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New Urban Earthquake Monitoring in Utah
Background
The University of Utah's earthquake-recording network is being modernized into a multipurpose, real-time earthquake information system. The aim is to improve earthquake safety in Utah's dramatically growing Wasatch Front area by providing faster and better information - especially for emergency response and earthquake engineering.
With funding from the U.S. Geological Survey, the University of Utah Seismograph Stations (UUSS) is installing new infrastructure for this modernized system. Our new system can provide:
- automated broadcasts of the location and size of a potentially disruptive earthquake, within a few minutes of its occurrence, and
- automated computer maps (called ShakeMaps), available on the World Wide Web within several minutes of any significant earthquake, showing the geographic distribution and severity of ground shaking (see an example of ShakeMap).
As of January 2004, seventy-five modern digital strong-motion instruments (described below), have been added to the University of Utah's seismic network. These sites are located chiefly in the Ogden-Salt Lake City-Provo urban corridor. Similar urban networks, modeled after one in southern California, are being installed in Seattle, San Francisco, Reno, Memphis, and Anchorage.
The urban networks are being built with seed-funding for an Advanced National Seismic System (ANSS), a large-scale initiative now pending before Congress (see U.S. Geological Survey Circular 1188 ). If the ANSS receives full funding, Utah's urban network would eventually expand to about 500 stations along the Wasatch Front.
Phased Installation (see map)
- Completed September 30, 2000: 20 new earthquake-recording stations in the urban parts of Weber, Davis, Salt Lake and Utah counties; continuous real-time telemetry and recording at the University of Utah's seismic network center.
- Completed September 30, 2001: 25 additional stations installed in Wasatch Front urban corridor.
- Completed December 31, 2001: Full implementation of automated emergency notification system and ShakeMaps.
- Completed September 30, 2002: 20 additional stations in the expanded urban corridor area installed and continuously recorded.
- Completed December 31, 2003: 10 additional stations in the expanded urban corridor area installed and continuously recorded.
Technical Installation Details
The new recording network consists of sensors (called accelerometers) capable of recording strong ground motions (up to 2 g) on scale. The existing UUSS seismograph network generally consists of sensors designed to record weak ground motions and will not remain on-scale during even a moderate-sized earthquake. Data from the new sensors are continuously telemetered to the University of Utah campus via either an existing Internet connection, a telephone frame-relay connection, or a spread-spectrum radio network. The telephone/radio connections are operated entirely at our own expense. Stations will be installed within existing small buildings (typically a one-story reinforced structure less than 4000 square feet in area) or we will fabricate a small enclosure if the unit is installed away from existing structures. Regardless of the type of installation, all construction and installation work will be coordinated with someone designated by the property owner. The complete installation will be at no expense to the property owner.
Building Installations
If installed in an existing building, the sensor and associated electronics will require an area on a concrete floor of about 3 feet by 3 feet and a vertical space about the instruments of about 3 feet. The sensor will be bolted to the concrete floor with a single bolt. The installation should be in an area of the building where the occupants are not routinely working and where items on nearby shelves will not topple onto our equipment.
The unit requires AC power (110/115VAC) and should be installed in a location with access to a dedicated outlet within about 10 feet. If an AC outlet is not available in the immediate vicinity of the instrumentation, we will contract with a licensed electrician to install a more convenient outlet. A backup battery will provide emergency power in case of electrical failure. The equipment draws a negligible amount of current (less than one amp). There is no fire hazard from this equipment.
Precise timing is provided to the instrument by a GPS clock. The GPS clock obtains a signal from orbiting satellites and therefore a small antenna will need to be located on the roof of the building or otherwise external to the building. The GPS antenna will be connected to the sensor via either existing conduit or via conduit we install. Additional electronics will connect the sensor to the telemetry system.
In some cases, we will install a radio transmitter and antenna on the roof next to the GPS antenna. The radio antenna will generally be yagi-style, approximately 2 feet long. A cable from the antenna will be connected to the sensor along the same conduit as the GPS cable. More typically, we will install (at our expense) a frame-relay telephone connection to the unit. Where possible, we will connect to the Internet for continuous data transmission back to our central recording system. If an Internet connection is used, we will work with on-site IT personnel to ensure that the equipment poses no security risks to the property owner.
Free-standing Installations
In situations where a suitable building is not available, we will fabricate housing for the sensor and its electronics. The installation will consist of a small (3 feet x 3 feet) concrete pad (installed using hand tools) with a locked fiberglass weatherproof hut installed over the instrumentation and secured to the concrete pad. It may be necessary to dig a small trench in which we will place conduit containing cables connecting the sensor to a nearby power, telephone, or Internet connection. In such cases, the trench will be dug using hand tools, completely buried with minimal impact to the environment.
Some of these installations may be solar powered, in which case we will install a small radio tower (8 to 10 feet high, possibly as high as 20 feet, with a 12 inch triangular base in a concrete footing). We will mount the solar panels (approximately 3 feet x 3 feet), a radio transmit antenna, and GPS antenna on the tower. A 3 foot diameter x 2 foot deep barrel containing 12-volt batteries will be buried in the ground adjacent to the tower.
Return to UUSS Urban Earthquake Monitoring home page.
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Salt Lake City, Utah 84112-0111 «» Phone 801-581-6274 «» Fax 801-585-5585 E-mail UUSS! |
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