Paul Tregoning

On Sunday 3 February a splinter group met to discuss the geodetic aspects of RETINA. Specifically, the discussion was about what were the requirements/expectation of the geodetic component in the Azores and how these could be addressed. Paul Tregoning suggested that a good starting point for RETINA would be to establish the regional tectonic setting from existing GPS data/results from previous programs.

It became immediately obvious that there have been several, independent GPS tectonic programs in the Azores - some are historical and some are ongoing. Also, the data from these programs are not going to be available to the participants of RETINA. In some cases the data form the basis of graduate studies, in other cases the data have not yet produced scientific results and it is unreasonable to expect the scientists to make it available. There is, however, one site on San Miguel (PDEL) which is part of the EUREF GPS network; therefore, the data from this site are freely available to anyone and can be used by RETINA participants. The discussion moved on to the actual plans of Antonio and Joao Gaspar for the geodetic work on San Miguel. They listed the GPS equipment at their disposal:

1 Ashtech Z-12 GPS permanently installed at site PDEL

2 Ashtech Z-12 GPS available for campaign GPS work

2 GPS systems to be purchased through the RETINA funding

They suggested that two new continuous GPS sites be installed on Fogo and Furnas volcanos. The suggestion was made that purchasing GPS equipment through a US university at the much-reduced UNAVCO price (roughly 11 kUSD) would result in there being enough RETINA funding to purchase two receivers rather than only one at the normal prices. The feasibility of using Eric Calais to purchase through UNAVCO was discussed and Joao was going to investigate the possibility of making an international call for tender, thereby permitting Eric Calais to make a bid. CVUA has observed in 2000 a network of several sites around San Miguel in campaign-style operation, with generally 24 hours observation on each site. It was agreed that this was an excellent use of the available resources and that this mode of monitoring should be continued (i.e. 3 CGPS sites and regular observations on many additional sites, strategically placed on either volcanoes or potential landslide sites).

Joao indicated that the monitoring of landslides in the Azores was a much more difficult task than in the French Alps primarily because, unlike in the Alps, it is not known where the next landslide is likely to occur. He suggested that it was going to be very difficult to install an effective landslide monitoring system at this stage and that the GPS resources would be better used in monitoring the volcanoes instead. There was general agreement on this.

Antonio said that they had purchased a license for the Bernese software and he had it running under Windows. The question was asked whether they should also consider running GAMIT, a Unix-based system used by Kurt Feigl and Paul Tregoning (the Icelandic GPS analysis is done with Bernese). There was mutual agreement that the problems associated with running a unix system in the Azores (without an experienced systems administrator would be prohibitive and counter-productive. Kurt, Paul and Freystenn were in agreement that Antonio should stick with the Bernese software and not consider learning GAMIT (and unix) as well.Antonio indicated that he was going to attend a Bernese training course in March and the suggestion was made that at the next RETINA meeting in June he could stay a little bit longer to spend time with the people in Iceland who are proficient at using the Bernese software.

The meeting concluded that evening.

Antonio and Kurt continued the discussion the following afternoon (Monday) agreeing on the objective of having the CGPS receivers installed and recording data by Christmas, 2002. We evaluated the internet connection between CVUA in the Azores and REGAL in Nice. The transfer speed using ftp was sufficiently fast (30 to 40 kbyte/s), that transfering several Mbyte per day is quite feasible. The best plan would be to store data from RETINA GPS work on the REGAL server in a private directory to which Antonio has the right to write. Antonio's plan for disk storage using a dedicated file server within CVUA is sound because it has a back-up mechanism, good security, and an uninteruptable power supply. Antonio will inquire at the University about firewalls, with a view to Paul's being able to login to computers at CVUA from Nice.