Assessing fault criticality using seismic monitoring and fluid pressure analysis

2020 ◽  
Author(s):  
Léa Perrochet ◽  
Giona Preisig ◽  
Benoît Valley
Keyword(s):  
Time Lag ◽  
Fluid Pressure ◽  
Back Analysis ◽  
Local Stress ◽  
Seismic Monitoring ◽  
Spring Discharge ◽  
Stress Regime ◽  
Groundwater Level Fluctuations ◽  
Area Of Interest ◽  
Discharge Rates

<p>The stability of a critically stressed fault depends on the surrounding stresses acting on it. Fluids, by reducing the effective normal stress, play a major role. It has been observed that in karstic regions, an increase in groundwater pressure following significant recharge (precipitations and/or seasonal snowmelt) can result in a fault re-activation, inducing microseismicity. This study combines the natural microseismicity and the groundwater level fluctuations observations to estimate the fault criticality. The research is carried out on two major strike-slip faults in the folded Jura in Switzerland – La Lance Fault and La Ferrière Fault – most likely critically stressed according to their position in the global stress-regime. Data acquisition mainly consists in hydrogeologic and seismic monitoring. The objectives are to have continuous discharge rates of the major karstic springs and to produce a seismic catalog for the area of interest. Combining both data sets will allow to determine relations between increasing spring discharge rates and low magnitude earthquakes and eventually to acquire a quantitative knowledge on what pressure change is affecting the fault’s stability. This knowledge will be used to develop a straighforward methodology to assess fault criticality.  In addition, the study of a possible time lag between aquifer response and fault activation, as well as back-analysis of seismic events can provide, respectively, important information about the deep-seated fluid circulation and the local stress-regime.</p>

Effects of heterogeneity on frictional-viscous deformation and the depth-extent of the seismogenic zone

2021 ◽  
Author(s):  
Ake Fagereng ◽  
Adam Beall
Keyword(s):  
Shear Stress ◽  
Yield Strength ◽  
Fault Zone ◽  
Fluid Pressure ◽  
Local Stress ◽  
Seismogenic Zone ◽  
Depth Range ◽  
Viscous Deformation ◽  
Viscosity Contrast ◽  
Depth Extent

<p>Current conceptual fault models define a seismogenic zone, where earthquakes nucleate, characterised by velocity-weakening fault rocks in a dominantly frictional regime. The base of the seismogenic zone is commonly inferred to coincide with a thermally controlled onset of velocity-strengthening slip or distributed viscous deformation. The top of the seismogenic zone may be determined by low-temperature diagenetic processes and the state of consolidation and alteration. Overall, the seismogenic zone is therefore described as bounded by transitions in frictional and rheological properties. These properties are relatively well-determined for monomineralic systems and simple, planar geometries; but, many exceptions, including deep earthquakes, slow slip, and shallow creep, imply processes involving compositional, structural, or environmental heterogeneities. We explore how such heterogeneities may alter the extent of the seismogenic zone.</p><p> </p><p>We consider mixed viscous-frictional deformation and suggest a simple rule of thumb to estimate the role of heterogeneities by a combination of the viscosity contrast within the fault, and the ratio between the bulk shear stress and the yield strength of the strongest fault zone component. In this model, slip behaviour can change dynamically in response to stress and strength variations with depth and time. We quantify the model numerically, and illustrate the idea with a few field-based examples: 1) earthquakes within the viscous regime, deeper than the thermally-controlled seismogenic zone, can be triggered by an increase in the ratio of shear stress to yield strength, either by increased fluid pressure or increased local stress; 2) there is commonly a depth range of transitional behaviour at the base of the seismogenic zone – the thickness of this zone increases markedly with increased viscosity contrast within the fault zone; and 3) fault zone weakening by phyllosilicate growth and foliation development increases viscosity ratio and decreases bulk shear stress, leading to efficient, stable, fault zone creep. These examples are not new interpretations or observations, but given the substantial complexity of heterogeneous fault zones, we suggest that a simplified, conceptual model based on basic strength and stress parameters is useful in describing and assessing the effect of heterogeneities on fault slip behaviour.         </p>

scholarly journals Estimating perturbed stress from 3-D borehole displacements induced by fluid injection in fractured or faulted shales

2020 ◽  
Vol 221 (3) ◽  
pp. 1684-1695 ◽  
Author(s):  
Yves Guglielmi ◽  
Christophe Nussbaum ◽  
Jonny Rutqvist ◽  
Frédéric Cappa ◽  
Pierre Jeanne ◽  
...  
Keyword(s):  
Principal Stress ◽  
Fluid Pressure ◽  
Injection Pressure ◽  
Local Stress ◽  
Opalinus Clay ◽  
Step Rate ◽  
Pressure Step ◽  
Heterogeneous Rock ◽  
Magnitude Variation ◽  
Mont Terri

