Unraveling Stress and Energy Variations Through Spectral Analysis of Seismic Sources in the East Anatolian Fault Zone (Türkiye)

ABSTRACT We present a spectral decomposition applied to nearly 10,000 earthquakes (ML 2.0–5.5) recorded along the East Anatolian Fault Zone (EAFZ) between January 2019 and February 2024, focusing on spatial and temporal variations in source parameters surrounding the 6 February 2023 seismic doublet. Results indicate that M0–fc scaling is consistent with approximate self-similarity, with nearly constant stress drop Δσ across the analyzed magnitude range. The observed linear relationship between M0 and radiated energy Er demonstrates the internal consistency of the estimated source parameters, although this relationship alone should not be interpreted as evidence of stable energy partitioning. Despite the structural segmentation of the EAFZ, Δσ remains statistically similar across the Nurdağı and Sürgü segments, indicating no clear segment-scale difference in Δσ within the analyzed dataset. To investigate spatial variations across fault segments, we examined normalized stress-drop and scaled-energy anomalies (Δσ* and E˜r*, respectively) as proxies for mechanical heterogeneity and scaled radiated energy. Δσ* exhibits relatively smooth spatial variations, whereas E˜r* shows more localized variability. These distinct spatial patterns may reflect differences in the sensitivity of the two parameters to stress conditions and local structural or mechanical heterogeneities. Our results indicate that small-magnitude earthquakes encode meaningful insights into fault segmentation and stress evolution, providing a multiscale perspective on rupture mechanics. These observations can enable detailed segment-level analyses and offer a transferable framework applicable to other tectonically complex fault systems, improving our understanding of earthquake physics and mechanical heterogeneity in strike-slip environments.