Table Of ContentRock Physics
and Natural Hazards
Edited by
Sergio Vinciguerra
Yves Bernabé
Birkhäuser
Basel · Boston · Berlin
Reprint from Pure and Applied Geophysics
(PAGEOPH), Volume 166 (2009) No. 5 – 7
Editors
Sergio Vinciguerra Yves Bernabé
Sezione di Sismologia e Dept. Earth, Atmosphere
Tettonofisica & Planetary Sciences
Istituto Nazionale di Geofisica e Massachussets Institute of Technology
Vulcanologia (INGV) 77, Massachussets Ave.
Via di Vigna Murata 605 Cambridge, MA 02139
00143 Roma USA
Italy Email: [email protected]
Email: [email protected]
Library of Congress Control Number: 2009930008
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ISBN 978-3-0346-0121-4 Birkhäuser Verlag AG, Basel · Boston · Berlin
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Printed on acid-free paper produced from chlorine-free pulp. TCF ∞
Cover graphic: Based on a graphic from the article “Axial and Radial Permeability Evolutions
of Compressed Sandstones: End Effects and Shear-band Induced Permeability Anisotropy”
by J. Dautriat, N. Gland, J. Guelard, A. Dimanov and J. L. Raphanel.
Printed in Germany
ISBN 978-3-0346-0121-4 e-ISBN 978-3-0346-0122-1
9 8 7 6 5 4 3 2 1 www.birkhauser.ch
Pureappl.geophys.166(2009)737–739 (cid:3)Birkha¨userVerlag,Basel,2009
0033–4553/09/050737–3 Pure and Applied Geophysics
DOI10.1007/s00024-009-0507-0
Introduction
SERGIO VINCIGUERRA1 and YVES BERNABE´2
Natural hazards events such as earthquakes or volcanic eruptions involve activation of
coupled thermo-hydro-chemo-mechanical processes in rocks. The 7th Euro-Conference
of Rock Physics and Geomechanics, sponsored by the Italian Istituto Nazionale di
GeofisicaeVulcanologia(INGV),theFrenchCentreNationaldeRechercheScientifique
(CNRS) and Exxon-Mobil, was held September 25 to 30, 2007, in Erice (Italy), to
explore how rock physics experiments and models can facilitate understanding and
constraint of natural hazards’ mechanisms, and, to foster cross-disciplinary collabora-
tions. The Erice Conference was organized around six sessions: 1) fault healing, sealing
and rupture process, 2) rock deformation and coupled processes in rocks, 3) fault
structure and mechanics, from laboratory to exploratory drilling of major faults, 4)
fracture and flow in volcanic and geothermal areas, and physical properties of volcanic
rocks, 5) reservoir characterization and stimulation, 6) scaling laws, applications to
rupture mechanicsandfluidflow.Thepresenttopicalissue originatedfrom thedesireto
assemble in a single volume unpublished contributions to the Erice Conference. This
volumepresentsnewlaboratorydata,theoreticalandnumericalrockphysicsmodelsand
field observations relevant to the study of natural hazards.
The bulk of this topical issue is devoted to questions related to rock failure and
earthquake source mechanisms. BIZZARRI presents a review of various competing
mechanismswhichcontroldynamicfailureduringlargeearthquakesandattemptstoinfer
arealisticearthquakesourcemodelfromthem.GROBetal.advancethefactthat,despite
the huge reduction in scale, laboratory experiments sometimes display phenomena
strikingly similar to field observations and can therefore provide insight into natural
phenomena.Here,thetemporal andspatialdistributions ofevents during interface crack
propagation suggest that dynamic fracture propagation is controlled by elastic interac-
tions between structural heterogeneities. At the laboratory scale, NASSERI et al. explore
the relationship between fracture toughness and roughness in thermally (up to 850(cid:2)C)
treated Westerlygranite,whileFORTINetal.,STANCHITSetal.andBAUDetal.investigate
the relationship between competing deformation micro-mechanisms, as measured and
1 IstitutoNazionalediGeofisicaeVulcanologia, SezionediRoma1,ViadiVignaMurata605,
00143Rome,Italy.
2 Earth, Atmospheric and Planetary Sciences Department, Massachusetts Institute of Technology,
Cambridge,MA02139,U.S.A.
738 S.VinciguerraandY.Bernabe´ Pureappl.geophys.,
characterized by acoustic emission activity and microstructural observations, and strain
localization in sandstones and carbonates. The effect of a number of factors such as
confining pressure, porosity, and the presence or absence of water is investigated.
Pressure solution is another important example of a deformation mechanism involving
coupledchemicalandmechanicalprocesses.BERNABE´ etal.presentmicroscalenumerical
simulations of pressure solution creep, and attempt to interpret them via a commonly
used, generic creep law. This creep law could be, in turn, incorporated into models of
fault gouge healing during the seismic cycle. Mechanical and transport properties of
rocks are known to be coupled in many field situations. In order to help constrain this
typeofproblem,NASSERIetal.proposeaneffectivemedium-basedinversionschemeand
employ it to infer the mechanical properties and permeability of thermally cracked
Westerly granite under isostatic compression from experimental data. The transport
propertiesofrocksare,ofcourse,primarilycontrolledbythegeometryoftheporespace.
