January 26th - Cascadia Earthquake

On this day, in 1700, the magnitude 9 Cascadia earthquake occurred off the west coast of North America. This is only known because the Japanese kept records about earthquakes. The native Americans also kept records but didn't backup their files properly and Chief Clicking Mouse shut down without saving.

 

This earthquake is known as a megathrust earthquake. If you don't know what megathrust is then picture me with some cycling shorts on. If that doesn't explain it for you then the more scientific explanation is that amegathrust earthquake is a big earthquake that occurs at subduction zones. If you don't know what a subduction zone is then picture me with some cycling shorts on. Another more technical definition is that asubduction zone is where tectonic plates meet and move above and below each other. Just like when I'm wearing bicycle shorts.

 

Specifically, this quake had a fault rupture of about 1000km and an average slip of 20m. If you don't know what a fault rupture or a slip are then picture me in with bicycle shorts on. The quake caused a tsunami that struck the east coast of Japan. The Japanese thought it was pretty impressive so they made a note of it, and it is thanks to their tireless efforts that we know about the quake today. It is also thanks to their efforts that we have affordable, quality-built automobiles.

 

If you dare to doubt the meticulous record-keeping tradition of the Japanese then please to direct your attention to the Pacific Northwest's red cedar tree population. They're lovely aren't they? Yes, lovely and smart because the pattern of their growth rings show that the trees were killed by flooding caused by the earthquake. These rings were created in the last growing season of 1699, one year before the earthquake that definitely happened. May you never doubt the Japanese again, particularly when it comes to record-keeping and zany, humiliating TV game-shows.

 

The earthquake was magnitude 9, but this isn't the Richter scale magnitude; that would be too easy. This magnitude 9 is similar to the Richter scale and just slightly different. When Richter conceived of his scale he was short-sighted. It only works for medium-size quakes, so in 1979 a new scale was introduced called the Moment Magnitude andthis is the magnitude by which the Cascadia earthquake is known.

It doesn't matter how you measure earthquakes, whether it be with moment magnitude, Richter scale, or toppled goat count, this quake was a big one. An earthquake that has a moment magnitude of five is thirty times more powerful than an earthquake with a magnitude of four. A little bit of simple maths will tell you that a magnitude nine earthquake is one big, wholelotta toppled goats.

 

It is estimated that these major earthquakes occur about once every five hundred years. We can only hope that the Japanese will still be around to record them.