Description: Mt. Etna is the largest and one of the best-studied volcanoes in Europe. It represents a highly active basaltic volcano on top of the active Apennine thrust belt. The instability of its eastern flank has been described as an important preconditioning factor for the occurrence of submarine mass wasting events. In order to better understand the processes that may cause submarine slope failures, a new dataset including seismic, hydroacoustic and core data was collected during RV Meteor cruise M86/2 from December 2011 to January 2012. Seismic profiles and sediment cores reveal repeated mass transport deposits (MTD), indicating a long history of landslides in the working area. Some of the sampled MTDs and their surrounding strata contain volcaniclastic debris, indicating that slope failures may be controlled by volcanic and non-volcanic processes. Several tephra layers directly cover MTDs, which is regarded as an indicator for the possibility that several flank failures occur immediately before or very early during an eruption.

Description: Summary The continental margins of southern Italy are located along converging plate boundaries, which are affected by intense seismicity and volcanic activity. Most of the coastal areas experienced severe earthquakes, landslides, and tsunamis in historical and/or modern times. The most prominent example is the Messina earthquake of Dec. 28, 1908 (Ms=7.3; 80,000 casualties), which was characterized by the worst tsunami Italy experienced in the historical time (~2000 casualties). It is, however, still unclear, whether this tsunami was triggered by a sudden vertical movement along a major fault during the earthquake or as a result of a giant marine slide initiated by the earthquake. The recurrence rates of major landslides and therefore the risk associated with landslides is also unknown. Based on detailed bathymetric data sets collected by Italian colleagues in the frame of the MaGIC Project (Marine Geohazards along the Italian Coast), we collected seismic data (2D and 3D) and gravity cores in three working areas (The Messina Straits, off Eastern Sicily, the Gioia Basin). A dense grid of new 2D-seismic data in the Messina Straits will allow to map fault patterns in great detail. One interesting outcome in this context is the identification of a set of normal faults striking in an EW-direction, which is almost perpendicular to the previously postulated faults. This EW-striking faults seem to be active. The area off eastern Sicily is characterized by numerous landslides and a complex deformation pattern. A 3D-seismic data set has been collected during the cruise using the so called P-cable in order to investigate these deformation patterns in detail. The new data will be the basis for a risk assessment in the working areas.

Description: The active tectonics of the Southern Apennines of Italy (Calabrian Arc excluded) is mainly characterized by SW-NE extension, which accounts for large earthquakes generated by NW-SE striking normal faults. However, the 2002 Molise earthquakes occurred along an E-W striking right-lateral seismogenic structure located to the NE of the Southern Apennines axis. This and other lines of evidence suggested that the frontal part of the chain and the adjacent foreland are affected by E-W striking, right-lateral active faults systems. The 2002 Molise seismic sources, in particular, are located along the western part of a regional fault system, the Molise-Gondola shear zone (MGsz). On land, this system is mainly represented by the Mattinata Fault, an important structure of the foreland that has already been intensely investigated from a regional, structural and seismotectonic point of view. A polyphase activity (since Mesozoic times) has been recognized, and the complex fault kinematics is still matter of debate. Nevertheless, most investigators agree on a present-day activity with right-lateral sense of motion, as confirmed by the focal mechanism of the 19 June 1975 earthquake, GPS data, geomorphological and paleoseismological investigations. Indeed, the Mattinata Fault has already been interpreted as the source of historical earthquakes (e.g., 493 AD, 1875), and instrumental seismicity is normally recorded within the first 25 km of the crust of the Gargano area. These data indicate that inherited E-W striking high-angle fault systems are solicited under the present-day stress field. Off-shore the Gargano Promontory, the Mattinata Fault seems to be aligned with a regional (ca. 150 km in extent) E-W to NW-SE oriented deformation belt (known in the literature as Gondola Line), including a main fault and fold system known as Gondola Fault and Gondola Ridge, respectively. In the past, this structure has been investigated using multi-channel seismic reflection profiles and well-log data. Several investigators proposed a Mesozoic origin for the Gondola Line, followed by a complex pattern of repeated re-activation during the Cenozoic. Kinematics and timing of post-Mesozoic re-activation are still debated; however, most investigators agree that only deposits older than Miocene appear severely deformed, whereas Plio-Pleistocene units yield little or no deformation at all. This multi-history deformation pattern shown along the Gondola Line closely resembles the long-term complex evolution recorded along the Mattinata Fault, except for the lack of significant seismicity. Therefore, although one could expect the Gondola Line to be subjected to the same stress field responsible for recent re-activation of the Mattinata Fault, direct evidence is not available from historical and present-day seismicity. However, in recent years, evidence of recent tectonic deformation off-shore Gargano has arisen from very-high resolution seismic stratigraphy based on a dense grid of Chirp-Sonar profiles. These data allowed the identification of low amplitude fold systems and shallow sub-vertical faults propagating in middle-late Pleistocene and Holocene deposits, particularly along the E-W (on the continental shelf) and NW-SE (on the slope) segments of the Gondola Line. Several of these faults either affect Holocene units younger than 5.5 ka (based on bio-chronostratigraphic analyses from core samples), or even offset the seafloor. Altogether, both recent seismicity related to E-W dextral strike-slip tectonics along the westernmost part of the MGsz and along the Mattinata Fault itself, and very recent (〈 5.5 ka) deformation features along the Gondola Line, suggest that the MGsz as a whole is being actively deformed, although variably along-strike. In order to verify this hypothesis, we attempt a comparison between on- and off-shore data supporting recent activity along E-W oriented foreland structures. The integration of such heterogeneous yet complementary datasets may contribute to discuss late Quaternary tectonics of the Southern Apennines foreland domain, and provide comprehensive (on-shore / to / off-shore) scenarios for investigating recent / active tectonics of the MGsz and evaluating its possible seismogenic character.

