Survey on mud flow occurrence Šnon- occurrence judgement methods for volcanic regions

Sakurai W., Watari M., Nakazato I., Yamada T., Kikuchi H.

In volcanic regions, the occurrence of mud flows is influenced by conditions such as the quantity of volcanic ash deposition and its permeability. It is, therefore, presumed that when predicting the occurrence of mud flows, it will be possible to predict mud flow occurrence locations more precisely by using a mudflow occurrence - non-occurrence judgement method that reflects the state of volcanic ash deposition. So in addition to rainfall and topography, the mean thickness of volcanic ash deposits in the drainage basin was added to causes of mud flows, and multiple discriminant analysis and the neural network method were used to judge whether mudflows would or would not occur at Usuzan Volcano from its eruption of 1977 until 1981. As a result, a comparison of the judgements of the occurrence or non-occurrence of mudflows made before and after the first use of the mean thickness of volcanic ash deposition in the drainage basin as a causal factor has shown that the precision of such judgements by multiple discriminant analysis has improved; to a maximum of about 20% for occurrence and about 30% for non-occurrence.

2002/1 135-143