Earth and Planetary Science Letters 225 (2004) 163 – 176
www.elsevier.com/locate/epsl

Slip history of the Magnola fault (Apennines, Central Italy)
from 36Cl surface exposure dating: evidence for strong
earthquakes over the Holocene
Luigi Palumboa,*, Lucilla Benedettib, Didier Bourlèsb, Aldo Cinquea, Robert Finkelc
aDipartimento di Scienze della Terra, Università bFederico II Q di Napoli, Largo S. Marcellino 10, 80138 Napoli, Italy
CEREGE, UMR CNRS 6635, Université Aix-Marseille III, BP 80, plateau de l’Arbois, 13545 Aix en Provence, Cedex 04, FrancecLawrence Livermore National Laboratory–Center for Accelerator Mass Spectrometry, L-206, 7000 East Ave., Livermore, CA 94550, USAb

Received 30 March 2004; received in revised form 17 June 2004; accepted 18 June 2004
Editor: V. Courtillot

Abstract
To better understand the mechanics of deformation in the Mediterranean and the role that the convergence between Africa
and Europe plays, it is necessary to know the deformation field at different time scales. Here we use in situ 36Cl surface
exposure dating of exposed bedrock fault scarps to determine earthquake time-slip histories and to quantify slip rates over thelast several thousand years. This information allows us to delineate the seismic history of normal faulting within the
Mediterranean area over that time period.
We have studied the limestone scarp produced by the Magnola fault in the Central Apennines, Italy. The Magnola fault, in
the Fucino area, is an active, 15-km long, normal fault striking WNW and dipping SSW. The range front morphology,
characterised by steep triangular facets separated by V-shaped valleys and wine-glass canyons, suggests that the Magnola fault
has been active for at least the last several hundred thousand years. At the base of the facets, the fault cuts limestone bedrock to
produce a well-preserved normal fault scarp 10 to 12 m high.
The distribution of 36Cl concentration versus the height along that scarp is best explained by a minimum of five and amaximum of seven successive earthquake exhumations, with slips varying between 1.5 and 3 m. An age of ~5 ka at the base of
the scarp and of ~12 ka at the top yields a slip rate of ~0.8 mm/year. The absence of any event on this fault during the last 5000
years suggests either that a future event is imminent on the Magnola fault or that the fault has entered a quiescent period with* Corresponding author. Present address: CEREGE, UMR CNRS 6635, Université Aix-Marseille III, BP 80, plateau de l’Arbois, 13545 Aix
en Provence, Cedex 04, France.
E-mail addresses: palumbo@cerege.fr (L. Palumbo)8 benedetti@cerege.fr (L. Benedetti)8 bourles@cerege.fr (D. Bourlès)8cinque@unina.it (A. Cinque)8 rfinkel@llnl.gov (R. Finkel).
0012-821X/$ - see front matter D 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.epsl.2004.06.012

164

L. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176

much longer recurrence time. Our study confirms that the Magnola fault scarp is post-glacial and supports the hypothesis thatsimilar scarps in the Mediterranean are also post-glacial.
D 2004 Elsevier B.V. All rights reserved.
Keywords: Apennines; seismotectonic; paleoseismology; Italy; cosmogenic dating; chlorine 36

1. Introduction
It is difficult to decipher the earthquake histories anddisplacement rates of faults whose only record ofactivity lies in bedrock scarps. However, chlorine 36
surface exposure dating of limestone scarps has
recently been successfully applied to recover theseismic history of normal faults in Greece and in theLevant area [1–3].

The active tectonics of the Apennine chain isdominated by extension as suggested by focal mechanisms [4], (Fig. 1). The central and southern
Apennines are the sites of the most significant
historical and instrumental seismicity in western
Europe (Benevento earthquake in 1456, Mc7, Napolitan earthquake in 1857, Mc7, Avezzano earthquake
in 1915, Mc7, Irpinia earthquake in 1980, M s=6.9),[5,6]. Based on combined analysis of satellite images,

Fig. 1. Seismotectonic map of central and southern Apennines, modified from Benedetti [13]. Grey circles indicate location of historicalearthquakes [5,6]; fault plane solutions are CMT solutions from Harvard (http://www.seismology.harvard.edu/data/).

L. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176

topographical and geological maps and field observations, the active faults of this region have been mapped(Fig. 1), their most recent activity being commonly
expressed by well-preserved limestone scarps [7–10].
However, most of the faults responsible for the major
earthquakes are unknown and there is no long-term
slip rate data in the Apennines.
Indeed, limestone scarps, while well adapted tochlorine 36 cosmogenic method, are ill-adapted to
traditional trenching, rendering the techniques thathave proved successful in other parts of the world,much less effective in Italy.
Recent deformation in Italy results from theconvergence between Africa and Europe [11,12].
However, up to now, there is no kinematic model that
integrates and explains the recent deformation of Italy,
Africa’s northernmost penetration into Europe in theplate tectonic framework [13]. Assessing long-term
slip rates on the major active faults of Italy is essential
in unraveling this problem. The approach we propose
here will thus provide a way to recover paleoevents andto measure long-term slip rates on the active faults of
Italy.

