Revisiting the Fault Locking of the Central Himalayan Thrust with a Viscoelastic Earthquake-Cycle Deformation Model

2021 ◽  
Author(s):  
Faqi Diao ◽  
Rongjiang Wang ◽  
Yage Zhu ◽  
Xiong Xiong
Keyword(s):  
Viscoelastic Model ◽  
Slip Rate ◽  
Relaxation Effect ◽  
Deformation Model ◽  
Far Field ◽  
Viscoelastic Relaxation ◽  
Earthquake Cycle ◽  
2015 Gorkha Earthquake ◽  
Fault Kinematics ◽  
Fault Locking

Abstract Based on a viscoelastic earthquake-cycle deformation model, we revisit the fault locking of the central Himalayan thrust using geodetic data acquired in the past three decades. By incorporating the viscoelastic relaxation effect induced by stress buildup and release, our viscoelastic model is capable of explaining the far-field observation with similar fault locking width obtained in previous studies. Elastic models underestimate the far-field deformation and consequently underestimate the fault slip rate by attributing the far-field deformation to stable intraplate deformation. A steady-state viscosity of ∼1019  Pa·s is required for the lower crust beneath south Tibet to best fit the crustal velocity. The optimal slip rate and locking width of the central Main Himalayan Thrust are estimated to 18.8 ± 1.6 mm/a and 85 ± 2.1 km, respectively. The inferred fault locking width, along with the down-dip rupture extension of the 2015 Gorkha earthquake, agrees well with the identified mid-crustal ramp, which leads to an interpretation that the fault geometry of the central Himalayan thrust plays an important role on fault kinematics. Our results highlight that viscoelastic relaxation during the earthquake cycle should be incorporated for robust estimation of fault locking parameters and reasonable data fitting.

scholarly journals Locking Status and Earthquake Potential Hazard along the Middle-South Xianshuihe Fault

2018 ◽  
Vol 10 (12) ◽  
pp. 2048 ◽  
Author(s):  
Rumeng Guo ◽  
Yong Zheng ◽  
Wen Tian ◽  
Jianqiao Xu ◽  
Wenting Zhang
Keyword(s):  
Slip Rate ◽  
Relaxation Effect ◽  
Historical Earthquakes ◽  
Coulomb Stress ◽  
Deformation Model ◽  
Potential Hazard ◽  
Viscoelastic Deformation ◽  
Strong Earthquakes ◽  
Coulomb Stress Changes ◽  
Stress Changes

By combining the seismogenic environment, seismic recurrence periods of strong historical earthquakes, precise locations of small–moderate earthquakes, and Coulomb stress changes of moderate–strong earthquakes, we analyze the potential locking status of a seismically quiet segment of Xianshuihe fault between Daofu County and Kangding City (SDK). The interseismic surface velocities between 1999 and 2017 are obtained from updated global positioning system (GPS) observations in this region. After removing the post-seismic relaxation effect caused by the 2008 Mw 7.9 Wenchuan earthquake that occurred around the fault segment, the observed velocities reveal a pronounced symmetric slip pattern along the SDK trace. The far field slip rate is 7.8 ± 0.4 mm/a, and the fault SDK is confirmed to be in an interseismic silent phase. The optimal locking depth is estimated at 7 km, which is perfectly distributed on the upper edge of the relocated hypocenters. A moment deficit analysis shows cumulative seismic moment between 1955 and 2018, corresponding to an Mw 6.6 event. Finally, based on a viscoelastic deformation model, we find that moderate–strong earthquakes in the surrounding area increase the Coulomb stress level by up to 2 bars on the SDK, significantly enhancing the future seismic potential.

scholarly journals Slip Rate Variation Along the Kunlun Fault (Tibet): Results From New GPS Observations and a Viscoelastic Earthquake‐Cycle Deformation Model

2019 ◽  
Vol 46 (5) ◽  
pp. 2524-2533 ◽  
Author(s):  
Faqi Diao ◽  
Xiong Xiong ◽  
Rongjiang Wang ◽  
Thomas R. Walter ◽  
Yuebing Wang ◽  
...  
Keyword(s):  
Slip Rate ◽  
Rate Variation ◽  
Deformation Model ◽  
Earthquake Cycle ◽  
Gps Observations

scholarly journals Kinematics of Crustal Deformation along the Central Himalaya

2021 ◽  
Author(s):  
Yogendra Sharma ◽  
Sumanta Pasari ◽  
Kuo-En Ching
Keyword(s):  
Crustal Deformation ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
Central Himalaya ◽  
Maximum Shear Strain ◽  
Nepal Himalaya ◽  
Posterior Probability Distribution ◽  
Background Seismicity ◽  
Fault Kinematics ◽  
Fault Locking

