Spatial Distribution and Seasonal Variability of Weak Seismicity in the Lena Delta (Laptev Sea Region)

This study examines the spatiotemporal distribution of microearthquakes in the Lena Delta based on local seismological monitoring data from 2016 to 2018. Results show that microearthquake sources are concentrated along the Olenek segment of the Lena–Taimyr boundary uplifts, which mark the Siberian Platform–Verkhoyansk fold-and-thrust belt boundary. The Olenek segment fault zone is traced by hypocenters up to the Moho at a depth of about 40 km. Microearthquakes are distributed unevenly in both space and time, forming clusters in different parts of the fault zone. Seasonal variability in the number of recorded weak earthquakes in the Lena Delta has been found. An extended regional catalog (2003–2022) was also used to analyze the seasonal seismicity modulation. The average number of events per day increases by approximately a factor of two during cold seasons. The results were compared with snow cover thickness, Lena River water level, GNSS and gravity data, and modeled Coulomb stresses. Seasonal increases in seismicity correlate with positive additional Coulomb stresses, given the dominance of normal faults in the Olenek segment.