Magnetic field and electron density as ionospheric precursors of earthquakes from satellites

Abstract:

This presentation is based on the results we obtained during the last five years in the framework of the projects SAFE (SwArm For Earthquake study), funded by ESA, and LIMADOU, funded by ASI.

Our aim was to give an answer to the question whether there is a statistical correlation between medium-large (M5.5+) worldwide earthquakes and ionospheric electron density and magnetic field anomalies as measured by satellites, during quiet magnetic activity.

We applied a superposed epoch and space approach in the all-available space-time domain for six-year magnetic field and electron density data of the ESA Swarm satellite mission together with one-year electron density data of Chinese Seismo-Electromagnetic satellite (CSES).

We introduced two statistical quantities: d (how much the largest anomaly concentration is higher than a random distribution) and n (how many standard deviations the real data deviate from random distribution), in order to assess the statistical significance of our results, considered positive if d≥1.5 and n≥4.

By searching within the Dobrovolsky’s area (the theoretical extension of the earthquake preparation area) around each considered earthquake epicentre, we obtained significant and better results for the case of Swarm satellite Y magnetic field component.

The correlation with earthquakes seems slightly less effective for the electron density, but still better than a homogeneous random distribution of anomalies. However, the addition of CSES electron density data improves the results.

From our statistical analysis, we can affirm that the in-situ magnetic field and electron density at ionospheric height are statistically correlated with a large number of seismic events, and the coupling phenomenon can be originated by a lithospheric diffusion process, similar to slow earthquakes.