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REMOTE MONITORING OF MINE SEISMICITY AND EARTHQUAKES USING RADIO 

TELEMETRY, COMPUTERS, AND THE INTERNET 

D. Denton, M. Stickney , T. Williams, and R. Langston 

ABSTRACT 

 The National Institute for Occupational Safety and Health and the Stillwater Mining Company worked 

cooperatively with the Montana Bureau of Mines and Geology to develop a system that would collect seismic data 

at the Stillwater and East Boulder mines. The purpose was to obtain baseline information on the magnitude and 

location of mining-induced seismicity to determine if the mines needed multi-channel in-mine monitoring systems. 

Seismic data recorded at field sites near the mines are being telemetered via FM radio through a series of repeaters 

to a central recording site where the seismic signals are digitized using an Earthworm data acquisition system. The 

Earthworm system performs several data analysis tasks in near-real time and places raw seismic data, preliminary 

hypocenter locations, and magnitudes on a Website within 5 min of a seismic event. Such rapid access to seismic 

data allows personnel at the Stillwater Mine, Spokane Research Laboratory, and Earthquake Studies Office to 

evaluate seismic events quickly and respond in ways that may improve the safety of mine personnel underground. 

Installation of the system also broadened earthquake coverage to south-central Montana, a region previously not 

covered by the seismograph network. 

1. INTRODUCTION 

 The Stillwater and East Boulder mines in south-central Montana are underground mines that produce palladium 

and platinum from a geologic structure known as the JM Reef. The JM Reef is part of the Stillwater complex, a 42-

km (26-mile) long, layered stratiform, mafic-to-ultramafic igneous intrusion approximately 2.7 billion years old 

(Czamanske and Zeintek, 1985; Hess, 1960). Currently, the Stillwater Mine produces ore using variations on 

horizontal cut-and-fill mining, but longhole stoping practices are playing an increasingly important role. The East 

Boulder Mine uses longhole stoping for most of its extraction. 

 Engineers at the Stillwater Mining Company and at the National Institute for Occupational Safety and Health 

(NIOSH) have become concerned about the potential for hazardous rockbursts as mining proceeds deeper into the 

highly stressed, hard, brittle rock (Johnson et al., 2003). Rockbursts are defined as “a sudden and violent failure of 

overstressed rock resulting in an instantaneous release of large amounts of accumulated energy,” according to the 

regulatory definition (30 CFR 57.3000) applicable to U. S. mines. Rockbursts are a common problem in many 

mines throughout the world, some of which have hard, brittle rock similar to that found at the Stillwater Mine 

(Whyatt et al., 2002). 

 Many rockburst-prone mines have sophisticated and expensive in-mine monitoring systems to determine the 

locations and magnitudes of mining-induced seismic events (Girard et al., 1995). The purpose of this study was to 

determine the amount of seismicity at the Stillwater and East Boulder mines before the mines decided whether to 

install expensive in-mine seismic systems. Therefore, NIOSH researchers installed relatively inexpensive surface 

seismic stations as a first step in identifying the level of the seismic activity near the mines. The problem was how 

to measure frequency-of-occurrence and event-magnitude data from mining-induced seismicity in a timely manner 

and get this information to rock mechanics engineers responsible for the mine sites and to researchers at NIOSH’s 

Spokane Research Laboratory in Spokane, WA, 960 km (600 miles) from the mines. 

 NIOSH approached the Earthquake Studies Office (ESO) of the Montana Bureau of Mines and Geology in Butte 

about expanding the regional seismic network in the vicinity of the mines. Much of western Montana was already 

being monitored by ESO. The agency was also experienced in using radio telemetry to retrieve seismic signals from 

remote sites. Adding monitoring sites near the mines would benefit ESO by including south-central Montana in 

Montana’s seismograph network. Fortuitously, the U.S. Geologic Survey (USGS) had recently developed the 
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Earthworm1 data acquisition and analysis system, and ESO had installed this system in June 1999 for its Montana 

seismic monitoring program. Not only does the Earthworm system dramatically improve seismic analysis

capabilities, but its use has led to better cooperation and data-sharing among ESO, USGS, and other regional seismic 

monitoring centers. 

