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Geosciences LibreTexts

10.1: Introduction

  • Page ID
    6098
  • Module 10

    Earthquakes

    m10_padang_full.jpg
    Figure 1. Damage from the 2009 Padang eartquake, Indonesia.

    Introduction

    It was the deadliest day in the history of Mt. Everest. On April 25, 2015, a 7.8 magnitude earthquake hit Nepal. This triggered an avalanche that killed 19 climbers on Mt. Everest. In Nepal, over 8,800 people died, and many more were injured and made homeless. Hundreds of aftershocks (smaller earthquakes that follow a larger earthquake) have occurred since that day.

    m10_Nepal1_full.png
    Figure 2. A map of the main earthquake to hit Nepal on April 25, 2015, along with a major aftershock on May 12, and numerous (>100) other aftershocks (shown in red). Note the magnitude scale in the upper right.

     

    Earthquakes are not new to this region. A similar death toll was experienced in a 1934 earthquake, and many other smaller earthquakes have occurred within historical times. An 1833 quake of similar magnitude resulted in less than 500 deaths, though this was most likely due to two very large foreshocks (smaller earthquakes that precede the main earthquake) that sent most residents out of doors in alarm, which was safer for them. Worldwide, there have been much deadlier and stronger earthquakes in just this century (e.g. Haiti, 2010 – 316,000 dead; Sumatra, 2004 – 227,000 dead; a large number of deaths in each of these events was due to ground shaking and the other hazards that were created by the earthquake). Earthquakes give geologists valuable information about Earth’s interior and about conditions at Earth’s surface. As you have learned, most earthquakes occur at plate boundaries.

    Select an image to view larger

     

    m11_FaultLineScarp_150.jpg
    Figure 3. A fault scarp in the Gobi Desert of Mongolia. A fault scarp is an offset in the ground surface where one side of a fault has moved up or down relative to the other side, revealing the “face” of the fault.

     

    m10_streetcracking_150.jpg
    Figure 4. River Road in Christchurch, New Zealand with earthquake damage from the February 22, 2011 event.

     

    m10_tsunami_150.jpg
    Figure 5. A boat and trash sit in the front parking lot of a church after a tsunami caused a great amount of structural damage to the island and its villages Oct. 1, 2009, in Pago Pago, American Samoa.
    m10_Seismometer_150.jpg
    Figure 6. Housed in a vacuum under a protective dome inside a vault in the Santa Catalina Mountains north of Tucson, a seismometer similar to this one (which is located in Antarctica) registered the Nepal earthquake 15 minutes after the ground started shaking in the Himalayas.

    Module Objectives

    At the completion of this module you will be able to:

    1. Explain how the principle of elastic deformation applies to earthquakes.
    2. Describe how the main shock and the immediate aftershocks define the rupture surface of an earthquake, and explain how stress transfer is related to aftershocks.
    3. Describe the relationship between earthquakes and plate tectonics.
    4. Distinguish between earthquake magnitude and intensity, and explain some of the ways of estimating magnitude.
    5. Describe how earthquakes lead to the destruction of buildings and other infrastructure, fires, slope failures, liquefaction, and tsunamis.
    6. Discuss the value of earthquake predictions, and describe some of the steps that governments and individuals can take to minimize the impacts of large earthquakes.

    Activities Overview

    See the Schedule of Work for dates of availability and due dates.

    Be sure to read through the directions for all of this module’s activities before getting started so that you can plan your time accordingly. You are expected to work on this course throughout the week.

    Read

    Physical Geology by Steven Earle

    • Chapter 11 (Earthquakes)

    Discussion 4

    30 points, class participation

    For this week’s “Current Events in Geology” topic, you should earn 30 points towards the 150 points of class participation. It is important that you feel engaged in this class. Discussion topics are very flexible, and can cover anything in geology or a related field, including hydrology or water resources, environmental or climate science, paleontology, planetary geology, etc. This is a great opportunity for you to learn about topics in geology that interest YOU, and to see that many interesting things relating to geology are currently making headlines in the news. You are also helping your instructor to become aware of what is going on and to learn new things, so I appreciate your efforts and look forward to reading what you find!

    Discussion 4 Instructions

    Pay close attention to the Course Schedule for when each of your posts are due. Some are due earlier than others. Failure to post on time will result in lost points.

    Module 10 Quiz

    10 points

    Module 10 Quiz has 10 multiple-choice questions and is based on the content of the Module 10 readings.

    The quiz is worth a total of 10 points (1 points per question). You will have only 10 minutes to complete the quiz, and you may take this quiz only once. Note: that is not enough time to look up the answers!

    Make sure that you fully understand all of the concepts presented and study for this quiz as though it were going to be proctored in a classroom, or you will likely find yourself running out of time.

    Keep track of the time, and be sure to look over your full quiz results after you have submitted it for a grade.

    Exam 2

    75 points

    The questions in this exam are “deep-thinking” questions designed to cultivate critical thinking based on what you have learned in the course up to this point. Each question will be worth 25 points (25 points x 3 questions = 75 points total). You will submit this exam in the Assignments tool.

    Exam 2

    Your Questions and Concerns…

    Please contact me if you have any questions or concerns.

    General course questions: If your question is of a general nature such that other students would benefit from the answer, then go to the discussions area and post it as a question thread in the “General course questions” discussion area.

    Personal questions: If your question is personal, (e.g. regarding my comments to you specifically), then send me an email from within this course.