Details

Autor(en) / Beteiligte

• Enayat, Mohammad
• Ghods, Abdolreza

Titel

3D Shear‐Wave Velocity Model of Central Makran Using Ambient‐Noise Adjoint Tomography

Ist Teil von

• Journal of geophysical research. Solid earth, 2023-11, Vol.128 (11)

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2023

Link zum Volltext

Quelle

Wiley Online Library Journals

Beschreibungen/Notizen

• Abstract The Makran subduction zone is unique in its wide onshore thick accretionary prism, and volcanic arc not parallel to the E–W trend of the Makran accretionary prism. To investigate the internal structure of the accretionary prism, the crustal nature of Jaz Murian Depression, and the trend of the subducting plate hinge, we have calculated a 3D shear‐wave velocity model for a region around the border between eastern and western Makran using ambient‐noise adjoint tomography and data from IASBS/CAM Makran temporary seismic network. In close agreement with previous works, our velocity model shows that the onshore accretionary prism consists of a low‐velocity zone in the south and a high‐velocity zone in the north with an average thickness of accreted sediments of 22 and 30 km, respectively. The young age of the surface rocks of the high‐velocity part of the prism suggests the presence of a significant volume of igneous rocks and metamorphosed sedimentary rocks. The velocity model indicates a continental crust of ∼40 km with a thick sedimentary cover of ∼20 km for the eastern part of Jaz Murian Depression. The presence of a NE‐SW trending low‐velocity region at a depth interval of 40–60 km subparallel with the trend of the volcanic arc, intermediate‐depth earthquakes, and geometry of the overriding plate might be related to the trend of the subducting plate hinge. This implies that the observed NE‐SW trending volcanic arc might be related to the geometry of the subducting plate hinge and not the eastward reduction of the subduction angle. Plain Language Summary We use ambient‐noise tomography to study shear‐wave velocity variations in the onshore part of the Central Makran subduction zone using data from a 4‐year‐long temporary seismic network installed at the border of western and eastern Makran. The variations of shear‐wave velocity are related to the main geological and structural features of the crust. Knowledge of the crustal structures present in the overriding plate and the accretionary prism are essential inputs for accurate estimation of earthquake hazard in the study area. The calculated 3D shear‐wave velocity model shows that the wide onshore accretionary prism of Makran subduction zone is made up of southern low‐ and northern high‐velocity regions, and the fore‐arc Jaz Murian Depression is underlined by a continental crust of ∼40 km thick with a sedimentary cover of ∼20 km. We also found a NE‐SW low‐velocity zone centered at a depth of ∼50 km and subparallel to the trend of volcanic arc and intermediate‐depth earthquakes. We attributed the trend of the low‐velocity zone to the trend of the subducting plate hinge. Key Points We calculate a 3D shear‐wave model in Central Makran using Ambient‐noise adjoint tomography The onshore accretionary prism consists of a southern low‐velocity and a northern high‐velocity zones Jaz Murian Depression is underlined by a continental crust of ∼40 km thick with a sedimentary cover of ∼20 km