grabens borded by normal faults. This tectonic extension process is associated
whith diffuse CO2 degassing (Chiodini et al., 2004). The question whether the CO2 has a metamorphic
and/or magmatic upper crust origin is more debated (Minissale et al., 2000; Chiodini et al., 2004; Minissale,
2004; Heinicke et al., 2006). Instrumental seismicity is concentrated in a relatively shallow layer that
deepens from the internal to external areas (Chiarabba and Amato, 2003). High fluid pressures (85% of the
lithostatic pressure) encountered at shallow crustal depth suggest that deep fluids from deeper layers could
play a key role in triggering earthquakes (Chiodini et al., 2004; Antonioli et al., 2005) and seem to control
also the spatio-temporal evolution of the seismicity (Piccinini & Antonioli, 2007). Our study area is confined
by the Upper Tiber Valley (NSE), Casentino (W), Mugello (NW) and the Montefeltro seismic area (NE). We
analysed the seismic events recorded both by the National Seismic Network (1981-2001, CSI 1.1; data-set
was extracted online, http://www.ingv.it/CSI/) and by two temporal local seismic networks installed by
INGV-Arezzo Observatory (OSCAR) during 2002-2003 (CAESAR experiment) and 2005-2006 (M88-2005
experiment). In order to obtain a better azimuthal coverage we integrated this data-set with on-line database
of the Rete Sismometrica Marchigiana (DBRSM, http://protezionecivile.regione.marche.it/dbrsm/) and
the monthly seismic bulletin of the INGV. We extracted the events located inside the area of interest in order
to retrieve a detailed local 1D velocity model used for successive location with VELEST-code (Kissling et
al., 1994) and relocation using HYPOELLIPSE (Lahr, 1989). We discuss the main seismicity patterns of
several seismic clusters by integrating the results of previous studies with newly determined hypocentral
locations and focal mechanisms. Our results are interpreted as a function of the historical seismicity, the
structural and geodynamic setting and the carbon dioxide degassing.
collision (Oligo-Miocene) between the European plate (Sardinia-Corsica block) and the Adriatic microplate,
once the westward subduction of the Tethyan oceanic lithosphere was completed (Alvarez, 1972; Reutter et
al., 1980; Argnani, 2002). This mountain chain is dominated by concomitant extension and compression in
two adjacent areas: inner zone of the belt and outer zone (Frepoli and Amato, 1997; Collettini and Barchi,
2002). Our study area is located in the inner zone characterised by Pliocene-Quaternary sedimentation
developed in grabens and half-grabens borded by normal faults. This tectonic extension process is associated
whith diffuse CO2 degassing (Chiodini et al., 2004). The question whether the CO2 has a metamorphic
and/or magmatic upper crust origin is more debated (Minissale et al., 2000; Chiodini et al., 2004; Minissale,
2004; Heinicke et al., 2006). Instrumental seismicity is concentrated in a relatively shallow layer that
deepens from the internal to external areas (Chiarabba and Amato, 2003). High fluid pressures (85% of the
lithostatic pressure) encountered at shallow crustal depth suggest that deep fluids from deeper layers could
play a key role in triggering earthquakes (Chiodini et al., 2004; Antonioli et al., 2005) and seem to control
also the spatio-temporal evolution of the seismicity (Piccinini & Antonioli, 2007). Our study area is confined
by the Upper Tiber Valley (NSE), Casentino (W), Mugello (NW) and the Montefeltro seismic area (NE). We
analysed the seismic events recorded both by the National Seismic Network (1981-2001, CSI 1.1; data-set
was extracted online, http://www.ingv.it/CSI/) and by two temporal local seismic networks installed by
INGV-Arezzo Observatory (OSCAR) during 2002-2003 (CAESAR experiment) and 2005-2006 (M88-2005
experiment). In order to obtain a better azimuthal coverage we integrated this data-set with on-line database
of the Rete Sismometrica Marchigiana (DBRSM, http://protezionecivile.regione.marche.it/dbrsm/) and
the monthly seismic bulletin of the INGV. We extracted the events located inside the area of interest in order
to retrieve a detailed local 1D velocity model used for successive location with VELEST-code (Kissling et
al., 1994) and relocation using HYPOELLIPSE (Lahr, 1989). We discuss the main seismicity patterns of
several seismic clusters by integrating the results of previous studies with newly determined hypocentral
locations and focal mechanisms. Our results are interpreted as a function of the historical seismicity, the
structural and geodynamic setting and the carbon dioxide degassing.
References
Alvarez W. (1972).”Rotation of the Corsica Sardinia microplate”. Nature, 235, 103-115.
Antonioli A., Piccinini D., Chiaraluce L. and Cocco M. (2005).”Fluid flow and seismicity pattern; evidence from the 1997 Umbria-
Marche (central Italy) seismic sequence”. Geophys. Res. Lett., 32/10, 4 pp.
