Why so many earthquakes?

Here is a video discussing the topic of the the cluster of earthquakes that have been happening in the past 6 years.  

This will be my last post, as the semester has come to an end.  I want to thank those of you have been following the blog.  This blog has helped me learn the best ways to communicate with different audiences.  I hope that you have taken something from my posts.  Enjoy!

Mississippi Levee Breached = Missouri Farmland Flooded

The U.S. Army Corps blew up a levee to flood 130,00 acres in Missouri starting last night.  The result was the flooding of rich farmland.  The reason behind breaching the levee was to bring down the river levels and save the city of Cairo, Illinois as well as other communities.

The decision to breach the levee appears to be working.  The Ohio River at Cairo peaked at 61.72 feet just before the blast.  By 6 a.m. this morning, the level has dropped to 60.62 feet.  The previous recorded for the river was 59.5 feet in 1937, which is still less than what is was this morning.  The breach could cause river levels to fall by three to four feet over the next few days, according to Maj. Gen. Michael Walsh, commander of the Corps' Mississippi River Valley Division.  The city of Cairo's residents were ordered to evacuate because of the induced flooding.

Source: CNN

Missouri took the Corps to court over the intentional breaching of the levee.  The state argued that the flooding would deposit silt over the 130,000 acres of productive farmland.  The silt would take years to clear.  The U.S. Supreme Court refused to interfere, making it possible for the Major General to blow the levee.  Maj. Gen. Walsh stated that the fate of Cairo was one of many factors in his decision.  Water levels and flooding have hit record highs in many spots, putting strains on systems meant to prevent uncontrolled floods and the resulting loss of life and property.  


The breaching of the levee, I think was necessary action.  The damage caused by not breaching the levee would significantly outweigh the damage caused by breaching the levee.  


A video can be found of the blasting by following this link Click here

Global Seismograph Network Completed

The Global Seismograph Network is a network of 150 monitoring stations, globally distributed to collect information about earthquake activity. The final station was recently installed in Sharjah, near the Zagros Fault, the boundary between the Arabian and Eurasian plates.  This network provides free, realtime, open access to data and information on earthquake locations, earthquake hazards mitigation, and earthquake emergency response.  Below is a map of the location of these 150 stations.

Source: IRIS

Within hours of the earthquake, that data is automatically collected and made available through the Internet.  The Global Seismograph Network is a took that makes it possible to explore the Earth's interior and to mitigate earthquake hazards. Not only this, but it also addresses the needs of society.  

Would you ever bomb a volcano?

Bombing a volcano seems like at crazy idea at first, but after you think about it can be a successful mitigation technique for diverting lava flow.  Picking the right place to bomb is essential though.  The depth of the magma center also has to be considered.  Magmatic systems are kilometers below the Earth's surface.  However, bombing of a volcano could also prove to be insufficient and cause the volcano to erupt, rather than prevent it.  The United States have been involved in some examples of bombing a volcano.  Three times in Hawaii and once in Italy at Etna.

In 1992, Mt. Etna began erupting.  The lava was threatening some important structures on Etna, so it was decided that the lava would try to be diverted from the town.  Earthen barriers were constructed to keep the lava from flowing into the town.  Concrete blocks were also dropped on the lava flows in attempt to divert the lava.  The plan included blowing a hole in a lava tube at high elevations and then fill the lava tube with concrete blocks to stop the flow of lava in the tube. (See Figure below).  This attempt was successful in sparing the towns, but some still debate if diverting lava flows at Etna by bombing a volcano is a good idea.

Earthen barriers attempt to divert lava flows from Etna in 1992.  Source: Big Think

Concrete blocks dropped at Etna during 1992 eruption.  Source: Claude Grandpey

Another example is Mauna Loa in Hawaii.  Targeted bombing campaigns on vulnerable parts of a volcano,  mainly spatter cones that are the source of lava tubes high on the slopes of Mauna Loa, might cause sufficient diversion as to prevent lava flows from reaching the town of Hilo on the big island (Lockwood and Togerson, 1980). The first attempt to bomb Mauna Loa in Hawaii was in 1935, some of the bombing was caught on video shown here.  A second attempt in 1942, was done on Mauna Loa.  Both attempts did not provide noticeable results.  

In the 1970s, tests were performed by the U.S. Air Force and Hawaiian Volcano Observatory (HVO) scientists to see what might be the most effective means of bombing a volcano. These tests were on an older lava field with no active lava flows and were performed using relatively modern military supplies. It was found that if you target spatter cones that feed lava tube systems, then lava flow disruption occurred where the surface was most fragile and not dense, solid rocks like above some lava tubes. Bombing the actual lava tubes or flow levees didn't seem to be very effective (Lockwood and Togerson). 

