These are generally referred to as Nankai Trough Earthquakes. Time sequence for issuance of information on tsunamis and earthquakesĪlong the Nankai Trough, megathrust earthquakes with a magnitude 8 or more occur repeatedly. > Map of Tsunami Forecast Regions (PDF Image) If tsunamis are generated by seismic events far from Japan, the Agency engages in coordinated action with the Pacific Tsunami Warning Center (PTWC) in Hawaii and issues warnings for long-propagating tsunamis. JMA issues a Tsunami Warning/Advisory for each region within around two to three minutes of the quake. If a damaging tsunami is expected in coastal regions, When an earthquake occurs, JMA estimates the possibility of tsunami generation from seismic observation data. To reduce and mitigate catastrophic losses caused by tsunamis, immediate provision of tsunami information for coastal regions is essential. The Earthquake Early Warning system is aimed at mitigating earthquake-related damage by allowing countermeasures such as promptly slowing down trains, controlling elevators to avoid danger and enabling people to quickly protect themselves in various environments such as factories, offices, houses and near cliffs.
These estimations are based on prompt analysis of the quake's focus and magnitude using waveform data obtained from seismographs near the epicenter. The Earthquake Early Warning system provides advance announcement of the estimated seismic intensity and expected arrival time of principal motion when an earthquake occurs. Summary of Tables explaining the JMA Seismic Intensity Scale (PDF 197 KB) "Tables explaining the JMA Seismic Intensity Scale" describes the situations and damage which may be caused by seismic motion of each seismic intensity. The seisimic intensity is measured with a seisimic intensity meter. JMA's seismic intensity scale has 10 degrees (0 (imperceptible), 1, 2, 3, 4, 5 lower, 5 upper, 6 lower, 6 upper, 7). It varies with the distance from the epicenter and the surface geology at each point. Seismic intensity describes the scale of the ground motion at a particular location. This information also plays a vital role as a trigger for the initiation of rescue and relief operations related to earthquake disasters. The information is provided to disaster prevention authorities via dedicated lines, and reaches the public through local governments and the media. If the seismic intensity is 3 or greater, the Agency issues a Seismic Intensity Information report within one and a half minutes. When an earthquake occurs, JMA immediately issues information on its hypocenter, magnitude and observed seismic intensity. The data collected are input to the Earthquake Phenomena Observation System (EPOS) at the headquarters in Tokyo and the Osaka District Meteorological Observatory on a real-time basis. It also collects data from over 3,600 seismic intensity meters managed by local governments and the National Research Institute for Earth Science and Disaster Prevention (NIED). To monitor earthquakes, JMA operates an earthquake observation network comprised of about 200 seismographs and 600 seismic intensity meters. Monitoring of Earthquakes and Provision of Information JMA operationally monitors seismic and volcanic activity throughout the country and issues relevant warnings and information to mitigate damage caused by disasters related to earthquakes, tsunamis and volcanic eruptions.Įarthquake distribution around Japan (1960-2011) Located in one of the most active seismic and volcanic zones in the world, Japan is frequently affected by earthquakes and volcanic disasters. Monitoring of Earthquakes, Tsunamis and Volcanic Activity
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