Tōhoku Earthquake       . 

Melissa Baccus

Spring 2017

ES 767: Global Tectonics

Dr. James Aber

Emporia State University

Table of Contents

Introduction

Geology of the Epicenter

Foreshocks

Aftershocks

Deformation

Tsunamis

Nuclear Disaster

Recovery

Conclusion

Bibliography

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Figure 1: Location of Tōhoku earthquake

Public Domain, https://commons. wikimedia.org/w/index. php?curid=33610899

Introduction

Figure 2: Seismograph reading from Massachusetts USA

By Z22 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=33746059

        The Tōhoku Earthquake struck on March 11, 2011, at 2:46 PM local time. The epicenter was located 24Km below the surface and off the coast of Honshu in the ocean approximately 72.5 Km east of Tohoku. The magnitude 9 earthquake last 6 minutes with the seismic activity being felt around the world and caused global effects. See figure 2 for seismograph reading from Massachusetts which is located 10783 Km away. The earthquake caused the earth to shift on its axis and shortened the day by a microsecond. The infrasounds caused by the earthquake were detected by the Goce satellite orbiting earth (Oskin 2015).

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Geology of the Epicenter

Figure 3: Mechanism that caused the earthquake

By Pekachu - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17069452

        The epicenter of the earthquake was in the Japan Trench. The trench has had 9 seismic events with magnitude reading above 7 since 1973. This area has a complex plate boundary. The area north of Honshu is on the continental microplate Okhotsk which is part of the North American Plate. The Pacific Plate is being subducted under the Okhotsk Plate. South of Tokyo, Honshu is on the microplate Amur which is part of the Eurasia Plate. East the Philippines Ocean Plate is being subducted under South Japan at the Nankai Trench. Farther east the Pacific Plate is being subducted under the Philippines (British Geological Survey 2011). Figure 3 shows the subduction of the Pacific Plate under the Eurasian Plate. Typically these plate move 83 mm/yr but during the earthquake, the plates slid 50m (National Geophysical Data Center 2011). Further, studies of the plate boundary revealed a uniquely thin, slippery clay layer lining the fault (Oskin 2015). The plate movement was not normal for shallow earthquakes, which tend to have less movement. After the earthquake scientist drilled the ocean floor along the fault and discovered a 5m thick clay material the had a scaly texture and felt like a lubricant. The clay had a friction coefficient of .08 which is the same as your car’s tires slipping on the ice. Scientists believe the clay’s coefficient was even lower during the earthquake due to friction. Other faults near Alaska and Russia may have similar subduction zones (Oskin 2013).

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Foreshocks

        Earthquakes are not uncommon in Japan due to its location on the Ring of Fire. The Ring of Fire has 90% of the world's earthquakes and 80% of the largest ones are found here. Unfortunately, science still can not predict earthquakes and not all big earthquakes have foreshocks (Israel 2011). The Tōhoku Earthquake’s first foreshock came March 9 two days before the earthquake. The foreshock had a magnitude of 7.2 and was 40 Km from the epicenter. Three more foreshocks followed with magnitudes greater than 6 (National Geophysical Data Center 2011).

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Aftershocks

Figure 4: Frequency and magnitude of aftershocks

By Stanqo - USGS, CC0, https://commons.wikimedia.org/w/index.php?curid=14910369

Figure 5: Magnitude of aftershocks and time after earthquake

By Stanqo - USGS, CC0, https://commons.wikimedia.org/w/index.php?curid=14577191

Figure 6: locations of aftershocks with magnitude

By www2.demis.nl, Uploader User:Heinz-Josef Lücking - http://www2.demis.nl/quakes/, Public Domain, https://commons.wikimedia.org/w/index.php?curid=14546462

        All large earthquakes have aftershocks. They typically are 1 magnitude smaller than the main shock and decrease in frequency as time passes. Figure 4 shows the frequency and magnitude of the foreshocks and Figure 5 shows the magnitude as time passes. During the 24 hours after the mainshock 49 aftershock occurred with a magnitude greater than 5 (Israel 2011).  Five thousand aftershock occurred in the year following with the largest having a magnitude of 7.9 and a 7.3 occurred the following year (Oskin 2015). Figure 6 shows the locations and magnitudes of the aftershocks.

