Earthquakes are common occurrences along the Pacific Coast of Mexico S and SE of Acapulco, between there and the mid-point of the Pacific Coast of Oaxaca; it's probably the most active earthquake zone in the country. Earthquakes occur on an almost daily basis; sometimes two or three a day. Serious damage doesn't typically result from earthquakes, but international organizations may consider the city/area "high risk" because if its proximity to the earthquake zone and/or because of the poor construction techniques utilized in years past.
However, if you have a chance to observe some of the new condominium construction in the Diamante Zone and south of there you'll note the special measures being taken to shore-up the new buildings in case a quake strikes. Some tourists feel the earthquakes, many don't; most of us probably sleep or drink our way through them!
The Mexican government maintains a website detailing earthquake activity and you can have a look at it if you're interested:
