| Presented at Pan Pacific Conference on Earthquakes, Volcanoes, and Tsunamis, Vancouver, British Columbia, Canada, July 29 - August 2, 1996 |
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Seismic monitoring and alarm systems are being
installed by two railway companies and a water utility to
document vibrations or relay multiple levels of warning to
operations centers. Eleven Los Angeles subway locations will
be instrumented with digital accelerographs with dual seismic
alarms. Following a low-level alarm, dispatchers will direct
subway operators to slow down and stop at the next station;
following a high-level alarm, they will direct subway operators
to slow to a crawl and stop at the next station, and will
also activate large tunnel exhaust fans. A commuter railway
being built in Puerto Rico will install six dual seismic alarms;
5 at ground level and 1 in a subway. The low-level alarm will
alert the operations center that an earthquake has occurred;
the high-level alarm will automatically stop the trains. A
water utility in the San Francisco Bay area is installing
an error-tolerant system consisting of an accelerograph, 3
triaxial sensors, dual seismic alarms, and a 2-of-3 logic
switch at each of 2 valves on distribution lines near fault
crossings. The utility is also monitoring the roof, a freefield
site, and a valve pit at 2 above-ground concrete water reservoirs
with an accelerograph, 3 triaxial sensors, and dual seismic
alarms at each site. For each of these 4 sites, the utility's
SCADA alarm system will relay the seismic alarm(s) to the
operations center, whose manager will consider them along
with pressure and flow data, plus news from TV or radio, before
directing any site's motorized valve to close.
| LOS ANGELES RED LINE SUBWAY |
| Civic Center: |
An accelerograph/single-alarm seismic switch
& a single-alarm seismic switch |
| Union Sta. : |
Two single-alarm seismic switches |
| Westlake Sta. : |
each |
| 11 locations: |
2 accelerograph/dual-alarm seismic switches
(inst. bet. 1995 & 2000) |
| Setpoints: |
0.10g (warning) & 0.20g (alarm)
Human intervention is required to direct trains to slow
or stop |
 |
| TREN URBANO LIGHT URBAN RAIL |
| 6 stations: |
An adjustable dual-level seismic switch |
| Setpoints: |
0.06g (Warning; human intervention)
0.12g (Stop-the-train; automatic) |
| Completion: |
2001 AD |
 |
| EAST BAY M.U.D. WATER SYSTEM |
| 2 valves at reservoirs: |
An accelerograph/dual-alarm seismic switch with one internal and two external triaxial accelerometers |
| 2 valves at Hayward: |
An accelerograph/dual-alarm, 2-of-3- accelerometers |
| Fault: |
Triaxial |
| Setpoints: |
High-level alarm to be preset at 0.15g |
| Use of Data: |
Seismic alarms, plus pressure & flow data, plus info. from TV/radio, will all be considered prior to closing valves. |
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