(Here's an updated science blog on the Hayward Fault from
KQED's Andrew Alden).
There's been news of lots of not-so-little earthquakes lately. Three mid-sized 'quakes (and a few mini shakes) on the
Hayward Fault (
San Andreas Fault's daughter-sister-cousin) in Berkeley—a fault that hasn't ruptured since
1868, and it has an eons-long distinguished track record of rupturing every 140 years. Not quite on the dot. But pretty close.
We're sort of overdue for another Big One on the Hayward Fault. Not that one can actually predict earthquakes. Not even the scientists. Earthquakes are notoriously wily. You'd have better luck at the Las Vegas gaming tables.
Living between two faultlines, I know lots of little earthquakes are always good. (No, not Tori Amos' album.) They're like little earthgasms. They relieve the stress of transcontinental
strike-slip faults where the
Pacific tectonic plate is crawling two inches a year north atop the subducting westward travelin' gung-ho!
North American plate. It's a slow fender-bender love affair measured over eons of time—or in 140-year-increments, as in the Hayward Fault's case.
The latest Hayward Fault earthquakes are centered smack dab between the Greek Theater and the Cal Memorial Stadium which happens to be p
erched directly on top of the fault. Yep. In the GoogleEarth screenshot (below) you can see how the Hayward Fault literally strings "
goal post to goal post." On the UC Berkeley campus you can
trace the faultline by the displacement of city curbs and stadium walls. Piedmont, and Hayward too—if you know where to look.
(NB: 2 more little 'quakes near Piedmont on Nov 5th—I guess it was feeling left out.—must be in celebration of Guy Fawkes Day! Piedmont-epicentered earthquakes are a regular occurrence—the Berkeley-epicentered ones are not. Check out the displacement on the firehouse steps nest time you're in Piedmont.)
A few months ago, there was a lot of activity on the Hayward Fault beneath the Oakland Zoo which drove the lions and elephants crazy. I don't know what was roaring louder, the earth or the lions (or the San Franciscans—who felt it too).
And before that, Fremont and Alum Rock (south of the Oakland Zoo) were rattling and rolling—so clearly the tectonic stress is translating north. But there's been no major movement on the Hayward Fault for 143 years, and significantly, north of Berkeley—171 years. So you can surmise we're getting a little squirrely about those 'quakes stacking up on the Hayward Fault these days. It's not a case of if, but when.
The trouble is, living between two major faultlines is that The Big One could strike from either fault—or worse—both at the same time!
We were just reminiscing where we all were when the last Big One (
Loma Prieta) struck on the San Andreas Fault. The magnitude 6.9M or 7.1M 'quake (depending upon who you talk to) struck on October 17th at 5:04 PM—during rush hour and the historic Oakland A's vs the SF Giants World Series game in 1989. Bases were really loaded and down for the count.
I was in Forestville and, like the critters, I felt the 'quake coming long before it struck—I was being interviewed by Susan Schwartz for a feature article in the Press Democrat. In the middle of the interview, I was suddenly nauseous like I've never been before, and exceedingly tired with a horrible stomach ache. I put my head on the table and wanted to croak. It was as if I was suddenly dead drunk or hung over. Or both.
I, who was so thrilled to finally be interviewed for all my hard work (and awards) in the local and national poetry scene—long overdue—suddenly couldn't wait for Susan to leave. I practically pushed her out the door so I could lay down.
My bloated stomach hurt so much, I took off my jeans and flopped down on the bed. Some relief, but then I thought the cats were fighting in the basement—only I didn't have a basement. Or any cats. Then the mirror moved, the knotty pineboard wall groaned and rippled like a slinky, surely I was hallucinating. WTF? The squirrels were shaking the oak limbs so hard, it was raining acorns everywhere—including my thin roof like a drum staccato.
Then it hit me: 'Quake! Oops. Big one. I ran out into the driveway in my knickers & T-shirt and it was the longest 15 seconds of my life. It could be that in the hinterlands, the 'quake lasted a lot longer. But that 7.1M temblor was like trying to surf on a rolling barrel or stand on a bucking horse for 15 seconds. Your knees were trying to make contact with your jaw and everything else in between. The earth growled and there were myriad distant explosions—like small bombs or propane tanks blowing up.
