Tech．Rep．Meteorol。Res．Inst．No．121984

Abstract

TheMete・r・1・gica1Researchlnstitutehasc・nductedv・lcan・1。gicalresearchf。rthe

purp・se・fpredicti・nanddisasterpreventi・n・fヤ・lcanicempti。ns．Itiseffectivef。rthe
preventi・nandmitigati・n・fsuchdisasterst・detectphen・menaprecediムgeruptiveactivitieSandtocopebeforehand

withthe玉roccurrence．

Ithasbeenkn・wnthatextra・rdinaryvariati・ns・fgr・md＆cmstaldef。rmati。ns，seism・1・gicalevents・v・lcanicc1・udejecti・hs，ge・thermalactivities，etc．，・ccurasprecurs。ryphen・mena・fv・1canicerupti・ns・ltwi11bep・ssiblet・predictthe・ccurrencetime，1。cati。n，magnitude，etcりof

volcanic

eruptionsbyprecisemeasurements

andanalysisof

thesephenomena．

Wehaveconductedtheinvestigationsinthelstand2ndNationalProjectsforPredictionofVolcanic

phenomena
magma

（lst

Eruptions（1974−1978and1980−1983），assuming

that

the

their

begimingof

undeてground

place

on

the

following

Magma

Activity

andtilloccurrence

sequences

from

the

eruptions

will

take

the

occurrenceofVolcanic

Activities

fromVolcanic

Eruptions，and

the

Their

Undergromd
Observations

andvarious

till

accompanying

activities
simpleof

modeL

theOccurrence

volcanic

activity．

ofResearchStage）

The

subgromd

magma

reservoir

Research

item：Observation＊Observation

ofbegins
oftovibrate

long・period

vibrations

ofbyactivation

seismic

magma

ofwaves．

reservoir

byvolcanologicallong・period

seismograph（1982−1983）＊Others．

（2ndStage）

Then，themagma

Research

reservoir

item：Cmstal＊Gromd＊Tilt

expands
andsurface

observation＊Undergromd（developed

groundstrainofand／ormovements

observation．

measurements

volcanostrainascends．

edificebybyobservationin1983）＊Others．

一5一

geodimeter（1974−1978）

tilt

bymeter（1974−1978）

volcanologicalvolumestrainmeter

Tech．Rep．Meteorol。Res．Inst．No。121984（3rdStage）

By

successive

earthquakes

ascentofmagma，mdergroundmaterials

aredestroyedandvolcanic

occur．

Research

item：Seismological＊Observationof（routinelyvolcanoes．The

observation．

volcanic

earthquakes

conducted
materialsandtremors

byshort−periodbytheJapan

Meteorologicalwereusedininvestigations）．

thegroundourAgency

seismographatdesignated＊Others．

（4thStage）

Magma

andvolcanic

increases，andResearchangases

activeapproachejection

item：Visual＊Observationofvolcanicobservation

ofof

cloudsvolcanic

wavelengthsof＊Thermalinspections

inclouds

volcanic

visible，infraredandsurface，thebyandgeothermal

temperature

occurs．

cloudsandmeansoffieldremoteinspections．

sensingtechniques（usingultraviolet，1980−1983）．

aroundactivecraters

byaerial

andgroundmeasurements（1974−1979）．
＊Others．

（5thStage）

OccurrenceofResearch

volcaniceruptions．

item：Observation

oflong・period

Observation
SeismologicalAs

observation．

Fieldinspection．

activities

occurrence

of

the

phenomena

thatoftheforemming

Thoughtherearesomecomplicatedwaveobservation，crustal／gromd

visualobservation

fundamental

Inandtechniques

thisspecialarehsted

forcomplicated，emption

in

the

deformation。

lst

alwaysproblems，themeasurement

items

of

long・period

deformation

measurement，seismologicalobservation，

in

importantvolcanological

shown

the

above

table

are

is

the

occurrence

