Relocation of the 2006 Mw 6.1 Silakhour, Iran, Earthquake Sequence: Details of Fault Segmentation on the Main Recent Fault

Ghods, Abdolreza; Rezapour, Mehdi; Bergman, Eric; Mortezanejad, Gholamreza; Talebian, Morteza

doi:10.1785/0120110009

Cited by 29 publications

(25 citation statements)

References 34 publications

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“…This fault likely accommodates most of the partitioned, range-parallel dextral shear at these longitudes (Authemayou et al, 2009;Vernant et al, 2004;Walpersdorf et al, 2006). The Main Recent Fault and its splays account for many of the largest earthquakes in the Zagros, including the 1909 M s 7.4 Silakhor, 1957 M w 6.7 Farsinaj, 1958 M w 6.7 Firuzabad, and 2006 M w 6.1 Silakhour earthquakes (Ambraseys & Melville, 1982;Ambraseys & Moinfar, 1973;Berberian, 2014;Berberian & Yeats, 2001;Ghods et al, 2012) and likely accommodate ∼2-12.5 mm/year of dextral motion (Authemayou et al, 2009;Vernant et al, 2004;Walpersdorf et al, 2006).…”

Section: Strike-slip Faultingmentioning

confidence: 99%

“…However, such analyses are not yet routine and can only be applied to events larger than M w ∼ 5–5.5. Recent studies show that regional moment tensors can constrain centroid depths for events larger than M w ∼ 3–3.5, with errors of 2–4 km (e.g., Ghods et al, ; Donner et al, , ), but these analyses require a good station distribution at regional distances.…”

Section: Introductionmentioning

confidence: 99%

“…However, such analyses are not yet routine and can only be applied to events larger than M w ∼ 5-5.5. Recent studies show that regional moment tensors can constrain centroid depths for events larger than M w ∼ 3-3.5, with errors of 2-4 km (e.g., Ghods et al, 2012;Donner et al, 2013Donner et al, , 2014, but these analyses require a good station distribution at regional distances. Berberian (1995) first suggested that seismic activity in the Zagros is concentrated on a small number of large, steeply dipping, basement-cored faults-termed "master blind thrusts"-that pass upward into the lower sedimentary cover where they control observed steps in exposed stratigraphic level.…”

Section: Introductionmentioning

confidence: 99%

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Seismotectonics of the Zagros (Iran) From Orogen‐Wide, Calibrated Earthquake Relocations

et al. 2019

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We use calibrated earthquake relocations to reassess the distribution and kinematics of faulting in the Zagros range, southwestern Iran. This is among the most seismically active fold‐and‐thrust belts globally, but knowledge of its active faulting is hampered by large errors in reported epicenters and controversy over earthquake depths. Mapped coseismic surface faulting is extremely rare, with most seismicity occurring on blind reverse faults buried beneath or within a thick, folded sedimentary cover. Therefore, the distribution of earthquakes provides vital information about the location of active faulting at depth. Using an advanced multievent relocation technique, we relocate ∼2,500 earthquakes across the Zagros mountains spanning the ∼70‐year instrumental record. Relocated events have epicentral uncertainties of 2–5 km; for ∼1,100 of them we also constrain origin time and focal depth, often to better than 5 km. Much of the apparently diffuse catalog seismicity now collapses into discrete trends highlighting major active faults. This reveals several zones of unmapped faulting, including possible conjugate left‐lateral faults in the central Zagros. It also confirms the activity of faults mapped previously on the basis of geomorphology, including oblique (dextral‐normal) faulting in the NW Zagros. We observe a primary difference between the Lurestan arc, where seismicity is focused close to the topographic range front, and the Fars arc, where out‐of‐sequence thrusting is evident over a width of ∼100–200 km. We establish a focal depth range of 4–25 km, confirming earlier suggestions that earthquakes are restricted to the upper crust but nucleate both within and beneath the sedimentary cover.

