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Unformatted text preview: Earthquake Scales
Richter Richter Scale - Charles Richter 1935
– Based on the magnitude of the earthquake on magnitude seismographs (how much energy is released) – 1 to 10 scale, log based Richter Richter Scale – Amplitude of the largest wave produced by an event is corrected for distance and assigned a value on an openopenended logarithmic scale 100,000 Richter Richter Scale 10,000 Earthquake Scales
Moment Moment Magnitude Scale
– Scale used currently – Based on the total amount of energy released during an earthquake – Measures the size of quake, not just the effect – Moment = length of fault * depth * amount of displacement * rock strength 1,000 Shortcomings: Shortcomings:
– Log scale makes it difficult to measure quakes >7 – Based on oldoldfashioned seismographs – Best for local quakes, not for waves that have traveled a long way 8 7 What are the Destructive Effects of Earthquakes?
Ground Ground Shaking
Seattle What are the Destructive Effects of Earthquakes?
Ground Ground Shaking
– amplitude, duration, and damage increases in poorly consolidated rocks 1 What are the Destructive Effects of Earthquakes? Damage from 1906 San Francisco earthquake Damage from 1906 San Francisco earthquake 2 Northridge earthquake damage 1971 L.A. earthquake Effects Effects of Earthquakes
– 80-90% damage in the 1906 San Francisco 80Earthquake Effects of Earthquakes
San Francisco, 1906 San Francisco, 1989 Effects of Earthquakes
– Triggered by ground shaking – Cause extensive damage 3 Effects of Earthquakes
– Water saturated soil or sediment tends to turns to slurry during earthquakes (quick sand) – Causes buildings to sink into the ground – Alaska 1964 Effects of Earthquakes
Liquefaction Liquefaction Liquefaction Liquefaction Liquefaction Anchorage, Alaska 1964 Anchorage, Alaska 1964 Liquefaction Liquefaction
San Francisco, 1906 4 Effects of Earthquakes
Permanent Permanent displacement of land surface
– Relative movement of rock bodies on opposite sides of fault Effects of Earthquakes
Tsunamis: caused Tsunamis: caused by submarine quakes
– Move at 800 km/hr – Travel across oceans Tsunamis Tsunamis
– 1960 tsunami generated off Chile
7 hr travel to Hawaii: killed 61 22 hr, 17,000 km to Japan, killed 180 Dec 26, 2004 Earthquake measuring 9.0 off the coast of Sumatra Dec Dec 26, 2004 Earthquake measuring 9.0 off the coast of Sumatra Most powerful earthquake in 40 years (Since Alaska, 1964.) Earthquake’s focus was 30km (18.6 miles) below sea level 15 meters (45 ft) of displacement along the fault Shift of mass slightly affected Earth’s rotation Earth wobbled on its axis by about 1 inch Shortened the length of a day by 2.68 microseconds (one billionth of a day) Smaller islands SW of Sumatra may have moved as much as 60-70 feet 60Northern tip of Sumatra may have moved as much as 120 feet 5 Tsunami Travel Time – Sumatra/Bay of Bengal Tsunami Travel Time – Indian Ocean Warnings Indian Ocean has no tsunami warning system Initial estimate of the earthquake’s magnitude was 8.1 Indian Ocean tsunamis are rare- last one in 1883 rareWave moved at a speed of about 500 mph AftermathAftermathInitiative to form an Indian Ocean warning system (1 year) Possibly form a global warning system Warnings Warnings 6 Damage Death tolltoll220,000+ (confirmed) DisplacedDisplacedas many as 1.5 million! Damage Indonesia Banda Aceh Damage Banda Aceh, Indonesia Damage Banda Aceh, Indonesia - Before Damage Damage Banda Aceh, Indonesia - After Damage Damage Banda Aceh, Indonesia - Before 7 Damage Banda Aceh, Indonesia - After Damage Damage Banda Aceh, Indonesia - Before Damage Damage Banda Aceh, Indonesia - After Damage Damage Gleebruk Village, Banda Aceh, Indonesia - Before Damage Damage Gleebruk Village, Banda Aceh, Indonesia - After Damage Damage Gleebruk Village, Banda Aceh, Indonesia - Before 8 ...
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This note was uploaded on 05/18/2011 for the course GEOL 105 taught by Professor Jack during the Spring '08 term at University of Louisiana at Lafayette.
- Spring '08