Gutscher, Marc-Andre

Nel 2018 è stato avviato il progetto FOCUS - Fiber Optic Cable Use For Seafloor Studies Of Earthquake - coordinato da Marc-André Gutscher del Laboratoire Géosciences Océan dell’Università di Brest, in Francia. Questo progetto indaga la sismicità e la struttura crostale del Mar Ionio attraverso l’analisi e l’interpretazione di dati raccolti da strumentazione sottomarina e da reti di monitoraggio disponibili o appositamente installate nelle zone di costa. In tale contesto, l’Osservatorio Nazionale Terremoti (ONT) e l’Osservatorio Etneo (OE), entrambe Sezioni dell’Istituto Nazionale di Geofisica e Vulcanologia (INGV), e il Laboratorio di Sismologia dell'Università della Calabria (UniCal), hanno contribuito al progetto con l’installazione di una rete sismica temporanea lungo la costa ionica calabro-siciliana a integrazione della rete permanente presente nell’area dello Stretto di Messina. La rete temporanea, costituita da 13 stazioni, ha acquisito dal mese di dicembre 2021 al mese di giugno 2023. Nel gennaio 2022, i partner internazionali del progetto FOCUS hanno installato una rete temporanea di sismometri OBS e sensori di pressione per fondali marini. La grande quantità di dati raccolta e la loro integrazione, consentirà di migliorare il monitoraggio sismico e le conoscenze relative alla struttura terrestre dell’area con particolare attenzione alle strutture sismogenetiche con un dettaglio mai raggiunto fino a ora. Tutte le istituzioni coinvolte in FOCUS collaborano per l’acquisizione e l’elaborazione dei dati, l’imaging dell’interno della Terra attraverso l’utilizzo di tecniche avanzate, l’interpretazione e la modellazione dei dati. Il presente lavoro descrive la progettazione, la realizzazione e la gestione della rete temporanea a terra definita FXland, fornendo indicazioni relative sul suo generale funzionamento e sulle caratteristiche del dataset acquisito.

The INGV is the operational center for earthquake monitoring in Italy, https://www.ingv.it/en/monitoraggio-e-infrastrutture/sorveglianza/servizio-di-sorveglianza-sismica, it operates the Italian National Seismic Network and other networks at different scales and is a primary node of EIDA for archiving and distributing seismic recordings. INGV provides earthquake information to the Department of Civil Protection and to the public. In the frame of the FOCUS (Fiber Optic Cable Use for seafloor studies of earthquake hazard and deformation) project, https://www.geo-ocean.fr/Recherche/Projets-de-Recherche/ERC-FOCUS, we deployed a temporary seismic network, FXLand (1J), for a passive seismological experiment to record regional seismicity and teleseismic events. This experiment aims to improve the detection of seismicity; the accuracy of earthquake locations, and to define the crustal structure of the region. The seismicity in the Ionian area is possibly the result of two types of tectonic activity at different depths: a gently NW dipping subduction interface of the Calabrian subduction zone, and the strike-slip fault systems in the Ionian Sea, well expressed in the morpho-bathymetry and observed in previous seismic profiles.

In the frame of FocusX2 project INGV (Osservatorio Nazionale Terremoti and Osservatorio Etneo) and UniCal (Laboratorio di Sismologia) are deploying, from the end of 2021 to January 2023 a temporary seismic network for an active/passive seismological experiment to record regional and global seismicity in the Ionian Sea. The goal of this experiment is to improve the detection of seismicity in the Ionian Sea area and the accuracy of the locations; to better define the crustal structure of the region and find patterns related to fault systems. The seismicity in the area is possibly the result of two types of tectonic activity at different depths: a gently NW dipping subduction interface of the Calabrian subduction zone, and the strike-slip fault systems in the Ionian Sea, well expressed in the morpho-bathymetry and observed in previous seismic profiles. The deployment of 13 temporary land stations, FocusX temporary land (network code 1J) https://doi.org/10.13127/SD/O5QWM6WJCD along the coasts of eastern Sicily and SW Calabria, is going to complement the permanent networks (network codes IV, MN and IY); in the same period OBS stations are deployed at sea: FocusX temporary OBS-network (network code XH). The land stations are equipped with two different type of digitizers: Reftek 130 (12), and SaraSL06 (2); and with three different type of velocimeters: Trillium 120C (10), Le 5s (2) and ss08 60s (2). Continuous data are transmitted in real time at the INGV Rome acquisition system, used in the seismic surveillance, archived and distributed in EIDA https://eida.ingv.it/it/. In the deployment period 23rd December 2021 - 9th May 2022 regional seismicity (area between Lat 36.5-38.2 Lon 14.5-16.0) include 390 events located by the INGV seismic surveillance system, two of them with magnitude larger than 4.0 as well as 56 teleseismic earthquakes with magnitude larger than magnitude 6.0, two of them larger than 7.0. The two local events with M>4.0 and some of their aftershocks, were analyzed by the analysts of the Italian Seismic Bulletin including all the stations of the FXland 1J network.

