Mineral resources office warns of sinkholes in Mae Hong Son

Six sinkholes were found on an agricultural plot in the Ban Mae Surin village between March 29-30, following the earthquake, with diameters ranging from two to 30 metres. The holes have been showing continuous subsidence and expansion.

The office reported that the sinkholes are clustered in a north-south direction along the active Mae Hong Son fault line.

The soil in the sinkholes consists of clay mixed with sand, which results in the water pooling in the sinkholes appearing murky, the office explained. The mouths of the sinkholes are conical in shape, indicating that the soil layers have collapsed vertically into a void below.

The sinkholes were caused by seismic vibrations from the earthquake, which led to rapid fluctuations in groundwater levels. This caused changes in pressure within the underground voids, resulting in the erosion of soil layers.

As the voids expanded and the roof of the void thinned, it could no longer support the weight of the soil above, leading to a collapse and the formation of sinkholes.

The office has advised locals to:

1. Surround the area with fencing, preventing people and pets from approaching, and install warning signs.
2. Monitor and track ground subsidence, as cracks are still visible in the area.
3. Refrain from applying fertiliser or pesticides in the area until the sinkholes are filled in to prevent contamination of groundwater.
4. Conduct a geophysical survey of the underground, with the results being used to determine ways to mitigate the impact.
5. Explain the causes and prevention measures to the relevant agencies and the local community.