Determination of causative fault parameters for some recent Iranian ...

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H. Hamzehloo / Journal of Asian Earth Sciences 25 (2005) 621–628
These results are in agreement with tectonic situation in
this area. First, the Ipak Fault, which was responsible for the
1962 Buin-Zahra earthquake, has a reverse mechanism with
left-lateral component (Fig. 5) dipping toward the southwest
(Hessami et al., 2003). Secondly, the Soltanieh Fault shows
a dip toward the southwest (Fig. 5). Also, the 2002
Avaj earthquake, which occurred between the Ipak and
Soltanieh faults show reverse motion with dip toward the
southwest.
5.4. The 2003 Jahrom earthquake
The Harvard Centroid Moment Tensor (CMT) solution
suggest values of strike, dip and rake for the 2003 Jahrom
earthquake of 3058,428, and 1188, respectively, while NEIC
suggest strikeZ2988, dipZ478 and rakeZ1158. It is
observed that the values of strikeZ3008, dipZ428 and
rakeZ1188 from this study are in fair agreement with HRV
and NEIC estimates. The focal mechanism, which was
obtained from analysis of SH-waves, shows reverse motion.
The fault plane solution of the 2003 Jahrom earthquake
shows reverse faulting parallel to the local strike of the belt
and dipping towards north.
6. Conclusions
On the basis of analysis of SH-wave data for the 1994
Zanjiran, the 1997 Ardebil, the 1999 Kareh Bas, the 2002
Avaj, the 2003 Jahrom earthquakes the following conclusions
have emerged:
1. The SH-Waves analysis of near field accelerographs
can distinguish the fault plane from the auxiliary
plane. This method is especially helpful, when the
lack of information such as surface rupture, aftershocks
data and an isoseismal map make it difficult to
identify the causative fault plane in the HRV or NEIC
solutions.
2. The 1994 Zanjiran and the 1999 Kareh Bas earthquakes
show strike-slip motion with a approximately north–
south strike direction, which confirms the presence of
strike-slip motion in a folded and thrust belt. While the
2003 Jahrom earthquake shows reverse motion with the
fault plane parallel to the local strike of the belt and
dipping towards the north.
3. The 1997 Ardebil earthquake shows strike-slip motion
with an approximately north–south strike.
4. The 2002 Avaj earthquake shows reverse mechanism
with a fault plane dipping towards the southwest, which
is similar to the 1962 Buin-Zahra earthquake.
5. The estimated fault plane parameters from inversion of
the near field data based on the point source model for
these earthquakes are in fair agreement with solutions
given by HRV and NEIC.
Acknowledgements
I am grateful to International Institute of Earthquake
Engineering, and Seismology for supporting this research
work and Building and Housing Research Center, Tehran,
I.R. Iran for providing the strong ground motion data. I am
thankful to Dr John Milsom and Dr A.J. Barber for their
constructive comments on the manuscript.
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