Oblique convergence and the lobate mountain belts of western Pakistan

Haq, Saad S.B.; Davis, Daniel M.

doi:10.1130/0091-7613(1997)025<0023:ocatlm>2.3.co;2

Cited by 54 publications

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“…Some previous attempts to explain the geometry, topography and tectonics of the Sulaiman Range have focussed on modelling the fold-thrust belt as a thin-skinned frictional wedge overlying the rigid, underthrusting Indian Plate (Humayon et al 1991;Davis & Lillie 1994;Haq & Davis 1997;Macedo & Marshak 1999). Observations of surface geology and seismic reflection profiles from the eastern and southern range front indicate duplex-style thrusting under a passive roof thrust (Banks & Warburton 1986;Humayon et al 1991;Jadoon et al 1993).…”

Section: Previous Workmentioning

confidence: 99%

“…Davis & Engelder 1985;Dahlen 1990), the great across-strike width, flat top and gentle taper are taken as evidence for the presence of a weak basal decollement, thought to be provided by thin Eocambrian salt or evaporites, such as those seen in the Salt Range to the north (Sarwar & De Jong 1979;Banks & Warburton 1986;Humayon et al 1991). Both Haq & Davis (1997) and Macedo & Marshak (1999) use sandbox models to investigate the development of the Sulaiman Range. Haq & Davis (1997) infer the presence of a fault-bounded rigid block at the western boundary of the Sulaiman Range, which is free to translate along the Chaman Fault and generate a variety of structures in the foreland basin sediments thrust against it.…”

Section: Previous Workmentioning

confidence: 99%

“…1a), forms a strongly curved, asymmetric lobe with ∼300 km across-strike width. This range has experienced plentiful earthquakes during the instrumental period, and has been the subject of several competing hypotheses about the behaviour and mechanics of fold-thrust belts (Humayon et al 1991;Jadoon & Khurshid 1996;Haq & Davis 1997;Macedo & Marshak 1999;Bernard et al 2000;Reiter et al 2011). In this paper, we study the Sulaiman Range in order to gain insights into the dynamics and evolution of the range, and the mechanics of curve formation.…”

Section: Introductionmentioning

confidence: 99%

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Evolution and dynamics of a fold-thrust belt: the Sulaiman Range of Pakistan

Reynolds

Copley

Hussain

2015

Geophysical Journal International

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S U M M A R YWe present observations and models of the Sulaiman Range of western Pakistan that shed new light on the evolution and deformation of fold-thrust belts. Earthquake source inversions show that the seismic deformation in the range is concentrated in the thick pile of sediments overlying the underthrusting lithosphere of the Indian subcontinent. The slip vectors of the earthquakes vary in strike around the margin of the range, in tandem with the shape of the topography, suggesting that gravitational driving forces arising from the topography play an important role in governing the deformation of the region. Numerical models suggest that the active deformation, and the extreme plan-view curvature of the range, are governed by the presence of weak sediments in a pre-existing basin on the underthrusting Indian Plate. These sediments affect the stress-state in the over-riding mountain range and allow for the rapid propagation of the nose of the range and the development of extreme curvature and laterally varying surface gradients.Key words: Seismicity and tectonics; Continental neotectonics; Dynamics: gravity and tectonics; Dynamics: seismotectonics. I N T RO D U C T I O NPlan-view curvature of geological structures and range-front topography has long been a recognized and debated feature of both ancient and active fold-thrust belts (e.g. Argand 1924;Carey 1955;Hindle & Burkhard 1999;Marshak 2004). Though poorly understood, the relationship between the size and shape of a mountain range, surface deformation, and continental rheology, is key to our understanding of mountain-building processes. As the largest active mountain ranges on Earth, much of the body of work surrounding this topic has focused on the Tibetan Plateau and the Andes (e.g. Argand 1924;Suárez et al. 1983;Dewey et al. 1988;England & Houseman 1988;Isacks 1988;Molnar & Lyon-Caen 1989;Whitman et al. 1996;Lamb & Hoke 1997;Barke et al. 2007;Royden et al. 2008). However, a full understanding of continental tectonics and rheology requires knowledge of the deformation, evolution and dynamics of not just the planet's largest and most rapidly deforming regions, but also of smaller deformation zones (e.g. Batt & Braun 1999;Macedo & Marshak 1999;Nissen et al. 2011b). A lack of published data, extremely limited geodetic coverage and difficulty of access mean there have been relatively few studies of the western part of the Himalaya-Tibetan Plateau system, where the Himalaya curve to the southwest into the lobate fold-thrust belts of Pakistan. The widest of these, the Sulaiman Range (Fig. 1a), forms a strongly curved, asymmetric lobe with ∼300 km across-strike width. This range has experienced plentiful earthquakes during the instrumental period, and has been the subject of several competing hypotheses about the behaviour and mechanics of fold-thrust belts (Humayon et al. 1991;Jadoon & Khurshid 1996;Haq & Davis 1997;Macedo & Marshak 1999;Bernard et al. 2000;Reiter et al. 2011). In this paper, we study the Sulaiman Range in order to gain insights into the ...

