Scholarly record
THERMAL STRUCTURE AND SEISMOGENIC LAYER THICKNESS IN THE LENA DELTA REGION, RUSSIAN ARCTIC
Abstract
This study examines the thermal control of the lower boundary of seismicity in the Lena Delta, eastern Russian Arctic, using the depth distribution of local earthquakes recorded by temporary seismic networks in 2016–2018 together with temperature–depth curves derived from crustal heat-flow modeling. This study contributes by comparing the observed lower cutoff of local seismicity with modeled crustal temperatures, thereby adding a seismological constraint to previous seismic, thermal, and magnetic interpretations of the Lena Delta–Laptev Sea region. The local catalog indicates a well-defined seismogenic layer extending to about 30 km depth, with most hypocenters concentrated in the 10–20 km interval and only isolated events below 30 km. To interpret this depth limit, we consider a selected surface heat-flow range of 40–50 mW/m2. and the corresponding conductive geotherms for the study area. The resulting temperature curves indicate Curie isotherm depths of about 40–60 km, consistent with independent magnetic estimates, and predict temperatures of approximately 350–450°C at 30 km depth. This temperature interval corresponds to estimates of the brittle–ductile transition in continental crust inferred from laboratory studies and extrapolation to geological strain rates. In this framework, the lower boundary of seismicity in the Lena Delta is interpreted as primarily thermally controlled, marking the transition from dominantly brittle failure to increasingly ductile deformation at depth. The results support a coherent link between the observed hypocenter distribution and the crustal thermal regime, and provide a basis for future integrated analysis combining seismological, thermal, magnetic, and structural constraints in the Laptev Sea rift–Siberian Platform transition zone.
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