Aseismic sliding of active faults by pressure solution creep: Evidence from the San Andreas Fault Observatory at Depth

Gratier, Jean‐Pierre; Richard, J.; Renard, François; Mittempergher, Silvia; Doan, Mai‐Linh; Toro, Giulio Di; Hadizadeh, J.; Boullier, Anne-Marie

doi:10.1130/g32073.1

Cited by 121 publications

(118 citation statements)

References 21 publications

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“…Dissolutione precipitation processes are operative during co-seismic and aseismic slip (Gratier and Gamond, 1990;Gratier et al, 2011;Chen et al, 2013). Pressure-solution seams and soluble minerals such as feldspar, quartz and calcite are present in SAFOD as well as TCDP samples.…”

Section: Dissolutioneprecipitation Processesmentioning

confidence: 99%

Faulting processes in active faults – Evidences from TCDP and SAFOD drill core samples

Janssen

Wirth

Wenk

et al. 2014

Journal of Structural Geology

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a b s t r a c tThe microstructures, mineralogy and chemistry of representative samples collected from the cores of the San Andreas Fault drill hole (SAFOD) and the Taiwan Chelungpu-Fault Drilling project (TCDP) have been studied using optical microscopy, TEM, SEM, XRD and XRF analyses. SAFOD samples provide a transect across undeformed host rock, the fault damage zone and currently active deforming zones of the San Andreas Fault. TCDP samples are retrieved from the principal slip zone (PSZ) and from the surrounding damage zone of the Chelungpu Fault. Substantial differences exist in the clay mineralogy of SAFOD and TCDP fault gouge samples. Amorphous material has been observed in SAFOD as well as TCDP samples. In line with previous publications, we propose that melt, observed in TCDP black gouge samples, was produced by seismic slip (melt origin) whereas amorphous material in SAFOD samples was formed by comminution of grains (crush origin) rather than by melting. Dauphiné twins in quartz grains of SAFOD and TCDP samples may indicate high seismic stress. The differences in the crystallographic preferred orientation of calcite between SAFOD and TCDP samples are significant. Microstructures resulting from dissolutioneprecipitation processes were observed in both faults but are more frequently found in SAFOD samples than in TCDP fault rocks. As already described for many other fault zones clay-gouge fabrics are quite weak in SAFOD and TCDP samples. Clay-clast aggregates (CCAs), proposed to indicate frictional heating and thermal pressurization, occur in material taken from the PSZ of the Chelungpu Fault, as well as within and outside of the SAFOD deforming zones, indicating that these microstructures were formed over a wide range of slip rates.

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Section: Dissolutioneprecipitation Processesmentioning

confidence: 99%

Faulting processes in active faults – Evidences from TCDP and SAFOD drill core samples

Janssen

Wirth

Wenk

et al. 2014

Journal of Structural Geology

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“…These initiatives have recovered samples of fault rock and gouge and conducted measurements of in situ stress, fluid chemistry, and temperature at depths where earthquakes nucleate. Samples and data emerging from these drilling projects provide an unparalleled opportunity to gain new insight into absolute fault strength [e.g., Brune et al, 1969;Zoback et al, 1987;Scholz, 2000;Carpenter et al, 2012], causes of apparent fault weakness [e.g., Rice, 1992;Faulkner and Rutter, 2001;Brantut et al, 2011;Gratier et al, 2011;Lockner et al, 2011], and the laws that govern fault slip and failure [e.g., Dieterich, 1979;Marone, 1998a;Ikari et al, 2009;Carpenter et al, 2011;Sone et al, 2012].…”

Section: Introductionmentioning

confidence: 99%

Frictional properties of the active San Andreas Fault at SAFOD: Implications for fault strength and slip behavior

