Ⓔ

Holocene Paleoearthquakes and Early–Late Pleistocene Slip

Rate on the Sulmona Fault (Central Apeninnes, Italy)

by Paolo Galli,* Biagio Giaccio, Edoardo Peronace, and Paolo Messina

Abstract The 23 km long Sulmona normal fault flanks the southwestern slope of theMount Morrone range in the central Apennines. To date, the recent activity of this struc-ture is uncertain, as the faulting evidence concerns only undated deposits and the faultcannot be associated with any of the strong historical earthquakes (Mw >6:5) of theregion. Our observation from∼1 Ma offset slope breccias, coupled with new tephrochro-nological data on faulted early Last Glacial lacustrine infilling of the Sulmona basin,implies a vertical slip rate of ∼0:5 mm=yr over both the long term and middle term.Moreover, at the apex of a Late Pleistocene alluvial fan, radiocarbon dating of offsetstratigraphy uncovered in four paleoseismological trenches shows that repeated earth-quakes resulted in more than 4 m of vertical offset since ∼9 ka, providing again a mini-mum Holocene vertical slip rate of ∼0:5 mm=yr. In combination with the results of thetrench exposure, we define four faulting events in the past ∼9 kyB:P:, and at least onebefore then. The most recent is constrained by robust radiocarbon dates as the middle ofthe second century A.D. The penultimate event was around the middle of the fifth mil-lennium B.P., whereas the other two events are dated in a time between 8.5 ky to 6.5 kyB.P. and around 9 ky cal B.P. The oldest occurred before 9.5 ky B.P. As well as revealingthe unexpected paleoseismic history of the Sulmona silent fault, our data provide a re-currence time forMw ≥6:5 earthquakes of ∼2:4 ky versus an elapsed time of ∼1:85 kysince the last event. The latter matches with an earthquake previously hypothesizedthrough archaeoseismic clues collected from several Roman settlements of the SulmonaPlain, all of which were dated to halfway through the second century A.D.

Online Material: Table of major-element compositions, field photos, and Harkerdiagrams.

Introduction

At the end of the last century, Galadini and Galli (1999)claimed the existence of at least two parallel sets of seismo-genic normal-fault systems running along the backbone of thecentral Apennines. These systems accommodate the dominantnortheast–southwest extensional processes that have affectedthe Apennine chain since the Middle Pleistocene, with avelocity currently rated at ∼3 mm=yr using Global Position-ing System data (D’Agostino, 2014). The western fault setwas responsible for all of the Mw 6.3–7.0 historical earth-quakes (and last, but not least, the 2009 Mw 6.3 L’Aquilaevent), whereas the eastern fault set has been defined as silent(no historical earthquakes), and with an elapsed time sincethe last fault rupture of longer than 1500 years (Galadini andGalli, 2000). As historical and paleoseismological studies

demonstrated that this time span often exceeds the averagerecurrence interval for Mw ≥6:5 Apennine earthquakes, itappears likely that future strong earthquakes might also oc-cur along faults of this eastern set (i.e., the Vettore, Laga,Campo Imperatore, and Sulmona faults [SFs] in Galli et al.,2008, and references therein; see v, l, c, and s, respectively,in Fig. 1b).

The northwest–southeast-striking SF is one of thesesilent structures. It affects the western slope of the MountMorrone ramp anticline (2061 meters above sea level[m.a.s.l.]), with two parallel splays that run at different ele-vations (Fig. 1a), and that join at a few kilometers in depthbeneath the Quaternary Sulmona basin. Previously, Vittoriet al. (1995) reported on the metric displacement of Pleisto-cene alluvial fan sediments along secondary, north–south-trending faults, whereas Galadini and Galli (2000) showedboth the offset of Late Pleistocene slope deposits along theeastern splay and of Early Pleistocene breccias along the

*Also at Consiglio Nazionale delle Ricerche-Istituto di Geologia Ambi-entale e Geoingegneria, Area di Ricerca Roma1, Via Salaria km 29.3, Mon-telibretti, Italy; e-mail: paolo.galli@protezionecivile.it.

1

Bulletin of the Seismological Society of America, Vol. 105, No. 1, pp. 1–13, February 2015, doi: 10.1785/0120140029

western splay, hypothesizing an overall, long-term (1 Ma),vertical slip rate of 0:50–0:66 mm=yr. Recently, Gori et al.(2011) published other indications of Late Pleistocene faultactivity that were also accompanied by large-scale gravitydeformations (Gori et al., 2014).

As far as the local seismicity is concerned, neither im-portant historical earthquakes nor moderate instrumental epi-centers are known to have occurred within the Sulmona Plainor can be intuitively associated with the SF (Fig. 1b). Theonly strong event close to this area occurred beyond the

Figure 1. (a) Simplified geological map of the Sulmona basin: UST, upper Sulmona terrace; 1, Neapolitan Yellow Tuff tephra (∼15 ka);2, Albano-7 tephra (36 ka); 3, ∼35–45 ka paleosols; 4, C-22 tephra (∼92 ka); 5, Sabatini Fall A tephra (499 ka); lpl, Late Pleistocene, earlyLast Glacial lacustrine mud; S6, location of the geological profile shown in inset (d). DSGS (dotted line) is a deep-seated gravity slide. Box Bindicates the area of Figure 2a. Diamonds indicate sites with archaeoseismic evidence of collapse in the second century A.D. (HC, HerculesCurinus sanctuary; FA, Fonte d’Amore Roman remains) and triangles indicate top of a mountain. (b) The locations of primary active faults incentral Italy and 6 < Mw ≤ 7 earthquakes are shown (modified from Galli et al., 2011); box A shows the location of the detailed map in (a); v,l, c, and s represent Vettore, Laga, Campo Imperatore, and Sulmona faults of the eastern fault system, respectively, and ca is the Colli Albanivolcano. (c) The simplified section of the continental Late Pleistocene filling of the Sulmona basin shows the following units: L, early LastGlacial whitish lacustrine carbonate mud with tephra layers; F, fluvial sand and gravel (SUL4); and A, alluvial fan gravel with dated paleosoland tephra (SUL3-2). Scale bars on the far right of are 1 m. (d) The simplified geological profile crosses the Early (epl) and Late (lpl)Pleistocene lacustrine deposits and indicates the elevation of some idiosyncratic tephra (preQ, pre-Quaternary bedrock). The color versionof this figure is available only in the electronic edition.

2 P. Galli, B. Giaccio, E. Peronace, and P. Messina

eastern fault systems (the 1706 event; Mw 6.8 in versionDBMI11 of the Italian Macroseismic Database, 2011), andits damage distribution does not fit at all with the SF (Gal-adini and Galli, 2007).

Notwithstanding these pieces of evidence, the lack offaulted post-last-glacial maximum–Holocene deposits hasso far prevented any conclusive assessment regarding the realactivity of this structure or its seismogenic behavior. There-fore, to cast light on this unresolved issue, following aerialphotographs, light detection and ranging interpretation, geo-logical field surveys, high-precision topographic leveling,geoelectrical exploration (e.g., electrical resistivity tomogra-phy [ERT]), chronometric dating (Table 1), and tephra analy-ses, we finally decided to open four paleoseismologicaltrenches across the western basal fault.

