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Earthquake Characteristics Affected by Magma Viscosity

2:06 AM · Apr 8, 2021

In a new article published in Nature from Diana Roman, with former USGS-HVO seismologist Brian Shiro as a co-author, the properties of earthquakes in the Lower East Rift Zone (LERZ) are correlated to different phases before, during and after the eruption. There are a few interesting aspects of this research, which suggests that sometime during the eruption of Pu‘u ‘Ō‘ō a batch of magma stagnated below the 35 year eruption site and formed a partially crystalized barrier between the LERZ. Increased magmatic pressure in Kilauea caused inflation, and then ruptured that barrier on April 30th, and magma rapidly drained into the LERZ. The quakes show variations during specific times and places associated with the movement of more viscous magma: the collapse and draining of Puʻuʻōʻō, the eruption of Fissure 17, and the final stages of Ahuʻailāʻau (Fissure 8) after the end of fountaining in early August. As Ahuʻailāʻau (Fissure 8) ceased erupting lava, a final reorganization of residual cool and crystal-rich magma occurred. The researchers suggest a “local sub-surface redistribution of high viscosity magma once the major throughput of hotter more primitive magma ended.” EDITED BY Philip Ong CAPTIONS FOR IMAGES 1) Lava fountaining from the most productive eruptive fissure, called fissure 8 at the time and now named Ahu'aila'au, built a cinder cone 55 meters high, about the height of a 10-story building. Most of the 2018 lower East Rift Zone eruption's 0.8 cubic kilometers of lava erupted from this point. (Credit: B. Shiro, USGS) 2) A fast-moving lava channel flowed from the Ahu'aila'au cone about 10 kilometers away to the ocean, where it covered about 36 square kilometers of land along the way and created 3.5-square-kilometers of new land along the coast. Where the channel slowed down in flat areas, it spread out and formed a braided pattern, seen here. (Credit: B. Shiro, USGS) 3) (Credit: B. Shiro, USGS) Full view-only PDF, "Earthquakes indicated magma viscosity during Kīlauea’s 2018 eruption" Article from Carnegie Science: