Locating Earthquake Epicenters

Earthquakes and Their Impact

• Earthquakes release massive amounts of energy, with some natural phenomena like lightning bolts and tornadoes releasing equivalent amounts.
• The size and duration of an earthquake determine its intensity, but the nature of the material and design of structures are also important factors in determining damage.
• Liquefaction occurs when shaking causes water to come out of the ground, destroying foundational support and causing buildings to collapse.
• Factors that contribute to damage include poorly built structures, fires caused by broken gas lines, and tsunamis caused by underwater earthquakes, explosions, or landslides.
• Tsunamis are caused by a wave of water that is pushed up by vertical motion, and they can move at speeds of up to 500 miles per hour.
• Earthquakes occur in specific areas along plate boundaries, which define the edges of tectonic plates.
• The depth of earthquakes is related to the angle of the plate, with shallow earthquakes occurring near the edge and deep earthquakes occurring further away.
• There is currently no reliable way to predict earthquakes, with predictions based on historical data and patterns.
• Chile is an example of a country that is well-prepared for earthquakes, with reinforced buildings and infrastructure.
• The 1906 San Francisco earthquake caused a lot of damage due to fires caused by broken gas lines.
• The Cascadia mega thrust is a prime area for tsunamis to develop due to the subduction of one plate beneath another.
• Landslides can also be caused by earthquakes and can have devastating effects, as seen in the 1980 Mount St. Helens eruption.

Understanding Earthquakes and Using Waves to See Inside the Earth

• Animals behaving differently before an earthquake is not a reliable predictor of earthquakes, as they may sense lower frequency waves than humans.
• Sediments from layers of earth can be radiocarbon dated to determine the exact dates of previous earthquakes, providing a sense of when they occur.
• Earthquake prediction for the future is not possible, but building redesign and retrofitting, as well as earthquake warning systems, can minimize damage and save lives.
• Earthquake waves can be used to see inside the Earth, similar to how sonograms are used to see inside humans.
• Earthquake waves bend and refract differently depending on the density of the materials they pass through, allowing scientists to identify the difference between waves that have been double reflected or refracted.
• Primary waves (P-waves) and secondary waves (S-waves) behave differently when passing through solids and liquids, allowing scientists to determine the properties of the Earth's layers.
• S-waves are stopped completely by liquids, creating a shadow zone that indicates the presence of a liquid layer.
• Earth's crust is the thin outer rocky layer, with oceanic crust being about five miles thick and continental crust being about 40 miles thick.
• Continental crust is primarily composed of granitic rocks, while oceanic crust is denser and mainly composed of basalt.
• The mantle is the thickest layer of the Earth, and the outer core is a liquid layer that creates the Earth's magnetic field.
• The inner core is a solid layer, and the temperature and pressure increase towards the center of the Earth.
• Understanding the Earth's layered structure and properties is possible because of the study of earthquake waves and their interactions with different materials.