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Palano M., Cannavò F., Ferranti L., Mattia M. and Mazzella E.; 2011: Strain and stress fields in the Southern Apennines (Italy)
constrained by geodetic, seismological and borehole data. Geophysical Journal International, 187 (3), 1270-1282,
doi:10.1111/j.1365-246X.2011.05234.x.
Quennell A.M.; 1958: The structural and geomorphic evolution of the Dead Sea rift. Quarterly Journal of the Geological Society,
114, 1-24, doi:10.1144/?gsjgs.114.1.0001.
Searle M.P., Chung S.L. and Lo C.H.; 2010: Geological offsets and age constraints along the northern Dead Sea Fault, Syria.
Journal of the Geological Society, London, 167, 1001-1008, doi:10.1144/0016-76492010-009.
Sbeinati M.R., Darawcheh R. and Mouty M.; 2005: The historical earthquakes of Syria: an analysis of large and moderate
earthquakes from 1365 BC to 1900 AD. Annals of Geophysics, 48 (3), 347-435, doi:10.4401/ag-3206.
Vannucci G. and Gasperini P.; 2003: A database of revised fault plane solutions for Italy and surrounding regions. Computers &
Geosciences, 29 (7), 903-909, doi:10.1016/S0098-3004(03)00094-3.
Vannucci G. and Gasperini P.; 2004: The new release of the database of Earthquake Mechanisms of the Mediterranean Area
(EMMA Version 2). Annals of Geophysics, 47 (1S), 307-334.
Vannucci G., Imprescia P. and Gasperini P.; 2010: A new release (3.1) of the database of Earthquake Mechanisms of the
Mediterranean Area (EMMA). European Seismological Commission 32nd General Assembly, September 6–10, Montpellier,
France.
Walley C.D.; 1988: A braided strike-slip model for the northern continuation of the Dead Sea fault, and its implications to Levantine
tectonics. Tectonophysics, 145, 63-72, doi:10.1016/0040-1951(88)90316-2.
Weber M., Abu-Ayyash K., Abueladas A., Agnon A., Alasonati Tasárová Z., Al-Zubi H., Babeyko A., Bartov Y., Bauer K., Becken
M., Bedrosia P. A., Ben-Avraham Z., Bock G., Bohnhoff M., Bribach J., Dulski P., Ebbing J., El-Kelani R., Förster A., Förster
H.J., Frieslander U., Garfunkel Z., Goetze H. J., Haak V., Haberland C., Hassouneh M., Helwig S., Hofstetter A., HoffmannRothe A., Jäckel K.H., Janssen C., Jaser D., Kesten D., Khatib M., Kind R., Koch O., Koulakov I., Laske G., Maercklin N.,
Masarweh R., Masri A., Matar A., Mechie J., Meqbel N., Plessen B., Möller P., Mohsen A., Oberhänsli R., Oreshin S., Petrunin
A.G., Qabbani I., Rabba I., Ritter O., Romer R.L., Rümpker G., Rybakov M., Ryberg T., Saul J., Scherbaum F., Schmidt S.,
Schulze A., Sobolev S.V., Stiller M., Stromeyer D., Tarawneh K., Trela C., Weckmann U., Wetzel H.U. and Wylegalla K.; 2009:
Anatomy of the Dead Sea Transform from lithospheric to microscopic scale. Reviews of Geophysics, 47, RG2002,
doi:10.1029/2008RG000264.
