Wednesday, September 25, 2013
Tuesday, September 24, 2013
Wednesday, September 18, 2013
Posted by Guihon at 8:46 AM
Although the overall number of earthquakes recorded on the United States Geological Survey’s real time earthquake map for the week of 12-18 September isn’t significantly different from the previous week, it was nevertheless relatively quiet at the top end of the scale with just one earthquake of at least magnitude 6 (≥M6.0) and 18 of ≥M5.0.
These larger tremors were scattered across the globe, with noteworthy events on ocean ridges in the South Atlantic and eastern Pacific and tremors in Greece and Georgia.
The Week’s Largest Earthquake: M6.1 Alaska
At just M6.1, the largest earthquake of the week was nothing out of the ordinary, particularly not for its location. Along with three more of the ten largest tremors, this quake represents an aftershock from the M7.0 which struck on 30 August.
So far there have been around 60 aftershocks of at least M4.5 and over 300 of all magnitudes. The repercussions of major shocks such as this can be expected to carry on for weeks or even months.
Arguably the most interesting earthquake this week is the M5.0 which occurred in Eritrea. Geologically, this area is fascinating: A rising plume of rock sourced from deep within the earth is lifting the crust and will in time initiate continental breakup of Africa, with a new ocean forming between Ethiopia and Sudan.
The M5.0 of 18 September had its epicentre in Eritrea, north of the main hot spot.
This region is known as a triple junction, with ocean ridges along the axes of the Red Sea and Gulf of Aden already splitting Arabia from Africa and creating new ocean crust. The third arm, the East African Rift, propagates southwards to become the Great Rift Valley. With such dynamic processes in action, it’s unsurprising that this area is characterised by extensive volcanism and accompanied by earth tremors, although large earthquakes in the area are rare.
US Earthquakes: The Western States
The majority of significant earthquake activity in the States this week continued to be in Alaska. Elsewhere there was no outstanding noteworthy event, but this in itself offers an opportunity to look at the overall pattern of tremors and to get some idea of the relationship between earthquakes and topography.
The San Andreas fault zone, a major plate boundary, is clearly dominant but other, older margins are equally important.
To understand the complex geological history of California, even at a very simple level, we need to understand that the US west of the Rockies is made up of various geological blocks which over time have ‘docked’ with continental North America. The boundaries of these blocks are structurally relatively weak – as is indicated by the broadly linear pattern of seismic activity. It’s also worth noting the scattering of tremors in and around Montana-Idaho-Wyoming, which results primarily from volcanic activity associated with the Yellowstone hot spot.
Creative Processes Cause Earthquakes
The Eritrean earthquake, and its association with the Afar mantle plume, is exciting because it reminds us that earthquakes are not merely part of a destructive process – even though most major tremors are associated with subduction and melting of oceanic crust. The constructive processes by which new crust is created also involve enormous crustal forces and, as a result, are capable of generating noteworthy earthquakes.
United States Geological Survey. Real time earthquake map. Accessed 18 September 2013.
Yeats, R. Active Faults of the World. (2012). Cambridge University Press.
Posted by Guihon at 8:01 AM
Monday, September 9, 2013
By SARAH PARVINI Associated Press
In the backyard of his remote Southern California home, Bernie Jones is etching an unconventional blueprint: a construction plan to build his underground survival shelter. It won't be the typical, cramped Cold War-era bunker. It will hold 20 people.
Part of a small but vocal group of survivalists in Menifee, some 80 miles east of Los Angeles, Jones, 46, has pushed for the right to build a bunker on his 1-acre property for nearly a year. He wants to be ready for anything, be it natural disaster or a nuclear attack.
"The world is taking a change," he says. "I want to be prepared. I want my family to survive."
Residents of the small city once known for its farming and mining can begin applying for permits to build their subterranean housing this month after the City Council passed a hotly contested ordinance allowing the practice.
Americans have been building underground bunkers for decades, their interest in such shelters waxing and waning with current events. Many dug backyard fallout shelters during the Cold War, fearing a nuclear war.
This next generation of bunkers comes as many survivalists face heightened concerns of a terrorist attack, economic meltdown and for some, even solar flares or meteor showers.
"The bunker is a type of security blanket," says Stephen O'Leary, an expert in apocalyptic and end-of-the-world theories at the University of Southern California. "They are concerned with what's happening in the world on a massive scale."
The move to allow below-ground bunkers has created waves among city officials who are concerned with earthquake faults in the area, safety of police and first responders answering emergency calls and the potential for owners to hide criminal activity, such as drug manufacturing.
"Most people are going to use their bunkers for good reason, but you do have some sick people out there," Deputy Mayor Wallace Edgerton says. "Children have been held in bunkers."
In February, a 5-year-old boy was held hostage for six days in an Alabama underground bunker, which was rigged with explosive devices.
City Councilman Tom Fuhrman calls the ordinance a victory for property rights, not for those looking to break the law. "Criminal activity isn't going to be stopped by not allowing people to build bunkers," Fuhrman says. "A criminal will find a place to commit crime."
There are signs survival bunkers are making a comeback throughout the country.
Ronald Hubbard, who runs Atlas Survival Shelters near Los Angeles, ships his luxury bunkers out of state. Unlike Cold War-era shelters, he builds ones that are half the length of a basketball court and have a master bedroom, dining nook and a couch to watch a 47-inch flat screen TV.
Hubbard says his phones rang nonstop last December as people attempted to prepare for the end of the world that never came. A 5,125-year cycle in the Mayan calendar passed by, sans disaster.
The Perseid meteors soaring through the sky last month had customers calling him constantly, looking for a way to stay safe in case one hit Earth — even though it's an annual celestial event. He insists his customers are practical people — not radical doomsday preppers.
"I'm not fear mongering," Hubbard said, standing beside a $65,000 shelter in his warehouse. "Why do we buy insurance? Just in case."
The Vivos shelter networks in Indiana and Kansas offer the equivalent of doomsday timeshares in underground communities in the event of the apocalypse. The network aims to protect its inhabitants for up to a year from myriad catastrophes, including a nuclear disaster.
Preppers — who dedicate their time to ensuring they are ready for a host of deadly scenarios — even have their own reality TV show.
People should spend time preparing for likely disasters instead of Armageddon, said Steve Davis, president of emergency management company All Hands Consulting.
"In California, you have earthquakes. On the East Coast, you have winter storms," Davis says. "People should be focusing on basic preparedness."
Jones, who has six children and seven grandchildren, says he simply wants to protect his loved ones. The contractor has already stocked his home with medical kits and enough food for his family to survive for about three months should a disaster strike.
He keeps a bag in his truck packed with five days' worth of food and water, a raincoat, a thermal and "the world's smallest sleeping bag."
"It's all part of being ready for whatever happens," Jones says.
Follow Sarah Parvini on Twitter at http://www.twitter.com/parviniparlance
Posted by Guihon at 1:40 PM