Great Earthquakes and Related Tsunamis

In Great Earthquakes and Related Tsunamis, you'll learn ...

• The characteristics of great earthquakes
• The forces within the earth that generate such disasters
• The types of seismic waves that are generated by earthquakes
• The laws that govern the propagation of seismic waves

Overview

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Credit: 2 PDH

Length: 37 pages

The topic of great earthquakes and related tsunamis is examined in this course through the characteristics and impacts of the Great Japan Tohoku-oki Earthquake and Tsunami that struck Northeastern Honshu on March 11, 2011. This disaster came first in the form of an earthquake so powerful that it knocked the earth off its axis of rotation. This great earthquake and its ensuing devastating tsunami resulted in about 20,000 fatalities and caused major damage and destruction to buildings, infrastructure and nuclear power plants in the coastal zone of Northeastern Japan. That region was violently shaken and flooded, resulting in large societal disruptions and grave socio-economic consequences.

The forces within the earth that generated this epic disaster are examined. Every detail of this tragedy was recorded real-time by seismic instruments thus enabling scientists to reconstruct and know exactly what happened. Combined with extensive recordings from global seismic networks, the data from these multitudes of gauges and sensors make this seismic event the best recorded in history. The flood of these real time data confirmed the value of applying modern technologies to earthquake and tsunami mitigation efforts. In addition, strain accumulation measurements, offshore fault-zone observations, and early detection and warning of earthquake and tsunami all contributed to some extent in saving lives in the most heavily damaged areas. The tectonic plates that cover the earth's surface are presented and the segment along the boundary between the two plates that was dislocated during the occurrence of this great earthquake is highlighted. The instantaneous strain release which occurred at the plate boundary was so large that it generated seismic, tsunami and atmospheric waves that spread through the Earth. The course describes the types of seismic waves that are generated by an earthquake and explains which of these waves are likely to cause the most damage as they propagate away from the epicenter. The course also explains how these seismic waves are used to elucidate the internal structure of the Earth, showing that it is composed of a thin crust resting on an upper mantle and below which is a lower mantle, an outer core and an inner core.

The propagation of the seismic waves, outward from the epicenter, and the effect of seismic shaking on various types of engineered structures, including the Fukushima Daiichi Nuclear Power Station, are presented. The process leading to the formation of the initial tsunami swell, its collapse and the development of the immense waves that spread in all directions is illustrated in a sequence of diagrams that clarify the process of tsunami generation and propagation. In addition, the postulated mechanism that resulted in the amplification of the initial tsunami swell, adding to the built-in destructive force of its waves as they spread towards the shore, is advanced with supportive evidence. The course concludes with the presentation of the current thinking about effective strategies developed to protect vulnerable populations from the devastating effects of tsunamis. Finally the equations used to compute the velocity of seismic waves are presented in the appendix.

At the end of this course you should be able to understand the causes that unleash these catastrophic natural phenomena. A sudden sea-floor displacement triggered this massive earthquake and generated a monstrous tsunami that devastated hundreds of kilometers of coastline along the islands of Honshu and Hokkaido.

Specific Knowledge or Skill Obtained

This course teaches the following specific knowledge and skills:

• The characteristics of great earthquakes
• The forces within the earth that generate such disasters
• The types of seismic waves that are generated by earthquakes
• The laws that govern the propagation of seismic waves
• The travel times of seismic waves
• The interior structure of the earth
• The paths of seismic waves through the earth
• The mechanisms that lead to the initiation and amplification of tsunamis
• How tsunamis are detected, tracked and their propagation forecasted
• The tsunami effects on the nuclear power plants at Fukushima Daiichi
• The sequence of events that led to the nuclear accident
• The most efficient way to protect against a tsunami

Certificate of Completion

You will be able to immediately print a certificate of completion after passing a multiple-choice quiz consisting of 22 questions. PDH credits are not awarded until the course is completed and quiz is passed.