Geoscience Reference
In-Depth Information
were destroyed. They were built on land reclaimed from an ancient lake and the earthquake
waves resonated to and fro through the mud for nearly three minutes, liquefying it so that
it could no longer support buildings. However deep the foundations of buildings are, they
don't provide much support if the ground turns to liquid. In both the 1906 and 1989 quakes
near San Francisco, the worst-damaged buildings were in the Marina district, built on re-
claimed land.
Fire
One of the greatest dangers when an earthquake strikes a city is fire. Both in San Francisco
in 1906 and Tokyo in 1923, more people lost their lives in fires than in the quakes them-
selves. Fires can start easily as cooking stoves are overturned, and spread quickly in the
tangled ruins of wooden buildings, fuelled by fractured gas pipes. In San Francisco, the fire
services were inadequate; fire engines were trapped in their garages or by blocked streets,
and fractured water mains drained the city's water supply. Today, quake-prone cities such
as San Francisco are developing systems of so-called 'smart pipes', both for gas and water,
that will quickly and automatically shut off sections of pipe where the pressure falls sud-
denly due to a break.
Saving lives
The safest place to be during an earthquake is in open, flat countryside. Just about the worst
thing to do is to panic. In a city, falling glass and masonry outside can be more of a haz-
ard than staying indoors under strong structures such as stairways. Schoolchildren in Japan
and California have regular training in how to protect themselves. Yet, in real earthquake
situations, most people still tend either to freeze where they are or panic and run into the
open. If people are caught in a collapsed building, there's a whole range of heat-sensitive
cameras and listening devices to find them, and every disaster brings tales of miraculous
rescues as well as tragedy.
Chance and chaos
In one way, earthquakes can be predicted with certainty. Cities such as San Francisco,
Tokyo, and Mexico City will definitely experience another earthquake. But that knowledge
is not much use to those who live there. They want to know precisely when the Big One
will come and how severe it will be. But that is just what geologists cannot tell them. Like
the weather, the Earth is a complex system in which a tiny cause can have a big effect. Like
the imaginary Amazonian butterfly that can supposedly influence the weather in Europe by
flapping its wings, so a pebble stuck in a fault could lead to an earthquake. Although it may
