A slow-slip "silent" quake under the North Island's East Coast has been triggered by last Monday's massive Kaikoura earthquake.
Monitoring equipment has detected a large ongoing slow-slip deep below the Earth's surface under Hawke's Bay and Gisborne.
The silent quake has moved GPS stations 2-3cm.
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GNS scientists believe the unfolding quake, which could last months, was triggered by passing seismic waves from the 7.8 earthquake.