Strain

Elastic Rebound

Focus (point on surface directly above the focus) (point of rupture)

Surface

P Waves Fastest waves, first to arrive

S Waves Slower waves, second to arrive

Surface Waves Slowest waves, last to arrive Orbital motion Do the most damage

Seismometer

Seismogram

Travel-time graph Fit the time difference between the first P-wave and first S-wave in-between the blue curves Read off distance to epicenter

Great circles Travel-time graph tells you how far away you are from the epicenter, but not the direction. Need three seisomgraph stations to triangulate the location of the epicenter.

Magnitude

Intensity Evaluation of the severity of an earthquake at a given location. Variables: 1.Distance from the earthquake 2. Total amount of energy released by the earthquake 3. Material type

Liquefaction Water-rich clays liquefy during shaking

Mercalli Intensity Scale XII - Damage nearly total. Large rock masses displaced. XI - Rails bent greatly. Underground pipelines completely out of service. X - Most masonry and frame structures destroyed. Some well-built wooden structures and bridges destroyed. Serious damage to dams, dikes, embankments. Large landslides. Rails bent slightly. IX - General Panic. Poor masonry destroyed, ordinary masonry heavily damaged, sometimes with complete collapse, reinforced masonry damaged, general damage to foundations. Frame structures, if not bolted, shifted off foundations. Frames racked. Underground pipes broken. Conspicuous cracks in ground. Liquefaction in areas of sand and mud. VIII - Steering of cars affected. Damage to ordinary masonry, partial collapse. Twisting, fall of chimneys, factory stacks, monuments, towers, elevated tanks. Frame houses moved on foundations if not bolted down; loose panel walls thrown out. Cracks in wet ground and on steep slopes. VII - Difficult to stand. Noticed by car drivers. Furniture broken. Damage to weak masonry, some cracks in ordinary masonry. Weak chimneys broken at roof line. Fall of plaster, loose bricks, stones, tiles and unbraced parapets. VI - Felt by all. Persons walk unsteadily. Windows dishes and glasses broken. Pictures off walls. Furniture moved or overturned. Weak plaster and masonry cracked. V - Felt outdoors, sleepers wakened. Liquids disturbed or spilled. Small unstable objects displaced or upset. Pictures move. IV - Hanging objects swing. Windows, doors, dishes rattle. Vibration like passing of heavy truck or jolt like a heavy ball striking the walls. III - Felt indoors. Hanging objects swing. Vibration like passing of light trucks. II - Felt by persons at rest, on upper floors, or favorably placed. I - Not felt. Measures the intensity of a ‘quake relative to a given location away from the epicenter.

Earthquake severity

Intensity Map

1971 San Fernando Earthquake

Magnitude Total amount of energy released by the earthquake Richter Scale

Richter Magnitude How many kilograms of TNT would have this much energy? * Smallest quake people can normally feel * Most people near epicenter feel the quake * Nearly 100,000 occur every year of size * A small fission atomic bomb * Quakes above 4.5 can cause local damage * A standard fission bomb, similar to the first bomb tested in New Mexico, U.S * A hydrogen bomb; can cause great damage locally * About 100 shallow quakes of size 6.0 every year billion* Major earthquake; about 14 every year * Enough energy to heat New York City for 1 year * Large enough to be detected all over globe billion * Largest known: 8.9 in Japan and in Chile/Ecuador * San Francisco destroyed by 8.25 in trillion * Roughly the world’s energy usage in a year Each unit is 32-fold energy increase

Earthquake Distribution Map

Earthquake Hazards Map

Some Famous Earthquakes 1811 New Madrid, Missouri: Charleston, South Carolina: San Francisco, California: Anchorage, Alaska: Saranac Lake, New York Loma Prieta, California: Northridge, California: Kobe, Japan: 6.8

New Madrid

San Andreas Fault

Alaska

1964 Alaskan Quake

Anchorage

Tsunami

Tsunami Picture Unimak Island, Alaska. Wave moving at 800km/hr, 18m high ??

Tsunami Damage Map

P wave shadow zone P waves slow down and are refracted in liquids

S wave shadow zone S waves do not travel through molten metallic liquids