Mechanisms for permeability modification in the damage zone of a normal fault, northern Perth Basin, Western Australia

La Garriga-Samal&#250;s geothermal system is located in the Catalan Coastal Ranges (CCR) (NE Spain). The CCR is a NE-SW horst and graben system with two lifted mountain chains, the Precoastal (PR) and Coastal ranges (CR), separated by the Vall&#232;s basin. An Hercynian highly fractured granodiorite thrusts the Paleozoic metamorphic units in the northern part of the PR. Towards the south, the intrusive unit is in contact with the Miocene rocks of the Vall&#232;s basin by a major Neogene normal fault, the Vall&#232;s fault.Previous works in this area showed that the fractured zone associated to the Vall&#232;s normal fault, located in the Hercynian granodiorite, could act as the geothermal reservoir as well as the fast-ascending path for the hot fluids. Although some geophysical prospections and exploration boreholes have been made in La Garriga-Samal&#250;s area, it is still necessary to understand and model the fracture network.This study presents a multiscale fracture analysis of the granodiorite from outcrops and boreholes samples. This multiscale analysis combines satellite pictures, field studies and laboratory measurements of both field and borehole samples.The fracture data collection has allowed the identification of 3 major fracture sets related to the main tectonic events of the CCR, in addition to 7 other minor fracture groups. Through the variation of fracture density in the footwall, a 10 meters fault core, and an asymmetric damage zone of approximately 300 m, have been identified. The damage zone shows an increasing fracture density towards the northern and southern limits of the granodiorite, which are an alpine thrust and the Vall&#232;s fault, respectively. In the fault core, the presence of cemented rocks like cataclasites with hydrothermal sealed fractures result in low porosity and permeability. Contrary, the damage zone consists of minor faults and related fractures which may enhance fault permeability with respect the core and its protolith.In order to characterize fractures in depth, the borehole samples have been digitized via photogrammetry method. The study of the point cloud related to this samples have allowed the identification and characterization of some of the fractures sets at greater depths. The permeability differences between the fault core and the damage zone can be also identified in the borehole samples. The presence of centimetric open fractures, cavities, and hydrothermal minerals, confirm the circulation of thermal fluids. Meanwhile, other samples within the fault trace are compact rocks, with slickensides and high-pressure alteration minerals.These fracture results have been also correlated with a previous 2D magnetotelluric (MT) model which shows the Vall&#232;s fault zone as a low resistivity unit. The fault zone may give a low resistivity value only if it is permeable and water saturated. Therefore, our results identify the damage zone of the Vall&#232;s fault as the potential reservoir of La Garriga-Samal&#250;s geothermal system.

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Controls on damage zone asymmetry of a normal fault zone: outcrop analyses of a segment of the Moab fault, SE Utah

Journal of Structural Geology ◽

10.1016/j.jsg.2005.04.012 ◽

2005 ◽

Vol 27 (10) ◽

pp. 1803-1822 ◽

Cited By ~ 115

Author(s):

Silje S. Berg ◽

Tore Skar

Keyword(s):

Fault Zone ◽

Damage Zone ◽

Normal Fault

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Monitoring the response of volcanic CO2 emissions to changes in the Los Humeros hydrothermal system

Scientific Reports ◽

10.1038/s41598-021-97023-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Anna Jentsch ◽

Walter Duesing ◽

Egbert Jolie ◽

Martin Zimmer

Keyword(s):

Fluid Flow ◽

Hydrothermal System ◽

Damage Zone ◽

Inverse Correlation ◽

Normal Fault ◽

Atmospheric Effects ◽

Volcanic Complex ◽

Geothermal Resources ◽

Gas Emissions ◽

Soil Degassing

AbstractCarbon dioxide is the most abundant, non-condensable gas in volcanic systems, released into the atmosphere through either diffuse or advective fluid flow. The emission of substantial amounts of CO2 at Earth’s surface is not only controlled by volcanic plumes during periods of eruptive activity or fumaroles, but also by soil degassing along permeable structures in the subsurface. Monitoring of these processes is of utmost importance for volcanic hazard analyses, and is also relevant for managing geothermal resources. Fluid-bearing faults are key elements of economic value for geothermal power generation. Here, we describe for the first time how sensitively and quickly natural gas emissions react to changes within a deep hydrothermal system due to geothermal fluid reinjection. For this purpose, we deployed an automated, multi-chamber CO2 flux monitoring system within the damage zone of a deep-rooted major normal fault in the Los Humeros Volcanic Complex (LHVC) in Mexico and recorded data over a period of five months. After removing the atmospheric effects on variations in CO2 flux, we calculated correlation coefficients between residual CO2 emissions and reinjection rates, identifying an inverse correlation of ρ = − 0.51 to − 0.66. Our results indicate that gas emissions respond to changes in reinjection rates within 24 h, proving an active hydraulic communication between the hydrothermal system and Earth’s surface. This finding is a promising indication not only for geothermal reservoir monitoring but also for advanced long-term volcanic risk analysis. Response times allow for estimation of fluid migration velocities, which is a key constraint for conceptual and numerical modelling of fluid flow in fracture-dominated systems.

