1. Chart of Japanese Tsunamis
| | | |
| Aug-10-1901 | Japan (Sanriku) | 18 |
| Jul-07-1905 | Japan (Fukushima) | 41 |
| Jan-12-1914 | Japan (Seikaido) | 35 |
| Sep-01-1923 | Japan (Tokaido) | 2,144 |
| Mar-07-1927 | Japan (South-West Honshu) | 325 |
| Mar-02-1933 | Japan (Sanriku) | 3,000 |
| May-29-1938 | Japan (Hokkaido) | 1 |
| Aug-02-1940 | Japan (Hokkaido) | 7 |
| Nov-18-1941 | Japan (Seikado) | 2 |
| Dec-21-1946 | Japan (Nankaido) | 1,997 |
| Mar-04-1952 | Japan (Southeast Hokkaido) | 33 |
| May 16-1968 | Japan Trench | 52 |
| May-26-1983 | Japan (Noshro) | 103 |
| Jul-12-1993 | Japan | 120 |
The 1700 Cascadia Earthquake
On January 6, 1700, at about 9:00 p.m. Pacific Standard Time, a gigantic earthquake occurred sixty to seventy miles off the Pacific Northwest coast. The quake violently shook the ground for three to five minutes and was felt along the coastal interior of the Pacific Northwest. A tsunami formed, reaching about 33 feet high along the coast, and then traveled across the Pacific Ocean and hit the east coast of Japan.
The earthquake ruptured what is known as the Cascadia subduction zone - the area of overlap between two of the tectonic plates that make up the earth's surface. These plates are the Juan de Fuca and the North American. The Cascadia subduction zone extends from Vancouver Island, British Columbia south to cape Mendocino in Northern California. The earthquake dropped the entire Pacific Northwest ocean coastline three to six feet.
The tsunami traveled across the Pacific Ocean for some 10 hours and at midnight on January 27, 1700, local time, it hit the east coast of Japan. By then the tsunami was only 6-10 feet high but it still did significant damage.
The very existence of this magnitude 9 earthquake was unknown just twenty years ago. An early breakthrough came in 1987 when U.S. Geological Survey geologist Brian Atwater reported geological traces of giant earthquakes along Washington's Pacific coast. These traces included groves of trees that were killed when an earthquake lowered forests into the salt water. Another important clue was reported a few years later when the earthquake was dated to the decades between 1680 and 1720. This clue came from radiocarbon tests by Minze Stuiver of the University of Washington. Meanwhile in Japan, several researchers were following these developments. They consulted their nation's archives of old writings about earthquakes and tsunamis. For the period between 1680 and 1720 they found one orphan tsunami that could have come from Cascadia. That tsunami occurred in January of 1700. Finally, a final clue was found in the groves of killed trees on the Washington coast. Using annual growth rings in the trees, David Yamaguchi of Seattle and Gordon Jacoby of Columbia University showed that the trees lived through the 1699 growing season but were dead by the following spring - exactly the dates expected if the earthquake occurred in January 1700.
Article on the 1700 tsunami - "Rememberance of Waves Past"
December 31, 1703 - Genroku
The Genroku Earthquake is thought to have been an interplate earthquake whose focal region extended from Sagami Bay to the tip of the Boso Peninsula as well as the area along the Sagami Trough in the open sea southeast of the Boso Peninsula. It generated strong ground motion over a wide area centered in the southern Kanto region. Reports on the damage theorized that ground motion corresponded to a seismic intensity of 6 on the Richter scale. This earthquake then resulted in a tsunami that hit the coastal areas of Japan and the Boso Peninsula. The tsunami caused more than 6,500 fatalities on the peninsula. In Awa, Japan, however, the tsunami was reported to have killed more than 100,000 people - possibly the most destructive tsunami ever.
| Date (UTC) | Time (UTC) | Source Location | Magnitude | Source Type | Max Runup in AOR (m) |
| June 15, 1896 | 10:32:00 | 39.5N 144.0E | 7.2 | Earthquake | 1.5 |
The earthquake occurred on the evening of the Boy's Festival Day (Tango-no-sekku) on the lunar calendar, and many people had gathered indoors for the parties. This delayed evacuation and is the reason cited for the drowning deaths of thousands. The tsunami, which was generated by the earthquake off the coast of Sanriku, Japan, attained a height of 25 meters and instantly swept away all houses and people when it reached land.
One hundred years after this earthquake, two researchers became determined to figure out its source. Yuichiro Tanioka of the Department of Geological Science of the University of Michigan, and Ann Arbor and Kenji Satake of the Seismotectonics Section of the Geological Survey of Japan, Tsukuba, developed a model using a modern computer simulation. The results of their research indicate that the source of the earthquake was very close to the Japan trench. They estimated that the fault that generated the earthquake had a width of 50 kilometers, and the movement along the fault was 5.7 meters. The earthquake ruptured beneath an accretionary wedge, a relatively shallow area. If a substantial occurs in the same area in the future, a resulting tsunami could be unusually large, like the 1896 event.
