"Powerful" Earthquake?

So Fox News is reporting that a "powerful earthquake" struck Anchorage on Thursday morning, but no damage or injuries were reported.

This leaves us scratching our collective head ... powerful?  It was only a 5.2; we have stronger 'quakes than that all the time.And if no damage or injuries resulted, then what are we? The luckiest people on earth? The city with the best earthquake code built into the building requirements?

Both.

But the fact is that a 5.2 shake isn't da bomb, unless the epicenter is under your feet. We've had a couple of 4.2 and 4.3 'quakes within a few miles of town, and we'd have sworn they were much stronger. This one was 50 miles away, and 35 miles down. That's quite a distance.

So what led to the description of a "powerful" quake?

It hit with a sharp jolt, you see ... not all of them do. Earthquakes generate two types of tectonic movement: S-waves and P-waves.  The S-wave is just what you'd expect - a series of rolling waves.

A P-wave hits with a sharp jolt and then a diminishing shudder, and is frequently accompanied by S-waves, as well.

Some of the closer epicenters have hit with an audible bang as the underlying rock strata slide against and across each other. It's a little spooky, actually, to hear it a second before you feel it. Not a rumble, but a very loud boom that makes you wonder what just blew up.

Sometimes the jolt from a P-wave is vertical, and sometimes side-to-side. One such 'quake hit near downtown, several years ago, and all the equipment on my desk - computer and all - jumped an inch-and-a-half off the top, and then landed again as the side-to-side shaking began. That one was a little scary. It was a 4-point-something, but only 7 miles north of town.

So yesterday's tremor was a sharp side-to-side motion, followed by several seconds of shuddering (the earth, I mean - although some people may have been doing shuddering of their own).

So, as in most of what passes for "news", don't believe everything you hear. It might better be acknowledged as a starting point for your own investigation into the event(s).

Just another tip from your friendly neighborhood preacher, coming to you from Alaska: a place that gets more earthquakes every day than the rest of the country combined.


You're now free to move about the cabin. That is all.