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J-SHIS EARTHQUAKE SOURCE MODEL

Ayasegawa fault (Kounosu-Ina segment)

綾瀬川断層鴻巣－伊奈区間

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

Reference model · not a forecast
Modelled magnitudeMw 6.5

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 6.5. Its source elements span depths of 5–20.32 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

Colour shows generalised depthShallow5 kmMid-range12.7 kmDeep20.3 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 6.5

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.

Average recurrence interval
45,000 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
15,000 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. Namegawa Town
  2. Shiraoka City
  3. Bando City
  4. Sakai Town
  5. Chiyoda Town
  6. Tokorozawa City
  7. Tsurugashima City
  8. Miyoshi Town
  9. Hatoyama Town
  10. Miyashiro Town
  11. Goka Town
  12. Tatebayashi City
Show 48 more places
  1. Itakura Town
  2. Meiwa Town
  3. Saitama Nishi Ward
  4. Saitama Kita Ward
  5. Saitama Omiya Ward
  6. Saitama Minuma Ward
  7. Saitama Chuo Ward
  8. Saitama Sakura Ward
  9. Saitama Urawa Ward
  10. Saitama Minami Ward
  11. Saitama Midori Ward
  12. Saitama Iwatsuki Ward
  13. Kumagaya City
  14. Kawaguchi City
  15. Kasukabe City
  16. Ageo City
  17. Koshigaya City
  18. Warabi City
  19. Toda City
  20. Asaka City
  21. Shiki City
  22. Wako City
  23. Niiza City
  24. Okegawa City
  25. Kuki City
  26. Kitamoto City
  27. Fujimi City
  28. Hasuda City
  29. Fujimino City
  30. Ina Town
  31. Matsudo City
  32. Noda City
  33. Nagareyama City
  34. Itabashi City
  35. Kawagoe City
  36. Gyoda City
  37. Kazo City
  38. Hanyu City
  39. Kounosu City
  40. Soka City
  41. Yashio City
  42. Misato City
  43. Sakado City
  44. Satte City
  45. Yoshikawa City
  46. Kawajima Town
  47. Yoshimi Town
  48. Sugito Town

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
F014821
The identifier used for this model inside J-SHIS.
Estimation method code
BSI
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
5–20.32 km
The modelled depth range below the ground surface.
Element length
20 km
The length of individual source elements, not necessarily the total length of a fault zone.
Element width
20 km
The width of the inclined source elements below ground.
Dip angle
50 °
The element’s tilt from horizontal: 0° is horizontal and 90° is vertical.
Strike
130.2 °
The compass direction in which an element extends, measured clockwise from north.
Display grid cells
9
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 →