مجله ژئوفیزیک ایران

مجله ژئوفیزیک ایران

Evaluation of crustal stress from estimation of b-value based on tectonic regions in the north part of the Zagros in Iran

نوع مقاله : مقاله پژوهشی‌

نویسندگان
Samira Musavian 1
Mehrdad Mostafazadeh 2
1 Ph.D. Candidate, International Institute of Earthquake Engineering and Seismology, Tehran, Iran
2 Assistant Professor in Seismology, International Institute of Earthquake Engineering and Seismology, Tehran, Iran
10.30499/ijg.2024.441596.1573
چکیده
In this study, a high-resolution map of the Gutenberg–Richter b-value and differential stress field and stress drop contour map are provided for the north part of the Zagros region. This region is important because more than 10 earthquakes with magnitude greater than 6 occurred in this region in the last century. In order to understand the tectonic stress pattern of the region, the catalogue of seismicity between 1900 and 2020 was used (most of the events that could be used in this region) in order to explore the spatial and temporal variations of the b-value, which corresponds to the slope of the frequency-magnitude distribution of the earthquakes. The differential crustal stress from the
b-value was estimated and focused on estimating the b-value first in the whole north of the Zagros belt and then in 3 sub-regions. For the entire north of Zagros and its sub-regions, the average content of Mc is 4.0 for the region that has catalogs with different Mc in the time domain and the content of b-value in this region is around 1.03 to 1.12 and the b-value is gradually have lower value, from west to the East of Zagros. In all earlier studies, the b-value was estimated for the entire Zagros but in this study, we estimated the b-value based on the tectonic units of the region. In a temporal variation of b-value, one minimum in the diagram of b-value in MFF region can be seen exactly before the 12 Nov. 2017 Ezgeleh earthquake (Mw=7.3) and another minimum in the diagram would be related to the 18 August 2014 Mormori earthquake (Mw=6.2).
   The stress drop was estimated from M0 for the north part of the Zagros and then this value was compared in the time period before and after the Ezgele earthquake. The stress drop value before and after the Ezgeleh earthquake, around the epicenter, was changed between 0.024-0.03 before the earthquake to 0.13-0.261 MPa after the earthquake respectively.  Finally, the differential stress value is calculated in the time period before and after Ezgele Earthquake, around the epicenter, and it is changed between 300-322 MPa before the earthquake to 238-295 MPa after the earthquake respectively. Therefore, we infer that stress is transmitted from the northern part of the area to the central part of it.
کلیدواژه‌ها
b-value
differential stress
Ezgele
north of Zagros
seismicity
stress drop

موضوعات

عنوان مقاله English

Evaluation of crustal stress from estimation of b-value based on tectonic regions in the north part of the Zagros in Iran

نویسندگان English

Samira Musavian 1
Mehrdad Mostafazadeh 2
1 Ph.D. Candidate, International Institute of Earthquake Engineering and Seismology, Tehran, Iran
2 Assistant Professor in Seismology, International Institute of Earthquake Engineering and Seismology, Tehran, Iran
چکیده English

In this study, a high-resolution map of the Gutenberg–Richter b-value and differential stress field and stress drop contour map are provided for the north part of the Zagros region. This region is important because more than 10 earthquakes with magnitude greater than 6 occurred in this region in the last century. In order to understand the tectonic stress pattern of the region, the catalogue of seismicity between 1900 and 2020 was used (most of the events that could be used in this region) in order to explore the spatial and temporal variations of the b-value, which corresponds to the slope of the frequency-magnitude distribution of the earthquakes. The differential crustal stress from the
b-value was estimated and focused on estimating the b-value first in the whole north of the Zagros belt and then in 3 sub-regions. For the entire north of Zagros and its sub-regions, the average content of Mc is 4.0 for the region that has catalogs with different Mc in the time domain and the content of b-value in this region is around 1.03 to 1.12 and the b-value is gradually have lower value, from west to the East of Zagros. In all earlier studies, the b-value was estimated for the entire Zagros but in this study, we estimated the b-value based on the tectonic units of the region. In a temporal variation of b-value, one minimum in the diagram of b-value in MFF region can be seen exactly before the 12 Nov. 2017 Ezgeleh earthquake (Mw=7.3) and another minimum in the diagram would be related to the 18 August 2014 Mormori earthquake (Mw=6.2).
   The stress drop was estimated from M0 for the north part of the Zagros and then this value was compared in the time period before and after the Ezgele earthquake. The stress drop value before and after the Ezgeleh earthquake, around the epicenter, was changed between 0.024-0.03 before the earthquake to 0.13-0.261 MPa after the earthquake respectively.  Finally, the differential stress value is calculated in the time period before and after Ezgele Earthquake, around the epicenter, and it is changed between 300-322 MPa before the earthquake to 238-295 MPa after the earthquake respectively. Therefore, we infer that stress is transmitted from the northern part of the area to the central part of it.

کلیدواژه‌ها English

b-value
differential stress
Ezgele
north of Zagros
seismicity
stress drop
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مجله ژئوفیزیک ایران
دوره 19، شماره 3
مرداد و شهریور 1404
صفحه 1-23