Macroseismology as a Component of Seismicity Assessments in an Intraplate Region : Studies of Northern Europe with Emphasis on Finland

• Main Author: Mäntyniemi, Päivi
• Other Authors: Labak, Peter, Institute of Seismology, University of Helsinki, University of Helsinki, Faculty of Science, Department of Physical Sciences, Division of Atmospheric Sciences and Geophysics, Helsingin yliopisto, matemaattis-luonnontieteellinen tiedekunta, fysikaalisten tieteiden laitos, Helsingfors universitet, matematisk-naturvetenskapliga fakulteten, institutionen för fysikaliska vetenskaper, Vesala, Timo
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Helsingin yliopisto 2010
• Subjects: geofysiikka; Haparanda; Tornio; Piteå
• Online Access: http://hdl.handle.net/10138/23156

This work focuses on the role of macroseismology in the assessment of seismicity and probabilistic seismic hazard in Northern Europe. The main type of data under consideration is a set of macroseismic observations available for a given earthquake. The macroseismic questionnaires used to collect earthquake observations from local residents since the late 1800s constitute a special part of the seismological heritage in the region. Information of the earthquakes felt on the coasts of the Gulf of Bothnia between 31 March and 2 April 1883 and on 28 July 1888 was retrieved from the contemporary Finnish and Swedish newspapers, while the earthquake of 4 November 1898 GMT is an example of an early systematic macroseismic survey in the region. A data set of more than 1200 macroseismic questionnaires is available for the earthquake in Central Finland on 16 November 1931. Basic macroseismic investigations including preparation of new intensity data point (IDP) maps were conducted for these earthquakes. Previously disregarded usable observations were found in the press. The improved collection of IDPs of the 1888 earthquake shows that this event was a rare occurrence in the area. In contrast to earlier notions it was felt on both sides of the Gulf of Bothnia. The data on the earthquake of 4 November 1898 GMT were augmented with historical background information discovered in various archives and libraries. This earthquake was of some concern to the authorities, because extra fire inspections were conducted in three towns at least, i.e. Tornio, Haparanda and Piteå, located in the centre of the area of perceptibility. This event posed the indirect hazard of fire, although its magnitude around 4.6 was minor on the global scale. The distribution of slightly damaging intensities was larger than previously outlined. This may have resulted from the amplification of the ground shaking in the soft soil of the coast and river valleys where most of the population was found. The large data set of the 1931 earthquake provided an ...