鈥淚F YOU鈥橠 been standing here on 18 April 1906, you鈥檇 have seen that hill over
there move about two metres to the right.鈥� Allan Lindh is pointing to a hillock
a few hundred metres away. Now he gestures to the dry scrub beneath his feet.
鈥淭his would have been moving back and forwards, up and down by metres. You鈥檇
have been on your knees, then flat out, yelling, trying to get up, wondering
what in the world was going on.鈥�
Lindh is describing the last really big quake to hit California. Up here on
the crest of the Santa Cruz mountains, around 40 kilometres south of San
Francisco, it鈥檚 hard to imagine such sudden drama. The air is still, and all
around the scene is reassuringly solid and unchanging. It鈥檚 silent, but for a
steady hum from the countless insects that live in the scrub. The only odd note
is struck by a narrow green trench, luxuriant with vegetation, disappearing off
to the southeast into the next valley.
But it鈥檚 that trench and the many others threading through this landscape
that make all the difference. They are part of the San Andreas rift zone, and
each fault trace grows lush and green where the rock has been pulverised by the
fault motion into impervious clay that traps surface water. This is where the
Pacific and North American plates grind against each other, crushing and folding
the rocks, creating mountains, valleys and, of course, earthquakes. The Big One
that struck in 1906 ripped through here at around 2 kilometres a second after
devastating San Francisco and taking hundreds of lives. And though a long period
of calm followed, activity has been picking up again over the past 20 years.
Nine years ago this week, the most recent serious quake hit near Loma Prieta, a
squarish mountain just visible through the haze to the south, before setting off
on its destructive path through cities, homes and lives.
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Californians spend every day not knowing whether an earthquake will strike.
It seems like a terrible flaw in a beautiful and wealthy place. But that鈥檚 not
the way Lindh sees it. A seismologist from the US Geological Survey at Menlo
Park, he has studied the fault system for the past 25 years. 鈥淓arthquakes are
not an optional add-on sent by the devil to make life more difficult in
California,鈥� he says. 鈥淭hey鈥檙e an integral part of the 蝉测蝉迟别尘.鈥� Or, to put it
another way, the same thing that brings the quakes also creates the beauty, the
wealth and everything else that makes California unique.
Lindh wants to give the San Andreas its due, and for years now he has been
spreading his message on TV and radio shows and in local newspapers. Everyone
knows the fault鈥檚 destructive power, he says, but not everyone gives it credit
for the good things it brings. Partly, he wants to use this message to try and
encourage people to put more money into quake-proofing their buildings to reduce
the death toll when the quakes do hit. Partly, it鈥檚 a geologist鈥檚 desire to
redress the fault鈥檚 bad press. And according to his calculations, it gives much
more than it takes.
The beaches, for instance. From here in the Santa Cruz Mountains, the road
snakes down through redwood groves to San Gregorio beach. There you can walk for
miles on the sand, between the Pacific Ocean and the high crumbling cliffs. The
whole coast is made up of long stretches of beaches like this, broken by high
mountains and capes jutting into the ocean. 鈥淭hey鈥檙e not just boring, flat
beaches that go on for ever,鈥� says Lindh. 鈥淭here are wild places, with mountains
above them, streams running down, great high points where you can look out over
the ocean.鈥�
That, he says, is a classic landscape produced by the geological
process called transform faulting. As the plates grind past one another,
irregularities in their curving fault lines catch and snag, pushing up great
folds in the land. As a result, the cliffs are rising far faster than they can
be eroded by the waves.
The combination of mountains and shoreline is certainly spectacular, but the
high ground created by the fault system is good for more than just the scenery.
It also gathers the water that is vital for California鈥檚 agriculture and
industry. Moist air arriving from the ocean is forced to rise, cool and deposit
its load into the mountain aquifers. Without the mountains, that precious
moisture would be blown eastwards into the interior, leaving the coast arid.
