Failure Knowledge Database / 100 Selected Cases

Eruption of Mount Usu
March 31, 2000 at Mt. Usu in Hokkaido
Masayuki Nakao (Institute of Engineering Innovation, School of Engineering, The University of Tokyo)
On March 27, 2000, volcanic activity and the number of earthquakes started to show an increase around Mount
Usu located on the No rthern Japanese island of Hokkaido. Some fault lines were found in the western side of
Mt. Usu. At 13:07 o n March 31, the western flank o f th e mountain er upted f or t he first time in 2 3 y ears,
sending white smoke and ash over a large area including the towns of Abuta, Soubetsu, Otaki and the cities ofTomakomai and Chitose (Figure 1). The second eruption from Mt. Kompira spewed hot rock and steaming mud
towards the hot spring resort towns, swallowing bridges nearby.
Experts say that Mt. Usu erupted because a lava dome located 10 k m below the surface grew as a deeper core
eruption spewed lava into it.
Despite th e thr eat of powerful vol canic activity, ther e we re no inj uries or fat alities. It was lar gely due toeffective crisis management, whic h enab led quic k ci rculation o f in formation, cooperation of agencies,
preparation of a hazard map, and safety consciousness of residents. As a result, 234 homes were destroyed and217 homes were damaged. The overall damage amounted to 10.3 billion yen. Photo 1 shows the first eruptionof Mt. Usu.

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Failure Knowledge Database / 100 Selected Cases
Photo 1. Mt. Usu Eruption with Pyroclastic Flows, the First Time in 23 Years [1]1. Event
On March 27 , 2000, vo lcanic tem blor and activ ity a nd the nu mber of e arthquakes st arted t o show anincrease around Mt. Usu located on the Northern Japanese island of Hokkaido. Some fault lines were foundin the western side of Mt. Usu. At 13:07 on March 31, the western flank of the mountain erupted for the
first time in 23 y ears, sen ding whit e smoke a nd a sh over a la rge ar ea i ncluding th e to wns of Abuta,
Soubetsu, Ota ki an d t he cities of Tomakomai a nd Chitose ( Figure 1). The second eruption from M t.
Kompira s pewed hot rock and steamin g mud towar ds the hot spri ng re sort towns, swallowing b ridges
nearby.
Despite the threat of powerful volcanic activity, there have not been any injuries or fatalities.
As a result, 234 hom es were des troyed and 217 ho mes were da maged. The overall damage amo unted to10.3 billion yen. Photo 1 shows the first eruption of Mt. Usu.

