This page last updated on 21-Jan-2004
Prof. Stephen A. Nelson
Earthquake Hazards and Risks
Many seismologists have said that "earthquakes don't kill people, buildings do". This is
because most deaths from earthquakes are caused by buildings or other human
construction falling down during an earthquake.
Earthquakes located in isolated areas far from human population rarely cause any deaths.
Thus, earthquake hazard risk
1. Population density
2. Construction standards (building codes)
3. Emergency preparedness
Worst earthquake in recorded history occurred in 1556 in Shaaxi, China.
people, most living in caves excavated in poorly consolidated loess (wind deposited silt
Worst earthquake in this century also occurred in China (T'ang Shan Province), killed
240,000 in 1976.
Occurred at 3:42 AM, Magnitude 7.8 Earthquake and magnitude 7.1
Deaths were due to collapse of masonry (brick) buildings.
Contrast - In earthquake prone areas like California, in order to reduce earthquake risk,
there are strict building codes requiring the design and construction of buildings and
other structures that will withstand a large earthquake. While this program is not always
completely successful, one fact stands out to prove its effectiveness.
In 1989 an
earthquake near San Francisco, California (The Loma Prieta, or World Series
Earthquake) with a Richter Magnitude of 7.1 killed about 62 people.
Most were killed
when a double decked freeway in Oakland collapsed.
About 10 months later, an
earthquake with magnitude 6.9 occurred in Armenia, where no earthquake- proof
building codes existed. The death toll in the latter earthquake was about 25,000!
Computer simulations for large cities, like San Francisco or Los Angeles, California,
indicate that a magnitude >8.0 earthquake would cause between 3,000 and 13,000 deaths.
3,000 if at night, when populace is asleep in wood frame houses
13,000 if during day when populace is in masonry buildings and on freeways.
Page 1 of 6