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Aneweraofearthquakescience

Humanactivitysometimescausesearthquakes–particularlywhenlargemassesofmaterialaremovedfromoneareatoanother,orwhenfluidsareextractedorinjectedintothesubsurface.Impoundmentofwateronthesurfacebehinddams,openpitandundergroundmining,andwastewaterinjectionhaveallbeenlinkedto

changesinthefrequencyofregionalearthquakes.Someofthesechanges,suchasthosethatoccurinareasofgeothermalpowergeneration,aresubtle,sincetheyoccurinregionsthatmaynaturallyexperiencefrequentearthquakes.Others,suchasthosenowoccurringinthecentralUnitedStates,representasignificantchange.

UnderstandingInducedEarthquakes

Earthquakesarenowoccurringinareaswithlittlehistoricalseismicityasaresultofactivitiesassociatedwithresourceextraction.TheNISARsatellitemissionwillimproveourabilitytocharacterizesuchinducedearthquakes,andincreaseourunderstandingofchangingearthquakelikelihoods.

TheNISARMission–Reliable,ConsistentObservations

TheNASA–ISROSyntheticApertureRadar(NISAR)mission,acollaborationbetweentheNationalAeronauticsandSpaceAdministration(NASA)andtheIndianSpaceResearchOrganization(ISRO),willprovideall-weather,day/nightimagingofnearlytheentirelandandicemassesoftheEarthrepeated4-6timespermonth.NISAR’sorbitingradarswillimageatresolutionsof5-10meterstoidentifyandtracksubtlemovementoftheEarth’slandanditsseaice,andevenprovideinformationaboutwhatishappeningbelowthesurface. Its repeatedsetofhigh resolution images can inform resourcemanagementandbeusedtodetectsmall-scalechangesbeforetheyarevisibletotheeye.Productsareexpectedtobeavailable1-2daysafterobservation,andwithinhoursinresponsetodisasters,providingactionable,timelydataformanyapplications.

The changing landscape of earthquake hazards

Overthepastseveraldecades,thenumberofearthquakesobservedinthecentralandeasternUnitedStateshasjumpeddramatically,fromanaverageof21earthquakesper yearwithmagnitude threeor larger from1973to2008,upto659in2014.Theincreaseisstrongestinareasthatalsosawastrong upward trend in the volume of wastewater injected into thesubsurface.Observationsofhowthegroundsurfacerisesorfallsduringanearthquakeallowscientiststodeterminewheretheearthquakeoccurred,howdeepandlarge it was, and whether there is evidence of additional motion thatoccurredmoreslowlybeforeoraftertheevent.Image(clockwise):USGS,USBR(CCBY-SA2.0),USGS,Ficelloguy/EnglishWikipedia(CCBY-SA3.0)

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Continuedfromfrontpage

The past decade has seen a substantial increase inthe number of earthquakes triggered by humanactivity,particularlythe injectionandproductionofsubsurface fluids associated with hydrocarbonproduction. Oklahoma now experiences moreearthquakes each year than California. Efforts toreduce our society’s reliance on fossil fuels alsocompound the problem, with increases inearthquake frequency associated with energyproductionatgeothermalpowerplantsandatlargedams that contribute hydrothermal power to theelectricitygrid.The increased frequency of earthquakes in regionssuch as the central United States create newchallenges, particularly since the energy andresource needs of our population are likely tocontinue to grow. Even forecasting the expecteddamagefromthesenewtypesofearthquakesisnotjust“businessasusual.”Analysesofshakingreportsfrom the central United States suggest that thedistribution of damage from these earthquakes,which tend to be shallower and could have moreinvolvementfromfluidswithintherock,aredifferentfrom the damage expected from “traditional”

earthquakes,whichoftenoccurdeepunderground.Preciseestimatesofthelocationandtimingoftheseearthquakes are needed to characterize how theyinteractwitheachotherandwiththeperturbationstothesubsurfacethataredrivingthem.The upcoming NISAR radar mission includes adependable,regularobservationplanthatwillcollecthighresolutionimagesover90%oftheEarth’slandsurfacesatweeklyintervals.NISAR’sfocusonregularand repeated observations contrasts with that ofexisting satellite synthetic aperture radars, whichtypicallyfocusonlyonareasofinteresttoaspecificgovernment or scientific agency. This leaves outmuchoftheUnitedStates,becausenoneoftheotherradars are U.S.missions. For instance, the centraland eastern United States was not observedfrequently,ifatall,bymostpreviousmissions.TheobservationsmadeoverthelifetimeofNISARwillbeagiantstepforwardinourunderstandingofinducedseismicity, and will inform the next generation ofmethods for characterizing and managing thesehazards.

Numberofearthquakesequenceseachyearthatcontainatleastonemagnitude3orlargerearthquake,since1973,forCalifornia(lightblue)andOklahoma(darkblue).FromMcGarretal.,2015,inthejournalScience.

Recentadvancesinthetechnologyusedinhydrocarbonproduction,including enhanced oil recovery and increases in the volume ofwastewater injected into the subsurface, are associated with adramatic increase in earthquakes felt in the centralUnited Statessince the mid-2000’s. Damaging earthquakes only appear to berelatedtoasmallfractionofwells,butthereisnotyetenoughdatatodefinitively determine in advance the safetyof operations at aparticularsite.Earthquake locationsderived from seismicdata (see figure at left)illuminatepart of the picture – new research shows that inducedearthquakes may behave in slightly different ways than “natural”events,providingapotentialpathwaytobetterunderstandingandmanagement. However, seismic data is blind to the slow, longertermdeformationof the ground surfaceassociatedwithpumping,injection and even incipient creep on faults that will eventuallyrupture in a more damaging earthquake. NISAR can provide themissinglinktothispuzzle,complementingtheavailableseismicdataandhelpingtotrackhowpatternsoffluidflowbeneaththesurfacerelatetopatternsofobservedearthquakes.

