I believe there is a substantial risk of an earthquake of a magnitude 7.2-8.2 striking California within 60 miles of Parkfield on the San Andreas Fault prior to February 15, 2005. I put the probability at about 30%.

I've been studying California earthquakes for many years and my area of study has been from Parkfield, northward up through the SF Bay Area.

The largest known earthquake to ever strike California occurred on January 9, 1857 at 8:20 AM. The earthquake is called the Fort Tejon earthquake because that is the area that suffered the largest measured displacement of the fault. The quake was estimated to be a magnitude 8.0-8.25. The exact epicenter has never been determined although it is generally considered to be 15-50 miles southeast of Parkfield on the San Andreas fault.

Scientists estimate that there is a great quake on this area of the San Andreas every 140 years. In January it will be 148 years since the last quake.

One thing that is not widely known, is that in the days and hours prior to the great quake of 1857, there were two Magnitude 6.0 quakes at Parkfield. The two large quakes struck less than 9 hours before the Ft. Tejon quake. There are also scattered reports of smaller quakes striking the area prior to the Magnitude 6.0 quakes, but it is very difficult to find detailed information regarding these smaller quakes.

There were some other events worthy of note that preceded the great quake on January 9, 1857. On September 3, 1856, and again on September 9, 1856 were two quakes estimated to be about M 5.5 that struck Santa Cruz to the north. On December 18, 1856, a new warm water sulfur spring was discovered on the beach in Santa Barbara, which suffered extensive damage in the quake less than three weeks later. There was also a light earthquake felt in San Francisco on October 18, 1856. It is unknown where the epicenter of this quake was located.

Fast forward to the year 2003. On December 22, 2003 at 11:15 AM, a Magnitude 6.5 quake struck San Simeon, some 40 miles or so west of Parkfield. Based upon instrument readings and the aftershock pattern, I correctly predicted on April 1, 2004 that the next strong earthquake in California would strike within 15 miles of Parkfield. Although I predicted the magnitude at 6.2, I was precisely on target with the location.
http://www.timebomb2000.com/vb/showthread.php?t=95336

On September 28, 2004 a magnitude 6.0 quake struck the town of Parkfield. Researchers have been expecting a quake there for some time. Parkfield has had earthquakes in 1857, 1881, 1901, 1922, 1934, 1966, and again in 2004. Prior to the 2004 quake, the mean time between quakes was 22 years. Also worthy of note is that the time between the 1934 and 1966 quakes was 32 years, and the 1966-2004 quakes was 38 years.

I have been closely monitoring the various instruments at Parkfield following the quake in September. See:
http://quake.wr.usgs.gov/research/d...ta/lftable.html
The instruments at Parkfield all suggest to me that there is something much larger in store for the general area.

If you look at research regarding Parkfield earthquakes that was written prior to the September quake, nearly every researcher suggests that the next Parkfield quake could be a foreshock to a repeat of the 1857 Fort Tejon quake.

From: http://quake.usgs.gov/research/park...kunLindh85.html
"It is possible that the next characteristic Parkfield earthquake might break through the en echelon offset at the southeast end of the rupture zone and continue southeast along the San Andreas fault, growing into a major earthquake. Alternatively, the characteristic earthquake might stop at the en echelon offset and, by analogy to the triggering mechanism of the early foreshock of ML 5.0 in 1934, increase the right-Lateral shear stress on the fault southeast of the rupture zone. The latter case has been suggested (9) as the triggering mechanism for the great Fort Tejon earthquake of 1857.

Slip in 1857 along the 50-km-Long section of the San Andreas fault southeast of Cholame was about 3.5 m, appreciably less than the 9-m offset farther southeast (50). Continuation of a Parkfield earthquake southeast might result in a rupture length of about 90 km, which is consistent with a magnitude 6.5 to 7 earthquake (2). Since the average Holocene offset rate across the San Andreas fault at Wallace Creek is 3.5 cm per year (51), it seems likely that the 3.5 m of slip in 1857 has largely been recovered, so that the possibility of an earthquake breaking this segment must be taken seriously. There are few data available to suggest what precursors there might be for this hypothetical larger shock. Minor differences in the stress field near the offset, the strength of the offset, and the dynamic stress ahead of the rupture could all be important (52). Although fore shocks or deformation (or both) at the southeast end of the Parkfield rupture zone might portend a shock significantly larger than a characteristic Parkfield earthquake, there is certainly no evidence that such precursors need occur."

From: http://quake.wr.usgs.gov/research/p...ld/bakun79.html
"Finding a means for predicting future Parkfield earthquakes is especially significant in light of recent suggestions (1) that the great 1857 earthquake of southern California was preceded by foreshocks near Parkfield and that its epicenter may also have been located there."

From: http://www.johnmartin.com/earthquak...rs/00000075.htm
"Accounts of the 1857 shocks indicate that several small to moderate size central California earthquakes preceded the great 1857 earthquake by 1 to 9 hours. Two large foreshocks were widely felt. A comparison of the felt areas and intensity distributions of these two felt foreshocks by Professor Kerry Sieh of the California Institute of Technology (CIT) suggests that the foreshocks were similar to the Parkfield main shocks of 1901, 1922, 1934, and 1966. Sieh concluded that the 1857 foreshocks were magnitude 5 to 6 earthquakes located within an area of about 60 km radius that includes the Parkfield section. Because foreshocks generally occur near the epicenter of the ensuing larger main shock, Sieh suggested that the great Fort Tejon earthquake in 1857 began near Parkfield at the northwest end of the rupture zone."

