Clues to the identification of a seismogenic source from environmental effects: the case of the 1905 Calabria (Southern Italy) earthquake

Abstract

Abstract. The 8 September 1905 Calabria (Southern Italy) earthquake belongs to a peculiar family of highly destructive (I 0 =XI) seismic events, occurred at the dawning of the instrumental seismology, for which the location, geometry and size of the causative source are still substantially unconstrained. During the century elapsed since the earthquake, previous Authors identified three different epicenters that are more than 50 km apart and proposed magnitudes ranging from M≤6.2 to M=7.9. Even larger uncertainties were found when the geometry of the earthquake source was estimated. In this study, we constrain the magnitude, location and kinematics of the 1905 earthquake through the analysis of the remarkable environmental effects produced by the event (117 reviewed observations at 73 different localities throughout Calabria). The data used in our analysis include ground effects (landslides, rock falls and lateral spreads) and hydrological changes (streamflow variations, liquefaction, rise of water temperature and turbidity). To better define the magnitude of the event we use a number of empirical relations between seismic source parameters and distribution of ground effects and hydrological changes. In order to provide constraints to the location of the event and to the geometry of the source, we reproduce the coseismic static strain associated with different possible 1905 causative faults and compare its pattern to the documented streamflow changes. From the analysis of the seismically-induced environmental changes we find that: 1) the 1905 earthquake had a minimum magnitude M=6.7; 2) the event occurred in an offshore area west of the epicenters proposed by the historical seismic Catalogs; 3) it most likely occurred along a 100 • N oriented normal fault with a left-lateral component, consistently with the seismotectonic setting of the area.

Streamflow response in small upland catchments in the Chilean coastal range to the MW 8.8 Maule earthquake on 27 February 2010

“…In quantitative terms, the increase in the mean base flow after the earthquake is the most striking hydrological signal. In contrast to the widely reported increase in streamflow [e.g., Manga et al , 2003; Montgomery and Manga , 2003; Muir‐Wood and King , 1993; Rojstaczer et al , 1995] an initial decline in streamflow is reported rarely [ Rojstaczer and Wolf , 1992; Tertulliani and Cucci , 2009]. In all of the study catchments, the magnitude of post‐seismic streamflow increase greatly exceeded the co‐seismic drop.…”

Constraints to the Cause of Three Historical Tsunamis (1908, 1783, and 1693) in the Messina Straits Region, Sicily, Southern Italy

“…We conclude that, given the recurrence in the study area of strong earthquakes ) and related mass failures (Ryan and Heezen 1965;Murphy 1995;Keefer 2002;Tertulliani and Cucci 2009), the Messina Straits area is at risk of earthquake-related landslide-tsunamis. This conclusion is corroborated by historical evidence presented in this paper and previously about the 1908, 1783, and 1693 tsunamis (e.g., ▲ Figure 2.…”

“…The susceptibility to mass failures of the Messina Straits region is also largely demonstrated by several onshore studies (e.g., Pantano et al 2002 andTertulliani andCucci 2009, among others), three of which, at least, report on large sets of inland landslides triggered by the 1908, 1783, and 1693 earthquakes (Murphy 1995;Keefer 2002;Nicoletti and Parise 2002).…”

The Capo Vaticano (Calabria) coastal terraces and the 1905 M7 earthquake: the geomorphological signature of regional uplift and coseismic slip in southern Italy

“…We want to assess whether the displacement resulting from repeated earthquakes similar to the 1905 event may explain the pattern of residual deformation. As uncertainties exist about the fault responsible for the 1905 event (Tertulliani and Cucci, 2009), we select four likely potential sources based on inversion of instrumental and intensity data (Boschi et al. , 1995; Cucci and Tertulliani, 2006; Michelini et al.…”

“…The Capo Vaticano Fault (CV), Western Offshore Fault (WO), Macroseismic Fault (MF) and Coccorino Fault (CC) are the four potential seismogenic sources (hachures on the downthrown block) selected on the basis of seismological, seismotectonic and bathymetric data, potentially associated with the 1905 event (see text). Asterisks mark three different epicentral locations of the 1905 earthquake proposed by different authors since the event occurred (for a complete review of the uncertainties about this earthquake see Tertulliani and Cucci, 2009). Black circles indicate M > 5.5 historical earthquakes (CPTI Working Group 2004).…”