IDENTIFICATION OF THE SEISMOGENIC STRUCTURE IN THE AREA OF THE CHUPA (NORTH KARELIA) AND PARAMETERIZATION OF PALEOEARTHQUAKES IN THE KANDALAKSHA GRABEN REGION
Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences
Journal: Problems of Engineering Seismology
UDK: 550.34.063 + 551.242.1 + 551.248.2
Keywords: paleoearthquakes, seismic hazard, seismic dislocation, macroseismic field equation, peak velocities, seismic catalogs, nuclear facilities of Russia, Kandalaksha neotectonic graben, White Sea
Аnnotation: In the area of the village Chupa, three isolated ranges of paleoseismic dislocations marking the linear seismogenerating structure of NW strike, with a total length of more than 14 km, were revealed. Dislocations are young tectonic ditches and cracks, mainly NW strike, mass displacements of blocks, including against the slope, stone chaos and seismic landslides. Using the nature of the distribution of seismic dislocations for two areas, isoseismic maps were constructed that made it possible to estimate the magnitudes of paleoseismic events using the macroseismic technique. They amounted to 3.7 and 2.9, respectively, with the focal depth H ≤ 1 km under the assumption that each range corresponds to a local seismic source. The isolated character of the distribution of the identified ranges may be associated with one more severe paleoearthquake, the traces of which were preserved mainly in elevated areas of the relief (above 80 m). In the Early Holocene, these sites were separate islands, since the conditions for the formation of dislocations were limited in subaquatic spaces. For this option, M = 5.5 and H = 5 km were calculated; the age of the event is the Early Holocene. The results, taking into account data on the micrograben of the Velikaya Salma Strait, indicate the periodic occurrence of coastal and mainland faults, subparallel to the axis of the Kandalaksha graben, Holocene shallow-focus earthquakes of medium magnitude with epicentral intensity up to VIII points on the ESI-2007 scale. A catalog of the post-glacial paleoearthquakes of the Kandalaksha graben region has been compiled (5 events), which can be used to construct earthquake recurrence graphs. This will make it possible to substantially refine the seismic regime of this structure.