Abstract Using an updated set of GPS surface velocities, the present study provides fault locking behavior and slip rate distribution of the Main Himalayan Thrust (MHT) along the central Himalaya. The two-dimensional velocity field is inverted through Bayesian inversion to estimate fault geometry and kinematic parameters of the MHT along the central Himalaya. The modeling results reveal that: (1) MHT is fully locked in the upper flat (0-9 km), partially locked along the mid-crustal ramp (15-21 km), and it is creeping in the deeper flat (> 21 km); (2) there is an insignificant slip rate of MHT along the locked-to-creeping transition zone, indicating its partially coupled/locked behavior; (3) along the deeper flat of the MHT, the estimated creeping rate is ~16.3 mm/yr, ~14.7 mm/yr, and ~14.3 mm/yr along western, central, and eastern Nepal, respectively; and (4) along the MHT on the upper crust, the modeled locking width turns out to be 97 km, 106 km, and 129 km in the western, central, and eastern Nepal, respectively. In addition, the posterior probability distribution of the locking width exhibits a bimodal Gaussian distribution coinciding with the two ramp geometry of the MHT along the western Nepal. Along the foothills of the Higher Himalaya, the inferred locking line is also aligned to the estimated maximum shear strain concentration and observed seismicity along the central Himalaya. With a general agreement to the previous geodetic results, geological estimates, and background seismicity, our findings provide a promising avenue of the contemporary crustal deformation along the Nepal Himalaya. The estimated inversion results in a Bayesian framework exhibit updated fault kinematics of the MHT and hence provides valuable inputs for seismic hazard assessment along the central Himalaya.

scholarly journals Studies on dielectric relaxation in relation to viscosity of some anilines, phenol, and their binary mixtures at microwave frequencies

2019 ◽  
Vol 97 (2) ◽  
pp. 210-215
Author(s):  
C.V. Maridevarmath ◽  
G.H. Malimath
Keyword(s):  
Relaxation Time ◽  
Steady State ◽  
Dynamic Viscosity ◽  
Room Temperature ◽  
Viscoelastic Model ◽  
Frictional Resistance ◽  
Nonlinear Behaviour ◽  
Viscoelastic Relaxation ◽  
Microwave Frequencies ◽  
Loss Formula

In the present work, the study of variation of relaxation time (τ) with viscosity of the medium (η) is carried out on four polar samples: 2-Nitroaniline, 4-Bromoaniline, 4-Chloroaniline, 4-Chlorophenol, and also on the binary mixture of 2-Nitroaniline + 4-Bromoaniline at room temperature by using microwave bench operating at a frequency of 9.59 GHz. In this regard, the different parameters like dielectric constant ([Formula: see text]), dielectric loss ([Formula: see text]), relaxation time (τs), macroscopic steady state viscosity (ηs), dynamic viscosity (ηd), and viscoelastic relaxation time (τve) were determined for all the systems. It is observed that the relaxation time (τs) increases with the increase in the viscosity of the medium for all the systems. Plots of log(τs) versus log(ηs) for all the systems show that variation of relaxation time is found to be nonlinear in the higher viscosity regions. This suggests the failure of Debye’s theory at these regions. Further, the nonlinear behaviour of relaxation time with the viscosity is explained by using the viscoelastic model suggested by Barlow et al. (Proc. R. Soc. A 309, 473 (1969). doi: 10.1098/rspa.1969.0053 ). It is also observed that macroscopic steady state viscosity (ηs) values are greater than the dynamic viscosity (ηd), and viscoelastic relaxation time (τve) values were found to be lower compared to the relaxation time (τs). These results suggest that the effective frictional resistance experienced by the molecules during reorientation is lower and the measured values of macroscopic steady state viscosity (ηs) are frequency dependent.

scholarly journals Hillslope denudation and morphologic response to a rock uplift gradient

2020 ◽  
Vol 8 (2) ◽  
pp. 221-243 ◽  
Author(s):  
Vincent Godard ◽  
Jean-Claude Hippolyte ◽  
Edward Cushing ◽  
Nicolas Espurt ◽  
Jules Fleury ◽  
...  
Keyword(s):  
High Resolution ◽  
Strong Dependence ◽  
Digital Terrain Model ◽  
Slip Rate ◽  
Joint Analysis ◽  
Deformation Model ◽  
Base Level ◽  
Denudation Rates ◽  
Blind Thrust ◽  
Thrust System

