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Terremoto vs. seísmo vs. sismo vs. temblor

Word practice demo
In Spanish, the words terremoto, seísmo, sismo and temblor all refer to the phenomenon of an earthquake. However, they are used in slightly different contexts and have minor differences in connotations.

Terremoto

B1
This term is commonly used in most Spanish-speaking countries to refer to a very strong earthquake. It comes from the Latin word terraemotus, which means earth movement.
El terremoto en México de 1985 fue uno de los más destructivos en la historia del país.
(The 1985 earthquake in Mexico was one of the most destructive in the country's history.)

Seísmo

B2
This is a more technical and scientific term for an earthquake. It is derived from the Greek word seismos, which means shake.
Los científicos están investigando el seísmo que ocurrió ayer en California.
(Scientists are investigating the earthquake that occurred yesterday in California.)

Sismo

B1
Sismo is generally used interchangeably with seísmo, but it is more common in Latin American countries.
El sismo provocó graves daños en las infraestructuras de la ciudad.
(The earthquake caused serious damage to the city's infrastructure.)

Temblor

A2
While temblor also refers to an earthquake, it emphasizes the sensation of trembling or shaking associated with seismic events. It is usually used to refer to less severe earthquakes.
Sentí un temblor ligero esta mañana; creo que hubo un pequeño terremoto.
(I felt a slight trembling this morning; I think there was a small earthquake.)

Summary

While all four words refer to an earthquake, there are slight differences: terremoto implies a strong quake, seísmo and sismo are more scientific terms and often interchangeable, whereas temblor emphasize the sensation of shaking during an earthquake and usually refers to less severe events.