At 9:28 a.m. April 3, the Hawaiian Volcano Observatory’s seismographic network recorded a magnitude-3.2 earthquake. This earthquake occurred roughly nine miles west of HVO on one of the faults comprising the Kaoiki fault system that lies between Kilauea and Mauna Loa volcanoes.
Hundreds of earthquakes each year are associated with faults in the Kaoiki system. This area is also where some of the largest earthquakes ever recorded in Hawaii have occurred. We view the April 3 earthquake as part of the background earthquake activity occurring in the Kaoiki system as the volcanoes evolve and the Earth’s crust responds.
The April 3 earthquake is noteworthy because HVO recorded it on all of our deployed NetQuakes sensors. In late March, we completed installation of our current allotment of NetQuakes seismic recorders in Hawaii County. This is a significant advance for the U.S. Geological Survey and HVO in seismic monitoring and our partnerships in citizen science.
The concept of the NetQuakes recorders arose from a need to better understand details of strong earthquake shaking and its effects on structures by recording damaging earthquakes on greater numbers of instruments deployed in affected areas. In order to achieve this, it was necessary to try something new.
Traditional seismic monitoring involves deploying many expensive sensors connected to a central data processing computer facility, such as HVO, via expensive radio links. If we augment this coverage with less precise, but cheaper, sensors, we could improve our monitoring coverage at low cost.
Not only are NetQuake sensors cheap, but they use the Internet, rather than radios, to send the data to the monitoring center. This is where USGS citizen science is key.
From generous responses to earlier Volcano Watch articles and to the NetQuakes website — earthquake.usgs.gov/monitoring/netquakes — we have been able to find volunteer hosts who have agreed to house our instruments in their homes. The USGS provides and installs the instrument, and the hosts provide AC power and Internet access. When there is no seismic activity, the instruments send scheduled status messages to California.
Significant shaking triggers the NetQuakes instrument. Data are stored in memory and written to compact flash cards. After the strong shaking subsides, each NetQuakes sensor automatically sends its data over the Internet to USGS computers in California. The data are subsequently posted to the Web, where they can be viewed at the NetQuakes site.
Data associated with a recognized earthquake, such as the one April 3, is distributed to other USGS computers for further processing. At HVO, the NetQuakes data is incorporated into our earthquake location and magnitude post-processing.
HVO, for example, records large numbers of earthquakes originating from the Puna District on the eastern side of Hawaii Island. However, the slope and breadth of Kilauea’s rift zone and adjacent flank have made this area difficult to establish stations with the requisite lines of sight for radio data transmission. Additional seismic stations are needed to improve our understanding of earthquake and volcanic processes there.
Thanks to our NetQuake citizen hosts, we now have a number of additional seismic stations in lower Puna. While we anticipate that these stations will provide very important recordings of large, damaging earthquakes such as those occurring beneath Kilauea’s southeast flank — most recently in 1975 and 1989 — we have also demonstrated that we can use the NetQuakes data in our studies of smaller earthquakes, as well.
Because of limited numbers of available NetQuakes, we already have more volunteers than instruments to deploy. At the same time, we ask that interested members of the community indicate their willingness to help by filling out a volunteer form at the NetQuakes website. As we receive instruments, we will deploy them according to our monitoring requirements.
Kilauea activity update
A lava lake within the Halemaumau Overlook vent produced nighttime glow visible from the Jaggar Museum overlook and via HVO’s webcam during the past week. The lake level was relatively steady over the past week due to the lack of deflation-inflation cycles, and was roughly 160 feet below the floor of Halemaumau.
On Kilauea’s east rift zone, breakouts from the Peace Day tube remain active above the pali and on the coastal plain. Small ocean entries are active on both sides of the Hawaii Volcanoes National Park boundary. In addition, the Kahaualea flow, fed directly from a spatter cone on the northeastern edge of Puu Oo’s crater floor, continues to advance very slowly toward the northeast across a plain of 1980s-era aa flows. The flow had traveled about three miles when measured Monday.
There were several felt events across the State of Hawaii in the past week. At 6:11 p.m. April 4, a magnitude-2.7 earthquake occurred four miles west of Kailua-Kona at a depth of seven miles. At 6:06 p.m. April 5, a magnitude-2.8 earthquake occurred 11 miles southeast of Waimea at a depth of 14 miles. At 9:44 p.m. April 6, a magnitude-2.6 earthquake occurred five miles south of Honokaa at a depth of eight miles. At 4:27 a.m. Thursday, a magnitude-2.6 earthquake occurred 25 miles east of Kailua, Oahu, at a depth of six miles. At 7:25 a.m. Thursday, a magnitude-3.3 earthquake occurred nine miles southeast of Volcano Village at a depth of four miles.
Visit 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 is a weekly article and activity update written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.
