For Review Only

Italian Journal of Geosciences

A fresh look at the seismotectonics of the Abruzzi (Central Apennines) following the 6 April 2009 L’Aquila earthquake (Mw 6.3) For Review Only

Journal: Italian Journal of Geosciences

Manuscript ID: IJG-2011-0103.R1

Manuscript Type: Original Article

Date Submitted by the n/a Author:

Complete List of Authors: Vannoli, Paola; Istituto Nazionale di Geofisica e Vulcanologia, Sismologia e Tettonofisica Burrato, Pierfrancesco; Istituto Nazionale di Geofisica e Vulcanologia, Sismologia e Tettonofisica Fracassi, Umberto; Istituto Nazionale di Geofisica e Vulcanologia, Sismologia e Tettonofisica Valensise, Gianluca; Istituto Nazionale di Geofisica e Vulcanologia, Sismologia e Tettonofisica

6 April 2009 L’Aquila earthquake, Seismogenic Sources, Active faults, Keywords: Active tectonics, Abruzzi region

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1 2 3 A fresh look at the seismotectonics of the Abruzzi (Central Apennines) 4 following the 6 April 2009 L’Aquila earthquake (M w 6.3) 5 6 Uno sguardo d’insieme alla sismotettonica abruzzese all’indomani del 7 terremoto de L’Aquila del 6 aprile 2009 (M w 6.3) 8 9 10 PAOLA VANNOLI, PIERFRANCESCO BURRATO, UMBERTO FRACASSI, 11 GIANLUCA VALENSISE 12 13 14 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Sismologia e Tettonofisica, Via di Vigna 15 Murata 605, 00143 Rome, Italy. 16 17 Corresponding author: 18 Paola Vannoli 19 Phone: +39 06 51860513 20 For Review Only 21 Fax: +39 06 51860507 22 E-mail: [email protected] 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1 2 3 4 ABSTRACT 5 6 7 This work aims at providing an updated and augmented view of present-day tectonics and seismogenic 8 sources of the Abruzzi Apennines, focusing on its extensional domain. This paper was spurred by the 6 9 April 2009, L’Aquila earthquake (M w 6.3), an event from which geologists learned important lessons – 10 including rather surprising ones. Although the earthquake was not major compared with other 11 catastrophic events that occurred in Italy and elsewhere, this destructive earthquake led to a thorough 12 13 review of the geometry - and style, in some instances - that characterises earthquake faulting in this 14 region. The poorly expressed field evidence of the 6 April event, especially in light of the damage it 15 caused in the mesoseismal area, stressed the intrinsic limitation of the earthquake geologists’ toolbox. 16 Abruzzi is the region of a true "seismological paradox": despite the rather long earthquake 17 history available for the region, the number of potential sources for earthquakes of M ≥ 6.0 proposed in 18 the literature is two to five times larger than the number of events that appear in the full earthquake 19 20 record. This circumstanceFor is made Review even more paradoxical Only by recent palaeoseismological work that 21 proposed recurrence times of only a few centuries for individual seismogenic sources. Do the evident 22 faults mapped by previous workers all correspond to potential seismogenic sources? 23 We aim at addressing this paradox by drawing an updated seismotectonic model of Abruzzi 24 based on the lessons learned following the 2009 earthquake. The model is based on selected 25 26 geological, geomorphological, seismological, historical and geodetic data and will ultimately feed an 27 updated version of the DISS database (http://diss.rm.ingv.it/diss/). 28 29 KEY WORDS : 6 April 2009 L’Aquila earthquake, Active faults, Seismogenic Sources, Active tectonics, 30 Seismic hazard, Abruzzi region, Central Apennines. 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1 2 1 1. INTRODUCTION 3 2 4 5 3 Having a potential for shallow M 7 earthquakes, the Abruzzi Apennines comprise one of the most 6 4 threatening seismogenic regions in Europe. Until recently, the active tectonics of this part of the 7 5 Apennines belt was believed to be especially well understood, which was seen as the basis for an 8 6 effective mitigation of the local seismic risk. The Abruzzi landscape is criss-crossed by a number of 9 10 7 faults of all sizes, and many of them show both evidence for sustained activity and credible 11 8 relationships with one of the many earthquakes that have struck this region historically. 12 9 The 6 April 2009, M w 6.3 L’Aquila earthquake challenged this belief. The surface expression 13 10 of its causative source turned out to be a barely visible fault mapped by only a few investigators, while 14 11 the more obvious faults nearby were not involved. Many scientists were taken by surprise also by the 15 12 geometry of the fault rupture, as the earthquake was caused by slip over a plane dipping around 45° 16 17 13 while most of the faults seen at the surface dip from 60° to subvertical, and by its depth which, from 18 14 aftershock data, extended from about 2.5-3.0 to 10 km. 19 15 The 2009 L’Aquila earthquake has spurred a number of studies - at least 100 papers have 20 16 already appeared in the For international Review literature in just twoOnly years - focusing on its source and the 21 17 relationships with the surface geology. Nevertheless we believe this earthquake calls for a careful 22 23 18 reconsideration of the geological and tectonic observations and models based on pre-2009 24 19 understanding of the seismotectonics of Abruzzi. Our paper aims at 1) reconstructing how this 25 20 understanding has developed throughout the past few decades, 2) establishing whether the knowledge 26 21 and wisdom accrued for other portions of Abruzzi is still acceptable in view of the lessons learned in 27 22 2009, and 3) verifying if there exists a model of the main seismogenic sources that is both reliable and 28 29 23 shared by most of the earthquake geology community. 30 24 31 25 1.1. MORE FAULTS , MORE EARTHQUAKES , MORE HAZARD ? 32 26 33 27 Perhaps the first scientific account on active faulting in Abruzzi is the report written by Emilio 34 28 Oddone, a physicist who devoted most of his career to the investigation of the Earth geodynamics, 35 36 29 following the catastrophic 13 January 1915, M w 7.0, intensity XI, Avezzano (Fucino, central 37 30 Apennines) earthquake (GRUPPO DI LAVORO CPTI, 2004). In the early days of seismology, when the 38 31 very nature of earthquakes was still being debated, ODDONE (1915) described the formation of several 39 32 strands of ground breaks that could not be explained as strictly surficial effects and that had to be 40 33 somehow related with the deep earthquake source. 41 42 34 After 1915, Abruzzi remained seismically quiet for many years. Furthermore, similar surface 43 35 effects were not reported following any of the earthquakes that occurred in the rest of the peninsula in 44 36 the following decades. Nevertheless, thanks to the vicinity of Rome with its many research centers and 45 37 to the beautifully exposed geology, Abruzzi became the focus of numerous geological investigations. 46 38 In the context of the preparation of the 1:100,000 geological map of Italy, the region offered a perfect 47 39 viewpoint for understanding how the Apennines were constructed, from the initial involvement of 48 49 40 open sea sediments of the Tethys ocean to its current fold-and-thrust configuration. In the 1940s 50 41 Abruzzi had become a playground for developing innovative tectonic models to be used in the 51 42 booming oil industry, such as the theory of tectonic wedges (“cunei composti”) by Tuscan geologist 52 43 MIGLIORINI (1948). Later on, ACCORDI (1966) used observations from Abruzzi faults and folds to 53 44 develop a model for the (“tettonica traslativa”) that would explain the major 54 translational tectonics 55 45 shortening and the simultaneous creation of thrust and normal faults in a typical fold-and-thrust-belt. 56 46 In the framework of the new interest for the hazard posed by active fault to major 57 47 infrastructures, in the 1970s Abruzzi became the target of new investigations on active faulting. Unlike 58 48 other similarly active areas of the Apennines, where the evidence for tectonic activity is much more 59 49 subdued, Abruzzi offered a large number and variety of faults that could be easily recognised even by 60 50 non-geologists. BOSI (1975) and BERTINI & BOSI (1978) mapped a number of active or potentially

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1 2 51 active faults (Fig. 1) in a large region stretching from the Apennines piedmont east of Rome to the 3 52 Adriatic coast. The faults shared the following characteristics: 4 53 mostly extensional, striking NW-SE and dipping at 50°-70° to the SW; 5 • 6 54 • individual strands seldom longer than 10 km; 7 55 • observed in bedrock (limestone), often perched at high elevation over the adjacent basin/valley 8 56 floor and lined by unconsolidated talus (scree); 9 57 • often marked by a white ribbon of fresh limestone (“ nastrino di faglia ”, fault ribbon) contrasting 10 58 with the grey colour of the rest of the fault plane and of the adjacent bedrock; 11 12 59 • often seen to mimic the orientation and length of the main thrusts, but never cutting beyond their 13 60 ends. 14 61 15 62 The faults mapped by BOSI (1975) and BERTINI & BOSI (1978) indeed agreed with the 16 63 extensional regime currently active along most of the Apennines. Yet, the mapped faults were not 17 18 64 considered to be the source of the largest earthquake but rather “ ….faults that are believed to be 19 65 significant for identifying the deeper shear zone that generates earthquakes... ” (BOSI , 1975). Although 20 66 in those days the perceptionFor of fault Review scaling relationships Onlywas crude, this belief was correct and in fact 21 67 rather wise. According to current catalogues, the region under investigation suffered at least five 22 68 earthquakes of M 6.0 or larger over the past four centuries, an interval for which the information on 23 24 69 damaging earthquakes is considered complete over the entire country (STUCCHI et alii , 2004). Even 25 70 assuming that all of these earthquakes were generated by surface-breaking faults, based on current 26 71 empirical relationships (e.g. WELLS & COPPERSMITH , 1994) each one of them would justify the 27 72 existence of a single fault with a length of 10-30 km. In contrast, and purely based on fault length, 28 73 several maps and compilations that discuss active faulting in the extensional core of the Abruzzi 29 74 Apennines show a number of potential sources for earthquakes of M 6.0 from two up to perhaps five 30 ≥ 31 75 times larger, depending on the author(s), on the size of the study area and on when the interpretation 32 76 was presented (more recent papers tend to present fewer large potential sources). Notice that the above 33 77 reasoning does not take into account: 1) expected fault width from scaling relationships, 2) the 3D 34 78 geometrical relationships among closely-spaced faults (i.e., when lateral distance is 2-3 km or less and 35 79 almost one order of magnitude smaller than fault length), and, consequently, 3) possible fault 36 37 80 interaction and mutual stress shadow (see HARRIS , 1998; KENNER & SEGALL , 1999) . If each one of 38 81 these faults slips at 0.5 to 1.2 mm/a and has generated its largest earthquake every 1,000-2,000 years, 39 82 as commonly accepted based on palaeoseismological studies (GALLI et alii , 2008; see also BASILI et 40 83 alii , 2008; DISS WORKING GROUP , 2010, and references therein), and assuming a characteristic 41 84 earthquake behaviour for simplicity (see SCHWARTZ & COPPERSMITH , 1984; WESNOUSKY , 1994), we 42 85 would expect 10-15 earthquakes of M 6.0 and larger over the four-century completeness window 43 44 86 discussed above - which is not the case. Furthermore, palaeoseismological investigations carried out in 45 87 the damage area of the 6 April 2009 earthquake (CINTI et alii , 2011; GALLI et alii , 2011) propose 46 88 recurrence times of only a few centuries, making the discrepancy even bigger and harder to explain. 47 89 Many investigators followed Bosi’s first reconnaissance work. It is now widely accepted that 48 90 the Central Apennines are cut by a large number of high-angle normal faults, most of which trend NW 49 50 91 and dip to the SW (e.g. GALADINI et alii , 2000, and references therein). Typically these faults have 51 92 been seen as controlling the location and evolution of the Pleistocene-Holocene intramontane basins 52 93 filled by continental deposits, and are often characterised by prominent morphological scarps, well- 53 94 preserved free-faces, and wide cataclasite zones. Nevertheless, the scientific community has 54 95 contrasting opinions on the rate of activity of these otherwise evident faults, on their association with 55 96 historical earthquakes, on the relationship between each seismogenic source and the overlying surface 56 57 97 faults, and hence in general on their seismogenic potential. 58 98 Although it qualifies as a moderate-size event, the 6 April 2009 makes a unique case for testing 59 99 and improving our seismotectonic understanding of the Apennines, thanks to the amount and quality of 60 100 the data collected during and after the earthquake and to the nature of the issues it raised, most of 101 which are shared by other central and southern Apennines earthquakes. VALENSISE & PANTOSTI

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1 2 102 (2001a) outlined the differences between geological and seismological evidence for Italian seismicity 3 103 and discussed four circumstances that make the identification of Italian seismogenic faults particularly 4 104 difficult: 1) the complexity of the inherited tectonic history; 2) the large number of blind faults; 3) the 5 105 relatively low rates of tectonic deformation; and 4) the recency of the latest major change in the 6 7 106 tectonic regime. We will discuss in the following sections if and how these circumstances are relevant 8 107 to Abruzzi faults and what is the knowledge that can be considered established. 9 108 10 109 11 110 12 2. GEOLOGICAL AND SEISMOTECTONIC FRAMEWORK OF THE ABRUZZI 13 111 APENNINES 14 112 15 113 2.1. REGIONAL TECTONIC FRAMEWORK 16 114 17 115 The central Apennines thrustbelt results from the convergence between the Hercynian European plate 18 116 and the westward subducted Paleozoic Adriatic lithosphere (for a summary see PATACCA & 19 20 117 SCANDONE , 2004, and referencesFor therein).Review From Oligocene Only to Pliocene times, the development of an 21 118 accretionary wedge deformed different stratigraphic sequences of Mesozoic and Tertiary age. From 22 119 Oligocene time onwards, continental collision occurred against the Adriatic plate (GHISETTI & 23 120 VEZZANI , 2000). Large-scale contraction at the core of the Apennines belt has been highlighted using 24 121 deep seismic reflection profiles (BIGI , 1991a, 1995; PATACCA , 2008; DI LUZIO , 25 et alii et alii et alii 26 122 2009), which supplied ample evidence for large, imbricate duplex systems (GHISETTI & VEZZANI , 27 123 2000; PATACCA et alii , 2008). 28 124 The Late Tertiary collisional system involved the entire Triassic to Upper Miocene sequence. 29 125 The upper portion of the sedimentary stack was further overthrusted onto Upper Miocene to Early 30 126 Pliocene syn-tectonic foreland units, made of thick siliciclastic sequences (GHISETTI , 1987). 31 127 Contraction is highlighted by NE-verging thrusts and folds (thus indicating shortening roughly 32 33 128 oriented SW-NE), while the underlying Hercynian basement was partially involved in decollément 34 129 layers at various crustal depths (see BIGI et alii , 1991a, b, 1995; PATACCA et alii , 2008; DI LUZIO et 35 130 alii , 2009). 36 131 To the west and northwest the boundary of the Abruzzi Apennines is represented by the contact 37 132 between units overlain onto the Latium-Abruzzi carbonate platforms (Late Triassic to Late Miocene) 38 39 133 and those belonging to the Umbro-Marchean Apennines; the surface trace of such contact is marked by 40 134 the Olevano-Antrodoco-Sibillini Line (OASL; PATACCA et alii , 1990; BIGI et alii , 1991a; GALADINI , 41 135 1999; PIZZI & SCISCIANI , 2000; CENTAMORE & ROSSI , 2009; PIZZI & GALADINI , 2009; CALAMITA et 42 136 alii , 2011; see Fig. 2b). East and southeast of the Abruzzi Apennines, Oligo-Miocene flysch units of 43 137 the Molise domain are separated from Latium-Abruzzi units by the Ortona-Roccamonfina Line (ORL), 44 138 a regional lineament straddling the full width of the boundary between the central and southern 45 46 139 Apennines (LOCARDI , 1982, 1988; DI BUCCI & TOZZI , 1991; PECCERILLO , 2005; MILANO et alii , 2008; 47 140 CENTAMORE & ROSSI , 2009; PIZZI & GALADINI , 2009; see Fig. 2b). Although the nature, role and 48 141 degree of activity (if any) of both OASL and ORL are still debated in the literature, they indeed border 49 142 the Abruzzi Apennines and its SW-dipping, normal fault systems that we discuss further on in this 50 143 work. 51 52 144 Finally, Plio-Quaternary marine deposits seal thrusted units near the Adriatic coast and its 53 145 offshore (see among others: CENTAMORE & ROSSI , 2009). This piedmont sector of the Abruzzi 54 146 Apennines is a portion of the Apennines Foredeep (BIGI et alii , 1991b) and is thought to contain active 55 147 thrusts, as shown by offshore seismic reflection and seismicity data (SCISCIANI & CALAMITA , 2009), 56 148 and by regional analyses of seismic and geological cross-sections and modeling of the source 57 149 kinematics of destructive historical earthquakes (LAVECCHIA , 2010). 58 et alii 59 150 60 151 2.2. HISTORICAL AND INSTRUMENTAL SEISMICITY 152

