Maintaining Monitoring Equipment on Mount Rainier
U.S. Geological Survey Cascades Volcano Observatory (CVO) regularly perform repairs, upgrades, and maintenance on the monitoring equipment on Mount Rainier. Installed in 2007- 2008, the stations provide a continuous stream of real-time seismic and deformation measurements from one of the most hazardous volcanoes in the Cascade Range. Scientists from CVO work together with partners at the Pacific Northwest Seismic Network (PNSN) to ensure all station equipment works well and continues to provide continuous data streams that are critical for detecting signs of unrest at Mount Rainier. In addition, data from the USGS/PNSN network creates research opportunities for USGS and academic scientists who investigate the inner workings of the volcano and study seismic swarms.
Why is it important to maintain the remote monitoring stations on Mount Rainier?
- The 2007-2008 expansion of real-time monitoring stations increased the number of continuous GPS (Global Positioning System) stations operating within Mount Rainier National Park from one to seven, the number of tiltmeters from zero to two, and the number of seismic stations from five to eight.
- The expansion of the seismic network has improved the ability to detect and locate earthquakes beneath Mount Rainier. In the four years preceding the expansion, the PNSN located 345 total earthquakes, or 86 events per year. In the four years following the expansion, the PNSN located 579 total earthquakes beneath the Rainier summit, or 144 events per year. This increase is almost entirely due to improved sensitivity to very small earthquakes, as the number of earthquakes greater than magnitude 1.5 is the same for both time periods.
- Increased instrumentation at Mount Rainier has increased the robustness of the network, making it less susceptible to individual station outages. The post-expansion increase in sensitivity to small earthquakes occurred despite having several Rainier stations go offline during each winter in 2009, 2010, and 2011. Therefore, the new stations enhance the Rainier network capabilities and prevent system-wide degradation when one or two stations stop working.
- Although no ground deformation has been detected so far, the new continuous GPS stations and the two tiltmeters have provided important information on the state of the volcano (specifically that the volcano was not deforming) following a seismic swarm in September 2009 and after several moderate-sized earthquakes (greater than magnitude 2) beneath the summit in 2010 and 2011.
- A GPS survey of 24 benchmarks conducted in 2008-2009 found no evidence of significant deformation since the 1994-1999 survey of Rainier geodetic benchmarks. This information is important for maintaining up to date hazard assessments.
- Data from the new seismic stations, particularly those high on the volcano, have resulted in precise recalculation of the locations of hundreds of small earthquakes that occurred during the September 20-22, 2009, swarm. These relocations show a complex faulting pattern thought to reflect injection of hydrothermal fluids, and the swarm is the subject of ongoing research efforts by USGS scientists.
- The new seismic stations have also allowed for improved detection, and in some cases location, of long-lasting sequences of repetitive glacier-quakes. These events are the subject of ongoing research by University of Washington and USGS scientists.
- The new seismic stations have increased the amount of data available for seismic imaging of the interior of Mount Rainier, and researchers from the University of Wisconsin and CVO are currently engaged in a study using data from the expanded Rainier network to develop improved models of the Mount Rainier magmatic system.