Imaging Poro-Elastic Effects induced by a Normal Fault Aseismic-to-Seismic Dislocation in Shales

2020 ◽  
Author(s):  
Yves Guglielmi ◽  
Jens Birkholzer ◽  
Jonathan Ajo-Franklin ◽  
Christophe Nussbaum ◽  
Frederic Cappa ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Fault Zone ◽  
Hanging Wall ◽  
Three Dimensional ◽  
Normal Fault ◽  
Fault Reactivation ◽  
Foot Wall ◽  
Fault Activation ◽  
Strain Monitoring ◽  
Receiver Array

<p>Understanding fault reactivation as a result of subsurface fluid injection in shales is critical in geologic CO<sub>2</sub> sequestration and in assessing the performance of radioactive waste repositories in shale formations. Since 2015, two semi-controlled fault activation projects, called FS and FS-B, have been conducted in a fault zone intersecting a claystone formation at 300 m depth in the Mont Terri Underground Research Laboratory (Switzerland). In 2015, the FS project involved injection into 5 borehole intervals set at different locations within the fault zone. Detailed pressure and strain monitoring showed that injected fluids can only penetrate the fault when it is at or above the Coulomb failure criterion, highlighting complex mixed opening and slipping activation modes. Rupture modes were strongly driven by the structural complexity of the thick fault. An overall normal fault activation was observed. One key parameter affecting the reactivation behavior is the way the fault’s initial very low permeability dynamically increases at rupture. Such complexity may also explain a complex interplay between aseismic and seismic activation periods. Intact rock pore pressure variations were observed in a large volume around the rupture patch, producing pore pressure drops of ~4 10<sup>-4</sup> MPa up to 20 m away from the ruptured fault patch. Fully coupled three-dimensional numerical analyses indicated that the observed pressure signals are in good accordance with a poro-elastic stress transfer triggered by the fault dislocation.</p><p> </p><p>In 2019, the FS-B experiment started in the same fault, this time activating a larger fault zone volume of about 100 m extent near (and partially including) the initial FS testbed. In addition to the monitoring methods employed in the earlier experiment, FS-B features time-lapse geophysical imaging of long-term fluid flow and rupture processes. Five inclined holes were drilled parallel to the Main Fault dip at a distance of about 2-to-5m from the fault core “boundary”, with three boreholes drilled in the hanging wall and two boreholes drilled in the foot wall. An active seismic source-receiver array deployed in these five inclined boreholes allows tracking the variations of p- and s-wave velocities during fault leakage associated with rupture, post-rupture and eventually self-sealing behavior. The geophysical measurements are complemented by local three-dimensional displacements and pore pressures measurements distributed in three vertical boreholes drilled across the fault zone. DSS, DTS and DAS optical fibers cemented behind casing allow for the distributed strain monitoring in all the boreholes. Twelve acoustic emission sensors are cemented in two boreholes set across the fault zone and close to the injection borehole. Preliminary results from the new FS-B fault activation experiment will be discussed.</p>

Validation of Coupled FDM-DEM Approach on the Soil-Raft Foundation Interaction Subjected to Normal Faulting

2021 ◽  
Author(s):  
Fang Ru-Ya ◽  
Lin Cheng-Han ◽  
Lin Ming-Lang
Keyword(s):  
Active Fault ◽  
Ground Deformation ◽  
Numerical Models ◽  
Hanging Wall ◽  
Normal Fault ◽  
Small Scale ◽  
Foot Wall ◽  
Normal Faulting ◽  
Raft Foundation ◽  
Overburden Soil