Figure 1. Communities Affected by Eruption of Mt. Usu
2. Course
On Mar ch 2 7, the Muroran L ocal Meteorological Ob servatory and th e Usu Volcano Observatory o f
Hokkaido University obtained readings of three earthquake activities near Mt. Usu by noon. The frequencyof earthquakes increased every hour. The number of earthquakes in an hour almost multiplied to 7, 13, 24,
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Failure Knowledge Database / 100 Selected Cases
and 42 t remors starting at 19:00 on the same day. There were total 109 earthquakes on that day (normally
20 to 30 a month).
On March 28, out of 590 volcanic earthquakes, 69 were noticeable to the residents of nearby towns.
On March 29, volcanic activity intensified around Mt. Usu. The area had 1,628 tremors including the onesof magnitude 3.4 and 3.5 occurred at 7:08 and 9:42 respectively, in wh ich 6 28 were n oticeable to theresidents.
On March 30, Japan Ground Self-Defense Force sent a helicopter to the site just above the hypocenter of
volcanic earthquakes, and experts including Professor Okada, director of the Usu Volcano Observatory of
Hokkaido University (located in the mountainside of the Sobetsu hot spring resort) observed new chains ofcracks as long as 100 meters in the nor thwestern part of the caldera rim (at the west r idge of the no rth
Byobu mountain). New fault lines were also found in front of Toya Kyokai Clinic in the hot s pring resort
town of Lake Toya as well as near the hot spring r esort town of Sobetsu. The daily volcanic earthquakes
had increased to 2,454, in which 537 were noticeable to the residents.
On March 31, the volcano erupted at 13:07 after two decades of silence, spewing a plume of ash and smokeover the surrounding areas. At 14:00, a plu me of ash rose over 3,200 meters into the sky from the crater
located at th e western p art of the su mmit, and was car ried east-northeast by the wind. Although theemission of ash and cinders declined to 800 meters in height as the eruption declined about 2 hours later ataround 15:0 0, volcanic ash reached a la rge area including t he towns o f Abuta, Soubetsu, Otak i and thecities of Tomakomai and Chitose.
In the early morning at 3:12 on Apr il 1, while the l argest tremors of magnitude 4.8 (5.0 in Sobetsu), were
jolting the area, a nother er uption o ccurred near the R oute 230 in t he flank o f M ount Konpira located a tnorthwest of the craters that er upted on the prev ious day. The third eruption occurred at 11:50 about 350
meters south of th e hot spring resort town of Lake Toya, which was 600 meters east of the craters that had
already erupted.
On April 2, the eruption activity continued at Mt . Konpira. Hot rock, gas and a p lume of ash and smoke
billowed ov er the tow ns ne arby. The steaming mud flowed dow n t he mou ntain t owards the h ot spring
resort town of Lake Toya.
On April 9, the steaming mud flowed over a landslide prevention barrier at t he Nishiyama River channel
and into a drain that runs through the resort area.
On April 10, the steaming mud washed away two bridges at the Nishiyama River.
As se ismic activity near the v olcano b egan to increase, approximately 16, 000 r esidents of the Usu
communities of Date, Sobetsu and Abuta moved to evacuation centers, where people stayed for 5 days atleast and 5 months at most.
3. Cause
The eruptions of Mt. Usu were most likely caused by subsurface magma movements. A lava dome located
10 km below Mt. Usu grew as a deeper core eruption spewed lava into it. Volcanic earthquakes took place3

Failure Knowledge Database / 100 Selected Cases
as the magma in the lava dome sought surface vents and broke bedrocks (precursors to a volcanic eruption).
Magnitude of earth quakes became s tronger as the magmas ascended to the s urface. Cracks occur on thefragile parts of the bedrocks as magmas ascended to a depth of 2 to 3 km. Magmas then passed through theaquifers located 100 meters be low the sur face, c ausing v iolent water-assisted explosions t hat spewed
fragmented magmas.
Figure 2 (1) through (6) illustrate the steps from outbreak to end of the eruptions.

