Crustal Deformation Prior to the 2017 Jiuzhaigou, Northeastern Tibetan Plateau (China), Ms 7.0 Earthquake Derived from GPS Observations

The 2017 Jiuzhaigou Ms 7.0 earthquake occurred on the northeastern margin of the Tibetan Plateau, with no noticeable rupture surface recognized. We characterized the pre-seismic deformation of the earthquake from GPS (Global Positioning System) data at eight continuous and 73 campaign sites acquired over the 2009–2017 period. With respect to the Eurasian plate, the velocity field showed a noticeable decrease, from west of the epicenter of the Jiuzhaigou earthquake to the western edge of the Longmenshan fault, in the southeast direction. The total northwest west–southeast east shortening rate in the vicinity of the epicentral area was in the range of 1.5 mm/y to 3.1 mm/y. With a GPS velocity transect across the Huya fault (HYF), where the epicenter was located, we estimated the activity of the HYF, showing a dominant left-lateral slip rate of 3.3 ± 0.2 mm/y. We calculated strain rates using a spherical wavelet-based multiscale approach that solved for the surface GPS velocity according to multiscale wavelet basis functions while accounting for spatially variable spacing of observations. Multiscale components of the two-dimensional strain rate tensor showed a complex crustal deformation pattern. Our estimates of strain rate components at the scale of seven and eight revealed extensional strain rate on the northern extension of the HYF. The Jiuzhaigou earthquake occurred at the buffer zone between extensional and compressional deformation, and with significant maximum shear rates being 100–140 nanostrain/y. In addition, a maximum shear strain rate of 60–120 nanostrain/y appeared around the epicenter of the 2013 Ms 6.6 Minxian–Zhangxian earthquake. These findings imply that inherent multiscale strain rates could be separated to identify strain accumulation related to medium- and large-sized earthquakes.

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Crustal Deformation on the Northeastern Margin of the Tibetan Plateau from Continuous GPS Observations

Remote Sensing ◽

10.3390/rs11010034 ◽

2018 ◽

Vol 11 (1) ◽

pp. 34 ◽

Cited By ~ 5

Author(s):

Xiaoning Su ◽

Lianbi Yao ◽

Weiwei Wu ◽

Guojie Meng ◽

Lina Su ◽

...

Keyword(s):

Tibetan Plateau ◽

Crustal Deformation ◽

Flicker Noise ◽

Noise Model ◽

Tectonic Deformation ◽

Deformation Pattern ◽

The Tibetan Plateau ◽

Strain Rates ◽

Strain Accumulation ◽

Strain Partitioning

We installed 10 continuous Global Positioning System (GPS) stations on the northeast margin of the Tibetan Plateau at the end of 2012, in order to qualitatively investigate strain accumulation across the Liupanshan Fault (LPSF). We integrated our newly built stations with 48 other existing GPS stations to provide new insights into three-dimensional tectonic deformation. We employed white plus flicker noise model as a statistical model to obtain realistic velocities and corresponding uncertainties in the ITRF2014 and Ordos-fixed reference frame. The total velocity decrease from northwest to southeast in the Longxi Block (LXB) was 5.3 mm/yr within the range of 200 km west of the LPSF on the horizontal component. The first-order characteristic of the vertical crustal deformation was uplift for the northeastern margin of the Tibetan Plateau. The uplift rates in the LXB and the Ordos Block (ORB) were 1.0 and 2.0 mm/yr, respectively. We adopted an improved spherical wavelet algorithm to invert for multiscale strain rates and rotation rates. Multiscale strain rates showed a complex crustal deformation pattern. A significant clockwise rotation of about 30 nradians/yr (10−9 radians/year) was identified around the Dingxi. Localized strain accumulation was determined around the intersectional region between the Haiyuan Fault (HYF) and the LPSF. The deformation pattern across the LFPS was similar to that of the Longmengshan Fault (LMSF) before the 2008 Wenchuan MS 8.0 earthquake. Furthermore, according to the distributed second invariant of strain rates at different spatial scale, strain partitioning has already spatially localized along the Xiaokou–Liupanshan–Longxian–Baoji fault belt (XLLBF). The tectonic deformation and localized strain buildup together with seismicity imply a high probability for a potential earthquake in this zone.

