Abstract
Abstract. A comprehensive catalogue of historical earthquakes, with accurate epicentres and harmonised magnitudes is a crucial resource for seismic hazard mapping. Here we update and combine catalogues from several sources to compile a catalogue of earthquakes in and near Iceland, in the years 1900–2019. In particular the epicentres are based on local information, whereas the magnitudes are based on teleseismic observations, primarily from international online catalogues. The most reliable epicentre information comes from the catalogue of the Icelandic Meteorological Office, but this is complemented with information from several technical reports, scientific publications, and newspaper articles. The catalogue contains 1281 moment magnitude (Mw) ≥4 events, and the estimated completeness magnitude is Mw 5.5 in the first years, going down to Mw 4.5 for recent years. The largest magnitude is Mw 7.0. Such merging of local data and teleseismic catalogues has not been done before for Icelandic earthquakes, and the result is an earthquake map with much more accurate locations than earlier maps. The catalogue also lists 5640 additional earthquakes on the Mid-Atlantic Ridge, north of 43∘, with both epicentres and magnitudes determined teleseismically. When moment magnitudes are not available, proxy Mw values are computed using χ2 regression, normally on the surface-wave magnitude but exceptionally on the body-wave magnitude. Magnitudes of Mw≥4.5 have associated uncertainty estimates. The actual combined seismic moment released in the Icelandic earthquakes is found to be consistent with the moment estimated using a simple plate motion model, indicating that the seismic activity of the catalogue period might be typical of any 120-year time span. The catalogue is named ICEL-NMAR, and it is available online at http://data.mendeley.com (last access: 19 July 2021).
Highlights
Seismic hazard in Iceland is the highest in northern Europe and is comparable to that in southern Europe
The Icelandic Meteorological Office (IMO) in Reykjavík has been responsible for monitoring earthquakes in Iceland since shortly after its foundation in 1920 when the Mainka seismograph mentioned in the introduction was reinstalled there in 1925
To obtain some indication of the uncertainty in event locations in the international catalogues we have looked at the variability between different catalogues, which can be considered a proxy for the precision of the locations
Summary
Selection criteria for inclusion are that the earthquake was instrumentally recorded by seismic centres outside Iceland and assigned a surfacewave, body-wave, or moment magnitude (Ms, mb, or Mw) and that it is listed either in the International Seismological Centre (ISC) Bulletin event catalogue (ISC, 2020) or in the catalogue of Ambraseys and Sigbjörnsson (2000), which lists and reappraises internationally recorded earthquakes in the region 62–68◦ N, 12–26◦ W (Fig. 1), in the period 1896– 1995 This catalogue will be referred to as the AMB-SIG catalogue. Grünthal and Wahlström (2003) compiled a historical catalogue of earthquakes in central and northern Europe up to 1993, with magnitudes and locations in Iceland taken from a data file obtained from the IMO. Panzera et al (2016) compiled a catalogue of earthquakes in South Iceland 1991–2013 It reports locations and magnitudes from IMO’s database, cleaned and corrected, as well as proxy Mw values based on regression of GCMT magnitudes on the IMO data, like the CENEC and EMEC catalogues. The final section contains details of the catalogue, including how to retrieve it, as well as a discussion of completeness magnitude, comparison with ISC-GEM, and comparison with the total moment of a simple plate motion model
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