Index

Formula

Explanation and significance of formula

Coefficient of variation

CV = 100 % × i = 1 n ( S i S ¯ ) 2 n S ¯ (1)

CV represents the coefficient of variation of Tyson polygon area in characteristic town; S i denotes the area of the ith Tyson polygon; n is the number of Tyson polygon; i = 1 n ( S i S ¯ ) 2 n is standard deviation; S ¯ is average value; 33% < CV < 64% is random distribution; CV ≥ 64% is clustered distribution; CV ≤ 33% is uniform distribution

Nuclear density estimation

f ( x ) = 1 T h i = 1 T k ( x X i h ) (2)

f ( x ) is the nuclear density estimates; k ( x X i h ) is a kernel function; T denotes the number of characteristic towns; h > 0 is bandwidth; ( x X i ) is the distance from the valuation point x to the event point X i . The larger the nuclear density estimation, the more dense the points, the higher the probability of regional events.