Hiking Lake Elsinore

Yesterday, as a means of combating the sloth and gluttony inherent in Thanksgiving weekend, some friends and I went on a nine mile hike in the Santa Ana Mountains, above Lake Elsinore. It was a trip intended just for walking and being outside, rather than a specifically geological venture, but I was still pretty psyched about getting to hike around in a fault zone with which I didn't have much up close experience. To my disappointment, the trail we selected was far enough up into the mountains that the fault trace itself wasn't actually visible, and all of the outcrops we encountered were between granite and granodiorite, with rounded weathering, and undeformed/unmetamorphosed. (I was not the only one slightly bummed - the only bugs we saw were termites, which was a disappointment to the entomologist on the hike, and the two plant biologists were not thrilled that most of the vegetation was invasive.) That said, it was still a wonderful hike. The weather was great, the scenery was gorgeous despite its lack of faults, and it just plain felt good to get out and walk without the purpose of going somewhere. I wish I could afford the time to go and do this more often in the middle of the quarter. Backlogged homework would kill me dead if I tried, though.

On the drive down from the trailhead, there were some fantastic views:
You can see three of southern California's most prominent peaks from here: from left to right, Mt. Baldy (highest in the San Gabriels), Mt. San Gorgonio (highest in the San Bernardinos), and Mt. San Jacinto (highest in the San Jacintos). You also get a great look at three major fault zones: the San Andreas runs at the foot of the San Bernardinos, from just to the right of Mt. Baldy off to the end of the page; the San Jacinto runs in front of its like-named mountain, branching off the San Andreas to the right of Mt. Baldy and continuing in the other direction toward the end of the image; the Elsinore is in the foreground, with one strand on either side of the lake. Lake Elsinore is, in fact, there to begin with because of this extensional stepover in the fault (and I miiight even look at the possible dynamics of that particular stepover in my thesis, maybe).

This panorama also illustrates a particularly heinous case of Houses On Faults. The houses directly on the banks of Lake Elsinore are smack dab on the fault trace, but the neighborhoods that sit between the base of the Santa Ana mountains and the lower string of hills directly opposite the lake are sandwiched in that extensional zone. That does not bode well for ground motion in and of itself, but it becomes an even sticker situation when you consider the soft lake sediment around there. I also wouldn't be surprised if the liquefaction hazard there is much higher than in pretty much the rest of the Inland Empire (though I'd have to look it up - I haven't done that yet). The houses we drove past also look pretty new, likely newer than the Alquist-Priolo act. I guess most of them fall within the fifty-feet-away clause, but really, what's fifty feet compared to the speed of P-waves? The Elsinore may not have one of the higher seismic hazards in California according to this spring's figures, and it may not be as well known of a fault, but it definitely does still move (last September's 4.7 was on the Elsinore), and I definitely wouldn't want to live on it.

I would, however, be more than glad to hike there again.

UC Riverside Shakes Out!

Thursday the 13th was the Great Southern California ShakeOut, a regionwide drill preparing for a magnitude 7.8 earthquake on the southern San Andreas Fault. I first heard about it - though before it was named - in an article in the local newspaper comemmorating the 150th anniversary of the 1857 quake. I guess it was obvious at the time that UCR would be involved; when I found out that we weren't planning anything, I was shocked and disappointed. My adviser and I were ashamed to not raise our hands at the SCEC conference when Lucy Jones asked whose institutions were participating, and it was then that we decided we really need to push for UCR to participate in the drill after all.

My adviser did an an amazing amount of work in a small amount of time, and all kinds of things fell into place. On 21 October, Dr. Lucy Jones of the USGS, local go-to seismologist on the news after any sort of quake, and one of the driving forces behind the science backing up the ShakeOut drill (not to mention someone with whom I have played chamber music), came to our campus and gave a speech discussing the science of the fault and the impact on life and infrastructure that such a quake would have. The talk was geared toward people who do not study earthquakes, and while the turnout was less than we hoped, those who did come asked some really good questions and seemed really effected by Jones' description of the rupture's progress and what it would mean for southern California. I've heard Jones talk about ShakeOut before (at SCEC) and have read some of the publications about it, but the simulation and its ramifications still make me personally shake a little each time I hear about them. Watching that animation of the rupture's progress makes my heart beat very fast, and hearing about the damage draws inevitable (and totally fair) comparisons with 1906, in terms of how much is different now, but how much would end up so close to the same.

