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3
2▶Earthquake/Tsunami Information
Current Warnings/Advisories is displayed with icons andcolor-coding for at-a-glance determination of risk levels.

Home ＞ Earthquakes / Volcanoes
Users can switch between nationwide, prefecturaland municipal display and specify areas for Warning/
Advisory information.
Select Prefecture / Municipality

312
2
1 12 2

JMA sends various information through SNS as well as the website.

Twitter

For press releases and event information.

For emergency press conferences.

For disaster mitigation information. Current
situations and prospects relating to extreme
conditions such as typhoons, heavy rain,earthquakes and volcanic eruptions.

For on-site presentations to residents, leaflets, DVD content and other information
supporting safety awareness and utilizationof weather data.

3

2
22
2
2 2

3

Earthquakes
2

and

2 2

1
2

1

Tsunamis

Observation and Disaster Mitigation
3-6-9 Toranomon, Minato-ku, Tokyo 105-8431, Japan
TEL:+81-3-6758-3900
FAX: +81-3-3584-8644

JMA website (Japanese)
https://www.jma.go.jp/

JMA website (English)
https://www.jma.go.jp/jma/indexe.html

Japan Meteorological Agency

Cover: Seismic Intensity map of the 2016 Kumamoto Earthquake (Apr. 16, M7.3)

March 2023

Contents
Introduction... 2

Observation Network... 4

Flow of
Warnings/Information... 6

Timing ofWarnings/Information
EEW: Earthquake Early
Warning
TsunamiWarnings/Advisories
Information on Tsunami
Observations
Earthquake Information:
Flow and Content
Information on
Long-Period Ground
MotionOther Information andCommentary on
Earthquakes and Tsunamis
Nankai TroughEarthquake Information
Off the Coast of
Hokkaido and Sanriku
Subsequent Earthquake
Advisory

Around a tenth part of all earthquakes occur in and around Japan, making it one of the world’s mostearthquake-prone countries.

Earthquakes with IJMA6- or higheror those creating tsunami withheights of 1 m or more in Japan  
since 1991

Japan has suffered serious damage from earthquakes and tsunamis on a number of occasions.
Earthquakes cause massive destruction nationwide, with the potential for massive strikes anywhere.
Even distant earthquakes far from Japan also can cause damage in Japan due to the tsunami thatcame across the sea.

* The Upper(+) and Lower(-) IJMA classifications wereintroduced in 1995.
* M, IJMA and tsunami height are given as maximum
values for the whole event.

... 8
Depth
[km] 0... 10100–

North American Plate
Eurasian Plate

ArabianPlate... 12

Pacific Plate... 16South AmericanPlate... 20... 22... 25

Protect yourself from
Earthquake
Protect yourself fromTsunamiNazca Plate

Depth[km] 01994 Hokkaido-Toho-Oki Earthquake
M8.2, IJMA6, 1.7 m tsunami
and 10 dead/missing

100–

Brokenwindows▲ World distribution of earthquakes (over M5 since 1960) and major tectonic plates

Mechanism of Earthquakes in and around Japan

Photo by
Fukuoka City

2016 Kumamoto Earthquake
M7.3, IJMA7 and 273 dead2007 Niigataken Chuetsu-oki Earthquake
M6.8, IJMA6+ and 15 dead

IJMA: JMA Seismic Intensity Scale → p.16
(0, 1, 2, 3, 4, 5-Lower(5-), 5-Upper(5+),
6-Lower(6-), 6-Upper(6+), 7)

1994 Sanriku-haruka-oki Earthquake
M7.6, IJMA6 and 3 dead2000 Western Tottori Pref. Earrthquake
M7.3, IJMA6+

2008 Iwate-Miyagi Nairiku Earhquake
M7.2, IJMA6+ and 17 dead2001 Geiyo Earthquake
M6.7, IJMA6-, and 2 dead2011Off the Pacific coast of Tohoku Earthquake
M9.0*1, IJMA7, 40 m*2 tsunami
and 22,312 dead/missing

There are three mechanisms behind earthquakes occurring in and around Japan as in the lower figure. All earthquakes can bring down houses and cause landslides in and around residential areas.
Large seabed earthquake can generate tsunami waves that cause massive damage to coastal areas.

Shallow Crustal Earthquake2018 Northern Osaka Pref.
M6.1, IJMA6- and 6 deadInter Plate Earthquake• 2016 Kumamoto Earthquake• 1944 Tonankai Earthquake• 2018 Hokkaido Eastern Iburi Earthquake• 1946 Nankai Earthquake

1995Southern Hyogo Pref. Earthquake
M7.3, IJMA7 and
6,437 dead/missing

Two earthquakes of IJMA7Collapsed buildings and landslides• 2011 off the Pacific coast of Tohoku
Earthquake    
 

1995 Near Amami-Oshima Is.
M6.9, IJMA5, 2.7m tsunami

Photo by Kogakuin Univ.

   

Distant Earthquakes:... 27

M: Magnitude(overall earthquake scale)2003 Tokachi-oki Earthquake
M8.0, IJMA6-, 4.4 m tsunami
and 2 dead/missing

2007 Noto Hanto Earthquake
M6.9, IJMA6+ and 1 deadAntarctic Plate... 26: Notes when you use
the information

1993 Kushiro-Oki Earthquake
M7.5, IJMA6 and 2 deadEarthquakes exceeding M6 in the JMA
Earthquake Catalog (1923–2022)

2005 West off Fukuoka Pref.
M7.0, IJMA6- and 1 deadIndo-Australian Plate• 1995 Southern Hyogo Prefecture Earthquake... 24

2004 Mid Niigata Pref. Earthquake
M6.8, IJMA7 and 68 deadCocos Plate

Hypocenter data is based on the United States Geological Survey (USGS)... 18Large landslides over a wide area

Philippine Sea
Plate

African Plate... 152018 Hokkaido Eastern Iburi Earthquake
M6.7, IJMA7 and 43 deadEarthquake and Tsunami Disasters in Japan• 2003 Tokachi-oki Earthquake

International
Cooperation

2

Introduction

1993 Off the Southwest coast of Hokkaido Earthquake
M7.8, IJMA5, 29 m tsunami and 230 dead/missing

1996 Off New Guinea M8.1,
1.0 m tsunami at Chichijima Is.

Intra Plate Earthquakein Oceanic Plates• 1993 Southern Off-Kushiro Earthquake• 1994 East Off-Hokkaido Earthquake* Statistics on fatalities/missing people are from the Chronological Scientific
Tables 2022 and the Fire and Disaster Management Agency (as of Jan. 2023).
*1 Moment Magnitude*2 The 2011 Tohoku Earthquake Tsunami Joint Survey (TTJS) Group2010 Coast of central Chile
M8.8*1, 1.9 m tsunami at Iwate  

Damage to high-rise buildings far from the
hypocenter as a result of long-period ground motion

Major earthquakes and tsunamis(1991 – 2022) and resulting damage
3

Observation Network
JMA collects real-time data from its own seismometers, Seismic Intensity meters, sea-level gauges
and other instruments and those of other organizations to support the monitoring of earthquakes
and tsunamis.
T

r

e

n

c

h

*As of Jan 1, 2023

JMA
others700+
3,700+

c

a

k

a

K

u

r

i

l

-

K

Seismic Intensity Meters measure the intensity of earthquake shakings as observed
Seismic Intensity values based on acceleration records. JMA manages around 700 suchmeters nationwide, and also collects Seismic Intensity data from another 3,700 stations
operated by local governments and NIED*1. These data are used for Earthquake Information issued by JMA.

Tsunami Meters

Seismic Intensity Meters of JMA are equipped with satellite communications
system that enables data transmission in the event of landline malfunction. If an earthquake causes serious damage, JMA assesses the integrity of its Seismic Intensity Meters
and/or sets up temporary observation sites as necessary.

