Shear Fault-bend Folding

2004 ◽  
pp. 309-329
Keyword(s):  
Fault Bend

FLEXIBLE APPROACHES TO KINEMATIC FORWARD MODELING OF FAULT-BEND FOLDING

2019 ◽  
Author(s):  
Christopher D. Connors ◽  
◽  
Amanda Hughes
Keyword(s):  
Forward Modeling ◽  
Fault Bend

RELAXED KINEMATIC FAULT-BEND FOLDING CONSTRAINTS INFORMED BY MECHANICAL MODELING

2019 ◽  
Author(s):  
Amanda N. Hughes ◽  
◽  
Christopher D. Connors
Keyword(s):  
Mechanical Modeling ◽  
Fault Bend

Lower Portion Rupture of a Thrust Fault during the 2017 Mw 6.3 Jinghe Earthquake: Implications to Seismic Hazards in the Tian Shan Region

2021 ◽  
Author(s):  
Zongkai Hu ◽  
Tao Li ◽  
Jessica Thompson Jobe ◽  
Xiaoping Yang
Keyword(s):  
Land Surface ◽  
Geometric Model ◽  
Interferometric Synthetic Aperture Radar ◽  
Coseismic Slip ◽  
Surface Mapping ◽  
Strong Earthquakes ◽  
Fault Bend ◽  
Large Earthquakes ◽  
Rupture Pattern ◽  
Tian Shan

Abstract The 2017 Mw 6.3 Jinghe earthquake represents one of the few large earthquakes that are well recorded by seismic instruments and Interferometric Synthetic Aperture Radar (InSAR) observations in the seismically active Tian Shan region. In this study, we use the rupture fault solution (dip, dip direction, and slip sense) from seismologic and InSAR results, along with analysis of our collected surface mapping data, to determine the subsurface fault-plane geometry of the seismogenic Jinghenan fault. This geometric model, integrated with the coseismic slip distribution from seismologic and InSAR data, reveals that: (1) the Jinghenan fault extends downward from the land surface at a dip of ∼46° S (upper ramp), then bends to ∼42° S (lower ramp) at the depth of 9–13 km; (2) the coseismic rupture is confined within the Jinghenan lower ramp, and its upper limitation is approximately coincident with the fault-bend location. This coseismic rupture pattern and seismic behavior can be broadened to other active thrust faults within the Tian Shan, suggesting that, during moderate-strong earthquakes, such faults may only rupture partially in the down-dip extension, and the unruptured fault portion remains to pose high-seismic risk in the future.

The Role of Frontal Thrusts in Tsunami Earthquake Generation

2021 ◽  
Author(s):  
Raquel P. Felix ◽  
Judith A. Hubbard ◽  
James D. P. Moore ◽  
Adam D. Switzer
Keyword(s):  
Subduction Zones ◽  
Generation Process ◽  
Lower Amplitude ◽  
Tsunami Earthquakes ◽  
Fault Bend ◽  
Wave Heights ◽  
Seafloor Deformation ◽  
Tsunami Earthquake ◽  
Tsunami Energy ◽  
The Impact

ABSTRACT The frontal sections of subduction zones are the source of a poorly understood hazard: “tsunami earthquakes,” which generate larger-than-expected tsunamis given their seismic shaking. Slip on frontal thrusts is considered to be the cause of increased wave heights in these earthquakes, but the impact of this mechanism has thus far not been quantified. Here, we explore how frontal thrust slip can contribute to tsunami wave generation by modeling the resulting seafloor deformation using fault-bend folding theory. We then quantify wave heights in 2D and expected tsunami energies in 3D for both thrust splays (using fault-bend folding) and down-dip décollement ruptures (modeled as elastic). We present an analytical solution for the damping effect of the water column and show that, because the narrow band of seafloor uplift produced by frontal thrust slip is damped, initial tsunami heights and resulting energies are relatively low. Although the geometry of the thrust can modify seafloor deformation, water damping reduces these differences; tsunami energy is generally insensitive to thrust ramp parameters, such as fault dip, geological evolution, sedimentation, and erosion. Tsunami energy depends primarily on three features: décollement depth below the seafloor, water depth, and coseismic slip. Because frontal ruptures of subduction zones include slip on both the frontal thrust and the down-dip décollement, we compare their tsunami energies. We find that thrust ramps generate significantly lower energies than the paired slip on the décollement. Using a case study of the 25 October 2010 Mw 7.8 Mentawai tsunami earthquake, we show that although slip on the décollement and frontal thrust together can generate the required tsunami energy, <10% was contributed by the frontal thrust. Overall, our results demonstrate that the wider, lower amplitude uplift produced by décollement slip must play a dominant role in the tsunami generation process for tsunami earthquakes.

Sandbox models of fault-bend folding: A new investigation with a pre-existing fault ramp

2019 ◽  
Vol 127 ◽  
pp. 103864
Author(s):  
Marcela Lopes Zanon ◽  
Caroline Janette Souza Gomes
Keyword(s):  
Fault Bend

scholarly journals Throw variations and strain partitioning associated with fault-bend folding along normal faults

2019 ◽  
Author(s):  
Efstratios Delogkos ◽  
Muhammad Mudasar Saqab ◽  
John J. Walsh ◽  
Vincent Roche ◽  
Conrad Childs
Keyword(s):  
Large Scale ◽  
Full Range ◽  
Quantitative Model ◽  
Normal Faults ◽  
Strain Partitioning ◽  
Fault Surface ◽  
Irregular Geometries ◽  
Surface Irregularities ◽  
Fault Bend ◽  
Constant Displacement

Abstract. Normal faults have irregular geometries on a range of scales arising from different processes including refraction and segmentation. A fault with an average dip and constant displacement on a large-scale, will have irregular geometries on smaller scales, the presence of which will generate fault-related folds, with major implications for across-fault throw variations. A quantitative model has been presented which illustrates the range of deformation arising from movement on fault surface irregularities, with fault-bend folding generating geometries reminiscent of normal drag and reverse drag. The model highlights how along-fault displacements are partitioned between continuous (i.e. folding) and discontinuous (i.e. discrete displacement) strain along fault bends characterised by the full range of fault dip changes. Strain partitioning has a profound effect on measured throw values across faults, if account is not taken of the continuous strains accommodated by folding and bed rotations. We show that fault throw can be subject to errors of up to ca. 50 % for realistic fault bend geometries (up to ca. 40°), even on otherwise sub-planar faults with constant displacement. This effect will provide apparently more irregular variations in throw and bed geometries that must be accounted for in associated kinematic interpretations.

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