165

The Fucino, located in the central Apennines, is oneof the most seismically active areas of Italy and was theepicentre of the catastrophic 1915 Avezzano earthquake(IcXI, M sc7.0) [5,6,14,15]. The area has been
extensively studied by trenching (Table 1 and references
therein). Reliable data on the seismic cycle of the area
reach to about 5000 years before present and indicate
recurrence times for strong events to be on the order of athousand years. Up to now, no data exist for the longerterm earthquake history recorded in the bedrock scarpsof the most prominent faults around the Fucino.
The Magnola fault, one of the main faults of theFucino area, is capable of generating earthquakes up
to magnitude 6.5 [7,9,16,17]. This fault is anapproximately 15-km long active normal fault, striking WNW and dipping SSW in the Fucino area, about
80 km east of Rome (Fig. 2), whose most recent
activity is expressed by a continuous limestone fault
scarp. Using in situ produced cosmogenic 36Cl, we
have directly determined the continuous time-slip
history for the last ~12,000 years. After a brief
description of the morphology of the Magnola–Velino
fault system, we then present the 36Cl results collected

Table 1Synthesis of paleoseismological data for the most prominent faults in the Fucino area based on (1) Giraudi [34], (2) Giraudi [35], (3) Giraudi[36], (4) Pantosti et al. [37], (5) Galadini and Galli [33], (6) Michetti et al. [38] and (7) this study. Star is for the 1915 event.

166

L. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176

Fig. 2. Seismotectonic map of the Fucino area, modified from Piccardi et al. [9]. Circles mark locations of the studied site. The 1915 epicentre
location is from [15] and from Monachesi and Stucchi [5] for the 1904 event. The 1915 surface ruptures are from Oddone [31] and Galadini andGalli [33].

at one site on the fault and the processes by which36
Cl accumulates on the scarp. The numerical model
used to interpret those data is described and our
deduction of the most likely seismic history of the
Magnola fault is discussed and confronted to theresults obtained from previous studies on the paleoseismicity of the Fucino area.

2. The Magnola fault
The Apennine chain was formed during the Mio–
Pliocene as the result of the subduction of the Adriatic

under the opening Tyrrhenian Sea [11,12,18,19]. The
associated thrust belt with NE shortening and NE
verging built up the Central Apennines [18,20] (Fig.
1). It is not yet clear as to when or how the transition
from Mio–Pliocene compression to present-day extension occurred. The timing of initiation of extension in
the Apennines is still a matter of debate, with ages
varying from early Quaternary to mid-Pleistocene[18,21,22].
The Apennines culminate at Gran Sasso with amaximum altitude of 2912 m a.s.l. Lying within
mountains which culminate above 2000 m, theFucino Basin is a very flat plain, about 30-km wide,L. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176

15-km long and with a mean elevation of about 650
m a.s.l. After deglaciation, the basin was flooded,
forming a lake which was first drained by the
Romans (c50 AD) and then again in 1875 [23].
The basin is landlocked by active normal faults andappears roughly rhomb-shaped, with sides oriented
NW–SE and ENE–WSW (Fig. 2).

167

North of the Fucino Basin, recent deformation istaken up by two major normal fault systems: theMagnola–Velino Fault and the Ovindoli–Pezza Fault(Fig. 2).
The Magnola and Velino faults, each about 15 km
long, display the most spectacular topographic andgeomorphic signatures of the faults that surround theFig. 3. Field views of the Magnola fault. (a) Picture of the Magnola fault. Arrows outlined the fault trace. The prominent triangular facets inthis view are about 500-m high and note the perched valley just above the village named Forme. Note the regularity of scarp height and its
continuity along the range front. (b) Close-up of cumulative scarp near Forme and sampling site. White mark is about 10-m high. (c) View ofthe sampling site. Samples are 20-cm wide, less than 2.5-cm deep and were divided into ~15 cm sections for measurement.

168

L. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176

basin. They delimit the steep southwestern flank of the
Magnola–Velino Mountains (2220–2468 m a.s.l.,respectively), joining at an angle of 1408 north of
Magliano (Fig. 2).
The Magnola fault dips SSW and its trace runs for
c15 km along the base of the SW slope of the
Magnola mountain. There are two principal segments
c10 and c5 km long, striking N110E and N130E,
respectively. The two segments meet in a complex
corner where faulting occurs along several parallel
scarps on the hanging wall of the main fault escarpment (for a complete description of the fault, pleaserefer to [9]).
Ongoing slip on this fault throughout the Quaternary is attested by the presence of triangular facets
up to 500 m high with a slope greater than 308, by
the convex shape of mountain-front profiles and bywine-glass and perched valleys (Fig. 3a),[7,9,13,24,25]. At the base of the facets, a continuous cumulative scarp, with a steepness of about 508
with well-preserved dip-slip slicksensides present
along its entire height, marks the contact between
the Meso–Cenozoic carbonates and the colluvial
deposits (Fig. 3) [9,16]. The maximum height ofthe scarp is 15–17 m, progressively decreasing
towards the tips of the fault segments. There are
few local variations on the scarp height due todifferential erosion from active streams that cause thescarp to be locally higher (Fig. 3b). The regularity ofthe scarp (Fig. 3a) is powerful evidence that the
scarp surface is due to fault slip alone and that there
was no significant erosion or deposition on the
hanging wall (except near active gullies) because thescarp began to form.
From detailed topographic profiles of the scarp,
Piccardi et al. [9] infer a 3-m high maximum slip for thelast event on this fault. They therefore deduced that the
Magnola fault ruptured at least five times with anearthquake of magnitude up to M w=6.7–7.0 during the
Holocene and with recurrence times of 3000 to 1000
years. The throw rate they obtained is on the order of
0.7F0.3 mm/year.

