Source Parameters for Moderate Earthquakes in the Zagros Mountains with Implications for the Depth Extent of Seismicity

Adams, A. N.; Brazier, Richard; Nyblade, A.; Rodgers, Arthur R.; Alamri, Abdullah

doi:10.1785/0120080314

Cited by 26 publications

(22 citation statements)

References 29 publications

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“…They have probably resulted from buckling and subsequent detachment folding of a 12 km thick sediment cover enabled by the detachment in the Cambrian Hormuz salt Mouthereau et al 2007). Active faulting is rare but does occur in the competent cover as argued from recent seismological studies (Adams et al 2009;Nissen et al 2010;Roustaei et al 2010). The pre-Cambrian basement of the Arabian margin is also actively deforming, as indicated by a number of morphotectonic observations in the Fars (Molinaro et al 2004;Lacombe et al 2006;Mouthereau et al 2007) and seismicity (Talebian & Jackson, 2004).…”

Section: A Zagros Folded Belt (Zfb)mentioning

confidence: 98%

Timing of uplift in the Zagros belt/Iranian plateau and accommodation of late Cenozoic Arabia–Eurasia convergence

Mouthereau¹

2011

Geol. Mag.

145

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-The motion of Arabia was stable with respect to Eurasia over the past 22 Ma. Deformation and exhumation in the Zagros is seen to initiate at the same time as argued by new detrital thermochronologic constraints and increasing accumulation rates in synorogenic sediments. A recent magnetostratigraphic dating of the Bakhtyari conglomerates in the northern Fars region of the Zagros further suggests that shortening and uplift in the Zagros Folded Belt accelerated after 12.4 Ma. Available temporal constraints from surrounding collision belts indicate that shortening and uplift focused in regions bordering the Iranian plateau to the south between 15 and 5 Ma. As boundary velocity was kept constant this requires concomitant decreasing strain rates in the Iranian plateau. Slab detachment has been proposed to explain the observed changes as well as mantle delamination, but the insignificant change in the Arabian slab motion and lack of unambiguous constraints make both hypotheses difficult to account for. It is proposed based on a review of shortening estimates provided throughout the Arabia-Eurasia collision that the total 440 km of convergence predicted by geodesy and plate reconstruction over the past 22 Ma can be accounted for by distributed shortening. I suggest that the topography and expansion of the Iranian plateau over Late Miocene-Pliocene time can be reproduced by the progressive thickening of the originally thin Iranian continental lithosphere presumably thermally weakened during the Eocene extensional and magmatic event.

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Section: A Zagros Folded Belt (Zfb)mentioning

confidence: 98%

Timing of uplift in the Zagros belt/Iranian plateau and accommodation of late Cenozoic Arabia–Eurasia convergence

Mouthereau¹

2011

Geol. Mag.

145

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“…A regional unconformity at the base of the Quaternary is associated with the end of the main folding event within the Zagros, and a thin veneer of undeformed Pleistocene-Holocene sediments was deposited on top of this unconformity (Aqrawi et al, 2010). However, recent seismicity data indicate that the Zagros fold belt is still tectonically active today (e.g., Adams et al, 2009;Nissen et al, 2010;Roustaei et al, 2010). …”

Section: Cenozoic: Evolution Of the Mesopotamian Foredeep And Zagros mentioning

confidence: 99%

Geologic evolution of the Iraqi Zagros, and its influence on the distribution of hydrocarbons in the Kurdistan region