Tsunamis constitute a significant hazard for European coastal populations, and the impact of tsunami events worldwide can extend well beyond the coastal regions directly affected. Understanding the complex mechanisms of tsunami generation, propagation, and inundation, as well as managing the tsunami risk, requires multidisciplinary research and infrastructures that cross national boundaries. Recent decades have seen both great advances in tsunami science and consolidation of the European tsunami research community. A recurring theme has been the need for a sustainable platform for coordinated tsunami community activities and a hub for tsunami services. Following about three years of preparation, in July 2021, the European tsunami community attained the status of Candidate Thematic Core Service (cTCS) within the European Plate Observing System (EPOS) Research Infrastructure. Within a transition period of three years, the Tsunami candidate TCS is anticipated to develop into a fully operational EPOS TCS. We here outline the path taken to reach this point, and the envisaged form of the future EPOS TCS Tsunami. Our cTCS is planned to be organised within four thematic pillars: (1) Support to Tsunami Service Providers, (2) Tsunami Data, (3) Numerical Models, and (4) Hazard and Risk Products. We outline how identified needs in tsunami science and tsunami risk mitigation will be addressed within this structure and how participation within EPOS will become an integration point for community development.

Tectono-stratigraphic interpretation and sequential restoration modelling was performed over two high-resolution seismic profiles crossing the Western Ionian Basin of southern Italy. This analysis was undertaken in order to provide greater insights and a more reliable assessment of the deformation rate affecting the area. Offshore seismic profiling illuminates the sub-seafloor setting where a belt of active normal faults slice across the foot of the Malta Escarpment, a regional-scale structural boundary inherited from the Permo-Triassic palaeotectonic setting. A sequential restoration workflow was established to back-deform the entire investigated sector with the primary aim of analysing the deformation history of the three major normal faults affecting the area. Restoration of the tectono-stratigraphic model reveals how deformation rates evolved through time. In the early stage, the studied area experienced a significant deformation with the horizontal component prevailing over the vertical element. In this context, the three major faults contribute to only one third of the total deformation. The overall throw and extension then notably reduced through time towards the present day and, since the middle Pliocene, ongoing crustal deformation is accommodated almost entirely by the three major normal faults. Unloading and decompaction indicate that when compared to the unrestored seismic sections, a revision and a reduction of roughly one third of the vertical displacement of the faults offset is required. This analysis ultimately allows us to better understand the seismic potential of the region.

Argnani (2021) provides a commentary (hereafter ARGN) on our paper titled: “Deformation Pattern of the Northern Sector of the Malta Escarpment: Fault Dimension, Slip Prediction, and Seismotectonic Implications,” which was published in the journal Frontiers in Earth Science in January 2021 (Gambino et al., 2021, hereafter GAMB). Through the interpretation of eight new seismic profiles (six of which are reported in Supplementary Figure S1 of GAMB) crossing the Malta Escarpment, GAMB pointed to a better definition of the geometry of three active faults (F1, F2, F3) and their seismic potential by employing slip tendency modeling and forward analysis. The results suggest that F3 is prone to be reactivated under the achieved stress field and has the capacity of generating M > 7 earthquakes. ARGN raises concerns about the higher resolution and less penetration of the eight newly acquired high-resolution multichannel reflection seismic profiles and the seismic-stratigraphic pattern proposed by GAMB. According to ARGN, “the seismic profiles analyzed by GAMB belong to different sets and have very different seismic characters and resolution, making seismic facies correlation pretty difficult, also because no tie lines are available. As a result, stratigraphic correlations are highly speculative and the ensuing uncertainties undermine the timing of the tectonic evolution envisaged by GAMB, as well as the age and rate of activity of tectonic structures.” Furthermore, ARGN argues on the hypothesis of an early large-scale slope instability affecting the area. Most of the statements of ARGN seem to be based on his available older multichannel reflection seismic profiles, which have, indeed, a higher penetration but less resolution. We also agree that high-resolution digital multichannel seismic profiles are not easily comparable with low-resolution multichannel seismic lines, but we see the clear advantage of a state-of-the-art technology to image the upper strata of sedimentary systems. The used system proved its robustness in many different settings worldwide and has been successfully used for many pre-site surveys for drilling campaigns for the IODP and ICDP. As a result, we rebut point-by-point ARGN’s comments and stand by our model on the active deformation pattern and seismotectonics of the northern sector of the Malta Escarpment.