General Background and New Hints on the SulmonaBasin Infilling and Fault System

Stratigraphy and Chronology

The Sulmona intermontane basin has been deepening inthe hanging wall of the SF since the Early Pleistocene and wasprogressively filled with alternating lacustrine–fluvial deposits(e.g., Miccadei et al., 1998, and references therein). Accordingto recent data (Giaccio, Messina, et al., 2009), the Quaternarysuccession is mainly composed of three unconformity-boundedalluvial–fluvial–lacustrine units (SUL6-SUL5-SUL4), whichwere robustly dated using 40Ar=39Ar analysis, tephrochronol-

ogy, and magnetostratigraphy within the intervals: ante 814–530 ka (SUL6), 530–post 457 ka (SUL5), and ante 110–post90 ka (SUL4) (Giaccio, Nomade, et al., 2012; Giaccio,Arienzo, et al., 2013; Giaccio, Castorina, et al., 2013; Giaccioet al., 2014). The SUL4 lacustrine calcareous mud deposits(i.e., late marine isotope stage [MIS] 5; see tephra and agesreported in the stratigraphic column of Fig. 1c and Table 2)pass upward to the Last Glacial fluvial–alluvial sedimentsof unit SUL3, which in turn forms the wide upper Sulmonaterrace surface (UST in Fig. 1a,c; ∼400–350 m.a.s.l., fromsouth to north) and the older coalescing fan system alongthe Mount Morrone slope. A late generation of alluvial cones(SUL2) partly covers, or is carved within, the previous fansurface and the UST (Fig. 1a,c).

This general stratigraphic framework is completed by theearliest continental Quaternary deposits that outcrop alongthe slopes around the Sulmona Plain. Between the villagesof Roccacasale and Pacentro, stratified breccia slabs (areas la-beled a in Fig. 1a) that represent remnants of ancient cementedslope deposits are downthrown in the hanging wall of the SFbelow the plain, where they originally joined the lacustrinelayers. The same unit outcrops in the slope facing Raiano(western side of the basin in Fig. 1a), where it is unconform-ably covered by younger fan gravels that interdigitate basin-ward with the SUL6 lacustrine mud (∼0:8–0:5 Ma), thuspostdating the breccias to the Early Pleistocene.

As previous studies have mainly dealt with the innersediments of the basin, we have carried out new tephrostrati-graphic investigations and radiocarbon dating that are aimed

Table 1Radiocarbon Dates of Samples Collected in the Investigated Area

Trench (T) orSulmona (SUL) Unit Trench Unit Sample Laboratory Code Analysis* Dated Material 14C Age (yr B.P.) 2σ Cal. 95%†

T1 2c′ Pop-08/09 Beta354242 AMS Charcoal 4470 ± 30‡ 5280–4970 yr B.P.1 Pop-11 Beta354244 AMS Charcoal 250 ± 30‡ 1630–1670 A.D.3 Pop-12 Beta354245 AMS Organic sediment 8080 ± 40‡ 9090–8980 yr B.P.2c′ Pop-17c Beta354247 AMS Charcoal 3750 ± 30‡ 4150–3980 yr B.P.2 Pop-18c Beta355860 AMS Charcoal 1310 ± 30‡ 650–710 A.D.

T2 3 Pop-01 Beta354241 AMS Charcoal 7920 ± 40‡ 8980–8600 yr B.P.2b Pop-15 Beta355861 AMS Organic sediment 1880 ± 30‡ 80–130 A.D.3 Pop-16 Beta354246 AMS Organic sediment 8310 ± 40‡ 9440–9140 yr B.P.

T3 2 Pop-19 Beta355862 AMS Organic sediment 1830 ± 30‡ 80–240 A.D.2 Pop-19c Beta354248 AMS Organic sediment 2330 ± 30‡ 410–380 B.C.

T4 3 Pop-20 Beta376371 AMS Organic sediment 5620 ± 30‡ 6450–6315 yr B.P.3 Pop-21 Beta376372 AMS Organic sediment 7610 ± 40‡ 8540–8370 yr B.P.2 Pop-25 Beta376373 AMS Charcoal 370 ± 30‡ 1450–1640 A.D.2c′ Pop-27 Beta376374 AMS Organic sediment 4720 ± 30‡ 5580–5325 yr B.P.2c′ Pop-28 Beta376375 AMS Organic sediment 3200 ± 30‡ 3475–3370 yr B.P.2h Pop-30 Beta376376 AMS Charcoal 3300 ± 30‡ 3635–3470 yr B.P.

SUL3 — SUL-01 Beta181014 RAD Paleosol 33980 ± 540‡ 37276–40416 yr B.P.— SUL-02 Beta181013 RAD Paleosol 41830 ± 2130‡ 44059–46546 yr B.P.

Tephra MT2 SUL-03 CEDADLTL565 AMS Shell 31585 ± 210§ 36594–35295 yr B.P.

All samples have been pretreated and analyzed in the Beta Analytic Inc. laboratories of Miami, Florida, except one at the University of Lecce,Italy (labeled CEDAD).*AMS, accelerator mass spectrometry; RAD, standard radiometric analysis.†2σ calibration was obtained with software Calib 6.0.1 (see Data and Resources).‡Present study.§Giaccio et al. (2007).

Holocene Paleoearthquakes and Early–Late Pleistocene Slip Rate on the Sulmona Fault (Central Apeninnes, Italy) 3

at refining the chronology of the alluvial–fluvial units thatoutcrop along the northeastern margin of the plain; that is,close to the SF system. As well as the new data on the MIS 5lacustrine deposits (L in Fig. 1c; Giaccio, Nomade, et al.,2012), we found two idiosyncratic tephra layers in severalplaces near the top of units SUL2 and SUL3 (MT1 and MT2,respectively; numbers 1 and 2 in Fig. 1a,c), whereas anothertephra (MT3) was discovered in the proximal alluvial–lacustrine sediments of unit SUL5 (number 5, near the townof Popoli in Fig. 1a). Here, we briefly describe these tephrasand their ages; Ⓔ the major-element compositions and totalalkali versus silica diagrams, as well as some photographs,are available in Table S1 and Figures S1–S3 of the electronicsupplement to this article.

MT1: Glass composition matches the tephra from thecaldera-forming Neapolitan Yellow Tuff eruption thatoccurred in the 160 km distant Campi Flegrei volcanic field.Its age is ∼15 ka (e.g., Deino et al., 2004), and it is widelydispersed all over the central-southern Apennines (e.g.,Giraudi et al., 2013).

MT2: The peculiar foiditic composition of the melt in-clusions in clinopyroxene crystals, along with the strontiumisotope composition (Giaccio et al., 2007), conclusivelymatch the Albano-7 tephra, which is a widely dispersed ashlayer in the central Apennines (Giaccio, Arienzo, et al.,

2013) from the last explosive eruption of the Colli Albanivolcanic district (labeled ca in Fig. 1b). This was dated at36� 1 ka (Freda et al., 2006), which fits with the radiocar-bon age obtained from a snail shell found inside the MT2layer (36,594–35,295 B.P., 2σ cal.; Giaccio et al., 2007).These data are also consistent with the radiocarbon datingof several paleosols embedded in the SUL3 alluvial gravelsjust below MT2 (number 3 in Fig. 1a,c), which yielded agesbetween 44,059–46,546 B.P. and 37,276–40,416 B.P.(2σ cal.; samples SUL-02 and SUL-01 in Table 1), overallconstraining the age of unit SUL3 to the interval ante45–post 36 ka.

MT3: Compositional and lithological features match atephra we found in the inner lacustrine sediments of theSUL5 unit, which has already been attributed to the FallA eruptive unit from the Sabatini volcanic district (layerSUL5-1c in Giaccio et al., 2014) and dated to ∼499 kaby Marra et al. (2014).

