The 2012 August 11<i>M</i><sub>W</sub>6.5, 6.4 Ahar-Varzghan earthquakes, NW Iran: aftershock sequence analysis and evidence for activity migration

Rezapour, Mehdi

doi:10.1093/gji/ggv491

Cited by 7 publications

(8 citation statements)

References 41 publications

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“…Thus, we cannot make a fair comparison between our obtained M2 rupture model and previous ones. Still, Ghods et al (2015) and Rezapour (2016) have proposed geometries for M2 fault that are close to our obtained geometry, although these authors have not investigated the source parameters of the M2.…”

Section: Discussion a N D C O N C L U S I O Nsupporting

confidence: 66%

“…Previous studies based on seismology, InSAR and field observations reach different conclusions on the localization and rupture geometry of these two main events (Alipour 2013;Copley et al 2013;Donner et al 2015;Ghods et al 2015;Zafarani et al 2015;Rezapour 2016;Yadav et al 2016;Amini et al 2018;Momeni & Tatar 2018;Yazdi et al 2018; see Table 1). Most of them agree on the EW strike of M1, while there is no agreement on its dip and the strike and dip of the M2 fault plane.…”

Section: U N C E Rta I N T I E S O N T H E L O C a L I Z At I O N A N...mentioning

confidence: 92%

“…For Yadav et al (2016), M2 fault model dips towards the east and starts from the eastern termination of the M1 fault plane extending towards the north. Rezapour (2016) has relocated the hypocentres of the main shocks and the aftershocks (Figs A1 and B1). The seismicity tends to align along a ∼E-W striking vertical dip fault plane for M1.…”

Section: U N C E Rta I N T I E S O N T H E L O C a L I Z At I O N A N...mentioning

confidence: 99%

“…The seismicity tends to align along a ∼E-W striking vertical dip fault plane for M1. For M2, Rezapour (2016) proposes a ∼ENE-WSW striking fault which dips toward the NNW, and is situated a few kilometres to the north of the M1 fault. He has determined the relative locations of the main shock faults along the N-S direction.…”

Section: U N C E Rta I N T I E S O N T H E L O C a L I Z At I O N A N...mentioning

confidence: 99%

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Kinematics of the 2012 Ahar–Varzaghan complex earthquake doublet (Mw6.5 and Mw6.3)

Momeni

Aoudia

Tatar

et al. 2019

Geophysical Journal International

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an earthquake doublet (M w 6.5 and M w 6.3), separated in time by 11 min, occur in the northwest of Iran. The hypocentres of these earthquakes are close (∼6 km) and located near the cities of Ahar and Varzaghan. The rupture process of both main shocks is retrieved by inverting the near-field strong motions data and using the elliptical subfault approximation method. Our calculations show that the two earthquakes are occurring on two distinct fault planes: the first main shock (M1) has nucleated at a depth of ∼8.5 km, and is located ∼4 km east of the eastern termination of the E-W trending surface rupture. The slip reaches the ground surface west of the hypocentre on an E-W striking fault (N88 • E) that dips almost vertically (80 • S). This earthquake exhibits a right-lateral strike-slip mechanism. The entire slip is imaged on a single patch that ruptures with an average speed of 2.4 km s −1 . The rupture duration is ∼5.6 s and the earthquake releases a seismic moment of ∼8.41E + 18 N•m. The slip reaches the surface with a right-lateral dislocation value of ∼1 m, which is consistent with the observed surface rupture. About 11 min later, the second main shock (M2) nucleates ∼5 km to the west and 4 km to the north with respect to the hypocentre of the M1, and at a depth of ∼16.5 km. The M2 rupture evolves toward shallower depths and to the west on an ENE-WSW oriented fault plane (strike ∼256 • ) with a dip of ∼60 • northward. The slip is essentially distributed on two distinct patches with strike-slip and reverse mechanisms, respectively. The first patch has a pure right-lateral strike-slip mechanism, and ruptures at a relatively fast speed of over 2.8 km s −1 , and last for about 2.6 s until it reaches the second patch. The latter has a reverse mechanism (rake∼112 • ) and extends the rupture toward shallow depths, and to the west at a speed of ∼2.5 km s −1 , and its rupture lasts for ∼2.5 s. The top of the slip distribution of M2 stops at a depth of ∼8 km. We observe that aftershocks surround the M1 and most of the M2 slip models. They are not distributed in the region of high slip (∼3.1 m) of M1. We show that the rupture of M2 is controlled by the static Coulomb stress changes caused by M1, with the maximum slip of M2 located in the positive Coulomb stress caused by M1. The M2 rupture stops where it reaches the area of high negative Coulomb stress change (over −10 bars). The cumulative Coulomb stress fields of both main shocks show a transfer of positive static Coulomb stress change of >0.1 bars on the eastern segment of the North Tabriz Fault. This segment did not rupture since the 1721 M∼7.6-7.7 event that has destroyed the city of Tabriz, and that currently hosts 2 million people. The occurrence of this earthquake doublet with different mechanisms reveals the slip partitioning of the oblique convergence regime of NW Iran on the Ahar-Varzaghan complex fault system.