It should also be noted that Jack Coles has been receiving precursor radio signals for a large quake in California for several months. While he could have easily claimed the Parkfield quake as the one he has been receiving signals for, he has been adamant that "his" quake would be much larger.

The final piece of the puzzle lies in the fact that the strongest tides of the year occur in December and January and coincide with the new moon. Tomorrow the difference between the high tide and low tide at the Golden Gate Bridge will be 9 feet. That is the largest tide of the year, and a nearly identical tide will take place in January as it always does. Jim Berkland theorizes that gravitational forces associated with extreme tides plays a role in triggering earthquakes. I share his point of view. You can follow Jack Coles' predictions on the Syzygy site at: http://www.syzygyjob.net/jackcoles/

I'm not in the business of predicting extremely large earthquakes like this one, but I feel there is a confluence of factors pointing at the same thing. I only post this here so that it is on record. You won't hear a word of this from the USGS even if they think it a possibility. Can you imagine the USGS predicting a magnitude 8.2 quake for California? Prior to the quake in September many people thought the next Parkfield quake would be a precursor event to the next Fort Tejon quake. It's easy to discuss and predict a huge quake when it is still years away. When it could be weeks or months away it gets a little more difficult to talk about.

One more thing to keep in mind: A magnitude 8.1 quake releases approximately 31 times the amount of energy as a magnitude 7.1 quake. Remember the Loma Prieta quake in 1989? That was a magnitude 7.1 quake and the shaking lasted 15-20 seconds. The 1857 quake shook for nearly 3 minutes.

Link to map of Parkfield, CA : http://maps.yahoo.com/maps_result?e...ew=1&name=&qty=


Thanks, Larry, for the heads up. In your opinion, is this something I should call to the attention of friends/family in Santa Monica, LA and Berkley?


nanna

It is always good to be prepared for an earthquake. I can't think of any differences in preparing for a magnitude 7 quake versus a magnitude 8 quake short of leaving the state (and I wouldn't do that!). If you feel like passing the information on to your friends, that is fine. I would tell them keep an eye on what Jack Coles is saying. If he sounds the alarm in the next 60 days I will likely upgrade my probability.

Here is a good graphic for Parkfield:

I should mention that two days ago there was an interesting article in the SF Chronicle about Parkfield and some strange seismic activity in the area. This article did not influence my feelings about the potential earthquake and may or may not be related to any of this.

Tremors rock earth deep beneath San Andreas Fault
Puzzling vibrations baffle researchers

- David Perlman, Chronicle Science Editor
Friday, December 10, 2004


Mysterious tremors deep beneath the San Andreas Fault near the quake-prone town of Parkfield are shaking the earth's brittle crust, far below the region where earthquakes normally strike -- and scientists say they can't understand what's happening or what the motions mean.

Seismic researchers are monitoring the strange vibrations closely. But whether the faint underground tremors -- termed "chatter" by some seismologists -- portend an increased likelihood of a major quake in the area is an unsolved puzzle.

Robert Nadeau, a geophysicist at the UC Berkeley Seismological Laboratory, charted more than 110 of the faint vibrations since they were first detected by the lab's High Resolution Seismic Network in Parkfield three years ago. What concerns Nadeau and his colleagues is that the epicenter of the great 1857 Fort Tejon earthquake, whose magnitude has been estimated at 7.8 to 8, was located almost exactly where the deep tremors are now occurring -- beneath the San Luis Obispo County village of Cholame, some 17 miles south of Parkfield.

The episodes of chatter last from four to 20 minutes and are being recorded from as deep as 40 miles beneath the surface -- up to four times the depth of normal earthquakes, which originate in what scientists call the "seismogenic zone." That zone reaches no deeper than 9 or 10 miles below the Earth's surface.

What's most striking is that deep tremors like the Cholame series have never been recorded before on a strike-slip fault such as the San Andreas, Nadeau said.

"We see this kind of tremor activity inside volcanoes like Mount St. Helens," Nadeau said, "but that's due to the movement of rising magma, and in the tremors we've recorded there's no evidence of volcanism and no seismic waves typical of ordinary earthquakes."

Nadeau and David Dolenc, a graduate student in his lab, are publishing the first report on the mysterious sequence of deep tremors today in Science Express, the online edition of the journal Science. They conclude that "future increases in San Andreas Fault tremor activity may signal periods of increased probability for the next large earthquake on the Cholame segment."

The Fort Tejon event rocked the ground violently and ruptured the fault for 225 miles, from northwest of Parkfield to San Bernardino. It was at least as large as the 1906 San Francisco quake. But because the Cholame region was virtually unpopulated at the time, it killed only two people and destroyed only the Tejon Army post, midway along the affected section of the fault.

The area is still sparsely populated; Cholame itself boasts only 2,125 inhabitants. But Paso Robles, with a population of more than 25,000, is only 25 miles west of the village -- and it was badly damaged by a magnitude 6.5 quake only a year ago.

Scientists have estimated that the Cholame segment of the fault has ruptured in a large quake roughly every 140 years. It is now 148 years since the Fort Tejon event, so the possibility of another one may be steadily increasing, they say.

