MEXICO
CITY — A 7.2-magnitude earthquake struck Mexico’s southern Pacific
Coast on Friday, according to the United States Geological Survey.
The
quake was reported at 5:39 p.m. local time, shaking buildings about 225
miles away in Mexico City, where the memory of a Sept. 19 earthquake
that killed more than 300 people in the capital and other parts of the
country is still fresh. Friday’s tremors left tall buildings swaying for
more than two minutes.
The epicenter of the quake was near the town of Pinotepa Nacional, in the Pacific state of Oaxaca.
A
presidential spokesman, Eduardo Sánchez, told the Televisa network two
hours after the earthquake that there were no reports of deaths or
injuries.
Luis Felipe Puente, Mexico’s national coordinator of civil protection, wrote on Twitter
that there were no immediate reports of major damage. In Oaxaca, the
state director of civil protection, Heliodoro Díaz Escárraga, said that
homes were damaged in the town of Santa María Chimalapas and walls fell
in the town of Jamiltepec.
In
Mexico City, the capital, residents streamed from buildings and into
the streets, texting to see if their loved ones were safe, gripped by a
sense of dread just a few months old.
Residents
of the Condesa and Roma neighborhoods of Mexico City, which suffered
some of the worst damage in September, ran out into the streets in
panic, looking up at the buildings as the earthquake warning system went
off. Once in the streets, they searched for signs of damage to their
buildings.
Last
September’s seismic eruption has left people frightened at the
slightest tremor, and the tears in the faces of those who endured the
last major quake were easy to spot on the streets.
Many could be heard repeating the words “Oh God, not again.”
Video
footage from inside the Mexico City newsroom of a daily newspaper,
Milenio, showed employees ducking underneath desks as light fixtures
swung wildly..
The initial 7.2-magnitude shock was followed 57 minutes later by a magnitude-5.8 aftershock.
The
epicenter of Friday’s earthquake was between those of a magnitude-8.2
quake on Sept. 8 and the 7.1-magnitude quake on Sept. 19. But from a
geological standpoint, all three occurred in the same general area — a
so-called subduction zone, where one piece of the earth’s crust, in this
case the Cocos Plate, is slowly sliding under another, the North
American.
Like
other subduction zones around the Pacific and elsewhere, this region is
the source of many earthquakes, some of them very strong and
destructive. The movement of the two plates relative to each other is
very slow — about two to three inches a year — but it causes stresses to
build, either at the boundary between the two plates or, as was the
case with the September quakes, within one of them. At some point the
stresses become too much and the rock formations slip, releasing energy
as an earthquake.
Shortly
after Friday’s quake, the United States Geological Survey released a
brief initial analysis, saying that it occurred “on or near” the
boundary between the two plates, and about 55 miles north of the Middle
America Trench, where the Cocos begins its slide beneath the North
America plate.
In
addition to local destruction, strong Mexican earthquakes often cause
damage in Mexico City — even if, as in this case, the capital is miles
away. Mexico City was built on an ancient lake bed, and the sediments of
sand and clay amplify the seismic waves as they arrive from the
epicenter.
Depending
on the amount of energy released, the depth of the epicenter and its
distance from Mexico City, the seismic waves from a quake can affect
some buildings in the capital more than others. In the Sept. 19 quake,
mostly shorter buildings were knocked down. But in a 1985 quake that
killed 10,000 people, most of the buildings that were severely damaged
or destroyed were six to 16 stories tall.
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