Geology Notes Part 8 1

What causes earthquakes? When plates slide past each other, collide, or move part http://news.bbc.co.uk/cbbcnews/hi/newsid_4130000/newsid_4132300/4132319.stm 2

http://earthquake.usgs.gov/eqcenter/recenteqsww/Maps/region/N_America.php 3

What is the elastic rebound theory? It explains how rocks spring back into their original shape after they have been deformed by seismic forces 4

What is a seismograph? Instruments that record the vibrations of the Earth during an earthquake It creates a seismogram 5

How are earthquakes measured? The Richter scale of magnitude is a scale used that measures the amplitude (height) of seismic waves 6

Richter Scale 1.0 = 32 x energy 2.0 =1024 x 3.0 = 32,000 x 4.0 = 1,000,000 5.0 = 32,000,000 6.0 = 1,000,000,000 7.0 = 32,000,000,000 8.0 = 1,000,000,000,000 9.0 = 32 x 1013 (320000000000000) 7

What is the epicenter? What is the focus? The position on the Earth’s surface directly above the focus of an earthquake What is the focus? The point at which stress breaks the friction lock between two plates of the Earth’s crust 8

What is the relationship between plate tectonics and earthquakes? Most earthquakes occur along plate boundaries. Most large earthquakes occur along convergent plate boundaries. Earthquakes occur deeper and deeper as on plate is being subducted under another plate. 9

What impact do earthquakes have on humans? Earthquakes cause buildings and other structures to collapse which causes the most injury and death. Other dangers include landslides, fires, explosions from broken gas lines, and floods from collapsing dams. 10

Where would you be most likely to feel a minor earthquake? Someone on the top floors of a tall building. Look at the distance the top of the building travels 11