Fiji earthquakes

M6.6 earthquake Fiji region

A magnitude 6.6 earthquake struck in the Fiji region on Thu, Aug 29, 1985, 9:50 AM GMT+13 (20:50 UTC), 625 km (388 mi) below the surface.

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The earthquake

Magnitude: 6.6 (Mw, moment), strong
Magnitude from: USGS National Earthquake Information Center
Local time: Thu, Aug 29, 1985, 9:50 AM GMT+13
UTC: 1985-08-28 20:50:48 UTC
Depth: 624.6 km (388.1 mi), deep
Epicenter: 21.011° S, 178.981° W
Region: Fiji
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
6.6	Mw, moment	USGS National Earthquake Information Center	Preferred · Reviewed
6.59	Mw, moment	ISC-GEM global catalog	Final · ±0.1
6.6	Mwc, centroid moment	Global CMT project	Preliminary

What happened

The USGS’s account of the effects of this earthquake.

FAULT PLANE SOLUTION: P-Waves NP1:Strike=48 Dip=83 Slip=-80 NP2:Strike=173 Dip=12 Slip=-145 Principal Axes: (T) Plg=37 Azm=129 (P) Plg=51 Azm=329 Comment: The focal mechanism is moderately well controlled and corresponds to normal faulting with a small strike-slip component. The preferred fault plane is not determined. MOMENT TENSOR SOLUTION Dep 638 No. of sta: 13 Moment Tensor; Scale 10**25 d-cm Mrr=-7.16 Mtt=3.69 Mff=3.46 Mrt=-4.66 Mrf=-4.55 Mtf=3.56 Principal axes: (T) Val=9.66 Plg=21 Azm=136 (N) Val=0.02 Plg=0 Azm=46 (P) Val=-9.68 Plg=69 Azm=315 Best Double Couple:Mo=9.7*10**25 NP1:Strike=226 Dip=24 Slip=-90 NP2:Strike=46 Dip=66 Slip=-90 CENTROID, MOMENT TENSOR (HRV) Data Used: GDSN L.P.B.: 21S, 51C M.W.: 12S, 25C Centroid Location: Origin Time 20:50:55.5 0.2 Lat 20.89S 0.01 Lon 179.00W 0.01 Dep 640.4 1.1 Half-duration 7.5 Moment Tensor; Scale 10**25 D-CM Mrr=-6.98 0.08 Mtt=2.33 0.11 Mff=4.65 0.12 Mrt=-4.37 0.09 Mrf=-5.07 0.09 Mtf=2.93 0.09 Principal Axes: (T) Val=9.36 Plg=22 Azm=126 (N) Val=0.38 Plg=3 Azm=217 (P) Val=-9.74 Plg=68 Azm=315 Best Double Couple:Mo=9.6*10**25 NP1:Strike=210 Dip=23 Slip=-98 NP2:Strike=39 Dip=67 Slip=-87

From the USGS event page for usp0002j7t. U.S. Geological Survey text and figures are in the public domain.

Did you feel it?

No one has reported feeling this quake to the USGS.

How well it is located

Reviewed by a seismologist.

Depth from: CONSTRAINED_BY_DEPTH_PHASES

Nearest places

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

Nuku‘alofa, TongaPopulation 22,400. Forecast392 kmW

Nearby

Within 100 km, magnitude 3.6 and up: 11 in the 60 days after this one and 8 in the 30 days before it.

After

Before

Earthquakes today Fiji earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event usp0002j7t (also filed as gcmtc082885b, gcmt19850828205048, iscgem519097). Read Fri, Oct 2, 2026, 8:57 PM UTC.