SUMMARY Hydrofracturing stress measurements in fractured and anisotropic shales are notoriously difficult, because opening of existing geological features tends to prevent the creation of a pure hydraulic fracture perpendicular to the least compressive principal stress. Here we show how adding 3-D borehole-displacement measurements while conducting the hydraulic injection test helps to better constrain the principal stress orientations and magnitudes. We developed a 3-D fully coupled hydromechanical numerical model to analyse the displacement, fluid pressure and injection flow-rate data measured during an injection pressure-step-rate test conducted to activate a faulted borehole interval in the Mont Terri Opalinus Clay (Switzerland). We find that injected fluids can only penetrate the fault when it is at or above the Coulomb failure pressure. Borehole displacement orientations are sensitive to a ∼15° variation in the stress–tensor orientation and a 1 MPa stress magnitude variation. Although some dispersion occurs while rupture is propagating along the fault plane ∼4 m away from the borehole, the maximum density of displacement orientations consistently informs about the stress orientation. Thus, an extended injection step-rate approach coupled with an accurate in situ measurement of the borehole wall displacements can be used to better constrain the local stress field perturbations in fractured shales and in heterogeneous rock in general.

scholarly journals Rapid accretion of dissolved organic carbon in the springs of Florida: the most organic-poor natural waters

2010 ◽  
Vol 7 (12) ◽  
pp. 4051-4057 ◽  
Author(s):  
C. M. Duarte ◽  
Y. T. Prairie ◽  
T. K. Frazer ◽  
M. V. Hoyer ◽  
S. K. Notestein ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Primary Production ◽  
Natural Waters ◽  
Gross Primary Production ◽  
Spring Discharge ◽  
High Discharge ◽  
Discharge Rates ◽  
Receiving Waters ◽  
Flowing Waters

Abstract. The concentration of dissolved organic carbon (DOC) in groundwater emanating as spring discharge at several locations in Florida, USA and the net increase in DOC in the downstream receiving waters were measured as part of a larger investigation of carbon dynamics in flowing waters. Springs with high discharge (>2.8 m3 s−1) were found to be the most organic-poor natural waters yet reported (13 ± 1.6 μmol C L−1), while springs with lesser discharge exhibited somewhat higher DOC concentrations (values ranging from 30 to 77 μmol C L−1). DOC concentrations increased rapidly downstream from the point of spring discharge, with the calculated net areal input rate of DOC ranging from 0.04 to 1.64 mol C m−2 d−1 across springs. Rates of DOC increase were generally greater in those springs with high discharge rates. These input rates compare favorably with values reported for gross primary production in these macrophyte-dominated spring systems, assuming that 17% of macrophyte primary production is lost, on average, as DOC. The measures reported here are possible only because of the remarkably low DOC levels in the up-surging groundwaters and the short residency times of the water in the spring-runs themselves.

Hydraulic fracturing operations within an extremely complex stress regime: The case of Fort St. John, British Columbia, Canada

2020 ◽  
Author(s):  
Rebecca O. Salvage ◽  
David W. Eaton
Keyword(s):  
British Columbia ◽  
Hydraulic Fracturing ◽  
Large Scale ◽  
Vertical Plane ◽  
Local Stress ◽  
Complex Stress ◽  
Tectonic Structures ◽  
Principal Stresses ◽  
Stress Regime ◽  
North West

<p>On 30 November 2018, three felt earthquakes occurred in quick succession close to the city of Fort St. John, British Columbia, likely as a direct response to a hydraulic fracturing operation in the area. Events appear tightly clustered spatially within the upper 10 km of the crust. Hypocenters locate at the confluence between a large scale reverse faulting regime (in the north-west, probably due to the influence of the Rocky Mountain fold and thrust belt) and an oblique strike slip faulting regime (in the south-east, probably due to the influence of the Fort St. John Graben), resulting in a variety of focal mechanisms and a very complex local stress regime. Further analysis of the principal stresses suggests that σ<sub>1</sub> is well constrained and close to horizontal, whereas σ<sub>2</sub> and σ<sub>3</sub> are poorly constrained, and can alternate between the horizontal and the vertical plane. Here, we present an overview of the temporal and spatial evolution of this seismic sequence and its relationship to hydraulic fracturing operations in the area, and examine the influence of large-scale regional tectonic structures on the generation of seismicity on this occasion.</p><p> </p>

scholarly journals Rapid accretion of dissolved organic carbon in the Springs of Florida: the most organic-poor natural waters

2010 ◽  
Vol 7 (4) ◽  
pp. 5253-5267
Author(s):  
C. M. Duarte ◽  
R. Martínez ◽  
Y. T. Prairie ◽  
T. K. Frazer ◽  
M. V. Hoyer ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Primary Production ◽  
Natural Waters ◽  
Gross Primary Production ◽  
Spring Discharge ◽  
High Discharge ◽  
Discharge Rates ◽  
Receiving Waters ◽  
Flowing Waters

