The area has been shaken by dozens of quakes over the last week
(Recasts, adds comments, background)
By Rosalba O'Brien
SANTIAGO, April 28 (Reuters) - A cluster of tremors shook central Chile on Friday afternoon, leaving locals worried that a bigger earthquake may be imminent and prompting some early closures of schools and workplaces.
At least seven tremors struck offshore the coastal city of Valparaiso in less than an hour, with the largest rattling buildings in the Chilean capital Santiago some 102 kilometers (63 miles) away.
The United States Geological Survey said the most powerful tremor, which hit at around 1:05 p.m. local time (1605 GMT), was magnitude 5.7, with a depth of 9 miles (14 km) and an epicenter 12 miles (20 km) west of Valparaiso.
No damage was reported by the emergency office and the navy said the quake had not been severe enough to cause a tsunami.
But worried locals hurried home from work and schools were told to finish early.
"This chain of tremors has caused a lot of worry and families want to be together," Valparaiso city Mayor Jorge Sharp said in broadcast comments. Authorities advised citizens to ensure that they had emergency kits ready.
Chile, on the Pacific 'ring of fire', is one of the most earthquake-prone countries in the world. Builders follow strict construction codes and Chileans are usually stoic about the country's regular tremors.
But the string of tremors on Friday follows an entire week of smaller ones centered close to Valparaiso after a 6.9 magnitude quake offshore on Monday.
"Services are functioning. The problem is the anguish and anxiety that we are living through, this has not happened before," said Gabriel Aldoney, mayor of the region of Valparaiso.
Scientists said that the string of tremors did not necessarily mean that a larger quake was imminent, but that such an event could not be ruled out.
"We think that the Nazca and South American tectonic plates are converging at about 6.5 centimeters a year," said Sergio Barrientos, the director of the national seismological center.
"That is pretty high in terms of plate movement."
In 1960 Chile was hit by a 9.5 magnitude quake, the strongest in recorded history.
In recent years, the biggest quake to hit Chile was an 8.8 magnitude tremor that struck the central-southern region in 2010, triggering a tsunami and killing more than 500 people.
(Reporting by Rosalba O'Brien, Gram Slattery and Reuters TV; Editing by Mary Milliken)
Our Standards: The Thomson Reuters Trust Principles.