An urban revolution
In 1977, Congress
authorized the creation of the National Earthquake Hazards Reduction Program
(NEHRP), a joint effort of the Federal Emergency Management Agency (FEMA), the
National Institute of Standards and Technology, the National Science Foundation
and the U.S. Geological Survey (USGS). The legislation gave USGS the responsibility
for monitoring earthquakes nationwide. Since that time, USGS has assessed and
monitored earthquake hazards through the regional seismic networks and the NEIC.
At rush hour on Oct. 17, 1989, as more than 62,000 fans filled Candlestick Park for the third game of the World Series, a magnitude-7.1 earthquake struck about 60 miles south of San Francisco. The effects of the 20-second quake spread across the area, causing as much as $10 billion in in damage, with $2 billion of damage in San Francisco. Sixty-two people died. The collapse of several structures at the Pacific Garden Mall in Santa Cruz, shown here, had rescue workers scrambling to find victims. C.E. Meyer, USGS
Most seismic networks developed in the 1960s and 1970s to study the distribution and characteristics of small to moderate-sized earthquakes. The original equipment consisted of a weak-motion seismometer coupled with a recording system. These old, analog instruments had a recording range of three magnitude units. For example, a seismometer designed to record magnitude-2.0 earthquakes would clip a signal that came in at magnitude 6.0. Seismologists were then mostly interested in recording the numbers of earthquakes. Only engineers were interested in measuring the ground motion associated with larger earthquakes. They would place strong motion instruments into buildings and then spend up to a year processing data after earthquakes to measure their effects.
Seismologists would choose remote locations in which to place their weak-motion seismometers. So rather than putting seismometers in downtown Washington, D.C., we would try to put them in the Blue Ridge Mountains, where there was lower background noise, says John Filson, coordinator of the USGS Earthquake Hazards Program. An instrument in the Blue Ridge could tell seismologists much about the nature of earthquakes, but provide little data on strong ground shaking and the potential damage associated with urban quakes.
Modern seismographs are now broadband recording both weak and strong motion, up to six orders of magnitude. And, in a major philosophical shift, seismologists have come to realize the importance of the urban monitoring of earthquakes. Its okay to have some seismometers in the Blue Ridge, but its very important to have seismometers in the cities, Filson says. Seismologists need to understand the nature of ground shaking in cities to create earthquake-resistant buildings, and to be able to map and understand the severity of shaking in an urban area after an earthquake.
With these new technological capabilities in mind, Filson and others at USGS decided that the United States needed a complete modernization and expansion of its seismic networks, particularly in urban areas. We needed to modernize the types of instruments. And we needed to expand the number of instruments in urban areas, Filson says. In 1997, during NEHRPs reauthorization process, Congress asked USGS to prepare an assessment of the status and needs of earthquake monitoring.
The resulting report called for 7,000 new seismic instruments, with 6,000 of these strong-motion sensors in 26 at-risk urban areas. About half of these urban instruments would sit in buildings and structures. USGS also expressed the need to integrate all regional and national networks into one system, which would be ANSS, so that the software theyre using in Southern California to measure magnitudes is the same as the software in Memphis, Utah and Seattle, Filson says.
In 1999, Congress authorized the full funding of ANSS for $30 million each year for five years, 2002 through 2006. But, Filson says, Authorization opens the bank account and says that this is a good idea, but it doesnt put any money in the account. To date, the $170 million ANSS project is at about 10 percent funding. Last year, Congress appropriated about $3.9 million for this years ANSS budget.
Appropriators have followed the lead of the administrations, says a key appropriations staff member in the House of Representatives. Both Presidents Clinton and Bush requested funding for ANSS at a tenth of its authorized amount. Generally, the lack of funding has nothing to do with the value of the program, but rather represents a budgetary decision to cut costs. Until the next major U.S. earthquake, the House staffer explains, ANSS will likely remain off the budgetary radar screen.
