Deployment of New Strong Motion Seismographs of K-NET and KiK-net

Following the occurrence of the 1995 Hyogoken-Nanbu (Kobe) earthquake, National Research Institute for Earth Science and Disaster Prevention (NIED) has constructed two strong motion seismograph networks, K-NET and KiK-net. These networks cover uniformly the country with an inter-station interval of about 20–25 km, and a total number of the stations is about 1,700. To grasp the hazard (ground motion) of urban or downtown areas, most stations of K-NET are located in public offices, schools and parks, and a three-component accelerometer is installed on the free-surface. On the other hand, KiK-net stations are located in quiet places to avoid the artificial noise. Each KiK-net station has a borehole of 100 m or more in depth and strong motion seismographs have been installed both on the ground surface (uphole) and at the bottom of the boreholes (downhole ). Recently, based on the request for quicker hazard information, all instruments of the K-NET and KiK-net have been renewed by including the change of accelerometers at the surface, new recorders, and also a new data collection system between stations and the Data Management Center (DMC) in Tsukuba. The newly developed instruments, which are state of the art in strong motion instrumentation, have several advantages such as real-time capability, larger measurable range and lower noise. This paper explains the new generation system of K-NET and KiK-net.