MACROSEISMIC INVESTIGATION OF THE 2012 PO PLAIN SEQUENCE USING
THE ESI2007 SCALE, AND COMPARISON WITH THE MCS SCALE
F. Livio1, A.M. Michetti1, P. Di Manna2, A. Berlusconi1, L. Bonadeo1, D. Castaldini4, V. Comerci2,
F. Ferrario1, R. Gambillara1 , L. Guerrieri2, L. Piccardi3, M. Roncoroni1, E. Vittori2 , E. Esposito5 and
S. Porfido5
Department of Science and High Technology – University of Insubria, Como, Italy
ISPRA, Roma, Italy
3
CNR – Istituto di Geoscienze e Georisorse, Firenze, Italy
4
Department of Earth Sciences - University of Modena and Reggio Emilia, Modena, Italy
5
CNR – Istituto per l’Ambiente Marino Costiero, Napoli, Italy
1
2
Introduction and seismotectonic framework. We performed a study of the ESI2007 intensity
distribution in the epicentral area of the May-June 2012 seismic sequence in the Po Plain. The
widespread occurrence of coseismic environmental effects, in particular related to liquefaction and
lateral spreading, allow to succesfully apply this intensity scale, providing essential data to
complement the use of traditional, damage-based intensity scales, such as the MCS scale, for a
proper definition of the macroseismic field of this event. The integration of ESI2007 and MCS
scales in Italy might represent an essential tool for the characterization of earthquake hazards (e.g.,
Serva et al., 2007).
The 2012 seismic sequence that affected the Emilia Romagna and Lombardia regions, occurred
in a lowland area between the Modena, Ferrara and Mantova Provinces. Two mainshocks, followed
each by a dense cloud of aftershocks, hit the region in two adjacent sectors: the May 20, 2012 Mw
6.1, announced by a Mw 4.3 foreshock, and the Mw 6.0, May 29 event, located in a western portion.
To date 7 events of Magnitude greater than 5 have been recorded in the area. On the whole the
distribution of aftershocks identifies an about 40 km long, WNW-ESE trending zone, characterized
by NNE-SSW nearly pure compression, as indicated by focal mechanisms (e.g., QRCMT, 2012).
Evidence from extensive stratigraphic, morphologic, geodetic and seismic reflection data
illustrates an active convergence of NE-verging Apennininic and S-verging Southalpine structures
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(e.g. Serva, 1990; Castiglioni et al., 1997; Boccaletti et al., 2004; Toscani et al., 2009; Boccaletti et
al., 2011; Comerci et al., 2012; Michetti et al., 2012, and references therein). This evidence is also
confirmed by earthquake focal mechanisms (Frepoli and Amato, 1997) and other stress indicators
(Montone et al., 2004). In detail, the area is characterized by the presence of a buried fold and thrust
belt belonging to western sector of the Emilia-Ferrara arc. Two thrusts could be possibly related to
the seismic sequence: the Ferrara thrust and the inner Mirandola thrust (Fig.1). Scrocca et al.
(2007), basing on syn-growth strata analysis, calculate for the Mirandola fault-related fold an uplift
rate decreasing from 0.53 to 0.15 mm/yr during a middle to late Pleistocene time window.
Interferometric data clearly shows a ca. 8 km wide deformation field, subdivided into two main
uplifted areas, possibly related to the aforementioned structures. Maximum detected coseismic
uplift is ca. 15 cm (Bignami et al., in press).
Historical and instrumental seismicity. According to the available historical and instrumental
seismic catalogues, the epicentral area has never been interested by Mw > 5.5 earthquakes, with the
only exception of the Mw 5.8 , 1346 event, an earthquake reported only by scarce and inaccurate
sources (e.g., Galli et al., 2012). The epicentral location of this event is very dubitative and
correlations with known seismogenic structures is not possible to date.
A seismic sequence, characterized by a very large number of felt events and by a prolonged duration
of the sequence itself, interested the Ferrara area between the 1570 and the 1574 (main event Nov. 17,
1570, Mw 5.46). Actually this sequence was characterized by many main shocks and in 1571 the
prolonged seismic crisis even temporarily compelled the court of the ducal family of Este to be settled
in the country side under tents.
It is noteworthy that also for the Ferrara sequence many liquefaction phenomena have been reported
around the epicentral area.
ESI scale: earthquake induced environmental effects. During the May – June 2012 seismic
sequence more than five hundred environmental effects (liquefaction-type phenomena, ground
ruptures and hydrogeological anomalies) have been observed, spread over an area of about 700 km2.
