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EAR Chap3 and Chap4
Earthquakes
| Question | Answer |
|---|---|
| What is an earthquake? | An earthquake is a rupture of earth's rock along the fault. Rocks on opposite sides of a fault move suddenly, and energy is released in the form of seismic waves. |
| What are the main causes of earthquakes? | The main cause of an earthquake is the sudden movement of the Earth's tectonic plates along underground fracture zones called faults |
| Explain the difference between the focus (hypocenter) and the epicenter of an earthquake | Focus is directly below the epicenter. Epicenter is the point on the surface that is above the focus. |
| Describe the types of seismic waves and their characteristics | Surface waves travel along the outer part of Earth. Body waves are caused by a release of energy from rupture of a fault. P waves (push/pull) move faster than S waves (up/down motion) Surface waves move along Earth's surface and travel more slowly. |
| How are earthquakes measured? Explain the Richter scale and the moment magnitude scale. | Earthquakes are measured by magnitude and intensity. The size, or magnitude, of an earthquake is expressed as a decimal number is Richter scale . Moment magnitude = along a fault plane during the quake, movement along the fault, rigidity near focus |
| What is the Modified Mercalli Intensity scale, and how does it differ from the Richter scale? | The Modified Mercalli Intensity Scale measures the degree to which an earthquake affects people, property, and the ground. Richter scale measures magnitude, while Modified measures intensity |
| How do plate tectonics relate to the occurrence of earthquakes? | Plate tectonics are the movement of Earth's plate. This relate to the occurrence of earthquakes because the plates moving can build up pressure until it ruptures. In other words, it is the reason for the build up of pressure in the rocks. |
| Explain the phenomenon of liquefaction and its impact during an earthquake. | Intense seismic shaking can cause water-saturated loose sediment to change from a solid to a liquid. Shaking is more violent in areas where materials contain a lot of liquid. |
| What is a tsunami, and how is it related to earthquakes? | A tsunami is a series of waves caused by the displacement of a large volume of water, typically in an ocean or a large lake. It is related to earthquakes because they tend to arrive not long after one. The release of pressure pushes the water up |
| How is a tsunami different from a typical ocean wave? | A tsunami is different from a typical ocean wave because of its speed and amplitude. In addition, a tsunami is usually the result of a sudden vertical increase of the sea floor following an earthquake. A typical ocean wave is caused by wind. |
| Name at least three natural events that can trigger a tsunami and explain how each event generates the wave. | Earthquake, landslide, and volcano (though rare). Earthquake, of at least 7.5 M or more, uplifts or downshifts the seafloor; dome collapses and generates a tsunami wave; volc. too Submarine landslides displaces water vertically. Land = rock avalanches, |
| What are the key factors that determine the size and speed of the tsunami? | The depth of the ocean determines the size and speed of the tsunami. Deeper water allows the tsunami to move faster. Depth of ocean decreases = slowing tsunami waves; more water piles = increasing amplitudes and frequency. |
| What happens to their speed, wavelength, and wave height as they travel from deep water to shallow coastal areas? | The speed decreases, the wavelength shortens, and its height (amplitude) increases. |
| What is the deadliest Tsunami? What caused it, and why was it so devastating in terms of loss of life and property? What were some of the compounding factors that made this event particularly catastrophic? | The 2004 Indian Ocean tsunami was the deadliest, killing over 230,000 people. The Sumatran earthquake (M 9.1+) caused it. Devastating because of population increase. Prompted one of the largest humanitarian relief efforts. Even traveled to East Africa. |
| What technologies are used to detect tsunamis, and how are coastal populations alerted? | Seismographs to detect earthquakes, automated tidal gauges to determine sea level changes, Buoy sensors with tsunameter detect small changes in ocean pressure. Warning sirens are used to elert the public. |
| How do landslide-generated tsunamis differ from earthquake- generated ones in terms of wave behavior and impact? | Landslide-generated tsunamis produce extremely high waves and severe localized destruction near their source, but they lose energy quickly and rarely cross entire oceans, unlike broad, fast-moving tectonic tsunamis caused by earthquakes. |
| How do features like bays, inlets, and offshore barriers influence the severity of a tsunami? | They are near sources of a tsunami; all oceans and some lake shorelines have some risk. In addition, the greatest risk is to areas near or across from subduction zones. Many villages that were spared were |
| Why are some coastal areas less affected by tsunamis despite being close to the source? | Features, such as vegetation, protect the land from the energy of the tsunami. Protective vegetation could be retained or planted between the development and the ocean to provide protection from at least small tsunami |
| What is a Tsunami Watch? | a notification that an earthquake that could cause a tsunami has occurred |
| What is a Tsunami Warning? | indicates that a tsunami has been detected and is moving across the ocean toward their area |
| What must a community have to be Tsunami ready? | Have an emergency operation centre with 24-hour capability, ways to receive tsunami warnings from responsible provincial and state agencies , ways to alert the public , a tsunami preparedness plan, community awareness of tsunami hazards |
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