Week 3: Earthquakes

This week we're going to discuss earthquakes. An earthquake is a shaking of the earth's surface caused by a release of energy which creates seismic waves. Earthquakes are caused by the breaking and shifting of rock beneath the earth's surface. They usually occur along fault lines, or cracks that occur within the Earth’s crust. Worldwide, people feel an estimated 1 million earthquakes a year. (Keller 53) The magnitude of an earthquake is a measured value of the earthquake size. Most people who live in California are familiar with earthquakes and their damage due to the San Andreas fault line running through the state but there are many countries where earthquakes are not such a concern to the residents.

Even though Iceland is a very seismically active country they've only had a few large earthquakes in the past 50 years. They had a big (over M5.9) earthquake in 2008 where only 30 people were injured with no human fatalities reported (a number of sheep perished though). That earthquake registered in at M6.1 and caused some structural damage to the towns around the epicenter. In June 2000 they were also hit with two earthquakes (one recorded as a M6.6 and one at M6.5) a few days apart, but even then the damage was more to their road and older building infrastructure and again there were no casualties. 

June 2000 earthquake

You can check out Iceland's earthquake activity by visiting the Iceland Met page. It gives a really great summary of the last 48 hours of seismic activity for Iceland. It also gives you a really good summary of the activity per week. Just in the week of February 1-7th they measured 350 different earthquakes but none of them registered over M3.1 which seems to be the normal for Iceland. Because of it's location on the Mid Atlantic Ridge and it's proximity to two tectonic plate boundaries, Iceland is an area prone to volcanoes and earthquakes but big earthquakes are rare.

Activity 02/14-02/16/16

The largest earthquakes in Iceland occur within transform zones which connect the north east volcanic zones and eastern volcanic zones of the island with the active ocean ridge off shore (the Tjornes Fracture Zone (TFZ) and South Iceland Seismic Zone (SISZ)) and at the centre of the island at the junction between three volcanic zones. The SISZ is the most seismic active zone in Northern Europe.

As few injuries resulted from the June 2000 earthquakes, a blasé attitude may exist that earthquake vulnerability is low and that earthquakes are a bit of fun to experience once in a while. Iceland's attitude towards earthquakes appears (to me) to be pretty laid back. They do take some precautionary measures such as awareness and preparedness guidelines for earthquakes though, because they can cause landslides and rocks to fall and many homes are built at the base of steep mountains. Also, for Iceland, often times an earthquake is accompanied by volcanic activity. Iceland's warning systems and awareness campaigns focus mostly on volcanic activity (which we'll discuss in week five) and they don't put as much concern into risk assessment and preparedness for an earthquake.  Their Civil Protection Department website does list preventative measures for a number of situations and they suggest the same Duck, Cover, Hold technique that we teach in the US. 

As to structural reinforcement in Iceland, they already construct many of their buildings to withstand an earthquake. According to the OECD, after devastating earthquakes in 1896 and 1929, reinforced buildings became the usual standard for construction. "Engineers recognised the importance of reinforcing concrete with steel bars as well as the continuity built into concrete structures poured in situ." (OECD) After 1976 Iceland also used the California Uniform Building Code as a model for construction although now they are moving towards the Eurocode 8 for their seismic design. (OECD) Accordingly, this has lowered the chance of major structural damage from future earthquakes.



Works cited: 
Keller, Edward and Duane DeVecchio. Natural Hazards. New Jersey: Prentice, 2012. Print.

OECD. Educational Facilities and Risk Management Natural Disasters: Natural Disasters. France: OECD Publication. 2004. Print.

link to ebook (I specifically used page 86 for information)


Images: 

2000 earthquake image: uk/Tectonics%20and%20Seismicity%20in%20Iceland/Inrtoduction.html

Map of Iceland earthquake activity: 
http://en.vedur.is/





Thanks for reading!!

Jennifer