This paper describes the hardware and software needed to transfer mine seismicity data into the Earthworm 

system and provides examples of data display.

2. SEISMIC MONITORING

NIOSH purchased and helped install the seismic monitoring equipment specified by ESO. At each monitoring 

site, ground movement is detected using a model L4 moving-coil seismometer. These seismometers have a natural 

period of 1 sec and respond to ground velocity rather than to acceleration or displacement. The seismometers are 

typically buried less than 0.5 m (2 ft) below the ground surface on or near bedrock and are connected to an

electronics package with a 15-m- (50-ft-) long, direct burial cable. 

The electronics package consists of a preamplifier, a voltage-controlled oscillator (VCO), a dc power supply, and

a signal multiplexer. It also contains a voltage regulator/power supply that regulates the output of a solar panel and 

charges a 12-V deep-cycle battery. The battery, in turn, powers the VCO and the telemetry radio. The preamplifier

amplifies and filters the signal from the seismometer. The VCO uses the amplified seismic signal to modulate the 

carrier frequencies up to a maximum of ±125 Hz. Eight standard audio carrier frequencies range from 680 to 3060

Hz in 340-Hz steps. The signal multiplexer in the electronics package 

allows multiple VCO signals to be mixed together (either multiple

seismic channels from a single site or signals from different sites) for 

telemetry on a single communications channel. In this manner, as 

many as eight different seismic signals can be transmitted on one

communications channel (either an FM radio link or a voice-grade

telephone circuit). 

The telemetry radios are small FM radios that operate in the VHF

band (162 to 171 MHz) with power outputs typically below 0.25 W. 

The low output power of the radio transmitter requires that all

telemetry paths be line-of-sight, requiring placement of most seismic

stations and repeater sites on ridges or mountaintops. 

The electronics package, telemetry radio, and battery are housed in a 

sealed, 200-L (55-gal) drum (Figure 1). A 50-W solar panel and YAGI

(directional) radio antenna are mounted on a 50-mm (2-in) in diameter

steel pole near the drum. The seismometer is placed as far as possible

from the pole to minimize recording wind-generated pole vibrations. 

The seismic stations are designed to operate under severe weather 

conditions, including high winds, deep snow, and bitter cold, and will

run for at least 20 days without solar input. The seismic data from both 

mine seismographs are telemetered by radio through a series of

repeater stations to ESO, located on the campus of Montana Tech of 

the University of Montana in Butte, a distance of approximately 320 

km (200 miles) from the mine. 

Figure 1. Seismic monitoring 

electronics In addition to the seismograph stations at the mines, each repeater 

location also includes a seismograph to supplement seismic coverage

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 Mention of specific products and manufacturers does not imply endorsement by the National Institute for 

Occupational Safety and Health. 
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near the mines and also to improve regional

seismic monitoring coverage. In all, five

sites are monitored within 60 km (40 miles) 

of the mines. Figure 2 shows the Mission

Creek repeater station with the Chrome

Mountain seismograph site above the East

Boulder Mine (background). The radio 

telemetry path from the mines to ESO is 

shown in Figure 3. Collecting usable data

telemetered through the six relay links is 

possible because meticulous attention is

paid to matching signal levels at each relay

point. At the ESO central recording facility

in Butte, the radio telemetry signal is 

received, and individual analog seismic 

signals are recovered from the audio carrier

frequencies by means of an FM discriminator (essentially a narrow-band audio filter 

and a frequency-to-voltage converter). 

Figure 2. Mission Creek repeater station 

3. EARTHWORM SEISMIC DATA ACQUISITION 

AND ANALYSIS SYSTEM

The Earthworm seismic system consists of computer

software modules that perform specific tasks with 

seismic data. These tasks include digitizing analog 

waveforms, picking seismic phase arrivals in real time, 

determining hypocenter locations and event

magnitudes, and posting information to Websites. 

