Thursday, January 8, 2009

4.5 in the Inland Empire

There was a magnitude 4.5 earthquake in San Bernardino tonight, with a depth of 8 miles and a fault plane solution that suggests strike-slip, but not the San Jacinto or the San Andreas.

I would have liked to have live-blogged this from the epicentral region, but my iPod didn't want to pick up the coffeeshop's internet, so I had to drive home. But when I say "epicentral region," I mean it. I was about four and a half miles from the epicenter when the quake it. I've been closer to them before, but those were all much smaller - as in, 2.6. 4.5 was a whole different kind of experience this close.

I was at a coffeeshop in Redlands with some friends; we were all sitting at a table outside. I felt a little wiggle, and apparently so did a few of the others, since someone said, "Hey, is that an earthquake?" There was time for some confused looks before the shaking got stronger, and the general response was, "Oh yeah, earthquake!" It then proceeded to get even stronger for a little bit, before fading. I'd say that, on the whole, it could have been up to fifteen seconds of shaking. The thing that really excited me, though, was feeling three wave arrivals. I know I felt S and Surface for Chino Hills in July, but I wouldn't have felt P in a car with good shocks. Sitting outside, though, there's no such damping. There were definitely three different jolts, each stronger than the last. This one was a really good ride, and it made my day.

I'm also really curious to see how well QCN did in terms of picking this one up, since many more people are running the software than there were for Chino Hills. I know that my laptop picked up a good waveform for that one, and I'm hoping it did for this one as well, since the computer was by itself and not being used at the time of the quake. There isn't a way for me to scroll back that far through my computer's own records to see if I picked it up, so I'm guessing I won't know until tomorrow, at least, providing that those of us who picked up the signal get an email about it, like last time. I'll post on here about it if I do find out.

There was also a magnitude 3.3 aftershock about an hour after the mainshock, but I didn't feel it because I was in the car. I think I was actually going over the dreaded 10-215 interchange (which goes directly over the San Jacinto Fault) at the time, so it's really good that I didn't feel it. I admit that, every time I go over that interchange, I think, "Not now, San Jacinto, not now!" Feeling a shake on that overpass would probably break my brain.


Kim said...

Would it be ridiculously geeky to say that that's the perfect magnitude to experience? Big enough to feel what's going on, small enough that nobody gets hurt and you don't have to feel guilty about the thrill?

MJC Rocks said...

My daughter (28 years old) was in Colton, practically on top of it. I was so proud, she said she jumped under a desk the way she was supposed to!