HAWAIIAN VOLCANO OBSERVATORY characterized a recent swarm of earthquakes as a possible, but not definite, precursor to the next eruption of Mauna Loa. While the swarm was small in historical terms, it was the first cluster of earthquakes in this region of Mauna Loa since the volcano’s 1984 eruption. “Only through continued monitoring over the coming weeks to months will the true meaning of the … swarm be known,” HVO said in the current issue of Volcano Watch. HVO seismic networks recorded a small, three-day-long earthquake swarm just west of Mauna Loa’s summit Sept. 5 through Sept. 7. The swarm consisted of more than 350 detected and tightly clustered earthquakes at a depth of about four miles, but only about 25 were strong enough to be located. The strongest was a magnitude 2.4, and none were reported as felt. The swarm was in the same region where earthquakes began to occur a year or more before Mauna Loa’s 1975 and 1984 eruptions. It’s an area to which HVO pays especially close attention because of this connection. The swarm is not the only Mauna Loa activity to have occurred recently. After the eruption in 1984, Mauna Loa immediately began re-inflating as magma once again filled and pressurized storage reservoirs beneath the summit caldera. Inflation waned in 1993, then resumed in May 2002. In the second half of 2004, there was an intense swarm of about 2,000 long-period earthquakes more than 19 miles below the summit of the volcano. This swarm was possibly part of the deep magma system that fed the ongoing inflation, HVO reported. The rate of inflation increased in 2004, but started to slow in 2006. These data fit the pattern produced by magma intruding 2.5 to five miles beneath the summit area. After 2009, Mauna Loa inflation continued, but very slowly and sporadically, “so the volcano is poised for its next eruption,” according to HVO. Mauna Loa is still the largest active volcano on Earth. A volcano off the east coast of Japan, recently touted as the largest volcano in the solar system, last erupted 146 million years ago, possibly around the time the Pacific Ocean Basin was first formed. Mauna Loa, on the other hand, has erupted 33 times in the past 170 years, and future eruptions are a certainty, HVO said. With recently upgraded monitoring networks, HVO keeps a close watch on any changes beneath the volcano that might signal its next eruption. HVO offers increased availability of real-time earthquake data to the public. Locations and the actual seismometer traces (webicorders) can be viewed at hvo.wr.usgs.gov/seismic/volcweb/earthquakes/. To view webicorder sites closest to the area in which the recent swarm occurred, click on Webicorders and choose ALEP or TOUO. “For now, there’s no need to worry, but we should never lose sight of the fact that Mauna Loa is an active volcano, the largest on Earth, and it will erupt again,” HVO reported.
Posted on: Wed, 18 Sep 2013 00:28:50 +0000
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