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When Dr. Michael
Reichle, chief seismologist for the
Department of Conservation’s California
Geological Survey (CGS), meets
non-scientists for the first time, the
conversation is almost a given.
“The first thing
people say to me when they find out I’m
a seismologist is `You’ll tell me when
the big one’s coming, won’t you?’ ”
Reichle said. “I usually tell them,
`There’s a good chance you’ll know
before I do.’ ”
The public has many
misconceptions about earthquakes –
whether it’s the inevitability of
California falling into the ocean or the
wisdom of standing in a doorway during
heavy shaking -- and about science’s
ability to predict them. As the April 18
centennial of the 1906 San Francisco
earthquake approaches, CGS hopes to
debunk some common quake myths and help
the public become better informed about
the potential hazard.
Take the issue of
prediction, for example. Science cannot
predict earthquakes -- and may never
have the ability.
“There doesn’t seem
to be a light at the end of the tunnel
for prediction,” CGS Supervising
Geologist Charles Real said. “What we’ve
learned in the last three decades or so
is that the earthquake process is highly
complex. The number of variables that go
into creating an earthquake, and how big
that quake gets, is so large and
difficult to measure that it has made
the development of a good model for how
the process works intractable.
“Imagine looking at a
freshly plastered wall and trying to
predict where the first crack will show
up. That’s where we’re at with
earthquake prediction right now.”
Real heads the
Seismic Hazards Zonation Program for CGS.
The program has produced more than 100
regulatory maps showing zones where
there’s a relatively higher potential
for liquefaction and landslides during
large earthquakes.
“My personal feeling
is that the ability to predict
earthquakes is so far off in the
distance that we’re better off expending
our resources on learning how to better
deal with earthquakes when they happen,”
he said. “That’s why our emphasis is on
mitigation by defining where earthquakes
and associated hazards are most likely
to take place, so we can focus our
resources toward earthquake-safe
development.”
Reichle, who heads
CGS’ Seismic Hazards Assessment Program,
agrees with Real, saying that science
lacks the proper tools to predict
earthquakes.
“Before the advent of
satellites, weather predictions were
rather chancy,” Reichle said. “After
there were weather satellites in orbit,
meteorologists could see the storms
developing in the ocean and do a better
job of predicting what would be coming
ashore. In earthquake prediction, we
haven’t found our equivalent of the
weather satellite yet. We don’t have a
good prediction tool, and I’m not
certain we will ever be able to say with
any certainty that there will be an
earthquake on this particular section of
a fault within the next day or week.”
Instead of
prediction, CGS and other scientific
organizations have conducted and
routinely update probability studies
that estimate the likelihood that a
rupture will occur on a fault. For
example, while the 1987 Loma Prieta
earthquake wasn’t predicted, it was
centered in an area that was believed to
have a relatively high probability of
experiencing a large quake.
“We routinely review
and revise the probability studies,”
said Dr. John Parrish, who heads CGS as
the California State Geologist. “We
participate on the California Earthquake
Prediction Evaluation Council, a group
that reviews the predictions of others
and advises the Governor and the Office
of Emergency Services. But we don’t
claim any special insight into when
earthquakes will occur – simply the
knowledge that they’ve occurred in the
past and will occur in the future.”
There are individuals
who claim they possess unique knowledge
of impending temblors – sort of a “sixth
sense.” Supervising Geologist Chris
Wills, head of CGS’ Geologic Mapping
Program, doesn’t buy that notion.
“Those claims are all
based on random chance, as far as I
know,” he said. “There’s a magnitude 6
earthquake somewhere in the world about
every week. There’s a magnitude 3 in
California every day. So it’s pretty
easy – and not very helpful – to say
something as vague as, `I predict
there’s going to be an earthquake soon.’
Earthquakes are frequent enough that
sometimes predictions will be right.”
While there are
reports of predictions that have
accurately stated the time, location and
magnitude of an earthquake, frequently
such reports aren’t examined in a
scientifically rigorous fashion. Wills
believe that the human tendency to seek
out patterns to make sense of things –
as well as selective memory – are behind
many claims of inside knowledge of what
the Earth is up to.
“Let’s say the bunion
on your left foot is sore, and there
happens to be an earthquake,” Wills
said. “You might remember that and
consider your sore bunion a precursor to
an earthquake. But you’re probably not
going to remember all the times your
bunion was sore and there wasn’t an
earthquake. It’s just wishful thinking
to believe it’s something that simple.”
