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P-Wave Attenuation Structure and Melting Processes of the Tonga-Lau Mantle Wedge

Description: 

The fast-converging Tonga subduction zone and its adjacent Lau back-arc form a complex system where the melting mechanisms show significant along-strike variations. To estimate melt fraction and further investigate the thermal and rheological structures in the Tonga Lau mantle wedge, we present an improved P-wave attenuation tomography model. We first incorporate independently constrained source parameters to invert for the path-average attenuation operator t*. Then, based on the refined t* dataset, we apply a Bayesian Markov chain Monte Carlo technique to image the Tonga-Lau subduction system's 3D attenuation structure. The tomography results exhibit high attenuation anomalies in the Tonga-Lau back-arc mantle and beneath the Taveuni Volcano. Compared to the previous attenuation model in the Tonga-Lau mantle wedge, this new high-resolution model is more consistent with published velocity tomography models. With the help of the Very Broadband Rheology (VBR) Calculator, we can quantitively estimate along-strike variations in melt fraction and temperature. Preliminary results show an increasing trend of melt fraction from south to north. The highest melt fraction reaches up to ~6.5% in the Central Lau Spreading Centers in the north.

Session: Subduction Zone Structure From Trench to Arc

Type: Oral

Date: 4/19/2023

Presentation Time: 09:00 AM (local time)

Presenting Author: Yurong Zhang

Student Presenter: Yes

Invited Presentation: 

Authors