Two earthquakes shake South Island

18:53, Jul 10 2012

Two earthquakes, measuring magnitude 4.5 and 4.6, shook the South Island within a minute of each other last night, GNS Science says.

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The first quake, a shallow magnitude-4.5 shake was strongly felt in Christchurch when it struck at 11.32pm, GNS Science reported. It was centred 10 kilometres southwest of Christchurch and was 11km deep.

The quake's strength was revised down after earlier being reported as magnitude 5.0.

The first quake was followed less than a minute later by a 4.6 quake, 20km northwest of Blenheim. The 70km deep quake was felt in Marlborough, GNS Science said.

GNS seismologist Dr Bill Fry said it was possible that the shaking of the Christchurch quake had trigged the Blenheim quake, though they had occurred on different fault lines.

A police communications spokesman said there were no immediate reports of damage following the earthquakes.

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