Earthquake Causes and Seismology Quiz

Seismology

• Scientific study of earthquakes and elastic wave propagation through the Earth.
• Origin of the term from Greek "seismos" (earthquake) and "logos" (science).
• Seismologists analyze earthquakes, predict occurrences, and study effects like seismic waves and tsunamis.

Key Seismologists

• Charles Francis Richter: Developed the Richter Scale (1953) for measuring earthquake magnitude; the scale is logarithmic, where each whole number increase represents a tenfold increase in amplitude.
• Inge Lehmann: Danish seismologist who discovered Earth's core structure in 1936, analyzing how earthquake energy travels through the Earth.

Seismic Waves

• Mechanical waves generated by earthquakes, categorized into body waves and surface waves.
• Body Waves:
  • P-Waves (Primary Waves): Fastest seismic waves, move through solid, liquid, and gas; cause forward and backward motion.
  • S-Waves (Secondary Waves): Slower than P-waves, travel only through solids; cause up-and-down movement.
• Surface Waves:
  • Love Waves: Move side to side, perpendicular to wave direction.
  • Rayleigh Waves: Roll in a circular motion along the surface.

Origin of Earthquakes

• Earthquakes are sudden ground shakes caused by seismic wave passage through Earth's rocks.
• Focus (Hypocenter): The point within the Earth where the earthquake originates.
• Epicenter: The point on Earth's surface directly above the focus, often experiencing strongest effects.

Components of an Earthquake

• Fault: Fracture or zone of fractures between rock blocks, where movement triggers earthquakes. Types include normal, reverse (thrust), and strike-slip faults.
• Aftershocks: Smaller quakes following the main event as the crust adjusts.
• Foreshocks: Smaller tremors preceding the main earthquake, can occur days to years before.
• Seismograph: Instrument that detects and records seismic waves, determining quake magnitude and location.

Causes of Earthquakes

• Earthquakes result from sudden energy release in the Earth's crust, leading to various impacts.
• Major causes include natural events and human activities.

Volcanic Activity

• Earthquakes can occur due to magma rising and causing pressure that leads to volcanic eruptions, causing localized tremors.

Tectonic Movement

• Earth's crust is composed of moving plates; stress release from their collision, separation, or sliding past each other causes earthquakes.

Geological Faults

• Displacement along fault lines causes tectonic earthquakes, prevalent globally, mainly at tectonic plate boundaries.

Examples of Significant Earthquakes

• San Francisco Earthquake (1906): Resulted from the San Andreas Fault, causing widespread destruction.
• Tohoku Earthquake (2011): Triggered a tsunami, showcasing the interconnection of natural disasters.
• Eastern Mindanao Earthquake (2024): Resulted from renewed movement of an extinct fracture zone.

Volcanic Earthquakes

• Occur with volcanic activity, typically before or after eruptions; indicate magma movement.
• Example: The 1991 eruption of Mount Pinatubo was preceded by warning volcanic earthquakes.

Explosion Earthquakes

• Result from the explosion of chemical or nuclear devices, distinguished from natural seismic events.

Test your knowledge on seismology and understand the origins and causes of earthquakes. This quiz covers fundamental concepts related to seismic activities and their implications. Perfect for students studying civil engineering or related fields.