During a recent total
eclipse of the sun, residents of
Turkey’s Tokat province camped out in
tents, fearing an earthquake. Although
the scientific community offered
reassurance that there’s no connection
between eclipses and quakes, residents
remembered that in August 1999, 17,000
people in northwestern Turkey died when
an earthquake struck six days after an
eclipse.
“Everyone draws
connections where they don’t exist,”
Wills said. “If you’re a sports fan and
your favorite team wins every time you
watch the game sitting in a particular
chair and loses when you don’t, you may
start to think that you have some
control over the outcome. You don’t, of
course, but everyone wants to find
patterns.”
Added Real: “There’s
no real physical basis for those type of
claims … Frankly, it’s hogwash.”
Speaking of hogs,
Real thinks there may be a little
something to claims that some animals
can sense an impending earthquake.
“There have been some
observations that tend to support animal
sensitivity,” he said. “In China,
there’s a well-known case of successful
earthquake prediction based on a variety
of evidence, including animal behavior.
It was winter (February), and one of the
things they observed was snakes that
typically hibernate underground coming
to the surface only to freeze to death
in the days leading up to the
earthquake. One wonders what the snakes
were sensing.”
The China State
Seismological Bureau ordered an
evacuation of 1 million people from the
city of Haicheng on Feburary 3, 1975.
The next day, a magnitude 7.3 earthquake
struck; the evacuation probably saved
countless lives. However …
“The following year,
there was another earthquake that wasn’t
predicted (the magnitude 7.8 Tangshan
quake),” Reichle said. “Officially, it
killed about 250,000 people.
Unofficially, it might have killed
600,000. The point is, consistency of
the precursors has always been a problem
in earthquake prediction research.”
Like his colleague
Real, Reichle finds the reports about
the behavior of snakes prior to the
Haicheng earthquake interesting. Still,
he believes from personal experience
that animals are just as inconsistent as
people when it comes to predicting
quakes.
“My cats had no idea
that the (magnitude 5.1) Santa Barbara
earthquake was coming in 1978,” he said.
“They weren’t acting any stranger than
normal, and when the quake struck and
they bolted, they left wet spots on the
carpet. So they were certainly as
surprised as I was.”
Wills’ favorite myth
comes out of the 1906 earthquake, when
it was widely reported that the Earth
opened up and swallowed a cow.
“The story went that
the Earth opened up, a cow fell into the
fissure, and then the Earth closed
around it,” Wills said. “A geologist
visited the ranch where this happened,
and a ranch hand took him to where he
could see cow legs sticking up from
underground. The real story came out 50
years later, when the ranch hand
admitted that he’d found a dead cow that
he needed to dispose of. He tipped it
into the fissure and covered it with
dirt. Fissures open and things can fall
in. But the fissures don’t close up.”
Of course, seemingly
every fictional portrayal of earthquakes
includes a person, car, building or
something disappearing into the vengeful
soil.
Other favorites
include earthquake weather and the
notion of California tumbling into the
sea.
The notion of
earthquake weather can be traced to the
Greek philosopher Aristotle in the
fourth century B.C. He believed that
earthquakes were caused by winds trapped
underground in caves. That idea evolved
into the belief that still, sultry
weather (because of the lack of wind) is
associated with quakes.
“The causes of
earthquakes happen tens of thousands of
feet below the Earth’s surface, while
the weather is created in the atmosphere
tens of thousands of feet above the
Earth’s surface,” Parrish noted. “The
tectonic plate boundaries don’t care if
it’s sunny or rainy or balmy or
freezing.”
Added Reichle: “I
grew up in a part of California
(Imperial County) that has lots of
earthquakes, and I’ve never experienced
earthquake weather.”
He doesn’t expect to
experience California falling into the
Pacific, either, no matter how big the
quake.
“The San Andreas
fault moves horizontally, not
vertically,” he explained. “Los Angeles
is moving northwest very slowly. At some
point, San Francisco and Los Angeles
will be next to each other on either
side of the fault. Of course, we’re not
going to be around to see it.”
Oh, and about that
notion of standing in the doorway during
an earthquake?
“For those of us who
live in an unreinforced adobe home, it’s
the right thing to do,” Parrish said.
“But if you’re in a some other type of a
building, the doorway is no safer than
anywhere else, and perhaps more
hazardous. If you’re in an office
building and you stand in the doorway,
you’re likely to get trampled by people
running out. The best bet is to get
under a sturdy desk or table and hang
on.”
But don’t hang on to
misplaced myths.
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