Preliminary report on the Jam earthquake (Bushehr Province), M 5.4 (26 November 2010)
M.Foroutan, M.A. Shokri, B.Oveisi
An earthquake of 2010 Nov 26 (5Azar 1389) with magnitude of 5.4 in Richter scale, occurred at 12:33:44 UTC (16:03:44 local time on Friday) in east of Jam city (Bushehr province) with about 45000 people and 52, 77 and 173 km far from Kangan, Firouz Abad and Boushehr cities, respectively. The instrumental epicenter of this event given by ISC is N28.24˚; E052.44˚ that located at the 35 km SW of Qir fault system and 45 km NE of Zagros Mountain Front Fault (MFF).
Primary aftershock with ML 4.1 occurred at 16:57 about one hour after the main shock that has been reported by IIEES. Also in following two more events occurred in 60 km south of Firouz Abad city at 21:46 and 23:43 with ML of 3.7 and 3.5, respectively.
The epicenter of the Jam Earthquake is located close to the Halikhan Fault. This fault for the first time was mentioned by Oveisi et al. (2008). The Halikan anticline is located between two major fault-related topographic steps associated with the Surmeh fault and the MFF, and is a structure generally interpreted to result from thin-skinned folding of the sedimentary cover (Oveisi et al., 2008). They interpret the structure of the Halikan anticline as representing a relatively immature and symmetric fault propagation fold. The anticlinal axis of Halikan fold plunges westward and the topographic elevation of the anticlinal hinge decreases concomitantly from ~1500 to ~500 m, suggesting westward propagation of the fold (consistent with the westward deflection of the Mand River behind it). Based on this they suggest that development of the Halikan fold is not controlled by the Karebas-Surmeh fault system.
The terrace profiles along the Mand River suggest a major zone of incision and uplift across the Kuh e Halikan anticline (Figure 2). The modern long profile of the Mand River is consistent with such a pattern of recent deformation (for more information refer to Oveisi et al., 2008).
Figure1) Compilation of LANDSAT-7 and 90m SRTM (Shuttle Radar Thematic Map) data with major active faults from Hessami et al(2003).
Figure2) Isoseismal lines of Jam earthquakes (Bushehr province) in MM scale.
Figure3) Structural cross section across the Halikhan anticline and Surmeh-Karehbas fault system (Oveisi et al., 2008). For location of C- C´ points see figure 1.