This paper focuses on the seismogenic structure responsible for the 5 February 1783 earthquake (M > 7, Calabria, southern Italy), in particular the slip rate and recurrence time along the Cittanova fault, thus giving new insights on the seismic hazards and seismotectonics of the region. The 1783 earthquake, one of the strongest earthquake of the Mediterranean area, caused more than 30,000 casualties and radically changed the physiography of the local landscape. Until now, the Cittanova fault (or Aspromonte fault) has been generally identified as the surficial expression of the seismogenetic structure, even though its youthful activity has never been demonstrated. Recently, the shortage of geologic evidence of middle‐upper Pleistocene activity on this fault led some authors to locate the 1783 fault elsewhere. In our study we used a multidisciplinary approach (paleoseismology, geomorphology, historical seismology, archaeoseismology); our analysis of contemporary literary sources strengthened our interpretation of the coseismic origin of many geological features and, sometimes, oriented our field research toward specific areas. In particular, we excavated trenches and pits at three different sites along the trace of the Cittanova fault for paleoseismological analysis and 14C dating. Our data document the Holocene and present activity of the Cittanova fault, providing a minimum vertical slip rate of 0.44 mm/yr and a possible return time of 1350–1800 years for earthquakes similar to 1783. The penultimate event has been dated to the 4th century A.D., a time when southern Calabria and eastern Sicily were devastated by an earthquake documented by archaeoseismic analyses.
The reanalyses of all the primary historical sources of the catastrophic March–June 1638 Calabrian earthquakes permitted to split up the seismic sequence in different events that occurred in conterminous areas and to direct our geological surveys of the June shock inside the Sila massif (northern Calabria). We carried out paleoseismological analyses along the Lakes fault (LF), a previously unknown fault. LF (trending NW‐SE) cuts the eastern sector of the Sila massif and dips southwestward, damming the drainage network that runs toward the Ionian Sea. We opened four trenches close to or inside some of the small marshes and ponds created by the footwall uplift, finding evidence of several displacement events, the last one being the June 1638 earthquake (M = 6.7). The fault location fits with the historical description of a long fracture opened during the event, our trenching area being still named by the natives “the earthquake sag.” The young geomorphic expression of LF recalls that of the 1980 Irpinia fault, suggesting its relatively recent activation within the extensional regime characterizing the Calabrian arc. Conversely, the northern continuation of LF (Cecita Lake fault), which we argue to be active too, is not associated to any historical earthquake of the Italian seismic catalogue, this fact evidencing a long, at least 1000 years, elapsed time. Our study permits (1) the relocation of the June 1638 earthquake inside the Sila massif, the epicenter being shifted with respect to the macroseismically derived one, (2) the revision of the whole 1638 sequence, (3) the discovery of the LF, (4) the recognition of the evidence of the June 1638 surface faulting plus four previous paleoearthquakes, and (5) the evaluation of its slip rates and return interval. Finally, the relationship of LF with the neighboring faults casts light to the seismotectonic of the region, providing a new insight to the seismic hazard analysis.
Although southern Apennines are characterized by the strongest crustal earthquakes of centralwestern Mediterranean region, local active tectonics is still poorly known, at least for seismogenic fault-recognition is concerned. Research carried out in the Maddalena Mts. (southeast of Irpinia, the region struck by the M w =6.9, 1980 earthquake) indicates historical ruptures along a 17-km-long, N120°normal fault system (Caggiano fault). The system is characterized by a bedrock fault scarp carved in carbonate rocks, which continues laterally into a retreating and eroded smoothed scarp, affecting the clayey-siliciclastic units, and by smart scarps and discontinuous free-faces in Holocene cemented slope-debris and in modern alluvial fan deposits. The geometry of the structure in depth has been depicted by means of electrical resistivity tomography, while paleoseismic analysis carried out in three trenches revealed surface-faulting events during the past 7 ky BP ( 14 C age), the latest occurred in the past 2 ky BP ( 14 C age) and, probably, during/after slopedebris deposition related to the little ice age ($1400-1800 A.D.). Preliminary evaluation accounts for minimum slip rates of 0.3-0.4 mm/year, which is the same order of rates estimated for many active faults along the Apennine chain. Associated earthquakes might be in the order of M w =6.6, to be compared to the historical events occurred in the area (e.g., 1561 and 1857 p.p. earthquakes).
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