Seismic strain and b value are used to quantify seismic potential in the Zagros region (Iran). Small b values (0.69 and 0.69) are related to large seismic moment rates (9.96×10 17 and 4.12×10 17) in southern zones of the Zagros, indicating more frequent large earthquakes. Medium to large b values (0.72 and 0.92) are related to small seismic moment rates (2.94×10 16 and 6.80×10 16) in middle zones of the Zagros, indicating less frequent large earthquakes. Small b value (0.64) is related to medium seismic moment rate (1.38×10 17) in middle to northern zone of the Zagros, indicating frequent large earthquakes. Large b value (0.87) is related to large seismic moment rate (2.29×10 17) in northwestern zone, indicating more frequent large earthquakes. Recurrence intervals of large earthquakes (M > 6) are short in southern (10 and 14 years) and northwestern (13 years) zones, while the recurrence intervals are long in the middle (46 and 114 years) and middle to northern (25 years) zones.
The source mechanism derived from the inversion of long-period body waves revealed that the earthquake occurred on a north-south trending strikeslip fault with a thrust component. According to the source model estimated in this study, the 2003 Bam, Iran, earthquake was a multiple event formed by two subevents. The rupture following subevent one started at a depth of about 8 km. However, the depth of subevent two is about 10 km. The total seismic moment estimated from inversion processes is 8.34ϫ 10 18 Nm. The pulse duration of subevent one and subevent two was determined from source time function as 1.7 s and 0.8 s, respectively. Corner frequency and source radius have been calculated by using major pulse duration. The corner frequency and source radius are 0.187 Hz and 5.47 km, respectively. The aftershock events distributed along a 30 km north-south striking fault. The focal depths of aftershocks distribution show a nearly vertical alignment of aftershocks located between 6 and 20 km depth. The focal mechanism solutions of aftershocks indicate right-lateral strike-slip faulting on a north-south trending fault, parallel to the previously known Bam fault trace in the east of Bam.
In this paper, high-resolution map of the Gutenberg–Richter b-value and differential stress field and stress drop 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 past. In order to understand 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. We estimate the differential crustal stress from the b-value using a relationship published by Scholz (GeophytsRes Lett 42:1399–1402, 2015) and focused on estimating b-value first in the whole north of Zagros belt and then in 3 sub regions. For entire north of Zagros and sub regions, the average content of Mc is 4.0 (Based on Kijko-Sellevoll (Bull Seism Soc Am 79(3):645–654, 1989)) and content of b-value in this regions 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, b-value was estimated for the entire of the Zagros but in this study, we estimated the b-value based on tectonic units of the region. In temporal variation of b-value, one minimum in the diagram of b-value in MFF region can be seen exactly before 12 Nov. 2017Ezgeleh earthquake (Mw=7.3) and another minimum in diagram is related to the 18 August 2014 Mormori earthquake (Mw=6.2). The stress drop was estimated from M0 for north part of the Zagros and compared this value in time period before and after Ezgele earthquake. The stress drop value before and after Ezgeleh earthquake, around the epicenter was changed between 0.024–0.03 before earthquake to 0.13–0.261 MPa after the earthquake respectively. Finally we are calculated the differential stress value in time period before and after Ezgele Earthquake, around the epicenter, and it is changed between 300–322 MPa before earthquake to 238–295 MPa after the earthquake respectively. Also it seems that stress transmitted from north part of the Zagros to the central part of it.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.