We study the Makran subduction zone, along the southern coasts of Iran and Pakistan, to gain insights into the kinematics and dynamics of accretionary prism deformation. By combining techniques from seismology, geodesy and geomorphology, we are able to put constraints on the shape of the subduction interface and the style of strain across the prism. We also address the long-standing tectonic problem of how the right-lateral shear taken up by strike-slip faulting in the Sistan Suture Zone in eastern Iran is accommodated at the zone's southern end. We find that the subduction interface in the western Makran may be locked, accumulating elastic strain, and move in megathrust earthquakes. Such earthquakes, and associated tsunamis, present a significant hazard to populations around the Arabian Sea.

S U M M A R YThe source parameters and slip distribution of the 2013 May 11 M w 6.1 Minab earthquake are studied using seismology, geodesy and field observations. We observe left-lateral strike-slip motion on a fault striking ENE-WSW; approximately perpendicular to previously studied faults in the Minab-Zendan-Palami fault zone. The fault that ruptured in 2013 is one of a series of ∼E-W striking left-lateral faults visible in the geology and geomorphology. These accommodate a velocity field equivalent to right-lateral shear on ∼N-S striking planes by clockwise rotations about vertical axes. The presence of these faults can reconcile differences in estimates of fault slip rates in the western Makran from GPS and Quaternary dating. The longitudinal range of shear in the western Makran is likely to be controlled by the distance over which the underthrusting Arabian lithosphere deepens in the transition from continentcontinent collision in the Zagros to oceanic subduction in the Makran.Key words: Earthquake source observations; Continental neotectonics; Asia. I N T RO D U C T I O NThe 2013 May 11 M w 6.1 Minab earthquake occurred in the sparsely populated desert to the east of the Strait of Hormuz, in SE Iran (Fig. 1). The earthquake occurred in the western part of the Makran subduction zone, where Arabian oceanic lithosphere is thrust beneath southern Iran and Pakistan. To the west, this oceanic subduction transitions into continent-continent collision in the Zagros mountains of Iran. The Minab earthquake presents an opportunity to address a number of open questions, such as those raised by the M w 7.7 Balochistan earthquake in 2013; a strike-slip event that ruptured a curved fault at the eastern end of the Makran subduction zone (Avouac et al. 2014;Jolivet et al. 2014). That event highlighted that the onshore part of the accretionary wedge built above the subduction interface can be seismically active and characterized by strike-slip faulting. We examine the 2013 Minab event to better understand the deformation of the accretionary wedge in the Zagros-Makran transition zone. This earthquake is also important from the perspective of understanding the regional tectonics and distribution of strain in the western Makran, which give insights into both earthquake hazard and the factors controlling the distribution and style of faulting in the continents. This paper addresses these issues by studying the 2013 Minab earthquake using a combination of seismology, satellite geodesy and field observations. We then consider the implications of our results for the driving forces and distribution of faulting in the region. B O DY WAV E F O R M M O D E L L I N GTeleseismic P and SH waveforms in the epicentral distance range 30-80• were extracted from the IRIS DMC. The seismograms were deconvolved from their instrument responses and reconvolved with the response of a World-Wide Standardised Seismographic Network Long Period (15-100) seismometer. In this period range, a moderate-size earthquake can be approximated as a point source....

The formation of fold-thrust belts at convergent margins is a dynamic process. Accretion of weak sediments to the front of the overriding plate results in crustal thickening and continued flexural subsidence of the underthrusting plate. Fold-thrust belts are often treated as a Coulomb wedge having self-similar geometries with a critical taper, and either a rigid or isostatically compensated base. In this paper we build upon this work by developing a new dynamic model to investigate both the role of the thickness and material properties of the incoming sediment, and the flexure in the underthrusting plate in controlling the behaviour and evolution of fold-thrust belts. Our analysis shows that the evolution of fold-thrust belts can be dominated 2 T. V. Ball, C. E. Penney, J. A. Neufeld, A. C. Copley by either gravitational spreading or vertical thickening, depending on the relative importance of sediment flux, material properties and flexure. We apply our model to the Makran accretionary prism and the Indo-Burman Ranges, and show that for the Makran flexure must be considered in order to explain the dip of the sedimentbasement interface from seismic reflection profiles. In the Indo-Burman Ranges, we show that incoming sediment thickness has a first-order control on the variations in the characteristics of the topography from north to south of the Shillong Plateau.

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