3. 36Cl production on the Magnola fault
We have used 36Cl cosmic ray exposure dating toassess the earthquake slip history of the Magnola fault

by determining exposure ages as a function of height on
the cumulative scarp [cf. 1–3].
36
Cl is produced primarily through interactions ofcosmic ray secondary neutrons and muons with Ca
within the scarp limestone (CaCO3), [26]. The
production rate decreases exponentially with depth
and 36Cl thus mostly accumulates near the surface(Fig. 4). At sea level and high latitude, the 36Cl
production rate from Ca by fast neutrons is 48.8F3.4
atom/gCa/year and by muons is 2.1F0.4 atom/gCa/year [26,27].
In the central part of the fault, near the village ofForme, a continuous 20-cm-wide and about 2.5-cmthick sample was collected along the limestone fault
scarp. The particularly well-preserved scarp surface
sampled was chosen far away from the river in order
to avoid erosion and scarp exhumation due to river
incision (Fig. 3b). It is therefore assumed that no
significant erosion has affected the scarp. This
assumption is supported by the morphological observations discussed above that are consistent with nosignificant erosion or deposition on the hanging wall.
The scarp was about 10-m high at the samplingsite and was divided into ~15 cm sections foranalysis. After grinding, leaching and chemical
extraction of chlorine by precipitation of silver
chloride in the CEREGE preparation laboratory, the36
Cl and chloride concentrations in the carbonate
were determined for 65 subsamples by isotope
dilution accelerator mass spectrometry at the Lawrence Livermore National Laboratory CAMS facility(Table 2 and Fig. 5). Blanks were two orders ofmagnitude lower than the samples and replicatesagreed to better than 5%.
The measured height profile of 36Cl along the scarp
was compared to synthetic 36Cl profiles in order todetermine whether the measured profile is consistent
with seismic exhumation (Fig. 4). The model used
includes all sources of production (energetic neutrons,
thermal neutrons from various sources including
slowed down energetic neutrons, stopped muons,Bremsstrahlung and spontaneous fission of U/Th)
and uses sea-level, high-latitude production rates from
Stone et al. [27]. These production rates were thenscaled to the sampling latitude and elevation using thefactors of Lal [28] and normalized to eliminate theeffects of shielding by local topography following
Gosse and Phillips [29] and references therein.

L. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176

169

Fig. 4. Synthetic profiles for a scarp due to one (Q1), two (Q2) and three events (Q3), successively, with 4 m of slip each at 4000-year intervals.
Because each earthquake uplifts a new portion of the scarp above the surface, the 36Cl concentration along the scarp is the sum of 36Cl
accumulated before the earthquake below the surface and of 36Cl accumulated after the earthquake above the surface. Modelling includes all
sources of 36Cl production from Stone et al. [26,27].

Fig. 4 shows synthetic profiles modelled for a
scarp due to one, two and three successive events.
Because each earthquake uplifts a new portion of

the scarp above the surface, the 36Cl concentration
along the scarp is the sum of that 36Cl produced
below the surface prior to the earthquake and that

170

L. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176

Table 236
Cl and chloride concentrations in the carbonate were determined by isotope dilution accelerator mass spectrometry at the LLNL CAMS
facility
Sample name

Height
(cm)

mrock
(g)

[Cl]
ppm

36

Cl/37Cl in rockMAG 01
MAG 02MAG 04MAG 05MAG 06
MAG 07MAG 10MAG 11
MAG 13MAG 14MAG 15MAG 16MAG 17MAG 18MAG 19MAG 20MAG 21
MAG 24
MAG 25MAG 26MAG 27MAG 28MAG 29MAG 31
MAG 33MAG 35MAG 37MAG 39MAG 41
MAG 43MAG 45
MAG 47
MAG 49MAG 50MAG 52MAG 53MAG 55MAG 57MAG 58MAG 60MAG 62MAG 63MAG 65MAG 66MAG 67
MAG 69MAG 70MAG 72MAG 73MAG 75MAG 76

1010
1000
981
970
960
950
920
910
885
875
284
275
265
255
245
234
225
845
835
825
815
804
794
774
755
734
714
695
675
655
636
214
195
187
166
156
131
111
101
81
61
51
28
615
605
585
574
554
545
525
515

23.54
32.78
20.80
27.30
30.84
26.44
29.97
30.64
23.61
28.26
22.18
14.70
40.51
27.57
25.70
30.65
30.55
19.38
30.26
38.45
35.23
37.02
30.12
31.27
28.05
31.44
26.18
25.94
27.01
28.48
31.87
25.38
19.83
29.41
24.68
28.48
22.16
24.63
27.60
29.24
28.44
25.70
30.32
39.36
29.59
29.20
23.47
32.08
24.54
25.42
25.37

16.3
14.1
18.0
14.7
17.1
17.3
22.9
20.3
22.4
21.2
10.8
12.7
10.7
16.1
13.8
18.6
13.9
22.2
19.7
18.3
22.3
22.8
22.9
19.1
23.6
26.0
25.5
20.1
9.9
8.9
9.8
15.3
15.7
13.6
13.8
12.8
12.3
9.4
10.3
11.5
11.0
10.8
11.9
9.1
9.3
12.3
12.9
11.5
12.7
14.4
13.7

7.2E128.1E126.3E127.4E126.6E12
6.5E125.8E125.5E125.0E125.1E12
6.1E124.9E12
6.0E125.0E124.7E124.3E124.6E124.8E125.2E125.6E124.5E124.2E124.3E125.3E124.2E124.5E123.8E124.4E128.7E129.6E129.1E124.2E124.0E124.3E124.1E124.9E125.7E125.7E125.2E124.6E124.6E125.0E124.7E128.8E129.1E126.6E126.6E12
6.7E126.2E125.1E125.4E12F

