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M6.6 earthquake, Alaska, 1917-12-21

MagnitudeM6.6mw

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Depth15 km

Time (UTC)1917-12-21 17:54

Rank in 191729 / 87among M6+

Rank since 19003289 / 14,458

Energy vs an M6×9approx.

88 km SSE of Old Harbor, Alaska · 56.45, -152.84

M6.5+ within 300 km (largest first)

2018 M7.9M7.9

1900 M7.9M7.9

1912 M7.1M7.1

1923 M7.0M7.0

1989 M7.0M7.0

1912 M7.0M7.0

1999 M7.0M7.0

1951 M6.9M6.9

1964 M6.9M6.9

2021 M6.9M6.9

2001 M6.9M6.9

2015 M6.8M6.8

Earlier M6+ within 300 km

Event	Time (UTC)	Depth	Place
M6.1 1912-12-05	1912-12-05 12:27	35 km	13 km S of Akhiok, Alaska
M7.1 1912-11-07	1912-11-07 07:40	35 km	4 km ENE of Karluk, Alaska
M6.2 1912-06-17	1912-06-17 11:28	–	Event 50 Novarupta-Mount Katmai area, Alaska Peninsula
M6.1 1912-06-12	1912-06-12 07:04	–	Event 49 Novarupta-Mount Katmai area, Alaska Peninsula
M6.8 1912-06-10	1912-06-10 16:06	5 km	Event 48 Novarupta-Mount Katmai area, Alaska Peninsula
M6.0 1912-06-09	1912-06-09 17:14	–	Event 43 Novarupta-Mount Katmai area, Alaska Peninsula
M6.6 1912-06-08	1912-06-08 13:00	–	Event 39 Novarupta-Mount Katmai area, Alaska Peninsula
M6.2 1912-06-08	1912-06-08 10:29	–	Event 38 Novarupta-Mount Katmai area, Alaska Peninsula
M6.8 1912-06-08	1912-06-08 08:48	–	Event 37 Novarupta-Mount Katmai area, Alaska Peninsula
M7.0 1912-06-08	1912-06-08 07:36	–	Event 36 Novarupta-Mount Katmai area, Alaska Peninsula

Energy ratio uses the rule that one magnitude unit is about 32 times the energy. Magnitudes and locations are USGS values and can differ from national agencies. Older records are less complete and less precise.