Earthquake in Gävle October 20th

2018-10-23

An earthquake with magnitude 3.0 occurred at 13:57 on October 20 in the northern parts of Gävle. The earthquake occurred relatively shallow, about 5 km deep, and was felt strongly in the immediate area as a distinct shake and/or as a loud rumble. So far we have received thirty reports to SNSN (Swedish National Seismological Network), all from Gävle or near Gävle. The earthquake have thus not been felt only locally. A small aftershock occurred at 10:36 on October 22. Despite it measuring only a magnitude of 0.4 it was perceived by at least one person. 

The event north of Gävle was the fourth earthquake in Sweden this year with magnitude of 3 or greater. The former ones occurred outside of Boden in February, with a magnitude of 3.1, outside of Skara on June 23 with magnitude 3.2 and south of Kalix on June 27 with magnitude 3.3. On the average, we have one or two earthquakes over magnitude 3 per year in Sweden, but it varies a bit up and down. 2013, 2011 and 2006 we had no event of that size, while in 2015 we had 4 of them.

There is no indication that the number of larger, or smaller, earthquakes in Sweden increases over time. Earthquakes are caused by movement of the tectonic plates movement the Earth’s surface, and this does not change much over several million years. The stresses that the plate movement induces in the Swedish crust does not trigger quakes evenly over shorter time periods, but rather, during some periods they occur a bit more frequent, during others less.

Most earthquakes in Sweden take place along the Norrland coast from Gävle to Haparanda, and in an area in the vicinity of Lake Vänern. The larger events also mainly occur in these areas. Sometimes however, such as the magnitude 4.1 earthquake south of Sveg 2014, Swedish earthquakes may occur in unexpected places. The likelihood, or the risk, that there soon will be another, more powerful, earthquake in Gävle is a very small. It is more likely that this will occur elsewhere.

See seismic data from Swedish earthquake at SNSN.

text: Björn Lund seismologist

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