<p>Recent earthquake events have shown that besides the strong ground motions, the coseismic faulting often caused substantial ground deformation and destructions of near-fault structures. In Taiwan, many high-rise buildings with raft foundation are close to the active fault due to the dense population. The Shanchiao Fault, which is a famous active fault, is the potentially dangerous normal fault to the capital of Taiwan (Taipei). This study aims to use coupled FDM-DEM approach for parametrically analyzing the soil-raft foundation interaction subjected to normal faulting. The coupled FDM-DEM approach includes two numerical frameworks: the DEM-based model to capture the deformation behavior of overburden soil, and the FDM-based model to investigate the responses of raft foundation. The analytical approach was first verified by three  benchmark cases and theoretical solutions. After the verification, a series of small-scale sandbox model was used to validate the performance of the coupled FDM-DEM model in simulating deformation behaviors of overburden soil and structure elements. The full-scale numerical models were then built to understand the effects of relative location between the fault tip and foundation in the normal fault-soil-raft foundation behavior. Preliminary results show that the raft foundation located above the fault tip suffered to greater displacement, rotation, and inclination due to the intense deformation of the triangular shear zone in the overburden soil. The raft foundation also exhibited distortion during faulting. Based on the results, we suggest different adaptive strategies for the raft foundation located on foot wall and hanging wall if the buildings are necessary to be constructed within the active fault zone. It is the first time that the coupled FDM-DEM approach has been carefully validated and applied to study the normal fault-soil-raft foundation problems. The novel numerical framework is expected to contribute to design aids in future practical engineering.</p><p><strong>Keywords</strong>: Coupled FDM-DEM approach; normal faulting; ground deformation; soil-foundation interaction; raft foundation.</p>

Outcrops and well logs as a practicum for calibrating the accuracy of traveltime tomograms

2015 ◽  
Vol 3 (3) ◽  
pp. SY27-SY40 ◽  
Author(s):  
Sherif M. Hanafy ◽  
Ann Mattson ◽  
Ronald L. Bruhn ◽  
Shengdong Liu ◽  
Gerard T. Schuster
Keyword(s):  
High Resolution ◽  
Fault Zone ◽  
Great Basin ◽  
Seismic Tomography ◽  
Seismic Data ◽  
Hanging Wall ◽  
Normal Fault ◽  
Well Logs ◽  
Drill Core ◽  
Sufficient Detail

We have developed two case studies demonstrating the use of high-resolution seismic tomography and reflection imaging in the field of paleoseismology. The first study, of the Washington fault in southern Utah, USA, evaluated the subsurface deposits in the hanging wall of the normal fault. The second study, of the Mercur fault in the eastern Great Basin of Utah, USA, helped to establish borehole locations for sampling subsurface colluvial deposits buried deeper than those previously trenched along the fault zone. We evaluated the seismic data interpretations by comparison with data obtained by trenching and logging deposits across the Washington fault, and by drill-core sampling and video logging of boreholes penetrating imaged deposits along the Mercur fault. The seismic tomograms provided critical information on colluvial wedges and faults but lacked sufficient detail to resolve individual paleoearthquakes.

scholarly journals Sevier Fault at Red Canyon

Geosites ◽  
2019 ◽  
Vol 1 ◽  
pp. 1-6
Author(s):  
Robert Biek
Keyword(s):  
Lava Flow ◽  
Fault Zone ◽  
Hanging Wall ◽  
Slip Rate ◽  
Normal Fault ◽  
Coarse Grained ◽  
Seismic Reflection Data ◽  
The North ◽  
Total Displacement ◽  
Reflection Data

The Sevier fault is spectacularly displayed on the north side of Utah Highway 12 at the entrance to Red Canyon, where it offsets a 500,000-year-old basaltic lava flow. The fault is one of several active, major faults that break apart the western margin of the Colorado Plateau in southwestern Utah. The Sevier fault is a “normal” fault, a type of fault that forms during extension of the earth’s crust, where one side of the fault moves down relative to the other side. In this case, the down-dropped side (the hanging wall) is west of the fault; the upthrown side (the footwall) lies to the east. The contrasting colors of rocks across the fault make the fault stand out in vivid detail. Immediately south of Red Canyon, the 5-million-year-old Rock Canyon lava flow, which erupted on the eastern slope of the Markagunt Plateau, flowed eastward and crossed the fault (which at the time juxtaposed non-resistant fan alluvium against coarse-grained volcaniclastic deposits) (Biek and others, 2015). The flow is now offset 775 to 1130 feet (235-345 m) along the main strand of the fault, yielding an anomalously low vertical slip rate of about 0.05 mm/yr (Lund and others, 2008). However, this eastern branch of the Sevier fault accounts for only part of the total displacement on the fault zone. A concealed, down-to-the-west fault is present west of coarse-grained volcaniclastic strata at the base of the Claron cliffs. Seismic reflection data indicate that the total displacement on the fault zone in this area is about 3000 feet (900 m) (Lundin, 1987, 1989; Davis, 1999).