Earthworm software will run on either Unix or

Windows 2000 operating systems. The USGS Earthworm Website, http://gldbrick.cr.usgs.gov/ew-doc/, 

describes the Earthworm system in detail and provides 

links and instructions for downloading this free 

software package. 

At ESO, the Earthworm system is divided into two 

general parts—an automatic, real-time portion that

collects and processes seismic data, and an interactive 

portion that allows users to view, and in some cases edit, seismic data. The automatic portion includes a National

Instruments PCI-6040E multifunction I/O board installed on a PC running Windows 2000. This digitizer samples 

22 analog data streams (including the two mines’ seismographs and three repeater site seismographs) at a rate of 100 

samples per second and stores the resulting digital data on large hard drives. Other modules scan the seismic data 

streams and pick seismic phase arrivals, associate these arrivals into coherent events, determine hypocenter locations

and magnitudes, and report these data to a database and a Website. 

Figure 3. Radio telemetry path to Butte

The interactive portion of the Earthworm system includes a Website where preliminary hypocenter locations and 

magnitudes are listed within 5 min of their occurrence (http://mbmgquake.mtech.edu/earthworm/). The Butte 

Earthworm system introduces reasonable preliminary hypocenter locations for most seismic events of magnitude 2.0 

or greater within the Montana regional seismic network, but on occasion, it also produces spurious events caused by

large distant earthquakes or radio telemetry noise glitches. After review by a seismologist, updated earthquake 

hypocenters and magnitudes are listed at http://mbmgquake.mtech.edu/reviewed_events.html. 
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The ESO Website (Figure 4) also

includes graphic representations of the raw 

seismic data from all stations in the 

network. These images, known as webicorders, are designed to resemble paper 

seismograms recorded by analog seismic 

drum recorders. Two sizes of webicorder

images are generated, a smaller version 

(http://mbmgquake.mtech.edu/earthworm/

wavef_disp/welcome.html) that shows 24

hours of seismic data in a 200- by 290-mm 

(8- by 111⁄2-in) page format for all 35

stations in the Montana network, plus 

selected regional stations, and a larger

280- by 965-mm (11- by 38-in) version 

(http://mbmgquake.mtech.edu/earthworm/

large_wavef_disp/welcome.html) that 

closely resembles the old paper seismograms produced by a drum recorder. The larger images are only generated for 19 of the better-quality seismograph 

stations in the network. All webicorder images are automatically updated every 5 min and are available on-line for

the period covering the past 14 days. The mine webicorder images are available in both size formats by selecting 

either CRMT EHZ MB for the Chrome Mountain station or STMT EHZ MB for the Stillwater Mine station. 

Figure 4. Earthquake Studies Office main Web page

The interactive portion of the Earthworm system includes an Oracle database that stores the original seismic trace

as well as the hypocenter locations and other information produced by the Earthworm system. The Oracle database 

is also available on a Website, but it is password-protected to prevent system overload by multiple users

(particularly following a significant earthquake) and unauthorized editing of seismic data by the public. Posting raw 

seismic data and preliminary event information on the Website within 5 min makes the data rapidly available to a 

wide variety of users, including mine managers, health and safety experts, and seismologists. 

Another tool for viewing seismic data collected on an Earthworm system is a software package called 

Waveviewer. Waveviewer connects to the wavetanks of an Earthworm computer through a network connection and 

displays time-series seismic trace data for groups of stations selected by the user. It is useful for quickly observing

the arrival sequence of P-waves on the seismic network and for zooming in to check first-arrival polarities from a

given seismic station. However, public use of Waveviewer is not allowed because of the potential for overloading 

the Earthworm computer and its network connections. 

4. DATA ANALYSIS

Documenting seismicity rates and characteristics of mining-related seismicity at the two mines motivated this 

project. An objective is to identify changes in seismic trends before seismic events become a problem at the mine.

Each day, the seismic data are reviewed to determine the number of mine blasts and mining-related seismic events. 

Figure 5. Chrome Mountain site in relation to East 

Boulder Mine workings.

