Science Types of Earthquakes


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Google Earth showing 'The Ring' of Fire' running from beyond Southern Japan to the Aleutian Islands

Notice the subduction of the oceanic plate as it 'dives' beneath the continental plate.

In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's crust,

Yesterday we talked about the low probability of having a huge earthquake in our area of Bruce County.  See:


Science We live in stable geologic area.  See map....  Read More

So many local people have been wondering about quakes that we thought we'd delve into them at least on the surface.

There are three basic types of quakes.  We will ignore man-made explosive forces like underground nuclear testing or natural volcanic eruptions that cause tremors.

Types of Quakes:

  1. Shallow Earthquakes ("Crustal" quakes) are caused by faults in the continental plates, as they result from the relative motion of sections of the plates. They are usually 1 to 5 magnitude, less than 15 miles deep, occur seemingly at random and are at present unpredictable and most of them are not even felt
  2. Deep Earthquakes ("Intra Plate" quakes) occur between the subducting oceanic plates as they bend beneath the continental plates. They are 6.0 to 8.0 magnitude, occur up to 40 miles deep and occur every 20 to 30 years along a given fault line.
  3. Major Subduction Earthquakes are huge quakes that result when the boundary between the oceanic and continental plates ruptures

It's not clear whether the recent magnitude 9 quake in Japan was an exceptional 2 or a more rare 3.

In any event, examining the Google Earth depiction shown above makes it clear why Japan is such a dangerous place to live due to earthquakes.

Furthermore, because of the thrusting up of the islands of Japan, most of the population is located on or near the water.

Locating Nuclear Power Plants on the oceanfront in Japan requires very special precautions.  It seems that the old style Boiling Water Reactors are questionable for Japan.  Will they look at CANDU designs?


Science Fukushima Crisis  Read More

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Wednesday, April 25, 2012