Love the photo of Ejyafjallajokull! Thanks for sharing...
From: "geology2@yahoogroups.com" <geology2@yahoogroups.com>
To: geology2@yahoogroups.com
Sent: Tuesday, April 22, 2014 3:51 AM
Subject: [Geology2] Digest Number 3276
There are 4 messages in this issue.
Topics in this digest:
1. The Mountain That Jumped
From: Lin Kerns
2. Will We Ever Be Able to Predict Earthquakes?
From: Lin Kerns
3. Chaiten Makes Snopes
From: Kim Noyes
4. Another Ejyafjallajokull Stunner
From: Kim Noyes
Messages
________________________________________________________________________
1. The Mountain That Jumped
Posted by: "Lin Kerns" linkerns@gmail.com lin.kerns
Date: Mon Apr 21, 2014 5:09 am ((PDT))
The Mountain That Jumped
The GPS station installed at the top of Brown Mountain last summer recorded
that the mountain "jumped" 7mm during a recent nearby seismic event. The
GPS station was originally installed to measure land uplift and tectonic
plate movements. The recording of the effect of nearby earthquakes was not
one of the expected outcomes within the first year of the installation.
Nevertheless, measurements during seismic activity along the South and
North Scotia Ridge Transforms on the 17th and 24th November 2013,
respectively, were recorded. The large earthquake of the 17th had an
epicentre to the west of the South Orkney Islands (60.27°S, 46.40°W) along
the South Scotia Ridge Transform, the most active section of the entire
plate boundary of Antarctica. The resulting seismic waves travelling
through the Earth's crust shook Brown Mountain displacing it by 7mm before
settling back to its normal position. Although this is sufficient for
people to feel the earth shaking, no one at KEP recollected being aware of
it, possibly because it occurred at night. Much closer to the epicentre,
the Argentine science station at Orcadas in the South Orkney Islands was
seriously shaken and permanently displaced by 60cm towards East, 20cm
towards South and 0.3cm up!
[image: Brown Mountain with arrow showing the site of the GPS station.
Based on a photo by British Antarctic
Survey.]<http://www.sgisland.gs/index.php/Image:1March14.jpg>
<http://www.sgisland.gs/index.php/Image:1March14.jpg>
Brown Mountain with arrow showing the site of the GPS station. Based on a
photo by British Antarctic Survey.
The GPS station on Brown Mountain is linked to the tide gauge fixed to the
jetty at King Edward Point (KEP) and the data shows that a small tsunami
wave followed the earthquake. The tsunami arrived at KEP at 8:34, around
two and a half hours after the earthquake, reaching a maximum wave height
of 15 cm. Since the very large earthquakes in recent years (Indonesia,
Chile, Japan), it is being realized that the analysis of readings from a
network of GPS stations recording data every second can lead to a better
estimation of the magnitude of these seismic events than from data of the
specialist seismic stations. A quick and reliable estimation of the
magnitude is important for the very large events that trigger tsunamis.
That said, GPS will not replace the specialist seismic instruments which
are far more sensitive and can detect even the slightest tremors; there is
a seismic station on KEP too.
The GPS data is also being used to analyse the effect of greenhouse gases.
To enable the position of the mountain to be measured to the millimetre,
the GPS signals need to be processed very carefully; en-route the signal
travels through the Earth's atmosphere but the signal is affected by water
vapour in the atmosphere. Water vapour is a potent greenhouse gas; as the
atmosphere warms it can hold more water vapour which increases global
warming. This effect of the water vapour on the GPS signal is measureable,
giving scientists another powerful tool to monitor climate change and any
resultant global warming.
During their visit in March the two scientists, Dr Norman Teferle and Dr
Addisu Hunegnaw of the University of Luxembourg, which is funding the
project, installed a further GPS station on KEP. The combined measurements
recorded by the two stations will now enable more accurate and comparative
results to be obtained. The first year results from the station on Brown
Mountain indicate that Brown Mountain is steadily moving north and possibly
subsiding, though the movements are only at the millimetre level and much
more data is needed to be sure. With another station now installed they
will be able to see if both stations are recording the same land motion or
not. It will be possible, for instance, to see if there are changes within
the gravel spit that forms KEP or if there is subsidence of the jetty due
perhaps to heavy traffic use. The latter affects the readings of the tide
gauge measuring sea level.
The GPS stations have been installed because relatively little is known
about the motion of the Scotia Sea Plate, and to test a theory that South
Georgia could be a micro-continent. What is known is that relative to the
Scotia Plate, the South American Plate is moving westward (8-9 mm/yr), and
the Antarctic Plate is moving eastward (6-7 mm/yr). The terminus of the
Scotia plate is marked by the East Scotia Rift, separating the Scotia Plate
from the South Sandwich Plate upon which the chain of seismically active
volcanic islands - the South Sandwich Islands - sits. To better cover the
area Dr Norman Teferle hopes to return and install other GPS stations in
the region.