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1 2 153 Historical and instrumental earthquake catalogues show that the Abruzzi Apennines have been struck 3 154 by numerous earthquakes (Fig. 2a; Tables 1 and 2), ranging from sparse background seismicity up to 4 155 Mw 7.0 events - i.e. the 13 January 1915 earthquake. Most of the major earthquakes are concentrated in 5 156 the inner extensional sector, with few yet significant exceptions. 6 7 157 The epicentral location and magnitude estimate of any pre-instrumental earthquake depends on 8 158 the quality of the historical records, and specifically on the number of intensity datapoints available. 9 159 The data are treated with automated procedures and hence bear an additionl uncertainty due to the 10 160 selected analytical approach (e.g., GASPERINI et alii , 1999), although recent algorithms have much 11 161 improved the reliability of the results (GASPERINI , 2010). For older earthquakes - for instance, 12 et alii 13 162 prior to and including the Middle Ages - and for events that occurred in scarcely populated areas, such 14 163 as the inner Abruzzi Apennines, epicentral locations and magnitude estimates bear large uncertainties. 15 164 This is the case for the 9 September 1349 multiple earthquakes, a seismic crisis that affected several 16 165 regions of the central Apennines. Although historical information is certainly highly fragmentary, 17 166 GUIDOBONI & COMASTRI (2005) proposed three distinct areas of maximum damage (including the 18 167 region highlighted by the label in Fig. 2a) and, therefore, three distinct epicentral areas corresponding 19 20 168 to three events, arguably Forrelated to oneReview another. Only 21 169 The 5 and 30 December 1456 seismic sequence also is a very problematic case. The 22 170 earthquakes affected most of central and southern Italy, causing 30,000-80,000 casualties and 23 171 widespread devastation. GUIDOBONI & COMASTRI (2005) identified three main damage zones, two in 24 172 the southern Apennines and a smaller yet significant one near the northern termination of the Maiella 25 26 173 Massif. Based on this information, FRACASSI & VALENSISE (2007) subdivided the 1456 sequence into 27 174 at least three large subevents, including one on the eastern border of the Abruzzi Apennines, believed 28 175 by these investigators to have occurred on 30 December (blue label in Fig. 2a). 29 176 Significantly, the 1456 earthquakes occurred only five years before the 26 November 1461 30 177 Aquilano earthquake (M w 6.5), believed by some investigators to be a twin of the 6 April 2009 event, 31 178 either based on macroseismic studies (e.g. TERTULLIANI , 2010) or on palaeoseismological 32 et alii 33 179 trenching (CINTI et alii , 2011) (see § 4). Available data for the 1461 earthquake (GRUPPO DI LAVORO 34 180 CPTI, 2004; GUIDOBONI & COMASTRI , 2005) show a small mesoseismal area supported by 5-6 closely 35 181 spaced reports of intensity IX-X and X. The full extent of the damage field remains unknown but for 36 182 very few reports of intensity IV and V. The currently accepted location of this strong earthquake raises 37 183 a number of issues (for further details see DISS WORKING GROUP , 2010). Both the 1456 and 1461 38 39 184 earthquakes occurred at a time when restoring buildings in scarcely populated areas was not a priority 40 185 for the ruling powers (the “Regno delle Due Sicile” in Naples). The macroseismic field of the 30 41 186 December 1456 Abruzzi sub-event shows that this earthquake has occurred virtually adjacent to the 42 187 1461 earthquake. Keeping in mind that a) no intermediate level damage (intensity V/VI through IX) is 43 188 known for the latter event, that b) the two events are very close in time and space, and that c) the non- 44 189 strategic socio-economic role of the area did not compel immediate rebuilding, one could infer that the 45 46 190 1456 earthquake may have partially hindered or lessened the reliability of historical accounts of the 47 191 1461 event, the ultimate effect being an apparent shift of its epicenter to the NW and possibily a 48 192 reduction of its magnitude. This hard to resolve issue is crucial for assessing the earthquake potential 49 193 of the seismogenic sources located SE of the region struck by the 6 April 2009 earthquake. 50 194 The 6 October 1762 (M 6.0) earthquake is another example of uncertain location and 51 w 52 195 magnitude estimate. GUIDOBONI et alii (2007) reported that various localities were uninhabitable after 53 196 this earthquake, and proposed a slightly larger magnitude than that (Mw 5.9) reported by GRUPPO DI 54 197 LAVORO CPTI (2004) (Table 1). Similarly to the case of the 1461 earthquake, however, the damage 55 198 estimates are based on 3-4 intensity datapoints only, thus leading to a poorly constrained epicentral 56 199 location and magnitude estimate. Once again, whether the location of the 1762 earthquake is reliable 57 200 or not is a critical issue for the assessment of local seismic hazard (DISS WORKING GROUP , 2010; DI 58 59 201 BUCCI et alii , 2011a). 60 202 The 2 February 1703 earthquake (M w 6.6), which struck the northern portion of the study area, 203 may have shared many similarities to its 14 January predecessor (M w 6.8), which occurred about 30

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1 2 204 km to the northwest. The 2 February event caused major devastation in the city of L’Aquila and its 3 205 currently accepted location is just north of the 6 April 2009 earthquake (for an in-depth review of this 4 206 recent event, see § 4). 5 207 The 13 January 1915 (M 7.0) Avezzano earthquake is to date the largest event to have ever 6 w 7 208 occurred in the Abruzzi Apennines, and is certainly one of the strongest earthquakes reported in the 8 209 Italian historical and instrumental catalogs. Possibly preceded a decade earlier by a much smaller yet 9 210 damaging earthquake located to the northwest (24 February 1904, M w 5.7), the 1915 earthquake 10 211 produced widespread devastation throughout the entire region and beyond, causing VI/VII intensity 11 212 damage in Rome. As mentioned in § 1.1, several investigators have studied this earthquake based on 12 13 213 the vast amount of available data (for a summary see: http://diss.rm.ingv.it/diss/; DISS WORKING 14 214 GROUP , 2010), including detailed felt reports, instrumental recordings, geological and geodetic 15 215 information. 16 216 The 7 May 1984 (M w 5.9) earthquake and its strong 11 May aftershock occurred near the 17 217 southern end of the study region. This sequence has been the topic of a number of investigations (see 18 218 PACE , 2002, and references therein) and has been recently reassessed by MILANO & DI 19 et alii 20 219 GIOVAMBATTISTA (2011),For who reanalyzed Review all available instrumental Only data; they maintain that ORL (see 21 220 § 2.1) has played a key role in controlling the spatial pattern of the full sequence, including the 22 221 mainshocks. 23 222 Two areas, both located in the piedmont east of the Apennines thrustbelt (Fig. 2), have been the 24 223 locus of isolated earthquakes apparently unrelated with the main extensional belt responsible for the 25 26 224 major seismicity discussed so far. The 5 September 1950 (M w 5.7) earthquake is a relatively deep 27 225 event that occurred near the city of Teramo (TERTULLIANI et alii , 2006). Further to the southeast, two 28 226 relatively large earthquakes occurred on the eastern flank of the Maiella Mt. on 3 November 1706 (M w 29 227 6.6) and 26 September 1933 (M w 5.7). According to LAVECCHIA et alii (2010), these earthquakes have 30 228 both been caused by E-verging reverse faulting underneath the Maiella Mt. (see Composite 31 229 ITCS078 in DISS WORKING GROUP , 2010). Finally, moderate-size earthquakes 32 Seismogenic Source 33 230 have occurred further to the northeast, between the piedmont and the Adriatic coastline, the largest one 34 231 being the 10 September 1881 event (M w 5.6). 35 232 36 233 2.3. PRESENT -DAY DEFORMATION , PREVIOUS FAULT COMPILATIONS AND PALAEOSEISMOLOGICAL 37 234 STUDIES OF ACTIVE FAULTS 38 39 235 40 236 The tectonic grain of the inner Abruzzi Apennines is defined by a number of up to ca. 10 km long, 41 237 SW-dipping normal faults, broadly arranged along two to three main, NW-SE trending systems. Such 42 238 arrangement and orientation reflects the current extensional regime (MONTONE et alii , 2004; ANZIDEI 43 239 , 2005; SERPELLONI , 2005, 2007; D’A GOSTINO , 2008; MARIUCCI , 2010; 44 et alii et alii et alii et alii 240 D’A GOSTINO , 2011; Fig. 2a). Since the Early Pleistocene (see among others, VEZZANI & 45 et alii 46 241 GHISETTI , 1998; GALADINI , 1999), the extension, which trends nearly parallel to the former 47 242 contractional axis, favoured the development of normal faults that have either downthrown the back- 48 243 limb of the pre-existing, large thrust systems, or have somehow disrupted the landscape that resulted 49 244 from the paleogeographic domains and the contractional phases we account for in § 2.1. A genetic 50 245 relationship between the thrusts and the overlying normal faults is suggested by the observation that 51 52 246 these faults appear to be contained within the thrusts themselves and are never seen to cut their 53 247 terminations. 54 248 As discussed earlier, active faulting of Abruzzi has been thoroughly investigated over the past 55 249 40 years and, despite the diverse views on the rate of activity of the numerous fault segments (see Figs. 56 250 2b and 3; Table 3, and references therein), a broad consensus exists regarding the main regional trends 57 251 (for a summary: GALADINI , 2000). Unfortuntely, individual faults or fault segments (depending 58 et alii 59 252 on the specific interpretations) are often interpreted differently by different research groups (Table 3), 60 253 partial exceptions being represented by those that have long been associated with an instrumental 254 earthquake - as is the case for the catastrophic 13 January 1915 event (M w 7.0: WARD & VALENSISE ,

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1 2 255 1989). 3 256 In some key cases, major faults border sizable basins, as is the case for the Fucino Plain, the 4 257 largest in the Abruzzi Apennines (among others: SERVA et alii , 1986; MICHETTI et alii , 1996; 5 258 GALADINI & GALLI , 1999; PICCARDI , 1999). Recent activity (i.e. since the Late Pleistocene; 6 et alii 7 259 HIPPOLYTE et alii , 1994) of some of these large fault systems, however, may be markedly different 8 260 from what their tectonic arrangement would suggest (GALADINI & MESSINA , 2004). Again, this is in 9 261 part due to the earlier extensional stages of the Lower Quaternary that have caused major offset and 10 262 large geomorphic footprint on given fault segments that may no longer be favourably oriented with 11 263 respect to the current extensional trend. 12 13 264 A vast amount of literature has dealt with the extensional tectonics of the Abruzzi Apennines, 14 265 either due to the early Quaternary phases or to present-day tectonics. Some of these works have been 15 266 conducted at regional scale and hence propose a broader view (e.g. AMBROSETTI et alii , 1983; BIGI et 16 267 alii , 1991b), some concentrated on specific parts of the Apennines (CELLO et alii , 1997), and others 17 268 focused on the current activity of individual faults (e.g. SCHLAGENHAUF et alii , 2011). Given the 18 269 volume of available literature, we selected a subset of papers that a) are representative of different 19 20 270 research groups, and b) For have addressed Review the seismotectonic Only potential of broad areas of the Abruzzi 21 271 Apennines with homogeneous criteria. In Table 3 we made an attempt to portray the diversity of views 22 272 among the various research groups. The reader should notice that the Paganica Fault (PA), considered 23 273 by several investigators to be the surface expression of the seismogenic source of the 2009 L’Aquila 24 274 earthquake (see § 4), was recognised before the occurrence of the 2009 earthquake by only a few 25 26 275 workers. This sole fact fully explains the need for a re-examination of what was known and what was 27 276 unexplored before and after the 6 April 2009 earthquake. 28 277 29 278 30 279 3. SEISMOGENIC SOURCES 31 280 32 33 281 3.1. DEFINITION OF A SEISMOGENIC SOURCE 34 282 35 283 Over the past 15 years, the DISS Working Group developed a strategy for identifying, characterizing 36 284 and archiving in a permanent database the major seismogenic sources that occur in and around the 37 285 Italian peninsula, i.e. those that are believed to be capable of producing M 5.5 or larger earthquakes 38 39 286 (VALENSISE & PANTOSTI , 2001b; B ASILI et alii , 2008). This strategy, which is currently being extended 40 287 to the rest of Europe within the EC-funded project SHARE (B ASILI et alii , 2010), is based on two 41 288 categories of sources, identified on the basis of their hierarchical relationships and of the detailedness 42 289 and quality of the associated geometrical and kinematic parameters: the Individual Seismogenic 43 290 Sources and the Composite Seismogenic Sources (BASILI et alii , 2009; see also: 44 291 ). The first category consists of well-defined individual 45 http://diss.rm.ingv.it/diss/UserManual.html 46 292 fault segments that are often associated with a specific historical or instrumental earthquake. 47 293 Conversely, the second category of sources is formed by longer fault systems that include the 48 294 Individual Seismogenic Sources and that normally contain historical earthquakes. 49 295 The recognition and characterization of a seismogenic source is always based on original and 50 296 bibliographical geological and geophysical data, on seismological constraints from historical and/or 51 52 297 instrumental seismicity and on geodynamic considerations. DISS incorporates seismogenic sources 53 298 capable of generating M w ≥ 5.5 earthquakes, thus including the majority of the most damaging 54 299 earthquakes reported in Italian catalogues. 55 300 An Individual Seismogenic Source (ISS) is represented as planar rectangular fault projected 56 301 onto the Earth’s surface, and is characterised by a set of geometric (strike, dip, length, width and 57 302 depth), kinematic (rake, average displacement and slip rate) and seismological parameters (magnitude 58 59 303 and recurrence interval). ISSs are assumed to exhibit “characteristic” behaviour with respect to rupture 60 304 length/width and expected magnitude. These sources are tested against worldwide databases for 305 internal consistency in terms of length, width, average displacement and magnitude, and can be

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1 2 306 complemented with information on fault scarps and other surface features, when documented. This 3 307 category of sources can be used for deterministic assessment of seismic hazard, for calculating the 4 308 probability of the occurrence of strong earthquakes for the sources themselves, for calculating 5 309 earthquake and tsunami scenarios and for tectonic and geodynamic investigations. 6 7 310 A Composite Seismogenic Source (CSS) is represented as a planar fault system projected onto 8 311 the Earth’s surface, and is characterised by geometric (strike, dip, width and depth), kinematic (rake, 9 312 slip rate) and seismological parameters (maximum expected magnitude). Its length is equal to the 10 313 entire fault system and may contain any number of ISSs. They are not assumed to be capable of a 11 314 specific earthquake but their potential can be derived from existing earthquake catalogues. A CSS is 12 13 315 essentially identified on the basis of the knowledge gained from specific large earthquakes of the past 14 316 combined with regional surface and subsurface geological data. In conjunction with seismicity and 15 317 modern strain data, CSSs can thus be used for regional probabilistic seismic hazard assessment and for 16 318 investigating large-scale geodynamic processes (see BASILI et alii , 2008 for further details). 17 319 18 320 3.2. A MULTI -STEP PROCEDURE FOR CONSTRUCTING A SEISMOGENIC SOURCE 19 20 321 For Review Only 21 322 The geometric and kinematic parameters of the seismogenic sources are evaluated following a multi- 22 323 step procedure that includes the original elaborations of geophysical and geological data and studies of 23 324 specific instrumental and historical earthquakes. Table 4 shows a list of common analyses and 24 325 procedures that may help constraining the parameters of the Seismogenic Sources. 25 26 326 All possible case histories in developing a Seismogenic Source can be summarised in four basic 27 327 typologies: 28 328 1) the ISS is responsible for a well-studied recent instrumental earthquake, and a large amount of 29 329 seismological, geodetic and geological data are jointly interpreted to obtain the location, geometry 30 330 and kinematics of the source (e.g., the 6 April 2009 L’Aquila earthquake: see Table 4); the 31 331 dimensions (length and width) of the source are scaled with the earthquake moment magnitude 32 33 332 (M w) using empirical relationships (WELLS & COPPERSMITH , 1994) and are constrained by 34 333 analytical laws relating rupture area and coseismic displacement to the seismic moment (HANKS & 35 334 KANAMORI , 1979); 36 335 2) the ISS is responsible for an older instrumental event (e.g., the 1915 Fucino earthquake): the 37 336 location, geometry and kinematics of the source are obtained from analytical modeling of the 38 39 337 available data constrained by geological, macroseismic, and morphotectonic analyses, and the 40 338 dimensions are scaled to the M w of the earthquake; 41 339 3) an ISS is responsible for a pre-instrumental historical earthquake (e.g., the 1703 Aquilano 42 340 earthquake): its dimensions are scaled to the M w of the earthquake obtained from macroseismic data 43 341 and verified against geological observations, while its location and geometry are based on 44 342 geological, macroseismic, and morphotectonic analyses; 45 46 343 4) an ISS identified on the basis of geological and morphotectonic analysis is not associated with any 47 344 historical or instrumental earthquake (e.g., the San Pio delle Camere Source): the M w of the 48 345 hypothetical future earthquakes is derived from the geologically constrained source dimension 49 346 using empirical relationships (WELLS & COPPERSMITH , 1994). 50 347 51 52 348 The approach used when dealing with instrumental earthquakes is to verify the consistency of 53 349 the geometry and size of the faults resulting from geological field studies with the corresponding 54 350 seismological parameters. This step of the procedure uses empirical and analytical relationships among 55 351 length, width, slip and moment magnitude (HANKS & KANAMORI , 1979; WELLS & COPPERSMITH , 56 352 1994). In contrast, the approach taken when dealing with historical earthquakes involves the 57 353 assessment of the completeness (in terms of intensity classes) and spatial distribution of the intensity 58 59 354 data. For older and larger events, the magnitude reported in parametric earthquakes catalogues is 60 355 compared with the actual macroseismic pattern to infer any complexity of the causative source in time 356 and space. Simplified dislocation modeling is often used to constrain the location and geometry of a