In order to properly define the macroseismic field of the 2012 earthquake, we applied in the
epicentral area the ESI 2007 scale (Guerrieri and Vittori, 2007), that is entirely based on the
characteristics and size of earthquake-induced environmental effects. The scale have been tested on
several modern historical events and older paleo-earthquakes (e.g., Reicherter et al., 2009 and
bibliography therein; Lalinde and Sanchez, 2007; Lekkas, 2010).
In the following a brief summary of the observed ground effects is given. For a more detailed
description see Di Manna et al. (in press)
Ground cracks and liquefactions.Liquefaction features have been the most common type of
earthquake-induced effect. Ejection of sand generally occurred along ground cracks, as highlighted
by the typical local alignment of emission points. The zone with the most evident and widespread
effects, induced by the May 20 event, is around San Carlo, a hamlet belonging to the municipality
of Sant’Agostino.
Liquefaction features in the Sant’Agostino area are located on the right embankment of a NESW trending abandoned bed of the Reno river, definitely abandoned since 1751 (Cremonini and
Scarin, 2007). Here, the topographic effect (lateral spreading) has played an important role, added
to the shaking and the sand liquefaction, in determining the observed damages.
Repeated surveys have shown a post-seismic increase of throw (up to 60 cm) and opening of
ground cracks (more than 1 m) in the weeks following the main events.
Widespread liquefaction-type effects and ground cracks were produced also by the second main
shock (May 29). In particular, large ground ruptures with emission of sand have been documented
mainly in the Cavezzo, San Possidonio, Moglia and Quistello territorial municipalities.
Such phenomena have been particularly frequent in Moglia, where, according to eyewitnesses,
the occurrence of sand emission has to be related with the two strong aftershocks (M ≈ 5.1),
occurred on May 29 at about 1 p.m.
In some localities the bottom of irrigation canals showed uplift, bulging and cracks, effect of
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Fig. 1 - Seismotectonic map of the area hit by the May 2012 seismic sequence. Grey lines indicate main buried
thrusts (triangles in the hangingwall); CPTI11 catalogue seismicity (Rovida et al. 2011, modified) is shown by the
faded colored circles (the 1346 earthquake epicenter and estimated Magnitude in reported as indicated in the
catalogue at the Sept, 2011); black dots indicate the ESI quoted points; localities cited in the text are shown in light
green. Hollow black stars indicate the location of the two mainshocks while the Boxer4 calculated macroseismic
epicenter is indicated by the red star.
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sand injection under a bed of cohesive mud. This phenomenon was also observed at San Carlo
where the church floor appeared strongly deformed.
Hydrological anomalies. In the epicentral area, local people often reported a significant increase
of the most superficial water-table level observed in the water wells. The outflow of water from
water wells, where occurred, has continued for hours after the earthquake. In some instances, warm
water has been emitted from wells. Also a sharp smell of H2S has been sometimes noted, reportedly
occurring also many days before the event.
The total area where ground effects occurred, possibly relative to each event, is ca. 300-400 km2
wide. This value would indicate an ESI epicentral intensity for each of the two main shocks ca.
equal to VIII degree. Furthermore, ESI local intensity values in excess of VIII, possibly reaching the
IX degree have been recorded in two localities (San Carlo and Mirabello), surely due to the specific
vulnerability of the natural environment at local scale.
ESI and MCS macroseismic field: a brief comparison. We applied the Boxer4 algorithm to
the ESI data. Over 500 ground effects have been reported, typically clustered. These have been
summarized into 53 intensity data point, considering the most frequent value of each cluster over
homogeneous localities, in order to smooth very local variations and reduce data redundancy (see
Guerrieri and Vittori, 2007, for a detailed description of methodological aspects).
The Boxer4 algorithm calculates seismogenic focal parameters of earthquakes from intensity
point distribution (e.g. Gasperini and Ferrari, 2000). In particular it calculates macroseismic
epicenter location, derived fault azimuth and intensity derived magnitude, based on isoseismal radii
method.
