48 small quakes and counting on the Big Island as of Wednesday morning
HAWAII VOLCANOES NATIONAL PARK, Hawaii: Scientists at the USGS Hawaiian Volcano Observatory are keeping an eye on a swarm of small earthquakes around the active Kilauea volcano.
In its morning status report, HVO wrote that there “is an ongoing seismic swarm just northwest of the summit.”
From the Wednesday status report, updated at 7:29 HST:
A swarm of shallow earthquakes started after midnight last night about 5 km (3 mi) northwest of Halema`uma`u Crater that was ongoing as of this posting. Forty-eight earthquakes were strong enough to be located beneath Kilauea: 39 quakes within the swarm so far at a maximum rate of 6/hr (including a preliminary magnitude-3.4 quake at 6:56 am), two deep quakes beneath the southwest rift zone, two beneath the southeast summit caldera, one within the upper east rift zone, four on south flank faults. Seismic tremor levels were low and dropped slightly during deflation.
Most of the quakes have been in the magnitude 2.0 vicinity, but a few reached over 3.0.
Seismic activity on the rift zone is not rare, however this number of small earthquakes is high for the present eruptive activity.
UPDATE (4:00 pm Feb. 22nd) Media release from the USGS Hawaiian Volcano Observatory:
The U.S. Geological Survey’s Hawaiian Volcano Observatory (HVO) recorded an earthquake 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 Kilauea volcano’s summit, near Namakanipaio in Hawai‘i Volcanoes National Park, at depths of 2–5 km (1–3 mi).
The seismic swarm, which continues as of 3:00 p.m., has included more than 60 earthquakes, 14 of which were greater than magnitude-2. The largest was a magnitude-3.2 earthquake at 6:55 a.m.
These small earthquakes have not been widely felt on the Island of Hawai‘i. The USGS “Did you feel it?” Web site (http://earthquake.usgs.gov/eqcenter/dyfi/) received less than 10 felt reports in the first12 hours following the onset of the swarm.
The earthquakes are located along the Ka‘oiki Pali, a southeast-dipping normal fault near the boundary between Mauna Loa and Kilauea volcanoes. This area has experienced episodic seismicity since the magnitude-6.6 Ka‘oiki earthquake that occurred in November 1983.
Previous earthquake swarms have occurred along the Ka‘oiki seismic zone in 1990, 1993, 1997, and, most recently, in February-March 2006. These swarms lasted from 1 day to several weeks, with earthquakes rarely exceeding magnitude-4.
Seismic swarms in the Ka‘oiki area have sometimes heralded changes in Kilauea’s ongoing east rift zone eruption, but as of this writing, HVO monitoring networks have not detected any apparent changes in Kilauea’s summit or east rift zone eruptions or on Mauna Loa resulting from today’s swarm.
For more information on recent earthquakes in Hawai‘i and eruption updates, visit the Hawaiian Volcano Observatory website at http://hvo.wr.usgs.gov.