Taking a tour of California’s biggest mover and shaker.
The exhibit area includes antique seismometers…
…historic artifacts about local earthquakes…
…and other devices that were once used in the field of seismic research.
A segment from the Pallett Creek trench, the first place where scientists realized that they could trace and date ancient earthquakes in an effort to predict future quakes.
After the exhibit, Stan Schwarz, the system administrator for USGS’s earthquake detection system who built and currently runs their Earthquake Notification System, took us upstairs to see the lab. You would think a Seismological Laboratory would be located in a single story building, right? While I’m not sure if any retrofitting was ever done to the 1974 building, I do know that it is equipped with outdoor power feeds to accommodate news trucks for LIVE broadcasts, often of interviews about earthquakes with Caltech and USGS personnel
The hallways on the second floor are lined with numerous earthquake related maps, some highlighting the age of our seafloors…
…others measuring the distance and amount of shaking that was felt during the Northridge quake…
…and one showing California’s scary earthquake history.
The Seismological Laboratory is the working environment of the people who study earthquakes.
Following any major earthquake, it’s the scientists from this lab that you see being interviewed on TV. Established in 1921, the lab is where scientists investigate, research and inform the public about earthquakes that occur in Southern California and beyond. BTW – A moving stylus on a roll of paper is a thing of the past in the earthquake monitoring business. All earthquake events are now recorded digitally.
The 1971 San Fernando earthquake (also referred to as the Sylmar quake) still ranks among the worst earthquakes in California history. The best place to still see proof of it is along the Sylmar segment.
Taking the Hubbard exit off the I-210 and driving about a mile southwest, you’ll arrive at a McDonald’s [1955 Glenoaks Blvd, San Fernando, CA) where you can still see a 6 foot surface break that ruptured during the Sylmar quake. It appears that the restaurant and parking lot were built after the earthquake, and that the owners decided to landscape the scarp rather than smooth it out (or have a pesky bump in their parking lot). Would you like a burger with that shake?
Once you know where to look, the San Andreas is easy to spot. There’s a pullout on the northbound Hwy. 14 (Lamont Odett overlook) where you can park safely and stand above the valley of the San Andreas and visually follow it across the landscape.
Immediately in front of you is a former sag pond (natural bodies of water accumulating along fault zones as water percolates up the fault barrier), which has been dammed to form Lake Palmdale. Then you look to your east and see the big notch on the north flank of the San Gabriel Mountains where the fault cuts through, and the town of Wrightwood is located. During the 1857 Fort Tejon earthquake, the entire Pacific Plate (southern) side of the San Andreas fault jumped about 30 feet to the northwest in a matter of seconds. Since then, that stretch of the San Andreas (from about Taft down to Palm Springs) has been locked for over 158 years. Seismologists expect that when this part of the locked San Andreas finally moves, it will again jump 20-30 feet, all the roads and structures that cross it will be offset by at least that much (including almost all the roads out of LA, including I-5, I-15, and Hwy. 14), and the damage to Palmdale and the other towns near the fault will be catastrophic.
Heading further up Hwy 14 near Ave S, we arrive at our next stop, which required a short hike. On top of a roadcut above Hwy 14…
…the fault is rather obvious.
A view of the Pliocene Anaverde Formation (an old sag pond deposit formed only 2 million years ago) all crumpled and folded like a huge collapsed carpet by the pressure of the fault zone just to the south.
Viewing the San Andreas during the first half of the day was sweet but all that traveling on a hot fall day kind of required a little refueling, so we stopped at Charlie Brown Farms.
I mean we really stopped, which forced everyone to make an early exit in order to reduce the vehicles weight and remove it from the parking lot driveway.
After everyone tinkled…
…a little shopping & food was in order.
Unfortunately they didn’t have my size.
Like any good roadside attraction, this place made absolutely no sense…
…had a mini faux ghost town…
…and kept animals [farm not exotic] out in the scorching hot sun for visitors to harass and molest.
Approx. 8 miles from Charlie Brown Farms is the famous San Andreas Fault sign which can found along Pallett Creek Rd. between the towns of Juniper Valley and Valyermo.
This is one of only two areas where you’ll find a road sign along its 800 mile length. The other sign can be found in Parkfield, CA near the Parkfield bridge, which runs over the San Andreas fault and separates the North American Plate from the Pacific Plate.
