The Fucino Basin, the largest tectonic basin within the Central Apennines orogen, is bounded by normal faults that have controlled the deposition of over 1 km of Pliocene-Quaternary continental deposits above a Messinian substratum. Conflicting interpretations from legacy seismic profiles have hindered a full understanding of the basin's stratigraphy, age, evolution, and fault systems, creating uncertainties for tectonic reconstructions, seismic response analysis and hazard assessment. To resolve these uncertainties, we acquired new high-resolution datasets through three complementary active-passive seismic surveys. These include seismic reflection profiles covering similar to 10 km, a nodal ambient noise campaign deploying 258 short-period nodes over 16 km2, preceded by two pilot array tests, and finally a basin-wide ambient noise survey comprising 1-hour recordings at 42 sites. Our analysis focused on the San Benedetto and Trasacco Faults-responsible for the 1915, M7.1, Marsica earthquake-and the main depocenter (the Bacinetto) associated with the San Benedetto Fault. This paper presents experimental setup, recorded data, and initial findings that provide new insights into basin stratigraphy, fault geometry, and spatial distribution of the fundamental resonance frequency (f0). The seismic reflection data show excellent imaging quality, resolution, and penetration exceeding 1 km. The Bacinetto hosts up to 850-900 m of continuous lacustrine succession and lower fluvio-lacustrine deposits that record sustained syn-sedimentary slip along the San Benedetto Fault from the Late Pliocene to Recent times. No evidence is found for significant synthetic or antithetic faulting beneath the depocenter, contradicting earlier structural models. The intra-basin Trasacco Fault forms a clear basement step and localized sediment thickening that tapers northwestward f0 varies from 1 to 2 Hz near the basin margins to similar to 0.2 Hz in the Bacinetto, reflecting progressive sediment thickening, whereas it varies abruptly across fault zones. f0 estimates from nodal and station data show good consistency.

While 3D seismic reflection is well established in hydrocarbon exploration at the kilometer scale in relatively simple offshore settings, its application to shallow faulting in continental basins is rare, owing to difficulties in adapting acquisition and processing to rugged terrains and complex near-surface conditions. We present the first high-resolution 3D seismic study of a seismogenic fault in a structurally complex intramontane basin at depths < 200 m. The survey focuses on the Pantano–Ripa Rossa Fault, ruptured during the 1980 Mw 6.9 Irpinia earthquake, the largest Italian event of the past century. This fault cuts across the Pantano di San Gregorio Magno, a small basin filled with Quaternary sediments and showing modest cumulative displacement. Our results demonstrate that in such environments, where morphotectonic analysis and 2D geophysics provide limited constraints, high-resolution 3D seismic imaging is crucial to resolve fault geometry and to assess surface-faulting hazard. The 3D volume reveals a ~35–40 m wide intra-basin deformation zone beneath the 1980 rupture, composed of synthetic and antithetic splays, and highlights lateral variations in fault geometry and stratigraphy. Deformation is distributed and complex, with fault-controlled depocenters, variable sedimentary architectures, and rapid basement-depth changes—features unresolved by 2D data. We infer that the Pantano–Ripa Rossa Fault is relatively young, active since the late Middle Pleistocene, and developed in the hanging wall of the NE-dipping southern basin-bounding fault, challenging previous models that located the master fault along the northern basin margin.

