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Geo 2
| Question | Answer |
|---|---|
| What do you think? Earthquake magnitudes, timing, location and amount of shaking are predictable. | False, Amount of shaking, however is somewhat predictable...depending on circumstances. |
| Earthquakes are a release of energy when rocks snap, or fracture. What rheological layer do most earthquakes occur in? | Lithosphere |
| Which of the following is NOT likely to cause an earthquake? | Flood. Earthquakes can be generated by any disruption that sends energy through rocks. Most common is release of energy from rocks stored by plate movement. |
| What location is at the least risk for an earthquake? | The east coast of South America is the only location on this list that is not a plate boundary (i.e. it is a passive margin) |
| What is the best definition of a fault? | Faults are fractures upon which the rocks have moved |
| Which of the following DOES NOT determine the magnitude of a quake? | The distance between you and the epicenter |
| How many earthquakes are shown? Fill in the events shown. | 2 that look like waves |
| Choose the correct order of processes that generate an earthquake. | Stress is applied, strain is stored, rocks break, and then rocks rebound |
| How many types of seismic waves are there? | 3, P waves, S waves, Surface waves |
| What type of seismic wave causes a vertical jolt? | P = Primary; P waves are compressional waves which cause a vertical jolt when they reach the Earth’s surface. |
| How does wave amplitude relate to shaking? | The higher the amplitude shown on the seismogram the stronger the shaking |
| What approximate length of fault will rupture during a Mw8 earthquake? | 600 km (311 mi) |
| Three measurements are needed to calculate Moment Magnitude (Mw) of an earthquake. | Depth to the focus |
| Which of these TRUE statements is not a description of earthquake intensity? | The area of the fault ruptured during the 2011 M9 Tohoku earthquake was much larger than originally thought |
| Which of the following locations has not had a major eq (>Mw 7.0) in the last 10 years? | All of these locations have had major earthquakes California has not had a Mw 8 or higher in recorded history. Largest recorded were Mw 7.9 in 1906 and 1857 Nepal’s last Mw 8 or higher was in 1934 and before that was 1833. |
| Which scale do we use to measure the amount of shaking that occurred because of an earthquake? | Mercalli Intensity Scale |
| What is an aftershock? | An earthquake that occurs after a main shock along the area of fault that ruptured during the main shock |
| Approximately how many >M3 aftershocks do you think are related to the M9 Tohoku EQ (Japan, 2011) (within 1 week of the event)? | ~3000!!! |
| What is liquefaction? | The process of wet sediment fluidizing during an earthquake. No liquificiation on bedrock |
| Why is ground shaking amplified in less dense rock and sediment? | Seismic waves (P&S) slow down which increases wave amplitude |
| Which of the following factors does not contribute to landslides? | Age of the rock |
| Why do earthquakes often cause landslides? | Earthquakes reduce friction between layers of rock or sediment, reducing resisting forces |
| Q3: Here is a picture from Arches National Park in Utah. What is this telling you about earthquakes in this area? | This area has not experienced a major earthquake in a long time. |
| How do geologists study earthquakes - both past and present? | Measure orientation, dimensions, and offset of surface fault ruptures. Dig trenches across a fault to study its history of movement. Look for changes in the landscape. Drill and instrument deep holes across faults to record data on active faulting |
| Tsunami look like curling, breaking waves when they reach the coastline | False |
| Tsunami are created by earthquakes only | False. Tsunami can be generated by landslides, asteroid impacts, and volcanic eruptions |
| Earthquakes occur under Earth’s oceans frequently, but tsunami are only generated by some of them...not all. | True. High magnitude earthquakes ~ M7 or greater (on dip-slip faults), may generate a tsunami. Smaller magnitude earthquakes don’t move the seafloor enough. |
| Tsunami can travel across all oceans (e.g. from one side of the Pacific Ocean to the other) | YES! This has been documented many times, particularly when tsunami result from high magnitude earthquakes |
| The water from the beach can withdraw before a tsunami arrives. | True. When the trough of the wave approaches the shore, it will quickly draw in water, leaving boats and fish stranded. This is an important warning sign. |
| How high was the highest tsunami ever recorded? (remember there are 3.28 feet in every meter) | 524 m . This was caused by an earthquake-induced landslide into a small bay in Alaska, 1958 |
| Tsunami are caused by seismic energy moving through the ocean | NO! This is a common misconception. Tsunami are created when a large amount of water is displaced by (1) movement on a fault & elastic rebound due to an earthquake, (2) landslides, (3) an asteroid impact or (4) volcanic eruption |
| What are the characteristics of places at risk for tsunami? | Coastal Areas Tectonically active areas Pacific ‘Ring of Fire’ - highest risk |
| Most Waves are generated by…. | Wind. Particles in the air collide with the surface of the water and transfer energy. The faster the wind, the bigger the wave. |
| What is wavelength? | The horizontal distance between two consecutive wave crests = wavelength |
| Choose the best statement that describes the tsunami shown in the previous animation. | Rupture along a length of fault on the seafloor displaces water. Water domes along the length and spreads outward in all directions as a wave. The wave grows in height as it approaches the shoreline. |
| What controls how much water will be drawn back into a tsunami when it approaches shore? | Slope of the seafloor Wavelength of the tsunami |
| Why does tsunami wave height increase as it moves towards shore? | The tsunami slows down in shallow water |
| How is wave height different from run-up height? | Wave height is the height of the wave before it breaks; run-up height is vertical distance between sea level and the maximum height of the water on land. |
| Which of the following characteristics does not contribute to run-up height? | Trigger event of the tsunami (earthquake, volcanic eruption, landslide) |
Created by:
mme293