Other work done by the visiting scientists during their stay included
reactivating a GPS station on the slopes of Mt Duse and installing a tide
board on the KEP jetty. In another side-use of the GPS data, the GPS
signals sent down from the satellites are partly bounced off the sea
surface before being received by the GPS station on KEP. Under certain
circumstances this bounce is also measurable and can be used to record the
sea level, giving a neat check to the tide gauge data.
http://www.sgisland.gs/index.php/%28h%29South_Georgia_News_and_Events
--
V <http://goog_333603103>ei8 <http://goog_333603103>-Volcanoes of the World
Webcams <http://vei8home.blogspot.com/>
Roxxfoxx~~Adventures in Geology <http://1roxxfoxx.blogspot.com/>
Penguin News Today <http://penguinnewstoday.blogspot.com/>
Penguinology: The Science of Penguins <http://penguinology.blogspot.com/>
Gentoo Penguins of Gars O'Higgins Station,
Antarctica<http://wiinterrr.blogspot.com/>
Canis lupus 101 <http://canislupus101.blogspot.com/>
Through Golden Eyes <http://throughgoldeneyes.blogspot.com/>
Follow me on Pinterest <http://pinterest.com/wiinterrr/>!
Messages in this topic (1)
________________________________________________________________________
________________________________________________________________________
2. Will We Ever Be Able to Predict Earthquakes?
Posted by: "Lin Kerns" linkerns@gmail.com lin.kerns
Date: Mon Apr 21, 2014 4:46 pm ((PDT))
Will We Ever Be Able to Predict Earthquakes?
<http://www.facebook.com/sharer.php?s=100&p[title]=The+Parkfield+Experiment+Was+the+Closest+We%E2%80%99ve+Ever+Come+to+Predicting+an+Earthquake.+We+Were+Still+Dead+Wrong.&p[summary]=Excerpted+from+Earthquake+Storms:+The+Fascinating+History+and+Volatile+Future+of+the+San+Andreas+Fault+by+John+Dvorak,+out+now+from+Pegasus.+Reporter:+Did+anyone+predict+last+night%E2%80%99s+earthquake?+Charles+Richter:+Not+yet.+The+1970s+was+to+be+the+decade+when+earthquake+prediction+became+a+reality.+In+1975+the+Chinese...&p[ref]=sl_live&p[images][0]=http://www.slate.com/content/dam/slate/articles/technology/technology/2014/04/140421_TECH_SanAndreasFault.jpg/_jcr_content/renditions/cq5dam.web.1280.1280.jpeg&p[url]=http://www.slate.com/articles/technology/technology/2014/04/earthquake_prediction_why_the_future_of_the_san_andreas_and_other_fault.html>
<http://www.slate.com/articles/technology/technology/2014/04/earthquake_prediction_why_the_future_of_the_san_andreas_and_other_fault.html#comments>
Once, seismologists correctly predicted a major quake. They were only 12
years off on the timing.
By John Dvorak <http://www.slate.com/authors.john_dvorak.html>
[image: Layers of earth are deformed by the collision of the Pacific
and North American tectonic plates along the southern San Andreas
Fault.]Layers of earth are deformed by the collision of the Pacific
and North
American plates along the southern San Andreas Fault north of the Salton
Sea near Mecca, Calif.
Photo by David McNew/Getty Images
*Excerpted from *Earthquake Storms: The Fascinating History and Volatile
Future of the San Andreas
Fault<http://www.amazon.com/dp/1605984957/?tag=slatmaga-20>*
by John Dvorak, out now from Pegasus.*
Reporter: Did anyone predict last night's earthquake?
Charles Richter: Not yet.
The 1970s was to be the decade when earthquake prediction became a
reality. In 1975 the Chinese government announced that it had ordered an
evacuation of a major city hours before a major quake struck. The Russians
were saying that they were using a variety of techniques routinely to
predict not only large earthquakes but moderate ones, too. And in the
United States, scientists had discovered a number of anomalies near Los
Angeles—a broad uplift of the ground, a slowing of seismic waves, increased
emission of radon gas—that indicated the city would soon be razed by strong
seismic shaking.
And then it all collapsed—that is, the effort to predict earthquakes
collapsed.
In 1976 the greatest seismic calamity yet left hundreds of thousands of
people dead in China—and government officials gave no indication that they
knew such a disaster was coming. The evidence used by Russian scientists
was scrutinized by other scientists who concluded the Russian effort was
plagued by inconsistencies and unsubstantiated claims. And in the United
States, additional measurements showed that the anomalies that seemed to
doom Los Angeles had either disappeared, or, maybe, had never existed at
all.
And the world community of seismologists remains divided—at times,
vehemently—over the issue of whether it will ever be possible to predict
earthquakes. It's a question that's been raised again as the network of
faults in Southern California has awakened with seismic
activity<http://www.ocregister.com/articles/quake-607523-earthquake-magnitude.html>in
recent months. It is a complex problem. And, to date, no one has yet
predicted an earthquake.
An attempt to predict an earthquake near Parkfield, Calif., in the 1980s
failed. But this effort was the closest anyone has come to predicting an
earthquake—that is, to identifying the fault, giving the magnitude, and
limiting the time period when the calamity would occur.
* * *
The San Andreas Fault can be divided into three main segments. The northern
segment runs from Cape Mendocino to San Juan Bautista—the part of the fault
that ruptured in 1906. The southern segment begins around Cholame, just
north of Carrizo Plain, and runs south, eventually forming the southern
boundary of the Mojave Desert, continues through Cajon Pass and San
Gorgonio Pass, can be picked up 20 miles east of Palm Springs in Coachella
Valley, and ends at Bombay Beach on the east side of the Salton Sea. The
northern half of the southern segment—from Cholame to Cajon Pass—ruptured
in 1857; the southern half of the southern segment—from San Gorgonio Pass
to Bombay Beach—did so in about 1690. So all of the San Andreas Fault has
broken during a major earthquake in the last few hundred years except for a
short middle segment that runs from San Juan Bautista to Cholame and
includes the ranching community of Parkfield. This 150-mile segment of the
San Andreas Fault is distinctly different from the other parts of the
fault: Here the fault is slowly and continuously sliding.
