Failure Knowledge Database / 100 Selected Cases

Japan Sea Earthquake
May 26, 1983 along the coast of the Sea of Japan between Akita and Aomori
Masayuki Nakao (Institute of Engineering Innovation, School of Engineering, The University of Tokyo)
A po werful ea rthquake of m agnitude 7 .7 occurred 70 km northwest off the Oga pen insula in Akita andunleashed a tsunami that devastated 8 prefectures located along the coast of the Sea of Japan. Waves struck thecoastal towns bef ore and after a warning was issued, claiming lives of more than 100 people. The earthquakeitself damaged Akita and Ao mori th e m ost, k illing 4 peo ple and dest royed structures, roa ds, rail roads andembankments. Ground liquefaction that occurred as a r esult of combination of earthquake and tsunami heavily
increased the damages. The disaster killed 104 people and destroyed 3,049 homes for a total of $180 billion inproperty damage.
1. Event
A powerful earthquake of m agnitude 7.7 occurred at around noon o n May 26, 1983, at the central JapanSea 70 k m n orthwest off the Oga pe ninsula. I t unleas hed a tsunami that d evastated 8 pr efectures loc atedalong th e c oast of the S ea of J apan and claimed li ves of more than 10 0 p eople. The earthquake itself
damaged Akita an d Aomori th e most, killi ng 4 p eople an d des troyed str uctures, roads, railroads andembankments. Gr ound liquefaction heavily increased the damages in various regions. T he disaster killed
104 people, destroyed hundreds of boats, and damaged 3,049 homes for a total of $180 billion in property
damage.
2. Course
From th e b eginning of May 1983 before th e t sunami-earthquake occurred, there had been several l ittle
earthquakes north west off the Oga pe ninsula, i ncluding t he ones mea sured at m agnitude 5.0 o n May 14(observed magnitude 1 in Akita and Morioka), magnitude 2.3 and 2.4 on May 22.
At around noon on May 26, 1983, a strong earthquake of magnitude 7.7 occurred 70 km northwest off theOga peninsula.
The earthqu ake trans mitted moderate sh ocks of magnitude 5 in Fukaura (Ao mori), Mu tsu (Aomo ri) an d
Akita, and those of magnitude 4 in Aomori and Hashinohe (Aomori). It is reported that residents in various
regions from Hokkaido down to Chugoku noticed tremors under their feet.
Figure 1 shows the epicenter and the intensity of the earthquake.
The earthqu ake generated a des tructive ts unami in the Sea of Jap an. T he fir st tsunami wave t ook only 7
minutes after the earthquake to strike the coast of Fukaura. At 12:07, the sea abruptly withdrew away fromthe shore, t hen 8 minutes l ater at 1 2:15, it r ushed b ack onto t he s hore. The first wave w as fo llowed bynumbers of r unups and backwashes in 10-minute cycle, raising the runup heights of the tsunami wave tothe maximum 65 cm at 13:36 in Fukuhara (initially reported to be 55 cm), 53 cm at 12:08 in Oga, 194 cm
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Failure Knowledge Database / 100 Selected Cases
at 12:24 in Noshiro ( Akita) and 82 cm at 12: 42 in Sakata (Akita). The field stu dy reported that the wave
height was 5 – 6 meters along the coast between Aomori and the Oga peninsula, by 3 – 4 meters in theOkushiri Island (Hokkaido), and by 2 – 3 meters in Sado (Niigata), the Noto peninsula (Ishikawa) and Oki(Shimane).

Figure 1. Epicenter and Intensity of Japan Sea Earthquake [1]At 12:14, the Sendai District Meteorological Observatory issued tsunami warnings for the coastline of theSea of J apan in the Tohoku r egion and the Mutsu bay. Ho wever, t sunami waves had already devas tated2Failure Knowledge Database / 100 Selected Cases
Fukaura and Oga by the time the warnings reached the area.
The earthquake and the tsu nami killed 104 people, destroyed 706 boats, and damaged 3,049 homes for atotal of $180 billion in property damage. The di saster devastated 8 prefectures located along the co ast of
the Sea of Japan. Among the dead, 100 people were killed by tsunami waves. The earthquake caused theheaviest d amage in Akita an d Ao mori, killing 4 people and destr oyed str uctures, r oads, r ailroads a ndembankments. Ground liquefaction heavily increased the damages in various regions.
3. Cause
The tsunami-earthquake occurred just off the west coast of the main island where the North American andEurasian plates collide. It is likely that the earthquake was caused by the Eurasian plate being subductedunderneath J apan. I t is i nevitable t o receive str uctural da mages to buil dings, r oads, r ailroads andembankments wh en a n earthq uake occurs. Ho wever, it is regrettable th at a total of 10 0 of th e 104
earthquake-related fatalities were caused by the tsunami.
The S endai D istrict Me teorological O bservatory issued tsun ami warnings at 1 2:14, but it w as t oo l ate tosave lives of people in Fuk aura and Oga. The fo cal r egion of th e earthquake was c lose to la nd, s o th etsunami struck the coast very quickly after the earthquake. This r esulted in the death of many people who
were unable to flee in time.
Table 1. Victims of the Japan Sea Earthquake [5]Death Caus

