Spatial and temporal analysis of earthquakes in Iran During the years 1907 to 2023

Document Type : Research Article

Author

• Hamid Ganjaeian

PhD in Geomorphology, University of Tehran, Tehrn, Iran

10.22067/geoeh.2024.87246.1470

Abstract

Extended Abstract
Introduction
The geological situation of Iran and the presence of active faults have resulted in frequent earthquakes occurring in Iran every year. In some cases, large earthquakes have caused significant human and financial losses. Earthquake risk has always been a major concern due to the substantial damage it can cause, but unfortunately, no method has yet been developed to accurately predict the time of its occurrence. This challenge has led to the adoption of statistical methods for approximate earthquake prediction. Given the importance of earthquakes and Iran's high seismic potential, this research focuses on the spatial and temporal analysis of earthquakes that have occurred in Iran. As no comprehensive studies have been conducted on earthquake spatial and temporal analysis, the purpose of this research is to assess the earthquake situation in Iran and identify high-risk areas. Additionally, another aim of this research is to address questions and rumors about the timing of earthquakes at different hours of the day and night. To achieve these objectives, the analysis uses data on earthquake epicenters recorded in Iran between the years 1286 to 1402 (1907 to 2023).
Material and Methods
This research is based on quantitative methods. The key datasets include the SRTM 30-meter digital elevation model, a digital layer of Iran's faults, and information about earthquake epicenters recorded in Iran from 1286 to 1402 (1907 to 2023), sourced from the USGS website. The primary research tools are ArcGIS (for map preparation) and SPSS (for data analysis). According to the research objectives, the study was conducted in two main stages. In the first stage, after gathering statistical data on earthquake epicenters, the spatial analysis of earthquakes was performed by examining magnitude, political divisions, and proximity to major faults. In the second stage, temporal analysis was conducted by evaluating earthquakes across different months and times of the day and night.
Discussion and Results
In this research, earthquakes that occurred in Iran from 1286 to 1402 were analyzed. The results revealed that during the study period, 7139 earthquakes with a magnitude greater than 3 Richter were recorded in Iran, including 12 earthquakes exceeding 7 Richter. This indicates that, on average, an earthquake with a magnitude greater than 7 occurs approximately once every 10 years. The spatial analysis of earthquakes based on political divisions showed that the highest number of earthquake centers were located in the provinces of Hormozgan, Fars, and Kerman, where 1187, 1175, and 796 earthquakes with magnitudes greater than 3 Richter were recorded, respectively. Conversely, the provinces of Alborz, Markazi, and Qom recorded the lowest number of earthquake centers, with 4, 8, and 11 centers, respectively.
The spatial analysis of earthquakes in relation to major faults indicated that the highest earthquake density occurred near the Zagros fault and the Kazeroon fault. Additionally, experts observed that earthquakes with magnitudes greater than 6 Richter were more frequently associated with these faults.
Conclusion
The results of the spatial analysis of earthquakes showed that, in terms of quantity and the number of earthquake foci, the southwestern regions of the country have the highest seismic potential. However, regarding high-magnitude earthquakes (7 Richter), the eastern and northwestern regions of the country exhibit the highest potential. The results also indicate that while the Zagros fault has caused numerous earthquakes, the Nayband fault has played a significant role in high-magnitude earthquakes. Temporal analysis was also conducted, showing that the majority of earthquakes occurred during the months of May and April, with a general decrease in earthquake frequency from May to February. Analysis of the time of occurrence revealed that the highest number of earthquakes occurred between 24:00 and 6:00, while the fewest occurred between 6:00 and 12:00. Overall, earthquake frequency increased from early afternoon until midnight and decreased thereafter until noon. The findings suggest that the early hours of the morning, along with the months of May and April, exhibit the highest earthquake frequency.

Keywords

• Earthquake Risk Zoning
• Seismic Hazard Analysis
• Spatial and Temporal Earthquake Analysis
• Active Faults
• Zagros and Nayband Faults

Main Subjects

• Risk management

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