BBC Focus - 04.2020_

Q&A

ARETHEREANY
ADVANCESIN
THE PIPELINE?

Theabilitytopredictearthquakes
hasbeenclaimedforallsortsof
things,fromoddanimalbehaviour
andchangesinrockproperties,to
electromagneticsignalsinthecrust,
andso-called‘earthquakelights’

• electricaldischargesthathave
  beenobservedintheskybefore
  someearthquakes.Nonehave
  provedtobeuptothejob.Butthere
  maybelightonthehorizon.
  ScientistsmonitoringtheCascadia
  Fault,offthewestcoastoftheUS
  andCanada,havegivena machine-
  learningalgorithmtheirdata,with
  thehopethatit canfindpatternsin
  theseismicrecordthatcouldhelp
  predict the fault’snextbigquake.

WOULDACCURATE

PREDICTIONBEAGOOD

THING, ANYWAY?

Whatif weknewthata largemagnitudeearthquake

wasgoingtostrikea majorcity– saySanFrancisco

• inexactlythreemonths’time?Makingsucha
  predictionpublicwouldcausewidespreadpanicand
  a massexodusfromthecity.Businesseswouldclose
  andshifttheirstockout– manyperhapsforgood.
  Sharesinlocalcompanieswouldplummet.California
  stateauthoritieswouldneedtosetupcampsforthe
  hundredsofthousandsfleeingthecity,andfeed
  themformonths.Muchbetter,saymany
  seismologistsandearthquakeengineers,is toforget
  prediction,andfocusinsteadonmakingbuildings
  ‘life-safe’.Inotherwords,constructthemwell
  enoughsothattheydon’tfalldownwhena quake
  strikes,andbringoldbuildingsuptoa similar
  standard(retrofitting ).Thisway,damageis
  minimised,thedeathtollis massivelyreduced,and
  the economy and infrastructure little affected.

WILL WE EVER BE ABLE TO PREDICT EARTHQUAKES?

Someseismologistsconsidertrueearthquakepredictiontobeintrinsicallyimpossiblebecausethe

Earth’scrustis ina stateofso-called‘self-organisedcriticality’.If thisis thecase,it wouldmeanthatany

tremor– howeversmall– hassomeprobabilityofballooningintoa majorshock.Othersarguethat

predictionis difficult,butwewilleventuallyfinda way.If predictionis evertohaveanyuseatall,

however,it willhavetobeaccurate,andit willhavetoberighteverytime.Falsealarmswouldleadto

widespreadpublicangeranddisillusionment,andthey could also mean that people ignore the correct

call when it comes, leading to unnecessary deaths.

byP R O FB I L L

MCGUIRE

Billis professor

emeritusof

geophysicaland

climatehazardsat

UCL.Hisnovel,

Skyseed, willbe

publishedin

September.

Aerialviewofthe

SanAndreasFault,

runningthroughthe

CarrizoPlainin

California

Modelshowing

earthquakerisk

forecastforSan

Francisco,where

changesincolour

indicateground

displacement

SanFranciscoliesona

systemofsignificant

faultzones,including

theSanAndreasFault,

meaningthereis a high

risk of earthquakes