Tide Gauges

h
c
n

300+
1,500+
P l a t e

JMAothers

6
210+

a
p
a

a

o

u

P l a t e

Strainmetersi

JMA
others

O

n

k

r

-

a

25
14

N

g
a
s

To detect crustal deformation caused by slow slips and other phenomena related to plate coupling along the Nankai Trough, JMA collects observational data from strainmeters in real time(in addition to data provided by AIST*7 and the Shizuoka Prefectural Government) for issuanceof Nankai Trough Earthquake Information.

aJMA, NIED and other organizations operate cable ocean-bottom
seismometers and tsunami meters along the Japan Trench and the Nankai Trough. Data from both offshore and onshore stations are sent to JMA
and used for the issuance and updating of Earthquake Early Warnings andTsunami Warnings/Advisories.

w

S e a

P l a t ea

P h i l i p p i n e

r
a

n

r

At Minami-TorishimaIsland, JMA operates atsunami meter for early
detection of tsunami
coming from far away.

Minami-Torishima
Is.

h

a

s

c

e

l

d

n

s

s

n

e

T

r

T

I

n

e

c

h

*1 NIED: National Research Institute for Earth Seicence and Disaster Resilience*2 JAMSTEC: Japan Agency for Marine-Earth Science and Technology*3 PHB/MLIT: Ports and Harbours Bureau, Ministry of Land, Infrastructure, Transport and Tourism*4 GSI: Geospatial Information Authority of Japan*5 JCG: Japan Coast Guard*6 ERI: Earthquake Research Institute, The University of Tokyo*7 AIST:National Institute of Advanced Industrial Science and Technology

N

Ocean-bottom Tsunami Meters

18

u

T

h

z

Earthquakes can occur both at land and under the sea. In particular, theplate boundaries at which megathrust earthquakes occur are mostly
located under the sea bed. Against this background, data from seafloor
seismometers are highly useful in the monitoring and early detectionof earthquakes in such areas. Tsunami meters on the seafloor are also
helpful to detect tsunami waves before they reach coastal areas.

gI● Seafloor observation networksaP a c i f i c

J

For the issuance of Earthquake Early Warnings, Tsunami Warnings/Advisories
and Earthquake Information, JMA also uses seismic data observed using seismometers
managed by other organizations (such as NIED, JAMSTEC*2 and universities).

4

othersJMA also uses about 20 GPS buoys (managed by PHB/MLIT) and about 210 Ocean-bottom
Tsunami Meters (JMA, NIED, JAMSTEC and ERI*6) for Tsunami Information (Tsunami Observations at Offshore Gauges) as well as warning updates.

n

C o n t i n e n t a l

T

JMA operates a seismic network with about 300 seismometers to monitor seismic
activity. Among these, accelerometers and velocity seismometers are used to identify/analyze seismic waveforms for Seismic Intensity Information and Earthquake
Early Warnings, and transmit Seismic Intensity data and other analytical data as well
as seismic waveform data to JMA. These seismic observation facilities are equippedwith satellite mobile phone communication capability for backup, and have a power
supply that can keep the whole system operational for about 72 hours in the event of
power failure.

80+
100+

When tsunamis are detected, JMA issues tsunami observation information containing data on
arrival times and the highest waves observed at each observation station. In coastal areas, JMA
operates about 80 tide gauges and also collects real-time sea level data from gauges operated
by PHB/MLIT*3, GSI*4, JCG*5 and other organizations. Currently, JMA issues Tsunami Information (Tsunami Observations) using data from about 180 stations.

e

JMAothersGPS buoys

JMA
othersr

Seismometers

h

t

m

５弱

a

Seismic Intensity
Metersi5Flow of Warnings/Information
From Observation Data to Information

From Information to Disaster Mitigation

JMA collects data from its own observatories and those of other organizations in real time and monitors earthquakes and tsunamis on a 24/7
basis under the Earthquake Phenomena Observation System (EPOS).

JMA’s various types of Information on earthquakes and tsunami are provided in various ways suitable for purpose, and are utilized for disaster mitigation correspondence.

When an earthquake is detected, JMA immediately determines
its scale, the location of its epicenter, the risk of shaking and tsunami.
Based on this information, JMA creates and issues Earthquake Early
Warnings, Tsunami Warnings/Advisories and various other types of information.

Information that prompts urgent evasive action and evacuation, such
as Earthquake Early Warnings and Tsunami Warnings/Advisories, is provided immediately to local residents via TV and radio, mobile phone andEmergency broadcast system (J-ALERT).

TOKYO

Other types of information are provided to central and local government bodies, disaster prevention organizations, the media and other parties,
and are also published on the JMA website for use in initial response, checking of damaged areas and resident evacuation/rescue.

Mirror-operation centers are run in Tokyo and Osaka so thatwarnings and information can still be issued if one is seriously damaged
in a large-scale disaster.

At the stage of restoration work by municipalities, related organizations and local residents, careful attention is required to the risk of secondary
disasters such as residential collapse and landslides associated with subsequent earthquakes, as well as to forming an accurate and comprehensive
picture of the damage. To support planning and implementation in relation
to associated tasks, JMA issues Prompt Reports with information including
seismic intensity distribution, the current situation and prospects for earthquake activity/tsunami as well as notes on disaster mitigation. JMA staff also
provide commentary at disaster management headquarters and press briefings.

OSAKA
JMA

Disaster management headquarters

Emergency broadcast system
Photo by Chiyoda City, Tokyo

５弱

Seismic Intensity
Meters700+
3,700+

Seismometers
JMA
others300+
1,500+

Tsunami Meters
JMA
others80+
330+

Strainmeters
JMA
others
625
14* As of Jan. 1, 2023

Various types of information
Earthquake Early Warning

Tsunami Warning/Advisory

Earthquake Information
Tsunami Information

Emergency Alert E-mailMobile network operators
Transmission company or
Licensed company for forecasting

Dedicated device/Apps

TV, radio

NHK and other
Broadcasting media
Fire and Disaster Management
Agency / J-ALERT system

Emergency broadcast system

Prefectural government

Local
municipalities

PoliceSeismic Intensity
Information
Nankai TroughEarthquake Information
Off the Coast of
Hokkaido and Sanriku
Subsequent Earthquake Advisory
Other Information
Prompt report

General public

JMA
othersData analysis
and assembling information

Nippon Telegraphand Telephone Corporation
Ministry of Land,
Infrastructure and Transport

Air traffic
controls

Japan Coast Guard

Ships

Designated administrative organs

Designated public institution

JMA
WebsiteInternet

7

Timing of Warnings/Information➡p.21

JMA issues various types of information on earthquakes and tsunami with particulartiming after the earthquake, and the accuracy of the content essentially increases
with time.

      

  
地震発生
   ◆ 

      
➡ｐ.��

       ◆               
     

➡p.21

➡p.22

­          
   

➡p.22

­  
    
 
  ◆  

   

➡p.12

   



◆                ◆­                           
        ◆             
   

➡p.17

➡p.17

 

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➡p.16
   

➡p.17


   

  

 ➡p.15

         


8       

山路を登りながら➡p.16

     

    

 ➡p.10


  
  
9

EEW: Earthquake Early Warning
Appropriate Preparation and Response

Earthquake Early Warnings (EEWs) provide advance notice of estimated Seismic Intensities andexpected arrival times of principal motion just after an earthquake occurs. Although strong motion hits within just a few tens of seconds, EEWs can be utilized in various situations to mitigate
earthquake-related damage by providing precious seconds before shaking starts.

It is important to understand the different issuance criteria/characteristics and respond
appropriately.

