Earthquake dynamics and source inversion Jean-Paul Ampuero



Yüklə 478 b.
tarix31.07.2018
ölçüsü478 b.


Earthquake dynamics and source inversion

  • Jean-Paul Ampuero

  • ETH Zurich


Overview

  • The forward problem: challenges, open questions

  • Dynamic properties inferred from kinematic models

  • Direct inversion for dynamic properties: which parameters can be resolved ?

  • Perspectives



The “standard” dynamic rupture problem





Fault geometry and velocity model ?



Initial conditions ?



Fault constitutive law (“friction law”) ?

  • Input:

    • Geological field observations
    • Geophysical boreholes
    • Laboratory
    • Strong motion seismology
  • Candidate ingredients:

    • Dry friction
    • Frictional heating
    • Melting
    • Fluid thermal pressurization
    • Off-fault damage
    • Compaction / porosity evolution


Fault constitutive law (“friction law”) ?

  • Input:

    • Geological field observations
    • Geophysical boreholes
    • Laboratory
    • Strong motion seismology


Fault constitutive law (“friction law”) ?



Inferring fault dynamic properties from seismograms



Inferring fault dynamic properties from seismograms





Fracture energy Gc controls dynamic rupture

  • Inversion of dynamic friction parameters with frequency band-limited data suffers from strong trade-off



Scale contraction issue



Scale contraction issue



The view from classical fracture mechanics



Gc controls dynamic rupture: theory

  • Classical fracture mechanics +Griffith criterion

  •  local energy balance at the rupture front:

  • Gc = G(vr, L, )

  • crack tip equation of motion relates rupture speed to Gc

  • Gc = f(vr) Gstatic(L,)

  • Gc = f(vr) K2(L,)/2

  • where: stress intensity factor = K ≈ √L

  • and f(vr) is a universal decreasing function



Summary

  • So far:

    • The development of dynamic source inversion methodologies is in its infancy
    • Parameterization issue
    • Resolution limited by:
      • Data band-pass filtering
      • Attenuation
      • Inaccurate Green’s functions, poor knowledge of the crust
      • Scarce instrumentation
      • Coarse parameterization, computational cost
  • Ideal wish-list:

    • Reach higher frequencies
    • Understand the meaning of the inferred macroscopic parameters
    • Faster, better forward solvers


2.5D dynamic inversion

  • Dynamic source inversion = from seismograms +GPS +InSAR to spatial distribution of initial stress and fracture energy along the fault

  • Computationally expensive and low vertical resolution

  • Reduce the problem dimensionality:

  • solve rupture dynamics averaged over the seismogenic depth (3D wave equation  2D Klein-Gordon equation)





Dostları ilə paylaş:


Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur ©genderi.org 2019
rəhbərliyinə müraciət

    Ana səhifə