Similar deep tremors have been detected recently along the coast of the Pacific Northwest, known as the Cascadia Subduction Zone, as well as in Japan -- and there, too, scientists are struggling to understand what their import is. In those areas, giant slabs of the earth's crust are dipping downward and sliding ponderously beneath other great crustal slabs, and scientists believe that fluids -- most likely seabed water saturating the slabs -- are causing the tremors, according to Herbert Dragert of Canada's Geological Survey in British Columbia and Kazushige Obara of Japan's National Research Institute for Earth Science and Disaster Prevention.

In an interview, Dragert said the tremors appear to add stress to a major thrust fault in the Puget Sound region, and that scientists in Canada and Washington are trying to determine whether the tremors might "play a significant role in triggering great earthquakes."

In California, the most mystifying feature of the unexplained tremors is that they are occurring right on the deepest part of the San Andreas -- a fault that does not involve subduction or volcanic activity. Instead, two sides of the earth's crust are sliding horizontally past each other in a motion seismologists call "right-lateral strike slip." In an earthquake, that slip can be an abrupt jolt, and in big quakes, a violent one.

The tremors are occurring at such great depth, Nadeau said, that they must be at the very bottom of the brittle crust -- where the earth's hot, viscous upper mantle begins -- which has been under stress for millions of years.

It's possible that the mantle there resembles something like Silly Putty, Nadeau said, with great chunks of embedded rock grinding against each other to generate the tremor signals. That's purely a speculation, Nadeau conceded, but so far it's the only one around.

"No one really knows what the tremors mean," said David Schwartz, a geophysicist at the U.S. Geological Survey in Menlo Park. "As to what they imply for the possibility of some future quake, we can't tell, and right now we can only wait and see."

A long-awaited magnitude 6 quake struck Parkfield in September at a depth of about 5 miles. That quake was seen as the latest in a series of quakes that have hit around Parkfield on an average of every 22 years between 1857 and 1966.

The Parkfield section of the San Andreas, in southern Monterey County, is the most intensively instrumented seismic danger region in the United States. A borehole 2 miles deep, carrying an array of instruments and called the San Andreas Fault Observatory at Depth, is to be completed next summer.

Whether its instruments solve the mystery of the tremors and determine whether they portend a future Cholame earthquake remains to be seen.

Page A - 1
URL: http://sfgate.com/cgi-bin/article.c.../10/TREMORS.TMP


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©2004 San Francisco Chronicle | Feedback | FAQ

for bringing your obvious years of following & learning about quakes here. Like many I find them dascinating but know very little about the science of them. It's good to read posts like ours that give info, REFERENCE it & make it understandable without dumbing it down.

Much appreciated.

__________________
Bunnies love me, this I know
'Cause Arubi tells me so.

Fascinating series of posts!

Here in eastern Washington State, over 200 miles away from Puget Sound, I was amazed to feel the Mw6.8 Nisqually Earthquake on February 28, 2001. All my life I had assumed that the Cascade range and the Columbia basalt would have considerable buffering effect against Puget Sound earthquakes. Possibly some buffering did take place, but not enough to damp the noticeable rocking. These leads me to believe an 8 or 9 on the coast would cause significant damage over here, and obliterate the coastal areas. It is only a matter of time until Mother Nature substantially remodels the west coast of the U.S, by part and parcel.

Bump...

See the Jack Coles earthquake prediction on this forum....

i posted this response at "another forum," though you haven't yet responded, so i assume you are cozy here?
--

i have taken advantage of an acquaintence i have at USGS. he is one of the scientists who does the data analysis for earthquakes. when you see "This event has been reviewed by a seismologist," he's one of those scientists. you might be interested in his comments (or might not if you choose to remain in the dark). he has interspersed his comments in Mr_Larry's original post -

Was the Parkfield earthquake a foreshock to a much larger (~M 8.0) quake?
--------------------------------------------------------------------------------
I believe there is a substantial risk of an earthquake of a magnitude 7.2-8.2 striking California within 60 miles of Parkfield on the San Andreas Fault prior to February 15, 2005. I put the probability at about 30%.


I don't know how the author derived this number. What does 30% mean? Over 5 days? 5 weeks? 5 years? 5 centuries? I suspect this number is pulled out of the air.

I've been studying California earthquakes for many years and my area of study has been from Parkfield, northward up through the SF Bay Area.

The largest known earthquake to ever strike California occurred on January 9, 1857 at 8:20 AM. The earthquake is called the Fort Tejon earthquake because that is the area that suffered the largest measured displacement of the fault. The quake was estimated to be a magnitude 8.0-8.25. The exact epicenter has never been determined although it is generally considered to be 15-50 miles southeast of Parkfield on the San Andreas fault.

Scientists estimate that there is a great quake on this area of the San Andreas every 140 years. In January it will be 148 years since the last quake.

One thing that is not widely known, is that in the days and hours prior to the great quake of 1857, there were two Magnitude 6.0 quakes at Parkfield. The two large quakes struck less than 9 hours before the Ft. Tejon quake.

Not widely known? Hardly. The most widely used historic catalog of CA earthquakes has this information readily available at http://www.consrv.ca.gov/CGS/rghm/q...cgs2000_fnl.txt and the background research was published decades ago (by Toppozada, I believe).

There are also scattered reports of smaller quakes striking the area prior to the Magnitude 6.0 quakes, but it is very difficult to find detailed information regarding these smaller quakes.

