Potential Earthquake Dangers at the PGPD
Common Terminology
When scientists discuss the potential danger of an earthquake, they frequently use the following terms:
1) Seismic - Of, subject to, or caused by an earthquake or earth vibration. Earthshaking: an issue of seismic proportions and ramifications.
2) Seismicity – the frequency or magnitude earthquake activity in a particular area
3) Earthquake Magnitude – a mathematical measure of the strength of an earthquake based on the maximum size of the seismic waves produced. The magnitude of an earthquake is normal expressed in terms of a number associated with the Richter scale.
http://www.google.com/search?q=define%3A+richter+scale&sourceid=ie
4) Seismic Risk – the probability of an earthquake of a particular magnitude
5) Seismic Hazard – the probability of damage of a particular magnitude
Sometimes geologists or seismologists (scientists who study earthquakes) use the terms seismic risk and seismic hazards interchangeably, which can add to people’s confusion. Perhaps one way to distinguish these two terms is to think of the old children’s story about the Three Little Pigs and the Big Bad Wolf. If you remember, the story tells about three little pigs, one who built a house out of straw, one that build a house out of wood, and one that built a house out of bricks. It also tells the story about how a Big Bad Wolf would come to each of their houses saying “Little Pig, Little Pig, let me in” to which the pig would say, “Not by the hair of my chinning chin chin” to which the Big Bad Wolf would reply – “Then I’ll huff and I’ll puff and I’ll blow your house in.” If you remember the story, the Wolf was successful in blowing the houses in of the first two pigs but not the third – the one made out of bricks.
http://www.free-stories.net/fairy-tales/the-three-little-pigs.html
At this point you might be asking yourself, what does this have to do with earthquakes – well, the point of this is that in comparison to seismic risk and seismic hazard – we would say the magnitude of the Wolf’s blowing is analogous to seismic risk while the impact of the Wolf’s blowing is analogous to seismic hazard. Thus in our case, the seismic hazard is related to what type of precautions have been taken (or design modifications made) to protect against a particular seismic risk. Thus in many cases, just because there is a significant seismic risk does not necessarily mean there is a significant seismic hazard. While it may certainly cost a lot more money to build a structure with the same seismic hazard in an earthquake zone than one not in an earthquake zone, that does not mean that it is impossible to do so. Thus we find as an example, that California has several nuclear power plants – http://www.energy.ca.gov/nuclear/california.html.