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1 2 357 seismogenic source with the expected shape or trend or displacement of selected geologic and 3 358 geomorphic features (i.e., attitude of sedimentary beds, drainage patterns, location and shape of 4 359 syntectonic basins, fault-scale morphologies like mountain fronts or anticline axes). 5 360 Our updated seismotectonic portrait of the Central Apennines includes an ISS responsible of 6 7 361 the 6 April 2009 earthquake. To define its geometry (see Table 4 and § 4), we analysed and selected 8 362 the best constrained of all seismological parameters and geological data proposed in the literature (e.g., 9 363 seismic moment; hypocentral location; strike, dip and rake from focal mechanisms; slip at depth and 10 364 surface slip). Other parameters have been derived using dislocation modeling by comparing the 11 365 expected surface displacement with observed geologic and geomorphic features (e.g., the location of 12 13 366 maximum subsidence area with respect to the active sedimentary trends, the location of the line of null 14 367 vertical displacement, etc.). 15 368 16 369 17 370 4. AN OVERVIEW OF THE 6 APRIL 2009 EARTHQUAKE SOURCE 18 371 19 20 372 The 6 April 2009 earthquakeFor (Mw 6.3)Review occurred close to theOnly city of L’Aquila in the Abruzzi Apennines 21 373 and was followed by more than 20,000 aftershocks (ISIDE , 2010), the two largest ones on 7 April (Mw 22 374 5.4), and on 9 April (Mw 5.2) (CHIARALUCE et alii , 2011). The normal faulting focal mechanisms 23 375 computed for the largest shocks agree with the tectonic regime of the region (PONDRELLI et alii , 2010; 24 376 SCOGNAMIGLIO , 2010; HERRMANN , 2011). Seismological, geodetic, and geological data 25 et alii et alii 26 377 available for this earthquake sequence were extraordinary both in amount and quality, thus supplying 27 378 fundamental insight into the source characteristics and complexity. Nevertheless, the range of the 28 379 conclusions reached by different investigators is unexpectedly wide (Table 5), and some key questions 29 380 remain unsolved. 30 381 There is general consensus that the upward prolongation of the subsurface rupture plane 31 382 intersects the ground surface near the Paganica Fault, a poorly known tectonic feature having a subtle 32 33 383 geomorphic expression (BAGNAIA et alii , 1989; PACE et alii , 2006) referred to as an “uncertain or 34 384 buried fault” in the digital version of the official geological maps of Italy (SERVIZIO GEOLOGICO 35 385 D’I TALIA , 2006). The seismological evidence that aftershocks were confined below 2 km depth 36 386 (CHIARABBA et alii , 2009; CHIARALUCE et alii , 2011) suggests that only minor slip took place along 37 387 the shallower portion of the fault, which agrees with surface observations (see discussion below). The 38 39 388 fact that the deep seismogenic source may have complex relationships with the surface Paganica Fault 40 389 is also suggested by the relatively low dip angle of the rupture plane (see Table 5) and by its projection 41 390 in the foot-wall of the Paganica Fault itself, as seen in the seismological sections published by 42 391 CHIARABBA et alii (2009) and CHIARALUCE et alii (2011). 43 392 The rupture area and slip distribution of the activated fault have been constrained by various 44 393 investigators through modelling of GPS, SAR and seismological data. The subsurface rupture length 45 46 394 varies in the range 12 to 19 km (Table 5; ANZIDEI et alii , 2009; ATZORI et alii , 2009; CHELONI et alii , 47 395 2010; TRASATTI et alii , 2011). The maximum slip at depth was about 1 m with only a few centimeters 48 396 of slip predicted on the shallower portion of the fault (e.g. CIRELLA et alii , 2009). In contrast, field 49 397 reconnaissance of surface co-seismic ruptures showed only discontinuous ground cracks and surface 50 398 faulting with few centimeters of ground displacement: the total length and the geometry of the mapped 51 52 399 surface breaks also varied greatly according to the different investigators (Table 5; see also discussion 53 400 in GORI et alii , this issue). Accordingly, the surface evidence has been described 1) as a discontinuous 54 401 2.5 to 6 km-long segment of the Paganica Fault (EMERGEO WORKING GROUP , 2009; CINTI et alii , 55 402 2011 ; VITTORI et alii , 2011), 2) as three discontinuous 10 km-long en-echelon segments of the Paganica 56 403 Fault (FALCUCCI et alii , 2009), 3) as three narrow discontinuous 13 km-long fracture zones (BONCIO et 57 404 , 2010), 4) as three discontinuous 19 km-long sub-parallel splays of the Paganica-San Demetrio 58 alii 59 405 fault system (GALLI et alii , 2010a), and 5) as 12-13 km long surface breaks along three en echelon 60 406 splays (GORI et alii , this issue).

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1 2 407 As regards the predecessors of the 2009 event, based on the analysis of historical intensity 3 408 reports, TERTULLIANI et alii (2010) suggested that both the M w 6.5, 1461 and the M w 5.9, 1762 4 409 earthquakes (Table 1) were generated by the same source as the 2009 event, or by an antithetic 5 410 structure cutting through the same seismogenic volume. Palaeoseismological studies across different 6 7 411 segments of the Paganica and San Demetrio Faults returned different results: on the one hand GALLI et 8 412 alii (2010a; 2011) contended that the Paganica Fault ruptured during the 1461 and the 2 February 1703 9 413 (M w 6.7) earthquakes, while on the other hand CINTI et alii (2011) recognised five paleo-events which 10 414 include the 1461 but not the 1703 earthquake. Based on the long-term fault scarp geomorphology, 11 415 however, they also suggested that the Paganica Fault could occasionally generate larger earthquakes. 12 13 416 This large amount of data and their interpretation have raised several issues, the main ones 14 417 concerning 1) the deep source geometry and its relationships with surface active faults, 2) the repeat 15 418 time of 2009-type earthquakes, and 3) the ability of the fault system to generate larger earthquakes 16 419 involving simultaneous activation of adjoining segments (this last point refers to the geometry of the 17 420 fault system itself). 18 421 The solution proposed in the DISS database comes from a joint reassessment of all these data. 19 20 422 The parameters of our PaganicaFor SeismogenicReview Source fitOnly the wide range of results proposed in the 21 423 literature (Tables 5 and 7). We believe that the geometry of the Paganica Source highlighted by the 22 424 occurrence of the 2009 earthquakes should represent guidance for identifying correctly and 23 425 characterising other nearby sources. 24 426 25 26 427 27 428 5. SEISMOGENIC SOURCES OF THE CENTRAL APENNINES 28 429 29 430 This section contains a description of the seismogenic sources included in the DISS database (v. 3.1.1). 30 431 For each CSS and ISS we describe the geological and geophysical background derived from original 31 432 and literature data that we collected and interpreted, and present the workflow we followed for 32 33 433 defining the parameters for each source. The sources are described starting from the CSS that contains 34 434 the ISS of the 6 April 2009 earthquake (ITCS013); each CSS will be described from north to south. 35 435 For the inner extensional portion of the Abruzzi Apennines DISS lists three parallel, about 100 36 436 km-long CSSs (Table 6; Fig. 3), each one including two or more ISSs (Table 7; Fig. 3). These 37 437 seismogenic sources straddle the crests of the central Apennines following a regional NW-SE trend 38 39 438 delineated by the location of the largest historical earthquakes; they dip to the SW and are 40 439 characterised by normal faulting (see § 2.3). Simple consideration of the distribution of historical 41 440 eartquake release in the Abruzzi Apennines shows that here tectonic extension is accommodated 42 441 differently from the adjoining regions to the north and to the south. In particular, seismic release 43 442 follows three independent trends and affects a much wider area across the mountain belt. The reason 44 443 for this probably lies in the different rheology of the crust resulting from the presence of the thick and 45 46 444 rigid Latium-Abruzzi carbonate platforms. 47 445 The three CSSs terminate to the northwest and to the southeast at the transverse OASL and 48 446 ORL, respectively (Figs. 2b and 3; see § 2.1). These are two NNE-striking, inherited tectonic 49 447 lineaments that bound paleogeographic domains and define a major change in the surface geology. 50 448 They are thought to act as effective boundaries to the dynamic earthquake propagation, segmenting 51 52 449 also the Quaternary extensional fault systems (PIZZI & GALADINI , 2009). The OASL to the north 53 450 separates the Abruzzi extensional domain from the structures related to the Alto Tiberina normal fault 54 451 system developed in the Umbria-Marche Apennines, and marks a change in the dip direction of the 55 452 master fault (Fig. 3): northwest of OASL the extensional fault system downthrows to the NE, while to 56 453 the southeast it downthrows to the SW. The ORL defines the boundary with the Southern Apennines 57 454 extensional belt just southeast of the 1984 earthquake epicentral area and close to the intersection with 58 59 455 the E-W Molise-Gondola Shear Zone (DI BUCCI et alii , 2010). In contrast with the Abruzzi, in the 60 456 Southern Apennines a single system of NE-dipping seismogenic sources follows the hinge of the 457 mountain chain; in its turn this system is segmented by regional E-W shear zones responsible for the

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1 2 458 earthquakes located east of the drainage divide (e.g., the 1456 seismic sequence, FRACASSI & 3 459 VALENSISE , 2007). The location and geometry of the CSSs described in this section follows a careful 4 460 revision of the historical and instrumental seismicity, combined with the analysis and interpretation of 5 461 geological and geophysical data and of active fault trends. This diverse dataset is helpful to define in 6 7 462 3D the structures and fully characterise the seismogenic sources. 8 463 One of the primary lines of evidence used to identify earthquake-generating faults is basic 9 464 structural mapping (see § 1.1). The main active fault systems associated with the shallower portion of 10 465 the CSS are shown in bold in Figure 3. The reader must be aware that the faults associated with each 11 466 seismogenic source are a selection made by the DISS Working Group among the many faults 12 13 467 identified in the literature. For example the Gran Sasso Range, the easternmost reach of mountain 14 468 building of the Abruzzi Apennines, that lies to the southeast of the ITCS028 source, has been dissected 15 469 by normal faulting in the early Pleistocene (Fig. 3), but whether these faults are still active and large 16 470 enough to be potentially seismogenic remains the object of a lively debate. Several workers (e.g. 17 471 GIRAUDI & FREZZOTTI , 1995; GALADINI et alii , 2000; GALLI et alii , 2002) focused on the south 18 472 dipping border fault of the Campo Imperatore Plain, a large depression within the Gran Sasso Range, 19 20 473 and used palaeoseismologicalFor evidence Review to suggest that thisOnly is a major potential seismogenic source. 21 474 H/V analyses carried out on the Holocene sedimentary filling of the Campo Imperatore Plain, 22 475 however, do not show the presence of a basin associated with the Campo Imperatore master fault 23 476 (F RACASSI , 2001), suggesting that the fault has not been active during the Holocene. In addition to that, 24 477 a survey carried out by ROBERTS (2009) along the main faults of the Gran Sasso Massif showed 25 et alii 26 478 mixed soil/rock and snow avalanches and ground cracks in the vicinity of the trench excavated by 27 479 GALLI et alii (2002). Although ROBERTS and coworkers did not rule out the possibility that these 28 480 features were actual earthquake ruptures, subsequent analyses based on SAR imagery and geodetic 29 481 data showed that the Gran Sasso Range lies outside the region affected by coseismic strains in 2009. 30 482 One may conclude that ROBERTS et alii (2009) have witnessed recurrent phenomena of compaction 31 483 and sliding of surficial sediments, which raises legitimate doubts on the tectonic meaning of the fault 32 33 484 ruptures excavated by GALLI et alii (2002) and hence on their current state of activity. For all of these 34 485 reasons the Campo Imperatore normal faults have not been associated with any CSS. 35 486 Aside from the problem of identifying correctly the active fault and separating them from 36 487 inactive or non-tectonic features, the relationships between the deep seismogenic source and the faults 37 488 mapped at the surface is rather complex. This is demonstrated by the M 7.0, 1915 Avezzano 38 w 39 489 earthquake, a large historical event for which both instrumental information and field evidence exist, 40 490 but also by the M w 6.3, 2009 L’Aquila earthquake, a much smaller but extremely well documented 41 491 event. The 1915 earthquake produced surface faulting on parallel, en-echelon , synthetic fault strands in 42 492 the source hanging-wall, near the area of maximum coseismic subsidence, partly activating range- 43 493 bounding faults (e.g. VALENSISE & PANTOSTI , 2001a). The 2009 earthquake was caused by a fault 44 494 having a subdued morphology, such that several investigators did not include it among the main active 45 46 495 faults and some did not map it at all (see Table 3), and produced only a few centimetres of coseismic 47 496 slip along the Paganica Fault (see § 4). In both cases the earthquakes activated more than one surface 48 497 fault strand, none of which are correctly scaled in length to the magnitude of the earthquake. 49 498 The lesson that must be learned from these two earthquakes is that in areas of complex geology 50 499 such as the Abruzzi Apennines, where the current structural grain results from the superposition of 51 52 500 different tectonic regimes, assuming the most visible active faults are the major seismogenic faults is 53 501 often misguided. In fact the main active fault systems are discontinuous and fragmented in segments 54 502 with various orientations and lengths, are often associated with synthetic and antithetic secondary 55 503 faults, and their map traces cannot be taken alone to draw a geometrically coherent seismogenic model 56 504 and to predict a realistic expected magnitude. We defined the parameters of our seismogenic sources 57 505 following these lines of reasoning. For each source analysed in detail the structural and geologic 58 59 506 setting at seismogenic depth and all morphotectonic phenomena at the scale of the entire investigated 60 507 region, so as to unveil the source long-term activity and reduce the inherent ambiguities of bedrock 508 geology.

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1 2 509 3 510 4 511 5.1. ITCS013 - BORBONA -L'A QUILA -AREMOGNA COMPOSITE SOURCE 5 512 6 7 513 This CSS straddles the backbone of the central Apennines, including the Montereale Basin (to the 8 514 northwest), the Upper and Middle Aterno Valley, the Subequana Valley, and the Cinque Miglia Plain 9 515 (to the southeast, Fig. 3). 10 516 Earthquake catalogues (B OSCHI et alii , 2000; GRUPPO DI LAVORO CPTI, 2004; GUIDOBONI et 11 517 , 2007) show a remarkable concentration of damaging and catastrophic earthquakes within this 12 alii 13 518 area: 26 November 1461 (M w 6.5, Aquilano), 2 February 1703 (M w 6.7, Aquilano; the southernmost 14 519 event of the largest seismic sequence in central Italy), January 1791 (M w 5.4, L’Aquila), 22 April 1916 15 520 (M w 5.2, Aquilano), 24 June 1958 (M w 5.2, Aquilano). The 6 April 2009 L’Aquila earthquake also falls 16 521 within this CSS. 17 522 The Montereale basin, which includes all faults reported by BLUMETTI (1995) and CELLO et alii 18 523 (1998) as having been activated during the 1703 seismic sequence, falls at the northernmost end of this 19 20 524 CSS. BLUMETTI (1995) For reviewed theReview historical descriptions Only of surface phenomena reported in the 21 525 Norcia-L'Aquila area during the 1703 earthquakes and compared them with field evidence with the 22 526 goal of locating the surface ruptures. The observed ruptures occurred close to pre-existing normal 23 527 faults bounding Meso-Cenozoic ridges that are part of a 50 km-long, 5 km-wide NNW-striking belt. 24 528 The surface ruptures associated with the 2 February 1703 earthquake occurred at three locations: 1) the 25 26 529 western side of Mt. Laghetto Ridge (Cittareale Fault, west-side down), 2) the western side of 27 530 Montereale basin (Montereale Fault, east-side down), and 3) the Rotigliano Plain (Rotigliano Fault, 28 531 west-side down). Secondary effects were reported along the Mt. Marine Ridge (Arischia Fault, west- 29 532 side down). A trench dug across the Arischia Fault at a construction site exposed a faulted stratigraphic 30 533 sequence with at least two faulting events (BLUMETTI , 1995). The activity of the Pizzoli Fault is 31 534 demonstrated in the Arischia area by faulted slope deposits and by the occurrence of liquefaction 32 33 535 phenomena during the 1703 earthquake. The activity of the three major N-S striking faults is testified 34 536 west of L'Aquila and south of Arischia by faulted and tilted slope deposits and faulted Quaternary 35 537 fluvio-lacustrine deposits (CELLO et alii , 1997). 36 538 The area struck by the 6 April 2009 earthquake falls to the southeast of the Montereale Basin. 37 539 For an overview of the source of this earthquake the reader may refer to a) § 4; b) Table 4 for the 38 39 540 procedures we used to determine the parameters of the Paganica Seismogenic Source; c) Table 5 for a 40 541 review of the geometrical-kinematics parameters of the source published in the literature; d) Table 7 41 542 for the parameters of the ITIS131 Paganica; and e) Fig. 3 for the projection to ground surface of the 42 543 Paganica Source. This source extends from L'Aquila to around San Demetrio né Vestini; to the 43 544 southeast, it dies out against a prominent geomorphologic transverse structure, where the 6 April 2009 44 545 sequence ends its south-easterly trend. 45 46 546 Southeast of the Paganica Source, the fault system shows an en-echelon pattern with the 15 to 47 547 20 km-long Middle Aterno Valley Fault. Its surface expression is represented by continuous and 48 548 evident fault scarps and ribbons, well-visible along the left bank slope of the valley (B AGNAIA et alii , 49 549 1989), where there is no tectonic depression filled by Quaternary deposits. MORO et alii (2010) dug 50 550 two palaeoseismological trenches along the Middle Aterno Valley slope, concluding that the 51 52 551 penultimate rupture event occurred between 5480-5310 B.C. and 3574 B.P. while the last event 53 552 occurred around 10-140 A.D. A maximum Mw 6.6 has been attributed to the Middle Aterno Valley 54 553 fault by PACE et alii (2006). 55 554 The Middle Aterno Valley Fault is en-echelon to the 10 km-long Subequana Valley Fault to the 56 555 southeast. The surface expression of this structure is represented by fault scarps visible along the 57 556 southwestern slopes of Mt. Urano, where a tectonic depression has undergone continental deposition 58 59 557 since the early Quaternary (BOSI & BERTINI , 1970). According to FALCUCCI et alii (2011), the two 60 558 structures of the Middle Aterno Valley Fault and the Subequana Valley Fault overlap over a distance 559 of about 0.5 km along a transfer fault that cut and re-used a NE-SW-trending regional shear zone

