Reviewed by USGS29y ago
M4.1 earthquake in Kermadec Islands region
Sunday, July 20, 1997, 15:48:31 UTC · 31.852°S, 178.907°W
A magnitude 4.1 earthquake struck in Kermadec Islands region on Sunday, July 20, 1997, 15:48:31 UTC, at a depth of 150.0 km (intermediate).
- Magnitude
- 4.1
- Light · mb
- Depth
- 150 km
- Intermediate
- 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
21 tons of TNT
That is about 1/707 of the Hiroshima bomb. A magnitude 5.0 releases about 22 times more energy.
Tectonic setting
76 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: intermediate
150 km
Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.
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 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M4.8 on August 5, 1997. 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 1,084 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.21917 Kermadec Islands, New Zealand EarthquakeMay 1, 1917 · 226 km E of this epicenter
- 7.5Kermadec Islands, New ZealandNovember 16, 1917 · 245 km NE of this epicenter
- 7.3Kermadec Islands, New ZealandMarch 26, 1963 · 238 km NE of this epicenter
- 7.3Kermadec Islands, New ZealandJuly 25, 1968 · 138 km NE of this epicenter
- 7.2Kermadec Islands, New ZealandFebruary 9, 1978 · 196 km NE of this epicenter
- 7.2Kermadec Islands, New ZealandAugust 2, 1941 · 262 km NE of this epicenter
- 7.2Kermadec Islands, New ZealandApril 17, 1919 · 166 km NE of this epicenter
- 7.1Kermadec Islands, New ZealandJune 29, 1910 · 201 km NE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 4 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1968M7.3
S Of, Raoul
25 Jul 1968 · 127 km away
Limited damage (under $1M)tsunami
- 1976M7.8
Kermadec Islands
14 Jan 1976 · 268 km away · intensity VIII
- 1978M7.7
S Of
9 Feb 1978 · 196 km away
- 1943M7.6
S Of
14 Sep 1943 · 275 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.