Earthquakes Flashcards
When does an earthquake happen?
when rocks get stressed by movement of tectonic plates, and finally break, causing movement along a fault.
Where do most earthquakes happen?
in subduction zones (convergent boundaries) at plate edges
Where are most of the world’s earthquakes and volcanoes located?
Pacific Rim of Fire (outlines Pacific Ocean)
Which travels slower?
S waves or P waves
S waves
What happens between s waves and p waves, the closer you are to an earthquakes
their arrival times are closer together
What is a focus (in regards to earthquakes)?
the place underground where the actual movement along a fault occurred during an earthquake
What is an epicenter?
the location at Earth’s surface just above the focus
What does damage from an earthquake depend on?
-4 things
1-nearness to epicenter (closer- more damage)
2-types of rocks underlying (igneous & metamorphic are stronger- less shaking)
3-whether tsunami results from earthquake
4- whether or not buildings have been built to withstand earthquakes
Earthquake disaster preparation
-4 things
1- evacuation plan
2- conduct drills in the home
3- first aid kit
4- supply of water, food, battery-operated radio, flashlights, cash, medications, special items for babies/elderly
What is pangea?
the name scientists have given to the “supercontinent” that existed about 250 million years ago, when all of Earth’s major landmasses were joined together.
What do p waves travel through?
solids and liquids (compressional)
What do s waves travel through?
solids only (shear)
How many seismic stations are necessary to locate an epicenter?
THREE
What makes tectonic plates move?
convection currents in the mantle
compare and contrast the Modified Mercalli Scale and the Richter Scale
The Modified Mercalli Scale measures the intensity of an earthquake based on its observed effects on people and structures at a specific location, while the Richter Scale measures the magnitude of an earthquake, which is a quantitative measurement of the energy released at the earthquake’s source, making the Mercalli scale subjective and location-dependent, while the Richter scale is objective and based on seismic wave data recorded by a seismograph.
Describe the relationship between earthquakes and volcanoes
Both volcanoes and earthquakes occur due to movement of the Earth’s tectonic plates. They are both caused by the heat and energy releasing from the Earth’s core. Earthquakes can trigger volcanic eruptions through severe movement of tectonic plates.
Earthquakes frequently precede volcanic eruptions, and volcanoes are often sources of small to intermediate size earthquakes resulting from the movement of magma within the volcano’s plumbing system.
What is a tsunami and what may result from one?
A tsunami is a series of giant waves caused by a sudden displacement of a large volume of ocean water
Loss of life and injury: Tsunamis can cause mass injuries and loss of life, often due to drowning.
Damage to property: Tsunamis can destroy or damage homes, businesses, ports, harbors, and other structures. They can also contaminate drinking water and cause fires.
Disruption of services: Tsunamis can disrupt access to power, water, and other basic services.
Flooding: Tsunamis can cause dangerous coastal flooding that can last for days.
Movement of debris: Tsunamis can move large rocks, boats, and other debris hundreds of feet inland.
Hazardous currents: Tsunamis can create strong currents that can injure and drown swimmers and damage boats.
Landslides: Tsunamis can cause landslides.
What is a shadow zone?
A “shadow zone” refers to an area on Earth’s surface where seismic waves from an earthquake cannot be detected, primarily because they are either blocked or significantly bent by the Earth’s liquid outer core, creating a “shadow” where seismic data is missing
How do you determine the location of an epicenter using arrival times from seismic stations?
measuring the time difference between the arrival of P-waves and S-waves at multiple seismic stations, then plotting circles on a map with radii representing those distances; the point where all the circles intersect is the epicenter
How do you determine the distance from an epicenter by p wave and s wave arrival times?
measure the time difference between when the P-wave arrives and when the S-wave arrives at a seismic station
How do you determine the time origin of an earthquake?
scientists use seismographs to record the arrival times of the P-waves and S-waves at multiple seismic stations, then calculate the time difference between the arrivals, which allows them to estimate the distance to the earthquake’s epicenter; by comparing this data across several stations, they can pinpoint the earthquake’s origin time through a process called triangulation.
