Satellites, buoys and sensors help scientists track earth and ocean conditions.

A host of technologies to protect Southern California from natural disasters are either in place or in development. Some of them cost millions of dollars, others mere thousands, but all are aimed at providing better, earlier warnings of pending calamities. Here's a review:

Tsunameters

The Pacific tsunami warning system is anchored by seven buoys tethered to the ocean floor. The state-federal DART program, an acronym for Deep-Ocean Assessment and Reporting of Tsunamis, has planted buoys off the coasts of Alaska, Hawaii and the Pacific Northwest. The government of Chile has another buoy anchored 300 miles off of South America.

Each one weighs 1,200 pounds and modems on the buoys transmit data to satellites from sensors on the ocean floor, so any pressure change on the earth's crust can be matched with information the buoy is reading on the water's surface, such as wave height.

Rapid changes trip an alarm that alerts that satellite of a possible earthquake or tsunami, according to Christian Meinig, head of the engineering division of National Oceanographic and Atmospheric Administration's Pacific Marine Environmental Lab in Pasadena. The information is beamed to the Pacific Tsunami Warning Center in Hawaii and to the West Coast Alaska Warning Center.

The system is still being expanded. The next buoy to be installed will be in Hawaii, followed by Alaska. In about three years, Meinig said, a buoy will be placed off the coast of Northern California.

GPS Receivers

The receivers planted by the Southern California Integrated GPS Network look like mini-UFOs. About 260 have landed in Southern California spots over the past six years.

The receivers are used by satellites passing overhead to bounce radar waves off the earth, checking for ground movements, said JPL geophysicist Andrea Donnellan.

The GPS Network is managed through the University of Southern California and involves JPL, the U.S. Geological Survey and the University of California at San Diego.

The receiver sits on a tripod whose legs are drilled between 30 and 50 feet into the earth's crust. If the satellite passes over the same place and the ground has moved even slightly, it can show strains on a fault line before earthquakes happen.

There are no satellites in space dedicated to monitoring the GPS Network. In the past, JPL has used Japanese and European satellites but they are no longer in service. Canadian satellites with the main purpose of monitoring ice sheets sometimes pass over the sensors and collect data, but they are not optimized for this purpose, said Donnellan.

Adapting them would cost hundreds of millions of dollars, but would also allow researchers to forecast earthquakes five years ahead of time. The current data only allows a less-useful 10-year forecast.

Receivers of this type helped predict Mt. St. Helens' recent volcanic activity and warn nearby residents.

Dial-a-Buoy

Surfers have long been plugged into a network of 27 moored buoys and stations along the Southern California coast that monitor ocean and weather activity. The buoys are part of a network along U.S. coasts, managed by the National Data Buoy Center in Mississippi.

Through phone calls to Dial-A-Buoy or visits to its Web site, commercial and recreational fishermen can check weather, wave and tidal conditions in a particular area for safety information.

The center receives more than a million hits per month on its Web site averaged 200 to 300 calls per day last year.

Automated photographic monitors

If scientists now want a closer look at a satellite photograph that's beamed back to earth, they have to send up instructions for the satellite the next time it orbits, a process that can take up to a week.

Rob Sherwood, manager for JPL's Autonomous Sciencecraft Experiment, has developed software that decides on its own if a picture is scientifically interesting. "It's like artificial intelligence," Sherwood said, and it shortens the process to a few hours instead of days.

The satellite will also send an alert the next time it contacts the ground.

The software runs on NASA's Earth Orbiting 1 satellite, which orbits the earth every 90 minutes and passes five ground stations for communication. But the software could be installed on almost any satellite, Sherwood said.

The software was able to detect activity on a remote volcano in Antarctica and zeroed in for more pictures without any commands from the ground. But in order to monitor the same place continuously, he said, it would need to be installed on many different satellites.

Spreading the word

As the senior communications coordinator for the State Warning Center in Sacramento, Randy Schulley has four phones on his desk with about 40 phone lines each.

He has an open phone line to all 58 counties and one to the seven National Weather Service districts covering California. Schulley can talk directly to the tsunami centers in Alaska or Hawaii on another line.

But Schulley's most far-reaching tool is the automated notification system, a reverse-911 phone line that can immediately blast an emergency phone message to local government officials.