The 2007 Kahak and 2010 Kazerun Earthquakes: Constrained Non-Negative Least-Squares Linear Finite Fault Inversion for Slip Distribution

Document Type : Research

Authors

1 M.Sc. Graduated, Department of Seismology, Institute of Geophysics, University of Tehran, Tehran, Iran

2 Associate Professor, Department of Seismology, Institute of Geophysics, University of Tehran, Tehran, Iran

3 Professor, Department of Seismology, Institute of Geophysics, University of Tehran, Tehran, Iran

Abstract

Here we study slip distribution of the June 18, 2007 Mw 5.5 Kahak and September 27, 2010 Mw 5.9 Kazerun earthquakes by using constrained non-negative least-squares linear slip inversion method for regional broadband seismic data. Hundreds of inversions were carried out to obtain the optimal parameters used in the process, including rupture velocity and rise time. We used the rupture velocity of 2.6 km/s (0.75 Vs) and the rise time of 1.4 s for the first event, and 2.8 km/s (0.75 Vs) and 2.1 s for the second one. Results show the rupture with the peak slip of 8.6 cm and 14.3 cm, and the total seismic moment release of 1.59×1024 dyne-cm and 2.80×1025 dyne-cm for the Kahak and Kazerun earthquakes, respectively. Owing to the non-uniqueness of the inversion problem, we presented a set of solutions for both events. Furthermore, the sensitivity of the slip models to some influential parameters such as rupture velocity and rise time was explored. Moreover, we used two ways for identifying the main/preferred fault plane, which are compatible with one another: First, discerning the main fault plane by using the slip inversion method; second, distinguishing the main fault plane by the use of aftershocks. To the best of our knowledge, this is the first time to apply the linear finite-fault inversion method to moderate earthquakes in Central Iran and Zagros seismotectonic provinces to model a set of rupture histories at regional distances.

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Abercrombie, R. E., Bannister, S., Pancha, A., Webb, T. H. and Mori, J. J., 2001, Determination of fault planes in a complex aftershock sequence using two-dimensional slip inversion. Geophys. J. Int., 146(1), 134-142.
Ashtari, M., Hatzfeld, D. and Kamalian, N., 2005, Microseismicity in the region of Tehran. Tectonophysics, 395(3), 193-208.
Baker, C., Jackson, J. and Priestley, K., 1993, Earthquakes on the Kazerun Line in the Zagros Mountains of Iran: strike-slip faulting within a fold-and-thrust belt. Geophys. J. Int., 115(1), 41-61.
Bazargan, S., Asaadi, N., Shomali, Z. H. and Rezapour, M., 2018, Slip distribution of the 2010 August 27 Mw 5.8 Kuh-Zar earthquake from finite-fault modeling. IJAA, 5(1), 41-9.
Berberian, M., 1981, Active faulting and tectonics of Iran. Zagros Hindu Kush Himalaya Geodynamic Evolution, 33-69.
Berberian, M., 1995, Master “blind” thrust faults hidden under the Zagros folds: active basement tectonics and surface morphotectonics. Tectonophysics, 241(3), 193-224.
Berberian, M. and Tcanlenco, J., 1976, Earthquakes of the southern Zagros (Iran): Bushehr region. Geol. Surv. Iran, 39, 343-370.
Delouis, B., Giardini, D., Lundgren, P. and Salichon, J., 2002, Joint inversion of InSAR, GPS, teleseismic, and strong-motion data for the spatial and temporal distribution of earthquake slip: Application to the 1999 Izmit mainshock. Bull. Seismol. Soc. Am., 92(1), 278–299.
Doser, D. I. and Kanamori, H., 1986, Depth of seismicity in the Imperial Valley region (1977-1983) and its relationship to heatflow, crustal structure, and the October 15, 1979 earthquake. J. Geophys. Res., 91(B1), 675-688.
Hartzell, S. H. and Heaton, T. H., 1983, Inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 Imperial Valley, California, earthquake. Bull. Seismol. Soc. Am., 73(6A), 1553-1583.
Hartzell, S. H. and Heaton, T. H., 1986, Rupture history of the 1984 Morgan Hill, California, earthquake from the inversion of strong motion records. Bull. Seismol. Soc. Am., 76(3), 649-674.
Hartzell, S., Liu, P., Mendoza, C., Ji, C. and Larson, K. M., 2007, Stability and uncertainty of finite-fault slip inversions: Application to the 2004 Parkfield, California, earthquake. Bull. Seismol. Soc. Am., 97, 1911-1934.
Hatzfeld, D., Tatar, M., Priestly, K. and Ghafory-Ashtiany, M., 2003, Seismological constraints on the crustal structure beneath the Zagros Mountain belt (Iran). Geophys. J. Int., 155, 403-410.
Jackson, J. and McKenzie, D., 1988, The relationship between plate motions and seismic moment tensors, and the rates of active deformation in the Mediterranean and Middle East. Geophys. J. Int., 93(1), 45-73.
Lay, T. and Wallace, T.C., 1995, Modern global seismology. Academic Press, San Diego.
Mendoza, C. and Hartzell, S. H., 1988, Aftershock patterns and main shock faulting. Bull. Seismol. Soc. Am., 78, 1438-1449.
Mirzaei, N., Mengtan, G. and Yuntai, C., 1998, Seismic source regionalization for seismic zoning of Iran: major seismotectonic provinces. J. Earth. Predict. Res., 7, 465-495.
Reasenberg, P. and Ellsworth, W. L., 1982, Aftershocks of the Coyote Lake, California, earthquake of August 6, 1979: A detailed study. J. Geophys. Res., 87(B13), 10637-10655. 
Saikia, C. K., 1994, Modified frequency-wave-number algorithm for regional seismograms using Filon’s quadrature–modeling of L(g) waves in eastern North America. Geophys. J. Int., 118, 142–158.
Scholz, C. H., 1990, The mechanics of earthquakes and faulting. Cambridge University Press, Cambridge, 227.
Talbot, C. J., 1998, Extrusion of Hormuz salt in Iran. Geol. Soc. Spec. Publ., 143, 315–334.
Wells, D. L. and Coppersmith, K. J., 1994, New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement. Bull. Seismol. Soc. Am., 84(4), 974-1002.
Yamini-Fard, F., Hatzfeld, H., Tatar, M. and Mokhtari, M., 2006, Microearthquake seismicity at the intersection between the Kazerun fault and the Main Recent Fault (Zagros, Iran). Geophys. J. Int., 166, 186-196.