Seismic source parameters analysis in Southeastern Alps and associated tectonic implications

We present a comprehensive analysis of earthquake source parameters in the Southeastern Alps, a tectonically complex region located at the junction of the Eastern Alps and the Dinarides. Using single station spectral inversion of S-wave displacement spectra from 1521 well-recorded earthquakes (1.3 ≤ M W ≤ 4.3) occurring between 2016 and 2023, we estimated seismic moment, corner frequency, static and apparent stress drop, radiated energy, and seismic efficiency. Our results reveal a small deviation from self-similar scaling condition, with static stress drop values ranging mostly from 0.1 to 10 MPa (median ≈ 0.84 MPa) and apparent stress stabilizing above 1 MPa for moderate events. The Savage-Wood efficiency values suggest a dominant overshoot rupture regime, indicating that only a fraction of the available stress is radiated as seismic energy. The spatial patterns of stress drop and attenuation correlate with the underlying tectonic domains. Regions characterized by strong, competent crust exhibit higher stress drops and lower attenuation, whereas areas with fractured, fluid-rich fault zones show lower stress drops and stronger attenuation. This study highlights the value of high-resolution spectral analysis and dense seismic networks for characterizing rupture processes and provides a new regional reference dataset for ground motion prediction and seismic hazard assessment in Southeastern Alps and comparable intraplate environments.