Location/Activity(Number of People)ePort construction site

41

Fishing 17

Tsunami100Total
104

On the sea

8Sight seeing

14

Seaweed harvesting2

On the quay

1

Refitting a ship

1

Farm working

4

Others 4
Earthquake4

Shocks of the earthquake

2

Fall of a billboard

1

Fall of a chimney

1

The Graduate School of Engineering at Tohoku University analyzed and published an interesting documentof the study on life-or-death factors. The work discussed the cause of heavy toll of lives in this disaster.
According to the study, 41 among 100 tsunami victims were working at the port construction site, 17 werefishing and 13 were children sight seeing at that time as shown in Table 1.
Based on the interviews and the news ar ticles, t he study team obtained whereabouts o f 20 1 p eople (101survived and 100 de ad) at t he time when the earthquake and the tsunami occurred. It found out wher e the3Failure Knowledge Database / 100 Selected Cases
victims were, what they were doing, when they evacuated, whether or not they heart earthquake warnings,
and whether or not they were swallowed up by the waves. The obtained information were then put together
with the t ime wh en the waves s truck the c oast t owns, the time wh en warn ings w ere iss ued, thecircumstances and the survival determination. Figure 2 summarizes the factors that determined survival ofpeople in the catastrophic event.

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Failure Knowledge Database / 100 Selected Cases

Figure 2. Life-or-Death Decisions and Factors [5]What determined the fate of people were their actions taken before waves reached the shore, and once on
the water, their strength to keep being afloat until they are rescued.
The study team found the following factors that caused a delay in evacuation:
5

Failure Knowledge Database / 100 Selected Cases(1) People were underestimated the power of the earthquake. (Some, including children on a field trip andthose who were fishing, did not know that an earthquake occurred.)(2) People did not expect that the earthquake would generate a tsunami. (The agency issued tsunami
warnings 14 minutes after the earthquake, which gave only 7 minutes for people to escape from thefirst tsunami wave. Some residents evacuated to a nearby beach because they remembered that it wassafe in the past earthquake disasters. Some went to check on their boats after the earthquake.)(3) Evacuation directives were issued too late to save lives. (Concerned only about the earthquake, the port
construction workers simply followed the site supervisor’s instruction. People received evacuation
directives too late to escape from the waves. There was no means to quickly convey evacuation
directives.)(4) People did not have a device to receive tsunami warnings. (Those who were fishing at the time)(5) There was no safe place nearby. (People, such as those who were fishing, were on a rock or an island
where a high ground was nowhere to be found.)4. Immediate Action
To pr epare for aft ershocks, the Gradu ate School of Sci ence, Tohoku Un iversity conducted a special
observation in Oga and Gojome to further enhance the existing micro-earthquake observation network. To
observe aftershock activities in all s urrounding areas, Tohoku University and Hirosaki University worked
together to enabl e process ing of all data collected from each un iversity’s sei smograph net works. The
seismic waveform data was co llected from two s eismograph stations at Iwasaki and Minmaya, which arelocated close to the focal region, and transmitted via a dedicated circuit to Akita and then to Sendai.
Immediately after the e arthquake, the S endai District Meteorological Obs ervatory and t he Ao mori Loca lMeteorological Observatory set up an investigation team and conducted a field study on the tsunami waves
along the coast of the Sea of Japan. Figure 3 shows the direction and runups of tsunami waves measured atcoastal locations indicated by numbers.

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Figure 3. Direction and Runups of Tsunami Waves [1]As shown above, th e wave height o f a tsu nami can be high ly variable i n a lo cal area d epending o n theunderwater topography, orientation to the oncoming wave, the tidal level, and the natural period of the bay.
For exam ple, the Ko domari peninsula has two nearby ports, the Kodomari p ort on its northand theShitamae port o n it s s outh. Tsunami w aves that travel fro m th e northwest w ill resu lt in dif ferent w aveheights at these two ports. Compare to the other ports, smaller waves were observed in Ajigasawa, which isprobably because the shoreline defenses such as breakwaters were effective in weakening the magnitude ofthe tsunami.
5. Countermeasure
In ord er to prepare for a tsunami further, seven ministries, Cabin et Of fice of Government of Japan ,National Police Agency, Ministry of Land, Japan Coast Guard, Japan Mete orological Agency, Ministry ofPosts and Telecommunications, and Fire and Disaster Management Agency, had a meeting “Tsunami KeihoKankei Syocyo Ren raku Kaigi (m eeting of va rious bureaus in go vernment ministries re sponsible for t hetsunami warning)” on June 198 3. On July 1 5, the government min istries and agencies arr ived at aconsensus about improvement in tsunami warning system on coastal areas.
The Akita prefecture improved the system to collect an d transmit inf ormation, as well a s the earthquake
disaster prevention and tsunami risk reduction measures.
Based on the d ata o btained from t his dis aster, t he go vernment de veloped t he r ecovery plan and7

