What typically precedes a major earthquake?

Foreshocks are smaller earthquakes that occur in the same general area as a larger earthquake that follows. They can happen days, weeks, or even potentially years before the main seismic event. Identifying foreshocks is significant because they indicate that stress is building up in the Earth's crust along a fault line, which can lead to a larger earthquake. This sequence of smaller quakes can sometimes provide valuable clues for scientists and geologists in understanding the likelihood of an impending significant seismic event.

The other options, while they may be related to geological processes or natural disasters, are not typically indicative of an upcoming major earthquake. For instance, while volcanic eruptions can occur due to tectonic activity, they are not directly connected to the occurrence of earthquakes in all cases, as earthquakes can occur in regions far from volcanic activity. Landslides might result from seismic activity or other geological factors but are not a precursor to earthquakes. Heavy rainfall can indeed exacerbate landslides or soil instability but does not have a direct causal relationship with the occurrence of earthquakes.