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From the AP

PORTLAND, Ore. (AP) -- A widespread earthquake is taking place beneath the Northwest, slowly unleashing energy that may be equivalent to the magnitude 6.7 Nisqually quake that rocked the region two years ago, experts say.

But the so-called "silent" or "slow" earthquake is releasing that energy over weeks rather than in the sharp, seconds-long jolts of a typical quake. No one can feel it.

The event started Feb. 26 and seems to be sputtering to a halt far beneath northwest Washington and southwest British Columbia. The quake originated beneath the Strait of Juan de Fuca near Friday Harbor, Wash., and Victoria, British Columbia.

Recently discovered silent quakes, which can only be detected with sensitive instruments, aren't as harmless as they may seem.

Scientists say they may be adding to the tremendous pressure in an area where the brittle rocks of two tectonic plates are locked offshore.

Evidence shows that every few hundred years, the jammed plates release that stress in huge magnitude 8 or 9 earthquakes that can rattle the entire Northwest coast and generate lethal tsunamis. The last such powerful subduction-zone quake occurred about 300 years ago.

"These slow slips aren't reducing the stress on the locked zone," said Herb Dragert, a research scientist with the Geological Survey of Canada in Sidney, British Columbia. "They're actually, in little pulses, adding a tiny bit of stress to the locked zone."

About every 14 to 15 months, the slow-motion earthquakes are generated about 15 to 30 miles deep at the interface of the lower Juan de Fuca tectonic plate and the upper North American plate.

In that area, called the "slip" zone, the rocks are hotter and more flexible than in the locked zone 30 to 60 miles farther west, allowing the plates to pass each other more easily.

"What is going on for those 14 to 15 months is that things are stickier in the slip zone," Dragert said. "Then the slip happens -- the sticky portion is released -- which adds stress to the locked zone" as the North American plate shifts westward toward it.

The locked zone is causing the western edge of the normally westward-moving North American plate to compress and be shoved eastward about a half inch each year along the coast. However, each slow earthquake reverses that eastward motion, allowing the North American plate to rebound westward by about 0.08 to 0.16 inches during the course of the quake.

The earthquakes weren't detected until data was obtained from the global positioning system, or GPS, a network of 24 orbiting satellites with instruments that can measure tiny movements of ground-based stations.

Scientists have found that the silent earthquakes' signals show up on seismographs, but until recently they were overlooked because they don't look similar to the signals from regular earthquakes.

The discovery of the silent quakes provides a new tool for monitoring the fault zone that could rupture into a powerful subduction zone earthquake, an event that occurs near the coast on average about every 500 years.

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If you live in the ``pink'' or ``red'' zones, you could be in trouble, scientists and government officials warned in San Jose today as they unveiled a new earthquake shaking map for the state of California.

For the Bay Area as well as most of Southern California, the map colors are very, very warm. In fact, nearly all of coastal California from north of Eureka to the Mexican border, where more than 70 percent of the state's population lives, is red. So are the southern inland deserts.

The new seismic shaking map shows the potential danger of the strongest earthquakes over the next half century based on fault lines, shaking intensity, earthquake intervals and soil conditions.

Using different colors to show intensity, the map indicates the maximum shaking that could occur from likely sources of future temblors throughout the state.

Areas in pink and red are at the greatest risk of a damage by earthquakes; at the other end of the map's spectrum, those in dark green have the lowest risk.

But the entire state is ``at risk for earthquake damage,'' said Dallas Jones, director of the state Office of Emergency Services. The map, he said, ``serves as a reminder for California residents to practice earthquake preparedness.''

The map was unveiled during the Disaster Resistant California Conference at the downtown Fairmont Hotel, attended by several hundred scientists, emergency, city and school officials and private and nonprofit organizations from throughout the state.

It is different than the ``ShakeMaps'' created online with data from sensors all over the state that show shaking from a single earthquake minutes after it occurs. This map shows the potential damage to help emergency managers focus limited resources on areas that computer models indicate are at greatest risk, Jones said.

The map is a joint product of the Governor's Office of Emergency Services, the California Seismic Safety Commission, the California Department of Conservation's Geological Survey and the U.S. Geological Survey. It is available online at http://www.seismic.ca.gov/sscpub.htm

State OES director Darrell Young said this map is purposely broad. But specific maps showing the risk for individual blocks can also be downloaded from the same site.

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Yellowstone Park Getting
Hotter - Closes Volcanic Basin
From The Yellowstone Newsletter
8-1-3

Yellowstone National Park Superintendent Suzanne Lewis announced that due to high ground temperatures and increased thermal activity that could affect visitor and employee safety, a portion of the Back Basin at Norris Geyser Basin on the west side of the park has been temporarily closed. Yellowstone's more popular features within the Norris Geyser Basin, including Steamboat and Echinus Geysers and all of Porcelain Basin, remain open to the public.

The temporary closure is clearly marked and covers most of the western portion of the Back Basin trail starting at the Norris Museum. There are approximately 12,500 feet of trails in the Norris Geyser Basin-with approximately 5,800 feet affected by the temporary closure.

Norris is the hottest and most seismically active geyser basin in Yellowstone. Recent activity in the Norris Geyser Basin has included formation of new mud pots, an eruption of Porkchop Geyser (dormant since 1989), the draining of several geysers, creating steam vents and significantly increased measured ground temperatures (up to 200 degrees Fahrenheit). Additional observations include vegetation dying due to thermal activity and the changing of several geysers' eruption intervals. Vixen Geyser has become more frequent and Echinus Geyser has become more regular.

Park staff continue to monitor temperatures and thermal features in the area. When conditions have returned to acceptable ground temperatures and stable surface conditions have improved, the trail will be reopened. Norris is another example of Yellowstone's thermal features that are constantly evolving and changing.

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Johannesburg

United Nations agencies in the Comoros on Monday said plans for the evacuation of civilians were underway following reports of a possible volcanic eruption on the main island of Grande Comore.

"Some of the major UN agencies are currently working together to come up with an emergency response contingency plan. It still is not clear when the eruption will occur, or if it will occur at all, but we are preparing for a number of possible scenarios," acting UN Resident Coordinator Kalula Kalambay told IRIN.

Since last week the country's National Scientific Research and Documentation Centre has reported an increase in seismic activity around the Kartala volcano, situated in the centre of the southern half of Grande Comore. The volcano last erupted in July 1991.

Kalambay added that in the worst-case scenario, up to 70,000 residents may be affected. "But it is difficult to put an exact number on just how many people are likely to need assistance. We are concerned mainly for villagers living in the southern and central parts of the island. But these things are unpredictable - if Moroni is affected, all the islands will be affected, since all of them depend on services which they mainly get from the capital," he said.

There were also possible health concerns, but Kalumbay said aid agencies were equipped to set up epidemic surveillance systems. "Should safe drinking water become scarce, we will be looking at signs of diarrhoea and cholera. Fortunately, there are coordinating mechanisms in place to deal with cholera, so we are prepared," he said.

Another concern was the ongoing tension between the Union government and authorities on Grande Comore. Since the devolution process in 2001, the three islands of Moheli, Anjouan and Grande Comore assumed authority over most of their own affairs. However, there has been growing confusion over administrative functions and Kalambay said this stalemate could undermine preparations to counter the effects of a possible eruption.

"We have impressed upon the relevant authorities the need for them to start talking to each other, so that we all can come up with a comprehensive emergency plan which would benefit all the people of the island," Kalambay stressed.

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