Cracks in the road are gonna happen along a faultline whether you like it or not.
Mention the word “Pallett Creek” to any geologist or geophysicist in the region, and they immediately recognize it, because it is the Mecca of Paleoseismology—the first place where scientists realized that they could trace and date ancient earthquakes in an effort to predict future quakes.
At Pallett Creek, there are sag pond deposits that have covered the San Andreas fault for over 2000 years, now uplifted into a terrace as the creek cuts down.
In the late 1970s, Stanford Ph.D. student (and now Caltech professor) Kerry Sieh had the bright idea of using backhoes to dig big trenches through these old pond deposits. Once the walls of the trenches are exposed, you can carefully photograph and map the layers going across.
There are many exposures that show ancient faults that cut some of the lower, older layers, but are then buried by the upper layers. Thus, you can constrain the age of that particular fault by the youngest layer it cuts, and the oldest one that is not cut.
All that is needed is dates on the layers, and these are provided by the fragments of charcoal or actual peat layers (when the pond was swampy), which are datable by radiocarbon.
Once Sieh got his radiocarbon dates back from the lab, he was able to bracket the age of over 20 prehistoric earthquakes in the past 2000 years. Originally, he got an age estimate of 137 ± 8 years between quakes on this branch of the San Andreas, then later published a revised estimate of 145 ± 8 years. Recent redating using new radiocarbon methods gives an estimate of 135 years. Either way, the fault has not moved in 158 years, outside the error limits of the current dating of past quakes.
No wonder seismologists are so worried about this part of the San Andreas that is way overdue to break, a “seismic gap” in their parlance.
Our next stop was in Angeles National Forest, near Big Pine, CA…
…where harsh mountain weather [and earthquake faults] often erode the hillsides in strange ways.
Fortunately we had Seismo Sue…
…aka USGS geophysicist Sue Hough to explain what’s really going on here and what’s really going on is called a sandy fault gouge.
Rock that has been ground to a fine powder or clay along faults is known as “fault gouge”.
These zones of fault gouge can be as wide as 25 feet or as narrow as one inch.
With continued movement…
…can be turned into clay as evidenced in many places along the San Andreas Fault Zone.
The Mystery of Lost Lake in the Cajon Pass – Web exerpt:
“I was there swimming not to long ago and saw a man catch a fish that looked like a bass but the eyes were huge and almost popping out! He was gonna take it home to find out what it was but released it fearing it might die and it turn out to be a pre historic fish. I just believe that its a bass that was way deep down under and its eyes popped out as it was surfaced. But what has my attention is the rumors of lost lake having no bottom! Any info?
Anonymous (not verified) on Mon, 09/06/2010 – 9:32pm.
THATZ TRUE LOST LAKE HAVE NO BOTTOM THEY CHECK ALREADY”
Lost Lake is a sag pond along the fault trace, which is fed by springs (groundwater is often forced to the surface along fault lines). The “bottomless” rumor came along when the association of the lake with the fault became locally known… a line of thinking that might go… “faults go to the center of the earth, or something like that, so a lake on the fault won’t have a bottom either”. Of course one can see the bottom of the lake via GoogleEarth and a crime report I found noted that divers looking for a body recently, mentioned that the the lake was barely 20 feet deep. The lake has been a trash heap and hangout for undesirable people over the years, but the Forest Service has recently been trying to improve the situation or so it seems.
The water was chilly but not icy cold, and although the lake has not been stocked with fish for many years, people still try their luck and toss a line in. When I asked the family that was fishing if they have had any luck, they claimed to have caught one very small fish. I guess it’s still a mystery.
Anyone can tour California’s biggest fault, there’s tons of information online but the best source I found is all contained within this handy guide, “Field Guide to the San Andreas Fault” by David K. Lynch. Seismo Sue has also written three books on the subject: “Finding Fault in California”, “Predicting the Unpredictable” and “Richter’s Scale” which includes the following juicy information: “Richter was an avid nudist, a frustrated but prolific poet, a Trekkie, a devoted backpacker profiled in the pages of Field and Stream, and a philandering spouse who was quite possibly in love with his sister and whose globe-trotting wife may have been a lesbian.” Don’t blame me if you don’t like it, it’s not my FAULT.