Terremoto vs. seísmo vs. sismo vs. temblor
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
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
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
'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
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.