The evidence against blasting at Södermalm: Seismological waves

The evidence against blasting at Sodermalm Seismological waves

Published: Less than 10 min ago

The 17-year-old’s bomb produced results on Uppsala University’s seismological instruments.

It became part of the evidence against him.

– It is not often that you have such a clear time marker, says Alexander Nilsson, councilor at Solna district court.

On September 24, 2022, a bomb exploded outside an apartment building on Södermalm.

Today, a 17-year-old boy was sentenced to one year and eight months in closed youth care for gross public damage. A 46-year-old taxi driver is sentenced for aggravated protection of a criminal because he drove the 17-year-old to and from the crime scene.

The blast was strong enough to kill, according to the Total Defense Research Institute, which concluded that the explosive charge consisted of between 3-5 kilos of dynamite.

But it wasn’t just the 30 or so evacuees who felt the impact.

A seismological measuring station at Vaxholm, 11 kilometers from the crime scene, registered the detonation on its extremely sensitive instruments that are prone to sensing earthquakes.

full screen Photo: Aftonbladet
full screen Photo: Aftonbladet

Be on the spot

It helped the prosecution to prove the exact time of the crime.

– Often when trying to set a time for an event, it is usually a call to SOS that may be the first safe time marker for an event. But here we have an exact time, says Alexander Nilsson, councilor at Solna district court.

The 17-year-old has admitted that he was at the scene, but his defense has highlighted that there could have been an alternative perpetrator. The exact time therefore becomes very relevant, as it is matched with a witness statement.

And with the help of the seismological data, the detonation has been able to be determined with only tenths of a margin.

– There have been some, among many other tasks, that have been important, says Alexander Nilsson.

The question comes more often

It is becoming increasingly common that the seismological institutes receive requests for their instruments known by bombings.

– Yes, it is interesting that you can use our data for something that it was not intended for, of course, says Björn Lund, who wrote the submission to the police that the prosecutor has relied on.

But unfortunately, it is not common that they can actually help. The measuring stations are often quite far away from the explosions – and the explosions take place on top of the ground. Even though there is a very large explosion that causes great destruction, it may not be noticeable on the instruments, because the vibrations do not reach down to the mountain.

– But in this particular case, we have a measuring station only 11 kilometers from Södermalm, and then we were able to identify waves that have to do with the explosions.

Last fall, his unit identified the Nordstream explosions.

– We are of course happy to help as much and as often as they want, says Björn Lund.