# Volcano Watch — Keep Maui's 1938 earthquake in mind

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An ancient Japanese proverb says that the most recent disaster fades from memory just before the next one strikes. Recently our friend Garret Hew of East Maui Irrigation inquired about the great 1938 Maui earthquake. That's good news; that earthquake hasn't faded from memory yet.

An ancient Japanese proverb says that the most recent disaster fades from memory just before the next one strikes. Recently our friend Garret Hew of East Maui Irrigation inquired about the great 1938 Maui earthquake. That's good news; that earthquake hasn't faded from memory yet.

On January 22, 1938, at about 10:03 p.m. local time, a magnitude 6.8 earthquake struck the central part of the Hawaiian island chain. The submarine earthquake was located about 20 km (12 mi) northeast of Keanae Point (East Maui) at a depth of roughly 20 km (12 mi). For the people who lived closest, the quake might as well have been beneath their feet.

The north coast of Maui took the brunt of the damage. Landslides blocked the road to Hana and completely severed communications for several days. Two large oil tanks near Hana shattered, and 110,000 liters (30,000 gallons) of oil flowed into the sea. Ranches in southeastern Maui suffered heavy damage as water tanks and stone walls were razed. Fortunately, no lives were lost, and injuries were few. No tsunami accompanied the shock. Central and west Maui weren't spared from damage. Concrete buildings cracked from Kahului to Lahaina. The fire station tower in Kahului shifted 13 mm (0.5 in.)

The 1938 earthquake was one of the few Hawaii earthquakes felt throughout the islands. Kauai residents reported it as the severest shock in memory, but damage was trifling. On Oahu rocks rolled onto roadways, and some plaster cracked and fell in buildings. Most damage, however, was limited to broken crockery and glassware. Molokai and Lanai had small cracks open in the ground. Water pipes broke in a few places.

Big Island residents, accustomed as they were to earthquakes, remained calm compared to others in the state. The shock was felt by most people but was no greater in intensity than the temblors that commonly occur. Dishes were broken, pictures fell from the walls, and plaster cracked.

A phenomenon called "earthquake lights" accompanied the 1938 earthquake. During and immediately after the earthquake, intense bursts, glows, or flashes of white-to-bluish light, lasting from a few seconds to about a minute, were observed in many parts of Hawaii—even by campers as far away as Halape on the Big Island's south coast, 210 km (125 mi) from the epicenter. Although there is no generally accepted scientific explanation for their occurrence, these lights apparently result from earthquake-induced oscillations or distortions of the atmosphere.

The 1938 Maui earthquake was unrelated to volcanism. It's an example of the other type of Hawaiian earthquake, the tectonic kind, that results from loading and bending of the Earth's crust by the mass of each island. These earthquakes diminish in frequency as each island moves off the hotspot and away from the zone of flexure associated with the larger islands.

University of Hawaii seismologists think that, for Maui County, magnitude 6 earthquakes of this type could occur about once every 50 years, and magnitude 7 earthquakes about once every 250 years. The occurrence of magnitude 7 earthquakes on the Big Island is more frequent. With improved monitoring, we hope to better understand the mechanism of the next large deep earthquake in the Hawaiian island chain.

### Volcano Activity Update

Lava continues to erupt from Puu O`o and flow through a network of tubes from the vent to the sea near Kamokuna. A slow-moving pahoehoe flow emanating from a breach in the tube system remains active on the coastal flats since Friday, March 26. The flow is 1.7 km (1.0 mi) long, and the distal end is about 0.9 km (0.54 mi) from the ocean. The public is reminded that the ocean entry areas are extremely hazardous, with explosions accompanying frequent collapses of the new land. The steam clouds are also very hazardous, being highly acidic and laced with glass particles.

There were no felt earthquakes since March 18.