Unit 2

Virtual Field Trips #3:  Alaska & San Francisco

Slide 1:  More Earthquakes!  Visit Alaska & San Francisco to get a glimpse into the effects of major earthquakes.  Photos courtesy of the U.S. Geological Survey

Image 2:  Alaska Earthquake, March 27, 1964. The geologist on the left stands in front of the Hanning Bay fault scarp on Montague Island. During the earthquake, the scarp formed when the rocks on the right dropped suddenly relative to the rocks on the left--the scarp is 12 feet high beside the geologist, and 14 feet high near the trees in the background.

Image 3:  Alaska Earthquake, March 27, 1964. The Four Seasons Apartments in Anchorage was a six-story lift-slab reinforced concrete building, which cracked to the ground during the earthquake. The building was under construction, but structurally completed, at the time of the earthquake.

Image 4:  Alaska Earthquake, March 27, 1964. The shaking caused some land to slide toward the ocean. Everything in the lower-left corner of the picture moved about 11 feet farther to the lower left in the direction shown by the magenta arrow, toward the ocean bluffs that are just out of the picture in that direction. The strip of land between the yellow arrows dropped by 7 to 10 feet, as indicated by those arrows. Notice that several houses were left hanging over the void, to be destroyed later. The collapsed apartment building from the previous slide is visible at the top of this picture (blue arrow).
  
Image 5:  Alaska Earthquake, March 27, 1964. The shaking caused the banks on both sides of the river to landslide toward the water carrying the rails along, as shown by the blue arrows at the bottom. This in turn caused the rails to bend, and also buckled up the center of the bridge, as shown here. This is near the head of Turnagain Arm, not far from Anchorage.

Image 6:  Alaska Earthquake, March 27, 1964. The Denali Theater was built on a block that dropped as the shaking of the earthquake moved land toward the sea, but Fourth Avenue was just beyond that moving block and did not drop. The marquee is now at eye-level.

Image 7:  Alaska Earthquake, March 27, 1964. This was the Government Hill Elementary School in Anchorage. It was not designed as a split-level.

Image 8:  Alaska Earthquake, March 27, 1964. Bridges and buildings are usually designed so that they don’t fall down. An earthquake moves the ground horizontally as well as vertically, so buildings and bridges often fail by falling sideways, as happened to the “Million Dollar” railroad bridge over the Copper River.

Image 9:  Loma Prieta, California, Earthquake, October 17, 1989. The Bay Bridge between San Francisco and Oakland failed during the earthquake, with the upper deck falling onto the lower deck of the double-decker bridge, killing one person.

Image 10:  Loma Prieta, California, Earthquake, October 17, 1989. The shaking of the earthquake caused landsliding and other land motion, destroying this driveway in the Santa Cruz Mountains.

Image 11:  Loma Prieta, California, Earthquake, October 17, 1989. The shaking knocked this section of Highway 1 near Watsonville off its bridge supports, which poked through the road bed.

Image 12:  Loma Prieta, California, Earthquake, October 17, 1989. The shaking of the earthquake caused collapse of the Cypress Viaduct of Interstate 880 in Oakland. 40 of the 67 fatalities caused directly by the earthquake happened here, primarily to drivers on the lower deck who were crushed by falling of the upper deck.