Reviewed by USGS40y ago
M6.6 earthquake south of the Kermadec Islands
Saturday, August 23, 1986, 23:47:48 UTC · 34.549°S, 179.288°E
A magnitude 6.6 earthquake struck south of the Kermadec Islands on Saturday, August 23, 1986, 23:47:48 UTC, at a depth of 32.2 km (shallow). It is the strongest earthquake within 300 km since an M6.9 on September 26, 1985.
- Magnitude
- 6.6
- Strong · mw
- Depth
- 32 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 100 km aftershock search area
In context
How big was it, and why here?
Energy released
120 kilotons of TNT
That is about 8 times the Hiroshima bomb. It released about 251 times the energy of a magnitude 5.0.
Tectonic setting
38 km
from the nearest mapped plate boundary, between the Kermadec and Australian plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
32 km
Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.
Did You Feel It?
Where it was felt
No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.
I felt it — report to USGS ↗USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.
After the main event
Aftershocks within 100 km
USGS lists 1 M2.5+ earthquake within 100 km in the following 30 days; the largest was M5.2 on September 9, 1986. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 253 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 6.9south of the Kermadec IslandsSeptember 26, 1985 · 189 km E of this epicenter
- 6.8150 km N of Opotiki, New ZealandDecember 30, 1984 · 285 km SW of this epicenter
- 6.8south of the Kermadec IslandsJanuary 8, 1970 · 57 km SW of this epicenter
- 6.7south of the Kermadec IslandsFebruary 13, 1949 · 297 km E of this epicenter
- 6.6off the east coast of the North Island of New ZealandFebruary 13, 1938 · 155 km S of this epicenter
- 6.6south of the Kermadec IslandsSeptember 1, 1937 · 239 km NE of this epicenter
- 6.5south of the Kermadec IslandsNovember 13, 1957 · 243 km NE of this epicenter
- 6.5east of the North Island of New ZealandNovember 7, 1985 · 147 km SE of this epicenter