English¹,

Lunn²,

Ferreira³

et al. 2015

Bulletin

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A B S T R A C TWhereas the vast majority of discovered hydrocarbon reserves in Iraq reside in Cretaceous and Cenozoic reservoirs, numerous oil and gas fields have been discovered recently in deeper Jurassic and Triassic reservoirs in the Kurdistan region of Iraq. This study presents a Middle-Upper Jurassic thermal maturity map for the Kurdistan region of Iraq and demonstrates that regional first-order trends in Jurassic source rock maturity show a close correlation to the spatial distribution of oil gravities within the overlying Jurassic (and Cretaceous) reservoirs. This distribution is consistent with compartmentalization of the active source rock kitchens due to Zagros folding, resulting in relatively short-distance migration and charge of the anticlinal structures from the adjacent synclinal lows. The thermal maturity map confirms relatively low maturity over the Mosul high, where the Cretaceous and Cenozoic section overlying the source rock interval is relatively thin, and increasing maturity to the southeast as the thickness of the Cenozoic foredeep sediments increases toward the depocenter located in the southeastern Iraqi Zagros and the adjacent Iranian Zagros. The correlative trend in oil gravities is exemplified by the recent Jurassic discoveries: low to medium gravity oils (14-27°API) in Shaikan and Atrush to the northwest, light oil (39-47°API) in Mirawa and Bina Bawi, and gas condensate (55°API) in Miran West to the southeast. Understanding thermal maturity patterns and hydrocarbon fluid-type distributions will help to guide risk assessment for remaining prospectivity and future exploration drilling within the Kurdistan region of Iraq. is an exploration geologist with over 6 years' experience in the Kurdistan region with Hess Corporation and Perenco. He received a B.Sc. degree (2006) in geology and an M.Sc. degree (2007) in petroleum geology from Royal Holloway, University of London. He currently works for OMV Exploration and Production.

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“…Earthquake depths provide valuable information about the style of local deformation and the strength profile of the lithosphere. Zagros earthquake studies confirm that the crystalline basement deforms at up to depths of 20 km with earthquakes of M ~5–6, but no deeper [ Baker et al ., ; Maggi et al ., ; Talebian and Jackson , ; Tatar et al ., ; Adams et al ., ; Nissen et al ., ]. There is some deeper microseismicity in a few areas, such as at Fin (Figure ), where there is an abundance of aftershocks at 20–25 km and a few as deep as 30 km, and near Kermanshah (Figure ), where there are also a few well located events at ~30 km [ Nissen et al ., ].…”

Section: Regional Tectonicsmentioning

confidence: 99%

Orogenic plateau growth: Expansion of the Turkish‐Iranian Plateau across the Zagros fold‐and‐thrust belt

et al. 2013

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[1] This paper shows how the Turkish-Iranian Plateau grows laterally by incrementally incorporating adjacent parts of the Zagros fold-and-thrust belt. The limit of significant, seismogenic, thrusting in the Zagros (M w > 5) occurs close to the regional 1250 m elevation contour. The seismicity cutoff is not a significant bedrock geology boundary. Elevations increase northward, toward regional plateau elevations of~2 km, implying that another process produced the extra elevation. Between the seismogenic limit of thrusting and the suture, this process is a plausibly ductile thickening of the basement, suggesting depth-dependent strain during compression. Similar depth-dependant crustal strain may explain why the Tibetan plateau has regional elevations~1500 m greater than the elevation limit of seismogenic thrusting at its margins. We estimate~68 km shortening across the Zagros Simply Folded Belt in the Fars region, and~120 km total shortening of the Arabian plate. The Dezful Embayment is a low strain zone in the western Zagros. Deformation is more intense to its northeast, in the Bakhtyari Culmination. The orogenic taper (across strike topographic gradient) across the Dezful Embayment is 0.0004, and across the Bakhtyari Culmination, 0.022. Lateral plateau growth is more pronounced farther east (Fars), where a more uniform structure has a taper of~0.010 up to elevations of~1750 m. A >100 km wide region of the Zagros further northeast has a taper of 0.002 and is effectively part of the Turkish-Iranian Plateau. Internal drainage enhances plateau development but is not a pre-requisite. Aspects of the seismicity, structure, and geomorphology of the Zagros do not support critical taper models for fold-and-thrust belts.

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Source Parameters for Moderate Earthquakes in the Zagros Mountains with Implications for the Depth Extent of Seismicity

Cited by 26 publications

References 29 publications

Timing of uplift in the Zagros belt/Iranian plateau and accommodation of late Cenozoic Arabia–Eurasia convergence

Timing of uplift in the Zagros belt/Iranian plateau and accommodation of late Cenozoic Arabia–Eurasia convergence

Geologic evolution of the Iraqi Zagros, and its influence on the distribution of hydrocarbons in the Kurdistan region

Orogenic plateau growth: Expansion of the Turkish‐Iranian Plateau across the Zagros fold‐and‐thrust belt

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