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Unusual Fault Pattern Surfaces in Earthquake Study
 This 3-D view of the surface rupture of the April 4, 2010, El Mayor-Cucapah earthquake (red line) reveals a new fault line connecting the Gulf of California with the Elsinore fault, which could become a major part of the boundary between the Pacific and the North America Plates. Image credit: Caltech Tectonics Observatory |
Like scars that remain on the skin long after a wound has healed, earthquake fault lines can be traced on Earth’s surface long after their initial rupture. Typically, this line of intersection between the area where the fault slips and the ground is more complicated at the surface than at depth.
But a new study of the April 4, 2010, El Mayor-Cucapah earthquake in Mexico reveals a reversal of this trend. While the fault involved in the event appeared to be superficially straight, the fault zone is warped and complicated at depth.
The study-led by researchers at the California Institute of Technology (Caltech) and documenting findings from the magnitude 7.2 event, which was centered in the Baja California state of Mexico-is available online in the journal Nature Geoscience.
The El Mayor-Cucapah earthquake happened along a system of Read more…
Scientists warn volcanoes in Australia are due to erupt
Scientists are now warning that volcanoes in Western Victoria and South Australia are due to erupt. The prediction comes just hours after two earthquakes hit the state this morning.
Using new dating techniques, University of Melbourne scientists have found that the volcanoes usually erupt every 2000 years, with the last eruption at Mt Gambier, South Australia, 5000 years ago. It comes as Victorians are warned to brace themselves for more tremors after a shallow magnitude quake hit at 11.32am, sending shockwaves through towns and suburbs more than 100 kilometres away. A series of tremors lasting up to 15 seconds have been felt across Melbourne’s CBD and southeastern suburbs. A second, smaller quake shook Korumburra, with reports it was again felt in Melbourne, at 12.37pm
Some Victorians say their houses shook violently for about 10 seconds, and many reported hearing the earth rumble. Experts say the quake struck 8 kilometres underground, and said the epicentre was about 7km west of Korumburra. So far, there are no reports of any major damage, except hairline cracks in some peoples’ homes. The area in Gippsland is prone to Read more…
Case Study: Tsunami in Seaside, Oregon
Oregon Coast’s Vulnerability
Recent research suggests that a Cascadia Subduction Zone earthquake could create tsunami waves that impact over 1,000-km of coastline in the U.S. and Canada. Source: USGSThe northwestern coast of Oregon is susceptible to both local and far-field tsunamis. The Cascadia Subduction Zone, where the eastward moving Juan de Fuca plate meets the westward moving North American Plate, is just off the Pacific Northwest coast of the United States and Canada. It is a 750-kilometer long fault zone. This area is very active tectonically, and therefore has the potential to produce large earthquakes and possibly, subsequent tsunamis. This subduction zone is thought to have last ruptured in 1700.
Additionally, far-field earthquakes throughout the Pacific are also capable of spawning tsunamis that could eventually reach the Oregon coast. Historical records show that since 1812, about 28 tsunamis with wave heights greater than one meter have reached the U.S. west coast. The March 1964 “Good Friday” earthquake created the most devastating of these tsunamis. The epicenter of this earthquake was near Anchorage, Alaska. The tsunami that followed this earthquake reached coasts all along the western U.S. within six hours. Cannon Beach, a small coastal community in northwestern Oregon was inundated during Read more…
Tectonic plates rattle- more turbulence at the South Pole
June 21, 2011 – ANTARCTICA – A 5.5 magnitude earthquake struck the South Sandwich Islands region, situated around 750km south east of South Georgia, in the South Atlantic early Sunday. It was the latest in a series of quakes to hit the Antarctic Region during the past 24 hours. The moderate quake struck at 9.37am GMT at a depth of 137km and was centered 69 km (42 miles) NNW of Visokoi Island and 330 km (205 miles) NNW of Bristol Island. The last significant earthquake to be recorded in the South Sandwich Islands region occurred on Read more…
Magma Proves Undersea Volcanoes Do Explode
Deep-sea volcanoes can explode instead of just oozing, scientists now confirm.
