Figure 5.1 Depth of foci. That earthquake foci are shallow beneath oceanic tranches and become progressively deeper under tectonically active continental margin (such as South America) had been known for decades before the plate-tectonic revolution (from The Changing Earth - Introduction to Geology (2nd ed.), by Mears, Jr., D. Van Nostrand Co., 1977).




Figure 5.2 Benioff zones. In the plate-tectonic era, the progressively deepening earthquake foci are called Benioff zones and are related to subducting (descending) sea-floor plates (from The Changing Earth - Introduction to Geology (2nd ed.), by Mears, Jr., D. Van Nostrand Co., 1977).]

A. All earthquakes.


B. Earthquakes with foci deeper than 100 km.

Figure 5.3 Epicenters of earthquakes between 1961 and 1967. (from The Dynamic Earth - an introduction to physical geology, by Skinner and Porter, John Wiley & Sons, Inc., 1989).

Table 5.1 Modified Mercalli Scale of Earthquake Intensities.




Table 5.2 The relationship between the Richter Magnitude and the Mercalli Intensity Scales at the epicenter of an earthquake.




Figure 5.4 Relation of earthquake damage to foundation material (from The Changing Earth - Introduction to Geology (2nd ed.), by Mears, Jr., D. Van Nostrand Co., 1977).

Figure 5.5 Map of the reported intensity of the March 22, 1957, earthquake. Movement apparently occurred on the San Andreas fault that is also shown. After Cloud, 1959 (from General Geology (5th ed.), by Foster, Merrill Publishing Co., 1988).

A. Destructive and near-destructive earthquakes through 1964.


B. Seismic risk map for conterminous United States.

Figure 5.6 Earthquakes and seismic risk maps in the United States (from General Geology (5th ed.), by Foster, Merrill Publishing Co., 1988).

• Midcontinent Earthquakes

  
  
  Figure 5.7 Intensity maps for the San Fransisco earthquake of April 18, 1906, and the Mississippi Valley earthquake of December 16, 1811 (The damage area would correspond to those of Modified Mercalli intensity VII and greater.).
  
  
  

• Ohio Earthquakes

  
  
  Figure 5.8 Ohio earthquake epicenters (from Earthquakes in Ohio, by Hansen, Ohio Geological Survey, 1994).
  
  
  

Figure 5.9 Schematic drawing of a tsunami generated by displacement of the ocean floor. The size and spacing of the swells are not to scale (from The Earth - An Introduction to Physical Geology (2nd ed.), by Tarbuck & Lutgens, Merrill Publishing Co., 1984).




Figure 5.10 Seismic sea waves at Hilo, Hawaii, April 1, 1946. The wave is smashing a warehouse. Seconds later it will sweep the man to his death. Photo taken from a ship's deck by Corps of Engineers, U.S. Army (from Physical Geology (3rd ed.), by Leet & Judson, Prentice-Hall Inc., 1965).