ISNS ch 4

The 1964 earthquake in Alaska was very powerful (9.2Mw), yet the loss of human life was not as high as it could have been. What factors helped to limit the loss of life?

==Above-average temperatures helped to prevent cold-related deaths as heating systems were being repaired. ==Alaska is not a very densely inhabited area. ==The tsunami struck when the tides were low.

The recurrence interval for magnitude 6 to 7 earthquakes in the San Francisco Bay region is approximately 10 years, whereas that for magnitude 8 earthquakes is * years.

100

Tectonic plates slide past one another at transform faults, collide due to * motions, and move away from each other due to * motions. (Enter only one word per blank.)

convergent divergent

As a descending slab in a subduction zone is heated from the outside to the inside, its ability to produce large earthquakes ______ because the rocks' rigidity ______.

decreases; decreases

What technology is used to determine the rate and direction of tectonic motion wherever it is placed along the ground?

global position systems (GPS)

Plates slide past each other horizontally at * plate boundaries. (Enter only one word per blank.)

transform

Why are the interiors of subducting slabs the only places on the slab where powerful earthquakes can occur at great depth?

They are the only places left on the descending slabs still cold enough to resist the pressures before breaking in a rigid manner.

The earthquake forecasting strategy that involves plotting the distribution of earthquakes along a fault to identify the locations at which earthquakes may be overdue is called the ______ method.

seismic-gap

Small earthquakes too weak to knock over buildings or cause fatalities in Iceland are located at ______.

spreading centers