10 years of observations of earthquakes with Swarm satellites: results and open questions

The Swarm mission was successfully launched in November 2013 and it’s still in orbit and providing global continues measurements of Earth’s magnetic field and plasma parameters such as electron density (Ne).

In this presentation, several examples of research of pre-earthquake electromagnetic phenomena in the occasion of medium (M6+) or large (M7.5+) seismic events by using Swarm magnetic and electron density data will be shown. In most cases, an acceleration of the Y-East magnetic component of the anomalies has been detected one week to months in advance with respect to the incoming earthquake.

A recent study, based on the first 8 years of Swarm magnetic field and Ne data, shows statistical proof of the correlation between Swarm anomalies and incoming M5.5+ earthquakes. In particular, it was identified that the anticipation time of the anomalies increases with earthquake magnitude and in addition that earthquakes with an epicentre on the sea tend to show higher frequency (period = 2s-10s) anomalies than land earthquakes (period = 25s-50s). A possible influence of the focal mechanism was also investigated but the results are not statistically significant and further studies are necessary.

On 2^nd February 2018, China successfully launched its first satellite completely dedicated to studying earthquakes, called China Seismo-Electromagnetic Satellite (CSES-01) or ZhangHeng-01 (ZH-01). CSES-01 is equipped with several payloads to measure the magnetic and electric fields, ionospheric plasma properties, and two particle detectors with the purpose of understanding the possible ionospheric disturbances induced by earthquakes. This data from CSES-01 allowed us to better understand the ionospheric environment together with the Swarm mission and we will show how the join use of the two missions can highly help to characterize the ionosphere and possible pre-earthquake phenomena. For example, before the occurrence of Mw=7.5 Indonesia 2018, Mw=7.1 Ridgecrest 2019 or Mw=7.7 Jamaica 2020 earthquakes, an enhancement of the electron density has been detected and better described by multi-missions (Swarm and CSES) investigation.

Finally, a test of the quasi-real-time application of Swarm data to monitor earthquakes will be shown. In fact, a very quick investigation of the seismicity that occurred North of Rome, Italy (Guidonia city) on December 2022 and 1^st January 2023 (ML=3.3) has been conducted identifying an anomalous Swarm track which is compatible with seismic acceleration that occurred before these events, but further explanations are possible. This test, even if still a manual analysis shows the capability to implement in near future an automatic monitoring system which could get further advantage from the Swarm data produced by the proposed FAST processor by ESA, even though not strictly crucial.