The Sulmona Fault

The SF is expressed at the surface by a main basal, 23 kmlong fault, and by an eastern splay that roughly parallels thewestern slope of the Morrone range (Fig. 1a). Together withother intermediate splays, these faults account for more than2 km of stratigraphical offset of the Mesozoic carbonate

Table 2Ages of Tephra Collected in the Investigated Area and Associated Correlative Tephra and/or Eruption with Relative Age

Sulmona Tephra Correlative Tephra and/or Eruption

StratigraphicUnit Name

40Ar=39Ar Age(ka� 2σ) Name 40Ar=39Ar Age (ka) Reference

SUL2 MT1 Neapolitan YellowTuff

The present study

14.9±0.4 ka (2σ) Deino et al. (2004)SUL3 MT2 Albano-7 The present study, Giaccio et al. (2007)

35.9±0.6 Freda et al. (2006)33.0±4.0 Giaccio, Marra, et al. (2009)

SUL4 POP1 92.4±4.6 C-22 Giaccio, Nomade, et al. (2012)POP3 106.2±1.3 X-5 Giaccio, Nomade, et al. (2012)

105±2 Allen et al. (1999)POP4 X-6 Author’s unpublished data

108.9±1.8 Iorio et al. (2013)SUL5 SUL-PR 457.4±1.7 Giaccio, Arienzo, et al. (2013)

Pozzolane Rosse Giaccio, Arienzo, et al. (2013),Freda et al. (2011)

457±4 (recalculated) Marra et al. (2009)MT3 Sabatini Fall A This present study, Giaccio et al. (2014)

Mercure SC3 Giaccio et al. (2014)499±3 Marra et al. (2014)

SUL1-5 Tufo Bagni Albule Giaccio, Arienzo, et al. (2013)527±2 Marra et al. (2009)

SUL6 SUL2-1 722.8±2.4 Parmenide ash Giaccio, Castorina, et al. (2013)719.5±12.6 Ciaranfi et al. (2010)

SUL2-15 773.7±1.6

SUL2-16 781.3±2.3 Sagnotti et al. (2014)

SUL2-22 791.9±1.9

SUL2-29 813.8±3.3 Giaccio, Castorina, et al. (2013)

4 P. Galli, B. Giaccio, E. Peronace, and P. Messina

multilayer. Most of these are inherited Pliocene reverse struc-tures (Giovannelli, 1992) that appear to have been inverted asgravity faults during the Early Pleistocene tectonic uplift of theMorrone ramp anticline and that later accommodated—at muchlower rates—the northeast–southwest Middle–Late Pleistocenecrustal extension (e.g., in Patacca et al., 2008). The easternsplay runs mainly at 1100–1200 m.a.s.l. in the northern partof the massif, and it is revealed by an impressive, 25–35 m highrock fault scarp that was sculpted in the Jurassic limestone (ⒺFigs. S4, S5). In the hanging wall, this splay drags and cuts athick sequence of cemented slope debris that appears to haveformed during the cold and arid phases of the Last Glacial (Gal-adini and Galli, 2000). In turn, the main western fault runsalong the entire base of the foothill, roughly between 300 and400m.a.s.l., from the northern outskirts of the town of Popoli toPacentro village. Near Roccacasale, it is revealed by a rock faultscarp that shows a smoothly polished slickenside (e.g., in Bon-cio et al., 2012), with almost pure dip-slip striae.

Most of the surficial evidence of the basal splay ismasked or buried below the several, coalescing alluvial fansof units SUL3 and SUL2 that form a thick apron, the distallimb of which rests over the UST (Fig. 1a). Here, quarry andgully exposures have revealed the meter-scale displacementsof the SUL3 fan gravels, even along north–south transferfaults between the major en echelon strands (e.g., Vittoriet al., 1995; Miccadei et al., 1998).

Finally, in the northern Sulmona basin, our new inves-tigations allowed the identification of a set of en echelon an-tithetic splays that accommodate the eastward downthrow ofthe hanging wall of the SF. Here the antithetic system hasslipped almost at the same rate as the master fault, as shownby the above-described correlative SUL5-1c and MT3 tephralayers (Fig. 1a, number 5) that lie at similar elevation in thetwo sides of the hanging wall (profile S6 in Fig. 1d).

Paleoseismological Analyses

Based on this revised stratigraphic and geomorphologi-cal background, we focused our studies along the fault seg-ments that were not totally buried by both the alluvial conesand the debris flows. This occurred in the northernmost sec-tor of the Sulmona Plain, near the Popoli basin outlet (∼250m.a.s.l.), where the UST has been dismantled by the retro-gressive erosion of the Aterno fluvial network. This resultedin the progressive lowering of the basal level of LatePleistocene–Late Glacial fans by ∼100 m (Ⓔ Fig. S6). Here,at the deeply entrenched mouth of the Malepasso Valley, thehanging remnant of the Santopadre alluvial fan apex (box Bin Fig. 1a; Fig. 2a) is cut by a fault scarp with a vertical sep-aration of 13.5 m. This value, which we obtained throughgeodetic leveling (profile S5 in Fig. 2), represents the mini-mum offset, as the total vertical separation on the abandonedfan surface might be greater due to an unknown amount ofhanging wall that is buried by younger colluvia and to con-temporary footwall erosion. The Santopadre cone shows evi-dence of at least four different alluvial depositional/erosional

phases, with each one related to a different level of the plainand with the younger terraces (stages II–III, SUL2) progres-sively carved into the older and higher one (stage IV, SUL3).At present, a telescopic cone gently widens in the AternoRiver plain (∼250 m.a.s.l., the same elevation as the basinoutlet; I in Fig. 2a), whereas the oldest and highest one (IVin Fig. 2a) has a relic top surface that reaches to ∼400m.a.s.l.in the hanging wall, which implies an original base level thatmatched the UST (locally at 340 m.a.s.l.). The minimum ageof the oldest, faulted fan is robustly constrained by thefoiditic Albano-7 tephra (MT2) that outcrops extensively∼3–4 m below the original top surface of its apex (black starsin Fig. 2a), as in many other outcrops below the whole of theUST or in other alluvial fans (number 2 in Fig. 1a; Giaccioet al., 2007; Gori et al., 2011).

Along the northern tail of the Santopadre fan, where itjoins and interdigitates with the Colle Ferrano slope wash(Fig. 2a), the fault is revealed by a subdued scarp that hasbeen deeply reshaped, and has retreated uphill by millennial(e.g., post-Neolithic) agricultural activities. The scarp trendhighlights here the presence of two en echelon segments thatoverlap by ∼200 m. We decided to open here the first of fourpaleoseismological trenches that were preceded by an ERTanalysis and by some high-precision topographic leveling(T1–T4, E1, S1–S4, respectively, in Fig. 2a).

The ERT results (see Galli, Giaccio, et al., 2013) showeda sharp lateral contact at depth between terrains with differentresistivities, which possibly reflects the faulting of the fan grav-els (i.e., >300 ohm·m) against silty colluvia (<30 ohm·m).In turn, the four topographic profiles (profiles S1–S4 in Fig. 2)confirmed the offset measured at the fan apex (profile S5 inFig. 2), giving ∼12 m of vertical separation of the fan topsurface across both segments. Indeed, in the overlap zone,this offset is the sum of the discrete displacements of thetwo segment tips (e.g., 4:5 m� 7:5 m; profile S2 in Fig. 2),whereas it strongly decreases in the east–west strand of thestepover (5.5 m in S3) where the slip should be partly accom-modated by right-lateral motion. Also in these cases, the ver-tical separation should be added to an unknown amount ofburied hanging wall.

