Upper crustal structure, seismicity and pore pressure variations
in an extensional seismic belt through 3-D and 4-D VP and VP/VS models:
The example of the Val d'Agri area (southern Italy)
We use local earthquake tomography and background seismicity to investigate
static and transient features of the crustal velocity structure in
the Val d'Agri (southern Apennines, Italy), one of the regions in
central Mediterranean with the highest seismogenic potential. The
upper crust is dominated by two broad high-velocity anticlines of
the buried Apulia Carbonate Platform ramping on two parallel high-angle
thrusts interpreted as preexisting inverted normal faults. The deep
core of the anticlines consists of very high VP (up to 6.9 km/s)
and low VP/VS rocks, suggesting the involvement of the Apulian crystalline
basement in the Apennine belt. These results provide valuable constraints
on the Apennine belt tectonic evolution, supporting a thick-skinned
interpretation for the Pliocene terminal phase of the compressional
tectonics. The geometry of the Val d'Agri Quaternary basin is controlled
by these inherited compressive features, whereas the presently active
extensional tectonics barely reworked the structure. We find inconsistency
between the structure of the Apulia Carbonate Platform and the location
and geometry of the Quaternary normal faults mapped at the surface.
This suggests either the immaturity of the normal faults or their
secondary role in accommodating the extension. We observe spatiotemporal
(4-D) changes of VP and VP/VS models defining transient variations
of pore fluid pressure in the upper crust. A strong change in the
VP/VS ratio heralds a raise in the seismicity rate that can be related
to large water level changes in a nearby artificial lake. This evidence
is consistent with a mechanism of reservoir-induced seismicity by
fluid pressure increase and pore pressure diffusion. The 4-D velocity
variations are confined in the shallow portion of the upper crust
(3-6 km depth) where fluids are stored in a highly fractured medium.
Pore pressure fluctuations can affect the strength of fault segments,
favoring seismicity rate changes along the active faults and possibly
promoting large future earthquakes.
%0 Journal Article
%1 valoroso_etal:2011
%A Valoroso, L.
%A Improta, L.
%A De Gori, P.
%A Chiarabba, C.
%D 2011
%J Journal of Geophysical Research
%K geophysics seismology
%N B7
%P B07303+
%R 10.1029/2010JB007661
%T Upper crustal structure, seismicity and pore pressure variations
in an extensional seismic belt through 3-D and 4-D VP and VP/VS models:
The example of the Val d'Agri area (southern Italy)
%U http://dx.doi.org/10.1029/2010JB007661
%V 116
%X We use local earthquake tomography and background seismicity to investigate
static and transient features of the crustal velocity structure in
the Val d'Agri (southern Apennines, Italy), one of the regions in
central Mediterranean with the highest seismogenic potential. The
upper crust is dominated by two broad high-velocity anticlines of
the buried Apulia Carbonate Platform ramping on two parallel high-angle
thrusts interpreted as preexisting inverted normal faults. The deep
core of the anticlines consists of very high VP (up to 6.9 km/s)
and low VP/VS rocks, suggesting the involvement of the Apulian crystalline
basement in the Apennine belt. These results provide valuable constraints
on the Apennine belt tectonic evolution, supporting a thick-skinned
interpretation for the Pliocene terminal phase of the compressional
tectonics. The geometry of the Val d'Agri Quaternary basin is controlled
by these inherited compressive features, whereas the presently active
extensional tectonics barely reworked the structure. We find inconsistency
between the structure of the Apulia Carbonate Platform and the location
and geometry of the Quaternary normal faults mapped at the surface.
This suggests either the immaturity of the normal faults or their
secondary role in accommodating the extension. We observe spatiotemporal
(4-D) changes of VP and VP/VS models defining transient variations
of pore fluid pressure in the upper crust. A strong change in the
VP/VS ratio heralds a raise in the seismicity rate that can be related
to large water level changes in a nearby artificial lake. This evidence
is consistent with a mechanism of reservoir-induced seismicity by
fluid pressure increase and pore pressure diffusion. The 4-D velocity
variations are confined in the shallow portion of the upper crust
(3-6 km depth) where fluids are stored in a highly fractured medium.
Pore pressure fluctuations can affect the strength of fault segments,
favoring seismicity rate changes along the active faults and possibly
promoting large future earthquakes.
@article{valoroso_etal:2011,
abstract = {We use local earthquake tomography and background seismicity to investigate
static and transient features of the crustal velocity structure in
the Val d'Agri (southern Apennines, Italy), one of the regions in
central Mediterranean with the highest seismogenic potential. The
upper crust is dominated by two broad high-velocity anticlines of
the buried Apulia Carbonate Platform ramping on two parallel high-angle
thrusts interpreted as preexisting inverted normal faults. The deep
core of the anticlines consists of very high VP (up to 6.9 km/s)
and low VP/VS rocks, suggesting the involvement of the Apulian crystalline
basement in the Apennine belt. These results provide valuable constraints
on the Apennine belt tectonic evolution, supporting a thick-skinned
interpretation for the Pliocene terminal phase of the compressional
tectonics. The geometry of the Val d'Agri Quaternary basin is controlled
by these inherited compressive features, whereas the presently active
extensional tectonics barely reworked the structure. We find inconsistency
between the structure of the Apulia Carbonate Platform and the location
and geometry of the Quaternary normal faults mapped at the surface.
This suggests either the immaturity of the normal faults or their
secondary role in accommodating the extension. We observe spatiotemporal
(4-D) changes of VP and VP/VS models defining transient variations
of pore fluid pressure in the upper crust. A strong change in the
VP/VS ratio heralds a raise in the seismicity rate that can be related
to large water level changes in a nearby artificial lake. This evidence
is consistent with a mechanism of reservoir-induced seismicity by
fluid pressure increase and pore pressure diffusion. The 4-D velocity
variations are confined in the shallow portion of the upper crust
(3-6 km depth) where fluids are stored in a highly fractured medium.
Pore pressure fluctuations can affect the strength of fault segments,
favoring seismicity rate changes along the active faults and possibly
promoting large future earthquakes.},
added-at = {2012-09-01T13:08:21.000+0200},
author = {Valoroso, L. and Improta, L. and De Gori, P. and Chiarabba, C.},
biburl = {https://www.bibsonomy.org/bibtex/2223dba3f30d93494853a7bf360a0b0f1/nilsma},
day = 15,
doi = {10.1029/2010JB007661},
interhash = {792e9f02d4dd04855a3efebbcbd6904b},
intrahash = {223dba3f30d93494853a7bf360a0b0f1},
issn = {0148-0227},
journal = {Journal of Geophysical Research},
keywords = {geophysics seismology},
month = jul,
number = {B7},
pages = {B07303+},
timestamp = {2021-02-09T13:26:58.000+0100},
title = {Upper crustal structure, seismicity and pore pressure variations
in an extensional seismic belt through 3-D and 4-D VP and VP/VS models:
The example of the Val d'Agri area (southern Italy)},
url = {http://dx.doi.org/10.1029/2010JB007661},
volume = 116,
year = 2011
}