Seismic Velocity Anomalies and Fault Activity in the Târgu Jiu - Romania Region: A Tomographic Perspective

Seismic tomography is an essential geophysical method for investigating subsurface structures by analyzing variations in P-wave (Vp) and S-wave (Vs) velocities. This study focuses on the Târgu Jiu region, an area with moderate seismic activity, aiming to charac-terize the crustal structure and identify potential zones of seismic hazard. The dataset used for tomography included the travel times from 5281 seismic events. Tomographic models reveal significant velocity anomalies correlated with the region’s tectonic frame-work. High Vp and Vs values in the northern and northeastern areas suggest the presence of dense, rigid geological formations, likely associated with consolidated magmatic or metamorphic units. In contrast, the central region exhibits low Vs values, coinciding with an active seismic zone and intersecting major fault structures. This suggests the presence of highly fractured and weakly consolidated rocks, potentially saturated with fluids. The Vp/Vs ratio in the central region reaches values of ≥1.8–1.9, indicating fluid-filled fractures that may influence fault dynamics and earthquake occurrence. In the southern region, ve-locity anomalies suggest weakly consolidated sedimentary units with a high degree of fracturing. These findings contribute to a better understanding of the geodynamic behav-ior of the Târgu Jiu area and its seismic hazard potential.