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Volcanowatch

April 15, 2010

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.


NetQuakes Offer More Community Partnering in USGS Seismic Monitoring

Records of the April 14, 2010, M3.8 earthquake, obtained from the Honomu, Hawai`i, NetQuakes seismograph. From top to bottom, the records show ground acceleration in east-west, north-south, and vertical directions. The records show roughly two minutes of time, starting at 7:37:10 a.m., H.s.t. (large tick marks indicate 10-second intervals).
Records of the April 14, 2010, M3.8 earthquake, obtained from the Honomu, Hawai`i, NetQuakes seismograph. From top to bottom, the records show ground acceleration in east-west, north-south, and vertical directions. The records show roughly two minutes of time, starting at 7:37:10 a.m., H.s.t. (large tick marks indicate 10-second intervals).

Wednesday, April 14, 2010, 7:37 a.m., Hawaii Standard Time: "Uh. Oh, oh. Did you feel that? It felt like an earthquake."

By now, many people are familiar with U.S. Geological Survey (USGS) earthquake reporting utilities. First, there's the Earthquake Notification Service (https://sslearthquake.usgs.gov/ens/) that sends email to lists of subscribers. Messages are sent according to user profiles specifying regions of interest, earthquake magnitude or size, and even times of day when a user wishes to receive an earthquake email notification.

There are also the USGS "recent earthquakes" Web pages that can be accessed via http://earthquake.usgs.gov/earthquakes/ or, simply, earthquake.gov. These Web pages show earthquake times and locations, as determined by the USGS or its seismic network cooperating partners in different parts of the United States and the world.

To display the effects of significant earthquakes, the USGS has developed a family of earthquake information products related to its ShakeMap software (http://earthquake.usgs.gov/earthquakes/shakemap/). Within minutes of a significant earthquake, ShakeMap provides maps of strong ground shaking and shaking intensity that are used to help guide earthquake response and recovery. ShakeMaps are also used as input to post-earthquake impact assessments and, even long after the actual event, as tools for earthquake preparation and response planning.

Separate but complementary to ShakeMaps are the Community Internet Intensity Maps, or "Did You Feel It?" maps (http://earthquake.usgs.gov/earthquakes/dyfi/). Using information collected via a Web questionnaire about earthquake effects, these maps graphically show the distribution of damage and other earthquake effects. After a large earthquake, the volume and density of "Did You Feel It?" information submitted by the general public are great compared to the number of instrumental recordings. "Did You Feel It?" reports are incorporated into ShakeMaps.

While combining "Did You Feel It?" and ShakeMap has proven to be quite effective, the USGS would like to have better instrumental recordings of strong earthquakes with increased numbers of modern instruments. This has resulted in a recently launched project called NetQuakes (http://earthquake.usgs.gov/earthquakes/waveforms/netq/).

The NetQuakes project uses new and relatively low-cost digital seismographs that report data to the USGS via the Internet. These seismographs have been designed to be installed in private homes, businesses, public buildings and schools where there is an existing broadband Internet connection.

A NetQuakes digital seismograph with WiFi antenna and power cord attached (pencil shows scale).
A NetQuakes digital seismograph with WiFi antenna and power cord attached (pencil shows scale).

At the heart of the NetQuakes project are people who are willing to host the NetQuakes seismographs, which access the Internet via a wireless router connected to the hosts' existing broadband Internet connection. The seismographs transmit data only after earthquakes above about magnitude 3 have been recorded and otherwise do not consume any significant bandwidth.

The USGS is focused on getting large numbers of NetQuakes instruments installed in high-hazard urban areas like San Francisco, Los Angeles or Seattle, but the Hawaiian Volcano Observatory (HVO) has received a small number of NetQuakes seismographs to use in Hawai`i. We have found a number of hosts and have begun to install the NetQuakes instruments.

Following the magnitude-3.8 earthquake on Wednesday morning, April 14, our first NetQuakes record was automatically retrieved and posted online. This came from our host in Honomu, where, because of the high mountains, it is challenging and costly for us to retrieve data from instruments using our typical means of data transfer. As we expand the NetQuakes footprint, we expect to record additional data that will help us better understand the distribution of earthquake effects. In Hawai`i, we look forward to being able to deploy a larger number of NetQuakes seismographs.

Wednesday's earthquake was a lithospheric adjustment to the weight of the island. The USGS received 127 "Did You Feel It?" reports on the earthquake, which was felt across the Island of Hawai`i.

Kīlauea Activity Update

On Kīlauea's east rift zone, breakouts along the east margin of the Thanksgiving Eve Breakout (TEB) flow remain active on the Pulama pali. The active flow front was just a few hundred yards from rejoining the main TEB flow field on the coastal plain on Thursday, April 15. If lava supply to these flows continues, they are expected to migrate south along the east margin of the TEB flow field, near the public viewing area. The flows may also stall before reaching the coast due to ongoing lava supply fluctuations.

At Kīlauea's summit, a ponded, circulating lava surface deep within the collapse pit inset within the floor of Halema`uma`u Crater was visible via Webcam during much of the past week. Volcanic gas emissions remain elevated, resulting in high concentrations of sulfur dioxide downwind.

One earthquake beneath Hawai`i Island was reported felt during the past week. The magnitude-3.8 earthquake occurred at 7:37 a.m., H.s.t., on Wednesday, April 14, 2010, and was located 4 km (2 miles) west of Pahala, at a depth of 38.2 km (23.7 miles).

Visit our Web site (http://hvo.wr.usgs.gov) for detailed Kīlauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes, and more; call (808) 967-8862 for a Kīlauea activity summary; email questions to askHVO@usgs.gov.

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Updated: April 20, 2010 (pnf)