The scientific project TESIRA (TEst Site IRpinia fAult), funded in 2021 by the University of Naples “Federico II”, aims, through the integration of a multivariate dataset, to achieve a high-resolution 3D geophysical imaging of the shallow structure of the southern branch of the 1980 Ms=6.9 Fault at Pantano San Gregorio Magno (SA). The set of data acquired during the project life-span included: a microgravimetric survey; 3D and 2D Electrical Resistivity measurements; aeromagnetic and GPR surveys by drone; a CO2 surface degassing measurement and a full-waver electric investigation. Specifically, the active-source seismic dataset acquired at Pantano consists of four high- to very-high resolution seismic profiles spanning a total length of 3150 m and a high-resolution seismic volume covering an area of 12.5 acres. The seismic experiment's location was strategically chosen to illuminate key features of the Pantano basin affected by coseismic surface faulting, such as the rupture during the November 23,1980 Irpinia earthquake and the southern segment of the Pantano-San Gregorio Fault System (PSGM). We share the early findings obtained through standard Common Depth Point processing and post-stack depth migration. Even at this initial stage, the results offer a clear picture of the intricate 3D structure of the basin, revealing a complex pattern of the carbonatic basement resulting from active faulting. Additionally, the seismic images underscore the evident influence of active faulting on the basin's formation and recent sedimentation. Future analyses, including full-waveform inversion and post-stack depth migration, are planned to enhance the imaging of this critical sector in the southern Apennines. Although seismic data present the highest resolution among the geophysical datasets at Pantano, their integration with the extensive data collected during the TESIRA project will facilitate a reliable interpretation of the complex basin subsurface, useful to improve our understanding of the interplay between active surface faulting and recent basin growth pattern.

The Molise-Sannio region, in the axial portion of the Southern Apennines (Italy), is a fold-and-thrust belt where the Late Miocene to Early Pleistocene compressional tectonics has been overprinted by a younger extensional stress regime responsible for a significant degree of seismicity, and which is coexisting with strike-slip faulting to the north-east. Active faults in this area are known to be capable of generating M6+ earthquakes. The goal of the MOSAICMO project (Molise SAnnio integrated crustal Model) is to develop a comprehensive multiscale crustal model of the Molise-Sannio region by combining seismological, geophysical and geological data, with a specific focus on the Quaternary intramontane Bojano basin (BB). The latter is a NE-trending depression whose genesis is debated, since according to recent studies it appears to be controlled by a system of NE-dipping active fault segments present on the southern side, while other studies claim the importance of SW-dipping faults on the other side of the basin. Indeed, the subsurface geometry and deep structure of the BB are poorly constrained by available geological data, which hampers a correct recognition of the master faults and their possible seismogenic significance. Resolving this ambiguity is a priority task that can be accomplished through an integrated geological and geophysical approach. In this project framework, multi-disciplinary geophysical studies were conducted to study the BB at different scales and resolutions, by interpreting subsurface geophysical parameters (e.g. electrical resistivity, seismic velocities, etc.) in terms of lithology and mechanical properties. Electrical methods have proven to be a powerful tool in imaging complex subsurface geology. By measuring the resistance of subsurface materials to electrical current flow, these methods can differentiate between various geological structures such as faults, basin infill sediments and basement rock types, providing high spatial resolution and significant investigation depth. 3D electrical resistivity tomography has often been used in recent years to image conductive bodies covering high-resistivity structures, such as tectonic basins or hydrothermal systems in volcanic regions. Here, we present a challenging case study for 3D geoelectrical imaging: a continental tectonic basin filled with low to moderately resistive sediments emplaced on conductive clayey-arenaceous rocks. The integration of different resistivity data (ERT and ResLog) with other geophysical methods, like seismic and magnetic surveys, further refines subsurface imaging, ensuring robust and reliable geological interpretations. We present the first 3D electrical resistivity model of the BB, down to 500 m depth, complemented by several 2-D ERT profiles calibrated with shallow boreholes. Subsurface geophysical models were further constrained by a scientific drilling, 170-m-deep, that we performed also to obtain new stratigraphic and geochronological data on the basin sedimentary sequence. This represents an important contribution to the understanding of the regional seismotectonic setting and, locally, the seismogenic sources surrounding the BB.

