It was the second strong quake to rock the region in two months. In December, coal mining operations in Russia's largest coal producing region, the Kuzbass, were suspended when a 6.9 magnitude quake hit near Kyzyl. Residents in Kyzyl's city centre gathered outside as the local emergencies ministry warned of potential aftershocks.
to maintain what I consider the most enviable of all titles,
the character of an honest man.**
George Washington
LARGEST QUAKES -
This morning -
5.3 TARAPACA, CHILE
5.0 SOUTHWESTERN SIBERIA, RUSSIA
6.8 SOUTHWESTERN SIBERIA, RUSSIA
5.7 SOUTH OF FIJI ISLANDS
5.1 SOUTH OF FIJI ISLANDS
5.9 TAIWAN
Yesterday -
2/25/12 -
5.1 KURIL ISLANDS
5.2 SAMAR, PHILIPPINES
5.0 KURIL ISLANDS
5.2 KURIL ISLANDS
5.2 SOUTH OF FIJI ISLANDS
5.2 MAUG ISLANDS REG, N. MARIANA IS.
2/24/12 -
5.1 SOUTHERN SUMATRA, INDONESIA
5.3 MOLUCCA SEA
5.2 NORTHERN COLOMBIA
5.0 LEYTE, PHILIPPINES
Japan's earthquake could bode ill for U.S. Pacific Northwest - Scientists are still unraveling last year's giant earthquake and tsunami in Japan, and some of what they're finding doesn't bode well for the Pacific Northwest. Detailed analyses of the way the Earth warped along the Japanese coast suggest that shaking from a Cascadia megaquake could be stronger than expected along the coasts of Washington, Oregon and British Columbia. "The Cascadia subduction zone can be seen as a mirror image of the Tohoku, (Japan) area."
In Japan, the biggest jolts occurred underwater. The seafloor was displaced by 150 feet or more in some places, triggering the massive tsunami. But in the Northwest, it's the land that will be rocked hardest -- because the Pacific coast here lies so close to the subduction zone. "The ground motions that we have from Tohoku may actually be an indication that there could be much stronger shaking in the coastal areas of British Columbia, Washington and Oregon." Cities like Seattle, Portland and Vancouver, B.C., are far enough from the coast that they might dodge the most violent hammering. But all of the urban areas sit on geologic basins that can amplify ground motion like waves in a bathtub. The U.S. Geological Survey is already at work on a new analysis of how hard the ground is likely to shake and how close the rupture zone might come to urban areas the next time the Cascadia subduction zone really lets loose. The last time was in 1700, and the resulting quake was a magnitude 9 -- just like the monster that struck Japan on March 11, 2010.
Japanese scientists are struggling to answer several haunting questions: Why was the quake so big? How did the tsunami swell to such giant proportions? And why was it such a surprise to the world's most earthquake-savvy nation? Seismologists were fooled by a series of small quakes that rocked the area every 35 years or so. They believed each small quake relieved the pressure on the subduction zone -- the boundary where two geologic plates slip past each other as the ocean floor shoves under the continent. Now they realize strain continues to build until the series of small quakes is punctuated by a giant one about every 700 years. Similar quakes and tsunamis struck in the years 869 and 1896, but Japanese scientists failed to look far enough into their own history.
The longest record for a subduction zone is from Cascadia, where scientists have linked buried marshes and submarine landslides with a series of about 22 megaquake quakes going back 10,000 years. The time between quakes ranges from 200 to 1,000 years, with an average of about 500 years. There's no obvious "supercyle" of supergiant quake in Japan. But it is clear that quakes on Cascadia have varied in size. Some geologists argue the magnitude-9 quake 300 years ago was simply average and that the Northwest has been slammed by quakes twice as big in the distant past. Most earthquake scenarios for the Northwest coast project tsunamis of about 30 feet, and scientists still don't know how much that needs to be ratcheted up post-Tohoku. Walls of water up to 120 feet high washed away entire communities on the Japanese coast. "Does Cascadia also have a 40-meter tsunami coming onshore?"
One emerging theory suggests seafloor topography might be key. Oceanic plates dotted with mountains seem to hang up and slip more frequently as they scrape under continental plates. The result is a series of smaller quakes that occur when segments of the fault break. Giant quakes seem to occur most frequently where the seafloor is smooth and featureless, as off the Northwest coast. With no surface bumps and hills to interfere, the two plates can stick together over vast distances. When they slip, the whole fault breaks at once.
'We've got a billion dollar problem, but we don't have a billion dollars.' - Liquefaction in the recent subduction zone earthquake in Japan caused entire buildings to sink several feet lower than they had been previously. The repercussions of last year’s subduction zone earthquake and tsunami in Japan are now being felt in the Pacific Northwest, as experts and disaster managers better understand the enormous risks facing this region, plan for the challenges ahead and prioritize the most urgent needs.
