The Seismolgy Division deploys two broadband seismograph networks: one in the Netherlands (FDSN code: NL) and one in the Netherlands Antilles (FDSN code: NA). The main purpose of these networks is the monitoring of the actual seismicity in both the Netherlands and its surrounding as well as in the Caribbean.

The Netherlands broadband seismograph network has 4 permanent stations: HGN, WTSB, WIT and OPLO and a number of mobile stations. Our stations are equipped with Quanterra data-loggers (Q330, Q330-HR, Q730), Guralp dataloggers (DM-24), Streckeisen sensors (STS-1, STS-2) and Guralp sensors (CMG-3T). The NA network is build of 3 permanent stations: SABA, SEUS and SMRT. Data acquisition and real-time transfer of data to the KNMI is managed by SeisComp/SeedLink - running on Linux PC's at the seismic station. Data communication from the stations to the KNMI is over Internet using dedicated telephone lines, DSL and GPRS. The data-loggers are configured to produce data-streams with different sample rates for each channel: 100 samples per second (sps), 40 sps and 1 sps. To minimize hardware failures - and hence dataloss - we are currently replacing the PC's with fanless PC barebones.

The current broad-band network consists of the following stations:

At the KNMI, data from all stations is collected by a SeisComp/SeedLink system. This system acts as a hub (1) to archive the data at the KNMI, (2) to process the data in real-time using SeisComP3, and (3) to feed data in real-time to ORFEUS. Through ORFEUS our stations HGN, OPLO, WIT, WTSB, SABA, SEUS and SMRT contribute to the Virtual European Broadband Seismograph Network (VEBSN). From the ORFEUS Data Center (ODC), data is forwarded directly to the international community and IRIS-DMC using SeedLink.

Routine analysis of waveform data from HGN, WTSB and WIT is carried out on a daily basis, using SeismicHandler and SeisComP3. Phase readings and magnitudes are reported by e-mail to the ISC, EMSC-CSEM and interested users in the IMS1.0 format following the IASPEI standard seismic phase list.

An automatic procedure at the KNMI shows the continuous data of our broadband stations on the Internet. This 'Live Seismogram' service is updated every 15 minutes and can be found here. Also, an automatic procedure monitors the Power Spectral Density of the background noise at each station which provides a tool to monitor the quality of the site, instrumentation and data throughout the year. Automatic detections of seismic energy are indicated in blue, based on a auto-regressive modelling of the P-phase. A detailed description of the method is described by Sleeman and van Eck (1999).

Waveform data from the broadband stations are available to the user through different services at ORFEUS Data Center.

• R. Sleeman and T. van Eck, Robust automatic P-phase picking: an on-line implementation in the analysis of broadband seismogram recordings.
  Physics of the Earth and Planetary Interiors 113, 265-275.