This study investigates subsurface pore pressures in the Irpinia region of southern Apennines, Italy, one of the central Mediterranean areas with the highest seismic activity. The Apennine thrust belt consists of stacked thrust sheets formed from both deep- and shallow-water environments during the pre-orogenic phase and later involved in the Neogene compressional phase. In the ongoing post-orogenic phase, the region is experiencing an extensional tectonic regime, as evidenced by the 1980 Ms. 6.9 normal fault Irpinia earthquake. Eleven exploration wells drilled to depth of 1.7-5.9 km intersect the main tectonostratigraphic units of the chain, providing valuable data on drilling mud weights and fluid chemical features, allowing for the reconstruction of vertical pore pressure trends and fluid circulation through the upper crust up to nearly 6 km of depth. The data analysis reveals that the carbonate platform and basin Meso-Cenozoic deposits generally exhibit hydrostatic or nearly hydrostatic conditions in the upper 2-4 km depth. However, moderate to high overpressure gradients are observed in Meso-Cenozoic basin sequences, Messinian evaporites, tectonic melange, and foredeep Pliocene shales. These overpressures are typically associated with reverse faults and are not correlated with occurrences of gas. Conversely, slight overpressure gradients at shallower depths are related to shaly lithologies containing gas traces. Notably, the pressure profile of San Gregorio Magno-1 well, intersecting the causative fault of the 1980 earthquake, suggests a uniform distribution of fluids throughout intensively fractured nappes, including carbonate platform units and deep-water basin formations. Moreover, wells that penetrated the buried platform carbonates, known as Apulian carbonates, display hydrostatic or low overpressure gradients, even when overpressured shales seal the carbonate reservoirs, challenging previous seismological interpretations of overpressured Apulian carbonates. Finally, the analysis of diffusion mechanisms has provided insights into the timing of the geological disturbance that caused the locally observed overpressures and their maintenance.

The Einstein Telescope (ET) will be the first European underground observatory of gravitational waves. The observatory's interferometric detectors will be housed in a large underground infrastructure,which necessitates a stable and quiet geological context. We present the results of a geognostic campaign conducted for the Italian candidate site in Sardinia, during which two similar to 270 m-deep boreholes were drilled in granites and orthogneiss at two sites that are possible locations of the ET infrastructure. We acquired high-resolution, dense seismic and electrical resistivity tomography (ERT) profiles to complement borehole data, constraining the thickness of the weathered layer and characterizing the rock properties in terms of intact versus fractured zones down to depths of 100-240 m. At depths >50 m, we observed high P-wave velocity (Vp similar to 5000-5500 m/s, while very high Vp (similar to 6000 m/s) paired with very high resistivity (rho > 1000 Omega m) was found at depths of 150-200 m, suggesting unfractured or weakly fractured rocks consistent with borehole logs and literature data on geophysical surveys on crystalline rocks. We recognized a couple of sub-vertical low-Vp (similar to 4250-4500 m/s) and low-resistivity anomalies (rho < 500 Omega m), up to similar to 15-35 m-wide, suggesting the occurrence of fracture zones with groundwater, matching the intersection with fault zones mapped at the surface. Comparison with co-located resistivity sections, downhole seismic surveys, well logs, and field-based structural and morphostructural analyses allowed us to attribute these anomalies to fault zones similar to 0.3-0.5 km-long that belong to an immature fault network with shallow water circulation. This methodological approach highlights the utility of tomographic techniques combined with structural investigations and represents a guideline that can be applied in similar contexts characterized by poorly fractured crystalline rocks.

