On the Sumatra Earthquake

I. Courses of Action of the Central Weather Bureau

A strong earthquake of magnitude 9.0 struck Sumatra, Indonesia at 8:58 a.m. Taiwan time on December 26, 2004. The Central Weather Bureau (CWB) recorded seismic waves within 6 minutes of the occurrence and, within 15 minutes, received a tsunami warning message issued by the Pacific Tsunami Warning Center (PTWC) located in Hawaii, indicating no possibility of tsunami around the Pacific Rim. With the epicenter being 3,500 km away from Taiwan, the CWB released a message through the media urging people not to panic.

II. Tsunami environment in Taiwan

In the past decades, there were several major tsunamis occurred around the Pacific Rim region. Examples are the 1960 Chile tsunami and the 1964 Alaska tsunami, both having impact in the region. However, these tsunamis had only minor impact on Taiwan because the accompanying energy triggered by distant earthquakes had dissipated long before reaching the island.

As for Taiwan's nearby earthquakes, academic research suggests that the magnitude above which a triggered tsunami needs to be seriously guarded among various regions - 7 for Taitung region, 7.8 for Hualien region and 8 for Lanyu region. It can be concluded that the combined effects of seabed topography, earthquake, and regional coastal configuration make the coastal areas of Keelung, Yilan, and Hualien more prone to strikes of disastrous tsunamis caused by large inshore earthquakes.

Located in the Pacific Rim seismic zone, Taiwan is frequently struck by earthquakes, of which some have had magnitudes over 6 in the past century. Most of them did not trigger tsunamis and, even when they did, the triggered tsunamis were non-disastrous with small wave heights. This is because most inshore earthquakes occurred on the eastern side of Taiwan where the steeply descending offshore seabed prevents energy accumulation for tsunami. As for the western side of Taiwan where the seabed terrain is shallow, there are fewer earthquakes due to limitation in plate conditions, which reduce the probability of tsunami occurrence.

III. Historical tsunami records in Taiwan

According to historical records dating from 1661, Taiwan has been struck by six disastrous tsunamis, occurring in 1661, 1721, 1781, 1792, 1866, and 1867. Except for the one that occurred in 1867, only summary descriptions with no clearly quantifiable scientific evidence were recorded. The 1867 tsunami occurred in the Keelung region of northern Taiwan and was clearly determined as having been triggered by an inshore earthquake. Other than this, over 20 tsunamis in the Taiwan region have been recorded with no reports of damage.

IV. Tsunami warning system in Taiwan

Taiwan's tsunami warnings are issued by the CWB. After a distant earthquake occurs, the CWB will instantly obtain tsunami warnings issued by the Pacific Tsunami Warning Center. It will then estimate the potential impact on Taiwan before sending out a tsunami warning message via SMS or fax to relevant coast guards, central emergency management authorities, and to mass media, in an effort to reduce damage caused on shore by the tsunami.

The PTWC, a United States federal agency located in Hawaii, has contributed substantially to reducing damage caused by natural calamities such as tsunamis. After detecting a major earthquake in the Pacific Rim region, it will begin a comprehensive study on whether or not a tsunami will be triggered and will issue warnings to countries and regions that potentially will be struck by the tsunami, including direct notification to the CWB.

Tsunami related websites

Foreign research unit websites
U.S. Geological Survey Magnitude 9.0 - SUMATRA-ANDAMAN ISLANDS EARTHQUAKE FAQ
Pacific Tsunami Warning Center (PTWC)
British Geological Survey SEISMIC ALERT
Japan Active Fault Research Center
December 26 Tsunami in Indian Ocean-Japanese
December 26 Tsunami in Indian Ocean-English
Japan International Institute of Seismology and Earthquake Engineering Off Coast of Northern Sumatra Earthquake
 
Foreign academic unit websites
Earthquake Research Institute, the University of Tokyo Special Event Page - Off the West Coast of Northern Sumatra Earthquake
 
Domestic research unit websites
National Space Organization (NSPO)
FORMOSAT-2 image of Phuket Island after the South Asia earthquake - news
FORMOSAT-2 image of Phuket Island after the South Asia earthquake - photo
FORMOSAT-2 image of Phuket Island after the South Asia earthquake - analysis
FORMOSAT-2 image of Sumatra Island after the South Asia earthquake - news
FORMOSAT-2 image of Sumatra Island after the South Asia earthquake - analysis
FORMOSAT-2 image of Car Nicobar after the South Asia earthquake - news
FORMOSAT-2 image of Car Nicobar after the South Asia earthquake - analysis
FORMOSAT-2 image of Andaman Islands after the South Asia earthquake - analysis
FORMOSAT-2 image of Maldives Island after the South Asia earthquake - news
FORMOSAT-2 images after the South Asia earthquake (summary) - 1,2,3,4,5
 
Domestic academic unit websites
Graduate School of Geosciences, National Taiwan University
12/26/2004 Sumatra Earthquake
Tsunami triggered by undersea earthquake: a case study of the Sumatra Earthquake
Investigating new tectonic activities in Sumatra's subduction zone via intermittent coral growth
Department of Geology, Chinese Culture University
Information on Sumatra Earthquake: Tsunami - Sumatra
Taipei First Girls' High School - Earth Science Learning Site Briefing on Sumatra Tsunami

 

Well-known news websites Well-known information portals Links to tsunami introduction
The Epoch Times SINA (Mainland China) on tsunami Wikipedia (Chinese) - looking up for tsunami
Reuters Yahoo (Taiwan) on tsunami Wikipedia (English)
Time Magazine Yahoo (India) on tsunami
NBC special on tsunami Yahoo (Asia) on tsunami
CNN special on tsunami Yahoo on tsunami
Hong Kong Epoch Times special on tsunami Yahoo (Hong Kong) on tsunami
New York Times special on tsunami
RTHK special on tsunami
Xinhua News Agency special on tsunami
BBC special on tsunami
BBC special on tsunami (Chinese)