Iran is one of the most seismically active regions in the world. Considering the growing field of earthquake prediction, it seems to be one of the strategies for reducing earthquake damage and managing crises during earthquakes. Given its successful application in various parts of the world, we examined the performance of the Pattern Informatics (PI) method in forecasting earthquakes in Iran's Zagros region. The PI method has a suitable physical basis and clarity in computational procedures. Unlike many other methods, it does not require processing such as windowing or declustering of earthquake catalogs. It considers the seismic patterns of quiescence and anomalous activity without predefined conditions or patterns. The main criterion in this method is the number of events exceeding a specific threshold and counted in regional cells that have been networked using a particular algorithm. In the modified method, besides counting the earthquakes in the central cell, the effects of eight neighboring cells are also considered, influencing the probability of an earthquake event in the central cell. This study investigates the application of the original and modified global versions of this method to the selected seismic catalogs of Iran. To reduce the effect of varying seismic nature and to prevent errors arising from different averaging methods in the seismic regions of Iran with diverse tectonic characteristics, the Zagros tectonic province was chosen based on the division of Iran's provinces.
In this tectonic province, retrospective predictions were conducted along with evaluations and comparisons of the results to validate the method. The results showed that with acceptable spatial accuracy, this method could be used to predict earthquakes larger than the catalog’s completeness threshold. For this purpose, the success rate and false alarm rate were calculated by changing the cell dimensions and plotting Molchan and ROC (receiver operating characteristic) evaluation diagrams, given that changes in spatial parameters have the most significant impact on the calculations in this method. The optimal method was determined between the original and modified versions with the most suitable cell dimensions. Based on the results, the original PI method with a ∆x = 0.3° grid showed the best evaluation results for the Zagros region.
The catalog used in this study was compiled from the Iranian Seismological Center (ISC) and the International Seismological Center (ISCR) from 1980 to 2021 within the geographical range of 44° to 64° longitude east and 25° to 40° north latitude.