Anatomy of a crustal-scale accretionary complex: Insights from deep seismic sounding of the onshore western Makran subduction zone, Iran

Geology ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 3-7 ◽  
Author(s):  
Christian Haberland ◽  
Mohammad Mokhtari ◽  
Hassan Ali Babaei ◽  
Trond Ryberg ◽  
Mehdi Masoodi ◽  
...  
Keyword(s):  
Subduction Zone ◽  
P Wave ◽  
Deep Seismic Sounding ◽  
Accretionary Wedge ◽  
Makran Subduction Zone ◽  
Line Drawings ◽  
Seismic Sounding ◽  
Surface Geology ◽  
Shallow Structure ◽  
Shed Light

Abstract The Makran subduction zone has produced M 8+ earthquakes and subsequent tsunamis in historic times, hence indicating high risk for the coastal regions of southern Iran, Pakistan, and neighboring countries. Besides this, the Makran subduction zone is an end-member subduction zone featuring extreme properties, with one of the largest sediment inputs and the widest accretionary wedge on Earth. While surface geology and shallow structure of the offshore wedge have been relatively well studied, primary information on the deeper structure of the onshore part is largely absent. We present three crustal-scale, trench-perpendicular, deep seismic sounding profiles crossing the subaerial part of the accretionary wedge of the western Makran subduction zone in Iran. P-wave travel-time tomography based on a Monte Carlo Markov chain algorithm as well as the migration of automatic line drawings of wide-angle reflections reveal the crustal structure of the wedge and geometry of the subducting oceanic plate at high resolution. The images shed light on the accretionary processes, in particular the generation of continental crust by basal accretion, and provide vital basic information for hazard assessment and tsunami modeling.

Crustal P wave velocity structure beneath the SE margin of the Tibetan Plateau from Deep Seismic Sounding results

2019 ◽  
Vol 755 ◽  
pp. 109-126
Author(s):  
Jiyan Lin ◽  
Walter D. Mooney ◽  
Fuyun Wang ◽  
Yonghong Duan ◽  
Xiaofeng Tian ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Wave Velocity ◽  
Velocity Structure ◽  
P Wave ◽  
Deep Seismic Sounding ◽  
The Tibetan Plateau ◽  
P Wave Velocity ◽  
Seismic Sounding ◽  
P Wave Velocity Structure

Toward Simultaneous Determination of Bulk Crustal Properties Using Virtual Deep Seismic Sounding

2020 ◽  
Vol 110 (3) ◽  
pp. 1387-1392 ◽  
Author(s):  
Qing Chen ◽  
Wang-Ping Chen
Keyword(s):  
Wave Train ◽  
Silica Content ◽  
P Wave ◽  
Deep Seismic Sounding ◽  
Wide Angle ◽  
Virtual Source ◽  
S Wave ◽  
Large Signal ◽  
Seismic Sounding ◽  
Central Tibet

ABSTRACT We augment the method of virtual deep seismic sounding (VDSS) by adding the phases Sp, the SV-P conversion across the Moho, to determine the average speed of the S wave (VS) in the crust. VDSS uses the strong SV-P conversion below the free surface from teleseismic earthquakes as a virtual source for wide-angle reflections of the P wave. The large signal generated by the virtual source is the strongest aspect of VDSS in which no stacking is necessary to build up the signal. Previous work used the large moveout of the wide-angle reflection, phase SsPmp, relative to the direct S-wave arrival, phase Ss, to minimize the trade-off between bulk P-wave speed (VP) and thickness of the crust (H). It is then straightforward to use the timing of the phase Sp to constrain VS. As examples, we show that this method works for data from both temporary and permanent seismic deployments in contrasting tectonic settings. Specifically, VS under station FORT in western Australia and H1620 in central Tibet are 3.77±0.08 and 3.42±0.11  km/s, respectively. This development complements the undertaking of using information from only the S-wave train to extract all three seismic parameters of the bulk crust, VP, VS, and H. These parameters are important for constraining overall silica content of the crust.

scholarly journals Megathrust and accretionary wedge properties and behaviour in the Makran subduction zone

2017 ◽  
Vol 209 (3) ◽  
pp. 1800-1830 ◽  
Author(s):  
Camilla Penney ◽  
Farokh Tavakoli ◽  
Abdolreza Saadat ◽  
Hamid Reza Nankali ◽  
Morteza Sedighi ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Accretionary Wedge ◽  
Makran Subduction Zone

scholarly journals A review of the seismotectonics of the Makran Subduction Zone as a baseline for Tsunami Hazard Assessments

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Mohammad Mokhtari ◽  
Ahmad Ala Amjadi ◽  
Leila Mahshadnia ◽  
Mandana Rafizadeh
Keyword(s):  
Subduction Zone ◽  
Tectonic Setting ◽  
Accretionary Prism ◽  
Tsunami Hazard ◽  
Indian Plate ◽  
Arabian Plate ◽  
Accretionary Wedge ◽  
The West ◽  
Makran Subduction Zone ◽  
Velocity Models

Abstract The Makran Accretionary Wedge (900 km across) is a consequence of northward subduction of the oceanic part of the Arabian Plate beneath the Lut and Afghan blocks in the northwestern Indian Ocean. It has a complicated tectonic setting as it is located at a triple junction with the Indian Plate. Thick sedimentary layers, a shallow angle of the subducting slab and a large width of the subduction zone, ca. 500–600 km from volcanic arc to active wedge front, are some of the foremost and distinctive characteristics of the Makran Subduction Zone (MSZ). The MSZ is likely divided into at least two segments: the west and the east possibly separated by a sinistral fault known as the Sonne Fault. A division is also inferred from seismicity as it is higher in the east when compared to the west. With the exception of a notable trench, all other characteristics of an accretionary prism observed in well-studied subduction zone can be identified or inferred in the Makran. Three long seismic profiles of the western Makran (200 km long each, with shot points interval of 20 km and receivers interval of 700 m) have recently been acquired. Using these datasets, improved structural/velocity models for the western Makran were developed. This review aims to contribute to achieving a better understanding of the seismotectonic setting and dynamics of the Makran Subduction Zone as it feeds to a refined understanding of the tsunami hazard in the region.

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