ASSESSMENT OF THE SEISMIC THREATS TO MALAYSIA FROM MAJOR

FORUM ON SEISMIC AND TSUNAMI
HAZARDS AND RISKS STUDY IN
MALAYSIA
ASSESSMENT OF THE SEISMIC THREATS TO
MALAYSIA FROM MAJOR EARTHQUAKES
IN THE SOUTHEAST ASIAN REGION
AND
SEISMOTECTONIC MAP OF MALAYSIA AND
FAULT LINE/ZONE STUDY
By
Mineral and Geosciences
Department Malaysia
29 September 2009, PICC
PUTRAJAYA
INTRODUCTION
Two studies were completed by JMG:
1. The Geological and
Seismotectonic Information of
Malaysia – 2006
2. Assessment of the Seismic
Threats to Malaysia from Major
Earthquakes in the SE Asian
region - 2008
SCOPE OF WORK – 1st STUDY
1.
To collect and summarize the geological
and seismotectonic information
I. Collate and review the regional
geology and tectonic of Malaysia
II. Cataloguing all available data of past
& recent earthquakes that occurred
within Malaysia
III. Prepare and update the
Seismotectonic map of Malaysia
2. To identify, investigate and monitor
active fault lines/zones in the field.
SCOPE OF WORK - 2nd STUDY
1.
2.
3.
To collect and analyse all past major
and great earthquakes in the Southeast
Asian Region and make general
assessment of the threats to Malaysia
Collecting data and updating the
Seismotectonic map of Southeast Asian
Region, and
Identifying vulnerable areas that are
exposed to seismic-induced hazards,
i.e. landslides, sinkholes and
subsidence that can be triggered by
major earthquakes
SEISMOTECTONIC MAP OF
MALAYSIA (3rd EDITION)
Some of the major findings
TECTONIC FRAMEWORK
• Malaysia – situated within the relatively
stable Sundaland and considered a low
seismic country
• Bordered to the west and to the south
by the seismically active Sunda-Banda
Volcanic Arc; subduction of the IndianAustralian plate at 6-8 cm/yr
• To the east by the Philippines-Pacific
Plate which moves at 11 cm/yr
INTERACTION BETWEEN THREE MAJOR
TECTONIC PLATES
5 cm/yr
Eurasian –
Sunda Plate
10 cm/yr
Phillipines-Pacific
Plate
10.5 cm/yr
Major
Earthquakes
>7Mb
7 cm/yr
Indian-Australian
Plate
Source: USGS
REGIONAL FAULTS AND TECTONIC PLATES
DIFFERENTIAL EXTRUSION OF
INDOSINIAN CRUSTAL SLABS
8
7
1
SUNDA
PLATFORM
c
Ina
h
nc
tre
e
tiv
NCH
TRE
NE
IPPI
PHIL
SOUTH CHINA
SEA BASIN
~11 cm
/y
MINDANAO
CONVER
GENCE O
F
PACIFIC
PLATE
12
4
EQUATOR
8
RA
TE
MA
SU
2
KALIMANTAN
11
6
9
5
IRIAN JAYA
4
SULAWESI
Me
lan
ge
4
10
3
8
JAWA
12
SAHUL
PLATFORM
SUNDA TREN
CH
~ 6 cm/y
CONVERGENCE OF
INDIAN - AUSTRALIAN PLATE
100
104
108
112
116
120
124
140
132
FAULTS AND PLATE EDGES - SINCE MIDDLE MIOCENE
144
stressSundalandIRS05
FAULTS : 1 = PEUSANGAN 2 = SUMATRA 3 = MADURA STRAIT 4 = TARERA-AIDUNA 5 = PAPUA
6 = IRIAN/SORONG 7 = PHILIPPINE 8 = GORONTALO 9 = MATANO 10 = UN-NAMED
11 = PALU 12 = BALABAC
Source: Tjia, 2006
SEISMOTECTONIC MAP OF
PENINSULAR MALAYSIA
MALAY BASIN
AK
UB
BA
IR
LEB
TON
L
FAU
BE N
T
UL
FA
T
T
GS
KI
BU
G
E
LT
AU
IF
R
UTU
NG
TI
KL FAULT
WEST
NATUNA
BASIN
PENYU BASIN
SEISMOTECTONIC OF
SARAWAK
• Since 1874 – 21 earthquakes,
magnitude from 3.5 – 5.3 Mb
• Major Faults
– Lupar Line; former subduction
– Bukit Mersing Line
– Kelawit fault
– West Baram Line
– Tubau fault
EARTHQUAKES IN SARAWAK
SEISMOTECTONIC OF SABAH
• Sabah has the most earthquakes
– 78 , from 1897-2007
– Two destructive earthquakes – in 1976 and
1991, caused substantial damage
• North-West Sabah - influenced by the
spreading and opening of the South China
Sea Basin, that ceased 17 Ma ago.
