Geology 15                                                                                          West Valley College

Geology of California                                                                            Robert Lopez

Study Questions 18: Earthquakes and Faults


1)      What is Stress?  What is strain?


2)      What are the types of stress and what tectonic setting are they associated with?



3)      Does the San Andreas Transform have all three types of stresses?



4)      Strain is the result of what kind of changes in a rock?



5)      Where is strain energy stored?



6)      What are the three ways in which rocks strain as a result of stress?


7)      What are the links between deformation, energy, and earthquakes?


8)      How are earthquakes and faults related?


9)      Describe briefly the elastic rebound theory.



10)  Describe or sketch the relationship between the focus, epicenter, and surface rupture for a dipping fault plane (fig. 2, attached).  Where do deep focus earthquakes occur, what is the maximum depth to their focus, and what controls this limit?  What are typical focal depths of California earthquakes?



11)  What is a fault scarp?


12)  How are active faults officially defined?


13)  What are the differences among P, S, and surface waves? 


14)  What is the evidence that the outer core is liquid? 


15)  Sketch a simple seismogram tracing showing the there types of waves.


16)  What is a seismograph?






17)  How the epicenter of an earthquake can be located?





18)  What specifically controls the Richter magnitude?  Be able to compare the amplitudes of seismic waves yielding different Richter magnitudes (e.g., compare amplitudes of magnitude 4 and 6 quakes).




19)  What is the principal problem with the Richter magnitude?  (“The Richter magnitude does not directly measure the overall mechanical power of the seismic source, just as the strongest wind gust is not a reliable measure of the overall force of a wind storm.” Bolt, 1993, p. 59).





20)  What is MW, why is it “better” than the Ricther magnitude, and what three factors are considered in its calculation?  Compare ML and MW for the 1989 Loma Prieta and 1906 San Francisco earthquakes (see Harden, Table 13-1, p. 298).





21)  A change in magnitude of one unit corresponds to an energy change of what (also see Fig. 3, attached)?




22)  How does “earthquake intensity” differ from magnitude, how is it measured, and what factors influence it (Harden, Table 13-2)?





23)   Outline the five effects of earthquakes below.


24)  What are Tsunamis? What is the origin of the word?


25)  What type of earthquakes usually result in Tsunamis?