What Causes Earthquakes?
Earthquakes are caused by the sudden release of energy in the Earth's crust, creating seismic waves. This release is usually due to tectonic plate movements, volcanic activity, or man-made explosions.
Measuring Earthquake Magnitude
Seismologists use the Richter scale to measure earthquake magnitude. The scale is logarithmic, meaning each whole number increase represents a tenfold increase in measured amplitude and roughly 31.6 times more energy release.
Intensity vs Magnitude
Magnitude measures the energy released at the source of the earthquake. Intensity, on the other hand, measures the strength of shaking produced by the earthquake at a specific location.
Seismic Wave Types
There are primary (P) waves, which are compressional and travel fastest, and secondary (S) waves, which are shear and slower. Surface waves, like Rayleigh and Love waves, cause the most damage.
Ground Motion Prediction
Ground motion prediction equations (GMPEs) estimate the expected ground motion at a site given the magnitude, distance, and other quake characteristics, crucial for engineering and hazard assessment.
Soil Amplification Effect
The type of soil or rock can amplify seismic waves. Soft sediments can increase shaking intensity, while bedrock can reduce it. This is why similar earthquakes can cause different damage levels.
Predicting Earthquake Occurrence
Despite advances in seismology, precise earthquake prediction remains elusive. Current research focuses on probabilistic seismic hazard analysis, which estimates the likelihood of certain magnitudes occurring within a region over time.