Tonga earthquakes

M5.6 earthquake 112 km ESE of Pangai, Tonga

A magnitude 5.6 earthquake struck 112 km ESE of Pangai, Tonga on Mon, Jul 17, 2017, 6:06 AM GMT+13 (17:06 UTC), 16 km (10 mi) below the surface.

A larger quake followed: M5.7 119 km ESE of Pangai, Tonga. This one was a foreshock.

Nuku‘alofa forecast More in Tonga

Map

Where this earthquake was located, with the others nearby. Select one for its page.

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The earthquake

Magnitude: 5.6 (Mww, W-phase moment), moderate
Magnitude from: USGS National Earthquake Information Center
Local time: Mon, Jul 17, 2017, 6:06 AM GMT+13
UTC: 2017-07-16 17:06:43 UTC
Depth: 15.5 km (9.6 mi), shallow
Epicenter: 20.380° S, 173.461° W
Region: Tonga
Strongest shaking: III, weak shaking
PAGER alert: Green
Tsunami flag: No
Status: Reviewed by a seismologist

Magnitude estimates

Different scales measure different things and differ by a few tenths. The USGS marks one as preferred, and it is the one this page uses.

Mag.	Scale	Computed by	Notes
5.6	Mww, W-phase moment	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.073 · 18 stations
5.58	Mw, moment	ISC-GEM global catalog	Final · ±0.1
5.7	Mwb, body-wave moment	USGS National Earthquake Information Center	Moment tensor · Reviewed

Shaking

The USGS ShakeMap: shaking estimated from seismic stations and the quake’s size, on the Modified Mercalli intensity scale.

Strongest estimated: III, weak shaking
Peak ground acceleration: 118.0% of gravity
Peak ground velocity: 0.6 cm/s
Map: Automatic

USGS ShakeMap: estimated shaking intensity around the epicenter — Estimated shaking intensity. Map: USGS ShakeMap.

Did you feel it?

No one has reported feeling this quake to the USGS.

Estimated impact

The USGS PAGER system estimates deaths and economic losses from the shaking and the population and buildings exposed to it.

Alert level: Green: little or no damage or loss of life expected

Deaths: estimated chance of each range
Range	Chance
Under 1	65%
1 to 10	30%
10 to 100	4%
100 to 1,000	Under 1%
1,000 to 10,000	Under 1%
10,000 to 100,000	Under 1%
100,000 to 10,000,000	Under 1%

Economic losses: estimated chance of each range
Range, million USD	Chance
Under 1	65%
1 to 10	30%
10 to 100	4%
100 to 1,000	Under 1%
1,000 to 10,000	Under 1%
10,000 to 100,000	Under 1%
100,000 to 10,000,000	Under 1%

Fault motion and ground failure

How the rock slipped, from the moment tensor, and the USGS estimate of landslides and liquefaction.

Faulting: Reverse (thrust)
Moment magnitude: 5.6 Mww
Nodal plane 1: Strike 232°, dip 26°, rake 111°
Nodal plane 2: Strike 28°, dip 66°, rake 80°

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 8.4 km horizontally, 1.8 km in depth
Magnitude uncertainty: ±0.07
Depth from: From modeling of broad-band P waveforms
Station coverage gap: 70°
Stations used: 99

Nearest places

Distance and direction from each place to the epicenter, with its forecast.

Nuku‘alofa, TongaPopulation 22,400. Forecast200 kmENE

Nearby

Within 100 km, magnitude 2.6 and up: 14 in the 60 days after this one and 7 in the 30 days before it.

After

Before

Earthquakes today Tonga earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us20009wsf (also filed as iscgem612794926). Read Sun, Oct 4, 2026, 8:03 AM UTC.