Sumatra-Andaman Earthquake 2004

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Lessons from the 2004 Sumatra−Andaman earthquake
Hiroo Kanamori Phil. Trans. R. Soc. A 2006 364, 1927-1945 doi: 10.1098/rsta.2006.1806

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Phil. Trans. R. Soc. A (2006) 364, 1927–1945doi:10.1098/rsta.2006.1806 Published online 27 June 2006

Lessons from the 2004 Sumatra–Andaman earthquake
B Y H IROO K ANAMORI *
Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125, USA
The 2004 Sumatra–Andaman earthquake (MwZ9.0–9.3) is one of the greatest earthquakes ever recorded. In terms of its physical size, it is comparable to the 1960 Chilean (MwZ9.5) andthe 1965 Alaskan (MwZ9.2) earthquakes. However, the damage caused by this earthquake is far greater than that caused by other great earthquakes. The 2004 Sumatra–Andaman earthquake has been studied in great detail over broad time-scales, from a fraction of seconds to hours and months, using the modern seismic data available from global seismic networks and the Global Positioning System data. Wesummarize the findings obtained mainly from seismic data, and discuss the unique feature of this earthquake, and possible directions of research to minimize the impact of great earthquakes on our society.
Keywords: Sumatra–Andaman earthquake; earthquake prediction; scenario earthquakes; tsunami warning; earthquake early warning; damaging earthquakes

1. Introduction The 2004 Sumatra–Andamanearthquake (December 26, 2004, 3.30 N, 95.78 E, 10 km, MwZ9.2) is one of the largest earthquakes instrumentally recorded. It ruptured the boundary between the Indo-Australian plate and the Eurasian plate along the northwestern Sumatra, the Nicobar Is and the Andaman Is (figure 1). The faulting occurred on a low-angle thrust fault dipping ca 108 northeast with the Indo-Australian plate moving northeastrelative to the Eurasian plate. Since several papers have been already written on this earthquake (e.g. Ammon et al. 2005; Lay et al. 2005), here we only summarize the results (figure 1). We first define several important earthquake parameters. An earthquake occurs due to failure of rocks in the Earth caused by stresses produced mainly by plate motion. If the stress at a point exceeds the localstrength of the rock, an earthquake occurs. A rupture initiates at a point, propagates at a speed V over a fault plane, and eventually stops when either the driving stress drops or the rupture encounters a strong obstacle. We let L, S, t and D be the rupture length, fault area, duration of rupture and the average displacement (offset) across the fault plane, respectively. The rupture speed V*hiroo@gps.caltech.edu One contribution of 20 to a Discussion Meeting Issue ‘Extreme natural hazards’.

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varies from earthquake to earthquake. In most earthquakes, V is ca 2–3.5 km sK1, but faster and slower rupture speeds have been observed in a few cases. Ideally, it is desirableto quantify the size of an earthquake by the total amount of energy released. However, it is technically difficult even now to accurately estimate the energy release. The seismic moment M0, defined by M0 Z mDS ð1:1Þ

is used instead to represent the size of an earthquake. In the above, m is the shear modulus of the rock surrounding the fault (Aki 1966). Although M0 has the unit of energy, it is...