Physics
Today: Chile is a highly seismic area because of its
proximity to the stressed
Nazca
and
South
American tectonic plates which are converging at a rate of
80 mm per year, one of the fastest rates on Earth. Since 1973
there have been 13 events of magnitude 7.0 or greater on the
richter
scale.Sometimes the earlier quakes in the region, such as
the
1960
9.5 earthquake of May, 1960—the largest earthquake
worldwide in the last 200 years or more—can cause
increased stress that leads to other earthquakes.
Geologist
Jian Lin of the Woods Hole Oceanographic Institution says
this is what happened on Saturday, 27 February, when a
8.8-magnitude
earthquake struck Chile in an offshore zone about 230 km
north of the source region of the 1960 quake. The quake was
approximately 300-500 times more powerful that
the
one that hit Haiti. A large and powerful set of aftershocks
can be expected from this earthquake.The earthquake, was
centered some 65 miles west-southwest of Talca, Chile, about
21.7 miles below the ocean's surface, "relatively shallow for a
subduction quake," said Lin. It occurred at the interface
between the two plates, with the "subducting" Nazca plate
moving down and landward below the South American plate,
uplifting a large patch of the seafloor.Saturday's earthquake
had a "much longer" rupture zone–500-600 km–than
that of the Haiti quake–35-50 km.
Related link
Tracking
the geologic impacts of earthquakes NPR
Tsunami effectsTypically, earthquakes in the
region have caused tsunami's: the 1960 earthquake caused a
tsunami that engulfed the Pacific Ocean, causing a loss of life
in Chile, Japan, Hawaii, and the Philippines while a 8.5
earthquake in November 1922 caused a 9 meter local tsunami that
inundated the Chile coast near the town of Coquimbo; it also
also crossed the Pacific, washing away boats in Hilo harbor,
Hawaii.This earthquake also dispatched tsunami waves onshore to
Chile and across the Pacific Ocean.Twenty three minutes after
the earthquake, waves 1.6 meters above normal hit Talcahuano
near Concepcion.Although the predicted tsunami waves did reach
Hawaii, California, New Zealand and other Pacific Rim regions,
they proved to be relatively small and had minimal impact.The
reason may be
harmonic
resonance, as the the waves caused by the earthquake were
20 minutes apart and the natural resonant period for the
geology of region is different. This allowed the waves to get
out of sync, without focus or coordinated energy said Gerard
Fryer, a geophysicist with the
Pacific Tsunami Warning
Center to the
Star
Bulletin
.
A predictionThe quake
had been
predicted six years ago by Lin and Ross S. Stein in the
Journal of
Geophysical Research
.The geological mechanisms are very similar to the 26
December, 2004 magnitude-9.0 Sumatra earthquake which was
followed by a magnitude 8.7 quake on its southern end on 28
March 2005. "The only difference is that it took 50 years for
the northern neighboring section of the 1960 [Chile] earthquake
to rupture, while it took only 3 months for the southern
adjacent segment to rupture in Sumatra," said Lin.
Loss of lifeRoger Bilham, a seismologist at
the University of Colorado at Boulder
tells
NPR than earthquakes are becoming deadlier simply because
there are more people on the planet than there were 100 years
ago.The latest Chile quake, which had killed more than 700
people as of 1 March was much less catastrophic that the
Haitian earthquake despite only being about 200 miles southwest
of Santiago, the country's capitol.Chile was luckier than Haiti
because it is wealthier and infinitely better prepared, with
strict building codes, robust emergency response and a long
history of handling seismic catastrophe
says
Associated Press reporter Frank Bajak.Lin also points out
that they are also more used to it, with 13 significant
magnitude events in the last 30 years. "In contrast, the last
catastrophic earthquake in Haiti was 240 years ago," he
adds."The contrasts between the aftermaths of the Chile and
Haiti quakes reminded us, once again, that
âearthquakes do not kill people, buildings
do.'"Paul Guinnessy
Geologist
Jian Lin of the Woods Hole Oceanographic Institution says
this is what happened on Saturday, 27 February, when a
8.8-magnitude
earthquake struck Chile in an offshore zone about 230 km
north of the source region of the 1960 quake. The quake was
approximately 300-500 times more powerful that
the
one that hit Haiti. A large and powerful set of aftershocks
can be expected from this earthquake.The earthquake, was
centered some 65 miles west-southwest of Talca, Chile, about
21.7 miles below the ocean's surface, "relatively shallow for a
subduction quake," said Lin. It occurred at the interface
between the two plates, with the "subducting" Nazca plate
moving down and landward below the South American plate,
uplifting a large patch of the seafloor.Saturday's earthquake
had a "much longer" rupture zone–500-600 km–than
that of the Haiti quake–35-50 km.
Related link
Tracking
the geologic impacts of earthquakes NPR
Tsunami effectsTypically, earthquakes in the
region have caused tsunami's: the 1960 earthquake caused a
tsunami that engulfed the Pacific Ocean, causing a loss of life
in Chile, Japan, Hawaii, and the Philippines while a 8.5
earthquake in November 1922 caused a 9 meter local tsunami that
inundated the Chile coast near the town of Coquimbo; it also
also crossed the Pacific, washing away boats in Hilo harbor,
Hawaii.This earthquake also dispatched tsunami waves onshore to
Chile and across the Pacific Ocean.Twenty three minutes after
the earthquake, waves 1.6 meters above normal hit Talcahuano
near Concepcion.Although the predicted tsunami waves did reach
Hawaii, California, New Zealand and other Pacific Rim regions,
they proved to be relatively small and had minimal impact.The
reason may be
harmonic
resonance, as the the waves caused by the earthquake were
20 minutes apart and the natural resonant period for the
geology of region is different. This allowed the waves to get
out of sync, without focus or coordinated energy said Gerard
Fryer, a geophysicist with the
Pacific Tsunami Warning
Center to the
Star
Bulletin
.
A predictionThe quake
had been
predicted six years ago by Lin and Ross S. Stein in the
Journal of
Geophysical Research
.The geological mechanisms are very similar to the 26
December, 2004 magnitude-9.0 Sumatra earthquake which was
followed by a magnitude 8.7 quake on its southern end on 28
March 2005. "The only difference is that it took 50 years for
the northern neighboring section of the 1960 [Chile] earthquake
to rupture, while it took only 3 months for the southern
adjacent segment to rupture in Sumatra," said Lin.
Loss of lifeRoger Bilham, a seismologist at
the University of Colorado at Boulder
tells
NPR than earthquakes are becoming deadlier simply because
there are more people on the planet than there were 100 years
ago.The latest Chile quake, which had killed more than 700
people as of 1 March was much less catastrophic that the
Haitian earthquake despite only being about 200 miles southwest
of Santiago, the country's capitol.Chile was luckier than Haiti
because it is wealthier and infinitely better prepared, with
strict building codes, robust emergency response and a long
history of handling seismic catastrophe
says
Associated Press reporter Frank Bajak.Lin also points out
that they are also more used to it, with 13 significant
magnitude events in the last 30 years. "In contrast, the last
catastrophic earthquake in Haiti was 240 years ago," he
adds."The contrasts between the aftermaths of the Chile and
Haiti quakes reminded us, once again, that
âearthquakes do not kill people, buildings
do.'"Paul Guinnessy
