Formation of Earthquakes
Earthquakes form primarily due to the movement of Earth's tectonic plates, which make up the lithosphere and float on the semi-fluid asthenosphere. These plates interact at boundaries where they converge, diverge, or slide past each other, building up stress in the rocks. When the stress exceeds the rock's strength, it fractures along faults, releasing stored energy as seismic waves that shake the ground.
Key Principles of Earthquake Measurement
The Richter scale, developed in 1935 by Charles F. Richter, measures the magnitude of an earthquake logarithmically based on the amplitude of seismic waves recorded by seismographs, adjusted for distance from the epicenter. Each whole number increase on the scale represents a tenfold increase in wave amplitude and approximately 31 times more energy release, allowing comparison of earthquake sizes worldwide.
Practical Example: The 1906 San Francisco Earthquake
The 1906 San Francisco earthquake, caused by slippage along the San Andreas Fault, had a Richter magnitude of about 7.9. This release of energy from accumulated tectonic stress along the transform boundary produced intense shaking, surface ruptures up to 270 miles long, and widespread destruction, illustrating how plate movement triggers seismic events and how the scale captures their power.
Importance and Real-World Applications
Understanding earthquake formation aids in hazard assessment and building resilient infrastructure in seismically active areas. The Richter scale, though largely replaced by the moment magnitude scale for larger events, remains a foundational tool for public communication, emergency response, and educating communities on risks, enabling better preparedness and reducing potential loss of life and property.