We used all the effects, not distinguished by earthquake, since a) not every environmental effect
has been readily reported or noted by local people, so for some of the effects. it’s not possible to
distinguish between the two triggering mainshocks and b) our attention has focused on the
interpretation of historical intensity data calibrated through contemporary observations. In this line
it is evident that environmental effects caused by two mainshocks closely located both in time and
space would obviously had been reported as generally due to the same seismic sequence by an
historical source. Cumulative effects are the typical data coming from prolonged seismic sequences
that have to be treated and interpreted by historical seismologists and also these data have to give
back a reliable value of earthquake magnitude.
Galli et al. (2012) stated that the equivalent magnitude estimated through Boxer4 algorithm from
MCS Intensity data is ca. Mw 5.23, a much lower value than the recorded ones. Also recorded PGA
values (between 0.23 and 0.28 for the epicentral area) would be typically correlated to a MCS IX
degree, instead of the I0 VII (or VII-VIII for the May, 29 earthquake). It should be noted, however,
that in the current practice of MCS investigations in Italy the environmental effects are deliberately
excluded from the intensity diagnostics; this is not consistent with the original definition of the
MCS scale as defined by Sieberg (1930).
Boxer4 calculated from ESI data points a macroseismic epicenter located between the two main
shocks, (Fig. 1). Seismic source azimuth is equal to N105 ± 8, and the derived Magnitude is equal
to 5.82 ± 0.3, a value much more closer to the observed ones (Mw ≥ 6.0).
The relevant mismatching between MCS data and the Boxer4 solutions for the seismogenic
source, as well as the better fitting shown by the ESI data, should be fully addressed and analyzed,
since the results coming out from the Boxer4 algorithm are used to compile the CPTI11 official
Italian seismic catalogue.
Discussions. The May, 2012 seismic crisis that hit central Po Plain is the first moderate-tostrong earthquake sequence that was recorded through modern seismic instrumentation.
This region is characterized by the presence of moderate-to-strong earthquakes, the strongest
corresponding to the oldest one, and probably by a long recurrence time. The area hit by the seismic
sequence is representative in this line: seismic catalogues did not reported any strong event for this
sector, at least for the last 800 years; nevertheless geological evidence pointed out a medium-term
uplift rate of ca. 0.15 mm/yr (Scrocca et al., 2007). The two mainshocks of the last sequence caused
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a suddenly uplift, above the seismogenic structures, of ca. 150 mm, thus fully recovering the
calculated medium-term uplift rate. In such a framework historical seismology is a critical phase of
SHA and this one, as well as other recent seismic crisis, can be seen as a natural laboratory where
past models and interpretations can be calibrated.
Comparing the ESI local intensity values with the macroseismic intensity evaluations (MCS,
Galli et al., 2012) it is evident that the whole distribution of the effects is generally comparable even
though a) epicentral intensity evaluations are slightly higher for the ESI scale and b) environmental
effects are spread over a wider area, even if clustered in liquefaction-prone settings.
Galli et al. (2012) postulated different possible explanation for the systematic underestimation
of earthquake magnitude from MCS data (e.g., systematic differences in the quality of buildings
between modern and ancient ones, the overall good quality of masonry and even a filtering effect
on earthquake-wave frequency due to the deep alluvial infilling of the Po Plain) none of which can
fully explain the observed mismatching.
We think that, where available, environmental effects can be an essential tool for local intensity
assessment, since they are independent from the type of construction, but are governed directly by
the true geological (s.l.) site conditions.
For these reasons, a macroseismic intensity field which integrates ESI and MCS intensity
evaluations represents a better tool to characterize this sequence and could be considered also for
the evaluation of intensity derived Magnitude, at least in the frame of the seismic hazard assessment
of the Po Plain area.