Warnings“Warnings” and “Forecasts”
Criteria

Forecasts

Warnings

Categories• For estimated IJMA5- or greater. (Provided
for areas where IJMA is expected to be 4
or greater)• For estimated Long-Period Ground
Motion (LPGM) class 3 or greater• For estimated IJMA3 or greater• For estimated LPGM class 1 or greater• For estimated magnitude is 3.5 orgreater

Details

Features• Generally issued only once, except for large
earthquakes• Estimated origin time and hypocenter• Areas with estimated IJMA 4 or LPGM class
3 or greater• Information is provided on TV and via phones
to urge protection from strong shaking• Estimated origin time, hypocenter andmagnitude• Areas with LPGM class 1 or greater/Estimated LPGM class/Estimated arrival time

How it Worksestimated arrival times are updated on an ongoing basis for equipment control and otherearthquake countermeasures* Earthquake Early Warnings incorporating prediction of shaking with
IJMA 6- or greater and LPGM class 4 are issued in the classification of
Emergency Warnings.


 




When an earthquake occurs, seismic waves propagate. The main types are primary waves(P-waves) and secondary waves (S-waves), the latter of which propagate more slowly (4 vs. 7km/s) but are much stronger and can cause far more serious damage.
JMA analyzes data from seismometers that detect P-waves near the hypocenter andestimates the hypocenter location, magnitude and expected seismic intensity. If the results
meet set criteria, EEW Warnings and Forecasts are issued. The process is automatic and rapid,
enabling EEW output before the arrival of S-waves.

P-waveFaster

EEW broadcast(NHK)※要 NHK 使用許可

NHK alarm can be previewed
on the NHK website.

To support the rapid implementation of self-preservation measures, TV/radio and cellphones/smartphones emit individually unique
alarms. Get to know the sounds they make so that you will recognize
an alert as soon as it is issued.

https://www.nhk.or.jp/sonae/bousai/

EEW via Emergency Alert Email(“Area Mail”: NTT DOCOMO)

Forecasts
Forecasts are issued quickly even when the accuracy of available information remains limited, and are updated iteratively with increasing precision over time. As a result, Forecasts can provide alerts ofshaking before Warnings in some cases.
Some corporate operators licensed for forecasting predict seismic intensities and times at which strong shaking will start in specificlocations based on forecast data from JMA. This information can beused to enable advance preparations such as mechanical control ofmachinery/equipment and issuance of automatic announcements inindoor environments.

3 LEFT10s.

INT.

Users can subscribe to these forecasts by contracting with therelevant licensed company or installing dedicated applications.

In areas close to the hypocenter, Warnings may not arrivein time before strong shaking hits.

If strong motion is detected by a seismometer, JMA predicts continued local strong
shaking and issues EEWs via the automatic processing system to warn people of imminent
seismic motion.
The EEW system is generally based on science and technology for analysis and estimation, observation systems capable of quickly detecting the occurrence of an earthquake, andinformation and communications technology for prompt delivery of EEWs.

It is advisable to prepare in advance by creating a safe space andimplementing drills for immediate self-protection in the event of a
Warning.

• Detailed information such as IJMA values and• Areas with estimated IJMA 4 or greater/Estimated IJMA /Estimated arrival time

JMA added LPGM class values to its IJMA predictions in Earthquake Early Warnings as shown in
the table. However, the action to be taken remains the same; shelter in a safe place until shaking subsides. See page 18 for LPGM details.

Warnings are issued widely through various media such as not only
TV and radio, but also cellphones smartphones and emergency
broadcast systems to help people protect themselves from strong
shaking.

Lead time from EEW until strong shaking
Apr. 7, 2011 Off Miyagi Pref.

EEW Seismic Intensity estimations have an error marginof ±1 or so.
  
 

Lead time: 10s

Apr. 11, 2011 Hamadori, Fukushima Pref.

Lead time: 10s

Warning accuracy may vary due to calculation with thelimited data available immediately after an earthquake.

NO lead time10

P-waveCheck other points to note for response to EEWs
on the JMA website (in Japanese only).

https://www.data.jma.go.jp/eew/data/nc/shikumi/
tokusei.html

In the case of large earthquakes distantfromlandareas,aleadtimeofseveralseconds
is expected before strong shaking begins.
Estimated Seismic Intensity

4

5-

5+

6-

6+

In the case of shallow crustal earthquakes, strong shaking may begin before
an EEW can be issued.

hypocenter
The numbers in the figures indicate the times (in seconds) at whichstrong shaking (S-wave) is expected to start after EEW issuance.

11

Tsunami Warnings/Advisories
When issuing Tsunami Warnings/Advisories, JMA also provides information on estimated tsunami
arrival times of the first wave and maximum tsunami heights for relevant forecast regions and dataon high-tide times and estimated arrival times of the first wave at selected points.

Tsunami strikes can cause serious damage and loss of life. When an earthquake occurs, JMA
estimates whether a tsunami has been generated based on the earthquake's location andmagnitude. If disastrous waves are expected in coastal regions, JMA issues Tsunami Warnings/
Advisories.

Tsunami Information(Estimates Tsunami Arrival Times and Heights)

Tsunami Warnings/Advisories

TsunamiForecastRegion Est.initialtsunamiarrivaltimes Est.max.tsunamiheights
Fukushima Pref.
06:10 JST, 22 Nov.
3m

Immediately after an earthquake, JMA estimates the earthquake's location/magnitude
and potential maximum tsunami heights in coastal regions of Japan with reference toa tsunami database. If damage is expected, Tsunami Warnings/Advisories are issued
for the relevant forecast regions within around three minutes of the earthquake. JMA
generally expresses maximum tsunami heights in five quantitative levels.

Tsunami Information (High Tide Times and EstimatedTsunami Arrival Times for individual location)
TsunamiForecastRegion/ObservationSite High tide times Est.initialtsunamiarrivaltimes
Fukushima Pref.
06:10 JST, 22 Nov.
Iwaki-shi Onahama
10:34 JST, 22 Nov.
06:30 JST, 22 Nov.
Soma
10:19 JST, 22 Nov.
06:40 JST, 22 Nov.

However, it takes time to determine the exact scale of earthquakes with a magnitude of 8 or more. In such cases, JMA issues an initial warning based on the predefined maximum magnitude to avoid underestimation. When such values areused, estimated maximum tsunami heights are expressed in qualitative terms suchas “Huge” and “High” rather than quantitatively.
Once the exact magnitude is determined, JMA updates the Warning withquantitatively estimated maximum tsunami heights, which are included in subsequent tsunami information.

Tsunami Forecast Region
Fukushima Pref.

Category of Tsunami Warning/Advisory
TSUNAMI WARNING

Estimated arrival times (the time at which a tsunami is expected to hit firstin any part of an area) and maximum heights for relevant tsunami forecast
regions are indicated.

High-tide times and estimated initial tsunami arrival times at selected
points are also indicated. Tsunami arrival at high tide boosts wave heightand increases the scope of potential damage.

Estimatedmaximumtsunamiheights
in Tsunami Information
Qualitative
expression

Tsunami Forecast
Criteria

Huge(10 m - )10 m

(5 - 10 m)

Maximum tsunami heightis estimated to beover 3 m.

5m(3 - 5 m)

High

Expected damage and action to be taken ()

Quantitative expression

over 10 m(no expression)

TsunamiAdvisory TsunamiWarning MajorTsunamiWarning Categories*In JMA XML telegrams and on the JMA website, Tsunami Information (Estimated Tsunami
Arrival Time and Height) is combined with Tsunami Warning/Advisory.

3m(1 - 3 m)

1m(0.2 - 1 m)

Maximum tsunami heightis estimated to beup to 3 m.

Maximum tsunami heightis estimated to beup to 1 m.