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Section: Discussion a N D C O N C L U S I O Nsupporting

confidence: 66%

Section: U N C E Rta I N T I E S O N T H E L O C a L I Z At I O N A N...mentioning

confidence: 92%

Section: U N C E Rta I N T I E S O N T H E L O C a L I Z At I O N A N...mentioning

confidence: 99%

Section: U N C E Rta I N T I E S O N T H E L O C a L I Z At I O N A N...mentioning

confidence: 99%

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Kinematics of the 2012 Ahar–Varzaghan complex earthquake doublet (Mw6.5 and Mw6.3)

Momeni

Aoudia

Tatar

et al. 2019

Geophysical Journal International

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“…The Ahar-Varzaghan earthquake has a secondary sequence that occurred approximately 90 days after the main shock. The aftershocks migrated in both along-strike and up-dip directions [Rezapour, 2016]. We studied the Ahar-Varzaghan earthquake in a 90 days period, this is why the time windows of the two earthquakes mentioned are not accordance with the time windows in Gardner and Knopoff [1974], as presented in Table 2.…”

Section: Decay Modelsmentioning

confidence: 99%

Temporal properties of aftershock sequences of large earthquakes in Iran - Analysis of primary and secondary aftershocks of the Ezgeleh sequence

Lavasani

Shabani²

2020

Annals of Geophysics

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In this study, the decay of earthquake aftershock sequences of some major earthquakes in different tectonic regimes in the Iranian plateau is discussed. The studied earthquakes are Rigan [2010], Ahar-Varzaghan [2012], Goharan [2013], Sefidsang [2017] and Ezgeleh [2017]. The spatial and temporal windows are considered based on the method proposed by Gardner and Knopoff [1974] to compute decay parameters for each sequence. The decay rates of sequences were compared to well-known models to find the best fit for each sequence. The results showed that the modified Omori is the best fit for Ahar-Varzaghan and Ezgeleh sequences, for Rigan and Sefidsang sequences the modified Omori and the Kisslinger ones found as the best fits. The values of the p parameter of the Reasenberg and Shcherbakov models were larger compared to the Omori model, but the parameter of the Kisslinger model was slightly smaller compared to the Omori one. The c parameter showed an inverse relation to the threshold magnitude. The correlation between the p and c parameters and also the and the Gutenberg and Richter (G-R) parameters were investigated. In addition, we made use of a graphical method to analyze the seismic sequence of the Ezgeleh earthquake during 13 months after the main event. The graphical method was successful to estimate the occurrence of an event with an approximate magnitude of M=6.4 in the sequence.

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Moderate earthquakes striking Tehran metropolitan area: a case study of 2017 Malard and 2020 Damavand seismic sequences

Niazpour,

Shomali

2024

J Seismol

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The 2012 August 11M_W6.5, 6.4 Ahar-Varzghan earthquakes, NW Iran: aftershock sequence analysis and evidence for activity migration

Cited by 7 publications

References 41 publications

Kinematics of the 2012 Ahar–Varzaghan complex earthquake doublet (Mw6.5 and Mw6.3)

Kinematics of the 2012 Ahar–Varzaghan complex earthquake doublet (Mw6.5 and Mw6.3)

Temporal properties of aftershock sequences of large earthquakes in Iran - Analysis of primary and secondary aftershocks of the Ezgeleh sequence

Moderate earthquakes striking Tehran metropolitan area: a case study of 2017 Malard and 2020 Damavand seismic sequences

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The 2012 August 11MW6.5, 6.4 Ahar-Varzghan earthquakes, NW Iran: aftershock sequence analysis and evidence for activity migration

Cited by 7 publications

References 41 publications

Kinematics of the 2012 Ahar–Varzaghan complex earthquake doublet (Mw6.5 and Mw6.3)

Kinematics of the 2012 Ahar–Varzaghan complex earthquake doublet (Mw6.5 and Mw6.3)

Temporal properties of aftershock sequences of large earthquakes in Iran - Analysis of primary and secondary aftershocks of the Ezgeleh sequence

Moderate earthquakes striking Tehran metropolitan area: a case study of 2017 Malard and 2020 Damavand seismic sequences

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The 2012 August 11M_W6.5, 6.4 Ahar-Varzghan earthquakes, NW Iran: aftershock sequence analysis and evidence for activity migration