The East Boulder Mine detonates production rounds

at approximately 6:00 in the morning and evening 

local time, and these blasts show up well on the 

Chrome Mountain seismograph located approximately

900 m (3,000 ft) above the active mine workings

(Figure 5). Production blasts consist of a series of 

drill holes loaded with high explosives and detonated 

in a specific sequence via time-delayed blasting caps.

The seismic recordings clearly show multiple holes 

fired over 6 to 10 sec. Figure 6 is a portion of a large- 
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Figure 6. Web page showing large waveform display. B = mine blasts, E = mine seismic events, and Q = a local 

earthquake. 

format webicorder image for the Chrome Mountain seismograph

recorded on May 15, 2003, showing production blasts (B), mining-related 

seismic events (E), and a regional earthquake from Yellowstone Park (Q). 

Figure 7 shows a seismic record from Chrome Mountain using Waveviewer to show a single production blast at the East Boulder Mine lasting

7 sec. The P-wave arrival for this event is positive, indicating a compressional wave. 

In contrast to blasts,

mining-related seismic

events are single events

of short duration, typically lasting less than 1 

sec. From November 

2002 through April 2003

the Chrome Mountain 

seismograph recorded an average of 2.4 mining-related seismic 

events each day. Measured S-P intervals for 232 of these events

ranged from 0.11 up to 0.62 sec with a mean of 0.24 sec (Figure 8).

These S-P intervals indicate that most events occurred within 6,500

feet of the seismograph station. Mining-related seismic events were 

clearly related to production blasting; 84% of the mining-related

events occurred between 5:20 p.m. and 7:00 p.m. (Figure 9) during

the afternoon blasting period. Only 7.6% of the mining-related 

events occurred during the early morning blasting period. The 

remaining 8.5% of the events occurred at other times throughout the

day. 

Figure 7. Waveviewer image of typical production blast at East Boulder

Mine showing compressional P-wave

(positive) arrival for first hole fired.

The P-wave onset for most mining-related events (about 81%) 

was very impulsive, and the P-wave first motion is clearly recorded

on the seismogram (Figure 10). About 47% of the mining-related 

seismic events had downward (dilatational) impulsive P-wave first 

Figure 8. S-P intervals for 239 miningrelated seismic events recorded at Chrome

Mountain station. 
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Figure 10. Mining-related seismic event at East Boulder 

Mine showing negative P-wave arrival. The 0.18-sec S-P 

interval indicates a source distance of about 4,700 ft. 

motions. Blasts generate a P-wave first motion that is a

push away from the source, and if recorded at a surface 

seismograph station, this first motion will be compressional, 

an upward movement of the ground. Thus the miningrelated events with dilatational first motions cannot possibly 

result from blasting. Mining-related seismic events with 

dilatational first motions are well known in the Coeur 

d’Alene Mining District of north Idaho (Stickney and

Sprenke, 1993) and are related to closure of mine openings 

at depth (Sprenke et al., 2002). To date, none of the

mining-related seismic events has been large enough to be

recorded at more than one seismograph station. Richter 

magnitude estimates of these events using signal duration

measurements range from –1.0 to slightly more than 0.0. 

Figure 9. Mining-related seismic events as a 

function of time of day. Four-hundred forty-six 

nonblast events were binned in 10-min intervals 

and plotted as a polar histogram.

Figure 11. Local 1.0-M earthquake centered 11.9

miles from Chrome Mountain seismograph. S-P 

interval was 2.75 sec.

The Chrome Mountain seismograph station also records 

local and regional tectonic earthquakes and large distant

earthquakes. Figure 11 shows the seismogram of a magnitude 1.0 earthquake located 19 km (12 miles) west-northwest of the seismograph station. This microearthquake was

recorded by nine stations in the Montana regional

seismograph network and demonstrates that seismic events,

mining-related or natural, are well recorded by the network. 

However, without seismograph stations installed close to 

the mines, low-magnitude but frequent mining-related

seismic events will go undetected by the regional network.

