The topography of the solid Earth is constantly changing due to continental drift and more localised magmatic, climatic and anthropogenic processes. The results are earthquakes, volcanic eruptions, landslides or subsidence. Earthquakes are amongst the most fatal and expensive geo-risks; according to the reinsurance company ‘Munich Re’. In urban areas like Tokyo, a single, strong future earthquake could cause damage of 1000 to 2000 billion US$. The redoubtable Tokai-Quake is still expected; however the Tohoku-Quake further north in 2012 caused a damage of around 360 billion euro and is so far today the most expensive natural disaster in history. Beside earthquakes, also volcano eruptions and landslides cause massive damage and are not local phenomena only, as it could be observed in 2010 with the eruption of the Ejyafjallajökull in Iceland, that disturbed the aerospace over several weeks and causing around 4.7 billion euro costs.
The mission scenarios of previous satellites didn’t allow a systematic monitoring of risk areas. For example, between 2010 and 2012 the TanDEM-X mission took a very accurate snapshot of the Earth 3-D topography, however, this mission is not suitable for a regular, global long-term survey, due to the very short wavelength and the small coverage. Tandem-L will facilitate this for the first time.
The Tandem-L mission operating in the Deformation Mode will constantly monitor the global topographic changes with accuracies from centimetres down to millimetres. Thanks to these large-area deformation measurements (i.e. not just selected point measurements with permanent GPS stations), geophysical models can be developed much more precisely, hence increasing the knowledge of the underlying processes in the Earth’s crust.