Instrumental monitoring of earthquake activity in Switzerland began at the onset of the 20th century (see complete history of the SED). Ever since, Switzerland has been at the forefront of seismic monitoring in Europe.
By the 1970s, a high-gain, short-period, seismic telemetry network had been installed, which recorded data on microfilm.
By the mid-1980s, the network consisted of a dense network of high-gain sensors with radio communications digitised on a central computer system with automatic processing for earthquake detection. These sensors were placed on solid rock in very-low-noise locations to enable them to record background seismicity in Switzerland.
In the early 1990s, the Swiss Strong Motion Network (SSMNet) was established, with dial-up 12 to 16-bit triggered instrumentation. Stations were installed at 70 free-field sites, mainly in urban settings, and in arrays at 6 dam sites. This network targeted areas where the seismic risk is high and where strong local effects could be expected to amplify ground motion caused by earthquakes.
In the late 1990s, broadband sensors fitted with 24-bit data loggers replaced the short-period sensors and GPS timing was introduced. Communications were also upgraded to a secure, high- bandwidth, internet system.
In the 2000s, strong-motion sensors of similar quality began to be installed, too. The new, modern system combining the Swiss Digital Seismic Network (SDSNet) and the Swiss Strong Motion Network (SSMNet) is called the Swiss National Network (CHNet).