The Irpinia Fault, also known as the Monte Marzano Fault System, located in the Southern Apennines (Italy), is one of the most seismically active structures in the Mediterranean. It is the source of the 1980, Ms 6.9, multi-segment rupture earthquake that caused significant damage and nearly 3,000 casualties. Paleoseismological surveys indicate that this structure has generated at least four Mw ~ 7 surface-rupturing earthquakes in the past 2 ka. This paper presents a comprehensive, high-resolution geophysical investigation focused on the southernmost fault segment of the Monte Marzano Fault System, i.e., the Pantano-Ripa Rossa Fault, outcropping within the Pantano di San Gregorio Magno intramontane basin. The project, named TEst Site IRpinia fAult (TESIRA), was supported by the University of Napoli Federico II to study the near-surface structure of this intra-basin fault splay that repeatedly ruptured co-seismically in the past thousands of years. Our imaging approach included 2D and 3D electrical and seismic surveys, gravimetry, 3D FullWaver electrical tomography, drone-borne GPR and magnetic surveys, and CO2 soil flux assessment across the surface rupture. This multidisciplinary investigation improved our understanding of the basin shallow structure, providing an image of a rather complex subsurface fault and basin geometry. Seismic data suggest that fault activity at the Pantano segment of MMFS is characterized by a near-surface cumulative displacement greater than previous estimations, calling into question earlier assumptions about the timing of its activation. Despite some challenges with our drone-mounted survey equipment, the integrated dataset provides a comprehensive and reliable image of the subsurface structure. This work demonstrates the utility of developing an integrated approach at high-resolution geophysical imaging and interpretation of fault zones with weak morphological expressions.

Subsurface pore pressure studies are crucial for understanding the geomechanical behaviours of the geological formations and for preventing the failure conditions of the rocks. Although the interplay between pore pressure changes and rock deformation is nowadays widely treated in the literature, the magnitude and the distribution of the fluid pressure regimes at depth is not completely clear, especially in those areas, such as the fold and thrust belts, characterised by a complex tectonostratigraphic setting. The proposed study deals with the subsurface fluid dynamics of the Irpinia region, located in the Southern Apennines (Italy) and marked by intense tectonic activity and seismicity. In that area, the most recent and notable Italian earthquake occurred in November 1980 (6.9 Mw) and caused significant damage and loss of life. Irpinia area is also a site of deep gas rising to the surface and exhibits clear correlations between crustal deformation and groundwater circulation. The pressure analysis herein proposed has been performed using direct and indirect pressure measurements collected from 13 hydrocarbon exploration wells available in open source. It provides a detailed description of the methodology used to identify where overpressures develop within the sediments of both autochthonous and allochthonous layers. It also investigates the relationship between pore pressures, gas occurrences found at well sites, and the possible sources of overpressures. The results show that the carbonate successions of the South-Apennines and Apulian Platforms are characterized by predominantly hydrostatic pressure regimes, while the shale-rich successions of the Lagonegrese pelagic basin and the Miocene-Pliocene foredeep basin locally demonstrate moderate overpressured gradients. Finally, the highest overpressures are observed in the evaporitic deposits and Pliocene shales.

The incompleteness of earthquake catalogs is a well-known issue caused by our technical limitation in detecting the small- to very small-magnitude seismicity falling near or below the level of background seismic noise. According to Gutenberg-Richter distribution, small earthquakes represent the majority of the events occurring in a certain area and their detection is key for improving our knowledge of: i) the geometry and kinematics of seismogenic sources; ii) the spatio-temporal characteristics of seismicity, thus leading to better models for seismic hazard. Template-matching (TM) is a well-known and powerful technique based on similarity measure that allows to find earthquakes hidden in the continuous recording, similar to to known events (templates). Nowadays, the larger availability of computational resources, allows the application of such technique to regional areas. This work represents the first application of template-matching to Southern Apennines (Italy), using about 4.000 high-quality events as templates and scanning 6-years long continuous recording (2009-2014) at more than 180 stations of the INGV network. About 20.000 new events are found, showing a comparable quality to the template catalog in terms of hypocentral solution, and reaching a decrease of the magnitude of completeness of about one unit. In order to highlight the improved quality of the TM catalog, we report on two main examples regarding the Sannio-Matese area, where TM allowed us to unravel relevant details on the spatio-temporal distribution of the local seismicity, providing useful insights for the understanding of the seismic hazard.

