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Magnitude 9.0 - SUMATRA-ANDAMAN ISLANDS EARTHQUAKE
OFF THE WEST COAST OF NORTHERN SUMATRA
2004 December 26 00:58:53 UTC
Magnitude 9.0
Current
Earthquakes
Date-Time Sunday, December 26, 2004 at 00:58:53 (UTC)
= Coordinated Universal Time
Sunday, December 26, 2004 at 7:58:53 AM
= local time at epicenter
Time of Earthquake in other Time Zones
USA
World
Location 3.307° N 95.947° E
NEIC Current
Earthquake
Information
Depth 30 km (18.6 miles) set by location program
Region OFF THE WEST COAST OF NORTHERN SUMATRA
Distances
ShakeMaps
255 km (155 miles) SSE of Banda Aceh, Sumatra, Indonesia
310 km (195 miles) W of Medan, Sumatra, Indonesia
1260 km (780 miles) SSW of BANGKOK, Thailand
1605 km (990 miles) NW of JAKARTA, Java, Indonesia
Seismogram
Displays
Location Uncertainty horizontal +/- 5.6 km (3.5 miles); depth fixed by location
program
Past & Historical
Earthquakes
Parameters Nst=370, Nph=488, Dmin=644.5 km, Rmss=1.17 sec, Gp= 29°,
M-type=teleseismic moment magnitude (Mw), Version=U
Source USGS NEIC (WDCS-D)
Earthquake
Notification E-mail
Event ID usslav
Felt Reports: This is the fourth largest earthquake in the world since 1900 and is the largest since the
1964 Prince William Sound, Alaska earthquake. In total, more than 283,100 people were killed, 14,100
are still listed as missing, and 1,126,900 were displaced by the earthquake and subsequent tsunami in 10
countries in South Asia and East Africa.The earthquake itself caused severe damage and casualties in
northern Sumatra, Indonesia and in the Nicobar Islands, India. It was felt (IX) at Banda Aceh, (VIII) at
Meulaboh and (IV) at Medan, Sumatra; (VII) at Port Blair, Andaman Islands, India; (III-V) in parts of
Bangladesh, mainland India, Malaysia, Maldives, Myanmar, Singapore, Sri Lanka and Thailand. The
tsunami caused more casualties than any other in recorded history and was recorded nearly world-wide
on tide gauges in the Indian, Pacific and Atlantic Oceans. At least 108,100 people were killed and
127,700 are missing and presumed killed by the earthquake and tsunami in Indonesia. Tsunamis killed at
least 30,900 people in Sri Lanka, 10,700 in India, 5,300 in Thailand, 150 in Somalia, 90 in Myanmar, 82 in
Maldives, 68 in Malaysia, 10 in Tanzania, 3 in Seychelles, 2 in Bangladesh and 1 in Kenya. Tsunamis
caused damage in Madagascar and Mauritius and caused minor damage at two places on the west coast
of Australia. Seiches were observed in India and the United States and water level fluctuations occurred
in wells in various parts of the United States. Subsidence and landslides were observed in Sumatra. A
mud volcano near Baratang, Andaman Islands became active on December 28 and gas emissions were
reported in Arakan, Myanmar. (last updated 2/15/05)
http://earthquake.usgs.gov/eqinthenews/2004/usslav/ (1 of 3)11/3/2005 6:33:43 AM
USGS Earthquake Hazards Program-Latest Earthquakes
The devastating megathrust earthquake of December 26th, 2004 occurred on the interface of
the India and Burma plates and was caused by the release of stresses that develop as the
India plate subducts beneath the overriding Burma plate. The India plate begins its descent
into the mantle at the Sunda trench which lies to the west of the earthquake's epicenter. The
trench is the surface expression of the plate interface between the Australia and India plates,
situated to the southwest of the trench, and the Burma and Sunda plates, situated to the
northeast. MORE...
Click on images for larger versions.
Maps & Overview of Earthquake:
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Earthquake Summary
Earthquake Summary Poster
Rupture Area of Fault Compared to
Cascadia Subduction Zone
Did You Feel It?
News Release
FAQ - Everything Else you want to know..
