Publication Date:
2021-12-16
Description:
While itiswidelyrecognizedthatfluidsinfluencefaultstrengthandearthquakenucleation,propaga-
tion andarrest,theireffectsonco-seismicslidingfrictionareonlyconjectured.Toshedlightonthese
effects,55highvelocity(41 m s 1) frictionexperimentswereconductedatroomtemperatureon
Carraramarblesamplesinthepresenceofporefluid(upto15MPaporepressure),room-humidityand
‘‘vacuum’’(10 4 mbar)conditions.Inalltheexperiments,thefrictioncoefficientevolvedfromapeak
value of0.6–0.8toasteady-statevalueof0.1inabout1–1.5mofslip.However,experiments
performedinthepresenceofporefluidhadalargeandmoreabruptdecreaseinfrictionatthe
initiationofsliding(65%after20mmofslip),whereasexperimentsperformedundervacuumandroom
humidityconditionsshowedinitialvelocity-strengtheningbehaviorfollowedbyamoregradual
reductioninfriction.Thisindicatesthatcalcite-bearingrocksaremorepronetoslipinthepresence
of water.Underroom-humidityconditions,CO2 was detectedduringtheentiredurationofthe
experiment.Inthepresenceofporefluid,HCO3 and Ca2þ were detectedforslips 40.1 m.Thelack
of decarbonationproducts(HCO3 and Ca2þ) inporefluidexperimentsforslip o0.1 mimpliesthat
the abruptweakeningisnotrelatedtodecarbonation(orthattheabundanceofthereactionproductsis
below theresolutionoftheanalyticalmethods).Giventhemodestthermalexpansionofwater,
the estimatedthermalpressurizationduringtheabruptweakeningappearstobenegligible.Instead,
we suggestthatabruptweakeningisduetosubcriticalcrack-growth,hydrolyticweakeningandbrittle
failureoftheasperitiesontheslidingsurfaces.Modelingshowsthattheoccurrenceinnatureof
co-seismic(water-present)decarbonationreactionssimilartothosetriggeredinthelaboratorycould
yield sufficientreactionproducttobedetectedinaquiferslocatedintheproximityofactivefaults.
Description:
Published
Description:
74-84
Description:
JCR Journal
Description:
restricted
Keywords:
earthquakes friction pore fluid carbonate-bearing rocks
;
04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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