Continuously Operating GPS-Based Volcano Deformation Monitoring in Indonesia: The Technical and Logistical Challenges

In the past decade or so there has been increasing interest in the use of permanent, continuously-operating GPS networks, with a small number of continuous networks having been deployed in the USA, Japan, Canada and Europe for large scale crustal motion studies. However, only in Japan has a country-wide continuous GPS network to support seismic research been established by the Geographical Survey Institute (GSI). Even with such a dense network of dual-frequency GPS receivers the station separation is of the order of 20km or more. There are, however, applications of GPS-based deformation systems which require receiver densities of the order of just a few kilometres. Furthermore, the high cost of geodetic GPS receivers means that many countries cannot afford to establish such networks. Applications of dense permanent GPS arrays include monitoring of volcano flanks, micro-faults, ground subsidence due to underground mining or fluid extraction, slope stability, and even engineering structures such as dams, bridges, etc. This paper describes a low-cost design of an automatic GPS-based volcano deformation system that has recently been deployed by the authors on the Papandayan volcano in Indonesia. The critical problems that had to be overcome will be described, and early results presented.