Abstract. The concentration of dissolved organic carbon (DOC) in groundwater emanating as spring discharge at several locations in Florida, USA, and the net rate of DOC increase in the downstream receiving waters were measured as part of a larger investigation of carbon dynamics in flowing waters. Springs with high discharge (>2.8 m3 s−1) were found to be the most organic-poor natural waters yet reported (13 ±1.6 μmol C L−1), while springs with lesser discharge exhibited somewhat higher DOC concentrations (values ranging from 30 to 77 μmol C L−1). DOC concentrations increased rapidly downstream from the point of spring discharge, with the calculated net areal input rate of DOC ranging from 0.04 to 1.64 mol C m−2 d−1 across springs. Rates of DOC increase were generally greater in those springs with high discharge rates. These input rates compare favorably with values reported for gross primary production in these macrophyte-dominated spring systems, assuming that 17% of macrophyte primary production is lost, on average, as DOC. The measures reported here are possible only because of the remarkably low DOC levels in the up-surging groundwaters and the short residency times of the water in the spring-runs themselves.

Research on Dynamic Process of Large-Scale High-Speed Landslide Disasters

2011 ◽  
Vol 243-249 ◽  
pp. 5101-5105
Author(s):  
Yun Yun Fan ◽  
Xiao Li Liu ◽  
En Zhi Wang ◽  
Si Jing Wang
Keyword(s):  
Dynamic Process ◽  
High Speed ◽  
Large Scale ◽  
Fluid Pressure ◽  
Back Analysis ◽  
Sliding Surface ◽  
Friction Resistance ◽  
Finite Volume Discretization ◽  
Calculation Results ◽  
High Normal Stress

The large-scale high-speed landslide has a strong destructive power which seriously threatens human lives and belongings. In order to study the dynamic process of large-scale high-speed landslide disasters and find the causes, the back analysis is made to study the Frank slide, a typical large-scale high-speed landslide disaster which happened in Canada, by combining dynamic model equation and method of finite volume discretization. At the same time, the simulation realizes the reappearance of the dynamic process of large-scale high-speed landslide disasters. It is can be seen from the calculation results which are identical to the actual situation that the established theoretical model and the numerical solution are effective. Besides, the low bottom friction parameter obtained from the back analysis shows that the decrease of the friction resistance is one of the most important causes of large-scale high-speed landslide. The further analysis reveals that several factors such as high-speed motion, fluid pressure on the sliding surface and high normal stress can reduce the friction resistance on the sliding surface.

scholarly journals Dynamic Fault Interaction during a Fluid-Injection-Induced Earthquake: The 2017 Mw 5.5 Pohang Event

2020 ◽  
Vol 110 (5) ◽  
pp. 2328-2349
Author(s):  
Kadek Hendrawan Palgunadi ◽  
Alice-Agnes Gabriel ◽  
Thomas Ulrich ◽  
José Ángel López-Comino ◽  
Paul Martin Mai
Keyword(s):  
Fault Plane ◽  
Fluid Pressure ◽  
Local Stress ◽  
Stress Conditions ◽  
Fluid Injection ◽  
Geothermal System ◽  
Dynamic Rupture ◽  
Fault Interaction ◽  
Induced Earthquake ◽  
Secondary Fault

ABSTRACT The 15 November 2017 Mw 5.5 Pohang, South Korea, earthquake has been linked to hydraulic stimulation and fluid injections, making it the largest induced seismic event associated with an enhanced geothermal system. To understand its source dynamics and fault interactions, we conduct the first 3D high-resolution spontaneous dynamic rupture simulations of an induced earthquake. We account for topography, off-fault plastic deformation under depth-dependent bulk cohesion, rapid velocity weakening friction, and 1D subsurface structure. A guided fault reconstruction approach that clusters spatiotemporal aftershock locations (including their uncertainties) is used to identify a main and a secondary fault plane that intersect under a shallow angle of 15°. Based on simple Mohr–Coulomb failure analysis and 180 dynamic rupture experiments in which we vary local stress loading conditions, fluid pressure, and relative fault strength, we identify a preferred two-fault-plane scenario that well reproduces observations. We find that the regional far-field tectonic stress regime promotes pure strike-slip faulting, whereas local stress conditions constrained by borehole logging generate the observed thrust-faulting component. Our preferred model is characterized by overpressurized pore fluids, nonoptimally oriented but dynamically weak faults and a close-to-critical local stress state. In our model, earthquake rupture “jumps” to the secondary fault by dynamic triggering, generating a measurable non-double-couple component. Our simulations suggest that complex dynamic fault interaction may occur during fluid-injection-induced earthquakes and that local stress perturbations dominate over regional stress conditions. Therefore, our findings have important implications for seismic hazard in active georeservoir.