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Erebus Glacier Tongue, Mcmurdo Sound, Antarctica

Journal of Glaciology ◽

10.1017/s0022143000023340 ◽

1974 ◽

Vol 13 (67) ◽

pp. 27-35 ◽

Cited By ~ 39

Author(s):

G. Holdsworth

Keyword(s):

Shear Stress ◽

Strain Rate ◽

Shear Strain ◽

Longitudinal Strain ◽

Strain Rates ◽

Shear Strain Rate ◽

Mcmurdo Sound ◽

Glacier Tongue ◽

The Past ◽

Image Position

Examination of the past and present behaviour of the Erebus Glacier tongue over the last 60 years indicates that a major calving from the tongue appears to be imminent. Calculations of the regime of the tongue indicate that bottom melt rates may exceed 1 m a−1. By successive mapping of the ice tongue between the years 1947 and 1970, longitudinal strain-rates were determined using the change in distance between a set of 15 teeth, which are a prominent marginal feature of the tongue. Assuming a flow law for ice of the form where τ is the effective shear stress and is the effective shear strain-rate, values of the exponent n = 3 and B = 1 × 108 N m−2 are determined. These are in fair agreement with published values.

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Strain Rates On Rutford Ice Stream, Antarctica (Abstract)

Annals of Glaciology ◽

10.1017/s0260305500001592 ◽

1986 ◽

Vol 8 ◽

pp. 207

Author(s):

N. Stephenson ◽

C.S.M. Doake

Keyword(s):

Strain Rate ◽

Velocity Gradient ◽

Surface Strain ◽

Lateral Strain ◽

Strain Rate Tensor ◽

Strain Rates ◽

Average Value ◽

Divergent Flow ◽

Ice Stream ◽

Thickness Variations

In a study of the Rutford Ice Stream, strain rates were measured on a transverse section. Magnitudes ranged up to 40 × 10−3 a−1 but were typically in the order of 3 × 10−3 a−1 with an error of 0.1 χ 10−3 a−1. Variations in the strain rate between adjacent stakes of 0.2 χ 10−3 a−1 to 2 × 10−3 a−1 were matched to the thickness variations on the glacier. For each set of three adjacent stakes, the velocity gradient components of the surface strain rate tensor were calculated by assuming that the gradients were linear over the distance between adjacent stakes. When plotted against distance across the ice stream, each strain rate component revealed different aspects of the flow field. The longitudinal strain rate was compressive, with an almost constant magnitude of 10−3 a−1. The lateral strain rate is extensive, with an average value of 1.1 × 10−3 a−1 which agreed with the angle between the divergent flow lines observed on a Landsat image. Peaks in the lateral strain rate, corresponding to longitudinal bands of thicker ice, showed that these thicker bands were spreading more rapidly at the expense of thinner areas. The two velocity gradient components of the shear rate tensor also reflected differences in ice thickness.

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Dynamics and Structure of Griesgletscher, Switzerland

Journal of Glaciology ◽

10.1017/s0022143000010455 ◽

1980 ◽

Vol 25 (92) ◽

pp. 215-228 ◽

Cited By ~ 30

Author(s):

M. J. Hambrey ◽

A. G. Milnes ◽

H. Siegenthaler

Keyword(s):

