Understanding Fault Lines and Earthquakes

Seismographs and Earthquakes

• A seismograph measures seismic waves generated by earthquakes, recording the ground motion caused by the waves.

Tectonic Plates

• Tectonic plates are large, rigid slabs of the Earth's lithosphere that fit together like a jigsaw puzzle.

Faults

• The location on Earth's surface where a fault can be seen is called a fault trace.

Earthquake Prediction

• Geologists are unable to predict when earthquakes will occur because the complex processes leading up to an earthquake are not yet fully understood.

Earthquake Occurrence

• When two tectonic plates suddenly slip along a fault, they release energy in the form of seismic waves, causing an earthquake.

Foreshocks and Aftershocks

• A foreshock is a smaller earthquake that occurs before a larger earthquake (mainshock).
• Foreshocks are different from aftershocks in that they occur before the mainshock, whereas aftershocks occur after the mainshock.
• Aftershocks are caused by the continuing adjustment of the Earth's crust after the mainshock.
• Aftershocks can last for days, weeks, months, or even years after the mainshock.
• If an aftershock is stronger than the mainshock, it becomes the new mainshock, and the original mainshock is reclassified as a foreshock.