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J-SHIS EARTHQUAKE SOURCE MODEL

Yamagata-ken-Oki Earthquake

山形県沖の地震

What this earthquake source model represents and how to read its data.

Reference model · not a forecast
Modelled magnitudeMw 7.7

The range of earthquake sizes represented by the whole model.

Chance within 30 years1.48%

The long-term chance that an earthquake represented by this model occurs within that period.

Chance within 50 years2.44%

The long-term chance that an earthquake represented by this model occurs within that period.

This model in plain language

This is a model of a broad plate boundary where one plate descends beneath another. Different sections may rupture in different combinations. The model covers an overall magnitude of Mw 7.7. Its source elements span depths of 0–34.64 km below the surface. Its 30-year long-term probability is 1.48%, not a prediction of a date.

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

Colour shows generalised depthShallow0 kmMid-range17.3 kmDeep34.6 km

The 3D terrain gives geographic and city context. The coloured surfaces are coarse regular display cells projected from the underground source area—not the original J-SHIS geometry. They do not show future epicentres or shaking intensity.

How to read the model data

Modelled magnitudeMw 7.7

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.

Occurrence probability
Within 30 years1.48%Within 50 years2.44%

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
1,000 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
186.1 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.

  1. Oga City
  2. Hachirogata Town
  3. Tsuruoka City
  4. Yuza Town
  5. Awashimaura Village
  6. Akita
  7. Akita City
  8. Yurihonjo City
  9. Katagami City
  10. Daisen City
  11. Nikaho City
  12. Gojome Town
Show 36 more places
  1. Ikawa Town
  2. Ogata Village
  3. Sakata City
  4. Mikawa Town
  5. Shonai Town
  6. Niigata Kita Ward
  7. Niigata Higashi Ward
  8. Niigata Konan Ward
  9. Yuzawa City
  10. Semboku City
  11. Mitane Town
  12. Misato Town
  13. Ugo Town
  14. Yamagata
  15. Tozawa Village
  16. Niigata Chuo Ward
  17. Niigata Nishi Ward
  18. Sado City
  19. Seiro Town
  20. Sekikawa Village
  21. Yokote City
  22. Niigata
  23. Niigata Akiha Ward
  24. Niigata Minami Ward
  25. Niigata Nishikan Ward
  26. Murakami City
  27. Agano City
  28. Shinjo City
  29. Okura Village
  30. Gosen City
  31. Tagami Town
  32. Shibata City
  33. Kamo City
  34. Tsubame City
  35. Tainai City
  36. Yahiko Village

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
AYMGA
The identifier used for this model inside J-SHIS.
Estimation method code
COM
An abbreviation for the statistical process used to calculate probability. It is not a danger grade.
Source elements
2
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
0–34.64 km
The modelled depth range below the ground surface.
Element length
50–70 km
The length of individual source elements, not necessarily the total length of a fault zone.
Element width
40 km
The width of the inclined source elements below ground.
Dip angle
60 °
The element’s tilt from horizontal: 0° is horizontal and 90° is vertical.
Strike
11–40 °
The compass direction in which an element extends, measured clockwise from north.
Display grid cells
44
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

Open the source data in J-SHIS ↗J-SHIS terms of use ↗Explore local earthquake history →