PAPE and CLAUSER propose a novel model linking the Nuclear Magnetic Resonance T1
andT2distributionstopermeabilityinrockswithfractalporespace.Contrarytoprevious
models,whichassumethatporesareisolated,thenewmodelincludestheeffectofproton
diffusioncouplingbetweenconnectedpores.BERNABE´ revisitsACflowofacompressible
fluidthroughasingledeformablepipeandheterogeneouspipenetworks.TheseACflow
waves may occur in open fractures, possibly causing resonance effects such as might be
involved in volcanic tremors. Shear deformation in the Earth, ductile and/or brittle, is
often associated with anisotropy of the rock physical properties. CIRRINCIONE et al.
document microstructural evidence of this process in naturally deformed leuco-gneiss
from an Alpine shear zone while CHEN et al. characterize the anisotropy of permeability
in cores from the Chelungpu fault and assess the implications of their findings to fault
models and weakening mechanisms inferred for the Chi-Chi Earthquake. At the
laboratory scale, DAUTRIAT et al. and LOUIS et al. investigate stress-induced anisotropy
and its possible control by the transport properties and pre-existing fabric, respectively.
Finally, rock physics techniques and models can be applied or tested in geotechnical
applications such as geothermal energy recovery or oil/gas production. The work of
ZIMMERMANNetal.andBLO¨CHERetal.stresstheimportanceofhydro-mechanicalcoupling
foroptimalreservoirmanagement.PAPEetal.estimaterockpermeabilityatthewell-bore
and core scale, based on Nuclear Magnetic Resonance T1 and T2 measurements.
Although most studies in this topical issue are not directly devoted to natural hazards,
they present rock physics data and models that can be applied to the rock mechanisms
and processes occurring during events such as earthquakes or volcanic eruptions.
Acknowledgements
Theguesteditorsarethankfultothecontributorsfortheircommitmentandenthusiasm
andtoRenataDmowskaforprovidingeditorialguidance.Theyalsorecognizetheefforts
of the colleagues who conscientiously performed critical reviews of the papers:
M.Balme,P.Baud,P.Benson,Y.Bernabe´,P.Besuelle,A.Bizzarri,M.Cocco,C.David,
Vol.166,2009 Introduction 739
G. Dresen, D. Faulkner, J. Fortin, P. Glover, J-P. Gratier, Y. Gue´guen, B. Haimson, M.
Heap,H.Kern,I.Main,A.Maineult,C.Marone,P.Meredith,A.Niemeijer,D.Olgaard,
T. Reuschle´, F. Rossetti, J. Rudnicki, A. Schubnel, S. Shapiro, S. Stanchits, T.-f. Wong,
W. Zhu.
Pureappl.geophys.166(2009)741–776 (cid:3)Birkha¨userVerlag,Basel,2009
0033–4553/09/050741–36 Pure and Applied Geophysics
DOI10.1007/s00024-009-0494-1
WhatDoesControlEarthquakeRupturesandDynamicFaulting?AReview
ofDifferent Competing Mechanisms
ANDREA BIZZARRI
Abstract—Thefaultweakeningoccurringduringanearthquakeandthetemporalevolutionofthetraction
onaseismogenicfaultdependonseveralphysicalmechanisms,potentiallyconcurrentandinteracting.Recent
laboratoryexperimentsandgeologicalfieldobservationsofnaturalfaultsrevealedthepresence,andsometime
thecoexistence,ofthermallyactivatedprocesses(suchasthermalpressurizationofporefluids,meltingofgouge
and rocks, material property changes, thermally-induced chemical environment evolution), elasto-dynamic
lubrication,porosityandpermeabilityevolution,gougefragmentationandwear,etc.Inthispaper,byreviewing
inaunifyingsketchallpossiblechemico–physicalmechanismsthatcanaffectthetractionevolution,wesuggest
how they can be incorporated in a realistic fault governing equation. We will also show that simplified
theoreticalmodelsthatidealisticallyneglectthesephenomenaappeartobeinadequatetodescribeasrealistically
aspossiblethedetailsofbreakdownprocess(i.e.,thestressrelease)andtheconsequenthighfrequencyseismic
waveradiation.Quantitativeestimatesshowthatinmostcasestheincorporationofsuchnonlinearphenomena
has significant, often dramatic, effects on the fault weakening and on the dynamic rupture propagation.The
range of variability of the value of some parameters, the uncertainties in the relative weight of the various
competingmechanisms,andthedifferenceintheircharacteristiclengthandtimescalessometimeindicatethat
the formulation of a realistic governing law still requires joint efforts from theoretical models, laboratory
experimentsandfieldobservations.
Keywords: Rheologyandfrictionofthefaultzones,constitutivelaws,mechanicsoffaulting,earthquake
dynamics,computationalseismology.
1. Introduction
Contrary to other ambits of physics, seismology presently lacks knowledge of exact
physical law which governs natural faults and makes the understanding of earthquakes
feasiblefromadeterministicpointofview.Inadditiontotheubiquitousignoranceofthe
initial conditions (i.e., the initial state) of the seismogenic region of interest, we also
ignoretheequationsthatcontrolthetractionevolutiononthefaultsurface;thishasbeen
recently recognized as one of the grand challenges for seismology (http://www.iris.edu/
hq/lrsps/seis_lrp_12_08_08.pdf, December 2008). Indirect information comes from
theoreticalandnumericalstudies,which,undersomeassumptionsandhypotheses,tryto
reproduce real–world events and aim to infer some constraints from a systematic
IstitutoNazionalediGeofisicaeVulcanologia,SezionediBologna,Italy.E-mail:[email protected]