scholarly journals Three-Dimensional Hydromechanical Modeling during Shearing by Nonuniform Crust Movement

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Yuqing Zhao ◽  
You-Kuan Zhang ◽  
Xiuyu Liang
Keyword(s):  
Fluid Flow ◽  
Pore Pressure ◽  
Fault Zone ◽  
Numerical Models ◽  
Three Dimensional ◽  
Practical Investigations ◽  
Geological Formation ◽  
Distribution Of Stress ◽  
Coupling Processes ◽  
Fluid Interaction

Hydromechanical modeling of a geological formation under shearing by the nonuniform crust movement during 10000 years was carried out to investigate the solid stress and pore pressure coupling processes of the formation from the intact to the fractured or faulted. Two three-dimensional numerical models were built and velocities in opposite directions were applied on the boundaries to produce the shearing due to the nonuniform crust movement. The results show that the stress and pore pressure became more and more concentrated in and around the middle of the formation as time progresses. In Model I with no fault, stress and pore pressure are concentrated in the middle of the model during shearing; however, in Model II with a fault zone of weakened mechanical properties, they are more complex and concentrated along the sides of the fault zone and the magnitudes decreased. The distribution of stress determines pore pressure which in turn controls fluid flow. Fluid flow occurs in the middle in Model I but along the sides of the fault zone in Model II. The results of this study improve our understanding of the rock-fluid interaction processes affected by crustal movement and may guide practical investigations in geological formations.

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

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

<p>The Italian Central Apennines are one of the most seismically active areas in the Mediterranean (e.g., L’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.</p><p>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.</p><p>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  thick  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 ∼100 m in proximity of subsidiary faults striking NNE-SSW. The latter could be reactivated inherited structures.</p><p>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.</p><p>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).  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.</p>

scholarly journals Relevant aspects to the recognition of extensional environments in the field

2021 ◽  
Vol 48 (2) ◽  
pp. 95-106
Author(s):  
Ana Milena Suárez Arias ◽  
Julián Andrés López Isaza ◽  
Anny Juieth Forero Ortega ◽  
Mario Andrés Cuéllar Cárdenas ◽  
Carlos Augusto Quiroz Prada ◽  
...  
Keyword(s):  
Hanging Wall ◽  
Image Interpretation ◽  
Three Dimensional ◽  
Normal Fault ◽  
Structural Data ◽  
Structural Aspect ◽  
Half Graben ◽  
Regional Tectonic ◽  
History Of ◽  
Definition Of

The understanding of each geological-structural aspect in the field is fundamental to be able to reconstruct the geological history of a region and to give a geological meaning to the data acquired in the outcrop. The description of a brittle extensional environment, which is dominated by normal fault systems, is based on: (I)  image interpretation, which aims to find evidence suggestive of an extensional geological environment, such  as the presence of scarp lines and fault scarps, horst, graben and/or half-graben, among others, that allow the identification of the footwall and hanging wall blocks; ii) definition of the sites of interest for testing; and  iii) analysis of the outcrops, following a systematic procedure that consists of the observation and identification of the deformation markers, their three-dimensional schematic representation, and their  subsequent interpretation, including the stereographic representation in the outcrop. This procedure implies the unification of the parameters of structural data acquisition in the field, mentioning the minimum fields  necessary for the registration of the data in tables. Additionally, the integration of geological and structural observations of the outcrop allows to understand the nature of the geological units, the deformation related to the extensional environment and the regional tectonic context of the study area.

Exhumation history of the Lomas de Olmedo basin: constraining multi-phase deformation using low-temperature thermochronology

2021 ◽  
Author(s):  
Willemijn S.M.T. van Kooten ◽  
Edward R. Sobel ◽  
Cecilia del Papa ◽  
Patricio Payrola ◽  
Alejandro Bande ◽  
...  
Keyword(s):  
Low Temperature ◽  
Late Miocene ◽  
Hanging Wall ◽  
Normal Fault ◽  
Fault Reactivation ◽  
Normal Faults ◽  
Northwestern Part ◽  
Rift Basin ◽  
The South ◽  
Northern Margin

