Seismology has not still been able to foresee when the earthquake is going to happen. Therefore in the estimates of developing the seismic activity in the future statistical-probabilistic methods are used to determine probabilities for certain time intervals. This way so-called project seismic parameters are defined which represent input data for dynamic analysis of answers for constructions to earthquake as an impulse of their motions. The final object of these researches is planning and building constructions resistant to earthquakes' activity. Reliability of those calculations essentially depends on credibility of different seismic and seismically-tectonic models used while doing so. They are more reliable if the input data are of higher quality and richer. On the basis of the input data those models generate i.e. when speaking of seismic data it is important to have a lot of data about parameters of all earthquakes that occur at certain areas. That is ensured by very dense net of highly sensitive seismographs that register even the weakest earthquakes with high quality.
On the territory of Croatia presently there are 17 highly sensitive digital seismographs in operation. It has also been installed 19 accelerographs – a kind of seismographs that record only. Places where they are placed have been presented on Picture 9. Under the NATO project "Harmonisation of seismic maps in the countries of the West Balkans" as one of the projects in the NATO programme "Science for peace and security" five new modern seismographs were granted and they will soon be put in operation. The city of Zagreb ensured the means for purchasing 2 new seismographs for the network of Zagreb. In the near future the territory of Croatia will have in total 24 seismographs in operation. This makes a reliable but still not enough dense net-work according to the standards of developed countries located in the seismically active regions. It is evident from the Picture 11 that 3 seismographs have been put in operation in the wider area of Dubrovnik. They have been installed in Dubrovnik (County Centre for informing), in the bay of Bistrina near Ston (Developing-Research Centre for marine culture) and in the village Stravča in the Konavle mountains. All three locations send data in Zagreb. Accelerographs have been installed in Solana Ston and at three locations in Dubrovnik: 2 instruments in the Institute for Restoration of Dubrovnik, one in the Rector's Palace, one in Sponza Palace and one in the hotel Excelsior. This network of seismographs and accelerographs in Dubrovnik alike the whole network of Croatia has not been dense enough. It is particularly relating to the accelerographs in Dubrovnik where it should be necessary to instrument a number of other valuable monuments.