Bombing the lava flow to divert it, is a relatively low cost, especially if you look at the cost of lava flows reaching the populated area.  The result of the bombing, if successful, is very effective, however, not all eruption of volcanoes will have vulnerable spots that are obvious to bomb if that was decided and could have unintended effects.   

Soil collapse after Japan earthquake

Severe liquefaction and shift in soil occurred as a result of the 9.0 earthquake in Japan this year.   As a reminder from one of my previous posts, the processes of liquefaction temporarily changes sand from a solid to a liquid state causing piles of sand to erupt on the surface.  Japan's liquefaction occurred over hundreds of miles.  This surprised experienced engineers.

Questions about whether existing building codes in other vulnerable locations here in the United States are adequate since the levels of liquefaction were higher than expected in Japan.  Hopefully we will learn something from Japan and be able to mitigate risks in other similar events.  


"We've seen localized examples of soil liquefaction as extreme as this before, but the distance and extent of damage in Japan were unusually severe," said Scott Ashford, a study team member from Oregon State University.


It is speculated that the long duration of five minutes of the Japan earthquake, is the key to severe liquefaction.  This may force researchers to reconsider the extent to which liquefaction is possible.  The age of the sediments is another factor the extent of liquefaction.  Younger, clean sediments cause higher liquefaction.  Shallow groundwater contributes to a higher level of liquefaction.  


Engineers can apparently still be surprised....

Soil sank nearly 3 feet.  Source: msnbc.com

Click here for the article.

2010 in review

Here is a fact that may make shout "Jiminy Cricket!"...almost 300 million people were affected by natural disasters in 2010!
Here is a list of the more major disasters in 2010:

• Haiti-earthquake
• Chile-earthquake
• Iceland-Eyjafjallajökull volcano spewing ash
• Russia-wildfires
• Pakistan-flooding
• China-flooding

The article that I read was concerned with the response due to some of these disasters and how the US communicated them.  For example, 130 million Chinese alone were affected by the worst flooding in recent history.  However, the floods received very little international attention.  Far less than either Pakistan and Haiti, which combined, was five times less than the amount of people affected by the flooding in China.  The article points out that one of the dilemmas in response to natural disasters, is that even major ones, receive significantly diverging media coverage (Ferris, 2011).  Very little international assistance was given or requested in response to the flooding in China.

This article suggests a lack of good science communication.  Response to natural disasters should not vary so much as the example, especially when China was a very significant disaster.  I think that part of reason why the flooding in China was not well communicated is that China is a different government than the United States and most other countries and didn't want to speak much about the event with them.  They are very independent.  This is just a speculation however.  

Here is a link to the article A Year of Living Dangerously: A Review of Natural Disasters in 2010

21 quakes in 24 hours

Source: Google Images
The Taal Volcano in the province of Batangas (Philippines) has been very active recently.  It is one of the most active volcanoes in the country.  Taal volcano is unique because it has a lake inside its crater called Crater Lake. State volcanologists recorded 21 volcanic quakes in one day on the 18th of last month.  The magma has been rising toward the surface, carbon dioxide is being released in Crater Lake, and this increase in seismic activity have caused alarm.  The water temperature of Crater Lake has also increased.  It is being said by The Phillippine Institute of Volcanology and Seismology (Phivolcs) that sudden hazardous steam-driven explosions may occur and high concentrations of toxic gases may accumulate, so three sites are off limits.  These high concentrations of gases are harmful to humans and animals and can be lethal, as well as damage vegetation.  Permanent settlement on the island is strictly not recommended.

Source: explorevolcanoesnow.com

The number of earthquakes have increased.  From 9 earthquakes on April 15 to 21 on the 18th!  Officials have done a good job of recognizing the signs of an eruption and have evacuated residents.  We'll see when it erupts...

Landslide in Saint-Jude Quebec

Source: Canadian Press.  A landslide last year taken May 11, 2010

The above photo was taken a little less than a year ago in Saint-Jude Quebec.  Now there are signs that another landslide in the area may occur.  Nine families are waiting to hear if they can return to their homes, after a riverbank collapsed last Wednesday.  A large section off the Salvail River eroded and collapsed into the water.  Officials are taking precautions in order to avoid another disaster as last years landslide resulted in a family of four that died.  

So what are these signs that are predicting another landslide?

Over the past week heavy rains have caused the ground to be less stable.  The ground in the area overlies a clay seabed where water can get in between the clay particles.  Water in between clay particles = unstable.  The soil becomes weak, even worse if there are buildings providing a load on it.

It makes you wonder why homes were ever built on this clay layer in the first place.  Testing is usually done before houses are even constructed to know the types of material the foundation is going to be built upon.  These homes have probably been there a long time and testing was not available when they were being built. Now a days, homes would not be built without having lab tests done on the soil. 

Municipal and provincial officials will spend the next two months assessing the safety of the area and mitigating the erosion problem along the Salvail River.  To stabilize the shore will take six to eight weeks.  

To read the original article click here