Seismic distribution in the south of Zagros using the statistical correlation between b-Value and fractal dimension

Document Type : Research Article

Authors

1 M.Sc. Student, Department of Geophysics, Faculty of Nano and Bio Science and Technology, Persian Gulf University, Bushehr, Iran

2 Assistant Professor, Department of Geophysics, Faculty of Nano and Bio Science and Technology, Persian Gulf University, Bushehr, Iran

3 Expert of Bushehr Regional Water Company, Bushehr, Iran

Abstract

During the last two decades, the south part of seismotectonic zone of Zagros (Fars) was active. The Zagros seismotectonic belt consists of a series of fault-related folds that within their evolution, seismic areas and hydrocarbon reservoirs formed. Although the characteristics of Zagros are well known, the distribution of active deformations, style of fault-related folds, and its seismotectonic behavior are among the features that require further investigation.
    In this study, changes in seismic rate based on changes in seismic parameter (b-value) and fractal dimension of seismicity (D-value) have been investigated using instrumental seismic data in the period of 2000 to 2021. Total amount of b-value and D-value were calculated by the least square’s method and the correlation integral method, respectively. The map of these parameters was plotted by interpolation method.
    Frequency-magnitude distribution power law (logN=a–bM) relates the cumulative number of earthquakes (N) to their magnitude (M). This ratio is frequently used in seismic studies. In this relationship, a-value describes the productivity and b-value characterizes relative size distribution of earthquakes. Most b-value studies associate the seismicity parameter with the physical properties of a particular zone.
    Since the introduction of fractal in 1976, the fractal concept has covered a wide range of pure mathematics and many experimental aspects of engineering. It has found a comprehensive concept. We analyzed seismicity using the IIEES and IRSC catalog. Decreasing the b-value in the northeastern of study area indicates that stress is increasing, which may signal a future sizable earthquake. The spatial variation of b-value suggests that the SW segment is less stressed compared to the NE segment. Considering that the correlation coefficient is about -0.78, the probability of occurrence of large earthquakes on large area faults increases. The zoning map parameter b-value to D-value ratio found valuable information on the invariance property of the seismic variation scale in the area. These results suggest that this approach can be used as a useful tool to evaluate seismic power distribution on active seismotectonic regions.
    According to the zoning maps and the identification of high stress zone in the study area, the north parts of MFF, around Jam and Farashband and in the later stages, Khormuj will be the main candidate areas for future earthquakes. The seismicity pattern analyzed does hold the key to understand the seismotectonics of the region.

Keywords

References

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Iranian Journal of Geophysics
Volume 17, Issue 1
March 2023
Pages 89-107

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