There were some other events worthy of note that preceded the great quake on January 9, 1857. On September 3, 1856, and again on September 9, 1856 were two quakes estimated to be about M 5.5 that struck Santa Cruz to the north. On December 18, 1856, a new warm water sulfur spring was discovered on the beach in Santa Barbara, which suffered extensive damage in the quake less than three weeks later. There was also a light earthquake felt in San Francisco on October 18, 1856. It is unknown where the epicenter of this quake was located.

Fast forward to the year 2003. On December 22, 2003 at 11:15 AM, a Magnitude 6.5 quake struck San Simeon, some 40 miles or so west of Parkfield. Based upon instrument readings and the aftershock pattern, I correctly predicted on April 1, 2004 that the next strong earthquake in California would strike within 15 miles of Parkfield. Although I predicted the magnitude at 6.2, I was precisely on target with the location.
http://www.timebomb2000.com/vb/showthread.php?t=95336

On September 28, 2004 a magnitude 6.0 quake struck the town of Parkfield. Researchers have been expecting a quake there for some time. Parkfield has had earthquakes in 1857, 1881, 1901, 1922, 1934, 1966, and again in 2004. Prior to the 2004 quake, the mean time between quakes was 22 years. Also worthy of note is that the time between the 1934 and 1966 quakes was 32 years, and the 1966-2004 quakes was 38 years.

I have been closely monitoring the various instruments at Parkfield following the quake in September. See:
http://quake.wr.usgs.gov/research/d...ta/lftable.html

The instruments at Parkfield all suggest to me that there is something much larger in store for the general area.

That is contrary to the opinions of the people who understand and operate the instrumentation, perform the data processing, and interpret these data. There is nothing in the data that would indicate such alarm. In fact, it's just the opposite. There was nothing in the strain data or seismic data before the Parkfield quake that showed any precursory signal above background noise. This was one of the most densely instrumented places on the planet. So, if we didn't see precursory activity for the Parkfield quake, the case for the (mostly uninstrumented) Mojave section to the south is even more dubious.

If you look at research regarding Parkfield earthquakes that was written prior to the September quake, nearly every researcher suggests that the next Parkfield quake could be a foreshock to a repeat of the 1857 Fort Tejon quake.

I do not agree. Lindh's opinion does not represent "nearly every researcher". Given what we learned form the 2004 Parkfield quake, I would say this notion is falling out of favor. Statistically, 5-10% of all quakes have foreshocks within 3 days. As time lengthens, the odds decrease rapidly (see Reasenberg and Jones papers in JGR and Science). The odds were never better than the above.

From: http://quake.usgs.gov/research/park...kunLindh85.html
"It is possible that the next characteristic Parkfield earthquake might break through the en echelon offset at the southeast end of the rupture zone and continue southeast along the San Andreas fault, growing into a major earthquake. Alternatively, the characteristic earthquake might stop at the en echelon offset and, by analogy to the triggering mechanism of the early foreshock of ML 5.0 in 1934, increase the right-Lateral shear stress on the fault southeast of the rupture zone. The latter case has been suggested (9) as the triggering mechanism for the great Fort Tejon earthquake of 1857.

Slip in 1857 along the 50-km-Long section of the San Andreas fault southeast of Cholame was about 3.5 m, appreciably less than the 9-m offset farther southeast (50).

Continuation of a Parkfield earthquake southeast might result in a rupture length of about 90 km, which is consistent with a magnitude 6.5 to 7 earthquake (2). Since the average Holocene offset rate across the San Andreas fault at Wallace Creek is 3.5 cm per year (51), it seems likely that the 3.5 m of slip in 1857 has largely been recovered, so that the possibility of an earthquake breaking this segment must be taken seriously. There are few data available to suggest what precursors there might be for this hypothetical larger shock. Minor differences in the stress field near the offset, the strength of the offset, and the dynamic stress ahead of the rupture could all be important (52). Although fore shocks or deformation (or both) at the southeast end of the Parkfield rupture zone might portend a shock significantly larger than a characteristic Parkfield earthquake, there is certainly no evidence that such precursors need occur."


From: http://quake.wr.usgs.gov/research/p...ld/bakun79.html
"Finding a means for predicting future Parkfield earthquakes is especially significant in light of recent suggestions (1) that the great 1857 earthquake of southern California was preceded by foreshocks near Parkfield and that its epicenter may also have been located there."

From: http://www.johnmartin.com/earthquak...rs/00000075.htm
"Accounts of the 1857 shocks indicate that several small to moderate size central California earthquakes preceded the great 1857 earthquake by 1 to 9 hours. Two large foreshocks were widely felt. A comparison of the felt areas and intensity distributions of these two felt foreshocks by Professor Kerry Sieh of the California Institute of Technology (CIT) suggests that the foreshocks were similar to the Parkfield main shocks of 1901, 1922, 1934, and 1966. Sieh concluded that the 1857 foreshocks were magnitude 5 to 6 earthquakes located within an area of about 60 km radius that includes the Parkfield section. Because foreshocks generally occur near the epicenter of the ensuing larger main shock, Sieh suggested that the great Fort Tejon earthquake in 1857 began near Parkfield at the northwest end of the rupture zone."

It should also be noted that Jack Coles has been receiving precursor radio signals for a large quake in California for several months. While he could have easily claimed the Parkfield quake as the one he has been receiving signals for, he has been adamant that "his" quake would be much larger.