We turned on the news and watched an image of fallen upper tier on the Bay Bridge—cars like little toys. People in them. No longer alive. Then we were cut off from all news for several hours. No TV or radio signal, no phone either. Complete isolation blackout—only the emergency broadcasting handshake noise. Only this wasn't a test. And there we were, safe in the hinterlands, imagining what it was like in the Bay Area.
We didn't yet know about the collapse of the Cypress Freeway in Oakland, or all the houses in the San Francisco
Marina district on fire. Needless to say, my interview was bumped because of the earthquake. We got the news in increments.
I digress in all this in gory detail, because when the Hayward Fault goes, it doesn't take much imagination to surmise that it will be much, much worse than the Loma Prieta earthquake. All the East Bay freeways and hospitals, emergency rescue and water storage facilities are perilously close to, or directly atop of the faultline. Oakland Airport is built on manmade alluvium.
And we witnessed the how the
Marina sand and mud shook and liquified into quicksand in San Francisco. All major Bay Area roads and freeways will be damaged and/or blocked, there will be no water to fight the fires—save Lake Merritt and the bay itself.
Image of the collapsed Cypress Viaduct.
The Loma Prieta epicenter was not even in San Francisco, it was much farther south, some 60 miles from San Francisco in the Santa Cruz mountains—northeast of Aptos. And we were another 60+ miles north of San Francisco. More than 120 miles from the epicenter, we were all
resoundingly shaken. Whether the Loma Prieta 'quake was 6.9M or 7.1M—the force was stupendous.
Loma Prieta was the largest earthquake to strike the Bay Area since San Francisco's famous
1906 Great Earthquake. The epicenter for the April 18 San Francisco earthquake, estimated between a 7.9M to an 8.2M on the
Richter Scale, was two miles offshore at Mussel Rock, near the Cliff House. The 1906 earthquake was felt from Oregon to LA to central Nevada. Santa Rosa (some view the
Rogers Creek Fault as an extension of the Hayward Fault)—was completely flattened.
Towns close to the Loma Prieta epicenter also fared badly. The 'quake flattened downtown Santa Cruz—10 miles away. Ditto Watsonville and Hollister. Loma Prieta killed 63 people total, injured 3757 more, squashed a whole lot of cars, shook houses off their foundations and left some 12,000 either or homeless or with extensive damage to their abodes.
Oakland racked up the most deaths at 42, because of the collapse of the freeways. And we still haven't replaced the Bay Bridge 22 years later.
Caltrans is still working on it. It should be ready in time for the next 'quake.
Some say the Hayward Fault will rupture in Berkeley—this is all a rather moot point—as the entire Bay Area will be the epicenter. To up the ante, the northern portion of the Hayward fault hasn't moved or ruptured since the 1700s. That makes it about 171 years overdue.
Check out KQED QUEST'S Geological Outings Around the Bay: Point Pinole and the Hayward fault by Andrew Alden. And the USGS GoogleEarth Virtual tour of the Hayward Fault is pretty cool.
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| GoogleEarth virtual tour of Hayward Fault. Hwy 580 & Hwy 13 north are on the faults. |
Much of the East Bay infrastructure where most residents live and work is on the flatlands. Alluvium and liquefaction—not a good combination. Imagine large resonant vibration waves converging at conflicting oscillations that will damage whatever the 'quake doesn't directly shake down. The Bay Area will be like one vast tuning fork, or glockenspiel. Increasing the damage potential by a factor of ten doesn't even begin to cover it.
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| Red is most susceptible to liquefaction, then orange, yellow... USGS map. |
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| Screenshot from GoogleEarth USGS virtual tour of Hayward Fault |
The East Bay is one vast sprawling metropolis that cradles major cities: Richmond, El Cerrito, Berkeley, Oakland, San Leandro, Hayward, Fremont, and San Jose. Yep, Silicon Valley too—where the Hayward Fault merges with the Calaveras Fault. In fact, it may be one large sister-fault system. (Sugar skulls—calaveras—anyone? El Día de los Muertos is on the horizon of when, not if. And the Lawrence Livermore Lab is located where? Shades of Fukushima!)