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Geometry and kinematics of the Baza Fault (central Betic Cordillera, South Spain): insights into its seismic potential

Geologica Acta ◽

10.1344/geologicaacta2020.18.11 ◽

2020 ◽

Vol 18 ◽

pp. 1-25

Author(s):

I. Medina-Cascales ◽

I. Martin-Rojas ◽

F.J. García-Tortosa ◽

J.A. Peláez ◽

P. Alfaro

Keyword(s):

Structural Characterization ◽

Damage Zone ◽

Active Faults ◽

Normal Fault ◽

Betic Cordillera ◽

Surface Geometry ◽

Seismic Potential ◽

Vertical Displacements ◽

Fault Kinematics ◽

Geometry And Kinematics

The geometry and kinematics of active faults have a significant impact on their seismic potential. In this work, a structural characterization of the active Baza Fault (central Betic Cordillera, southern Spain) combining surface and subsurface data is presented. Two sectors are defined based on their surface geometry: a northern sector striking N–S to NNW–SSE with a narrow damage zone and a southern sector striking NW–SE with a wide damage zone. A kinematic analysis shows pure normal fault kinematics along most of the fault. Geometric differences between the northern and southern sectors are caused by i) a heterogeneous basement controlling the fault geometry at depth and in the cover; ii) different orientations of the Baza Fault in the basement with respect to the regional extension direction and iii) interaction with other active faults. We use this structural characterization to analyse the segmentation of the Baza Fault. According to segmentation criteria, the entire Baza Fault should be considered a single fault seismogenic segment. Consequently, the seismic potential of the fault is defined for a complete rupture. Magnitude for the Mmax event is calculated using several scale relationships, obtaining values ranging between Mw 6.6 and Mw 7.1. Recurrence times range between approximately 2,000 and 2,200 years for Mmax events and between 5,300 and 5,400 years for palaeo-events. A geodetic scenario modelled for an Mmax event of Mw 6.7 shows permanent vertical displacements of more than 0.40m and an overall WSW–ENE extension during entire ruptures of the Baza Fault.

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Structural characterization of fault damage zones in carbonates (Central Apennines, Italy)

10.5194/egusphere-egu21-1525 ◽

2021 ◽

Author(s):

Miriana Chinello ◽

Michele Fondriest ◽

Giulio Di Toro

Keyword(s):

