DOI: 10.23729/201d4846-a5da-4338-944c-2ae53aca9e0c
title: A joint Fennoscandian earthquake catalogue FENCAT, subcatalogue FENCAT17_Seismic_risk

description: A joint Fennoscandian earthquake catalogue (FENCAT; updated after Ahjos and Uski, 1992) is an open-access catalogue providing all available non-instrumental and instrumental earthquake records in Fennoscandia and the adjacent offshore areas and it is compiled by Institute of Seismology, University of Helsinki, Finland. The catalogue covers earthquakes from 1467 to near present day. The original catalogue has been updated several times for different purposes.

The published versions are called FENCAT14, FENCAT17, FENCATxx, the number post text indicating the last year whose data are included in the dataset. FENCAT has been updated previously at the Institute of Seismology’s web sites and older versions have previously been called FENCAT catalogues without versioning.

In the current version FENCAT14, Data in the catalogue covers the area of 54°-75°N and 0°-45°E including Finland, Estonia, Latvia, Sweden, Norway, Denmark, and adjacent offshore areas, as well as parts of northern Lithuania and northwestern Russia.

Because of the different degree of accuracy and homogeneity of the parameter data, the events were divided into historical (1375–1970) and instrumental (1971–) datasets. The source parameters for historical events are mainly macroseismic and for the instrumental data they are obtained by various iterative location procedures. The catalogue has been continuously updated with data from earthquake bulletins by the Institute of Seismology at the University of Helsinki (HEL), by the Department of Earth Science at the University of Bergen (BER), by the Department of Earth Sciences at the University of Uppsala (UPP), and since 2006 by the Geological Survey of Estonia (EST).

The catalogue provides information about the time, location, depth, magnitudes, intensity and origin of data for the events. Since the beginning of year 2000, the catalogue lists the number of seismic stations included in the calculation of the location, the distance to the closest station, and the azimuthal gap of the stations, needed in the quality estimates of the location parameters. From 2009 onwards, all events that have less than four stations in their location solution are omitted from the catalogue. All versions of the catalogues published after FENCAT17 include information on the homogenized magnitudes of the earthquakes. The process of homogenization of the magnitudes is described in detail in an article under preparation by Oinonen et. al. (information will be updated later).

The catalogue has been cleaned from explosions, induced and frost related events to the extent possible. In the old versions of the catalogue, up to FENCAT14, some events of questionable tectonic origin have been included with a special comment. From FENCAT17 onwards, those events have been removed. The removed data can, however, be requested from the Institute of Seismology, University of Helsinki.

FENCAT14 is a sub catalogue of FENCAT that has been available through the website of the Institute of Seismology, University of Helsinki https://www.seismo.helsinki.fi/bulletin/list/catalog/Scandia_updated.html 20.5.2024. Later that web site will contain the newest version of the catalog and links to the older versions.

The FENCAT17 is a version of FENCAT made specifically for the Research Council of Finland’s project 337913 “Seismic Risk - Mitigation of induced seismic risk in urban environments” for calculating the seismic hazard for Finland and adjacent areas. Opening of the Nordic part of the data set has been partly funded through NordForsk grant 97318: “Nordic EPOS - A FAIR Nordic EPOS Data Hub”. The catalogue has been updated from the previous FENCAT14 for example by calculating homogenized magnitudes for the earthquakes.

The subcatalogue FENCAT17_Seismic_Risk is a subcatalogue of FENCAT17 where the dependent events (i.e., fore- and aftershocks) have been removed. Fore- and aftershocks were searched using a windowing algorithm that followed the technique presented by Gardner and Knopoff (1974). Tis purpose was to also identify swarm events and include then in a specific main shock cluster. The distance and time limits between event and its possible fore- and aftershocks were set 10 km and 15 days for M≥1 events and 5 km and 7 days for microearthquakes. Finally, the clusters were manually checked to identify erroneous associations and rebuild affected clusters.

References:

T. Ahjos and M. Uski, 1992: Earthquakes in northern Europe in 1375-1989. Tectonophysics, 207, 1-23.

J.K. Gardner and L. Knopoff, 1974. Is the sequence of earthquakes in Southern California, with aftershocks removed, Poissonian? Bull. Seism. Soc. Am. 64, 1363-1367.