• Eastern Sabah – influenced by the Cagayan
Ridge Volcanic Arc in te NE, the Sulu Trench
and the Sulu Sea Volcanic Arc.
SEISMIC ZONES OF SABAH
• Earthquakes occurred in Sabah over a
wide area.
• Three main seismic zones which have a
high concentration of earthquake, namely:
1) the Central-North (Ranau) Zone,
2) the Labuk Bay - Sandakan Basin Zone,
and
3) the Dent - Semporna Peninsula Zone
SEISMIC ZONES OF SABAH
CENTRALNORTH
ZONE
LABUK BAYSANDAKAN
BASIN ZONE
DENTSEMPORNA
PENINSULA
ZONE
ACTIVE FAULT ZONES
• Crocker Fault Zone (CFZ) – extends from
Tenom in the south.
• Active and potentially active fault
segments of CFZ
– Mamut
– Mensaban,
– Lobou-Lobou,
– Nalapak and
– Parancangan Fault
CR
OC
KE
R
FA
U
LT
ZO
N
E
RANAU AREA
Massive structure damage to the rubbish
chute wall of the teacher's quarter, SM
Mat Salleh, Ranau, Sabah by the
earthquake on 26/5/91 .
KUNDASANG AREA
• Recently, two active faults have
been recognized
–Lobou-Lobou Fault, left-lateral
o
strike-slip, trending N20 E
–Mensaban Faults, normaloblique, striking WNW-ESE
CR
OC
KE
R
FA
U
LT
ZO
N
E
RANAU-KUNDASANG AREA
LOBOU-LOBOU FAULT
LOBOU-LOBOU FAULT CUTTING ACROSS
THE KUNDASANG-RANAU HIGHWAY
AN ACTIVE FAULT PARALLEL TO LOBOU-LOBOU
FAULT CUTTING ACROSS SMK KUNDASANG
MENSABAN FAULT ZONE
MENSABAN FAULT CUTTING THROUGH
THE ACCESS ROAD TO THE TEACHERS’
QUARTER OF SMK KUNDASANG
LABUK BAY – SANDAKAN BASIN ZONE
DENT-SEMPORNA PENINSULA ZONE
• Has the most and frequent earthquake
occurrences in Sabah
• Darvel Bay- Lahad Datu area
– 1976 earthquake caused by ENE-trending
normal fault
– Magnitude 5.8 Mb, depth 33 km, caused
damage to several buildings in Lahad Datu
• Dent Peninsula
– earthquake caused by the active Tabin
Thrust Fault,
– FMS of the 1994 earthquake, located on
the Tabin Fault of magnitude 5.7Mw, depth
34 km
DENT-SEMPORNA PENINSULA ZONE
Assessment of the Seismic Threats to
Malaysia from Major Earthquakes in the
SE Asian region
About 70 earthquakes of Mw > 7.0, from
1977 to 2007 in the SE Asian region.
1)The Sunda subduction zone to the west of
Sumatera, extends to the Banda Basin
2)Double subduction zones of the
Philippines and Talaud Ridge
3)North arm of Sulawesi
4)Borders of Sula Spur
5)Teluk Sarera- Doberai Peninsula and the
rump of Papua
Major Earthquake > 7.0
AREAS CONSIDERED AS POSSIBLE
GENERATORS OF SEISMIC THREAT
A. Andaman Sea - northern Sumatera,
B. Straits of Malacca,
C. South China Sea,
D. Borneo region
E. Taiwan area,
F. The Philippine Islands
G. Sulawesi, and
H. Molucca Sea.
AREAS CONSIDERED AS POSSIBLE GENERATORS
OF SEISMIC THREAT
ANADAMAN – NORTHERN SUMATERA
STRAITS OF MALACCA
SOUTH CHINA SEA AND BORNEO REGION
TAIWAN REGION
THE PHILIPPINES
SULAWESI REGION
MAKASSAR STRAIT
MOLUCCA SEA REGION
(SUB )MARINE VOLCANIC ACTIVITY
SANGIR
Group
SIGNIFICANT TSUNAMIS
DEGREE OF RISKS
Risks to Malaysia are principally dependent on the
following factors:
1) Locations of population concentration;
2) Concentration of high-rise buildings, elevated and
subterranean transport lines, communication
lines, tunnels, and bridges;
3) Topographic relief (natural and man-made) - steep
slopes are liable to mass movements and
landslides;
4) Geological conditions- limestone bedrock prone to
sinkhole development, and unconsolidated
subsurface material tend to subsidence;
5) Area with history of disasters; and
6) Proximity to major seismic areas.