Earthquake Information for Indonesia
Andaman Sea Swarm
Technical Earthquake Information:
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Tsunami Information:
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Tsunami Information Links
Can a tsunami like this happen in the U.S.?
Worldwide Tsunami Statistics - NOAA (PDF
version)
West Coast & Alaska Tsunami Warning
Center - Latest Bulletin
West Coast & Alaska Tsunami Warning
Center Indian Ocean Tsunami Webpage
Pacific Tsunami Warning Center - Latest
Bulletin
NOAA Tsunami Research
Spotlight Images & Animations from NOAA
National Geophysical Data Center
International Coordination Group for the
Tsunami Warning System in the Pacific
USGS Tsunami Research
USC Tsunami Research Center
Tsunami Animation - Natl. Inst. of Advanced
Industrial Science & Technology, Japan
http://earthquake.usgs.gov/eqinthenews/2004/usslav/ (2 of 3)11/3/2005 6:33:43 AM
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NEIC Moment Tensor Solution
Historical Moment Tensor Solutions
Harvard Moment Tensor Solution
Theoretical P-Wave Travel Times
Energy and Broadband Solution
Phase Data
Seismic Record Section
Earthquake Density Maps
Finite Fault Model
Cumulative Moment Release from Great
EQs (PDF version) - Harvard
USGS National Map Hazards Data
Distribution System
IRIS Special Event Webpage
Small Threat, But Warning sounded for
Tsunami Research - article in AusGeo
News 75, 09/04
USAID - The United States Agency for
International Development
Foreign Embassies of Washington, D.C.
U.S. Department of State: Current Travel
Warnings
Relief Web
Information about U.S. Citizens
U.S. State Department Hotline
For information about U.S. Citizens
affected by the Asian Earthquake:
888-407-4747 : within the U.S.,
tollfree
317-472-2328 : outside the U.S.
USGS Earthquake Hazards Program-Latest Earthquakes
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Tsunami Lab Info - Intl. Tsunami Info Center
India Tide Guage Data - Natl. Inst. of
Oceanography
ASC India Tsunami Information
International Centre for Geohazards
202-647-5225 : Washington, D.C.
area
Global Earthquake Facts and Lists:
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Note: The earthquake locations and magnitudes cited in these
bulletins are very preliminary, and may disagree with the more accuate
USGS locations and magnitudes computed using more extensive data
sets.
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Magnitude 7 and Greater Earthquakes for
2004
Magnitude 8 and greater earthquakes since
1990
Largest earthquakes in the world since 1900
News Links:
Educational Links :
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News Links from Google
Sounding the Alarm on a Tsunami is
Complex and Expensive - NY Times
(registration required)
At Warning Center, Alert for the Quake,
None for a Tsunami - NY Times (registration
required)
Agency Answers Critics Over No Tsunami
Warning - CNN
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Wikipedia Encyclopedia Entry
PBS - Savage Earth: Waves of Destruction
Discovery School: Understanding Tsunamis
NASA - Tsunami: The Big Wave
On the Cutting Edge - Tsunami
Visualizations
Preliminary Reports :
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The December 26, 2004 Indian Ocean
Tsunami:
Initial Findings on Tsunami Sand Deposits,
Damage, and Inundation in Sri Lanka
EERI Reconnaissance Report
Contacts
The official magnitude for this earthquake is indicated at the top of this page. This was the best available estimate
of the earthquake's size, at the time that this page was created. Other magnitudes associated with web pages
linked from here are those determined at various times following the earthquake with different types of seismic
data. Although, given the data used, they are legitimate estimates of magnitude, they are not considered the
official magnitude.
FAQ about Earthquakes | Earthquake Preparedness
The USGS Earthquake Hazards Program (EHP) of the U.S. Geological Survey (USGS)
is part of the National Earthquake Hazards Reduction Program (NEHRP)
led by the Federal Emergency Management Agency (FEMA).
