Seismic stations are established which record the motion of the ground continuously. These data are analyzed for the presence of small earthquakes, industrial blasts, or ambient vibration levels.
Tectonically active structures are active over a wide range in the size of the events they cause. Mapping the smaller events yields information about the location and activity of the tectonic structure. Blasts and vibrating machinery can also be monitored for potential seismic damage to fragile structures.
Calibration and wide frequency response are required to obtain interpretable data. To locate micro-earthquakes, a geographically distributed network is required. Recordings from each station are time stamped and transmitted to a central location.
Insufficient stations and lack of maintenance cause the failure of seismic networks to record and locate the objective events. After analysis the precision and accuracy of the locations is often overestimated.
Installation and operation of an earthquake recording network is a major undertaking. After installation, operation may be required for many years to obtain the information sought. Blast monitoring, while not requiring the same level of commitment, does require multiple stations and pre-blast inspections. Vibration monitoring can be done with one instrument but persistence and focus are required to obtain useful results.
Maps of earthquake locations and interpretations of the efficacy of the network, progress towards the stated goals of network operation, and housekeeping details comprise the continuous reporting process from a seismic network. Blast or vibration monitoring reports compare the recordings to legal limits for such activities.