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1 2 560 known as the Avezzano-Bussi Fault. The Subequana Valley Fault is exposed in a quarry bearing 3 561 displaced slope deposits. FALCUCCI et alii (2011) dug two palaeoseismological trenches across this 4 562 fault and suggested that, along with the Middle Aterno Valley Fault, these two structures belong to the 5 563 same 25 to 30 km-long fault system. The two faults represent the branching at surface of the same 6 7 564 deep seismogenic source, which ruptured twice during the late Holocene - the last activation having th st 8 565 occurred between the 4 and 1 century B.C. Analysis of the Coulomb stress diffusion induced by the 9 566 6 April 2009 earthquake revealed a stress increase along the Middle Aterno Valley and the Subequana 10 567 faults (FALCUCCI et alii , 2011). 11 568 At the southeastern end of this Composite Source, the Aremogna-Cinque Miglia Fault is 12 13 569 believed by D’A DDEZIO et alii (2001) to have caused two large earthquakes on 801 A.D. and 1349 14 570 A.D. (the latter probably being a series of large earthquake that hit three different areas of central Italy; 15 571 see GUIDOBONI & COMASTRI , 2005). The source is located at the transition between the dominantly 16 572 SW-dipping normal fault systems of the central Apennines to the dominantly NE-dipping systems seen 17 573 in the southern Apennines. In his review of active faulting in central Italy, BOSI (1975) described for 18 574 the first time the fault scarp of the Cinque Miglia Plain as "likely active" (Fig. 1), but this source is 19 20 575 mainly based on the geomorphicFor andReview palaeoseismological Only work of D'A DDEZIO et alii (2001), who 21 576 analysed the earthquake potential of the Aremogna-Cinque Miglia Fault and mapped a 16 km-long, up 22 577 to 6 m-high complex fault scarp. In their view, this 16-km long fault is composed by two main 23 578 sections, one being in the Aremogna plain, the other one in the Cinque Miglia plain. They reported a 24 579 recurrence interval in the range 2140-5080 years, a Holocene throw-rate of 0.1-0.5 mm/a, a 0.3-1.0 m 25 26 580 slip per event, and a 6.5-6.8 magnitude assuming that each of these earthquakes ruptured the entire 27 581 length of the Aremogna-Cinque Miglia Fault. 28 582 29 583 5.2. ITCS025 - SALTO LAKE -OVINDOLI -BARREA SOURCE 30 584 31 585 The Salto Lake-Ovindoli-Barrea CSS straddles the backbone of the central Apennines between the 32 33 586 Rieti Plain, to the northwest, and the higher Sangro River valley, to the southeast, stretching across the 34 587 Fucino Plain. The source falls within the core of the SW-dipping, inner Abruzzo normal fault system, 35 588 marking the western extensional border of the central Apennines, and includes the Salto Valley Fault, 36 589 the Velino-Magnola fault system, the Fucino Basin and the Barrea fault. 37 590 Historical and instrumental catalogues (B OSCHI , 2000; GRUPPO DI LAVORO CPTI, 2004; 38 et alii 39 591 GUIDOBONI et alii , 2007) show a particularly dense level of seismicity near the damage threshold (4.5 40 592 < M w < 5.0) in this area. This source is believed to be responsible for some complex, highly destructive 41 593 earthquakes that rank among the largest in the entire Italian history i.e., the 9 September 1349 (M w 6.5, 42 594 I=X, Aquilano) and the 13 January 1915 (M w 7.0, I=XI, Avezzano). Between the mesoseismal areas of 43 595 the 1349 and 1915 earthquakes lies the epicentral area of the 24 February 1904 event (M w 5.7, I=IX, 44 596 Marsica). Finally, the 7 May 1984 (M 5.9, I=VIII; Appennino abruzzese) earthquake occurred near 45 w 46 597 the southern end of this Composite Source. 47 598 The most significant tectonic feature at the northern end of this CSS is the SW-dipping Salto 48 599 Valley Fault. According to BOSI (1975) and MARIOTTI & CAPOTORTI (1988), the fault is at least 24 km 49 600 long and its fault plane is exposed along a 7 km-long bedrock scarp in the Fiamignano area. The scarp 50 601 height (offsetting 18 ka sediments) varies from 10 m in the center of the fault to less of 4 m toward its 51 52 602 tips. This is a Plio-Quaternary normal fault considered active by MOREWOOD & ROBERTS (2000), who 53 603 calculated throw rates of 0.22-0.56 mm/a for the past 18 ka. GALADINI & MESSINA (2001), however, 54 604 interpreted the late-Quaternary displacement evidence of the Salto Valley Fault as due to deep-seated 55 605 gravitational movements rather than to tectonic displacement, and GALADINI (2006) maintained that 56 606 the fault has played a passive role, since it only bounds the sliding mass and coincides with the surface 57 607 expressions of the sliding plane. Also BONCIO (2004) considered the Salto Valley Fault to be at 58 et alii 59 608 least questionable. 60 609 According to BOSI (1975) and ACCORDI et alii (1986), southeast of the Salto Valley Fault the 610 Mt. Velino-Mt. Magnola Fault cuts along the southwestern, NW-striking steep slopes of Mt. Velino

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1 2 611 and along the southern WNW-striking steep slopes of Mt. Magnola, over a length of about 21 km. 3 612 According to MOREWOOD & ROBERTS (2000), the limestone fault plane is almost continuously 4 613 exposed, and the scarp height reaches 5.0 m in the central part of the fault. According to FREZZOTTI & 5 614 GIRAUDI (1992), NW-striking, 2.5 m-high fault scarps cut across outwash fan deposits of the Majelama 6 7 615 Valley but do not appear to have much affected their evolution, being more recent than the main 8 616 deposition phases (upper Pleistocene last glacial maximum). MOREWOOD & ROBERTS (2000) assumed 9 617 an age of 18 ka and proposed rates of throw and displacement of 0.08-0.19 mm/a and 0.09-0.23 mm/a, 10 618 respectively, and rates of horizontal extension of 0.04-0.17 mm/a. Other investigators, such as 11 619 PALUMBO et alii (2004) and more recently SCHLAGENHAUF et alii (2011), quantified the activity of the 12 36 13 620 Mt. Magnola Fault by measuring Cl accumulation on the exposed fault plane. They found that the 14 621 fault, in the last 15 ka, ruptured its entire length during at least nine large earthquakes, with maximum 15 622 surface slip of 3 m. GALLI et alii (2010b) opened trenches at the site studied by SCHLAGENHAUF et alii 16 623 (2011) and identified evidence of surface faulting during the late Holocene. 17 624 Based on aerial-photo interpretation BIASINI (1966) identified two faults scarps at Piano di 18 625 Pezza and Campo Porcaro, to the west of the Mt. Velino-Mt. Magnola Fault. These scarps are 19 20 626 interpreted as the surfaceFor evidence Reviewof an active normal faultOnly that produced as much as 9 m of post- 21 627 Wurm displacement. According to PANTOSTI et alii (1996), the Ovindoli-Pezza is a NW-striking, SW- 22 628 dipping fault a generating large earthquakes with an average recurrence time of 1,000-3,300 years. 23 629 Their estimated extension rates, from palaeoseismological and geomorphic observations, are 0.3-0.5 24 630 mm/a and 0.4-1.1 mm/a, respectively. A controversy exists about the kinematics of the Ovindoli-Pezza 25 26 631 Fault, however, because GALADINI (1999) and PICCARDI et alii (1999) observed significant left-lateral 27 632 displacements. In contrast MOREWOOD & ROBERTS (2000) described only dip-slip movement, with an 28 633 offset glacial surfaces yield rates of throw and displacement of 0.13-0.16 mm/a and 0.17-0.18 mm/a, 29 634 respectively. According BONCIO et alii (2004) the fault has a dip ranging from 45° to 80°, a length of 30 635 26.5 km, and pure dip slip to transtensional (left lateral) kinematics. 31 636 Southeast of the Ovindoli-Pezza Fault, the Fucino Basin Source is a surface-breaking, N145° 32 33 637 striking, 60° dipping, 30 km-long normal fault. The source aligns with direct observations of the 34 638 coseismic fault scarps formed during the 13 January 1915 earthquake (ODDONE , 1915), with the model 35 639 fault obtained by inversion of 1915 coseismic elevation changes (WARD & VALENSISE , 1989), with 36 640 palaeoseismological observations of the main fault scarps (summarised in GALADINI & GALLI , 1999). 37 641 Although the exact kinematics of the fault are still debated, most workers agree that the lateral 38 39 642 component of motion is a small fraction of the vertical. The exposure of a white ribbon of fresh 40 643 limestone fault plane reported along the southwestern slope of Mt. Serrone after the earthquake is 41 644 suggestive of coseismic reactivation, although it is clearly difficult to discriminate between tectonic 42 645 and gravitational movements. GALADINI & GALLI (1999) regarded the Mt. Parasano and the San 43 646 Benedetto-Gioia dei Marsi Faults as the main branches of a single NW-striking, SW-dipping pure 44 647 normal fault. These faults slip always simultaneously with characteristic displacements per event; 45 46 648 conversely the Trasacco and Luco dei Marsi Fault branches move only passively. There is no 47 649 consensus on the present activity of the Ventrino Fault (see Table 3), considered to be an early 48 650 Pleistocene fault. Based on a thorough investigation of the geometry of the depositional bodies, 49 651 CAVINATO et alii (2002) concluded that the Fucino Basin was formed as a half-graben type structure 50 652 during Plio-Quaternary extensional events. 51 52 653 There is a 20-km-long gap between the Fucino Basin source and the southeastern Barrea 53 654 Source, parallel to the crest of the Apennines. The Barrea Source is a N152°-striking, 50°W-dipping 54 655 fault rupturing between 5 and 11 km depth. This fault is characterised by prevalent normal slip, in 55 656 agreement with WESTAWAY et alii (1989) and PACE et alii (2002). The distribution of the aftershocks, 56 657 however, that concentrated within a cluster oriented ENE-WSW, is rather anomalous. According to 57 658 PACE (2002) they are controlled by two kinematically compatible structures: the main normal 58 et alii 59 659 fault and a right-lateral normal oblique fault, assumed to have played the role of a transfer fault and of 60 660 a barrier for the propagation of the rupture. MILANO & DI GIOVAMBATTISTA (2011) suggested that the 661 1984 sequence nucleated in several stages with different strain pattern. These workers also suggested

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1 2 662 that the beginning of the sequence nucleated on a NE-SW striking fault, that subsequent events 3 663 nucleated along an E-W fault, and that overall the 1984 sequence originated on a fault segment 4 664 belonging to ORL. 5 665 6 7 666 5.3 ITCS040 - BARISCIANO -SULMONA SOURCE 8 667 9 668 This CSS straddles the backbone of the central Apennines, from Barisciano to the northwest to the 10 669 higher Pescara River valley to the southeast, and is the easternmost strand of the SW-dipping 11 670 extensional system of the central Apennines 12 13 671 Historical and instrumental catalogues (B OSCHI et alii , 2000; GRUPPO DI LAVORO CPTI, 2004; 14 672 GUIDOBONI et alii , 2007) show sparse intermediate (4.5 < M w < 5.0) to damaging seismicity within the 15 673 area. Furthermore, this source is responsible for destructive earthquakes such as the 6 October 1762

16 674 (M w 5.9, Aquilano) and 3 December 1315 (M w 6.0, Italia centrale) events. The large 3 November 1706 17 675 Maiella earthquake (M w 6.6) occurred to the southeast of this source. 18 676 This CSS is located near the southeastern edge of the 6 April 2009 seismic sequence and 19 20 677 includes the basin runningFor from Barisciano Review to Civitaretenga-Navelli Only. According to BOSI (1975) and 21 678 other investigators (see Table 3), an active fault borders the eastern slope of the valley. Through a 22 679 detailed morphotectonic, geological and structural analysis, DI BUCCI et alii (2011a) first identified the 23 680 San Pio delle Camere Seismogenic Source and defined its earthquake potential. This ISS is formed by 24 681 a NW-SE-striking, 50°-dipping, 16 km-long normal fault having a potential for a M 6.2 shock. 25 w 26 682 MESSINA et alii (2011), however, objected to the activity of the San Pio delle Camere Fault. In their 27 683 response, DI BUCCI et alii (2011b) showed recent lacustrine silts tilted toward the fault depocentre and 28 684 other lines of evidence supporting the recent activity of the fault. 29 685 Southeast of the San Pio delle Camere Source, the Mt. Morrone borders the Sulmona 30 686 intramontane basin. The Quaternary activity of the NW-SE normal fault along the Mt. Morrone 31 687 southwestern slope has been documented in different works (e.g. VITTORI , 1995; MICCADEI 32 et alii et 33 688 alii , 2002). According to GORI et alii (2011) this tectonic structure comprises two parallel fault 34 689 segments and is responsible for earthquakes of magnitude > 6.5. They identified the displacements of 35 690 alluvial fans, attributed to middle and late Pleistocene, and evaluated the slip rate of the western branch 36 691 of the structure to be 0.4+-0.07 mm/a. 37 692 38 39 693 5.4 ITCS028 - COLFIORITO -CAMPOTOSTO SOURCE 40 694 41 695 We briefly describe this source that mostly runs outside the study area since its geometry was 42 696 highlighted by the occurrence close to its southern portion of two of the strongest aftershocks of the 43 697 2009 L’Aquila earthquake and by the related sequence; one on 6 April (23:15 UTC, M 5.0) and one 44 w 698 on 9 April (00:53 UTC, M 5.2; CHIARALUCE , 2011). 45 w et alii 46 699 As a whole, this CSS straddles a section of the Umbria-Marche Apennines between Gualdo 47 700 Tadino (Umbria Region) to the north and the Campotosto Lake to the south, close to the western 48 701 reaches of the Gran Sasso mountain range. This is the easternmost SW-dipping normal fault system of 49 702 the central Apennines; it dips at a relatively low-angle and locates just west of the region where 50 703 tectonic compression prevails (DISS WORKING GROUP , 2010). Most of the information on this source 51 52 704 comes from studies that followed the 1997-98 Umbria-Marche earthquake sequence and, for its 53 705 southern portion, from the analysis of the 2009 sequence. This CSS includes the three ISSs of the main 54 706 shocks of the 1997-98 sequence and that associated with the 14 January 1703 earthquake (M w 6.8: 55 707 refer to Table 6 for the source parameters). 56 708 The geometry of the southern portion of this CSS was based on the lessons learned from the 57 709 2009 seismic sequence. Fault plane solutions of the largest shocks and seismicity distribution showed 58 59 710 the activation of a 14 km-long, low-angle, deeper structure forming a right-lateral step with the source 60 711 of the 6 April main shock (CHIARALUCE et alii , 2011). Other distinguishing features were the absence 712 of seismicity above 5 km depth and the different strike followed by the sequence with respect to the

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1 2 713 surface trace of the Monti della Laga Fault. The 2009 sequence demonstrated that this surface fault, 3 714 like many others in the region, can not be considered as the surface expression of a deep seismogenic 4 715 source because 1) it strikes at an angle with respect to the trend highlighted by seismicity and 2) its 5 716 high-angle geometry can hardly be reconciled with that of the seismogenic fault at depth. 6 7 717 8 718 6. SUMMARY 9 719 10 720 Our update of the Abruzzi extensional seismogenic sources in view of the 6 April 2009 earthquake 11 721 supplies a fresh look at the seismotectonics of this stretch of the Apennines (Table 8). The first insight 12 13 722 that can be derived from the seismogenic sources is the regularity in the pattern of present tectonic 14 723 deformation. Most of the seismic moment is released along three parallel extensional, SW-dipping 15 724 CSSs having similar depth of nucleation and slip rate. These extensional sources are bounded by well- 16 725 known, pre-existing major tectonic lineaments that have credibly played an important role in the 17 726 evolution of the Abruzzi Apennines, a region that can be considered rather uniform at least from a 18 727 paleogeographic and tectonic viewpoint. 19 20 728 In the following weFor briefly summariseReview the main improvements Only and novelties: 21 729 1) an improved understanding of three parallel extensional fault systems, implying the need to define 22 730 their most credible geometry and extent and to understand their mutual kinematic relationships, also 23 731 as a function of their respective arrangement; 24 732 2) the greater depth of the Campotosto Source as highlighted by the newly-available seismological 25 26 733 data, leading to a careful reconsideration of the geological evidence that used to be considered 27 734 crucial for this source; 28 735 3) updates of the geometric properties of seismogenic sources and new interpretations of faults that are 29 736 thought to have generated a number of historical earthquakes. In particular, we believe that the 30 737 relatively shallow dip, the depth of the upper tip at 2-3 km below the ground surface, and the 31 738 complex relationships with surface active faults do not represent an anomaly; instead, they must be 32 33 739 regarded as common features of the seismogenic sources responsible for moderate earthquakes in 34 740 the region; 35 741 4) the role (passive, active - any at all?) of two regional tectonic lineaments that cross the entire central 36 742 Apennines edifice from the Tyrrhenian to the Adriatic Sea; OASL to the north, and ORL to the 37 743 south; 38 39 744 5) the identification of seismic gaps along the three main CSSs. For example, the Sulmona Basin and 40 745 the Subequana Valley have not been the locus of major historical earthquakes at least over the past 41 746 seven centuries, and can hence be considered as two independent seismic gaps. 42 747 43 748 The revised seismogenic sources presented in this work improve the degree of completeness of 44 749 the seismotectonic framework of the Abruzzi region, yielding a synoptic view of seismogenic 45 46 750 processes in the central Apennines area. They also comprise a homogeneous database for quantifying 47 751 tectonic strains and the associated seismogenic potential at regional scale. 48 752 49 753 50 754 ACKNOWLEDGEMENTS 51 52 755 This work was partly supported by the Italian Dipartimento di Protezione Civile. The authors are very 53 756 grateful to the other colleagues of the DISS Working Group, who helped characterising the new 54 757 seismogenic sources of the Abruzzi Apennines after the 6 April 2009 earthquake. We thank the 55 758 Associate Editor, Paolo Boncio, Kathy Haller and an anonymous reviewer for their careful reviews. 56 57 58 59 60

