Tonga earthquakes

M6.1 earthquake 103 km SE of Pangai, Tonga

A magnitude 6.1 earthquake struck 103 km SE of Pangai, Tonga on Thu, Oct 19, 2017, 1:00 AM GMT+13 (12:00 UTC), 10 km (6 mi) below the surface.

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: 6.1 (Mww, W-phase moment), strong
Magnitude from: USGS National Earthquake Information Center
Local time: Thu, Oct 19, 2017, 1:00 AM GMT+13
UTC: 2017-10-18 12:00:59 UTC
Depth: 10.0 km (6.2 mi), shallow
Epicenter: 20.591° S, 173.802° W
Region: Tonga
Felt reports: 2
Strongest shaking: IV, light 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
6.1	Mww, W-phase moment	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.058 · 29 stations
6.12	Mw, moment	ISC-GEM global catalog	Final · ±0.1

Shaking

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

Strongest estimated: IV, light shaking
Peak ground acceleration: 185.0% of gravity
Peak ground velocity: 2.3 cm/s
Map: Automatic

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

Did you feel it?

2 people reported to the USGS what they felt; the strongest reported shaking was IV, light shaking.

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: 6.1 Mww
Nodal plane 1: Strike 202°, dip 27°, rake 79°
Nodal plane 2: Strike 34°, dip 64°, rake 96°

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 8.2 km horizontally, 1.7 km in depth
Magnitude uncertainty: ±0.06
Depth from: Operator assigned
Station coverage gap: 31°
Stations used: 142

Nearest places

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

Nuku‘alofa, TongaPopulation 22,400. Forecast157 kmENE

Nearby

Within 100 km, magnitude 3.1 and up: 16 in the 60 days after this one and 2 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 us1000atnb (also filed as iscgem615211684). Read Mon, Oct 5, 2026, 4:40 AM UTC.