The earthquake location also influences the type of survey response. Earthquakes near urban centres, rivers, dams, nuclear power plants, military installations and other critical facilities may require a response with special considerations for future safety. Already existing geodetic control including the spatial distribution, type, and history of pre-earthquake geodetic measurements are decisive for the possibility of deriving a good mathematical description of crustal deformation by re-surveying. For example, horizontal motions will usually not be well detected, if only levelling surveys predated the earthquake. Very sparse or poorly located configurations of pre-earthquake measurements have little potential to reveal deformation by re-surveying