Jack Coles has no credibility in the mainstream community. Why? Because he does not publish his results in peer-reviewed journals. While that's no guarantee that it's correct, at least it had to have the data to plausibly back up the interpretations. Anyone can put up a web page. It doesn't mean that the content has validity.


The final piece of the puzzle lies in the fact that the strongest tides of the year occur in December and January and coincide with the new moon. Tomorrow the difference between the high tide and low tide at the Golden Gate Bridge will be 9 feet. That is the largest tide of the year, and a nearly identical tide will take place in January as it always does. Jim Berkland theorizes that gravitational forces associated with extreme tides plays a role in triggering earthquakes. I share his point of view. You can follow Jack Coles' predictions on the Syzygy site at: http://www.syzygyjob.net/jackcoles/


Tides have been debunked in the published literature by Vidale et al in Geophysical Research Letters. Their study showed a very marginal probability gain during tidal peaks on the San Andreas fault. The community has looked at this time and again with better data and more sophisticated methods. If there was anything to it, we would build it into our models. The fact that we don't should tell you something.

If you want to ignore the literature, that's your right, of course. Like Coles, Berkland has also not published his results in peer-reviewed literature. I note that he makes money at his website through subscriptions at $40/year.


I'm not in the business of predicting extremely large earthquakes like this one, but I feel there is a confluence of factors pointing at the same thing. I only post this here so that it is on record. You won't hear a word of this from the USGS even if they think it a possibility. Can you imagine the USGS predicting a magnitude 8.2 quake for California?

Such paranoia... In fact, we openly discuss these issues in the popular press, which is quite knowledgeable about this situation and frequently ask the very question.

More to the point, immediately following the Parkfield quake scientists from the USGS and the California Earthquake Prediction Evaluation Council conferred with the CA Office of Emergency Services on this topic, and they released a statement at http://www.oes.ca.gov/Operational/O...3B?OpenDocument
that specifically references the possibility of a M7 (which represents a rupture of the Mojave segment). Note that it does not mention the possibility of a M8 quake for the entire 1857 rupture. In our opinion, there has not been sufficient strain accumulation on the entire segment to warrant that type of advisory, and the recurrence data supports that interpretation. So the assertion that the USGS sits on information is incorrect. We thought it was a possibility, particularly in the first week when the probability that Parkfield was a foreshock was elevanted, and advised OES who released a statement. At this time, the likelihood that Parkfield is a foreshock to a M7 quake is nearly the same as the background rate.

So, what's the "confluence" of factors other than some quakes have foreshocks and others don't. I don't find this argument compelling.


Prior to the quake in September many people thought the next Parkfield quake would be a precursor event to the next Fort Tejon quake. It's easy to discuss and predict a huge quake when it is still years away. When it could be weeks or months away it gets a little more difficult to talk about.

The Parkfield earthquake illustrates how good data eliminates simple models. Earthquakes don't repeat like clockwork. Their ruptures are variable. Sometimes they have foreshocks, and other times they don't. Sometimes they rupture from south to north, other times north to south, and probably bi-laterally if we watch for a few centuries. Sometimes they rupture small segments, or like in Landers jump on to what were thought to be discrete faults that would not rupture in a single quake.

Here's a suggestion. Attend the American Geophysical Meeting this week and listen to what the scientific community has to say. Read the literature. It's in any university library or at the USGS library. It's all there for the taking, but it's a lot more work than visiting a few amateur websites or trading insults about the USGS in email groups.

One more thing to keep in mind: A magnitude 8.1 quake releases approximately 31 times the amount of energy as a magnitude 7.1 quake. Remember the Loma Prieta quake in 1989? That was a magnitude 7.1 quake and the shaking lasted 15-20 seconds. The 1857 quake shook for nearly 3 minutes.

member 31, I haven't time today to read your whole post, but I will at some point.

First, Jim Berkland doesn't charge for his message board online (if that's what you're speaking about). I read it daily.

Second, just because Berkland and Cole don't publish in peer-reviewed journals doesn't mean they can't observe. Anyone can. I can, and I don't have the background the "official" scientific community has. That's a really elitist view. Kind of like a doctor claiming to know your body better than you who lives in it.

i posted this response at "another forum," though you haven't yet responded, so i assume you are cozy here?

I did not see this response on my thread at TimeBomb. Must have been one of the people I have on ignore! I'll do my best to address these issues.

On a related note, I wrote to the original author and perhaps the foremost authority on seismicity of this area of the San Andreas Fault. William Bakun has written extensively on his studies of Parkfield and the surrounding areas. I have not yet heard back from Mr. Bakun, but I have found USGS employees to be very responsive to my questions in the past when I have written to them. I will post his comments if he writes back to me.
--

i have taken advantage of an acquaintence i have at USGS. he is one of the scientists who does the data analysis for earthquakes. when you see "This event has been reviewed by a seismologist," he's one of those scientists. you might be interested in his comments (or might not if you choose to remain in the dark). he has interspersed his comments in Mr_Larry's original post -


Was the Parkfield earthquake a foreshock to a much larger (~M 8.0) quake?
--------------------------------------------------------------------------------
I believe there is a substantial risk of an earthquake of a magnitude 7.2-8.2 striking California within 60 miles of Parkfield on the San Andreas Fault prior to February 15, 2005. I put the probability at about 30%.


I don't know how the author derived this number. What does 30% mean? Over 5 days? 5 weeks? 5 years? 5 centuries? I suspect this number is pulled out of the air.

