Saturday, January 17, 2009

Northridge At Fifteen

I don't actually remember Northridge. I was nine years old at the time, but I also happened to be living just outside of Washington DC at the time. January of 1994 was memorable, but mostly because it was single digit temperatures, the furnace broke in our house, and so much ice fell out of the sky that my friends and I literally ice skated on the front lawn on Super Bowl Sunday. I'm sure I did hear about the earthquake in Los Angeles at some point, but I don't actually remember it.

It seems like there isn't a whole lot of remembering going on in the media today, either. The LA Times website has a photo gallery, but it's not a top-story link, and it wasn't in the print edition. They did run a short story about building codes, specifically about how soft first story buildings are bad, but the article was rather impersonal to my mind. Cal State Northridge's website mentions nothing. Papers more local to me (which are, admittedly, not super close to Northridge) mention nothing. This strikes me as weird, because I know so many people who have Northridge stories. Granted, they don't just volunteer them; the stories tend to come out when I mention the quake specifically (as I often do, as an example of why blind thrust faults are very scary), or when I mention that I've never personally felt ground motion strong enough to scare me. Once the topic is breached, they seem glad to tell me where they were, exactly what they were doing, how it all felt. Their stories are generally quite detailed, particularly considering most of my friends were also pretty little at the time.

And yet, despite the details, it takes pulling to get those stories out. I'm wondering if that comes from the larger culture of the region, the whole image Southern California as sun-drenched carefree paradise and home to the stars. What could possibly go wrong here? We don't have wildfires! We don't have earthquakes! Because if we let anyone know that we do, nobody will come here anymore. For these reasons, I really shouldn't have been surprised that media coverage of the anniversary has been unimpressive. The annual ceremony at Lotta's Fountain this most certainly is not.

I think the stories need to stay out there. They should be collected and available. They shouldn't be allowed to leave the public consciousness. Sure, they may reside in the minds of people who were here, but to everyone who has moved out here in the past fifteen years, what about them? As a relative newcomer to the West Coast myself, I wouldn't have heard the personal details unless, as I said, I started the conversation about them. The information needs to be out there, not to scare people, but to keep them informed and safer. Stories about, say, 1906 might be ample and fascinating, but that's a different city and a different age and a much bigger earthquake. The Los Angeles of 1994 was not that drastically different from now, and Northridge therefore shows the effect of a quake on a modern city. Not to mention that it shows that you don't need The Big One in order to still be Big Enough. How can anyone prepare if they're only hearing the scientific side of what we're in for, rather than the personal side as well?

Last week, after the 4.5, the LA Times ran a short article about how 2008 had more moderate-sized quakes than 2007, and how it was the most seismically active year since 1999 (which included the 7.1 Hector Mine quake and its aftershock sequence). My immediate wonder was if this means that any stress shadows left behind by Landers, Hector Mine, and Northridge are starting to dissipate. It is, of course, far too early to say if this will be a continuing trend, and no seismologist who cares about his or her reputation is going to use those figures to predict anything. But let's say, for argument's sake, that seismicity continues to be higher in the next few years. Shouldn't we be trying to pull people's awareness out of that post-Northridge stress shadow as well?

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.