Interseismic Deformation of the Altyn Tagh Fault Determined by Interferometric Synthetic Aperture Radar (InSAR) Measurements

Zhu, Sen; Xu, Caijun; Wen, Yangmao; Yang, Liu

doi:10.3390/rs8030233

Cited by 21 publications

(23 citation statements)

References 81 publications

(146 reference statements)

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“…I assume that loading of the Aksay bend is in shear parallel to the stem segments (Figure b) with no component of dilation across the fault zone. This assumption is supported by a recent study across ATF based on interferometric synthetic aperture radar measurements (Zhu et al, ), which also reports a maximum shear strain rate γ of about 3.9 × 10 −15 /s across ATF. This loading rate is used in this study.…”

Section: Modelssupporting

confidence: 62%

Multicycle Dynamics of the Aksay Bend Along the Altyn Tagh Fault in Northwest China: 1. A Simplified Double Bend

Duan

2019

Tectonics

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I perform multicycle dynamic simulations of a restraining double bend that is simplified from the Aksay bend along the Altyn Tagh Fault in northwest China. The earthquake cycle includes a coseismic dynamic rupture phase and an interseismic stress loading and relaxation phase. The double bend fault system has two fault strands and each strand comprises a stem segment that strikes parallel to the maximum shear loading direction and a bend segment that deviates from the loading direction. I find that the restraining double bend is an effective barrier to dynamically propagating ruptures over multiple earthquake cycles, with a probability of rupture jumping from one strand to the other varying from 0% to 10%, depending on parameter values of the rate dependence of friction during the dynamic phase and the viscosity for stress relaxation during the interseismic phase. The critical condition for the primary rupture on the first strand to jump onto the second strand is that the preshear stress is close enough to the shear strength over a certain size of the fault patch on the second strand. These results on the simplified double bend provide important insights into rupture behavior of geometrically complex faults over multiple earthquake cycles in general and a reference to explore rupture behavior of the Aksay bend in particular.

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Section: Modelssupporting

confidence: 62%

Multicycle Dynamics of the Aksay Bend Along the Altyn Tagh Fault in Northwest China: 1. A Simplified Double Bend

Duan

2019

Tectonics

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“…InSAR provides continuous maps of deformation throughout broad regions and therefore precisely constrains the fault's interseismic loading and its lateral variations. However, because of many data processing challenges, only a few studies attempted to measure interseismic deformation in the western part of Tibet (e.g., Bell et al, ; Elliott et al, ; Garthwaite et al, ; Jolivet et al, ; Wang & Wright, ; Wright et al, ; Zhu et al, ).…”

Section: Introductionmentioning

confidence: 99%

Strain Partitioning and Present‐Day Fault Kinematics in NW Tibet From Envisat SAR Interferometry

et al. 2018

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An 8 year archive of Envisat synthetic aperture radar (SAR) data over a 300 × 500 km2 wide area in northwestern Tibet is analyzed to construct a line‐of‐sight map of the current surface velocity field. The resulting velocity map reveals (1) a velocity gradient across the Altyn Tagh fault, (2) a sharp velocity change along a structure following the base of the alluvial fans in southern Tarim, and (3) a broad velocity gradient, following the Jinsha suture. The interferometric synthetic aperture radar velocity field is combined with published GPS data to constrain the geometry and slip rates of a fault model consisting of a vertical fault plane under the Altyn Tagh fault and a shallow flat décollement ending in a steeper ramp on the Tarim side. The solutions converge toward 0.7 mm/yr of pure thrusting on the décollement‐ramp system and 10.5 mm/yr of left‐lateral strike‐slip movement on the Altyn Tagh fault, below a 17 km locking depth. A simple elastic dislocation model across the Jinsha suture shows that data are consistent with 4–8 mm/yr of left‐lateral shear across this structure. Interferometric synthetic aperture radar processing steps include implementing a stepwise unwrapping method starting with high‐quality interferograms to assist in unwrapping noisier interferograms, iteratively estimating long‐wavelength spatial ramps, and referencing all interferograms to bedrock pixels surrounding sedimentary basins. A specific focus on atmospheric delay estimation using the ERA‐Interim model decreases the uncertainty on the velocity across the Tibet border by a factor of 2.

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“…We remark that one may choose another set of the frictional coefficients with lower values and what matter in the models are the relative values of these frictional coefficients. A loading rate of 3.9 × 10 −15 /s is chosen as the maximum shear strain rate γ that operates along the regional fault strike (e.g., parallel to the x axis), based on a recent study of InSAR measurements in the region (Zhu et al, ).…”

Section: Methods and Modelsmentioning

confidence: 99%

Multicycle Dynamics of the Aksay Bend Along the Altyn Tagh Fault in Northwest China: 2. The Realistically Complex Fault Geometry

2019

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We study rupture behavior of the Aksay bend along the Altyn Tagh fault in northwest China over multiple earthquake cycles. A finite element method is used to numerically simulate spontaneous rupture during a coseismic process, and a viscoelastic model is used to analytically compute the fault stresses during an interseismic process. We find that the Aksay bend is an effective barrier to halt dynamically propagating ruptures from either side of the bend within a range of model parameters, with statistically only about 10% of ruptures jumping across the bend and propagating through almost the entire local fault system. Secondary complexities in fault geometry within the bend, in particular those portions that align relatively well with the regional strike of the fault system, play a critical role in these occasionally jumping ruptures. Well-developed fault patches with shear stress close to shear strength allow dynamically propagating ruptures to penetrate into the bend and are more susceptible to the dynamic triggering that enables rupture to jump across the bend onto the other strand. We identify additionally nine large rupture scenarios with different occurrences, and most of them rupture one strand outside the bend with triggered slip on some portions of the same or the other strand within the bend. Slip rate distributions from the models show significantly reduced fault slip within the bend and a permanently locked portion on the south strand near the peak of the Altun Mountains. These findings have important implications for seismic hazard assessments of complex fault systems worldwide.

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Interseismic Deformation of the Altyn Tagh Fault Determined by Interferometric Synthetic Aperture Radar (InSAR) Measurements

Cited by 21 publications

References 81 publications

Multicycle Dynamics of the Aksay Bend Along the Altyn Tagh Fault in Northwest China: 1. A Simplified Double Bend

Multicycle Dynamics of the Aksay Bend Along the Altyn Tagh Fault in Northwest China: 1. A Simplified Double Bend

Strain Partitioning and Present‐Day Fault Kinematics in NW Tibet From Envisat SAR Interferometry

Multicycle Dynamics of the Aksay Bend Along the Altyn Tagh Fault in Northwest China: 2. The Realistically Complex Fault Geometry

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