Crustal rheology of southern Tibet constrained from lake-induced viscoelastic deformation

Henriquet, Maxime; Avouac, J. P.; Bills, B. G.

doi:10.1016/j.epsl.2018.11.014

Cited by 23 publications

(17 citation statements)

References 45 publications

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“…Despite these caveats, our estimates fall in the middle of the range of values inferred from previous studies of postseismic deformation in this region; in particular, their agreement with the post‐Gorkha estimate of Tian et al (2020) is encouraging. The deformation of early Holocene paleolake high‐stand shorelines in southern Tibet implies that the long‐term viscosity of the middle crust of Tibet is >10 18 Pa·s (England et al, 2013; Henriquet et al, 2019), and so the estimates derived here likely represent a transient viscosity that may be less prevalent over such timescales.…”

Section: Discussionmentioning

confidence: 85%

Postseismic Deformation Following the 2015 M_w7.8 Gorkha (Nepal) Earthquake: New GPS Data, Kinematic and Dynamic Models, and the Roles of Afterslip and Viscoelastic Relaxation

et al. 2020

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We report Global Positioning System (GPS) measurements of postseismic deformation following the 2015 M w 7.8 Gorkha (Nepal) earthquake, including previously unpublished data from 13 continuous GPS stations installed in southern Tibet shortly after the earthquake. We use variational Bayesian Independent Component Analysis (vbICA) to extract the signal of postseismic deformation from the GPS time series, revealing a broad displacement field extending >150 km northward from the rupture. Kinematic inversions and dynamic forward models show that these displacements could have been produced solely by afterslip on the Main Himalayan Thrust (MHT) but would require a broad distribution of afterslip extending similarly far north. This would require the constitutive parameter (a − b)σ to decrease northward on the MHT to ≤0.05 MPa (an extreme sensitivity of creep rate to stress change) and seems unlikely in light of the low interseismic coupling and high midcrustal temperatures beneath southern Tibet. We conclude that the northward reach of postseismic deformation more likely results from distributed viscoelastic relaxation, possibly in a midcrustal shear zone extending northward from the seismogenic MHT. Assuming a shear zone 5-20 km thick, we estimate an effective shear-zone viscosity of 3•10 16-3•10 17 Pa•s over the first 1.12 postseismic years. Near-field deformation can be more plausibly explained by afterslip itself and implies (a − b)σ~0.5-1 MPa, consistent with other afterslip studies. This near-field afterslip by itself would have re-increased the Coulomb stress by ≥0.05 MPa over >30% of the Gorkha rupture zone in the first postseismic year, and deformation further north would have compounded this reloading. However, the data used in previous studies of post-Gorkha deformation provided limited resolution of this key region north of the rupture: Global Positioning System (GPS) data (Figures 1a and 1b, open squares) were either confined to Nepal (

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Section: Discussionmentioning

confidence: 85%

Postseismic Deformation Following the 2015 M_w7.8 Gorkha (Nepal) Earthquake: New GPS Data, Kinematic and Dynamic Models, and the Roles of Afterslip and Viscoelastic Relaxation

et al. 2020

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“…Based on Model F, the transient viscosity of LC south of the Jinsha River suture might be ~4.0 × 10 17 Pa s; the corresponding effective viscosity at the decadal time scale should be an order of magnitude larger (>4.0 × 10 18 Pa s), and the steady‐state viscosities of LC elsewhere in the northern Tibetan Plateau are of the order of 10 19 Pa s, at least an order of magnitude larger than the corresponding value required by the “channel flow” model (<10 18 Pa s). Furthermore, short‐term estimates of the lower crustal viscosity may increase by one to two orders when the data for a longer time scale response are used to constrain a specific mechanical model (e.g., Henriquet et al, ). This finding, when combined with our results, suggests that geodetic data may not support the “channel flow” model for the northern Tibetan Plateau.…”

