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

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.

Download Full-text

Slip rate of the seismogenic fault of the 2021 Maduo earthquake in western China inferred from GPS observations

Science China Earth Sciences ◽

10.1007/s11430-021-9808-0 ◽

2021 ◽

Author(s):

Yage Zhu ◽

Faqi Diao ◽

Yuchao Fu ◽

Chengli Liu ◽

Xiong Xiong

Keyword(s):

Slip Rate ◽

Western China ◽

Seismogenic Fault ◽

Gps Observations

Download Full-text

Hillslope denudation and morphologic response to a rock uplift gradient

Earth Surface Dynamics ◽

10.5194/esurf-8-221-2020 ◽

2020 ◽

Vol 8 (2) ◽

pp. 221-243 ◽

Cited By ~ 1

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.

Download Full-text

A combinatorial approach to determine earthquake magnitude distributions on a variable slip-rate fault

Geophysical Journal International ◽

10.1093/gji/ggz294 ◽

2019 ◽

Vol 219 (2) ◽

pp. 734-752 ◽

Cited By ~ 2

Author(s):

Eric L Geist ◽

Tom Parsons

Keyword(s):

Spatial Distribution ◽

Integer Programming ◽

Slip Rate ◽

Rate Function ◽

Programming Method ◽

Sequential Algorithm ◽

Rate Variation ◽

Finite Sample ◽

Decision Vector ◽

Lower Magnitude

SUMMARY Combinatorial methods are used to determine the spatial distribution of earthquake magnitudes on a fault whose slip rate varies along strike. Input to the problem is a finite sample of earthquake magnitudes that span 5 kyr drawn from a truncated Pareto distribution. The primary constraints to the problem are maximum and minimum values around the target slip-rate function indicating where feasible solutions can occur. Two methods are used to determine the spatial distribution of earthquakes: integer programming and the greedy-sequential algorithm. For the integer-programming method, the binary decision vector includes all possible locations along the fault where each earthquake can occur. Once a set of solutions that satisfy the constraints is found, the cumulative slip misfit on the fault is globally minimized relative to the target slip-rate function. The greedy algorithm sequentially places earthquakes to locally optimize slip accumulation. As a case study, we calculate how earthquakes are distributed along the megathrust of the Nankai subduction zone, in which the slip rate varies significantly along strike. For both methods, the spatial distribution of magnitudes depends on slip rate, except for the largest magnitude earthquakes that span multiple sections of the fault. The greedy-sequential algorithm, previously applied to this fault (Parsons et al., 2012), tends to produce smoother spatial distributions and fewer lower magnitude earthquakes in the low slip-rate section of the fault compared to the integer-programming method. Differences in results from the two methods relate to how much emphasis is placed on minimizing the misfit to the target slip rate (integer programming) compared to finding a solution within the slip-rate constraints (greedy sequential). Specifics of the spatial distribution of magnitudes also depend on the shape of the target slip-rate function: that is, stepped at the section boundaries versus a smooth function. This study isolates the effects of slip-rate variation along a single fault in determining the spatial distribution of earthquake magnitudes, helping to better interpret results from more complex, interconnected fault systems.

Download Full-text

How much of GPS noise refers to hydrology loading? An insight from GRACE-assimilating hydrological modeling

10.5194/egusphere-egu2020-5697 ◽

2020 ◽

Author(s):

Anna Klos ◽

Makan A. Karegar ◽

Jürgen Kusche ◽

Anne Springer

Keyword(s):

