Saturday, October 3, 2009

The Keeler Earthquake Swarm




The U.S. Geological Survey (and my department seismometer) is reporting a vigorous swarm of small and moderate quakes about seven miles south of Keeler, California. The swarm has included two 5+ magnitude shocks, and at least 22 events between magnitude 3 and 5. Smaller events number in the hundreds.

Keeler is a small village along the former shoreline of Owens Lake at the south end of the Owens Valley. The pictures provide some context: the Owens Valley is the first of the Basin and Range Province grabens east of the Sierra Nevada, with the White/Inyo Mountains forming the east side. The top picture shows the Sierra crest, including the peaks in the vicinity of Mt. Whitney, the tallest mountain in the lower 48 states. The bouldery Alabama Hills and the town of Lone Pine are in the bottom of the valley, center-left, and the Inyo Mountains form the right-side skyline. With the valley floor at 4,000 feet and the surrounding mountains ranging up to 14,000 feet, the valley is twice as deep as the Grand Canyon. Although the Owens River flows through the valley (sort of), it is a faulted graben, not a river-cut valley.

The second photo (from the same vantage point on the Cottonwood Lakes road) shows Owens Lake, the south end of the Inyo Mountains, and the domes and craters of the Coso Mountains Volcanic Field on the right. Owens Lake is one of the pluvial ice age lakes that formed when glacial meltwater from Sierra glaciers drained into the desert. Unlike most of the dry lakes across the Basin and Range, Owens Lake actually had water until the 1920's. Los Angeles diverted the streams that flowed into the lake and sent the water south through a massive aqueduct to the growing city. Keeler was a depot for silver and lead being mined high in the Inyo Mountains at the Cerro Gordo Mine in the late 1800's. Ores were carried down to the town by aerial tramway, and then loaded on a steamship to cross the lake to railroad station.

The epicenters of the swarm would be in about the center of the second photo. Why are there quakes here? As noted before, the entire valley is a fault graben, so quakes are not at all unusual. One of California's largest historical earthquakes, the 1872 Lone Pine earthquake (mag. 7.8 or so) happened just north of here. Swarms have happened in the local region in the past, including some magnitude 5 events in the 1990's.

The Coso Volcanic Field lies just to the south. A collection of basalt flows and rhyolite domes, it was last active around 40,000 years ago, though a few cones may be younger.

UPDATE: not of the earthquake, but of the Coso Volcanic Field. It might be an actively forming metamorphic core complex! In 2 to 4 million years, the detachment surface may be exposed. I always enjoy learning something I didn't know before...

UPDATE #2: Loads of info on the quake swarm on the SCSN Pages here. The largest quakes are showing right lateral focal plane solutions, which is in keeping with the regional structural trends on the Owens Valley floor. This strongly suggests to me that the quakes are tectonic and not related to any kind of volcanic activity (but I'm not claiming expertise in the matter).

UPDATE #3: Reports of sand boils on the Owens Lakebed (see the comments) have been confirmed by the SCSN and USGS office in Pasadena (personal communications, no link).

UPDATE #4: See down in the comments for a correction on the history of Keeler from Roger Vargo, who is the sometimes caretaker at Cerro Gordo. Thanks for the correction, I was operating off the memory of a field trip from 25 years ago.

18 comments:

MarkL said...

Thanks for the Info. I have been watching this swarm on the usgs page for a couple of days. Nice to see some real details.

Lockwood said...

It's been many years since I've been up on that road; thanks for the reminder of how spectacular the view is. Have there been any reports of surface ruptures? I would think they would be easy to spot in the flat sediments.

Journeyin' Lady... said...

We've been in Lone Pine for the past week. It sure has been rockin' and rollin' for the past 2 days! Latest was at abour 4:25am. Even though I'm a Californian I didn't understand what a "swarm" was until this week!

~carol said...

Am wondering....

Is there a Geothermal plant near Keeler/Olancha?
(As by The Geysers & 'Cerro Prieto' geothermal fields, which are also swarming, big-time.)

...& if SO, might be more than a coincidence (?)

Everchanging said...

Thank you Mr Hayes for your research and answering a question that just did not seem right to me for a while and explaining these event (aka swarm earthquakes) within this area of California near Keeler. I had researched these quakes earlier this year with no clear answer and associated these earthquakes to mining and the old abandoned mines shafts in the area, until reading these post today.
I have also noticed these swarms quakes for some time as well in Puerto Rico, which is almost as common on a daily bases too.

andrew said...

Thanks for the photos from the area! The swarm looks to me like background seismicity related to the rotation/translation of the Sierra Nevada microplate. It would be nice if it were due to the dewatering of Owens Lake, but the lake wasn't very deep.

Garry Hayes said...

Thanks for all the comments! I haven't heard of any surface ruptures; the quakes may be too small to generate them. I remember the ones from the Landers quake: they were spectacular.

I am not aware of any geothermal plants in the area, but I would not be surprised if they were there. A large part of the Coso Range is on military lands and presumably closed to development.

~carol said...

I just had a (geology-buff type) revelation !!

