Big Earthquakes Spark Jolts Worldwide

[Shiloh]

Source: http://www.sciencedaily.com/releases/2008/05/080525132352.htm
Big Earthquakes Spark Jolts Worldwide

ScienceDaily (May 26, 2008) ? Until 1992, when California's magnitude-7.3 Landers earthquake set off small jolts as far away as Yellowstone National Park, scientists did not believe large earthquakes sparked smaller tremors at distant locations. Now, a definitive study shows large earthquakes routinely trigger smaller jolts worldwide, including on the opposite side of the planet and in areas not prone to quakes.

"Previously it was thought seismically active regions or geothermal areas were most vulnerable to large earthquake triggers," says Kris Pankow, a seismologist at the University of Utah Seismograph Stations and a co-author of the new study.

But Pankow and colleagues analyzed 15 major earthquakes stronger than magnitude-7.0 since 1992, and found that at least 12 of them triggered small quakes hundreds and even thousands of miles away, according to the findings published online May 25, 2008 in the journal Nature Geoscience.

"We conclude that dynamic triggering is a ubiquitous phenomenon," they wrote.

Pankow conducted the study with seismologist Aaron Velasco and undergraduate student Stephen Hernandez, both at the University of Texas at El Paso; and seismologist Tom Parsons, of U.S. Geological Survey in Menlo Park, Calif.

They analyzed data from more than 500 seismic recording stations five hours before and five hours after earthquakes that registered more than 7.0 on the "moment magnitude" scale, which scientists say is the most accurate scale for large earthquakes. (The frequently cited Richter scale measures only relatively small, nearby quakes).

The data -- obtained from the Incorporated Research Institutions for Seismology, a consortium of universities -- included 15 major earthquakes from 1992 through 2006, including the 1992 Landers quake in California 800 miles southwest of Yellowstone, the magnitude-7.9 Denali fault quake in Alaska in 2002, and the magnitude-9.2 Sumatra-Andaman Islands quake near Indonesia in 2004 that generated a catastrophic tsunami blamed for most of the quake's 227,898 deaths in South Asia and East Africa.

Scientists previously noted that those three major quakes triggered not only nearby aftershocks, but small quakes at great distances. The new study is the first to systematically analyze all the world's big quakes during 1992-2006 and find that most of them triggered distant, smaller tremors. These are different than aftershocks, which occur fairly close to the main quake. After the devastating 2004 Sumatra earthquake, triggered quakes even occurred in Ecuador, on the opposite side of the Earth.

Earthquakes Release Waves of Energy

When an earthquake begins, energy is released in the form of shock waves that move through the ground. The first waves are called P or pressure waves, which move at high speed with an up-and-down motion. The next waves are S or shear waves. These move from side to side, causing much damage from an earthquake. The next waves are two types of surface waves: Love waves move in a shearing fashion, followed by Rayleigh waves, which have a rolling motion.

Pankow and colleagues showed that magnitude-4 or smaller seismic events often are triggered when either Love or Rayleigh waves from a major quake pass a given point.

"We can recognize the different kinds of waves as they pass and can filter out everything except the small seismic events, which are presumed to be local small earthquakes," says Pankow.

There are about 600 small seismic events around the Earth every five minutes. For five hours after the arrival of Love waves from a major quake, the researchers saw a 37 percent increase in the number of small quakes worldwide. And after Rayleigh waves from the same large quake followed the Love waves, the number of small quakes worldwide shot up by 60 percent during the five hours after the major quake.

"It is interesting that Rayleigh and Love waves, two very different types of surface waves, are both able to trigger these events," says Pankow.

In addition to the 1992 Landers, 2002 Denali and 2004 Sumatra-Andaman Islands quakes, the other 12 major quakes in the study (and their moment magnitudes) were: 1998 Balleny Island near Antarctica (8.1), 1999 Izmit, Turkey (7.6), 1999 Hector Mine, Calif. (7.1), 2000 New Ireland, Papua New Guinea (8.0), 2001 Peru (8.4), 2001 Kunlun, China (7.8), 2003 Hokkaido, Japan (8.3), 2003 Siberia, Russia (7.3), 2004 Macquarie Ridge, near New Zealand (8.1), 2005 Sumatra, Indonesia (8.7), 2006 Java, Indonesia (7.7) and 2006 Kuril Islands, Russia (8.3).

Only the Hector Mine, Siberia, and Kuril Islands quakes did not show triggering events in the study. But it is known from previous studies that the Hector Mine earthquake indeed triggered smaller quakes near California's Salton Sea. Those were not included in the study, because they were within about 680 miles of the main shock's epicenter. Researchers excluded triggered quakes within that distance to avoid counting aftershocks in the same category as more distant triggered quakes.

How do the surface waves trigger small earthquakes at distant locations?

"The physical mechanism is not known," says Pankow. "It has been proposed that the passage of the waves may change the water flow in a fault, possibly increasing the number of conduits that water can flow through which could cause the fault to slip."

Other theories are that surface waves may increase the strain on a fault, or loosen a fault so that it prematurely breaks or slides, she adds.


The study was funded by the United States Geological Survey and the National Science Foundation, Pankow says.
Adapted from materials provided by University of Utah.