Figure 2. Outbreak to end of eruption [1]Despite the massive steam explosions, there were no injuries or fatalities. In the next section, we will see in4Failure Knowledge Database / 100 Selected Cases
details on the crisis management taken during the volcanic activity.
4. Immediate Action
The government and agencies took various actions as they observed a development of volcanic activity.
There are four types of volcanic information that a meteorological observatory issues.
In or der to wat ch v olcanic acti vity f ull-time, se ismographs a nd ob servation cameras ar e se t up at t heobservations sites of five active volcanoes, Mt. Meakan, Mt. Tokachi, Mt. Tarumae, Mt. Kom aga and Mt.
Usu. A meteorol ogical ob servatory issues “perio dic volcanic information” to repor t the up-to-date
information on volcanic activity on a regular basis. Of the higher degree of urgency than this is “volcano
observation infor mation” which a m eteorological o bservatory i ssues to re port det ailed i nformation on
volcanic a ctivity either per iodically or as ne eded. The next ur gently issued is “special bull etin” which a
meteorological obs ervatory i ssues to w arn the public of ab normal volc anic a ctivity. Then, “ emergency
volcanic alert” is issued t o alert the public when volcanic activity is inten sified and p otentially lif e
threatening.
At 0 :50 on March 2 8, t he Mu roran L ocal Meteorological Obs ervatory issued t he firs t sp ecial bulletin
reporting “Earthquake activities increased near Mt. Usu. The focal area of noticeable tremors was near Mt.
Usu”. At 1 1:00, a press conference was held at the Sobetsu town office, and Professor Hiromu Okada of
Hokkaido University reported a possible volcanic earthquake in a near future. At 11:50, Yoshiaki Iida, thechairman of the Co ordinating Co mmittee for P rediction of V olcanic Eruptions (Japan Me teorological
Agency) warned th e public of a poss ible volcan ic er uption. Officials issued a v oluntary ev acuation
advisory to certain areas of the towns of Date, Abuta and Sobetsu. About 400 residents were evacuated.
At 11:10 on March 29, the Muroran Local Meteorological Observatory issued the first emergency volcanic
alert alarming the public of the increasing frequency of earthquakes as a signal of an imminent eruption. At
18:15, Professor Okada had a press conference and reported an increased likelihood of an eruption from thenorthwest flank of Mt. Usu in the next few days, if not definitely in a week. Officials issued an e vacuation
advisory, whi ch w as soon r aised to a n eva cuation dir ective at 1 8:30, to th e to wns of Date, Abuta a nd
Sobetsu. About 9,500 residents left their homes. (Out of 1,628 tremors on that day, 628 were noticeable t o
the residents.)
At 10:00 on March 30 , the Mt. Usu F ield Liaison an d Coordination Co mmittee stu died the hazard map(Figure 3).
At 3:20, the M uroran Local Meteorological Observatory issued the second e mergency volcanic a lert
alarming the public of th e n ew chains of cracks as long as 100 meters in th e northwestern p art o f thecaldera rim ( at th e west r idge o f the n orth By obu mountain). Officials iss ued a n e vacuation d irective toresidents (475 households and 1,319 residents total) of Tsukiura, Irie and Takasago in the town of Hikita.
(The daily volcanic earthquakes had increased to 2,454, in which 537 were noticeable to the residents.)
At 13:07 on March 31, the volcano erupted from the western flank of the mountain for the first time in 23
years.
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Failure Knowledge Database / 100 Selected Cases
At 14:00, a cabinet meeting was held in the office of the Prime Minister to su pport the setting up of two
emergency centers, the Mount Usu Eruption Emergency Center and the Field E mergency Center (at Date
City Hall). Officials issued an evacuation directive to all areas of the town of Hi kita except Shimizu andHanawa. (The evacuated reached 15,815 in total.)
On April 1, another eruption occurred in the flank of Mount Konpira.
On April 2, the eruption activity continued at Mt. Konpira spewing hot rock, steaming mud, a plume of ash
and smoke. The steaming mud flowed down the mountain towards the hot spring resort town of Lake Toya.
Officials lifted the evacuation order for selected areas (total 123 households and 375 residents) in the cityof Date. Among the Abuta residents staying at the Toyoura shelters, 2,000 were relocated to shelters in thetowns of Osyamanbe and Toya.