Section: Discussionmentioning

confidence: 99%

“…This finding, when combined with our results, suggests that geodetic data may not support the "channel flow" model for the northern Tibetan Plateau. However, estimates of the lower crustal viscosity scale with the layer thickness of the modeled lower crust to a power three (e.g., Henriquet et al, 2019). If we adjust the thickness of the lower crust from~50 km (as in our model) to 15 km (as in the "channel flow" model), south of the Jinsha River suture, geodetic estimates of lower crustal viscosity will decrease by almost 1 order of magnitude, to~10 16 Pa s, which is consistent with that of the "channel flow" model.…”

Section: Rheological Structure Beneath the Northern Tibetan Plateaumentioning

confidence: 99%

“…If we adjust the thickness of the lower crust from~50 km (as in our model) to 15 km (as in the "channel flow" model), south of the Jinsha River suture, geodetic estimates of lower crustal viscosity will decrease by almost 1 order of magnitude, to~10 16 Pa s, which is consistent with that of the "channel flow" model. Nonetheless, it remains unclear where the 15km thick layer would be located in the lower crust (at the top, at the bottom, or at the intermediate depth of the lower crust); when we consider the effects of time-dependent increase of the estimates of viscosity, geodetic estimates might not support the "channel flow" model for the northern Tibetan Plateau (e.g., Henriquet et al, 2019). For the other regions in the northern Tibetan Plateau (e.g., Sonpan-Ganzi terrane), the geodetic estimates are still larger than the corresponding value of the "channel flow" model.…”

Section: Rheological Structure Beneath the Northern Tibetan Plateaumentioning

confidence: 99%

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Lower Crustal Heterogeneity Beneath the Northern Tibetan Plateau Constrained by GPS Measurements Following the 2001 Mw7.8 Kokoxili Earthquake

Liu

Klinger

et al. 2019

JGR Solid Earth

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We use GPS measurements across the Xidatan segment of the Kunlun fault in the Tibetan Plateau to investigate the surface deformation following the 2001 Mw 7.8 Kokoxili earthquake. We find significant postseismic deformation during the period 2007-2015, characterized by an asymmetric shear across the 2001 rupture, with average velocities reaching~10 mm/year about 30-45 km south of the coseismic rupture. We also find that the postseismic transients diffused away from the coseismic rupture through time, with a shift of the maximum transient rates from~20-30 km south of the rupture in 2001-2002 to~30-45 km in 2007-2015. Viscoelastic relaxation is the dominant physical process during the period 2007-2015. The estimated effective viscosity of the lower crust beneath the Songpan-Ganzi terrane is 2 × 10 18 -3 × 10 18 Pa s from the 2001-2002 data, and it has increased to~2 × 10 19 Pa s for the period 6 to 14 years after the event. The large asymmetry in the postseismic deformation field indicates a laterally heterogeneous lower crust beneath the northern Tibetan Plateau. Viscoelastic relaxation models show that the viscosity of the lower crust beneath the Qaidam basin is~2 and~4 times larger than the viscosity of the lower crust beneath the Songpan-Ganzi terrane in 2001-2002 and 2007-2015, respectively. Based on these data and results from previous studies, we postulate that the Kunlun fault itself is not the unique rheological boundary and that additional domains with viscosity increasing from the Qiangtang terrane to the Qaidam basin appear to be required.Plain Language Summary Viscoelastic relaxation of earthquake-induced deviatoric stress change can last for several decades. In 2001, the Mw7.8 Kokoxili earthquake occurred along the Kunlun fault in the northern Tibetan Plateau. GPS measurements in the first two decades after the 2001 event show (1) that postseismic transients diffused away from the fault and (2) that postseismic transients are asymmetric across the coseismic rupture. We find that lower crustal viscosity heterogeneity leads to the observed asymmetric deformation. Although geodetic data constraints with better spatial and temporal coverage are needed, we find that lower crustal viscosity may exhibit northward stepwise increase across the Jinsha River suture, Kunlun fault, and the southern margin of the Qaidam basin. Our findings provide new constraints on the lithospheric structure and tectonic deformation in the northern Tibetan Plateau.