<p>The Cretaceous period in NW Argentina is dominated by the formation of the Salta rift basin, an intracontinental rift basin with multiple branches extending from the central Salta-Jujuy High. One of these branches is the ENE-WSW striking Lomas de Olmedo sub-basin, which hosts up to 5 km of syn- and post-rift deposits of the Salta Group, accommodated by substantial throw along SW-NE striking normal faults and subsequent thermal subsidence during the Cretaceous-Paleogene. Early compressive movement in the Eastern Cordillera led to the formation of a foreland basin setting that was further dissected in the Neogene by the uplift of basement-cored ranges. As a consequence, the northwestern part of the Lomas de Olmedo sub-basin was disconnected from the Andean foreland and local depocenters such as the Cianzo basin were formed, whereas the eastern sub-basin area is still part of the Andean foreland. Thus, the majority of the Salta Group to the east is located in the subsurface and has been extensively explored for petroleum, while in northwestern part of the sub-basin, the Salta Group is increasingly deformed and is fully exposed in the km-scale Cianzo syncline of the Hornocal ranges. The SW-NE striking Hornocal fault delimits the Cianzo basin to the south and the Cianzo syncline to the north. During the Cretaceous, it formed the northern margin of the Lomas de Olmedo sub-basin, which is indicated by an increasing thickness of the syn-rift deposits towards the Hornocal fault, as well as a lack of syn-rift deposits on the footwall block. Structural mapping and unpublished apatite fission track (AFT) data show that the Hornocal normal fault was reactivated and inverted during the Miocene. Although structural and sedimentary features of the Cianzo basin infill provide information about the relative timing of fault activity, there is a lack of low-temperature thermochronology. Herein, we aim to constrain the exhumation of the Lomas de Olmedo sub-basin during the Cretaceous rifting phase, as well as the onset and magnitude of fault reactivation in the Miocene. We collected 74 samples for low-temperature thermochronology along two major NW-SE transects in the Cianzo basin and adjacent areas. Of these samples, 59 have been analyzed using apatite and/or zircon (U-Th-Sm)/He thermochronology (AHe, ZHe). Furthermore, 49 samples have been prepared for AFT analysis. The ages are incorporated in thermo-kinematic modelling using Pecube in order to test the robustness of uplift and exhumation scenarios. On the hanging wall block of the N-S striking east-vergent Cianzo thrust north of the Hornocal fault, Jurassic ZHe ages are attributed to pre-Salta Group exhumation. However, associated thrusts to the south show ZHe ages as young as Eocene-Oligocene, which might indicate early post-rift activity along those thrusts. AHe data from the Cianzo syncline show a direct age-elevation relationship with Late Miocene-Pliocene cooling ages, indicating the onset of rapid exhumation along the Hornocal fault in the Miocene. This is consistent with regional data and suggests that pre-existing extensional structures were reactivated during Late Miocene-Pliocene compressive movement within this part of the Central Andes.</p>

scholarly journals Earthquake Hazards of the Grand Teton National Park Emphasizing the Teton Fault

1987 ◽  
Vol 11 ◽  
pp. 106-130
Author(s):  
D. Susong ◽  
R. Smith ◽  
R. Bruhn
Keyword(s):  
Fault Zone ◽  
Gravity Data ◽  
Hanging Wall ◽  
Regional Scale ◽  
Normal Fault ◽  
Earthquake Hazards ◽  
Eastern Front ◽  
The North ◽  
Teton Range ◽  
Structural Boundary

The Teton normal-fault zone extends for over 80 km along the eastern front of the Teton Range. Mapping and profiling of Quaternary fault scarps shows that the scarps are nearly continous for 55 km with scarp heights varying from about 10 m to 40 m. The largest scarps occur adjacent to the topographically highest parts of the Teton range. The scarps locally offset glacial moraine crests in a left-lateral sense. On a regional scale the scarps exhibit a right-stepping, en echelon geometry that is also consistent with a component of left-lateral displacenent. The Teton fault is structurally subdivided into three segments. One prominent geometrical segment boundary occurs just south Taggart Lake, where the range front bends through an angle of 23° and a major structural boundary extends through the hanging wall basin, as inferred by gravity data. This boundary may have influenced the history of Quaternary earthquake occurrences because vertical offset across faults scarps is greater to the north of the boundary, than to the south. The lengths of the proposed segments and scarp size are consistent with M7 to 7.5 earthquakes for the Teton fault zone.