U.S. Geological Survey, a bureau of the U.S. Department of the Interior
This page is brought to you by the Earthquake Hazards Program
URL: http://earthquake.usgs.gov/eqinthenews/
Maintained by: Web Team
Last modification: Thursday, 25-Aug-2005 13:41
Contact Us: Web_Team
USGS Privacy Statement | | Disclaimer | | FOIA | | Accessibility
http://earthquake.usgs.gov/eqinthenews/2004/usslav/ (3 of 3)11/3/2005 6:33:43 AM
Glossary
Earthquake
Activity
Recent Earthquakes - Glossary
Maps
Current Earthquakes
Maps
USA: M1+
World: M2.5+/4+
Lists
USA: M1+, M3+
World: M2.5+/4+, M5
+,
Last 8-30 Days
Maps at various scales show the location of the event. Some maps for
locations in California and Nevada also show faults with fault names
revealed as you move the mouse over the fault (if you have Javascript
enabled in your browser). Links to additional location maps are often
listed farther down in the event description page.
Magnitude
Seismologists indicate the size of an earthquake in units of magnitude.
There are many different ways that magnitude is measured from
seismograms because each method only works over a limited range of
magnitudes and with different types of seismometers. Some methods
are based on body waves (which travel deep within the structure of the
earth), some based on surface waves (which primarily travel along the
uppermost layers of the earth), and some based on completely different
methodologies. However, all of the methods are designed to agree well
over the range of magnitudes where they are reliable.
RSS 2.0
RSS
Instructions & Info
Earthquake magnitude is a logarithmic measure of earthquake size. In
simple terms, this means that at the same distance from the earthquake,
the shaking will be 10 times as large during a magnitude 5 earthquake
as during a magnitude 4 earthquake. The total amount of energy
released by the earthquake, however, goes up by a factor of 32.
ShakeMaps
Magnitudes commonly used by seismic networks include:
Seismogram Displays
Earthquake Data
Magnitude
type
Applicable
magnitude
range
Past & Historical
Earthquakes
Earthquake Notification
E-mail
http://earthquake.usgs.gov/recenteqsww/glossary.htm (1 of 7)11/3/2005 6:33:56 AM
Distance range
Comments
Glossary
0-400 km
Based on the
duration of shaking
as measured by the
time decay of the
amplitude of the
seismogram. Often
used to compute
magnitude from
seismograms with
"clipped"
waveforms due to
limited dynamic
recording range of
analog
instrumentation,
which makes it
impossible to
measure peak
amplitudes.
0-400 km
The original
magnitude
relationship defined
by Richter and
Gutenberg for local
earthquakes in
1935. It is based on
the maximum
amplitude of a
seismogram
recorded on a
Wood-Anderson
torsion
seismograph.
Although these
instruments are no
longer widely in
use, ML values are
calculated using
modern
instrumentation with
appropriate
adjustments.
Large Significant
Earthquakes This Year
Significant Earthquake
Posters
Fast Moment Tensor
Solutions
Duration (Md)
<4
Latest Energy &
Broadband Solutions
Region Maps
Africa
Asia
Australia
Europe
North
America
North Pole
South
America
South
Pacific
South Pole
Local (ML)
2-6
Hemisphere Maps
West
East
North
South
Other Maps
Guam
Hawaii
WorldMercator
http://earthquake.usgs.gov/recenteqsww/glossary.htm (2 of 7)11/3/2005 6:33:56 AM
Glossary
5-8
A magnitude for
distant earthquakes
based on the
amplitude of
20-180 degrees
Rayleigh surface
waves measured at
a period near 20
sec.
>3.5
Based on the
moment of the
earthquake, which
is equal to the
rigidity of the earth
times the average
amount of slip on
the fault times the
amount of fault area
that slipped.
Animations
Data Sources
Surface wave
(Ms)
FAQ About These Maps
Network Contacts
Moment (Mw)
Body (Mb)
4-7
all
Based on the
amplitude of P body16-100 degrees
waves. This scale is
(only deep
most appropriate
earthquakes)
for deep-focus
earthquakes.
