| The
magnitude 9.0 earthquake near Sumatra on December 26, 2004 was one of
the most significant seismic events on Earth during the past 100 years.
While earthquake damage and casualties were limited to the immediate
vicinity of the earthquake, tsumanis generated by this event caused
over 150,000 deaths in the Indian ocean region spanning more than 10
nations. This record section plot displays vertical
displacements of the Earth's surface recorded by seismometers plotted
with time (since the earthquake initiation) on the horizontal axis, and
vertical displacements of the Earth on the vertical axis (note the 1 cm
scale bar at the bottom for scale). The traces are arranged by distance
from the epicenter in degrees. The earliest, lower amplitude, signal is
that of the compressional (P) wave, which takes about 22 minutes to
reach the other side of the planet (the antipode). The largest
amplitude signals are seismic surface waves which reach the antipode
after about 100 minutes. The surface waves can be clearly seen to
reinforce near the antipode (with the closest seismic stationsin
Ecuador), and to subsequently circle the planet to return to the
epicentral region after about 200 minutes. A major aftershock
(magnitude 7.1) can be seen at the closest stations starting just after
the 200 minute mark (note the relative size of this aftershock, which
would be considered a major earthquake under ordinary circumstances,
compared to the mainshock).
Credits: Data provided by the Global Seismic, EarthScope USArray, and
IDA networks, and distributed through the IRIS Data Management System.
Seismic stations are operated by the IRIS Consortium, US Geological
Survey, and the University of California, San Diego. Support for these
networks is provided by the National Science Foundation and U.S.
Geological Survey. Figure by Richard Aster, New Mexico Institute of
Mining and Technology. |
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