Estimated initial tsunami arrival times are the earliest predictions for each tsunami forecast region.
As the arrival time in each region depends on the location, tsunamis may hit some coastal areas tens of minutes ormore after the estimated time.

A huge tsunami is expected to cause serious damage. Evacuate immediately to a safer place such as high ground or an evacuation building.
Tsunami waves are expected to hit repeatedly. Do not leave safe ground
until the warning is lifted.

A tsunami of this scale is expected to cause damage in low-lying areas. Woodenbuildings will be flooded and people will be caught in tsunami currents.
A tsunami is expected to cause damage. Evacuate immediately to asafer place such as high ground or an evacuation building. Tsunami waves
are expected to hit repeatedly. Do not leave safe ground until the warning
is lifted.
A tsunami of this scale is expected to result in people being caught in strong
currents in the sea. Fish farming facilities will be washed away and small
vessels will capsize.
It is dangerous in the sea or near the coast. Get out of the water andleave coastal regions immediately. Due to the risk of ongoing strong currents, do not enter the sea or approach coastal regions until the advisory
is lifted.

p.16) .

Maximum tsunami heights may exceed estimates in some regions.

Wooden buildings will be completely destroyed and/or washed away, and people will be caught in tsunami currents.

* Major Tsunami Warnings are issued in the classification of Emergency Warnings.

12

JMA issues Tsunami Forecast or Earthquake Information to indicate no tsunami threat in association with an earthquake (Tsunami waves may hit before Tsunami Warnings/Advisories are issued if the source region is near the coast.
When the exact magnitude is determined or tsunami waves are observed, JMA may update Tsunami
Warnings/Advisories.

● Approximate relationship between tsunami height and damage (Modified Shuto[1993])
Height ▶

1m

Aquaculture raft

Damaged2m

Fishing boat
Tsunamicontrol forest

Damage begins

DAMAGE ▶ Slight

4m

Damage ratio 50%

Moderate

EFFECT▶ Tsunami buffering / Debris capture Debris capture

Wooden house
Stone house
Reinforced concrete building

Partial damage

8m

16m

32m

Damage ratio 100%ExtremeIneffective

Destruction
Destruction

IntactIntactDestruction

Heights indicated for Tsunami control forest, Wooden house, Stone house and Reinforced concrete building are from the ground (inundation depth). Actual values may differ significantly.

13

Information on Tsunami Observations
Estimation of Tsunami Heights and Arrival Times

JMA and other public agencies have placed coastal and offshore tsunami meters, and JMA collects data from these stations in real time. When tsunamis are observed at these stations, JMA
announces in tsunami information bulletins and updates or lifts Tsunami Warnings /Advisories.

Tsunami waves strike near-field coastal areas soon after the occurrence of atsunamigenic earthquake. However, due to the time-consuming nature oftsunami simulation, timely processing is impossible if calculation is begun
only after an earthquake occurs.

Tsunami Information(Tsunami Observations at Offshore Gauges)

Tsunami Information (Tsunami Observations)

To address this situation, JMA simulates tsunami propagation in advance with a variety of earthquake scenarios, locations and magnitudes todetermine arrival times and wave heights for particular coastal areas. The
results are stored in a database to be referenced in the event of an actual
earthquake for issuance of appropriate Warnings and Advisories.



JMA also uses data recorded by tsunami meters to update and/or lift
Advisories and Warnings as necessary. Coastal tsunami heights are estimated
1. via simple conversion from observed offshore heights, and 2. more accurately based on reproduction of the tsunami source and propagation processfrom offshore tsunami waveforms.




Tsunami Observations
at coastal areas
Kuji-koMiyakoKamaishi

Initial Tsunami
Current Largest Tsunami
Movement
Arrival time
HeightArrival time
07:25 JST, 22 Nov. Fall
07:54 JST, 22 Nov. 0.8m (increased)
07:07 JST, 22 Nov. Fall
08:09 JST, 22 Nov. 0.4m (increased)(unconfirmed)
07:15 JST, 22 Nov. 0.2m

When tsunamis are observed at coastal meters, JMA announces arrival
times and initial movement (rise/fall) of the observed first waves in coastal areas as well as the arrival times and scale of the maximum waves observed as of the times of issuance for each tsunami observation site.

Tsunami Warning Timeline
   

Maximum height“Information pending”

arrival time of
maximum wave

To prevent delays in evacuation, JMA does not issue observation/
estimation values if the maximum wave height is below the evacuation trigger threshold. When observed tsunamis are smaller thanestimated, JMA uses the phrase “Information pending” rather thanproviding actual values to avoid creating a false sense of security inregions where Major Tsunami Warnings and/or Tsunami Warnings arein effect.

Initial movement

Fukushima Pref.
Ibaraki Pref.

 

 
 

 

     
     Norm

ascent”Rise”
descent ”Fall”

Sea 

al Seallevearrival time of
the first wave

Level

● Observation equipment

Coastal observation equipment● What is "tsunami height"?

Offshore observation equipment

Tsunami meter

Tsunami height figures in JMA Warnings/Advisories referto the height of the wave crest from normal sea level (i.e.,that in the absence of tsunami conditions) at the coast.
JMA also references "run-up height" (the heightof a tsunami running inland) and "trace height" (the heightof tsunami-related traces such as mud marks on inlandstructures). These figures may exceed the tsunami height.

Measures the distance between
transmitters/receivers set on sea
dikes or piers and the sea surface
using ultrasonic or radio waves.

GPS buoy

Measures the distance to the sea
surface in a stilling well using radio
waves or a float.

Coastal Gauge

Tsunami Height
Normal Sea Level

Current Largest Tsunami
Est. arrival time
Est. height
06:22 JST, 22 Nov.
Information pending
06:50 JST, 22 Nov. 07:00 JST, 22 Nov.
1m

● “First wave” and “maximum wave”






Est. Tsunami Heights and Initial tsunami
ArrivalTimesatcoastalareas Est. arrival time

When tsunamis are observed at offshore meters, JMA announces arrival
times and initial movement (rise/fall) of the observed first waves as well as
the arrival times and scale of the highest waves observed as of the timesof issuance. In addition, JMA issue estimated values such as arrival time ofinitial wave and arrival time and height of current largest wave for eachtsunami forecast region from these offshore data.

    



Initial tsunami
Current Largest Tsunami
Arrival time Movement
Arrival time
HeightFukushimaOnahama-oki 06:06 JST, 22 Nov. Fall
Information pending
Ibaraki Kamisu-oki 06:30 JST, 22 Nov. Fall 06:40 JST, 22 Nov. 0.1m
Tsunami Observations at
Offshore Gauges

Ocean bottom tsunami meter
Tide gauge
Inundation Depth

Trace Height

Measures water levels with pressure
sensors on the ocean floor.

Measures the distance to the sea surface ina stilling well using radio waves or a float.

Run-up Height

Huge tsunami meter
Measures water levels withpressure sensors in the sea.

14

15  Information:

Earthquake
Flow and Content
When an earthquake occurs, JMA promptly issues related information basedon seismic intensity (IJMA) observations and determines its time of occurrence,
hypocenter and magnitude.

Announcement of Local Seismic
Intensity and Locations

Earthquake Information

Announcement of No Tsunami Risk
Seismic Intensity Information

Announcement of Shaking
This information specifies the time of earthquake occurrence
and identifies sub-prefectural regions where IJMA3 or greater
has been observed (issued within 90 seconds of the earth-

Estimated Seismic Intensity Distribution Maps

Earthquake and Seismic Intensity Information

Indication of Seismic Intensity
Distribution in Map Form

If IJMA1 or greater are observed, the following information is

When the observed maximum IJMA is 5- or greater, JMA issues

This information specifies the hypocenter and magnitude

provided:

Estimated Seismic Intensity Distribution Maps showing

with the information “No threat of tsunami” or “Sea levels may

Hypocenter and magnitude
Points where IJMA1 or greater have been observed, and relat-

expected Seismic Intensity based on observation data in con-ed seismic intensity
Localities where IJMA3 or greater have been observed

has been estimated.

fluctuate slightly, but no danger is expected” for earthquakes
with IJMA3 or greater.
*Relevant information is issued for Tsunami Warnings/Advisories.
See page 12 for details.

sideration of site amplification to areas where IJMA4 or greater

The information also identifies localities with estimated IJMA5-

quake).

or greater where related observation data are incomplete.

