4.2.1. Rupture process using one elliptical slip patch
Ten final rupture models resulted from different inversions of the near
field displacement waveforms are evaluated (see Fig. 3a; Table S3). They
describe the mainshock slip using one elliptical slip patch. These
rupture models were calculated on a planar fault with a strike/dip of
292°/60°N and with the hypocenter obtained in section-3. They have a
minimum wave misfit of ~42%. Most of the misfit is due
to the late part of the displacement fields which mainly contain the
surface waves and site effects (see figures S2 to S11). For all of these
models, the slip extends to the West of the hypocenter with large values
located at depths ranging between 13 km to 10 km. This range is within
our obtained depth range for the maximum waveform correlation in the
moment tensor inversion as well as the IRSC result. The rupture has a
left-lateral strike-slip mechanism (rakes =14°-18°) and does not reach
the surface.
All the models had sub-shear rupture speeds between 2.2 km/s to 2.8 km/s
(Vs=3.5 km/s) and almost the same duration, between 2.1 s to 2.8 s. The
rise time changes between 0.02s to 0.26s. Models with higher rise times
exhibit mostly higher rupture speeds, which is consistent with the
results of dynamic simulations from Schmedes et al. (2010). The maximum
slip changes from 3 cm to 9 cm, depending on the rupture dimension.
The inversions converge to a seismic moment release between 3.8e+16 Nm
to 4.3e+16 Nm, which are smaller than the estimated scalar moment
obtained by regional waveform inversion (4.8 e+16 Nm). We stress that
the low-frequency noises in the strong motions limited inversion to use
frequencies below 0.08 Hz. While in section 2, we use frequency ranges
down to 0.03 Hz. All the rupture models can satisfy the strong motion
data. We make an average of the ten final models as our preferred model.
This rupture model shows nucleation at the depth of ~14
km (Fig. 4a). The slip mostly extends toward the west and to the shallow
depths with an average speed of 2.75 km/s. The maximum slip is estimated
as ~4 cm between depths ranging from 13km to 11km. The
rupture lasts for ~2.8 s and releases a total scalar
seismic moment of 4.04 E+16 Nm equal to Mw 5.0. That is less than the
point-source moment tensor results in section 2. The maximum slip is
situated 2.5 km West and ~0.5 km South of the hypocenter
and at a depth of 12 km. The rupture stops at a depth of 10 km. The
rupture length of ~9 km for an M5.0 event is remarkable,
proposing its comfort extension.