function [sigma_direction] = StrDir(sigma_1_alpha,sigma_1_beta,sigma_2_alpha,sigma_2_beta)
sigma_1_alpha =sigma_1_alpha*3.1415926/180;
sigma_1_beta = sigma_1_beta*3.1415926/180 ;
sigma_2_alpha =sigma_2_alpha *3.1415926/180;
sigma_2_beta = sigma_2_beta*3.1415926/180 ;
sigma_1_direction=[cos(sigma_1_beta)*sin(sigma_1_alpha),cos(sigma_1_beta)*cos(sigma_1_alpha),sin(sigma_1_beta)];
sigma_2_direction=[cos(sigma_2_beta)*sin(sigma_2_alpha),cos(sigma_2_beta)*cos(sigma_2_alpha),sin(sigma_2_beta)];
sigma_3_direction= cross(sigma_1_direction,sigma_2_direction);
sigma_direction=[sigma_1_direction;sigma_2_direction;sigma_3_direction]%LT是主应力坐标系在大地坐标系下的特征矩阵
end