Earthquake Information
Occurred at(JST)

Latitude Longitude(degree) (degree) Depth Magnitude Region Name

07:58 JST18 Jun. 2018

34.8N

135.6E 10 km

5.9

Osaka-fu
HokubuThis earthquake poses no tsunami risk.

From Earthquake

1 min● Summary of the JMA Seismic Intensity Scale0

Imperceptible
to people.

1

Felt slightly bysome people
keeping quiet
in buildings.

2

Felt by many
peoplekeeping quiet
in buildings.

3

Felt by mostpeople inbuildings.

16

4

Most people are startled.
Hanging objects such as lamps
swing significantly.
Unstable ornaments may fall.

5LowerMany people are frightened andfeel the need to hold onto
something stable.
Dishes in cupboards and items on
bookshelves may fall.
Unsecured furniture may move,and unstable furniture may topple
over.

5UpperMany people find it difficult to walkwithout holding onto something
stable.
Dishes in cupboards and items on
bookshelves are more likely to fall.
Unsecured furniture may topple
over.
Unreinforced concrete-block walls
may collapse.

Earthquake/Magnitude Calculation

Collection of Seismic Intensity Data

3 min

10 min5 min

Estimated Seismic Intensity Calculation
15 minInformation on Long-Period Ground Motion

6Lower

It is difficult to remain standing.
Many unsecured furniture moves and may
topple over. Doors may be stuck.
Wall tiles and windows may sustain damage
and fall.
In wooden houses with low earthquake
resistance, tiles may fall and buildings maylean or collapse.

Long-Period Ground Motion Class Calculation

Indication of Long-Period Ground Motion not represented
by Seismic Intensity Values Alone
For long-period ground motion with LPGM class 1 or greater, the class atthe observation site and areas are indicated. If IJMA4 or less and LPGM class 3
or greater have been observed, these areas are also indicated.
High earthquake resistance Low earthquake resistance

6Upper

It is impossible to move without crawling.
People may be thrown through the air.
Most of unsecured furniture moves, and is more
likely to topple over.
Wooden houses with high earthquake
resistance may lean in some cases.
Large cracks may form, and large landslides andmassif collapses may be seen.
High earthquake resistance Low earthquake resistance7

Wooden houses with low earthquake
resistance are even more likely to lean orcollapse.
Wooden houses with high earthquake
resistance may lean in some cases.
Reinforced-concrete buildings with low
High earthquake resistanceearthquake resistance are more likely to collapse.

Seismic Intensity measured at observation sites even in the same city or block may differ with a margin of ±1 because
ground motion is affected by ground conditions and topography.
Earthquakes in very shallow parts of the crust may be felt even if their magnitude is small. Tremors are often felt over alimited area, and those with a Seismic Intensity of 1 or less may not be observed if there is no Seismic Intensity meter
nearby. In such cases, no earthquake information is issued.

Low earthquake resistanceAs estimated intensity values have a margin of error, these maps should be used to determine the approximate extent
and distribution of strong ground motion rather than for focus on the estimated values in each grid.
17

Information on Long-Period Ground Motion
JMA Intensity Scale for Long-Period Ground Motion

When a major earthquake occurs, Long-Period Ground Motion may cause greater damage toupper floors of buildings than at ground level. Information is provided to clarify the characteristics of long-period shaking in such structures and support mitigation of related damage.

Human perception

Indoor situation

class1• Felt by most people inbuildings. Some people arestartled.

• Hanging items such as lamps and blinds swing
significantly.

class2• Many people find it difficult
to walk without holding onto
something stable.

• Furniture on casters moves slightly.
• Items in cupboards and bookshelves may fall.
• Some of unsecured moves and may topple over.

• It’s difficult to remain
standing.

• Furniture on casters moves significantly.
• Some of unsecured moves and may topple over.
• Partition walls may crack.

• It’s impossible to remain
standing or move without
crawling.
People are at the mercy of
shaking.

• Furniture on casters moves significantly and may
topple over.
• Unsecured furniture moves and may topple over.
• Partition walls are likely to crack.

Long-Period Ground Motion(LPGM) class

Long-Period Ground Motion
Earthquakes generate ground motion with various periods – the term given to thetime between one wave and the next. Major earthquakes such as the 2011 off the
Pacific coast of Tohoku Earthquake bring notable Long-Period Ground Motion(LPGM), which does not attenuate as readily as its short-period counterpart andpropagates over great distances. Such shaking is especially amplified and tends tolast longer in soft strata such as those found on sedimentary plains.
Artificial structures also have their own natural periods. If the predominantperiod of ground motion is close to the natural period of a building, the structure
resonates and the amplitude increases. As the natural periods of high-rise buildings are longer than those of low-rise types, the former tend to resonate more with
LPGM and undergo longer-lasting extreme shaking.
Furniture and fixtures in high-rise buildings subjected to extreme shaking
may topple over or shift, and elevators may cease to operate. The amplitude tends
to increase on higher floors, causing greater damage.

Resonatewith high-risebuilding
Resonatewith low-risebuildingclass3
Short-Period Ground Motion

Long-Period Ground Motion● Severe and extended
shaking in high-rise building

As the high-rise buildings found extensively on sedimentary plains in metropolitan areas of Japan such as Tokyo, Nagoya and Osaka are vulnerable to extreme
shaking in association with LPGM, there are concerns that the anticipated Nankai
Trough Earthquake could cause large-scale damage in these areas.

class4

Earthquakes producing LPGM class 3 or higher (since Mar. 2013)s
mic waveeriod seis
nces
ta
is
d
g
● Long-pnover lo
te
a
g
a
p
ro
p

● Effects of Long-Period Ground Motion

The scale quantifies the effects of shaking in a high-rise building witha natural period of around 1.5 to 8 seconds (approx. 14 stories or more).
There are four classes based on degrees of human perception and damage,such as toppling or shifting of furniture and fixtures. The conditions indicated are a rough guide, and actual damage may differ. Effects also vary withfactors such as building/structural conditions and the duration of earthquake motion.

24F

Furniture/fixture toppling and shift
In the 2011 off the Pacific coast of Tohoku Earthquake,
upper floors of high-rise buildings swayed significantly
and fixtures toppled over or shifted even in areas far
away from the epicenter such as Tokyo.

As Seismic Intensity data only partially express the strength of long-period shaking on higher floors, JMA is using a four-category intensity scale
for LPGM to indicate the strength of shaking in high-rise buildings and thepossibility of related damage.

2F

M

IJMA

LPGM
class

2014/11/22 22:08 Northern Nagano Pref.

6.7

6-

3

2015/05/13 06:12 Off Miyagi Pref.

6.8

5+

3

2016/04/14 21:26 Kumamoto Pref.

6.5

7

3

2016/04/15 00:03 Kumamoto Pref.

6.4

6+

4

2016/04/16 01:25 Kumamoto Pref.

7.3

7

4

2016/10/21 14:07 Middle Tottori Pref.

6.6

6-

3

2018/09/06 03:07 Middle Eastern Iburi, Hokkaido

6.7

7

4

2019/06/18 22:22 Off Yamagata Pref.

6.7

6+

3

2021/02/13 23:07 Off Fukushima Pref.