Strain Rate ◽

Flow Line ◽

Compressive Strain ◽

Local Deformation ◽

Strain History ◽

Strain Rates ◽

Shear Strain Rate ◽

Maximum Shear Strain ◽

Alpine Valley ◽

Ablation Area

AbstractA detailed investigation has been carried out on the dynamics of an Alpine valley glacier of relatively simple shape and the results are considered in relation to the development of secondary structures. Ice velocity reaches a maximum near the top of a small ice fall (40 m a−1) which also coincides approximately with the equilibrium line. Flow lines converge in the accumulation area but are roughly parallel in the ablation area. The “regional” strain-rate pattern is rather complex. Approximate longitudinal extension is evident in the accumulation area and strain-rates reach high values at the south margin and in the ice fall (up to 0.12 a−1). In the ablation area, strain-rates are comparatively small and in general indicate longitudinal compression. “Local” deformation rates obtained in the area beneath the ice fall and along a flow line near one of the margins reveal complex patterns of deformation within small areas.There is no clear relationship between foliation and strain-rates (and by analogy stresses), except in the case of longitudinal foliation in marginal areas which, if actively developing, lies approximately parallel to a direction of maximum shear strain-rate. It is more important to consider the relationship of this structure to strain history. Results from this study indicate that, regardless of the initial orientation of the foliation in relation to the strain ellipse, it attains approximate parallelism with the long axis of the ellipse as deformation progresses.It is also shown that many foliations originate from pre-existing layered structures such as stratification or crevasse traces. This problem is discussed particularly with reference to an arcuate foliation which originates in the ice fall and is believed to represent tensional veins, subsequently subjected to compressive strain within and below the ice fall.

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INTEGRATION OF GNSS-GPS NETWORKS (cGPS) FOR OBTAINING STRESS AND STRAIN MODELS FOR THE SPINA REGION (SOUTH OF THE IBERIAN PENINSULA AND NORTH AFRICA)

10.5194/egusphere-egu2020-19570 ◽

2020 ◽

Author(s):

Alejandro Pérez-Peña ◽

Alberto Fernández-Ros ◽

Belen Rosado ◽

Amós De Gil ◽

Gonzalo Prates ◽

...

Keyword(s):

Strain Rate ◽

Iberian Peninsula ◽

Least Squares Method ◽

Weighted Least Squares ◽

Ductile Deformation ◽

Series Data ◽

Strain Rate Tensor ◽

Shear Strain Rate ◽

Geodynamic Processes ◽

Gnss Data

Nowadays, both, the number of observations and the accuracy of satellite-based geodesic measurements, like GNSS, have increased. Therefore, GNSS provides more data as displacement values and velocities. This paper demonstrates that GNSS data analysis is a powerful tool to study geodynamic processes.In this study, the analyzed GNSS data correspond to continuously recorded GPS (CGPS) stations, what we call the SPINA network. These stations are located in a region called Ibero-Maghrebian which includes the southern areas of the Iberian Peninsula and northern Africa.The CGPS stations are included in the following organizations: RENEP (National Network of Permanent Stations), RAP (Andalusian Positioning Network), the Murcia Region CGPS Networks, ERVA (Valencian Reference Stations Network), IGN (National Geographic Institute) and the network TOPOIBERIA. The velocity was obtained in two steps: (1) preprocessing position time-series data of daily GPS measurements and (2) applying a combined model using the weighted least-squares method.The prior knowledge of the crustal strain rate tensor provides a description of geodynamic processes such as the fault strain accumulation.Based on the distribution of the GNSS stations, several grid sizes were tested to identify the best resolution. A Python script was used to compute the full two-dimensional velocity gradient tensor by means of inverting the GNSS velocities. The tensorial analysis provides different aspects of deformation, such as the maximum shear strain rate, including its direction, and the dilatation strain rate. These parameters can be used to characterize the mechanism of the current deformation.Based on the computations from the GNSS-data model of components of horizontal deformations, the rates of both principal, values and axes, of the Earth&#8217;s crust deformation were found. Deformations measured in the Ibero-Maghrebian region with GPS could be interpreted in terms of either elastic loading or ductile deformation.