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Section: Previous Workmentioning

confidence: 99%

Section: Previous Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evolution and dynamics of a fold-thrust belt: the Sulaiman Range of Pakistan

Reynolds

Copley

Hussain

2015

Geophysical Journal International

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“…The average seismic moment release rate in the last century in the entire region is 2.28 X 1026 dyn cm yr -•, which is -42% of the total minimum moment release rate predicted by optimal model 3 ( Table 4) ................................................................................ We describe here numerical models that behave in a manner equivalent to Newtonian viscosity and are thick-skinned, in the sense that there is no shear around a horizontal axis. Conversely, the model of Haq and Davis [1997] is a frictional analog model with extensive thin-skinned deformation. However, the two types of models share three conditions: in each case we impose a north-south convergent plate motion, we have an obliquely trending (Chaman) strike-slip boundary, and we allow a relatively rigid (Katawaz) block to migrate along that boundary.…”

Section: Moment Ratesmentioning

confidence: 99%

Kinematics of active deformation in the Sulaiman Lobe and Range, Pakistan

Bernard¹,

Shen-Tu²,

Holt³

et al. 2000

J. Geophys. Res.

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Abstract. The western margin of the Indian plate is highly oblique to the direction of convergence between India and Asia and represents an excellent example of large-scale oblique continent-continent collision. Determining the strain field in western Pakistan and how it relates to the plate motion and plate margin geometry affords an exceptional opportunity for understanding oblique margin processes in general. Through the inversion of regional and teleseismic body waves, we have determined the source parameters of 10 moderate-sized earthquakes that occurred between 1964 and 1985 in and around the Sulaiman Range, Pakistan. The earthquakes are dominantly thrust events with slip vectors that are approximately perpendicular to the lobate Sulaiman mountain front. Slip vector orientations rotate 600-70 ø from a N-S to a WNW-ESE direction of compression, consistent with the geometries of the complex, festoon-shaped mountain belts of this margin. We have estimated the spatial variation of the horizontal strain rate and velocity fields within Sulaiman using vertically averaged models that accommodate plate motion constraints within a deforming layer. The most important factors determining the style of strain rotation in the Sulaiman Lobe and Range are the presence of pure strike-slip motion along the Chaman Fault, and the relatively rigid and undeformed Katawaz Basin that is therefore allowed to translate obliquely relative to India. This same conclusion is obtained using either a three-dimensional, frictional, analogue model with significant basal tractions or a thin sheet viscous numerical model without basal tractions. Thrusting in a predominantly NW-SE direction in the Sulaiman Range accommodates 5-14 mm/yr of N-S motion between India-Eurasia and 3-6 mm/yr of E-W shortening. Seismic moment release this century within the India-Eurasia plate boundary zone, west of the western Himalayan Syntaxis, constitutes roughly 40% of the expected total seismic moment release l•br this time period. Particularly significant moment rate deficits exist within the Sulaiman Range and along the Chaman Fault.

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“…1 and 2). Based on sandbox modeling, Haq and Davis (1997) suggested that the relatively rigid Katawaz block, north of the Sulaiman Lobe, played an important role in partitioning the strain. Bernard et al (2000) reached a similar conclusion from an inversion for the strain field.…”

Section: Introductionmentioning

confidence: 99%

Complex faulting in the Quetta Syntaxis: fault source modeling of the October 28, 2008 earthquake sequence in Baluchistan, Pakistan, based on ALOS/PALSAR InSAR data

Usman

Furuya

2015

Earth Planet Sp

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The Quetta Syntaxis in western Baluchistan, Pakistan, is the result of an oroclinal bend of the western mountain belt and serves as a junction for different faults. As this area also lies close to the left-lateral strike-slip Chaman fault, which marks the boundary between the Indian and Eurasian plates, the resulting seismological behavior of this regime is very complex. In the region of the Quetta Syntaxis, close to the fold and thrust belt of the Sulaiman and Kirthar Ranges, an earthquake with a magnitude of 6.4 (Mw) occurred on October 28, 2008, which was followed by a doublet on the very next day. Six more shocks associated with these major events then occurred (one foreshock and five aftershocks), with moment magnitudes greater than 4. Numerous researchers have tried to explain the source of this sequence based on seismological, GPS, and Environmental Satellite (ENVISAT)/Advanced Synthetic Aperture Radar (ASAR) data. Here, we used Advanced Land Observing Satellite (ALOS)/Phased Array-type L-band Synthetic Aperture Radar (PALSAR) InSAR data sets from both ascending and descending orbits that allow us to more completely detect the deformation signals around the epicentral region. The results indicated that the shock sequence can be explained by two right-lateral and two left-lateral strike-slip faults that also included reverse slip. The right-lateral faults have a curved geometry. Moreover, whereas previous studies have explained the aftershock crustal deformation with a different fault source, we found that the same left-lateral segment of the conjugate fault was responsible for the aftershocks. We thus confirmed the complex surface deformation signals from the moderate-sized earthquake. Intra-plate crustal bending and shortening often seem to be accommodated as conjugate faulting, without any single preferred fault orientation. We also detected two possible landslide areas along with the crustal deformation pattern.

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Oblique convergence and the lobate mountain belts of western Pakistan

Cited by 54 publications

References 0 publications

Evolution and dynamics of a fold-thrust belt: the Sulaiman Range of Pakistan

Evolution and dynamics of a fold-thrust belt: the Sulaiman Range of Pakistan

Kinematics of active deformation in the Sulaiman Lobe and Range, Pakistan

Complex faulting in the Quetta Syntaxis: fault source modeling of the October 28, 2008 earthquake sequence in Baluchistan, Pakistan, based on ALOS/PALSAR InSAR data

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