Date and Time
We indicate the date and time when the earthquake initiates rupture,
which is known as the "origin" time. Note that large earthquakes can
continue rupturing for many 10's of seconds. We provide time in UTC
(Coordinated Universal Time). Seismologists use UTC to avoid
confusion caused by local time zones and daylight savings time. On the
individual event text pages, times are also provided in local US
timezones
Location
An earthquake begins to rupture at a hypocenter which is defined by a
position on the surface of the earth (epicenter) and a depth below this
point (focal depth). We provide the coordinates of the epicenter in units
of latitude and longitude. The latitude is the number of degrees north (N)
or south (S) of the equator and varies from 0 at the equator to 90 at the
poles. The longitude is the number of degrees east (E) or west (W) of
the prime meridian which runs through Greenwich, England. The
longitude varies from 0 at Greenwich to 180 and the E or W shows the
http://earthquake.usgs.gov/recenteqsww/glossary.htm (3 of 7)11/3/2005 6:33:56 AM
Glossary
direction from Greenwich. Coordinates are given in the WGS84
reference frame. The position uncertainty of the hypocenter location
varies from about 100 m horizontally and 300 meters vertically for the
best located events, those in the middle of densely spaced seismograph
networks, to 10s of kilometers for global events in many parts of the
world.
Depth
The depth where the earthquake begins to rupture. This depth may be
relative to mean sea-level or the average elevation of the seismic
stations which provided arrival-time data for the earthquake location.
The choice of reference depth is dependent on the method used to
locate the earthquake. Sometimes when depth is poorly contrained by
available seismic data, the location program will set the depth at a fixed
value. For example, 33 km is often used as a default depth for
earthquakes determined to be shallow, but whose depth is not
satisfactorily determined by the data, whereas default depths of 5 or 10
km are often used in mid-continental areas and on mid-ocean ridges
since earthquakes in these areas are usually shallower than 33 km.
Region
The region name is an automatically generated name from the FlinnEngdahl (F-E) seismic and geographical regionalization scheme,
proposed in 1965, defined in 1974 and revised in 1995. The boundaries
of these regions are defined at one-degree intervals and therefore differ
from irregular political boundaries. For example, F-E region 545
(Northern Italy) also includes small parts of France, Switzerland, Austria
and Slovenia and F-E region 493 (Chesapeake Bay Region) includes all
of the State of Delaware, plus parts of the District of Columbia,
Maryland, New Jersey, Pennsylvania and Virginia. Beginning with
January 2000, the 1995 revision to the F-E code has been used in the
QED and PDE listings. This revision includes 28 additional regions,
which were defined by subdividing larger regions to provide better
coverage for Northwest Africa, Southeast Asia and seismic zones along
oceanic ridges. (More info here.)
Distances
We provide distances and directions from nearby geographical reference
points to the earthquake. The reference points are towns, cities, and
major geographic features (gazetteer info). We realize that these
distances are uncertain both because of the errors inherent in locating
earthquake (typically one or more kilometers) and because of the
http://earthquake.usgs.gov/recenteqsww/glossary.htm (4 of 7)11/3/2005 6:33:56 AM
Glossary
impossibility of describing the location of a city by a single longitudelatitude entry in a table. For places in the US, rather than rounding off
distances to, say, the nearest 10 kilometers, we chose to trust the user's
common sense in interpreting the accuracy of these distances. For
places outside the US, distances are rounded depending on the
location uncertainty. If the computed location is close to an operating
quarry which is known to use explosives in its operations, we indicate
that the event may be a quarry explosion. We try to always provide at
least one widely recognized reference point in the list on the event page,
even if the earthquake occurs in a remote location.
Location Uncertainty
The horizontal and vertical uncertainties in an event's location are based
on values Ehro and Erzz described below. We assign an "unknown"
value if the contributing seismic network does not supply the necessary
information to generate a uncertainty estimates. The position uncertainty
of the hypocenter location varies from about 100 m horizontally and 300
meters vertically for the best located events, those in the middle of
densely spaced seismograph networks, to 10s of kilometers for global
events in many parts of the world.
Parameters
These parameters provide information on the reliability of the earthquake
location. Zero values usually indicate that the contributing seismic
network did not supply the information.
Nst
Number of seismic stations which reported P- and S-arrival
times for this earthquake. This number may be larger than
Nph if arrival times are rejected because the distance to a
seismic station exceeds the maximum allowable distance or
because the arrival-time observation is inconsistent with the
solution.
