Boso Offshore (房総沖) — Earthquake Risk & History
Kanto region · Based on HERP official data
The waters off Boso Peninsula sit above a complex triple junction of the Pacific, North American, and Philippine Sea Plates. Slow-slip events are observed on a roughly 5-year cycle, and their potential to trigger larger earthquakes is under active study.
Fault Lines & Seismic Characteristics
Active Faults & Trenches
- Boso Triple Junction
- Japan Trench
The waters off Boso Peninsula sit above a complex triple junction of the Pacific, North American, and Philippine Sea Plates. Slow-slip events are observed on a roughly 5-year cycle, and their potential to trigger larger earthquakes is under active study.
Earthquake History
- M9.0
Future Probability — HERP Official Assessment
Long-term probability for this area is available on the HERP official website.
🔗 HERP Official Website →Traveler Safety Information
Finding Evacuation Shelters
- ✅ Search "避難所" (hinanjo) on Google Maps to find the nearest shelter from your current location
- ✅ Install NHK World or Safety tips (Japan Tourism Agency app) — both send English earthquake alerts
Basic Action Rules
- ✅ At check-in, locate emergency exits and escape routes
- ✅ On strong shaking: protect your head, open a door to secure an exit, do not use elevators
- ✅ Near coasts or rivers: move to high ground immediately — do not wait for a tsunami warning
- ✅ Emergency numbers: Police 110 · Ambulance/Fire 119
- ✅ Contact your embassy in Tokyo for emergency consular assistance
Research & Official Sources AI summary
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Boso Peninsula slow-slip and earthquake triggering risk
Slow-slip (silent fault creep) events are observed offshore Boso Peninsula approximately every 5 years. If one of these episodes triggers a regular earthquake rupture, it could directly impact the greater Tokyo metropolitan area.
Source: 방재과학기술연구소 (2023)
Related Guides
Seismic characteristics and research summaries on this page are AI-generated from publicly available data by JMA, Cabinet Office, and HERP. Historical earthquake data (year, magnitude, damage) is based on official records, but key figures should always be cross-checked with the latest official sources. This page does not predict future earthquakes.