scholarly journals Control of fault plane geometry on the formation of a normal fault-related anticline: an experimental approach

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Wei Long ◽  
Zhongquan Li ◽  
Ying Li ◽  
Junliang Chen ◽  
Hongkui Li ◽  
...  
Keyword(s):  
Experimental Approach ◽  
Fault Plane ◽  
Normal Fault ◽  
Plane Geometry

scholarly journals Seismic-Scale Evidence of Thrust-Perpendicular Normal Faulting in the Western Outer Carpathians, Poland

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1252
Author(s):  
Jan Barmuta ◽  
Krzysztof Starzec ◽  
Wojciech Schnabel
Keyword(s):  
Large Scale ◽  
Fault Plane ◽  
Normal Fault ◽  
Normal Faulting ◽  
Seismic Profiles ◽  
Horizontal Movement ◽  
Outer Carpathians ◽  
Differential Uplift ◽  
Seismic Scale ◽  
Detachment Surface

Based on the interpretation of 2D seismic profiles integrated with surface geological investigations, a mechanism responsible for the formation of a large scale normal fault zone has been proposed. The fault, here referred to as the Rycerka Fault, has a predominantly normal dip-slip component with the detachment surface located at the base of Carpathian units. The fault developed due to the formation of an anticlinal stack within the Dukla Unit overlain by the Magura Units. Stacking of a relatively narrow duplex led to the growth of a dome-like culmination in the lower unit, i.e., the Dukla Unit, and, as a consequence of differential uplift of the unit above and outside the duplex, the upper unit (the Magura Unit) was subjected to stretching. This process invoked normal faulting along the lateral culmination wall and was facilitated by the regional, syn-thrusting arc–parallel extension. Horizontal movement along the fault plane is a result of tear faulting accommodating a varied rate of advancement of Carpathian units. The time of the fault formation is not well constrained; however, based on superposition criterion, the syn -thrusting origin is anticipated.

Normal fault growth and segment linkage in a gravitationally detached delta system: evidence from 3D seismic reflection data from the Ceduna Sub-basin, Great Australian Bight

2015 ◽  
Vol 55 (2) ◽  
pp. 467
Author(s):  
Alexander Robson ◽  
Rosalind King ◽  
Simon Holford
Keyword(s):  
Seismic Reflection ◽  
Fault Plane ◽  
Structural Evolution ◽  
Normal Fault ◽  
Fault System ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Listric Fault ◽  
Dip Angle ◽  
Fault Growth

The authors used three-dimensional (3D) seismic reflection data from the central Ceduna Sub-Basin, Australia, to establish the structural evolution of a linked normal fault assemblage at the extensional top of a gravitationally driven delta system. The fault assemblage presented is decoupled at the base of a marine mud from the late Albian age. Strike-linkage has created a northwest–southeast oriented assemblage of normal fault segments and dip-linkage through Santonian strata, which connects a post-Santonian normal fault system to a Cenomanian-Santonian listric fault system. Cenomanian-Santonian fault growth is on the kilometre scale and builds an underlying structural grain, defining the geometry of the post-Santonian fault system. A fault plane dip-angle model has been created and established through simplistic depth conversion. This converts throw into fault plane dip-slip displacement, incorporating increasing heave of a listric fault and decreasing in dip-angle with depth. The analysis constrains fault growth into six evolutionary stages: early Cenomanian nucleation and radial growth of isolated fault segments; linkage of fault segments by the latest Cenomanian; latest Santonian Cessation of fault growth; erosion and heavy incision during the continental break-up of Australia and Antarctica (c. 83 Ma); vertically independent nucleation of the post-Santonian fault segments with rapid length establishment before significant displacement accumulation; and, continued displacement into the Cenozoic. The structural evolution of this fault system is compatible with the isolated fault model and segmented coherent fault model, indicating that these fault growth models do not need to be mutually exclusive to the growth of normal fault assemblages.

scholarly journals A functional tool to explore the reliability of micro-earthquake focal mechanism solutions for seismotectonic purposes

Solid Earth ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 65-83
Author(s):  
Guido Maria Adinolfi ◽  
Raffaella De Matteis ◽  
Rita de Nardis ◽  
Aldo Zollo
Keyword(s):  
Focal Mechanism ◽  
Fault Plane ◽  
Normal Fault ◽  
Focal Mechanisms ◽  
Seismic Network ◽  
Fault System ◽  
Fault Plane Solutions ◽  
Stress Regime ◽  
Focal Mechanism Solutions ◽  
Earthquake Focal Mechanism

