Description: Highlights • We identify the largest active fault systems of the Alboran Basin. • Characterization of faults is key for accurate tsunamigenic potential estimations. • Alboran largest fault systems may generate Mw 〉 7 earthquakes. • These earthquakes have the potential to generate significant tsunami waves approaching the coast. Abstract The westernmost Mediterranean hosts part of the plate boundary between the European and African tectonic plates. Based on the scattered instrumental seismicity, this boundary has been traditionally interpreted as a wide zone of diffuse deformation. However, recent seismic images and seafloor mapping studies support that most of the plate convergence may be accommodated in a few tectonic structures, rather than in a broad region. Historical earthquakes with magnitudes Mw 〉 6 and historical tsunamis support that the low-to-moderate instrumental seismicity might also have led to underestimation of the seismogenic and tsunamigenic potential of the area. We evaluate the largest active faults of the westernmost Mediterranean: the reverse Alboran Ridge, and the strike-slip Carboneras, Yusuf and Al-Idrissi fault systems. For the first time, we use a dense grid of modern seismic data to characterize the entire dimensions of the main fault systems, accurately describe the geometry of these structures and estimate their seismic source parameters. Tsunami scenarios have been tested based on 3D-surfaces and seismic source parameters, using both uniform and heterogeneous slip distributions. The comparison of our results with previous studies, based on limited information on the fault geometry and kinematics, indicates that accurate fault geometries and heterogeneous slip distributions are needed to properly assess the seismic and tsunamigenic potential in this area. Based on fault scaling relations, the four fault systems have a large seismogenic potential, being able to generate earthquakes with Mw 〉 7. The reverse Alboran Ridge Fault System has the largest tsunamigenic potential, being able to generate a tsunami wave amplitude greater than 3 m in front of the coasts of Southern Spain and Northern Africa.

Description: Abstract We present the first rupture models of the two mainshocks of the 2012 northern Italy sequence, determined by jointly inverting seismic and geodetic data. We aim at providing new insights into the mainshocks for which contrasting seismotectonic interpretations are proposed in literature. Sources' geometric parameters were constrained by seismic reflection profiles, 3-D relocations and focal mechanisms of mainshocks/aftershocks. Site-specific velocity profiles were used to model accelerograms affected by strong propagation effects related to the Po basin. Our source models differ significantly from previous ones relying on either seismic or geodetic data. Their comparison against geological sections and aftershock distribution provides new insights about the ruptured thrust faults. The May 20th Mw6.1 mainshock activated the Middle Ferrara thrust-ramp dipping ∼45° SSW-wards, breaking a main eastern slip patch 4–15 km deep in Mesozoic carbonates (maximum slip 0.7–0.8 m) and Paleozoic-Triassic basement rocks, and a small western patch in the basement. The May 29th Mw6.0 mainshock featured two separated asperities along the Mirandola thrustramp dipping ∼42° S-wards: an eastern asperity 4–15 km deep in Mesozoic carbonates and basement rocks (maximum slip 0.7 m) and a deeper western one (7–16 km depth) mainly in the basement (slip peak 0.8 m). On-fault aftershocks were concentrated within the basement and Mesozoic carbonates, devoiding highslip zones. Slip and aftershock distribution was controlled by the rheological transition between Mesozoic carbonates and Cenozoic sediments. Unlike previous thin-skinned tectonic interpretations, our results point to a complex rupture process along moderately dipping (40°–45°) thrust-ramps deeply rooted into the Paleozoic crystalline basement. Plain Language Summary The two M6 mainshocks of the 2012 Italy sequence are the strongest earthquakes ever observed in the Po Plain, a strategic region for the Italian economy. The mainshocks ruptured blind thrust-faults, however their source models and seismotectonic interpretation are still debated because the thrust-system architecture is controversial. Contrasting thick-skinned and thin-skinned tectonic models are proposed. In thick-skinned interpretations, shortening is accommodated by thrust-ramps rooted into the crystalline basement that represent main seismogenic structures, whereas in thin-skinned interpretations, shortening and seismicity are controlled by listric faults splaying out from dècollement levels in the sedimentary crust. A comprehensive analysis of the mainshocks' source represents an opportunity to provide new insights into the seismogenesis in northern Italy and on a broader scale into seismotectonics of thrust-and-fold belts. We get a complete picture of the mainshocks kinematics by jointly inverting, for the first time, seismic and geodetic data, and unravel rupture heterogeneities not resolved by previous studies. By integrating source models with aftershock locations and geological models, we propose a comprehensive seismotectonic interpretation of the sequence. We conclusively identify the ruptured faults that correspond to thrust-ramps rooted into the crystalline basement and evidence the key role played by lithological changes in the rupture process.

Description: Published

Description: e2022JB026278

Description: OST3 Vicino alla faglia

Description: JCR Journal

Description: The “Giornata ONT 2023” arises from the will to let know within INGV how many activities do people from the Osservatorio Nazionale Terremoti (ONT), and how strong is their contribution to the INGV missions: Research, Services, Education, Communication. In the nearly seven years of the current management the ONT has experienced a continuous evolutionary, sometimes complex, path. But it is always a straight path to pursue the objective of a continuous growth of the ONT. During these years the ONT has changed its name (from Centro Nazionale Terremoti – CNT, to ONT); it has experienced the coming out of some employees that moved to create the Irpinia new Section; it has lived the novelty of incoming people (example from the Centro Allerta Tsunami). It has also faced the need to overcome the limitations due to the worldwide pandemic emergency COVID19, either for the h24 services or for the research activities. Therefore in 2020 and 2021 we have only remotely attended the ONT days. The drive to be “in presenza” comes from this latter issue. We strongly want to meet, to talk face to face, to “Welcome” the young colleagues who are the injection of new ideas and perspectives, that are the necessary fuel to evolve the knowledge. As a matter of fact it emerges from the DNA of the ONT, i.e. the inclusiveness and the multidisciplinarity. This latter is widely testified by the ONT activities that are shared among the three Departments and their strategic objectives. The agenda of the “Giornata ONT 2023” has specifically emphasized the variety of the technical and scientific contents, that for sake of simplicity have been collected in the following themes: • Infrastructures, Data­Sharing and Laboratories • Analysis, Modelling, Interpretation of Geophysical Phenomena • National and International Projects (Research Results and Products from Completed Projects; Ongoing Projects) • Society ­ Communication, Dissemination, Emergency Management • Seismic Surveillance And Tsunami Warning Overall, the contributions have been 100, most of which are posters (77) and the remaining (23) in different exhibit formats. The wide interest about the proposed contents and the positive feedback from the attendance, pushed the decision to collect and publish the contributions in a Miscellanea INGV, where the documents can be easily found. And we are finally ready to make the Miscellanea available to the reader. I would warmly thank the Authors for their enthusiastic acceptance to contribute, the Conveners of the “Giornata ONT 2023” Sessions for their availability to organise and manage the submitted poster/exhibits, the Editorial Board members for their hidden work that led to this Miscellanea. In conclusion, let me spend a few words about my personal journey as Director of the ONT. After 2504 days it has come to an end and the “Giornata ONT 2023” and the Miscellanea are, somehow, the cherry on top. It is really difficult to say “Thanks” one by one to the people who helped me along this complex and long path. So, please, let me simply say Grazie a tutti voi! Salvatore Stramondo - Director ONT (2017-2023)

Description: Published

Description: 1-206

Description: N/A or not JCR