Over the last 30 days, USGS has reported that 922 earthquakes, mainly weak ones, have struck in and around Hawaii’s Big Island, a volcanic island home to the Kilauea, Mauna Loa, and Hualalai volcanoes. The volume of earthquakes, and a few specific swarm events near the Kilauea Volcano, have captured the attention of USGS’s Hawaiian Volcano Observatory (HVO), who started issuing daily status updates on the volcano earlier this month. 18 of the 922 earthquakes were over a magnitude 3.0 and one was a magnitude 4.3 event. No damage of substance has been reported by the ongoing high level of earthquake activity on Hawaii Island.
HVO says Kilauea isn’t yet erupting but is indeed exhibiting signs of unrest which could be indicative of an eruption soon.
In an update released by HVO today, they write, “Elevated seismic activity continued through yesterday, without swarm activity and still concentrated in an area south of Kilauea’s summit caldera. Most earthquakes have been at a depth of 1-2 miles below the surface, with no upward migration. Summit tiltmeters began to show inflationary tilt this morning, returning to the trend of high inflationary deformation that has been observed over the past several months.”
Tiltmeter reading show the volcano is “swelling”‘; combined with the recent surge in earthquake activity, HVO says it is clear the volcano is becoming increasingly pressurized. However, while that could signal that an eruption could occur soon, it’s also possible that no eruption may occur in the short term. “Similar episodes of earthquake and ground deformation activity occurred in November 2020 and August 2021, prior to eruptions in December 2020 and September 2021,” HVO said in today’s update. But nothing may happen too; HVO added, “The activity could also decrease due to intrusion of magma underground or other changes, resulting in no eruption.”
For now, the activity is currently confined within Kilauea’s summit region and if it does continue, it’s possible it could escalate to an eruption in the coming days. While Kilauea is showing signs of unrest and earthquakes have struck all around the Big Island, HVO and USGS also say things are quiet at Mauna Loa, which happens to be the world’s largest active volcano, and Hualalai which stands just east of Kona’s International Airport.
Mauna Loa erupted last November and December sending lava down its slopes into an undeveloped/unpopulated area of Hawaii’s Big Island. There was a notable increase in deep earthquakes beneath and southwest of Mauna Loa’s summit caldera during the past month, USGS reported in a monthly update in early August. But shallower seismicity remained stable while overall most seismic events were smaller than a magnitude 2.0 event. HVO says data from Global Positioning System (GPS) instruments on Mauna Loa indicate there is slow inflation underway as magma replenishes the summit reservoir system, but gas and temperature data from a station on the Southwest Rift Zone showed no significant changes over the past month. “HVO continues to monitor the volcano closely and will issue another update in one month, or earlier should conditions change significantly,” they wrote in their last update issued on August 3.
Hualalai is even more quiet than Mauna Loa, with no noteworthy activity observed in recent weeks. Though Hualalai is not nearly as active as Mauna Loa or Kilauea, USGS says geologic mapping of the volcano shows that 80% of the volcano’s surface has been covered by lava flows in the past 5,000 years. In the past few decades, when most of the resorts, homes, and commercial buildings were built on the flanks of Hualalai, earthquake activity beneath the volcano has been low. In 1929, however, an intense swarm of more than 6,200 earthquakes rattled the area around the volcano for more than a month. The earthquakes were most likely caused by an intrusion of magma beneath the volcano. Two large earthquakes, each about a magnitude 6.5 event, destroyed houses, water tanks, stone fences, and roadways. “For these reasons, Hualalai is considered a potentially dangerous volcano that is likely to erupt again,” warns USGS in their last update on the volcano.
For now, only Kilauea carries any kind of advisory in Hawaii. Currently, the alert level is set at ADVISORY while the color code is set to YELLOW. In the U.S., the USGS and volcano observatory units are responsible for issuing Aviation Codes and Volcanic Activity Alert Levels. Aviation Codes are green, yellow, orange, or red. When ground-based instrumentation is insufficient to establish that a volcano is at a typical background level of activity, it is simply “unassigned.” While green means typical activity associated with a non-eruptive state, yellow means a volcano is exhibiting signs of elevated unrest above known background levels. When a volcano exhibits heightened or escalating unrest with the increased potential of eruption, it jumps to orange. Finally, when an eruption is imminent with significant emission of volcanic ash expected in the atmosphere or an eruption is underway with significant emission of volcanic ash into the atmosphere, the code becomes red. Volcanic Activity Alert levels are normal, advisory, watch, or warning. As with aviation codes, if data is insufficient, it is simply labeled as “unassigned.” When the volcano is at typical background activity in a non-eruptive state, it is considered normal. If the volcano exhibits signs of elevated unrest above background level, an advisory is issued. If a volcano exhibits heightened or escalating unrest, a watch is issued while a warning is issued when a hazardous eruption is imminent.