I thought my 30% was pretty self explanatory: 30% chance of this quake happening by February 15, 2005. Actually this number was not pulled out of the air; it was pulled out of my ass! The entire prediction is based upon my observations of several factors that are difficult to quantify. I used 30% to reflect less than 50%, but still a substantial risk of occurring.

I've been studying California earthquakes for many years and my area of study has been from Parkfield, northward up through the SF Bay Area.

The largest known earthquake to ever strike California occurred on January 9, 1857 at 8:20 AM. The earthquake is called the Fort Tejon earthquake because that is the area that suffered the largest measured displacement of the fault. The quake was estimated to be a magnitude 8.0-8.25. The exact epicenter has never been determined although it is generally considered to be 15-50 miles southeast of Parkfield on the San Andreas fault.

Scientists estimate that there is a great quake on this area of the San Andreas every 140 years. In January it will be 148 years since the last quake.

One thing that is not widely known, is that in the days and hours prior to the great quake of 1857, there were two Magnitude 6.0 quakes at Parkfield. The two large quakes struck less than 9 hours before the Ft. Tejon quake.

Not widely known? Hardly. The most widely used historic catalog of CA earthquakes has this information readily available at http://www.consrv.ca.gov/CGS/rghm/q...cgs2000_fnl.txt and the background research was published decades ago (by Toppozada, I believe).
When I said that this is not widely known, I was referring to the lay person with a passing interest in earthquakes. By no means was I inferring that there were hoards of actual geologists in the dark about this

There are also scattered reports of smaller quakes striking the area prior to the Magnitude 6.0 quakes, but it is very difficult to find detailed information regarding these smaller quakes.

There were some other events worthy of note that preceded the great quake on January 9, 1857. On September 3, 1856, and again on September 9, 1856 were two quakes estimated to be about M 5.5 that struck Santa Cruz to the north. On December 18, 1856, a new warm water sulfur spring was discovered on the beach in Santa Barbara, which suffered extensive damage in the quake less than three weeks later. There was also a light earthquake felt in San Francisco on October 18, 1856. It is unknown where the epicenter of this quake was located.

Fast forward to the year 2003. On December 22, 2003 at 11:15 AM, a Magnitude 6.5 quake struck San Simeon, some 40 miles or so west of Parkfield. Based upon instrument readings and the aftershock pattern, I correctly predicted on April 1, 2004 that the next strong earthquake in California would strike within 15 miles of Parkfield. Although I predicted the magnitude at 6.2, I was precisely on target with the location.
http://www.timebomb2000.com/vb/showthread.php?t=95336

On September 28, 2004 a magnitude 6.0 quake struck the town of Parkfield. Researchers have been expecting a quake there for some time. Parkfield has had earthquakes in 1857, 1881, 1901, 1922, 1934, 1966, and again in 2004. Prior to the 2004 quake, the mean time between quakes was 22 years. Also worthy of note is that the time between the 1934 and 1966 quakes was 32 years, and the 1966-2004 quakes was 38 years.

I have been closely monitoring the various instruments at Parkfield following the quake in September. See:
http://quake.wr.usgs.gov/research/d...ta/lftable.html

The instruments at Parkfield all suggest to me that there is something much larger in store for the general area.

That is contrary to the opinions of the people who understand and operate the instrumentation, perform the data processing, and interpret these data. There is nothing in the data that would indicate such alarm. In fact, it's just the opposite. There was nothing in the strain data or seismic data before the Parkfield quake that showed any precursory signal above background noise. This was one of the most densely instrumented places on the planet. So, if we didn't see precursory activity for the Parkfield quake, the case for the (mostly uninstrumented) Mojave section to the south is even more dubious.


I take issue with the statements above. First of all, the Jack Canyon strainmeter showed dramatic changes approximately three weeks prior to the San Simeon quake in 2003. The Jack Canyon strainmeter also showed a significant change in the weeks prior to the Parkfield quake. Second of all, most of the instruments at Parkfield continue to show unparalleled activity never before seen. But more importantly, the USGS scientists do not know exactly what a precursory signal looks like. If they do know, they certainly have never published their research. My point here is that no one is an expert at determining what constitutes a precursory signal.

If you look at research regarding Parkfield earthquakes that was written prior to the September quake, nearly every researcher suggests that the next Parkfield quake could be a foreshock to a repeat of the 1857 Fort Tejon quake.

I do not agree. Lindh's opinion does not represent "nearly every researcher". Given what we learned form the 2004 Parkfield quake, I would say this notion is falling out of favor. Statistically, 5-10% of all quakes have foreshocks within 3 days. As time lengthens, the odds decrease rapidly (see Reasenberg and Jones papers in JGR and Science). The odds were never better than the above.

I must admit that when I wrote "nearly every researcher" I was looking at three different research papers that all had one common author involved: William Bakun. As I have said previously, I have written to Mr. Bakun asking him about his old theories that the next Parkfield quake could be a catalyst for the next event similar in size and location as the 1857 Ft. Tejon event.

From: http://quake.usgs.gov/research/park...kunLindh85.html
"It is possible that the next characteristic Parkfield earthquake might break through the en echelon offset at the southeast end of the rupture zone and continue southeast along the San Andreas fault, growing into a major earthquake. Alternatively, the characteristic earthquake might stop at the en echelon offset and, by analogy to the triggering mechanism of the early foreshock of ML 5.0 in 1934, increase the right-Lateral shear stress on the fault southeast of the rupture zone. The latter case has been suggested (9) as the triggering mechanism for the great Fort Tejon earthquake of 1857.

