Analog Science Fiction and Fact - June 2013

have had some history of seismicity in the
1700s, but have been quiescent since. In
earthquake risk, that’s not a good thing.
“There is a possibility to fit a very large earthquake
in there—up to magnitude 9—which
would be bad for the Philippines in addition
to the local islands,” Okal says.
The Philippines themselves, he adds, are a
“tectonic mess.” Mega earthquakes have never
occurred there in recorded history, he says,
but it’s possible that a region known as the Luzon
Trench might produce such an earthquake.
“If all of this were to rupture at
once—and there is no reason to think it could
not—you could have a major event,” he says.
The resulting wave, he adds, would be a disaster
in the South China Sea, which borders not
just Manila but much of Southeast Asia. “It
could be one of the very few scenarios in
which the coastlines of Vietnam, western
Malaya, and perhaps Singapore, could be
threatened,” he says, adding that Hong Kong
might also be hit by the resulting wave.
It’s a very poorly understood area, tectonically,
but—for those worried about mega-disasters—probably
the scariest setting we’ve yet
discussed, simply because of the enormous
number of people living along the coast and
their lack of tsunami preparedness. 9
Continuing south, Okal says an earthquake
on the southern coast of the Indonesian island
of Java would not only be disastrous for local
communities, but is one of the few that could
produce a wave that would hit Western Australia,
including the harbor city of Perth. “Economically,
that is of great concern to our
friends Down Under,” he says.
The final big risk in the Pacific is Tonga,
which lies near a subduction zone that shares
some characteristics with Indonesia’s Sunda
zone. But, Okal says, it’s another “big question
mark” because we don’t know much about its
seismic history.
Luckily, it’s not a densely populated area.
Other than Tahiti, Okal notes, an earthquake
there would beam its tsunami energy mainly
at uninhabited areas—though, he says, an
1865 event in the region did produce a tsunami
that hit the Marquesas Islands.
* * *
JUNE 2013
Sloshing the Middle East
The Ring of Fire is well known. But other
than the South China Sea, some of the globe’s
most dangerous tsunami zones may be elsewhere.
One such potential disaster area is the
Makran Subduction Zone, which lies in the
Arabian Sea, paralleling the coasts of Pakistan
and Iran. Virtually unknown to Americans,
this region’s most recent large event was a
magnitude 8.5 quake in November, 1945,
which produced waves reported to be as high
as forty-five feet and killed four thousand people
in southern Pakistan.
One might think that this released all of the
accumulating strain, but only about one-third
of the “available” fault ruptured, Okal says. Is
the rest primed to go any day? Who knows.
But, Okal says, “There is a concern. We are
talking about a major impact on places like
Karachi and Mumbai.”
Another place that’s ripe for a major tsunami
might be Istanbul, Turkey.
It’s another place most of us wouldn’t associate
with tsunamis. After all, it’s inland, miles
from either the Black Sea or the Aegean. But it
happens to lie on a body of water known as
the Sea of Marmara, which is the lake-like
zone between the Black and Aegean Sea. And
Turkey’s most dangerous fault, the North Anatolian
Fault, runs right along the northern
edge of Turkey, directly toward that sea, says
Costas Synolakis, a tsunami expert at the University
of Southern California and president of
the Hellenic Center for Marine Research in
Greece.
Since 1939, that fault has been rupturing,
piecemeal, starting at the eastern end, and
heading toward Istanbul. The most recent
earthquake, in 1999, was a magnitude 7.4 in
Izmit (only sixty miles east of Istanbul) that
left seventeen thousand dead and produced a
small tsunami in the Sea of Marmara.
The 1999 tsunami wasn’t a major source of
destruction, but the next segment of the fault
lies directly beneath the sea and is likely to
produce a more substantial tsunami, Okal
9 It is only very recently that the Vietnamese appear to have become aware of the risk. See, “Tsunami
in Vietnam is the Real Risk,” VietnamNet English, April 2012, http://en.baomoi.com/ Info/Tsunamiin-Vietnam-is-the-real-risk/6/256298.epi.
WAVES OF THE FUTURE
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