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Monitoring of Subrosion Induced Mass Changes by Time-Lapse Gravity Surveys — Two Case Studies from Germany
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 25th European Meeting of Environmental and Engineering Geophysics, Sep 2019, Volume 2019, p.1 - 5
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Abstract
Subrosion is a geological process, which occurs worldwide. In extreme cases, it leads to the development of collapse sinkholes, which can pose a severe hazard, especially in urban areas. Hence, concepts are required to monitor the processes, which are related to subrosion. In two case studies we show the feasibility and the success of an approach that combines repeated levelling and time-lapse gravity surveys in the subrosion-prone urban areas of Bad Frankenhausen and Hamburg-Flottbek in Germany. Over several years of observation, in which quarterly measurement campaigns were carried out, we found both evidence of ongoing subsidence and mass redistribution in the subsurface. Especially for the known sinkhole areas, a decrease of gravity in the order of up to 2 µGal.a-1 suggests ongoing underground leaching and mass loss at both locations. In the context of data processing, we successfully applied a correction of the effects of varying soil water content on the adjusted gravity differences using the global model GLDAS Noah.