Slip in 1857 along the 50-km-Long section of the San Andreas fault southeast of Cholame was about 3.5 m, appreciably less than the 9-m offset farther southeast (50).

Continuation of a Parkfield earthquake southeast might result in a rupture length of about 90 km, which is consistent with a magnitude 6.5 to 7 earthquake (2). Since the average Holocene offset rate across the San Andreas fault at Wallace Creek is 3.5 cm per year (51), it seems likely that the 3.5 m of slip in 1857 has largely been recovered, so that the possibility of an earthquake breaking this segment must be taken seriously. There are few data available to suggest what precursors there might be for this hypothetical larger shock. Minor differences in the stress field near the offset, the strength of the offset, and the dynamic stress ahead of the rupture could all be important (52). Although fore shocks or deformation (or both) at the southeast end of the Parkfield rupture zone might portend a shock significantly larger than a characteristic Parkfield earthquake, there is certainly no evidence that such precursors need occur."


From: http://quake.wr.usgs.gov/research/p...ld/bakun79.html
"Finding a means for predicting future Parkfield earthquakes is especially significant in light of recent suggestions (1) that the great 1857 earthquake of southern California was preceded by foreshocks near Parkfield and that its epicenter may also have been located there."

From: http://www.johnmartin.com/earthquak...rs/00000075.htm
"Accounts of the 1857 shocks indicate that several small to moderate size central California earthquakes preceded the great 1857 earthquake by 1 to 9 hours. Two large foreshocks were widely felt. A comparison of the felt areas and intensity distributions of these two felt foreshocks by Professor Kerry Sieh of the California Institute of Technology (CIT) suggests that the foreshocks were similar to the Parkfield main shocks of 1901, 1922, 1934, and 1966. Sieh concluded that the 1857 foreshocks were magnitude 5 to 6 earthquakes located within an area of about 60 km radius that includes the Parkfield section. Because foreshocks generally occur near the epicenter of the ensuing larger main shock, Sieh suggested that the great Fort Tejon earthquake in 1857 began near Parkfield at the northwest end of the rupture zone."

It should also be noted that Jack Coles has been receiving precursor radio signals for a large quake in California for several months. While he could have easily claimed the Parkfield quake as the one he has been receiving signals for, he has been adamant that "his" quake would be much larger.

Jack Coles has no credibility in the mainstream community. Why? Because he does not publish his results in peer-reviewed journals. While that's no guarantee that it's correct, at least it had to have the data to plausibly back up the interpretations. Anyone can put up a web page. It doesn't mean that the content has validity.


While Jack Coles does not publish his results in peer-reviewed journals, that alone does not have any bearing on the validity of his research. It would be nice if he had the necessary equipment and a few assistants to help in this regard, however that is impossible due to his circumstances.

The final piece of the puzzle lies in the fact that the strongest tides of the year occur in December and January and coincide with the new moon. Tomorrow the difference between the high tide and low tide at the Golden Gate Bridge will be 9 feet. That is the largest tide of the year, and a nearly identical tide will take place in January as it always does. Jim Berkland theorizes that gravitational forces associated with extreme tides plays a role in triggering earthquakes. I share his point of view. You can follow Jack Coles' predictions on the Syzygy site at: http://www.syzygyjob.net/jackcoles/


Tides have been debunked in the published literature by Vidale et al in Geophysical Research Letters. Their study showed a very marginal probability gain during tidal peaks on the San Andreas fault. The community has looked at this time and again with better data and more sophisticated methods. If there was anything to it, we would build it into our models. The fact that we don't should tell you something.

If you want to ignore the literature, that's your right, of course. Like Coles, Berkland has also not published his results in peer-reviewed literature. I note that he makes money at his website through subscriptions at $40/year.


I have read about a study that seemed to debunk some of Berkland's ideas regarding the effects the lunar cycle and gravitational forces may play in regards to being a catalyst for triggering earthquakes. Unfortunaletly, I only read an article about the research and did not have access to the research itself.

As to Jim Berkland not publishing his research, this has always been a gripe of mine. With access to databases of earthquakes and lunar information going back to the beginning of time, it would be easy to compile the research and present a paper on the subject.

It might be that the lunar effect only affects certain types of fault systems and not others. From what research that has been performed in this area, I do not believe that this has been taken into consideration.

I'm not in the business of predicting extremely large earthquakes like this one, but I feel there is a confluence of factors pointing at the same thing. I only post this here so that it is on record. You won't hear a word of this from the USGS even if they think it a possibility. Can you imagine the USGS predicting a magnitude 8.2 quake for California?

Such paranoia... In fact, we openly discuss these issues in the popular press, which is quite knowledgeable about this situation and frequently ask the very question.

More to the point, immediately following the Parkfield quake scientists from the USGS and the California Earthquake Prediction Evaluation Council conferred with the CA Office of Emergency Services on this topic, and they released a statement at http://www.oes.ca.gov/Operational/O...3B?OpenDocument
that specifically references the possibility of a M7 (which represents a rupture of the Mojave segment). Note that it does not mention the possibility of a M8 quake for the entire 1857 rupture. In our opinion, there has not been sufficient strain accumulation on the entire segment to warrant that type of advisory, and the recurrence data supports that interpretation. So the assertion that the USGS sits on information is incorrect. We thought it was a possibility, particularly in the first week when the probability that Parkfield was a foreshock was elevanted, and advised OES who released a statement. At this time, the likelihood that Parkfield is a foreshock to a M7 quake is nearly the same as the background rate.

