Exercise 3:
1a. Draw red arrows away from the mid-ocean ridge (divergent)
Draw red arrows towards the South American west coast from both directions (convergent)
Draw red arrows parallel to the West Coast of North America (transform)
Draw red arrows towards the Aleutian Islands (convergent)
Draw red arrows towards the south and east coasts of Japan (convergent)
Draw red arrows towards Indonesia from the south (convergent)

1b. Sea floor spreading
1c. Subduction
1d. Tsunami (if subduction occurs in shallow waters and lots of energy is transferred into the water)
1e. Large magnitude earthquakes are rare along divergent boundaries because the tectonic plates are not clashing together or moving under each other. Therefore, all the energy is dissipated. Convergent boundaries produce large earthquakes because one plate subducts underneath the other, creating dramatic pressure that builds over time and is released suddenly (see the Indonesian 2004 Boxing Day Earthquake/Tsunami)

2) Surface waves cause the most damage to human structures because they shear the surface either rotationally (Rayleigh waves) or perpendicularly (Love waves). Rayleigh waves cause the ground to move in an up-down and side-to-side motion and are sometimes at fault for liquefaction in extremely powerful earthquakes. Rayleigh waves can also move opposite to the direction of propagation causing shear near the surface. Love waves cause perpendicular shear against the direction of propagation, which can also cause liquefaction and break gas lines and/or building foundations in urban areas.

3) For Figure 3.3, Draw X-bracing between the boxes (Xs)
Draw beams in triangles near each ceiling corner
Draw a separate foundation with beams connecting to the bottom floor

4) The resonance of a building occurs when the frequency content of the ground motion is close or equal to the building’s natural frequency. Each building has its own frequency, which increases by about 0.1 times per story in a structure. The Mexico City earthquake in 1985 was a shocking demonstration of how resonance caused by earthquakes killed thousands. Since the period of the surface waves was approximately 2.0 seconds, that corresponded to buildings between 18 and 22 stories tall being most exposed to damage due to the matching resonance. For that reason, most buildings of that size collapsed with residents inside. However, most of the smaller buildings that were up to code survived the earthquake and the super-skyscrapers also survived.

5a and b) Using a black pencil: outline the area of loose sediment from the middle of the picture to the extreme right; this is where ground amplification will occur. More amplification will occur in areas underlain by less bedrock. Add labels to

1. On each of the seismograms on page 3, analyze the recorded groun...