Ten miles south of San Juan Bautista is DeRose Vineyards. It is a
family-owned business where the winemaking and tasting room is located in a
large building with a concrete floor and metal walls and roof. On the day I
visited, I identified myself as an earthquake tourist. The person who was
pouring the wine pointed immediately to the center of the building and
said, "It's over there."
Here the trace of the San Andreas Fault is all too apparent. Running along
the floor is a line of broken concrete slabs, up to a foot across, that
extends the full length of the building. Where the fault runs beneath a
metal wall, the wall has been sheared apart, the two halves now standing as
much as two feet apart. Broken ends of twisted rebar are exposed where the
metal wall once connected to the concrete floor. A plaque attached to a
wall in the center of the DeRose Winery building proclaims the San Andreas
Fault at this spot to be a registered natural landmark.
If one drives south of DeRose Vineyards, one can find sets of cracks
running diagonally across the pavement. These, too, are the San Andreas
Fault. They are visible, as is the slow destruction of the winery at DeRose
Vineyards, because along this segment the fault is always sliding. And the
sliding can be found as far south as Parkfield, where the fault runs under
a bridge. As one might expect, the bridge has a distinct bend over the
exact place where it crosses the San Andreas Fault.
The slow sliding is known as seismic creep, caused in part by a constant
jitter of small earthquakes. At DeRose Vineyards, the fault slides about an
inch a year. At Parkfield, it is half that amount, which means occasionally
the Parkfield section has to catch up. It does so with a jolt—a moderate
earthquake.
Six times—in 1857, 1881, 1901, 1922, 1934, and 1966—the Parkfield section
has surged forward. Each event has been nearly identical in
size—corresponding to a magnitude-6 earthquake—and each successive event
has occurred, on average, 22 years after the previous one. Moreover, there
seemed to be definite precursory signs before the last two events. The main
shocks in 1934 and again in 1966 were preceded 17 minutes by a strong
foreshock that was felt over a wide area. Furthermore, an irrigation pipe
that crossed the rupture zone separated nine hours before the 1966 event.
All this gave credence to the idea that the next Parkfield earthquake might
be predicted.
In 1985 a panel of 12 scientists, formally known as the National Earthquake
Prediction Evaluation Council, endorsed a Parkfield prediction, saying that
there was a 95 percent chance that a magnitude-6 earthquake would occur
along the Parkfield section of the San Andreas Fault by 1993. A dense
network of instruments was installed in the hopes of trapping the
earthquake, to detect precursory signs that might occur in seismic
patterns, in ground movements, in electric or magnetic fields, in radon-gas
emission, or in the chemistry or level of water wells. And then people
waited.
Twice, an "A"-level alert was issued, on Oct. 19, 1992, and again on Nov.
14, 1993. Both alerts were triggered after felt earthquakes, similar in
size to what preceded the 1934 and 1966 events, occurred. Both times there
was an increased awareness that the predicted earthquake might occur within
the next 72 hours. California state agencies and emergency services were
notified. And both times ... nothing happened.
The year 1993 came and went, and no earthquake. Then 1994, 1995, and so on.
Finally, at 10:15 in the morning on Sept. 28, 2004, a magnitude-6
earthquake ruptured the Parkfield section of the San Andreas Fault. The
predicted earthquake had occurred. Or had it?
[image: 140421_TECH_EarthquakeStorms]<http://www.amazon.com/dp/1605984957/?tag=slatmaga-20>
There were important differences between the events of 1934 and 1966 and
the one that occurred in 2004. First, in 1934 and 1966, the ground rupture
began north of Parkfield and propagated south. In 2004 it was in the
opposite direction: The rupture started south of Parkfield and propagated
north. More important, in the dense network of instruments there were no
precursors recorded minutes, hours, or days before the event. There was no
foreshock or increase of seismic activity before the event. There was no
damage to irrigation pipes. There was no measured change in electric or
magnetic fields or in chemistry or level of water wells. Most
disconcerting, there was no measured ground movement: There was no warping
or rise or fall of the ground surface. There was no underground compression
or slight expansion of rock—no dilatancy—and this could be measured with
great precision.
Five instruments known as borehole strainmeters were installed within a few
miles of where the 2004 rupture formed. Essentially, each instrument
consists of a fluid-filled bag stuffed deep down a borehole. If the
surrounding rock is compressed or stretched by a tiny amount—equivalent to
taking a 100-mile-long rigid bar and compressing or stretching one end by
the diameter of a human hair—the bag undergoes a small compression or
expansion. But no change was recorded for weeks to seconds before the
earthquake. As far as anyone can tell, the 2004 Parkfield earthquake was a
spontaneous event.
The Parkfield experiment was successful in identifying *where *an
earthquake would occur and *how *big it would be, though the
all-important *when
*was missed; the event came 12 years too late. Which raises the question:
Will it ever be possible to predict earthquakes?
The answer, as it is seen today, is: maybe.
The question of earthquake prediction can be reduced to a more tractable
and straightforward question: What triggers a large earthquake?
