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CSMIP Receives Award from Applied Technology Council

April 2006

The California Geological Survey’s Strong Motion Instrumentation Program (SMIP), which studies the effect of earthquake shaking on structures and soil to help guide engineering practices and protect public safety, has been honored as one of the top seismic programs of the 20th century by the Applied Technology Council.

“This award comes from an organization whose members use the data we produce, so this is a tremendous honor,” said State Geologist John Parrish, head of CGS. “We’re very pleased with and grateful for this recognition,” said Supervising Geologist Anthony Shakal, who heads SMIP. “The fact that the engineering community, which is the target of our work, recognizes the value of what we do tells us that we’re successful.”

The Applied Technology Council (ATC) is a nonprofit corporation headquartered in Redwood City. It was established in 1973 through the efforts of the Structural Engineers Association of California. ATC develops and promotes state-of-the-art, user-friendly engineering resources and applications for use in mitigating the effects of natural and other hazards on construction. ATC also identifies and encourages needed research and develops consensus opinions on structural engineering issues.

ATC’s board of directors includes representatives appointed by the American Society of Civil Engineers, the National Council of Structural Engineers Associations, the Structural Engineers Association of California, the Western Council of Structural Engineers Associations, and four at-large representatives involved in the field of structural engineering.

An ATC-commissioned jury selected award recipients. SMIP and the other winners were honored at a joint ATC-Engineering News Record event April 17 – the eve of the centennial anniversary of the Great San Francisco Earthquake -- at the Westin St. Francs Hotel in San Francisco.

Moh Huang, Supervising Geologist Tony Shakal, Carl Petersen and Hamid Haddadi

 

 

Strong Motion Instrumentation Program colleagues (from left) Moh Huang, Supervising Geologist Tony Shakal, Carl Petersen and Hamid Haddadi celebrate an award from the Applied Technology Council.

 



SMIP – recently renamed the Earthquake Engineering Program -- was established in 1971 after the devastating San Fernando earthquake. It was tasked with obtaining vital data for the engineering and scientific communities through a statewide network of instruments. When activated by earthquake shaking, these “accelerographs” produce a record from which the critical characteristics of ground motion -- acceleration, velocity and displacement -- can be calculated.

The information is processed and disseminated to seismologists, engineers, building officials, local governments and emergency response personnel throughout the state. The data is used primarily to recommend changes to building codes, and assist local governments in their general plan process. SMIP also partners with the USGS, California Institute of Technology and UC Berkeley in the California Integrated Seismic Network. Real-time data collected by the network is used to produce a “ShakeMap” within minutes of a strong earthquake to help guide emergency response efforts.

SMIP has installed and maintains recording instruments at more than 1,000 locations statewide. The devices are housed in a variety of structures, including major bridges, high-rise buildings, dams, hospitals and industrial facilities. Among the instrumented sites are the city halls of Los Angeles, San Francisco and Oakland, and the state capitol. Accelerographs also are placed in open land to measure the motion of the ground and the effects of earthquake shaking on different types of soils. An advisory committee of engineers and scientists representing industry, government and universities help select SMIP’s station locations.

“I have a high regard for the work that SMIP does,’ said Christopher Rojahn, executive director of the ATC and a former research engineer involved in USGS’ strong motion program. “The program is very well organized. They’ve sought out the best advice in designing their program and provide a great service. The data SMIP got from its instrumentation in Parkfield is fundamentally important to our understanding of ground shaking.”

More than two decades of patience paid off for SMIP on September 28, 2004 when a magnitude 6.0 earthquake struck in Parkfield, a hamlet of 18 people located in rural southern Monterey County about midway between highways 5 and 101. The quake was centered almost directly underneath an array of 44 CGS and 10 USGS instruments. As a result, an unprecedented amount of information about how earthquakes work has been collected.

SMIP began placing instruments around Parkfield in 1982. Why there? Parkfield had experienced earthquakes in the magnitude 5.5 -6 range every couple of decades going back to 1857. The 2004 event was a late arrival: the previous significant quake in the self-proclaimed “Earthquake Capital of the World” occurred in 1966.

