Document Type : Research
Phd Candidate, Geoscience faculty, Kharazmi university
Department of Geology, Faculty of Science, Ferdowsi University
Faculty of civil engineering and environent, Amirkabir university
The analysis of the basic parameters of the foreshocks is one of the most applied researches for risk reduction of earthquake. Because identification of behavioral pattern of foreshocks can help to researchers in detection of the active fault conditions in different areas. Also accurate analysis of these parameters help to study of earthquake prediction as more effective. In this study, we study about behavioral pattern of foreshocks in different tectonic zone in Iran. This research was conducted to prediction of probability the earthquakes with M>5 in Iran. According to this research, accurate analysis the basic seismic parameters of foreshocks (including: relationship between depth and magnitude of foreshocks) studied with target the prediction of big earthquake in various zone for a ten-year period (from 2007 until 2017). The results of this research suggest that there are the certain similarities to the magnitude - depth models for the one zone and also different for various zones. Therefore, this can be used as a precursor in earthquake prediction with Magnitude>5 for different zones in Iran.
The important results presented in this article can be presented in the following cases:
- Investigation of the information of seismicity parameters of foreshocks regarding the relationship between the focal depth of the main earthquake and the frequency of the foreshocks that used in some parts of the world as a precursor of earthquake suggested that main shocks with M>5 and shallow depth have foreshocks with more abundance (Fig 2).
- Due to the relationship between the type of fault with the occurrence and non-occurrence of aftershocks in different parts of the world, in the case of earthquakes greater than 5 in Iran, in earthquakes with reverse faults, relatively more aftershocks have been recorded compared to strike-slip faults.
- The results of the statistical study conducted in this study show, for earthquakes with reverse fault, the frequency of foreshocks increases with magnitude. However, we do not see such conditions for earthquakes with faults causing strike-slip.
- The result of this study shows, the more earthquake especially in Zagros zone and in the near of salt domes happened without foreshock. The reason for this is related to effect of salt dome on movement fault from slide to creep. The creep is a gradual movement and it is not usually accompanied by rapid movement such as slides that lead to large and recordable earthquakes.
- Based on the present study on earthquakes, for the Zagros (especially in the northern and central part) and Central Iran and Sanandaj-Sirjan, can be used more confidently as a precursor of earthquake because in this zones earthquakes happened with more foreshock.
- In Zagros and Iran Markazi zone the relationship between variations of the depth and magnitude of foreshocks is fruitful for predicting of the main shocks.
- For other zones we need to more complete data bank that has earthquakes with higher frequency of foreshocks. Based on this data bank we can presented suitable relations and models for the study of foreshock with the aim of prediction the big earthquakes.