Imagine this: Initially, an earthquake fault, such as the San Andreas, is
relatively quiet. Only a few small earthquakes are occurring, popping off,
in a familiar analogy, like kernels of heated popcorn. Then the popping of
one earthquake kernel happens to set off more kernels, and those set off
more kernels until there is an explosion, or cascade, of kernels popping, a
rupture forms, and a large earthquake is produced.
Or imagine this: The lower region of the San Andreas Fault is slowly
sliding—without earthquakes—because here the rocks are hot and plastic and
are driven to slide smoothly by the slow and constant movement of the
Pacific and North American plates. As the slipping region grows, the
sliding accelerates until it reaches a critical speed to where a rupture
forms in the brittle overlying rock, and a larger earthquake is produced.
In the former case—the cascade model of earthquake kernels—the beginning of
any large earthquake is no different from the beginnings of countless small
ones, which means it is impossible to ever predict large earthquakes.
In the latter case—the pre-slip model—a long process occurs that prepares
the San Andreas for a sudden and major slip. In that case, earthquakes
might be predicted if we can figure out how to measure the slow sliding and
subsequent buildup.
Which idea is true—or whether earthquakes work in some other manner
entirely—is still the focus of much research today and is hotly debated.
But this much is true: When there is a major earthquake, the probability of
another major earthquake happening soon after in the same region goes way
up. Once the Earth's crust starts to adjust to the slow buildup of pressure
between the tectonic plates, that pressure may not be relieved simply as a
single large event but as one—or more—major earthquakes happening in a
short time period.
To put this in concrete numbers: History shows that whenever there is a
major earthquake in California, say a magnitude-6 event, which can do
substantial damage—there is a 1-i- 20 chance that another earthquake of
equal or greater magnitude will happen in the same general area *within the
next three days.*
This leads to a practical concern. After a major earthquake, people should
brace themselves for an equal or larger event. Emergency services, such as
fire and police stations and hospitals, need to prepare for additional
injuries and for the disruption of still more roads and utilities. And for
those who are attempting to rescue people who are already trapped under
debris, those rescuers should be aware that a larger earthquake could
strike and a greater catastrophe may happen.
*Excerpted from *Earthquake Storms: The Fascinating History and Volatile
Future of the San Andreas
Fault<http://www.amazon.com/dp/1605984957/?tag=slatmaga-20>*
by John Dvorak, out now from Pegasus.*
John Dvorak, Ph.D., has worked on volcanoes and earthquakes for the U.S.
Geological Survey.
http://www.slate.com/articles/technology/technology/2014/04/earthquake_prediction_why_the_future_of_the_san_andreas_and_other_fault.html
--
V <http://goog_333603103>ei8 <http://goog_333603103>-Volcanoes of the World
Webcams <http://vei8home.blogspot.com/>
Roxxfoxx~~Adventures in Geology <http://1roxxfoxx.blogspot.com/>
Penguin News Today <http://penguinnewstoday.blogspot.com/>
Penguinology: The Science of Penguins <http://penguinology.blogspot.com/>
Gentoo Penguins of Gars O'Higgins Station,
Antarctica<http://wiinterrr.blogspot.com/>
Canis lupus 101 <http://canislupus101.blogspot.com/>
Through Golden Eyes <http://throughgoldeneyes.blogspot.com/>
Follow me on Pinterest <http://pinterest.com/wiinterrr/>!
Messages in this topic (1)
________________________________________________________________________
________________________________________________________________________
3. Chaiten Makes Snopes
Posted by: "Kim Noyes" kimnoyes@gmail.com noyeskim
Date: Tue Apr 22, 2014 12:59 am ((PDT))
Chile's Chaiten Volcano's eruption of 2008 makes Snopes.com:
http://www.snopes.com/photos/natural/chaiten.asp
--
Check out http://groups.yahoo.com/group/californiadisasters/
Read my blog at http://eclecticarcania.blogspot.com/
My Facebook: http://www.facebook.com/derkimster
Linkedin profile: http://www.linkedin.com/pub/kim-noyes/9/3a1/2b8
Follow me on Twitter @DisasterKim
Messages in this topic (1)
________________________________________________________________________
________________________________________________________________________
4. Another Ejyafjallajokull Stunner
Posted by: "Kim Noyes" kimnoyes@gmail.com noyeskim
Date: Tue Apr 22, 2014 1:23 am ((PDT))
I found this quite by accident... a lucky fortuitous accident:
http://eclecticarcania.blogspot.com/2014/04/another-ejyafjallajokull-stunner.html
--
Check out http://groups.yahoo.com/group/californiadisasters/
Read my blog at http://eclecticarcania.blogspot.com/
My Facebook: http://www.facebook.com/derkimster
Linkedin profile: http://www.linkedin.com/pub/kim-noyes/9/3a1/2b8
Follow me on Twitter @DisasterKim
Messages in this topic (1)
------------------------------------------------------------------------
Yahoo Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/geology2/
<*> Your email settings:
Digest Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/geology2/join
(Yahoo! ID required)
<*> To change settings via email:
geology2-normal@yahoogroups.com
geology2-fullfeatured@yahoogroups.com
<*> To unsubscribe from this group, send an email to:
geology2-unsubscribe@yahoogroups.com
<*> Your use of Yahoo Groups is subject to:
https://info.yahoo.com/legal/us/yahoo/utos/terms/
------------------------------------------------------------------------
From: "geology2@yahoogroups.com" <geology2@yahoogroups.com>
To: geology2@yahoogroups.com
Sent: Tuesday, April 22, 2014 3:51 AM
Subject: [Geology2] Digest Number 3276
There are 4 messages in this issue.
