M5.1 earthquake 4 km SE of Sukayama, Chiba, Japan
A magnitude 5.1 earthquake struck 4 km SE of Sukayama, Chiba, Japan at 21:27 local time (12:27 UTC) on 1 Oct 2026, at a depth of 50 km, according to JMA, GFZ and USGS. The solution is preliminary and may be revised.
Reported by 3 agencies
Data: JMA, GFZ, USGS · updated 2026-10-01 12:46 UTC · automatic solution
- Magnitude
- 5.1moderate
JMA magnitude (Mj) - Depth
- 50 km
- Status
- Automatic
- Origin time
- 2026-10-01 12:27:00 UTC
- Local: 1 Oct 2026, 21:27:00 (Asia/Tokyo)
- Epicentre
- 35.800° N, 140.700° E
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Circles show this event and others within 45 km from 7 days before to 30 days after. Lines: plate boundaries and GEM active faults. Open on the live map
Nearby places
| Place | Distance | Est. shaking |
|---|---|---|
| SukayamaChiba, Japan · pop. 13,228 | 4 km | IVLight |
| OmigawaChiba, Japan · pop. 25,763 | 9 km | IVLight |
| AsahiChiba, Japan · pop. 64,690 | 10 km | IVLight |
| KamisuIbaraki, Japan · pop. 95,454 | 11 km | IVLight |
| ChoshiChiba, Japan · pop. 58,431 | 14 km | IVLight |
| ChibaJapan · pop. 979,768 | 57 km | IIIWeak |
| IchiharaChiba, Japan · pop. 283,531 | 64 km | IIIWeak |
| MitoIbaraki, Japan · pop. 270,685 | 65 km | IIIWeak |
Shaking is an estimate from the intensity prediction equation of Allen, Wald & Worden (2012), not an observation. Local ground and buildings can change it by a level or more. Likely felt out to about 133 km.
Every agency's solution
Agencies locate earthquakes with their own stations and methods, so their numbers differ. We match reports of the same event by time, distance and magnitude and show them side by side. The headline uses JMA.
| Agency | Magnitude | Depth | Epicentre | Time offset | Status |
|---|---|---|---|---|---|
| JMAheadlineJMA via Japan Meteorological Agency | 5.1 Mj | 50 km | 35.80° N, 140.70° E | – | Automatic |
| GFZGFZ via GEOFON, GFZ Helmholtz Centre for Geosciences | 5.4 Mwwas 5.3 | 46.6 km | 35.63° N, 140.54° E | +12.6 s | Automatic · 2 revisions |
| USGSUSGS NEIC via U.S. Geological Survey | 5.3 mww | 41.6 km | 35.70° N, 140.55° E | +11.9 s | Reviewed |
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How big was it?
Felt by most people over a wide area. Can damage poorly built structures close to the epicentre.
It released roughly the energy of 674 t of TNT. Magnitude is logarithmic: each whole step means about 32 times more energy and 10 times larger waves on a seismogram. Depth matters too: at 50 km this was a shallow earthquake, which is felt more strongly at the surface than a deeper one of the same size.
M5.1 releases about 32× the energy of M4.1, and its waves are about 10× taller on a seismogram. Energy: 674 t of TNT vs 21 t of TNT.
Each square is the energy of one M4.1. Energy from log₁₀E = 1.5M + 4.8.
Aftershocks and nearby activity
2 later earthquakes within 45 km; the largest was M3.6 1 h 17 min ago. 5 in the 7 days before. Aftershock rates usually fall off roughly in proportion to 1/time.
Mainshock M5.1
2 later earthquakes nearby. Aftershock rates typically fall off roughly as 1/time (Omori's law).
| Time after mainshock (hours) | Magnitude | Depth (km) |
|---|---|---|
| 0.07 | 3.6 | 40 |
| 0.40 | 3.3 | 40 |
Did you feel it?
Reports from people help show where shaking was strong. They are anonymous and shown here in aggregate.
Reports on SeismoAtlas
No reports yet.
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Event id jma20261001212719. First recorded here 1 Oct 2026, 12:30:31 UTC. Solutions: JMA (jma:20261001212719); GFZ (geofon:gfz2026tfsz); USGS (usgs:us6000tytg). Cite as: SeismoAtlas, “M5.1 earthquake 4 km SE of Sukayama, Chiba, Japan”, https://seismoatlas.com/earthquake/jma20261001212719-m5-1-earthquake-4-km-se-of-sukayama-chiba-japan, data from JMA, GFZ, USGS.
JSON: /api/v1/events/jma20261001212719. SeismoAtlas is not an official warning service.