Trench 1

This ∼30 m long, >4 m deep excavation was openedinside an olive grove (T1 in Fig. 2a; Ⓔ Fig. S7). Its locationwas based on the ERT results, because the secular agriculturalactivities had erased the scarp traces here. The walls exposedwell-stratified alluvial fan and massive debris flow deposits(footwall units 8 and 6, and unit 5, respectively, in Fig. 3) ofthe oldest Santopadre fan stage (IV in Fig. 2a) that are offsetacross several fault strands against younger, faintly cemented,alluvial sands (unit 4 in Fig. 3), as well as slope- and scarp-derived colluvia (hanging-wall units 3 and 2;Ⓔ Figs. S8–S9).The whitish, carbonate fan gravels contain a hazel, sandy level(unit 7), which is slightly pedogenized and eroded upward bycoarse, sandy gravels, with an indurated horizon at the

Holocene Paleoearthquakes and Early–Late Pleistocene Slip Rate on the Sulmona Fault (Central Apeninnes, Italy) 5

interface (unit 6b). Unit 7 is an aborted paleosol; together withthe coarse sandy infilling of paleocanal unit 6a, this containsabundant volcanic ash that has been reworked from the 36 kaAlbano-7 tephra layer. The hanging wall has a strip of stronglydeformed deposits that are dragged along the main 65°-dip-ping fault plane (unit 3a), as well as one sharp fissure that cutinto the orange alluvial sands of unit 4 (fault B) and is filled by

the dark-brownish silty sands of the above pedogenized col-luvium (unit 3). Another wide, wedge-shaped fissure openedin unit 3 and was filled by the reddish, sandy unit 2c′, whereastwo coherent blocks of unit 4 (or derived from this, as block4a) were dragged along the fault zone and/or floated withinunit 3. Secondary faults/fractures affect units 3 and 4 but aretruncated upward by the erosional surface that separates units

Figure 2. (a) Details of the Santopadre alluvial fan; see the index map in (b) and box B in Figure 1a. I–IV, alluvial phases; V, late MIS 5lacustrine mud; S1–S5, topographic leveling; T1–T4, location of paleoseismological trenches; E1, electrical resistivity tomography; light stars,outcrops of tephra layers C-22, X-5, and X-6, dated at 92.4, 106.2, and 108.9 ka, respectively; and black stars are Albano-7 tephra, dated at∼36 ka.Geological profiles for S1, S2, and S5 are shown in the lower panels of (a). The color version of this figure is available only in the electronic edition.

6 P. Galli, B. Giaccio, E. Peronace, and P. Messina

2 and 3. On the whole, the faulting and warping has affectedall of the horizons, except for the uppermost relic layer of unit2 and for unit 1, which in turn, truncates and seals the entiresuccession. However, some secondary fault strands do not cutthe succession affected by the main fault, as they are sealed byintermediate or deeper layers, such as by unit 5 in the footwallor units 3 and 2c in the hanging wall.

Trench 2

We opened this 15 m long, and 3.5 m deep trench a fewmeters northwest of the previous trench, in the same olivegrove. The stratigraphic succession is similar to trench 1,as the geometry of the deformation is both brittle (with amain fault dragging the oldest Santopadre fan gravels inthe footwall and the colluvia in the hanging wall) and ductile(with a gentle warping of the hanging-wall units that causedtheir upward truncation as they neared the fault) (Figs. 4 andⒺ S10). The main feature that makes the difference here isthe preservation of the uppermost layers of unit 2 near thefault zone, which was very thin or was lacking in trench 1.Indeed, as well as some fault splays that cut through unit 2c,this trench exposed a well-preserved scarp-derived colluvialwedge (unit 2b and CW in the inset photograph in Fig. 4),which deposited at the foot of the free face that was gener-ated by the last surface rupture (almost entirely dismantled),sealing the fault A strands below.

Trench 3

We made the third excavation a dozen meters away fromthe second trench, inside a thick scrub of holm oaks andbrooms. Basing on vintage air photographs (1945 Royal AirForce images), this terrain has not been cultivated for morethan 70 years, thus avoiding the presence of deep ploughingand/or reworking of the upper layers in the fault zone. Wedug a short, 5 m long, and 2.5 m deep pit here across theassumed fault trace that exposed roughly the same alluvialsuccession as trenches 1 and 2 in the footwall and analogousreddish and brownish colluvia in the hanging wall (Figs. 4andⒺ S11). Because of the thinner reworked layer (less than0.5 m), the upper horizons of unit 2 are more preserved here,and they clearly mantle the whole footwall, sealing all of thefault strands and then thickening in the hanging wall.

Trench 4

This 25 m long trench was dug across a different faultsegment, 300 m northwest of the previous trenches (T4 inFig. 2). Here the fault scarp was ∼11 m high, and the faultintersects the surface 15 m away from the foot of the cliff(profile S1 in Fig. 2). The trench was 4–5 m deep, and itexposed well-organized alluvial fan gravels in the footwall(units 6 and 8 in Fig. 5; i.e., the oldest Santopadre fan stage,with Mousterian flint artifacts) that were faulted againstalluvial sands (unit 4) and stratified slope colluvia (units 3and 2), similar to colluvia 3 and 2 in trenches 1–3. Three

Figure 3. Trench log of the southern wall of trench 1 (see Fig. 2a for location). Samples labeled with asterisks were collected in trenchT2, in the same stratigraphical position. Photographic inset (a) is a detail of the fault zone (net 1 m) and (b) is the view looking east of theuphill side of trench 1. The color version of this figure is available only in the electronic edition.

Holocene Paleoearthquakes and Early–Late Pleistocene Slip Rate on the Sulmona Fault (Central Apeninnes, Italy) 7

prominent CWs made up of coarse carbonate gravels fallenfrom the coseismic free faces in units 6 and 8 were faulted anddragged along the fault zone (units 5, 3a–3a′, and 2c′–2c″),which probably indicates four surface-faulting events (ⒺFigs. S12–S13). Surprisingly, we also found traces of a humansettlement over the eroded top of unit 3, which appeared to be ahut floor with traces of fire (abundant charcoal) and with regu-lar prismatic stones and pottery shards that dated from betweenthe Early andMiddle Bronze Ages (3600–3800 B.P.; M. Rolfo,personal comm., 2014; unit 2h). Thewhole colluvia successionwas faulted and dragged by the main fault, apart from unit 1(the present soil) and probably the upper layers of colluvium 2,which has been eroded over the fault zone.

Age Constraints and Surface Ruptures Timing

As well as the robust age indication that was provided bythe 36 ka Albano-7 tephra (predating unit 7 in trench 1), we

collected several bulk and charcoal samples from the trenchwalls for radiocarbon dating, which together with the potteryshards, provided a reliable time constraint to the exposedunits, and consequently, for the individuated rupture events.Sixteen accelerator mass spectrometry dates constrain the en-tire colluvial sequence of the hanging wall between 9.4 kyB.P. and the Modern Age, allowing the definition of the timespan for each of the units (Table 1, see 2σ calculated ages andother details). Briefly, unit 3 was deposited between 9.4 kyB.P. (bottom of fault B footwall in trenches 1 and 2) and atleast 6.4 ky B.P. (middle-upper portion in the hanging wall intrench 4). Considering that this is a pedogenized colluvium,the radiocarbon age of the organic portion of the sedimentshould be roughly representative of this unit. The over-laid unit 2c, which unconformably truncates unit 3, has anage of ∼5 ky B.P. at the bottom and ∼4 ky B.P. at thetop. In trench 4, this extends into the Bronze Age, as testified

Figure 4. Sketch logs of southern wall of trenches 2–3 (T2–T3; see location in Fig. 2a). Samples labeled with asterisks were collected intrench T1, in the same stratigraphical position. The photographic inset shows details of the fault zone of trench T2, with the colluvial wedge(CW) 2b indicating the ultimate event. Labels are as in Figure 3. The color version of this figure is available only in the electronic edition.