Topics in this digest:
1. The Mountain That Jumped
From: Lin Kerns
2. Will We Ever Be Able to Predict Earthquakes?
From: Lin Kerns
3. Chaiten Makes Snopes
From: Kim Noyes
4. Another Ejyafjallajokull Stunner
From: Kim Noyes
Messages
________________________________________________________________________
1. The Mountain That Jumped
Posted by: "Lin Kerns" linkerns@gmail.com lin.kerns
Date: Mon Apr 21, 2014 5:09 am ((PDT))
The Mountain That Jumped
The GPS station installed at the top of Brown Mountain last summer recorded
that the mountain "jumped" 7mm during a recent nearby seismic event. The
GPS station was originally installed to measure land uplift and tectonic
plate movements. The recording of the effect of nearby earthquakes was not
one of the expected outcomes within the first year of the installation.
Nevertheless, measurements during seismic activity along the South and
North Scotia Ridge Transforms on the 17th and 24th November 2013,
respectively, were recorded. The large earthquake of the 17th had an
epicentre to the west of the South Orkney Islands (60.27°S, 46.40°W) along
the South Scotia Ridge Transform, the most active section of the entire
plate boundary of Antarctica. The resulting seismic waves travelling
through the Earth's crust shook Brown Mountain displacing it by 7mm before
settling back to its normal position. Although this is sufficient for
people to feel the earth shaking, no one at KEP recollected being aware of
it, possibly because it occurred at night. Much closer to the epicentre,
the Argentine science station at Orcadas in the South Orkney Islands was
seriously shaken and permanently displaced by 60cm towards East, 20cm
towards South and 0.3cm up!
[image: Brown Mountain with arrow showing the site of the GPS station.
Based on a photo by British Antarctic
Survey.]<http://www.sgisland.gs/index.php/Image:1March14.jpg>
<http://www.sgisland.gs/index.php/Image:1March14.jpg>
Brown Mountain with arrow showing the site of the GPS station. Based on a
photo by British Antarctic Survey.
The GPS station on Brown Mountain is linked to the tide gauge fixed to the
jetty at King Edward Point (KEP) and the data shows that a small tsunami
wave followed the earthquake. The tsunami arrived at KEP at 8:34, around
two and a half hours after the earthquake, reaching a maximum wave height
of 15 cm. Since the very large earthquakes in recent years (Indonesia,
Chile, Japan), it is being realized that the analysis of readings from a
network of GPS stations recording data every second can lead to a better
estimation of the magnitude of these seismic events than from data of the
specialist seismic stations. A quick and reliable estimation of the
magnitude is important for the very large events that trigger tsunamis.
That said, GPS will not replace the specialist seismic instruments which
are far more sensitive and can detect even the slightest tremors; there is
a seismic station on KEP too.
The GPS data is also being used to analyse the effect of greenhouse gases.
To enable the position of the mountain to be measured to the millimetre,
the GPS signals need to be processed very carefully; en-route the signal
travels through the Earth's atmosphere but the signal is affected by water
vapour in the atmosphere. Water vapour is a potent greenhouse gas; as the
atmosphere warms it can hold more water vapour which increases global
warming. This effect of the water vapour on the GPS signal is measureable,
giving scientists another powerful tool to monitor climate change and any
resultant global warming.
During their visit in March the two scientists, Dr Norman Teferle and Dr
Addisu Hunegnaw of the University of Luxembourg, which is funding the
project, installed a further GPS station on KEP. The combined measurements
recorded by the two stations will now enable more accurate and comparative
results to be obtained. The first year results from the station on Brown
Mountain indicate that Brown Mountain is steadily moving north and possibly
subsiding, though the movements are only at the millimetre level and much
more data is needed to be sure. With another station now installed they
will be able to see if both stations are recording the same land motion or
not. It will be possible, for instance, to see if there are changes within
the gravel spit that forms KEP or if there is subsidence of the jetty due
perhaps to heavy traffic use. The latter affects the readings of the tide
gauge measuring sea level.
The GPS stations have been installed because relatively little is known
about the motion of the Scotia Sea Plate, and to test a theory that South
Georgia could be a micro-continent. What is known is that relative to the
Scotia Plate, the South American Plate is moving westward (8-9 mm/yr), and
the Antarctic Plate is moving eastward (6-7 mm/yr). The terminus of the
Scotia plate is marked by the East Scotia Rift, separating the Scotia Plate
from the South Sandwich Plate upon which the chain of seismically active
volcanic islands - the South Sandwich Islands - sits. To better cover the
area Dr Norman Teferle hopes to return and install other GPS stations in
the region.
