Seismotectonics of Southeast Asia

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Seismotectonics of Southeast Asia with special
reference to Sri Lanka
J R Kayal Geological Survey of India Kolkata e-mai
l jr_kayal_at_hotmail.com
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Tectonic Setting and Large Earthquakes in NE
India (Kayal et al. 2005, Curr Sci )
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Seismicity Map of NE India (1964-1996 )

(Kayal, 1998)
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GRAVITY MAP OF NORTHEAST INDIA ( Verma and
Mukhopadhyay, 1977 )
DF Dauki Fault, OF Oldham Fault, BF Brahmaputra
Fault, NT Naga Thrust, MBT Main Boundary Thrust
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Mishra, Zhao and Kayal, 2006
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Historic Large / Great Earthquakes
SUMATRA 1833 ( M 9 ) 1861 (M 8.5) 2000 (M
w 7.2) ANDAMAN 1881 ( M 7.9) 1941 (M 7.9)
Tectonic Setting of Andaman-Sumatra Region
(modified from Kayal et al, BSSA,2004)
Rupture areas of the Large Earthquakes are shown.
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Depth sections across the
Burma-Andaman-Sunda-Java subduction zone
AA India-Burma 200 km BB India-Burma
230 km CC Australia-Sunda 680 km DD
Australia-Sunda 700 km
Rao et al. 2006
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Worlds 12 largest earthquakes since 1900
No. Location Date UTC Mag Lat Long Associated Plates
1. Chile 1960 05 22 9.5 38.24 S 73.05 W NZ, SA, AN
2. Prince William Sound, Alaska 1964 03 28 9.2 61.02 N 147.65 W PA, NA
3. Andreanof Islands, Alaska 1957 03 09 9.1 51.56 N 175.39 W PA, NA
4. Kamchatka 1952 11 04 9.0 52.76 N 160.06 E PA, NA, OK
5. Off the West Coast of Northern Sumatra 2004 12 26 9.0 3.30 N 95.78 E IN, BU, AU, SU
6. Off the Coast of Ecuador 1906 01 31 8.8 1.0 N 81.5 W NZ, SA, CO, CA
7. Rat Islands, Alaska 1965 02 04 8.7 51.21 N 178.50 E PA, NA
8. Off the West Coast of Northern Sumatra 2005 03 28 8.7 2.07 N 97.01 E AU, SU, IN, BU
9. Assam Tibet 1950 08 15 8.6 28.5 N 96.5 E IN, EU, BU, SU
10. Kamchatka 1923 02 03 8.5 54.0 N 161.0 E PA, NA, OK
11. Banda Sea, Indonesia 1938 02 01 8.5 5.05 S 131.62 E AU, SU, PS, PA
12. Kuril Islands 1963 10 13 8.5 44.9 N 149.6 E PA, PS, EU, OK
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Worlds 12 largest earthquakes since 1900 and
their correlation with plate boundary junctions
Rao et al. 2006
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Plate boundaries and relative motions in South
Asia
Rao et al. 2006
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Global Earthquakes 1900-1999 (Centennial
Earthquake Catalog)
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World Stress Map
Normal faulting are shown in red, Strike-slip
faulting in green and Thrust faulting in black
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Regional Seismicity map (Mgt5.0), 1965 to December
26, 2004 (NEIC), showing rupture zones of the
previous events
(Lay et al., 2005.)
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• A Barrier that separates . . .
• Distinct plate pairs
• Distinct zones of stress build-up
• Distinct styles of subduction
• Distinct velocities of subduction

A Tectonic Model for the Sumatra earthquakes
Rao et al. 2006
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Initial fast rupture zones and maximum slips of
the 2004 Megathrust Earthquake
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SLIP AMPLITUDE AND DIRECTION OF MOTION
                                               
                                  
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Rupture history First one min 100 km rupture
(slowly) Rupture accelerated to 3km/s for the
next 4 min. Rupture at 2.5 km/s For next 6
min. Then slow rupture for 25 min, and very
slow for 5 min that generated free oscillation of
the Earth.
Total Rupture length 1600 km. Tsunami generated
by the southern 650 km Rupture.
Rupture Zones Slip Mechanisms for the 2004
Sumatra-Andaman Earthquake (Bilham, 2005)
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Source Mechanisms of the 2004 and 2005 Earthquake
Sequences (Lay et al., 2005)
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Cross sections through the 2004 rupture zone
(Bilham et al.,2005)
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CMT Solutions of the 2004 Sumatra Earthquake
Sequence
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Aftershocks of the 2002 Main Shock Mw 6.5 in
North Andaman
( Kayal et al. 2004, BSSA )
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( Kayal et al. 2004, BSSA )
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Tectonic Model and Gravity Anomaly, North Andaman
( Kayal et al. 2004, BSSA )
( Kayal et al. 2004, BSSA )
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Correlation of the Lineaments
CC-M Cape Comorin Matara Lineament An-Rt
Achankavil- Ratnapura Lineament V-KO
Vaigai-Kal- Oya Lineament JTS
Jaffna-Thanjuvur Salem Lineament C Cauvery
Lineament. GM-PS Gulf of Mannar - Palk Strait
Lineament
Mesozoic
Gondwana
Tectonic map of south India and Sri Lanka
(Eremenko, 1968)
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Reconstruction Models (A) Smith Hallman
(1970), (B) Crawford (1974).
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A Precambrian Correlation
B Initial Rifting in Gondwana times
showing three Triple Junctions
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Tectonic Evolution Stage Late
Cretaceous Stage Late Paleocene Stage
Miocene
1
2
3
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Paleotectonic map of south India and Sri Lanka
showing Gondwana Rift along Precambrian
Proto-Boundary Fault (PBF), After Katz, 1978
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Geologic and Tectonic Correlations between India,
Sri Lanka and Antarctica 1Achankovil shear
zone, 2 C B, 3G R, 4 M R, 5 Lambert Rift,
6 Napier complex 7 Western Vijayan 8 Highland
and 9 Eastern Vijayan complexes. aProterozoic
Granulite, bArchaean and c Proterozoic Gneiss .
(Yoshida et al. 1992)
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Lineaments M Moyar BH
Bhavani P-C Palaghat-Cauvery A Achankovil
Deccan Traps
Dharwar Craton
Present Tectonic Setting of South India and Sri
Lanka (Agarwal and Pandey, 1999)
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Locations
1 Nartamali 2 Tiruchirapalli 3 Gingee 4
Nagapattinam 5 Jaffna 6 Pondicherry
Gravity Anomaly
A Palk Strait B Eastern Vijayan Series
Bouguer Anomaly map over southeastern part of
India and Sri Lanka (Agarwal Pandey, 1999)
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Aeromagnetic map (Total Intensity) and the PBF
(Reddi et al., 1988)
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Seismicity in south India is at the transition
that separates Greenstone granite and
Granulite zones. Seismicity in Sri Lanka is
concentrated in the Highland Complex zone. No
activity at the PBF
Seismicity Map of South India and Sri Lanka
(Ramakrishna Rao, 1989)
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m
CO Cochin CC Cape Comorin PON Pondicherry
Pre-break up position of Sri Lank with respect to
Antarctica and India (Yoshida et al., 1992),
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Lineaments
1. Bongolava-Ranotsara 2. Moyar 3. Bhavani 4.
Achankovil
Geotectonic Correlation between Madagaskar,
India, Sri Lanka and Antarctica, (Agarwal
Pandey, 1999)
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Geological morphotectonic map of Sri Lanka
(Vitanage 1972)
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Regional Earthquakes and Microseismicity in Sri
Lanka (Fernando Kulasinghe,1986)
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Thank you