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1 2 759 Figure Captions 3 760 4 761 - Active or potentially active faults (from BOSI , 1975, modified and adapted). 5 Figure 1 6 762 7 763 Figure 2 - a) Historical and instrumental earthquakes in the Abruzzi Apennines and its surroundings. 8 764 Notice the concentration of the largest events along the backbone of the Apennines. 9 765 Macroseismic earthquake data from GRUPPO DI LAVORO CPTI (2004), instrumental seismicity from 10 766 CASTELLO (2006), and vectors (cumulative from borehole breakouts, focal mechanisms, 11 et alii Sh-min 12 767 palaeoseismology) from MONTONE et alii (2004) and MARIUCCI et alii (2010). 13 768 The small dots locate earthquakes belonging to the sequence preceding and following the 6 April 2009, 14 769 L’Aquila earthquake (M w 6.3), as recorded from 1 April to 31 July 2009 by the INGV national seismic 15 770 network (ISIDE , 2010); the epicenter of the 6 April 2009 mainshock is shown by the larger white star; 16 771 the smaller black stars show the epicenters of the 7 April (M w 5.4, to the south) and 9 April (M w 5.2, to 17 772 the north) earthquakes, respectively. 18 19 773 Focal mechanisms by authors listed in Table 2. Present-day extensional axis (red arrows) from 20 774 SERPELLONI et alii (2005).For Labelled Review earthquakes are key Onlyevents (both historical and instrumental) that 21 775 have occurred within the study area; those with coloured background are associated with the following 22 776 Composite Seismogenic Sources : ITCS025 (green), ITCS013 (yellow), ITCS028 (orange), and 23 777 ITCS040 (cyan), respectively (see § 5 and Fig. 3). The location of the 1456 earthquake (white text in 24 25 778 blue label) is from FRACASSI & VALENSISE (2007). 26 779 b) Geological summary of the central Apennines and its environs (modified, from DI BUCCI et alii , 27 780 2006). Notice how OASL (auct., see PATACCA et alii , 1990) to the north, and ORL (auct., see 28 781 LOCARDI , 1988) to the south border the Abruzzi Apennines and its large normal fault systems 29 782 discussed in this work. 30 783 Key: 1 - marine and continental clastic deposits (Pliocene-Quaternary); 2 - volcanics (Pleistocene); 3 - 31 32 784 clayey and carbonate turbidites (Cretaceous-Eocene); 4 - Apennines carbonate platform; 5 - Apennines 33 785 slope and margin deposits (Lias-Miocene); 6 - Apulia carbonate platform and slope deposits (Trias- 34 786 Miocene); 7 - Molise-Sannio-Lagonegro pelagic deposits (Meso-Cenozoic); 8 - syn-orogenic hemi- 35 787 pelagic and turbiditic sequences (Tortonian-Pliocene); 9 - thrust faults; 10 - normal faults. 36 788 37 38 789 Figure 3 - Seismotectonic setting of the Central Apennines. Yellow box: Individual Seismogenic 39 790 Source (ISS) projection onto the ground surface; yellow line: up-dip projection of the ISS onto the 40 791 surface; red polygon: Composite Seismogenic Source (CSS) projection on the ground surface; red line: 41 792 upper edge of the CSS (DISS WORKING GROUP , 2010); black line: active faults mentioned in Table 3; 42 793 grey line: other faults. 43 794 Key to fault names: PI: Pizzoli; MP: Mt. Pettino; PA: Paganica; MAV: Middle Aterno Valley; SV: 44 45 795 Subequana Valley; ACM: Aremogna-Cinque Miglia; FS: Fiamignano-Salto; VM: Val di Malito: VE: 46 796 Velino; MA: Magnola; OP: Ovindoli-Pezza; TM: Tre Monti; SB: San Benedetto-Gioia dei Marsi; 47 797 MPA: Monte Parasano; AI: Aielli; TR: Trasacco; VN: Ventrino; USV: Upper Sangro Valley; MG: 48 798 Monte Greco; BA: Barrea; SP: San Pio delle Camere; SU: Sulmona; MOR: Morrone; MO: 49 799 Montereale; ML: Monti della Laga. OASL: Olevano-Antrodoco-Sibillini Line; ORL: Ortona- 50 51 800 Roccamonfina Line. 52 53 54 55 56 57 58 59 60

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1 2 801 Table Captions 3 802 4 803 - Location and parameters of earthquakes of M > 5.0 that have occurred in the study region 5 Table 1 6 804 and surroundings and for which macroseismic data are available (GRUPPO DI LAVORO CPTI, 2004). 7 805 Earthquakes listed here are those labelled in Fig. 2a. Date is in YYYY MM DD format (months and 8 806 days may be missing for older earthquakes); Intensity is in MCS scale; N Data is number of localities 9 807 for which macroseismic data are avalaible; Source is the code of the Composite Seismogenic Source 10 808 the earthquake has been associated with: a dash in this column indicates that no association has been 11 12 809 made or deemed sufficiently constrained, while OS (Other Source) indicates that the earthquake has 13 810 been associated to a source either lying outside the extensional core of the Abruzzi Apennines and/or 14 811 not mentioned in the text. 15 812 16 813 Table 2 - Location and parameters of the largest instrumental earthquakes that occurred in the study 17 814 region and for which focal mechanisms are available. Earthquakes listed here are those shown with 18 19 815 focal mechanisms in Fig. 2a. Date is in YYYY MM DD format; Time is local (Italian); Reference(s) 20 816 indicates the paper(s) usedFor to derive Review the parameters; Source Only is the code of the Individual Seismogenic 21 817 Source and/or Composite Seismogenic Source the earthquake has been associated with: a dash in this 22 818 column indicates that no association has been made or deemed sufficiently constrained. 23 819 24 25 820 Table 3 - Synoptic view of the active faults or active fault systems reported in regional tectonic 26 821 overviews. Notice the diversity of views concerning the degree of activity of any given fault system. 27 822 Fault systems for which there is consensus across the various research groups are highlighted in bold. 28 823 Key to fault names: PI: Pizzoli; MP: M. Pettino; PA: Paganica; MAV: Middle Aterno Valley; SV: 29 824 Subequana Valley; ACM: Aremogna-Cinque Miglia; FS: Fiamignano-Salto; VM: Val di Malito: VE: 30 825 Velino; MA: Magnola; OP: Ovindoli-Pezza; TM: Tre Monti; SB: San Benedetto-Gioia dei Marsi; 31 32 826 MPA: Monte Parasano; AI: Aielli; TR: Trasacco; VN: Ventrino; USV: Upper Sangro Valley; MG: 33 827 Monte Greco; BA: Barrea; SP: San Pio delle Camere; SU: Sulmona; MOR: Morrone; MO: 34 828 Montereale; ML: Monti della Laga. Key to fault properties: 1 - possible; 2 - subordinate; 3 - 35 829 secondary; 4 - inferred; 5 - no consensus; 6 - Quaternary faults for which no evidence of Upper 36 830 Pleistocene-Holocene activity is available; 7 - doubtful longitudinal continuity and/or seismogenic 37 38 831 role. The active faults are labelled in Fig. 3. *ITHACA database: www.apat.gov.it/site/en- 39 832 GB/Projects/ITHACA_- ITaly_HAzards_from_CApable_faults/default.html. 40 833 41 834 Table 4 - Principal types of analyses, procedures or data used to determine the parameters of 42 835 seismogenic sources (modified from BASILI et alii , 2008). The lists in the second column are not 43 836 intended to be exhaustive. The analyses or procedures used to determine the parameters of 6 April 44 45 837 2009 earthquake source are highlighted in bold. * These data were not available in July 2010, when 46 838 version 3.1.1 of the DISS was published online. 47 839 48 840 Table 5 – Geometric and kinematic parameters of the 2009 L’Aquila earthquake as proposed by 49 841 various investigators. Key: 1 - strike fixed from CMT solution; 2 - available at: 50 51 842 http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/; 3 - available at: http://mednet.rm.ingv.it/; 4 - available 52 843 at: http://www.globalcmt.org/CMTsearch.html; 5 - available at: http://earthquake.usgs.gov/; 6 - 53 844 variable slip models; 7 - uniform slip models; 8 - from aftershock profiles; 9 - total length of mapped 54 845 surface faulting. 55 846 56 847 – Geometric and kinematics parameters of the extensional CSSs of the Central Apennines. 57 Table 6 58 848 Explanatory notes and published source(s) for each single parameter plus a commentary and a full 59 849 reference list can be found on the DISS web interface (http://diss.rm.ingv.it/diss/). 60 850

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1 2 851 Table 7 – Geometric and kinematics parameters of the extensional ISSs of the Central Apennines. 3 852 Explanatory notes and published source(s) for each single parameter plus a commentary and a full 4 853 reference list can be found on the DISS web interface (http://diss.rm.ingv.it/diss/). 5 854 *These data were not available in July 2010, when version 3.1.1 of the Database was published online. 6 7 855 8 856 Table 8 – Main updates and changes of ISS and CSS resulting from the review of the seismotectonic 9 857 regional model, according to the numerous studies that followed the 2009 L’Aquila earthquake. 10 11 12 13 14 15 16 17 18 19 20 For Review Only 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1 2 858 REFERENCES 3 859 4 860 ACCORDI B. (1966) - La componente traslativa nella tettonica dell’Appennino laziale-abruzzese . 5 861 Geologica Romana, , 355-406. 6 5 7 862 ACCORDI G., CARBONE F., CIVITELLI G., CORDA L., DE RITA D., ESU D., FUNICIELLO R., KOTSAKIS T., 8 863 MARIOTTI G. & SPOSATO A. (1986) - Lithofacies map of the Latium-Abruzzi and neighbouring 9 864 areas . C.N.R., Progetto Finalizzato Geodinamica, Sottoprogetto 4. 10 865 AMBROSETTI P., BOSI C., CARRARO F., CIARANFI N, PANIZZA M., PAPANI G., VEZZANI L. & 11 866 ZANFERRARI A. (1983) - . C.N.R. Progetto Finalizzato 12 Carta Neotettonica d’Italia 13 867 Geodinamica, L.A.C., Firenze. 14 868 ANZIDEI M., BALDI P., PESCI A., ESPOSITO A., GALVANI A., LODDO F., CRISTOFOLETTI P., MASSUCCI A. 15 869 & DEL MESE S. (2005) - Geodetic deformation across the Central Apennines from GPS data in 16 870 the time span 1999-2003 . Ann. Geophys., 48 , 2, 259-271. 17 871 ANZIDEI M., BOSCHI E., CANNELLI V., DEVOTI R., ESPOSITO A., GALVANI A., MELINI D., 18 872 PIETRANTONIO G., RIGUZZI F., SEPE V. & SERPELLONI E. (2009) - 19 Coseismic deformation of the 20 873 destructive April For 6, 2009 L’Aquila Review earthquake (centralOnly Italy) from GPS data. Geophys. Res. 21 874 Lett., 36 , L17307, doi:10.1029/2009GL039145. 22 875 ATZORI S., HUNSTAD I., CHINI M., SALVI S., TOLOMEI C., BIGNAMI C., STRAMONDO S., TRASATTI E., 23 876 ANTONIOLI A. & BOSCHI E. (2009) - Finite fault inversion of DInSAR coseismic displacement of 24 877 Geophys. Res. Lett., , L15305, 25 the 2009 L’Aquila earthquake (central Italy). 36 26 878 doi:10.1029/2009GL039293. 27 879 BAGNAIA R., D' EPIFANIO A. & SYLOS LABINI S. (1989) - Aquila and Subequan basins: an example of 28 880 Quaternary evolution in central apennines, Italy . Quaternaria Nova, 1, 1-23. 29 881 BASILI R., VALENSISE G., VANNOLI P., BURRATO P., FRACASSI U., MARIANO S., TIBERTI M.M. & 30 882 BOSCHI E. (2008) - The Database of Individual Seismogenic Sources (DISS), version 3: 31 883 Tectonophysics, , 20-43, 32 summarizing 20 years of research on Italy's earthquake geology. 453 33 884 doi: 10.1016/j.tecto.2007.04.014. 34 885 BASILI R., KASTELIC V., VALENSISE G. & DISS WORKING GROUP (2009) - DISS3 tutorial series: 35 886 Guidelines for compiling records of the Database of Individual Seismogenic Sources, version 3. 36 887 Rapp. Tecn. INGV, 108 , 5-16. http://portale.ingv.it/produzione-scientifica/rapporti-tecnici- 37 888 ingv/archivio/rapporti-tecnici-2009/ . 38 39 889 BASILI R., GARCIA MORENO D., KASTELIC V., NEMSER E., PETRICCA P., SBORAS S. & VALENSISE G. 40 890 (2010) - Developing seismogenic source models based on geologic fault data in the Euro- 41 891 Mediterranean area: SHARE mission accomplished? Proc. 32nd General Assembly of 42 892 European Seismological Commission, Montpellier, 6-10 September 2010. 43 893 http://www.esc2010.eu/cd/documents/Abstracts.pdf. 44 894 BERTINI T. & BOSI C. (1978) - 45 Dati preliminari sulla tettonica dei Fogli 145 “Avezzano ” e 146 46 895 “Sulmona ”. C.N.R., Progetto Finalizzato “Geodinamica ”, 155 , 21-34. 47 896 BIASINI A. (1966) - Elementi morfotettonici, tratti da un rilievo fotogeologico al margine dell’altipiano 48 897 di Ovindoli (Abruzzo) . Geologica Romana, 5, 303-312. 49 898 BIGI S., CALAMITA F., CENTAMORE E., DEIANA G., RIDOLFI M. & SALVUCCI R. (1991a) - Assetto 50 899 51 strutturale e cronologia della deformazione della “zona d ’incontro ” tra le aree umbro- 52 900 marchigiana e laziale-abruzzese (Marche meridionali e Lazio-Abruzzo settentrionali ). Studi 53 901 Geol. Camerti, vol. spec. 1991/2, CROP 11, 21-26. 54 902 BIGI S., CALAMITA F. & PALTRINIERI W. (1995) - Modi e tempi della strutturazione della catena 55 903 centroappenninica abruzzese dal Gran Sasso alla costa adriatica. In: CELLO G., DEIANA G. & 56 904 PIERANTONI P.P. (eds.), “Geodinamica e tettonica attiva del sistema Tirreno-Appennino”, Studi 57 905 Geol. Camerti, vol. spec. , 77-85. 58 1995/2 59 906 BIGI G. , COLI M. , COSENTINO D. , PAROTTO M. , PRATURLON A. , SARTORI R. , SCANDONE P. & TURCO E. 60 907 (1991b) - Structural model of Italy and gravity map, scale 1:500,000, Sheet N. 4 . C.N.R. 908 Progetto Finalizzato Geodinamica. Quad. Ric. Scientif., 3, 114.

http://mc.manuscriptcentral.com/ijg Italian Journal of Geosciences Page 22 of 69

1 2 909 BLUMETTI A.M. (1995) - Neotectonics investigations and evidence of paleoseismicity in the epicentral 3 910 area of the January-February 1703, Central Italy, earthquakes . in: SERVA L. & SLEMMONS 4 911 D.B. (eds): "Perspectives in Paleoseismology", A.E.G. Special Publication, 6, 83-100. 5 912 BONCIO P., LAVECCHIA G. & PACE B. (2004) - 6 Defining a model of 3D seismogenic sources for Seismic 7 913 Hazard Assessment applications: The case of central Apennines (Italy) . J. Seismol., spec. vol., 8 914 8, 3, 407-425. 9 915 BONCIO P., PIZZI A., BROZZETTI F., POMPOSO G., LAVECCHIA G., DI NACCIO D. & FERRARINI F. (2010) 10 916 - Coseismic ground deformation of the 6 April 2009 L’Aquila earthquake (central Italy, Mw 11 917 Geophys. Res. Lett., , L06308, doi:10.1029/2010GL042807. 12 6.3). 37 13 918 BOSCHI E., GUIDOBONI E., FERRARI G., MARIOTTI D., VALENSISE G. & GASPERINI P. (2000) - 14 919 Catalogue of Strong Italian Earthquakes, 461 b.C. to 1997 . Ann. Geofis., 43 , 609-868, with 15 920 database on CD-ROM. 16 921 BOSI C. & BERTINI T. (1970) - La geologia della media valle dell'Aterno . Mem. Soc. Geol. It., 9, 719- 17 922 777. 18 923 BOSI C. (1975) - . 19 Osservazioni preliminari su faglie probabilmente attive nell’Appennino Centrale 20 924 Boll. Soc. Geol. It.,For 94 , 827-859. Review Only 21 925 BOSI C., GALADINI F. & MESSINA P. (1993) - Neotectonic significance of bedrock fault scarps: case 22 926 studies from the Lazio-Abruzzi Apennines (central Italy) . Z. Geomorphol., Suppl. Bd. 94 , 187- 23 927 206. 24 928 CALAMITA F., SATOLLI S., SCISCIANI V., ESESTIME P. & PACE B. (2011) - 25 Contrasting styles of fault 26 929 reactivation in curved orogenic belts: Examples from the Central Apennines (Italy) , Geol. Soc. 27 930 Amer, Bull., 123 , 1097-1111, doi: 10.1130/B30276.1. 28 931 CASTELLO B., SELVAGGI G., CHIARABBA C. & AMATO A. (2006) - CSI Catalogo della sismicità 29 932 italiana 1981-2002, versione 1.1 . INGV-CNT, Roma. http://csi.rm.ingv.it/. 30 933 CAVINATO G.P., CARUSI C., DALL ’A STA M., MICCADEI E. & PIACENTINI T. (2002) - Sedimentary and 31 934 32 tectonic evolution of Plio-Pleistocene alluvial and lacustrine deposits of Fucino Basin (central 33 935 Italy). Sedimentary Geology, 148 , 29-59. 34 936 CELLO G., MAZZOLI S., TONDI E. & TURCO E. (1997) - Active tectonics in the central Apennines and 35 937 possible implications for seismic hazard analysis in peninsular Italy . Tectonophysics, 272 , 43- 36 938 68. 37 939 CELLO G., MAZZOLI S. & TONDI E. (1998) - 38 The crustal fault structure responsible for the 1703 39 940 earthquake sequence of central Italy . J. Geodyn., 26 , 2-4, 443-460. 40 941 CENTAMORE E. & ROSSI D. (2009) - Neogene-Quaternary tectonics and sedimentation in the Central 41 942 Apennines . Ital. J. Geosci. (Boll. Soc. Geol. It.), 128 , 1, 73-88. 42 943 CHELONI D., D’A GOSTINO N., D’A NASTASIO E., AVALLONE A., MANTENUTO S., GIULIANI R., 43 944 MATTONE M., CALCATERRA S., GAMBINO P., DOMINICI D., RADICIONI F. & FASTELLINI G. 44 945 (2010) - 45 Coseismic and initial post-seismic slip of the 2009 Mw 6.3 L’Aquila earthquake, Italy, 46 946 from GPS measurements. Geophys. J. Int., 181 , 1539-1546, doi: 10.1111/j.1365- 47 947 246X.2010.04584.x. 48 948 CHIARABBA C., AMATO A., ANSELMI M., BACCHESCHI P., BIANCHI I., CATTANEO M., CECERE G., 49 949 CHIARALUCE L., CIACCIO M.G., DE GORI P., DE LUCA G., DI BONA M., DI STEFANO R., FAENZA 50 950 L., GOVONI A., IMPROTA L., LUCENTE F.P., MARCHETTI A., MARGHERITI L., MELE F., 51 52 951 MICHELINI A., MONACHESI G., MORETTI M., PASTORI M., PIANA AGOSTINETTI N., PICCININI D., 53 952 ROSELLI P., SECCIA D. & VALOROSO L. (2009) - The 2009 L’Aquila (central Italy) Mw 6.3 54 953 earthquake: Main shock and aftershocks. Geophys. Res. Lett., 36 , L18308, 55 954 doi:10.1029/2009GL039627. 56 955 CHIARALUCE L., CHIARABBA C., DE GORI P., DI STEFANO R., IMPROTA L., PICCINI D., SCHLAGENHAUF 57 956 A., TRAVERSA P., VALOROSO L. & VOISIN C. (2011) - 58 The 2009 L'Aquila (Central Italy) seismic 59 957 sequence. In: AMATO A., GALLI P., MUCCIARELLI M. (eds.), Bollettino di Geofisica Teorica e 60 958 Applicata, Spec. Vol. “The Abruzzo Earthquake”, 52 , 3, 367-387, doi: 10.4430/bgta0019.

