The initial survey shows that although the total number of all the stations is difficult to estimate, the number of strong-motion instruments operating in the free-field is close to 3,000 (Smit, 1999).
The survey also showed these networks and individual stations have been established and are maintained with recurrent government subsidies or short term grants. They operate as independent state, industrial or university units with little or no coordination between them. Some of these networks are very well run but because of the closed system within which they operate, even within the same country, few cooperative research programmes have developed between them and only a fraction of their output reaches end-users, engineers and earth scientists alike. However, this situation is changing with more agencies making their data accessible to end-users via the Internet and CD-ROMs.