Mapping The Big One: GIS/GPS helps pinpoint seismic trouble spots

Residents of San Francisco had been expecting The Big One for years. And while they all agreed that Loma Prieta, which devastated the city in 1989, was not it, they certainly had to admire its timing.

The magnitude 7.1 earthquake struck as the San Francisco Giants and the Oakland A’s were preparing to take the field in what would be the first game of the World Series. Television cameras from around the world, there to record something as non-threatening as a baseball game, were pressed into service to film the near-destruction of one of America’s most beautiful cities.

Americans were riveted to TV sets showing buckled freeways, crushed buildings and fires raging through the city’s tony Marina District.

But if geologists and seismologists working in California have their way, there will not be a rerun.

Technology takes on nature

Loma Prieta was a wakeup call. The disastrous losses galvanized the state legislature, which in 1990 passed the California Seismic Hazards Mapping Act.

That act required the state geologist to map seismic hazard zones in order to identify areas prone to ground failure. But, more importantly, the act requires evaluation of those hazards before construction projects in potentially affected areas may proceed.

Predicting earthquakes is a dicey proposition at best. Especially in California, where fault lines criss-cross like a diagram of the New York subway system, the best that seismologists can offer is, “Stay here long enough, and you will experience an earthquake.”

Still, you can’t prepare if you can’t predict, and preparation is what it’s all about.

That, at least, is the philosophy behind research being done by the Association of Bay Area Governments (ABAG), a consortium of cities, towns and counties that combine resources to address issues of local concern.

With funding from the National Science Foundation and the Interior Department’s U.S. Geological Survey (USGS), ABAG has been using GIS to produce hazard maps that pinpoint potential trouble spots.

Jeanne Perkins, ABAG’s Earthquake Program Manager, has spearheaded this effort since 1975. With the data provided by these maps, she and Jack Boatwright, a seismologist with the USGS, produced a comprehensive report called “On Shaky Ground,” that was designed to be the definitive work on earthquake preparedness in the Bay Area. Perkins has produced a virtual library of reports for ABAG on everything from local government liability to seismic retrofits.

Additionally, ABAG offers mitigation options that can help local governments minimize the effects of an earthquake on their populations. Such mitigation options include:

• land use and zoning controls, particularly for critical or hazardous facilities;

• special building design requirements;

• disaster response planning;

• infrastructure and lifeline requirements; and

• programs to strengthen housing.

ABAG’s files include — or soon will include — maps that designate fault traces, fault study zones, ground-shaking intensity, dam failure inundation areas and tsunami inundation areas.

Additionally, the U.S. Census Bureau’s TIGER files, which include streets, city boundaries, county boundaries and census tract boundaries, can be combined with ABAG’s files.

Hazard Management

GIS and GPS have become an indispensable aspect of what experts call “hazard management,” so indispensable in fact that they are often linked in engineering courses on the subject. The Hazards Research Laboratory at the University of South Carolina in Columbia, for instance, bills itself as “one of the primary centers of GIS/hazards research in the nation” and maintains a directory of researchers using or investigating the use of GIS in hazards/disaster management. Likewise, the National Information Service for Earthquake Engineering at the University of California-Berkeley has established a discussion list for anyone interested in GIS use in hazards management and research, especially that involving earthquakes.

“In California,” says Michael Scott, a PhD candidate in geography at South Carolina, “GIS consultants and providers are making earthquakes their business.”

One of those is Paul Wilson, president of Dallas-based MapFrame, which has provided GIS mapping and analysis software to ABAG for years. Wilson was ABAG’s principal planner and chief of its technical information division when the group began exploring the possibilities of mapping earthquakes with GIS. He and Perkins began building the database that would become ABAG’s technological foundation, but Proposition 13, California’s infamous tax initiative, resulted in funding cuts that left the association unable to sustain their work.

After unsuccessfully shopping the data to other agencies, Wilson decided that the only feasible way to maintain it was to start his own company.

Now MapFrame markets GIS software to a number of local governments, and Wilson, an outspoken admirer of Perkins, continues to work with ABAG because “it’s work that is done for a good reason.”

“Seismic hazard maps are the connection between earthquake research and the mitigation of earthquake hazards,” says Art Frankel, a seismologist with USGS and director of the National Seismic Hazard Mapping Project, a joint project of the USGS and the California Division of Mines and Geology. “These maps convey the ground motions that have a specified chance of occurring over a certain period of time.”

The USGS has been publishing “probabilistic” maps for earthquake hazards since 1976. These maps have served as the basis for seismic zonation in model building codes and are used by city and county planners, engineers, emergency services departments and the general public.

“Our goal is damage minimization,” Frankel says. “A major point of making these maps is to provide information on expected ground shaking so that buildings, bridges and other structures can be designed to withstand any expected shaking.”

