INGV Sezione Irpinia

SKS splitting at the Calabrian subduction zone, with delay times ( δ t) up to 3s, reveals the presence of a strong anisotropic fabric. Fast directions (ϕ) are oriented NNE‐SSW in the Calabrian Arc (C.A.) and rotate NNW‐SSE to the north following the arcuate shape of the subducting plate. We interpret the trench‐parallel ϕ as local‐scale mantle flow driven by the retrograde motion of the slab; the absence of trench perpendicular ϕ below the Southern Apennines (S.A.) excludes the presence of a seismically detectable return flow at its NE edge. This may be due to the relative youth and limited width of the S.A. slab tear. A possible return flow is identified farther north at the boundary of the S.A. and Central Apennines. Different and weaker anisotropy is present below the Apulian Platform (A.P.). This implies that the influence of the slab rollback in the sub‐slab mantle is limited to less then 100 km from the slab.

Abstract On 2 April 2024, an M W 7.4 earthquake struck the northern Longitudinal Valley in eastern Taiwan, about 18 km SSW of Hualien, causing damage and casualties. In this study, we investigated a comprehensive geodetic data set, employing Global Navigation Satellite Systems (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) measurements to assess the rupture geometry associated with earthquake sequence. Although geodetic data can be satisfactorily reproduced by simple single‐fault models (i.e., a high‐angle E‐dipping plane related to the Longitudinal Valley Fault (LVF), or a gentle W‐dipping surface associated with the Central Range Fault, CRF), a composite model involving the rupture of different fault segments (a major CRF‐related W‐dipping fault, a deep segment of the E‐dipping LVF, and the Milun Fault) is able to explain the observations, the distribution of seismicity, and the complex structural arrangement of the northernmost sector of the Longitudinal Valley.

The interpretation of coseismic surface deformation measurements through inversion techniques is of major importance to understand the mechanical behaviour of a seismic fault. Dense geodetic data sets in the vicinity of the ruptured fault provide unique constraints on detailed fault geometry and slip distribution at depth, making them complementary to seismological data.

Abstract The seismic‐electromagnetic phenomenon entails the generation of transient electromagnetic signals, which can be observed both simultaneously (co‐seismic) and preceding (pre‐seismic) a seismic wave arrival. Following the most accredited hypothesis, these signals are mainly due to electrokinetic effects, generated on microscopic scale in porous media containing electrolytic fluids. Thus, the seismic‐electromagnetic signals are expected to be suitable for the detection and tracking of crustal fluids. Despite the growing interest in this phenomenon, there is a lack of freely available observational database of earthquake‐related electromagnetic signals recorded at co‐located seismic and magnetotelluric stations. To fill this gap, we set up two multicomponent monitoring stations in two seismically active areas of Southern Italy: the Gargano Promontory and the High Agri Valley. This work is both aimed to systematically analyse earthquake‐generated seismic‐electromagnetic recordings and to make the collected database accessible to the scientific community.