36

F

2.7E133.0E132.2E13
2.3E132.0E13
2.4E13
2.7E132.0E13
1.3E13
1.9E13
2.9E13
1.2E132.0E13
2.3E13
1.8E13
1.9E13
1.7E13
1.3E13
1.7E13
2.1E13
1.7E13
1.0E13
1.6E13
2.3E13
2.1E13
2.1E13
1.4E13
1.1E13
2.6E13
4.1E13
4.5E132.0E13
1.8E13
1.6E139.2E14
1.5E13
2.7E13
3.5E13
2.9E13
2.7E13
1.6E132.0E13
1.5E13
3.8E13
3.4E13
2.5E13
2.4E13
3.5E13
1.5E13
2.3E13
1.6E13

4.81E+05
4.71E+05
4.67E+05
4.51E+05
4.68E+05
4.62E+05
4.73E+05
4.59E+05
4.59E+05
4.46E+05
2.73E+05
2.55E+05
2.65E+05
2.84E+05
2.68E+05
2.81E+05
2.65E+05
4.39E+05
4.17E+05
4.22E+05
4.09E+05
4.07E+05
4.07E+05
4.20E+05
4.12E+05
4.25E+05
4.01E+05
3.74E+05
3.53E+05
3.54E+05
3.70E+05
2.62E+05
2.58E+05
2.41E+05
2.39E+05
2.60E+05
2.45E+05
2.20E+05
2.20E+05
2.16E+05
2.09E+05
2.21E+05
2.29E+05
3.29E+05
3.49E+05
3.33E+05
3.49E+05
3.17E+05
3.27E+05
3.05E+05
3.03E+05

1.79E+04
1.74E+04
1.19E+04
1.39E+04
1.45E+04
1.70E+04
1.78E+04
1.64E+04
1.25E+04
1.64E+04
1.29E+04
4.99E+03
8.68E+03
1.07E+04
9.96E+03
1.01E+04
9.89E+03
9.59E+03
1.38E+04
1.58E+04
1.58E+04
8.39E+03
1.52E+04
1.79E+04
2.02E+04
1.61E+04
1.49E+04
7.89E+03
1.09E+04
1.52E+04
1.81E+04
1.24E+04
1.15E+04
8.92E+03
3.94E+03
7.97E+03
9.26E+03
1.35E+04
1.24E+04
1.28E+04
7.48E+03
8.66E+03
7.54E+03
1.42E+04
1.30E+04
1.25E+04
1.29E+04
1.65E+04
6.44E+03
1.38E+04
9.37E+03

Cl/g of rockL. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176

171

Table 2 (continued)
Sample name

Height
(cm)

mrock
(g)

[Cl]
ppm

36

Cl/37Cl in rockF

36

MAG 77MAG 78MAG 80MAG 82MAG 83MAG 84MAG 85MAG 86MAG 88MAG 89MAG 90MAG 91
MAG 92MAG 93

504
494
474
455
445
435
425
414
394
387
383
373
363
353

30.19
25.56
16.53
30.00
26.02
28.24
24.83
26.31
31.43
29.66
35.59
29.14
29.11
29.47

12.1
9.1
6.5
6.5
9.0
13.6
10.9
10.9
16.2
16.7
12.6
15.3
15.1
15.5

6.3E127.9E12
1.1E11
1.3E118.2E124.9E12
6.1E12
6.0E124.2E124.0E125.5E125.2E124.5E124.4E122.3E13
2.9E13
3.3E13
5.9E13
2.8E13
1.9E13
1.7E13
3.9E13
1.2E13
1.5E13
2.1E13
2.4E13
1.7E13
1.3E13

3.12E+05
2.97E+05
2.98E+05
2.90E+05
3.03E+05
2.73E+05
2.75E+05
2.76E+05
2.81E+05
2.75E+05
2.84E+05
2.79E+05
2.78E+05
2.83E+05

Cl/g of rockF
1.14E+04
1.11E+04
6.81E+03
1.10E+04
1.03E+04
1.07E+04
5.47E+03
1.47E+04
6.00E+03
1.02E+04
1.06E+04
1.06E+04
1.04E+04
6.84E+03

Calcium content was measured every 40 cm along the scarp by ICP at CEREGE, with an average of 36% of calcium in each samples. Stone etal. [26,27] production rate derived from Ca-rich mineral was used. 36Cl measurements were standardized relative to NIST 36Cl standard.
Replicates were within 5% and blanks were two orders lower than the samples.

accumulated above the surface after the earthquake(Fig. 4). The model is therefore iterative, with thenumber of events, their timing and the magnitude of
the associated slip strongly influencing the shape of
the whole profile. This is clearly depicted in Fig. 4.
For a scarp being seismically exhumed, the characteristic profile is therefore a series of exponentials
with discontinuities marking the earthquakes.
Various scarp emplacement scenarios were tested.
They include scarp formed by steady creep (modelwith several small events with slip of less than 10
cm per event), by differential erosion (model with acontinuous movement of various height at various
period of time), by a unique event (equivalent to a
scenario of gravitational collapse) and by seismic
events (model with instantaneous events at various
periods of time and with varying slip). For eachscenario, the best fit was determined by calculating
the root-mean-square between the data and the model[30], with n as the number of data points:sﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ
X
2
36
36 Cl
RMS ¼
measured  Clmodel Þ =nnThen the bbestQ scenario was determined by
calculating for each bbestQ model scenario the Aikake
Information Criterion (Fig. 5b). This criterion
includes not only the bgoodness-of-fitQ between themodel and the data, but also the number ofparameters included in the model [30], with n thenumber of data points and p the number of
independent parameters which corresponds to thenumber of events:½

AIC ¼ nlog

X 36

2



ð Clmeasured 36 Clmodel Þ =n þ 2p

n

4. Seismic history of the Magnola fault
The results obtained on the sampled scarp show that
the Magnola fault scarp was not formed by steadycreep, differential erosion or gravitational collapse, butrather by at least four earthquakes (Fig. 5b). In
agreement with the experimental profile where four
discontinuities, two at the top and two at bottom, areprominent, displacement scenarios considering lessthan four events or more than eight are clearly lessconsistent with the data (Fig. 5b). The scenario with six
earthquakes yield the best AIC value, but models withseven or five events do not have significantly higher
AIC value (Fig. 5b). All three models yield similar
displacement scenarios for the bottom and top parts ofthe scarp, while in the central part of the profile,modelling is less straightforward (Fig. 5c). Five events
at 4.8, 6.7, 7.4, 10.5 and 12.0 ka with slips varying from
275 to 155 cm are well constrained by the modelling.