The new proof — higher-than-expected levels of carbon dioxide in the magma from a volcano off the coast of Oregon —suggests the volcanoes may play a greater role in global climate than thought.
Of all the volcanic activity on Earth, 75 to 80 percent of it takes place at deep-sea ridges in the middle of the oceans. Most of these volcanoes apparently spew out huge volumes of lava instead of erupting explosively, as many volcanoes on land do.
It is a high level of gas trapped in a volcano’s magma that normally fuels explosive volcanic bursts. This level has long been thought to be low at mid-ocean ridges; moreover, potential undersea explosions would be suppressed by the crushing pressure from the surrounding water.
However, based on volcanic ash found at certain sites, geologists have speculated over the last decade that explosive eruptions do take place in deep-sea volcanoes. Now researchers say they have proof.
The Juan de Fuca ridge lies between the separating Pacific and Juan de Fuca tectonic plates. Credit: USGS
A team of scientists used ion beams to analyze the composition of materials recovered from ash deposits on Axial Volcano, on the Juan de Fuca Ridge off the coast of Oregon. Trapped within crystals from the deposits were droplets of magma containing very high levels of carbon dioxide. These droplets revealed that the magma was indeed rich in gas, at concentrations high enough to generate bubbles in the molten rock for explosive underwater eruptions.
“Direct evidence for high carbon dioxide concentrations in a mid-ocean-ridge volcano was unexpected and surprising,” researcher Christoph Helo, a volcanologist at McGill University in Montreal, told OurAmazingPlanet.
These findings suggest the amount of the global-warming gas carbon dioxide that is released from the deeper mantle into the Earth’s atmosphere at mid-ocean ridges falls within the higher end of past estimates, nearly 10 times more than the lowest end. That could have key implications for climate change.
Still, Helo said, volcanic carbon dioxide, unlike man-made emissions, “is not a variable that has undergone drastic changes within the past century.”
The scientists detailed their findings online March 13 in the journal Nature Geoscience.
Geologists warn another earthquake could tear Tokyo in two after weakening of fault line below capital
Geologists have warned that another powerful earthquake could inflict terrible damage on Tokyo because the Size 9 monster which struck on March 11 has altered the earth’s surface.
The quake has put pressure on the fault lines near the Japanese capital and experts have suggested that a size 7.5 magnitude earthquake could hit.
The structure of the tectonic plates and fault lines around the city makes it unlikely that Tokyo, home to 13million people, would be hit by a quake anywhere near the intensity of the one 10 days ago, said Roger Musson of the British Geological Survey.
Bustling: The busy Japanese capital Tokyo has 13million people living in its centre – and it could be Read more…The megaquake connection: Are huge earthquakes linked?
The recent cluster of huge quakes around the Pacific Ocean has fuelled speculation that they are seismically linked. New Scientist examines the evidence
A wave of activity (Image: Bernd Settnik/EPA/Corbis)
AT 2.46 pm local time on Friday last week, Japan shook like never before. The magnitude 9.0 earthquake wrenched the main island of Honshu 2.5 metres closer to the US and nudged the tilt of Earth’s axis by 16 centimetres. At the epicentre, 130 kilometres offshore, the Pacific tectonic plate lurched westwards, and a 10-metre-high tsunami sped towards the coastal city of Sendai and the surrounding region.
The devastation caused by the events is difficult to exaggerate – estimates suggest the number of fatalities could top 10,000. One of the few consolations is that quakes of magnitude 8.5 and above are rare: the Sendai earthquake is in the top 10 of the highest-magnitude quakes of the last 100 years.
Yet three of these – the December 2004 Sumatra quake, the February 2010 Chile quake, and now Sendai – have struck in just over six years. This presents a horrifying possibility: Read more…
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