Marine seismic reflection data coupled with on-land structural measurements improve our knowledge about the active deformation pattern of the northern sector of the Malta Escarpment, a bathymetric and structural discontinuity in the near-offshore of Eastern Sicily. As favourably oriented to be reactivated within the Neogene Africa–Europe convergence, it is believed that the Malta Escarpment has a significant role in the recent seismotectonic framework of the Western Ionian Basin and the Hyblean foreland domain of SE Sicily, where some of the largest and most destructive Mediterranean earthquakes are located according to available historical catalogs. Offshore seismic data along with bathymetric grids illuminate the shallow subseafloor setting and allow more accurate mapping of the seafloor expression of previously identified faults in the area. The seismic interpretation and the nearfault sediment pattern analysis provide constraints on fault 3D geometries as well as on their through-time tectonic activity, suggesting also that part of the observed deformation may have been caused by nontectonic processes. Identified faults form currently an E-dipping, roughly N–S trending, and 60 km-long extensional belt deforming the seafloor with a significant displacement amount in the Ionian offshore between Catania and Siracusa. 3-dimensional parameters of faults were then used to derive expected magnitudes and their reactivation propensity. Empirical scaling relationships and forward methods point to a high seismic potential for the detected fault as well as predict the fault slip behavior according to the fieldderived differential stress. This combined analysis along with faults displacement measurements pointed out how the longest and most continuous fault could be capable of generating M > 7 seismic events, putting forward strong seismotectonic implications for the adjacent and densely populated Hyblean Plateau. The expected magnitude and the estimated recurrence time interval are compatible with those inferred for large historical earthquakes in the area even if other offshore seismic sources cannot be ruled out.

iXblue company develops technologies to listen and image the Earth dynamics. Among them, Echoes high-resolution sub-bottom profilers, Seapix 3D multibeam echosounder, Canopus transponder and blueSeis rotational seismometers are particularly useful for imaging and monitoring marine and continental volcanic activities. Here, we present recent implementations and acquisitions of those systems, demonstrate the great potential of these technologies to record present and past volcanic dynamics in Hawaii, Stromboli, Sicilia and Eifel region, and emphasize their benefits to better anticipate volcanic hazard. The Hawaii island experienced a dramatic volcanic crisis during the summer of 2018. To demonstrate the potential of observing the complete ground motion in the nearfield of seismic sources, Geophysical Observatory (LMU, Munich, Germany), in cooperation with USGS Hawaiian Volcano Observatory (USA), installed a high sensitive rotational motion sensor (blueSeis-3A) near the erupting crater returning spectacular data for almost daily M5 seismic events due to the collapse of the caldera. BlueSeis-3A, based on fiber optical gyroscope technology, at very close distance from the Stromboli volcano in 2016 and 2018, was installed together with classical instrumentation (i.e., translational seismometer, infra sound and tilt meter) and recorded four weeks of permanent strombolian activity at Stromboli during these two experiments. The resulting six axis measurements reveal clear rotations around all three-coordinate axis. We are furthermore able to demonstrate how these six component measurements can helpto improve solving the inversion problem on large and complex system like volcanoes. Eight Canopus transponders are involved in an ERC project in underwater geodesy, the FOCUS project headed by IUEM laboratory (Brest, France). Together with a 6 km-longoptical fiber deployed across the trench at the base of the Etna volcano, two groups of four Canopus will be installed on tripods each side of the trench at 1500-2000 m of water depth. This will help quantify the speed of the southeastern flank collapsing of Etna volcano into the Ionian Sea.In collaboration with French, Belgian and German geoscience laboratories, Echoes 10 000 (10 kHz) sub-bottom profiler and Seapix 3D multibeam echosounder, both installed on the kiXkat cataraft and remotely controlled, were mobilized to produce images of the water column and sediments of a lake formed in a volcanic crater in Germany (Laacher See). By using Seapix to obtain backscatter profiles of elements in the water column, it was possible to clearly distinguish fish and gas bubbles, which demonstrates a potential for the development of an automatic gas detection module using the Seapix software. Meanwhile, the Echoes 10 000 provided high-resolution images of the architecture of the lake deposits and visualized in real time using Delph Software. More than 30 m of penetration with a theoretical 8 cm-resolution highlight paleoenvironmental and paleoclimatic reconstruction perspectives and 3D modeling of remobilized materials and tephra deposits from volcanic activity.

The Calabrian subduction zone is one of the narrowest arcs on Earth and a key area to understand the geodynamic evolution of the Mediterranean and other marginal seas. Here in the Ionian Sea, the African plate subducts beneath Eurasia. Imaging the boundary between the downgoing slab and the upper plate along the Calabrian subduction zone is important for assessing the potential of the subduction zone to generate mega‐thrust earthquakes and was the main objective of this study. Here we present and analyze the results from a 380 km long, wide‐angle seismic profile spanning the complete subduction zone, from the deep Ionian Basin and the accretionary wedge to NE Sicily, with additional constraints offered by 3‐D Gravity modeling and the analysis of earthquake hypocenters. The velocity model for the wide‐angle seismic profile images thin oceanic crust throughout the basin.

Andrea Argnani in his comment on Dellong et al. (2020, https://doi.org/10.1029/2019gc008586) (Geometry of the deep Calabrian subduction (Central Mediterranean Sea) from wide‐angle seismic data and 3‐D gravity modeling) proposes an alternate interpretation of the wide‐angle seismic velocity models presented by Dellong et al. (2018, https://doi.org/10.1002/2017JB015312) and Dellong et al. (2020) and proposes a correction of the literature citations in these paper. In this reply, we discuss in detail all points raised by Andrea Argnani.