The 2nd century AD earthquake in central Italy: archaeoseismological data and seismotectonic implications

Abstract

The 2nd century AD earthquake in central Italy is only known by an epigraph that mentions restorations to a damaged weighing-house at the ancient locality of Pagus Interpromium. The available seismic catalogues report this event with the conventional date of 101 AD, a magnitude M aw of 6.3, and an epicentral location at the village of San Valentino in Abruzzo Citeriore, in the province of Pescara. In order to improve the knowledge of the damage pattern, we gathered all the archaeological data collected during modern excavations at sites located in the area, which were presumably struck by the earthquake. This information is mainly represented by (1) stratigraphic units due to the sudden collapse of buildings over still frequented floors; (2) stratigraphic units demonstrating restoration or re-building of edifices; (3) stratigraphic units formed as the result of the abandonment of sites or of their lack of frequentation for decades or centuries. Only stratigraphic evidence consistent with an earthquake occurrence during the 2nd century AD has been considered. The most recent archaeological material found in a collapsed unit is a coin of Antoninus Pius, dated at 147-148 AD. This may represent a post quem date very close to the occurrence of the earthquake. The gathered information, plus the stratigraphic data that excluded the earthquake occurrence at some sites, has allowed us to roughly delineate an area of possible damage, including the Sulmona Plain and surrounding areas. Comparisons between the possible 2nd century damage distribution and (i) the damage patterns of more recent historical events that have struck the investigated area, (ii) the distribution of virtual intensities obtained by simulating an earthquake having an epicenter in the Sulmona Plain and applying an intensity attenuation relationship and (iii) a shaking E. Ceccaroni Soprintendenza per i Beni Archeologici dell'scenario obtained by modelling the activation of the major active fault of the Sulmona Plain area (the Mt. Morrone fault) have revealed consistency between the ancient earthquake and the activation of this fault. Since no other historical events can be attributed to this active fault, we conclude that the time that has elapsed since the last fault activation should be in the order of 1,850 years, i.e. a time span that is very close to the recurrence interval of Apennine seismogenic sources. Moreover, considering the fault length, the causative source may be responsible for earthquakes with M up to 6.6-6.7. The comparison between the presumed 2nd century damage and the shaking scenario suggests that the magnitude mentioned is consistent with the presumed effects of the ancient earthquake. Finally, considering that Sulmona (the most important town in the region investigated) is located in the middle of the Mt. Morrone fault hanging wall, we consider it as the probable epicentral area. Therefore, to summarise the information on the 2nd century AD earthquake, we can conclude that (i) it occurred shortly after 147-148 AD; (ii) a magnitude ...

Active normal faulting along the Mt. Morrone south-western slopes (central Apennines, Italy)

“…This fault system shows evidence of Late Pleistocene-Holocene activity (e.g. Vittori et al 1995;Miccadei et al 1998;Galadini and Galli 2000), and according to Galadini and Galli (2001) and Ceccaroni et al (2009), was probably activated about 1800 years ago (i.e. during the second century AD).…”

“…Archeoseismological data have indicated an episode of widespread destruction in the Sulmona area during the second century AD, which was probably related to the occurrence of a large-magnitude earthquake of local origin (Tuteri 1996;Galadini and Galli 2001;Ceccaroni et al 2009. If this archaeoseismological evidence is associated with the Mt.…”

“…Morrone fault occurred during the second century (Galadini and Galli 2001;Ceccaroni et al 2009), and assuming that the fault did not experience aseismic creep, the total maximum slip rate proposed, which is between [ 0.4 ± 0.07 and \ 0.8 ± 0.09 mm/year, may provide a displacement per event of about 0.5-2.0 m. This derives by considering the mean recurrence interval per central Apennines fault that ranges from 1400 to 2600 years (Galadini and Galli 2000). Hence, by using the above-mentioned empirical equation of Wells and Coppersmith (1994) and the obtained possible displacement per event, an earthquake that originates along the Mt.…”

Defining a mid-Holocene earthquake through speleoseismological and independent data: implications for the outer Central Apennines (Italy) seismotectonic framework

“…Contractional or strikeslip tectonics prevail in the Adriatic foreland area, to the east. Epicenter location and macroseismic intensity (Io), or equivalent moment magnitude (M aw ) and moment magnitude (M w ), of historical and recent earthquakes (Working Group CPTI, 2004;Rovida et al, 2011 andCeccaroni et al, 2009 for the 2nd century AD earthquake) indicate stronger seismicity within the inner extensional domain and only moderate events in the outer contractional zone. Some events, such as those in 1706 and 1933, localized in the Maiella Massif (i.e., at the extension/contraction transitional domain), still have an uncertain source and kinematics.…”

“…No large-magnitude historical seismic events can be strictly related to these structures which, however, show evidence of late Pleistocene-Holocene activity (Barchi et al, 2000;Galadini and Galli, 2000;Papanikolaou et al, 2005, and references therein). Only recently has the 2nd century AD earthquake that occurred in central Italy been associated with the Sulmona fault system through archaeoseismological and paleoseismological evidence (Ceccaroni et al, 2009;Galli et al, 2015). This lack of data could be due to long recurrence intervals (1400-2600 years; Galadini and Galli, 2000) and/or to the incompleteness of the available historical seismic catalogues (e.g., Stucchi et al, 2004), suggesting high seismic hazard levels and raising critical questions about the identification of the seismogenic structures and the true seismic potential of these areas.…”