Other work done by the visiting scientists during their stay included
reactivating a GPS station on the slopes of Mt Duse and installing a tide
board on the KEP jetty. In another side-use of the GPS data, the GPS
signals sent down from the satellites are partly bounced off the sea
surface before being received by the GPS station on KEP. Under certain
circumstances this bounce is also measurable and can be used to record the
sea level, giving a neat check to the tide gauge data.
http://www.sgisland.gs/index.php/%28h%29South_Georgia_News_and_Events
--
V <http://goog_333603103>ei8 <http://goog_333603103>-Volcanoes of the World
Webcams <http://vei8home.blogspot.com/>
Roxxfoxx~~Adventures in Geology <http://1roxxfoxx.blogspot.com/>
Penguin News Today <http://penguinnewstoday.blogspot.com/>
Penguinology: The Science of Penguins <http://penguinology.blogspot.com/>
Gentoo Penguins of Gars O'Higgins Station,
Antarctica<http://wiinterrr.blogspot.com/>
Canis lupus 101 <http://canislupus101.blogspot.com/>
Through Golden Eyes <http://throughgoldeneyes.blogspot.com/>
Follow me on Pinterest <http://pinterest.com/wiinterrr/>!
Messages in this topic (1)
________________________________________________________________________
________________________________________________________________________
2. Will We Ever Be Able to Predict Earthquakes?
Posted by: "Lin Kerns" linkerns@gmail.com lin.kerns
Date: Mon Apr 21, 2014 4:46 pm ((PDT))
Will We Ever Be Able to Predict Earthquakes?
<http://www.facebook.com/sharer.php?s=100&p[title]=The+Parkfield+Experiment+Was+the+Closest+We%E2%80%99ve+Ever+Come+to+Predicting+an+Earthquake.+We+Were+Still+Dead+Wrong.&p[summary]=Excerpted+from+Earthquake+Storms:+The+Fascinating+History+and+Volatile+Future+of+the+San+Andreas+Fault+by+John+Dvorak,+out+now+from+Pegasus.+Reporter:+Did+anyone+predict+last+night%E2%80%99s+earthquake?+Charles+Richter:+Not+yet.+The+1970s+was+to+be+the+decade+when+earthquake+prediction+became+a+reality.+In+1975+the+Chinese...&p[ref]=sl_live&p[images][0]=http://www.slate.com/content/dam/slate/articles/technology/technology/2014/04/140421_TECH_SanAndreasFault.jpg/_jcr_content/renditions/cq5dam.web.1280.1280.jpeg&p[url]=http://www.slate.com/articles/technology/technology/2014/04/earthquake_prediction_why_the_future_of_the_san_andreas_and_other_fault.html>
<http://www.slate.com/articles/technology/technology/2014/04/earthquake_prediction_why_the_future_of_the_san_andreas_and_other_fault.html#comments>
Once, seismologists correctly predicted a major quake. They were only 12
years off on the timing.
By John Dvorak <http://www.slate.com/authors.john_dvorak.html>
[image: Layers of earth are deformed by the collision of the Pacific
and North American tectonic plates along the southern San Andreas
Fault.]Layers of earth are deformed by the collision of the Pacific
and North
American plates along the southern San Andreas Fault north of the Salton
Sea near Mecca, Calif.
Photo by David McNew/Getty Images
*Excerpted from *Earthquake Storms: The Fascinating History and Volatile
Future of the San Andreas
Fault<http://www.amazon.com/dp/1605984957/?tag=slatmaga-20>*
by John Dvorak, out now from Pegasus.*
Reporter: Did anyone predict last night's earthquake?
Charles Richter: Not yet.
The 1970s was to be the decade when earthquake prediction became a
reality. In 1975 the Chinese government announced that it had ordered an
evacuation of a major city hours before a major quake struck. The Russians
were saying that they were using a variety of techniques routinely to
predict not only large earthquakes but moderate ones, too. And in the
United States, scientists had discovered a number of anomalies near Los
Angeles—a broad uplift of the ground, a slowing of seismic waves, increased
emission of radon gas—that indicated the city would soon be razed by strong
seismic shaking.
And then it all collapsed—that is, the effort to predict earthquakes
collapsed.
In 1976 the greatest seismic calamity yet left hundreds of thousands of
people dead in China—and government officials gave no indication that they
knew such a disaster was coming. The evidence used by Russian scientists
was scrutinized by other scientists who concluded the Russian effort was
plagued by inconsistencies and unsubstantiated claims. And in the United
States, additional measurements showed that the anomalies that seemed to
doom Los Angeles had either disappeared, or, maybe, had never existed at
all.
And the world community of seismologists remains divided—at times,
vehemently—over the issue of whether it will ever be possible to predict
earthquakes. It's a question that's been raised again as the network of
faults in Southern California has awakened with seismic
activity<http://www.ocregister.com/articles/quake-607523-earthquake-magnitude.html>in
recent months. It is a complex problem. And, to date, no one has yet
predicted an earthquake.
An attempt to predict an earthquake near Parkfield, Calif., in the 1980s
failed. But this effort was the closest anyone has come to predicting an
earthquake—that is, to identifying the fault, giving the magnitude, and
limiting the time period when the calamity would occur.
* * *
The San Andreas Fault can be divided into three main segments. The northern
segment runs from Cape Mendocino to San Juan Bautista—the part of the fault
that ruptured in 1906. The southern segment begins around Cholame, just
north of Carrizo Plain, and runs south, eventually forming the southern
boundary of the Mojave Desert, continues through Cajon Pass and San
Gorgonio Pass, can be picked up 20 miles east of Palm Springs in Coachella
Valley, and ends at Bombay Beach on the east side of the Salton Sea. The
northern half of the southern segment—from Cholame to Cajon Pass—ruptured
in 1857; the southern half of the southern segment—from San Gorgonio Pass
to Bombay Beach—did so in about 1690. So all of the San Andreas Fault has
broken during a major earthquake in the last few hundred years except for a
short middle segment that runs from San Juan Bautista to Cholame and
includes the ranching community of Parkfield. This 150-mile segment of the
San Andreas Fault is distinctly different from the other parts of the
fault: Here the fault is slowly and continuously sliding.
