The 2007 Kahak and 2010 Kazerun earthquakes: constrained non-negative least-squares linear finite fault inversion for slip distribution

Abstract

We study slip distribution of the 2007 June 18 Mw 5.5 Kahak and 2010 September 27 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.