Ka`u Calendar News Briefs Friday, Oct. 7, 2016

      “We respect the court’s decisions and will consider them carefully to determine what impact, if any, they have on future matters before the state land board, including the Thirty Meter Telescope,” Hawai`i Attorney General Doug Chin said. “The justices continue to stress the importance of conducting a fair process for all projects on public lands.”
      To read comments, add your own, and like this story, see Facebook. Follow us on Instagram and Twitter.

WHY EARTHQUAKE MEASUREMENT SOMETIMES CHANGE is explained by Hawaiian Volcano Observatory scientists in the current issue of Volcano Watch.

      “Characterizing earthquakes is one of the most important activities we do at the USGS Hawaiian Volcano Observatory,” the article states. “Seismicity helps us monitor the ‘pulse’ of volcanoes and can be a first indication of an impending eruption. 

      “Earthquakes also pose a hazard in their own right, and the entire state of Hawai`i is at risk from damaging earthquakes. They occur abruptly, so we must be vigilant and prepared.
      “HVO posts preliminary information about earthquake location and size (magnitude) as soon as possible after one occurs. Later, we update the information as more data becomes available. Sometimes the reported magnitude changes during this process.
      “When the earth shakes, vibrating seismic waves radiate outward from the source. These waves are picked up by sensitive instruments called seismometers, which are located across the state. Seismic data is relayed in near real-time to HVO, where computers trained to look for earthquake patterns keep watch around the clock. When four or more stations detect an earthquake, the computer automatically estimates the location and magnitude of the event.
      “If the earthquake magnitude is above 3.0, the computer posts the information to HVO’s website without human intervention. The USGS Earthquake Notification Service then alerts subscribers. This generally happens within five minutes of the earthquake.
      “HVO’s seismologists then spring to action to review the data. They recalculate the earthquake parameters and, if needed, overwrite the previously posted automatic ones. For magnitude-4.0 and higher earthquakes, we complete our manual review within two hours and issue a news release. Events smaller than magnitude-4.0 are reviewed routinely within a few days.

      “Upon review by a seismologist, the earthquake’s magnitude can go up or down by a few tenths. Different groups, such as the Pacific Tsunami Warning Center and the USGS National Earthquake Information Center, might also report slightly different magnitudes. To understand these differences, let’s review what magnitude means. 

      “The concept of earthquake magnitude dates back to 1935, when Charles Richter created a way to compare the relative sizes of earthquakes in southern California. He measured how the amplitude of shaking recorded by seismometers decreased with distance from an earthquake. Using the logarithm of the maximum amplitude, Richter was able to derive a scale that conveyed the wide range of earthquake sizes, which can vary by several orders of magnitude (hence the name). For example, on this scale, the amplitude of a magnitude-4.0 earthquake is ten times higher than that of a magnitude-3.0 earthquake.
      “Today, there are numerous types of earthquake magnitudes that take advantage of advances in seismic instrumentation and cover a wide range of situations. For earthquakes higher than about magnitude-5.5, the most common measure of magnitude is called moment magnitude, which relates fundamentally to the energy released by an earthquake's fault motion. For every 0.2 increase in moment magnitude, the energy doubles. For example, a magnitude-6.2 earthquake releases roughly twice as much energy as a magnitude-6.0 event.
      “For smaller earthquakes, like those that happen daily in Hawai`i, HVO computes two types of magnitude based on either the duration or amplitude of the shaking recorded by seismometers. Duration magnitude tends to work better for smaller earthquakes (less than about magnitude-2.0) that are located shallower than 20 kilometers (12 miles) beneath the surface. Amplitude magnitude, which is a modern-day formulation of Richter’s magnitude, works better for local earthquakes with magnitudes between about 2.0 and 5.5.
      “Any reported magnitude is actually an average of values computed for each seismometer that recorded the earthquake. These values vary depending on distance, direction, instrument and the type of material type along the seismic wave’s path. HVO seismologists evaluate which stations provide the most reliable and objective magnitude estimates, average them together and select either duration or amplitude as the preferred magnitude type for each event.
      “Magnitudes can change following a seismologist’s review and analysis of the computer’s automatic magnitude assignment. This process provides the best information available at any given time and offers a window into how the science of real-time seismology unfolds.
      “What matters more than a number, however, is what you do if you feel shaking during an earthquake. On Oct. 20, we encourage you to take part in the world’s largest earthquake preparedness exercise by practicing ‘Drop, Cover, and Hold On!’ during the Great Hawai`i ShakeOut.”
      See hvo.wr.usgs.gov/volcanowatch.
      To read comments, add your own, and like this story, see Facebook. Follow us on Instagram and Twitter.

OCEAN VIEW’S PANCAKE BREAKFAST tomorrow includes a yard sale. Last Saturday’s sale was so well supported by donors that even highly desirable items went unsold. This will be a second chance for bargain hunters to unearth more treasures in the surplus inventory. If you missed Saturday’s event, be sure to attend the pancake breakfast on Saturday, from 8 – 11 a.m. at the community center on Leilani Circle. Most clothing items are priced at a dollar, and many household items at 50c. Proceeds will go towards a new roof for the community center.

LEARN ABOUT `OHI`A LEHUA SUNDAY at 9:30 a.m. at the Kahuku Unit of Hawai`i Volcanoes National Park. Participants learn about the vital role of the trees in native Hawaiian forests, its many forms and flower on this free, easy, one-mile walk.

VOTER REGISTRATION DEADLINE IS MONDAY to participate in the Nov. 8 General Election. Registrants must have a current Hawai`i driver’s license or state ID to complete an application online at www.olvr.hawaii.gov.

      Applications are also available at libraries and post offices.
      Residents can also apply in person at the County Clerk’s office in Hilo. 

SUPPORT OUR SPONSORS AT PAHALAPLANTATIONCOTTAGES.COM AND KAUCOFFEEMILL.COM. KA`U COFFEE MILL IS OPEN SEVEN DAYS A WEEK.