7.3

6+

4

2021/03/20 18:09 Off Miyagi Pref.

6.9

5+

3

2022/03/16 23:36 Off Fukushima Pref.

7.4

6+

4

Date(JST)

Hypocenter

Photos by Kogakuin University

How the high-rise building shakes varies depending on its height, shape and structure. LPGM class may not be accurate due to individual building.

Elevator and Interior damage
In the Mid Niigata prefecture Earthquake in 2004, damage
to elevator wires occurred in high-rise buildings in Tokyo(IJMA 3) approximately 200 km from the epicenter.
In the 2011 off the Pacific coast of Tohoku Earthquake,high-rise buildings swayed significantly even in Osaka (IJMA
3) approximately 700 km from the hypocenter, interiormaterials and fire doors were damaged, and many people
were trapped in stopped elevators.
18

Oil tank damage
In the Tokachi-oki Earthquake in
2003, petroleum complexes inTomakomai approximately 250 km
from the hypocenter experienced
sloshing of liquid in tanks. Floatingroofs on tanks sank, and a fullsurface fire broke out.
Photo by National Research Institute of Fire and Disaster

The characteristics of shaking in high-rise buildings differ between higher and lower floors.
The top of a building may be more severely shaken than scale values suggest.
As buildings with a seismic isolation structure have a long natural period, the damping effect is strong with short-period seismic motion but may be larger seismic motion with long-period motion.
Structural measures are taken against major earthquakes, and work is undertaken to raise awareness of action to betaken with the assumption of no major architectural failure.

19

Other Information and Commentary n
Earthquakes and Tsunamis
Distant Earthquake Information

Information on Seismic Activity in the Eastern Izu District

JMA monitors seismic activity not only around Japan but also worldwide. When an earthquake with a magnitude of 7.0 or larger or with a remarkable magnitude that may causesignificant damage to nearby cities occurs outside Japan, JMA issues Distant Earthquake
Information to the public within about 30 minutes after the earthquake occurs. Its content
includes the date, time, epicenter and magnitude of the earthquake as well as the estimatedimpact and observation of tsunami generated by the quake.

In the eastern Izu district, seismic swarms related to magma activity have frequently occurred in the past.
Based on the data obtained from past activities, JMA evaluates the transition and prospect of further earthquakes in eastern Izu.

Occurred at Latitude Longitde Depth Magnitude Region Name(JST)
(degree) (degree)
13:18 JST 22.1S 169.2E - 7.6
SouthernPacific05 Dec 2018
Ocean
Earthquake parameters by PTWC.
There is a possibility of a destructive regional tsunami in the Pacific
Ocean.

If anomalous crustal deformation caused by magma rising is detected and active seismicity is expected, JMA issues information on the maximum possible magnitude and Seismic Intensity of the largest
earthquake, the expected number of earthquakes with a Seismic Intensity of 1 or greater, and the expected
duration of the activity.
Atami

When a head time of hours is expected before tsunami could reach the country, JMA evaluates the possibility of strikes andissues Tsunami Warnings/Advisories if necessary hours before the estimated arrival time.
If Distant Earthquake Information indicates the risk of a tsunami or indicates that the possibility of such is under evaluation,
look out for further information from JMA.

The region of the seismic swarms

ItoIn the event of a tsunami caused by a volcanic eruption or similar, JMA calls for caution and vigilance via its Tsunami Warning/Advisory system.
• Information is also provided on any potential for tsunami occurring due to volcanic eruptions overseas.
• Tsunami Warnings/Advisories are generally based on domestic tide level observations.
For tsunami caused by volcanic eruptions, the action to be taken is the same as that for tsunami
caused by earthquakes (table, P.12).

Anticipation of tsunami caused by volcanic eruptions and issuance of Tsunami
Warnings/Advisories before coastal impact may be imprecise due to the difficulty of prediction. Volcanic phenomena causing tsunami may also not berecognized.
The information here will be updated as necessary. Be sure to check back regularly.

Information on Numbers of Earthquakes andOther Variables

When hypocenter and magnitude of significant earthquakes are scrutinized, JMA issues information on update of hypocenter and magnitude.
20

time

Izu Peninsula➂ Strainobservation

Seismic activity➀ Rising magma

If the relationship cannot be applied (e.g., when the source region of the seismic activity differs from past instances),
provision of this information may be omitted.
In cases where magma rises to shallow areas, this information will be included in reports on volcanoes,
and Volcanic Warnings and other related information will be issued.

Immediately after the Earthquake

When a large earthquake with around IJMA4 or greater shaking occurs, or when Tsunami Warnings/Advisories are in effect, JMA issues • There is about 10–20% of cases where similar earthquakes occurred in the past in thevicinity.
Prompt Reports on Large Earthquakes and Tsunamis to provide information on the hypocenter, magnitude, tsunami (if observed), distri- • Caution should be exercised for a week or so after earthquakes with IJMA7 shakings.
bution of Seismic Intensity, historical earthquake activity around the• Further major earthquakes often occur within a few days in the vicinity of large
hypocenter and other data. If there is a risk of serious damage, JMA
earthquakes.
issues information on the earthquake and provides important notifications to the public through the media (via news releases) and to▲ • There is an active fault zone near the hypocenter of the earthquake.
disaster management authorities.
Comments on expected maximum Seismic • According to the Headquarters for Earthquake Research Promotion, aIntensity and the period during which
IJMA value of 6+ or greater is expected for a major earthquake on thisWhen further damage is expected (as is ofcaution against strong shaking is required
active fault.
ten the case after earthquakes with IJMA5- orbased on past seismic activity and regional
greater shaking), JMA details the prospectcharacteristics▲ Notification of nearby active faultsof further earthquakes in press releases andAfter one week or more
provides information on the period during◀ As a numerical prospect based on the subsewhich caution is required, expected seismic
quent seismic activity, we describe the occurrence• The probability of earthquakes with IJMA5+ or
intensity, and related points to note (suchprobability of earthquakes with IJMA5- or greater
greater shakings is 1/7 of that immediately
shaking with the expression as a ratio to the correas the presence of nearby active faults andafter the main earthquake. However, this is stillsponding probability before or just after the largpossible major subduction-zone earthconsiderably higher (more than 100 times) thanest earthquake.
quakes). Reporting also includes seismic
normal.
◀ We also detail regularly about the period during
activity observation data, information on• Caution should be exercised for a week or sowhich earthquakes exceeding a certain scale are
weather conditions and calls for attention
expected.
after earthquakes with around IJMA5- shakings.
Press Briefing
to the developing situation.

Tsunamis are often caused by earthquakes, but also result from other factors such as volcanic eruptions
and landslides. In January 2022, atmospheric pressure waves generated by a volcanic eruption in Tonga
in the South Pacific caused sea level changes of 1 m or more as far away as Japan.

JMA provides a frequency of earthquakes with maximum seismic intensity 1 or greater, omitting issuance of intensity information of each of earthquakes with maximum seismic intensity 1 or 2, if many earthquakes occur within a short period of time.

Number ofearthquakes➁ Crustal
deformation

Prompt Reports and Press Briefings
Information on Tsunamis Caused by Volcanic
Eruptions and Similarfrom crustal deformation data

Strainmeter




➃ Estimation of seismic activity

Shimoda

The Pacific Tsunami Warning Center has issued a Tsunami Bulletin.
“-” in the above information represents an indeterminable value.

Izu



The possibility of tsunami generation toward Japan iscurrently under evaluation.

Crustal deformation

Information release for tide-level changes
caused by atmospheric pressure waves associated with volcanic eruptions

Regular Reports on
Earthquake Activity

Weekly Report

JMA announces summary of earthquake activities. Reports are published on JMA website. In
addition, JMA issues the monthly summary as
news releases in early next month.