Abstract. Improving the knowledge of seismogenic faults requires the integration of geological, seismological, and geophysical information. Among several analyses, the definition of earthquake focal mechanisms plays an essential role in providing information about the geometry of individual faults and the stress regime acting in a region. Fault plane solutions can be retrieved by several techniques operating in specific magnitude ranges, both in the time and frequency domain and using different data. For earthquakes of low magnitude, the limited number of available data and their uncertainties can compromise the stability of fault plane solutions. In this work, we propose a useful methodology to evaluate how well a seismic network, used to monitor natural and/or induced micro-seismicity, estimates focal mechanisms as a function of magnitude, location, and kinematics of seismic source and consequently their reliability in defining seismotectonic models. To study the consistency of focal mechanism solutions, we use a Bayesian approach that jointly inverts the P/S long-period spectral-level ratios and the P polarities to infer the fault plane solutions. We applied this methodology, by computing synthetic data, to the local seismic network operating in the Campania–Lucania Apennines (southern Italy) aimed to monitor the complex normal fault system activated during the Ms 6.9, 1980 earthquake. We demonstrate that the method we propose is effective and can be adapted for other case studies with a double purpose. It can be a valid tool to design or to test the performance of local seismic networks, and more generally it can be used to assign an absolute uncertainty to focal mechanism solutions fundamental for seismotectonic studies.

Characteristics of Seismicity in the Eagle Ford Shale Play, Southern Texas, Constrained by Earthquake Relocation and Centroid Moment Tensor Inversion

2021 ◽  
Author(s):  
Peng Li ◽  
Guo-Chin D. Huang ◽  
Alexandros Savvaidis ◽  
Florentia Kavoura ◽  
Robert W. Porritt
Keyword(s):  
Stress Field ◽  
Energy Release ◽  
Fault Plane ◽  
Anthropogenic Activities ◽  
Moment Tensor ◽  
Normal Fault ◽  
Strike Slip ◽  
Eagle Ford Shale ◽  
Eagle Ford ◽  
Earthquake Energy

Abstract Analysis of earthquake locations and centroid moment tensors (CMTs) is critical in assessing seismogenic structures and connecting earthquakes to anthropogenic activities. The objective of this study was to gain insights into the seismotectonics of the Eagle Ford Shale play (EF), southern Texas, through relative relocation of earthquakes, assessment of CMT solutions, and investigation of the background stress field. Using Texas Seismological Network (TexNet) data from 2017 through 2019, we were able to relocate 326 earthquakes and obtain CMT solutions for 37 ML≥2.0 earthquakes. These earthquakes are located in the sedimentary basin and uppermost crust, with depths ranging from 2 to 10 km. The earthquake groups in the northeastern EF are linearly distributed along the Karnes fault zone, whereas the southern and western groups are spatially scattered around mapped or unmapped faults. CMT solutions identified 32 normal fault earthquakes and five strike-slip earthquakes. The orientation of the fault plane of most normal fault earthquakes is southwest–northeast, whereas the possible fault plane of the strike-slip fault is from north-northwest to south-southeast, which is roughly perpendicular to the normal faults. Normal and strike-slip faults in the EF are of high dip angles, with the dip angles of the most faults ranging from 60° to 80°. Stress inversion results show that the major orientation of maximum horizontal stress (SHmax) is southwest–northeast, with minor local stress-field rotations. We further estimated earthquake energy release in the EF region using moment magnitude from the CMT solutions, and the cumulative earthquake energy release curve reveals three notable increases in cumulative seismic moment, which occurred in January–July 2018 and January–March 2019, and May–August 2019. Whether these energy releases were caused by anthropogenic activities is a matter for further investigation.

Recent instrumental seismicity of the southwest Matese Massif (Sannio-Matese area - Italy): a contribution on the seismotectonics setting.

