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The prompt identification of faults responsible for moderate‐to‐large earthquakes is fundamental for understanding the likelihood of further, potentially damaging events. This is increasingly challenging when the activated fault is an offshore buried thrust, where neither coseismic surface ruptures nor GPS/InSAR deformation data are available after an earthquake. We show that on 9 November 2022, an Mw 5.5 earthquake offshore Pesaro ruptured a portion of the buried Northern Apennines thrust front (the Cornelia thrust system [CTS]). By post‐processing and interpreting the seismic reflection profiles crossing this thrust system, we determined that the activated fault (CTS) is an arcuate 30‐km‐long, NW‐SE striking, SW dipping thrust and that older structures at its footwall possibly influenced its position and geometry. The activation of adjacent segments of the thrust system is a plausible scenario that deserves to be further investigated to understand the full earthquake potential of this offshore seismogenic source. Plain Language Summary The Northern Apennines chain is characterized by thrust faults running from the Po Plain to the Adriatic Sea on the northeastern side of peninsular Italy. These thrusts are buried below ≈2,000 m cover of Plio‐Pleistocene deposits. Controversies arose about these thrust faults' activity and earthquake potential based on their hidden geological signature and the scanty seismicity that could be associated with them. The earthquake (magnitude 5.5) that occurred on 9 November 2022, offshore Pesaro revived this argument. In this work, we analyze the geological structure of the crustal volume affected by the seismic sequence, exploiting seismic reflection profiles and well‐log data to identify the earthquake causative fault. Our results demonstrate that the earthquake ruptured a well‐known fault of the Northern Apennines' buried thrust front, supporting that it is indeed active and seismogenic. The size and architecture of this thrust front suggest that it could generate even larger earthquakes (Mw > 6.5). This type of geological study is instrumental to understanding the geometry of earthquake faults, particularly in offshore areas, because they constitute reliable inputs for earthquake hazard models and, when done promptly after an earthquake, provide key elements for other studies on the seismic source and the unfolding of the ongoing seismic sequence. Key Points 9 November 2022, earthquake consistent with activity of the Cornelia thrust, a fault system running off the central Adriatic coast The seismic reflection profiles in the area allowed for delineating the thrust and its earthquake potential with a much finer resolution The properties of the causative fault suggest that the activation of adjacent segments is a plausible scenario that deserves consideration

The use of the HVSR (Horizontal-to-Vertical Spectral Ratio) method on single-station microtremor measurements is well documented in small alluvial plains for bedrock mapping. In large sedimentary basins, like the Po Plain, its application is still debated. To shed some light on this issue, we investigated two seismogenic structures buried below the Po Plain Quaternary deposits: the Mirandola and Casaglia anticlines. We acquired and analysed a dense distribution of HVSR data covering the two areas and mapped the frequency and amplitude values of the observed resonance peaks. The top of both anticlines is highlighted by high amplitude peaks picturing E-W elongated sectors with high-impedance contrast, where Quaternary deposits are reduced in thickness to about 60–130 m and directly overlay the Pliocene (Mirandola) and Miocene (Casaglia) marine units. In Mirandola, the high-amplitude peaks also correspond to higher resonance frequencies, while in Casaglia, the distribution of resonance frequencies is relatively uniform suggesting a flatter crestal region and the lateral continuity of the resonance surface. The combination of peak frequency and amplitude information on a dense grid of measurement points is thus confirmed to be useful for identifying and mapping buried geological structures such as structural highs. Further modelling is being carried out to estimate the depth of the surface responsible for the observed resonances, through calibration with borehole information. Graphical Abstract

The Mirandola anticline represents a buried fault-propagation fold which has been growing during Quaternary due to the seismogenic activity of a blind segment belonging to the broader Ferrara Arc. The last reactivation occurred during the May 2012 Emilia sequence. In correspondence with this structure, the thickness of the marine and continental deposits of the Po Plain foredeep is particularly reduced. In order to better define the shallow geometry of this tectonic structure, and hence its recent activity, we investigated in a depth range which is intermediate between the surficial morphological observations and seismic profiles information. In particular, we carried out numerous passive seismic measurements (single-station microtremor) for obtaining the horizontal-to-vertical spectral ratio. The results of a combined analysis of the peak frequency and its amplitude nicely fit the available geological information, suggesting that this low-cost geophysical technique could be successfully applied in other sectors of wide morphologically flat alluvial plains to investigate blind and completely buried potential seismogenic structures.

During the seismic crisis of May–June 2012, that strongly affected the central sector of the Ferrara Arc, relevant coseismic effects were observed, such as ground deformations and amplification phenomena due to low quality mechanical characteristics of the shallow subsurface (i.e. few hundreds of meters). This portion of the subsurface is not investigated by neither hydrocarbon explorations (too deep) nor geotechnical surveys (too shallow). Furthermore, direct analysis is not cost effective to carry out over such a wide area. To overcome these limitations, we exploited seismic noise-based strategies, which are not invasive and do not require expensive equipment. We carried out several single-station and array measurements (i.e. ESAC, Re-Mi, and HVSR), across some of the major tectonic structures of the eastern Po Plain, belonging to the most advanced buried sector of the Northern Apennines. Such investigations were performed along two profiles, about 27 km-long and oriented SSW–NNE, i.e. almost perpendicular to the regional trend of the Ferrara Arc structures. Our results clearly document lateral shear wave velocity variations and the occurrence of resonance phenomena between 0.52 and 0.85 Hz. Additionally, based on inversion procedures, we were able to infer the depth of the resonant interface(s) and we associated such interface(s) to the major known stratigraphic discontinuities, thus emphasizing the recent tectonic activity of the blind thrusts affecting this sector of the Ferrara Arc.