4. September 1, 1923 - Kanto
The morning of Saturday, September 1, 1923, was very hot with strong gusts of wind that followed rain. Soon it was almost noon and the area around Sagami Bay, Japan began to shake in what amounted to a magnitude 8.3 earthquake. A section of the fault under the bay was measured to have been displaced nearly 240m, and although no surface faults appeared, new ridges 180 to 300 ft tall appeared on the sea floor in line with a pre-existing volcanic chain. The ground was uplifted and hundreds of landslides were triggered. This Kanto Earthquake generated a tsunami approximately 30-40ft high which crashed unto shore about 5 minutes later. Many were killed, houses were destroyed, and nearly 45% of the population was left unemployed. In all, seven prefectures were affected by the tsunami. These were Tokyo, Kanagawa, Shizuoka, Chiba, Saitama, Yamanashi, and Ibaraki. The greatest destruction occurred at Yokohama, which at the time was the premier commercial port of Japan. An unusual characteristic of the Great Kanto Earthquake was the dramatic upheaval and depression of the ground. The earth was uplifted as high as 24ft, substantially changing the shape of the shoreline.
No less ferocious in nature than the earthquake itself was the conflagration that followed. When it struck, coal or charcoal cooking stoves were in use throughout Toyko and Yokohama in preparation for the noon-time meal and fires sprang up everywhere within moments of the quake. Fire-induced wind spawned numerous cyclones, which further spread the flames. The uplifting and depression of the land also resulted in landslides. Towns were buried by a massive mudflow, killing hundreds.
The combination of the earthquake and tsunami created massive destruction. The total number of houses partially or completely destroyed numbered in excess of 694,000. In addition to houses, the list of damage includes buildings, dams, tanks, tunnels, sewers, towers, canals, retaining walls, and lighthouses. Telephone and telegraph systems were demolished leaving the people completely cut off from the outside world. Streets were choked with rubble making them impassible by automobile.
5. December 21, 1946 & March 4, 1952
The Nankai Earthquake of December 21, 1946, was an interplate earthquake with a source region in an area along the Nankai Trough. The seismic ground motion from this earthquake is estimated to have corresponded to a seismic intensity of 6 in JMA scale. A tsunami generated by this earthquake caused significant damage in many areas. The tsunami height was 4 to 7 meters along the Pacific coast. It did reach as high as 11m in some places, however. This tsunami caused damage through the reversed flow in the Kizugawa River and the Ajigawa River in Osaka. There were a total of 1,443 dead or missing, 3,842 injured, and 9,000 houses completely collapsed. There were a total of forty aftershocks of magnitude 5 or larger accompanying this earthquake that lasted until April of 1947, resulting in crustal deformation of the land.
According to the Japan Meteorological Agency, the March 4, 1952 Tokachi-oki Earthquake corresponded to a seismic intensity of 8.1. The maximum tsunami height reached 3 to 4m on the Pacific coast f eastern Hokkaido. It caused 28 deaths, injured 287, and destroyed 8,534 houses.
A tsunami occurred on May 26, 1983, at the middle of the East Sea and propagated across the basin and caused substantial damages along the coasts of Japan and Korea. The tsunami, generated by a magnitude 7.9 earthquake destroyed 700 boats and 59 houses for a total of $800 million in property damage in Japan. 104 people drowned in Japan and 3 in Korea. The earthquake itself damaged 5,100 houses and ended several lives. As a result of the combination of earthquake and tsunami, a process of liquefaction occurred. Liquefaction happens in areas where unconsolidated materials are saturated with water. Under these conditions, what had been a stable soil turns into a fluid that is not capable of supporting buildings or other structures.
Liquefaction
July 12, 1993
Over the years, the Japanese people have grown accustomed to the numerous tsunami occurrences. They know that they cannot control the forces of nature, but they can become prepared. On the night of July 12, 1993, their preparations faced a brutal test. A magnitude 7.8 earthquake in the Sea of Japan generated a tsunami that struck various parts of the small island of Okushiri.
Simulation of the 1993 tsunami
Five minutes after the main shock the Japan Meteorological Agency issued a warning over television and radio that a major tsunami was on its way. By then, 10- to 20-meter waves had struck the coastline nearest the sources, claiming a number of victims before they could flee. However, 1,200 people escaped the waves when they ran inland after feeling the shaking.
The $600 million in property losses were attributed to the tsunami. This tsunami causes spectacular localized damage, especially on the southwestern shores of Hokkaido and on Okushiri Island. Numerous fires, fueled by above-ground kerosene and propane tanks, broke out following the tsunami, adding to the property loss and misery. The tsunami stripped plants and grasses from the hillside leaving debris in the overhead utility wires. Vertical runup measurements varied between 15 and 30m over a 20km portion of the southern part of Okushiri Island, with several 10m values on the northern portion. As of July 21, 185 fatalities were confirmed, with 120 attributed to the tsunami. The death toll was expected to rise, as missing persons were included among the fatalities.
Article on the July 12, 1993 tsunami - Okushiri, Japan
Recent Destructive Tsunamis
| Location | Date | Damage (in Millions) | Earthquake Magnitude | Max Runup | Deaths |
| Nicaragua | September 1992 | Extensive | 7.2 | 9.7 | 170 |
| Indonesia | December 1992 | Extreme | 7.5 | 26.0 | 1000 |
| Japan Sea | July 1993 | 600 | 7.8 | 31 | 185 |
| Indonesia | June 1994 | 2.2 | 7.2 | 14 | 250 |
| Kuril Islands | October 1994 | Local | 6.8 | ? | 1 |
| Alaska | November 1994 | 21 | Landslide | 10 | 1 |
| Philippines | November 1994 | 25 | 7.0 | 10 | 62 |
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