Direct Evidence of a Slow‐Slip Transient Modulating the Spatiotemporal and Frequency‐Magnitude Earthquake Distribution: Insights From the Armutlu Peninsula, Northwestern Turkey

Earthquakes and slow‐slip events interact, however, detailed studies investigating their interplay are still limited. We generate the highest resolution microseismicity catalog to date for the northern Armutlu Peninsula in a ∼1‐year period to perform a detailed seismicity distribution analysis and correlate the results with a local, geodetically observed slow‐slip transient within the same period. Seismicity shows a transition of cluster‐type behavior from swarm‐like to burst‐like, accompanied by an increasing relative proportion of clustered (non‐Poissonian) relative to background (Poissonian) seismicity and gradually decreasing b‐value as the geodetically observed slow‐slip transient ends. The observed slow‐slip transient decay correlates with gradually increasing effective‐stress‐drop values. The observed correlation between the b‐value and geodetic transient highlights the influence of aseismic deformation on seismic deformation and the impact of slow‐slip transients on local seismic hazard. Plain Language Summary Seismic and aseismic slip on faults can change the stress state in the crust and affect the recurrence time of earthquakes. Observations of how earthquakes and aseismic fault slip influence each other are limited because of the dearth of synchronous high‐resolution seismological and geodetic data. Here we use high‐resolution earthquake data in the northern Armutlu Peninsula along the Marmara seismic gap of the North Anatolian Fault (Turkey) to correlate the earthquake distribution with a local slow‐slip transient that occurred in the same period. We find that the slow‐slip transient modulates the spatiotemporal and frequency‐magnitude evolution of earthquakes, which highlights the influence of slow fault creep on fast fault slip. Our study demonstrates the importance of considering slow‐slip transients for seismic hazard assessment. Key Points Seismicity analysis suggests that both external and internal forcing drive deformation in the Armutlu Peninsula Temporal correlation between a slow‐slip transient and seismic b‐value highlights interactions between aseismic and seismic deformation Slow‐slip transients modulate the frequency‐magnitude and spatiotemporal earthquake distribution