Revealing Sinkholes of Karst-Suffosion Origin in Moscow

Nearly thirty ground collapses were registered in the northwestern district of Moscow in 1960–1970s. These catastrophic phenomena were triggered by the intense technogenic intake of groundwater from the Carboniferous aquifer, which caused the downward migration of Quaternary sand to the underlying karstified limestone of Carboniferous age. Since those years, the northwestern district of Moscow has been considered to be particularly prone to karst-suffosion phenomena. IEG RAS has collected a substantial database on sinkholes of different origin that occurred in Moscow since the early 20th century. Using this database, we attempted to identify sinkholes of karst-suffosion origin in other districts of Moscow. Our research procedure included the following stages: analysis of engineering geological conditions around the sinkholes using the borehole data obtained in different years and stored in the IEG RAS database; calculation of possible sinkhole diameter using the original computational models; comparison of calculated to actual sinkhole diameters. This approach permitted us to identify the collapses in the historical center of Moscow as of karst-suffosion origin. This unexpected conclusion contradicts with the former boundaries of regions showing the different degree of karst-suffosion hazard outlined on engineering geological maps earlier.