New Scientist - USA (2019-07-13)

13 July 2019 | New Scientist | 7

IS THE much feared “big one”

about to strike? That question

is back in the minds of many in

California after the strongest

quakes for two decades struck

the state. But we don’t know if

these have made an even bigger

earthquake any more or less likely.

A magnitude 6.4 tremor struck

southern California on 4 July,

followed by a magnitude 7.1 quake

on 5 July, with hundreds of smaller

aftershocks in their wake. It was

fortunate that the epicentres were

under a sparsely populated region,

near the city of Ridgecrest.

No one was killed, but the

quakes were felt across the state.

They left a long crack in the desert

and damaged buildings and roads

in the area (pictured above).

The San Andreas fault runs the

length of California and lies near

major cities such as Los Angeles

and San Francisco. A major quake,

possibly of magnitude 8 or greater,

could occur on the fault at any

time, potentially killing thousands

of people and causing hundreds

of billions of dollars in damage.

However, the latest tremors

occurred on different faults far

from the San Andreas. Geologists

don’t know whether these latest

quakes have made a major

earthquake on the San Andreas

fault more likely or not.

There is no way to predict big

quakes hours or days in advance,

and some think it may never be

possible. Some regions have early

warning systems that issue alerts

as soon as the first tremors are

detected, giving people a few

seconds or more of warning

before the most dangerous

shaking starts. The US Geological

Survey is currently developing

such a “ShakeAlert” system for

the west coast.

Modern buildings in California

are designed to withstand sizeable

earthquakes, though many could

still be left unusable. However,

the state has many older buildings

that need retrofitting to be safe.

The vast Sacramento river delta

is also protected by embankments

that could fail in a big quake. If that

happened and seawater floods the

delta, it would cut off a lot of the

fresh water supply to southern

California for a year or more. ❚

Two large tremors just a day apart in California have got people

asking if there is a bigger quake coming, reports Michael Le Page

Artificial intelligence

Sheet of glass can

recognise numbers

IT IS the smartest piece of

glass in the world. A team at

the University of Wisconsin–

Madison has made an

artificially intelligent piece of

the stuff that can distinguish

images of numbers.

Bubbles and impurities in

the glass bend light waves

as they pass through it.

Depending on which of the

digits 0 to 9 is written on a

piece of paper held up to the

glass, the light waves are

brought to different focal

points, allowing the material

to identify digits (Photonics

Research, doi.org/c73h).

The glass AI could

eventually be used as a kind

of “biometric lock”, say the

researchers. ❚ Donna Lu

Global warming

Attenborough talks

up climate action

THE UK must take radical

steps to meet its climate

change targets, David

Attenborough told a UK

parliamentary committee

on Tuesday. But he warned

ministers must carry the

public with them because

of the cost of such action.

“We cannot be radical

enough in dealing with these

issues,” he said when asked

if the UK should bring

forward its target of cutting

greenhouse gas emissions

to net zero by 2050. But he

said the real issue was what

is politically possible. “The

question of how fast we can

go is how fast we can carry

the electorate with us.” ❚

Adam Vaughan

Earthquakes hit California

News

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