scholarly journals Constraints on the viscosity of the continental crust and mantle from GPS measurements and postseismic deformation models in western Mongolia

2003 ◽  
Vol 108 (B10) ◽  
Author(s):  
Mathilde Vergnolle ◽  
Fred Pollitz ◽  
Eric Calais
Keyword(s):  
Continental Crust ◽  
Postseismic Deformation ◽  
Gps Measurements ◽  
Western Mongolia ◽  
Deformation Models

scholarly journals Coseismic and early postseismic deformation due to the 25 April 2015, M w 7.8 Gorkha, Nepal, earthquake from InSAR and GPS measurements

2016 ◽  
Vol 43 (7) ◽  
pp. 3160-3168 ◽  
Author(s):  
K. M. Sreejith ◽  
P. S. Sunil ◽  
Ritesh Agrawal ◽  
Ajish P. Saji ◽  
D. S. Ramesh ◽  
...  
Keyword(s):  
Postseismic Deformation ◽  
Gps Measurements ◽  
Nepal Earthquake

Constraints on the rheology of the mid- to lower continental crust from geodetic studies of the earthquake deformation cycle

2020 ◽  
Author(s):  
Tim Wright ◽  
Tom Ingleby ◽  
Ekbal Hussain
Keyword(s):  
Shear Zone ◽  
Continental Crust ◽  
Power Law ◽  
Lower Crust ◽  
Postseismic Deformation ◽  
Strain Accumulation ◽  
Earthquake Cycle ◽  
Accumulation Rates ◽  
Deformation Cycle ◽  
Time Invariant

<p>In this presentation I will review geodetic constraints on the rheology of the mid- to lower continental crust from observations and models of all phases of the earthquake deformation cycle. I will focus on observations of slow interseismic strain accumulation and rapid postseismic strain transients, both of which result primarily from deformation in the mid- to lower crust. I will argue that, with a few exceptions, interseismic strain is focused in zones around faults with widths that are compatible with strain at depth being focused on a fault or distributed in a shear zone up to ~3 x the seismogenic layer thickness. I will show that for the North Anatolian Fault, the strain accumulation rate appears to be approximately constant for the entire earthquake cycle, once the postseismic transient has decayed. This is consistent with observations at other fault where geodetic measurements were made prior to major earthquakes; the broad agreement between geological and geodetic estimates of slip rate is also consistent with interseismic strain accumulation rates being relatively time invariant. Time-invariant interseismic strain accumulation rates require a relatively strong mid- to lower crust, where relaxation times are equal to or greater than the average earthquake revisit time. Postseismic deformation transients are commonly observed following most earthquakes, but they are interpreted using a variety of very different deformation mechanisms. By compiling all observations of postseismic deformation we show that the largest transient postseismic velocities decay following a simple t<sup>-1</sup> power-law, analogous to Omori’s law for aftershock decay. This is consistent with frictional afterslip and/or power-law creep in a narrow shear zone. This model of a weak shear zone embedded within a stronger substrate can explain most observations of the earthquake deformation cycle. Exceptions to this simple model might occur in locations where the lower crust is weaker, perhaps due to the presence of partial melt. Geological constraints on rheology are critical for making further progress in understanding the earthquake deformation cycle – geological models for the mid- to lower crust can be tested by comparing geodetic observations with geologically-realistic earthquake cycle models.</p>

scholarly journals Co- and postseismic slip behaviors extracted from decadal seafloor geodesy after the 2011 Tohoku-oki earthquake

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Shun-ichi Watanabe ◽  
Tadashi Ishikawa ◽  
Yuto Nakamura ◽  
Yusuke Yokota
Keyword(s):  
Source Region ◽  
Geodetic Data ◽  
Japan Trench ◽  
Postseismic Deformation ◽  
Viscoelastic Relaxation ◽  
Essential Information ◽  
Seafloor Geodesy ◽  
Spatial Coverage ◽  
Deformation Models

AbstractInvestigations of the co- and postseismic processes of the 2011 Tohoku-oki earthquake provide essential information on the seismic cycle in the Japan Trench. Although almost all of the source region lies beneath the seafloor, recent seafloor geophysical instruments have enabled to detect the near-field signals of both the coseismic rupture and the postseismic stress relaxation phenomena. Annual-scale seafloor geodesy contributed to refining the postseismic deformation models, specifically to the incorporation of viscoelastic effects. However, because of the insufficiency in the spatial coverage and observation period of seafloor geodetic observations, no consensus on crustal deformation models has been reached, especially on the along-strike extent of the main rupture, even for the coseismic process. To decompose the postseismic transient processes in and around the source region, i.e., viscoelastic relaxation and afterslip, long-term postseismic geodetic observations on the seafloor play an essential role. Here, from decadal seafloor geodetic data, we provide empirical evidence for offshore aseismic afterslip on the rupture edges that had almost decayed within 2–3 year. The afterslip regions are considered to have stopped the north–south rupture propagation due to their velocity strengthening frictional properties. In the southern source region (~ 37° N), despite not being resolved by coseismic geodetic data, shallow tsunamigenic slip near the trench is inferred from postseismic seafloor geodesy as a subsequent viscoelastic deformation causing persistent seafloor subsidence at a geodetic site off-Fukushima. After a decade from the earthquake, the long-term viscoelastic relaxation process in the oceanic asthenosphere is currently in progress and is still dominant not only in the rupture area, but also in the off-Fukushima region.

Postseismic deformation of the Ms 8.1 Nepal earthquake in 2015 from GPS observations

2020 ◽  
Author(s):  
Xiaoning Su ◽  
Guojie Meng
Keyword(s):  
Temporal Distribution ◽  
Exponential Model ◽  
Deformation Field ◽  
Monte Carlo Algorithm ◽  
Coseismic Deformation ◽  
Postseismic Deformation ◽  
Model Parameters ◽  
Southern Tibet ◽  
Logarithmic Model ◽  
Deformation Models

<p>On April 25, 2015, the Nepal M<sub>S</sub> 8.1 earthquake took place in the Himalayan seismic belt on the southern margin of Tibetan Plateau. After the earthquake, the China Earthquake Administration established Immediately 13 GPS continuous stations in the southern Tibetan region. In this study, such data, the data of China’s crustal movement observation network in the southern Tibet region and the data of GPS continuous stations in Nepal are used to estimate the postseismic deformation of the GPS station. Three postseismic deformation models, i.e., a logarithmic model, an exponential model and an integrated combination, are used for fitting GPS postseismic deformation. The Markov Chain Monte Carlo algorithm, based on a Bayesian framework, is applied to invert model parameters. The results show that the integrated model for the logarithmic model and exponential model can accurately fit the postseismic deformation observed by GPS, indicating that the postseismic deformation observed by GPS may involve two different deformation mechanisms with multi-scale characteristics. Based on the analysis of the spatial-temporal distribution of the postseismic deformation field and its comparison with the coseismic deformation field, it is considered that the afterslip mainly occurs in the deep area where the coseismic rupture extends northward, while the seismic risk in the shallow area where the coseismic rupture is not broken still deserves further attention.</p>

Crust-mantle interactions during subduction of oceanic & continental crust

2014 ◽  
Vol 6 (1.3) ◽  
pp. 1-73 ◽  
Author(s):  
Daniele Castelli ◽  
Roberto Compagnoni ◽  
Bruno Lombardo ◽  
Samuele Angiboust ◽  
Gianni Balestro ◽  
...  
Keyword(s):  
Continental Crust
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