Causes
Earthquakes occur following the release of energy when tectonic plates move apart. These plates move within Earth's lithosphere, and their edges, mapped to fault lines, sometimes collide. When the plates meet and become stuck, energy from the current becomes trapped until the plates shift apart, generating seismic waves. These waves cause earthquakes as they radiate outward and shake the earth, affecting the surface when they reach it.
Consequences
There is currently no way to predict an earthquake, so they strike without warning. The most powerful earthquakes can devastate entire cities, leaving them in ruins and requiring potentially years for recovery. Earthquakes are often followed by aftershocks as the fault in Earth's crust readjusts following the initial release of energy. While aftershocks are usually less intense, in some cases, they may surpass the original seismic activity, becoming the main event and reclassifying the previous tremor as a foreshock.
Classification
There are two main ways to classify an earthquake:
- Magnitude: This is the estimated size or strength of the earthquake. Measuring the exact size can be challenging, as effects may be felt far from the epicenter, so magnitude is typically an estimate based on relative impact.
- Intensity: This measures the strength of shaking at a specific location. The strongest intensity generally occurs near the epicenter and diminishes with distance.
Satellite data
Since it is not possible to predict earthquakes before they occur, satellites are used primarily for post-event assessment. Optical and radar data provided by the International Charter: Space and Major Disasters assist first responders by mapping and evaluating damage quickly. This information helps identify areas where survivors may be in the greatest need and provides crucial intelligence on locations that may be difficult to access from the ground.