A top Spanish seismologist warned of a possible destructive earthquake "shortly," less than three months before Wednesday's killer 5.1-magnitude tremor.

Luis Suarez, president of the Official Geological College, said in a February 28 interview that Spain lay in a moderately active seismic zone and was not in a particularly intense period.

But a destructive earthquake could hit "shortly, in the not-distant future," he was quoted as telling Spanish news agency Europa Press, identifying the southern Murcia and Andalucia regions as a danger zone.

In the February 28 interview, he said statistically Spain was hit with a major destructive earthquake every 70 years and the last one occurred in 1884 killing 900 people.

There were no instruments capable of accurately forecasting a tremor, so statistics were the only guide, he said.

A 5.1-magnitude quake struck at 6:47 pm (1647 GMT) on Wednesday with a depth of 10 kilometres (six miles) in the Murcia region and could be felt as far away as the capital Madrid.

It toppled buildings in the southeastern city of Lorca, killing eight people and injuring at least 130.

Suarez was not immediately available to comment on his earlier quake prediction.

The seismologist was quoted by Spanish paper El Publico on Wednesday as saying buildings in Lorca "should not have toppled" in a quake of only 5.1-magnitude.

The area is quake prone and should have been better prepared, the seismologist reportedly said, adding that older buildings can be strengthened to survive such a quake, saving lives.

The US Geological Survey said Wednesday's quake occurred within the plate region that separates the Eurasia and Africa plates.

At the longitude of the earthquake, the Africa plate is moving northwest with respect to the Eurasia plate at a speed of six millimetres, or a quarter-inch, a year, it said.

The epicenter was near a major fault, the Alhama de Murcia fault, but the USGS said the quake could also have been unleashed on a nearby fault in the Earth's crust.