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Earthquake swarm beneath Kamaʻehuakanaloa (Lōʻihi) seamount likely the result of magma movement, Hawai’i

loihi seamount eq swarm july 2022

The Hawaiian Volcano Observatory (HVO) has detected increased seismic activity beneath Kamaʻehuakanaloa (formerly known as Lōʻihi) seamount, south of the Island of Hawaiʻi, over the past few days. The activity is likely the result of magma movement beneath Kamaʻehuakanaloa seamount and currently shows no sign of leading to an eruption. The last eruption at this volcano took place in 1996 (VEI 0).

  • Intermittent earthquake activity has been recorded in the vicinity of Kama‘ehuakanaloa since as early as 1952. The most energetic earthquake sequence occurred in July – August 1996, which included more than 4 000 earthquakes, with nearly 300 events larger than M3.0 and 95 events in the M4.0 to 4.9 range.
  • More recently, a swarm of 100 earthquakes occurred on May 11, 2020, with 18 events in the M3.0 to 3.9 range.
  • There are no working monitoring instruments on Kama‘ehuakanaloa volcano, whose peak is about 1 000 m (3 280 feet) below sea level. All real-time information about the volcano is derived from land-based seismometers on the Island of Hawai‘i.

Increased seismic activity beneath Kamaʻehuakanaloa (Lōʻihi) seamount began at approximately 12:00 UTC on July 16, 2022, when HVO detected seismic tremor marked by pulses of seismic energy every 15 – 20 seconds, which was still ongoing at the time of its latest update released at 00:53 UTC on July 18.1

Approximately 24 hours after this activity began, two dozen M1.8 – M3.0 earthquakes occurred from 11:30 UTC to 16:00 on July 17.

“This seismic activity is likely the result of magma movement beneath Kamaʻehuakanaloa seamount and currently shows no sign of leading to an eruption,” HVO Scientist-in-Charge Ken Hon said.

“If the swarm intensifies or changes significantly, HVO will issue an additional notice.

“Because of the great depth of the volcano within the ocean and style of Hawaiian eruptions, an eruption of Kamaʻehuakanaloa would pose no threat to the Island of Hawaiʻi. Neither Mauna Loa nor Kīlauea volcanoes show any change in activity associated with this earthquake swarm.”

The last eruption at this volcano took place from February to August 1996 (VEI 0).

On September 10, 2001, an earthquake swarm began at the volcano with a Magnitude-5.0 earthquake, followed by M3.5 – 4.9 earthquakes until September 13. This was the most severe swarm at Kama‘ehuakanaloa since July 1996, when the summit collapsed.2

Earthquake swarms in this area have also been detected in 2005, 2017 and 2020.

“This swarm may represent a brief magmatic intrusion or movement of magmatic fluids within the volcanic edifice,” USGS said in a statement released on May 12, 2020. “Although the swarm appears to have diminished in intensity if earthquakes become shallower, it could lead to the beginning of a submarine eruption, similar to what occurred in 1996.”3

If an eruption would occur, USGS said it may cause partial draining of its summit magma chamber, as well as summit collapse. Abrupt changes to the volcano’s surface could displace massive volumes of ocean water, which may generate small local tsunami waves.

If an eruption or stronger earthquakes occur, very small tsunami waves may affect southeast shores of the Island of Hawaiʻi. Relatively low-energy, steam- and gas-driven explosions can occur at the depth of Kama‘ehuakanaloa, but with limited local effects on the volcano and surrounding ocean water.

Geological summary

Kama‘ehuakanaloa seamount, the youngest volcano of the Hawaiian chain, lies about 35 km (21.7 miles) off the SE coast of the island of Hawaii. Kama‘ehuakanaloa has an elongated morphology dominated by two curving rift zones extending north and south of the summit.

The summit region contains a caldera about 3 x 4 km (1.8 x 2.5 miles) wide and is dotted with numerous lava cones, the highest of which is about 975 m (3 200 feet) below the sea surface. The summit platform includes two well-defined pit craters, sediment-free glassy lava, and low-temperature hydrothermal venting.

An arcuate chain of small cones on the western edge of the summit extends north and south of the pit craters and merges into the crests prominent rift zones.

Deep and shallow seismicity indicate a magmatic plumbing system distinct from that of Kilauea.

During 1996 a new pit crater was formed at the summit, and lava flows were erupted. Continued volcanism is expected to eventually build a new island; time estimates for the summit to reach the sea surface range from roughly 10 000 to 100 000 years.4

References:

1 Kamaʻehuakanaloa (Lōʻihi) seamount – USGS HVO Information Statement – July 18, 2022

2 Global Volcanism Program, 2001. Report on Kama’ehuakanaloa (United States). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 5 September-11 September 2001. Smithsonian Institution and US Geological Survey.

3 Increased seismic activity at underwater Lō‘ihi volcano, Hawaii – The Watchers – June 28, 2017

4 Kamaʻehuakanaloa (Lōʻihi) seamount – Geological summary – GVP

Featured image credit: USGS

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