USGS HVO Press Release - Magnitude-4.3 Earthquake Northwest of Pāhala, Hawai‘i

Release Date:

A magnitude-4.3 earthquake was located on the south flank of Mauna Loa by the U.S. Geological Survey's Hawaiian Volcano Observatory (HVO) on Monday, January 18, at 1:01 p.m. HST. The earthquake was located 6 km (4 miles) WNW of Pāhala, Hawai‘i at a depth of 6 km (4 miles).

The earthquake was reported felt over most of the Island of Hawai‘i. As of Tuesday morning, January 19, the USGS "Did you feel it?" Web site (http://earthquake.usgs.gov/eqcenter/dyfi/) had received 123 felt reports.

The initial magnitude of this earthquake was estimated as M3.8 by HVO's automated software system. After review by HVO seismic analysts this morning, the magnitude was increased to M4.3.

There are several methods for estimating an earthquake's magnitude, and some methods are better than others for different magnitude ranges. Through the analysts' review, it was determined that amplitude magnitude (M4.3) is a more accurate measure for Monday's earthquake than duration magnitude (M3.8). Duration magnitude is less reliable for earthquakes above magnitude-4.0.

Over the past 25 years, the region near Monday's M4.3 earthquake has experienced, on average, one earthquake greater than magnitude-4.0 every two years. The source mechanism for this earthquake reflects the southward movement of Mauna Loa's southern flank, which is consistent with past earthquakes in the Pāhala area.

Daily updates about ongoing eruptions, recent images and videos of summit and East Rift Zone volcanic activity, maps, and data about recent earthquakes in Hawaii are posted on the HVO website at https://volcanoes.usgs.gov/observatories/hvo

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