Hawaii Earthquakes and Volcanoes

Did anyone feel the series of earthquakes this past weekend in and around the Hawaiian Islands? It served as a good reminder of just how seismically active the region remains.

On Sunday, Oahu was struck with an unusual magnitude 3.5 tremor which occurred 15 miles south of Honolulu. A series of 14 other moderate earthquakes have been felt on the Big Island in the past week.

Oahu’s last earthquake was nearly ten years ago (2002 – 3.9 magnitude), and the prior one was thirty years ago (1980 – 4.0 magnitude).

Earthquakes and Volcanoes.

Hawaii earthquakes are linked primarily to volcanic activity. They represent an aspect of the island-building processes that have shaped the geology. “All earthquakes in Hawaii ultimately result from the underlying processes that build the volcanoes.” This according to Hawaii’s Institute of Geophysics and Planetology. Eruptions and magma movement within the active volcanoes are typically accompanied by numerous small earthquakes.

Thousands of earthquakes occur annually beneath the Big Island, and earthquakes there have been reported for hundreds of years both in concert with volcanic activity and without. Here is a USGS map of recent earthquakes, and  a Google Maps version.

Historic Hawaii Earthquakes.

• In early 1868, a quake estimated at 7.9 magnitude struck the Big Island, while smoke was seen rising from Mauna Loa volcano.  A lava flow followed. Nearly 100 people died as a result of the quake and resulting tidal wave. In a period of two weeks, over 2000 distinct shocks were felt in the region.
• On January 22, 1938, a magnitude on 6.7 quake struck Hawaii.  It was centered 40 miles east of Molokai, which is as far north as earthquakes typically occur in the Hawaiian chain. It was felt widely on the Big Island, as well as on Maui and Molokai, Oahu and Lanai.
• On November 29, 1975, a magnitude 5.7 quake struck the Big Island.  It was soon followed by a magnitude 7.2 earthquake, and the eruption of Kilauea caldera.

Tsunamis in Hawaii.

Another earthquake effect felt here in Hawaii is tsunamis.  These were first reported in the early 1800′s.  Most have originated either in the northwest Pacific or near the coast of South America. Tsunamis result in more lives lost than the total of all other local disasters here.

• An 1837 Chilean earthquake resulted in 20 foot high waves in Hilo, killing 62 people.
• In 1946, an Aleutian Islands earthquake sent 55 feet high waves crashing into Hilo. 173 were killed, 163 injured, 488 buildings were demolished and 936 more were damaged. The severity of the damage and loss of life prompted the formation of today’s Tsunami Warning System.
• In 1960, the largest earthquake ever recorded (magnitude 9.5), off Chile, generated a tsunami that killed 61 people in Hawaii, destroying much of Hilo.

Earlier this year, a magnitude 8.8 earthquake again struck near Chile, which resulted in a tsunami warning here in Hawaii.

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Photo credit:  USGS.

PS:  This week have been very active for the Big Island’s Kilauea volcano.  Here’s a photo of the Kalapana area’s recent lava flow.