HAWAI‘I ISLAND, Hawaii – The U.S. Geological Survey's Hawaiian Volcano Observatory (HVO) has recorded more than 100 earthquakes in a swarm that began around 1:17 a.m., HST, on Wednesday, February 22, 2012. The earthquakes are located about 5 km (3 mi) north-northwest of Kīlauea volcano's summit, near Nāmakanipaio in Hawai‘i Volcanoes National Park, at depths of 2–5 km (1–3 mi).
The largest earthquakes of the ongoing swarm have been a magnitude-4.1 quake at 9:02 p.m. last night and a magnitude-4.3 quake at 3:52 a.m. this morning. These earthquakes were widely felt on the Island of Hawai‘i. As of 9:00 a.m. Friday, the USGS “Did you feel it?” website had received 74 felt reports for the 9:02 p.m. earthquake and more than 60 felt reports for the 3:52 a.m. event.
The initial magnitude of the 9:02 p.m. earthquake was estimated at 4.1 by HVO’s automated software system, but then increased to magnitude-4.3. After close review by HVO seismic analysts this morning, the earthquake’s magnitude has been calculated to be 4.1.
The effects of the early morning magnitude-4.3 earthquake were evident at the Hawaiian Volcano Observatory building, which is located less than 4 km (2.5 mi) from the swarm’s center. HVO staff noticed that a few books and other items had fallen off shelves and some small ceiling fixtures were dislodged. Several residents of the Volcano Golf Course subdivision, located about 3 km (2 mi) from the earthquake epicenter, also reported items falling from shelves, causing some minor breakage.
As of this morning, the seismic swarm has also included 3 earthquakes with magnitudes between 3.0 and 3.9, and 25 earthquakes with magnitudes of 2.0 to 2.9. The magnitudes of another 88 located earthquakes are between 1.0 and 1.9.
The earthquake swarm is located at the north end of the Ka‘ōiki Pali, near the boundary between Mauna Loa and Kīlauea volcanoes. This area has experienced previous seismic swarms in 1990, 1993, 1997, and 2006, each of which lasted from 1 day to several weeks.
According to Jim Kauahikaua, HVO’s Scientist-in-Charge, it’s likely that high rates of seismicity could continue in this area for several days. He added that the earthquake swarm has not caused any obvious changes in Kīlauea’s magma plumbing system or ongoing eruptions, but that the magnitude-4.3 earthquake did cause a small rockfall in the active vent located within Halema‘uma‘u Crater at the summit of Kīlauea.