Lobe weight gain and vascular, alveolar, and peribronchial interstitial fluid pressures

1982 ◽  
Vol 52 (1) ◽  
pp. 173-183 ◽  
Author(s):  
W. Hida ◽  
H. Inoue ◽  
J. Hildebrandt
Keyword(s):  
Weight Gain ◽  
Filtration Rate ◽  
Interstitial Fluid ◽  
Time Lag ◽  
Fluid Pressure ◽  
Steady Increase ◽  
Pressure Gradients ◽  
Alveolar Pressure ◽  
Interstitial Edema ◽  
Lobar Bronchus

Interstitial fluid movements in acute pulmonary edema were studied by recording interstitial fluid pressure [Px (f)] relative to pleural pressure (atmospheric), together with lobe weight gain or loss (delta W). Px (f) was measured by wicks inserted between lobar bronchus and artery while alveolar pressure (PA) was fixed at either 5 or 20 cmH2O. When vascular pressure (Pvas) was raised abruptly from -5 to +25 cmH2O by air inflation for 60 min, Px (f) became abruptly less negative, then remained stable. However, during vascular inflation with plasma, delta W began a steady increase, but plotted against delta W, Px(f) became less negative in several phases. After an immediate rise due to interdependence effects following vascular distension, Px (f) remained almost unchanged for 4–7 min as delta W increased 15–80% of initial lobe weight (Wi), representing a transport lag between leakage and measuring sites and suggesting that interstitial edema was not homogeneous. Next, Px (f) increased progressively as weight increased a further 70–200% of Wi and finally slowed its rise near zero pressure. When Pvas was lowered, Px (f) became abruptly more negative, again by interdependence; however, as delta W then decreased 20–50% of Wi over 30 min, Px (f) did not change consistently. It was possible to relate the rate of weight gain occurring between 2 and 5 min after Pvas was raised to two pressure gradients, Pvas - Px (f) and Pvas - PA, and to relate the time lag to filtration rate and Pvas - Px (f).

scholarly journals The dynamics of cultivation and floods in arable lands of Central Argentina

2009 ◽  
Vol 13 (4) ◽  
pp. 491-502 ◽  
Author(s):  
E. F. Viglizzo ◽  
E. G. Jobbágy ◽  
L. Carreño ◽  
F. C. Frank ◽  
R. Aragón ◽  
...  
Keyword(s):  
Land Use ◽  
Groundwater Level ◽  
Time Lag ◽  
Groundwater Levels ◽  
Groundwater Level Fluctuations ◽  
Central Argentina ◽  
Cyclic Mechanism ◽  
Subsurface Lateral Flow ◽  
Flooded Area ◽  
One Year

Abstract. Although floods in watersheds have been associated with land-use change since ancient times, the dynamics of flooding is still incompletely understood. In this paper we explored the relations between rainfall, groundwater level, and cultivation to explain the dynamics of floods in the extremely flat and valuable arable lands of the Quinto river watershed, in central Argentina. The analysis involved an area of 12.4 million hectare during a 26-year period (1978–2003), which comprised two extensive flooding episodes in 1983–1988 and 1996–2003. Supported by information from surveys as well as field and remote sensing measurements, we explored the correlation among precipitation, groundwater levels, flooded area and land use. Flood extension was associated to the dynamics of groundwater level. While no correlation with rainfall was recorded in lowlands, a significant correlation (P<0.01) between groundwater and rainfall in highlands was found when estimations comprise a time lag of one year. Correlations between groundwater level and flood extension were positive in all cases, but while highly significant relations (P<0.01) were found in highlands, non significant relations (P>0.05) predominate in lowlands. Our analysis supports the existence of a cyclic mechanism driven by the reciprocal influence between cultivation and groundwater in highlands. This cycle would involve the following stages: (a) cultivation boosts the elevation of groundwater levels through decreased evapotranspiration; (b) as groundwater level rises, floods spread causing a decline of land cultivation; (c) flooding propitiates higher evapotranspiration favouring its own retraction; (d) cultivation expands again following the retreat of floods. Thus, cultivation would trigger a destabilizing feedback self affecting future cultivation in the highlands. It is unlikely that such sequence can work in lowlands. The results suggest that rather than responding directly and solely to the same mechanism, floods in lowlands may be the combined result of various factors like local rainfall, groundwater level fluctuations, surface and subsurface lateral flow, and water-body interlinking. Although the hypothetical mechanisms proposed here require additional understanding efforts, they suggest a promising avenue of environmental management in which cultivation could be steered in the region to smooth the undesirable impacts of floods.

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