So, what's the "confluence" of factors other than some quakes have foreshocks and others don't. I don't find this argument compelling.


I hardly consider myself to be the paranoid type that thinks the USGS is involved in any type of coverup, or is in the business of hiding information. My point was, that if someone within the USGS thought there was a significant risk of an impending M8.2 quake, it would be a very difficult subject to discuss publicly.

Prior to the quake in September many people thought the next Parkfield quake would be a precursor event to the next Fort Tejon quake. It's easy to discuss and predict a huge quake when it is still years away. When it could be weeks or months away it gets a little more difficult to talk about.

The Parkfield earthquake illustrates how good data eliminates simple models. Earthquakes don't repeat like clockwork. Their ruptures are variable. Sometimes they have foreshocks, and other times they don't. Sometimes they rupture from south to north, other times north to south, and probably bi-laterally if we watch for a few centuries. Sometimes they rupture small segments, or like in Landers jump on to what were thought to be discrete faults that would not rupture in a single quake.

Here's a suggestion. Attend the American Geophysical Meeting this week and listen to what the scientific community has to say. Read the literature. It's in any university library or at the USGS library. It's all there for the taking, but it's a lot more work than visiting a few amateur websites or trading insults about the USGS in email groups.

I have never insulted the USGS, In fact, I have defended the USGS on multiple occasions and in multiple venues. I have been a big supporter of the USGS. In the area of earthquake prediction however, I think they can be a little slow to embrace new ideas.

One more thing to keep in mind: A magnitude 8.1 quake releases approximately 31 times the amount of energy as a magnitude 7.1 quake. Remember the Loma Prieta quake in 1989? That was a magnitude 7.1 quake and the shaking lasted 15-20 seconds. The 1857 quake shook for nearly 3 minutes.

regarding Berkland's tidal/lunar theory, I knew I had read something in the news about that influence recently.

http://www.naturalworldtours.co.uk/...ctober2304i.htm

Strong Earth tides can trigger earthquakes, UCLA scientists report


University of California - Los Angeles


Earthquakes can be triggered by the Earth's tides, UCLA scientists confirmed Oct. 21 in Science Express, the online journal of Science. Earth tides are produced by the gravitational pull of the moon and the sun on the Earth, causing the ocean's waters to slosh, which in turn raise and lower stress on faults roughly twice a day.


Scientists have wondered about the effects of Earth tides for more than 100 years. (The research will be published in the print version of Science in November.)


"Large tides have a significant effect in triggering earthquakes," said Elizabeth Cochran, a UCLA graduate student in Earth and space sciences and lead author of the Science paper. "The earthquakes would have happened anyway, but they can be pushed sooner or later by the stress fluctuations of the tides."


"Scientists have long suspected the tides played a role, but no one has been able to prove that for earthquakes worldwide until now," said John Vidale, UCLA professor of Earth and space sciences, interim director of UCLA's Institute of Geophysics and Planetary Physics, and co-author of the paper. "Earthquakes have shown such clear correlations in only a few special settings, such as just below the sea-floor or near volcanoes."


"There are many mysteries about how earthquakes occur, and this clears up one of them," Vidale said. "We find that it takes about the force arising from changing the sea level by a couple of meters of water to noticeably affect the rate of earthquakes. This is a concrete step in understanding what it takes to set off an earthquake."


Cochran, Vidale and co-author Sachiko Tanaka are the first researchers to factor in both the phase of the tides and the size of the tides, and are using calculations of the effects of the tides more accurate than were available just three years ago. Tanaka is a seismologist with Japan's National Research Institute for Earth Science and Disaster Prevention.


Cochran and Vidale analyzed more than 2,000 earthquakes worldwide, magnitude 5.5 and higher, which struck from 1977 to 2000. They studied earthquakes in "subduction zones" where one tectonic plate dives under another, such as near the coasts of Alaska, Japan, New Zealand and western South America. "These earthquakes show a correlation with tides because along continent edges ocean tides are strong," Vidale said, "and the orientation of the fault plane is better known than for faults elsewhere."


Cochran conducted a statistical analysis of the earthquakes and tidal stress data, using state-of-the-science tide calculations from Tanaka and the best global earthquake data, which came from Harvard seismologists. This research follows up on a 2002 study by Tanaka. The current research was funded by the National Science Foundation and the Laurence Livermore National Laboratory.


Cochran and Vidale found a strong correlation between when earthquakes strike and when tidal stress on fault planes is high, and the likelihood of these results occurring by chance is less than one in 10,000, Cochran said. They found that strong tides impose enough stress on shallow faults to trigger earthquakes. If the tides are very large, more than two meters, three quarters of the earthquakes occur when tidal stress acts to encourage triggering, she found. Fewer earthquakes are triggered when the tides are smaller.


In California, and in fact in most places in the world, the correlation between earthquakes and tides is considerably smaller, Vidale said. In California, tides may vary the rate of earthquakes at most one or two percent; the overall effect of the tides is smaller, he said, because the faults studied are many miles inland from the coast and the tides are not particularly large.