1945 Mikawa earthquake

What Happened

At 03:38 on the morning of 13 January 1945, the ground shook beneath the coast of Aichi Prefecture in central Japan. The earthquake is known as the 1945 Mikawa earthquake (三河地震, Mikawa jishin). Its epicentre lay offshore, at roughly 34.7° north and 137.1° east, a point in the sea south of the Chita Peninsula and the old Mikawa region.

The timing was catastrophic. The shaking struck in the middle of the night, when families were asleep in wooden houses with heavy tiled roofs and open hearths. Fires broke out in the dark, and the collapse of buildings trapped people inside them. The earthquake struck Japan in the twentieth year of the Shōwa era (昭和20年), the same year the country would surrender to end the Second World War.

Because Japan was still at war, the government suppressed news of the disaster. Reporting on the earthquake was censored, and the scale of the destruction was kept from the public. That secrecy directly hampered relief efforts: outside help was slow to arrive, and the dead and injured could not be accounted for in the usual way. The censorship is widely understood to have contributed to the high death toll.

Background

The Mikawa earthquake belongs to a well-documented pattern of seismic activity in central Japan. The islands sit at the junction of several tectonic plates, and the region around Aichi, Shizuoka and Mie prefectures has produced repeated destructive earthquakes over the centuries. The Mikawa event was one of a cluster of large earthquakes that struck Japan during the 1940s.

By January 1945, Japan had been at war for more than three years, and since 1941 had been fighting the United States and its allies across the Pacific. The country was under strict wartime controls. Newspapers and radio were instruments of the state, and the government had a standing policy of concealing information that might damage morale or reveal weakness. Natural disasters fell squarely under that policy.

The name "Mikawa" refers to Mikawa Province (三河国, Mikawa no kuni), an old administrative region that corresponds to the eastern part of present-day Aichi Prefecture. Provinces of this kind were the basic geographical units of Japan for centuries before the modern prefecture system replaced them in the Meiji period. Earthquakes in Japan are traditionally named after the province or region where the damage was greatest, and this one took its name from Mikawa.

Why It Mattered

The most consequential fact about the Mikawa earthquake is not its magnitude but the response to it. Wartime censorship meant that the disaster was not reported as it happened. People outside the affected area did not know the extent of the damage, and the machinery of relief that might have mobilised was not set in motion. The result was a higher death toll than the earthquake alone would have caused.

The episode became a lasting example of how information control can cost lives. In a country as earthquake-prone as Japan, the free flow of information after a disaster is now treated as a basic element of public safety. The Mikawa earthquake is remembered as a case where the priorities of the state and the safety of ordinary people came into direct conflict — and the state's priorities won.

The earthquake also came at a moment when Japan's attention was fixed elsewhere. In the final year of the war, cities across the country were being destroyed by bombing, and the government was focused on the war effort. A disaster in a rural coastal region, however deadly, was easy to bury. The full story of what happened in Mikawa only emerged after the war ended.

The Name in Japanese

The Japanese name of the earthquake is 三河地震. Its reading in kana is みかわじしん, and its romaji is Mikawa jishin.

Breaking it down character by character:

• 三 — read here as み (mi). It means "three". It is one of the most basic numerals in Japanese, and it appears in a great many place names.
• 河 — read here as かわ (kawa). It means "river". Note that the reading is kawa, not the other common reading ka, because the two characters 三河 are read together as a single place name.
• 地 — read here as じ (ji). It means "earth" or "ground". It is the first element in a large family of Japanese words relating to the earth and to disasters.
• 震 — read here as しん (shin). It means "shake" or "quake". It is the character used for seismic phenomena.

The compound 地震 (じしん, jishin) is the ordinary Japanese word for "earthquake". It is worth remembering as a unit: 地 "earth" plus 震 "shake" gives "earthquake", and the same two characters appear in words for aftershocks, seismic intensity and earthquake preparedness.

The first two characters, 三河 (みかわ, Mikawa), are the name of the old province. So the whole name means, literally, "Mikawa earthquake" — the earthquake of Mikawa. The same naming pattern appears throughout Japanese seismology: the place name comes first, and 地震 comes second.

One small reading note for learners: when 三河 appears as a place name, the 河 is read kawa, not ka. Japanese place names frequently use readings that differ from the ones a dictionary gives for a character in isolation, and Mikawa is a standard example.

Key Figures

The historical record for this earthquake centres on the event itself rather than on named individuals. The essential facts are these:

• Date and time: 13 January 1945, at 03:38 in the morning.
• Location: offshore near Aichi Prefecture, Japan, at approximately 34.7° north, 137.1° east.
• Region affected: the Mikawa area, corresponding to eastern Aichi Prefecture.
• Historical period: the Shōwa period (1926–1989), in the twentieth year of the Shōwa era.
• Named after: Mikawa Province (三河国, Mikawa no kuni).
• Defining circumstance: the earthquake occurred during the Second World War, and news of it was censored by the Japanese government. The suppression of information hampered relief efforts and contributed to the high death toll.