USGS is trying to make the most of that 10 percent, however, by purchasing a few new instruments at a time for high-risk urban areas. Last year, ANSS money purchased 10 new instruments for Anchorage. The plan calls for about 300 strong-motion sensors there. Just this year, in time for the 2002 Winter Olympic Games, the Salt Lake City area gained 40 new strong-motion sites to monitor earthquakes along the Wasatch Front urban corridor (Geotimes, March 2002). Little by little, ANSS is trying to build its way toward national urban earthquake monitoring.
Despite its lack of funding, ANSS has garnered the attention and support of
regional seismologists across the country. ANSS will have a national center,
likely co-located with the NEIC in Golden, but its success will depend largely
on the cooperative efforts of the already existing regional networks. While
large damaging earthquakes that occur within the United States and its territories
are a national problem, their immediate impact is local. The regional centers
are the direct contact to local, regional and state emergency response communities
and end-users of seismic monitoring products and services, says Harley
Benz, ANSS manager.
The best place to look to find out how ANSS will play out after completion is an already fully operating regional network. The USGS Pasadena office is just one regional center where researchers are working arduously to bring ANSS closer to reality. The entire history of Southern Californias regional seismic network, as told by Lucy Jones, scientist-in-charge of the USGS Pasadena office, sounds like an alphabet soup imbedded in a tale of technological evolution, funding challenges and political barriers. Sound familiar? Indeed, Jones says the ANSS project is essentially taking their regional idea nationwide.
Starting in 1997, Caltech, USGS and the California Division of Mines and Geology teamed up to create TriNet. Each organization had been operating separate seismic networks for decades. The idea behind TriNet, like ANSS, was to leverage the resources of many groups into one, to modernize seismic instrumentation in Southern California.
Until then, the region, like most others, had only a handful of modern, broadband, digital seismographs. It used to be that if we could get the information out in a few hours, that was really good, Jones says. When the magnitude-6.7 Northridge earthquake hit the Los Angeles area on Jan. 17, 1994, they realized a few hours wasnt good enough. Although Northridge caused few casualties, it incurred $20 billion in damage, and, Jones says, USGS was not prepared.
So FEMA stepped in to fund TriNet, which would install 600 seismograph stations and end up motivating new technologies to monitor urban earthquakes, including mapping programs that show the extent of ground shaking. Like ANSS, TriNet focused on expanding earthquake monitoring to buildings by bringing together seismologists and engineers, who traditionally have worked separately.
Last year, TriNets funding for earthquake mitigation in Southern California ended, and now Southern California is joining forces with Northern California in the California Integrated Seismic Network (CISN). Collaborating with the University of California at Berkeley and USGS at Menlo Park, CISN is providing another testing ground for taking TriNet to a grander scale: statewide. CISN is now the California regional network for ANSS.
This move is forcing Southern California and Northern California to work together in ways they never have before. Historically, a straight line called the Gutenberg-Byerly line has seismically divided the state into two networks, mostly because the region is so large. With advances in digital technology, this line has become outdated; distance does not affect the ability to access data. However, a major challenge facing CISN is finding a way for the seismic data to cross that line and join together the two networks once again mirroring ANSS challenge to create multiple points of information sharing and redundancy. That way, if an earthquake incapacitates the Pasadena office, for example, the USGS at Menlo Park would be fully equipped to analyze the data and communicate it to the public. The ANSS national office would provide another point of redundancy.
The idea of redundancy is one that Doug Given, the USGS manager of CISN for Southern California, is working on for both California and ANSS. For an earthquake that occurs around the border of the Gutenberg-Byerly line, for example, he is developing a protocol to decide which network, North or South, will report the quake to the public. In the past, Given says, situations like that have created friction between the networks and institutions. Its not just pettiness between the groups; it confuses the public, he says.
For ANSS, each regional network and the national center in Golden need to be able to report the same magnitude earthquake, requiring standardized software and data management, Given says. How centralized the system will be has yet to be determined. Given favors a more distributed system of redundancy, rather than totally streamlining the data to a central point. That way, regional systems can exchange data, but still work in individual environments that foster innovation.
In California, CISN has its work cut out to create synchronized yet individual systems, but Given is hopeful that their hard work in California will pay off and help create a model for other ANSS regions. If California can get together as a region, anywhere can.
