Variation of Fault Creep Along the Overdue Istanbul-Marmara Seismic Gap in NW Türkiye

Abstract

Strain energy from tectonic loading can be partly released through aseismic creep. Earthquake repeaters, repeatedly activated brittle fault patches surrounded by creep, indicate steady-state creep that affects the amount of seismic energy available for the next large earthquake along a plate contact. The offshore Main Marmara Fault (MMF) of the North Anatolian Fault Zone represents a seismic gap capable of generating a M > 7 earthquake in direct vicinity to the mega-city Istanbul. Based on a newly compiled seismicity catalog, we identify repeating earthquakes to resolve the spatial creep variability along the MMF during a 15-year period. We observe a maximum of seismic repeaters indicating creep along the central and western MMF segments tapering off toward the locked onshore Ganos fault in the west, and the locked offshore Princes Islands segment immediately south of Istanbul in the east. This indicates a high degree of spatial creep variability along the Istanbul-Marmara seismic gap.