Description: Unpublished

Description: Vienna International Center Vienna Austria

Description: open

Description: Recent seismicity in and around the Gargano Promontory, an uplifted portion of the Southern Adriatic Foreland domain, indicates active E–W strike-slip faulting in a region that has also been struck by large historical earthquakes, particularly along the Mattinata Fault. Seismic profiles published in the past two decades show that the pattern of tectonic deformation along the E–W-trending segment of the Gondola Fault Zone, the offshore counterpart of the Mattinata Fault, is strikingly similar to that observed onshore during the Eocene–Pliocene interval. Based on the lack of instrumental seismicity in the south Adriatic offshore, however, and on standard seismic reflection data showing an undisturbed Quaternary succession above the Gondola Fault Zone, this fault zone has been interpreted as essentially inactive since the Pliocene. Nevertheless, many investigators emphasised the genetic relationships and physical continuity between the Mattinata Fault, a positively active tectonic feature, and the Gondola Fault Zone. The seismotectonic potential of the system formed by these two faults has never been investigated in detail. Recent investigations of Quaternary sedimentary successions on the Adriatic shelf, by means of very high-resolution seismic–stratigraphic data, have led to the identification of fold growth and fault propagation in Middle–Upper Pleistocene and Holocene units. The inferred pattern of gentle folding and shallow faulting indicates that sediments deposited during the past ca. 450 ka were recurrently deformed along the E–W branch of the Gondola Fault Zone. We performed a detailed reconstruction and kinematic interpretation of the most recent deformation observed along the Gondola Fault Zone and interpret it in the broader context of the seismotectonic setting of the Southern Apennines-foreland region. We hypothesise that the entire 180 km-long Molise–Gondola Shear Zone is presently active and speculate that also its offshore portion, the Gondola Fault Zone, has a seismogenic behaviour.

Description: Study supported by ISMAR-CNR projects EUROSTRATAFORM (EVK3-CT-2002-00079) and “Rischi Sottomarini”(GNDT 2000–2004) and by the Project S2 funded in the framework of the 2004–2006 agreement between the Italian Department of Civil Protection and INGV (Research Unit 2.4). This is ISMAR-CNR (Bologna) contribution n. 1570.