Shaking it up
On the year anniversary of the Northridge quake, another, more deadly earthquake
struck Kobe, Japan, killing more than 6,000 people. Filson spoke with the head
of emergency management for Kobe a couple years after the quake and asked him
what he would have liked to have known that he did not. He said I
didnt know the scope of the problem, so I had so many ambulances, fire
trucks and crews to send out on a first-come, first-serve basis. By the time
I realized how big the problem was I didnt have anything else to send,
Recognizing the same problem after Northridge, USGS shifted its focus toward processing earthquake information faster. So, USGS scientist David Wald led the development of ShakeMap a rapidly generated computer map that shows the location, severity and extent of strong ground shaking within only five minutes after an earthquake. The information, generated by data from seismic instruments in urban areas, then goes automatically to the programs Web site and directly to emergency managers. It allows us to better portray both the shaking and the potential damage, Wald says.
ShakeMap has the potential to revolutionize the response time of emergency managers to an earthquake, but its success depends on further deployment of instruments. As it modernizes seismic networks, ANSS hopes to enable ShakeMap in every seismically active urban area, as it did for the Winter Olympics in Salt Lake City this year. Because many parts of California and the nation are sparsely covered by seismographs and because the underlying geology is so complex, the resulting ShakeMaps [in these areas] are of limited value in emergency response, wrote Tony Shakal of the California Division of Mines and Geology in the agencys newsletter last year.
USGS has created ShakeMaps for moderate-sized earthquakes in California and the Pacific Northwest, as well as for the larger Nisqually earthquake that hit the Seattle area in February 2001. Anchorage is now receiving new instruments through ANSS and is working with USGS to install ShakeMap software. Wald is working to set up a remotely operated system whereby the Pasadena office, for example, can produce maps with the seismic information collected in Alaska in addition to the local area itself, creating more redundancy.
Measuring the full range of ground shaking in real time with seismometers in
both remote and urban regions has made ShakeMap possible, created the ability
to monitor structural shaking in real time, and thus combined the often diverging
seismic goals of engineers and seismologists, Given says. TriNet was the first
initiative to bring engineers and seismologists together to study both weak
and strong motion. This kind of incursion into strong motion is a relatively
new endeavor [for seismologists], Given says, but one that can change
the way engineers build earthquake-ready structures.
Earthquake engineer Erdill Safak of USGS has been studying ground shaking in two multi-story buildings. The nine-story Millikan Library at Caltech has 36 strong-motion sensors, and the 17-story Factor Building at the University of California-Los Angeles has 72 instruments. While both instrumentations are complete, they are not yet recording data in real time. However, that will change in the next few months, as ANSS funds will install telemetry capabilities into Millikan, allowing researchers to gather real-time data. Given says that the data will be able to tell researchers much about the fragility of a building both before and after an earthquake, as well as tell emergency managers and engineers where to go to mitigate the worst damage.
Down the line, Given says, this sort of real-time instrumentation could appear in other structures, like dams and pipelines. Many such structures already have non-telemetry, strong-motion sensors. Whats new is not figuring out what happened days later, but knowing what happened minutes later, he says. In Japan, for example, which has a very dense seismic network, detection of an offshore earthquake or ground shaking will shut down the Bullet Train. Japans system is also allowing seismologists there to more realistically pursue early warnings of earthquakes.
ANSS seismologists would also like to explore ways to give any early warning
of ground shaking in urban areas. This is one application of ANSS that
is high and out there on the horizon, Filson says.
If an earthquake occurs along the San Andreas, he explains, 50 miles from downtown Los Angeles, and its waves are moving at two miles per second, then the network has 25 seconds to get the data, analyze it and then broadcast it as an early warning for Los Angeles residents. Technically, its possible.
Indeed, according to research published in last months Bulletin of the Seismological Society of America, it is possible to warn large urban centers that strong ground shaking is coming, if the earthquakes epicenter is far enough away from the city. Even 20 seconds, notes lead author Ta-liang Teng of the Southern California Earthquake Center, is enough time to shut off main gas pipelines.