The latest Hayward Fault 'quake (3.6M) woke me at 5:30 AM—it was like a horse getting up and shaking dust from its coat after a good roll in the hot sand. But there were no aftershocks. So far, so good. Cozy shaking. Nowhere near as strong as the earlier 4.0M. My Ansel Adams photo of the San Francisco Bay, sans bridges—is at a rakish angle, as are all the other frames on the wall. I get tired of straightening them.
And
I haven't even mentioned those minute magnitudes of measurement we're
so fond of quoting: a magnitude 5.0M earthquake is not just a little
bigger than a 4.0M 'quake—it's ten times bigger! Geology teacher and blogger Garry Hayes @geotripper
explains: "Recurrence intervals are very tricky, and magnitudes differ
10x amplitude of waves, but 30x the energy release." I understand the Richter Scale is a base-10 logarithmic measurement. OK. Think exponential. But the 32x energy thing? Surface waves and body waves?
Yiiii! Math/physics were never my strong suit. I'm still trying to wrap my mind around that one.
Poetic justice that Charles Richter's Richter Scale inspiration
was the language of measuring the magnitude scale used to describe the
brightness of stars and celestial events themselves.
In his Geotripper blog,
Garry advises: be "prepared at ALL times (extra water, food, radio,
flashlight, batteries, first aid kit), especially in California and the
Bay Area along the San Andreas and Hayward faults." I have EQ kits,
stoves/heating coils and food in both cars too—plus a few bottles of
vintage Russian River wine. Keys, cell, cash, wallet always always
within reach. I even have a fashionista plan. Someone once said: "in
case of an earthquake or disaster, grab all your dirty clothes—they're
the ones you wear the most and will be most useful." (Knickers not
included.)
I
often check the 'quake map alerts on Twitter. Lately I've been watching
the global 'quakes and there are many, many 'quakes that clock in at 4.0M
or or so—daily. Nothing to worry about. Many tremors in Japan and
Turkey. That's to be expected. Peru's been taking a bit of a shaking.
Haiti's still experiencing large aftershocks as well.
Chile
moved its coastline last year, growing the Andes with the big one at
magnitude 8.8—the sixth largest earthquake to ever be recorded on a seismograph.
Then, the released tectonic stress must also translate right up the
coast. Eventually to our back door. Tremors were recorded from Buenos
Aires, Argentina to Ica, Peru, 2400 km north. The epicenter was about 2
miles off the coast where the Nazca and the South American tectonic
plates converge and collide and subduct—at about three inches a year.
Today: magnitude 6.9M earthquake strikes Ica in southern Peru. Right where the offshore fault comes closest to Peru. Ica, 300 miles south of Lima, is the part of Peru that juts out the most westward (like Pt. Arena in California) and it is closest to the offshore fault.
Pisco (and the desert plains of
Paracas as well as Nazca to the south) is no stranger to The Big Temblors: there was an 8.0 in 2007 that flattened the town.
The
only reason why I seriously digress and focus on Peru's earthquakes
(there are so many major cataclysms to choose from) is proximity. I've
been there. And
it crossed my mind that in a rather farfetched sense, they are a
continuum of sister faults linked to our own infamous San Andreas Fault.
I've traveled most the length of the San Andreas Fault—from Baja to
Point Arena. I once snorkeled too far out off Cabo San Lucas, over the
rift, and the shore dropped off so deep, that it was like looking back
up into the evening sky replete with stars.
And in the skimpy midriff section of the San Andreas Fault, the Salton Sea-Laguna de Salida (I once swam there too before it dried up) Méxicali region has certainly had more than its fair share of temblors. Last year's 7.2M Baja Easter 'quake was so significant—it shook eons of dust off the nearby mountains of La Rumorosa, Tecate, like a large dog (followed by 500+ aftershocks). No rumor, the San Andreas Fault is definitely in the commute lane in SoCal. Talk about road rage!
