Sensitivity of GGP superconducting gravimeters in detecting pre-seismic gravity anomalies

• SGs can detect both the seismic wave signals and low-frequency pre-seismic gravity anomalies. • SGs in Europe have a high sensitivity in detecting pre-seismic gravity anomalies for the local geological structure. • Low-frequency pre-seismic gravity anomalies occurred during hours or even days before a huge earthquake. Pre-seismic anomalies are attracting more and more attention in seismology. However, this issue has not been thoroughly researched. Superconducting gravimeters have high observation accuracy (10 −9 ∼ 10 −10 m/s 2 ) and can be used to study low-frequency pre-seismic gravity anomalies (the contribution of the internal mass redistribution). We extracted the pre-seismic gravity anomalies of 2010 Maule earthquake ( M w 8.8) and 2011 Tohoku-Oki earthquake ( M w 9.0) from the data of Global Geodynamics Project network. Through power spectrum density analysis and band-pass filtering of the gravity data, we found pre-seismic gravity anomalies continued for 126 h before the Maule earthquake, and the maximum reached 6 μgal. For the Tohoku-Oki earthquake, the pre-seismic anomalies continued for 89 h before the main shock, and the maximum anomaly was 26.5 μgal. Furthermore, all the SGs in Europe had detected clear pre-seismic gravity changes more than 3 μgal, but some other stations not. This discrepancy may be due to differences in local geological structure and sensitivity, despite the gravimeters having the same observation accuracy. From the results of great earthquakes, we found the gravimeters in Europe have a high sensitivity in detecting pre-seismic gravity anomalies.