In this perspective, we think that the 2012 Emilia event should be regarded as a relatively minor
event compared to the “reference earthquakes” of the Po Plain, which, as demonstrated by the 1117
Verona and 1222 Brescia earthquakes (e.g., Serva 1990; Michetti et al., 2012), are characterized by
an intensity I0 of IX to X degrees, in either the damage-based macroseismic scales and the ESI 2007
scale.
References
Bignami C., Burrato P., Cannelli V., Chini M., Falcucci E., Ferretti A., Gori S., Kryakoupolos C., Melini D., Moro M., Novali F.,
Saroli M., Stramondo S., Valensise G. and Cannoli P.; in press: Coseismic deformation pattern of the Emilia 2012 seismic
sequence imaged by Radarsat-1 interferometry. Annals of Geophysics, special Issue ““The Emilia seismic sequence of MayJune, 2012: preliminary data and results”.
Boccaletti M., Bonini M., Corti G., Gasperini P., Martelli L., Piccardi L., Severi P. and Vannucci G.; 2004: Carta sismotettonica
della Regione Emilia Romagna. Scala 1:250000. SELCA, Firenze.
Boccaletti M., Corti G. and Martelli L.; 2011: Recent and active tectonics of the external zone of the Northern Apennines (Italy).
Int. J. Earth Sci. (Geol. Rundsch), 100(6), 1331-1348. DOI: 10.1007/s00531-010-0545-y
Castiglioni G.B. et al.; 1997: Carta geomorfologica della Pianura Padana alla scala 1:250.000. SELCA, Firenze.
Comerci V., Blumetti A.M., Di Manna P., Fiorenza D., Guerrieri L., Lucarini M., Serva L. and Vittori E.; 2012: Il Progetto ITHACA
e le Faglie Capaci della Pianura Padana, Ingegneria Sismica. Vol. Speciale “Rischio Sismico in Pianura Padana”, in press.
Cremonini S. and Scarin M.L.; 2007: Osservazioni stratigrafiche e considerazioni paleo ambientali preliminari nell’area di Galliera
(Bologna). Una prospettiva di ricerca integrata nei rapporti tra insediamento e paleoambiente nella pianura d’età medievale. In:
Galetti P. (acura di) – Una terra di confine. Storia e archeologia di Galliera nel Medioevo, Bologna 2007. Pp. 163 – 220.
Di Manna P., Guerrieri L., Piccardi L., Vittori E., Castaldini D., Berlusconi A., Bonadeo L., Comerci V., Ferrario F., Gambillara R.,
Livio F., Lucarini M. and Michetti A.M.; in press: Ground effects induced by the 2012 seismic sequence in Emilia: implications
for seismic hazard assessment in the Po Plain. Annals of Geophysics, special Issue ““The Emilia seismic sequence of May-June,
2012: preliminary data and results”.
Frepoli A. and Amato A.; 1997: Contemporaneous extension and compression in the Northern Apennines from earthquake faultplane solutions. Geophys. Journ. Int., 129(2), 368–388, doi 10.1111/j.1365-246X.1997.tb01589.x
Galli P., Castenetto S. and Peronace E.; 2012: May 2012 Emilia earthquakes (Mw 6, northern Italy): macroseismic effects
distribution and seismotectonic implications. Alpine and Mediterranean Quaternary, 25(2), 105 – 123.
Gasperini P. and Ferrari G.; 2000: Deriving numerical estimates from descriptive information: the computation of earthquake
parameters. Annali di Geofisica, 43, 729-746.
Guerrieri, L. and Vittori E.; 2007: Intensity Scale ESI 2007, Memorie Descrittive Carta Geologica. d’Italia, 74, Servizio Geologico
d’Italia – Dipartimento Difesa del Suolo, APAT, Roma, 53 pp.
Lalinde C.P. and Sanchez J.A.; 2007: Earthquake and environmental effects in Colombia in the last 35 years. INQUA Scale Project.
Bulletin of the Seismological Society of America, 97(2), 646–654.
