Skellefteå earthquake: did the earth move for you?

On Saturday, a 2.9 magnitude earthquake rattled the Skellefteå region. However, the Android Earthquake Alert system reported a much higher magnitude of 4.3.

Skellefteå2024-05-11 17:14

UPDATE: 17:10: 

Peter Schmidt, a seismologist at the Swedish National Seismic Network (Svenska Nationella Seismiska Nätet) expressed skepticism towards the higher figure. Their own measurements consistently indicated a 2.9 magnitude quake.

– A magnitude 4 earthquake is exceptionally rare in Sweden, occurring perhaps once per decade, explained Schmidt.

– We've only ever recorded one earthquake larger, at a magnitude of 4.5.

The source of the Android Earthquake Alert system's higher magnitude is unclear. Schmidt suggests data limitations might be a factor.

– Foreign services may struggle with accurate location and magnitude readings when data availability is limited, he noted.

– Factors like distance and ground composition can also influence how strongly an earthquake is felt.

Adding to the complexity, different earthquake measurement methods exist. As Schmidt emphasizes:

– Using the wrong measurement method or magnitude scale can lead to misleading results.

Therefore, is the 4.3 magnitude reported by the Android Earthquake Alert system inaccurate?

– Yes, it's bullshit.

UPDATE: 15:20

– This is a significant earthquake for Sweden, Björn Lund of the Swedish National Seismic Network (Svenska Nationella Seismiska Nätet) said. 

– We typically only experience earthquakes of this magnitude about once a year.

Norran readers described the effects of the small earthquake:

  • Burträsk: "It was a big rumble and shook the windows and rattled the whole house."
  • Bodbysund: "I was making a cup of tea and the cup wobbled and fell off the kitchen counter."
  • Bjurträsk: "It was like a large excavator driving by the house."

UPDATE: 14:55:

The earthquake's epicentre was near Bureå and happened at 10.51 on Saturday.

Norrland earthquakes

The most seismic activity occurs along the Norrland coast and Norrbotten.

These northern earthquakes often originate from post-glacial faults, remnants of powerful earthquakes (up to magnitude 8) during the last ice age.

The Burträsk fault, south of Skellefteå, is Sweden's most active seismic zone, experiencing several minor quakes annually.

Most Swedish earthquakes are small (under magnitude 2) and go unnoticed.

Approximately ten earthquakes reach magnitudes between 2 and 3 each year.

Earthquakes exceeding magnitude 3 occur roughly once a year. 

(Source: Uppsala University)