The situation in Seismic System Lut, Iran after the earthquake of 20 December 2010, M6.6 in eastern province of Kerman. Peculiarity of this earthquake lies in the fact that it happened on unknown paleofault, or was a consequence of the formation of a new fracture.                                                                                     /December 24, 2010/

SS Lut (Central and SE Iran)

• II level (well determined).

• Lenght 1500 km.

• Depth 33 km.

• Threshold magnitude 6.7.

• Monitoring with 2005.

• Predicted quakes 0.

Large cities: Kerman, Birjand, Yazd, Zahedan, Bum, Ferdows.

Seismicity is caused by the interaction of the Arabian plate with the Iranian and Lut microplates.

The last devastating earthquake hit Bum on Dec. 26 2003, М=6.8 (with epicentre in central Iran, Kerman Province, killing 30.000 people).

 Forecast earthquake Hoseynabad from December 20, 2010 ☼. Peculiarity of the earthquake is - the formation of a new fracture (see below). In SS the formation of a new fault if on the track diagram the trajectory approaches the boundary of the attractor, and tends to draw out from it. In such cases, in the SS take place "atypical" earthquake (an earthquake on the fault is not proved themselves a strong earthquake during the description of the system or on a newly formed fault, missing on the seismotectonic map). Location of such earthquakes predicted very bad, but they usually occur at the boundaries of the SS.

Earthquake Hoseynabad on different networks data had a spread of magnitude Ms=6.5-6.7. In SS Lut (Ms≥6.7) we have accepted it as an indicator of earthquake M6.6, and in the Kerman (Ms≥6.2) as a strong earthquake (see Fig.1). Fragment of track preparation of strong earthquakes in SS Kerman is shown in Fig.2. In the Bulletin 003 for SS Lut we predicted that if seismic activity will not be, until the end of 2014 a major atypical earthquake will occur because track close to the boundary of the attractor, but for SS Kerman, we have not provided that option. Based on Fig.2, we predicted that the seismic activity on the SE of Kerman, at fault Golbarh Shirh (zone C1 in Fig.1) can be prepared a strong earthquake with M6.9, i.e., the track has been closer to the attractor to points of the earthquakes of 1998 and 1981. But the SS Kerman no seismic activity has occurred, the track went away from the attractor near the instability point of Bam earthquake 2003 and the earthquake occurred on the SE boundary of the system in Zone C (Fig.1). After ☼ earthquake predictions have changed.

А. SS Lut. Forecast earthquakes with Мs≥6.7. The track is located in the attractor. Earthquake ☼ compensate for a deficiency of energy indicator-earthquakes. Is preparing an earthquake with М=7.2-7.4. Until mid 2012 system comes seismic gap, and then to the end of 2012 is dangerous to be in zone А (the eastern province of Khorasan, Fig.1), there may be prepared by a strong earthquake with М=7.2. Potentially dangerous to the east of Baluchistan, in zone В (Fig.1). The probability of strong earthquake after Dec. 20 increase by 13% and equal to Р=68%  (PW=80%, PK=85%)  (see Fig.4).

В. Central Iran, provinces of Kerman and Yazd. Forecast earthquakes with 6.2≤Ms<6.7. The system is not dangerous, a strong earthquake is not expected.

PECULIARITY EARTHQUAKE ☼. Peculiarity of this earthquake lies in the fact that it occurred on an unknown fault (fault had not mapped), it was a result of a new faulting or activation of the healed old geological fracture. As in the case of an earthquake in Haiti (see Communication from 31.01.2010), the map of seismic hazard again gave a misfire. The earthquake occurred in the VI-VII intensity area on the map of seismic hazard (see Fig.4). But in reality, in the epicentral area of the earthquake intensity was VIII-IX. Fortunately the earthquake occurred in a relatively sparsely populated province of Kerman, so there were few casualties and damage (see Fig.5). Because of the remoteness of the focal area earthquake and littered roads there is no evidence of faultings on the Earth's surface, which would determine the direction of the main strike-slip. By focal mechanisms ☼  and distribution of aftershocks (see Fig.5) we have restored the option strike-slip in the epicentral area. Presumably, it extended from SW to NE, as in the case of Bam earthquake in 2003 had the character of right strike-slip with the thrust component. We have such a mechanism explains the counterclockwise rotation of Lut plate (see Fig.6). In 2003, 21 August 100 km north-east of the earthquake 2010.12.20 occur earthquake with Ms=5.8 with a right strike-slip, and December 26 100 km northwest of the devastating earthquake hit Bam with Ms=6.9. As a result, these two events after 7 years ago could lead to stress concentration and formation of a new fault in the focal zone of earthquake Hoseynabad.  

Fig.1. The Iran. Controlled area of SS Lut (M≥6.7) and the system of Kerman (M≥6.2). Until the end of 2012 in Zone A can be prepared earthquake with M=7.2. Potentially dangerous in the zone B. Predicted waiting area earthquake zone C1 and C, where the earthquake hit on Dec. 20, 2010.

Fig.4. Map of seismic hazard in Southern Iran and the epicenter of Dec. 20, 2010 quake. It is evident that the earthquake occurred in the VI-VII ball zone.

Fig..5. Epicenter and aftershocks of the earthquake on Dec. 20, 2010 and the proposed mechanism of rupture. It is seen that the main settlements are at a relatively safe distance from the source.

Fig.3. Dynamics of an increase the probability of strong earthquake with M≥6.7 in SS Lut after the  Dec. 20, 2010 earthquake.

Fig.2. Fragment of track diagram for SS Kerman (M≥6.2). Track earthquake 2010.12 retired from the attractor near the instability area of Bam earthquake 2003.

Fig.6. The scheme of counterclockwise rotation of microplate Lut, which could lead to an earthquake 20.12.2010. This could contribute to the earthquake of 2003.

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☼ Earthquake Hoseynabad on the east of Kerman Province, Iran

2010.12.20  18:41:59  28.49N  59.12E  H=12 km  Мs=6.6  

Focal mechanism, Intensity