Abstract. Documenting the spatial variability of tectonic processes from topography is routinely undertaken through the analysis of river profiles, since a direct relationship between fluvial gradient and rock uplift has been identified by incision models. Similarly, theoretical formulations of hillslope profiles predict a strong dependence on their base-level lowering rate, which in most situations is set by channel incision. However, the reduced sensitivity of near-threshold hillslopes and the limited availability of high-resolution topographic data has often been a major limitation for their use to investigate tectonic gradients. Here we combined high-resolution analysis of hillslope morphology and cosmogenic-nuclide-derived denudation rates to unravel the distribution of rock uplift across a blind thrust system at the southwestern Alpine front in France. Our study is located in the Mio-Pliocene Valensole molassic basin, where a series of folds and thrusts has deformed a plateau surface. We focused on a series of catchments aligned perpendicular to the main structures. Using a 1 m lidar digital terrain model, we extracted hillslope topographic properties such as hilltop curvature CHT and nondimensional erosion rates E∗. We observed systematic variation of these metrics coincident with the location of a major underlying thrust system identified by seismic surveys. Using a simple deformation model, the inversion of the E∗ pattern allows us to propose a location and dip for a blind thrust, which are consistent with available geological and geophysical data. We also sampled clasts from eroding conglomerates at several hilltop locations for 10Be and 26Al concentration measurements. Calculated hilltop denudation rates range from 40 to 120 mm kyr−1. These denudation rates appear to be correlated with E∗ and CHT that were extracted from the morphological analysis, and these rates are used to derive absolute estimates for the fault slip rate. This high-resolution hillslope analysis allows us to resolve short-wavelength variations in rock uplift that would not be possible to unravel using commonly used channel-profile-based methods. Our joint analysis of topography and geochronological data supports the interpretation of active thrusting at the southwestern Alpine front, and such approaches may bring crucial complementary constraints to morphotectonic analysis for the study of slowly slipping faults.

scholarly journals Various far-field hydrological responses during 2015 Gorkha earthquake at two distant wells

2020 ◽  
Author(s):  
Xudong Huang ◽  
Yu Zhang
Keyword(s):  
Water Level ◽  
Seismic Waves ◽  
Amplitude Ratio ◽  
Unconfined Aquifer ◽  
Water Levels ◽  
Earth Tides ◽  
Tibet Plateau ◽  
Far Field ◽  
Gorkha Earthquake ◽  
2015 Gorkha Earthquake

Abstract Aquifer hydraulic parameter can change during earthquakes. Continuous monitoring of the response of water level to seismic waves or solid Earth tides provides an opportunity to document how earthquakes influence hydrological properties. Here we use data of two groundwater wells, Dian-22 (D22) and Lijiang (LJ) well, in southeast Tibet Plateau in response to the 2015 Mw 7.8 Gorkha earthquake to illustrate hydrological implications. The coherences of water level and seismic wave before and after the far-field earthquake show systematic variations, which may confirm the coseismic dynamic shaking influence at high frequencies (f > 8 cpd). The tidal response of water levels in these wells shows abrupt coseismic changes of both phase shift and amplitude ratio after the earthquake, which may be interpreted as an occurrence in the vertical permeability of a switched semiconfined aquifer in the D22 well, or an enhancement unconfined aquifer in the LJ well . Using the continuous transmissivity monitoring, we show that the possible coseismic response for about 10 days and instant healing after 10 days to the earthquake. Thus, the dynamic shaking during the Gorkha earthquake may have caused the short term aquifer responses by reopening of preexisting vertical fractures and later healing at epicentral distances about 1500 km.

Kinematics of Subduction Processes during the Earthquake Cycle in Central Chile

2019 ◽  
Author(s):  
Leonardo Aguirre ◽  
Klaus Bataille ◽  
Camila Novoa ◽  
Carlos Peña ◽  
Felipe Vera
Keyword(s):  
Subduction Zones ◽  
Slip Rate ◽  
Convergent Margins ◽  
Earthquake Cycle ◽  
Central Chile ◽  
The North ◽  
The Future ◽  
Maule Earthquake ◽  
Kinematic Models ◽  
Inversion Techniques

ABSTRACT Subduction processes at convergent margins produce complex temporal and spatial crustal displacements during different periods of the earthquake cycle. Satellite geodesy observations provide important clues to constrain kinematic models at subduction zones. Here, we analyze geodetic observations in central Chile, where two large earthquakes occurred: 2010 Mw 8.8 Maule and 2015 Mw 8.3 Illapel. We propose a model that considers the motion along both interfaces of the brittle subducting slab as the sources responsible for the movement of the crust in the different periods of the earthquake cycle. Using standard inversion techniques, we provide a consistent framework of the kinematic displacement during each period of the earthquake cycle. We show that during the interseismic period prior to the Maule and Illapel earthquakes, two patches of slip rate on the lower interface are determined. These patches are located just below the future hypocenters. Because the interseismic period corresponds to the loading process and the coseismic to the unloading process, it is interesting to note that the area where loading is stronger corresponds to the area where unloading is also strong. Furthermore, we show that the Maule earthquake causes a significant displacement on the lower interface, just below the epicenter of the future Illapel earthquake to the north, a few years later. We speculate that the interaction between motions along both interfaces is the key to understanding the evolution of stress and the occurrence of earthquakes at subduction zones. This framework improves the understanding of the observed loading and unloading processes and potential triggering between subduction earthquakes.

