As we watched tropical storm Flossie weaken and change course from the path that would have landed it directly on the Island of Hawaii, a collective sigh of relief swept across Hawaii County.
As we watched tropical storm Flossie weaken and change course from the path that would have landed it directly on the Island of Hawaii, a collective sigh of relief swept across Hawaii County.
At the same time, curious onlookers may have been disappointed about not witnessing, first hand, nature’s forces associated with tropical storms. These storms, like the volcanoes and earthquakes monitored by the U.S. Geological Survey’s Hawaiian Volcano Observatory, are very much part of life in Hawaii.
It’s important to understand the potential effects of nature’s fury and how to live safely in communities that can withstand extreme natural phenomena. During Flossie, the National Weather Service, state and county emergency managers and news media performed well, collecting critical observations and data and providing useful and understandable information through the storm’s approach and passage across the state. The ability to watch Flossie — via satellite and radar images and video — form in the eastern Pacific, intensify as she moved westward, and then weaken as she reached and eventually passed Hawaii, was fantastic, at times worrisome and, ultimately, reassuring.
A challenge that HVO scientists face as we work with volcanic and seismic phenomena is that much of what we need to monitor occurs deep within the Earth, beyond any ability to make visual or direct observations and measurements. When volcanoes erupt, we are rewarded with opportunities to record visual observations, with both ground and satellite technologies. Until then, we depend on our various instrumental monitors for understanding what the volcanoes are doing.
As we know, it is not yet routinely possible to accurately predict earthquakes. Nor is it possible to successfully forecast earthquake behavior in a manner similar to how weather or a tropical storm track is forecast.
We have learned that when there are unusual patterns of small earthquakes in certain parts of the volcanoes, they are likely indicating magma movement within. Patterns of shallow earthquakes can actually herald the onset of an eruption or possible changes to an ongoing eruption.
Large and potentially damaging earthquakes, however, pose a special problem. These earthquakes occur at depths within the Earth, where it is not possible to identify, let alone measure, all of the factors potentially controlling earthquake behavior. Understanding these factors and their interactions remains an area of active earthquake research.
Years of earthquake study and observation have provided important lessons. One of the most basic lessons is that, in places where large earthquakes have occurred, it is reasonable to expect future large earthquakes.
Another important lesson is that large earthquakes occur at somewhat regular intervals, when viewed in a geologic context. The aspect of earthquake recurrence interval is an important part of modeling seismic hazards.
Combining the two lessons above, Professor Bruce Bolt, noted seismologist at the University of California at Berkeley from 1963 to 2005, would lecture, “The longer it has been since the last large earthquake, the closer we are to the next one.”
A list of earthquakes that caused damage in Hawaii County during the last 100 years is currently posted on HVO’s website home page (http://hvo.wr.usgs.gov/). Many residents may remember the earthquakes centered in North Kona and Kohala in 2006. It has been nearly a quarter of a century, however, since the 1989 damaging earthquake occurred beneath the southeastern part of the Island of Hawaii, where Hawaii’s largest recorded earthquakes have struck.
To further promote public awareness of what to do when a large earthquake strikes, HVO is partnering with Civil Defense and other organizations in the first Great Hawaii ShakeOut on Oct. 17. Additional information about this earthquake drill is available at http://shakeout.org/hawaii/.
Kilauea
activity update
A lava lake within the Halema‘uma‘u Overlook vent produced nighttime glow that was visible from the Jaggar Museum overlook and via HVO’s webcam during the past week. The lava lake level fluctuated slightly over the past week as it responded to deflation-inflation (DI) cycles at the summit. On Kilauea’s East Rift Zone, breakouts from the Peace Day tube remain active on the coastal plain, and a single small ocean entry is active just east of the Hawaii Volcanoes National Park boundary. A new breakout, which started on Thursday, sent channelized flows to the base of Pulama pali. The Kahauale‘a 2 flow, fed from a spatter cone on the northeast edge of the Pu‘u ‘O‘o crater, continues to advance slowly along the edge of the forest north of Pu‘u ‘O‘o. The front of this flow was 2 miles north of Pu‘u ‘O‘o when mapped on July 26. There were two earthquakes reported felt in the state of Hawaii this past week. On Monday at 10:30 a.m., a magnitude-3.7 earthquake occurred 9 miles southeast of Waimanalo, Oahu, at a depth of 20 miles. On Wednesday at 9:43 a.m., a magnitude-2.7 earthquake occurred 4 miles southeast of Pahoa at a depth of 2 miles.
Visit the HVO website (http://hvo.wr.usgs.gov) for Kilauea, Mauna Loa and Hualalai activity updates, recent volcano photos, recent earthquakes and more; call 967-8862 for a Kilauea summary; email questions to askHVO@usgs.gov.
Volcano Watch (http://hvo.wr.usgs.gov/volcanowatch/) is a weekly article and activity update written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.