Strike-slip quakes involve the horizontal movement of colliding earth plates, and are typically less powerful than those where there is vertical movement. They are also less likely to trigger big tsunamis, or tidal waves. Sumatra, the westernmost island in the sprawling Indonesian archipelago, has a history of powerful quakes and tsunamis, most triggered by an offshore zone along its entire length, where the Indian-Australian tectonic plate is forced under the Eurasian plate. This creates a deep ocean trench as one plate slides under the other at a rate of several centimeters a year. In this zone, called the Sunda megathrust, stress builds up when the subducting Indian-Australian plate bends the Eurasian plate like a spring board as it moves down into the Earth's crust. Eventually enough stress builds up that the edge of Eurasian plate suddenly jolts upward, triggering an earthquake. The sudden uplift of the seafloor and huge pulse of seawater triggers a tsunami.
Over the centuries, repeated magnitude 8 and 9 quakes have struck along portions of the megathrust zone off the coast of Sumatra, flattening towns and killing thousands of people. Wednesday's event was different, because it occurred further west from the megathrust zone in a fault that runs north-south. This strike-slip fault involved a sudden horizontal movement of the Indian and Australian plates along hundreds of kilometers, preliminary data suggest. The Indian plate and Australian plate are moving relative to each other horizontally at about 1 cm a year. "If all of that ... is taken up on this one fault and if you make some crude calculations about how much slip occurred during this earthquake, say 20 meters. It means that this earthquake shouldn't happen more than once every 2,000 years."
Wednesday's quake caused few casualties and triggered very small waves, despite its magnitude. But the sting in the tale is that it likely to have INCREASED stress on the plate boundaries near Aceh, increasing the risks of another major earthquake in the same area as the 2004 disaster. In addition, research published in 2010 showed that the 2004 Aceh quake only relieved about half the stress that has built up over the centuries along a 400 km portion of the megathrust faultline. That makes another major quake in the area a matter of time.
Adding to concerns, further south along another 700 km portion of the megathrust fault under the Mentawai islands, separate 2008 research said so much stress was building up on this section that one or more major quakes were likely within years. The Mentawai islands, a popular surfing destination, are a chain of about 70 islands off the western coast of Sumatra. They face the city of Padang on Sumatra, home to about one million people and likely to be in the path of any tsunami that is triggered. "I am very confident that we are very likely to have within the next few decades to have this great Mentawai earthquake that will have a magnitude at least as big as yesterday's." And when it does, history shows there will be more than one quake within a few years. A magnitude 8.4 quake in 2007 that struck this part of the megathrust relieved only a small portion of the pent-up pressure. The last time it ruptured was a magnitude 9 quake in 1833 and an 8.4 quake in 1797. "We've had so many big earthquakes around in Sumatra in the past few years that it seems like an awful lot of the faults around there seem ready to go."
'Odd Duck' Indonesia 8.6 Quake Surprises - Scientists say it's RARE for strike-slip quakes to be this large. "It's clearly a bit of an odd duck." Wednesday's quake was followed by a magnitude-8.2 aftershock. Both were strike-slip quakes. The biggest earthquakes tend to occur in subduction zones where one plate of the Earth's crust dives under another. This grind produced the 2004 magnitude-9.1 Indian Ocean disaster and the magnitude-9 Japan quake last year. Wednesday's magnitude-8.6 occurred along a strike-slip fault line similar to California's San Andreas Fault. "A week ago, we wouldn't have thought we could have a strike-slip earthquake of this size. This is very, very large." Wednesday's shaker was the 11th largest since 1900. It's probably the largest strike-slip event though there's debate about whether a similar-sized Tibet quake in 1950 was the same kind. A preliminary analysis indicates one side of the fault lurched 70 feet past the other -- a major reason for the quake's size. By contrast, during the 1906 magnitude-7.8 San Francisco earthquake along the San Andreas - perhaps the best known strike-slip event - the ground shifted 15 feet. The Sumatra coast has been rattled by three strong strike-slip quakes since 2004, but Wednesday's was the largest.
while burly sinners run the world.**
John Dewey
LARGEST QUAKES -
Live Seismograms - Worldwide (They update every 30 minutes)
This morning -
5.0 VANUATU
Yesterday -
4/12/12 -
5.0 OFF W COAST OF NORTHERN SUMATRA
5.3 OFF W COAST OF NORTHERN SUMATRA
5.1 OFF W COAST OF NORTHERN SUMATRA
5.0 OFF W COAST OF NORTHERN SUMATRA
5.1 OFF W COAST OF NORTHERN SUMATRA
5.0 NORTH INDIAN OCEAN
5.1 NORTH INDIAN OCEAN
5.7 NEAR EAST COAST OF HONSHU, JAPAN
5.2 NEAR EAST COAST OF HONSHU, JAPAN
5.0 GULF OF CALIFORNIA
7.0 GULF OF CALIFORNIA
6.0 GULF OF CALIFORNIA
Mexico hit by strong quakes hours, miles apart - Authorities said neither quake left major damage nor victims. The US Geological Survey reported a 6.9 magnitude quake hit the waters between the Baja peninsula and the northern state of Sonora at 12:15 am local time early on Thursday morning in a sparsely populated region, shaking buildings as far away as the capital and sending people rushing out of offices onto the streets.
