Geoscience Reference
In-Depth Information
Just mention the word “earthquake” and immediately it conjures up images of Japan, Haiti, San
Francisco, Los Angeles, or perhaps Alaska. How many of us realize that the largest North
American earthquakes in recorded history were not in California or Alaska, but along the Mis-
sissippi river near the town of New Madrid, Missouri, in late 1811 and early 1812? The quakes
were so powerful that they shook down chimneys 360 miles away in Cincinnati, changed the
course of the Mississippi River for more than 100 miles, and were felt strongly over an area of
roughly 50,000 square miles (140,000 square kilometers).
Earthquake faults crisscross North America. Just because an earthquake fault has not
moved much in recent history does not mean it can't or won't. Most people do not realize it,
but even New England is not safe from earthquakes and is overdue for another big one. Prior
destructive New England quakes include the 1755 Cape Ann quake, estimated at a magnitude
of 6.2, and a 1638 New Hampshire quake, estimated at 7.0 (Miller 2006). If a magnitude 7.0
earthquake were to strike a city like Boston, Saint Louis, or New York City, the devastation
would look much like what we saw in the Kobe, Japan, and Haiti earthquakes. These cities
have many older buildings, and they do not have the same kind of strict earthquake-resistant
building codes that they have in places like California or Japan where earthquakes are much
more commonplace.
When a major earthquake strikes a metropolitan area, in addition to collapsing buildings
and bridges, water and natural gas pipelines typically rupture, resulting in wildfires that burn
out of control since there is no water pressure at the fire hydrants to help fight the fires. Not
only do you have massive injuries to cope with, and thousands of instantly homeless people,
but also many of the medical workers will themselves be injured, or stay home to help their
friends and families cope, so the few that are left to service the public will be overwhelmed and
overloaded.
Each single number on the Richter scale is a factor of ten, so a 7.0 quake is ten times as
strong as a 6.0 quake, and an 8.0 quake is 100 times as strong. The 1994 Northridge earth-
quake, centered about twenty miles northwest of downtown Los Angeles, had a magnitude of
6.7. It caused 72 deaths, over 9,000 injuries, and about $20 billion in damage. If it had been the
same size as the Japanese mega quake of 2011 (a magnitude of 9.0), it would have been 200
times as strong. Instead of collapsing only 6 freeway interchanges, somewhere on the order of
600 or more freeway overpasses would have fallen down, and the vast majority of the buildings
in the northern Los Angeles basin would have either collapsed or suffered irreparable structural
damage. How do you begin to rebuild a major metro area like Los Angeles, when practically all