Failure Knowledge Database / 100 Selected Casesimplementation of liquefaction countermeasures for lifeline utilities.
6. SummaryThe 1983 J apan Sea earthquake was the strongest of all th at occurred on the Sea of Japan in history. Thearea h ad not have an earthquake as p owerful as magnitude 5 s ince May 16, 1968 when the Tokachi-Oki
earthquake of magnitude 7 .9 occurr ed at th e J apan T rench. Japan Meteorological Agency named thisearthquake “Nihonkai-Chubu (Japan Sea) Earthquake of 1983”.
In addition to the earthquake, tsunami waves caused extensive damages to the communities. A total of 100of the 104 earthquake-related fatalities were caused by the tsunami. The resulting death tol l indicates thatthe people failed to evacuate within the period of time between the earthquake and the tsunami.
While foresh ock act ivity was ob served beg inning on May 14 i n an area n ear the ep icenter of th e main
shock, crisis management may not have been strong enough to prepare for th e main shock and a tsunami.
Local residents, who had b een advis ed in the pas t to evacuate to a beach during a n ear thquake, f ailed totake an appropriate action for a rare tsunami-earthquake on the Sea of Japan.
7. Knowledge
Personal judgmen t, co mmon sense and o ther p eople’s action d etermine the fate of p eople in a tsu nami
disaster. The learned lessons are:
(1) A tsunami may strike coastal towns before tsunami warnings.
(2) An efficient and reliable means of communication is required for a better assessment of the situation.
(3) A local community must be prepared for disaster relief and rescue plan.
(4) People must know how to keep afloat on the water without needlessly exhausting themselves.
8. Background
Since the beginning of th e S howa er a (1926) unt il the 1983 Japan S ea e arthquake, ther e h ad b een threeearthquakes occurred west off the Tohoku region in the Sea of Japan as shown in Table 2. None of them did
much damage with tsunamis.
There is also the Niigata earthquake occurred off the main island in the Sea of Japan on June 16, 1964 thatmeasured magnitude 7.5. It did not cause any damage in Aomori.
Table 2. Earthquakes Occurred West off Tohoku in the Sea of Japan during the Showa Era [1]Date EpicLMay 1, 1939
May 7, 1964
Dec. 11, 1964

atitude
40.1
40.3
40.4

Longitude
139.5
139.0
138.9

enter
Depth0 km0 km
40 km

Area
Off Akita
Off Akita
Off Akita

8Scale(Magnitude)
6.8
6.9
6.3

Magnitude
FukauraAomori43
43
33TsunamiTsunamiWeak tsunami
Very weaktsunami

Failure Knowledge Database / 100 Selected Cases
It is als o docu mented that in th e p eriod between September 19 78 an d th e fall of 19 79, a series o fearthquakes had occurred in the town of Iwasaki located at west coast of Aomori. While earthquake swarm
activities had rarely occurred in th e ar ea, such a ctivities are doc umented in Oma goshi about 1 0 y ears
before the powerful earthquake in Aomori and Akita. Before that in history were in 1694 (Genroku 7) andin 17 04 ( Hoei 1 ). Un derstanding th e pa ttern, H irosaki Univ ersity decide d to obs erve th e ar ea a fter theearthquake swarm activities calmed down. It planed to install a seismograph on the Kyuroku Island located
40 km off the town of Iwasaki in Aomori, and visited the island in 1980. However, the plan was aborted
because it found that the island and surging waves did not provide desirable surroundings for observation.
References[1] Nihon-Kai Cyubu Jishin (Japan Sea Earthquake),
http://www.bousai.pref.aomori.jp/jisinsouran/nihonkai/select_menu.htm[2] Ministry of Land, “Bosai Home Page (Disaster Prevention Home Page),
http://www.bousai.go.jp/kazan/sinkasai/s311.htm[3] Ministry of Land, “Waga Kuni-no Jishin Taisaku-no Hensen, Mitei-ko (Changes in Japan’s Earthquake
Disaster Prevention Measures, under review), http://www.bousai.go.jp/jishin/chubou/taisaku/8/sankou1.pdf[4] Akita Local Meteorological Observatory, “Bosai Memo (Notes on Disaster Prevention) – 20 Years from the1983 (Showa 58) Japan Sea Earthquake”, http://www.sendai-jma.go.jp/tidai/akita/pdf/2003_4.pdf[5] Motoko Kaneda, et al., “Tsunami Raisyu-ji-ni Seishi-o Wake-ta Yooin (Factors Determined Survival inTsunami Disaster) – Case Study of 1983 Japan Sea Earthquake”, Koen Gaiyoo (Summary of Lecture) at
Tohoku Chapter, Japan Society of Civil Engineers, Graduate School of Engineering, Tohoku University.

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