Iwan, Wilfred D.

English

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Preface to the Special Issue on the Great
Sumatra Earthquakes and Indian
Ocean Tsunamis of 26 December 2004
and 28 March 2005
Wilfred D. Iwan,a… M.EERI
DOI: 10.1193/1.2241982
At 7:58 A.M. local time on Sunday, 26 December 2004, a great earthquake occurred
in the Indian Ocean approximately 250 km west of Sumatra, Indonesia. With a moment
magnitude of 9.1–9.3, this was the second largest instrumentally recorded earthquake in
history. The earthquake had an average source duration of about 500 seconds, the long-
est ever recorded, and a rupture length of about 1,300 km, the largest ever determined
instrumentally. This earthquake generated one of the most devastating tsunamis in re-
corded history.
The tsunami of December 26 affected at least 16 nations directly, and indirectly af-
fected the entire globe. The initial impact of the tsunami was the inundation of the cities
of Banda Aceh and Meulaboh along the northwestern coast of the island of Sumatra.
There were 131,000 confirmed deaths in this region and 37,000 people were listed as
missing. Over 80,000 houses sustained damage or collapsed, and it is estimated that
518,000 people were displaced from their homes. Within hours the tsunami brought
death and destruction to the shores of Thailand to the east and to Sri Lanka, India, and
the Maldives to the west. The tsunami also caused death and destruction in Somalia and
other nations along the east coast of Africa. The death toll from the tsunami has been
estimated to be about 300,000. This includes local residents of the affected regions as
well as a sizeable number of tourists from Europe, Asia, and the Americas. In addition to
the direct loss of life was the extensive damage to homes, hospitals, schools, centers of
worship, government buildings, infrastructure, and the social fabric of the affected com-
munities. It will be years before the affected regions will return to anything like a “nor-
mal” existence.
Three months after the December earthquake, on 28 March 2005, another large
earthquake with a moment magnitude of about 8.7 struck off the coast of Sumatra near
the island of Nias. This earthquake generated only a rather small tsunami. However, ap-
proximately 900 people died and 22,000 people were displaced by the event.
Immediately following the December 26 event, EERI dispatched and participated in
the sending of a number of reconnaissance teams of scientists and engineers to the af-
fected region to make on-site observations and collect perishable data. These teams in-
cluded experts in seismology, geology, tsunamis, structures and lifelines, disaster re-
a Professor Emeritus, California Institute of Technology, MC 104-44, Pasadena, CA 91125; E-mail:
wdiwan@caltech.edu
xi
Earthquake Spectra, Volume 22, No. S3, pages xi–xii, June 2006; © 2006, Earthquake Engineering Research Institute
xii PREFACEsponse, and societal issues. Team members came from many of the affected countries as
well as from other countries, including the United States, New Zealand, Canada, and
Japan. This special issue of Earthquake Spectra contains the reports of these teams. Be-
cause of the enormous magnitude of the disaster that resulted from the December 26 and
March 28 events and the unprecedented scope of the reconnaissance effort that followed
these events, it is believed that this special issue provides a valuable resource for future
analysis and action regarding such mega-events. At the same time, it must be acknowl-
edged that data on some aspects of the disaster, such as the effectiveness of recovery and
rebuilding efforts, will not be known for many years.
Since the geographic region of the earthquake and tsunami was so large, different
teams of researchers focused on different regions, although there was some overlap
within the same region. Because of the geographic overlap of some teams, it is possible
to draw some significant conclusions about the inherent variability in the observations of
different teams examining the same data from a disastrous event. Also, some teams vis-
ited the regions at different times from other teams and therefore had a different per-
spective on what they saw, allowing conclusions about the effect of time on disaster re-
connaissance observations. The teams dispatched also had different mixes of disciplines
among their members. Obviously, members from different disciplines see the same event
from different perspectives, demonstrating the value of a multidisciplinary approach. For
these reasons, the reports of different teams have not been edited to bring all observa-
tions into conformity. The differences between reports are an important part of the re-
connaissance process, and need to be understood.
This special issue is organized into topical sections as follows: Seismology; Geology
and Geophysics; Tsunami Field Surveys and Analyses; Performance of Structures and
Lifelines; Preparedness; Societal Impacts; and Recovery and Reconstruction. The large
number of authors and papers reflects the unique nature of this event. The issue includes
an overview paper on tsunami runup measurements from all over the Indian Ocean, as
well as papers on individual tsunami field surveys from 12 countries. Comprehensive
papers on the seismologic and geologic aspects of the two large earthquakes are also
included, as well as many papers describing the impacts of these events on communities
throughout the region.
Oversight for the organization and preparation of the special issue was provided by
an Editorial Board consisting of Donald Ballantyne, C. B. Crouse, Lori Dengler, Mar-
jorie Greene, Kenneth Hudnut, Wilfred Iwan, Hiroo Kanamori, Costas Synolakis, Kath-
leen Tierney, and Loring Wyllie. As a compendium to this special issue, the Editorial
Board has prepared a summary and conclusions report that will be published separately
by EERI. This compendium will summarize the major findings from the many articles in
this large issue, and synthesize some of the most important lessons, both for the coun-
tries and communities affected by the tsunami and for countries and communities facing
future risk from tsunamis. Support for this publication was provided to EERI’s Learning
from Earthquakes Program by the U.S. National Science Foundation under grant CMS-
0131895.
Received 15 June 2006; accepted 6 July 2006


Preface to the Special Issue on the Great Sumatra Earthquakes and Indian Ocean Tsunamis of 26 December 2004 and 28 March 2005

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Preface to the Special Issue on the Great Sumatra Earthquakes and Indian Ocean Tsunamis of 26 December 2004 and 28 March 2005

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