 

[Sunshine123]

Re: Big Earthquakes Spark Jolts Worldwide

EXTRACT FROM DOUG COPP'S ARTICLE ON THE: 'TRIANGLE OF LIFE'

My name is Doug Copp. I am the Rescue Chief and Disaster Manager of the
American Rescue Team International (ARTI), the world's most experienced
rescue team. The information in this article will save lives in an earthquake.

I have crawled inside 875 collapsed buildings, worked with rescue teams
from 60 countries, founded rescue teams in several countries, and I am a
member of many rescue teams from many countries.

I was the United Nations expert in Disaster Mitigation for two years. I
have worked at every major disaster in the world since 1985, except for
simultaneous disasters.

The first building I ever crawled inside of was a school in Mexico City
during the 1985 earthquake. Every child was under its desk. Every child
was crushed to the thickness of their bones.. They could have survived by
lying down next to their desks in the aisles. It was obscene, unnecessary and
I wondered why the children were not in the aisles. I didn't at the time
know that the children were told to hide under something.

Simply stated, when buildings collapse, the weight of the ceilings
falling upon the objects or furniture inside crushes these objects, leaving a
space or void next to them. This space is what I call the 'triangle of life'.
The larger the object, the stronger, the less it will compact. The less the
object compacts, the larger the void, the greater the probability that
the person who is using this void for safety will not be injured. The next
time you watch collapsed buildings, on television, count the 'triangles' you
see formed. They are everywhere. It is the most common shape, you will see,
in a collapsed building..

TIPS FOR EARTHQUAKE SAFETY

1) Most everyone who s imply 'ducks and covers' WHEN BUILDINGS COLLAPSE are crushed to death. People who get under objects, like desks or cars, are crushed.

2) Cats, dogs and babies often naturally curl up in the fetal position.
You should too in an earthquake. It is a natural safety/ survival instinct. You can survive in a smaller void. Get next to an object, next to a sofa, next to a large bulky object that will compress slightly but leave a void next to it.

3) Wooden buildings are the safest type of construction to be in during
an earthquake. Wood is flexible and moves with the force of the earthquake.
If the wooden building does collapse, large survival voids are created.
Also, the wooden building has less concentrated, crushing weight. Brick
buildings will break into individual bricks. Bricks will cause many injuries but
less squashed bodies than concrete slabs.

4) If you are in bed during the night and an earthquake occurs, simply
roll off the bed. A safe void will exist around the bed. Hotels can achieve a
much greater survival rate in earthquakes, simply by posting a sign on The back of the door of every room telling occupants to lie down on the floor, next to the bottom of the bed during an earthquake.

5) If an earthquake happens and you cannot easily escape by getting out
the door or window, then lie down and curl up in the fetal position next to
a sofa, or large chair.

6) Mos t everyone who gets under a doorway when buildings collapse is
killed. How? If you stand under a doorway and the doorjamb falls forward or
backward you will be crushed by the ceiling above. If the door jam falls sideways you will be cut in half by the doorway. In either case, you will be killed!

7) Never go to the stairs. The stairs have a different 'moment of
frequency' (they swing separately from the main part of the building).
The stairs and remainder of the building continuously bump into each
other until structural failure of the stairs takes place. The people who get
on stairs before they fail ar e chopped up by the stair treads - horribly
mutilated. Even if the building doesn't collapse, stay away from the
stairs. The stairs are a likely part of the building to be damaged. Even if the
stairs are not collapsed by the earthquake, they may collapse later when
overloaded by fleeing people. They should always be checked for safety,
even when the rest of the building is not damaged.


8) Get Near the Outer Walls Of Buildings Or Outside Of Them If Possible
- It is much better to be near the outside of the building rather than
the interior. The farther inside you are from the outside perimeter of the
building the greater the probability that your escape route will be
blocked.

9) People inside of their vehicles are crushed when the road above falls
in an earthquake and crushes their vehicles; which is exactly what happened
with the slabs between the decks of the Nimitz Freeway. The victims of
the San Francisco earthquake all stayed inside of their vehicles. They were
all killed. They could have easily survived by getting out and sitting or
lying next to their vehicles. Everyone killed would have survived if they had
been able to get out of their cars and sit or lie next to them. All the
crushed cars had voids 3 feet high next to them, except for the cars that had
columns fall directly across them.

10) I discovered, while crawling inside of collapsed newspaper offices
and other offices with a lot of paper, that paper does not compact.
Large voids are found surrounding stacks of paper.

Spread the word and save someone's life... The Entire world is
experiencing natural calamities so be prepared!

'We are but angels with one wing, it takes two to fly'

In 1996 we made a film, which proved my survival methodology to be
correct. The Turkish Federal Government, City of Istanbul , University of
Istanbul Case Productions and ARTI cooperated to film this practical, scientific
test. We collapsed a school and a home with 20 mannequins inside. Ten
mannequins did 'duck and cover,' and ten mannequins I used in my
'triangle of life' survival method. After the simulated earthquake collapse we
crawled through the rubble and entered the building to film and document the
results. The film, in which I practiced my survival techniques under
directly observable, scientific conditions , relevant to building collapse, showed there would have been zero per cent survival for those doing duck
and cover.

There would likely have been 100 percent survivability for people using
my method of the 'triangle of life.' This film has been seen by millions
of viewers on television in Turkey and the rest of Europe , and it was seen
in the USA , Canada and Latin America on the TV program Real TV


Kurt Clausen