8.3 Destruction from Earthquakes Damage to structures depends on … Intensity and duration of vibrations. Nature of the material on which the structure is built. Design of the structure. Building Design How a Building Collapses with shaking http://quake.usgs.gov/research/deformation/modeling/animations/ How a Building Survives Shaking http://www.apawood.org/level_b.cfm?content=srv_newsinfo_34

Peru BEFORE 1970 Earthquake. Peru AFTER 1970 Earthquake.

LIQUEFACTION Liquefaction Lab *Take a plastic cup, carefully cut off the bottom of it, and place it upside-down in a pie plate *Hold the cup in place and carefully pour fine sand (beach sand works well) into the upside-down cup until it is about � of the way full *Put a mass of some sort on the surface of the sand *Pour water into the pie plate (outside of the cup) while still holding the cup firmly in place *Tap on the side of the cup, but be sure to hold the cup in place *Watch as the mass falls through the sand as if through liquid *This is what sometimes occurs during earthquakes and is known as liquefaction LIQUEFACTION

Liquifaction = when otherwise stable soil becomes weak and liquid-like beneath buildings.

TSUNAMI Incorrectly called Tidal Waves. Occurs when… Earthquake displaces ocean floor vertically along a fault. Vibration of a quake sets off an underwater landslide. Travels at 500-950 mph!

Once formed, a tsunami resembles ripples in a pond.

At landfall. In the open ocean… At about 5500 meters depth. At 900 meters depth. At 20 meters depth. At landfall.

Pg 230 Figure 11

After a large tsunami hit Hawaii, the Tsunami Warning System was developed for the Pacific. Similar systems have been adopted throughout much of the world.

Turkey Tsunami http://video.pbs.org/video/1281662767/program/979359664 (52:53)

EARTHQUAKES CAUSE LANDSLIDES Damage isn’t limited to shaking and waves! Sumatra land slide killed 10 people. Ireland Union Pacific Railway, Seattle WA

Ground subsidence = sinking of the ground That sinking feeling… Ground subsidence = sinking of the ground It looks like a flood. It feels like a flood. But the water didn’t rise. School in Alaska The GROUND SUNK! Alaska Earthquake March 27, 1964. The village of Portage, at the head of Turnagain Arm of Cook Inlet, is now flooded at high tide as a result of 6 feet of tectonic subsidence during the earthquake. 1964.

EARTHQUAKES CAUSE FIRES Japan Gas line on fire.

Why do we need to predict Earthquakes?

So far short term predictions have NOT been successful. Can we predict Earthquakes in the short-term to provide early warning systems? Scientists measure… uplift subsidence strain on rocks near active faults water levels and pressure in wells radon gas emissions small changes in electromagnetic properties of rocks So far short term predictions have NOT been successful.

So far long term predictions have NOT been successful… Can we predict Earthquakes in the long-term to provide probabilities that a certain magnitude of earthquake will occur within 30-100 years? Based on the idea that earthquakes are cyclic (they occur in a somewhat regular cycle). As soon as an earthquake occurs (and releases the pressure) the pressure begins to build again. Scientists study the history of the earthquakes looking for patterns. Scientists study SEISMIC GAPS (areas along a fault where there has not been activity for a long time.) So far long term predictions have NOT been successful… but we’ll keep trying.