Midterm Exam Study Questions - Earthquakes and Seismic Hazards | GEOL 344, Exams of Geology

Download Midterm Exam Study Questions - Earthquakes and Seismic Hazards | GEOL 344 and more Exams Geology in PDF only on Docsity! GEOL 344: EARTHQUAKES AND SEISMIC HAZARDS (SPRING 2006) MIDTERM EXAM NAME: ___________________________________ GRADE: ______ / 132 TIME AVAILABLE: 75 MINUTES Instructions: There are EIGHT pages of questions. Take a minute or so now to page through the entire exam and to get a feeling for the length. Answer the easier questions first. Do not waste time struggling through any one question. Move on to another question and come back to the ones with which you were having difficulty. READ THE QUESTIONS CAREFULLY. Think carefully about your wording, trying to avoid ambiguity and unclear answers. PART 1: True or False (24 points) For each of the following statements, circle whether the statement is true or false. IF THE STATEMENT IS FALSE, provide a corrected statement. Hint: FOUR of the statements are false. 1. There is ample evidence to suggest that if a fault has not ruptured in the past 10,000 years, it is no longer active. TRUE / FALSE 2. Examples of seismic hazards that involve the effects of water include liquefaction, seiches, and tsunamis. TRUE / FALSE 3. Earthquakes occur in the lithosphere, which is made up of the crust and the upper mantle. TRUE / FALSE 4. The strength of rocks consistently increases with depth. TRUE / FALSE 5. If the only stress present in an area is lithostatic stress, earthquakes are nonetheless possible. TRUE / FALSE 6. The dynamic frictional strength of a fault is less than the static frictional strength. TRUE / FALSE 7. All seismic waves emanate away from the epicenter of an earthquake. TRUE / FALSE 8. In a focal mechanism solution, the T-axis always plots within one of the compressive quadrants. TRUE / FALSE 2 PART 2: Multiple Choice (20 points) Circle the correct answer from those provided for each question. 1. The largest death toll of any earthquake on record was 830,000 in 1556 in: (2) ( Iran / Indonesia / China ) 2. The average thickness of continental crust is: (2) ( 20 km / 35 km / 90 km ) 3. The world’s deepest earthquakes occur no deeper than: (2) ( 680 km / 120 km / 30 km ) 4. Lithostatic pressure is calculated as the product of depth, gravity, and: (2) ( volume / stress / density ) 5. If strain is recoverable, the type of rock rheology being referred to is: (2) ( elastic / plastic / brittle ) 6. The instrument that measures arriving seismic waves is called a: (2) ( seismoscope / seismogram / seismograph ) 7. The type of seismic wave that is sometimes called a transverse wave is the: (2) ( P-wave / S-wave / Rayleigh wave ) 8. The energy release between two earthquakes that differ in magnitude by 1 is different by a factor of: (2) ( 1 / 30 / 100 ) 9. The magnitude scale used to measure most of the world’s earthquakes (i.e., Richter scale) is abbreviated as: (2) ( ML / Mb / Ms / MW ) 10. In a lower hemisphere stereographic projection, a horizontal fault plane would be represented by a: (2) ( straight line / curved line within the circle / curved line around the circle’s edge ) 5 B. EARTHQUAKE GEOLOGY IN PICTURES (40 points) From the eight illustrations shown below, choose FIVE and answer the specific questions regarding the illustration. Make sure that you answer ALL aspects of the question! 1. Label the boxes in the figure below. Then write a few sentences explaining what this figure tells us about crustal strength, the depth range of earthquakes in the crust, and the typical nucleation points of most large earthquakes. (8) 2. Indicate what this map is showing, and elaborate on at least 3 of the 4 red dots. (8) 6 3. Describe what is being illustrated with these plots of earthquake focus locations. Be sure to mention the term used to describe this pattern of earthquakes as a function of depth. Also, mention the type of tectonic environment implied by these earthquakes. Say something about relative tectonic plate motions and interactions implied by the earthquake distribution. Also, comment on why there is a lower limit to the depth at which the earthquakes occur. (8) 4. In the figure below, comment on what the four rock samples are illustrating, and how these samples came to look the way they do (i.e., what was the nature of the experiment performed on them?). For the “low confining pressure” sample, comment on what structures are present in the sample, and why they formed with the specific angles and patterns that they did. (8) 7 5. What is being illustrated in this figure? Be sure to comment on the specific earthquake event being represented, the meaning of the rectangular area with contoured colors, the pattern of the contoured colors, and the relevance of the red star. (8) 6. Explain what is being represented with this figure, and why it is useful for determining the likelihood of an earthquake in a region. Label the sloping line and indicate a general formula that describes it. Label the term that describes the intercept between this line and the τ axis. Indicate the importance of the slope of the line and how it can be calculated. Finally, explain what is meant by the phrase “optimal failure angle.” (8) !n "