AS048, Eilat, Israel
Thumbnail profile: Eilat
Eilat (Hebrew: אֵילַת) is named after the Biblical Elath, believed to correspond with modern day Aqaba. Today a bustling tourist resort and port located at the northern tip of the Red Sea on the Gulf of Aqaba, Eilat is Israel's southernmost city.
Home to 50,000 people, Eilat belongs to the Southern Negev Desert and straddles the southern end of the geographic line that separates Africa from Asia. Its location is adjacent to the Egyptian village of Taba to the south, and the Jordanian port city of Aqaba to the east.
Eilat is ancient, having been mentioned several times in the Bible, first as one of the stations of the “children of Israel” after their exodus from Egypt. In the modern era, Eilat was designated as part of the Jewish state in the 1947 UN Partition Plan. Having started out as a military outpost, Eilat quickly grew as the area's resources were surveyed and developed. Following peace treaties signed with Egypt in 1979 and Jordan in 1994, Eilat's borders with its neighbours were finally opened. Today some 20% or over 10,000 of Eilat's population is made up of foreign workers, employed as caregivers, hotel staff or construction workers. Eilat became a free trade zone in 1985.
Geology and Environment
The scenery around Eilat is stunning in its sparseness, surrounded by the spacious monochrome desert and overlooked by the tiers of arid mountain ranges.
The Amram Massif is comprised of a late Precambrian magmatic rock, exposed over an area of six km² and overlain by Cambrian formation. These magmatic rocks belong to the final stage in the evolution of the Arabian Nubian Shield of crystalline rocks on the flanks of the Red Sea.
Further north, the Dead Sea fault system forms deep basins filled by more than 1,000 metres of clastic sediments (i.e. rocks composed predominantly of broken pieces or “clasts” of older weathered and eroded rocks).
Eilat's semi-arid desert climate is moderated by its proximity to the tropical Red Sea. While air temperatures often exceed 40°C in summer and 22°C in winter, water temperatures range between 22-28°C. There are less than 20 days of rain a year and less than 100 mm of rainfall per year. The city's beaches, nightlife and desert landscapes make it a popular destination for domestic and international tourism.
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. 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.
IMS Station Location
The International Monitoring System (IMS) auxiliary seismic station AS48 is located in southern Israel, about 12 km north of the city of Eilat at the head of the Red Sea. Its parent network, the Israel Seismic Network, which is used to monitor earthquake hazards, is funded and operated by the Geophysical Institute of Israel (GII).
Inside a long tunnel excavated in granite from Mt. Amram, the station is located on the flanks of the Arava Valley, part of the Dead Sea rift valley, about five km west of the Eilat-Beer Sheva highway. Aqaba airfield is located about 16 km away. The site is accessible all year round.
AS48 station is located at the Adolpho Bloch Geophysical Observatory on Mt Amram and near Eilat, Israel. The observatory was established in 1969 by the Department of Applied Mathematics of the Weizmann Institute of Science in Rehovot, Israel as part of the Worldwide Standard Seismograph Network (WWSSN).
For a decade it has operated as one of the most sensitive of the network’s auxiliary seismic stations. After the observatory ceased functioning in 1979, the Weizmann Institute of Science granted the Seismology Division of the GII permission to use the site as a geophysical observatory.
In terms of seismic equipment, the observatory is located in a 175-metre long tunnel that is 3x3 metres in diameter. It houses equipment installed both before and after 1995, when the GII assumed responsibility for station operation, and also contains equipment installed by the IMS.
The tunnel is separated into four parts by three thick, heavy doors, as in a submarine, to minimize variations in air temperature and pressure in order to ensure that the seismic measurements are as precise as possible. Temperature conditions are very stable at this depth into the bedrock. The digitizer (i.e. a device that converts analog signals into digital signals) installed in the tunnel is connected to an external Global Positioning System (GPS) via a fiber-optic link. The GPS antenna is installed outside the tunnel with good radio visibility of the sky.
The site is unmanned. The tunnel entrance is locked with a double-patented lock and fenced with barbed wire.
Testing and Certification
IMS equipment was installed at AS48 in June 2005 and the station was connected to the IMS for testing purposes. After the successful implementation of data authentication measures, confirmation of data flow via the Global Communications Infrastructure (GCI), and a favourable data availability figure exceeding the 98% annual mission-capable data availability requirement, AS48 was certified on 21 November 2006.
In addition to AS48, Israel hosts one other auxiliary seismic station and one radionuclide laboratory.