8 P. Galli, B. Giaccio, E. Peronace, and P. Messina

by both the radiocarbon dating (∼3:5 ky B.P.) and the potteryshards. We interpreted the chronological hiatus betweenunits 3 and 2 as an unconformity boundary due to slope in-stability; this is typical of some abrupt climate cooling eventsthat were recorded during the Holocene thermal maximum(11–5 ka), which occurred around 8.2 and 5.5 ka (Kobashiet al., 2007; Müller et al., 2012).

In the hanging wall of fault A, CW 2b overlays unit 2c′

(trench 2) and has an age of 80–130 A.D. (2σ cal. age).Above these, and above the overlaid layer 2a—which is astone line that appears to testify to another sedimentary hia-tus—the reddish colluvia of unit 2 includes three historicalages, as well as the generic Roman pottery shards and tile frag-ments (trench 3). The time span bounded by these samplesextends from 80–240 A.D. (2σ cal. age) to 650–710 A.D.(2σ cal. age), with a further age of 1630–1670 A.D.(2σ cal. age) collected above an important erosional surfacebetween units 2 and 1 (1450–1640 A.D. in trench 4, in whichunit 2 had not been mixed into the ploughed layer). On thewhole, all of these ages allowed the entire faulted successionto be placed within the end of the Late Pleistocene and up tohistorical times. In particular, the footwall in the three trenchescontains mainly the ∼36 ka fan gravels, which were faultedagainst Middle–Late Holocene and Roman deposits andfinally sealed by Middle Age–Modern colluvia.

Because of the proximity of the four trenches, it seemsobvious that as well as sharing the same stratigraphy, thesealso share the same earthquake history, as proposed hereinand as summarized in Figure 6, which shows the samples’ages and their interpretations in terms of ante, post, andad quem termini. The last rupture event (Eq1 in Fig. 6) intrenches 1–3 caused both the faulting of the uppermost layers

of the exposed succession (up to unit 2c) and the formationof CW 2b, dated 80–130 A.D. (2σ cal. age). This was sealedby unit 2, the bottom of which is dated 80–240 A.D. (2σ cal.age). Therefore, considering the former as the terminus adquem (or, alternatively, post quem, if the age should belongto the parent material from which the colluvium originated)and the latter as the terminus ante quem, the paleoearthquakeoccurred very close or slightly after 80–130 A.D. and before80–240 A.D. We can approximate that it occurred in the sec-ond half of the second century A.D.

A penultimate event (Eq2 in Fig. 6) is testified by thepresence of a faulted colluvium that filled a funnel-shapedfissure in trenches 1 and 2 (unit 2c′ in Figs. 3 and 4), justbelow CW 2b (faults A–A′). The filling material is indistin-guishable from its parent material (unit 2c), which at the timewas also in the footwall. Its age is subsequent to that of char-coals pop8–pop9 (average 2σ cal. age is 5280–4970 B.P.)and preceded that of the detrital charcoal pop17c (4150–3980 B.P.; 2σ cal. age). In trench 4, CW 2c″ has an agebounded between 5580 and 3370 ky B.P. (pop27–pop28),and it was formed well before the Bronze settlement. There-fore, it can be fixed at around 4.5 ky B.P. (Figs. 5 and 6).

The previous event (Eq3) is not well constrained intrenches 1–3, either geometrically or temporally, but it is wellrepresented in trench 4 by CW 3a (Fig. 5). It is possibly seenin trench 1, where a wedge of coherent sands of unit 4 (4a inFig. 3) is seen within unit 3, as it was successively faultedand dragged along fault A–A′. In trench 3, it can be seen bythe faulted wedge between units 3 and 8 (Fig. 4), which ismade up from deposits colluviated from the footwall andmainly belonging to the alluvial gravels and sands of unit 4.However this will have occurred between 8450 and 6315 ky

Figure 5. Sketch log of southern wall of trench 4 (see location in Fig. 2a). Samples labeled with asterisks were collected in the northernwall of this trench, in the same stratigraphical position. The color version of this figure is available only in the electronic edition.

Holocene Paleoearthquakes and Early–Late Pleistocene Slip Rate on the Sulmona Fault (Central Apeninnes, Italy) 9

B.P., as indicated by the age of samples pop21–pop20 intrench 4 (Figs. 5 and 6).

The oldest datable paleoearthquake (Eq4) is revealedwell by the deep fissure along fault B in trench 1, and bythe associated offset of the top of unit 4. The faulting intrenches 1 and 2 was sealed by unit 2c, which appears to haveoccurred after the deposition of the bottom of unit 3 (dated at9440–9149 B.P.) and during the deposition of the same unit(∼8980–8600 B.P., or slightly after), which also fill the frac-ture. In trench 4, this event is suggested by fault B, which wassealed by unit 3a before 8450–8370 B.P. In other words, thisoccurred around or slightly after 9 ky B.P. (Fig. 6).

A previous event (Eq5; not in Fig. 6) can be inferred bythe presence of CW 5 in trench 4. However, its age cannot beconstrained; we can only suggest that it happened well before9440–9140 B.P. and also before the deposition of unit 4.

Long-Term to Short-Term Slip Rate, Recurrence, andElapsed Time

Topographic profiles across the gently dipping top sur-face of Early Pleistocene breccias hanging over the westernfault scarp (areas labeled a in Fig. 1a; outer edge at 800�100 m.a.s.l.) show vertical separations of 475� 75 m withrespect to the elevation reached by the same breccias in thehanging wall (i.e., areas labeled a in Fig. 1a in the Raianoarea, ∼250 m.a.s.l.). As these breccias are older than 800 ka,and as they appear to be contemporary to analogous brecciasthat outcrop ubiquitously in the Abruzzo chain with a reversalmagnetic signal (∼1� 0:2 Ma; see D’Agostino et al., 1997;Galli et al., 2012, and reference therein; Giaccio, Arienzo,et al., 2013), we can estimate a long-term slip rate of 0:5�0:15 mm=yr across the western main splay (Table 3), or evenmore hypothesizing the deepening of the sediments close tothe normal fault. In the middle term, apart from the MiddlePleistocene breccias near Pacentro (areas labeled b in Fig. 1a)that are offset by ∼130 m (160 m in Gori et al., 2011; in

Table 3, we tentatively correlate these breccias to fluvial de-posits near Raiano dated around 450 ka; Giaccio, Galli, et al.,2012), we did not find correlative deposits in the footwall ofthe main fault. Nevertheless, because topographic profilesacross the antithetic faults facing Popoli show a vertical sep-aration of ∼35 m between the same tephra layer dated∼92 kyB.P. in the horizontal, lacustrine mud strata (number 4 inFig. 1a; C-22 in Fig. 1b,c), we can assume a minimum0:4 mm=yr slip rate during the Late Pleistocene. Moreover,topographic leveling across the fault scarp at the Santopadrefan apex (S1–S5 in Fig. 2) shows vertical separations of 12–13.5 m; as the top surface depositional age is younger than∼36 ka, and by adding theminimum 3–4m of the hanging-wallburial observed in the trenches (units 1–3 in Figs. 3–5), here theslip rate is∼0:5 mm=yr. Finally, the data from the trenches pro-vide evidence for a minimum vertical offset of ∼4 m in the past∼9 ka, which gives a Holocene slip rate of >0:45 mm=yr.Altogether, these data show a constant ∼0:5 mm=yr verticalslip rate of the main SF from the end of the Early Pleistoceneto the present, whereas we did not find indications for the evalu-ation of the eventual contribution of the eastern fault splay.

