Publication Date:
2017-04-04
Description:
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 4e+5 and
2e+7 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.
Description:
Published
Description:
B12303
Description:
3.1. Fisica dei terremoti
Description:
JCR Journal
Description:
reserved
Keywords:
Earthquake dynamics and mechanics
;
Earthquake modeling
;
04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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