Earthquakes Near Tonga

The series of earthquakes occurring near Tonga in the wake of yesterday’s magnitude 7.9 quake appears to be settling into an earthquake/aftershock sequence.

Seismologists will be watching activity over the few days to confirm the sequence.

With the passage of time, seismologists have been able to refine the size of the initial earthquake that occurred at 3:27 a.m. yesterday. Initial estimates put the magnitude of the earthquake at values between 7.8 and 8.1, and additional analysis has settled at magnitude 7.9.

There have been six aftershocks of magnitude 5 and four of magnitude 4, with a magnitude 6 quake occurring at 11:26 last night.

A rule of thumb with earthquake and aftershock sequences is that one of the aftershocks is usually one order of magnitude lower than the main shock. Therefore an earthquake of about magnitude 7 can still be expected near Tonga if this is a normal sequence.

Earthquake activity in areas nearby has continued at the slightly elevated rates that have been experienced intermittently in recent months, with two events near Vanuatu and one near Fiji.

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