The latest major
earthquake to make headlines hit Eastern Turkey on early Monday morning.
It registered 6.0 on the Richter scale, and has claimed the lives of
some 57 people so far. Meanwhile, major tremors in Taiwan, Chile and
Haiti are still dominating news cycles.
But although some
evidence suggests these earthquakes may be related, a connection hasn't
been scientifically proven, scientists say.
The number
of earthquakes around the globe is fairly constant, albeit fluctuating,
according to Wolfgang Friederich, a professor of geoscience at the Ruhr
University in Bochum.
Statistics from the US
Geological Survey's Earthquake Hazard Program show that the number of
earthquakes that measure between 7.0 and 7.9 magnitude on the Richter
scale remained fairly stable in the last decade, averaging about 13 per
year.
Bildunterschrift: Großansicht des Bildes
mit der Bildunterschrift: Science
can't prove a causal link between quakes
There were no more
than four quakes that measured 8.0 to 9.9 in that time. And the number
of small quakes and shocks to be measured is almost infinite, Ruhr
Univeristy's Friedrich said.
Ring of Fire
The earth is composed
of four layers: the inner core, outer core, mantle and crust. Together,
the crust and the upper mantle comprise the lithosphere, a 50 kilometer
(30 mile) thick layer that is made up of sections called tectonic
plates.
These plates are known
to shift, and contain many faults that cause the pieces to slip past
one another. Most earthquakes occur along these faults.
"The plates can move
horizontally or they move vertically so that one plate moves beneath
another plate," Friedrich said. "Plate movement can be a mix of
horizontal and vertical."
Much of the world's
earthquake activity takes place in the area in the Pacific known as the
Ring of Fire, a horseshoe-shaped area encircling the coast of the
Pacific Ocean along countries such as New Zealand, Japan, Alaska and
Chile. Some other major, well-known earthquake areas are the
Mid-Atlantic Ridge and the San Andreas Fault in California.
Coincidence,
or connection?
According to
Friedrich, seismologic modeling and mathematical calculation of stresses
has shown an increase of stresses in other parts of the world after an
earthquake occurs. This, combined with statistical data, has created a
theory that a large earthquake such as the recent ones in Haiti and
Chile can relieve stress in one part of a plate and increase it in
another, potentially causing a follow-up quake in another part of the
world.
"The problem is that
you have to prove that it is not a coincidence, which is really hard,"
he said.
Bildunterschrift: News
about the tremor in Haiti captivated the world
Some scientists say
they are relatively sure that after an earthquake, stress is
redistributed to other locations on the tectonic plate. But connecting
the effect to a second, later earthquake is not so easy, they maintain.
That the Chile
earthquake occurred not long after the Haiti one, is still likely to be a
coincidence, Friedrich said.
Reiner Kind, a
researcher at the GFZ German Research Center for Geosciences, concurs.
"No one has so far successfully proved that earthquakes on one side of a
plate are linked with earthquakes on the other side of the plate," he
said.
Better detection
methods
In fact, other factors
may contribute to a perception that the number of earthquakes is
increasing. For instance, the frequency and accuracy of quake
measurement has improved.
"In the last decades,
seismology has made a great deal of progress," Kind said.
As recently as thirty
years ago, Kind said, recording was still done mostly on paper and there
were few measuring stations worldwide. Now there are many more stations
and with digital equipment at their disposal, scientists can
immediately record any earthquake at any location.
"Ten minutes after an
earthquake happens, we know where it is and how big it is," he said.
Scientists also know
that if a fault is broken once, it will break again, Kind added. But
they still do not know when that next earthquake will occur, or how big
it may be.
The role of the
media
Another factor in the
public's perception that there are more earthquakes today than there
used to be, could be the media. When the earthquakes struck Haiti and
Chili, news organizations arrived quickly on the scene. Within minutes,
their updates were beamed around the globe.
Bildunterschrift:
Großansicht des Bildes
mit der Bildunterschrift: Media
focus on natural disasters is strong
"The media is working
much better than before. They are much better at communicating
information," Kind said.
A spokesman for the
Science Media Center in London, which aims to promote accurate
scientific reporting, noted that the earthquakes in Haiti and Chile were
covered extensively in the media.
"It makes an exciting
story because people see what it would be like for themselves," said Tom
Sheldon, a spokesman for the center, adding that for the viewer, it is
like watching a disaster movie.
Wolfgang Friedrich
from the Ruhr University notes that news of earthquakes tends to reach
the public when they cause a lot of damage and many people are hurt.
This increases the ominous perception that the earthquake threat is
increasing.
But according to
Sheldon, when the media focuses only on major earthquakes, it can make
it seem like there are fewer tremors than there really are. In fact,
there are hundreds of minor earthquakes that normally occur each year.
"Some earthquakes
happen in the middle of the Pacific and can be quite strong, but nobody
will be interested except seismologists," Friedrich said.
Author: Alina Dain
Editor: Mark
Mattox/jen