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1 2 959 CINTI F., PANTOSTI D., DE MARTINI P. M., PUCCI S., CIVICO R., PIERDOMINICI S., CUCCI L., BRUNORI C. 3 960 A., PINZI S. & PATERA A. (2011) - Evidence for surface faulting events along the Paganica 4 961 Fault prior to the April 6, 2009 L'Aquila earthquake (Central Italy) . J. Geophys. Res., 116 , 5 962 doi:10.1029/2010JB007988. 6 7 963 CIRELLA A., PIATANESI A., COCCO M., TINTI E., SCOGNAMIGLIO L., MICHELINI A., LOMAX A. & 8 964 BOSCHI E. (2009) - Rupture history of the 2009 L’Aquila (Italy) earthquake from non-linear 9 965 joint inversion of strong motion and GPS data . Geophys. Res. Lett., 36 , L19304, 10 966 10.1029/2009GL039795. 11 967 D’A DDEZIO G., MASANA E. & PANTOSTI D. (2001) - 12 The Holocene paleoseismicity of the Aremogna- 13 968 Cinque Miglia Fault (Central Italy) . J. Seismol., 5, 181-205. 14 969 D’A GOSTINO N., AVALLONE A., CHELONI D., D’A NASTASIO E., MANTENUTO S. & SELVAGGI G. (2008) 15 970 - Active tectonics of the Adriatic region from GPS and earthquake slip vectors . J. Geophys. 16 971 Res., 113 , B12413, doi: 10.1029/2008JB005860. 17 972 D'A GOSTINO N., MANTENUTO S., D'A NASTASIO E., GIULIANI R., MATTONE M., CALCATERRA S., 18 973 GAMBINO P. & BONCI L. (2011) - 19 Evidence for localized active extension in the central 20 974 Apennines (Italy) Forfrom global Review positioning system Onlyobservations. Geology, 39 , 4, 291-295. doi: 21 975 10.1130/G31796.1. 22 976 DI BUCCI D. & TOZZI M. (1991) - La linea “Ortona – Roccamonfina”: revisione dei dati esistenti e 23 977 nuovi contributi per il settore settentrionale (media Valle del Sangro) , Studi Geol. Cam., Vol. 24 978 Spec. 1991/2, CROP 11, 397-406. 25 26 979 DI BUCCI D., RAVAGLIA A., SENO S., TOSCANI G., FRACASSI U., & VALENSISE G. (2006) - 27 980 Seismotectonics of the Southern Apennines and Adriatic foreland: insights on active regional 28 981 E-W shear zones from analogue modeling . Tectonics, 25 , TC4015, doi: 29 982 10.1029/2005TC001898. 30 983 DI BUCCI D., BURRATO P., VANNOLI P. & VALENSISE G. (2010) - Tectonic evidence for the ongoing 31 984 32 Africa-Eurasia convergence in central Mediterranean foreland areas: A journey among long- 33 985 lived shear zones, large earthquakes, and elusive fault motions . J. Geophys. Res., 115 , B12404, 34 986 doi:10.1029/2009JB006480. 35 987 DI BUCCI D., VANNOLI P., BURRATO P., FRACASSI U. & VALENSISE G. (2011a) - Insights from the Mw 36 988 6.3, 2009 L’Aquila earthquake (Central Apennines) to unveil new seismogenic sources through 37 989 Terra Nova, , 108-115. 38 their surface signature: the adjacent San Pio Fault. 23 39 990 DI BUCCI D., VANNOLI P., BURRATO P., FRACASSI U. & VALENSISE G. (2011b) - Reply to Comment on 40 991 Insights from the Mw 6.3, 2009 L’Aquila earthquake (Central Apennines) to unveil new 41 992 seismogenic sources through their surface signature: the adjacent San Pio Fault. Terra Nova, 42 993 10.1111/j.1365-3121.2011.01026.x. 43 994 DI LUZIO E., MELE G., TIBERTI M.M., CAVINATO G.P., & PAROTTO M. (2009) - Moho deepening and 44 995 . Earth. Planet. Sci. Lett., 45 shallow upper crustal delamination beneath the central Apennines 46 996 280 , 1-12. doi: 10.1016/j.epsl.2008.09.018. 47 997 DISS WORKING GROUP (2010) - Database of Individual Seismogenic Sources (DISS), Version 3.1.1: A 48 998 compilation of potential sources for earthquakes larger than M 5.5 in Italy and surrounding 49 999 areas . http://diss.rm.ingv.it/diss/, © INGV 2010 - Istituto Nazionale di Geofisica e 501000 Vulcanologia. 51 521001 EMERGEO WORKING GROUP (2010) - Evidence for surface rupture associated with the Mw 6.3 531002 L’Aquila earthquake sequence of April 2009 (central Italy) . Terra Nova, 22 , 43-51, doi: 541003 10.1111/j.1365-3121.2009.00915.x. 551004 FALCUCCI E., GORI S., PERONACE E., FUBELLI G., MORO M., SAROLI M., GIACCIO B., MESSINA P., 561005 NASO G., SCARDIA G., SPOSATO A., VOLTAGGIO M., GALLI P. & GALADINI F. (2009) - The 571006 58 Paganica fault and surface coseismic ruptures due to the April 6, 2009 earthquake (L’Aquila, 591007 Central Italy). Seismol. Res. Lett., 80 , 6, doi:10.1785/gssrl.80.6.940. 60

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1 21008 FALCUCCI E., GORI S., MORO M., PISANI A.R., MELINI D., GALADINI F. & FREDI P. (2011) - The 2009 31009 L'Aquila earthquake (Italy): What's next in the region? Hints from stress diffusion analysis and 41010 normal fault activity . Earth Plan. Sci. Lett., 305 , 350-358, doi:10.1016/j.epsl.2011.03.016. 5 1011 FRACASSI U. (2001) - 6 Morphotectonic signature of the Campo Imperatore intermontane basin (Central 71012 Apennines): implications for the seismotectonics of Central Italy . Unpublished Ph.D. thesis, 81013 123 pp, Consorzio Università di Parma-Firenze-Ferrara. 91014 FRACASSI U. & VALENSISE G. (2007) - Unveiling the sources of the catastrophic 1456 multiple 101015 earthquake: Hints to an unexplored tectonic mechanism in Southern Italy . Bull. Seismol. Soc. 111016 Am., , 3, 725-748, doi: 10.1785/0120050250. 12 97 131017 FREZZOTTI M. & GIRAUDI C. (1992) - Evoluzione geologica tardo-pleistocenica ed olocenica del 141018 conoide complesso di Valle Majelama (Massiccio del Velino, Abruzzo) , Il Quaternario, 5, 1, 33- 151019 50. 161020 GALADINI F. (1999) - Pleistocene changes in the central Apennine fault kinematics: A key to decipher 171021 active tectonics in central Italy . Tectonics, 18 , 877-894. doi: 10.1029/1999TC900020. 18 1022 GALADINI F. (2006) - 19 Quaternary tectonics and large-scale gravitational deformations with evidence 201023 of rock-slide displacementsFor inReview the Central Apennines Only (central Italy). Geomorphology, 82 , 201- 211024 228, doi: 10.1016/j.geomorph.2006.05.003. 221025 GALADINI F. & GALLI P. (1999) - The Holocene paleoeartquakes on the 1915 Avezzano earthquake 231026 faults (central Italy): implications for active tectonics in the central Apennines . 241027 Tectonophysics, , 143-170. 25 308 261028 GALADINI F. & GALLI P. (2000) - Active tectonics in the Central Apennines (Italy) - Input data for 271029 seismic hazard assessment . Nat. Hazards, 22 , 225-270. 281030 GALADINI F., MELETTI C. & REBEZ A. (eds.) (2000) - Le ricerche del GNDT nel campo della 291031 pericolosità sismica (1996–1999) . CNR-Gruppo Nazionale per la Difesa dai Terremoti - Roma, 301032 397 pp. 31 1033 GALADINI F. & MESSINA P. (2001) - 32 Plio-Quaternary changes of the normal fault architecture in the 331034 Central Apennines (Italy). Geodin. Acta, 14 , 6, 321-344. 341035 GALADINI F. & MESSINA P. (2004) - Early-Middle Pleistocene eastward migration of the Abruzzi 351036 Apennine (central Italy) extensional domain . J. Geodynamics, 37 , 57-81. doi: 361037 10.1016/j.jog.2003.10.002. 37 1038 GALLI P., GALADINI F., MORO M. & GIRAUDI C. (2002) - 38 New paleoseismological data from the 391039 Gran Sasso d'Italia area (central Apennines) . Geophys. Res. Lett., 29 , 401040 doi: 10.1029/2001GL013292. 411041 GALLI P., GALADINI F. & PANTOSTI D. (2008) - Twenty years of paleoseismology in Italy , Earth 421042 Sci. Rev., 88 , 89-117, doi:10.1016/j.earscirev.2008.01.001. 431043 GALLI P., GIACCIO B. & MESSINA P. (2010a) - The 2009 central Italy earthquake seen through 0.5 441044 . Quaternary Sci. Rev., , 3768-3789. 45 Myr-long tectonic history of the L'Aquila faults system 29 461045 GALLI P., MESSINA P., GIACCIO B., PERONACE E. & QUADRIO B. (2010b) - Indicating of Late Holocene 471046 activity along the Magnola Fault (central Italy) . 10° Convegno Nazionale Gruppo Nazionale di 481047 Geofisica della Terra Solida , Prato, 26-28 October 2010. 491048 GALLI P.A.C., GIACCIO B., MESSINA P., PERONACE E. & ZUPPI G.M. (2011) - Palaeoseismology of the 501049 51 L’Aquila faults (central Italy, 2009, M w 6.3 earthquake): implications for active fault linkare. 521050 Geoph. J. Int., doi: 10.1111/j.1365-246x.2011.05233.x. 531051 GASPERINI P., BERNARDINI F., VALENSISE G. & BOSCHI E. (1999) - Defining Seismogenic Sources from 541052 Historical Earthquake Felt Reports . Bull. Seismol. Soc. Am., 89 , 94-110. 551053 GASPERINI P., VANNUCCI G., TRIPONE D. & BOSCHI E. (2010) - The Location and Sizing of Historical 561054 Earthquakes Using the Attenuation of Macroseismic Intensity with Distance . Bull. Seismol. 571055 Soc. Am., , 5A, 2035-2066. doi: 10.1785/0120090330. 58 100 591056 GHISETTI F. (1987) - Mechanisms of thrust faulting in the Gran Sasso chain, Central Apennines, Italy. 601057 J. Struct. Geol ., 9, 955-967. doi: 10.1016/0191-8141(87)90004-6.

http://mc.manuscriptcentral.com/ijg Page 25 of 69 Italian Journal of Geosciences

1 21058 GHISETTI F. & VEZZANI L. (2000) - Detachments and normal faulting in the Marche fold-and-thrust 31059 belt (central Apennines, Italy): inferences on fluid migration paths. J. Geodynamics, 29 , 345- 41060 369. doi: 10.1016/S0264-3707(99)00057-5. 5 1061 GIRAUDI C. & FREZZOTI M. (1995) - 6 Palaeoseismicity in the Gran Sasso Massif (Abruzzo, Central 71062 Italy) . Quat. Int., 25 , 81-93, doi: 10.1016/1040-6182(94)P3716-L. 81063 GORI S., GIACCIO B., GALADINI F., FALCUCCI E., MESSINA P., SPOSATO A. & DRAMIS F. (2011) - Active 91064 normal faulting along the Mt. Morrone south-western slopes (central Apennines, Italy), Int. J. 101065 Earth Sci., 100 , 157-171, 10.1007/s00531-009-0505-6. 11 1066 GORI S., FALCUCCI E., ATZORI S., CHINI M., MORO M., SERPELLONI E., FUBELLI G., SAROLI M., DEVOTI 12 131067 R., STRAMONDO S., GALADINI F. & SALVI S. (this issue) - Constraining primary surface 141068 rupture length along the Paganica fault (L’Aquila earthquake) with geological and geodetic 151069 (DInSAR and GPS) evidence . Italian Journal of Geosciences. 161070 GRUPPO DI LAVORO CPTI (2004) - Catalogo Parametrico dei Terremoti Italiani, versione 2004 171071 (CPTI04) . INGV, Bologna. http://emidius.mi.ingv.it/CPTI/. 18 1072 GUERRIERI L., BAER G., HAMIEL Y., AMIT R., BLUMETTI A. M., COMERCI V., DI MANNA P., MICHETTI 19 201073 A. M., SALAMON ForA., MUSHKIN Review A., SILEO G. & V ITTORIOnly E. (2011) - InSAR data as a field guide 211074 for mapping minor earthquake surface ruptures: Ground displacements along the Paganica 221075 Fault during the 6 April 2009 L'Aquila earthquake . J. Geophys. Res., 115, B12331, 231076 doi:10.1029/2010JB007579. 24 1077 GUIDOBONI E. & COMASTRI A. (2005) - Catalogue of earthquakes and tsunamis in the Mediterranean 25 261078 area from the 11th to the 15th century. Istituto Nazionale di Geofisica e Vulcanologia - SGA, 271079 Bologna, 1037 pp. 281080 GUIDOBONI E., FERRARI G., MARIOTTI D., COMASTRI A., TARABUSI G. & VALENSISE G. (2007) - 291081 CFTI4Med, Catalogue of Strong Earthquakes in Italy (461 B.C.-1997) and Mediterranean 301082 Area (760 B.C.-1500) . INGV-SGA. Available from http://storing.ingv.it/cfti4med/. 31 1083 HANKS T. & KANAMORI H. (1979) - . J. Geophys. Res., , B5, 2348-2350. 32 A moment magnitude scale 84 331084 HARRIS R.A. (1998) - Introduction to special section: stress triggers, stress shadows, and implications 341085 for seismic hazard . J. Geophys. Res., 103 , B10, 24347-24358, doi: 10.1029/98JB01576. 351086 HERRMANN R.B., MALAGNINI L. & MUNAFÒ I. (2011) - Regional Moment Tensors of the 2009 361087 L’Aquila Earthquake Sequence. Bull. Seism. Soc. Am., 101, 975-993, doi: 371088 10.1785/0120100184. 38 391089 HIPPOLYTE J.-C., ANGELIER J. & ROURE F. (1994) - A major geodynamic change revealed by 401090 Quaternary stress patterns in the southern Apennines (Italy) . Tectonophysics, 230 , 199-210, 411091 doi: 10.1016/0040-1951(94)90135-X. 421092 ISIDE (2010) - Italian Seismic Instrumental and parametric Data-basE . 431093 http://iside.rm.ingv.it/iside/standard/index.jsp. © Italian Seismic Bulletin, Istituto Nazionale di 441094 Geofisica e Vulcanologia - All rights reserved. 45 461095 KENNER S. & SEGALL P. (1999) - Time-dependence of the stress shadowing effect and its relation to 471096 the structure of the lower crust . Geology, 27 , 2, 119-122. 481097 LAVECCHIA G., DE NARDIS R. & FERRARINI F. (2010) - Seismogenic sources of major earthquakes of 491098 the Maiella and Abruzzo foothill areas: constraints from macroseismic field simulation and 501099 . Poster at DPC-INGV 2007-2009 Final Meeting, Rome, 30 June-2 51 regional seismotectonic data 521100 July 2010. 531101 LOCARDI E. (1982) - Individuazione di Strutture sismogenetiche dall’esame dell’evoluzione 541102 vulcanotettonica dell’Appennino e del Tirreno , Mem. Soc. Geol. Ital., 24 , 569-596. 551103 LOCARDI E. (1988) - The origin of the Apenninic Arcs . In: WEZEL F.C. (ed.), The Origin and Evolution 561104 Tectonophysics, , 105-123. 57 of Arcs, 146 1105 MARIOTTI G. & CAPOTORTI F. (1988) - 58 Analisi ed interpretazione di alcuni elementi tettonici recenti 591106 nella media Valle del Salto (Rieti) . Rend. Soc. Geol. It., 11 , 79-84. 60