Teng and his colleagues tested the early warning capability in Taiwan over a seven-month period using a virtual subnetwork. During that time, the system correctly detected and reported 54 earthquakes between magnitudes 3.5 and 6.3, with an average of 22 seconds between the initiation of the earthquake and the issuance of a warning. Teng suggests that a modern, integrated seismic network for the United States would make a similar system feasible a possibility Filson and others at USGS have been keenly aware of throughout the development of ANSS.
One of the biggest advantages of such an early warning system, Filson says, would be in the classrooms. The Northridge earthquake occurred at 4:30 a.m. local time. After the Northridge earthquake, people walked through some of the schools and saw fallen bookshelves, light fixtures, television sets. If kids had been in classrooms, the fatalities would have gone up, Filson says. If the quake had occurred later in the day, an early warning of even a few seconds would have given children enough time to get under their desks.
With full funding to instrument urban areas nationally, Filson believes it is possible to better prepare U.S. cities for the unexpected nature of Earths movements. Now the main challenges, Filson says, are societal and financial: convincing people of the benefits of investing in earthquake hazard mitigation. While ANSS represents a change in goals from those formed back at Kresge more than 80 years ago, its possibilities would make Richter, Gutenberg and Wood proud. Their legacy has taken modern seismology to a new level of technological capability. The ultimate goal remains the same: to save lives.
Earthquake monitoring is not the only field that will benefit from the Advanced National Seismic System (ANSS); so too will the investigation of exotic seismic events unexpected, manmade sources that create seismic signals. Terry Wallace of the University of Arizona, who has analyzed seismic signals from the sinking of the Russian submarine Kursk in 2000 (Geotimes, February 2001) and from the 1998 bombing of the U.S. Embassy in Nairobi, Kenya, says that the modernized national coverage promised by ANSS holds great potential for the burgeoning field of forensic seismology the more instruments out recording seismic signals, the more ears to the ground (Geotimes, August 2002).
The Cowlitz County PUDs Swift Power Canal collapsed on April 21, destroying a section of Washington State Route 530. Seismologists for the Pacific Northwest Seismic Network (PNSN) are analyzing the seismic signals generated by the collapse to help determine what exactly caused the accident. PNSN is one of the regional networks for the Advanced National Seismic System. Terry Low, PacifiCorp
Wallace points to a recent seismic analysis conducted by the Pacific Northwest Seismograph Network (PNSN), which is the northwest region for ANSS, to study the collapse of the Swift Reservoir Power Canal near Mount St. Helens in Washington State. On April 21, 2002, the canal collapsed, spilling out almost 800 million gallons of water and washing out part of a state highway in a matter of hours.
In the investigation currently underway to determine the exact cause of the canal failure, the PNSN seismic analysis is helping to pinpoint the timing of the events that weakened the canals integrity. Around and after 6:30 a.m., several bursts of energy occurred against an increase in seismic background levels, indicating the initial failure of the canal. These background signals died off over the following 15 minutes. The seismic signal recorded at about 6:56 a.m. was strong enough on several PNSN stations to trigger an automatic earthquake locator. That signal represents the final failure that caused the sudden collapse. The PNSN signal analysis corroborated the water-level reports provided by the Cascade Volcano Observatory and eyewitness accounts of the event.
The Swift Power canal collapse inundated the Swift 2 Powerhouse. An evaluation is underway by Cowlitz County PUD to determine if portions of the powerhouse can be salvaged. There is also an investigation underway to determine the exact cause of the canal failure.Terry Low, PacifiCorp
This incident shows the value of seismic instrumentation for purposes beyond earthquake monitoring, says Robert Norris, a USGS seismologist at the University of Washington, who worked with PNSN seismologists to interpret the canal collapse seismogram. Norris is now working to get water-level data from the reservoir operators for the morning of the collapse. It would be interesting to plot the time history of the water level along with the seismic data.
Early evidence suggests that a sinkhole connected with lava tubes, produced by Mount St. Helens, behind the canal wall may have been a factor. Ultimately, the PNSN data could help investigators piece together what happened at the canal.
Lisa M. Pinsker
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