Fig. 7From: Estimation of phase velocity using array observation of microtremors with arbitrary shapeHistogram of phase velocities determined by PSO for various shapes of triangular arrays. The equilateral triangle (R4-R6-R7) shows the smallest variance and the most-flattened triangle (R1-R6-R7) shows the largest variance. The legend is the same as that in Fig. 6Back to article page