Gunma Prefecture (群馬県) — Earthquake Risk & History
Kanto region · Based on HERP official data
Gunma is mostly inland mountains with limited exposure to trench earthquakes. However, active volcanoes (Kusatsu-Shirane, Asama) generate volcanic earthquakes with little warning, and the prefecture lies within the broader Kanto earthquake influence zone.
Fault Lines & Seismic Characteristics
Active Faults & Trenches
- NW Kanto Plain Margin Fault Zone
Seismic Characteristics
Gunma has active volcanoes including Kusatsu-Shirane and Asama, where volcanic earthquakes can occur with little warning. The Northwest Kanto Plain Margin Fault Zone traverses the southern part of the prefecture. There is no direct tsunami risk in this landlocked prefecture.
Earthquake History
- M6.9
1931
Nishi-Saitama earthquake — near Gunma–Saitama border; significant building damage
- M4.3
2018
Kusatsu-Shirane eruption — phreatic eruption near ski slopes; 1 JSDF soldier killed, 11 injured
※ Showing M6+ or Intensity 4+ events. Source: JMA database.
Future Probability — HERP Official Assessment
30-Year Probability (Official Figure)
Long-term evaluation by the Earthquake Research Committee. Volcanic earthquake activity is difficult to predict — always check JMA volcanic alert levels when visiting Kusatsu-Shirane.
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
- ✅ Gunma Prefecture official disaster prevention page (Japanese) — includes shelter maps
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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Kusatsu-Shirane volcano and volcanic earthquakes
Volcanic earthquakes occur frequently around Kusatsu-Shirane. The 2018 phreatic eruption near a ski slope killed one person and injured 11 — with very little advance warning.
Source: 기상청 화산과 (2020) -
Volcanic tourism safety at Kusatsu, Haruna, and Akagi
Always check JMA volcanic alert levels (1–5) before visiting active volcanic areas. Kusatsu-Shirane remains active and some hiking routes may be restricted. Volcanic earthquakes can strike without warning near active craters.
Source: 기상청 화산과·군마현 관광국 (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.