Top: Number of earthquakes per week during the past year (blue bars). The red line is the cumulative moment (energy) release. Bottom: Depth of earthquakes (circles) during the past year. Circle-size represents magnitude and color indicates depth of an earthquake. Automatic and reviewed earthquake locations in the area of Mauna Loa shown on the map at right above magnitude-1.7 are plotted in both figures. An interactive earthquake plot can be found at http://hvo.wr.usgs.gov/seismic/volcweb/earthquakes/
Changes in distance between two GPS stations on opposite sides of Mokuʻāweoweo, Mauna Loa's summit caldera. Extension across the caldera is often an indication of inflation of the shallow summit magma reservoir.
Vertical motion of a GPS station on the SE side of Mauna Loa's summit caldera. This station is in an area that has historically shown the largest amount of uplift with inflation.
Top: Hypocenter map showing locations of earthquakes during the past week. Bottom: Depth of earthquake during the past week in the area shown on the map above, plotted along a line from the NW to SE corners of the map. On both figures, circle-size represents magnitude and color indicates depth of each earthquake. Automatic and reviewed earthquake locations above magnitude- 1.7 are shown. An interactive earthquake plot can be found at http://hvo.wr.usgs.gov/seismic/volcweb/earthquakes/
Tilt data from a site near the northwest rim of Mauna Loa's summit caldera. The tiltmeter responds to daily and seasonal temperature fluctuations as well as possible changes in Mauna Loa's magma storage system.
The webcams are operational 24/7 and faithfully record the dark of night if there are no sources of incandescence or other lights. At times, clouds and rain obscure visibility. The cameras are subject to sporadic breakdown, and may not be repaired immediately. The full suite of webcams can be found at http://hvo.wr.usgs.gov/cams/
This map shows HVO's network of continuously recording Global Positioning System (GPS) stations, electronic tiltmeters, seismometers, gas monitoring stations and webcams located on Mauna Loa. These instruments detect changes in the volcano and are key to understanding the processes at work within the volcano. Historical lava flows refer to the period since 1843.
This map shows geographic relationship between historical (since 1843) lava flows (red) and towns (black dots) on the Island of Hawai`i. Geographic placenames on Mauna Loa are also shown.
This map illustrates the summit area and rift zones of Mauna Loa, along with historical lava flows (since 1843, in red).
Seismic Moment: A measurement of the energy release from an earthquake. The moment is tied to physical parameters of the fault that the earthquake occurred on.
Hypocenter: The earthquake location, including depth.
Epicenter: The earthquake location, plotted at the surface of the earth.
Global Positioning System (GPS): Instruments that communicate with satellites to track very small changes in movement, which may be caused by inflation or deflation of a magma body, or movement of volcanic fluids from one area to another within the volcano. At Mauna Loa, GPS stations are positioned to monitor accumulation of magma beneath Mauna Loa's summit, as well as the potential movement of magma into the volcano's northeast and southwest rift zones, and into radial vents on its northwest flank.
For more information on how GPS is used to monitor deformation of Mauna Loa and Kilauea volcanoes, see the explanation for inflation-deflation cycles of summit magma chambers in How Hawaiian Volcanoes Work.
Electronic Tiltmeters: Tiltmeters are highly sensitive instruments designed to detect minuscule changes in slope on the surface of the volcano. Unfortunately, their great sensitivity causes electronic tiltmeters to also respond to signals that have nothing to do with volcanic processes.
For example, as the ground heats and cools, it deforms slightly, which results in measurable tilt. Consequently, tilt records contain diurnal signals corresponding to daily temperature fluctuations, as well as annual signals corresponding to seasonal temperature changes. Tiltmeters can also be affected by rainfall, so rain gauges are commonly located with them to help determine when a tilt change is so affected.
Although electronic tiltmeters are less useful than GPS receivers for tracking relatively slow, long-lived processes, they excel at imaging fast, short-term events in real time and providing the earliest possible warning of changes that could lead to an eruption.
For more information on how electronic tiltmeters help monitor deformation of Mauna Loa and Kilauea volcanoes, see the explanation for inflation-deflation cycles of summit magma chambers in How Hawaiian Volcanoes Work.
Seismometers: Seismometers measure seismic waves created from a variety of volcanic processes. Earthquake activity nearly always increases prior to an eruption (as it did prior to eruptions in 1975 and 1984).
See the Long-term Monitoring Page for more information on the 1975 and 1984 eruptions and the earthquakes that preceded them.