Week end

News Release

Early next month

Monthly report

Late next month

Monthly report (Catalog)
on the web

A few months later

Summary

Analysis

Evaluation

Close Analysis

21

Nankai Trough Earthquake Information
What is the Nankai Trough Earthquake?
The Nankai Trough, which runs from Japan’s Suruga Bay to the Hyuganada sea region,is an oceanic trench where the Philippine Sea Plate subducts underneath the Eurasianplate (continental plate) at a rate of several centimeters a year. In some places the twoplates stick together, causing the lower plate to pull the upper one downward andcreating an accumulation of strain. When this build-up exceeds the bearable limit,
the upper plate snaps back and a Nankai Trough Earthquake occurs. The Philippine
Sea Plate continues to subside along the trough, and the cycle of pulling down andsnapping back repeats.

te
pla
ea
eS
n
i
p
ilip
Ph

Strainaccumulation● Subduction● Snap backTosa Basin

Hyuga
Basin

MurotoBasin

JMA monitors seismicity and crustal deformation along the Nankai Trough around the clock. If anomalous phenomena are detected or the possibility ofan earthquake along the Nankai Trough is considered relatively high, Nankai Trough Earthquake Information is issued as outlined below.

Enshu
Basin

KumanoBasin

Information

684 Hakuho(Tenmu)
Source area

Certain
Probable

Continental
plate

Nankai Trough Earthquake Information

The anticipated focal region
along the Nankai TroughLikelyPossible203
3 yrs.

Nankai TroughEarthquake Extra
Information

887 Ninna

209 yrs.

212 yrs.

1096 Eicho Tokai

1099 Kowa Nankai

265 yrs.

262
2 yrs.
1361 Shohei(Koan) Nankai

1361 Shohei(Koan) Tokai
1498 Meio

Nankai Trough Earthquakes occur with a cycle of roughly 100-150 years withvarious repetition intervals and source areas. In some cases multiple earthquakes
occur within a certain period, and in others most of the trough can rupture at once.
About 80 years have passed since the massive 1944 Showa Tonankai and 1946 Showa
Nankai earthquakes, suggesting that another may be imminent.

1６０５ Keicho（Probably Tsunami Earthquake）

102 yrs.

1662

147
7 yrs.
1854 Ansei Tokai

90 yrs.

92
2 yrs.
1968
年

1946 Showa Nankai

2 yrs.

• When analysis results are issued

Nankai Trough• When analysis results are reported at regular meetings of the Nankai Trough Earthquake Assessment Committee (except for
Earthquake-Related Nankai Trough Earthquake Extra Information)
Commentary* Once necessary disaster prevention measures have been taken, information on analysis status and results may be issued in
Nankai Trough Earthquake-Related Commentary

Keywords of Nankai Trough Earthquake Extra Information
Nanaki Trough Earthquake Extra Information is issued with the title Nankai Trough Earthquake Extra Information (Megathrust Earthquake Alert) withappended keywords. Examples of keywords and disaster prevention measures are shown below.

1707 Hoei

1854 Ansei Nankai• When analysis is performed to determine whether anomalies may be Nankai Trough Earthquake precursors• When analysis results are updated

137
7 yrs.
107
7 yrs.

Conditions

1944 Showa Tonankai▲ Time sequence and source areas of historical Nankai TroughEarthquakes

Modified from a December 2018 report by a working group set up under
the Central Disaster Management Council

Tea ch m e a bo u t t h e N a n k a i Tro u g h !
Can Nankai Trough earthquakes be predicted?
Current technology does not enable accurate prediction of earthquake timings, locations and magnitudes,
which is valuable for advance evacuation. However, historical books and related studies indicate that thepotential for Nankai Trough earthquakes is higher when anomalous phenomena are observed.

Keywords

Conditions

Under Analysis

When analysis is underway to determine whether anomalies relate to the Nankai Trough Earthquake

Megathrust Earth- For an earthquake of Mw*8.0 or more considered to have occurred at a plate boundary with an anticipated focal region along
the Nankai Troughquake Alert
For an earthquake of Mw7.0 or more considered to have occurred with an anticipated focal region and surroundings along the
Nankai Trough (except in Megathrust Earthquake Alerts)

Megathrust Earthquake Attention For an unusual slow slip considered to have occurred at a plate boundary with an anticipated focal region along the Nankai
TroughWhen the results of analysis indicate that the anomalies are not classified into either Megathrust Earthquake Alert or Megathrust

Analysis Complete Earthquake Attention output*Mw: Moment magnitude. It is a type of magnitude calculated based on the scale of rupture area along source fault, average slip, and rigidity of rocks.

● Mw8.0 or more Earthquake

What are anomalous phenomena?

？

Things like unexpected large earthquakes are considered anomalous.

Mw8● Mw7.0 or more Earthquake？

Mw●Unusual slow slip
slow slip？

People often think that there wonʼt be a major earthquake for a while after one occurs.
If a large earthquake occurs along the Nankai Trough, others may occur in nearby areas. Large earthquakes
have previously occurred with a periodicity of two days or two years after the prior one. However, based on
world cases, large earthquakes rarely occur successively. *So, the information isnʼt always right. Why is it issued if thereʼs little certainty?
A massive Nankai Trough earthquake could cause serious damage. Even if the probability is low, we call for
vigilance and caution to minimize damage.

Issuance of Nankai Trough Earthquake Extra Information
and Disaster Prevention Measures• Take action to protect yourself

Under as necessary
Analysis • Pay attention to subsequent
information issuanceOh, right. You never know when an earthquake might hit, so it's important to be ready.

Nankai Trough Earthquake
Assessment Committee
meetingThatʼs right. Even simple preparations can help. Nobody knows when a big quake might strike.

22*Global records indicate that an earthquake with a magnitude of 7.8 or higher will follow one with a magnitude of 8.0 or higher in 1 in 12 cases within a week,
or follow one with a magnitude of 7.0 or higher in 1 in every few 100 cases within a week.

Anomalous
phenomena

5-30
minutes• Remain prepared for an earthquake on a daily basis

Megathrustin advance if it may not be possible to evacuate before a
Earthquake Alert • Act
tsunami arrives
Megathrust• Remain prepared for an earthquake on a daily basis
Earthquake
Attention
Analysis Com- • Consider the potential for earthquakes in your daily routine
plete

About
2 hours23

O ff the Coast of Hok k aido and Sanr ik u
Subsequent Ear thquake Advisor yInternational Cooperation

Megathrust Earthquake Along the Japan Trench and the Chishima Trench

International Tsunami Information

The Pacific Plate subducting beneath Japan forms the Japan Trench (off the Estimated Seismic Intensities and Tsunami Heights Associated withcoast of the Boso Peninsula to the east of Aomori Prefecture) and the Chishima Megathrust Earthquakes Along the Japan Trench and the Chishima Trench
Trench (off the coast of Tokachi toward off the coast of Etorofu and eastward),
where many large earthquakes have occurred in the past. A large earthquake
which causes a massive tsunami and strong ground motions could well happen in the area in the future.
As multiple large earthquakes have occurred locally within clusters of afew days, there is a need for precaution both against initial large earthquakes
and against following large ones.

Since 2005, JMA has served as the Northwest Pacific Tsunami Advisory Center(NWPTAC) and monitored earthquakes and tsunamis within its Area of Service(AoS), which covers the Northwest Pacific region. When a major earthquakewith a magnitude of 6.5 or greater occurs inside the AoS, the NWPTAC provides
Northwest Pacific Tsunami Advisories (NWPTA) to the countries concerned. Advisories report the origin time, hypocenter and magnitude of the earthquake, as
well as estimated arrival times and heights of tsunami at coastal Forecast Points(FPs). Subsequent analysis of seismic observation data revealing the mechanismof the earthquake will be used to perform real-time numerical simulation andissue related NWPTA updates. Information on the height of any tsunami waves
observed is also included. JMA has also issued tsunami information for the Sea
of Japan to surrounding countries since 2001.

