The May 8, 1991 earthquake
M5.5Hawaii region, Hawaii
A magnitude 5.5 earthquake 18.0 miles deep, 20.2 miles off Hawaii County. The 49th strongest in Hawaii’s record since 1900, and the strongest within 50 miles since a magnitude 5.6 on January 21, 1982. 5 aftershocks of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 5.5
- local magnitude (ml)
- Depth
- 18.0 mi
- 28.9 km below the surface
- Local time
- Wednesday, May 8, 1991
- 08:21 HST; 18:21 UTC
- In Hawaii’s record
- 49th
- strongest of 39,637 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event hv373679 (“Hawaii region, Hawaii”). The USGS event page carries the ShakeMap, felt reports and the official summary.
Aftershocks
Earthquakes of magnitude 2.5 or more within 20 miles of the epicentre in the 30 days after.
5
Aftershocks in 30 days
4.2
Largest aftershock, May 9, 1991
5
On the first day
0
In the 7 days before
- The search radius is the surface rupture length expected for an earthquake of this magnitude (Wells and Coppersmith, 1994), at least 20 and at most 600 miles, so a great earthquake's sequence is counted along its whole fault.
Counties and cities within 50 miles
Distance from the epicentre to each county boundary (zero when inside) and to each city centre.
Counties
- Hawaii CountyHI · 20.2 mi
Earthquakes around the epicentre
1,280 earthquakes of magnitude 3 or more within 50 miles of this epicentre since 1973.
Earlier earthquakes of magnitude 5 or more within 50 miles, strongest first
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.