Gravity and crustal thickness in New Zealand

Gravity observations in New Zealand yield a mean Bouguer anomaly of +8 mgal at sea level, ‐ 26 mgal at the mean elevation of the land surface, and a gradient with height of ‐78 mgal/km. According to formulae derived by Worzel and Shurbet, Andreev, Demenickaja, and Woollard, relating crustal thickness to Bouguer anomalies, this would indicate a “normal” thickness of the crust at sea level of the order of 29 to 34 km, and an average thickness of 32 to 39 km, which is consistent with the evidence provided by dispersive earthquake waves.