Figure 3. Hazard Map of Mt. Usu, Modified after 2000 Eruption [1]On April 5, the Coordinating Co mmittee fo r Pr ediction of Volcanic Erupt ions of Mt. Usu (Japan
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Failure Knowledge Database / 100 Selected Cases
Meteorological Agency) rePORT 68,166,190,246,130,116
eruption could occur within the couple of days, if not within the next two weeks.
On April 7, the government s tarted building regular relocation facilities to provide 500 ho mes forevacuated people.
On April 8, officials allowed one-hour visit of resid ents to their homes in the town of Sy owa-Shinzan andthe hot spring resort town of Sobetsu.
On April 9, the steaming mud flowed over a landslide prevention barrier at t he Nishiyama River channel
and into a drain that runs through the resort area.
On April 10, the steaming mud washed away two bridges at the Nishiyama River.
On April 12 , the Coordinating Co mmittee for Prediction o f Volcanic E ruptions ( Japan M eteorological
Agency) announced that there was no s ign of a violent eruption and the volcanic activity might r emain in
the present state for a while.
On A pril 13, 4 ,700 residents of on e ci ty and tw o towns began to r eturn home af ter officials lifted someevacuation or ders that had bee n in pla ce. All r esidents of th e city of Da te wer e allowed to leave theevacuation sites.
On April 22, the Coordinating Committee for Prediction of Volcanic Eruptions and experts reported that the
volcano appeared to calm down.
On May 2, the government completed construction of regular relocation facilities in the towns of Sobetsu
and Toyoura.
On May 22 , th e Coordinating Committee fo r Pr ediction of Volcanic Erupt ions and ex perts rep orted th atvolcanic activity would begin to s ubside, b ut the co mmunities near th e er uption si tes w ould r equirecontinued vigilance against volcanic activity.
On June 8, JR started normal operation on the Muroran main line.
On July 10, the Coordinating Committee for Prediction of Volcanic Eruptions and experts reported that thelava dome located below the volcano stopped growing and underground magma activity began to subside.
Two of the hotels in the hot spring resort town of Lake Toya were reopened.
On July 13, the Mt. Usu cable car started its normal operation.
On July 18 , of ficials a llowed r eopening o f 1 6 bu sinesses out of 1 9 businesses p articipating in th e Toya
Tourist Association.
On August 8, the Hokkaido government proposed to zone the areas near Mt. Utu into 4 at the meeti ng ofvarious project managers in municipality o f t he vicinity of Mt. Usu ( Mt. Usu sy uhen k ankei c hi-cyo
kikaku kacyo kaigi).
On August 10, the Coordinating Committee for Pr ediction of Volcanic Eruptions o f Mt. Usu reported that
tectonic activity subsided near the western flank of the mountain.
On August 11, officials closed the Mount Usu Eruption Field Emergency Center.
On August 27, the town of Abuta closed its two shelters. All shelters were closed.
On November 1, the Coordinating C ommittee f or Pr ediction of Volcanic Er uptions an d experts r eported
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Failure Knowledge Database / 100 Selected Cases
that underground mag ma activity b egan to s ubside, but the commu nities near t he erupti on sites wou ld
require continued vigilance against volcanic cinders and geothermal activity.
On December 28, the Hokkaido government announced its plan for reconstruction of the areas affected byvolcanic activity.
On May 28 , 2001, th e Coordinating Co mmittee f or Pr ediction of V olcanic Eruptions reported that
underground magma activity has subsided, and closed its Mt. Usu subcommittee.
5. Countermeasure
In late J une 2000, the Hok kaido g overnment h ad wo rking-level talks with three local agencies to plan
reconstruction of local communities affected by volcanic activity. After studying the report created in 1980
by Hok kaido an d its project t eam of v olcano an d torrent co ntrol e xperts, of ficials disc ussed zoning ofresidential a nd business in a town/ city (Professor Oka da explains th at the r eport was s ubmitted 3 y ears
after the 1977 eruption, which was too late to b e used for reconstruction efforts. He also remembers thatthe suggestions made in the report were not i mplemented because local agencies were not involved in the
project). While tour ist-related bus inesses remain in the cur rent hot spring resort ar eas, cit ies and to wns
encourage residential ho mes and pu blic fa cilities su ch as schools to loca te in sa fer ar eas by enforcing
zoning regu lations. In addition to zon ing, P rofessor T adahide U i of H okkaido University sug gested toconvert an affected area into an eruption memorial park by preserving some standing bridges and homes in
the area. Such a p ark can be used to ed ucate the public and students on s chool tr ips about the threat of
volcanic activity. It can also work as a torrent control structure in case of a mudflow.
On July 23, the city of Date and the towns of Abuta and Sobetsu announced their plans for reco nstructionof the ar eas affected by volcanic activity, in which zoning would be implemented to enc ourage relocationof housing communities to areas safe from the threat of f uture eruptions. O fficials emphasized that theirreconstruction plans would set an example for development of communities nationwide.
Figure 4 and 5 show the zoning plan and the zoning map.
The h azard map o f Mt. Us u, which p roved its usefulness during ev acuations in the 200 0 er uptions, wasupdated and distributed in 2002.