172

L. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176

Fig. 5. (a) The black curve represents the envelop of the 36Cl concentration per gram of rock versus the height of the scarp including error bars
(less than 7% for each sample). See Table 2 for details on the data points of the curve. The colour lines (see online version of this article)
represent the three models best fitting the data with 5, 6 and 7 earthquakes. (b) AIC versus the number of earthquakes for each best model
scenario. Note that AIC values are high with 1 event or with more than 10. AIC is minimised for displacement scenario with more than four
events and with less than eight. (c) Seismic history of the Magnola fault. Cumulative slip versus the age of seismic events for the three bestmodels. Note that the first two events and the last two events are well constrained. 36Cl synthetic profiles were calculated with a 36Cl decay
constant of 2.303 106 year1, shielding factor is 0.72 [29]. At sea level and high latitude, the 36Cl production rate by fast neutrons is 48.8F3.4
atom/gCa/year and by muons 2.1F0.4 atom/gCa/year [26,27]. Correction factors for the production rate at our site latitude (42.128) and altitude(1252 m) were 2.75 and 1.71 for neutrons and muons, respectively [28].

L. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176

Two additional events at 8 and 8.8 ka, with slips of 90
and 100 cm, respectively, are inferred but remain
hypothetical (Fig. 5c). The age of the last earthquakewith an associated slip of 155F15 cm on the Magnola
fault scarp is thus 4850F450 ka, while from the oldest
to the most recent, intervals of 1500, 3100, 700 and1900 years separate the five earthquakes of the
proposed sequence.

5. Paleoseismicity of the Fucino area
On January 15, 1915, an earthquake, IcXI MCS,
M sc7.0, destroyed most of the villages around theFucino Plain, causing more than 30,000 victims (Fig.
2) [14]. The surface faulting, striking NW–SE, along
the Serrone and Parasano faults on the east side of theFucino Basin, was mapped by several authors with amaximum vertical throw of 3 m (Fig. 2) [31,32]. The
Trasacco fault is also supposed to have ruptured
during this event [33]. Only 11 years before, in 1904,
an event of intensity IX struck the northern Fucinoarea, damaging several villages on the slopes of Mt.
Velino [5,14]. No surface rupture was reported and thefault responsible for this event is unknown.
Palaeoseismological studies infer the occurrence ofother earthquakes similar to that of 1915 in the Fucino
Basin during the Late Pleistocene and Holocene(Table 1).
Based on dating of glacial deposits that have been
offset by normal faults, Giraudi [34] infers that the
Tre-Monti fault (Fig. 2) ruptured during an event thatmight have occurred between 20 and 13 years B.P.
(Table 1).
On the northeastern slope of Mt. Magnola (Fig. 2),
Giraudi [35] mapped small scarps (c1-km long each)striking WNW–ESE, reaching 6-m high, offsetting
moraine deposits he assigned to a period of glacial
retreat between 16 and 13 kyr B.P. (Table 1).
Lastly, on the E–W segment of the Ovindoli–Pezza
fault system, which strikes parallel to Mt. Magnola
scarps and runs a few km north (Fig. 2), Giraudi [36]suggests that two distinct events occurred, the first one
between 18 and 15 kyr B.P., and the second between 7
and 5 kyr B.P. (Table 1). From detailed geomorphological study and logging of several trenches dug acrossthe Ovindoli–Pezza fault, Pantosti et al. [37] demonstrated the occurrence of three earthquakes on this fault

173

over the Holocene. The first one occurred between
5000 and 3300 BC, the second about 1900 BC and thelast one between 860 and 1300 AD, the slip per event
ranging from 2 to 3 m high (Table 1). Based on thoseresults and on geomorphic features, Pantosti et al. [37]calculate a long-term slip-rate of 0.7–1.2 mm/year. Thisimplies a recurrence time on this fault of 1000 to 3000
years. Therefore, two independent studies [36,37],
based on different types of observation, suggest thatan important event occurred on the Ovindoli–Pezza
fault between 7000 and 5000 years B.P. (Table 1).
Geomorphological and paleontological observations suggest that the Serrone fault (Fig. 2) was active
around 5500–5000 years B.P. and about 3100 years
ago, while fault scarps in the centre of the former lakesuggest a late-Roman or Middle Ages (2000 years B.P.
to 1000 years B.P.) seismic event [34]. Trench
investigations showed evidence for two paleo-earthquakes on this same fault [38]: one constrained to haveoccurred between the 6th and 9th centuries AD andassociated with the 801 AD historical event that struck
Central Italy [5,6]; the second constrained between the10th century AD and 1349 AD (Table 1). Other authors[33] infer that three events occurred on this fault, thefirst one between 10,231 and 5576 BC, the second
between 1700 and 833 BC, and the one prior to 1915,
between 426 and 782 AD. Therefore, these studies
agree on one event, which might have occurred
between the 6th and 9th centuries AD on the Serrone
fault (Table 1).
Trench investigation across the Parasano fault (Fig.
2) produced evidence for three ruptures prior to 1915
during the last 19 kyr [33].
Based on hand-borehole observations and trench
investigations, the same authors deduced that the
Trasacco fault (Fig. 2) ruptured four times before
1915. The first event occurred between 10,729 and5576 BC, the second in 3944–3618 BC, the third
between the 16th and 15th centuries BC and the lastone between the 5th and 6th centuries AD.
The studies presented above suggest that theParasano, Serrone and Trasacco faults could haveruptured simultaneously as they did in 1915.
Recurrence times on the Ovindoli–Pezza fault, inagreement with the one proposed by Piccardi et al.
[9] on the Magnola fault, are between 3000 and1000 years, much longer than that inferred on thesouthern faults.

