Solid Earth Overview
Space surveillance shows that the ground beneath our feet is not quite as solid as it seems. Earth's crust is continuously in motion, driven by gradual geological shifting that occasionally speeds up, in the potentially destructive form of earthquakes or volcanoes.
Looking down on Earth from hundreds of kilometres away in space has proven a surprisingly accurate way of detecting slight sub-centimetre-scale motion across tens of kilometres of terrain that might otherwise go unobserved.
Combining together multiple radar images of the same location through a technique called Synthetic Aperture Radar Interferometry highlights tiny land changes that have occurred between acquisitions. It's a technique that has been used to survey the seismically active belts that make up around 15% of global land area, in order to search out previously unknown fault lines.
InSAR has also been used to survey supposedly extinct volcanoes – slight signs of ‘breathing' indicate continued active status.
ESA's GOCE mission peered deeper into solid Earth until 2013 by measuring slight variations in Earth's gravity field to detect hidden features, such as subsurface water aquifers, deep ocean currents, volcanic magma plumes and polar ice sheets.
Solid Earth News
It was five years ago this month that ESA's GOCE gravity-mapping satellite finally gave way to gravity, but its results are still yielding buried treasure – giving a new view of the remnants of lost continents hidden deep under the ice sheet of Antarctica.
A magnitude 6.6 earthquake occurred in the Aegean Sea on 20 July 2017, affecting the Greek island of Kos and Bodrum in south-west Turkey. Images from the Copernicus Sentinel-1 mission were used to map the ground deformation, providing valuable data for analysis.
Specific Topics on Solid Earth
The use of satellite data in the detailed study and precise measurement of the Earth's geoid in order to improve our understanding both of the Earth's interior, and dynamic topography of the world's oceans.
Observations show that geomagnetic field lines follow closely the atmospheric circulation patterns and that geomagnetic field variations are precursors to climate change. Therefore close monitoring of the local and global geomagnetic field variations by satellite systems will assist prediction of hurricane tracks, intensification and also long-term weather trends.
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