Accelerographic Network

Strong motion instruments are used to record the strong ground shaking.  Strong motion sensors are designed to record the high-frequency seismic waves of large local earthquakes. These instruments are called accelerographs because they record the ground acceleration.

The degree of damage due to a strong earthquake is often described by the macroseismic intensity, which is determined after the evaluation of the macroseismic questionnaires. Since a more objective measure of ground shaking is preferred by scientists (seismologists, engineers, urban planners, etc.), accelerographs are manufactured to provide an instrumental measure of the ground shaking at a specific site. Thus, by using strong motion records, scientists want to understand the effect of the source-to-site path, as well as the one of the local geological conditions on the formation of the shaking. The data provided by accelerogrphs are used to improve the earthquake resistant codes and to design earthquake hazard maps.

Geodynamic Institute of the National Observatory of Athens (N.O.A.G.I.) has been operating a permanent strong motion network since 1972. The main turn points of the history of this network are the beginning of its deployment in 1972 by the installation of 15 analogue SMA-1 type accelerographs - the first ever used in Greece -, the increase of the installed instruments to 40 in 1986 and the gradual use of digital instruments of A-800 type since 1995. At the present state, after the doubling of the instrument number and their gradual replacement by digital instruments (A800/A900, QDR, ETNA and CMG-5TD), only 6 are of analogue SMA-1 type.

The network is improved continuously under the financial support of the State or within the frame of scientific projects.  The majority of the instruments are located in urban complexes, taking into account the population density and the seismicity of the Greek territory. Local strong motion arrays are also developed in some cities. The most important of these is the one covering the broader area of Athens. Limited number of instruments are installed at archaeological and historical sites.

The telemetric connection of the installed instruments, which is in progress during the last years, improve the reliability of the network.

For any information concerning the strong motion networks of N.O.A.G.I. contact  Dr. Ioannis Kalogeras

Last update: March 2009