174

L. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176

6. Discussion and conclusions
The 36Cl concentrations measured along the Magnola fault scarp indicate that slip has accumulated on
this scarp over the last 12 kyr. This yields a cumulative
slip rate of 0.8F0.1 mm/year, similar to that of
0.7F0.3 mm/year proposed for the same fault by
Piccardi et al. [9] and to that of 0.7–1.2 mm/year
proposed for the Ovindoli–Pezza fault by Pantosti etal. [37]. If constant over several thousand of years, thisslip rate implies that the 500-m high triangular facets
have been created in about a million years.
When compared to modelled synthetic 36Cl profiles, the experimental 36Cl profile obtained on the
Magnola fault yields recurrence times between 3000
to 1000 years, in agreement with those deduced fromvarious trenching and geomorphological studies doneon faults north of the Fucino [9,34,35,37].
The experimental 36Cl profile also shows that thelast event on the Magnola fault occurred at 4850F450
ka, with a slip of 155F15 cm. This is in agreementwith geomorphological observations completed bydetailed topographic profiles suggesting that the last
event on this fault occurred about 5000 years ago,
with a slip between 3 and 1 m [9]. If the whole 15-kmlong fault ruptured, the magnitude of the event would
have been ~6.7 [39]. However, the slip amplitudes of
all four previous events range from 200 to 280 cm.
Considering scaling laws [39,40], events this large
should have simultaneously ruptured the northern
Velino segment and thus produce seismic events witha magnitude close to 7, similar to that of the 1915
earthquake.
Pantosti et al. [37] suggested that two events, one
between 5300 and 7000 and the other ~3900 years
B.P. ago, occurred on the Ovindoli–Pezza fault with aslip per event ranging from 2 to 3 m (Fig. 2 and Table1). The E–W segments of the Ovindoli–Pezza fault
are located a few kilometres north of the Magnola
fault and strike parallel to it (Fig. 2). The ages of theearthquakes inferred by Pantosti et al. [37] on thosesegments are close to the ages of the penultimate andultimate events we deduced on the Magnola fault(Table 1). The geometry of those faults suggests thatthey should connect at depth. Therefore, in terms of
their seismic behaviour, this might imply that either
they could have ruptured simultaneously, as theParasano and Serrrone faults did in 1915, or that an

event on one could have triggered another event on
the second fault. Dating the limestone fault scarp on
the Ovindoli–Pezza fault would allow to farther
evaluating the relationships of those two faults inthe past through comparison of their seismic behaviour during the last 12 kyr. This is important because
the last event recorded on the Ovindoli–Pezza fault by
Pantosti et al. [37] occurred 1200 to 700 years ago. On
the other hand, our results show that the last event on
the Magnola fault occurred ~4850 years ago, twice theaverage recurrence time deduced for the previous four
events. This might suggest either that a future event isimminent on the Magnola fault or that the fault hasentered a more quiescent period with much longer
recurrence time. This latter could be due to a change
in the loading rate on the Magnola fault because ofstress interactions with the surrounding faults, forexample, the Ovindoli–Pezza, as previously inferredin other regions [2,41].
This study confirms that the Magnola fault scarp is
post-glacial and adds support to the hypothesis thatall such similar scarps in the Mediterranean are postglacial [2,9,42]. Indeed, several authors have suggested that similar fault scarps in the Mediterranean
are post-glacial in age [2,9,16,42]. In Greece, a recent
36
Cl study has also quantitatively confirmed thishypothesis, with a maximum age for such limestonefault scarps of about 12 ka [2]. During the last glacial
maximum, the prevailing dry, cold climate [43,44]
inhibited the formation of vegetation cover on themountain slopes, thus exposing newly formed scarps
to burial by periglacial superficial mass transport.
After deglaciation, vegetation reoccupied the mountain slopes due to the prevailing wet, warm climate.
Consequently, superficial mass transport was interrupted and increments of throw along the fault trace
were no longer buried. These changed conditions
allowed the preservation of post-glacial scarps andthe steady growth of the cumulative scarp as theresult of successive earthquakes [2,42].
This result opens new possibilities of calculating
Holocene deformation rate in Italy, which has been
impossible up to now. When compared with the datafrom the dense GPS networks in the region [45], thiswill provide a unique view of the deformation field at
different time scales, important to understand themechanics of deformation in the Mediterranean andthe relationships with the Africa–Europe convergence.

L. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176

Acknowledgments
We are grateful to Philippe Chamaret and Fabio
Villani for helping us in field work. Alessandro Ercole
and Corpo Forestale are greatly acknowledged forauthorizing us to work in the Velino Park. This work
benefited from fruitful discussions with Alessandra
Ascione, Régis Braucher, Olivier Bellier and Bruno
Hamelin. We acknowledge the two referees for theirthorough reviews that improved the manuscript. This
work was supported by the Fondi Vinci from the
Italian–French University, prot. UFI2I4CH7T. Dating
was performed under the auspices of U.S. Departmentof Energy by the University of California, Lawrence
Livermore National Laboratory under Contract No.
W-7405-Eng-48.

