Abstract
AN Earth tilt meter at Wellington, New Zealand (lat 41°14′S, long 174°47′E) has been operating since 1972 in old underground tunnels which are about 15 m below the surface. Installation transients, at first of the order of several microadians per year, have decayed slowly and are now about 0.3 µrad yr−1. As is well known1,2 rainfall and evaporation, in all but very deep sites, usually completely obscure any obvious relationship with tectonic events. Wood and King3 have made one unsuccessful attempt to deal with this problem but the largest earthquake occurring was only of magnitude 5.2. A new approach, described here, has yielded significant correlations of tilt with two, and possibly three, earthquakes of magnitudes 5 to 6.2. The precursor times are in fair agreement with Rikitake's4 equation.
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