http://mc.manuscriptcentral.com/ijg Italian Journal of Geosciences Page 26 of 69

1 21107 MARIUCCI M.T., MONTONE P. & PIERDOMINICI S. (2010) - Present-day stress in the surroundings of 31108 2009 L’Aquila seismic sequence (Italy) . Geophys. J. Int., 182 , 2, 1096-1102, doi: 41109 10.1111/j.1365-246X.2010.04679.x. 5 1110 MESSINA P., P. GALLI & B. GIACCIO (2011) - Comment on 6 Insights from the Mw 6.3, 2009 L’Aquila 71111 earthquake (Central Apennines) to unveil new seismogenic sources through their surface 81112 signature: the adjacent San Pio Fault by DI BUCCI D., VANNOLI P., BURRATO P., FRACASSI U. 91113 & VALENSISE G. (2011) - Terra Nova, 23 , 4, 280-282, 10.1111/j.1365-3121.2011.01010.x . 101114 MICCADEI E., PIACENTINI T. & BARBERI R. (2002) - Uplift and local tectonic subsidence in the 111115 12 evolution of in tramontane basins: the example of the sulmona basin (central Appennines, 131116 Italy) . In: DRAMIS F., FARABOLLINI P. & MOLIN P. (eds.), Large-scale movements and related 141117 gravitational processes . International Workshop Camerino-Rome, 21-26 June 1999, Studi 151118 Geologici Camerti, Camerino, 119-134. 161119 MICHETTI A.M., BRUNAMONTE F., SERVA L. & VITTORI E. (1996) - Trench investigations of the 1915 171120 Fucino earthquake fault scarp (Abruzzo, central Italy): geological evidence of large historical 181121 . J. Geophys. Res., , B3, 5921-5936. 19 events 101 201122 MIGLIORINI C.I. (1948) - ForI cunei composti Review nell’orogenesi . OnlyBoll. Soc. Geol. It., 67 , 29-142. 211123 MILANO G. & DI GIOVAMBATTISTA R. (2011) - Seismicity at the border between Central and Southern 221124 Apennines (Italy): Re-evaluation of the early 1984 instrumental earthquake , Tectonophysics, 231125 499 , 92-104, doi: 10.1016/j.tecto.2010.12.008. 24 1126 MILANO G., DI GIOVAMBATTISTA R. & VENTURA G. (2008) - 25 Seismic activity in the transition zone 261127 between Southern and Central Apennines (Italy): evidences of longitudinal extension inside the 271128 Ortona-Roccamonfina tectonic line . Tectonophysics, 457 , 102-110, 281129 doi:10.1016/j.tecto.2008.05.034. 291130 MONTONE P., MARIUCCI M.T., PONDRELLI S. & AMATO A. (2004) - An improved stress map for Italy 301131 and surrounding regions (central Mediterranean) . J. Geophys. Res., 109 , B10410, 1-22, doi: 311132 10.1029/1003JB002703. 32 331133 MOREWOOD N.C. & ROBERTS G.P. (2000) - The geometry, kinematics and rates of deformation within 341134 an en echelon normal fault segment boundary, central Italy . Journal Structural Geology, 22 , 351135 1027-1047. 361136 MORO M., FALCUCCI E ., GORI S ., SAROLI M., PISANI A.R., MELINI D ., FUBELLI G., GALADINI F. & SALVI 371137 S. (2010) - 38 Nuovi dati paleosismologici sul sistema di faglie della Valle dell’Aterno e 391138 distribuzione dello stress a seguito del terremoto da L’Aquila del 2009 . 10° Convegno 401139 Nazionale Gruppo Nazionale di Geofisica della Terra Solida , Prato, 26-28 October 2010. 411140 ODDONE E. (1915) - Gli elementi fisici del grande terremoto marsicano-fucense del 13 gennaio 1915 . 421141 Boll. Soc. Sism. It., 19 , 71-291. 431142 PACE B, BONCIO P. & LAVECCHIA G. (2002) - The 1984 Abruzzo earthquake: an example of 441143 . 45 seismogenic process controlled by interaction between differently oriented synkinematic faults 461144 Tectonophysics, 350 , 3, 237-254, doi: 10.1016/S0040-1951(02)00118-X. 471145 PACE B., PERUZZA L., LAVECCHIA G. & BONCIO P. (2006) - Layered seismogenic source model and 481146 probabilistic seismic-hazard analyses in Central Italy . B. Seismol. Soc. Am., 96 , 1, 107-132, 491147 doi: 10.1785/0120040231. 50 1148 PALUMBO L., BENEDETTI L., BOURLÈS D., CINQUE A. & FINKEL R. (2004) - 51 Slip history of the Magnola 521149 fault (Apennines, Central Italy) from 36Cl surface exposure dating: evidence for strong 531150 earthquake over the Holocene . Earth Planet. Sci. Lett., 225 , 163-176. 541151 PANTOSTI D., D’A DDEZIO G. & CINTI F.R. (1996) - Paleoseismicity of the Ovindoli-Pezza fault,central 551152 Apennines, Italy: a history including a large, previously unrecorded earthquake in Middle Ages 561153 . J. Geophys. Res., , 5937-5959. 57 (886-1300 A.D.) 101 1154 PATACCA E., & SCANDONE P. (2004) - 58 The Plio-Pleistocene thrust belt - foredeep system in the 591155 Southern Apennines and Sicily (Italy) . In: Geology of Italy (CRESCENTI U., D’O FFIZI S., 601156 MERLINI S. & LACCHI L., eds.). Soc. Geol. It., Roma, 93-129.

http://mc.manuscriptcentral.com/ijg Page 27 of 69 Italian Journal of Geosciences

1 21157 PATACCA E., SARTORI R. & SCANDONE P. (1990). Tyrrhenian basin and Apenninic arc: kinematic 31158 relations since Late Tortorian times . Mem. Soc. Geol. Ital., 45 , 425-451. 41159 PATACCA E., SCANDONE P., DI LUZIO E., CAVINATO G.P. & PAROTTO M. (2008) - Structural 51160 6 architecture of the central Apennines: Interpretation of the CROP 11 seismic profile from the 71161 Adriatic coast to the orographic divide . Tectonics, 27 , TC3006, doi: 10.1029/2005TC001917. 81162 PECCERILLO A. (2005) - Plio-Quaternary Volcanism in Italy: Petrology, Geochemistry, Geodynamics. 91163 Springer Books, 365 pp., doi: 10.1007/3-540-29092-3. 101164 PICCARDI L., GAUDEMER Y., TAPPONIER P. & BOCCALETTI M. (1999) - Active oblique extension in the 111165 . Geophys. J. Int., , 499-530. 12 central Apennines (Italy): evidence from the Fucino region 139 131166 PIZZI A. & SCISCIANI V. (2000) - Methods for determining the Pleistocene–Holocene component of 141167 displacement on active faults reactivating pre-Quaternary structures: examples from the 151168 Central Apennines (Italy) . Journal of Geodynamics, 29 , 3-5, 445-457. 161169 PIZZI A., CALAMITA F., COLTORTI M. & PIERUCCINI P. (2002) - Quaternary normal faults, in 171170 tramontane basins and seismicity in the Umbria-Marche-Abruzzi Apennine Ridge (Italy): 181171 . Boll. Soc. Geol. It., vol. 19 contribution of neotectonic analysis to seismic hazard assessment 201172 spec. 1, 923-929. For Review Only 211173 PIZZI A. & GALADINI F. (2009) - Pre-existing cross-structures and active fault segmentation in the 221174 northern-central Apennines . Tectonophysics, 476 , 304-319, doi: 10.1016/j.tecto.2009.03.018. 231175 PONDRELLI , S., SALIMBENI S., MORELLI A., EKSTRÖM G., OLIVIERI M. & BOSCHI E. (2010) - Seismic 241176 Geophys. J. 25 moment tensors of the April 2009, L’Aquila (Central Italy) earthquake sequence. 261177 Int., 180 , 238-242, doi: 10.1111/j.1365-246X.2009.04418.x. 271178 ROBERTS G.P. & MICHETTI A.M. (2004) - Spatial and temporal variations in growth rates along active 281179 normal fault systems: an example from The Lazio–Abruzzo Apennines, central Italy . J. Struct. 291180 Geol., 26 , 2, 339-376. 301181 ROBERTS G.P., PHILLIPS R., MCCAFFREY K. & WILKINSON M. (2009) - L’Aquila Earthquake: 311182 13 th April 2009. 32 Preliminary report, unpublished, 331183 SCHLAGENHAUF A., MANIGHETTI I., BENEDETTI L., GAUDEMER Y., FINKEL R., MALAVIEILLE J. & POU 341184 K. (2011) - Earthquake supercycles in Central Italy, inferred from 36Cl exposure dating. Earth 351185 Planet. Sci. Lett., 307 , 3-4, 487-500, doi:10.1016/j.epsl.2011.05.022. 361186 SCHWARTZ D.P. & COPPERSMITH K.J. (1984) - Fault behaviour and characteristic earthquakes: 371187 . J. Geophys. Res., , 5681-5698. 38 examples from Wasatch and San Andreas faults 89 391188 SCISCIANI V. & CALAMITA F. (2009) - Active intraplate deformation within Adria: Examples from the 401189 Adriatic region . Tectonophysics, 476 , 57-72, doi: 10.1016/j.tecto.2008.10.030. 411190 SCOGNAMIGLIO , L., TINTI E., MICHELINI A., DREGER D., CIRELLA A., COCCO M., MAZZA S., & 421191 PIATANESI A. (2010) - Fast determination of moment tensors and rupture history: Application 431192 to the April 6th 2009, L’Aquila earthquake. Seismol. Res. Lett., 81 , 6, 892-906, doi: 441193 10.1785/gssrl.81.6.892. 45 461194 SERPELLONI E., ANZIDEI M., BALDI , P., CASULA G. & GALVANI A. (2005) - Crustal velocity and strain 471195 rate fields in Italy and surrounding regions: new results from the analysis of permanent and 481196 non-permanent GPS networks . Geophys. J. Int., 161 , 861-880, doi: 10.1111/j.1365- 491197 246X.2005.02618.x. 50 1198 SERPELLONI E., VANNUCCI G., PONDRELLI S., ARGNANI A., CASULA G., ANZIDEI M., BALDI P. & 51 521199 GASPERINI P. (2007) - Kinematics of the Western Africa-Eurasia plate boundary from focal 531200 mechanisms and GPS data . Geophys. J. Int . 189 , 1180-1200, doi: 10.1111/j.1365- 541201 246X.2007.03367.x. 551202 SERPELLONI E., ANDERLINI L., ANZIDEI M., DEVOTI R., ESPOSITO A., GALVANI A., PIETRANTONIO G., 561203 RIGUZZI F., SEPE V. & BELARDINELLI M.E. (2010) - Fault Geometry, Co-Seismic and Post- 571204 58 Seismic Slip Distribution of the April 6, L’Aquila Earthquake Imaged From Inversion of GPS 591205 Data. Geophysical Research Abstracts, 12 , EGU2010-10934. 60

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1 21206 SERVA L., BLUMETTI A.M. & MICHETTI A.M. (1986) - Gli effetti sul terreno del terremoto del Fucino 31207 (13 gennaio 1915); tentativo di interpretazione della evoluzione tettonica recente di alcune 41208 strutture . Mem. Soc. Geol. It., 35 , 893-907. 5 1209 SERVIZIO GEOLOGICO D ’I TALIA (2006) - , sheet L’Aquila n. 359, scale 6 Carta Geologica d’Italia 71210 1:50,000, CARG Project, APAT. 81211 STUCCHI M., P. ALBINI , C. MIRTO & A. REBEZ (2004) - Assessing the completeness of Italian historical 91212 earthquake data. Ann. Geophys., 47 , 2-3, 659-673. 10 111213 TERTULLIANI A., GALADINI F., MASTINO F., ROSSI A. E VECCHI M. (2006) - Studio macrosismico 121214 del terremoto del Gran Sasso del 5 settembre 1950 . Il Quaternario, 19 , 2, 195-214. 13 1215 TERTULLIANI A., ROSSI A., CUCCI L. & VECCHI M. (2010) - 14 L’Aquila (Central Italy) Earthquakes: The 151216 Predecessors of the April 6, 2009 Event . Seismol. Res. Lett., 80 , 6, 1008-1014, 161217 10.1785/gssrl.80.6.1008. 171218 TRASATTI E., KYRIAKOPOULOS C. & CHINI M. (2011) - Finite element inversion of DInSAR data from 181219 the Mw 6.3 L’Aquila earthquake, 2009 (Italy). Geophys. Res. Lett., 38 , L08306, 191220 doi:10.1029/2011GL046714. 20 For Review Only 1221 VALENSISE G. & PANTOSTI D. (2001a) - 21 The investigation of potential earthquake sources in peninsular 221222 Italy: a review. J. Seismol., 5, 287-306. 231223 VALENSISE G. & PANTOSTI D. (eds.) (2001b) - Database of Potential Sources for Earthquakes Larger 241224 than M 5.5 in Italy (DISS version 2.0). Ann. Geofis., 44 , Suppl. 1, CD-ROM . 251225 VEZZANI L. & GHISETTI F. (1998) - Carta geologica dell'Abruzzo , Scale 1:100,000, S.EL.CA., Firenze. 26 1226 VEZZANI L., GHISETTI F. & FESTA A. (2009) - 27 Caratterizzazione strutturale dei principali sistemi di 281227 faglie dell’Abruzzo Aquilano . Geoitalia, 28 , 4-12, doi: 10.1474/Geoitalia-28-03. 291228 VITTORI E., CAVINATO G.P. & MICCADEI E. (1995) - Active faulting along the northeastern edge of the 301229 Sulmona basin, central Apennines, Italy . In: SERVA L. & BURTON SLEMMONS D. (eds.), 311230 Perspective in paleoseismology . Spec. Publ.-Association of Engineering Geologists, 6, 115- 321231 126. 33 341232 VITTORI E., DI MANNA P., BLUMETTI A. M., COMERCI V., GUERRIERI L., ESPOSITO E., MICHETTI A. M., 351233 PORFIDO S., PICCARDI L., ROBERTS G. P., BERLUSCONI A., LIVIO F., SILEO G., WILKINSON M., 361234 MCCAFFREY K. J. W., PHILLIPS R. J. & COWIE P. A. (2011) - Surface Faulting of the 6 April 371235 2009 Mw 6.3 L’Aquila Earthquake in Central Italy . Bull. Seism. Soc. Am., 101 , 4, 1507-1530, 381236 doi:10.1785/0120100140. 39 1237 WALTERS , R.J., ELLIOTT J.R., D’A GOSTINO N., ENGLAND P.C., HUNSTAD I., JACKSON J.A., PARSONS B., 40 411238 PHILLIPS R.J. & ROBERTS G. (2009) - The 2009 L’Aquila earthquake (central Italy): A source 421239 mechanism and implications for seismic hazard. Geophys. Res. Lett., 36 , L17312, 431240 doi:10.1029/2009GL039337. 441241 WARD S.N. & VALENSISE G. (1989) - Fault parameters and slip distribution of the 1915, Avezzano, 451242 . Bull. Seism. Soc. Am., , 690-710. 46 Italy earthquake derived from geodetic observations 79 471243 WELLS D.L. & COPPERSMITH K.J. (1994) - New empirical relationships among magnitude, rupture 481244 length, rupture width, rupture area, and surface displacement . Bull. Seismol. Soc. Am., 84 , 491245 974-1002. 501246 WESNOUSKY S.G. ( 1994) - The Gutenberg-Richter or characteristic earthquake distribution, which is 511247 it? Bull. Seismol. Soc. Am., 84 , 6, 1940-1959. 52 1248 WESTAWAY R., GAWTHORPE R. & TOZZI M. (1989) - 53 Seismological and field observations of the 1984 541249 Lazio-Abruzzo earthquakes: implications for the active tectonics of Italy . Geophysical J., 98 , 551250 489-514. 56 57 58 59 60

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1 21251 TABLES 31252 41253 Table 1 51254 6 7 Date Time Locality Lat (°) Lon (°) Intensity Mw N Data Source - 8 101 ------S. Valentino in Ab. Cit. 42.230 13.980 IX-X 6.3 1 1315 12 03 09 30 -- Italia centrale 42.000 13.970 IX 6.0 15 ITCS040 9 1328 12 01 ------Norcia 42.856 13.018 X 6.4 13 ITCS028 10 1349 09 09 ------Aquilano 42.170 13.380 IX-X 6.5 22 ITCS025 11 1461 11 26 21 30 -- Aquilano 42.308 13.543 X 6.5 10 ITCS013 12 1639 10 07 00 30 -- Amatrice 42.636 13.252 X 6.3 27 ITCS028 13 1654 07 23 00 25 -- Sorano-Marsica 41.630 13.680 IX-X 6.2 44 - 14 1703 01 14 18 -- -- Appennino reatino 42.680 13.120 XI 6.8 196 ITCS028 15 1703 02 02 11 05 -- Aquilano 42.470 13.200 X 6.7 70 ITCS013 1706 11 03 13 -- -- Maiella 42.080 14.080 IX-X 6.6 99 OS 16 1762 10 06 12 10 -- Aquilano 42.300 13.580 IX 5.9 6 ITCS040 17 1791 01 ------L'Aquila 42.356 13.396 VII-VIII 5.4 1 ITCS013 18 1838 02 14 ------Valnerina 42.875 12.886 VIII 5.6 9 ITCS028 19 1881 09 10 07 -- -- Abruzzo meridionale 42.230 14.280 VIII 5.6 29 OS 20 1882 02 12 ------Chieti For Review 42.290 14.347 VII Only 5.3 8 OS 21 1904 02 24 15 53 26 Marsica 42.100 13.320 VIII-IX 5.7 56 ITCS025 22 1915 01 13 06 52 -- Avezzano 42.013 13.530 XI 7.0 1041 ITCS025 1916 04 22 04 33 -- Aquilano 42.294 13.396 VI-VII 5.2 9 ITCS013 23 1933 09 26 03 33 29 Maiella 42.050 14.180 VIII-IX 5.7 326 OS 24 1950 09 05 04 08 -- Gran Sasso 42.516 13.657 VIII 5.7 137 OS 25 1958 06 24 06 07 -- Aquilano 42.340 13.477 VII 5.2 14 ITCS013 26 1979 09 19 21 35 37 Valnerina 42.720 13.070 VIII-IX 5.9 691 ITCS028 27 1984 05 07 17 49 42 Appennino abruzzese 41.666 14.057 VIII 5.9 913 ITCS025 28 2002 10 31 10 33 00 Molise 41.694 14.925 VII-VIII 5.8 51 OS 291255 301256 Table 2 311257