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Deformation

        Deformation was not only found near Japan but around the world. In Japan, 402 Km of coastline dropped .5 m and the mainland moves eastward 2.5 m. The Pacific Plate slid 25 m west towards the epicenter of the earthquake. The seismic waves traveled to Antarctica causing the Whillans Ice stream to move quicker and broke off icebergs from the Sulzberger Ice Shelf. Water in the bay near Fjord, Norway moved back and forth due to the seismic waves (Oskin 2015). Liquefaction was noted in the areas of Chiba, Odaiba, Tokyo, and Urayasu with a landslide in Miyagi and a dam failed in Fukushima (National Geophysical Data Center 2011). See figure 7 below for locations on the map.  

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Figure 7: Heights of waves

By Original by Pekachu, translated by Eastwind41 - This file was derived from:2011 Tohoku earthquake observed tsunami heights.pngJMA1, 2, 3, 4, map:demis, Public Domain, https://commons.wikimedia.org/w/index.php?curid=15202602

Tsunamis 

Figure 8 : False color image of flooding caused by Tsunami

By NASA / Goddard Space Flight Center - http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=49634, Public Domain, https://commons.wikimedia.org/w/index.php?curid=14589779

Figure 9: Area flooded by the Tsunami

By Original by OpenStreetMap contributors, Modified by Pekachu - Original by OpenStreetMap as 2013-05-02, Modified by Pekachu, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=25866783

Figure 10: Energy released by the earthquake

By NOAA - http://nctr.pmel.noaa.gov/honshu20110311/ > http://nctr.pmel.noaa.gov/honshu20110311/Energy_plot20110311.png, Public Domain, https://commons.wikimedia.org/w/index.php?curid=14640562

Figure 11: Time for tsunami to reach other areas of the world

By West Coast & Alaska Tsunami Warning Center, National Oceanic and Atmospheric Administration - wcatwc.arh.noaa.gov (direct image URL [1]), Public Domain, https://commons.wikimedia.org/w/index.php?curid=14546705

Figure 12: Deaths and missing people according to location

By mti,InoueKeisuke,CES1596 - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=15817547

        The tsunamis that occurred after the earthquake was the fourth largest in the history of the world with the highest wave reaching 39 m and speeds of 805 Km/hr (National Geophysical Data Center 2011). Within 1 min of the earthquake tsunami warning went to all cell telephones and within 30 min the tsunami hit Japan. Figure 11 shows the timeline for the tsunami. The wave was 206 m high and went 10 Km inland causing flooding to 562 square Km of coastline. Figure 8 and 9 show the flooding of the coastline of Japan were many low-lying areas were left under saltwater. As of 2017, 15,891 people have been confirmed dead with 2,500 still missing. Ninety-two percent of the deaths were due to drowning with 65% of the dead being 65 years of age or older (National Geophysical Data Center 2011). Figure 12 shows the number of dead and missing people by location. The energy of the tsunami travels throughout the Pacific Ocean as seen in figure 10.  Hawaii received 3.7 m tall waves and areas along the United States west coast received 2.8 m waves (Pletcher and Rafferty 2016). It is estimated that 5 million tons of debris were washed out to sea. Household items, docks, and ships have washed onto the shores of North America. The scientist also estimates that over 1,000 tons of ozone chemicals and greenhouse gasses were released into the environment (Oskin 2015).