Fault Zone ◽

Hanging Wall ◽

Damage Zone ◽

Normal Fault ◽

Vertical Displacement ◽

Fault System ◽

Normal Faults ◽

Central Apennines ◽

Fault Surface ◽

Fracture Intensity

The Italian Central Apennines are one of the most seismically active areas in the Mediterranean (e.g., L&#8217;Aquila 2009, Mw 6.3 earthquake). The mainshocks and the aftershocks of these earthquake sequences propagate and often nucleate in fault zones cutting km-thick limestones and dolostones formations. An impressive feature of these faults is the presence, at their footwall, of few meters to hundreds of meters thick damage zones. However, the mechanism of formation of these damage zones and their role during (1) individual seismic ruptures (e.g., rupture arrest), (2) seismic sequences (e.g., aftershock evolution) and (3) seismic cycle (e.g., long term fault zone healing) are unknown. This limitation is also due to the lack of knowledge regarding the distribution, along strike and with depth, of damage with wall rock lithology, geometrical characteristics (fault length, inherited structures, etc.) and kinematic properties (cumulative displacement, strain rate, etc.) of the associated main faults.Previous high-resolution field structural surveys were performed on the Vado di Corno Fault Zone, a segment of the ca. 20 km long Campo Imperatore normal fault system, which accommodated ~ 1500 m of vertical displacement (Fondriest et al., 2020). The damage zone was up to 400 m thick and dominated by intensely fractured (1-2 cm spaced joints) dolomitized limestones with the thickest volumes at fault oversteps and where the fault cuts through an older thrust zone. Here we describe two minor faults located in the same area (Central Apennines), but with shorter length along strike. They both strike NNW-SSE and accommodated a vertical displacement of ~300 m.The Subequana Valley Fault is about 9 km long and consists of multiple segments disposed in an en-echelon array. The fault juxtaposes pelagic limestones at the footwall and quaternary deposits at the hanging wall. The damage zone is < 25 m &#160;thick &#160;and comprises fractured (1-2 cm spaced joints) limestones beds with decreasing fracture intensity moving away from the master fault. However, the damage zone thickness increases up to &#8764;100 m in proximity of subsidiary faults striking NNE-SSW. The latter could be reactivated inherited structures.The Monte Capo di Serre Fault is about 8 km long and characterized by a sharp ultra-polished master fault surface which cuts locally dolomitized Jurassic platform limestones. The damage zone is up to 120 m thick and cut by 10-20 cm spaced joints, but it reaches an higher fracture intensity where is cut by subsidiary, possibly inherited, faults striking NNE-SSW.Based on these preliminary observations, faults with similar displacement show comparable damage zone thicknesses. The most relevant damage zone thickness variations are related to geometrical complexities rather than changes in lithology (platform vs pelagic carbonates). &#160;In particular, the largest values of damage zone thickness and fracture intensity occur at fault overstep or are associated to inherited structures. The latter, by acting as strong or weak barriers (sensu Das and Aki, 1977) during the propagation of seismic ruptures, have a key role in the formation of damage zones and the growth of normal faults.

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Episodic fluid flow in an active fault

Geology ◽

10.1130/g46254.1 ◽

2019 ◽

Vol 47 (10) ◽

pp. 938-942 ◽

Cited By ~ 8

Author(s):

Sarah Louis ◽

Elco Luijendijk ◽

István Dunkl ◽

Mark Person

Keyword(s):

Fluid Flow ◽

Numerical Models ◽

Damage Zone ◽

Normal Fault ◽

Geothermal Gradient ◽

Hydrothermal Activity ◽

The Past ◽

Discharge Rates ◽

Fault Damage Zone ◽

Wide Zone

Abstract We present a reconstruction of episodic fluid flow over the past ∼250 k.y. along the Malpais normal fault, which hosts the Beowawe hydrothermal system (Nevada, USA), using a novel combination of the apatite (U-Th)/He (AHe) thermochronometer and a model of the thermal effects of fluid flow. Samples show partial resetting of the AHe thermochronometer in a 40-m-wide zone around the fault. Numerical models using current fluid temperatures and discharge rates indicate that fluid flow events lasting 2 k.y. or more lead to fully reset samples. Episodic fluid pulses lasting 1 k.y. result in partially reset samples, with 30–40 individual fluid pulses required to match the data. Episodic fluid flow is also supported by an overturned geothermal gradient in a borehole that crosses the fault, and by breaks in stable isotope trends in hydrothermal sinter deposits that coincide with two independently dated earthquakes in the past 20 k.y. This suggests a system where fluid flow is triggered by repeated seismic activity, and that seals itself over ∼1 k.y. due to the formation of clays and silicates in the fault damage zone. Hydrothermal activity is younger than the 6–10 Ma age of the fault, which means that deep (∼5 km) fluid flow was initiated only after a large part of the 230 m of fault offset had taken place.

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Character and structural evolution of the Mała Łąka Fault in the Tatra Mts., Carpathians, Poland

Acta Geologica Polonica ◽

10.2478/agp-2013-0005 ◽

2013 ◽

Vol 63 (1) ◽

pp. 137-151 ◽

Cited By ~ 2

Author(s):

Magdalena Dąbrowska ◽

Edyta Jurewicz

Keyword(s):

