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Field Survey of earthquake and tsunami of Sumatra
Mentawai Islands in 2010

KUMAGAI Kentaro, Senior Researcher
Coastal and Marine Department(Key words) Tsunami, Field survey, Indonesia, Mentawai Islands, Remote island
1. Introduction
On October 25, 2010, at 23:42 JST (21:42 on thesame day in local time), an M7.7 earthquake
occurred under the seabed, west of Sumatra Islandin Indonesia. It caused a tsunami disaster centeredon the Mentawai Islands (Fig. 1). From November
10 to 13, 2010, a joint survey team of NILIM andthe Port and Airport Research Institute (PARI)
conducted a field survey of the damage of theearthquake and tsunami in cooperation with theMinistry of Maritime Affairs and Fisheries(MMAF) of Indonesia. 
2. Outline of the survey
Measurements of trace heights of the tsunami
clarified the tsunami height on North Pagai andSouth Pagai Islands, which are part of Mentawai
Islands. And interviews with residents clarified thestate of inundation and the way the residents
evacuated. The only way to reach Mentawai Island
is a ferry service and it takes 10 hours under thenormal conditions. The ferry service, however, wassuspended because of the disaster. The team wasable to access Pagai Islands with the help of MMAF.
There were difficult conditions not only the ferry
service but also the mobile phone service.
Tsunami with height of about 6m above sea levelstruck North Pagai and South Pagai Islands, anddamaged buildings. Brick houses were completelydestroyed. At several villages, the tsunami reached
between 7 and 8m in height (Fig. 2).
The human damage varied greatly between
communities. For example, no human damage
occurred at one village of the South Pagai, because
one villager, who is the first witness of tsunami inthe village, instructed the other residents to evacuate
to the safe place by screaming in loud voice.
䉴䊙䊃䊤ፉ
Sumatra
Padang䊌䉻䊮

NIndonesia䉟䊮䊄䊈䉲䉝

Hypocenter
5GKUOKEUQWTEG㔡Ḯ䊛Mentawai䊮䉺䊪䉟Islands⻉ፉ

500 km䉳Jakarta䊞䉦䊦䉺Figure 1. Location of the Mentawai Islands
Photo 1. Measuring trace height (white line shows
trace height)

Inundation
Inundationᶐ᳓㜞
depthheight

RunupInflow height㆚਄㜞Latitude✲ᐲNheight⊕䋺࿖✚⎇䊶᷼ⓨ⎇⺞䈼
White:NILIM, PARI Investigation
Black: MMAF Investigation

North Pagaiർ䊌䉧䉟ፉ㤥䋺ᶏᵗ᳓↥⋭╬⺞䈼

2o40'S

19

Mentawai Islands䊛䊮䉺䊪䉟⻉ፉ

7,8,20Sikakap

䉲䉦䉦䉾䊒

5,6

1-4, 12-16

3o00'S

11SouthPagai
ධ䊌䉧䉟ፉ
9,10
17,18

3o20'S
864

2Traceheight (m)∥〔㜞䋨m䋩

00

10 20 km
100o00'E

100o30'E⚻ ᐲ
Longitude

1-4,Malakopa
12-16䋺䊙䊤䉮䊌5, 6䋺䊛䊮䉺䉟䊋䊦䊋䊦7, 8,8,20䋺䉰䊔䉫䊮䉫䊮
1-4, 12-16:
5, 6:
Muntebarubaru 7,20: Sabeugunkgung
9, 10䋺䉰䉡䊙䊮䉫 11䋺䊋䉬 17, 18䋺䊑䊤䉰䉾䊃 19䋺䉲䊤䊑
9,10: Saumang, 11: Bake, 17, 18: Bulasat, 19: Silabu

Figure 2. Distribution of Trace Height of Tsunami
3. Supplement
The region surveyed was a remote island, isolated
from the country’s major land areas. Performing thesurvey in circumstances in which the transportationand communication services were almost suspended,
it was found to be difficult to supply materials andtransmit information to restore disaster damage inthe remote islands. Risks similar to the remoteisland disaster will be found in case an earthquake
disaster strikes Japanese remote islands. We wish to
thank everyone who helped us with this survey. [Sources]
T. Tomita, T. Arikawa, K. Kumagai, D. Tatsumi, G.
S. Yeom: Field survey of the 2010 Mentawai
tsunami disaster, Technical Note of the Port andAirport Research Institute, 2011.