GIS has been particularly useful, according to Frankel, in creating hybrid maps that combine maps of expected ground motion in specific areas with map layers depicting population density, building type and other factors (dams, utility lines, the potential for tsunamis) that would have direct bearing on the potential for catastrophe.

Of course, the accuracy that GIS brings to the process is a big plus as well. ABAG’s mapping system is based on grid cells 100 meters by 100 meters — 2.1 million of them in the Bay Area. The resulting maps can contain a hundred different layers of information, different combinations based on what seismologists think is more likely to happen.

“They call that the ‘largest credible earthquake’ on that particular fault,” says MapFrame’s Wilson. “You layer it with maps that include all the bad stuff that can get you.”

Additionally, the maps are easily convertible to other useful formats. For instance, Perkins handled a project for the California Department of Transportation (Caltrans) in which she produced a file of bridges and overpasses that was then overlaid on an earthquake model. Caltrans could then determine the vulnerability of various overpasses and bridges in various earthquake scenarios and plan its retrofitting programs.

BARD

But ABAG and the USGS are not the only initials involved in helping plan mitigation programs for the Bay Area. The Bay Area Regional Deformation Network (BARD) is keeping close track of strain accumulation along Bay Area faults, and again GIS and GPS are playing a major role. In fact, GPS receivers from Ashtech and Trimble Navigation, two Sunnyvale, Calif., providers, form the basis of the BARD system, which covers a 200-mile area stretching from the Sierra Nevada foothills to the Farallon Islands. BARD is a collaborative effort of UC-Berkeley’s seismographic station, the USGS, Stanford University, the University of California-Davis, the University of California-Santa Cruz, Trimble, Ashtech, the Lawrence Livermore National Laboratory, the U.S. Coast Guard, the National Geodetic Survey, the Scripps Institute of Oceanography and the Jet Propulsion Lab. Its purpose is mapping crustal deformation (movements in the earth’s crust that can be earthquake predictive). GPS stations, mounted in rock for stability, receive information from orbiting satellites and record that data every 30 seconds, 24 hours a day. Minute changes — “equal to the rate at which a fingernail grows,” according to Seismographic Station Chief Engineer Bill Karavas — are recorded. This represents a giant leap forward for the seismologists, who formerly relied on analog ‘strain’ or ‘creep’ meters, which measured changes over a 100-foot stretch of land that were then extrapolated for a larger area.

“Ultimately,” Karavas says, “we hope to be able to use all this data to predict earthquakes.”

“Previously there was no way to get this type of data over wide areas,” says Ashtech’s Mark Eustis. “Six or seven years ago, you had to buy a mainframe computer. Now, using the web, you can go to ESRI’s home page, pull down maps and put them into a desktop PC that runs complete, usable GIS software. It’s brought affordability to the local researcher level.”

It has also made Californians safer and ensured local governments “safer communities [now] and stronger economies following future earthquakes,” as Perkins says.

For More Information

From ABAG:

• Earthquake Recovery: A Survival Manual for Local Governments;

• Earthquake Vulnerability Analysis for Local Governments;

• Liability of Local Governments for Earthquake Hazards and Losses: A Guide to the Law and its Impact in the states of California, Alaska, Utah and Washington;

• Seismic Retrofit Incentive Programs: A Handbook for Local Governments.

ABAG’s address is P.O. Box 2050, Oakland, CA 94604. Its web site is www.abag.ca.gov.

To access the UC-Berkeley GIS/hazards management discussion list, send an e-mail to [email protected] with the text “subscribe gis_group” in the body of the message.

To access the University of South Carolina’s Hazards Research Laboratory, e-mail [email protected].

The USGS web site address is http://quake.wr.usgs.gov/QUAKES.

Interoperability method developed

A group of GIS technology providers has announced the development of a CORBA/Java-based method for interoperability of GIS data and systems based on object-oriented technology.

The technology was developed by Bentley Systems, Genasys, Lock-heed Martin, Mitre, Oracle, Sedona GeoServices and Sun Microsystems. The CORBA architecture of multiple platform support is compatible with existing GIS systems and the trend toward data-servers and Internet clients.

If accepted by the Open GIS Consortium (OGC), which includes Bentley, Oracle, ESRI and Intergraph, the implementation will become the industry’s CORBA-based interoperability benchmark for use between member GIS systems.

OGC is creating the Open Geodata Interoperability Specification, a set of software specifications for sharing geographic information across tools and organizations. Last summer, OGC issued an RFP for interface standards in the areas of CORBA, OEL, ODBC and the Internet.

Final decisions on these standards are planned for late 1997. For more information on OGC, contact Lance McKee, (508) 655-5858.

GPS/GIS conference slated for May

The seventh annual GPS/GIS ’97 Conference will be held May 13-16 in Annapolis, Md. Designed for agency planners, industry leaders and researchers who need accurate, up-to-the-minute data to manage their organizations efficiently, the conference offers a program of training opportunities, speaker presentations and field mapping expeditions.