Area of Service
Forecast Points

JMA’s international tsunami information helps recipient countries to issue
their own domestic tsunami warnings and/or evacuation recommendations.

Estimated seismic intensities and tsunami heights is based on data ▶
from the Central Disaster Mitigation Council, 2022.

Off the Coast of Hokkaido and Sanriku Subsequent Earthquake Advisory
If an earthquake with a Mw (moment magnitude) value of 7.0 or more
occurs in or around the anticipated focal regions of megathrust earthquakes along the Japan Trench and the Chishima Trench, the potential
for a large subsequent earthquake is considered to be relatively high.
JMA issues Off the Coast of Hokkaido and Sanriku Subsequent Earthquake Advisory in such cases, even though probability
based on actual worldwide records is only about 1/100.

The NWPTAC is operated under the auspices of the Intergovernmental
Coordination Group for the Pacific Tsunami Warning and Mitigation System(ICG/PTWS) under the Intergovernmental Oceanographic Commission of theUnited Nations Educational, Scientific and Cultural Organization (UNESCO/IOC),and contributes to tsunami disaster mitigation systems of Pacific countries incollaboration with the US Pacific Tsunami Warning Center (PTWC), which monitors earthquakes and tsunamis throughout the Pacific region and provides tsunami information accordingly.
▲ Area of Service (AoS) of the Northwest Pacific Tsunami Advisory
Center (NWPTAC) and its Forecast Points (FPs) as of March 2023

Technical Assistance
JMA contributes in various ways to the improvement of disaster mitigation
systems in other countries and to the establishment of international tsunami
warning systems.

Bilateral AssistanceIssuance of Off the Coast of Hokkaido and Sanriku Subsequent Earthquake Advisory
and Disaster Mitigation Measures
Advisory issuance does not necessarily indicate a need to evacuate. During the following week, people can go about their daily activities, but should be aware of
the potential need to evacuate in the event of strong ground motion or tsunami warnings, in addition to making sure that earthquake preparations are in place.

In conjunction with the Japan International Cooperation Agency (JICA) and other bodies, JMA hosts trainees from other countries at its offices and dispatches
experts to overseas organizations based on its experience of earthquake/tsunami early detection and information provision.
For countries and regions seeking to strengthen their tsunami warning
capabilities, JMA provides technical support on various matters ranging fromobservation and analysis of earthquakes and tsunamis to information provisionand disaster mitigation measures. Since the Indian Ocean Tsunami of 2004, JMA
has received numerous support requests and provided technical assistance torelated parties in Indonesia, Malaysia, Myanmar, Turkey, Chile, the Philippines, El
Salvador, Ecuador, Nicaragua and Vanuatu.

▲ Presentation course in Nicaragua

Multilateral Assistance● Advisory issuance is not a certain indication of a subsequent megathrust earthquake.
● Such advisory advises preparation for earthquakes during the following week, but does not call for advance evacuation.
● It is important to be prepared for earthquakes on a daily basis, as large earthquakes may occur without warning regardless of the timing of advisory issuance.
24

JMA contributes to the establishment of tsunami warning systems in various
regions of the world through international conferences, workshops and the likewithin UNESCO/IOC framework. For instance, NWPTAC contributes to annual/biennial Exercise Pacific Wave (PacWave) efforts by assisting with the productionof exercise scenarios, manuals and products so that the countries concerned
can conduct their own tsunami warning exercises.

▲ IOC Executive Council at UNESCO headquarters in Paris
25

Protect yourself from Earthquake

Protect yourself from Tsunami

Earthquake Readiness

Learn About Tsunami

Earthquakes strike out of the blue. Get to know your surroundings and evacuationroutes, both indoors and outdoors, to prepare for tremors so that you can protect
yourself.

Tsunami form as a result of sea wave propagation caused by upliftor sedimentation of the seafloor due to an earthquake.

Stock provisions and other necessary items
Have a store of water and food, and keep an emergency kit.

Secure a Safe Space
Create a “Safe Space” in your homewhere nothing can fall, topple over or move.

Base document: Tokyo Fire Department

5000 m

500 m

100 m

TsunamiSpeed

800km/h

250km/h

110km/h 36km/h

10 m

Examples of tsunami-amplifying topography

Speed: If you see a tsunami, it’s already too late to evacuate.
Power: Even knee-high tsunamis can wash people away.

Safe Space(Hallway)

Image of preparation in the room

Escalation: As a tsunami approaches the coast andthe sea becomes shallower, it grows much higher.
Heights may exceed estimates in some regions due to coastal
topography characteristics and other factors.

Depth

Recurrence: Tsunami can hit repeatedly due to reflection and refraction.
Later waves may be higher.
Duration: It may be several hours before the largest waves are recorded astsunami-related sea level changes are observed.
Precursor variety: Tsunami may be preceded by an ebb tide or a rising tide,
the assumption of a preceding ebb tide only may be a fatal error.

Tsunami Readiness
Check tsunami hazard areas

Safe Space(Bed room)

Stabilize furniture
Secure furniture appropriately andconsider placement to ensure an
evacuation route if the securement
fails.

Check for surrounding hazards
Check for hazardous areas andmaterials along commonly takenroutes.

Drill!

Rainfall may trigger landslides on andaround soft ground or terrain loosenedby earthquakes.

Can you really protect yourself
in emergency?
Take part in drills to learn calm
self-protect techniques.

Be sure to check your surroundings.

If you feel shaking...
If you see/hear an EEW...

Plan post-earthquake meet-up points
and communications with family
members.

Outdoors

Look out for collapsing concrete-block walls
Be careful of falling signs and broken a

Evacuate to “Safe Space”
Protect your head and shelter under a table
Do NOT rush outside
Prioritize self-protection over firefighting
26

Drill!

Check tsunami safety areas
Check where tsunami evacuation areas andtsunami evacuation buildings are. Consider
evacuation routes with local residents. Have
multiple evacuation spots and areas of higher
ground in mind.

Cape tip
As a tsunami travels
perpendicular to the coastline, energy concentrates at
the tip of the cape.

Take part in disaster mitigation drills
such as walking along evacuationroute.

Establish methods of contact

Stay calm and Secure your safety!

at HomeFamiliarize yourself with the locations of tsunami hazard areas around your home and schoolor workplace with local government tsunami
hazard map and topographical characteristics.

V-shaped bay
Tsunami energy isconcentrated at the backof the bay.

in Elevator

Stop the elevator at the nearest floor
and get off immediately

on Bus or Train

Hold on tight to a strap or a handrail

Tsunami hazard zone

Tsunami refuge building/areaThis indicates a DANGER of tsunami.

This indicates a SAFE refuge from tsunami.

Leave coastal areas andIf you feel a strong shaking at seaside...
If you feel long-lasting slow shaking...

Go to higher ground!
Be careful even during Advisory status

If you see or hear a Tsunami Warning...

Remain on alert until Warnings are lifted
Since tsunamis may strike repeatedly,remain on alert and keep evacuating until a
Tsunami Warning/Advisory is lifted.
Never return to a coastal area while a
Tsunami Warning is in effect.

Bathing or fishing in coastal areas even during a
Tsunami Advisory is hazardous. Move away fromthe water and leave coastal areas immediately.

Get accurate information
Accurate information can comefrom TV, radio, announcement
vehicles, radio broadcast systems
and the Internet.

Tsunami evacuation flag
This red and white checkered flag indicates that Tsunami
Warning/Advisory information has been issued. Evacuate
as soon as possible.
27