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dc.contributor.authorSegall, Paul
dc.contributor.authorRubin, Allan M.
dc.contributor.authorBradley, Andrew M.
dc.contributor.authorRice, James R.
dc.date.accessioned2011-07-15T18:22:06Z
dc.date.issued2010
dc.identifier.citationSegall, Paul, Allan M. Rubin, Andrew M. Bradley, and James R. Rice. 2010. Dilatant strengthening as a mechanism for slow slip events. Journal of Geophysical Research 115:B12305.en_US
dc.identifier.issn0148-0227en_US
dc.identifier.urihttp://nrs.harvard.edu/urn-3:HUL.InstRepos:5026690
dc.description.abstractThe mechanics of slow slip events (SSE) in subduction zones remain unresolved. We suggest that SSE nucleate in areas of unstable friction under drained conditions, but as slip accelerates dilatancy reduces pore pressure \(p\) quenching instability. Competition between dilatant strengthening and thermal pressurization may control whether slip is slow or fast. We model SSE with 2‐D elasticity, rate-state friction, and a dilatancy law where porosity \(\phi\) evolves toward steady state \(\phi_{ss}\) over distance \(d_c\) and \(\phi_{ss}=\phi_0+\epsilon ln(v/v_0)\); \(v\) is slip speed. We consider two diffusion models. Membrane diffusion (MD) is approximated by \(-(p-p^{\infty})/t_f\) where \(p\) and \(p^{\infty}\) are shear zone and remote pore pressure and \(t_f\) is a characteristic diffusion time. Homogeneous diffusion (HD) accurately models fault-normal flow with diffusivity \(C_{hyd}\). For MD, linearized analysis defines a boundary \(\epsilon \equiv 1-a/b\) between slow and fast slip, where \(\epsilon \equiv f_0 \epsilon /\beta b(\sigma-p^{\infty})\), \(f_0\), \(a\), and \(b\) are friction parameters and \(\beta\) is compressibility. When \(\epsilon < 1-a/b\) slip accelerates to instability for sufficiently large faults, whereas for \(\epsilon > 1-a/b\) slip speeds remain quasi-static. For \(HD\), \(E_p\equiv \epsilon h/(\beta (\sigma-p^{\infty})\sqrt{v^\infty / C_{hyd}d_c} )\) defines dilatancy efficiency, where \(h\) is shear zone thickness and \(v^{\infty}\) is plate viscosity. SSE are favored by large \(\epsilon h\) and low effective stress. The ratio \(E_p\) to thermal pressurization efficiency scales with \(1/(\sigma - p^{\infty})\), so high \(p^{\infty}\) favors SSE, consistent with seismic observations. Model updip propagation speeds are comparable to those observed along-strike. Many simulations exhibit slow phases driven by steady downdip slip and faster phases that relax the accumulated stress. Model SSE accomodate only a fraction of pale motion; the remaining deficit must be accommodated during coseismic or postseismic slip.en_US
dc.description.sponsorshipEarth and Planetary Sciencesen_US
dc.description.sponsorshipEngineering and Applied Sciencesen_US
dc.language.isoen_USen_US
dc.publisherAmerican Geophysical Unionen_US
dc.relation.isversionofdoi:10.1029/2010JB007449en_US
dash.licenseLAA
dc.titleDilatant Strengthening as a Mechanism for Slow Slip Eventsen_US
dc.typeJournal Articleen_US
dc.description.versionVersion of Recorden_US
dc.relation.journalJournal of Geophysical Researchen_US
dash.depositing.authorRice, James R.
dc.date.available2011-07-15T18:22:06Z
dc.identifier.doi10.1029/2010JB007449*
dash.contributor.affiliatedRice, James


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