scholarly journals Nonrigid Bookshelf Kinematics of Northeastern Tibet: Constrains from Fault Slip Rates around the Qinghai Lake and Chaka-Gonghe Basins

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 2) ◽  
Author(s):  
Chen Gan ◽  
Ai Ming ◽  
Zheng Wenjun ◽  
Bi Haiyun ◽  
Liu Jinrui ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Slip Rate ◽  
Qinghai Lake ◽  
Deformation Model ◽  
Stream Channels ◽  
Slip Rates ◽  
Regional Deformation ◽  
Northeastern Tibet ◽  
Uplift Rates ◽  
Major Strike

Abstract The Elashan fault (ELSF) and Qinghainanshan fault (QHNF), two major faults developed around the Qinghai Lake and Chaka-Gonghe basins, are of great importance for investigating the deformation model of the internal northeastern Tibetan Plateau. However, their late Pleistocene slip rates remain poorly constrained. In this study, we combine high-resolution topography acquired from unmanned aerial vehicles (UAV) and geomorphological dating to calculate the slip rates of the two faults. We visited the central ELSF and western QHNF and measured displaced terraces and stream channels. We collected 10Be samples on the surface of terraces to constrain the abandonment ages. The dextral slip rate of the central segment of the Elashan fault is estimated to be 2.6±1.2 mm/yr. The uplift rates since the late Pleistocene of the Elashan and Qinghainanshan faults are 0.4±0.04 mm/yr and 0.2±0.03 mm/yr, respectively. Comparing the geological rates with the newly published global positioning system (GPS) rates, we find that the slip rates of the major strike-slip faults around the Qinghai Lake and Chaka-Gonghe basins are approximately consistent from the late Pleistocene to the present day. The overall NE shortening rates by summing up the geological slip rates on major faults between the East Kunlun and Haiyuan faults are ~3.4 mm/yr, smaller than the geodetic shortening rates (~4.9 to 6.4 mm/yr), indicating that distributed deformation plays an important role in accommodating the regional deformation. By analyzing the geometrical and kinematic characteristics of the major faults surrounding the basins, we suggest that the kinematic deformation of the internal northeastern Tibet is a nonrigid bookshelf model that consists of counterclockwise rotation (~0.8° Myr-1) and distributed thrusting.

scholarly journals Probing afterslip and viscoelastic relaxation following the 2015 Mw 7.8 Gorkha earthquake based on the 3-D Finite Element Model

2020 ◽  
Author(s):  
Lina Su ◽  
Fuqiang Shi ◽  
Weijun Gan ◽  
Xiaoning Su ◽  
Junyi Yan
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Material Properties ◽  
Element Model ◽  
Postseismic Deformation ◽  
Earth Model ◽  
Viscoelastic Relaxation ◽  
Gorkha Earthquake ◽  
2015 Gorkha Earthquake ◽  
Continuous Gps

Abstract We analyzed GPS coordinate time series from 34 continuous GPS stations in Nepal and 5 continuous GPS stations in South Tibet of China, and extracted the first 4.8 years postseismic displacements after the 2015 Mw7.8 Gorkha earthquake. With the longer duration GPS observations, we found that postseismic displacements mainly exhibit the southward and uplift movement at the epcientral area. To study the postseismic afterslip and viscoelastic relaxation, we then built 3-D spherical finite element model (FEM) with heterogeneous material properties and surface topography across the Himalayan range, accounting for the strong variations of material properties and surface elevation along central Himalayan arc. The sophisticated FEM is more realistic and perform better than the flat layered earth model. On the basis of it, we reveal that the predicted viscoelastic relaxation of cm level is opposite to the observed postseismic deformation; the postseismic deformation with viscoelastic relaxation deducted is well explained by afterslip downdip of coseismic rupture, which indicates the afterslip is still dominant during 4.8 years postseismic deformation after the 2015 Mw7.8 Gorkha earthquake; The lack of slip on a shallow portion and western segment of the MHT during and after the 2015 Gorkha earthquake implies continued seismic hazard in the future.

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