178 Engineering Ethics: An Industrial Perspective
Figure 15.1 Sumatra-Andaman Earthquake Map.
Courtesy of http://www.NPR.org, National Public Radio, Inc., all rights reserved.
trench at the plate interface. One example of this subduction zone is the
plunging of the Indo-Australian plate beneath the Eurasian plate.
On December 26, 2004, this fault ruptured, allowing the edge of the
Eurasian plate to spring back up. The fault slipped by as much as 50 feet in
places, averaging about 33 feet of displacement along the segment off the
northwestern tip of Sumatra, where the quake was centered. From the epi-
center, the rupture expanded along the fault at a speed of about 1.5 miles
per second toward the north-northwest, for about 720 to 780 miles.
Eventually, the northern part of the fault slipped about as much as the
southern part, uplifting and tilting the Andaman Islands (Figure 15.1).
Although most earthquakes last only a few seconds, this earthquake
lasted about 10 minutes. The seismic magnitude of the earthquake was
estimated as between 9.1 to 9.3 (NSF, 2005). The earthquake also caused
sustained vibrational free oscillations at periods greater than 1000 seconds.
These oscillations remained observable for weeks in broadband seismic
data from global networks. The frequencies and decay rates of earth’s free
oscillations offered strong constraints on our planet’s interior composition,
mineralogy, and dynamics. Upon analysis, these data are expected to
provide new perspectives on Earth’s structure (Park, 2005).
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