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J-SHIS EARTHQUAKE SOURCE MODEL

Fukaya/Ayasegawa fault zone (Fukaya fault zone/Kounosu-Ina segment)

深谷断層・綾瀬川断層（深谷断層と鴻巣－伊奈区間が同時に活動）

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

Reference model · not a forecast
Modelled magnitudeMw 7.4

The range of earthquake sizes represented by the whole model.

Chance within 30 years—

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

Chance within 50 years—

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 7.4. Its source elements span depths of 5–20.59 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

Colour shows generalised depthShallow5 kmMid-range12.8 kmDeep20.6 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 7.4

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 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.

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. Kanna Town
  2. Nakanojo Town
  3. Naganohara Town
  4. Kawaba Village
  5. Numata City
  6. Shinto Village
  7. Shimonita Town
  8. Higashiagatsuma Town
  9. Yokoze Town
  10. Ogano Town
  11. Tsuchiura City
  12. Koga City
Show 48 more places
  1. Ishioka City
  2. Shimotsuma City
  3. Inashiki City
  4. Kasumigaura City
  5. Miho Village
  6. Ami Town
  7. Kawachi Town
  8. Yachiyo Town
  9. Tone Town
  10. Shimotsuke City
  11. Nogi Town
  12. Takasaki City
  13. Fujioka City
  14. Tomioka City
  15. Annaka City
  16. Yoshioka Town
  17. Kanra Town
  18. Tamamura Town
  19. Chichibu City
  20. Namegawa Town
  21. Ranzan Town
  22. Minano Town
  23. Nagatoro Town
  24. Kamikawa Town
  25. Kamisato Town
  26. Chiba Chuo Ward
  27. Chiba Hanamigawa Ward
  28. Chiba Inage Ward
  29. Chiba Midori Ward
  30. Chiba Mihama Ward
  31. Narita City
  32. Sakura City
  33. Kamagaya City
  34. Yotsukaido City
  35. Shiroi City
  36. Katori City
  37. Shisui Town
  38. Kozaki Town
  39. Tako Town
  40. Fuchu City
  41. Akishima City
  42. Chofu City
  43. Kunitachi City
  44. Fussa City
  45. Komae City
  46. Tama City
  47. Inagi City
  48. Hamura 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
F01482A
The identifier used for this model inside J-SHIS.
Estimation method code
SIM
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
5–20.59 km
The modelled depth range below the ground surface.
Element length
20–72 km
The length of individual source elements, not necessarily the total length of a fault zone.
Element width
18–20 km
The width of the inclined source elements below ground.
Dip angle
50–60 °
The element’s tilt from horizontal: 0° is horizontal and 90° is vertical.
Strike
122.1–130.2 °
The compass direction in which an element extends, measured clockwise from north.
Display grid cells
24
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 →