We present the first 3D crustal model of the epicentral region of the 1980, M-w 6.9, normal-faulting Irpinia earthquake (southern Italy) determined by jointly interpreting the CROP-04 deep seismic profile, a grid of commercial seismic lines, deep exploration wells, and a high-resolution Local Earthquake Tomography. Despite numerous seismotectonic surveys and source studies of the background seismicity recorded by dense networks, a complete 3D geological model of the mid-upper crust was still lacking in the region. The architecture of the Neogene fold-and-thrust belt is also debated, with competing thin- and thick-skinned tectonic interpretations. We use the 3D geological model derived from subsurface exploration data to interpret the upper crustal tomographic velocities in terms of rock physical properties, while V(p )and V-p/V-s anomalies provide inferences on the deep structural setting down to 12 km depth. We find that a thick-skinned deformation style allows explaining the geometry of Pliocene fold-and-thrust systems deforming the Apulian carbonates but also deeper Permo-Triassic metasediments and the Paleozoic crystalline femic basement. Inherited compressional structures and lithological heterogeneities control background seismicity occurring at two crustal levels. Fluid-driven shallow seismicity (<4-6 km) concentrates in a high-V-p/V-s wedge of fractured, brine-saturated Mesozoic stiff rocks delimited by the 1980 earthquake faults. Deep seismicity (9-14 km) clusters instead within the low-V-p/V-s crystalline basement underneath the Apulian carbonate ramp-anticlines. Commercial seismic data allow us to identify the Irpinia Fault, the main fault ruptured by the 1980 earthquake, reinforcing its previous interpretations as an immature structure with subtle geological and geophysical evidence.

We investigate the variability of Brune stress drop (Delta sigma), apparent stress (tau a), and Savage- Wood radiation efficiency (eta sw = tau a=Delta sigma), in the 2013-2014 Mw 5.0 earthquake sequence that struck the Matese area in the southern Apennines range of Italy. The sequence is clustered in a relatively small crustal volume in the 13-22 km depth range, which is greater than that of background seismicity and normal-faulting sequences that occurred under the range axis, usually located in the first 15 km of the crust. We find high Savage- Wood radiation efficiency values for most of the analyzed earthquakes located in a narrow crustal volume, with values ranging from well above the self-similarity value to very high values as high as 0.55. In addition, a large variability in radiation efficiency (up to 90%) is observed for two similar magnitude events at different depths. Previous studies reported seismic evidence of fluid involvement in the nucleation process of the Matese earthquakes. By integrating our results with crustal geophysical data published recently, we propose that most of the earthquakes characterized by high values of eta sw are nucleated within high pore pressure zones located in the crystalline midcrust of Adria. We reckon that high pore pressure fluids of deep origin played a role in the rupture process and were responsible for the mixed shear-tensile sources inferred from the analysis of the S-wave/P-wave spectral amplitude ratio for most of 2013-2014 earthquakes.

We present a detailed analysis of the small magnitude ( M L < 3) Reservoir Induced Seismicity associated with the Pertusillo water reservoir located in the high seismic hazard zone of Val d'Agri (Southern Italy). We apply template‐matching detection to a 13‐month‐long dense passive survey, obtaining a final high‐precision double‐difference catalog of 5,070 earthquakes (−0.7 < M L < 2.6, M C = 0.2). The new catalog allows precisely tracking the spatiotemporal distribution of the swarm‐seismicity and to map the b‐value of the Gutenberg‐Richter law. We combine seismicity data with available subsurface geophysical data, fostering an improved interpretation of the induced seismicity. We identify four seismicity‐clusters showing rapid changes in seismic rate which correlate to severe seasonal oscillations. Seismicity unravels new km‐scale faults or better define faults partially‐illuminated by template earthquakes. b‐value shows a significant spatial variability, with very‐high b‐value (up to 2) within areas of distributed seismicity and lower (∼1.3) b‐value for on‐fault seismicity featuring larger magnitude events. Seismicity is confined within a brine‐saturated fractured carbonate reservoir, while earthquake distribution and rate are controlled by the fault architecture and rock properties (e.g., inherited fluid pathways, rock fracturing, pore fluid pressure). In particular, most earthquakes reactivate, with extensional kinematics, pre‐existing reverse/transpressional faults favorably oriented in the present‐day extension. All observations suggest that a poroelastic stress transmission mechanism, due to the seasonal water level oscillation, can explain the Pertusillo lake seismicity. This study confirms the importance of investigating the complex interaction among stress changes caused by human activities, pre‐existing faults and local stress field to correctly assess the hazard posed by induced seismicity.

