Re-evaluation of b-value distributions in the Fethiye–Burdur Fault Zone (FBFZ), in south-western Turkey, for the period 2012-2024

The Fethiye–Burdur Fault Zone (FBFZ) in south-western Turkey represents a seismically active region where complex interactions between tectonic stress and geothermal activity are associated with earthquake occurrence patterns, the understanding of which is improved by evolving seismic monitoring capabilities. This study analyses a declustered earthquake catalogue (2012–2024) to investigate spatiotemporal variations in completeness magnitude and b-values, providing insights into regional seismic hazard. The frequency-magnitude distribution yields a regional b-value of 0.82 ± 0.01, with temporal fluctuations showing precursory declines before significant earthquakes (e.g. the 2019 M 5.7 event), consistent with the interpretation of b-values as stress-sensitive parameters. Spatially, b-values increase from NE to SW, correlating with geothermal activity in the SW, where elevated values align with global geothermal/volcanic systems. Conversely, the Tefenni segment's persistently low b-value (~0.58) and historical quiescence may indicate that this is a mechanically important segment. These findings highlight the heterogeneous stress regime along the FBFZ, where geothermal fluids may modulate seismicity in the south-western sector while locked segments such as Tefenni accumulate strain under ongoing tectonic loading.