4.1 Tremor is Part of Earthquake Swarm Beneath Kīlauea’s Lower SW Rift Zone

Pāhala earthquake (8.18.21) PC: USGS.

A 4.1 magnitude earthquake located east of Pāhala at 2:02 a.m. HST on Wednesday, Aug. 18, is believed to be part of an ongoing seismic swarm under the Pāhala area, which started in August 2019, according to scientists.

Experts with the US Geological Survey’s Hawaiian Volcano Observatory say the swarm is located beneath Kīlauea’s lower Southwest Rift Zone, beneath Pāhala and extending about 6 miles offshore.

HVO Scientist-in-Charge, Ken Hon, said the earthquake had no observable impact on Mauna Loa and Kīlauea volcanoes. According to the HVO, earthquakes in this region have been observed at least as far back as the 1960s and are believed to be related to “deep magma pathways under the island.” 

Today’s earthquake occurred at a depth of about 20 miles and was centered about five miles east of Pāhala.

The USGS reports that the following locations were located in proximity to the earthquake:

  • Pāhala, Hawaii 5.6 miles W
  • Hawaiian Paradise Park 37.9 miles NE
  • Hilo, Hawaii 40.7 miles NNE
  • Kailua-Kona, Hawaii 49.3 miles NW
  • Honolulu, Hawaii 215.6 miles NW

The USGS “Did you feel it?” service received more than 25 felt reports within the first half-hour of the earthquake. The majority of felt reports were filed in Kailua-Kona, and the quake was felt as far away as Honokaʻa. 

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