Variable Thickness ◽

Damage Zone ◽

Structural Evolution ◽

Normal Fault ◽

Northern Margin ◽

Tatra Mts ◽

Tectonic Contact ◽

Main Activity ◽

Stream Waters ◽

Flowing Stream

63 Abstract Dąbrowska, M. and Jurewicz, E. 2013. Character and structural evolution of the Mała Łąka Fault in the Tatra Mts., Carpathians, Poland. Acta Geologica Polonica, (1), 137-151. Warszawa. The Mała Łąka Fault in the Tatra Mts. is a synsedimentary normal fault responsible for the variable thickness of Eocene deposits in the area. Its main activity took place in the interval from the sedimentation of red conglomerates to the appearance of nummulitic limestones. The estimated throw is up to 350 m. Near the northern margin of the Tatra Mts., the trend of the fault changes from N-S to NE-SW. This part of the fault could have been activated during the Neogene uplift of the Tatra Mts. and rejuvenated as a sinistral fault. In the upper reach of the Mała Łąka Stream, the fault trend does not follow the course of the Mała Łąka Valley. Here, the flowing stream waters used extensional fractures within a damage zone associated with the Mała Łąka Fault rather than the lithological boundary at the tectonic contact between the Triassic dolomites and the Eocene conglomerates. The fault has a hingelike character; its hinge was located in the present-day Kościeliska Valley, c. 2.5 km west of the Mała Łąka Valley.

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Nonlinear fault damage zone scaling revealed through analog modeling

Geology ◽

10.1130/g48760.1 ◽

2021 ◽

Author(s):

Sylvain Mayolle ◽

Roger Soliva ◽

Stéphane Dominguez ◽

Christopher Wibberley ◽

Yannick Caniven

Keyword(s):

Failure Modes ◽

Damage Zone ◽

Normal Fault ◽

Fault Segment ◽

Mechanical Unit ◽

Analog Modeling ◽

Fault Damage Zone ◽

Fault Growth ◽

Fault Displacement ◽

Zone Growth

Fault damage zones strongly influence fluid flow and seismogenic behavior of faults and are thought to scale linearly with fault displacement until reaching a threshold thickness. Using analog modeling with different frictional layer thicknesses, we investigate damage zone dynamic evolution during normal fault growth. We show that experimental damage zone growth with displacement is not linear but progressively tends toward a threshold thickness, being larger in the thicker models. This threshold thickness increases significantly at fault segment relay zones. As the thickness threshold is approached, the failure mode progressively transitions from dilational shear to isochoric shear. This process affects the whole layer thickness and develops as a consequence of fault segment linkage as inferred in nature when the fault matures. These findings suggest that fault damage zone widths are limited both by different scales of mechanical unit thickness and the evolution of failure modes, ultimately controlled in nature by lithology and deformation conditions.

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Spatiotemporal history of fault–fluid interaction in the Hurricane fault, western USA

Solid Earth ◽

10.5194/se-11-1969-2020 ◽

2020 ◽

Vol 11 (6) ◽

pp. 1969-1985

Author(s):

Jace M. Koger ◽

Dennis L. Newell

Keyword(s):

Damage Zone ◽

Carbon Sources ◽

Normal Fault ◽

Western Usa ◽

Calcite Vein ◽

Regional Flow ◽

Fault Strength ◽

History Of ◽

Fault Damage Zone ◽

Fluid Interaction

Abstract. The Hurricane fault is a ∼250 km long, west-dipping, segmented normal fault zone located along the transition between the Colorado Plateau and the Basin and Range tectonic provinces in the western USA. Extensive evidence of fault–fluid interaction includes calcite mineralization and veining. Calcite vein carbon (δ13CVPDB) and oxygen (δ18OVPDB) stable isotope ratios range from −4.5 ‰ to 3.8 ‰ and from −22.1 ‰ to −1.1 ‰, respectively. Fluid inclusion microthermometry constrains paleofluid temperatures and salinities from 45 to 160 ∘C and from 1.4 wt % to 11.0 wt % as NaCl, respectively. These data suggest mixing between two primary fluid sources, including infiltrating meteoric water (70±10 ∘C, ∼1.5 wt % NaCl, δ18OVSMOW ∼-10 ‰) and sedimentary brine (100±25 ∘C, ∼11 wt % NaCl, δ18OVSMOW ∼ 5 ‰). Interpreted carbon sources include crustal- or magmatic-derived CO2, carbonate bedrock, and hydrocarbons. Uranium–thorium (U–Th) dates from five calcite vein samples indicate punctuated fluid flow and fracture healing at 539±10.8 (1σ), 287.9±5.8, 86.2±1.7, and 86.0±0.2 ka in the upper 500 m of the crust. Collectively, data predominantly from the footwall damage zone imply that the Hurricane fault imparts a strong influence on the regional flow of crustal fluids and that the formation of veins in the shallow parts of the fault damage zone has important implications for the evolution of fault strength and permeability.

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