References[1] S. Gran Mitchell, A. Matmon, P.R. Bierman, M. Caffee, D.
Rizzo, Displacement history of a limestone normal fault scarp,
northern Israel, from cosmogenic 36Cl, J. Geophys. Res. 106(2001) 4247 – 4264.
[2] L. Benedetti, R. Finkel, D. Papanastassiou, G. King, R.
Armijo, F.J. Ryerson, D. Farber, F. Flerit, Post-glacial slip
history of the Sparta fault (Greece) determined by 36Cl
cosmogenic dating: evidence for non-periodic earthquakes,
Geophys. Res. Lett. 27 (2002) doi:10.1029/2001GL014510.
[3] L. Benedetti, R. Finkel, G. King, R. Armijo, D. Papanastassiou, F.J. Ryerson, F. Flerit, D. Farber, G. Stvrakakis, Motion
on the Kaparelli fault (Greece) prior to the 1981 earthquake
sequence determined from 36Cl cosmogenic dating, Terra
Nova 15 (2003) 118 – 124.
[4] A. Frepoli, A. Amato, Contemporaneous extension andcompression in the Northern Apennines from earthquakes
fault-plane solutions, Geophys. J. Int. 129 (1997) 368 – 388.
[5] G. Monachesi, M. Stucchi, DOM4.1, un database di osservazioni macrosismiche di terremoti di area italiana al di sopra dellasoglia di danno, GNDT, Milan, available on the world wide web
at http://emidius.itim.mi.cnr.it/DOM/home.html, 1997.
[6] E. Boschi, G. Ferrari, P. Gasperini, E. Guidoboni, G. Smriglio,
G. Valensise, Catalogo dei Forti Terremoti in Italia dal 461
a.C. al 1980, ING e SGA, 1995, 973 pp.
[7] C. Bosi, Osservazioni preliminari su faglie probabilmente
attive nell’Appennino centrale, Boll. Soc. Geol. Ital. 94 (1975)
827 – 859.
[8] A.M. Blumetti, F. Dramis, A.M. Michetti, Fault-generated
mountain in the Central Apennines (Central Italy): geomorphological features and seismotectonics implications,
Earth Surface Landf. 18 (1993) 203 – 223.
[9] L. Piccardi, Y. Gaudemer, P. Tapponier, M. Boccaletti,
Active oblique extension in the central Apennines (Italy):

175

evidence from the Fucino region, Geophys. J. Int. 139 (1999)
499 – 530.
[10] C. Giraudi, Consideration on the significance of some postglacial fault scarps in the Abruzzo Apennines (Central Italy),
Quat. Int. 25 (1995) 33 – 45.
[11] D.P. McKenzie, Active tectonics of the Mediterranean region,
Geophys. J. R. Astron. Soc. 30 (1972) 109 – 185.
[12] P. Tapponnier, Évolution tectonique du système alpin en
Méditerranée: poinçonnement et écrasement rigide-plastique,Bull. Soc. Geol. Fr. 7 (1977) 437 – 460.
[13] L. Benedetti, Sismotectonique de l’Italie et des régions
adjacentes: fragmentation du promontoire adriatique, Thèsede Doctorat de l’Université Paris VII, 1999, p. 358.
[14] C. Margottini, S. Screpanti, Attribuzione della magnitudo al
terremoto di Avezzano del 13 gennaio 1915 e studiodell’evoluzione temporale della crisi sismica associata, in: S.
Castanetto, F. Galadini (Eds.), 13 gennaio 1915—il terremotodella Marsica, Servizio Sismico Nazionale, CNR-IRTR,
Roma, 1999, pp. 301 – 318.
[15] D. Molin, F. Galadini, P. Galli, L. Mucci, A. Rossi, Terremotodel Fucino del 13 gennaio 1915. Studio Macrosismico, in: S.
Castanetto, F. Galadini (Eds.), 13 gennaio 1915—il terremotodella Marsica, Servizio Sismico Nazionale, CNR-IRTR,
Roma, 1999, pp. 321 – 340.
[16] G.P. Roberts, A.M. Michetti, Spatial and temporal variations ingrowth rates along active normal fault systems: an example
from The Lazio–Abruzzo Apennines, central Italy, J. Struct.
Geol. 26 (2004) 339 – 376.
[17] N.C. Morewood, G.P. Roberts, The geometry, kinematics andrates of deformation within an en échelon normal fault segment
boundary, central Italy, J. Struct. Geol. 22 (2000) 1027 – 1047.
[18] A. Malinverno, W.B.F. Ryan, Extension in the Tyrrhenian sea
and shortening in the Apennines as result of arc migration driven
by sinking of the lithosphere, Tectonics 5 (1986) 227 – 245.
[19] E. Patacca, P. Scandone, Post-Tortonian mountain buildingin the Apennines: the role of the passive sinking of a reliclithospheric slab, in: A. Boriani, et al. (Eds.), The Lithosphere in Italy, Academia Nazionale dei Lincei, Roma,
1989, pp. 157 – 176.
[20] E. Patacca, R. Sartori, P. Scandone, Tyrrhenian Basin and
Apenninic arcs: kinematic relations since Late Tortonian times,
Mem. Soc. Geol. Ital. 45 (1990) 425 – 451.
[21] A. Cinque, E. Patacca, P. Scandone, M. Tozzi, Quaternary
kinematic evolution of the Southern Apennines. Relationshipbetween surface geological features and deep lithosphericstructures, Ann. Geofis. 36 (1993) 443 – 460.
[22] J.C. Hippolyte, J. Angelier, F. Roure, A major geodynamicchange revealed by Quaternary stress patterns in the Southern
Apennines (Italy), Tectonophysics 230 (1994) 199 – 210.
[23] C. Giraudi, Lake levels and climate for the last 30000 years in
the Fucino area (Abruzzo, Central Italy): a review, Palaeogeogr.
Palaeoclimatol. Palaeoecol. 70 (1989) 249 – 260.
[24] C. Giraudi, Faglie ad attività olocenica nella Piana del Fucino(Abbruzzo), Mem. Soc. Geol. Ital. 35 (1986) 875 – 880.
[25] C. Giraudi, Considerations on the significance of some postglacial fault scarps in the Abruzzo Apennines (central Italy),
Quat. Int. 25 (1995) 33 – 45.

