Earthquakes can happen anytime, anywhere, and currently no matter how magnificent our technology, they are still beyond our control. Why? Let’s learn a bit about geophysics.
The entire surface of our planet is covered with giant puzzle-piece shaped plates, most of which are bigger than any continent. They are all afloat on a thick, viscous sea of molten rock that lies approximately 100 km (60 miles) beneath them. The North American Plate and the European Plate are currently moving away from each other at the prodigious rate of one sport field (soccer pitch/football field) every 4,000 years. Maybe that explains why airfares keep going up… That extra 2.5 cm (1”) every year adds up over time…
Nevertheless, these plates are all jostling about. Some are moving away from each other, allowing the land between them to sink and form valleys, or even opening space between them, so that lava can come up and form new land.
In some cases one plate rides up on top of another plate, forcing the other one down into the molten rock below where it melts. This is called subduction, and an interesting theory holds that some of our petrochemical reserves are created at this juncture. This is a place of very intense heat, pressure, and chemical reactions. If so, speculation holds that we may have a great deal of non-fossil fuel left to exploit.
Still others are moving towards each other, crushing together and raising new mountains. In other cases they run parallel to each other, but in opposite directions. All these motions release a lot of energy, but only a little bit at a time. The problem arises when two of the plates lock together and a lot of kinetic potential energy is built up.
Eventually friction is overcome and the land gives way suddenly, often catastrophically. While a few inches per year may not seem like much, when things are NOT moving for years or decades, the plates end up accumulating a massive amount of energy. Suppose that the piece of ground beneath you suddenly decided to move left, by less than the length of a car.
Even if there were no cracks in the ground (that might be miles away), you would be knocked off your feet. Anything fixed to the ground would have to bear the stress of the sudden shift. Everything in your immediate environment would appear to move to the right by the same distance. People, cars, houses would literally have the ground pulled out from under them.
For all those people who think that they’re immune from earthquakes because they don’t live in an earthquake zone, nature as little surprise for you. The somewhat rare Intraplate Earthquake can occur anywhere, no matter how remote from the edge of a tectonic plate. These catch people by surprise because they are completely unpredictable.
We’ve all seen those painful-to-watch videos of kids on skateboards sliding down the handrails of staircases (“grinding”). Sometimes the board breaks, and they end up landing astride the handrail, resulting in a very painful injury, particularly for boys. Despite the fact that you’re wincing right now as you contemplate it, it makes a very good analogy to explain intraplate earthquakes.
Even a tectonic plate has a breaking-point, and uneven pressure from different directions can cause splintering and fractures in the middle of them. It can take the form of a V-shaped trench, or one portion rising above another portion (or one side dropping away from the other).
Tectonic plates don’t shatter nearly as dramatically as that skateboard, but even little cracks, on our relatively tiny human scale, create large seismic waves. And they are sufficient to damage levees, compromise dikes, down power lines, and destroy homes. And quite often they propagate over a fairly large area, compared to the reasonably localised events that we hear about in the news.
Large earthquakes are reasonably rare. Seismologists record dozens of little quakes and tremblors of level 2 or 3 on the Richter scale that most people cannot even feel. They are so common that they are not even considered worthy of a line or two in the local newspaper, or a jocular remark by a radio personality.
The Richter scale measures how much energy is released during an earthquake, and is useful for comparing one earthquake to another. There are other methodologies for making that measurement, incorporating amplitude of the shockwave, distance from the measuring device, and the duration, but they were all designed to be consistent with the Richter scale, which was the first, invented in 1934.
The Richter scale experiences some limitations since it was designed for use in California. Larger earthquakes, especially in different geologic conditions, offered challenges to the form of measurement so the Moment Magnitude (MW) scale was created. It works over a much larger range of measurement.
A 4.3 event can actually be felt. People tend to expect to hear something about it and receive assurances that everything is all right. Those people, who experience earthquakes fairly frequently, take a quick look at their earthquake supplies. They make sure everything is as it should be, and carry on with their lives.
In those locations well removed from known or familiar earthquake zones, people just go on smugly believing that they are perfectly safe. These are the people we need to reach; to convince that there is a possibility; to emphasize that even the most basic preparation is better than nothing.
Compared to earthquakes, global warming is inconsequential. Climate change might, decades or centuries from now, change the way we live on Earth. A single Earthquake could destroy your property, shatter your hopes and dreams, or kill you, or your family members, in a matter of seconds. Isn’t that worth at least one day out of your weekend to assemble an earthquake kit?