Before the event, scientists knew that similar concerns faced Oregon, Washington, northern California and British Columbia from the Cascadia Subduction Zone. But they have now seen how such long-lasting events produce soil “liquefaction” far worse than expected, the potential for devastated roads and bridges, a collapsed infrastructure and even threats to their economic future. “Just in Oregon we’ve got a billion dollar problem, but we don’t have a billion dollars. The challenge for Oregon and our neighboring states is to prioritize the concerns, and figure out some way to preserve the most critical lifelines – key roads, airports, port facilities and utility networks. In Japan, nearly 30,000 people died, many in the days after the disaster because no one could reach them. We don’t want that to happen here, and we don’t want our economy to collapse.”
The Japanese event has galvanized some action, but much more remains to be done. It prompted the legislature to call for an Oregon Resilience Plan that will explore many of these issues – an emergency transportation plan, needed seismic upgrades, ways to protect life and public safety and allow a shattered region to rebuild. One of the primary lessons from Japan is the enormous damage done by liquefaction - a continued shaking of the ground that turns soils into mush. In events such as this, it is amplified by the sheer length of the event, an earthquake that can shake not just for 30 seconds but up to five minutes.
Many of the soils in Portland, parts of the Willamette Valley and other areas of Oregon, Washington and California are particularly vulnerable to this phenomenon, , which can magnify the distance and extent of damage. “In Japan, entire structures were tilting and sinking into the sediments, even while they remained intact. The shifts in soil destroyed water, sewer and gas pipelines, crippling the utilities and infrastructure these communities need to function. We saw some places that sank as much as four feet.” The data provided by analyzing the Japanese earthquake is now being used by OSU and others to improve understanding of this soil phenomenon and better prepare for it. Many areas from northern California to British Columbia have younger soils vulnerable to liquefaction - on the coast, near river deposits or in areas with filled ground. The “young” sediments, in geologic terms, may be those deposited within the past 10,000 years or more. In Oregon, for instance, that describes much of downtown Portland, the Portland International Airport, nearby industrial facilities and other cities and parts of the Willamette Valley.
The Oregon Department of Transportation has concluded that 1,100 bridges in Oregon are at risk, and fewer than 15 percent of them have been retrofitted to prevent collapse. Lateral movement is also a concern. “Buildings that are built on soils vulnerable to liquefaction not only tend to sink or tilt during an earthquake, but slide downhill if there’s any slope, like toward a nearby river. This is called lateral spreading. In Portland we might expect this sideways sliding of more than four feet in some cases, more than enough to tear apart buildings and buried pipelines.” Japan had excellent building codes, researchers say, and was far better prepared for this type of earthquake than the U.S. will be. Much of the “legacy” infrastructure in the Pacific Northwest was built before these risks were known. “The disaster in Japan just clarifies what we need to do. And it’s not something we can do in a year or two, but something that will take a decade or two. At stake are the lives of our people and the future of our economy, and that’s something that should matter to every individual.”
VOLCANOES -
Hawaii - An UNUSUAL seismic swarm is occurring near the summit of Kīlauea volcano, Hawai`i, and continued to increase as of Saturday. The Ka`oiki seismic swarm began about 5 km (3 mi) northwest of Halema`uma`u Crater on 21 February and has produced more than 1000 quakes so far. Increased activity overnight included four magnitude 4+ earthquakes amongst more than 70 additional earthquakes in the past 24 hours. 78 earthquakes were strong enough to be located beneath Kilauea in the past day: 74 quakes were related to the earthquake swarm, 2 were within the upper east rift zone, and 2 were on south flank faults.
Some of the quakes were felt at the Hawai`i Volcano Observatory where the shaking caused books fall off shelves, and minor damage was reported at the Volcano Golf Course, which is the closest inhabited area located about 3 km from the earthquakes' epicentre. Many of these earthquakes were widely felt on-island. Swarms in this area typically indicate movement between Mauna Loa and Kīlauea volcanoes unrelated to magma migration, but continued long-term pressurization of Kīlauea's summit complicates the local stress field and may have some bearing on the current seismic activity. Similar swarms have occurred in 1990, 1993, 1997, and 2006, some of which lasted up to several weeks.
Iceland - Katla volcano activity update: Minor earthquake cluster. A cluster of minor earthquakes has been showing up under the Katla volcano caldera. This has been following a gradual increase in seismic activity under Katla during the past few weeks. It could be a signal of new volcanic activity to be expected on a timescale of few weeks to months. A new eruption would probably be heralded by a strong seismic swarm, and could start and build up rapidly. It did so in July 2011 when a sudden increase in earthquake activity occurred and there was an small eruption without warning.
TROPICAL STORMS -
No current tropical storms.