176

L. Palumbo et al. / Earth and Planetary Science Letters 225 (2004) 163–176[26] J.O.H. Stone, L.K. Fifield, G.L. Allan, R.G. Cresswell,
Cosmogenic chlorine-36 from calcium spallation, Geochim.
Cosmochim. Acta 60 (1996) 679 – 692.
[27] J.O.H. Stone, J.M. Evans, L.K. Fifield, G.L. Allan, R.G.
Cresswell, Cosmogenic chlorine-36 production in calcite bymuons, Geochim. Cosmochim. Acta 62 (1998) 433 – 454.
[28] D. Lal, Cosmic ray labelling of erosion surfaces: in situ
nuclide production rates and erosion model, Earth Planet. Sci.
Lett. 104 (1991) 424 – 439.
[29] J.C. Gosse, F.M. Philllips, Terrestrial in situ cosmogenic
nuclides: theory and application, Quat. Sci. Rev. 20 (2001)
1475 – 1560.
[30] J.R. Taylor, An Introduction to Error Analysis, the Study ofUncertainties in Physical Measurements, 2nd ed., University
Science Books, Sausalito, CA, 1997, 327 pp.
[31] E. Oddone, Gli elementi fisici del grande terremoto marsicano
fucense del 13 gennaio 1915, Boll. Soc. Sismol. Ital. 19 (1915)
71 – 215.
[32] L. Serva, A.M. Blumetti, A.M. Michetti, Gli effetti sul terrenodel terremoto del Fucino (13 Gennaio 1915); tentativo diinterpretazione della evoluzione tettonica recente di alcune
strutture, Mem. Soc. Geol. Ital. 35 (1986) 893 – 907.
[33] F. Galadini, P. Galli, The Holocene paleoearthquakes on the1915 Avezzano earthquake faults (central Italy): implications
for active tectonics in the central Apennines, Tectonophysics
308 (1999) 143 – 170.
[34] C. Giraudi, Evoluzione geologica della piana del Fucino(Abruzzo) negli ultimi 30000 anni, Quaternario 1 (1988)
131 – 159.
[35] C. Giraudi, Segnalazione di scarpate di faglia tardo-pleistoceniche sui monti della Magnola (Massiccio del Velino–
Abruzzo), Quaternario 5 (1992) 27 – 32.
[36] C. Giraudi, Datazione con metodi geologici delle scarpate difaglia post-glaciali di Ovindoli–Piano di Pezza (Abruzzo–
Italia Centrale): implicazioni, Mem. Soc. Geol. Ital. 42(1989) 29 – 39.

[37] D. Pantosti, G. D’Adezzio, F.R. Cinti, Paleoseismicity of the
Ovindoli–Pezza fault, central Apennines, Italy: a history
including a large, previously unrecorded earthquake in the
Middle Ages (860–1300 A.D.), J. Geophys. Res. 101 (1996)
5937 – 5959.
[38] A.M. Michetti, F. Brunamonte, L. Serva, E. Vittori, Trench
investigations of the 1915 Fucino Earthquakes, J. Geophys.
Res. 101 (1996) 5921 – 5936.
[39] C.H. Scholz, The Mechanics of Earthquakes and Faulting,Cambridge Univ. Press, Cambridge, 439 pp.
[40] D.L. Wells, K.J. Coppersmith, New empirical relationshipamong magnitude, rupture length, rupture width, rupture area,and surface displacement, Bull. Seismol. Soc. Am. 79 (1989)
947 – 1002.
[41] A. Nur, E.H. Cline, Poseidon’s horses: plate tectonics andearthquake storms in the late Bronze Age Aegean and Eastern
Mediterranean, J. Archaeol. Sci. 27 (2000) 43 – 63.
[42] R. Armijo, H. Lyon-Caen, East–West extension and Holocene
normal-fault scarps in the Hellenic arc, Geology 20 (1992)
491 – 494.
[43] J.R.M. Allen, U. Brandt, A. Brauer, H.W. Hubberten, B.
Huntley, J. Keller, M. Kraml, A. Mackensen, J. Mingram,
J.F.W. Negendak, N.R. Nowaczyck, H. Oberh7nsli, W.A.
Watts, S. Wulf, B. Zolitschka, Rapid environmental changes
in southern Europe during the last glacial period, Nature 400(1999) 740 – 743.
[44] O. Peyron, J. Guiot, R. Cheddadi, P. Tarasov, M. Reille, J.L. deBeaulieu, S. Bottema, V. Andrieu, Climatic reconstruction in
Europe for 18,000 yr B.P. from pollen data, Quat. Res. 49(1998) 183 – 196.
[45] N. D’Agostino, R. Giuliani, M. Mattone, L. Bonci, Active
crustal extension in the central Apennines (Italy) inferred fromGPS measurements in the interval 1994–1999, Geophys. Res.
Lett. 28 (2001) 2121 – 2124.