- [Narrator] A series of powerful successive earthquakes
struck the Turkish-Syrian border on February 6th.
The first and most powerful was a 7.8 magnitude quake.
- This region certainly
hasn't seen an earthquake this size in centuries.
- [Narrator] Destruction followed
(buildings shaking)
as aftershocks hit the region.
Then a second 7.5 magnitude quake hit in the afternoon,
followed by its own series of aftershocks.
In their wake, a humanitarian and economic crisis.
(building collapsing)
Thousands of people are reported dead
and even more are still missing.
It's not the first time this region
has suffered a violent quake and it won't be the last.
To understand why, you have to look
under the surface where three tectonic plates converge.
Together, these plates cause a unique
and potentially devastating type of earthquake.
The first quake was located here,
11 miles under the town of Gazientep, Turkey.
11 miles may sound deep
but that's actually shallow for a major quake.
The town is especially vulnerable
because it sits near the meeting of two tectonic plates.
Tectonic plates are massive slabs of rock
on the Earth's crust from 10 miles
to 160 miles thick that are always slowly moving.
- You can take the Earth and divide it up
into several large plates that are all moving
around each other, and most earthquakes occur
at the boundaries between those plates.
- [Narrator] This one is called the Anatolia tectonic plate.
It's actually a microplate due
to its tiny size and it's constantly under pressure.
That's because it's being pressed upward
against the Eurasia plate by the Arabia plate.
That pressure is squeezing the Anatolia plate westward
where it faces even more friction from the Africa plate,
which is also moving upward.
- The Anatolian microplate is caught
in a vise between the Arabian plate moving
to the north against the Eurasian plate,
and this small plate is being pushed aside
as a result of that motion.
- [Narrator] That means the boundaries
between the Anatolia plate and the Africa
and Arabia plates are trying to slide against each other
as the Anatolia moves to the west
and the Africa and Arabia move to the east.
These borders are called strike-slip faults
and when the friction builds up between the plates
as they're pushed in different directions
until it's too much, they slip.
That's a strike-slip earthquake.
- The strain will build up and finally, it will rupture
and release all that accumulated strain
in a large earthquake.
That's what happened in Gazientep,
resulting in that 7.8 magnitude quake.
USGS estimates that the strike-slip occurred
along about 100 miles of the fault
about 20 miles shorter than most strike-slip earthquakes.
- These are significant earthquakes for this fault system
and so that is probably an accumulation
of 3 to 500 years' worth
of strain that's built up since the last earthquake.
- [Narrator] Experts say the energy released
in that slip is comparable
to that released during the explosive
1980 Mount St. Helen's volcanic eruption.
The same thing happened nine hours later in Ekinozu,
resulting in a 7.5 magnitude quake.
This one was just six miles down.
More than 285 aftershocks have followed both quakes.
USGS has called the area tectonically active and unstable.
- This region is certainly one
of the more complicated parts of the world
because there are four different plates interacting,
so it becomes a region with very complex tectonics.
- [Narrator] Those complex tectonics are responsible
for a long history of devastating quakes,
like this quake from 1966 that killed over 2,000 people.
- [Reporter] Towns and villages
in 19 provinces are almost totally destroyed.
- [Narrator] The 600-mile North Anatolian fault
produced seven large strike-slip earthquakes
from 1939 to 1999,
and three earthquakes of magnitude six or larger
have occurred within 155 miles of Monday's earthquakes
since 1970 but there hasn't been
a large earthquake since 1999.
- Because this region hasn't seen a large earthquake
for a while, it was was overdue.
- [Narrator] That 1999 quake was a 7.4 magnitude
and caused an estimated 17,000 deaths.
For now, USGS estimates there could be billions
in economic losses.
- The biggest thing is the destruction and loss of life
and it's gonna take them years for recovery.
- [Narrator] But will there be more disruption
if the two quakes spark a third?
Experts aren't sure.
- It may put extra strain on some of the nearby faults
or it may relieve some of the strain on the nearby faults,
so it'll take some time to figure out
whether further earthquakes are more likely
or less likely in this region.
- [Narrator] But due to the three-plate convergence,
it's not a question of if there will be another earthquake,
it's a question of when.
(pensive music)