Seismogenic and rheological behaviours from time-dependent analysis of earthquake depth distribution in the Corinth Rift

Understanding earthquake depth distribution is critical for improving seismogenesis models. While the spatiotemporal pattern of earthquakes is well studied, transient changes in depth distribution remain poorly explored. In this study, we investigate how crustal rheological parameters influence the depth of earthquakes through time, focusing on the Corinth rift, a well-monitored region experiencing a high-level seismic activity in a homogeneous extensional stress field. To calculate crustal yield strength profiles, we compile geophysical and geological data, including heat flow, rock compositions and properties, Moho depth and strain rate. These estimates are then compared to a high-quality 11-year seismic catalogue of the region. An inversion approach is applied to identify crustal layers associated with persistent versus sporadic seismicity defined here instead of the conventional background versus clustered seismicity. Our time analysis reveals that the persistent seismicity nicely matches the theoretical brittle–ductile transition and allows us to confidently define the seismogenic thickness, while sporadic seismicity is clustered at depths associated with swarm occurrences. Both distributions are subject to kilometer-scale changes after magnitude 4.0 – 5.5 earthquakes, evidencing a relaxation process even after moderate magnitude events. We conclude that in specific case studies aiming to compare depth distribution and yield strength in the crust, the application of declustering methods may not be optimal for examining the potential rheological controls on earthquake depth distribution and their temporal variations. Instead, the analysis of persistent and sporadic seismicity defined in this study is more accurate and reliable than a declustering approach and offers new and valuable insights for this comparison. • The study aims to identify specific crustal layers based on persistent and sporadic seismic activity using a high-quality earthquake catalogue from the Corinth Gulf, Greece. • It introduces a novel approach to compare earthquake depth distributions with predicted yield strength envelopes, integrating depth uncertainties and rheological influences. • Persistent seismicity shows a quasi-Gaussian distribution centred around the brittle–ductile transition at approximately 10 km depth, indicating a strong correlation with crustal rheology. • Sporadic seismicity in depth deviates from this pattern, often occurring near material property discontinuities or/and close to the period of clustered seismicity, suggesting the possible influence of transient processes such as fluid.