Understanding Earthquakes

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 As survivalists and preppers we all know that there are dangers available at every location or state in America. It is our responsibility to minimize these hazards as much as we possibly can. As such it would behoove us to know how to read an earthquake. Often we complain about asinine and petty government requirements particularly where building structures are concerned. But wait one minute! Are these established codes really as off beat as we might suspect?

  Although we may feel insulted when we are told just how we can construct structures on our own property we must admit that some reasonable regulation are actually necessary otherwise we could readily find that we too are in the same type of situation as Haiti. Don’t even think for one moment that earthquakes are reserved strictly for California. Over the past year we have seen the magnitudes of earthquakes increase and they have been appearing at locations that are not traditionally supportive of these types of occurrences. Just last month a minor quake was reported in Chicago, before that there was one in New Jersey. These are not states which exist in the earthquake belt.

  The great San Francisco earthquake of 1989 measured a 7.0 on the Richter scale. This was mild when compared to that of Haiti’s 7.3.

“Mild,” you may be asking. “How can you compare a 7.0 and call a 7.3 considerably worse.”

  Okay my friends. It is education time. For today’s survival topic let’s discuss earthquakes. Earthquakes are frequently measured in one of two ways. These are intensity and magnitude relating to the quake itself. Intensity indicates a measurement relative to the amount of damage done to the earth’s surface and its effects upon the involved humans. The usual scale which is employed for this measurement in intensity is a Modified Mercalli Intensity Scale. Keep in mind that the magnitude of an earthquake does not depend upon the population of the area or merely the effects to the various ground structures, but rather it is based upon the earthquake wave amplitude as well as the distance it is from the epicenter. There are various formulas and related seismograph information that is used to determine this magnitude.

  The scale that is used to measure the magnitude on the other hand is known as the Richter scale. Each earthquake is different and each has its own unique magnitude which causes its effect to vary greatly in accordance to its distance, the ground condition, the areas construction standards, as well as other related factors. Depending upon the location, the size and the nature of the earthquake in question, seismologists may use several different methods in order to estimate the magnitude. These methods have an uncertainty of plus or minus .3 units in magnitude. The actual figures are constantly under change as the seismologists tend to frequently revise the magnitude estimates per newly analyzed data. Under the Richter magnitudes earthquakes tend to create the following effects:

  * 3.5 or less – One generally does not feel these quakes but they are recorded never-the-less.

  * 3.5 to 5.4 – These quakes are often felt, however they rarely cause any conceivable damage.

  * 5.4 to 6.0 – These earthquakes will cause a slight amount of damage to the well designed building but can cause considerable damage if the structure is poorly constructed.

  * 6.1 to 6.9 – These can be very destructive in areas to about 100 kilometers wide where people may be living.

  * 7.0 to 7.9 – These are considered to be major earthquakes and are capable of causing serious damage over very large areas.

  * 8.0 or greater – Lastly we have the great earthquakes. These major quakes are well able to cause some serious damage within areas of several hundred kilometers wide.

  With this information fresh in our minds let’s get back to our comparison of the 7.0 earthquake to the 7.3 version. Since we are looking at a logarithmic type system each increase in integer represents an increase in magnitude. The 7.0 is actually ten times as strong as a 6.0, whereas the 6.0 is actually 10 times as strong as the 5. Should we experience a magnitude of 8.0 the earthquake would be 10 times that of a magnitude 7, or 100 times that of a magnitude 6. Going even further it would be 1,000 times that of a magnitude 5, and 10,000 times that of a magnitude 4, and so on.

  Now when you hear the news reports concerning 7.0 or 7.3 quakes taking place you can readily appreciate the destructive power contained in them. It isn’t a matter of if but rather when the big ones hit. Hopefully we will be ready when it does.

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