&lt;p&gt;The Irpinia region in the Southern Apennines is one of the areas with the highest seismic hazard in Italy, as also testified by several recent and historical earthquakes ranging between M&lt;sub&gt;w&lt;/sub&gt; 6.6-6.9 (1694, 1732, 1930, 1980). The shallow crust structural setting of this area is characterized by multiple deformational stages, which caused the tectonic stacking of Meso-Cenozoic sedimentary sequences deposited in different paleogeographic domains. The overall structure of the chain still contends between the thin-skinned and thick-skinned models.&lt;br&gt;We present a 3D geological model of key stratigraphic and tectonic elements based on the analysis of 2D seismic reflection profiles, integrated with well data and surface geology information. We also computed a 3D velocity model of the upper crust (V&lt;sub&gt;p&lt;/sub&gt; and V&lt;sub&gt;p&lt;/sub&gt;/V&lt;sub&gt;s&lt;/sub&gt;) through a local earthquake tomography (LET) to provide inferences on the structure and rock properties of the deep Apulian tectonic stack, especially where this is poorly imaged by seismic reflection imaging. We propose an integrated interpretation of the deep structure based on the analysis of the CROP-04 deep seismic profile and Vp and Vp/Vs patterns.&lt;br&gt;Our results highlight the presence of a regional thrust separating a shallow domain, characterized by relatively low-angle thrust surfaces (Allochthonous domain), from a deeper domain characterized by high-angle buried thrusts that affect the Apulian carbonate platform&lt;strong&gt;. &lt;/strong&gt;The Plio-Pleistocene Apulian compressional architecture seems to control the rock physical properties in the upper crust and the seismotectonic of the area related to NE-SW regional extension active since the Middle Pleistocene. We observed that background seismicity concentrates in high-V, high-V&lt;sub&gt;p&lt;/sub&gt;/V&lt;sub&gt;s&lt;/sub&gt; regions that follow the Apulian structural trends and strictly correlate with the main crustal ramp anticlines. Furthermore, our structural model provides new geological insight regarding the destructive 1980 Irpinia earthquake (M&lt;sub&gt;w&lt;/sub&gt;=6.9), which ruptured three main fault segments.&lt;br&gt;From a methodological point of view, the integration of 3D geological model and LET is suitable for future earthquake relocations based on a data-driven velocity model reconstruction that considers the 3D geological complexities.&lt;/p&gt;

SUMMARY We present the results from a fully unconstrained moment tensor inversion of induced seismic events in a complex and high seismic hazard region (Val d'Agri basin, Southern Italy). The study area hosts two well-documented cases of induced microseismicity linked to (i) a wastewater injection well of a giant oilfield (the largest in onshore Europe), and (ii) severe seasonal level changes of an artificial lake. In order to gather information on the non-double-couple components of the source and to better understand the rupture mechanisms, we analyse seismic events recorded during daily injection tests in the disposal well. The computed moment tensors have significant non-double-couple components that correlate with the well-head injection pressure. The injection parameters strongly influence the rupture mechanism that can be interpreted as due to the opening/closing of a fracture network inside a fault zone of a pre-existing thrust fault. For the case of the reservoir-induced seismicity, no direct correlations are observed with the loading/unloading of the reservoir.

