Volcano Watch — NetQuakes—Extending seismic monitoring with citizen science

Hundreds of earthquakes each year are associated with faults in the Ka‘ōiki system. This area is also where some of the largest earthquakes ever recorded in Hawai‘i have occurred. We view the April 3 earthquake as part of the background earthquake activity occurring in the Ka‘ōiki 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 installations of our current allotment of NetQuakes seismic recorders in Hawai‘i County. This is a significant advance for the U.S. Geological Survey (USGS) 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 (like HVO) via expensive radio links. If we augment this coverage with less precise and less costly sensors, however, we could improve our monitoring coverage at a lower cost.

Not only are NetQuake sensors less costly, 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 (http://http://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 the California computers.

Significant shaking triggers the NetQuakes instrument. Data are stored in memory and written to CompactFlash cards. After the strong shaking subsides, each NetQuakes sensor automatically sends its data over the public 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, like the April 3 earthquake here, are distributed to other USGS computers for further processing. At HVO, the NetQuakes data are 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 the island of Hawai‘i. However, the slope and breadth of Kīlauea'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 like those occurring beneath Kīlauea's southeast flank—most recently in 1989 and 1975—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 named above. As we receive instruments, we will deploy them according to our monitoring requirements.

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Volcano 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 lake level was relatively steady over the past week due to the lack of deflation-inflation cycles, and was roughly 50 m (160 ft) below the floor of Halema‘uma‘u.

On Kīlauea'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 Hawai‘i Volcanoes National Park boundary. In addition, the Kahauale‘a flow, fed directly from a spatter cone on the northeastern edge of Pu‘u ‘Ō‘ō's crater floor, continues to advance very slowly toward the northeast across a plain of 1980s-era ‘a‘ā flows. The flow had traveled about 4.9 km (3 miles) when last measured on April 8.

There were several felt events across the State of Hawaii in the past week. On April 4 at 6:11 p.m., a magnitude-2.7 earthquake occurred 6 km (4 mi) west of Kailua-Kona at a depth of 11 km (7 mi). On April 5 at 6:06 p.m., a magnitude-2.8 earthquake occurred 18 km (11 mi) southeast of Waimea at a depth of 22 km (14 mi). On April 6 at 9:44 p.m. a magnitude-2.6 earthquake occurred 8 km (5 mi) south of Honoka‘a at a depth of 13 km (8 mi). On April 11 at 04:27 a.m., a magnitude-2.6 earthquake occurred 50 km (25 mi) east of Kailua, O‘ahu, at a depth of 10 km (6 mi). Also on April 11 at 7:25 a.m., a magnitude-3.3 earthquake occurred 15 km (9 mi) southeast of Volcano Village at a depth of 7 km (4 mi).