Can InSAR contribute with new insights into possible earthquake precursors?
This controversial issue is under analysis in a paper co-authored by Fabrizio Novali, R&D manager of TRE ALTAMIRA, now published in Scientific Reports – Nature.
Seismologists at INGV (Istituto Nazionale di Geofisica e Vulcanologica) have analysed ground displacements before and after the L’Aquila earthquake, which struck the central part of Italy in April 2009 and caused about 300 causalities. INGV used, among others, TRE ALTAMIRA’s SqueeSAR™ data, with the aim of identifying any seismic precursory signals associated with surface deformation.
For sure, data confirmed that the area affected by the earthquake was not stable before 2009 and the local dynamics were severely changed after the seismic event.
From the article Abstract: “…satellite data have showed that up to 15 mm of subsidence occurred beginning three years before the main shock. This deformation occurred within two Quaternary basins that are located close to the epicentral area and are filled with sediments hosting multi-layer aquifers. After the earthquake, the same basins experienced up to 12 mm of uplift over approximately nine months. Before the earthquake, the rocks at depth dilated, and fractures opened. Consequently, fluids migrated into the dilated volume, thereby lowering the groundwater table in the carbonate hydrostructure and in the hydrologically connected multi-layer aquifers within the basins. This process caused the elastic consolidation of the fine-grained sediments within the basins, resulting in the detected subsidence. After the earthquake, the fractures closed, and the deep fluids were squeezed out. The pre-seismic ground displacements were then recovered because the groundwater table rose and natural recharge of the shallow multi-layer aquifers occurred, which caused the observed uplift”.
This paper is not “the answer” to whether or not InSAR data can play a key role in earthquake prediction, but it is new evidence of the fact that areas affected by seismic events sometimes exhibit quite peculiar deformation signals, which can bring important insights for risk assessment.
To read the full paper published in Scientific Reports – Nature, please click here.