A major
earthquake (M7.0-7.9 termed as "major")
occurred in the Indian Ocean to the west
of the island of Sumatra in Indonesia, on
11 January 2012
at 01:37 AM local
time (WIT) in Indonesia or 00:07
AM in the Nicobar Islands, India. It had a magnitude of Mw=7.2.
This earthquake was centred
290 kms W of Laban (Pulau Simuelue, Sumatra), Indonesia,
381 kms SW of Meulaboh (Sumatra), Indonesia,
424 kms SSW of Banda Aceh (Sumatra), Indonesia,
503 kms SSW of Campbell Bay (Nicobar Islands), India,
508 kms NW of Gunungsitoli (Sumatra), Indonesia,
882 kms NW of Padang (Sumatra), Indonesia,
953 kms W of Kuala Lumpur, Malaysia,
1034 kms S of Port Blair (Andaman Islands), India,
1561 kms ESE of Colombo, Sri Lanka,
1854 kms SE of Chennai (Tamil Nadu), India.
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Tremors have been felt
in parts of Sumatra, Indonesia in the provinces of Nanggroe Aceh
Darussalam, Sumatera Utara, Sumatera Barat, Bengkulu and Lampung. Strong tremors were felt for a long
duration on the island of Simuelue nearest to the epicentre
causing panic.
The earthquake was strong and caused panic at Meulaboh in Aceh Barat
where people
went outdoors. Tremors lasting as long as a minute were felt by
people awake at the time in Banda Aceh and the rest of Aceh Besar. People went outdoors in Banda Aceh including in the Darussaalam
and Lamgugob in Syiah Kuala district and in the Ulee Kareng
district.
Shaking was experienced as far as Malaysia, Singapore and Sri
Lanka. In Malaysia the earthquake was felt in Kedah, Perak and Pinang. There are no reports yet of the effects
of this earthquake in the Nicobar Islands, India. In isolated
instances, mild tremors were felt by individuals at Dhaka,
Bangladesh and at Cuttack in Odisha, India.
There was some panic in Aceh province in Indonesia, especially in
the capital, Banda Aceh. Residents in coastal areas such as
Keutepang, Lambaro, Mata Ie, Pante Pirak, Peuniti, Simpang
Surabaya and Ulee Lhue fled to higher ground fearing a tsunami.
Many residents continued to seek shelter on the Pante Pirak Bridge
hours after the tsunami warning was lifted. Residents in the
Geulumpang and Lampaseh areas in the city also spent the night
outdoors. In coastal areas such as Meulaboh and the Nagan Raya
regency people hurried to higher ground in panic. The residents of the island of Simuelue were also
reported to have been on alert for a possible tsunami.
This earthquake appears to have occurred within the Indian Plate
at a depth of ~30-kilometres. The MT and CMT solutions indicate a
predominance of strike-slip faulting. Due to the style of faulting
and the location of this earthquake, the chances of a tsunami in
the Indian Ocean were lower than would have been the case, had
this earthquake occurred along the subduction interface to the
east. Nevertheless, eyewitnesses in Meulaboh reported a drop in
the sea level that was later confirmed by the local disaster
management authority, BPBD.
A local tsunami warning was issued in Indonesia but was lifted two
hours later. A tsunami advisory was also issued by INCOIS
immediately after the earthquake. A final bulletin followed after
no significant tsunami was observed by tide gauges monitored by
them with the caveat that local conditions could cause significant
variations in observed tsunami activity.
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References
01) National Earthquake Information
Centre (PDE),
Golden, USA.
02)
Harvard Centroid Moment Tensor Solution (HRV),
Harvard, USA.
03) Macroseismic information has been
compiled by the ASC from reports by local media and local NGO
personnel.
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