Zone

Zones to implement disaster measures in response to the 2000 Mt. Usu eruption
Zone A

Description

Development plan

Areas where craters arelocated or near a crater.
Heavily damaged by hot
rocks and mudflows.
The damaged areas by2000 eruptions are andwill be at high risk ofmudflows and hot rocks.
All types of structures areprohibited within thezone. All structures will be

Zone X
Areas that were notdamaged by the 2000
eruptions, but are at highrisk of mudflows.
Areas are at high risk ofmudflows that may
devastate the community.
All types of structures areprohibited within thezone. All structures will be
moved to an appropriate

8Zones to implement
disaster measures for the
future eruptions

Zone B

Zone C

Neighboring areas of Zone
A. Damaged by hot rocks.

Areas that are notincluded in the zones A, Bor X.

In order to ensure safetyof the community, alltypes of structures areprohibited within thezone. All structures will be
moved to an appropriate
zone over a short/medium

In order to minimize
damage from future
volcanic eruptions,
hospitals, schools andsocial welfare facilities
will be constructed within
the zone over a

Failure Knowledge Database / 100 Selected Cases

Land use

moved to an appropriate
zone. The area will be
used for torrent control.

zone. The area will be
used for torrent control.

Disaster-prevention
facilities, intercepting
green (green space), areas
preserving structures
damaged by volcanic
activity, natural park.

Disaster-prevention
facilities.

term. The area will be
used as a buffer zone
between urban districts
and disaster-prevention
facilities.
Buffer zone (open space,park, etc.)

short/medium term. Upon
further discussion withresidents, residential
structures will be moved
to safer areas.
Businesses (commerce
and industry, agriculture,services, etc.) and public
institutions (mairie, etc.)

Figure 4. Zoning Adopted by Reconstruction Plan after the 2000 Mt. Usu Eruption [1]9Failure Knowledge Database / 100 Selected Cases

Figure 5. Zoning Map Adopted by Reconstruction Plan after the 2000 Mt. Usu Eruption [1]6. Summary
The significant outcome from the 2000 Mt. Usu er uption was the effectiveness of the crisis management,
which wa s credited for quic k action and evacuation of 16,0 00 people . Experts prov ided ac curate
predictions of Mt. Usu eruptions, saving lives of residents.
Mt. Us u had a lon g history of v olcanic activity, whi ch en abled e xperts to st udy the characteristics of its
subsurface magma activity. Also, Mt. Usu did not “betray the expert predictions” as Professor Okada says,
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Failure Knowledge Database / 100 Selected Cases
and it had many observation sites already set up. Another factor that contributed the zero-casualties was thehazard map. Based on th e damages caused by the pas t eruptions, officials had created a hazard map thatshowed a reas p otentially th reatened by an eruption, and d istributed a c opy of it to every home in t hecommunities near Mt. Usu. Note that a hazard map itself does not help saving lives. It must be utilized toeffectively wa rn the public of a volcanic eruption a l ot ear lier t han i t a ctually occ urs. F or exa mple, t he1985 erup tion of the Nevado del Ru iz v olcano in Co lombia caused devastating damages (devastated th e
town of Ar mero and killed 20,000 people) as predicted by the hazard map. Although a preliminary hazard
map for Ruiz was completed one month before the 1985 eruption, it was not adequately utilized to save thelives lost when the mudflows struck.
The cases illustrate the difference in transferring information of the continually changing situations.
The Usu Volcano Observatory of Hokkaido University (Professor Okada, director) provided information to
two independent agenci es th at h ad resp onsibility in different c risis-management du ties: the Sapporo
District MeteorologicalObservatory th at issues of ficial volcanic information, and th e Hokka ido