Increasing rates of earthquakes in the central United States.

-California-Oklahoma

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Inducedearthquakesimagedfromspace: Satellite-basedradarimagery,whenavailable,canbean extraordinary tool for characterizing how theEarth’s surface warps and deforms before, during,and after induced earthquakes. However, theseobservations cannot be made when the groundsurface changes significantly between imageacquisitions. Growthofcrops,tillingoffields,treessheddingtheirleavesareallprocessesthatdegradedataquality. Theexamplesofinducedearthquakesin thecentralUnitedStatesshownbelowarecaseswherewewerefortunatetohavedatabothbefore

andaftertheearthquake.Manyotherearthquakesin these regions have been impossible to studybecause of the complete lack of data before theevent.This situationcanchange in the future:NISARdatawouldbeacquired regularlyover theentireUnitedStates, allowing imaging of areas like Oklahoma,Texas andKansas that haveboth active agricultureandhydrocarbon/waterresourcedevelopment.

Right:Eventinyearthquakescanbeimagedwhenenoughdatais available. This image uses data from the European SpaceAgency’s TerraSAR-X platform to constrain subsidence of theground during a 2013 magnitude 3.2 earthquake within theChicagometropolitanarea,triggeredbyablastatalimestonequarry. Color indicates displacement of the ground surfacetowardsorawayfromthesatellite,whichwastravelingtothenorthwestinthedirectionofthebluearrowandaimeddowntowardstheEarthinthedirectionoftheredarrow.Theobserveddisplacement shown here tightly constrains the depth of thisearthquaketo700meters,muchshallowerthanthezonewhere“natural”earthquakesoccur.

Examples:

Left: NISAR data will permit systematic mapping and monitoring ofearthquakes,eveninagriculturallyactiveareas.Inthisexample,usingdatafromtheEuropeanSpaceAgency’sSentinel-1aand-1bplatforms,wecanseeseveralcentimetersofdisplacementovera10kmx10kmregionassociatedwiththe2016magnitude5.8Pawnee,Oklahoma,earthquake.Themainearthquakelocation(redstar)andaftershocks(blackdots)outlineacomplicatedpatternthatprovidesinsightintothepatternsofweaknessinthesubsurface.Alsointhisimage(redbandonleft)isthesignatureofalargestormthatwaspresentduringoneoftheimageacquisitions.Whenmanyimagesareavailable,suchaswouldbeprovidedbyNISAR,suchatmosphericeffectscanbeaveragedoutmoreeffectivelytodeterminethetruegroundmovement.

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Formoreinformation:

Generalintroduction:https://earthquake.usgs.gov/research/induced/http://nisar.jpl.nasa.gov/

CommunityreportsPetersen,M.D.etal.(2016),2016One-yearseismichazardforecastfortheCentralandEasternUnited

Statesfrominducedandnaturalearthquakes,U.S.GeologicalSurveyOpen-FileReport2016-1035,52p.,doi:10.3133/ofr20161035.

McGarr,A.etal.(2015),Copingwithearthquakesinducedbyfluidinjection,Science,347;doi:10.1126/science.aaa0494.

NationalResearchCouncil(2013),CommitteeonInducedSeismicityPotentialinEnergyTechnologies.

Inducedseismicitypotentialinenergytechnologies.NationalAcademiesPress,2013.NationalEarthquakeResilience:Research,Implementation,andOutreach(2011),NationalAcademies

Press,Washington,D.C.

Relevantscientificpapers.Jha,B.,etal.(2015),Reservoircharacterizationinanundergroundgasstoragefieldusingjointinversion

offlowandgeodeticdata,Int.J.Numer.Anal.Meth.Geomech,39,1619–1638.Yang,Qi.,etal.(2015),InSARmonitoringofgrounddeformationduetoCO2injectionatanenhancedoil

recoverysite,WestTexas,InternationalJournalofGreenhouseGasControl41;doi:10.1016/j.ijggc.2015.06.016.

Hough,S.E.(2015),Shakingintensityfrominjection-inducedversustectonicearthquakesinthecentral-

easternUnitedStates,TheLeadingEdge34;doi:10.1190/tle34060690.1.Keranen,K.M.etal.(2014),SharpincreaseincentralOklahomaseismicitysince2008inducedbymassive

wastewaterinjection,Science,345;doi:10.1126/science.1255802.Barnhart,W.etal.(2014),Seismologicalandgeodeticconstraintsonthe2011Mw5.3Trinidad,Colorado

earthquakeandinduceddeformationintheRatonBasin,J.Geophys.Res.,119;doi:10.1002/2014JB011227.

Ellsworth,W.L.(2013),Injection-inducedearthquakes,Science,341;doi:10.1126/science.1225942.González,P.J.etal.(2012),The2011Lorcaearthquakeslipdistributioncontrolledbygroundwater

crustalunloading,NatureGeoscience,5;doi:10.1038/ngeo1610.Ketelaar,V.B.H.(2009),SubsidenceduetohydrocarbonproductionintheNetherlands,In:Satellite

RadarInterferometry:SubsidenceMonitoringTechniques,Springer,London,doi:10.1007/978-1-4020-9428-6_2

NationalAeronauticsandSpaceAdministration Formoreinformation,visithttp://nisar.jpl.nasa.gov/applications

JetPropulsionLaboratory/CaliforniaInstituteofTechnology/Pasadena,California/www.jpl.nasa.gov