Any 'quake clocking in at over a magnitude of 4.0M, I take notice. I remember the Good Friday Alaska 9.2 earthquake of 1964.
I was a child in West Marin and the wall up and bitchslapped me on the
back of my head while I was sitting on the couch coloring. The couch
then skittered across the floor like a nervous deer on pavement.
The offshore
1980 Gorda Basin 7.2M earthquake near Eureka, shook Sea View Ridge, near
Cazadero, so hard, I was nearly tossed from the top bunkbed. Only the
rail saved me from a fall. We could hear the surf crashing nearly 2000
feet below us. The 30-foot waves pummeling Salt Point cliffs were
straight out of Hokusai. I saw the sea roil up those 30-50-foot
cliffs—then spray another 30 feet over our heads on the bluffs. Nothing
calm about the Pacific.
In retrospect, it may have been the aftermath of
a tsunami. And that was a 7.2M (or 7.3M)—with the epicenter far away, I might add.
Plate boundary earthquakes are common along California's most seismically active earthquake region, because of the
Mendocino Triple Junction. (which included the
Pacific,
Gorda, and
North American Plates.) In 1992 there was another
7.2M earthquake at Cape Mendocino, the Lost Coast, near Petrrolia. The Mendocino Triple Junction includes the
Cascadia subduction zone, the
San Andreas Fault, and the
Mendocino Fracture Zone. And yes, a tsunami also followed that 'quake.
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| "Behind the Great Wave at Kanagawa" 1823-29 Hokusai, Wikipedia Commons. |
I was in LA after the 6.6M Northridge 'quake in 1994—it was like a war-zone. All the overpasses flattened. The ground shook like jelly for days and nights—5.0M aftershocks both woke us and rocked us to sleep.
And I can't even begin to process the damage of the
Tōhoku 9.0M earthquake and tsunami— in size, scope,
damage—and the damaged Fukushima reactors. Part of me is still stunned by the news. I was hiking in The Valley of Fire looking up at the thunderclouds, admiring striations of time in geologic scale, knowing there was radiation fallout being recorded in the Las Vegas desert. The geoglyphs took on a new level of meaning. Old and new. The Easter wind whistled through the sandstone like an ocariña dirge. But I digress.
Both the diminutive Caribbean (remember Haiti?) and the Cocos plates join the Pacific plate in Central America. The Cocos plate subducts beneath the Caribbean plate creating all those lovely volcanoes from México to Costa Rica. It gets complicated with the young offshore upstart, the Nazca plate, subducting and squeezing into another torrid geologic love triangle with the Pacific plate. The ring of fire.
The Nazca plate is the co-parent of several
hoptspots including the equatorial Galápagos Islands. (
Galápagos triple junction). I swam in a geologic rift that is splitting
Santa Crúz island in twain. The landlocked channel was once open to the Pacific ocean via underwater fissures so myriad oceanic fish schooled in the brackish water. The only other time I've seen anything like that was when I swam in a Yucatan
cenote at Xelhá, far from shore. (Fresh water floats on top of salt water so the sea entrance is often a deep fissure or cave.).
I spent a winter in Ica, Perú in the 1980s. It's a strange place. It never rains in the
Atacama Desert or its northern sub-region, the
Sechura Desert. Strange, dry landscape. Land of few rivers. I met people who had never experienced rain in their lifetime. (See my blog on
Atacama Civilizations.)
And what of the anomaly of all those "waterworn" Andean boulders strewn across the floor of a desert of no rain? Now scientists say they've been joggled by earthquakes, rubbing shoulders with each other for millions of years. Rounding down those sharp edges to rounded shoulders.
It seems our continents are rubbing shoulders along the faultlines.
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Metamorphic rocks, García River, Point Arena, westernmost point in California,
where the San Andreas Fault heads out to sea. |
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The García riverbed is also the bed of the San Andreas Fault.
I expected to find quartz, jasper and blueshcist but not sandstone!
I didn't find any of the usual suspects—serpentine or granite—
very little by way of volcanic rock, but lots of soft gray mudstones
that I never learned the names of.
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