32 Date Time Locality Lat (°) Lon (°) Mw Strike (°) Dip (°) Rake (°) Reference(s) Source(s) 33 ITIS002 1915 01 13 06 52 Avezzano 42.01 13.53 7.0 135 63 -90 WARD & VALENSISE (1989) 34 ITCS025 ITIS028 35 1984 05 07 17 49 Barrea 41.66 14.06 5.8 123 48 -96 WESTAWAY et alii (1989) ITCS025 36 CHIARABBA et alii (2009) ITIS131 2009 04 06 03 32 L’Aquila 42.42 13.45 6.3 134 56 -97 37 PONDRELLI et alii (2010) ITCS013 338 73 -58 CHIARALUCE et alii (2011) 38 2009 04 07 19 47 L’Aquila 42.36 13.52 5.4 - 39 93 36 -151 SCOGNAMIGLIO et alii (2010) CHIARALUCE et alii (2011) 2009 04 09 02 53 L’Aquila 42.53 13.44 5.2 136 46 -99 ITCS028 40 PONDRELLI et alii (2010) 411258 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1 21259 Table 3 31260 4 5 6

7 2011 , 2000 2000 ,

, , 2004 2004 , 2000 2000

8 2009

1989 1999 , , ,

2009

,2011

, , , 2000 1997 ,

, 2004 ,

9 2002 ,

2006 2006 , et alii et

ALLI , 10 OBERTS 1975 1975 ICHETTI

G R

, et alii et et alii, et et alii et et alii et

et alii et

et alii et 11 M , ALADINI & et alii et

& et alii et & G OSI

12 ITHACA* ITCSXXX B ALADINI & Fault Fault System 13 IZZI ELLO ELLO G P ONCIO EZZANI EZZANI ALADINI AGNAIA ICCARDI C ALCUCCI IZZI ALADINI ALADINI B

14 V B P G F P G OBERTS OBERTS 15 CHLAGENHAUF OREWOOD OREWOOD R S

16 M

17 CompositeSeismogenic Source - 18 PI 013 Yes Yes Yes Yes n/a Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 19 MP 013 Yes Yes Yes Yes n/a Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 20 PA 013 No Yes For Yes n/a Review n/a No No No Only Yes Yes 7 No No Yes Yes Yes Yes 21 MAV 013 Yes Yes 2 Yes n/a n/a No Yes Yes Yes Yes No Yes Yes Yes Yes Yes 22 SV 013 Yes 1 No Yes n/a n/a No No No Yes No No No Yes No Yes Yes 23 ACM 013 Yes Yes n/a n/a n/a n/a Yes Yes n/a Yes Yes Yes Yes Yes Yes Yes 24 FS 025 Yes Yes n/a n/a n/a Yes Yes 5 No No Yes Yes Yes No No Yes 3 No 25 VM 025 Yes No n/a n/a n/a Yes 4 No No Yes No No Yes No Yes Yes No 26 VE 025 Yes Yes n/a n/a Yes Yes No No Yes Yes Yes No No Yes Yes No 27 MA 025 Yes Yes n/a Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 28 OP 025 Yes Yes n/a Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 29 TM -- Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes No Yes Yes Yes No 30 SB 025 Yes 1 Yes n/a Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 31 MPA 025 Yes Yes n/a Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 32 AI 025 No No n/a No Yes 3 No No No No No No No No Yes Yes No 33 025 2 34 TR Yes Yes n/a Yes Yes Yes No Yes Yes No Yes Yes Yes Yes Yes No VN -- Yes No n/a No Yes Yes No No No No Yes No No No Yes 3 No 35 2 36 USV 025 Yes Yes n/a n/a Yes Yes Yes Yes n/a Yes Yes Yes Yes Yes Yes Yes MG 025 Yes Yes 2 n/a n/a n/a n/a Yes 6 Yes n/a Yes Yes No Yes Yes Yes Yes 37 2 38 BA 025 Yes Yes n/a n/a n/a n/a No No n/a Yes No Yes Yes Yes Yes n/a 39 SP 040 Yes Yes Yes n/a n/a Yes No No Yes No Yes No Yes Yes No No 40 SU 040 Yes Yes n/a n/a n/a Yes No Yes Yes Yes Yes No Yes Yes Yes Yes 41 MOR 040 Yes Yes n/a n/a n/a No Yes Yes Yes No Yes Yes Yes Yes Yes Yes 1 42 MO 028 Yes Yes No Yes n/a n/a Yes Yes Yes Yes Yes Yes Yes No Yes Yes

43 ML 028 n/a Yes n/a Yes n/a n/a Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1 21261 Table 4 31262 4 5 Parameter Data and methods 6 historical and/or . Location • Location of instrumental earthquakes 7 • Analysis of geologically, geomorphically and geodetically detected deformation. 8 9 • Maps of surface active faults. 10 • Inversion of seismological and geodetic data. Geological sections across the active fault system. 11 • Length (L) • Length of the area deformed by slip at depth identified as the area of 1) displaced or warped 12 geological layers (folds) or geomorphic features (e.g. alluvial and coastal terraces), 2) forced or 13 anomalous drainage pattern (e.g. stream/river migration/avulsion), and 3) vertical 14 displacements as identified by satellite geodesy . 15 • Scaling relationship between length and moment magnitude (e.g. LogL = a + b × Mw). 16 17 • Geological sections across the active fault system. 18 • Estimation from depth interval and dip. Width of the area deformed by slip at depth identified as the area of 1) displaced or warped 19 • Width (W) geological layers (folds) or geomorphic features (e.g. alluvial and coastal terraces), 2) forced or 20 Foranomalous Review drainage pattern (e.g. stream/river Only migration/avulsion), and 3) vertical 21 displacements as identified by satellite geodesy . 22 • Scaling relationship between width and moment magnitude (e.g. LogW = a + b × Mw). 23 24 • Depth distribution of instrumental earthquakes . 25 • Inversion of geodetic and seismological observations. Geological sections across the active fault system. 26 Depth • 27 • Rheological profiles of the region. Seismic tomography of the region. 28 • Combined analysis with the estimation of width. 29 • 30 • Displacement components of geological markers in maps and cross sections. 31 • Measures obtained on faults exposed at the ground surface. 32 Strike, Dip, and Rake • Focal mechanisms of the associated earthquake. 33 • Physical properties such as principal stress and strain axes. 34 • Modeling of satellite geodesy data. 35 Displacement of dated geological markers.* 36 • • Displacement observed through geodetic measurements. 37 Slip Rate (SR) • Displacement calculated from seismic or geodetic strain. 38 • Calculated from recurrence time and slip per event (SR = D / RI). 39 • Assumed from geodynamic constraints. 40 Time lag between successive event horizons identified in palaeoseismological trenches.* 41 Recurrence Interval (RI) • 42 • Derivation from long-term slip rate (RI = D / SR) . 43 • Based on seismological data. 44 • Displaced geologic or geomorphic markers. 45 Slip per Event (D) • Analytical formulation of seismic moment based on the double-couple model (D = M 0 / S 46 where is rigidity, S is fault area, and M 0 is seismic moment). 47 48 • Magnitude of associated earthquake measured instrumentally. 49 • Largest magnitude of associated historical earthquake(s) estimated from intensity data. Magnitude inferred from the area of the largest associated fault or fault set. 50 Magnitude (Mw) • 51 • Magnitude inferred from a physical model that includes deformation data of any sort (e.g. 52 geodetic, seismic). • Scaling relationship between magnitude and fault size. 53 541263 55 56 57 58 59 60

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1 21264 Table 5 31265 4 Min Max Avg Length Width Strike Dip Rake (6) (7) M 5 Reference depth Slip Slip o M Method (km) (km) (deg) (deg) (deg) (Nm) w 6 (km) (cm) (cm) 7 Geodetic and seismological inversion ANZIDEI et alii , 8 (1) 13±0.9 15.7±1.3 -- 140 55.3±1.8 -98±1.9 -- 50±3 3.20e+18 6.3 GPS data inversion 9 2009 ATZORI , DInSAR and GPS 10 et alii 12.2±0.4 14.1±0.7 1.9±0.2 133±2 47±1 -103±2 90 56±2 2.90e+18 6.3 2009 data inversion 11 CHELONI et 12 17.4 0.6 135.8 50.4 -98.5 100 62 3.90e+18 6.4 GPS data inversion 12 alii , 2010 13 Relocated CHIARABBA 14 et 16 11.3 2 135 45 ------6.3 aftershock alii , 2009 15 distribution Relocated CHIARALUCE 16 et 16 10.4 2-3(8) 135 50±3 ------6.1 aftershock 17 alii , 2011 distribution 18 CIRELLA Strong motion and et 18 17.5 0.5 133 54 -102 110 -- 3.50e+18 6.3 19 alii , 2009 GPS data inversion InSAR inversion 20 GUERRIERI For133- Review Only et 18.5 -- 0 45 -- 80 -- 2.88e+18 6.2 and field mapping 21 alii , 2011 147 of surface effects 22 Broadband HERMANN 23 et ------135 55 -95 -- -- 1.97e+18 6.1 waveform alii , 2011 (2) 24 inversion SERPELLONI 25 et 12.5 15.9 0.8 138 50.6 -- 110 -- 2.61e+18 6.3 GPS data inversion alii , 2010 26 Finite element TRASATTI 110- 27 et 12.5±0.5 10.8±0.8 2.3±0.7 142±2 42±2 -96±4 53±5 2.50e+18 6.2 geodetic data , 2011 120 28 alii inversion DInSAR and 29 WALTERS et 12.2 10.8 3 144 54 -105 80 66 2.80e+18 6.2 body-waves data 30 alii , 2009 inversion 31 Focal Mechanism 32 PONDRELLI Regional Centroid et ------134 56 -97 ------6.3 33 alii , 2010 Moment Tensor SCOGNAMIGLIO Time Domain 34 ------139 48 -87 80 16.9 1.62e+18 6.1 35 et alii , 2010 Moment Tensor INGV Regional Centroid 36 ------147 43 -88 -- -- 3.70e+18 6.3 (3) Moment Tensor 37 QRCMT HARVARD Centroid Moment ------120 54 -113 -- -- 3.66e+18 6.3 38 CMT (4) Tensor 39 Centroid Moment USGS (5) ------122 53 -112 -- -- 3.40e+18 6.3 40 Tensor Body-Wave 41 USGS (5) ------113 60 -118 -- -- 2.80e+18 6.2 42 Moment Tensor WPhase Moment USGS (5) ------121 43 -122 -- -- 2.90e+18 6.2 43 Tensor Solution 44 Surface breaking 45 Field mapping of BONCIO et alii , (9) 130- 46 13 ------surface coseismic 2010 140 effects 47 Field mapping and CINTI , 130- 48 et alii 3(9) ------paleoseismological 2011 140 49 trenching EMERGEO 50 2.5 to 130- Field mapping of 51 WORKING (9) ------surface coseismic 6 140 effects 52 GROUP , 2010 Field mapping of FALCUCCI 53 et 10 (9) -- -- 130 ------surface coseismic 54 alii , 2009 effects 55 Field mapping and GALLI et alii , (9) 56 19 -- -- 130 ------paleoseismological 2010a trenching 57 InSAR and GPS 58 GORI , inversion and field et alii 12-13 (9) -- -- 136 50 -100 110 -- 3.31e+18 6.3 59 this issue mapping of surface 60 effects Field mapping of VITTORI , 120- et alii 2.6 (9) ------surface coseismic 2011 140 effects 32

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1 21266 Table 6 31267 4 Depth Strike Dip Rake Slip Rate 5 ID Name Max M (km) (deg) (deg) (deg) (mm/a) 6 7 ITCS013 Borbona-L’Aquila-Aremogna 2.0-14.0 130-150 40-60 260-280 0.1-1.0 6.5 8 ITCS025 Salto Lake-Ovindoli-Barrea 1.0-14.5 130-150 40-65 260-280 0.1-1.7 6.7 9 10 ITCS028 Colfiorito-Campotosto 2.5-14.0 130-150 35-55 260-280 0.1-1.0 6.5 11 ITCS040 Barisciano-Sulmona 1.0-14.0 120-140 40-65 260-280 0.1-1.0 6.4 12 131268 141269 Table 7 151270 16 Average Slip 17 Length Width Depth Strike Dip Rake ID Name Slip Rate Latest Eq M 18 (km) (km) (km) (deg) (deg) (deg) 19 (m) (mm/a) 20 1.5- 13 January ITIS002 28.0For 15.5 Review135 60 Only 270 1.06 1.2-1.7 6.7 21 Fucino Basin 14.9 1915 22 5.0- ITIS028 Barrea 10.0 7.5 152 50 264 0.27 0.1-1.0 7 May 1984 5.8 23 10.7 3.0- 2 February 24 ITIS015 Montereale 23.4 13.6 132 50 270 0.72 0.1-1.0 6.5 13.4 1703 25 Basin 3.0- 0.1- 6 April 26 ITIS131 14.0 9.5 133 43 275 0.60 6.3 Paganica 9.5 1.0 * 2009 27 3.0- 800 B.C- 28 ITIS003 Aremogna- 20.0 12.2 144 50 270 0.66 0.1-0.6 6.4 Cinque Miglia 12.3 1030 A.D. 29 0.8- ITIS132 San Pio delle 16.2 10.5 127 50 270 0.50 0.1-1.0 Unknown 6.2 30 Camere 8.7 31 1.0- 3 December ITIS027 20.0 12.2 135 60 270 0.66 0.6-0.7 6.4 32 Sulmona Basin 11.6 1315 33 3.0- 14 January ITIS016 Norcia Basin 25.0 13.6 150 50 270 0.64 0.1-0.6 6.5 34 13.4 1703 351271 361272 Table 8 371273 38 ID Change What/why 39 Individual Seismogenic Source 40 ITIS131 New Based on observations following the 6 April 2009 earthquake. 41 ITIS132 New According to DI BUCCI et alii (2011). 42 ITIS015 Modified Minimum depth (shifted downwards), dip (lowered), strike (rotated counter clockwise). 43 ITIS016 Modified Minimum depth (shifted downwards), dip (lowered), strike (rotated counter clockwise). 44 ITIS002 Modified Depth (shifted downwards), strike (rotated counter clockwise). 45 ITIS003 Modified Minimum depth (shifted downwards), dip (lowered), strike (rotated counter clockwise). 46 ITIS001 Deleted Following reconsideration of the regional structural and seismotectonic model. 47 ITIS025 Deleted Depth range not compatible with new seismological and geological data. 48 ITIS026 Deleted Depth range not compatible with new seismological and geological data. Composite Seismogenic Source 49 ITCS013 Modified Lengthened northwest-ward to include ITIS131 and ITIS015. M w (raised), depth range (shifted 50 downwards) and dip (lowered). 51 ITCS025 Modified Shortened in its northwestern end to terminate close to Olevano-Antrodoco-Sibillini Line. Dip (lowered) 52 and strike (counter clockwise).

53 ITCS028 Modified Lengthened southeast-ward. M w (decreased), depth range (deepened minimum depth), strike and dip. 54 ITCS040 Modified Shortened in its northwestern end to include ITIS132. M w (decreased), depth range (shifted downwards) 55 and dip. 561274 57 58 59 60

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 For Review Only 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Figure 1 - Active or potentially active faults (from BOSI, 1975, modified and adapted). 37 69x60mm (300 x 300 DPI) 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ijg Page 35 of 69 Italian Journal of Geosciences

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 For Review Only 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 Figure 2 - a) Historical and instrumental earthquakes that have affected the Abruzzi Apennines and its surroundings. Notice the concentration of the largest events along the backbone of the 48 Apennines. 49 Credits: macroseismic earthquake data from GRUPPO DI LAVORO CPTI (2004); instrumental 50 seismicity from CASTELLO et alii (2006); Sh-min vectors (cumulative from borehole breakouts, focal 51 mechanisms, paleoseismology) from MONTONE et alii (2004) and MARIUCCI et alii (2010). 52 The small dots show the seismic sequence preceding and following the 6 April 2009, L’Aquila 53 earthquake (Mw 6.3), as recorded from 1 April to 31 July by the INGV national seismic network 54 (ISIDE, 2010); the epicenter of the 6 April 2009 mainshock is shown by the larger white star; the 55 smaller bl ack stars show the epicenters of the 7 April (Mw 5.7, to the south), and of the 9 April (Mw 5.4, to the north) earthquakes, respectively. 56 Focal mechanisms by authors listed in Table 2. Present-day extensional axis (red arrows) arrows 57 from SERPELLONI et alii (2005). Labelled earthquakes are the key ones (both historical and 58 59 60 http://mc.manuscriptcentral.com/ijg Italian Journal of Geosciences Page 36 of 69

1 2 3 instrumental) that have occurred within the study area; those with colored background are 4 associated with the following DISS Composite Seismogenic Sources: ITCS025 (green), ITCS013 5 (yellow), ITCS028 (orange), and ITCS040 (cyan), respectively (see § 5). Location of the 1456 6 earthquake (white text in blue label) is from FRACASSI & VALENSISE (2007). 7 b) Geological summary of the central Apennines and its environs (modified, from DI BUCCI et alii, 8 2006). Notice how the Olevano-Antrodoco-Sibillini Line (auct., see PATACCA et alii, 1990) to the 9 north, and the Ortona-Roccamonfina Line (auct., see LOCARDI, 1988) to the south border the Abruzzi Apennines and its large normal fault systems discussed in this work. 10 Key: 1) marine and continental clastic deposits (Pliocene-Quaternary); 2) Volcanics (Pleistocene); 11 3) clayey and carbonate turbidites (Cretaceous-Eocene); 4) Apennine carbonate platform; 5) 12 Apennine slope and margin deposits (Lias-Miocene); 6) Apulia carbonate platform and slope 13 deposits (Trias-Miocene); 7) Molise-Sannio-Lagonegro pelagic deposits (Meso-Cenozoic); 8) syn- 14 orogenic hemi-pelagic and turbiditic sequences (Tortonian-Pliocene); 9) thrust faults; 10) normal 15 faults. 234x297mm (300 x 300 DPI) 16 17 18 For Review Only 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ijg Page 37 of 69 Italian Journal of Geosciences

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 For Review Only 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

38 165x151mm (300 x 300 DPI) 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ijg