With all the swarming by Keeler, the Salton Sea, and following the San Andreas fault south thru large quakes in upper Baja California grabens on down to the tip of the Gulf of California....

I NOW can see why southern CA actually Could end up as an Island!! (And, I'd laughed at the chicken littles who said that. Guess I won't be around long enough to have beachfront property, tho.)

Garry Hayes said...

Yes, California will be an island, after a few tens of thousands of magnitude 8 quakes once every century or two that move it northwest at an average rate of 2" per year! We'll be able to see it pretty clearly in about 20 million years!

~carol said...

oh....I didn't even consider the CA 'movement' part--
just visualized the Gulf of California'a seawater simply oozing upwards via the San Andreas fault line because of all the recent activity thereabouts. (Yes, I need Geology 101.) Thanks for response.

Anonymous said...

Yes, there is a geothermal plant just east of Coso Junction, and it is within the boundaries of China Lake Naval Weapons Center (or whatever name it goes by now).

Linda J said...

You have an interesting site, Gary. I'm glad I found it.

Technically the road you took the pictures from is named Horseshoe Meadows Road, although you're right, it leads up to the trail head for the Cottonwood Lakes region.

We live in Lone Pine and we've been enjoying the quakes. (Conversation in our house - "There goes another one - what do you think the magnitude was?" Then we keep refreshing the USGS pages until the earthquake appears.)

The next day after the first quake was Saturday, so that morning we headed out for the epicenter using GPS coordinates. While we had fun looking, we did not find any cracks in the sand, nor did we experience any aftershocks while we were out there.

My husband said there were reports of "sand volcanoes" very close to the Owens Lake shoreline in the area. Supposedly the shaking threw some sand in the air forming little piles. This info probably came from workers out on the lake itself.

Garry Hayes said...

Thanks for your comments, Linda. I should have remembered Horseshoe Meadows Road, I've been on it enough times! If there were sand volcanoes, that would be the result of saturated silt and sand beneath the surface being shaken loose ("liquefying") and rushing up to the surface in little gushers of sand and water. They were common in agricultural fields around Santa Cruz and Watsonville after the 1989 quake. I've wanted to live in a place like Lone Pine! The mountains are too far away in the Central Valley.

Linda J said...

Thanks for the information about the sand volcanoes. That's pretty cool. When we were out there, I was thinking about how all the loose fill and sand would liquify. I guess it really did.

My husband, Dana, lived in Santa Cruz in 1989 and experienced the Loma Prieta quake first hand. Not long after, I joined him. When we decided to move from the area, Dana insisted it be to a place that was geologically interesting. Lone Pine fit the bill!

Jim James said...

The folks at the Array Network Facility at UCSD have a great page for this swarm, with an interactive Google map of all the events: http://anf.ucsd.edu/spevents/2009/274/b/

These are the guys responsible for data collection from the USArray experiment. I think they make pages when a significant earthquake occurs.

Garry Hayes said...
This comment has been removed by the author.
Garry Hayes said...

A correction on my history note above from Roger Vargo:

Keeler was a depot, but not for silver and lead in the 1800's. It
wasn't even there during Cerro Gordo's bonanza period (c 1868-1876).
Keeler was the terminus of the Carson and Colorado railroad which was
completed in 1883. Cerro Gordo is pretty much ghosted by then. The
town was called Hawley at the time.

Keeler's depot for ore and the tramway came after the turn of the
century during Cerro Gordo's zinc period with L.D. Gordon in charge
(c 1911-1920).

During the bonanza period, most ore was not carried off the mountain.
Transportation was too expensive. The Owens Lake Silver and Lead Co.
did transport its ore down to Swansea for processing. Both at Swansea
and in Cerro Gordo, the ore was processed (concentrated) into
silver-lead dory bars weighing 83-85 pounds each and containing, at
best, about 20% silver. The Union mine produced about 120 of these
bars daily at its peak. These bars or "loaves" as they were called
were transported to LA by wagon. The Bessie Brady steamship was used
after about 1872 to transport the loaves across the lake to Cartago,
then back on to wagons. This saved about four days of travel.

The railroad "across the lake" was the Southern Pacific standard
gauge line from Mojave, but it wasn't built until 1910 for the aqueduct.

The freight wagons went to LA, then (initially) to the harbor at San
Pedro. Later, the LA-San Pedro RR was completed, and the wagons
unloaded in LA. The loaves were transported by steamship (frequently
the Orizaba) to the Selby Smelter in San Francisco (and sometimes to
Wales in the UK) for refining. The recovery of lead paid for the
transportation and smelting costs, and the silver recovered was pure profit.

While it's too late in the season now, if you're interested we could
talk about a late spring field trip to Cerro Grodo for your students.

Regards,

Roger Vargo
(occasional Cerro Gordo caretaker)
and wrangler of assorted facts

Explore Historic California!
www.explorehistoricalif.com
www.trips.explorehistoricalif.com

Anonymous said...

They're baaack! 4.5 on 5/3/11 with continuing aftershocks in the same spot the 2009 swarm happened. Shallow.