| Abstrakt: |
Contemporary correspondence testifying to a sequence of low-magnitude earthquakes in present Southeastern Finland in 1751-1752 is investigated. The preserved original correspondence, 11 pages in total, is lavish by local standards: Earthquake entries from the 1700s in the national database are typically attested to by a solitary source, such as a concise newspaper account. Over 30 distinct events between the end of October and December 1751 (Julian calendar) can be discerned. The assignment of macroseismic intensity to the earthquakes is hampered by loud acoustic effects that accompany and/or constitute the observations. Maximum intensities are assessed at IV-V (European Macroseismic Scale 1998), and maximum macroseismic magnitudes in the range of MM2.0-2.4. The events have probably been shallow and were observed at short epicentral distances. The data from 1751 provide an analog to modern macroseismic observations from geothermal stimulation experiments that have acted as a spur for considering seismic risk from low-magnitude earthquakes whose consequences have seldom previously been a matter for concern. [ABSTRACT FROM AUTHOR] |