Among the most interesting findings out of Parkfield: an oddity noted in the measured peak acceleration, or movement. Shaking occurred at about a third the force of gravity in Parkfield, which is about six miles northwest of the epicenter and within a half-mile of the main branch of the San Andreas fault. However, both northwest and southeast of the village, SMIP instruments measured shaking that was three times as intense as the shaking in Parkfield.

“We were stunned with how much the ground shaking varied over a relatively short distance,” Shakal said.

That knowledge has called into question whether one of SMIP’s goals – at least one seismic instrument in every California zip code – is adequate. But as Shakal noted, the data gathered at Parkfield showed the benefits of sticking with a plan.

“Our greatest success so far probably has been staying the course,” Shakal said. “Thanks in no small part to our advisory committee, our stations have been well-placed and we’ve done a good job of maintaining them in the long haul. Those two things go hand-in-hand. The excellent performance we received from our 20-year-old instruments at Parkfield is a tribute to our field technicians.

Among SMIP’s current projects are the instrumentation of the new San Francisco Bay Bridge, several hospitals around the state, and wharfs at the Oakland, Long Beach and Los Angeles harbors. SMIP is also updating its older instruments, which capture ground shaking on film that has to be manually retrieved, with digital devices that report in real time to a central computer.

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SMIP Crew Reaches an Instrumental Milestone

CGS Has Installed 400 Seismic Monitors in Southern California

If a baseball player bats .400 for a season or slugs 400 home runs during his career, chances are he'll be in the hall of fame. Likewise, a quarterback who throws 400 touchdown passes during his career is destined for immortality.

If CGS's Strong Motion Instrumentation Program had a hall of fame Jim Agnew, Steve Fife and Ron Ayala undoubtedly would be in it. And they probably wouldn't charge $10 for an autograph, either.

400th TriNet StationThose three recently reached a significant milestone, installing SMIP's 400th seismic instrument in Southern California as five years of work on the TriNet program concluded. Their work was recognized with Sustained Superior Accomplishment Awards at the recent DOC holiday party.

"There's a sense of accomplishment and pride throughout the whole SMIP team in getting 400 stations going," Fife said. "There was a lot of field time involved and a lot of coordination from headquarters. We were managing up to 60 ongoing projects at a time -- the instruments that were being installed, the ones that had just been installed and the next group to be installed."

Added Ayala: "The instruments will supply data that could help with emergency response if there's a major earthquake, so it's a good feeling to have contributed."

TriNet was one of the things to shake out of the 1994 Northridge earthquake. All 400 of SMIP's accelerographs are capable of dialing up a computer at CGS headquarters after recording strong shaking and transmitting their data over phone lines. With that information, CGS and its TriNet partners -- Caltech and the USGS -- can create a ShakeMap within minutes of a major quake. A ShakeMap pinpoints the location of greatest shaking intensity, which helps emergency response crews decide where to concentrate their efforts.

There were already some instruments in the field when the TriNet project began, but they were relatively low-tech. Someone had to retrieve the data from those instruments, a time-consuming process that was adequate for scientific research but not for emergency response.

"Our goal was to install 400 stations, either new ones or upgrades of the old analog ones, and Jim, Steve and Ron were the central people in getting that accomplished," said Tony Shakal, supervising geologist of SMIP.

The 400th SMIP instrument was placed in Los Angeles Fire Department Station 34 -- appropriate, since many of the accelerographs are housed in fire stations.

"We wanted to do things with a cost- and effort-minimizing approach, and we found that working through municipal agencies was a very effective way to go," Shakal explained. "Fire departments were the most receptive."

Initially, gaining permission to put in the instruments was challenging. The Los Angeles County Fire Department was the first to agree to installations. As the work continued, word got out about the potential benefit of ShakeMap to fire departments and other emergency workers, and more doors began to open.