Additionally, a technology fair will showcase new developments in the rapidly evolving technology.

Topics covered during the conference include environmental mapping, asset inventory, emergency response, county planning and national defense. County land use planners will have an opportunity to see how GPS/GIS technology can help them quickly integrate public safety information into their databases. Speakers include Andrew Battin, EPA’s National GIS Program Manager; Dorsey Worthy, national GPS coordinator for the National Coastal Service Center; Joel Morrison, chief of the geography division at the U.S. Census Bureau; Don Lauer, chief of the EROS Data Center of the USGS; and Jerome Kreuser, chairman of The World Bank’s GIS task force.

A day-long boat mapping expedition on the Chesapeake Bay will be led by Stephen Leatherman, director of the University of Maryland Laboratory for Coastal Research.

Information on the conference is available at http://www.geore-search.com/confer.html.

Finding the past with GIS

Historical photographs and sketches are now being explored as a potential key to accurately reconstructing Civil War battlefield events and locales. In an innovative pilot project, the National Park Service (NPS) will use advanced GPS/GIS technology to spatially position events and cultural features from historical photographs and old sketches of Antietam National Battlefield. These historical sources will be scanned and geo-referenced to archived imagery of the battlefield area, and GPS/GIS will be used to locate the cultural features.

Stephen Potter, chief archaeologist for NPS’ National Capital area, hopes that the project will “develop a quick and inexpensive process to locate historical features that are difficult to find on the ground today.”

The NPS has contracted with Greiner, Timonium, Md., which will be working with Bethesda, Md.-based GeoResearch to develop and refine this new archaeological and historical technique. During the project, advanced GPS/GIS technology will be used to orthorectify historical imagery in the field. While in the field, cultural features indicated on the imagery will also be assigned coordinate points. A contemporary photograph of the same area will then be scanned and registered. By calibrating the two images through the selection of similar points, a three-dimensional data set will be generated. Cultural features shown in the historical images will be queried for their data coordinates, and a 3-D digital object for each cultural feature under study will also be generated.

The historical and contemporary imagery will then be superimposed, rendering accurate locations for the field’s historical features.

Once the sites are located, the team will use the GeoLink GPS/GIS Field Mapping System to display images in the field, enabling the field inspector to walk the sites and use the GPS/GIS software to view both images until they correctly line up.

“If this experiment is successful,” says Potter, “it could catapult the archaeological study of historic landscapes well into the 21st century.”

GIS blows away Hurricane Fran

Officials in Raleigh, N.C., knew on Sept. 4, 1996, that Hurricane Fran was headed their way. But instead of panicking, they began to plan.

When Fran struck one day later, they were ready. Within a few hours after the storm, the city’s 911 Command Center was jammed with calls about fallen trees, downed power lines and other emergencies. Knowing that city personnel needed to pinpoint the exact location of power line damage, flooded streets and downed trees, Raleigh GIS Manager Colleen Sharpe went to work producing maps.

“We mapped everything we could that first night,” she says. “We followed our snow plan and made sure all major thoroughfares were cleared before starting on residential streets.”

Within the first 24 hours after the storm, maps produced using GIS software from Graphic Data Systems, Englewood, Colo., were being used by city personnel who traveled up and down streets to assess the damage. From that GIS-assisted field survey, officials brought back information on 2,000 actual damaged properties, each of which was categorized in the GIS database by severity of damage and type of structure. In the days following the hurricane, the GIS was used to help coordinate efforts between the Federal Emergency Management Agency, the U.S. Army Corps of Engineers and local contractors to deploy thousands of pieces of debris removal equipment.

By early winter, mulch piles, some 50 to 60 feet high and covering several acres, had been built around the city as crews completed their cleanup work.

Officials within the city’s public utilities department also used the GIS to locate water lines disprupted as falling trees pulled up roots along with buried pipes. It was also used to locate fire hydrants, some of which were hidden beneath debris piles and needed to be safeguarded as front-end loaders and other heavy equipment moved in.

Once the immediate crisis passed, Sharpe and her staff turned their attentions to plotting maps on the GIS that would allow them to plan a response to all less critical, unresolved problems. Those maps were used by the National Guard and numerous contractors to help clear streets and repair power lines.

“The night of the storm, there were a lot of questions about power so we plugged our workstations right into the generators,” Sharpe says. “We felt it best to generate maps during the storm because they would be useful for sending people out right after it was over.”

The response to Hurricane Fran using GIS provided a marked contrast to the situation when, in 1988, a tornado ripped through a 20-mile section of Raleigh.

At that time, mapping damage was a manual task, which took three weeks and produced just three maps. After Fran, Sharpe’s department was able to generate maps, produce damage assessment reports and provide other assistance in the first 36 hours.