Ten miles south of San Juan Bautista is DeRose Vineyards. It is a
family-owned business where the winemaking and tasting room is located in a
large building with a concrete floor and metal walls and roof. On the day I
visited, I identified myself as an earthquake tourist. The person who was
pouring the wine pointed immediately to the center of the building and
said, "It's over there."
Here the trace of the San Andreas Fault is all too apparent. Running along
the floor is a line of broken concrete slabs, up to a foot across, that
extends the full length of the building. Where the fault runs beneath a
metal wall, the wall has been sheared apart, the two halves now standing as
much as two feet apart. Broken ends of twisted rebar are exposed where the
metal wall once connected to the concrete floor. A plaque attached to a
wall in the center of the DeRose Winery building proclaims the San Andreas
Fault at this spot to be a registered natural landmark.
If one drives south of DeRose Vineyards, one can find sets of cracks
running diagonally across the pavement. These, too, are the San Andreas
Fault. They are visible, as is the slow destruction of the winery at DeRose
Vineyards, because along this segment the fault is always sliding. And the
sliding can be found as far south as Parkfield, where the fault runs under
a bridge. As one might expect, the bridge has a distinct bend over the
exact place where it crosses the San Andreas Fault.
The slow sliding is known as seismic creep, caused in part by a constant
jitter of small earthquakes. At DeRose Vineyards, the fault slides about an
inch a year. At Parkfield, it is half that amount, which means occasionally
the Parkfield section has to catch up. It does so with a jolt—a moderate
earthquake.
Six times—in 1857, 1881, 1901, 1922, 1934, and 1966—the Parkfield section
has surged forward. Each event has been nearly identical in
size—corresponding to a magnitude-6 earthquake—and each successive event
has occurred, on average, 22 years after the previous one. Moreover, there
seemed to be definite precursory signs before the last two events. The main
shocks in 1934 and again in 1966 were preceded 17 minutes by a strong
foreshock that was felt over a wide area. Furthermore, an irrigation pipe
that crossed the rupture zone separated nine hours before the 1966 event.
All this gave credence to the idea that the next Parkfield earthquake might
be predicted.
In 1985 a panel of 12 scientists, formally known as the National Earthquake
Prediction Evaluation Council, endorsed a Parkfield prediction, saying that
there was a 95 percent chance that a magnitude-6 earthquake would occur
along the Parkfield section of the San Andreas Fault by 1993. A dense
network of instruments was installed in the hopes of trapping the
earthquake, to detect precursory signs that might occur in seismic
patterns, in ground movements, in electric or magnetic fields, in radon-gas
emission, or in the chemistry or level of water wells. And then people
waited.
Twice, an "A"-level alert was issued, on Oct. 19, 1992, and again on Nov.
14, 1993. Both alerts were triggered after felt earthquakes, similar in
size to what preceded the 1934 and 1966 events, occurred. Both times there
was an increased awareness that the predicted earthquake might occur within
the next 72 hours. California state agencies and emergency services were
notified. And both times ... nothing happened.
The year 1993 came and went, and no earthquake. Then 1994, 1995, and so on.
Finally, at 10:15 in the morning on Sept. 28, 2004, a magnitude-6
earthquake ruptured the Parkfield section of the San Andreas Fault. The
predicted earthquake had occurred. Or had it?
[image: 140421_TECH_EarthquakeStorms]<http://www.amazon.com/dp/1605984957/?tag=slatmaga-20>
There were important differences between the events of 1934 and 1966 and
the one that occurred in 2004. First, in 1934 and 1966, the ground rupture
began north of Parkfield and propagated south. In 2004 it was in the
opposite direction: The rupture started south of Parkfield and propagated
north. More important, in the dense network of instruments there were no
precursors recorded minutes, hours, or days before the event. There was no
foreshock or increase of seismic activity before the event. There was no
damage to irrigation pipes. There was no measured change in electric or
magnetic fields or in chemistry or level of water wells. Most
disconcerting, there was no measured ground movement: There was no warping
or rise or fall of the ground surface. There was no underground compression
or slight expansion of rock—no dilatancy—and this could be measured with
great precision.
Five instruments known as borehole strainmeters were installed within a few
miles of where the 2004 rupture formed. Essentially, each instrument
consists of a fluid-filled bag stuffed deep down a borehole. If the
surrounding rock is compressed or stretched by a tiny amount—equivalent to
taking a 100-mile-long rigid bar and compressing or stretching one end by
the diameter of a human hair—the bag undergoes a small compression or
expansion. But no change was recorded for weeks to seconds before the
earthquake. As far as anyone can tell, the 2004 Parkfield earthquake was a
spontaneous event.
The Parkfield experiment was successful in identifying *where *an
earthquake would occur and *how *big it would be, though the
all-important *when
*was missed; the event came 12 years too late. Which raises the question:
Will it ever be possible to predict earthquakes?
The answer, as it is seen today, is: maybe.
The question of earthquake prediction can be reduced to a more tractable
and straightforward question: What triggers a large earthquake?
