The range of earthquake sizes represented by the whole model.
Nagao fault zone
長尾断層帯
What this earthquake source model represents and how to read its data.
Reference model · not a forecastThe long-term chance that an earthquake represented by this model occurs within that period.
The long-term chance that an earthquake represented by this model occurs within that period.
This model in plain language
J-SHIS classifies this as a major active-fault model. It represents the underground area that may rupture along the fault, not one predicted earthquake. The model covers an overall magnitude of Mw 6.8. Its source elements span depths of 2–12.32 km below the surface.
Japan terrain and the source model in 3D
Use the terrain map and city labels to locate the approximate source area, then switch below ground to inspect its generalised extent and depth. It does not reproduce the original source elements or show future epicentres or rupture progression.
Ctrl-drag to tilt · city names remain visible on the map
How to read the model data
Magnitude describes the overall size of the modelled earthquake, not the Shindo felt in a particular place. The same magnitude can produce different shaking depending on distance, depth and ground conditions. A range shows both model limits.
Within 30 years—Within 50 years—
Probabilities are long-term values in the Y2020 model. They do not predict an earthquake on a particular day, in a particular year or at one exact location. Some models do not provide a value.
- Average recurrence interval
- 30,000 years A long-term average derived from the activity assessment. It is not a timetable or a countdown to the next event.
- Time since latest modelled activity
- 1,320 years How much time the model treats as having passed since the latest activity. It is uncertain and is not the time remaining until another earthquake.
Do not subtract the elapsed time from the average interval to calculate a countdown to the next earthquake.
Places where J-SHIS considers this model
In J-SHIS calculations, this model is among the leading earthquake sources for these places. It does not mean the earthquake will start inside their boundaries or that every place would shake in the same way.
Technical model data
J-SHIS identifiers and calculation parameters. You do not need them for an everyday reading of this page.
- Model version
- Y2020 The edition of J-SHIS data used on this page.
- Probability case
- MAX MAX is the J-SHIS calculation case used on this page. It does not mean a certain ‘worst case’ event.
- J-SHIS code
- F022131 The identifier used for this model inside J-SHIS.
- Estimation method code
- BPT An abbreviation for the statistical process used to calculate probability. It is not a danger grade.
- Source elements
- 1 Source elements are the pieces J-SHIS uses to build the source shape. A larger count means a more detailed or complex model; it is not a hazard score, a fault count or the number of expected earthquakes.
- Depth
- 2–12.32 km The modelled depth range below the ground surface.
- Element length
- 32 km The length of individual source elements, not necessarily the total length of a fault zone.
- Element width
- 18 km The width of the inclined source elements below ground.
- Dip angle
- 35 ° The element’s tilt from horizontal: 0° is horizontal and 90° is vertical.
- Strike
- 87.1 ° The compass direction in which an element extends, measured clockwise from north.
- Display grid cells
- 12 Regular aggregated grid cells used to depict the source area. This is not the number of source records or original shapes.
Source and limitations
Source: J-SHIS, operated by Japan’s National Research Institute for Earth Science and Disaster Resilience (NIED). JISHINDESU organises the Y2020 maximum-case data for presentation. This page is not an earthquake prediction, building-safety assessment or evacuation notice. Use current JMA and local-authority information for safety decisions.
In accordance with the J-SHIS terms, we publish only model-level summaries and coarse display geometry that cannot reproduce the original vertex sequences. This is not a redistributed copy of the source dataset.
Data retrieved: 05/09/2026