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Yes, Virginia, it was an earthquake.

It was immediately apparent from the news coverage on Tuesday, August 23, 2011 that people on the East Coast of the United States are not at all accustomed to having the ground move beneath them. Reactions ranged from “I thought it was a terrorist attack” to “Scary!”, and the story displaced other national and even international news stories for days.

People generally did the wrong thing during the quake – many ran outside, even though FEMA recommends that people who are inside a building stay where they are , drop, take cover, and stay away from windows and other glass (http://www.fema.gov/hazard/earthquake/eq_during.shtm). Even the US Geological Survey office in Reston, Virginia was evacuated!

On the West Coast, where I happened to be during the quake (in Seattle), people in general (and news anchors in particular) took great pleasure in comparing the Virginia quake to others of similar magnitude that happen much more frequently in the seismically active Northwest. Lots of ribbing and mocking – mostly good natured – took place in the days that followed the quake.

East Coast earthquakes are much less common than West Coast earthquakes, because the eastern edge of the United States is what is called a passive continental margin. It is the edge of a continent (North America), but it is not the edge of a plate, and the edges of plates are where most seismic activity tends to occur. The edge of the plate on which the North American continent is riding is in the middle of the Atlantic Ocean, at the Mid-Atlantic Rift. That is where the North American Plate is moving apart from the Eurasian Plate (and, further to the south, the African Plate); earthquakes (and volcanic activity, as well) do indeed occur along that rift boundary.

Actually, East Coast earthquakes happen all the time; they’re just usually not this powerful. The August 23 quake was the strongest ever measured in Virginia. The causes of many of these intraplate earthquakes are not thoroughly understood. Some involve the activation of old, deep-seated faults. The area in which this particular quake occurred, the Central Virginia Seismic Zone, had experienced seismic activity before, but not along known, measured faults. The largest known historic earthquake in this area was a bit father to the west, in 1875, and was likely a bit less powerful than the 2011 quake. 

One geophysicist explained the cause of intraplate earthquakes like this: Imagine a plate the size of North America that is being jostled around on all sides by interactions with other plates. Obviously most of the earthquake activity will take place around the edges, but you’re also bound to be building up some stresses in the middle of the plate, too, which will eventually cause earthquakes to occur in the middle of the plate.

The details of the 2011 and historic quakes in the Central Virginia Seismic Zone can be found at the USGS Earthquake Hazards website (http://earthquake.usgs.gov/) . This is a truly rich resource that you should check out, if you haven’t already.

Of real concern is the lack of earthquake preparedness in the East. The general panic and uncertainty about what to do highlights this lack of preparedness. Another aspect is the general state of earthquake resistance of buildings in the East. Many older buildings are actually better suited to survive earthquake shaking than modern high-rises, which – unless specifically engineered to be earthquake-resistant, as they are typically now on the West Coast – are more likely to be rigid and subject to failure during seismic shaking. An interesting site with much information about cutting-edge research on earthquake engineering, damage assessment, and architecture is the Consortium of Universities for Research in Earthquake Engineering (http://www.curee.org/).

An additional educational resource that is worth checking out is Teachable Moments, provided by the University of Portland and IRIS Education and Outreach (IRIS is Incorporated Research Institutions for Seismology). You can find a Teachable Moment about the August 23 Virginia earthquake at http://www.iris.edu/hq/retm, and you can sign up to be on the Teachable Moments list-serv at the IRIS website (http://www.iris.edu/hq/programs/education_and_outreach/).

 Barbara Murck

CHANGING GEOGRAPHIES: THE DOMINO “THEORY” AND THE ARAB “SPRING”

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Geomorphology and Archeology

Archaeology is a fascinating discipline that allows scientists to visualize how people lived in the past. Although such investigations are usually associated in most people’s minds with Native American sites, they can also tell us a lot about overall American history. Because archeological sites are most commonly found buried in Earth, geomorphologists often assist with site interpretation to understand the depositional environment associated with the site. The following video demonstrates this interrelationship at Michigan State University where a team of scientists were given access to what was thought to be a sand dune on the campus to test its age. The accompanying photo shows this feature, which is covered with pine trees planted in 1913 to protect it from the wind. Apparently, blowing sand was a problem in the early days of the university. Given my interests in sand dunes, I had long been interested in the age and formation of this landform. It sure looked like a stabilized sand dune, but its location in the middle of the MSU campus was weird. What are the odds that an old sand dune was in the middle of the MSU campus? I needed to look inside the landform, and collect samples for dating, but was unable to gain access to the feature until the campus archaeologist was told some new trees would be planted. What we learned surprised all of us. The video also discusses the campus archaeology program at the university and it has contributed to our understanding of MSU’s past.