scholarly journals The Mechanical Criterion of Activation and Instability of Normal Fault Induced by the Movement of Key Stratum and Its Disaster-Causing Mechanism of Rockburst in the Hanging Wall Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Lyu Pengfei ◽  
Lu Jiabin ◽  
Wang Eryu ◽  
Chen Xuehua
Keyword(s):  
Coal Mine ◽  
Static Load ◽  
Hanging Wall ◽  
Coal Pillar ◽  
Normal Fault ◽  
Fault Slip ◽  
Fault Activation ◽  
Key Stratum ◽  
Two Factors ◽  
And Control

Coal mine rockburst is closely related to the complex geological structure. Understanding the criterion of the fault activation instability and the disaster-causing mechanism of rockburst under the influence of mining is the theoretical premise and important guarantee of safe and efficient coal mining. In this paper, based on the theory of key stratum, the mechanical model of fault slip instability in the normal fault during the hanging wall mining was established, and the instability criterion was derived. It is concluded that the fault slip instability of the hanging wall is mainly controlled by two factors: (1) the distance between coal seams and key stratum and (2) the distance between working face and fault. Moreover, these two factors have an inverse relation to the occurrence of rockburst. Subsequently, three conceptual models of rockburst induced by the fault stress transfer, stress concentration of coal pillars, and fault structural instability were proposed. Based on the rock mechanics theory, the rockburst carrier system model of “roof-coal seam-floor” near the fault was established. The mechanical essence of fault rockburst was obtained as follows: under the action of fault, the static load of fault coal pillar was increased and superimposed with the fault activation dynamic load, leading to high-strength rockburst disaster. Based on the occurrence mechanism of fault rockburst, the monitoring and prevention concept and technical measures were proposed in three aspects, including the monitoring and control of fault activation dynamic loads, the monitoring of high static load in fault coal pillar and stress release, and the strengthening roadway support. These prevention and control measures were verified in the panel 103down02 of the Baodian Coal Mine in engineering, and the effectiveness of these measures was proved.

Influence of faulting on reservoir overpressure distribution in the Northern Carnarvon Basin

2015 ◽  
Vol 55 (1) ◽  
pp. 35
Author(s):  
Edward Hoskin ◽  
Stephen O'Connor ◽  
Stephen Robertson ◽  
Jurgen Streit ◽  
Chris Ward ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Hanging Wall ◽  
Foot Wall ◽  
Geological History ◽  
Pore Pressure Prediction ◽  
Northern Carnarvon Basin ◽  
Well Data ◽  
Carnarvon Basin

The Northern Carnarvon Basin has a complicated geological history, with numerous sub-basins containing varying formation thicknesses, lithology types, and structural histories. These settings make pre-drill pore pressure prediction problematic; the high number of kicks taken in wells shows this. Kicks suggest unexpected pore pressure was encountered and mudweights used were below formation pressure. The horst block penetrated by the Parker–1 well is focused on in this peer-reviewed paper. This horst is one of many lying along Rankin Trend’s strike. In this well, kicks up to 17.2 ppg (pounds per gallon) were taken in the Mungaroo reservoir. The authors investigate whether the kicks represent shale pressure—or rather, represent pressure transferred into foot-wall sandstones—by using well data from Forrest 1/1A/1AST1 and Withnell–1, and wells located in the Dampier Sub-basin and the hanging-wall to the horst. This anomalous pressure could result from either cross-fault flow from juxtaposed overpressured Dingo Claystone or transfer up faults from a deeper source. Using a well data derived Vp versus VES trend, the authors establish that the kicks taken in Parker–1 are more likely to result from pressure transfer using faults as conduits. These data lie off a loading trend and appear unloaded but likely represent elevated sand pressures and not in situ shale pressure. Pressure charging up faults in the Northern Carnarvon Basin has been recognised in Venture 1/1ST1, however, this paper presents a focused case study. Pressure transfer is noted in other basins, notably Brunei. From unpublished data, the authors believe that buried horst blocks, up-fault charging and adjacent overpressured shale may explain high reservoir pressures in other basins, including Nam Con Son in Vietnam.

Sign in / Sign up

Export Citation Format

Share Document