Lekkas E.L.; 2010: The 12 May 2008 Mw 7.9 Wenchuan, China, Earthquake: Macroseismic Intensity Assessment Using the EMS98 and ESI 2007 Scales and Their Correlation with the Geological Structure. Bulletin of the Seismological Society of America,
100(5B), 2791–2804, doi: 10.1785/0120090244.
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Michetti, A.M., Giardina F., Livio F., Mueller K., Serva L., Sileo ., Vittori E., Devoti R., Riguzzi F., Carcano C., Rogledi S.,
Bonadeo L., Brunamonte F. and Fioraso G.; 2012: Active compressional tectonics, Quaternary capable faults and the seismic
landscape of the Po Plain (N Italy). Annals of Geophysics, accepted.
Montone P., Mariucci, M.T., Pondrelli S. and Amato A.; 2004: An improved stress map for Italy and surrounding regions (central
Mediterranean). Journal of Geophysical Research, 109(B10410), 22 pp,. doi: 10.1029/2003JB002703
QRCMT; 2012: Quick Regional Centroid Moment Tensor, INGV-Bologna, http://autorcmt.bo.ingv.it/quicks.html.
Reicherter, K., Michetti A.M. and Silva Barroso P.G.; 2009: Palaeoseismology: historical and prehistorical records of earthquake
ground effects for seismic hazard assessment – introduction. In Reicherter, K., Michetti, A.M. and Silva, P.G. (eds)
Palaeoseismology: Historical and Prehistorical Records of Earthquake Ground Effects for Seismic Hazard Assessment. The
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KINEMATICS OF SICILY IN THE FRAMEWORK OF THE NUBIA-EURASIA PLATE
CONVERGENCE: NEW INSIGHTS INTO MICROPLATE FRAGMENTATION AND ELASTIC
STRAIN ACCUMULATION AT FAULTS FROM MODELLING OF GPS VELOCITIES
B. Mastrolembo Ventura1, E. Serpelloni2, A. Argnani3, A. Bonforte4, M. Anzidei2, P. Baldi5 and
G. Puglisi4
Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna
Istituto Nazionale di Geofisica e Vulcanologia, Centro Nazionale Terremoti
3
ISMAR-CNR, Istituto di Scienze Marine, Sede di Bologna
4
Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo
5
Università di Bologna, Dipartimento di Fisica, Settore di Geofisica
1
2
Introduction. Sicily and Calabria lye at the boundary between the converging Nubia and
Eurasian plates and this sector of the plate boundary is consensually recognized as a key area for
understanding the ongoing kinematics and geodynamics of the Mediterranean region. The
kinematics of the complex microplates mosaic that characterizes the Central Mediterranean, and
particularly southern Italy, is, in fact, still matter of debate. Here, GPS play a key role in providing
quantitative constraints on both plate and microplate motions and strain accumulation at plates
contacts, with important implications for both geodynamic modeling and seismic hazard
evaluations. Sicily and Calabria, in fact, are among the most seismically active regions of the
Mediterranean, and locus of the strongest historical earthquakes.
Although early crustal motion rates derived from GPS stations showed that Sicily move along an
African-like trajectory, i.e., NW-ward oriented (D’Agostino and Selvaggi, 2004; Serpelloni et al.,
2005), the increasing number of stations from mid-2000 showed that GPS velocities of stations located
on the Pelagian-Sicilian domain significantly deviate from the velocities predicted by a geodeticallydefined Africa/Nubia Euler rotation pole (e.g., Serpelloni et al., 2007; D’Agostino et al., 2008;
Serpelloni et al., 2010). Moreover, GPS data highlight a non-rigid behavior of the Sicilian block on land
(Serpelloni et al., 2007, 2010), revealing internal deformation both in N-S and E-W directions.
Serpelloni et al. (2010) suggested a relatively independent motion of a NE-Sicily block, where GPS
velocities are much faster than velocities in central and southern Sicily. Palano et al. (2012) have
discussed a compressive velocity gradient along the northern rim of the Hyblean Plateau (south-eastern
Sicily). However, the way the observed velocity gradients within Sicily are presently accommodated by
75