Imagine this: Initially, an earthquake fault, such as the San Andreas, is
relatively quiet. Only a few small earthquakes are occurring, popping off,
in a familiar analogy, like kernels of heated popcorn. Then the popping of
one earthquake kernel happens to set off more kernels, and those set off
more kernels until there is an explosion, or cascade, of kernels popping, a
rupture forms, and a large earthquake is produced.
Or imagine this: The lower region of the San Andreas Fault is slowly
sliding—without earthquakes—because here the rocks are hot and plastic and
are driven to slide smoothly by the slow and constant movement of the
Pacific and North American plates. As the slipping region grows, the
sliding accelerates until it reaches a critical speed to where a rupture
forms in the brittle overlying rock, and a larger earthquake is produced.
In the former case—the cascade model of earthquake kernels—the beginning of
any large earthquake is no different from the beginnings of countless small
ones, which means it is impossible to ever predict large earthquakes.
In the latter case—the pre-slip model—a long process occurs that prepares
the San Andreas for a sudden and major slip. In that case, earthquakes
might be predicted if we can figure out how to measure the slow sliding and
subsequent buildup.
Which idea is true—or whether earthquakes work in some other manner
entirely—is still the focus of much research today and is hotly debated.
But this much is true: When there is a major earthquake, the probability of
another major earthquake happening soon after in the same region goes way
up. Once the Earth's crust starts to adjust to the slow buildup of pressure
between the tectonic plates, that pressure may not be relieved simply as a
single large event but as one—or more—major earthquakes happening in a
short time period.
To put this in concrete numbers: History shows that whenever there is a
major earthquake in California, say a magnitude-6 event, which can do
substantial damage—there is a 1-i- 20 chance that another earthquake of
equal or greater magnitude will happen in the same general area *within the
next three days.*
This leads to a practical concern. After a major earthquake, people should
brace themselves for an equal or larger event. Emergency services, such as
fire and police stations and hospitals, need to prepare for additional
injuries and for the disruption of still more roads and utilities. And for
those who are attempting to rescue people who are already trapped under
debris, those rescuers should be aware that a larger earthquake could
strike and a greater catastrophe may happen.
*Excerpted from *Earthquake Storms: The Fascinating History and Volatile
Future of the San Andreas
Fault<http://www.amazon.com/dp/1605984957/?tag=slatmaga-20>*
by John Dvorak, out now from Pegasus.*
John Dvorak, Ph.D., has worked on volcanoes and earthquakes for the U.S.
Geological Survey.
http://www.slate.com/articles/technology/technology/2014/04/earthquake_prediction_why_the_future_of_the_san_andreas_and_other_fault.html
--
V <http://goog_333603103>ei8 <http://goog_333603103>-Volcanoes of the World
Webcams <http://vei8home.blogspot.com/>
Roxxfoxx~~Adventures in Geology <http://1roxxfoxx.blogspot.com/>
Penguin News Today <http://penguinnewstoday.blogspot.com/>
Penguinology: The Science of Penguins <http://penguinology.blogspot.com/>
Gentoo Penguins of Gars O'Higgins Station,
Antarctica<http://wiinterrr.blogspot.com/>
Canis lupus 101 <http://canislupus101.blogspot.com/>
Through Golden Eyes <http://throughgoldeneyes.blogspot.com/>
Follow me on Pinterest <http://pinterest.com/wiinterrr/>!
Messages in this topic (1)
________________________________________________________________________
________________________________________________________________________
3. Chaiten Makes Snopes
Posted by: "Kim Noyes" kimnoyes@gmail.com noyeskim
Date: Tue Apr 22, 2014 12:59 am ((PDT))
Chile's Chaiten Volcano's eruption of 2008 makes Snopes.com:
http://www.snopes.com/photos/natural/chaiten.asp
--
Check out http://groups.yahoo.com/group/californiadisasters/
Read my blog at http://eclecticarcania.blogspot.com/
My Facebook: http://www.facebook.com/derkimster
Linkedin profile: http://www.linkedin.com/pub/kim-noyes/9/3a1/2b8
Follow me on Twitter @DisasterKim
Messages in this topic (1)
________________________________________________________________________
________________________________________________________________________
4. Another Ejyafjallajokull Stunner
Posted by: "Kim Noyes" kimnoyes@gmail.com noyeskim
Date: Tue Apr 22, 2014 1:23 am ((PDT))
I found this quite by accident... a lucky fortuitous accident:
http://eclecticarcania.blogspot.com/2014/04/another-ejyafjallajokull-stunner.html
--
Check out http://groups.yahoo.com/group/californiadisasters/
Read my blog at http://eclecticarcania.blogspot.com/
My Facebook: http://www.facebook.com/derkimster
Linkedin profile: http://www.linkedin.com/pub/kim-noyes/9/3a1/2b8
Follow me on Twitter @DisasterKim
Messages in this topic (1)
------------------------------------------------------------------------
Yahoo Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/geology2/
<*> Your email settings:
Digest Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/geology2/join
(Yahoo! ID required)
<*> To change settings via email:
geology2-normal@yahoogroups.com
geology2-fullfeatured@yahoogroups.com
<*> To unsubscribe from this group, send an email to:
geology2-unsubscribe@yahoogroups.com
<*> Your use of Yahoo Groups is subject to:
https://info.yahoo.com/legal/us/yahoo/utos/terms/
------------------------------------------------------------------------
__._,_.___
No comments:
Post a Comment