Land Surface ◽

Seasonal Changes ◽

Harmonic Functions ◽

Hydrological Modeling ◽

Hydrological Model ◽

Surface Model ◽

Deformation Model ◽

Essential Information ◽

Noise Parameters ◽

Gps Observations

<p>Global Positioning System (GPS) observations are able to resolve Earth&#8217;s surface vertical deformation which originates among others from continental hydrological mass changes. Although long-term signals and seasonal changes of hydrology loading are well-captured by GPS observations, it is still unanswered whether GPS detects also the short-term hydrology-related deformations or not. In this presentation, we use predictions of vertical deformations from a GRACE (Gravity Recovery and Climate Experiment)-assimilating land surface model to separate deterministic and stochastic parts of GPS height changes observed by a set of 221 European EPN (EUREF Permanent GNSS Network) stations. This approach is compared to conventional harmonic functions approach, in which deterministic and stochastic parts are separated by pre-defined annual and semi-annual periods. For the stochastic parts associated with two methods, the noise parameters (spectral indices and amplitudes of power-law noise) are estimated using the Maximum Likelihood Estimation (MLE). Comparing original GPS displacements to displacements reduced for hydrological loading, we notice that annual and semi-annual frequencies are significantly explained by the hydrological model, resulting 60% reduction on average in amplitudes. This means that large part of seasonal crustal deformation arises from hydrological loading or unloading of the lithosphere. We find that the annual and semi-annual peaks are greatly reduced (72% on average) once conventional harmonic functions approach is used instead of GRACE-assimilating hydrological model, but no physical interpretation can be made here since it is difficult to identify the magnitude of each individual processes contributing to seasonal changes. The GRACE-assimilated model can remove the effect of high-frequency hydrological deformations, producing residuals with spectrum closer to the white noise process. Many oscillations present in GPS displacements at periods between 15 and 90 days are well-explained by GRACE-assimilating deformation model. We find the greatest improvement in noise parameters for stations located in the eastern and central regions of Europe, encompassing the Rhine, Elbe, Danube and Oder drainage basins where hydrological mass changes are relatively larger comparing to western Europe. Using GRACE-assimilated model as a deterministic part of GPS displacement time series, we provide a totally new estimates of noise parameters for European sites, which has never been presented before. Our results show that GRACE-assimilating water storage re-analyses can provide essential information for obtaining improved unbiased estimates of GPS vertical velocity, including their uncertainty, which are essential for a range of applications such as upcoming reference frame realizations.</p>

Download Full-text

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

Remote Sensing ◽

10.3390/rs10122048 ◽

2018 ◽

Vol 10 (12) ◽

pp. 2048 ◽

Cited By ~ 1

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.

Download Full-text

Kinematics of Subduction Processes during the Earthquake Cycle in Central Chile

Seismological Research Letters ◽

10.1785/0220180391 ◽

2019 ◽

Cited By ~ 1

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.

Download Full-text

Slip Rate Variation During the Last ∼210 ka on a Slow Fault in a Transpressive Regime: The Carrascoy Fault (Eastern Betic Shear Zone, SE Spain)

Frontiers in Earth Science ◽

10.3389/feart.2020.599608 ◽

2021 ◽

Vol 8 ◽

Author(s):

Raquel Martín-Banda ◽

Juan Miguel Insua-Arévalo ◽

Julián García-Mayordomo

Keyword(s):

High Activity ◽

Shear Zone ◽

Slip Rate ◽

Fault Slip ◽

Rate Variation ◽

Se Spain ◽

Alluvial Deposits ◽

Slip Rates ◽

Fault Systems ◽

Low Activity

Fault slip rate variability over time is a crucial aspect for understanding how single faults interact among each other in fault systems. Several studies worldwide evidence the occurrence of high activity periods with clustering of events and synchronization among faults, followed by long periods of low activity (super-cycles). The increasing gathering of evidence of these phenomena is making fault hazard models quickly evolving and challenging seismic hazard assessment. However, in moderately active fault systems, a determination of fault slip rates can present large uncertainties, that have to be carefully considered when slip rate histories are determined. In this work, we estimate the variation of slip rate in the last ∼210 ky of the NE segment of the left-lateral reverse Carrascoy Fault, one of the main faults forming the Eastern Betic Shear Zone in SE Spain. We study two selected field sites where we have been able to measure offsets and date the sediments along with uncertainties. The first site shows a progressive discordance drawn by different calcretes developed on alluvial deposits. The vertical throw is calculated by modeling the growth of the discordance. The vertical slip rates are estimated dating the deformed calcretes by Uranium Series and by comparing them with a complete regional calcrete dates database compiled from the literature. On the second site, we analyze the geomorphology of different Upper Pleistocene alluvial fans, where three incised channels are offset by the fault, providing the net slip for the last ∼124 ky. We discuss the influence of different factors on the estimate of net slip rates using data from different sources. This analysis highlights the importance of determining an accurate fault geometry and how local data can provide misleading deformation rates. Our results suggest the existence of long periods of low activity disturbed by short high activity periods. Such a pattern of activity along time is defined for the first time in the Eastern Betic Shear Zone, with interesting implications in the seismogenic behavior of the rest of the slow faults within the region.

Download Full-text

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

Lithosphere ◽

10.2113/2021/4115729 ◽

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.

Download Full-text