Reporting Earthquakes to the Public

In late June, a local television station broadcast a false report of an earthquake (see "How a False Mammoth Quake Report Got on the Air," June 29, 1996, Los Angeles Times, page F2). As a result, we have noticed a surge of interest in how earthquakes are reported in Southern California. In response, we thought the public would like to know how the Southern California Seismic Network normally reports earthquakes.

Caltech and the U.S. Geological Survey jointly monitor regional earthquake activity by means of the Southern California Seismic Network, which consists of about 320 seismographic instruments located at more than 250 sites throughout Southern California. Some of the stations are very simple, using 1970s technology. Others use the most advanced digital recording systems available. Each monitors the ground motion at its site, and each sends its data in real time or near real time to our computers at Caltech.

There is a popular misconception that the Seismological Laboratory is staffed 24 hours a day. In fact, we do not have enough money to do this. Instead, the computers are on duty 24 hours a day, and one seismologist is designated each week to be the "duty seismologist." The duty seismologist carries two pagers, a laptop computer, and a cellular telephone at all times and will respond to all inquiries within a few minutes. The Caltech Public Relations Office also has a person on call to respond to reporters when the office is closed.

To ensure accurate reports, every earthquake larger than magnitude 3.0 and every earthquake that is felt is verified by the duty seismologist. This verification process normally takes about 15 minutes, including waking up and finding the light in the middle of the night. While the seismologist verifies an earthquake, the computer's automatic estimates, which are correct more than 90% of the time, are available to the press and the public via the Internet and CUBE, which is an earthquake information paging system. The following describes what happens when an earthquake occurs.

Here's what happens automatically: o The earthquake fault slips, creating seismic waves o The seismic waves travel outward o Seismographic stations detect the waves o The stations send data to Caltech by radio o The computer at Caltech records the data o The computer estimates the arrival time of the waves and the size of the largest seismic wave (peak motion) at each station o The computer estimates the earthquake's location and magnitude o The computer sends a page, including time, location, and magnitude, to CUBE o If the quake is above magnitude 3.0, the computer also sends the same information to the duty seismologist's pager o It the quake is above magnitude 2.0, the computer updates lists of recent earthquakes on the Internet

Here's how people respond: o The public feels the earthquake o Some people call the news media o Reporters call the Caltech Public Relations duty person o PR person calls duty seismologist

Meanwhile: o The duty seismologist feels the earthquake, gets the computer's page, or receives a call from the PR staffer o Duty seismologist checks the accuracy of the computer's estimates and gives the correct time, magnitude, and location to PR duty person o The duty seismologist updates the Internet and CUBE information o The duty seismologist updates the Seismo Lab recorded phone message o The duty seismologist may also change the information for other, usually smaller, recent earthquakes as needed

Simultaneously: o PR duty person updates Caltech PR recorded phone message o PR duty person returns phone calls from reporters

Within a week: o The arrival time for all earthquakes at all stations is checked by a human o Magnitudes of all quakes are checked by a human o Quality assurance software detects duplicate entries and other problems o Seismologist writes and distributes a weekly report, which lists all earthquakes larger than magnitude 2.0

Earthquake information can be found on the World Wide Web at "http://www.scecdc.scec.org", where there are links to several other interesting Home Pages. For Internet users without access to the World Wide Web, a list of earthquakes that occurred over the past seven days can be obtained with the command "finger quake@scec.gps.caltech.edu". The same output will be sent to you if you send e-mail to "quake@scec.gps.caltech.edu".

Kate Hutton is a staff seismologist at Caltech's Seismological Laboratory. Lucy Jones is a seismologist with the U. S. Geological Survey in Pasadena. Both speak frequently with reporters following major earthquakes, and both take their turns as the duty seismologist.