inspection

above．It

after

of

or

table

place

order

occur

the

take

theto

the4thnotinfailtodoesStagesphenomena

field

crusta1／gromd

waves．

Observation．

Visualvolcanic

someofseismicmaylikelychange．

seismicandsurveillance。

research，Investigation

on

一6一

theTechniquesforVolcanic

Activity

Tech．Rep．Meteorol．Res．Inst．No．121984

Surveillance

Volcanic（1980−1983）conducted

Eruptions，developments

measurements
magma
onofvolcanic

reservoir

thefollowing

threeMeansofa．

inon

It

asfor

Nationaltechniques

observation

ofof

Project

for

for

Prediction

quantitativelong−period

undergroundandvibrations

strainhaveofdynamic

generatedbeenbyconduct6d

items：

Measurements

of

the

SurfaceStateofVolcanoes

byDetection

ofActivityof

theMagma

Reservoir

byVolcanological

Seismograph（1982−1983）

ofresults

brief

the

2nd

observations

QuantitativeLong−Period

ThetheRemote−sensing（1980−1983）b。Investigationc。Development

andresearch

onofclouds，foractivities

a・Investigation

areundertheofVolcanologicalthese

Volumeinvestigations，asStrainreporte（iMeter（1983）

in

the

respective

sectionsin

Chapter1，follows：

wasconfirmed

that

the

systemdeveloped

more

precisely

than

the

conventional

canobservation

method，thetheof100m，andthe、expandedvolcanfc

seven．However，thenewlyheight．of

developed

state

ofvolcanic

cloudsobservations．In

thecaseofthebeenobserved

inclouds（quantity）havebeen

observedinvisualconventionalorder

observesystemthevolcanic

cloudscanmeasure

thehasheightofvolcanic

clouds

in10morder，andcanmeasuretheexpansionofcloudsintheorderof100m2．
Furthermore，thecloudstheandtechniques

concentrations

conventional

forofmeasuring

SO2gasesmethod，were

the

in

sur∫aceclouds，which

volcanic

activityof

AsoVolcano

calm

state

throughout

theinvestigation

of

the

quantity

ofseason，i．e．，about10times

risinginSO2concentrations

volcanicThe

cloudsatresults

research−workinperiod

wascarriedoutwasperiod．However，remarkableclouds，which

great

inwinterinwinter．Thesetendencyofsomeincreasecarriedoutinrisingduring

this

above

was

SO2measurements
themeasurements

ofarebelow．Values

showncrater−rim

summereffects．There

winter．The
slightly

thevolcanic

一7一

season，were

the

amual

lower

telhperaturessummer

very

ain

the

the

isina

meteorologicalpositionsofvolcanic

this

indicatedmeterstowherecrater・rim）also

of

due

research

by

above

severalarebeenaromd

about

phenomenaout

notclouds（atvolcanic

highercarri￠dhaveofofshowing

volcanic

quantity

temperature

variationrisingthesurfacetens

ofdeveloped，Thevariations

temperature

and
awere

orobserved．The

ataheightclearof

amual

crater・rim．

cloudsinby

thenewsystemparentheses

aremeanones．

Tech．Rep．Meteorol．Res。Inst．No．121984

Height：50−200m（120m）
Width：50−220m（140m）
Verticalprofile：5×103−4×104m2（2×104m2）

Estimated
Velocity

volume：1×105−5×106m3（2×106m3）
ofrisingcloud：1−8m／sec（2．7m／sec）

Temperature：3−230C（13。C）

SO2concentration：100−650ppm−m（310ppm−m）

The

quantity

of

water

vapour（W），thermalenergyrelease（Q）andquantity

of

SO2

gases（G）ejectedbyvolcaniccloudswereestimatedasW二7×103ton／day，Q＝5×107
cal／secandG＝11ton／day，respectively．
b．

