Subsidence refers to the gradual sinking or settling of the ground, and it can occur for various reasons. From natural geological processes to human-induced activities, understanding the dynamics of subsidence is pivotal in preserving the integrity of structural built upon the Earth's surface.
Satellite remote sensing, particularly Interferometric Synthetic Aperture Radar (InSAR), allows us to monitor ground movement with unparalleled precision. Natural factors like soil compaction, geological shifts, or even human activities such as mining and groundwater extraction can contribute to subsidence. Identifying these factors is crucial for effective infrastructure management.
In terms of house foundations, some degree of subsidence is not uncommon. Natural settling of the soil beneath a structure is a normal process that often occurs shortly after construction. However, the key lies in distinguishing between typical settling and potentially problematic subsidence.
Asset owners should be vigilant if they observe:
Cracks in Walls or Foundation: Vertical cracks are often normal, but horizontal cracks or stair-step patterns can indicate significant movement.
Uneven Floors: Subsidence may lead to a sloping or uneven floor, signalling potential foundation issues.
Sticking Doors and Windows: Difficulty in opening or closing doors and windows ma be a result of subsidence-induced structural distortions.
Excessive Gaps Around Windows and Doors: Noticeable spaces between frames and walls could also indicate subsidence.
Advanced satellite-based monitoring techniques, including InSAR, allow for the detection of subtle ground movement, providing early warning and enabling proactive measures. InSAR starts with the acquisition of a baseline radar image of the Earth's surface. Over time, additional radar images of the same area are collected during subsequent satellite passes.
InSAR compares the phase difference between the baseline and repeat images. Changes in ground elevation cause a measurable phase shift in the radar waves. The results are displayed in colourful interferograms, where different colours represent varying degrees of ground movement. This allows us to create detailed deformation maps.
Timely intervention can significantly mitigate potential risks and safeguard investments. Reach out with a message to learn more about how satellite remote sensing is revolutionising infrastructure monitoring.
Interested to learn more? Geofem conducted an InSAR study of a residential area in south Cyprus to detect subsidence and uplift. Read the case study on our website.
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