Earthquakes & Seismic Waves

Earthquakes

• Vibrations in the earth's ground are due to the movement of plate at fault lines and are called earthquakes
• Most earthquakes occur along plate boundaries

Faults

• Faults: A break in earth's lithosphere where one block of rock moves towards, away from or past another block of rock
• Strike slip faults occur at transform plate boundaries
• Normal faults occur at a divergent plate boundaries
• Reverse faults occur at convergent late boundaries

Earthquakes Components

• Seismic Waves: Energy that travels as vibrations
• Focus: A point inside the earth where the earthquakes first start
• Epicenter: The location on earth's surface directly above the focus

Types of Seismic Waves

• Primary Waves: Travels in push pull motion, fastest moving seismic waves, and can travel through solids and liquids.
• Secondary waves: Moves in a rolling motion, slowest seismic wave, causes the most damage to Earth's surface
• Surface waves: Moves in a rolling motion, slowest seismic wave, courses most damage to earth's surface

Earths Interior

• S-waves cannot travel through liquids, but p-waves can travel through both solid and liquids leading scientist to discover that the outer core is liquid

Finding an Epicenter Through Triangulation

• Find the difference between the arrival time of the p-wave and the arrival time of the s-wave
• Determine the distance of the epicenter using a earthquake distance graph
• A circle with the correct distance around the station must be drawn and repeated for two more stations
• Where the circles intersect, is the epicenter

Scales to Measure Earthquakes

• Richter scale: Measures the amount of ground motion at a given distance
• Moment magnitude: Measures the total amount of energy release by an earthquake
• Modified Mercalli scale: Measures the intensity of an earthquake Based on amount of damage and has levels 1 - XII

Earthquake Risks

• Seismologist use 5 indicators to assess earthquake risk
• Namely past earthquakes, probability, population density, geology around a fault, & building design

Volcano

• Volcano: A vent earth crust trough which molten rck flows

Volcano Formation

• Convergent boundaries: Two plates collide and one plate subduct under another plate causing volcanoes to form
• Divergent boundaries: Two plates separate and magma comes out for example mid-ocean ridges and rift valleys
• Hot spots: Volcanoes that are not associated with plate boundaries such as Hawaii

Types of Volcanoes

• Shield volcano: Large shield shaped Volcanoes with gentle slopes and gentle eruptions
• Composite volcano: Large steep-sided Volcanoes, that result from explosive eruptions
• Cinder cone volcano: small, steep-sided volcanoes that erupt gas rich, basaltic lavas. Moderately explosive eruptions

Caldera

• Caldera: Large volcanic depression create when the summit of the volcano collapsed during a violent eruption

Types of Eruptions

• Violent Eruptions: Lava has high viscosity thick lava and high gas content
• Quiet Eruptions: Lava has low viscosity thin lava and low gas content

Effects of Volcanic Eruptions

• Lava flow: Moves slowly, can destroy towns, and are rarely deadly
• Ash fall: Cases breathing problems, can cool earth's atmosphere and can disrupt Air traffic
• Mudflow: Causes snow and ice to melt, which mixes with mud ash
• Pyroclastic Flows: Can be deadly, produced from violent eruptions, and throw gas, ash and Rock into the air

Predicting Volcanoes

• Through Ground deformation observed, increase in earthquakes, volcanic gas increases and water near the volcano that becomes more acidic

Climate

• Volcanic eruptions blocks the sun and causes a decrease in global temperatures & also causes acid rain

Learn about earthquakes, the vibrations caused by plate movement at fault lines. Explore different types of faults like strike-slip, normal, and reverse faults. Understand earthquake components such as seismic waves, focus, epicenter, and the types of seismic waves.