The daily summaries of the number of mine blasts and the time, maximum amplitude, and duration of mininginduced seismic events are recorded on an Excel spreadsheet at ESO. Monthly summaries are provided to engineers 

at the Stillwater Mining Company and NIOSH. Monitoring shows that mining-related seismicity occurs with

blasting. There are no miners in the workings at this time, so the events do not pose a danger to miners. These data

show that seismicity does result from mining, but has not become an operational problem or safety hazard yet.

These data are reviewed continually for changes in trends that could indicate mining-induced seismicity is becoming

a hazard. 
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5. CONCLUSIONS 

 NIOSH researchers have utilized solar-powered, remote, seismic monitoring equipment; FM radio telemetry; 

PC’s; and the Internet to provide near-real time data on mine seismicity to researchers at distant locations. This 

innovative technology works well and helps to ensure the safety of miners working in Montana’s underground 

platinum/palladium mines. The cooperative project between the Stillwater Mining Company, ESO, and SRLNIOSH has benefited all parties by providing quality seismic data for multiple uses in a timely fashion. 

REFERENCES 

Czamanske, G.K., and M.L. Zeintek: Stillwater Complex. Montana Bur. Mines and Geol. Spec. Pub. 92, 1985, 396 

pp. 

Girard, J.M., T.J. McMahon, W. Blake, and T.J. Williams: Installation of PC-Based Seismic Monitoring Systems, 

With Examples from the Homestake, Sunshine, and Lucky Friday Mines.. In Maleki, H, P.F. Wopat, R.C. Repshar, 

and R.J. Tuchman (eds.), Proceedings, Mechanics and Mitigation of Violent Failure in Coal and Hard-Rock Mines, 

USBM Spec. Pub. 01-95, 1995, pp. 303-312. 

Hess, H.H. Hess: Stillwater Igneous Complex, Montana. Geol. Soc. Amer. Memoir 80, 1960, 225 pp. 

Johnson, J., M. MacLaughlin, R. Langston, and H. Kirsten: In Situ Stress Measurements at the Stillwater Mine, 

Nye, Montana. Proceedings, 39th U.S. Rock Mechanics Symposium, Cambridge, MA, June 22-26, 2003, In press. 

Sprenke, K.F., B.G. White, A.C Rohay., J.K. Whyatt, and M.C. Stickney: Comparison of Body Wave Displacement 

with Damage Observations of a Rockburst, Coeur d'Alene Mining District, Idaho. Bull. Seismol. Soc. Amer., v. 92, 

2002, pp. 3321-3328. 

Stickney, M.C., and K.F. Sprenke: Seismic Events with Implosional Focal Mechanisms in the Coeur d'Alene Mining 

District, Northern Idaho. J. Geophy. Res., v. 90, 1993, pp. 6523-6528. 

Whyatt, J., W. Blake, T. Williams, and B. White: 60 Years of Rockbursting in the Coeur d’Alene District of 

Northern Idaho, USA: Lessons Learned and Remaining Issues. Presentation at 109th annual exhibit and meeting, 

Society for Mining, Metallurgy, and Exploration, Feb. 25-27, 2002, Phoenix, AZ. Preprint 02-164, 8 pp. Available 

on CD-ROM from SME and the author. 
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REMOTE MONITORING OF MINE SEISMICITY AND EARTHQUAKES USING RADIO 

TELEMETRY, COMPUTERS, AND THE INTERNET 

D. Denton, Spokane Research Laboratory, National Institute for Occupational Safety and Health, E. 315 

Montgomery, Spokane, WA (509) 354-8000 

M. Stickney, Office of Earthquake Studies, Montana Bureau of Mines and Geology, 1300 W. Park St., 

Butte, MT 59701 (406) 496-4332 mstickney@MTech.edu 

*T. Williams, Spokane Research Laboratory, National Institute for Occupational Safety and 

Health, E. 315 Montgomery, Spokane, WA (509) 354-8060 TJWilliams@cdc.gov 

R. Langston, Stillwater Mining Co., P.O. Box 365, Nye, MT 59601 (406) 328-8406 

RLangston@stillwatermining.com 

*To whom inquiries should be addressed.