Island Watch: Strong Aftershock Near Tonga

A strong aftershock of the magnitude 7.9 earthquake of May 4th near Tonga occurred this afternoon.

A magnitude 6.7 earthquake, 50 km deep struck 145 km NNE of Nuku’Alofa at 3:36 this afternoon, New Zealand time.

Following the major earthquake of May 4th, earthquake activity near Tonga rapidly declined in both frequency and strength of events.

This afternoon’s quake may now indicate that earthquake activity near Tonga is following a more normal pattern. The usual rule of thumb is that a major event will be followed by an aftershock about one order of magnitude lower than the main event. However, post-quake activity near Tonga rapidly declined, indicating that other effects were involved.

Continued earthquake activity south of Fiji and in the Kermadec Islands also indicated that the plate boundary might have been more active than expected.

However, today’s earthquake could indicate that seismicity is returning to normal as the plate boundary reacts to the change in stress caused by the major earthquake. This should be confirmed by activity over the next week.

One Response to “Island Watch: Strong Aftershock Near Tonga”

  1. Chris says:

    What I understand is that we had an Earthquake in Indonesia on Saturday, followed by 2 earthquakes over magnitude 6 – one near tonga and the other near Papua New Guinea.

    Plus 3 or 4 volcano’s that have shown signs of increased activity in Vanuatu.

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