AS002, Ushuaia, Argentina
Thumbnail profile: Ushuaia
Ushuaia (population 60,000), capital of the Argentine province of Tierra del Fuego, claims to be the world's southernmost “city at the end of the world”.
Settled by British colonists in the first half of the 20th century, it was named Ushuaia, which means “bay overlooking the West” in the local yámana language.
Initially centred around a prison for serious criminals, it followed the example of the British in Australia or the French on Devil's Island: escaping from a Tierra del Fuego prison was virtually impossible. The prisoners thus became forced colonists, spending their time cutting wood in the forest near the prison and building the town.
Geography and Weather
Located on the southern coast of the Beagle Channel and surrounded by the Martial mountain range to the north and Mounts Olivia and Cinco Hermanos to the East, Ushuaia offers a unique landscape, which combines mountains, glaciers, forests and the sea.
It is surrounded by sub polar forests with a “landscape of magnificent greenness”. Its geography, plus its location close to the South Pole, means that it enjoys over 18 hours of daylight in summer but only seven in winter.
Ushuaia has a sub polar oceanic climate and is very wet with an average of 160 rainy days a year. Snowfall is common in winter, even occurring occasionally in summer.
Average temperatures do not vary greatly, ranging from 1°C to 9°C. Very strong winds whip the town, which is why tree growth reflects the direction of prevailing winds and has given them the name "flag-trees" because of the way they are bent by the wind.
Mandate of Auxiliary Seismic Stations
Auxiliary seismic stations are mandated to provide data to the International Data Centre (IDC) upon request only but then with immediate availability. The purpose of this additional data is to improve location accuracy of seismic events detected by the primary seismic network of the International Monitoring System (IMS). It is also to characterize the seismic sources with greater precision in order to ascertain what kind of event has taken place; for example, an earthquake or an explosion.
When fully operational, the worldwide system of auxiliary seismic stations will transmit data upon request in real time via satellite to the IDC. There the data will be analyzed in combination with the other three technologies to produce bulletins of detected events for the Treaty’s Member States.
Auxiliary seismic station AS02 at Ushuaia is a new facility installed for the purposes of Comprehensive Nuclear-Test-Ban Treaty verification. It is the southernmost IMS station on the American continent. The relative remoteness of the site, with low levels of interfering seismic signals from human activity, allows for high-precision seismic measurements.
For the same reasons, the site also hosts IMS infrasound station IS02. The site survey was carried out in September 1996 by staff of the Argentinean National Institute "Instituto Nacional de Prevención Sísmica" (INPRES). The station infrastructure consists of a seismic vault (i.e. a small, secure building erected around the seismometer that protects it and associated equipment from theft, weather and wild animals) and an adjacent building where the digitizer, communications and electronic equipment are housed.
IMS Station Location
AS02 is located about ten km west of the city of Ushuaia, in Argentine Patagonia. The land has been fenced, mainly for protection against animals. The Municipality of Ushuaia has granted INPRES the right to use this land for an indefinite period to carry out seismic studies and evaluate seismic risks in the province of Tierra del Fuego.
Overall site access is possible by flying to Ushuaia airport and travelling from there by car. The station can be reached throughout the year; however, during the winter (i.e. between May and September), snow and ice can render access more difficult.
Testing and Certification
A preliminary station evaluation was carried out in April 2001 and installation was completed in November 2002. Digitizer testing already took place in May 2000 at Sandia National Laboratories under the supervision of International Monitoring System (IMS) staff.
Additional visits were made in November 2002 and November 2003 in order to install IMS equipment, upgrade the power system and verify that the station was ready to be considered for certification. Data availability since completion of the installation visit on November 2003 has been at a record level of 100%. AS02 was therefore certified on 19 December 2003.
In addition to AS02, Argentina hosts one other auxiliary seismic station, one primary seismic station, two infrasound stations, three radionuclide stations and one radionuclide laboratory.