Argnani A. (2002). “The northern Apennines and the kinematics of Africa-Europe convergence”. Boll. Soc. Geol. It., Vol. Spec. 1,
47-60.
Chiarabba C. and Amato A. (2003).”Vp and Vp/Vs images in the Mw 6.0 Colfiorito fault region (central Italy); a contribution tl the
understanding of seismotectonic and seismogenic processes”. J. Geophys. Res., 108/B5, 17 pp.
Chiodini G., Cardellini C., Amato A., Boschi E., Caliro S., Frondini F. and Ventura G. (2004).”Carbon dioxide earth degassing and
seismogenesis in central and southern Italy”. Geophys. Res. Lett., 31, L07615, doi:10.1029/2004GL019480.
Collettini C. & Barchi M.R. (2002). “A low-angle normal fault in the Umbria region (Central Italy): a mechanical model for the
related microseismicity”. Tectonophysics, 359, 97-115.
Frepoli A., Amato A. (1997). “Contemporaneous extension and compression in the Northern Apennines from earthquake fault-plain
solutions”. Geophys. J. Int., 129/2, 368-388.
Heinicke J., Braun T., Burgassi P., Italiano F. and Martinelli G. (2006).”Gas flow anomalies in seismogenic zones in the upper Tiber
Valley, central Italy”. Geophys. J. Int., 167/2, 794-806.
Kissling E., Ellsworth W.L., Eberharth-Phillips D. and Kradolfer U. (1994).”Initial reference model in local earthquake
tomography”. J. Geophys. Res., 99, 19635-19646.
Lahr J. C. (1989).”HYPOELLIPSE/version 2.0; a computer program for determining local earthquake hydrocentral parameters,
magnitude and first motion pattern”. Open-File Report-U. S. Geological Survey, Report: OF 89-0116, 81 pp.
Minissale A., Magro G., Martinelli G., Vaselli O. and Tassi G.F. (2000).”Fluid geochemical transect in the Northern Apennines
(central-northern Italy); fluid genesis and migration and tectonic implications”. Tectonophysics, 319/3, 199-222.
Minissale A. (2004).”Origin, transport and discharge of CO2 in central Italy”. Earth-Science Reviews, 66/1-2, 89-141.
Antonioli A., Piccinini D., Chiaraluce L. and Cocco M. (2005).”Fluid flow and seismicity pattern; evidence from the 1997 Umbria-
Marche (central Italy) seismic sequence”. Geophys. Res. Lett., 32/10, 4 pp.
Argnani A. (2002). “The northern Apennines and the kinematics of Africa-Europe convergence”. Boll. Soc. Geol. It., Vol. Spec. 1,
47-60.
Chiarabba C. and Amato A. (2003).”Vp and Vp/Vs images in the Mw 6.0 Colfiorito fault region (central Italy); a contribution tl the
understanding of seismotectonic and seismogenic processes”. J. Geophys. Res., 108/B5, 17 pp.
Chiodini G., Cardellini C., Amato A., Boschi E., Caliro S., Frondini F. and Ventura G. (2004).”Carbon dioxide earth degassing and
seismogenesis in central and southern Italy”. Geophys. Res. Lett., 31, L07615, doi:10.1029/2004GL019480.
Collettini C. & Barchi M.R. (2002). “A low-angle normal fault in the Umbria region (Central Italy): a mechanical model for the
related microseismicity”. Tectonophysics, 359, 97-115.
Frepoli A., Amato A. (1997). “Contemporaneous extension and compression in the Northern Apennines from earthquake fault-plain
solutions”. Geophys. J. Int., 129/2, 368-388.
Heinicke J., Braun T., Burgassi P., Italiano F. and Martinelli G. (2006).”Gas flow anomalies in seismogenic zones in the upper Tiber
Valley, central Italy”. Geophys. J. Int., 167/2, 794-806.
Kissling E., Ellsworth W.L., Eberharth-Phillips D. and Kradolfer U. (1994).”Initial reference model in local earthquake
tomography”. J. Geophys. Res., 99, 19635-19646.
Lahr J. C. (1989).”HYPOELLIPSE/version 2.0; a computer program for determining local earthquake hydrocentral parameters,
magnitude and first motion pattern”. Open-File Report-U. S. Geological Survey, Report: OF 89-0116, 81 pp.
Minissale A., Magro G., Martinelli G., Vaselli O. and Tassi G.F. (2000).”Fluid geochemical transect in the Northern Apennines
(central-northern Italy); fluid genesis and migration and tectonic implications”. Tectonophysics, 319/3, 199-222.
Minissale A. (2004).”Origin, transport and discharge of CO2 in central Italy”. Earth-Science Reviews, 66/1-2, 89-141.
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