In this paper we describe an advanced database for the site characterization of seismic stations, named “CRISP—Caratterizzazione della RIsposta sismica dei Siti Permanenti della rete sismica” ( http://crisp.ingv.it , quoted with https://doi.org/10.13127/crisp ), designed for the Italian National Seismic Network (Rete Sismica Nazionale, RSN, operated by Istituto Nazionale di Geofisica e Vulcanologia). For each site, CRISP collects easily accessible station information, such as position, type(s) of instrumentation, instrument housing, thematic map(s) and descriptive attributes (e.g., geological characteristics, etc.), seismic analysis of recordings, and available geophysical investigations (shear-wave velocity [ V S ] profile, non-linear decay curve). The archive also provides key proxy indicators derived from the available data, such as the time-averaged shear-wave velocity of the upper 30 m from the surface (V S30 ) and site and topographic classes according to the different seismic codes. Standardized procedures have been applied as motivated by the need for a homogenous set of information for all the stations. According to European Plate Observing System infrastructural objectives for the standardization of seismological data, CRISP is integrated into pre-existing INGV instrument infrastructures, shares content with the Italian Accelerometric Archive, and complies map information about the stations, as well as local geology, through web services managed by Istituto Superiore per la Protezione e la Ricerca Ambientale. The design of the CRISP archive allows the database to be continually updated and expanded whenever new data are available from the scientific community, such as the ones related to new seismic stations, map information, geophysical surveys, and seismological analyses.

We provide a database of the surface ruptures produced by the 26 December 2018 Mw 4.9 earthquake that struck the eastern flank of Mt. Etna volcano in Sicily (southern Italy). Despite its relatively small magnitude, this shallow earthquake caused about 8 km of surface faulting, along the trace of the NNW-trending active Fiandaca Fault. Detailed field surveys have been performed in the epicentral area to map the ruptures and to characterize their kinematics. The surface ruptures show a dominant right-oblique sense of displacement with an average slip of about 0.09 m and a maximum value of 0.35 m. We have parsed and organized all observations in a concise database, with 932 homogeneous georeferenced records. The Fiandaca Fault is part of the complex active Timpe faults system affecting the eastern flank of Etna, and its seismic history indicates a prominent surface-faulting potential. Therefore, this database is essential for unravelling the seismotectonics of shallow earthquakes in volcanic areas, and contributes updating empirical scaling regressions that relate magnitude and extent of surface faulting. Measurement(s) coseismic surface rupture • surface rupture kinematics • surface rupture displacement • surface rupture location Technology Type(s) field survey • GPS navigation system Factor Type(s) offset • strike • angle • length • latitude • longitude • elevation Sample Characteristic - Environment volcanic field Sample Characteristic - Location Island of Sicily • Mount Etna Machine-accessible metadata file describing the reported data: https://doi.org/10.6084/m9.figshare.11673027

We provide a database of the surface ruptures produced by the 26 December 2018 Mw 4.9 earthquake that struck the eastern flank of Mt. Etna volcano in Sicily (southern Italy). Despite its relatively small magnitude, this shallow earthquake caused about 8 km of surface faulting, along the trace of the NNW-trending active Fiandaca Fault. Detailed field surveys have been performed in the epicentral area to map the ruptures and to characterize their kinematics. The surface ruptures show a dominant right-oblique sense of displacement with an average slip of about 0.09 m and a maximum value of 0.35 m. We have parsed and organized all observations in a concise database, with 932 homogeneous georeferenced records. The Fiandaca Fault is part of the complex active Timpe faults system affecting the eastern flank of Etna, and its seismic history indicates a prominent surface-faulting potential. Therefore, this database is essential for unravelling the seismotectonics of shallow earthquakes in volcanic areas, and contributes updating empirical scaling regressions that relate magnitude and extent of surface faulting.

This paper illustrates the activities of EMERSITO, an emergency task force of the Istituto Nazionale di Geofisica e Vulcanologia (INGV, Italy) devoted to site effects and microzonation studies during the seismic sequence that occurred close to the Adriatic coast in central Italy starting from 9 November 2022, following the Mw 5.5 mainshock localized in the sea. In particular, we describe the steps that led to the deployment of a temporary network of seismic stations in the urban area of Ancona, the main city of the Adriatic coastline. Data collected by the temporary Ancona network (identification code 6N; 10.13127/sd/qctgd6c-3a, EMERSITO Working Group, 2024) from November 2022 to the end of February 2023 have been preliminary analyzed with different techniques to characterize the deployment sites and are now available for further and detailed studies.

In the original version of the Data Descriptor the surname of author Anne Socquet was misspelled. This has now been corrected in the HTML and PDF versions of the Data Descriptor. Some authors were also not appropriately associated with their affiliations in the HTML version, due to formatting errors made by the publisher. This has now been corrected in the HTML version of the Data Descriptor, the affiliations in the PDF were correct from the time of publication.