The Campo Felice basin, in the central Apennines seismic belt (Italy), developed in the hangingwall of a 30 km-long system of NW-trending normal faults with Holocene paleoseismic activity and potential sources of M 6-7 earthquakes. We provide the first subsurface images of a key portion of the basin bounded by the Mt. Cefalone fault along two intersecting profiles trending NNE-SSW (CF-Dip, 1195 m-long) and WNW-ESE (CF-Strike, 1315-m long). We combined high-resolution depth-migrated reflection sections with P-wave velocity and electrical re-sistivity tomography models. CF-Dip profile displays a wedge-like syn-tectonic sedimentary sequence of alluvial and glacial deposits with Vp similar to 2500-3000 m/s and resistivity > 500 Omega m in the hangingwall of Mt. Cefalone fault, overlying a high-Vp (>4000 m/s) limestone bedrock similar to 300 m deep. The whole sequence displays reflectors truncated by the Mt. Cefalone fault zone and subsidiary antithetic faults. CF-Strike profile, tied to three 80-110 m-deep boreholes, shows a thick fluvio-lacustrine sequence with low-Vp (<2000 m/s) and low resistivity (<100 Omega m), and a bedrock that deepens to the southeast (>450 m). Single-station ambient noise measurements display Horizontal to Vertical Spectral Ratios with peaks at similar to 1 Hz, decreasing to similar to 0.8 Hz to the southeast in agreement with the bedrock deepening indicated by seismic profiling. According to our results, the Campo Felice basin is a deep asymmetric half-graben controlled by faulting whose activity likely started before the Middle Pleistocene. Our minimum displacement estimate accrued in the past 0.5 Ma by the Mt. Cefalone fault is in the range of similar to 100-250 m.

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 M(w)6.1 mainshock activated the Middle Ferrara thrust-ramp dipping similar to 45 degrees 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 M(w)6.0 mainshock featured two separated asperities along the Mirandola thrust ramp dipping similar to 42 degrees 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 high slip 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 degrees-45 degrees) thrust-ramps deeply rooted into the Paleozoic crystalline basement.

The scientific project TESIRA (TEst Site IRpinia fAult), funded in 2021 by the University of Naples “Federico II”, aims at acquiring multidisciplinary geophysical data above an active fault in an intramontane basin of the Southern Apennines and to achieve, through the integration of this multivariate dataset, an accurate 3D geophysical imaging of the shallow structure of the fault zone in order to understand the link between shallow faulting and petrophysical changes, which affect rock permeability and surface degassing. The target structure is the southern branch of the Irpinia Fault, one of the structures with highest seismogenic potential in the Mediterranean region, causing the 4th Italian earthquake of last century (1980, Ms=6.9, Pantosti & Valensise, 1990) and generating a modest surface throw at Pantano San Gregorio Magno (Salerno).A microgravimetric survey and a 3D and 2D Electrical Resistivity measurements survey were acquired between September 2021 and January 2022. 3D seismic data were acquired in July 2022, using two overlapping arrays with a dense geophone distribution covering an area of about four hectares, with a detail of 2.5x2.5m. Moreover, four 2D seismic profiles intersect the 3D volume. An aeromagnetic survey, an extension of the gravimetric survey and a sampling of the CO2 surface degassing will be completed within this year. We will show the preliminary results of the individual surveys. Later, the different geophysical and geochemical measurements will be integrated using cooperative inversion and machine learning techniques. We hope that this multidisciplinary approach will provide a more comprehensive understanding of the interaction between surface faulting and basin development in this key area of the Southern Apennines. ReferencesPantosti, D.; Valensise, G.; [1990] Faulting Mechanism and Complexity of the November 23, 1980, Campania-Lucania Earthquake, Inferred From Surface Observations, JGR, 95, 319-34