AS067, Tsumeb, Namibia
Thumbnail profile: Tsumeb
Regarded as Namibia’s "gateway to the north", Tsumeb is the capital of the country’s Oshikoto region and the town located closest to Etosha National Park.
Its local name, generally pronounced "SOO-meb", is thought to mean either "Place of the moss" or "Place of the frog" and may have something to do with the huge natural hill of green, oxidized copper ore that existed there before it was destroyed by mining.
Today’s town, which celebrated its 100th anniversary in 2005, was founded in 1905 by Germany - the colonial power that called the country German Southwest Africa.
Geology and Geography
Since its founding, Tsumebhas been primarily a mining town. The huge mineralized pipe that lead to its foundation makes it unique. Although its origin has been hotly debated, the fact remains that this pipe penetrates more or less vertically through the Precambrian Otavi dolomite for at least 1,300 m. Mined from prehistoric times, most of the pipe’s ore—primarily copper, lead, silver, gold, arsenic and germanium—was removed in the 20th century when the pipe became famous for its richness.
Near Tsumeb are two large sinkhole lakes, Lake Otjikoto and Lake Guinas, the depths of which are unknown since the bottom of each lake disappears into lateral cave systems. In addition, the largest meteorite in the world—a nickel-iron meteorite weighing about 60 tons—lies in a field about 40 minutes east of the city.
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 the location accuracy of seismic events detected by the primary seismic network. 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.
International Monitoring System Station Location
The auxiliary seismic station AS67 located at Tsumeb in northeastern Namibia is one of the stations designated in the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty.
AS67 is an auxiliary seismic station of the IMS network that is equipped with a seismometer, located in a surface vault on a concrete pier firmly coupled to bedrock. It measures and records the size and force of seismic waves. The station also has a digitizer and IMS-developed Standard Station Interface to provide data authentication and connectivity to the Global Communications Infrastructure (GCI).
The Tsumeb station is located within a government-owned research facility. The land rights use as a seismic station is covered in a Memorandum of Understanding between the United States Geological Survey (USGS) and the host country, Namibia. The USGS Albuquerque Seismic Laboratory is the Parent Network Operator.
Due to the absence of major human settlements or industries and the distance from the Pacific Ocean, the level of interfering seismic ‘noise’ is very low, allowing for high precision seismic measurements.
For the same reasons, this site was chosen for the second IMS station hosted by Namibia, infrasound station IS35.
Testing and Certification
The AS67 station upgrade was completed in June of 2003, and the station was connected to the IMS Testbed on 9 June 2003. The station parameters were accepted by the IDC. AS67 was visited in June 2003 by IMS staff for interface installation and testing, in combination with the station upgrade visit.
This station, like most stations designated as auxiliary stations of the IMS network, uses the original digitizer installed, operated and maintained by the Parent Network Operator. This station was connected to IDC Operations on 22 April 2004.
Data availability registered 100% in April 2004 and 99% in June 2004. Successful implementation of authentication measures, confirmation of data flow via the GCI and a favourable data availability figure indicated that the station was capable of meeting the 98% annual mission-capable data availability requirement. AS67 was therefore certified on 26 July 2004.