鈥淭he water that keeps California alive comes almost entirely from the
mountains,鈥� says Lindh. 鈥淎nd they are a direct product of the San Andreas
蝉测蝉迟别尘.鈥�
The list continues. Not only does California have more than its share of
water, it also has plenty of large, fertile valleys. And guess what鈥攖hat鈥檚
down to the San Andreas, too. 鈥淲hen you push mountains up, something else has to
go down,鈥� says Lindh. In California鈥檚 case, that鈥檚 valleys like the Imperial
Valley and the San Joaquin Valley, where most of the state鈥檚 fruit and
vegetables are grown. These vast trenches, filled with rich young soil that has
eroded from the surrounding hills, bask in the long hot growing season of the
desert climate, and are supplied with plentiful water trapped by the mountains.
Then there are the friendly microclimates of the wine country in the north.
Small wonder California鈥檚 agriculture is so productive.
And there鈥檚 oil, too. It forms in places where in the past copious organic
material has been deposited and buried. Then it must be carried downwards and
cooked at temperatures and pressures that will turn it into petroleum. Finally,
folding and faulting are needed to create traps where oil collects. All this,
says Lindh, is just what happens in a tectonically active region. 鈥淭hey鈥檝e taken
an enormous amount of oil out of the Los Angeles Basin and it鈥檚 all down to the
蹿补耻濒迟颈苍驳.鈥�
Even San Francisco鈥檚 extraordinary bay was formed by the fault system. This
part of coastal California is a collage, made up of sundry pieces of crust that
have been assembled by the plate motion over millions of years. The block
beneath the bay is a piece of dense oceanic crust, forced downwards by the
combined geometry of the San Andreas Fault to the west and the Hayward Fault to
the east to create one of the most famous natural harbours in the world.
It was thinking about agriculture and oil that set Lindh wondering just how
many dollars the fault brings in. Add up the oil, agriculture, wine and tourism
and Lindh reckons it earns the state a cool $10 billion to $20
billion a year. Compare that with the cost of earthquakes from the faults. There
is a really big quake once every 50 to 100 years, says Lindh, and he puts the
cost at around $100 billion a time. So even at a conservative estimate,
the fault is bringing five to ten times as much into the Californian economy as
it takes out, Lindh reckons.
Of course, earthquakes don鈥檛 just cost money. They also take lives. But Lindh
points out that it鈥檚 bad buildings that kill, not the earthquakes themselves.
Falling masonry from poorly constructed buildings is the biggest danger, and out
here in the open, if an earthquake ripped by, the worst you鈥檇 have to worry
about is the thorns. In fact, it鈥檚 partly because of poorly designed and
constructed buildings that he did his calculation. 鈥淚t is California鈥檚 poorest
citizens who are often most at risk in a great earthquake,鈥� he says. 鈥淭hey live
and work in the worst buildings, and share least in the state鈥檚 bounty.鈥� More of
the riches that the fault brings to the state should be funnelled back into
making them safe, he believes. 鈥淚t鈥檚 up to us to share just a little of the
wealth so everyone has a secure place to live and work.鈥�
Lindh is also exasperated by Californians鈥� habit of complaining about the
dangers of living in an earthquake zone, without also acknowledging the
benefits. 鈥淐alifornia and Japan鈥攁ren鈥檛 they among the richest places in
the world? Do you think it鈥檚 coincidence that they are also two of the most
tectonically active? I think more interesting people come to more interesting
辫濒补肠别蝉.鈥�
And he has a tale to back this claim. It concerns the Santa Clara Valley just
down Page Mill Road on the other side of the Santa Cruz hills. Better known as
Silicon Valley, the cradle of the modern computer industry, it is home to many
of the world鈥檚 top IT companies. But why is it here in California?
It started, says Lindh, with Jane and Leland Stanford, who made their fortune
in the 19th century building the first railroad to cross America. They built a
vast country estate in a beautiful valley south of San Francisco, within
striking distance of the ocean, yet protected by mountains from the fog that
plagues San Francisco. When their only child died of typhoid, they converted
their home into a university in his memory. By the end of the Second World War,
Stanford University had become home to many applied materials scientists, and
the conditions for the silicon revolution were ripe.
鈥淚 think it鈥檚 all because it was such a pretty place,鈥� says Lindh. 鈥淚鈥檓
sorry, but it just wouldn鈥檛 have happened in Des Moines.鈥