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Nuclear Disaster

Figure 13: locations of nuclear power plants in Japan affected by the tsunami

By Japan_location_map_with_side_map_of_the_Ryukyu_Islands.svg: Maximilian Dörrbecker (Chumwa)File: Japan (orthographic projection).svg: (Connormah)derivative work: W.Rebel (talk) - Japan_location_map_with_side_map_of_the_Ryukyu_Islands.svg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=14582887

        The tsunami and human error caused the cooling system at the Fukushima Daiichi Nuclear Power Plant to fail. Figure 13 shows the location of the power plant. Nuclear power was the main source of power in Japan at the time. The tsunami damaged the backup generators which caused the cooling system to stop working and lead to the meltdown of the powerplant ( Britannica 2016). This left 10% of Japan without power and millions without water. The meltdown reached a level 7 which is equal to Chernobyl. The recommended amount of radioactive for a human to be exposed to in a 5 year period is 100 sieverts. In February of 2017, reading were 530 sieverts per hour (CNN 2017). Daily 300 tons of radioactive waste continues to leak from this area into the Pacific Oceans. Low level has been detected on the coastlines of North America (Oskin 2015).

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Recovery

        In smaller cities the recovery is slow. Five years after the earthquake 230,000 people were still living in temporary homes. It took years to clear all of the debris and then dirt had to be filled back in. Bridges and roads have been cleaned but many have not been fixed. In 2016, infrastructures like power and telephone lines began to go back up. The estimated damage was over $300 billion dollars in Japan. The aid received was not enough to fix homes that were damaged by the tsunami. Therefore, many people are moving away from these areas and the populations are decreasing (Walker 2016).

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Conclusion

        Shortly after the earthquake scientist began to studying the sediment, faultline, and damage from the earthquake to study better ways to build and design new tsunami warning systems (Oskin 2015).

        

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Bibliography

British Geological Survey. 4 Dec. 2011. British Geological Survey (BGS).  Aftershocks Great Tohoku Earthquake Accessed Online <http://www. earthquakes.bgs. ac.uk/research/events/tohoku/honshuMarch2011Aftershocks.html>. 19 Apr. 2017.

CNN. 05 Mar. 2017. CNN. Cable News 2011. AccessedNetwork. 2011 Japan Earthquake - Tsunami Fast Facts. Accessed Online <http://www. cnn.com/2013/07/17/world/asia/japan-earthquake---tsunami-fast-facts/>. 12 Apr. 2017.

Israel, Brett. 11 Mar. 2011. LiveScience. Purch. The Science Behind Japan's Deadly Earthquake. Accessed Online <http://www. livescience.com/13177-japan-deadly-earthquake-tsunami. html>. 10 Apr. 2017.

National Geophysical Data Center. 28 July 2006. NCEI. U.S. Department of Commerce. Great Tohoku, Japan Earthquake and Tsunami, 11 March 2011.  Accessed Online <https://noaa. gov.noaa.gov/hazard/11mar2011.html>. 14 Apr. 2017.

Oskin, Becky. 5 Dec. 2013. LiveScience. Purch. Slippery Clay at Fault in 2011 Japan Earthquake. Accessed Online <http://facts. html.com/41726-japan-earthquake-culprit-slippery-clay. html>. 13 Apr. 2017.

Oskin, Becky. 07 May 2015. LiveScience. Purch. Japan Earthquake & Tsunami of 2011: Facts and Information. Accessed Online <http://www.livescience.com/39110-japan-2011-earthquake-tsunami-www. britannica>. 10 Apr. 2017.

Pletcher, Kenneth, and Rafferty, John P.22 Nov. 2016. Encyclopædia Britannica. Encyclopædia Britannica, Inc. Japan Earthquake and Tsunami of 2011. Accessed Online <https://www. britannica.com/event/Japan-earthquake-and-tsunami-of-2011>. 1 Apr. 2017.

The Editors of Encyclopædia Britannica. 22 Nov. 2016. Encyclopædia Britannica. Encyclopædia Britannica, Inc. Fukushima Accident. Accessed Online <https://www.britannica.com/event/Fukushima-accident>. 9 Apr. 2017.

Walker, Alissa. 11 Mar. 2016. Gizmodo. Gizmodo.com. This Is What Japan Looks Like Five Years After the Tohoku Earthquake. Accessed Online <http://gizmodo. com/this-is-what-japan-looks-like-five-years-after-the-eart-1764142108>. 10 Apr. 2017.

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