"We like putting our monitors in fire departments because there's someone there 24 hours a day, so we don't have to worry about our $5,000 instruments disappearing," Agnew said.

SMIP has suffered its share of losses due to theft and/or vandalism over the years. Several years ago, instruments were stolen from a remote Mojave Desert location. So far, Agnew reports, no instruments placed in a fire department have been stolen. And none has caught fire.

Agnew's primary responsibility with TriNet was finding likely locales for instruments. When he spotted one-story structures of wood frame construction less than 4,000 square feet in size on a cement slab, Agnew had hit the jackpot. He was well-qualified for the job, having worked 18 years in private industry with a firm that installed seismic networks all over the country. He then worked at the Yucca Mountain nuclear waste storage facility in Nevada. Agnew wanted something a bit more challenging, and found it when he joined SMIP in March of 1998.

"Since the idea was to place one instrument per zip code, Jim had to work with a GIS map in his head," Shakal said. "He might come back from a field trip with 20 to 30 sites in mind, and maybe half of those survive our screening process."

In doing his scouting, Agnew flew into Los Angeles three or four times a month, hopped in a car and started fighting traffic in a frantic effort to see as many sites as quickly as possible.

"My record was 26 fire stations in one day," he said. "I didn't stop and talk to people, just drove by and took pictures. I got to know my way around Los Angeles to the point that I could probably get by without my Thomas Brothers map now, but I wouldn't want to try because the city's so big."

While Fife didn't tighten any nuts and bolts -- that was Ayala's role -- he was the nuts and bolts guy. A Senior Precision Electronic Specialist who has been with SMIP 11 1/2 years and on the TriNet project from the start, Fife took care of the details once Agnew did his scouting and made initial contact with the building's occupants. For example, Fife worked with fire chiefs to decide where the instrument would go in a station and where to put the GPS antenna.

Station Installation"I made sure that Ron knew the project was doable before he went in to do his installations," Fife summarized.

Ayala, who estimates that he installed 280-300 of the 400 accelerographs, could probably mount an instrument and battery box in his sleep at this stage. But that was only half the battle. The other half was more complicated.

"In order to install an instrument, you need to get a phone line to it and hook it up to the antenna," he said. "Sometimes it got tricky -- for example, maybe the phone line I needed to tap into was in another building. Plus, when you're working in a fire station, you try to do your job while staying out of the way as much as possible."

The instruments often were placed under stairs or workbenches, places unlikely to trip up a hurried firefighter. Ayala discovered that gaining access to an installed accelerograph isn't always easy, even when it was placed in the perfect spot. One fire station put ductwork all around the instrument. "I have to do some crawling to get to that one," said Ayala, who celebrated his 10th year with SMIP on December 23.

SMIP's work in Southern California has wrapped up, at least for now. For the first time, however, there is money in the state budget to start installing instruments in Northern California, where there is, Shakal said, "a big vacuum." TriNet has become the California Integrated Seismic Network with the addition of UC Berkeley and the Menlo Park USGS network to the CGS-USGS-Caltech partnership. SMIP will install 150 instruments over the next five years from Bakersfield to Crescent City. But SMIP's work won't stop there.

"The goal remains one per zip code throughout the entire state, and there are 3,000 zip codes in the state," Shakal noted. "There are about 1,000 instruments running right now, and about half the Southern California zip codes are instrumented. But about 500 of those instruments are the old type that require someone to go out and retrieve the data. Those need to be replaced eventually. So there's a lot of work ahead of us."

