A Harmonised Instrumental Earthquake Catalogue for Iceland and the
Northern Mid-Atlantic Ridge
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 on-line 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 additional 5640 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 chi-squared-regression, normally on the surface-wave magnitude,
but exceptionally on the body-wave magnitude. Magnitudes 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 for any 120
year timespan. The catalogue is named ICEL-NMAR and it is available
online on http://data.mendeley.com.