Nph
Number of P and S arrival-time observations used to compute
the hypocenter location. Increased numbers of arrival-time
observations generally result in improved earthquake
locations.
Dmin
Horizontal distance from the epicenter to the nearest station
(in km). In general, the smaller this number, the more reliable
is the calculated depth of the earthquake.
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Glossary
Rmss
The root-mean-square (RMS) travel time residual, in sec,
using all weights. This parameter provides a measure of the fit
of the observed arrival times to the predicted arrival times for
this location. Smaller numbers reflect a better fit of the data.
The value is dependent on the accuracy of the velocity model
used to compute the earthquake location, the quality weights
assigned to the arrival time data, and the procedure used to
locate the earthquake.
Erho
The horizontal location error, in km, defined as the length of
the largest projection of the three principal errors on a
horizontal plane. The principal errors are the major axes of
the error ellipsoid, and are mutually perpendicular. Erho thus
approximates the major axis of the epicenter's error ellipse.
Erzz
The depth error, in km, defined as the largest projection of the
three principal errors on a vertical line. See Erho
Gp
The largest azimuthal gap between azimuthally adjacent
stations (in degrees). In general, the smaller this number, the
more reliable is the calculated horizontal position of the
earthquake. Earthquake locations in which the azimuthal gap
exceeds 180 degrees typically have large Erho and Erzz
values.
M-type Magnitude type, discussed at greater length above under
Magnitude
Version Computers automatically update the WWW pages as more
reliable information about the earthquake is computed,
particularly in the first 10 minutes following the earthquake.
The highest version number is always considered
authoritative.
Source
The organization supplying the information provided here.
Event ID
A combination of a 2-letter Seismic Network Code and a number
assigned by the contributing seismic network.
Additional Information
Depending on the magnitude of the earthquake, additional information is
sometimes available. Location map links point to maps on which the
http://earthquake.usgs.gov/recenteqsww/glossary.htm (6 of 7)11/3/2005 6:33:56 AM
Glossary
earthquake appears. "Waveforms" are commonly available for a number
of instruments which detected the event. If the event is large enough,
focal mechanisms, aftershock probabilities and other kinds of
information may also be available.
FAQ about Earthquakes | Earthquake Preparedness
The USGS Earthquake Hazards Program (EHP) of the U.S. Geological
Survey (USGS)
is part of the National Earthquake Hazards Reduction Program (NEHRP)
led by the National Institute of Standards and Technology (NIST).
U.S. Department of the Interior, U.S. Geological Survey
This page is brought to you by the Earthquake Hazards Program
URL: http://earthquake.usgs.gov/recenteqsww/glossary.htm
Maintained by: Web Team
Last modification: 21 October 2005
Contact Us: Web_Team
USGS Privacy Statement | | Disclaimer | | FOIA | | Accessibility
http://earthquake.usgs.gov/recenteqsww/glossary.htm (7 of 7)11/3/2005 6:33:56 AM
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USGS Earthquake Hazards Program: FAQ: OFF W COAST OF NORTHERN SUMATRA
Latest
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Summary of Magnitude 9.0 SumatraAndaman Islands Earthquake & Tsunami
Sunday, December 26, 2004 at 00:58:53 UTC
This is the fourth largest earthquake in the world since 1900 and is
the largest since the 1964 Prince William Sound, Alaska
earthquake. The earthquake itself caused severe damage and
casualties in northern Sumatra, Indonesia and in the Nicobar
Islands, India. The earthquake casualties are included with the
tsunami statistics below.
