Tiltmeter Results from Adak

Abstract

We have been measuring tilt on Adak since the summer of 1975 in an attempt to establish a correlation between the occurrence of earthquakes and a supposed precursory tilting of the ground. The problem is twofold: firstly, to establish the nature and size of the assumed precursory tilts, and secondly, to devise a way of installing and operating a network of tiltmeters capable of observing these tilts under the constraints imposed by the Aleutian conditions. USGS experience in California is of little help in predicting the character of precursory tilts in the Aleutians, because the tectonic setting is very different — a subduction zone rather than a strike-slip fault. The Aleutian conditions mean that, away from the immediate vicinity of the Adak townsite, sites are only accessible by helicopter, the instruments must be capable of unattended operation on batteries for one year, and the information must be telemetered in to Adak Observatory. So far we have only worked in the vicinity of the Adak townsite, but the ultimate requirement to cut the unbilical “hard wire” cord and move out to remote sites has played an important role in governing the techniques employed.