Description: Published

Description: 110-121

Description: 3.2. Tettonica attiva

Description: JCR Journal

Description: reserved

Description: The western Adriatic margin was intensely deformed during the Meso-Cenozoic evolution of the Adriatic region from a passive margin to a foreland basin. In the offshore area north and south of Gargano Promontory, several deformation belts develop parallel or cross-strike to the margin. Based on high-resolution seismic data, deformation along these inherited tectonic structures continued during the Quaternary, resulting in small-scale faults and folds affecting the upper-most 50-100 m of the sedimentary succession. This stratigraphic interval corresponds to the last ca. 450 ka and is composed of four depositional sequences, each recording 100 ka glacio-eustatic cycles, overlain by transgressive and highstand units of the last deglacial interval (the last ca. 20 ka). Locally, faults propagate through Holocene deposits and offset the sea floor; vertical displacements of reflectors is variable along the faults, ranging from few metres up to ca. 15-20 m, but usually decreases up-section, to less than 1 m within Holocene units. In some cases, active deformation along inherited tectonic lineaments is confirmed by recent seismicity. On the western margin of Adria, seismicity is mostly concentrated along the Apennines. However, in the Adriatic Sea, an overall W-E trending seismic belt extends offshore Gargano Promontory. The existence of this cross-strike seismicity belt, that also encompasses the Tremiti Islands, is documented by moderate but significant earthquakes. More in general, based on instrumental records, the offshore area north of Gargano Promontory appears more seismic than the area south of it, where instrumental seismicity is reduced, while it is more frequent on the Gargano Promontory. We focus on a deformation belt extending NE of Gargano Promontory, within the offshore area yielding significant instrumental seismicity. The NE-Gargano deformation belt comprises: 1) a faulted anticline on the sloping southern side of the Pelagosa sill, 2) a fault system on the outer shelf and 3) a syncline on the inner shelf. The anticline on the slope is the most remarkable feature within this deformation belt, and clearly affects seafloor relief. The set of sub-vertical faults that dissect the anticline also displace the sea floor, delimiting a graben-like feature. The comparison of high-resolution tectono-stratigraphic reconstructions and seismicity records can give information on the active deformation of “Adria”, and provide new insight on the existence of potential seismo-genic structures in the Adriatic offshore, where also evidence of slope instability is diffused. More in general, these results show the importance of using very high-resolution geophysical data and sequence-stratigraphic reconstructions to constrain present-day active tectonics.

Description: Unpublished

Description: Urbino (PU), Italy

Description: open

Description: Recent seismicity in and around the Gargano Promontory, an uplifted portion of the southern Adriatic Foreland domain, indicates active E-W strike-slip faulting in a region that has also been struck by large historical earthquakes, particularly along the Mattinata Fault. Seismic profiles published in the past two decades show that the pattern of tectonic deformation along the E-W–trending segment of the Gondola Fault Zone, the offshore counterpart of the Mattinata Fault, is strikingly similar to that observed onshore during the Eocene-Pliocene interval. Based on the lack of instrumental seismicity in the south Adriatic offshore, however, and on standard seismic reflection data showing an undisturbed Quaternary succession above the Gondola Fault Zone, this fault zone has been interpreted as essentially inactive since the Pliocene. Nevertheless, many investigators emphasised the genetic relationships and physical continuity between the Mattinata Fault, a positively active tectonic feature, and the Gondola Fault Zone. The seismotectonic potential of the system formed by these two faults has never been investigated in detail. Recent investigations of Quaternary sedimentary successions on the Adriatic shelf, by means of very high-resolution seismic-stratigraphic data, have led to the identification of fold growth and fault propagation in Middle-Upper Pleistocene and Holocene units. The inferred pattern of gentle folding and shallow faulting indicates that sediments deposited during the past ca. 450 ka were recurrently deformed along the E-W branch of the Gondola Fault Zone. We performed a detailed reconstruction and kinematic interpretation of the most recent deformation observed along the Gondola Fault Zone and interpret it in the broader context of the seismotectonic setting of the southern Apennines-foreland region. We hypothesise that the entire 180 km-long Molise-Gondola Shear Zone is presently active and speculate that also its offshore portion, the Gondola Fault Zone, has a seismogenic behaviour.

Description: DPC-INGV S2 U.R. 2.4

Description: In press

Description: 3.2. Tettonica attiva

Description: JCR Journal

Description: open