The earthquake was felt at the following selected localities:
Seismogram
Displays
Past & Historical
Earthquakes
Earthquake E-Mail
Notification
Indonesia: IX at Banda Aceh VIII at Meulaboh
IV at Medan and Sampali
III at Bukittinggi, Parapat and Payakumbuh
Felt at Jakarta
India: VII at Port Blair, Andaman Islands
IV at Madras
III at Bengaluru and Vishakhapatnam
Felt at Bangalore, Bhubaneshwar, Calcutta and Kochi
Malaysia: V at Gelugor Estate
IV at Sungai Ara
III at Alor Setar, George Town, Kampong Tanjong Bunga,
Kuala Lumpur and Kulim
Earthquake Activity
in the Last 8 - 30
Thailand: V at Hat Yai
IV at Bangkok
http://earthquake.usgs.gov/eqinthenews/2004/usslav/eqsummary.html (1 of 7)11/3/2005 6:34:58 AM
USGS Earthquake Hazards Program: FAQ: OFF W COAST OF NORTHERN SUMATRA
Days
III at Chiang Mai and Phuket
Large/Significant
Earthquakes This
Year
Myanmar: IV at Mandalay
III at Rangoon
Significant
Earthquake Posters
Fast Moment Tensor
Solutions
Singapore: II on Singapore
Bangladesh: III at Dhaka
Felt at Chittagong
Sri Lanka: II at Kandy and in other parts of Sri Lanka
Maldives: IV at Male (nearly 2500 km from the epicenter)
Latest Energy and
Broadband
Solutions
Guam: Felt by people in a high rise building at Hagatna (more than
5400 km from the epicenter)
The tsunami from this earthquake caused extreme destruction in
South Asia, was recorded nearly world-wide and killed more people
than any tsunami in recorded history. In total, at least 283,100
people were killed, 14,100 are missing and 1,126,900 were
displaced by the earthquake and tsunami:
At least 108,100 people were killed, 127,700 are missing and
presumed dead and 426,800 were displaced by the earthquake
and tsunami in Aceh and Sumatera Utara Provinces, Indonesia.
About 70 percent of the small-scale fishing fleet was destroyed.
Tsunami runup heights of more than 30 meters were observed
along the west coast of Sumatra.
At least 30,900 people were killed, 5,400 missing and 552,600
displaced by the tsunami in Sri Lanka, where wave heights were
estimated to be 5-10 meters. About 66 percent of the fishing fleet
was destroyed and 10 of 12 major fishing harbors in the country
had some damage.
At least 10,700 people were killed, 5,600 missing and 112,500
displaced in Andhra Pradesh, Kerala, Pondicherry, Tamil Nadu and
Andaman and Nicobar Islands, India. Wave heights were estimated
to be more than 20 meters in the Andaman Islands and 10 meters
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USGS Earthquake Hazards Program: FAQ: OFF W COAST OF NORTHERN SUMATRA
on the east coast of India.
At least 5,300 people were killed, 8,400 injured and 3,100 missing
along the west coast of Thailand, where waves heights were
estimated to be as high as 3-5 meters in the Phuket area.
The tsunami also caused casualties and/or damage in the following
countries:
Somalia: at least 150 people killed and about 5,000 displaced.
Maldives: 82 people killed, 26 missing and more than 21,600
displaced.
Malaysia: 68 people killed, 6 missing and about 4,200 displaced.
Myanmar: 90 people killed, 10 missing and 3,200 displaced.
Tanzania: 10 people killed.
Seychelles: 3 people killed.
Bangladesh: 2 people killed.
Kenya: 1 person killed.
Madagascar: about 1,000 people displaced.
Mauritius: some damage.
Mozambique: tsunami was observed, but no damage reported.
In Australia, the tsunami caused minor damage at Geraldton and
Mangles Bay. A 30 centimeter wave was observed at Penguin
Island. People were swept into the ocean at Delambre Island and
Geographe Bay, but all survived. The tsunami was observed at
Busselton.
