Fig. 4

L-function (\( \widehat{L}(d) \)) statistic for Harrat Rahat (HR) and Auckland Volcanic field (AVF) vent locations within various field boundaries. Thin lines represent upper and lower 95 % significance levels from 1000 random (Poisson) simulations. Thick black lines represent vent location based values. a HR All boundaries, b AVF convex hull, c AVF ellipse, d AVF rectangle, e AVF isocontour, f AVF anisocontour. See Fig. 2 for boundary illustrations, and text for L-function definition