InSAR Models Research Articles

Post-seismic motion following the 1997 Manyi (Tibet) earthquake: InSAR observations and modelling

SUMMARY On November 8 1997 a Mw 7.6 earthquake occurred in the Manyi region of northern Tibet, near the western end of the Kunlun Fault. Over 7 m of left-lateral slip occurred on a 200-kmlong fault. Here we use InSAR observations of post-seismic surface deformation following the Manyi earthquake to investigate possible causal mechanisms. Time-series of deformation are constructed from 26 interferograms, covering the entire length of the fault for nearly 4 yr after the earthquake. Three different modelling approaches are used to try and understand the observed variations in surface displacement. First order poroelastic models predict displacement fields which do not match those observed. Modelling of viscoelastic stress relaxation in a half-space with standard linear solid rheology beneath an elastic lid provides a reasonable fit to the observations, and demonstrates that two relaxation times are needed to characterize the post-seismic transient. The best-fitting viscosity is 4 £ 10 18 Pa s, and the fully-relaxed shear modulus is 32 per cent of the purely elastic value. A model with a Maxwell viscoelastic halfspace underlying the lid cannot explain the observations: at later times, larger viscosities are required than at earlier times. This increase in effective viscosity with time may be consistent with stress relaxation occurring in a power-law rheology. The time-series are also inverted for distributed afterslip on an extension of the coseismic rupture. Along-strike correlation of coseismic and post-seismic slip maxima suggests that afterslip is a plausible mechanism. The maximum slip in the afterslip model is 0.72 m after 3 yr, and the equivalent moment release is approximately 20 per cent of the coseismic moment. This study shows that it is possible to rule out certain mechanisms as the dominant post-seismic process, but with the current InSAR data set it is difficult to distinguish between other plausible options.

Earthquake Processes: Physical Modelling, Numerical Simulation and Data Analysis

A. Earthquake Cycles, Crustal Deformation and Plate Dynamics.- 3-D Simulation of Earthquake Generation Cycles and Evolution of Fault Constitutive Properties.- Interplate Earthquake Fault Slip During Periodic Earthquake Cycles in a Viscoelastic Medium at a Subduction Zone.- Development of a Finite Element Simulator for Crustal Deformation with Large Fault Slipping.- 3-D Viscoelastic FEM Modeling of Crustal Deformation in Northeast Japan.- Combined GPS and InSAR Models of Postseismic Deformation from the Northridge Earthquake.- A Hidden Markov Model Based Tool for Geophysical Data Exploration.- Geophysical Applications of Multidimensional Filtering with Wavelets.- Large Amplitude Folding in Finely Layered Viscoelastic Rock Structures.- Mantle Convection Modeling with Viscoelastic/Brittle Lithosphere: Numerical Methodology and Plate Tectonic Modeling.- GEM Plate Boundary Simulations for the Plate Boundary Observatory: A Program for Understanding the Physics of Earthquakes on Complex Fault Networks via Observations, Theory and Numerical Simulation.- B. Seismicity Change and its Physical Interpretation.- Accelerated Seismic Release and Related Aspects of Seismicity Patterns on Earthquake Faults.- Stress Correlation Function Evolution in Lattice Solid Elasto-dynamic Models of Shear and Fracture Zones and Earthquake Prediction.- Pattern Dynamics and Forecast Methods in Seismically Active Regions.- Long-range Automaton Models of Earthquakes: Power-law Accelerations, Correlation Evolution, and Mode-switching.- Critical Sensitivity and Trans-scale Fluctuations in Catastrophic Rupture.- Load-Unload Response Ratio and Accelerating Moment/Energy Release Critical Region Scaling and Earthquake Prediction.- Simulation of the Load-Unload Response Ratio and Critical Sensitivity in the Lattice Solid Model.