Are the four big North America West Coast quakes in two days connected? - It's possible, geophysicists say, that quakes off the coast of Oregon, Michoacan, Mexico, and in the Gulf of California ranging from magnitudes 5.9 to 6.9 on the Richter Scale had something to do with the large earthquake that struck near Indonesia.
The 8.6-magnitude earthquake that hit off the coast of Sumatra, Indonesia Wednesday was followed by several decent-size shakes along the west coast of North America, but researchers can't say for certain whether all the temblors were related. But the West Coast quakes were fairly standard for their location. "The Earth is in constant motion. I wouldn't necessarily say it's unusual, but we will definitely be looking at these earthquakes to see if there's any link between them."
It's undeniable that earthquakes can trigger other quakes at close range over a short period of time, phenomena known as aftershocks. At a distance, though, the picture is murkier. Quakes can trigger other quakes in two ways. First, they can put stress on nearby faults, deforming the crust and making another rupture more likely. That mechanism is limited to regions close to the original quake. But earthquakes also send surface waves over long distances. The shaking from Wednesday's Sumatra quake, for example, was picked up by seismic monitoring stations in the United States. The shaking may not deform the crust, but researchers leave open the possibility that it could still jump-start small quakes. "My guess is that the shaking was strong enough to actually trigger a little bit of activity." . But if the West Coast activity of the last few days was related to the Sumatra quake, it wasn't out of the ordinary. "The activity it triggered isn't that much more than was already there. It doesn't add much to the overall danger." Proving that two earthquakes are linked over long distances or more than a couple of hours of time is "one of the toughest challenges we face." With the earthquake records that are available, it hasn't yet been possible to find any firm patterns. "We don't have enough data to say yes, and we don't have enough data to say no."
What researchers do know is that the Sumatra quake was interesting on its own. The quake was a strike-slip quake, meaning the fault moved horizontally, not vertically like the enormous 2004 earthquake that triggered the devastating Indian Ocean tsunami. "This particular earthquake is THE BIGGEST STRIKE-SLIP EARTHQUAKE THAT WE'VE SEEN ANYWHERE, and people are trying to figure out how much motion was on the fault. Either the fault went deeper or was under more strain than seismologists had realized. It's too soon to say exactly what we'll learn. "So far, we're just surprised."
Easter 2010 Baja earthquake shook up view of Southern California faults - A new scientific study reveals that fault networks near the Salton Sea are even more complex than previously known — but what that may mean for earthquake potential in the region remains uncertain.
The U.S. Geological Survey and California Geological Survey released a study last month that found the Easter Day quake in northern Baja California on April 4, 2010 — the biggest quake to shake the Coachella Valley in recent years — triggered surface movement on many faults in the Imperial and Coachella valleys. The magnitude-7.2 quake revealed faults southwest of the Salton Sea that were not previously known to scientists, and confirmed that other known faults were active. It's not a finding that will quickly lead to the development of a reliable earthquake warning system, a primary goal of scientists. But it advances knowledge and will direct future research on one of the most intricate and studied fault zones on Earth.
The Baja earthquake “has provided a geological treasure trove to our understanding of what is happening tectonically in this expansive region of northern Mexico and Southern California." The 2010 Easter Day quake, dubbed the El Mayor-Cucapah quake by scientists, killed four people and injured more than 100 in Mexico and caused an estimated $440 million in damage in the Mexicali Valley of Baja California and $90 million in damage in the Imperial Valley. The movements the quake caused on Southern California faults occurred at the surface and were very small, only centimeters. Similar fault movements were also observed after a magnitude-5.7 aftershock on June 14, 2010. The discoveries show earth scientists that “the transfer of strain among the various faults in this region is not as simple as we thought before."
Earthquakes like the El Mayor-Cucapah quake involve the sudden release of built-up energy from two of the Earth's tectonic plates moving against each other as one of the plates slips past the other. The quake was the largest in the northern Baja region in the past 120 years. Research shows that historically, the southern San Andreas fault that runs along the Coachella Valley's northern edge has had a major earthquake every 150 years. But it's been at least 300 years since the last major temblor on that section of the fault.
