earthquakes at transform plate boundaries

california

As you learned in the chapter Plate Tectonics, the boundary between the Pacific and North American plates runs through much of California as the San Andreas Fault zone. As you can see in the (Figure 1.1), there is more than just one fault running through the area. There is really a fault zone. The San Andreas Fault runs from south to north up the peninsula, through San Francisco, gets through part of Marin north of the bay, and then goes out to sea. The other faults are part of the fault zone, and they too can be deadly. The faults along the San Andreas Fault zone produce around 10,000 earthquakes a year. Most are tiny, but occasion- ally one is massive. In the San Francisco Bay Area, the Hayward Fault was the site of a magnitude 7.0 earthquake in 1868. The 1906 quake on the San Andreas Fault had a magnitude estimated at about 7.9 (Figure 1.1). About 3,000 people died and 28,000 buildings were lost, mostly in the fire that followed the earthquake. (a) The San Andreas Fault zone in the San Francisco Bay Area. (b) The 1906 San Francisco earthquake is still the most costly natural disaster in California history. Recent California earthquakes occurred in: 1989: Loma Prieta earthquake near Santa Cruz, California. Magnitude 7.1 quake, 63 deaths, 3,756 injuries, 12,000+ people homeless, property damage about $6 billion. 1994: Northridge earthquake on a blind thrust fault near Los Angeles. Magnitude 6.7, 72 deaths, 12,000 injuries, damage estimated at $12.5 billion. In this video, the boundaries between three different tectonic plates and the earthquakes that result from their interactions are explored. Click image to the left or use the URL below. URL:

textbook_image

transform plate boundaries

Deadly earthquakes occur at transform plate boundaries. Transform faults have shallow focus earthquakes. Why do you think this is so?

new zealand

New Zealand also has a transform fault with strike-slip motion, causing about 20,000 earthquakes a year! Only a small percentage of those are large enough to be felt. A 6.3 quake in Christchurch in February 2011 killed about 180 people.

instructional diagrams

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questions

this is the type of stress at a transform boundary, which causes an earthquake.

a) convergent

b) divergent

-->  c) shearing

d) none of the above

the boundary between the pacific and north american plates is the

a) junction fault

-->  b) san andreas fault

c) california fault

d) hayward fault

in the san francisco bay area, the san andreas fault creates

a) a single fault line.

-->  b) a zone of active faults.

c) two active faults, the san andreas and the hayward.

d) a large bend where most of the seismic activity is.

transform boundaries have shallow focus earthquakes.

-->  a) true

b) false

the san andreas fault

a) runs through all of california.

b) is a straight line plate boundary.

c) is responsible for enormous earthquakes at least once per decade.

-->  d) none of these.

transform boundaries produce this type of fault.

-->  a) strike-slip fault

b) normal fault

c) reverse fault

d) dip-slip fault

the san andreas fault is unique since it is the only transform fault on earth with major earthquakes.

a) true

-->  b) false

the focus of the northridge earthquake was deep.

a) true

-->  b) false

nearly all major earthquakes occur on transform faults.

a) true

-->  b) false

the loma prieta earthquake

a) was on the main san andreas fault.

b) was the costliest natural disaster in california history.

-->  c) occurred in the hills above santa cruz, california.

d) had a magnitude equal to the 1906 san francisco quake.

diagram questions

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