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PR02:230
FOR IMMEDIATE RELEASE
04/23/2002
GOVERNOR DAVIS ANNOUNCES NEW STATEWIDE SEISMIC MONITORING NETWORK 4/23/2002
New System Includes Online "ShakeMaps" for Emergency Responders
SACRAMENTO

Governor Gray Davis today announced the creation of the California Integrated Seismic Network (CISN). The Governor's $2.9 million allocation will allow for the integration and expansion of existing regional earthquake monitoring networks and production of data for online "ShakeMaps" and other rapid information that will enhance the timeliness and efficiency of emergency response to devastating earthquakes. "It's imperative that first responders have the best tools available to them to get to the victims of devastating earthquakes," Governor Davis said. "CISN will create the system for generating real-time information for real-time response. "The Governor's Office of Emergency Services, which will provide overall leadership for CISN, has had a long-term interest in coordinated earthquake monitoring. The historical separation between seismic network operations in northern and southern California and between strong-motion and weak-motion networks statewide resulted in fragmentation and delays in providing information for earthquake response. Among the benefits of CISN will be the production of "ShakeMaps," that use a color scheme to map the shaking intensity surrounding the epicenter of an earthquake. Data for the maps are generated from seismic monitoring stations located throughout the state. CISN will also provide rapid and accurate information on the magnitude, location and suspected fault for any significant earthquake in California and deliver that information to OES via robust and redundant communication links from across the state. "In the past, it has taken too long to locate where the most severe damage has occurred following a major quake," Office of Emergency Services Director Dallas Jones said. "CISN's "ShakeMaps" and other resources show us immediately where the most serious shaking has occurred and allows us to quickly dispatch crews to where they are needed most." Recent advances in technology have made it possible to integrate existing, separate earthquake monitoring networks in California into a single seismic monitoring system. Participating agencies and organizations in CISN include the Department of Conservation's California Geological Survey, the Caltech Seismological Laboratory, the Berkeley Seismological Laboratory, and the United States Geological Survey's offices in Menlo Park and Pasadena. CISN will also serve as a model for the nation and be part of the Advanced National Seismic System, a federally funded initiative to modernize and coordinate earthquake monitoring nationwide. "The ability to gather vital seismic information quickly will not only help immediate response and recovery efforts, the data will also help us build stronger, safer structures in the future," Department of Conservation Director Darryl Young said. "We are proud to be partners in this important work. "For more information on CISN, go online at www.cisn.org.

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Pictures taken on April 23 at a press conference at the headquarters of Office of Emergency Services in Rancho Cordova in the State Operation Center

OES Director Speaks at New Operations Center

 

OES Director Dallas Jones addresses the audience from the State Operation Center.

 

 

 

 

 

 

DOC Director Speaks at OES

 

Department of Conservation Director Darryl Young discusses the seismic monitors used throughout the state.

 

 

 

 

 

 

OES State Operations Center

 

The gathering to view the press conference from the balcony overlooking the State Operations Center.

 

 

 

 

 

 

CISN Discussion at OES

 

Director Jones discusses CISN with several of the state's leading seismologists prior to the press conference.

 

 

 

 

 

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Quake Response in Two Shakes (from “Wired News”)
2:00 a.m. April 29, 2002 PDT

(page 2)

Although modern instruments have increased response times, technology has yet to be developed that will predict earthquakes before they occur.

"We can't predict earthquakes, but we do know how to locate them once they occur," Gee said. "Once an earthquake occurs, we can tell you about it."

"Prediction has been a Holy Grail for a number of years," Gee said. "Unfortunately, we haven't developed that capability yet. At this point, there are no clear-cut tools, no clear-cut mechanisms that we fully understand (to make predictions)."

The CISN will establish two processing centers, which will each locate earthquakes across the state. So if a major temblor hits the Hayward fault and UC Berkeley's facility is damaged, seismologists at Caltech will be able to provide the same ShakeMap data.

This robust "T1 ring" will allow the monitoring centers to be able to function independently even if the Internet goes down.

"Our efforts are very vulnerable to a damaging event in our own backyard," Gee said. "We don't want to be dependent on a single point of failure."

CISN's data will likely help engineers build safer, stronger structures, seismologists agree.

"The more data we record, the more projects (will be developed) to improve building codes and structural design," Gee said.

While scientists have been measuring seismic activity for decades, only recently have modern instruments been introduced that can help speed response times.