On 4 November, Dr. Kim Olsen of San Diego State University came and spoke specifically to the Earth Sciences department about ShakeOut, and how several different types of models of the same rupture scenario had been run by several different institutions. The main ShakeOut drill is based on a kinematic model that makes for high shaking along the fault itself, as well as intense wave guide action focusing equally high shaking into Los Angeles itself. Olsen showed that this kinematic model need not be the gospel of what would happen on this hypothetical rupture pattern anyway; dynamic models of the same thing still show higher shaking in the same places as the kinematic models, but that the intensity of shaking is less all around. It still wouldn't be [i]good[/i], but it could make a difference. (After the talk, Olsen joined our department at the local pizza place/pub to watch election results pour in. Like with charts where red represents high shaking, we were all glad to see much less red than we feared on those election maps.)

In the process of planning for getting the entire campus in on the actual ShakeOut drill, we decided that some sort of earthquake awareness fair on campus would help people understand what they were getting under the desk for, and that there is a real and scientific basis for this whole event, rather than just nebulous fear of a hypothetical "Big One." We decided that the display should have a section on the ShakeOut model/scenario itself, coupled with further information on what one should do in a quake, a section discussing historical earthquakes in California or of magnitude/impact comparable to the ShakeOut Drill (we featured 1906, Wenchuan, Northridge, Chino Hills, Sumatra-Andaman, and the 1690, 1812, and 1857 San Andreas quakes), and a few posters and computer screens showing off the particular work being done in our department. We also slathered posters advertising the drill and fair all over campus - three rounds of posters over the course of the quarter, in fact. The last set said, "A magnitude 7.8 earthquake will hit southern California. We don't know when. Wouldn't you rather be ready sooner than later?" We figured scaring them a little bit would be more likely to get some attention in a place that seems pretty jaded or in denial about its seismicity.

The actual drill was on the 13th, as it was across the state. Our campus' response didn't involve elaborate emergency simulation complete with fake blood and guts, but every teacher holding a class at 10 AM was supposed to lead their students in a minute of Drop Cover And Hold On: a length of time that could be a minimum for shaking in this sort of earthquake. In the case of our department, it was the total opposite of any real earthquake - we stopped what we were doing with setup for the fair, went inside, and got under the table at the right time. I don't know how many other students actually paid attention to the publicity we had for this, and while I hope most of them knew, I kind of also hope some were genuinely surprised, as everyone really would be. I also have no idea how many teachers actually did the drill, but I'm hoping that it was most to all. There was a siren on campus that was supposed to aid in the "emergency" feel of this, but everything I've heard from people suggests that it just plain wasn't loud enough. Our department was the only one that did the actual evacuation as well, and that did go smoothly, though not without loud overacted remarks to be careful of all the rubble.

The fair ended up being a huge success. Many people stopped by to at least look at things, and many more asked questions. I didn't see how many people bought things from the emergency supply vendors we had come in, but they seemed pleased when it was all over as well. I was personally manning the booth about historical earthquakes, and I got a lot of good questions and stories - I met someone who had been in Anchorage in the massive (9.2) 1964 quake, and I met someone else whose grandmother had been in San Francisco in 1906. I also unintentionally scared the crap out of some recent east coast transplants by merely mentioning that the southernmost San Andreas has been paleoseismically shown to go about every 150 years, but hasn't popped since 1690ish. I guess I shouldn't be too surprised by that, even though I felt bad, since that little statistic scared the snot out of me when I first moved out here. We definitely opened the eyes of a few native Californians, though, which was so much of the goal.

At the end of the day, our whole department was feeling pretty awesome, but in the middle of our celebrating that success, I had to keep looking back toward the San Andreas, the real "star" of the show, so to speak. It was, of course, smooth and quiet at the base of the San Bernardino Mountains, something you probably wouldn't think of if you didn't know it was there (or, well, if you weren't an earth scientist). As the sun started going down, I couldn't help but imagine a dark surface rupture scar ripped along there, and that the usual SoCal smog was quake-induced smoke. That mental image was enough to make me want to thank the fault for not doing that yet, for waiting until after ShakeOut, for allowing people to explain to others what the Fault can do rather than showing everyone itself.