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“…One recent estimate of stagnant lid planets (Thiriet et al 2019) sets η = 10 20 − 10 21 Pa·s for dry mantle rheologies. On Earth, for the Tibetan crust and lithosphere, η = 10 18 − 10 20 Pa·s (Henriquet et al 2019), whereas for the Earth's mantle, η = 10 20 − 10 24 Pa·s (Mitrovica & Forte 2004).…”

Section: Variable Initial Conditions and Parameters Across Simulationsmentioning

confidence: 99%

Orbital relaxation and excitation of planets tidally interacting with white dwarfs

Veras

Efroimsky

Макаров

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Observational evidence of white dwarf planetary systems is dominated by the remains of exo-asteroids through accreted metals, debris discs, and orbiting planetesimals. However, exo-planets in these systems play crucial roles as perturbing agents, and can themselves be perturbed close to the white dwarf Roche radius. Here, we illustrate a procedure for computing the tidal interaction between a white dwarf and a near-spherical solid planet. This method determines the planet's inward and/or outward drift, and whether the planet will reach the Roche radius and be destroyed. We avoid constant tidal lag formulations and instead employ the self-consistent secular Darwin-Kaula expansions from Boué & Efroimsky (2019), which feature an arbitrary frequency dependence on the quality functions. We adopt wide ranges of dynamic viscosities and spin rates for the planet in order to straddle many possible outcomes, and provide a foundation for the future study of individual systems with known or assumed rheologies. We find that: (i) massive Super-Earths are destroyed more readily than minor planets (such as the ones orbiting WD 1145+017 and SDSS J1228+1040), (ii) low-viscosity planets are destroyed more easily than high-viscosity planets, and (iii) the boundary between survival and destruction is likely to be fractal and chaotic.

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Crustal rheology of southern Tibet constrained from lake-induced viscoelastic deformation

Cited by 23 publications

References 45 publications

Postseismic Deformation Following the 2015 M_w7.8 Gorkha (Nepal) Earthquake: New GPS Data, Kinematic and Dynamic Models, and the Roles of Afterslip and Viscoelastic Relaxation

Postseismic Deformation Following the 2015 M_w7.8 Gorkha (Nepal) Earthquake: New GPS Data, Kinematic and Dynamic Models, and the Roles of Afterslip and Viscoelastic Relaxation

Lower Crustal Heterogeneity Beneath the Northern Tibetan Plateau Constrained by GPS Measurements Following the 2001 Mw7.8 Kokoxili Earthquake

Orbital relaxation and excitation of planets tidally interacting with white dwarfs

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Crustal rheology of southern Tibet constrained from lake-induced viscoelastic deformation

Cited by 23 publications

References 45 publications

Postseismic Deformation Following the 2015 Mw7.8 Gorkha (Nepal) Earthquake: New GPS Data, Kinematic and Dynamic Models, and the Roles of Afterslip and Viscoelastic Relaxation

Postseismic Deformation Following the 2015 Mw7.8 Gorkha (Nepal) Earthquake: New GPS Data, Kinematic and Dynamic Models, and the Roles of Afterslip and Viscoelastic Relaxation

Lower Crustal Heterogeneity Beneath the Northern Tibetan Plateau Constrained by GPS Measurements Following the 2001 Mw7.8 Kokoxili Earthquake

Orbital relaxation and excitation of planets tidally interacting with white dwarfs

Contact Info

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Postseismic Deformation Following the 2015 M_w7.8 Gorkha (Nepal) Earthquake: New GPS Data, Kinematic and Dynamic Models, and the Roles of Afterslip and Viscoelastic Relaxation

Postseismic Deformation Following the 2015 M_w7.8 Gorkha (Nepal) Earthquake: New GPS Data, Kinematic and Dynamic Models, and the Roles of Afterslip and Viscoelastic Relaxation