government th at determines n ecessary e mergency m easures. While a meteorological observatory was
responsible for observation and disclosure of volcanic activity, the Fire and Disaster Prevention Division of
the Hokkaido government was responsible for issuance of evacuation advisories and directives. In addition
to the se two agencies, the Usu Volcano Obs ervatory of Hokka ido University ha d pr ess conf erences to
explain th e ongoing volcanic acti vity in a tim ely manner t o the pu blic. This co mmunication system wasproven effective in providing accurate information in time to minimize damages. As a social psychologist
said, “warning is effective for saving lives, if the hazardous situation is presented in an easy -to-understandmanner to the people in crisis”.
Learned fr om the Mt. Unz en er uption i n the pas t, of ficials had bee n e mphasizing th e i mportance of th e
hazard map and encouraging the local residents to study it thoroughly just in case of Mt. Usu eruption. The
fact that the residents all knew about the Mt. Usu hazard map made a quick evacuation possible.
Officials all placed maximum priority on human life. Mayors of cities and towns made efforts to persuade
residents to evacu ate of ficially through em ergency bullet ins as w ell as uno fficially th rough interv iews
taken by mass media. A fter th e firs t eruption of Mt. Usu , the Cabinet Security Affairs and Cris isManagement Of fice or dered railways to provide extr a service for eva cuation of r esidents (railways
suspended express ser vices at the Osy amanbe Station an d brought the r ailcars t o Toya). Compare t o t heevacuation e fforts in the 1995 Great H anshin-Awaji Earthquake, of ficials a nd agencies sh owed a vast
improvement in crisis management.
7. Knowledge
An effective communication system is essential for efficient and quick evacuation of residents.
Disaster prevention requires people’s cooperation and understanding on disaster through evacuation drills
and education.
Professor Okada pointed out in his research paper, which was published before the 2000 Mt. Usu eruption,
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Failure Knowledge Database / 100 Selected Cases
that sc ientists, of ficials a nd mass media coul d ass ist p eople by collab orating cl osely to assur e s afety ofcommunity. This attitude (in his words, the scheme “mitigation tetrahedron relation”) works for all types ofdisasters and accidents.
Also t he important is a sw ift dev elopment of r econstruction plan a fter a disaster. As t he proverb s ays,
“Strike the iron while it is hot”. Otherwise, a plan becomes difficult to execute.
8. Background
Mt. Usu is said to have 100,000-year long history of volcanic activity. A caldera was formed about 100,000
yeas ago when a large eruption emptied the magma chamber beneath the volcano. The island at the centerof the water-filled caldera was formed as the result of a series of eruptions occurred about 40,000 years ago.
The current stratovolcano was formed as ma ny eruptions occurred in the southern part of the caldera rim
about 20,000 years ago. The current shape of the southwestern frank was f ormed about 7,000 y ears ago.
The next eruption o f Mt. Usu w as in 1663, for th e first tim e in 7 ,000 y ears. S ince th en, th ere wer e 8
eruptions, once in every 20 to 50 years. All 8 activ ities continued for 1 to 2 y ears before Mt. Usu rested
again for decades.
All eruptions in the past accompanied noticeable precursors, which lasted 3 to 10 days. The longest term ofprecursors was 6 months recorded in the 1944 eruption, and the shortest term was 32 hours recorded in the
1977 eruption, which killed 3 people in mudflows.
References[1] The Hokkaido Shimbun Press (Editor) (2002) 2000-Nen Usu-Zan Funka (The 2000 Mt. Usu Eruption), The
Hokkaido Shimbun Press.

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