Reviewed by USGS41y ago
M4.6 earthquake south of the Kermadec Islands
Friday, October 11, 1985, 04:55:25 UTC · 34.986°S, 179.070°W
A magnitude 4.6 earthquake struck south of the Kermadec Islands on Friday, October 11, 1985, 04:55:25 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M4.6 on October 3, 1985.
- Magnitude
- 4.6
- Light · mb
- Depth
- 33 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: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
120 tons of TNT
That is about 1/126 of the Hiroshima bomb. A magnitude 5.0 releases about 4 times more energy.
Tectonic setting
35 km
from the nearest mapped plate boundary, between the Kermadec and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
33 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 50 km
USGS lists 5 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M6.5 on November 7, 1985. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 6.5east of the North Island of New Zealand41y ago · 39 km SW of this epicenter
- 5.0east of the North Island of New Zealand41y ago · 31 km E of this epicenter
- 5.4south of the Kermadec Islands41y ago · 19 km E of this epicenter
- 4.3south of the Kermadec Islands41y ago · 41 km N of this epicenter
- 4.5south of the Kermadec Islands41y ago · 18 km NE of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 229 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 · 50 km NE of this epicenter
- 6.9south of the Kermadec IslandsJuly 11, 1943 · 280 km N of this epicenter
- 6.8south of the Kermadec IslandsJanuary 8, 1970 · 196 km W of this epicenter
- 6.7south of the Kermadec IslandsFebruary 13, 1949 · 203 km NE of this epicenter
- 6.6off the east coast of the North Island of New ZealandFebruary 13, 1938 · 169 km SW of this epicenter
- 6.6south of the Kermadec IslandsSeptember 1, 1937 · 249 km N of this epicenter
- 6.5south of the Kermadec IslandsOctober 14, 1947 · 240 km NE of this epicenter
- 6.5south of the Kermadec IslandsMay 27, 1942 · 258 km NE of this epicenter