Coda-derived source properties estimated using local earthquakes in the Sea of Marmara, Türkiye

Abstract. Accurate estimates of the moment magnitude of earthquakes that physically measures the earthquake source energy are crucial for improving our understanding of seismic hazards in regions prone to tectonic activity. To address this need, a method involving coda wave modelling was employed to estimate the moment magnitudes of earthquakes in the Sea of Marmara. This approach enabled to model the source displacement spectrum of 303 local earthquakes recorded at 49 seismic stations between 2018 and 2020 in this region. The coda wave traces of individual events were inverted across twelve frequency ranges between 0.3 and 16 Hz. The resultant coda-derived moment magnitudes were found to be in good accordance with the standard local magnitude estimates. However, the notable move-out between local magnitude and coda-derived moment magnitude estimates for smaller earthquakes less than a magnitude of 3.5 likely occurs due to potential biases arising from incorrect assumptions for anelastic attenuation and the finite sampling intervals of seismic recordings. Scaling relations between the total radiated energy and seismic moment imply a nonself-similar behaviour for the earthquakes in the Sea of Marmara. Our findings suggest that larger earthquakes in the Sea of Marmara exhibit distinct rupture dynamics compared to smaller ones, resulting in a more efficient release of seismic energy. In conclusion, here we introduce an empirical relationship devised from the scatter between local magnitude and coda-derived moment magnitude estimates.