SAN JOSE (Reuters) - A strong 6.5 magnitude quake struck the Pacific coast of Costa Rica near its capital city San Jose on Sunday night, but there were no initial reports of injuries or significant damage to infrastructure. Costa Rican President Luis Guillermo Solis said authorities were gathering information and asked residents to remain calm and to be prepared for any possible aftershocks.  A Reuters witness said the quake was felt very briefly in San Jose, but it was enough to startle residents.   We re very scared. It s been years since we felt such a strong one,  said Otto Vargas, a university professor in San Jose, who was home with his family when the shaking started. The quake hit in a rural area near the popular beach tourism city of Jaco, where there are few tall buildings. It did not trigger a tsunami threat in the Pacific.  Firefighters in Jaco said there were no reports of victims or major damage, but said there were some electrical poles that had come loose and fallen. Social media showed images of supermarkets in Jaco with merchandise strewn across the aisles. The Costa Rican Red Cross said it had no reports of casualties.  Neighboring El Salvador s civil protection agency tweeted that the quake caused some electrical posts to fall, while the civil protection agency in neighboring Panama said there were no reports of damage there. The quake, initially measured as much as 6.8 magnitude, was centered 43 miles (69 km) southwest of San Jose at a depth of 12.3 miles (20 km), the U.S. Geological Survey said. 