On the other hand, we cannot evaluate the finite slip perevent in the trenches, because we do not have either the cor-relative layers across fault A (trenches 1, 2, and 4) or the origi-nal thickness of the CWs. However, as the total vertical offsetobserved in the trenches is >4 m, each of the four events hada vertical displacement of ∼1 m, on average. For instance, onone hand, this fits with the offset of unit 4 across fault B(which we have related to the oldest event of Eq4 in trench 1),and on the other hand, it fits with the minimum preservedthickness of CW 2b (>0:6 m in trench 2 of Fig. 4; Eq1 inFig. 6) or 2c″ (>1 m in trench 4 of Fig. 5; Eq2 in Fig. 6).

The dating of the four paleoearthquakes revealed by thefour trenches (Eq1–4 in Fig. 6) also allows an average recur-rence time to be estimated for these characteristic earthquakeson the SF. By dividing the entire interval between the Eq4 and

Figure 6. Chronogram of the surface-rupture events identified from within the four trenches. Each radiocarbon sample is reported with its2σ calibrated interval. Tones suggest ad quem (black), post quem (dark), and ante quem (light) terms. Bronze age pottery (T4) and MiddleAge-Modern pottery (T1–T3) are also shown. Horizontal arrows point to the assumed paleoevent age (dashed if related to uncertain in-dication). Vertical bars suggest the most probable earthquake interval (Eq1–Eq4), as deduced from the samples age and considering the natureof the surrounding deposits (see text for further details). The color version of this figure is available only in the electronic edition.

10 P. Galli, B. Giaccio, E. Peronace, and P. Messina

Eq1 and considering also the single or partial intervals be-tween event pairs, the recurrence time is 2:4� 0:2 ky. There-fore, as the elapsed time since the last event is ∼1850 yr, itappears likely that the next big earthquake will occur in thenext 600� 200 years.

Discussion and Concluding Remarks

The revision of the Late Pleistocene stratigraphic evolu-tion of the Sulmona basin (which we have defined based onboth new tephra analyses and chronometric dating), coupledwith the observations from the Santopadre fan trenches, pro-vide original information on the slip rates, timing, and sizeof the Holocene surface-rupturing earthquakes on the SF.Although previous studies hypothesized the possible activityof this structure, the present data on one hand fully confirmthe silent state of the eastern central Apennine fault systemand on the other quantify its potential seismic hazard.

Indeed, the new insights into the Quaternary geology ofthe basin allowed us to first evaluate the SF slip rate for dif-ferent time windows, which consistently indicates around0:5 mm=yr. This relatively low rate accounts for the longreturn time for surface-rupturing events along the SF (ratedhere at ∼2:4 ky), at least if compared with other primary,paleoseismologically investigated faults in the Apennines;for example, 0:8–2:8 mm=yr, with return times also of a fewcenturies (Galadini and Galli, 2000; Galli and Galadini,2003; Galli and Naso, 2009; Galli, Peronace, et al., 2013;Galli and Peronace, 2014). However, it is worth noting thatthis rate is related to the main western fault, as we found noindications of rejuvenation along the shorter and discontinu-ous eastern splay, which today can only have a passive rolewithin the extensional process that is probably enhanced bygravity-driven phenomena (Gori et al., 2014).

Indeed, by matching the observations and combining theevidence from the exposure of the four trenches, this pro-vides a record of a most recent event that occurred in the

middle of the second century A.D. (Eq1), a penultimate eventaround 4.5 ka (Eq2), a second-from-last event between 8.4and 6.4 ka (Eq3), and a most distant event around 9 ka (Eq4).An event that is older still occurred before 9.5 ka (Eq5). Inthe lack of correlative layers and well-preserved CWs, weestimated an average slip per event of ∼1 m or more, whichwhen coupled with the surface length of the SF (23 km) sug-gests Mw 6:7� 0:1 (i.e., Mw 6.66 according to Wells andCoppersmith, 1994;Mw 6.76 according toWesnousky, 2008;and Mw 6.56 according to Galli et al., 2008).

Obviously, all of these earthquakes are not reported inany seismic collection, and even the last one (dated in his-torical time) was not recorded by any classic literary source.Indeed, this applies to all but one of these sources, becausethere is a Roman epigraph (CIL IX, 3046, from Interpro-mium in Fig. 1a and dated to the second century A.D.;Ⓔ Fig. S14; see Data and Resources) that mentions a dis-ruptive earthquake, the damage from which was repairedby Primus and Fortunatus, two freemen (liberti) of the Ro-man Sulmo. Starting from this evidence, Galadini and Galli(2001) collected robust indications of extensive and contem-porary collapse and restoration in the ancient Sulmona andfor several other archaeological settlements of the plain (e.g.,Corfinio, Raiano, Cansano, Hercules Curinus sanctuary, andrelated buildings at Fonte d’Amore; Fig. 1a). All were dat-able around halfway through the second century A.D. (e.g.,coins of Antoninus Pius, 138–161 A.D., were buried belowthe collapse) and allow the hypothesis of the occurrence of astrong earthquake that was probably caused by the SF. This isa rare and outstanding case in which archaeoseismic and pa-leoseismic results provide independent evidence for the sameunknown earthquake, indicating a consistent age, damagescenario, and magnitude.

Today the SF dips beneath a highly populated alluvialplain, with >50;000 inhabitants in the area. Considering boththe high vulnerability class of the old building estate, and thehigh shaking effects that would be induced by the SF rupture if

Table 3Slip Rate of Different Geological Features Displaced by the Sulmona Fault

Period Geological Feature Age (ka) Offset (m) Slip Rate (mm/yr)

Long term Early Pleistocene Morrone slope breccias* ∼1000� 200 475±75 0.5±0.15Middleterm

MiddlePleistocene

Pacentro slope/fan breccias† (<457)‡ ∼130 (>0:3)

Late Pleistocene Popoli MIS 5 lacustrine mud with tephra layer C-22§ ∼92 ∼35‖ >0:4Short term Late Pleistocene Santopadre alluvial fan (stages IV) with Albano-7 tephra# <36 12–13.5±3–4 0.45±0.05

Holocene 14C dated colluvia (paleoseismological trenches)** ∼9 ∼4 >0:45

Uncertain data are indicated in brackets.*Areas labeled a in Figure 1a.†Areas labeled b in Figure 1a.‡Age presumed by correlating with fluvial deposits which contain Pozzolane Rosse tephra (∼457 ka near Raiano; see Giaccio, Galli, et al., 2012;Giaccio et al., 2014).§Labeled number 4 in Figure 1a.‖Offset measured across an antithetic splay.#Labeled number 2 in Figure 1a.**T1–T4 in Figure 2.

Holocene Paleoearthquakes and Early–Late Pleistocene Slip Rate on the Sulmona Fault (Central Apeninnes, Italy) 11

an earthquake like those investigated in our trenches were tooccur on this fault now, it would result in a very severe damagescenario. This would be likely to involve massive collapse,with many inhabitants caught in the ruins, both in the SulmonaPlain and in the neighboring zones.

Data and Resources

All data used in the present study were collected duringthe duration of this study or came from published sourceslisted in the references. The electron microprobe analysiswas carried out at the Istituto di Geologia Ambientale e Geo-ingegneria of the Consiglio Nazionale delle Ricerche (IGAG-CNR) (Rome, Italy) using a Cameca SX50 electron microp-robe equipped with a five-wavelength dispersive spectrometer.Information on macroseismic data is in the Italian Macroseis-mic Database (version DBMI11), available at http://emidius.mi.ingv.it/DBMI11 (last accessed January 2014). The Calibprogram for 14C calibration age (version 6.0html) is availableat http://calib.qub.ac.uk/calib/ (last accessed January 2014).Information on Roman inscriptions is available in Corpus In-scriptionum Latinarum (CIL), Berlin-Brandenburg Academyof Sciences and Humanities, at http://cil.bbaw.de/cil_en/index_en.html (last accessed January 2014).

Acknowledgments

The authors are grateful to the municipality of the town of Popoli andin particular to F. Visconti who helped to provide all of the permissions andfacilities for the excavation of the trenches; B. Quadrio who helped in trenchlogging and topographic leveling; to G. Gregori who gifted us with his kindexpertise on the age of the Roman epigraph attesting to the earthquake; andto M. Rolfo who kindly studied the pottery shards. The constructive criticismof the associate editor and of an anonymous reviewer helped us to improvethe quality of the original manuscript. The views and conclusions containedhere are those of the authors and should not be interpreted as necessarilyrepresenting official policies, either expressed or implied, of the ItalianGovernment.

References

Allen, J. R. M., U. Brandt, A. Brauer, H. W. Hubberten, B. Huntley, J. Keller,M. Kraml, A. Mackensen, J. Mingram, J. F. W. Negendank, N. R.Nowaczyk, H. Oberhänsli, W. A. Watts, S. Wulf, and B. Zolitschka(1999). Rapid environmental changes in southern Europe during thelast glacial period, Nature 400, 740–743.

Boncio, P., P. Galli, G. Naso, and A. Pizzi (2012). Surface fault rupturehazard along normal faults: Insight from the 2009 L’Aquila earthquake(Mw 6.3, central Italy), observations from global normal faulting earth-quakes and implications for earthquake fault zoning, Bull. Seismol.Soc. Am. 102, 918–935.

Ciaranfi, N., F. Lirer, L. J. Lourens, P. Maiorano, P. Marino, M. Petrosino, P.Sprovieri, M. Stefanelli, S. Brilli, M. Girone, A. Joannin, S. Pelosi, andN. Vallefuoco (2010). Integrated stratigraphy and astronomical tuningof lower-middle Pleistocene Montalbano Jonico section (southernItaly), Quaternary Int. 219, 109–120.

D’Agostino, N. (2014). Complete seismic release of tectonic strain andearthquake recurrence in the Apennines (Italy), Geophys. Res. Lett.41, doi: 10.1002/2014GL059230.

D’Agostino, N., F. Speranza, and R. Funiciello (1997). Le brecce Mortadelladell’Appennino Centrale: Primi risultati di stratigrafia magnetica, IlQuaternario 10, 385–388.

Deino, A. L., G. Orsi, M. Piochi, and S. de Vita (2004). The age of theNeapolitan Yellow Tuff caldera-forming eruption (Campi Flegrei cal-dera, Italy) assessed by 40 Ar=39 Ar dating method, J. Volcanol.Geoth. Res. 133, 157–170.

Freda, C., M. Gaeta, B. Giaccio, F. Marra, D. M. Palladino, P. Scarlato, andG. Sottili (2011). CO2-driven large mafic explosive eruptions: ThePozzolane Rosse Case Study from the Colli Albani volcanic district(Italy), Bull. Volcanol. 73, 241–256.

Freda, C., M. Gaeta, D. B. Karner, F. Marra, P. R. Renne, J. Taddeucci,P. Scarlato, J. Christensen, and L. Dallai (2006). Eruptive historyand petrologic evolution of the Albano multiple maar (Alban Hills,central Italy), Bull. Volcanol. 68, 567–591.

Galadini, F., and P. Galli (1999). The Holocene paleoearthquakes on the1915 Avezzano earthquake faults (central Italy): Implications for activetectonics in the central Apennines, Tectonophysics 308, 143–170.

Galadini, F., and P. Galli (2000). Active tectonics in the central Apennines(Italy)—Input data for seismic hazard assessment, Nat. Hazards 22,202–223.

Galadini, F., and P. Galli (2001). Archaeoseismology in Italy: Case studiesand implications on long-term seismicity, J. Earthq. Eng. 5, 35–68.

Galadini, F., and P. Galli (2007). Inquadramento sismotettonico della regioneinteressata dai terremoti del 1703 e 1706, in Settecento abruzzese:Eventi sismici, mutamenti economico-sociali e ricerca storiografica,Atti del convegno L’Aquila, L’Aquila, Italy, 29–31 October 2004,17–41.

Galli, P., and F. Galadini (2003). Disruptive earthquakes revealed by faultedarchaeological relics in Samnium (Molise, southern Italy), Geophys.Res. Lett. 30, 1–4.

Galli, P., and G. Naso (2009). Unmasking the 1349 earthquake source(southern Italy): Paleoseismological and archaeoseismological indica-tions from the Aquae Iuliae fault, J. Struct. Geol. 31, 128–149.

Galli, P., and E. Peronace (2014). New paleoseismic data from the Irpiniafault. A different seismogenic perspective for southern Apennines(Italy), Earth Sci. Rev. 136, 175–201.

Galli, P., F. Galadini, and D. Pantosti (2008). Twenty years of paleoseismol-ogy in Italy, Earth Sci. Rev. 88, 89–117.

Galli, P., B. Giaccio, P. Messina, E. Peronace, B. Quadrio, J. Bellanova, andS. Piscitelli (2013). First paleoseismic result from the Mount Morronefault (Sulmona, central Apeninnes), in Atti del 32° ConvegnoNazionale, Trieste, Italy, 19–21 November 2013, Vol. 1, 53–58.

Galli, P., B. Giaccio, P. Messina, E. Peronace, and G. M. Zuppi (2011).Palaeoseismology of the L’Aquila faults (central Italy, 2009, Mw 6.3earthquake): Implications for active fault linkage, Geophys. J. Int. 187,1119–1134.

Galli, P., P. Messina, B. Giaccio, E. Peronace, and B. Quadrio (2012).Early Pleistocene to Late Holocene activity of the Magnola fault(Fucino fault system, central Italy), Boll. Geofis. Teor. Appl. 53,435–458.

Galli, P., E. Peronace, B. Quadrio, and G. Esposito (2013). Earthquakefingerprints along fault scarps: A case study of the Irpinia 1980 earth-quake fault (southern Apennines), Geomorphology 206, 97–106.

Giaccio, B., I. Arienzo, G. Sottili, F. Castorina, M. Gaeta, S. Nomade,P. Galli, and P. Messina (2013). Isotopic (Sr-Nd) and major elementfingerprinting of distal tephras: An application to the Middle-LatePleistocene markers from the Colli Albani volcano, central Italy,Quaternary Sci. Rev. 67, 190–206.