"We can still use data (after an earthquake occurs) to improve building codes, but the real step forward is that we can also use this data to improve emergency response," said Tony Shakal, of the California Geological Survey.

These new instruments have dynamic range and resolution so seismologists can measure even low levels of shaking and calculate frequencies shortly after earthquakes occur.

"Now we can convert raw measured data into useable information about shaking to understand the impact for a structure," Shakal said. "Five years ago it was not possible to do this."

CISN will likely serve as a model and will be part of the Advanced National Seismic System, a federal effort to modernize instruments and coordinate earthquake monitoring across the nation.

"California has been on the leading edge of seismic monitoring," Gee said. "We have the earthquakes and we have the population."

But California isn't alone in its earthquake risk. Just two weeks ago, a 5.0 earthquake shook New York.

"While California has the leading risk, earthquake hazard exists in any state," Gee said.

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Earthquake Monitoring to Be Expanded to All Parts of State (from San Francisco Chronicle)
Tuesday, April 23, 2002

(04-23) 23:28 PDT SACRAMENTO (AP) --

California's network of earthquake monitoring stations will cover the entire state under a new appropriation announced Tuesday.

After the federal government announced last year it would cut funding for the monitoring stations, the state stepped up with a $2.9-million program that will add 600 stations in Northern California and help Caltech operate its network of 600 stations in Southern California, Dallas Jones, director of the state Office of Emergency Services, told a news conference.

When complete, officials say, the system will enable state scientific and emergency authorities to pinpoint the precise location and damage pattern of any sizable quake within minutes of its occurrence anywhere in California.

Gov. Gray Davis said the California Integrated Seismic Network, a new umbrella group that incorporates the efforts of the Geological Survey, Caltech, University of California, Berkeley, and the California Geological Survey, has been created to coordinate quake monitoring in the state.

In both of California's most damaging quakes of recent years -- the 1989 Loma Prieta temblor in the Bay Area and the 1994 Northridge quake -- authorities were unsure for up to two days just where all the most severely damaged areas were.

That problem could be ameliorated by the new setup.

A vital feature of the Southern California network has been so-called shake maps, which depict the shaking in sizable quakes not only near the epicenter but in all areas where the quake is felt. Officials said these maps also notify authorities within the hour where emergency teams are needed.

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Ready to Rock
DMG Installs Seismic Instrumentation
Throughout New Cal/EPA Building in Sacramento

DOC had planned to move its headquarters to the Cal/EPA building in downtown Sacramento. But the 950,000 square feet of space in the new 25-story structure filled up quickly, leaving the department in the "Darth Vader" building a few blocks away.

Cal/EPA InstrumentationHowever, there's still a bit of DOC in the core of the latest addition to the city's skyline.

As the Cal/EPA building was going up, technicians from DMG's Strong Motion Instrumentation Program (SMIP) were installing seismic monitors that will help engineers and the scientific community better understand how tall buildings react to strong seismic waves.

SMIP has installed monitors in about 170 buildings around the state, including 25 hospitals. The Cal/EPA building has by far the most modern monitoring system of the three instrumented structures in Sacramento; the Capitol and Office Building 8 (the "Twin Towers") are the others.

Cal/EPA BuildingMost Sacramentans probably worry more about potential flooding than earthquakes. So why invest $50,000 or more to place seismic recorders on buildings in a city so far removed from major known faults? Moh Huang, a structural engineer who is deputy program manager of SMIP, explained the logic.

"Back in 1985, there was a large earthquake in Mexico that was centered about 250 miles from Mexico City, yet the tall buildings in Mexico City swayed back and forth," Huang said during a March 22 tour of the Cal/EPA building. "When the Loma Prieta earthquake occurred in 1989, the Renaissance Tower (DOC headquarters) was just being completed and didn't have

any tenants, but the building manager reported feeling the shaking. A strong earthquake can be felt far away from the epicenter. Downtown Sacramento is less than 100 miles from San Francisco, so we need to know how our buildings react, too."

