1871 Lāna`i earthquake

An earthquake struck near the Hawaiian island of Lanai on February 19, at 10:11 pm HST with an estimated magnitude of 7.0–7.5 on the Richter scale. It remains one of the largest seismic events to hit the Hawaiian Islands since the 1868, with its effects being felt throughout the entire archipelago. It caused severe damage on the islands of Lanai, Molokai and Maui.[1] A tsunami may have been generated however there are speculations of it had really happened. Despite the size of the quake and extent of damage, no lives were lost.

1871 Lāna`i earthquake
UTC time1871-02-20 08:45:00
USGS-ANSSComCat
Local date19 February 1871
Local time22:11 HST
Magnitude7.5 Mw
7.0-7.5 Ms
6.8 Mfa
Epicenter20.7°N 156.0°W / 20.7; -156.0
TypeUnknown
Areas affectedHawaii
Total damageModerate
Max. intensityXI (Extreme) to VIII (Severe)
TsunamiUncertain
LandslidesYes
AftershocksYes

Tectonic setting

The Hawaiian Islands is situated in the middle of the Pacific Plate, far from any known plate boundary, where most of the world's earthquakes occur. This island chain is a product of hotspot volcanism where magma is able to make its way up to the crust and onto the surface, creating volcanoes. Hawai'i or the Big Island is the youngest volcanic island and marks where the hotspot currently is.

Earthquake

The estimated magnitude 7.5 earthquake is currently the third-largest to occur in the Kingdom of Hawaii, behind the 1868 and 1975 quakes. The most likely source of this event is the Molokai Fracture Zone, a structure in the Pacific Ocean seafloor that separates 85 million-year-old and 100 million-year-old oceanic lithosphere. It runs through the island chain near Lanai and Maui. Along this part of the fracture zone, the weight of the Hawaiian Islands may have resulted in slippage along the structure at a depth greater than The same seismic zone is suspected to have produced an Mw 6.8 earthquake in 1938 near Maui.[2]

Tsunami

A tsunami was thought to have accompanied the earthquake shortly after, as mentioned in several local newspapers and reports.[3] This claim however is doubtful as the claims were vague and other eyewitnesses along the shores did not report any large waves.[3][4]

Impact

Lanai
MMI by location
MMI Locations
XI (Extreme)–VIII (Severe) Maui, Lanai, Molokai
VII (Very strong)–VI (Strong) Oahu, Hawai'i,
V (Moderate)–IV (Light) Kauai, Niihau

The earthquake reportedly lasted 55 seconds to a minute with shaking directed in a northeast to southwest motion. The most extreme shaking was felt on the islands of Maui and Lanai where the values on the Mercalli intensity scale range from VIII to XI. There, fractures formed along the slopes, and rocks that broke off from peaks collapsed. Between Manele Bay and Kamaiki Point, Pali Kaholo; a well-known cliff, collapsed into the ocean.

In Lahaina, almost every adobe and brick building was destroyed.[5] A mission church sustained cracks in its walls. The courthouse and a stone building were also damaged. It was reported that every fence and walls fell towards the north. At the pier, a crack 14.6 meters long appeared.

Oahu

In Oahu, the earthquake cracked walls and split two houses. In Ewa, the belfry of a Catholic church supported by cast-iron pillars was completely destroyed. In Waianae, ground fissures and land slumps were widely reported.[6] Some landslides and rockfalls resulted in road blockage. Plasters on homes, offices and a courthouse fell down in Honolulu. In addition, chimneys at the Punahou School in Honolulu were also knocked off.

On the Mercalli intensity scale, the earthquake's intensity was likely VI (Strong), and it lasted some 30 to 45 seconds. The quake caused panic and hysteria, some residents fainted while others began praying. Some residents reported feeling nauseated and started to vomit. Overall, damage in Oahu was moderate, with some structures compromised and a number of collapses reported.

Molokai

In Molokai, the earthquake overturned furniture and kitchen items in homes. Stone houses began to crack as the ground shook. Parts of a Catholic church fell to the ground, and plasters came off most buildings in the area.[7] Ground fissures tore through the landscape, breaking roads.[1] The severity of shaking corresponds towards VIII to IX. North-central Molokai had weaker intensities at VI to VII.

Hawaii

A direct observer wrote in a letter stating that the shaking was "as severe as" the 1868 earthquake. The sound of roaring was heard during the quake, which was described as having a great intensity and weakening, ending with an extremely violent shock before the shaking had stopped. Stone walls everywhere toppled in Kawaihae.

See also

References
  1. Carl W. Stover; Jerry L. Coffman (1993). Seismicity of the United States, 1568-1989 (revised). Denver, Colorado: United States Government Publishing Office, Washington. United States Geological Survey.
  2. Butler, Rhett (2020). "The 1871 Lāna'i Earthquake in the Hawaiian Islands" (PDF). Seismological Research Letters. 91 (6): 3612–3621.
  3. Doak C. Cox; Joseph Morgan (1977). Local tsunamis and possible local tsunamis in Hawaii. United States: University of Hawaii. pp. 32–33.
  4. "Tsunami Event Information HAWAII". NGDC. Retrieved 27 January 2021.
  5. Cox, Doak C. (1985). "The Lanai Earthquake of February 1871". Environmental Center Special Reports. Environmental Center, University of Hawaii at Manoa.
  6. Charles H. Fletcher III, Eric E. Grossman, Bruce M. Richmond, and Ann E. Gibbs (2002). "Atlas of Natural Hazards in the Hawaiian Coastal Zone" (PDF). United States Geological Survey. Retrieved 27 January 2021.CS1 maint: multiple names: authors list (link)
  7. Cook, T. E. (4 March 1872). "The Earthquake on Molokai". The Honolulu Advertiser. Retrieved 27 January 2021.
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