Maximum tsunami heights, peak to trough in centimeters,
were recorded at the following selected tide stations:
Indian Ocean:
Kochi, India 130
Tuticorin, India 210
Vishakhapatnam, India 240
Diego Garcia, Chagos Archipelago 80
Colombo, Sri Lanka 260
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USGS Earthquake Hazards Program: FAQ: OFF W COAST OF NORTHERN SUMATRA
Salalah, Oman 250
Lamu, Kenya 120
Zanzibar, Tanzania 80
Male, Maldives 210
Port Louis, Mauritius 210
Port Elizabeth, South Africa 273
Richards Bay, South Africa 165
East Ongul Island, Antarctica 75
Cocos Island, Australia 42
Esperance, Western Australia, Australia 80
Hillarys, Western Australia, Australia 90
Portland, Victoria, Australia 85
Mid-ocean, about 5 S, SSE of Sri Lanka 100 approximate (from
Jason 1 satellite altimeter)
Pacific Ocean:
Rosslyn Bay, Queensland, Australia 25 Spring Bay, Tasmania,
Australia 60
Chatham Island, New Zealand 35
Jackson Bay, South Island, New Zealand 65
Napier, North Island, New Zealand 30
Timaru, South Island, New Zealand 80
Port Vila, Vanuatu 15
Nukualofa, Tonga 10
Suva, Fiji 11
Pago Pago, American Samoa 10
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USGS Earthquake Hazards Program: FAQ: OFF W COAST OF NORTHERN SUMATRA
Nuku Hiva, French Polynesia 5
Noumea, New Caledonia 10
Severo-Kurilsk, Russia 29
Bella Bella, British Columbia, Canada 9
Tofino, British Columbia, Canada 15
Adak, Alaska, U.S. 21
Sand Point, Alaska, U.S. 28
Crescent City, California, U.S. 61
Point Reyes, California, U.S. 39
Port San Luis, California, U.S. 53
San Diego, California, U.S. 32
Hilo, Hawaii, U.S. 18
Kahului, Hawaii, U.S. 30
Neah Bay, Washington, U.S. 13
Cabo San Lucas, Mexico 24
Manzanillo, Mexico 80
Acajutla, El Salvador 32
Baltra Island, Galapagos, Ecuador 36
Callao, Peru 68
Arica, Chile 72
Puerto Williams, Chile 29
Valparaiso, Chile 18
Atlantic Ocean:
Cape Town, South Africa 96
Port Noloth, South Africa 50
Newlyn, United Kingdom 16
Halifax, Nova Scotia, Canada 43
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USGS Earthquake Hazards Program: FAQ: OFF W COAST OF NORTHERN SUMATRA
Atlantic City, New Jersey, U.S. 22
Port Canaveral, Florida, U.S. 34
San Juan, Puerto Rico 4
Charlotte Amalie, Virgin Islands 18
Bermuda 12
Imbituba, Brazil 150 approximate
Rio de Janiero, Brazil 30
K. Abe has computed a tsunami magnitude (Mt) of 9.1 for this
event.
Landslides and approximately 2 meters of subsidence were
observed in Sumatra. A mud volcano became active near
Baratang, Andaman Islands on December 28. Gas emissions were
reported in Arakan, Myanmar. Seiches occurred in Jharkhand,
Maharashtra, Orissa and West Bengal, India and as far away as
Tulsa County, Oklahoma, United States. Water level fluctuations
occurred in wells as far away as Florida, Nebraska and Virginia,
United States.
Principal sources:
U.N. Office for Coordination of Humanitarian Affairs, Situation
Reports and ReliefWeb website as of 2 Feb 2005. For updates, see
http://www.reliefweb.int/rw/dbc.nsf/doc100?OpenForm.
A. Rabinovich and J. Gower, Institute of Ocean Sciences, Canada,
website http://www-sci.pac.dfo-mpo.gc.ca/osap/projects/tsunami/
default_e.htm.
NOAA, West Coast and Alaska Tsunami Warning Center, webpage
on the Indian Ocean tsunami, http://wcatwc.arh.noaa.gov/
IndianOSite/IndianO12-26-04.htm.
K. Abe and Y. Tsuji, et al., Earthquake Research Institute,
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USGS Earthquake Hazards Program: FAQ: OFF W COAST OF NORTHERN SUMATRA
University of Tokyo, Special Event Page, at http://www.eri.u-tokyo.
ac.jp/topics/SUMATRA2004/index-e.html
S. Martin, Amateur Seismic Centre, Pune, India, Special Event
page, at http://asc-india.org/events/041226_bob.htm.
V. Dent, University of Western Australia, Asian Tsunami effects in
Western Australia, at http://www.seismicity.segs.uwa.edu.au/
welcome/asian_tsunami_in_wa
CNN website, at http://www.cnn.com/.
BBC World Service website, at http://www.bbc.co.uk/worldservice/
index.shtml.\
Felt reports contributed to USGS "Did you feel it?" webpages, at:
http://pasadena.wr.usgs.gov/shake/ous/index.html.
