K-NET (Kyoshin network) is a nation-wide strong-motion seismograph network, which consists of more than 1,000 observation stations distributed every 20 km uniformly covering Japan. K-NET has been operated by the National Research Institute for Earth Science and Disaster Prevention (NIED) since June, 1996. At each K-NET station, a seismograph is installed on the ground surface with standardized observation facilities.

KiK-net (Kiban Kyoshin network) is a strong-motion seismograph network, which consists of pairs of seismographs installed in a borehole together with high sensitivity seismographs (Hi-net) as well as on the ground surface, deployed at approximately 700 locations nationwide. NIED constructed KiK-net under the plan 'Fundamental Survey and Observation for Earthquake Research' directed by 'the Headquarters for Earthquake Research Promotion'.