Giaccio, B., F. Castorina, D. Nomade, G. Scardia, M. Voltaggio, andL. Sagnotti (2013). Revised chronology of the Sulmona lacustrinesuccession, central Italy, J. Quaternary Sci. 28, 545–551.

Giaccio, B., P. Galli, P. Messina, E. Peronace, G. Scardia, G. Sottili,A. Sposato, E. Chiarini, B. Jicha, and S. Silvestri (2012). Fault and basindepocentre migration over the last 2Ma in the L’Aquila 2009 earthquakeregion, central Italian Apennines, Quaternary Sci. Rev. 56, 69–88.

Giaccio, B., P. Galli, E. Peronace, I. Arienzo, S. Nomade, G. Cavinato,M. Mancini, P. Messina, and G. Sottili (2014). A 560–440 ka tephrarecord from the Mercure basin, southern Italy: Volcanological andtephrochronological implications, J. Quaternary Sci. 29, 232–248.

12 P. Galli, B. Giaccio, E. Peronace, and P. Messina

Giaccio, B., F. Marra, I. Hajdas, D. B. Karner, P. R. Renne, and A. Sposato(2009). 40 Ar=39 Ar and 14C geochronology of the Albano maar de-posits: Implications for defining the age and eruptive style of the mostrecent explosive activity at Colli Albani Volcanic District, central Italy,J. Volcanol. Geoth. Res. 185, 203–213.

Giaccio, B., P. Messina, A. Sposato, M. Voltaggio, G. Zanchetta, F. Galadini,S. Gori, and R. Santacroce (2009). Tephra layers from Holocene lakesediments of the Sulmona basin, central Italy: Implications for vol-canic activity in peninsular Italy and tephrostratigraphy in the centralMediterranean area, Quaternary Sci. Rev. 28, 2710–2733.

Giaccio, B., S. Nomade, S. Wulf, R. Isaia, G. Sottili, G. Cavuoto, P. Galli,P. Messina, A. Sposato, R. Sulpizio, and A. Zanchetta (2012). The lateMIS 5 Mediterranean tephra markers: A reappraisal from peninsularItaly terrestrial records, Quaternary Sci. Rev. 56, 31–45.

Giaccio, B., A. Sposato, M. Gaeta, F. Marra, D. M. Palladino, J. Taddeucci,M. Barbieri, P. Messina, and M. F. Rolfo (2007). Mid-distal occur-rences of the Albano Maar pyroclastic deposits and their relevancefor reassessing the eruptive scenarios of the most recent activity atthe Colli Albani Volcanic District, central Italy, Quaternary Int.171/172, 160–178.

Giovannelli, A. (1992). Le unità carbonatiche circostanti la pianura diSulmona (AQ). Stratigrafia, analisi di facies e paleogeografia, Ph.D.Thesis, Università degli studi di Roma “La Sapienza.”

Giraudi, C., G. Zanchetta, and R. Sulpizio (2013). A Late-Pleistocene phaseof Saharian dust deposition in the high Apennine mountains (Italy),Alpine Medit. Quat. 26, 110–122.

Gori, S., E. Falcucci, F. Dramis, F. Galadini, P. Galli, B. Giaccio, P. Messina,A. Pizzi, A. Sposato, and D. Cosentino (2014). Deep-seated gravita-tional slope deformation, large-scale rock failure, and active normalfaulting along Mt. Morrone (Sulmona basin, central Italy): Geomorpho-logical and paleoseismological analyses, Geomorphology 208, 88–101.

Gori, S., B. Giaccio, F. Galadini, E. Falcucci, P. Messina, A. Sposato, andF. Dramis (2011). Active normal faulting along the Mt. Morronesouth-western slopes (central Apennines, Italy), Int. J. Earth. Sci.100, 157–171.

Iorio, M., J. Liddicoat, F. Budillon, A. Incoronato, R. S. Coe, D. Donatella,D. Insinga, W. Cassata, C. Lubritto, A. Angelino, and S. Tamburrino(2013). Combined palaeomagnetic secular variation and petrophysicalrecords to time constrain geological and hazardous events: An examplefrom the eastern Tyrrhenian Sea over the last 120 ka, Global Planet.Changes 113, 91–109.

Kobashi, T., J. P. Severinghaus, E. J. Brook, J. M. Barnola, and A. M.Grachev (2007). Precise timing and characterization of abrupt climatechange 8,200 years ago from air trapped in polar ice, Quaternary Sci.Rev. 26, 1212–1222.

Marra, F., D. B. Karner, C. Freda, M. Gaeta, and P. Renne (2009). ). Largemafic eruptions at Alban Hills volcanic district (Central Italy):Chronostratigraphy, petrography and eruptive behavior, J. Volcanol.Geotherm. Res. 179, 217–232.

Marra, F., G. Sottili, M. Gaeta, B. Giaccio, B. Jicha, M. Masotta, D. M.Palladino, and D. M. Deocampo (2014). Major explosive activity in

the Monti Sabatini Volcanic District (central Italy) over the 800–390 ka interval: Geochronological–geochemical overview and tephros-tratigraphic implications, Quaternary Sci. Rev. 94, 74–101.

Miccadei, E., R. Barberi, and G. P. Cavinato (1998). La geologia quaternariadella conca di Sulmona (Abruzzo, Italia centrale), Geologica Romana34, 59–86.

Müller, J., K. Werner, R. Stein, K. Fahl, M. Moros, and E. Jansen (2012).Holocene cooling culminates in sea ice oscillations in Fram Strait,Quaternary Sci. Rev. 47, 1–14.

Patacca, E., P. Scandone, E. Di Luzio, G. P. Cavinato, and M. Parotto (2008).Structural architecture of the central Apennines: Interpretation of theCROP 11 seismic profile from the Adriatic coast to the orographicdivide, Tectonics 27, doi: 10.1029/2005TC001917.

Sagnotti, L., G. Scardia, B. Giaccio, J. C. Liddicoat, S. Nomade, P. R.Renne, and C. J. Sprain (2014). Extremely rapid directional changeduring Matuyama–Brunhes geomagnetic polarity reversal, Geophys.J. Int. 199, 1110–1124.

Vittori, E., G. P. Cavinato, and E. Miccadei (1995). Active faulting alongthe northeastern edge of the Sulmona basin, central Apennines, Italy,in Perspective in Paleoseismology, L. Serva and B. D. Slemmons(Editors), Special Publication, Vol. 6, Association of EngineeringGeologists, Sudbury, Washington, 115–126.

Wells, D. L., and K. J. Coppersmith (1994). New empirical relationshipsamong magnitude, rupture length, rupture width, rupture area, andsurface displacement, Bull. Seismol. Soc. Am. 84, 974–1002.

Wesnousky, S. G. (2008). Displacement and geometrical characteristics ofearthquake surface ruptures: Issues and implications for seismic hazardanalysis and the earthquake rupture process, Bull. Seismol. Soc. Am.98, 1609–1632.

Dipartimento della Protezione Civile NazionaleVia Vitorchiano 400189 Rome, Italy

(P.G.)

Consiglio Nazionale delle Ricerche-Istituto di Geologia Ambientale eGeoingegneriaArea di Ricerca Roma 1Via Salaria km 29.3Montelibretti, Italybiagio.giaccio@cnr.itedoardo.peronace@igag.cnr.itpaolo.messina@cnr.it

(B.G., E.P., P.M.)

Manuscript received 28 January 2014;Published Online 2 December 2014

Holocene Paleoearthquakes and Early–Late Pleistocene Slip Rate on the Sulmona Fault (Central Apeninnes, Italy) 13