2015

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We present results from a comprehensive laboratory study of the frictional strength and constitutive properties for all three active strands of the San Andreas Fault penetrated in the San Andreas Observatory at Depth (SAFOD). The SAFOD borehole penetrated the Southwest Deforming Zone (SDZ), the Central Deforming Zone (CDZ), both of which are actively creeping, and the Northeast Boundary Fault (NBF). Our results include measurements of the frictional properties of cuttings and core samples recovered at depths of ~2.7 km. We find that materials from the two actively creeping faults exhibit low frictional strengths (μ = ~0.1), velocity‐strengthening friction behavior, and near‐zero or negative rates of frictional healing. Our experimental data set shows that the center of the CDZ is the weakest section of the San Andreas Fault, with μ = ~0.10. Fault weakness is highly localized and likely caused by abundant magnesium‐rich clays. In contrast, serpentine from within the SDZ, and wall rock of both the SDZ and CDZ, exhibits velocity‐weakening friction behavior and positive healing rates, consistent with nearby repeating microearthquakes. Finally, we document higher friction coefficients (μ > 0.4) and complex rate‐dependent behavior for samples recovered across the NBF. In total, our data provide an integrated view of fault behavior for the three active fault strands encountered at SAFOD and offer a consistent explanation for observations of creep and microearthquakes along weak fault zones within a strong crust.

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“…The mineralogical assemblage is partially inherited from the host rock but displays a stronger fabric with well-expressed CS structures. Aseismic sliding of active fault by pressure solution creep has been well documented in the San Andreas Fault observatory at depth by Gratier et al (2011) who demonstrate that such mechanism can accommodate 20 mm/year sliding.…”

Section: Discussionmentioning

confidence: 99%

“…Takahashi et al 2007;Ikari et al 2011). In the San Andrea fault observatory at depth (SAFOD) core samples, the weakening of the San Andreas fault zone down to depths of at least 3 km is attributed to the pervasive development of interconnected networks of low friction smectitic phyllosilicates and to the operation of stress-induced solutionprecipitation creep mechanisms (Holdsworth et al 2011;Gratier et al 2011). Morrow et al (2000) have demonstrated that the frictional strength of clay minerals is inversely dependant on their capacity to adsorb water and therefore, may influence fault behaviour.…”

Section: Introductionmentioning

confidence: 99%

Microtextural investigation (SEM and TEM study) of phyllosilicates in a major thrust fault zone (Monte Perdido, southern Pyrenees): impact on fault reactivation

et al. 2012

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Thrusting fault zone in foreland basins are characterized by highly foliated zones generally enriched in phyllosilicates which can play a major role on the mechanical behaviour of the fault. In this context, investigations of synkinematic clay minerals permit to determine the origin of the fluid from which they precipitated as well as the mechanisms of deformation. Our study is focused on clay mineral assemblages (illite and chlorite) in a major thrust fault located in the Monte Perdido massif (southern Pyrenees), a shallow thrust that affects upper cretaceouspaleocene platform carbonates and lower Eocene marls and turbidites. It implied 3 km of displacement of the Monte Perdido thrust unit with respect to the underlying Gavarnie unit. In this area the cleavage development by pressuresolution is linked to the Monte Perdido and Gavarnie thrust activity. The core zone of the fault, about 6 m thick, consists of an interval of intensely deformed clay-bearing rocks bounded by major shear surfaces. The deformed sediment is markedly darker than the protolith. Calcitequartz shear veins along the shear planes are abundant. Detailed SEM and TEM observations of highly deformed fault zone samples indicate that clay mineral enrichment in the core zone of the fault is not only related to passive increase by pressure-solution mechanism but that dissolution-recrystallization of phyllosilicates occurs during deformation. A mineral segregation is observed in the highly deformed zone. Newly formed 2M 1 muscovite is present along the cleavage whereas IIb chlorite crystals fill S V 2 shear veins suggesting syntectonic growth of phyllosilicates in the presence of fluids in low-grade metamorphic conditions. These mineralogical reactions act as weakening processes and would favour Monte Perdido fault creeping.

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Aseismic sliding of active faults by pressure solution creep: Evidence from the San Andreas Fault Observatory at Depth

Cited by 121 publications

References 21 publications

Faulting processes in active faults – Evidences from TCDP and SAFOD drill core samples

Faulting processes in active faults – Evidences from TCDP and SAFOD drill core samples

Frictional properties of the active San Andreas Fault at SAFOD: Implications for fault strength and slip behavior

Microtextural investigation (SEM and TEM study) of phyllosilicates in a major thrust fault zone (Monte Perdido, southern Pyrenees): impact on fault reactivation

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