There are 15 sensors, which cost about $1,000 apiece and are made by a Pasadena company, in the Cal/EPA building: four on the ninth floor, three each in the basement and on the roof, two on floors four and 20, and one on the first floor. The sensors are arranged to measure three types of motion in the event of strong ground shaking: East to West, North to South and torsion (whether the building twists).

"We don’t have any data from this building so far -- and that's OK, too," said Carl Petersen, SMIP's network operations manager. "That means there hasn't been any significant shaking."

Construction Techniques of Cal/EPA BuildingConstruction techniques used in the Cal/EPA buildings to minimize potential damage from shaking include heavy steel braces -- some four feet wide -- around the elevator shafts. And the welds holding the structural steel together are stronger than those used in the last generation of steel-frame buildings; the 6.7 Northridge Earthquake of 1994 broke the welds in some buildings. The building is designed to sway up to a foot and a half in the event of a large earthquake.

"The structural engineer that worked on this building also did a 73-story building in Los Angeles and he assured us that we're in good hands," Huang said.

"Dynamic analysis" of the Cal/EPA building from the structural engineer helped SMIP, with input from its advisory committee, decide where to place their sensors, small black instruments contained in locked gray boxes marked "Do not open -- scientific equipment."

Someone pounding on the wall or a stiff wind can't fool the sensors; it would take an earthquake in the magnitude-6 range in the Bay Area to awaken the three devices in the basement, which in turn trigger the other sensors. All 15 monitors are wired into a recording device on the first floor that is connected by phone lines to a computer in SMIP's office. In the event of a substantial reading, the computer automatically pages SMIP personnel.

Instrumented Recorder"We don't need a lot of access to the sensors," Petersen said. "Our recorders automatically dial up our computers if there's an earthquake and they are automatically dialed up weekly to check

on their health. We only send someone to look at them is something's wrong, and the batteries only need to be changed every three to four years."

Petersen oversees a staff of 18 technicians who work all over the state -- primarily in the greater Los Angeles area and Bay Area -- installing and maintaining instruments. At any given time, DMG personnel are in various stages of perhaps a dozen projects. SMIP data is used to recommend changes to building codes, assist local governments in their general plan process and aid emergency response personnel in the event of a disaster.

"The idea behind all this work is to have safer buildings sooner," Huang said.

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Media Members Find Out What's Shaking
With DMG's SMIP Program in San Mateo

On April 18, the 94th anniversary of the San Francisco Earthquake, the Division of Mines and Geology's Strong Motion Instrumentation Program made a small rumble in the Bay Area.

At a well-attended news conference and demonstration at the western approach of the San Mateo Bridge, DOC Director Darryl Young and SMIP Supervising Geologist Tony Shakal introduced media members to an ongoing program of instrumentation on Caltrans toll bridges.

SMIP's work at San Mateo is nearly done after about four years, with the

Carquinez and Benicia-Martinez bridges next on the agenda. The instrumentation will, in the event of a magnitude 4 or greater earthquake, help demonstrate whether Caltrans' retrofitting work has been effective. Information provided by the SMIP accelerometers also will help engineers make a proposed new bridge from San Francisco to Oakland more earthquake-resistant.

SMIP Instrumentation at San Mateo BridgeAbout 20 technical staff members are either installing or doing maintenance on instruments at any given time. SMIP instruments are placed on buildings, dams, bridges and other structures, in open fields and "downhole" (as deep as 300 feet underground).

On the San Mateo Bridge, some of the sensors are inside the steel box girders, some are on the base of the columns at the water level and some are on the concrete piers below the road base to measure an earthquake's effect on different parts of the bridge. There also is a "downhole" array at the approach to the bridge.

Installing instruments on a bridge is an adventure -- and a workout. At San Mateo, there were two ways to get to the base of the pillars. The first involved boarding a barge and going out over the water on a "man lift" similar to what linemen use. The second involved climbing down -- and back up -- a ladder inside the pillar. The highest pillar on the San Mateo Bridge is 160 feet.

