The earthquake at Kamchatka July 30, 2025 23:24:51 UTC, has generated significant Free Oscillations.

We list a few links where you can see the response of the Superconducting Gravimeter OSG_054 at Onsala Space Obeservatory.

Waveforms

Diagrams, acceleration in nm/s2, can be seen here: SCG-monitor
In the fields to fill out you can easily advance at full hours by entering date 2025-07-30, hour 00, and dt 60 and then clicking on  Submit query.
The ringing in the light-blue curve, dP/dt in hPa/s, at midnight is an artefact of Fourier interpolation. It recurs systematically. Awaiting the re-hooking of the OSG accompanying barometer soon to happen, the stand-in instrument that samples at a lower rate is still in use, so we interpolate its record. Thanks to the opportunity of the mega-seismic event the problem has been noted---a little late though.

Spectrograms


The spectrogram is renewed daily and will be until the 0S0 mode has waned below the noise level. It's the balloon mode which involves very little energy dissipation as sheer strain in the mantle is limited to occur at boundaries like crust-ocean.  

The event on day 43 (Sep. 9) was caused by a coldhead change.

Periodograms showing the amplitude spectrum up to 6 mHz and 3 mHz with periodograms added for four-day stretches the week after the earthquake.
Another one shows the spectrum for the period from July 31 to August 3 together with the situation in the week before the earthquake.