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California to Develop Earthquake Early Warning System

作者:Mario Ritter Jr 发布日期:7-10-2019

Californian officials say they will spend more than $40 million on an earthquake early warning system.

The announcement comes after two powerful earthquakes shook parts of the state last week. On Thursday, a 6.4-magnitude earthquake struck an area in the Mojave Desert, but the effects could be felt as far away as Los Angeles. Then on Friday, a 7.1-magnitude earthquake struck near Ridgecrest, California, causing damage to houses and roads.

The proposed early warning system would let the public know of a possible quake. Officials say it also would automatically halt trains and open fire station doors moments before a major quake strikes.

California Governor Gavin Newsom made an announcement after Friday's quake. He said that the state has already put in place 70 percent of 1,115 sensors needed for a statewide system.

Ryan Arba is with the governor's Office of Emergency Services. He said, "I think the whole state's on notice right now about the opportunity that's in front of us."

Emergency officials have said they hope to have the statewide warning system in place by the middle of 2021.

The recent strong earthquakes were the first in 20 years in Southern California. They brought increased attention to the development of the state's early warning system.

Japan developed the world's most modern earthquake early warning system after the 1995 Kobe earthquake. It relies on more than 4,000 sensors and is based on the same laws of physics that California is using to build its system.

P-waves can provide early warning

As in Japan, the California system is designed to detect the fast-moving seismic P-waves that are produced by earthquakes. These waves can reach a sensor before the ground starts moving. The U.S. Geological Survey says that many animals are able to feel P-waves.

Communities farthest from the epicenter of a quake would receive the earliest warning.

Arba says, for example, that a quake on the San Andreas Fault near California's border with Mexico would give Los Angeles 60 seconds of warning before the ground began to shake there. However, communities very close to a quake's center would receive little or no warning.

Bottles of wine are strewn in the middle of an aisle in the Eastridge Market in Ridgecrest, California, July 6,2019, after Friday night's 7.1-magnitude earthquake, which jolted an area from Sacramento to Mexico.
Bottles of wine are strewn in the middle of an aisle in the Eastridge Market in Ridgecrest, California, July 6,2019, after Friday night's 7.1-magnitude earthquake, which jolted an area from Sacramento to Mexico.

Officials in Los Angeles County in January introduced a "ShakeAlertLA" mobile phone application. It can send an early warning to residents who have the app. The "ShakeAlertLA" app, however, was not activated for either of the recent quakes. The U.S. Geological Survey said this was because they were not strong enough.

Trains at risk during earthquakes

The Bay Area Rapid Transit (BART) system in and around San Francisco has connected the early detection system to its rail service. The system is designed to automatically slow down trains, Arba said.

Southern California's Metrolink commuter rail system halted service after Friday's 7.1 earthquake in Ridgecrest. But, a spokesman said orders to stop the trains only went out by radio when shaking was felt by officials at the operations center in Pomona, east of Los Angeles.

The Metrolink board has voted to spend $4.9 million in public money to automate the halting of its trains when a quake is detected, the spokesman said.

University of California at Los Angeles engineering professor John Wallace said there are many possible uses for the early warning system.

"Once you provide the system, you'd be surprised how many ways people will find to use it," he said.

I'm Mario Ritter Jr.

Alex Dobuzinskis reported this story for Reuters. Mario Ritter Jr. adapted it for VOA Learning English. Caty Weaver was the editor.

Words in This Story

automatically –adv. done without being directly controlled by a person

on notice –adj. to be warned or told about something

detect –v. to discover or notice the presence of something

opportunity –n. an amount of time or a situation in which something can be done; a chance

seismic –adj. related to earthquakes

epicenter –n. the place on the earth that is directly above where an earthquake starts

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