Instrumented RecorderThe Strong Motion Instrumentation Program came into being after the 1971 San Fernando earthquake. The damage done to the Bay Bridge by the 1989 Loma Prieta earthquake (magnitude 6.9) provided the impetus for the extensive instrumentation of the Golden Gate Bridge as well as Caltrans' 20 toll bridges.

The first fully instrumented bridge was near San Bernardino at the I-10/I-215 interchange. It produced data from the 7.3 Landers quake of 1992 and the 7.1 Hector Mine quake of last year.

Shakal likened the ongoing instrumentation to "setting the trap" for an earthquake. "Now all we need is the critter to come. The best data from the bridge instruments is yet to come, because we've had few earthquakes to get data from. The ideal would be to learn from an event that isn't traumatic and then make adjustments to the designs."

 

 

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EARTHQUAKE MONITORS INSTALLED AT SAN FRANCISCO CITY HALL

Sensors Will Provide Emergency Data, Determine Effectiveness of Retrofitting

SAN FRANCISCO -- It has beauty and a brain. Inside beautiful San Francisco City Hall, an electronic brain with an army of sensors is ready to respond to the next Bay Area earthquake.

State officials today demonstrated the new seismic monitoring system at the historic structure as part of an extensive earthquake retrofitting project.

The California Department of Conservation has installed 18 sensors. Divided among the four levels and dome of City Hall, the devices measure seismic waves shaking the building. During an earthquake, these "accelerometers" report to a central computer the shaking that occurs at several key points in the structure from the foundation to the top of the dome. The instruments provide valuable data about earthquake shaking and the building's response.

"We can't stop earthquakes from happening, but we can better prepare ourselves by improving the way we build new structures and retrofit older ones," said Darryl Young, director of the Department of Conservation. "These strong-motion sensors provide the latest technology to help us do that."

The installation project conducted by DOC's Strong Motion Instrumentation Program (SMIP) began in 1999 as part of the mammoth earthquake retrofit of City Hall.

The sensors also serve as watchdogs, automatically phoning an alert to computers at SMIP headquarters in Sacramento when strong ground motion occurs (generally magnitude 3.5 or greater in the San Francisco Bay Area.)

In addition to City Hall, accelerometers have been installed on other structures in the San Francisco area, such as the Golden Gate Bridge and San Mateo Bridge. In the event of a large earthquake, information gathered by the sensors can be analyzed by DOC computers and seismologists and help emergency crews determine the hardest-hit areas within minutes after the quake. During the 1989 Loma Prieta earthquake, the City Hall dome twisted like a bottle cap, moving two inches. Walls and concrete floor slabs cracked on all levels.

In 1995 engineers began a "base isolation" retrofit of the entire building. Base isolation helps buffer a building from seismic waves. There are 590 rubber cylinders at the base of City Hall's support columns that dampen the effect of the seismic waves. Base isolation also allows the building to move more than two feet in any direction during an earthquake, further minimizing quake damage.

Data gathered by SMIP sensors on how structures react to temblors is being applied by engineers to create stronger, safer building plans for new construction and retrofits.

The Strong Motion Instrumentation Program is part of the DOC's Division of Mines and Geology, which is California's State Geological Survey. SMIP instruments, in combination with sensors from the U.S. Geological Survey, California Institute of Technology and UC Berkeley, are the backbone of a developing integrated seismic network that will cover most of the state's earthquake-prone areas. This consortium of institutions will jointly produce maps of the shaking to help guide emergency response. With more than 800 stations in place, the state's Strong Motion Instrument Program, established in 1971 following the San Fernando earthquake, is one of the largest of its kind in the world.

In addition to studying and mapping earthquakes and other geologic phenomena, the Department of Conservation maps and classifies areas containing mineral deposits; ensures reclamation of land used for mining; regulates oil, gas and geothermal wells; administers agricultural and open-space land conservation programs; and promotes beverage container recycling. More information on DOC programs is available online at www.conservation.ca.gov