The 2010 event, a so-called triggered slip, occurred near the surface, from a few hundred meters to about 3 kilometers in depth — not far enough down to set off a major earthquake on the San Andreas. “Those big earthquakes happen about 10 to 15 kilometers below the surface. These triggered slips do not affect that area, so they are not loading or unloading the faults.” Many of the new faults are in remote areas of federal land managed by the U.S. Bureau of Land Management and are unlikely for development. “Now that we know about all of these new faults, it may be just the first step in understanding what the seismic hazard is down there."
Southern Utah quake is a reminder of what's to come - Utah has had several small earthquakes within a year with the most recent being a 4.8 Wednesday night. However, the state is expecting "the big one" at any time. Utahns are gearing up. “I just think about the glass breaking. That would be pretty scary." Buildings like Utah’s Capital have been remodeled, but some run the risk of collapsing. “So what you have underneath the capital are 264 base isolators. Each one weighs 5 thousand pounds and they are designed to move independently of the capital." An earthquake won't show mercy. “It can cause landslides, rock falls, it can set a home loose from its foundation and send it down a cliff."
VOLCANOES -
Iceland - Signs point to imminent major volcanic eruption. This month marks the second anniversary of the eruption of Iceland's Eyjafjal-lajokull volcano, which sent up ash that closed European airspace, stranded mil-lions and cost airlines $200 million a day for six days. Alarmingly, there are signs of high activity beneath the much larger, neighbouring Katla caldera in Iceland. For centuries, Katla has erupted on average every 60 years, so it is 30 years over-due. Instruments have detected ground movement and rising heat levels inside Katla, indications that magma has risen to shallower depths. Katla's eruption in 1918 produced five times as much ash as the 2010 Eyjafjallajokull one. A major eruption could result in large parts of Iceland being flooded as snow and ice melt, significant poisoning of Icelandic agriculture, destruction of property, and grounding of aircraft across Europe. [Media hype?]
UK in Talks with Iceland to Tap Geo Thermal Energy from Volcanoes - The UK government is planning to power up British homes with the help of geo thermal energy, generated from the Icelandic volcanoes. Plans are on the pipeline to lay thousands of miles of high-voltage cables across the ocean floor to pump low-carbon electricity into the UK. "We are in active discussions with the Icelandic government and they are very keen."
The energy minister is planning to visit Iceland in May to discuss connecting the country to its abundant geothermal energy resources. He claims that by using the geo thermal energy produced by the volcano, energy bills in Europe can be reduced. The geo thermal energy would be transported with a huge Interconnector cable which would have to be 1,000 to 1,500 km long. "The cables are an absolutely critical part of energy security and for low carbon energy." The UK government officials said that the interconnectors will require large investment. The Britain and Netherland interconnector cost around £500 million.
"Interconnectors are the cheapest way of backing up wind, because you avoid the greater capital cost of building power stations. We will of course be buying power in when the wind is not blowing, but the interconnectors mean we can sell our wind power when it does, and we have the best wind resource in Europe." But the head of the environment and energy at the think-tank Policy Exchange is of the opinion that major new interconnection in north Western Europe might not offset much of the backup plant due to high pressure winter and weather patterns that can extend low wind conditions right across Europe.
TROPICAL STORMS -
No current tropical storms.
EXTREME HEAT & DROUGHT / WILDFIRES / CLIMATE CHANGE -
Drought and floods fears in England: Experts warn of extreme weather shift - Two unusually dry years have left large parts of England suffering from drought or dry conditions. The drought conditions gripping swathes of England could increase the risk of flash flooding in the face of heavy rain, the Environment Agency warns. Two unusually dry years have left the whole of the South East, East Anglia and parts of Yorkshire in a state of drought, with parts of the South West and the Midlands also suffering from dry conditions.
Seven water companies introduced hosepipe bans in a bid to conserve supplies in the face of low river, reservoir and groundwater levels - a move that was followed by widespread rain, which proved a welcome relief for gardeners. But the Environment Agency is warning that future heavy rain could lead to flash flooding as a result of the drought conditions. Dry, compacted soils mean that rainfall is less easily absorbed into the ground, increasing the likelihood of flooding if the country is hit by storms. The Environment Agency said a dry winter and spring in 2007 contributed in some areas to the devastating floods in the summer of that year, which hit the West Country, Midlands and Yorkshire. Parts of the country had similar conditions as those currently seen in drought-afflicted areas, before the heavy rain hit in June and July 2007.
The Environment Agency made its warning about the increased risk of flash flooding as it launched the first social media flood warning application on Facebook. "Floodalerts", which can be found by putting the term into Facebook's search facility, uses live flood warning data from the Environment Agency. The Environment Agency hopes the new measure will complement its existing Floodline Hotline and website updates to help warn people of the risk of flooding. "As the drought in England continues, the thought of flooding may be far from people's minds, but we cannot ignore the risk. Dry and compacted ground means that there is a greater risk of flash flooding if there is heavy rainfall, and stormy seas and high tides can produce floods at any time. Being prepared is vital to help reduce the risk of flooding."
