The Earthquake Studies Office (ESO) opened in June 1980 when the Montana Bureau of Mines and Geology (MBMG) assumed operation of the Butte seismograph station. Montana Tech operated the station until it lost federal funding in 1980. The Butte seismograph began operation in 1936 following the destructive 1935 Helena earthquakes and is the longest continuously operating seismograph in Montana. After the USGS declared the original seismometers, photographic drum recorders, and station clock surplus and sold them to a private individual, the MBMG purchased a Wood-Anderson equivalent seismograph in 1982. This seismograph consisted of two horizontal, short period seismometers filtered to emulate the frequency response of a Wood-Anderson seismograph and recorded on an ink-pen drum recorder. True Richter magnitudes could be computed for local and regional earthquakes from these seismograms. This equipment operated continuously until June 2017 when a water leak destroyed the electronics. A broadband seismograph replaced this equipment in 2019.
The MBMG installed the first permanent telemetered (remote from ESO) seismograph station on Limekiln Ridge (station LRM) in the Highland Mountains south of Butte in 1980. The ESO installed several additional telemetered seismograph stations in southwestern Montana and by 1982, there were enough operating seismograph stations to begin locating earthquakes, marking the beginning of the modern Montana earthearthquake catalog. In 1984, the MBMG installed four new stations around Butte to monitor potential seismicity after underground mine de-watering stopped and the Berkeley Pit began to flood. These stations detected no significant seismicity in the vicinity of the flooded mine so, in 1988, the four Butte area stations were relocated to expand network coverage in more active areas of southwest Montana (however this new configuration still provided monitoring coverage of the Butte region).
In August 1989, the ESO installed a PC-based data acquisition system to better locate and analyze seismic data. In 1990, the ESO had seismic monitoring coverage extending southeastward to Earthquake Lake where the US Forest Service seasonally operates a seismograph at their Visitor's Center.
In 1996 the ESO received a grant from the US Geological Survey to install nine additional stations along the Lewis and Clark zone, an area of ancient faults extending from the Helena area, west-northwestward to Coeur d'Alene, Idaho. Continuous data from three new stations northwest of Missoula were telemetered to Missoula and recorded along with data from two other stations operated by the Geology Department of the University of Montana. Also in 1996, the ESO assisted the Confederated Salish and Kootenai Tribes of the Flathead Reservation with installation and operation of six seismograph stations in the southern Flathead Valley. Data from the Flathead portion of the Montana seismograph network was telemetered to Ronan for recording.
In 1998, with assistance from the Spokane Research Center of the National Institute of Safety and Health (NIOSH), the ESO relocated an existing Bozeman area seismograph station (operating since 1988) to a new site near Bozeman Pass. Two new south-central Montana stations, one near Greycliff, and the second near the Stillwater Mine, southwest of Absaroka, were also added. In 1999, the Montana Seismic Network consisted of 31 seismograph stations. Additional data from surrounding seismograph networks in Yellowstone National Park, Idaho National Environmental and Engineering Laboratory, Boise State University, and the Canadian Geological Survey were forwarded to ESO via email. In November 1999, Montana's first permanent broadband seismograph station (BOZ) became operational as a cooperating station in the United States National Seismic Network. Bringing the total stations in the network to 35 seismic stations.
The recording capabilities improved dramatically in 1999 with the installation of Earthworm software, which allowed the real-time recording of seismic data in Butte, from Ronan and Missoula, as well as from other stations in the region. Since August 15, 2001, continuous seismic data from the Montana network are archived at the Incorporated Research Institutions for Seismology (IRIS) Data Management Center, where it is publically available.
In 2001, in cooperation with the NIOSH, the MBMG installed a seismograph station (Chrome Mountain, CRMT) above the East Boulder Mine and another station southeast of Livingston (Mission Creek, MSMT) that serves as a telemetry repeater site.
In 2003, the MRSN became a supported member of the ANSS, which provided salary support for a seismic analyst/IT support person and funding for seismic station and telemetry repeater site repair and maintenance. MRSN failed to secure continued ANSS support in 2015 due to an inadequate USGS budget and left the ANSS. Although quite challenging without ANSS support, the MBMG has continued to operate the MRSN, and analyze and report seismicity in the northern Rocky Mountain region.
In 2004, the MBMG installed the first (and still only) seismograph station in the Bitterroot Valley near Victor (VCMT). Although the Bitterroot Valley historically has a very low seismicity rate, there are a few events located there and the valley is bounded on its western side by a large fault, the Bitterroot Fault, which has clear evidence of major late Quaternary earthquakes.
The MBMG installed a seismograph on Mount Belmont (BEMT) in 2005. We utilized this site for a telemetry repeater so installing a sensor was relatively easy and inexpensive.
In 2006, a station originally installed along the north edge of the Ninemile Valley on private property, and since plagued with problems, was relocated about 20 km to the southeast to a site on Ellis Mountain, north of Alberton (ALMT). This site is located within 4 km of I-90 and active railroad lines, so it does see some cultural noise.
In 2015, the MBMG learned of Army Corps of Engineers plans to demolish the Libby Dam seismic vault located about 4 miles upstream from the dam. The MBMG proposed to reoccupy the site (LDM), which was built in 1969 and had sat unused since 1986. Initially, we deployed a triggered short-period instrument there and replaced it with a telemetered broadband seismograph in July 2016. Because there is no cell phone service at this site nor any internet access nearby, we had to install a VSAT (very small aperture satellite) link to transmit the signal in real time. Also, there is no AC power available (ironic because the largest hydroelectric generating facility in northwestern Montana is just 4 miles away), so the seismic equipment and the VSAT are powered by a solar power system.
The USGS provide MBMG with five NetQuakes [link: https://earthquake.usgs.gov/monitoring/netquakes] strong motion seismographs in 2010. We deployed these instruments at volunteered homes, fire stations and the West Yellowstone Ranger Station, where they trigger and record on earthquakes that are typically strong enough to feel. Although these sites are noisy compared to our typical seismic monitoring sites, they do provide useful data for larger events.
The USGS National Strong Motion Program operates several stations in Montana in triggered mode. The MBMG installed short period vertical seismometers on the 4th channel of the dataloggers operated at four of these stations since 2016 and began to record continuous data. Augmented NSMP stations include Butte (NP.2255 (network.station)), Helena (NP.2202), West Yellowstone (NP.7220), and Bozeman (NP.2205) (still resolving firewall issues).
The most significant recent development for the MRSN was the implementation of ANSS (Advanced National Seismic System) Quake Management System (AQMS [link: https://vault.gps.caltech.edu/trac/cisn]) in September 2015. After about five years of planning and coordination with the University of Utah Seismograph Stations (UUSS), the system became functional. All seismic trace data collected by the MRSN, along with automatically determined parameters are sent to an AQMS database running at the UUSS in Salt Lake City. MBMG seismic analysts use Jiggle [link: https://pasadena.wr.usgs.gov/jiggle/] software to connect to the UUSS database and analyze seismic events recorded on the MRSN and report their locations and magnitudes (exclusive of the Yellowstone authoritative region [link: https://quake.utah.edu/earthquake-center/quake-map]) to the USGS Comprehensive Catalog [link: https://earthquake.usgs.gov/earthquakes/search/] . The use of AQMS to locate and report seismicity greatly improves analyst efficiency and accuracy.