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J-SHIS EARTHQUAKE SOURCE MODEL

Sagami Trough earthquakes (M8 class)

相模トラフ沿いのM8クラスの地震

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

Reference model · not a forecast
Modelled magnitudeMw 7.9–8.6

The range of earthquake sizes represented by the whole model.

Chance within 30 years5.7%

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

Chance within 50 years11%

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 7.9–8.6. Its source elements span depths of 4.02–55.29 km below the surface. It considers 10 rupture patterns; this is not the number of expected earthquakes. Its 30-year long-term probability is 5.7%, 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 depthShallow4 kmMid-range29.7 kmDeep55.3 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 7.9–8.6

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 years5.7%Within 50 years11%

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.

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. Shirakawa City
  2. Izumizaki Village
  3. Nakajima Village
  4. Yabuki Town
  5. Ishikawa Town
  6. Tamakawa Village
  7. Ibaraki
  8. Mito City
  9. Tsuchiura City
  10. Koga City
  11. Ishioka City
  12. Yuki City
Show 48 more places
  1. Ryugasaki City
  2. Shimotsuma City
  3. Joso City
  4. Hitachiota City
  5. Kasama City
  6. Toride City
  7. Ushiku City
  8. Tsukuba City
  9. Hitachinaka City
  10. Kashima City
  11. Itako City
  12. Moriya City
  13. Hitachiomiya City
  14. Naka City
  15. Chikusei City
  16. Bando City
  17. Inashiki City
  18. Kasumigaura City
  19. Sakuragawa City
  20. Kamisu City
  21. Namegata City
  22. Hokota City
  23. Tsukubamirai City
  24. Omitama City
  25. Ibaraki Town
  26. Oarai Town
  27. Shirosato Town
  28. Tokai Village
  29. Miho Village
  30. Ami Town
  31. Kawachi Town
  32. Yachiyo Town
  33. Goka Town
  34. Sakai Town
  35. Tone Town
  36. Tochigi
  37. Utsunomiya City
  38. Tochigi City
  39. Sano City
  40. Kanuma City
  41. Imaichi, Nikko City
  42. Oyama City
  43. Moka City
  44. Ohtawara City
  45. Yaita City
  46. Sakura City
  47. Nasukarasuyama City
  48. Shimotsuke City

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
ASGMI
The identifier used for this model inside J-SHIS.
Estimation method code
XXX
An abbreviation for the statistical process used to calculate probability. It is not a danger grade.
Source elements
32,080
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
4.02–55.29 km
The modelled depth range below the ground surface.
Rupture patterns
10
Alternative rupture arrangements or sequences considered by the model.
Display grid cells
416
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 →