A、It breaks down at times. B、The alarms sometimes do not sound. C、There are a lot of false alarms for small quakes. D、The comput

American engineers Paul Flores and Jim Gibbson are studying Mexico’s earthquake warning system. They hope such a system could be implemented in California where earthquakes are quite common even if it could give only a few seconds of warning before an earthquake.
    "With just a couple of seconds’ warning, teachers, for example, can get the children under the desks before things on the shelves start failing onto their heads, "Flores said, "That’s what early warning could do in the States."
    Flores and Gibbson have a one-year, $ 50,000grant from the National Science Foundation to study Mexico’s early warning system. The system is made up of 12 earthquake monitors buried 305 kilometers south of Mexico City along the coast.
    When an earthquake measuring 3.5 or greater on the Richter scale strikes, the monitors detect the shack waves and instantly send out an electronic signal to computers in Mexico City. The computers process the information and continue to pass it to radio stations and public speakers that sound earthquake alarms. City residents can then be warned to get to safe places. Since the electronic signal travels faster than the quake’s shock waves, the city can receive a warning of about one minute before the quake strikes.
    But a similar system in California would not be able to give that long a warning because earthquake centers are much closer to population centers.
    Gibbson noted that problems do exist with Mexico’s system, including false alarms issued by small earthquakes. "But people shouldn’t lose confidence in the warning system," Gibbson said. And according to an earthquake expert in Mexico City, there are more benefits than problems. "We still have a lot to learn, but the more we learn, the better it will be for people in California to be able to use a system one day based on our actual experience," the expert said.