At

volcanoes，itobservations
heavy

forisvery

tooperate

seismic

waves

bylong・period

pendulums，which

variationsdifficultapttoairtemperatureandgroundof

arepresent

research，anew

typeofPeriodSeismograph，has

beensecondperiodstablelO−second

periodBycontinuous

observations

lose

generatedresearch

beworkwithoccurrence

registeredperiod，thefrequencyofbyto

atdisturbances

great

seismograph，called

andelectricalseismograph．

thisseismograph

very

the

Asolargealtitudes．For

theVolcanologicalthe

Weather

Station，10ng−

kind

the

conventional

we11．This

typeofvolcanic

activitykindofof

AsoVolcanomagma

volcanic

exising2−

system，isby

the

Long−

feedback

secondofusingofdetected

vibrations

secondatwave−train＄（thewell

volcanic

the

slope

type

been

to

owing

seismologicalseismograhps

themicrotremor），which

consideredlong−peridtransducer

seismic

bethecontimousseismograph，combiningperiod（6−10seconds）volcanic

seismographs，couldonlong−period

displacement

notbalanceanddeveloped．This

electromagnetic

have

existing

their
tilts

stableofavolcanic

short・period
has

been

reservoir．During

the

has

tremorbeen

microtremorcalm，andwas

theseveral−150

times／month．
c．

Usually，avolcanic

large

horizontal

regions，andvariations。The
of10−5andanewlydistance

there

developed

volumestraingromd

temperatureindrillvariationasbeinstalledvery

highsoto

strainmeter，theof

arearesolution

highofpossiblytime

designedstrainlO−5／mderground
meter
ofhole，isthermometer

一8一

is

year

takes

place

in

activetemperatures

with

their

time

operableundera

O．30C．The

strainmeter

composedthree

mits：theusingofthesamelarge

princplestrainsensor，as

volumetheTech．Rep．Meteoro1．Res．Inst．No．121984

volumestrain

meter

proof

cylinder．The

almostthesamediodeandprediction．The

Volcanologicalearthquake

VolumeStraindiodethermometeris2／1000℃．

The

performance

ofand

Ontakearoundthe0ntakeEruption

thecrater．A

Scienceandcraters

after

results

ofgroundstrainmeter

indeveloped

resolution

to

in

deep

andhasoperationiscalledtemperaturebythe

experiments

satisfactory

pressure−

meter

ofgromd

subjected
the100m

straininobservation

variouswelloftheoperationinresultsforremarkableeruptions

and

big

damagethethere

hadfor

both

been

nowas

routineeruptions

Agencyandthevariations

eruptionsbyair−bome

on

Aso

areVolcano，thedistributedof

thiswererelations

andnearthermoscamers

wereChapter2，areinbrief

ofvolcanic

betweentheofthisvolcano．Throughthis

Ontakeinvestigation，aimagesby

of

and

theof

this

at

eruption

detected

variations

ofshape，state

December，1979throughima3eanalysisusingvisible

MSS

imageswasnewly

theresults

thisactiveactivity

inspections

wereofalso

thefollows；

becameanomalies

time

thermaltechniqueetc．wereasanalysis，ithigh・thermalvolcano．The

from

Nationalinvestigated．The

results

flrstofareasobservation

Volcano，theslopehigh−temperaturestate

theclearandexistingthat

theleve1．

on

this

one

facilities．

in

activitieson

unexpectedstate

thermalhighutterly

thermalbyaarea．The1979

ofinspected

atvolcanoラan

recent

wide

fund

were

in1980was

aof

Aso

constructions

the

in

the

overoftobyofreported

greatest

conducted

infrared

analyzingtwoobservation

volcanic

ofactivity

crater

near

where

research

volcanic

thehistory

investigations，which

activity

areas

of

was

the

activity

ashfallone

inlocationsinfraredthethevictims

andthisonEruption

event

researchupper

newly

awere

first

the

thosecauseddone．Existencetheoperated

volumeinsideresearch，there

theTechnology

the

this

ashes

wasonofofresearches

InshowedquantityThe

thermalconducted

large

volcano∫naterials

istypeMeter。The

Institute

perioderuption

thisthermalwater・pressures

Researchbore−holestrain−meter

Volcanoes．The1979Aso

activities．The

thetheencasedregions．

In1979，during

In

the

threesystemoftheofcontrol

aspurposevolcanic

thermometer，allcharacteristics

theMeteorological

for

the

amplification

fortemperatures

andandinvestigatedandvolcano．

一9一

toand

March，1980were
process

wereusedin

weresites

intensityofandtheanalyzed．Throughgeographicaldeveloped．Then，thevolcano

correctionsofdistributionsofassessing

thestateof