Relationships of porosity, density, crack area, and compressional wave velocity for Rotokawa Andesite. (A) Connected porosity versus dry bulk density for Rotokawa Andesite calculated using the dual weight method of (Ulusay and Hudson ). (B) Crack area per unit volume (Sv) plotted versus connected porosity for samples representing the range of values measured within the measured dataset. (C) Connected porosity (vol%) using the dual weight method versus axial compressional wave velocity (Vp) as measured under a stress of 10 MPa which was determined to be below the crack closure stress (see text for further detail). (D) Crack area per unit volume (Sv) versus compressional wave velocity (Vp).