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Geology Exam 2
| Term | Definition |
|---|---|
| Mallet (1857) | Mapped earthquake zones around the Mediterranean, produced contour maps of equal devastation, suggested that earthquakes are electric wave of compression caused by the sudden flexing or fracturing of the earth’s crust. |
| Milne | Founder of modern earthquake studies and Seismology, noted 3 types of earthquake motion (P-waves, S-waves, L-waves), the time interval between the first wave and the later waves was related to the distance from the earthquake (epicenter). Seismograph. |
| Mercalli (1902) | Mercalli scale, 1-12, qualitative (mercaLLi, quaLitative). Based on personal accounts, movement of objects, building damage |
| Reid (1906) | Elastic rebound theory after San Francisco earthquake |
| Richter (1935) | Richter scale, 1-8 quantitative, based on seismograph amplitude |
| Winthrop (1755) | Quakes are waves in the earth (they rise and drop) |
| Mitchell (1760) | Quakes caused by shifting rocks. Epicenter calculation. |
| Elastic Rebound Theory | The gradual movement on either side of a fault builds elastic strain in the surrounding rocks.When the fault breaks, it releases energy in form of earthquakes. Waves radiate from focus, and then there won't be another quake there for some time. |
| Seismograph | There is a piece of paper on a slowly turning spoon and a pen shakes as a result of the earthquake. The pen draws on the paper and you can see the waves. One rotation= 15 minutes. Each vertical line= 1 minute. |
| Effects of Lisbon earthquake | It changed the intellectual thought at the time (the “Age of Reason”) because it was so devastating it changed people thinking that 1)Man was capable of discovering all laws of the universe and 2) These laws were divinely ordered, harmonious and good. |
| Tension | Stretching. Normal Faults. Hanging wall moves downward. |
| Compression | Folding. Reverse and thrust faults. Hanging wall moves upward. |
| Shear | Bending. Transform/strike-slip faults, no vertical motion. |
| Strike | Horizontal line along fault plane |
| Dip | Angle of fault plane. |
| Horst | Hill formed as other blocks move up. |
| Graben | Valley formed as one block moves down. |
| Body waves | Through the earth; P-waves and S-waves |
| Surface waves | Only on the surface. Most destructive. Love waves and Rayleigh waves; slightly slower than S-waves. |
| P-waves | First to arrive (primary). Pressure. 460 km/min. |
| S-waves | Second to arrive (secondary). Up and down. 260 km/min. |
| Love waves | Side to side motion |
| Rayleigh waves | Water wave motion |
| Distance to epicenter (miles) | 5.7 x (S-P interval) |
| Finding amplitude | Find the most extreme wave from the base line, follow horizontally to y-axis to find amplitude in mm. |
| Causes of Tsunamis | Caused by faulting (quakes), landslides, and eruptions. |
| Wave speed of tsunamis | Wave speed is proportional to the depth of the ocean. Speed = sq. root of (gravity x water depth) |
| Great Alaskan Quake (1964) | Magnitude 8.4-9.2 (off the scale!) Caused by North American and Pacific plates-subduction; vertical motion caused uplift of 6 feet up to 38 feet; subsidence 2-8 feet. Damage from shaking, slumping, fire, tsunami. |
| San Francisco (1906) | Epicenter: N of San Francisco on San Andreas transform fault, caused damage through shaking but more through fires. Led to elastic rebound theory. 10-20 feet movement, damage along 250 mile of fault.Oregon and Nevada.wrecked 5 sq mi, killed 700 people. |
| Sumatran Quake (2004) | Megathrust fault along Australian plate, hit Indonesia, malaysai, Thailand, india, sri lanka, Maldives, Somalia, Madagascar, Tanzania. Magnitude 9.0. Triggered massive tsunami. |
| Loma Prieta (1989) | affected San Fran, collapsed bridges and highways (refer to slides) |
| Quake Damage | Faulting, shaking, Slumping, Fire, Tsunami, Liquefaction |
| Liquefaction | o Rocks behave like liquids when shaken (thixotronic) o Soft sands, clays, water-ogged sediment, land-fill o Can lead to landslides, slumping, collapse, sand boils |
| Seismic Gap Theory | Active regions that have been seismically dormant for some time are building elastic strain. The longer they go with no quake, the larger the strain. It is likely there will be a quake relatively soon. |
| Earthquake monitoring | Measure changes in distance, ground elevation, or the physical properties of a rock in order to monitor movement along faults and the build-up of elastic strain. Measuremnts include geodetic (distance), tilt (change in slope), electrical conductivity |
| Tsunami Warning System | Pacific ocean-wide network of seismic stations, tsunami buoys, coastguards, and civil defense. |
| Foreshocks | Sometimes larger earthquakes are preceded by a period of days of months of smaller earthquakes. |
| Aftershocks | After an earthquake, the crust around the fault is highly unstable and takes movement to readjust. This causes more smaller earthquakes. |
Created by:
dobrien820
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