RCI Geo. Dept.

Earthquakes can have a variety of harmful effects, some obvious, some more subtle. Earthquakes of the same magnitude (size) can cause very different amounts of damage, depending on such variables as the: Nature of the local geology Whether the area affected is near the coast Whether the terrain is steep or flat Distance from the epicenter

- Ground Motion: Earthquakes occur along fault zones in the Earth that may experience relative motion. Rocks that slide against each other in a fault accumulate energy for centuries and release it almost instantaneously. This energy radiates out as a series of waves, causing an earthquake. - The offset between rocks on opposite sides of a fault can break power lines, pipelines, buildings, roads, bridges and other structures that cross the fault

Smaller earthquakes that occur after a main earthquake. They happen because the main E.Q changes the stress patterns at the epicenter, and the crust must adjust to this. The main shock usually causes the most damage, but when aftershocks are many and are nearly as strong as the main shock, they lso cause serious destruction 1,260 aftershocks were measured after the 1964 Alaskan Earthquake!

Because power lines may be knocked down and because natural gas lines may rupture due to an E.Q, fires often start after earthquakes At the same time, water lines are also broken, leaving no way to fight the fires effectively Fires may be more devastating than ground mvnt! In the 1906 San Fran E.Q, 80% of the damage was due to fire An E.Q in Tokyo, Japan in 1923 burned 500,000 buildings and killed 105,385 people

A)Landslides - In mountainous regions subjected to earthquakes ground shaking may trigger landslides, rock and debris falls, and debris avalanches - Example of land sliding during an E.Q occurred in Jamaica in 1692, when the entire city of Port Royal slid into sea (50 feet of water)

B)Liquefaction -A process that occurs in water-saturated unconsolidated (not bedrock) sediment due to shaking -When wet soil is shaken by an E.Q, the soil particles may be jarred apart, allowing water to seep b/w them. Causes the ground to become somewhat like quicksand -It becomes incapable of supporting much weight!

Giant ocean waves that rapidly travel across oceans, generated by earthquakes that occur beneath sea level and along coastal areas Tsunami’s can cause damage thousands of kilometers away on the other side of the ocean Contrary to modern movie fiction, tsunamis are not seen as huge breakers in the open ocean that topple ocean liners In the open ocean, the tsunamis are only broad swells on the watersurface As they approach land, they develop into large breaking waves which can be over 15 m high and may travel at speeds of 1000 km/hr

Indonesia, 2004 Japan, 2011

-Changes in Ground Level - E.Q’s may cause both uplift and subsidence of the land surface, sometimes up to 15 meters!