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Section: Strike-slip Faultingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Seismotectonics of the Zagros (Iran) From Orogen‐Wide, Calibrated Earthquake Relocations

et al. 2019

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“…Calibrated relocations allow us to determine accurate hypocenters for events not recorded by the month‐long local aftershock deployment, including the main shock itself. The approach used to obtain calibrated locations for the Khaki sequence, using regional and teleseismically recorded phases for the period 1966–2013 (mainly 1999–onward), is identical to that used in many prior studies [ Ghods et al , ; Zanjani et al , ; Walker et al , , ; McNamara et al , , and references therein]. Relative locations of the events in a cluster (spanning a limited area but unrestricted in time) are constrained using the program mloc , based on the Hypocentroidal Decomposition (HD) method of Jordan and Sverdrup [] with extensive development since its original applications to reduce location bias of the absolute locations.…”

Section: The Seismology Of the Khaki Earthquake Sequencementioning

confidence: 99%

The 2013M_w6.2 Khaki‐Shonbe (Iran) Earthquake: Insights into seismic and aseismic shortening of the Zagros sedimentary cover

Elliott

Bergman

Copley

et al. 2015

Earth and Space Science

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Determining the relationship between folding and faulting in fold and thrust belts is important for understanding the growth of geological structures, the depth extent of seismic slip, and consequently, the potential earthquake hazard. The 2013 M w 6.2 Khaki-Shonbe earthquake occurred in the Simply Folded Belt of the Zagros Mountains, Iran. We combine seismological solutions, aftershock relocations, satellite interferometry, and field observations to determine fault geometry and its relationship with the structure, stratigraphy, and tectonics of the central Zagros. We find reverse slip on two along-strike, southwest dipping fault segments. The main shock rupture initiated at the lower northern end of the larger northwest segment. Based upon the hypocenter and rupture duration, slip on the smaller southern segment is likely aseismic. Both faults verge away from the foreland, toward the high-range interior, contrary to the fault geometries depicted in many structural cross sections of the Zagros. The modeled slip occurred over two mutually exclusive depth ranges above 10 km, resulting in long (∼16 km), narrow rupture segments (∼7 km). Aftershocks cluster in the depth range 3-14 km. This indicates reverse slip and coseismic shortening occurred mostly or exclusively in the sedimentary cover, with slip distributions likely to be lithologically controlled in depth by the Hormuz salt at the base of the sedimentary cover (∼10-12 km), and the Kazhdumi Formation mudrocks at upper levels (∼4-5 km). Our findings suggest lithology plays a significant role in the depth extent of slip found in reverse faults in folded belts, providing an important control on the potential size of earthquakes.

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“…A hypocentral depth ranging between 6 and 14 km was reported by several agencies [Peyret et al 2008, Ghods et al 2012. According to field investigations no significant surface rupture was observed and a maximum intensity of VIII was reported by Moghadam et al [2006].…”

Section: Introductionmentioning

confidence: 85%

Attenuation characteristics, source parameters and site effects from inversion of S waves of the March 31, 2006 Silakhor aftershocks

Ahmadzadeh

Parolai

Doloei

et al. 2017

Annals of Geophysics

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Relocation of the 2006 Mw 6.1 Silakhour, Iran, Earthquake Sequence: Details of Fault Segmentation on the Main Recent Fault

Cited by 29 publications

References 34 publications

Seismotectonics of the Zagros (Iran) From Orogen‐Wide, Calibrated Earthquake Relocations

Seismotectonics of the Zagros (Iran) From Orogen‐Wide, Calibrated Earthquake Relocations

The 2013M_w6.2 Khaki‐Shonbe (Iran) Earthquake: Insights into seismic and aseismic shortening of the Zagros sedimentary cover

Attenuation characteristics, source parameters and site effects from inversion of S waves of the March 31, 2006 Silakhor aftershocks

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Relocation of the 2006 Mw 6.1 Silakhour, Iran, Earthquake Sequence: Details of Fault Segmentation on the Main Recent Fault

Cited by 29 publications

References 34 publications

Seismotectonics of the Zagros (Iran) From Orogen‐Wide, Calibrated Earthquake Relocations

Seismotectonics of the Zagros (Iran) From Orogen‐Wide, Calibrated Earthquake Relocations

The 2013Mw6.2 Khaki‐Shonbe (Iran) Earthquake: Insights into seismic and aseismic shortening of the Zagros sedimentary cover

Attenuation characteristics, source parameters and site effects from inversion of S waves of the March 31, 2006 Silakhor aftershocks

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The 2013M_w6.2 Khaki‐Shonbe (Iran) Earthquake: Insights into seismic and aseismic shortening of the Zagros sedimentary cover