Earthquake fracture energy inferred from kinematic rupture models on extended faults

We estimate fracture energy on extended faults for several recent earthquakes by retrieving dynamic traction evolution at each point on the fault plane from slip history imaged by inverting ground motion waveforms. We define the breakdown work (Wb) as the excess of work over some minimum traction le...

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Bibliographic Details
Published in:Journal of Geophysical Research - Solid Earth 2005-12, Vol.110 (B12), p.B12303-n/a
Main Authors: Tinti, E., Spudich, P., Cocco, M.
Format: Article
Language:English
Subjects:
Breakdown
Dynamics
Dynamics and mechanics of faulting
Earthquake dynamics
earthquake scaling
Earthquake source observations
Estimates
Faults
fracture energy
Mathematical models
Seismic phenomena
Seismology
seismotectonics
Slip
Tectonophysics
Theory
Traction
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Summary:We estimate fracture energy on extended faults for several recent earthquakes by retrieving dynamic traction evolution at each point on the fault plane from slip history imaged by inverting ground motion waveforms. We define the breakdown work (Wb) as the excess of work over some minimum traction level achieved during slip. Wb is equivalent to "seismological" fracture energy (G) in previous investigations. Our numerical approach uses slip velocity as a boundary condition on the fault. We employ a three‐dimensional finite difference algorithm to compute the dynamic traction evolution in the time domain during the earthquake rupture. We estimate Wb by calculating the scalar product between dynamic traction and slip velocity vectors. This approach does not require specifying a constitutive law and assuming dynamic traction to be collinear with slip velocity. If these vectors are not collinear, the inferred breakdown work depends on the initial traction level. We show that breakdown work depends on the square of slip. The spatial distribution of breakdown work in a single earthquake is strongly correlated with the slip distribution. Breakdown work density and its integral over the fault, breakdown energy, scale with seismic moment according to a power law (with exponent 0.59 and 1.18, respectively). Our estimates of breakdown work range between 4 × 105 and 2 × 107 J/m2 for earthquakes having moment magnitudes between 5.6 and 7.2. We also compare our inferred values with geologic surface energies. This comparison might suggest that breakdown work for large earthquakes goes primarily into heat production.
ISSN:0148-0227
2169-9313
2156-2202
2169-9356
DOI:10.1029/2005JB003644