Seismic equipment at one element of an array station, PS02, in Warramunga, Australia

Seismic network

• The seismological monitoring system detects and locates seismic events.

• The CTBT seismic network is composed of 50 primary stations, which send their data in real time to the International Data Centre (IDC) in Vienna, and 120 auxiliary stations that make their data available upon request from the IDC.

• The principal use of the seismic data in the verification system is to locate seismic events and to distinguish between an underground nuclear explosion and the numerous earthquakes that occur around the globe.

There are two different types of seismic stations:

	1. Three-component stations have sensors at a single site to measure the three components of the waves (up/down, east/west and north/south) caused by seismic events including earthquakes and explosions.
PS21, a three component seismic station located near Tehran, Islamic Republic of Iran
2. Array stations are sets of 9-25 geometrically arranged seismic sensors distributed over an area of up to 500 kmē. Seismic array stations have an enhanced detection capacity and independently measure the direction of and distance to the source of an event.
	GCI communications equipment at PS47, an array station in Mina, Nevada, USA

Seismograms showing the difference between a nuclear explosion and an earthquake