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A Method of Determining the Strain-Rate Tensor at the Surface of a Glacier

Journal of Glaciology ◽

10.1017/s0022143000017093 ◽

1959 ◽

Vol 3 (25) ◽

pp. 409-419 ◽

Cited By ~ 85

Author(s):

J. F. Nye

Keyword(s):

Strain Rate ◽

Least Squares Method ◽

Strain Tensor ◽

Rate Of Change ◽

Principal Strain ◽

Strain Rate Tensor ◽

Strain Rates ◽

Principal Stresses ◽

Independent Components ◽

Good Agreement

AbstractThe rate of strain tensor at a point on the surface of a glacier may be determined by setting up a number of stakes in a pattern and measuring the rate of change of the distances between them. A suitable pattern consists of four stakes at the corners of a square with one stake at the center. Five such patterns were used on Austerdalsbreen, Norway, in August 1956. The problem is to deduce the best values of the 3 independent components of the strain-rate tensor from the 8 measured quantities, and, for this purpose, a least-squares method, invented by Bond for the analogous problem in crystal physics, is used. The principal strain-rates are found to within about ±0.005 yr.−1and their directions relative to the stake system to within about ±0.5°. The directions and magnitudes of the principal stresses are then deduced from Glen’s flow law and a suitable general theory. The directions of the principal strain-rates are in good agreement with the directions of the crevasses, but the experiment is inconclusive on the question of the magnitude of the stress needed to form a crevasse.

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High Strain Rate Behavior of Metals

Applied Mechanics Reviews ◽

10.1115/1.3120862 ◽

1990 ◽

Vol 43 (5S) ◽

pp. S9-S22 ◽

Cited By ~ 51

Author(s):

R. J. Clifton

Keyword(s):

Flow Stress ◽

High Strain Rate ◽

Strain Rate ◽

High Strain ◽

Rate Sensitivity ◽

Strong Increase ◽

Strain Rates ◽

Shear Strain Rate ◽

High Strain Rates ◽

Strain Rate Change

Experimental results on the high strain rate response of polycrystalline metals are reviewed, with emphasis on the behavior of pure metals. A strong increase in flow stress with increasing strain rate is reported for strain rates of approximately 105s−1 and higher. This increase is observed in pressure-shear plate impact experiments at nominally constant strain rates from 105s−1 to 106s−1. To improve understanding of the increased rate sensitivity at high strain rates, pressure-shear, strain-rate-change experiments have been conducted on OFHC copper specimens. These experiments have been analyzed using a conventional viscoplasticity formulation and an internal variable formulation in which the hardening rate depends on the rate of deformation. Only the latter formulation is successful in describing the observed response to the change in strain rate. This observation is discussed in terms of its implications for interpreting other dynamic plasticity experiments and for improved understanding of the underlying dislocation mechanisms. The enhanced rate sensitivity at high strain rates is concluded to be related primarily to the rate sensitivity of strain hardening, not the rate sensitivity of the flow stress at constant structure.

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A Method of Determining the Strain-Rate Tensor at the Surface of a Glacier

Journal of Glaciology ◽

10.3189/s0022143000017093 ◽

1959 ◽

Vol 3 (25) ◽

pp. 409-419 ◽

Cited By ~ 5

Author(s):

J. F. Nye

Keyword(s):

Strain Rate ◽

Least Squares Method ◽

Strain Tensor ◽

Rate Of Change ◽

Principal Strain ◽

Strain Rate Tensor ◽

Strain Rates ◽

Principal Stresses ◽

Independent Components ◽

Good Agreement

AbstractThe rate of strain tensor at a point on the surface of a glacier may be determined by setting up a number of stakes in a pattern and measuring the rate of change of the distances between them. A suitable pattern consists of four stakes at the corners of a square with one stake at the center. Five such patterns were used on Austerdalsbreen, Norway, in August 1956. The problem is to deduce the best values of the 3 independent components of the strain-rate tensor from the 8 measured quantities, and, for this purpose, a least-squares method, invented by Bond for the analogous problem in crystal physics, is used. The principal strain-rates are found to within about ±0.005 yr.−1 and their directions relative to the stake system to within about ±0.5°. The directions and magnitudes of the principal stresses are then deduced from Glen’s flow law and a suitable general theory. The directions of the principal strain-rates are in good agreement with the directions of the crevasses, but the experiment is inconclusive on the question of the magnitude of the stress needed to form a crevasse.