Have a look at the video at:

I can be followed on twitter at: www.twitter.com/ArbogastDPG

Posted by: Alan Arbogast, Michigan State University

Japan’s Tsunami

The most active tectonic boundary on earth is the Pacific Ring of fire. This boundary occurs along the edge of the Pacific tectonic plate and ranges from western South America, west to New Zealand, north through the Philippines and Japan, across the northern rim of the Pacific Ocean into Alaska, and southward along the West Coast of North America. The vast majority of earthquakes and volcanoes on Earth occur along this very active tectonic boundary. The largest earthquake in recorded history was a magnitude 9.5 quake that struck Chile in 1960. A similar devastating earthquake (magnitude 9.4) occurred in Alaska in 1964. In 2004, a magnitude 9.1 earthquake struck Indonesia and generated a powerful tsunami that devastated numerous coastal locations along the Indian Ocean. In February of this year a magnitude 6.3 earthquake shook the South Island of New Zealand and was the strongest quake reported in that country for 80 years.

The active nature of the Pacific Ring of fire was observed again today (Friday, 3/11/11) when a magnitude 8.9 earthquake rocked Japan. The epicenter for this earthquake was located offshore, approximately 230 miles northeast of Tokyo. This earthquake is the strongest in recorded Japanese history and aftershocks continue, the strongest of which were magnitude 7.1. In addition to the destruction caused by the earthquake itself, a massive tsunami was generated that crashed into the shore of Japan. The highest wave associated with this surge was measured at 30 feet. In a manner very consistent with the 2004 tsunami, surging water along the coast of Japan devastated coastal communities and spread with incredible power as far as 6 miles inland. Many scores of people likely perished in the disaster and the extent of loss is currently undetermined.

Although the tsunami is certainly a catastrophic disaster in Japan, this situation demonstrates the benefits of the tsunami warning system that was installed in the Pacific Ocean basin in 1949. As a result of the system, a tsunami warning was rapidly given and no doubt saved some lives in Japan. A warning was also generated for Hawaii, in the middle of the Pacific Ocean, and the West Coast of the United States. Coastal communities in these locations thus had ample time to prepare and move people out of potential danger. In stark contrast, no such warning system existed in the Indian Ocean basin at the time of the Indonesian earthquake. As a result, people in coastal communities far away from the earthquake epicenter were unaware of the approaching tsunami and over 250,000 deaths occurred. This contrast demonstrates why it is necessary to understand natural hazards and plan effectively for them.

Submitted by: Alan Arbogast, Michigan State University

2011 Pacific Coast Tsunami

Honolulu, Hawaii, 3/11/11: Last night, as I was trying to convince my son to finish his homework so we could go to bed, my email and cell phone started buzzing. My geologist friends on the mainland, and colleagues here in Hawaii were calling about the mega-quake that hit Japan. Amazing and horrifying footage on CNN showed a tsunami sweeping across the flat coastal plain at Sendai:
http://www.latimes.com/news/nationworld/world/la-fg-japan-quake-20110311,0,1950058.story
This is the first clear aerial footage of a major tsunami in history – we’ll be showing this in classrooms for years.

By 10pm we learned that the alert in Hawaii was upgraded from “Tsunami watch” to “Tsunami warning” and we started packing a cooler with ice, food and water. Searching the web I found that the Pacific Tsunami Warning Center models predicted a 2m wave…ok, significant, but not catastrophic.

I live on Kailua Beach, Oahu and have obvious exposure to coastal hazards such as this: http://ptwc.weather.gov/ but I figured at worst the water would crest the dune, and roll into the yard but not cause serious damage where I live…I considered not evacuating, but decided against that.

By 11pm the sirens started, and by midnight the evacuation was in full swing. Police cars and firetrucks drove through the neighborhood blaring horns and broadcasting the message “This is State Civil Defense. A tsunami is approaching. Please evacuate to higher ground now.” Every house in the neighborhood was alight and bustling with activity. We tried grabbing a few hours sleep before the predicted arrival time of 3:20AM – but this was hard with all the noise in the street.

Our family friends the Luis’s, living a mile away offered their home to us and by 2AM we were on their floor trying to get to sleep between blaring emergency sirens every 30 minutes. I woke at 5am, and we drove back home.

The roadblocks were gone and the usual early morning commute was absent…totally empty streets. A quick trip to the beach in front of our home revealed that indeed a wave had washed up and crested the dune and stalled there – but the power of this wave was revealed in how flat and planned off the beach profile looked; no foreshore, no berm crest, no sub aerial beach, just a flat gentle slope rising out of the water….and incredible amount of sand must have been eroded.

As I write this we are still under tsunami warning, and in a similar event in the 1930′s from the same part of Japan, the worst damage in Hawaii was caused by the tenth wave. so it may be awhile before this is over.

Submitted By Chip Fletcher, University of Hawai’i