Volcano Minute — Hawaii’s deep earthquakes explained

Aloha, it's your weekly Volcano Minute, brought to you by the USGS Hawaiian Volcano Observatory. 

If you’ve felt earthquake shaking lately, you’re not alone. Over the past several months, a handful of large, deep earthquakes have rattled the Island of Hawaiʻi—including the magnitude‑6.0 that was felt state-wide on May 22nd, followed by magnitude‑4.6 and 4.7 earthquakes in early June. 

Many of the earthquakes on the Island of Hawaiʻi are related to magma movement and pressure changes or faulting within the volcanoes that make up the island, but these larger, deep earthquakes aren’t caused by magma. Instead, they come from the enormous weight of the Hawaiian Islands themselves. Hawaii’s massive volcanoes press down on the Earth’s lithosphere, the brittle upper and outermost layer of the Earth. The weight causes the lithosphere to bend and creates flexures—areas where rocks eventually break and move, releasing energy as an earthquake. 

Because these flexure events happen deep within the Earth, their shaking travels farther, making them more widely felt. They’re different from the earthquakes that occur deep beneath Pāhala and the southeast part of the Island of Hawaiʻi, which are thought to be related to magma transport from the hot spot. 

Even though earthquakes in Hawaii come from different processes, your response should always be the same: drop, cover, and hold on when you feel shaking. And if you’re near the coast, move to higher ground until you know that a tsunami hasn’t been generated. 

A quick update on Kīlauea: Episode 50 of lava fountaining happened at the summit on June 27. Kīlauea summit region has shown inflationary ground tilt since then and models currently indicate that episode 51 of lava fountaining could occur between July 11^th and 15^th.  

Mahalo for listening, I’m Katie Mulliken and this was your weekly volcano minute brought to you by the USGS Hawaiian Volcano Observatory.