Detecting P-waves

Earthquake Warning System Coming

American Association of Petroleum Geologists (AAPG)

I feel the earth move under my feet …
– Carole King

Considering they both sneak up on you, earthquakes and love have at least one thing in common.

Clearly, both need early detection systems.

Efforts have been made for at least one of them to have it.

Richard Allen, the director of the Berkeley Seismological Laboratory at the University of California, Berkeley, is the man behind an Earthquake Early Warning System (EEWS), which will give residents of California precious extra time to prepare for such an event, thus saving their lives.

“This is a very exciting time for earthquake early warning in the United States,” he said.

His system – at present, just available to other scientists – will employ seismometers across California that will rapidly detect movements of earthquakes, predict their severity and then issue warnings to those residents who will momentarily – and we mean momentarily – be affected.

The hope is that there will be fewer injuries and death from broken windows, falling ceilings and flying books for individuals – and a less crippled infrastructure for the state.

Specifically, the system will detect the first pulses of energy to reach the surface – the P-wave, or compressional wave, which is the seismic body wave that shakes the ground back and forth in the same direction the wave is moving.

These waves do not carry much energy – but what they do carry, is information, which can be translated into a prediction of the much larger, much more powerful S-waves that come next, shaking the ground back and forth perpendicular to the direction the wave is moving.

Allen says, the more advanced the warning, the less the panic:

“We don’t want people to start running out of buildings.”

‘Roll’ Models

The concept, while fascinating, is not altogether new.

“There are several early warning systems throughout the world,” says Serdar Kuyuk, a post-doctoral Research Fellow at Berkeley, who is working with Allen on the project, “mainly in Japan, Taiwan, Mexico, Istanbul, Italy, Romania.” Kuyuk, in fact, has spent the past four years in Japan studying its early warning systems and says they work – even if they don’t all work the same way.

“As a general concept,” he says, “all systems in the world aim to put seismometers closer to the faults, however, this is not always possible,” he said. “Like Japan, most disastrous earthquakes occur offshore. Fortunately almost all earthquakes are inland events in California.”

The Californian system, as mentioned, already is operational, but until now has been in something of a Beta mode.

“We have about 35 users,” he said, “mainly scientists and test user groups. Our system is not publicly available at the moment.”

That’s changing, Allen says, and that’s exciting.

“We now have the funding to build a prototype system and will be able to fully evaluate what a full public system could do for the West Coast,” Allen said. “Our initial studies have been very encouraging, but now we will be able to start delivering the alerts to a small group of test users and get feedback from the user perspective.”

The hope is that with more state and federal funding, the entire system can be upgraded, which will include sophisticated seismometers that can process the new data.

“Current networks in the United States are not designed for EEW purposes,” Allen said, “because the loggers are not up-to-date and produce high telemetry delays.”

The cost of upgrading the entire California system, Kuyuk estimates, is around $80 million.

Predictions? No!

But even if all the money were allocated and the system worked perfectly, Kuyuk wants to make something clear.

“One of the misconceptions about Earthquake Early Warning Systems is that some people believe it is a prediction of earthquakes,” he commented. “This is absolutely not true. (See the accompanying story on this page.)

“If there is a word to explain what EEWS does,” he says, emphasizing the system’s basic operation, “it is ‘forecasting.’ EEWS uses priory released energy (information) to forecast or to estimate the later disastrous secondary energy.”

For the state, in practical terms, the system would provide enough of a warning for transportation, utility grids, nuclear facilities and schools to take precautionary measures and not designed to give homeowners more time to secure the china or cover up the big screen Panasonic. Further, early warning measures are useless at the quake’s origin because the tremors radiate out almost simultaneously and too quickly to be effective.

To put this another way, Kuyuk said, “Prediction is not possible.”

But the warnings – anywhere from seconds for those closest to the epicenter to as much as a half hour for those hundreds of miles away – will be huge.

It may not be perfect, may not sound like a lot of time, but, as Allen says, it will give those in the quake’s path more time to react.

“You want to get under a sturdy table before things start falling off the wall.”

Smart words … whether it’s the earth or love that starts to rumble.

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Fish Are Flopping And Atlas Shrugs

The Greeks thought earthquakes occurred when Atlas, who held the Earth on his shoulders, literally shrugged.

An ancient Indian tribe in southern Mexico believed they happened when a giant jaguar brushed up against the pillars of the world.

Some ancient Japanese culture believe they were the result of a giant catfish flopping around inside Earth.

And some popes in the 18th century thought they were God’s retribution for humanity’s lack of faith.

Earthquakes – the myths surrounding why they occur are as fanciful as the myths surrounding who can predict them.

Here are a few of those:

Myth 1: Animals can predict quakes.

Various studies, including those by California Geology, indicate that as far back as 373 BC, weasels, rats, snakes and centipedes knew days before a destructive earthquake occurred, but the evidence is anecdotal at best and the rodents aren’t talking.

Myth 2: There are people who can sense an earthquake is about to happen.

True. But these people have about a 50 percent failure rate.

Myth 3: Earthquakes develop in one kind of weather.

Aristotle thought so and said they were caused by winds trapped in subterranean caves.

He was wrong.

Earthquakes occur about equally in cold weather, hot weather and rainy weather.

Myth 4: The ground opens up during an earthquake.

While shallow crevasses can form during earthquake-induced landslides, faults do not open up during an earthquake and swallow up suburban families in mini vans. Movement occurs along the plane of a fault, not perpendicular to it. If it were that way, the friction needed to cause a quake wouldn’t exist.

Myth 5: The position of the moon is a precursor.

Not only is there no significant correlation between the position of the moon and earthquakes, the position of the rest of the planets also have scant little to do with plate tectonics here on earth.

Myth 6: California eventually will break off into the ocean.

It won’t. And the reason is, most of the motion between the Pacific and North American plates is horizontal, not vertical.

It is true, however, that Los Angeles is ever-so-gradually creeping northward and someday will be a suburb of San Francisco! You don’t even want to think about property values when it gets there.

Myth 7: We are having more earthquakes.

Throughout the past century, the number of earthquakes of magnitude 7.0 or greater have remained pretty constant. In fact, data indicate in the past decade the number of quakes actually has decreased.

Worldwide, according to the U.S. Geological Survey’s National Earthquake Information Center, there were 22,235 earthquakes in 2011– or about 61 a day.


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