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Strain Rate Dependent Constitutive Model of Multiaxial Ratchetting of 63Sn–37Pb Solder

Journal of Electronic Packaging ◽

10.1115/1.2753917 ◽

2006 ◽

Vol 129 (3) ◽

pp. 278-286 ◽

Cited By ~ 5

Author(s):

Gang Chen ◽

Xu Chen ◽

Kwang Soo Kim ◽

Mohammad Abdel-Karim ◽

Masao Sakane

Keyword(s):

Constitutive Model ◽

Strain Rate ◽

Shear Strain ◽

Kinematic Hardening ◽

Axial Stress ◽

Strain Range ◽

Strain Rates ◽

Shear Strain Rate ◽

Viscous Term ◽

Ratcheting Strain

A series of multiaxial ratcheting tests were conducted on 63Sn–37Pb solder. A unified viscoplastic constitutive model was developed on the basis of the Ohno–Wang kinematic hardening model, and the rate dependence of the material was taken into consideration by introducing a viscous term. The stress-strain hysteresis loop of 63Sn–37Pb under different strain rates can be simulated reasonably well by the model. However, since the axial ratcheting strain rate of 63Sn–37Pb solder is strongly dependent on the applied shear strain rates in axial/torsional ratcheting, the original constitutive model fails to describe the effect of shear strain rate on the ratcheting strain. To improve the rate sensitivity of the model, the material parameter μi was correlated to the strain rate. Comparisons of the experimental and simulated results verify that the modified constitutive model is able to predict the complicated deformation of 63Sn–37Pb. The effects of axial stress, shear strain range, loading history, and strain rate on ratcheting behavior can be reflected fairly well.

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Strain Transformation Adjacent to the West Qinling Orogen: Implications for the Growth of the Northeastern Tibetan Plateau

Frontiers in Earth Science ◽

10.3389/feart.2021.689087 ◽

2021 ◽

Vol 9 ◽

Author(s):

Zhangjun Li ◽

Feng Cheng ◽

Ming Hao ◽

Zachary M. Young ◽

Shangwu Song ◽

...

Keyword(s):

Tibetan Plateau ◽

Crustal Deformation ◽

Deformation Pattern ◽

Qinling Orogen ◽

The West ◽

West Qinling ◽

Vertical Land Motion ◽

Northeastern Tibetan Plateau ◽

Strain Transformation ◽

West Qinling Orogen

The West Qinling orogen has played an important role in accommodating the deformation in the northeastern Tibetan Plateau induced by the India-Eurasia convergence. Here we construct a vertical land motion (VLM) model based on the latest leveling observations adjacent to the West Qinling orogen. Combined with the horizontal deformation field, the crustal deformation pattern in this area is investigated. Additionally, slip rate and coupling coefficients of the West Qinling fault, the longest fault separating the West Qinling orogen from the Lanzhou (Longxi) block, are inverted and constrained with GPS and VLM observations. Results show that the West Qinling fault slips slowly at a rate of 1–2 mm/yr and is strongly coupled with a moment magnitude deficit of Mw7.4. The crustal uplift rates adjacent to the West Qinling orogen are 0–3 mm/yr; which combined with 0–12.5 × 10−9/yr contraction rates, suggests that strain transformation plays a key role in controlling the tectonic uplift in the West Qinling orogen, and furthers our understanding of the contemporary geomorphic and topographic features. We identify a significant deformation transition belt at longitudes of 105°–106°E, which indicates that crustal deformation, induced from the northeastern expansion of the Tibetan Plateau, is mainly constrained to the plateau, rather than accommodated by crustal materials escaping eastward along the Qinling Mountains.

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