1982 Urakawa earthquake

What Happened

At 11:32 on the morning of 21 March 1982, a magnitude 6.9 earthquake struck off the coast of Urakawa, a town on the southern coast of Hokkaidō, the northernmost of Japan's four main islands. The epicentre lay beneath the sea at 42.1°N, 142.6°E, in the waters of the Hidaka Subprefecture. The shaking was felt across a wide stretch of southern Hokkaidō, and it caused 167 injuries.

Damage was recorded in Tomakomai, an industrial port city on Hokkaidō's south-central coast, and in Sapporo, the island's largest city and the prefectural capital. The earthquake was the largest ever recorded in the history of the region.

Background

Japan sits at the junction of four tectonic plates, and the whole archipelago is earthquake country. Hokkaidō's southern coast, where the Hidaka Subprefecture meets the Pacific, is one of the more active stretches. The 1982 event was a shallow offshore quake — the kind that strikes without warning and is felt almost immediately along the nearest coastline.

The date places the earthquake in the Shōwa period (昭和, しょうわ), the reign of Emperor Hirohito, which ran from 1926 to 1989. In the Japanese calendar, 1982 was Shōwa 57, the fifty-seventh year of the era. By the early 1980s, Japan had a dense network of seismic monitoring stations and a well-developed system for recording and reporting earthquakes, which is why the location, depth and magnitude of this event were documented precisely.

Urakawa itself is a small fishing town on Uchiura Bay, facing the open Pacific to the south. Its economy has long depended on the sea, and its position directly above an active offshore fault zone means it has experienced repeated seismic activity.

Why It Mattered

The 1982 Urakawa earthquake stands out in the record because it was the largest earthquake in the history of the region. For the communities of southern Hokkaidō, it was a reminder of how much damage a moderate offshore quake can do even without a major tsunami or widespread collapse of buildings.

The injury toll of 167 shows how the harm from a strong earthquake is often spread across a wide area rather than concentrated in a single disaster zone. Sapporo and Tomakomai, both well away from the epicentre, still recorded damage. The event fed into the broader Japanese effort to understand the seismic behaviour of the Hidaka region, which lies near the boundary where the Pacific Plate dives beneath Hokkaidō.

The Name in Japanese

The Japanese name of the earthquake is 浦河沖地震. It is read in kana as うらかわおきじしん, and in romaji as Urakawa-oki jishin. The name is built from four kanji, and each one carries a distinct piece of meaning.

浦 (read うら, ura) — a small inlet, bay or coastal creek. It appears in place names all over Japan to describe a sheltered stretch of shoreline.

河 (read かわ, kawa) — river. Together, 浦河 (Urakawa) is the name of the town on Hokkaidō's southern coast, written with the characters for "inlet" and "river."

沖 (read おき, oki) — offshore, or the open sea away from the shore. This is the key element in Japanese earthquake names. When 沖 follows a place name, it means the epicentre was located in the sea off that place, not on land beneath it. The same pattern appears in names like 東北地方太平洋沖地震 (the 2011 Tōhoku earthquake), where 沖 signals an offshore epicentre.

地震 (read じしん, jishin) — earthquake. The first character, 地 (ち, chi), means ground or earth; the second, 震 (しん, shin), means to shake or quake. Put together, 地震 is the standard Japanese word for an earthquake.

So the full name translates literally as "the offshore Urakawa earthquake" — the earthquake whose epicentre lay in the sea off the town of Urakawa. Japanese earthquake names follow this template closely: place name, then 沖 if the epicentre was offshore, then 地震. Once a learner recognises 沖 and 地震, the structure of dozens of Japanese earthquake names becomes immediately readable.

Key Figures

• Magnitude: 6.9 (Mw)
• Date and time: 21 March 1982, 11:32 Japan Standard Time
• Epicentre: 42.1°N, 142.6°E, offshore from Urakawa in the Hidaka Subprefecture
• Injuries: 167
• Damage reported in: Tomakomai and Sapporo
• Era: Shōwa 57 (1982), during the reign of Emperor Hirohito