New insights into the structural heterogeneity and geodynamics of the Indo-Burma subduction zone from ambient noise tomography

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Journal Article

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The absence of fine lithospheric-scale velocity models beneath Myanmar makes it difficult to understand the neotectonics and geodynamics along the Indo-Burma subduction zone. In this study, we present a high-resolution crustal and uppermost mantle 3-D shear-wave velocity (Vs) model of Myanmar to fill this knowledge gap, using ambient noise data from newly deployed seismic arrays. In the upper crust, our model reveals two thick (>10 km) N-S-elongated basins between the Indo-Burman Ranges and the Central Myanmar Basin. At middle to lower crustal depths, low velocities dominate the Indo-Burman Ranges, especially in its northern part where Vs is observed to be as low as ∼3.2 km/s in the lower crust. This feature is interpreted as sediments that were deposited west of the ranges and have since been subducted northeastward and accreted onto the overriding plate. Furthermore, our model reveals an N-S trending high-velocity anomaly beneath the Sagaing Fault, which could be explained by solidified basaltic magma that intruded upwards from the mantle where a low-velocity anomaly is imaged. In the upper mantle, the subducting Indian Plate is clearly imaged beneath Myanmar as an east-dipping high-velocity zone, overlain by a prominent wedge-shaped low-velocity body (Vs < 4.3="" km/s).="" we="" interpret="" this="" low-velocity="" anomaly="" to="" represent="" partial="" serpentinization="" (19–38%)="" in="" the="" forearc="" mantle.="" the="" size="" and="" amplitude="" of="" this="" anomaly="" decrease="" towards="" the="" north,="" suggesting="" a="" northward="" reduction="" in="" serpentinization="" level="" within="" the="" forearc="" mantle,="" possibly="" related="" to="" a="" northward="" reduction="" of="" water="" in="" the="" subduction="" zone.="" this="" could="" be="" associated="" with="" lower="" water="" content="" in="" the="" subducting="" plate,="" as="" the="" thick="" sediments="" deposited="" in="" the="" north="" may="" have="" driven="" water="" out="" of="" the="" lowermost="" section,="" while="" the="" upper="" sedimentary="" section,="" which="" could="" still="" have="" been="" carrying="" water,="" would="" have="" been="" scraped="" off="" of="" the="" downgoing="" plate="" and="" accreted="" onto="" the="" overriding="" plate,="" forming="" part="" of="" the="" indo-burman="">


ambient noise tomography, basaltic intrusion, forearc mantle serpentinization, Indo-Burma subduction zone, Myanmar, oblique subduction

Publication Details


Earth and Planetary Science Letters



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