CONCLUSION
Type & Geographical
Origin
Potential
Threat
Assessment
1) Earthquakes in
Sabah
Ground
shaking
Light to moderate damage (Lahad Datu,
1976); Landslides in Ranau (1991)
2) Earthquakes in
northern Sarawak
Ground
shaking
Light damage (Niah area, 2005); could
trigger mass movements on steep
slopes.
3) Earthquakes in
Andaman – Sumatera
Region
Ground
shaking
Affect west coast of Peninsula M’sia;
damage is light to moderate; sinkhole
development in limestone
basement in KL, Kinta Valley & Perlis;
ground subsidence in western coastal
plain underlain by thick unconsolidated
sediments.
CONCLUSION
Type & Geographical
Origin
Potential
Threat
Assessment
4) Earthquake on
Sunda Trench, off
Sumatera-Andaman
(26 Dec 2004, 9.0Mb)
Tsunami
Affected Langkawi, P. Pinang, Kedah
coast; runups 3m; 68 lives lost; property
damage to fishing boats & coastal
dwelings. Recurrence time of similar
magnitude earthquake estimate to
exceed a century. Probable earthquake
induced subsea slides off Andaman
islands.
5) Earthquake on SW Tsunami
side of the Philippines;
by subduction along
the Gorontalo trench,
off the northern arm
Of Sulawesi.
Threats to eastern and southern Sabah
coasts. No records of past events in
Sabah. Produced local tsunamis with
runups estimated 3 to 5 m.
CONCLUSION
Type & Geographical
Origin
Potential
Threat
Assessment
6) Earthquake in
Strait of
Makassar
Tsunami
Threats to southern Sabah coasts.
coast; No records of past events in
Sabah. Produced local tsunamis with
runups estimated 3 to 5 m.
7) Large –scale submarine sliding on the
Baram Delta front,
offshore Sarawak.
Tsunami
Large submarine slides probably occur
on the actively prograding Baram Delta
front. Tsunami may cause damaging
runups on the coasts of western Sabah
and Sarawak.
8) Eruption of large
volcanic islands or
subsea volcanic
eruption & large scale
collapse of volcanoes.
Tsunami
Risk to Sabah east coast. No known
records but probability of tsunami is high
considering the frequent activity of half
a dozen of the Sangir volcanoes.
RECOMMENDATIONS
1) A study of available tide records of the Sabah
coasts is proposed to determine anomalies that
may indicate past tsunamis originating from the
southern Philippines and Sulawesi.
2) Growth patterns of micro-atolls in the Sabah
offshore could well indicate anomalies
associated with ground tilting and/or tsunami
damage.
3) Selected tidal flats and areas in the lower coastal
plains of the Straits of Melaka could contain
sedimentological evidence of previous tsunami
runups originating from large earthquakes off
northern Sumatera and in the Andaman Sea
area.
RECOMMENDATIONS
4) A similar study in selected tidal flats and lower
coastal plains of Sarawak and of Sabah could
provide evidence for anomalous disturbances
associated with major earthquakes at distant
locations of the South China Sea.
5) The threats from large-scale subsea slides of the
actively prograding Baram Delta front could be
assessed by studying seismic sections and the
so called “site survey” reports that are required
studies on the potential of shallow hazards along
planned pipe line routes and sitting of oil rigs.
RECOMMENDATIONS
6) Establish hazard zoning in terms of probable shaking
intensity due to distant earthquakes for Peninsular
Malaysia, and those generated by local earthquakes in
Sabah and northern Sarawak with geological factors
such as the unconsolidated nature of the coastal
plains along the Straits of Melaka and the extent of
limestone basement in the Kuala Lumpur, Kinta Valley,
Perlis and Bau areas.
7) Establish a tsunami EWS off eastern Sabah to address
the high potential of tsunami being generated by the
frequent and very strong subduction earthquakes at
the Gorontalo Trench off northern Sulawesi.
8) Peroidic public awareness campaigns on the seismic
threats and risks should be conducted.
THANK YOU