2020 ◽  
Author(s):  
Girolamo Milano
Keyword(s):  
Fault Plane ◽  
Normal Fault ◽  
Focal Mechanisms ◽  
Common Element ◽  
Mountain Range ◽  
Depth Range ◽  
Main Shocks ◽  
Southern Side ◽  
A Minor ◽  
Low Magnitude

<p>The Matese Massif is the major mountain range of the Sannio-Matese, which is the transition area between central and southern Apennines. The Massif is located among the seismogenic sources of large destructive historical Earthquakes (e.g. 1349, M<sub>W</sub> =7.0; 1688, M<sub>W</sub> = 6.6; 1805, M<sub>W</sub> = 6.8). Previous studies on the instrumental seismicity of the Sannio-Matese have shown that the seismic activity along and close to the Matese Massif is prevalently characterized by the occurrence of sparse low magnitude events (M<sub>L</sub><2.5) and by seismic sequences with low to moderate magnitude (M<sub>Wmax</sub>=5.0) with hypocenters within the uppermost crust. Last relevant seismic sequence occurred between the late 2013-early 2014 following an M<sub>W</sub>=5.0 earthquake. This sequence struck the internal southern side of the Massif in an area where no evidence of active faulting has been recorded so far. Multidisciplinary investigation on this sequence suggest that the sequence has developed along a SW dipping NNW-SSE striking normal fault, ~10 km long, confined in the 10-20 km depth range. The 1805 Earthquake affected the northern slope of the Massif whereas the 1349 and 1688 Earthquakes affected the southern side. The 1349 Earthquake, that includes at least three main shocks, given its age, stands out due to the lack of reliable and sufficiently vast historical documentation. Geological, geomorphological and historical analysis on this Earthquake evidenced a SW dipping 125 striking 22 km length normal fault, named Aquae Iuliae Fault (AIF), as responsible for one of the main shocks of this Earthquake. In order to provide further information on the seismotectonics setting of the southwest sector of the Matese Massif, here is analyzed the instrumental seismicity occurred in 2009-2019 time interval in the area of the 1349 Earthquake. The spatial distribution of the relocated seismicity mainly consists of single events with magnitude M<sub>L</sub>≤3.5. The single events are localized prevalently nearby AIF and have foci falling generally in the first 15 km of the crust. The focal mechanisms of the most energetic events show normal dip-slip solutions, with NW-SE striking planes and NE-SW striking T-axes. The epicentral distribution of a low magnitude seismic swarm, triggered by an earthquake of ML 3.3 and constituted by about 120 events,  shows a roughly WNW-ESE alignment. The hypocenters, confined in the range 5-15 km depth, roughly depict a SW dipping plane. The fault plane solutions of the very few events of this swarm with M<sub>L</sub> > 2.0 show both normal dip slip solutions, with a minor strike component, and strike-slip solutions, with a minor dip component. The common element of these focal mechanisms is the presence of a SW dipping fault plane, striking from NW-SE to NNW-SSE. The preliminary results of this study, taking into account the dipping plane of the 2013-2014 sequence and that of the AIF, suggest that the release of seismic energy in the southwest side of the Matese Massif occur on very small fault segments, with SW dipping.</p>

scholarly journals Analysis of Gas Content and Permeability Change Pattern of a Coal Reservoir in the Tectonic Positions Based on a THM Coupled Model

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Zhenni Ye ◽  
Enke Hou ◽  
Huantong Li ◽  
Zhonghui Duan ◽  
Fan Wu
Keyword(s):  
Coal Seam ◽  
Fault Plane ◽  
Normal Fault ◽  
Geological Structure ◽  
Gas Content ◽  
High Permeability ◽  
Reservoir Permeability ◽  
Variation Distance ◽  
Hinge Zone ◽  
Coal Reservoir

The theory of coalbed methane distribution controlled by tectonism is a hot issue in the field of geofluid-geotectonic interaction research. Taking the geological structure in the scale range of the 1302 working face of a Guojiahe wellfield in a Yonglong mining area as the background, this paper focuses on the basic research problem of the influence of geological structure on the control of coal reservoir gas content and uses a THM coupling model to analyze the change of coalbed gas content and distribution characteristics of different tectonic positions. The change of CBM content and permeability in the anticline, syncline, and faults is analyzed. Accordingly, the variation distance of gas content and reservoir permeability controlled by tectonism of different geological structures is quantified to provide guidance for the selection of CBM-favorable areas. The research results show that the gentle dip syncline hinge zone is a potential gas-rich area with heat preservation and low permeability, while the gentle dip anticline hinge zone is a gas-poor area with low temperature and low pressure and high permeability. The thick coal seam zone of the syncline hinge zone is the potential gas accumulation zone, and the high-permeability area is near the fault plane of a normal fault. The coal matrix near the normal fault is subjected to tensile tectonic stresses to form tensional fissures, and the coal seam in the fault plane area is susceptible to coalbed gas dispersion and increases the permeability of the coal reservoir. The variation distance of gas content and reservoir permeability controlled by the normal fault within the Guojiahe wellfield is 37 m and 54 m from the fault plane, respectively.

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