AS043, Parapat, Indonesia

Thumbnail profile: Sumatra (Parapat)

Parapat, Indonesia

The town of Parapat is located inland in the northern part of the island of Sumatra, the sixth largest island in the world (about 470,000 km²) and the largest island belonging entirely to Indonesia. Today it is also the fourth most populous island in the world with major urban centres located at Medan in the north and Palembang in the centre.

The ancient name for Sumatra was Swarna Dwipa, Sanskrit for the “Isle of Gold”, an apparent reference to the fact that Sumatra’s highland mines exported gold from early times. Today Sumatra also produces “black gold”—that is, oil, as well as palm oil.

Geography, Geology and Natural Disasters

Grand Mosque of Medan, North Sumatra

Sumatra extends almost 1,800 km from northwest to southeast, and is located on both sides of the Equator. The maximum width is 435 km. The two main geographical regions are: the swampy plains in the east and, in the west, the Barisan Mountain chain that forms the backbone of the island. The Great Sumatran Transform Fault runs the entire length of the island. Pressure on this fault increased dramatically since the 2004 earthquake, and seismologists fear a major earthquake will occur soon. The fault ends directly below the city of Banda Aceh.

The active volcano, Mount Kerinci, is the highest point at 3,805 m. Volcanic activity in this region is responsible for this area’s fertility and stunning scenery, especially around the Lake Toba where the town of Parapat is located.


On 26 December 2004, northern and western Sumatra, particularly Aceh province, were devastated by a 15 m high tsunami following a 9.2-magnitude earthquake in the Indian Ocean. The death toll exceeded 170,000 in Indonesia alone, primarily in Aceh. In 2005 an 8.7 magnitude aftershock of the previous earthquake occurred.

After the 2004 tsunami, the Preparatory Commission of the Comprehensive Nuclear-Test-Ban-Treaty Organization (CTBTO) decided to provide relevant International Monitoring System (IMS) data to tsunami warning centres in the region on a provisional basis. With the help of the reliable provision of high quality IMS data in almost real-time, these tsunami warning centres are now able to issue warnings several minutes earlier.


Read more on the disaster mitigation potential of IMS data here.

IMS Station Location

Parapat auxiliary seismic station AS43 is located close to Lake Toba in North Sumatra. It takes approximately four hours to drive there from Medan, the closest city with flight connections to and from Jakarta. AS43 is located on the premises of the local meteorological office of the Indonesian Meteorological Service (Badan Meteorologi dan Geofisika - BMG).

The site is accessible all year round, which is important for minimizing outage time in case of a malfunction. Due to the relative remoteness from major human settlements and industries, the level of seismic interference from human activity is low, allowing for high precision seismic measurements.

Station Profile

Auxiliary seismic stations are mandated to provide data to the IDC upon request only.

The original seismic station at Parapat was installed in 1970 to monitor the intense seismic and volcanic activity in the region. It is now part of the Comprehensive Nuclear-Test-Ban Treaty's (CTBT) IMS. The BMG is the Parent Network Operator (PNO).

This station has a three-component array design with a Central Recording Facility (CRF) and a vault, which is a reinforced room where the equipment is protected, partly by a remote alarm system. Facilities, which are shared with BMG, are powered through an AC power line and backed up with a diesel generator set. The seismometer and the digitizer are installed inside the vault.

Learn more about how the seismic technology works.

Testing and Certification

Officer performing certification measurements.

After the station was upgraded in January 2004, the station was connected to the IMS for testing purposes. This was followed by the successful implementation of data authentication measures and the confirmation of data flow via the Global Communications Infrastructure (GCI).

A favorable data availability figure confirmed that the station was capable of meeting the 98% annual mission-capable data availability requirements. Therefore, AS43 was officially certified on 29 November 2005.

The Future Network

When fully operational, this worldwide system of 120 auxiliary seismic stations will transmit data upon request in real time via satellite to the International Data Centre (IDC) in Vienna, Austria. There the data will be analyzed in combination with the other three technologies to produce bulletins of detected events for Treaty Member States.

In addition to auxiliary seismic station AS43, Indonesia hosts five other IMS auxiliary seismic stations.


Learn more about Indonesia and the CTBT.