Tectonic Summary
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Earthquake Hazards Program: Poster of the Sumatra-Andaman Islands Earthquake of 26 December 2004
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DISCUSSION
The devastating earthquake of 26 December 2004 occurred as thrust-faulting on the interface of the
India plate and the Burma microplate. In a period of minutes, the faulting released elastic strains that
had accumulated for centuries from ongoing subduction of the India plate beneath the overriding
Burma microplate.
In a broad sense, the India and Australian plates move toward the north-northeast with respect to the
interior of the Eurasia plate with velocities of about 60 mm/y in the region of the earthquake. This
results in oblique convergence at the Sunda trench. The oblique motion is partitioned into thrustfaulting, which occurs on the interface between the India plate and the Burma microplate and involves
slip directed at a large angle to the orientation of the trench, and strike-slip faulting, which occurs on the
eastern boundary of the Burma microplate and involves slip directed approximately parallel to the
trench. Details of the velocity of the Burma microplate remain to be determined and may, in fact, be
clarified by further analysis of the December main shock and its aftershocks.
Currently available models of the 26 December main-shock fault displacement differ in many
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Earthquake Hazards Program: Poster of the Sumatra-Andaman Islands Earthquake of 26 December 2004
interesting details, but are consistent in implying that fault-rupture propagated to the northwest from the
epicenter and that substantial fault-rupture occurred hundreds of kilometers northwest of the epicenter.
The data upon which the modeling is based do not permit confident resolution of the extent of rupture
beyond about 500 km northwest of the main-shock epicenter. The finite fault model shown here implies
that the width of the earthquake rupture, measured perpendicular to the Sunda trench, was about 150
kilometers, and that the maximum displacement on the fault plane was about 20 meters. The sea floor
overlying the thrust fault would have been uplifted by several meters as a result of the earthquake.
The zone of aftershocks to the 26 December earthquake is over 1300 km long. Because aftershocks
occur on and very near the fault planes of main shocks, the length of the aftershock zone suggests that
main-shock fault-rupture may have extended north of epicenter by an amount significantly larger than
500 km. However, a great earthquake may also trigger earthquake activity on faults that are distinct
from the main-shock fault plane and separated from it by tens or even hundreds of kilometers. We will
not know until further analysis how much of the 26 December aftershock zone may correspond to
activity in the immediate vicinity of the main-shock rupture, and how much may correspond to activity
remote from the main-shock rupture.
Since 1900, earthquakes similarly sized or larger than the 26 December earthquake have been the
magnitude 9.0 1952 Kamchatka earthquake, the magnitude 9.1 1957 Andreanof Islands, Alaska,
earthquake, the magnitude 9.5 1960 Chile earthquake, and the magnitude 9.2 1964 Prince William
Sound, Alaska, earthquake. All of these earthquakes, like the 26 December earthquake, were megathrust events, occurring where one tectonic plate subducts beneath another. All produced destructive
tsunamis, although deaths and damage from the 26 December tsunami have far exceeded those
caused by tsunamis associated with the earlier earthquakes.
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USGS Earthquake Hazards Program: Rupture Area: OFF W COAST OF NORTHERN SUMATRA
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Comparable Rupture Area
Magnitude 9.0 OFF W COAST OF NORTHERN
SUMATRA
Sunday, December 26, 2004 at 00:58:49 UTC
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Download PDF of image.
When an earthquake occurs, it ruptures a patch along a fault.
Generally speaking, the larger the earthquake magnitude, the larger
the rupture patch. Initial estimates, based on the distribution of
aftershocks, suggest that the magnitude 9.0 Sumatra-Andaman
Islands Earthquake ruptured a fault patch roughly the size of the
entire Cascadia Subduction Zone (see map above) that extends under
northern California, Oregon, Washington, and southern British
Colombia. Initial modeling of the seismic waves suggests that most of
the slip occurred in the southern 400 kilometers of the fault rupture.
For comparison, a magnitude 5 earthquake would rupture a patch
roughly the size of New York City's Central Park.
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2004 December 26, Sumatra-Andaman Islands, Indonesia, 9.0M
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2005 March 28, Northern Sumatra, Indonesia 8.7M
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